Revenue Recognition

Generally Accepted Accounting Principles: Generally Accepted Accounting Principles (GAAP) are general guidelines, which instruct firms on how to form their financial statements and how to accurately measure their profit levels. Generally Accepted Accounting Principles (GAAP) forms a conceptual framework that defines the nature and purpose of accounting and provides a theoretical framework regarding the manner in which transactions should be treated. The principles governing accounting procedures, however, may be amended or changed over time, and this may mean that new rules are devised regarding how transactions should be measured, reported, and presented to users (Hodgdon et al, 2009). There should be consistency in the principles used for accounting purposes to promote reliability in financial statements and ensure that all transactions are treated equally by all firms, otherwise there are high chances of financial statements being inaccurate (Wustemann & Kierzek, 2005). The essay will describe the principles of revenue re cognition, the difference between â€Å"income† and â€Å"revenue†, measurement issues between historical cost and value, matching of revenue and expenses, and the differences between the previous conceptual framework and the amendments made in the new revenue recognition model. The essay will conclude with a summary of the main points made in the answer and an analysis of whether the new proposed model has caused concern to respondents. The principles of accounting form a framework that enables users to properly understand the data included in financial statements and make it useful. It enhances the relevancy of the information, makes it free from error, neutral, and comparable to the financial statements of other firms. One of the current issues prevailing in accounting standards includes the issue of the principles of revenue recognition. (Schipper et al, 2009). iAS 18 and New Proposals Made: There are two main revenue recognition standards which incude iAS 18Revenue and iAS 11 Construction Contracts. However, the main problem with these revenue recognition models is that they may be difficult to comprehend and their application may also be a hassle. Moreover, iAS 18 does not thoroughly provide guidance on the topic of revenue recognition arrangements which have multiple elements. The iASB has decided to revise the accounting standard on revenue recognition as inconsistencies and weaknesses exist in the standard. The proposals for improvement in iAS 18 include removing inconsistencies and weaknesses in the existing revenue recognition framework, improving the standard of comparability of revenue recognition practices across industries, disclosing more vital information in financial statements, and the simplification of the preparation of financial statements. One of the main important distinctions made in the revenue recognition model is the distinction between â€Å"inc ome† and â€Å"revenue†. Income is defined as the economic benefits that a firm may generate in the course of an accounting period which include an increase in the inflows or the value of assets or the decrease liabilities that in turn increases equity. This does not include the additional contributions made by existing and new equity holders. However, revenue is defined as the income that arises in the course of ordinary activities of an entity such as the sale of goods etc. The prevailing issue in accounting standards is when to recognize revenue and how to measure it reliably. According to the new accounting standard, revenue is recognized through the selling goods, the provision of services, and third party’s using the entity’s assets which results in yielding interest, royalties, and dividends. Another major issue in the revenue recognition model is how to measure assets or liabilities and whether to measure them at cost price or at value. Using the c ost method may be considered reliable as the cost is known, yet the problem arising in the use of cost is that it relies on past figures (Cairns, 2006).Using the value method may be considered more useful or reliable as it uses up-to-date information but may not always be accurate as the current value of assets or liabilites may vary in measurement from firm to firm (Cairns, 2006). According to IAS 18 (Olsen & Weirich, 2010) revenue shall be measured at fair value which is the amount at which an asset or liability can be settled between two knowledgeable willing parties in a transaction conducted at arm’s length. There are various conditions which result in the recognition of sales, such as when the entity has transferred to the buyer the significant risks and rewards associated with the ownership rights of the goods, the entity holds no managerial or controlling rights over the goods sold, the revenue generated and calculated from the sales can be measured reliably, the enti ty will benefit from the economic benefits of the transaction, and the costs incurred with respect to the transaction can be reliably calculated (Olsen & Weirich, 2010). Problems with Proposed Standard: The costs associated with each of the transactions must be matched to the revenue generated and these costs are categorized as expenses. Each sale results in the occurrence of an expense which must be recognized in coordination with the revenue generated and put in its respective category in order to ensure the balancing of the income statement. However, the new proposed standard has given rise to significant feedback from users which includes the suggestion that while the recognition of revenue generated through selling goods, includes the transfer of control or an assessment of whether risks and rewards have been transferred, it should also include a collectability clause (Olsen &Weirich, 2010). However, other respondents have asked â€Å"transfer of control† to be particularly defined before it is included in the model (Wagenhofer, 2013). While the new revenue recognition model provides a detailed basis for accounting standards and has defined a wide scope for the proper cl assification of transactions, the feedback received has suggested that the model is too complex and confusing for immediate implementation as it is inconsistent with previous frameworks and would require practice and getting used to in implementation. Moreover, other users have also mentioned that the model requires additional information regarding the meaning of certain rules and terms in order to be accurately implemented and used within all firms such as the meaning of â€Å"collaborator†. It is suggested that the Board review the new accounting principles that it has introduced and provide detailed explanations and examples of how to appropriately apply the standards to financial statements. It is also highly suggested that in order to improve the applicability of the new revenue recognition model, the inconsistencies between the previous model and the new model must be removed, the terms used in the new model must be clarified, and the suggested additions may be made. References Cairns, D. (2006). â€Å"The use of fair value in IFRS.† Accounting in Europe. Vol. 3(1) pp. 5-22. Hodgdon, C., Tondkar, R. H., Adhikari, A., & Harless, D. W. (2009). â€Å"Compliance with International Financial Reporting Standards and auditor choice: New evidence on the importance of the statutory audit.† The International Journal of Accounting. Vol.44(1) pp.33-55. Olsen, L., & Weirich, T. R. (2010). â€Å"New revenue?recognition model.† Journal of Corporate Accounting & Finance. Vol.22(1) pp. 55-61. Schipper, K. A., Schrand, C. M., Shevlin, T., & Wilks, T. J. (2009). â€Å"Reconsidering revenue recognition.† Accounting Horizons. Vol. 23(1) pp. 55-68. Wagenhofer, A. (2013). The Role of Revenue Recognition in Performance Reporting. Working Paper, University of Graz. Wustemann, J., & Kierzek, S. (2005). â€Å"Revenue recognition under IFRS revisited: conceptual models, current proposals and practical consequences.† Accounting in Europe. Vol. 2(1) pp.69-106.

The Fibre Optics Technology Engineering Essay

In the past year the information is fetched on developments, inventions and hereafter is explained in perceptible mode In add-on to the aforesaid benefits, fibre optics overseas telegrams have high electrical opposition, are non affected by electromagnetic Fieldss, secure, and low weight. Even so, short distance communications usually rely on electrical Cu wiring due to its much lower cost, easiness of usage, and ability to transport a current. Other utilizations of fibre optics include medical imagination and as centripetal tools. A The subject about the integrated-optic modulators in high velocity fiber-optic links, operation of devices used to externally modulate light beginnings used with fiber-optic ushers has been explained in a perceptible modeIntroductionA fiber-optic communicating system uses the same basic functional constituents as a copper-based communicating system-a sender, receiving system and transmittal medium-except that a fibre-optical nexus ( FOL ) uses optical fiber ( in topographic point of Cu overseas telegram ) as the transmittal medium. Here the optical fiber connects the sender and the receiving system. It carries information in the signifier of light and mainly consists of three parts, viz. , the nucleus, the facing, and the buffer or coating that is used to give strength and protection to the fiber overseas telegram. The nucleus is the cardinal portion of the fiber through which light base on ballss because of the procedure of entire internal contemplation. The cladding surrounds the nucleus, with a different refractile index so that light go throughing through the nucleus stays in that part. The sender consists of an electrical interface, optical modulator and light emitter, and a optical maser rectifying tube or LED for encoding. At the other side, to change over visible radiation into an electrical signal, the receiving system uses either a PIN photodiode or an avalanche photodiode ( APD ) . Several other constituents take portion in set uping an optical fiber nexus ; for illustration, multiplexer, de-multiplexer, signal regenerators, signal repeaters ( or optical amplifiers ) , couplings and splitters. In an optical transmittal system, pick of optical modulators plays an of import portion in the overall public presentation of the system. In this article, we ‘ll concentrate on high-velocity optical modulators, but before we dwell on them in item have a expression at the rudimentss of optical modulators.Optical ModulatorsConverting information in the si gnifier of electric signals into light moving ridges is known as optical transition. This sort of transition can be achieved either straight or externally. In direct transition, information in the signifier of electric signals is applied straight to the light beginning. Many links use this sort of technique to cut down complexness of the system, but when informations rates or the length of the nexus additions, ‘on'/'off ‘ velocity restriction of the optical maser generates waveguide chirp and stage transition. This causes amplitude transition deformation at the receiving system side, which is unwanted for high-definition, high-data-rate communicating. In such a state of affairs, a continuously-‘on ‘ optical maser beginning provides a better solution. That is the basic thought of indirect transition or external transition. In direct transition, digital logic province ‘1'/'0 ‘ is applied straight as ‘on'/'off ‘ electric signal or two dif ferent degrees of electromotive force to the light beginning. In these fortunes, factors like clip invariable of the drive circuitry, building of the visible radiation beginning itself and the features of the transmittal medium ( say, optical fibre ) affect the highest frequence at which the visible radiation beginning can run. Using high-velocity layout and microwave design techniques and high velocity short-pulse integrating ; the job with the circuit and transmittal medium can be minimized. But as stated earlier, the major restriction of this technique is exchanging of the visible radiation beginning itself. In a typical optical maser beginning, this shift cause ‘s electrical and thermic emphasis, which consequences in a frequence displacement known as ‘chirp, ‘ transients and decreased life of the light beginning? In external transition, the optical maser rectifying tube itself stays unmodulated. Data is delivered straight to electrically modulate the crystalli ne stuff like Li niobate. This device can repeatedly exchange visible radiation without impacting the light beginning. Three types of external modulators are normally used: electro-absorption modulators based on Ga – arsenide ( GaAs ) or indium-phosphate ( InP ) semiconducting material, electro ocular modulators based on polarized polymers, and modulators based on electro ocular crystals like Li niobate and other stuffs. Fig. 2 shows the basic difference between direct and external modulators. Over the period, external modulators based on Li niobate ( LiNbO3 ) have become more popular because of its low optical loss and high electro ocular coefficient. Next is described the working of amplitude and stage modulators, followed by their comparing with semiconducting material modulators based on GaAs ( gallium arsenide ) and InP ( indium phosphate ) . There are two normally used types of optical modulators in fibber ocular communicating systems: the electro soaking up modulator ( EAM ) and the Mach-Zehnder modulator ( MZM ) . Electro Absorption Modulator ( EAM ) EAM is little and can be integrated with the optical maser on the same substrate. An EAM combined with a CW optical maser beginning is known as an electro soaking up modulated optical maser. An EML consist of a CW DFB optical maser followed by an EAM, as shown above. Both devices can be integrated monolithically on the same InP substrate, taking to a compact design and low yoke losingss between the two devices. The EAM consists of an active semiconducting material part sandwiched in between a p- and n-doped bed, organizing a p-n junction. The EAM works on the rule known as Franz-Keldysh consequence, harmonizing to which the effectual set spread of a semiconducting material decreases with increasing electric field. Without bias electromotive force across the p-n junction, the set spread of the active part is merely broad plenty to be crystalline at the wavelength of the optical maser visible radiation. However, when a sufficiently big contrary prejudice is applied across the p-n junction, the effectual set spread is reduced to the point where the active part begins to absorb the optical maser visible radiation and therefore becomes opaque. In practical EAMs, the active part normally is structured as an MQW, supplying a stronger field-dependent soaking up consequence ( known as the quantum-confined Stark consequence ) . The relationship between the optical end product power, Pout, and the applied contrary electromotive force, Vm, of an EAM is described by the alleged shift curve. The undermentioned figure illustrates such a curve together with the accomplishable ER for a given shift electromotive force, Vsw. The electromotive force for exchanging the modulator from the on province to the off province, the shift electromotive force Vsw, typically is in the scope of 1.5 to 4 V, and the dynamic ER normally is in the scope of 11 to 13 dubnium. Because the electric field in the active part non merely modulates the soaking up features, but besides the refractile index, the EAM produces some chirp. However, this chirp normally is much less than that of a straight modulated optical maser. A little on-state ( prejudice ) electromotive force about 0 to 1 V frequently is applied to minimise the modulator chirp. Lithium Niobate Mach-Zehnder Modulator ( MZ Modulator ) Lithium Niobate Mach-Zehnder modulators are suited for usage in tube, long-haul ( LH ) and extremist long-haul ( ULH ) optical conveyance applications. The incoming optical signal is split every bit and is sent down two different optical waies. After a few centimeters, the two waies recombine, doing the optical moving ridges to interfere with each other. Such an agreement is known as an interferometer. If the stage displacement between the two moving ridges is 0A ° , so the intervention is constructive and the light strength at the end product is high ( on province ) ; if the stage displacement is 180A ° , so the intervention is destructive and the light strength is zero ( off province ) .The stage displacement, and therefore the end product strength, is controlled by altering the hold through one or both of the optical waies by agencies of the electro-optic consequence. This consequence occurs in some stuffs such as Li niobate ( LiNbO3 ) , some semiconducting materials, every bit good as some polymers and causes the refractile index to alter in the presence of an electric field. The guided-wave LiNbO3 interferometers used to modulate optical maser beams was fabricated every bit early as 1980. LiNbO3 has been the stuff of pick for electro-optic MZ modulator because it combines the desirable qualities of high electro-optic coefficient and high optical transparence in the near-infrared wavelength used for telecommunications.LiNbO3 MZ modulator can run satisfactorily over a wavelength scope of 1300 – 1550nm. It has been widely used in today ‘s high-velocity digital fiber communicating. LiNbO3 MZ modulators with stable operation over a broad temperature scope, really low bias-voltage impetus rates, and bias-free operation are commercially available. High-speed, low-chirp modulators are needed to take advantage of the broad bandwidth of optical fibers. Modulators have became a critical constituent both in the high-velocity time-domain-multiplexing ( TDM ) and wavelength-division-multiplexing systems ( WDM ) . Modulators have been traditionally used to modulate a uninterrupted moving ridge ( CW ) optical maser to bring forth the digital signal to be transmitted through a fiber. High-speed modulator with & gt ; 40GHz bandwidth has been fabricated. Low drive-voltage operation is the key to brining such modulators into practical usage because this eliminates the demand for high-octane electrical amplifiers. There is general a trade off between the velocity and the thrust electromotive force. The modulator chirp must besides be taken into consideration in the nexus design. The design of the modulator and the associated chirp can be used as a grade of freedom to widen nexus distance.Indium Phosphide Mach Zehnder Modulator with DWDM LaserFigure 1 shows the construction of the n-i-n optical wave guide. The construction consists of n-InP facing, an undoped InGaAlAs/InAlAs MQW ( I »PL = 1.37 I?m ) , an Fe-doped SI-InP bed ( Semi-Insulating InP bed ) , and an n-InP facing laminated in this sequence on an SI-InP substrate. In order to avoid losingss of the electrical signal and the optical signal caused by the p-type semiconducting material bed, both the signal and land electrode beds are made with n-type semiconducting material beds in which the loss is about 1/20 of that in the p-type. Besides, a high dislocation electromotive force feature is assured by infixing an SI-InP bed doped with Fe between the n-type clad bed and the i-MQW optical guiding bed. The SI-InP and i-MQW beds are 1.0 and 0.3 I?m. Since the electric field is applied in the limited part within the SI-InP and i-MQW beds, the efficiency of transition of the refractile index by the electro ocular consequence can be made larger. Therefore, low-tension operation and optical transition with a short electrode length can be realized. Fig. 1. Cross-sectional geometry of the n-i-n wave guide In LiNbO3 and III-V semiconducting materials, they are I?33 = 30.8 pm/V ( LiNbO3 modulator ) I?41 a†°? 1.4 pm/V ( InP modulator ) The coefficient in the semiconducting material is about 1/20 that of LiNbO3. However, while the refractile index of LiNbO3 is 2.2, that of the semiconducting material is about 3.2, so that the existent fluctuation of the refractile index in the semiconducting material is 1/7 that of LiNbO3. Therefore, when an optical modulator utilizing the electrooptic consequence is fabricated, the key to size decrease is how the high-density electric field is applied to the optical field. When the constructions of the optical wave guides are compared, the breadth of the n-i-n optical wave guide is A? that in the LiNbO3 modulator and the electrode spacing is from 1/30 to 1/50, so that an electric field more than 100 times as great is applied. Therefore, even with a shorter electrode, fluctuations of the refractile index take topographic point and stage transition can be achieved. To run an optical modulator, an electrode constellation with a distributed component type is effectual, since it is non band-limited by the CR clip changeless. In this manner, a going moving ridge electrode constellation is formed, along which the electrical signal propagates in the same way as the optical moving ridge for optical transition. In order to execute ultra-fast, high-efficiency optical transition with a going moving ridge electrode, two conditions, speed fiting between the optical and electrical moving ridges, and electric resistance matching with a drive system, are of import.a exposure of the bundle for the push-pull constellationFeaturesaˆ? Voltage programmable end product power control aˆ? Long draw public presentation with negligible punishment aˆ? Integral Etalon wavelength stabilization to within A ± 20 autopsy over life aˆ? Differential or individual 50 Ohm low electromotive force thrust transition input aˆ? Integral thermo-electric ice chest with preciseness NTC thermal resistor for temperature control aˆ? Hermetically sealed butterfly manner bundle with SMA RF connections aˆ? ITU Wavelengths available from 1527 nanometer to 1608 nanometer aˆ? 50 GHz channel spacing Parameter Conditions Min Typ Max UnitFIBER OPTIC TECHNOLOGY MICROWAVE AND MILLIMETER WAVE SYSTEMSSide igniter eliminates the dead-zone.Fibre ocular engineering, traditionally used for long draw communications, is happening new applications in short draw communicating systems in military airborne and shipboard platforms. New commercial services such as fibre-to-the-premise for broadband to the concern and place, broadband radio Internet, and digital picture services are being installed across the USA. The service suppliers and installers of these new systems require new methods of proving fibre ocular nexus public presentation in distances from a few metres to less than 1 Km. Optical clip sphere reflect metres ( OTDRs ) traditionally are used for long haul communicating systems but are limited in their usage in military systems and new commercial services due to dead zones. Artisan Laboratories Corporation has developed the Side igniter ( Patent Pending. ) ; a new trial and measuring system eliminates the dead-zone associated with OTDRs therefore doing it attractive for both military and new commercial applications. The Side igniter has a declaration of a few centimeters and is field portable.Radar and Communication System TestingRadar and communicating system trials require out-of-door scopes to find system public presentation. Using an out-of-door scope is expensive and clip devouring so alternate solutions are sought. Radar trials use fixed marks stat mis off from the radio detection and ranging for standardization. Microwave clip holds can be used to imitate marks that allow for proving in a research lab puting. Many bidirectional ( Patent pending ) microwave communicating channel simulator for two manner wireless have been developed the designed demonstrated transmittal at RF and micro-cook frequences that advanced microwave mark allow testing in a research lab environment.CommunicationssFibre ocular transmittal of digital informations for long draw and met ro entree is widely used in the telecommunications industry. As new services are being developed and offered, such as PCS, Broadband Wireless Internet, Digital Video, and Passive Optical Networks, new chances for parallel fibre ocular distribution are emerging. The presentation of a DWDM parallel fibre ocular system used to administer PCS and Broadband. Wireless Internet showed that administering RF over fibre up to 3 GHz has the advantage of simplifying the system architecture and cut downing base station complexness. In this presentation, a DWDM broadband photonic conveyance system was able to run into the demands for both IS-95 Personal Communications Services operating at 1.9 GHz and Broadband Wireless Internet operating over the set of 2.5 to 2.7 GHz. Each DWDM channel operates from 1 to 3 GHz and conveyances services up to 80 Km.Artisan Laboratories Corporation presently offers optical transmittal equipment suited for these applications.SpacecraftNew developments for the following coevals of communicating orbiters and infinite based radio detection and ranging systems include the application of active phased array aerial. In communicating systems, active phased array aerial offer on-board reconfigurability and multi-beam operation. These characteristics greatly cut down concern hazard by leting the beam form to alter depending on client demands. Fibre ocular distribution has been proposed for the transmittal of microwave signals from the orbiter coach to the phased array aerial. The advantage s of utilizing this engineering are higher stage stableness with temperature due to the fibre mechanical to belongingss ; lighter weight and flexibleness of the fiber ; and smaller size of the optical interconnect and optical power splitters. The usage of fiber besides allows for a high degree of integrating with antenna elements therefore cut downing size and weight. Developers are presently developing multi-level microwave photonic faculties that utilize such integrating. While these new developments show promise, fibre ocular distribution has the disadvantage of high power ingestion compared with inactive webs such as coaxal transmittal lines. The increased demand on power ingestion can do the usage of fiber in ballistic capsule prohibitive. To do fibre ocular signal distribution competitory with other transmittal engineerings, Scientists are presently developing a new type of fibre ocular engineering call Ultra visible radiation Fibre Optic Link that can significantly cut down the premier power ingestion of the distribution system.Satellite CommunicationssSATCOM applications make usage of fibre ocular links to have signals from the aerial at a distant location such as a shelter. These links are normally available and operate at an IF of 70 MHz. This architecture requires a low noise amplifier ( LNA ) , frequency interlingual rendition circuitry ( down- convertors ) , local oscillators, filters and a optical maser sender all located at the aerial sit e. Architecture allows for the transmittal of the RF or micro-cook frequence from the orbiter aerial straight over fiber to an integrated exposure receiving system and down-converter system located at a shelter. This architecture reduces the equipment required at the aerial site to the LNA and optical maser sender. Many research labs are offering a high public presentation Low Noise Optical Transmitter System and Integrated Photo receiver Down-Converter System that directs the signal straight from the aerial to a microwave modem. The Low Noise Optical Transmitter System is connected straight to satellite antenna systems extinguishing the demand for a separate low noise amplifier. The Integrated Photo receiver Down-Converter System is an all- in-one system that detects RF and microwave signals over fiber, amplifies the signals, and down-converts them to an intermediate frequence ( IF ) to interface with commercially available microwave informations modems. This system can observe RF over fiber at transition frequences up to 6 GHz and can change over the transition to an IF of 70 MHz or 140 MHz. In applications in which signals from multiple SATCOM aerial must be combined and distributed, DWDM parallel fibre ocular transmittal can be employed. DWDM sender and receiving system capableness include signal transmittal over 100 Km and bandwidth that exceeds multiple octaves with a CNR of 32 dubnium in the set of 950 to 2150 MHz.light beginnings used with fiber-opticOptical BeginningThe basic demands for the visible radiations beginnings used in optical communicating systems depend on the nature of the intended application ( long-haul communicating, local-area web, etc. ) . Both light-emitting rectifying tubes ( LEDs ) and laser rectifying tubes are used as beginnings. Laser rectifying tubes have the advantage of high power ( 10s of mW ) , high velocities, and narrow spectral breadth. LEDs have the advantages of huskiness, dependability, lower cost, long life-time, and simpleness of design. However, they suffer from comparatively broader line breadth and lower bandwidth. If we use external wavelength filters, this may diminish the power coupled. Even at a individual â€Å" colour † ( wavelength ) several manners may be present. Matching to a single-mode fibre will lose the power in these other manners. Therefore the chief characteristics for a light beginning are: 1 ) Power. The beginning power must be sufficiently high so that after transmittal through the fibre the standard signal is noticeable with the needed truth. This includes stableness of that power both in amplitude and frequence. 2 ) Speed. It must be possible to modulate the beginning power at the coveted rate. 3 ) Spectral line breadth. The beginning must hold a narrow spectral line breadth so that the consequence of chromatic scattering in the fibre is minimized. What is the consequence of a finite I†I » ( scattering ) on your system? 4 ) Noise. The beginning must be free of random fluctuations. 5 ) Emission wavelength. Contrast to fiber fading. 6 ) Emission pattern – The beginning power must be coupled to the fibre. Both light end product country and manner distribution in the beam can be of import. Light moving ridges travel in the optical fibre in the signifier of manners, each with a distinguishable spacial distribution, polarisation, extension invariable, group speed, and fading coefficient. Thus the fibre chosen for your system must run into the design ends after consideration of: 1 ) Multi-mode fibre whether step-index, or graded-index. Single-mode fibre. 2 ) Core size 3 ) Core refractile index profile 4 ) Bandwidth and scattering features 5 ) Attenuation dB/km ( including any connections and splicings ) which is a map of cardinal wavelength. Fibers are widely used in light applications. They are used as light ushers in medical and other applications where bright visible radiation demands to be shone on a mark without a clear line-of-sight way. In some edifices, optical fibres are used to route sunshine from the roof to other parts of the edifice ( see non-imaging optics ) . Optical fiber light is besides used for cosmetic applications, including marks, art, and unreal Christmas trees. Swarovski dress shops use optical fibres to light their crystal show windows from many different angles while merely using one light beginning. Optical fiber is an intrinsic portion of the light-transmitting concrete edifice merchandise, LiTraCon. A Frisbee illuminated by fiber optics A fiber-optic Christmas Tree A fiber-optic Christmas Tree Optical fiber is besides used in imaging optics. A consistent package of fibers is used, sometimes along with lenses, for a long, thin imagination device called an endoscope, which is used to see objects through a little hole. Medical endoscopes are used for minimally invasive exploratory or surgical processs ( endoscopy ) . Industrial endoscopes ( see fiberscope or bore range ) are used for inspecting anything difficult to make, such as jet engine insides. An optical fiber doped with certain rare-earth elements such as Er can be used as the addition medium of a optical maser or optical amplifier. Rare-earth doped optical fibres can be used to supply signal elaboration by splicing a short subdivision of doped fiber into a regular ( undoped ) optical fiber line. The doped fiber is optically pumped with a 2nd optical maser wavelength that is coupled into the line in add-on to the signal moving ridge. Both wavelengths of visible radiation are transmitted through the doped fiber, which transfers energy from the 2nd pump wavelength to the signal moving ridge. The procedure that causes the elaboration is stimulated emanation. Optical fibers doped with a wavelength shifter are used to roll up scintillation visible radiation in physics experiments. Optical fiber can be used to provide a low degree of power ( around one W ) to electronics situated in a hard electrical environment. Examples of this are electronics in high-octane aerial elements and measuring devices used in high electromotive force transmittal equipment. Optical fibers are besides used in fibre ocular gyroscopes, and other interferometers instruments.Principle of operationAn optical fiber is a cylindrical insulator wave guide that transmits light along its axis, by the procedure of entire internal contemplation. The fibre consists of a nucleus surrounded by a facing bed. To restrict the optical signal in the nucleus, the refractile index of the nucleus must be greater than that of the facing. The boundary between the nucleus and facing may either be disconnected, in step-index fiber, or gradual, in graded-index fiber.Multimode fiberThe extens ion of visible radiation through a multi-mode optical fiber. Fiber with big ( greater than 10A I?m ) core diameter may be analyzed by geometric optics. Such fiber is called multimode fiber, from the electromagnetic analysis ( see below ) . In a step-index multimode fiber, beams of visible radiation are guided along the fiber nucleus by entire internal contemplation. Rays that run into the core-cladding boundary at a high angle ( measured relation to a line normal to the boundary ) , greater than the critical angle for this boundary, are wholly reflected. The critical angle ( minimal angle for entire internal contemplation ) is determined by the difference in index of refraction between the nucleus and facing stuffs. Beams that meet the boundary at a low angle are refracted from the nucleus into the facing, and do non convey visible radiation and hence information along the fiber. The critical angle determines the credence angle of the fiber, frequently reported as a numerical aperture. A high numerical aperture allows visible radiation to prop agate down the fibre in beams both close to the axis and at assorted angles, leting efficient yoke of visible radiation into the fiber. However, this high numerical aperture increases the sum of scattering as beams at different angles have different way lengths and hence take different times to track the fiber. A low numerical aperture may hence be desirable. A typical single-mode optical fiber, demoing diameters of the constituent beds. Optical fiber types. In graded-index fibre, the index of refraction in the nucleus decreases continuously between the axis and the facing. This causes light beams to flex swimmingly as they approach the facing, instead than reflecting suddenly from the core-cladding boundary. The ensuing curving waies cut down multi-path scattering because high angle beams pass more through the lower-index fringe of the nucleus, instead than the high-index centre. The index profile is chosen to minimise the difference in axial extension velocities of the assorted beams in the fiber. This ideal index profile is really near to a parabolic relationship between the index and the distance from the axis.Single manner fiberFibre with a nucleus diameter less than approximately 10 times the wavelength of the propagating visible radiation can non be modelled utilizing geometric optics. Alternatively, it must be analyzed as an electromagnetic construction, by solution of Maxwell ‘s equations as reduced to the electromagnetic moving ridge equation. The electromagnetic analysis may besides be required to understand behaviors such as spot that occur when coherent visible radiation propagates in multi-mode fiber. As an optical wave guide, the fiber supports one or more confined transverse manners by which visible radiation can propagate along the fiber. Fibre back uping merely one manner is called single-mode or mono-mode fiber. The behavior of larger-core multimode fiber can besides be modelled utilizing the moving ridge equation, which shows that such fibre supports more than one manner of extension ( hence the name ) . The consequences of such modeling of multi-mode fiber about agree with the anticipations of geometric optics, if the fiber nucleus is big plenty to back up more than a few manners. The wave guide analysis shows that the light energy in the fiber is non wholly confined in the nucleus. Alternatively, particularly in single-mode fibers, a important fraction of the energy in the edge manner travels in the facing as an evanescent moving ridge. The most common type of single-mode fiber has a nucleus diameter of 8 to 10 I?m and is designed for usage in the close infrared. The manner construction depends on the wavelength of the visible radiation used, so that this fibre really supports a little figure of extra manners at seeable wavelengths. Multi-mode fiber, by comparing, is manufactured with nucleus diameters every bit little as 50 micrometres and every bit big as 100s of micrometres.Special-purpose fiberSome special-purpose optical fiber is constructed with a non-cylindrical nucleus and/or cladding bed, normally with an egg-shaped or rectangular cross-section. These include polarization-maintaining fiber and fiber designed to stamp down whispering gallery manner extension. Photonic crystal fiber is made with a regular form of index fluctuation ( frequently in the signifier of cylindrical holes that run along the length of the fibre ) . Such fibre utilizations diffraction effects alternatively of or in add-on to entire internal contemplation, to restrict visible radiation to the fiber ‘s nucleus. The belongingss of the fiber can be tailored to a broad assortment of applications.

Duality in A Tale of Two Cities by Charles Dickens

In A Tale of Two Cities by Charles Dickens, it uses duality throughout the story. Duality often refers to having two parts and is usually used with opposite meanings. Charles Dickens wanted us to know about duality by the very first paragraph of his novel. One of the dualities has to deal with the two cities of the title, London, England and Paris, France. Also, some of the dualities show us opposite parallels dealing with two or more people. The two emotions love and hate also have something to do with the theme. I think the use of the doubles is significant First off, Charles Dickens’ very first paragraph says, â€Å"It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the spring of hope, it was the winter of despair, we had everything before us, we had nothing before us, we were all going direct to Heaven, we were all going direct the other way-in sh ort, the period was so far like the present period, that some of its noisiest authorities insisted on its being received, for good or for evil, in the superlative degree of comparison only†¦(Dickens 5)†. This is how he introduces duality in the book. I think that it is important that Charles Dickens used duality because he did not only want us to know that he used it but also explained the dualities throughout the story. The two cities London, England and Paris, France are completeShow MoreRelatedA Tale of Two Cities by Charles Dickens Essay1393 Words   |  6 Pagescritical acclaim, A Tale of Two Cities occupies a central place in the cannon of Charles Dickens’ work. A Tale of Two Cities, published in serial form starting on April 30, 1859, is a historical fiction novel. A dominant theme in this historical novel is the duality found in many of Dickens’ characters. Dickens’ A Tale of Two Cities is somewhat autobiographical; emphasizes the key element s of theme, plot, and character; and has received extensive criticism. A Tale of Two Cities is told in three partsRead MoreA Tale Of Two Cities By Charles Dickens987 Words   |  4 PagesIn a Tale of Two cities. Dickens juxtapositions suspense and humor in a intricate tale of love and loyalty. The book takes place in the late 18th century, during the french revolution. the book is set in England and France, more specifically London and Paris. These are the two cities that the book centers around. In the city of London, the neighborhood of SoHo, and Paris, the french countryside, and city of Dover. b city houses, palace of Versailles. The house in Paris where the Darnay s stayedRead MoreAnalysis Of The Novel Tale Of Two Cities 947 Words   |  4 Pages In the novel Tale of Two Cities, author Charles Dickens defines character Madame Defarge’s symbolism of knitting as an expression of how it weaves its way in the themes of fate and duality. Throughout the novel Dickens uses knitting in a way of affecting other people’s lives, for ins tance, the Evremonde family, related blood Charles Darnay with wife Lucie, and their daughter. 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The debate as to the nature of man is vividly illustrated by the contrasting views of two famous philosophers of the 17th and 18th centuries, Thomas Hobbes and Jean Jacques Rousseau. Hobbes coined the famous expression that primitive human life was nasty, brutish, and short. For Hobbes therefore, Man was inherently bad and it was civilisationRead MoreA Tale Of Two Cities By Charles Dickens1269 Words   |  6 PagesAs described by Charles Dickens through his novel A Tale of Two Cities, he states, â€Å"It was the best of times, it was the worst of times†. (1) The novel, set in 1775 is in the midst of the French Revolution, a time that was embodied by dualities. Love and hate. Misery and happiness. Light and darkness. Hope and despair. The novel utilizes devices such as juxtaposition and repetition to help add meaning to the novel. One such example can be found in the last passage of the novel. With the use of imageryRead MoreThe Castelia City Times Analysis1189 Words   |   5 PagesHello everyone, Today marks the beginning of a new series of articles I wish to work on, the Castelia City Times. Name is still pending but as of now, thats what Im sticking with. In essence, thisll be a (hopefully) weekly article dedicated to non-Pokemon stuff, be it movies, other games, music, or anything else I feel like sharing with the rest of the League. I was originally planning on starting this series strong with Spider-Man Homecoming and Transformers: The Last Knight reviews, but my laptopRead MoreAll The Light We Can Not See By Anthony Doerr Essay1493 Words   |  6 PagesFrance during World War II. It is about a blind girl and a German boy who meet and they both try to survive the war that was going on. I think this would be a good book for me because I enjoy 2) Winter’s Tale by Mark Helprin – New York Times last 25 years -The book setting is in New York City at the beginning and at the end of the twentieth century. This story is about burglar from Ireland, Peter Lake, and a young rich woman, Beverly Young. I think this would be a good book for me because I likeRead MoreVictorian Novel9605 Words   |  39 Pagesdates frame the period of Victorian literature, it is commonly accepted that it was the reign of Queen Victoria (1837-1901) that saw the novel emerge and flourish, all the more that the 1937 was the year when Dickens’ Oliver Twist, the first major work of fiction. The first readers of both, Dickens and Eliot were not conscious they lived in the ‘Victorian period’. They thought that this was a modern era marked with turbulent transition. However, the most crucial writers of the period grew up in the earlierRead MoreMetz Film Language a Semiotics of the Cinema PDF100902 Words   |  316 Pagesmaking them more easily available, originated with Mikel Dufrenne, Professor at the University of Paris-Nanterre and editor of the series in which this work was published in French. He has my very warm gratitude. C . M. Cannes August 1967 here. On two or three definite and important points, this text no longer corresponds to the present state of the problems it confronts. I have taken this opportunity to clarify it and place it in perspective by means of footnotes, for the method and the structure

Acute Human Immunodeficiency Virus ( Hiv ) Infection

Acute Human Immunodeficiency Virus (HIV) infection is the small period of time after a person has been exposed to HIV and before they have seroconverted. Seroconversion is the process in which the body starts to create antibodies to fight the HIV virus (Pietrangelo, 2013). During this period of time, which is usually a few days, the virus replicates rapidly. The rapid replication results in extremely high amounts of HIV in the blood because the body has not had time to respond to the infection. As the viral load increases more CD4 white cells are destroyed. CD4 cells are a responsible in protecting the body from infection. When these cells are destroyed they no longer are able to adequately activate the body s immune system. (AIDS.GOV).†¦show more content†¦Signs/symptoms of Acute HIV Infection Including HP Not all patients with HIV will have signs or symptoms during the acute infection phase. If a patient is having symptoms they can often times think that they have the flu. Acute HIV infection symptoms can show up 2-4 weeks after exposure and last from a few days to several weeks (Cherney, 2014). If they are exhibiting symptoms they may present as having a fever, swollen lymph nodes, skin rashes, myalgia, diarrhea, oral ulcers or thrush, and fatigue. Lab results may also show leukopenia, thrombocytopenia, or an elevation in transaminase (DHHS, 2015). Differential diagnoses include the flu or Epstein- Barr Virus since these also present with similar symptoms. A thorough health history must be taken with patients before an exam in order to identify risk behavior. Important things to ask about are sexual history, partners and possible exposures, any drug use (especially intravenously), and any current STI’s (HRSA, 2014). Upon physical exam things to look for or may see with an acute HIV infection would be ecchymosis, purpura, petechiae, Kaposi sarcoma, lymphadenopathy, oral candidiasis, or hepatosplenomegaly (Aberg et al., 2014). Cultural Implications The numbers of new HIV infections per year has remained relatively the same since the 1990’s (CDC, 2015). Out of

Essay on King Hammurabi’s Efforts to Unify Mesopotamia

During this era, ancient Mesopotamia was under the rule of theocratic monarchies. It was believed that the sole ruler was governing specifically for the gods and catering to their wishes. Mesopotamians were polytheistic, or worshippers of multiple gods, and extremely devout in their faith. They believed that the gods determined all situations and occurrences. As a ruler, King Hammurabi found Mesopotamia to be tremendously divided. At the time of his rule, Mesopotamia was dissected into separate city-states that were often feuding. The creation of King Hammurabi’s code of laws was a means to provide unification for all of the people of Mesopotamia. It was King Hammurabi’s hope that a central system of laws would bind the separate†¦show more content†¦This can be seen with law 200, which stipulates that if one is to knock out the teeth of someone in equal social class status, the same will be done to him. This law also demonstrates the immense importance that was placed on social class. The judiciary system deemed punishments based on the offender and victim’s social classes. This can be seen with laws 197, 198, and 199. Although the crime is the same in all these three laws, breaking someone’s bones or damaging his eyes, the punishment is drastically reduced with decreasing social class of the victim. The subject matter of the laws clearly signify the importance that ancient Mesopotamian society placed upon agriculture. Law 53 notes that if a man’s dam is faulty and breaks and then subsequently floods the surrounding fields, he is at fault. As punishment, the man’s dam will be sold to pay for the damage. Law 53 elaborates on this law, noting that if the man can not replace the damaged grain of the surrounding fields, his possessions will be equally divided between those whose crops have been damaged in the wake of his error. These laws are quite strict in their punishment, noting the vitality that agriculture was to an average Mesopotamian’s wellbeing and livelihood. King Hammurabi’s laws were also quite personal. The laws delvedShow MoreRelatedThe Birth of Civilization18947 Words   |  76 Pages1 The Birth of Civilization Mohenjo-Daro Figure. Scholars believe this limestone statue from about 2500 B.C.E. depicts a king or a priest from Mohenjo-Daro in the Indus valley in present-day Pakistan. Does this figure seem to emphasize the features of a particular person or the attributes of a particular role? Hear the Audio for Chapter 1 at www.myhistorylab.com CRAIMC01_xxxii-031hr2.qxp 2/17/11 3:22 PM Page xxxii EARLY HUMANS AND THEIR CULTURE page 1 WHY IS â€Å"culture† considered a defining

Transducers Used in the Cardiac Ultrasound Machine. free essay sample

Abstract Ultrasound imaging depends on the ability of piezoelectric crystals to generate sound when excited with alternating current and the reverse effect of charge accumulation or current flow when such crystals are subjected to pressure from sound waves. The first known ultrasound imaging machine was designed by K. T. Dussik in Australia in 1937. However, despite its widespread acceptance today, medical ultrasound did not develop as rapidly as X-ray imaging. Despite the relatively slow start, medical ultrasound imaging is very widely accepted today because there is no ionising radiation involved and hence the procedure is relatively safe. Ultrasound equipment is also cheaper as compared to X-ray imaging, magnetic resonance imaging, MRI and other techniques associated with nuclear medicine. The procedure involves minimal patient discomfort and is very useful for examining the soft tissues or the developing foetus. A dramatic increase in the number of older patients with chronic heart and valve disease has resulted in a prolific demand for the ultrasound cardiac imaging machines which can satisfy the requirements associated with fast and cost effective measurement of cardiac anatomy or function. We will write a custom essay sample on Transducers Used in the Cardiac Ultrasound Machine. or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page One of the critical elements in the medical ultrasound imaging system is the ultrasound transducer without which signal processing and visualisation of the soft tissue images is impossible. Although many naturally occurring substances such as quartz exhibit the piezoelectric effect, lead zirconate titanate (PZT) ceramic ferroelectric materials have for many years been used for biomedical applications because of their superior characteristics for soft tissue imaging. Polyvinylidene difluoride (PVDF), transducer material has demonstrated advantages as a high frequency receiver. Single or multilayer transducers made of these elements can be used for ultrasound imaging as single transducers operating in A-mode or a two or three dimensional transducer array for B-mode, C-mode or M-mode ultrasound imaging. This brief essay takes a look at transducers for medical ultrasound. Introduction The principle of operation of a cardiac ultrasound imaging device is based on the information that is provided by the varying delay times of echoes that are reflected from various depths of the human body tissue as a result of the ultrasound pulses that are generated by an ultrasound transducer being incident on the body tissue. Delay times of echoes from different depths are different and ultrasound is reflected from the interface of different types of tissues. A Doppler shift in frequency is also generated as a result of moving objects and the attenuation of ultrasound waves depends on the type of tissue that the ultrasound wave is travelling through. The ultrasound transducer which is responsible for the generation and detection of reflected ultrasound is, therefore, an essential component of the ultrasound imaging device. Ultrasound transducers work on the basis of the piezoelectric effect in which an alternating voltage applied to piezoelectric crystal material causes the crystals to become electrically polarised as a result of the applied electric field and hence vibrate with the alternating voltage to produce sound. Such crystals also become electrically polarised when stress is applied to them and hence any sound waves which are incident on them result in charge accumulation on the crystal surface and hence the generation of an alternating voltage. Thus, an ultrasound transducer consists of a suitable piezoelectric material sandwiched between electrodes that are used to provide a fluctuating electric field when the transducer is required to generate ultrasound. When the transducer is required to detect ultrasound, the electrodes may be used to detect any fluctuating voltages produced as a result of the polarisation of the crystals of the piezoelectric material in response to incident sound which generates fluctuating mechanical stresses on the material. Piezoelectric materials include quartz, ferroelectric crystals such as tourmaline and Rochelle salt as well as the group of materials known as the piezoelectric ceramics, which include lead titanate (PbTiO3) and lead zirconate (PbZrO3). These materials are also known as piezoelectric ceramics which are used in ultrasound transducers for biomedical applications. Polyvinylidene difluoride (PVDF) is another transducer material which has demonstrated advantages as a high frequency receiver. Piezoelectric ceramics are sold with the brand name PXE by Philips Company and are solid solutions of lead titanate (PbTiO3), and lead zirconate (PbZrO3) which have been modified by additives which are a group of piezoelectric ceramics known as PZT. PXE materials are hard, chemically inert and unaffected by a humid environment. The crystals in a ferroelectric material of which PXE is made up of align themselves randomly in a number of directions. With such a random orientation of crystals, the material will exhibit no piezoelectric effect. In order to have a piezoelectric material which is capable of being used for ultrasound transducers, the material has to be subjected to a strong electric field at high temperatures. This has the effect of permanently locking the crystals in the direction of the applied electric field and making the crystal piezoelectric in the direction of the electric field. Hence, a piezoelectric ceramic material may be converted into a piezoelectric material in any given direction by applying a strong electric field to the material in the given direction at an elevated temperature. This treatment, which is known as poling, is the final stage in the manufacture of a PXE piezoelectric. Metal electrodes perpendicular to the poling axis are deposited on the material so that an alternating electric field may be applied to generate ultrasound or ultrasound vibrations may be sensed by sensing the electric field across the piezoelectric material. The voltage across a piezoelectric ceramic PXE material is usually directly proportional to the applied stress. The construction of a simple, single element piezoelectric transducer is as shown below. The Construction of a Single Element Piezoelectric Transducer Ultrasound imaging in the A-mode directs a narrow beam of ultrasound into the tissue being scanned and the echo which may be displayed on a CRT screen provides a measure of the distance between reflecting surfaces in the body. In the B-scan mode, the echo signal is brightness modulated which makes it possible for information related to tissue depth to be displayed on the screen in a visually effective manner. An ultrasound transducer array operating in B-mode permits a picture of the tissues within a patient’s body to be displayed on a CRT device. M-mode ultrasound imaging presents tissue movement by scanning an A or B – line on a monitor as a function of time and movements in this line indicate movements in the tissues within the body. In C-mode ultrasound imaging a second transducer is used to detect echoes sent out by the first transducer, presenting a 2-D map of the ultrasound attenuation within tissues. Having discussed the principles of operation of a piezoelectric medical ultrasound transducer, it is now appropriate to consider the practical problems associated with the construction of such transducers. This is done below. The Design of Ultrasound Transducers A transducer which is constructed out of piezoelectric material will have a natural frequency of resonance and it is appropriate that the transducer should be excited with alternating electric field which matches the natural resonant frequency of oscillation of the material. The ultrasound frequencies that are used in medical imaging applications range from 1 MHz to 15 MHz and echocardiography is usually performed at frequencies of 2. 5 MHz. Hence, transducers which are used for ultrasound imaging have to be tuned for different frequencies. For a transducer material in which ultrasound waves travel at the speed c, with a resonant frequency f, the thickness of the material is related by the formula f=c/2d. Hence, it is possible to tune various transducers constructed of the same material to different frequencies by adjusting the thickness of the material. The ultrasound transducer can be excited by a continuous wave, a pulsed wave, or a single voltage pulse depending on the requirements for observing a continuous image, echo ranging or other tissue measurements. The rear face of the piezoelectric crystal material is usually supported by a backing material which is tungsten loaded araldite, so that the vibrations in the piezoelectric material are rapidly damped after the initial excitation. It is important to couple the piezoelectric transducer to the body of a patient so that the incident ultrasound energy can be effectively transmitted into the body tissue that is being scanned. In order to do this, matching layers of suitable acoustic material are used along with a gel which makes it possible for the ultrasound waves to penetrate the tissue more efficiently. As far as possible, the characteristic acoustic impedance of the tissue being scanned is matched with the acoustic impedance of the transducer. The characteristic acoustic impedance of the tissue is defined as: In the formula, c is the speed of ultrasound in human tissue which is about 1540 m/sec with a variation of +/- 6% and is the tissue density. K is the bulk elastic modulus of the tissue being scanned. The acoustic parameters of an ultrasound transducer include its nominal frequency, the peak frequency which is the highest frequency response measured from the frequency spectrum, the bandwidth of the transducer which is the difference between the highest and the lowest – 6 dB level in the frequency spectrum, the pulse width response time of the transducer, which is the time duration of the time domain envelope which is 20 dB above the rising and decaying cycles of a transducer response, the loop sensitivity for a medium on which a test is performed which is characterised by: Here, Vo is the excitation pulse voltage in volts, while Vx is the received signal voltage from the transducer. The signal to noise ratio for a biomedical ultrasound transducer is also an important parameter for an ultrasound transducer and this is defined as: In the above expression, Vx is the received signal voltage from the transducer in volts in response to a specified tone burst or pulse and Vn is the noise floor in volts. The signal to noise ratio for an ultrasound transducer is a measure of the noise associated with the transducer, measuring instrument or cables and this is a good measure of how sensitive a transducer is. In addition to the previously mentioned parameters, geometrical parameters for a transducer describe how the acoustic pressure generated by a transducer varies across the axial and cross-sectional fields of a transducer. These variations are illustrated below: Axial Beam Profile for an Ultrasound Transducer Cross – Sectional Beam Profile for an Ultrasound Transducer he detailed construction of an ultrasound transducer for medical applications involving the shaping of the piezoelectric material, matching layers, housing and backing materials etc is presently conducted using computational techniques such as Finite Element Modelling of ultrasound transducers through the use of software packages such as Ultrasim and other commercially available software. In the overall design, efforts have to be made to ensure that the overall design will be optimised so as to deliver a sufficiently high power of ultrasound into the tissue being imaged and as far as possible there is best possible sound impedance matching between the transducer and the scanned tissue. Design of the backing material in an ultrasound transducer is important because this design determines the ring down time of the transducer, which is critical for low noise and optimal axial resolution of the transducer. Trends in Transducer Design for Echocardiography Order Now. It takes less than 2 minutes. * Name * Email * Phone * Submit your essay question: (please give as much detail as possible) Only the simplest equipment for echocardiography will use a single ultrasound transducer and there is a trend towards design of echocardiography equipment which uses two or even three dimensional arrays of ultrasound transducers to provide superior quality 2 –D or 3-D computer generated pictures of the organ being imaged. Even the relatively simpler equipment being used these days has two or more ultrasound transducers fitted into the transducer probe. The array of transducers are capable of generating a shaped beam of ultrasound which can be appropriately focused using electronic digital signal processing techniques to provide better images and resolution. Although the relatively simple medical ultrasound scanners cost about ? 1000 per piece, reasonably decent transducer assemblies for a decent Philips or Toshiba ultrasound machines can cost ? 1500 for the transducer alone. Transducer arrays for two or three dimensional ultrasound imaging equipment can be much more expensive because of the large number of transducers that are employed in such imaging equipment. For better quality ultrasonic imaging to be possible, there is a requirement for enhanced bandwidth transducers, higher frequency transducer arrays and sophisticated digital signal processing circuits. There is also a trend towards transducer miniaturisation which will make intracavitary, intraurethral, or intravascular ultrasound (IVUS) investigation possible. The current imaging frequency range of 1 MHz to 15 MHz is expected to be increased to 20 MHz to 100 MHz and at these frequencies, microsonography devices using miniature ultrasound transducers with higher sensitivities are expected to provide much better and higher resolution images using catheter based transducers which are less then 2mm in diameter and are capable of being placed in veins. New ultrasound transducer materials are likely to provide transducers which are far more sensitive then those available presently and consume lower power. These transducers can be operated from battery powered portable equipment and there are indications in literature that with the availability of such devices, it is likely that the stethoscope will be replaced by miniature ultrasound equipment. New trends in ultrasound transducer construction are also moving towards composite transducer construction in which a composite of two piezoelectric materials is used to design the transducer. Ultrasound transducers are fairly rugged and the piezoelectric material does not loose its properties unless exposed to high temperatures approaching the Curie temperature for the material are reached or there are strong alternating or direct electrical fields opposing the direction of poling for the material. Mechanical stresses imposed on the piezoelectric materials should not exceed the specified limits and although the specified limits vary for different types of materials, mechanical stress in excess of 2. 5 MPa may be considered as likely to cause permanent damage. Ultrasound transducers are capable of being designed to operate in liquid mediums and the piezoelectric material does not react with water or gel. Conclusion Materials with piezoelectric properties such as lead titanate (PbTiO3) and lead zirconate (PbZrO3) lend themselves to being treated by poling to generate as well as detect ultrasound waves when subjected to alternating electric fields or mechanical stresses. Ultrasound transducers can be made out of these materials and these transducers can be designed for specified resonance frequencies for use in medical imaging. The detailed design of such transducers is an exciting and involving undertaking which is capable of being assisted by finite element simulations. Advances in transducer design involving the use of new materials, miniaturisation and the use of arrays of transducers promises to revolutionise medical imaging in the future by providing high resolution 3-D ultrasound images and the field is full of promise for device designers as well as computer engineers of the future. References/ Bibliography Web Sources 1. Abboud, Najib N et al. â€Å"Finite Element Modelling for Ultrasonic Transducers†. Weidlinger Associates Inc. SPIE Int. Symp. Medical Imaging 1998, San Diego, Feb 21-27, 1998. August 4, 2005. http://www. wai. com/AppliedScience/Software/Pzflex/Papers/pzflex-spie_mi98. pdf 2. Binder, T. â€Å"Three-Dimensional Echocardiography Principles and Promises†. Journal of Clinical and Basic Cardiology 2002; 5 (Issue 2), 149-152. August 4, 2005. http://www. kup. at/kup/pdf/1137. df 3. Brandt, Einar. â€Å"Segmentation Techniques for Echocardiographic Image Sequences†. University of Linkopings. 1998. August 4, 2005. http://www. imv. liu. se/klinfys/einar/publications/pdf_open/Ex1934. pdf 4. Bridal, Lori S et al. â€Å"Milestones on the Road to Higher Resolution, Quantitative, and Functional Ultrasonic Imaging†. PROCEEDINGS OF THE IEEE, VOL. 91, NO. 10, OCTOBER 2003. August 6, 2005. http://dei-s1. dei. uminho. pt/outraslic/lebiom/ultra/ultrasonic0123219 2. pdf

Never let me go book report free essay sample

Never let me go by Kazuo Ishiguro is about a group of human clones in a dystopian society raised only to become organ donors. The plot creates controversy. In the book, the clones are presented as sub-human and not permitted to be considered as equal to regular humans. Thus, it becomes acceptable for them to die a short life in order for others to live a longer one. It is here where we become aware of one theme, the poor treatment of those we believe to be beneath us in order to get ahead in the world. Another theme we can find in the book is that of conformity. We find that many times the characters seem accept their fate, without really putting up much of a struggle. They all seem to accept their fate as donors and the inevitability of their demise at 30 years old. This is especially present in today’s society, as many people would rather be seen as normal than abnormal and subsequently sticking to the status quo. We will write a custom essay sample on Never let me go book report or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page My favorite theme in the novel and the one I will be expanding on is the identity crisis the main characters and mostly the clones have throughout the book. This part of the novel I feel really relates to the real world and how a lot of individuals struggle to become their own person. Often looking in other places to blend into their personalities. These themes become coherent through Kathy’s eyes. As the main protagonist of the book, never actually becoming permanently attached to the situation many times only describing her observations and analysis of it. Then moving on to the next phase in her life. This theme resonates within me, since I have gone through the same identity crisis at some point of my life and often forget who I am in some circumstances. I also feel that the most part of the world has also experienced this. This does not only pertain to individuals, but can also be applied to countries as well. The main theme I’d like to discuss is the identity crisis experienced by many characters within the book. Kathys identity search is motivated by feelings of being alone in her own outlook. The sexual desires she experiences as young women upset her when she can not get validation from Ruth, another main character in the novel, that they are common. Ruth, seen as a social leader in the group, shows confidence but is in fact insecure of who she really is. Through Kathy’s eyes we perceive how Ruth often copies  her mannerism from older clones and television characters. Ruth relies much on others to define her own identity. Even Tommy, who acknowledges who he is, but has trouble believing it since he thinks others do not think the same. There are many passages in the book that implies this theme. Ruth states on page 120-121 in last paragraph, â€Å"There was something I noticed about these veteran couples at the cottages†¦ and this was how so many of their mannerisms were copied from the television†¦ the way they gestured to each other, sat together on sofas, even the way they argued and stormed out of rooms. † Even other characters notice this and try to fix the status quo. Miss Lucy, a guardian for the clones, tells them on page 80, â€Å"If you’re to live decent lives, you have to know who you are and what lies ahead of you, every one of you. † The first quote shows how people that do not know who they are and are hard press to find a way to individualize themselves may look to outside sources. The characters are in search of what makes them different from other clones and even the person they are cloned from. They hope to find a reason for their existence, much like citizens in the real world do. Countries also do this in a way. It could be by individual motivation or external influence. Smaller 3rd World Countries will try to model themselves after 1st world Countries believing they will share in the same success. This causes an identity crisis for their country. They have their own culture that separates them from the rest, but yet modeling themselves like another could alter the culture and lead to a lost in identity. This type of phenomena has happen in the past and could happen again. This topic brings up many questions in my mind. How the larger 1st world country influences the identity of a 3rd world country? I feel if the more powerful country really wanted too, they could have the 3rd world country model themselves after the 1st world. Which I think is what often happens, so they can more influence in structure of the world. How does one create their own identity is another question I would ask. If allowed to without any outside influences, what identity would a person or a country take on? I’d like to comprehend what having an identity really means.