WorldWideScience

Sample records for cdte linear arrays

  1. Directivity of basic linear arrays

    DEFF Research Database (Denmark)

    Bach, Henning

    1970-01-01

    For a linear uniform array ofnelements, an expression is derived for the directivity as a function of the spacing and the phase constants. The cases of isotropic elements, collinear short dipoles, and parallel short dipoles are included. The formula obtained is discussed in some detail and contour...

  2. Technical evaluation of Solar Cells, Inc., CdTe module and array at NREL

    Energy Technology Data Exchange (ETDEWEB)

    Kroposki, B.; Strand, T.; Hansen, R. [National Renewable Energy Lab., Golden, CO (United States); Powell, R.; Sasala, R. [Solar Cells, Inc., Toledo, OH (United States)

    1996-05-01

    The Engineering and Technology Validation Team at the National Renewable Energy Laboratory (NREL) conducts in-situ technical evaluations of polycrystalline thin-film photovoltaic (PV) modules and arrays. This paper focuses on the technical evaluation of Solar Cells, Inc., (SCI) cadmium telluride (CdTe) module and array performance by attempting to correlate individual module and array performance. This is done by examining the performance and stability of the modules and array over a period of more than one year. Temperature coefficients for module and array parameters (P{sub max}, V{sub oc}, V{sub max}, I{sub sc}, I{sub max}) are also calculated.

  3. Radiation Hardened Bolometer Linear Array Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA has developed space-based thermal instrument spectrometers based on thermopile detectors linear arrays that are intrinsically radiation hard. Micro-bolometers...

  4. Communication Behavior of Linear Arrays of Processes

    OpenAIRE

    Lee, Tak K.

    1988-01-01

    This paper investigates the communication behavior of a linear array of processes, each process implementing the same program. For programs with cyclic communication patterns, simple criteria for determining whether they induce constant response time on the array are established. Also, an algorithm is developed for characterizing programs with more general communication patterns.

  5. CdZnTe and CdTe detector arrays for hard X-ray and gamma-ray astronomy

    International Nuclear Information System (INIS)

    A variety of CdZnTe and CdTe detector arrays were fabricated at NASA/GSFC for use in hard X-ray and gamma-ray astronomy. Mosaic, pixel, and 3-D position-sensitive detector arrays were built to demonstrate the capabilities for high-resolution imaging and spectroscopy for 10 to 2 MeV. This paper will summarize the different arrays and their applications for instruments being developed at NASA/GSFC. Specific topics to be addressed include materials characterization, fabrication of detectors, ASIC readout electronics, and imaging and spectroscopy tests

  6. CdZnTe and CdTe detector arrays for hard X-ray and gamma-ray astronomy

    Energy Technology Data Exchange (ETDEWEB)

    Stahle, C.M. E-mail: carl.stahle@gsfc.nasa.gov; Parker, B.H.; Parsons, A.M.; Barbier, L.M.; Barthelmy, S.D.; Gehrels, N.A.; Palmer, D.M.; Snodgrass, S.J.; Tueller, J

    1999-10-21

    A variety of CdZnTe and CdTe detector arrays were fabricated at NASA/GSFC for use in hard X-ray and gamma-ray astronomy. Mosaic, pixel, and 3-D position-sensitive detector arrays were built to demonstrate the capabilities for high-resolution imaging and spectroscopy for 10 to 2 MeV. This paper will summarize the different arrays and their applications for instruments being developed at NASA/GSFC. Specific topics to be addressed include materials characterization, fabrication of detectors, ASIC readout electronics, and imaging and spectroscopy tests.

  7. Linear Microbolometric Array Based on VOx Thin Film

    Science.gov (United States)

    Chen, Xi-Qu

    2010-05-01

    In this paper, a linear microbolometric array based on VOx thin film is proposed. The linear microbolometric array is fabricated by using micromachining technology, and its thermo-sensitive VOx thin film has excellent infrared response spectrum and TCR characteristics. Integrated with CMOS circuit, an experimentally prototypical monolithic linear microbolometric array is designed and fabricated. The testing results of the experimental linear array show that the responsivity of linear array can approach 18KV/W and is potential for infrared image systems.

  8. Modified GA Optimization of Linear Sparse Array

    Institute of Scientific and Technical Information of China (English)

    CHEN Ke-song; HE Zi-shu; HAN Chun-lin

    2006-01-01

    With a goal to optimize the element positions to reduce the peak sidelobe level (PSLL) of the array pattern, a modified real Genetic Algorithms (MGA) for the synthesis of sparse linear arrays is described. The multiple optimization constrains include the number of elements, the aperture and the minimum element spacing. The advanced new approach reduces the size of the searching area of GA by means of indirect description of chromosome and avoids infeasible solution during the optimization process by designing the new genetic operators. The elementary steps of MGA are presented. The simulated results confirm the great efficiency and the robustness of this algorithm.

  9. Linear array CCD sensor for multispectral camera

    Science.gov (United States)

    Chabbal, J.; Boucharlat, G.; Capppechi, F.; Benoit-Gonin, R.

    1985-10-01

    Design, operational and performance features are described for a new 2048 element CCD array in a ceramic package for beam sharing focal plane arrangements on remote sensing satellites. The device, labeled the TH 7805, furnishes 13 micron square pixels at 13 microns pitch over the 480-930 nm interval, two video outputs and a single-phase, buried channel CCD register. Each n-p photodiode is linked to a Si coating by a gate storing the photocharges. Crosstalk between elements is less than 1 percent and the rms noise level is 180 micro-V. The array output sensitivity is 1.37 micro-V/electron, linearity to less than 1 percent, and a 10 MHz maximum data rate. The entire sensor package draws under 150 mW power from the spacecraft. The TH 7805 has withstood over 10 krads in tests without exhibiting faults.

  10. Imaging radiometers employing linear thermoelectric arrays

    Science.gov (United States)

    McManus, Timothy J.; Mickelson, Steve

    1999-07-01

    Infrared Solutions, Inc. has developed a family of radiometers which employ silicon microstructure uncooled linear thermoelectric arrays, prepared by Honeywell Technology Center. Included in the family is a handheld imaging radiometer for predictive and preventive maintenance having a frame time of 1.4 sec, a linescanner radiometer for monitoring of industrial web process, an imaging radiometer for monitoring stationary industrial processes such as a die casting, and a linescanner radiometer for monitoring the temperature distribution of railcar wheels on trains moving at speeds up to 80 mph.

  11. Stripe filters on multispectral linear arrays

    Science.gov (United States)

    Hall, J. H.; Blaha, F. C.; Frias, B. R.; Halvis, J.; Hubbard, E.

    1982-01-01

    Dielectric interference filters deposited directly on top of existing 200 element charge coupled device linear imaging arrays were designed, fabricated and evaluated. The optical performance of the filters was verified with regard to crosstalk between adjacent detector elements. The filters showed an average in-band transmittance greater than 80% and a total out of band transmittance of less than 5%. Filter stability was adequate for operation in a space environment. The filter elements were definable in 12 to 25 micron element size compatible with existing silicon detectors. These type of measurement were made: (1) spectral transmission of the filter as deposited on witness plates; (2) spectral response of the silicon sensing device; (3) any optical interaction between filter and sensing device; (4) the response of the filter/sensor combination; and (5) repeatability and uniformity of filter characteristics. Detailed discussion of these evaluations are given.

  12. THE DEGENERACY PROBLEM OF TWO-DIMENSIONAL LINEAR RECURRING ARRAYS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The degeneracy degree and degeneracy position sets of a wo-dimensional linear recurrence relation set are characterized. The fact that a linear recurring array is essentially a doubly periodic array is shown. By using the Grbner base theory, a calculation formula for degeneracy degree is given and the existence of a special degeneracy position set is proved. In the present paper, the degeneracy problem of the two-dimensional linear recurring arrays is completely solved.

  13. Linearly tapered slot antenna circular array for mobile communications

    Science.gov (United States)

    Simons, Rainee N.; Kelly, Eron; Lee, Richard Q.; Taub, Susan R.

    1993-01-01

    The design, fabrication and testing of a conformal K-band circular array is presented. The array consists of sixteen linearly tapered slot antennas (LTSA). It is fed by a 1:16 microstrip line power splitter via electromagnetic coupling. The array has an omni-directional pattern in the azimuth plane. In the elevation plane the beam is displaced above the horizon.

  14. Analytical synthesis technique for linear uniform‐amplitude sparse arrays

    NARCIS (Netherlands)

    Caratelli, D.; Viganó, M.C.

    2011-01-01

    A novel analytical approach to the synthesis of linear sparse arrays with uniform‐amplitude excitation is presented and thoroughly discussed in this paper. The proposed technique, based on the auxiliary array factor concept, is aimed at the deterministic determination of the optimal array element de

  15. Underwater Imaging Using a 1 × 16 CMUT Linear Array

    OpenAIRE

    Rui Zhang; Wendong Zhang; Changde He; Yongmei Zhang; Jinlong Song; Chenyang Xue

    2016-01-01

    A 1 × 16 capacitive micro-machined ultrasonic transducer linear array was designed, fabricated, and tested for underwater imaging in the low frequency range. The linear array was fabricated using Si-SOI bonding techniques. Underwater transmission performance was tested in a water tank, and the array has a resonant frequency of 700 kHz, with pressure amplitude 182 dB ( μ Pa · m / V ) at 1 m. The −3 dB main beam width of the designed dense linear array is approximately 5 degrees. Synthetic aper...

  16. Linear and mass attenuation coefficient for CdTe compound of X-rays from 10 to 100 keV energy range in different phases

    International Nuclear Information System (INIS)

    The Full Potential Linear Muffin Tin Orbitals method within the density functional theory has been utilized to calculate structural and electronic properties of the CdTe compound. We have checked that the CdTe has two phase-transitions from zinc-blend to cinnabar and from cinnabar to rocksalt. We have found that the rigidity, the energy and the nature of the gap change according to the phase change, so we can predict that a CdTe detector may have different behaviors in different phase conditions. In order to investigate this behavior change, the linear and the mass attenuation coefficients of X-ray in rocksalt, zinc-blend and cinnabar structures are calculated from 10 keV to100 keV, using the XCOM data. We have found that when CdTe undergoes a phase transition from zinc-blend to cinnabar, its linear attenuation coefficient decreases down to a value of about 100 times smaller than its initial one, and when it undergoes a transition from cinnabar to rocksalt it increases up to a value about 90 times larger than its initial one

  17. Modelling and 3D optimisation of CdTe pixels detector array geometry - Extension to small pixels

    Energy Technology Data Exchange (ETDEWEB)

    Zumbiehl, A. E-mail: zumbiehl@phase.c-strasbourg.fr; Hage-Ali, M.; Fougeres, P.; Koebel, J.M.; Regal, R.; Rit, C.; Ayoub, M.; Siffert, P

    2001-08-11

    CdTe and CdZnTe pixel detectors offer great interest for many applications, especially for medical and industrial imaging. Up to now, the material, generally, used and investigated for pixel arrays was CZT (Hamel et al., IEEE Trans. Nucl. Sci. 43 (3) (1996) 1422; Barrett et al., Phys. Rev. Lett. 75 (1) (1995) 156; Bennett et al., Nucl. Instr. and Meth. A 392 (1997) 260; Eskin et al., J. Appl. Phys. 85 (2) (1999) 647; Brunett et al., J. Appl. Phys. 86 (7) (1999) 3926; Luke, Nucl. Instr. and Meth. A 380 (1996) 232), but cadmium telluride can also be an appropriate choice, as shown here. However, we clearly demonstrate here that the optimal pixel configuration is highly dependent on the electrical transport properties of the material. Depending on the field of primary interest, either energy resolution or counting rate efficiency in the photopeak, the geometry for each case has to be optimised. For that purpose, we have developed a calculation of the signal induced onto the pixel. Two distinct parts are used: after showing our approach for the weighting potential calculation, we present our results performed by a 'pseudo-Monte Carlo' simulation. Results are supported by a few experimental comparisons. We argue about the optimum sizes with clarifying the problems caused by too small and too large pixel sizes. The study field is chosen to be vast, i.e. pixel size to detector thickness ratios (W/L) of 1/8-1, and detector thickness of 1.0-8.0 mm. In addition, several electrical transport properties are used. Since efficiency is often of primary interest, thick detectors could be very attractive, which are shown to be really feasible even on CdTe.

  18. Modelling and 3D optimisation of CdTe pixels detector array geometry - Extension to small pixels

    Science.gov (United States)

    Zumbiehl, A.; Hage-Ali, M.; Fougeres, P.; Koebel, J. M.; Regal, R.; Rit, C.; Ayoub, M.; Siffert, P.

    2001-08-01

    CdTe and CdZnTe pixel detectors offer great interest for many applications, especially for medical and industrial imaging. Up to now, the material, generally, used and investigated for pixel arrays was CZT (Hamel et al., IEEE Trans. Nucl. Sci. 43 (3) (1996) 1422; Barrett et al., Phys. Rev. Lett. 75 (1) (1995) 156; Bennett et al., Nucl. Instr. and Meth. A 392 (1997) 260; Eskin et al., J. Appl. Phys. 85 (2) (1999) 647; Brunett et al., J. Appl. Phys. 86 (7) (1999) 3926; Luke, Nucl. Instr. and Meth. A 380 (1996) 232), but cadmium telluride can also be an appropriate choice, as shown here. However, we clearly demonstrate here that the optimal pixel configuration is highly dependent on the electrical transport properties of the material. Depending on the field of primary interest, either energy resolution or counting rate efficiency in the photopeak, the geometry for each case has to be optimised. For that purpose, we have developed a calculation of the signal induced onto the pixel. Two distinct parts are used: after showing our approach for the weighting potential calculation, we present our results performed by a "pseudo-Monte Carlo" simulation. Results are supported by a few experimental comparisons. We argue about the optimum sizes with clarifying the problems caused by too small and too large pixel sizes. The study field is chosen to be vast, i.e. pixel size to detector thickness ratios ( W/ L) of 1/8-1, and detector thickness of 1.0-8.0 mm. In addition, several electrical transport properties are used. Since efficiency is often of primary interest, thick detectors could be very attractive, which are shown to be really feasible even on CdTe.

  19. Underwater Imaging Using a 1 × 16 CMUT Linear Array.

    Science.gov (United States)

    Zhang, Rui; Zhang, Wendong; He, Changde; Zhang, Yongmei; Song, Jinlong; Xue, Chenyang

    2016-01-01

    A 1 × 16 capacitive micro-machined ultrasonic transducer linear array was designed, fabricated, and tested for underwater imaging in the low frequency range. The linear array was fabricated using Si-SOI bonding techniques. Underwater transmission performance was tested in a water tank, and the array has a resonant frequency of 700 kHz, with pressure amplitude 182 dB (μPa·m/V) at 1 m. The -3 dB main beam width of the designed dense linear array is approximately 5 degrees. Synthetic aperture focusing technique was applied to improve the resolution of reconstructed images, with promising results. Thus, the proposed array was shown to be suitable for underwater imaging applications. PMID:26938536

  20. Multispectral linear array (MLA) focal plane mechanical and thermal design

    Science.gov (United States)

    Mitchell, A. S.; Kaminski, E. F.

    1982-01-01

    The mechanical and thermal design of an integrated focal plane subsystem of a Multispectral Linear Array (MLA) instrument is discussed in terms of focal-plane alignment, thermoelastic performance, and thermal requirements. The modular construction and thermal control of the focal plane array are discussed.

  1. Preliminary Results from Small-Pixel CdZnTe and CdTe Arrays

    Science.gov (United States)

    Ramsey, B. D.; Sharma, D. P.; Meisner, J.; Austin, R. A.

    1999-01-01

    We have evaluated 2 small-pixel (0.75 mm) Cadmium-Zinc-Telluride arrays, and one Cadmium-Telluride array, all fabricated for MSFC by Metorex (Finland) and Baltic Science Institute (Riga, Latvia). Each array was optimized for operating temperature and collection bias. It was then exposed to Cadmium-109 and Iron-55 laboratory isotopes, to measure the energy resolution for each pixel and was then scanned with a finely-collimated x-ray beam, of width 50 micron, to examine pixel to pixel and inter-pixel charge collections efficiency. Preliminary results from these array tests will be presented.

  2. Mercury Cadmium Telluride Photoconductive Long Wave Infrared Linear Array Detectors

    Directory of Open Access Journals (Sweden)

    Risal Singh

    2003-07-01

    Full Text Available Mercury cadmium telluride (Hg1-x, CdxTe (MCT photoconductive long wave infrared linear arrays are still in demand due to several advantages. The linear array technology is well established, easier, economical and is quite relevant to thermal imaging even today. The scan thermal imaging systems based on this technology offer wider field of view coverage and capacity for higher resolution in the scan direction relative to staring systems that use expensive and yet to mature focal plane array detector technology. A critical review on photoconductive n-Hg1-x CdxTe linear array detector technology for the long wave infrared range has been presented. The emphasis lies on detector design and processing technology. The critical issues of diffusion and drift effects, Hi-Lo and heterostructure blocking contacts, surface passivation, and other related aspects have been considered from the detector design angle. The device processing technology aspects are of vital importance

  3. Design of magnet arrays for permanent magnetic linear motor

    Institute of Scientific and Technical Information of China (English)

    Junhong MAO; Junhang LUO; Qiang JIANG; Youbai XIE

    2008-01-01

    An iron-less single side permanent magnetic linear motor structure is presented,and two-dimensional analytical formulae for its magnetic field are deduced to design the types of magnetic arrays,the thickness of permanent magnet,and the duty ratio of magnet arrays,etc.With certain design parameters,conventional arrays are used instead of a piecewise Halbach arrays,and the machining and assembling of the motor are greatly simplified.Calculation results coincide with that of ANSYS.The analytical formulae can be used in designing cored linear motors by modifying boundary conditions.A linear motor driven bench with a single degree of freedom is realized,where the travel reaches 27 mm,the mass of the moving parts is 1.4 kg,and the maximum acceleration iS 11.5 m/s2.

  4. Linear antenna array optimization using flower pollination algorithm.

    Science.gov (United States)

    Saxena, Prerna; Kothari, Ashwin

    2016-01-01

    Flower pollination algorithm (FPA) is a new nature-inspired evolutionary algorithm used to solve multi-objective optimization problems. The aim of this paper is to introduce FPA to the electromagnetics and antenna community for the optimization of linear antenna arrays. FPA is applied for the first time to linear array so as to obtain optimized antenna positions in order to achieve an array pattern with minimum side lobe level along with placement of deep nulls in desired directions. Various design examples are presented that illustrate the use of FPA for linear antenna array optimization, and subsequently the results are validated by benchmarking along with results obtained using other state-of-the-art, nature-inspired evolutionary algorithms such as particle swarm optimization, ant colony optimization and cat swarm optimization. The results suggest that in most cases, FPA outperforms the other evolutionary algorithms and at times it yields a similar performance. PMID:27066339

  5. Linear complexity for multidimensional arrays - a numerical invariant

    DEFF Research Database (Denmark)

    Gomez-Perez, Domingo; Høholdt, Tom; Moreno, Oscar;

    2015-01-01

    Linear complexity is a measure of how complex a one dimensional sequence can be. In this paper we extend the concept of linear complexity to multiple dimensions and present a definition that is invariant under well-orderings of the arrays. As a result we find that our new definition for the proce...

  6. Fiber Optic Spectrophotometer With Photodiode Linear Array

    Science.gov (United States)

    Velluet, M. T.; Blanc, F.; Vernet, P.

    1989-01-01

    Spectrophotometric measurements are used in a great number of industrial processes (chemical, pharmaceutical, farm-produce...) in nuclear environment and with optical precision components. Especially the evolution of a chemical process or of an optical coating could be followed by these measurements. Spectrophotometers, using optical fibers to transport the signal out of the instrument make possible the measurement "in-situ" and in real time. The advantage of using a diode array to detect the signal is an instantaneous measurement all over the spectral range without moving parts. It allows an excellent reproductibility of the measurements. The instrument is controlled by a micro computer. The spectrophotometer will be described and its technical performs presented. An extension using optical fibers on a "classical" spectrophotometer (a H.P. one) will be also described and its technical performs with such a system presented.

  7. Modelling and 3D optimisation of CdTe pixels detector array geometry - Extension to small pixels

    CERN Document Server

    Zumbiehl, A; Fougeres, P; Koebel, J M; Regal, R; Rit, C; Ayoub, M; Siffert, P

    2001-01-01

    CdTe and CdZnTe pixel detectors offer great interest for many applications, especially for medical and industrial imaging. Up to now, the material, generally, used and investigated for pixel arrays was CZT (Hamel et al., IEEE Trans. Nucl. Sci. 43 (3) (1996) 1422; Barrett et al., Phys. Rev. Lett. 75 (1) (1995) 156; Bennett et al., Nucl. Instr. and Meth. A 392 (1997) 260; Eskin et al., J. Appl. Phys. 85 (2) (1999) 647; Brunett et al., J. Appl. Phys. 86 (7) (1999) 3926; Luke, Nucl. Instr. and Meth. A 380 (1996) 232), but cadmium telluride can also be an appropriate choice, as shown here. However, we clearly demonstrate here that the optimal pixel configuration is highly dependent on the electrical transport properties of the material. Depending on the field of primary interest, either energy resolution or counting rate efficiency in the photopeak, the geometry for each case has to be optimised. For that purpose, we have developed a calculation of the signal induced onto the pixel. Two distinct parts are used: af...

  8. Double Exchange Genetic Algorithm for the Synthesis of Linear Array

    Directory of Open Access Journals (Sweden)

    Zhang Jian-Hua

    2012-01-01

    Full Text Available The development of Synthesis of Linear array put forward higher request for complex optimization solutions. This article improves the basic genetic algorithm according to the traditional genetic algorithm easily prematuring convergence and later evolution slow convergence shortcoming. And then, adopt double exchange operator in reproductive strategies and implement dynamic mutation rate in variation operations. Combined characteristics of guarantee to the population diversity based on fitness shared niche while iteration times exponential diminishing, this article creats niche double exchangegenetic algorithm, and applies in pattern synthesis of homogeneous linear array, and simulates multi-objective complex array problem. The result turns out much better in effectively preventing premature and improving the searching efficiency of genetic algorithm than original genetic algorithm and immune genetic algorithm, what will achieve the broad prospect in the antenna array comprehensive field.

  9. On the scattering cross section of passive linear arrays

    DEFF Research Database (Denmark)

    Solymar, L.

    1973-01-01

    A general formula is derived for the scattering cross section of a passiven-element linear array consisting of isotropic radiators. When all the reactances are tuned out and scattering in the mirror direction is investigated, it is found thatA_{sr}, the relative scattering cross section is equal...... to the square of the maximum gain the array can produce. As a consequence, for forward scattering in the limiting case of zero spacing between the elements,A_{sr} = n^{4}....

  10. Stochastic resonance in a parallel array of linear elements

    Institute of Scientific and Technical Information of China (English)

    Dong Xiao-Juan

    2009-01-01

    This paper studies stochastic resonance (SR) phenomenon in a parallel array of linear elements with noise. Employing the signal-to-noise ratio (SNR) theory, it obtains the output SNR, and investigates the effects on the output SNR of the system with signal-independent noise and signal-dependent noise respectively. Numerical results show: the curve of the output SNR is monotone with signal-independent noise; whereas SR appears with signal-dependent noise. Moreover, the output SNR enhances rapidly with the increase of N which is the number of elements in this parallel array linear system. This result may provide smart array of simple linear sensors which are capable of acting as noise-aided amplifiers.

  11. Study of Far—Field Directivity Pattern for Linear Arrays

    Science.gov (United States)

    Ana-Maria, Chiselev; Luminita, Moraru; Laura, Onose

    2011-10-01

    A model to calculate directivity pattern in far field is developed in this paper. Based on this model, the three-dimensional beam pattern is introduced and analyzed in order to investigate geometric parameters of linear arrays and their influences on the directivity pattern. Simulations in azimuthal plane are made to highlight the influence of transducers parameters, including number of elements and inter-element spacing. It is true that these parameters are important factors that influence the directivity pattern and the appearance of side-lobes for linear arrays.

  12. Vertically aligned TiO2/(CdS, CdTe, CdSTe) core/shell nanowire array for photoelectrochemical hydrogen generation

    Science.gov (United States)

    Ai, Guanjie; Mo, Rong; Xu, Hang; Chen, Qiong; Yang, Sui; Li, Hongxing; Zhong, Jianxin

    2015-04-01

    Type-II TiO2/CdS, TiO2/CdTe and TiO2/CdSTe heterostructured core/shell nanowire arrays (NWAs) on FTO substrates are synthesized via physical vapor deposition of CdS, CdTe and the alloyed CdSTe layer onto the hydrothermally pre-grown TiO2 NWAs. Their morphologies, microstructures, and optical properties are characterized in detail. As photoanodes for photoelectrochemical (PEC) hydrogen generation, the ternary CdSTe alloy sensitized TiO2 NWAs exhibits a photocurrent density of 4.52 mA cm-2 under 1 sun illumination at 0.4261 V vs. RHE, much higher than that of the TiO2/CdS (2.97 mA cm-2) and TiO2/CdTe (0.46 mA cm-2) electrodes. This highest photocurrent density level of the alloy TiO2/CdSTe electrode is attributed to the broadened light absorption range and enhanced charge separation efficiency according to the optical and electrochemical impedance spectra investigation. Our result implies a promising application of CdSTe sensitized TiO2 photoelectrode in PEC cell and other photoelectronic devices.

  13. Some linear-time algorithms for systolic arrays

    CERN Document Server

    Brent, Richard P; Kung, H T

    2010-01-01

    We survey some results on linear-time algorithms for systolic arrays. In particular, we show how the greatest common divisor (GCD) of two polynomials of degree n over a finite field can be computed in time O(n) on a linear systolic array of O(n) cells; similarly for the GCD of two n-bit binary numbers. We show how n * n Toeplitz systems of linear equations can be solved in time O(n) on a linear array of O(n) cells, each of which has constant memory size (independent of n). Finally, we outline how a two-dimensional square array of O(n)* O(n) cells can be used to solve (to working accuracy) the eigenvalue problem for a symmetric real n* n matrix in time O(nS(n)). Here S(n) is a slowly growing function of n; for practical purposes S(n) can be regarded as a constant. In addition to their theoretical interest, these results have potential applications in the areas of error-correcting codes, symbolic and algebraic computations, signal processing and image processing.

  14. Design and Analysis of MEMS Linear Phased Array

    Directory of Open Access Journals (Sweden)

    Guoxiang Fan

    2016-01-01

    Full Text Available A structure of micro-electro-mechanical system (MEMS linear phased array based on “multi-cell” element is designed to increase radiation sound pressure of transducer working in bending vibration mode at high frequency. In order to more accurately predict the resonant frequency of an element, the theoretical analysis of the dynamic equation of a fixed rectangular composite plate and finite element method simulation are adopted. The effects of the parameters both in the lateral and elevation direction on the three-dimensional beam directivity characteristics are comprehensively analyzed. The key parameters in the analysis include the “cell” number of element, “cell” size, “inter-cell” spacing and the number of elements, element width. The simulation results show that optimizing the linear array parameters both in the lateral and elevation direction can greatly improve the three-dimensional beam focusing for MEMS linear phased array, which is obviously different from the traditional linear array.

  15. Fiber Optic Coupling of CW Linear Laser Diode Array

    Institute of Scientific and Technical Information of China (English)

    WANG Xiaowei; XIAO Jianwei; MA Xiaoyu; WANG Zhongming; FANG Gaozhan

    2002-01-01

    Based on a set of microoptics the output radiation from a continuous wave (CW) linear laser diode array is coupled into a multi-mode optical fiber of 400 μm diameter.The CW linear laser diode array is a 1 cm laser diode bar with 19 stripes with 100 μm aperture spaced on 500 μm centers.The coupling system contains packaged laser diode bar,fast axis collimator,slow axis collimation array,beam transformation system and focusing system.The high brightness,high power density and single fiber output of a laser diode bar is achieved.The coupling efficiency is 65% and the power density is up to 1.03×104 W/cm2.

  16. Cuckoo search optimization for linear antenna arrays synthesis

    OpenAIRE

    Ahmed Haffane; Abdelhafid Hasni

    2013-01-01

    A recently developed metaheuristic optimization algorithm, the Cuckoo search algorithm, is used in this paper for the synthesis of symmetric uniformly spaced linear microstrip antennas array. Cuckoo search is based on the breeding strategy of Cuckoos augmented by a Levy flight behaviour found in the foraging habits of other species. This metaheuristic is tested on amplitude only pattern synthesis and amplitude and phase pattern synthesis. In both case, the ...

  17. Chaos in extended linear arrays of Josephson weak links

    Energy Technology Data Exchange (ETDEWEB)

    Nerenberg, M.A.H.; Spiteri, R.J. (Department of Applied Mathematics, University of Western Ontario, London, Ontario, Canada N6A 5B9 (CA)); Blackburn, J.A. (Department of Physics and Computing, Wilfred Laurier University, Waterloo, Ontario, Canada N2L 3C5 (CA))

    1989-12-01

    Extended linear arrays of interacting Josephson weak links are studied by numerical simulation using the resistively shunted junction model. The minimum coupling strength for chaotic behavior is determined as a function of the number of links. This strength is found to diminish steadily with increasing number, despite the inclusion of only nearest-neighbor interaction. The implications for Josephson technology are briefly discussed. Mathematically, the results are confirmation of the Ruelle-Takens scenario for chaos.

  18. Design of Linear Systolic Arrays for Matrix Multiplication

    OpenAIRE

    MILOVANOVIC, E. I.; STOJCEV, M. K.; MILOVANOVIC, I. Z.; NIKOLIC, T. R.

    2014-01-01

    This paper presents architecture for matrix multiplication optimized to be integrated as an accelerator unit to a host computer. Two linear systolic arrays with unidirectional data flow (ULSA), used as hardware accelerators, where synthesized in this paper. The solution proposed here is designed to accelerate both the computation and communication by employing hardware address generator units (AGUs). The proposed design has been implemented on Xilinx Spartan-2E and Virtex4 FPG...

  19. One-dimensional CdTe nanorod arrays preparation by the magnetron sputtering method%磁控溅射法制备一维CdTe纳米棒阵列研究∗

    Institute of Scientific and Technical Information of China (English)

    罗炳威; 邓元; 高歌

    2015-01-01

    利用磁控溅射法,研究了不同基底温度和工作气压对 CdTe 薄膜微纳米结构的影响. XRD 和SEM表征结果表明,基底温度直接决定着 CdTe 粒子的生长和表面扩散能力,工作气压会直接影响入射在衬底表面的粒子能量,溅射功率决定提供 CdTe 粒子的量.通过生长条件的进一步探索和优化,最终在溅射功率为84 W、工作气压为0.4 Pa和石英基底温度为200~450℃时成功获得直径约150 nm,形貌均一的一维CdTe纳米棒阵列.%The different microstructures of CdTe thin films are prepared by magnetron sputtering method through changing the substrate temperature,working pressure and sputtering power.The XRD and SEM re-sults show that the abilities of growth and surface diffusion of CdTe particles are directly determined by the substrate temperature.Meanwhile,the working pressure can affect the energy of incident CdTe particles and the quantities of the CdTe particles are determined by the sputtering power.Finally,the uniform one-dimen-sional CdTe nanorod arrays with diameter about 150 nm are achieved at sputtering power of 84 W,working pressure of 0.4 Pa and the temperature of quartz substrate within 200-450 ℃.

  20. Spatial Signature Estimation with an Uncalibrated Uniform Linear Array

    Directory of Open Access Journals (Sweden)

    Xiang Cao

    2015-06-01

    Full Text Available In this paper, the problem of spatial signature estimation using a uniform linear array (ULA with unknown sensor gain and phase errors is considered. As is well known, the directions-of-arrival (DOAs can only be determined within an unknown rotational angle in this array model. However, the phase ambiguity has no impact on the identification of the spatial signature. Two auto-calibration methods are presented for spatial signature estimation. In our methods, the rotational DOAs and model error parameters are firstly obtained, and the spatial signature is subsequently calculated. The first method extracts two subarrays from the ULA to construct an estimator, and the elements of the array can be used several times in one subarray. The other fully exploits multiple invariances in the interior of the sensor array, and a multidimensional nonlinear problem is formulated. A Gauss–Newton iterative algorithm is applied for solving it. The first method can provide excellent initial inputs for the second one. The effectiveness of the proposed algorithms is demonstrated by several simulation results.

  1. Cuckoo search optimization for linear antenna arrays synthesis

    Directory of Open Access Journals (Sweden)

    Ahmed Haffane

    2013-01-01

    Full Text Available A recently developed metaheuristic optimization algorithm, the Cuckoo search algorithm, is used in this paper for the synthesis of symmetric uniformly spaced linear microstrip antennas array. Cuckoo search is based on the breeding strategy of Cuckoos augmented by a Levy flight behaviour found in the foraging habits of other species. This metaheuristic is tested on amplitude only pattern synthesis and amplitude and phase pattern synthesis. In both case, the objective, is to determinate the optimal excitations element that produce a synthesized radiation pattern within given bounds specified by a pattern mask.

  2. Efficient linear systolic array for the knapsack problem

    OpenAIRE

    Andonov, Rumen; Quinton, Patrice

    1992-01-01

    A processor-efficient systolic algorithm for the dynamic programming approach to the knapsack problem is presented in this paper. The algorithm is implemented on a linear systolic array where the number of cells q, the cell memory storage a and the input/output requirements are design parameters. These are independent of the problem size given by the number of the objects m and the knapsack capacity c. The time complexity of the algorithm is Q(mc/q+m) and both the time speedup and the process...

  3. Spatial frequency multiplier with active linearly tapered slot antenna array

    Science.gov (United States)

    Simons, Rainee N.; Lee, Richard Q.

    1994-01-01

    A frequency multiplier with active linearly tapered slot antennas (LTSA's) has been demonstrated at the second harmonic frequency. In each antenna element, a GaAs monolithic microwave integrated circuit (MMIC) distributed amplifier is integrated with two LTSA's. The multiplier has a very wide bandwidth and large dynamic range. The fundamental-to-second harmonic conversion efficiency is 8.1 percent. The spatially combined second harmonic signal is 50 dB above the noise level. The design is suitable for constructing a large array using monolithic integration techniques.

  4. Space Power Amplification with Active Linearly Tapered Slot Antenna Array

    Science.gov (United States)

    Simons, Rainee N.; Lee, Richard Q.

    1993-01-01

    A space power amplifier composed of active linearly tapered slot antennas (LTSA's) has been demonstrated and shown to have a gain of 30 dB at 20 GHz. In each of the antenna elements, a GaAs monolithic microwave integrated circuit (MMIC) three-stage power amplifier is integrated with two LTSA's. The LTSA and the MMIC power amplifier has a gain of 11 dB and power added efficiency of 14 percent respectively. The design is suitable for constructing a large array using monolithic integration techniques.

  5. A 128 pixel linear array for radiotherapy quality assurance

    Energy Technology Data Exchange (ETDEWEB)

    Franco, L. [Departmento de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, campus sur s/n, 15782 Santiago de Compostela (Spain); Gomez, F. [Departmento de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, campus sur s/n, 15782 Santiago de Compostela (Spain)]. E-mail: faustgr@usc.es; Iglesias, A. [Departmento de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, campus sur s/n, 15782 Santiago de Compostela (Spain); Lobato, R. [Hospital Clinico Universitario de Santiago, 15706 Santiago (Spain); Marin, J. [CIEMAT, Laboratorio de Electronica y Automatica, 28040 Madrid Spain (Spain); Mosquera, J. [Hospital Clinico Universitario de Santiago, 15706 Santiago (Spain); Pardo, J. [Departmento de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, campus sur s/n, 15782 Santiago de Compostela (Spain)]. E-mail: juanpm@usc.es; Pazos, A. [Departmento de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, campus sur s/n, 15782 Santiago de Compostela (Spain); Pena, J. [Departmento de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, campus sur s/n, 15782 Santiago de Compostela (Spain); Pombar, M. [Hospital Clinico Universitario de Santiago, 15706 Santiago (Spain); Rodriguez, A. [Departmento de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, campus sur s/n, 15782 Santiago de Compostela (Spain); Saavedra, D. [Universidade da Coruna, Dpto. de Enxeneria Industrial II, 15403 Ferrol Spain (Spain); Sendon, J. [Hospital Clinico Universitario de Santiago, 15706 Santiago (Spain); Yanez, A. [Universidade da Coruna, Dpto. de Enxeneria Industrial II, 15403 Ferrol Spain (Spain)

    2004-12-11

    New radiotherapy techniques require detectors able to verify and monitor the clinical beam with high spatial resolution and fast response. Room temperature organic liquid ionization detectors are becoming an alternative to standard air ionization chambers, due to their tissue equivalent behavior, their sensibility and small directional dependence. A liquid isooctane filled ionization linear array for radiotherapy quality assurance has been designed, built and tested. The detector consists of 128 pixels, each of them with an area of 1.7mmx1.7mm and a gap of 0.5mm. The small pixel size makes the detector ideal for high gradient beam profiles like those present in Intensity Modulated Radiation Therapy. The gap and the polarization voltage have been chosen in order to guarantee a linear relationship between the dose rate and the readout signal at high dose rates. As readout electronics we use the X-ray Data Acquisition System with the Xchip developed by the CCLRC.In the first device tests we have confirmed linearity up to a 6.7Gy/min dose rate with a deviation less than 1%. A profile with a signal-to-noise ratio around 500 can be obtained for a 4Gy/min dose rate with a 10 ms integration time.

  6. The compact linear antenna array system of the short-wave band consisting of "butterfly" radiators

    OpenAIRE

    Kudzin, Viktor P.; Lozovsky, V. N.; N.I. Shlyk

    2014-01-01

    The broadband linear antenna array system of vertical polarization for a short-wave band operation consisting of "butterfly" radiators is offered. Antenna system consists of two arrays located before each other. Array 1 operates in frequency band 4–8 MHz, array 2 – in band 8–16 MHz. Wire reflector serves for array 1 and the last serves as reflector for array 2. Advantage of antenna system is "planeness" of a design and absence of high-frequency insulators.

  7. Human Respiration Localization Method Using UWB Linear Antenna Array

    Directory of Open Access Journals (Sweden)

    Yuan Liu

    2015-01-01

    Full Text Available Human respiration is the basic vital sign in remote monitoring. There has been remarkable progress in this area, but some challenges still remain to obtain the angle-of-arrival (AOA and distinguish the individual signals. This paper presents a 2D noncontact human respiration localization method using Ultra-Wideband (UWB 1D linear antenna array. The imaging reconstruction based on beamforming is used to estimate the AOA of the human chest. The distance-slow time 2D matrix at the estimated AOA is processed to obtain the distance and respiration frequency of the vital sign. The proposed method can be used to isolate signals from individual targets when more than one human object is located in the surveillance space. The feasibility of the proposed method is demonstrated via the simulation and experiment results.

  8. Design of Linear Systolic Arrays for Matrix Multiplication

    Directory of Open Access Journals (Sweden)

    MILOVANOVIC, E. I.

    2014-02-01

    Full Text Available This paper presents architecture for matrix multiplication optimized to be integrated as an accelerator unit to a host computer. Two linear systolic arrays with unidirectional data flow (ULSA, used as hardware accelerators, where synthesized in this paper. The solution proposed here is designed to accelerate both the computation and communication by employing hardware address generator units (AGUs. The proposed design has been implemented on Xilinx Spartan-2E and Virtex4 FPGAs. In order to evaluate performance of the proposed solution, we have introduced quantitative and qualitative performance criteria. For the ULSA with n processing elements (PEs, the speed-up is O(n/2. Average gain factor of hardware AGUs is about 2.7, with hardware overhead of 0.6% for 32-bit PEs.

  9. Thermal crosstalk simulation and measurement of linear terahertz detector arrays

    Science.gov (United States)

    Li, Weizhi; Huang, Zehua; Wang, Jun; Li, Mingyu; Gou, Jun; Jiang, Yadong

    2015-11-01

    Thermal simulation of differently structured linear terahertz detector arrays (TDAs) based on lithium tantalate was performed by finite element analysis (FEA). Simulation results revealed that a relatively simple TDA structure can have good thermal insulation, i.e., low thermal crosstalk effect (TCE), between adjacent pixels, which was thus selected for the real fabrication of TDA sample. Current responsivity (Ri) of the sample for a 2.52 THz source was measured to be 6.66 × 10-6 A/W and non-uniformity (NU) of Ri was 4.1%, showing good performance of the sample. TCE test result demonstrated that small TCE existed in the sample, which was in good agreement with the simulation results.

  10. Specificity of the Linear Array HPV Genotyping Test for detecting human papillomavirus genotype 52 (HPV-52):

    OpenAIRE

    Kocjan, Boštjan; Poljak, Mario; Oštrbenk, Anja

    2014-01-01

    Introduction: HPV-52 is one of the most frequent human papillomavirus (HPV) genotypes causing significant cervical pathology. The most widely used HPV genotyping assay, the Roche Linear Array HPV Genotyping Test (Linear Array), is unable to identify HPV- 52 status in samples containing HPV-33, HPV-35, and/or HPV-58. Methods: Linear Array HPV-52 analytical specificity was established by testing 100 specimens reactive with the Linear Array HPV- 33/35/52/58 cross-reactive probe, but not with the...

  11. Ultrasonic linear array validation via concrete test blocks

    Energy Technology Data Exchange (ETDEWEB)

    Hoegh, Kyle, E-mail: hoeg0021@umn.edu; Khazanovich, Lev, E-mail: hoeg0021@umn.edu [University of Minnesota Department of Civil, Environmental, and Geo- Engineering 500 Pillsbury Drive S.E. Minneapolis, MN 55455-0116 (United States); Ferraro, Chris [Lynch and Ferraro Engineering, Inc., 2570 Greenhill Way, Oviedo, FL 32765 (United States); Clayton, Dwight [Oak Ridge National Laboratory (United States)

    2015-03-31

    Oak Ridge National Laboratory (ORNL) comparatively evaluated the ability of a number of NDE techniques to generate an image of the volume of 6.5′ X 5.0′ X 10″ concrete specimens fabricated at the Florida Department of Transportation (FDOT) NDE Validation Facility in Gainesville, Florida. These test blocks were fabricated to test the ability of various NDE methods to characterize various placements and sizes of rebar as well as simulated cracking and non-consolidation flaws. The first version of the ultrasonic linear array device, MIRA [version 1], was one of 7 different NDE equipment used to characterize the specimens. This paper deals with the ability of this equipment to determine subsurface characterizations such as reinforcing steel relative size, concrete thickness, irregularities, and inclusions using Kirchhoff-based migration techniques. The ability of individual synthetic aperture focusing technique (SAFT) B-scan cross sections resulting from self-contained scans are compared with various processing, analysis, and interpretation methods using the various features fabricated in the specimens for validation. The performance is detailed, especially with respect to the limitations and implications for evaluation of a thicker, more heavily reinforced concrete structures.

  12. Polarisation measurements with a CdTe pixel array detector for Laue hard X-ray focusing telescopes

    CERN Document Server

    Caroli, E; Pisa, A; Stephen, J B; Frontera, F; Castanheira, M T D; Sordo, S; Caroli, Ezio; Silva, Rui M. Curado da; Pisa, Alessandro; Stephen, John B.; Frontera, Filippo; Castanheira, Matilde T. D.; Sordo, Stefano del

    2006-01-01

    Polarimetry is an area of high energy astrophysics which is still relatively unexplored, even though it is recognized that this type of measurement could drastically increase our knowledge of the physics and geometry of high energy sources. For this reason, in the context of the design of a Gamma-Ray Imager based on new hard-X and soft gamma ray focusing optics for the next ESA Cosmic Vision call for proposals (Cosmic Vision 2015-2025), it is important that this capability should be implemented in the principal on-board instrumentation. For the particular case of wide band-pass Laue optics we propose a focal plane based on a thick pixelated CdTe detector operating with high efficiency between 60-600 keV. The high segmentation of this type of detector (1-2 mm pixel size) and the good energy resolution (a few keV FWHM at 500 keV) will allow high sensitivity polarisation measurements (a few % for a 10 mCrab source in 106s) to be performed. We have evaluated the modulation Q factors and minimum detectable polaris...

  13. A generation method for a kind of linear independentLatin arrays

    Institute of Scientific and Technical Information of China (English)

    陶仁骥; 陈世华

    1995-01-01

    The concept of correlation of Latin array is introduced and the generation problem of Latin arrays with independence degree ≥1 is discussed. A method is given to generate such Latin arrays, that is, shifting invertible Boolean vector functions with independence degree ≥1. Finally, a generation method of linearly independent invertible Boolean vector functions is given.

  14. Breadboard linear array scan imager using LSI solid-state technology

    Science.gov (United States)

    Tracy, R. A.; Brennan, J. A.; Frankel, D. G.; Noll, R. E.

    1976-01-01

    The performance of large scale integration photodiode arrays in a linear array scan (pushbroom) breadboard was evaluated for application to multispectral remote sensing of the earth's resources. The technical approach, implementation, and test results of the program are described. Several self scanned linear array visible photodetector focal plane arrays were fabricated and evaluated in an optical bench configuration. A 1728-detector array operating in four bands (0.5 - 1.1 micrometer) was evaluated for noise, spectral response, dynamic range, crosstalk, MTF, noise equivalent irradiance, linearity, and image quality. Other results include image artifact data, temporal characteristics, radiometric accuracy, calibration experience, chip alignment, and array fabrication experience. Special studies and experimentation were included in long array fabrication and real-time image processing for low-cost ground stations, including the use of computer image processing. High quality images were produced and all objectives of the program were attained.

  15. Characterization of CdTe Sensors with Schottky Contacts Coupled to Charge-Integrating Pixel Array Detectors for X-Ray Science

    CERN Document Server

    Becker, Julian; Shanks, Katherine S; Philipp, Hugh T; Weiss, Joel T; Purohit, Prafull; Chamberlain, Darol; Ruff, Jacob P C; Gruner, Sol M

    2016-01-01

    Pixel Array Detectors (PADs) consist of an x-ray sensor layer bonded pixel-by-pixel to an underlying readout chip. This approach allows both the sensor and the custom pixel electronics to be tailored independently to best match the x-ray imaging requirements. Here we present characterizations of CdTe sensors hybridized with two different charge-integrating readout chips, the Keck PAD and the Mixed-Mode PAD (MM-PAD), both developed previously in our laboratory. The charge-integrating architecture of each of these PADs extends the instantaneous counting rate by many orders of magnitude beyond that obtainable with photon counting architectures. The Keck PAD chip consists of rapid, 8-frame, in-pixel storage elements with framing periods $<$150 ns. The second detector, the MM-PAD, has an extended dynamic range by utilizing an in-pixel overflow counter coupled with charge removal circuitry activated at each overflow. This allows the recording of signals from the single-photon level to tens of millions of x-rays/...

  16. Active cancellation of probing in linear dipole phased array

    CERN Document Server

    Singh, Hema; Jha, Rakesh Mohan

    2015-01-01

    In this book, a modified improved LMS algorithm is employed for weight adaptation of dipole array for the generation of beam pattern in multiple signal environments. In phased arrays, the generation of adapted pattern according to the signal scenario requires an efficient adaptive algorithm. The antenna array is expected to maintain sufficient gain towards each of the desired source while at the same time suppress the probing sources. This cancels the signal transmission towards each of the hostile probing sources leading to active cancellation. In the book, the performance of dipole phased array is demonstrated in terms of fast convergence, output noise power and output signal-to-interference-and noise ratio. The mutual coupling effect and role of edge elements are taken into account. It is established that dipole array along with an efficient algorithm is able to maintain multilobe beamforming with accurate and deep nulls towards each probing source. This work has application to the active radar cross secti...

  17. Influence of Cu2+ dopant in optical property of CdTe quantum dots and photoelectrochemical performance of CdTe:Cu2+/TiO2 nanotube arrays

    Science.gov (United States)

    Chen, Qian; Geng, Yue; Zhou, Chunyan; Song, Jiahui; Zhou, Liya

    2016-05-01

    A novel one-step synthesis process was used to prepare CdTe:Cu2+/TiO2 nanotube arrays (TNTAs). X-ray powder diffraction and high-resolution transmission electron microscopy analyses confirmed that the obtained CdTe:Cu2+ quantum dots (QDs) possess cubic structures, which are approximately spherical, and a small particle size (2.95 nm). The photoluminescent and UV-visible absorption spectra of CdTe:Cu2+ QDs also display an obvious redshift, which was attributed to the replacement of Cd2+ with Cu2+. Compared with that of the TNTAs and CdTe/TNTAs, the photoelectric conversion efficiency of CdTe:5% Cu2+/TNTAs increased by 785.7% and 103.3%, respectively. The incident photo-to-current conversion efficiency of CdTe:5% Cu2+/TNTAs was 50.6%, which indicated the potential use of QDs in photochemical solar cells.

  18. Is cell migration or proliferation dominant in the formation of linear arrays of oligodendrocytes?

    Science.gov (United States)

    Walsh, Darragh M; Röth, Philipp T; Holmes, William R; Landman, Kerry A; Merson, Tobias D; Hughes, Barry D

    2016-10-01

    Oligodendrocytes are the myelin-producing cells of the central nervous system that are responsible for electrically insulating axons to speed the propagation of electrical impulses. A striking feature of oligodendrocyte development within white matter is that the cell bodies of many oligodendrocyte progenitor cells become organised into discrete linear arrays of three or more cells before they differentiate into myelin-producing oligodendrocytes. These linear arrays align parallel to the direction of the axons within white matter tracts and are believed to play an important role in the co-ordination of myelination. Guided by experimental data on the abundance and composition of linear arrays in the corpus callosum of the postnatal mouse brain, we construct discrete and continuous models of linear array generation to specifically investigate the relative influence of cell migration, proliferation, differentiation and death of oligodendroglia upon the genesis of linear arrays during early postnatal development. We demonstrate that only models that incorporate significant cell migration can replicate all of the experimental observations on number of arrays, number of cells in arrays and total cell count of oligodendroglia within a given area of the corpus callosum. These models are also necessary to accurately reflect experimental data on the abundance of linear arrays composed of oligodendrocytes that derive from progenitors of different clonal origins. PMID:27343034

  19. Design of Non-Uniform Linear Antenna Arrays Using DolphChebyshev and Binomial Methods

    Directory of Open Access Journals (Sweden)

    Jean-François D. Essiben

    2015-08-01

    Full Text Available This paper explores the analytical methods of synthesizing linear antenna arrays. The synthesis employed is based on non-uniform methods. In particular, the Dolph-Chebyshev and binomial methods are used, so as to improve the directivity of the array and to reduce the level of the secondary lobes by adjusting the geometrical and electric parameters of the array. The radiation patterns, the directivity, and the array factors of the uniform and the non-uniform methods are presented. It is shown that the Chebyshev arrays have better directivity than binomial arrays for the same number of elements and separation distance, while binomial arrays have very low side lobes compared with Chebyshev and uniform excitation arrays. Finally, numerical results of both methods are analyzed and compared.

  20. Research on Motion Compensation for Airborne Forward Looking Synthetic Aperture Radar with Linear Array Antennas

    Directory of Open Access Journals (Sweden)

    Zhang Ying-jie

    2013-06-01

    Full Text Available Combined with Frequency-Modulated Continuous-Wave (FMCW technology, airborne forward-looking Synthetic Aperture Radar (SAR with linear array antennas can obtain the image in front of the aircraft and also have the advantages of FMCW radar such as small size and lightweight. Moreover, it is suitable to be installed on platform like helicopter and small unmanned aerial vehicle. Motion compensation for forward-looking SAR with linear array antennas is one of the key problems to obtain the image in front of the aircraft in practice. This paper analyses the influence of motion error in aircraft on echo model based on the geometry of forward looking SAR with linear array antennas, and proposes a motion compensation scheme. Moreover, the compensation scheme is applicable to an improved frequency scaling algorithm (FSA for FMCW forward looking SAR with linear array antennas. Finally, the compensation scheme is verified with the simulation.

  1. Least-Square Collaborative Beamforming Linear Array for Steering Capability in Green Wireless Sensor Networks

    Institute of Scientific and Technical Information of China (English)

    NikNoordini NikAbdMalik; Mazlina Esa; Nurul Mu’azzah Abdul Latiff

    2016-01-01

    Abstract-This paper presents a collaborative beamforming (CB) technique to organize the sensor node’s location in a linear array for green wireless sensor network (WSN) applications. In this method, only selected clusters and active CB nodes are needed each time to perform CB in WSNs. The proposed least-square linear array (LSLA) manages to select nodes to perform as a linear antenna array (LAA), which is similar to and as outstanding as the conventional uniform linear array (ULA). The LSLA technique is also able to solve positioning error problems that exist in the random nodes deployment. The beampattern fluctuations have been analyzed due to the random positions of sensor nodes. Performances in terms of normalized power gains are given. It is demonstrated by a simulation that the proposed technique gives similar performances to the conventional ULA and at the same time exhibits lower complexity.

  2. Optimum linear array for aperture synthesis imaging based on redundant spacing calibration

    Science.gov (United States)

    Liu, Li; He, Yuntao; Zhang, Jianguo; Jia, Huayu; Ma, Jun

    2014-05-01

    Aperture synthesis imaging has been proved to be attractive in surveillance and detection applications. Such an imaging process is inevitably subject to aberrations introduced by instrument defects and/or turbulent media. Redundant spacing calibration (RSC) technique allows continuous calibration of these errors at any electromagnetic wavelength. However, it is based on specially designed array, in which just enough redundancy is included to permit the successful implementation of RSC. A new design criterion for linear RSC array is described, which introduces coverage efficiency and redundancy efficiency factors, aiming to find the perfect configurations, which have as complete uv-plane coverage as possible while containing required redundancy. Optimum linear arrays for N (number of subapertures) up to 10 are listed based on simulated annealing algorithm. The comparisons with existing linear RSC arrays with equivalent subaperture number are implemented. Results show that the optimized arrays have better performance of both optical transfer function, point spread function, and object reconstruction with reasonable value of the matrix condition number. After that, linear arrays are used to construct two-dimensional (2-D) pseudo-Y-shaped RSC arrays, which give a way to design 2-D RSC arrays without exhaustive searches.

  3. Linear and nonlinear excitations in two stacks of parallel arrays of long Josephson junctions

    DEFF Research Database (Denmark)

    Carapella, G.; Constabile, Giovanni; Latempa, R.;

    2000-01-01

    We investigate a structure consisting of two parallel arrays of long Josephson junctions sharing a common electrode that allows inductive coupling between the arrays. A model for this structure is derived starting from the description of its continuous limit. The excitation of linear cavity modes...

  4. Optimized Hyper Beamforming of Linear Antenna Arrays Using Collective Animal Behaviour

    OpenAIRE

    Gopi Ram; Durbadal Mandal; Rajib Kar; Sakti Prasad Ghoshal

    2013-01-01

    A novel optimization technique which is developed on mimicking the collective animal behaviour (CAB) is applied for the optimal design of hyper beamforming of linear antenna arrays. Hyper beamforming is based on sum and difference beam patterns of the array, each raised to the power of a hyperbeam exponent parameter. The optimized hyperbeam is achieved by optimization of current excitation weights and uniform interelement spacing. As compared to conventional hyper beamforming of linear antenn...

  5. RCS estimation of linear and planar dipole phased arrays approximate model

    CERN Document Server

    Singh, Hema; Jha, Rakesh Mohan

    2016-01-01

    In this book, the RCS of a parallel-fed linear and planar dipole array is derived using an approximate method. The signal propagation within the phased array system determines the radar cross section (RCS) of phased array. The reflection and transmission coefficients for a signal at different levels of the phased-in scattering array system depend on the impedance mismatch and the design parameters. Moreover the mutual coupling effect in between the antenna elements is an important factor. A phased array system comprises of radiating elements followed by phase shifters, couplers, and terminating load impedance. These components lead to respective impedances towards the incoming signal that travels through them before reaching receive port of the array system. In this book, the RCS is approximated in terms of array factor, neglecting the phase terms. The mutual coupling effect is taken into account. The dependence of the RCS pattern on the design parameters is analyzed. The approximate model is established as a...

  6. Pattern Synthesis of Dual-band Shared Aperture Interleaved Linear Antenna Arrays

    Directory of Open Access Journals (Sweden)

    H. Guo

    2014-09-01

    Full Text Available This paper presents an approach to improve the efficiency of an array aperture by interleaving two different arrays in the same aperture area. Two sub-arrays working at different frequencies are interleaved in the same linear aperture area. The available aperture area is efficiently used. The element positions of antenna array are optimized by using Invasive Weed Optimization (IWO to reduce the peak side lobe level (PSLL of the radiation pattern. To overcome the shortness of traditional methods which can only fulfill the design of shared aperture antenna array working at the same frequency, this method can achieve the design of dual-band antenna array with wide working frequency range. Simulation results show that the proposed method is feasible and efficient in the synthesis of dual-band shared aperture antenna array.

  7. Focusing Modeling of OPFC Linear Array Transducer by Using Distributed Point Source Method

    Directory of Open Access Journals (Sweden)

    Ziping Wang

    2014-01-01

    Full Text Available The improvement of ultrasonic phased array detection technology is a major concern of engineering community. Orthotropic piezoelectric fiber composite (OPFC can be constructed to multielement linear array which may be applied conveniently to actuators and sensors. The phased array transducers can generate special directional strong actuator power and high sensitivity for its orthotropic performance. Focusing beam of the linear phased array transducer is obtained simply only by adjusting a parabolic time delay. In this work, the distributed point source method (DPSM is used to model the ultrasonic field. DPSM is a newly developed mesh-free numerical technique that has been developed for solving a variety of engineering problems. This work gives the basic theory of this method and solves the problems from the application of new OPFC phased array transducer. Compared with traditional transducer, the interaction effect of two OPFC linear phased array transducers is also modeled in the same medium, which shows that the pressure beam produced by the new transducer is narrower or more collimated than that produced by the conventional transducer at different angles. DPSM can be used to analyze and optimally design the OPFC linear phased array transducer.

  8. Micro-Machined High-Frequency (80 MHz) PZT Thick Film Linear Arrays

    Science.gov (United States)

    Zhou, Qifa; Wu, Dawei; Liu, Changgeng; Zhu, Benpeng; Djuth, Frank; Shung, K. Kirk

    2010-01-01

    This paper presents the development of a micro-machined high-frequency linear array using PZT piezoelectric thick films. The linear array has 32 elements with an element width of 24 μm and an element length of 4 mm. Array elements were fabricated by deep reactive ion etching of PZT thick films, which were prepared from spin-coating of PZT solgel composite. Detailed fabrication processes, especially PZT thick film etching conditions and a novel transferring-and-etching method, are presented and discussed. Array designs were evaluated by simulation. Experimental measurements show that the array had a center frequency of 80 MHz and a fractional bandwidth (−6 dB) of 60%. An insertion loss of −41 dB and adjacent element crosstalk of −21 dB were found at the center frequency. PMID:20889407

  9. A 400 KHz line rate 2048-pixel stitched SWIR linear array

    Science.gov (United States)

    Anchlia, Ankur; Vinella, Rosa M.; Gielen, Daphne; Wouters, Kristof; Vervenne, Vincent; Hooylaerts, Peter; Deroo, Pieter; Ruythooren, Wouter; De Gaspari, Danny; Das, Jo; Merken, Patrick

    2016-05-01

    Xenics has developed a family of stitched SWIR long linear arrays that operate up to 400 KHz of line rate. These arrays serve medical and industrial applications that require high line rates as well as space applications that require long linear arrays. The arrays are based on a modular ROIC design concept: modules of 512 pixels are stitched during fabrication to achieve 512, 1024 and 2048 pixel arrays. Each 512-pixel module has its own on-chip digital sequencer, analog readout chain and 4 output buffers. This modular concept enables a long array to run at a high line rates irrespective of the array length, which limits the line rate in a traditional linear array. The ROIC is flip-chipped with InGaAs detector arrays. The FPA has a pixel pitch of 12.5μm and has two pixel flavors: square (12.5μm) and rectangular (250μm). The frontend circuit is based on Capacitive Trans-impedance Amplifier (CTIA) to attain stable detector bias, and good linearity and signal integrity, especially at high speeds. The CTIA has an input auto-zero mechanism that allows to have low detector bias (<20mV). An on-chip Correlated Double Sample (CDS) facilitates removal of CTIA KTC and 1/f noise, and other offsets, achieving low noise performance. There are five gain modes in the FPA giving the full well range from 85Ke- to 40Me-. The measured input referred noise is 35e-rms in the highest gain mode. The FPA operates in Integrate While Read mode and, at a master clock rate of 60MHz and a minimum integration time of 1.4μs, achieves the highest line rate of 400 KHz. In this paper, design details and measurements results are presented in order to demonstrate the array performance.

  10. Non-linear, adaptive array processing for acoustic interference suppression.

    Science.gov (United States)

    Hoppe, Elizabeth; Roan, Michael

    2009-06-01

    A method is introduced where blind source separation of acoustical sources is combined with spatial processing to remove non-Gaussian, broadband interferers from space-time displays such as bearing track recorder displays. This differs from most standard techniques such as generalized sidelobe cancellers in that the separation of signals is not done spatially. The algorithm performance is compared to adaptive beamforming techniques such as minimum variance distortionless response beamforming. Simulations and experiments using two acoustic sources were used to verify the performance of the algorithm. Simulations were also used to determine the effectiveness of the algorithm under various signal to interference, signal to noise, and array geometry conditions. A voice activity detection algorithm was used to benchmark the performance of the source isolation.

  11. Validity and reliability of rectus femoris ultrasound measurements: Comparison of curved-array and linear-array transducers

    Directory of Open Access Journals (Sweden)

    Kendra Hammond, MD

    2014-11-01

    Full Text Available Muscle-mass loss augers increased morbidity and mortality in critically ill patients. Muscle-mass loss can be assessed by wide linear-array ultrasound transducers connected to cumbersome, expensive console units. Whether cheaper, hand-carried units equipped with curved-array transducers can be used as alternatives is unknown. Accordingly, our primary aim was to investigate in 15 nondisabled subjects the validity of measurements of rectus femoris cross-sectional area by using a curved-array transducer against a linear-array transducer—the reference-standard technique. In these subjects, we also determined the reliability of measurements obtained by a novice operator versus measurements obtained by an experienced operator. Lastly, the relationship between quadriceps strength and rectus area recorded by two experienced operators with a curved-array transducer was assessed in 17 patients with chronic obstructive pulmonary disease (COPD. In nondisabled subjects, the rectus cross-sectional area measured with the curved-array transducer by the novice and experienced operators was valid (intraclass correlation coefficient [ICC]: 0.98, typical percentage error [%TE]: 3.7% and reliable (ICC: 0.79, %TE: 9.7%. In the subjects with COPD, both reliability (ICC: 0.99 and repeatability (%TE: 7.6% and 9.8% were high. Rectus area was related to quadriceps strength in COPD for both experienced operators (coefficient of determination: 0.67 and 0.70. In conclusion, measurements of rectus femoris cross-sectional area recorded with a curved-array transducer connected to a hand-carried unit are valid, reliable, and reproducible, leading us to contend that this technique is suitable for cross-sectional and longitudinal studies.

  12. Characterization of InGaAs linear array for applications to remote sensing

    Science.gov (United States)

    Garcia, Christopher S.; Refaat, Tamer F.; Farnsworth, Glenn R.; Abedin, M. N.; Elsayed-Ali, Hani E.

    2005-05-01

    An Indium Gallium Arsenide linear photodiode array in the 1.1-2.5 μm spectral range was characterized. The array has 1024X1 pixels with a 25 μm pitch and was manufactured by Sensors Unlimited, Inc. Characterization and analysis of the electrical and optical properties of a camera system were carried out at room temperature to obtain detector performance parameters. The signal and noise were measured while the array was uniformly illuminated at varying exposure levels. A photon transfer curve was generated by plotting noise as a function of average signal to obtain the camera gain constant. The spectral responsivity was also measured, and the quantum efficiency, read noise and full-well capacity were determined. This paper describes the characterization procedure, analyzes the experimental results, and discusses the applications of the InGaAs linear array to future earth and planetary remote sensing mission.

  13. Linear CCD attitude measurement system based on the identification of the auxiliary array CCD

    Science.gov (United States)

    Hu, Yinghui; Yuan, Feng; Li, Kai; Wang, Yan

    2015-10-01

    Object to the high precision flying target attitude measurement issues of a large space and large field of view, comparing existing measurement methods, the idea is proposed of using two array CCD to assist in identifying the three linear CCD with multi-cooperative target attitude measurement system, and to address the existing nonlinear system errors and calibration parameters and more problems with nine linear CCD spectroscopic test system of too complicated constraints among camera position caused by excessive. The mathematical model of binocular vision and three linear CCD test system are established, co-spot composition triangle utilize three red LED position light, three points' coordinates are given in advance by Cooperate Measuring Machine, the red LED in the composition of the three sides of a triangle adds three blue LED light points as an auxiliary, so that array CCD is easier to identify three red LED light points, and linear CCD camera is installed of a red filter to filter out the blue LED light points while reducing stray light. Using array CCD to measure the spot, identifying and calculating the spatial coordinates solutions of red LED light points, while utilizing linear CCD to measure three red LED spot for solving linear CCD test system, which can be drawn from 27 solution. Measured with array CCD coordinates auxiliary linear CCD has achieved spot identification, and has solved the difficult problems of multi-objective linear CCD identification. Unique combination of linear CCD imaging features, linear CCD special cylindrical lens system is developed using telecentric optical design, the energy center of the spot position in the depth range of convergence in the direction is perpendicular to the optical axis of the small changes ensuring highprecision image quality, and the entire test system improves spatial object attitude measurement speed and precision.

  14. A Wide Dynamic Range Tapped Linear Array Image Sensor

    Science.gov (United States)

    Washkurak, William D.; Chamberlain, Savvas G.; Prince, N. Daryl

    1988-08-01

    magnitide are obtained. To achieve the short integration times necessary in acousto-optic applications. t he wide dynamic range detector has been implemented into a tapped array architecture with eight outputs and 256 photoelements. Operation of each 01)1,1)111 at 16 MHz yields detector integration times of 2 micro-seconds. Buried channel two phase CCD shift register technology is utilized to minimize image sensor noise improve video output rates and increase ease of operation.

  15. Short-wave band linear antenna array consisting of 'butterfly' radiators

    OpenAIRE

    Kudzin, Viktor P.; Lozovsky, V. N.; N.I. Shlyk

    2011-01-01

    The broadband linear antenna array of vertical polarisation for a short-wave band operation consisting of "butterfly" radiators is offered. The given radiator represents the modified flat wire antenna. The one-sided radiation pattern is provided by means of aperiodic reflector.The specific feature of the offered array is that the adjacent radiators are galvanic connected with each other. It provides improvement of radio engineering characteristics and obvious constructive and economic advanta...

  16. An absorption detection approach for multiplexed capillary electrophoresis using a linear photodiode array.

    Science.gov (United States)

    Gong, X; Yeung, E S

    1999-11-01

    A novel absorption detection method for highly multiplexed capillary electrophoresis is presented for zone electrophoresis and for micellar electrokinetic chromatography. The approach involves the use of a linear photodiode array on which a capillary array is imaged by a camera lens. Either a tungsten lamp or a mercury lamp can be used as the light source such that all common wavelengths for absorption detection are accessible by simply interchanging narrow-band filters. Each capillary spans several diodes in the photodiode array for absorption measurements. Over 100 densely packed capillaries can be monitored by a single photodiode array element with 1024 diodes. The detection limit for rhodamine 6G for each capillary in the multiplexed array is ∼1.8 × 10(-)(8) M injected (S/N = 2). The cross-talk between adjacent capillaries is less than 0.2%. Simultaneous analysis of 96 samples is demonstrated. PMID:21662842

  17. Development of 2D Bi-SQUID Arrays with High Linearity

    CERN Document Server

    Berggren, S; Longhini, P; Palacios, A; Mukhanov, O A; de Escobar, A Leese; Taylor, B J; de Andrade, M C; Nisenoff, M; Fagaly, R L; Wong, T; Cho, E; Wong, E; In, V

    2013-01-01

    We develop a two-dimensional (2D) Superconducting Quantum Interference Filter (SQIF) array based on recently introduced high-linearity tri-junction bi-SQUIDs. Our bi-SQUID SQIF array design is based on a tight integration of individual bi- SQUID cells sharing inductances with adjacent cells. We provide extensive computer simulations, analysis and experimental measurements, in which we explore the phase dynamics and linearity of the array voltage response. The non-uniformity in inductances of the bi-SQUIDs produces a pronounced zero-field single antipeak in the voltage response. The anti-peak linearity and size can be optimized by varying the critical current of the additional junction of each bi-SQUID. The layout implementation of the tight 2D array integration leads to a distinct geometrical diamond shape formed by the merged dual bi-SQUID cells. Different size 2D arrays are fabricated using standard HYPRES niobium 4.5 kA/cm2 fabrication process. The measured linearity, power gain, and noise properties will ...

  18. The 2D Linearly Polarized Near-Field Focusing Based on Angularly Discretized Slot Arrays

    CERN Document Server

    Chen, Menglin; Ma, Zilong; Jiang, Lijun

    2014-01-01

    A 2-D near-field focusing design is proposed based on the circular slot array waveguide structures, synthesized using the array-factor theory, and demonstrated by full-wave simulations. The principle of beam-focusing is extended to the 2-D angularly discretized configuration using regular center-fed linear slots arranged in a circular pattern. By the mirror image arrangement of the slots, a linearly polarized focus in the near-field of the antenna, with negligible cross-polarization is achieved. Its beam-focusing properties are discussed in details and demonstrated by simulations.

  19. Optimized Hyper Beamforming of Linear Antenna Arrays Using Collective Animal Behaviour

    Directory of Open Access Journals (Sweden)

    Gopi Ram

    2013-01-01

    Full Text Available A novel optimization technique which is developed on mimicking the collective animal behaviour (CAB is applied for the optimal design of hyper beamforming of linear antenna arrays. Hyper beamforming is based on sum and difference beam patterns of the array, each raised to the power of a hyperbeam exponent parameter. The optimized hyperbeam is achieved by optimization of current excitation weights and uniform interelement spacing. As compared to conventional hyper beamforming of linear antenna array, real coded genetic algorithm (RGA, particle swarm optimization (PSO, and differential evolution (DE applied to the hyper beam of the same array can achieve reduction in sidelobe level (SLL and same or less first null beam width (FNBW, keeping the same value of hyperbeam exponent. Again, further reductions of sidelobe level (SLL and first null beam width (FNBW have been achieved by the proposed collective animal behaviour (CAB algorithm. CAB finds near global optimal solution unlike RGA, PSO, and DE in the present problem. The above comparative optimization is illustrated through 10-, 14-, and 20-element linear antenna arrays to establish the optimization efficacy of CAB.

  20. Electromagnetic Wave Propagation in a Quasi-1D Rhombic Linear Optical Waveguide Array

    CERN Document Server

    Maimistov, Andrey I

    2016-01-01

    The quasi-one-dimensional rhombic array of the waveguides is considered. System of equations describing coupled waves in the waveguide in the linear limit is solved exactly. The electric field distribution was found both for the diffractionless (or dispersionless) flat band modes and for the dispersive modes.

  1. Ultrasound pulse-echo measurements on rough surfaces with linear array transducers

    DEFF Research Database (Denmark)

    Sjøj, Sidsel M. N.; Blanco, Esther N.; Wilhjelm, Jens E.;

    2012-01-01

    The echo from planar surfaces with rms roughness, Rq, in the range from 0-155 μm was measured with a clinical linear array transducer at different angles of incidence at 6 MHz and 12 MHz. The echo-pulse from the surfaces was isolated with an equal sized window and the power of the echo-pulse was ...

  2. EFFECTS OF RANDOM ERRORS ON THE SIDELOBE FOR THE LINEAR ARRAY

    Institute of Scientific and Technical Information of China (English)

    Cheng Gang; Lin Wei; Lin Shiming

    2002-01-01

    The effects of statistically dependent random errors on the sidelobe are analyzed for the linear array. It is shown that the random errors cause a rise in the sidelobe level. The simple formulas can also be obtained for the case of independent random errors.

  3. EFFECTS OF RANDOM ERRORS ON THE SIDELOBE FOR THE LINEAR ARRAY

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The effects of statistically dependent random errors on the sidelobe are analyzed for the linear array.It is shown that the random errors cause a rise in the sidelobe level.The simple formulas can also be obtained for the case of independent random errors.

  4. A Multiple Beamforming Network for Unequally Spaced Linear Array Based on CORPS

    Directory of Open Access Journals (Sweden)

    Armando Arce

    2015-01-01

    Full Text Available This paper proposes an alternative and innovative way to design a simpler beamforming network (BFN based on balancing alternated power combiners and dividers, to feed a nonuniformly spaced linear array with Gaussian amplitude and coherent (in-phase signals. Thus, a two-beam design configuration of the feeding network for a nonuniform array with beam steering capability is proposed and analyzed. The nonuniform aperture and the complex inputs of the feeding network are optimized by means of a differential evolution algorithm. In addition, a comparative analysis between a uniform and nonuniform linear array with the proposed feeding network is performed. Simulation results show the advantages and effectiveness of the proposed feeding network exploiting the nonuniformity of the antenna elements, in terms of side lobe level and directivity. Furthermore, research results show an inherent reduction in hardware complexity of the network.

  5. A Low-Complexity ESPRIT-Based DOA Estimation Method for Co-Prime Linear Arrays.

    Science.gov (United States)

    Sun, Fenggang; Gao, Bin; Chen, Lizhen; Lan, Peng

    2016-01-01

    The problem of direction-of-arrival (DOA) estimation is investigated for co-prime array, where the co-prime array consists of two uniform sparse linear subarrays with extended inter-element spacing. For each sparse subarray, true DOAs are mapped into several equivalent angles impinging on the traditional uniform linear array with half-wavelength spacing. Then, by applying the estimation of signal parameters via rotational invariance technique (ESPRIT), the equivalent DOAs are estimated, and the candidate DOAs are recovered according to the relationship among equivalent and true DOAs. Finally, the true DOAs are estimated by combining the results of the two subarrays. The proposed method achieves a better complexity-performance tradeoff as compared to other existing methods. PMID:27571079

  6. Research on geometric rectification of the Large FOV Linear Array Whiskbroom Image

    Science.gov (United States)

    Liu, Dia; Liu, Hui-tong; Dong, Hao; Liu, Xiao-bo

    2015-08-01

    To solve the geometric distortion problem of large FOV linear array whiskbroom image, a model of multi center central projection collinearity equation was founded considering its whiskbroom and linear CCD imaging feature, and the principle of distortion was analyzed. Based on the rectification method with POS, we introduced the angular position sensor data of the servo system, and restored the geometric imaging process exactly. An indirect rectification scheme aiming at linear array imaging with best scanline searching method was adopted, matrixes for calculating the exterior orientation elements was redesigned. We improved two iterative algorithms for this device, and did comparison and analysis. The rectification for the images of airborne imaging experiment showed ideal effect.

  7. Airborne Linear Array Image Geometric Rectification Method Based on Unequal Segmentation

    Science.gov (United States)

    Li, J. M.; Li, C. R.; Zhou, M.; Hu, J.; Yang, C. M.

    2016-06-01

    As the linear array sensor such as multispectral and hyperspectral sensor has great potential in disaster monitoring and geological survey, the quality of the image geometric rectification should be guaranteed. Different from the geometric rectification of airborne planar array images or multi linear array images, exterior orientation elements need to be determined for each scan line of single linear array images. Internal distortion persists after applying GPS/IMU data directly to geometrical rectification. Straight lines may be curving and jagged. Straight line feature -based geometrical rectification algorithm was applied to solve this problem, whereby the exterior orientation elements were fitted by piecewise polynomial and evaluated with the straight line feature as constraint. However, atmospheric turbulence during the flight is unstable, equal piecewise can hardly provide good fitting, resulting in limited precision improvement of geometric rectification or, in a worse case, the iteration cannot converge. To solve this problem, drawing on dynamic programming ideas, unequal segmentation of line feature-based geometric rectification method is developed. The angle elements fitting error is minimized to determine the optimum boundary. Then the exterior orientation elements of each segment are fitted and evaluated with the straight line feature as constraint. The result indicates that the algorithm is effective in improving the precision of geometric rectification.

  8. A linear monolithic 4-6 on silicon IR detector array

    Science.gov (United States)

    Vandamme, J.; Vermeiren, J.; Zogg, H.; Masek, J.; Fabbricotti, M.

    1992-12-01

    A linear array of monolithically grown PbTe and PbSnSe detectors on (111)-Si for MWIR and TIR imaging applications was designed and processed. The array consists of a staggered row of 2 by 128 detectors on a 100 micrometers pitch. The readout circuitry, integrated on the Si substrate consists of a COS multiplexer with a direct injection input stage, a charge reduction stage and charge to voltage conversion stage for each individual detector. This XDI (MultipeXed Direct Injection) circuit also allows for on-chip nonuniformity compensation with a switched capacitor network.

  9. Power Pattern Sensitivity to Calibration Errors and Mutual Coupling in Linear Arrays through Circular Interval Arithmetics.

    Science.gov (United States)

    Anselmi, Nicola; Salucci, Marco; Rocca, Paolo; Massa, Andrea

    2016-01-01

    The sensitivity to both calibration errors and mutual coupling effects of the power pattern radiated by a linear array is addressed. Starting from the knowledge of the nominal excitations of the array elements and the maximum uncertainty on their amplitudes, the bounds of the pattern deviations from the ideal one are analytically derived by exploiting the Circular Interval Analysis (CIA). A set of representative numerical results is reported and discussed to assess the effectiveness and the reliability of the proposed approach also in comparison with state-of-the-art methods and full-wave simulations. PMID:27258274

  10. FPGA IMPLEMENTATION OF RSA PUBLIC-KEY CRYPTOGRAPHIC COPROCESSOR BASED ON SYSTOLIC LINEAR ARRAY ARCHITECTURE

    Institute of Scientific and Technical Information of China (English)

    Wen Nuan; Dai Zibin; Zhang Yongfu

    2006-01-01

    In order to make the typical Montgomery's algorithm suitable for implementation on FPGA, a modified version is proposed and then a high-performance systolic linear array architecture is designed for RSA cryptosystem on the basis of the optimized algorithm. The proposed systolic array architecture has distinctive features, i.e. not only the computation speed is significantly fast but also the hardware overhead is drastically decreased. As a major practical result, the paper shows that it is possible to implement public-key cryptosystem at secure bit lengths on a single commercially available FPGA.

  11. General polynomial factorization-based design of sparse periodic linear arrays.

    Science.gov (United States)

    Mitra, Sanjit K; Mondal, Kalyan; Tchobanou, Mikhail K; Dolecek, Gordana Jovanovic

    2010-09-01

    We have developed several methods of designing sparse periodic arrays based upon the polynomial factorization method. In these methods, transmit and receive aperture polynomials are selected such that their product results in a polynomial representing the desired combined transmit/receive (T/R) effective aperture function. A desired combined T/R effective aperture is simply an aperture with an appropriate width exhibiting a spectrum that corresponds to the desired two-way radiation pattern. At least one of the two aperture functions that constitute the combined T/R effective aperture function will be a sparse polynomial. A measure of sparsity of the designed array is defined in terms of the element reduction factor. We show that elements of a linear array can be reduced with varying degrees of beam mainlobe width to sidelobe reduction properties.

  12. CdTe and graphene co-sensitized TiO2 nanotube array photoanodes for protection of 304SS under visible light

    Science.gov (United States)

    Li, Hong; Wang, Xiutong; Zhang, Liang; Hou, Baorong

    2015-04-01

    CdTe/graphene/TiO2 films that served as photoanodes for cathodic protection application were prepared by an electrochemical deposition method. The deposition of graphene and CdTe nanoparticles (NPs) on the surface of the TiO2 nanotubes was confirmed by scanning electron microscope and transmission electron microscopy. The composites exhibited high light absorption in both the UV and visible light region. The results indicated that TiO2 nanotube photoelectrodes sensitized by 20-cycle graphene and 30-cycle CdTe NPs exhibited effective photocathodic protection properties for 304 stainless steel (304SS) under the visible-light illumination, with an photopotential of -750 mV versus saturated calomel electrode and a current density of 560 μA cm-2. Due to the efficient photogenerated charge separation, the three-component CdTe/graphene/TiO2 showed stronger photoresponse than pure TiO2 under visible-light illumination. In summary, the CdTe/graphene could improve the photocathodic protection properties of TiO2 films.

  13. CdTe and graphene co-sensitized TiO2 nanotube array photoanodes for protection of 304SS under visible light

    International Nuclear Information System (INIS)

    CdTe/graphene/TiO2 films that served as photoanodes for cathodic protection application were prepared by an electrochemical deposition method. The deposition of graphene and CdTe nanoparticles (NPs) on the surface of the TiO2 nanotubes was confirmed by scanning electron microscope and transmission electron microscopy. The composites exhibited high light absorption in both the UV and visible light region. The results indicated that TiO2 nanotube photoelectrodes sensitized by 20-cycle graphene and 30-cycle CdTe NPs exhibited effective photocathodic protection properties for 304 stainless steel (304SS) under the visible-light illumination, with an photopotential of −750 mV versus saturated calomel electrode and a current density of 560 μA cm−2. Due to the efficient photogenerated charge separation, the three-component CdTe/graphene/TiO2 showed stronger photoresponse than pure TiO2 under visible-light illumination. In summary, the CdTe/graphene could improve the photocathodic protection properties of TiO2 films. (paper)

  14. Two-dimensional Fast ESPRIT Algorithm for Linear Array SAR Imaging

    Directory of Open Access Journals (Sweden)

    Zhao Yi-chao

    2015-10-01

    Full Text Available The linear array Synthetic Aperture Radar (SAR system is a popular research tool, because it can realize three-dimensional imaging. However, owning to limitations of the aircraft platform and actual conditions, resolution improvement is difficult in cross-track and along-track directions. In this study, a twodimensional fast Estimation of Signal Parameters by Rotational Invariance Technique (ESPRIT algorithm for linear array SAR imaging is proposed to overcome these limitations. This approach combines the Gerschgorin disks method and the ESPRIT algorithm to estimate the positions of scatterers in cross and along-rack directions. Moreover, the reflectivity of scatterers is obtained by a modified pairing method based on “region growing”, replacing the least-squares method. The simulation results demonstrate the applicability of the algorithm with high resolution, quick calculation, and good real-time response.

  15. Covariance analysis and phase ambiguity resolution for a linear interferometer antenna array

    Science.gov (United States)

    Johnson, James Andrew

    This thesis explores the application of mathematical techniques for estimating the angle of arrival (AOA) using a receiving platform having a linear interferometer antenna array. It addresses the estimation accuracy of interferometer phase measurements of a signal with superposed Gaussian noise from multiple antenna baselines, and provides a method for resolving the modulo two-pi problem inherent to many phase measurement systems. The study extends prior theoretical work (Hanna, C., 1983) by laying a mathematical foundation to complement his geometrical approach, provides a robust method of performance prediction for such a system. Key elements include estimation accuracy of a signal parameter with additive noise; the design of the linear antenna array element spacings and the relationship to Diophantine equations; and the application of the Cramer-Rao lower bound on variance of parameter estimation. It is hoped that the work presented here will serve as a practical guide for research scientists and engineers.

  16. Double-Linear Approximation Algorithm to Achieve Maximum-Power-Point Tracking for Photovoltaic Arrays

    Directory of Open Access Journals (Sweden)

    Chih-Lung Shen

    2012-06-01

    Full Text Available In this paper, a double-linear approximation algorithm (DLAA to achieve maximum-power-point tracking (MPPT for photovoltaic (PV arrays is proposed. The DLAA is based on the approximation that the maximum power point varies linearly with irradiation and temperature. With the DLAA, a maximum power point can be determined instantaneously. Moreover, complicated calculations and perturbations about an optimal point can be avoided. The paper also proposes a corresponding circuit to realize the DLAA. The configuration of the DLAA circuit is simple such that it is cost-effective and can be embedded into PV arrays easily. An example of implementation of a PV power supply system with the proposed MPPT is designed and the DLAA is compared with the perturb-and-observe method. Simulated and experimental results have demonstrated the feasibility of the PV power system and verified the advantages of the proposed DLAA.

  17. Cross-polarization and sidelobe suppression in dual linear polarization antenna arrays

    DEFF Research Database (Denmark)

    Woelders, Kim; Granholm, Johan

    1997-01-01

    In recent years, there has been an increasing interest in dual linear polarization antennas for various purposes, e.g. polarimetric synthetic aperture radar (SAR) imaging. A key design goal for dual polarization antennas is to obtain a high cross-polarization suppression. When using standard...... techniques for improving the cross-polarization suppression in dual linear polarization antenna arrays undesired sidelobes appear. This paper describes the properties of some known cross-polarization suppression methods and presents a new method for obtaining high cross-polarization suppression...

  18. Nature-inspired Cuckoo Search Algorithm for Side Lobe Suppression in a Symmetric Linear Antenna Array

    Directory of Open Access Journals (Sweden)

    K. N. Abdul Rani

    2012-09-01

    Full Text Available In this paper, we proposed a newly modified cuckoo search (MCS algorithm integrated with the Roulette wheel selection operator and the inertia weight controlling the search ability towards synthesizing symmetric linear array geometry with minimum side lobe level (SLL and/or nulls control. The basic cuckoo search (CS algorithm is primarily based on the natural obligate brood parasitic behavior of some cuckoo species in combination with the Levy flight behavior of some birds and fruit flies. The CS metaheuristic approach is straightforward and capable of solving effectively general N-dimensional, linear and nonlinear optimization problems. The array geometry synthesis is first formulated as an optimization problem with the goal of SLL suppression and/or null prescribed placement in certain directions, and then solved by the newly MCS algorithm for the optimum element or isotropic radiator locations in the azimuth-plane or xy-plane. The study also focuses on the four internal parameters of MCS algorithm specifically on their implicit effects in the array synthesis. The optimal inter-element spacing solutions obtained by the MCS-optimizer are validated through comparisons with the standard CS-optimizer and the conventional array within the uniform and the Dolph-Chebyshev envelope patterns using MATLABTM. Finally, we also compared the fine-tuned MCS algorithm with two popular evolutionary algorithm (EA techniques include particle swarm optimization (PSO and genetic algorithms (GA.

  19. Broadband ultrasonic linear array using ternary PIN-PMN-PT single crystal.

    Science.gov (United States)

    Wang, Wei; Zhao, Xiangyong; Or, Siu Wing; Leung, Chung Ming; Zhang, Yaoyao; Jiao, Jie; Luo, Haosu

    2012-09-01

    Ternary Pb(In(1/2)Nb(1/2))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) single crystal was investigated for potential application in ultrasonic linear array. Orientation and temperature dependences of height extensional electromechanical coupling coefficient k'(33) for PIN-PMN-PT single crystal were studied. It was found that the [001] poled PIN-PMN-PT diced along the [100] direction would achieve a maximum k'(33) (~87%) and the service temperature was up to 110 °C. Ultrasonic linear arrays using PIN-PMN-PT single crystal and PZT ceramic were fabricated and compared. The bandwidth at -6 dB, two-way insertion loss and pulse length of the PIN-PMN-PT array were 98.6%, -45.1 dB, and 0.28 μs, respectively, which were about 25% broader, 3.7dB higher, and 0.08 μs shorter than those of the PZT array. The experimental results agreed well with the theoretical simulation. These superior performances were attributable to the excellent piezoelectric properties of PIN-PMN-PT single crystal. PMID:23020406

  20. FAILURE CORRECTION OF LINEAR ARRAY ANTENNA WITH MULTIPLE NULL PLACEMENT USING CUCKOO SEARCH ALGORITHM

    OpenAIRE

    Muralidaran, R.; A. Vallavaraj; Hemant Patidar; Mahanti, G. K.

    2014-01-01

    The influence of evolutionary algorithms enhanced its scope of getting its existence in almost every complex optimization problems. In this paper, cuckoo search algorithm, an algorithm based on the brood parasite behavior along with Levy weights has been proposed for the radiation pattern correction of a linear array of isotropic antennas with uniform spacing when failed with more than one antenna element. Even though deterioration produced by the failure of antenna elements results in variou...

  1. Nature-inspired Cuckoo Search Algorithm for Side Lobe Suppression in a Symmetric Linear Antenna Array

    OpenAIRE

    Abdul Rani, K. N.; M. F. Abdul Malek; N. Siew-Chin

    2012-01-01

    In this paper, we proposed a newly modified cuckoo search (MCS) algorithm integrated with the Roulette wheel selection operator and the inertia weight controlling the search ability towards synthesizing symmetric linear array geometry with minimum side lobe level (SLL) and/or nulls control. The basic cuckoo search (CS) algorithm is primarily based on the natural obligate brood parasitic behavior of some cuckoo species in combination with the Levy flight behavior of some birds and fruit flies....

  2. Direct X-Ray Response Of Charge-Coupled Devices And Photodiode Linear Arrays

    Science.gov (United States)

    Launspach, J.; Bourgade, J. L.; Cavailler, C.; de Mascureau, J.; Mens, A.; Sauneuf, R.

    1986-08-01

    For x-ray calibration of detectors used on laser created plasma experiments we have developed and characterized two kinds of sources : classical continuous x-ray sources operating at 1.8 keV and 5.4 keV and a pulsed source obtained by modifying a plasma Focus device. Calibration data for x-ray Charge - Coupled Devices (CCD) and photodiode linear array cameras are presented.

  3. Evaluation of Linear Array Human Papillomavirus Genotyping Using Automatic Optical Imaging Software▿

    OpenAIRE

    Jeronimo, J; Wentzensen, N; R. Long; Schiffman, M; Dunn, S. T.; Allen, R A; Walker, J L; Gold, M.A.; Zuna, R. E.; Sherman, M E; Wacholder, S.; Wang, S S

    2008-01-01

    Variations in biological behavior suggest that each carcinogenic human papillomavirus (HPV) type should be considered individually in etiologic studies. HPV genotyping assays might have clinical applications if they are approved for use by the FDA. A widely used genotyping assay is the Roche Linear Array HPV genotyping test (LA). We used LA to genotype the HPV isolates from cervical specimens from women with the full spectrum of cervical disease: cervical cancer, cervical intraepithelial neop...

  4. Optical Analysis of a Linear-Array Thermal Radiation Detector for Geostationary Earth Radiation Budget Applications

    OpenAIRE

    Sanchez, Maria Cristina

    1998-01-01

    The Thermal Radiation Group, a laboratory in the Department of Mechanical Engineering at Virginia Polytechnic Institute and State University, is currently working to develop a new technology for thermal radiation detectors. The Group is also studying the viability of replacing current Earth Radiation Budget radiometers with this new concept. This next-generation detector consists of a thermopile linear array thermal radiation detector. The principal objective of t...

  5. Correction of linear-array lidar intensity data using an optimal beam shaping approach

    Science.gov (United States)

    Xu, Fan; Wang, Yuanqing; Yang, Xingyu; Zhang, Bingqing; Li, Fenfang

    2016-08-01

    The linear-array lidar has been recently developed and applied for its superiority of vertically non-scanning, large field of view, high sensitivity and high precision. The beam shaper is the key component for the linear-array detection. However, the traditional beam shaping approaches can hardly satisfy our requirement for obtaining unbiased and complete backscattered intensity data. The required beam distribution should roughly be oblate U-shaped rather than Gaussian or uniform. Thus, an optimal beam shaping approach is proposed in this paper. By employing a pair of conical lenses and a cylindrical lens behind the beam expander, the expanded Gaussian laser was shaped to a line-shaped beam whose intensity distribution is more consistent with the required distribution. To provide a better fit to the requirement, off-axis method is adopted. The design of the optimal beam shaping module is mathematically explained and the experimental verification of the module performance is also presented in this paper. The experimental results indicate that the optimal beam shaping approach can effectively correct the intensity image and provide ~30% gain of detection area over traditional approach, thus improving the imaging quality of linear-array lidar.

  6. A 400 KHz line rate 2048 pixel modular SWIR linear array for earth observation applications

    Science.gov (United States)

    Anchlia, Ankur; Vinella, Rosa M.; Wouters, Kristof; Gielen, Daphne; Hooylaerts, Peter; Deroo, Pieter; Ruythooren, Wouter; van der Zanden, Koen; Vermeiren, Jan; Merken, Patrick

    2015-10-01

    In this paper, we report about a family of linear imaging FPAs sensitive in the [0.9 - 1.7um] band, developed for high speed applications such as LIDAR, wavelength references and OCT analyzers and also for earth observation applications. Fast linear FPAs can also be used in a wide variety of terrestrial applications, including high speed sorting, electro- and photo-luminesce and medical applications. The arrays are based on a modular ROIC design concept: modules of 512 pixels are stitched during fabrication to achieve 512, 1024 and 2048 pixel arrays. In principle, this concept can be extended to any multiple of 512 pixels, the limiting factor being the pixel yield of long InGaAs arrays and the CTE differences in the hybrid setup. Each 512-pixel module has its own on-chip digital sequencer, analog readout chain and 4 output buffers. This modular concept enables a long-linear array to run at a high line rate of 400 KHz irrespective of the array length, which limits the line rate in a traditional linear array. The pixel has a pitch of 12.5um. The detector frontend is based on CTIA (Capacitor Trans-impedance Amplifier), having 5 selectable integration capacitors giving full well from 62x103e- (gain0) to 40x106e- (gain4). An auto-zero circuit limits the detector bias non-uniformity to 5-10mV across broad intensity levels, limiting the input referred dark signal noise to 20e-rms for Tint=3ms at room temperature. An on-chip CDS that follows the CTIA facilitates removal of Reset/KTC noise, CTIA offsets and most of the 1/f noise. The measured noise of the ROIC is 35e-rms in gain0. At a master clock rate of 60MHz and a minimum integration time of 1.4us, the FPAs reach the highest line rate of 400 KHz.

  7. High-sensitive thermal video camera with self-scanned 128 InSb linear array

    Science.gov (United States)

    Fujisada, Hiroyuki

    1991-12-01

    A compact thermal video camera with very high sensitivity has been developed by using a self-scanned 128 InSb linear array photodiode. Two-dimensional images are formed by a self- scanning function of the linear array focal plane assembly in the horizontal direction and by a vibration mirror in the vertical direction. Images with 128 X 128 pixel number are obtained every 1/30 seconds. A small size InSb detector array with a total length of 7.68 mm is utilized in order to build the compact system. In addition, special consideration is given to a configuration of optics, vibration mirror, and focal plane assembly. Real-time signal processing by a microprocessor is carried out to compensate inhomogeneous sensitivities and irradiances for each detector. The standard NTSC TV format is employed for output video signals. The thermal video camera developed had a very high radiometric sensitivity. Minimum resolvable temperature difference (MRTD) is estimated at about 0.02 K for 300 K target. The stable operation is possible without blackbody reference, because of very small stray radiation.

  8. Mixed Linear/Square-Root Encoded Single Slope Ramp Provides a Fast, Low Noise Analog to Digital Converter with Very High Linearity for Focal Plane Arrays

    Science.gov (United States)

    Wrigley, Christopher James (Inventor); Hancock, Bruce R. (Inventor); Newton, Kenneth W. (Inventor); Cunningham, Thomas J. (Inventor)

    2014-01-01

    An analog-to-digital converter (ADC) converts pixel voltages from a CMOS image into a digital output. A voltage ramp generator generates a voltage ramp that has a linear first portion and a non-linear second portion. A digital output generator generates a digital output based on the voltage ramp, the pixel voltages, and comparator output from an array of comparators that compare the voltage ramp to the pixel voltages. A return lookup table linearizes the digital output values.

  9. Polarized Uniform Linear Array System: Beam Radiation Pattern, Beamforming Diversity Order, and Channel Capacity

    Directory of Open Access Journals (Sweden)

    Xin Su

    2015-01-01

    Full Text Available There have been many studies regarding antenna polarization; however, there have been few publications on the analysis of the channel capacity for polarized antenna systems using the beamforming technique. According to Chung et al., the channel capacity is determined by the density of scatterers and the transmission power, which is obtained based on the assumption that scatterers are uniformly distributed on a 3D spherical scattering model. However, it contradicts the practical scenario, where scatterers may not be uniformly distributed under outdoor environment, and lacks the consideration of fading channel gain. In this study, we derive the channel capacity of polarized uniform linear array (PULA systems using the beamforming technique in a practical scattering environment. The results show that, for PULA systems, the channel capacity, which is boosted by beamforming diversity, can be determined using the channel gain, beam radiation pattern, and beamforming diversity order (BDO, where the BDO is dependent on the antenna characteristics and array configurations.

  10. Plasmon enhanced linear and nonlinear photoluminescence in planar nanoparticle arrays (Presentation Recording)

    Science.gov (United States)

    Walsh, Gary F.; Dal Negro, Luca

    2015-09-01

    Light emission from metal nanoparticles has potential appications as a highly sensitive refractive index detector. In order for this protential to be realized the mechanics of plasmon enhanced photoluminescence (PL) in planar nanoparticle arrays must be understude. We present an experimental exploreation of emission spectra and realitive efficiency of gold PL in nanoplasmonic arrays. We demonstrate tunability of metal PL by nanoparticle size and discover the critical role of near-field interparticle coupling on emission efficiency. We show that direct excition of plasmon resonances by photoexcited electron-hole pairs is the primary contributer to the metalic nanoparticle emission spectrum. We additionally show that emission is quenched by near-field interactions between nanoparticles leading to spectral broading by increased non-radiative plasmon decay. Finally, we show a correlation between plasmon life-time and PL efficiency. We explore this phenominan for both linear and nonlinear PL. Experimental results are supported by numerical simulations of plasmon life-time.

  11. An Efficient VLSI Linear Array for DCT/IDCT Using Subband Decomposition Algorithm

    Directory of Open Access Journals (Sweden)

    Tze-Yun Sung

    2010-01-01

    Full Text Available Discrete Cosine transform (DCT and inverse DCT (IDCT have been widely used in many image processing systems and real-time computation of nonlinear time series. In this paper, a novel lineararray of DCT and IDCT is derived from the data flow of subband decompositions representing the factorized coefficient matrices in the matrix formulation of the recursive algorithm. For increasing the throughput as well as decreasing the hardware cost, the input and output data are reordered. The proposed 8-point DCT/IDCT processor with four multipliers, simple adders, and less registers and ROM storing the immediate results and coefficients, respectively, has been implemented on FPGA (field programmable gate array and SoC (system on chip. The linear-array DCT/IDCT processor with the computation complexity O(5N/8 and hardware complexity O(5N/8 is fully pipelined and scalable for variable-length DCT/IDCT computations.

  12. Image quality evaluation of linear plastic scintillating fiber array detector for X-ray imaging

    Institute of Scientific and Technical Information of China (English)

    Mohammad Mehdi NASSERI; MA Qing-Li; YIN Ze-Jie

    2004-01-01

    It is important to assess image quality, in order to ensure that the imaging system is performing optimally and also identify the weak points in an imaging system. Three parameters mostly leading to image degradation are contrast, spatial resolution and noise. There is always a trade-off between spatial resolution and signal to noise ratio,but in scintillating fiber array detectors spatial resolution is not as important as signal to noise ratio, so we paid more attention to contrast and SNR of the system. By using GEANT4 Monte Carlo detector simulation toolkit, some effective parameters of the linear plastic scintillating fiber (PSF) array as an imaging detector were investigated. Finally we show that it is possible to use this kind of detector to take CT and DR (Digital Radiography) image under certain conditions.

  13. NDT and SHM of Carbon Fiber Composites using Linear Drive MWM-Arrays

    Science.gov (United States)

    Washabaugh, Andrew; Martin, Christopher; Lyons, Robert; Grundy, David; Goldfine, Neil; Russell, Richard; Wincheski, Russell

    2012-01-01

    Carbon fiber composites are used in a wide range of structural applications due to their excellent specific strength and stiffness. However, the anisotropic mechanical and electrical properties associated with the fibers within each composite layer present challenges, and opportunities, for Nondestructive Testing (NDT) methods used to characterize and assess the structure condition. This includes composite condition after manufacture (such as fiber orientation and density, porosity, delamination, and bond strength) and during usage (such as damage from impact, fiber breakage, thermal exposure or applied stress). Ultrasonic and thermographic methods can address some of these challenges, but eddy current methods provide an alternative method for composite structures that contain a conducting material, such as carbon fibers or a metallic liner. This presentation reviews recent advances in the development of eddy current sensors and arrays for carbon fiber composite NDT and Structural Health Monitoring (SHM) applications. The focus is on eddy current sensor constructs with linear drive windings, such as MWM -Arrays, that induce currents primarily within the linear fibers of the composite. By combining this type of sensor construct with micromechanical models that relate composite constituent properties to measurable sensor responses, insight is obtained into the volumetric distribution of electrical properties within the composite and the associated manufacturing, damage, or strain conditions. With knowledge of the fiber layup, this MWM-Array technology is able to detect damage and strain/stress as a function of depth and fiber orientation. This work has been funded by NASA, NA V AIR and the Army for applications ranging from composite overwrapped pressure vessels (COPVs) to aircraft structures and rotorcraft blades. This presentation will specifically present background on the MWM-Array technology, results from the micromechanical modeling effort, and results from

  14. Comparative Analysis of Linear and Nonlinear Pattern Synthesis of Hemispherical Antenna Array Using Adaptive Evolutionary Techniques

    Directory of Open Access Journals (Sweden)

    K. R. Subhashini

    2014-01-01

    synthesis is termed as the variation in the element excitation amplitude and nonlinear synthesis is process of variation in element angular position. Both ADE and AFA are a high-performance stochastic evolutionary algorithm used to solve N-dimensional problems. These methods are used to determine a set of parameters of antenna elements that provide the desired radiation pattern. The effectiveness of the algorithms for the design of conformal antenna array is shown by means of numerical results. Comparison with other methods is made whenever possible. The results reveal that nonlinear synthesis, aided by the discussed techniques, provides considerable enhancements compared to linear synthesis.

  15. Fabrication of High power, High-Efficiency Linear Array Diode Lasers by Pulse Anodic Oxidation

    Science.gov (United States)

    Gao, Xin; Zhang, Jing; Li, Hui; Qu, Yi; Bo, Baoxue

    2006-09-01

    InGaAlAs/AlGaAs/GaAs double-quantum-well (DQW) linear array diode lasers with asymmetric wide waveguide have been successfully fabricated by pulse anodic oxidation upon molecular beam epitaxy material growth. High-efficiency and high-power quasi-continuous-wave (QCW) output has been realized at 808 nm wavelength. The threshold current and slope efficiency of the prepared high-fill-factor QCW devices are 24 A and 1.25 A/W, respectively, and a maximum wall-plug efficiency of 51% has been achieved.

  16. Joint Estimation of 2-D DOA and Polarization by Using the Linear Array with Diverse Polarizations

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A linear array of diversely polarized antennas with one pair of identical sensors is used to obtain closed-form unambiguous estimation of 2-D direction of arrival (DOA) and polarization. Spatial phase information together with weighted 3-D polarization-angular coherence structure (PACS) are first recovered with fourth-order cumulants manipulation via a new 2-D ESPRIT variant. Spatial filtering is performed to obtain the scaled PACS, from which the closed-form 2-D DOA and polarization estimates can be derived with only quadrant ambiguity involved. The undesired quadrant ambiguity can be further resolved by using the acquired estimate of spatial phase factor.

  17. Correction of rolling wheel images captured by a linear array camera.

    Science.gov (United States)

    Xu, Jiayuan; Sun, Ran; Tian, Yupeng; Xie, Qi; Yang, Ying; Liu, Hongdan; Cao, Lei

    2015-11-20

    As a critical part of the train, wheels affect railway transport security to a large extent. This paper introduces an online method to detect the wheel tread of a train. The wheel tread images are collected by industrial linear array charge coupled device (CCD) cameras when the train is moving at a low velocity. This study defines the positioning of the cameras and determines how to select other parameters such as the horizontal angle and the scanning range. The deformation of the wheel tread image can be calculated based on these parameters and corrected by gray interpolation. PMID:26836530

  18. Algorithm for the synthesis of linear antenna arrays with desired radiation pattern and integral amplitude coefficients

    Directory of Open Access Journals (Sweden)

    Sadchenko A. V.

    2015-06-01

    Full Text Available Ahe problem of technical implementation of phased array antennas (PAR with the required radiation pattern (RP is the complexity of the construction of the beamforming device that consists of a set of controlled attenuators and phase shifters. It is possible to simplify the technical implementation of PAR, if complex representation of coefficients of amplitude-phase distribution of the field along the lattice is approximated by real values in the synthesis stage. It is known that the amplitude distribution of the field in the aperture of the antenna array and the radiation pattern are associated with Fourier transform. Thus, the amplitude and phase coefficients are first calculated using the Fourier transform, and then processed according to the selected type of circuit realization of attenuators and phase shifters. The calculation of the inverse Fourier transform of the modified coefficients allows calculating the synthesized orientation function. This study aims to develop a search algorithm for amplitude and phase coefficients, taking into account the fact that integer-valued amplitudes and phases are technically easier to implement than real ones. Synthesis algorithm for equidistant linear array with a half-wavelength irradiators pitch (&l;/2 is as follows. From a given directivity function the discrete Fourier transform (DFT in the form of an array of complex numbers is found, the resulting array is then transformed into a set of attenuations for attenuators and phase shifts for phase shifters, while the amplitude coefficients are rounded off to integers, and phases are binarizated (0, ?. The practical value of this algorithm is particularly high when using controlled phase shifters and attenuators integrally. The work confirms the possibility of a thermoelectric converter of human body application for an electronic medical thermometer power supply.

  19. Characterization of an advanced focal plane for multispectral linear array (MLA) application

    Science.gov (United States)

    King, P.; Botts, S.; Orias, G.; Yang, H. B.

    1984-01-01

    It is pointed out that the MLA instrument represents the next generation in the Landsat series of earth resources satellites. The MLA sensor concept utilizes a pushbroom scan mode to eliminate electromechanical scan mirrors, and the lower reliabililty and higher power dissipation which accompany their employment. The pushbroom scanner makes use of a linear array which consists generally of thousands of detectors oriented perpendicular to the along-track direction of the satellite. Test techniques have been developed for the measurement of the module parameters which are critical to MLA focal plane performance. These measurements include the determination of infrared responsivity, linearity over the dynamic range, temporal noise, and fixed pattern effects on each detector element of each module tested. Tests related to spectral response, crosstalk, and spot scan profiles are also conducted. A description is provided of the test equipment involved.

  20. A Multibeam Dual-Band Orthogonal Linearly Polarized Antenna Array for Satellite Communication on the Move

    Directory of Open Access Journals (Sweden)

    Yi Liu

    2015-01-01

    Full Text Available The design and simulation of a 10 × 8 multibeam dual-band orthogonal linearly polarized antenna array operating at Ku-band are presented for transmit-receive applications. By using patches with different coupling methods as elements, both perpendicular polarization in 12.25–12.75 GHz band and horizontal polarization in 14.0–14.5 GHz band are realized in a shared antenna aperture. A microstrip Rotman lens is employed as the beamforming network with 7 input ports, which can generate a corresponding number of beams to cover −30°–30° with 5 dB beamwidth along one dimension. This type of multibeam orthogonal linearly polarized planar antenna is a good candidate for satellite communication (SatCom.

  1. Choosing processor array configuration by performance modeling for a highly parallel linear algebra algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Littlefield, R.J.; Maschhoff, K.J.

    1991-04-01

    Many linear algebra algorithms utilize an array of processors across which matrices are distributed. Given a particular matrix size and a maximum number of processors, what configuration of processors, i.e., what size and shape array, will execute the fastest The answer to this question depends on tradeoffs between load balancing, communication startup and transfer costs, and computational overhead. In this paper we analyze in detail one algorithm: the blocked factored Jacobi method for solving dense eigensystems. A performance model is developed to predict execution time as a function of the processor array and matrix sizes, plus the basic computation and communication speeds of the underlying computer system. In experiments on a large hypercube (up to 512 processors), this model has been found to be highly accurate (mean error {approximately} 2%) over a wide range of matrix sizes (10 {times} 10 through 200 {times} 200) and processor counts (1 to 512). The model reveals, and direct experiment confirms, that the tradeoffs mentioned above can be surprisingly complex and counterintuitive. We propose decision procedures based directly on the performance model to choose configurations for fastest execution. The model-based decision procedures are compared to a heuristic strategy and shown to be significantly better. 7 refs., 8 figs., 1 tab.

  2. Two-dimensional imaging via a narrowband MIMO radar system with two perpendicular linear arrays.

    Science.gov (United States)

    Wang, Dang-wei; Ma, Xiao-yan; Su, Yi

    2010-05-01

    This paper presents a system model and method for the 2-D imaging application via a narrowband multiple-input multiple-output (MIMO) radar system with two perpendicular linear arrays. Furthermore, the imaging formulation for our method is developed through a Fourier integral processing, and the parameters of antenna array including the cross-range resolution, required size, and sampling interval are also examined. Different from the spatial sequential procedure sampling the scattered echoes during multiple snapshot illuminations in inverse synthetic aperture radar (ISAR) imaging, the proposed method utilizes a spatial parallel procedure to sample the scattered echoes during a single snapshot illumination. Consequently, the complex motion compensation in ISAR imaging can be avoided. Moreover, in our array configuration, multiple narrowband spectrum-shared waveforms coded with orthogonal polyphase sequences are employed. The mainlobes of the compressed echoes from the different filter band could be located in the same range bin, and thus, the range alignment in classical ISAR imaging is not necessary. Numerical simulations based on synthetic data are provided for testing our proposed method. PMID:20040416

  3. First Experiments with Planar Wire Arrays on U Michigan's Linear Transformer Driver

    Science.gov (United States)

    Safronova, A. S.; Kantsyrev, V. L.; Weller, M. E.; Shrestha, I. K.; Shlyaptseva, V. V.; Cooper, M. C.; Lorance, M.; Stafford, A.; Patel, S. G.; Steiner, A. M.; Yager-Elorriaga, D. A.; Jordan, N. M.; Gilgenbach, R. M.

    2014-10-01

    For petawatt-class Z-pinch accelerators, a Linear Transformer Driver (LTD)-driven accelerator promises to be (at a given pinch current and implosion time) more efficient than the conventionally used Marx-driven accelerator. Because there exists almost no data on how wire arrays radiate on LTD-based machines in the USA, it is very important to perform radiation and plasma physics studies on this new type of generator. We report on the first outcome of the new partnership with University of Michigan (UM), which resulted in successful UNR-UM experiments on the low-impedance MAIZE generator with planar wire arrays (PWA). PWA is a novel wire array load that was introduced and tested in detail on high-impedance Zebra at UNR during the last years and found to be the most efficient radiator. Implosion of Al Double PWAs of different configurations were achieved on MAIZE, observed with a set of various diagnostics which include x-ray diode detectors, x-ray spectroscopy and imaging, and shadowgraphy. Al and Mg plasmas of more than 450 eV were studied in detail. Research supported by NNSA under DOE Cooperative Agreement DE-NA0001984. S. G. Patel and A. M. Steiner supported by Sandia National Laboratories. D. A. Yager-Elorriaga supported by NSF GF.

  4. Development of a 64 channel ultrasonic high frequency linear array imaging system

    Science.gov (United States)

    Hu, ChangHong; Zhang, Lequan; Cannata, Jonathan M.; Yen, Jesse; Shung, K. Kirk

    2011-01-01

    In order to improve the lateral resolution and extend the field of view of a previously reported 48 element 30 MHz ultrasound linear array and 16-channel digital imaging system, the development of a 256 element 30 MHz linear array and an ultrasound imaging system with increased channel count has been undertaken. This paper reports the design and testing of a 64 channel digital imaging system which consists of an analog front-end pulser/receiver, 64 channels of Time-Gain Compensation (TGC), 64 channels of high-speed digitizer as well as a beamformer. A Personal Computer (PC) is used as the user interface to display real-time images. This system is designed as a platform for the purpose of testing the performance of high frequency linear arrays that have been developed in house. Therefore conventional approaches were taken it its implementation. Flexibility and ease of use are of primary concern whereas consideration of cost-effectiveness and novelty in design are only secondary. Even so, there are many issues at higher frequencies but do not exist at lower frequencies need to be solved. The system provides 64 channels of excitation pulsers while receiving simultaneously at a 20 MHz–120 MHz sampling rate to 12-bits. The digitized data from all channels are first fed through Field Programmable Gate Arrays (FPGAs), and then stored in memories. These raw data are accessed by the beamforming processor to re-build the image or to be downloaded to the PC for further processing. The beamformer that applies delays to the echoes of each channel is implemented with the strategy that combines coarse (8.3ns) and fine delays (2 ns). The coarse delays are integer multiples of the sampling clock rate and are achieved by controlling the write enable pin of the First-In-First-Out (FIFO) memory to obtain valid beamforming data. The fine delays are accomplished with interpolation filters. This system is capable of achieving a maximum frame rate of 50 frames per second. Wire phantom

  5. Development of a 64 channel ultrasonic high frequency linear array imaging system.

    Science.gov (United States)

    Hu, ChangHong; Zhang, Lequan; Cannata, Jonathan M; Yen, Jesse; Shung, K Kirk

    2011-12-01

    In order to improve the lateral resolution and extend the field of view of a previously reported 48 element 30 MHz ultrasound linear array and 16-channel digital imaging system, the development of a 256 element 30 MHz linear array and an ultrasound imaging system with increased channel count has been undertaken. This paper reports the design and testing of a 64 channel digital imaging system which consists of an analog front-end pulser/receiver, 64 channels of Time-Gain Compensation (TGC), 64 channels of high-speed digitizer as well as a beamformer. A Personal Computer (PC) is used as the user interface to display real-time images. This system is designed as a platform for the purpose of testing the performance of high frequency linear arrays that have been developed in house. Therefore conventional approaches were taken it its implementation. Flexibility and ease of use are of primary concern whereas consideration of cost-effectiveness and novelty in design are only secondary. Even so, there are many issues at higher frequencies but do not exist at lower frequencies need to be solved. The system provides 64 channels of excitation pulsers while receiving simultaneously at a 20-120 MHz sampling rate to 12-bits. The digitized data from all channels are first fed through Field Programmable Gate Arrays (FPGAs), and then stored in memories. These raw data are accessed by the beamforming processor to re-build the image or to be downloaded to the PC for further processing. The beamformer that applies delays to the echoes of each channel is implemented with the strategy that combines coarse (8.3 ns) and fine delays (2 ns). The coarse delays are integer multiples of the sampling clock rate and are achieved by controlling the write enable pin of the First-In-First-Out (FIFO) memory to obtain valid beamforming data. The fine delays are accomplished with interpolation filters. This system is capable of achieving a maximum frame rate of 50 frames per second. Wire phantom images

  6. Linear bolometer array using a high TCR VOx-Au film

    Science.gov (United States)

    Smith, Evan M.; Ginn, James C.; Warren, Andrew P.; Long, Christopher J.; Panjwani, Deep; Peale, Robert E.; Shelton, David J.

    2014-06-01

    We present a design for a low-noise bolometer linear array based on the temperature-dependent conductivity of a VOx- Au film. Typical thin film bolometers must compromise between low resistivity to limit Johnson noise and high temperature coefficient of resistivity (TCR) to maximize responsivity. Our vanadium oxide is alloyed with a small concentration of gold by co-sputtering, which gives very low resistivity and very high TCR simultaneously. The film is fabricated on an air bridge device having high thermal conductivity and small thermal time constant optimized for 30 to 60 Hz frame rates. The linear array functions as a low-power profile sensor with a modulated bias. For 1 V bias, we predict responsivity exceeding 1200 V/W. Johnson noise dominates with predicted NEP values as low as 1.0 × 10-11 W/Hz1/2. Preliminary device testing shows film resistivity below 2.5 Ω-cm with TCR exceeding -2.0%. Preliminary measurements of NEP and D* are reported.

  7. Robot Eve-In-Hand Using Solid State Linear Array Sensor

    Science.gov (United States)

    Luo, R. C.; Chern, M. Y.

    1985-12-01

    An intelligent robot control system based on dynamic sensing feedback using visual eye-in-hand systems have attracted great research efforts, because these systems have several advantages over the use of a fixed external video camera system. For example, it ignores inadequate lighting and background contrast, optical shadows, environmental lighting variables, and an increased maneuverability to access widely scattered or hidden parts. This paper presents an eye-in-hand system using a solid-state linear line scanner as the sensing element. The system currently has the ability to determine the pose and shape of objects, and also is capable of defining the proper grasping site prior to grasping. The paper also describes the system configuration and the proposed object learning and recognition procedure using line scan methods in detail. In this research, an experimental model is built which is used to simulate a fully opened parallel jaw gripper. A photodiode array is embedded in one side of the finger. A Compaq microcomputer based on the Intel 8088 microprocessor is used as the host. An interface between linear array video scanning signals, CPU and Video RAM is built and successfully tested.

  8. Handheld Thermoacoustic Scanning System Based on a Linear-array Transducer.

    Science.gov (United States)

    Ji, Zhong; Ding, Wenzheng; Ye, Fanghao; Lou, Cunguang

    2016-07-01

    To receive the information necessary for imaging, traditional microwave-induced thermoacoustic imaging systems (MITISs) use a type of circular-scanning mode using single or arc detectors. However, the use of MITISs for body scanning is complicated by restrictions in space and imaging time. A linear-array detector, the most widely used transducer in medical ultrasound imaging systems for body scanning, is a possible alternative to MITISs for scanning biological tissues, such as from the breast or limbs. In this paper, a handheld MITIS, based on a linear-array detector and a multiple data acquisition system, is described, and the capacity of the system is explored experimentally. First, the vertical and lateral resolution of the system is discussed. Next, real-time imaging of a moving object, obtained with an image capture rate of 20 frame/s, is described. Finally, a phantom experiment is detailed, investigating the overall imaging capability. The results show that this system achieves rapid scanning with a large field of view. The system has the obvious advantages of being handheld, not using coupled fluids, and achieving real-time imaging with a large field of view, which make this MITIS more suitable for clinical applications.

  9. Calibration and linearity verification of capacitance type cryo level indicators using cryogenically multiplexed diode array

    Science.gov (United States)

    Karunanithi, R.; Jacob, Subhash; Singh Gour, Abhay Singh; Das, M.; Nadig, D. S.; Prasad, M. V. N.

    2012-06-01

    In space application the precision level measurement of cryogenic liquids in the storage tanks is done using triple redundant capacitance level sensor, for control and safety point of view. The linearity of each sensor element depends upon the cylindricity and concentricity of the internal and external electrodes. The complexity of calibrating all sensors together has been addressed by two step calibration methodology which has been developed and used for the calibration of six capacitance sensors. All calibrations are done using Liquid Nitrogen (LN2) as a cryogenic fluid. In the first step of calibration, one of the elements of Liquid Hydrogen (LH2) level sensor is calibrated using 700mm eleven point discrete diode array. Four wire method has been used for the diode array. Thus a linearity curve for a single element of LH2 is obtained. In second step of calibration, using the equation thus obtained for the above sensor, it is considered as a reference for calibrating remaining elements of the same LH2 sensor and other level sensor (either Liquid Oxygen (LOX) or LH2). The elimination of stray capacitance for the capacitance level probes has been attempted. The automatic data logging of capacitance values through GPIB is done using LabVIEW 8.5.

  10. Low complexity MIMO sonar imaging using a virtual sparse linear array

    Institute of Scientific and Technical Information of China (English)

    Xionghou Liu; Chao Sun; Yixin Yang; Jie Zhuo; Yina Han

    2016-01-01

    A multiple-input multiple-output (MIMO) sonar can synthesize a large-aperture virtual uniform linear array (ULA) from a smal number of physical elements. However, the large aperture is obtained at the cost of a great number of matched filters with much heavy computation load. To reduce the com-putation load, a MIMO sonar imaging method using a virtual sparse linear array (SLA) is proposed, which contains the offline and online processing. In the offline processing, the virtual ULA of the MIMO sonar is thinned to a virtual SLA by the simulated annealing algorithm, and matched filters corre-sponding to inactive virtual elements are removed. In the online processing, outputs of matched filters corresponding to active elements are colected for further multibeam processing and hence, the number of matched filters in the echo proc-essing procedure is effectively reduced. Numerical simula-tions show that the proposed method can reduce the compu-tation load effectively while obtaining a similar imaging per-formance as the traditional method.

  11. Embeddings of Linear Arrays, Rings and 2-D Meshes on Extended Lucas Cube Networks

    CERN Document Server

    Ernastuti,

    2011-01-01

    A Fibonacci string is a length n binary string containing no two consecutive 1s. Fibonacci cubes (FC), Extended Fibonacci cubes (ELC) and Lucas cubes (LC) are subgraphs of hypercube defined in terms of Fibonacci strings. All these cubes were introduced in the last ten years as models for interconnection networks and shown that their network topology posseses many interesting properties that are important in parallel processor network design and parallel applications. In this paper, we propose a new family of Fibonacci-like cube, namely Extended Lucas Cube (ELC). We address the following network simulation problem : Given a linear array, a ring or a two-dimensional mesh; how can its nodes be assigned to ELC nodes so as to keep their adjacent nodes near each other in ELC ?. We first show a simple fact that there is a Hamiltonian path and cycle in any ELC. We prove that any linear array and ring network can be embedded into its corresponding optimum ELC (the smallest ELC with at least the number of nodes in the ...

  12. Analysis of experimental data of the solid towed linear array sonar and liquid towed linear array sonar%固态拖线阵和液态拖线阵的试验分析

    Institute of Scientific and Technical Information of China (English)

    张祥; 李淑秋; 王文博

    2012-01-01

    Towed linear array sonar attracts attention for its properties of low frequency and large aperture. As an important part of the wet-end, the towed linear array has been developed rapidly. The liquid towed linear array is mature due to being used earlier. Meanwhile, more studies on solid towed linear array have been done for its special feature. To compare the consistency of hydrophones and the beam forming performance between the two kinds of towed linear arrays, the lake experimental results are presented. The analysis results show that the liquid towed linear array has almost the same performance as the solid towed linear array in consistency among different hydrophones. In the aspect of beam forming, the performances of the two kinds of arrays have no significant differences in static state; but under the condition of towing, the solid towed linear array is better than the liquid towed linear array because it's less sensitive to the noise while towing.%拖曳线列阵声纳以低频、大孔径等特点而受到关注.作为湿端的主要组成部分,拖线阵的发展也比较迅速.由于应用较早,液态拖线阵技术已经比较成熟.相比于液态拖线阵,固态拖线阵具有自身的特点,因此近年来对固态拖线阵的研究也逐渐增多.为了比较两种成阵工艺对拖曳线列阵性能的影响,进行了湖试,通过对湖试数据进行分析,比较两种拖线阵中阵元一致性和拖线阵波束形成性能的差异.结果表明,在阵元一致性方面,液态拖线阵和固态拖线阵的性能基本相似;在波束形成性能方面,静态时两者性能无明显的差别;在拖曳状态下,固态拖线阵对拖曳时产生的噪声敏感性低,因而具有更好的波束形成性能.

  13. Effects of a near-field rigid sphere scatterer on the performance of linear microphone array beamformers.

    Science.gov (United States)

    Hu, Yuxiang; Zhou, Haoran; Lu, Jing; Qiu, Xiaojun

    2016-08-01

    Beamformers enable a microphone array to capture acoustic signals from a sound source with high signal to noise ratio in a noisy environment, and the linear microphone array is of particular importance, in practice, due to its simplicity and easy implementation. A linear microphone array sometimes is used near some scattering objects, which affect its beamforming performance. This paper develops a numerical model with a linear microphone array near a rigid sphere for both far-field plane wave and near-field sources. The effects of the scatterer on two typical beamformers, i.e., the delay-and-sum beamformer and the superdirective beamformer, are investigated by both simulations and experiments. It is found that the directivity factor of both beamformers improves due to the increased equivalent array aperture when the size of the array is no larger than that of the scatter. With the increase of the array size, the directivity factor tends to deteriorate at high frequencies because of the rising side-lobes. When the array size is significantly larger than that of the scatterer, the scattering has hardly any influence on the beamforming performance. PMID:27586725

  14. High-frequency Ultrasound Doppler System for Biomedical Applications with a 30 MHz Linear Array

    Science.gov (United States)

    Xu, Xiaochen; Sun, Lei; Cannata, Jonathan M.; Yen, Jesse T.; Shung, K. Kirk

    2008-01-01

    In this paper, we report the development of the first high-frequency (HF) pulsed-wave Doppler system using a 30 MHz linear array transducer to assess the cardiovascular functions in small animal. This array based pulsed-wave Doppler system included a 16-channel HF analog beamformer, a HF pulsed-wave Doppler module, timing circuits, HF bipolar pulsers, and analog front-ends. The beamformed echoes acquired by the 16 channel analog beamformer, were directly fed to the HF pulsed-wave Doppler module. Then the in-phase and quadrature-phase (IQ) audio Doppler signals were digitized by either a sound card or a Gage digitizer and stored in a PC. The Doppler spectrogram was displayed on a PC in real time. The two-way beam-widths were determined to be 160 μm to 320 μm when the array was electronically focused at different focal points at depths from 5–10 mm. A micro flow phantom, consisting of a polyimide tube with inner diameter of 127 μm, and the wire phantom were used to evaluate and calibrate the system. The results show that the system is capable of detecting motion velocity of the wire phantom as low as 0.1 mm/s, and detecting blood-mimicking flow velocity in the 127 μm tube lower than 7 mm/s. The system was subsequently used to measure the blood flow in vivo in two mouse abdominal superficial vessels with diameters of approximately 200 μm, and a mouse aorta close to the heart. These results demonstrated that this system may become an indispensable part of the current HF array based imaging systems for small animal studies. PMID:17993243

  15. Design Methodology of a Dual-Halbach Array Linear Actuator with Thermal-Electromagnetic Coupling.

    Science.gov (United States)

    Eckert, Paulo Roberto; Flores Filho, Aly Ferreira; Perondi, Eduardo; Ferri, Jeferson; Goltz, Evandro

    2016-01-01

    This paper proposes a design methodology for linear actuators, considering thermal and electromagnetic coupling with geometrical and temperature constraints, that maximizes force density and minimizes force ripple. The method allows defining an actuator for given specifications in a step-by-step way so that requirements are met and the temperature within the device is maintained under or equal to its maximum allowed for continuous operation. According to the proposed method, the electromagnetic and thermal models are built with quasi-static parametric finite element models. The methodology was successfully applied to the design of a linear cylindrical actuator with a dual quasi-Halbach array of permanent magnets and a moving-coil. The actuator can produce an axial force of 120 N and a stroke of 80 mm. The paper also presents a comparative analysis between results obtained considering only an electromagnetic model and the thermal-electromagnetic coupled model. This comparison shows that the final designs for both cases differ significantly, especially regarding its active volume and its electrical and magnetic loading. Although in this paper the methodology was employed to design a specific actuator, its structure can be used to design a wide range of linear devices if the parametric models are adjusted for each particular actuator.

  16. Design Methodology of a Dual-Halbach Array Linear Actuator with Thermal-Electromagnetic Coupling.

    Science.gov (United States)

    Eckert, Paulo Roberto; Flores Filho, Aly Ferreira; Perondi, Eduardo; Ferri, Jeferson; Goltz, Evandro

    2016-01-01

    This paper proposes a design methodology for linear actuators, considering thermal and electromagnetic coupling with geometrical and temperature constraints, that maximizes force density and minimizes force ripple. The method allows defining an actuator for given specifications in a step-by-step way so that requirements are met and the temperature within the device is maintained under or equal to its maximum allowed for continuous operation. According to the proposed method, the electromagnetic and thermal models are built with quasi-static parametric finite element models. The methodology was successfully applied to the design of a linear cylindrical actuator with a dual quasi-Halbach array of permanent magnets and a moving-coil. The actuator can produce an axial force of 120 N and a stroke of 80 mm. The paper also presents a comparative analysis between results obtained considering only an electromagnetic model and the thermal-electromagnetic coupled model. This comparison shows that the final designs for both cases differ significantly, especially regarding its active volume and its electrical and magnetic loading. Although in this paper the methodology was employed to design a specific actuator, its structure can be used to design a wide range of linear devices if the parametric models are adjusted for each particular actuator. PMID:26978370

  17. Position-sensitive CdTe detector using improved crystal growth method

    Science.gov (United States)

    1988-09-01

    The feasibility of developing a position-sensitive CdTe detector array for astronomical observations in the hard X-ray, soft gamma ray region is demonstrated. In principle, it was possible to improve the resolution capability for imaging measurements in this region by orders of magnitude over what is now possible through the use of CdTe detector arrays. The objective was to show that CdTe crystals of the quality, size and uniformity required for this application can be obtained with a new high pressure growth technique. The approach was to fabricate, characterize and analyze a 100 element square array and several single-element detectors using crystals from the new growth process. Results show that detectors fabricated from transversely sliced, 7 cm diameter wafers of CdTe exhibit efficient counting capability and a high degree of uniformity over their entire areas. A 100 element square array of 1 sq mm detectors was fabricated and operated.

  18. Design and optimization of multi-class series-parallel linear electromagnetic array artificial muscle.

    Science.gov (United States)

    Li, Jing; Ji, Zhenyu; Shi, Xuetao; You, Fusheng; Fu, Feng; Liu, Ruigang; Xia, Junying; Wang, Nan; Bai, Jing; Wang, Zhanxi; Qin, Xiansheng; Dong, Xiuzhen

    2014-01-01

    Skeletal muscle exhibiting complex and excellent precision has evolved for millions of years. Skeletal muscle has better performance and simpler structure compared with existing driving modes. Artificial muscle may be designed by analyzing and imitating properties and structure of skeletal muscle based on bionics, which has been focused on by bionic researchers, and a structure mode of linear electromagnetic array artificial muscle has been designed in this paper. Half sarcomere is the minimum unit of artificial muscle and electromagnetic model has been built. The structural parameters of artificial half sarcomere actuator were optimized to achieve better movement performance. Experimental results show that artificial half sarcomere actuator possesses great motion performance such as high response speed, great acceleration, small weight and size, robustness, etc., which presents a promising application prospect of artificial half sarcomere actuator.

  19. Investigation of the spatial correlations of flow noise in vector hydrophone towed linear array

    Institute of Scientific and Technical Information of China (English)

    YANG Xiuting; SUN Guiqing; LI Mini; LI Qihu

    2008-01-01

    Following the wall pressure spectrum of the turbulent boundary layer developed by Corcos, a method in the frequency-wavenumber space was presented to analyze the flow noise in the vector hydrophone towed linear array. The general forms of the acoustic pressure and particle velocity in the flow noise field were obtained, and the spatial correlations of the flow noise were calculated. The numerical analysis results based on wavenumber integration show that: (1) The spatial correlations of flow noise drops rapidly with increasing axial separation between the elements, so the flow noise received by different vector hydrophones usually sampled in a half-wavelength rate can be considered as independent; (2) The flow noise is highly correlated in the radial direction at low frequency, and only those of high frequency componet can be neglected.

  20. Linear array of photodiodes to track a human speaker for video recording

    Science.gov (United States)

    DeTone, D.; Neal, H.; Lougheed, R.

    2012-12-01

    Communication and collaboration using stored digital media has garnered more interest by many areas of business, government and education in recent years. This is due primarily to improvements in the quality of cameras and speed of computers. An advantage of digital media is that it can serve as an effective alternative when physical interaction is not possible. Video recordings that allow for viewers to discern a presenter's facial features, lips and hand motions are more effective than videos that do not. To attain this, one must maintain a video capture in which the speaker occupies a significant portion of the captured pixels. However, camera operators are costly, and often do an imperfect job of tracking presenters in unrehearsed situations. This creates motivation for a robust, automated system that directs a video camera to follow a presenter as he or she walks anywhere in the front of a lecture hall or large conference room. Such a system is presented. The system consists of a commercial, off-the-shelf pan/tilt/zoom (PTZ) color video camera, a necklace of infrared LEDs and a linear photodiode array detector. Electronic output from the photodiode array is processed to generate the location of the LED necklace, which is worn by a human speaker. The computer controls the video camera movements to record video of the speaker. The speaker's vertical position and depth are assumed to remain relatively constant- the video camera is sent only panning (horizontal) movement commands. The LED necklace is flashed at 70Hz at a 50% duty cycle to provide noise-filtering capability. The benefit to using a photodiode array versus a standard video camera is its higher frame rate (4kHz vs. 60Hz). The higher frame rate allows for the filtering of infrared noise such as sunlight and indoor lighting-a capability absent from other tracking technologies. The system has been tested in a large lecture hall and is shown to be effective.

  1. Imaging of downward-looking linear array SAR using three-dimensional spatial smoothing MUSIC algorithm

    Science.gov (United States)

    Zhang, Siqian; Kuang, Gangyao

    2014-10-01

    In this paper, a novel three-dimensional imaging algorithm of downward-looking linear array SAR is presented. To improve the resolution, multiple signal classification (MUSIC) algorithm has been used. However, since the scattering centers are always correlated in real SAR system, the estimated covariance matrix becomes singular. To address the problem, a three-dimensional spatial smoothing method is proposed in this paper to restore the singular covariance matrix to a full-rank one. The three-dimensional signal matrix can be divided into a set of orthogonal three-dimensional subspaces. The main idea of the method is based on extracting the array correlation matrix as the average of all correlation matrices from the subspaces. In addition, the spectral height of the peaks contains no information with regard to the scattering intensity of the different scattering centers, thus it is difficulty to reconstruct the backscattering information. The least square strategy is used to estimate the amplitude of the scattering center in this paper. The above results of the theoretical analysis are verified by 3-D scene simulations and experiments on real data.

  2. Contrast-based moving target detection with the randomized linear receive array

    Science.gov (United States)

    Ranney, Kenneth; Martone, Anthony; Innocenti, Roberto; Nguyen, Lam

    2012-06-01

    The Army Research Laboratory (ARL) has, in the past, demonstrated the effectiveness of low frequency, ultrawideband radar for detection of slow-moving targets located behind walls. While these initial results were promising, they also indicated that sidelobe artifacts produced by moving target indication (MTI) processing could pose serious problems. Such artifacts induced false alarms and necessitated the introduction of a tracker stage to eliminate them. Of course, the tracker algorithm was also imperfect, and it tended to pass any persistent, nearly collocated false alarms. In this work we describe the incorporation of a sidelobe-reduction technique-the randomized linear receiver array (RA)-into our MTI processing chain. To perform this investigation, we leverage data collected by ARL's synchronous impulse reconstruction (SIRE) radar. We begin by calculating MTI imagery using both the non-random and randomized array methods. We then compare the sidelobe levels in each image and quantify the differences. Finally, we apply a local-contrast target detection algorithm based on constant false alarm rate (CFAR) principles, and we analyze probabilities of detection and false alarm for each MTI image.

  3. Thermal-independent properties of PIN-PMN-PT single-crystal linear-array ultrasonic transducers.

    Science.gov (United States)

    Chen, Ruimin; Wu, Jinchuan; Ho Lam, Kwok; Yao, Liheng; Zhou, Qifa; Tian, Jian; Han, Pengdi; Shung, K Kirk

    2012-12-01

    In this paper, low-frequency 32-element linear-array ultrasonic transducers were designed and fabricated using both ternary Pb(In(1/2)Nb(1/2))-Pb(Mg(1/3)Nb(2/3))-PbTiO(3) (PIN-PMN-PT) and binary Pb(Mg(1/3)Nb(2/3))-PbTiO(3) (PMNPT) single crystals. Performance of the array transducers was characterized as a function of temperature ranging from room temperature to 160°C. It was found that the array transducers fabricated using the PIN-PMN-PT single crystal were capable of satisfactory performance at 160°C, having a -6-dB bandwidth of 66% and an insertion loss of 37 dB. The results suggest that the potential of PIN-PMN-PT linear-array ultrasonic transducers for high-temperature ultrasonic transducer applications is promising. PMID:23221227

  4. Preliminary results from a novel CdZnTe linear pad detector array x-ray imaging system

    International Nuclear Information System (INIS)

    The excellent energy-resolution and short charge collection time, especially the possibility of room temperature operation, make CdZnTe semiconductor detectors an excellent candidate for x-ray imaging and spectroscopic application in nuclear physics. Because of these characteristics, CdZnTe pad detectors with a novel geometry and approximately 1 mm2 pad area have been developed. These pad type linear arrays are new and important for many scanning type applications using a wide energy range from about 10 to 300 keV energies. A prototype x-ray imaging system has been developed consisting of a state-of-the-art pad type linear array of CdZnTe detectors manufactured by eV Products and low noise readout electronics developed by NOVA R and D, Inc. A series of measurements on the temperature dependence of the performance of CdZnTe linear pad detector arrays has been performed at NOVA R and D, Inc. The changes in dark (leakage) current against temperature have been studied. High resolution x-ray spectra has been obtained using 57Co source at different temperatures. A low noise front-end electronics ASIC chip for reading out the detector array was developed that can achieve fast data acquisition with dual energy imaging capability. Several prototype CdZnTe pad detector arrays are placed next to each other to form an approximately 30 cm long linear array. This array is used to make preliminary dual energy scanned images of complex objects using a 90 kV x-ray generator. Some of the images will be presented. The results show that the system is excellent for applications in industrial and medical imaging

  5. The feasibility of MRI-guided whole prostate ablation with a linear aperiodic intracavitary ultrasound phased array

    Energy Technology Data Exchange (ETDEWEB)

    Sokka, S.D. [MIT Harvard Division of Health Sciences and Technology, Boston, MA 02115 (United States); Brigham and Women' s Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115 (United States); Hynynen, K.H. [Brigham and Women' s Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115 (United States)

    2000-11-01

    Over the past decade, numerous minimally invasive thermal procedures have been investigated to treat benign prostate hyperplasia and prostate cancer. Of these methods, ultrasound has shown considerable promise due to its ability to produce more precise and deeper thermal foci. In this study, a linear, transrectal ultrasound phased array capable of ablating large tissue volumes was fabricated and evaluated. The device was designed to be compatible for use with MRI guidance and thermometry. The intracavitary applicator increases treatable tissue volume by using an ultrasonic motor to provide a mechanical rotation angle of up to 100 deg. to a 62-element 1D ultrasound array. An aperiodic array geometry was used to reduce grating lobes. In addition, a specially designed Kapton interconnect was used to reduce cable crosstalk and hence also improve the acoustic efficiency of the array. MRI-guided in vivo and ex vivo experiments were performed to verify the array's large-volume ablative capabilities. Ex vivo bovine experiments were performed to assess the focusing range of the applicator. The array generated foci in a 3 cm (2 to 5 cm from the array surface along the axis normal to the array) by 5.5 cm (along the long axis of the array) by 6 cm (along the transverse axis of the array at a depth of 4 cm) volume. In vivo rabbit thigh experiments were performed to evaluate the lesion-producing capabilities in perfused tissue. The array generated 3 cm x 2 cm x 2 cm lesions with 8 to 12 half-minute sonications equally spaced in the volume. The results indicate that transrectal ultrasound coagulation of the whole prostate is feasible with the developed device. (author)

  6. Interventional multispectral photoacoustic imaging with a clinical linear array ultrasound probe for guiding nerve blocks

    Science.gov (United States)

    Xia, Wenfeng; West, Simeon J.; Nikitichev, Daniil I.; Ourselin, Sebastien; Beard, Paul C.; Desjardins, Adrien E.

    2016-03-01

    Accurate identification of tissue structures such as nerves and blood vessels is critically important for interventional procedures such as nerve blocks. Ultrasound imaging is widely used as a guidance modality to visualize anatomical structures in real-time. However, identification of nerves and small blood vessels can be very challenging, and accidental intra-neural or intra-vascular injections can result in significant complications. Multi-spectral photoacoustic imaging can provide high sensitivity and specificity for discriminating hemoglobin- and lipid-rich tissues. However, conventional surface-illumination-based photoacoustic systems suffer from limited sensitivity at large depths. In this study, for the first time, an interventional multispectral photoacoustic imaging (IMPA) system was used to image nerves in a swine model in vivo. Pulsed excitation light with wavelengths in the ranges of 750 - 900 nm and 1150 - 1300 nm was delivered inside the body through an optical fiber positioned within the cannula of an injection needle. Ultrasound waves were received at the tissue surface using a clinical linear array imaging probe. Co-registered B-mode ultrasound images were acquired using the same imaging probe. Nerve identification was performed using a combination of B-mode ultrasound imaging and electrical stimulation. Using a linear model, spectral-unmixing of the photoacoustic data was performed to provide image contrast for oxygenated and de-oxygenated hemoglobin, water and lipids. Good correspondence between a known nerve location and a lipid-rich region in the photoacoustic images was observed. The results indicate that IMPA is a promising modality for guiding nerve blocks and other interventional procedures. Challenges involved with clinical translation are discussed.

  7. A Mixed-Integer Linear Programming approach to wind farm layout and inter-array cable routing

    DEFF Research Database (Denmark)

    Fischetti, Martina; Leth, John-Josef; Borchersen, Anders Bech

    2015-01-01

    A Mixed-Integer Linear Programming (MILP) approach is proposed to optimize the turbine allocation and inter-array offshore cable routing. The two problems are considered with a two steps strategy, solving the layout problem first and then the cable problem. We give an introduction to both problems...

  8. FAILURE CORRECTION OF LINEAR ARRAY ANTENNA WITH MULTIPLE NULL PLACEMENT USING CUCKOO SEARCH ALGORITHM

    Directory of Open Access Journals (Sweden)

    R. Muralidaran

    2014-03-01

    Full Text Available The influence of evolutionary algorithms enhanced its scope of getting its existence in almost every complex optimization problems. In this paper, cuckoo search algorithm, an algorithm based on the brood parasite behavior along with Levy weights has been proposed for the radiation pattern correction of a linear array of isotropic antennas with uniform spacing when failed with more than one antenna element. Even though deterioration produced by the failure of antenna elements results in various undesirable effects, consideration in this paper is given to the correction of side lobe level and null placement at two places. Various articles in the past have already shown that the idea to correct the radiation pattern is to alter the amplitude weights of the remaining unfailed elements, instead of replacing the faulty elements. This approach is made use of modifying the current excitations of unfailed elements using cuckoo search algorithm such that the resulting radiation pattern is similar to the unfailed original pattern in terms of side lobe level and null placement at two places. Examples shown in this paper demonstrate the effectiveness of this algorithm in achieving the desired objectives.

  9. JOINT SPACE-FREQUENCY MULTIUSER SYMBOL DETECTOR FOR MC-CDMA SYSTEM WITH UNIFORM LINEAR ARRAY

    Institute of Scientific and Technical Information of China (English)

    Wu Xiaojun; Yin Qinye; Feng Aigang; Zhao Zheng; Zhang Jianguo

    2002-01-01

    The MultiCarrier Code Division Multiple Access (MC-CDMA) scheme is promising for relieving capacity limit problems of Direct Sequence (DS-) CDMA systems due to serious InterChip Interference (ICI) and MultiUser Interference (MUI) in high-data-rate wireless communication systems. In this paper, the Uniform Linear Array (ULA) is applied to the base station of macrocellular MC-CDMA systems in a frequency-selective fading channel environment. A joint space-frequency multiuser symbol sequence detector is developed for all active users within one macrocell without space-frequency channel estimation. Simultaneously, Directions-Of-Arrivals (DOAs) of all active users can also be estimated. By dividing the ULA into two identical overlapping subarrays, a specific auxiliary matrix is constructed, which includes both symbol sequence and DOA information of all active users. Then, based on the subspace method, performing the eigen decomposition on such auxiliary matrix, the closed-form solution of symbol sequences and DOAs for all active users can be obtained. In comparison with schemes based on channel estimation, our algorithm need not explicitly estimate the space-frequency channel for each active user,so it has lower computation complexity. Extensive computer simulations demonstrate the overall performance of this novel scheme.

  10. JOINT SPACE-FREQUENCY MULTIUSER SYMBOL DETECTOR FOR MC-CDMA SYSTEM WITH UNIFORM LINEAR ARRAY

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The MultiCarrier COde Division Multiple Access (MC-CDMA) scheme is promising for relieving capacity limit problems of Direct Sequence(DS-CDMA systems due to serious InterCip Interference(ICI) and MultiUser Interference(MUI)in high-data-rate wireless communication systems.In this paper the Uniform Linear Array(ULA) is applied to the base station of macrocellular MC-CDMA systems in a frequency-selective fading channel environment.A joint space-frequency multiuser symblo sequence detector is developed for all active users within one macrocell without space-frequency channel estimation.Simultaneously,Directions-of -Arrivals (ODAs)of all active users can also be estimated.By dividing the ULA into two identical overlapping subarrays,a specific auxiliary matrix is constructed,which includes both symbol sequence and DOA information of all active users,Then,based on the subspace method,performing the eigen decomposition on such auxiliary matrix,the closed-form solution of symbol sequences and DOAs for all active users can be obtained.In comparison with schemes based on channel estimation,our algorithm need not explicitly estimate the space-frequency channel for each active user,so it has lower computation complexity,Extensive computer simulations demonstrate the overall performance of this novel scheme.

  11. CdTe ambulatory ventricular function monitor

    International Nuclear Information System (INIS)

    A prototype device consisting of two arrays of CdTe detectors, ECG amplifiers and gate, microprocessor, and tape recorder was devised to record simultaneous ECG and radionuclide blood pool data from the left ventricle for extended periods during normal activity. The device is intended to record information concerning both normal and abnormal physiology of the heart and to permit the evaluation of new pharmaceuticals under everyday conditions. Preliminary results indicate that the device is capable of recording and reading out data from both phantoms and patients

  12. Current role of radial and curved-linear arrayed EUS scopes for diagnosis of pancreatic abnormalities in Japan.

    Science.gov (United States)

    Irisawa, Atsushi

    2011-05-01

    To elucidate the current status of radial and curved-linear arrayed endoscopic ultrasonography (EUS), the author conducted a survey using a questionnaire at different institutions to assess the following. 1. Number of EUS procedures conducted annually for pancreatic malignancies. 2. Role of radial arrayed EUS for pancreatic abnormalities. 3. Role of curved-linear arrayed EUS for pancreatic abnormalities. 4. Indication of EUS-guided fine-needle aspiration biopsy (EUS-FNA) for pancreatic abnormalities. 5. Percentage of EUS-FNA among the cases carried out with EUS for pancreatic abnormalities. 6. Experience of EUS with contrast harmonic echo for pancreatic malignancies and its indications. 7. Experience of elastography on EUS for pancreatic abnormalities. In Japan, although usage of curved-linear arrayed EUS has become popular for both EUS-FNA and for screening, radial EUS is widely used for diagnosing pancreatic abnormalities. Endosonographers must understand the respective advantages and disadvantages of EUS devices and carry out EUS procedures appropriately. PMID:21535192

  13. Linear mode photon counting from visible to MWIR with HgCdTe avalanche photodiode focal plane arrays

    Science.gov (United States)

    Sullivan, William; Beck, Jeffrey; Scritchfield, Richard; Skokan, Mark; Mitra, Pradip; Sun, Xiaoli; Abshire, James; Carpenter, Darren; Lane, Barry

    2015-05-01

    Results of characterization data on linear mode photon counting (LMPC) HgCdTe electron-initiated avalanche photodiode (e-APD)focal plane arrays (FPA) are presented that reveal an improved understanding and the growing maturity of the technology. The first successful 2x8 LMPC FPA was fabricated in 2010 [1]. Since then a process validation lot of 2x8 arrays was fabricated. Five arrays from this lot were characterized that replicated the previous 2x8 LMPC array performance. In addition, it was unambiguously verified that readout integrated circuit (ROIC) glow was responsible for most of the false event rate (FER) of the 2010 array. The application of a single layer metal blocking layer between the ROIC and the detector array and optimization of the ROIC biases reduced the FER by an order of magnitude. Photon detection efficiencies (PDEs) of greater than 50% were routinely demonstrated across 5 arrays, with one array reaching a PDE of 70%. High resolution pixel-surface spot scans were performed and the junction diameters of the diodes were measured. The junction diameter was decreased from 31 μm to 25 μm resulting in a 2x increase in E-APD gain from 470 on the 2010 array to 1100 on one of the 2013 FPAs. Mean single photon signal to noise ratios of >12 were demonstrated at excess noise factors of 1.2-1.3. NASA Goddard Space Flight Center (GSFC) performed measurements on the delivered FPA that verified the PDE and FER data.

  14. CdTe Timepix detectors for single-photon spectroscopy and linear polarimetry of high-flux hard x-ray radiation

    Science.gov (United States)

    Hahn, C.; Weber, G.; Märtin, R.; Höfer, S.; Kämpfer, T.; Stöhlker, Th.

    2016-04-01

    Single-photon spectroscopy of pulsed, high-intensity sources of hard X-rays — such as laser-generated plasmas — is often hampered by the pileup of several photons absorbed by the unsegmented, large-volume sensors routinely used for the detection of high-energy radiation. Detectors based on the Timepix chip, with a segmentation pitch of 55 μm and the possibility to be equipped with high-Z sensor chips, constitute an attractive alternative to commonly used passive solutions such as image plates. In this report, we present energy calibration and characterization measurements of such devices. The achievable energy resolution is comparable to that of scintillators for γ spectroscopy. Moreover, we also introduce a simple two-detector Compton polarimeter setup with a polarimeter quality of (98 ± 1)%. Finally, a proof-of-principle polarimetry experiment is discussed, where we studied the linear polarization of bremsstrahlung emitted by a laser-driven plasma and found an indication of the X-ray polarization direction depending on the polarization state of the incident laser pulse.

  15. CdTe Timepix detectors for single-photon spectroscopy and linear polarimetry of high-flux hard x-ray radiation.

    Science.gov (United States)

    Hahn, C; Weber, G; Märtin, R; Höfer, S; Kämpfer, T; Stöhlker, Th

    2016-04-01

    Single-photon spectroscopy of pulsed, high-intensity sources of hard X-rays - such as laser-generated plasmas - is often hampered by the pileup of several photons absorbed by the unsegmented, large-volume sensors routinely used for the detection of high-energy radiation. Detectors based on the Timepix chip, with a segmentation pitch of 55 μm and the possibility to be equipped with high-Z sensor chips, constitute an attractive alternative to commonly used passive solutions such as image plates. In this report, we present energy calibration and characterization measurements of such devices. The achievable energy resolution is comparable to that of scintillators for γ spectroscopy. Moreover, we also introduce a simple two-detector Compton polarimeter setup with a polarimeter quality of (98 ± 1)%. Finally, a proof-of-principle polarimetry experiment is discussed, where we studied the linear polarization of bremsstrahlung emitted by a laser-driven plasma and found an indication of the X-ray polarization direction depending on the polarization state of the incident laser pulse. PMID:27131653

  16. Shift of the Acoustic Center of a Closed-Box Loudspeaker in a Linear Array: Investigation Using the Beamforming Technique

    DEFF Research Database (Denmark)

    Chang, Ji-Ho; Jensen, Joe; Agerkvist, Finn T.

    2015-01-01

    loudspeaker case. In order to estimate the acoustic center based on the wave fronts, a method is proposed that measures sound pressure around the loudspeaker with an array of microphones and uses the beamforming method for the reduction of the effect of the experimental errors. Experimental results show......The center of the spherical waves radiated from a loudspeaker is defined as its acoustic center. This study aims to investigate how the acoustic center of a closed-box loudspeaker is shifted when the loudspeaker is placed in a linear array. That is, the acoustic center of the loudspeaker...

  17. High linearity SPAD and TDC array for TCSPC and 3D ranging applications

    Science.gov (United States)

    Villa, Federica; Lussana, Rudi; Bronzi, Danilo; Dalla Mora, Alberto; Contini, Davide; Tisa, Simone; Tosi, Alberto; Zappa, Franco

    2015-01-01

    An array of 32x32 Single-Photon Avalanche-Diodes (SPADs) and Time-to-Digital Converters (TDCs) has been fabricated in a 0.35 μm automotive-certified CMOS technology. The overall dimension of the chip is 9x9 mm2. Each pixel is able to detect photons in the 300 nm - 900 nm wavelength range with a fill-factor of 3.14% and either to count them or to time stamp their arrival time. In photon-counting mode an in-pixel 6-bit counter provides photon-numberresolved intensity movies at 100 kfps, whereas in photon-timing mode the 10-bit in-pixel TDC provides time-resolved maps (Time-Correlated Single-Photon Counting measurements) or 3D depth-resolved (through direct time-of-flight technique) images and movies, with 312 ps resolution. The photodetector is a 30 μm diameter SPAD with low Dark Count Rate (120 cps at room temperature, 3% hot-pixels) and 55% peak Photon Detection Efficiency (PDE) at 450 nm. The TDC has a 6-bit counter and a 4-bit fine interpolator, based on a Delay Locked Loop (DLL) line, which makes the TDC insensitive to process, voltage, and temperature drifts. The implemented sliding-scale technique improves linearity, giving 2% LSB DNL and 10% LSB INL. The single-shot precision is 260 ps rms, comprising SPAD, TDC and driving board jitter. Both optical and electrical crosstalk among SPADs and TDCs are negligible. 2D fast movies and 3D reconstructions with centimeter resolution are reported.

  18. Evaluation of linear array human papillomavirus genotyping using automatic optical imaging software.

    Science.gov (United States)

    Jeronimo, J; Wentzensen, N; Long, R; Schiffman, M; Dunn, S T; Allen, R A; Walker, J L; Gold, M A; Zuna, R E; Sherman, M E; Wacholder, S; Wang, S S

    2008-08-01

    Variations in biological behavior suggest that each carcinogenic human papillomavirus (HPV) type should be considered individually in etiologic studies. HPV genotyping assays might have clinical applications if they are approved for use by the FDA. A widely used genotyping assay is the Roche Linear Array HPV genotyping test (LA). We used LA to genotype the HPV isolates from cervical specimens from women with the full spectrum of cervical disease: cervical cancer, cervical intraepithelial neoplasia (CIN), and HPV infections. To explore the feasibility and value of the automated reading of the LA results, we custom-designed novel, optical imaging software that provides optical density measurements of LA bands. We compared unmagnified visual examination with the automated measurements. The two measurements were highly associated. By either method, the threshold between a negative and a positive result was fairly sharp, with a clear bimodal distribution. Visually, most positive results were judged to be strong or medium, with fewer equivocal results categorized as weak (9.5% of positive samples), very weak (6.5% of positive samples), or extremely weak (7.7% of positive samples). The automated measurements of the intensities were significantly associated with the strength of the visual categories (P or = 120 units), the bands were almost always categorized visually as negative and positive, respectively. In the equivocal zone (20 to 119 units), specimens were more increasingly likely to be judged to be visually positive as the number of other, definite infections on the same strip increased (P for trend or = 25% of HPV infections; thus, any systematic visual tendency that influences their evaluation when the result is equivocal should be minimized. Therefore, automated reading is probably worth development if easy-to-calibrate hardware and software can be optimized. PMID:18550741

  19. Comparative Study on Synthesizing Reconfigurable Time- Modulated Linear Arrays using Differential Evolution, Artificial Bee Colony and Particle Swarm Optimization

    Science.gov (United States)

    Mandal, S. K.; Singh, Harshavardhan; Mahanti, G. K.; Ghatak, Rowdra

    2014-10-01

    This paper presents a new technique based on optimization tools to design phase only, digitally controlled, reconfigurable antenna arrays through time modulation. In the proposed approach, the on-time durations of the time-modulated elements and the static amplitudes of the array elements are perturbed in such a way that the same on-time sequence and discrete values of static amplitudes for four bit digital attenuators produces either a pencil or a flat-top beam pattern, depending on the suitable discrete phase distributions of five bit digital phase shifters. In order to illustrate the technique, three optimization tools: differential evolution (DE), artificial bee colony (ABC), and particle swarm optimization (PSO) are employed and their performances are compared. The numerical results for a 20-element linear array are presented.

  20. Thermal-Independent Properties of PIN-PMN-PT Single-Crystal Linear-Array Ultrasonic Transducers

    OpenAIRE

    Chen, Ruimin; Wu, Jinchuan; Lam, Kwok Ho; Yao, Liheng; Zhou, Qifa; Tian, Jian; Han, Pengdi; Shung, K. Kirk

    2012-01-01

    In this paper, low-frequency 32-element linear-array ultrasonic transducers were designed and fabricated using both ternary Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 (PIN-PMN-PT) and binary Pb(Mg1/3Nb2/3)–PbTiO3 (PMN-PT) single crystals. Performance of the array transducers was characterized as a function of temperature ranging from room temperature to 160°C. It was found that the array transducers fabricated using the PIN-PMN-PT single crystal were capable of satisfactory performance at 160°C, ha...

  1. A new method of linear control for optimum transfer of power from a solar cell array to the distribution network

    Science.gov (United States)

    Ray, G. C.; Jha, R.

    1984-08-01

    The paper describes a new method of linear control for transfer of optimum power from a Solar Cell Array (SCA) to the distribution network. It is shown that the current corresponding to the optimum power varies almost linearly with the level of illumination. By connecting a storage battery in parallel to the SCA, the charging current to the battery is continuously adjusted by sensing the ilumination level and current simultaneously. Variation of the charging current keeps the operating point on the optimum power locus. In the ac distribution network the power is to be fed through a current-source inverter and a step up/down transformer.

  2. High efficiency pixellated CdTe detector

    International Nuclear Information System (INIS)

    Position sensitive detectors constructed from compound semiconductors (CdTe, CdZnTe, HgI2) are being developed for a variety of applications where high sensitivity and improved energy resolution are significant advantages over scintillator or gas based systems. We have investigated the possibility of using a CdTe detector array in a SPECT gamma camera that would require a high efficiency at 140 keV. The problem of worsening photopeak efficiencies in thick detectors (due to incomplete charge collection) makes it difficult to maintain a high efficiency which, ironically, is the primary reason for choosing a thicker detector. Recent research has shown that following a simple geometrical design criterion can greatly reduce this deleterious effect. This paper reports on the results from a small prototype pixellated array fabricated using this design. We verify the 'small pixel effect' for a detector thickness and pixel size significantly larger than those used in most other work. A 9-element detector (1 x 1 mm pixels, 4 mm thick) has been fabricated and characterized in terms of energy resolution, peak-to-valley ratio and detection efficiency. Testing of the detector in a fast pulse mode to obtain its high count rate response has also been performed. (orig.)

  3. Designing Adaptive Linear Array Antenna to Achieve Pattern Steering Optimization by Phase-Amplitude Perturbations Using Genetic Algorithms

    Institute of Scientific and Technical Information of China (English)

    HSUChaohsing; CHENTsongyi; PanJengshyang

    2005-01-01

    In this paper, a phase-amplitude perturbation method of an adaptive array factor based on the genetic algorithm is proposed. The design for an optimal beam pattern of an adaptive antenna is able to not only suppress interference by placing nulls at the directions of the interfering sources but also provide a maximized main lobe in the direction of the desired signal, i.e., to maximizethe Signal interference ratio (SIR). In order to achieve this goal, a kind of new convergent skill called the two-way convergent method for genetic algorithms is proposed. The phase-amplitude perturbation method is applied to realize the optimal beam pattern of an adaptively linear array antenna. The Genetic algorithms are applied to find the optimal phase-amplitude weighting vector of adaptive array factor. An optimal beam pattern of linear array is derived by phase-amplitude perturbations using a genetic algorithm. Computer simulation result is given to demonstrate the effectiveness of the proposed method.

  4. Linear array of conserved sequence motifs to discriminate protein subfamilies: study on pyridine nucleotide-disulfide reductases

    Directory of Open Access Journals (Sweden)

    De Las Rivas Javier

    2007-03-01

    Full Text Available Abstract Background The pyridine nucleotide disulfide reductase (PNDR is a large and heterogeneous protein family divided into two classes (I and II, which reflect the divergent evolution of its characteristic disulfide redox active site. However, not all the PNDR members fit into these categories and this suggests the need of further studies to achieve a more comprehensive classification of this complex family. Results A workflow to improve the clusterization of protein families based on the array of linear conserved motifs is designed. The method is applied to the PNDR large family finding two main groups, which correspond to PNDR classes I and II. However, two other separate protein clusters, previously classified as class I in most databases, are outgrouped: the peroxide reductases (NAOX, NAPE and the type II NADH dehydrogenases (NDH-2. In this way, two novel PNDR classes III and IV for NAOX/NAPE and NDH-2 respectively are proposed. By knowledge-driven biochemical and functional data analyses done on the new class IV, a linear array of motifs putatively related to Cu(II-reductase activity is detected in a specific subset of NDH-2. Conclusion The results presented are a novel contribution to the classification of the complex and large PNDR protein family, supporting its reclusterization into four classes. The linear array of motifs detected within the class IV PNDR subfamily could be useful as a signature for a particular subgroup of NDH-2.

  5. X-ray detection with a linear silicon photo-diode array

    Energy Technology Data Exchange (ETDEWEB)

    Zutavern, F.; Aton, T.; Franck, C; Schnatterly, S.

    1982-01-01

    A phosphor-coated silicon photo-diode array has been used as the detector in an ultra-high vacuum, soft X-ray emission spectrograph. In developing this detection system, measurements on a bare array, a phosphor coated array, and a phosphor coated photo-multiplier tube were made at the Synchrotron Ultraviolet Radiation Facility (SURF), NBS, Washington, D.C. The results of these measurements and the performance of this detection system will be discussed. These results will then be extrapolated into the X-ray energy range used by crystallographers.

  6. A High-Frequency High Frame Rate Duplex Ultrasound Linear Array Imaging System for Small Animal Imaging

    Science.gov (United States)

    Zhang, Lequan; Xu, Xiaochen; Hu, Changhong; Sun, Lei; Yen, Jesse T.; Cannata, Jonathan M.; Shung, K. Kirk

    2010-01-01

    High-frequency (HF) ultrasound imaging has been shown to be useful for non-invasively imaging anatomical structures of the eye and small animals in biological and pharmaceutical research, achieving superior spatial resolution. Cardiovascular research utilizing mice requires not only real-time B-scan imaging, but also ultrasound Doppler to evaluate both anatomy and blood flow of the mouse heart. This paper reports the development of a high frequency ultrasound duplex imaging system capable of both B-mode imaging and Doppler flow measurements, using a 64-element linear array. The system included a HF pulsed-wave Doppler module, a 32-channel HF B-mode imaging module, a PC with a 200 MS/s 14-bit A/D card, and real-time LabView software. A 50dB signal-to-noise ratio (SNR) and a depth of penetration of larger than 12 mm were achieved using a 35 MHz linear array with 50 μm pitch. The two-way beam widths were determined to be 165 μm to 260 μm and the clutter energy to total energy ratio (CTR) were 9.1 dB to 12 dB, when the array was electronically focused at different focal points at depths from 4.8 mm to 9.6 mm. The system is capable of acquiring real-time B-mode images at a rate greater than 400 frames per second (fps) for a 4.8 × 13 mm field of view, using a 30 MHz 64-element linear array with 100 μm pitch. Sample in vivo cardiac high frame rate images and duplex images of mouse hearts are shown to assess its current imaging capability and performance for small animals. PMID:20639149

  7. Visible and infrared linear detector arrays for the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

    International Nuclear Information System (INIS)

    The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument uses four separate focal plane assemblies consisting of line array detectors that are multiplexed to a common J-FET preamp using a FET switch multiplexing (MUX) technique. A 32-element silicon line array covers the spectral range from 0.41 to 0.70 microns. Three additional 64-element indium antimonide (InSb) line arrays cover the spectral range from 0.68 to 2.45 microns. The spectral sampling interval per detector element is nominally 9.8 nm, giving a total of 224 spectral channels. All focal planes operate at liquid nitrogen temperature and are housed in separate dewars. Electrical performance characteristics include a read noise of less than 1000 e(-) in all channels, response and dark nonuniformity of 5 percent peak to peak, and quantum efficiency of greater than 60 percent

  8. Study on data acquisition circuit used in SSPA linear array detector X-ray detection

    CERN Document Server

    Wei Biao; Che Zhen Ping

    2002-01-01

    After SSPA used as X-ray array detector is developed, the authors take a research on the data acquisition circuit applied to the detector. The experiment designed has verified the feasibility of application of this array detector and its data acquisition circuit to X-ray computed tomography (X-CT). The preliminary test results indicate that the method of the X-ray detection is feasible for industry X-CT nondestructive testing, which brings about advantage for detecting and measuring with high resolution, good efficiency and low cost

  9. Cross-correlation, triangulation, and curved-wavefront focusing of coral reef sound using a bi-linear hydrophone array.

    Science.gov (United States)

    Freeman, Simon E; Buckingham, Michael J; Freeman, Lauren A; Lammers, Marc O; D'Spain, Gerald L

    2015-01-01

    A seven element, bi-linear hydrophone array was deployed over a coral reef in the Papahãnaumokuãkea Marine National Monument, Northwest Hawaiian Islands, in order to investigate the spatial, temporal, and spectral properties of biological sound in an environment free of anthropogenic influences. Local biological sound sources, including snapping shrimp and other organisms, produced curved-wavefront acoustic arrivals at the array, allowing source location via focusing to be performed over an area of 1600 m(2). Initially, however, a rough estimate of source location was obtained from triangulation of pair-wise cross-correlations of the sound. Refinements to these initial source locations, and source frequency information, were then obtained using two techniques, conventional and adaptive focusing. It was found that most of the sources were situated on or inside the reef structure itself, rather than over adjacent sandy areas. Snapping-shrimp-like sounds, all with similar spectral characteristics, originated from individual sources predominantly in one area to the east of the array. To the west, the spectral and spatial distributions of the sources were more varied, suggesting the presence of a multitude of heterogeneous biological processes. In addition to the biological sounds, some low-frequency noise due to distant breaking waves was received from end-fire north of the array.

  10. High-resolution dynamic CT scanner based on a variable-zoom XRII and a linear photodiode array

    Science.gov (United States)

    Drangova, Maria; Holdsworth, David W.; Fenster, Aaron

    1993-09-01

    We have developed a CT scanner with high temporal and spatial resolution which can be used to acquire dynamic images of objects undergoing periodic motion. Our system comprises of an x-ray image intensifier (XRII) optically coupled to a linear photo-diode array (PDA) camera. The XRII has been modified to vary electronically the magnification of the image continuously over fields-of-view (FOV) ranging between 8 and 24 cm, and thus increasing the resolution from 1.4 mm-1 to 3.8 mm-1. In this way, we can select a magnification which maximizes the image resolution for a given object.

  11. Lock-in thermo-electric detector arrays: thermal cross-talk prediction by non-linear model

    OpenAIRE

    Vandermeiren, W; Stiens, J; G. Shkerdin; De Tandt, C; R. Vounckx

    2011-01-01

    Abstract A non-linear numerical finite element method (FEM) model of a thermo-electric focal plane array (FPA) detector is presented here. Laser induced thermo-voltage profiles tend to spread out for small lock-in frequencies as the thermal diffusion length is inversely proportional to the square-root of the lock-in frequency. This leads to a frequency and spatial dependent thermal cross-talk level. In this paper we investigate the thermal cross-talk level quantitatively in function of spa...

  12. Comparison of analytical and clinical performance of CLART HPV2 genotyping assay to Linear Array and Hybrid Capture 2

    DEFF Research Database (Denmark)

    Ejegod, Ditte Møller; Rebolj, Matejka; Bonde, Jesper

    2015-01-01

    BACKGROUND: Human Papillomavirus (HPV) genotyping has an increasingly important role in cervical cancer screening and vaccination monitoring, however, without an internationally agreed standard reference assay. The test results from the most widely used genotyping assays are read manually and hence...... prone to inter-observer variability. The reading of test results on the CLART HPV2 genotyping assay is, on the other hand, automated. The aim of our study was to directly compare the detection of HPV genotypes and high-grade cervical intraepithelial neoplasia (CIN) by CLART, Linear Array (LA...

  13. Performance of parallel linear algebra algorithms on an interleaved array processor

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, G.

    1986-01-01

    This thesis investigates the performance of numerical algorithms that take advantage of the unique properties of a new type of array processor. This processor, called an Interleaved Array Processor (IAP), is characterized by its ability to use multiple Programmable Functional Units (PFU's) with local data and instruction memories. Unlike conventional array processors, which can only execute simple arithmetic vector operations such as addition and multiplication, the IAP can execute complex vector operations defined by the user. These operations are specified by small programs that can contain conditional branching as well as arithmetic and data movement instructions in each processor. The author calls these programs High-Level Vector Operations (HLVO's). Ways to partition the algorithms and the data among the processing units in the system are presented so that in such a way that the computation time in every processing unit is increased, and at the same time the data movement on the system bus, is reduced. In this way the bus can be timeshared among several functional units, allowing several operations on different vector components to be executed simultaneously and overlapped with the transfer of operands and results.

  14. 最小冗余线阵的DOA估计%A Study on DOA Estimation of Minimum-Redundancy Linear Arrays

    Institute of Scientific and Technical Information of China (English)

    张利强; 全厚德

    2012-01-01

    波达方向(DOA)估计是智能天线技术研究热点之一.研究了最小冗余线阵的DOA估计问题.通过引入阵列冗余度,对非均匀线阵的阵元配置进行研究,在对MUSIC算法进行分析的基础上,利用Matlab对最小冗余线阵的DOA性能进行仿真,通过与均匀线阵进行对比,结果表明,在相同阵元数目的前提下,最小冗余线阵获得了较高的空间谱分辨力和较低的估计均方误差,提高了DOA估计性能.%DOA estimation is a heat point in the smart antenna technology research. In the paper, DOA estimation based on minimum-redundancy linear arrays is researched. Array redundancy is introduced into Non-Uniformity Linear Array (NULA),and the NULA's array configure is studied. Based on the analysis of MUSIC arithmetic, the DOA performance of minimum-redundancy linear arrays is simulated by using Matlab. The DOA performance of minimum-redundancy linear arrays with that of ULA(Nniformity Linear Array) are compared by experiments. It is shown that, on condition of the same number arrays, minimum-redundancy linear arrays has better quality of spectrum resolution and lower estimates mean-square error, and the performance of DOA estimation is enhanced.

  15. Super non-linear RRAM with ultra-low power for 3D vertical nano-crossbar arrays.

    Science.gov (United States)

    Luo, Qing; Xu, Xiaoxin; Liu, Hongtao; Lv, Hangbing; Gong, Tiancheng; Long, Shibing; Liu, Qi; Sun, Haitao; Banerjee, Writam; Li, Ling; Gao, Jianfeng; Lu, Nianduan; Liu, Ming

    2016-08-25

    Vertical crossbar arrays provide a cost-effective approach for high density three-dimensional (3D) integration of resistive random access memory. However, an individual selector device is not allowed to be integrated with the memory cell separately. The development of V-RRAM has impeded the lack of satisfactory self-selective cells. In this study, we have developed a high performance bilayer self-selective device using HfO2 as the memory switching layer and a mixed ionic and electron conductor as the selective layer. The device exhibits high non-linearity (>10(3)) and ultra-low half-select leakage (vertical crossbar array was successfully demonstrated based on the developed self-selective device. High uniformity, ultra-low leakage, sub-nA operation, self-compliance, and excellent read/write disturbance immunity were achieved. The robust array level performance shows attractive potential for low power and high density 3D data storage applications. PMID:27510434

  16. Monte-Carlo simulation for determining SNR and DQE of linear array plastic scintillating fiber

    Institute of Scientific and Technical Information of China (English)

    Mohammad Mehdi NASSERI; MA Qing-Li; YIN Ze-Jie; WU Xiao-Yi

    2004-01-01

    Fundamental characteristics of the plastic-scintillating fiber (PSF) for wide energy range of electromagnetic radiation (X & γ) have been studied to evaluate possibility of using the PSF as an imaging detector for industrial purposes. Monte-Carlo simulation program (GEANT4.5.1, 2003) was used to generate the data. In order to evaluate image quality of the detector, fiber array was irradiated under various energy and fluxes. Signal to noise ratio (SNR)as well as detector quantum efficiency (DQE) were obtained.

  17. Mixed Linear/Square-Root Encoded Single-Slope Ramp Provides Low-Noise ADC with High Linearity for Focal Plane Arrays

    Science.gov (United States)

    Wrigley, Chris J.; Hancock, Bruce R.; Newton, Kenneth W.; Cunningham, Thomas J.

    2013-01-01

    Single-slope analog-to-digital converters (ADCs) are particularly useful for onchip digitization in focal plane arrays (FPAs) because of their inherent monotonicity, relative simplicity, and efficiency for column-parallel applications, but they are comparatively slow. Squareroot encoding can allow the number of code values to be reduced without loss of signal-to-noise ratio (SNR) by keeping the quantization noise just below the signal shot noise. This encoding can be implemented directly by using a quadratic ramp. The reduction in the number of code values can substantially increase the quantization speed. However, in an FPA, the fixed pattern noise (FPN) limits the use of small quantization steps at low signal levels. If the zero-point is adjusted so that the lowest column is onscale, the other columns, including those at the center of the distribution, will be pushed up the ramp where the quantization noise is higher. Additionally, the finite frequency response of the ramp buffer amplifier and the comparator distort the shape of the ramp, so that the effective ramp value at the time the comparator trips differs from the intended value, resulting in errors. Allowing increased settling time decreases the quantization speed, while increasing the bandwidth increases the noise. The FPN problem is solved by breaking the ramp into two portions, with some fraction of the available code values allocated to a linear ramp and the remainder to a quadratic ramp. To avoid large transients, both the value and the slope of the linear and quadratic portions should be equal where they join. The span of the linear portion must cover the minimum offset, but not necessarily the maximum, since the fraction of the pixels above the upper limit will still be correctly quantized, albeit with increased quantization noise. The required linear span, maximum signal and ratio of quantization noise to shot noise at high signal, along with the continuity requirement, determines the number of

  18. A linear laser-driver array for optical transmission in the LHC experiments

    CERN Document Server

    Cervelli, G; Moreira, P; Vasey, F

    2000-01-01

    A 4-way linear laser driver has been designed and implemented in a commercial 0.25 mu m CMOS technology. The full-custom IC is intended for analogue and digital data transmission as part of the 50 000 optical fibre links of the CMS particle tracking system. Intrinsic radiation tolerance and specific design methodologies enable the device to operate over 10 years in the harsh radiation environment of the innermost LHC detectors. Although optimised for analogue operation the driver is compatible with LVDS digital signalling. A combination of linearization methods achieves good analogue performance (8-bit equivalent dynamic range with a bandwidth of 100 MHz), while maintaining wide input common-mode range (+or-350 mV) and limited power dissipation. The linearly amplified signal is added to a DC current, which can be set over a wide range (-60 mA to +60 mA). The latter capability allows tracking of changes in laser threshold due to ageing or radiation damage. The driver gain and bias current are set via a serial ...

  19. Effects of Spatial Characteristics on Smart Antenna System with Uniform Linear Antenna Array

    Institute of Scientific and Technical Information of China (English)

    CAO Wei-feng; WANG Wen-bo

    2005-01-01

    The effect of the spatial characteristics of antenna array on smart antenna systems can not be neglected. In the paper, the relation between spatial correlation and inter-antenna distance, impinging angle, angle spread is first investigated. With the same beamforming algorithm, we simulate the performance of smart antenna system with different Angle Spread (AS) values on the conditions of ideal and real Angle of Arrival (AOA) estimation. The results show that with the ideal AOA estimation, the AOA is enough accurate to guarantee that the system only has little performance degradation even in the case of 20 degreee AS value while the real AOA estimation influenced by channel environment degrades the performance very obviously, up to about 7 dB.

  20. CdTe quantum dots as a novel biosensor for Serratia marcescens and Lipopolysaccharide.

    Science.gov (United States)

    Ebrahim, Sh; Reda, M; Hussien, A; Zayed, D

    2015-01-01

    The main objective of this work is to synthesize CdTe quantum dots (QDs) conjugated with Concanavalin A (Con A) as a novel biosensor to be selective and specific for the detection of Lipopolysaccharide (LPS). In addition, the conjugated CdTe QDs-Con A was used as fluorescence labels to capture Serratia marcescens bacteria through the recognition between CdTe QDs-Con A and LPS of S. marcescens. The appearance of the lattice plans in the high resolution transmission electron photograph indicated a high crystalline with an average size of 4-5 nm for the CdTe QDs. The results showed that the relative fluorescence intensity of CdTe QDs-Con A decreased linearly with LPS concentration in the range from 10 to 90 fg/mL and with correlation coefficient (R(2)) equal to 0.9713. LPS surrounding the S. marcescens bacteria was bound to the CdTe QDs-Con A and leads to quenching of PL intensity. It was found that a good linear relationship between the relative PL intensity and the logarithmic of cell population of S. marcescens in range from 1×10 to 1×10(6) CFU/mL at pH 7 with R(2) of 0.952 was established.

  1. Research of thermal stress between long linear MCT arrays and lead board using FEM

    Science.gov (United States)

    Wu, Wen; Wu, Yonghong; Liu, Dafu

    2010-10-01

    For the long wavelength infrared detection, HgCdTe (MCT) photoconductive devices are selected as the core of next-generation meteorological because of its mature fabrication technique and stable performance. During the assembly process, an innovative multilayer ceramic board providing mechanical support is designed as the electrical interconnection between MCT chips and external circuits for cryogenic application. Furthermore, due to its brittleness, long linear MCT device is normally glued to sapphire substrates on the multilayer ceramic board with cryogenic glue. Thus, it can be seen clearly that the assembly structure is a multilayer configuration which comprises various kinds of materials, including ceramic broad, sapphire, MCT and glues. As a result, the difference in Thermal Expansion Coefficient (TEC) between the layers could create the potential to introduce thermal stress at working environmental temperature (approximately 70K), which could result in device performance degradation, even die crack. This article analyzes the thermal stress between long linear MCT devices and a multilayer ceramic board by using Finite Element Method (FEM). According to analysis results, two factors are revealed as the most significant causes for introducing thermal stress: one is the sapphire substrate thickness; the other is the parameters of various materials, for instance Yong's modulus and TEC. Since the structure of MCT detector is determined by system requirements and is under the limitation of manufacture technology, this article reveals two effective approaches to reduce the unavoidable thermal stress: first, choosing the appropriate thickness of ceramic board which is made by Al2O3; second, adding another metal cushion Invar. With the above considerations, the distribution of thermal stress is simulated using FEM under different parameter conditions. Based on the results of simulations, an optimal design of package structure which could improve the reliability of

  2. Structural and optical characterization of CdTe quantum dots thin films

    International Nuclear Information System (INIS)

    Highlights: • CdTe QDs are prepared by hot injection method. • Thermally evaporated CdTeQDs thin films were prepared. • Structural characterization and analysis were done. • Optical parameters were studied. - Abstract: Cadmium telluride quantum dots (CdTe QDs) have been synthesized using hot-injection chemical technique. The CdTe QDs thin films were deposited onto optical flat fused quartz substrates using thermal evaporation technique. The CdTe QDs powder and the as deposited films were characterized using X-ray diffraction and high resolution transmission electron microscope (HRTEM). The X-ray analysis shows that both CdTe QDs powder and the as deposited films crystallize in cubic zinc-blende type structure with lattice parameter 6.46 Å and 6.45 Å, respectively. The X-ray calculation shows that the average crystallite size of the as deposited CdTe QDs films varied from 1.1 nm for the powder to 2.3 nm for the thin film. The HRTEM examination of the as deposited films shows that the average particle size vary from 2.5 nm for the powder to 2.7 nm for the thin film. For the as deposited films, the dependence of (αhν)2 on the incident photon energy indicates that the optical transitions within the film are allowed direct with energies observed at Eg1≅2eV and Eg2≅2.3eV which attributed to quantum confinement effect. The optical band gap increases from 1.5 eV for microstructure CdTe to 2 eV for nanostructure quantum dots which corresponding to wavelength(620 nm) so it is a great benefit to use CdTe quantum dots as solar harvesting devices application in solar spectrum region (400–800 nm). Urbach energy is calculated and found to be 360 meV which is higher than microstructure CdTe. The refractive index and refractive index dispersion of the as deposited CdTe QDs film has been calculated from transmission and reflection spectra. It has been found that the refractive index is reduced from (2.66) for microstructure CdTe to be (1.7) for CdTe quantum dots

  3. A Versatile Multiple Target Detection System Based on DNA Nano-assembled Linear FRET Arrays.

    Science.gov (United States)

    Li, Yansheng; Du, Hongwu; Wang, Wenqian; Zhang, Peixun; Xu, Liping; Wen, Yongqiang; Zhang, Xueji

    2016-05-27

    DNA molecules have been utilized both as powerful synthetic building blocks to create nanoscale architectures and as inconstant programmable templates for assembly of biosensors. In this paper, a versatile, scalable and multiplex detection system is reported based on an extending fluorescent resonance energy transfer (FRET) cascades on a linear DNA assemblies. Seven combinations of three kinds of targets are successfully detected through the changes of fluorescence spectra because of the three-steps FRET or non-FRET continuity mechanisms. This nano-assembled FRET-based nanowire is extremely significant for the development of rapid, simple and sensitive detection system. The method used here could be extended to a general platform for multiplex detection through more-step FRET process.

  4. Implementation of Shor's Algorithm on a Linear Nearest Neighbour Qubit Array

    CERN Document Server

    Fowler, A G; Hollenberg, L C L; Fowler, Austin G.; Devitt, Simon J.; Hollenberg, Lloyd C. L.

    2004-01-01

    Shor's algorithm, which given appropriate hardware can factorise an integer $N$ in a time polynomial in its binary length $L$, has arguable spurred the race to build a practical quantum computer. Several different quantum circuits implementing Shor's algorithm have been designed, but each tacitly assumes that arbitrary pairs of qubits within the computer can be interacted. While some quantum computer architectures possess this property, many promising proposals are best suited to realising a single line of qubits with nearest neighbour interactions only. In light of this, we present a circuit implementing Shor's factorisation algorithm designed for such a linear nearest neighbour architecture. Despite the interaction restrictions, the circuit requires just $2L+4$ qubits and to first order requires $8L^{4}$ gates arranged in a circuit of depth $32L^{3}$ -- identical to first order to that possible using an architecture that can interact arbitrary pairs of qubits.

  5. A Low Velocity Zone along the Chaochou Fault in Southern Taiwan: Seismic Image Revealed by a Linear Seismic Array

    Directory of Open Access Journals (Sweden)

    Hsin-Chieh Pu

    2010-01-01

    Full Text Available The Chaochou fault is one of the major boundary faults in southern Taiwan where strong convergence has taken place between the Eurasian and Philippine Sea plates. The surface fault trace between the Pingtung plain and the Central Range follows a nearly N-S direction and stretches to 80 km in length. In order to examine the subsurface structures along the Chaochou fault, a linear seismic array with 14 short-period stations was deployed across the fault to record seismic data between August and December 2001. Detailed examination of seismic data generated by 10 local earthquakes and recorded by the linear array has shown that the incidence angles of the first P-waves recorded by several seismic stations at the fault zone were significantly larger than those located farther away from the fault zone. This difference might reflect the lateral variation of velocity structures across the Chaochou fault. Further examination of ray-paths of seismic wave propagation indicates that a low-velocity zone along the Chaochou fault is needed to explain the significant change in incidence angles across the fault zone. Although we do not have adequate information to calculate the exact geometry of the fault zone well, the variation in incidence angles across the fault can be explained by the existence of a low-velocity zone that is about 3 km in width on the surface and extends downward to a depth of 5 km. The low-velocity zone along the Chaochou fault might imply that the fault system consists of several splay faults on the hanging wall in the Central Range.

  6. Evaluation of linear array MOSFET detectors for in vivo dosimetry to measure rectal dose in HDR brachytherapy.

    Science.gov (United States)

    Haughey, Aisling; Coalter, George; Mugabe, Koki

    2011-09-01

    The study aimed to assess the suitability of linear array metal oxide semiconductor field effect transistor detectors (MOSFETs) as in vivo dosimeters to measure rectal dose in high dose rate brachytherapy treatments. The MOSFET arrays were calibrated with an Ir192 source and phantom measurements were performed to check agreement with the treatment planning system. The angular dependence, linearity and constancy of the detectors were evaluated. For in vivo measurements two sites were investigated, transperineal needle implants for prostate cancer and Fletcher suites for cervical cancer. The MOSFETs were inserted into the patients' rectum in theatre inside a modified flatus tube. The patients were then CT scanned for treatment planning. Measured rectal doses during treatment were compared with point dose measurements predicted by the TPS. The MOSFETs were found to require individual calibration factors. The calibration was found to drift by approximately 1% ±0.8 per 500 mV accumulated and varies with distance from source due to energy dependence. In vivo results for prostate patients found only 33% of measured doses agreed with the TPS within ±10%. For cervix cases 42% of measured doses agreed with the TPS within ±10%, however of those not agreeing variations of up to 70% were observed. One of the most limiting factors in this study was found to be the inability to prevent the MOSFET moving internally between the time of CT and treatment. Due to the many uncertainties associated with MOSFETs including calibration drift, angular dependence and the inability to know their exact position at the time of treatment, we consider them to be unsuitable for in vivo dosimetry in rectum for HDR brachytherapy. PMID:21710233

  7. Real time image synthesis on a SIMD linear array processor: algorithms and architectures

    International Nuclear Information System (INIS)

    Nowadays, image synthesis has become a widely used technique. The impressive computing power required for real time applications necessitates the use of parallel architectures. In this context, we evaluate an SIMD linear parallel architecture, SYMPATI2, dedicated to image processing. The objective of this study is to propose a cost-effective graphics accelerator relying on SYMPATI2's modular and programmable structure. The parallelization of basic image synthesis algorithms on SYMPATI2 enables us to determine its limits in this application field. These limits lead us to evaluate a new structure with a fast intercommunication network between processors, but processors have to support the message consistency, which brings about a strong decrease in performance. To solve this problem, we suggest a simple network whose access priorities are represented by tokens. The simulations of this new architecture indicate that the SIMD mode causes a drastic cut in parallelism. To cope with this drawback, we propose a context switching procedure which reduces the SIMD rigidity and increases the parallelism rate significantly. Then, the graphics accelerator we propose is compared with existing graphics workstations. This comparison indicates that our structure, which is able to accelerate both image synthesis and image processing, is competitive and well-suited for multimedia applications. (author)

  8. CdTe devices and method of manufacturing same

    Science.gov (United States)

    Gessert, Timothy A.; Noufi, Rommel; Dhere, Ramesh G.; Albin, David S.; Barnes, Teresa; Burst, James; Duenow, Joel N.; Reese, Matthew

    2015-09-29

    A method of producing polycrystalline CdTe materials and devices that incorporate the polycrystalline CdTe materials are provided. In particular, a method of producing polycrystalline p-doped CdTe thin films for use in CdTe solar cells in which the CdTe thin films possess enhanced acceptor densities and minority carrier lifetimes, resulting in enhanced efficiency of the solar cells containing the CdTe material are provided.

  9. Design of a 5-MA 100-ns linear-transformer-driver accelerator for wire array Z-pinch experiments

    Science.gov (United States)

    Zhou, Lin; Li, Zhenghong; Wang, Zhen; Liang, Chuan; Li, Mingjia; Qi, Jianmin; Chu, Yanyun

    2016-03-01

    The linear-transformer-driver (LTD) is a recently developed pulsed-power technology that shows great promise for a number of applications. These include a Z -pinch-driven fission-fusion-hybrid reactor that is being developed by the Chinese Academy of Engineering Physics. In support of the reactor development effort, we are planning to build an LTD-based accelerator that is optimized for driving wire-array Z -pinch loads. The accelerator comprises six modules in parallel, each of which has eight series 0.8-MA LTD cavities in a voltage-adder configuration. Vacuum transmission lines are used from the interior of the adder to the central vacuum chamber where the load is placed. Thus the traditional stack-flashover problem is eliminated. The machine is 3.2 m tall and 12 m in outer diameter including supports. A prototype cavity was built and tested for more than 6000 shots intermittently at a repetition rate of 0.1 Hz. A novel trigger, in which only one input trigger pulse is needed by utilizing an internal trigger brick, was developed and successfully verified in these shots. A full circuit modeling was conducted for the accelerator. The simulation result shows that a current pulse rising to 5.2 MA in 91 ns (10%-90%) can be delivered to the wire-array load, which is 1.5 cm in height, 1.2 cm in initial radius, and 1 mg in mass. The maximum implosion velocity of the load is 32 cm /μ s when compressed to 0.1 of the initial radius. The maximum kinetic energy is 78 kJ, which is 11.7% of the electric energy stored in the capacitors. This accelerator is supposed to enable a radiation energy efficiency of 20%-30%, providing a high efficient facility for research on the fast Z pinch and technologies for repetition-rate-operated accelerators.

  10. Evaluation of Compton gamma camera prototype based on pixelated CdTe detectors

    OpenAIRE

    Calderón, Y.; Chmeissani, M.; Kolstein, M.; De Lorenzo, G.

    2014-01-01

    A proposed Compton camera prototype based on pixelated CdTe is simulated and evaluated in order to establish its feasibility and expected performance in real laboratory tests. The system is based on module units containing a 2×4 array of square CdTe detectors of 10×10 mm2 area and 2 mm thickness. The detectors are pixelated and stacked forming a 3D detector with voxel sizes of 2 × 1 × 2 mm3. The camera performance is simulated with Geant4-based Architecture for Medicine-Oriented Simulations(G...

  11. An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator

    Directory of Open Access Journals (Sweden)

    Maria Calado

    2012-06-01

    Full Text Available This paper proposes a distributed system for analysis and monitoring (DSAM of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs. The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications.

  12. An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance Actuator

    Science.gov (United States)

    Salvado, José; Espírito-Santo, António; Calado, Maria

    2012-01-01

    This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications. PMID:22969364

  13. An intelligent sensor array distributed system for vibration analysis and acoustic noise characterization of a linear switched reluctance actuator.

    Science.gov (United States)

    Salvado, José; Espírito-Santo, António; Calado, Maria

    2012-01-01

    This paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications.

  14. Certain investigations on the reduction of side lobe level of an uniform linear antenna array using biogeography based optimization technique with sinusoidal migration model and simplified-BBO

    Indian Academy of Sciences (India)

    T S Jeyali Laseetha; R Sukanesh

    2014-02-01

    In this paper, we propose biogeography based optimization technique, with linear and sinusoidal migration models and simplified biogeography based optimization (S-BBO), for uniformly spaced linear antenna array synthesis to maximize the reduction of side lobe level (SLL). This paper explores biogeography theory. It generalizes two migration models in BBO namely, linear migration model and sinusoidal migration model. The performance of SLL reduction in ULA is investigated. Our performance study shows that among the two, sinusoidal migration model is a promising candidate for optimization. In our work, simplified – BBO algorithmis also deployed. This determines an optimum set value for amplitude excitations of antenna array elements that generate a radiation pattern with maximum side lobe level reduction. Our detailed investigation also shows that sinusoidal migration model of BBO performs better compared to the other evolutionary algorithms discussed in this paper.

  15. Manufacturing of CSS CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Bonnet, D. [ANTEC Solar GmbH, Rudisleben (Germany)

    2000-02-21

    Due to its basic physical and chemical properties CdTe has become a favoured base material for thin film solar cells, using robust, high-throughput manufacturing procedures. The technology shows significant potential for attaining cost levels of <0.5 Euro/W{sub p}. Close-spaced sublimation (CSS) is the fastest and simplest deposition process for both semiconductors used, CdTe and CdS, permitting in-line production at a high linear speed of about 1 m/min. The individual manufacturing steps for integrated modules are explained in view of their incorporation into the production line. ANTEC solar GmbH is engaged to enter the production of CdTe thin film modules on a scale of 10 MW{sub p} (100000 m{sup 2}) per annum, using CSS as the deposition procedure for the semiconductor films, and high-rate in-line sputtering for transparent and opaque contacts. Standard module size will be 60 x 120 cm{sup 2}. The production line is presently under construction. (orig.)

  16. Feasibility of Concurrent Treatment with the Scanning Ultrasound Reflector Linear Array System (SURLAS) and the Helical Tomotherapy System

    Science.gov (United States)

    Peñagarícano, José A.; Moros, Eduardo; Novák, Petr; Yan, Yulong; Corry, Peter

    2010-01-01

    Purpose To evaluate the feasibility of concurrent treatment with the Scanning Ultrasound Reflector Linear Array System (SURLAS) and helical tomotherapy (HT) intensity modulated radiation therapy (IMRT). Methods The SURLAS was placed on a RANDO phantom simulating a patient with superficial or deep recurrent breast cancer. A Megavoltage CT (MVCT) of the phantom with and without the SURLAS was obtained in the HT system. MVCT images with the SURLAS were obtained for two configurations: i) with the SURLAS' long axis parallel and ii) perpendicular to the longitudinal axis of the phantom. The MVCT simulation data set was then transferred to a radiation therapy planning station. Organs at risk (OAR) were contoured including the lungs, heart, abdomen and spinal cord. The metallic parts of the SURLAS were contoured as well and constraints were assigned to completely or directionally block radiation through them. The MVCT-simulation data set and regions of interest (ROI) files were subsequently transferred to the HT planning station. Several HT plans were obtained with optimization parameters that are usually used in the clinic. For comparison purposes, planning was also performed without the SURLAS on the phantom. Results All plans with the SURLAS on the phantom showed adequate dose covering 95% of the planning target volume (PTV D95%), average dose and coefficient of variation of the planning target volume (PTV) dose distribution regardless of the SURLAS' orientation with respect to the RANDO phantom. Likewise, all OAR showed clinically acceptable dose values. Spatial dose distributions and dose-volume histogram (DVH) evaluation showed negligible plan degradation due to the presence of the SURLAS. Beam-on time varied depending on the selected optimization parameters. Conclusion From the perspective of the radiation dosage, concurrent treatment with the SURLAS and HT IMRT is feasible as demonstrated by the obtained clinically acceptable treatment plans. In addition, proper

  17. Coexistence of optically active radial and axial CdTe insertions in single ZnTe nanowire.

    Science.gov (United States)

    Wojnar, P; Płachta, J; Zaleszczyk, W; Kret, S; Sanchez, Ana M; Rudniewski, R; Raczkowska, K; Szymura, M; Karczewski, G; Baczewski, L T; Pietruczik, A; Wojtowicz, T; Kossut, J

    2016-03-14

    We report on the growth, cathodoluminescence and micro-photoluminescence of individual radial and axial CdTe insertions in ZnTe nanowires. In particular, the cathodoluminescence technique is used to determine the position of each emitting object inside the nanowire. It is demonstrated that depending on the CdTe deposition temperature, one can obtain an emission either from axial CdTe insertions only, or from both, radial and axial heterostructures, simultaneously. At 350 °C CdTe grows only axially, whereas at 310 °C and 290 °C, there is also significant deposition on the nanowire sidewalls resulting in radial core/shell heterostructures. The presence of Cd atoms on the sidewalls is confirmed by energy dispersive X-ray spectroscopy. Micro-photoluminescence study reveals a strong linear polarization of the emission from both types of heterostructures in the direction along the nanowire axis. PMID:26903109

  18. BSA activated CdTe quantum dot nanosensor for antimony ion detection.

    Science.gov (United States)

    Ge, Shenguang; Zhang, Congcong; Zhu, Yuanna; Yu, Jinghua; Zhang, Shuangshuang

    2010-01-01

    A novel fluorescent nanosensor for Sb(3+) determination was reported based on thioglycolic acid (TGA)-capped CdTe quantum dot (QD) nanoparticles. It was the first antimony ion sensor using QD nanoparticles in a receptor-fluorophore system. The water-soluable TGA-capped CdTe QDs were prepared through a hydrothermal route, NaHTe was used as the Te precursor for CdTe QDs synthesis. Bovine serum albumin (BSA) conjugated to TGA-capped CdTe via an amide link interacting with carboxyl of the TGA-capped CdTe. When antimony ion enters the BSA, the lone pair electrons of the nitrogen and oxygen atom become involved in the coordination, switching off the QD emission and a dramatic quenching of the fluorescence intensity results, allowing the detection of low concentrations of antimony ions. Using the operating principle, the antimony ion sensor based on QD nanoparticles showed a very good linearity in the range 0.10-22.0 microg L(-1), with the detection limit lower than 2.94 x 10(-8) g L(-1) and the relative standard deviation (RSD) 2.54% (n = 6). In a study of interferences, the antimony-sensitive TGA-QD-BSA sensor showed good selectivity. Therefore, a simple, fast, sensitive, and highly selective assay for antimony has been built. The presented method has been applied successfully to the determination of antimony in real water samples (n = 6) with satisfactory results.

  19. Quantitative determination of uric acid using CdTe nanoparticles as fluorescence probes.

    Science.gov (United States)

    Jin, Dongri; Seo, Min-Ho; Huy, Bui The; Pham, Quoc-Thai; Conte, Maxwell L; Thangadurai, Daniel; Lee, Yong-Ill

    2016-03-15

    A convenient enzymatic optical method for uric acid detection was developed based on the fluorescence quenching of ligand-capped CdTe nanoparticles by H2O2 which was generated from the enzymatic reaction of uric acid. The interactions between the CdTe nanoparticles capped with different ligands (glutathione, 3-mercaptopropionic acid, and thioglycerol) and H2O2 were investigated. The fluorescence quenching studies of GSH-capped CdTe nanoparticles demonstrated an excellent sensitivity to H2O2. The effects of uric acid, uricase and H2O2 on the fluorescence intensity of CdTe nanoparticles were also explored. The detection conditions, reaction time, pH value, incubation period and the concentration of uricase and uric acid were optimized. The detection limit of uric acid was found to be 0.10 µM and the linear range was 0.22-6 µM under the optimized experimental conditions. These results typify that CdTe nanoparticles could be used as a fluorescent probe for uric acid detection. PMID:26433069

  20. 3D Ta/TaO x /TiO2/Ti synaptic array and linearity tuning of weight update for hardware neural network applications

    Science.gov (United States)

    Wang, I.-Ting; Chang, Chih-Cheng; Chiu, Li-Wen; Chou, Teyuh; Hou, Tuo-Hung

    2016-09-01

    The implementation of highly anticipated hardware neural networks (HNNs) hinges largely on the successful development of a low-power, high-density, and reliable analog electronic synaptic array. In this study, we demonstrate a two-layer Ta/TaO x /TiO2/Ti cross-point synaptic array that emulates the high-density three-dimensional network architecture of human brains. Excellent uniformity and reproducibility among intralayer and interlayer cells were realized. Moreover, at least 50 analog synaptic weight states could be precisely controlled with minimal drifting during a cycling endurance test of 5000 training pulses at an operating voltage of 3 V. We also propose a new state-independent bipolar-pulse-training scheme to improve the linearity of weight updates. The improved linearity considerably enhances the fault tolerance of HNNs, thus improving the training accuracy.

  1. Linear array measurements of enhanced dynamic wedge and treatment planning system (TPS) calculation for 15 MV photon beam and comparison with electronic portal imaging device (EPID) measurements

    Science.gov (United States)

    Petrovic, Borislava; Grzadziel, Aleksandra; Rutonjski, Laza; Slosarek, Krzysztof

    2010-01-01

    Introduction. Enhanced dynamic wedges (EDW) are known to increase drastically the radiation therapy treatment efficiency. This paper has the aim to compare linear array measurements of EDW with the calculations of treatment planning system (TPS) and the electronic portal imaging device (EPID) for 15 MV photon energy. Materials and methods. The range of different field sizes and wedge angles (for 15 MV photon beam) were measured by the linear chamber array CA 24 in Blue water phantom. The measurement conditions were applied to the calculations of the commercial treatment planning system XIO CMS v.4.2.0 using convolution algorithm. EPID measurements were done on EPID-focus distance of 100 cm, and beam parameters being the same as for CA24 measurements. Results Both depth doses and profiles were measured. EDW linear array measurements of profiles to XIO CMS TPS calculation differ around 0.5%. Profiles in non-wedged direction and open field profiles practically do not differ. Percentage depth doses (PDDs) for all EDW measurements show the difference of not more than 0.2%, while the open field PDD is almost the same as EDW PDD. Wedge factors for 60 deg wedge angle were also examined, and the difference is up to 4%. EPID to linear array differs up to 5%. Conclusions The implementation of EDW in radiation therapy treatments provides clinicians with an effective tool for the conformal radiotherapy treatment planning. If modelling of EDW beam in TPS is done correctly, a very good agreement between measurements and calculation is obtained, but EPID cannot be used for reference measurements. PMID:22933916

  2. Linear array measurements of enhanced dynamic wedge and treatment planning system (TPS) calculation for 15 MV photon beam and comparison with electronic portal imaging device (EPID) measurements

    International Nuclear Information System (INIS)

    Enhanced dynamic wedges (EDW) are known to increase drastically the radiation therapy treatment efficiency. This paper has the aim to compare linear array measurements of EDW with the calculations of treatment planning system (TPS) and the electronic portal imaging device (EPID) for 15 MV photon energy. The range of different field sizes and wedge angles (for 15 MV photon beam) were measured by the linear chamber array CA 24 in Blue water phantom. The measurement conditions were applied to the calculations of the commercial treatment planning system XIO CMS v.4.2.0 using convolution algorithm. EPID measurements were done on EPID-focus distance of 100 cm, and beam parameters being the same as for CA24 measurements. Both depth doses and profiles were measured. EDW linear array measurements of profiles to XIO CMS TPS calculation differ around 0.5%. Profiles in non-wedged direction and open field profiles practically do not differ. Percentage depth doses (PDDs) for all EDW measurements show the difference of not more than 0.2%, while the open field PDD is almost the same as EDW PDD. Wedge factors for 60 deg wedge angle were also examined, and the difference is up to 4%. EPID to linear array differs up to 5%. The implementation of EDW in radiation therapy treatments provides clinicians with an effective tool for the conformal radiotherapy treatment planning. If modelling of EDW beam in TPS is done correctly, a very good agreement between measurements and calculation is obtained, but EPID cannot be used for reference measurements

  3. A design for a linear array PIN photodiode for use in a Computed mammo-Tomography (CmT) system

    Energy Technology Data Exchange (ETDEWEB)

    Park, Shin-Woong [Department of Electronics and Information Engineering, Korea University, 1.5ka Anam-dong, Sungbuk-gu, Seoul 136-701 (Korea, Republic of); Yuk, Sunwoo [Department of Electronics and Control, Korea Orthopedics and Rehabilitation Engineering Center, 47-3, Gusan-dong, Bupyung-gu, Incheon 403-712 (Korea, Republic of); Park, Jung-Byung [DRGEM Corporation, 6th Floor Research Institute, Asan Medical Center, Pungnap-2dong, Songpa-gu, Seoul 138-736 (Korea, Republic of); Yi, Yun [Department of Electronics and Information Engineering, Korea University, 1.5ka Anam-dong, Sungbuk-gu, Seoul 136-701 (Korea, Republic of)], E-mail: yunyi@korea.ac.kr

    2009-10-21

    A p-i-n (PIN) photodiode has been used in a solid-state detector for X-ray detection as a photosensor of visible light from the scintillator. The most sensitive material used as low-energy X-ray detector in the mammography system is a Gd{sub 2}O{sub 2}S (GOS). As the light from GOS having a short wavelength in the range of 450-700 nm (peak at 510 nm) is absorbed within a very shallow layer near the surface of photodiode before arriving at depletion region and does not contribute to the signal. For designing the PIN photodiode, it is important to make p-layer as shallow as possible. In order to achieve shallow junction, the optimum conditions of ion implantation such as thickness of SiO{sub 2} oxide barrier, tilting angle of the wafer with respect to incident ion beam, and annealing conditions, have been determined using simulation results. The penetration depths are about 2 {mu}m for 510 nm, and 7 {mu}m for 700 nm. It is necessary for adequate depletion depth (about 10 {mu}m) to acquire the entire incident light. So far, wafers of {>=}1000 and {>=}150 {omega} cm resistivity were chosen, which offer about 15 and 6 {mu}m depletion depth, respectively. The pixel pitch of photodiode is 0.4 mmx3.0 mm and one module has 64 channels in linear array. Depth of the active p-layer is under 0.3 {mu}m in zero bias. Measured leakage currents under 10 pA/mm{sup 2} for both diodes and junction capacitances are 16 and 29 pF/mm{sup 2} in zero bias for the diodes of {>=}150 and {>=}1000 {omega} cm resistivity, respectively. The breast phantom, which was scanned by the Computed mammo-Tomography (CmT) system with two different detector modules and the data acquisition system, was developed. Little differences for distinct light absorption were shown in the three-dimensional images acquired in this study.

  4. Motion Compensation for Airborne Forward Looking Synthetic Aperture Radar with Linear Array Antennas%机载前视阵列SAR运动补偿研究

    Institute of Scientific and Technical Information of China (English)

    张英杰; 王彦平; 谭维贤; 洪文

    2013-01-01

      Combined with Frequency-Modulated Continuous-Wave (FMCW) technology, airborne forward-looking Synthetic Aperture Radar (SAR) with linear array antennas can obtain the images in front of an aircraft, while having the advantages of FMCW radar such as small size and lightweight. Moreover, it is suitable for installation on platforms such as helicopters and small unmanned aerial vehicles. In practice, motion compensation for forward-looking SAR with linear array antennas is one of the key problems to obtaining the images in front of aircraft. This paper uses linear array antennas to analyses the influence of motion error in aircraft on an echo model based on the geometry of forward looking SAR, with linear array antennas, and proposes a motion compensation scheme. Moreover, the compensation scheme is applied to an improved Frequency Scaling Algorithm (FSA) for FMCW forward looking SAR with linear array antennas. Finally, the compensation scheme is verified using simulations.%  结合调频连续波(FMCW)技术的机载前视阵列合成孔径雷达(SAR)既能够获取飞机前下方区域图像,又具有FMCW体制雷达体积小、重量轻的优势,易于安装在直升机等轻小型平台。前视阵列SAR的运动补偿是获得前视图像信息的关键问题之一。该文根据前视阵列SAR的几何模型,分析了载机平台运动误差对回波的影响,研究了相应的运动补偿方法。在此基础上,将补偿方法嵌入到一种基于FMCW的前视阵列SAR的改进频率变标算法(FSA)中。最后通过仿真实验验证了该补偿方法的有效性。

  5. Semiconductor arrays with multiplexer readout for gamma-ray imaging: results for a 48 × 48 Ge array

    Science.gov (United States)

    Barber, H. B.; Augustine, F. L.; Barrett, H. H.; Dereniak, E. L.; Matherson, K. L.; Meyers, T. J.; Perry, D. L.; Venzon, J. E.; Woolfenden, J. M.; Young, E. T.

    1994-12-01

    We are developing a new kind of gamma-ray imaging device that has sub-millimeter spatial resolution and excellent energy resolution. The device is composed of a slab of semiconductor detector partitioned into an array of detector cells by photolithography and connected to a monolithic circuit chip called a multiplexer (MUX) for readout. Our application is for an ultra-high-resolution SPECT system for functional brain imaging using an injected radiotracer. We report here on results obtained with a Hughes 48 × 48 Ge PIN-photodiode array with MUX readout, originally developed as an infrared focal-plane-array imaging sensor. The device functions as an array of individual gamma-ray detectors with minimal interpixel crosstalk. Linearity of energy response is excellent up to at least 140 keV. The array exhibits excellent energy resolution, ˜ 2 keV at ≤ 140 keV or 1.5% FWHM at 140 keV. The energy resolution is dominated by MUX readout noise and so should improve with MUX optimization for gamma-ray detection. The spatial resolution of the 48 × 48 Ge array is essentially the same as the pixel spacing, 125 μm. The quantum efficiency is limited by the thin Ge detector (0.25 mm), but this approach is readily applicable to thicker Ge detectors and room-temperature semiconductor detectors such as CdTe, HgI 2 and CdZnTe.

  6. Experimental evaluation of a-Se and CdTe flat-panel x-ray detectors for digital radiography and fluoroscopy

    Science.gov (United States)

    Adachi, Susumu; Hori, Naoyuki; Sato, Kenji; Tokuda, Satoshi; Sato, Toshiyuki; Uehara, Kazuhiro; Izumi, Yoshihiro; Nagata, Hisashi; Yoshimura, Youji; Yamada, Satoshi

    2000-04-01

    Described are two types of direct-detection flat-panel X-ray detectors utilizing amorphous selenium (a-Se) and cadmium telluride (CdTe). The a-Se detector is fabricated using direct deposition onto a thin film transistor (TFT) substrate, whereas the CdTe detector is fabricated using a novel hybrid method, in which CdTe is pre-deposited onto a glass substrate and then connected to a TFT substrate. The detector array format is 512 X 512 with a pixel pitch of 150 micrometer. The imaging properties of both detectors have been evaluated with respect to X-ray sensitivity, lag, spatial resolution, and detective quantum efficiency (DQE). The modulation transfer functions (MTFs) measured at 1 lp/mm were 0.96 for a- Se and 0.65 for CdTe. The imaging lags after 33 ms were about 4% for a-Se and 22% for CdTe. The DQE values measured at zero spatial frequency were 0.75 for a-Se and 0.22 for CdTe. The results indicate that the a-Se and CdTe detectors have high potential as new digital X-ray imaging devices for both radiography and fluoroscopy.

  7. Quantized Nanocrystalline CdTe Thin Films

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Nanocrystalline CdTe thin films were prepared by asymmetric rectangular pulse electrodeposition in organic solution at 110°C. STM image shows a porous network morphology constructed by interconnected spherical CdTe crystallites with a mean diameter of 4.2 nm. A pronounced size quantization was indicated in the action and absorption spectra. Potentials dependence dual conductive behavior was revealed in the photocurrent-potential (I-V) curves.

  8. Chlorine diffusion in CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Sadaiyandi, K.; Ramachandran, K. (School of Physics, Madurai Kamaraj Univ. (India))

    1991-06-01

    The experimental results of chlorine diffusion in CdTe reveal that the dominant mechanism for diffusion is through neutral defect pair such as (V{sub Cd}V{sub Te}){sup *}. Here, theoretical calculations are carried out for all the possible mechanisms such as single vacancy, single interstitial, neutral defect pair, and Frenkel defect pair. The results suggest that the most possible mechanism for Cl diffusion in CdTe is that through neutral defect pair, supporting the experiment. (orig.).

  9. Behaviour of reconstructed attenuation values with X-ray tube voltage in an experimental third-generation industrial CT system using Xscan linear detector array

    CERN Document Server

    Kumar, U; Pendharkar, A S; Singh, G

    2002-01-01

    The present paper discusses the adaptation of a digital radiographic scintillator-based linear detector array (LDA) in a third-generation continuous-rotate X-ray industrial tomographic imaging system. The LDA has been used in a collinear configuration. Behaviour of the reconstructed parameter, i.e., approximate linear absorption coefficient at the 'effective energy' with varying anode voltage of the constant potential X-ray tube is studied. Experiments have been carried out with a solid cylindrical Perspex block (50 mm dia.) in 50-150 kV tube voltage range. The experimentally reconstructed attenuation values were used to predict the effective energy of the X-ray beam. The present study also includes a discussion on the statistical behaviour of the reconstructed linear attenuation values.

  10. Array of Hall Effect Sensors for Linear Positioning of a Magnet Independently of Its Strength Variation. A Case Study: Monitoring Milk Yield during Milking in Goats

    Directory of Open Access Journals (Sweden)

    Cristófol Peris

    2013-06-01

    Full Text Available In this study we propose an electronic system for linear positioning of a magnet independent of its modulus, which could vary because of aging, different fabrication process, etc. The system comprises a linear array of 24 Hall Effect sensors of proportional response. The data from all sensors are subject to a pretreatment (normalization by row (position making them independent on the temporary variation of its magnetic field strength. We analyze the particular case of the individual flow in milking of goats. The multiple regression analysis allowed us to calibrate the electronic system with a percentage of explanation R2 = 99.96%. In our case, the uncertainty in the linear position of the magnet is 0.51 mm that represents 0.019 L of goat milk. The test in farm compared the results obtained by direct reading of the volume with those obtained by the proposed electronic calibrated system, achieving a percentage of explanation of 99.05%.

  11. Applications of CdTe to nuclear medicine. Annual report, February 1, 1979-January 31, 1980

    International Nuclear Information System (INIS)

    The application of CdTe gamma detectors in nuclear medicine is reported on. An internal probe was developed which can be inserted into the heart to measure the efficiency of various radiopharmaceuticals in the treatment of heart attacks. A second application is an array of detectors which is light enough to be worn by ambulatory patients and can measure the change in cardiac output over an eight hour period during heart attack treatment. The instrument includes an on board tape recorder

  12. Synthesis of Mn-modified CdTe nanoparticles and their application as fluorescence probe

    International Nuclear Information System (INIS)

    Mn-modified CdTe nanoparticles (NPs) were synthesized via a novel, facile method at low temperature. The modified NPs were directly synthesized in aqueous solution by mixing CdCl2·2.5H2O, fresh NaHTe solution, thioglycolic acid (TGA) and MnCl2·4H2O under suitable conditions. Mn-modified CdTe NPs were evaluated as fluorescence probe for bovine serum albumin (BSA) in aqueous solution. Experiment results showed that the fluorescence emission of Mn-modified CdTe NPs was enhanced significantly by BSA, while other substances exhibited no significant effect on NPs. Under the optimal conditions, the response was linearly proportional to the concentration of BSA ranging from 5.0×10−9 to 7.0×10−7 mol/L with detection limit 5.26×10−10 mol/L. Based on the distinct optical properties of Mn-modified CdTe NPs with BSA, Mn-modified CdTe NPs can be developed as a potential identified fluorescence probe for BSA in aqueous solution. -- Highlights: • Mn-modified CdTe nanoparticles were synthesized via a facile method at low temperature. • The fluorescence properties and morphology of Mn-CdTe nanoparticles were studied clearly. • Mn-CdTe nanoparticles show superior response to the bovine serum albumin molecular on the fluorescence emission. • This detection method was sensitive and provides a wide range of bovine serum albumin concentrations

  13. Diode array pumped, non-linear mirror Q-switched and mode-locked Nd : YVO4 laser – a good tool for powder SHG measurement

    Indian Academy of Sciences (India)

    P K Datta; Chandrajit Basu; S Mukhopadhyay; S K Das; G K Samanta; Antonio Agnesi

    2004-11-01

    A non-linear mirror consisting of a lithium triborate crystal and a dichroic output coupler are used to mode-lock (passively) an Nd : YVO4 laser, pumped by a diode laser array. The laser can operate both in cw mode-locked and simultaneously Q-switched and mode-locked (QML) regime. The peak power of the laser while operating in QML regime is much higher but pulses suffers from poor amplitude stability. The incorporation of an acousto-optic modulator as an active Q-switch enhances the stability of the QML pulse envelope. The second-order non-linearity of powdered crystalline urea is conclusively measured with respect to KDP while the laser is operating in passively Q-switched and passively mode-locked regime as well as in actively Q-switched and passively mode-locked regime.

  14. Non-linear interactions in a boundary layer developing over an array of cubes using stochastic estimation

    Science.gov (United States)

    Blackman, Karin; Perret, Laurent

    2016-09-01

    In the present work, a boundary layer developing over a rough-wall consisting of staggered cubes with a plan area packing density, λp = 25%, is studied within a wind tunnel using combined particle image velocimetry and hot-wire anemometry to investigate the non-linear interactions between large-scale momentum regions and small-scale structures induced by the presence of the roughness. Due to the highly turbulent nature of the roughness sub-layer and measurement equipment limitations, temporally resolved flow measurements are not feasible, making the conventional filtering methods used for triple decomposition unsuitable for the present work. Thus, multi-time delay linear stochastic estimation is used to decompose the flow into large-scales and small-scales. Analysis of the scale-decomposed skewness of the turbulent velocity (u') shows a significant contribution of the non-linear term uL ' uS ' 2 ¯ , which represents the influence of the large-scales ( uL ' ) onto the small-scales ( uS ' ). It is shown that this non-linear influence of the large-scale momentum regions occurs with all three components of velocity in a similar manner. Finally, through two-point spatio-temporal correlation analysis, it is shown quantitatively that large-scale momentum regions influence small-scale structures throughout the boundary layer through a non-linear top-down mechanism.

  15. The theory and experiment of very-long-wavelength 256×1 GaAs/AlxGa1-xAs quantum well infrared detector linear arrays

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The 256×1 linear array of multiple quantum wells infrared photodetector (QWIP) is designed and fabricated for the peak response wavelength at λP=14.6 μm. The response spectral width is bigger than 2.2 μm. The two-dimensional (2D) diffractive coupling grating has been formed on the top QWIP photosensitive pixel for coupling the infrared radiation to the infrared detective layers. The performance of the device at VB=3 V and T=45 K has the responsibility 4.28×10-2 (A/W), the blackbody detectivity Db*=5.14×109 (cm·Hz1/2/W), and the peak detectivity Dλ*=4.24× 1010 (cm·Hz1/2/W). The sensor pixels are connected with CMOS read out circuit (ROC) hybridization by indium bumps. When integral time is 100 μs, the linear array has the effective pixel of QWIP FPA Nef of 99.2%, the average responsibility  (V/W) of 3.48×106 (V/W), the average peak detectivity Dλ* of 8.29×109 (cm·Hz1/2/W), and the non-uniformity UR of 5.83%. This device is ready for the thermal image application.

  16. Three-Dimensional X-ray Observation of Atmospheric Biological Samples by Linear-Array Scanning-Electron Generation X-ray Microscope System

    Science.gov (United States)

    Ogura, Toshihiko

    2011-01-01

    Recently, we developed a soft X-ray microscope called the scanning-electron generation X-ray microscope (SGXM), which consists of a simple X-ray detection system that detects X-rays emitted from the interaction between a scanning electron beam (EB) and the thin film of the sample mount. We present herein a three-dimensional (3D) X-ray detection system that is based on the SGXM technology and designed for studying atmospheric biological samples. This 3D X-ray detection system contains a linear X-ray photodiode (PD) array. The specimens are placed under a CuZn-coated Si3N4 thin film, which is attached to an atmospheric sample holder. Multiple tilt X-ray images of the samples are detected simultaneously by the linear array of X-ray PDs, and the 3D structure is calculated by a new 3D reconstruction method that uses a simulated-annealing algorithm. The resulting 3D models clearly reveal the inner structure of the bacterium. In addition, the proposed method can easily be used for diverse samples in a broad range of scientific fields. PMID:21731770

  17. Three-dimensional X-ray observation of atmospheric biological samples by linear-array scanning-electron generation X-ray microscope system.

    Science.gov (United States)

    Ogura, Toshihiko

    2011-01-01

    Recently, we developed a soft X-ray microscope called the scanning-electron generation X-ray microscope (SGXM), which consists of a simple X-ray detection system that detects X-rays emitted from the interaction between a scanning electron beam (EB) and the thin film of the sample mount. We present herein a three-dimensional (3D) X-ray detection system that is based on the SGXM technology and designed for studying atmospheric biological samples. This 3D X-ray detection system contains a linear X-ray photodiode (PD) array. The specimens are placed under a CuZn-coated Si₃N₄ thin film, which is attached to an atmospheric sample holder. Multiple tilt X-ray images of the samples are detected simultaneously by the linear array of X-ray PDs, and the 3D structure is calculated by a new 3D reconstruction method that uses a simulated-annealing algorithm. The resulting 3D models clearly reveal the inner structure of the bacterium. In addition, the proposed method can easily be used for diverse samples in a broad range of scientific fields.

  18. Three-dimensional X-ray observation of atmospheric biological samples by linear-array scanning-electron generation X-ray microscope system.

    Directory of Open Access Journals (Sweden)

    Toshihiko Ogura

    Full Text Available Recently, we developed a soft X-ray microscope called the scanning-electron generation X-ray microscope (SGXM, which consists of a simple X-ray detection system that detects X-rays emitted from the interaction between a scanning electron beam (EB and the thin film of the sample mount. We present herein a three-dimensional (3D X-ray detection system that is based on the SGXM technology and designed for studying atmospheric biological samples. This 3D X-ray detection system contains a linear X-ray photodiode (PD array. The specimens are placed under a CuZn-coated Si₃N₄ thin film, which is attached to an atmospheric sample holder. Multiple tilt X-ray images of the samples are detected simultaneously by the linear array of X-ray PDs, and the 3D structure is calculated by a new 3D reconstruction method that uses a simulated-annealing algorithm. The resulting 3D models clearly reveal the inner structure of the bacterium. In addition, the proposed method can easily be used for diverse samples in a broad range of scientific fields.

  19. Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications

    Science.gov (United States)

    Barber, W. C.; Wessel, J. C.; Nygard, E.; Iwanczyk, J. S.

    2015-06-01

    -flux ASICs with a two dimensional (2D) array of inputs for readout from the sensors. The sensors are guard ring free and have a 2D array of pixels and can be tiled in 2D while preserving pixel pitch. The 2D ASICs have four energy bins with a linear energy response across sufficient dynamic range for clinical CT and some NDT applications. The ASICs can also be tiled in 2D and are designed to fit within the active area of the sensors. We have measured several important performance parameters including: the output count rate (OCR) in excess of 20 million counts per second per square mm with a minimum loss of counts due to pulse pile-up, an energy resolution of 7 keV full width at half-maximum (FWHM) across the entire dynamic range, and a noise floor about 20 keV. This is achieved by directly interconnecting the ASIC inputs to the pixels of the CdZnTe sensors incurring very little input capacitance to the ASICs. We present measurements of the performance of the CdTe and CdZnTe sensors including the OCR, FWHM energy resolution, noise floor, as well as the temporal stability and uniformity under the rapidly varying high flux expected in CT and NDT applications.

  20. A Design Of Feeding Network For A Dual-Linear Polarization, Stacked, Probe-Fed Microstrip Patch Antenna Array

    DEFF Research Database (Denmark)

    Jaworski, G.; Krozer, Viktor

    2004-01-01

    Components of multilayer feed network are presented for application in broad-band dual-linear polarized stacked C-band antenna. Measurement results of wide band matching circuits and different types of power divider networks constituting parts of BFN demonstrate wideband operation. Suitable...

  1. Crystal Growth of CdTe by Gradient Freeze in Universal Multizone Crystallizator (UMC)

    Science.gov (United States)

    Su, Ching-Hua; Lehoczky, S. L.; Li, C.; Knuteson, D.; Raghothamachar, B.; Dudley, M.; Szoke, J.; Barczy, P.

    2004-01-01

    In the case of unsealed melt growth of an array of II-VI compounds, namely, CdTe, CdZnTe and ZnSe, there is a tremendous amount of experimental data describing the correlations between melt conditions and crystal quality. The results imply that the crystallinity quality can be improved if the melt was markedly superheated or long-time held before growth. It is speculated that after high superheating the associated complex dissociate and the spontaneous nucleation is retarded. In this study, crystals of CdTe were grown from melts which have undergone different thermal history by the unseeded gradient freeze method using the Universal Multizone Crystallizator (UMC). The effects of melt conditions on the quality of grown crystal were studied by various characterization techniques, including Synchrotron White Beam X-ray Topography (SWSXT), infrared microscopy, chemical analysis by glow discharge mass spectroscopy (GDMS), electrical conductivity and Hall measurements.

  2. Deposition and properties of CdTe nanowires prepared by template replication

    Energy Technology Data Exchange (ETDEWEB)

    Enculescu, Ionut; Sima, Marian; Enculescu, Monica; Enache, Mihaela [National Institute for Materials Physics, Bucharest-Magurele (Romania); Ion, Lucian; Antohe, Stefan [Faculty of Physics, University of Bucharest (Romania); Neumann, Reinhard [Gesellschaft fuer Schwerionenforschung, Darmstadt (Germany)

    2007-05-15

    We used the template method to prepare CdTe wires with diameters ranging from 80 nm to 1 {mu}m. As templates we used polycarbonate and polyethilene terephtalate ion track membranes and as the method of filling the pores of such membranes we employed electrochemical deposition. The conditions (i.e. bath composition and deposition potential) necessary to obtain the stoichiometric composition of the semiconductor were found. Scanning and transmission electron microscopy were employed for morphological characterization of the nano and microwires. Energy dispersive X-ray analysis was employed for determining the Cd/Te ratio. Selected area electron diffraction was employed for structural measurements. Reflection spectroscopy measurements were performed on nanowire arrays for determining the band gap of the deposited nanostructures. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Non-destructive visualization of linear explosive-induced Pyroshock using phase arrayed laser-induced shock in a space launcher composite

    Science.gov (United States)

    kyeong Jang, Jae; Ryul Lee, Jung

    2015-07-01

    Separation mechanism of Space launch vehicles are used in various separation systems and pyrotechnic devices. The operation of these pyrotechnic devices generates Pyroshock that can cause failures in electronic components. The prediction of high frequency structural response, especially the shock response spectrum (SRS), is important. This paper presents a non-destructive visualization and simulation of linear explosive-induced Pyroshock using phase arrayed Laser-induced shock. The proposed method includes a laser shock test based on laser beam and filtering zone conditioning to predict the SRS of Pyroshock. A ballistic test based on linear explosive and non-contact Laser Doppler Vibrometers and a nondestructive Laser shock measurement using laser excitation and several PZT sensors, are performed using a carbon composite sandwich panel. The similarity of the SRS of the conditioned laser shock to that of the real explosive Pyroshock is evaluated with the Mean Acceleration Difference. The average of MADs over the two training points was 33.64%. And, MAD at verification point was improved to 31.99%. After that, experimentally found optimal conditions are applied to any arbitrary points in laser scanning area. Finally, it is shown that linear explosive-induced real Pyroshock wave propagation can be visualized with high similarity based on the proposed laser technology.

  4. 基于双路线阵CCD的自动电子数粒机%Automatic electronic granulation counter based on double linear array CCD

    Institute of Scientific and Technical Information of China (English)

    隋修武; 齐晓光; 李大鹏

    2012-01-01

    In order to meet the need of medicine packaging industry for high speed and precision, the electronic granulation counter is developed. The counter consists of LED light source, double linear array CCD chip TCD1209D,synchronously driving circuit for the double linear array CCD chip based on CPLD EPM 3064A, synchronously data acquisition card of the high speed A/D converter TLC 5510, and host computer. The test channel is 400 mm wide;the horizontal resolution on the medicine pill is 0.1 nun,the driving frequency of linear array CCD is 10 MHz and the vertical resolution on the medicine pill is 0.3 mm, software binarization method is used for identification on the medicine tablets with different light transmittance. The experimental results show that the count of electronic granulation counter is accurate and reliable,counting speed is 8000 particles/min, and can correctly distinguish the broken tablets and the overlap tablets.%为满足医药包装工业对药粒计数的高速高精度的要求,设计了基于双路线阵CCD的电子数粒机.数粒机由LED光源,双路线阵CCD芯片TCD1209D,EPM 3064A型CPLD作为双路CCD的同步驱动电路,以高速A/D转换器TLC 5510为核心的同步数据采集卡,主控计算机组成.检测通道宽度400 mm,对药粒的水平分辨率为0.1mm,线阵CCD的驱动频率为10 MHz,对药粒的垂直分辨率为0.3 mm,采用软件二值化方法实现了对透光性不同的药粒的识别.实验表明:数粒机的计数准确可靠,计数速度达8 000粒/min,并可以准确地识别残片与重叠药粒.

  5. Demonstration of a micromachined planar distribution network in gap waveguide technology for a linear slot array antenna at 100 GHz

    Science.gov (United States)

    Rahiminejad, S.; Zaman, A. U.; Haasl, S.; Kildal, P.-S.; Enoksson, P.

    2016-07-01

    The need for high frequency antennas is rapidly increasing with the development of new wireless rate communication technology. Planar antennas have an attractive form factor, but they require a distribution network. Microstrip technology is most commonly used at low frequency but suffers from large dielectric and ohmic losses at higher frequencies and particularly above 100 GHz. Substrate-integrated waveguides also suffer from dielectric losses. In addition, standard rectangular waveguide interfaces are inconvenient due to the four flange screws that must be tightly fastened to the antenna to avoid leakage. The current paper presents a planar slot array antenna that does not suffer from any of these problems. The distribution network is realized by micromachining using low-loss gap waveguide technology, and it can be connected to a standard rectangular waveguide flange without using any screws or additional packaging. To realize the antenna at these frequencies, it was fabricated with micromachining, which offers the required high precision, and a low-cost fabrication method. The antenna was micromachined with DRIE in two parts, one silicon-on-insulator plate and one Si plate, which were both covered with Au to achieve conductivity. The input reflection coefficient was measured to be below 10 dB over a 15.5% bandwidth, and the antenna gain was measured to be 10.4 dBi, both of which are in agreement with simulations.

  6. Photoinduced tellurium precipitation in CdTe

    Science.gov (United States)

    Sugai, Shunji

    1991-06-01

    Tellurium precipitation in CdTe is found to be induced by photoirradiation with energy higher than the energy gap at 240 W/sq cm. It is suggested that this photoinduced precipitation is related with the strong electron-phonon interactions, possibly self-trapped excitons. This irreducible tellurium precipitation may cause a serious problem for the life of semiconductor devices.

  7. Miniature hybrid preamplifier for CdTe detectors

    International Nuclear Information System (INIS)

    Aeronutronic Ford has developed a rugged, miniature, room temperature operable, gamma ray detector package containing a CdTe photon detector, a charge amplifier and a pulse shaper circuit. Photon detection efficiencies between 10 percent and 40 percent are achieved for various photon energies between 100 keV and 1000 keV in a detector area of .032 square inches. The resulting package weighs approximately 8 grams and occupies approximately 0.1 cubic inch. Prototypes have been tested for aging and temperature effects on gamma detection efficiency. The intended application of the device is calibrated gamma ray counting in a warm environment while subjected to high intensity acoustic and vibration stresses as well as very large linear accelerations

  8. CLOSED-FORM SPACE-TIME CHANNEL BLIND ESTIMATION FOR SPACE-TIME CODED MC-CDMA SYTEMS WITH UNIFORM LINEAR ARRAY

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper proposes a closed-form joint space-time channel and Direction Of Arrival (DOA) blind estimation algorithm for space-time coded Multi-Carrier Code Division Multiple Access (MC-CDMA) systems equipped with a Uniform Linear Array (ULA) at the base station in frequency-selective fading environments. The algorithm uses an ESPRIT-like method to separate multiple co-channel users with different impinging DOAs. As a result, the DOAs for multiple users are obtained. In particular, a set of signal subspaces,every one of which is spanned by the space-time vector channels of an individual user, are also obtained. From these signal subspaces, the space-time channels of multiple users are estimated using the subspace method.Computer simulations illustrate both the validity and the overall performance of the proposed scheme.

  9. Synthesis of Linear Array of Parallel Dipole Antennas with Minimum Standing Wave Ratio Using Simulated Annealing and Particle Swarm Optimization approach

    Directory of Open Access Journals (Sweden)

    Banani Basu

    2010-05-01

    Full Text Available In this paper, we propose a technique based on two evolutionary algorithms simulated annealing and particle swarm optimization to design a linear array of half wavelength long parallel dipole antennas that will generate a pencil beam in the horizontal plane with minimum standing wave ratio (SWR and fixed side lobe level (SLL. Dynamic range ratio of current amplitude distribution is kept at a fixed value. Two different methods have been proposed withdifferent inter-element spacing but with same current amplitude distribution. First one uses a fixed geometry and optimizes the excitation distribution on it. In the second case further reduction of SWR is done via optimization of interelement spacing while keeping the amplitude distribution same as before. Coupling effect between the elements is analyzed using induced EMF method and minimized interms of SWR. Numerical results obtained from SA are validated by comparing with results obtained using PSO.

  10. Operation in the turbulent jet field of a linear array of multiple rectangular jets using a two-dimensional jet (Variation of mean velocity field

    Directory of Open Access Journals (Sweden)

    Fujita Shigetaka

    2016-01-01

    Full Text Available The mean flowfield of a linear array of multiple rectangular jets run through transversely with a two-dimensional jet, has been investigated, experimentally. The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The reason of the adoption of this nozzle exit shape was caused by the reports of authors in which the cruciform nozzle promoted the inward secondary flows strongly on both the two jet axes. Aspect ratio of the rectangular nozzle used in this experiment was 12.5. Reynolds number based on the nozzle width d and the exit mean velocity Ue (≅ 39 m / s was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (lh = 3.1 μm in diameter, dh = 0.6 mm effective length : dh / lh = 194 operated by the linearized constant temperature anemometers (DANTEC, and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 60 seconds. From this experiment, it was revealed that the magnitude of the inward secondary flows on both the y and z axes in the upstream region of the present jet was promoted by a two-dimensional jet which run through transversely perpendicular to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet extended 2.3 times longer than that of the multiple rectangular jets, and the half-velocity width on the rectangular jet axis of the present jet was suppressed 41% shorter compared with that of the multiple rectangular jets.

  11. Performance Summary for the First Solar CdTe 1-kW System: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Marion, B.; del Cueto, J.; McNutt, P.; Rose, D.

    2001-10-01

    Presented at the 2001 NCPV Program Review Meeting: Describes performance of 1-kWac CdTe PV array from First Solar operated at NREL from 6/95 to 14/00. This paper describes the performance of a 1-kW{sub ac} CdTe PV array from First Solar (formerly Solar Cells, Inc.) operated at NREL from June 1995 to November 2000. The PV array operating efficiencies over the 5.5-year period were calculated from 15-minute averages to determine changes in seasonal and annual performance. Performance measurements of each module were also made before installing the modules outdoors and again in August 2000 using NREL's indoor SPIRE 240A pulsed solar simulator and the Standard Outdoor Measurement System (SOMS). Although some modules showed increases in efficiency and others decreases, the average efficiency of the modules in the PV array did not change. For modules that showed changes in efficiency, analysis of module I-V parameters indicated that the changes in efficiency were primarily a consequence of changes in fill factor.

  12. A modified genetic algorithm used for synthesis of linear arrays%一种用于线性阵列综合的改进遗传算法

    Institute of Scientific and Technical Information of China (English)

    董建刚; 王新宽

    2014-01-01

    In order to improve the convergence speed and the target array synthesis function of local optimum,the deficien⁃cies of the existing genetic algorithm are analyzed,and a modified genetic algorithm for synthesis of linear arrays is proposed in this paper because the existing genetic algorithm is easy to occur the local convergence when it conducts the synthesis of linear arrays. A search scheme to enhance the scope of individual search program so as to jump out of the local optimal solution is pro⁃posed in consideration of the problems that the existing algorithms are not strong in real⁃coded search capability and is easy to trap in the local optima solution. It′s an effective way to solve the problem. Simulation results show that the modified algorithm can make the object function jump out of local optimum solution rapidly,and the convergence speed is substantially increased by at least 2~10 times,comparing with the origin method.%为了提高阵列综合收敛速度,实现目标函数局部最优,分析了现有的遗传算法存在的不足,提出了一种应用于线性阵列综合的改进遗传算法。该算法根据现有算法对实数编码搜索能力不强,容易陷于局部最优解的缺陷,提出了能够增强个体寻优范围的搜索方案,以跳出局部最优解,是解决问题的有效途径。仿真结果表明,改进后的算法能够使目标函数迅速跳出局部最优解,收敛速度至少增加了2~10倍。

  13. A Three-Dimensional Range Migration Algorithm for Downward-Looking 3D-SAR with Single-Transmitting and Multiple-Receiving Linear Array Antennas

    Science.gov (United States)

    Du, Lei; Wang, Yanping; Hong, Wen; Tan, Weixian; Wu, Yirong

    2010-12-01

    This paper presents a three-dimensional (3D) range migration algorithm (RMA) suitable for downward-looking 3D-SAR with single-transmitting and multiple-receiving linear array antennas (STMR-LAA). As the round-trip range equation in 3D-SAR with STMR-LAA is a dual square root, the signal spectrum in 3D wavenumber domain contains nonlinear phase terms besides constant and linear phase terms. In this paper, the approximate expression of the signal spectrum is derived by expanding the implicit phase term to its Taylor series. Then the constant and nonlinear phase terms are calculated and compensated by multiplying the wavenumber filters. Finally, a 3D wavenumber mapping is proposed to make the signal evenly sampled in 3D wavenumber domain. Some simulating results are presented to validate the correctness of the analysis and the feasibility of the algorithm. In addition, the required accuracy on the platform position is analyzed at the end of the paper.

  14. Synthesis and Surface Modification of CdTe Nanocrystals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    CdTe nanocrystals were prepared in aqueous solution via the reaction between Cd2+ and NaHTe in the presence of mercaptoacetic acid. Interactions between CdTe nanocrystals and phenylalanine were formed via electrostatic/coordinate self-assembly. The photoluminescence intensity of CdTe nanocrystals was improved obviously. The interaction mechanism was discussed and was considered to be surface passivation.

  15. CdTe Films Deposited by Closed-space Sublimation

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    CdTe films are prepared by closed-space sublimation technology. Dependence of film crystalline on substrate materials and substrate temperature is investigated. It is found that films exhibit higher crystallinity at substrate temperature higher than 400℃. And the CdTe films deposited on CdS films with higher crystallinity have bigger crystallite and higher uniformity. Treatment with CdCl2 methanol solution promotes the crystallite growth of CdTe films during annealing.

  16. Growth and optical properties of CdTe quantum dots in ZnTe nanowires

    International Nuclear Information System (INIS)

    We report on the formation of optically active CdTe quantum dots in ZnTe nanowires. The CdTe/ZnTe nanostructures have been grown by a gold nanocatalyst assisted molecular beam epitaxy in a vapor-liquid solid growth process. The presence of CdTe insertions in ZnTe nanowire results in the appearance of a strong photoluminescence band in the 2.0 eV-2.25 eV energy range. Spatially resolved photoluminescence measurements reveal that this broad emission consists of several sharp lines with the spectral width of about 2 meV. The large degree of linear polarization of these individual emission lines confirms their nanowire origin, whereas the zero-dimensional confinement is proved by photon correlation spectroscopy.

  17. Visualization and simulation of a linear explosive-induced pyroshock wave using Q-switched laser and phased array transducers in a space launcher composite structure

    Science.gov (United States)

    Lee, Jung-Ryul; Jang, Jae-Kyeong; Choi, Mijin; Kong, Cheol-Won

    2015-04-01

    During space flights, pyrotechnic devices are used for various purposes such as separation of boosters, satellites, fairings, and stages. In particular, the prediction of high shock structural response induced by linear explosives is important for safe operation of pyrotechnic devices. In general, repetitive explosive testing using distributed accelerometers is widely used, but multiple test structures are usually necessary because they are easily damaged and not reusable. This paper pertains to a nondestructive technology to replace the damage-causing, time-consuming, expensive, dangerous, and low-repeatability explosive test with a laser-induced shock test. The method proposed in this paper predicts nondestructively the linear explosive-induced pyroshock wave, visualizes its propagation, and allows the simulation of some detonation conditions. A ballistic test based on a linear explosive and noncontact laser Doppler vibrometer (LDV) as well as a nondestructive pyroshock test using laser-induced shock and PZT array sensors is performed in a 12.68-mm thick composite sandwich panel. The optimal laser-induced shock experimental conditions to predict real pyroshock response spectra (SRSs) are investigated by controlling the optical characteristics of the laser beam and adjusting the frequency bands in signal acquisition. The similarity of the SRS of the conditioned laser-induced shock to that of the real explosive pyroshock is evaluated with the mean acceleration difference. Next, the experimentally-determined optimal conditions are applied to arbitrary points in the laser-induced shock scanning area. Finally, it is shown that the proposed method will allow nondestructive and quantitative pyroshock testing, pyroshock wave propagation visualization showing the direction and magnitude of principal wave propagation, and detonation speed simulation depending on explosive type and detonation initiation point and direction.

  18. Hard x-ray polarimetry with a thick CdTe position sensitive spectrometer

    Science.gov (United States)

    Caroli, Ezio; Bertuccio, Giuseppe; Cola, Adriano; Curado da Silva, R. M.; Donati, Ariano; Dusi, Waldes; Landini, Gianni; Siffert, Paul; Sampietro, Marco; Stephen, John B.

    2000-12-01

    Even though it is recognized that the study of polarization from cosmic high-energy sources can give very important information about the nature of the emission mechanism, to date very few measurements have been attempted. For several years we have proposed the use of a thick CdTe array as a position sensitive spectrometer for hard X- and soft gamma-ray astronomy, a design which is also efficient for use as a polarimeter at energies above approximately 100 keV. Herein we describe the preliminary results of our study of a polarimeter based on 4096 CdTe microcrystals that we would like to develop for a high altitude balloon experiment. We present the telescope concept with a description of each subsystem together with some results on activities devoted to the optimization of the CdTe detector units' response. Furthermore we give an evaluation of the telescope performance in terms of achievable spectroscopic and polarimetric performance. In particular we will show the results of Monte Carlo simulations developed to evaluate the efficiency of our detector as a hard X ray polarimeter.

  19. Analysis of rocking curve width and bound exciton linewidth of MOCVD grown CdTe layers in relation with substrate type and crystalline orientation

    Science.gov (United States)

    Tromson-Carli, A.; Svob, L.; Marfaing, Y.; Druilhe, R.; Desjonqueres, F.; Triboulet, R.

    1991-12-01

    X-ray double diffraction and photoluminescence experiments were performed on a series of CdTe layers grown by MOVPE on CdTe, CdZnTe and GaAs substrates. Some correlation appears between the measured rocking curve widths and impurity-bound exciton linewidth. To analyze these results, a model relating the exciton linewidth to the average strain induced by an array of random dislocations has been developed. It appears that X-ray diffraction is also sensitive to non-random dislocation configurations which do not affect luminescence linewidth.

  20. Cyclodextrin capped CdTe quantum dots as versatile fluorescence sensors for nitrophenol isomers

    Science.gov (United States)

    Zhang, Zhixing; Zhou, Jie; Liu, Yun; Tang, Jian; Tang, Weihua

    2015-11-01

    Cyclodextrin (CD) capped CdTe quantum dots (QDs) were prepared with uniform dimension (average diameter ~5 nm) and high quantum yield (ca. 65%). By taking advantage of the inclusion complexation of CD, β-CD-CdTe QDs exhibited strong fluorescence quenching in a linear relationship with the concentration of o-, m- and p-nitrophenol in the range of 20-100 μM. The detection limit reached 0.05 μM for o-/p-nitrophenol and 0.3 μM for m-nitrophenol. The fluorescence decay study revealed the stabilization effect of CD covering on CdTe QDs and fine-tuning of the fluorescence for selective ultrasensitive detection of nitrophenol isomers.Cyclodextrin (CD) capped CdTe quantum dots (QDs) were prepared with uniform dimension (average diameter ~5 nm) and high quantum yield (ca. 65%). By taking advantage of the inclusion complexation of CD, β-CD-CdTe QDs exhibited strong fluorescence quenching in a linear relationship with the concentration of o-, m- and p-nitrophenol in the range of 20-100 μM. The detection limit reached 0.05 μM for o-/p-nitrophenol and 0.3 μM for m-nitrophenol. The fluorescence decay study revealed the stabilization effect of CD covering on CdTe QDs and fine-tuning of the fluorescence for selective ultrasensitive detection of nitrophenol isomers. Electronic supplementary information (ESI) available: Experimental procedure and characterization for new materials. See DOI: 10.1039/c5nr06073g

  1. Photovoltaic minimodule based on CdTe

    International Nuclear Information System (INIS)

    CdS/CdTe solar cells were fabricated without antireflection coatings by successive growth without intermediate processing from the close space sublimation of CdS and CdTe thin layers on conductive and transparent SnO2/glass substrates. At 300 K and 100 mW/cm2 the following best photoelectric parameters were obtained: Isc= (18-19)mA/cm2 and Voc=(0,80-0,82)V. The conversion efficiency is around 10%. The quantum efficiency (QE) in the 510 nm and 845 nm range of wavelengths is on the order of 80-85%. The minimodule fabricated on the basis of the CdTe cells shows power of 0.45 W, corresponding to a voltage of 3 V, and current of 150 mA. (authors)

  2. Recycling of CdTe photovoltaic waste

    Science.gov (United States)

    Goozner, Robert E.; Long, Mark O.; Drinkard, Jr., William F.

    1999-01-01

    A method for extracting and reclaiming metals from scrap CdTe photovoltaic cells and manufacturing waste by leaching the waste with a leaching solution comprising nitric acid and water, skimming any plastic material from the top of the leaching solution, separating the glass substrate from the liquid leachate and electrolyzing the leachate to separate Cd from Te, wherein the Te is deposits onto a cathode while the Cd remains in solution.

  3. Analysis of Resolutions for SAR 3D Imaging Using Linear Array Antennas%线阵 SAR 三维成像分辨率分析

    Institute of Scientific and Technical Information of China (English)

    王斌; 王彦平; 洪文; 吴一戎

    2011-01-01

    Linear array antennas synthetic aperture radar (LASAR) can acquire the echoes of the target from different observation angles, and it can realize three-dimensional (3D) imaging for the targets.In order to get the 3D images with high resolutions, the relationship between the resolutions and the observation geometry is studied in this paper.Firstly, the signal model for LASAR 3D imaging is derived, and the 3D resolutions related with the geometry of the LASAR are obtained.Then the variance of the resolution in the elevation direction with array antenna angle and referenced look angle is analyzed.And then we conclude that the best resolution is obtained when the array antenna angle is equal to the referenced look angle.Finally, the simulation results of LASAR 3D imaging with MATLAB software are given, and the resolutions of 3D imaging under different observation geometry are analyzed and compared.%研究阵列无线 SAR 系统优化问题,关于线阵合成孔径雷达(SAR)使用阵列天线获取观测目标不同入射角的回波信号,能够实现对目标的三维成像.为了获取高分辨率的三维成像结果,研究了线阵 SAR 三维成像分辨率与观测几何的关系.采用线阵 SAR 实现三维成像的信号模型,得到了与线阵 SAR 几何相关的三维分辨率,根据高度向分辨率随着参考视角和线阵角度的变化,得到在线阵角度的三维成像分辨率.并运用运用 MATLAB 仿真平台进行了线阵 SAR 三维成像仿真,结果表明目标三维成像得到了高分辨率的结果.

  4. Thin-film CdTe cells: Reducing the CdTe

    International Nuclear Information System (INIS)

    Polycrystalline thin-film CdTe is currently the dominant thin-film technology in world-wide PV manufacturing. With finite Te resources world-wide, it is appropriate to consider the limits to reducing the thickness of the CdTe layer in these devices. In our laboratory we have emphasized the use of magnetron sputtering for both CdS and CdTe achieving AM1.5 efficiency over 13% on 3 mm soda-lime glass with commercial TCO and 14% on 1 mm aluminosilicate glass. This deposition technique is well suited to good control of very thin layers and yields relatively small grain size which also facilitates high performance with ultra-thin layers. This paper describes our magnetron sputtering studies for fabrication of very thin CdTe cells. Our thinnest cells had CdTe thicknesses of 1 μm, 0.5 μm and 0.3 μm and yielded efficiencies of 12%, 9.7% and 6.8% respectively. With thinner cells Voc, FF and Jsc are reduced. Current-voltage (J-V), temperature dependent J-V (J-V-T) and apparent quantum efficiency (AQE) measurements provide valuable information for understanding and optimizing cell performance. We find that the stability under light soak appears not to depend on CdTe thickness from 2.5 to 0.5 μm. The use of semitransparent back contacts allows the study of bifacial response which is particularly useful in understanding carrier collection in the very thin devices.

  5. Growth of CdTe: Al films

    International Nuclear Information System (INIS)

    CdTe: AI films were grown by the close space vapor transport technique combined with free evaporation (CSVT-FE). The Aluminum (Al) evaporation was made by two kinds of sources: one made of graphite and the other of tantalum. The films were deposited on glass substrates. The Al source temperature was varied maintaining the CdTe source temperature fixed as well as the substrate temperature. The films were characterized by x-ray energy dispersive analysis (EDAX), x-ray diffraction and optical transmission. The results showed for the films grown with the graphite source for Al evaporation, the Al did not incorporate in the CdTe matrix, at least to the level of EDAX sensitivity; they maintained the same crystal structure and band gap. For the samples grown with the tantalum source, we were able to incorporate the Al. The x-ray diffraction patterns show that the films have a crystal structure that depends on Al concentration. They were cubic up to 2.16 at. % Al concentration; for 19.65 at. % we found a mixed phase; for Al concentration higher than 21 at. % the films were amorphous. For samples with cubic structure it was found that the lattice parameter decreases and the band gap increases with Al concentration. (Author)

  6. Non-uniformity Correction of Linear Array Detector Based on FPGA%基于FPGA的线阵探测器非均匀校正的实现

    Institute of Scientific and Technical Information of China (English)

    高文清; 徐世伟; 刘严严; 丁艳艳

    2012-01-01

      充分利用了FPGA的硬件资源,提出一种采用电路逻辑设计的FPGA来实现两点校正;利用FPGA中的浮点加法器、浮点除法器、浮点乘法器,以及内部RAM、 ROM存储器,可以实时计算校正系数,然后对线阵红外探测器进行非均匀性校正,保证了校正精度。同时,充分利用FPGA并行处理能力强的特点,使系数、图像数据的读取在一个时钟周期内完成%  Based on the FPGA hardware resources, a FPGA in the logic circuit design is presented to achieve the two-point correction. The floating-point adder, floating-point divider, floating-point multiplier and the inter⁃nal RAM, ROM memory in FPGA can be used to calculate the correction factors in real time, and then the non-uni⁃formity correction is completed on the linear array infrared detector, thus the correction accuracy is ensured. At the same time, the coefficient and the reading of image data can be completed in a clock cycle by using the parallel pro⁃cessing ability of the FPGA.

  7. Rapid long-wave infrared laser-induced breakdown spectroscopy measurements using a mercury-cadmium-telluride linear array detection system.

    Science.gov (United States)

    Yang, Clayton S-C; Brown, Eiei; Kumi-Barimah, Eric; Hommerich, Uwe; Jin, Feng; Jia, Yingqing; Trivedi, Sudhir; D'souza, Arvind I; Decuir, Eric A; Wijewarnasuriya, Priyalal S; Samuels, Alan C

    2015-11-20

    In this work, we develop a mercury-cadmium-telluride linear array detection system that is capable of rapidly capturing (∼1-5  s) a broad spectrum of atomic and molecular laser-induced breakdown spectroscopy (LIBS) emissions in the long-wave infrared (LWIR) region (∼5.6-10  μm). Similar to the conventional UV-Vis LIBS, a broadband emission spectrum of condensed phase samples covering the whole 5.6-10 μm region can be acquired from just a single laser-induced microplasma or averaging a few single laser-induced microplasmas. Atomic and molecular signature emission spectra of solid inorganic and organic tablets and thin liquid films deposited on a rough asphalt surface are observed. This setup is capable of rapidly probing samples "as is" without the need of elaborate sample preparation and also offers the possibility of a simultaneous UV-Vis and LWIR LIBS measurement.

  8. Automatic inline defect detection for a thin film transistor–liquid crystal display array process using locally linear embedding and support vector data description

    International Nuclear Information System (INIS)

    Defect detection plays a critical role in thin film transistor liquid crystal display (TFT-LCD) manufacturing. This paper proposes an inline defect-detection (IDD) system, by which the defects can be automatically detected in a TFT array process. The IDD system is composed of three stages: the image preprocessing, the appearance-based classification and the decision-making stages. In the first stage, the pixels can be segmented from an input image based on the designed pixel segmentation method. The pixels are then sent into the appearance-based classification stage for defect and non-defect classification. Two novel methods are embedded in this stage: the locally linear embedding (LLE) and the support vector data description (SVDD). LLE is able to substantially reduce the dimensions of the input pixels by manifold learning and SVDD is able to effectively discriminate the normal pixels from the defective ones with a hypersphere by one-class classification. After aggregating the classification results, the third stage outputs the final detection result. Experimental results, carried out on real images provided by a LCD manufacturer, show that the IDD system can not only achieve a high defect-detection rate of over 98%, but also accomplish the task of inline defect detection within 4 s for one input image

  9. The glycosylphosphatidylinositol-PLC in Trypanosoma brucei forms a linear array on the exterior of the flagellar membrane before and after activation.

    Science.gov (United States)

    Hanrahan, Orla; Webb, Helena; O'Byrne, Robert; Brabazon, Elaine; Treumann, Achim; Sunter, Jack D; Carrington, Mark; Voorheis, H Paul

    2009-06-01

    Bloodstream forms of Trypanosoma brucei contain a glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC) that cleaves the GPI-anchor of the variable surface glycoprotein (VSG). Its location in trypanosomes has been controversial. Here, using confocal microscopy and surface labelling techniques, we show that the GPI-PLC is located exclusively in a linear array on the outside of the flagellar membrane, close to the flagellar attachment zone, but does not co-localize with the flagellar attachment zone protein, FAZ1. Consequently, the GPI-PLC and the VSG occupy the same plasma membrane leaflet, which resolves the topological problem associated with the cleavage reaction if the VSG and the GPI-PLC were on opposite sides of the membrane. The exterior location requires the enzyme to be tightly regulated to prevent VSG release under basal conditions. During stimulated VSG release in intact cells, the GPI-PLC did not change location, suggesting that the release mechanism involves lateral diffusion of the VSG in the plane of the membrane to the fixed position of the GPI-PLC.

  10. NDT of a Nickel Coated Inconel Specimen Using by the Complex Induced Current - Magnetic Flux Leakage Method and Linearly Integrated Hall Sensor Array

    Energy Technology Data Exchange (ETDEWEB)

    Jun, Jong Woo; Lee, Jin Yi [Chosun University, Gwangju (Korea, Republic of); Park, Duk Keun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2007-10-15

    Nondestructive testing (NDT) by using the electromagnetic methods are useful for detecting cracks on the surface and subsurface of the metal. However, when the material contains both ferromagnetic and paramagnetic materials, it is difficult for NDT to detect and analyze cracks using this method. In addition the existence of a partial ferromagnetic material can be incorrectly characterized as a crack in the several cases. On the other hand a large crack has sometimes been misunderstood as a partially magnetized region. Inconel 600 is an important material in atomic energy plant. A nickel film is coated when a crack a appears on an Inconel substrate. Cracks are difficult to detect on the combined material of an Inconel substrate with a nickel film, which are paramagnetic and ferromagnetic material respectively. In this paper, a scan type magnetic camera, which uses a complex induced current-magnetic flux leakage (CIC-MFL) method as a magnetic source and a linearly integrated Hall sensor array (LIHaS) on a wafer as the magnetic sensors, was examined for its ability to detect cracks on the combined material. The evaluation probability of a crack is discussed. In addition the detection probability of the minimum depth was reported

  11. Temperature dependent electroreflectance study of CdTe solar cells

    International Nuclear Information System (INIS)

    Cadmium telluride is a promising material for large scale photovoltaic applications. In this paper we study CdS/CdTe heterojunction solar cells with electroreflectance spectroscopy. Both CdS and CdTe layers in solar cells were grown sequentially without intermediate processing by the close-space sublimation method. Electroreflectance measurements were performed in the temperature range of T = 100–300 K. Two solar cells were investigated with conversion efficiencies of 4.1% and 9.6%. The main focus in this work was to study the temperature dependent behavior of the broadening parameter and the bandgap energy of CdTe thin film in solar cells. Room temperature bandgap values of CdTe were Eg = 1.499 eV and Eg = 1.481 eV for higher and lower efficiency solar cells, respectively. Measured bandgap energies are lower than for single crystal CdTe. The formation of CdTe1−xSx solid solution layer on the surface of CdTe is proposed as a possible cause of lower bandgap energies. - Highlights: ► Temperature dependent electroreflectance measurements of CdS/CdTe solar cells ► Investigation of junction properties between CdS and CdTe ► Formation of CdTe1− xSx solid solution layer in the junction area

  12. Homogeneous CdTe quantum dots-carbon nanotubes heterostructures

    International Nuclear Information System (INIS)

    The development of homogeneous CdTe quantum dots-carbon nanotubes heterostructures based on electrostatic interactions has been investigated. We report a simple and reproducible non-covalent functionalization route that can be accomplished at room temperature, to prepare colloidal composites consisting of CdTe nanocrystals deposited onto multi-walled carbon nanotubes (MWCNTs) functionalized with a thin layer of polyelectrolytes by layer-by-layer technique. Specifically, physical adsorption of polyelectrolytes such as poly (4-styrene sulfonate) and poly (diallyldimethylammonium chloride) was used to deagglomerate and disperse MWCNTs, onto which we deposited CdTe quantum dots coated with mercaptopropionic acid (MPA), as surface ligand, via electrostatic interactions. Confirmation of the CdTe quantum dots/carbon nanotubes heterostructures was done by transmission and scanning electron microscopies (TEM and SEM), dynamic-light scattering (DLS) together with absorption, emission, Raman and infrared spectroscopies (UV–vis, PL, Raman and FT-IR). Almost complete quenching of the PL band of the CdTe quantum dots was observed after adsorption on the MWCNTs, presumably through efficient energy transfer process from photoexcited CdTe to MWCNTs. - Highlights: • Highly homogeneous CdTe-carbon nanotubes heterostructures were prepared. • Simple and reproducible non-covalent functionalization route. • CdTe nanocrystals homogeneously deposited onto multi-walled carbon nanotubes. • Efficient energy transfer process from photoexcited CdTe to MWCNTs

  13. Homogeneous CdTe quantum dots-carbon nanotubes heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, Kayo Oliveira [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil); Bettini, Jefferson [Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, CEP 13083-970, Campinas, SP (Brazil); Ferrari, Jefferson Luis [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil); Schiavon, Marco Antonio, E-mail: schiavon@ufsj.edu.br [Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP 36301-160, São João del-Rei, MG (Brazil)

    2015-01-15

    The development of homogeneous CdTe quantum dots-carbon nanotubes heterostructures based on electrostatic interactions has been investigated. We report a simple and reproducible non-covalent functionalization route that can be accomplished at room temperature, to prepare colloidal composites consisting of CdTe nanocrystals deposited onto multi-walled carbon nanotubes (MWCNTs) functionalized with a thin layer of polyelectrolytes by layer-by-layer technique. Specifically, physical adsorption of polyelectrolytes such as poly (4-styrene sulfonate) and poly (diallyldimethylammonium chloride) was used to deagglomerate and disperse MWCNTs, onto which we deposited CdTe quantum dots coated with mercaptopropionic acid (MPA), as surface ligand, via electrostatic interactions. Confirmation of the CdTe quantum dots/carbon nanotubes heterostructures was done by transmission and scanning electron microscopies (TEM and SEM), dynamic-light scattering (DLS) together with absorption, emission, Raman and infrared spectroscopies (UV–vis, PL, Raman and FT-IR). Almost complete quenching of the PL band of the CdTe quantum dots was observed after adsorption on the MWCNTs, presumably through efficient energy transfer process from photoexcited CdTe to MWCNTs. - Highlights: • Highly homogeneous CdTe-carbon nanotubes heterostructures were prepared. • Simple and reproducible non-covalent functionalization route. • CdTe nanocrystals homogeneously deposited onto multi-walled carbon nanotubes. • Efficient energy transfer process from photoexcited CdTe to MWCNTs.

  14. Carbon analysis in CdTe by nuclear activation

    Science.gov (United States)

    Chibani, H.; Stoquert, J. P.; Hage-Ali, M.; Koebel, J. M.; Abdesselam, M.; Siffert, P.

    1991-06-01

    We describe the capabilities of the nuclear reaction 12C(d, n) 13Nlimit→β +13C the measurement of absolute concentrations of C in CdTe by the charged particle activation (CPA) method. This technique is used to determine the segregation coefficient of C introduced as an impurity in CdTe.

  15. CdTe and CdZnTe materials for room-temperature X-ray and gamma ray detectors

    Science.gov (United States)

    Eisen, Y.; Shor, A.

    1998-02-01

    Among the semiconductor materials of a wide band gap, CdTe and CdZnTe have attracted most attention as room-temperature X-ray and gamma-ray detectors. Suitable CdTe materials for nuclear detectors and, in particular, for spectrometers, have been developed over the past few decades and are mainly grown via the traveling heater method (THM). However, the manufacture of large homogeneous ingots at relatively low cost has not reached yet a proven stage. Cd 1- xZn xTe (CZT) materials, mainly grown via the high-pressure Bridgman (HPB) technique, possess several advantages over CdTe and appear to better approach the practicality of providing large volume X-ray and gamma-ray detectors at moderate costs. Continuing effort is still underway to improve the characteristics of both CdTe and CZT materials in order to achieve reproducible detectors for either low- and high-energy gamma rays. This review paper is divided into three parts: The first part describes different structural designs of detectors to improve their spectroscopic characteristics. These include hemispherical detectors, coplanar strip-electrode detectors and monolithic, two-dimensional segmented electrode arrays with pad sizes smaller than their thickness. This part will also describe various electronic methods to compensate for the poor charge collection of holes. The second part compares the characteristics of planar CdTe and CZT nuclear detectors containing metal contacts. Characteristics include: charge collection efficiencies for both electrons and holes indicated by the mobility-lifetime product, energy resolutions, leakage currents and robustness in field use. The third part is devoted to field uses of these detectors. Those include: X-ray fluorescent spectrometers, large volume spectrometers and a new generation nuclear gamma camera for medical diagnostics based on room-temperature solid-state spectrometers.

  16. A 2D 4×4 Channel Readout ASIC for Pixelated CdTe Detectors for Medical Imaging Applications

    OpenAIRE

    Macias-Montero, Jose-Gabriel; Sarraj, Maher; Chmeissani, Mokhtar; Martínez, Ricardo; Puigdengoles, Carles

    2015-01-01

    We present a 16-channel readout integrated circuit (ROIC) with nanosecond-resolution time to digital converter (TDC) for pixelated Cadmium Telluride (CdTe) gamma-ray detectors. The 4 × 4 pixel array ROIC is the proof of concept of the 10 × 10 pixel array readout ASIC for positron-emission tomography (PET) scanner, positron-emission mammography (PEM) scanner, and Compton gamma camera. The electronics of each individual pixel integrates an analog front-end with switchable gain, an analog to dig...

  17. Simple synthesis of thioglycolic acid-coated CdTe quantum dots as probes for Norfloxacin lactate detection

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Xiao; Zhou, Zhiping; Hao, Tongfan [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Li, Hongji [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Dai, Jiangdong [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Gao, Lin; Zheng, Xudong; Wang, Jixiang [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Yan, Yongsheng, E-mail: weixiaokeyan@163.com [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

    2015-05-15

    In this study, a simple and effective fluorometry method has been developed and used for the determination of Norfloxacin lactate (NOR-L) by the fluorescence quenching of thioglycolic acid (TGA)-coated CdTe quantum dots (QDs). The TGA-CdTe QDs were obtained in a simple way without precursor preparation, heating, pH adjustment and N{sub 2} protection. The CdTe QDs were characterized by TEM, UV–vis spectrophotometer and spectrofluorometer. Meanwhile, spectrofluorometer was used to evaluation of simple, convenient and highly sensitive determination of NOR-L. After the experimental conditions were optimized, a good linear relationship was obtained from 0.1–100 μg/mL with the coefficient of determination (0.99342) and the limit of detection (LOD) was 0.031 μg/mL. Moreover, a possible quenching mechanism was investigated and the CdTe QDs were also successfully used to confirm the NOR-L in pharmaceutical formations. The proposed method is rapid, simple, and applied. - Highlights: • The synthesis procedures were very simple. • The CdTe QDs were used to detect Norfloxacin lactate. • The mechanism of the proposed reaction was discussed.

  18. Simple synthesis of thioglycolic acid-coated CdTe quantum dots as probes for Norfloxacin lactate detection

    International Nuclear Information System (INIS)

    In this study, a simple and effective fluorometry method has been developed and used for the determination of Norfloxacin lactate (NOR-L) by the fluorescence quenching of thioglycolic acid (TGA)-coated CdTe quantum dots (QDs). The TGA-CdTe QDs were obtained in a simple way without precursor preparation, heating, pH adjustment and N2 protection. The CdTe QDs were characterized by TEM, UV–vis spectrophotometer and spectrofluorometer. Meanwhile, spectrofluorometer was used to evaluation of simple, convenient and highly sensitive determination of NOR-L. After the experimental conditions were optimized, a good linear relationship was obtained from 0.1–100 μg/mL with the coefficient of determination (0.99342) and the limit of detection (LOD) was 0.031 μg/mL. Moreover, a possible quenching mechanism was investigated and the CdTe QDs were also successfully used to confirm the NOR-L in pharmaceutical formations. The proposed method is rapid, simple, and applied. - Highlights: • The synthesis procedures were very simple. • The CdTe QDs were used to detect Norfloxacin lactate. • The mechanism of the proposed reaction was discussed

  19. Performance of the digene LQ, RH and PS HPVs genotyping systems on clinical samples and comparison with HC2 and PCR-based Linear Array

    Directory of Open Access Journals (Sweden)

    Godínez Jose M

    2011-11-01

    Full Text Available Abstract Background Certain Human Papillomaviruses (HPVs are the infectious agents involved in cervical cancer development. Detection of HPVs DNA is part of the cervical cancer screening protocols and HPVs genotyping has been proposed for its inclusion in these preventive programs. The aim of this study was to evaluate three novel genotyping tests, namely Qiagen LQ, RH and PS, in clinical samples with and without abnormalities. For this, 305 cervical samples were processed and the results of the evaluated techniques were compared with those obtained in the HPVs diagnostic process in our lab, by using HC2 and Linear Array (LA technologies. Results The concordances and kappa statistics (k for each technique compared with HC2 were 98.69% (k = 0.94 for LQ, 98.03% (k = 0.91 for RH and 91.80% (k = 0.82 for PS. There was a very good agreement in HPVs type-specific concordance for the most prevalent types HPV16 (kappa range = 0.83-0.90, HPV18 (k.r.= 0.74-0.80 and HPV45 (k.r.= 0.82-0.90. Conclusions The three tests showed an overall good concordance for HPVs detection when compared with HR-HC2 system. LQ and RH rendered lower detection rate for multiple infections than LA genotyping. However, our understanding of the clinical significance of multiple HPVs infections is still incomplete and therefore the relevance of the lower ability to detect multiple infections needs to be evaluated.

  20. Endosonography with linear array instead of endoscopic retrograde cholangiography as the diagnostic tool in patients with moderate suspicion of common bile duct stones

    Institute of Scientific and Technical Information of China (English)

    Maciej Kohut; Andrzej Nowak; Ewa Nowakowska-Dutawa; Tomasz Marek; Roman Kaczor

    2003-01-01

    AIM: To evaluate the diagnostic efficiency of endoscopic ultrasound (EUS) as the main imaging modality in patients with moderate suspicion of common bile duct stones (CBDS).METHODS: 55 patients with moderate clinical suspicion of CBDS were prospectively included to the study and evaluated with EUS. This study was done in single blind method in the clinical and biochemical data of patients. EUS was done with echo-endoscope Pentax FG 32-UA (f=5-7,5 MHz) and Hitachi EUB 405 ultrasound machine. Patients diagnosed with CBDS by EUS were excluded from this study and treated with ERC. All the other patients were included to the follow up study obtained by mail every 6 months for clinical evaluation (need of ERC or surgery).RESULTS: CBDS was found in 4 patients by EUS. Diagnosis was confirmed in all cases on ERC. The remaining 51 patients without CBDS on EUS were followed up for 6-26 months (meanly 13 months) There were: 40 women, 42cholecystectomized patients, aged: 55 (mean). Biochemical values (mean values) were as follows: bilirubin: 14,9 μmol.L-1,alkaline phosphatase: 95 IU.L-,1 γ-GTP: 131 IU.L-1, ALT: 50IU.L-1, AST: 49 IU.L-1, Only 1 patient was lost for follow up.In the remaining 50 patients with follow up, there was only 1 (2 %) patient with persistent biliary symptoms in whom CBDS was finally diagnosed by ERC with ES. All other patients remained symptoms free on follow up and did not require ERC or biliary surgery.CONCLUSION: Vast majority of patients with moderate suspicion of CBDS and no stones on EUS with linear array can avoid invasive evaluation of biliary tree with ERC.

  1. Thermal lensing and frequency chirp in a heated CdTe modulator crystal and its effects on laser radar performance

    Science.gov (United States)

    Eng, R. S.; Kachelmyer, A. L.; Harris, N. W.

    1991-08-01

    The effects of optical and microwave heatings and thermally-induced birefringence in a CdTe modulator crystal on the performance of a linear FM CO2 laser radar are examined. This is conducted in terms of reductions in beam Strehl ratio and dynamic ranges of the Doppler shift and range for given optical and microwave powers. An analysis of the thermal lenses generated by these heatings is presented.

  2. Cu Migration in Polycrystalline CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Da [Arizona State University; Akis, Richard [Arizona State University; Brinkman, Daniel [Arizona State University; Sankin, Igor [First Solar; Fang, Tian [First Solar; Vasileska, Dragica [Arizona State University; Ringhofer, Christian [Arizona State University

    2014-03-12

    An impurity reaction-diffusion model is applied to Cu defects and related intrinsic defects in polycrystalline CdTe for a better understanding of Cu’s role in the cell level reliability of CdTe PV devices. The simulation yields transient Cu distributions in polycrystalline CdTe during solar cell processing and stressing. Preliminary results for Cu migration using available diffusivity and solubility data show that Cu accumulates near the back contact, a phenomena that is commonly observed in devices after back-contact processing or stress conditions.

  3. Auger relative sensitivivity factors for CdTe oxide

    OpenAIRE

    Bartolo-Pérez, P.; Peña, J. L.; M.H. Farías

    1999-01-01

    The Auger lineshape of Te MNN in measurements of Auger spectra of CdTe oxide films with various degrees of oxidation was analyzed. By using standards from stoichiometric compounds, Auger relative sensitivity factors (RSF´s) of Cd, Te and O for CdTe oxide thin films were obtained. The value of the RFS of oxygen is about constant, 0.27-0.28, for the standard compound, CdO, TeO2 and CdTeO3 (considering the RSF of Cd as 1). However, the obtained RSF of Te changes from 0.69 in CdTe up to 0.87 in C...

  4. Counting efficiency of a CdTe detector

    International Nuclear Information System (INIS)

    The purpose of this work is to obtain some data about the energy dependence of the sensitivity of a CdTe detector in order to use it for a miniature dose rate meter. The intrinsic efficiencies of the CdTe detector were measured for several photon energies between 22 and 835 keV. The results showed the great dependence of the efficiency of the CdTe detector on photon energy, for example, the intrinsic efficiencies for the photons of 122 keV and 835 keV were 71% and 8.7% respectively. Some further problems were also presented and discussed. (author)

  5. Spin dynamics in bulk CdTe at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Nahalkova, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Nemec, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic)]. E-mail: nemec@karlov.mff.cuni.cz; Sprinzl, D. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Belas, E. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Horodysky, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Franc, J. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Hlidek, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Maly, P. [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic)

    2006-01-25

    In this paper, we report on the room temperature dynamics of spin-polarized carriers in undoped bulk CdTe. Platelets of CdTe with different concentration of preparation-induced dislocations were prepared by combining the mechanical polishing and chemical etching. Using the polarization-resolved pump-probe experiment in transmission geometry, we have observed a systematic decrease of both the signal polarization and the electron spin dephasing time (from 52 to 36 ps) with the increased concentration of defects. We have suggested that the Elliot-Yafet mechanism might be the dominant spin dephasing mechanism in platelets of CdTe at room temperature.

  6. Spin dynamics in bulk CdTe at room temperature

    International Nuclear Information System (INIS)

    In this paper, we report on the room temperature dynamics of spin-polarized carriers in undoped bulk CdTe. Platelets of CdTe with different concentration of preparation-induced dislocations were prepared by combining the mechanical polishing and chemical etching. Using the polarization-resolved pump-probe experiment in transmission geometry, we have observed a systematic decrease of both the signal polarization and the electron spin dephasing time (from 52 to 36 ps) with the increased concentration of defects. We have suggested that the Elliot-Yafet mechanism might be the dominant spin dephasing mechanism in platelets of CdTe at room temperature

  7. Process Development for High Voc CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Ferekides, C. S.; Morel, D. L.

    2011-05-01

    This is a cumulative and final report for Phases I, II and III of this NREL funded project (subcontract # XXL-5-44205-10). The main research activities of this project focused on the open-circuit voltage of the CdTe thin film solar cells. Although, thin film CdTe continues to be one of the leading materials for large-scale cost-effective production of photovoltaics, the efficiency of the CdTe solar cells have been stagnant for the last few years. This report describes and summarizes the results for this 3-year research project.

  8. Annealing conditions for intrinsic CdTe

    Science.gov (United States)

    Berding, M. A.

    1999-01-01

    Equilibrium native defect densities in CdTe are calculated from ab initio methods, and compared with experimental results. We find that CdTe is highly compensated p type under tellurium-saturated conditions, with the cadmium vacancy as the dominant acceptor and the tellurium antisite as the compensating donor. This finding is in agreement with recent experiments that find a much larger deviation from stoichiometry than would be predicted by the electrically active defects. Under cadmium-saturated conditions, cadmium interstitials are predicted to dominate and the material is found to be n type. Native defect concentrations and the corresponding carrier concentrations are predicted as a function of processing conditions, and can serve as a guide to postgrowth anneals to manipulate the conductivity of undoped material for applications in x- and γ-ray spectrometers. Furthermore, we show that by choosing appropriate annealing conditions and extrinsic dopants, one can increase the operating efficiency of nuclear spectrometers by reducing the density of specific native defects that produce midgap trapping states.

  9. Preparation and properties of evaporated CdTe films compared with single crystal CdTe

    Science.gov (United States)

    Bube, R. H.

    The hot wall vacuum deposition system is discussed and is is good temperature tracking between the furnace core and the CdTe source itself are indicated. Homojunction cells prepared by HWVE deposition of n-CdTe on p-CdTe substrates show no significant change in dark or light properties after open circuit storage for the next 9 months. CdTe single crystal boules were grown with P, As and Cs impurity. For P impurity it appears that the segregation coefficient is close to unity, that the value of hole density is controlled by the P, and that growth with excess Cd gives slightly higher values of hole density than growth with excess Te. CdTe:As crystals appear similar to CdTe:P crystals.

  10. Growth of CdTe: Al films; Crecimiento de peliculas de CdTe: Al

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez A, M.; Zapata T, M. [CICATA-IPN, 89600 Altamira, Tamaulipas (Mexico); Melendez L, M. [CINVESTAV-IPN, A.P. 14-740, 07000 Mexico D.F. (Mexico); Pena, J.L. [CINVESTAV-IPN, A.P. 73 Cordemex, 97310 Merida, Yucatan (Mexico)

    2006-07-01

    CdTe: AI films were grown by the close space vapor transport technique combined with free evaporation (CSVT-FE). The Aluminum (Al) evaporation was made by two kinds of sources: one made of graphite and the other of tantalum. The films were deposited on glass substrates. The Al source temperature was varied maintaining the CdTe source temperature fixed as well as the substrate temperature. The films were characterized by x-ray energy dispersive analysis (EDAX), x-ray diffraction and optical transmission. The results showed for the films grown with the graphite source for Al evaporation, the Al did not incorporate in the CdTe matrix, at least to the level of EDAX sensitivity; they maintained the same crystal structure and band gap. For the samples grown with the tantalum source, we were able to incorporate the Al. The x-ray diffraction patterns show that the films have a crystal structure that depends on Al concentration. They were cubic up to 2.16 at. % Al concentration; for 19.65 at. % we found a mixed phase; for Al concentration higher than 21 at. % the films were amorphous. For samples with cubic structure it was found that the lattice parameter decreases and the band gap increases with Al concentration. (Author)

  11. Device Fabrication using Crystalline CdTe and CdTe Ternary Alloys Grown by MBE

    Energy Technology Data Exchange (ETDEWEB)

    Zaunbrecher, Katherine; Burst, James; Seyedmohammadi, Shahram; Malik, Roger; Li, Jian V.; Gessert, Timothy A.; Barnes, Teresa

    2015-06-14

    We fabricated epitaxial CdTe:In/CdTe:As homojunction and CdZnTe/CdTe and CdMgTe/CdTe heterojunction devices grown on bulk CdTe substrates in order to study the fundamental device physics of CdTe solar cells. Selection of emitter-layer alloys was based on passivation studies using double heterostructures as well as band alignment. Initial results show significant device integration challenges, including low dopant activation, high resistivity substrates and the development of low-resistance contacts. To date, the highest open-circuit voltage is 715 mV in a CdZnTe/CdTe heterojunction following anneal, while the highest fill factor of 52% was attained in an annealed CdTe homojunction. In general, all currentvoltage measurements show high series resistance, capacitancevoltages measurements show variable doping, and quantum efficiency measurements show low collection. Ongoing work includes overcoming the high resistance in these devices and addressing other possible device limitations such as non-optimum junction depth, interface recombination, and reduced bulk lifetime due to structural defects.

  12. 基于非均匀阵列天线的MUSIC算法性能分析%Performance Analysis of MUSIC Algorithm Based on Non-uniform Spaced Linear Arrays

    Institute of Scientific and Technical Information of China (English)

    杨桂芹; 房琪; 胡滢

    2012-01-01

    在非均匀线阵上应用MUSIC算法进行测向.阵列模型采用最小冗余阵列,排除了测向模糊的影响.本文通过仿真,分析了信噪比、快拍数、阵元数等因素对MUSIC算法的影响,同时表明,非均匀阵列的测向分辨率精度高于均匀阵列的分辨率精度.%MUSIC algorithm is used to estimate the Direction-of-Arrival (DOA) in non-uniform arrays. To achieve unambiguous DOA estimation,the minimum-redundant linear array is applied to the array model. Through the simulation,the influence of SNR,number of snapshots and array elements on MUSIC,is analyzed and the result proves that higher resolution can be achieved in the non-uniform arrays.

  13. Extracting Cu Diffusion Parameters in Polycrystalline CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Akis, Richard [Arizona State Univeristy; Brinkman, Daniel [Arizona State Univeristy; Sankin, Igor [First Solar; Fang, Tian [First Solar; Guo, Da [Arizona State Univeristy; Dragica, Vasileska [Arizona State Univeristy; Ringhofer, Christian [Arizona State University

    2014-06-13

    It is well known that Cu plays an important role in CdTe solar cell performance as a dopant. In this work, a finite-difference method is developed and used to simulate Cu diffusion in CdTe solar cells. In the simulations, which are done on a two-dimensional (2D) domain, the CdTe is assumed to be polycrystal-line, with the individual grains separated by grain boundaries. When used to fit experimental Cu concentration data, bulk and grain boundary diffusion coefficients and activation energies for CdTe can be extracted. In the past, diffusion coefficients have been typically obtained by fitting data to simple functional forms of limited validity. By doing full simulations, the simplifying assumptions used in those analytical models are avoided and diffusion parameters can thus be determined more accurately.

  14. CdTe Solar Cells: The Role of Copper

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Da [Arizona State University; Akis, Richard [Arizona State University; Brinkman, Daniel [Arizona State University; Sankin, Igor [First Solar; Fang, Tian [First Solar; Vasileska, Dragica [Arizona State University; Ringhofer, Christain [Arizona State University

    2014-06-06

    In this work, we report on developing 1D reaction-diffusion solver to understand the kinetics of p-type doping formation in CdTe absorbers and to shine some light on underlying causes of metastabilities observed in CdTe PV devices. Evolution of intrinsic and Cu-related defects in CdTe solar cell has been studied in time-space domain self-consistently with free carrier transport and Poisson equation. Resulting device performance was simulated as a function of Cu diffusion anneal time showing pronounced effect the evolution of associated acceptor and donor states can cause on device characteristics. Although 1D simulation has intrinsic limitations when applied to poly-crystalline films, the results suggest strong potential of the approach in better understanding of the performance and metastabilities of CdTe photovoltaic device.

  15. Modeling Copper Diffusion in Polycrystalline CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Akis, Richard [Arizona State University; Brinkman, Daniel [Arizona State University; Sankin, Igor [First Solar; Fang, Tian [First Solar; Guo, Da [Arizona State Univeristy; Vasileska, Dragica [Arizona State University; Ringhofer, Christain [Arizona State University

    2014-06-06

    It is well known that Cu plays an important role in CdTe solar cell performance as a dopant. In this work, a finite-difference method is developed and used to simulate Cu diffusion in CdTe solar cells. In the simulations, which are done on a two-dimensional (2D) domain, the CdTe is assumed to be polycrystalline, with the individual grains separated by grain boundaries. When used to fit experimental Cu concentration data, bulk and grain boundary diffusion coefficients and activation energies for CdTe can be extracted. In the past, diffusion coefficients have been typically obtained by fitting data to simple functional forms of limited validity. By doing full simulations, the simplifying assumptions used in those analytical models are avoided and diffusion parameters can thus be determined more accurately

  16. Radiative and interfacial recombination in CdTe heterostructures

    International Nuclear Information System (INIS)

    Double heterostructures (DH) were produced consisting of a CdTe film between two wide band gap barriers of CdMgTe alloy. A combined method was developed to quantify radiative and non-radiative recombination rates by examining the dependence of photoluminescence (PL) on both excitation intensity and time. The measured PL characteristics, and the interface state density extracted by modeling, indicate that the radiative efficiency of CdMgTe/CdTe DHs is comparable to that of AlGaAs/GaAs DHs, with interface state densities in the low 1010 cm−2 and carrier lifetimes as long as 240 ns. The radiative recombination coefficient of CdTe is found to be near 10−10 cm3s−1. CdTe film growth on bulk CdTe substrates resulted in a homoepitaxial interface layer with a high non-radiative recombination rate

  17. Studies of key technologies for CdTe solar modules

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper, CdS thin films, which act as the window layer and n-type partner to the p-type CdTe layer, were prepared by chemical bath deposition (CBD). CdTe thin films were deposited by the close-spaced sublimation (CSS) method. To obtain high-quality back contacts, a Te-rich layer was created with chemical etching and back contact materials were applied after CdTe annealing. The results indicate that the ZnTe/ZnTe:Cu complex layers show superior performance over other back contacts. Finally, by using laser scribing and mechanical scribing, the CdTe mini-modules were fabricated, in which a glass/SnO2:F/CdS/CdTe/ZnTe/ZnTe:Cu/Ni solar module with a PWQC-confirmed total-area efficiency of 7.03% (54 cm2) was achieved.

  18. Interaction of porphyrins with CdTe quantum dots

    International Nuclear Information System (INIS)

    Porphyrins may be used as photosensitizers for photodynamic therapy, photocatalysts for organic pollutant dissociation, agents for medical imaging and diagnostics, applications in luminescence and electronics. The detection of porphyrins is significantly important and here the interaction of protoporphyrin-IX (PPIX) with CdTe quantum dots was studied. It was observed that the luminescence of CdTe quantum dots was quenched dramatically in the presence of PPIX. When CdTe quantum dots were embedded into silica layers, almost no quenching by PPIX was observed. This indicates that PPIX may interact and alter CdTe quantum dots and thus quench their luminescence. The oxidation of the stabilizers such as thioglycolic acid (TGA) as well as the nanoparticles by the singlet oxygen generated from PPIX is most likely responsible for the luminescence quenching. The quenching of quantum dot luminescence by porphyrins may provide a new method for photosensitizer detection.

  19. Controlled Synthesis of Nanoscale CdTe Urchins

    Institute of Scientific and Technical Information of China (English)

    BAO Jian; SHEN Yue; SUN Yan; YUE Yang; CHEN Xin; DAI Ning

    2009-01-01

    We presented a simple route to prepare nanoscale CdTe urchins in a tri-n-octylphosphine oxide(TOPO)system.CdTe urchins consisted of a core and several attached arms.The arms were ca.3 nm wide,and their lengths could be controlled with the reaction time.The authors investigated the optical absorption and structural properties of the prepared CdTe.The lengths of the arms could be tuned into CdTe nanourchins,which led to a change in the photophysical properties of the nanoscale CdTe urchins.The results,including transmission electron microscopy(TEM) and absorption spectra,indicated that mesoporous silica and aminopropyltriethoxysilane(APTES) contributed to the formation of nanoscale CdTe urchins.

  20. CdTe Photovoltaics for Sustainable Electricity Generation

    Science.gov (United States)

    Munshi, Amit; Sampath, Walajabad

    2016-04-01

    Thin film CdTe (cadmium telluride) is an important technology in the development of sustainable and affordable electricity generation. More than 10 GW of installations have been carried out using this technology around the globe. It has been demonstrated as a sustainable, green, renewable, affordable and abundant source of electricity. An advanced sublimation tool has been developed that allows highly controlled deposition of CdTe films onto commercial soda lime glass substrates. All deposition and treatment steps can be performed without breaking the vacuum within a single chamber in an inline process that can be conveniently scaled to a commercial process. In addition, an advanced cosublimation source has been developed to allow the deposition of ternary alloys such as Cd x Mg1-x Te to form an electron reflector layer which is expected to address the voltage deficits in current CdTe devices and to achieve very high efficiency. Extensive materials characterization, including but not limited to scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, high resolution transmission electron microscopy and electron back-scatter diffraction, has been performed to get a better understanding of the effects of processing conditions on CdTe thin film photovoltaics. This combined with computer modeling such as density function theory modeling gives a new insight into the mechanism of CdTe photovoltaic function. With all these efforts, CdTe photovoltaics has seen great progress in the last few years. Currently, it has been recorded as the cheapest source of electricity in the USA on a commercial scale, and further improvements are predicted to further reduce the cost while increasing its utilization. Here, we give an overview of the advantages of thin film CdTe photovoltaics as well as a brief review of the challenges that need to be addressed. Some fundamental studies of processing conditions for thin film CdTe are also presented

  1. Electrical properties of single CdTe nanowires

    OpenAIRE

    Elena Matei; Camelia Florica; Andreea Costas; María Eugenia Toimil-Molares; Ionut Enculescu

    2015-01-01

    Ion track, nanoporous membranes were employed as templates for the preparation of CdTe nanowires. For this purpose, electrochemical deposition from a bath containing Cd and Te ions was employed. This process leads to high aspect ratio CdTe nanowires, which were harvested and placed on a substrate with lithographically patterned, interdigitated electrodes. Focused ion beam-induced metallization was used to produce individual nanowires with electrical contacts and electrical measurements were p...

  2. CdTe Photovoltaics for Sustainable Electricity Generation

    Science.gov (United States)

    Munshi, Amit; Sampath, Walajabad

    2016-09-01

    Thin film CdTe (cadmium telluride) is an important technology in the development of sustainable and affordable electricity generation. More than 10 GW of installations have been carried out using this technology around the globe. It has been demonstrated as a sustainable, green, renewable, affordable and abundant source of electricity. An advanced sublimation tool has been developed that allows highly controlled deposition of CdTe films onto commercial soda lime glass substrates. All deposition and treatment steps can be performed without breaking the vacuum within a single chamber in an inline process that can be conveniently scaled to a commercial process. In addition, an advanced cosublimation source has been developed to allow the deposition of ternary alloys such as Cd x Mg1- x Te to form an electron reflector layer which is expected to address the voltage deficits in current CdTe devices and to achieve very high efficiency. Extensive materials characterization, including but not limited to scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, high resolution transmission electron microscopy and electron back-scatter diffraction, has been performed to get a better understanding of the effects of processing conditions on CdTe thin film photovoltaics. This combined with computer modeling such as density function theory modeling gives a new insight into the mechanism of CdTe photovoltaic function. With all these efforts, CdTe photovoltaics has seen great progress in the last few years. Currently, it has been recorded as the cheapest source of electricity in the USA on a commercial scale, and further improvements are predicted to further reduce the cost while increasing its utilization. Here, we give an overview of the advantages of thin film CdTe photovoltaics as well as a brief review of the challenges that need to be addressed. Some fundamental studies of processing conditions for thin film CdTe are also presented

  3. Temperature dependent electroreflectance study of CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Raadik, T., E-mail: taavi.raadik@ttu.ee [Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Krustok, J.; Josepson, R.; Hiie, J. [Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Potlog, T.; Spalatu, N. [Moldova State University, A. Mateevici str. 60, MD-2009 Chisinau (Moldova, Republic of)

    2013-05-01

    Cadmium telluride is a promising material for large scale photovoltaic applications. In this paper we study CdS/CdTe heterojunction solar cells with electroreflectance spectroscopy. Both CdS and CdTe layers in solar cells were grown sequentially without intermediate processing by the close-space sublimation method. Electroreflectance measurements were performed in the temperature range of T = 100–300 K. Two solar cells were investigated with conversion efficiencies of 4.1% and 9.6%. The main focus in this work was to study the temperature dependent behavior of the broadening parameter and the bandgap energy of CdTe thin film in solar cells. Room temperature bandgap values of CdTe were E{sub g} = 1.499 eV and E{sub g} = 1.481 eV for higher and lower efficiency solar cells, respectively. Measured bandgap energies are lower than for single crystal CdTe. The formation of CdTe{sub 1−x}S{sub x} solid solution layer on the surface of CdTe is proposed as a possible cause of lower bandgap energies. - Highlights: ► Temperature dependent electroreflectance measurements of CdS/CdTe solar cells ► Investigation of junction properties between CdS and CdTe ► Formation of CdTe{sub 1−} {sub x}S{sub x} solid solution layer in the junction area.

  4. High-quality CdTe films from nanoparticle precursors

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, D.L.; Pehnt, M.; Urgiles, E. [National Renewable Energy Lab., Golden, CO (United States)] [and others

    1996-05-01

    In this paper the authors demonstrate that nanoparticulate precursors coupled with spray deposition offers an attractive route into electronic materials with improved smoothness, density, and lower processing temperatures. Employing a metathesis approach, cadmium iodide was reacted with sodium telluride in methanol solvent, resulting in the formation of soluble NaI and insoluble CdTe nanoparticles. After appropriate chemical workup, methanol-capped CdTe colloids were isolated. CdTe thin film formation was achieved by spray depositing the nanoparticle colloids (25-75 {Angstrom} diameter) onto substrates at elevated temperatures (T = 280-440{degrees}C) with no further thermal treatment. These films were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Cubic CdTe phase formation was observed by XRD, with a contaminant oxide phase also detected. XPS analysis showed that CdTe films produced by this one-step method contained no Na or C and substantial O. AFM gave CdTe grain sizes of {approx}0.1-0.3 {mu}m for film sprayed at 400{degrees}C. A layer-by-layer film growth mechanism proposed for the one-step spray deposition of nanoparticle precursors will be discussed.

  5. Evaluation of Compton gamma camera prototype based on pixelated CdTe detectors.

    Science.gov (United States)

    Calderón, Y; Chmeissani, M; Kolstein, M; De Lorenzo, G

    2014-06-01

    A proposed Compton camera prototype based on pixelated CdTe is simulated and evaluated in order to establish its feasibility and expected performance in real laboratory tests. The system is based on module units containing a 2×4 array of square CdTe detectors of 10×10 mm(2) area and 2 mm thickness. The detectors are pixelated and stacked forming a 3D detector with voxel sizes of 2 × 1 × 2 mm(3). The camera performance is simulated with Geant4-based Architecture for Medicine-Oriented Simulations(GAMOS) and the Origin Ensemble(OE) algorithm is used for the image reconstruction. The simulation shows that the camera can operate with up to 10(4) Bq source activities with equal efficiency and is completely saturated at 10(9) Bq. The efficiency of the system is evaluated using a simulated (18) F point source phantom in the center of the Field-of-View (FOV) achieving an intrinsic efficiency of 0.4 counts per second per kilobecquerel. The spatial resolution measured from the point spread function (PSF) shows a FWHM of 1.5 mm along the direction perpendicular to the scatterer, making it possible to distinguish two points at 3 mm separation with a peak-to-valley ratio of 8. PMID:24932209

  6. CdTe Thin Film Solar Cells and Modules Tutorial; NREL (National Renewable Energy Laboratory)

    Energy Technology Data Exchange (ETDEWEB)

    Albin, David S.

    2015-06-13

    This is a tutorial presented at the 42nd IEEE Photovoltaics Specialists Conference to cover the introduction, background, and updates on CdTe cell and module technology, including CdTe cell and module structure and fabrication.

  7. Growth of CdTe films on GaAs by ionized cluster beam epitaxy

    Science.gov (United States)

    Tang, H. P.; Feng, J. Y.; Fan, Y. D.; Li, H. D.

    1991-06-01

    Stoichiometric epitaxial films of CdTe were grown on (100)GaAs substrates by ionized cluster beam (ICB) epitaxy. Streaky RHEED patterns indicated good crystallinity and surface flatness of the epitaxial CdTe films. CdTe(100) orientation was obtained when the substrate preheating temperature was 480°C, while CdTe growth inboth (100) and (111) orientations occured when the substrate preheating temperature was above 550°C. The characteristics of the ICB growth process were investigated and the cluster-involving growth behavior has been evidenced. When sufficient clusters were generated in the deposition beam under adequate source vapor pressures, the crystalline quality of the resulting CdTe epilayers improved significantly with the increase of kinetic energy of the CdTe clusters. The best CdTe epilayer obtained exhibited a CdTe(400) double crystal rocking curve (DCRC) having a FWHM of 630 arc sec.

  8. Growth of CdTe films on GaAs by ionized cluster beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Tang, H.P.; Feng, J.Y.; Fan, Y.D.; Li, H.D. (Dept. of Materials Science and Engineering, Tsinghua Univ., Beijing (China))

    1991-06-01

    Stoichiometric epitaxial films of CdTe were grown on (100)GaAs substrates by ionized cluster beam (ICB) epitaxy. Streaky RHEED patterns indicated good crystallinity and surface flatness of the epitaxial CdTe films. CdTe(100) orientation was obtained when the substrate preheating temperature was 480degC, while CdTe growth in both (100) and (111) orientations occurred when the substrate preheating temperature was above 550degC. The characteristics of the ICB growth process were investigated and the cluster-involving growth behavior has been evidenced. When sufficient clusters were generated in the deposition beam under adequate source vapor pressures, the crystalline quality of the resulting CdTe epilayers improved significantly with the increase of kinetic energy of the CdTe clusters. The best CdTe epilayer obtained exhibited a CdTe(400) double crystal rocking curve (DCRC) having a FWHM of 630 arc sec. (orig.).

  9. Comparative study of CdTe sources used for deposition of CdTe thin films by close spaced sublimation technique

    Directory of Open Access Journals (Sweden)

    Wagner Anacleto Pinheiro

    2006-03-01

    Full Text Available Unlike other thin film deposition techniques, close spaced sublimation (CSS requires a short source-substrate distance. The kind of source used in this technique strongly affects the control of the deposition parameters, especially the deposition rate. When depositing CdTe thin films by CSS, the most common CdTe sources are: single-crystal or polycrystalline wafers, powders, pellets or pieces, a thick CdTe film deposited onto glass or molybdenum substrate (CdTe source-plate and a sintered CdTe powder. In this work, CdTe thin films were deposited by CSS technique from different CdTe sources: particles, powder, compact powder, a paste made of CdTe and propylene glycol and source-plates (CdTe/Mo and CdTe/glass. The largest deposition rate was achieved when a paste made of CdTe and propylene glycol was used as the source. CdTe source-plates led to lower rates, probably due to the poor heat transmission, caused by the introduction of the plate substrate. The results also showed that compacting the powder the deposition rate increases due to the better thermal contact between powder particles.

  10. Research on Linear Electromagnetic Series-parallel Array Artificial Muscle Design%直线电磁驱动串并联阵列人工肌肉设计研究

    Institute of Scientific and Technical Information of China (English)

    李靖; 秦现生; 张雪峰; 王战玺

    2012-01-01

    Through analysis of skeletal muscle structure and function of the animal,a bio-inspired linear electromagnetic series-parallel array artificial muscle was proposed.The performances of different kinds of artificial muscle were compared.The electromagnetic field of artificial sarcomere actuator was simulated based on finite element analysis.A model machine was made and tested at different loads and the different control strategies.The experiments show that the linear electromagnetic series-parallel array artificial muscle has good characteristics,such as high response speed,small volume,light quality,high power density ect.The linear electromagnetic series-parallel array artificial muscle has good engineering application prospects.%在分析动物骨骼肌的结构和运动形式的基础上,设计了基于电磁力的类肌肉肌纤维多肌小节串并联构成的阵列式人工肌肉。首先对构成人工肌肉的驱动器进行了性能对比,而后对类肌小节驱动器电磁场进行了有限元仿真分析,并完成了样机制作、不同负载及不同控制策略的多组开闭环实验测试。通过分析样机实验数据可知,该方案具有响应速度高、体积小、质量小、加速度高等特点。

  11. Impact of thermal annealing on physical properties of vacuum evaporated polycrystalline CdTe thin films for solar cell applications

    Science.gov (United States)

    Chander, Subhash; Dhaka, M. S.

    2016-06-01

    A study on impact of post-deposition thermal annealing on the physical properties of CdTe thin films is undertaken in this paper. The thin films of thickness 500 nm were grown on ITO and glass substrates employing thermal vacuum evaporation followed by post-deposition thermal annealing in air atmosphere within low temperature range 150-350 °C. These films were subjected to the XRD, UV-Vis NIR spectrophotometer, source meter, SEM coupled with EDS and AFM for structural, optical, electrical and surface topographical analysis respectively. The diffraction patterns reveal that the films are having zinc-blende cubic structure with preferred orientation along (111) and polycrystalline in nature. The crystallographic parameters are calculated and discussed in detail. The optical band gap is found in the range 1.48-1.64 eV and observed to decrease with thermal annealing. The current-voltage characteristics show that the CdTe films exhibit linear ohmic behavior. The SEM studies show that the as-grown films are homogeneous, uniform and free from defects. The AFM studies reveal that the surface roughness of films is observed to increase with annealing. The experimental results reveal that the thermal annealing has significant impact on the physical properties of CdTe thin films and may be used as absorber layer to the CdTe/CdS thin films solar cells.

  12. Ultrasensitive fluorescence immunoassay for detection of ochratoxin A using catalase-mediated fluorescence quenching of CdTe QDs.

    Science.gov (United States)

    Huang, Xiaolin; Zhan, Shengnan; Xu, Hengyi; Meng, Xianwei; Xiong, Yonghua; Chen, Xiaoyuan

    2016-04-28

    Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to perform a dynamic linear detection of OTA ranging from 0.05 pg mL(-1) to 10 pg mL(-1). The half maximal inhibitory concentration was 0.53 pg mL(-1) and the limit of detection was 0.05 pg mL(-1). These values were approximately 283- and 300-folds lower than those of horseradish peroxidase (HRP)-based conventional ELISA, respectively. The reported method is accurate, highly reproducible, and specific against other mycotoxins in agricultural products as well. In summary, the developed fluorescence immunoassay based on H2O2-induced fluorescence quenching of CdTe QDs can be used for the rapid and highly sensitive detection of mycotoxins or haptens in food safety monitoring. PMID:27093176

  13. Correlation of the Cd-to-Te ratio on CdTe surfaces with the surface structure

    Science.gov (United States)

    Wu, Y. S.; Becker, C. R.; Waag, A.; Kraus, M. M.; Bicknell-Tassius, R. N.; Landwehr, G.

    1991-10-01

    We report here that reconstruction on (100), (111)A, and (111)B CdTe surfaces is either c(2×2), (2×2), and (1×1) or (2×1), (1×1), and (1×1) when they are Cd or Te stabilized, respectively. There is a mixed region between Cd and Te stabilization in which the reflected high-energy electron-diffraction (RHEED) patterns contain characteristics of both Cd- and Te-stabilized surfaces. We have also found that the Cd-to-Te ratio of the x-ray photoelectron intensities of their 3d3/2 core levels is about 20% larger for a Cd-stabilized (111)A, (111)B, or (100) CdTe surface than for a Te-stabilized one. According to a simple model calculation, which was normalized by means of the photoelectron intensity ratio of a Cd-stabilized (111)A and a Te-stabilized (111)B CdTe surface, the experimental data for CdTe surfaces can be explained by a linear dependence of the photoelectron-intensity ratio on the fraction of Cd in the uppermost monatomic layer. This surface composition can be correlated with the surface structure, i.e., the corresponding RHEED patterns. This correlation can in turn be employed to determine Te and Cd evaporation rates. The Te reevaporation rate is increasingly slower for the Te-stabilized (111)A, (111)B, and (100) surfaces, while the opposite is true for Cd from Cd-stabilized (111)A and (111)B surfaces. In addition, Te is much more easily evaporated from all the investigated surfaces than is Cd, if the substrate is kept at normal molecular-beam-epitaxy growth temperatures ranging from 200 °C to 300 °C.

  14. Design of a thin film CdTe solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Meyers, P.V.

    1988-01-15

    Cadmium telluride was originally considered for thin film solar cells because of its optimum band gap, high optical absorption coefficient and ability to be doped. Furthermore, it is a stable compound which can be produced by a wide variety of methods from stable raw materials. As thin film photovoltaics mature, however, it is clear that several more subtle attributes have a significant impact on the viability of commercialization. We discuss the observations which have provided insight and direction to Ametek's CdTe solar cell program. Rather than try to modify the inherent material properties of CdTe, advances have been made by designing a solar cell that exploits existing properties. Specifically, the tendency to self-compensate, which makes low resistance contacting difficult, is turned into an advantage in the n-i-p configuration; the CdTe provides an intrinsic layer with good carrier collection efficiency.

  15. Study of Back Contacts for CdTe Solar Cells

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    ZnTe/ZnTe∶Cu layer is used as a complex back contact. The parameters of CdTe solar cells with and without the complex back contacts are compared. The effects of un-doped layer thickness, doped concentration and post-deposition annealing temperature of the complex layer on solar cells performance are investigated.The results show that ZnTe/ZnTe∶Cu layer can improve back contacts and largely increase the conversion efficiency of CdTe solar cells. Un-doped layer and post-deposition annealing of high temperature can increase open voltage. Using the complex back contact, a small CdTe cell with fill factor of 73.14% and conversion efficiency of 12.93% is obtained.

  16. Resetting the Defect Chemistry in CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Metzger, Wyatt K.; Burst, James; Albin, David; Colegrove, Eric; Moseley, John; Duenow, Joel; Farrell, Stuart; Moutinho, Helio; Reese, Matt; Johnston, Steve; Barnes, Teresa; Perkins, Craig; Guthrey, Harvey; Al-Jassim, Mowafak

    2015-06-14

    CdTe cell efficiencies have increased from 17% to 21% in the past three years and now rival polycrystalline Si [1]. Research is now targeting 25% to displace Si, attain costs less than 40 cents/W, and reach grid parity. Recent efficiency gains have come largely from greater photocurrent. There is still headroom to lower costs and improve performance by increasing open-circuit voltage (Voc) and fill factor. Record-efficiency CdTe cells have been limited to Voc <; 880 mV, whereas GaAs can attain Voc of 1.10 V with a slightly smaller bandgap [2,3]. To overcome this barrier, we seek to understand and increase lifetime and carrier concentration in CdTe. In polycrystalline structures, lifetime can be limited by interface and grain-boundary recombination, and attaining high carrier concentration is complicated by morphology.

  17. Dynamics Research of Linear Array Deployable Structures Based on Structure of Scissor-like Element%剪式机构线性阵列可展结构的动力学特性研究

    Institute of Scientific and Technical Information of China (English)

    孙远涛; 王三民; 刘霞

    2012-01-01

    基于笛卡儿坐标系建立了剪式机构线性阵列组成的可展结构动力学模型,利用运动副等约束条件建立了剪式可展结构的运动约束方程.采用Runge-Kutta法进行数值计算,获得了该种机构式结构运动过程中的速度和加速度等规律,绘制了阵列组合机构的运动曲线,为该种结构的应用奠定了基础.结果表明,剪式机构线性阵列在展开过程中具有不一致的水平速度.%Based on the Cartesian frame,the paper established a dynamics model of the linear array deployable structures based on scissor-like element. The motion constraint equations can be established by constraints' conditions such as kinematic pairs. Using Runge-Kutta method for numerical calculation,the laws of the structure,such as velocity and acceleration,can be obtained in motion,and kinematic curve is also able to be drawn,and then it provides the foundation of this structure of the application. The results show that the linear array SLE in an process does not have consistent level speed.

  18. Coal mining applications of CdTe gamma ray sensors

    Energy Technology Data Exchange (ETDEWEB)

    Entine, G.; Tiernan, T.; Waer, P.; Hazlett, T. (Radiation Monitoring Devices, Inc., Watertown, MA (USA))

    1990-01-01

    Cadmium telluride (CdTe) solid-state radiation detectors have been used in the development of instrumentation that improves the efficiency of coal-mining operations by helping to locate coal seams and preventing the mining of high-sulfur coal near the edges of the seam. CdTe detectors were selected for these applications because while they are small and durable, they offer good stopping power, deliver adequate spectral response and operate at low voltage. These CdTe-based instruments have passed the mine-safety standards and are now in operation in the mine. (author).

  19. Advances in CdTe n-i-p photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Meyers, P.V. (Ametek Applied Materials Lab., Harleysville, PA (USA))

    1989-10-15

    Development of the CdTe n-i-p solar cell has enabled researchers to produce 11% efficient solar cells while eliminating stability problems associated with a low-resistance back contact. Furthermore, loss analysis indicates that significant increases in efficiency can still be realized through reduction of absorption and reflection and by passivation of recombination centers at the interfaces. Simplifications in the interconnection procedures make the CdTe n-i-p solar module more ''manufacturable''. A submodule with four interconnected cells has been produced. It has an aperture area efficiency over 8% with an area ratio of 0.91. (orig.).

  20. RELAXATION LONGUE DUREE DE LA PHOTOCONDUCTIVITE DANS CdTe

    OpenAIRE

    Zozime, A.; Schröter, W.

    1983-01-01

    Différents aspects des mesures de photoconductivité faites sur des monocristaux de CdTe sont présentés. Les signaux montrent l'existence d'un processus de relaxation de longue durée. Les spectres suivent une loi de variation du type loi d'Urbach. Enfin, le seuil d'énergie correspondant à la limite de détection des signaux mesurés dans CdTe de type n correspond à un niveau profond dans la bande interdite, associé aux dislocations.

  1. Coal mining applications of CdTe gamma ray sensors

    International Nuclear Information System (INIS)

    Cadmium telluride (CdTe) solid-state radiation detectors have been used in the development of instrumentation that improves the efficiency of coal-mining operations by helping to locate coal seams and preventing the mining of high-sulfur coal near the edges of the seam. CdTe detectors were selected for these applications because while they are small and durable, they offer good stopping power, deliver adequate spectral response and operate at low voltage. These CdTe-based instruments have passed the mine-safety standards and are now in operation in the mine. (author)

  2. Electrical properties of single CdTe nanowires

    Directory of Open Access Journals (Sweden)

    Elena Matei

    2015-02-01

    Full Text Available Ion track, nanoporous membranes were employed as templates for the preparation of CdTe nanowires. For this purpose, electrochemical deposition from a bath containing Cd and Te ions was employed. This process leads to high aspect ratio CdTe nanowires, which were harvested and placed on a substrate with lithographically patterned, interdigitated electrodes. Focused ion beam-induced metallization was used to produce individual nanowires with electrical contacts and electrical measurements were performed on these individual nanowires. The influence of a bottom gate was investigated and it was found that surface passivation leads to improved transport properties.

  3. Comparative study of CdTe sources used for deposition of CdTe thin films by close spaced sublimation technique

    OpenAIRE

    Wagner Anacleto Pinheiro; Vivienne Denise Falcão; Leila Rosa de Oliveira Cruz; Carlos Luiz Ferreira

    2006-01-01

    Unlike other thin film deposition techniques, close spaced sublimation (CSS) requires a short source-substrate distance. The kind of source used in this technique strongly affects the control of the deposition parameters, especially the deposition rate. When depositing CdTe thin films by CSS, the most common CdTe sources are: single-crystal or polycrystalline wafers, powders, pellets or pieces, a thick CdTe film deposited onto glass or molybdenum substrate (CdTe source-plate) and a sintered C...

  4. A Study on MIMO-SAR Linear Array Antenna Configuration and Function%MIMO-SAR 线性合成阵列模式及性能研究

    Institute of Scientific and Technical Information of China (English)

    谢超; 王力宝; 王党卫; 汪枫; 王玲

    2016-01-01

    Since synthetic aperture radar(SAR)realise the high azimuth resolution through synthesizing virtual array in azimuth,which is formed by spatial parallel sampling in a snapshot and spatial serial sampling in several snapshots.Multi-input multi-output(MIMO)radar SAR provides great convenience for the config-uration of antenna array and complex function of increasing the number of spatial parallel samples,which is achieved by using space diversity and waveform diversity technology.The uniform linear array(ULA)model of MIMO-SAR is studied,and according to the equivalent array in one snapshot,three kinds of pulse repeti-tion frequency(PRF)in MIMO-SAR mode are revealed.Then the performance of maximum unambiguous range,wide swath and clutter suppression in different array modes are analyzed,in order to supply the basis for the ways of array synthetic and function design in different applications.%合成孔径雷达(SAR)通过方位向的合成阵列实现方位高分辨,其中合成阵列是由单次快拍内的并行空间采样与多次快拍内的串行空间采样而构成。多输入多输出合成孔径雷达(MIMO-SAR)利用波形分集特性,可在单次快拍内获得大于实际阵元数目的并行空间采样,为阵列模式配置及功能复合提供了便利。针对 MIMO-SAR 线性合成阵列模式问题,以单次快拍等效阵列为基础,设计了3种脉冲重复频率条件下的阵列模式。进而对比分析了不同阵列模式下最大不模糊距离、测绘带宽度和杂波抑制性能,这为不同应用的 MIMO-SAR 阵列合成及功能设计提供了依据。

  5. A simple fluorescence quenching method for berberine determination using water-soluble CdTe quantum dots as probes

    Science.gov (United States)

    Cao, Ming; Liu, Meigui; Cao, Chun; Xia, Yunsheng; Bao, Linjun; Jin, Yingqiong; Yang, Song; Zhu, Changqing

    2010-03-01

    A novel method for the determination of berberine has been developed based on quenching of the fluorescence of thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) by berberine in aqueous solutions. Under optimum conditions, the relative fluorescence intensity was linearly proportional to the concentration of berberine between 2.5 × 10 -8 and 8.0 × 10 -6 mol L -1 with a detection limit of 6.0 × 10 -9 mol L -1. The method has been applied to the determination of berberine in real samples, and satisfactory results were obtained. The mechanism of the proposed reaction was also discussed.

  6. Structural, Optical, and Magnetic Properties of Co Doped CdTe Alloy Powders Prepared by Solid-State Reaction Method

    Directory of Open Access Journals (Sweden)

    M. Rigana Begam

    2013-01-01

    Full Text Available Co doped CdTe powder samples were prepared by solid-state reaction method. In the present work effect of Co doping on structural, optical, and magnetic properties has been studied. X-ray diffraction studies confirm zinc blend structure for all the samples. The lattice parameter showed linear increase with the increase in Co content. The elemental constituents were characterized by EDAX. Optical studies showed the increase in band gap with increase in Co level. The samples were diluted magnetic semiconductors and exhibited clear hysteresis loop showing room temperature ferromagnetism as confirmed by vibrating sample magnetometer.

  7. Efficient fluorescence energy transfer system between fluorescein isothiocyanate and CdTe quantum dots for the detection of silver ions.

    Science.gov (United States)

    Feng, Yueshu; Liu, Liwei; Hu, Siyi; Zou, Peng; Zhang, Jiaqi; Huang, Chen; Wang, Yue; Wang, Sihan; Zhang, Xihe

    2016-03-01

    We report a fluorescence resonance energy transfer (FRET) system in which the fluorescent donor is fluorescein isothiocyanate (FITC) dye and the fluorescent acceptor is CdTe quantum dot (QDs). Based on FRET quenching theory, we designed a method to detect the concentration of silver ions (Ag(+)). The results revealed a good linear trend over Ag(+) concentrations in the range 0.01-8.96 nmol/L, a range that was larger than with other methods; the quenching coefficient is 0.442. The FRET mechanism and physical mechanisms responsible for dynamic quenching are also discussed. PMID:26277997

  8. Radiation induced polarization in CdTe detectors

    Science.gov (United States)

    Vartsky, D.; Goldberg, M.; Eisen, Y.; Shamai, Y.; Dukhan, R.; Siffert, P.; Koebel, J. M.; Regal, R.; Gerber, J.

    1988-01-01

    Polarization induced by irradiation with intense gamma ray sources has been studied in chlorine-compensated CdTe detectors. The influence of several parameters, such as applied field strength, temperature and incident photon flux, on the polarization effect have been investigated. A relationship was found between the degree of polarization, detector efficiency and detector leakage current.

  9. Radiation induced polarization in CdTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Vartsky, D.; Goldberg, M.; Eisen, Y.; Shamai, Y.; Dukhan, R.; Siffert, P.; Koebel, J.M.; Regal, R.; Gerber, J.

    1988-01-15

    Polarization induced by irradiation with intense gamma ray sources has been studied in chlorine-compensated CdTe detectors. The influence of several parameters, such as applied field strength, temperature and incident photon flux, on the polarization effect have been investigated. A relationship was found between the degree of polarization, detector efficiency and detector leakage current.

  10. Highly luminescent water-soluble CdTe quantum dots

    NARCIS (Netherlands)

    Wuister, SF; Swart, A.N.; van Driel, F; Hickey, SG; Donega, CD; Swart, Ingmar

    2003-01-01

    Colloidal CdTe quantum dots prepared in TOP/DDA (trioctylphosphine/dodecylamine) are transferred into water by the use of aminoethanethiol.HCl (AET) or mercaptopropionic acid (MPA). This results in an increase in the photoluminescence quantum efficiency and a longer exciton lifetime. For the first t

  11. Thermal stability of substitutional ag in CdTe

    NARCIS (Netherlands)

    Jahn, SG; Hofsass, H; Restle, M; Ronning, C; Quintel, H; BharuthRam, K; Wahl, U

    1996-01-01

    The thermal stability of substitutional Ag in CdTe was deduced from lattice location measurements at different temperatures. Substitutional Ag probe atoms were generated via transmutation doping from radioactive Cd isotopes. The lattice sites of Ag isotopes were determined by measuring the channelin

  12. Intracavity CdTe modulators for CO2 lasers.

    Science.gov (United States)

    Kiefer, J. E.; Nussmeier, T. A.; Goodwin, F. E.

    1972-01-01

    The use of cadmium telluride as an electrooptic material for intracavity modulation of CO2 lasers is described. Included are the predicted and measured effects of CdTe intracavity modulators on laser performance. Coupling and frequency modulation are discussed and experimental results compared with theoretically predicted performance for both techniques. Limitations on the frequency response of the two types of modulation are determined.

  13. Electron transient transport in CdTe polycrystalline films

    Science.gov (United States)

    Ramírez-Bon, R.; Sánchez-Sinencio, F.; González de la Cruz, G.; Zelaya, O.

    1991-11-01

    Electron transient currents between coplanar electrodes have been measured in intrinsic polycrystalline films of CdTe, by means of the time of flight technique. The experimental results: electron transient current vs time, transit time vs voltage and the temperature dependence of the electron drift mobility, show features characteristics of dispersive electrical transport similar to that observed in disordered solids.

  14. EBIC INVESTIGATIONS OF EXTENDED DEFECTS IN CdTe

    OpenAIRE

    Panin, G.; Yakimov, E.

    1991-01-01

    The EBIC and remote contact EBIC (REBIC) techniques have been used to reveal grain boundaries and precipitates in CdTe crystals and to study their recombination contrast as a function of the electron beam parameters and temperature. The results obtained are discussed taking into account the defect charge state and the recombination properties of their environment.

  15. Applications of CdTe to nuclear medicine. Final report

    International Nuclear Information System (INIS)

    Uses of cadmium telluride (CdTe) nuclear detectors in medicine are briefly described. They include surgical probes and a system for measuring cerebral blood flow in the intensive care unit. Other uses include nuclear dentistry, x-ray exposure control, cardiology, diabetes, and the testing of new pharmaceuticals

  16. Catalytic growth of CdTe nanowires by closed space sublimation method

    International Nuclear Information System (INIS)

    CdTe nano-/micro-structures with various morphologies were grown by using the closed space sublimation (CSS) method on a sapphire substrate by Au-catalyzed vapor–liquid–solid (VLS) mechanism. Length, diameter, and morphology of the CdTe nano-/micro-structures depended on the growth time and temperature gradient between the substrate and powdered CdTe source. Scanning electron microscopy images showed that an Au catalyst droplet existed at the tips of CdTe nanowires, which confirms that CdTe nanowires were grown by an Au-catalyzed VLS mechanism. Also, we observed that the two-dimensional CdTe film layer initially formed before the growth of the CdTe nano-/micro-wires. The optical and structural properties of CdTe nano-/micro-structures were characterized by X-ray diffraction technique and micro-Raman spectroscopy. Our study demonstrates that diverse CdTe nano-/micro-structures can be fabricated by using Au-catalyzed VLS growth process in a simple CSS chamber by controlling the temperature gradient and growth time. - Highlights: • We demonstrated CdTe nanowires using closed space sublimation method. • Au-catalyst droplets at the tips confirmed vapor–liquid–solid mechanism. • Diameters and lengths increased with increasing temperature gradient and time

  17. Carbon nanotube nanoelectrode arrays

    Science.gov (United States)

    Ren, Zhifeng; Lin, Yuehe; Yantasee, Wassana; Liu, Guodong; Lu, Fang; Tu, Yi

    2008-11-18

    The present invention relates to microelectode arrays (MEAs), and more particularly to carbon nanotube nanoelectrode arrays (CNT-NEAs) for chemical and biological sensing, and methods of use. A nanoelectrode array includes a carbon nanotube material comprising an array of substantially linear carbon nanotubes each having a proximal end and a distal end, the proximal end of the carbon nanotubes are attached to a catalyst substrate material so as to form the array with a pre-determined site density, wherein the carbon nanotubes are aligned with respect to one another within the array; an electrically insulating layer on the surface of the carbon nanotube material, whereby the distal end of the carbon nanotubes extend beyond the electrically insulating layer; a second adhesive electrically insulating layer on the surface of the electrically insulating layer, whereby the distal end of the carbon nanotubes extend beyond the second adhesive electrically insulating layer; and a metal wire attached to the catalyst substrate material.

  18. Particulate contacts to Si and CdTe: Al, Ag, Hg-Cu-Te, and Sb-Te

    Science.gov (United States)

    Schulz, Douglas L.; Ribelin, Rosine; Curtis, Calvin J.; Ginley, David S.

    1999-03-01

    Our team has been investigating the use of particle-based contacts in both Si and CdTe solar cell technologies. First, in the area of contacts to Si, powders of Al and Ag prepared by an electroexplosion process have been characterized by transmission electron microscopy (TEM), TEM elemental determination X-ray spectroscopy (TEM-EDS), and TEM electron diffraction (TEM-ED). These Al and Ag particles were slurried and tested as contacts to p- and n-type silicon wafers, respectively. Linear current-voltage (I-V) was observed for Ag on n-type Si, indicative of an ohmic contact, whereas the Al on p-type Si sample was non-ideal. A wet-chemical surface treatment was performed on one Al sample and TEM-EDS indicated a substantial decrease in the O contaminant level. The treated Al on p-type Si films exhibited linear I-V after annealing. Second, in the area of contacts to CdTe, particles of Hg-Cu-Te and Sb-Te have been applied as contacts to CdTe/CdS/SnO2 heterostructures prepared by the standard NREL protocol. First, Hg-Cu-Te and Sb-Te were prepared by a metathesis reaction. After CdCl2 treatment and NP etch of the CdTe layer, particle contacts were applied. The Hg-Cu-Te contacted cells exhibited good electrical characteristics, with Voc>810 mV and efficiencies > 11.5% for most cells. Although Voc>800 mV were observed for the Sb-Te contacted cells, efficiencies in these devices were limited to 9.1% presumably by a large series resistance (>20 Ω) observed in all samples.

  19. Rational design of binder-free noble metal/metal oxide arrays with nanocauliflower structure for wide linear range nonenzymatic glucose detection

    KAUST Repository

    Li, Zhenzhen

    2015-06-12

    One-dimensional nanocomposites of metal-oxide and noble metal were expected to present superior performance for nonenzymatic glucose detection due to its good conductivity and high catalytic activity inherited from noble metal and metal oxide respectively. As a proof of concept, we synthesized gold and copper oxide (Au/CuO) composite with unique one-dimensional nanocauliflowers structure. Due to the nature of the synthesis method, no any foreign binder was needed in keeping either Au or CuO in place. To the best of our knowledge, this is the first attempt in combining metal oxide and noble metal in a binder-free style for fabricating nonenzymatic glucose sensor. The Au/CuO nanocauliflowers with large electrochemical active surface and high electrolyte contact area would promise a wide linear range and high sensitive detection of glucose with good stability and reproducibility due to its good electrical conductivity of Au and high electrocatalytic activity of CuO.

  20. A Study on Airborne MIMO-SAR Linear Array Antenna Configuration%机载MIMO-SAR线性阵列天线配置研究

    Institute of Scientific and Technical Information of China (English)

    李云涛; 陈永光; 邓云凯; 尹灿斌

    2012-01-01

    The application of the effective phase center (EPC) principle provides a more freedom of degree for antenna configuration of multi-input multi-output SAR( MIMO-SAR). EPC principle is expatiated. Traditional ARTINO antenna configuration is analyzed. The transmitting elements are violent vibrating for locating at the wing tips, which blurs the image. Then, antenna array is ameliorated for the traditional ARTINO. Center-transmitter collocated model and center-receiver collocated model are put forward. Finally, antenna pattern of the above models is simulated. The simulation results indicated that MIMO SAR antenna configuration design using EPC principle could ensure the favorable pattern directionality, and improve the design flexibility of the antenna geometry and reducing cost.%等效相位中心原理的应用为多发多收合成孔径雷达(MIMO-SAR)的天线设计提供了更大的自由度.文中阐述了等效相位中心原理,分析了传统ARTINO天线配置,指出由于其发射阵元布设于机翼处而剧烈抖动造成图像模糊的问题.然后,对传统ARTINO天线结构进行了改进,并提出了发射居中紧凑和接收居中紧凑2种天线构形.最后,对4种天线构形的方向图进行了仿真.结果表明,MIMO-SAR采用等效相位中心原理进行天线结构配置,可以在保证天线方向图具有良好指向性的同时,提高天线配置的灵活性并降低成本.

  1. PV型HgCdTe线阵探测器的光学串扰%Optical crosstalk of HgCdTe PV linear array detector

    Institute of Scientific and Technical Information of China (English)

    邱伟成; 王睿; 许中杰; 江天; 程湘爱

    2012-01-01

    针对MCT红外焦平面阵列器件普遍存在的光串扰问题进行研究,从器件内部结构上,建立了线阵器件理论计算模型,并基于载流子连续性方程,利用Corsol软件对光串扰的大小进行了数值定量计算,研究了不同探测器结构尺寸、温度和材料等参数对光串扰的影响;从器件外部结构上,利用几何光学,研究了外部光学结构对光串扰的影响.研究结果表明,器件内部的衬底外延层厚度与器件外部的真空层对光串扰的影响最大,为今后红外焦平面器件结构的改进提供了一定的理论指导.%The optical crosstalk of MCT infrared focal plane arrays is studied in a systematic way. Considering detector's different structure and material parameters, including the external optical structure, temperature, pixel size, epitaxial thickness, minority carrier lifetime, and absorption coefficient, the amplitude of optical crosstalk are calculated. Results show that the thickness of substrate's epitaxial layer in the internal structure and the vacuum layer in the external optical structure are the major influencing factors for the amplitude of optical crosstalk.

  2. Characterization of CdTe Films Deposited at Various Bath Temperatures and Concentrations Using Electrophoretic Deposition

    Directory of Open Access Journals (Sweden)

    Zulkarnain Zainal

    2012-05-01

    Full Text Available CdTe film was deposited using the electrophoretic deposition technique onto an ITO glass at various bath temperatures. Four batch film compositions were used by mixing 1 to 4 wt% concentration of CdTe powder with 10 mL of a solution of methanol and toluene. X-ray Diffraction analysis showed that the films exhibited polycrystalline nature of zinc-blende structure with the (111 orientation as the most prominent peak. From the Atomic Force Microscopy, the thickness and surface roughness of the CdTe film increased with the increase of CdTe concentration. The optical energy band gap of film decreased with the increase of CdTe concentration, and with the increase of isothermal bath temperature. The film thickness increased with respect to the increase of CdTe concentration and bath temperature, and following, the numerical expression for the film thickness with respect to these two variables has been established.

  3. Characterization of M-π-n CdTe pixel detectors coupled to HEXITEC readout chip

    Science.gov (United States)

    Veale, M. C.; Kalliopuska, J.; Pohjonen, H.; Andersson, H.; Nenonen, S.; Seller, P.; Wilson, M. D.

    2012-01-01

    Segmentation of the anode-side of an M-π-n CdTe diode, where the pn-junction is diffused into the detector bulk, produces large improvements in the spatial and energy resolution of CdTe pixel detectors. It has been shown that this fabrication technique produces very high inter-pixel resistance and low leakage currents are obtained by physical isolation of the pixels of M-π-n CdTe detectors. In this paper the results from M-π-n CdTe detectors stud bonded to a spectroscopic readout ASIC are reported. The CdTe pixel detectors have 250 μm pitch and an area of 5 × 5 mm2 with thicknesses of 1 and 2 mm. The polarization and energy resolution dependence of the M-π-n CdTe detectors as a function of detector thickness are discussed.

  4. First-principles study of roles of Cu and Cl in polycrystalline CdTe

    International Nuclear Information System (INIS)

    Cu and Cl treatments are important processes to achieve high efficiency polycrystalline cadmium telluride (CdTe) solar cells, thus it will be beneficial to understand the roles they play in both bulk CdTe and CdTe grain boundaries (GBs). Using first-principles calculations, we systematically study Cu and Cl-related defects in bulk CdTe. We find that Cl has only a limited effect on improving p-type doping and too much Cl can induce deep traps in bulk CdTe, whereas Cu can enhance p-type doping of bulk CdTe. In the presence of GBs, we find that, in general, Cl and Cu will prefer to stay at GBs, especially for those with Te-Te wrong bonds, in agreement with experimental observations

  5. First-principles study of roles of Cu and Cl in polycrystalline CdTe

    Science.gov (United States)

    Yang, Ji-Hui; Yin, Wan-Jian; Park, Ji-Sang; Metzger, Wyatt; Wei, Su-Huai

    2016-01-01

    Cu and Cl treatments are important processes to achieve high efficiency polycrystalline cadmium telluride (CdTe) solar cells, thus it will be beneficial to understand the roles they play in both bulk CdTe and CdTe grain boundaries (GBs). Using first-principles calculations, we systematically study Cu and Cl-related defects in bulk CdTe. We find that Cl has only a limited effect on improving p-type doping and too much Cl can induce deep traps in bulk CdTe, whereas Cu can enhance p-type doping of bulk CdTe. In the presence of GBs, we find that, in general, Cl and Cu will prefer to stay at GBs, especially for those with Te-Te wrong bonds, in agreement with experimental observations.

  6. First-principles study of roles of Cu and Cl in polycrystalline CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ji-Hui; Park, Ji-Sang; Metzger, Wyatt [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Yin, Wan-Jian [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); College of Physics, Optoelectronics and Energy and Collaborative, Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Wei, Su-Huai, E-mail: suhuaiwei@csrc.ac.cn [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Beijing Computational Science Research Center, Beijing 100094 (China)

    2016-01-28

    Cu and Cl treatments are important processes to achieve high efficiency polycrystalline cadmium telluride (CdTe) solar cells, thus it will be beneficial to understand the roles they play in both bulk CdTe and CdTe grain boundaries (GBs). Using first-principles calculations, we systematically study Cu and Cl-related defects in bulk CdTe. We find that Cl has only a limited effect on improving p-type doping and too much Cl can induce deep traps in bulk CdTe, whereas Cu can enhance p-type doping of bulk CdTe. In the presence of GBs, we find that, in general, Cl and Cu will prefer to stay at GBs, especially for those with Te-Te wrong bonds, in agreement with experimental observations.

  7. Kronecker Product of Two-dimensional Arrays

    Institute of Scientific and Technical Information of China (English)

    Lei Hu

    2006-01-01

    Kronecker sequences constructed from short sequences are good sequences for spread spectrum communication systems. In this paper we study a similar problem for two-dimensional arrays, and we determine the linear complexity of the Kronecker product of two arrays. Our result shows that similar good property on linear complexity holds for Kronecker product of arrays.

  8. High Efficiency Thin Film CdTe and a-Si Based Solar Cells: Annual Technical Report, 4 March 1999 - 3 March 2000

    Energy Technology Data Exchange (ETDEWEB)

    Compaan, A. D.; Deng, X.; Bohn, R. G. (The University of Toledo)

    2001-08-29

    This report describes the research on high-efficiency CdTe-based thin-film solar cells and on high-efficiency a-Si-based thin-film solar cells. Implemented a diode-array spectrograph system and used optical emission spectroscopy to help optimize the reactive sputtering of N-doped ZnTe for CdTe back-contact structures. Identified the photoluminescence signatures of various defect states in CdTe related to Cd vacancies, CuCd acceptors, Cu-VCd complexes, and donor-acceptor pairs, and related these states to instabilities in the hole concentration at room temperature. Showed that Cu is an important non-radiative center in CdS, reducing the PL efficiency. Studied band tailing in CdS weakly alloyed with CdTe and CdTe weakly alloyed with CdS. Fabricated superstrate ITO/CdS/CdTe cells on Mo substrates with efficiencies above 7.5%. Collaborated in studies of EXAFS of Cu in CdTe which indicate a Cu-Te bond length of 2.62 {angstrom} or 6.7% shorter than the CdTe, bond in agreement with calculations of Wei et al. Provided assistance to two groups on laser scribing. Comparatively studied the performance of a-SiGe solar cells and properties of a-SiGe single-layer films deposited using a wide range of H dilution, observed transition from a-SiGe to {mu}c-SiGe at high H dilution and the impact on cell performances. Comparatively studied the performance of a-SiGe solar cells and properties of a-SiGe single-layer films with different Ge contents, suitable for use as component cells of triple-junction devices. Fabricated a-Si-based solar cells on ultra-thin stainless-steel substrate (7.5 micron) and obtained equivalent performance and yield as on the regular SS substrates (127 microns). Comparatively studied the performance of a-Si-based solar cells on SS substrates and on SnO2-coated glass substrates. Studied the performance of p-layers deposited under various deposition conditions for n-i-p type solar cells. Performed an analysis for the component cell current-matching within a

  9. High Efficiency Thin Film CdTe and a-Si Based Solar Cells: Annual Technical Report, 4 March 1999 - 3 March 2000; ANNUAL

    International Nuclear Information System (INIS)

    This report describes the research on high-efficiency CdTe-based thin-film solar cells and on high-efficiency a-Si-based thin-film solar cells. Implemented a diode-array spectrograph system and used optical emission spectroscopy to help optimize the reactive sputtering of N-doped ZnTe for CdTe back-contact structures. Identified the photoluminescence signatures of various defect states in CdTe related to Cd vacancies, CuCd acceptors, Cu-VCd complexes, and donor-acceptor pairs, and related these states to instabilities in the hole concentration at room temperature. Showed that Cu is an important non-radiative center in CdS, reducing the PL efficiency. Studied band tailing in CdS weakly alloyed with CdTe and CdTe weakly alloyed with CdS. Fabricated superstrate ITO/CdS/CdTe cells on Mo substrates with efficiencies above 7.5%. Collaborated in studies of EXAFS of Cu in CdTe which indicate a Cu-Te bond length of 2.62(angstrom) or 6.7% shorter than the CdTe, bond in agreement with calculations of Wei et al. Provided assistance to two groups on laser scribing. Comparatively studied the performance of a-SiGe solar cells and properties of a-SiGe single-layer films deposited using a wide range of H dilution, observed transition from a-SiGe to(mu)c-SiGe at high H dilution and the impact on cell performances. Comparatively studied the performance of a-SiGe solar cells and properties of a-SiGe single-layer films with different Ge contents, suitable for use as component cells of triple-junction devices. Fabricated a-Si-based solar cells on ultra-thin stainless-steel substrate (7.5 micron) and obtained equivalent performance and yield as on the regular SS substrates (127 microns). Comparatively studied the performance of a-Si-based solar cells on SS substrates and on SnO2-coated glass substrates. Studied the performance of p-layers deposited under various deposition conditions for n-i-p type solar cells. Performed an analysis for the component cell current-matching within a triple

  10. Rational design of binder-free noble metal/metal oxide arrays with nanocauliflower structure for wide linear range nonenzymatic glucose detection

    Science.gov (United States)

    Li, Zhenzhen; Xin, Yanmei; Zhang, Zhonghai; Wu, Hongjun; Wang, Peng

    2015-01-01

    One-dimensional nanocomposites of metal-oxide and noble metal were expected to present superior performance for nonenzymatic glucose detection due to its good conductivity and high catalytic activity inherited from noble metal and metal oxide respectively. As a proof of concept, we synthesized gold and copper oxide (Au/CuO) composite with unique one-dimensional nanocauliflowers structure. Due to the nature of the synthesis method, no any foreign binder was needed in keeping either Au or CuO in place. To the best of our knowledge, this is the first attempt in combining metal oxide and noble metal in a binder-free style for fabricating nonenzymatic glucose sensor. The Au/CuO nanocauliflowers with large electrochemical active surface and high electrolyte contact area would promise a wide linear range and high sensitive detection of glucose with good stability and reproducibility due to its good electrical conductivity of Au and high electrocatalytic activity of CuO. PMID:26068705

  11. FEM-based linear inverse modeling using a 3D source array to image magma chambers with free geometry. Application to InSAR data from Rabaul Caldera (PNG).

    Science.gov (United States)

    Ronchin, Erika; Masterlark, Timothy; Dawson, John; Saunders, Steve; Martí Molist, Joan

    2015-04-01

    In this study, we present a method to fully integrate a family of finite element models (FEMs) into the regularized linear inversion of InSAR data collected at Rabaul caldera (PNG) between February 2007 and December 2010. During this period the caldera experienced a long-term steady subsidence that characterized surface movement both inside the caldera and outside, on its western side. The inversion is based on an array of FEM sources in the sense that the Green's function matrix is a library of forward numerical displacement solutions generated by the sources of an array common to all FEMs. Each entry of the library is the LOS surface displacement generated by injecting a unity mass of fluid, of known density and bulk modulus, into a different source cavity of the array for each FEM. By using FEMs, we are taking advantage of their capability of including topography and heterogeneous distribution of elastic material properties. All FEMs of the family share the same mesh in which only one source is activated at the time by removing the corresponding elements and applying the unity fluid flux. The domain therefore only needs to be discretized once. This precludes remeshing for each activated source, thus reducing computational requirements, often a downside of FEM-based inversions. Without imposing an a-priori source, the method allows us to identify, from a least-squares standpoint, a complex distribution of fluid flux (or change in pressure) with a 3D free geometry within the source array, as dictated by the data. The results of applying the proposed inversion to Rabaul InSAR data show a shallow magmatic system under the caldera made of two interconnected lobes located at the two opposite sides of the caldera. These lobes could be consistent with feeding reservoirs of the ongoing Tavuvur volcano eruption of andesitic products, on the eastern side, and of the past Vulcan volcano eruptions of more evolved materials, on the western side. The interconnection and

  12. CdTe polycrystalline films on Ni foil substrates by screen printing and their photoelectric performance

    International Nuclear Information System (INIS)

    Highlights: • The sintered CdTe polycrystalline films by a simple screen printing. • The flexible Ni foil was chose as substrates to reduce the weight of the electrode. • The compact CdTe film was obtained at 550 °C sintering temperature. • The photoelectric activity of the CdTe polycrystalline films was excellent. - Abstract: CdTe polycrystalline films were prepared on flexible Ni foil substrates by sequential screen printing and sintering in a nitrogen atmosphere for the first time. The effect of temperature on the quality of the screen-printed film was investigated in our work. The high-quality CdTe films were obtained after sintering at 550 °C for 2 h. The properties of the sintered CdTe films were characterized by scanning electron microscopy, X-ray diffraction pattern and UV–visible spectroscopy. The high-quality CdTe films have the photocurrent was 2.04 mA/cm2, which is higher than that of samples prepared at other temperatures. Furthermore, CdCl2 treatment reduced the band gap of the CdTe film due to the larger grain size. The photocurrent of photoelectrode based on high crystalline CdTe polycrystalline films after CdCl2 treatment improved to 2.97 mA/cm2, indicating a potential application in photovoltaic devices

  13. Aluminum doping of CdTe polycrystalline films starting from the heterostructure CdTe/Al

    OpenAIRE

    Becerril, M.; O. Vigil-Galán; G. Contreras-Puente; O. Zelaya-Angel

    2011-01-01

    Aluminum doped CdTe polycrystalline films were obtained from the heterostructure CdTe/Al/Corning glass. The aluminum was deposited by thermal vacuum evaporation and the CdTe by sputtering of a CdTe target. The aluminum was introduced into the lattice of the CdTe from a thermal annealed to the CdTe/Al/Corning glas heterostructure. The electrical, structural, nd optical properties were analyzed as a function of the Al concentrations. It found that when Al is incorporated, the electrical resisti...

  14. CdTe polycrystalline films on Ni foil substrates by screen printing and their photoelectric performance

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Huizhen [National Key Lab of Superhard Materials, Jilin University, Changchun 130012 (China); Ma, Jinwen [College of New Energy, Bohai University, Jinzhou, Liaoning 121013 (China); Mu, Yannan [National Key Lab of Superhard Materials, Jilin University, Changchun 130012 (China); Department of Physics and Chemistry, Heihe University, Heihe 164300 (China); Su, Shi; Lv, Pin; Zhang, Xiaoling; Zhou, Liying; Li, Xue; Liu, Li; Fu, Wuyou [National Key Lab of Superhard Materials, Jilin University, Changchun 130012 (China); Yang, Haibin, E-mail: yanghb@jlu.edu.cn [National Key Lab of Superhard Materials, Jilin University, Changchun 130012 (China)

    2015-06-15

    Highlights: • The sintered CdTe polycrystalline films by a simple screen printing. • The flexible Ni foil was chose as substrates to reduce the weight of the electrode. • The compact CdTe film was obtained at 550 °C sintering temperature. • The photoelectric activity of the CdTe polycrystalline films was excellent. - Abstract: CdTe polycrystalline films were prepared on flexible Ni foil substrates by sequential screen printing and sintering in a nitrogen atmosphere for the first time. The effect of temperature on the quality of the screen-printed film was investigated in our work. The high-quality CdTe films were obtained after sintering at 550 °C for 2 h. The properties of the sintered CdTe films were characterized by scanning electron microscopy, X-ray diffraction pattern and UV–visible spectroscopy. The high-quality CdTe films have the photocurrent was 2.04 mA/cm{sup 2}, which is higher than that of samples prepared at other temperatures. Furthermore, CdCl{sub 2} treatment reduced the band gap of the CdTe film due to the larger grain size. The photocurrent of photoelectrode based on high crystalline CdTe polycrystalline films after CdCl{sub 2} treatment improved to 2.97 mA/cm{sup 2}, indicating a potential application in photovoltaic devices.

  15. Photoluminescence and Electroluminescence Properties of CdTe Nanoparticles in Conjugated Polymer Hosts

    Institute of Scientific and Technical Information of China (English)

    GUO, Fengqi; XIE, Puhui

    2009-01-01

    The photoinduced energy transfer process from conjugated polymer (PPE4+) to CdTe nanocrystals was found both in solutions and in thin films by a fluorescence spectroscopic technique. Films of PPE4+ blended with CdTe-2 nanocrystals were formed by an electrostatic layer-by-layer assembly technique. Light emitting diodes were fabricated using CdTe-2 as an emitter in PPE4+ host. PPE4+ works as a molecular wire in the energy transfer process from the polymer to the CdTe-2 nanocrystals.

  16. Phenothiazine-bridged cyclic porphyrin dimers as high-affinity hosts for fullerenes and linear array of C60 in self-assembled porphyrin nanotube.

    Science.gov (United States)

    Sakaguchi, Ken-ichi; Kamimura, Takuya; Uno, Hidemitsu; Mori, Shigeki; Ozako, Shuwa; Nobukuni, Hirofumi; Ishida, Masatoshi; Tani, Fumito

    2014-04-01

    Free-bases and a nickel(II) complex of phenothiazine-bridged cyclic porphyrin dimers bearing self-assembling 4-pyridyl groups (M2-Ptz-CPDPy(OCn); M = H2 or Ni, OCn = OC6 or OC3) at opposite meso-positions have been prepared as host molecules for fullerenes. The free-base dimer (H4-Ptz-CPDPy(OC6)) includes fullerenes with remarkably high association constants such as 3.9 ± 0.7 × 10(6) M(-1) for C60 and 7.4 ± 0.8 × 10(7) M(-1) for C70 in toluene. This C60 affinity is the highest value ever among reported receptors composed of free-base porphyrins. The nickel dimer (Ni2-Ptz-CPDPy(OC6)) also shows high affinities for C60 (1.3 ± 0.2 × 10(6) M(-1)) and C70 (over 10(7) M(-1)). In the crystal structure of the inclusion complex of C60 within H4-Ptz-CPDpy(OC3), the C60 molecule is located just above the centers of the porphyrins. The two porphyrin planes are almost parallel to each other and the center-to-center distance (12.454 Å) is close to the optimal separation (∼12.5 Å) for C60 inclusion. The cyclic porphyrin dimer forms a nanotube through its self-assembly induced by C-H···N hydrogen bonds between porphyrin β-CH groups and pyridyl nitrogens as well as π-π interactions of the pyridyl groups. The C60 molecules are linearly arranged in the inner channel of this nanotube.

  17. Hard-X and gamma-ray imaging detector for astrophysics based on pixelated CdTe semiconductors

    Science.gov (United States)

    Gálvez, J.-L.; Hernanz, M.; Álvarez, L.; Artigues, B.; Ullán, M.; Lozano, M.; Pellegrini, G.; Cabruja, E.; Martínez, R.; Chmeissani, M.; Puigdengoles, C.

    2016-01-01

    Stellar explosions are astrophysical phenomena of great importance and interest. Instruments with high sensitivities are essential to perform detailed studies of cosmic explosions and cosmic accelerators. In order to achieve the needed performance, a hard-X and gamma-ray imaging detector with mm spatial resolution and large enough efficiency is required. We present a detector module which consists of a single CdTe crystal of 12.5 × 12.5mm 2 and 2mm thick with a planar cathode and with the anode segmented in an 11x11 pixel array with a pixel pitch of 1 mm attached to the readout chip. Two possible detector module configurations are considered: the so-called Planar Transverse Field (PTF) and the Parallel Planar Field (PPF). The combination of several modules in PTF or PPF configuration will achieve the desired performance of the imaging detector. The sum energy resolution of all pixels of the CdTe module measured at 122 keV and 356 keV is 3.8% and 2% respectively, in the following operating conditions: PPF irradiation, bias voltage -500 V and temperature -10̂ C.

  18. Surface-wave amplitude analysis for array data with non-linear waveform fitting: Toward high-resolution attenuation models of the upper mantle

    Science.gov (United States)

    Hamada, K.; Yoshizawa, K.

    2013-12-01

    Anelastic attenuation of seismic waves provides us with valuable information on temperature and water content in the Earth's mantle. While seismic velocity models have been investigated by many researchers, anelastic attenuation (or Q) models have yet to be investigated in detail mainly due to the intrinsic difficulties and uncertainties in the amplitude analysis of observed seismic waveforms. To increase the horizontal resolution of surface wave attenuation models on a regional scale, we have developed a new method of fully non-linear waveform fitting to measure inter-station phase velocities and amplitude ratios simultaneously, using the Neighborhood Algorithm (NA) as a global optimizer. Model parameter space (perturbations of phase speed and amplitude ratio) is explored to fit two observed waveforms on a common great-circle path by perturbing both phase and amplitude of the fundamental-mode surface waves. This method has been applied to observed waveform data of the USArray from 2007 to 2008, and a large-number of inter-station amplitude and phase speed data are corrected in a period range from 20 to 200 seconds. We have constructed preliminary phase speed and attenuation models using the observed phase and amplitude data, with careful considerations of the effects of elastic focusing and station correction factors for amplitude data. The phase velocity models indicate good correlation with the conventional tomographic results in North America on a large-scale; e.g., significant slow velocity anomaly in volcanic regions in the western United States. The preliminary results of surface-wave attenuation achieved a better variance reduction when the amplitude data are inverted for attenuation models in conjunction with corrections for receiver factors. We have also taken into account the amplitude correction for elastic focusing based on a geometrical ray theory, but its effects on the final model is somewhat limited and our attenuation model show anti

  19. Ultrasensitive fluorescence immunoassay for detection of ochratoxin A using catalase-mediated fluorescence quenching of CdTe QDs

    Science.gov (United States)

    Huang, Xiaolin; Zhan, Shengnan; Xu, Hengyi; Meng, Xianwei; Xiong, Yonghua; Chen, Xiaoyuan

    2016-04-01

    Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to perform a dynamic linear detection of OTA ranging from 0.05 pg mL-1 to 10 pg mL-1. The half maximal inhibitory concentration was 0.53 pg mL-1 and the limit of detection was 0.05 pg mL-1. These values were approximately 283- and 300-folds lower than those of horseradish peroxidase (HRP)-based conventional ELISA, respectively. The reported method is accurate, highly reproducible, and specific against other mycotoxins in agricultural products as well. In summary, the developed fluorescence immunoassay based on H2O2-induced fluorescence quenching of CdTe QDs can be used for the rapid and highly sensitive detection of mycotoxins or haptens in food safety monitoring.Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to

  20. Digital pulse-shape processing for CdTe detectors

    Science.gov (United States)

    Bargholtz, Chr.; Fumero, E.; Mårtensson, L.; Wachtmeister, S.

    2001-09-01

    CdTe detectors suffer from low photo-peak efficiency and poor energy resolution. These problems are due to the drift properties of charge carriers in CdTe where particularly the holes have small mobility and trapping time. This is reflected in the amplitude and the shape of the detector output. To improve this situation a digital method is introduced where a sampling ADC is used to make a detailed measurement of the time evolution of the pulse. The measured pulse shape is fitted with a model. For the detector under study a model taking hole trapping into account significantly improves the photo-peak efficiency. The description of the hole component is, however, not fully satisfactory since for pulses with a large hole contribution a broadening of the full-energy peak occurs. Allowing for inhomogeneities in the detector material within the model partially remedies this deficiency.

  1. Digital pulse-shape processing for CdTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Bargholtz, Chr.; Fumero, E.; Maartensson, L. E-mail: martensson@physto.se; Wachtmeister, S

    2001-09-21

    CdTe detectors suffer from low photo-peak efficiency and poor energy resolution. These problems are due to the drift properties of charge carriers in CdTe where particularly the holes have small mobility and trapping time. This is reflected in the amplitude and the shape of the detector output. To improve this situation a digital method is introduced where a sampling ADC is used to make a detailed measurement of the time evolution of the pulse. The measured pulse shape is fitted with a model. For the detector under study a model taking hole trapping into account significantly improves the photo-peak efficiency. The description of the hole component is, however, not fully satisfactory since for pulses with a large hole contribution a broadening of the full-energy peak occurs. Allowing for inhomogeneities in the detector material within the model partially remedies this deficiency.

  2. Digital pulse-shape processing for CdTe detectors

    CERN Document Server

    Bargholtz, C; Maartensson, L; Wachtmeister, S

    2001-01-01

    CdTe detectors suffer from low photo-peak efficiency and poor energy resolution. These problems are due to the drift properties of charge carriers in CdTe where particularly the holes have small mobility and trapping time. This is reflected in the amplitude and the shape of the detector output. To improve this situation a digital method is introduced where a sampling ADC is used to make a detailed measurement of the time evolution of the pulse. The measured pulse shape is fitted with a model. For the detector under study a model taking hole trapping into account significantly improves the photo-peak efficiency. The description of the hole component is, however, not fully satisfactory since for pulses with a large hole contribution a broadening of the full-energy peak occurs. Allowing for inhomogeneities in the detector material within the model partially remedies this deficiency.

  3. Phosphorus Doping of Polycrystalline CdTe by Diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Colegrove, Eric; Albin, David S.; Guthrey, Harvey; Harvey, Steve; Burst, James; Moutinho, Helio; Farrell, Stuart; Al-Jassim, Mowafak; Metzger, Wyatt K.

    2015-06-14

    Phosphorus diffusion in single crystal and polycrystalline CdTe material is explored using various methods. Dynamic secondary ion mass spectroscopy (SIMS) is used to determine 1D P diffusion profiles. A 2D diffusion model is used to determine the expected cross-sectional distribution of P in CdTe after diffusion anneals. Time of flight SIMS and cross-sectional cathodoluminescence corroborates expected P distributions. Devices fabricated with diffused P exhibit hole concentrations up to low 1015 cm-3, however a subsequent activation anneal enabled hole concentrations greater than 1016 cm-3. CdCl2 treatments and Cu based contacts were also explored in conjunction with the P doping process.

  4. First principles modeling of grain boundaries in CdTe

    Science.gov (United States)

    Chan, Maria K. Y.; Sen, Fatih; Buurma, Christopher; Paulauskas, Tadas; Sun, Ce; Kim, Moon; Klie, Robert

    The role of extended defects is of significant interest for semiconductors, especially photovoltaics since energy conversion efficiencies are often affected by such defects. In particular, grain boundaries in CdTe photovoltaics are enigmatic since the achievable efficiencies of CdTe photovoltaics are higher in polycrystalline devices as compared to single crystalline devices. Yet, despite recent advances, the efficiency of poly-CdTe devices are still substantially below the theoretical maximum. We carry out an atomistic-level study using Scanning Transmission Electron Microscopy (STEM), together with first principles density functional theory (DFT) modeling, in order to understand the properties of specific bicrystals, i.e. artificial grain boundaries, constructed using wafer bonding. We discuss examples of bicrystals, including some involving large scale DFT calculations, and trends in defect and electronic properties. This work was funded by DOE SunShot BRIDGE program.

  5. Photoluminescence study of Cu diffusion in CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Grecu, D.; Compaan, A.D. [Department of Physics, University of Toledo, Toledo, Ohio (United States)

    1999-03-01

    We report changes in the photoluminescence spectra associated with the diffusion of Cu in CdTe thin films used in CdTe/CdS solar cells. Films grown by vapor transport deposition and radio-frequency sputtering as well as single crystal CdTe were included in the study. The main effects of Cu diffusion appear to be the quenching of a donor-acceptor transition associated with Cd vacancies and the increase in intensity of a lower energy broad-band transition. The PL is subsequently used to explore the effects of electric fields on Cu diffusion. The role of Te as a diffusion barrier for Cu is investigated. {copyright} {ital 1999 American Institute of Physics.}

  6. Dependence of CdTe response of bias history

    Energy Technology Data Exchange (ETDEWEB)

    Sites, J.R.; Sasala, R.A.; Eisgruber, I.L. [Colorado State Univ., Boulder, CO (United States)

    1995-11-01

    Several time-dependent effect have been observed in CdTe cells and modules in recent years. Some appear to be related to degradation at the back contact, some to changes in temperature at the thin-film junction, and some to the bias history of the cell or module. Back-contact difficulties only occur in some cases, and the other two effects are reversible. Nevertheless, confusion in data interpretation can arise when these effects are not characterized. This confusion can be particularly acute when more than one time-dependent effect occurs during the same measurement cycle. The purpose of this presentation is to help categorize time-dependent effects in CdTe and other thin-film cells to elucidate those related to bias history, and to note differences between cell and module analysis.

  7. Optical modeling of graphene contacted CdTe solar cells

    Science.gov (United States)

    Aldosari, Marouf; Sohrabpoor, Hamed; Gorji, Nima E.

    2016-04-01

    For the first time, an optical model is applied on CdS/CdTe thin film solar cells with graphene front or back contact. Graphene is highly conductive and is as thin as a single atom which reduces the light reflection and absorption, and thus enhances the light transmission to CdTe layer for a wide range of wavelengths including IR. Graphene as front electrode of CdTe devices led to loss in short circuit current density of 10% ΔJsc ≤ 15% compared to the conventional electrodes of TCO and ITO at CdS thickness of dCdS = 100 nm. In addition, all the multilayer graphene electrodes with 2, 4, and 7 graphene layers led to Jsc ≤ 20 mA/cm2. Therefore, we conclude that a single monolayer graphene with hexagonal carbon network reduces optical losses and enhances the carrier collection measured as Jsc. In another structure design, we applied the optical model to graphene back contacted CdS/CdTe device. This scheme allows double side irradiation of the cell which is expected to enhance the Jsc. We obtained 1 ∼ 6 , 23, and 38 mA/cm2 for back, front and bifacial illumination of graphene contacted CdTe cell with CdS = 100 nm. The bifacial irradiated cell, to be efficient, requires an ultrathin CdTe film with dCdTe ≤ 1 μm. In this case, the junction electric field extends to the back region and collects out the generated carriers efficiently. This was modelled by absorptivity rather than transmission rate and optical losses. Since the literature suggest that ZnO can increase the graphene conductivity and enhance the Jsc, we performed our simulations for a graphene/ZnO electrode (ZnO = 100 nm) instead of a single graphene layer.

  8. CdTe Nanowires studied by Transient Absorption Microscopy

    Directory of Open Access Journals (Sweden)

    Kuno M.

    2013-03-01

    Full Text Available Transient absorption measurements were performed on single CdTe nanowires. The traces show fast decays that were assigned to charge carrier trapping at surface states. The observed power dependence suggests the existence of a trap-filling mechanism. Acoustic phonon modes were also observed, which were assigned to breathing modes of the nanowires. Both the fundamental breathing mode and the first overtone were observed, and the dephasing times provide information about how the nanowires interact with their environment.

  9. Simulation of charge transport in pixelated CdTe

    OpenAIRE

    Kolstein, M.; Ariño, G.; Chmeissani, M.; De Lorenzo, G.

    2014-01-01

    The Voxel Imaging PET (VIP) Pathfinder project intends to show the advantages of using pixelated semiconductor technology for nuclear medicine applications to achieve an improved image reconstruction without efficiency loss. It proposes designs for Positron Emission Tomography (PET), Positron Emission Mammography (PEM) and Compton gamma camera detectors with a large number of signal channels (of the order of 106). The design is based on the use of a pixelated CdTe Schottky detector to have op...

  10. Highly luminescent water-soluble CdTe quantum dots

    OpenAIRE

    Wuister, SF; Swart, A.N.; van Driel, F; Hickey, SG; Donega, CD; Swart, Ingmar

    2003-01-01

    Colloidal CdTe quantum dots prepared in TOP/DDA (trioctylphosphine/dodecylamine) are transferred into water by the use of aminoethanethiol.HCl (AET) or mercaptopropionic acid (MPA). This results in an increase in the photoluminescence quantum efficiency and a longer exciton lifetime. For the first time, water-soluble semiconductor nanocrystals presenting simultaneously high band-edge photoluminescence quantum efficiencies (as high as 60% at room temperature), monoexponential exciton decays, a...

  11. Determining energy production of CdTe photovoltaic system

    OpenAIRE

    Virtič, Peter; Šlamberger, Jan

    2015-01-01

    This paper presents a method for determining energy production of Cadmium-Telluride photovoltaic system, which has a different working performance than the most used Silicon photovoltaic systems. The main difference is sensitivity to the temperature and the solar irradiance. The CdTe cells are less sensitive to the temperature and in contrast to the Si Cells they have a higher efficiency at lower irradiance.

  12. The basic component of the ISGRI CdTe γ-ray camera for space telescope IBIS on board the INTEGRAL satellite

    International Nuclear Information System (INIS)

    The γ-ray imager telescope IBIS, on board the INTEGRAL satellite, features a coded mask aperture and two detector arrays. The first detector array (ISGRI) is an assembly of 16 384 CdTe detectors (4x4 mm2 large, 2 mm thick) operating at room temperature under 100 V bias. ISGRI covers the lower part (20 keV-1 MeV) of the IBIS energy range (20 keV-10 MeV). The polycell is the basic component of the ISGRI detector array. It is made of 16 CdTe pixels and their front-end electronics. In order to improve the response of the instrument, a charge loss correction based on the charge-drift time is necessary. Therefore, the front-end electronics performs the rise-time measurement in addition to the standard pulse-height measure. On the other hand, the necessarily tight packaging and the limited available power requires the use of ASICs. These 4-channel analog-digital ASICs should be radiation resistant either through the use of a latch up free technology or by applying an appropriate layout design. The optimal operating temperature (around 0 deg. C) is ensured under vacuum conditions by radiative cooling. This paper describes the ISGRI design with particular emphasis on the ASICs and polycells, and reports preliminary performance measurements

  13. Studium vlastností CdTe senzorů

    OpenAIRE

    Vašíček, Martin

    2011-01-01

    Tato bakalářská práce se zabývá studiem vlastností CdTe detektorů. Popisuje analýzu transportních a šumových charakteristik vzorků CdTe při různých teplotách. Vyhodnocení získaných výsledků dokazuje, že se rozhraní CdTe chová jako dvojice antisériově zapojených diod. Průběhy VA charakteristik se vyznačují lineárním nebo lehce exponenciálním růstem. Při vzrůstající teplotě roste i vodivost vzorků. Měření prokázala rozdíl vodivosti testovaných vzorků při stejné teplotě. Dále je zřejmé, že v roz...

  14. Challenges in p-type Doping of CdTe

    Science.gov (United States)

    McCoy, Jedidiah; Swain, Santosh; Lynn, Kelvin

    We have made progress in defect identification of arsenic and phosphorous doped CdTe to understand the self-compensation mechanism which will help improve minority bulk carrier lifetime and net acceptor density. Combining previous measurements of un-doped CdTe, we performed a systematic comparison of defects between different types of crystals and confirmed the defects impacting the doping efficiency. CdTe bulk crystals have been grown via vertical Bridgman based melt growth technique with varying arsenic and phosphorous dopant schemes to attain p-type material. Furnace temperature profiles were varied to influence dopant solubility. Large carrier densities have been reproducibly obtained from these boules indicating successful incorporation of dopants into the lattice. However, these values are orders of magnitude lower than theoretical solubility values. Infrared Microscopy has revealed a plethora of geometrically abnormal second phase defects and X-ray Fluorescence has been used to identify the elemental composition of these defects. We believe that dopants become incorporated into these second phase defects as Cd compounds which act to inhibit dopant solubility in the lattice.

  15. High efficiency CSS CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ferekides, C.S.; Marinskiy, D.; Viswanathan, V.; Tetali, B.; Palekis, V.; Selvaraj, P.; Morel, D.L. [University of South Florida, Tampa, FL (United States). Dept. of Electrical Engineering

    2000-02-21

    Cadmium telluride (CdTe) has long been recognized as a strong candidate for thin film solar cell applications. It has a bandgap of 1.45 eV, which is nearly ideal for photovoltaic energy conversion. Due to its high optical absorption coefficient essentially all incident radiation with energy above its band-gap is absorbed within 1-2 {mu}m from the surface. Thin film CdTe solar cells are typically heterojunctions, with cadmium sulfide (CdS) being the n-type junction partner. Small area efficiencies have reached the 16.0% level and considerable efforts are underway to commercialize this technology. This paper will present work carried out at the University South Florida sponsored by the National Renewable Energy Laboratory of the United States Department of Energy, on CdTe/CdS solar cells fabricated using the close spaced sublimation (CSS) process. The CSS technology has attractive features for large area applications such as high deposition rates and efficient material utilization. The structural and optical properties of CSS CdTe and CdS films and junctions will be presented and the influence of some important CSS process parameters will be discussed. (orig.)

  16. Approaches to improve the Voc of CDTE devices: Device modeling and thinner devices, alternative back contacts

    Science.gov (United States)

    Walkons, Curtis J.

    An existing commercial process to develop thin film CdTe superstrate cells with a lifetime tau=1-3 ns results in Voc= 810-850 mV which is 350 mV lower than expected for CdTe with a bandgap EG = 1.5 eV. Voc is limited by 1.) SRH recombination in the space charge region; and 2.) the Cu2Te back contact to CdTe, which, assuming a 0.3 eV CdTe/Cu2Te barrier, exhibits a work function of phi Cu2Te= 5.5 eV compared to the CdTe valence band of Ev,CdTe=5.8 eV. Proposed solutions to develop CdTe devices with increased Voc are: 1.) reduce SRH recombination by thinning the CdTe layer to ≤ 1 mum; and 2.) develop an ohmic contact back contact using a material with phi BC≥5.8 eV. This is consistent with simulations using 1DSCAPS modeling of CdTe/CdS superstrate cells under AM 1.5 conditions. Two types of CdTe devices are presented. The first type of CdTe device utilizes a window/CdTe stack device with an initial 3-9 mum CdTe layer which is then chemically thinned resulting in regions of the CdTe film with thickness less than 1 mum. The CdTe surface was contacted with a liquid junction quinhydrone-Pt (QH-Pt) probe which enables rapid repeatable Voc measurements on CdTe before and after thinning. In four separate experiments, the window/CdTe stack devices with thinned CdTe exhibited a Voc increase of 30-170 mV, which if implemented using a solid state contact could cut the Voc deficit in half. The second type of CdTe device utilizes C61 PCBM as a back contact to the CdTe, selected since PCBM has a valence band maximum energy (VBM) of 5.8 eV. The PCBM films were grown by two different chemistries and the characterization of the film properties and device results are discussed. The device results show that PCBM exhibits a blocking contact with a 0.6 eV Schottky barrier and possible work function of phiPCBM = 5.2 eV.

  17. Single-Crystal CdTe Homojunction Structures for Solar Cell Applications

    Science.gov (United States)

    Su, Peng-Yu; Dahal, Rajendra; Wang, Gwo-Ching; Zhang, Shengbai; Lu, Toh-Ming; Bhat, Ishwara B.

    2015-09-01

    We report two different CdTe homojunction solar cell structures. Single-crystal CdTe homojunction solar cells were grown on GaAs single-crystal substrates by metalorganic chemical vapor deposition. Arsenic and iodine were used as dopants for p-type and n-type CdTe, respectively. Another homojunction solar cell structure was fabricated by growing n-type CdTe directly on bulk p-type CdTe single-crystal substrates. The electrical properties of the different layers were characterized by Hall measurements. When arsine was used as arsenic source, the highest hole concentration was ~6 × 1016 cm-3 and the activation efficiency was ~3%. Very abrupt arsenic doping profiles were observed by secondary ion mass spectrometry. For n-type CdTe with a growth temperature of 250°C and a high Cd/Te ratio the electron concentration was ~4.5 × 1016 cm-3. Because of the 300 nm thick n-type CdTe layer, the short circuit current of the solar cell grown on the bulk CdTe substrate was less than 10 mA/cm2. The open circuit voltage of the device was 0.86 V. According to a prediction based on measurement of short circuit current density ( J sc) as a function of open circuit voltage ( V oc), an open circuit voltage of 0.92 V could be achieved by growing CdTe solar cells on bulk CdTe substrates.

  18. Aptamer-based fluorescent screening assay for acetamiprid via inner filter effect of gold nanoparticles on the fluorescence of CdTe quantum dots.

    Science.gov (United States)

    Guo, Jiajia; Li, Ying; Wang, Luokai; Xu, Jingyue; Huang, Yanjun; Luo, Yeli; Shen, Fei; Sun, Chunyan; Meng, Rizeng

    2016-01-01

    This paper reports a novel aptamer-based fluorescent detection method for small molecules represented by acetamiprid based on the specific binding of aptamers with acetamiprid, and the inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (CdTe QDs). When CdTe QDs were mixed with AuNPs, the fluorescence of CdTe QDs was significantly quenched via IFE. The IFE efficiency could be readily modulated by the absorption and the aggregation state of AuNPs. The presence of salt could easily induce the aggregation of AuNPs, resulting in the fluorescence recovery of the quenched QDs. Acetamiprid-binding aptamer (ABA) could adsorb on the negatively charged AuNPs through the coordination interaction to protect AuNPs from salt-induced aggregation, so the fluorescence of CdTe QDs would be quenched by the IFE of AuNPs. However, the specific binding of ABA with acetamiprid could release the ABA from the surfaces of AuNPs and decrease the salt tolerance of AuNPs, so the IFE-decreased fluorescence of CdTe QDs was regained with the presence of acetamiprid, and the fluorescence enhancement efficiency was driven by the concentration of acetamiprid. Based on this principle, the aptamer-based fluorescent method for acetamiprid has been established and optimized. The assay exhibited excellent selectivity towards acetamiprid over its analogues and other pesticides which may coexist with acetamiprid. Under the optimum experiment conditions, the established method could be applied for the determination of acetamiprid with a wide linear range from 0.05 to 1.0 μM, and a low detection limit of 7.29 nM (3σ). Furthermore, this IFE-based method has been successfully utilized to detect acetamiprid in six types of vegetables, and the results were in full agreement with those from HPLC and LC-MS. The proposed method displays remarkable advantages of high sensitivity, rapid analysis, excellent selectivity, and would be suitable for the practical application

  19. 基于线阵APD探测器的脉冲式一维非扫描激光雷达系统%Pulsed one-dimensional scannerless LiDAR system based on linear APD array

    Institute of Scientific and Technical Information of China (English)

    郑睿童; 吴冠豪

    2012-01-01

    The principle of scannerless LiDAR was introduced. The developed one -dimensional scannerless LiDAR system based on linear APD was described. Linear array APD and infrared pulsed nanosecond laser were employed as detector and probe light source respectively. By using the time-of-flight pulsed laser rangefinding technique, the one-dimensional scannerless distance image of the target could be obtained. Parallel multi-channel pre-amplifiers were implemented and high-speed relays were used to switch between channels, by which, the isolation of channels were improved effectively. Several groups of one-dimensional distance imaging experiments were carried out. The results illustrate that the resolutions of multi-channel distance imaging are better than 10 cm and the average standard deviation for channels is approximate to 8.6 cm. The design in this system provides the basis on developing the two-dimensional scannerless LiDAR by APD planar array.%介绍了非扫描激光雷达的原理,描述了研制的基于线阵APD雪崩光电二极管的一维非扫描激光雷达系统.该系统使用线阵APD作为探测器,红外脉冲式纳秒激光器作为探测光源,利用飞行时间法实现了目标的一维距离图像的非扫描测量.系统使用了APD多通道并行前置放大电路,并利用模拟开关控制高速继电器进行多通道轮询切换,实现了APD阵列的多通道驱动,并有效地降低了通道间的串扰.进行了多组6~18m的一维距离成像实验,结果表明系统的距离分辨率优于10 cm,各通道的平均测距标准偏差约为8.6 cm.该系统的设计为将来的面阵APD二维非扫描激光雷达的研制奠定了基础.

  20. Characterisation of vapour phase grown CdTe and (Cd,Zn)Te for detector applications

    CERN Document Server

    Fiederle, M; Rogalla, M; Meinhardt, J; Ludwig, J; Runge, K; Benz, W

    1999-01-01

    The growth of CdTe from the vapour phase offers several improvements in crystal quality and homogeneity. CdTe and (Cd, Zn)Te were grown by the modified Markov technique. The transport properties and the detector performance are given and compared to melt grown material. (author)

  1. Temperature-dependent photoluminescence of highly luminescent water-soluble CdTe quantum dots

    Institute of Scientific and Technical Information of China (English)

    Ji Wei Liu; Yu Zhang; Cun Wang Ge; Yong Long Jin; Sun Ling Hu; Ning Gu

    2009-01-01

    Highly luminescent water-soluble CdTe quantum dots (QDs) have been synthesized with an electrogenerated precursor. The obtained CdTe QDs can possess good crystallizability, high quantum yield (QY) and favorable stability. Furthermore, a detection system is designed firstly for the investigation of the temperature-dependent PL of the QDs.

  2. A new fluorimetric method for determination of valproic acid using TGA-capped CdTe quantum dots as proton sensor

    International Nuclear Information System (INIS)

    Valproic acid (VA) is an acidic anticonvulsant and mood stabilizing drug with very weak fluorescence and absorption properties. A simple, inexpensive and sensitive method was established for determination of VA using thiogycolic acid (TGA)-capped CdTe quantum dots (QDs) based on pH-dependent fluorescence of the prepared QDs. The TGA-capped CdTe QDs of various sizes were successfully synthesized in aqueous medium and characterized by fluorescence spectroscopy, UV–vis absorption spectra, infrared spectroscopy and transmission electron microscopy (TEM). Under the optimal conditions, plotting ln(F0/F) versus concentration of VA showed a linear relationship in the range of 0.3–7.5 mg/L with correlation coefficient of 0.998. The limit of detection (LOD) was 0.24 µg mL−1. The proposed method was successfully applied for determination of VA in commercial tablets, human serum, and urine samples satisfactorily. -- Highlights: • Development of a new simple and sensitive method for determination of valproic acid. • Based on pH-dependent fluorescence of thiogycolic acid-capped CdTe of the prepared quantum dots. • The first report of direct spectroscopic determination of VA with high sensitivity. • Capable of measuring VA in pharmaceutical and biological samples

  3. Mercaptopropionic acid-capped CdTe quantum dots as fluorescence probe for the determination of salicylic acid in pharmaceutical products.

    Science.gov (United States)

    Bunkoed, Opas; Kanatharana, Proespichaya

    2015-11-01

    Mercaptopropionic acid (MPA)-capped cadmium telluride (CdTe) quantum dot (QDs) fluorescent probes were synthesized in aqueous solution and used for the determination of salicylic acid. The interaction between the MPA-capped CdTe QDs and salicylic acid was studied using fluorescence spectroscopy and some parameters that could modify the fluorescence were investigated to optimize the measurements. Under optimum conditions, the quenched fluorescence intensity of MPA-capped CdTe QDs was linearly proportional to the concentration of salicylic acid in the range of 0.5-40 µg mL(-1) with a coefficient of determination of 0.998, and the limit of detection was 0.15 µg mL(-1). The method was successfully applied to the determination of salicylic acid in pharmaceutical products, and satisfactory results were obtained that were in agreement with both the high pressure liquid chromatography (HPLC) method and the claimed values. The recovery of the method was in the range 99 ± 3% to 105 ± 9%. The proposed method is simple, rapid, cost effective, highly sensitivity and eminently suitable for the quality control of pharmaceutical preparation. The possible mechanisms for the observed quenching reaction was also discussed.

  4. Translocation and neurotoxicity of CdTe quantum dots in RMEs motor neurons in nematode Caenorhabditis elegans

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yunli; Wang, Xiong; Wu, Qiuli; Li, Yiping; Wang, Dayong, E-mail: dayongw@seu.edu.cn

    2015-02-11

    Graphical abstract: - Highlights: • We investigated in vivo neurotoxicity of CdTe QDs on RMEs motor neurons in C. elegans. • CdTe QDs in the range of μg/L caused neurotoxicity on RMEs motor neurons. • Bioavailability of CdTe QDs may be the primary inducer for CdTe QDs neurotoxicity. • Both oxidative stress and cell identity regulate the CdTe QDs neurotoxicity. • CdTe QDs were translocated and deposited into RMEs motor neurons. - Abstract: We employed Caenorhabditis elegans assay system to investigate in vivo neurotoxicity of CdTe quantum dots (QDs) on RMEs motor neurons, which are involved in controlling foraging behavior, and the underlying mechanism of such neurotoxicity. After prolonged exposure to 0.1–1 μg/L of CdTe QDs, abnormal foraging behavior and deficits in development of RMEs motor neurons were observed. The observed neurotoxicity from CdTe QDs on RMEs motor neurons might be not due to released Cd{sup 2+}. Overexpression of genes encoding Mn-SODs or unc-30 gene controlling cell identity of RMEs neurons prevented neurotoxic effects of CdTe QDs on RMEs motor neurons, suggesting the crucial roles of oxidative stress and cell identity in regulating CdTe QDs neurotoxicity. In nematodes, CdTe QDs could be translocated through intestinal barrier and be deposited in RMEs motor neurons. In contrast, CdTe@ZnS QDs could not be translocated into RMEs motor neurons and therefore, could only moderately accumulated in intestinal cells, suggesting that ZnS coating might reduce neurotoxicity of CdTe QDs on RMEs motor neurons. Therefore, the combinational effects of oxidative stress, cell identity, and bioavailability may contribute greatly to the mechanism of CdTe QDs neurotoxicity on RMEs motor neurons. Our results provide insights into understanding the potential risks of CdTe QDs on the development and function of nervous systems in animals.

  5. Translocation and neurotoxicity of CdTe quantum dots in RMEs motor neurons in nematode Caenorhabditis elegans

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • We investigated in vivo neurotoxicity of CdTe QDs on RMEs motor neurons in C. elegans. • CdTe QDs in the range of μg/L caused neurotoxicity on RMEs motor neurons. • Bioavailability of CdTe QDs may be the primary inducer for CdTe QDs neurotoxicity. • Both oxidative stress and cell identity regulate the CdTe QDs neurotoxicity. • CdTe QDs were translocated and deposited into RMEs motor neurons. - Abstract: We employed Caenorhabditis elegans assay system to investigate in vivo neurotoxicity of CdTe quantum dots (QDs) on RMEs motor neurons, which are involved in controlling foraging behavior, and the underlying mechanism of such neurotoxicity. After prolonged exposure to 0.1–1 μg/L of CdTe QDs, abnormal foraging behavior and deficits in development of RMEs motor neurons were observed. The observed neurotoxicity from CdTe QDs on RMEs motor neurons might be not due to released Cd2+. Overexpression of genes encoding Mn-SODs or unc-30 gene controlling cell identity of RMEs neurons prevented neurotoxic effects of CdTe QDs on RMEs motor neurons, suggesting the crucial roles of oxidative stress and cell identity in regulating CdTe QDs neurotoxicity. In nematodes, CdTe QDs could be translocated through intestinal barrier and be deposited in RMEs motor neurons. In contrast, CdTe@ZnS QDs could not be translocated into RMEs motor neurons and therefore, could only moderately accumulated in intestinal cells, suggesting that ZnS coating might reduce neurotoxicity of CdTe QDs on RMEs motor neurons. Therefore, the combinational effects of oxidative stress, cell identity, and bioavailability may contribute greatly to the mechanism of CdTe QDs neurotoxicity on RMEs motor neurons. Our results provide insights into understanding the potential risks of CdTe QDs on the development and function of nervous systems in animals

  6. Growth of CdTe thin films on graphene by close-spaced sublimation method

    International Nuclear Information System (INIS)

    CdTe thin films grown on bi-layer graphene were demonstrated by using the close-spaced sublimation method, where CdTe was selectively grown on the graphene. The density of the CdTe domains was increased with increasing the number of the defective sites in the graphene, which was controlled by the duration of UV exposure. The CdTe growth rate on the bi-layer graphene electrodes was 400 nm/min with a bandgap energy of 1.45–1.49 eV. Scanning electron microscopy, micro-Raman spectroscopy, micro-photoluminescence, and X-ray diffraction technique were used to confirm the high quality of the CdTe thin films grown on the graphene electrodes

  7. Development of a CdTe thermal neutron detector for neutron imaging

    International Nuclear Information System (INIS)

    A thin CdTe thermal neutron detector has been developed and its suitability for neutron imaging has been investigated. Simulations of the interaction of neutrons with a 0.5 mm-thick CdTe detector demonstrate the advantages of using 96 keV prompt gamma rays produced by neutron capture in 113Cd as a neutron event. Specifically, they provide a high spatial resolution and approximately the same detection efficiency as 558 keV prompt gamma rays, which are commonly used for detecting thermal neutrons in CdTe detectors. We fabricated a thin CdTe detector. Measurements using a 133Ba gamma-ray source revealed that the detector has a gamma-ray energy resolution of 3 keV at 80 keV, while measurements using a 252Cf neutron source demonstrated that the CdTe detector has good neutron/gamma ray discrimination.

  8. Vapor phase epitaxy of CdTe on sapphire and GaAs

    Science.gov (United States)

    Kasuga, Masanobu; Futami, Hiroyuki; Iba, Yoshihiro

    1991-12-01

    CdTe films were deposited on three kinds of sapphire substrate and two kinds of GaAs substrate by open tube vapor transport. X-ray Laue diffraction study showed that CdTe(111) film grew on every kind of sapphire substrate used, i.e. on the (0001) basal plane, the (11 overline20)A plane and the (1 overline102)R plane, and that there exist a few degrees of tilt angel between CdTe(111) and the lattice plane of each substrate. The process of making the tilt angle may be explained by the atomistic mismatch model of the Cd and Al arrangement which is projected on the film-substrate interface. On GaAs(100), either CdTe(111) or CdTe(100) was obtained, whereas only a twin crystalline film was obtained on GaAs(111). These results are also consistent with the mismatch model of Cd and Ga atoms.

  9. Homo-epitaxial growth of CdTe by sublimation under low pressure

    Science.gov (United States)

    Yoshioka, Yasushi; Yoda, Hiroki; Kasuga, Masanobu

    1991-12-01

    A new method to obtain a twin-free single crystal of CdTe on a CdTe substrate by sublimation is described. When CdTe(111)A substrates were employed for the homo-epitaxial growth of CdTe, twin crystals were frequently obtained. The substrate of CdTe(211)A and (211)B, however, gave no twins resulting in single crystals of high quality. The difference may come from the existence of many steps, sufficient to suppress two-dimensional nucleation and to promote step flow mechanism. To obtain twin-free films, therefore, a fairly large tilt angle of the substrate from a singular plane and a fairly low supersaturation are essential.

  10. NREL Collaboration Breaks 1-Volt Barrier in CdTe Solar Technology

    Energy Technology Data Exchange (ETDEWEB)

    2016-05-01

    NREL scientists have worked with Washington State University and the University of Tennessee to improve the maximum voltage available from CdTe solar cells. Changes in dopants, stoichiometry, interface design, and defect chemistry improved the CdTe conductivity and carrier lifetime by orders of magnitude, thus enabling CdTe solar cells with open-circuit voltages exceeding 1 volt for the first time. Values of current density and fill factor for CdTe solar cells are already at high levels, but sub-par voltages has been a barrier to improved efficiencies. With voltages pushed beyond 1 volt, CdTe cells have a path to produce electricity at costs less than fossil fuels.

  11. Thermopile Area Array Readout Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA/JPL thermopile detector linear arrays, wire bonded to Black Forest Engineering (BFE) CMOS readout integrated circuits (ROICs), have been utilized in NASA...

  12. Highly selective detection of microRNA based on distance-dependent electrochemiluminescence resonance energy transfer between CdTe nanocrystals and Au nanoclusters.

    Science.gov (United States)

    Cheng, Yan; Lei, Jianping; Chen, Yunlong; Ju, Huangxian

    2014-01-15

    A distance-dependent electrochemiluminescence resonance energy transfer (ERET) system based on CdTe nanocrystals and Au nanoclusters (Au NCs) was designed with the aid of ligase for highly selective detection of microRNA (miRNA). First, Au NCs functionalized hairpin DNA was synthesized via Au-S chemistry, and characterized with transmission electron microscopy and dynamic light scattering. The resulting hairpin DNA-Au NCs composite can be bound to the carboxylated CdTe nanocrystals via amide reaction on glass carbon electrode. The strong interaction between CdTe nanocrystals and AuNCs led to the electrochemiluminescence (ECL) quenching of CdTe nanocrystals. In the presence of assistant DNA and miRNA, the ligase can selectively ligate both of them on the strand of the hairpin DNA to form long DNA-RNA heteroduplexes. Thus the ECL signal was recovered due to the blocking of the ERET. As a comparison, when directly opening the hairpin DNA by the target, the ECL emission signal is weak owing to the presence of ERET effect at the short distance. Based on the distance-dependent ERET, a 'signal on' ECL system was utilized for the detection of miRNA with the advantages of 6 orders magnitude linear range and excellent sequence specificity. The total detection processing time of the biosensor was approximately 70 min. By substituting the hairpin DNA with different sequences, this strategy as a new signal transduction approach could be conveniently extended for detection of other short miRNA and DNA.

  13. Resonance light-scattering spectrometric study of interaction between enzyme and MPA-modified CdTe nanoparticles

    Science.gov (United States)

    Li, Juan; Li, Minjie; Tang, Jieli; Li, Xiaozhou; Zhang, Hanqi; Zhang, Yihua

    2008-08-01

    This paper described a novel assay of enzyme based on the measurement of enhanced resonance light-scattering (RLS) signals resulting from the electrostatic and coordination interaction of functionalized CdTe nanoparticles with enzyme. The CdTe nanoparticles which were modified with 3-mercaptocarboxylic acid (MPA) have abundant carboxylic groups ( sbnd COOH). So the nanoparticles are water-soluble, stable and biocompatible. At pH 8.3 phosphate buffered saline (PBS), the RLS signals of functionalized nano-CdTe are greatly enhanced by bromelain and papain in the region of 220-800 nm characterized by the peak around 318-314 nm, respectively. The optimization conditions of the reaction were also examined and selected. Under the selected conditions, the enhanced RLS intensity is linearly proportional to the concentration of bromelain and papain. The liner range is (0.09-0.9) × 10 -6 mol/L for bromelain and (0.048-0.702) × 10 -6 mol/L for papain. The influences of some foreign substances were also examined. This method can be applied to the determination of enzyme.

  14. Submillimeter resolution in one-dimensional position measurements of γ-ray photons by using a CsI(Tl) scintillator coupled to a linear array of silicon drift detectors

    Science.gov (United States)

    Fiorini, C.; Labanti, C.; Perotti, F.

    2000-08-01

    We present the one-dimensional (1D) position and energy resolution results obtained by a γ-ray detector based on a single CsI(Tl) scintillator coupled to a linear array of silicon drift detectors (SDDs). The present prototype has been realized in order to investigate the basic performances of this new architecture in view of the realization of Anger cameras for 2D imaging in nuclear medicine, based on the use of SDDs instead of photomultiplier tubes. The SDD provides a high value of quantum efficiency to the scintillation light, typical of a silicon photodetector, and is moreover characterized by a lower value of electronics noise with respect to conventional silicon photodiodes, thanks to the low value of output capacitance. At 122 keV the present detector shows a position resolution better than 0.5 mm FWHM, and an energy resolution of about 13% FWHM. The experimental setup is described and the most significant experimental results are presented.

  15. 基于三维立体线阵的全方位DOA估计方法%A method of estimation of omnidirectional DOA based on 3D linear array

    Institute of Scientific and Technical Information of China (English)

    杨正权; 李思敏

    2001-01-01

    本文基于3D立体线阵以及累量的灵活定义,实现了信号DOA的全方位估计。该算法不依赖于信号的具体结构,并构造了三个累量域DOA矩阵。通过对DOA矩阵的特征分解得到配对特征向量,从而获得信号DOA的全方位估计。该方法避免了2D或1D的谱峰搜索,仿真实验结果表明了这种方法的正确性。%In this paper, based on 3D linear array and on the flexible definition of cumulant, a new method is proposed to achieve estimation of omnidirectional DOA. The method does not depend on definite signal structure,and constructs three DOA matrixes in cumulant domain. Pairing signature vectors are acquired via eigen-decomposition of the matrixes and finally lead to estimation of omnidirectional DOA. Moreover, the method can avoid 1D or 2D spectral peak searching. Computer simulations make sure its availability.

  16. Design of Automatic Central Position Control System for Stripped-material Based on Linear Array CCD%基于线阵CCD带材自动对中系统的设计

    Institute of Scientific and Technical Information of China (English)

    丁忠林; 于秀丽

    2012-01-01

    为了解决钢厂带钢在切割中的跑偏问题,设计了以TMS320LF2407微处理器为控制核心及线阵CCD为边缘检测器件的自动对中系统.系统采用CPLD设计线阵CCD动态驱动电路,解决了CCD输出信号受环境影响而产生的饱和失真和背景与物体无法分开的问题,大大提高系统的抗干扰能力.系统检测精度高、运行速度快、实时性强.%In order to resolve the problem of bias in cutting of steel belts in steel factories, a automatically centering system based on TMS320DLF2407 MCU and CCD linear array was presented. CPLD was used in the CCD dynamic driving circuit so as to resolve the problem of saturation distortion and mixture of background and detecting object, which was caused by the affection of environment to the CCD output signal. As a result, the system has very good anti-interference ability, high measurement precision, short running time and can work in real-time situation.

  17. Characterization and identification of the chemical constituents from tartary buckwheat (Fagopyrum tataricum Gaertn) by high performance liquid chromatography/photodiode array detector/linear ion trap FTICR hybrid mass spectrometry.

    Science.gov (United States)

    Ren, Qiang; Wu, Caisheng; Ren, Yan; Zhang, Jinlan

    2013-02-15

    In recent years tartary buckwheat has become popular healthful food due to its antioxidant, antidiabetic and antitumor activities. However, its chemical constituents have not yet been fully characterized and identified. In this paper, a novel high performance liquid chromatography coupled with photodiode array detector and linear ion trap FTICR hybrid mass spectrometry (HPLC-PDA/LTQ-FTICRMS) method was established to characterize and identify a total of 36 compounds by a single run. The retention time, maximum UV absorption wavelength, accurate mass weight and characteristic fragment ions were collected on line. To confirm the structures, 11 compounds were isolated and identified by MS and NMR experiments. 1, 3, 6, 6'-tetra-feruloyl sucrose named taroside was a new phenlypropanoid glycoside, together with 3, 6-di-p-coumaroyl-1, 6'-di-feruloyl sucrose, 1, 6, 6'-tri-feruloyl-3-p-coumaroyl sucrose, N-trans-feruloyltyramine and quercetin-3-O-[β-D-xyloxyl-(1→2)-α-L-rhamnoside] were isolated for the first time from the Fagopyrum species. The research enriched the chemical information of tartary buckwheat.

  18. On the Clean Governance Education in Private Universities Based on the Linear Array%基于线阵构建的民办高校廉政教育论

    Institute of Scientific and Technical Information of China (English)

    陈金波

    2011-01-01

    从突破惯式,找准"切入点"构筑"个性线";因"角"施教,把好"契合点"构筑"层次线";创新导航,立足"关键点"构筑"新视线"三个层面创新民办高校廉政教育的治理思维,是有效构筑起利国、利校、利师生廉政教育线阵架构的重要途径。%The essay is trying to discuss a workable approach toward clean governance education in private colleges and universities in line with the aptitude,the post and the accountability of the leading bodies,thus constructing a linear array-like mechanism to consolidate lean administration instructions to the benefit of teachers and students,the nation,and the university.

  19. Degradation and capacitance: voltage hysteresis in CdTe devices

    Science.gov (United States)

    Albin, D. S.; Dhere, R. G.; Glynn, S. C.; del Cueto, J. A.; Metzger, W. K.

    2009-08-01

    CdS/CdTe photovoltaic solar cells were made on two different transparent conducting oxide (TCO) structures in order to identify differences in fabrication, performance, and reliability. In one set of cells, chemical vapor deposition (CVD) was used to deposit a bi-layer TCO on Corning 7059 borosilicate glass consisting of a F-doped, conductive tin-oxide (cSnO2) layer capped by an insulating (undoped), buffer (iSnO2) layer. In the other set, a more advanced bi-layer structure consisting of sputtered cadmium stannate (Cd2SnO4; CTO) as the conducting layer and zinc stannate (Zn2SnO4; ZTO) as the buffer layer was used. CTO/ZTO substrates yielded higher performance devices however performance uniformity was worse due to possible strain effects associated with TCO layer fabrication. Cells using the SnO2-based structure were only slightly lower in performance, but exhibited considerably greater performance uniformity. When subjected to accelerated lifetime testing (ALT) at 85 - 100 °C under 1-sun illumination and open-circuit bias, more degradation was observed in CdTe cells deposited on the CTO/ZTO substrates. Considerable C-V hysteresis, defined as the depletion width difference between reverse and forward direction scans, was observed in all Cu-doped CdTe cells. These same effects can also be observed in thin-film modules. Hysteresis was observed to increase with increasing stress and degradation. The mechanism for hysteresis is discussed in terms of both an ionic-drift model and one involving majority carrier emission in the space-charge region (SCR). The increased generation of hysteresis observed in CdTe cells deposited on CTO/ZTO substrates suggests potential decomposition of these latter oxides when subjected to stress testing.

  20. 剪式单元直线阵列可展结构的稳定性%Stability of linear array deployable structures based on structure of scissor-like element

    Institute of Scientific and Technical Information of China (English)

    李博; 王三民; 袁茹

    2014-01-01

    为获得剪式可展结构失稳时的临界载荷,开展剪式单元直线阵列可展结构的稳定性研究。首先基于杆件的弹性变形分析,建立了剪式单元的结构失稳极限载荷表达式,然后将其应用于阵列组合而成的可展结构,获得了这种结构的稳定性条件。结果表明:单元个数、杆件柔度和位置角等参数共同影响结构失稳时的临界载荷,随着单元个数增加或杆件柔度增大,结构稳定性逐渐降低;位置角受到单元个数影响,不能单独作为判断结构失稳的依据。最后进行可展结构稳定性仿真分析,并将仿真结果与理论分析结果对比,两者吻合性较好,证实了本文提出方法的正确性。%In order to get the buckling load of deployable structures, stability of linear array deployable structures based on structure of SLE were studied. The paper established a structural instability limit load expression of SLE based on analysis of the elastic deformation of bar, which is applied to the array combination of deployable structure. Then the condition of the stability of this structure is obtained. Results indicate that:Buckling critical load were affected by the bar parameters such as the number of units, bar flexibility and position angle. With the increase of the number of units or the bar flexibility, structural stability gradually reduced;The position angle were affected by unit number, which cannot be used separately as the basis for judging structure instability. Deployable structure stability simulation analysis results and the theoretical analysis results are compared each other, confirming the correctness of the proposed method in this paper because of the experiment data well.

  1. W波段16元完全采样焦平面线性阵列天线设计%Design of W-band 16 elements full sampling focal plane linear array

    Institute of Scientific and Technical Information of China (English)

    陈其科; 李良超; 樊勇; 杨建宇; 张永鸿

    2013-01-01

    针对毫米波被动成像应用,设计了工作频率为84 ~ 94 GHz的16阵元焦平面阵列天线.聚焦天线采用500 mm口径的旋转抛物面以获得0.47°角分辨率;16馈源排成4×4阵列,相邻列馈源在垂直方向交错排列,使天线在垂直方向采样波束密度增加一倍,满足Nyquist采样要求;采用电流分布法并利用MATLAB编程计算馈源偏焦时天线辐射场分布,对馈源阵列排列参数进行优化设计.成像实验结果表明,天线沿水平方向扫描一次即可获得场景成像二维完全采样数据,成像耗时比传统扫描采样方式减少一倍.%A 16-element focal plane linear array (FPLA) operating at 84 ~94GHz for passive millimeter-wave imaging was designed.The parabolic reflector with 500mm diameter was used to obtain an angular resolution of 0.47°.The 16 feed-horns are arranged as 4 x4 array and the adjacent feed-homs are stagger at vertical direction, which doubles the scene sampling density in vertical direction and satisfies Nyquist theorem.The radiation field of the antenna was calculated in MATLAB by using current distribution method, and the location of the feed horns was optimized based on the results.Imaging results indicate that the full sampling imaging data of scene can be obtained when the FPLA scanning is done in horizontal direction for only one time and imaging time is reduced to half that of the traditional scanning way.

  2. INCORPORATION DU PHOSPHORE DANS CdTe PAR RECUIT LASER

    OpenAIRE

    Uzan, C.; Legros, R.; Marfaing, Y.

    1983-01-01

    La méthode du recuit laser a été utilisée pour incorporer du phosphore dans CdTe à partir d'une couche de Cd3P2 déposée en surface. La caractérisation par photoluminescence et mesure de profil à l'analyseur ionique montre le caractère actif du phosphore introduit et permet d'évaluer à 1018cm-3 la concentration atteinte à 1 µm de profondeur.

  3. Study of fluorination of CdTe surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Koichi; Mori, Koichi; Miyake, Hideto (Dept. of Electrical Engineering, Mie Univ., Tsu-shi (Japan))

    1991-03-20

    In this paper we deal with fluorination of CdTe(100) single crystals in a 2% fluorine-98% nitrogen atmosphere for different temperatures and times. The fluorination process has been investigated by the use of microscopy, X-ray diffraction, energy-dispersive X-ray microanalysis, X-ray photoelectron spectroscopy and Auger electron spectroscopy measurements. Three temperature regions are found to be distinguished for the fluorination process. The fluorinated layer is mainly composed of CdF{sub 2} crystals, but an intermediate layer is shown to exist beneath the fluoride layer except for fluorination at low temperature. The formation mechanisms of the fluoride and intermediate layers are discussed. (orig.).

  4. High-Efficiency, Commercial Ready CdTe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Sites, James R. [Colorado State Univ., Fort Collins, CO (United States)

    2015-11-19

    Colorado State’s F-PACE project explored several ways to increase the efficiency of CdTe solar cells and to better understand the device physics of those cells under study. Increases in voltage, current, and fill factor resulted in efficiencies above 17%. The three project tasks and additional studies are described in detail in the final report. Most cells studied were fabricated at Colorado State using an industry-compatible single-vacuum closed-space-sublimation (CSS) chamber for deposition of the key semiconductor layers. Additionally, some cells were supplied by First Solar for comparison purposes, and a small number of modules were supplied by Abound Solar.

  5. CdTe Focal Plane Detector for Hard X-Ray Focusing Optics

    Science.gov (United States)

    Seller, Paul; Wilson, Matthew D.; Veale, Matthew C.; Schneider, Andreas; Gaskin, Jessica; Wilson-Hodge, Colleen; Christe, Steven; Shih, Albert Y.; Inglis, Andrew; Panessa, Marco

    2015-01-01

    The demand for higher resolution x-ray optics (a few arcseconds or better) in the areas of astrophysics and solar science has, in turn, driven the development of complementary detectors. These detectors should have fine pixels, necessary to appropriately oversample the optics at a given focal length, and an energy response also matched to that of the optics. Rutherford Appleton Laboratory have developed a 3-side buttable, 20 millimeter x 20 millimeter CdTe-based detector with 250 micrometer square pixels (80 x 80 pixels) which achieves 1 kiloelectronvolt FWHM (Full-Width Half-Maximum) @ 60 kiloelectronvolts and gives full spectroscopy between 5 kiloelectronvolts and 200 kiloelectronvolts. An added advantage of these detectors is that they have a full-frame readout rate of 10 kilohertz. Working with NASA Goddard Space Flight Center and Marshall Space Flight Center, 4 of these 1 millimeter-thick CdTe detectors are tiled into a 2 x 2 array for use at the focal plane of a balloon-borne hard-x-ray telescope, and a similar configuration could be suitable for astrophysics and solar space-based missions. This effort encompasses the fabrication and testing of flight-suitable front-end electronics and calibration of the assembled detector arrays. We explain the operation of the pixelated ASIC readout and measurements, front-end electronics development, preliminary X-ray imaging and spectral performance, and plans for full calibration of the detector assemblies. Work done in conjunction with the NASA Centers is funded through the NASA Science Mission Directorate Astrophysics Research and Analysis Program.

  6. Synthesis and characterization of TGA-capped CdTe nanoparticles embedded in PVA matrix

    International Nuclear Information System (INIS)

    This paper reports the synthesis and characterization of TGA-capped CdTe nanoparticles and its nanocomposite in a PVA matrix prepared by ex situ technique. The crystallite sizes of the CdTe nanoparticles and nanocomposite calculated from X-ray diffraction patterns are 6.07 and 7.75 nm with hexagonal structure, respectively. The spherical nature of the CdTe nanoparticles is confirmed from transmission electron microscopy measurements. Fourier transform infrared spectroscopy shows good interaction between the CdTe nanoparticles and PVA matrix. The absorption and emission spectra have also been studied. The stability of the TGA-capped CdTe nanoparticles increases after dispersion in a PVA matrix. In electrical measurements, the dark conductivity and the steady-state photoconductivity of CdTe nanocomposite thin films have been studied. The effect of temperature and intensity on the transient photoconductivity of CdTe nanocomposite is also studied. The values of differential life time have been calculated from the decay of photocurrent with time. The non-exponential decay of photoconductivity is observed indicating that the traps exist at all the energies in the band gap, making these materials suitable for various optoelectronic devices. (orig.)

  7. Conformal array design on arbitrary polygon surface with transformation optics

    Science.gov (United States)

    Deng, Li; Wu, Yongle; Hong, Weijun; Zhu, Jianfeng; Peng, Biao; Li, Shufang

    2016-06-01

    A transformation-optics based method to design a conformal antenna array on an arbitrary polygon surface is proposed and demonstrated in this paper. This conformal antenna array can be adjusted to behave equivalently as a uniformly spaced linear array by applying an appropriate transformation medium. An typical example of general arbitrary polygon conformal arrays, not limited to circular array, is presented, verifying the proposed approach. In summary, the novel arbitrary polygon surface conformal array can be utilized in array synthesis and beam-forming, maintaining all benefits of linear array.

  8. Conformal array design on arbitrary polygon surface with transformation optics

    Directory of Open Access Journals (Sweden)

    Li Deng

    2016-06-01

    Full Text Available A transformation-optics based method to design a conformal antenna array on an arbitrary polygon surface is proposed and demonstrated in this paper. This conformal antenna array can be adjusted to behave equivalently as a uniformly spaced linear array by applying an appropriate transformation medium. An typical example of general arbitrary polygon conformal arrays, not limited to circular array, is presented, verifying the proposed approach. In summary, the novel arbitrary polygon surface conformal array can be utilized in array synthesis and beam-forming, maintaining all benefits of linear array.

  9. Comparison of three types of XPAD3.2/CdTe single chip hybrids for hard X-ray applications in material science and biomedical imaging

    Energy Technology Data Exchange (ETDEWEB)

    Buton, C., E-mail: clement.buton@synchrotron-soleil.fr [Synchrotron SOLEIL, L´Orme des Merisiers, Saint-Aubin — BP 48 91192, Gif-sur-Yvette Cedex (France); Dawiec, A. [Synchrotron SOLEIL, L´Orme des Merisiers, Saint-Aubin — BP 48 91192, Gif-sur-Yvette Cedex (France); Graber-Bolis, J.; Arnaud, K. [CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille (France); Bérar, J.F.; Blanc, N.; Boudet, N. [Université Grenoble Alpes, Institut NÉEL, F-38042 Grenoble (France); CNRS, Institut NÉEL, F-38042 Grenoble (France); Clémens, J.C.; Debarbieux, F. [CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille (France); Delpierre, P.; Dinkespiler, B. [imXPAD SAS — Espace Mistral, Athélia IV, 297 avenue du Mistral, 13600 La Ciotat (France); Gastaldi, T. [CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille (France); Hustache, S. [Synchrotron SOLEIL, L´Orme des Merisiers, Saint-Aubin — BP 48 91192, Gif-sur-Yvette Cedex (France); Morel, C.; Pangaud, P. [CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille (France); Perez-Ponce, H. [imXPAD SAS — Espace Mistral, Athélia IV, 297 avenue du Mistral, 13600 La Ciotat (France); Vigeolas, E. [CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille (France)

    2014-09-11

    The CHIPSPECT consortium aims at building a large multi-modules CdTe based photon counting detector for hard X-ray applications. For this purpose, we tested nine XPAD3.2 single chip hybrids in various configurations (i.e. Ohmic vs. Schottky contacts or electrons vs. holes collection mode) in order to select the most performing and best suited configuration for our experimental requirements. Measurements have been done using both X-ray synchrotron beams and {sup 241}Am source. Preliminary results on the image quality, calibration, stability, homogeneity and linearity of the different types of detectors are presented.

  10. Studies and development of a readout ASIC for pixelated CdTe detectors for space applications

    International Nuclear Information System (INIS)

    designed two ASICs. The first one, Caterpylar, is a test-chip, which enables the characterization of differently dimensioned CSA circuits to choose the most suitable one for the final application. It is optimized for readout of the target CdTe detector with 300 μm pixel pitch and the corresponding input parameters. With this circuit I have also analyzed possible filtering methods, in particular the semi-Gaussian shaping and the Multi-Correlated Double Sampling (MCDS). Their comparison is preceded by the theoretical analysis of these shapers. The second ASIC D2R1 is a complete readout circuit, containing 256 channels to readout CdTe detector with the same number of pixels, arranged in 16 *16 array. Each channel fits into a layout area of 300 μm - 300 μm. It is based on the MCDS processing with self-triggering capabilities. The mean electronic noise measured over all channels is 29 electrons rms when characterized without the detector. The corresponding power consumption is 315 μW/channel. With these results the future measurements with the detector give prospects for reaching an FWHM spectral resolution in the order of 600 eV at 60 keV. (author)

  11. Magnetic and dielectric properties of one-dimensional array of S = 1/2 linear trimer system Na{sub 2}Cu{sub 3}Ge{sub 4}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Yasui, Yukio, E-mail: yyasui@meiji.ac.jp [Department of Physics, School of Science and Technology, Meiji University, Kawasaki 214-8571 (Japan); Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Kawamura, Yuji; Kobayashi, Yoshiaki [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Sato, Masatoshi [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Comprehensive Research Organization for Science and Society, Tokai 319-1106 (Japan)

    2014-05-07

    Magnetic susceptibility χ, specific heat C, capacitance C{sub p}, and {sup 23}Na-NMR measurements have been carried out on polycrystalline samples of quantum spin linear trimer system Na{sub 2}Cu{sub 3}Ge{sub 4}O{sub 12}, which has the one-dimensional array of Cu{sub 3}O{sub 8} trimers formed of edge-sharing three CuO{sub 4} square planes. The exchange interactions between the Cu{sup 2+} (S = 1/2) spins have been determined by analyzing χ-T and C-T curves. By employing the isolated S = 1/2 Heisenberg trimer model above 70 K, the nearest-neighbor exchange couplings J{sub 1} and the second-neighbor one J{sub 2} in trimer have been evaluated to J{sub 1}/k{sub B} = 30 ± 20 K (antiferromagnetic) and J{sub 2}/k{sub B} = 340 ± 20 K. At low temperature region, two spins of the edge in the Cu{sub 3}O{sub 8} trimers form a nonmagnetic singlet by strong antiferromagnetic interaction J{sub 2}, and the spin left in the center of the Cu{sub 3}O{sub 8} trimer forms one-dimensional chains by the exchange interaction J{sub 3} between the trimers. By employing the S = 1/2 uniform Heisenberg chain model below 70 K, we have evaluated to J{sub 3}/k{sub B} = 18 ± 1 K. The mechanism of multiferroic behavior at T{sub c} = 2 K is discussed.

  12. Linear algebra

    CERN Document Server

    Shilov, Georgi E

    1977-01-01

    Covers determinants, linear spaces, systems of linear equations, linear functions of a vector argument, coordinate transformations, the canonical form of the matrix of a linear operator, bilinear and quadratic forms, Euclidean spaces, unitary spaces, quadratic forms in Euclidean and unitary spaces, finite-dimensional space. Problems with hints and answers.

  13. Preparation of CdTe nanocrystal-polymer composite microspheres in aqueous solution by dispersing method

    Institute of Scientific and Technical Information of China (English)

    LI Minjie; WANG Chunlei; HAN Kun; YANG Bai

    2005-01-01

    Highly fluorescent CdTe nanocrystals were synthesized in aqueous solution, and then processible CdTe nanocrystal-polymer composites were fabricated by coating the aqueous nanocrystals with copolymers of styrene and octadecyl-p-vinyl-benzyldimethylammonium chloride (SOV- DAC) directly. A dichloromethane solution of CdTe nano- crystal-polymer composites was dispersed in the aqueous solution of poly (vinyl alcohol) (PVA) generating highly fluorescent microspheres. Experimental parameters such as the concentration of nanocrystal-polymer composites, the concentration of PVA, and stirring speed which had important effect on the preparation of the microspheres were investigated in detail with fluorescent microscope characterization.

  14. PC/FRAM plutonium isotopic analysis of CdTe gamma-ray spectra

    CERN Document Server

    Vo, D T

    2002-01-01

    This paper reports the results of isotopics measurements of plutonium with the new CdTe gamma-ray spectrometer. These are the first wide-range plutonium gamma-ray isotopics analysis results obtained with other than germanium spectrometers. The CdTe spectrometer measured small plutonium reference samples in reasonable count times, covering the range from low to high burnup. The complete experimental hardware included the new, commercial, portable CdTe detector and two commercial portable multichannel analyzers. Version 4 of FRAM is the software that performed the isotopics analysis.

  15. PC/FRAM plutonium isotopic analysis of CdTe gamma-ray spectra

    Science.gov (United States)

    Vo, D. T.; Russo, P. A.

    2002-07-01

    This paper reports the results of isotopics measurements of plutonium with the new CdTe gamma-ray spectrometer. These are the first wide-range plutonium gamma-ray isotopics analysis results obtained with other than germanium spectrometers. The CdTe spectrometer measured small plutonium reference samples in reasonable count times, covering the range from low to high burnup. The complete experimental hardware included the new, commercial, portable CdTe detector and two commercial portable multichannel analyzers. Version 4 of FRAM is the software that performed the isotopics analysis.

  16. Selective growth of CdTe on patterned CdTe/Si(211)

    OpenAIRE

    Seldrum, T.; Bommena, R.; Samain, Louise; Sivananthan, S.; Sporken, R.; Dumont, J.

    2008-01-01

    The authors have studied selective growth of cadmium telluride on Si(211) by molecular beam epitaxy (MBE). Patterned substrates were produced by optical lithography of MBE-grown CdTe/As/Si(211). Photoemission microscopy was used as the main tool to study selective growth. This is very powerful because Si or SiO2 can be very easily distinguished from areas covered with even small amounts of CdTe due to contrast from work function differences. It was found that CdTe grows on CdTe without sticki...

  17. Ultra low density of CdTe quantum dots grown by MBE

    OpenAIRE

    Kobak, J.; Rousset, J. -G.; Rudniewski, R.; Janik, E.; S\\lupiński; Kossacki, P.; Golnik, A.; Pacuski, W.

    2012-01-01

    This work presents methods of controlling the density of self-assembled CdTe quantum dots (QDs) grown by molecular beam epitaxy. Two approaches are discussed: increasing the deposition temperature of CdTe and the reduction of CdTe layer thickness. Photoluminescence (PL) measurements at low temperature confirms that both methods can be used for significant reduction of QDs density from 1010QD/cm2 to 107-108QD/cm2. For very low QDs density, identification of all QDs lines observed in the spectr...

  18. Shape Control of CdTe Nanocrystals: Influence of the Solvent Composition and Ligand Effects

    OpenAIRE

    Xiaoping Jin; Jürgen Parisi; Joanna Kolny-Olesiak

    2013-01-01

    CdTe nanocrystals were synthesized by the hot-injection method with a mixture of oleylamine and octadecene as a solvent. The influence of the composition of the solvent and of the injection solution on the shape of CdTe nanoparticles was investigated. Various shapes of CdTe nanocrystals, such as nanodots, nanorods, multipods, and nanowires, could be obtained by changing the reaction conditions. Tuning the reactivity of both the cadmium and the tellurium precursors at the same time was found t...

  19. Electronic structure of the quantum spin Hall parent compound CdTe and related topological issues

    Science.gov (United States)

    Ren, Jie; Bian, Guang; Fu, Li; Liu, Chang; Wang, Tao; Zha, Gangqiang; Jie, Wanqi; Neupane, Madhab; Miller, T.; Hasan, M. Z.; Chiang, T.-C.

    2014-11-01

    Cadmium telluride (CdTe), a compound widely used in devices, is a key base material for the experimental realization of the quantum spin Hall phase. We report herein a study of the electronic structure of CdTe by angle-resolved photoemission spectroscopy from well-ordered (110) surfaces. The results are compared with first-principles calculations to illustrate the topological distinction between CdTe and a closely related compound HgTe. Through a theoretical simulation a topological phase transition as well as the Dirac-Kane semimetal phase at the critical point was demonstrated in the mixed compound H gxC d1 -xTe .

  20. Narrowing the size distribution of CdTe nanocrystals using digestive ripening

    Indian Academy of Sciences (India)

    Mona Mittal; Sameer Sapra

    2015-06-01

    Digestive ripening of polydispersed colloidal CdTe nanocrystals is performed which results in monodispersed nanocrystals (NCs) as studied by optical spectroscopy. Optimization of ligand and refluxing time is carried out. Monodispersed NCs are obtained using mercaptopropionic acid (MPA) as a digestive ripening agent at a refluxing time of 1–2 h. Digestive ripening of CdTe NCs, which are less polydispersed, is also executed and it leads to more monodispersed NCs. In all the cases, there is a shift of maximum emission wavelength of CdTe NCs after digestive ripening that may be due to Ostwald ripening along with digestive ripening.

  1. Aqueous Synthesis of CdTe Quantum Dot Using Dithiol-Functionalized Ionic Liquid

    Directory of Open Access Journals (Sweden)

    Suk Young Choi

    2012-01-01

    Full Text Available We report on an aqueous synthesis of cadmium telluride (CdTe nanocrystals by using dithiol-functionalized ionic liquids (dTFILs. The dTFILs were designed to have dithiol and vinylimidazolium functional groups and used as a ligand molecule of CdTe quantum dot (QD to utilize the bidendate chelate interaction afforded by the dithiol groups of dTFILs. The photoluminescence quantum yield of dTFIL-capped CdTe QDs reached up to ~40%, and their luminescent property was maintained for 8 weeks, suggesting an improved stability in water phase. This approach will provide a new synthetic route to the water soluble QDs.

  2. Enhanced Specificity of Multiplex Polymerase Chain Reaction via CdTe Quantum Dots

    OpenAIRE

    Liang Gaofeng; Ma Chao; Zhu Yanliang; Li Shuchun; Shao Youhua; Wang Yong; Xiao Zhongdang

    2010-01-01

    Abstract Nanoparticles were recently reported to be able to improve both efficiency and specificity in polymerase chain reaction (PCR). Here, CdTe QDs were introduced into multi-PCR systems. It was found that an appropriate concentration of CdTe QDs could enhance the performance of multi-PCR by reducing the formation of nonspecific products in the complex system, but an excessive amount of CdTe QDs could suppress the PCR. The effects of QDs on PCR can be reversed by increasing the polymerase ...

  3. APPROACHING CRYOGENIC GE PERFORMANCE WITH PELTIER COOLED CDTE

    Energy Technology Data Exchange (ETDEWEB)

    Khusainov, A. K. (A. Kh.); Iwanczyk, J. S. (Jan S.); Patt, B. E. (Bradley E.); Prirogov, A. M. (Alexandre M.); Vo, Duc T.

    2001-01-01

    A new class of hand-held, portable spectrometers based on large area (lcm2) CdTe detectors of thickness up to 3mm has been demonstrated to produce energy resolution of between 0.3 and 0.5% FWHM at 662 keV. The system uses a charge loss correction circuit for improved efficiency, and detector temperature stabilization to ensure consistent operation of the detector during field measurements over a wide range of ambient temperature. The system can operate continuously for up to 8hrs on rechargeable batteries. The signal output from the charge loss corrector is compatible with most analog and digital spectroscopy amplifiers and multi channel analyzers. Using a detector measuring 11.2 by 9.1 by 2.13 mm3, we have recently been able to obtain the first wide-range plutonium gamma-ray isotopic analysis with other than a cryogenically cooled germanium spectrometer. The CdTe spectrometer is capable of measuring small plutonium reference samples in about one hour, covering the range from low to high burnup. The isotopic analysis software used to obtain these results was FRAM, Version 4 from LANL. The new spectrometer is expected to be useful for low-grade assay, as well as for some in-situ plutonium gamma-ray isotopics in lieu of cryogenically cooled Ge.

  4. Research on single-crystal CdTe solar cells

    Science.gov (United States)

    Borrego, J. M.; Ghandhi, S. K.

    1987-10-01

    This report outlines two years of work on the growth and characterization of single-crystal CdTe layers, to explore their potential for high-efficiency solar cells. It was demonstrated that high-quality layers can be grown by organometallic vapor phase epitaxy (OMVPE), whose photoluminescence peak has a FWHM of 5.8 MeV, the lowest value for them yet achieved. CdTe layers were extrinsically doped both n- and p-type with indium and arsenic, respectively. The doping level achieved for p-type is the highest yet reported in the literature, achieved for the first time in an OMVPE system. A hole lifetime of 2.0 microns was measured. In the n-type material, five deep levels were isolated; their capture cross section, energy level, and concentration were determined. A thermodynamic analysis was made to identify their defect character. Both Schottky and p-n junction devices were produced on these layers. The diode characteristics were superior to those of GaAs so this is a potentially superior material for solar cells.

  5. Patterning thick diffused junctions on CdTe

    CERN Document Server

    Kalliopuska, Juha; Sipilä, Heikki; Andersson, Hans; Vähänen, Sami; Eränen, Simo; Tlustos, Lukas

    2009-01-01

    Dividing the detector crystal into discrete pixels enables making an imaging detector, in which the charge collected by each pixel can be read separately. Even if the detector is not meant for imaging, patterns on the crystal surface may be used as guard structures that control and limit the flow of charges in the crystal. This has been exceedingly hard for the detector crystals having thick diffused layers. The paper reports a patterning method of the thick diffused junctions on CdTe. The patterning method of In-diffused pn-junction on CdTe chip is demonstrated by using a diamond blade. The patterning is done by removing material from the pn-junction side of the chip, so that the trenches penetrate the diffused layer. As the trenches extend deeper into the bulk than the junction, the regions separated by the trench are electrically isolated. Electrical characterization results are reported for the strips separated by trenches with various depths. The strip isolation is clearly seen in both measured leakage c...

  6. Advanced CdTe Photovoltaic Technology: September 2007 - March 2009

    Energy Technology Data Exchange (ETDEWEB)

    Barth, K.

    2011-05-01

    During the last eighteen months, Abound Solar (formerly AVA Solar) has enjoyed significant success under the SAI program. During this time, a fully automated manufacturing line has been developed, fabricated and commissioned in Longmont, Colorado. The facility is fully integrated, converting glass and semiconductor materials into complete modules beneath its roof. At capacity, a glass panel will enter the factory every 10 seconds and emerge as a completed module two hours later. This facility is currently undergoing trials in preparation for large volume production of 120 x 60 cm thin film CdTe modules. Preceding the development of the large volume manufacturing capability, Abound Solar demonstrated long duration processing with excellent materials utilization for the manufacture of high efficiency 42 cm square modules. Abound Solar prototype modules have been measured with over 9% aperture area efficiency by NREL. Abound Solar demonstrated the ability to produce modules at industry leading low costs to NREL representatives. Costing models show manufacturing costs below $1/Watt and capital equipment costs below $1.50 per watt of annual manufacturing capacity. Under this SAI program, Abound Solar supported a significant research and development program at Colorado State University. The CSU team continues to make progress on device and materials analysis. Modeling for increased device performance and the effects of processing conditions on properties of CdTe PV were investigated.

  7. Water-Soluble N-Acetyl-L-cysteine-Capped CdTe Quantum Dots Application for Hg(II Detection

    Directory of Open Access Journals (Sweden)

    Tianming Yang

    2013-01-01

    Full Text Available A simple, rapid, and specific method for Hg(II detection has been proposed based on the fluorescence change of N-acetyl-L-cysteine-capped CdTe quantum dots (QDs. The presence of Hg(II ions could quench the fluorescence of QDs at 565 nm and meanwhile produce new peak in 700–860 nm wavelength range. The linear response range is 20–430 nM with the detection limit at 8.0 nM Hg(II. It was found that the position of the new peak was irrelevant to the size of QDs. Furthermore, the mechanism of the quenching of QDs fluorescence by Hg(II and the appearance of new peak in near-infrared area were also discussed and deduced through ultraviolet absorption spectrum, fluorescence spectrum, and X-ray photoelectron spectrum.

  8. Effects of thermal diffuse scattering and surface tilt on diffraction and channeling of fast electrons in CdTe

    International Nuclear Information System (INIS)

    A Bloch-wave model for propagating a fast-electron wave through a noncentrosymmetric crystal for non-normal incidence is discussed, as well as approximations for linearizing the equations. Calculations which simulate /111/ systematic row diffraction conditions in CdTe are used to illustrate how the tilt of the surface with respect to the diffracting planes affects the fast-electron wave function in the crystal. The influence of thermal diffuse scattering (TDS) removes possible ambiguity from the interpretation of ''ALchEmI-type'' experiments [J. C. H. Spence and J. TaftoX, J. Microsc. 130, 147 (1983)] in determining the polarity of noncentrosymmetric crystals. The inclusion of mean and anomalous absorption, using a quantitative Einstein model for TDS, allows direct correlation between theory and experiment for convergent-beam electron diffraction, again allowing direct measurement of crystal polarity

  9. A large surface X-ray camera based on XPAD3/CdTe single chip hybrids

    Science.gov (United States)

    Cassol, F.; Blanc, N.; Bompard, F.; Boudet, N.; Boursier, Y.; Buton, C.; Clémens, J.-C.; Dawiec, A.; Debarbieux, F.; Delpierre, P.; Dupont, M.; Graber-Bolis, J.; Hustache, S.; Morel, C.; Perez-Ponce, H.; Portal, L.; Vigeolas, E.

    2015-11-01

    The XPAD3 chip bump-bonded to a Si sensor has been widely used in preclinical micro-computed tomography and in synchrotron experiments. Although the XPAD3 chip is linear up to 60 keV, the performance of the XPAD3/Si hybrid detector is limited to energies below 30 keV, for which detection efficiencies remain above 20%. To overcome this limitation on detection efficiency in order to access imaging at higher energies, we decided to develop a camera based on XPAD3 single chips bump-bonded to high-Z CdTe sensors. We will first present the construction of this new camera, from the first tests of the single chip hybrids to the actual mechanical assembly. Then, we will show first images and stability tests performed on the D2AM beam line at ESRF synchrotron facility with the fully assembled camera.

  10. Orientational domains in metalorganic chemical vapor deposited CdTe(111) film on cube-textured Ni

    International Nuclear Information System (INIS)

    CdTe thin film was grown by metal organic chemical vapor deposition on cube-textured Ni substrate. The microstructures of the CdTe film and Ni substrate were studied using transmission electron microscopy (TEM) lattice imaging in cross sectional. The orientational relationships of multiple hetereoepitaxial domains in the CdTe film were examined by TEM diffraction. The observed epitaxy is [111]CdTe//[001]Ni. The adjacent domains in CdTe film have a 30° rotation with respect to each other as inferred by the observed different diffraction patterns obtained from different zone axes. The high resolution lattice imaging shows that lamellar twins dominate within each domain. Our results are compared with CdTe(111) film epitaxially grown on Si(001) substrate by molecular beam epitaxy reported in the literature. - Highlights: ► Epitaxial CdTe film grew on textured Ni at 350 °C despite of a large lattice mismatch. ► Epitaxial relationship is CdTe(111) parallel to Ni(001). ► 30° CdTe orientation domains inferred from transmission electron microscopy patterns ► Local inclined angle between CdTe and Ni at the interface is due to vertical mismatch. ► Single crystal-like epitaxial semiconductors can be grown on low cost metal sheet

  11. CdTe quantum dots and gold nanoparticle based spectral methods for determination of lincomycin

    Science.gov (United States)

    Ge, Baoyu; Li, Zhigang; Xie, Yuanzhe; Yang, Lingling; Wang, Ruiyong

    2015-05-01

    Two novel and convenient methods for the determination of lincomycin (LCM) in aqueous solutions have been developed. The first method was based on the enhanced fluorescence of thioglycolic acidcapped CdTe quantum dots (TGA-CdTe QDs) by LCM. For the second method, the introduction of LCM could induce the aggregation of gold nanoparticles (AuNPs), displaying distinct changes in color and in UVvis spectra. Under optimal conditions, the enhanced fluorescence intensity was linearly proportional to LCM concentration in the range of 1-240 μg mL-1 with a detection limit of 2.63 × 10-1 μg mL-1. The second platform is capable of determining LCM in ranges from 1.00 × 10-3 to 2.00 × 10-2 μg mL-1 and from 3.00 × 10-2 to 1.20 × 10-1 μg mL-1 with a detection limit of 1.27 × 10-4 μg mL-1. Both methods were used for rapid detection of LCM in real samples with satisfactory results. Comparisons between the two methods were made.

  12. Properties of CdTe nanocrystalline thin films grown on different substrates by low temperature sputtering

    Institute of Scientific and Technical Information of China (English)

    Chen Huimin; Guo Fuqiang; Zhang Baohua

    2009-01-01

    CdTe nanocrystalline thin films have been prepared on glass, Si and Al2O3 substrates by radio-frequency magnetron sputtering at liquid nitrogen temperature. The crystal structure and morphology of the films were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The XRD examinations revealed that CdTe films on glass and Si had a better crystal quality and higher preferential orientation along the (111) plane than the Al2O3. FESEM observations revealed a continuous and dense morphology of CdTe films on glass and Si substrates. Optical properties of nanocrystalline CdTe films deposited on glass substrates for different deposited times were studied.

  13. Shape Control of CdTe Nanocrystals: Influence of the Solvent Composition and Ligand Effects

    Directory of Open Access Journals (Sweden)

    Xiaoping Jin

    2013-01-01

    Full Text Available CdTe nanocrystals were synthesized by the hot-injection method with a mixture of oleylamine and octadecene as a solvent. The influence of the composition of the solvent and of the injection solution on the shape of CdTe nanoparticles was investigated. Various shapes of CdTe nanocrystals, such as nanodots, nanorods, multipods, and nanowires, could be obtained by changing the reaction conditions. Tuning the reactivity of both the cadmium and the tellurium precursors at the same time was found to be the main reason for the shape control of CdTe nanocrystals in this reaction system. The reactivity of the Cd precursor was controlled by the composition of the solvent, while the activity of the Te precursor could be influenced by using trioctylphosphine and tributylphosphine in the injection solution.

  14. Synthesis of CdTe Quantum Dots with Tunable Photoluminescence Using Tellurium Dioxide as Tellurium Source

    Institute of Scientific and Technical Information of China (English)

    刘声燕; 王益林; 杨昆; 周立亚

    2012-01-01

    A simple and convenient method has been developed for synthesis of water-soluble CdTe quantum dots (QDs) under ambient atmospheric conditions. In contrast to the traditional aqueous synthesis, green to red emitting CdTe QDs were prepared by using TeO2 to replace Te or AIzTe3 as tellurium source in this method. The influences of ex- perimental variables, including pH value, 3-mercaptopropionic acid (MPA)/Cd and Te/Cd molar ratios, on the emis- sion peak and photoluminescence (PL) quantum yield (QY) of the obtained CdTe QDs have been systematically investigated. Experimental results indicate that green to red emitting CdTe QDs with a maximum photolumines- cence quantum yield of 35.4% can be prepared at pH 11.3 and rt(Cd) : n(Te) : n(MPA)= 1 : 0.1 : 1.7.

  15. Effects of high-temperature annealing on ultra-thin CdTe solar cells

    International Nuclear Information System (INIS)

    High-temperature annealing (HTA), a process step prior to vapor cadmium chloride (VCC) treatment, has been found to be useful for improving the crystallinity of CdTe films and the efficiency of ultra-thin CdTe solar cells. Scanning electron microscopy, optical absorption, photoluminescence measurements and analyses on photoluminescence results using spectral deconvolution reveal that the additional HTA step produces substantial grain growth and reduces grain boundary defects. It also reduces excessive sulfur diffusion across the junction that can occur during the VCC treatment. The HTA step helps to produce pinhole-free CdTe films and reduce electrical shorts in ultra-thin CdTe solar cells. An efficiency of about 11.6% has been demonstrated for ultra-thin CdS/CdTe solar cells processed with HTA step.

  16. Enhanced Specificity of Multiplex Polymerase Chain Reaction via CdTe Quantum Dots

    Directory of Open Access Journals (Sweden)

    Liang Gaofeng

    2011-01-01

    Full Text Available Abstract Nanoparticles were recently reported to be able to improve both efficiency and specificity in polymerase chain reaction (PCR. Here, CdTe QDs were introduced into multi-PCR systems. It was found that an appropriate concentration of CdTe QDs could enhance the performance of multi-PCR by reducing the formation of nonspecific products in the complex system, but an excessive amount of CdTe QDs could suppress the PCR. The effects of QDs on PCR can be reversed by increasing the polymerase concentration or by adding bovine serum albumin (BSA. The mechanisms underlying these effects were also discussed. The results indicated that CdTe QDs could be used to optimize the amplification products of the PCR, especially in the multi-PCR system with different primers annealing temperatures, which is of great significance for molecular diagnosis.

  17. Effects of high-temperature annealing on ultra-thin CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Xia Wei; Lin Hao; Wu, Hsiang N.; Tang, Ching W., E-mail: chtang@che.rochester.edu

    2011-10-31

    High-temperature annealing (HTA), a process step prior to vapor cadmium chloride (VCC) treatment, has been found to be useful for improving the crystallinity of CdTe films and the efficiency of ultra-thin CdTe solar cells. Scanning electron microscopy, optical absorption, photoluminescence measurements and analyses on photoluminescence results using spectral deconvolution reveal that the additional HTA step produces substantial grain growth and reduces grain boundary defects. It also reduces excessive sulfur diffusion across the junction that can occur during the VCC treatment. The HTA step helps to produce pinhole-free CdTe films and reduce electrical shorts in ultra-thin CdTe solar cells. An efficiency of about 11.6% has been demonstrated for ultra-thin CdS/CdTe solar cells processed with HTA step.

  18. Interface reactions in CdTe solar cell processing

    Energy Technology Data Exchange (ETDEWEB)

    Albin, D.; Dhere, R.; Swartzlander-Guest, A. [National Renewable Energy Lab., Golden, CO (United States)] [and others

    1998-12-31

    Currently, the best performing CdS/CdTe solar cells use a superstrate structure in which CdTe is deposited on a heated CdS/SnO{sub 2}/Glass substrate. In the close-spaced-sublimation (CSS) process, substrate temperatures in the range 550 C to 620 C are common. Understanding how these high processing temperatures impact reactions at the CdS/CdTe interface in addition to reactions between previously deposited layers is critical. At the SnO{sub 2}/CdS interface the authors have determined that SnO{sub 2} can be susceptible to reduction, particularly in H{sub 2} ambients. Room-temperature sputtered SnO{sub 2} shows the most susceptibility. In contrast, higher growth temperature chemical vapor deposited (CVD) SnO{sub 2} appears to be much more stable. Elimination of unstable SnO{sub 2} layers, and the substitution of thermal treatments for H{sub 2} anneals has produced total-area solar conversion efficiencies of 13.6% using non-optimized SnO{sub 2} substrates and chemical-bath deposited (CBD) CdS. Alloying and interdiffusion at the CdS/CdTe interface was studied using a new lift-off approach which allows enhanced compositional and structural analysis at the interface. Small-grained CdS, grown by a low-temperature CBD process, results in more CdTe{sub 1{minus}x}S{sub x} alloying (x = 12--13%) relative to larger-grained CdS grown by high-temperature CSS (x{approximately}2--3%). Interdiffusion of S and Te at the interface, measured with lift-off samples, appears to be inversely proportional to the amount of oxygen used during the CSS CdTe deposition. The highest efficiency to date using CSS-grown CdS is 10.7% and was accomplished by eliminating oxygen during the CdTe deposition.

  19. Deposition of Cl-doped CdTe polycrystalline films by close-spaced sublimation

    International Nuclear Information System (INIS)

    The effects of Cl-doping on the CdTe layers by the close-spaced sublimation (CSS) deposition were investigated. Cl-doped CdTe polycrystalline films were deposited on graphite substrates by CSS method using a mixture of CdTe and CdCl2 powder as a source. In X-ray diffraction (XRD) patterns of the obtained films with various deposition times, many diffraction peaks other than CdTe peaks were observed in the deposition times lower than 10 min. These diffraction peaks were probably due to the formation of chlorides of Cd, Te and C, such as CdCl2, TeCl4, Te3Cl2 and C10Cl8. X-ray fluorescence (XRF) and secondary ion mass spectrometry (SIMS) analyses revealed that a large amount of chlorine was contained in the films with the deposition times lower than 10 min, and that Cl concentration decreased with increasing the deposition time above 3 min. These results indicate that the films containing the chlorides of Cd, Te and C in addition to CdTe are formed in the initial stage of the CSS deposition using a mixture of CdTe and CdCl2 powder as a source. Cross-sectional images revealed that the grain size was decreased by the effect of Cl-doping. Furthermore, current-voltage (I -V) characteristics of the CdTe/graphite structures were measured, and it was found that the resistivity of the Cl-doped CdTe layer was much higher than that of the undoped CdTe layer. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. PENINGKATAN KUALITAS FILM TIPIS CdTe SEBAGAI ABSORBER SEL SURYA DENGAN MENGGUNAKAN DOPING TEMBAGA (Cu)

    OpenAIRE

    P. Marwoto; N.M. Darmaputra; Sugianto -; Othaman, Z.; E. Wibowo; S.Y. Astuti

    2012-01-01

    Film tipis CdTe dengan doping tembaga (Cu) berkonsenterasi 2% telah berhasil ditumbuhkan di atas substrat Indium Tin Oxide (ITO) dengan metode dc magnetron sputtering. Penelitian ini dilakukan untuk mengetahui pengaruh doping Cu(2%) terhadap struktur morfologi, struktur kristal, fotoluminisensi dan resistivitas listrik film CdTe. Citra morfologi Scanning Electron Microscopy (SEM) dan hasil analisis struktur dengan X-Ray Diffraction (XRD) menunjukkan bahwa film CdTe:Cu(2%) mempunyai citra perm...

  1. Fluorescence Quenching of CdTe Nanocrystals by Bound Gold Nanoparticles in Aqueous Solution

    OpenAIRE

    Jian ZHANG; Badugu, Ramachandram; Lakowicz, Joseph R.

    2008-01-01

    Water-soluble gold nanoparticles with an average diameter of 5 nm were prepared with carboxylic acid terminated thiol ligands. These ligands contain zero to eight methylene moieties. CdTe nanocrystals with an average diameter of 5 nm were synthesized with aminoethanethiol capping. These nanocrystals displayed characteristic absorption and emission spectra of quantum dots. The amine terminated CdTe nanocrystals and carboxylic-acid-terminated gold nanoparticles were conjugated in aqueous soluti...

  2. Preparation and biological investigation of luminescent water soluble CdTe nanoparticles

    OpenAIRE

    Byrne, S.J.; O'Driscoll, C.M.; Corr, S.A.; Gun'ko, Y. K.; Mitchell, S.; Volkov, Y.

    2005-01-01

    In this study CdTe quantum dots have been successfully prepared in aqueous medium using several different thiol stabilizers. The resulting nanocrystals were purified and the photoluminescence efficiency was subsequently enhanced through post preparative procedures such as photochemical etching and ageing. An optical study was carried out on the resulting CdTe nanocrystals as proof as their improvement. Preliminary tests of the thiol stabilised QDs as potential biolabels have been performed. I...

  3. Untersuchung von CdTe als Sensormaterial für die spektroskopische Röntgenbildgebung

    OpenAIRE

    Guni, Ewald

    2012-01-01

    Detektorkonzepte mit photonenzählender Ausleseelektronik gewinnen zunehmend an Bedeutung in der medizinischen Bildgebung. Materialien mit hohem Absorptionsvermögen, wie CdTe, sind dabei die bevorzugten Sensormaterialien. Ziel dieser Arbeit war es, CdTe als Sensormaterial in Verbindung mit dem photonenzählenden Auslesechip Medipix2-MXR, im Hinblick auf die Eignung zur spektroskopischen Röntgenbildgebung, zu untersuchen. Das Augenmerk richtete sich dabei auf den Nachweis von Kontrastmitteln in ...

  4. CdTe and HgI2 crystals and detectors: present state and future

    International Nuclear Information System (INIS)

    After recalling the main properties of CdTe and HgI2 crystals from which the characteristics of these detectors will arise, the fabrication cycle is analysed at its various stages. The results at present achieved on CdTe and HgI2 detectors are analysed with a number of concrete applications in view such as medium power (0-200 keV) X and γ spectrometry, localisation of γ photons and solid ionisation chambers

  5. RF sputtering deposition of CdTe on GaAs substrate

    Science.gov (United States)

    Adamiec, Krzysztof; Rutkowski, Jaroslaw; Bednarek, S.; Michalski, E.

    1997-06-01

    The fabrication of HgCdTe IR detectors demands high-quality CdTe or CdZnTe substrates. Bulk CdTe tends to twin, therefore large single crystals are generally not available. This problem could be circumvented by growing CdTe epilayers on an alternative large area substrate. Several studies have been made on the growth of CdTe on different substrates such as InSb, GaAs, Si and sapphire by MOCVD and MBE techniques. We report the initial results for the growth of CdTe buffer films on GaAs (100) substrates by sputter epitaxy. This crystal was chosen as the substrate material because of its transparency to IR radiation and availability as large area wafers with high structural perfection. Epitaxial films of CdTe were deposited in a sputtering system with a base pressure of 2 X 10-4 Pa. The GaAs substrate was degreased, etched in standard solution, and mounted immediately on a cooper substrate holder in the system. The substrates were ion etched in the sputtering system to remove surface oxide. The CdTe films were deposited in a wide substrate temperature range from 50 to 450 degrees C. Film thickness ranged from 0.1 to 5 micrometers , and deposition rates from 1 to 5 micrometers /h. The orientations and crystalline quality epitaxial films were characterized by x-ray diffraction. The surface morphology and the cross section of the gown CdTe layers were investigated by Nomarski interference contrast microscope. The optical and the electrical properties of the epitaxial films were investigated too. Structural characterization reveals that crystalline quality is a function of temperature of substrates. The single-crystals films grown at 300 degrees C on GaAs showed a best surface morphology.

  6. Transferring CdTe Nanoparticles from Liquid Phase to Polyvinylpyrrolidone Nanofibers by Electrospinning and Detecting Its Photoluminescence Property

    Institute of Scientific and Technical Information of China (English)

    WANG Shu-gang; YANG Qing-biao; BAI Jie; SONG Yan; ZHANG Chao-qun; LI Yao-xian

    2008-01-01

    The major aim of this work was to synthesize thio-stabilized CdTe nanoparticles(NPs) in an aqueous solution,which was then enwrapped with cetyltrimethylammonium bromide(CTAB),and finally transferred to the polyvinylpyrrolidone(PVP) matrix by electrospinning,The PVP nanofibers containing CdTe NPs were characterized by scanning electron microscopy(SEM) and transmission electron microscopy(TEM),to observe the morphology of the nanofibers and the distribution of CdTe NPs,The selective area electronic diffraction(SAED) pattern verified that CdTe NPs were cubic lattice,The photoluminescence(PL) spectrum indicated that CdTe NPs existed in an optical style in PVP nanofibers,Moreover,X-ray photoelectron spectra(XPS) revealed that thiol-stabilized CdTe NPs were enwrapped by CTAB,and PVP acted as a dispersant in the process of electrospinning.

  7. The Submillimeter Array Polarimeter

    OpenAIRE

    Marrone, Daniel P.; Rao, Ramprasad

    2008-01-01

    We describe the Submillimeter Array (SMA) Polarimeter, a polarization converter and feed multiplexer installed on the SMA. The polarimeter uses narrow-band quarter-wave plates to generate circular polarization sensitivity from the linearly-polarized SMA feeds. The wave plates are mounted in rotation stages under computer control so that the polarization handedness of each antenna is rapidly selectable. Positioning of the wave plates is found to be highly repeatable, better than 0.2 degrees. A...

  8. Formation and Properties of Polycrystalline p-Type High-Conductivity CdTe Films by Coevaporation of CdTe and Te

    Science.gov (United States)

    Hayashi, Toshiya; Hayashi, Hiroaki; Fukaya, Mitsuru; Ema, Yoshinori

    1991-10-01

    Polycrystalline p-type high-dark-conductivity CdTe films have been prepared by coevaporation of CdTe and Te. The structural and electrical properties were investigated. The dark conductivity of the films at 300 K ranged from 6.32× 10-8 to 3.41 S cm-1. The film structure was of the zincblende type with a preferential orientation of the (111) planes parallel to the substrate. The crystallinity was rather good. From the measurements of the carrier concentration versus ambient temperature characteristics, it was found that the high-conductivity p-type conduction of the films was due to the formation of Cd vacancies, acceptors resulting from the coevaporation of CdTe and Te. It is shown that the high-conductivity films obtained are suitable for p-CdTe/n-CdS solar cells.

  9. Studies on interaction between CdTe quantum dots and -chymotrypsin by molecular spectroscopy

    Indian Academy of Sciences (India)

    Jianniao tian; Shengzhi Wei; Yanchun Zhao; Rongjun Liu; Shulin Zhao

    2010-05-01

    In this article, the interaction between -Chymotrypsin and CdTe QDs was investigated by fluorescence, synchronous fluorescence, and circular dichroism (CD) spectroscopic methods at pH 7.20 and pH 9.05. The intrinsic fluorescence of -Chy is quenched by CdTe QDs. Under different pH conditions, the level of binding constants is determined to be 103 from fluorescence data. The hydrogen bond or van der Waals force is involved in the binding process when pH is 9.05, while the hydrophobic and electrostatic interactions play main role in the binding process when pH is 7.20. The red-shift of synchronous fluorescence spectral peak of protein after the addition of CdTe QDs reveals that the microenvironments around tryptophan residues are disturbed by CdTe QDs. The secondary structure of -Chy undergoes slight changes as similar by far-UV CD data. The activity and stability of -Chy in the presence of CdTe QDs were also studied. -Chy can maintain its high activity and stability under different pH conditions for 24 h in the presence of CdTe QDs.

  10. Facile synthesis of straight and branched CdTe nanowires using CdO as precursor.

    Science.gov (United States)

    Liu, Sheng; Yang, Chunyan; Zhang, Wen-Hua; Li, Can

    2011-12-01

    High-quality colloidal CdTe nanowires (NWs) containing both straight and branched ones were controllably prepared via a solution-based approach, using a low melting Bi nanoparticles as catalysts, CdO and tributylphosphine telluride (TBP-Te) as precursors, and a tri-n-octylphosphine oxide/tri-n-octylphosphine (TOPO/TOP) mixture as solvent. The resulting straight CdTe NWs have typical diameters below 20 nm accompanying with lengths exceeding 10 microm. In the case of branched CdTe NWs, tripod, V-shaped and y-shaped morphologies are obtained by decreasing the apparent Cd/Te molar ratio. It is found that, as the surface capping ligands, di-n-octylphosphinic acid (DOPA) is superior to decylphosphonic acid (DPA) in the reproducible growth of high-quality CdTe NWs. Since highly toxic dimethylcadmium, a cadmium precursor widely used in literatures, is replaced by CdO and the amount of the TOPO/TOP solvent mixture is significantly reduced, a relative safe and economical synthetic approach of high-quality colloidal CdTe NWs with controllable morphology is thus presented.

  11. Electrodeposited CdTe and HgCdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Basol, B.M.

    1988-01-15

    The processing steps necessary for producing high efficiency electrodeposited CdTe and HgCdTe solar cells are described. The key step in obtaining solar cell grade p-type CdTe and HgCdTe is the 'type conversion-junction formation' (TCJF) process. The TCJF process involves the heat treatment of the as-deposited n-type CdTe and HgCdTe layers at around 400 /sup 0/C. This procedure converts these n-type films into high resistivity p type and forms a rectifying junction between them and the underlying n-type window layers. Possible effects of oxygen on the TCJF process are discussed. The results of studies made on the structural, electrical and optical properties of the electrodeposited CdS, CdTe and HgCdTe films are presented. The resistivity of the electrodeposited HgCdTe can be made lower than that of CdTe. Consequently, solar cells made using the HgCdTe films have, on the average, better fill factors than those made using the CdTe layers, HgCdTe is also attractive for tandem-cell applications because of its variable band gap which can be easily tuned to the desired value. CdS/CdTe and CdS/HgCdTe heterojunction solar cells with 10.3% and 10.6% efficiency have been demonstrated using electrodeposition techniques and the TCJF process.

  12. Properties of RF sputtered cadmium telluride (CdTe) thin films: Influence of deposition pressure

    Science.gov (United States)

    Kulkarni, R. R.; Pawbake, A. S.; Waykar, R. G.; Rondiya, S. R.; Jadhavar, A. A.; Pandharkar, S. M.; Karpe, S. D.; Diwate, K. D.; Jadkar, S. R.

    2016-04-01

    Influence of deposition pressure on structural, morphology, electrical and optical properties of CdTe thin films deposited at low substrate temperature (100°C) by RF magnetron sputtering was investigated. The formation of CdTe was confirmed by low angle XRD and Raman spectroscopy. The low angle XRD analysis revealed that the CdTe films have zinc blende (cubic) structure with crystallites having preferred orientation in (111) direction. Raman spectra show the longitudinal optical (LO) phonon mode peak ˜ 165.4 cm-1 suggesting high quality CdTe film were obtained over the entire range of deposition pressure studied. Scanning electron microscopy analysis showed that films are smooth, homogenous, and crack-free with no evidence of voids. The EDAX data revealed that CdTe films deposited at low deposition pressure are high-quality stoichiometric. However, for all deposition pressures, films are rich in Cd relative to Te. The UV-Visible spectroscopy analysis show the blue shift in absorption edge with increasing the deposition pressure while the band gap show decreasing trend. The highest electrical conductivity was obtained for the film deposited at deposition pressure 1 Pa which indicates that the optimized deposition pressure for our sputtering unit is 1 Pa. Based on the experimental results, these CdTe films can be useful for the application in the flexible solar cells and other opto-electronic devices.

  13. Scanning Kelvin probe measurements on As-doped CdTe solar cells

    International Nuclear Information System (INIS)

    Scanning Kelvin probe microscopy (SKPM) has been used to study the Fermi level shift in arsenic (As) doped cadmium telluride (CdTe) photovoltaic devices. The contact potential difference (CPD) between probe tip and sample surface revealed that increasing As concentrations in CdTe led to a decrease in CPD. This highlighted a downward shift in the CdTe Fermi level and an increase in the CdTe work function. Using a highly oriented pyrolytic graphite sample in ambient conditions as a reference, the absolute work functions of the CdTe samples were estimated to vary from 3.88 to 4.09 eV. High-resolution SKPM measurements revealed localized shifts in CPD at CdTe grain boundaries. This was directly correlated to As doping concentrations, and indicated the segregation of As to grain boundaries. A mechanism is proposed where localized band bending at grain boundaries channels minority carriers away from the grain boundary, leading to reduced carrier recombination. (paper)

  14. Physical vapor deposition of CdTe thin films at low temperature for solar cell applications

    International Nuclear Information System (INIS)

    Cadmium telluride is successfully utilized as an absorber material for thin film solar cells. Industrial production makes use of high substrate temperatures for the deposition of CdTe absorber layers. However, in order to exploit flexible substrates and to simplify the manufacturing process, lower deposition temperatures are beneficial. Based on the phase diagram of CdTe, predictions on the stoichiometry of CdTe thin films grown at low substrate temperatures are made in this work. These predictions were verified experimentally using additional sources of Cd and Te during the deposition of the CdTe thin films at different substrate temperatures. The deposited layers were analyzed with energy-dispersive X-ray spectroscopy. In case of CdTe layers which were deposited at substrate temperatures lower than 200 C without usage of additional sources we found a non-stoichiometric growth of the CdTe layers. The application of the additional sources leads to a stoichiometric growth for substrate temperatures down to 100 C which is a significant reduction of the substrate temperature during deposition.

  15. Glutathione-capped CdTe nanocrystals as probe for the determination of fenbendazole

    Science.gov (United States)

    Li, Qin; Tan, Xuanping; Li, Jin; Pan, Li; Liu, Xiaorong

    2015-04-01

    Water-soluble glutathione (GSH)-capped CdTe quantum dots (QDs) were synthesized. In pH 7.1 PBS buffer solution, the interaction between GSH-capped CdTe QDs and fenbendazole (FBZ) was investigated by spectroscopic methods, including fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, and resonance Rayleigh scattering (RRS) spectroscopy. In GSH-capped CdTe QDs solution, the addition of FBZ results in the fluorescence quenching and RRS enhancement of GSH-capped CdTe QDs. And the quenching intensity (enhanced RRS intensity) was proportional to the concentration of FBZ in a certain range. Investigation of the interaction mechanism, proved that the fluorescence quenching and RRS enhancement of GSH-capped CdTe QDs by FBZ is the result of electrostatic attraction. Based on the quenching of fluorescence (enhancement of RRS) of GSH-capped CdTe QDs by FBZ, a novel, simple, rapid and specific method for FBZ determination was proposed. The detection limit for FBZ was 42 ng mL-1 (3.4 ng mL-1) and the quantitative determination range was 0-2.8 μg mL-1 with a correlation of 0.9985 (0.9979). The method has been applied to detect FBZ in real simples and with satisfactory results.

  16. Orientation of CdTe epitaxial films on GaAs(100) grown by vacuum evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Houng Mauphon; Fu Shenli; Jenq Fenqlin (Dept. of Electrical Engineering, National Cheng-Kung Univ., Tainan (Taiwan)); Chen Jiannruey (Dept. of Materials Science and Engineering, National Tsing Hua Univ., Hsinchu (Taiwan))

    1991-08-15

    The growth of (100)- and (111)-oriented CdTe epitaxial layers on (100)-oriented GaAs substrates were investigated. Ar{sup +} plasma bombardment was used to remove the surface oxide layer, while preheating the substrate before evaporation was performed to deplete arsenic on the GaAs substrate surface. Results indicate that the CdTe(100) will grow on GaAs(100) with an oxide layer remaining on the surface. For the GaAs(100) substrate with the oxide layer removed by plasma bombardment, CdTe(100) will grow on the arsenic-depleted GaAs substrate, while CdTe(111) will grow on the GaAs substrate without arsenic depletion. A model is proposed that a tellurium-rich surface is formed on the arsenic-depleted GaAs surface through Ga-Te bonding on which the CdTe(100) will grow, whereas CdTe(111) will grow on a tellurium-poor surface. The photoluminescence investigation conforms to our proposed model. (orig.).

  17. On the doping problem of CdTe films: The bismuth case

    Energy Technology Data Exchange (ETDEWEB)

    Vigil-Galan, O. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico); Brown, M. [Department of Physics and Astronomy, The University of Toledo, 43606 Toledo, OH (United States); Ruiz, C.M. [Depto. Fisica de Materiales, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Vidal-Borbolla, M.A. [Instituto de Investigacion en Comunicacion Optica, Av. Karakorum 1470, Lomas 4a. Secc., 78210 San Luis Potosi, SLP (Mexico); Ramirez-Bon, R. [CINVESTAV-IPN, U. Queretaro, Libramiento Norponiente No. 2000, Fracc. Real de Juriquilla, 76230 Santiago de Queretaro, Qro. (Mexico); Sanchez-Meza, E. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico); Tufino-Velazquez, M. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico)], E-mail: mtufinovel@yahoo.com.mx; Calixto, M. Estela [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico); Compaan, A.D. [Department of Physics and Astronomy, The University of Toledo, 43606 Toledo, OH (United States); Contreras-Puente, G. [Escuela Superior de Fisica y Matematicas del IPN, Edif. 9, UPALM, 07738 Mexico, D. F. (Mexico)

    2008-08-30

    The controlled increase of hole concentration is an important issue and still an unsolved problem for polycrystalline CdTe-based solar cells. The typical hole concentration of as-grown CdTe thin-films goes up to 10{sup 13} cm{sup -3}, depending on the specific growth technique. The highest electron concentration obtained for CdS, the suitable window partner material of CdTe, is around 10{sup 15} cm{sup -3}. Thus, the PV-performance of a CdS/CdTe device can be optimized if the hole concentration in CdTe is increased. We have faced up this problem by studying the electrical properties of two types of CdTe films: CdTe films grown by Close Space Vapor Transport using a CdTe:Bi powder as the starting material and CdTe sputtered films doped by implantation with different Bi-doses. Temperature-dependent resistivity and Hall effect measurements and a discussion on the efficiency of both doping processes are presented.

  18. Oxygen Incorporation During Fabrication of Substrate CdTe Photovoltaic Devices: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Duenow, J. N.; Dhere, R. G.; Kuciauskas, D.; Li, J. V.; Pankow, J. W.; DeHart, C. M.; Gessert, T. A.

    2012-06-01

    Recently, CdTe photovoltaic (PV) devices fabricated in the nonstandard substrate configuration have attracted increasing interest because of their potential compatibility with flexible substrates such as metal foils and polymer films. This compatibility could lead to the suitability of CdTe for roll-to-roll processing and building-integrated PV. Currently, however, the efficiencies of substrate CdTe devices reported in the literature are significantly lower ({approx}6%-8%) than those of high-performance superstrate devices ({approx}17%) because of significantly lower open-circuit voltage (Voc) and fill factor (FF). In our recent device development efforts, we have found that processing parameters required to fabricate high-efficiency substrate CdTe PV devices differ from those necessary for traditional superstrate CdTe devices. Here, we investigate how oxygen incorporation in the CdTe deposition, CdCl2 heat treatment, CdS deposition, and post-deposition heat treatment affect device characteristics through their effects on the junction. By adjusting whether oxygen is incorporated during these processing steps, we have achieved Voc values greater than 860 mV and efficiencies greater than 10%.

  19. A new structure to increase the photostability of CdTe quantum dot sensitized solar cells

    International Nuclear Information System (INIS)

    In this paper a new cell structure is introduced to reduce the rate of CdTe corrosion in quantum dot sensitized solar cells (QDSSCs) using I-/I3- electrolyte. In this cell, one electrode is a titania nanorod that was sensitized with CdTe quantum dots as the working electrode. A thin gold layer is sputtered on the electrode to act as a protective layer against the I-/I3- corrosive electrolyte and to passivate the CdTe surface traps which are the main recombination centres in a QDSSC. In addition, a Schottky barrier formed at the interface of Au and CdTe prevents direct electron recombination from the CdTe conduction band with I3- ions. The mechanism of charge transfer and quantum dot regeneration in the presence of gold layer is discussed and our results show that the solar cells made of TiO2/CdTe/Au photoanode have more photostability and a higher fill factor relative to the TiO2/CdTe photoanodes.

  20. On the doping problem of CdTe films: The bismuth case

    International Nuclear Information System (INIS)

    The controlled increase of hole concentration is an important issue and still an unsolved problem for polycrystalline CdTe-based solar cells. The typical hole concentration of as-grown CdTe thin-films goes up to 1013 cm-3, depending on the specific growth technique. The highest electron concentration obtained for CdS, the suitable window partner material of CdTe, is around 1015 cm-3. Thus, the PV-performance of a CdS/CdTe device can be optimized if the hole concentration in CdTe is increased. We have faced up this problem by studying the electrical properties of two types of CdTe films: CdTe films grown by Close Space Vapor Transport using a CdTe:Bi powder as the starting material and CdTe sputtered films doped by implantation with different Bi-doses. Temperature-dependent resistivity and Hall effect measurements and a discussion on the efficiency of both doping processes are presented

  1. Synthesis of Aqueous CdTe Nanocrystals with High Efficient Blue-Green Emission of Exciton

    Institute of Scientific and Technical Information of China (English)

    邵海宝; 王春雷; 李荣青; 徐淑宏; 张海升; 崔一平

    2012-01-01

    As one of the most popular nanocrystals (NCs), aqueous CdTe NCs have very weak green emission under con- ventional synthesis conditions. In this work, we report the first example of blue-emitting CdTe NCs directly synthe- sized in aqueous solution by slowing down the growth rate after nucleation. The key for the synthesis is the optimi- zation of NC growth conditions, namely pH range of 7.5 to 8.5, TGA/Cd ratio of 3.6, Cd/Te ratio of 10, and Te concentration of 2 × 10-5 mol/L, to get a slow growth rate after nucleation. The as-prepared blue-emitting CdTe NCs have small size (as small as 1.9 nm) and bright emission [with 4% photoluminescence quantum yield (PL QY) at 486 nm and 17% PLQY at 500 nm]. Transmission electron microscopy (TEM) images of the as-prepared CdTe show monodispersed NCs which exhibit cubic zinc blend structure. Moreover, time-resolved PL decay and X-ray photoelectron spectroscopy (XPS) results show the as-prepared NCs have better surface modification by ligand, which makes these luminescent small CdTe NCs have higher photoluminescence quantum yield, compared with NCs synthesized under conventional conditions.

  2. Cu2S as ohmic back contact for CdTe solar cells

    International Nuclear Information System (INIS)

    We prepared a back contact for CdTe solar cells with Cu2S as primary contact. Cu2S was evaporated on CdCl2 treated CdTe solar cells in superstrate configuration. The CdTe and CdS layers were deposited by Closed Space Sublimation. Direct interface studies with X-ray photoelectron spectroscopy have revealed a strongly reactive interface between CdTe and Cu2S. A valence band offset of 0.4-0.6 eV has been determined. The performance of solar cells with Cu2S back contacts was studied in comparison to cells with an Au contact that deposited onto a CdCl2-treated CdTe surface that was chemically etched using a nitric-phosphoric etch. The solar cells were analyzed by current-voltage curves and external quantum efficiency measurements. After several post deposition annealing steps, 13% efficiency was reached with the Cu2S back contact, which was significantly higher than the ones obtained for the NP-etched back contacts. - Highlights: • A new back contact for CdTe solar out of Cu2S has been tested. • With a direct interface experiment the valence band offset was determined. • Post deposition heat treatment has been carried out for the solar cells. • 13% efficiency has been reached with the Cu2S back contact

  3. Phosphorus Diffusion Mechanisms and Deep Incorporation in Polycrystalline and Single-Crystalline CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Colegrove, Eric; Harvey, Steven P.; Yang, Ji-Hui; Burst, James M.; Albin, David S.; Wei, Su-Huai; Metzger, Wyatt K.

    2016-05-01

    A key challenge in cadmium telluride (CdTe) semiconductors is obtaining stable and high hole density. Group I elements substituting Cd can form ideal acceptors but easily self-compensate and diffuse quickly. For example, CdTe photovoltaics have relied on copper as a dopant, but copper creates stability problems and hole density that has not exceeded 1015 cm-3. If hole density can be increased beyond 10^16 cm-3, CdTe solar technology can exceed multicrystalline silicon and provide levelized costs of electricity below conventional energy sources. Group V elements substituting Te offer a solution, but are very difficult to incorporate. Using time-of-flight secondary-ion mass spectrometry, we examine bulk and grain boundary (GB) diffusion of phosphorous (P) in CdTe in Cd-rich conditions. We find that in addition to slow bulk diffusion and fast GB diffusion, there is a fast bulk diffusion component that enables deep P incorporation in CdTe. Detailed first-principles calculations indicate the slow bulk diffusion component is caused by substitutional P diffusion through the Te sublattice, whereas the fast bulk diffusion component is caused by P diffusing through interstitial lattice sites following the combination of a kick-out step and two rotation steps. The latter is limited in magnitude by high formation energy, but is sufficient to manipulate P incorporation. In addition to an increased physical understanding, this result opens up new experimental possibilities for Group V doping in CdTe materials.

  4. Luminescent properties of CdTe quantum dots synthesized using 3-mercaptopropionic acid reduction of tellurium dioxide directly

    OpenAIRE

    Shen, Mao; Jia, Wenping; You, Yujing; Hu, Yan; Li, Fang; Tian, Shidong; Li, Jian; Jin, Yanxian; Han, Deman

    2013-01-01

    A facile one-step synthesis of CdTe quantum dots (QDs) in aqueous solution by atmospheric microwave reactor has been developed using 3-mercaptopropionic acid reduction of TeO2 directly. The obtained CdTe QDs were characterized by ultraviolet–visible spectroscopy, fluorescent spectroscopy, X-ray powder diffraction, multifunctional imaging electron spectrometer (XPS), and high-resolution transmission electron microscopy. Green- to red-emitting CdTe QDs with a maximum photoluminescence quantum y...

  5. First principles study of Bi dopen CdTe thin film solar cells: electronic and optical properties

    OpenAIRE

    Seminóvski Pérez, Yohanna; Palacios Clemente, Pablo; Wahnón Benarroch, Perla

    2011-01-01

    Nowadays, efficiency improvement of solar cells is one of the most important issues in photovoltaic systems and CdTe is one of the most promising thin film photovoltaic materials we can found. CdTe reported efficiencies in solar energy conversion have been as good as that found in polycrystalline Si thin film cell [1], besides CdTe can be easily produced at industrial scale.

  6. Reflectance anisotropy spectra of CdTe(001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez-Nava, R.A.; Arzate, N.; Mendoza, B.S. [Photonics Division, Centro de Investigaciones en Optica A. C., Leon, Guanajuato (Mexico)

    2010-08-15

    We present first-principles calculations of reflectance anisotropy spectra (RAS) of the more common CdTe(001) surface reconstructions: Te-terminated (2 x 1) and Cd-terminated (2 x 1) and c(2 x 2). The last two reconstructions with a Cd coverage of half atomic layers. Calculations have been performed by using the density-functional formalism within the local-density approximation + scissors corrections. The electron-ion interaction has been modeled by ab initio, relativistic norm-conserving pseudopotentials. We have also calculated RAS spectra using a semi-empirical tight binding method (SETB) within a sp{sup 3} s{sup *} basis. We show RAS of each surface reconstruction and compare our theoretical results with experimental results reported in the literature and we found a good agreement between experimental and theoretical spectra for the (2 x 1) reconstructions. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  7. Theoretical study of intrinsic defects in CdTe

    Science.gov (United States)

    Menéndez-Proupin, E.; Orellana, W.

    2016-05-01

    The quantum states and thermodynamical properties of the Cd and Te vacancies in CdTe are studied by first principles calculations. It is shown that the band structure of a cubic 64-atoms supercell with a Te vacancy is dramatically different from the band structure of the perfect crystal, suggesting that it cannot be used as model to calculate isolated defects. This flaw is solved modeling the Te vacancy within a cubic 216-atoms supercell. However, even with this large supercell, the 2— charge state relaxes to an incorrect distorted structure. This distortion is driven by partial filling of the conduction band induced by the k-point sampling. The correct structures and formation energies are obtained by relaxation with restriction of system symmetry, followed by band-filling correction to the energy, or by using a larger supercell that allows sampling the Brillouin zone with a single k-point.

  8. Flexible CdTe solar cells on polymer films

    Energy Technology Data Exchange (ETDEWEB)

    Tiwari, A.N.; Romeo, A.; Baetzner, D.; Zogg, H. [ETH Swiss Federal Inst. of Technology, Thin Film Physics Group, Zurich (Switzerland)

    2001-07-01

    Lightweight and flexible CdTe/CdS solar cells on polyimide films have been developed in a 'superstrate configuration' where the light is absorbed in CdTe after passing through the polyimide substrate. The average optical transmission of the approximately 10-{mu}m-thin spin-coated polyimide substrate layer is more than {approx}75% for wavelengths above 550 nm. RF magnetron sputtering was used to grow transparent conducting ZnO:Al layers on polyimide films. CdTe/CdS layers were grown by evaporation of compounds, and a CdCl{sub 2} annealing treatment was applied for the recrystallisation and junction activation. Solar cells of 8.6% efficiency with V{sub oc} = 763 mV, I{sub sc} = 20.3 mA/cm{sup 2} and FF = 55.7% were obtained. (Author)

  9. Ion-assisted doping of CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Fahrenbruch, A.L.; Chien, K.F.; Kim, D.; Lopez-Otero, A.; Sharps, P.; Bube, R.H. (Dept. of Materials Science and Engineering, Stanford Univ., CA (USA))

    1989-10-15

    The possibility of using ion-assisted doping during growth of p-CdTe films for solar cells has been investigated, to obtain higher doping densities than previously obtained with conventional film deposition processes. For the first time, controlled doping has been demonstrated with low-energy phosphorus ions to obtain hole densities of up to 2 x 10{sup 17} cm{sup -3} in homoepitaxial films deposited by vacuum evaporation on single-crystal CdTe. Solar cells made with these films suggest that ion damage reduces the diffusion length in the most highly doped films and that the active region of such cells must be made with considerably lower doping densities. For polycrystalline films on alumina, preliminary results indicate that the hole densities obtained are not sufficient to overcome grain boundary barrier limited conductivity. (orig.).

  10. Spatial correlations of donor charges in MBE CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Suski, T.; Wisniewski, P.; Litwin-Staszewska, E. [Unipress, Polish Academy of Sciences, Warsaw (Poland); Wasik, D.; Przybytek, J.; Baj, M. [Institute of Experimental Physics, Warsaw University, Warsaw (Poland); Karczewski, G.; Wojtowicz, T.; Zakrzewski, A.; Kossut, J. [Institute of Physics, Polish Academy of Sciences, Warsaw (Poland)

    1995-12-31

    We present experimental evidence that at high pressures indium donors in CdTe localize electrons in spatially correlated manner. We have studied Hall mobility,{mu}{sub H}, as a function of electron concentration, n{sub H}, at T = 77 K. Changes of n{sub H} have been achieved by two methods. High pressure freeze-out of electrons onto localized states of In-donors leads to the mobility enhancement with respect to the situation when n{sub H} has been modified by means of a subsequent annealing of the sample. As a result, depending on the degree of spatial correlations in the impurity charges arrangement, different values of {mu}{sub H} correspond to the same value of n{sub H}. The variation of mobility with electron concentration suggests that the localized state of In-donor represents likely negatively charged DX state. (author). 5 refs, 1 fig.

  11. Emitter/absorber interface of CdTe solar cells

    Science.gov (United States)

    Song, Tao; Kanevce, Ana; Sites, James R.

    2016-06-01

    The performance of CdTe solar cells can be very sensitive to the emitter/absorber interface, especially for high-efficiency cells with high bulk lifetime. Performance losses from acceptor-type interface defects can be significant when interface defect states are located near mid-gap energies. Numerical simulations show that the emitter/absorber band alignment, the emitter doping and thickness, and the defect properties of the interface (i.e., defect density, defect type, and defect energy) can all play significant roles in the interface recombination. In particular, a type I heterojunction with small conduction-band offset (0.1 eV ≤ ΔEC ≤ 0.3 eV) can help maintain good cell efficiency in spite of high interface defect density, much like with Cu(In,Ga)Se2 (CIGS) cells. The basic principle is that positive ΔEC, often referred to as a "spike," creates an absorber inversion and hence a large hole barrier adjacent to the interface. As a result, the electron-hole recombination is suppressed due to an insufficient hole supply at the interface. A large spike (ΔEC ≥ 0.4 eV), however, can impede electron transport and lead to a reduction of photocurrent and fill-factor. In contrast to the spike, a "cliff" (ΔEC CdTe solar cells, but the CdS/CdTe interface is in the cliff category and is not favorable from the band-offset perspective. The ΔEC of other n-type emitter choices, such as (Mg,Zn)O, Cd(S,O), or (Cd,Mg)Te, can be tuned by varying the elemental ratio for an optimal positive value of ΔEC. These materials are predicted to yield higher voltages and would therefore be better candidates for the CdTe-cell emitter.

  12. Nanowire and core-shell-structures on flexible Mo Foil for CdTe solar cell applications

    OpenAIRE

    Williams, Ben; Durose, Ken; Kartopu, Giray; Barrioz, Vincent; Lamb, Daniel; Irvine, Stuart; Zoppi, Guillaume; Forbes, Ian

    2011-01-01

    CdTe films, nanowires, film-nanowire combinations and CdS-CdTe core-shell structures have been fabricated in a preliminary survey of growth methods that will generate structures for PV applications. Selectivity between film, nanowire and film plus nanowire growth was achieved by varying the pressure of N2 gas present during Au-catalysed VLS growth of CdTe, on either Mo or Si substrates. Metamorphic growth of CdTe nanowires on sputtered CdTe films, deposited on glass substrates, was demonstrat...

  13. Array tomography: imaging stained arrays.

    Science.gov (United States)

    Micheva, Kristina D; O'Rourke, Nancy; Busse, Brad; Smith, Stephen J

    2010-11-01

    Array tomography is a volumetric microscopy method based on physical serial sectioning. Ultrathin sections of a plastic-embedded tissue are cut using an ultramicrotome, bonded in an ordered array to a glass coverslip, stained as desired, and imaged. The resulting two-dimensional image tiles can then be reconstructed computationally into three-dimensional volume images for visualization and quantitative analysis. The minimal thickness of individual sections permits high-quality rapid staining and imaging, whereas the array format allows reliable and convenient section handling, staining, and automated imaging. Also, the physical stability of the arrays permits images to be acquired and registered from repeated cycles of staining, imaging, and stain elution, as well as from imaging using multiple modalities (e.g., fluorescence and electron microscopy). Array tomography makes it possible to visualize and quantify previously inaccessible features of tissue structure and molecular architecture. However, careful preparation of the tissue is essential for successful array tomography; these steps can be time-consuming and require some practice to perfect. In this protocol, tissue arrays are imaged using conventional wide-field fluorescence microscopy. Images can be captured manually or, with the appropriate software and hardware, the process can be automated. PMID:21041399

  14. Array tomography: production of arrays.

    Science.gov (United States)

    Micheva, Kristina D; O'Rourke, Nancy; Busse, Brad; Smith, Stephen J

    2010-11-01

    Array tomography is a volumetric microscopy method based on physical serial sectioning. Ultrathin sections of a plastic-embedded tissue are cut using an ultramicrotome, bonded in an ordered array to a glass coverslip, stained as desired, and imaged. The resulting two-dimensional image tiles can then be reconstructed computationally into three-dimensional volume images for visualization and quantitative analysis. The minimal thickness of individual sections permits high-quality rapid staining and imaging, whereas the array format allows reliable and convenient section handling, staining, and automated imaging. Also, the physical stability of the arrays permits images to be acquired and registered from repeated cycles of staining, imaging, and stain elution, as well as from imaging using multiple modalities (e.g., fluorescence and electron microscopy). Array tomography makes it possible to visualize and quantify previously inaccessible features of tissue structure and molecular architecture. However, careful preparation of the tissue is essential for successful array tomography; these steps can be time consuming and require some practice to perfect. This protocol describes the sectioning of embedded tissues and the mounting of the serial arrays. The procedures require some familiarity with the techniques used for ultramicrotome sectioning for electron microscopy. PMID:21041397

  15. Novel {beta}-cyclodextrin modified CdTe quantum dots as fluorescence nanosensor for acetylsalicylic acid and metabolites

    Energy Technology Data Exchange (ETDEWEB)

    Algarra, M. [Centro de Geologia do Porto, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Campos, B.B.; Aguiar, F.R.; Rodriguez-Borges, J.E. [Centro de Investigacao em Quimica (CIQ-UP), Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 169-007 Porto (Portugal); Esteves da Silva, J.C.G., E-mail: jcsilva@fc.up.pt [Centro de Investigacao em Quimica (CIQ-UP), Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 169-007 Porto (Portugal)

    2012-05-01

    {beta}-Cyclodextrin was modified with 11-[(ethoxycarbonyl)thio]undecanoic acid and used as a capping agent, together with mercaptosuccinic acid, to prepare water-stable CdTe quantum dots. The water soluble quantum dot obtained displays fluorescence with a maximum emission at 425 nm (under excitation at 300 nm) with lifetimes of 0.53, 4.8, 181, and 44.1 ns, respectively. The S-{beta}CD-MSA-CdTe can act as a nanoprobe that is due to the affinity of the cyclodextrin moiety for selected substances such as acetylsalicylic acid (ASA) and its metabolites as foreign species. The fluorescence of the S-{beta}CD-MSA-CdTe is enhanced on addition of ASA. Linear calibration plots are observed with ASA in concentrations between 0 and 1 mg/l, with a limit of detection at 8.5 Multiplication-Sign 10{sup -9} mol/l (1.5 ng/ml) and a precision as relative standard deviation of 1% (0.05 mg/l). The interference effect of certain compounds as ascorbic acid and its main metabolites such as salicylic, gentisic and salicyluric acid upon the obtained procedure was studied. Highlights: Black-Right-Pointing-Pointer Nanosensors constituted by CdTe quantum dots capped with modified cyclodextrin. Black-Right-Pointing-Pointer This nanomaterial shows fluorescence properties compatible with a semiconductor quantum dot. Black-Right-Pointing-Pointer The nanosensor shows fluorescence enhancement when inclusion complexes are formed with acetylsalicylic acid. Black-Right-Pointing-Pointer This nanomaterial has nanosensor potential taking into consideration the formation stability of the inclusion complex.

  16. Linear Accelerators

    CERN Document Server

    Vretenar, M

    2014-01-01

    The main features of radio-frequency linear accelerators are introduced, reviewing the different types of accelerating structures and presenting the main characteristics aspects of linac beam dynamics.

  17. ANTENNAS ARRAY ADJUST WITH ADAPTIVE NEURONAL SYSTEM

    Directory of Open Access Journals (Sweden)

    A. Padrón

    2004-12-01

    Full Text Available In this work an array failure correction for Linear Antenna Array (LAA is presented. This is carried out by means ofan Adaptive Artificial Neural Network (AANN that adjusts the amplitude and phase at beamforming. Theappropriated corrections are given, when one, or two, or three elements have a failure in the antenna linear array.The AANN corrects the corresponding parameters in the radiation pattern obtained due to the failure, when weknow the coefficients of the array factor (AF. This yields a reduction of side lobe level and some interferencesdisappear.

  18. Fundamentals of ultrasonic phased arrays

    CERN Document Server

    Schmerr, Lester W

    2014-01-01

    This book describes in detail the physical and mathematical foundations of ultrasonic phased array measurements.?The book uses linear systems theory to develop a comprehensive model of the signals and images that can be formed with phased arrays. Engineers working in the field of ultrasonic nondestructive evaluation (NDE) will find in this approach a wealth of information on how to design, optimize and interpret ultrasonic inspections with phased arrays. The fundamentals and models described in the book will also be of significant interest to other fields, including the medical ultrasound and

  19. CdTe quantum dots functionalized with 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion

    Energy Technology Data Exchange (ETDEWEB)

    Adegoke, Oluwasesan [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa); Hosten, Eric; McCleland, Cedric [Department of Chemistry, Nelson Mandela Metropolitan University (South Campus), Port Elizabeth 6031 (South Africa); Nyokong, Tebello, E-mail: t.nyokong@ru.ac.za [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa)

    2012-04-06

    Graphical abstract: A bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) showed a high selectivity and sensitivity for the determination of bromide ion using fluorescence recovery. Highlights: Black-Right-Pointing-Pointer Water soluble CdTe quantum dots interact with tetramethylpiperidine-N-oxide. Black-Right-Pointing-Pointer Quantum dots fluorescence is quenched by the radical. Black-Right-Pointing-Pointer In the presence of bromide ions the fluorescence is restored. Black-Right-Pointing-Pointer The sensor is more selective to bromine ions than other common ions. - Abstract: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 {mu}M. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.

  20. An in vitro study of vascular endothelial toxicity of CdTe quantum dots

    International Nuclear Information System (INIS)

    Quantum dots (QDs), as novel bioimaging and drug delivery agents, are generally introduced into vascular system by injection, and thus directly exposed to vascular endothelial cells (ECs). However, the adverse effects of QDs on ECs are poorly understood. In this study, employing human umbilical vein ECs (HUVECs), we investigated the potential vascular endothelial toxicity of mercaptosuccinic acid (MSA)-capped CdTe QDs in vitro. In the experiment, water-soluble and pH stable CdTe QDs were synthesized; and the cell viability assays showed that CdTe QDs (0.1-100 μg/mL) dose-dependently decreased the cell viability of HUVECs, indicating CdTe QDs induced significant endothelial toxicity. The flow cytometric and immunofluorescence results revealed that 10 μg/mL CdTe QDs elicited significant oxidative stress, mitochondrial network fragmentation as well as disruption of mitochondrial membrane potential (Δψm); whereas ROS scavenger could protect HUVECs from QDs-induced mitochondrial dysfunction. Moreover, upon 24 h exposure to 10 μg/mL CdTe QDs, the apoptotic HUVECs dramatically increased by 402.01%, accompanied with alternative expression of apoptosis proteins, which were upregulation of Bax, downregulation of Bcl-2, release of mitochondrial cytochrome c and cleavage of caspase-9/caspase-3. These results suggested that CdTe QDs could not only impair mitochondria but also exert endothelial toxicity through activation of mitochondrial death pathway and induction of endothelial apoptosis. Our results provide strong evidences of the direct toxic effects of QDs on human vascular ECs, and reveal that exposure to QDs is a significant risk for the development of cardiovascular diseases. These results also provide helpful guidance on the future safe use and manipulation of QDs to make them more suitable tools in nanomedicine.

  1. Influence of CdTe thickness on structural and electrical properties of CdTe/CdS solar cells

    International Nuclear Information System (INIS)

    Due to its high scalability and low production cost, CdTe solar cells have shown a very strong potential for large scale energy production. Although the number of modules produced could be limited by tellurium scarcity, it has been reported that reducing CdTe thickness down to 1.5 μm would solve this issue. There are, however, issues to be considered when reducing thickness, such as formation of pinholes, lower crystallization, and different possible effects on material diffusion within the interfaces. In this work, we present the study of CdTe solar cells fabricated by vacuum evaporation with different CdTe thicknesses. Several cells with a CdTe thickness ranging from 0.7 to 6 μm have been fabricated. The deposition process has been optimized accordingly and their physical and electrical properties have been studied. Thin cells show a different electrical behavior in terms of open circuit voltage and fill factor. Efficiencies range from 7% for thin CdTe cells to 13.5% for the standard thickness. - Highlights: ► Ultra thin CdTe absorbers have been prepared and studied. ► Grain size is depending on the CdTe thickness but spread in the grains increases. ► Lattice parameter is reduced only for ultra thin CdTe. ► The band gap reveals an intermixed CdTe absorber. ► The reason for lower efficiency of ultra thin CdTe is explained

  2. Comparison of an electrically-small planar antenna array with a conventional monopole array

    OpenAIRE

    Rogers, PR; Hilton, GS; Craddock, IJ; Fletcher, PN

    2002-01-01

    A new type of linear array is proposed which utilises annular slot antennas operating in the 'DC' mode. These conformal elements are electrically-small and have wire-monopole-like radiation patterns. A thorough analysis of this array's performance is provided, with a comparison against the performance of an equivalent wire monopole array given at each stage. It is shown that, overall, the characteristics of the conformal, electrically-small, annular-slot array are very similar to that of the ...

  3. Linear colliders

    International Nuclear Information System (INIS)

    From November 28 to December 9, the Stanford Linear Accelerator Center hosted an International Workshop on Next Generation Linear Colliders. The attendance, including delegations from CERN, Frascati (Italy), KEK (Japan), Livermore (US), Novosibirsk (USSR), Drsay (France) and SLAC itself reflected the international interest in this new approach to higher energies

  4. Plane-wave scattering from half-wave dipole arrays

    DEFF Research Database (Denmark)

    Jensen, Niels E.

    1970-01-01

    A matrix equation for determination of plane-wave scattering from arrays of thin short-circuited dipoles of lengths about half a wavelength is derived. Numerical and experimental results are presented for linear, circular, and concentric circular arrays.......A matrix equation for determination of plane-wave scattering from arrays of thin short-circuited dipoles of lengths about half a wavelength is derived. Numerical and experimental results are presented for linear, circular, and concentric circular arrays....

  5. Array processors based on Gaussian fraction-free method

    Energy Technology Data Exchange (ETDEWEB)

    Peng, S.; Sedukhin, S. [Aizu Univ., Aizuwakamatsu, Fukushima (Japan); Sedukhin, I.

    1998-03-01

    The design of algorithmic array processors for solving linear systems of equations using fraction-free Gaussian elimination method is presented. The design is based on a formal approach which constructs a family of planar array processors systematically. These array processors are synthesized and analyzed. It is shown that some array processors are optimal in the framework of linear allocation of computations and in terms of number of processing elements and computing time. (author)

  6. PENINGKATAN KUALITAS FILM TIPIS CdTe SEBAGAI ABSORBER SEL SURYA DENGAN MENGGUNAKAN DOPING TEMBAGA (Cu

    Directory of Open Access Journals (Sweden)

    P. Marwoto

    2012-12-01

    Full Text Available Film tipis CdTe dengan doping tembaga (Cu berkonsenterasi 2% telah berhasil ditumbuhkan di atas substrat Indium Tin Oxide (ITO dengan metode dc magnetron sputtering. Penelitian ini dilakukan untuk mengetahui pengaruh doping Cu(2% terhadap struktur morfologi, struktur kristal, fotoluminisensi dan resistivitas listrik film CdTe. Citra morfologi Scanning Electron Microscopy (SEM dan hasil analisis struktur dengan X-Ray Diffraction (XRD menunjukkan bahwa film CdTe:Cu(2% mempunyai citra permukaan dan struktur kristal yang lebih sempurna dibandingkan film CdTe tanpa doping. Hasil analisis spektrometer fotoluminisensi menunjukkan bahwa film CdTe dan CdTe(2% mempunyai puncak fotoluminisensi pada tiga panjang gelombang yang identik yaitu 685 nm (1,81 eV, 725 nm (1,71 eV dan 740 nm (1,67 eV. Film CdTe dengan doping Cu(2% memiliki intensitas puncak fotoluminisensi yang lebih tajam pada pita energi 1,81 eV dibandingkan dengan film CdTe tanpa doping. Pengukuran arus dan tegangan (I-V menunjukkan bahwa pemberian doping Cu(2% dapat menurunkan resistivitas film dari 8,40x109 Ωcm menjadi 6,92x105 Ωcm. Sebagai absorber sel surya, kualitas film tipis CdTe telah berhasil ditingkatkan dengan pemberian doping Cu(2%.CdTe:Cu(2% thin film has been successfully grown on Indium Tin Oxide (ITO substrates by using dc magnetron sputtering. This study was carried out in order to investigate the effect of Cu(2% doping on the morphologycal structure, crystal structure, photoluminesence, and resistivity of CdTe thin film. Scanning Electron Microscopy (SEM  images and X-Ray Diffraction (XRD results showed that CdTe:Cu(2% thin film has morphologycal and crystal structures more perfect than undoped CdTe film. Photoluminesence spectroscopy results showed that CdTe and CdTe:Cu(2% thin films have luminesence peak at three identical wevelength regions i.e. 685 nm (1.81 eV, 725 nm (1.71 eV and 740 nm (1.67 eV however CdTe:Cu(2% film shows sharper photoluminescence peak at band

  7. Photoluminescence of CdTe nanocrystals grown by pulsed laser ablation on a template of Si nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Guillen-Cervantes, A.; Silva-Lopez, H.; Becerril-Silva, M.; Arias-Ceron, J.S.; Campos-Gonzalez, E.; Zelaya-Angel, O. [CINVESTAV-IPN, Physics Department, Apdo. Postal 14-740, Mexico (Mexico); Medina-Torres, A.C. [Escuela Superior de Fisica y Matematicas del IPN, Mexico (Mexico)

    2014-11-12

    CdTe nanocrystals were grown on eroded Si (111) substrates at room temperature by pulsed laser ablation. Before growth, Si substrates were subjected to different erosion time in order to investigate the effect on the CdTe samples. The erosion process consists of exposition to a pulsed high-voltage electric arc. The surface consequence of the erosion process consists of Si nanoparticles which acted as a template for the growth of CdTe nanocrystals. CdTe samples were studied by X-ray diffraction (XRD), room temperature photoluminescence (RT PL) and high-resolution transmission electron microscopy (HRTEM). CdTe nanocrystals grew in the stable cubic phase, according to XRD spectra. A strong visible emission was detected in photoluminescence (PL) experiments. The PL signal was centered at 540 nm (∝2.34 eV). With the effective mass approximation, the size of the CdTe crystals was estimated around 3.5 nm. HRTEM images corroborated the physical characteristics of CdTe nanocrystals. These results could be useful for the development of CdTe optoelectronic devices. (orig.)

  8. Photoluminescence of CdTe nanocrystals grown by pulsed laser ablation on a template of Si nanoparticles

    International Nuclear Information System (INIS)

    CdTe nanocrystals were grown on eroded Si (111) substrates at room temperature by pulsed laser ablation. Before growth, Si substrates were subjected to different erosion time in order to investigate the effect on the CdTe samples. The erosion process consists of exposition to a pulsed high-voltage electric arc. The surface consequence of the erosion process consists of Si nanoparticles which acted as a template for the growth of CdTe nanocrystals. CdTe samples were studied by X-ray diffraction (XRD), room temperature photoluminescence (RT PL) and high-resolution transmission electron microscopy (HRTEM). CdTe nanocrystals grew in the stable cubic phase, according to XRD spectra. A strong visible emission was detected in photoluminescence (PL) experiments. The PL signal was centered at 540 nm (∝2.34 eV). With the effective mass approximation, the size of the CdTe crystals was estimated around 3.5 nm. HRTEM images corroborated the physical characteristics of CdTe nanocrystals. These results could be useful for the development of CdTe optoelectronic devices. (orig.)

  9. Photodegradation of Mercaptopropionic Acid- and Thioglycollic Acid-Capped CdTe Quantum Dots in Buffer Solutions.

    Science.gov (United States)

    Miao, Yanping; Yang, Ping; Zhao, Jie; Du, Yingying; He, Haiyan; Liu, Yunshi

    2015-06-01

    CdTe quantum dots (QDs) were synthesized by 3-mercaptopropionic acid (MPA) and thioglycollic acid (TGA) as capping agents. It is confirmed that TGA and MPA molecules were attached on the surface of the QDs using Fourier transform infrared (FT-IR) spectra. The movement of the QDs in agarose gel electrophoresis indicated that MPA-capped CdTe QDs had small hydrodynamic diameter. The photoluminescence (PL) intensity of TGA-capped QDs is higher than that of MPA-capped QDs at same QD concentration because of the surface passivation of TGA. To systemically investigate the photodegradation, CdTe QDs with various PL peak wavelengths were dispersed in phosphate buffered saline (PBS) and Tris-borate-ethylenediaminetetraacetic acid (TBE) buffer solutions. It was found that the PL intensity of the QDs in PBS decreased with time. The PL peak wavelengths of the QDs in PBS solutions remained unchanged. As for TGA-capped CdTe QDs, the results of PL peak wavelengths in TBE buffer solutions indicated that S(2-) released by TGA attached to Cd(2+) and formed CdS-like clusters layer on the surface of aqueous CdTe QDs. In addition, the number of TGA on the CdTe QDs surface was more than that of MPA. When the QDs were added to buffer solutions, agents were removed from the surface of CdTe QDs, which decreased the passivation of agents thus resulted in photodegradation of CdTe QDs in buffer solutions.

  10. Emitter/absorber interface of CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Song, Tao [Physics Department, Colorado State University, Fort Collins, Colorado 80523, USA; Kanevce, Ana [National Renewable Energy Laboratory, Golden, Colorado 80401, USA; Sites, James R. [Physics Department, Colorado State University, Fort Collins, Colorado 80523, USA

    2016-06-17

    The performance of CdTe solar cells can be very sensitive to their emitter/absorber interfaces, especially for high-efficiency cells with improved bulk properties. When interface defect states are located at efficient recombination energies, performance losses from acceptor-type interface defects can be significant. Numerical simulations show that the emitter/absorber band alignment, the emitter doping and thickness, and the defect properties of the interface (i.e. defect density, defect type, and defect energy) can all play significant roles in the interface recombination. In particular, a type I heterojunction with small conduction-band offset (0.1 eV /= 0.4 eV), however, can impede electron transport and lead to a reduction of photocurrent and fill-factor. In contrast to the spike, a 'cliff' (.delta..EC < 0 eV) is likely to allow many holes in the vicinity of the interface, which will assist interface recombination and result in a reduced open-circuit voltage. In addition, a thin and highly-doped emitter can invert the absorber, form a large hole barrier, and decrease device performance losses due to high interface defect density. CdS is the most common emitter material used in CdTe solar cells, but the CdS/CdTe interface is in the cliff category and is not favorable from the band-offset perspective. Other n-type emitter choices, such as (Mg,Zn)O, Cd(S,O), or (Cd,Mg)Te, can be tuned by varying the elemental ratio for an optimal positive value of ..delta..EC. These materials are predicted

  11. Effects on Moisture on CdTe Cell I-V Characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, L. C.; Kundu, S.; Englehard, M.; Asher, S. E.; Perkins, C.

    2006-01-01

    This paper focuses on the effect of water on CdTe solar cells provided by Dr. Sampath's group at Colorado State University, that have not been encapsulated.. Bare cells were subjected to damp heat conditions defined by 60 degC and 90% Relative Humidity (RH). Current voltage characteristics were acquired periodically over a thousand hour period. Bare, unencapsulated CdTe cells appear to exhibit changes in current collection and current loss mechanisms as well as degradation of contact interfaces as a result of damp heat. XPS analyses have been conducted in an effort to identify effects of moisture ingress. The XPS studies indicate that one possible effect of moisture on CdTe cells is to convert the CdO at grain boundaries to Cd(OH){sub 2}. Since it is generally assumed that CdO acts as an effective electron reflector on CdTe grain boundaries, formation of the hydroxide could explain the degradation of current voltage characteristics of CdTe cells subjected to damp heat.

  12. Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

    Directory of Open Access Journals (Sweden)

    M. M. Aliyu

    2012-01-01

    Full Text Available This study investigates the key issues in the fabrication of CdTe solar cells on metallic substrates, their trends, and characteristics as well as effects on solar cell performance. Previous research works are reviewed while the successes, potentials, and problems of such technology are highlighted. Flexible solar cells offer several advantages in terms of production, cost, and application over glass-based types. Of all the metals studied as substrates for CdTe solar cells, molybdenum appears the most favorable candidate, while close spaced sublimation (CSS, electrodeposition (ED, magnetic sputtering (MS, and high vacuum thermal evaporation (HVE have been found to be most common deposition technologies used for CdTe on metal foils. The advantages of these techniques include large grain size (CSS, ease of constituent control (ED, high material incorporation (MS, and low temperature process (MS, HVE, ED. These invert-structured thin film CdTe solar cells, like their superstrate counterparts, suffer from problems of poor ohmic contact at the back electrode. Thus similar strategies are applied to minimize this problem. Despite the challenges faced by flexible structures, efficiencies of up to 13.8% and 7.8% have been achieved in superstrate and substrate cell, respectively. Based on these analyses, new strategies have been proposed for obtaining cheaper, more efficient, and viable flexible CdTe solar cells of the future.

  13. Radiative recombination mechanisms in CdTe thin films deposited by elemental vapor transport

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Shamara [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States); Vatavu, Sergiu, E-mail: svatavu@usm.md [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States); Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., Chisinau, MD-2009, Republic of Moldova (Moldova, Republic of); Evani, Vamsi; Khan, Md; Bakhshi, Sara; Palekis, Vasilios [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States); Rotaru, Corneliu [Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., Chisinau, MD-2009, Republic of Moldova (Moldova, Republic of); Ferekides, Chris [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States)

    2015-05-01

    A photoluminesence (PL) study of the radiative recombination mechanisms for CdTe films deposited under different Cd and Te overpressure by elemental vapor transport is presented. The experiment and analysis have been carried out in the temperature range of 12-130 K. The intensity of the PL laser excitation beam was varied by two orders of magnitude. It has been established that the bands in the 1.47-1.50 eV are determined by transitions involving shallow D and A states and the 1.36x-1.37x eV band is due to band to level transitions. Deep transitions at 1.042 eV and 1.129 eV are due to radiative transitions to levels determined by CdTe native defects. - Highlights: • Photoluminescense (PL) of CdTe thin films is present in the 0.8-1.6 eV spectral region. • High intensity excitonic peaks are among the main radiative paths. • Radiative transitions at 1.36x eV are assisted by dislocations caused levels. • Extremal Cd/Te overpressure ratios enhance PL for 1.497 eV, 1.486 eV, 1.474 eV bands. • PL intensity reaches its max value for the 0.45 and 1.25 Cd/Te overpressure ratios.

  14. In vitro and in vivo toxicity of CdTe nanoparticles.

    Science.gov (United States)

    Zhang, Yongbin; Chen, Wei; Zhang, Jun; Liu, Jing; Chen, Guangping; Pope, Carey

    2007-02-01

    Cadmium telluride (CdTe) nanoparticles exhibit strong and stable fluorescence that is attractive for many applications such as biological probing and solid state lighting. The evaluation of nanoparticle toxicity is important for realizing these practical applications. However, no systematic studies of CdTe nanoparticle toxicity have been reported. We investigated and compared the size- and concentration-dependent cytotoxicity of CdTe nanoparticles in human hepatoma HepG2 cells using the MTT assay. CdTe nanoparticles elicited cytotoxicity in a concentration- and size-dependent manner, with smaller-sized particles exhibiting somewhat higher potency. Lesser cytotoxicity of partially purified CdTe-Red particles (following methanol precipitation and resuspension) suggested that free cadmium ions may contribute to cytotoxicity. We also evaluated the acute toxicity of CdTe-Red particles following intravenous exposure in male rats (2 micromol/kg). Few signs of functional toxicity or clinical (urinary or blood) changes were noted. Interestingly, motor activity was transiently reduced (2 hours after treatment) and then significantly increased at a later timepoint (24 hours after dosing). These studies provide a framework for further characterizing the in vitro and in vivo toxic potential of different types of CdTe nanoparticles and suggest that the nervous system may be targeted by these nanoparticles under some conditions.

  15. Luminescent behavior of CdTe quantum dots: Neodymium(III) complex-capped nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Margarida S. [Centro de Geologia do Porto, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal); Algarra, Manuel, E-mail: magonzal@fc.up.pt [Centro de Geologia do Porto, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal); Jimenez-Jimenez, Jose; Rodriguez-Castellon, Enrique [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos s/n 29071, Malaga (Spain); Campos, Bruno B.; Esteves da Silva, Joaquim C.G. [Centro de Investigacao em Quimica (CIQ-UP), Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal)

    2013-02-15

    A water soluble complex of neodymium(III) with CdTe quantum dots nanoparticles was synthesized. The obtained homogeneous solutions were characterized by fluorescence, X-ray photoelectron and energy dispersive X-ray spectroscopies. The effect of the refluxing time of the reaction on the fluorescence intensity and emission wavelength has been studied. It was found that the emission wavelength of the solutions of neodymium(III) complex capped CdTe QDs nanoparticles shifted from about 540 to 735 nm. For an emission wavelength of 668 nm, the most reproducible nanoparticles obtained, the pH effect over the fluorescence emission and its intensity were studied. The purified and lyophilized solid obtained was morphologically characterized by transmission electron microscopy (TEM). The quantitative composition was determined by fluorescence X-ray spectroscopy (EDAX) and the X-ray photoelectron analysis (XPS) confirmed the presence of neodymium(III) at the surface of the CdTe nanoparticles forming a complex with the carboxylate groups from 3-mercaptopropanoic acid of the CdTe QDs. Due to the optical behavior of this complex, it could be of potential interest as a light source in optical devices. - Highlights: Black-Right-Pointing-Pointer CdTe quantum dots nanoparticles. Black-Right-Pointing-Pointer Neodymium(III) complexed quantum dots. Black-Right-Pointing-Pointer Strong red fluorescent emission nanomaterial soluble in water.

  16. Native Defect Control of CdTe Thin Film Solar Cells by Close-Spaced Sublimation

    Science.gov (United States)

    Okamoto, Tamotsu; Kitamoto, Shinji; Yamada, Akira; Konagai, Makoto

    2001-05-01

    The control of native defects in the CdTe thin film solar cells was investigated using a novel source for close-spaced sublimation (CSS) process which was prepared by vacuum evaporation with elemental Cd and Te (evaporated source). The evaporated sources were prepared on glass substrates at room temperature, and the Cd/Te ratio was controlled by varying the Cd and Te beam equivalent pressures. In the cells using the Te-rich source, the conversion efficiency was less than 0.2% because of the extremely low shunt resistance. On the other hand, a conversion efficiency above 15% was obtained by using the Cd-rich source. Capacitance-voltage (C-V) characteristics revealed that the acceptor concentration in the CdTe layer increased with increasing Cd/Te ratio of the evaporated source. Furthermore, photoluminescence spectra implied that the formation of the Cd vacancies in the CdTe layer was suppressed using the Cd-rich source.

  17. Performance of a new Schottky CdTe detector for hard x-ray spectroscopy

    Science.gov (United States)

    Takahashi, Tadayuki; Hirose, K.; Matsumoto, Chiho; Takizawa, Kyoko; Ohno, Ryouichi; Ozaki, Tsutomu; Mori, Kunishiro; Tomita, Yasuhiro

    1998-07-01

    We report a significant improvement of the spectral properties of a cadmium telluride (CdTe) detector. With the use of a high quality CdTe crystal, we formed a high Schottky barrier for the holes on a CdTe surface using a low work-function metal, indium. For a 2 X 2 mm(superscript 2) detector with a thickness of 0.5 mm the leakage current was measured to be 0.7 nA at room temperature (20 degree(s)C) and 10 pA at -20 degree(s)C for a 400 V bias voltage. The low-leakage current of the detector allows us to operate the detector at a higher bias voltage than previous CdTe detectors. The improved charge collection efficiency and the low-leakage current leads to an energy resolution of 1.1 - 2.5 keV FWHM in the energy range 2 keV to 150 keV at 20 degree(s)C without charge loss correction electronics. We confirmed that once a high electric field of several kV/cm is applied, the Schottky CdTe has a very good energy resolution as well as sufficient stability to be used for practical applications.

  18. Fabrication of pixelated CdTe and CdZnTe radiation detectors

    International Nuclear Information System (INIS)

    Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) are compound semiconductor characterized by wide semiconducting band gap and high photon stopping power due to its high atomic number and density. The mobility-life time product (μ t product) for holes in the materials is smaller than that for electrons. Hence, the effect of trapping losses is more pronounced on holes than on electrons. The trapping losses for holes limit achievable energy resolutions for planar detectors. In this study, pixelated CdTe detectors and pixelated CdZnTe detectors were fabricated and tested by 662 KeV gamma-rays of 137Cs at room temperature. Electrodes were formed on both sides of CdTe crystals and CdZnTe crystals by vacuum evaporation of gold. For purpose of comparison, a planar CdTe detector and a planar CdZnTe detector were evaluated. Since the pixelated CdTe detectors and the pixelated CdZnTe detectors operated as a single-polarity charge sensing device, the obtained energy resolutions were significantly higher than those for the planar detectors. Further improvement of energy resolutions of the detectors will be achieved by optimizing electrode structures. (M. Suetake)

  19. Optical and electrical properties of hydrothermally prepared CdTe nanowires

    Science.gov (United States)

    Hadia, N. M. A.; Awad, M. A.; Mohamed, S. H.; Ibrahim, E. M. M.

    2016-10-01

    The hydrothermal process was used to synthesize CdTe nanowires (NWs). Various analytical techniques were used to characterize the obtained NWs. The wire diameters were in the range 35-60 nm, and the lengths were >5 μm. The CdTe NWs had zinc-blende crystal structure. The NWs had high uniformity and high yield. FTIR analysis revealed the presence of the characteristic vibrational spectra of oxygen and hydrogen bounded to Cd and Te in CdTe NWs. The optical band gap value was 2.09 eV. The CdTe NWs showed a strong red emission band centered around 620.3 nm. The conductivity measurements were carried out in the temperature range 300-500 K and in air atmosphere. Two types of conduction mechanisms were observed with activation energies of 0.27 and 0.17 eV at high and low temperature regions, respectively. These results validate the potential of CdTe NWs for optoelectronic applications.

  20. A simple fluorescence quenching method for roxithromycin determination using CdTe quantum dots as probes

    Energy Technology Data Exchange (ETDEWEB)

    Peng Jinyun, E-mail: pengjinyun@yeah.ne [Department of Chemistry and Biological Science, Guangxi Normal University of Nationalities, Chongzuo 532200 (China); College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Hu Xiaoya, E-mail: xyhu@yzu.edu.c [College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China)

    2011-05-15

    A new method for the determination of roxithromycin based on the fluorescence quenching of 3-mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) was developed. In ethanol medium, the fluorescence of CdTe quantum dots at 552 nm was quenched in the presence of roxithromycin. Based on this a simple, sensitive, and selective method for rapid determination of roxithromycin was described. Reaction time, interfering substances on the fluorescence quenching, and mechanism of the interaction of CdTe QDs with roxithromycin were investigated. After optimization, the proposed method allows the determination of roxithromycin over the range 25.0-350.0 {mu}g ml{sup -1}. The detection limit is 4.6 {mu}g ml{sup -1}. The proposed method was successfully applied to commercial capsules and tablets with satisfactory results. The recovery of the method was in the range of 96.8-102.5%. - Research highlights: {yields} CdTe quantum dots as a probe of fluorescence quenching method to determine roxithromycin at nanogram levels was developed. {yields} Reaction time, interfering substances on the fluorescence quenching, and mechanism of the interaction of CdTe QDs with roxithromycin were investigated. {yields} This method was applied for analysis of roxithromycin in capsules and tablets. {yields} Comparison with other reported methods, this method is not only sensitive, simple, but also reliable and suitable for application.

  1. The Role of Dopant Concentration on Conductivity and Mobility of CdTe Thin Films

    Directory of Open Access Journals (Sweden)

    Ala J. Al-Douri

    2011-01-01

    Full Text Available Films of CdTe pure and doped with various atomic percentages of Al and Sb (0.5, 1.5 & 2.5 were prepared, and their electrical properties were investigated. The films were prepared by thermal evaporation on glass substrates at two substrate temperatures (Ts=RT & 423 K. The results showed that the conduction phenomena of all the investigated CdTe thin films on glass substrates are caused by two distinct mechanisms. Room temperature DC conductivity increases by a factor of four for undoped CdTe thin films as Ts increases and by 1-2 orders of magnitude with increasing dopant percentage of Al and Sb. In general, films doped with Sb are more efficient than Al-doped films. The activation energy (Ea2 decreases with increasing Ts and dopant percentage for both Al and Sb. Undoped CdTe films deposited at RT are p-type convert to n-type with increasing Ts and upon doping with Al at more than 0.5%. The carrier concentration decreases as Ts increases while it increases with increasing dopant percentage. Hall mobility decreases more than three times as Al increases whereas it increases about one order of magnitude with increasing Sb percentage in CdTe thin films deposited at 423 K and RT, respectively.

  2. Synthesis of CdTe thin films on flexible metal foil by electrodeposition

    Science.gov (United States)

    Luo, H.; Ma, L. G.; Xie, W. M.; Wei, Z. L.; Gao, K. G.; Zhang, F. M.; Wu, X. S.

    2016-04-01

    CdTe thin films have been deposited onto the Mo foil from aqueous acidic bath via electrodeposition method with water-soluble Na2TeO3 instead of the usually used TeO2. X-ray diffraction studies indicate that the CdTe thin films are crystallized in zinc-blende symmetry. The effect of tellurite concentration on the morphology of the deposited thin film is investigated. In such case, the Cd:Te molar ratios in the films are both stoichiometric at different tellurite concentrations. In addition, the reduction in tellurite concentration leads to the porous thin film and weakens the crystallinity of thin film. The island growth model is used to interpret the growth mechanism of CdTe. The bandgap of the CdTe thin films is assigned to be 1.49 eV from the UV-Vis spectroscopy measurement, which is considered to serve as a promising candidate for the heterojunction solar cells.

  3. The growth of high quality CdTe on GaAs by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Reno, J.L.; Carr, M.J.; Gourley, P.L. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (US))

    1990-03-01

    We have grown CdTe (111) on oriented and misoriented GaAs (100) and have characterized the layers by photoluminescence microscopy (PLM) and transmission electron microscopy (TEM). Photoluminescence microscopy showed a totally different type of defect structure for the oriented substrate than for the misoriented substrates. The CdTe grown on the misoriented substrates exhibited only threading dislocations. The CdTe grown on oriented GaAs showed fewer threading dislocations but exhibited a random structure of loops. The loop structure observed by PLM has been identified by TEM as the boundary between twinned crystallites which extend from the CdTe/GaAs interface to the CdTe surface. When viewed along the growth axis, these boundaries between the columnar twins appear as loops and segments. Surface roughness of the GaAs substrate contributes to the initial growth of twinned material. This leads to competitive growth between the twins and the creation of the observed columnar twins. We present for the first time the growth of CdTe on patterned GaAs substrates. By growing on oriented GaAs(100) substrates that had been patterned prior to growth with 12 {mu}m mesas, it is possible to grow material on the mesa top that is twin free and has a low dislocation density.

  4. Studying nanotoxic effects of CdTe quantum dots in Trypanosoma cruzi

    Directory of Open Access Journals (Sweden)

    Cecilia Stahl Vieira

    2011-03-01

    Full Text Available Semiconductor nanoparticles, such as quantum dots (QDs, were used to carry out experiments in vivo and ex vivo with Trypanosoma cruzi. However, questions have been raised regarding the nanotoxicity of QDs in living cells, microorganisms, tissues and whole animals. The objective of this paper was to conduct a QD nanotoxicity study on living T. cruzi protozoa using analytical methods. This was accomplished using in vitro experiments to test the interference of the QDs on parasite development, morphology and viability. Our results show that after 72 h, a 200 μM cadmium telluride (CdTe QD solution induced important morphological alterations in T. cruzi, such as DNA damage, plasma membrane blebbing and mitochondrial swelling. Flow cytometry assays showed no damage to the plasma membrane when incubated with 200 μM CdTe QDs for up to 72 h (propidium iodide cells, giving no evidence of classical necrosis. Parasites incubated with 2 μM CdTe QDs still proliferated after seven days. In summary, a low concentration of CdTe QDs (2 μM is optimal for bioimaging, whereas a high concentration (200 μM CdTe could be toxic to cells. Taken together, our data indicate that 2 μM QD can be used for the successful long-term study of the parasite-vector interaction in real time.

  5. Synthesis of CdTe thin films on flexible metal foil by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Luo, H.; Ma, L.G.; Xie, W.M.; Wei, Z.L.; Gao, K.G.; Zhang, F.M.; Wu, X.S. [Nanjing University, Collaborative Innovation Center of Advanced Microstructures, Lab of Solid State Microstructures, School of Physics, Nanjing (China)

    2016-04-15

    CdTe thin films have been deposited onto the Mo foil from aqueous acidic bath via electrodeposition method with water-soluble Na{sub 2}TeO{sub 3} instead of the usually used TeO{sub 2}. X-ray diffraction studies indicate that the CdTe thin films are crystallized in zinc-blende symmetry. The effect of tellurite concentration on the morphology of the deposited thin film is investigated. In such case, the Cd:Te molar ratios in the films are both stoichiometric at different tellurite concentrations. In addition, the reduction in tellurite concentration leads to the porous thin film and weakens the crystallinity of thin film. The island growth model is used to interpret the growth mechanism of CdTe. The bandgap of the CdTe thin films is assigned to be 1.49 eV from the UV-Vis spectroscopy measurement, which is considered to serve as a promising candidate for the heterojunction solar cells. (orig.)

  6. Improvement of the sensitivity of CdTe semiconductor detector in the high energy region

    International Nuclear Information System (INIS)

    Cadmium Telluride, CdTe, semiconductor detectors have sufficient band gap energy (1.47 eV) to use at room temperature, and their atomic number are so large (48 and 52) that their photon detection efficiency is more excellent than that of Si or Ge. Recently CdTe crystals have become easily available because of improvements in the crystal growth method. It is a useful X-ray detector, because it has good energy resolution and high efficiency at the full energy peak at less than a few hundred keV of incident photon energy. However, if the incident photon energy become higher, the efficiency of the full energy peak become worse, and it is very difficult to distinguish the full energy peak above 1 MeV, because the mobility of charge carriers in the CdTe crystal is much smaller than in Si and Ge and it is difficult to produce a larger volume element. In order to analyze the energy of several radioisotopes, it is necessary to improve the sensitivity of CdTe detectors in high energy regions. We have previously suggested a multilayered structure of CdTe elements. This paper describes a simulation and experiment to improve the efficiency of the full energy peak in the high energy region above 1 MeV. (author)

  7. A Simple Sb2Te3 Back-Contact Process for CdTe Solar Cells

    Science.gov (United States)

    Siepchen, B.; Späth, B.; Drost, C.; Krishnakumar, V.; Kraft, C.; Winkler, M.; König, J.; Bartholomé, K.; Peng, S.

    2015-10-01

    CdTe solar technology has proved to be a cost-efficient solution for energy production. Formation of the back contact is an important and critical step in preparing high-efficiency, stable CdTe solar cells. In this paper we report a simple CdTe solar cell (Sb2Te3) back contact-formation process. The CdS and CdTe layers were deposited by close-space sublimation. After CdCl2 annealing treatment, the CdTe surface was etched by use of a mixture of nitric and phosphoric acids to obtain a Te-rich surface. Elemental Sb was sputtered on the etched surface and successive post-annealing treatment induced Sb2Te3 alloy formation. Structural characterization by x-ray diffraction analysis confirmed formation of the Sb2Te3 phase. The performance of solar cells with nanoalloyed Sb2Te3 back contacts was comparable with that of reference solar cells prepared with sputtered Sb2Te3 back contact from a compound sputter target.

  8. A sensitive and selective sensing platform based on CdTe QDs in the presence of l-cysteine for detection of silver, mercury and copper ions in water and various drinks.

    Science.gov (United States)

    Gong, Tingting; Liu, Junfeng; Liu, Xinxin; Liu, Jie; Xiang, Jinkun; Wu, Yiwei

    2016-12-15

    Water soluble CdTe quantum dots (QDs) have been prepared simply by one-pot method using potassium tellurite as stable tellurium source and thioglycolic acid (TGA) as stabilizer. The fluorescence of CdTe QDs can be improved 1.3-fold in the presence of l-cysteine (Cys), however, highly efficiently quenched in the presence of silver or mercury or copper ions. A sensitive and selective sensing platform for analysis of silver, mercury and copper ions has been simply established based on CdTe QDs in the presence of l-cysteine. Under the optimum conditions, excellent linear relationships exist between the quenching degree of the sensing platform and the concentrations of Ag(+), Hg(2+) and Cu(2+) ranging from 0.5 to 40ngmL(-1). By using masking agents of sodium diethyldithiocarbamate (DDTC) for Ag(+) and Cu(2+), NH4OH for Ag(+) and Hg(2+) and 1-(2-Pyridylazo)-2-naphthol (PAN) for Hg(2+) and Cu(2+), Hg(2+), Cu(2+) and Ag(+) can be exclusively detected in coexistence with other two ions, and the detection limits (3σ) were 0.65, 0.063 and 0.088ngmL(-1) for Ag(+), Hg(2+) and Cu(2+), respectively. This effective sensing platform has been used to detection of Ag(+), Hg(2+) and Cu(2+) in water and various drinks with satisfactory results. PMID:27451185

  9. Linear algebra

    CERN Document Server

    Stoll, R R

    1968-01-01

    Linear Algebra is intended to be used as a text for a one-semester course in linear algebra at the undergraduate level. The treatment of the subject will be both useful to students of mathematics and those interested primarily in applications of the theory. The major prerequisite for mastering the material is the readiness of the student to reason abstractly. Specifically, this calls for an understanding of the fact that axioms are assumptions and that theorems are logical consequences of one or more axioms. Familiarity with calculus and linear differential equations is required for understand

  10. Stable Water-dispersed CdTe Nanocrystals Dependent on Stoichiometric Ratio of Cd to Te Precursor

    Institute of Scientific and Technical Information of China (English)

    张旭瑞; 王李欣; 郭佳; 杨武利

    2012-01-01

    The improved properties of CdTe nanocrystals (NCs) synthesized by hydrothermal method were introduced. The experimental results indicated that the NCs properties could be dramatically influenced by means of changing Cd-to-Te molar ratio (the molar ratio of CdC12 and NaHTe in the precursor) of the MPA-capped CdTe NCs. With the increase of the ratio from 2 : 1 to 10 : 1, the formation time of near-infrared-emitting CdTe NCs was shortened. In particular, high Cd-to-Te molar ratio brought about MPA-capped CdTe NCs of superior radical oxidation-resis- tance and photostability. As a result, the optimum ratio was found to be 8 : 1 or 10 : 1 in the study in order to efficiently attain stable, water-dispersed CdTe NCs.

  11. Time-Resolved Photoluminescence Spectroscopy Evaluation of CdTe and CdTe/CdS Quantum Dots

    OpenAIRE

    Yuan, Zhimin; Yang, Ping; Cao, Yongqiang

    2012-01-01

    CdTe and CdTe/CdS quantum dots (QDs) were prepared in aqueous solutions using thioglycolic acid as a stabilizing agent. The photoluminescence (PL) wavelength of the QDs depended strongly on the size of CdTe cores and the thickness of CdS shells. Being kept at room temperature for 130 days, the PL wavelength of CdTe and CdTe/CdS QDs was red-shifted. However the red-shifted degree of CdTe QDs is larger than that of CdTe/CdS QDs. The size of CdTe QDs and the thickness of CdS play important roles...

  12. Developments of gamma-ray imagers using CdTe semiconductors based on the analog ASIC technology

    International Nuclear Information System (INIS)

    Cadmium Telluride (CdTe) is one of the most promising semiconductor materials for hard X-ray and gamma-ray detection because of the high detection efficiency, and of the good energy resolution. Moreover, CdTe detectors with Schottky junction work as diode detectors, and show superior energy resolution. Based on the CdTe diode devices, we have developed CdTe pixel/strip imagers, and also realized a Si/CdTe Compton camera. These devices will be used for the Hard X-ray Imager (HXI) and the Soft Gamma-ray Detector (SGD) onboard ASTRO-H X-ray satellite to be launched in 2015. These developments are briefly reported in this article. We also describe our recent development of low-noise analog readout ASICs to be used for future development of CdTe gamma-ray imagers. (author)

  13. Linear algebra

    CERN Document Server

    Liesen, Jörg

    2015-01-01

    This self-contained textbook takes a matrix-oriented approach to linear algebra and presents a complete theory, including all details and proofs, culminating in the Jordan canonical form and its proof. Throughout the development, the applicability of the results is highlighted. Additionally, the book presents special topics from applied linear algebra including matrix functions, the singular value decomposition, the Kronecker product and linear matrix equations. The matrix-oriented approach to linear algebra leads to a better intuition and a deeper understanding of the abstract concepts, and therefore simplifies their use in real world applications. Some of these applications are presented in detailed examples. In several ‘MATLAB-Minutes’ students can comprehend the concepts and results using computational experiments. Necessary basics for the use of MATLAB are presented in a short introduction. Students can also actively work with the material and practice their mathematical skills in more than 300 exerc...

  14. Ultrasensitive electrochemical sensor based on CdTe quantum dots-decorated poly(diallyldimethylammonium chloride)-functionalized graphene nanocomposite modified glassy carbon electrode for the determination of puerarin in biological samples

    International Nuclear Information System (INIS)

    Highlights: •CdTe-PDDA-Gr was synthesized via in situ reduction of exfoliated graphite oxides in the presence of PDDA and CdTe QDs. •CdTe-PDDA-Gr is used to build a supersensitive sensor for determination of puerarin. •Such a sensitive determination was comparable with that of liquid chromatography-mass spectrometry (LC-MS). •The method was applied to the determination of puerarin in complex biological samples. -- Abstract: In the present study, a CdTe quantum dot (QD)-decorated poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene (CdTe-PDDA-Gr) nanocomposite was synthesized via a simple one-step chemical reduction of exfoliated graphite oxides in the presence of PDDA and CdTe QDs. Characterization of as-prepared nanocomposite using transmission electron microscopy (TEM) and x-ray diffraction (XRD) clearly demonstrate the successful attachment of PDDA and CdTe QDs to the Gr sheets. The CdTe-PDDA-Gr showed an ultrafast electron transfer property and a strong absorption effect for puerarin and thus yields excellent electrocatalytic activity towards the oxidation of puerarin. Differential pulse voltammetry (DPV) was applied for the determination of puerarin, a good linear relationship of the oxidation peak current and the concentrations of puerarin in the range of 0.001 to 1.0 μM was achieved. The detection limit was 0.6 nM (SNR of 3) which was comparable with that of liquid chromatography-mass spectrometry (LC-MS). The proposed method was successfully applied for the determination of puerarin in human plasma and pharmaceutical injections with good recoveries

  15. Optical linear algebra

    Energy Technology Data Exchange (ETDEWEB)

    Casasent, D.; Ghosh, A.

    1983-01-01

    Many of the linear algebra operations and algorithms possible on optical matrix-vector processors are reviewed. Emphasis is given to the use of direct solutions and their realization on systolic optical processors. As an example, implicit and explicit solutions to partial differential equations are considered. The matrix-decomposition required is found to be the major operation recommended for optical realization. The pipelining and flow of data and operations are noted to be key issues in the realization of any algorithm on an optical systolic array processor. A realization of the direct solution by householder qr decomposition is provided as a specific case study. 19 references.

  16. Surface molecular imprinting on hybrid SiO2-coated CdTe nanocrystals for selective optosensing of bisphenol A and its optimal design

    Science.gov (United States)

    Qiu, Chunxiao; Xing, Youhong; Yang, Wenming; Zhou, Zhiping; Wang, Yingchun; Liu, Hong; Xu, Wanzhen

    2015-08-01

    Twenty molecular dynamics (MD) simulations of molecular imprinting prepolymerization systems had been performed to optimize the imprinting shell of the fluorescent sensor. The results revealed that the system with a Bisphenol A (BPA): 3-aminopropyltriethoxysilane (APTES): tetraethylorthosilicate (TEOS) mole ratio of 10:15:60 had the most stable template (T)-functional monomer (FM) cluster. Correspondingly, five kinds of imprinted and non-imprinted polymers were synthesized to assess the reliability and validity of the simulation results. Hybrid SiO2-coated CdTe NCs (HS-QD) were synthesized by a simple reflux procedure including a sol-gel reaction that resulted in the formation of a hybrid SiO2 layer with CdS-like clusters on a CdTe core. Based on the optimal component ratio of the prepolymerization system, MIP shells were anchored on the surface of HS-QD to build a fluorescent MIP sensor. A linear relationship between relative fluorescence intensity and the concentration of BPA had been obtained covering the concentration range of 0.05-10 μmol L-1 with a limit of detection of 6 nmol L-1. The feasibility of the fluorescent sensor was successfully evaluated through the analysis of BPA in river water and milk. The recoveries are above 96.31%, and the relative standard deviation (RSD) ranged from 1.55% to 2.78%.

  17. Design and fabrication of an aptasensor for chloramphenicol based on energy transfer of CdTe quantum dots to graphene oxide sheet.

    Science.gov (United States)

    Alibolandi, Mona; Hadizadeh, Farzin; Vajhedin, Fereshteh; Abnous, Khalil; Ramezani, Mohammad

    2015-03-01

    Detection and quantification of chloramphenicol have played essential roles in the effort to minimize food safety risk. Herein, a sophisticated "turn on" aptasensor based on aptamer-CdTe quantum dots (Apt-QDs) and graphene oxide (GO) was developed for chloramphenicol sensing. In this assay, the fluorescence of CdTe QDs-Apt was efficiently quenched through energy transfer from QDs-Apt to GO, and chloramphenicol was detected by recovering the quenched fluorescence due to specific binding between aptamer and chloramphenicol. The results indicated that the addition of a CdTe QDs-labeled aptamer to a GO solution (250μg/mL) led to a high quenching efficiency, yielding over 90% fluorescence quenching. Using a series of chloramphenicol concentrations (0.1 to 10nM) aptasensor provides a limit of detection and limit of quantification at 98pM and 987pM, respectively. Linearity of response over chloramphenicol was demonstrated (r>0.99). Furthermore, the GO-based aptasensor exhibited excellent selectivity toward chloramphenicol compared to other synthetic drugs with similar structures such as thiamphenicol, metronidazole and nitrofurantoin. Good reproducibility and precision (RSD 4.73%, n=10) of the assay indicates the ability of the aptasensor for routine quantitative trace analysis of chloramphenicol. Our results suggested that the prepared aptasensor was also well qualified for the detection of chloramphenicol in milk with a limit of detection of 0.2ppb. PMID:25579964

  18. Wide-range plutonium isotopic analysis with CDTE detector

    Energy Technology Data Exchange (ETDEWEB)

    Vo, Duc T.; Russo, P. A. (Phyllis A.)

    2001-01-01

    Nondestructive analysis (NDA) techniques applied to bulk nuclear materials (NM) are important for nuclear safeguards and material control because of timeliness, cost-effectiveness and containment integrity. The common NDA techniques, calorimetry and neutron coincidence counting, require knowledge of the isotopic composition of the material quantitative interpretation of these measurements. Gamma-ray spectroscopy with high-resolution detectors is a well-developed NDA technique for isotopics. The use of intrinsic germanium detectors cooled to cryogenic temperatures for isotopic measurements is sometimes difficult or even impossible because of severe access limitations with the sensitive, heavy detectors. Highly portable isotopics measurements are needed for in-situ verification of bulk NM quantities or, in many cases, for measurements of holdup quantities. This paper summarizes the gamma-ray measurements with a new, portable CdTe detector. It also presents the detailed results of the wide-range isotopic analysis of plutonium with FRAM v4, the first results of this kind for a non-cryogenic detector.

  19. CdTe detector based PIXE mapping of geological samples

    Energy Technology Data Exchange (ETDEWEB)

    Chaves, P.C., E-mail: cchaves@ctn.ist.utl.pt [Centro de Física Atómica da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Campus Tecnológico e Nuclear, EN10, 2686-953 Sacavém (Portugal); Taborda, A. [Centro de Física Atómica da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Campus Tecnológico e Nuclear, EN10, 2686-953 Sacavém (Portugal); Oliveira, D.P.S. de [Laboratório Nacional de Energia e Geologia (LNEG), Apartado 7586, 2611-901 Alfragide (Portugal); Reis, M.A. [Centro de Física Atómica da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Campus Tecnológico e Nuclear, EN10, 2686-953 Sacavém (Portugal)

    2014-01-01

    A sample collected from a borehole drilled approximately 10 km ESE of Bragança, Trás-os-Montes, was analysed by standard and high energy PIXE at both CTN (previous ITN) PIXE setups. The sample is a fine-grained metapyroxenite grading to coarse-grained in the base with disseminated sulphides and fine veinlets of pyrrhotite and pyrite. Matrix composition was obtained at the standard PIXE setup using a 1.25 MeV H{sup +} beam at three different spots. Medium and high Z elemental concentrations were then determined using the DT2fit and DT2simul codes (Reis et al., 2008, 2013 [1,2]), on the spectra obtained in the High Resolution and High Energy (HRHE)-PIXE setup (Chaves et al., 2013 [3]) by irradiation of the sample with a 3.8 MeV proton beam provided by the CTN 3 MV Tandetron accelerator. In this paper we present results, discuss detection limits of the method and the added value of the use of the CdTe detector in this context.

  20. TEM studies of Er sup + - implanted CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Morawiec, J.; Golacki, Z. (Inst. of Physics, Polish Academy of Sciences, Warsaw (Poland))

    1991-01-01

    The structure and the depth distribution of radiation damage caused by erbium implantation (E{sub i}=100 keV, D=5x10{sup 15} cm{sup -2}, T{sub i}=LNT) in <111> cadmium telluride have been investigated by means of planar-view and cross-sectional TEM techniques. It is found that the implantation disturbes the CdTe target up to the depth well-beyond the calculated projected range (that is > or approx.x5R{sub p}). The resulting damage structure consists of well-defined defects: precipitates, stacking faults, dislocation loops, and dislocation networks, which appear to be segregated with depth forming a sequence of homogeneously faulted zones. This characteristical and deep damage is suggested to be formed on dynamic annealing in response to internal stresses (caused by lattice parameter mismatch) which are high enough to produce plastic relaxation with dislocation generation and slip. This study is aimed at describing the ion-implantation-induced damage in single crystal cadmium telluride caused by Er{sup +} ions by means of transmission electron microscopy. (orig.).