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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
301

Development of high efficieny CdTe thin-film solar cell

Huang, Yein-rein 29 August 2011 (has links)
CdTe films were deposited by sputtering technique and were then carried out by CdCl2 treatment. The SEM micrographs show that the grain sizes of the as-deposited CdTe film were normally ranged from 50 nm to 100 nm, and they were recrystallized after CdCl2 treatment to obtain the grain sizes in the range of 1~3 £gm. A new device structure for CdTe thin-film solar cells has been proposed to exceed the cell efficiency of current record. The superstrate structure with the layer sequence of Glass/AZO/ZnO/CdS/CdTe/CI(G)S/Mo compared with the conventional device structure of Glass/FTO/CdS/CdTe/metal contact would have the following advantages:(1) a highly conductive AZO layer combined with a thin undoped ZnO layer will have higher optical transmission than that of FTO; (2) the use of p-type CIS under the CdTe layer with the same conductivity type can extend the light absorption to longer wavelength range (the band gaps of CdTe and CIS are 1.45eV and 1.04eV, respectively); (3) the proper addition of Ga to CIS may form CIGS quaternary compounds with a bandgap gradient which produce an electric field in the neutral region of a p-n junction to reduce the carrier recombination; (4) the use of Mo contact to CI(G)S is quite stable as compared with the metal contact normally used for p-CdTe. AMPS-1D simulation had been applied to evaluate the newly designed device structure and the results indicated a great improvement in device performance, i.e. the cell efficiency could exceed 20%. The I-V curve of a CdTe solar cell using the new device structure showed a nearly linear characteristic indicating the failure to form a p-n junction. We speculated that Cu might diffuse through the CdTe layer to the depletion region of the p-n junction formed at the CdS/CdTe interface. This would cause the junction failure. Based on the calculation on the Cu diffusion during the deposition of CIS layer at different temperatures even as low as 150˚C, it always had the chance to diffuse through the CdTe layer. An alternate device fabrication process was the use of the substrate structure for preparing CdTe solar cells, i.e. Glass/Mo/CIS/CdTe/CdS/ZnO/AZO/Al. However, the desired diode behavior was not observed until the thickness of CdTe layer was cut down to 10 nm. The electrical properties of that particular solar cell is the following:Voc=0.36V, Isc=4.991mA/cm2, F.F.=25.3%, efficiency=0.472%. It is probably that the lattice mismatch between CIS and CdTe is large that may cause the formation of interfacial defects and the reduction of photo excited carriers through the recombination processes. The annealing processes had been conducted in order to promote the interdiffusion between CdTe and CIS and minimize the lattice mismatch. However, the films peered off after annealing. Further experiments should be done to solve this problem.
302

Design and Fabrication of Suspending Micro-thermoelectric Generator with Transmissivity and Parallel Array Structure

Ma, Ling-Yu 05 September 2011 (has links)
This thesis aimed to design and develop a novel micro-thermal electric generator (£g-TEG) with a transparent parallel-array bridge microstructure using the ANSYS finite element analysis software and Micro Electro Mechanical Systems (MEMS) technology. The presented £g-TEG can convert the temperature difference between the indoor and outdoor planes of building glass window into a useful electrical power. The thermoelectrically transferred output electrical power is suitable for recharging various mobile communication products. Conventional £g-TEG presented a high fabrication cost, low integration compatibility with IC processes and non-transparent characteristics. To improve these disadvantages, this research utilizes a batch production surface micromachining technology to implement the Poly-Si based parallel-array £g-TEG on a transparent quartz glass substrate and the main fabrication processes adopted in this research are including six thin-film deposition processes and five photolithography processes. The implemented Poly-Si based transparent £g-TEG has successfully demonstrates a maximum temperature difference of 1.38¢J between the hot plane (substrate) and cold plane (suspending microstructure), a maximum output voltage of 13.28 mV/cm2, a maximum output power of 110.22 nW/cm2 and a maximum light transmission of 40%.
303

Design and fabrication of PVDF electrospun piezo- energy harvester with interdigital electrode

Tsai, Cheng-Hsien 01 September 2011 (has links)
This study used electrospinning to fabricate a polyvinylidene fluoride (PVDF) piezoelectric nanofiber harvesting device with interdigitated electrode to capture ambient energy. According to d33 mechanical-electric energy conversion mode, the energy harvesting device can be applied on the low frequency ambient vibration and impact abilities for the transformation mechanical energy into electrical energy effectively. First, the PVDF powder was mixed in acetone solution uniformly and the dimethyl sulfoxide (DMSO) was mixed with multi-walled carbon nanotube (MWCNT) to prepare PVDF macromolecular solution. The mixed solution was filled in a metals needle injector and contacted hundreds of voltage. After the PVDF drop in the needle was subjected to high electric field, the drop overcame surface tension of the solution itself, then extremely fine PVDF fiber was formed and spun out. The electrospun was collected orderly using X-Y digital control stage and the linear diameter of electrospun can be controlled easily by adjusting the travelling speed of the stage. In the spinning process, as affected by stretching strain and electric field at the same time, the PVDF piezoelectric fiber resulted in electric polarization and transformed £] piezoelectric crystal phase, in which the dipoles are oriented in the same direction. Furthermore, MWCNT was added to improve the mechanical properties of fiber and increase £] phase, to enhance the tensile strength and piezoelectric property of PVDF fiber effectively. Finally, the photolithography was used to fabricate interdigitated electrodes with 100£gm gap on the flexible PI substrate. The PVDF fibers, with a length and diameter of approximately 1cm and 700-1000nm, were aligned on interdigitated electrodes and packaged with the PI film. In order to increase the conversion efficiency of piezoelectric fiber in d33 mode, the PVDF fibers were repolarized in a high electric field. The results showed that the PVDF fiber energy harvesting device can generate 15mV open-circuit voltage under low frequency vibration of 4Hz and generate above 30mV open-circuit voltage under 6Hz vibrations. As compared with the piezoelectric fiber not repolarized by interdigitated electrode, its output voltage was increased by1- 2 times.
304

Highly Miniaturized Bandpass Filters for Wireless System-in-Package Applications

Chen, Chien-Hsun 14 March 2012 (has links)
This dissertation studies and implements highly miniaturized bandpass filter designs for wireless System-in-Package (SiP) applications. Based on the coupling matrix synthesis method, the external quality factors and coupling coefficients can be extracted by selecting the proper tapped-line feeding position and coupling spacing in geometrical configuration. Despite their high performance, most conventional microstrip bandpass filter designs require a bulky area for achieving, making them difficult to implement SiP applications. This dissertation first develops a stacked LC resonator and a stacked spiral resonator (SSR) in an embedded passive substrate (EPS) for realizing miniature single- and multi-band bandpass filters. Moreover, multiple transmission zeros created on both sides of each passband provide high stopband roll-off rates. The designed performance and size are comparable to those of low-temperature co-fired ceramic (LTCC) bandpass filters. As another conventional means of implementing RF passive components, the integrated passive device (IPD) process can produce large-value inductors and high-density capacitors, simultaneously. This dissertation fully utilizes the advantages of IPD technology to implement very compact bandpass filter designs with multiple transmission-zero frequencies at stopband by using a high-density wiring planar transformer configuration. Furthermore, due to the fully symmetric geometry, the transformer-coupled bandpass filter can be easily converted into a balun bandpass filter, capable of providing a superior balance performance with a significantly higher common mode rejection ratio (CMRR) level. The electromagnetic (EM) simulation results, as obtained by using Ansys-Ansoft HFSS, agree with the measurement results for all of the proposed designs in this dissertation.
305

Piezoelectric transducers based on double-sided AlN thin filmson stainless steel substrates

Zhong, I-Zhan 09 August 2012 (has links)
This investigation examines a novel means of integrating high-performance AlN piezoelectric thin films with a flexible stainless steel substrate (SUS 304) to fabricate a double-sided piezoelectric transducer. Various sputtering parameters, such as sputtering pressure, substrate temperature, nitrogen concentration, and RF power, were investigated to improve the piezoelectric characteristics of AlN thin films. Scanning electron microscopy and X-ray diffraction of AlN piezoelectric film reveal a rigid surface structure and highly c-axis-preferring orientation. The maximum output power per unit thickness was discussed, and the optimal sputtering parameters were determined. The double-sided piezoelectric transducer is constructed by depositing AlN piezoelectric thin films on both the front and the back sides of SUS 304 substrate. The titanium (Ti) and platinum(Pt) layers were deposited using a dual-gun DC sputtering system between the AlN piezoelectric thin film and the SUS 304 substrate. The optimal deposition parameters for AlN thin films are sputtering pressure of 5 mTorr, substrate temperature of 300 ¢J, nitrogen concentration of 40 %, and RF power of 250 W. The maximum open circuit voltage of the transducer under the vibrational frequency of 80 Hz, vibration amplitude of 4mm, and mass loading of 0.5g, is approximately 20 V, or 5.3 V/£gm. After full-wave rectification and filtering through a 33 nF capacitor, a specific output power of 1.462 £gW/cm2 is obtained from the transducer with a load resistance of 7 M£[.
306

New cylindrical near-field electrospun PVDF fibers

Ou, Zong-Yu 13 August 2012 (has links)
In this study, a cylindrical near-field electrospining (CNFES) process will be used to fabricate permanent piezoelectricity of polyvinylidene fluoride (PVDF) piezoelectric fibers, and a piezoelectric fiber harvesting device with parallel electrode was fabricated to capture ambient energy. First, the PVDF powder was mixed in acetone solution uniformly and the dimethyl sulfoxide (DMSO) was mixed with fluorosurfactant to prepare PVDF macromolecular solution. The PVDF macromolecular solution was filled in a metals needle injector and contacted a high power supply, after the PVDF drops in the needle was subjected to high electric field, the drops became a Taylor cone and overcame surface tension of the solution itself, extremely fine PVDF fiber was formed and jetted out. The fibers were collected numerous and quickly by homemade cylindrical collector and the diameter of fiber could be controlled easily by adjusting the rotating speed of the cylinder and the electric field. From the observation of XRD (X-ray diffraction), it reveals a high diffraction peak at 2£c=20.7¢X of piezoelectric crystal £]-phase structure by adjusting PVDF concentrations and DC voltage. By providing 7Hz shake and 0.23% strain, the piezoelectric fiber harvesting device with parallel electrode could generate 76mV; by providing 7Hz shake and 0.14% strain, the device could generate 1.1nA.
307

Full-wave Surface Integral Equation Method for Electromagnetic-circuit Simulation of Three-dimensional Interconnects in Layered Media

Karsilayan, Nur 2010 May 1900 (has links)
A new full-wave surface impedance integral equation method is presented for three-dimensional arbitrary-shaped interconnect parasitic extraction in layered media. Various new ways of applying voltage and current excitations for electromagnetic-circuit simulation are introduced. A new algorithm is proposed for matrix formation of electromagnetic-circuit simulation, low frequency solution and layered media so that it can be easily integrated to a Rao-Wilton-Glisson based method of moment code. Two mixed potential integral equation forms of the electric field integral equation are adapted along with the Michalski-Mosig formulations for layered kernels to model electromagnetic interactions of interconnects in layered media over a conducting substrate. The layered kernels are computed directly for controllable accuracy. The proposed methods are validated against existing methods for both electromagnetic and electromagnetic-circuit problems.
308

Lipid Metabolism, Gene Expression, Substrate Oxidation, and Meat Quality of Growing-finishing Pigs Supplemented with Conjugated Linoleic Acid and Arginine

Go, Gwang-Woong, 1979- 2010 December 1900 (has links)
We hypothesized that supplementation of dietary conjugated linoleic acid (CLA) and arginine singly or in combination would increase animal performance and meat quality by decreasing adiposity and increasing lean mass in growing-finishing pigs. Sixteen pigs (80 kg) were assigned to four treatments in a 2 x 2 factorial design, differing in dietary fatty acid and amino acid composition [control: 2.05% alanine (isonitrogenous control) plus 1% canola oil (lipid control); CLA: 2.05% alanine + 1% CLA; arginine: 1% arginine + 1% canola oil; arginine + CLA: 1% arginine + 1 CLA]. Preliminary tests indicated that up to 2% arginine was acceptable without interfering with lysine absorption. Pigs were allowed to feed free choice until reaching 110 kg. There were no significant differences across treatments in feed intake, weight gain, or feed efficiency. CLA tended to decrease carcass length (P = 0.06), whereas backfat thickness tended to be greater in pigs supplemented with arginine (P = 0.08). Arginine decreased muscle pH at 45 min postmortem (P = 0.001) and tended to increase lightness of muscle at 24 h postmortem (P = 0.07). CLA supplementation increased the concentrations of trans-isomers of 18:1 (P = 0.001) and SFA (P = 0.01) in s.c. and r.p. adipose tissue. CLA supplementation increased palmitate incorporation into total lipids in longissimus muscle (P = 0.01). Glucose oxidation to CO₂ in r.p. and s.c. adipose tissue were greater in pigs supplemented with CLA in the absence or presence of arginine (P = 0.03 and P = 0.04, respectively). The volume of s.c. adipocytes in s.c. and r.p. adipose tissues was greater in pigs supplemented with CLA, arginine, or CLA plus arginine than in control pigs (P = 0.001). Neither CLA nor arginine affected the expression of PGC-1[alpha],AMPK, mTOR, CPT-1A, FAS, or SCD (P > 0.05) in any tissues. We conclude that there was no significant interaction between arginine and CLA. Supplementary CLA or arginine to finishing-growing pigs did not modulate growth performance and did not reduce adiposity. CLA increased intramuscular fat content without deteriorating meat quality traits and increased saturated fatty acids and substrate oxidation in adipose tissues. In the presence of 1% of canola oil or CLA in the diet, arginine has the potential to deteriorate meat quality by reducing early postmortem pH and by increasing carcass fatness.
309

Tunable Substrate Integrated Waveguide Filters Implemented with PIN Diodes and RF MEMS Switches

Armendariz, Marcelino 2010 December 1900 (has links)
This thesis presents the first fully tunable substrate integrated waveguide (SIW) filter implemented with PIN diodes and RF MEMS switches. The methodology for tuning SIW filters is explained in detail and is used to create three separate designs. Each SIW cavity is tuned by perturbing via posts connecting or disconnecting to/from the cavity's top metal layer. In order to separate the biasing network from the SIW filter, a three-layer PCB is fabricated using Rogers RT/duroid substrates. The first tunable design utilizes the Philips BAP55L PIN diode. This two-pole filter provides six frequency states ranging from 1.55 GHz to 2.0 GHz. Fractional bandwidth ranges from 2.3 percent – 3.0 percent with insertion loss and return loss better than 5.4 dB and 14 dB respectively for all frequency tuning states. The second tunable design utilizes the Radant RMSW-100 MEMS switch, providing six states ranging from 1.65 GHz to 2.1 GHz. Fractional bandwidth for this filter varies from 2.5 percent - 3.0 percent with insertion loss and return loss better than 12.4 dB and 16 dB respectively for all states. The third design utilizes the OMRON 2SMES-01 RF MEMS relay, providing fourteen states ranging from 1.19 GHz to 1.58 GHz. Fractional bandwidth ranges from 3.6 percent - 4.4 percent with insertion loss and return loss better than 4.1 dB and 15 dB respectively for all frequency states. Two of the three designs (Philips PIN diode and OMRON MEMS) produced good results validating the new SIW filter tuning methodology. Finally, to illustrate the advantage of microstrip planar structures integrated with SIW structures, low pass filters (LPFs) are implemented along the input and output microstrip-to-SIW transition regions of the tunable SIW filter. With minimal change to the overall filter size, this provides spurious suppression for the additional resonant modes inherently present in waveguide structures. The implemented design utilizes the same OMRON MEMS tunable SIW filter specifications. This two-pole tunable filter provides the same performance as the previous OMRON MEMS design with exception to an added 0.7 dB insertion loss and spurious suppression of -28 dB up to 4.0 GHz for all frequency tuning states.
310

Passive Component Wire Bonding Evaluation in a Hybrid IC Package

Chen, Ying-Chou 12 February 2007 (has links)
As the IC assembly technology fast developing in the modern electrical industries. Demand of high performance electric product is glowing up day by day. New generation of the hybrid IC assembly package has become the major role recently. In order to prevent the package defects occurring in end customer sites, in this paper we try to improve the IC assembly method by using a totally different process to fix the passive component on a BGA substrate. We found that the passive component can be proceeded the current gold wire bonding process. In case of the Hybrid BGA with the current passive component attaching process, we can find the thermal effect during the surface mount process. Since the solder can be melt every time during each heating process. Therefore, we plan to improve it without solder attachment. The new improvement is to fix the passive component by a non-conductive thermal cure glue. The glue can be done in one time cure, thus the further process would not influence the quality of passive component. However in the evaluation experiment, the component coated by Gold is the best choice, but we intend to just put it in a comparison model because of the cost consideration. Both works on passive component coated by Gold and Solder were proved. The customer support for the further study on the real products is suggested.

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