Browsing by Issue Date, starting with "2006-06-25"

Now showing 1 - 20 of 63131

A novel design of high-speed divide-by-3/4 counter for a dual-modulus prescaler
(2006-06-25)
Shih, Yi-Shing
;
Tarng, Jenn-Hwan
;
電信工程研究所
;
Institute of Communications Engineering
A novel design for a high-speed divide-by-3/4 counter is presented. The proposed design reduces not only the critical path delay but also the feedback path delay, hence it can increase the operating speed. With this divide-by-3/4 counter, a divide-by-127/128 dual-modulus prescaler (DMP), implemented in 0.18 mu m CMOS technology, shows a maximum operating frequency of 7.0 GHz with 2.4mW power consumption at 1.8V supply voltage, which has 25% speed improvement and still consumes less power as well compared to the recently-reported one.
Study on the interface thermal stability of metal-oxide-semiconductor structures by inelastic electron tunneling spectroscopy
(2006-06-26)
Huang, CF
;
Tsui, BY
;
Tzeng, PJ
;
Lee, LS
;
Tsai, MJ
The bias polarity-dependent inelastic electron tunneling spectroscopy is employed to detect the thermal stability of the Ta-Pt/SiO2/Si and Ta-Pt/HfO2/Si structures. This work provides a direct evidence that the Fermi-level pinning of metal gates is counted for the generation of extrinsic states due to interface interaction. A Ta2O5 layer forms at the Ta-Pt/SiO2 interface during thermal annealing whereas only an intermittent Ta-O bond is observed at the Ta-Pt/HfO2 interface. Although the heat of formation of HfO2 is lower than that of SiO2, Si presumably diffuses into HfO2 layer and replaces Hf atoms during the high-temperature annealing. (c) 2006 American Institute of Physics.
Band gap engineering and spatial confinement of optical phonon in ZnO quantum dots
(2006-06-26)
Lin, KF
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Cheng, HM
;
Hsu, HC
;
Hsieh, WF
;
光電工程學系
Both band gap engineering and spatial confinement of optical phonon were observed depending upon the size of ZnO quantum dots at room temperature. Size-dependent blueshifts of photoluminescence and absorption spectra reveal the quantum confinement effect. The measured Raman spectral shift and asymmetry for the E-2(high) mode caused by localization of optical phonons agree well with that calculated by using the modified spatial correlation model. (c) 2006 American Institute of Physics.
Size dependence of photoluminescence and resonant Raman scattering from ZnO quantum dots
(2006-06-26)
Cheng, HM
;
Lin, KF
;
Hsu, HC
;
Hsieh, WF
;
光電工程學系
ZnO quantum dots (QDs) of controlled sizes have been fabricated by a simple sol-gel method. The blueshift of room-temperature photoluminescence measurement from free exciton transition are observed decreasing with the QD size that is ascribed to the quantum confinement effect. From the resonant Raman scattering, the coupling strength between electron and longitudinal optical phonon, deduced from the ratio of the second- to the first-order Raman scattering intensity, diminishes with reducing the ZnO QD diameter. The size dependence of electron-phonon coupling is principally a result of the Frohlich interaction.
Guided three-dimensional molecular self-assembly on silicon substrates
(2006-06-26)
Chang, CC
;
Sun, KW
;
Kan, LS
;
Kuan, CH
;
生物科技學系
We demonstrate three-dimensional (3D) self-assemble growth of the metallothionein (Mn,Cd-MT-2) molecules on patterned semiconductor substrates. The MT molecules deposited on the patterned substrates were found to grow into 3D rod or ring-type nanostructures, depending on the shape of patterned nanostructures on the substrates. Dense arrays of 3D molecular nanorods or rings with an area density close to 10(10) cm(-2) were demonstrated with a pore size of 20 nm and a pitch size of 100 nm. Those engineered molecular nanostructures provide an excellent opportunity for biological applications, sensing sources of nanodevices, biochemical reactions on surfaces, and even single molecule studies. (c) 2006 American Institute of Physics.
Synthesis and characterization of poly(fluorene)-based copolymers containing various 1,3,4-oxadiazole dendritic pendants
(2006-06-27)
Wu, Chung-Wen
;
Tsai, Chien-Min
;
Lin, Hong-Cheu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A series of poly( fluorene)s (PFs) containing different generations of poly( benzyl ether) dendritic wedges with oxadiazole (OXD) peripheral functional groups, including copolymers bearing carbazole (CAZ) pendent groups, were synthesized. The dendritic side-chain polymers possessed excellent solubility in common solvents and good thermal stability with decomposition temperatures of 5% weight loss at more than 370 degrees C. Photophysical studies reveal that the photoluminescent ( PL) properties of the dendronized polymers were greatly affected by the size of the dendritic side chains. The G1- and G2-substituted PF derivatives greatly suppress the aggregation PF backbones and thus to induce pure blue PL emission ( with shorter wavelengths than PF). Excitation of the peripheral functional groups leads to substantial energy transfer from the dendrons to the poly( fluorene) backbones. In addition, the excitation of PF bearing G2 dendrons (G2-OXD) at 303 nm creates stronger fluorescence than that at 390 nm, indicating that the intensity of the sensitized emission ( by OXD absorption at 303 nm) is even stronger than that of a direct poly( fluorene) emission ( by PF backbone absorption at 390 nm). Double-layer light-emitting diode ( LED) devices with the configuration of ITO/PEDOT/polymer/LiF/Al were fabricated and reported. The device with PF bearing G0 dendrons and CAZ pendants (G0-OXDCAZ) as an emitter shows a turn-on voltage of 4.5 V and a bright luminescence of 2446 cd/m(2) at 12 V with a power efficiency of 0.24 cd/A at 100 mA/cm(2).
Infrared absorption of CH3SO2 detected with time-resolved Fourier-transform spectroscopy
(2006-06-28)
Chu, LK
;
Lee, YP
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
A step-scan Fourier-transform spectrometer coupled with a 6.4 m multipass absorption cell was employed to detect time-resolved infrared absorption spectra of the reaction intermediate CH3SO2 radical, produced upon irradiation of a flowing gaseous mixture of CH3I and SO2 in CO2 at 248 nm. Two transient bands with origins at 1280 and 1076 cm(-1) were observed and are assigned to the SO2-antisymmetric and SO2-symmetric stretching modes of CH3SO2, respectively. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predicted the geometry, vibrational, and rotational parameters of CH3SO2 and CH3OSO. Based on predicted rotational parameters, the simulated absorption band of the SO2-antisymmetric stretching mode that is dominated by the b-type rotational structure agrees satisfactorily with experimental results. In addition, a band near 1159 cm(-1) observed at a later period is tentatively attributed to CH3SO2I. The reaction kinetics of CH3+SO2 -> CH3SO2 and CH3SO2+I -> CH3SO2I based on the rise and decay of absorption bands of CH3SO2 and CH3SO2I agree satisfactorily with previous reports. (c) 2006 American Institute of Physics.
Nitride-based LEDs with nano-scale textured sidewalls using natural lithography
(2006-06-28)
Huang, HW
;
Kuo, HC
;
Chu, JT
;
Lai, CF
;
Kao, CC
This investigation describes the development of a InGaN/GaN light-emitting diode (LED) with textured sidewalls using natural lithography with polystyrene spheres (PSs) as the etching mask and dry etching the epitaxial layers of LEDs to achieve nano-scale textured sidewalls. The LED with textured sidewalls increased the output power of the InGaN - GaN multiple quantum well (MQW) LEDs by a factor of 1.3, indicating that the LED with nano-scale textured sidewalls had larger light extraction efficiency. The wall-plug efficiency of nitride-based LEDs was increased by 30% using textured sidewalls.
On the existence of hyper-L triple-loop networks
(2006-06-28)
Chen, CY
;
Hung, CS
;
Tang, WS
;
應用數學系
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Department of Applied Mathematics
Aguilo-Gost [New dense families of triple loop Networks, Discrete Math. 197/198 (1999) 15-27] has presented a new type of hyper-L tiles and used it to derive a new dense family of triple-loop networks. While Aguilo-Gost's hyper-L tile seems to be a promising tool for studying the triple-loop networks, we need to verify that the hyper-L tile producing good result is indeed the MDD of some triple-loop network. In this paper, we give necessary and sufficient conditions for the existence of Aguilo-Gost's hyper-L triple-loop networks and we correct some flaws in [F. Aguilo-Gost, New dense families of triple loop networks, Discrete Math. 197/198 (1999) 15-27]. (c) 2006 Elsevier B.V. All rights reserved.
The dynamical correlation in spacer-mediated electron transfer couplings
(2006-06-28)
Yang, CH
;
Hsu, CP
;
應用化學系分子科學碩博班
;
Institute of Molecular science
The dynamical correlation effect in electron transfer (ET) coupling was studied in this work, for cases where electrons tunnel through a many-electron environment. The ET couplings for three different bridge-mediated model systems were calculated: (I) trans-alkyl chains [H2C-(CH2)(n)-CH2, n=2-10], (II) two isomers of trans-1,4-dimethylenecyclohexane, and (III) two ethylenes spaced by a saturated ethane molecule. The couplings were calculated as half energy gaps of the two lowest adiabatic states. The dynamical correlation was included with spin-flip (SF) and ionization potential or electron affinity coupled-cluster singles and doubles (SF-CCSD and IP/EA-CCSD) and a Delta CCSD scheme. The direct coupling (DC) scheme is also used as a way to obtain a solution with nondynamical correlation, since DC uses approximated eigenstates that are symmetry-restoring linear combinations of two symmetry-broken unrestricted Hartree-Fock configurations. For all cases tested except for one, results from the DC scheme closely follow the CCSD data, indicating that the dual-configuration solutions can be a good approximation of wave functions with nondynamical correlation included, but there exist exceptions. Comparing the DC results with SF-CCSD and IP or EA-CCSD data, we concluded that the dynamical correlation effect is small for most of the cases we tested. (c) American Institute of Physics.
Tessellating polyominos in the plane
(2006-06-28)
Chen, MY
;
Hwang, FK
;
Yen, CH
;
應用數學系
;
Department of Applied Mathematics
Let the R-2 space be divided into unit squares where a polyomino is a finite, connected set of unit squares. In this paper, we give a necessary and sufficient condition on tessellating polyominos by observing an unexpected relation between such tessellations and systems of arithmetic progressions. (c) 2006 Elsevier B.V. All rights reserved.
Evanescent-field optical amplifiers and lasers
(2006-06-29)
Chen, Nan-Kuang
;
Chi, Sien
;
Tseng, Shiao-Min
;
Lai, Yinchieh
An optical amplifier and a laser generator based on the fiber side-polished technology, having a high pumping efficiency, a low noise figure and a small footprint are provided in this application. The optical amplifier and the laser, which have a very long effective interaction length in conjunction with highly doped Erbium glass attached to its surface and an addition of a slanted fiber grating inscribed in the guiding core at the polished region can spatially separate the signal and pump power to simultaneously improve the pumping efficiency and optimize the penetrated depth of the signal evanescent-field. The spontaneous emission is kept from being amplified and therefore a high quality amplified signal is produced.
Phase transformations in a Cu-35 at.% Mn-25 at.% Al alloy
(2006-06-29)
Yang, SY
;
Liu, TF
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The phase transformations in the Cu-35 at.% Mn-25 at.% Al alloy have been investigated by means of transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometry (EDS). In as-quenched condition, the microstructure of the alloy was a mixture of (L2(1)+B2+L-J) phases. This is different from that observed by previous workers in the Cu3-xMnxAl alloys with x <= 1.0. When the as-quenched alloy was aged at 460 degrees C for short times, gamma-brass precipitates started to occur at anti-phase boundaries (APBs). After prolonged aging at 460 degrees C, the gamma-brass precipitates grew and beta-Mn precipitates were formed at the regions contiguous to the gamma-brass precipitates. The coexistence of (gamma-brass + beta-Mn) has never been observed by previous workers in Cu-Mn-Al alloy systems before. (c) 2005 Elsevier B.V. All rights reserved.
Interfacial reaction and shear strength of Pb-free SnAg2.5Cu0.86b0.5 and SnAg3.0Cu0.5Sb0.2 solder bumps on Au/Ni(P) metallization
(2006-06-29)
Hsu, YC
;
Huang, YM
;
Chen, C
;
Wang, H
;
材料科學與工程學系
This study investigates the metallurgical reaction and shear strength of Pb-free SnAg2.5Cu0.8Sb0.5 and SnAg3.0Cu0.5Sb0.2 solder bumps on Au/Ni(P) metallization pads. It is found that (Cu,Ni)(6)Sn-5 intermetallic compound (IMC) formed at the interface between the Sn2.5Ag0.8Cu0.5Sb solder and the metallization pad; whereas (Cu,Ni)(6)Sn-5 and (Ni,Cu)(3)Sn-4 IMCs formed when the SnAg3.0Cu0.5Sb0.2 reacted with the Au/Ni(P) metallization pad. The difference in the Cu concentration in the two solders may be responsible for the different interfacial IMC formation. The shear strengths for the SnAg2.5Cu0.8Sb0.5, SnAg3.0Cu0.5Sb0.2, SnAg3.0Cu0.5, and SnAg4.0Cu0.5 solders were also measured. The shear strength test revealed that the SnAg2.5Cu0.8Sb0.5 solder has the highest shear strength, which may be due to the solid-solution strengthening of the Sb atoms. (c) 2005 Elsevier B.V. All rights reserved.
A growing structure near the deformation front in SW Taiwan as deduced from SAR interferometry and geodetic observation
(2006-06-30)
Huang, Mong-Han
;
Hu, Jyr-Ching
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Hsieh, Chia-Sheng
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Ching, Kuo-En
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Rau, Ruey-Juin
We apply the D-InSAR technique to monitor the active growing structure on the Tainan Tableland near the deformation front in SW Taiwan using ERS SAR images in the period of 1996 - 2000. Interferometric processing of six SAR images reveals the average slant range displacement (SRD) to be similar to 12.5 mm/yr, and it increases from the west edge of the Tainan Tableland and decreases across the Houchiali fault. The GPS campaign data indicate an average horizontal movement of 12 +/- 4 mm/yr in the direction of N44 degrees W for the Tainan Tableland with respect to the western coastline. Five precise leveling surveys across the Tainan Tableland over two years show an uplift rate of similar to 14 mm/yr for the benchmarks on the Tableland. By combining the horizontal velocity of GPS data and the SRD of D-InSAR we transfer the SRD into vertical deformation and discuss the deformation pattern and seismic hazards in the Tainan area.
Effect of nitrogen contents on the temperature dependence of photoluminescence in InGaAsN/GaAs single quantum wells
(2006-07-01)
Lai, Fang-I
;
Kuo, S. Y.
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Wang, J. S.
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Kuo, H. C.
;
Wang, S. C.
A series of InGaAsN/GaAs single-quantum wells (SQWs) with N contents varied from 0% to 5.3% were grown by molecular-beam epitaxy using a solid As and a nitrogen plasma sources. The impact of nitrogen concentration on the optical properties, as determined by the temperature dependence of photoluminescence (PL), of a 6 nm SQW was investigated. In the low-temperature region, a pronounced temperature-dependent S-shaped peak position was observed in PL spectra while increasing the nitrogen concentration. Quenching behavior reveals that the defect-related nonradiative processes might be enhanced in the highly nitrogen incorporated samples and thus influence the recombination dynamics. In addition, the evolution of the peak position of the InGaAsN/GaAs samples was in agreement with the empirical Varshni model in the high-temperature region. A significant reduction in the temperature dependence of the emission peak position is analyzed as well, and further confirms the prediction of proposed band anticrossing model of the electronic structure of III-N-V alloys. (c) 2006 American Vacuum Society.
(PS)(2): protein structure prediction server
(2006-07-01)
Chen, Chih-Chieh
;
Hwang, Jenn-Kang
;
Yang, Jinn-Moon
;
生物科技學系
;
生物資訊及系統生物研究所
Protein structure prediction provides valuable insights into function, and comparative modeling is one of the most reliable methods to predict 3D structures directly from amino acid sequences. However, critical problems arise during the selection of the correct templates and the alignment of query sequences therewith. We have developed an automatic protein structure prediction server, (PS)(2), which uses an effective consensus strategy both in template selection, which combines PSI-BLAST and IMPALA, and target-template alignment integrating PSI-BLAST, IMPALA and T-Coffee. (PS)(2) was evaluated for 47 comparative modeling targets in CASP6 (Critical Assessment of Techniques for Protein Structure Prediction). For the benchmark dataset, the predictive performance of (PS)(2), based on the mean GTD_TS score, was superior to 10 other automatic servers. Our method is based solely on the consensus sequence and thus is considerably faster than other methods that rely on the additional structural consensus of templates. Our results show that (PS)(2), coupled with suitable consensus strategies and anew similarity score, can significantly improve structure prediction. Our approach should be useful in structure prediction and modeling. The (PS)(2) is available through the website at http://ps2.life.nctu.edu.tw/.
A power-aware motion estimation architecture using content-based subsampling
(2006-07-01)
Cheng, Hsien-Wen
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Dung, Lan-Rong
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電控工程研究所
;
Institute of Electrical and Control Engineering
This paper presents a novel power-aware motion estimation architecture for battery-powered multimedia devices. As the battery status changes, the proposed architecture adaptively performs graceful tradeoffs between power consumption and compression quality. The tradeoffs are considered to be graceful in that the proposed architecture is scalable with changing conditions and the compression quality is slightly degraded as the available energy is depleted. The key to such tradeoffs lies in a content-based subsample algorithm, first proposed in this paper. As the available energy decreases, the algorithm raises the subsample rate for maximizing the battery lifetime. Differently from the existing subsample algorithms, the content-based algorithm first extracts edge pixels from a macro-block and then subsamples the remaining low-frequency part. By doing so, we can alleviate the aliasing problem and, thus, limit the quality degradation as the subsample rate increases. Given a power consumption mode, the proposed architecture first performs edge extraction to generate a turn-off mask and then uses the turn-off mask to reduce the switch activities of processing elements (PEs) in a semi-systolic array. The reduction of switch activities results in significant power consumption savings. To achieve a high degree of scalability and qualified power-awareness, we use an adaptive control mechanism to set the threshold value for edge determination and make the reduction of switch activities rather stationary. As shown by experimental results, the architecture can dynamically operate in different power consumption modes with little quality degradation according to the remaining capacity of the battery pack while the power overhead of edge extraction is kept under 0.8%.
Effect of dispersant on preparation of colloidal magnetite nanocrystals
(2006-07-01)
Shauo, Chang-Neng
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Chao, Chuen-Guang
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材料科學與工程學系
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Department of Materials Science and Engineering
Nanometer scale magnetite particles were prepared in a very low concentration dispersing system with a dispersant. The average size of the particles prepared under optimum conditions was determined by transmission electron microscopy to be approximately 1.8 nm. The magnetic properties were investigated using a superconducting quantum interference device (SQUID) magnetometer. The dried samples exhibited approximately super-paramagnetic behavior. Rhelogical property measurement shows that the colloidal magnetite both with and without polyurethane reveals shear thinning. The surface morphology of the films of the magnetite nanoparticles on the glass, as shown by atomic force microscopy (AFM) images, produces well-formed surface structure's that are evenly spaced by the magnetite nanoparticles. It also shows that this is an effective method of surface modification for nanometer scale magnetite.
Non-lethal Candida albicans cph1/cph1 efg1/efg1 transcription factor mutant establishing restricted zone of infection in a mouse model of systemic infection
(2006-07-01)
Chen, C. G.
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Yang, Y. L.
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Cheng, H. H.
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Su, C. L.
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Huang, S. F.
The cph1/cph1 efg1/efg1andida albicans mutant cells were non-lethal in a mouse model of systemic infection. We investigated in vivo proliferation and invasion of C albicans cells in infected mice to elucidate the interaction between the host and the pathogen. Homogenates of kidneys from the mice infected with the wild-type and the mutant C albicans cells yielded a mean of 2.1 x 10(7)CFU/g and 2.2 x 10(6) CFU/g, respectively. The kidneys from the mice infected with the wild-type cells showed extensive renal cortical necrosis associated with neutrophilic infiltration. There were also wild-type hyphal cells present in abundance. Hence, tubular necrosis leading to renal failure in the mice may be the cause of death. Although the cph1/cph1 efg1/efg1 mutant cells were not lethal, they were capable of establishing restricted zones of infection and colonization near the renal pelvis instead of simply being cleared by the immune system in mice.