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901.
Dongwon Yoo Limb J. Jae-Hyun Ryou Yun Zhang Shyh-Chiang Shen Dupuis R.D. Hanser D. Preble E. Evans K. 《Photonics Technology Letters, IEEE》2007,19(17):1313-1315
AlxGa1-xN (x=0.05) ultraviolet (UV) avalanche photodiodes grown on a GaN substrate are reported. The epitaxial structure was grown by metal-organic chemical vapor deposition on a free-standing bulk GaN substrate having low dislocation density. The growth conditions for AlxGa1-xN epitaxial layers on GaN substrates were optimized to achieve improved crystalline and structural quality. With UV illumination at lambda~250 nm, devices with mesa diameters of ~30 mum achieve stable maximum optical gains of ~50 at a reverse bias voltage of ~87 V. 相似文献
902.
An efficient non-coherent demodulation algorithm to compensate for the frequency offset effectively is proposed for IEEE 802.15.4 LR-WPAN systems working in the 868/915 MHz band. In the proposed algorithm, the decision criterion is changed depending on the frequency offset estimated in the preamble, and the received signal is differentially demodulated by using the phase difference between two consecutive bits. Simulation results show that the proposed method achieves better performance compared to conventional non-coherent algorithms, without increasing hardware costs significantly. 相似文献
903.
Sunyoung Kim Namjun Cho Seong-Jun Song Hoi-Jun Yoo 《Solid-State Circuits, IEEE Journal of》2007,42(11):2432-2440
A 0.9 V 96 muW fully operational low-power digital hearing aid chip is proposed and implemented. An internal status controller is introduced to achieve full operation of the adaptive-SNR analog front end. Dedicated DSP with an additional volume control parameter eliminates any internal overflow and enables the hearing aid to be customized for each individual user. When the input audio band is split into a low band and a high band, the audio signal can be processed coarsely. In addition, fine processing of the high-band signal can be obtained with a low-power automatic gain control (AGC) comprising a digital comparator and a subtraction unit. A heterogeneous Sigma-Delta DAC reduces the power consumption of the interpolation filter without degrading performance by allowing different frequencies between the input signal and the sampling clock of the Sigma-Delta modulator. Compared with a conventional Sigma-Delta DAC, the heterogeneous Sigma-Delta DAC reduces the power dissipation by 40.4% and the area occupation by 40.5%, and it has a reported error rate of only 0.16%. The fabricated chip achieves a 79 dB peak SNR with 4.1 muVrms of input-referred noise voltage. The core area is 2.8 mm x 1.1 mm in a 0.18 mum standard CMOS process. 相似文献
904.
Youngchul Cho Nacer-Eddine Zergainoh Sungjoo Yoo Ahmed Amine Jerraya Kiyoung Choi 《Design Automation for Embedded Systems》2007,11(2-3):167-191
In multiprocessor system-on-chip, tasks and communications should be scheduled carefully since their execution order affects
the performance of the entire system. When we implement an MPSoC according to the scheduling result, we may find that the
scheduling result is not correct or timing constraints are not met unless it takes into account the delays of MPSoC architecture.
The unexpected scheduling results are mainly caused from inaccurate communication delays and or runtime scheduler’s overhead.
Due to the big complexity of scheduling problem, most previous work neglects the inter-processor communication, or just assumes
a fixed delay proportional to the communication volume, without taking into consideration subtle effects like the communication
congestion and synchronization delay, which may change dynamically throughout tasks execution. In this paper, we propose an
accurate scheduling model of hardware/software communication architecture to improve timing accuracy by taking into account
the effects of dynamic software synchronization and detailed hardware resource constraints such as communication congestion
and buffer sharing. We also propose a method for runtime scheduler implementation and consider its performance overhead in
scheduling. In particular, we introduce efficient hardware and software scheduler architectures. Furthermore, we address the
issue of centralized implementation versus distributed implementation of the schedulers. We investigate the pros and cons
of the two different scheduler implementations. Through experiments with significant demonstration examples, we show the effectiveness
of the proposed approach. 相似文献
905.
T. S. Argunova E. I. Belyakova I. V. Grekhov A. G. Zabrodskiĭ L. S. Kostina L. M. Sorokin N. M. Shmidt J. M. Yi J. W. Jung J. H. Je N. V. Abrosimov 《Semiconductors》2007,41(6):679-683
The results of studying the structural and electrical properties of structures produced by the method of direct bonding of Ge x Si1?x and Si wafers are reported. The wafers were cut from the crystals grown by the Czochralski method. Continuity of the interface and the crystal-lattice defects were studied by X-ray methods using synchrotron radiation and by scanning electron microscopy. Measurements of the forward and reverse current-voltage characteristics of the p-Ge x Si1?x /n-Si diodes made it possible to assess the effect of the crystallattice defects on the electrical properties of heterojunctions. Satisfactory electrical parameters suggest that the technology of direct bonding is promising for the fabrication of large-area Ge x Si1?x /Si heterojunctions. 相似文献
906.
Sang Hyun Jin Young-Bin Park Kwan Han Yoon 《Composites Science and Technology》2007,67(15-16):3434-3441
Poly(ethylene terephthalate) (PET)/multi-walled carbon nanotube (MWCNT) composites were prepared by in situ polymerization. To improve the dispersion of MWCNTs in PET matrix, the surface modified MWCNTs having acid groups (acid-MWCNT) and diamine groups (diamine-MWCNT) were used. The functional groups on the surface of modified MWCNTs were confirmed by infrared (IR) spectrometry. SEM analysis showed better dispersion of diamine-MWCNTs as compared to pristine-MWCNTs and acid-MWCNTs in the PET. The reaction between PET and diamine-MWCNTs was evidenced by the shifting of the G band to a higher frequency in Raman spectroscopy and an increase of the complex viscosity in rheological properties. The composites containing functionalized MWCNTs showed a large increase in the tensile strength and modulus. The PET/diamine-MWCNT composites showed maximum tensile strength and modulus increases by 350% and 290% at 0.5 and 2.0 wt%, respectively, as compared to pure PET. 相似文献
907.
Young‐Hwan Lee Baek Ho Jung Tapan K. Sarkar Mengtao Yuan Zhong Ji Seong‐Ook Park 《ETRI Journal》2007,29(1):8-17
In this paper, we present a time domain combined field integral equation formulation (TD‐CFIE) to analyze the transient electromagnetic response from dielectric objects. The solution method is based on the method of moments which involves separate spatial and temporal testing procedures. A set of the RWG functions is used for spatial expansion of the equivalent electric and magnetic current densities, and a combination of RWG and its orthogonal component is used for spatial testing. The time domain unknowns are approximated by a set of orthonormal basis functions derived from the Laguerre polynomials. These basis functions are also used for temporal testing. Use of this temporal expansion function characterizing the time variable makes it possible to handle the time derivative terms in the integral equation and decouples the space‐time continuum in an analytic fashion. Numerical results computed by the proposed formulation are compared with the solutions of the frequency domain combined field integral equation. 相似文献
908.
As pervasive computing is widely adopted and reliable networks are becoming more easily accessible, there is a rapidly growing need to develop a mechanism to analyze and evaluate the performance of ubiquitous environments. This paper presents an information processing model which characterizes a ubiquitous environment where a variety of pieces of information need to be exchanged among devices within a system. The proposed model not only provides analytical tools to evaluate the performance of devices, but also makes it possible to identify key factors in designing a ubiquitous environment. For illustrative purposes, a test bed is constructed and the performance of the system is assessed based on the proposed model. 相似文献
909.
Dae‐Sik Lee Hyoung Gil Choi Kwang Hyo Chung Bun Yeoul Lee Hyeon‐Bong Pyo Hyun C. Yoon 《ETRI Journal》2007,29(5):667-669
This letter presents a smart integrated microfluidic device which can be applied to actively immobilize proteins on demand. The active component in the device is a temperature‐controllable microelectrode array with a smart polymer film, poly(N‐isopropylacrylamide) (PNIPAAm) which can be thermally switched between hydrophilic and hydrophobic states. It is integrated into a micro hot diaphragm having an integrated micro heater and temperature sensors on a 2‐micrometer‐thick silicon oxide/silicon nitride/silicon oxide (O/N/O) template. Only 36 mW is required to heat the large template area of 2 mm×16 mm to 40°C within 1 second. To relay the stimulus‐response activity to the microelectrode surface, the interface is modified with a smart polymer. For a model biomolecular affinity test, an anti‐6‐(2, 4‐dinitrophenyl) aminohexanoic acid (DNP) antibody protein immobilization on the microelectrodes is demonstrated by fluorescence patterns. 相似文献
910.
Ju-Yeon Lee Jin-Hyang Kim Won-Taek Jung Young Kum Park 《Journal of Materials Science》2007,42(11):3936-3943
2,3-Di-(2′-hydroxyethoxy)benzylidenemalononitrile (3) was prepared and condensed with 2,4-toluenediisocyanate and 3,3′-dimethoxy-4,4′-biphenylenediisocyanate to yield novel Y-type
polyurethanes 4–5 containing 2,3-dioxy benzylidenemalononitrile group as a nonlinear optical (NLO)-chromophore, which constituted parts of
the polymer backbones. Polyurethanes 4–5 were soluble in common organic solvents such as acetone and N,N-dimethylformamide. They showed a thermal stability up to 270 °C in thermogravimetric analysis thermograms and the glass-transition
temperatures (T
g) obtained from differential scanning calorimetry thermograms were around 116–135 °C. The second harmonic generation (SHG)
coefficients (d
33) of poled polymer films at 106.4 mm−1 fundamental wavelength were around 9.07 × 10−19 C (2.72 × 10−9 esu). The dipole alignment exhibited high thermal stability up to 10 °C higher than T
g, and there was no SHG decay below 145 °C due to the partial main-chain character of the polymer structure, which was acceptable
for nonlinear optical device applications. 相似文献