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121.
Harukazu Yoshino Zeynel Bayindir Joydeep Roy Ben Shaw Heon-ick Ha Andrei Lebed Michael J. Naughton 《Journal of Low Temperature Physics》2006,142(3-4):323-326
A new TTP donor, Me-DH-TTP (2-methyl-5-(1,3-dithiolan-2-yliden)-1,3,4,6-tetrathiapentalene), was designed to realize a system
with large on-site Coulomb repulsion as compared with the previously known bis-fused type TTP donors. Probably as a consequence,
(Me-DH-TTP)2AsF6 exhibits semiconducting behavior from room temperature to liquid helium temperature. By increasing pressure, metallic behavior
appears below 300 K, and with distinct metal-insulator (M-I) transition up to 2.2 GPa. This M-I transition suddenly disappears
beyond 2.5 GPa, and metallic state is stabilized down to 2.6 K. We discuss the possibility of quantum critical point around
2.4 GPa. 相似文献
122.
Carbon nanotubes (CNTs) were grown using a dc arc discharge process and relevant process parameters were investigated. Unlike the usual process in which a carbon anode is filled with metal catalyst powder, CNTs were prepared using a carbon cathode on which the metal catalyst had been deposited using an electroplating system. Various transition metals were investigated. The results show that multi walled carbon nanotubes (MWNTs) and single walled carbon nanotubes (SWNTs) can both be synthesized using this technique. SWNTs are detected in the soot sample collected around the cathode, whereas the MWNTs are detected mainly in the deposit sample collected from the central area of the cathode. The CNT yield varies depending on the catalyst used and the properties of a good catalyst are discussed. 相似文献
123.
A method for evaluating fault coverage using simulated fault injection for digitalized systems in nuclear power plants 总被引:1,自引:0,他引:1
Suk Joon Kim Poong Hyun Seong Jun Seok Lee Man Cheol Kim Hyun Gook Kang Seung Cheol Jang 《Reliability Engineering & System Safety》2006,91(5):614-623
The fault coverage for digital system in nuclear power plants is evaluated using a simulated fault injection method. Digital systems have numerous advantages, such as hardware elements share and hardware replication of the needed number of independent channels. However, the application of digital systems to safety-critical systems in nuclear power plants has been limited due to reliability concerns. In the reliability issues, fault coverage is one of the most important factors. In this study, we propose an evaluation method of the fault coverage for safety-critical digital systems in nuclear power plants. The system under assessment is a local coincidence logic processor for a digital plant protection system at Ulchin nuclear power plant units 5 and 6. The assessed system is simplified and then a simulated fault injection method is applied to evaluate the fault coverage of two fault detection mechanisms. From the simulated fault injection experiment, the fault detection coverage of the watchdog timer is 44.2% and that of the read only memory (ROM) checksum is 50.5%. Our experiments show that the fault coverage of a safety-critical digital system is effectively quantified using the simulated fault injection method. 相似文献
124.
Jae Hong Park Tae Yun Kwon Hyung Joon Kim Seung Rae Kim Dae Sung Yoon Chae-Il Cheon Hwan Kim Tae Song Kim 《Journal of Electroceramics》2006,17(2-4):565-572
The PZT thick film cantilever devices fabricated via MEMS process have much attraction because they are appropriate for biological
transducer or sensor, resulting from their large actuating force and relatively high sensitivity especially in liquid. By
means of resonance behavior, theoretical calculation and experimental verification of the PZT thick film cantilever devices
have not been studied before. Accordingly, we focused on the sensitivity analysis and interpretation of the PZT thick film
cantilevers in this study. Especially, the investigation for mass sensitivity of the PZT thick film cantilever is of importance
for physical, chemical and biological sensing application. The PZT thick film cantilever devices were constructed on Pt/TiO2/SiN
X
/Si substrates using screen printing method and MEMS process. The harmonic oscillation response (resonance frequency) was
measured using an optical laser interferometric vibrometer. The effect of cantilever geometry on the resonance frequency change
was investigated. Compared with the theoretical resonant frequency change by mass loading, the experimental resonant frequency
change of the PZT micromechanical thick film cantilever shows a variation of less than 2%. Mass sensitivities are estimated
to be 30.7, 57.1 and 152.0 pg/Hz for the 400 × 380 μm, 400 × 480 μm and 400 × 580 μm cantilever, respectively. 相似文献
125.
Jung-Hyuk Koh Mun-Su Ha Soon-Jong Jeong Jae-Sung Song Tae-geun Kim Sang-Mo Koo Jae-geun Ha 《Journal of Electroceramics》2006,16(4):403-406
The solid solution of Pb(Mg,Nb)O3-Pb(Zr,TiO) O3 materials have high piezoelectric constant of 600 ∼650 pC/N and electromechanical coupling coefficient k
p of 0.65. Due to such high piezoelectric constant and electromechanical coupling coefficient, Pb(Mg,Nb)O3-Pb(Zr,TiO)O3 materials have been attracted attentions for the applications of multilayer ceramic actuators. Actuators can be produced
by staking piezoelectric ceramic materials and inner electrodes, alternatively. However, it is difficult to fabricate huge
ceramic actuators without any serious problems during the process conditions. Because ceramic are easily cracked during the
sintering process, due to strikingly different shrinkage rate between the ceramic materials and metal electrodes. In this
research, new jointing methods will be proposed for huge ceramic actuators, and then their electrical properties were investigated.
Time dependent leakage current and impedance spectroscopy were employed to expect device performances. 相似文献
126.
利用压实热拌沥青混合料的空隙率和矿料间隙率等体积特性,考虑集料吸收沥青的情况,提出了“有效油石体积比”的概念,依据最佳有效油石体积比,分析研究了同类级配矿料的最佳油石比之间的关系,建立了具有普遍意义的关系式,并与新的公路沥青路面施工技术规范提供的预估公式作了比较. 相似文献
127.
Seok-In Na Ga-Young Ha Dae-Seob Han Seok-Soon Kim Ja-Yeon Kim Jae-Hong Lim Dong-Joon Kim Kyeong-Ik Min Seong-Ju Park 《Photonics Technology Letters, IEEE》2006,18(14):1512-1514
The selective wet etching of a p-GaN layer by using a solution of KOH in ethylene glycol (KE) was studied to enhance the optical and electrical performance of the GaN-based light-emitting diodes (LEDs). The surface of the p-GaN, which was selectively etched in the KE solution, showed hexagonal-shaped etch pits. The light-output power of etched LEDs was improved by 29.4% compared to that of the nonetched LED. This improvement was attributed to the increase in the probability of photons to escape due to the increased surface area of textured surface and the reduction in contact resistance of the ohmic layer resulting from the increased contact area and hole concentration on the textured p-GaN. The reverse leakage current of the LED was also greatly decreased due to the surface passivation and the removal of defective regions from the p-GaN. 相似文献
128.
Operation, system architectures, and physical Layer design considerations of distributed MAC protocols for UWB 总被引:2,自引:0,他引:2
Impulse-based ultra wideband (I-UWB) is an attractive radio technology for large ad hoc and sensor networks due to its robustness to harmful multipath effects, sub-centimeter ranging ability, simple hardware, and low radiated power. To scale to large sizes, networks often implement distributed medium access control (MAC) protocols. However, most MAC protocols for I-UWB are centralized, and they target small wireless personal area networks and cellular networks. We propose three distributed MAC protocols suitable for I-UWB. Two multichannel protocols, called multichannel pulse sense multiple access (M-PSMA) and multichannel ALOHA achieve high aggregate throughput. A busy-signal protocol, called busy-signal multiple access (BSMA), reduces the energy wasted from re-transmitted packets. This paper describes the three protocols in terms of the protocol's operation, the supporting system architecture, and the I-UWB physical layer. Physical layer simulations confirm the feasibility of implementing the proposed systems and also provide parameters for network simulations. Network simulations show that the throughput of M-PSMA exceeds that of a centralized time-division multiple-access protocol and that the energy efficiency of BSMA far surpasses that of other distributed protocols. 相似文献
129.
Symbol error rate of selection amplify-and-forward relay systems 总被引:8,自引:0,他引:8
Cooperative diversity schemes significantly improve the performance of wireless networks by transmitting the same information through several nodes. The amplify-and-forward (AF) relaying method is one of the most attractive cooperative diversity schemes due to its low complexity. Selection AF relaying has recently been proven to achieve the same diversity order as and lower outage probability than all-participate relays. In this letter, we present an asymptotic analysis of the symbol error rates of a selection AF network, and compare it with the conventional all-participate scheme 相似文献
130.
Recrystallization and grain growth of a cold-rolled gold sheet with 98 pct reduction in area (RA) were investigated with electron
backscatter diffraction (EBSD) and X-ray diffraction (XRD). Gold with some dopants (Be, Ca, and La) was used in this research
and its recrystallization temperature was 320 °C. Isothermal annealing experiments at 400 °C, 500 °C, and 600 °C were carried
out for the cold-rolled gold sheet, and recrystallization texture was examined. In the cold-rolled gold sheet, α- and β-fibers were measured mainly and some shear texture components were found on the surface. Shear texture components remained
on the surface for 2 hours at 400 °C and were consumed by other recrystallized grains after 24 hours at 400 °C. Microstructure
and texture evolution during in-situ annealing at 400 °C were investigated from the cold-rolled state to the fully recrystallized state using EBSD. Most of the
newly, recrystallized grains came from the deformed β-fiber regions and consisted of β-fiber, cube, and other random orientations. 相似文献