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111.
Large amounts of well-aligned carbon nanotubes (CNTs) with open tips have been produced by pyrolysis of iron(II) phthalocyanine. The aligned CNTs have an average length about 10 μm and diameters ranging from 92 to 229 nm. Some of produced CNTs showed Y-junction structure due to the self-joint growth of two neighboring CNTs. The well-aligned CNTs indicated a bamboo-shaped multiwalled structure and fairly good crystallinity. The aligned CNTs follow tip growth mechanism. 相似文献
112.
J.J. Chen F.S. Choa P.S. Cho J.S. Wey J. Goldhar D.L. Butler G.L. Burdge 《Photonics Technology Letters, IEEE》1997,9(6):755-757
The gain recovery in a semiconductor optical amplifier (SOA) follows a two-step process: (1) an ultrafast gain recovery process through the nonlinear gain decompression effect and (2) a slower carrier recovery process that is dominated by carrier effects like Auger recombination or carrier diffusion. We discuss and numerically demonstrate how to control this decompression gain and apply it to very fast wavelength conversions. 相似文献
113.
Guk-Hwan An Tae-Yeon Hwang Yong-Ho Choa Kyoosik Shin 《Journal of Electronic Materials》2014,43(9):3574-3581
Strontium hexaferrite (SrFe12O19, SrM) suitable for high-performance permanent magnet applications was synthesized by salt-assisted ultrasonic spray pyrolysis (SA-USP) and subsequent calcination. To control the particle size, the intermediate phase of SrM was collected by SA-USP and various sizes of SrM were obtained by calcining the as-prepared sample at temperatures ranging from 800°C to 1050°C. The synthesized SrM was magnetically aligned by using an external magnetic field to improve remanence. The synthesized particles were of nano- to submicron scale and nonagglomerated. The magnetic properties and squareness of the material depended on the particle size and distribution. Additionally, the NaCl added during synthesis facilitated the formation of nonagglomerated particles, while enhancing and controlling particle growth. The optimum magnetic properties were achieved at calcination temperature of 1000°C, resulting in coercivity of 5646 Oe, saturation magnetization of 73.3 emu/g, and remanence of 59.1 emu/g (80.6% of M s). 相似文献
114.
Dongho Park Yong-Ho Kim Chul Woo Park Jungho Hwang Yong-Jun Kim 《Journal of aerosol science》2009,40(5):415-422
For collection and concentration of bioaerosols, we designed and evaluated a single stage virtual impactor, which was fabricated by micro-electro-mechanical systems (MEMS) process. The cut-off diameter of 1 μm was selected, since 1 μm is the lowest size as used in the US Government Joint Biological Point Detection System [Haglund, J. S., & McFarland, A. R. (2004). A circumferential slot virtual impactor. Aerosol Science and Technology, 38, 664–674; Moshier, T., & Buonaugurio, T. (2000). Joint Biological Point Detection System (JBPDS) requirements and design interplay. Proceedings of the First Joint Conference on Point Detection for Chemical and Biological Defense, October 23–27, 2000, Williamsburg, VA.] The design value of a 1 μm cut-off diameter required a nozzle width and thickness of 880 and 200 μm, respectively. The virtual impactor was evaluated for physical and biological collection efficiencies. For the performance evaluation of physical collection efficiency and wall loss, polystyrene latex (PSL) particles were generated from an atomizer and their size distribution was measured using an aerodynamic particle sizer (APS, TSI model 3321) and a scanning mobility particle sizer (SMPS, TSI model 3936). The measured cut-off diameter was 0.95 μm, which agreed with the calculated results (=0.94 μm) determined with a commercial computational fluid dynamics (CFD) package, FLUENT, and the measured wall loss was below 33.5%. For the performance evaluation of biological collection efficiency, Staphylococcus epidermidis bioaerosols were dispersed into air by a nebulizer. The bioaerosols were measured using APS and sampled with a bioaerosol sampler. The overall physical collection efficiency based on the number concentration was 73.8±3%, which was similar to the one based on the number of colonies (=76.7±7%). We found that most of the bioaerosols collected and concentrated by our virtual impactor were viable. 相似文献
115.
Jin-Mok Kim Yong-Ho Lee Hyukchan Kwon Kiwoong Kim Sasada I. 《Applied Superconductivity, IEEE Transactions on》2007,17(1):13-19
A double relaxation oscillation SQUID with a reference junction (RJ-DROS) already has a fixed reference current, so that it holds a fixed flux-to-voltage characteristics when fabricated. When an additional current flows through the reference junction but not through the signal junction in the RJ-DROS, we have obtained the variation of its characteristics. The additional reference current has an effect on reducing the fixed reference current, which results in changing averaged relaxation voltage and transfer coefficient. In particular, while the critical current of the signal SQUID exceeds the reference current, the averaged relaxation voltage at the reference junction is enlarged by the added bias current combined with an additional current and an initial bias current. Therefore the additional reference current can provide the RJ-DROS with variable modulation depth and width within the operating range. Although the characteristics of RJ-DROSs are fixed differently each to each when they are fabricated, the additional current can adjust their characteristics to the same one, which is useful for controlling DROSs in a multichannel DROS system. However, an input-bias current in the preamplifier detecting the outputs at the reference junction, acts as an additional current, and then makes the reference current shift from the optimum current or deviate from the operating range, the input-bias current needs to be regulated within the operating range 相似文献
116.
Package-level integrated antennas based on LTCC technology 总被引:1,自引:0,他引:1
Sang-Hyuk Wi Yong-Bin Sun In-Sang Song Sung-Hoon Choa Koh I.-S. Yong-Shik Lee Jong-Gwan Yook 《Antennas and Propagation, IEEE Transactions on》2006,54(8):2190-2197
We propose a novel package topology integrating multilayer miniaturized antennas. Such a functional package is suitable for the design of a system-on-chip device, or of system-on-package applications. A stacked patch antenna is designed and integrated in a package using a low temperature co-fired ceramic process. The overall size of the package is 10.3/spl times/10.3/spl times/1.3 mm/sup 3/, and this package contains an 8.3/spl times/8.3/spl times/0.7 mm/sup 3/ internal space for the integration of chip-scale packaged components. The package is mounted on a 20/spl times/20 mm/sup 2/ ground plane to miniaturize the volume of the system. The antenna is designed to have two neighboring resonant frequencies at 5.264 and 5.355 GHz, resulting in a 140 MHz impedance bandwidth. However, the measured resonant frequencies occur at slightly higher frequencies due to manufacturing tolerances. Radiation patterns are similar to a conventional patch antenna. In addition, various parasitic effects rooted in the package size, ground size, antenna height, SMA connector, via misalignment, and the number of via holes and their locations are fully investigated. 相似文献
117.
Conductive rubber materials for pressure sensors 总被引:2,自引:0,他引:2
118.
119.
Reliability of vacuum packaged MEMS gyroscopes 总被引:11,自引:0,他引:11
The greatest challenge for the successful commercialization of MEMS (micro-electro-mechanical system) technology is proving its reliability. Of concern in particular are the reliability and long-term stability of wafer level vacuum packaged MEMS gyroscope sensors subjected to cyclic mechanical stresses at high frequencies. In this study, we carried out several reliability tests and investigated the failure mechanisms of the anodically bonded vacuum gyroscope sensors designed for commercial electronic products. Particularly we studied mechanical reliability issues such as fatigue, shock, and vibration. It was found that successful vacuum packaging could be achieved through the optimization of the bonding process by reducing leakage and the deposition of titanium coating for reducing out-gassing inside the cavity. The effects of the pre-baking process are also described in this study. The current design of the gyroscope structure is found to be safe from fatigue failure for the 1000 h of operation test. The MEMS gyroscope sensor survives the drop and vibration qualification tests for electronic products without any damage, indicating the robustness of the sensor. The reliability test results presented in this study demonstrate that the MEMS gyroscope sensor is very close to commercialization. 相似文献
120.
Reports a tunable receiver based on a MQW-DBR laser biased just below threshold. The device simultaneously integrates the functions of a tunable filter, optical amplifier, photodetector and, if desired, an FSK discrimination. Using identical devices for both a transmitter and a receiver, we demonstrate FSK transmission up to 250 Mbit/s with sensitivities in the approximately -30 dBm range for 10/sup -9/ BER. Speed is limited by the transmitter FM response, and independent speed measurements indicate a detection bandwidth of at least 1.7 GHz.<> 相似文献