排序方式: 共有23条查询结果,搜索用时 31 毫秒
1.
Seong-Sik Myoung Yongshik Lee Jong-Gwan Yook 《Microwave Theory and Techniques》2007,55(7):1531-1538
This paper proposes a bandwidth-compensation method for miniaturized filters based on short-ended parallel coupled lines. Capacitive loading of such coupled lines is a relatively simple means of reducing the line lengths. In this study, a method is developed that predicts exactly the degree of reduction in the fractional bandwidth due to miniaturization. Using this method, the fractional bandwidth of the prototype coupled line filter can be adjusted, enabling miniaturized filters to maintain the targeted fractional bandwidth. The proposed bandwidth-compensation method applies for any type of filters with coupled lines realized with various transmission lines, with uniform or nonuniform line lengths. Experimental results are also presented that verify the validity of the method. 相似文献
2.
Miyamoto R.Y. Leong K.M.K.H. Seong-Sik Jeon Yuanxun Wang Yongxi Qian Itoh T. 《Vehicular Technology, IEEE Transactions on》2003,52(5):1181-1188
A wireless sensor server is developed based on a reconfigurable active smart-antenna/retrodirective array. The system can serve as both a retrodirective array transponder and a smart-antenna receiver simply by changing the frequency of the local oscillator applied to the mixers, enabling it to utilize its hardware best to suit its communication environment. When operating as a direct-conversion receiver, the receiver array successfully demodulates a quaternary phase-shift keying (QPSK) modulated signal with circuit gain of 7 dB, and E/sub b//N/sub 0/ for BER=10/sup -4/ is approximately 12 dB without any error correction. In the retrodirective array mode, the system provides 20 dB circuit gain and 20 dB radio-frequency/intermediate-frequency isolation at the center frequency as well as phase conjugation, exhibiting excellent retrodirectivity. The mixers perform phase conjugation and modulation simultaneously, enabling the transmission of locally stored data. The local data is successfully extracted by an interrogator. 相似文献
3.
In-Gyu Park Chang-Soon Lee Seong-Sik Hwang Hong-Pyo Kim Joung-Soo Kim 《Metals and Materials International》2005,11(5):401-409
In order to evaluate the stress corrosion cracking resistance for commercial alloys (C600MA, C600TT, C690TT) and Korean-made
alloys (K600MA, K690TT), C-ring tests were performed in a caustic environment of 4, 10, 20, 30, and 50% NaOH solution at 315°C,
for 480 h with an applied potential of 125 mV vs. OCP. Different stress corrosion cracking phenomena were observed according
to the NaOH concentration. The rate of caustic IGSCC attack did not appear to increase monotonically with caustic concentrations,
but peaked at a concentration between 4 and 50% caustic, or approximately 30% NaOH. Intergranular stress corrosion cracking
was found for C600MA in 10, 20, and 30% NaOH solutions, while no cracking was observed in the 4 and 50% NaOH solutions. In
30% NaOH solution, transgrnular stress corrosion cracking was detected in C690TT, which may be related with the large amount
of plastic strain (150% yield) and the applied potential (125 mV vs. OCP). The overall data clearly indicate that C600MA has
the worst SCC resistance while K690TT offers the best resistance. There is also fairly good correlation between the caustic
SCC susceptibility and some metallurgical parameters, particularly the grain size and the yield strength at room temperature.
Specifically, materials having larger grain size and lower yield strength exhibited higher caustic SCC resistance. 相似文献
4.
Safe arm design with MR-based passive compliant joints and visco—elastic covering for service robot applications 总被引:1,自引:0,他引:1
Seong-Sik Yoon Sungchul Kang Seung-kook Yun Seung-Jong Kim Young-Hwan Kim Munsang Kim 《Journal of Mechanical Science and Technology》2005,19(10):1835-1845
In this paper a safe arm with passive compliant joints and visco—elastic covering is designed for human-friendly service robots.
The passive compliant joint (PCJ) is composed of a magnetorheological (MR) damper and a rotary spring. In addition to a spring
component, a damper is introduced for damping effect and works as a rotary viscous damper by controlling the electric current
according to the angular velocity of spring displacement. When a manipulator interacts with human or environment, the joints
and cover passively operate and attenuate the applied collision force. The force attenuation property is verified through
collision experiments showing that the proposed passive arm is safe in view of some evaluation measures. 相似文献
5.
While an equation of state (EOS) plays a critical role in estimating thermodynamic properties, employing it in the determination
of binary interaction parameters is extremely important. In general, these parameters can be determined from phase equilibrium
data. However, data collection from experiments is a time-consuming and tedious process. In this study, after measuring the
excess enthalpies of binary systems containing CO2 by high-pressure flow isothermal microcalorimetry (IMC), we determined the EOS binary interaction parameters, specifically,
the Peng-Robinson EOS binary interaction parameters. These binary interaction parameters obtained by IMC were compared with
those obtained by vapor-liquid equilibrium (VLE) experiments. Hence, high-pressure flow IMC appears to be an effective method
for the determination of interaction parameters that are used in the estimation of thermodynamic properties. Further, the
Flory-Huggins interaction parameters of a binary mixture CO2 containing with various mole compositions were also estimated by employing high-pressure IMC. 相似文献
6.
Kim Sang-Wook Lee Yun-Soo Lee Ji-Woon Lim Seong-Sik Jung Taek-Kyun Hyun Soong-Keun 《Metals and Materials International》2020,26(5):660-667
Metals and Materials International - Lotus-type porous copper was fabricated by a centrifugal casting. The long cylindrical pores aligned along single direction was formed during unidirectional... 相似文献
7.
High isolation dual-polarized patch antenna using integrated defected ground structure 总被引:3,自引:0,他引:3
Younkyu Chung Seong-Sik Jeon Ahn D. Jae-Ick Choi Itoh T. 《Microwave and Wireless Components Letters, IEEE》2004,14(1):4-6
This letter presents a high isolation dual-frequency orthogonally polarized rectangular patch antenna utilizing microstrip feed line integrated with a defected ground structure (DGS). The demonstrated approach results in a significant improvement in port isolation in comparison to a conventional dual-polarized antenna fed by simple microstrip lines. Measurements show an improvement of 20 dB in port isolation relative to the conventional antenna, operating at 2 and 2.5 GHz. Image impedance of a microstrip line with DGS is controlled by the DGS geometry without modifying the dimension of the line. A 150 /spl Omega/ high impedance line is effectively implemented using a microstrip line with 75 /spl Omega/ line width by incorporating the DGS. 相似文献
8.
Seong-Sik Song Dong-Gu Im Hong-Teuk Kim Kwyro Lee 《Microwave and Wireless Components Letters, IEEE》2008,18(2):118-120
A differential wideband low-noise amplifier (LNA) based on the current amplification scheme is presented for digital TV tuners. In order to highly improve the linearity and exploit the noise cancellation, a common-gate stage with positive current feedback is integrated in parallel with a common-source stage using the current mirror amplifier. The proposed 0.18-mum CMOS LNA exhibits a power gain of 20.5 dB, an IIP3 of 2.7 dBm, an IIP2 of 43 dBm, and an average noise figure of 3.3 dB with 32.4 mW power consumption at a 1.8-V power supply and 0.12 mm2 area. 相似文献
9.
It is difficult to find physical properties data for systems containing ionic liquids, excess molar enthalpies, binary interaction parameter, etc. In this study, the excess molar enthalpies were measured for water+ethanol+ionic liquid system using a isothermal microcalorimeter at 298.15 K. The ionic liquid used was 1-butyl 3-methyl imidazolium tetrafluoroborate, [BMIM] [BF4]. The isothermal microcalorimeter (IMC) is a flow-type calorimeter that measures the heat of mixing directly, using specific mixing cell. By employing NRTL, electrolyte-NRTL and UNIQUAC models, binary interaction parameters were determined and investigated for the correlation with vapor liquid equilibrium (VLE). The e-NRTL model with the partial dissociation was employed to correlate the ionic liquid system. The binary data of VLE system were used from literatures. Specifically, UNIQUAC volume and surface area parameters were determined using Bondi radius. 相似文献
10.
An RF model of the accumulation-mode MOS varactor valid in both accumulation and depletion regions 总被引:2,自引:0,他引:2
Seong-Sik Song Hyungcheol Shin 《Electron Devices, IEEE Transactions on》2003,50(9):1997-1999
This work presents an RF model of an accumulation-mode MOS varactor with physical lumped elements derived from the device structure. The channel resistance was modeled by three resistance components to cover both accumulation and depletion regions with single equivalent circuit. With parameter values obtained by direct extraction, this model could accurately describe characteristics of the device without any optimization steps in the frequency range up to 18 GHz, as well as over a wide bias range. Due to the single topology, easy integration of the model into common circuit simulators is possible. 相似文献