김문일 교수

A monolithic true-time delay (TTD) network containing sixteen metal-to-metal contact RF microelectromechanical systems (MEMS) switches has been successfully fabricated and characterized. The TTD network was designed to produce flat delay time over a dc-to-40 GHz bandwidth with full 360-degree phase control at 22.5-degree intervals at 10.8 GHz. Measurements show a close match to the designed delay times for all sixteen switch states with 2.2 to 2.6 dB of insertion loss at 10 GHz. The worst group

A 100-element 10-GHz grid amplifier has been developed. The active devices in the grid are chips with heterojunction-bipolar-transistor (HBT) differential pairs. The metal grid pattern was empirically designed to provide effective coupling between the HBTs and free space. Two independent measurements, one with focusing lenses and the other without, were used to characterize the grid. In each case, the peak gain was 10 dB at 10 GHz with a 3-dB bandwidth of 1 GHz. The input and output return losse

RF MEMS switches have been successfully integrated with HEMT MMIC circuits on a GaAs substrate to construct a dual-path power amplifier at X-band. The amplifier uses two MEMS switches at the input to guide the RF signal between two paths. Each path provides single-stage amplification using different size HEMT devices, one with 80-μm width and the other with 640-μm. Depending on the required output power level, one of the two paths is selected to minimize the dc power consumption. Measurements sh

A field-effect transistor (FET) is one of the most commonly used semiconductor devices. Recently, increasing interest has been given to FET-based biosensors owing totheir outstanding benefits, which are likely to include a greater signal-to-noise ratio (SNR), fast measurement capabilities, and compact or portable instrumentation. Thus far, a number of FET-based biosensors have been developed to study biomolecular interactions, which are the key drivers of biological responses in in vitro or in v

Thin photonic crystal substrates are used to produce a TEM mode in a rectangular waveguide. Hexagonal pads arranged in honeycomb lattice and connected to the ground plane by substrate vias form the photonic crystal waveguide walls. Measurements on a Ku-band waveguide with two photonic crystal sidewalls showed a Field Flatness Efficiency (FFE) of better than 80% between 14.9 and 15.4 GHz, a substantial increase compared to the 50% of conventional rectangular waveguide. Simulations of a striped ph

An innovative anaerobic digestion elutriated phased treatment (ADEPT) has been evaluated at mesophilic (M-ADEPT) (35°C) and thermophilic (T-ADEPT) (55°C) temperatures in which the organic loading rate (OLR) was increased until reactor failure (pH<5.5). Single-stage continuously stirred tank reactors (CSTRs) at both temperatures were also operated as controls (M-CSTR for 35°C and T-CSTR for 55°C). The T-CSTR failed at an OLR of 7.4 g volatile solid (VS)/L day and the M-CSTR at an OLR of 10 g VS/L

A new phased-array antenna system concept for narrow-band frequency beam steering is introduced. The phase shift between neighboring antennas in the array is controlled by changing the frequency of the signal traveling along fixed delay lines in a series feed network. Diode mixers are added before each antenna to convert the frequency of the control signal to a constant radiating frequency. A complete transmit system, using microstrip patch antennas, was built on a 4/spl times/6 in/sup 2/ printe

BACKGROUND: Skin surface evaluation has been studied using various imaging techniques. However, all these studies had limited impact because they were performed using visual exam only. To improve on this scenario with haptic feedback, we propose 3D reconstruction of the skin surface using a single image. Unlike extant 3D skin surface reconstruction algorithms, we utilize the local texture and global curvature regions, combining the results for reconstruction. MATERIALS AND METHODS: The first ent

Abstract A thermal alkali pre‐treatment anaerobic digestion elutriated phased treatment (T‐ADEPT) was developed by combining the thermal‐alkali pre‐treatment (TAP) with the anaerobic digestion elutriated phased treatment (ADEPT) for the anaerobic co‐digestion of food waste (FW) and dewatered sewage sludge (SS). To improve the solubilization efficiency and methane yield, the optimal conditions for the TAP and ADEPT processes were identified. The soluble chemical oxygen demand (SCOD) solubilizatio

Municipal solid waste materials (MSWs) in landfills need a long period of stabilization because lignin compounds in MSWs and leachate are not readily biodegraded, but inhibit methanogenic metabolism. Recirculation of leachate into the landfill offers the potential advantage of increasing the rate of decomposition of organic matter. However, the degradation of lignin by leachate recirculation alone is quite difficult. Several recent studies have demonstrated that sulfate-reducing bacteria (SRB) w

본 연구에서는 우리나라 주요 수종을 대상으로 간벌강도 및 주기에 따른 흉고직경생장을 예측할 수 있는 동적생장모형을 개발하였다. 그동안 산림청에서 구축한 정적생장모형인 임분수확표를 이용하여 총 8개 수종에 대한 동적생장모형을 구축하였다. 간벌종류는 하층간벌을 전제로 하였으며, 간벌강도별로 간벌후의 흉고직경변화를 예측할 수 있는 함수식을 구축하였다. 또한, 임령, 지위지수 이외에도 ha당 본수를 설명변수로 하는 흉고직경여 총함수식을 유도하였다. 이와 같이 구축된수확표를 이여 모형을 이용하여 간벌강도 및 주기별로 확표를 이 다양하이여 될 수 있었다. 본 연구를 통해 개발된수확표를 용하여 모형을 이용해 숲가꾸기 등의 산림시업이 산림용하 및 임목축분수변화에 미치는 효과를 파악할 수 있으며, 나아이산림의 탄소흡수능력을 평가하는데 본 연구결과가 유용하게 활용될 수 있을 것이다.