• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.2
• /
• pp.67-71
• /
• 2012

In this paper, a push-push oscillator at K-band with a double H-shape metamaterial resonator (DHMR) based on high-Q is proposed with metamaterial structure to improve the phase noise and output power. The proposed oscillator shows low phase noise and high output power. DHMR is designed to be high-Q at resonance frequency through strong coupling of E-field. oscillators which are combined in push-push structure improve output power. The propose push-push oscillator shows the output power of 3.1 dBm, the fundamental signal suppression of -23.7 dBc and phase noise of -116.28 dBc at 100 kHz offset frequency and 20.20 GHz center frequency.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.3
• /
• pp.225-231
• /
• 2004

Disturbance observer (DOB) has been studied extensively and applied to many motion control fields during the last decades, but relatively few studies have been devoted to the development of analytic, systematic design methods for DOB itself, This paper thus aims to provide an analytic, systematic design method for DOB. To do this, DOB is structurally analyzed and the generalized disturbance compensation framework named robust internal-loop compensator (RIC) is introduced. Through this, the inherent equivalence between DOB and RIC is found, and the mixed sensitivity optimization problem of DOB is solved. Q-filter design is completely separated from the mixed sensitivity optimization problems of DOB although the proposed method has implicit .elation with Q-filter. Also, although the Q-fille. is separately designed with sensitivity function, the proposed DOB framework has the exactly same characteristic as the original DOB.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.7
• /
• pp.774-780
• /
• 2016

In this paper noise source and transfer path of tactical vehicle are analyzed with partial coherence function and spectrum analysis. Engine, transmission, structure panel and aerodynamic are main source of cabin noise. To reduce cabin noise, identifying transfer path of sources and analyzing their contribution is important. With modeling of transfer path and partial coherence function, transfer path and principal noise source can be identified. Engine/transmission and structural resonance are principal source of low frequency noise and by adding stiffener and sound absorbing material, resonance of vibration and inflow air problem can be solved.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.4
• /
• pp.365-374
• /
• 2016

The underwater radiated noise can be reduced by decreasing the structure borne noise of the on-board equipment. Therefore, the structure borne noise of the onborad installed equipment is strongly restricted by ROK navy with MIL-Std 740-2. Usually, the vibration transmissibility from the equipment to the hull of the ship is dependent on its mount characteristics. Even though the double mount structure is proper to apply for ship board application rather than single mount, it is not widely applied due to the weight and volume resriction of the ship. Therefore, in this research, the base using sandwitch panel which can act as double mount structure is suggested and its noise reduction capacity is verified with analytic calculation as well as experiment.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.08a
• /
• pp.82-83
• /
• 2000

굴절율이 외부보다 큰 실린더 (cylinder)나 스피어 (sphere)는 경계면에서의 전반사에 의해 손실이 매우 적은 high-Q 공진기가 될 수 있음이 잘 알려져 있다. 크기가 수 십 $mu extrm{m}$ 되는 실린더나 스피어에서의 공명모드는 편광(TM, TE), 모드 수 (mode number) n, 모드 순서 (mode order) l에 의해 정의되고 WGM (whispering gallery mode)라고도 불리워진다$^{(1)}$ . 모드 수n 이 클수록 모드 순서 l이 작을수록 공명모드의 Q 값은 큰 경향을 가진다. 액체 방울이나 액체 제트와 같이 열적 섭동에 민감한 마이크로 공진기 (micro-cavity)의 경우 Q값이 $10^{7}$ 정도로 제약되나, 실리카 마이크로 스피어 (micro-sphere)와 같은 고체 구에서 측정된 Q값은 약 $101^{10}$ 정도로 손실이 매우 적은 공진기가 될 수 있다$^{(2)}$ . 이와 같은 마이크로 공진기 특성을 이용하여 다양한 형태의 마이크로 공진기 레이저 대한 연구가 진행되어 왔다. 색소가 첨가된 고체구, 액체 방울, 액체 제트 등에서 기본적인 실험이 이루어졌고 반도체마이크로 스피어 구조에서 WGM 레이저$^{(3)}$ , polymer disc laser$^{(4)}$ , 광양자테 (photonic quantum ring)$^{(5)}$ 특성 연구 등이 실용가능성을 목표로 진행되고 있다. (중략)

• Review of KIISC
• /
• v.18 no.4
• /
• pp.30-41
• /
• 2008

국제표준화기구 ITU-T에서는 SG17 WP2 그룹이 정보통신 보안에 관한 표준화를 리드하는 연구그룹으로, 산하 7개의 연구과제(Question)를 구성하여 정보보호 국제표준을 개발하고 있다. 이 연구과제들 중 Q.9(의장, 염흥열, 순천향대)에서 는 안전한 통신 서비스라는 주제로 모바일 보안, 홈네트워크 보안, 웹 서비스 보안, P2P보안, 멀티캐스트 보안, USN 보안, NID(RFID) 보안, IPTV 보안, 응용서비스 및 응용 프로토콜 보안 등 정보통신 환경에서 다양하게 응용될 수 있는 국제표준들의 개발을 담당하고 있다. 현재, Q.9에서는 앞서 언급된 분야로 총 16건의 국제표준을 제정하였으며, 총 6건의 표준초안들이 개발중에 있다. 본 논문에서는 Q.9에서 개발한 국제표준들과 개발중에 있는 표준초안들에 대해 간단히 소개하고, 차기 연구회기(’09${\sim}$’12) 구조조정 방향에 따른 향후 추진방향을 제시하고자 한다.

• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.35-38
• /
• 2008

In this paper, study noise performance of LNA to enhance Q-factor of input circuit by patterned ground shield is inserted inductor using TSMC 0.18um. Applied LNA technology is cascode method. The input matching circuit was constituted on-chip and wirebonding inductor. Taguchi's method is used for the best suited structure of PGS. We confirmed enhancement of Q-factor by inserted PGS into inductor. The input matching circuit enhanced Q-factor by inductor with PGS improve noise figure of LNA.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.5B
• /
• pp.985-991
• /
• 2000

In this paper, the optimum structure of 2GHz magnetic thin film planar inductor were designed and fabricated to reduce the inductor area and to maximize the inductance L and quality factor Q of the inductor. The optimum design was performed utilizing Co90Fe10 layer multilayered with SiO2 layers to avoid the eddy-current skin effect and considering new lumped element model. New magnetic thin film inductors operating at 2GHz were fabricated on a Si substrate utilizing photo-lithography and lift-off techniques. The frequency characteristics of L, Q, and impedance in more than fifty identical inductors were measured using an RF Impedance Analyzer(HP4291B with HP16193A test fixture). The self-resonant frequencies(SRF) of the inductors were measured by a Vector Network Analyzer(HP8510). The developed inductors have SRF of 1.8 to 2.3GHz, L of 47 to 68nH, and Q of 70 to 80 near 1GHz. Finally, high frequency, high performance, planar micro-inductor(area=30.8 x 30.8il$^2$) with maximized L and Q were fabricated succefully.

• Korean Journal of Environment and Ecology
• /
• v.6 no.2
• /
• pp.113-126
• /
• 1993

To investigate the structure of the forest community of Huibang valley in Sobaeksan National Park, twenty five plots were set up and surveyed. According to the analysis of classification by DCA community divided 4 groups. The divided groups are Pinus densiflora community, Q. mongolica -P. densiflora community. Q. mongolica-Stewartia koreana-Carpinus laxiflora community, and Q. mongolica- Acer pseudosieboldianum community. In the analysis by ordination, CCA which points out the relationship among the environmental variables, species and plots indicated primary step of secondary succession. The successional trends of both techniques. seem to be from P. densiflora through Q. mongolica, Q. serrate to C. laxiflora(or S. koreana) in canopy layer below an altitude of 800 meters, and from Rhododendron mucronulaltum. Rh. schlippenbachli. Rhus trichocarpa through Styrax obassia. Lindera obtusiloba to Magnolia sieboldii, Corylus sieboldiana in subtree and shrub layer. The positive correlation between the stand ordination scores .and soil moisture and soil humus were calculated.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.11
• /
• pp.1207-1214
• /
• 2014

Under excessive plasticity, the fracture toughness of a material depends on its size and geometry. Under fully yielded conditions, the stresses in a material near its crack tip are not unique but rather depend on the geometry. Therefore, the single-parameter J-approach is limited to a high-constraint crack geometry. The JQ theory has been proposed for establishing the crack geometry constraints. This approach assumes that the crack-tip fields have two degrees of freedom. In this study, the crack-tip stress field of a fully circumferential surface-cracked pipe under combined loads is investigated on the basis of the JQ theory by using finite element analysis. The combined loads are a tensile axial force and the thermal gradient in the radial direction. Q-stresses of the crack geometry and its loading state are used to determine the constraint effects. The constraint effects of secondary loading are found to be greater than those of primary loading. Therefore, thermal shock is believed to be the most severe loading condition of constraint effects.