• 한국전자통신학회논문지
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• 제9권11호
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• pp.1215-1220
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• 2014

본 논문은 GaAs MESFET를 이용하여 X-band 레이더용 국부발진기를 설계 및 제작하였다. GaAs MESFET는 매우 낮은 저잡음특성과 높은 전자이동도를 가지기 때문에 초고주파용 저잡음 발진기에 적합하다. 본 논문의 발진기 설계 방법은 RF 공진기를 사용하지 않고 능동소자의 부성저항 특성과 임피던스 정합법에 의해 이루어진다. 따라서 RF 공진기가 차지하는 면적을 줄일 수 있고 MMIC화가 가능하여 발진기의 크기를 소형화할 수 있는 장점이 있다. 설계된 발진기는 중심주파수 10.545 GHz에서 출력 2.30 dBm을 나타낸다.

• 대한한의학회지
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• 제25권4호
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• pp.43-50
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• 2004

Objective : Obesity is associated with degenerative arthropathy giving stress on joints. It also amplifies loads of weight bearing joints by changing the gravity line of the body. Our aim is to investigate the correlation between obesity and lumbar lordosis in obese pre-menopausal Korean females. The hypothesis was tested that there is a correlation between obesity and lumbar lordosis. Methods : A cross-sectional evaluation of 44 Females (baseline age 30.77 ± 6.46) with BMI 31.53 ± 3.82 (kg/㎡) was done. Body composition was measured using bio-impedance analysis (BIA), and anthropometry was done by the same observer. A lateral whole spine X-ray was taken in standing position to measure the lumbar lordotic angle (LLA), Ferguson angle (FA) and lumbar gravity line (LGL). A Pearson correlation was used to measure the correlation between obesity and lumbar lordosis (SPSS 10.0 for windows). Results : Body mass index (BMI kg/㎡) had a negative relationship with LLA((equation omitted)=-0.469), FA((equation omitted) =-0.347) and LGL((equation omitted)=-0.389). Body fat rate had a negative relationship with LLA only(γ=-0.385). Waist circumference had a negative relationship with LLA((equation omitted)=-0.345) and LGL((equation omitted)=-0.346). WH ratio had no relationship with lumbar lordosis. Conclusion : These data show that obesity is related to mechanical structures, such as lumbar lordosis. BMI was the most useful index, which reflects a change of mechanical structure of lumbar, more than other variables in this study.

• 대한전자공학회논문지
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• 제4권1호
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• pp.13-21
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• 1967

RC-NIC LPF 설계를 해석적으로 하는 방법을 취급하였으며 4차 타원함수특성을 갖도록 실제LPF를 설계하여 실험적으로 그 동작특성을 고찰하였다.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2000년도 하계학술발표대회 논문집 제19권 1호
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• pp.369-372
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• 2000

PZT 세라믹 트랜스듀서와 같은 압전 세라믹 진동자를 사용하는데 있어서 품질계수(quality factor)를 제어할 수 있다는 것은 전기-기계 결합계수나 삽입손실 등을 개선 할 수 있으므로 매우 유용한 것이다 본 연구에서는 압전 진동자의 품질계수를 제어하는 방법으로써 압전 진동자의 제동용량과 저항성분을 전기적으로 상쇄시킬 수 있는 부임피던스 변환회로(negative impedance converter circuit)를 적용하였다. 그 결과 부임피던스 변환회로를 적용하지 않은 경우에 비해 압전 진동자의 품질계수가 수십 배정도 까지 제어됨을 실험으로 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제28권10호
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• pp.1729-1734
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• 2007

The electrochemical behaviors of estrone in the presence of various surfactants were examined with great details. It is found that a cationic surfactant, cetyltrimethylammonium bromide (CTAB), obviously facilitates the electro-oxidation of estrone at carbon paste electrode (CPE) from the significant peak current enhancement and the negative shift of peak potential. Additionally, chronocoulometry and electrochemical impedance spectroscopy (EIS) were also used for further investigation of the electrode process of estrone, indicating that low concentration of CTAB exhibits excellent enhancement effects on the electrochemical oxidation of estrone, greatly enhances the diffusion coefficient and the electron transfer rate. Based on this, an electrochemical method was proposed for the determination of estrone. The oxidation peak current is proportional to the concentration of estrone in the ranges over 9.0 × 10?8 - 8.0 × 10?6 mol/L, and a low detection limit of 4.0 × 10?8 mol/L was obtained for 180s accumulation at open circuit (S/N = 3). Finally, this proposed method was demonstrated using estrone tablets with good satisfaction.

• 대한전자공학회논문지
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• 제19권5호
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• pp.20-25
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• 1982

무조건 안정한 트란지스터를 요구하는 주파수에서 케비티 공진궤환 루우프를 이용하여 마이크로파 발진기를 설계하는 방법을 제시한다. 필요한 주파수로 공진하는 높은 Q의 공진기를 궤환 루우프로 걸어줌으로써 그 주파수에서만 트란지스터치 출력 임피던스의 실수부가 부저항 특성을 갖게 할 수 있으므로, 주파수가 안정한 발진기를 구성한다. 본 연구에서는 실리콘 바이폴라 TR HXTR 2101과 Q가 크며, 실제 크기가 작은 리엔트런트 캐비티를 이용하여 발진 주파수 2.33GHz, 발진출력 10mW의 발진기를 실현하여 보았다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.429-432
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• 2005

This paper investigates how the PCB power-bus structure's characteristics are influenced by the loading of decoupling capacitors that are placed close to vias, on purpose or not. It is worthwhile to see the correlated effects of the aforementioned lumped elements in that when they inevitably share one DC power-bus they will result in positive or negative changes in the PCB EMC design. The EM fields and impedance profiles are rigously calculated on the PCB power-bus cases loaded with the above components and their effects will be given to bring better PCB EMC countermeasures.

• 전기학회논문지P
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• 제58권4호
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• pp.404-409
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• 2009

A DC power system has many loads with various functions. In particular, these sizable loads take the form of power electronic converters. When they are tightly regulated, the loads appear as constant power loads and result in negative incremental input impedance. Under certain conditions the effect of such loads on the power system is causes instability. In this paper, converter with a large storage capacitor and a lag compensator is proposed as a DC bus conditioner to mitigate the voltage transients on the bus. In addition, the proposed control approach has the advantage of performing both the functions of mitigating the voltage bus transients and maintaining the level of energy stored. Simulation and experimental results showed that the proposed control method was operated well in a small-scale DC power system that contained subsystems with constant power characteristics, such as DC/DC converters and electrical drives.

• 전기학회논문지P
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• 제54권4호
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• pp.163-170
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• 2005

This paper deals with an improved fault location algorithm with compensation ground capacitance through distributed parameter for a long parallel T/L. For the purpose of fault locating algorithm non-influenced by source impedance and fault resistance, the loop method was used in the system modeling analysis. This algorithm uses a positive and negative sequence of the fault current for high accuracy of fault locating calculation. Power system model of 160km and 300km long parallel T/L was simulated using EMTP software. To evaluate of the proposed algorithm, we used the several different cases 64 sampled data per cycle. The test results show that the proposed algorithm was minimized the error factor and speed of fault location estimation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.145-147
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• 2002

In this paper, the improved fault locating method using distributed parameter which calculating the reduced voltage and current according to the ground capacitance in long transmission line was proposed. For the purpose of the fault locating algorithm non influenced source impedance, the loop method was used in the system modeling analysis. To enhance the fault locating, zero sequence of the fault current which is variable according to ground capacitance was not used but positive and negative sequence. System model was simulated using EMTP software. To verify the accuracy of proposed method, in different cases 64 sampled data per cycle was used and 160km and 300km long transmission line has fault resistance $0{\Omega}\;and\;100{\Omega}$ respectively was compared.