• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.219-223
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• 2003

This paper describes an estimation of DOA(Direction Of Arrival) measurement system using DBF receiver with linear array antenna. This DBF receiver is composed of resistive FET mixer using low IF mettled. A radio frequency(RF), a local oscillator(LO) and ail intermediate frequency(IF) considered in this research are 2.09 GHz, 2.08 GHz and 10 MHz, respectively. This receiver is composed of a band-pass filter, a low-pass filter, a DC bias circuit. DOA measurement system is consist of linear array antenna, DBF receiver, AD control box and computer in the anechoic chamber. Receiving antenna is 4-array monopole antenna and DBF receiver is 4-Ch resistive FET mixer without amplifier. DOA algorithm is implemented using MUSIC algorithm with high resolution. We show that the results of DOA is $-30^{\circ},\;0^{\circ}$ and $60^{\circ}$, respectively. And we know that DOA estimation error occur by antenna radiation pattern and fabrication error of antenna array.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.483-488
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• 2003

Frictional heating in brakes causes thermoelastic distortion of the contacting bodies and hence affects the contact pressure distribution. The resulting thermo-mechanical coupling can cause thermoelastic instability (TEI) if the sliding speed is sufficiently high, leading to non-uniform heating called hot spots and low frequency vibration known as hot judder. The vibration of brakes to the known phenomenon of frictionally-excited thermoelastic instability is estimated studying the interface temperature and pressure evolution with time. A simple model has been considered where a layer with half-thickness ${\alpha}$ slides with speed V between two half-planes which are rigid and non-conducting. The advantage of this properly simple model permits us to deduce analytically the critical conditions for the onset of instability, which is the relation between the critical speed and the growth rate of the interface temperature and pressure. Symmetrical component of pressure and temperature distribution at the layer interfaces can be more unstable than antisymmetrical component. As the thickness ${\alpha}$ reduces, the system becomes more apt to thermoelastic instability. Moreover, the evolution of the system beyond the critical conditions has shown that even if low frequency perturbations are associated with low critical speed, it might be less critical than high frequency perturbations if the working sliding speed is much larger than the actual critical speed of the system.

• 대한전자공학회논문지SD
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• 제44권10호
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• pp.17-22
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• 2007

이 논문에서는 PHS용 new automatic tuning 방법을 가지는 baseband complex bandpass filter를 제안하였다. DC offset 문제를 해결하기 위한 Low_IF 구조로 CMOS로만 집적된 PHS용 수신기를 설계하였다. ACS 특성을 만족시키기 위해 3차 Chebyshev complex filter를 이용하여 baseband를 선택할 수 있는 filter를 설계하였다. 새롭게 제시한 Comer frequency tuning 방법은 공정의 변화에 보상을 해주는 방식이고, MOS 스위치에 의한 노이즈 레벨을 감소시킨다. 이 filter는 CMOS 0.35um 공정이며, 전력소모는 12mW였다.

• 경영과정보연구
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• 제26권
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• pp.181-204
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• 2008

This study is to categorize five types of conflict handling styles that employees can take when conflict occurs. The five types are integrating, avoiding, dominating, obliging, and compromising. I found these factors that explain conflicts handling styles divided them into organizational structure, task group functioning and need styles and how certain factors explain different kinds of conflict handling styles without other factors. To measure conflict handling styles, this study used the scale of conflict style devised Rahim. Data were collected by the survey method from employees engaged in the service industry located Seoul, the Province of Gyeonggi, and the Province of Gangwon. In addition, in order to prove my hypothesis, I used hierarchical regression analysis method to find the pure explanation that each factors have without multicollinearity. According to the study's result, in a person's type of needs, if the need for achievement is high, they prefer integrating style. In contrast, if the need for achievement is low, they prefer avoiding style. Also, if the need for affiliation is high, the employees prefer compromising style. But if the need for affiliation is low and the need for dominance is high, the employees favor dominating style. However, in task group functioning, group homogeneity, group cohesiveness, and group goal clarity are high, or the confidence in peers and management is high, the employees prefer obliging style to other conflicts handling styles. As well as if group homogeneity, group cohesiveness, and group goal clarity are high, it was found that they prefer compromising style. Also, if the role conflict that is related to organizational structure is serious, employees prefer obliging style, but they have weakenss in explanation. To sum up these results, if the employees have obliging style that shows lack of concerns over themselves and at the same time, have high concerns to others, is affected by task group or organization. And we can infer that the other conflicts handling styles are effected by personal characteristic.

• 대한예방의학회:학술대회논문집
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• 대한예방의학회 1994년도 교수 연수회(역학)
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• pp.150-153
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• 1994

Receiver operating characteristic (ROC) curves have been frequently used to compare probability models applied to medical problems. Though the curves are a measure of the discriminatory power of a model. they do not reflect the model's accuracy. A supplementary accuracy curve is derived which will be coincident with the ROC curve if the model is reliable. will be above the ROC curve if the model's probabilities are too high or below if they are too low. A clinical example of this new graphical presentation is given.

• 한국전자파학회논문지
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• 제11권4호
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• pp.599-609
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• 2000

In this paper, sub-harmonically pumped single balanced resistive mixers are presented . Frequency bandwidth is selected for a Ku-band, which is 11.75-12.25GHz for RF, 5.375∼5.625 GHz for LO, and 1 GHz for IF signals. A rat-race hybrid is designed for the accomplishment of single balanced type. A low pass filter (LPF) with photonic band gap(PBG) structure is used for good conversion loss and unwanted harmonics suppression. Two types of mixers are suggested, which are one with no gate bias for no DC power consumption and the other with the IF amplifier for conversion gain. When a LO signal with the power of 6 dBm at 5.5 GHz is injected, a conversion loss of 12.17dB and a conversion gain of 7.83 dB are obtained for each mixer. For the both mixers , LO to RF isolation of 20 dB and LO to IF isolation of 60dB are obtained. With the RF power of -30dBm to -3dBm, the mixer shows linear characteristics region of IF. this mixer can be applied for Ku-band and other microwave communication systems.

• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.626-635
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• 2012

Most of single frequency GPS receivers utilize low-quality crystal oscillators. If a lowquality crystal oscillator is utilized as the time reference of a GPS receiver, the receiver's clock bias grows very fast due to its inherent low precision and poor stability. To prevent the clock bias becoming too large, large clock jumps are intentionally injected to the clock bias and the time offset for clock steering purpose. The abrupt changes in the clock bias and the time offset, if not properly considered, induce serious accuracy degradation in relative differential positioning. To prevent the accuracy degradation, this paper proposes an efficient and systematic method to eliminate the undesirable clock jump effects. Experiment results based on real measurements verify the effectiveness of the propose method.

• 대한전자공학회논문지
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• 제11권4호
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• pp.9-16
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• 1974

The low channels with frequency range of 54~88MHz and the high channels with frequency range if 174~216 MHz are in use for TV broadcasting in Korea. Since the ratio of the highest frequency to the lowest frequency is 4 to 1, only a logarithmic periodic antenna cou1d cover such an wide frequency range. But, this log-periodic antenna should be big in size. Studies have been done on an antenna of small size with reasonable gain which combines through a channel filter a LPD antenna if low channel with boom length of 2m and a LPD antenna of high channel with boom length of 1.8m. The whole antenna is connected to feeder line through a talun. Experiment shows that the gain of low and high channels is 7 dB and 9 dB respectively, which are lower than theoretical values br nomore than ldB. The difference seemed to come from slight impedance mismatches between antennas and feeder lines, loss in the filter and measurement errors.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.287-291
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• 1992

Recently, electronic engine control system is used in many automotives for high efficiency and low pollution. In order to perform these requirements, fuel injection control, spark timing control, knock control, exhaust gas recirculation control and idle speed control should be implemented. In this paper, idle speed control system using microcontroller is developed, which is compact in hardware, but powerful in software performing efficient control and various compensations for engine condition and environments. If idle speed is low engine operation is not smooth, reversely if high, fuel consumption is increased. Therefore idle speed must be maintained as low as possible within the scope that ensures smooth operation of engine. Also, an engine signal simulator, which generates various signals from engine, is realized for test facility.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1031-1035
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• 2007

When vehicles running, vertical force and lateral force act except load of vehicles to rail and wheel. This force happens by complex motion at running. If mark vertical force by P and lateral force by Q, derailment coefficient displays Q/P, most important indicator pointer of running safety judgment. If Q is grown than P from derailment coefficient, than arrived to derailment because wheel climb or jumps over rail. Wheel climb derailment among kind of derailment is when attack angle is +, wheel and rail strike and flange rides to rail. This derailment occurs much in curved line and occurs in low speed. In this study, occurred when running at low speed on curved line, analyze cause of derailment and presented the countermeasure plan.