• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
• /
• pp.11-18
• /
• 2001

A close examination of the step calibrations for STS-2 seismometers installed by KMA has been done to deduce the response parameters of those instrument including angular corner frequency, damping factor and coil constant factor. A non-linear least square inversion method has been apple iud to estimate these parameters. The estimated parameters coincide with the manufactory specification with less than 1% error. This method will be extended near- future to deduce the response parameters for SS-1 short period seismometer.

• 대한전자공학회논문지
• /
• 제26권12호
• /
• pp.1910-1917
• /
• 1989

This paper shows the performances of asynchronous binary direct-sequence spread-spectrum multiple access communication systems with Rayleigh fading and White Gaussian noise. The performance measures considered are worst-case bit error probability and average SNR depending on code sequences and chip waveforms. The code sequences used are m-sequence and Gold sequence with period 31.The chip waveforms employed are rectangular, sinusoidal and something other chip waveforms.

• 한국지능시스템학회:학술대회논문집
• /
• 한국퍼지및지능시스템학회 1993년도 Fifth International Fuzzy Systems Association World Congress 93
• /
• pp.1203-1206
• /
• 1993

Fuzzy techniques are applied to the positioning of an elastic beam. The advantage is that the system model is not needed. A simple fuzzy friction compensator is also used. The final position is achieved within 3/2 the period of the fundamental mode. A fuzzy set of rules is applied for large-angle positioning, with adaptations that reduce the effects of shock. In this case, the final position is achieved within two fundamental periods. There is typically some final error attributed to the dry friction.

• International Journal of Reliability and Applications
• /
• 제2권1호
• /
• pp.49-56
• /
• 2001

In this paper we consider empirical Bayes estimation of the hazard rate and survival probabilities with right censored data under the assumption that the hazard function is constant over the period of observation and the prior distribution is gamma. We provide an estimator of the first derivative of the prior moment generating function that converges at each point to the true value in $L_2$ and use it to obtain, easy to compute, asymptotically optimal estimators under the squared error loss function.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.196.2-196.2
• /
• 2016

The design and development procedures of SF6 gas circuit breakers are still largely based on trial and error through testing although the development costs go higher every year. The computation cannot cover the testing satisfactorily because all the real processes arc not taken into account. But the knowledge of the arc behavior and the prediction of thermal plasmas inside SF6 interrupters by numerical simulations are more useful than those by experiments due to the difficulties to obtain physical quantities experimentally and the reduction of computational costs in recent years. In this paper, in order to get further information into the interruption process of a SF6 self-blast interrupter, which is based on the combination of thermal expansion and arc rotation, gas flow simulations with a CFD-arc modeling are performed during the whole switching process such as high-current period, pre-current zero period, and current-zero period. Through the complete work, the temperature of residual arcs as well as the breakdown index after current zero should be a good criterion to predict the dielectric capability of interrupters.

• 대한전자공학회논문지SD
• /
• 제37권8호
• /
• pp.48-56
• /
• 2000

회절격자의 인접한 반주기 길이 사이에 음의 상관관계가 있는 회절격자 반주기의 랜덤 변이가 QWS-DFB 레이저의 특성에 미치는 영향을 유효 굴절률 전달 매트릭스 방법을 이용하여 해석하였다. 상관계수가 0에서 -1로 가까이 감에 따라 랜덤 변이에 의한 회절격자 주기의 오차가 감소하면서 단일모드 안정성과 파장 정확도의 저하가 덜 심각해진다. 이는 랜덤 변이의 크기가 같다면 상관관계가 없는 전자빔 lithography 법으로 회절격자를 만들기보다는 optical lithography 법으로 만드는 것이 회절격자 주기 랜덤 변이의 영향을 줄이는 데에 유리함을 의미한다. 그리고 전자빔 lithography를 이용하여 DFB 레이저를 만들 때에 랜덤 변이의 영향을 줄이려면 분해능을 높이거나, 인접 반주기 길이의 랜덤 변이에 음의 상관관계를 주어야 한다.

• 전력전자학회논문지
• /
• 제25권1호
• /
• pp.1-5
• /
• 2020

Solar power generation systems require maximum power point tracking (MPPT) control to operate PV panels at their maximum power point (MPP). Most conventional MPPT algorithms are based on the slope-tracking concept. A typical slope-tracking method is the perturb and observe (P&O) algorithm. The P&O algorithm measures the current and voltage of a PV panel to find the operating point of the voltage at which the calculated power is maximized. However, the measurement error of the sensor causes irregularity in the calculation of the generated power and voltage control. This irregularity leads to the problem of not finding the correct MPP operating point. In this work, the power output of a PV panel based on the P&O algorithm is simulated by considering the insolation profiles from typical clear and cloudy weather conditions and the errors of current and voltage sensors. Simulation analysis suggests the optimal control period and perturbation voltage of MPPT to maximize its target efficiency under real weather conditions with sensor tolerance.

• 방송공학회논문지
• /
• 제11권1호
• /
• pp.100-106
• /
• 2006

본 논문에서는 지상파 디지털 방송시스템의 단일 주파수망 (SFN; Single Frequency Network) 구성을 위해 DTV (Digital Television)의 TxID (Transmitter Identification)용 저간섭 ZCD (Zero Correlation Duration) 확산코드를 제시하였다. ZCD 확산 코드는 코드발생기의 구현이 용이함과 동시에 ZCD 특성을 가짐으로 인해서, TxID에서 발생되는 인접코드 간섭 (ICI; Inter Code Interference) 및 다중경로 간섭 (MPI; Multi-Path Interference) 문제를 확산코딩기법을 이용하여 근원적으로 해결해주는 역할을 하고 있으며, 주기를 가변적으로 조절할 수 있어 TxID를 위한 워터마킹 (Watermarking)시에 발생하는 Truncated error 를 제거할 수 있다. 본 논문에서는 AWGN (Additive White Gaussian Noise) 잡음 및 ICI, MPI와 같은 다양한 간섭환경을 모의실험에 반영하여 도출된 DER (Detection Error Rate) 특성을 분석함으로써, TxID용 저간섭 ZCD 확산코드의 유용성을 입증하였다.

• 한국정보과학회논문지:시스템및이론
• /
• 제26권12호
• /
• pp.1493-1503
• /
• 1999

ATM Clustering System과 같이 SAN(System Area Network) 환경에서 동작하는 시스템은 낮은 지연시간과 넓은 대역폭의 네트워크가 필수적이나 기존의 에러 복구 프로토콜들은 이러한 요구를 충족시키기에는 큰 오버헤드를 가지고 있다. 제안된 새로운 에러 복구 프로토콜은 ATM Clustering System 환경에서 최적의 성능을 나타내는 light-weight 프로토콜로 에러가 없는 상황과 에러 복구가 진행중인 상황에 따라 acknowledgement 주기를 적응적으로 변화시키는 adaptive acknowledgement scheme를 제안하여 적용하였다. 제안된 프로토콜은 상용 툴인 SDT를 이용한 논리 검증 받았고, DEVSim++ 환경에서의 성능 분석을 통해 프로토콜이 최상의 성능을 보이기 위한 파라메터 값을 찾았고, 이 값을 적용하였을 때의 성능을 기존의 프로토콜과 비교하여 제안된 프로토콜이 더 우수함을 확인하였다.Abstract While a system working with SAN, such as ATM Clustering System, requires a network with low latency and wide bandwidth, the previous error recovery protocols have a serious network overhead to satisfy this requirement. The suggested error recovery protocol is a light-weight protocol which can shows its best performance at ATM Clustering System and uses a newly suggested adaptive acknowledgement scheme. In the adaptive acknowledgement scheme, the period of acknowledgement is dynamically changed depending on the state of the network. We proved the logical correctness of our protocol with SDT and did performance analysis with DEVSim++. From the analysis, we found the optimal parameter values for best performance and showed that our protocol works better than the previous error recovery protocols.

• 한국전문물리치료학회지
• /
• 제7권1호
• /
• pp.55-63
• /
• 2000

Physical therapists have been using balance and weight shifting training to induce improvements in standing and walking. This study compared the effects of kinetic feedback frequency and concurrent kinetic feedback on the performance and learning of a weight shifting skill in young, nondisabled adults. Sixteen young adults without known impairment of the neuromusculoskeletal system volunteered for the study. Subjects in each of three kinetic feedback groups performed a weight shifting task in an attempt to minimize error between their effort and a center of pressure (COP) template for a 12 second period. Feedback was provided: 1) concurrently (concurrent feedback), 2) after each trial (100% feedback), 3) after every other trial (50% feedback). Immediate and delayed (24 hour) retention tests were performed without feedback. During acquisition phase, the concurrent feedback group exhibited less error than either of the post response feedback group. For the immediate retention test, the 50% feedback group exhibited less error than did the 100% feedback and concurrent feedback. During the delayed retention, 50% feedback group displayed less error than did the other groups. But no significant differences were found between groups. These results suggest that practice with concurrent feedback is beneficial for the immediate performance, but not for the learning of this weight shifting skill. Lower frequency of feedback resulted in more permanent changes in the subject's ability to complete the task.