• 조명전기설비학회논문지
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• 제18권4호
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• pp.149-154
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• 2004

본 논문에서는, 구내용 저간섭 무선통신설비용 시스템으로서 이진 2m(zero-correlation duration) 확산코드를 이용한 저간섭 CDMA(code division multiple access)시스템을 제시하였다. 이진 ZCD확산코드는 확산코드의 주기가 N인 경우 그 값이 4부터 2의 배수로 계속 확장이 가능하기 때문에 코드발생기의 구현이 용이함과 동시에 ZCD 특성을 가짐으로 인해서, CDMA무선통신 시스템을 구내용 무선설비로 사용할 경우에 발생되는 다중접속 및 다중 경로로 인한 간섭문제를 확산코딩기법을 이용하여 근원적으로 해결해주는 역할을 한다. 본 논문에서는 제안한 이진 ZCD확산코드기반의 구내용 저간섭 CDMA시스템의 간섭완화 성능을 확인하기 위하여, AWGN(additive white gaussian noise) 및 MAI(multiple access interference), MPI(multi path interference)와 같은 잡음 및 다양한 간섭 환경 하에서의 BER(bit error rate)특성을 정량적으로 분석하고, 모의실험을 통해 제안시스템의 간섭완화 능력을 입증하였다.

• 전기학회논문지
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• 제60권10호
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• pp.1915-1923
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• 2011

For automated guidance control of a magnetically guided-all wheel steered vehicle, it is necessary to have information about position and orientation of the vehicle, and deviations from the reference path in real time. The magnet reference system considered here consists of three magnetic sensors mounted on the vehicle and magnetic markers, which are non-equidistantly buried in the road. This paper presents an observer to estimate such position and orientation at the center of gravity of the vehicle. This algorithm is based on the simple kinematic model of vehicle and uses the data of wheel velocity, steering angle, and the discrete measurements of marker positions. Since this algorithm requires the exact values of initial states, we have also proposed an algorithm of determining the initial position and orientation from the 16 successive magnet pole data, which are given by the magnetic measurement system(MMS). The proposed algorithm is capable of continuing to estimate for the case that the magnetic sensor fail to measure up to three successive magnets. It is shown through experimental data that the proposed algorithm works well within permissible error range.

• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.123-129
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• 1999

Ball-end milling process is widely used in the die and mold manufacturing because of suitable one for the machining of free-form surface. During the process, the pencil cutting operation can be adopted before finish cut to eliminate overload in uncut area caused by large diameter of ball-end mill. The ball-end mill cutter for the pencil cutting is easily deflected by cutting force due to the long and thin shape, and the tool deflection in pencil cutting is one of the main reason of the machining errors in a free-form surface. The purpose of this study is to find the characteristics of deflected cutter trajectory by constructing measurement system with eddy-current sensor. It was found that the severe reduction of corner radius produced the overcut during the plane cutting. Up cutting method induced the overcut both plane and slope cutting, but down cutting one induced the undercut. From the experiments, down cutting with upward cutting path can generate the small undercut surface.

• 소음진동
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• 제7권3호
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• pp.477-488
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• 1997

In order to control vibration in structures, it is desirable to be able to identify dominant paths of vibration transmission from sources through the structure to some points of interest. Structural intensity vector(power flow per width of cross section) using cross spectra is able to measure the vibration power flow at a point in a structure. This paper describes the structural intensity measurement of 2-dimensional structure. Structural intensity of 2-dimensional structure can be obtained from eight point cross spectral measurement per axis, or two point measurement per axis on the assumption of far field. Approximate formulation of the relation between bending waves in structures and structural intensity makes it possible to separate the wave components by which one can get a state of the vibration field. Experimental results are obtained on an infinite plate at the near and far field in flexural vibration. The measurement error of two point measurement is rather bigger than eight point measurement on account of the assumption that Poisson's ratio is 1. The structural intensity vectors on the plate are checked the ability to identify the path of vibration power flow in random excitation and 200Hz sine excitation, the result of two point measurememt is almost the same as the result of eight point measurement in 200Hz sine excitation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.598-603
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• 2007

The active control technique mostly uses the Least-Mean-Square (LMS) algorithm, because the LMS algorithm can easily obtain the complex transfer function in real-time, particularly when the Filtered-X LMS (FXLMS) algorithm is applied to an active noise control (ANC) system. However, FXLMS algorithm has the demerit that stability of the control is decreased when the step size become larger but the convergence speed is faster because the step size of FXLMS algorithm is fixed. As a result, the system has higher probability which the divergence occurs. Thus the Co-FXLMS algorithm was developed to solve this problem. The Co-FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. In this paper, the performance of the Co-FXLMS algorithm is presented in comparison with the FXLMS algorithm. Simulation results show that active noise control using Co-FXLMS is effective in reducing the noise in duct system.

• 한국대기환경학회지
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• 제17권4호
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• pp.313-319
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• 2001

The development of ozone SRP (Standard Reference Photometer) designated as a G-7 project by the Korean Ministry of Environment began 1997 and is now nearly completed. With the completion of the ozone SRP we will not only acquire a qualification to participate in the international ozone calibration system but also enhance calibration credibility of ozone similarly to that of other ambient air pollution monitors. As the ozone SRP uses highly cleaned blank air that can be distinguished from general ozone analyzer, it is possible to reduce errors associated with the determination of ozone via elongation of the absorption length as long as 1 meter In addition, gas chopping method hat been adopted to cut down interference of other substances and time drift. Furthermore, the system has also been modified to minimize the strayed ultra-violet noise along the light path. In this paper, a new method for uncertainty evaluation has been introduced, which is guided by the ISO (International Standard Organization) GUM (Guide to the Expression of Uncertainty in Measurement) through assessments of the uncertainty type B (that was impossible to estimate before) as well as the uncertainty type A (based on statistics).

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권11호
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• pp.2992-3007
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• 2012

Recently there has been an increasing interest in exploring the radio irregularity research problem in Wireless Sensor Networks (WSNs). Measurements on real test-beds provide insights and fundamental information for a radio irregularity model. In our previous work "LMAT", we solved the path planning problem of the mobile anchor node without taking into account the radio irregularity model. This paper further studies how the localization performance is affected by radio irregularity. There is high probability that unknown nodes cannot receive sufficient location messages under the radio irregularity model. Therefore, we dynamically adjust the anchor node's radio range to guarantee that all the unknown nodes can receive sufficient localization information. In order to improve localization accuracy, we propose a new 2-hop localization scheme. Furthermore, we point out the relationship between degree of irregularity (DOI) and communication distance, and the impact of radio irregularity on message receiving probability. Finally, simulations show that, compared with 1-hop localization scheme, the 2-hop localization scheme with the radio irregularity model reduces the average localization error by about 20.51%.

• 한국정보과학회논문지:정보통신
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• 제37권2호
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• pp.157-161
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• 2010

Vehicular Ad-Hoc Network(VANET)에서는 차량의 높은 이동성으로 인하여 빈번한 네트워크 단절이 일어난다. 본 논문에서는 이런 문제를 해결하기 위해 차량 밀도에 기반을 둔 경로 선택 알고리즘과 최소 홉 수를 유지하면서 end-to-end 패킷 전송 비율을 높이는 라우팅 알고리즘을 제시한다. 또한 교차로 근처에서 패킷을 전송할 때 건물로 인한 Packet Error Rate을 줄이는 다음 홉 노드 선택 알고리즘을 소개한다. 시뮬레이션 통하여 제안 알고리즘이 GPSR(Greedy Perimeter Stateless Routing for Wireless Networks)에 버퍼를 두어 패킷을 carry하도록 수정한 알고리즘보다 성능이 향상 된 것을 확인하였다.

• 한국항행학회논문지
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• 제5권2호
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• pp.158-164
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• 2001

본 논문은 도로 지면, 옆 차선의 차량 그리고 콘크리트 벽 반사를 포함하는 차량간 통신 시스템의 전파 모델을 제시했다. 그리고 광전파나 밀리미터파를 분석하는데 효과적인 Ray tracing 방법을 이용한 전파 손실과 지연 특성을 이론적으로 전개했다. 마지막으로 다이버시티, BCH 부호화 그리고 컨벌루션 부호화 기법을 이용하여 전파 특성의 향상을 보았다. 분석 결과, MRC 다이버시티와 BCH 부호화는 데이터 서비스 기준인 PER = $10^{-6}$을 만족할 수 없었다. 그러나 라이시안 페이딩에서 컨벌루션 부호화 기법을 채용했을 때 데이터 서비스 기준인 PER = $10^{-6}$을 만족하는 패킷 오율 특성을 얻음을 알 수 있었다.

• 대한의용생체공학회:의공학회지
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• 제33권3호
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• pp.105-113
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• 2012

Biopsy is a type of histopathological examinations, in which a physician samples cells or tissues from a patient's suspicious lesion. Such a lesion frequently resides deep inside human body, and then a percutaneous biopsy is therefore performed using a thick needle with the assistance of medical imaging such as computed tomography(CT) and magnetic resonance imaging(MRI). Recently modern robotic technology is being introduced to percutaneous biopsy in order to reduce any possible human error and hazard on physicians caused by medical imaging. After medical imaging locates the exact location of lesion, an optimization algorithm plans the path for a biopsy needle. Subsequently, a robot system moves the biopsy needle to the lesion in accurate and safe way with the control of a practitioner or automatically. In this article, we try to look into the state-of-art of percutaneous biopsy using such robotic technology. We classified percutaneous biopsy robots by mechanical characteristics and by imaging technology. Then, advantage and disadvantage of each class type are described as well as the basic description, and a few representative designs for each type are introduced. Current research issues of robotized percutaneous biopsy are subjectively selected for the readers' convenience. We emphasize the basic technology of actuator and sensors compatible with imaging technology to conclude this review.