• 대한원격탐사학회지
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• 제35권1호
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• pp.29-37
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• 2019

Synthetic Aperture Radar (SAR) observations are powerful tools to monitor surface's displacement very accurately, induced by earthquake, volcano, ground subsidence, glacier movement, etc. Especially, radar interferometry (InSAR) which utilizes phase information related to distance from sensor to target, can generate displacement map in line-of-sight direction with accuracy of a few cm or mm. Due to decorrelation effect, however, degradation of coherence in the InSAR application often prohibit from construction of differential interferogram. Offset tracking method is an alternative approach to make a two-dimensional displacement map using intensity information instead of the phase. However, there is limitation in that the offset tracking requires very intensive computation power and time. In this paper, efficiency of parallel computing has been investigated using high performance computer for estimation of glacier velocity. Two TanDEM-X SAR observations which were acquired on September 15, 2013 and September 26, 2013 over the Narsap Sermia in Southwestern Greenland were collected. Atotal of 56 of 2.4 GHz Intel Xeon processors(28 physical processors with hyperthreading) by operating with linux environment were utilized. The Gamma software was used for application of offset tracking by adjustment of the number of processors for the OpenMP parallel computing. The processing times of the offset tracking at the 256 by 256 pixels of window patch size at single and 56 cores are; 26,344 sec and 2,055 sec, respectively. It is impressive that the processing time could be reduced significantly about thirteen times (12.81) at the 56 cores usage. However, the parallel computing using all the processors prevent other background operations or functions. Except the offset tracking processing, optimum number of processors need to be evaluated for computing efficiency.

• 한국전자파학회논문지
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• 제19권1호
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• pp.46-53
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• 2008

일반적으로 카세그레 인 오프셋 복 반사경(Cassegrain Dual Offset Reflector)은 위성 통신용 안테나로 사용되지만, 여기서는 CPTR(Compact Payload Test Range)을 위한 반사경 시스템으로 해석하였다. 시험 영역의 근접 전계는 물리 광학법(Physical Optics)을 적용하여 계산하였다. CPTR은 균일한 평면파 제공을 목적으로 하며, 이를 위해 최소한의 진폭과 위상 리플(ripple)을 가져야 하며, 교차 편파 또한 작아야 한다. 따라서 본 논문에서는 반사경 구조 및 시험 영역의 위치에 따른 근접 전계 패턴을 구하여 전계의 리플, 테이퍼와 교차 편파를 고찰하였다. 특히 통신용 반사경 안테나에서는 나타나지 않는 안테나 축방향의 교차 편파 성분을 고찰하였다.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 1999년도 Proceedings of Pre-symposium of the 10th ISWPC
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• pp.149-152
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• 1999

A new process for deinking of colored offset newsprint, i.e. enzyme treatment in cooperation with ultrasonic wave was developed in the present study. The physical characteristics such as fiber length, coarseness, crystallinity index of the deinked pulps were investigated and the sugar residues released from the treatment were analyzed. It was found that colored offset newsprint could be deinked effectively by cellulase treatment when ultrasonic wave was applied. The brightness increased by 5% ISO over that of control experiment and the pigment content was reduced markedly. Though the ultrasonic wave had little effect on the strength and crystallinity of the pulp, the treatment of enzyme combined with ultrasonic wave reduced the coarseness and fiber length to some extent. It was also found that ultrasonic wave could accelerate the hydrolysis of cellulose and hemicellulose during the cellulase treatment.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 추계학술대회 학술발표 논문집
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• pp.187-190
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• 1998

The values of physical components of the plants and controllers as well as the relevant environmental conditions change in time, thus the output performance can be deteriorated during the operating span of the system. Naturally the duty of calibration or the prevention of performance deterioration due to excessive component sensitivity should be provided to the control system. The proposed controller, whenever necessary, measures the open-loop and close-loop characteristics, and then calculates the offset and sensor gain correction values based on the prepared standard measurements It is applied to the control of a flexible link system with the gain and offset calibration problems in the light sensor module for position to show the applicability. In this paper, we propose a digital controller which has the capability of calibration gain and offset adjustment using fuzzy methods.

• 제어로봇시스템학회논문지
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• 제21권7호
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• pp.669-676
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• 2015

In this paper, we described the simulation results of the phase offset performance of a clock in holdover mode which was normally operated in GPS Disciplined Oscillator (GPSDO). In the TIE model, we included the time error term caused by environmental temperature variation because one of the most important parameters of clock phase error is the frequency offset and drift caused by the variation of temperature. For the simulation, we employed Maximum Time Interval Error (MTIE) for the performance evaluation when the frequency offset and drift are estimated by using an Unbiased Finite Impulse Response (UFIR) filter with ladder algorithm. We assumed that the noise in the GPS measurement is white Gaussian with zero mean and 1 ns standard deviation, and temperature linearly varies with a slope of $1{^{\circ}C}$ per hour. From the simulation results, the followings were observed. First, with the estimation error of temperature of less than 3 % and the temperature compensation period of less than 900 seconds, the requirement of CDMA2000 phase synchronization under 10 us could be achieved for more than 40,000 seconds holdover time if we employ an OCXO (Oven Controlled Crystal Oscillator) clock. Second, in order to achieve the requirement of LTE-TDD under 1.5 us for more than 10,000 seconds holdover time, below 3 % estimation error and 500 seconds should be retained if a Rubidium clock is adopted.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.413-416
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• 1998

Sensitivity and calibration considerations are most important in the design and implementation of real control systems. Ideally parameter changes due to various causes should not appreciably affect the system's performances. But all the values of physical components of the plants and controllers as well as the relevant environmental conditions change in time, thus the output performance can be deteriorated during the operating span of the system. Naturally the duty of calibration or the prevention of performance deterioration due to excessive component sensitivity should be provided to the control system. In this paper, we propose a digital controller which has the capability of calibration and gain adjustment as well as the execution of control law. Specifically the problems of gain adjustment and offset calibration in the light source and CdS sensor module for position measurement in a flexible link system are considerably resolved. The parameters of measurement module are prone to change due to environmental brightness conditions resulting in poor steady state performance of the overall control system. Thus a proper method is necessary to provide correction to the changed values of gain and offset in the position measurement module. The proposed controller, whenever necessary, measures the open-loop characteristics, andthen calculates the offset and sensor gain correction values based on the prepared standard measurements. It is applied to the control of a flexible link system with the gain and offset calibration porblems in the light sensor module for position to show the applicability.

• 한국정밀공학회지
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• 제25권3호
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• pp.157-164
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• 2008

While developing physical prototype from CAD model, rapid prototyping mainly focuses on two key points reducing time and material consumption. So, we have to change from a traditional solid model to building a hollowed prototype. In this paper, a new method is presented to hollow out solid objects with uniform wall thickness to increase RP efficiency. To achieve uniform wall thickness, it is necessary to generate internal contour by slicing the offset model of an STL model. Due to many difficulties in this method, this paper proposes a new algorithm that computes internal contours computing offset model which is generated from external contour using wall thickness. Proposed method can easily compute the internal contour by slicing the offset surface defined by the sum of circle swept volumes of external contours without actual offset and the circle wept volumes. Internal contour existences are confirmed by using the external point. Presented algorithm uses the 2D geometric algorithm allowing RP implementation more efficient. Various examples have been tested with implementation of the algorithm, and some examples are presented for illustration.

• 공업화학
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• 제7권4호
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• pp.787-793
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• 1996

본 논문은 옵셋 잉크가 국내 신문고지의 탈묵에 미치는 영향을 조사하기 위해 국내신문 옵셋잉크의 조성분과, 그들 잉크로 옵셋 인쇄된 시료를 10, 30, 90, 180일 동안 열화시킨 후, 이들의 탈묵성을 비교하였다. 인쇄잉크의 조성분을 다르게 하여 인쇄한 시료는 열화기간이 증가될 수록 수율과 백색도가 감소되었다. 특히 아마인유의 첨가량이 많은 시료의 경우, 열화기간에 따라 많은 수율의 감소와 백색도의 저하를가져왔다. 따라서 아마인유의 첨가량은 탈묵에 결정적인 역할을 한다는 결론을 얻었다. 또한 로진변성페놀수지와 길소나이트가 포함된 시료는 열화과정을 통해 상대적으로 백색도의 감소가 있었다. 강도 측면에서 볼 경우, 열화기간에 따라 대체로 인장지수와 파열지수는 감소하였고, 인열지수는 증가했다. 그러나 아마인유만을 비이클 성분으로 사용한 시료의 경우 다른 시료에 비해 모든 강도가 낮았는데, 이것은 잉크와 섬유간의 강한 가교결합이 형성되어 초지 시 해리가 어렵기 때문이다.

• 한국전문물리치료학회지
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• 제12권1호
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• pp.91-99
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• 2005

We assessed whether the use of a symmetrical upper limb motion trainer in daily repetitive training for a 6-week period reduced spasticity and improved motor function in three chronic hemiparetic patients. Upper limb motor impairment and disability were measured by the Fugl-Meyer Assessment (FMA), Modified Ashworth Scale (MAS) and Manual Muscle Test (MMT), respectively. The electromyography (EMG) of the affected hand was recorded during isometric wrist flexion and extension. In all patients, FMA and MMT scores were significantly improved after the 6-week training. However, MAS scores of the affected wrist spasticity did not change considerably. Onset and Offset delays in muscle contraction significantly decreased in the affected wrist. The co-contraction ratio of flexor and extensor muscles significantly increased after the 6-week training. Onset and offset delays of the muscle contraction and co-contraction ratio correlated significantly with the patients' FMA. This study showed that repetitive, symmetric movement training can improve upper limb motor functions and abilities in chronic hemiparetic patients. Also, the EMG assessment of motor response is likely to provide insights into mechanisms and treatment strategies for motor recovery in chronic hemiparetic patients.

• 한국전문물리치료학회지
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• 제13권1호
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• pp.38-46
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• 2006

The purposes of this study were to investigate the median frequency (MDF) between initiation and termination of muscle contraction through surface electromyographic (sEMG) analysis and to propose the basis of clinical treatment for movement problems in early hemiparetic upper limbs. Thirteen patients who had stroke with onset less than 3 months prior to the study and seven control subjects participated in the study. The median frequency in initiation and termination of muscle contraction was recorded from wrist flexor and extensor muscles using the sEMG, with 3 second beeper signals, during maximal isometric wrist flexion and extension. Flexion and extension must be done as quickly and forcefully as possible. The results of the study were as follows: 1. The MDF of the onset and offset sections were significantly lower on the paretic than the nonparetic and control sides. 2. The MDF of the offset section significantly decreased on the paretic and nonparetic sides. Consequently, this study showed that the lowering of the MDF was due to the hemiparetic wrist motor impairment and muscle weakness. These results are also related to Fugl-Meyer motor assessment (FMA) scores in hemiparetic upper limbs. This study also suggests that since muscle weakness of early stroke patients affects the functional decrease of upper limbs, further studies must focus on the treatment to improve muscle agility and muscle fiber recruitment efficiency that can induce the functional recovery correlated to motor control.