• 한국광학회지
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• 제34권2호
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• pp.76-83
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• 2023

본 논문에서는 랜덤 디더링을 이용한 링레이저 자이로 주파수 잠김 깨짐 특성을 수치적 실험을 통해 분석한 결과를 나타내었다. 디더링 진폭잡음 크기에 따른 링레이저 자이로 주파수 잠김 특성 변화 관찰을 통해 주파수 잠김 깨짐을 유발하는 최소 진폭 잡음 크기를 분석할 수 있었다. 해당 결과는 평균 디더링 진폭에 상응하는 동적 주파수 잠김 크기 및 회전 각속도 입력에 대응하여 사냑 효과에 의해 발생하는 주파수 사이의 상대적인 차이와 밀접한 관련이 있음을 확인하였다.

• 한국항만학회지
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• 제12권1호
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• pp.75-86
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• 1998

To design a coastal structure in the nearshore region, engineers must have means to estimate wave climate. Waves, approaching the surf zone from offshore, experience changes caused by combined effects of bathymetric variations, interference of man-made structure, and nonlinear interactions among wave trains. This paper has attempted to find out the effects of two of the more subtle phenomena involving nonlinear shallow water waves, amplitude dispersion and secondary wave generation. Boussinesq-type equations can be used to model the nonlinear transformation of surface waves in shallow water due to effect of shoaling, refraction, diffraction, and reflection. In this paper, generalized Boussinesq equations under the complex bottom condition is derived using the depth averaged velocity with the series expansion of the velocity potential as a product of powers of the depth of flow. A time stepping finite difference method is used to solve the derived equation. Numerical results are compared to hydraulic model results. The result with the non-linear dispersive wave equation can describe an interesting transformation a sinusoidal wave to one with a cnoidal aspect of a rapid degradation into modulated high frequency waves and transient secondary waves in an intermediate region. The amplitude dispersion of the primary wave crest results in a convex wave front after passing through the shoal and the secondary waves generated by the shoal diffracted in a radial manner into surrounding waters.

• Journal of Biosystems Engineering
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• 제2권1호
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• pp.7-24
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• 1977

This paper is the forth and fifth one of the study on balanced type oscillating mole drainer. In the light of the results from previous reports about the model tests, some design criteria were established and a prototype machine was set up for experimental purpose. Motion characteristics and functionof the each parts of the machine were checked and analyzed. After that, performance tests of the prototype machine were carried out in thefield. Obtained results are summarized as follows ; 1. Ten centimeter of the bullet diameter was determined so as to be able to attach it to the tractors with capacity of 30 PS to 40 PS. 2. To maintain the balance between the moments of the front shank and rear shank, the oscillating amplitude of the rear bullet was determined to be larger than that of the front bullet. At the same time , the oscillating direction of the rear bullet was designed with the inclines of ten to thirty degrees. 3. An octagonal dynamo transduced was developed for measuring the compressive force of the upper link is measuring the draft force of the machine. Acceptable linear relationship between forces and strain responses from O.D.T. was obtained. 4. Analysing the balancing mechanism of the acting part of the machine , it was found that the total draft force of the machine was equal to the difference between the sum of the draft force produced from the right and left side bending moments of the lower drawber and the compressive force on the upper link. 5. There are acceptable linear relationship between the strain and twisting moment by driving shaft, and between strain and shank moment. Above results enable us to carry out the field experiment with prototype machine. 6. When the test machine was used in the field, it was possible to reduce the oscillating acceleration by forty percent in average as compared it with the single bullet mole drainer. 7. When the test machine was used under the oscillating condition, the dratt torce was reduced by 27 percent to 59 percent as compared it with the test machine under non-oscillating condition, while the draft force was increased by 7 percent to 20 percent as compared it with the mole drainer having oscillating single bullet. The reasoning behind this fact was considered as the resistance force due to the rear shank and bullet. 8. As the amplitude and frequency of the bullet were increased, the torque was increased accordingly. This tendency could be varied with the various characteristics of the given soils. And the larger frequency and amplitute, the more increasing oscil\ulcornerlating power but decreasing draft brce were needed, and draft force was increased as the velocity was increased.9. When the amplitude of the rear bullet was designed to be larger than that of the front bullet, the minimum value of the moment was lowered and oscillating acceleration was reduced. And when the oscillating direction of the rear bullet was declined back\ulcornerwards, oscillating acceleration was increased along with the increasing angle of decli\ulcornernation. When the test machine was operated in high speed, the difference between maximum moments and minimum ones became narrow. This varying magnitude of moments appeared on the moment oscillogram seems to be correlated to the oscillating acceleration and draft force. 10. From the analysis of variance, it was found that those factors such as frequency, amplitude, and operating velocity significantly affected in the oscillating acceleration, the draft resistance, the torque, the moment, and the total power required. And interaction between frequency and amplitude affected in the oscillating acceleration. 11. Within the given situation of this study, the most preferable operating conditions of the test machine were 7 Hz in oscillating frequency, 0.54 m/sec in operating velocity, and 39.1 mm in oscillating amplitude of front and rear bullets. However, it is necessary to select the proper frequency and magnitude of oscillation depending on the soil properties of the field in which the mole drainer is practiced by use of a bal1nced type oscillating mole drainer. 12. It is recommended that a comparative study of the mole drainers would be performed in the near future using two separate balanced oscillating bullet with the one which is operated by oscillating the movable bullet in a single cylinder or other balanced type which may be single oscillating bullet with spring, damper or balancing weight, and that of thing. To expand the applicability of the balanced type oscillating mole drainer in practical use, it is suggested to develop a new mechanism which perform mole drain with vinyl pipe or filling material such as rice hull.

• 지구물리와물리탐사
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• 제11권3호
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• pp.242-249
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• 2008

AVO 분석은 지하의 가스 존재에 대한 직접적인 지시자로서 최근 탄성파 지하구조 단면도와 함께 석유탐사에 널리 이용되어져 왔다. 동해가스전과 같이 해저면 심부에 위치한 저류층의 경우 때때로 중합단면도 상에서 명점은 보이나 CMP 단면도 상에서 AVO 반응을 관찰하기가 어려운 경우가 종종 발생한다. 심부저류층의 경우 고결성이 증가하기 때문에 매질의 공극유체가 가스로 치환되더라도 매질의 P파 속도가 크게 감소하지 않으며 이로 인해 AVO 반응을 나타내는 주요 요소인 상부층과의 포아송비 차이도 크게 증가하지 않는다. 본 연구에서는 상 하부층의 포아송비를 달리하면서 포아송비의 차이가 AVO 반응에 미치는 영향을 분석하였다. 이를 통해 상 하부층의 포아송비 차이가 작아질수록 입사각에 따른 반사진폭의 변화량이 작아져 AVO 반응이 미미해짐을 관찰할 수 있었다. 이 결과를 이용하여 동해가스전의 AVO 반응의 한계점을 고찰하기 위해 탄성파 자료와 물리검층 자료를 이용하여 고래 V구조를 모사한 속도모델을 만들고 합성탄성파 탐사자료를 생성하였다. 매질의 성질을 이용하여 이론적으로 계산한 AVO 반응과 실제 합성탄성파 자료를 처리하여 얻은 AVO 반응을 비교한 결과, 상 하부층의 포하송비의 차이가 작을 경우 입사각에 따른 반사진폭 변화가 매우 작으며 잡음이나 전처리 과정 중에서 발생하는 진폭 왜곡에 의해 AVO 반응 특성이 가려짐을 확인할 수 있었다. 이러한 심부저류층의 AVO 분석의 한계점을 극복하기 위해서는 자료취득 단계부터 정확한 반사파 진폭을 획득해야 하며 자료처리 과정에서도 반사파 진폭을 보존할 수 있는 기술이 필요하다.

• 한국안광학회지
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• 제17권2호
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• pp.153-158
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• 2012

목적: 이 연구의 목적은 양안시가 정상인 20대 초반 성인의 폭주성조절(CA/C, convergence accommodation/convergence ratio)비를 평가하고 나이, 조절력 및 동공간거리(PD, interpupillary distance)와의 관련성을 분석하고자 하였다. 방법: 건강한 눈을 가진 44명(평균나이 $21.75{\pm}1.16$세)을 대상으로 조사하였다. CA/C비는 가우시안의 차(DOG, difference of Gaussian) 시표를 이용하여 검영법으로 측정하였다. 결과: 측정결과 CA/C비는 평균 $0.052{\pm}0.017$ D/$\Delta$이었다. CA/C비와 나이는 중간 정도의 음의 상관관계(r = -0.50, p = 0.0005)를, CA/C비와 조절력은 강한 양의 상관관계(r = 0.79, p<0.0001)를 보였으며, PD와 CA/C비의 상관관계는 없었다. 결론: 제시된 CA/C비는 19세에서 25세의 건안상태의 20대 초반 성인을 기준으로 측정한 평균값이다. 조절력과 CA/C비는 높은 상관관계를 보였다. 따라서 이 자료는 외국의 자료와 연령별, 성별, 양안시이상별 비교에 기본 정보로 활용될 것으로 본다.

• Journal of Korean Neurosurgical Society
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• 제29권5호
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• pp.635-639
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• 2000

Objective : Surgery for the microvascular decompression is mostly concerned with injury to the cranial nerves or brain stem by cerebellar retraction. Intraopeartive brain stem auditory evoked potentials(BAEPs) has been continuously monitored on surgery to evaluate the extent of injury, recovery of the nerves and prognosis. Methods : Of the 161 cases of CP angle surgery from Feb. 1996 to Apr. 1998, 103 cases were monitored during operation. Thirty five patients who had undergone similar surgery were selected and evaluated ; 23 patients were monitored and 12 were not during surgery. If monitor showed more than 0.5 mSec delay of latency, surgeon was given a warning not to retract brain any more. If more than 1mSec delay, surgeon was informed to stop surgery and wait for the returning of evoked potentials. The level of amplitudes and delay of latencies during the initial stage of operation, opening the dura, insertion of teflon patches, and closing the dura and recovery were then compared. Resuls : Twenty patients were male and 15 were female. Their average age was 50.26 years. Mean amplitude during the initial stage of operation was $0.60{\pm}0.25mV$, at opening the dura $0.56{\pm}0.26$, after teflon patches insertion $0.49{\pm}0.20$, and after closure of dura $0.47{\pm}0.28mV$. Mean latency during the early stage of operation was $6.08{\pm}0.67mSec$, at opening of dura $6.38{\pm}0.55$, insertion of teflon $6.97{\pm}0.59$, and closing the dura $6.17{\pm}0.54$. There was statistical significance in the difference of amplitudes between each procedures, and in the difference of latencies. For the complete recovery of amplitude and latency, it usually took average 5.65 minutes(0-20 min). In monitored group, only one patient required more than 20 minutes to recover and suffered from hearing disturbance after surgery. Others were recovered within 10 minutes without complications. However, 4 out of 12 patients who were not monitored showed hearing disturbance, and 1 patient had temporary facial palsy and dizziness(p＝0.000). Conclusion : The results indicate that continuous intraoperative monitoring of BAEPs during CP angle surgery is seen mandatory procedure to prevent operative complications.

• 한국해양환경ㆍ에너지학회지
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• 제13권3호
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• pp.174-180
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• 2010

변동 수심에서의 파랑변형을 비균질 Helmholtz 방정식을 이용하여 계산하였다. 포텐셜 함수가 존재한다고 가정하였으며, 변수분리를 적용하였다. 본 논문에서는 조화파만을 고려하였다. 포텐셜 함수로 구성된 지배방정식을 정수면에 직접 적용하였고, 변동 수심에 대한 비균질 Helmholtz 방정식을 얻었다. 파랑의 진폭과 위상차로 얻어진 복합 포텐셜 함수의 지배방정식을 실수형 변수로 된 두 방정식으로 분리하였다. 분리된 방정식들은 각각 1차와 2차 상미분 방정식이며, 이 방정식들을 단순한 형태의 중앙차분 수치기법을 이용하여 차분식으로 변형하였다. 측면 경계조건에서의 파랑의 진폭, 진폭경사, 그리고 위상경사를 경계면에 적용하여 전방진행방법으로 전 영역에서 해를 구하였다 Booij의 경사면 있는 저면의 경우와 Bragg의 물결모양이 있는 저면의 경우에 적용하였다. 본 연구로 도출된 비균질 Helmholtz 방정식은 완전 선형방정식 계산 결과, Massel의 수정 완경사 방정식, 그리고 Berkhoff의 완경사 방정식의 적용 결과와 비교하였으며, 만족스러운 결과를 얻었다.

• 천문학회지
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• 제48권2호
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• pp.125-137
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• 2015

We report results of the performance evaluation of a new hardware correlator in Korea, the Daejeon correlator, developed by the Korea Astronomy and Space Science Institute (KASI) and the National Astronomical Observatory of Japan (NAOJ). We conduct Very Long Baseline Interferometry (VLBI) observations at 22 GHz with the Korean VLBI Network (KVN) in Korea and the VLBI Exploration of Radio Astrometry (VERA) in Japan, and correlated the aquired data with the Daejeon correlator. For evaluating the performance of the new hardware correlator, we compare the correlation outputs from the Daejeon correlator for KVN observations with those from a software correlator, the Distributed FX (DiFX). We investigate the correlated flux densities and brightness distributions of extragalactic compact radio sources. The comparison of the two correlator outputs shows that they are consistent with each other within < 8%, which is comparable with the amplitude calibration uncertainties of KVN observations at 22 GHz. We also find that the 8% difference in flux density is caused mainly by (a) the difference in the way of fringe phase tracking between the DiFX software correlator and the Daejeon hardware correlator, and (b) an unusual pattern (a double-layer pattern) of the amplitude correlation output from the Daejeon correlator. The visibility amplitude loss by the double-layer pattern is as small as 3%. We conclude that the new hardware correlator produces reasonable correlation outputs for continuum observations, which are consistent with the outputs from the DiFX software correlator.

• 한국기계가공학회지
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• 제13권5호
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• pp.35-42
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• 2014

The influence of sine wave striated surface roughness on load carrying capacity of a bearing is studied for thin film effect of slider bearing. A Reynolds equation appropriate for slider bearing is used in this paper for analysis and it is discussed using finite difference method of central difference scheme. For a slider bearing with sine wave simple roughness form, several parameters such as pressure, load capacity and shear stress of the bearing can be obtained and also this results can be stored in sequential data file for latter analysis. After all, their distribution can be displayed and analyzed easily by using the matlab GUI technique. The parameters such as amplitude, number of waviness and slope of the surface are used for discussing the load carrying capacity of the rectangular bearing. The results reported in this paper should be applied to the other slider bearing such as rectangular or round embossed surface of slider bearing.

• 음성과학
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• 제9권3호
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• pp.3-16
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• 2002

We examined some problems in speaker identification procedures: transformation of acoustic parameters into auditory scales, invalid measurement values, and comparability of spectral energy values across the frequency range. To resolve those problems, we analyzed the acoustic spectral energy of three Korean numbers produced by ten female students from narrow-band spectrograms at 19 proportional time points of each voiced segment. Then, cells of the first five spectral matrices were averaged to form a matrix model for each speaker. The correlation coefficients and sum of the absolute amplitude difference in each pair of the spectral models of the ten subjects were obtained. Also, some individual matrix models were compared to those of the same subject or the other subject with a similar spectral model. Results showed that in numbers '2' and '9' subjects could not be clearly distinguished from the others but in number '4' it shed some possibility of setting threshold values for speaker identification if we employed the coefficients and the sum of absolute difference. Further studies would be desirable on various combinations of the range of long-term average spectra and the degree of signal pre-emphasis.