• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2005년도 공동학술대회 논문집
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• pp.281-286
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• 2005

본 연구는 인공전류원 MT (CSAMT) 자료를 역산하기 위해 GRRI 알고리듬 분석을 실행하였다. 이 알고리듬은 MT 자료로부터 지반의 2차원 전도체 구조를 파악하기 위해 수정 RRI 알고리듬으로부터 독창적으로 개발된 것이나, 2.5차원 전진모델링을 결합시킬 수만 있다면, CSAMT자료까지 해석이 가능하다. 이러한 GRRI 근사감도는 정확한 1차원과 2.5차원의 감도와 비교함으로써 그 유용성을 검증할 수 있다. 그 결과, GRRI의 감도는 RRI 감도의 절반 정도이며 전반적으로 2.5차원의 감도와 매우 근사함을 보여준다. 비록 GRRI의 감도크기가 2.5차원의 감도보다 약간 크게 나타나고 있기는 하지만, 송신과 수신의 오프셋이 표피심도 1 보다 큰 경우의 감도는 유사하였다.

• 한국통신학회논문지
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• 제42권2호
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• pp.299-306
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• 2017

실수 M진 QAM 시스템은 PAPR을 낮추고 M 값을 점진적으로 증가시켜 채널 상태에 따라 전송 효율을 효과적으로 높일 수 있는 장점을 가지고 있으나, 분석의 복잡성으로 인해 근사적인 성능 분석만 수행되었다. 본 논문에서는 성상도 상의 신호 점들의 사용 빈도 차이로 인해 발생하는 경계선의 변화를 고려하는 정확한 성능분석을 수행한다. 그리고 PAPR에서 확연히 우수한 성능을 가지고 있는 2 시간 차원 ($3{\times}2^m$)진 QAM (홀수 m) 시스템의 성상도를 제안한다. 성능분석에 있어서 실수 M진 QAM에 대한 신호 점의 오류율과 비트 오류율을 m 값에 대하여 일반화하고 기존의 $2^k$진 QAM (정수 k)간의 성능을 비교한다.

• 대한기계학회논문집A
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• 제35권7호
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• pp.759-766
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• 2011

최근 가정용 에어컨은 냉방효율뿐 아니라 소음에 대한 중요성이 지속적으로 높아지고 있다. 로터리 압축기는 에어컨의 소음 중 매우 높은 영향도를 가지고 있으며, 압축기의 소음을 줄이기 위해 머플러 및 공명기에 관한 많은 연구들이 진행되어 왔다. 압축기의 부품 중 어큐뮬레이터는 큰 용적으로 인해 공명에 의한 추가 소음을 에어컨에 전달하는 소음 전달경로가 되며, 어큐뮬레이터의 내부구조는 소음저감을 위해 중요한 설계요소가 되나 지금까지는 연구결과가 미비한 수준이었다. 본 논문에서는 어큐뮬레이터의 소음 저감을 위해 목표주파수 대역에서의 투과손실이 최대가 되는 설계최적화를 수행하였다. 높은 비선형성을 가진 문제의 최적화를 위해 실험계획법과 반경기저신경망기법을 이용한 근사 모델을 사용하였으며, 유전알고리즘을 사용한 최적화를 수행하였다.

• 동의생리병리학회지
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• 제23권5호
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• pp.993-1002
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• 2009

The object of this study was to evaluate the single dose toxicity of Taeumjowui-tang(TUJWT), a polyherbal formula have been traditionally used as prevention or treatment agent for obesity, in male and female mice. Aqueous extracts of TUJWT (Yield = 10.5%) was administered to female and male ICR mice as an oral dose of 2000, 1000 and 500 mg/kg (body wt.) according to the recommendation of KFDA Guidelines. Animals were monitored for the mortality and changes in body weight, clinical signs and gross observation during 14 days after dosing, upon necropsy, organ weight and histopathology of 12 principle organs were examined. As results, we could not find any mortality, clinical signs, and changes in the body and organ weight except for diarrhea restricted in TUJWT 2000 mg/kg treated one male mouse at 1 day after administration, and increases of popliteal lymph node weights in all TUJWT administered groups. In addition, no TUJWT-treatment related abnormal gross findings and changes in histopathology of principle organs were detected except for increases of the frequency of hypertrophy and hyperplasia of lymphoid cells in the popliteal lymph nodes in all TUJWT treatment groups with some sporadic accidental findings. These increases of popliteal lymph node weights with hypertrophy and hyperplasia of lymphoid cells were considered that related to the immune modulate effect of TUJWT not toxicological signs. The results obtained in this study suggest that the TUJWT does not cause any toxicological signs. The 50% lethal dose and approximate lethal dose of TUJWT aqueous extracts in both female and male mice were considered as over 2000 mg/kg.

• Advances in Computational Design
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• 제5권4호
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• pp.363-380
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• 2020

In this paper, a cylindrical shell is immersed in a non-viscous fluid using first order shell theory of Sander. These equations are partial differential equations which are solved by approximate technique. Robust and efficient techniques are favored to get precise results. Employment of the Rayleigh-Ritz procedure gives birth to the shell frequency equation. Use of acoustic wave equation is done to incorporate the sound pressure produced in a fluid. Hankel's functions of second kind designate the fluid influence. Mathematically the integral form of the Lagrange energy functional is converted into a set of three partial differential equations. Throughout the computation, simply supported edge condition is used. Expressions for modal displacement functions, the three unknown functions are supposed in such way that the axial, circumferential and time variables are separated by the product method. Comparison is made for empty and fluid-filled cylindrical shell with circumferential wave number, length- and height-radius ratios, it is found that the fluid-filled frequencies are lower than that of without fluid. To generate the fundamental natural frequencies and for better accuracy and effectiveness, the computer software MATLAB is used.

• 한국음향학회지
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• 제20권8호
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• pp.3-11
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• 2001

본 연구에서는 SVD (Singular Value Decomposition)를 이용하여 다중입력과 다중출력을 가지는 시스템에서의 입력을 알아내기 위해 역변환 필터를 구현하였다. SISO (Single-Input and Single-Output)시스템의 입력과 출력의 관계에 대한 행렬공식화 작업을 확장하여 MIMO (Multi-Input and Multi-Output)시스템에 적용하였다. 그리고 시간영역과 주파수영역에서 최소위상 (Minimum phase)시스템과 비최소위상 (Non-minimum phase)시스템에 대한 그 역벽환에 대해 알아보았으며 비최소 위상요소에 대한 효과적인 역변환을 위해 SVD를 도입하였다. 먼저 전체시스템 행렬의 특이값 (singular value)을 계산하고 시스템의 위상에 대해 알아본다. 전체시스템이 비최소 위상인 경우 하나 이상의 매우 작은 특이값을 가지며 이는 시스템의 최소 위상/비최소 위상에 대한 정보를 가짐을 알 수 있다. 이를 이용하여 전체시스템에 대한 근사적인 역변환 필터를 구할 수 있으며 보다 근사적인 역변환 필터를 얻기 위하여 특이벡터를 이용하여 근사적인 역변환 필터를 얻었다. 수치적 예는 이러한 역변환 필터 행렬의 이용에 대한 잠재성을 보여준다.

• 한국운동역학회지
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• 제27권2호
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• pp.133-140
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• 2017

Objective: The purpose of this study was to determine the relationship between center of pressure (CoP) and local stability of the lower joints, which was calculated based on approximate entropy (ApEn) during walking in elderly women. Method: Eighteen elderly women were recruited (age: $66.4{\pm}1.2yrs$; mass: $55.4{\pm}8.3kg$; height: $1.56{\pm}0.04m$) for this study. Before collecting data, reflective marker triads composed of 3 non-collinear spheres were attached to the lateral surface of the thigh and shank near the mid-segment to measure motion of the thigh and shank segments. To measure foot motion, reflective markers were placed on the shoe at the heel, head of the fifth metatarsal, and lateral malleolus, and were also placed on the right anterior-superior iliac spine, left anterior-superior iliac spine, and sacrum to observe pelvic motion. During treadmill walking, kinematic data were recorded using 6 infrared cameras (Oqus 300, Qualisys, Sweden) with a 100 Hz sampling frequency and kinetic data were collected from a treadmill (Instrumented Treadmill, Bertec, USA) for 20 strides. From kinematic data, 3D angles of the lower extremity's joint were calculated using Cardan technique and then ApEn were computed for their angles to evaluate local stability. Range of CoP was determined from the kinetic data. Pearson product-moment and Spearman rank correlation coefficient were applied to find relationship between CoP and ApEn. The level of significance was determined at p<.05. Results: There was a negative linear correlation between CoP and ApEn of hip joint adduction-abduction motion (p<.05), but ApEn of other joint motion did not affect the CoP. Conclusion: It was conjectured that ApEn, local stability index, for adduction/abduction of the hip joint during walking could be useful as a fall predictor.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권6호
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• pp.1828-1847
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• 2014

Coordinated multi-point (CoMP) transmission has been regarded as a potential technology for LTE-Advanced. In frequency division duplexing systems, channel quantization is applied for reporting channel state information (CSI). Considering the dynamic number of cooperation base stations (BSs), asymmetry feature of CoMP channels and high searching complexity, simply increasing the size of the codebook used in traditional multiple antenna systems to quantize the global CSI of CoMP systems directly is infeasible. Per-cell codebook based channel quantization to quantize local CSI for each BS separately is an effective method. In this paper, the theoretical upper bounds of system throughput are derived for two codeword selection schemes, independent codeword selection (ICS) and joint codeword selection (JCS), respectively. The feedback overhead and selection complexity of these two schemes are analyzed. In the simulation, the system throughput of ICS and JCS is compared. Both analysis and simulation results show that JCS has a better tradeoff between system throughput and feedback overhead. The ICS has obvious advantage in complexity, but it needs additional phase information (PI) feedback for obtaining the approximate system throughput with JCS. Under the same number of feedback bits constraint, allocating the number of bits for channel direction information (CDI) and PI quantization can increase the system throughput, but ICS is still inferior to JCS. Based on theoretical analysis and simulation results, some recommendations are given with regard to the application of each scheme respectively.

• 한국전자파학회논문지
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• 제8권5호
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• pp.516-524
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• 1997

결합마이크로스트립 선로에서 여러형태의 펄스신호(가우시안 펄스, 구형 펄스, 사다리꼴 펄스, RF펄스)의 전 파특성을 해석하였다. 펼스신호의 시간영역의 응답을 구하기 위하여 비교적 정확성을 갖고 시율레이션하기에 편 리한 수치적분볍을 이용하였으며, 주파수에 따른 결합선로에서의 분산특성은 Kirschning과 Jansen의 closed f form 근사식을 사용하였다. 결합마이크로스트립 션로의 기하학적 구조(비유전율$\varepsilon_r$ , 기판두께 h, 스트립폭 w, 선로간의 간격 s)와 펄스폭 $\tau$ 등이 분산에 미치는 영향을 분석하였다. 그 결과 다른 파라미터에 비해 선로간의 거리가 펄스의 왜곡에 큰 영향을 주는 파라미터임을 알 수 있었다. 본 논문의 결과는 MIC 및 MMIC 회로의 설계시 마이크로스트립 선로의 비유전율, 기판두께, 스트립폭 그리고 선호 펄스의 펄스폭 등의 trade-off 결정에 적합하다.

• Wind and Structures
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• 제20권5호
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• pp.643-660
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• 2015

The wind tunnel test of large-scale sectional model and computational fluid dynamics (CFD) are employed for the purpose of studying the aerodynamic appendices and mechanism on suppression for the vortex-induced vibration (VIV). This paper takes the HongKong-Zhuhai-Macao Bridge as an example to conduct the wind tunnel test of large-scale sectional model. The results of wind tunnel test show that it is the crash barrier that induces the vertical VIV. CFD numerical simulation results show that the distance between the curb and crash barrier is not long enough to accelerate the flow velocity between them, resulting in an approximate stagnation region forming behind those two, where the continuous vortex-shedding occurs, giving rise to the vertical VIV in the end. According to the above, 3 types of wind fairing (trapezoidal, airfoil and smaller airfoil) are proposed to accelerate the flow velocity between the crash barrier and curb in order to avoid the continuous vortex-shedding. Both of the CFD numerical simulation and the velocity field measurement show that the flow velocity of all the measuring points in case of the section with airfoil wind fairing, can be increased greatly compared to the results of original section, and the energy is reduced considerably at the natural frequency, indicating that the wind fairing do accelerate the flow velocity behind the crash barrier. Wind tunnel tests in case of the sections with three different countermeasures mentioned above are conducted and the results compared with the original section show that all the three different countermeasures can be used to control VIV to varying degrees.