• Clinical and Experimental Reproductive Medicine
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• 제21권3호
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• pp.253-259
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• 1994

A clinical investigation was undertaken on primary male infertility patients of recent 5 years. The results obtained were as follow: 1. Suspective etiologic factors were: 1) testicular failure, 36.1 %; 2) varicocele, 18.7%; 3) endocrine abnormality, 13.5%; 4) obstruction, 13.5%; 5) idiopathic, 10.9%; 6) cryptorchidism, 2.6%; 7) necrospermia, 0.9%. 2. On semen analyses, azoospermia was found in 55.8%, single abnormal parameter in 21.5 %, and multiple/all abnormal parameter in 22.7% of the 163 cases. 3. For the evaluation of the sensitivity and specificity of noninvasive variables in predict in obstruction as the cause of azoospermia in patient who had undergone testicular biopsy, the testicular size and serum follicle-stimulating hormone(FSH) level revealed 100% of sensitivity. 4. Among the 43 patients with a testicular biopsy confirmed diagnosis there was a significant difference in testicular size, ejaculate volume(p<0.0001) and serum FSH(p<0.0001) between patients with testicular failure and those with ductal obstruction. 5. Of 93 treated patients with primary male infertility, 42 were managed by medical treatment including endocrine treament, retrograde ejaculation treatment, infection treatment and observation; 29 were managed by surgical treatment including varicocelectomy, vasovasostomy, vasoepididymostomy and TUR of ejaculatory duct; 20 were managed by sperm preparation treatment including artificial insemination(AI), electroejaculation plus AI and vibration ejaculation plus AI ; 2 were managed by microscopic epididymal sperm aspiration plus IVF, repectively. 6. 42 patients who could be followed-up, 21 patients(50%) impregnated their wives.

• 한국항공우주학회지
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• 제40권6호
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• pp.536-541
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• 2012

새로 설계된 항공기 장착용 외장형 포드의 비행 시험용 계측포드를 설계하였다. 계측포드는 하중, 진동환경 및 공력 가열등 일반적인 항목뿐만 아니라 공력음향 환경에 대한 측정이 가능하도록 제작하였다. 특히 본 논문에서는 국내 최초로 수행 예정인 비행공력 음향 환경 측정에 대하여 집중적으로 다루었다. 계측포드는 MIL-HDBK-1763과 MIL-STD-810 Method 515에서 요구한 공력음향 시험요구 조건을 만족하도록 설계/제작되었다. MIL-STD-810에서 제시한 방법을 활용하여 공력음향 센서의 위치와 측정범위를 결정하였다. 센서는 혹독한 비행시험 환경을 고려하여 ENDEVCO 8510B-2를 사용하였다. 완성된 계측포드의 성능 시험을 위하여 KF-16 Sta. 5에 장착 후 지상 Run-Up 시험을 수행하여 자료를 획득하였다. 자료 분석결과 시스템은 정상적으로 작동하였으나, 공력음향 센서의 측정 범위를 상회하는 음압이 측정되어 비행 시험시 측정범위의 변경이 요구되었다.

• 시스템엔지니어링학술지
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• 제4권1호
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• pp.35-43
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• 2008

Generally, in analysis of reliability of Design and Development Phase, reliability of electrical components is analyzed based on standards such as MIL-HDBK-217F, Bellcore Issue 4,5,6 by analyzing stress of architectural side (Power, Voltage, Current and quality level of components) of weapon system and stress of operational side (operational environment, operational temperature, Operational Profile). But the reliability of mechanical components is analyzed based on the data book of failure history of mechanical parts called NPRD-95(Nonelectronic Parts Reliability Data-95) without any analysis of above stress. However, even if it's the same mechanical parts, it might have different failure rate(fatigue, wear, corrosion) during operation depending on how weary(stress : pressure, vibration, temperature during operation) the parts are. Therefore, analyzing reliability using just data book can cause big difference in reliability instead of analyzing based upon stressfulness that parts might have, operational concept, and other various factors. Thus, This paper will guide the way of predicting reliability by organizing ways of predicting reliability for system organization and adopt ing NSWC-98/LE1(Naval Surface Warfare Center-98/LE1) for mechanical components.

• 대한의용생체공학회:의공학회지
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• 제27권4호
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• pp.143-153
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• 2006

The purpose of this work was to assess and quantify the beneficial effects of gas exchange, while testingto the various frequencies of the sinusoidal wave that was excited by the PZT actuator, for patients suffering from acute respiratory distress syndrome (ARDS) or chronic respiratory problems. Also, this paper considered a simulator to design a hollow type artificial lung, and a mathematical model was used to predict a behavior of blood. This simulation was carried out according to the Montecarno's simulation method, anda fourth order Runge-Kutta method was used to solve the equation. The experimental design and procedure are then applied to the construction of a new device to assess the effectiveness of the membrane vibrations. As a result, the vibration method is very effective in the increase of gas transport. The gas exchange efficiency for the vibrating intravascular lung assist device can be increased by emphasizing the following design features: consistent and reproducible fiber geometry, and most importantly, an active means of enhancing convective mixing of water around the hollow fiber membranes. The experimental results showed the effective performance of the vibrating intravascular lung assist device. Also, we concluded that important design parameters were blood flow rates, fiber outer diameter and oxygen pressure drop. Based on the present results, it was believed that the optimal level of blood flow rates was 200$cm^3$/min.

• 한국철도학회논문집
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• 제11권6호
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• pp.543-549
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• 2008

철도 교통은 다른 교통수단에 비해 승객과 화물을 많이 수송할 수 있을 뿐만 아니라 안전성, 정시성(定時性) 및 환경 친화성 등의 장점을 갖고 있다. 철도를 다른 교통수단과의 경쟁력을 강화시키기 위해서는 열차의 속도 및 여객수송의 품질 향상 등이 필요하다. 특히, 승객이 여객수송의 품질에 대해 최종적으로 평가한다는 점을 감안할 때 승차감을 일정한 수준이상으로 향상시키는 것이 필수적이다. 일반적으로 철도차량에 대한 승차감은 차량의 진동 가속도를 측정한 후 인간의 등가 감응량으로 정량화시켜 평가하는 방법을 사용한다. 본 논문에서는 UIC 513R 규격에 따라 측정된 한국형 고속열차의 승차감 지수를 t-검정, 분산분석(ANOVA), 회귀분석 등과 같은 추리통계적인 방법론을 적용하여 분석 및 평가하고자 한다.

• 화약ㆍ발파
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• 제39권3호
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• pp.1-14
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• 2021

록버스트는 암석의 돌연하고도 격렬한 파괴를 일컫는 말이다. 이 파괴과정에서 초과에너지가 지진에너지로 방출되면, 주변의 암반 중에는 지반진동이 발생한다. 이렇게 생성된 지반진동의 수준은 리히터 로컬 척도로 규모 4.5 이상에 이를 수 있다. 이와 같은 록버스트는 인명에 위해를 가할 뿐 아니라 지하작업장과 지상구조물에까지 손상을 일으킬 수 있다. 본 논문에서는 캐나다 록버스트 종합연구 1단계 및 2단계 보고서를 토대로 록버스트의 발생기구를 분석하였다. 아울러 단순화된 LS-DYNA 모델을 작성하여 채광막장 암반에서 발파 직후 발생되는 인장균열의 발생양상을 분석하여 보았다. 이 단순화 모델의 개념은 록버스트의 발생기구를 파악하기 위해 실험실에서 수행되는 소규모 시험에 적용한다면 매우 유용할 것이다.

• 한국ITS학회 논문지
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• 제18권3호
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• pp.58-67
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• 2019

한전의 저압전송전선로로 이용되고 있는 지중저압접속함은 지중선로의 분기나 접속을 목으로 하고 있다. 지중저압접속함은 거리의 미관을 고려하는 효용성에 비하여 여름철 집중호우나 도로의 침수에 의하여 감전사고가 발생하는 등 안전대책이 필요하다. 본 논문에서는 지중저압접속함 내부에 온습도, $CO_2$, 수위, 가속도, 진동 센서를 장착하고 센서 데이터를 지그비모듈을 이용하여 지상으로 데이터를 전송한다. 지상과의 통신을 위한 안테나(볼티드 안테나)를 제안하여 이를 통한 데이터 수신을 확인하였다. 전송된 데이터는 LF 모드 및 HEX모드에서 완벽한 수신 성공률이 확인되었으며, 볼티드 안테나는 난환경 사태에서 실험한 결과 지중상태와 수중상태의 차이는 보이고 있으나, 지중저압접속함으로부터 10m 정도 떨어진 지상과의 통신에는 충분히 수신감도라고 판단되었다. 수신된 데이터는 PC기반의 GUI를 통해 확인할 수 있었다.

• Advances in concrete construction
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• 제7권2호
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• pp.87-96
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• 2019

Self-compacting concretes (SCC) are highly fluid concrete which can flow without any vibration. Their composition requires a large quantity of fines to limit the risk of bleeding and segregation. The use of crushed sand rich in limestone fines could be an adequate solution for both economic and environmental reasons. This paper investigates the influence of quarry limestone fines from manufactured crushed sand on rheological, mechanical and durability properties of SCC. For this purpose, five mixtures of SCC with different limestone fines content as substitution of crushed sand (0, 5, 10, 15 and 20%) were prepared at constant water-to-cement ratio of 0.40 and $490kg/m^3$ of cement content. Fresh SCC mixtures were tested by slump flow test, V-funnel flow time test, L-box height ratio, segregation resistance and rheological test using a rheometer. Compressive and flexural strengths of SCC mixtures were evaluated at 28 days. Regarding durability properties, total porosity, capillary water absorption and chloride-ion migration were studied at 180 days. For the two test modes in fresh state, the results indicated compatibility between slump flow/yield stress (${\tau}_0$) and V-funnel flow time/plastic viscosity (${\mu}$). Increasing the substitution level of limestone fines in SCC mixtures, contributes to the decrease of the slump flow and the yield stress. All SCC mixtures investigated achieved adequate filling, adequate passing ability and exhibit no segregation. Moreover, the inclusion of limestone fines as crushed sand substitution reduces the capillary water absorption, chloride-ion migration and consequently enhances the durability performance.

• 한국인터넷방송통신학회논문지
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• 제22권5호
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• pp.111-116
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• 2022

전동기 소손의 원인으로는 과부하, 결상, 구속, 층간단락, 권선의 지락, 순간과전압의 유입, 회전자가 고정자에 닿는 경우 등 절연파괴로 이어져 고장 또는 전기 사고로 이어지고 있다. 따라서 기기 고장은 기기의 보수/수리에 필요한 비용에 의한 손실뿐만 아니라, 전동기가 포함된 공정 자체를 멈추기 때문에 공정 정지에 따른 생산성 저하에 의한 막대한 경제적 손실을 초래한다. 전동기의 고장을 진단하기 위한 현재의 기술의 수준은 진동, 열, 전력분석 방식을 이용하고 있지만, 고장에 따른 상당 부분의 시간이 진행되어야 문제점을 분석할 수 있는 한계점을 가지고 있다. 따라서 본 논문에서는 이러한 문제점을 해결하고자 DC AMP 신호를 이용하여 절연저항을 측정하는 장치 및 알고리즘을 산업용 전동기에 적용하여 절연저항 상태값을 추종하여 기존방식에서 해결되지 못한 전동기의 열화 및 고장 진단을 제안한다.

• Steel and Composite Structures
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• 제44권1호
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• pp.65-79
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• 2022

The main goal of this paper is to study the vibration of damaged core laminated annular plates with FG face sheets based on a three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. In this study the effect of microcracks on the vibrational characteristic of the sandwich plate is considered. In particular, the structures are made by an isotropic core that undergoes a progressive uniform damage, which is modeled as a decay of the mechanical properties expressed in terms of engineering constants. These defects are uniformly distributed and affect the central layer of the plates independently from the direction, this phenomenon is known as "isotropic damage" and it is fully described by a scalar parameter. Three complicated equations of motion for the sectorial plates under consideration are semi-analytically solved by using 2-D differential quadrature method. Using the 2-D differential quadrature method in the r- and z-directions, allows one to deal with sandwich annular plate with arbitrary thickness distribution of material properties and also to implement the effects of different boundary conditions of the structure efficiently and in an exact manner. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. The sandwich annular plate is assumed to have any arbitrary boundary conditions at the circular edges including simply supported, clamped and, free. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution, and boundary conditions.