• Structural Engineering and Mechanics
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• 제68권6호
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• pp.713-720
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• 2018

In this paper a new numerical method to determine the elastic curve of the simply supported beams of variable cross-section is demonstrated. In general case it needs to solve linear or small nonlinear second order differential equations with prescribed boundary conditions. For numerical solution the initial values of the slope and the deflection of the end cross-section of the beam is necessary. For obtaining the initial values a lively procedure is developed: it is a special application of the shooting method because boundary value problems can be transformed into initial value problems. As a result of these transformations the initial values of the differential equations are obtained with high accuracy. Procedure is applied for calculating of elastic curve of a simply supported beam of variable cross-section. Results of these numerical procedures, analytical solution of the linearized version and finite element method are compared. It is proved that the suggested procedure yields technically accurate results.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.401-413
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• 2022

This paper provides a simple method by which to estimate the cross-section stress profiles for nozzles designed according to ASME Code Section III. Further, this method validates the effectiveness of earlier work performed by the authors on standard nozzles. The method requires only the geometric information of the pressure vessel and the attached nozzle. A PWR direct vessel injection nozzle, a PWR outlet nozzle, a PWR inlet nozzle and a BWR recirculation outlet nozzle are selected based on their corresponding specific designs, e.g., a varying nozzle radius, a varying nozzle thickness and an outlet nozzle boss. A cross-section stress profile comparison shows that the estimates are in good agreement with the finite element analysis results. Differences in stress intensity factors calculated in accordance with ASME BPVC Section XI Appendix G are discussed. In addition, a change in the dimensions of an alternate nozzle design relative to the standard values is discussed, focusing on the stress concentration factors of the nozzle inside corner.

• 대한조선학회논문집
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• 제42권4호
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• pp.421-426
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• 2005

Scattering center extraction schemes for radar cross section reduction of large complex targets, like warships, was developed, which are an 1-D radar image method(range profile), and a direct analysis based on an object precision method. The analysis result of partial dihedral model shows that the presented direct analysis method is more efficient than the 1-D radar image method for scattering center extraction of interested targets, in terms of radar cross section reduction design, not signal processing. In order to verify the accuracy of the direct analysis method, a scattering center analysis of an naval weapon system was carried out, and the result was coincident with that of another well-known RCS analysis program. Finally, an analysis result of RCS and its scattering center of an 120m class warship-like model presented that the direct analysis method can be an efficient and powerful tools for radar cross section reduction of large complex targets.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.575-584
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• 2016

Considering the randomness and uncertainty of wind power, a reliability model of WTGs is established based on the combination of the Weibull distribution and the Markov chain. To analyze the failure mode quickly, we use the switch-section partitioning method. After defining the first-level load zone node, we can obtain the supply power sets of the first-level load zone nodes with each WTG. Based on the supply sets, we propose the dynamic division strategy of island operation. By adopting the fault analysis method with the attributes defined in the switch-section, we evaluate the reliability of the distribution network with WTGs using a sequential Monte Carlo simulation method. Finally, using the IEEE RBTS Bus6 test system, we demonstrate the efficacy of the proposed model and method by comparing different schemes to access the WTGs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.221-224
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• 2006

For structural engineers, design of pile cap causes difficulties since design of this member is not specifically addressed by codes. In general, pile cap is considered as deep beam and designed for shear and moment at specified critical section. This is called as traditional section method. However, many international design codes suggest the application of strut tie method for better design of this member. In this paper, a brief application of strut tie method to the design check of pile cap structure designed by section method is presented. Unlike well known pile cap with single column, the example pile cap has two columns. In order to find out proper load path under various load condition, three dimensional finite element method was carried out. The result indicates that provided reinforcement by traditional section method has sufficient capacity to meet the design requirements.

• Journal of Preventive Medicine and Public Health
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• 제31권4호
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• pp.751-769
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• 1998

본 연구는 임산부들의 분만전 분만방법에 대한 태도, 자신의 분만방법에 대한 이해 및 개입 정도, 분만후 분만방법에 대한 만족도 등을 평가하기 위하여 대구시내 1개 대학병원과 1개 산부인과 전문병원에서 산전진찰을 목적으로 내원한 임신 36주 이상의 임부 693명을 대상으로 분만전, 분만직후, 분만 1개월 후 3차례에 걸쳐 설문조사를 시행하였다. 임신기간 중 분만방법에 대한 교육이나 상담을 받은 임부는 24.0%였으며, 교육이나 상담을 받은 임부의 비율은 이전에 제왕절개분만을 한 임부에서 유의하게 높았다(p<0.05). 초산부, 자연분만을 했던 경산부, 제왕절개분만을 했던 경산부 모두 자연분만이 엄마나 아기의 건강에 더 좋다고 대답하였으나, 제왕절개분만을 했던 임부들 중 9.2%는 제왕절개분만이 아기의 건강에 더 좋다고 생각하였다. 분만전 선호하는 분만방법은 초산부와 자연분만을 했던 경산부는 90% 이상이 자연분만을 원했으나, 제왕절개분만을 했던 경산부는 85.6%가 제왕절개분만을 선호하였다. 분만전 자연분만을 선호하였던 임부들이 제왕절개 분만을 결정하게 된 이유는 의사의 권유가 81.9%, 남편의 권유가 0.8%, 충분히 상담후 결정한 경우가 4.7%, 산모가 원하여 12.6%였으며, 자연분만을 결정하게 된 이유는 대부분이 제왕절개분만을 할 특별한 사유가 없었거나(67.2%) 산모가 원한 것(30.6%)으로 나타났다. 제왕절개분만을 원했던 임부들의 제왕절개분만을 결정하게 된 이유는 의사의 권유가 76.2%, 산모가 원한 경우 20.0%, 남편의 권유가 1.3%, 의사와 충분히 상담후 결정한 경우는 2.5%였다. 의사의 권유로 제왕절개분만한 산모가 수술 이유에 대해 충분히 설명을 들은 경우는 55.1%였다. 제왕절개분만을 한 산모들의 수술 이유에 대한 의무기록과 산모 대답간의 일치율은 75.9%였으며, 반복 제왕절개분만일 경우와 산모가 원한 경우에 5% point 이상 응답을 차이가 났다. 초산부와 자연분만을 했던 경산부의 산전에 선호한 분만방법은 실제 분만방법과 유의한 관련성을 보였고(p<0.05), 제왕절개분만을 했던 경산부들은 선호도에 관계없이 100% 제왕절개분만을 하였다. 분만후 분만 방법별 자신의 분만방법에 만족하는 비율은 자연분만한 산모는 분만직후 84.9%, 분만 1개월 후 85.1%였으나 제왕절개분만을 한 산모는 분만직후 44.7%, 분만 1개월 후 42.0%로 나타냈다(p<0.05). 분만후 분만방법에 대한 선호도는 분만직후, 분만 1개월 후 모두 분만방법과 유의한 관계를 보였고, 각 시기별 분만방법에 대한 만족도와는 자연분만을 한 산모들은 자신의 분만방법에 만족할수록 자연분만을 선호하였지만, 제왕절개분만을 한 산모들은 만족 정도와 관계없이 제왕절개분만에 대한 선호도가 높았다. 이러한 결과는 그동안의 의사 중심의 전문적인 기술위주의 산전관리와 분만관리에서 기본적인 예방 및 건강증진 위주의 임부와 태아 중심 관리로의 방향 전환이 필요하며, 임부의 임신과 분만에 관한 적극적인 교육 및 상담이 필요하며, 분만방법 결정과정에 임부가 적극적으로 참여함으로써 제왕절개 분만율을 낮추고 제왕절개술후의 자연분만을 유도할 수 있을 뿐만 아니라 분만후 분만방법에 대한 만족도도 향상시킬 수 있음을 시사한다.

• 대한전자공학회논문지SD
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• 제39권7호
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• pp.26-36
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• 2002

z-cut $LiNbO_3$ 기판위에 3-section, 5-section 위상반전 전극을 가진 Mach-Zehnder형 진행파 광변조기를 설계 및 제작하였다. FDM(Finite Difference Method : 유한 차분법)을 이용하여 광도파로를 설계하였으며, MW(Microwave)전극 taper영역의 입${\cdot}$출력단에서는 CMM(Conformal Mapping Method: 등각사상법)을, 변조영역에서는 SOR(Successive Over Relaxation: 반복 이완법)을 이용하여 설계를 수행하였다. 제작된 소자의 S 파라미터를 측정하였다. 측정된 S파라미터를 이용하여 이론적으로 주파수응답 R(${\omega}$)을 구하였다. 3-section 전극의 경우 중심 주파수 25GHz에 ${\sim}$15GHz의 대역폭, 5-section의 경우 중심 주파수 45GHz에 ${\sim}$22GHz의 대역폭을 갖는 bandpass 동작을 나타낼 것으로 예측되었다.

• 대한조선학회논문집
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• 제45권6호
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• pp.695-702
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• 2008

In this paper, a new numerical method is proposed to analyze near-field sonar cross section of acoustically large-sized underwater targets such as submarines. A near-field problem is converted to a far-field problem using a spherical projection method with respect to the objective target. Then, sonar cross section is calculated with a physical optics well established in far-field acoustic wave scattering problems. The analysis results of a square flat plate compared with those obtained by other method show the accuracy of the proposed method. Moreover, it is noted that the sonar cross section is varied with respect to the targeting point as well as the range. Finally, numerical analysis results of real-like underwater target such as a submarine pressure hull are discussed.

• 한국정밀공학회지
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• 제15권9호
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• pp.175-181
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• 1998

The coil spring is used in the suspension of automotive vehicles and small omnibus. Recently, it can be adopted hardening type spring which spring constant is accompanied by increasing displacement to increase passenger comfortability. One of methods which assert this characteristic is cylindrical-taper section coil spring. In this paper we calculate ideal spring characteristic curve from the given vehicle conditions, and show the design method of the cylindrical-taper section coil spring.

• 한국군사과학기술학회지
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• 제14권1호
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• pp.100-105
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• 2011

Generally, because received signals from radar are very bulky, the data are divided into manageable size called section, and sections are distributed into several digital signal processors. And then, target detection algorithms are applied simultaneously in each processor. CFAR(Constant False Alarm Rate) algorithm, which is the most popular target detection algorithm, can estimate accurate threshold values to determine which signals are targets or noises within center-cut of section allocated to each processor. However, its estimation precision is diminished in section edge data because of insufficient surrounding data to be referred. Especially this edge problem of CFAR is too serious if we have many sections to be processed, because it causes many false alarms in most every section edges. This paper describes false alarm issues on MCA(Minimum Cell Average)-CFAR, and proposes a false alarm elimination method by changing section size alternatively. Real received data from multi-function radar were used to evaluate a proposed method, and we show that our method drastically decreases false alarms without missing real targets, and improves detection performance.