• Korean Journal of Mathematics
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• 제25권1호
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• pp.37-43
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• 2017

We study the existence of positive solutions of second order nonlinear separated boundary value problems of superlinear as well as sublinear type without imposing monotonicity restrictions on the problem. The type of problem investigated cannot be analyzed using the linearization about the trivial solution because either it does not exist (the sublinear case) or is trivial (the superlinear case). The results follow from a known fixed point theorem by noticing that the concavity of the solutions provides an important condition for the applicability of the fixed point result.

• Journal of Biosystems Engineering
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• 제20권4호
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• pp.313-322
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• 1995

This study was conducted to find the design factors of spraying device of the boom sprayer for low volume application. Specific objectives of this study were 1) to select proper nozzles for broadcast spraying and row crop spraying by the nozzle spray characterisic experiment, and 2) to investigate the coverage characteristic of rice plant at the row crop spraying. The results of this study are summarized as follows. (1) From the tested results on the droplet diameter spectrum and spray pattern the standard flat-fan nozzle and drift guard nozzle were judged as appropriate for the broadcasting. Even flat-fan nozzle showed similar span values to standard flat-fan nozzles and drift guard nozzle : however, the nozzles were found to be inappropriate for broadcasting because of their spray pattern. Hollow cone nozzle showed relatively small span values and uniform spray pattern. (2) For the upper and lower sides of the rice plants, coverage rates of even flat-fan nozzles and hollow cone nozzles were maximum at the second row, but decreased rapidly after the third row. For the middle side of the rice plants, coverage rates of them were maximum at the first row, but decreased rapidly. When one nozzle was tested, C.V. values were in the range of 90~160% and 60~160% on entire heights of rice plant for even flat-fan nozzles and hollow cone nozzles respectively. C.V. values at other parts were poor. Spray coverage rate at the middle part was improved by overlapping the nozzles whereas there was little difference on the upper and lower part of rice plants. (3) For spraying lower part of rice plant between rows, even flat-fan nozzles and hollow cone nozzle were judged as appropriate, but in order to ensure the uniform coverage, distance between nozzles, recommended to be less than 90cm.

• 한국항공우주학회지
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• 제49권1호
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• pp.21-30
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• 2021

탐색기를 탑재한 유도탄의 중기궤적은 탐색기 시야(FOV : Field-Of-View) 내에서 표적을 탐지하며, 전환 시점에서의 기동성을 최대화하도록 설계하는 것이 요구된다. 유도탄의 비행궤적 최적화 문제는 여러 구속조건이 적용된 비선형 문제로 일반적인 해석해를 도출하기 어렵기 때문에 그 동안 다양한 계산적인 방법들이 제시되어 왔다. 본 논문에서는 추진-활공 유도탄의 중기궤적 최적화 문제를 컨벡스 최적화 기법인 2차 원뿔 프로그래밍을 이용하여 산출하였다. 먼저, 운동방정식의 상태변수를 최소화하기 위해서 제어변수 구속조건이 추가된 제어변수 추가 형태의 운동방정식을 구성하였다. 또한, 자유 종말시간 문제와 추진시간 문제를 대처하기 위하여 정규화된 시간 변수를 독립 변수로 설정하였다. 그리고, 운동방정식과 제어변수 구속조건을 컨벡스 형태로 변환하기 위하여 각각 부분 선형화와 무손실 컨벡스 변환을 적용하였다. 마지막으로, 본 논문에서 제시된 방안의 타당성을 확인하기 위하여 비선형 최적화 프로그래밍 결과와 비교하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.711-722
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• 2020

An optimization framework using genetic algorithms has been developed towards an automated parametric optimization of the Octabuoy semi-submersible design. Compared with deep draft production units, the design of the shallow draught Octabuoy semi-submersible provides a floating system with improved motion characteristics, being less susceptible to vortex induced motions in loop currents. The relatively large water plane area results in a decreased natural heave period, which locates the floater in the wave period range with more wave energy. Considering this, the hull design of Octabuoy semi-submersible has been optimized to improve the floater's motion performance. The optimization has been conducted with optimized parameters of the pontoon's rectangular cross section area, the cone shaped section's height and diameter. Through numerical evaluations of both the 1st-order and 2nd-order hydrodynamics, the optimization through genetic algorithms has been proven to provide improved hydrodynamic performance, in terms of heave and pitch motions. This work presents a meaningful framework as a reference in the process of floating system's design.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제15권4호
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• pp.407-414
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• 2008

In this paper, we study the self-adjoint second order boundary value problem with integral boundary conditions: (p(t)x'(t))'+f(t,x(t))=0, t $${\in}$$ (0,1), x'(0)=0, x(1) = $${\int}_0^1$$ x(s)g(s)ds. A new result on the existence of positive solutions is obtained. The interesting points are: the first, we employ a new tool-the recent Leggett-Williams norm-type theorem for coincidences; the second, the boundary value problem is involved in integral condition; the third, the solutions obtained are positive.

• Journal of applied mathematics & informatics
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• 제27권3_4호
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• pp.475-487
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• 2009

This paper studies the iteration method of solving a type of second-order three-point boundary value problem with non-linear term f, which depends on the first order derivative. By using the upper and lower method, we obtain the sufficient conditions of the existence and uniqueness of solutions. Furthermore, the monotone iterative sequences generated by the method contribute to the minimum solution and the maximum solution. And the error estimate formula is also given under the condition of unique solution. We apply the solving process to a special boundary value problem, and the result is interesting.

• 대한방사선치료학회지
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• 제8권1호
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• pp.29-35
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• 1996

We are often faced with the clinical situations that is inevitably extended SSD for electron beam therapy due to anatomical restriction or applicator structure. But there are some difficulties in accurately predicting output and properties. In electron beam treatment , unlike photon beam the decrease in output for extended SSD does not follow inverse-square law accurately because of a loss of side scatter equilibrium, which is particularly significant for small cone size and low energies. The purpose of our study is to analyze the output in changing with the energy, cone size, air gap beyond the standard SSD and to compare inverse-square law factor derived from calculated effective SSD, mominal SSD with measured output factor. In addition, we have analyzed the change of PDD for several cones with different SSDs which range from 100cm to 120cm with 5cm step and with different energies(6MeV, 9MeV, 12MeV, 16MeV, 20MeV). In accordance with our study, an extended SSD produces a significant change in beam output, negligible change in depth dose which range from 100cm to 120cm SSDs. In order to deliver the more accurate dose to the neoplastic tissue, first of all we recommend inverse-square law using the table of effective SSDs with cone sizes and energies respectively or simply to create a table of extended SSD air gap correction factor. The second we need to have an insight into some change of dose distribution including PPD, penumbra caused by extended SSD for electron beam therapy.

• Imaging Science in Dentistry
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• 제45권4호
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• pp.205-211
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• 2015

Purpose: This study was performed to compare the accuracy of micro-computed tomography (CT) and cone-beam computed tomography (CBCT) in detecting accessory canals in primary molars. Materials and Methods: Forty-one extracted human primary first and second molars were embedded in wax blocks and scanned using micro-CT and CBCT. After the images were taken, the samples were processed using a clearing technique and examined under a stereomicroscope in order to establish the gold standard for this study. The specimens were classified into three groups: maxillary molars, mandibular molars with three canals, and mandibular molars with four canals. Differences between the gold standard and the observations made using the imaging methods were calculated using Spearman's rho correlation coefficient test. Results: The presence of accessory canals in micro-CT images of maxillary and mandibular root canals showed a statistically significant correlation with the stereomicroscopic images used as a gold standard. No statistically significant correlation was found between the CBCT findings and the stereomicroscopic images. Conclusion: Although micro-CT is not suitable for clinical use, it provides more detailed information about minor anatomical structures. However, CBCT is convenient for clinical use but may not be capable of adequately analyzing the internal anatomy of primary teeth.

• 구강회복응용과학지
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• 제37권4호
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• pp.268-273
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• 2021

Paramolar tubercle은 드문 발생학적 치아 기형으로 구치의 협면 또는 설면에서 나타나는 추가적인 교두로 정의된다. 영구치에 융합된 Paramolar tubercle의 존재는 근관치료를 어렵게 하는 원인이 될 수 있다. 그러므로 이러한 변이에 대한 적절한 이해가 성공적인 근관치료를 위해 중요하다. 콘빔 전산화 단층 촬영(CBCT)은 복잡한 증례에서 해부학적 구조를 이해하는 데 도움을 줄 수 있다. 따라서 본 증례는 Paramolar tubercle이 융합된 상악 제2소구치의 비외과적 근관치료에 대한 증례에 대해 보고하고자 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.311-316
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• 2001

The thin-layer Navier-Stokes equations are solved for the hypersonic flow over blunt cone configurations with applications to laminar as well as turbulent flows. The equations are expressed in the forms of flux-vector splitting and explicit algorithm. The upwind schemes of Steger-Warming and van Leer are investigated in their ability to accurately predict the heating loads along the surface of the body. A comparison with the second order extensions of these schemes is made and a hybrid scheme incorporating a combination of central differencing and flux-vector-splitting is presented. This scheme is also investigated in its ability to accurately predict heat transfer distributions.