• 한국군사과학기술학회지
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• 제26권5호
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• pp.371-383
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• 2023

Artillery gun tube experiences very high pressure according to the blast of propellant charge. Therfore, it is essential to guarantee the structural safety of the gun tube. On the other hand, weight reduction of gun tube is also a crucial design factor since the agility of artillery vehicle directly leads to its survivability. In this line of thought, this work proposed an efficient design procedure which utilizes the convex combination of breech pressure and projectile base pressure time histories. Its efficiency is verified by comparing with other procedures. Other procedures utilize different computed max pressure rather than the convex combination design pressure. Additionally, a transient analysis is carried out considering the projectile movement and the corresponding pressure distribution through the newly developed ABAQUS user-subroutine. The analysis confirms the structural safety of the lightweight gun tube designed by the proposed method.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제15권4호
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• pp.305-314
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• 2015

The work presented in this paper deals with a navigation problem for multiple mobile robot system in unknown indoor environments. The environment is completely unknown for all the robots and the surrounding information should be detected by the proximity sensors installed on the robots' bodies. In order to guide all the robots to move along collision-free paths and reach the goal positions, a navigation method based on the combination of a set of primary strategies has been developed. The indoor environments usually contain convex and concave obstacles. In this work, a danger judgment strategy in accordance with the sensors' data is used for avoiding small convex obstacles or moving objects which include both dynamic obstacles and other robots. For big convex obstacles or concave ones, a wall following strategy is designed for dealing with these special situations. In this paper, a state memorizing strategy is also proposed for the "infinite repetition" or "dead cycle" situations. Finally, when there is no collision risk, the robots will be guided towards the targets according to a target positioning strategy. Most of these strategies are achieved by the means of fuzzy logic controllers and uniformly applied for every robot. The simulation experiments verified that the proposed method has a positive effectiveness for the navigation problem.

• 대한의용생체공학회:의공학회지
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• 제36권5호
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• pp.211-220
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• 2015

Recently, model-based iterative reconstruction (MBIR) has played an important role in transmission tomography by significantly improving the quality of reconstructed images for low-dose scans. MBIR is based on the penalized-likelihood (PL) approach, where the penalty term (also known as the regularizer) stabilizes the unstable likelihood term, thereby suppressing the noise. In this work we further improve MBIR by using a more expressive regularizer which can restore the underlying image more accurately. Here we used a spline regularizer derived from a linear combination of the two-dimensional splines with first- and second-order spatial derivatives and applied it to a non-quadratic convex penalty function. To derive a PL algorithm with the spline regularizer, we used a separable paraboloidal surrogates algorithm for convex optimization. The experimental results demonstrate that our regularization method improves reconstruction accuracy in terms of both regional percentage error and contrast recovery coefficient by restoring smooth edges as well as sharp edges more accurately.

• 소성∙가공
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• 제13권4호
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• pp.326-333
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• 2004

The nanoprobe based on lithography, mainly represented by SPM based technologies, has been recognized as a potential application to fabricate the surface nanosctructures because of its operational versatility and simplicity. However, nanoprobe based on lithography itself is not suitable for mass production because it is time a consuming method and not economical for commercial applications. One solution is to fabricate a mold that will be used for mass production processes such as nanoimprint, PDMS casting, and others. The objective of this study is to fabricate the silicon stamper for PDMS casting process by a mastless fabrication technique using the combination of nano/micro machining by Nanoindenter XP and KOH wet etching. Effect of the Berkovich tip alignment on the deformation was investigated. Grooves were machined on a silicon surface, which has native oxide on it, by constant load scratch (CLS), and they were etched in KOH solutions to investigate chemical characteristics of the machined silicon surface. After the etching process, the convex structures was made because of the etch mask effect of the mechanically affected layer generated by nanoscratch. On the basis of this fact, some line patterns with convex structures were fabricated. Achieved groove and convex structures were used as a stamper for PDMS casting process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.648-649
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• 2011

This Paper presents an efficient approach for solving the economic dispatch (ED) problems with valve-point effects using an combination of particle swarm optimization and harmony search. To reduce a premature convergence effect of PSO algorithm, We proposed PSO-HS algorithm considering evolutionary using harmony search algorithm. To prove the ability of the PSO-HS in solving nonlinear optimization problems, ED problems with non-convex solution spaces are solved with three different approach(PSO, HS, combination of PSO and HS)

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2004년도 춘계학술대회 학술발표 논문집 제14권 제1호
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• pp.523-527
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• 2004

This paper presents a new design methods of the short-term load forecasting system (STLFS) using the data mining. The proposed predictor takes form of the convex combination of the linear time series predictors for each inputs. The problem of estimating the consequent parameters is formulated by the convex optimization problem, which is to minimize the norm distance between the real load and the output of the linear time series estimator, The problem of estimating the premise parameters is to find the parameter value minimizing the error between the real load and the overall output. Finally, to show the feasibility of the proposed method, this paper provides the short-term load forecasting example.

• 한국정보전자통신기술학회논문지
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• 제10권6호
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• pp.545-551
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• 2017

인체 중심 설계가 요구되는 제품 설계에서 인체 형상 정보의 효과적인 추출은 매우 중요하다. 다양한 형태의 부정형곡선으로 이루어진 인체 형상 정보는 일반적으로 3차원 스캐너를 사용하여 얻어진다. 3차원 스캐너는 높은 신뢰도를 가지고 있으나 비용이 많이 들고 이동성에 제한을 받는다는 단점을 가지고 있다. 3차원 스캐너에 비해 매우 적은 비용으로 운용 가능한 사진측량기법을 이용하여 부정형 곡선에 대한 3차원 곡선 모델을 제작하고 오차를 살펴보았다. 3차원 곡선 모델은 원형곡선 위에 160, 80, 40, 20, 10, 5개의 특징점을 일정한 거리마다 위치시켜 제작하였다. 볼록 곡선의 경우 160, 80, 40, 20개의 특징점을 사용한 모델에서 원 곡선에 비해 작은 차이를 나타냈다 (최대 0.13%). 볼록-오목 곡선의 경우 160, 80, 40개의 특징점을 사용한 모델에서 원곡선에 비해 낮은 수준의 차이를 나타냈다 (최대 0.29%). 볼록 곡선의 경우 전체 곡선 길이의 5% 길이 마다, 볼록-오목 곡선의 경우 전제 곡선 길이의 2.5% 길이 마다 특징점을 위치시킬 경우 낮은 수준의 오차를 나타내는 곡선 모델을 얻을 수 있을 것으로 나타났다. 사진측량기법은 3차원 스캐너에 비해 저비용과 이동성이라는 장점을 갖는 대체 방법으로 충분한 가능성을 갖는다고 할 수 있다.

• 호남수학학술지
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• 제38권3호
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• pp.495-506
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• 2016

In this paper, we introduce and investigate a new subclass of meromorphic functions associated with a certain integral operator on Hilbert space. For this class, we obtain several properties like the coefficient inequality, extreme points, radii of close-to-convexity, starlikeness and meromorphically convexity and integral transformation. Further, it is shown that this class is closed under convex linear combination.

• 호남수학학술지
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• 제32권4호
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• pp.689-699
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• 2010

We discuss in this paper the notions of extended negative quadrant dependence and its properties. We study a class of bivariate uniform distributions having extended negative quadrant dependence, which is derived by generalizing the uniform representation of a well-known Farlie-Gumbel-Morgenstern distribution. Finally, we also study the limit behavior on the extended negative quadrant dependence.

• Kyungpook Mathematical Journal
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• 제59권4호
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• pp.651-663
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• 2019

In this paper, we introduce and study a new subclass of p-valent harmonic functions defined by modified operator and obtain the basic properties such as coefficient characterization, distortion properties, extreme points, convolution properties, convex combination and also we apply integral operator for this class.