• Communications for Statistical Applications and Methods
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• 제16권1호
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• pp.137-141
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• 2009

We study on selecting the kernel weighting function in smoothing moment conditions for dependent processes. For hypothesis testing in Generalized Method of Moments or Generalized Empirical Likelihood context, we find that smoothing moment conditions by Bartlett kernel delivers smallest size distortions based on empirical Edgeworth expansions of the long-run variance estimator.

• Steel and Composite Structures
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• 제2권1호
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• pp.35-50
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• 2002

A series of tests on simple-welded plate specimens (SWPS) and T-stub tension specimens simulating some of the joint details in moment frame connections were conducted in this investigation. The effects of weld strength mismatch and weld metal toughness on structural behavior of these specimens were considered under both static and dynamic loading conditions. Finite element analyses were performed by taking into account typical weld residual stress distributions and weld metal strength mismatch conditions to facilitate the interpretation of the test results. The major findings are as follows: (a) Sufficient specimen size requirements are essential in simulating both load transfer and constraint conditions that are relevant to moment frame connections, (b) Weld residual stresses can significantly elevate stress triaxiality in addition to structural constraint effects, both of which can significantly reduce the plastic deformation capacity in moment frame connections, (c) Based on the test results, dynamic loading within a loading rate of 0.02 in/in/sec, as used in this study, premature brittle fractures were not seen, although a significant elevation of the yield strength can be clearly observed. However, brittle fracture features can be clearly identified in T-stub specimens in which severe constraint effects (stress triaxiality) are considered as the primary cause, (d) Based on both the test and FEA results, T-stub specimens provide a reasonable representation of the joint conditions in moment frame connections in simulating both complex load transfer mode and constraint conditions.

• 대한수학회보
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• 제54권3호
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• pp.917-933
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• 2017

In this paper, seven equivalent conditions of complete moment convergence and complete integral convergence for negatively orthant dependent (NOD, in short) sequences are shown under two cases: identical distribution and stochastic domination. The results obtained in the paper improve and generalize the corresponding ones of Liang et al. [10]). In addition, an extension of the Baum-Katz complete convergence theorem: six equivalent conditions of complete convergence is established.

• 임산에너지
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• 제18권2호
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• pp.84-91
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• 1999

The objective of this study was to present creep and the effects of mechano-sorptive deflection of drift pin moment resisting joint between LVL members under changing relative humidity (RH) conditions. The LVL members with steel gusset were jointed by a square pattern of eight injected drift pin. Three diameter drift pins were used to test specimens (6mm, 10mm, and 16mm). The creep test was conducted under two constant loading conditions : one at 30 kgf(840 kgf-cm) and the other at 60 kgf(1680 kgf-cm). The experiment was conducted in an open shed outside. (1)The total rotation creep model of moment resisting joing can be expressed as the sum of the creep of controlled environment (3-parameter model), dimensional change and mechano-sorptive deflection resulting from the variable environment. (2)Mechanosorptive rotation creep is recoverable as moisture content increases during adsorption. Least squares method for linear regression analysis was performed using mechano-sorptive rotation creep as the dependent variable and moisture content as the independent variable. The slope of low moment specimens are compared with those of high moment. This means that low moment condition is more easily affected by changes in humidity than high moment conditions. (3)Although creep deflection is higher for small diameter drift pin than for large diameter drift pin, the shape of creep deflection curves for all specimens is similar.

• 국제초고층학회논문집
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• 제2권4호
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• pp.355-365
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• 2013

The paper reports results of recent studies on the effects of column support conditions on the lateral displacements of moment frames at incipient collapse. The article presents a number of exercises in the plastic theory of structures that lead to useful design formulae. It has been shown that Drift Shifting (DS) is caused due to differences in the stiffnesses of adjoining columns, and that changes in drift ratios are more pronounced at first level column joints in both fixed as well as pinned base frames. In well proportioned moment frames, DS in the upper levels could be minimized, even reduced to zero. It has been demonstrated that DS can be eliminated in properly designed fixed and grade beam supported (GBS) moment frames. Several examples, including symbolic P-delta effects, have been provided to demonstrate the validity and the applications of the proposed ideas to the design and drift control of moment frames. The proposed methodology is exact within the bounds of the theoretical assumptions and is well suited for preliminary design and teaching purposes.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.357-364
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• 2004

A computational study on the supersonic flow around the lateral jet controlled missile has been performed. Case studies have been performed by comparing the normal force coefficient and the moment coefficient of a missile body for several different jet flow conditions, angle of attacks, circumferential jet locations, and spouting jet angles. For the several different jet flow conditions, which include the jet pressure, the jet Mach number, and the corresponding jet mass flow rate, the results show that the normal force coefficient is almost proportional to the jet thrust but the moment coefficient is not. Distinctly different flow phenomena can be noticed as the pressure ratio and the jet Mach number increase. By investigating the angle of attack effect to the normal force and the pitching moment, it has been identified that the normal force and the pitching moment show nonlinearity with respect to the angle of attack. From the detailed flow field analyses with respect to the jet flow conditions and the angle of attacks, it is verified that most of the normal force loss and the pitching moment generation are taken place at the low-pressure region behind the jet nozzle. Furthermore, the normal force and the pitching moment characteristics of the missile have been identified by comparing different circumferential jet locations and spouting jet angles.

• 대한수학회지
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• 제42권4호
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• pp.723-747
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• 2005

In this paper, we consider the quartic moment problem suggested by Curto-Fialkow[6]. Given complex numbers $\gamma{\equiv}{\gamma}^{(4)}\;:\;{\gamma00},\;{\gamma01},\;{\gamma10},\;{\gamma01},\;{\gamma11},\;{\gamma20},\;{\gamma03},\;{\gamma12},\;{\gamma21},\;{\gamma30},\;{\gamma04},\;{\gamma13},\;{\gamma22},\;{\gamma31},\;{\gamma40}$, with ${\gamma00},\;>0\;and\;{\gamma}_{ji}={\gamma}_{ij}$ we discuss the conditions for the existence of a positive Borel measure ${\mu}$, supported in the complex plane C such that ${\gamma}_{ij}=\int\;\={z}^i\;z^j\;d{\mu}(0{\leq}i+j{\leq}4)$. We obtain sufficient conditions for flat extension of the quartic moment matrix M(2). Moreover, we examine the existence of flat extensions for nonsingular positive quartic moment matrices M(2).

• 대한치과교정학회지
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• 제37권2호
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• pp.137-149
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• 2007

본 연구의 목적은 모멘트 변화에 따른 건조 환경과 타액 환경에서의 스테인리스강 브라켓과 여러 종류의 교정용 선재 사이의 마찰력을 비교하는 것이었다. 실험에는 $0.022"{\times}0.028"$ 스테인리스강 브라켓과 $0.019"{\times}0.025"$ 스테인리스강, 베타-티타늄, 니켈-티타늄 선재가 사용되었다. 활주 이동될 브라켓에는 0.9 mm 직경의 스테인리스강 선재로 제작된 길이 10 mm의 레버를 부착하였으며 레버에 100 g, 200 g의 추를 부착함으로써 브라켓에 각각 $1000g{\cdot}mm$ $(100g{\times}10mm)$, $2000g{\cdot}mm$ $(200g{\times}10mm)$의 모멘트를 가하고 만능시험기를 이용하여 마찰력을 측정하였다. 모든 조건에서 스테인리스강 선재가 가장 작은 마찰력을 보였으며 베타-티타늄과 니켈-티타늄 선재 사이에서는 $2000g{\cdot}mm$ 모멘트의 인공타액 하의 조건에서를 제외하고는 마찰력의 유의한 차이가 없었다 모든 선재에서 모멘트가 $1000g{\cdot}mm$인 때보다 $2000g{\cdot}mm$일 때 마찰력이 더 컸다. 건조 환경과 타액 환경의 비교에 있어서 $1000g{\cdot}mm$의 모멘트 하에서 인공타액에 의해 스테인리스강 선재의 마찰력은 증가하였으나 베타-티타늄과 니켈-티타늄의 마찰력은 증가하지 않았으며, $2000g{\cdot}mm$의 모멘트 하에서 인공타액에 의해 모든 종류의 선재에서 마찰력이 증가하였다.

• 대한조선학회논문집
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• 제61권4호
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• pp.236-246
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• 2024

The present study aims to identify the effects of the oblique inflow and vertical acceleration on a marine propeller's hydrodynamic force and moment. Computational Fluid Dynamics analysis is performed for a rotating propeller in open water conditions with heave motion after performing validation against experiment in straightforward conditions. The oblique inflow results in a linear increase of the off-axial component of the hydrodynamic force and moment rather than the axial one. Pitch and yaw moments due to the hull motion are dominated by the heave force and the moment arm of the propeller location. Additionally, the vertical acceleration leads to a linear augmentation of off-axial hydrodynamic force and moment, implying the added mass and moment of inertia. Notably, it is found that the off-axial hydrodynamic force and moment are dominated by the oblique inflow velocity rather than the acceleration.

• 한국산학기술학회논문지
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• 제20권12호
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• pp.418-424
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• 2019

백팩은 한쪽 어깨에 매는 가방에 비해 척추에 대칭적으로 무게분산이 가능하지만, 무게중심이 뒤쪽으로 이동하게 하여, 체간이 전방굴곡되는 자세 변형을 야기한다. 본 연구는 모멘트팔의 길이차이에 따른 가방 착용 시 균형과 보행에 미치는 영향에 대해 확인하였다. 정형외과적 손상 및 신경학적 손상이 없는 정상 성인 30명을 대상으로 하였다. 대상자는 1) 백팩 미 착용, 2) 일반적인 백팩, 3) 모멘트 길이를 감소시킨 백팩의 3가지 조건에서 각각 균형 및 보행을 측정하였다. 자세동요면적과 속도에서 백팩 미착용과, 일반적인 백팩, 특수 백팩의 3가지 조건에 따른 유의한 차이가 있었으나, 백팩의 모멘트팔의 길이에 따른 유의한 차이는 없었다. 양하지 지지기와 보행속도는 백팩 미착용과, 일반적인 백팩, 특수 백팩의 3가지 조건에서 유의한 차이가 있었으며, 양하지 지지기에서만 백팩의 모멘트팔의 길이에 따른 유의한 차이가 있었다. 본 연구의 결과를 통해 백팩 착용시 모멘트팔의 길이 변화가 보행에 도움이 될 수 있었다.