• Structural Engineering and Mechanics
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• 제77권1호
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• pp.103-114
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• 2021

Ultra high strength concrete (UHSC) originally proposed by Richards and Cheyrezy (1995) composed of cement, silica fume, quartz sand, quartz powder, steel fibers, superplasticizer etc. Later, other ingredients such as fly ash, GGBS, metakaoline, copper slag, fine aggregate of different sizes have been added to original UHSC. In the present investigation, the combined effect of coarse aggregate (6mm - 10mm) and steel fibers (0.50%, 1.0% and 1.5%) has been studied on UHSC mixes to evaluate mechanical and fracture properties. Compressive strength, split tensile strength and modulus of elasticity were determined for the three UHSC mixes. Size dependent fracture energy was evaluated by using RILEM work of fracture and size independent fracture energy was evaluated by using (i) RILEM work of fracture with tail correction to load - deflection plot (ii) boundary effect method. The constitutive relationship between the residual stress carrying capacity (σ) and the corresponding crack opening (w) has been constructed in an inverse manner based on the concept of a non-linear hinge from the load-crack mouth opening plots of notched three-point bend beams. It was found that (i) the size independent fracture energy obtained by using above two approaches yielded similar value and (ii) tensile stress increases with the increase of % of fibers. These two fracture properties will be very much useful for the analysis of cracked concrete structural components.

• Physical Therapy Rehabilitation Science
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• 제11권4호
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• pp.471-477
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• 2022

Objective: The greatest motor impairment after stroke is a decreased ability to walk. Most stroke patients achieve independent gait, but approximately 70% do not reach normal speed, making it difficult to reach a standard of daily living. Therefore, a wearable exoskeleton is recommended for optimal independent gait because different residual disorders hinder motor function after stroke. This review synthesized the effect on gait speed in randomized controlled trials (RCTs) in which gait training using a wearable exoskeleton was performed on post-stroke patients for qualitative and quantitative analysis. Design: A systematic review and meta-analysis of a randomized controlled trials Methods: RCTs using wearable exoskeletons in robotic rehabilitation of post-stroke patients were extracted from an international electronic database. For quality assessment and quantitative analysis, RevMan 5.4 was used. Quantitative analysis was calculated as the standardized mean difference (SMD) and presented as a random effect model. Results: Five studies involving 197 post-stroke patients were included in this review. As a result of the analysis using a random effect model, gait training using a wearable exoskeleton in post-stroke patients showed a significant improvement in gait speed compared to the non-wearing exoskeleton (SMD=1.15, 95% confidence interval: 0.52 to 1.78). Conclusions: This study concluded that a wearable exoskeleton was more effective than conventional gait training in improving the gait speed in post-stroke patients.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 2006년도 추계 학술대회
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• pp.195-198
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• 2006

In this paper, we propose a 2dimension Control Chart. Suggested which Control chart augments Schwart Control chart which is 1-dimensional and Independent variable and dependent variable interrelationship by using control chart. Schwart control chart cannot use input variable and output variable together. In this paper, we try to analysis input variable and output variable dependent and effect. So called 2-dimensional control char.

• 한국경영과학회지
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• 제21권1호
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• pp.163-170
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• 1996

An errors-in-variables model (EVM) differs from the classical regression model in that in the former the independent variable is also subject to error. This paper shows that to assess the applicability of the ordinary least squares (OLS) estimation procedure to the EVM, the relative dispersion of the independent variable to its error variance must be also considered in addition to Mandel's criterion. The effect of physically reducing the variance of errors in the independent variable on the performance of the OLS slope estimator is also discussed.

• 동력기계공학회지
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• 제20권3호
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• pp.36-42
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• 2016

A cylinder control system of the conventional construction machine has been controlled by hydraulic spool valves. This system is low-cost but system efficiency is not high. Recently, to improve this, all valves are controlled electronically and independently. Bu and Yao suggested four way electronic hydraulic control valve system. It is called IMVT(Independent Metering Valve Technology). The purpose of the study is to find proper IMV pressure control method for excavator and to validate excavator's bucket regeneration energy effect by controlling the IMV system. In this paper, we mathematically describe the bucket system of excavator first. And then, based on these results, we design the control system which is divided into two operations(none regeneration or regeneration).The results of the experiment show the desirable performance and usefulness of the designed control system.

• 소음진동
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• 제4권2호
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• pp.177-185
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• 1994

In this study, the effect of parameter errors on the closed-loop behavior of flexible structure is analyzed for IMSC(Independent Modal Space Control) with PPF(Positive Position Feedback). If the control force designed on the basis of structure model with the parameter errors is applied to control the actual system, the closed-loop performance of the actural system will be degraded depending on the degree of the errors. An asymptotic stability condition has been derived, using Lyapunov approach, which is independent of the dynamic characteristics of the structure being controlled. The extent of deviation of the closed-loop performance from the designed one is also derived and evaluated using operator techniques. It has been found that the extent of the deviation is proportational to the magnitude of the parameter errors, and that the proportional coefficient depends on the control algorithm.

• 경영과정보연구
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• 제7권
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• pp.293-315
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• 2001

In America, there has been increased empasis on corporates social responsbility in connect with corporate governance. Modern statutes have been enacted expressly empowering corporations to make donations for the public welfare or for charitable, scientiffic, or educational purposes. the Securities and Exchange Commission in the 1970's stressed improvement in corporate accountability by changing the traditional corporate governance, with emphasis on independent directors, and disintrested overview. The Korean Commerce Code and the Securities Exchange Law have introduced the independent outside-director and the audit committee. This outside-directors and the audit committee should supervise the corporate management by the managing directors to make donations for the public welfare or for charitable, scientiffic, or educational purposes. Korean statutes include many problems that would lose effect of corporates social responsbility in management. In order to become effective the corporates social responsbility, it should be established newly a provision of corporates social responsbility. And the outside-directors should be independent of and supervise the managing directors, and make donations for the public welfare. And the shareholders' supervisement rights on the managment should be strengthen.

• Bulletin of the Korean Chemical Society
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• 제24권11호
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• pp.1649-1654
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• 2003

We have investigated substituent effect on the stabilization energies, and nucleus-independent chemical shifts of pentafulvalenes and on the electronic structures of the corresponding polypentafulvalenes to design environmentally stable semiconductive or conductive polymers. Geometrical optimizations of the molecules were carried out at the density functional level of theory with B3LYP hybrid functional and 6-311+G(d) basis set. Stabilization energies were estimated using isodesmic and homodesmotic reactions. As a criterion of aromaticity nucleus-independent chemical shifts of the molecules were computed using GIAO approach. For the polymers the geometrical parameters were optimized through AM1 band calculations and the electronic structures were obtained through modified extended Huckel band calculations. It is found that strong electronwithdrawing substituents increase isodesmic and homodesmotic stabilization energies of pentafulvalene, though it does not increase the aromaticity. Nitro-substituted pentafulvalene is estimated to have stabilization energy as much as azulene. However, substitution either with electron-donating groups or with electronwithdrawing groups does not significantly affect the electronic structures of polypentafulvalene and poly (vinylenedioxypentafulvalene).

• International Journal of Reliability and Applications
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• 제18권2호
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• pp.45-63
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• 2017

In this paper, we have formulated optimum Accelerated Life Test (ALT) plan for a parallel system with two independent components using masked data with ramp-stress loading scheme and Type-I censoring. Consider a system of two independent and non-identical components connected in parallel. Such a system fails whenever all of its components has failed. The exact component that causes the system to fail is often unknown due to cost and time constraint. For each parallel system at test, we observe its system's failure time and a set of component that includes the component actually causing the system to fail. The stress-life relationship is modelled using inverse power law, and cumulative exposure model is assumed to model the effect of changing stress. The optimal plan consists in finding out the optimum stress rate using D-optimality criterion. The method developed has been explained using a numerical example and sensitivity analysis carried out.

• 응용통계연구
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• 제6권2호
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• pp.227-235
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• 1993

순서쌍으로 주어진 자료 $(x_i, y_i), i=1,2,\cdots,n$ 들에 대한 독립변수와 관련된 추정은 회귀분석과는 달리 교정(calibration)이라고 불리워진다. 본 논문에서는 정규상 등과 같은 가정을 하지않고 비모수적인 커널방법을 이용하여 교정함수를 추정하고 추정된 교정함수의 붓스트랩 신뢰대를 이용한 독립변수의 구간추정을 제안하고자 한다. 교정과 커널방법에 대해 설명하였으며 독립변수의 추정에 대한 문헌적 고찰과 함께 붓스트랩 신뢰대에 대하여 첨언하였고 실제 자료를 통하여 다른방법과 비교, 분석하였다.