• The Journal of Korean Physical Therapy
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• 제25권5호
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• pp.288-296
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• 2013

Purpose: This study was conducted in order to determine whether mechanical horseback-riding training depending on velocity can improve vestibular function and static postural balance on standing in healthy adults. Methods: For evaluation of vestibular function, electrooculography (EOG) of vertical and horizontal was performed for identification of the motion of eyes. For evaluation of static postural balance, COP distance, time spent on the sharpened Romberg test with neck extension (SRNE) were measured. Measurements were performed three times before training, three weeks after training, and six weeks after training. Participants were randomly assigned to three groups: fast velocity-mechanical horse -riding training (FV-MHRT, n=12), moderate velocity-mechanical horse-riding training (MV-MHRT, n=12), and slow velocity-mechanical horse-riding training (SV-MHRT, n=12). Results: According to the result for vertical, horizontal EOG, there was significant interaction in each group in accordance with the experiment time (p<0.05). The FV-MHRT group showed a significant decrease compared with the MV- MHRT, SV-MHRT groups (p<0.05). According to the result for static postural balance, the time spent, COP distance in SRNE showed significant interaction in each group in accordance with the experiment time (p<0.05). The time spent on the SRNE showed a significant increas in FV-MHRT, SV-MHRT (p<0.05). The COP distance of SRNE showed a significant increase in MV-MHRT (p<0.05). Conclusion: The MHRT velocity activated mechanism of vestibular spinal reflex (VSR), vestibular ocular reflex (VOR), also helped to strengthen vestibular function and static postural balance. In addition, it should be applied to different velocity of MHRT according to the specific purpose.

• 천문학회지
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• 제38권3호
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• pp.357-363
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• 2005

A deep stellar analysis is introduced for the poorly studied open cluster NGC 2509. The Near-IR database of the digital Two Micron All Sky Survey (2MASS) has been used to re-estimate and refine the fundamental parameters of the cluster, i.e. age, reddening, distance, and diameter. As well as, luminosity function, mass function, total mass, relaxation time, and mass segregation of NGC 2509 have been estimated here for the first time..

• 한국CDE학회논문집
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• 제12권3호
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• pp.220-232
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• 2007

Current geometric modeling and analysis are commonly based on B-Rep modeling and a finite elements method respectively. Furthermore, it is difficult to represent an object whose material property is heterogeneous using the B-Rep method because the B-Rep is basically used for homogeneous models. In addition, meshes are required to analyze a property of a model when the finite elements method is applied. However, the process of generating meshes from B-Rep is cumbersome and sometimes difficult especially when the model is deformed as time goes by because the topology of deforming meshes are changed. To overcome those problems in modeling and analysis including homogeneous and heterogeneous materials, we suggest a unified modeling and analysis method based on implicit representation of the model using R-function which is suggested by Rvachev. For implicit modeling of an object a distance field is approximated and blended for a complex object. Using the implicit function mesh-free analysis is possible where meshes are not necessary. Generally mesh-free analysis requires heavy computational cost compared to a finite elements method. To improve the computing time of function evaluation, we utilize GPU programming. Finally, we give an example of a simple pipe design problem and show modeling and analysis process using our unified modeling and analysis method.

• 대한수학교육학회지:학교수학
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• 제19권4호
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• pp.639-661
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• 2017

본 연구는 미분계수를 절차적 지식(거리함수 f(x)에서 a초에서 k초까지의 평균속력을 식으로 구성하여, 분모에 있는 인수를 약분한 다음 a에 k를 대입하여 속력함수를 구하는 방식)으로 구성한 고등학교 1학년 학생 세 명과의 교수실험 내용을 분석한 연구이다. 특히 본 연구에서는 분모에 있는 인수가 약분되기 어려운 거리함수(무리함수, 지수함수)에서 속력함수를 구성하는 과정을 중심으로 학생들이 구성한 절차적 지식에 대하여 학생 스스로의 고민과 표현이 어떠한지를 중심으로 분석하였다. 이 과정에서 학생들은 최초 구성한 절차적 지식에 대하여 다양한 고민과 표현의 변화를 보여주었다. 특히 학생B는 이 과정에서 기존에 자신이 알고 있는 지식을 모두 설명하지 못할 경우 자신이 구성한 미분계수를 구하는 절차에 대하여 고민하고 반성하는 모습을 보여주었다. 본 연구는 미분계수 학습에서 학생들의 계산 방식에 대한 이해를 더해주고, 미분계수를 구할 때 절차적 지식을 구성한 학생들에게 어떻게 자신들이 구성한 절차에 대하여 반성할 수 있는 기회를 제공할 것인지에 대하여 고민하였다는 점에서 의미를 갖는다.

• 전자공학회논문지T
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• 제35T권3호
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• pp.67-75
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• 1998

이 논문은 이동 장애물 회피를 위한 새로운 로봇 동작 계획을 제안한다. 이동 장애물의 운동성을 고려하여, 로봇과 장애물 사이의 관계를 위해 가상거리 함수를 정의한다. 각각의 샘플링 시간에, 장애물의 움직임을 고려한 인공 전위계를 구성하기 위해 가상거리 함수를 이용한다. 로봇은 인공 전위 함수에 의해 유도된 인력과 척력 벡터에 따라 이동한다. 제안된 알고리즘은 실시간으로 이동 장애물을 회피할 수 있었다. 시뮬레이션 결과를 통해 제안된 알고리즘의 효율성을 입증한다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.64-68
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• 2007

The classic graphical method to determine the epicenter uses differences between the arrival times of P and S waves at each station. In this research, a robust approach is proposed, which provides a fast and intuitive estimation of earthquake epicenters. This method uses an empirical relationship between epicentral distance and traveltime of the first arrival P phase of local or regional earthquake. The relationship enables us to estimate epicentral distances and draw epicentral circles from each station with P-traveltimes counted from a probable origin time. As the assigned time is getting close to the origin time of the earthquake, epicentral circles begin to intersect each other at a possible location of the epicenter. Then the possibility of the epicenter can be expressed by a function of the time and the space. We choose the location which gives the minimum standard deviation of the origin time as an estimated epicenter. In this research, 918 P arrival times from 84 events occurring from 2005 to 2006 listed in the KMA earthquake catalog are used to determine the empirical P-traveltime function of epicentral distances.

• 전기학회논문지
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• 제57권2호
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• pp.268-275
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• 2008

In this paper, we introduce a new method for detecting and estimating faults on a power line using the time-frequency domain reflectometry system. The system rests upon time-frequency signal analysis and uses a chirp signal which is multiplied by Gaussian envelope. The chirp signal is used as a reference signal, and we can get the reflected signal from a fault on a wire. To detect and estimate faults, we analyze the reflected signal by Wigner time-frequency distribution function and normalized time-frequency cross correlation function. In this paper we design an optimal reference signal for power line and implement a system for estimating fault distance on a power line with the TFDR implemented by PXI equipments. This approach is verified by some experiments with HIV 2.25mm power lines.

• Journal of Forest and Environmental Science
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• 제33권4호
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• pp.305-314
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• 2017

This study aimed to predict changes in forest area using a probability density function, in order to promote effective forest management in the area north of the civilian control line (known as the Minbuk area) in Korea. Time series analysis (2010 and 2016) of forest area using land cover maps and accessibility expressed by distance covariates (distance from buildings, roads, and civilian control line) was applied to a probability density function. In order to estimate the probability density function, mean and variance were calculated using three methods: area weight (AW), area rate weight (ARW), and sample area change rate weight (SRW). Forest area increases in regions with lower accessibility (i.e., greater distance) from buildings and roads, but no relationship with accessibility from the civilian control line was found. Estimation of forest area change using different distance covariates shows that SRW using distance from buildings provides the most accurate estimation, with around 0.98-fold difference from actual forest area change, and performs well in a Chi-Square test. Furthermore, estimation of forest area until 2028 using SRW and distance from buildings most closely replicates patterns of actual forest area changes, suggesting that estimation of future change could be possible using this method. The method allows investigation of the current status of land cover in the Minbuk area, as well as predictions of future changes in forest area that could be utilized in forest management planning and policymaking in the northern area.

• Korean Chemical Engineering Research
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• 제57권5호
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• pp.652-665
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• 2019

Analytical solutions of the reactant concentration inside porous spherical catalytic particles were obtained from unsteady reaction-diffusion equation by applying eigenfunction expansion method. Various surface concentrations as exponentially decaying or oscillating function were considered as boundary conditions to solve the unsteady partial differential equation as a function of radial distance and time. Dirac delta function was also used for the instantaneous injection of the reactant as the surface boundary condition to calculate average reactant concentration inside the particles as a function of time by Laplace transform. Besides spherical morphology, other geometries of particles, such as cylinder or slab, were considered to obtain the solution of the reaction-diffusion equation, and the results were compared with the solution in spherical coordinate. The concentration inside the particles based on calculation was compared with the bulk concentration of the reactant molecules measured by photocatalytic decomposition as a function of time.

• 한국항해항만학회지
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• 제27권6호
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• pp.619-624
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• 2003

Evaluating the risk of collision quantitatively plays a key role in developing the expert system of navigation and collision avoidance. This study analysed thoroughly how to determine the threshold function related to the avoidance time as described in the new evaluation of collision risk using sech function, and developed the appropriate equation as applicable.