• Korean Journal of Construction Engineering and Management
• /
• v.5 no.1 s.17
• /
• pp.114-123
• /
• 2004

Contract time determination for highway construction projects has never been easy despite considerable research efforts from academia as well as industry. High variations in crew production rates are considered one of the main barriers to accurate contract time determination. This paper presents a methodology for collecting field information on crew production rates which will help to enhance the accuracy of contract time determination for highway bridge construction. Based on a standard data collection tool developed, data on field crew production rates was collected from 14 on going projects in Texas, USA, over the past two years. The production rates based on the data collected were considered by industry practitioners to be more realistic and practical than those available to the current practices. As more data becomes available, key drivers influencing production rates could be identified and provide site personnel with a means to better plan and control production in a project specific context.

• Journal of the Korean Society of Safety
• /
• v.19 no.2
• /
• pp.34-40
• /
• 2004

This paper presents an analysis of SAR(Specific Absorption Rate) distribution characteristics in a head model using FDTD(Finite Difference Time Domain). In this study human head was modelled in four elements-layered structure, consisting of skin, fat, skull and brain. To calculate the electromagnetic fields wihtin the head model, FDTD method was used. In the FDTD method, the electromagnetic wave is analyzed by solving a Maxwell's equations repeatedly. For the calculation, distance between power source and head model increased by 10[m]. Power density and incident electric field intensity were calculated. Based on the incident electric field, the program which calaculated internal electric fields intensity and SAR calculation of the head model were developed. The results of developed program using FDTD were compared with those of a commericial programs, which showed the availability and usefulness of the suggested scheme in this paper.

• Journal of electromagnetic engineering and science
• /
• v.13 no.1
• /
• pp.16-21
• /
• 2013

This study presents the angular effects of virtual vertices inserted for effective treatment of the boundary edge laid on an infinite conducting surface in a half-space scattering problem. We investigated the angular effects of virtual vertices by first computing the radar cross section (RCS) of a specific scatterer; i.e., a tilted conducting plate in contact with the ground surface, by inserting the virtual vertex in half-space. Here, the electric field integral equation is used to solve this problem with various virtual vertex angles (${\theta}_{\nu}$) and conducting plate inclination angles (${\theta}_r$) ranging from $0^{\circ}$ to $180^{\circ}$. The effects of the angles ${\theta}_{\nu}$ and ${\theta}_r$ on the RCS computation are clearly shown with numerical results with and without the virtual vertices in free- and half-spaces.

• Journal of computational fluids engineering
• /
• v.5 no.3
• /
• pp.23-31
• /
• 2000

The three-dimensional unsteady compressible Full Navier-Stokes equation solver with sliding multi-block method has been applied to analyze three dimensional characteristics of the viscous flow field and compression wave around the high speed train which is entering into a tunnel. The numerical scheme of AF + ADI was used to efficiently solve Navier-Stokes equations in the curvilinear coordinate system. The vortex formation owing to the viscous interaction around the train was found and the generation of compression wave due to the blockage effects was observed ahead of the train in the form of plane wave. The three dimensional characteristics of the flow field compared to the analytic results were discussed in detail. The variation of pressure of tunnel wall surface and velocity profile of the train are identified as the train enters into a tunnel. The changes in aerodynamic forces and streamlines of each specific sections are also discussed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2001.10a
• /
• pp.185-189
• /
• 2001

In order to prevent the production defects the optimum design of product, jig and fixture putting in the field is very significant manufacturing method. Drilling Jig is the device according to industrial demand for multi manufacturing products on the growing at alarming rate. In the field of design and making for machine tool working, welding, assembling with jig and fixture for mass production is a specific division. They require analysis of many kinds of important factors, theory and practice of machine tool operating process and jig & fixture structure, machining condition for tool making, tool materials, heat treatment of jig & fixture components, know-how and so on. In this study we designed and constructed a drilling jig of mass production and performed tryout under the Auto CAD, Auto Lisp database, that we made by database, and window environment. Especially this study is reveals with the analysis of part drawing, jig planning, jig design etc, and then the result of drill jig's making try out.

• Journal of KSNVE
• /
• v.11 no.2
• /
• pp.354-364
• /
• 2001

The vibration induced by high speed train running on rail is dealt with as an environmental problem. The train induced vibration is characterized by moving loads at specific frequencies and soil conditions. In fact, it is predicted that the vibration sources are involved the wheel distance, number of cars, speed of operation, drift of rails, structural born vibration, etc. In this paper the characteristics of transferring vibration induced by the high-speed train in operation is discussed. Field measurements was conducted at region from Chungnam Yungj So-jung-myan to Chungbuk Chungwon hyun-do-myun. In the near future. these data will be used as the fundamental data for establishment of the countermeasure for vibrational reduction of high speed train using the results of the field measurements and quantitative prediction of the vibration level

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.25 no.12
• /
• pp.54-59
• /
• 2011

LED lightings typically do not fail catastrophically during use. However, over time the light output will gradually depreciate. Even if there are same LED lighting, they are so different at all. because of dissimilar the use and environment of each LED lighting. In this paper, we make a description of reliability analysis procedures for the degradation data using collected field data. Reliability analysis procedures are consisted of estimating degradation models and failure time, verification of distribution and parameters of the distribution, and reliability measures estimation. At some point in time, the light emitted from an LED lightings depreciates to a level where it is no longer considered adequate for a specific application.

• Journal for History of Mathematics
• /
• v.29 no.6
• /
• pp.353-363
• /
• 2016

In mathematical population ecology which is an academic field that studies how populations of biological species change as times flows at specific locations in their habitats, PDE models have been studied in many aspects and found to have different properties from the classical ODE models. And different approaches to PDE type models in mathematical biology are still being tried currently. This article investigate various forms to express diffusion effects and review the history of PDE models involving diffusion terms in mathematical ecology. Semi-linear systems representing the spatial movements of each individual as random simple diffusion and quasi-linear systems describing more complex diffusions reflecting interspecific interactions are studied. Also it introduce a few of important problems to be solved in this field.

• Structural Engineering and Mechanics
• /
• v.34 no.3
• /
• pp.285-300
• /
• 2010

The two-dimensional deformation of a homogeneous, isotropic thermoelastic half-space with voids with variable modulus of elasticity and thermal conductivity subjected to thermomechanical boundary conditions has been investigated. The formulation is applied to the coupled theory(CT) as well as generalized theories: Lord and Shulman theory with one relaxation time(LS), Green and Lindsay theory with two relaxation times(GL) Chandrasekharaiah and Tzou theory with dual phase lag(C-T) of thermoelasticity. The Laplace and Fourier transforms techniques are used to solve the problem. As an application, concentrated/uniformly distributed mechanical or thermal sources have been considered to illustrate the utility of the approach. The integral transforms have been inverted by using a numerical inversion technique to obtain the components of displacement, stress, changes in volume fraction field and temperature distribution in the physical domain. The effect of dependence of modulus of elasticity on the components of stress, changes in volume fraction field and temperature distribution are illustrated graphically for a specific model. Different special cases are also deduced.

• Electrical & Electronic Materials
• /
• v.9 no.5
• /
• pp.512-517
• /
• 1996

본 고는 반도체 재료가 갖는 자기효과를 이용하여 자기센서의 종류 및 특성등에 대하여 서술하였다. 반도체 LSI의 응용분야가 확대됨에 따라서 반도체 센서를 이용한 극소형화, 고성능화, 저가격화, 다기능화등이 가능하게 되었다. 이러한 상황에서 반도체를 이용한 홀 소자나 자기저항 소자와 같은 자기센서 등을 주변회로와 일체화시킨 초소형 시스템에 대한 연구가 활발하다. 특히 화합물 반도체는 자기센서에 적합한 물리적인 특성을 갖고 있기 때문에, 자기센서로 효율을 나타내고 있다. 반도체의 미세가공기술의 발전과 LSI제조기술의 발전을 이용하여 센서의 집적화, 저가격화를 가능하게 하였으며, 다른 종류의 반도체 센서들을 자기센서와 함께 하나의 칩위에 장착할 수 있는 응용집적센서(Application-specific Integrated Sensor)가 더욱 중요한 역할을 할 것이다.