• Tribology and Lubricants
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• 제6권1호
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• pp.108-115
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• 1990

Wear diagrams, which are the three dimensional representations of the dependence of the wear rate on the applied pressure and the sliding speed, were constructed with the pin on ring type wear test results using 52100 wear couples. The pressure and speed ranges from 0.45 MPa to 45.30 MPa and from 0.012 m/sec to 0.12 (0.120)m/sec, respectively. The results show the mild to severe transition, which suggests the change of the wear mechanisms as a function of the pressure and sliding speed. The SEM micrographs of the corresponding worn area shows clearly that different wear mechanisms dominate.

• Structural Engineering and Mechanics
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• 제11권5호
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• pp.503-518
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• 2001

In this paper, the procedure for deriving an infinite element that is compatible with the quadrilateral Q8 element is first summarized. Enhanced by a self mesh-expansion procedure for generating the impedance matrices of different frequencies for the region extending to infinity, the infinite element is used to simulate the far field of the soil-structure system. The structure considered here is of the box type and the soils are either homogeneous or resting on a bedrock. Using the finite/infinite element approach, a parametric study is conducted to investigate the effect of open and in-filled trenches in reducing the structural vibration caused by a train passing nearby, which is simulated as a harmonic line load. The key parameters that dominate the performance of wave barriers in reducing the structural vibrations are identified. The results presented herein serve as a useful guideline for the design of open and in-filled trenches concerning wave reduction.

• Research in Mathematical Education
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• 제19권4호
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• pp.247-265
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• 2015

Mathematics textbook plays a significant role in shaping students' learning of mathematics. Logic, rigor and abstraction as typical features of the formalization of mathematics, dominate mathematics textbooks around the world, which is regarded as one of the important origins of students' learning difficulties in mathematics. An innovative series of Chinese mathematic textbooks is presented in this paper. Supported by the supplementary materials excerpts from the textbooks, it gives a comprehensive theoretical analysis of the principles of design and implementation of this series of mathematics textbooks. The effectiveness of this series of textbooks is demonstrated by student achievement and secondary research data. It shows that series of Chinese mathematic textbooks has largely decreased students' learning difficulties in mathematics and enhance classroom teaching efficiency. It suggests that prioritizing the essence of mathematics and reducing abstraction is an important notion for mathematics textbook design and implementation.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.265-266
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• 2014

Due to global economic growth, there is an increasing need for energy. Fossil fuels will continue to dominate the world energy supplies in the 21st century and coal will play a significant role. Since coal is one of the most important fossil fuels in the world, coal gasification technology appears to be an inevitable choice for power and chemicals production and has a leading place in Clean Coal Technology (CCT). The most eminent environmental advantage of coal gasification lies in its inherent reaction features that produce negligible sulfur and nitrogen oxides, as well as other pollutants in a reducing atmosphere. The gasifier was operated for a throughput of 1.0 ton & 10.0ton coal per day at pressures of 1~20Bar. Gasification was conducted in a temperature range of $1,100{\sim}1,450^{\circ}C$.

• Wind and Structures
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• 제21권1호
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• pp.63-84
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• 2015

The shape of a tall building has significant impact on wind force generation and wind-induced dynamic response. To study the effect of recessed cavities, wind excitations on a wind-tunnel model of an H-section tall building were compared with those on a square-section building model. Characteristics of the fluctuating wind pressures on the side faces of the two tall buildings and their role in the generation of crosswind forces on the buildings were investigated with the space-time statistical tool of proper orthogonal decomposition (POD). This paper also compares the use of different pressure data sets for POD analysis in situations where pressures on two different surfaces are responsible for the generation of a wind force. The first POD mode is found to dominate the generation of crosswind excitation on the buildings.

• Journal of Industrial Technology
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• 제22권A호
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• pp.43-48
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• 2002

Acoustic modes of a vehicle compartment dominate the noise characteristics of the vehicle system in the low frequency range. Vehicle compartments have head liner and air gap of proper thickness to mount a interior lamp, as well as to have a good sound insulation and absorption performance. This study estimates the acoustic modal property of the medium size passenger car by experiment and by finite element analysis and also, investigates the effect of the head liner on the acoustic mode of the passenger compartment to obtain useful information for low noise compartment design.

• Journal of The Korean Astronomical Society
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• 제37권5호
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• pp.557-562
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• 2004

We discuss diffusion of particles in turbulent flows. In hydrodynamic turbulence, it is well known that distance between two particles imbedded in a turbulent flow exhibits a random walk behavior. The corresponding diffusion coefficient is ${\~}$ ${\upsilon}_{inj}{\iota}_{turb}$, where ${\upsilon}_{inj}$ is the amplitude of the turbulent velocity and ${\iota}_{turb}$ is the scale of the turbulent motions. It Is not clear whether or not we can use a similar expression for magnetohydrodynamic turbulence. However, numerical simulations show that mixing motions perpendicular to the local magnetic field are, up to high degree, hydrodynamical. This suggests that turbulent heat transport in magnetized turbulent fluid should be similar to that in non-magnetized one, which should have a diffusion coefficient ${\upsilon}_{inj}{\iota}_{turb}$. We review numerical simulations that support this conclusion. The application of this idea to thermal conductivity in clusters of galaxies shows that this mechanism may dominate the diffusion of heat and may be efficient enough to prevent cooling flow formation when turbulence is vigorous.

• Proceedings of the Korea Database Society Conference
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• 한국데이타베이스학회 1999년도 춘계공동학술대회: 지식경영과 지식공학
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• pp.403-413
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• 1999

Today's businesses are experiencing intensive global competition and the most accelerating pace of change ever. Competitors have sprung up that were not even on the business's radar. This environment impacts all decisions and strategies as business try to dominate their market or their industry merely to survive. So recently most of organizations are considering on building the data warehouse system to pursuit the business intelligence. We need the proper model to guide the approach to plan building data warehouse system when we want to plan it in considering the organizational status. Therefore we suggest a model to decide the approach to build data warehouse considering the project's environmental factors. First we review Ronald S. Swift(1998)'s five environmental factors that we have to consider when planing to build data warehouse. Then we propose a model to decide DW approach by the degree of those factors to be measured. DW approaches in this model are classified in conservative approach, technological approach, increasing approach. enterprise- wide approach, and ideal approach.

• The Korean Journal of Financial Studies
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• 제2권1호
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• pp.189-214
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• 1995

We examine the existence of the investment signaling equilibrium without assuming a specific utility function for the managers of the corporations. We assume the managers have the initial holdings of their own corporations as a form of the executive compensation. Under the different financing schemes to finance the investment, the new equity financing and the risky debt financing, we derive the investment signaling equilibrium and compare the the investment signaling equilibrium under each financing scheme. We show that the investment signaling equilibrium with each financing will obtain with the underinvestment of the high quality firm and that the investment signaling equilibrium with the risky debt financing will dominate the investment signaling equilibrium with the new equity financing.

• The korean journal of orthodontics
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• 제6권1호
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• pp.79-82
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• 1976

This study was undertaken to investigate the values of the cephalometric standards of Korean children which consisted of 57 boys and 61 girls with normal occlusion and harmony of the facial musculature. The following conclusions were obtained. 1) The relatively vertical inclination of nasal bone and flat contour of the frontal bone contribute to the flattening of the upper face. 2) Slight lack of chin prominence characterizes the lower face while procumbent incisors and their alveolar bone dominate the middle face. 3) A caudal skull base inclination is probably the most specific feature for Korean.