• Neonatal Medicine
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• 제18권2호
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• pp.165-176
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• 2011

The pathologic hallmark of new bronchopulmonary dysplasia (BPD) is an arrest in alveolarization and vascular development. Alveoli are the fully mature gas-exchange units and alveolarization denotes the process through which the developing lung attains its fully mature structure. In human, alveolarization is mainly a postnatal event and begins in utero around 35 postmenstrual weeks and continues to 2 postnatal years. Beginning of respiration with very immature lungs as a result of preterm delivery renders the immature lung to be exposed to various injuries such as mechanical stretch, hyperoxia, infection/inflammation and leads to a disruption of normal alveolarization process, which is a main pathologic finding of BPD. Better understanding of the control mechanisms of normal alveolarization process should help us to figure out the pathophysiology of BPD and discover effective preventive or therapeutic measures for BPD. In this review, the pathologic evolution of BPD from 'old' to 'new' BPD, the detailed mechanisms of normal alveolarization, and the factors that disrupt normal alveolarization will be discussed.

• Journal of Astronomy and Space Sciences
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• 제15권1호
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• pp.111-118
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• 1998

A method to determine normal vectors for boundaries of plasmas with a series of data acquired from a single spacecraft is investigated. The determination of the normal vector is possible through a set of Rankine-Hugoniot(R-H) relations that are conser-vation relations of plasmas across a boundary. It is assumed that the boundary is planar and that the structure of the boundary is not varing in the rest frame of plasmas. The present method utilizes a complete set of R-H relations and provieds self-consistent predictions of the plasma densities, bulk velocities, and temperatures a s well as mag-netic fields. It is expected that the present method provides a more accurate normal vector than the previous methods which employ only subsets of the available R-H relations.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1057-1062
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• 2000

The purpose of this study is to practice the method which can estimate 28-days strength of concrete in advance. This method is made for reliant quality control. Based on existing experiment, concrete that flyash added and normal concrete are placed into wall structure, and it is examined the difference between experiment use concrete and field use concrete. The result of this study are as follows : 1) Core test specimen have 10% lower strength to standard curing specimen. 2) At 28-days accelerated strength by microwave, average 35% in normal concrete, average 23% in flyash added concrete. 3) At coefficient of determination between compressive strength and accelerated strength, 0.84 in normal concrete core, 0.86 in standard curing normal concrete, 0.86 in flyash added concrete, 0.90 in standard curing flyash added concrete.

• Journal of the Korean Statistical Society
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• 제19권1호
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• pp.24-44
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• 1990

The purpose of this paper is to extend the idea of Tamhane and Bechhofer (1977, 1979) concerning the normal means problem to some general class of distributions. The key idea in Tamhane and Bechhofer is the derivation of the computable lower bounds on the probability of a correct selection. To derive such lower bounds, they used the specific covariance structure of a multivariate normal distribution. It is shown that such lower bounds can be obtained for a class of stochastically increasing distributions under certain conditions, which is sufficiently general so as to include the normal means problem as a special application. As an application of the general theory to the scale parameters problem, a two-stage elimination type procedure for selecting the population associated with the smallest variance from among several normal populations is proposed. The design constants are tabulated and the relative efficiencies are computed.

• 전기학회논문지P
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• 제57권3호
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• pp.332-337
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• 2008

We analyzed carbonization pattern and crystal structure of polyvinyl chloride wire by thermal stress. Copper that is oxidized at normal temperature is a reddish brown. If under the thermal stress range of 500 to 700 [$^{\circ}C$], carbonization and exfoliation occurrence. Section structure of electric wire is same as arrangement of particle in metallograph analysis. But, as thermal stress increases, size of particle is enlarged. Electric wire displays elongation structure in SEM image analysis and elongation structure collapses when receive thermal stress at 300 [$^{\circ}C$]. In EDX analysis, we get the spectra of CuL, CuK, OK, and ClK. FT-IR analysis was shown new spectra with in range of $1,440{\sim}1,430\;[cm^{-1}]$, 1,340 [$cm^{-1}$], 1,240 [$cm^{-1}$].

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.151-154
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• 2008

The field emission lamps have the advantages to their cold cathode-characteristic and the eco-friendly, We realized that the dual emitter system showed very simple structure which gate and cathode electrodes are formed on the same glass surface. In this paper, we reported the properties of dual emitters depended on variation of gate width and spacing for optimum panel structure. In combination of dual emitter structure and bi-polar driving, electron beam spreads more than normal gate structure or diode structure, and emission uniformity increased in dual emitter structure at 5"-diagonal.

• Journal of Plant Biology
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• 제34권1호
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• pp.9-18
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• 1991

본 연구는 자연상태에서 자란 12종의 왜소개체에 있어 목부구조의 변이에 대한 왜소생장의 영향을 검토하였다. 통수요소 및 섬유의 길이와 접선직경이 정상개체보다 왜소개체에서 더 짧고 좁게 나타났다. 방사조직의 높이도 정상개체보다 왜소개체에서 낮았다. 동일 연륜의 방사폭과 연륜내 세포수는 정상개체보다 왜소개체에서 좁고 적었다. 송백류에서 춘재에 대한 추재의 비는 정상개체보다 왜소개체에서 높게 나타났다. 피자식물의 도관요소의 mesomorphy 정도는 정상개체보다 왜소개체에서 낮았다. 이와 같이 왜소생장은 수분결핍과 같은 환경요인에 의해 극도로 느린 생장을 한 결과로 해석된다.

• 소음진동
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• 제9권5호
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• pp.975-983
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• 1999

This paper describes the dynamic characteristics of the joint structures in case of using the simplified beam model in the F. E. analysis. The modeling errors, when replace the shell with the beam, are investigated through F. E. normal modes analysis. Normal mode analysis were performed to obtain the natural frequencies of the L and T shaped joints with various type of channels. The results were analyzed to access the effects of the models on the accuracy of F.E. analysis by identifying the geometric factors which cause the error. The geometric factors considered are joint angle, channel length, thickness and area ratio of the hollow section to the filled one. The joint stiffness evaluation technique is developed in this study using normal modes analysis with Lumped Mass. With this method, the progressively improved results of F. E. analysis are obtained using the simplified beam model. The static and normal modes analysis are performed with the joint stiffness values obtained by the Kazunori Shimonkakis' virtual stiffness method and the proposed method and these simplified modeling errors are compared.

• Smart Structures and Systems
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• 제29권2호
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• pp.279-286
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• 2022

In this article, a novel propagation formulation of Rayleigh waves in a compressible isotropic half-space with impedance boundary condition is proposed by embedding the normal stress. In a two-dimensional case, it is assumed that a design boundary is free of normal traction and a shear traction depends on linearly a normal component of displacements multiplied by frequencies. Therefore, impedance boundary conditions affect the normal stress, where the impedance parameters correspond to dimensions of stresses over velocity. On the other hand, vanished impedance values are traction-free boundary conditions. The main purpose of this article is to present theoretically the existence and uniqueness of a Rayleigh wave formulation relying on secular equation's mathematical analyses. Its velocity varies along with the impedance parameters. Moreover, numerical experiments with different values for the velocity of Rayleigh waves are carried out. The present Rayleigh waves study is a fundamental step in analyzing the cause and effect of physical states such as building or structure damages resulting from natural dynamics. The results of the study generate a basic design formulation theory to test the effects of Rayleigh waves affecting structures when an earthquake occurs. The presence and uniqueness of the proposed formulation is verified by mutual comparisons of several numerical examples.

• 대한치과교정학회지
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• 제13권2호
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• pp.201-204
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• 1983

To study the calcification of second molars in Class I malocclusion with normal craniofacial structure, the author examined cephalograms, orthopantomograms, periapical films of 538 children from 7 y 0 m to 15y 11m old who had Class I malocclusion with normal craniofacial structure, and observed the calcification stage of upper and lower second molars. The results are as follows. 1. The mean ages of crown completion of upper and lower second molars are $8.82{\pm}1.14,\;8.72{\pm}0.75$ in boys, and $8.60{\pm}1.46,\;8.22{\pm}0.92$ in girls. 2. The mean ages of root completion of upper and lower second molars are $14.25{\pm}1.46,\;14.15{\pm}0.83$ in boys, and $14.12{\pm}0.93,\;14.15{\pm}0.83$ in girls. 3. There are no difference between the calcification stages of upper second molars and those of lower second molars in both sexes.