• 전산구조공학
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• 제9권3호
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• pp.115-123
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• 1996

배관을 구속시키기 위한 원통형 배관 지지대(Trunnion Pipe Support)가 부착된 배관의 응력해석을 위하여 유한요소해석을 사용하였다. 해석결과로 부터 얻어진 응력은 두께에 대한 평균(막응력) 및 선형 응력(굽힘응력)으로 분류되었으며, 분류된 응력값은 압력에 에 의한 일차응력계수(B/sub 1/)와 이차응력계수(C/sub 1/), 모멘트에 의한 일차응력계수(B/sub 28/, B/sub 2T/)와 이차응력계수(C/sub 28/, C/sub 2T/)를 추정하기 위하여 ASME Code에 정의된것과 일치하게 해석되었다. 무차원의 함수로써 응력계수에 대한 경험식을 개발하기 위하여 여러 모델의 해석을 수행하였다.

• 대한기계학회논문집A
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• 제26권6호
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• pp.1194-1202
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• 2002

A study on the topology optimization of a multi-spectral camera for space-use is presented. The optimization is carried out under self-weight and polishing pressure loading. A multi-spectral camera for space-use experiences degradation of optical image in the space, which can not be detected on the optical test bench on the earth. An optical surface deformation of a primary mirror, which is a principal component of the camera system, is an important factor affecting the optical performance of the whole camera system. In this study, topology optimization of the primary mirror of the camera is presented. As an objective function, a measure of Strehl ratio is used. Total mass of the primary mirror is given as a constraint to the optimization problem. The sensitivities of the objective function and constraint are calculated by direct differentiation method. Optimization procedure is carried out by an optimality criteria method. For the light-weight primary mirror design, a three dimensional model is treated. As a preliminary example, topology optimization considering a self-weight loading is treated. In the second example, the polishing pressure is also included as a loading in the topology optimization of the mirror. Results of the optimized design topology for the mirror with various mass constraints are presented.

• Geomechanics and Engineering
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• 제22권6호
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• pp.509-518
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• 2020

Multi-layered primary linings have been proved to be highly effective for tunneling in severe squeezing grounds. But there still has not existed well-established design method for it. Basically, there are two main critical problems in this method, including determinations of allowable deformation and distribution of support stiffness. In order to address such problems, an attempt to investigate the mechanical response of a circular tunnel with double primary linings is performed in this paper. Analytical solutions in closed form for stresses and displacements around tunnels are derived. In addition, the effectiveness and reliability of theoretical formulas provided are well validated by using the numerical method. Finally, based on the analytical solutions, a parametric investigation on the effects of allowable deformation and distribution of support stiffness on tunnel performance is conducted. Results show that the rock pressure and displacement are significantly affected by these two design parameters. It can be found that rock pressure decreases as either allowable deformation increases or stiffness of the first primary lining decreases, but rock displacement shows an opposite trend. This paper can provide a useful guidance for the design of multi-layered primary linings.

• Journal of Preventive Medicine and Public Health
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• 제24권2호
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• pp.161-170
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• 1991

The purpose of this study is to find the tracking of blood pressure in primary school-age children. A follow-up study was conducted from 1986 to 1990 on 330 first grade children attending primary schools in Kangwha County, Kyungki-Do. Basically we employed a linear regression model with random coefficients to figure out the relation between blood pressure changes and initial blood pressure. We obtained the following results ; 1. The mean blood pressures were increased grade went up in both sexs and were generally higher in female than male except for the systolic blood pressure at first grade. The size of difference was about 0.8 mmHg in mean systolic blood pressure and 1.5 mmHg in mean diastolic blood pressure. 2. The average annual increasing rates of systolic blood pressure were 2.5 mmHg in male and 3.1 mmHg in female respectively. For the diastolic blood pressure IV the average annual increasing rates were observed to be 3.0 mmHg in male and 2.9 mmHg in female respectively. Increasing rate of systolic blood pressure was significantly higher in female than male. 3. The adjusted regression coefficient of systolic blood pressure change on initial value was -0.11 in male and -0.13 in female and that coefficient of diastolic blood pressure change on initial value was -0.01 in male and -0.11 in female. This result shows that children with higher initial blood pressure do not pick up their blood pressure faster than others with lower initial blood pressure. There is no evidence of tracking of blood pressure in children. It is essential to find the earliest age having the tracking of blood pressure and we leave it for the further study.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.417-422
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• 2001

The shock structure of supersonic, dual, coaxial jet is experimentally investigated. Eight different kinds of coaxial, dual nozzles are employed to observe the major features of the near field shock structure of the supersonic, coaxial, dual jets. Four convergent-divergent supersonic nozzles having the Mach number of 2.0 and 3.0, and are used to compare the coaxial jet flows discharging from two sonic nozzles. The primary pressure ratio is changed in the range between 4.0 and 10.0 and the assistant jet pressure ratio from 1.0 to 4.0. The results obtained show that the impinging angle, nozzle geometry and pressure ratio significantly affect the near field shock structure, Mach disk location and Mach disk diameter. The annular shock system is found depending the assistant and primary jet pressure ratios.

• Nuclear Engineering and Technology
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• 제29권4호
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• pp.310-319
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• 1997

A finite element analysis of a trunnion pipe anchor is presented. The structure is analyzed for the case of internal pressure and moment loadings. The stress results are categorized into the average (membrane) stress, the linearly varying (bending) stress and the peak stress through the thickness. The resulting stresses are interpreted per Section III of the ASME Boiler and Pressure Vessel Code from which the Primary(B$_1$), Secondary(C$_1$) and Peak(K$_1$) stress indices for pressure, the Primary (B$_2$), Secondary(C$_2$) and Peak(K$_2$) stress indices for moment are developed. Based on the comparison between stress value by stress indices derived in this paper and stress value represented by the ASME Code Case N-391-1, the empirical equations for stress indices are effectively used in the piping stress analysis. Therefore, the use of empirical equations can simplify the procedure of evaluating the local stress in the piping design stage.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2977-2983
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• 2008

The combustion characteristics of a partially premixed flame in a dump combustor were studied to determine the effects of hydrogen enrichment in propane. Bluff-body was used for flame stabilization. Fuel mixtures containing a hydrogen mole fraction ranging from 0.1 to 0.5 were burnt at ambient pressure within a quartz chamber. Tests were carried out keeping the total reactant flow rate by adjusting the fuel and air flow rates. The fluctuations of pressure were measured by piezoelectric pressure sensor. The instantaneous flame structure and OH chemiluminescence images were described by High-speed Intensified Charged Coupled Device (HICCD) camera and Intensified Charged Coupled Device (ICCD) camera. The present results show that hydrogen enrichment in fuel changed the location of primary reaction zone from inner recirculation zone to turbulent shear layer and pressure signal. The reason is that chemical aspects take precedence over flow aspects in the hydrogen-enriched flame.

• 한국농공학회지
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• 제18권4호
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• pp.4242-4250
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• 1976

The determination of the pre-consolidation load known to have a great effect on the consolidation characteristics of the soil have been researched and discussed in detail by many other researchers. A study was undertaken to investigate and compare the effect of pre-consolidation loads on the coefficient of permeability and the consolidation characterisics of soil through the consolidation test on the three types of soil samples. The results of this study are follows; 1. Large compression index is dependent on initial void ratio of the sample being used and the pressure-void ratio curve shows a curved linear relationship in over-consolidated area but a linear relationship in normally consolidated area.2. Settlement-time curve is S-shaped where the pressure is larger than pre-consolidation load and regardless of over-burden pressure, it is a similar straight line respectively in the secondary consolidation area. 3. Primary consolidation ratio of the sample increases almost linearly with the increase of over-burden pressure but the coefficient of volume compressibility decreases linearly with the increase of it. 4. Time factor of a certain degree of consolidation increases with over-burden pressure but the coefficient of consolidation decreases with it in over-consolidated area. There is a linear relationship between them in normally consolidated area. 5. The void ratio of completion point of primary consolidation decreases linearly with over-burden pressure. 6. The coefficient of permeability of sample decreases linearly with over-burden pressure in normally consolidated area, also it increases linearly with increment of the void ratio of the sample.

• Geomechanics and Engineering
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• 제36권6호
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• pp.575-587
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• 2024

The contact pressure between the surrounding rock and the support is an important indicator of the surrounding rock pressure. There has been a bottleneck in the prediction of contact loads between surrounding rock and primary support in deep-buried mountain tunnels. The main reason is that a reliable method wasn't existed to quantify the contact loads. This study had been taken into account the flexible support role of the primary support, and the fitting curve of surrounding rock deformation for dynamic tunnel construction was proposed. New formulas for the calculation of contact loads between surrounding rock and primary support were obtained by inversion. Comparative analysis of the calculation results with numerical simulation verified the reliability of the calculation method in this study. It can be seen from the analyses that the contact load between surrounding rock and primary support increases, remains unchanged and decreases during acceleration, uniform velocity and deceleration, respectively, and the deformation of the surrounding rock in the acceleration and deceleration stages cannot completely converted into contact loads. The contact loads between surrounding rock and primary support of medium-strength and weak surrounding rock tunnels are generally within 150 kPa and 1 MPa, respectively. For tunnels with weak surrounding rock, advanced support can be installed to reduce the unique release coefficient λ₀ and the value of the constant D, with the purpose of reducing the contact loads between surrounding rock and primary support. Changes in support parameters have a small effect on the contact loads between surrounding rock and primary support, but increase or decrease the safety factor, resulting in a waste of resources or a situation that threatens the safety of the support. The results of this research provide guidance for the prediction of contact loads between surrounding rock and primary support for dynamic tunnel construction.

• Journal of Preventive Medicine and Public Health
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• 제22권3호
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• pp.303-312
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• 1989

To show the distribution and change of blood pressure according to age and to find factors affecting the level of blood pressure in primary school children, a follow-up study was conducted from 1986 to 1989 on 401 first grade children attending primary school in Kangwha County in 1986 and their parents. The blood pressure of the children was significantly increased according to age. The average annual increase was 1.8mmHg in systolic blood pressure and 2.5mmHg in diastolic blood pressure. The level of blood pressure did not show any significant difference in both sexes. Among children who were at or above the 80th percentile of blood pressure in the first grade, 35 and 30% of them have remained at the same level of systolic and diastolic blood pressure respectively in the fourth grade. But we could not find any significance in the tracking of blood pressure of children who were at or above the 90th percentile of blood pressure in the first grade. Weight and pulse rate were shown to be significant factors affecting systolic blood pressure in children of both sexes and mother's blood pressure and skinfold thickness were also affected systolic blood pressure in girls. The variables significantly affecting diastolic blood pressure were arm circumference and pulse rate for boys and height and pulse rate for girls.