• Journal of the Korean Wood Science and Technology
• /
• v.26 no.4
• /
• pp.1-5
• /
• 1998

In this study, it was examined the method to estimate equilibrium moisture content(EMC) at high vapor pressures and high temperatures above $100^{\circ}C$. The material used for the experiment was Sugi(Cryptomeria japonica). EMC was investigated at temperatures ranging from $100^{\circ}C$ to $160^{\circ}C$ and under saturated vapor pressures above 1 atm. The correlation between temperatures and vapor pressures have a good agreement with those observed by thermocouple and pressure gauge in the air state of autoclave, respectively. A sensitivity of quartz spring was 65mm/g. Moisture content(MC)s calculated from the quartz spring elongation by vapor sorption showed a good agreement with MCs by oven-dried method. Using this system, it was found that EMC at high vapor pressures and high temperatures above $100^{\circ}C$ were higher than EMC of wood in 1 atm pressure conditions. With this system, therefore, it was concluded that the EMCs of wood and wood-based materials at high temperatures were able to be evaluated.

• Wind and Structures
• /
• v.37 no.3
• /
• pp.211-227
• /
• 2023

To investigate the non-Gaussian feature of fluctuating wind pressures on rectangular high-rise buildings, wind tunnel tests were conducted on scale models with side ratios ranging from 1/9~9 in an open exposure for various wind directions. The high-order statistical moments, time histories, probability density distributions, and peak factors of pressure fluctuations are analyzed. The mixed normal-Weibull distribution, Gumbel-Weibull distribution, and lognormal-Weibull distribution are adopted to fit the probability density distribution of different non-Gaussian wind pressures. Zones of Gaussian and non-Gaussian are classified for rectangular buildings with various side ratios. The results indicate that on the side wall, the non-Gaussian wind pressures are related to the distance from the leading edge. Apart from the non-Gaussianity in the separated flow regions noted by some literature, wind pressures behind the area where reattachment happens present non-Gaussian nature as well. There is a new probability density distribution type of non-Gaussian wind pressure which has both long positive and negative tail found behind the reattachment regions. The correlation coefficient of wind pressures is proved to reflect the non-Gaussianity and a new method to estimate the mean reattachment length of rectangular high-rise building side wall is proposed by evaluating the correlation coefficient. For rectangular high-rise buildings, the mean reattachment length calculated by the correlation coefficient method along the height changes in a parabolic shape. Distributions of Gaussian and non-Gaussian wind pressures vary with side ratios. It is inappropriate to estimate the extreme loads of wind pressures using a fixed peak factor. The trend of the peak factor with side ratios on different walls is given.

• International Journal of High-Rise Buildings
• /
• v.2 no.3
• /
• pp.229-244
• /
• 2013

Twenty six pressure models of high rise buildings with various cross-sections including twisted models were tested in a boundary layer wind tunnel. The cross-sections were triangular, square, pentagon, hexagon, octagon, dodecagon, circular, and clover. This study investigates variations in peak pressures, and effects of various cross-sections and twist angles on peak pressures. To study the effects of various configurations and twist angles on peak pressures in detail, maximum positive and minimum negative peak pressures at each measurement point of the building for all wind directions are presented and discussed. The results show that peak pressures greatly depend on building cross-section and twist angle.

• Journal of Mechanical Science and Technology
• /
• v.18 no.2
• /
• pp.325-334
• /
• 2004

Computational experiments on fundamental un stretched laminar burning velocities and flame response to stretch (represented by the Markstein number) of hydrogen-air flames at high temperatures and pressures were conducted in order to understand the dynamics of the flames including hydrogen as an attractive energy carrier in conditions encountered in practical applications such as internal combustion engines. Outwardly propagating spherical premixed flames were considered for a fuel-equivalence ratio of 0.6, pressures of 5 to 50 atm, and temperatures of 298 to 1000 K. For these conditions, ratios of unstretched-to-stretched laminar burning velocities varied linearly with flame stretch (represented by the Karlovitz number), similar to the flames at normal temperature and normal to moderately elevated pressures, implying that the "local conditions" hypothesis can be extended to the practical conditions. Increasing temperatures tended to reduce tendencies toward preferential-diffusion instability behavior (increasing the Markstein number) whereas increasing pressures tended to increase tendencies toward preferential-diffusion instability behavior (decreasing the Markstein number).

• Nuclear Engineering and Technology
• /
• v.50 no.8
• /
• pp.1330-1338
• /
• 2018

High-density UMo/Zr monolithic nuclear fuel plates have a promising application prospect in high flux research and test reactors. The solid state welding method called co-rolling is used for their fabrication. Hot co-rolling simulations for the composite blanks of UMo/Zr monolithic nuclear fuel plates are performed. The effects of coupon sizes and mechanical property parameters on the contact pressures between the to-be-bonded surfaces are investigated and analyzed. The numerical simulation results indicate that 1) the maximum contact pressures between the fuel coupon and the Zircaloy cover exist near the central line along the plate length direction; as a whole the contact pressures decrease toward the edges in the plate width direction; and lower contact pressures appear at a large zone near the coupon corner, where de-bonding is easy to take place in the in-pile irradiation environments; 2) the maximum contact pressures between the fuel coupon and the Zircaloy parts increase with the initial coupon thickness; after reaching a certain thickness value, the contact pressures hardly change, which was mainly induced by the complex deformation mechanism and special mechanical constitutive relation of fuel coupon; 3) softer fuel coupon will result in lower contact pressures and form interfaces being more out-of-flatness.

• 한국연소학회:학술대회논문집
• /
• 1999.10a
• /
• pp.11-20
• /
• 1999

Acoustic pressure response and NO formation of hydrogen-air diffusion flames at various pressures are numerically studied by employing counterflow diffusion flame as a model flame let in turbulent flames in combustion chambers. The numerical results show that extinction strain rate increases linearly with pressure and then decreases, and increases again at high pressures. Thus, flames are classified into three pressure regimes. Such non-monotonic behavior is caused by the change in chemical kinetic behavior as pressure rises. Acoustic pressure response in each regime is investigated based on the Rayleigh criterion. At low pressures, pressure-rise causes the increase in flame temperature and chain branching/recombination reaction rates, resulting in increased heat release. Therefore, amplification in pressure oscillation is predicted. Similar phenomena are predicted at high pressures. At moderate pressures, weak amplification is predicted. Emission index of NO shows similar behaviors as to the peak-temperature variation with pressure.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1996.10a
• /
• pp.295-300
• /
• 1996

The design of formwork system for vertical form faces is controlled by pressures predicted to act against the formwork by fresh concrete. An overestimation of pressure results in heavy, and ex-pensive formwork. An underestimation results in malformed structure, of in some cases, it causes the failure of the formwork. This study is a preliminary step in determination lateral pressures with High folwable concrete. To estimate lateral formwork pressures, we measured tensile strain of formtie in the movable part of the form. From the experimental results maximum lateral pressure and the location at which maximum pressures occurs, were determined. The experimental results are compared with the results predicted by the Gardner & Qureshi's proposed equation and the accepted Korean Standard Specification for concrete and ACI equation.

• Wind and Structures
• /
• v.36 no.1
• /
• pp.15-29
• /
• 2023

To better estimate the non-Gaussian extreme wind pressures for high-rise buildings, a data-driven revised Hermitetype peak factor estimation model is proposed in this papar. Subsequently, a comparative study on three types of methods, such as Hermite-type models, short-time estimate Gumbel method (STE), and new translated-peak-process method (TPP) is carried out. The investigations show that the proposed Hermite-type peak factor has better accuracy and applicability than the other Hermite-type models, and its absolute accuracy is slightly inferior to the STE and new TPP methods for non-Gaussian wind pressures by comparing with the observed values. Moreover, these methods generally overestimate the Gaussian wind pressures especially the STE.

• Korean Journal of Health Education and Promotion
• /
• v.25 no.1
• /
• pp.13-23
• /
• 2008

Objective: The current study was to test if the developed sphygmomanometer was working well and blood pressure information could be collected and monitored systematically through the internet. We tested if the sphygmomanometer and services for blood pressure controlled high blood pressure significantly and the ubiquitous monitoring could be used further. Methods: Kyungwon University, KT Co., Gil Medical Center, LIG Nex1 Co., and Sujeong Health Center conducted an ubiquitous high blood control project in Sujeong-gu, Sungnam, Korea from Mar. 5 to May 16. We developed and applied sphygmomanometer. We distributed the devices to 27 high blood pressure patients. The blood pressures of the residents were monitored through the internet when they measured blood pressures in their homes. A nurse monitored and consulted their blood pressures in the monitoring center in Kyungwon University during the demonstration period. The consultant called them and consulted on their blood pressures in few seconds they used the sphygmomanometers. For the significance of change in blood pressure, we tested statistically with Generalized Additive Model(GAM) and Multi-level Analysis. Results: Both GAM and Multi-level Analysis showed that the blood pressures of persons with ubiquitous blood pressure management decreased significantly as time passed. Conclusions: The internet monitoring and services are considered to be promising because most of the participants were satisfied especially because somebody was caring their health. The decrease of blood pressures was significant by GAM and Multi-level Analysis. Thus, we can apply ubiquitous blood pressure management to health promotion projects.

• Journal of the Ergonomics Society of Korea
• /
• v.28 no.3
• /
• pp.95-102
• /
• 2009

Ten young females were participated in this study to investigate the effects of types of shoes (sneakers, high heels, kill heels), types of tasks (standing, walking floor, step up and down), and areas of foot (fore foot, middle foot, rear foot) on foot pressures as well as subjective discomfort ratings. Results showed that kill heels had the most discomfort shoes, followed by high heels and sneakers. Generally, as the heel was higher, the discomfort of foot increased. For the analyses of task types, generally discomfort ratings were highest for the step down and up, followed by walking floor and standing. Especially discomfort ratings of high heels and kill heels were more evident in case of step up and step down than standing and walking floor. Standing task was rated as the lowest levels of discomfort on users' foot. Peak and mean foot pressures were also evaluated in this study. The findings represented that there was no significant differences between types of shoes in both peak and mean foot pressures. The peak pressure (82.14kPa) and mean pressure (40.32kPa) for standing task were significantly lower than those of other tasks [walking floor (190.55kPa, 55.46kPa), step up (191.43kPa, 53.80kPa), and step down (200.66kPa, 52.62kPa)]. Generally discomfort ratings and peak/mean pressures associated with foot showed that fore foot had higher discomfort ratings as well as peak and mean pressures than middle and rear foots. In particularly, this trend was more obvious in case of high heels and kill heels. For the high heels and kill heels, the peak pressures of fore foot were 4.5~4.8 times and 2.3~2.5 times greater than that of middle foot and rear foot, respectively, whereas the peak pressures of fore foot were 2.9 times and 1.7 times greater than that of middle and rear foots, respectively, in case of sneakers.