• Wind and Structures
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• v.28 no.5
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• pp.299-313
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• 2019

In order to examine the effects of different wind deflectors on the wind load distribution characteristics of extra-large cooling towers, a comparative study of the distribution characteristics of wind pressures on the surface of three large cooling towers with typical wind deflectors and one tower without wind deflector was conducted using wind tunnel tests. These characteristics include aerodynamic parameters such as mean wind pressures, fluctuating wind pressures, peak factors, correlation coefficients, extreme wind pressures, drag coefficients and vorticity distribution. Then distribution regularities of different wind deflectors on global and local wind pressure of extra-large cooling towers was extracted, and finally the fitting formula of extreme wind pressure of the cooling towers with different wind deflectors was provided. The results showed that the large eddy simulation (LES) method used in this article could be used to accurately simulate wind loads of such extra-large cooling towers. The three typical wind deflectors could effectively reduce the average wind pressure of the negative pressure extreme regions in the central part of the tower, and were also effective in reducing the root of the variance of the fluctuating wind pressure in the upper-middle part of the windward side of the tower, with the curved air deflector showing particularly. All the different wind deflectors effectively reduced the wind pressure extremes of the middle and lower regions of the windward side of the tower and of the negative pressure extremes region, with the best effect occurring in the curved wind deflector. After the wind deflectors were installed the drag coefficient values of each layer of the middle and lower parts of the tower were significantly higher than that without wind deflector, but the effect on the drag coefficients of layers above the throat was weak. The peak factors for the windward side, the side and leeward side of the extra-large cooling towers with different wind deflectors were set as 3.29, 3.41 and 3.50, respectively.

• Korean Journal of Human Ecology
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• v.2 no.1
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• pp.114-128
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• 1999

In a turn a century, the skepticism, mysticism and eroticism used to prevail, the people becoming anxious, expectative and doubtful about an oncoming age. The costumes tend to become more exciting and erotic in the fashion. This thesis is on understanding “What would 21 century's clothes be\ulcorner” after analyzing the specific points in an end of the century. The characteristics found from 16th century to 20th century are going to the extremes in the shapes, consistent appearance of bustle style costumes and excessive ornaments which are closely interrelated with one another. I expect the fashion in 21st century would be changed in two ways. Firstly, going to the extremes and stressing on the buttock would be going down in the end of 1999. Secondly, the comfortable clothes highest in function and technology, and also friendly to the environment, might be the main stream, rather then outwardly good looking clothes, because spirit and environment is much more emphasized than the mode by the social impact or pressure in the next era. (Korean J Human Ecology 2(1) : 114~128, 1999)

• Water for future
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• v.17 no.2
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• pp.99-106
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• 1984

This paper resents frequency distribution of annual maxima of daily rainfall, temperature and pressure at twelve major meteorological stations in South Korea based on avaliable series of annual maxima. As a first step a traditional way of estimating the probabilities of extremes using Jenkinson's method was used here. The results are presented in the form of graph giving the various recurrence periods of rainfall, temperature and pressure and the frequency distributions obtained are discussed.

• International Journal of Computer Science & Network Security
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• v.21 no.5
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• pp.23-30
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• 2021

In recent years, hazardous flash flooding has caused deaths and damage to infrastructure in Saudi Arabia. In this paper, our aim is to assess patterns and trends in climate means and extremes affecting flash flood hazards and water resources in Saudi Arabia for the purpose to improve risk assessment for forecast capacity. We would like to examine temperature, precipitation climatology and trend magnitudes at surface stations in Saudi Arabia. Based on the assessment climate patterns maps and trends are accurately used to identify synoptic situations and tele-connections associated with flash flood risk. We also study local and regional changes in hydro-meteorological extremes over recent decades through new applications of statistical methods to weather station data and remote sensing based precipitation products; and develop remote sensing based high-resolution precipitation products that can aid to develop flash flood guidance system for the flood-prone areas. A dataset of extreme events has been developed using the multi-decadal station data, the statistical analysis has been performed to identify tele-connection indices, pressure and sea surface temperature patterns most predictive to heavy rainfall. It has been combined with time trends in extreme value occurrence to improve the potential for predicting and rapidly detecting storms. A methodology and algorithms has been developed for providing a well-calibrated precipitation product that can be used in the early warning systems for elevated risk of floods.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.1104-1109
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• 1991

Recently, Pneumatic Actuation System (PAS) has been used increasingly as a high performance fin-control servo actuation systems because of the special advantages of pneumatic units: primarily their low cost, small size, light weight, and tolerance to broad temperature extremes. In this study, a nonlinear model of PAS is derived through the detailed analysis of the major components in the typical system. The model includes nonlinear flow-pressure relationships of the flow through the solenoid valve openings and orifices, PWM algorithm for driving two solenoid valves as a closed-center 3-way valve for minimum gas consumption, solenoid valve dynamics, saturation, and friction. Simulation results are compared with the experimental ones for square and sinusoidal inputs to see the validity of the model. Independent of the shape and magnitude of the input signals, both results are in good agreements with minor difference.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.4
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• pp.88-101
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• 1992

Properties of water and steam are very important for the steam ejector CAD program as a subroutine and design of the Shell & Tube type steam condenser. Present formular programs are based on the Skeleton Table of ASME, and are able to calculate the thermodynamoc properties of water and steam throughout the whole of the region that extend in pressure from 0 to 1000 bar and temperature from 0.01 to 80$0^{\circ}C$. When comparing calculated values for specific volume, enthalpy and entropy with the Skeleton Table 1967 and IAPS Skeleton Table 1984, values fell well within tolerances specified except near the extremes of the range of interest at the critical point and triple point, where deviations were slightly larger.

• Atmosphere
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• v.33 no.1
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• pp.49-59
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• 2023

Blocking refers to a class of weather phenomena appearing in the mid and high latitudes, whose characteristics are blocked airflow of persistence. Frequently found over the Pacific and Atlantic regions of the Northern Hemisphere, blocking affects severe weather in the surrounding areas with different mechanisms depending on the type of blocking patterns. Along with lots of studies about persistent weather extremes focusing on the specific types of blocking, a new categorization using Rossby wave breaking has emerged. This study aims to apply this concept to the classification of blockings over the Pacific and examine how different wave breakings specify the associated cold weather in the Korean peninsula. At the same time, we investigate a strongly developing ridge around the Pacific by designing a new detection algorithm, where a reversal method is modified to distinguish ridge-type blocking patterns. As result, Kamchatka blocking (KB) and strong ridge over the Central Pacific are observed the most frequently during 20 years (2001~2020) of the studied period, and anomalous low pressures with cold air over the Korean Peninsula are accompanied by blocking events. When it considers the Rossby wave breaking, cyclonic wave-breaking is dominant in KB, which generates low-pressure anomalies over the Korean Peninsula. However, KB with anticyclone wave breaking appears with the high-pressure anomalies over the Korean Peninsula and it generates the warm temperature anomaly. Lastly, the low-pressure anomalies are also generated by the strong ridge over the Central Pacific, which persists for approximately three days and give a significant impact on cold surge on the Korean Peninsula.

• Korea journal of population studies
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• v.9 no.1
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• pp.54-68
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• 1986

This study was designed to make a comparative analysis of fertility control policies in developing countries selected from Asia and Latin America. Considering the size and the density of population, the history of the fertility control policy, and the availability of references, eight countries were chosen among Asian developing countries that have adopted the fertility control as an official policy. All of nine countries in Latin America that have adopted family planning as an official policy were included in this study. An attempt was made to formulate an analytical framework to be used for a comparative analysis of fertility control policies. It can be represented by a continuum which consists of individual approaches and structural approaches to fertility control at both extremes. It represents fairly well the controversies between those who advocate family planning and those who advocate measures beyond family planning, but assumes that the two sides of the controversy form a continuum of approaches to fertility control. Various fertility control policies of each country were placed along this continuum and analyzed. The results of the analysis can be summarized as follows: (a) Those countries that have higher population pressure in terms of either the size of population or the population density tend to adopt fertility control policies earlier in time. (b) Those countries that have higher population pressure in terms of either the size of population or the population density tend to adopt more comprehensive measures along the continuum of fertility control policies. (c) Those countries that adopted more comprehensive measures along the continuum seem to have succeeded in reducing their level of fertility more effectively. (d) Developing countries in Asia tend to adopt more comprehensive measures to control fertility than those in Latin American countries. (e) The reduction of fertility in developing countries seems to be associated with both the fertility control policies and the level of socioeconomic development.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.3
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• pp.213-220
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• 2023

In this study, we report the effect of starting materials on the grain size in a multi-component system at high pressure experiments. We used two different starting materials, glass and nano powders, to synthesize bridgmanite in the reduced conditions in the presence of calcium-ferrite-phase MgAl₂O₄ to compared the grain size of synthesized samples. After synthesizing the sample at 40 GPa, 2000 K for 20 hrs, the sample from glass showed the grain size of 50-200 nm whereas the one from nano powders has ~500 nm of grains. This difference may come from 1) the temperature of 2000 K which is low enough for glass starting materials to make more crystal nucleis than to grow crystal size or 2) the possible difference in the redox state of starting materials. It is suggested that the using of nano powders is better to synthesize bigger grains in high pressure experiments with multi-component systems rather than using glass starting materials.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.572-582
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• 1989

Elastic deformations of an infinitely long strip and a beam loaded by uniform pressure upon their upper surfaces, with the fixed-free end dondition, are considered within the range of small strains. All local governing equations are satisfied up to first order in strains, and to take into account the higher order terms neglected in the local governing equations, the overall equilibrium is imposed exactly up to the leading order. The success of the approach relies upon the semi-inverse method and the decomposition of deformations in which the classical linear theory guides the solution. The solution bridges the gap between the two extremes-the classical solutions valid only for infinitesimal deformations and the solutions form the technical theories for deformations with large rotations. The solutions may be used to confirm the technical theories and to verify numerical solutions obtained from finite element analysis.