• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.5
• /
• pp.572-577
• /
• 2011

Curve squealing of inter-city railway vehicle is a noise with high acoustic pressure and rather narrow frequency spectra. This noise turns out to be very annoying for the people living in the neighborhood of locations and the passenger in railway vehicle where this phenomenon occurs. Squealing is caused by a self-exited stick-slip oscillation in the wheel-rail contact. Curve squeal noise of railway vehicles that passed by a factor of the speed limit, so to overcome in order to improve running performance is one of the largest technology. In the present paper, characteristic of squeal noise behavior at the Hanvit-200 tilting train test-site. Curve squealing of railway wheels/rail contact occurs in R400~ R800 curves with a frequency range of about 4~11 kHz. If the curve is less than the radius of wheel frail contact due to |left-right| noise level difference (dBA) shows a significant effect of squeal noise were more likely.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.13 no.3
• /
• pp.31-38
• /
• 1993

The storage ring vacuum system for the Pohang Light Source (PLS) has been designed to maintain the vacuum pressure of $10^{-10}Torr$ which requires UHV welding to have helium leak rate less than $1{\times}10^{-10}Torr{\cdot}{\ell}/sec$. In order to develop new technique (PLS) welding technique), a prototype vacuum chamber has been welded by using Tungsten Inert Gas welding method and all the welded joints have been tested with a non-destructive method, so called helium leak detection, to investigate the vacuum tightness of the weld joints. The test was performed with a detection limit of $1{\times}10^{-10}Torr{\cdot}{\ell}/sec$ for helium and no detectable leaks were found for all the welded joints. Thus the performance of welding technique is proven to meet the criteria of helium leak rate required in the PLS Storage Ring. Both the principle and the procedure for the helium leak detection are also discussed.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.30 no.2
• /
• pp.226-235
• /
• 2020

Objectives: This study was to investigate the signs and notations of skin absorption, carcinogenicity, germ cell mutagenicity, and reproductive toxicity in the occupational exposure limits of Korea and of other advanced countries. Methods: Information on occupational exposure limits in Korea, the USA, the UK, Germany, and Japan was investigated through the Internet, and items marked as carcinogenicity and skin absorption were compared by country. Results: Legal occupational exposure limits have been greatly simplified. However, in the case of HSE WEL, skin absorption, carcinogenicity classification, sensitization, and in the case of DFG MAK, skin absorption, carcinogenicity, pregnancy risk group, germ cell mutagenicity, airway and skin sensitization, photo contact sensitization, and vapor pressure were provided. Conclusions: It is desirable to indicate the carcinogenicity and skin absorption within permissible limits, and to include information on critical effects in chemical substance exposure limits to uphold the right to know of industrial hygienists and workers in Korea. It is also necessary to clarify the precautions, limitations and protections for skin absorption.

• Journal of The Korean Astronomical Society
• /
• v.5 no.1
• /
• pp.7-14
• /
• 1972

We have investigated the structure of the general relativistic polytrope(G.R.P.) of n=5. The numerical solutions of the general relativistic Lane-Emden functions ${\upsilon}\;and\;{\theta}$ for the ratio of the central pressure to the central density ${\sigma}=0.1$, 0.3, 0.5 and 0.8333 are plotted graphically. We may summarize the results as follows: 1. As the invariant radius $\bar{\xi}$ increases, the numerical value of the mass parameter ${\upsilon}$ does not approach toward the assymptotic limit, as it does in the classical case $({\upsilon}{\sim}{\sqrt{3}})$, but it increases continuously with progressively smaller rate as compared with the classical case. 2. When $\bar{\xi}$ is less than ${\sim}5.5$, the value of the density function ${\theta}$ drops more rapidly than the classical one, whereas when $\bar{\xi}$ is greater than ${\sim}5.5$, ${\theta}$ becomes greater than the classical value. For the greater values of ${\sigma}$ these phenomena become significant. 3. From the above results it is expected that the equilibrium mass of the G.R.P. of n=5 must be larger than the classical masse $({\sqrt{3}})$ and the mass is more dispersed than the classical configuration (i.e. equilibrium with infinite radius).

• Proceedings of the IEEK Conference
• /
• 2001.06d
• /
• pp.151-154
• /
• 2001

In this Paper, a new harmonic imaging technique is proposed and evaluated experimentally. In the proposed method, a weighted chin signal with a hanning window is transmitted. The RF samples obtained on each array element are individually compressed by correlating with the reference signal defined as the 2nd harmonic (2f0) component of a transmitted chirp signal generated in a square-law system. The proposed method uses the compressed 2f0 component to form an image, for which the crosscorrelation term with f0 component should be suppressed below at least -60dB. After experiment, the 6dB pulse width and peak sidelobe level of the compressed 2f0 component were 0.7us and -60dB, respectively. This result shows that the proposed method can successfully eliminate the f0 component with a single transmit-receive event and therefore is more efficient than the conventional pulse inversion (PI) method in terms of frame rate. We also observed that the 2nd harmonic compont starts to decrease for source pressure higher than 210kPa in water, which implies that SNR of the 2nd harmonic imaging using short pulses cnanot be incresed beyond a certain limit.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.23 no.2
• /
• pp.129-141
• /
• 2005

The liquid film behavior between two rotating rollers has been analyzed for many years. Their contributions were, however, limited almost within the areas of polymer laminar flow in there. When the slip contact of two rotating rollers is used as a role of vehicle to distribute the liquid discharged on to each roller after splitting from the nip, there was few available relationship to control the roller speed and to design system. On this work it was possible to get out a certain relationship between the discharged film thickness ratio and the roller surface seeds without any help of pressure limit at the splitting point. The hydrodynamic analyzation of Newtonian liquid behavior around the point was well proved on some manipulative experiment. The thickness ratio increases along with the roll surface speed ratio increases. And the discharged volume flow rate ratio on each roller surface varies with square of the speed ratio. Both of these relationship have a decision factor also made up by the speed ratio.

• Journal of the Korean Institute of Rural Architecture
• /
• v.19 no.4
• /
• pp.77-85
• /
• 2017

In order to preserve beautiful coastal areas landscapes of Jeju Island's the landscape resource, Jeju Special Self-Governing Province is dedicated to protecting the landscape through legal regulations and deliberations. However, the Coastal Landscape of Jeju Island was continuously damaged by due to increased tourist and high development pressure. Based on buildings along the Coastal Road in Aeowal of Jeju Island, this study focused on Management Status of Coastal Areas Landscapes through the Analysis of Building Landscape Elements. As a result, 1) It was effective to limit the use and scale of buildings through legal regulations such as Use zoning. 2) The result of analysis on the physical landscape elements of buildings showed some of the them have the damage values despite passing the review of Architecture Committee. Therefore Landscape Policies required institutional maintenance. 3) As physical landscape Elements of buildings is a minimum quantitation criterion of not less than 1.5 for D/H, or less than a factor of $27^{\circ}$ for angle of elevation and not less than 7.8m for elevation blockage ratio was presented as a criterion for preventing damage to the minimum Coastal Landscape.

• Journal of Mechanical Science and Technology
• /
• v.15 no.11
• /
• pp.1533-1540
• /
• 2001

A high-temperature sodium stainless steel heat pipe was fabricated and its performance has been investigated. The working fluid was sodium and it was sealed inside a straight tube container made of stainless steel. The amount of sodium occupied approximately 20% of the total volume of the heat pipe and its weight was 65.7gram. The length of a stainless steel container is 1002mm and its outside diameter is 25.4mm. Performance tests were carried out in a room air condition under a free convective environment and the measured temperatures are presented. The start-up behavior of the heat pipe from a frozen state was investigated for various heat input values between 600W and 1205W. In steady state, axial temperature distributions of a heat pipe were measured and its heat transfer rates were estimated in the range of vapor temperature from 50$0^{\circ}C$ to 63$0^{\circ}C$. It is found that there are small temperature differences in the vapor core along the axial direction of a sodium heat pipe for the high operating temperatures. But for the range of low operating temperatures there are large temperature drops along the vapor core region of a sodium heat pipe, because a small vapor pressure drop makes a large temperature drop. The transition temperature was reached more rapidly in the cases of high heat input rate for the sodium heat pipe.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2017-2022
• /
• 2008

The crude oil pump system is the equipment for transporting crude oil and it consists of 3 major components, a motor and an impeller which discharge underground crude oil, a pipestack that transmits the cooling oil and power, and a cooling oil unit & junction box that provides cooling oil and electric power. When considering the system characteristics that it has to be installed at a depth of deeper than 100 m, a design technology for the efficient control of the heat occurring at a conductor and motor is necessary and it is the essential factor for ensuring system durability. In this paper, therefore, cooling oil flow has been calculated to satisfy the limit value of the system temperature by analyzing heat flow considering the related losses such as loss of conductor, contact resistor loss at the conductor connection, and operation loss of motor. And the operation temperature has been set up based on the temperature of crude oil and the heat of motor and conductor. Also, a design for cooling of crude oil pump system has been proposed by calculating the operation pressure loss and selecting the capacity of a cooling oil pump and a heat exchanger.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.7
• /
• pp.447-454
• /
• 2008

The regenerative evaporative cooler(REC) is to cool a stream of air using evaporative cooling effect without an increase in the humidity ratio. In the regenerative evaporative cooler, the air can be cooled down to a temperature lower than its inlet wet-bulb temperature. Besides the cooling performance, for practical application of the regenerative evaporative cooler, the compactness of the system is also a very important factor to be considered. In this respect, three different configurations, i.e., the flat plate type, the corrugated plate type, and the finned channel type are investigated and compared for the most compact configuration. The optimal structure of each configuration is obtained individually to minimize the volume for a given effectiveness within a limit of the pressure drop. Comparing the three optimal structures, the finned channel type is found to give the most compact structure among the considered configurations. The volume of the regenerative cooler can be reduced to 1/8 by adopting the finned channel type as compared to that of the flat plate type.