• Earthquakes and Structures
• /
• v.4 no.1
• /
• pp.63-84
• /
• 2013

A semi-active mass damping (SMD) system with magnetorheological (MR) dampers focusing on low- and mid-rise buildings is proposed in this paper. The main purpose of this study is to integrate the reliable characteristics of the traditional tuned mass damper (TMD) and the superior performance of the active mass damper (AMD) to the new system. In addition, the commonly seen solution of deploying dense seismic dampers throughout the structure nowadays to protect the main structure is also expected to switch to the developed SMD system on the roof with a similar reduction performance. In order to demonstrate this concept, a full-size three-story steel building representing a typical mid-rise building was used as the benchmark structure to verify its performance in real life. A numerical model with the interpolation technique integrated was first established to accurately predict the behavior of the MR dampers. The success of the method was proven through a performance test of the designated MR damper used in this research. With the support of the MR damper model, a specific control algorithm using a continuous-optimal control concept was then developed to protect the main structure while the response of the semi-active mass damper is discarded. The theoretical analysis and the experimental verification from a shaking table test both demonstrated the superior mitigation ability of the method. The proposed SMD system has been demonstrated to be readily implemented in practice.

• Tribology and Lubricants
• /
• v.30 no.4
• /
• pp.240-245
• /
• 2014

Low alloy heat resistant brake disk and sintered brake pad are applied to mechanical brake system for the speed-up of urban rapid transit. In this research, we analyzed how the frictional characteristics between brake disk and pad are influenced by the disk mass. At a high disk mass, the friction stability was the lower value as a result of the lack of tribofilm formation at the disk surface. Wear rates of friction materials showed the higher value at a low disk mass and wear rates of 10 mm and 15 mm showed the similar level. Average friction coefficient was the lower value at the 10 mm disk thickness and range of variation of average friction coefficient was also the smaller value at the 10 mm disk thickness. However, there were no significant changes in the friction coefficients under any of test conditions. Surface roughness of a disk showed the highest value at the 5 mm disk and surface roughnesses of 10 mm and 15 mm showed the similar level. As a result, friction characteristics of disk mass influenced the friction stability, as well as the wear rate of friction pad and disk, but not the friction coefficient.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1340-1345
• /
• 2004

Convective boiling heat transfer coefficients of R-22 were obtained in a flat extruded aluminum tube with $D_h=1.41mm$ . The test range covered mass flux from 200 to 600 $kg/m^2s$, heat flux from 5 to 15 $kW/m^2$ and saturation temperature from $5^{\circ}C$ to $15^{\circ}C$ . The heat transfer coefficient curve shows a decreasing trend after a certain quality(critical quality). The critical quality decreases as the heat flux increases, and as the mass flux decreases. The early dryout at a high heat flux results in a unique 'cross-over' of the heat transfer coefficient curves. The heat transfer coefficient increases as the mass flux increases. At a low quality region, however, the effect of mass flux is not prominent. The heat transfer coefficient increases as the saturation temperature increases. The effect of saturation temperature, however, diminishes as the heat flux decreases. Both the Shah and the Kandlikar correlations underpredict the low mass flux and overpredict the high mass flux data.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.12 no.3
• /
• pp.148-157
• /
• 2004

Convective boiling heat transfer coefficients of R-22 were obtained in a flat extruded aluminum tube with $D_h=1.41mm$. The test range covered mass flux from 200 to $600kg/m^{2}s$, heat flux from 5 to $15kW/m^2$ and saturation temperature from $5^{\circ}C\;to\;15^{\circ}C$. The heat transfer coefficient curve shows a decreasing trend after a certain quality (critical quality). The critical quality decreases as the heat flux increases, and as the mass flux decreases. The early dryout at a high heat flux results in a unique 'cross-over' of the heat transfer coefficient curves. The heat transfer coefficient increases as the mass flux increases. At a low quality region, however, the effect of mass flux is not prominent. The heat transfer coefficient increases as the saturation temperature increases. The effect of saturation temperature, however, diminishes as the heat flux decreases. Both the Shah and the Kandlikar correlations un-derpredict the low mass flux and overpredict the high mass flux data.

• Journal of Gastric Cancer
• /
• v.18 no.3
• /
• pp.274-286
• /
• 2018

Purpose: The aim of this study was to investigate the impact of preoperative low body mass index (BMI) on both the short- and long-term outcomes in patients with gastric cancer. Materials and Methods: A total of 510 patients with gastric cancer were divided into the following 3 groups: low BMI group (${\leq}18.5kg/m^2$, n=51), normal BMI group ($18.6-24.9kg/m^2$, n=308), and high BMI group (${\geq}25.0kg/m^2$, n=151). Results: There were significantly more stage III/IV patients in the low BMI group than in the other groups (P=0.001). Severe postoperative complications were more frequent (P=0.010) and the survival was worse (P<0.001) in the low BMI group. The subgroup analysis indicated that survival was worse in the low BMI group of the stage I/II subgroup (P=0.008). The severe postoperative complication rate was higher in the low BMI group of the stage III/IV subgroup (P=0.001), although the recurrence rate and survival did not differ in the stage III/IV subgroup among all the BMI groups. Low BMI was an independent poor prognostic factor in the stage I/II subgroup (disease-free survival: hazard ratio [HR], 13.521; 95% confidence interval [CI], 1.186-154.197; P=0.036 and overall survival: HR, 5.130; 95% CI, 1.644-16.010; P=0.005), whereas low BMI was an independent risk factor for severe postoperative complications in the stage III/IV subgroup (HR, 17.158; 95% CI, 1.383-212.940; P=0.027). Conclusions: Preoperative low BMI in patients with gastric cancer adversely affects survival among those with stage I/II disease and increases the severe postoperative complication rate among those with stage III/IV disease.

• Journal of Astronomy and Space Sciences
• /
• v.22 no.3
• /
• pp.223-232
• /
• 2005

New BVR CCD light curves of the low mass ratio contact binaries, V410 Aur and V776 Cas, were observed with the 61 cm reflector and a 2K CCD camera at the Sobaeksan Astronomical Observatory. The absolute dimensions of the low mass ratio contact binaries, V410 Aur and V776 Cas, were obtained using WD program from the published spectroscopic and newly observed photometric data. The evolutionary status of this type of binary system including V410 Aur and V776 Cas has been considered. We reconfirmed that the primary stars of the low mass contact binary system were located on the TAMS and secondary stars were located under the ZAMS in H-R diagram.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.4
• /
• pp.1481-1490
• /
• 1996

This study is intend to improve flow pattern within evaporator, which is low quality and low mass flux, by installing narrow horizontal annular crevice so that enhance heat transfer coefficient. The motive, which made to study heat transfer enhancement by using narrow annular crevice, came from capillary phenomena and pumping force of generating vapor on refrigerant boiling. Tests were run about 5 models of turbulence promoter with CFC-12, in the range of evaporating temperature (15.deg. C), mass flux (50 to 100 kg/m$\^$2/s), heat flux (3.4 to 6.7 kW/m$\^$2/), quality (0.1 to O.5). It is observed that flow pattern within evaporator is changed closely to semi-annular flow or annular flow, of which refrigerant liquid is reached to the upper side of tube by using narrow annular crevice. When the narrow annular crevice is installed in the evaporator tube, local heat transfer coefficient is generally more improved than that of smooth tube. That fact is according to observed result of flow pattern. It is learned that narrow annular crevice has more efficiency at a low mass flux. At the TP-5, enhancement of heat transfer rate is about 170% compare to that of smooth tube on a low mass flux (50 kg/m$\^$2/s), and it is about 134% on a high mass flux (100 kg/M$\^$2/S), so that we know that it is on a very high condition.

• Mass Spectrometry Letters
• /
• v.2 no.1
• /
• pp.1-7
• /
• 2011

China's rapid economic growth has resulted in significant environmental side effects. Therefore, China has been interested in reducing her dependence on foreign oil and gas by developing technologies needed for hydrogen, in addition to her increasing energy mix of nuclear and renewable energy form, such as solar and wind power. There are three isotopes of hydrogen, i.e. protium (P or H), deuterium (D), and tritium (T). Both deuterium and tritium are important materials in nuclear fuel cycle industry. Tritium is one of the critical radioactive nuclides. Planning for and implementing contamination control as a part of normal operation and maintenance activities is an important function in any hydrogen facility, especially tritium facility. The development of hydrogen isotopes analysis is the key issues in this area. Mass spectrometry (MS) with medium (about 600) and high resolution (> 1,400) is commercially available; however, the routine analysis of hydrogen isotopes is done with low-resolution MS (< 200) in China. This paper summarizes the progress of MS measurement technology for hydrogen isotope abundance in China, focusing on our lab's research program and technical status. An analyzing method has been introduced for accurate measurement of tritium abundance in the H.D.T system by low resolution MAT-253 MS. The quotient of compression ratio coefficient is determined by building up equipment for laboratory-scale preparation of secondary standard gases and by considering the difference in sensitivity between hydrogen isotopes. The results show that the measured value is reproducible within the relative error range of 0.8% for gas samples of different tritium abundance.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2010.05a
• /
• pp.37-39
• /
• 2010

In this study, with new office construction site of S Construction company as subject, to solve all the problems according to reduced hydration heat and temperature crack of mass concrete used mat foundation and placing time difference, low heat combination of coarse particle cement and fly-ash and setting time difference applied AE water reducing agent, and to prevent the early frost damage caused by low outdoor temperature, a heat insulation method using double bubble sheet was conducted. As a result, it was found that hydration heat and setting time difference was reduced by applying a low heat combination and setting time difference construction method, and that the high insulation capability of the double bubble sheet was able to not only prevent the early frost damage but also reduce temperature difference between the central part and the upper part of mass concrete.

• Journal of the Korean Society of Costume
• /
• v.59 no.1
• /
• pp.146-158
• /
• 2009

The purpose of this study was to identify hair salon's implementation strategies and current service condition for mass customization. The questionnaire was composed of 82 questions. 115 hair salon's directors were subjects of this study. The results were as follows: Hair salon's mass customization strategies were categorized into 6 factors such as staff's technique, communication service, electronic products, monetary support, man-to-man service, and dissatisfaction removal service. Hair salons were categorized into 2 groups of a high implementation group and a low implementation group. A high implementation group had a higher monthly sales and more regular customers and staff. The hair salons were franchises and were more spacious in the high group. They were located at fashion street, department store, or outlet mall, and offered fashionable hair styles. However, a low implementation group had a lower monthly sales and less regular customers and staffs. The size of hair salon was small in the low group. They were located in residential areas and offered basic hair styles.