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정수하 주성전문대학 2008 論文集 Vol.17 No.-
This study is to investigate the factors affecting dental health behaviors, among the students in the department of dental technic who will deal with dental health works The subject includes, 503 students majoring in dental technic of the three universities located in Chungbuk, Jeonbuk, and Gyeongbuk, and factors, affecting their characteristics in terms of sociology of population, conviction regarding dental health, and dental health behaviors are analyzed 1 After inverstigating the differences in the belief of the subjects in oral health according to their general characteristics, it has been found that there were no significant differences in smoking or non-smoking and the monthly income of householders, but there were significant differences in sex, school year, age, religion and academic career 2 In terms of the differences in the belief of the subjects in oral health depending on the behaviors as to oral health, it has been shown that there were significant differences in the frequency of tooth brushing, number of taking in a between-meal snack, the existence of experiencing dental clinics for dental treatments, the period of last visit to dental clinics, the presence of experiencing dental treatments for preventive purpose and the use of oral hygiene devices 3 With regards to the relationship between the attitudes, subjects toward oral health and their belief in oral health, it has been noted that they were positively correlated to usefulness and cues to action concerning the interest, importance of oral health and the belief in it and they were negatively correlated to seventy usefulness, sensitivity and obstacles concerning the conditions of oral health and the belief in it 4 One of the most significant variables that had the effects on the belief in oral health was subjective conditions of oral health and it has been shown that the healthier one considered one's oral conditions, the higher belief one had in oral health
Aerobic Biodegradability of Polyester/Polylactic Acid Composites for Automotive NVH Parts
Jeoung, Sun Kyoung,Ha, Jin Uk,Ko, Youn Ki,Kim, Bo-Ram,Yoo, Seung Eul,Lee, Ki Dong,Lee, Su Nam,Lee, Pyoung-Chan Korean Society for Precision Engineering 2014 International Journal of Precision Engineering and Vol.15 No.8
The biodegradability of the environmental dash isolation pad was determined under aerobic conditions (ISO-14855-1). The environmental dash isolation pad was fabricated with polyester fiber and low-melting PLA fiber (LM-PLA), instead of low-melting polyester fiber. The results showed a biodegradation of 27% under aerobic conditions within a period of 45 days of composting. The commercial dash isolation pad using LM-PET (polyethylene terephthalate) fiber did not biodegrade under aerobic condition. The decrement of tensile strength and weight loss of PET/30% LM-PLA composite after 40 days were 50% and 24%, respectively, since the LM-PLA was degraded due to the progression of biodegradation. The change of molecular weight of LM-PLA fiber was examined by Gel Permeation Chromatography (GPC). The degradation of the polymer chains was caused by aerobic bacteria and its molecular weight was gradually reduced. The environmental dash isolation pads were left with 18 months under atmospheres, however, the change of tensile strength were lowing 19.8%, while the commercial dash isolation pad resulted in 19.6%. It showed a reduction of 50% in its tensile strength under aerobic conditions, no deformation or cracks were observed after the durability test.
강선 이음형 PC 보-기둥 외부 접합부의 구조적 거동에 관한 실험적 연구
하상수(Ha Sang-Su),조경래(Cho Kyung-Rae),김승훈(Kim Seung Hun),문정호(Moon Jeoung-Ho),이리형(Lee Li-Hyung) 대한건축학회 2004 大韓建築學會論文集 : 構造系 Vol.20 No.10
In this study, new moment-resisting precast concrete beam-column joint system is proposed for the use in moderate seismic regions. It is attempted to devise connection details which improve workability and provide effective stress transfer mechanism in the region of connection. The beam-column connection is made of U-shaped reinforced beam and 7-wire strands which are embedded in the bottom part of half PC beam. The specimens were compared with a exterior beam-column joint with reinforced bars. The experimental study was carried out to investigate the behavior of the exterior joint subjected to reverse cyclic loading and constant axiall compressive load. The test variables were the number of strands in connection. Structural performance of exterior joint is evaluated on the basis of connection strength, stiffness, energy dissipation, drift capacity, and strain gage. Based on the test results, the precast connection is proved to be capable at matching or exceeding the performance of the monolithic connection and thereby provides the sufficient moment-resisting behavior to be applicable for moderate seismic regions.
Regeneration of deactivated H-ZSM-5 for aromatization by dielectric barrier discharge plasma
Kim, Mahnjung,Jeoung, Jaekwon,Kim, Juchan,Ha, Kyoung-Su Elsevier 2019 Applied Catalysis A Vol.575 No.-
<P><B>Abstract</B></P> <P>A dielectric barrier discharge (DBD) plasma regeneration reaction was conducted at atmospheric pressure and temperature. This method was found to be very effective in removing carbon deposits after a non-oxidative aromatization from acetylene. When a fresh H-ZSM-5 catalyst was used for the aromatization, coke was by-produced and it could be ascribed to the primary reason for deactivation. By applying the DBD plasma to the deactivated catalyst bed at ambient temperature and pressure, the removal of carbon deposition with microdischarge and aeration was very effective; therefore, it is believed that additional thermal activation might not be necessary. More amount of coke was removed by supplying higher power to the catalyst bed. According to the results of XRD, physisorption, <SUP>27</SUP>Al MAS NMR, and NH<SUB>3</SUB>-TPD analyses, it was confirmed that the structure and the acid site distribution of H-ZSM-5 were successfully retained even after the plasma treatment. Aromatization over the plasma-regenerated catalyst led to mild deactivation at the early stage and afforded comparable BTX selectivity to fresh H-ZSM-5 catalyst. Compared with the results obtained using the thermally regenerated catalyst, the structural stability was found to be higher and the BTX selectivity was kept higher during most of the reaction time for the plasma-regenerated catalyst.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Carbon deposit from aromatization is effectively removed by a DBD plasma. </LI> <LI> The method is conducted at ambient pressure and temperature. </LI> <LI> The method does not deform the structure of dielectric material in the bed. </LI> <LI> The plasma-regenerated catalyst suppresses the excessive wasting of acetylene. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Juchan,Jeoung, Jaekwon,Jeon, Jonghyun,Kim, Jip,Mok, Young Sun,Ha, Kyoung-Su Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.377 No.-
<P><B>Abstract</B></P> <P>A dielectric barrier discharge (DBD) plasma reactor was employed for non-oxidative coupling of methane. The coupling reaction in the DBD plasma bed was conducted near atmospheric pressure and room temperature. In the bed, dielectric materials such as ordered mesoporous silica (KIT-6), sea sand silica, and α-Al<SUB>2</SUB>O<SUB>3</SUB> were employed. This non-catalytic reaction system could successfully activate CH bond to produce methyl radicals and light hydrocarbons without additional thermal energy and oxidant molecules. The gap distance between dielectric particles was determined by their sizes, which was experimentally shown. The effects of gap distance were found significant on the conversion and the selectivity. The existence of maximum conversion at a specific gap distance was experimentally observed and could be described successfully by using a newly developed concept of micro-electrodes. Based on the concept, the minimum threshold electric potential difference between the dielectric particles could be successfully estimated, where the conversion was shown to be maximized. Furthermore, it seemed quite possible to control the compositions of ethane, ethylene, and acetylene by properly adjusting the size or the gap distance of particles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The methane conversion shows its maximum in terms of particle size. </LI> <LI> The concept of microelectrodes explains the existence of maximum conversion. </LI> <LI> By adjusting particle size, selectivity can be controlled without catalyst. </LI> <LI> In terms of coke formation, non-porous silica particles are favored. </LI> <LI> Coke is more produced when large particles are used. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>