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A Study on the Mitigation of Welding Distortion of a Precision Component for Automobile Transmission (자동차 변속기용 정밀 부품의 용접변형 감소화에 관한 연구)

  • Chung, Hoi-Yoon;Kim, Jae-Woong;Yun, Seok-Chul
    • Journal of Welding and Joining
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    • v.30 no.4
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    • pp.31-37
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    • 2012
  • In recent years, a demand for precision-welding is increasing in wide industrial fields for getting a high quality welded structures. Although laser welding is commonly used for precision-welding, gas tungsten arc (GTA) welding is also attempted as a precision-welding due to the cost benefit. However, welding heat causes an uneven temperature distribution leading to welding deformation. Since it causes geometric errors and degrades product quality, welding distortion recently rises as an important issue in the field of automobile parts. To control welding deformation, it is needed to design in shapes that can maximize stiffness against deformation during welding; control the welding sequence; minimize heat input; and weld allowing reverse deformation; etc. Thus it is necessary to find the one, among such approaches, that can minimize the deformation range by mathematical analysis and understand how effective it would be when it is actually used in industrial fields. This study performs analyses by numerical calculations and experiments for the De-Tent Lever, one of transmission part that requires precision the most among automobile parts, as the subject of experiment. Decrease in welding deformation is required for this part, since there is currently a trouble in guaranteeing precision due to angular deformation by welding between boss and plate. Finally the ways to minimize welding deformation has been suggested in this study through analyses on it.

Analysis of Radiation Shielding Effect of Soft Magnetic Material applied to Military Facility (경량 연자성 소재의 군 시설물 적용 시 방사선 차폐효과 분석)

  • Lee, Sangkyu;Lee, Sangmin;Choi, Gyoungjun;Lee, Byounghwak
    • Journal of the Korean Society of Radiology
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    • v.15 no.2
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    • pp.191-199
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    • 2021
  • The purpose of this research is to analyze the radiation shielding effect of soft magnetic material to confirm the applicability to the military facilities. The soft magnetic material is known to be effective in shielding EMP. If this material is also effective in radiation shielding, it is expected that it has a lot of applicability in military protection. In particular, this material contains boron, so it will be effective in shielding neutrons. In this research, experiments were conducted using Cs-137 and Co-60 sources to check the gamma ray shielding effect. In addition, the Monte Carlo N-Particle(MCNP) modeling was applied to evaluate the gamma ray and neutron shielding effect of a military command tent. As a result, as the soft magnetic thickness increased, the shielding performance improved according the linear attenuation law of gamma ray and neutron. Therefore, this research verified that the application of soft magnetic material for military purposes in radiation shielding would be effective.

IoT MQTT Security Protocol Design Using Chaotic Signals (혼돈신호를 이용한 IoT의 MQTT 보안 프로토콜 설계)

  • Yim, Geo-Su
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.11 no.6
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    • pp.778-783
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    • 2018
  • With the rapid advancement of information and communication technology and industrial technologies, a hyper-connected society is being realized to connect human beings, all programs and things via the Internet. IoT (Internet of Thing), which connects a thing and another thing, and things and human beings, gathers information to realize the hyper-connected society. MQTT (Message Queuing Telemetry Transport) is a push-technology-based light message transmission protocol that was developed to be optimized to the limited communication environment such as IoT. In pursuing the hyper-connected society, IoT's sensor environment information is now being used as a wide range of information on people's diseases and health management. Thus, security problems of such MQTT include not only the leak of environmental information but also the personal information infringement. To resolve such MQTT security problems, we have designed a new security MQTT communication by applying the initial-value sensitivity and pseudorandomness of the chaotic system to the integrity and confidentiality. The encryption method using our proposed chaotic system offers a simple structure and a small amount of calculation, and it is deemed to be suitable to the limited communication environment such as IoT.

Experimental and Analytical Study on Hydrogen-air Deflagrations in Open Atmosphere (개방 공간에서 발생하는 수소-공기 혼합 가스 폭연에 대한 실험적/해석적 연구)

  • Kim, Yangkyun;Park, Byoung Jik
    • Journal of the Korean Society of Safety
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    • v.36 no.1
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    • pp.64-71
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    • 2021
  • Experimental and analytical investigations are performed to explore the explosion characteristics of a hydrogen-air mixture in open atmosphere. A hydrogen-air mixture tent of total volume of 27 m3, with 40% hydrogen volume, is used to observe overpressure at a distance from the ignition source. Vapor cloud explosion analyses are performed using the TNO multi-energy model and Baker-Strehlow-Tang model. The results of these analyses are compared with experiment done from this study and references. The experimental results with and without obstacles indicate that the overpressure values measured at a distance of 4.5-21.5 m from the ignition source are about 9.4-3.6 kPa and 6.5-2 kPa, respectively. This implies that the overpressure with obstacles is approximately 1.7 times greater than that without obstacles. Analytical observation indicates that the results obtained with the Baker-Strehlow-Tang model with Mf = 0.2-0.35 are in good agreement with those of most of the previous studies, including that obtained from this study. Moreover, the TNO multi-energy model with a volume of 27 m3 well predicts the overpressure obtained from this study. Further studies should considered explosions in semi-confined spaces, which is more suitable for hydrogen refueling stations.

Influence of Days after Flowering and Cultural Environments on Changes of Alpha-Acid Content in Hops (Humulus lupulus L.) (홉프의 재배환경과 개화후 일수에 따른 $\alpha$-acid 함량 변화)

  • Park, Kyeong-Yeol;Ree, Dong-Woo;Min, In-Ki
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.32 no.1
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    • pp.97-102
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    • 1987
  • The objective was to obtain the basic information for the changes of the alpha-acid content according to days after flowering. altitude and weather of Hoeongseong, Korea. The alpha-acid of hops reached the highest con-tent in sixty one days after flowering, and the optimum time for cone picking was noted as 11-15th August. The altitude for the highest alpha-acid content was 190-260m of Hoeongseong. The year-to-year variations in the alpha-acid content of hops were higher than the altitude variations. The higher alpha-acid content was associated with a higher temperature and more amounts of sunshine in late July. Alpha-acid content and yield had a significant positive correlation.

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Promoted rooting of softwood cuttings of highbush blueberry 'Duke', 'Elizabeth', 'Elliot' (Vaccinium corymbosum L.) as affected by indole-3-butyric acid(IBA) dipping treatment (Indole-3-butyric acid(IBA) 침지처리에 의한 highbush blueberry 'Duke', 'Elizabeth', 'Elliot' (Vaccinium corymbosum L.)의 녹지삽목 발근 촉진)

  • Kang, S.K.
    • Journal of Practical Agriculture & Fisheries Research
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    • v.17 no.1
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    • pp.145-155
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    • 2015
  • To investigate the practicality of a small scale softwood propagation plastic film tent and the rooting promoting effect of indole-3-butyric acid(IBA) for northern highbush blueberry, softwood cuttings of 3 varieties (Duke, Elizabeth, Elliot) were made after dipping in the IBA solutions of 100ppm, 300ppm, 500ppm, 1,000ppm for 2 hour, and 3,000ppm for 20 seconds, respectively. Two-way ANOVA confirmed the significant differences in the percentage of rooting of cutting, longest root length and rooting volume index (RVI) induced by IBA treatment, as well as the percentage of rooting of cutting and RVI among examined varieties. In particular, the highly significant difference was observed in th RVI for IBA treatment. However, there was no interactions between the auxin treatments and varieties. Spontaneous rooting ability (control) depends on the varieties, showing that the lowest rooting ability was observed in the 'Duke' (45%) followed by 'Elliot'(85%) and 'Elizabeth' (90%). In addition, the rooting of the examined 3 varieties were enhanced by both of short time (20sec) dipping treatment of low level solutions, and long time (2hr) dipping treatment of high level solution, with the remarkably promoted rooting of the 'Duke' cuttings.

Suggestions for E-Learning Based on Four Years of Cyber University Experience

  • LEE, Okhwa
    • Educational Technology International
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    • v.6 no.1
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    • pp.41-63
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    • 2005
  • E-Learning is widely introduced with cyber universities in Korea from 2001 whencyber universities were first authorized by the Ministry of Education and Human Resource Development. E-learning amplified by cyber university gave a big impact in the campus based university which became the cause for the educational paradigm shift. The changes of status of cyber university shows important trend in college education which was analyzed by enrollment rate, types of cyber university, demography, and study areas. The enrollment rate of cyber universities is ever since 2001 and variety of study areas gives popularity to students. The demography of students is as expected older than traditional students. Female students at the cyber university outnumbered that at campus based university in Korea. For analyzing the trend of e-learning in Korea, there were studies twice in 2001 May-June from 213 faculty members and staff, 630 students and in 2004 May-June with 401 students. Most of e-learning students tent to spend less time yet, students feel more burden with e-learning. Professors tend to load more materials for the e-learning in 2001but in 2004 study, the difference no longer exists. Professors and students feel the academic achievement through e-learning is not as good as from the traditional classes. Difficulties for e-learning in 2001 were the lack of administrative information but in 2004, boring contents and lack of instructional strategies for e-learning. Technical problems still do exist but less serious. Suggestions for e-learning are blended learning, online students prefer video streaming with their own lecturer, new definition of instructor is needed, professional development for content development and online instruction is needed, success story of online learning should be encouraged, guidance for online students needed. The cyber university experiencegave a positive impact on the traditional universities such as rethinking the roles of universities, the quality control of classes, professional development, student oriented educational service of e-learning pedagogy.

A Three-year Study on the Leaf and Soil Nitrogen Contents Influenced by Irrigation Frequency, Clipping Return or Removal and Nitrogen Rate in a Creeping Bentgrass Fairway (크리핑 벤트그라스 훼어웨이에서 관수회수.예지물과 질소시비수준이 엽조직 및 토양 질소함유량에 미치는 효과)

  • 김경남;로버트쉬어만
    • Asian Journal of Turfgrass Science
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    • v.11 no.2
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    • pp.105-115
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    • 1997
  • Responses of 'Penncross' creeping bentgrass turf to various fairway cultural practices are not well-established or supported by research results. This study was initiated to evaluate the effects of irrigation frequency, clipping return or removal, and nitrogen rate on leaf and soil nitrogen con-tent in the 'Penncross' creeping bentgrass (Agrostis palustris Huds.) turf. A 'Penncross' creeping bentgrass turf was established in 1988 on a Sharpsburg silty-clay loam (Typic Argiudoll). The experiment was conducted from 1989 to 1991 under nontraffic conditions. A split-split-plot experimental design was used. Daily or biweekly irrigation, clipping return or removal, and 5, 15, or 25 g N $m-^2$ $yr-^1$ were the main-, sub-, and sub-sub-plot treatments, respectively. Treatments were replicated 3 times in a randomized complete block design. The turf was mowed 4 times weekly at a l3 mm height of cut. Leaf tissue nitrogen content was analyzed twice in 1989 and three times in both 1990 and 1991. Leaf samples were collected from turfgrass plants in the treatment plots, dried immediately at 70˚C for 48 hours, and evaluated for total-N content, using the Kjeldahl method. Concurrently, six soil cores (18mm diam. by 200 mm depth) were collected, air dried, and analyzed for total-N content. Nitrogen analysis on the soil and leaf samples were made in the Soil and Plant Analyical Laboratory, at the University of Nebraska, Lincoln, USA. Data were analyzed as a split-split-plot with analysis of variance (ANOVA), using the General Linear Model procedures of the Statistical Analysis System. The nitrogen content of the leaf tissue is variable in creeping bentgrass fairway turf with clip-ping recycles, nitrogen application rate and time after establishment. Leaf tissue nitrogen content increased with clipping return and nitrogen rate. Plots treated with clipping return had 8% and 5% more nitrogen content in the leaf tissue in 1989 and 1990, respectively, as compared to plots treated with clipping removal. Plots applied with high-N level (25g N $m-^2$ $yr-^1$)had 10%, 17%, and 13% more nitrogen content in leaf tissue in 1989, 1990, and 1991, respectively, when compared with plots applied with low-N level (5g N $m-^2$ $yr-^1$). Overall observations during the study indicated that leaf tissue nitrogen content increased at any nitrogen rate with time after establishment. At the low-N level treatment (5g N $m-^2$ $yr-^1$ ), plots sampled in 1991 had 15% more leaf nitrogen content, as compared to plots sampled in 1989. Similar responses were also found from the high-N level treatment (25g N $m-^2$ $yr-^1$ ).Plots analyzed in 1991 were 18% higher than that of plots analyzed in 1989. No significant treatment effects were observed for soil nitrogen content over the first 3 years after establishment. Strategic management application is necessary for the golf course turf, depending on whether clippings return or not. Different approaches should be addressed to turf fertilization program from a standpoint of clipping recycles. It is recommended that regular analysis of the soil and leaf tissue of golf course turf must be made and fertilization program should be developed through the interpretation of its analytic data result. In golf courses where clippings are recycled, the fertilization program need to be adjusted, being 20% to 30% less nitrogen input over the clipping-removed areas. Key words: Agrostis palustris Huds., 'Penncross' creeping bentgrass fairway, Irrigation frequency, Clipping return, Nitrogen rate, Leaf nitrogen content, Soil nitrogen content.

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Effects of Diffused Light Materials on Marketable Yield and Quality of Sunlight Dried Red Pepper (Capsicum annuum L.) in Plastic Film House (비닐하우스 이용 태양초 생산시 산광 재료가 상품 수량과 품질에 미치는 영향)

  • Lee, Guang-Jae;Song, Myung-Gyu;Kim, Si-Dong;Nam, Sang-Young;Lee, Ki-Yeol;Kim, Tae-Jung;Kim, Dong-Eok;Yoon, Jung-Beom;Choi, Kyu-Hong
    • Korean Journal of Plant Resources
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    • v.27 no.1
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    • pp.102-109
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    • 2014
  • This study was carried out to investigate the effects of diffused light materials on marketable yield and quality of sunlight dried red pepper in plastic film house. The after ripening methods were composed of 3 treatments; using electric bulk dryer (Bulk), sealing house (House), and PE sealing. The diffused light materials were control, tent, shading 35% (Shading net), white polypropylene (PP (white)), and black polypropylene (PP (Black)). The marketable yield was high in order of Bulk as 300 g, House as 275 g, and PE sealing as 112 g. The redness of PE sealing was the highest as 17.85 and that of Bulk was the lowest as 10.65. There was significant difference in redness among the treatments. The moisture content of red pepper was the most rapidly reduced in control, and was the most slowly reduced in Shading net treatment. The marketable yield index was the higher in PP (white) as 114% than control. The redness had a significant difference in PP (Black) and tent compared to the other treatments. The capsaicin content showed the highest as $160mg{\cdot}100g^{-1}$ in PP (white) treatment. Conclusively, the most effective method for sunlight drying red pepper was House with PP (White) treatment. It delayed drying for 2 days but increased marketable yield at 114% than control when sunlight dried red pepper in plastic house. Our results also provided an optimized method for improvement of drying red pepper with sunlight, and will be useful for further drying red pepper research.

A Study on the life of Yoon Cho Chang(尹草窓) and Cho-Chang-Kyeul(草窓訣) (윤초창(尹草窓)의 생애(生涯)와 초창결(草窓訣)에 관(關) 연구(硏究))

  • Kim, Joon Tae;Yoon, Chang Yeul
    • Journal of Korean Medical classics
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    • v.6
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    • pp.189-227
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    • 1993
  • I have studied life of Yoon-Dong-Li(尹東里), who applied Un-Ki(運氣) theory to medicine during Suk-Jong(肅宗) to Joong-Jo(正祖) in Yi-Dynasty and also studied his existing writings named ${\ll}$Cho-Chang-kyeol${\gg}$ (草窓訣). The referenced original work prints were based on 1980's print of Chung-Ku oriental medical society and National Central Library and The academy a korean studies possessed print. Studied with these books, I have concluded as follows. 1. Yoon-Dong-Li(尹東里) courtesy name is Ja-Mi(子美), pen name is Cho-Chang(草窓). He was born in 1705, Suk-Jong(肅宗) 31yrs, and died in 1784, Jeong-Jo(正祖) 8yrs in Yi-Dynasty. He had lineage of third-generationed-doctor and learned medicine from his uncle, Yoon-Woo-Kyo(尹雨敎). His father Yoon-Yi-Kyo(尹이敎) gaved him second influence. 2. Confucianal physician in Ming Dynasty You-Bu(劉溥) respected Ju-Ryeom-Kye(周溓溪), confucianist in Song-Dynasty and You-Bu(劉溥) does not removed grass in front of window (because in chinese, Cho-Charig(草窓) means grass in front of window), and named himself Cho-Chang(草窓). Yoon-Dong-Li(尹東里) followed this suit so called himself Cho-Chang (草窓). 3. The main contents of ${\ll}$Cho-Chang-Kyeol${\gg}$ (草窓訣), (運氣衍論) was written in 1725, when Yoon-Dong-Li(尹東里) was 21yrs old and printed in 1736. The other part of ${\ll}$Cho-Chang-Kyeol${\gg}$ (草窓訣), (用藥篇) was written in 1746. These two parts were not written in the satre time. The (運氣衍論) was written llyears earlier than (用藥). Two parts were combined another day and named (草窓訣). 4. Existing ${\ll}$Cho-Chang-Kyeol${\gg}$ (草窓訣) is transcribed printing with the con tent of "Five elements motion and the six kind of natural factors theory" (五運六氣設). Each edition is generally similar in content, but also has different points each other so naw we hardly finds a complete set of works. 5. ${\ll}$Cho-Chang-Kyeol${\gg}$ (草窓訣) is a first technical book which treats of Un-Ki(運氣) theory in korea. 6. The contents of (運氣衍論) of ${\ll}$Cho-Chang-Kyeol${\gg}$ (草窓訣) is mechanism of diease according to excess and insuffciency of five elements motion and six kinds of nalural faclors.and symploms and priscriptions, includes variated priscriptions. 7. Two parts in (運氣衍論) of ${\ll}$Cho-Chang-Kyeol${\gg}$ (草窓訣), 'Sang-tong' (相通) and 'Kak-Tong' (各通), threats of mochanisim of the disease according to five elements. with the principle of inter-promoting and inter-acting, in the change of ten heavenly stems and five elements motion. 8. In the (用藥篇) of ${\ll}$Cho-Chang-Kyeol${\gg}$ (草窓訣) describes priscription for clinical application according to Un-Ki(運氣) and also records about misuse of medicine. 9. In the ${\ll}$Cho-Chang-Kyeol${\gg}$ (草窓訣), most of priscription are common using one, which also found in ${\ll}$Dong-$\breve{U}$i-Bo-Garm${\gg}$ (東醫寶鑑) and there are few of priscriptions hy Yoon-Dong-Li(尹東里).

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