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점진성형에서 형상 정밀도에 영향을 미치는 공정 변수 (Effective Process Parameters on Shape Dimensional Accuracy in Incremental Sheet Metal Forming)

  • 강재관;정종윤
    • 산업경영시스템학회지
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    • 제38권4호
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    • pp.177-183
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    • 2015
  • Incremental sheet metal forming is a manufacturing process to produce thin parts using sheet metals by a series of small incremental deformation. The process rarely needs dedicated dies and molds, thus, preparation time for the process is relatively short as to be compared to conventional metal forming. Spring back in sheet metal working is very common, which causes critical errors in dimensions. Incremental sheet metal forming is not fully investigated yet. Hence, incremental sheet metal forming frequently produces inaccurate parts. This paper proposes a method to minimize dimensional errors to improve shape accuracy of products manufactured by incremental forming. This study conducts experiments using an exclusive incremental forming machine and the material for these experiments are sheets of aluminum AL1015. This research defines a process parameter and selects a few factors for the experiments. The parameters employed in this paper are tool feed rate, tool diameter, step depth, material thickness, forming method, dies applied, and tool path method. In addition, their levels for each factor are determined. The plan of the experiments is designed using orthogonal array $L_8$ ($2^7$) which requires minimum number of experiments. Based on the measurements, dimensional errors are collected both on the tool contacted surfaces and on the non-contacted surfaces. The distances between the formed surfaces and the CAD models are scanned and recorded using a commercial software product. These collected data are statistically analyzed and ANOVAs (analysis of variances) are drawn up. From the ANOVAs, this paper concludes that the process parameters of tool diameter, forming depth, and forming method are the significant factors to reduce the errors on the tool contacted surface. On the other hand, the experimental factors of forming method and dies applied are the significant factors on the non-contacted surface. However, the negative forming method always produces better accuracy than the positive forming method.

Study on Proactive Approach against a New Large-Scale Crisis of the Aviation and Tourism Industry such as COVID-19

  • Park, Yun-mi;Jeon, Aeeun
    • 한국항공운항학회지
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    • 제28권4호
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    • pp.176-181
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    • 2020
  • In the face of the unprecedented crisis of coronavirus disease (COVID-19), the aviation and tourism industry fell without help. The bigger problem is that a crisis like COVID-19 can always come back. A new variant of the virus that is more powerful than COVID-19 may emerge, and another crisis such as a massive war may come. In addition, there may be an unexpected large-scale crisis that could shake the survival of the aviation and tourism industry in place. At that time, the aviation and tourism industry should not be pushed into a survival crisis defenselessly. Taking the experience of the crisis caused by COVID-19 as a crucial lesson, sufficient protection measures should be prepared in advance, and within the protection measures, the overall capabilities of the aviation and tourism industry should be preserved, and preparation should be made for the aftermath of the crisis. There is a need to establish a support system in which financial resources that can be used in crisis situation can be secured in advance, and various support measures can be implemented as effectively as possible by using the secured financial resources. Regarding the preparation for financial resources, various fundraising, insurance, and compensation for losses by the state or local government may be considered as a priority, and in addition, there is a need to continuously consider ways to prepare additional financial resources. On the other hand, in terms of system construction, establishment of the system inside the aviation and tourism industry may need to be considered first, but the improvement of related laws and systems needs to be more actively discussed and related legislation needs to be actively promoted.

문제중심학습(PBL)이 현장실습수업 참여능력과문제해결력 향상에 미치는 영향 (Korean College Students' Perceptions of Offline Classes after COVID-19: Focused on Their Social Interactions and Senses of Community)

  • 나경희;백지연
    • 문화기술의 융합
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    • 제9권1호
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    • pp.169-174
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    • 2023
  • 본 연구는 포스트 코로나 시대에 비대면 교육 환경에서 대면 교육 환경으로 전환되면서 학생 간, 그리고 교수자-학생 간 상호작용 및 공동체 의식에 대한 대학생들의 인식을 조사, 분석하고자 하는 것을 목적으로 하였다. 한국의 대학생 49명이 본 연구에 참여하였으며, 그들은 지난 2년여 간 코로나 상황에서 비대면 수업을 경험한 뒤 대면수업 환경의 적응 시기에 있는 학생들이었다. 대상 학생들은 Rovai(2002)의 '교실공동체척도'(Classroom Community Scale, CCS)를 수정·보완한 설문조사에 응하였으며, 수집된 자료는 빈도분석 등의 분석방법을 통하여 분석되었다. 자료의 분석 결과, 학생들은 대면 수업에서의 수업 내용 이해도와 몰입도 면에서 긍정적으로 인식하고 있었으나, 대면수업 방식에 대한 적응 기간이 필요한 것으로 나타났으며, 교육 환경에 대한 정의적인 요인 등에 대하여도 고려되어야 할 것으로 나타났다.

주파수 특성이 향상된 커패시터 멀티플라이어 설계 및 제작 (Design and Fabrication of An Improved Capacitor Multiplier with Good Frequency Characteristics)

  • 이대환;백기주;한다인;유병선;김영석
    • 전자공학회논문지
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    • 제50권4호
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    • pp.59-64
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    • 2013
  • 본 논문에서는 주파수에 대해 영향을 적게 받는 커패시터 멀티플라이어를 제안하였다. 기존의 커패시터 멀티플라이어는 주파수에 대해 커패시턴스 변화가 크다는 단점이 있다. 반면에, 제안된 커패시터 멀티플라이어는 캐스코드 구조를 이용하여 주파수 변화에 대해서 커패시턴스 변화가 작은 특성을 갖도록 개선하였다. 기존의 커패시터 멀티플라이어와 제안된 커패시터 멀티플라이어를 삼성 $0.13{\mu}m$ CMOS 공정을 이용하여 제작하고, LPF를 구성하여 특성을 측정하였다. 주파수 100kHz에서 1MHz까지 측정한 결과, 기존의 커패시터 멀티플라이어는 최대 53% 오차를 보이는 반면에, 제안된 커패시터 멀티플라이어는 10% 이내의 오차를 보여, 향상된 주파수 특성을 가짐을 확인하였다.

사출/압축 및 RHCM 기술이 7인치 도광판 마이크로 패턴 전사성에 미치는 영향에 대한 실험적 연구 (An Experimental Study on the Replication Ratio of Micro Patterns of 7 inch LGP using Injection/Compression and RHCM)

  • 조성우;김종선;황철진;윤경환;강정진
    • 소성∙가공
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    • 제20권1호
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    • pp.11-16
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    • 2011
  • Recently, according to the rapid development of display, many display applications, such as, cellular phone, navigation, monitor and LCD TV have been changed from CRT type to LCD type. BLU(Back Light Unit) is one of main parts in LCD unit and generally, it consists of a light source, a reflective sheet, a LGP(Light Guide Plate), a diffuser sheet, and two prism sheets. The most important component of BLU is a light guide plate, which diffuses the input light to the TFT-LCD module uniformly. The LGP is usually made by injection molding process, and it has numerous optical micro patterns on the surface. In the present study the micro-patterned stamper which has cylindrical shape was fabricated by using the UV-LiGA process. And the replication characteristics have been compared among three different kinds of injection molding process; general injection molding, injection/compression molding and RHCM(Rapid Heating and Cooling Molding). Average replication ratios of CIM and ICM were 19.1% and 64.6%, respectively. On the other hand, the average replication ratio of RHCM process showed the higher value of 98.4% among these. It show that maintaining the mold surface above $T_g$ could increase the replication ratio of micro patterns substantially.

상반신의 부분별 발한량, 피부온과 주관적 감각 고찰 (The Analysis of the Sweating Rate, Skin Temperature on the Upper Body and Subjective Sensations)

  • 김성숙;김희은
    • 한국의류산업학회지
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    • 제15권6호
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    • pp.993-999
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    • 2013
  • This study aimed to measure the amount of sweating on 12 parts of the upper body using absorption fabric and analyze subjective sensations. The study was conducted with 9 male subjects in climate chamber controled at $30{\pm}0.5^{\circ}C$, and $55{\pm}5%$ RH. The result was that sweating amount of the upper back part was significantly more than upper front part. We assumed that forced convection flow cased by exercise decreased the sweating rate in the front. The skin temperature of upper front body rapidly decreased as soon as exercise starts and gradually increased with cessation of exercise. On the other hand, the skin temperature of palm increased with exercise and showed continuous increasing even exercise stopping all the experimental period. This is caused by thermoregulatory responses through vasodilatation on the peripheral area. Subjective sensations, such as thermal sensation, wet sensation, and thermal comfort showed the highest score at the time of exercise stop. This means the subjects felt more hot, wet, and uncomfortable after exercise stopped. Bur after wiping of sweat, subjective sensation scores were recovered rapidly. The present study has provided more detailed information on the upper body sweat distribution than previously available, which can be used in clothing design, thermo-physiological modeling, and thermal manikin design. We also think that results of the present study will play an important role in making the sweat distribution map.

아동 감염성 질환관리에 대한 보육교사의 역할인식, 지식, 실천 자신감 및 교육요구도 (Child Daycare Teachers' Role Perception, Knowledge, Self-confidence and Educational Needs Regarding Infectious Disease Management in Children)

  • 백성희;김진선
    • 한국콘텐츠학회논문지
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    • 제17권7호
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    • pp.253-264
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    • 2017
  • 본 연구는 보육시설 아동의 감염성 질환관리에 대한 보육교사의 역할인식, 지식, 실천 자신감 및 교육요구도를 알아보고, 이들 변수간의 관련성을 파악하기 위한 상관관계연구이다. 연구 대상자는 보육교사 180명이었다. 연구대상자의 78.9%는 감염성 질환관리에 대한 교육 경험이 없었으며, 감염성 질환관리에 대한 지식 정답률은 52.3%, 실천 자신감은 낮았다. 그러나 감염성 질환관리에 대한 역할인식은 전반적으로 높았으며, 감염성 질환관리에 대한 교육요구도는 높았다. 감염예방을 위한 손씻기 및 위생관리법, 감염성 질환차단방법, 감염성 질환별 관리 및 간호법, 감염성 질환별 증상에 대한 교육요구도가 높았다. 대상자들의 역할인식은 그들의 지식과 교육요구도와 유의한 상관관계가 있었다. 보육교사 대상 감염성 질환 예방 및 관리를 위한 교육 프로그램의 개발, 적용 및 평가가 요구된다. 특히 보육교사들의 감염성 질환관리에 대한 역할인식을 향상시키기 위한 노력이 요구된다.

색인사 연구

  • 박준식
    • 한국도서관정보학회지
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    • 제2권
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    • pp.23-59
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    • 1975
  • Indexes has not devcloped as an independent branch in library science from the beginning, but it has gradually evolved in a clo~eas sociation with catalog and under the direct influence of the development of publishing pro cesses and of the rapid social changes. Historically, index in the West can be traced back to eariler concordance. On the other hand, index in the Bast does not show a continuous development. It started with book catnlog, but other types of indexing were later 'adopted from the West. Indexing in the West and in the East can be summarized as follows: 1) In the West, Taylor considers Gesner's Pandectae was the first index but the Concordance of the Bible in 1247 was the first true index. Indexing method was first established later in 1545 in Gesner's Partitiones which appeared in three volumes. Classified index appeared after Partitions, but alphabetically ordered index was not developed until th eseventeenth century. The pxiodical index of La France S~auante in 1683 proved -its value, and Poole's An Alphabetical Index in the nineteenth century became the turning point in the development of indexing. After Poole's Index appeared periodical index and book catalog gradually began to be treated separately, and subject index and cross reference were incorporated into indexing. Also dictionary arrangement of the indexed items was adopted in the second half of the nincteenth, century after Charles A. Cutter developed his theory of rules for dictionary catalog and systematic studies of indexing were carried out by many scholars. In the twentieth century, index was mainly developed in the United States of America, especially by Wilson publishing Company. The general trend is to move away from the gcncral index to subject index. Also the ncwspapcr indcx such as The Times I~zdcx is 21 landmark in the history cf indcxing. 2) In China, thcs arc somc cvidcnccs that $Bizgluh(&), $ was the first indcx, but unforlunatcly the book itsclf has not been found as yet.

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음성적 모음 축소 현상에 영어 자음의 유무성 환경이 미치는 효과 (Phonetic Vowel Reduction Conditioned by Voicing of Adjacent Stops in English)

  • 오은진
    • 음성과학
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    • 제14권4호
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    • pp.81-98
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    • 2007
  • This study aims to investigate whether shortened vowel duration conditioned by a following voiceless stop induces phonetic reduction of vowel space in English, and whether the reduction appears more in the height dimension than in the backness dimension (Lindblom, 1963; Flemming, 2005). Fifteen native speakers of American English read minimal pairs containing ten American English vowels in [bVd] and [bVt] syllables in a carrier phrase. All the subjects produced shorter vowels in the voiceless than in the voiced context. However, a reduction in vowel space and a raising of low vowels due to the shortened vowel duration were generally not found. To the contrary, the speakers tended to exhibit even more lowering of low vowels in the voiceless context, and vowel space was more commonly compressed in the backness dimension than in the height dimension. Many speakers, in particular, demonstrated fronting of the high back vowel [u] in the voiceless context. It was interpreted that due to a relatively large number of English vowels in the narrower low vowel space, the raising of low vowels may give rise to confusion in vowel contrasts, and therefore the degree of phonetic vowel reduction is restricted in that region. On the other hand, the high vowel region, being relatively spacious in English, allows a certain degree of phonetic vowel reduction in the F2 dimension. It is possible that heavy requirements for maintaining vowel contrasts may cause speakers to overachieve vowel target values, especially when faced with vowels which are difficult to distinguish due to shortened vowel duration, leading to an over-lowering of the low vowels.

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오페라 "파우스트"의 무대의상 디자인 - 군중들을 중심으로 - (A Study on The Stage Costume Design of Opera $\lceil$Faust$\rfloor$ - Focused on The Crowd -)

  • 변지현;조진숙
    • 복식
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    • 제57권3호
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    • pp.90-107
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    • 2007
  • Modernization movement has affected classical operas. Today, classical operas are often re-interpreted from the modern perspective and played differently only with the storyline maintained. Also, operas are increasingly performed outside traditional theaters as the boundaries between stage and audience become less obvious. Accordingly, stage costumes are being differently designed than before. New attempts are being made to look costumes in a harmony with increasingly streamlined stage machinery. This helps increase public attention on operas, consequently promoting the opera industry. This study examines modernization of opera costumes. For this study, the author worked as one of costume design staff for "Faust," which was played in Sungnam Art Center from November 24, 2005 to November 27, 2005 in commemoration of the opening of the center. The following outcomes of the crowd are drawn from this study. A variety of splendid pink dresses, ribbons, dolls, hand mirror, and hair bands were used to express haughty girls with "Princess Syndrome." Fashion models, the envy of all woman, wore fashionable clothes including luxury dresses, fur-coats, high heels, purses, and hats, Models also had big shopping bags and gift boxes to symbolize shopping lovers in a modern society. Gay men wore tight leather trousers and vest and sleeves shirts with deeply cut neckline to express their preference for feminie style. their clothes were splendid colors that normally women liked such as gold, purple, light green, scarlet, and silver. Soldiers were in combat uniform representing their participation in the war. In particular, clothes stained with dirt, iron helmet, crutches, and canteens were used to vividly express soldiers coming back home from the war. Modern opera costumes now help reduce the time and space between stage and audience, improve economic efficiency, and meet the audience's needs for various style.