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Major Class Recommendation System based on Deep learning using Network Analysis (네트워크 분석을 활용한 딥러닝 기반 전공과목 추천 시스템)

  • Lee, Jae Kyu;Park, Heesung;Kim, Wooju
    • Journal of Intelligence and Information Systems
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    • v.27 no.3
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    • pp.95-112
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    • 2021
  • In university education, the choice of major class plays an important role in students' careers. However, in line with the changes in the industry, the fields of major subjects by department are diversifying and increasing in number in university education. As a result, students have difficulty to choose and take classes according to their career paths. In general, students choose classes based on experiences such as choices of peers or advice from seniors. This has the advantage of being able to take into account the general situation, but it does not reflect individual tendencies and considerations of existing courses, and has a problem that leads to information inequality that is shared only among specific students. In addition, as non-face-to-face classes have recently been conducted and exchanges between students have decreased, even experience-based decisions have not been made as well. Therefore, this study proposes a recommendation system model that can recommend college major classes suitable for individual characteristics based on data rather than experience. The recommendation system recommends information and content (music, movies, books, images, etc.) that a specific user may be interested in. It is already widely used in services where it is important to consider individual tendencies such as YouTube and Facebook, and you can experience it familiarly in providing personalized services in content services such as over-the-top media services (OTT). Classes are also a kind of content consumption in terms of selecting classes suitable for individuals from a set content list. However, unlike other content consumption, it is characterized by a large influence of selection results. For example, in the case of music and movies, it is usually consumed once and the time required to consume content is short. Therefore, the importance of each item is relatively low, and there is no deep concern in selecting. Major classes usually have a long consumption time because they have to be taken for one semester, and each item has a high importance and requires greater caution in choice because it affects many things such as career and graduation requirements depending on the composition of the selected classes. Depending on the unique characteristics of these major classes, the recommendation system in the education field supports decision-making that reflects individual characteristics that are meaningful and cannot be reflected in experience-based decision-making, even though it has a relatively small number of item ranges. This study aims to realize personalized education and enhance students' educational satisfaction by presenting a recommendation model for university major class. In the model study, class history data of undergraduate students at University from 2015 to 2017 were used, and students and their major names were used as metadata. The class history data is implicit feedback data that only indicates whether content is consumed, not reflecting preferences for classes. Therefore, when we derive embedding vectors that characterize students and classes, their expressive power is low. With these issues in mind, this study proposes a Net-NeuMF model that generates vectors of students, classes through network analysis and utilizes them as input values of the model. The model was based on the structure of NeuMF using one-hot vectors, a representative model using data with implicit feedback. The input vectors of the model are generated to represent the characteristic of students and classes through network analysis. To generate a vector representing a student, each student is set to a node and the edge is designed to connect with a weight if the two students take the same class. Similarly, to generate a vector representing the class, each class was set as a node, and the edge connected if any students had taken the classes in common. Thus, we utilize Node2Vec, a representation learning methodology that quantifies the characteristics of each node. For the evaluation of the model, we used four indicators that are mainly utilized by recommendation systems, and experiments were conducted on three different dimensions to analyze the impact of embedding dimensions on the model. The results show better performance on evaluation metrics regardless of dimension than when using one-hot vectors in existing NeuMF structures. Thus, this work contributes to a network of students (users) and classes (items) to increase expressiveness over existing one-hot embeddings, to match the characteristics of each structure that constitutes the model, and to show better performance on various kinds of evaluation metrics compared to existing methodologies.

A Design Direction for Mobile phones between Comparison of Users from Korea, China and Japan (한중일 사용자 비교분석을 통한 모바일폰 디자인 방향)

  • Eune, Ju-Hyun;Jung, Hee-Yun;Kim, Yun-Jun
    • Archives of design research
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    • v.20 no.3 s.71
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    • pp.29-38
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    • 2007
  • The competition to capture a larger slice of the market in Mobile Communication business is increasing among companies. In order to achieve and maintain a competitive advantage in the Asian market, it is critical to continue to develop new technology. Understanding the underlying distinctive characteristics and needs of each market and the cultural backgrounds that drive those needs is a necessary focus. Companies with marketing strategies based on a correct understanding of market needs will capture dominant positions in the market. The purpose of this study is to identify those differences in user behavior and cultural tendencies among different people in different countries in the mobile telecommunication market. This research is based on an on-line survey in three countries (Korea, China, and Japan). Below are the contents of the survey on the mobile phone based on: 1) User behavior 2) Design preference 3) Purchasing behavior 4) User awareness on manufacturer brand. Through the analysis of this questionnaire it is possible to identify the differences and similarities among countries dearly. 1) Cultural trends and perceptions related to mobile phone usage were largely caused by differences in the state of technology, policies and business strategies of mobile sonics carriers and manufacturers, and national tendencies, of each country. 2) Korean and Japanese users produced similar responses to the questions related to advanced technology, whereas Korean and Chinese users responded similarly to national tendency-related questions. 3) To the questions related to business strategies of mobile service carriers and manufacturers, users in all three countries displayed markedly different responses. Once again, accurate analysis of the differences and similarities related to mobile phone usage in each country will help the companies in this industry to gain a competitive edge in the market. This study should not stop at simple comparison but be a framework for giving companies a dear future direction for technological development.

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A Study on the Traditional Costumes and Tattoo of the Maori (마오리族 傳統 服飾과 文身 考察)

  • 황춘섭;정현주
    • The Research Journal of the Costume Culture
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    • v.3 no.2
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    • pp.241-260
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    • 1995
  • The Maori's traditional clothing materials, basic forms of dress, and the pattern and technique of tatoo were examined in the present study in order to deepen the appreciation of the cultural heritage of the Maori. The research method employed was the analysis of written materials. And a fild-trip was also made for the study. The study was limitted to the traditional culture of body adornment of the Maori including the clothing which is preserved and practicing by them at the present day, and the origin and the process of the historical development of those are not included in the scope of the present study. Followings are the results of the study: (1) By far the most widely used fiber for Maori clothing is abtained from what is commonly called New Zealand Flax. The fiber of kiekie(Freycinetia baueriana) and cabbage trees(Cordyline spp.) may also be used. The strong, long-lasting fiber of toi(cordyline indivisa) is used for a prestige warrior's cloak. Flat strips of ti kauka(Cordyline australi) are also used as thatch on rain cloaks. (2) Regardless of technique used, Maori weaving is always worked horizontally from left to right. Traditionally the work was suspended between two upright turuturu or weaving sticks. As the work progressed a second pair of uprights was used to keep the work off the ground. These uprights were moved forward as required. Because the weaver sat on the ground, the working edge was kept at a height that was comfortable to reach. No weaving tools are used, the wefts(aho) being manipulated by the fingers. The two main Maori weaving techniques are whatu aho patahi(single-pair twining) and whatu aho rua(double-pair twining). (3) The Maori wore two basic garments - a waist met and a cloak. The cloth of commoners were of plain manufacture, while those of people of rank were superior, sometimes being decorated with feather or dyed tags and decorated borders. Children ran more-or-less naked until puberty, being dressed only for special events. Some working dress consisted of nothing more than belts with leaves thrust under them. Chiefs and commoners usually went barefoot, using rough sandals on journeys over rough country (4) The adornment of men and women of rank was an important matter of tribal concern as it was in chiefly persons that prestige of the group was centred, The durable items of Maori persons adornment were either worn or carried. Ornaments of various kinds were draped about the neck or suspended from pierced earlobes. Combs decorated the head. Personal decorations not only enhanced the appearance of men and women, but many had protective magical function. The most evident personal ornament was the hei-tiki made of jade or other material. Maori weapons were treasured by their owners. They served on bottle and were also personal regalia. A man of rank was not fully dressed without a weapon in hand. Also weapons were essential to effective oratory. (5) No man or woman of rank went without some tattoo adornment except in extremely rare instances when a person was too sacred to have any blood shed. The untattooed were marked as beeing commoners of no social standing. This indelible mark of rank was begun, with appropriate rite and ritual, at puberty. And tattoo marked the person as being of a marriageable age. Maori tattoo was unlike most traditional tattoo in that its main line were 'engraved' on the face with deep cuts made by miniature bone chisels. The fill-in areas were not tattooed with cuts but with the multiple pricks of small bone 'combs' that only lightly penetrated the skin surface. The instrument of tattoo consisted of small pots of pumice or wood into which was placed a wetted black pigment made from burnt kauri gum, burnt vegetable caterpillars or other sooty materials. A bird bone chisel or comb set at right angles on a short wooden handle was dipped into the gigment, that a rod or stick was used to tap head of this miniature adze, causing penetration of the skin surface. Black pigment lodged under the skin took on a bluish tinge. A full made facial tattoo consisted of major spirals with smaller spirals on each side of the nose and sweeping curved lines radiating out from between the brows over the forehead and from the nose to the chin. The major patterns were cut deep, while the secondary koru patterns were lightly pricked into the skin.

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A Study on Problems with the ROK's Bioterrorism Response System and Ways to Improve it (생물테러 대응체제의 문제점과 개선방안 연구)

  • Jung, Yook-Sang
    • Korean Security Journal
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    • no.22
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    • pp.113-144
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    • 2010
  • Bioterrorism is becoming more attractive to terrorist groups owing to the dramatic increase in the utility and lethality of biological weapons in line with today's cutting-edge biological science and technology. The Republic of Korea is facing both internal and external terrorist threats, as well as the possible biological warfare by North Korea. Therefore, it is essential to establish an effective bioterrorism response system in the ROK. In order to come up with the adequate response system for the ROK, an in-depth study has been conducted on the current bioterrorism response system of the U.S. whose preparedness is considered relatively adamant. As a result, the following facts have been found: (1)the legislation with regard to bioterrorism has been established or amended according to the current situation in the U.S., (2)the counter terrorism activities have been integrated with the Department of the Homeland Security as the central agency in order to maximize the national CT capacity, (3)Specific procedures and instructions to cope with bioterrorism have been made into manuals so as to enhance the working-level response capabilities. Next, the analysis on the ROK's bioterrorism response system has been performed in various categories, including the legislation system, task role distribution, cooperative relations, and resource application. It turned out that the ROK's legislation basis is relatively weak and it lacks the apparatus to integrate the bioterrorism response activities on the national level. The shortage of the adequate response facilities and resources, as well as the poor management of manpower have also emerged as problems that hinder the effective CT implementations. Through an analytical and comparative study of the U.S. and the ROK systems, this paper presents several ways to ameliorate improve the current system in the ROK as follows: (1)establish the anti-terrorism law, which would be the basic legal basis for the bioterrorism-related matters; and make revisions to the disaster-related legislation, relevant to bioterrorism response activities, (2)establish an integrated body that has a powerful authority to coordinate the relevant CT agencies; and converge the decentralized functions to maximize the overall response capacity, (3)install the laboratories with a high biosafety level and secure enough of the strategic medical stock-pile, (4)enhance the ability of the inexperienced response personnel by providing with a manual that has detailed instructions.

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SURFACE CHANCE OF EXTERNAL HEXAGON OF IMPLANT FIXTURE AND INTERNAL HEXAGON OF ABUTMENT AFTER REPEATED DELIVERY AND REMOVAL OF ABUTMENT (지대주의 반복적인 착탈에 따른 임플랜트 고정체의 external hexagon과 지대주 internal hexagon의 변화에 관한 연구)

  • Jung Seok-Won;Kim Hee-Jung;Chung Chae-Heon
    • The Journal of Korean Academy of Prosthodontics
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    • v.43 no.4
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    • pp.528-543
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    • 2005
  • Statement of problem: Repeated delivery and removal of abutment cause some changes such as wear, scratch or defect of hexagonal structure. It may increase the value of rotational freedom(RF) between hexagonal structures. Purpose: The purpose of this study was to evaluate surface changes and rotational freedom between the external hexagon of the implant fixture and internal hexagon of abutment after repeated delivery and removal under SEM and toolmaker's microscope. Materials and methods: Implant systems used for this study were 3i and Avana. Seven pail's of implant fixture, abutment and abutment screws for each system were selected and all fixtures were perpendicularly mounted in liquid unsaturated polyesther with dental surveyor. Each one was embedded beneath the platform of fixture. Surfaces of hexagonal structure before repeated closing and opening of abutment were observed using SEM and rotational freedom was measured by using toolmaker's microscope. Each abutment was secured to the implant future by each abutment screw with recommended torque value using a digital torque controller and was repeatedly delivered and removed by 20 times respectively. After experiment, evaluation for the change of hexagonal structures and measurement of rotational freedom were performed. Result : The results were as follows; 1. Wear of contact area between implant fixture and abutment was considerable in both 3i and Avana system. Scratches and defects were frequently observed at the line-angle of hexagonal structures of implant fixture and abutment. 2. In the SEM view of the external hexagon of implant fixture, the point-angle areas at the corner edge of hexagon were severely worn out in both systems. It was more notable in the case of 3i systems than in that of Avana systems. 3. In the SEM view of the internal hexagon of abutment, Gingi-Hue abutment of 3i systems showed severe wear in micro-stop contacts that were machined into the corners to prevent rotation and cemented abutment of Avana systems showed wear in both surface area adjacent to the corner mating with external hexagon of implant fixture. 4 The mean values of rotational freedom between the external hexagon of the implant fixture and internal hexagon of abutment were 0.48$\pm$0.04$^{\circ}$ in pre-tested 3i systems and 1.18$\pm$0.25$^{\circ}$ after test, and 1.80$\pm$0.04$^{\circ}$ in pre-tested Avana systems and 2.61$\pm$0.16$^{\circ}$ after test. 5. Changes of rotational freedom after test shouted statistical)y a significant increase in both 3i and Avana systems(P<0.05, paired t-test). 6. Statistically, there was no significant difference between amount of increase in the rotational freedom of 3i systems and amount of increase in that of Avana ones(P>0.05, unpaired t-test). Conclusion: Conclusively, it was considered that repeated delivery and remove of abutment by 20 times would not have influence on screw joint stability. However, it caused statistically the significant change of rotational freedom in tested systems. Therefore, it is suggested that repeated delivery and remove of abutment should be minimal as possible as it could be and be done carefully Additionally, it is suggested that the means or treatment to prevent the wear of mating components should be devised.

A STUDY OF INTRAORAL ANATOMIC LANDMARKS OF KOREAN ADULT-UPPER JAW (성인 유치악자 상악골의 악궁과 치열궁의 형태에 관한 조사)

  • Oh, Yu-Ree;Lee, Sung-Bok;Park, Nam-Soo;Choi, Dae-Gyun
    • The Journal of Korean Academy of Prosthodontics
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    • v.33 no.4
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    • pp.753-768
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    • 1995
  • For accurate impression taking of dental patient and esthetic denture treatment of ednetulous patient, measuring between intraoral anatomic landmarks is useful.In this study the subjects selected at a random were two-jundred forty persons with a mean age 22.5(range 21-24) and were taken impression of by irreversible hydrocolloid impression material(Alginate). On the study model made by dental stone, each individual tray was made and final impresion was taken by border moilding. On final model measurings were performed with 3-dimensional measuring device and the values were analyzed by t-test The results is following : ABOUT THE MEASURED VALUES. 1. The width between maxillary right and left canine cusp tip was average 36.44mm(s.d. 2.48), man 36.67mm, woman 35.83mm(p<0.05). 2. The width between labial height of contour of maxillary right and left canine was average 40.08mm(s.d. 2.42), man 40.29mm, woman 39.52mm(p<0.05). 3. The width between mesio-lingual cusps of maxillary first molar was average 43.14mm(s.d. 3.33), man 43.56mm, woman 42.05mm(p<0.05). 4. The width between buccal alveolar ridge on axis of mesiolingual cusp of right and left maxillary first molar was average 64.89mm(s.d. 3.88), man 65.58mm, woman 62.92mm(p<0.05). 5. The width between buccal alveolar ridge on axis of mesiolingual cusp of right and left maxillary second molar was average 68.58mm(s.d. 3.91), man 69.29mm, woman 66.30mm (p<0.05). 6. The width between right and left hamular notch was average 49.80mm(s.d. 3.96), man 50.70mm, woman 48.20mm(p<0.05). 7. The length from labial heigth of contour of maxillary central incisor to center of incisive papilla was average 9.52mm(s.d. 1.18), man 9.46mm, woman 9.63mm(p>0.05). 8. The length from labial heigth of contour of maxillary central incisor to palatine fovea was average 53.27mm(s.d. 2.93), man 53.93mm, woman 52.08mm(p<0.05). 9. The center of incisive papilla ws located posterior to intercanine line at 0.40mm(s.d. 1.16), man 0.51mm, woman 0.11mm(p<0.05). 10. The height from incisal edge of maxillary central incisor to the labial vestibule was average 21.84mm(s.d. 1.38), man 22.01mm, woman 21.00mm(p<0.05). 11. The height from mesiolingual cusp of maxillary first molar to buccalvestible was average 17.45mm(s.d. 1.42), man 17.56mm, woman 17.08mm(p>0.05). 12. The height from hamular notch to standard occlusal plane was average 6.84mm(s.d. 1.06), man 6.91mm, woman 6.70mm(p>0.05). 13. The height from the deepest point of palatal vault to standard occlsalplane was average 19.95 mm(s.d. 2.03), man 20.19mm, woman 19.12mm(p<0.05). ABOUT THE ARCH FORM 1. The arch form was able to classify into four typr by the rate of the measured values. Each arch form distribution was that the 1 group had 32.46% the 2 group 2.19%, the 3 group 52.83%, the 4 group 12.72%. The sexual composition was that in 1 group man had 73.5%, woman 26.5%, in 2 group man had 40.0%, woman 60.0%, in 3 group man had 83.3%, woman 16.7%, and in 4 group man had 55.17%, woman 44.83%. 2. When canine cusp tip was marked as point O, the intersection point between labial height of contour of maxillary central incisor and intermaxillary suture as point A, height of contour of maxillary second molar buccal alveolar ridge as B point, ${\angle}$AOB was measured $133.8^{\circ}$for the 1 group, $133.0^{\circ}$for the 2 group, $132.3^{\circ}$for the 3 group, $128.9^{\circ}$for the 4 group.

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The Study on the Buttons (centering around 19th-20th Centuries) (단추에 관한 연구 -19, 20세기를 중심으로-)

  • 이영란
    • Journal of the Korean Society of Costume
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    • v.22
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    • pp.263-276
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    • 1994
  • The achievement of notable social reoforms attained during the period of 19th and 20th centuries needlessly speaking remodelded the social environmental into several different patterns such as :1) high industrialization 2) propensity to consume 3) up graded overall social stands. Accordingly the industrial world of the but-tons too established the mess production syhstem by breaking from convention of hand-craft work of 17th century. The raw materials used in the production line on buttons during the 20th century are almost all-kind of materials one can possibly named including cheap plastic which enabled production lines to produce cheaper but higher productivities of the buttons being produced, The design (incused design) used in the 19-20h centuries are : men landscape, sports features, birds, livestocks, bugs, or geomatric features, tec, 1, The classification o f the buttons by materials Techniques shapes colors marking (Incused design) used in the productionof buttons in the England United States of America Laska Italy france Denmark Japan and India are categolizzed as : natural raw materials and syntetical resines. 1) Of the natural raw materials used are : Matal Enamel Iodine Agate, Coral, Green jade(Jasper) Granite, Wood, Ivory, Horn and bone etc. 2) The sythetical resin used in the button in-dustries are : Artificial jewell glass Acrylic material Styroform Celluloid and Nylon etc. 2. The thecnique quoted in producing buttons are hand craft work inlay work precision casting press mosic dye etching, processing, engraving and embossed carving etc. 3. The major designs used in the buttons in -dustries are : Round shape however elliptical column angular and edge shape often used. 4. The colors used are : The multi-colors were highly used than mono-colored materials such as : Adjoining Color and Contrast Color. The highest consideration to be considered in choosing the colors for the buttons are harmonization and matching factor with the garment or dresses to be wore. 5. The major design(incused design) on the buttons are embodiment and the design were also used in order of abstractive-combination abstractive with has offers much surprising. The button industries during the 19th and 20th centuries were not only the determination factors those can judge the value of self-pride of Nation and which were far beyond the in-dustrial arts in those days but also highly refelected and influenced by cultural sense ideology and self-pride of the Nation of those period. The followings are details of the role of the buttons categolized in the order of functional ornamental and symbolical aspects : 1. The functional role : The functional role of the buttons were simply designed for dress how-ever the buttons beyond from this role of function now a days. 2. The ornamental role : The ornamental role of he button beyond from this role of the button were effectuated by : 1) shape materials colors 2) technique locations size and design (incused design) 3) The ramaterials used for buttons shall not be over looked because it is highly depends on the taste sense and combination of harmony with the garment to be wore. 4) The color of the buttons are made well contrasted with the color of garments just as in the case of other artistical area such as matchs with the color of garment of contrast with brigtness of colors contrasted as complementary color and so and so. 5) The technique being adoped are: precision casting press handcraft inlay work etching mosic etc,. Since the buttons are no longer a simple catching devise used to fasten together the different part of the dress but now it has formed own and occupied the independent role in the garment or dresses location can be de-termined and varying depending on the ideas of designers. The size of the buttons has no specific limits, However the variation has widely dependined on the entire circumperence rhythm contrast harmonization of the garments. 3. The symbolical role : Since the button is no longer a just a simple devise for catching and fastening device used fastening together the different part of the garments but now were built a independent area as major part of the Garment and well reflected all kinds of occupations political background cultural as-pect etc. on the buttons. The design of buttons in the western circles are more simplified but they are polished looks and their techniques of manufacturing are comination of both machanis and handcraft. The colors used in the buttons are pretty well harmonized with garment(dress). Almost all kind of materials can be used in the but-tons however materials used in the buttons are : Bone of livestocks ivory, turtle shell are no longer used because the prevention of cruely of animal. On the contraly the level of buttons indus-try of Korea is far to reach and catch up with the level of western circles. It is highly suggested therefore the but-tons industrial field of Republic of Korea shall place and encouragement in producing beter industrial environment of the buttons based on the traditional and cultural aspect of republic of Korea to produce both manufacturing of qulified and best designed and colored buttons.

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Dosimetric Characteristics on Penumbra Regions of the Multileaf Collimator as Compared with the Lead Alloy Block (다엽 콜리메이터(Multileaf Collimator)와 합금납 차폐물(Lead Alloy Block)의 반 그림자영역의 선량 분포상의 특성 비교)

  • Lee Sang Wook;Oh Young Tack;Kim Woo Cheol;Keum Ki Chang;Yoon Seong Ick;Kim Hyun Soo;Park Won;Chu Seong Sil;Kim Gwi Eon
    • Radiation Oncology Journal
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    • v.13 no.4
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    • pp.391-396
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    • 1995
  • Purpose : The Conformal Radiation Therapy has bee widely used under favour of development of computer technologies. The delivery of a large number of static radiation fields are being necessary for the conformal irradiation. In this paper we investigate dosimetric characteristics on penumbra regions of a multileaf collimator(MLC), and compare to those of lead alloy block for the optimal use of the system in 3-D conformal radiotherapy. Materials and Methods : The measurement of penumbra by MLC or lead alloy block was performed with 6 or 10 MV X-rays. The film was positioned at a dmax depth and 10 cm depth, and its optical density was determined using a scanning videodensitometer. The effective penumbra, the distance from $80{\%}$ to $20{\%}$ isodose lines and $90{\%}$ to $10{\%}$ were analyzed as a function of the angle between the direction of leaf motion and the edge defined by leaves. Results : Increasing MLC angle ($0-75^{\circ}$) was observed with increasing the penumbra widths and the scalloping effect. There was no definite differences of penumbra width from $80{\%}$ to $20{\%}$ isodose lines, while being the small increase of penumbra width from $90{\%}$ to $10{\%}$ isodose line varing the depth and energy. The effective penumbra width of lead alloy block are agree resonably with those of MLC within 4.8mm. Conclusion : The comparative qualitative study of the penumbra between MLC and lead alloy block demonstrate the clinical acceptability and suitability of the multileaf collimator for 3-D conformal radiotherapy.

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Contralateral Breast Dose Reduction Using a Virtual Wedge (가상쐐기를 이용한 반대측 유방선량감소)

  • Yeo, In-Hwan;Kim, Dae-Yong;Kim, Tae-Hyun;Shin, Kyung-Hwan;Chie, Eui-Kyu;Park, Won;Lim, Do-Hoon;Huh, Seung-Jae;Ahn, Yong-Chan
    • Radiation Oncology Journal
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    • v.23 no.4
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    • pp.230-235
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    • 2005
  • Purpose: To evaluate the contralateral breast dose using a virtual wedge compared with that using a Physical wedge and an open beam in a Siemens linear accelerator. Materials and Methods: The contralateral breast dose was measured using diodes placed on a humanoid phantom. Diodes were placed at 5.5 cm (position 1), 9.5 cm (position 2), and 14 cm (position 3) along the medial-lateral line from the medial edge of the treatment field. A 6-MV photon beam was used with tangential irradiation technique at 50 and 230 degrees of gantry angle. Asymmetrically collimated $17{\times}10cm$ field was used. for the first set of experiment, four treatment set-ups were used, which were an open medial beam with a 30-degree wedged lateral beam (physical and virtual wedges, respectively) and a 15-degree wedged medial beam with a 15-degree wedged lateral beam (physical and virtual wedges, respectively). The second set of experiment consists of setting with medial beam without wedge, a 15-degree wedge, and a 50-degree wedge (physical and virtual wedges, respectively). Identical monitor units were delivered. Each set of experiment was repeated for three times. Results: In the first set of experiment, the contralateral breast dose was the highest at the position 1 and decreased in order of the position 2 and 3. The contralateral breast dose was reduced with open beam on the medial side ($2.70{\pm}1.46%$) compared to medial beam with a wedge (both physical and virtual) ($3.25{\pm}1.59%$). The differences were larger with a physical wedge ($0.99{\pm}0.18%$) than a virtual wedge ($0.10{\pm}0.01%$) at all positions. The use of a virtual wedge reduced the contralateral breast dose by 0.12% to 1.20% of the proscribed dose compared to a physical wedge with same technique. In the second experiment, the contralateral breast dose decreased in order of the open beam, the virtual wedge, and the physical wedge at the position 1, and it decreased in order of a physical wedge, an open beam, and a virtual wedge at the position 2 and 3. Conclusion: The virtual wedge equipped in a Siemens linear accelerator was found to be useful in reducing dose to the contralateral breast. Our additional finding was that the surface dose distribution from the Siemens accelerator was different from a Varian accelerator.

STUDY ON THE ANCHOVY BOAT SEINE 1. On the Hydrodynamic Resistance and Performance of the Conventional Gear (기선기현강의 연구 1, 재래식 어구의 유구저황과 그물꼴에 관하여)

  • LEE Byoung-gee;YANG Yong-rim;SU Young-tae;SON Boo-il
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.4 no.3_4
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    • pp.79-91
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    • 1971
  • A boat seine has been used as a major fishing gear for catching anchovy (Engraulis japonica) in the southern coastal waters of Korea since 1920s. The original seine was operated by two rowing boats as the haul seine. The rowing boats were, in recent, replaced by powered boats. The net size was enlarged by more than three times the original nit as they began to by operated in the deeper waters of approximately sixty meters. However, there are many problems in the efficiency of the fishing gear to be improved. The authors studied on the hydrodynamic resistance and performance of the boat seine net of the 1/10 scale model in tow. The results are summaried as follows. 1. The hydrodynamic resistance converted from model experiment into the full scale is: $$R_1=30,000\;v^{1.2}\;(0.2{\leqq}v{\leqq}1.0)$$ $$R_2=16,000\;v^2\;(0.2{\leqq}v{\leqq}0.6)$$ where $R_1$ and $R_2$ denote the resistance of whole gear and of bag net in kg respectively, and v the speed of flow in m/sec. 2. In the extension wing, approximately seventy percent of the length of the ground rope from the towing end to the inside-wing slopes down from sea level toward the sea bottom, while the thirty percent of the inside of it remains parallel with th: 5:a level. The performance is regarded to b: inefficient for driving fish shoal into the inside-wing, especially for the shoal diving suddenly. 3. At the towing speed higher than 0.2 m/sec, the trailing edge of the inside-wing is blown backward beyond the seaming line connecting the inside-wing and the mouth of the bag net. It is regarded as an unreasonable performance to drive the fish shoal smoothly into the bag net. 4. At the towing speed higher than 0.2 m/sec, the posterior end of the lower bosom is lifted up above the level of the ground rope of the inside-wing. It is considered that the fish shoal diving suddenly can escape through the discrepancy between the lower bosom and the sea bottom, even if the ground rope of the inside-wing sweeps the sea bottom. 5. The angle of inclination of the upper bosom is estimated as $35\~40^{\circ}$. It seems that the inclination is too steep to drive smoothly the fish shoal diving toward the sea bottom into the bag net. 6. In structure, circumference of the posterior section of the bag net is wider by 1.3 times that of the anterior section. Actually in towing at a speed higher than 0.2m/sec, however, the circumference of the posterior section becomes smaller than that of the anterior section. It is recommended to be designed in a long cylindrical form.

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