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Modern Paper Quality Control

  • Olavi Komppa
    • Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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    • 2000.06a
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    • pp.16-23
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    • 2000
  • The increasing functional needs of top-quality printing papers and packaging paperboards, and especially the rapid developments in electronic printing processes and various computer printers during past few years, set new targets and requirements for modern paper quality. Most of these paper grades of today have relatively high filler content, are moderately or heavily calendered , and have many coating layers for the best appearance and performance. In practice, this means that many of the traditional quality assurance methods, mostly designed to measure papers made of pure. native pulp only, can not reliably (or at all) be used to analyze or rank the quality of modern papers. Hence, introduction of new measurement techniques is necessary to assure and further develop the paper quality today and in the future. Paper formation , i.e. small scale (millimeter scale) variation of basis weight, is the most important quality parameter of paper-making due to its influence on practically all the other quality properties of paper. The ideal paper would be completely uniform so that the basis weight of each small point (area) measured would be the same. In practice, of course, this is not possible because there always exists relatively large local variations in paper. However, these small scale basis weight variations are the major reason for many other quality problems, including calender blacking uneven coating result, uneven printing result, etc. The traditionally used visual inspection or optical measurement of the paper does not give us a reliable understanding of the material variations in the paper because in modern paper making process the optical behavior of paper is strongly affected by using e.g. fillers, dye or coating colors. Futhermore, the opacity (optical density) of the paper is changed at different process stages like wet pressing and calendering. The greatest advantage of using beta transmission method to measure paper formation is that it can be very reliably calibrated to measure true basis weight variation of all kinds of paper and board, independently on sample basis weight or paper grade. This gives us the possibility to measure, compare and judge papers made of different raw materials, different color, or even to measure heavily calendered, coated or printed papers. Scientific research of paper physics has shown that the orientation of the top layer (paper surface) fibers of the sheet paly the key role in paper curling and cockling , causing the typical practical problems (paper jam) with modern fax and copy machines, electronic printing , etc. On the other hand, the fiber orientation at the surface and middle layer of the sheet controls the bending stiffness of paperboard . Therefore, a reliable measurement of paper surface fiber orientation gives us a magnificent tool to investigate and predict paper curling and coclking tendency, and provides the necessary information to finetune, the manufacturing process for optimum quality. many papers, especially heavily calendered and coated grades, do resist liquid and gas penetration very much, bing beyond the measurement range of the traditional instruments or resulting invonveniently long measuring time per sample . The increased surface hardness and use of filler minerals and mechanical pulp make a reliable, nonleaking sample contact to the measurement head a challenge of its own. Paper surface coating causes, as expected, a layer which has completely different permeability characteristics compared to the other layer of the sheet. The latest developments in sensor technologies have made it possible to reliably measure gas flow in well controlled conditions, allowing us to investigate the gas penetration of open structures, such as cigarette paper, tissue or sack paper, and in the low permeability range analyze even fully greaseproof papers, silicon papers, heavily coated papers and boards or even detect defects in barrier coatings ! Even nitrogen or helium may be used as the gas, giving us completely new possibilities to rank the products or to find correlation to critical process or converting parameters. All the modern paper machines include many on-line measuring instruments which are used to give the necessary information for automatic process control systems. hence, the reliability of this information obtained from different sensors is vital for good optimizing and process stability. If any of these on-line sensors do not operate perfectly ass planned (having even small measurement error or malfunction ), the process control will set the machine to operate away from the optimum , resulting loss of profit or eventual problems in quality or runnability. To assure optimum operation of the paper machines, a novel quality assurance policy for the on-line measurements has been developed, including control procedures utilizing traceable, accredited standards for the best reliability and performance.

우리나라 농촌지역의 출산조절행태 및 출산조절행위의 결정요인 분석

  • Chung, Kyung-Hee;Han, Seung-Hyun;Bang, Sook
    • Korea journal of population studies
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    • v.11 no.2
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    • pp.33-53
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    • 1988
  • This study aimed at developing a desirable family planning policy and strategy by examining the current status of family planning practice in rural Korea and by indentifying the crucial factors which affect fertility control behavior. For this purpose, an analytical study was conducted, using the survey data collected in July 1985, on an interview basis, on 1, 440 married women living in the Soyi, Wonnam and Maingdong townships of Eumseong County(in North Chungcheong Province). This study population has the typical characteristics of rural areas, and the results of the analysis can be summarized as follows: 1. In regard to the demographic characteristics of the study population : their average age at marriage was 23.7, they had an average of 2.6 children( 1.3 boys, 1.3 girls) :10% experienced the death of their child (ren) :14% had spontaneous abortion(s) :4% weathered stillbirth(s) :35% went through induced abortion (s) : and 5.5% were currently pregnant. The average of their ideal numbers of children was 2.2, while 44% felt that they must have a son. 2. Looking at the contact rate with medical & health institutions, over the past 1 year, the visit rate to health subcenters was 43.7%, while 26.9% visited the (county) health center :59.6% had been to private clinics : and 41.5% went to the Soonchunhyang - Eumsung hospital : thus showing a relatively high rate of accessibility. 3. The utilization rate of family planning services was 76.5%, with tubectomy being the most prominent method at 52.3%, while the informants were health workers in 54.2% of the acceptors. Of the 8.4% who discontinued the use of contraceptive methods, only 26% did so due to want for pregnancy, natural infertility (meno - pause), or other reasons, while the remaining 74% stopped usage on account of side effects, failure in the methods themselves, and inconvenience of use, thus pointing to a situation where the proper choice of family planning methods have not yet been made. It can be noted that there is a strong motivation for early birth stopping as 35.3% practice family planning even with only one child, of which 38.3% have had sterilization operations. According to results of a multiple regression analysis, among the variables affecting contraception usage the most significant variable was the number of sons. 4. 34.8% experienced induced abortions. It was shown as a result of multiple regression analysis that the number of children and attitudes toward induced abortions extensively affected their frequency of abortions conducted. 5. In the regard to the relation between family planning and induced abortions, 33.7% of the women used both, while 52.0% of them used only the former(family planning), with only 1.4 % utilizing solely the latter(abortion), and 12.9% totally abstaining from fertility regulation : again, the discriminant analysis indicated that the choice of family planning and/or induced abortion was determined by the number of children and attitudes toward induced abortion. In view of the above mentioned results, the following are some comments and suggestions concerning problems related to the current family planning policies, in Korea : 1. It is difficult to expect a further quantitative expansion in family planning program operations, as there has been an excessive supply of target-oriented sterilization operations on women. From a maternal and child health care point of view, it will be desirable to have a diversification of service points in the future where family planning methods may be properly chosen, so that choices of methods which suit the mothers' characteristics and tastes may be made by the individuals themselves by strengthening their quality of family planning information services. 2. Along with the strengthening of the qualitative improvement of family planning services policies must be implemented to effectively promote the moral (ethical) deterrents to induced abortions and to preference for sons. From a maternal care standpoint, the social permissive norm toward induced abortion must be modified, and the bias towards son must be analyzed as the women with more daughters have a lower rate of family planning acceptance. Such changes in attitudes, however, can not be hoped to be accomplished with ad hoc policies, but will only be possible when an enhancement of the women's status(within the society) is brought about in a long - term perspective.

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A Comparative Study of the Oriental and the Occidental Medical Literature on the Etiologies & Treatments for Palmoplantar Hyperhidrosis (수족한(手足汗)의 원인(原因)과 치료법(治療法)에 대한 동(東).서의학적(西醫學的) 고찰(考察))

  • Ko, Young-Chul;Shin, Jo-Young
    • The Journal of Internal Korean Medicine
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    • v.18 no.2
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    • pp.268-295
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    • 1997
  • Sweating is natural phenomenon necessary for the regulation of an individual's body-temperature. The secretion of sweat is mediated by a portion of our vegetative nervous system(the sympathetic nervous system). In some people, this system is working at a very high activity level, far higher than needed to keep a constant temperature. This condition is referred to as hyperhidrosis. Especially excessive sweating of the hands and the feet is palmoplantar hyperhidrosis or volar hyperhidrosis. This is by far the most distressing condition. It was founded that the first important cause of this was emotional factor. The hands are much more exposed in social and prefessional activities than any other part of our body. Many individuals with palmoplantar hyperhidrosis are limited in their choice of proffession, because unable to manipulate materials sensitive to humidity or reluctant to shake hands; some patients arrive to the point to avoid social contact. The occidental medical treatments for palmoplantar hyperhidrosis include application of topical agents(chemical antiperspirants such as aluminum chloride), iontophoresis(treatment with electrical current), or surgery(thoracic sympathectomy). It was reported that the most effective treatment was thoracic sympathectomy. So this study was started to find the easy and effective oriental medical treatments against the occidental medical treatments through the oriental medical literature. The occidental medical idea for palmoplantar hyperhidrosis is only limited in neurologic system, so surgery is the best treatment. But the oriental medical idea for palmoplantar hyperhidrosis is much wider, so the oriental medical causes and treatments for this are able to be veriety. And the oriental medical teatment is freely in treating the patients of palmoplantar hyperhidrosis, because entire idea including pulse, facial color, mental condition, constitution and other symptom exists in the oriental medicine. The results of a bibliographic study of causes and treatments for palmoplantar are as follows; 1. The main causes of pa1moplantar hyperhidrosis are heat in the stomach, damp-heat in the spleen and the stomach, insufficiency of the spleen-qi and the stomach-qi, deficiency of the spleen-yin and the stomach-yin, and the others are the stomach-cold syndrome, stasis of blood and dyspepsia in the stomach, disorder of the liver-qi, deficiency of the heart-yin and the kidney-yin, deficiency of the heart-yang and the kidney-yang, stagnated heat in the liver and the spleen, the lung channel-heat etc. 2. The main methods of medical treatments for palmoplantar hyperhidrosis are clearing out the stomach-heat, eliminating dampness and heat in the spleen and the stomach, invigorating the spleen-qi and the stomach-qi, reinforcing the spleen-yin and the stomach-yin, warming the stomach, relaxing the liver and alleviating of mental depression and tonifying the heart and the kidney etc. 3. The main prescriptions of palmoplantar hyperhidrosis are Taesihotang, Palmultang-kakam, Samyeongbaechusan, Chongbisan, Sasammaekmundongtang, the others are Leejungtang, Hwangkikonjungtang, Seungkitang, Boyumtang, Baekhotang, Chongsimyonjayum, Moyrosan, etc. 4. Local medicine for external use are liquid after boiling alum in water for about 1 or 2 hours, liquid after boiling alum and pueraria root in water and liquid after boiling stragalus root, pueraria root, ledebouriella root and schizonepeta in water, etc. 5. The methods of acupuncture therapy include invigorating Bokyru, Yumkuk and purgating Hapkouk, or invigorating Bokyru, Kihae and purgating Hapkouk, or steadying Hapkouk, Nokung.

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A Study on the Roles and Ideological Development of Welfare Characteristics in Parks (공원복지 역할 및 이념 전개 양상에 관한 연구)

  • Han, So-Young;Cho, Han-Sol;Zoh, Kyung-Jin
    • Journal of the Korean Institute of Landscape Architecture
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    • v.43 no.1
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    • pp.69-81
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    • 2015
  • Under the premise that parks have been a performing field of welfare ideology that benefits the citizen from the past, the present study began with a basic question on what substance a park has and how it has worked. Therefore, this study tried to find out the theoretic background that can explain the roles of a park as an instrument for welfare, of which topic is currently being discussed, and examine how the ideology in the debate regarding welfare characteristics of parks are differentiated from those of social welfare. In addition, this study divided the process of development of parks defined by Galen Cranz in an attempt to view how welfare benefits offered by parks have changed in their development and looked into the roles and types of welfare functions that parks provided to the citizens under a certain social situation by period. Furthermore, the characteristics and development of the ideology underlying a welfare park were examined by function and element in its progression. The results of this study are as follows. The functions that parks have performed so far can be classified into three categories. First, they have a remedial function. Parks have given direct services to 'the socially disadvantaged' such as relief, fostering, and rehabilitation. Second, parks have played a preventive function. They aim to reinforce the functions of individual, family, group, and community. Third, they have exerted a developmental function. They function to promote change of society in a way for it to contribute to social development. Looking into the roles and functions of parks from the perspective of their beneficiary class and benefits, the following were discovered. First, the beneficiaries of welfare characteristics in parks have expanded to the general public from the poor class, and the benefits of parks have spread into the public including the underprivileged in a real sense. Second, the significance of welfare characteristics in parks has also changed from literal benefits to caring for basic human rights. Third, the purpose of welfare characteristics in parks has changed from providing minimal conditions to optimal conditions. At its beginning, the ideology of welfare in parks remained ideal, confining itself to their idealistic characteristics; but as time went on, they created several social benefits in response to various social demands, developing into a field where welfare ideology manifests and is realized in an active manner. Furthermore, it was witnessed that the parks and welfare of the present times are standing at the point of contact for participation and universal well-being. The present study reconsidered the meaning and value of parks from perspective of them as a provider of welfare benefits as well as examined how the welfare ideology of parks is connected to practice. By doing so, this study discovered the various roles, values, and ideology that parks should bear in the future. Therefore, this study is expected to be a good example for future research related to the topic.

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 on the Realities and the Subject of Environmental Management for Small and Medium-Sized Companies in Gangwon Area (강원지역 중소기업의 환경경영 실태와 과제)

  • Jeon, Yeong-Seung;Park, Eun-Jeong
    • Korean Business Review
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    • v.17
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    • pp.53-81
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    • 2004
  • The purpose of this study is to understand the realities and the subject of environmental management for small and medium-sized companies in Gwangwon area, through surveying the present status as to acquiring the certification of ISO14001, and to seek for a plan to facilitate environmental management. Given summarizing key results, those are as follows. First, while the number of companies in our country which acquired the certification of ISO14001, amounts to 1,215 businesses as of April of 2003, the number of small and medium-sized companies in Gwangwon area which obtained the certification of ISO14001 reached only 26 businesses, the lowest level among metropolitan municipalities. Second, for the reason that companies who didn't acquire the certification, strive not to receive the certification, it did present the point that' costs to be needed in acquiring and maintaining the certification are larger than practical benefit. Third, the biggest reason for either companies which did not acquire the certification of ISO14001 or companies which did (try to) acquire the certification of ISO1400, was, enhancement of a corporate image,' and the effect after a company who obtained the certification introduced the environmental management system, was also shown to be 'the improvement of a corporate image.' Fourth, many companies who acquired the certification of ISO1400 pointed out the response related to 'burden on document creation and costs' and 'lack of manpower' as problems when introducing the environmental management system. On the basis of major results of a study as the above, given presenting the subject and a plan for activating the environmental management of small and medium-sized companies in Gwangwon area, those are as follows. First, because most of companies who did not obtain the certification of ISO1400 have low recognition of ISO14001, it needs continuous and positive publicity, education and a training system. Second, it requires to carry out an educational program to nurture professional manpower due to lack of manpower relevant to environmental management, to expand payment of subsidies, to open exclusive-charge department and consulting contact, to have the relevant information be database and to develop software. Third, in order to make the certification obtained through inexpensive costs and simple procedures, it needs to positively consider the creation of public approval system for a small and medium-sized company, group approval system, industrial-complex approval system, and others.

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Goodness-of-Fit of Job Burnout Scale in Private Security Guards (민간경비원을 위한 직무소진 척도 문항의 적합도)

  • Lee, Jun-Woo;Lee, Jong-Hwan;Kim, Eui-Young
    • Korean Security Journal
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    • no.39
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    • pp.161-183
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    • 2014
  • The job burnout of the private security guards who provide services through contact with customers can affect the overall the private security industry. So the managers need to make efforts to diagnose and evaluate the job burnout and provide continuous provision for the repatriation effect. However, up to the present, the job burnout measure for the private security guards has not been provided, so the objectivity of the information is questionable. For this reason, in order to establish the goodness of fit of the job burnout scale for private security guards based on the contents of the job burnout scale that was being provided to other service employees, this research aims to provide the scale to provide objective information compared with that of the past by applying the Rasch model of the item response theory. To achieve this purpose, the data on 379 private security guards working for the private security guard companies in the Gyeonggi region were collected, and the data were processed to suit the research purpose using SPSS 18.0 and AMOS 18.0, Winsteps programs. Through these research procedures, the following conclusion was obtained. With regard to the private security guards' measure of job burnout, as a result of factor analysis through the collected data, 4 questions were deleted, and as a result of the analysis of the goodness of the fit based on 18 questions, 4 questions were found to be inappropriate questions that did not satisfy the standard value, and the scope of the difficulty level of the questions from - 98 to 1.30 and the response reaction of a 5-point scale were found to suit the final private security guards' job burnout scale. In other words, the conclusion that it is appropriate to measure the private security guards job burnout scale with 3 factors and 13 questions was obtained. So if private security guards companies collect systematic data using the scale established in this research, and practice refresher training accordingly, they can reduce the private security guards' job burnout.

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Formation of Clay Minerals by Water-Rock Interaction in the Fracture of Gneiss (편마암 열극에서의 물-암석 상호반응에 의한 점토광물 생성)

  • Jeong, Chan-Ho;Kim, Soo-Jin;Koh, Yong-Kwon
    • Journal of the Mineralogical Society of Korea
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    • v.7 no.1
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    • pp.49-61
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    • 1994
  • As the groundwater flows along the fractures of crystalline rocks, it will be in contact with the fracture walls mostly coated by secondary minerals which are quite different form those of host rocks. The presence of fracture-filling minerals in crystalline rocks is important on the view point of radioactive waste disposal because of their great surface reactivity. The Surichi drill hole of 200 m in depth in the Yugu area composed mainly of Precambrian gneiss was selected to study the formation process of clay minerals on the fracture wall of gneiss, and their relation with present groundwater. The water-rock interaction in fractures resulted in the formation of gibbsite and clay minerals. They are formed by two different processes : (1) Incongruent dissolution of feldspar by groundwater diffused from a fracture path into rock matrix produced smectite and illite in situ, (2) on the wall of fracture, gibbsite, kaolinite, smectite and illite are formed by precipitation of dissolved species in groundwater. They show the paragenetic sequence such as gibbsite${\leftrightarrow}$kaolinite${\leftrightarrow}$smectite or illite. The paragenetic sequence of fracture-filling minerals was controlled by increase of pH of groundwater, decrease of fracture permeability by precipitation of fillings, and immobility of alkali or alkaline earths in groundwater. The groundwater from the Surichi borehole is a $Na-HCO_{3}$ type with pH range of 8.6-9.2. The sodium and bicarbonate in groundwater would be supplied by the dissolution of albite and calcite, respectively. The saturation index of groundwater and surface water calculated by WATEQ4F indicates that gibbsite and kaolinite are under precipitation to equilibrium state, and that smectite and illite are under equilibrium to redissolution environment. The stability relation of clay minerals in the $Na_{2}O-Al_{2}O_{3}-SiO_{2}-H_{2}O$ system shows that kaolinite is stable for all waters.

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Study on the Performer's Transference and Mental Borderline in a Performance (공연에서 나타나는 '전이'와 배우의 '심리적 경계'에 관한 연구)

  • Kim, Jong-Gu
    • (The) Research of the performance art and culture
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    • no.25
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    • pp.57-89
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    • 2012
  • The performers preparing for a performance usually experience the process of mental transference, contacting with text (drama) for the first time. It is movement from their everyday life to space in the play, when they try to break the wall between cast and themselves. The transference happens actually at the physical space, such as a dressing room, wing, (place just before appearing at a stage), and a stage (place to contact with audience). Performers keep moving among each psychological and physical space repeatedly, until the performance finishes totally. The transference means moving to each space to another, and the mental borderline means the point of mental change the performers experience during the process of transference. The mental borderline can be guessed to exist through mental aspects the performers feel when they move from each space to another. The most typical example, that shows performer's mental borderline well, is stage fright shown as tension, or anxiety among the variety of aspects. According to a research, the most performers experience that kind of mental aspect just before appearing at a stage. The study on it is already referred by my article.' A Study on Korean Performer's Stage Fright. This study aims at examining the relationship among psychological and physical space the performers experience, mental borderline when transferring and penetrating those spaces, and performer's mental change First, the concept of mental borderline is to be understood totally with preceded research. And the space the performers experience and mental borderline at transference are to be reorganized. Secondly, the area of transference in the process of performance is to be reclassified into physical and mental space. Third, analyzing the actual case of performers experiencing the mental borderline, the diversified use should be searched to make use of mental borderline as a positive element. The psychological symptoms, performers experience in the performance, can have positive consequence beside negative one. The tension occurring at the area of borderline is positive, and it can be the actual borderline for the performers. It will be researched how the performers change at the mental borderline, the state of mind is maintained, and they perform in an overall performance, through the study on the relationship between the transference and the mental borderline. And the stress and concentration caused by stage fright, and shyness will be confirmed, and the positive element of a stage, which is used as various defense mechanism.

Comparison of the effect of removing artificial dental plaque depending on various interdental cleaning products on the interdental surface of zirconia crowns (치간 세정 용품에 따른 지르코니아 크라운 인접면의 인공 치면 세균막 제거 효과)

  • Kim, Hyun-Wook;Song, Ha-Kyung;Park, Eun-Jin
    • The Journal of Korean Academy of Prosthodontics
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    • v.59 no.3
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    • pp.291-298
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    • 2021
  • Purpose. The purpose of this study is to compare five interdental cleansing products' effectiveness on removing artificial dental plaque on the interdental space of zirconia crowns. Materials and methods. A model with abutments on the right mandibular second premolar and first molar were prepared. 10 zirconia crowns for each abutment were fabricated. After applying artificial dental plaque between the zirconia crowns, a single clinician attempted to remove the plaque with five products: interdental toothbrush, end-tuft toothbrush, dental floss, Easypick, Water pik. They were conducted 10 times per group. The aspect and area of removed surfaces were analyzed using images taken with a digital camera. One factor analysis of variance was performed as a statistical analysis, and a post-hoc test was performed using the Scheffé method (P < .05). Results. There were differences in the area and the pattern according to the characteristics of the products. The largest area, including the marginal portion, was removed in the dental floss group. Interdental toothbrush group was the most effective in removing the dental plaque at the marginal portion. Easypick was less effective than the interdental toothbrush. The end-tuft toothbrush showed better results than other products in cleansing mesiobuccal and distobuccal area, but could not cleanse the area directly below the contact point. In Water pik group, artificial dental plaque was scarcely removed. The removal rate of artificial dental plaque was in the order of floss (69.47%), end-tuft toothbrush (49.36%), interdental toothbrush (44.20%), Easy pick (13.04%), and Water pik (0.59%). Conclusion. Dental floss showed the highest removal rate in the interdental space restored with zirconia crowns, while interdental toothbrush was the most effective in removing the dental plaque at the marginal portion.