• Title/Summary/Keyword: Theoretical Study

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A review of Deepwater Horizon Oil Budget Calculator for its Application to Korea (딥워터 호라이즌호 유출유 수지분석 모델의 국내 적용성 검토)

  • Kim, Choong-Ki;Oh, Jeong-Hwan;Kang, Seong-Gil
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.19 no.4
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    • pp.322-331
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    • 2016
  • Oil budget calculator identifies the removal pathways of spilled oil by both natural and response methods, and estimates the remaining oil required response activities. A oil budget calculator was newly developed as a response tool for Deepwater Horizon oil spill incident in Gulf of Mexico in 2010 to inform clean up decisions for Incident Comment System, which was also successfully utilized to media and general public promotion of oil spill response activities. This study analyzed the theoretical background of the oil budget calculator and explored its future application to Korea. The oil budge calculation of four catastrophic marine pollution incidents indicates that 3~8% of spilled oil was removed mechanically by skimmers, 1~5% by in-situ burning, 4.8~16% by chemical dispersion due to dispersant operation, and 37~56% by weathering processes such as evaporation, dissolution, and natural dispersion. The results show that in-situ burning and chemical dispersion effectively remove spilled oil more than the mechanical removal by skimming, and natural weathering processes are also very effective to remove spilled oil. To apply the oil budget calculator in Korea, its parameters need to be optimized in response to the seasonal characteristics of marine environment, the characteristics of spilled oil and response technologies. A new algorithm also needs to be developed to estimate the oil budget due to shoreline cleanup activities. An oil budget calculator optimized in Korea can play a critical role in informing decisions for oil spill response activities and communicating spill prevention and response activities with the media and general public.

A study on the comparison by the methods of estimating the relaxation load of SEM-pile (SEM파일의 이완하중 산정방법별 이완하중량 비교 연구)

  • Kim, Hyeong-Gyu;Park, Eun-Hyung;Cho, Kook-Hwan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.3
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    • pp.543-560
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    • 2018
  • With the increased development in downtown underground space facilities that vertically cross under a railway at a shallow depth, the demand for non-open cut method is increasing. However, most construction sites still adopt the pipe roof method, where medium and large diameter steel pipes are pressed in to form a roof, enabling excavation of the inside space. Among the many factors that influence the loosening region and loads that occur while pressing in steel pipes, the size of the pipe has the largest impact, and this factor may correspond to the magnitude of load applied to the underground structure inside the steel pipe roof. The super equilibrium method (SEM) has been developed to minimize ground disturbance and loosening load, and uses small diameter pipes of approximately 114 mm instead of conventional medium and large diameter pipes. This small diameter steel pipe is called an SEM pile. After SEM piles are pressed in and the grouting reinforcement is constructed, a crossing structure is pressed in by using a hydraulic jack without ground subsidence or heaving. The SEM pile, which plays the role of timbering, is a fore-poling pile of approximately 5 m length that prevents ground collapse and supports surface load during excavation of toe part. The loosening region should be adequately calculated to estimate the spacing and construction length of the piles and stiffness of members. In this paper, we conducted a comparative analysis of calculations of loosening load that occurs during the press-in of SEM pile to obtain an optimal design of SEM. We analyzed the influence of factors in main theoretical and empirical formulas applied for calculating loosening regions, and carried out FEM analysis to see an appropriate loosening load to the SEM pile. In order to estimate the soil loosening caused by actual SEM-pile indentation and excavation, a steel pipe indentation reduction model test was conducted. Soil subsidence and soil loosening were investigated quantitatively according to soil/steel pipe (H/D).

Social Network Analysis for the Effective Adoption of Recommender Systems (추천시스템의 효과적 도입을 위한 소셜네트워크 분석)

  • Park, Jong-Hak;Cho, Yoon-Ho
    • Journal of Intelligence and Information Systems
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    • v.17 no.4
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    • pp.305-316
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    • 2011
  • Recommender system is the system which, by using automated information filtering technology, recommends products or services to the customers who are likely to be interested in. Those systems are widely used in many different Web retailers such as Amazon.com, Netfix.com, and CDNow.com. Various recommender systems have been developed. Among them, Collaborative Filtering (CF) has been known as the most successful and commonly used approach. CF identifies customers whose tastes are similar to those of a given customer, and recommends items those customers have liked in the past. Numerous CF algorithms have been developed to increase the performance of recommender systems. However, the relative performances of CF algorithms are known to be domain and data dependent. It is very time-consuming and expensive to implement and launce a CF recommender system, and also the system unsuited for the given domain provides customers with poor quality recommendations that make them easily annoyed. Therefore, predicting in advance whether the performance of CF recommender system is acceptable or not is practically important and needed. In this study, we propose a decision making guideline which helps decide whether CF is adoptable for a given application with certain transaction data characteristics. Several previous studies reported that sparsity, gray sheep, cold-start, coverage, and serendipity could affect the performance of CF, but the theoretical and empirical justification of such factors is lacking. Recently there are many studies paying attention to Social Network Analysis (SNA) as a method to analyze social relationships among people. SNA is a method to measure and visualize the linkage structure and status focusing on interaction among objects within communication group. CF analyzes the similarity among previous ratings or purchases of each customer, finds the relationships among the customers who have similarities, and then uses the relationships for recommendations. Thus CF can be modeled as a social network in which customers are nodes and purchase relationships between customers are links. Under the assumption that SNA could facilitate an exploration of the topological properties of the network structure that are implicit in transaction data for CF recommendations, we focus on density, clustering coefficient, and centralization which are ones of the most commonly used measures to capture topological properties of the social network structure. While network density, expressed as a proportion of the maximum possible number of links, captures the density of the whole network, the clustering coefficient captures the degree to which the overall network contains localized pockets of dense connectivity. Centralization reflects the extent to which connections are concentrated in a small number of nodes rather than distributed equally among all nodes. We explore how these SNA measures affect the performance of CF performance and how they interact to each other. Our experiments used sales transaction data from H department store, one of the well?known department stores in Korea. Total 396 data set were sampled to construct various types of social networks. The dependant variable measuring process consists of three steps; analysis of customer similarities, construction of a social network, and analysis of social network patterns. We used UCINET 6.0 for SNA. The experiments conducted the 3-way ANOVA which employs three SNA measures as dependant variables, and the recommendation accuracy measured by F1-measure as an independent variable. The experiments report that 1) each of three SNA measures affects the recommendation accuracy, 2) the density's effect to the performance overrides those of clustering coefficient and centralization (i.e., CF adoption is not a good decision if the density is low), and 3) however though the density is low, the performance of CF is comparatively good when the clustering coefficient is low. We expect that these experiment results help firms decide whether CF recommender system is adoptable for their business domain with certain transaction data characteristics.

A Study on the assignment of vicera of the pulsation examination method of the KiGu (기구맥진법(氣口脈診法)의 장부배속(藏府配屬)에 관한 연구(硏究))

  • Hwang, Won-Deok;Kim, Jung-Han
    • Journal of Korean Medical classics
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    • v.12 no.1
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    • pp.226-254
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    • 1999
  • For the first time, the theory of ChonKwanChuk(寸關尺) and the examination method of KyungJung(輕重法) of KiGu(氣口) were formed in "NanKyung(難經)". After that, the vicera assignment theory at left and right hands(左右守藏府記屬理論) was established in "MaekKyung(脈經)" After Reserching the theoretical relevance of the two books, theories between the doctors who understood the examination method of ChukBu(尺部診法) of "Somun MaekYoJungMiRon(素問 脈要精微論)" as the examination method of KyungJung(輕重法) and the doctors who understood that method as the method of ChonKwanChuk(寸關尺) were compared and researched. The results were as follows : 1. The posit ion of ChonKwanChuk(寸關尺) of the examination method of ChonKwanChuk(寸關尺法) is explained at 2nd Nan(二難) of "NanKyung" as follows. Chuk(尺) is the position which is 1Chon(1寸, unit) distant from Kwan(關) to the direction of ChukTaek acupuncture point(尺澤穴) and Chon(寸) is the position which is 9Pun(9分, unit) distant from Kwan(關) to the direction of EoJe acupuncture point(魚際穴). And the six vessels(六經) were assined to ChonKwanChuk(寸關尺) on the basis of OHangJaMoSnagSaeng(五行子母相生) at 18th Nan(18難) of NanKyung. After that Yang Hyun-Jo(楊玄操) at Dang Dynasty, Jung Deok-Yong(丁德用), Woo Seo(廬庶) at Song dynasty explaind the examination method of ChonKwanChuk(寸關尺法) of NanKyung as the method of ChonKwanChuk of two hands(兩手寸關尺法) from the viewpoint of "MaekKyung(脈經)". 2. From the viewpoint of MaeKyung, the vicera assignment of the two hand ChonKwanChuk method is as follows. At Chuk of left hand, the Heart and Small intestine are assigned. At Kwan of left hand, the Liver and Gall Bladder are assigned. At Chuk of left hand, the Kidney and Bladder are assigned. At Chuk of right hand, the Lung and Large in testine are assigned. At Kwan of right hand, the Spleen and Stomach are assigned. At Chuk of Right hand, the Vital Gate(命門) and Bladder are assigned. 3. For the first time, HwalSu(滑壽) at Won dynasty said that the paragraph "尺內兩傍${\cdots}{\cdots}$" of "Somun MaekYoJungMiRon" is the first of the examination method of KiGu(氣口診脈法). After that Ma Shi(馬蒔), Jang Gae-Bin(張介賓) of Myung Dynasty, Jang Ji-Chong(張志聰), Seo Dae-Chun(徐大椿) of Chung Dynasty who were influenced by him explained that paragraph as the method of KiGuChonKwanChuk(氣口寸關尺法). 4. Lee Kyu-Jun(李圭晙) explained the paragraph "尺內兩傍${\cdots}{\cdots}$" of "Somun MaekYoJungMiRon" as the method of KyungJung(輕重法) and explained Chok(尺) as the paragraph 'Chuk is low position of Kigu, and it means the depth(氣口之下位也, 言其深也)' and explained that 'the Left and the Right is layers(左右者層數). And he revised that the Jang(臟) must be examined at the inner part and the Bu(府) must be examined at the outer part. By this, he settled the theoratical basis of the method of KyungJung(輕重法). 5. The doctors who used the examination method of ChonKwanChok(寸關尺診法) settled their logical justification of the two hand examination method of ChonKwanChuk(兩手寸關尺診法) by connecting with "Somon MaekYoJungMi-Ron" from the viewpoint of 2nd Nan(難) and 18th Nan(難) of NanKyung and MaekKyung. On the contrary, the doctors who used the examination method of KyungJung(輕重診法) settled their logical justification of the examination method of KyungJung(輕重診法) by connecting with "Somun MaekYoJungMiRon" from the viewpoint of 4th Nan(四難) and 5th Nan(五難).

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Study on "Four Tantras", the Prime Textbook of Tibetan Medicine (티벳의학에 대한 연구 - "사부의전(四部醫典).근본의전(根本醫典)"을 중심으로)

  • Chang, Eun-Young;Yun, Chang-Yul
    • Journal of Korean Medical classics
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    • v.11 no.1
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    • pp.416-512
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    • 1998
  • The following conclusions are obtained from the studies on the chapters concerning phisiology, pathology, daily conduct, materia medica, pulse, and urinalysis from , of the "Four Tantras". 1. The theoretical basis forming the Tibetan Medicine is the substance of phlegm, bile, and wind each of which is divided into five kinds. These phisiological substances can be transformed into pathological factors when certain environment is formed. 2. In embryology, the semen of the father and menstral blood of mother is considered the most important condition in conception, and the Five factors are regarded as important. There is a detailed explanation of development of the fetus while it stays in the womb of mother during 38weeks, such as the formation of the viscera, channels, sense organs, etc. 3. There is metaphor which compares the human body with the king's palace. With the development of human anatomy, there is the detailed anatomical picture of anterior and posterior aspects of human body. And also there is the measurement of physiological constitution and the three fluids. 4. In division of the channels, they concerned the now of the blood and distribution of the nerve fibers, and each channel is connected with one another. The division of the cannel is namely embryonic channel, channel of existence, channel of connection, and the course of life principle. 5. The seven bodily constituents and three factors of phlegm, bile, and wind are important in sustaining the life of human body as well as growth and maturization, and when their equilibrium is broken, the human body is degnerated, and finally death comes. 6. The signs of death is divided into distant sign, remote sign, certain sign. and uncertain sign, and is used as a clue in diagnosis of the disease. Especially there is a mention about the mechanism of the dreams, and different dreams according to the condition of the patient. 7. In pathology, there is the cause of the disease, the environmental factors which can induce disease, the path by which disease come into the human body, the characteristics of the disease, and the kinds of disease. 8. There is a mention about the conduct, and it is divided into the daily conduct, the mental attitude, and the side-effects which can occur when one puts up with the physiological actions of the body. 9. The daily diet is divided into food and beverage. The food is divided again into grain, meat, fat, boiled food, and spiced food, and the beverage into milk, water, and wine. 10. The pulsation should be taken in lift hand to diagnose heart, small intestine, stomach, spleen, kidney, reproductive organ, and in right hand jungs, large intestine, liver, gall bladder, kidney, and bladder. In the healthy person, the pulse moves 5times in one perspiration, and the type of pulse is constant while the pulse moves 100times. But unhealthy person's pulse is different from this. The urinalysis is the unique part of Tibetan Medicine, and is important in examination of the disease. One should decide which of the three factors are dominant by the obervation of the color, amount of the steam and how long it lasts, odour, foam, and the shape of the swirl in three different states when the urine is hot, warm, and cold. One can determine the life of the patient and which viscera is the cause of the disease by the pulse, and whether the nature of the disease is hot or cold by the urinalysis. 11. The materia medica contains gemstones, minerals, plateau medication, and meat products.

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A SURVEY OF THE PSYCHOSIS AMONG SCHOOL VIOLENCE VICTIMS (학교폭력 피해자의 정신병 실태 조사)

  • Kwon, Seok-Woo;Shin, Min-Sup;Cho, Soo-Churl;Shin, Sung-Woong
    • Journal of the Korean Academy of Child and Adolescent Psychiatry
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    • v.11 no.1
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    • pp.124-143
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    • 2000
  • Objectives:The primary purpose of this study is to understand the psychopathology of the victims of school violence in terms of early psychosis. By doing this, the early detection of psychosis among the victims is possible, and early detection may lead to early intervention. Methods:Two-thousand and nine-hundred seventy two students from 16 middle schools in Seoul were asked to fill out questionnaire comprised of popularity and intellectual and school status of Piers-Harris Children's Self Concept Inventory, Symptom Check List-90-Revised, and Ostracism Scale. The subjects whose scores upon Ostracism Scale were higher than average by two standard deviation were labeled as ‘Repelled and Isolated group', and subjects whose scores on popularity were significantly lower than average and whose scores on psychoticism of SCL-90-R were higher than average were defined as 'tentative early psychosis group'. Odds ratios were calculated from the numbers of subjects with and without high psychoticism scores and high ostracism scores. On the subjects of 'tentative early psychotic group', we examined every clinical characteristic and conducted correlation analysis and regression analysis in order to find out the risk factors and to construct theoretical model that explains the psychoticism scores. Results:The results were as follows:1) Total 157(5.3%) subjects were rated significantly higher on ostracism scale, and among them, 47 subjects(29.9%) were rated significantly higher than average on psychoticism scale, while only 50 subjects among 2,135 students who were rated within normal range showed significantly higher score on psychoticism scale. Odds ratio for psychotic group of isolated group were 17.82 and it was statistically significant. 2) Forty-seven subjects(31 boys, 16 girls) who were rated as they were unpopular and rejected from peers had significantly higher psychoticism scores. They were not significantly different from simply high psychoticism subjects in anxiety, social anhedonia scale, magical thinking, obsessivecompulsive symptoms, phobic anxiety, psychoticism, somatization, but showed higher ostracism scores and paranoid tendencies. Among school violence victims, who rated themselves unpopular and showed higher psychoticism scores, the psychoticism scores were mainly explained by anxiety, depression, hostility, interpersonal sensitivity, obsessive-compulsive symptoms, paranoid tendency, somatization scales($r^2=0.93$). Conclusion:Thus, it can be concluded that the subjects with higher ostracism score have the substantially high risk for psychosis development. By these results, we propose that school violence victims with anxiety, depression, hostility, interpersonal sensitivity, obsessive-compulsive symptoms, paranoid tendency, somatization should be tested individually considering school adjustment, attentional deficit, concept formation problems.

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Study on Strain Measurement of Agricultural Machine Elements Using Microcomputer (Microcomputer를 이용(利用)한 농업기계요소(農業機械要素)의 Strain 측정(測定)에 관(關)한 연구(硏究))

  • Kim, Kee Dae;Kim, Tae Kyun;Kim, Soung Rai
    • Korean Journal of Agricultural Science
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    • v.8 no.1
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    • pp.90-96
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    • 1981
  • To design more efficient agricultural machinery, the accurately measuring system among many other factors is essential. A light-beam oscillographic recorder is generally used in measuring dynamic strain but it is not compatible with the extremely high speed measuring system such as 1,000 m/s, also is susceptable to damage due to vibration while using the system in field. The recorder used light sensitive paper for strip chart recording. The reading and analysis of data from the strip charts is very cumbersome, errorneous and time consuming. A microcomputer was interfaced with A/D converter, microcomputer program was developed for measuring, system calibration was done and the strain generated from a cantilever beam vibrator was measured. The results are summarized as follows. 1. Microcomputer program was developed to perform strain measuring of agricultural machine elements and could be controled freely the measuring intervals, no. of channels and no. of data. The maximum measuring speed was $62{\mu}s$. 2. Calibration the system was performed with triangle wave generated from a function generator and checked by an oscilloscope. The sampled data were processed using HP 3000 minicomputer of Chungnam National University computer center the graphical results were triangle same as input wave and so the system have been out of phase distorsion and amplitude distorsion. 3. The strain generated from a cantilever beam vibrator which has free vibration period of 0.019 second were measured by the system controlled to have l.0 ms of time interval and its computer output showing vibration curve which is well filted to theoretical value. 4. Using microcomputer on measuring the strain of agricultural machine elements could not only save analyzing time and recording papers but also get excellent adaptation to field experiment, especially in measurement requiring high speed and good precision.

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Adaptation Process to Menopause (폐경에 대한 적응 과정)

  • 이미라
    • Journal of Korean Academy of Nursing
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    • v.24 no.4
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    • pp.623-634
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    • 1994
  • Although the average menopausal age has not changed, women's life span has increased. Today's women live longer after their menopause than those in the past, and this calls for attention in both nursing and medical fields. Many studies have revealed how women reacted to menopause and suffered from it. But they did not discriminate the menopausal meaning and effects from the climacteric phenomena. So, this author tried to clarify what menopause itself meant to the climacteric women, by means of grounded theory methodology. The interviewees were 21 women, whose ages were between 46 and 60 years. They were selected by theoretical sampling technique, and the author tried to include all levels of important variables such as age, educational background, religion and job. Data were collected by the author through in -depth interviews and observations in July, 1994. The interviews were mostly done in the homes of the subjects, or in some cases at the author's office or in a hospital. Interviews took from 30 minutes to 2 hours. Interviews were tape recorded and transcribed later by a research assistant. Data were analyzed as gathered, by the constant comparative method proposed by Strauss and Corbin. Eleven concepts were discovered from the data, and they were grouped under six higher order categories. These six categories were "to give menopause a meaning", "to experience value change", "to have self-help strategies", "to have no strategies", "to live a life worth living", "to have a sense of powerlessness" Among these "to experionce value change" was . selected as the core category. Five major categories were systematically integrated around the core category. Women's adaptation to menopause was defined as proceeding as follows : Most women felt relief and sorrow at the same time when they faced menopause, and some only sorrow or agony. Then, they consulted with others about menopausal symptoms, or tried to think of them by themselves. Finally, they gave menopause a meaning, which was that menopause and its symptoms were natural phenomena. But menopause made women reflect on them-selves and their past lives. As they reflected on themselves, their value on life began to change. As their value changed, some women seeked self help strategies. Those self help strategies were what they had learned from collegues, professionals or mass media. The quality of their lives depended on whether they practiced self help strategies or not. Three types of lives were found. Twelve women enjoyed a life worth living, and practiced the self help strategies, because they accepted menopause a chance to change. They were characterized by a high educational level, having a professional job and a sincere faith in God. Seven women were living as usual, because they did not have the necessity to change. They were high school graduates and house wives. Two women recognized menopause a chance to change, but they did not try self help strategies. Their characteristic was low educational level. Those who did not try self help strategies complained of powerlessness to varying degrees. The educational background, full-time jobs and faith helped women adapt to menopause positively. But social support was not helpful to women's adaptation to menepause. Three hypotheses were derived from the analysis. (1) The higher the educational level, the more theneed to change. (2) Women with higher educational background will practice self help strategies more than those with lower edcational background. (3) The more women practice self help strategies, the worthier lives they will live. Suggestions for further studies are as follows. (1) Studies to test hypotheses are needed. (2) A study to find the relationship between the degree of practicing self help strategies and locus of control. (3) Spiritual approaches would better be applied to help menopausal women. (4) Education through mass media should be given mere frequently.

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A Theory Construction on the Care Experience for Spouses of Patients with Chronic Illness (만성질환자 배우자의 돌봄 경험에 대한 이론 구축)

  • Choi, Kyung-Sook;Eun, Young
    • Journal of Korean Academy of Nursing
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    • v.30 no.1
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    • pp.122-136
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    • 2000
  • Chronic illness requiring attention and management during a long period of time puts great burden onto patients, their family and society. For patients with chronic illnesses, providing social support is the most important, and the fundamental support comes from their spouses. Amount and quality of support from spouses seems to differentiated according to the sex of patients. Female patients tend to believe that their spouses are not very supportive. Therefore, the researchers assessed the burden of husbands of female arthritis patients to discover the factors that result in greater burden. Also, they developed a theoretical model of husbands′ care for their wives through a qualitative research into husbands′ experience. Method 1: The study material was 650 female arthritis patients registered in an arthritis clinic. The questionnaire about the disease experience of female arthritis patients and the burden of husbands were sent. Returned questionnaires numbered 210(32.3%) and 27 were excluded because of inadequate answers. The remaining 183 questionnaires were analyzed. The mean age of the patients was 51 years and the mean age of spouses was 55 years. The mean marital period was 28 years. The average duration since diagnosis was 9.1 years. Education level was varied from primary school to graduate school, and average income/month was 1,517,300 won. Method 2: Initial questionnaire studies on the burden of husbands were performed. Among 183 responding husbands, 23 consented to participate for a qualitative research. Data was obtained by direct and telephone interviews. The mean age of participants was 58 years, and the educational level and socioeconomic status also varied. Result: 1. Husbands′ burden: The average burden was 57.68 with a range of 6-96. 2. Burden and general characteristics: The husband′s burden correlated with the age of the patients, numbers in the family, therapy methods, patient′s level of discomfort, patient′s disease severity, patient′s level of dependence and the husband′s understanding of the level of severity. 3. Linear correlation analysis on burden: The husbands′ burden is explained in 22.5% by husband′s recognition of level of severity and husbands′ age. 4. There were four patterns of the burden on husbands: both objectve burden and subjective burden were high(pattern I), both of objectve burden and subjective burden were low(pattern II), objective burden was high but subjective burden was low(pattern III), objective burden was low but subjective burden was high(pattern IV). The pattern was correlated with the family income, educational level of the patients and their husbands, therapy methods, patient′s level of discomfort, patient′s disease severity, patient′s level of dependence and husband′s understanding of level of severity. 5. The core category of the caring experience of the husbands with arthritis patients was "companionship". The causal factor was the patients′ experience due to symptoms : physical disfigurement, pain, immobility, limitation of house chores, and limitation of social activities. Contextural factors are husbands′ identification of housework and husbands′ concern about the disease. The mediating factors are economic problems, fear of aging, feeling of limitation and family support. The strategy for interaction is mind control and how to solve emotional stress. The "companionship" resulted from caring activities, participation of household activities, helping patients′ to coping with emotional experience. 6. Companionship is established through the process of entering intervention, and caring state of mind. Entering intervention is the phase of participation of therapy and involvement of houseworks. The caring phase consists of decision on therapy, providing therapy, providing direct care, and taking over the household role of wife. Through caring phase, the changing phase set a stage in which husbands consolidate the relationship with their wives, and are reminded of the meaning of marriage. As a result, in changing phase, husbands′ companionship is enhanced. In conclusion, nursing care of chronic illnesses should include a family member especially the spouse. All information on disease shoud be provided to patients and whole family member. Strong support should also be provided to overcome difficulties in taking over role of other sex. Then the quality of life of patients and families will be much improved.

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The Comparison of Absolute Dose due to Differences of Measurement Condition and Calibration Protocols for Photon Beams (6MV 광자선에서 측정 조건의 변화와 측정법의 차이에 의한 절대 선량값의 비교)

  • 김회남;박성용;서태석;권수일;윤세철
    • Progress in Medical Physics
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    • v.8 no.2
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    • pp.87-102
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    • 1997
  • The absolute absorbed dose can be determined according to the measurement conditions; measurement material, detector, energy and calibration protocols. The purpose of this study is to compare the absolute absorbed dose due to the differences of measurement condition and calibration protocols for photon beams. Dosimetric measurements were performed with a farmer type PTW and NEL ionization chambers in water, solid water, and polystyrene phantoms using 6MV photon beams from Siemens linear accelerator. Measurements were made along the central axis of 10cm $\times$ 10cm field size for constant target to surface distance of 100cm for water, solid water and polystyrene phantom. Theoretical absorbed dose intercomparisons between TG21 and IAEA protocol were performed for various measurement combinations of phantom, ion chamber, and electrometer. There were no significant differences of absorbed dose value between TG21 and IAEA protocol. The differences between two protocols are within 1% while the average value of IAEA protocol was 0.5% smaller than TG21 protocol. For the purpose of comparison, all the relative absorbed dose were nomalized to NEL ion chamber with Keithley electrometer and water phantom, The average differences are within 1%, but individual discrepancies are in the range of - 2.5% to 1.2% depending upon the choice of measurement combination. The largest discrepancy of - 2.5% was observed when NEL ion chamber with Keithley electrometer is used in solid water phantom. The main cause for this discrepancy is due to the use of same parameters of stopping power, absorption coeficient, etc. as used in water phantom. It should be mentioned that the solid water phantom is not recommended for absolute dose calibration as the alternative of water, since absorbed dose show some dependency on phantom material other than water. In conclusion, the trend of variation was not much dependent on calibration protocol. However, it shows that absorbed dose could be affected by phantom material other than water.

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