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Predicting the Performance of Recommender Systems through Social Network Analysis and Artificial Neural Network (사회연결망분석과 인공신경망을 이용한 추천시스템 성능 예측)

  • Cho, Yoon-Ho;Kim, In-Hwan
    • Journal of Intelligence and Information Systems
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    • v.16 no.4
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    • pp.159-172
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    • 2010
  • The recommender system is one of the possible solutions to assist customers in finding the items they would like to purchase. To date, a variety of recommendation techniques have been developed. One of the most successful recommendation techniques is Collaborative Filtering (CF) that has been used in a number of different applications such as recommending Web pages, movies, music, articles and products. 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. Broadly, there are memory-based CF algorithms, model-based CF algorithms, and hybrid CF algorithms which combine CF with content-based techniques or other recommender systems. While many researchers have focused their efforts in improving CF performance, the theoretical justification of CF algorithms is lacking. That is, we do not know many things about how CF is done. Furthermore, 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 the performances of CF algorithms in advance is practically important and needed. In this study, we propose an efficient approach to predict the performance of CF. Social Network Analysis (SNA) and Artificial Neural Network (ANN) are applied to develop our prediction model. CF can be modeled as a social network in which customers are nodes and purchase relationships between customers are links. SNA facilitates an exploration of the topological properties of the network structure that are implicit in data for CF recommendations. An ANN model is developed through an analysis of network topology, such as network density, inclusiveness, clustering coefficient, network centralization, and Krackhardt's efficiency. 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. Inclusiveness refers to the number of nodes which are included within the various connected parts of the social network. Centralization reflects the extent to which connections are concentrated in a small number of nodes rather than distributed equally among all nodes. Krackhardt's efficiency characterizes how dense the social network is beyond that barely needed to keep the social group even indirectly connected to one another. We use these social network measures as input variables of the ANN model. As an output variable, we use the recommendation accuracy measured by F1-measure. In order to evaluate the effectiveness of the ANN model, sales transaction data from H department store, one of the well-known department stores in Korea, was used. Total 396 experimental samples were gathered, and we used 40%, 40%, and 20% of them, for training, test, and validation, respectively. The 5-fold cross validation was also conducted to enhance the reliability of our experiments. The input variable measuring process consists of following three steps; analysis of customer similarities, construction of a social network, and analysis of social network patterns. We used Net Miner 3 and UCINET 6.0 for SNA, and Clementine 11.1 for ANN modeling. The experiments reported that the ANN model has 92.61% estimated accuracy and 0.0049 RMSE. Thus, we can know that our prediction model helps decide whether CF is useful for a given application with certain data characteristics.

Mapping Categories of Heterogeneous Sources Using Text Analytics (텍스트 분석을 통한 이종 매체 카테고리 다중 매핑 방법론)

  • Kim, Dasom;Kim, Namgyu
    • Journal of Intelligence and Information Systems
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    • v.22 no.4
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    • pp.193-215
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    • 2016
  • In recent years, the proliferation of diverse social networking services has led users to use many mediums simultaneously depending on their individual purpose and taste. Besides, while collecting information about particular themes, they usually employ various mediums such as social networking services, Internet news, and blogs. However, in terms of management, each document circulated through diverse mediums is placed in different categories on the basis of each source's policy and standards, hindering any attempt to conduct research on a specific category across different kinds of sources. For example, documents containing content on "Application for a foreign travel" can be classified into "Information Technology," "Travel," or "Life and Culture" according to the peculiar standard of each source. Likewise, with different viewpoints of definition and levels of specification for each source, similar categories can be named and structured differently in accordance with each source. To overcome these limitations, this study proposes a plan for conducting category mapping between different sources with various mediums while maintaining the existing category system of the medium as it is. Specifically, by re-classifying individual documents from the viewpoint of diverse sources and storing the result of such a classification as extra attributes, this study proposes a logical layer by which users can search for a specific document from multiple heterogeneous sources with different category names as if they belong to the same source. Besides, by collecting 6,000 articles of news from two Internet news portals, experiments were conducted to compare accuracy among sources, supervised learning and semi-supervised learning, and homogeneous and heterogeneous learning data. It is particularly interesting that in some categories, classifying accuracy of semi-supervised learning using heterogeneous learning data proved to be higher than that of supervised learning and semi-supervised learning, which used homogeneous learning data. This study has the following significances. First, it proposes a logical plan for establishing a system to integrate and manage all the heterogeneous mediums in different classifying systems while maintaining the existing physical classifying system as it is. This study's results particularly exhibit very different classifying accuracies in accordance with the heterogeneity of learning data; this is expected to spur further studies for enhancing the performance of the proposed methodology through the analysis of characteristics by category. In addition, with an increasing demand for search, collection, and analysis of documents from diverse mediums, the scope of the Internet search is not restricted to one medium. However, since each medium has a different categorical structure and name, it is actually very difficult to search for a specific category insofar as encompassing heterogeneous mediums. The proposed methodology is also significant for presenting a plan that enquires into all the documents regarding the standards of the relevant sites' categorical classification when the users select the desired site, while maintaining the existing site's characteristics and structure as it is. This study's proposed methodology needs to be further complemented in the following aspects. First, though only an indirect comparison and evaluation was made on the performance of this proposed methodology, future studies would need to conduct more direct tests on its accuracy. That is, after re-classifying documents of the object source on the basis of the categorical system of the existing source, the extent to which the classification was accurate needs to be verified through evaluation by actual users. In addition, the accuracy in classification needs to be increased by making the methodology more sophisticated. Furthermore, an understanding is required that the characteristics of some categories that showed a rather higher classifying accuracy of heterogeneous semi-supervised learning than that of supervised learning might assist in obtaining heterogeneous documents from diverse mediums and seeking plans that enhance the accuracy of document classification through its usage.

BONE DENSITY AND HISTOMORPHOMETRY ASSESSMENT OF DENTAL IMPLANT USING COMPUTERIZED TOMOGRAPHY (컴퓨터 영상을 이용한 임플란트 식립부위의 골밀도와 조직학적 연구)

  • Son, Jang-Ho;Choi, Byung-Hwan;Park, Soo-Won;Cho, Yeong-Cheol;Sung, Iel-Yong;Lee, Ji-Ho;Byun, Ki-Jung
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.31 no.2
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    • pp.136-142
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    • 2009
  • Bone density in the recipient implant site seems to be an important factor for long term success of endosseous implants. Preoperative evaluation of bone density is very helpful to assist the clinician with the treatment planning of implant therapy. Accurate information on bone density will help the surgeon identify suitable implant sites, thereby improving the success rate of the procedure. Purpose; The aim of this study was to evaluate a correlation between bone density measured preoperatively with computerized tomography and histologically measured bone density by bone biopsy. Patients and methods; Twenty seven patients were selected. All the patients were in good health, with no systemic disorder and additional bone graft. Preoperatively the patients underwent CT scanning to evaluate Houmsfield Unit(HU). Each patients wore a surgical template for implant placement. During surgery 2mm in diameter and 6mm in length specimens were taken. Histomorphometric analysis was performed using digitalized image analysis software Axiovision 4.3. Also, the Resonance frequency analysis(RFA) and insertion torque values were recorded. Results; The highest histomorphometric values was found in the posterior mandible $32.3{\pm}3.8$, followed by $29.9{\pm}2.6$ for the posterior maxilla, $29.4{\pm}2.6$ for the anterior maxilla, $28.6{\pm}2.3$ for the anterior mandible(p=0.214). The hounsfield unit was $989.2{\pm}258.1$ in the posterior mandible, $845.0{\pm}241.5$ in the anterior maxilla, $744.5{\pm}92.6$ in the anterior mandible, $697.3{\pm}136.9$ in the posterior maxilla(p=0.045). This results may suggest that there are strong correlation between the histomorphometric values and hounsfield unit(r=0.760, p<0.05). The RF measurements were $81.9{\pm}2.4$ ISQ in the posterior mandible, $79.0{\pm}1.4$ ISQ in the anterior mandible, $78.3{\pm}4.6$ ISQ in the posterior maxilla, $76.5{\pm}5.0$ ISQ in the anterior maxilla(p=0.048). The insertion torque values was $43.2{\pm}4.2\;Ncm$ in the posterior mandible, $42.0{\pm}0.0\;Ncm$ in the anterior mandible, $41.3{\pm}4.1\;Ncm$ in the posterior maxilla, $40.8{\pm}3.8\;Ncm$ in the anterior maxilla(p=0.612). This results may suggest that there are statistical significance between the hounsfield unit and the insertion torque values(r=0.494, p<0.05), the histomorphometric values and the insertion torque values(r=0.689, p<0.05). But there was no correlation between histomorphometric values and ISQ. There was no statistical significance in age and gender effect on parameters. Conclusions; There was significant correlations between bone density and implant stability parameters. The bone density measurements using preoperative CT may help clinicians to predict primary stability before implant insertion, which is associated with implant survival rates.

Study on the Recognition of Brucellosis for Rural Residents (일부 농촌지역 주민의 브루셀라증 인지도)

  • Lim, Hyun-Sul;Min, Young-Sun
    • Journal of agricultural medicine and community health
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    • v.30 no.1
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    • pp.51-62
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    • 2005
  • Objectives: This study was conducted to understand the recognition on brucellosis in rural communities and to apply the results to counterplan for brucellosis control and prevention. Methods: The authors conducted a questionnaire survey from September 8 to 13, 2004 among the residents in 2 rural communities: 507 people at Gigye-myeon and 521 people at Buk-myeon. The authors developed a questionnaire which investigated age, gender, general recognition of brucellosis, status of cattle breeding, compensation for loss due to brucellosis and so on. Results: The study group contained 195 (19.0%) stock breeders (veterinarians and cattle merchants were included) and 833 (81.0%) non-stock breeders. For the question, 'Have you ever heard about brucellosis or do you know about brucellosis?', 283 respondents (27.5%) replied affirmatively. For the question, 'Do you know that pregnant women who suffer brucellosis may have a miscarriage?', 98 respondents (35.1%) replied affirmatively. For the question, 'Have your cattle ever aborted or calved a premature calf?', 28 respondents (14.9%) replied affirmatively. For the question, 'Have you ever handled an abortus or a premature calf with your bare hands?', 10 respondents (5.3%) replied affirmatively. For the question, 'Do you know that the government compensates for slaughter loss due to brucellosis?', 46 respondents (25.0%) replied affirmatively. Conclusions: Many people were ignorant about brucellosis. Therefore, their ignorance must be corrected by a publicity campaign. Some stock breeders handled the cattle abortus with their bare hand. Stock breeders must wear protective equipment during working. The authors expect that this study will assist in establishing both a safe cattle breeding environment and preventive strategies for diminishing the incidence of brucellosis.

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The Main Contents, Comment and Future Task for the Space Laws in Korea (한국에 있어 우주법의 주요내용, 논평과 장래의 과제)

  • Kim, Doo-Hwan
    • The Korean Journal of Air & Space Law and Policy
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    • v.24 no.1
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    • pp.119-152
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    • 2009
  • Korea now has a rapidly expanding and developing space programme with exploration aspirations. The government is giving priority to the aerospace industry and, to put it on a better footing, enacted an Aerospace Industry Development Promotion Act in I987, a Space Development Promotion Act in 2005 and a Space Compensation for Damage Act in 2007. I would like to describe briefly the legislative history, main contents and comment for these three space acts including especially launch licensing, registration of space objects, use of satellite information, astronaut rescue, liability for compensation, third party liability insurance and establishment of committee and plans to assist the Korean space effort. Furthermore author proposed to legislate a new draft for the establishment of a Korean Aerospace Development Agency (KADA: tentative title) to create a similar body to Japan Aerospace Exploration Agency (JAXA), British National Space Centre (BNSC) of UK, French Centre National d'Etudes Spatiales (CNES), German Aerospace Center (DLR), Swedish Space Corporation (SSC), China Aerospace Science and Industry Corporation (CASIC), Indian Space Research Organization (ISRO) as well as the Korean Space Agency (KSA: Tentative title) to create a similar body to Canadian Space Agency, European Space Agency, Russian Space Agency, Italian Space Agency, Israel Space Agency, Indian Department of Space, National Aeronautics and Space Administration (NASA) of USA, China National Space Administration in order to develope efficiently space industry. If the Korean government will be establish the Korean Space Agency as an governmental organization in future, it is necessary to revise the contents of the Government Organization Act. It is desirable and necessary for us to establish an Asian Space Agency (ASA), in order to develop our space industry and to promote research cooperation among Asian countries, based on oriental idea and creative powers.

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The Social Influence of the Landscape Architecture Engineer Examination on the Establishment of Authenticity in Landscaping History Department (조경기사 '조경사' 과목이 조경역사학(造景歷史學) 분야의 진정성 확립에 미친 사회적 영향)

  • Lee, Chang-Hun;Shin, Hyun-Sil;Kim, Kyu-Seob;Lee, Won-Ho
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.36 no.3
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    • pp.128-136
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    • 2018
  • This study was centered on the protested data of the issue of "History of Landscape Architecture" in the handwritten course of landscaping articles of National Qualifications Test. The purpose of this study is to examine the types of social problems in the process of correcting erroneous historical facts. The purpose of this study was to find alternatives for the development of the field of landscape and culture history that can assist in the verification of the historical facts of the landscape sciences examination questions. The main results are as follows. First, as a result of analyzing the contents of the landscape architects' subject matter, the establishment of concept of landscape style and form and the confirmation of historical facts were investigated as important types to be established for development of landscape landscape history department. It seems that the social consensus of the expert group is needed to supplement the lack of data to refer to landscape architectural theory. Second, the analysis of the problematic narrative contents resulted in a total of five types of questionnaires. The appeared in the Undefined style and form(52.94%), Unproven historical facts(25.13%), Obscurity Era classification(11.77%), Lack of specificity(6.95%), Content scope of obscurity events(3.21%) Third, it is not only the lack of information to learn the theory by comparing and analyzing the contents of the statements in the landscape architect 's question items, but also the difference of contents between books was analyzed as the main cause of the problem. As a result of examining the characteristics and examples of the issues raised in landscape architectural problems, it was related to the social phenomenon, and it was classified into cultural factors and political factors. Fourth, the resolution of problematic issues in landscape architects' landscaping articles, which are national technical qualification tests, shows positive results. The information determined in the process of solving the perceived content can be used directly in landscaping field, and it helps the accuracy of the verification process by identifying the types and characteristics of the issues.

Simultaneous Removal of $NO_x$ and $SO_2$ through the Combination of Sodium Chlorite Powder and Carbon-based Catalyst at Low Temperature ($NaClO_2(s)$와 탄소 분산형 촉매를 이용한 저온에서의 $NO_x$$SO_2$ 동시 제거)

  • Byun, Young-Chul;Lee, Ki-Man;Koh, Dong-Jun;Shin, Dong-Nam
    • Journal of Korean Society of Environmental Engineers
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    • v.33 no.1
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    • pp.39-46
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    • 2011
  • NO oxidation is an important prerequisite step to assist the selective catalytic reduction (SCR) at low temperatures ($<200^{\circ}C$). Therefore, we conducted the lab- and bench-scales experiments appling the sodium chlorite powder ($NaClO_2(s)$) for the oxidation of NO to $NO_2$ and the carbon-based catalyst for the reduction of $NO_x$ and $SO_2$; the lab- and bench-scales experiments were conducted in laboratory and iron-ore sintering plant, respectively. In the lab-scale experiment, known concentrations of $NO_x$ (200 ppm), $SO_2$ (75 ppm), $H_2O$ (10%) and $NH_3$ (400 ppm) in 2.6 L/min were introduced into a packed-bed reactor containing $NaClO_2(s)$, then gases produced by the reaction with $NaClO_2(s)$ were fed into the carbon-based catalyst (space velocity = $2,000hr^{-1}$) at $130^{\circ}C$. In the bench-scale experiment, flue gases of $50Nm^3/hr$ containing 120 ppm NO and 150 ppm $SO_2$ were taken out from the duct of iron-ore sintering plant, then introduced into the flow reactor; $NaClO_2(s)$ were injected into the flow reactor using a screw feeder. Gases produced by the reaction with $NaClO_2(s)$ were introduced into the carbon-based catalyst (space velocity = $1,000hr^{-1}$). Results have shown that, in both lab- and bench-scales experiments, NO was oxidized to $NO_2$ by $NaClO_2(s)$. In addition, above 90% of $NO_x$ and $SO_2$ removal were obtained at the carbon-based catalyst. These results lead us to suggest that the combination of $NaClO_2(s)$ with the carbon-based catalyst has the potential to achieve the simultaneous removal of $NO_x$ and $SO_2$ at low temperature ($<200^{\circ}C$).

A Numerical and Experimental Study for Fry-drying of Various Sludge (슬러지 유중 건조에 대한 전산 해석 및 실험적 연구)

  • Shin, Mi-Soo;Kim, Hey-Suk;Kim, Byeong-Gap;Hwang, Min-Jeong;Jang, Dong-Soon;Ohm, Tae-In
    • Journal of Korean Society of Environmental Engineers
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    • v.32 no.4
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    • pp.341-348
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    • 2010
  • The basic principle of fry drying process of sludge lies in the rapid pressure change of sludge material caused by the change of temperature between oil and moisture due to the difference of specific heat. Therefore, the rapid increase of pressure in drying sludge induces the efficient moisture escape through sludge pores toward heating oil media. The object of this study is to carry out a systematic investigation of the influence of various parameters associated with the sludge fry drying processes on the drying efficiency. To this end, a series of parametric experimental investigation has been made together with the numerical calculation in order to obtain typical drying curves as function of important parameters such as drying temperature, sludge diameter, oil type and sludge type. In the aspect of frying temperature, especially it is found that the operation higher than $140^{\circ}C$ was favorable in drying efficiency regardless of type of waste oil employed in this study. The same result was also noted consistently in the investigation of numerical calculation, that is, in that the sludge particle drying was efficiently made over $140^{\circ}C$ irrespective of the change of particle diameter. As expected, in general, the decrease of diameter in sludge was found efficient both experiment and numerical calculation in drying due to the increased surface area per unit volume. In the investigation of oil type and property, the effect of the viscosity of waste oil was found to be more influential in drying performance. In particular, when the oil with high viscosity, a visible time delay was noticed in moisture evaporation especially in the early stage of drying. However, the effect of high viscosity decreased significantly over the temperature of $140^{\circ}C$. There was no visible difference observed in the study of sludge type but the sewage sludge with a slightly better efficiency. The numerical study is considered to be a quite useful tool to assist in experiment with more detailed empirical modeling as further work.

Central Nervous System Complications of Coronary Artery Bypass Grafting - Comparison Between Off-Pump CABG and Conventional CABG (관상동맥 우회술 후의 중추신경계 합병증 - 심폐바이패스를 사용하지 않은 관상동맥 우회술과 기존의 관상동맥 우회술의 비교)

  • Chang, Ji-Min;Lee, Jeong-Sang;Kim, Ki-Bong;Ahn, Hyuk;Yoon, Byung-Woo;Kim, Yong-Jin
    • Journal of Chest Surgery
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    • v.33 no.12
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    • pp.941-947
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    • 2000
  • Background: Central nervous system complication after coronary artery bypass grafting(CABG) is one of the major prognostic determinants and the use of the cardiopulmonary bypass(CPB) may increase the incidence of this devastating complication. In this study, the outcomes after off-pump CABG were studied and compared with those following the conventional CABG using CPB. Material and Method: Among the consecutive isolated CABG's performed in SNUH during Feb. 1995 and Jun. 1999, 338 coronary artery bypass grafting were divided into two groups. 223 patients underwent CABG using the CPB(Group I), and 115 patients underwent CABG without CPB(OPCAB)(Group II). All patients enrolled in this study received extensive preoperative examinations including thorough neurologic examination before and after surgery, transcranial doppler study, carotid duplex ultrasonography, and magnetic resonance angiography if necessary. Central nervous system(CNS) complications were defined as stroke, seizure, metabolic or hypoxic encephalopathy and transient delirium after surgery. Result: There were 61 cases(27.3%) who developed postoperative CNS complication in Group I, whereas 8 cases(7.0%) of CNS complications developed postoperatively in group II(p<0.05). Statistically significant predictors of postoperative CNS complications in group I were age and the use of cardiac assist devices perioperatively. Conclusion: This study suggested that omitting the use of CPB in CABG resulted in significant decrease of the postoperative CNS complications. OPCAB should be more widely applied especially to the elderly who have preexisting cerebrovascular disease.

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Assessment of the Activities of General Physicians in Health Subcenters and a Scheme to Improve the Training Program (보건지소 공중보건 일반의사의 업무수행정도와 수련개선방안)

  • Park, Jung-Han;Chun, Byung-Yeol;Woo, Kuck-Hyeun
    • Journal of Preventive Medicine and Public Health
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    • v.19 no.2 s.20
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    • pp.193-202
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    • 1986
  • The activities of general physicians (GPs) in health subcenters and their competency for clinical skills were assessed to develop a scheme to improve the training program. One hundred-twenty GPs in southern four provinces (Kyungpook, Kyungnam, Chunpook, Chunnam) were randomly selected and 97 were interviewed between January 9 and February 10, 1984. Of the 97 GPs, 86 provided all the information we requested. Average number of patient visits per health subcenter in a day was 30-40 in the demonstration project area for the class II medical insurance whereas it was 3-4 visits in other area. The interviewees were asked to rate their competency in 63 clinical skills. The skills in which over 50% of the interviewees rated themselves competent were only 12 items including IM injection, IV injection, wound dressing, etc. Less than 10% of the interviewees rated themselves competent in such skills as maternal health care, emergency medical care, preventive and promotive health services. Most part of the training program of the NIH for the GPs were not applicable to their field work as the training contents were unrealistic. Clinical training at a local general hospital was of great help in 38.8% and the rest of training was not much helpful as the training was inadequate due to lack of trainer or indifference of the trainer. For more effective training of the GPs, the training program of the NIH should be modified to be more realistic and utilize competent field workers as the instructors. It may be more effective if the training is carried out at several local centers. Ideal length of the clinical training for the GPs is 4 months. A pocketbook should be developed that includes specific skills to master during the clinical training and require the trainer to confirm the achievement. The Ministry of Health and Social Affairs should provide the training hospitals with a training guideline and evaluate the training activities and make sure that the training hospital has specialist for each of the 4 major clinical departments. The Ministry of Health and Social Affairs should provide the GPs with a continuing education to assist the problem solving in the field and motivate them to actively carry out the health program. A province may be divided into several regions and a supervisory committee may be organized with specialists in each region. The committee may hold a meeting for the GPs periodically and respond to the specific questions of the GPs by mail.

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