• Radiation Oncology Journal
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• v.23 no.3
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• pp.186-193
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• 2005

Purpose: To improve the management of a medical linear accelerator, the records of operational failures of a Varian CL2l00C over a ten year period were retrospectively analyzed. Materials and Methods: The failures were classified according to the involved functional subunits, with each class rated Into one of three levels depending on the operational conditions. The relationships between the failure rate and working ratio and between the failure rate and outside temperature were investigated. In addition, the average life time of the main part and the operating efficiency over the last 4 years were analyzed. Results: Among the recorded failures (total 587 failures), the most frequent failure was observed in the parts related with the collimation system, including the monitor chamber, which accounted for $20\%$ of all failures. With regard to the operational conditions, 2nd level of failures, which temporally interrupted treatments, were the most frequent. Third level of failures, which interrupted treatment for more than several hours, were mostly caused by the accelerating subunit. The number of failures was increased with number of treatments and operating time. The average life-times of the Klystron and Thyratron became shorter as the working ratio increased, and were 42 and $83\%$ of the expected values, respectively. The operating efficiency was maintained at $95\%$ or higher, but this value slightly decreased. There was no significant correlation between the number of failures and the outside temperature. Conclusion: The maintenance of detailed equipment problems and failures records over a long period of time can provide good knowledge of equipment function as well as the capability of predicting future failure. Wore rigorous equipment maintenance Is required for old medical linear accelerators for the advanced avoidance of serious failure and to improve the qualify of patient treatment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.3 no.1
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• pp.26-27
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• 1978

It can be expected that intelligence and knowledge will be the core of the post-industrial society in a near future. Accordingly, the age of intelligence shall be accelerated extensively to find ourselves in an age of 'Communication' service enterprise. The communication actions will increase its efficiency and multiply its utility, indebted to its scientic principles and legal idea. The two basic elements of communication action, that is, communication station and communication men are considered to perform their function when they are properly supported and managed by the government administration. Since the communication action itself is composed of various factors, the elements such as communication stations and officials must be cultivated and managed by specialist or experts with continuous and extensive study practices concerned. With the above mind, this study reviewed our public service officials law with a view to improve it by providing some suggestions for communication experts and researchers to find suitable positions in the framework of government administration. In this study, I would like to suggest 'Occupational Group of Communication' that is consisted of a series of comm, management positions and research positions in parallel to the existing series of comm, technical position. The communication specialist or expert is required to be qualified with necessary scientific knowledge and techniques of communication, as well as prerequisites as government service officials. Communication experts must succeed in the first hand to obtain government licence concerned in with the government law and regulation, and international custom before they can be appointed to the official positions. This system of licence-prior-to-appointment is principally applied in the communication management position. And communication research positions are for those who shall engage themselves to the work of study and research in the field of both management and technical nature. It is hopefully expected that efficient and extensive management of communication activities, as well as scientific and continuous study over than communication enterprise will be upgraded at national dimensions.

• Korean Journal of Agricultural Science
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• v.16 no.2
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• pp.169-178
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• 1989

The study was carried out to elucidate the feedback mechanism on the hypothalamo-hypophyseal system from the functional changes of ovary in female rats. One hundred and forty-four mature female rats were lloted into the three groups; ovariectoimzed group, estradiol treated group and intact control group. The varies of 48 heads of rat were completely removed. Forty eight heads of rat were administered with $200{\mu}g$ of estradiol benzoate every 48 hours. Serum FSH, LH and prolactin levels were determined with radioimmunoassay method at 3,6,12,24 ours, and 5,10, and 15days after treatment. The rats were necropsied to measure the weights of hypophysis and to examin the histological changes in the organs. The results obtained were as follows: The weights of hypophysis were increased after ovariectomy and decreased after estradiol injection. The differences in hypophysis weights were significant between the group from 5 days after treatment. The histological changes in hypophysis were appeared from 5th day after ovariectomy. Proliferation and hypertrophy began to occur in basophilic from 10th day after ovariectomy, chromophobes were slightly hypertrophied and acidophilic cells were atrophied. In estradiol injected rats the histological findings were appeard to be contrary to those of ovariectomized rats. Serum FSH levels significantly changed after ovariectomy and estradiol injection and were higher in both the treated groups than in the intact control group. Within 18 hours after treatment the level was the highest in ovariectomized group, and thereafter the highest level was found in estradiol treated gorup. In ovariectomized rats the levels were rapidly increased 3 hours after treatment and maximum levels were found 18 hours after treatment. In estradiol treated rats the levels started to increase 18 hours after treatment and reached maximum levels 24 hours treatment. 4. Serum LH levels started to increase 3 hours after ovariectomy and estradiol injection and reached maximum levels 12 hours after ovariectomy and 24 hours after estradiol injection. There were significant differences in LH levels between the groups in each observation time. Up to 18 hours after treatment levels were higher in ovariectomized rats than in estradiol treated rats. but thereafter the levels were higher in estradiol treated rats than in ovariectomized rats. The multiple range test showed that a significant difference in LH levels was not found between ovariectomized group and estradiol treated group 18 hours and 5 days after treatment. 5. Serum prolactin levels were significantly changed after ovariectomy and estradiol injection. The levels were lower in ovariectomized rats than in intact control rats.

• Radiation Oncology Journal
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• v.20 no.2
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• pp.108-115
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• 2002

Purpose : A retrospective study was undertaken to determine the role of conventional radiotherapy with or without surgery for treating a supraglottic carcinoma in terms of the local control and survival. Materials and Methods : From Jan. 1986 to Oct. 1996, a total of 134 patients were treated for a supraglottic carcinoma by radiotherapy with or without surgery. Of them, 117 patients who had completed the radiotherapy formed the base of this study. The patients were redistributed according to the revised AJCC staging system (1997). The number of patients of stage I, II, III, IVA, IVB were $6\;(5\%),\;16\;(14\%),\;53\;(45\%),\;32\;(27\%),\;10\;(9\%)$, respectively. Eighty patients were treated by radical radiotherapy in the range of $61.2\~79.2\;Gy$ (mean : 69.2 Gy) to the primary tumor and $45.0\~93.6\;Gy$ (mean : 54.0 Gy) to regional lymphatics. All patients with stage I and IVB were treated by radiotherapy alone. Thirty-seven patients underwent surgery plus postoperative radiotherapy in the range of $45.0\~68.4\;Gy$ (mean : 56.1 Gy) to the primary tumor bed and $45.0\~59.4\;Gy$ (mean : 47.2 Gy) to the regional lymphatics. Of them, 33 patients received a total laryngectomy (${\pm}lymph$ node dissection), three had a supraglottic horizontal laryngectomy (${\pm}lymph$ node dissection), and one had a primary excision alone. Results : The 5-year survival rate (5YSR) of all patients was $43\%$. The 5YSRs of the patients with stage I+II, III+IV were $49.9\%,\;41.2\%$, respectively (p=0.27). However, the disease-specific survival rate of the patients with stage I (n=6) was $100\%$. The 5YSRs of patients who underwent surgery plus radiotherapy (S+RT) vs radiotherapy alone (RT) in stage II, III, IVA were $100\%\;vs\;43\%$ (p=0.17), $62\%\;vs\;52\%$ (p=0.32), $58\%\;vs\;6\%$ (p<0.001), respectively. The 5-year actuarial locoregional control rate (5YLCR) of all the patients was $57\%$. The 5YLCR of the patients with stage I, II, III, IVA, IVB was $100\%,\;74\%,\;60\%,\;44\%,\;30\%$, respectively (p=0.008). The 5YLCR of the patients with S+RT vs RT in stage II, III, IVA was $100\%\;vs\;68\%$ (p=0.29), $67\%\;vs\;55\%$ (p=0.23), $81\%\;vs\;20\%$ (p<0.001), respectively. In the radiotherapy alone group, the 5YLCR of the patients with a complete, partial, and minimal response were $76\%,\;20\%,\;0\%$, respectively (p<0.001). In all patients, multivariate analysis showed that the N-stage, surgery or not, and age were significant factors affecting the survival rate and that the N-stage, surgery or not, and the ECOG performance index were significant factors affecting the locoregional control. In the radiotherapy alone group, multivariate analysis showed that the radiation response and N-stage were significant factors affecting the overall survival rate as well as locoregional control. Conclusion : In early stage supraglottic carcinoma, conventional radiotherapy alone is an equally effective modality compared to surgery plus radiotherapy and could preserve the laryngeal function. However, in the advanced stages, radiotherapy combined with concurrent chemotherapy for laryngeal preservation or surgery should be considered. In bulky neck disease, all the possible planned neck dissections after induction chemotherapy or before radiotherapy should be attempted.

• Tuberculosis and Respiratory Diseases
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• v.66 no.3
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• pp.192-197
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• 2009

Background: Despite the benefits of home oxygen therapy in patients suffering chronic respiratory failure, previous reports in Korea revealed lower compliance to oxygen therapy and a shorter time for oxygen use than expected. However, these papers were published before oxygen therapy was covered by the national insurance system. Therefore, this study examined whether there were some changes in compliance, using time and other clinical features of home oxygen therapy after insurance coverage. Methods: This study reviewed the medical records of patients prescribed home oxygen therapy in our hospital from November 1, 2006 to September 31, 2008. The patients were interviewed either in person or by telephone to obtain information related to oxygen therapy. Results: During study period, a total 105 patients started home oxygen therapy. The mean age was 69 and 60 (57%) were male. The mean oxygen partial pressure in the arterial blood was 54.5 mmHg and oxygen saturation was 86.3%. Primary diseases that caused hypoxemia were COPD (n=64), lung cancer (n=14), Tb destroyed lung (n=12) and others. After oxygen therapy, more than 50% of patients experienced relief of their subjective dyspnea. The mean daily use of oxygen was 9.8${\pm}$7.3 hours and oxygen was not used during activity outside of their home (mean time, 5.4${\pm}$3.7 hours). Twenty four patients (36%) stopped using oxygen voluntarily 7${\pm}$4.7 months after being prescribed oxygen and showed a less severe pulmonary and right heart function. The causes of stopping were subjective symptom relief (n=11), inconvenience (n=6) and others (7). Conclusion: The prescription of home oxygen has increased since national insurance started to cover home oxygen therapy. However, the mean time for using oxygen is still shorter than expected. During activity of outside their home, patients could not use oxygen due to the absence of portable oxygen. Overall, continuous education to change the misunderstandings about oxygen therapy, more economic support from national insurance and coverage for portable oxygen are needed to extend the oxygen use time and maintain oxygen usage.

• Radiation Oncology Journal
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• v.14 no.1
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• pp.41-52
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• 1996

Purpose : This paper reports a dosimetric study of 88 patients treated with a combination of external radiotherapy and high dose rate ICR for FIGO stage IIB carcinoma of the cervix. The purpose is to investigate the correlation between the radiation doses to the rectum, external radiation dose to the whole pelvis, ICR reference volume, TDF BED and the incidence of late rectal complications, retrospectively. Materials and Methods : From November 1989 through December 1992, 88 patients with stage IIB cervical carcinoma received radical radiotherapy at Department of Radiation Oncology in Yonsei University Hospital. Radiotherapy consisted of 44-54 Gy(median 49 Gy) external beam irradiation plus high dose rate intracavitary brachytherapy with 5 Gy per fraction twice a week to a total dose of 30 Gy on point A. The maximum dose to the rectum by contrast(r, R) and reference rectal dose by ICRU 38(dr, DR) were calculated. The ICR reference volume was calculated by Gamma Dot 3.11 HDR planning system, retrospectively The time-dose factor(TDF) and the biologically effective dose (BED) were calculated. Results : Twenty seven($30.7\%$) of the 88 patients developed late rectal complications:12 patients($13.6\%$) for grade 1, 12 patients($13.6\%$) for grade 2 and 3 patients($3.4\%$) for grade 3. We found a significant correlation between the external whole pelvis irradiation dose and grade 2, 3 rectal complication. The mean dose to the whole pelvis for the group of patients with grade 2, 3 complication was Higher, $4093.3\pm453.1$ cGy, than that for the patients without complication, $3873.8\pm415.6$ (0.05$7163.0\pm838.5$ cGy, than that for the Patients without rectal complication, $0772.7\pm884.0$ (p<0.05). There was no correlation of the rate of grade 2, 3 rectal complication with the iCR rectal doses(r, dr), ICR reference volume, TDF and BED. Conclusion : This investigation has revealed a significant correlation between the dose calculated at the rectal dose by ICRU 38(DR) or the most anterior rectal dose by contrast(R) dose to the whole pelvis and the incidence of grade 2, 3 late rectal complications in patients with stage IIB cervical cancer undergoing external beam radiotherapy and HOR ICR. Thus these rectal reference points doses and whole pelvis dose appear to be useful Prognostic indicators of late rectal complication in high dose rate ICR treatment in cervical carcinoma.

• Journal of Chest Surgery
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• v.39 no.10 s.267
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• pp.739-748
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• 2006

Background: The purpose of this study is to ascertain the neuroprotective effect of cyclosporin A on the 25-min surgical ischemia model in the spinal cords of rabbits with neuropathological correlation and histoimmunochemical analyses, Material and Method: Thirty-two New Zealand white rabbits were randomly divided into four groups: Rabbits were randomly divided into four groups: the control 12 group (n=8), the control 17 group (n=8), the cyclosporin Cs2 group (n=8), and the cyclosporin Cs7 group (n=8). The 12 group underwent a 25-min aortic cross- clamp without intervention and were sacrificed on the 2nd day postoperatively, while the 17 group underwent a 25- min of aortic cross-clamp without intervention and were sacrificed on the 7th day postoperatively. The Cs2 group received cyclosporin A (25 mg/kg) intravenously 15 min after the 25-min cross-clamp and were sacrificed on the End day postoperatively, while the Cs7 group received cyclosporin A (25 mg/kg) intravenously 15 min after the 25-min cross-clamp and were sacrificed on the 7th day postoperatively. The rabbits underwent 25-min surgical aortic cross-clamp. Neurologic functions were evaluated on the 2nd day and 7th postoperative day using Tarlov scoring system. After scoring neurologic function, all rabbits were sacrificed for histopathologic observation. Result: All rabbits survived the experimental procedure. The values of Tarlov score did not show any differences between the control and cyclosporin groups on the 2nd day. The scores of group Cs7 ($2.75{\pm}0.89$) were significantly higher than those of group 17 ($1.25{\pm}1.39$) on the 7th day (p<0,05). On the histologic exanminations, specimens of the spinal cord showed necrosis and apoptosis. The pathologic scores of group Cs7 ($1,0{\pm}0.53$) was less than those of group 17 ($2.13{\pm}1.36$, p<0.05). TUNEL staing showed apoptosis of the specimen in group 12 and Cs2 but there was no stastically significant difference between groups on the score. There were more overexpression of HSP70 and nNOS in cyclosporine group than in control group. Conclusion: We think that cyclosporin A may decrease neuronal cell death with induced upregulation of HSP70 against 25-min ischemia of the spiral cord in the rabbit.

• Journal of Chest Surgery
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• v.39 no.1 s.258
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• pp.18-27
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• 2006

Background: Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital anomaly, but is one of the most common causes of myocardial ischemia which would result in high mortality within the first year of life. This is our early result of the surgical management for these patients. Material and Method: From June 1989 to July 2003, 6 patients with ALCAPA and one patient with ARCAPA (Anomalous origin of the Right coronary artery from the pulmonary artery) underwent surgical repair. We have reviewed the all medical records, electrocardiogram, chest X-ray and echocardiography retrospectively. Result: Three of the patients were boys and four were girls. The median age at the operation was 5.4 months (Range: 3$\∼$33 months). The average body weight of at the operation was 6.7 kg (Range: 3.7$\∼$11.3 kg). A mean follow up period was 18 months. Only 3 patients were initially diagnosed as ALCAPA. And 3 patients had moderate mitral regurgitation. Immediate coronary artery reimplantation on diagnosis with the aim of restoring a two-coronary system circulation was done. The average bypass time was 114$\pm$37 minutes, and the average aortic cross clamping time was 55$\pm$22 minutes. The average stay of intensive care unit was 5$\pm$3 days, the mean mechanical ventilator time was 38$\pm$45 hours and the hospital stay after operation was 12$\pm$5 days. There were significant improvements in electrocardiogram and chest X-ray of the all patients except one late death patient. The ventricular function showed almost normal recovery after operation; the EF (Ejection Fraction) increased from 41.2$\pm$ 10.3$\%$ to 60.5$\pm$ 15.8$\%$ within 1 month and to 59.8$\pm$13.9$\%$ within 1 year after operation, the SF (Shortening Fraction) increased from 23.6$\pm$4.7$\%$ to 38.6$\pm$8.4$\%$ within 1 month and to 37.4$\pm$7.9$\%$ within 1 year after operation, LVEDDI (Left Ventricular End-diastolic Dimension Index) decreased from 100.8$\pm$25.6 mm/$m^{2}$ to 90.3$\pm$ 19.2 mm/$m^{2}$ within f month and to 79.3$\pm$ 15.8 mm/$m^{2}$ within 1 year after operation. Concomitant mitral repair was done in two patients with anterior mitral leaflet prolapse. In every patient, mitral valve showed less than mild regurgitation during follow up. One late death occurred in which patient Dor procedure was applied 10 months after initial operation due to the dilated cardiomyopathy Conclusion: In the management of this rare and could be fatal Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA), early suspicion and correct diagnosis is of most important. But, after diagnosis, immediate restoration of 2 coronary systems could result in good outcome.

• The Journal of Dong Guk Oriental Medicine
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• v.4
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• pp.109-140
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• 1995

As we considered in the main subjects, investigations on the theory of 'Doctrine on five elements' motion and six kinds of natural factors(運氣學說)' through 'Wang Bing's Commentary(王氷 注本)' of 'The seven great chapters in The Yellow Emperor's Internal Classic Su Wen' ("黃帝內經素問 七篇大論") are as follows. (1) In The seven great chapters("七篇大論")' Wang Bing supplement theory and in the academic aspects as a interpreter, judging from 'forget(亡)' character. expressed in the 'The missing chapters("素問遺篇")', 'Bonbyung-ron("本病論")' and 'Jabeob-ron(刺法論)', 'The seven great chapters("七篇大論")' must be supplementary work by Wang Bing. Besides, he quoted such forty books as medical books, taoist books, confucianist books, miscellaneous books, etc in the commentary and the contents quoted in the 'Su Wen(素問)' and 'Ling Shu("靈樞")' scripture nearly occupy in the book. As a method of interpreting scripiure as scripture, he edited the order of 'Internal Classic("內經")' ascended from the ancient time and when he compensated for commentary, with exhaustive scholarly mind and by observing the natural phenomena practically and writing the pathology and the methods of treatment. We knew that the book is combined with the study of 'Doctrine on five elements motion and six kinds of natural factors(運氣學說)' (2) When we compare, analyze the similar phrase of 'The seven great chapters in The Yellow Emperor's Internal Classic Su Wen'("黃帝內經素問ㆍ七篇大論") through 'Wang Bing's Commentary(王氷 注本)', he tells abouts organized 'five elements(五行)' and 'heaven's regularly movement(天道運行)' rather than 'Emyangengsangdae-ron("陰陽應象大論")' in 'The seven great chapters("七篇大論")'. Also the 'Ohanunhangdae-ron("五運行大論")' because the repeated sentences with 'Emyangengsangdae-ron("陰陽應象大論")' is long they are omitted. And in the 'Youkmijidae-ron("六微旨大論")', 'Cheonjin ideology(天眞四象)' based on the 'Sanggocheonjin- ron("上古天眞論")', 'Sagijosindae-ron("四氣調神大論")' is written and in the 'Gigoupyondae-ron("氣交變大論")', the syndrome and symptom are explained in detail rather than 'Janggibeobsi-ron("藏氣法時論")', 'Okgijinjang-ron ("玉機眞藏論")' and in the 'Osangieongdae-ron("五常政大論")', the concept of 'five element(五行)' of the 'Gemgwejineon-ron("金櫃眞言論")' is expanded to 'the five elements' motion concept(五運槪念)' and in the 'Youkwonjeonggidae-ron("六元正紀大論")', explanations of 'The five elements' motion and six kinds of natural factors(運氣)' function are mentioned mainly and instead systematic pathology is not revealed rather than 'Emyangengsangdae-ron("陰陽應象大論")'. And in the 'Jijinyodae-ron("至眞要大論")', explanations of the change of atmosphere which correspond to treatment principle by 'The three Yin and Yang(三陰三陽)' as a progressed concepts are revealed. Therefore there are much similarity between the phrase of 'Emyangengsangdae-ron("陰陽應象大論")' and 'chapters of addition(補缺之篇)'. Generally, the doctrine which 'The seven great chapters("七篇大論")' are added by Wang Bing(王氷) is supported because there are more profound concepts rather than the other chapter in 'The seven great chapters("七篇大論")'. (3) When we study Wang Bing's(王氷) 'Pattern on five elements motion and six kinds of natural factors(運氣格局)' in 'The seven great chapter("七篇大論")', in the 'Cheonwongi-dae-ron("天元紀大論")', With 'Cheonjin ideology(天眞思想)' and the concepts of 'Owang(旺)'${\cdot}$'Sang(相)'${\cdot}$'Sa(死)'${\cdot}$'Su(囚)'${\cdot}$'Hu(休)' and 'Cheonbu(天符)'${\cdot}$'Sehwoi(歲會)' are measured time-spacially to the concept of 'Three Sum(三合)' the concept of 'Taeulcheonbu(太乙天符)' is explained. In the 'Ounhangdae-ron("五運行大論")', 'The calender Signs five Sum(天干五合)' is compared to the concepts of 'couples(夫婦)', 'weak-strong(柔强)' and in the 'Youkmijidae-ron("六微旨大論")', 'the relationship of obedience and disobedience(順逆關係)' which conform to the 'energy status(氣位)' change and 'monarch-minister(君相)' position is mentioned. In the 'Gikyobyeondae-ron("氣交變大論")', the concept of 'Sang-duk(相得)', 'Pyungsang(平常)' is emphasized but concrete measurement is mentioned. In the 'Osangieongdae-ron("五常政大論")', the detailed explanation with twenty three 'systemic of the five elements' motion(五運體系)' form and 'rountine-contrary treatment(正治. 反治)' with 'chill-fever-warm-cold(寒${\cdot}$熱${\cdot}$溫${\cdot}$凉)' are mentioned according to the 'analyse and differentiate pathological conditions in accordance with the eight principal syndromes(八綱辨證)'. In the 'Youkwonjeonggidae-ron("六元正紀大論")', Wang Bing of doesn't mention the concepts of 'Jungwun(中運)' that is seen in the original classic. In the new corrective edition, as the concepts of 'Jungwun, Dongcheonbu, Dongsehae and Taeulcheonbu(中運, 同天符, 同歲會, 太乙天符)' is appeared, Wang Bing seems to only use the concepts of 'Daewun, Juwun, and Gaekwun(大運, 主運, 客運)'. In the 'Jijinyodaeron("至眞要大論")', Wang Bing added detailed commentary to pathology and treatment doctrine by explaining the numerous appearances of 'Sebo, sufficiency, deficiency(歲步, 有餘, 不足)' and in the relation of 'victory-defeat(勝復)', he argued clearly that it is not mechanical estimation. (4) When we observe the Wang Bing's originality on the study of 'the theory of Doctrine on five elements' motion and six kinds of natural factors(運氣學說)', he emphasized 'The idea of Jeongindogi and Health preserving(全眞導氣${\cdot}$養生思想)' by adding 'Wang Bing's Commentary(王氷 注本)' of 'The seven great chapters("七篇大論")' and explained clearly 'The theory of Doctrine on five elements' motion and six kinds of natural factors(運氣學說)' and simpled and expanded the meaning of 'man, as a microcosm, is connected with the macrocosm(天人相應)' and with 'Atmosphere theory(大氣論)' also explained the meaning of 'rising and falling mechanism(升降氣機)'. In the sentence of 'By examining the pathology, take care of your health(審察病機 無失氣宜)'. he explained the meaning of pathology of 'heart-kidney-water-fire(心腎水火)' and suggested the doctrine and management of prescription. In the estimation and treatment, by suggesting 'asthenia and sthenia(虛實)' two method's estimation, 'contrary treatment(反治)' and treatment principals of 'falling heart fire tonifyng kidney water(降心火益腎水)', 'two class of chill and fever(寒熱二綱)' were demonstrated. There are 'inside and outside in the illness and so inner and outer in the treatment(病有中外 治有表囊)'. This sentence suggests concertedly. 'two class of superfies and interior(表囊二綱)' conforming to the position of disease. Therefore Wang Bing as an excellent theorist and introduced 'Cheoniin ideology(天眞思想)' as a clinician and realized the medical science. With these accomplishes mainly written in 'The theory of Doctrine on five elements' motion and six kinds of natural factors(運氣學說)' of 'The seven great chapters("七篇大論")', he interpreted the ancient medical scriptures and expanded the meaning of scriptures and conclusively contributed to the development of the study 'Korean Oriental Medicine(韓醫學)'.

• Journal of Intelligence and Information Systems
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• v.19 no.4
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• pp.55-79
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• 2013

In this paper, we propose a hybrid genetic algorithm (HGA) approach to effectively solve the reverse logistics network with centralized centers (RLNCC). For the proposed HGA approach, genetic algorithm (GA) is used as a main algorithm. For implementing GA, a new bit-string representation scheme using 0 and 1 values is suggested, which can easily make initial population of GA. As genetic operators, the elitist strategy in enlarged sampling space developed by Gen and Chang (1997), a new two-point crossover operator, and a new random mutation operator are used for selection, crossover and mutation, respectively. For hybrid concept of GA, an iterative hill climbing method (IHCM) developed by Michalewicz (1994) is inserted into HGA search loop. The IHCM is one of local search techniques and precisely explores the space converged by GA search. The RLNCC is composed of collection centers, remanufacturing centers, redistribution centers, and secondary markets in reverse logistics networks. Of the centers and secondary markets, only one collection center, remanufacturing center, redistribution center, and secondary market should be opened in reverse logistics networks. Some assumptions are considered for effectively implementing the RLNCC The RLNCC is represented by a mixed integer programming (MIP) model using indexes, parameters and decision variables. The objective function of the MIP model is to minimize the total cost which is consisted of transportation cost, fixed cost, and handling cost. The transportation cost is obtained by transporting the returned products between each centers and secondary markets. The fixed cost is calculated by opening or closing decision at each center and secondary markets. That is, if there are three collection centers (the opening costs of collection center 1 2, and 3 are 10.5, 12.1, 8.9, respectively), and the collection center 1 is opened and the remainders are all closed, then the fixed cost is 10.5. The handling cost means the cost of treating the products returned from customers at each center and secondary markets which are opened at each RLNCC stage. The RLNCC is solved by the proposed HGA approach. In numerical experiment, the proposed HGA and a conventional competing approach is compared with each other using various measures of performance. For the conventional competing approach, the GA approach by Yun (2013) is used. The GA approach has not any local search technique such as the IHCM proposed the HGA approach. As measures of performance, CPU time, optimal solution, and optimal setting are used. Two types of the RLNCC with different numbers of customers, collection centers, remanufacturing centers, redistribution centers and secondary markets are presented for comparing the performances of the HGA and GA approaches. The MIP models using the two types of the RLNCC are programmed by Visual Basic Version 6.0, and the computer implementing environment is the IBM compatible PC with 3.06Ghz CPU speed and 1GB RAM on Windows XP. The parameters used in the HGA and GA approaches are that the total number of generations is 10,000, population size 20, crossover rate 0.5, mutation rate 0.1, and the search range for the IHCM is 2.0. Total 20 iterations are made for eliminating the randomness of the searches of the HGA and GA approaches. With performance comparisons, network representations by opening/closing decision, and convergence processes using two types of the RLNCCs, the experimental result shows that the HGA has significantly better performance in terms of the optimal solution than the GA, though the GA is slightly quicker than the HGA in terms of the CPU time. Finally, it has been proved that the proposed HGA approach is more efficient than conventional GA approach in two types of the RLNCC since the former has a GA search process as well as a local search process for additional search scheme, while the latter has a GA search process alone. For a future study, much more large-sized RLNCCs will be tested for robustness of our approach.