• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.461-475
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• 2006

In this paper, it is described about the tri-band mobile antenna system design to provide broadband multimedia and direct broadcasting services using goo-stationary Koreasat 3, simultaneously operated in Ka/K/Ku band. The radiating part of the antenna system with a fan beam characteristic in the elevation plane is composed of the quasi-offset dual shaped reflector and the tri-band feeder. The tri-band feeder is also composed of the Ka/K dual band feeder with the protruding dielectric rod, the circular polarizer, the ortho-mode transducer and the circular-polarized Ku band feed array. Especially, the Ka/K dual band circular polarizer was realized firstly using the comb-type structure. For fast satellite-tracking on the movement, the Ku band feed array has the structure of the $2{\times}2$ active phased array which can make electrical beams. And, the circular-polarized characteristic in the feed array was improved by $90^{\circ}$ rotating arrangement of four radiating elements polarized circularly by a $90^{\circ}$ hybrid coupler, respectively. Four beam forming channels to make electrical beams at Ku band are divided into the main beam channel and the tracking beam channel in the output, and noise temperature characteristics of each channel were analyzed on the basis of the contributions of internal sub_units. From the fabricated antenna system, the output power at $P_{1dBc}$ of Ka_Tx channel was measured more than 34.1 dBm and the measured noise figures of K/Ku_Rx channels were less than 2.4 dB and 1.5 dB, respectively, over the operating band. The radiation patterns with co- and cross-polarization in the tri-band were measured using a near-field measurement in the anechoic chamber. Especially, Ku radiation patterns were measured after correcting each initial phase of active channels with partial radiation patterns obtained from the independent excitation of each channel. The antenna gains measured in Ka/K/Ku band of the antenna system were more than 39.6 dBi, 37.5 dBi, 29.6 dBi, respectively. And, the antenna system showed good system performances such as Ka_Tx EIRP more than 43.7 dBW and K/Ku_Rx G/T more than 13.2 dB/K and 7.12 dB/K, respectively.

• Journal of IKEEE
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• v.15 no.2
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• pp.179-189
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• 2011

This paper presents an SVC based multi-channel transmission technique. Transmission of high definition multimedia and its service efficiency can be significantly improved by the proposed method. In this method, the HD stream is divided into the two layer streams, i.e., a base layer stream and an enhancement layer stream. The divided streams are transmitted through a primary channel and an auxiliary channel, respectively. The proposed technique provides a noble mode switching technique which enables a seamless service of HD multimedia even under the conditions of abrupt and intermittent deterioration of the auxiliary channel. When the enhancement layer stream is disrupted by the channel monitoring in the mode switching algorithm, the algorithm works further to maintain the spatial and time resolution of the HD multimedia by upsampling and interpolating the base layer stream, consequently serving for the non disrupted play of the media. Moreover, the adoption of an adaptive switching algorithm significantly reduces the frequency of channel disruption avoiding the unnecessary switching for the short period variations of the channel. The feasibility of the proposed technique is verified through the simulation study with an example application to the simultaneous utilization of both Ku and Ka bands for HD multimedia broadcasting service. The rainfall modeling and the analysis of the satellite channel attenuation characteristics are performed to simulate the quality of service performance of the proposed HD broadcasting method. The simulation results obtained under a relatively poor channel (weather) situations show that the average lasting period of enhancement layer service is extended from 9.48[min] to 23.12[min] and the average switching frequency is reduced from 3.84[times/hour] to 1.68[times/hour]. It is verified in the satellite example that the proposed SVC based transmission technique best utilizes the Ka band channel for the service of HD broadcasting, although it is characterized by its inherent weather related poor reliability causing severe limitations in its independent application.

• The Korean Journal of Financial Management
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• v.25 no.1
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• pp.51-84
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• 2008

We investigate the signaling effect of repurchase preceding new equity issue using Korean data. In a short time span, firms announce stock repurchases and equity offerings. The proximity of two events in Korean firms indicates that those are not independent of each other. In this paper, we test the signaling effect of repurchase on equity offerings on the two measures. One is announcement effect, which is measured as CAR(0, +2). The other is the effectiveness which is measured as CAR(0, +30) because the price movement during this window influences on the price of new issues. Previous studies that stock repurchase convey positive signal to equity offerings-Billet and Xue(2004) and Jung(2004)-construct sample without the limit of time interval between two events. This causes the unclear relation between those because of the long time interval. In this study we consider only samples of being within one year each other to reduce this problem and clarify the signal of repurchase on equity offerings. Korean firms are allowed to repurchase own shares with two different method. One is direct repurchase as same as open market repurchase. The other is stock stabilization fund and stock trust fund which trust company or bank buy and sell their shares on the behalf of firms. Generally, the striking different characteristic between direct repurchase and indirect repurchase is following. Direct repurchase is applied by more strict regulation than indirect repurchase. Therefore, the direct repurchase is more informative signal to the equity offering than the indirect repurchase. We construct two sample firms- firms with direct repurchase preceding-equity offerings and indirect repurchase-preceding equity offering, and one control firms-equity offerings only firms-to investigate the announcement effect and the effectiveness of repurchases. Our findings are as follows. Direct repurchase favorably affect the price of new issues favorably. CAR(0, +2) of firms with direct repurchase is not different from that of equity offerings only firms but CAR(0, +30) is higher than that of equity offerings only firms. For firms with indirect repurchase and equity offerings, Both the announcement effect and the effectiveness does not exist. Jung(2004) suggest the possibilities of how indirect stock repurchase can be regarded as one of unfair trading practices on based on the survey results that financial managers of some of KSE listed firms have been asked of their opinion on the likelihood of the stock repurchase being used in unfair trading. This is not objective empirical evidence but opinion of financial managers. To investigate whether firms announce false signal before equity offerings to boost the price of new issues, we calculate the long-run performance following equity offerings. If firms have announced repurchase to boost the price of new issues intentionally, they would undergo the severe underperformance. The empirical results do not show the severer underperformance of both sample firms than equity offerings only firms. The suggestion of false signaling of repurchase preceding equity offerings is not supported by our evidence.

• Korean Journal of Health Education and Promotion
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• v.9 no.1
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• pp.1-13
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• 1992

The purpose of this thesis is to provide the framework of the health education curriculum on a school level which should be accomplishe in futrue and farthermore to establish the health education as a independent and regular course. The relation among the status in quo and the satisfaction degree of health education, the degree of the knowledge about health, the degree of the understanding of the health education and the degree of requirement for the health education curriculum has been analyzed in this paper. The research has been carried out through the questionnaire forms distributed to the girl students and the instructors at a few general senior high school and vocational senior high schools in Seoul, and the consequences are as follows : 1. As to the degree of understanding of the health education, it has been indicated that the health education should be performed one or two hours a week from the elementary school for all the boy and girl students by the experts trained in the departments concerned with health. 2. Concerning the degree of requirement for health education curriculum, the high school girl students have shown the need for first aid, sex education, environmental health, drinking, smoking, drug abuse, maternal and child health, industrial health, safety health, mental health, growth & development, epidemiology, the old health in the order named. On the other hand, the instructors have shown the need for drinking, smoking, drug abuse, sex education, maternal and child health, public health and industrial health also in the order named. The items having low degree of requirement are biostatistics, community health and health administration in case of the gril students and biostatistics, health administration and health economics in case of the instructors. 3. The status in quo and the satisfaction degree of the health education has proved higher in senior high school curriculums than in junior high school curriculums, and the most instructive course about health has turned out to be gymnastics in junior high school and the training course in senior high school respectively. 4. As to the degree of understanding of the health education in case of the girl students, the significance has been found between the health condition and the time for performing the health education, the monthly income and the objects for the health education, and the school records and the school hours per week. The significance has been shown only in regard to the school records in case of the degree of requriement for the health education curriculum. 5. The degree of requirement for the health education in case of the instructors has shown the significance between the teching career and the need for the health education. In addition, the degree of requirement for the health education curriculum has indicated significance with regard to sex and age. 6. The degress of the understanding of the health education according to the degree of knowledge about health and the degree of requirement for the health educatio curriculum have been all turned out to be statistically significant. 8. Among the factors which have an influence on the degree of the understanding of the health education, the recognition of the relation between the health course and the training course has significatly influenced the selection of the health education instructors. In additon, the understanding of the need for the health eduation has significantly influenced the objects for the instructors and the school hours, and the understanding of the need for establishing the health education course has significatly influenced the time for performing the health education.

• Journal of the Korean Institute of Landscape Architecture
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• v.46 no.5
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• pp.59-68
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• 2018

This study deals with post-occupancy evaluation (POE) of 'Kim Gwang-seok Street'as storytelling road for urban regeneration. The evaluation focused on image preference and use satisfaction of visitors. This is the initial project of popular singer-storytelling street as a new attraction, and the results could be used as basic data for the sustainable planning and management of storytelling streets. 200 respondents of visitor group were analyzed. Frequency analysis for demographics, use, behavior, reliability, and means, were evaluated. Factor analysis and multiple regression analysis were conducted for image preference and use satisfaction. Responses showed high frequency of twenties in age, who were typically students. In use motives and activities, strolling, sightseeing, and taking pictures were shown to be the most common. The mean scores of image variables showed symbolic (5.03), familiar (4.84), beautiful (4.71), and bright (4.63), the highest. The result of exploratory factor analysis, led to 3 factors being categorized; the mood of street, the design, and the dynamics. Due to the result of multiple regression analysis, the preference of space image was significantly influenced by 4 image variables; symbolic (${\beta}=.314$), stable (${\beta}=.248$), friendly (${\beta}=.204$), and fresh (${\beta}=.142$). In the use satisfaction analysis, the mean scores were highest concerning facility design (3.81), typical street (3.78), the image of street (3.81), continued use (3.66), and experiential tourism (3.53), respectively. The mean score of parking space (2.56) was the lowest. In factor analysis concerning use satisfaction, 3 factors were categorized; facility management, experience, and image. By the result of multiple regression analysis, the total satisfaction of use was significantly influenced by 4 independent variables; image of street (${\beta}=.296$), management (${\beta}=.277$), continued use (${\beta}=.205$), and typical street (${\beta}=.183$). As storytelling road for urban regeneration, 'Kim Gwang-seok Street' has shown considerable success in significant improvement of image preference and user satisfaction. Therefore, the enhancement of 'placeness' through storytelling of Kim Gwang-seok, and the strengthening of its identity and symbolism, should be the basic focus of development for the street in the future.

• Clinical and Experimental Pediatrics
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• v.51 no.7
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• pp.747-753
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• 2008

Purpose : Diabetes mellitus is a major risk factor for the development of cardiovascular disease. Early atherosclerotic changes in the arterial walls begin in adolescence and the risk factors are associated with its development. To assess the usefulness of carotid artery intima-media thickness (IMT), as a marker of early atherosclerosis, we evaluated the structural and functional characteristics of the carotid artery and investigated their relationshop with the metabolic and anthropometric parameters in children and adolescents with type 1 diabetes. Methods : For this study, we enrolled 23 children with type 1 diabet and 19 age and sex-equivalent healthy children as the control group. Metabolic and anthropometric parameters such as serum lipid levels, plasma glycated hemoglobin (HbA1c), and body mass index were measured after a 12-h fasting period. The carotid artery IMT was measured by a high-quality ultrasound system, and compliance, and distensibility were calculated by an equation. Results : There were no significant differences between the 2 groups with regard to the sex ratio, age, blood pressure and serum cholesterol levels' however, HbA1c levels were significantly higher in the diabetic children ($8.5{\pm}1.8$ vs. $5.0{\pm}0.2$, P=0.001). Ultrasonographic findings showed that compared with the control group, the diabetic group had higher IMT ($0.45{\pm}0.06mm$ vs. $0.41{\pm}0.04mm$, P=0.04), but there were no significant differences in compliance and distensibility. The HbA1c (P=0.002) and high-density lipoprotein cholesterol (P=0.026) levels were independent IMT predictors in the diabetic group. Conclusion : Here, the carotid artery IMT was higher in the diabetic group, and it is correlated with atherosclerotic risk factor. Thus, carotid IMT could be evaluated as a marker of early atherosclerosis in diabetic children.

• Journal of Bio-Environment Control
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• v.13 no.4
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• pp.217-225
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• 2004

This study was performed to provide the basic knowledge about the mushroom cultivation facilities. Classified current status of cultivation facilities in Gyeongnam province was investigated by questionnaire. The structure of Pleurotus eryngii cultivation facilities can be classified into the simple and permanent frame type. The simple frame structures were mostly single-span type, on the other hand, the permanent frame structures were more multi-span than simple structures. And the scale of cultivation facilities was very different regardless of structural type. But as a whole, the length, width and ridge height were prevailing approximately 20.0 m, $6.6\~7.0m$ and $4.6\~5.0m$ range, respectively. The floor area was about $132\~160\;m^2$, and floor was built with concrete to protect mushrooms from various harmful infection. The roof slope of the simple and permanent type showed about $41.5^{\circ}\;and\;18.6\~28.6^{\circ}$, respectively. The width and layer number of growing bed for mushroom cultivation were around $1.2\~1.6m$, 4 layers in common, respectively. Most of year round cultivation facilities were equipped with cooler, heater, humidifier, and ventilating fan. Hot water boiler was the most commonly used heating system, the next was electric heater and then steam boiler. The industrial air conditioner has been widely used for cooling. And humidity was controlled mostly by ultra-wave or centrifuging humidifier. But some farmers has been using nozzle system for auxiliary purpose. More then $90\%$ of the mushroom house had the independent environment control system. The inside temperature was usually controlled by sensor, but humidity and $CO_2$ concentration was controlled by timer for each growing stage. The capacity of medium bottle was generally 850 cc and 1100cc, some farms used 800 cc, 950 co and 1,250 cc. Most of mushroom producted has been usually shipped to both circulating company and joint market.

• Journal of Technology Innovation
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• v.23 no.3
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• pp.397-432
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• 2015

This paper investigates the effects of technology collaboration between the main supplier and buyer on buyer's new product development under dynamic environment. Based on 428 Korean manufacturing firms, we conducted regression analysis. The technology collaboration between the main supplier and buyer is adopted as a independent variable and quality, cost and lead time performance of new product development projects are used as dependents variables. Environment dynamic is also used as a moderate variables. We found that the in general, technology collaboration is positively associated with the performance of buyers' new product development, but in the high degree of dynamic environment, technology collaboration is negatively associated with the performance of buyers' new product development unlike our expectation. Thus, we divide our sample into two groups; shipbuilding industry with the low degree of environment dynamic and electronic and IT device industry with the high degree of environment dynamic and conducted a post hoc analysis. As a result, in ship building industry, the technology collaboration is significant to improve NPD projects performance, while in electronic and IT device industry, the technology collaboration with a main supplier is not significant as well as coefficient is negative. In that, under the highly dynamic condition with the fast change of technology and products obsolescence the NPD collaboration with the main supplier does not works unlike a stable environment. This implies that the NPD attributes of buyer are different by their environmental factor and the fit between given environmental feature and the collaboration synergy is critical factor for improving the effect of NPD collaboration between supplier and buyer.

• Journal of Chest Surgery
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• v.30 no.10
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• pp.973-978
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• 1997

We reviewed data of 64 patients who underwent reoperation because of prosthetic valve malfunction from January 1991 to December 1995. The indications for reoperation were prosthetic valve failure(primary tissue failure: 53 patients, 82.8%), prosthetic valve thrombosis(6 patients, 9.4%), paravalvular leak(3 patients, 4.7%), prosthetic valve endocarditis(2 patients, 3.6%). Prosthetic valve failure developed most frequently in mitral portion(40 patients, 75%), prosthetic valve thrombosis also in mitral portion(4 patients, 67%), paravalvular leak significantly in aortic portio (3 patients, 100%). Explant period was longest in prosthetic valve failure(mean 107.4 $\pm$ 24.6 months), shortest in prosthetic valve endocarditis with prosthetic valve thrombosis(1 patient, 1 month). Mean explant period, defined as from first valve replacement operation to redo-valve replacement operatopn, was 109.2$\pm$ 10.7 months in mitral portion, 97.8$\pm$ 10.4 months in aortic portion, 109.5$\pm$ 10.4 months in total. Overall hospital mortality was 9.38%. The most common cause of death was the low cardiac output(4 patients), other causes were bleeding(1 patient), CNS injury(1 patient). Preoperative NYHA class IV(P=0.011), emergency operation(P=0.011), prosthetic valve endocarditis(P=0.001) were the independent risk factors, but age, sex, explant period, ACC time, double valve replacement, valve position, second reoperation did not appear to be significant risk factors. Mean follow up period was 28.8 $\pm$ 17.8 months. Actuarial survival at 3 year was 92.0$\pm$6.2%, 2 year event-free survival w s 84.3$\pm$6.1%. We propose that patients undergoing reoperation because of prosthetic valve failure are carfully controlled and selected in regarding to above mentioned risk factors NYHA class IV, emergency operation, prosthetic valve endocarditis in preoperative state. About other risk factors possible, there is necessary of following study.

• Journal of Chest Surgery
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• v.42 no.1
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• pp.72-78
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• 2009

Background: Mediastinal neurogenic tumors are generally benign lesions and they are ideal candidates for performing resection via video-assisted thoracoscopic surgery (VATS). However, benign neurogenic tumors at the thoracic apex present technical problems for the surgeon because of the limited exposure of the neurovascular structures, and the optimal way to surgically access these tumors is still a matter of debate. This study aims to clarify the feasibility and safety of the VATS approach for performing surgical resection of benign apical neurogenic tumors (ANT). Material and Method: From January 1996 to September 2008, 31 patients with benign ANT (15 males/16 females, mean age: 45 years, range: 8~73), were operated on by various surgical methods: 14 VATS, 10 lateral thoracotomies, 6 cervical or cervicothoracic incisions and 1 median sternotomy. 3 patients had associated von Recklinhausen's disease. The perioperative variables and complications were retrospectively reviewed according to the surgical approaches, and the surgical results of VATS were compared with those of the other invasive surgeries. Result: In the VATS group, the histologic diagnosis was schwannoma in 9 cases, neurofibroma in 4 cases and ganglioneuroma in 1 case, and the median tumor size was 4.3 cm (range: 1.2~7.0 cm). The operation time, amount of chest tube drainage and the postoperative stay in the VATS group were significantly less than that in the other invasive surgical group (p<0.05). No conversion thoracotomy was required. There were 2 cases of Hornor's syndrome and 2 brachial plexus neuropathies in the VATS group; there was 1 case of Honor's syndrome, 1 brachial plexus neuropathy, 1 vocal cord palsy and 2 non-neurologic complications in the invasive surgical group, and all the complications developed postoperatively. The operative method was an independent predictor for postoperative neuropathies in the VATS group (that is, non-enucleation of the tumor) (p=0.029). Conclusion: The VATS approach for treating benign ANT is a less invasive, safe and feasible method. Enucleation of the tumor during the VATS procedure may be an important technique to decrease the postoperative neurological complications.