• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.29-38
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• 2009

Statement of problem: A casting connection technique is widely used for repair, correction and addition to base metal framework. However, a casting connection technique may increase the risk of failure in clinical situations when high stresses exist. Purpose: The purpose of this study was to investigate the mechanical retentive groove design comparatively to increase the joint strength by using the three-dimensional finite element analysis model of a 3-unit fixed partial denture. Material and methods: Ten finite element models were constructed. (Model A: One retentive groove, Model B: Two retentive grooves, Model C: Three retentive grooves, Model D: Four retentive grooves, Model E: One horizontal groove and two vertical grooves, Model F: Two horizontal grooves and one vertical groove, Model G: One groove with the enlarged dimension, Model H: Two grooves with the enlarged dimension, Model I: One groove with the increased height, Model J: One groove with the increased width of base). The vertical force was applied to the mesial and the distal fossa to the casting connection of mandibular first molar. Results: The main factors, affecting joint strength of casting connection were both the retention between the primary cast and the secondary cast and the thickness of the primary cast remaining after preparing retentive groove. The increase of retentive force, according to the numbers and the dimension of retentive groove had an effect on distributing stress. However, in some cases, the increase of retentive force resulted in the increase of stress by reducing thickness of the primary cast in the connection area. Conclusion: The design of retentive groove that limits number of retentive groove for metal thickness and increases the depth of retentive groove for retention is highly recommended.

• Asia pacific journal of information systems
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• v.19 no.3
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• pp.25-49
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• 2009

Advances in technology have resulted in the emergence of new information systems. The convergence of IT and manufacturing sectors has blurred the boundaries among industries. Also, such convergence has become established as a paradigm to build a new area. Especially the convergence of broadcasting and telecommunication, notably in the case of IPTV (Internet Protocol Television), is among the most salient examples of its kind in recent years as a major case of disruptive technology innovation. Despite its much fanfare, such convergence, however, has not fulfilled the expectation; it has not produced positive economic effects while negatively affecting the growth of IPIV. Stakeholders in and around IPIV including telecommunication companies, broadcasting corporations, and government bodies wish to gain control of IPTV under their wings. IPTV has drifted in the midst of conflicts among the stakeholders in and around IPTV, particularly telecommunication and broadcasting organizations in a broad sense. Our empirical research intends to deal with how audiences accept IPTV and how firms provide IPTV services to utilize their resources. Three research questions in this paper include, first, whether Technology Acceptance Model (TAM) can sufficiently explain the acceptance of IPTV as an information system. The second question concerns with empirically testing the playful aspect of IPTV to increase its audience acceptance. Last, but not least, this paper deals with how firms can efficiently and effectively allocate their limited resources to increase IPTV viewers. To answer those three main questions of our study, we collect data from 197 current subscribers of high speed internet service and/or cable/satellite television. Empirical results show that 'perceived usefulness (PU) $\rightarrow$ Intention to use' and 'perceived ease of use (PEU) $\rightarrow$ Intention to use' are significant. Also, 'perceived ease of use' is significantly related to 'perceived usefulness.' Perceived ease of handling IPTV without much effort can positively influence the perceived value of IPTV. In this regard, engineers and designers of IPTV should pay more attention to the user-friendly interface of IPTV. In addition, 'perceived playfulness (PP)' of IPTV is positively related to 'intention to use'. Flow, fun and entertainment have recently gained greater attention in the research concerned with information systems. Such attention is due to the changing features of information systems in recent years that combine the functional and leisure attributes. These results give practical implications to the design of IPTV that reflects not just leisure but also functional elements. This paper also investigates the relationship between 'perceived ease of use (PEU)' and 'perceived playfulness (PP).' PEU is positively related to pp. Audiences without fear can be attracted more easily to the user-friendly IPTV, thereby perceiving the fun and entertainment with ease. Practical implications from this finding are that, to attract more interest and involvement from the audience, IPTV needs to be designed with similar or even more user friendly interface. Of the factors related to 'intention to use', 'perceived usefulness (PU)' and 'perceived ease of use (PEU)' have greater impacts than 'perceived playfulness (PP).' Between PU and PEU, their impacts on 'intention to use' are not significantly different statistically. Managerial implications of this finding are that firms in preparation for the launch of IPTV service should prioritize the functions and interface of IPTV. This empirical paper also provides further insight into the ways in which firms can strategically allocate their limited resources so as to appeal to viewers, both current and potential, of IPTV.

• Journal of Yeungnam Medical Science
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• v.15 no.2
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• pp.325-340
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• 1998

A cross-sectional study was conducted to evaluate the relationship between sick building syndrome(SBS) and the environmental factors affecting SBS on 130 underground workers and 60 controls. The study consisted of 1) a review of environmental condition 2) measurement of temperature, $O_2$, $CO_2$, CO, and formaldehyde and 3) a questionnaire survey of symptom prevalence and perception of environmental conditions using indoor Air Quality questionnaire recommended by National Institute for Occupational Safety and Health. Bronchitis and dust allergy were more prevalent in underground workers significantly(p < 0.05). Among the 18 symptoms related to the indoor air pollution, the experience rate of dry, itching or irritated eyes, sore or dry throat, chest tightness, tired or strained eyes and dry or itchy skin symptom was significantly different between the underground workers and controls. The diagnostic criteria of SBS was defined as at least 1 symptom is experienced 1-3 times a week during the last 1 month among 18 indoor air pollution related symptoms which can be relieved by moving out of the underground. Applying the criteria, the mean symptom score was significant higher in underground workers than controls significantly (p < 0.05). These resalts indicated that underground workers are under inappropriate ergonomic and physical condition and inadequate ventilation. Their experience rate of symptoms related to indoor air pollution and prevalence of SBS was significantly higher than controls. To reduce the prevalence of SBS of underground workers, the surveillance system of indoor air quality, restriction of using fuel in underground and legislative regulations for the environment are needed to establish a better indoor air quality. Early detection, treatment and prevention of SBS through medical attention is also needed.

• Journal of dental hygiene science
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• v.11 no.5
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• pp.389-395
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• 2011

The purpose of this study was to examine dental hygiene students' achievement motivation and factors affecting dental hygiene students' achievement motivation by the general characteristics of subjects in this study. The subjects in this study were 450 who were selected by convenience sampling from three different three-year-course colleges. After a survey was conducted, the answer sheets from 421 respondents were analyzed. The collected data were analyzed, which made use of t-test, ANOVA and Kruscal-Wallis test. The findings of the study were as follows. 1. The dental hygiene students investigated got 3.34 in achievement motivation. They got the highest score of 3.78 in the item 'I perform what I have to do with a sense of responsibility.' and they got the lowest score of 2.67 in the item 'I like to do something risky.' 2. Concerning links between their general characteristics and achievement motivation, the students whose academic year was higher(p<0.001) and who had more clinical practice experiences (p<0.01) were better motivated than their counterparts. As to connections between achievement motivation and expected post-graduation length of service, those who replied that they planned to find another job after getting married were better motivated(p<0.05). Regarding relationship between achievement motivation and a will to work abroad, the students who had a stronger will to work abroad were better motivated. 3. As a result of checking the influence of their general characteristics on achievement motivation, stronger motivation was found among the students whose academic year was higher(p<0.01), who intended to work until marriage(p<0.01) and who didn't plan to keep working after marriage(p<0.05) when the other variables were controlled. Therefore dental hygiene students should be taught to look at things positively when they enter college, and they should also be educated to become progressive to keep working for their lifetime instead of just getting a temporary job after graduation.

• Korean Journal of Ecology and Environment
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• v.49 no.3
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• pp.197-207
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• 2016

This study aims at providing basic data to objectively evaluate the areas suitable for reintroduction of the species of Asiatic black bear (Ursus thibetanus) in order to effectively preserve the Asiatic black bears in the Korean protection areas including national parks, and for the species restoration success. To this end, this study predicted the potential habitats in East Asia, Southeast Asia and India, where there are the records of Asiatic black bears' appearances using the Maxent model and environmental variables related with climate, topography, road and land use. In addition, this study evaluated the effects of the relevant climate and environmental variables. This study also analyzed inhabitation range area suitable for Asiatic black and geographic change according to future climate change. As for the judgment accuracy of the Maxent model widely utilized for habitat distribution research of wildlife for preservation, AUC value was calculated as 0.893 (sd=0.121). This was useful in predicting Asiatic black bears' potential habitat and evaluate the habitat change characteristics according to future climate change. Compare to the distribution map of Asiatic black bears evaluated by IUCN, Habitat suitability by the Maxent model were regionally diverse in extant areas and low in the extinct areas from IUCN map. This can be the result reflecting the regional difference in the environmental conditions where Asiatic black bears inhabit. As for the environment affecting the potential habitat distribution of Asiatic black bears, inhabitation rate was the highest, according to land coverage type, compared to climate, topography and artificial factors like distance from road. Especially, the area of deciduous broadleaf forest was predicted to be preferred, in comparison with other land coverage types. Annual mean precipitation and the precipitation during the driest period were projected to affect more than temperature's annual range, and the inhabitation possibility was higher, as distance was farther from road. The reason is that Asiatic black bears are conjectured to prefer more stable area without human's intervention, as well as prey resource. The inhabitation range was predicted to be expanded gradually to the southern part of India, China's southeast coast and adjacent inland area, and Vietnam, Laos and Malaysia in the eastern coastal areas of Southeast Asia. The following areas are forecast to be the core areas, where Asiatic black bears can inhabit in the Asian region: Jeonnam, Jeonbuk and Gangwon areas in South Korea, Kyushu, Chugoku, Shikoku, Chubu, Kanto and Tohoku's border area in Japan, and Jiangxi, Zhejiang and Fujian border area in China. This study is expected to be used as basic data for the preservation and efficient management of Asiatic black bear's habitat, artificially introduced individual bear's release area selection, and the management of collision zones with humans.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.131-134
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• 2012

Purpose : The labeling efficiency of radiopharmaceuticals in nuclear medicine is important in terms of accuracy and reliability of the examination. Usually $^{99m}Tc$-HMPAO used for brain SPECT scan is chemically unstable since lots of impurities are existing. Therefore, occurrence of loss of labeling efficiency is easy to appear. In this paper, labeling and use of $^{99m}Tc$-HMPAO should be helpful through experiments on factors affecting the labeling efficiency of $^{99m}Tc$-HMPAO. Materials and Methods : Domestic HMPAO vials (Dong-A) used for brain SPECT scan were tested. Domestic Samyeong Generator 55.5 GBq (1,500 mCi), TLC measurement sets (ITLC-SG, butanone, saline, TLC chamber) and radio-TLC scanner (Advantest, Bioscan) were used. In the first experiment, after eluting generator at 1, 8, 16, 24, 28 hours apart, each eluted $^{99m}Tc$-pertechnetate were labeled with HMPAO and the labeling efficiency was measured. In the second experiment, after eluting $^{99m}Tc$-pertechnetate from a generator, $^{99m}Tc$-pertechnetate was drawn at 0, 1, 3, 6 hours. And each drawn $^{99m}Tc$-pertechnetate were labeled with HMPAO for measuring labeling efficiency. In the third experiment, labeling efficiency was measured at 0, 0.5, 3, 5, 7 hours after labeling $^{99m}Tc$-HMPAO. Results : In the first experiment, measured values were appeared 95.05, 94.64, 94.94, 95.64, 96.76% in passing order of time. In the second experiment, measured values were appeared 94.38, 94.23, 93.26, 91.03% in passing order of time. In the third experiment, measured values were appeared 95.76, 94.17, 88.19, 83.6, 76.86% in passing order of time. Conclusion : In the first experiment of this paper, labeling efficiency of $^{99m}Tc$-HMPAO labeled with $^{99m}Tc$-pertechnetate eluted after 24 hours from first elution. Additional experiments will be needed to discuss for usability. In the second experiment, the labeling efficiency was slightly decreased in chronological order, but it was measured higher than 90%. Also, additional experiments will be needed to discuss for usability. In the third experiment, the labeling efficiency was decreased considerably. Especially, within 3 hours after the labeling is recommended to use $^{99m}Tc$-HMPAO

• 한국해양학회지
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• v.30 no.5
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• pp.480-492
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• 1995

Petrographic investigation has been carried out to determine the composition of the beach sediments and the affecting factors which have controlled their compositional variations from Hyupjae, Aeweol, Iho, Samyang, Hamdeok, Sehwa, Pyoseon, Jungmun, and Hwasun areas along the coast of the Cheju Island. Average mean sizes of the beach sediments are Hyupjae 2.2ø, Aeweol 0.8ø, Iho 1.4ø, Samyang 2.4ø, Hamdeok 1.6ø, Sehwa 1.5ø, Pyoseon 2.1ø, Jungmun 0.4ø, and Hwasun 0.9ø, thus, aries from 0.4 to 2.4ø. The beach sediments from Pyoseon and Hwasun areas are poorly sorted, those from Aeweol and Jungmun areas are moderately sorted and those from the rest of the areas are moderately well sorted. While-colored beach sediments in Hyupjae, Aeweol, Hamdeok, Sehwa, and Pyoseon areas are mostly composed of calcareous shells (more than 85%) such as mollusk, red algae, benthic foraminiferas, etc., whereas volcanic rock fragment is the dominant component of the black-colored beach sediments in Iho, Samyang, and Hwasun areas. Especially, the relatively white-colored beach sediment in Jungmun area, which is on e of the carbonate-dominant areas, shows a higher content of rock fragments than the other carbonate-dominant areas. The beach sediments in Pyoseon area show a high content of carbonate intercalates. Considering the contributions by organisms according to grain size, grains with the size range of 1∼2ø are mostly composed of calcareous red algae fragments, and grains with the size range of 2∼3ø consist of mollusk fragments. It is also notable that bryozoan fragments comprise about 48% of the sediment in Samyang area with the size range of 0∼1ø. The composition of the beach sediments in Cheju Island appears o be controlled by the riverine supply rate of volcanic rock fragments, the lithology of the rocks distributed ear the beaches, the direction of alongshore currents, and the direction of storms, etc.. It is suggested that the beach sediments in Iho and Samyang areas show black color because of the higher supply rate of the volcanic rock fragments from the nearby rivers, whereas those in the rest of the areas show white color due to the relatively lower content of volcanic rock fragments and higher content of carbonate components transported from shallow marine environment. In Hwasun area, the content of volcanic rock fragments is high, and they are directly from the tuffaceous rocks distributed nearby. Also, the volcanic rock fragments in Jungmun area are transported not only from the rivers nearby but also from the nearby tuffs by storm activities. The beach sediment in Pyoseon area contains a high content of carbonate intercalates, which formed in the nearby shallow marine environment through marine cementation. This indicates that active marine cementation occurs in shallow marine environment near Pyoseon area.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.671-677
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• 2017

In this study, scattering factors affecting the quality of medical images were quantitatively analyzed and investigated. MCNPX simulation was conducted by using ANSI phantom, made of tissue equivalent materials, to calculate the scattering ratio occurred by the increase of the object thickness. Then, the result of the simulation was compared with the result of actual radiation measurement. In addition, we evaluated the image quality by the RMS evaluation, RSD and NPS analysis using X-ray images acquired with increasing object thickness. Furthermore, the scattering ratio was analyzed by increasing the thickness of acrylic phantom on chest phantom. The result showed that the scattering ratio was increased to 57.2%, 62.4%, and 66.8% from 48.9%, respectively, when the acrylic phantom thickness was increased by 1 inch from 6.1 inches. The results of MCNPX simulation and the actual measured scattering dose showed similar results. Also, as a result of RMS measurement from acquired x-ray images, the standard deviation decreased as the object thickness increased. However, in the RSD analysis considering the average incident dose, the results were increased from 0.028 to 0.039, 0.051, 0.062 as the acrylic phantom thickness was increased from 6.1 inches to 7.1 inch, 8.1 inch, and 9.1 inch, respectively. It can be seen that the increase of the scattering effect due to the increase of the object thickness reduces the SNR. Also, the NPS results obtained by measuring scattered radiation incident on the detector resulted in the increase of the noise as the object thickness increased.

• Journal of Korean Society of Forest Science
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• v.104 no.3
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• pp.360-367
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• 2015

The present study investigated the habitats of Korean fir trees (Abies koreana E. H. Wilson) on Mt. Baekwun (Baekwun-san), determined the current distribution, quantified the contribution of biological and non-biological environmental factors affecting the distribution, derived actual and potential habitats, presented a plan for the establishment of protected areas, applied RCP 8.5 climate change scenario to analyze the effects of climate change on the future distribution of Korean fir trees, and predicted future potential habitats. According to the results of the study, 3,325 Korean fir trees (DBH >= 2.5 cm) inhabited Mt. Baekwun, and their distribution area was approximately 150 ha. Populations of Korean fir trees were confirmed to exist at an altitude of 900 m above sea level and were distributed up to 1,200 m. Based on potential distribution, areas appropriate for habitation by Korean fir trees were analyzed to be 450 ha, three times the current distribution area, with a focus on Sang Peak (Sang-bong), Eokbul Peak (Eokbul-bong), Ddari Peak (Ddari-bong), and Dosol Peak (Dosol-bong). The forest stands near Sang Peak, the main peak, were evaluated as those with the most appropriate potential for the habitation of Korean fir trees, and populations of the trees tended to prefer the northern slope rather than the southern slope. When climate change scenario RCP 8.5 was applied and future potential distribution was analyzed, the habitats were expected to decrease in area to 20 ha by 2050, with a focus on Sang Peak, and areas appropriate for habitation were predicted not to exist by 2080. Judging from such results, as global warming accelerates, the habitats of Korean fir trees are clearly expected to move from lowlands to highlands.

• Journal of Mushroom
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• v.2 no.1
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• pp.15-20
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• 2004

Pleurotus ostreatus, the oyster mushroom, is one of the most widely cultivated and important edible mushrooms in the world. In order to study the developmental process of P. ostreatus and its regulatory mechanism, a new culturing method needs to be established for inducing the fruiting body and sporulation in the laboratory. In this study, we have examined whether the fruiting body of P. ostreatus can be formed on the plastic petri dish which are commonly used for cell culture in the laboratory. The strain was cultured on $60{\times}15mm$ plastic petri dish with potato dextrose agar media at $28^{\circ}C$ for mycelial growth and then at $18^{\circ}C$ for the formation of primordia and fruiting bodies within plant growth chamber. The development of primordia into fruiting bodies was achieved on cultured dishes under air ventilation. At the primordia stage, the normal formation of fruiting body was blocked by sealing the plastic dish with parafilm. The periods requiring for the formation of primordia and fruiting bodies were examined on the dish culture. About 96% and 76% of cultured samples formed primordia and fruiting bodies under the optimal conditions during ten weeks of culture, respectively. These culturing periods, however, were changed by the mechanical injury treatment to mycelia. As other factors affecting the fruiting body formation, the effects of light and cold shock have been tested. No fruiting formation was observed on the cultured dishes under the dark. The cold shock treatment by storing cultured dishes for one day at $4^{\circ}C$ did not have any significant effects in the fruiting body formation. Spores of fruiting bodies acquired from the petri dishes could be germinated on culture media at $28^{\circ}C$. These results suggest that the fruiting bodies of P. ostreatus can be formed on the experimental petri dish and this dish-culturing method is useful for understanding of the developmental process of P. ostreatus in the laboratory. Furthermore, the dish-culturing method is able to shorten the life cycle of P. ostreatus without requiring large area and expensive device.