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Polymerization of dual cured composites by different thickness (두께에 따른 이중 중합형 복합레진의 중합)

  • Kim, Yun-Ju;Jin, Myoung-Uk;Kim, Sung-Kyo;Kwon, Tae-Yub;Kim, Young-Kyung
    • Proceedings of the KACD Conference
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    • 2008.05a
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    • pp.169-176
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    • 2008
  • The purpose of this study was to evaluate the effect of thickness, filling methods and curing methods on the polymerization of dual cured core materials by means of microhardness test. Two dual cured core materials, MultiCore Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein) and Bis-Core (Bisco Inc., Schaumburg, IL, USA) were used in this study. 2 mm (bulky filled), 4 mm (bulky filled), 6 mm (bulky and incrementally filled) and 8 mm (bulky and incrementally filled)-thickness specimens were prepared with light cure or self cure mode. After storage at $37^{\circ}C$ for 24 hours, the Knoop hardness values (KHN) of top and bottom surfaces were measured and the microhardness ratio of top and bottom surfaces was calculated. The data were analyzed using one-way ANOVA and Scheffe multiple comparison test, with ${\alpha}=0.05$. The effect of thickness on the polymerization of dual cured composites showed material specific results. In 2, 4 and 6 mm groups, the KHN of two materials were not affected by thickness. However, in 8 mm group of MultiCore Flow, the KHN of the bottom surface was lower than those of other groups (p < 0.05). The effect of filling methods on the polymerization of dual cured composites was different by their thickness or materials. In 6 mm thickness, there was no significant difference between bulk and incremental filling groups. In 8 mm thickness, Bis-Core showed no significant difference between groups. However, in MultiCore Flow, the microhardness ratio of bulk filling group was lower than that of incremental filling group (p < 0.05). The effect of curing methods on the polymerization of dual cured composites showed material specific results. In Bis-Core, the KHN of dual cured group were higher than those of self cured group at both surfaces (p < 0.05). However, in MultiCore Flow, the results were not similar at both surfaces. At the top surface, dual cured group showed higher KHN than that of self cured group (p < 0.05). However, in the bottom surface, dual cured group showed lower value than that of self cured group (p < 0.05).

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The Relationship among Country of Origin, Brand Equity and Brand Loyalty: Comparison among USA, China and Korea (원산지효과, 상표자산 및 상표충성 간의 관계에 관한 연구: 미국, 중국, 한국의 비교분석)

  • Ko, Eun-Ju;Kim, Kyung-Hoon;Kim, Sook-Hyun;Li, Guo-Feng;Zou, Peng;Zhang, Hao
    • Journal of Global Scholars of Marketing Science
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    • v.19 no.1
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    • pp.47-58
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    • 2009
  • The marketing environment has become competitive to an extent that requires firms to target their products at markets that span national boundaries. However, competitive clout cannot be achieved in global consumer markets unless firms thoroughly understand and adequately respond to the core values and needs of those consumers. Brand equity is one of the most important assets to a company. Especially in sportswear markets, brand equity is the crucial value added to a product by its brand name. Factors such as country of origin also influence customer's attitude towards brand equity. Therefore, this paper discusses the relationship between country of origin effect and brand equity, and how they influence consumers' loyalty for respective brands. This paper focused on the sports shoes market, because it is an increasing area of opportunity for world manufacturers. The objectives of this study were the following. (1) Test the effect of country of origin on brand equity. (2) Test how brand equity influences consumers' brand loyalty. (3) Find whether there are differences in the effects of country of origin and brand equity among the three countries. (4) Find whether there are differences in the effects of country of origin and brand equity among the different lifestyles. Based on the review of literature results, the hypotheses are concluded as the following: H1-a: Country image has positive influence on country of origin. H1-b: Product perception has positive influence on country of origin. H2-a: Perceived quality has positive effect on brand equity. H2-b: Perceived price has positive effect on brand equity. H3: Country of origin has positive effect on brand equity. H4: Brand equity has a positive impact on brand loyalty. Research model was constructed (see Fig. 1). After data analysis, the following results were concluded: sports shoes purchase behavior showed significant differences among Korean, Chinese, and American consumers for favorite brand, purchased brand, purchased place, information usage, and favorite sports games. The results of this study also extend the research of the relationship among country of origin, brand equity and brand loyalty to the sports shoes market. Brand equity was proven to have a significant relationship with brand loyalty for all countries. The factors which can influence brand equity are different for different countries. The third finding of this paper is that we identified different three lifestyles, adventurer, follower, and laggard, for Korean, Chinese and American consumers. Without the nationality boundary, seeing the emergence of a new group of consumers who have similar preferences and buy similar brands is more important. All of the consumers consider brand equity to keep their brand loyalty. Perceived price is the only factor which can influence brand equity for adventurers; brand is more important for them. The laggards were not influenced by any factor. All of the factors expect perceived price are important for the followers. Marketing managers should consider brand equity when introducing their brand into a new market. Also localization is the basic strategy that all the sports shoes companies should understand. But as a global brand, understanding the same characteristics for each country is more important to build global strategy.

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Diagnostic Performance of HPV E6/E7 mRNA and HPV DNA Assays for the Detection and Screening of Oncogenic Human Papillomavirus Infection among Woman with Cervical Lesions in China

  • Wang, Hye-young;Lee, Dongsup;Park, Sunyoung;Kim, Geehyuk;Kim, Sunghyun;Han, Lin;Yubo, Ren;Li, Yingxue;Park, Kwang Hwa;Lee, Hyeyoung
    • Asian Pacific Journal of Cancer Prevention
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    • v.16 no.17
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    • pp.7633-7640
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    • 2015
  • Background: Human papillomavirus (HPV) is the most common sexually transmitted infection worldwide and it is responsible for most cases of cervical uterine cancer. Although HPV infections of the cervix do not always progress to cancer, 90% of cervical cancer cases have been found to be associated with high risk HPV (HR-HPV) infection. HPV DNA testing is widely used, along with Papanicolaou (Pap) testing, to screen for cervical abnormalities. However, there are no data on the prevalence of genotype-specific HPV infections assessed by measuring HPV E6/E7 mRNA in women representative of the Chinese population across a broad age range. Materials and Methods: In the present study, we compared the results with the CervicGen HPV RT-qDx assay, which detects 16 HR-HPV genotypes (Alpha-9: HPV 16, 31, 33, 35, 52, and 58; Alpha-7: HPV 18, 39, 45, 51, 59, and 68; and Alpha-5, 6: HPV 53, 56, 66, and 69), and the REBA HPV-ID assay, which detects 32 HPV genotypes based on the reverse blot hybridization assay (REBA) for the detection of oncogenic HPV infection according to cytological diagnosis. We also investigated the prevalence and genotype distribution of HPV infection with a total of 324 liquid-based cytology samples collected in western Shandong province, East China. Results: The overall HPV prevalences determined by HPV DNA and HPV E6/E7 mRNA assays in this study were 79.9% (259/324) and 55.6% (180/324), respectively. Although the positivity of HPV E6/E7 mRNA expression was significantly lower than HPV DNA positivity, the HPV E6/E7 mRNA assay showed greater specificity than the HPV DNA assay (88.6% vs. 48.1%) in normal cytology samples. The prevalence of Alpha-9 (HPV 16, 31, 33, 35, 52, and 58) HPV infection among these women accounted for up to 80.3% and 76.1% of the high-grade lesions detected in the HPV mRNA and DNA tests, respectively. The HR-HPV genotype distribution, based on HPV DNA and E6/E7 mRNA expression by age group in patients with cytologically confirmed lesions, was highest in women aged 40 to 49 years (35.9% for cytologically confirmed cases, Pearson correlation r value=0.993, p<0.001) for high-grade lesions. Among the oncogenic HR-HPV genotypes for all age groups, there was little difference in the distribution of HPV genotypes between the HPV DNA (HPV -16, 53, 18, 58, and 33) and HPV E6/E7 mRNA (HPV -16, 53, 33, 58, and 18) assays. HPV 16 was the most common HPV genotype among women with high-grade lesions. Conclusions: Our results suggest that the HPV E6/E7 mRNA assay can be a sensitive and specific tool for the screening and investigation of cervical cancer. Furthermore, it may provide useful information regarding the necessity for early cervical cancer screenings and the development of additional effective HPV vaccines, such as one for HPV 53 and 58. Additionally, gaining knowledge of HPV distribution may also inform us about ecological changes in HPV after the vaccination.

A Survey on the Status of Noisy Working Environment in Manufacturing Industries (제조업 산업장의 소음 작업환경 실태에 관한 조사 연구)

  • Kim, Joon-Youn;Kim, Byung-Soo;Lee, Chae-Un;Jun, Jin-Ho;Lee, Jong-Tae;Kim, Jin-Ok
    • Journal of Preventive Medicine and Public Health
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    • v.19 no.1 s.19
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    • pp.16-30
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    • 1986
  • In order to prepare the fundamental data for the improvement of noisy working environments and the effective hearing conservation program on workers exposed to industrial noise, the authors surveyed the working processes and evaluated the noise levels on 56 manufacturing industries in Pusan area from April to July in 1985. The results were summarized as follows : 1. The noise level was the highest in shipbuilding and repairing(95.6 dBA), and followed by steel rolling(94.0 dBA), manufacture of motor vehicles(93.1 dBA), manufacture of fishing nets(92.9 dBA), manufacture of testiles(92.5 dBA), iron and steel foundries(89.3 dBA), manufacture of metal products(89.1 dBA), preserving and processing of marine foods(87.0 dBA), manufacture of rubber products(85.3 dBA), manufacture of plywood(84.9 dBA) and manufacture of paints(84.5 dBA). 2. Among fifty surveyed working processes, the noise level of twenty-one processes (42%) exceeded the threshold limit value for 8 hours per day. 3. As the allowable exposure times by governmental threshold limit values to industrial noise level(dBA), cocking of shipbuilding and repairing and plating(CGL) of steel rolling were the shortest(30 minutes), and followed by assembling(rivet) of manufacture of motor vehicles(1 hour) weaving of manufacture of textiles and shot, machine, pipe laying of shipbuilding and repairing(2 hours). 4. By the result of octave band analysis on noisy working processes in excess of 90 dBA, the sound level was the highest at 2,000 Hz or 4,000 Hz. 5. It was recognized that the measurement of overall sound pressure level was also effective as octave band analysis in evaluating the industrial noise.

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Investigations of the Potential Fisheries Resources in the Southern Waters of Korea - Biological Composition of Demersal Trawl Catches - (한국 남해안의 잠재어업자원 조사연구 - 저층크롤 어획량의 생물학적 조성 -)

  • Lee, Dae-Jae;Kim, Jin-Kun;Shin, Hyong-Ho
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.34 no.3
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    • pp.241-258
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    • 1998
  • The experimental demersal trawl surveys to provide the essential information for the assessment, management and utilization of commercially important fish stocks in the southern waters of Korea were carried out during five research cruises between October 1996 and October 1997 by the training ship “KAYA” of Pukyong National University. The biological sampling was conducted by using the trawl net with a cover net of 36 mm in mesh size at 64 planned trawl stations during daylight to identify the biological characteristics of fish. Each catch was standardized into catch per unit of time and the catches at each trawl station were sorted, weighed and counted by species. The changes in catches of each fish species and the shifts in dominant species by seasions and sampling regions in the research area were analyzed, and the abundance of fish was estimated from the relationship between the trawl catches and the volume of the water column sampled by demersal trawls. The results obtained can be summarized as follows : 1. During the 64 demersal trawls conducted in the southern waters of Korea, 129 species including 112 species of fishes, 8 species of Cephalopoda and 7 species of Crustacea, were identified Also, during the 1996 and 1997 trawl surveys in the reseach area, a large number of commercially important species with small differences in proportion was found. me proportion of Japanese horse mackerel which comprised 19.8% of the total catch by weight was highest, followed by chub mackerel(15.0%), swordtip squid(9.0%), redwing searobin(6.2%), konoshiro gizzard shad(6.1%), Japanese flying squid(5.8%), silver pomfet(5.1%), blackmouth goosefish(5.1%), etc. Swordtip squid, Japanese flying squid, blackmouth goosefish and blackthroat seaperch were among the dominant species in all seasons with a relatively high and stab1e proportion(3.6~9.0%), and were widely distributed in the entire southern water of Korea. 2. The catch rates by cover net varied at 0.7~91.9% by weight of the total trawl catch by codend and cover net at 64 planned trawl stations and the mean catch rate was 44.4%. Species comprising a major portion of the catches by cover net mainly were swordtip squid, konoshiro gizzard shad, the juveniles of Japanese horse mackerel, blackthroat seaperch and chub mackerel, etc. 3. The distribution density of fish in terms of biomass per unit volume which derived from the catch data by 63 bottom trawl hauls in the southern waters of Korea ranged from 17.9 $\times$ 10-6 to 1,440.9 $\times$ 10-6kg/m3 with the mean value of 153.8 $\times$ 10-6 kg/m3. These fish densities varied between seasons, location of sampling stations and sea conditions. From these results, it is worth noting that the catch composition of multispecies and the increased occurrence of small fish in the southern waters of Korea may also result in new problems in determining the total allowable catch(TAC) levels for economically important species.

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CT Based 3-Dimensional Treatment Planning of Intracavitary Brachytherapy for Cancer of the Cervix : Comparison between Dose-Volume Histograms and ICRU Point Doses to the Rectum and Bladder

  • Hashim, Natasha;Jamalludin, Zulaikha;Ung, Ngie Min;Ho, Gwo Fuang;Malik, Rozita Abdul;Ee Phua, Vincent Chee
    • Asian Pacific Journal of Cancer Prevention
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    • v.15 no.13
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    • pp.5259-5264
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    • 2014
  • Background: CT based brachytherapy allows 3-dimensional (3D) assessment of organs at risk (OAR) doses with dose volume histograms (DVHs). The purpose of this study was to compare computed tomography (CT) based volumetric calculations and International Commission on Radiation Units and Measurements (ICRU) reference-point estimates of radiation doses to the bladder and rectum in patients with carcinoma of the cervix treated with high-dose-rate (HDR) intracavitary brachytherapy (ICBT). Materials and Methods: Between March 2011 and May 2012, 20 patients were treated with 55 fractions of brachytherapy using tandem and ovoids and underwent post-implant CT scans. The external beam radiotherapy (EBRT) dose was 48.6Gy in 27 fractions. HDR brachytherapy was delivered to a dose of 21 Gy in three fractions. The ICRU bladder and rectum point doses along with 4 additional rectal points were recorded. The maximum dose ($D_{Max}$) to rectum was the highest recorded dose at one of these five points. Using the HDRplus 2.6 brachyhtherapy treatment planning system, the bladder and rectum were retrospectively contoured on the 55 CT datasets. The DVHs for rectum and bladder were calculated and the minimum doses to the highest irradiated 2cc area of rectum and bladder were recorded ($D_{2cc}$) for all individual fractions. The mean $D_{2cc}$ of rectum was compared to the means of ICRU rectal point and rectal $D_{Max}$ using the Student's t-test. The mean $D_{2cc}$ of bladder was compared with the mean ICRU bladder point using the same statistical test. The total dose, combining EBRT and HDR brachytherapy, were biologically normalized to the conventional 2 Gy/fraction using the linear-quadratic model. (${\alpha}/{\beta}$ value of 10 Gy for target, 3 Gy for organs at risk). Results: The total prescribed dose was $77.5Gy{\alpha}/{\beta}10$. The mean dose to the rectum was $4.58{\pm}1.22Gy$ for $D_{2cc}$, $3.76{\pm}0.65Gy$ at $D_{ICRU}$ and $4.75{\pm}1.01Gy$ at $D_{Max}$. The mean rectal $D_{2cc}$ dose differed significantly from the mean dose calculated at the ICRU reference point (p<0.005); the mean difference was 0.82 Gy (0.48-1.19Gy). The mean EQD2 was $68.52{\pm}7.24Gy_{{\alpha}/{\beta}3}$ for $D_{2cc}$, $61.71{\pm}2.77Gy_{{\alpha}/{\beta}3}$ at $D_{ICRU}$ and $69.24{\pm}6.02Gy_{{\alpha}/{\beta}3}$ at $D_{Max}$. The mean ratio of $D_{2cc}$ rectum to $D_{ICRU}$ rectum was 1.25 and the mean ratio of $D_{2cc}$ rectum to $D_{Max}$ rectum was 0.98 for all individual fractions. The mean dose to the bladder was $6.00{\pm}1.90Gy$ for $D_{2cc}$ and $5.10{\pm}2.03Gy$ at $D_{ICRU}$. However, the mean $D_{2cc}$ dose did not differ significantly from the mean dose calculated at the ICRU reference point (p=0.307); the mean difference was 0.90 Gy (0.49-1.25Gy). The mean EQD2 was $81.85{\pm}13.03Gy_{{\alpha}/{\beta}3}$ for $D_{2cc}$ and $74.11{\pm}19.39Gy_{{\alpha}/{\beta}3}$ at $D_{ICRU}$. The mean ratio of $D_{2cc}$ bladder to $D_{ICRU}$ bladder was 1.24. In the majority of applications, the maximum dose point was not the ICRU point. On average, the rectum received 77% and bladder received 92% of the prescribed dose. Conclusions: OARs doses assessed by DVH criteria were higher than ICRU point doses. Our data suggest that the estimated dose to the ICRU bladder point may be a reasonable surrogate for the $D_{2cc}$ and rectal $D_{Max}$ for $D_{2cc}$. However, the dose to the ICRU rectal point does not appear to be a reasonable surrogate for the $D_{2cc}$.

The Stakeholder's Response and Future of Mountain Community Development Program in Rep. of Korea (한국 산촌개발사업에 대한 이해관계자의 의식과 향후 발전방안)

  • Yoo, Byoung Il;Kim, So Heui;Seo, Jeong-Weon
    • Journal of Korean Society of Forest Science
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    • v.94 no.4 s.161
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    • pp.214-225
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    • 2005
  • The mountain village development program in Korea started in the mountain villages, the 45.9% of total land and one of the typical marginal region, from 1995 to achieve the equilibrium development of national land and the sustainable mountain development in Chapter 13 in Agenda 21, and it has been accelerated to increase the happiness and the quality of life of mountain community residents through the expansion by province and the improvement of related laws and regulations. This study has been aimed to analyze the response of main stakeholder's -mountain village residents and local government officials - on mountain villages development, and to provide the future plan as community development. The survey and interview data were collected from the mountain villages which already developed 59 villages and developing 15 villages in 2003. The mountain village development program has achieved the positive aspects as community development plan in the several fields, - the voluntary participation of residents, the establishment of self-support spirit as the democratic civilians, the development of base of income increasement, the creation of comfortable living environment, the equilibrium development with the other regions. Especially the mountain residents and local government officials both highly satisfy with the development of base of income increasement and the creation of comfortable living environment which are the main concerns to both stakeholder. However through the mountain development program, it is not satisfied to increase the maintenance of local community and the strengthening of traditional value of mountain villages. Also to improve the sustainable income improvement effects, it is necessary to develop the income items and technical extension which good for the each region. In the decentralization era, it is necessary for local government should have the more active and multilateral activities for these. With this, the introduction of methods which the mountain community people and the local government officials could co-participate in the mountain villages' development from the initial stages and the renovation of related local government organizations and the cooperatives will be much helpful to the substantiality of mountain development program. Also it is essential for the assistance of central government to establish the complex plan and the mountain villages network for all mountain area and the exchange of information, the education and training of mountain villages leader who are the core factor for the developed mountain villages maintenance, the composition of national mountain villages representatives. In case the development proposals which based on the interests of the main stakeholder's on mountain community could be positively accepted, then the possibility of the mountain village development as one of community development will be successfully improved in future.

Effect of Tuberculin Skin Test on Ex-vivo Interferon-gamma Assay for Latent Tuberculosis Infection (투베르쿨린 검사가 결핵에 대한 체외 IFN-γ 검사 결과에 미치는 영향)

  • Lee, Jung Yeon;Choi, Hee Jin;Cho, Sang-Nae;Park, I-Nae;Oh, Yeon-Mok;Lee, Sang Do;Kim, Woo Sung;Kim, Dong Soon;Kim, Won Dong;Shim, Tae Sun
    • Tuberculosis and Respiratory Diseases
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    • v.59 no.4
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    • pp.406-412
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    • 2005
  • Background : Recently, two commercialized whole-blood assays, $QuantiFERON^{(R)}-TB$ Gold (QFT) and T $SPOT-TB^{(R)}$ (SPOT), which measure the $IFN-{\gamma}$ released in the whole blood after being incubation with mycobacterial antigens, were approved for the diagnosis of a latent tuberculosis infection (LTBI). However, there is data on whether or not the previously used PPD skin tests (TST) have any influence on the diagnostic ability of these ex-vivo $IFN-{\gamma}$ assays. Methods : Forty-six 15 year-old students who did not appear to be infected with Mycobacterium tuberculosis were enrolled in this study. The peripheral blood was collected and used for two $IFN-{\gamma}$ assays. The $IFN-{\gamma}$ assays and TST were performed at the baseline ($1^{st}$). The TST was repeated two months later ($2^{nd}$), and the $IFN-{\gamma}$ assays were repeated two ($2^{nd}$) and four months ($3^{rd}$) later only in those subjects who had negative results at the baseline in both the $IFN-{\gamma}$ assays and TST. An induration size > 10 mm was considered to be positive in the TST. Results : The mean TST value was $3.1{\pm}5.4mm$ (range: 0-20). Of the 46 subjects examined, 13 subjects (28.3%) showed positive results in the two-step TST. Nine (19.6%) were SPOT-positive and only one (2.2%) was QFT-positive. The $2^{nd}$ and $3^{rd}$ QFT were carried out in 23 and 25 all-negative subjects, respectively, and all showed negative results. The $2^{nd}$ SPOT was performed in 23 subjects and only one (4.3%) showed a weak-positive result. Conclusion : Even though there were some discrepancies in the results of the two ex-vivo $IFN-{\gamma}$ assays, it appears that their results were not influenced by a previous TST carried out in two or four months earlier.

Polymerization of dual cured composites by different thickness (두께에 따른 이중 중합형 복합레진의 중합)

  • Kim, Yun-Ju;Jin, Myoung-Uk;Kim, Sung-Kyo;Kwon, Tae-Yub;Kim, Young-Kyung
    • Restorative Dentistry and Endodontics
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    • v.33 no.3
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    • pp.169-176
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    • 2008
  • The purpose of this study was to evaluate the effect of thickness, filling methods and curing methods on the polymerization of dual cured core materials by means of microhardness test. Two dual cured core materials, MultiCore Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein) and Bis-Core (Bisco Inc., Schaumburg, IL, USA) were used in this study. 2 mm (bulky filled), 4 mm (bulky filled), 6 mm (bulky and incrementally filled) and 8 mm (bulky and incrementally filled)-thickness specimens were prepared with light cure or self cure mode. After storage at $37{\circ}C$ for 24 hours, the Knoop hardness values (KHN) of top and bottom surfaces were measured and the microhardness ratio of top and bottom surfaces was calculated. The data were analyzed using one-way ANOVA and Scheffe multiple comparison test, with ${\alpha}$= 0.05. The effect of thickness on the polymerization of dual cured composites showed material specific results. In 2, 4 and 6 mm groups, the KHN of two materials were not affected by thickness. However, in 8 mm group of MultiCore Flow, the KHN of the bottom surface was lower than those of other groups (p < 0.05). The effect of filling methods on the polymerization of dual cured composites was different by their thickness or materials. In 6 mm thickness, there was no significant difference between bulk and incremental filling groups. In 8 mm thickness, Bis-Core showed no significant difference between groups. However, in MultiCore Flow, the microhardness ratio of bulk filling group was lower than that of incremental filling group (p < 0.05). The effect of curing methods on the polymerization of dual cured composites showed material specific results. In Bis-Core, the KHN of dual cured group were higher than those of self cured group at both surfaces (p < 0.05). However, in MultiCore Flow, the results were not similar at both surfaces. At the top surface, dual cured group showed higher KHN than that of self cured group (p < 0.05). However, in the bottom surface, dual cured group showed lower value than that of self cured group (p < 0.05).

Technical Efficiency in Korea: Interindustry Determinants and Dynamic Stability (기술적(技術的) 효율성(效率性)의 결정요인(決定要因)과 동태적(動態的) 변화(變化))

  • Yoo, Seong-min
    • KDI Journal of Economic Policy
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    • v.12 no.4
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    • pp.21-46
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    • 1990
  • This paper, a sequel to Yoo and Lee (1990), attempts to investigate the interindustry determinants of technical efficiency in Korea's manufacturing industries, and also to conduct an exploratory analysis on the stability of technical efficiency over time. The hypotheses set forth in this paper are most found in the existing literature on technical efficiency. They are, however, revised and shed a new light upon, whenever possible, to accommodate any Korea-specific conditions. The set of regressors used in the cross-sectional analysis are chosen and the hypotheses are posed in such a way that our result can be made comparable to those of similar studies conducted for the U.S. and Japan by Caves and Barton (1990) and Uekusa and Torii (1987), respectively. It is interesting to observe a certain degree of similarity as well as differentiation between the cross-section evidence on Korea's manufacturing industries and that on the U.S. and Japanese industries. As for the similarities, we can find positive and significant effects on technical efficiency of relative size of production and the extent of specialization in production, and negative and significant effect of the variations in capital-labor ratio within industries. The curvature influence of concentration ratio on technical efficiency is also confirmed in the Korean case. There are differences, too. We cannot find any significant effects of capital vintage, R&D and foreign competition on technical efficiency, all of which were shown to be robust determinants of technical efficiency in the U.S. case. We note, however, that the variables measuring capital vintage effect, R&D and the degree of foreign competition in Korean markets are suspected to suffer from serious measurement errors incurred in data collection and/or conversion of industrial classification system into the KSIC (Korea Standard Industrial Classification) system. Thus, we are reluctant to accept the findings on the effects of these variables as definitive conclusions on Korea's industrial organization. Another finding that interests us is that the cross-industry evidence becomes consistently strong when we use the efficiency estimates based on gross output instead of value added, which provides us with an ex post empirical criterion to choose an output measure between the two in estimating the production frontier. We also conduct exploratory analyses on the stability of the estimates of technical efficiency in Korea's manufacturing industries. Though the method of testing stability employed in this paper is never a complete one, we cannot find strong evidence that our efficiency estimates are stable over time. The outcome is both surprising and disappointing. We can also show that the instability of technical efficiency over time is partly explained by the way we constructed our measures of technical efficiency. To the extent that our efficiency estimates depend on the shape of the empirical distribution of plants in the input-output space, any movements of the production frontier over time are not reflected in the estimates, and possibilities exist of associating a higher level of technical efficiency with a downward movement of the production frontier over time, and so on. Thus, we find that efficiency measures that take into account not only the distributional changes, but also the shifts of the production frontier over time, increase the extent of stability, and are more appropriate for use in a dynamic context. The remaining portion of the instability of technical efficiency over time is not explained satisfactorily in this paper, and future research should address this question.

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