• Title/Summary/Keyword: Difference-in-differences analysis

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The Impact of Human Resource Innovativeness, Learning Orientation, and Their Interaction on Innovation Effect and Business Performance : Comparison of Small and Medium-Sized vs. Large-Sized Companies (인적자원의 혁신성, 학습지향성, 이들의 상호작용이 혁신효과 및 사업성과에 미치는 영향 : 중소기업과 대기업의 비교연구)

  • Yoh, Eunah
    • Korean small business review
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    • v.31 no.2
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    • pp.19-37
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    • 2009
  • The purpose of this research is to explore differences between small and medium-sized companies and large-sized companies in the impact of human resource innovativeness(HRI), learning orientation(LO), and HRI-LO interaction on innovation effect and business performance. Although learning orientation has long been considered as a key factor influencing good performance of a business, little research was devoted to exploring the effect of HRI-LO interaction on innovation effect and business performance. In this study, it is investigated whether there is a synergy effect between innovative human workforce and learning orientation corporate culture, in addition to each by itself, to generate good business performance as well as a success of new innovations in the market. Research hypotheses were as follows, including H1) human resource innovativeness(HRI), learning orientation(LO), and interactions of HRI and LO(HRI-LO interaction) positively affect innovation effect, H2) there is a difference of the effect of HRI, LO, and HRI-LO interaction on innovation effect between large-sized and small-sized companies, H3) HRI, LO, HRI-LO interaction, innovation effect positively affect business performance, and H4) there is a difference of the effect of HRI, LO, HRI-LO interaction, and innovation effect on business performance between large-sized and small-sized companies. Data were obtained from 479 practitioners through a web survey since the web survey is an efficient method to collect a national data at a variety of fields. A single respondent from a company was allowed to participate in the study after checking whether they have more than 5-year work experiences in the company. To check whether a common source bias is existed in the sample, additional data from a convenient sample of 97 companies were gathered through the traditional survey method, and were used to confirm correlations between research variables of the original sample and the additional sample. Data were divided into two groups according to company size, such as 352 small and medium-sized companies with less than 300 employees and 127 large-sized companies with 300 or more employees. Data were analyzed through t-test and regression analyses. HRI which is the innovativeness of human resources in the company was measured with 9 items assessing the innovativenss of practitioners in staff, manager, and executive-level positions. LO is the company's effort to encourage employees' development, sharing, and utilizing of knowledge through consistent learning. LO was measured by 18 items assessing commitment to learning, vision sharing, and open-mindedness. Innovation effect which assesses a success of new products/services in the market, was measured with 3 items. Business performance was measured by respondents' evaluations on profitability, sales increase, market share, and general business performance, compared to other companies in the same field. All items were measured by using 6-point Likert scales. Means of multiple items measuring a construct were used as variables based on acceptable reliability and validity. To reduce multi-collinearity problems generated on the regression analysis of interaction terms, centered data were used for HRI, LO, and Innovation effect on regression analyses. In group comparison, large-sized companies were superior on annual sales, annual net profit, the number of new products/services in the last 3 years, the number of new processes advanced in the last 3 years, and the number of R&D personnel, compared to small and medium-sized companies. Also, large-sized companies indicated a higher level of HRI, LO, HRI-LO interaction, innovation effect and business performance than did small and medium-sized companies. The results indicate that large-sized companies tend to have more innovative human resources and invest more on learning orientation than did small-sized companies, therefore, large-sized companies tend to have more success of a new product/service in the market, generating better business performance. In order to test research hypotheses, a series of multiple-regression analysis was conducted. In the regression analysis examining the impact on innovation effect, important results were generated as : 1) HRI, LO, and HRI-LO affected innovation effect, and 2) company size indicated a moderating effect. Based on the result, the impact of HRI on innovation effect would be greater in small and medium-sized companies than in large-sized companies whereas the impact of LO on innovation effect would be greater in large-sized companies than in small and medium-sized companies. In other words, innovative workforce would be more important in making new products/services that would be successful in the market for small and medium-sized companies than for large-sized companies. Otherwise, learning orientation culture would be more effective in making successful products/services for large-sized companies than for small and medium-sized companies. Based on these results, research hypotheses 1 and 2 were supported. In the analysis of a regression examining the impact on business performance, important results were generated as : 1) innovation effect, LO, and HRI-LO affected business performance, 2) HRI by itself did not have a direct effect on business performance regardless of company size, and 3) company size indicated a moderating effect. Specifically, an effect of the HRI-LO interaction on business performance was stronger in large-sized companies than in small and medium-sized companies. It means that the synergy effect of innovative human resources and learning orientation culture tends to be stronger as company is larger. Referring to these result, research hypothesis 3 was partially supported whereas hypothesis 4 was supported. Based on research results, implications for companies were generated. Regardless of company size, companies need to develop the learning orientation corporate culture as well as human resources' innovativeness together in order to achieve successful development of innovative products and services as well as to improve sales and profits. However, the effectiveness of the HRI-LO interaction would be varied by company size. Specifically, the synergy effect of HRI-LO was stronger to make a success of new products/services in small and medium-sized companies than in large-sized companies. However, the synergy effect of HRI-LO was more effective to increase business performance of large-sized companies than that of small and medium-sized companies. In the case of small and medium-sized companies, business performance was achieved more through the success of new products/services than much directly affected by HRI-LO. The most meaningful result of this study is that the effect of HRI-LO interaction on innovation effect and business performance was confirmed. It was often ignored in the previous research. Also, it was found that the innovativeness of human workforce would not directly influence in generating good business performance, however, innovative human resources would indirectly affect making good business performance by contributing to achieving the development of new products/services that would be successful in the market. These findings would provide valuable managerial implications specifically in regard to the development of corporate culture and education program of small and medium-sized as well as large-sized companies in a variety of fields.

Individual Thinking Style leads its Emotional Perception: Development of Web-style Design Evaluation Model and Recommendation Algorithm Depending on Consumer Regulatory Focus (사고가 시각을 바꾼다: 조절 초점에 따른 소비자 감성 기반 웹 스타일 평가 모형 및 추천 알고리즘 개발)

  • Kim, Keon-Woo;Park, Do-Hyung
    • Journal of Intelligence and Information Systems
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    • v.24 no.4
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    • pp.171-196
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    • 2018
  • With the development of the web, two-way communication and evaluation became possible and marketing paradigms shifted. In order to meet the needs of consumers, web design trends are continuously responding to consumer feedback. As the web becomes more and more important, both academics and businesses are studying consumer emotions and satisfaction on the web. However, some consumer characteristics are not well considered. Demographic characteristics such as age and sex have been studied extensively, but few studies consider psychological characteristics such as regulatory focus (i.e., emotional regulation). In this study, we analyze the effect of web style on consumer emotion. Many studies analyze the relationship between the web and regulatory focus, but most concentrate on the purpose of web use, particularly motivation and information search, rather than on web style and design. The web communicates with users through visual elements. Because the human brain is influenced by all five senses, both design factors and emotional responses are important in the web environment. Therefore, in this study, we examine the relationship between consumer emotion and satisfaction and web style and design. Previous studies have considered the effects of web layout, structure, and color on emotions. In this study, however, we excluded these web components, in contrast to earlier studies, and analyzed the relationship between consumer satisfaction and emotional indexes of web-style only. To perform this analysis, we collected consumer surveys presenting 40 web style themes to 204 consumers. Each consumer evaluated four themes. The emotional adjectives evaluated by consumers were composed of 18 contrast pairs, and the upper emotional indexes were extracted through factor analysis. The emotional indexes were 'softness,' 'modernity,' 'clearness,' and 'jam.' Hypotheses were established based on the assumption that emotional indexes have different effects on consumer satisfaction. After the analysis, hypotheses 1, 2, and 3 were accepted and hypothesis 4 was rejected. While hypothesis 4 was rejected, its effect on consumer satisfaction was negative, not positive. This means that emotional indexes such as 'softness,' 'modernity,' and 'clearness' have a positive effect on consumer satisfaction. In other words, consumers prefer emotions that are soft, emotional, natural, rounded, dynamic, modern, elaborate, unique, bright, pure, and clear. 'Jam' has a negative effect on consumer satisfaction. It means, consumer prefer the emotion which is empty, plain, and simple. Regulatory focus shows differences in motivation and propensity in various domains. It is important to consider organizational behavior and decision making according to the regulatory focus tendency, and it affects not only political, cultural, ethical judgments and behavior but also broad psychological problems. Regulatory focus also differs from emotional response. Promotion focus responds more strongly to positive emotional responses. On the other hand, prevention focus has a strong response to negative emotions. Web style is a type of service, and consumer satisfaction is affected not only by cognitive evaluation but also by emotion. This emotional response depends on whether the consumer will benefit or harm himself. Therefore, it is necessary to confirm the difference of the consumer's emotional response according to the regulatory focus which is one of the characteristics and viewpoint of the consumers about the web style. After MMR analysis result, hypothesis 5.3 was accepted, and hypothesis 5.4 was rejected. But hypothesis 5.4 supported in the opposite direction to the hypothesis. After validation, we confirmed the mechanism of emotional response according to the tendency of regulatory focus. Using the results, we developed the structure of web-style recommendation system and recommend methods through regulatory focus. We classified the regulatory focus group in to three categories that promotion, grey, prevention. Then, we suggest web-style recommend method along the group. If we further develop this study, we expect that the existing regulatory focus theory can be extended not only to the motivational part but also to the emotional behavioral response according to the regulatory focus tendency. Moreover, we believe that it is possible to recommend web-style according to regulatory focus and emotional desire which consumers most prefer.

A Study on the Stress Distribution of Condylar Region and Edentulous Mandible with Implant-Supported Cantilever Fixed Prostheses by using 3-Dimensional Finite Element Method (임플란트 지지 캔틸레버 고정성 보철물 장착시 과두와 하악골의 응력 분포에 관한 3차원 유한요소법적 연구)

  • Kim, Yeon-Soo;Lee, Sung-Bok
    • Journal of Dental Rehabilitation and Applied Science
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    • v.17 no.4
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    • pp.283-305
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    • 2001
  • The purpose of this study was to analyze the stress distribution of condylar regions and edentulous mandible with implant-supported cantilever prostheses on the certain conditions, such as amount of load, location of load, direction of load, fixation or non-fixation on the condylar regions. Three dimensional finite element analysis was used for this study. FEM model was created by using commercial software, ANSYS(Swanson, Inc., U.S.A.). Fixed model which was fixed on the condylar regions was modeled with 74323 elements and 15387 nodes and spring model which was sprung on the condylar regions was modeled with 75020 elements and 15887 nodes. Six Br${\aa}$nemark implants with 3.75 mm diameter and 13 mm length were incorporated in the models. The placement was 4.4 mm from the midline for the first implant; the other two in each quardrant were 6.5 mm apart. The stress distribution on each model through the designed mandible was evaluated under 500N vertical load, 250N horizontal load linguobuccally, buccal 20 degree 250N oblique load and buccal 45 degree 250N oblique load. The load points were at 0 mm, 10 mm, 20 mm along the cantilever prostheses from the center of the distal fixture. The results were as follows; 1. The stress distribution of condylar regions between two models showed conspicuous differences. Fixed model showed conspicuous stress concentration on the condylar regions than spring model under vertical load only. On the other hand, spring model showed conspicuous stress concentration on the condylar regions than fixed model under 250N horizontal load linguobuccally, buccal 20 degree 250N oblique load and buccal 45 degree 250N oblique load. 2. Fixed model showed stress concentration on the posterior and mesial side of working and balancing condylar necks but spring model showed stress concentration on the posterior and mesial side of working condylar neck and the posterior and lateral side of balancing condylar neck under vertical load. 3. Fixed model showed stress concentration on the posterior and lateral side of working condylar neck and the anterior and mesial side of balancing condylar neck but spring model showed stress concentration on the anterior sides of working and balancing condylar necks under horizontal load linguobuccally. 4. Fixed model showed stress concentration on the posterior side of working condylar neck and the posterior and lateral side of balancing condylar neck but spring model showed stress concentration on the anterior side of working condylar neck and the anterior and lateral side of balancing condylar neck under buccal 20 degree oblique load. 5. Fixed model showed stress concentration on the anterior and lateral side of working condylar neck and the posterior and mesial side of balancing condylar neck but spring model showed stress concentration on the anterior side of working condylar neck and the anterior and lateral side of balancing condylar neck under buccal 45 degree oblique load.. 6. The stress distribution of bone around implants between two models revealed difference slightly. In general, magnitude of Von Mises stress was the greatest at the bone around the most distal implant and the progressive decrease more and more mesially. Under vertical load, the stress values were similar between implant neck and superstructure vertically, besides the greatest on the distal side horizontally. 7. Under horizontal load linguobuccally, buccal 20 degree oblique load and buccal 45 degree oblique load, the stress values were the greatest on the implant neck vertically, and great on the labial and lingual sides horizontally. After all, it was considered that spring model was an indispensable condition for the comprehension of the stress distributions of condylar regions.

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The effects of polishing technique and brushing on the surface roughness of acrylic resin (연마 방법과 칫솔질이 아크릴릭 레진의 표면 거칠기에 미치는 영향)

  • Lee, Ju-Ri;Jeong, Cheol-Ho;Choi, Jung-Han;Hwang, Jae-Woong;Lee, Dong-Hwan
    • The Journal of Korean Academy of Prosthodontics
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    • v.48 no.4
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    • pp.287-293
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    • 2010
  • Purpose: This study evaluated the effect of polishing techniques on surface roughness of polymethyl methacrylate (PMMA), as well as the influence of light-cured surface glaze and subsequent brushing on surface roughness. Materials and methods: A total of 60 PMMA specimens ($10{\times}10{\times}5\;mm$) were made and then divided into 6 groups of 10 each according to the polymerization methods (under pressure or atmosphere) and the surface polishing methods (mechanical or chemical polishing) including 2 control groups. The mechanical polishing was performed with the carbide denture bur, rubber points and then pumice and lathe wheel. The chemical polishing was performed by applying a light-cured surface glaze ($Plaquit^{(R)}$; Dreve-Dentamid GmbH). Accura $2000^{(R)}$, a non-contact, non-destructive, optical 3-dimensional surface analysis system, was used to measure the surface roughness (Ra) and 3-dimensional images were acquired. The surface roughness was again measured after ultrasonic tooth brushing in order to evaluate the influence of brushing on the surface roughness. The statistical analysis was performed with Mann-Whitney test and t-test using a 95% level of confidence. Results: The chemically polished group showed a statistically lower mean surface roughness in comparison to the mechanically polished group (P = .0045) and the specimens polymerized under the atmospheric pressure presented a more significant difference (P = .0138). After brushing, all of the groups, except the mechanically polished group, presented rougher surfaces and showed no statistically significant differences between groups. Conclusion: Although the surface roughness increased after brushing, the chemical polishing technique presented an improved surface condition in comparison to the mechanical polishing technique.

Changes of the Clinicopathological Characteristics and Survival Rates of Gastric Cancer with Gastrectomy - 1990s vs early 2000s (위절제 위암 환자의 임상병리학적 특성과 생존율의 변화: 1990년대와 2000년대 초기의 비교)

  • Sim, Young-Kwan;Kim, Chan-Young;Jeong, Yeon-Jun;Kim, Jong-Hun;Hwang, Yong;Yang, Doo-Hyun
    • Journal of Gastric Cancer
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    • v.9 no.4
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    • pp.200-206
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    • 2009
  • Purpose: The incidence of upper gastric cancer and especially the diffuse type have increased in western countries. The aim this study was to investigate the chronologic changes of the clinicopathological features and survival rates of Korean upper gastric cancer patients. Materials and Methods: 1,638 gastric cancer patients who underwent gastrectomy were included in this study and they were divided into two groups; the 1990's (1991~1999, n=987) and the early 2000's (2000~2003, n=651). We evaluated the differences of the clinicopathologic features and the factors that affected the survival rates by univariative and multivariative analysis. Results: The older age (>60) patients increased from 42.7% to 50.7% respectively. Being overweight (body mass index$\geq$23) also increased from 31.5% to 43.2%. For the pathology, the incidence of stage Ia gastric cancer increased (29.8% to 44.5%) and the incidence of stage IV gastric cancer decreased (23.5% to 11.8%). Yet there was no difference according to the WHO classification, Lauren's classification and the location of tumor between the groups. The 5 year survival rates increased 67.7% to 83.7%, according to the group. Multivariative analysis showed that the odd ratios of the early 2000s was 0.715 (95% CI; 0.555~0.921) as compared to that of the 1990s. Conclusion: There were no changes of the clinicopathologic features, like the pattern in western countries, although the incidence early gastric cancer, old age patients and overweight patients increased. The survival rate of early 2000s was better that that of the 1990s.

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Inter Simple Sequence Repeats (ISSR) Marker Analysis of Genetic Diversity in Korean Phasianus colchicus karpowi and Genetic Relationships Among Subspecies of Phasianus spp. (Inter Simple Sequence Repeats (ISSR) 표지자를 이용한 한국꿩의 유전적 다양성 및 아종간의 유연관계 분석)

  • Yoon, Seong-Il
    • Korean Journal of Environmental Biology
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    • v.26 no.2
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    • pp.66-75
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    • 2008
  • The level of genetic diversity and genetic relationships among Korean ring-necked pheasant (Phasianus colchicus karpowi) habitat and subspecies have been investigated based on Inter Simple Sequence Repeat (ISSR) markers. Wild and domesticated Korean ring-necked pheasant, hybrids between domesticated Korean ring-necked and foreign subspecies, and four foreign subspecies; Chinese ring-necked (P. c. torquatus), Melanistic mutant (P. c. mut. tenebrosus), XL White (P. c. mut) and Southern green (P. c. versicolor) were used for comparison. On the basis of the results of AMOV A, 94.08% of genetic diversity in Korean ring-necked was allocated among individuals within habitat differences. Estimate of $\Phi$st, which represents the degree of genetic differentiation among habitats was 5.9%. Based on the dendrogram reconstructed by UPGMA, Yangpyung habitat of the eight habitats turned out to be distinct from others habitat. Interestingly, domesticated Korean ring-necked and hybrid mixture showed closer genetic relationship with four foreign subspecies than Korean ring-necked. As a consequence of AMOVA, 96.63% of genetic diversity in four foreign subspecies was allocated among individuals within subspecies. Estimate of $\Phi$st representing the degree of genetic differentiation among subspecies was 3.4%, which was lower than that among habitats of Korean ring-necked. The lower level of genetic difference among four foreign subspecies showed that these subspecies were genetically closer even though they were morphologically classified into four different subspecies. When seven habitats of Korean ring-necked pheasant and four foreign subspecies were divided into Korean and Foreign Pheasant Groups, respectively, more than 17% of genetic diversity was allocated between groups (about 4% among habitats/subspecies within groups). This observation implied that Korean ring-necked pheasant is genetically quite different from four foreign subspecies. On the basis of cluster analysis, three foreign subspecies (Chinese ring-necked pheasant, Melanistic mutant pheasant, and XL White pheasant) formed a distinct group with domesticated Korean ring-necked pheasant and hybrid mixture at 98% confidence interval.

Relationships between Eating Behavior, Dietary Self-Efficacy, and Nutrition Knowledge of Elementary School Students by Food Service Type in Gangwon Province (강원지역 초등학생들의 급식유형(도시형, 농어촌형 및 도서벽지형) 별식행동과 식이자기효능감 및 영양지식과의 관계)

  • Won, Hyang-Rye;Shin, Gi-Beum
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.41 no.5
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    • pp.638-646
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    • 2012
  • The purpose of this study was to find a relationship between eating behavior, dietary self-efficacy and nutrition knowledge by comparing these items in elementary school students according to food service type. The survey was made through a questionnaire from 759 students in the 6th grade of elementary school in 39 Gangwon Province. The average score of eating behaviors according to food service type was highest for urban type, followed by agri-fishery type, and finally remote island and country type, for the questions asking about the application of nutrition knowledge and the frequency of eating out. The average score of nutrition knowledge according to food service type showed significant differences for the questions about eating snacks before going to sleep and weight increase as well as calorie comparisons between foods. For the correlation of eating behavior, dietary self-efficacy and nutrition knowledge, the agri-fishery type showed positive in all of the three items with significant differences. In the remote island and country type, there was a positive relationship between nutrition knowledge and dietary self-efficacy, and between eating behavior and dietary self-efficacy. However, there was no significant difference of correlation between nutrition knowledge and eating behavior. In order to confirm the predictable variables for eating behavior, a regression analysis was made by injecting variables in every stage with independent variables of dietary self-efficacy and nutrition knowledge, which showed a significant relationship with eating behavior. The results showed that, in the urban type, dietary self-efficacy and nutrition knowledge affected the eating behavior and, in the agriculture type and the remote island and country type, only dietary self-efficacy affected the eating behavior.

Leukocyte count and hypertension in the health screening data of some rural and urban residents (일부 농촌과 도시의 건강선별조사 자료로 본 백혈구수와 고혈압과의 관계)

  • Lee, Choong-Won;Yoon, Nung-Ki;Lee, Sung-Kwan
    • Journal of Preventive Medicine and Public Health
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    • v.24 no.3 s.35
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    • pp.363-372
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    • 1991
  • We used the health screening data of some rural and urban residents to examine the cross-sectional association between leukocyte count and hypertension. The 206 male and 203 female rural residents were selected by multi-stage cluster sampling method in Kyungsan-Kun area of Kyungbuk province in 1985 and 600 urban residents were selected by the same sampling method as the rural residents in Daegu city of the same province in 1986 compatible with age-sex distribution of Daegu city of 1985 census, but of whom 384 actually responded. The rest of 600 were replaced by age and sex with those who were members of the medical insurance plan visiting the health management department of the university hospital to get the biannual preventive medical checkups. Excluded in the analysis were those having hypertensive history, diseases and extreme outlying values of the screening tests, leaving 373 rural and 571 urban residents. Leukocyte count was measured with ELT-8 Laser shadow method and the unit $cells/mm^3$, Blood pressures were determined with an aneroid sphygmomanometer with pre-standardized method and hypertensives were defined as those showing systolic blood pressure more than 140mmHg and/or diastolic blood pressure more than 90mmHg. Total residents pooled (N=944) showed a significant difference between hypertensives and normotensives ($6965.93{\pm}1997.01\;vs\;6490.61{\pm}1941.32,\;P=0.00$) and in rural residents was noted the similar significant difference (P=0.03). None of significant differences were noted in any stratum stratified by residency and sex. Compared to the lowest quintile of WBC, 2/5 quintile showed odds ratio 0.99 (95% Confidence interval, Ci 0.62-1.59), 3/5 quintile 1.41 (95% CI 0.90-2.21), 4/5 quintile 1.76 (95% CI. 1.14-2.72), and highest quintile 1.80 (1.15-2.82) in the total residents. Likelihood ratio test for linear trend for it indicated a significant trend ($X^2_{trend}=5.53,\;df=1,\;P<0.05$). There were no other significant odds ratios compared to the lowest quintile of WBC in strata stratified by residency and sex. The odds ratios in total residents which had showed significant odds ratios became nonsignificant and of reduced magnitude after controlling age, frequency of smoking and drinking with multiple logistic. regression. In each stratum, it changed magnitudes of odds ratios slightly and unstably. None of the trend tests showed any significant trend. These results suggest that the Friedman et al's finding of association between leukocyte count and hypertension may be due to an statistical type I error resulting from the data dredging in an exploratory study, in which more than 800 variables were screened as possible predictors of hypertension.

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Influence of Microcrack on Brazilian Tensile Strength of Jurassic Granite in Hapcheon (미세균열이 합천지역 쥬라기 화강암의 압열인장강도에 미치는 영향)

  • Park, Deok-Won;Kim, Kyeong-Su
    • Korean Journal of Mineralogy and Petrology
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    • v.34 no.1
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    • pp.41-56
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    • 2021
  • The characteristics of the six rock cleavages(R1~H2) in Jurassic Hapcheon granite were analyzed using the distribution of ① microcrack lengths(N=230), ② microcrack spacings(N=150) and ③ Brazilian tensile strengths(N=30). The 18 cumulative graphs for these three factors measured in the directions parallel to the six rock cleavages were mutually contrasted. The main results of the analysis are summarized as follows. First, the frequency ratio(%) of Brazilian tensile strength values(kg/㎠) divided into nine class intervals increases in the order of 60~70(3.3) < 140~150(6.7) < 100~110·110~120(10.0) < 90~100(13.3) < 80~90(16.7) < 120~130·130~140(20.0). The distribution curve of strength according to the frequency of each class interval shows a bimodal distribution. Second, the graphs for the length, spacing and tensile strength were arranged in the order of H2 < H1 < G2 < G1 < R2 < R1. Exponent difference(λS-λL, Δλ) between the two graphs for the spacing and length increases in the order of H2(-1.59) < H1(-0.02) < G2(0.25) < G1(0.63) < R2(1.59) < R1(1.96)(2 < 1). From the related chart, the six graphs for the tensile strength move gradually to the left direction with the increase of the above exponent difference. The negative slope(a) of the graphs for the tensile strength, suggesting a degree of uniformity of the texture, increases in the order of H((H1+H2)/2, 0.116) < G((G1+G2)/2, 0.125) < R((R1+R2)/2, 0.191). Third, the order of arrangement between the two graphs for the two directions that make up each rock cleavage(R1·R2(R), G1·G2(G), H1·H2(H)) were compared. The order of arrangement of the two graphs for the length and spacing is reverse order with each other. The two graphs for the spacing and tensile strength is mutually consistent in the order of arrangement. The exponent differences(ΔλL and ΔλS) for the length and spacing increase in the order of rift(R, -0.08) < grain(G, 0.14) < hardway(H, 0.75) and hardway(H, 0.16) < grain(G, 0.23) < rift(R, 0.45), respectively. Fourth, the general chart for the six graphs showing the distribution characteristics of the microcrack lengths, microcrack spacings and Brazilian tensile strengths were made. According to the range of length, the six graphs show orders of G2 < H2 < H1 < R2 < G1 < R1(< 7 mm) and G2 < H1 < H2 < R2 < G1 < R1(≦2.38 mm). The six graphs for the spacing intersect each other by forming a bottleneck near the point corresponding to the cumulative frequency of 12 and the spacing of 0.53 mm. Fifth, the six values of each parameter representing the six rock cleavages were arranged in the order of increasing and decreasing. Among the 8 parameters related to the length, the total length(Lt) and the graph(≦2.38 mm) are mutually congruent in order of arrangement. Among the 7 parameters related to the spacing, the frequency of spacing(N), the mean spacing(Sm) and the graph (≦5 mm) are mutually consistent in order of arrangement. In terms of order of arrangement, the values of the above three parameters for the spacing are consistent with the maximum tensile strengths belonging to group E. As shown in Table 8, the order of arrangement of these parameter values is useful for prior recognition of the six rock cleavages and the three quarrying planes.

Effect of Different Fertilization Management Practices on Soil Microbial Activities and Community Structure in Volcanic Ash Citrus Orchard Soil (화산회토 감귤원 토양의 시비관리가 토양미생물활성 및 군집구조에 미치는 영향)

  • Joa, Jae-Ho;Han, Seung-Gap;Won, Hang-Yeon;Lim, Han-Cheol;Hyun, Hae-Nam;Suh, Jang-Sun
    • Korean Journal of Soil Science and Fertilizer
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    • v.42 no.3
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    • pp.222-229
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    • 2009
  • This study was performed to evaluate effect of different fertilization management practices on soil microbial activities and community structure using soil enzyme activities and PLFA contents in volcanic ash citrus orchard soil. Six experiment plots have differently managed based on the recommended application rate(NPK) of chemical fertilizer and compost for 13 years. Experiment plots were composed of no-fertilization(control), compost only, half amount of NPK with compost (1/2NPK+COM), NPK, NPK with compost(NPK+COM), and 3 times amount of NPK(3NPK). Soil samples collected in early March, May, July, and September 2007. Urease activity was high at NPK+COM in March, May, and September. It was higher in NPK+COM than in NPK. Urease activity decreased according to the order NPK>compost>control in March and May; compost>NPK>control in July and September. Dehydrogenase activity was significantly higher in 1/2NPK+COM($4.3ug\;TPF\;g^{-1}\;24h^{-1}$) than in control($2.4ug\;TPF\;g^{-1}\;24h^{-1}$), May. $\beta$-glucosidase activity was significantly higher in NPK and 1/2NPK+COM than in control, May. In March, Total PLFA contents were higher in NPK+COM($349.2n\;mol\;g^{-1}$) than in 3NPK($228.5n\;mol\;g^{-1}$). And that were higher in 1/2NPK+COM($237.8n\;mol\;g^{-1}$) than in 3NPK($133.1n\;mol\;g^{-1}$), May. Distribution ratio of soil microbial groups by PLFA biomaker were not significantly difference in between seasonal and treatments. Principal component analysis by PLFA profiles showed that microbial community in compost and 3NPK plot were different compared with other treatments in March. But Differences in compost and 3NPK plot were not found in May. Our result showed that the change of microbial community structure affected by fertilization effect and seasonable variation.