• Title/Summary/Keyword: Hypothesis Test

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The Analysis on the Relationship between Firms' Exposures to SNS and Stock Prices in Korea (기업의 SNS 노출과 주식 수익률간의 관계 분석)

  • Kim, Taehwan;Jung, Woo-Jin;Lee, Sang-Yong Tom
    • Asia pacific journal of information systems
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    • v.24 no.2
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    • pp.233-253
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    • 2014
  • Can the stock market really be predicted? Stock market prediction has attracted much attention from many fields including business, economics, statistics, and mathematics. Early research on stock market prediction was based on random walk theory (RWT) and the efficient market hypothesis (EMH). According to the EMH, stock market are largely driven by new information rather than present and past prices. Since it is unpredictable, stock market will follow a random walk. Even though these theories, Schumaker [2010] asserted that people keep trying to predict the stock market by using artificial intelligence, statistical estimates, and mathematical models. Mathematical approaches include Percolation Methods, Log-Periodic Oscillations and Wavelet Transforms to model future prices. Examples of artificial intelligence approaches that deals with optimization and machine learning are Genetic Algorithms, Support Vector Machines (SVM) and Neural Networks. Statistical approaches typically predicts the future by using past stock market data. Recently, financial engineers have started to predict the stock prices movement pattern by using the SNS data. SNS is the place where peoples opinions and ideas are freely flow and affect others' beliefs on certain things. Through word-of-mouth in SNS, people share product usage experiences, subjective feelings, and commonly accompanying sentiment or mood with others. An increasing number of empirical analyses of sentiment and mood are based on textual collections of public user generated data on the web. The Opinion mining is one domain of the data mining fields extracting public opinions exposed in SNS by utilizing data mining. There have been many studies on the issues of opinion mining from Web sources such as product reviews, forum posts and blogs. In relation to this literatures, we are trying to understand the effects of SNS exposures of firms on stock prices in Korea. Similarly to Bollen et al. [2011], we empirically analyze the impact of SNS exposures on stock return rates. We use Social Metrics by Daum Soft, an SNS big data analysis company in Korea. Social Metrics provides trends and public opinions in Twitter and blogs by using natural language process and analysis tools. It collects the sentences circulated in the Twitter in real time, and breaks down these sentences into the word units and then extracts keywords. In this study, we classify firms' exposures in SNS into two groups: positive and negative. To test the correlation and causation relationship between SNS exposures and stock price returns, we first collect 252 firms' stock prices and KRX100 index in the Korea Stock Exchange (KRX) from May 25, 2012 to September 1, 2012. We also gather the public attitudes (positive, negative) about these firms from Social Metrics over the same period of time. We conduct regression analysis between stock prices and the number of SNS exposures. Having checked the correlation between the two variables, we perform Granger causality test to see the causation direction between the two variables. The research result is that the number of total SNS exposures is positively related with stock market returns. The number of positive mentions of has also positive relationship with stock market returns. Contrarily, the number of negative mentions has negative relationship with stock market returns, but this relationship is statistically not significant. This means that the impact of positive mentions is statistically bigger than the impact of negative mentions. We also investigate whether the impacts are moderated by industry type and firm's size. We find that the SNS exposures impacts are bigger for IT firms than for non-IT firms, and bigger for small sized firms than for large sized firms. The results of Granger causality test shows change of stock price return is caused by SNS exposures, while the causation of the other way round is not significant. Therefore the correlation relationship between SNS exposures and stock prices has uni-direction causality. The more a firm is exposed in SNS, the more is the stock price likely to increase, while stock price changes may not cause more SNS mentions.

A study of the impact of using a nursing care standards on the quality of nursing care in gastrectomy patients (위절제술환자의 간호실무표준 사용이 간호의 질에 미치는 영향)

  • Woo, Young-Ja
    • Journal of Korean Academy of Nursing Administration
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    • v.2 no.2
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    • pp.97-107
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    • 1996
  • Nursing standards determine the type and extent of services that are delivered to the patients and define quality care and communicate the institution's expectations of care. Thus, taking the standard of care and incorporating it into a welldefined indicator of excellent patient care becomes one of the first activities in setting up the nursing service's quality assurance process. The purpose of this study was to determine the impact of using a nursing care standards for the quality of nursing care in gastrectomy patients. The subjects were composed of fourty-two under going gastrectomy patients with stomach cancer in general surgery nursing care unit of K University Hospital in Pusan. The data was collected from January 3 to April 13,1996. The subjects were divided into a control group - those admitted from Jan.3 to Feb.12 and an experimental group those admitted from Feb.18 to April 13. The instruments used for this study were a nursing care standards in gastrectomy patients developed by the investigator and an evaluation tool for the quality of nursing care in abdominal surgery patients developed by Byoung-Sook Lee in 1995. The data was analized by means of chi-square test, t-test and Cronbach-alpha test with the SAS System. The result was as follows : The hypothesis, that scores of the quality of nursing care in the experimental group would be higher than that of the control group. was supported(t=-6.12, p=0.00). The detailed results of each standards of evaluation tool were as follows : The mean score of the experimental group was significantly higher than that of the control group in audit standard 1:'Collection of basic data of the patients', (t=-3.76, p=0.00). The mean score of the experimental group was significantly higher than that of the control group in audit standard 2 : 'Defining nursing diagnoses(or nursing problems)', (t= (-), p= (-) ). The mean score of the experimental group was significantly higher than that of the control group in audit standard 3:'Estabilishment of nursing care plan according to nursing diagnoses(or nursing problems)',(t= (-), p= (-) ). The mean score of the experimental group was significantly higher than that of the control group in audit stndard 4:'Implimentation of nursing care plan', (t=-2.38, p=0.01). The mean score of the experimental group was significantly higher than that of the control group in audit standard 8 : 'Increase of the knowledge of health related to surgery',(t=-2.40, p=0.01). No significant differences between the mean scores of the experimental group and that of the control group in audit standard 5 : 'Recover and maintain of the physical function', audit standard 6:'Prevention of the post-operative complication', audit standard 7 : 'Decrease of discomfort caused by operation', and audit standard 9 : 'Patient satisfaction in nursing care' were found. The standards of evaluation tool were devided into two dimension. One was process dimension which contains four standards(audit standard 1 to 4), the other was outcome dimension which contains five standards(audit standard 5 to 9). The mean score of the experimental group was significantly higher than that of the control group in process dimension (t=-12.30, p=0.00), but no significant difference between the mean scores of the experimental group and that of the control group in outcome dimension was found. From these results, it is concluded that using a nursing care standards in gastrectomy patients promotes quality of nursing care and nursing care standards of various fields are necessary for effective nursing care.

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Fracture Resistance of Low Invasive Fixed Partial Dentures (수종 저 침습 고정성 국소의치의 수직하중에 대한 저항)

  • Choi, Jong-In;Kim, Yu-Lee;Shin, Chang-Yong;Dong, Jin-Keun
    • Journal of Dental Rehabilitation and Applied Science
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    • v.26 no.3
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    • pp.241-251
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    • 2010
  • This study aims at contributing to the restorative dentistry by examining results in the vertical load test of four different low invasive fixed partial dentures. Based on a hypothesis on the right upper first molar is missing, three units of FPDs were made for the second premolar and the second molar abutment. that is, twelve metal dies and FPDs were made for resin bonded FPD and Two Key Bridges and Human Bridge without occlusal rest and Human Bridge with occlusal rest. By using universal test machine, the numerical maximum value were recorded during the vertical load test of each FPDs after the bonding process treated by Maxcem which is resin cement. The failure process and its result of prosthesis were also observed. The maximum load was 7,295 N, 4,729 N, 2,190 N, 3,073 N from groups of resin bonded FPD, Two Key Bridge, Human Bridge without occlusal rest and Human Bridge with occlusal rest respectively. There was a statistical significance among the groups of resin bonded FPD, Two Key Bridge and Human Brides. However, there was no significant difference between Human Bridge without occlusal rest and Human Bridge with occlusal rest. Regarding the failure of prosthesis, the groups of Resin Bonded FPD and Two Key Bridge showed that one of the abutment teeth in the both side of retention part was highly failed earlier than the other one (83.2% and 66.6% respectively). While, Human Bridge without occlusal rest and Human Bridge with occlusal rest showed high percentage of failure in the abutment teeth in the both side of retention part at the same time (91.6% and 58.3% respectively). This study demonstrates that the group of Human Bridges has low resistance to the vertical loads of low invasive FPDs in comparison with the groups of resin bonded FPD and Two Key Bridge. Nevertheless, the maximum occlusal load of the restorative position, resistance to diverse restoration failure, amount of tooth reduction and patients' cooperation should be considered when they are applied in the clinic in order to choose an appropriate restoration for each patient.

The Moderating Effect of Social Capital between Organizational Slack and Managerial Practices for Open Innovation in Venture SMEs (벤처중소기업의 조직여유와 개방형 경영혁신 간의 관계에서 사회적 자본의 조절효과 연구)

  • Bae, Hoyoung
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.10 no.5
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    • pp.73-81
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    • 2015
  • This research is designed to analyze the moderating effect of social capital between organizational slack and managerial practices for open innovation. After controlling the firm size, firm age, and environmental uncertainty, we test two hypotheses. First, we test the hypothesis that organizational slack has a positive effect on managerial practices for open innovation. Especially we focus on the managerial innovation and open innovation because recently managerial innovation and open innovation are more and more important. Second, we test the moderating role of social capital between organizational slack and managerial practices for open innovation. Because social capital is a kind of networking activity, we assume that social capital can contribute to managerial practices for open innovation through the networking activity. For this research, we administered the questionnaire surveys, and got the 250 effective data (companies) in Korea. Then we used the validity, reliability, correlation and multiple regression analysis by means of SPSS 18.0. As a result, we can find the two meaningful results. First, organizational slack, especially not absorbed slack but unabsorbed slack, has positive effect on managerial practices for open innovation. It is because absorbed slack such as excessive facilities, machines, or employees is not useful in managerial practices for open innovation. On the other hand, unabsorbed slack is useful in managerial practices for open innovation because unabsorbed slack such as excessive money or securities is very flexible and active. Taken together, the relationship between managerial practices for open innovation and unabsorbed slack is proven in terms of flexibility. Second, social capital has a moderating effect positively between organizational slack, especially not absorbed slack but unabsorbed slack, and managerial practices for open innovation. A prior study related to the relationship between managerial practices for open innovation and social capital doesn't exist yet, so this analysis result is very meaningful in academic respect. But this research has some limitations. First, this research is analyzed by limited region (Korea) and samples (250 companies), so more global regions and samples are recommended in the future. Second, we focus on managerial practices for open innovation in this paper, so the studies about technological practices for open innovation are recommended in the future.

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The Relationship between the Stage of Exercise Behavior Change and Physical Self-Concept and Self-Efficacy of Casino Security Employees (카지노 시큐리티 종사자의 운동변화단계에 따른 신체적 자기개념과 자기 효능감의 관계)

  • Chun, Yong-Tae;Oh, Jung-Il
    • Korean Security Journal
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    • no.21
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    • pp.95-120
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    • 2009
  • This study was designed to investigate the relationship between the stages of exercise behavior change and physical self-concept and self-efficacy of security employees in hotel casinos. The sampling was drawn from employees at 8 casinos which had more than 30 employees. Participants were selected by convenience sampling method and they completed questionnaires about Physical Self-Concept and Self- Efficacy by self-administration method under supervision of trained researchers SPSS 16.0 (Statistical Package for the Social Science) was used for data analysis in the present study. Reliability and validity were examined for the present study. The principle component factor analysis and varimax rotation were used for the present study. Eigen value 1.0 was the criterion for selecting factors. Chi-square (X) 2 test was utilized for measuring the difference in gender and types of job duties at the stages of exercise behavior change. One-way ANOVA was employed to examine the relationship between the stages of exercise behavior change as an independent variable and physical self-concept and self-efficacy as dependent variables. The Scheffe method was used to determine mean differences of groups as a follow-up test. Multiple regression analysis was utilized to test the difference of physical self-concept as dependent variable and self-efficacy as independent variable. To verify hypothesis for the study, a statistical significance level of $\alpha$=.05 was used. The results were as follow: first, there were differences found for gender and types of job responsibilities in the stages of exercise behavior change. Secondly, as security employees progressed through the stages of exercise behavior change, their physical self-concept and self-efficacy improved. Finally, physical activity and body fat had significant main effects on self-efficacy.

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A Study on the Lifestyle and Coffee Consumption Motivation (라이프스타일과 커피소비동기에 관한 연구)

  • Jung, Ja Young;Kim, Kwang Jin
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.8 no.3
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    • pp.53-65
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    • 2013
  • In Korea recently the consumption of coffee has been drastically increased and majority of people who are more than $20^{th}$ are drinking more than a cup of coffee every day. Nowadays coffee a kind of essential items in modern urban society. As the popularity of the coffee is increasing, As the coffee consumption is growing, the studies on coffee also have been increased. Many of the studies on coffee were focused on the consumer attitudes, coffee shops and franchise coffee shops, and coffee components or ingredients. As the products of the coffee are becoming diverse, the consumers of coffee also becoming diverse. There was a study showing that coffee has variety of types, and that motivations and attitudes for coffee consumption are different depend on demographic statistics such as age and life styles. On this study main focus was life style and consumer's motivation on coffee consumption. For this study the survey was conducted on the people living in Seoul City and Kyengkido from March 1, 2013 to March 31, 2013. 600 questionnaires were distributed and 480 were collected and 470 were used for analysis of this study. The statistics program used in this study was SPSS. The method used in the analysis wee factors analysis test, reliability test, validity test, t-testy, One-Way ANOVA, and regression analysis. In this study according to the factor analysis, the life styles were classified the following six categories ; wellbeing pursuit, taste pursuit, atmosphere pursuit, dine-out pursuit, instant pursuit, and economic value pursuit. The factors of coffee consumption motivation were 6; wellbeing consumption motivation, changing mood consumption motivation, social consumption motivation, habitual consumption motivation, and emotional consumption motivation. The demographic factors used in this study were age, marital status, occupation, educational background, residence, income, and eating-out expenses. The hypothesis used in this study were two. The first hypo-thesis was whether the coffee consumption was affected by the life styles. The second hypo-thesis was whether there was any statistical differences on the motivation of coffee consumption according to the characteristics of life style. The outcome of this study demonstrated that life styles had partial impact on coffee consumption motivations. According to the characteristics of the life style, except for the habitual consumption motivation, all the other factors showed statistical differences on coffee consumption motivations according the characteristics of life styles.

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Evaluation of the Usefulness of Virtual Reality Equipment for Relieving Patients' Anxiety during Whole-Body Bone Scan (전신 뼈 검사 환자의 불안감 해소를 위한 가상현실 장비의 유용성 평가)

  • Kim, Hae-Rin;Kim, Jung-Yul;Lee, Seung-Jae;Baek, Song-Ee;Kim, Jin-Gu;Kim, Ga-Yoon;Nam-Koong, Hyuk;Kang, Chun-Goo;Kim, Jae-Sam
    • The Korean Journal of Nuclear Medicine Technology
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    • v.26 no.1
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    • pp.27-32
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    • 2022
  • Purpose When performing a whole-body bone scan, many patients are experiencing psychological difficulties due to the close distance to the detector. Recently, in the medical field, there is a report that using virtual reality (VR) equipment can give pain relief to pediatric patients with weak concentration or patients receiving severe treatment through a distraction method. Therefore, in this paper, VR equipment was used to provide psychological stability to patients during nuclear medicine tests, and it is intended to evaluate whether it can be used in clinical practice. Materials and Methods As VR equipment, ALLIP Z6 VR (ALLIP, Korea) was used and the experiment was conducted after connecting to a mobile phone. The subjects were 30 patients who underwent whole-body bone examination from September 1, 2021 to September 30, 2021. After intravenous injection of 99mTc-HDP, 3 to 6 hours later, VR equipment was put on and whole body images were obtained. After the test, a survey was conducted, and a Likert scale of 5 points was used for psychological anxiety and satisfaction with VR equipment. Hypothesis verification and reliability of the survey were analyzed using SPSS Statistics 25 (IBM, Corp., Armonk, NY, USA). Results Anxiety about the existing whole-body bone test was 3.03±1.53, whereas that of anxiety after wearing VR equipment was 2.0±1.21, indicating that anxiety decreased to 34%. When regression analysis of the effect of the patient's concentration on VR equipment on anxiety about the test, the B value was 0.750 (P<0.01) and the t value was 6.181 (P<0.01). decreased and showed an influence of 75%. In addition, overall satisfaction with VR equipment was 3.76±1.28, and the intention to reuse was 66%. The Cronbach α value of the reliability coefficient of the questionnaire was 0.901. Conclusion When using VR equipment, patients' attention was dispersed, anxiety was reduced, and psychological stability was found. In the future, as VR equipment technology develops, it is thought that if the equipment can be miniaturized and the resolution of VR content images is increased, it can be used in various clinical settings if it provides more realistic stability to the patient.

A Study on the Effectiveness of 3PL Logistics Information System : A Focus on the Role of Supply Chain Performance in Shipper and Long-term Relationship intention (3PL 물류정보시스템의 효과성에 관한 실증적 연구 : 화주기업의 공급사슬성과와 장기지향적관계성의 역할을 중심으로)

  • Cho, Jae-yong
    • Journal of Venture Innovation
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    • v.3 no.2
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    • pp.111-128
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    • 2020
  • Recently, in the process of globalization of companies, the use of third party logistics providers (3PL) has been strengthened. Therefore, the purpose of this study is to test the effectiveness of the logistics information system provided by 3PL companies. This study is to test the relationship between the effect of the characteristics of the 3PL logistics information system on the shipper's supply chain performance, that is, logistics performance, customer performance, and organizational performance, and the shipper's loyalty to the 3PL company, that is, 3PL corporate performance. In addition, long-term relationship orientation is to test whether there is a moderating effect between the shipper company and the 3PL company. Through this, this study aims to provide strategic implications for improving the competitiveness of 3PL companies. In this study, a total 205 data were collected and used for analysis of shippers companies for hypothesis testing, and analyzed using SPSS 21.0 and AMOS 21.0 statistical programs. The results of the study are summarized as follows. First, it was found that the accuracy, timeliness, and usefulness of the 3PL logistics information system all had a significant positive (+) effect on the performance of the shipper's supply chain. Second, it was found that the accuracy, timeliness, and usefulness of the 3PL logistics information system all had a significant positive (+) effect on 3PL corporate performance. Third, it was found that the performance of the supply chain of the shipper company had a significant positive (+) effect on the performance of the 3PL company. Finally, it was found that long-term relationship orientation had a moderating effect on the relationship between the performance of the shipper company's supply chain and the performance of the 3PL company. The purpose of this study is to provide academic and practical implications for securing competitive advantage through the logistics information system of 3PL logistics companies.

The Marketing Effect of Loyalty Program on Relational Market Behavior : Focusing in Franchise Membership Fitness Club (로열티 프로그램이 고객 참여와 소비자-브랜드 관계에 기초한 관계형 시장 행동에 미치는 영향 : 프랜차이즈 회원제 휘트니스클럽을 대상으로)

  • Yoon, Kyung-Goo;Shin, Geon-Cheol
    • Journal of Distribution Research
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    • v.17 no.2
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    • pp.1-28
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    • 2012
  • I. Introduction : The purpose of this study is to test empirically hypothetical causality among constructs used in previous studies to build the model of relational market behavior on customers' participation and consumer-brand relationship after introducing theories of relationship marketing, loyalty program, consumer-brand relationship, customers' participation in service marketing as previous studies with regard to relational market behavior, which Bagozzi(1995) and Peterson(1995) commented on constructs and definition suggested by Sheth and Parvatiyar (1995). For this purpose, loyalty program by the service provider, customers' participation and consumer-brand relationship as preceding variables explain relational market behavior defined by Sheth and Parvatiyar(1995). This study proposes that loyalty program as a tool of relationship marketing will be effective in that consumers' participation in marketing relationship results in a narrow range of choice(Sheth and Parvatiyar, 1995) because consumers think that their participation motive result in benefits(Peterson, 1995). Also, it is proposed that the quality of consumer-brand relationship explain the performance of relationship as well as the intermediary effect because the loyalty program could be evaluated based on relationship with customers. We reviewed the variables with regard to performance of relationship based on relation maintain in marketing literature, and then tested our hypotheses related to several performance variables including loyalty and intention of relation maintain based on the previous studies and constructs(Bendapudi and Berry, 1997 ; Bettencourt, 1997 ; Palmatier, Dant, Grewal and Evans, 2006 ; You Jae Yi and Soo Jin Lee, 2006). II. Study Model : Analyses about hypothetical causality were proceeded. The marketing effect of loyalty program on relational market behavior was empirically tested in study regarding a service provider. The research model in according to the path hypotheses (loyalty program ${\rightarrow}$ customers' participation ${\rightarrow}$ consumer-brand relationship ${\rightarrow}$ relational market behavior and loyalty program ${\rightarrow}$ consumer-brand relationship, and loyalty program ${\rightarrow}$ relational market behavior and customers' participation ${\rightarrow}$ consumer-brand relationship, and customers' participation ${\rightarrow}$ relational market behavior) proceeded as an activity for customer relation management was suggested. The main purpose of study is to see if relational market behavior could be brought as a result of developing relationship between consumers and a corporate into being stronger and more valuable when a corporate or a service provider try aggressively to build the relationship with customers (Bettencourt, 1997; Palmatier, Dant, Grewal and Evans, 2006; Sheth and Parvatiyar, 1995). III. Conclusion : The results of research into the membership fitness club, one of service areas with high level of customer participation (Bitner, Faranda, Hubbert and Zeithaml, 1997; Chase, 1978; Kelley, Donnelly, Jr. and Skinner, 1990) are as follows: First, causalities in according to path hypotheses were tested, after the preceding variables affecting relational market behavior and conceptual frame were suggested. In study, all hypotheses were supported as expected. This result confirms the proposition suggested by Sheth and Parvatiyar(1995), who claimed that intention of consumer and corporate to participate in marketing relationship brings high level of marketing productivity. Also, as a corporate or a service provider try aggressively to build relationship with customers, the relationship between consumers and a corporate can be developed into stronger and more valuable one (Bettencourt, 1997; Palmatier, Dant, Grewal and Evans, 2006). This finding supports the logic of relationship marketing. Second, because the question regarding the path hypothesis of consumer-brand relationship ${\rightarrow}$ relational market behavior are still at issue, the further analyses were conducted. In particular, there existed the mediating effects of consumer-brand relationship toward relational market behavior. Also, multiple regressions were conducted to see if which one strongly influences relational market behavior among specific question items with regard to consumer-brand relationship. As a result, the influence between items composing consumer-brand relationship and ones composing relational market behavior was different. Among items composing consumer-brand relationship, intimacy was an influence of sustaining relationship, word of mouth, and recommendation, intimacy and interdependence were influences of loyalty, intimacy and self-connection were influences of tolerance and advice. Notably, commitment among items measuring consumer-brand relationship had the negative influence with relational market behavior. This means that bringing relational market behavior is not consumer-brand relationship without personal commitment, but effort to build customer relationship like intimacy, interdependence, and self-connection. This finding confirms the results of Breivik and Thorbjornsen(2008). They reported that six variables composing the quality of consumer-brand relationship have higher explanation in regression model directly affecting performance of consumer-brand relationship. As a result of empirical analysis, among the constructs with regard to consumer-brand relationship, intimacy(B=0.512), interdependence(B=0.196), and quality of partner(B=0.153) had the effects on relation maintain. On the contrary, self-connection, love and passion, and commitment had little effect and did not show the statistical significance(p<0.05). On the other hand, intimacy(B=0.668) and interdependence(B=0.181) had the high regression estimates on word of mouth and recommendation. Regarding the effect on loyalty, explanation level of the model was high(R2=0.515), intimacy(0.538), interdependence(0.223), and quality of partner(0.177) showed the statistical significance(p<0.05). Furthermore, intimacy(0.441) had the strong effect as well as self-connection(0.201) and interdependence (0.163) had the effect on tolerance and forgive. And these three variables showed effects even on advice and suggestion, intimacy(0.373), self-connection(0.270), interdependence (0.155) respectively. Third, in study with regard to the positive effect(loyalty program ${\rightarrow}$ customers' participation, loyalty program ${\rightarrow}$ consumer-brand relationship, loyalty program ${\rightarrow}$ relational market behavior, customers' participation ${\rightarrow}$ consumer-brand relationship, customers' participation ${\rightarrow}$ relational market behavior, consumer-brand relationship ${\rightarrow}$ relational market behavior), the path hypothesis of customers' participation ${\rightarrow}$ consumer-brand relationship, was supported. The fact that path hypothesis of customers' participation ${\rightarrow}$ consumer-brand relationship was supported confirms assertion by Bitner(1995), Fournier(1994), Sheth and Parvatiyar(1995) about consumer relationship to participate in marketing relationship.

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Ischemic Preconditioning and Its Relation to Glycogen Depletion (허혈성 전처치와 당원 결핍과의 관계)

  • 장대영;김대중;원경준;조대윤;손동섭;양기민;라봉진;김호덕
    • Journal of Chest Surgery
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    • v.33 no.7
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    • pp.531-540
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    • 2000
  • Baclgrpimd; Recent studies have suggested that the cardioprotective effect of ischemic preconditioning(IP) is closely related to glycogen depletion and attenuation of intracellular acidosis. In the present study, the authors tested this hypothesis by perfusion isolated rabbit hearts with glucose(G) is closely related to glycogen depletion and attenuation of intracellular acidosis. In the present study, the authors tested this hypothesis by perfusion isolated rabbit hearts with glucose(G)-free perfusate. Material and Method; Hearts isolated from New Zealand white rabbits(1.5~2.0 kg body weight) were perfused with Tyrode solution by Langendorff technique. After stabilization of baseline hemodynamics, the hearts were subjected to 45 min global ischemia followed by 120 min reperfusion with IP(IP group, n=13) or without IP(ischemic control group, n=10). IP was induced by single episode of 5 min global ischemia and 10 min reperfusion. In the G-free preconditioned group(n=12), G depletion was induced by perfusionwith G-free Tyrode solution for 5 min and then perfused with G-containing Tyrode solution for 10 min; and 45 min ischemia and 120 min reperfusion. Left ventricular functionincluding developed pressure(LVDP), dP/dt, heart rate, left ventricular end-distolic pressure(LVEDP) and coronary flow (CF) were measured. Myocardial cytosolic and membrane PKC activities were measured by 32P-${\gamma}$-ATP incorporation into PKC-specific peptide and PKC isozymes were analyzed by Western blot with monoclonal antibodies. Infarct size was determined by staining with TTC(tetrazolium salt) and planimetry. Data were analyzed by one-way analysis of variance (ANOVA) and Turkey's post-hoc test. Result ; In comparison with the ischemic control group, IP significantly enhanced functional recovery of the left ventricle; in contrast, functional significantly enhanced functional recovery of the left ventricle; in contrast, functional recovery were not significantly different between the G-free preconditioned and the ischemic control groups. However, the infarct size was significantly reduced by IP or G-free preconditioning(39$\pm$2.7% in the ischemic control, 19$\pm$1.2% in the IP, and 15$\pm$3.9% in the G-free preconditioned, p<0.05). Membrane PKC activities were increased significantly after IP (119%), IP and 45 min ischemia(145%), G-free [recpmdotopmomg (150%), and G-free preconditioning and 45 min ischemia(127%); expression of membrane PKC isozymes, $\alpha$ and $\varepsilon$, tended to be increased after IP or G-free preconditioning. Conclusion; These results suggest that in isolated Langendorff-perfused rabbit heart model, G-free preconditioning (induced by single episode of 5 min G depletion and 10 min repletion) colud not improve post-ischemic contractile dysfunction(after 45-minute global ischemia); however, it has an infarct size-limiting effect.

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