• 제목/요약/키워드: validity analysis

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Validity Test for Molecular Markers Associated with Resistance to Phytophthora Root Rot in Chili Pepper (Capsicum annuum L.) (고추의 역병 저항성과 연관된 분자표지의 효용성 검정)

  • Lee, Won-Phil;Lee, Jun-Dae;Han, Jung-Heon;Kang, Byoung-Cheorl;Yoon, Jae-Bok
    • Horticultural Science & Technology
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    • v.30 no.1
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    • pp.64-72
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    • 2012
  • Phytophthora root rot has been causing a serious yield loss in pepper production. Since 2004, the year in which commercial cultivars resistant to the disease were firstly commercialized, it has been necessary to introduce the resistance into domestic pepper cultivars for dried red pepper. Therefore, developing molecular markers linked to the resistance is required for an accurate selection of resistant plants and increasing breeding efficiency. Until now, several markers associated with the major dominant gene resistant to Phytophthora root rot have been reported but they have some serious limitations for their usage. In this study, we aimed to develop molecular markers linked to the major dominant gene that can be used for almost of all genetic resources resistant to Phytophthora root rot. Two segregating $F_2$ populations derived from a 'Subicho' ${\times}$ 'CM334' combination and a commercial cultivar 'Dokyacheongcheong' were used to develop molecular markers associated with the resistance. After screening 1,024 AFLP primer combinations with bulked segregant analysis, three AFLP (AFLP1, AFLP2, and AFLP3) markers were identified and converted into three CAPS markers (M1-CAPS, M2-CAPS, and M3-CAPS), respectively. Among them, M3-CAPS marker was further studied in ten resistants, fourteen susceptibles, five hybrids and 53 commercial cultivars. As a result, M3-CAPS marker was more fitted to identify Phytophthora resistance than previously reported P5-SNAP and Phyto5.2-SCAR markers. The result indicated that the M3-CAPS marker will be useful for resistance breeding to Phytophthora root rot in chili pepper.

The Effect of E-SERVQUAL on e-Loyalty for Apparel Online Shopping (재망상복장구물중전자(在网上服装购物中电子)E-SERVQUAL 대전자충성도적영향(对电子忠诚度的影响))

  • Kim, Eun-Young;Jackson, Vanessa P.
    • Journal of Global Scholars of Marketing Science
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    • v.19 no.4
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    • pp.57-63
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    • 2009
  • With an exponential increase in electronic commerce (e-commerce), marketers are attempting to gain a competitive advantage by emphasizing service quality and post interaction service aspects, which leads to customer satisfaction or behavioral consequence. Particularly for apparel, service quality is one of the key determinants in encouraging customer e-loyalty, and hence the success of apparel retailing in the context of electronic commerce. Therefore, this study explores e-service quality (E-SERVQUAL) factors and their unique effects on e-loyalty for apparel online shopping based on Parasuraman et al' s (2005) framework. Specific objectives of this study are to identify underlying dimension of E-SERVQUAL, and analyze a structural model for examining the effect of E-SERVQUAL on e-loyalty for online apparel shopping. For the theoretical framework of service quality in the context of online shopping, literatures on traditional and electronic service quality factors were comparatively reviewed, and two aspects of core and recovery services were identified. This study hypothesized that E-SERVQUAL has an effect on e-loyalty; customer satisfaction has a positive effect on e-service loyalty for apparel online shopping; and customer satisfaction mediates in the effect of E-SERVQUAL on e-loyalty for apparel online shopping. A self-administered questionnaire was developed based on literatures. A total of 252 usable questionnaires were obtained from online consumers who had purchase experience with online shopping for apparel products and reside in standard metropolitan areas, in the United States. Factor analysis (e.g., exploratory, confirmatory) was conducted to assess the validity and reliability and the structural equation model including measurement and structural models was estimated via LISREL 8.8 program. Findings showed that the E-SERVQUAL of shopping websites for apparel consisted of five factors: Compensation, Fulfillment, Efficiency, System Availability, and Responsiveness. This supports Parasuraman (2005)'s E-S-QUAL encompassing two aspects of core service (e.g., fulfillment, efficiency, system availability) and recovery related service (e.g., compensation, responsiveness) in the context of apparel shopping online. In the structural equation model, there are five exogenous latent variables for e-SERVQUAL factors; and two endogenous latent variables (e.g., customer satisfaction, e-loyalty). For the measurement model, the factor loadings for each respective construct were statistically significant and were greater than .60 and internal consistency reliabilities ranged from .85 to .88. In the estimated structural model of the e-SERVEQUAL factors, the system availability was found to have direct and positive effect on e-loyalty, whereas efficiency had a negative effect on e-loyalty for apparel online shopping. However, fulfillment was not a significant predictor for explaining consequences of E-SERVQUAL for apparel online shopping. This finding implies that perceived service quality of system available was likely to increase customer satisfaction for apparel online shopping. However, it was not supported that e-loyalty was determined by service quality, because service quality has an indirect effect on e-loyalty (i.e., repurchase intention) by mediating effect of value or satisfaction in the context of online shopping for apparel. In addition, both compensation and responsiveness were found to have a significant impact on customer satisfaction, which influenced e-loyalty for apparel online shopping. Thus, there was significant indirect effect of compensation and responsiveness on e-loyalty. This suggests that the recovery-specific service factors play an important role in maximizing customer satisfaction levels and then maintaining customer loyalty to the online shopping site for apparel. The findings have both managerial and research implications. Fashion marketers can establish long-term relationship with their customers based on continuously measuring customer perceptions for recovery-related service quality, such as quick responses to problem and returns, and compensation for customers' problem after their purchases. In order to maintain e-loyalty, recovery services play an important role in the first choice websites for consumers to purchase clothing. Given that online consumers may shop anywhere, a marketing strategy for improving competitive advantages is to provide better service quality, maximize satisfaction, and turn to creating customers' e-loyalty for apparel online shopping. From a researcher's perspective, there are some limitations of this research that should be considered when interpreting its findings. For future research, findings provide a basis for the further study of this important topic along both theoretical and empirical dimensions. Based on the findings, more comprehensive models for predicting E-SERVQUAL's consequences can be developed and tested. For global fashion marketing, this study can expand to a cross-cultural approach into e-service quality for apparel by including multinational samples.

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Craniofacial morphologic alteration induced by bone-targeted mutants of FGFR2 causing Apert and Crouzon syndrome (어퍼트 및 크루즌 증후군을 유발하는 골조직 특이성 FGFR2 돌연변이에 의한 두개안면 형태의 변화)

  • Lee, Kee-Joon;Nah, Hyun-Duck;Tjoa, Stephen T. J.;Park, Young-Chel;Baik, Hyoung-Seon;Yun, Tae-Min;Song, Jin-Wook
    • The korean journal of orthodontics
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    • v.36 no.4
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    • pp.284-294
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    • 2006
  • Objective: Activating mutations in the fibroblast growth factor receptor-2 (FGFR2) have been shown to cause syndromic craniosynostosis such as Apert and Crouzon syndromes. The purpose of this pilot study was to investigate the resultant phenotypes induced by the two distinctive bone-targeted gene constructs of FGFR2, Pro253Arg and Cys278Phe, corresponding to human Apert and Crouzon syndromes respectively. Methods: Wild type and a transgenic mouse model with normal FGFR2 were used as controls to examine the validity of the microinjection. Micro-CT and morphometric analysis on the skull revealed the following results. Results: Both Apert and Crouzon mutants of FGFR2 induced fusion of calvarial sutures and anteroposteriorly constricted facial dimension, with anterior crossbite present only in Apert mice. Apert mice differed from Crouzon mice and transgenic mice with normal FGFR2 in the anterior cranial base flexure and calvarial flexure angle which implies a possible difference in the pathogenesis of the two mutations. In contrast, the transgenic mice with normal FGFR2 displayed normal craniofacial phenotype. Conclusion: Apert and Crouzon mutations appear to lead to genotype-specific phenotypes, possibly causing the distinctive sites and sequence of synostosis in the calvaria and cranial base. The exact function of the altered FGFR2 at each suture needs further investigation.

The Effects of Service Employee's Surface Acting on Counterproductive Work Behavior: The Mediating Roles of Emotional Exhaustion (서비스 종업원의 표면행위가 반생산적 과업행동에 미치는 효과에 관한 연구: 감정소모의 매개효과를 중심으로)

  • Kang, Seong-Ho;Chay, Jong-Hak;Lee, Ji-Ae;Hur, Won-Moo
    • Journal of Distribution Science
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    • v.14 no.2
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    • pp.73-82
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    • 2016
  • Purpose - Counterproductive work behavior(CWB) was typically categorized according to the behavior whether it targets other people(i.e., interpersonal CWB: I-CWB). Employing organizations(i.e., organizational CWB: O-CWB) has emerged as major concerns among researchers, managers, and the general public. An abundance of researches has informed us about the understanding for the antecedents of CWB, whereas little is known about the antecedents of CWB directed distribution service in employee's emotional labor. Therefore, the purpose of this research is to propose a research model in which surface acting enhances emotional exhaustion as an emotional labor strategy, which eventually increases counterproductive work behavior(including I-CWM and O-CWB). Research design, data, and methodology - This empirical research data were gathered from the samples of full time frontline hotel employees(including front office, call center, food/beverage, concierge, and room service) in South Korea. Six hotels were selected ranged from four to five stars, including privately owned and joint-venture properties. A convenience sampling method was used to select hotels. Full time frontline hotel employees from the six hotels were surveyed using a self-administered instrument for data collection. With the strong support of hotel managers, a total of 300 questionnaires were distributed, and 252 responses were collected indicating a response rate of 84.0%. In the process of working with the 252 samples, structural equation modeling is employed to test research hypotheses(H1: The relationship between surface acting and Interpersonal counterproductive work behavior(I-CWB) is mediated by emotional exhaustion, H2: The relationship between surface acting and organizational counterproductive work behavior(O-CWB) is mediated by emotional exhaustion). SPSS 18.0 and M-Plus 7.31 software were used for the data analysis. Descriptive statistics were used to assess the distribution of the employee profiles and correlations between factors. M-Plus 7.31 software was used to test the model fit, validity, and reliability of the factors, significance of the relationship between factors, and the effects of factors in the model. Results - To test our mediation hypotheses, we used an analytical strategy suggested by Preacher & Hayes (2008) and Shrout & Bolger (2002). This mediation approach directly tests the indirect effect between the predictor and the criterion variables through the mediator via a bootstrapping procedure. Thus, it addresses some weaknesses associated with the Sobel test. We found that surface acting was positively related to emotional exhaustion. Furthermore, emotional exhaustion was a significant predictor from the two kinds of counterproductive work behavior. In addition, surface acting was not significantly associated with the two kinds of counterproductive work behavior. These results indicated that the surface acting by frontline hotel employees was associated with higher emotional exhaustion, which is related with higher interpersonal counterproductive work behavior(I-CWB) and organizational counterproductive work behavior(O-CWB). In sum, we confirmed that the positive relationship between surface acting and the two kinds of counterproductive work behavior was fully mediated by emotional exhaustion. Conclusions - The current research broadens the conceptual work and empirical studies in counterproductive work behavior literature by representing a fundamental mechanism that how surface acting affects counterproductive work behavior.

A Study of the Relationship of Nurses' Personality Type and Job Satisfaction Level, according to the Career (근무경력별 간호사의 성격유형과 직무만족도와의 관련성(MBTI이용))

  • Park Young Sook;Park Kyung Min;Park Jeong Sook;Koh Hyo Jung;Kwon Young Sook;Kim Myung Ae;Kim Chung Nam;Park Cheong Ja;Shin Yeong Hee;Lee Kyung Hee;Lee Byung Sook
    • Journal of Korean Public Health Nursing
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    • v.15 no.2
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    • pp.301-313
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    • 2001
  • This study was to explore the relationship between nurses' personality type and their job satisfaction level. The subjects of the study were the 364 nurses who were serving at the general surgical department, psychiatric department, pediatric department and emergency room. The hospitals for which they were working were four university hospitals in Daegu and Busan, and six other university hospitals in Seoul were selected as sample hospitals. For data collection, questionnaires were self-reported to the subjects, under their agreement, from May to June, 2000. The following two instruments were used in the study: One was MBTI Test whose Korean version designed and verified to reliability and validity by Kim Jung Taek and Shim Hae Sook(1990): the other was the Nursing Job Satisfaction Instrument, 'The Index of Work Satisfaction' developed by Slavitt, et al.., (1978). The data were analyzed by frequency, t-test, one-way variance analysis, scheffe's post hoc contrast, and Pearson correlation coefficient with SPSS Win 10.0 program. The results this study were as follows ; 1. As a result of testing nurse's personality type by function at each career, it's found that the most personality type was expressed by the ST-type$(37.3\%)$ at 1-5 years, the SF-type$(29.4\%)$ at 6-10 years, the ST-type$(43.3\%)$ at more than 11 years. 2. As a result of testing the disparity in job satisfaction according to career, it appeared that the 6-10 years group showed higher job satisfaction, followed by the 6-10 years$(119.6\%),\;1-5 years(118.6\%)\;and\;more\;than\; 11 years(117.7\%)$ groups. 3. As a result of testing job satisfaction level according to nurse's personality type by function at each career, it's found that the most job satisfaction was expressed by the SF-type(F=8.50, p=0.00l) at 1-5 years. the ST-type(F=30.61, p=0.001) at 6-10 years. the SF-type(F=4.98, p=0.003) at more than 11 years groups. 4. As a result of testing a significant correlation between nurse's personality type by function and job satisfaction level. the SF(r=0.279, p=0.001) and ST(r=0.222, p=0.001) types showed significant positive correlation. and the NF(r=-0.201, p=0.001) and NT(r=-0.402, p=0.001) types revealed significant negative correlation. The nursing management is likely to be done more effectively, if managers in charge of nursing administration carefully reflect nurses' personal opinions in posting and personnel management, keeping in mind that there is a specific personality type that serves to raise job satisfaction at a specific career.

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Salt-Related Dietary Attitudes, Behaviors, and Nutrition Knowledge of University Students according to Estimated Salt Intake Using Urinary Salt Signal (일부 남녀 대학생의 소변 중 Salt Signal로 추정한 소금 섭취량에 따른 소금 섭취 관련 식태도, 식행동, 영양지식에 관한 연구)

  • Kim, Mi-Hyun;Min, Daun;Jang, Eungyoung;Yeon, Jee-Young;Kim, Jong Wook;Bae, Yun-Jung
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.44 no.2
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    • pp.226-233
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    • 2015
  • The purpose of this study was to evaluate salt-related dietary attitudes, behaviors, and nutrition knowledge according to urinary salt signal of university students. Based on urinary salt signal, we classified subjects into an "adequate Na intake (ANI)" group (n=52) (salt ${\leq}6g$) and "excess Na intake (ENI)" group (n=66) (salt >6 g). Subjects were asked about general characteristics, lifestyle, salt-related dietary attitudes, behaviors, and nutritional knowledge using questionnaire. The ENI group had more subjects who were drinkers (P<0.05) compared to the ANI group. The ENI group (33.45) showed a significantly lower score in terms of salt-related dietary attitudes compared to the ANI group (35.50) (P<0.05). There was no significant difference in the total score of salt-related dietary behavior between the groups. The score of nutrition knowledge was significantly higher in the ANI (9.77) group than in the ENI (8.82) group (P<0.05). The correlation analysis indicated that the urinary salt signal had a negative correlation with the salt-related dietary attitude score after adjustments for age, sex, and body mass index (r=-0.2100, P<0.05). These results support the validity of using the urinary salt signal to simplify estimation of sodium intake.

The Effect of an Art Therapy Program based on Reality Therapy on Weight Control, Body Image, and Self-esteem of College Students (현실요법에 기초한 미술치료 프로그램이 대학생의 체중조절과 신체상 및 자아존중감에 미치는 효과)

  • Kim, Won-Gyung;Park, Jeong-Hee
    • Journal of the Korean Society of School Health
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    • v.14 no.2
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    • pp.249-268
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    • 2001
  • This study was carried out to identify the effects of an art therapy program based on reality therapy on the weight control, body image, and self-esteem of college students. The program was developed by the authors. The design was a pretest-post test control group design. The subjects were college students attending M college : 8 in experimental group A, 6 in experimental group 2, who wanted to control their body weight and 16 in the control group who didn't attend the program those in the experimental group attended the program once (group A) or twice (group B) per week meeting a total of six times. The data were analyzed by quantity method (SPSS 10.0 program) and quality method(process analysis). The results were as follows : 1. The average obesity index of pre-test, post-test, and a follow-up test decreased from 8.9% to 6.1%, 3.7%. And the rate of decrease both pre-post and post-follow up were statistically significant 2. The average obesity index of group A decreased from 9.6% to 6.3%, 4.1% and the rate of decrease between pre and post were statistically significant. But the rate of decrease between post and follow-up were statistically not significant 3. The average obesity index of group B decreased from 7.8% to 5.8%, 3.1% and the rate of decrease between pre and post were not significant statistically. But the rate of decrease between post and follow-up were statistically significant 4. The average scores of pre and post body image increased and were statistically significant : group A from 129.0 to 153.5, group B from 127.7 to 155.2. 5. The average scores of pre and post semantic differential method increased and were statistically significant: group A from 38.1 to 44.1, group B from 38.0 to 45.0. 6. The average scores of pre and post self-esteem increased: group A increased from 37.3 to 40.3 and were statistically significant, group B increased from 36.5 to 39.5 but was statistically insignificant 7. The average scores of pre and post obesity rate, body image, semantic differential method and self-esteem in the control group were not statistically significant 8. The pre and post scores of body image(p=.001), semantic differential method(p=.001) and self-esteem(p=.039) between experimental and control group were statistically significant. 9. In Duncan multiple comparison, it was not statistically significant between group A and B, but statistically significant between group A and the control group, group B and the control group in obesity index, body image, semantic differential method. There was no statistically significance among the three groups in self esteem 10. In Duncan multiple comparison, group A gained higher scores than group B in obesity index(-1.2%), and self esteem(0. 3). Group B gained higher scores than group A in body image(3. 0), and semantic differential method(1. 0). So it is difficult to conclude whether group A or B is more effective. In conclusion, the art therapy program based on reality therapy was effective in weight the control program of college students: obesity was decreased, the scores of body image and semantic differential method and self-esteem were increased. The scores of group A were increased more than group Band were statistically significant, The time interval was a very important factor in this program. The recommendation is : the validity of this program has to be tested through various subjects and in various areas. And also this program has to be tested in other topics.

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The Application of Operations Research to Librarianship : Some Research Directions (운영연구(OR)의 도서관응용 -그 몇가지 잠재적응용분야에 대하여-)

  • Choi Sung Jin
    • Journal of the Korean Society for Library and Information Science
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    • v.4
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    • pp.43-71
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    • 1975
  • Operations research has developed rapidly since its origins in World War II. Practitioners of O. R. have contributed to almost every aspect of government and business. More recently, a number of operations researchers have turned their attention to library and information systems, and the author believes that significant research has resulted. It is the purpose of this essay to introduce the library audience to some of these accomplishments, to present some of the author's hypotheses on the subject of library management to which he belives O. R. has great potential, and to suggest some future research directions. Some problem areas in librianship where O. R. may play a part have been discussed and are summarized below. (1) Library location. It is usually necessary to make balance between accessibility and cost In location problems. Many mathematical methods are available for identifying the optimal locations once the balance between these two criteria has been decided. The major difficulties lie in relating cost to size and in taking future change into account when discriminating possible solutions. (2) Planning new facilities. Standard approaches to using mathematical models for simple investment decisions are well established. If the problem is one of choosing the most economical way of achieving a certain objective, one may compare th althenatives by using one of the discounted cash flow techniques. In other situations it may be necessary to use of cost-benefit approach. (3) Allocating library resources. In order to allocate the resources to best advantage the librarian needs to know how the effectiveness of the services he offers depends on the way he puts his resources. The O. R. approach to the problems is to construct a model representing effectiveness as a mathematical function of levels of different inputs(e.g., numbers of people in different jobs, acquisitions of different types, physical resources). (4) Long term planning. Resource allocation problems are generally concerned with up to one and a half years ahead. The longer term certainly offers both greater freedom of action and greater uncertainty. Thus it is difficult to generalize about long term planning problems. In other fields, however, O. R. has made a significant contribution to long range planning and it is likely to have one to make in librarianship as well. (5) Public relations. It is generally accepted that actual and potential users are too ignorant both of the range of library services provided and of how to make use of them. How should services be brought to the attention of potential users? The answer seems to lie in obtaining empirical evidence by controlled experiments in which a group of libraries participated. (6) Acquisition policy. In comparing alternative policies for acquisition of materials one needs to know the implications of each service which depends on the stock. Second is the relative importance to be ascribed to each service for each class of user. By reducing the level of the first, formal models will allow the librarian to concentrate his attention upon the value judgements which will be necessary for the second. (7) Loan policy. The approach to choosing between loan policies is much the same as the previous approach. (8) Manpower planning. For large library systems one should consider constructing models which will permit the skills necessary in the future with predictions of the skills that will be available, so as to allow informed decisions. (9) Management information system for libraries. A great deal of data can be available in libraries as a by-product of all recording activities. It is particularly tempting when procedures are computerized to make summary statistics available as a management information system. The values of information to particular decisions that may have to be taken future is best assessed in terms of a model of the relevant problem. (10) Management gaming. One of the most common uses of a management game is as a means of developing staff's to take decisions. The value of such exercises depends upon the validity of the computerized model. If the model were sufficiently simple to take the form of a mathematical equation, decision-makers would probably able to learn adequately from a graph. More complex situations require simulation models. (11) Diagnostics tools. Libraries are sufficiently complex systems that it would be useful to have available simple means of telling whether performance could be regarded as satisfactory which, if it could not, would also provide pointers to what was wrong. (12) Data banks. It would appear to be worth considering establishing a bank for certain types of data. It certain items on questionnaires were to take a standard form, a greater pool of data would de available for various analysis. (13) Effectiveness measures. The meaning of a library performance measure is not readily interpreted. Each measure must itself be assessed in relation to the corresponding measures for earlier periods of time and a standard measure that may be a corresponding measure in another library, the 'norm', the 'best practice', or user expectations.

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Analysis of Quantization Noise in Magnetic Resonance Imaging Systems (자기공명영상 시스템의 양자화잡음 분석)

  • Ahn C.B.
    • Investigative Magnetic Resonance Imaging
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    • v.8 no.1
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    • pp.42-49
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    • 2004
  • Purpose : The quantization noise in magnetic resonance imaging (MRI) systems is analyzed. The signal-to-quantization noise ratio (SQNR) in the reconstructed image is derived from the level of quantization in the signal in spatial frequency domain. Based on the derived formula, the SQNRs in various main magnetic fields with different receiver systems are evaluated. From the evaluation, the quantization noise could be a major noise source determining overall system signal-to-noise ratio (SNR) in high field MRI system. A few methods to reduce the quantization noise are suggested. Materials and methods : In Fourier imaging methods, spin density distribution is encoded by phase and frequency encoding gradients in such a way that it becomes a distribution in the spatial frequency domain. Thus the quantization noise in the spatial frequency domain is expressed in terms of the SQNR in the reconstructed image. The validity of the derived formula is confirmed by experiments and computer simulation. Results : Using the derived formula, the SQNRs in various main magnetic fields with various receiver systems are evaluated. Since the quantization noise is proportional to the signal amplitude, yet it cannot be reduced by simple signal averaging, it could be a serious problem in high field imaging. In many receiver systems employing analog-to-digital converters (ADC) of 16 bits/sample, the quantization noise could be a major noise source limiting overall system SNR, especially in a high field imaging. Conclusion : The field strength of MRI system keeps going higher for functional imaging and spectroscopy. In high field MRI system, signal amplitude becomes larger with more susceptibility effect and wider spectral separation. Since the quantization noise is proportional to the signal amplitude, if the conversion bits of the ADCs in the receiver system are not large enough, the increase of signal amplitude may not be fully utilized for the SNR enhancement due to the increase of the quantization noise. Evaluation of the SQNR for various systems using the formula shows that the quantization noise could be a major noise source limiting overall system SNR, especially in three dimensional imaging in a high field imaging. Oversampling and off-center sampling would be an alternative solution to reduce the quantization noise without replacement of the receiver system.

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Studies on Estimation of Fish Abundance Using an Echo Sounder ( 1 ) - Experimental Verification of the Theory for Estimating Fish Density- (어군탐지기에 의한 어군량 추정에 관한 기초적 연구 ( 1 ) - 어군량추정이론의 검증실험 -)

  • 이대재
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.27 no.1
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    • pp.1-12
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    • 1991
  • An experiment has been carefully designed and performed to verify the theory for the echointergration technique of estimating the density of fish school by the use of steel spheres in a laboratory tank. The spheres used to simulate a fish school were randomly distributed throughout the insonified volume to produce the acoustic echoes similar to those scattered from real fish schools. The backscattered echoes were measured as a function of target density at tow frequencies of 50kHz and 200kHz. Data acquisition, processing and analysis were performed by means of the microcomputer-based sonar-echo processor including a FFT analyzer. Acoustic scattering characteristics of a 36cm mackerel was investigated by measuring fish echoes with frequencies ranging from 47.8kHz to 52.0kHz. The fluctuation of bottom echoes caused by the effects of fish-school attenuation and multiple scattering which occurred in dense aggregations of fishes was also examined by analyzing the echograms of sardine schools obtained by a 50kHz telesounder in the set-net's bagnet, and the echograms obtained by a scientific echo sounder of 50kHz in the East China Sea, respectively. The results obtained can be summarized as follows: 1. The measured and the calculated echo shapes on the steel sphere used to simulate a fish school were in close agreement. 2. The waveform and amplitude of echo signals by a mackerel without swimbladder fluctuated irregularly with the measuring frequency. 3. When a collection of 30 targets/m super(3) lied the shadow region behind another collection of 5 targets/m super(3), the mean losses in echo energy for the 30 targets/m super(3) were about -0.4dB at 50kHz and about -0.2dB at 200kHz, respectively. 4. In the echograms obtained in the East China Sea, the bottom echoes fluctuated remarkably when the dense aggregations of fish appeared between transducer and seabed. Especially, in the case of the echograms of sardine school obtained in a set-net's bagnet, the disappearance of bottom echoes and the lengthening of the echo trace by fish aggregations were observed. Then the mean density of the sardine school was estimated as 36 fish/m super(3). It suggests that when the distribution density of fishes in oceans is greater than this density, the effects of fish-school attenuation and multiple scattering must be taken into account as a possible source of error in fish abundance estimates. 5. The relationship between mean backscattering strength (, dB) and target density ($\rho$, No./m super(3)) were expressed by the equations: =-46.2+13.7 Log($\rho$) at 50kHz and =-43.9+13.4 Log($\rho$) at 200kHz. 6. The difference between the experimentally derived number and the actual number of targets gradually decreased with an increase in the target density and was within 20% when the density was 30 targets/m super(3). From these results, we concluded that when the number of targets in the insonified volume is large, the validity of the echo-integration technique of estimating the density of fish schools could be expected.

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