• Title/Summary/Keyword: Design for reliability

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Optimization of impeller blade shape for high-performance and low-noise centrifugal pump (고성능 저소음 원심펌프 개발을 위한 임펠러 익형 최적설계)

  • Younguk Song;Seo-Yoon Ryu;Cheolung Cheong;Tae-hoon Kim;Junhyo Koo
    • The Journal of the Acoustical Society of Korea
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    • v.42 no.6
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    • pp.519-528
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    • 2023
  • The aim of this study was to enhance the flow rate and noise performance of a centrifugal pump in dishwashers by designing an optimized impeller shape through numerical and experimental investigations. To evaluate the performance of the target centrifugal pump, experiment was conducted using a pump performance tester and noise experiment was carried out in a semi-anechoic chamber with microphones and a reflecting wall behind the dishwasher. Through the use of advanced computational fluid dynamics techniques, numerical simulations were performed to analyze the flow and aeroacoustics performance of our target centrifugal pump impeller. To achieve this, numerical simulations were carried out using the Reynolds-Average Navier-Stokes equations and Ffowcs-Willliams and Hawkings equations as governing equations. In order to ensure the validity of numerical methods, a thorough comparison of numerical results with experimental results. After having confirmed the reliability of the current numerical method of this study, the optimization of the target centrifugal pump impeller was conducted. An improvement in flow rate was confirmed numerically, and a manufactured proto-type of the optimized model was used for experimental investigation. Furthermore, it was observed that by applying the fan law, we could effectively reduce noise levels without reducing the flow rate.

A Study on Design and Analysis of Module Control Method for Extended Use of Rechargeable Batteries in Mobile Devices (모바일 장치의 충전식 배터리 사용 연장을 위한 모듈 제어 방법 설계와 해석 연구)

  • Dohyeong Kim;jihoon Ryu;JinPyo Jo;JeongHo Kim
    • Journal of Platform Technology
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    • v.12 no.2
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    • pp.34-44
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    • 2024
  • This paper proposes a dynamic clock supply control algorithm and a system load power stabilization algorithm that minimizes the power consumption of the sensing system, which accounts for the largest percentage of power consumption in mobile devices, to extend the usage time of the rechargeable battery mounted on the mobile device. The dynamic clock supply control algorithm can reduce the power consumed by the sensing system by configuring a circuit to cut off the power of the sensing system and by recognizing the state of low sensor change and adjusting the measurement cycle. The system load power stabilization algorithm is an algorithm that controls the power of the surrounding module according to the power consumption state, and when it requires a lot of power, it controls the clock supply to stabilize the operation. The experimental results confirmed that applying only the dynamic clock supply control algorithm reduces the power consumed by the sensing system by 17%, and applying only the system load power stabilization algorithm reduces power consumption by 9.3%, enabling it to operate stably in situations that require a lot of power such as image processing. When both algorithms were applied, the power consumption of the battery was reduced by 67% compared to before applying the algorithm. Through this, the reliability of the proposed method was confirmed.

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Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2016 (설비공학 분야의 최근 연구 동향 : 2016년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.6
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    • pp.327-340
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    • 2017
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.

A study on the Degradation and By-products Formation of NDMA by the Photolysis with UV: Setup of Reaction Models and Assessment of Decomposition Characteristics by the Statistical Design of Experiment (DOE) based on the Box-Behnken Technique (UV 공정을 이용한 N-Nitrosodimethylamine (NDMA) 광분해 및 부산물 생성에 관한 연구: 박스-벤켄법 실험계획법을 이용한 통계학적 분해특성평가 및 반응모델 수립)

  • Chang, Soon-Woong;Lee, Si-Jin;Cho, Il-Hyoung
    • Journal of Korean Society of Environmental Engineers
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    • v.32 no.1
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    • pp.33-46
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    • 2010
  • We investigated and estimated at the characteristics of decomposition and by-products of N-Nitrosodimethylamine (NDMA) using a design of experiment (DOE) based on the Box-Behken design in an UV process, and also the main factors (variables) with UV intensity($X_2$) (range: $1.5{\sim}4.5\;mW/cm^2$), NDMA concentration ($X_2$) (range: 100~300 uM) and pH ($X_2$) (rang: 3~9) which consisted of 3 levels in each factor and 4 responses ($Y_1$ (% of NDMA removal), $Y_2$ (dimethylamine (DMA) reformation (uM)), $Y_3$ (dimethylformamide (DMF) reformation (uM), $Y_4$ ($NO_2$-N reformation (uM)) were set up to estimate the prediction model and the optimization conditions. The results of prediction model and optimization point using the canonical analysis in order to obtain the optimal operation conditions were $Y_1$ [% of NDMA removal] = $117+21X_1-0.3X_2-17.2X_3+{2.43X_1}^2+{0.001X_2}^2+{3.2X_3}^2-0.08X_1X_2-1.6X_1X_3-0.05X_2X_3$ ($R^2$= 96%, Adjusted $R^2$ = 88%) and 99.3% ($X_1:\;4.5\;mW/cm^2$, $X_2:\;190\;uM$, $X_3:\;3.2$), $Y_2$ [DMA conc] = $-101+18.5X_1+0.4X_2+21X_3-{3.3X_1}^2-{0.01X_2}^2-{1.5X_3}^2-0.01X_1X_2+0.07X_1X_3-0.01X_2X_3$ ($R^2$= 99.4%, 수정 $R^2$ = 95.7%) and 35.2 uM ($X_1$: 3 $mW/cm^2$, $X_2$: 220 uM, $X_3$: 6.3), $Y_3$ [DMF conc] = $-6.2+0.2X_1+0.02X_2+2X_3-0.26X_1^2-0.01X_2^2-0.2X_3^2-0.004X_1X_2+0.1X_1X_3-0.02X_2X_3$ ($R^2$= 98%, Adjusted $R^2$ = 94.4%) and 3.7 uM ($X_1:\;4.5\;$mW/cm^2$, $X_2:\;290\;uM$, $X_3:\;6.2$) and $Y_4$ [$NO_2$-N conc] = $-25+12.2X_1+0.15X_2+7.8X_3+{1.1X_1}^2+{0.001X_2}^2-{0.34X_3}^2+0.01X_1X_2+0.08X_1X_3-3.4X_2X_3$ ($R^2$= 98.5%, Adjusted $R^2$ = 95.7%) and 74.5 uM ($X_1:\;4.5\;mW/cm^2$, $X_2:\;220\;uM$, $X_3:\;3.1$). This study has demonstrated that the response surface methodology and the Box-Behnken statistical experiment design can provide statistically reliable results for decomposition and by-products of NDMA by the UV photolysis and also for determination of optimum conditions. Predictions obtained from the response functions were in good agreement with the experimental results indicating the reliability of the methodology used.

A Development of Evaluation Indicators for Performance Improvement of Horticultural Therapy Garden (원예치료정원의 성능개선을 위한 평가지표 개발)

  • Ahn, Je-Jun;Park, Yool-Jin
    • Journal of the Korean Institute of Traditional Landscape Architecture
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    • v.36 no.4
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    • pp.113-123
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    • 2018
  • The purpose of this research is to develop evaluation indicators forperformance improvement of horticultural therapy garden. In order to achieve a therapeutic purpose, the gardening activity held by the trained horticultural therapist. Moreover, horticultural therapy is 'a medical model' for the treatment and basic premise of the research was set, as horticultural therapy garden is characterized area to support activities of patients and horticultural therapist functionally and efficiently. For this study, three times of Delphi and AHP techniques were proceeded to export panels who were recruited by purposive sampling. Through these techniques, it was possible to deduct the evaluation indicator which maximizes the performance of the horticultural therapy garden. The evaluation items were prioritized by typing and stratification of the indicator. The results and discussions were stated as followings. Firstly, a questionnaire of experts was conducted to horticultural therapists and civil servants who were in charge of horticultural therapy. As results(horticultural therapists: 87.8%, civil servants: 75.2%), It is possible to conclude that both positions have the high recognition and agreed on the necessity of horticultural therapy. Secondly, Delphi investigation was conducted three times in order to develop the evaluation indicator for performance evaluation. After Delphi analysis, total 34 of evaluation elements to improve the performance of the horticultural therapy garden by reliability and validity analysis results. Thirdly, AHP analysis of each evaluation indicator was conducted on the relative importance and weighting. Moreover, the results showed 'interaction between nature and human' as the most important element, and in order of 'plan of the program', 'social interaction', 'sustainable environmental', and 'universal design rule', respectively. On the other hand, the exports from the university and research institute evaluated the importance of 'interaction between nature and human', while horticultural therapists chose 'plan of the program' as the most important element. Fourthly, the total weight was used to develop weight applied evaluation indicator for the performance evaluation of the horticultural therapy garden. The weight applying to evaluation index is generally calculated multiply the evaluation scores and the total weight using AHP analysis. Finally, 'the evaluation indicator and evaluation score sheet for performance improvement of the horticultural therapy garden' was finally stated based on the relative order of priority between evaluation indicators and analyzing the weight. If it was deducted the improvement points for the efficiency of already established horticultural therapy garden using the 'weight applied evaluation sheet', it is possible to expand it by judging the importance with the decision of the priority because the item importance decided by experts was reflected. Moreover, in the condition of new garden establishment, it is expected to be helpful in suggesting ways for performance improvement and in setting the guidelines by understanding the major indicators of performance improvement in horticultural therapy activity.

Psychometric Evaluation of a Six Dimension Scale of Nursing Performance and Student Nurse Stress Index Using an Objective Structured Clinical Examination - Modules for Asthma and Type 1 Diabetes (객관구조화 임상시험을 활용한 간호수행능력의 Six Dimension Scale과 간호학생 스트레스 평가지수의 도구 평가-천식 및 1형 당뇨 모듈을 중심으로)

  • Park, Kyong-Ok;Ahn, Young-Mee;Kang, Na-Rae;Lee, Mi-Jin;Sohn, Min
    • Child Health Nursing Research
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    • v.19 no.2
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    • pp.85-93
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    • 2013
  • Purpose: The study purposes were to describe the process of developing the Korean versions of the Six Dimension Scale of Nursing Performance (Six-D) and Student Nurse Stress Index (SNSI) and psychometric evaluation of the two measurements. Methods: This was a methodology study using a descriptive cross-sectional design with 51 nursing students in 4th year of university. Internal consistency reliability was assessed using Cronbach alphas. Construct validity was determined by exploring correlations among Six-D, SNSI, objective structured clinical examination (OSCE), self-efficacy and grade point average (GPA). Results: Internal consistency reliability of Six-D and SNSI was acceptable with Cronbach's ${\alpha}$ of .95 and .82. Correlation analysis to determine construct validity revealed that Six-D presented positive correlations with OSCE (r=.109~.272) and self-efficacy (r=.005~.161) and negative correlation with GPA (r=-.246~-.394), although all were not statistically significant. SNSI presented all negative correlations with OSCE (r= -.007~-.238), self-efficacy (r=-.246~-.394), and GPA (r=-.092~-.426) and were mostly statistically significant except OSCE. Conclusion: Six-D needs more evidence to confirm validity to predict observed clinical competency and theoretical relationships with self-efficacy and GPA. However, SNSI presented trends of expected relationships with relevant variables. Therefore, further research is recommended in testing validity of Six-D with other student populations.

Post Occupancy Evaluation of Image and Satisfaction for Storytelling Theme on the Kim Gwang-Seok Street (스토리텔링 테마골목 이미지 및 만족도에 관한 이용 후 평가 - '김광석다시그리기길'을 대상으로 -)

  • Koo, Min-Ah;Eom, Boong-Hoon
    • Journal of the Korean Institute of Landscape Architecture
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    • v.46 no.5
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    • pp.59-68
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    • 2018
  • This study deals with post-occupancy evaluation (POE) of 'Kim Gwang-seok Street'as storytelling road for urban regeneration. The evaluation focused on image preference and use satisfaction of visitors. This is the initial project of popular singer-storytelling street as a new attraction, and the results could be used as basic data for the sustainable planning and management of storytelling streets. 200 respondents of visitor group were analyzed. Frequency analysis for demographics, use, behavior, reliability, and means, were evaluated. Factor analysis and multiple regression analysis were conducted for image preference and use satisfaction. Responses showed high frequency of twenties in age, who were typically students. In use motives and activities, strolling, sightseeing, and taking pictures were shown to be the most common. The mean scores of image variables showed symbolic (5.03), familiar (4.84), beautiful (4.71), and bright (4.63), the highest. The result of exploratory factor analysis, led to 3 factors being categorized; the mood of street, the design, and the dynamics. Due to the result of multiple regression analysis, the preference of space image was significantly influenced by 4 image variables; symbolic (${\beta}=.314$), stable (${\beta}=.248$), friendly (${\beta}=.204$), and fresh (${\beta}=.142$). In the use satisfaction analysis, the mean scores were highest concerning facility design (3.81), typical street (3.78), the image of street (3.81), continued use (3.66), and experiential tourism (3.53), respectively. The mean score of parking space (2.56) was the lowest. In factor analysis concerning use satisfaction, 3 factors were categorized; facility management, experience, and image. By the result of multiple regression analysis, the total satisfaction of use was significantly influenced by 4 independent variables; image of street (${\beta}=.296$), management (${\beta}=.277$), continued use (${\beta}=.205$), and typical street (${\beta}=.183$). As storytelling road for urban regeneration, 'Kim Gwang-seok Street' has shown considerable success in significant improvement of image preference and user satisfaction. Therefore, the enhancement of 'placeness' through storytelling of Kim Gwang-seok, and the strengthening of its identity and symbolism, should be the basic focus of development for the street in the future.

Exploring the Creativity of the Scientific Gifted from Analyzing Descriptive Experiment-Design (서술적 실험 설계분석을 통한 과학 영재 창의성 탐색)

  • Kim, Se-Mi;Cho, Mi-Young;Kim, Sung-Won
    • Journal of The Korean Association For Science Education
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    • v.32 no.1
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    • pp.129-145
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    • 2012
  • This study investigated factors of creativity and interaction between factors that are revealed when gifted students designed scientific experiments. For this, we firstly developed items which required the written process of designing experiments to explore creativity factors. Then, we used these items as a part for letters of self-introduction to students who applied for 2011 correspondence education of general physics for the Korea Physics Olympiad. 513th letters of self-introduction which were analyzed to investigate factors of creativity in view of creativity definition after researchers' consultation, which specifically means a combination of divergent and convergent thinking. The results were as follows; (1) in the step of hypothesis building, we could not only find Originality and the Flexibility & Fluency, which were factors of divergent thinking, but also Coherency and Elaborateness, which were factors of convergent thinking. (2) in the step of the hypothesis testing, we could explore Originality, Flexibility & Fluency in divergent thinking and Coherency, Reliability, Clarity, Elaborateness in convergent thinking. (3) we also figured out three creativity types of gifted students from the viewpoint that creativity is a consequence of interaction between divergent thinking and convergent thinking; a) Type A showed divergent and convergent factors of creativity in the step of hypothesis building. However, type A did not include divergent factors of creativity on the process of the hypothesis testing. b) Type B had divergent and convergent factors of creativity on the process of the hypothesis testing, but it had not convergent factors of creativity on the step of hypothesis building. c) Finally, in Type C, only divergent factors of creativity appeared on the process of the hypothesis testing, but convergent factors of creativity could be found on the step of hypothesis building and hypothesis testing.

A Study on Visitor Motivation and Satisfaction of Urban Open Space - In the Case of Waterfront Open Space in Seoul - (도시 오픈스페이스 방문동기 및 만족도 연구 - 서울시 하천변 오픈스페이스를 중심으로 -)

  • Zoh, Kyung-Jin;Kim, Yong-Gook;Kim, Young-Hyun
    • Journal of the Korean Institute of Landscape Architecture
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    • v.42 no.1
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    • pp.27-40
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    • 2014
  • The functions of urban open space, which embraces community revitalization, are diverse. It is the means of public healthcare, learning centers for children, hub of arts and cultural programs, as well as promoter of urban tourism. However, in-depth discourse and research on the topic of urban open spaces has been limited so far. Hence, this study aims to investigate the motivations and satisfaction of visitation based on four representative waterfront open space in Seoul; Cheongyecheon Waterfront, Seoul Forest Park, Seonyudo Park and Banpo Hangang Park. The methods of study are literature review, observation investigation, and questionnaire survey. The findings are analyzed through the Exploratory Factor Analysis, Reliability Analysis, ANOVA Analysis and Regression Analysis by SPSS 18.0. The results of the study are as follows. First, urban waterfront open spaces in Seoul has 5 factors of visitor motivation; community amenity, nature access, cultural and educational assets, aesthetic enjoyment, and lastly means of escape. Second, factors of recognizing urban waterfront open spaces as community amenity and nature access indicate meaningful differences in visitor's perception by spatial characteristics. Third, distances between the destination and the visitor's residence influence significantly their perceived motivation. Close-range visitors perceived nature access as a principal factor, whilst medium to long-range visitors perceived visitation for aesthetic purposes more importantly. Lastly, the will to escape was shown as the influential factor in visitor satisfaction. Visiting open spaces for the enjoyment of nature and aesthetic purposes were factors that also closely relate to visitor satisfaction. In addition, it was found that there are different visitor motivations that influence visitor satisfaction in accordance with the spatial characteristics of each open space. In summary, it can be said that urban waterfront open space is a hybrid space connected to various types of urban contents beyond daily experiences. It was found that several visitor motivations including community development, design aesthetics, education and culture, entertainment, enjoyment of natural landscape, and relaxation, affect the overall satisfaction of the visiting experience. It is anticipated that the results of the study will be used by the local government in setting up strategies for the creation and management of successful urban waterfront open space, and for those involved in planning and design act as a starting point for spatial programming and amenities arrangement in accordance to the city's tourism and urban marketing approach.

Effects of Perceived Similarity between Consumers and Product Reviewers on Consumer Behaviors (상품후기 작성자에 대해 상품후기 독자가 느끼는 유사성이 상품후기 독자에게 미치는 영향)

  • Kim, Ji-Young;Suh, Eung-Kyo;Suh, Kil-Soo
    • Asia pacific journal of information systems
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    • v.18 no.3
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    • pp.67-90
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    • 2008
  • Prior to making choices among online products and services, consumers often search online product reviews written by other consumers. Online product reviews have great influences on consumer behavior because they are believed to be more reliable than information provided by sellers. However, ever-increasing lists of product reviews make it difficult for consumers to find the right information efficiently. A customized search mechanism is a method to provide personalized information which fits the user's requirements. This study examines effects of a customized search mechanism and perceived similarity between consumers and product reviewers on consumer behaviors. More specifically, we address the following research questions: (1) Can a customized search mechanism increase perceived similarity between product review authors and readers? (2) Are product reviews perceived as more credible when product reviews were written by the authors perceived similar to them? (3) Does credibility of product reviews have a positive impact on acceptance of product reviews? (4) Does acceptance of product reviews have an influence on purchase intention of the readers? To examine these research questions, a lab experiment with a between-subject factor (whether a customized search mechanism is provided or not) design was employed. In order to enhance mundane realism and increase generalizability of the findings, the experiment sites were built based on a real online store, cherrya.com (http://www.cherrya.com/). Sixty participants were drawn from a pool that consisted of undergraduate and graduate students in a large university. Participation was voluntary; all the participants received 5,000 won to encourage their motivation and involvement in the experiment tasks. In addition, 15 participants, who selected by a random draw, received 30,000 won to actually purchase the product that he or she decided to buy during the experiment. Of the 60 participants, 25 were male and 35 were female. In examining the homogeneity between the two groups, the results of t-tests revealed no significant difference in gender, age, academic years, online shopping experience, and Internet usage. To test our research model, we completed tests of the measurement models and the structural models using PLS Graph version 3.00. The analysis confirmed individual item reliability, internal consistency, and discriminant validity of measurements. The results show that participants feel more credible when product reviews were written by the authors perceived similar to them, credibility of product reviews have a positive impact on acceptance of product reviews, and acceptance of product reviews have an influence on purchase intention of the readers. However, a customized search mechanism did not increase perceived similarity between product review authors and readers. The results imply that there is an urgent need to develop a better customized search tool in order to increase perceived similarity between product review authors and readers.