• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.82-89
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• 2019

The importance of aviation safety has been emphasized recently due to the development of aviation industry. Despite the efforts of each country and the improvement of screening equipment, screening tasks are still difficult and detection failures are frequent. The purpose of this study was to examine the effect of feedback on improving signal detection performance applying a Simulated Baggage Screening Program(SBSP) for improving aviation safety. SBSP consists of three parts: image combination, option setting and experiment. The experimental images were color-coded to reflect the items' transmittance of the x-rays and could be combined as researchers' need. In the option, the researcher could set up the information, incentive, and comments needed for training to be delivered on a number of tasks and times. Experiment was conducted using SBSP and participant's performance information (hit, missed, false alarms, correct rejection, reaction time, etc.) was automatically calculated and stored. A total of 50 participants participated and each participant was randomly assigned to feedback and non-feedback group. Participants performed a total of 200 tasks and 20(10%) contained target object(gun and knife). The results showed that when the feedback was provided, the hit, correct rejection ratio and d′ were increased, however, the false alarms and miss decreased. However, there was no significant difference in response criteria(${\beta}$). In addition, implications, limitations of this study and future research were discussed.

• Environmental Analysis Health and Toxicology
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• v.31
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• pp.22.1-22.7
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• 2016

Objectives This study analyzed the associations between mobile phone call frequency and duration with non-specific symptoms. Methods This study was conducted with a population group including 532 non-patient adults established by the Korean Genome and Epidemiology Study. The pattern of phone call using a mobile phone was investigated through face-to-face interview. Structured methods applied to quantitatively assess health effects are Headache Impact Test-6 (HIT-6), Psychosocial Well-being Index-Short Form, Beck Depression Inventory, Korean-Instrumental Activities of Daily Living, Perceived Stress Scale (PSS), Pittsburgh Sleep Quality Index, and 12-item Short Form Health Survey where a higher score represents a higher greater health effect. Results The average daily phone call frequency showed a significant correlation with the PSS score in female subjects. Increases in the average duration of one phone call were significantly correlated with increases in the severity of headaches in both sexes. The mean (standard deviation) HIT-6 score in the subgroup of subjects whose average duration of one phone call was five minutes or longer was 45.98 (8.15), as compared with 42.48 (7.20) in those whose average duration of one phone call was <5 minutes. The severity of headaches was divided into three levels according to the HIT-6 score (little or no impact/moderate impact/substantial or severe impact), and a logistic regression analysis was performed to investigate the association between an increased phone call duration and the headache severity. When the average duration of one phone call was five minutes or longer, the odds ratio (ORs) and the 95% confidence intervals (CIs) for the moderate impact group were 2.22 and 1.18 to 4.19, respectively. The OR and 95% CI for the substantial or severe impact group were 4.44 and 2.11 to 8.90, respectively. Conclusions Mobile phone call duration was not significantly associated with stress, sleep, cognitive function, or depression, but was associated with the severity of headaches.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.873-889
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• 2014

IP address lookup is very crucial in performance of routers. Several works have been done on prefix caching to enhance the performance of IP address lookup. Since a prefix represents a range of IP addresses, a prefix cache shows better performance than an IP address cache. However, not every prefix is cacheable in itself. In a prefix cache it causes false hit to cache a non-leaf prefix because there is possibly the longer matching prefix in the routing table. Prefix expansion techniques such as complete prefix tree expansion (CPTE) make it possible to cache the non-leaf prefixes as the expanded forms, but it is hard to manage the expanded prefixes. The expanded prefixes sometimes incur a great deal of update overhead in a routing table. We propose a bitmap-based prefix cache (BMCache) to provide low update overhead as well as low cache miss ratio. The proposed scheme does not have any expanded prefixes in the routing table, but it can expand a non-leaf prefix using a bitmap on caching time. The trace-driven simulation shows that BMCache has very low miss ratio in spite of its low update overhead compared to other schemes.

• Journal of the Korean Wood Science and Technology
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• v.44 no.2
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• pp.274-282
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• 2016

This aims of this study were to investigate the relationship between non-destructive evaluation (NDE) and actual bending properties of particleboard, and to predict the bending properties of three-layer particleboard. Three kinds of raw materials, i.e. Hinoki (Chamaecyparis obtusa Endl.) strand, knife-milled Douglas-fir (Pseudotsuga manziesii (Mirb) Franco), and hammer-milled matoa (Pometia spp.) obtained from wooden industry, were utilized as furnish for experimental panel with methylene diphenyl diisocyanate (MDI) resin as binder. The NDE test was conducted by hit sounds using an FFT analyzer according to the spectrum peak of wave frequency, while the static bending test was conducted according to JIS A-5908. The results reveal that the dynamic Young's modulus as an NDE test has a potential for being used to predict the elastic bending of particleboards by a specific equation for adjusting its proper values. The values of NDE and static test are significantly different with a deviation range at 3-20%. The bending stiffness of three-layer particleboards manufactured from different wood species is predictable by observing the bending stiffness of two elements based on the thickness of its layers. The predicted values of bending stiffness and static test are significantly different with a deviation range at 5-24%.

• Asia pacific journal of information systems
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• v.12 no.1
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• pp.139-158
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• 2002

As the telecommunication market becomes mature in Korea, severe competition has already begun on the market. While service providers struggled for the last couple of years to acquire as many new customers as possible, nowadays they are making more efforts on retaining the current customers. The churn management by analyzing customers' demographic and transactional data becomes one of the key customer retention strategies which most companies pursue. However, the customer data analysis has still remained at the basic level in the industry, even though it has considerable potential as a tool for understanding customer behavior. This paper develops several churn prediction models using data mining techniques such as logistic regression, decision trees, and neural networks. For model-building, real data were used which were collected from one of the major telecommunication companies in Korea. This paper explores various ways of comparing model performance, while the hit ratio was mainly focused in the previous research. The comparison criteria used in this study include gain ratio, Kolmogorov-Smirnov statistics, distribution of the predicted values, and explanation ability. This paper also suggest some guidance for model selection in applying data mining techniques.

• The KIPS Transactions:PartA
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• v.10A no.3
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• pp.261-268
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• 2003

In this paper, we propose a new caching strategy for web servers. The proposed strategy collects only the statistics of the requested file, for example the popularity, when a request arrives. At a point of time, only files with higher forecasted popularity are cached all together. Forecasted popularity based lazy caching (FPLC) strategy uses exponential smoothing method for forecast popularity of web files. And, FPLC strategy shows that the cache hit ratio and the cache transfer ratio are better than those produced by other caching strategy. Furthermore, the experiment that is performed with real log files built from web servers shows our study on forecast method for popularity of web files improves cache efficiency.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.2
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• pp.197-204
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• 2021

In this study, the well-known non-destructive acoustic emission (AE) and electrical resistivity methods were employed to predict quantitative damage in the silo structure of the Wolsong Low and Intermediate Level Radioactive Waste Disposal Center (WLDC), Gyeongju, South Korea. Brazilian tensile test was conducted with a fully saturated specimen with a composition identical to that of the WLDC silo concrete. Bi-axial strain gauges, AE sensors, and electrodes were attached to the surface of the specimen to monitor changes. Both the AE hit and electrical resistance values helped in the anticipation of imminent specimen failure, which was further confirmed using a strain gauge. The quantitative damage (or damage variable) was defined according to the AE hits and electrical resistance and analyzed with stress ratio variations. Approximately 75% of the damage occurred when the stress ratio exceeded 0.5. Quantitative damage from AE hits and electrical resistance showed a good correlation (R = 0.988, RMSE = 0.044). This implies that AE and electrical resistivity can be complementarily used for damage assessment of the structure. In future, damage to dry and heated specimens will be examined using AE hits and electrical resistance, and the results will be compared with those from this study.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.256-258
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• 2005

현대 사회에서 무선 인터넷의 활용 분야가 날로 확대되어 가고 있으나 낮은 대역폭, 단말기 해상도의 다양성 등의 여러 가지 근본적인 문제들을 가지고 있다. 이러한 문제를 해결하기 위하여 무선인터넷 프록시 서버를 사용하며, 데이터에 대한 압축과 캐싱 방법을 사용한다. 캐싱 관점에서 해시의 사용은 캐시의 히트율(Hit ratio)을 높이며, 캐시간 협동성(Cooperative Caching)도 가지게 한다. 그러나 기존의 해시기반 스케줄링 알고리즘에서 사용자의 요청이 균등하게 분배되지 못하고 일부 서버로 몰리는 문제점을 가지고 있다. 본 논문에서는 해시 테이블을 이용한 라운드로빈 방식과 캐시 이용률을 이용한 스케줄링 방식을 제안하여, 캐시간 협동성과 사용자의 요청을 고르게 분포 시키도륵 하였다. 16대의 컴퓨터를 이용하여 실험을 수행하였고, 실험결과를 통해 제안된 방식이 기존 방식보다 클라이언트의 요청을 캐시 서버들 사이로 균일하게 분포시키고 이에 따라 전체 무선 인터넷 프록시 서버의 성능이 향상됨을 확인하였다.

• ETRI Journal
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• v.10 no.3
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• pp.83-91
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• 1988

This paper describes the architecture and the performance analysis of a multiprocessor system, which is based on the shared memory and single system bus. The system bus provides the pended protocol for the multiprocessor environment. Analyzing the processor utilization, address/data bus utilization and memory conflicts, we use a simulation model. The hit ratio of private cache memory is a major factor on the linear increase of the performance of a shared memory based multiprocessor system.

• Journal of Fashion Business
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• v.4 no.3
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• pp.103-114
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• 2000

The purpose of this study was to test the discriminant analysis model of Quick Response system and to examine the detailed relationship between each discriminant factor and Quick Response adoption. In this discriminant analysis model of Quick Response system, firm size, strategic type, product category, fashion trend, selling time and the Quick Response benefits were included as discriminant factors. Onehundred and two subjects were randomly selected for the survey study and discriminant analysis, descriptive analysis, t-test, and x square test were used for the data analysis. The results of this study were: 1. Wilks Lambda and F value support the discriminant analysis model that, taken together firm size, strategic type, product category, fashion trend, selling time and the Quick Response benefits significantly help to explain Quick Response adoption. 2. The importance of discriminant ability was, in order, firm size, the Quick Response benefits, women's wear, fashion trend, analyzer, selling time, reactor, defender and men's wear. 3. The discriminant function had the high hit ratio, so this can be well used for the classification of Quick Response adoption/nonadoption.