• Journal of KIISE:Databases
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• v.33 no.3
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• pp.271-281
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• 2006

Recently the need for Location-Based Service (LBS) has increased due to the development and widespread use of the mobile devices (e.g., PDAs, cellular phones, labtop computers, GPS, and RFID etc). The core technology of LBS is a moving-objects database that stores and manages the positions of moving objects. To search for information quickly, the database needs to contain an index that supports both real-time position tracking and management of large numbers of updates. As a result, the index requires a structure operating in the main memory for real-time processing and requires a technique to migrate part of the index from the main memory to disk storage (or from disk storage to the main memory) to manage large volumes of data. To satisfy these requirements, this paper suggests a unified index scheme unifying the main memory and the disk as well as migration policies for migrating part of the index from the memory to the disk during a restriction in memory space. Migration policy determines a group of nodes, called the migration subtree, and migrates the group as a unit to reduce disk I/O. This method takes advantage of bulk operations and dynamic clustering. The unified index is created by applying various migration policies. This paper measures and compares the performance of the migration policies using experimental evaluation.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.70-80
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• 2018

Due to the recent development of social media and mobile devices, graph data have been using in various fields. In addition, caching techniques for reducing I/O costs in the process of large capacity graph data have been studied. In this paper, we propose a multi-layer caching scheme considering the connectivity of the graph, which is the characteristics of the graph topology, and the history of the past subgraph usage. The proposed scheme divides a cache into Used Data Cache and Prefetched Cache. The Used Data Cache maintains data by weights according to the frequently used sub-graph patterns. The Prefetched Cache maintains the neighbor data of the recently used data that are not used. In order to extract the graph patterns, their past history information is used. Since the frequently used sub-graphs have high probabilities to be reused, they are cached. It uses a strategy to replace new data with less likely data to be used if the memory is full. Through the performance evaluation, we prove that the proposed caching scheme is superior to the existing cache management scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1383-1388
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• 2011

Due to many recent activities on enforcement of the intensified environmental regulation such as the policies of curbing the greenhouse gas and the Restriction of Hazardous Substances (RoHS), the usage of Light emitting diode (LED) has been rapidly increased and energy efficient management of LED light system is regarded as an important technology to enhance the energy efficiency. In this paper, we propose an energy-efficient control scheme of LED light, being composed of multiple light sources. The proposed scheme controls the intensity of LED light source to minimize the total intensity while providing the quality of lighting service. The intensity of light is assumed to be proportional to power consumption, thus the objective is to minimize the total power consumption. A linear programming problem is formulated to find the optimal intensity of each light source and procedure to apply the proposed scheme in the real system is suggested. The performance evaluation results elucidate that the proposed scheme achieves over 20% improvement in power consumption of light intensity in comparison with the conventional dimming control scheme.

• Journal of Korean Society on Water Environment
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• v.32 no.1
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• pp.30-35
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• 2016

Urban areas generate large amounts of stormwater and non-point source (NPS) pollutants during rainfall events. These are caused by various land use runoffs, vehicular and human activities and increased impervious cover. The increased runoff and NPS pollutants cause water quality deterioration in the receiving waters and adversely affect the aqua-ecosystem. These environmental impacts could be reduced through the application of low impact development (LID) techniques. In Korea, more than 80% of the total rainfall occurs in summer and most of these were 10 mm or less. Therefore, if the LIDs developed were able to cope with rainfall of 10 mm and below, NPS management could be efficiently conducted. This research was performed to determine the effect of varying amounts of rainfall on the performance capability of an established infiltration and filtration facility (IF facility) that can be applied to Korea's common rainfall ranges. The IF facility area was 1.75% of the catchment area, however the facility treated more than 40% and 60% runoff volume and pollutant reduction respectively for a 10 mm rainfall. Lastly, higher volume and pollutant reduction could be attained when the LID area was at least 2% of the entire catchment.

• Structural Monitoring and Maintenance
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• v.2 no.1
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• pp.77-93
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• 2015

The idea of using measured dynamic characteristics for damage detection is attractive because it allows for a global evaluation of the structural health and condition. However, vibration-based damage detection for complex structures such as long-span cable-supported bridges still remains a challenge. As a suspension or cable-stayed bridge involves in general thousands of structural components, the conventional damage detection methods based on model updating and/or parameter identification might result in ill-conditioning and non-uniqueness in the solution of inverse problems. Alternatively, methods that utilize, to the utmost extent, information from forward problems and avoid direct solution to inverse problems would be more suitable for vibration-based damage detection of long-span cable-supported bridges. The auto-associative neural network (ANN) technique and the probabilistic neural network (PNN) technique, that both eschew inverse problems, have been proposed for identifying and locating damage in suspension and cable-stayed bridges. Without the help of a structural model, ANNs with appropriate configuration can be trained using only the measured modal frequencies from healthy structure under varying environmental conditions, and a new set of modal frequency data acquired from an unknown state of the structure is then fed into the trained ANNs for damage presence identification. With the help of a structural model, PNNs can be configured using the relative changes of modal frequencies before and after damage by assuming damage at different locations, and then the measured modal frequencies from the structure can be presented to locate the damage. However, such formulated ANNs and PNNs may still be incompetent to identify damage occurring at the deck members of a cable-supported bridge because of very low modal sensitivity to the damage. The present study endeavors to enhance the damage identification capability of ANNs and PNNs when being applied for identification of damage incurred at deck members. Effort is first made to construct combined modal parameters which are synthesized from measured modal frequencies and modal shape components to train ANNs for damage alarming. With the purpose of improving identification accuracy, effort is then made to configure PNNs for damage localization by adapting the smoothing parameter in the Bayesian classifier to different values for different pattern classes. The performance of the ANNs with their input being modal frequencies and the combined modal parameters respectively and the PNNs with constant and adaptive smoothing parameters respectively is evaluated through simulation studies of identifying damage inflicted on different deck members of the double-deck suspension Tsing Ma Bridge.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.4
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• pp.79-86
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• 2016

Physical layer security is cryptography technique to protect information by using physical nature of signals. Currently, many works on physical layer security have been actively researching while those researching models still have some problems to be solved. Eavesdropper does not share its channel state information with legitimate users to hide its presence. And when node transmits signal, hardware impairments are occurred, whereas many current researches assume that node model is ideal node and does not consider hardware impairments. The main features and contributions of this paper to solve these problems are as follows. First, our proposed system model deploys torch node around legitimate user to obtain channel state information of eavesdropper and considers hardware impairments by using channel state information of torch node. Second, we derive closed-form expression of intercept probability for the proposed system model. The results of the performance evaluation through various simulations to find out the effects on proposed system model in physical layer security show that imperfect channel state information does not effect on intercept probability while imperfect node model effects on intercept probability, Ergodic secrecy capacity and secrecy capacity.

• Journal of Korean society of Dental Hygiene
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• v.9 no.4
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• pp.606-619
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• 2009

Objectives : This study was to examine the state of customized visiting oral health programs in a bid to help facilitate the unified operation of the programs and the development of required guidelines. Methods : The subjects in this study were 49 dental hygienists who were professionals responsible for customized visiting health care programs across the nation. Results : 1. Regarding the form of employment of the dental hygienists were investigated many contract and daily workers. 2. As to the possession of equipment necessary for visiting oral health programs, denture cleaners(12.2%) were most widely possessed in some regions, followed by mobile scalers(10.2%) and mobile suctions(8.2%). In terms of expendable devices and materials, dental mirrors, pincettes and explorers were the most widely possessed dental checkup devices, and the most widely possessed oral hygiene supplies were toothbrushes, interdental brushes and denture cleaners. Those devices and materials were in more possession than the other types of devices and materials. The most widely possessed equipment for educational purpose was laptop computers, followed by beam projectors and screens. The most widely possessed teaching materials were dentiform, followed by CD-ROMs. 3. Those whom they visited the most for oral health care service were elderly people, followed by the disabled and patients with chronic diseases. The dental hygienists who went out to visit those people outnumbered the others who stayed at public health centers. Concerning the types of visiting oral health care service, the most prevalent service provided to the elderly included denture cleaning/management, oral massage and preventive treatment against dental caries. The most dominant service provided to the disabled involved education of the oral health care act, preventive treatment against dental caries and toothbrushing by professionals. The most common service offered to patients with chronic diseases was education of the oral health care act and oral health education. The dental hygienists paid a visit to a mean of 5.8 households a day. The average weekly number of households cared by the dental hygienists was 27.3. It took a mean of 37.1 minutes for them to take care of each household. 4. As for satisfaction level with the implementation of the visiting oral health programs, they expressed the greatest satisfaction at teamwork with professionals($3.56{\pm}0.94$), followed by the professionalism of their work($3.21{\pm}0.94$) and workload($3.08{\pm}0.94$). Their satisfaction level with the work conditions required for creative job performance($2.75{\pm}0.98$) and partnership with other institutions($2.64{\pm}1.03$) was below 3.0. In regard to the impact of their characteristics, marital status made a statistically significant difference to satisfaction level with workload. The unmarried dental hygienists were more pleased with their workload than the married ones(p<0.05). 5. As to needs for education for professionalism improvement, they asked for education about visiting oral health care skills the most, followed by education about oral health care for patients with chronic diseases, education of planning/evaluation and education of oral health care for the disabled. Conclusions : The top priority for the vitalization of the programs was the procurement of budget, followed by the procurement of equipment and educational media and the procurement of human resources.

• Journal of Bio-Environment Control
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• v.22 no.2
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• pp.81-86
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• 2013

This experiment was carried out to select white asparagus varieties suitable for shading culture in greenhouse. Eight white and one green varieties were tested. Seeds were sown in 72-cell trays in a glasshouse on 24 Dec. 2008 and the seedlings were transplanted in a P.E house on 22 May 2009. Planting distances were 30 cm apart in a raw and 125 cm between the raws. For white asparagus production, small tunnel ($210cm{\times}160cm$) was established inside the P.E house, and covered with black and white P.E film (0.1 mm) on 5 March 2010. Days to sprouting took 5 days in 'Ravel' variety and took 16 to 18 days in 'Backlim', 'Horlim', 'Herkolim' varieties. The number of spear was highest in 'Ravel' with 6 and lowest in 'Backlim' with 3.7. The spear weight was heaviest in 'Herkolim' with 25.6 g and lightest in 'Ravel' with 15.6 g. The highest total yield was in 'Herkolim' with 296 kg/10a, followed by 'Super welcome' with 275 kg/10a and lowest in 'Rapsody' with 176 kg/10a. Marketable yields in 'Super welcome' and 'Herkolim' were 241 kg/10a and 239 kg/10a, respectively, and the yield was lowest in 'Rapsody' with 139 kg/10a. The L grade (over 20 g of spear weight) was highest in 'Herkolim'. Accordingly, 'Herkolim' was the most suitable white asparagus variety among the tested varieties for shading cultivation in greenhouse.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.492-500
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• 2018

The performance evaluation of cold weather clothing is mainly carried out with thermal resistance. However, the results of the revised test method regarding the same specimen were decreased compare to previous one. In addition, there were deviations of the results among the authorized testing institutes according to the different interpretation of the KS test method. This makes it a considerable difficulty to the quality assurance of combat supplies. The purpose of this study is to minimize the variation of the results before and after the revision by analyzing the cause of the decrease in the heat insulation rate according to the revised test method. For this purpose, the difference between the test conditions before and after the revision of KS is analyzed and the possible results are reviewed. In addition, we want to minimize the result deviation between testing laboratories by analyzing the cause of the result deviation between test laboratories according to arbitrary interpretation of the standard. Based on this, we propose a standardized test method to prevent the decrease of the heat insulation rate by checking the pre-revision test method and the condition with the least deviation.

• Korean Journal of Digital Imaging in Medicine
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• v.11 no.2
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• pp.115-119
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• 2009

I think this will be valuable reference for assuring consistency and homogeneity of clarity and managing dental radiation equipment by experimentation of dental radiation equipment permanent which based on KS C IEC 61223-3-4 standard and KS C IEC 61223-2-7. Put a dental radiation generator and experiment equipment as source and film(sensor) length within 30 em, place the step-wedge above the film(sensor). Tie up tube voltage 60 kVp, tube current 7 mA and then get an each image through CCD sensor and film by changing the exposure time as 0.12sec, 0.25sec, 0.4sec. Repeat the test 5times as a same method. Measure the concentration of each stage of film image, which gained by experiment, using photometer. And the image that gained by CCD sensor, analyze the pixel value's change by using image J, which is analyzing image program provided by NIH(National Institutes of Health). In case of film, while 0.12sec and 0.25sec show regular rising pattern of density gap as exposure time's increase, 0.4sec shows low rather than 0.12sec and 0.25sec. In case of CCD sensor density test, the result shows opposite pattern of film. This makes me think that pixels of CCD's sensor can have 0~255 value but it becomes saturation if the value is over 255. The way that getting clear reception during decreasing human's exposed radiation is one of maintaining an equipment as a best condition. So we should keeping a dental radiation equipment's condition steadily through cyclic permanent test after factor examination. Even digital equipment doesn't maintain a permanent, it can maintain a clarity by post processing of image so that hard to set it as standard of permanent test. Therefore it would be more increase the accuracy that compare a film as standard image. Thus I consider it will be an important measurement to care for dental radiation equipment and warrant homogeneity, consistency of dental image's clarity through comparing pattern which is the result from factor test against cyclic permanent test.