• Journal of The Korean Association For Science Education
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• v.28 no.5
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• pp.453-463
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• 2008

This study investigated the students' perceptions of environmental scientists and their work and the factors influencing the students' images of them by using the Draw-An-Environmental-Scientist-Test (DAEST). The DAEST was administered to 413 students in 10th and 11th grades selected from three high schools in Seoul. The results revealed that the students' images of environmental scientists were different from the stereotypical images of scientists. In the students' drawings, it was difficult to distinguish the gender and age of environmental scientists. Most students also perceived environmental scientists collecting data on environmental pollution by using experimental equipments and a laptop computer in the field. The students answered that the factors affecting their images of environmental scientists were mass media, school education, internet, and so on. According to the students' grade and gender, there were differences in the perceptions of environmental scientists and their work, and there were factors that influenced their images. Educational implications of these findings are discussed.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.7
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• pp.508-519
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• 2007

Flash memory based storage has been used in various mobile systems and now is to be used in Laptop computers in the name of Solid State Disk. The Flash memory has not only merits in terms of weight, shock resistance, and power consumption but also limitations like erase-before-write property. To overcome these limitations, Flash memory based storage requires special address mapping software called FTL(Flash-memory Translation Layer), which often performs merge operation for block recycling. In order to reduce block recycling cost in NAND Flash memory based storage, we introduce another block recycling scheme which we call migration. As a result, the FTL can select either merge or migration depending on their costs for each block recycling. Experimental results with Postmark benchmark and embedded system workload show that this cost-based selection of migration/merge operation improves the performance of Flash memory based storage. Also, we present a solution of macroscopic optimal migration/merge sequence that minimizes a block recycling cost for each migration/merge combination period. Experimental results show that the performance of Flash memory based storage can be more improved by the macroscopic optimization than the simple cost-based selection.

• Journal of Hydrogen and New Energy
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• v.31 no.1
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• pp.132-137
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• 2020

Lithium secondary batteries have become an important power source for portable electronic devices such as cellular phones, laptop computers. Presently, commercialized lithium-ion batteries use a LiCoO₂ cathode. However, due to the high cost and environmental problems resulting from cobalt, an intensive search for new electrode materials is being actively conducted. Recently, solid solution LiMn_1-xNi_xO₂ have become attractive because of high capacity and enhanced safety at high voltages over 4.5 V. The Li_1.6Ni_0.35Mn_0.65O₂ compounds were conventionally prepared by a sol-gel method, which can produce the layered Li-Ni-Mn-O compounds with a high homogeneity. And by adding a graphene 2wt% the first charge-discharge voltage profiles was increased over Li_1.6Ni_0.35Mn_0.65O₂ compound. Also, the variation s of the discharge capacities with cycling showed a higher capacity retention rater. In this study, material lifecycle evaluation was performed to analyze the environmental impact characteristics of Li_1.6Ni_0.35Mn_0.65O₂ & graphene 2wt% half-cell manufacturing process. The software of material life cycle assessment was Gabi. Through this, environmental impact assessment was performed for each process. The environmental loads induced by Li_1.6Ni_0.35Mn_0.65O₂ & graphene 2wt% synthesis process were quantified and analyzed, and the results showed that the amount of power had the greatest impact on the environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.715-720
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• 2016

This paper proposes a PWM (Pulse Width Modulation) voltage mode DC-DC step-up converter for portable devices. The converter, which is operated with a 1 MHz switching frequency, is capable of reducing the mounting area of passive devices, such as inductor and capacitor, and is suitable for compact mobile products. This step-up converter consists of a power stage and a control block. The circuit elements of the power stage are an inductor, output capacitor, MOS transistors Meanwhile, control block consist of OPAMP (operational amplifier), BGR (band gap reference), soft-start, hysteresis comparator, and non-overlap driver and some protection circuits (OVP, TSD, UVLO). The hysteresis comparator and non-overlapping drivers reduce the output ripple and the effects of noise to improve safety. The proposed step-up converter was designed and verified in Magnachip/Hynix 0.18um 1-poly, 6-metal CMOS process technology. The output voltage was 5 V with a 3.3 V input voltage, output current of 100 mA, output ripple less than 1% of the output voltage, and a switching frequency of 1 MHz. These designed DC-DC step-up converters could be applied to the Personal Digital Assistants(PDA), cellular Phones, Laptop Computer, etc.

• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.314-318
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• 2006

Direct formic acid fuel cells (DFAFCs) are potential alternative power sources for portable devices such as cellular phone, personal digital assistants (PDA) and laptop computers. In this study, we developed the catalysts for great performance of fuel cell, and investigated their characteristics by using EDS and SEM. Pt-Pd catalysts showed uniform size and homogeneous distribution. As the content of palladium increased, the performance of DFAFC increased. Pd black showed the greatest performance among the five catalysts tested. Also, Pt-Pd (1:1) catalyst had an excellent maximum power density of $120mW/cm^2$. As the operating temperature increased, fuel cell performance was increased due to a reaction activity increases of catalyst. But, temperature had only a slight effect on the performance of fuel cell in the best activity range of membrane.

• Journal of the Korean Society for information Management
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• v.30 no.2
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• pp.269-295
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• 2013

This study purported to study the uses of information and communication technology (ICT) tools in their daily life among the undergraduate and graduate students majoring science and engineering. It also examined the purposes of the uses of the major ICT tools, the differences in their information technology uses between graduate and undergraduate students. The data were collected from 83 undergraduate and graduate students from four universities using content analysis of an observational logs and a survey questionnaire. The observational logs were collected using an instant message application available on a smart phone. Study results revealed desktop computers, laptop computers, and smart phones as the three most heavily used ICT tools among the participants and typical situations students use each of the three tools. There were also sharp distinctions between graduate and undergraduate students in their selection of the tools, and distinctions between work and non-work situations. The findings of this study can be used to redesign information services and systems for the scientists and engineers in the next generation.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.9
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• pp.916-920
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• 2008

The personal workspace consists of user- specified computing environment such as user profile, applications and their configurations, and user data. Mobile computing devices (i.e., cellular phones, PDAs, laptop computers, and Ultra Mobile PC) are getting smaller and lighter to provide personal work-space ubiquitously. However, various personal work-space mobility solutions (c.f. VMWare Pocket ACE[1], Mojopac[2], u-PC[3], etc.) are appeared with the advance of virtualization technology and portable storage technology. The personal workspace can be loaded at public PC using above solutions. Especially, we proposed a framework called ubiquitous personal computing environment (u-PC) that supports mobility of personal workspace based on wireless iSCSI network storage in our previous work. However, previous u-PC could support limited applications, because it uses IRP (I/O Request Packet) forwarding technique at filter driver level on Windows operating system. In this paper, we implement OS-level virtualization technology using system call hooking on Windows operating system. It supports personal workspace mobility and covers previous u-PC limitation. Also, it overcomes personal workspace loading overhead that is limitation of other solutions (i.e., VMWare Pocket ACE, Mojopac, etc). We implement a prototype consisting of Windows XP-based host PC and Linux-based mobile device connected via WiNET protocol of UWB. We leverage several use~case models of our framework for proving its usability.

• Journal of the Korea Society of Computer and Information
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• v.16 no.12
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• pp.227-234
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• 2011

Many technologies for wireless internet are increasing as more and more laptop computers, net books, smart phone and other terminals, which provide wireless network, are created. IEEE 802.11 is computer wireless network technology that used in small area, called wireless LAN or Wi-Fi. IEEE 802.11 is a set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). AP (Access Point) is installed at cafes and public places providing wireless environment. It is more convenient to use wireless internet, however, It can be seen easily around us and possible to communicate with AP. IEEE 802.11 has many vulnerability, such as packet manipulation and information disclosure, so we should pay more attention when using IEEE 802.11. Therefore this paper developing monitoring system which can find out AP and Stations that connect with it, and capturing AP's information to find out vulnerability. This paper suggests monitoring system which traffic analysis in wireless environment.

• Physical Therapy Rehabilitation Science
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• v.5 no.3
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• pp.138-142
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• 2016

Objective: The purpose of this study was to investigate how light touch with a finger affects balance ability when a posture is maintained in the condition of visual information blockage and to provide a fundamental material for developing balance ability in the process of rehabilitation treatment. Design: Cross-sectional study. Methods: The study subjects were 17 healthy men and women in their twenties and thirties who were studying at S University in Seoul. The system was comprised of an equilateral triangular force platform. Subjects were asked to step on the foot position of the force platform (Good Balance, Finland) barefooted for 30 seconds, with eyes closed, hands hanging down loosely, and feet comfortably apart. It was connected to a laptop by using Bluetooth technology. An experiment was conducted in the following three circumstances: 1) no-touch trial, 2) light touch to the back (T7 area), and 3) light touch to the middle finger of the left hand. Each subject was given a 10-minute break between consecutive measurements. The experimental circumstances were performed randomly. Anteroposterior sway (APSV), mediolateral sway velocity (MLSV), and velocity moment (VM) were measured. Results: The APSVs (mm/s) were $9.32{\pm}3.37$ and $5.45{\pm}2.98$; the MLSVs (mm/s), $6.39{\pm}3.35$ and $3.31{\pm}2.48$; and VM ($mm^2/s$), $17.13{\pm}11.75$ and $6.76{\pm}8.31$ in the first and second experimental circumstances, respectively. APSV, MLSV, and VM values were significantly improved with the 1) no-touch trial and 2) light touch to the back trail conditions compared with the 3) light touch to the middle finger of the left hand condition (p<0.05). Conclusions: This study revealed that the balance ability for maintaining a body posture was influenced more by light touch to the back (T7) than by light touch with the sensitive fingertip and body sway diminished after visual information was blocked.

• 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.