• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.583-590
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• 2013

Variable emittance radiators can be used in a thermal management system in space because their total emittance changes depending on the temperature of the system. When the temperature of the system decreased, the emittance also decreased so as to minimize the heat loss to the environment. In contrast, when the temperature of the system increased, the emittance also increased such that radiation cooling could occur. Thermochromic materials, whose emittance is a function of the temperature, are often used in variable emittance radiators because no additional parts are needed. In this study, we fabricated a variable-emittance coating by using a sol-gel method based on LSMO ($La_{1-x}Sr_xMnO_3$) and experimentally characterized the emittance change with respect to temperature. Furthermore, we also examined the stability of LSMO film in space environments by exposing it to extremely low pressure and temperature.

• Journal of the Korean Wood Science and Technology
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• v.37 no.4
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• pp.330-339
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• 2009

The material properties of Cedar (Cryptomeria japonica) were evaluated according to heat treatment conditions. The special focus was made on the color control of cedar wood by heat treatment. The difference of color between sapwood and heartwood could be reduced by heat treatment at a temperature above $170^{\circ}C$. Long heating time was more effective in reducing the difference. The Equilibrium Moisture Content (EMC) of heat-treated wood was as low as 50 percent. The result obviously indicates that heat-treated wood is more dimensionally stable in the change of moisture condition than the control. The heat-treated wood was also effective in increasing the durability against wood rotting fungi. However, more study is required to develop heat treatment as an environmentally-friendly technology for wood preservation without chemical. The mechanical properties of heat-treated wood showed relatively higher performance than the control in general. Meanwhile the dramatic decrease in impact bending stress due to the loss of ductility may limit uses of heat-treated wood in certain cases. There were no significant changes in microscopic structure which may cause changes in mechanical properties. Further study on the chemical analysis of heat-treated wood is needed to scrutinize the causes of changes of material properties.

• Proceedings of the ESK Conference
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• 1993.10a
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• pp.65-75
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• 1993

원자력발전소에서 발생하는 고장정지 사건에 내포된 인적오류의 발생내용을 흥미있고 현장감 있게 묘사시킴과 동시에 종사원들의 인적오류를 저감시키기 위한 새로운 교육훈련방 법으로써 멀티미디어 기술의 사용을 고려하였다. 즉, 컴퓨터 환경하에서 숫자와 텍스트, 음 향 및 음성, 그래픽, 애니메이션, 화상 등의 미디어를 사용하여 인적오류로 인한 고장정지 사건발생의 내용을 전달하는 새로운 교육훈련 방법을 사용하는 것이다. 이를 위하여 고장정 지 사건과 관련한 원자력발전소 구성정보와 종사원의 활동정보를 입출력하기 위한 멀티미디어 인터페이스를 설계하였다. 설계는 멀티미디어 제공환경 구축과 인터페이스 운영논리 설정의 두단계로 구성한 절차에 따라 수행하였다. 멀티미디어 인터페이스는 원자력발전소 구성정보를 설계하여 저장시켜둔 퍼스널 컴퓨터 환경하에서 운영되며, 입력 및 출력의 두가지 인터페이스 를 갖는다. 입력 인터페이스는 인적 오류를 포함한 고장정지 사건의 발생내용을 숫자, 텍스트, 음성 미디어로 받아들여 출력 인터페이스에서 사용될 수 있도록 미디어 결합을 수행하고, 컴퓨터 저장장치에 저장하는 기능을 수행한다. 출력 인터페이스는 저장장치에 기록된 내용을 판독하여 고장정지의 진행경위와 인적오류의 발생내용을 숫자, 문자, 텍스트, 음성, 음향, 그래픽 애니메 이션, 정지화상으로 원자력발전소 종사원들에게 출력시켜 주는 기능을 수행한다. 멀티미디어 출력정보는 사용자가 CRT 화면에 제공되는 버튼 또는 Click Touch 메뉴를 사용함에 따라 이전, 이후의 출력정보로 전이할 수 있도록 하였다.상대적으로 중요한 검사 항목으로 나타났다. 또한 상대적 중요도 결과를 적용한 적성검사 성적이 적용하지 않은 적성검사 성적에 비해 비행성적에 대한 예측 능력이 좋은 것으로 평가되었다.al age)가 있다는 것을 의미하는 것이다. 한편, 생산현장에서는 자동화, 기계화가 진보되어 육체적인 노동이 경감된 결과, 중고령자라도 할 수 있는 작업이 많아지고 있다. 또, VDT (Visual Dislay Terminal) 작업과 같은 정보처리 작업의 수요가 증가하여 그 인재의 부족이 지적되고 있다. 따라서 중고령자의 기능을 조사하여 어떠한 작업에 적합한가를 판단하는 것이 중요한 과제로 되었다. 그러나 노동에는 많은 기능이 관여 하고, 그 내용에 따라서 요구되는 기능이 서로 다르기 때문에 노동적응능력의 기본적인 기능으로 보여지는 것에 좁혀서 작업능력의 연령증가 변화에 대하여다원적 평가를 하는 것이 실제적이라고 할 수 있다. 따라서 본 연구에서는 인간이 가지고 있는 다수의 기능중에서 수지교 치성과 연령증가와의 관계를 조사한다. 만약 연령증가 만으로 수지교치성을 평가 할 수 없는 경우에는 어떠한 요인이 수지기민성의 변화에 영향을 미치는가를 검토한다.t list)에서 자동적으로 사건들의 순서가 결정되도록 확장하였으며, 설비 제어방식에 있어서도 FIFO, LIFO, 우선 순위 방식등을 선택할 수 있도록 확장하였다. SIMPLE는 자료구조 및 프로그램이 공개되어 있으므로 프로그래머가 원하는 기능을 쉽게 추가할 수 있는 장점도 있다. 아울러 SMPLE에서 새로이 추가된 자료구조와 함수 및 설비제어 방식등

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.435-435
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• 2012

농경지 중에서 밭은 논보다 농약 비료 사용률이 매우 높기 때문에 논에 비해 비점오염물질 배출량이 훨씬 심각한 것으로 조사되고 있어 밭경지 비점오염저감기법 개발 및 체계적인 제어대책 수립이 무엇보다도 절실하다. 현재 선진국을 중심으로 다양하게 제시되고 있는 밭경지 비점오염 제어기법들 중 초생대에 대한 성공적 연구사례 및 적용사례에 대한 자료가 상당히 많이 제시되고 있으나, 우리나라의 경우 초생대를 적용한 밭경지 비점오염저감에 대한 기술개발 및 체계적인 연구가 아직 미비한 실정이다. 따라서 본 연구는 초생대의 현장설치 및 모니터링을 통해 초생대의 비점오염부하 저감효과에 대한 기초조사를 실시하고 우리나라 밭경지에서의 적용가능성을 알아보고자 한다. 초생대 현장 실험을 위한 시험포는 경상북도 군위군 효령면에 위치한 경북대 농생대 부속농장 밭경지 $1,500m^2$ (455평)를 선정하였다. 시험포는 1개의 대조구와 6개의 처리구로 구성하였으며, 각 시험구의 크기는 길이 12m ${\times}$ 폭 4m (초생대 길이 2m ${\times}$ 폭 4m 포함)로 하였다. 초생대 조성을 위한 초종선정은 초생대 조성이 용이하고 관리효율성이 높은 초종으로서 손쉽게 구할 수 있고, 우리나라 기후와 토양특성에 적합하며 초생대 기능에 부합한 것으로 선정하였다. 초생대 시험포장에 재배할 작물은 우리나라 대표 밭작물인 콩으로 선정하였으며, 작물재배를 위한 퇴비, 비료, 제초제 등은 농촌진흥청에서 제시한 표준재배법에 준하여 시용하였다. 초생대 비점오염저감효과를 평가하기 위해서 시험포장에 플륨, 수위계, 강우계 등으로 구성된 모니터링시스템을 설치하였으며, 플륨의 수위-유량 캘리브레이션을 실시하였다. 실험을 위해 2회의 인공강우와 1회의 자연강우에 대한 모니터링을 실시하였다. 그 결과 초생대 조성이 유출률에 상당한 영향을 미치는 것으로 조사되었다. 인공강우의 경우 초생대 설치에 따라 유출률의 범위가 14.5~95.8% 정도로 감소되는 현상을 보였으며, 자연강우에서도 6.1~11.3% 정도의 유출률 감소를 보였다. 초생대 시험구별 유출률에 차이를 나타낸 이유는 현장실험시의 시험구별 지면조건과 초생대 초종별 특성(초장, 경경, 밀도 등)의 차이에 기인한 결과로 사료되었다. 비점오염저감효과 측면에서는 기존 밭농사 방식을 그대로 채택한 대조구에 비해 초생대 시험구에서 TS의 경우 15.6~90.3%, T-P의 경우 49.9~87.8%, T-N의 경우 6.7~91.1%의 저감율을 각각 나타내었다. 이러한 결과들을 통해 초생대 기법이 우리나라 밭경지 비점오염부하를 저감시키는데 유용하게 활용될 수 있을 것으로 판단된다.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.901-908
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• 2018

Graphite is used as a sample anode active material. However, since the maximum theoretical capacity is limited to $372mA\;h\;g^{-1}$, a new anode active material is required for the development of a high capacity lithium ion battery. The maximum theoretical capacity of Si is $4200mA\;h\;g^{-1}$, which is higher than that of graphite. However, it is not suitable for direct application to the anode active material because it has a volume expansion of 400%. In order to minimize the decrease of the discharge capacity due to the volume expansion, the Si was pulverized by the dry method to reduce the mechanical stress and the volume change of the reaction phase, and the change of the volume was suppressed by coating the carbon layers to the particle size controlled Si particles. And carbon fiber is grown like a thread on the particle surface to control secondary volume expansion and improve electrical conductivity. The physical and chemical properties of the materials were measured by XRD, SEM and TEM, and their electrochemical properties were evaluated. In this study, we have investigated the synthesis method that can be used as anode active material by improving cycle characteristics of Si.

• Journal of Conservation Science
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• v.35 no.3
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• pp.217-225
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• 2019

The chimi(ridge-end tile) of Wangheungsa temple is the oldest in our country. The upper part of the chimi was excavated from the southern side of Wangheungsa temple and the lower part from the northern side. These parts are considered to be portions of the same chimi, because they are similar in shape and are excavated from two sides of the same temple structure. However, the original shape of the chimi cannot be determined owing to substantial deterioration. Hence, in this study, replicas of the deteriorated chimi portions of Wangheungsa temple were fabricated by employing 3D scanning technology and the computer numerical control machining method. While observing the bending phenomenon of the chimi, the proposed model was warped realistically on the basis of the bending direction of the actual chimi. Consequently, the restoration process was modified several times. The results indicated that no gaps can be found between the upper and lower parts, and the corresponding patterns connect naturally. Furthermore, the proposed method is contactless, safe, operable, reproducible, and appropriate for restoration of artifacts. Additionally, the modeling data is semi-permanent. Hence, if modelling data is appropriately applied as per the characteristics of artifacts, it can be utilized in various fields such as virtual exhibitions, hands-on exhibitions, cultural heritage restoration, and production of teaching aids and souvenirs.

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.6
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• pp.41-49
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• 2022

The Internet Engineering Task Force (IETF) has standardized RPL (IPv6 Routing Protocol for Low-power Lossy Network) as a routing protocol for Low Power and Lossy Networks (LLNs), a low power loss network environment. RPL creates a route through an Objective Function (OF) suitable for the service required by LLNs and builds a Destination Oriented Directed Acyclic Graph (DODAG). Existing studies check the residual energy of each node and select a parent with the highest residual energy to build a DODAG, but the energy exhaustion of the parent can not avoid the network disconnection of the children nodes. Therefore, this paper proposes EC-RPL (Enhanced Connectivity-RPL), in which ta node leaves DODAG in advance when the remaining energy of the node falls below the specified energy threshold. The proposed protocol is implemented in Contiki, an open-source IoT operating system, and its performance is evaluated in Cooja simulator, and the number of control messages is compared using Foren6. Experimental results show that EC-RPL has 6.9% lower latency and 5.8% fewer control messages than the existing RPL, and the packet delivery rate is 1.7% higher.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.2
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• pp.55-60
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• 2022

In this study, a heat treatment experiment was conducted to select a new melt composition that can easily control the unintentionally doped nitrogen (N-UID) without degrading the SiC single crystal quality during TSSG process. The experiment was carried out for about 2 hours at a temperature of 1900℃ under Ar atmosphere. The used melt composition is based on either Si-Ti 10 at% or Si-Cr 30 at%, and also Co or Sc transition metals, which are effective for carbon solubility, were added at 3 at%, respectively. After the experiment, the crucible was cross-sectionally cut, and evaluated the Si-C reaction layer on the crucible-melt interface. As a result, with Sc addition, Si-C reaction layers uniformly occurred with a Si-infiltrated layer (~550 ㎛) and a SiC interlayer (~23 ㎛). This result represented that the addition of Sc is an effective transition metal with high carbon solubility and can feed carbon sources into the melt homogeneously. In addition, Sc is well known to have low reactivity energy with nitrogen compared to other transition metals. Therefore, we expect that both growth rate and Nitrogen UID can be controlled by Si-Sc based melt in the TSSG process.

• Korean Journal of Agricultural Science
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• v.36 no.1
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• pp.73-85
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• 2009

An investigation was conducted to get the basic data for establishing structural safety and environmental management of tomato greenhouses in Chungnam region. The contents of the investigation consisted of actual state of greenhouse structures and environmental control facilities. Most of greenhouses were arch type single-span plastic houses and they had too low height for growing tomatoes. Frameworks of multi-span greenhouses were suitable, but those of single-span were mostly insufficient. Every greenhouse had thermal curtain movable or covering fixed inside the greenhouse for energy saving, and heating facilities were mostly warm air heater. Irrigation facilities were mostly drip tube and controlled by manual operation or timer. Almost all of the greenhouses didn't install high level of environmental control facilities such as ventilator, air circulation fan, $CO_2$ fertilizer, insect screen, supplemental light, and cooling device.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.8
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• pp.1296-1303
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• 2014

This study was conducted to develop predictive models for the growth of Bacillus cereus on carrot treated with slightly acidic electrolyzed water (SAcEW) and ultrasonication (US) at different storage temperatures. In addition, the inactivation of B. cereus by US with SAcEW was investigated. US treatment with a frequency of 40 kHz and an acoustic energy density of 400 W/L at $40^{\circ}C$ for 3 min showed the maximum reduction of 2.87 log CFU/g B. cereus on carrot, while combined treatment of US (400 W/L, $40^{\circ}C$, 3 min) with SAcEW reached to 3.1 log CFU/g reduction. Growth data of B. cereus on carrot treated with SAcEW and US at different temperatures (4, 10, 15, 20, 25, 30, and $35^{\circ}C$) were collected and used to develop predictive models. The modified Gompertz model was found to be more suitable to describe the growth data. The specific growth rate (SGR) and lag time (LT) obtained from the modified Gompertz model were employed to establish the secondary models. The newly developed secondary models were validated using the root mean square error, bias factor, and accuracy factor. All results of these factors were in the acceptable range of values. After compared SGR and LT of B. cereus on carrot, the results showed that the growth of B. cereus on carrot treated with SAcEW and US was slower than that of single treatment. This result indicates that shelf life of carrot treated with SAcEW and US could be extended. The developed predictive models might also be used to assess the microbiological risk of B. cereus infection in carrot treated with SAcEW and US.