• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.441-445
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• 2005

In the resent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. But, no detailed researches between the thermo-dynamic property in Nitinol alloy have been done yet. In this study, the thermal property of high temperature Nitinol shape memory alloy were evaluated using differential scanning calorimeter(DSC). The structure property was investigated using X-ray diffraction(XRD). A dynamic mechanical analyzer(DMA) with three point bending mode was used to study storage and loss modulus of shape memory alloy according to the thirteen frequencies in the temperature range between 30 and $200^{\circ}C$. The effects of the temperature heating/cooling rate, the frequency on the damping capacity have been systematically investigated. Such a frequency and temperature changes also influenced significantly to the damping behavior of the shape memory alloy. It was also found that Nitinol exhibited high damping capacity during phase transformation.

• 대한기계학회논문집B
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• 제31권2호
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• pp.141-150
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• 2007

This paper presents a lumped model to predict crosstalk characteristics of thermally driven inkjet print heads. Using the lumped R-C model, heating characteristics of the head are predicted to be in agreement with IR temperature measurements. The inter-channel crosstalk is simulated using the lumped R-L network. The values of viscous flow resistance, R and flow inertance, L of connecting channels are adjusted to accord with the 3-D numerical simulation results of three adjacent jets. The crosstalk behaviors of a back shooter head as well as a top shooter head have been investigated. Predictions of the proposed lumped model on the meniscus oscillations are consistent with numerical simulation results. Comparison of the lumped model with experimental results identifies that abnormal two-drop ejection phenomena are related to the increased meniscus oscillations because of the more severe crosstalk effects at higher printing speeds. The degree of crosstalk has been quantified using cross-correlations between neighboring channels and a critical channel dimension for acceptable crosstalk has been proposed and validated with the numerical simulations. Our model can be used as a design tool for a better design of thermal inkjet print heads to minimize crosstalk effects.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.29-36
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• 2007

The present study examined the mechanical properties of the friction welding of Ni-Cr-Mo to SM45C. Friction welding was conducted at welding conditions of 2,000 rpm, friction pressure of 100MPa, friction time of 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0 seconds, upset pressure of 150MPa, and upset time of 3.0 seconds. When the friction time was 1.6 seconds, the maximum tensile strength of the friction weld happened to be 1,020MPa, which is 120% of the base material's tensile strength(850MPa). At the same condition, the maximum shear strength was 438MPa, which is equivalent to 103% of the base material's shear strength(425MPa). At the same condition, the maximum vickers hardness was Hv490 at Ni-Cr-Mo nearby weld interface, which is higher Hv40 than condition of the friction time 0.8 seconds, and the maximum vickers hardness was Hv305 from weld interface of SM45C, which is higher Hv12 than condition of the friction time 0.8 seconds. The results of microstructure analysis show that the structures of two base materials have fined and rearranged along a column due to heating and axial force during friction, which has affected in raising hardness and tensile strength.

• 설비공학논문집
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• 제21권1호
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• pp.9-15
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• 2009

There are various types of energy simulation tool to predict both thermal load and energy use. However, the problem about these software is that they have too much input variables and need expert with skills to run the simulation. Therefore, the purpose of this study is to develop the thermal analysis simulation program with input variables which eliminates coordinates of building components instead of using full coordinates by using DOE2. Since the simulation engine of the program is DOE2, the validity of S-DOE is performed by comparing peak heating and cooling load results with VisualDOE and annual energy use results with actual energy use of 1996. The results have shown that there are little difference between VisualDOE and S-DOE. Also it showed that there are little difference between actual energy use and S-DOE energy use results. S-DOE took less time to model a building than VisualDOE. These results reveals that the application of S-DOE have potentials in accurately predicting both energy load and energy use of the building and still have an advantage of taking less time to model a building.

• 토지주택연구
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• 제1권1호
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• pp.27-34
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• 2010

본 연구에서는 그린 홈의 보급확대와 평가기법 개발을 목적으로 하고 있다. 구체적으로는 기 조사된 실측 데이터를 기본으로 시뮬레이션 결과 값의 보간 및 설비시스템의 교체에 따른 효과 검토를 통하여 에너지 절감량 및 이산화탄소 배출 삭감량 평가 프로그램을 개발하였다. 또한, 그린 홈의 보급확대에 따른 비용 검토를 통하여 그린홈을 건설하는 사업자에게는 지방세법 개정에 따른 취등록세 감면 등의 지원대책을 수립하였다.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.864-873
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• 2006

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.

• 한국염색가공학회지
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• 제31권3호
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• pp.155-164
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• 2019

This study comparatively analyzed hair bleaching and degree of damage by the temperature of a heating tool after coloring hair with a permanent, semi-permanent or plant hair dye. According to analysis by spectrophotometer, 'semi-permanent hair dye' was the highest, followed by 'permanent hair dye' and 'plant hair dye' in terms of changes in $L^*$ values. In terms of changes in hair shape when analyzed using FE-SEM, 'semi-permanent hair dye($150^{\circ}C$ or lower)' was the greatest, followed by 'plant hair dye($180^{\circ}C$ or lower)' and 'permanent hair dye($200^{\circ}C$ or lower)'. Therefore, it is reasonable to flat iron hair at low temperature. According to the test, amino acid values gradually decreased in both bleached and colored hair. The results obtained through TGA-based thermal analysis confirmed that as brightness increases, hair moisture contents decrease. This study aimed to protect hair by suggesting a correct use of a flat iron by the hair dye type during hair coloring. It appears that the study results would help hairdressers minimize hair damage by using a hair dye at proper temperature.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1654-1666
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• 2024

The goal of this research is to propose a way to maximize small modular reactor (SMR) utilization to gain better market feasibility in support of carbon neutrality. For that purpose, a comprehensive tool was developed, combining off-design thermohydraulic models, economic objective models (levelized cost of electricity, annual profit), non-economic models (saved CO2), a parameter input sampling method (Latin hypercube sampling, LHS), and a multi-objective evolutionary algorithm (Non-dominated Sorting Algorithm-2, NSGA2 method) for optimizing a SMR-combined heat and power cycle (CHP) system design. Considering multiple objectives, it was shown that NSGA2+LHS method can find better optimal solution sets with similar computational costs compared to a conventional weighted sum (WS) method. Out of multiple multi-objective optimal design configurations for a 105 MWe design generation rating, a chosen reference SMR-CHP system resulted in its levelized cost of electricity (LCOE) below $60/MWh for various heat prices, showing economic competitiveness for energy market conditions similar to South Korea. Examined economic feasibility may vary significantly based on CHP heat prices, and extensive consideration of the regional heat market may be required for SMR-CHP regional optimization. Nonetheless, with reasonable heat market prices (e.g. district heating prices comparable to those in Europe and Korea), SMR can still become highly competitive in the energy market if coupled with a CHP system.

• 한국식생활문화학회지
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• 제23권5호
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• pp.582-594
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• 2008

This study aimed at evaluating current sanitation management performances in Korean-Food restaurants by their operation types and to develop sanitary training posters based on the risk factors, in an attempt to improve the level of sanitation management in Korean food service facilities. Eighteen Korean-food restaurants that are managed by franchisor, franchisees as well as self-managed with large-scale and small-scale restaurants in Seoul and Gyeonggi-Do, were evaluated by on-the-spot inspectors with an auditing tool consisting of three dimensions, nine categories and thirty four items. Data were analyzed using SPSS. The total score of each group showed that restaurants managed by franchisees ranked the highest (59 out of 100 points), while self-managed, small-scale restaurants ranked the lowest (44 out of 100 points). In the categorization of sanitation management compliance, the dimensions of food hygiene during production recorded the lowest compliance rate of 47.7% (22.89/48.0 points) followed by the dimension of environmental hygiene 59.3% (20.17/34.0 points) and personal hygiene 60.5% (10.89/18.0 points). This indicated the need for urgent improvement. The items which showed the lowest compliance rates were 'proper thawing of frozen foods' (0%), 'notifying and observing heating/reheating temperature' (6%), 'using of hand-washing facility and proper hand-washing' (33%), 'monitoring temperature of frozen-foods and cold-foods' (35%), and 'prevention of cross-contamination' (36%) among thirty four items. Self-managed, small-scale restaurants, in particular, needed to improve sanitary practices such as 'sanitation education for employee', 'verifying the employee health inspection reports', 'storing food on the shelves 15 cm distance away from the wall', 'suitability of ventilation capacity of hoods' and 'cleanliness of drainage'. On the basis of the findings of this study, we developed sanitary training posters, especially for small-scale restaurant operators. This could be an effective tool to educate food service employees on sanitary knowledge and principles and could be used to improve the existing sanitary conditions in Korean food service facilities.

• Applied Biological Chemistry
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• 제49권1호
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• pp.60-64
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• 2006

원적외선 조사 및 일반 열처리가 감귤박의 항산화능에 미치는 영향을 조사하기 위하여 100, $150^{\circ}C$에서 각각 0, 10, 20, 30, 40, 50, 60분간 처리한 후, 70% 에탄올 추출물(EE)과 물추출물(WE)을 제조하여 DPPH 라디칼 소거능과 환원력을 측정하였다. 이들 측정 결과, 무처리구 EE의 라디칼 소거능과 환원력은 각각 14.9%, 0.290이었으나 $100^{\circ}C$에서 30분간 원적외선 조사한 EE는 44.2%, 0.886이었고, $100^{\circ}C$에서 60분간 열처리한 EE는 44.7%, 1.045로 크게 증가하였다. 또한, 무처리구 WE의 라디칼 소거능과 환원력은 각각 13.3%, 0.322였으나 $100^{\circ}C$에서 20분간 원적외선 조사한 WE는 54.0%, 0.938이었고, $100^{\circ}C$에서 50분간 열처리한 WE는 48.6%, 1.146로 각각 증가하였다. 이상의 결과는 적당한 조건에서의 원적외선 조사 및 열처리 공정이 감귤박의 항산화능을 향상시킴을 의미하였다.