• Advances in nano research
• /
• 제10권1호
• /
• pp.59-69
• /
• 2021

Electrospinning is a cost-effective and versatile method for producing submicron fibers. Although this method is relatively simple, at the theoretical level the interactions between process parameters and their influence on the fiber morphology are not yet fully understood. In this paper, the aim was finding optimal electrospinning parameters in order to obtain the smallest fiber diameter by using Taguchi's methodology. The nanofibers produced by electrospinning a solution of Thermoplastic Polyurethane (TPU) in Dimethylformamide (DMF). Polymer concentration and process parameters were considered as the effective factors. Taguchi's L9 orthogonal design (4 parameters, 3 levels) was applied to the experiential design. Optimal electrospinning conditions were determined using the signal-to-noise (S/N) ratio with Minitab 17 software. The morphology of the nanofibers was studied by a Scanning Electron Microscope (SEM). Thereafter, a tensile tester machine was used to assess mechanical properties of nanofibrous scaffolds. The analysis of DoE experiments showed that TPU concentration was the most significant parameter. An optimum combination to reach smallest diameters was yielded at 12 wt% polymer concentration, 16 kV of the supply voltage, 0.1 ml/h feed rate and 15 cm tip-to-distance. An empirical model was extracted and verified using confirmation test. The average diameter of nanofibers at the optimum conditions was in the range of 242.10 to 257.92 nm at a confidence level 95% which was in close agreement with the predicted value by the Taguchi technique. Also, the mechanical properties increased with decreasing fibers diameter. This study demonstrated Taguchi method was successfully applied to the optimization of electrospinning conditions for TPU nanofibers and the presented scaffold can mimic the structure of Extracellular Matrix (ECM).

• 산경연구논집
• /
• 제12권2호
• /
• pp.41-52
• /
• 2021

Purpose: This study aims to provide implications for the government's housing supply policy by analyzing the factors that determine the type of real estate holding and household debt. This study started from the awareness that the determinants of household debt differ depending on the type of real estate holding. Research design, data and methodology: Real estate ownership type was classified and analyzed into 4 models: model 1 (1 household 1 house and self-resident), model 2 (1 household multiple real estate ownership and self-resident), model 3 (1 household 1 house and rent residence), model 4 (1 household holds a large number of real estate and rent residence). The analysis method used multiple regression analysis. The dependent variable was household total debt. As independent variables, household debt, annual gross household income, financial assets, real estate net assets, annual repayment, demographic & residential characteristics were used. Results: 1) Model 4 has the highest household debt and the highest gross income, Model 2 has the most real estate mortgage loans and real estate net asset, and Model 1 has the highest real estate mortgage payments. 2) The positive factor of common household debt determinants is real estate net assets, and the negative factor is financial assets. 3) It was the net assets of real estate that acted as a positive factor in common for the four models. In other words, the more financial assets, the less household debt. It was analyzed that the more net assets of real estate, the more household debt. The annual repayment of financial liabilities had no influence on household debt, while the annual repayment of loan liabilities and household debt had a positive relationship. Conclusions: 1) It is necessary to introduce benefits and systems that can increase the proportion of household financial asset. Specific alternatives include tax benefits and reduced fees for financial asset investment. 2) In the case where a homeless person prepares one house for one household, it is necessary to prepare various support measures according to the income level. The specific alternative is to give additional points for pre-sale or apply an interest rate cut incentive for mortgage loans.

• 대한안전경영과학회지
• /
• 제22권4호
• /
• pp.9-15
• /
• 2020

As of 2018, total yield of lettuce and strawberry amounted to 93,543 tons (representing 1.0 percent) and 183,639 tons (2.0 percent), respectively, among total yields worth 9,185,889 tons in South Korea. Lettuce is affected by a combination of numerous elements such as varieties, cultivation methods and pests during each growth phase (Lee et al., 1999). It is mainly cultivated in spring and fall. Especially due to respiration rate after harvest leading to reduced quality and poor storage, maintaining annual supply is unavailable (Jang et al., 2018). With the distribution of new varieties, forcing culture and indoor insulated facilities for plant cultivation during winter, strawberries are produced every year except for late summer and early fall. Due to active respiration, transpiration, soft flesh and high water content, the fruit is vulnerable to go bad and got rotten compared to other fruits. Furthermore, it is difficult to maintain freshness due to the possibility of softening, discoloration and fungi (Lee et al., 2012). In this regard, developing improved storage and package techniques is needed to ensure maintaining quality and safety even just two to three days after harvest. In order to ensure improved quality and safety of strawberries and lettuce after harvest, the present study applied a modified atmosphere packaging (MAP) technology (Mostofi et. al., 2008). Going forward, it compared the quality and safety of the two products while being stored in a way that put them in an MAP-applied container and a plastic container at room temperature and 4 degree Celsius.

• 한국정보통신학회논문지
• /
• 제25권3호
• /
• pp.339-345
• /
• 2021

코로나19로 인해 온라인 교육이 발달하면서 교육에 AI, AR/VR등의 신기술을 결합한 에듀테크 시장이 급격히 성장하고 있다. 또한, 1가구 1자녀 가정이 늘면서 자녀에 대한 투자가 집중됨에 따라 매년 출산율이 줄어듦에도 불구하고 키즈 산업은 꾸준히 성장 중이다. 그러나 늘어나는 수요에 비해 에듀테크 시장의 콘텐츠 공급은 더딘 편이다. 이에 본 논문에서는 AR 기술을 이용하여 편의성, 실용성, 효율성을 갖춘 AR 키즈 콘텐츠를 개발하고 지원함으로써 이러한 문제를 해결 하는데 도움을 주는 것을 목적으로 한다. 유아 어휘 학습 지원용 AR 콘텐츠는 단순히 보고 듣는 것이 끝이 아니라, 콘텐츠를 직접 조작해볼 수 있는 관찰 조작형 모델이라 유아의 흥미를 유발하고 아동의 단어학습에 도움을 준다. 본 논문은 본격적인 언어발달이 나타나는 생후 15개월 이상 36개월 이하의 유아를 대상으로 한다.

• Tribology and Lubricants
• /
• 제37권3호
• /
• pp.91-98
• /
• 2021

This paper presents a hydrostatic bearing design and rotordynamic analysis of a turbo expander for a hydrogen liquefaction plant. Th~e turbo expander includes the turbine and compressor wheel assembled to a shaft supported by two hydrostatic radial and thrust bearings. The rated speed is 75,000 rpm and the rated power is 6 kW. For the bearing operation, we use pressurized air at 8.5 bar as the lubricant that is supplied to the bearing through the orifice restrictor. We calculate the bearing stiffness and flow rate for various gauge pressure ratios and select the orifice diameter providing the maximum bearing stiffness. Additionally, we conduct a rotordynamic analysis based on the calculated bearing stiffness and damping considering design parameters of the turbo expander. The predicted Cambell diagram indicates that there are two critical speeds under the rated speed and there exists a sufficient separation margin for the rated speed. In addition, the predicted rotor vibration is under 1 ㎛ at the rated speed. We conduct the operating test of the turbo expander in the test rig. For the operation, we supply pressurized air to the turbine and monitor the shaft vibration during the test. The test results show that there are two critical speeds under the rated speed, and the shaft vibration is controlled under 2.5 ㎛.

• 한국정보전자통신기술학회논문지
• /
• 제14권4호
• /
• pp.307-313
• /
• 2021

소상공인 업체들의 매장은 다수의 전기기기를 사용하는 매장들이 대부분이며 특히 냉장 시스템을 이용한 매장이 많아 여름, 겨울의 계절 변화에 따라 전력의 수요가 변화하고 온도의 급변에 냉장 시스템을 적용시키지 못할 시에 많은 전력부하가 발생되어 심할 경우 전력공급의 차단이 발생됨에 따라 매장 내 자산에 손실을 미칠 수 있다. 이에 따라 본 논문에서는 매장의 에너지 수요율을 측정하고 에너지를 절감하기 위하여 LSTM 기반의 전력 부하 예측 시스템을 설계하였다. 이는 데이터 기반의 중소 매장용 전력절감 시스템으로 사용될 수 있어 향후 소상공인 데이터 기반의 전력 수요 예측 시스템으로 사용되고, 전력 부하로 인한 피해 방지 분야에서 사용될 것으로 예상된다.

• 현장농수산연구지
• /
• 제22권2호
• /
• pp.115-122
• /
• 2020

In Korea, the agricultural machinery market has been generally on the rise, and particularly the demand for the diverse agricultural machine is increasing due to the radical changes in agriculture, such as a high supply of the advanced and automated agricultural machine and an increase in aged or female farmer population. Therefore, this study analyzes the technical trends in the precision agricultural machine domestically and globally to guide the direction of development of the ICT-based machine. The investigation of the precision agricultural machine in this study focuses on the production technology through analyzing the trends in sensor-related technology, the decision-making research, variable treatment technology, and academic publication. The result shows that information processing technology including the sensor and the decision-making requires various measurement factors and the established technologies are continually being developed.

• 한국융합학회논문지
• /
• 제12권5호
• /
• pp.303-311
• /
• 2021

본 연구에서는 한국복지패널(Korean Welfare Panal Study) 11차년도(2016년), 12차년도(2017년), 13차년도(2018년), 14차년도(2019년) 자료 중 가구주용 데이터와 가구원용 데이터를 활용하여 성인의 문제음주가 우울에 종단적 영향을 미치는지에 대해 검증하였다. 분석결과, 첫째, 우울의 초기값은 문제음주 초기값과 정적(+)인 관계가 있는 것으로 나타났고, 문제음주 변화율과도 유의미한 관계가 나타났다. 둘째, 수급가구의 경우는 우울의 초기값, 문제음주의 초기값과 정적(+)인 관계를 나타냈다. 셋째, 장애인의 경우는 우울의 초기값, 문제음주 초기값과 부적(-)인 관계를 나타냈다. 따라서 성인기 이전의 학교교육에서 음주문제 예방 프로그램 개발과 교육이 적극적으로 이루어져야 할 것을 제언하였다.

• Journal of Korea Trade
• /
• 제24권4호
• /
• pp.34-48
• /
• 2020

Purpose - The rapid rise of e-commerce enterprises has led to the development of the logistics industry. At the same time, some enterprises are motivated by the interests to start reducing costs and inputs, which on the contrary leads to low quality of service, thus reducing customer satisfaction. In recent years, vicious competition, violent express delivery and lack of professionalism in the logistics market have led to high annual customer complaint rate, which has resulted in the company losing many loyal customers, but also unable to obtain new customers. Therefore, to pay attention to and understand the psychological needs of customers and improve the quality of logistics distribution service has become a pressing problem for Every express company. Design/methodology - By analyzing the problems existing in logistics distribution of express companies, this paper explores various factors affecting customer satisfaction and takes consumer sentiment as a mediating variable. Through questionnaires to collect relevant data, put forward hypotheses for empirical analysis, use two different software including SPSS 21.0 and AMOS 21.0 to analyze the information, draw conclusions and make recommendations. Findings - According to the above research results, the reliability, convenience, efficiency, professional can have a positive impact on customer satisfaction through the mediating effect of their sentiment, convenience and professional on consumer sentiment and satisfaction are more significant. Originality/value - This paper the establishment of distribution service indicators related to customer satisfaction and empirical analysis can not only enrich and supplement the distribution service quality indicator system studied by the former, but also provide a theoretical basis for future research.

• 전기전자학회논문지
• /
• 제26권4호
• /
• pp.659-670
• /
• 2022

본 논문에서는 ×32 LPDDR2 메모리를 지원하는 컨트롤러를 위한 830-Mb/s/pin 송수신기가 설계된다. 여덟 개의 단위 회로로 구성된 송신단은 34Ω ∽ 240Ω 범위의 임피던스를 가지고 임피던스 보정 회로에 의해 제어된다. 송신되는 DQS의 신호는 DQ의 신호들 대비 90° 이동된 위상을 가진다. 수신 동작시 read time 보정은 바이트 내에서 per-pin 스큐 보정과 클록-도메인 전환을 통해 수행된다. 구현된 LPDDR2 메모리 컨트롤러를 위한 송수신기는 1.2V 공급 전압을 사용하는 55-nm 공정에서 설계되었으며 830-Mb/s/pin의 신호 전송률을 가진다. 각 lane의 면적과 전력 소모는 각각 0.664 mm²과 22.3 mW이다.