• 한국분무공학회지
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• 제28권1호
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• pp.16-23
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• 2023

The objective of this numerical study is to investigate the effect of the shape and material of the blower blade for the electrified speed sprayer on the blowing performance. The shape of the blade was changed to the bonding angle, the number of blades, the width of the blade, and the blade length based on the existing model. In order to obtain the reliability of the numerical model, the analysis of the grid dependence was performed in the numerical analysis. The numerical analysis results were compared and analyzed in terms of the agricultural chemical penetration length characteristics, flow uniformity characteristics, and velocity distribution characteristics. Furthermore, the effect of material change on weight reduction and structural characteristics was also compared and analyzed. As a result of the analysis, it was found that the optimal condition was that the blade angle was 45°, the number of blades was 12, and the width was 115 mm, which was confirmed through a comparison of the inlet mass flow rate. As a result of the equivalent stress lower than the yield strength due to the material change from aluminum to steel compared to the existing steel, structural defects do not appear, and it is judged that the operation time compared to the battery capacity will be improved through the weight reduction of the blade.

• 열처리공학회지
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• 제36권2호
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• pp.77-85
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• 2023

In this study, the mechanical properties of the Al-Mg-X (X=Cr, Si) alloy, which clearly showed the influence of the specimen and grain size, were investigated by changing the specimen size extensively. In addition, the effect on the specimen size, grain size and aging condition on the mechanical properties of the grain refining alloy according to the addition of Cr was clarified, and the relationship between these factors was studied. As the specimen size decreased, the yield stress decreased and the fracture elongation increased. This change was evident in alloys with coarse grain sizes. Through FEM analysis, it was confirmed that the plastic deformation was localized in the parallel part of specimen S2. Therefore, when designing a tensile specimen of plate material, the W/L balance should be considered along with the radius of curvature of the shoulder. In the case of under-aged materials of alloys with coarse grain size, the fracture pattern changed from intergranular fracture to transgranular fracture as W/d decreased, and δ increased. This is due to the decrease in the binding force between grains due to the decrease in W. In the specimen with W/d > 40 or more, intergranular fracture occurred, and local elongation did not appear. Under-aged materials of alloys with fine grain size always had transgranular fracture over a wide range of W/d = 70~400. As W/d decreased, δ increased, but the change was not as large as that of alloys with coarse grain sizes. Compared to the under-aged material, the peak-aged material did not show significant dependence on the specimen size of σ_0.2 and δ.

• 한국재료학회지
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• 제34권1호
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• pp.34-43
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• 2024

New piezoelectric and triboelectric materials for energy harvesting are being widely researched to reduce their processing cost and complexity and to improve their energy conversion efficiency. In this study, BaTiO₃ films of various thickness were deposited on Ni foams by R.F. magnetron sputtering to study the piezoelectric and triboelectric properties of the porous spongy structure materials. Then piezoelectric nanogenerators (PENGs) were prepared with spongy structured BaTiO₃ and PDMS composite. The output performance exhibited a positive dependence on the thickness of the BaTiO₃ film, pushing load, and poling. The PENG output voltage and current were 4.4 V and 0.453 ㎂ at an applied stress of 120 N when poled with a 300 kV/cm electric field. The electrical properties of the fabricated PENG were stable even after 5,000 cycles of durability testing. The triboelectric nanogenerators (TENGs) were fabricated using spongy structured BaTiO₃ and various polymer films as dielectrics and operated in a vertical contact separation mode. The maximum peak to peak voltage and current of the composite film-based triboelectric nanogenerator were 63.2 V and 6 ㎂, respectively. This study offers new insights into the design and fabrication of high output nanogenerators using spongy structured materials.

• 유변학
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• 제10권4호
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• pp.195-201
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• 1998

반도성 고분자인 폴리아닐린과 폴리파라페닐렌을 이용한 전기유변유체의 유변학적 및 전기적 특성을 고찰하였다. 이들 반도성 고분자 현탁액은 분산입자와 현탁매질의 전기전도도 차이로 인하여 직류 전기장 하에서 큰 점도 증가를 보였다. 전기유변효과로 기인한 동적 항복응력은 낮은 전기장 하에서는 전기장 제곱에의 의존성을 보였으나 높은 전기장 하에서는 전기장의 1승에 비례하는 거동을 나타내었다. 항복 응력은 분산입자의 전기전도도가 증가함에 따라 최대값을 보이다가 다시 감소하는 현상을 나타내었다. 직류 전기장 하에서의 이러한 항복 응력 거동은 전도도 효과에 의한 맥스웰-와그너 계면편극화로 설명되는 현탁액의 유전 특성과 관련됨을 발견하였다. 계면 편극화 효과가 전기유변현상에 미치는 영향에 대한 더 깊은 이해와 분산액의 침강 안정성 개선을 위하여, 전기유변 효과의 조절이 가능할 뿐 아니라 현탁액의 콜로이드 안정성을 향상시킬 수 있는 여러 가지의 계면 활성제의 영향을 피력하였다.

• 지질공학
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• 제25권3호
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• pp.377-385
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• 2015

본 연구에서는 강우강도에 따른 토층내 포화속도를 산정하기 위하여 모형실험장치를 개발하고 일련의 모형실험을 수행하였다. 모형실험장치는 모형토조, 강우재현장치 및 계측장치로 구성되어 있다. 모형지반(60 cm × 50 cm × 15 cm)은 상대밀도 75%의 주문진 표준사로 조성하였으며, 강우재현장치는 강우강도의 조절이 가능하도록 하였다. 그리고 토층내 강우침투시 깊이별 체적함수비 및 모관흡수력의 변화를 측정하기 위하여 TDR과 Tensiometer를 설치하였다. 모형실험결과 토층의 입도가 균등하고 투수계수가 상대적으로 크므로 강우시 지표면에서 습윤전선이 형성되어 하강하는 것이 아니라 하부 바닥면에서부터 지하수위가 형성되어 상승하면서 포화가 진행되었다. 강우시 토층내 흡입응력의 변화를 살펴본 결과 토층 내에서 체적함수비가 증가함에 따라 흡입응력은 감소하며, 체적함수비가 20-30% 사이에서 흡입응력은 비교적 빠르게 감소하였다. 강우강도와 토층의 평균포화속도를 회귀분석한 결과 강우강도에 따른 평균포화속도는 V_savg (cm/sec) = 0.068I_R (mm/hr)와 같이 제안할 수 있다.

• 공업화학
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• 제4권1호
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• pp.196-203
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• 1993

Glycerin monostearate, polyoxyethylene(100) monostearate, polyoxyethylene(20) sorbitan monostearate를 혼합한 유화제를 분산상인 liquid paraffin, beeswax 혼합물에 용해한 후 연속상인 propylene glycol 수용액을 첨가하는 방법인 agent-in-oil법을 적용한 반전유화법에 의해 O/W 에멀젼을 제조하였고, 제조과정에서 나타나는 상거동 및 점성거동을 관찰하였다. 연속상을 주가함에 따라 액정 영역과 백타겔 영역이 존재하는 유화제 조성(HLB 10.1~12.3)에서만 미세하고 균일한 에멀젼이 형성되었으며, 유상${\rightarrow}$액정상${\rightarrow}$겔상${\rightarrow}$O/W 에멀젼으로 상변화가 일어남을 알 수 있었다. 제조된 에멀젼의 전단속도에 따른 전단응력곡선으로부터 항복치가 존재함에 따라 에멀젼 입자간의 내부구조가 형성됨을 알 수 있었고, 전단력에 의한 내부구조의 파괴가 겉보기상으로는 완전히 비가역적으로 진행되며, 구조 파괴의 척도인 hysteresis loop의 면적은 유화제의 HLB값이 작을수록 큰 것을 알 수 있었다. 시간에 따른 전단응력 변화곡선에서소성점성도의 시간의존성이 큰 것을 확인하였고, 시간유동화현상에 따른 완화시간(${\lambda}$)으로부터 HLB값이 작을수록 상대적 안정성이 큼을 알 수 있었으며, homomixer로 제조한 에멀젼에 비해 반전유화법에 의해 제조한 에멀젼이 더 안정함을 알 수 있었다.

• 지역사회간호학회지
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• 제32권4호
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• pp.430-444
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• 2021

Purpose: This study is an integrated literature review to analyze health problems and social determinants of multicultural adolescents in South Korea. Methods: An integrative review was conducted according to Whittemore & Knafl's guideline. An electronic search that included publications from 2018 to 2020 in the PubMed, EMBASE, Cochrane Library, CINAHL, RISS, and KISS databases was conducted. Of a total of 67 records that were identified, 13 finally met full inclusion criteria. Text network analysis was also conducted to identify keywords network trends using NetMiner program. Results: The health problems of multicultural adolescents were classified into mental health (depression, anxiety, suicide and acculturative stress) and health risk behaviors (smoking, risky drinking, smartphone dependence and sexual behavior). As social determinants affecting the health of multicultural adolescents, the biological factors such as gender, age, and visible minority, and the psychological factors such as acculturative stress, self-esteem, family support, and ego-resiliency were identified. The sociocultural factors were identified as family economic status, residential area, parental education level, and parents' country of birth. As a result of text network analysis, a total of 41 words were identified. Conclusion: Based on these results, mental health and health risk behaviors should be considered as interventions for health promotion of multicultural adolescents. Our findings suggest that further research should be conducted to broaden the scope of health determinants to account for the effects of the physical environment and health care system.

• 한국수자원학회논문집
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• 제56권12호
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• pp.883-893
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• 2023

2020년 기준 한국의 곡물자급률은 20.2%에 불과하지만 곡물수출국에서 발생하는 가뭄이 국내에 미치는 영향은 아직 면밀히 분석되지 않았다. 본 연구에서는 증발산 기반 가뭄지수인 Evaporative Stress Index (ESI)를 이용해 세계 주요 곡물생산지역의 농업가뭄의 발생빈도, 장기추세, 자연진동과의 상관성을 분석하였다. 또한 국제 곡물거래가격과 작물생산지역의 가뭄면적을 비교하여 해외에서 발생한 가뭄이 한국 경제에 미치는 영향을 정성적으로 평가하였다. ERA5 기후재분석자료로 산정된 ESI는 전지구적으로 토양수분과 강한 상관성을 보였으며 특히 작물재배 지역에서의 둘의 상관성이 매우 강하게 나타났다. 작물재배지역에서의 높은 상관성은 강한 지면-대기결합을 의미하며, 이 때문에 작은 토양수분 부족이 상대적으로 큰 수확량 손실로 연결될 가능성이 크다. 1991-2022 기간 작물재배지역에서 ESI는 뚜렷한 감소추세를 보였으며 지구온난화와 함께 가뭄면적이 증가할 가능성이 있다. 2012년과 2022년에 급격히 상승한 국제곡물가격은 수출국에서 발생한 대규모 가뭄과 밀접한 관계가 있는 것으로 분석되었으며 한국의 생산자물가지수를 상승시킨 주요 원인 중 하나로 판단된다. 본 연구는 해외지역에서 일어나는 가뭄의 영향을 줄이기 위해 감시와 위험관리 전략이 필요함을 시사한다.

• 대한간호학회지
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• 제30권1호
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• pp.122-136
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• 2000

Chronic illness requiring attention and management during a long period of time puts great burden onto patients, their family and society. For patients with chronic illnesses, providing social support is the most important, and the fundamental support comes from their spouses. Amount and quality of support from spouses seems to differentiated according to the sex of patients. Female patients tend to believe that their spouses are not very supportive. Therefore, the researchers assessed the burden of husbands of female arthritis patients to discover the factors that result in greater burden. Also, they developed a theoretical model of husbands′ care for their wives through a qualitative research into husbands′ experience. Method 1: The study material was 650 female arthritis patients registered in an arthritis clinic. The questionnaire about the disease experience of female arthritis patients and the burden of husbands were sent. Returned questionnaires numbered 210(32.3%) and 27 were excluded because of inadequate answers. The remaining 183 questionnaires were analyzed. The mean age of the patients was 51 years and the mean age of spouses was 55 years. The mean marital period was 28 years. The average duration since diagnosis was 9.1 years. Education level was varied from primary school to graduate school, and average income/month was 1,517,300 won. Method 2: Initial questionnaire studies on the burden of husbands were performed. Among 183 responding husbands, 23 consented to participate for a qualitative research. Data was obtained by direct and telephone interviews. The mean age of participants was 58 years, and the educational level and socioeconomic status also varied. Result: 1. Husbands′ burden: The average burden was 57.68 with a range of 6-96. 2. Burden and general characteristics: The husband′s burden correlated with the age of the patients, numbers in the family, therapy methods, patient′s level of discomfort, patient′s disease severity, patient′s level of dependence and the husband′s understanding of the level of severity. 3. Linear correlation analysis on burden: The husbands′ burden is explained in 22.5% by husband′s recognition of level of severity and husbands′ age. 4. There were four patterns of the burden on husbands: both objectve burden and subjective burden were high(pattern I), both of objectve burden and subjective burden were low(pattern II), objective burden was high but subjective burden was low(pattern III), objective burden was low but subjective burden was high(pattern IV). The pattern was correlated with the family income, educational level of the patients and their husbands, therapy methods, patient′s level of discomfort, patient′s disease severity, patient′s level of dependence and husband′s understanding of level of severity. 5. The core category of the caring experience of the husbands with arthritis patients was "companionship". The causal factor was the patients′ experience due to symptoms : physical disfigurement, pain, immobility, limitation of house chores, and limitation of social activities. Contextural factors are husbands′ identification of housework and husbands′ concern about the disease. The mediating factors are economic problems, fear of aging, feeling of limitation and family support. The strategy for interaction is mind control and how to solve emotional stress. The "companionship" resulted from caring activities, participation of household activities, helping patients′ to coping with emotional experience. 6. Companionship is established through the process of entering intervention, and caring state of mind. Entering intervention is the phase of participation of therapy and involvement of houseworks. The caring phase consists of decision on therapy, providing therapy, providing direct care, and taking over the household role of wife. Through caring phase, the changing phase set a stage in which husbands consolidate the relationship with their wives, and are reminded of the meaning of marriage. As a result, in changing phase, husbands′ companionship is enhanced. In conclusion, nursing care of chronic illnesses should include a family member especially the spouse. All information on disease shoud be provided to patients and whole family member. Strong support should also be provided to overcome difficulties in taking over role of other sex. Then the quality of life of patients and families will be much improved.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제30권3호
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• pp.375-392
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• 2016

본 연구의 목적은 의사소통학적 관점에서 학생의 공유와 참여를 핵심가치로 하는 교수법 중에 하나인 동료 멘토링 방법의 변천과정을 분석하여 우리나라 교육과정에서 지속적으로 강조하는 수학적 과정에 대한 변화의 특징을 명시화하는 것이다. 의사소통학적 접근 방식에서 수학적 과정의 출발점인 동시에 수행의 핵심이라고 볼 수 있는 학습자의 수업 참여를 위해 17년 동안 동료 멘토링 수업 방법의 변화 과정 5단계를 교수법 변화 측면에서 분석하고자 하였다. 이를 위해 수학적 과정을 위한 교수법 변화와 연관된 요소를 학습 환경, 학습 과정, 평가 측면에서 단계별로 추출하였다. 분석 결과, 학습자의 상호작용을 촉진하고 이를 바탕으로 교실 공동체로 모든 학생들이 적극적으로 참여할 수 있도록 하는 수학적 과정을 위한 교수법 변화와 관련된 특징은 연속적인 상호작용성, 맥락의존성, 양방향성, 교사 역량, 학생 참여 원리를 발견할 수 있었다. 이 다섯 가지 원리를 바탕으로 수학적 과정의 효과적 변화의 저변에 깔려있는 원동력으로 공유된 창의성의 원리를 추출할 수 있었다.