• 제목/요약/키워드: Wear Behavior

검색결과 861건 처리시간 0.028초

고온가압소결을 이용한 YSZ-TiC 세라믹스 복합체의 제조와 특성 (Fabrication and Characteristics of YSZ-TiC Ceramics Composite by Using Hot Pressing)

  • 최재형;최지영;김성원
    • 한국분말재료학회지
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    • 제28권5호
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    • pp.381-388
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    • 2021
  • Zirconia has excellent mechanical properties, such as high fracture toughness, wear resistance, and flexural strength, which make it a candidate for application in bead mills as milling media as well as a variety of components. In addition, enhanced mechanical properties can be attained by adding oxide or non-oxide dispersing particles to zirconia ceramics. In this study, the densification and mechanical properties of YSZ-TiC ceramic composites with different TiC contents and sintering temperatures are investigated. YSZ - x vol.% TiC (x=10, 20, 30) system is selected as compositions of interest. The mixed powders are sintered using hot pressing (HP) at different temperatures of 1300, 1400, and 1500℃. The densification behavior and mechanical properties of sintered ceramics, such as hardness and fracture toughness, are examined.

Ni-25at.%Al 금속간화합물의 연소합성반응에 미치는 사전 Annealing 처리의 영향 (Effects of Pre-Annealing Treatment on the Combustion Synthesis of Ni3Al Intermetallics Coating)

  • 이한영;모남규
    • Tribology and Lubricants
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    • 제37권2호
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    • pp.62-70
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    • 2021
  • The problem with intermetallics coating using the heat of molten casting is that the heat generated during combustion synthesis dissolves the coating and the substrate metal. This study investigates whether pre-annealing before synthesis can control the reaction heat, with the aim of Ni3Al coating on the casting surface. Therefore, the effects of the annealing temperature and time on the combustion synthesis behavior of the powder compact of Ni-25at%Al after annealing were investigated. As results, the reaction heat when synthesized decreased as the annealing temperature was high and the annealing time was longer. This was attributed to the fact that Al was diffused to Ni particles during low temperature annealing and intermediate Ni-Al compounds were formed during high temperature annealing. After combustion synthesis, however, it was found that their microstructures were almost identical except for the amount of intermediate intermetallics. Furthermore, an annealing temperature above 450℃, at which intermediate compounds begin to form, is needed to prevent the dissolving problem during synthesizing. The intermetallics synthesized after annealing at higher temperature and prolonger annealing time showed a good wear resistance. This might be because much intermediate intermetallics of high hardness were remained in the microstructure.

Gift-giving Behaviors via SNS Mobile App: An Exploratory Study of Fashion Products

  • Ji Yoon Kim;Jiyeon Lee;Kyu-Hye Lee
    • 패션비즈니스
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    • 제27권6호
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    • pp.110-123
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    • 2023
  • As social distancing strengthened after the COVID-19 incident, people looked for things they could do alone. Additionally, as people have more financial resources, they purchase products they had previously considered purchasing, and the phenomenon of giving gifts to oneself has also appeared. Accordingly, this study analyzed fashion product reviews of KakaoTalk Gift, the service to exchange gift via SNS mobile app, to discover the phenomenon of self-gifting and the differences from interpersonal-gifting. For post-hoc data, in collected 18,354 pieces after excluding unnecessary data using a Python-based web crawling technique. The self-gifting behavior of KakaoTalk Gift different from the previous study for self-gift. Regardless of the gift-giving contexts, it determines that most self-gift products are material items. There are differences in product types and price levels when choosing gifts for others and oneself. As a self-gift, people typically buy luxury jewelry and branded bags/wallets to wear and show off. As interpersonal, among fashion products, people usually buy beauty products that reflect less personal tastes. When gift-giving to others, people buy products to appropriate prices to reduce the burden on both. When gift-giving to oneself, people buy wanted products regardless of the price. This study is significant because it suggests a new direction in self-gift research by limited online places to give gifts.

도시.농촌 지역 초등학생의 가족환경, 건강행위 및 건강상태에 관한 비교 (Comparision of Family Environment, Health Behavior and Health State of Elementary Students in Urban and Rural Areas)

  • 배연숙;박경민
    • 지역사회간호학회지
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    • 제9권2호
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    • pp.502-517
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    • 1998
  • This research intends to survey family environment, health behavior and health status of the students in urban-rural elementary schools and analyze those factors comparatively, and use the result as basic material for school health teacher to teach health education in connection with family and regional areas. It also intends to improve a pupil's self-abilitiy in health care. The subjects involve 2,774 students of urban elementary schools and 583 student in rural ones, who were selected by means of a multi -stage probability sampling. Using the questionnaire and school documents, we collected data on family environment, health behavior and health status for 19 days. Feb. 2nd 1998 through Feb. 20th 1998. The R -form of Family Environment Scale (Moos, 1974) was used in the analysis of family environment(Cronbach's Alpha =0.80). Questionnaires of Health Behavior in School-aged children used by the WHO in Europe(Aaro et al., 1986) and the ones developed by the Health Promotion Committee of the Western Pacific(WHO, 1995)(adapted by long Young-suk and Moon Young-hee(1996)) were used in the analysis of health behavior, as well documents on absences due to sickness, school health room-visits, levels of physical strength, height, weight and degree of obesity were used to determine health status. In next step, We used them with an $X^2$-test, t-test, Odds Ratio, and a 95% Confidence Interval. 1. In two dimensions of three, family-relationship (t=3.41, p=0.001) and system -maintenances(t= 2.41, p=0.0l6) the mean score of urban children were significantly higher than those of rural ones. In the personal development dimension however, there was little significant difference. Assorting family environment into 10 sub-fields and analyzing them, we recognized that urban children were superior to rural children in the sub-fields of expressiveness (t =3.47, p=0.001), conflict (t=0.48, p=0.001), active-recreational orientation (t = 1.97, p=0.049) and organization (t=4.33, p=0.000). 2. Referring to the Odds Ratios of urban-rural children's health behaviors, urban children set up more desirable behavior than rural children wear ing safety belts (Odds Ratio =0.32, p=0.000), washing hands after meals(Odds Ratio = 0.43, p= 0.000), washing hands after excreting (Odds Ratio = 0.39, p=O.OOO), washing hands after coming - home ( Odds Ratio = 0.75, p = 0.003), brushing teeth before sleeping(Odds Ratio =0.45, p=0.000), brushing teeth more than once a day (Odds Ratio =0.73, p=0.0l2), drinking boiled water (Odds Ratio = 0.49, p=0.000), collecting garbage at home(Odds Ratio=0.31, p=0.000) and in the school(Odds Ratio =0. 67, p=0.000). All these led to significant differences. As to taking milk(Odds Ratio = 1.50, p=0.000), taking care of eyesight(Odds Ratio=1.41, p=0.001) and getting physical exercise in(Odds Ratio = 1.33, p=0.0l9) and outside the school(Odds Ratio = 1.32, p=0.005), rural children had more desirable behavior which also revealed a significant difference. There was little significant difference in smoking, but the smoking rate of rural children(5.5%) was larger than that of urban children(3.9%). 3. Health status was analyzed in terms of absences, school health room-visits, levels of physical strength, and the degree of obesity, height and weight. Considering Odds Ratios of the health status of urban-rural children, the health status of rural children was significantly better than that of the urban ones in the level of physical strength(t=1.51, p=0.000) and the degree of obesity(t=1.84, p=0.000). The mean height of urban children ($150.4{\pm}7.5cm$) is taller than that of their counterparts($149.5{\pm}7.9$), which revealed a significant difference (t =2.47, p=0.0l4). The mean weight of urban children($42.9{\pm}8.6kg$) is larger than that of their counterparts($41.8{\pm}9.0kg$), which was also a significant difference(t=2.81, p=0.005). Considering the results above, we can recognize that there are significant differences in family environment, health behavior, and health status in urban-rural children. These results also suggestion ideas for health education. What we would suggest for the health program of elementary schools is that school health teachers should play an active role in promoting the need and importance of health education, develop the appropriate programs which correspond to the regional characteristics, and incorporate them into schools to improve children's ability to manage their own health management.

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고속철도차량용 차륜 불평형에 의한 동적 거동 특성 연구 (Study on the Dynamic Behavior Characteristics due to the Unbalance High Speed Railway Vehicle Wheel)

  • 이승일;송문석
    • 한국산학기술학회논문지
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    • 제17권7호
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    • pp.175-181
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    • 2016
  • 회전체는 질량 중심선이 축의 기하학적 중심선과 일치하지 않을 때 불평형이 발생한다. 윤축은 두 개의 차륜과 한 개의 차축으로 조립되어 철도차량을 주행시키는 회전체 역할을 하고, 차륜 재질의 불균일, 마모, 윤축 조립과정의 오차 등으로 인해 불평형이 발생할 수 있다. 또한 윤축은 축의 직경이 가늘고 고속으로 회전함으로 불평형 질량에 의한 진동의 영향이 더욱 두드러지게 나타나고 이로 인해 철도차량 고속 주행 시 주행안전성 및 주행거동에 영향을 미칠 수 있다. 그러므로 본 연구에서는 차륜 불평형이 고속철도차량의 동적 거동에 미치는 영향을 철도차량 다물체 동역학 해석 도구인 VI-Rail를 이용하여 해석을 수행하였다. 해석결과에서 차륜 불평형량이 증가할수록 철도차량 대차의 임계속도가 감소됨을 확인할 수 있었고, 차륜 불평형량이 주행 중 차량동적거동 악영향을 미침으로 고속주행에서는 반드시 차륜 불평형량에 대한 관리가 필요함을 확인할 수 있었다. 또한 이 연구로 차륜 불평형량의 정적 및 동적 관리 필요성을 국내 철도차량 운영기관에 제시하였다.

치과위생사의 방사선 안전관리 실태 및 피폭 불안감에 영향을 미치는 요인 (Factors affecting radiation safety management of dental hygienist and anxiety of radiation exposure)

  • 이혜경
    • 한국산학기술학회논문지
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    • 제19권6호
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    • pp.432-439
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    • 2018
  • 본 연구는 치과위생사를 대상으로 방사선 관리에 대한 지식, 태도, 안전관리 행위, 방사선 피폭 불안감을 분석하고 이에 영향을 미치는 요인들을 분석함으로써 방사선 안전 관리 수준을 향상하고 방사선 취급에 대한 올바른 인식 전환과 불안감을 줄이는 방안을 도출하고자 연구하였다. 연구기간은 2017년 9월 10일부터 10월 31일까지 전라북도에 근무하는 치과위생사 280명을 대상으로 SPSS 12.0 프로그램을 사용하여 빈도, 기술통계, 다중회귀분석을 실시하여 분석하여 다음과 같은 결과를 얻었다. 방사선 질 관리에 대한 지식 정도의 평균은 8.07 였고, 정답률은 75.3% 였다. 태도 정도는 96.1%가 긍정적인 태도를 보였으며, 방사선 안전관리 행위는 촬영자는 4.11 였고, '방사선 촬영 시 항상 TLD(개인선량계)를 착용한다'는 4.58 로 가장 높았다. 환자 방사선 안전관리 행위는 3.86 였고, '방사선촬영 전 가임기 여성의 임신 여부를 확인한다'는 4.69 로 가장 높았다. 방사선 피복 뷸안감은 3.86 였고, '임신 중 일 때 태아의 건강 문제로 염려된다'는 4.13로 가장 높았다. 방사선 피폭 불안감에 영향을 미치는 요인으로는 방사선 안전관리 행위가 낮을수록, 연령이 낮을수록, 방사선 촬영경력이 낮을수록, 최종학력이 높을수록, 월 소득이 많을수록, 직위가 높을수록 유의한 영향을 미치는 것으로 나타났다(p<0.05). 이상의 연구결과를 토대로 치과위생사는 방사선 질 관리에 대한 지식, 태도, 안전관리 행위는 높았으나, 방사선 피폭 불안감은 높은 불안감을 가지고 있어 방사선 안전 관리 수준을 향상시켜 방사선 피폭 불안감을 줄일 수 있는 방안 마련이 이루어져야 할 것으로 사료된다.

스마트 팩토리에서 그리드 분류 시스템의 협력적 다중 에이전트 강화 학습 기반 행동 제어 (Cooperative Multi-Agent Reinforcement Learning-Based Behavior Control of Grid Sortation Systems in Smart Factory)

  • 최호빈;김주봉;황규영;김귀훈;홍용근;한연희
    • 정보처리학회논문지:컴퓨터 및 통신 시스템
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    • 제9권8호
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    • pp.171-180
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    • 2020
  • 스마트 팩토리는 설계, 개발, 제조 및 유통 등 생산과정 전반이 디지털 자동화 솔루션으로 이루어져 있으며, 내부 설비와 기계에 사물인터넷(IoT)을 설치해 공정 데이터를 실시간으로 수집하고 이를 분석해 스스로 제어할 수 있게 하는 지능형 공장이다. 스마트 팩토리의 장비들은 게임과 같이 가상의 캐릭터가 하나의 객체 단위로 구동되는 것이 아니라 수많은 하드웨어가 물리적으로 조합되어 연동한다. 즉, 특정한 공동의 목표를 위해 다수의 장치가 개별적인 행동을 동시다발적으로 수행해야 한다. 공정 데이터를 실시간으로 수집할 수 있는 스마트 팩토리의 장점을 활용하여, 일반적인 기계 학습이 아닌 강화 학습을 사용하면 미리 요구되는 훈련 데이터 없이 행동 제어를 할 수 있다. 하지만, 현실 세계에서는 물리적 마모, 시간적 문제 등으로 인해 수천만 번 이상의 반복 학습이 불가능하다. 따라서, 본 논문에서는 시뮬레이터를 활용해 스마트 팩토리 분야에서 복잡한 환경 중 하나인 이송 설비에 초점을 둔 그리드 분류 시스템을 개발하고 협력적 다중 에이전트 기반의 강화 학습을 설계하여 효율적인 행동 제어가 가능함을 입증한다.

치면열구전색제의 도포 시 전색제에 따른 기포 발생 양태 (BUBBLE BEHAVIOR OF PIT AND FISSURE SEALANT)

  • 김현진;이난영;이상호
    • 대한소아치과학회지
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    • 제34권1호
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    • pp.99-105
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    • 2007
  • 치면열구전색제의 도포 시 발생하는 기포는 전색제의 두께 감소에 의한 강도의 저하로 파절 및 마모를 일으킬 수 있으며 특히 계면부에 발생한 경우 미세 누출 등의 임상적인 문제점을 가져온다. 본 조사에서는 치면열구전색제 중 Teethmate $F-1^{(R)}$(Kuraray, Japan), Ultraseal $XTplus^{(R)}$(Ultradent, USA), $Clinpro^{(R)}$(3M-ESPE, USA), $Helioseal^{(R)}$(Ivoclar-Vivadent, Liechtenstein)의 기포 발생 양태를 알아보고자 하였다. 자연치 교합면의 열구를 모방한 표준화된 시편을 제작하고 치면열구전색제를 각 군별 20개의 시편에 전색하고 광중합시킨 후 열구 중앙을 절단하여 stereoscope(Olympus SZ61, Japan)으로 확대하여 관찰하였고 컴퓨터 영상분석 프로그램(Image Pro plus Express, Mediacybermetics Co., U.S.A)을 통하여 기포의 발생 양태를 관찰하여 다음과 같은 결론을 얻었다. 1. 기포의 발생 빈도는 Ultraseal $XT^{(R)}$ plus에서 사용 시간과 관계없이 $Helioseal^{(R)}$에 Clinprotip과 metal canula tip을 적용한 경우보다 더 높게 나타났다(p<0.05). 2. 기포의 단면적 당 개수는 Ultraseal $XT^{(R)}$ plus old가 $Clinpro^{(R)}$, $TeethmateF-1^{(R)}$, $Helioseale^{(R)}$에 brush tip을 적용한 경우보다 많이 발생하였다(p<0.05). 3. 기포의 평균 단면적은 Teethmate $F-1^{(R)}$가 다른 군에 비해 큰 값을 보였다(p<0.05). 4. $Clinpro^{(R)}$와 적용 tip을 달리한 $Helioseal^{(R)}$의 경우 기포의 발생 빈도, 평균 개수, 평균 단면적 모두 유의차를 보이지 않았다(p>0.05).

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초경합금에 나노결정질 다이아몬드 코팅 시 금속 중간층의 효과 (Effect of Metal Interlayers on Nanocrystalline Diamond Coating over WC-Co Substrate)

  • 나봉권;강찬형
    • 한국표면공학회지
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    • 제46권2호
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    • pp.68-74
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    • 2013
  • For the coating of diamond films on WC-Co tools, a buffer interlayer is needed because Co catalyzes diamond into graphite. W and Ti were chosen as candidate interlayer materials to prevent the diffusion of Co during diamond deposition. W or Ti interlayer of $1{\mu}m$ thickness was deposited on WC-Co substrate under Ar in a DC magnetron sputter. After seeding treatment of the interlayer-deposited specimens in an ultrasonic bath containing nanometer diamond powders, $2{\mu}m$ thick nanocrystalline diamond (NCD) films were deposited at $600^{\circ}C$ over the metal layers in a 2.45 GHz microwave plasma CVD system. The cross-sectional morphology of films was observed by FESEM. X-ray diffraction and visual Raman spectroscopy were used to confirm the NCD crystal structure. Micro hardness was measured by nano-indenter. The coefficient of friction (COF) was measured by tribology test using ball on disk method. After tribology test, wear tracks were examined by optical microscope and alpha step profiler. Rockwell C indentation test was performed to characterize the adhesion between films and substrate. Ti and W were found good interlayer materials to act as Co diffusion barriers and diamond nucleation layers. The COFs on NCD films with W or Ti interlayer were measured as less than 0.1 whereas that on bare WC-Co was 0.6~1.0. However, W interlayer exhibited better results than Ti in terms of the adhesion to WC-Co substrate and to NCD film. This result is believed to be due to smaller difference in the coefficients of thermal expansion of the related films in the case of W interlayer than Ti one. By varying the thickness of W interlayer as 1, 2, and $4{\mu}m$ with a fixed $2{\mu}m$ thick NCD film, no difference in COF and wear behavior but a significant change in adhesion was observed. It was shown that the thicker the interlayer, the stronger the adhesion. It is suggested that thicker W interlayer is more effective in relieving the residual stress of NCD film during cooling after deposition and results in stronger adhesion.

패션 비주얼머천다이징의 뇌 과학적 접근 -fNIRS를 이용한 패션매장의 긍정적/부정적 VM에 대한 뇌 활성 비교- (Neuro-scientific Approach to Fashion Visual Merchandising -Comparison of Brain Activation to Positive/Negative VM in Fashion Store Using fNIRS-)

  • 김형숙;이진화
    • 한국의류학회지
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    • 제41권2호
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    • pp.254-265
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    • 2017
  • This study examines the possibility of a neuro-scientific approach to fashion Visual Merchandising (VM), by researching the brain activation of customers about fashion stores in terms of VM. Study subjects were in 20's-30's residing in Busan and ten ordinary person or fashion industry related individuals, it measures the change of cerebral blood flow on positive/negative photo stimulus in terms of VM using a functional Near Infrared Spectroscopy (fNIRS) device, and then compared the brain activation to the difference of the fashion store VM. Photo stimuli utilized in the experiment were selected through a preliminary study in advance. The results of this study are as follows. First, the brain activation was found in all 16 channels of stimulus ranges of fashion store VM regardless of positive/negative stimulus. This means that the VM of fashion store causes changes to the cerebral blood flow of consumers, which implies that consumer behavior can be affected by store VM. It also shows that the brain is more active in negative VM stimulus than positive VM despite slight differences in the subjects. In terms of VM, this suggests that the negative factors of fashion stores have a greater effect on the brains of consumers compared to the positive factors. Second, the reaction of the brain channel is different according to the positive/negative VM stimulus of the fashion store by product group and confirms that positive/negative VM stimulus can be distinguished by brain-reaction for the three product groups except for the underwear group among four product groups (men's wear store, women's wear store, underwear store, and sportswear store). The results indicate that more objective scientific measure and decision-making are possible through neuro-science in the strategic execution of VM. This study verified the possibility for a neuro-scientific approach to fashion VM; therefore, there are expectations for the various activation of interdisciplinary research and subsequent development of VM that utilize neuroscience in fashion marketing.