• 드라이브 ㆍ 컨트롤
• /
• 제15권1호
• /
• pp.10-15
• /
• 2018

The hydraulic cylinder seals are used not only to protect leakage of the working fluids but also to prevent incoming of foreign particles into the system. Chromium plating is generally applied to improve corrosion and wear resistance. It has been noticed that sealing surface damage occurs due to the hard foreign/wear particles contained in the hydraulic oil. In this study, a three-bodied sliding contact problem related with a PTFE seal, a spherical particle and chrome-plated steel substrate is modeled to investigate the relations to wear mechanism. Using the nonlinear finite element software, MARC/MENTAT, the deformed shapes, the von Mises and first principal stress distributions with plating thickness were compared. The sealing surface was mainly abraded by hard particles embedded in the seal. The plastic deformation of the steel substrate decreased with thicker plating. Hence it could be more effective to coat the sealing surface of a hydraulic cylinder with a hard material such as TiN, TiC and DLC.

• 한국전문물리치료학회지
• /
• 제14권2호
• /
• pp.85-90
• /
• 2007

In many manufacturing occupations, industrial workers reported foot or lower leg problems such as discomfort, pain or orthopedic deformities. This study investigated the effects of two different working conditions upon assembly worker's perception of discomfort and foot pain associated with various body parts. Twenty-three male volunteers performed work in the factory. Ergonomic intervention has been to modify the flooring in an attempt to alleviate the problems associated with constrained standing and walking work. The worker's standing conditions consisted of standing on a hard floor while wearing shoe insoles. Questions were asked regarding body discomfort and foot pain. Significant differences in body discomfort and foot pain were found when comparing the overall effects of wearing shoe insoles on a hard floor (p<.05). This investigation indicated that shoe insoles reduced body discomfort and foot pain (p<.05).

• 한국산업보건학회지
• /
• 제15권3호
• /
• pp.250-260
• /
• 2005

This study was designed to find the symptom prevalence rates of musculoskeletal disorders and the risk factors of musculoskeletal disorders among selected hair dressers. Methods; The survey were conducted from July 1 to 30, 2004 for 459 hair dressers working in Seoul and Gwangju using self-administration questionnaire. The risk factors on musculoskeletal disorders have analysed by multiple linear regression analysis. The results of this study are summarized as follows: The experience rate of musculoskeletal disorders symptom in the last one year was 56.4%. The experience rates of each body parts were 36.4% on the shoulders, 30.5% on the legs and the feet, 28.5% on the low back, 27.0% on the hand and the fingers, 23.3% on the neck and 17.0% on the arms and the elbows. The prevalence rate of musculoskeletal disorders symptom in the last one week was 40.5%, those of each body parts were 24.0% on the legs and the feet, 21.4% on the shoulders, 20.7% on the low back, 15.7% on the hand and the wrists, 15.0% on the neck, 9.4% on the arms. The risk factors on musculoskeletal disorders were working posture(${\beta}=0.32$), perceived stress(${\beta}=0.19$), working period(${\beta}=0.16$), standing working over 10 hour(${\beta}=0.16$), hard working(${\beta}=0.11$). The adjusted determinant coefficient($R^2$) of this regression model was 0.267. Based on the results, in order to prevent musculoskeletal disorders of hair dressers, working posture shall be improved and leisure opportunities to relieve stress, and health management program shall be provided.

• 전기화학회지
• /
• 제6권2호
• /
• pp.158-160
• /
• 2003

We have reported to make nanostructured cobalt oxide electrode that have large capacitance over than 400 F/g (specific capacitance) and good cycleability. But, it had serious demerits of low voltage range under 0.5 V and low power density. Therefore, we need to increase voltage range of cobalt oxide electrode. We report here on the electrochemical properties of sol-gel-derived nanoparticulate cobalt xerogel in 1M KOH solution and aqueous polymeric gel electrolyte. In solution electrolyte, cobalt oxide electrode had over 250 F/g capacitance consisted of EDLC and pseudocapacitance. In gel electrolyte, cobalt oxide electrode had around 100 F/g capacitance. This capacitance was only electric double layer capacitance of active surface area. In solution electrolyte, potassium ion as working ion reacted with both of layers easily. However, In gel electrolyte, reacted with only surface-active layer. Itis very hard to reach resistive layer. So, we have studied on pretreatment of electrode to contain working ions easily. We'll report more details.

• 한국기계가공학회지
• /
• 제11권4호
• /
• pp.51-54
• /
• 2012

This paper aims to design and analyze the stationary fixture type automatic rotary drilling machine and estimate the safety of the machine through simulations. Working conditions of typical rock excavating machines are mostly affected by geographical conditions on the sea, such as by the ebb and flow of the tide or high waves. Due to the size of machines, it is difficult to move and install machines. So it is necessary to develop a machine that not only can be moved and installed more easily also be operated more quickly and automatically. To validate the safety of the designed structure of the machine, static analysis has been carried out. The results of stress and deformation analysises show that the designed machine is stable and safe in hard working condition.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
• /
• pp.93-96
• /
• 2001

We have reported to make nanostructured cobalt oxide electrode that have large capacitance over than 400F/g (specific capacitance) and good cycleability. But, It had serious demerits of low voltage range under 0.5V and low power density. Therefore, we need to increase voltage range of cobalt oxide electrode. we report here on the electrochemical properties of sol-gel-derived nanoparticulate cobalt xerogel in 1M KOH solution and aqueous polymeric gel electrolyte. In solution electrolyte, cobalt oxide electrode had over than 250F/g capacitance consisted of EDLC and pseudocapacitance. In gel electrolyte, cobalt oxide electrode had around l00F/g capacitance. This capacitance was only surface EDLC. In solution electrolyte, potassium ion as working ion reacted with both of layers easily. However, In gel electrolyte, reacted with only surface-active layer. Its very hard to reach resistive layer. So, we have studied on pretreatment of electrode to contain working ions easily. We'll report more details.

• 대한조선학회 특별논문집
• /
• 대한조선학회 2008년도 특별논문집
• /
• pp.112-117
• /
• 2008

The Insulation, which is consist of the glass wool, mineral wool or perforated SUS plate, installed on the wall or under ceiling for the protecting heat and the blocking the noise of engine room area. In our shipyard, designing the structure model of insulation is hard and difficult, Because designed the insulation model is considered of any factors which are hull model properties of panel shape, direction and thickness and service of area. In this paper, We issue the way to utilize shape and direction of the hull model information and specific character of working space in engine room.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2017년도 추계 학술논문 발표대회
• /
• pp.58-59
• /
• 2017

As the construction industry has been increasingly complex, aging workers, hard-working avoiding young generation, foreign workers having language problem for the past decades, delivering of construction qualified workers has been a rising problem. This misalignment between the complex jobs and the number of skilled workers will continue to be in issue that the construction industry will face for following decades. Construction field workers who are working outside in uncontrollable condition unlike manufacturing industry are exposed to easily construction safety accident. There are so many efforts to prevent and control the construction accident. However, the relationships between the construction works and construction safety accident has not been well dealt and investigated based on objective accident data except for the qualitative study through interview, delphi and so on. Therefore this study analyzes job risk matrix exposed to safety accidents based on statistic data for 20 years from Korean Occupational Safety & Health Agency in order to prevent the construction field accidents.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 추계학술대회 논문집
• /
• pp.93-96
• /
• 2001

We have reported to make nanostructured cobalt oxide electrode that have large capacitance over than 400F/g (specific capacitance) and good cycleability. But, It had serious demerits of low voltage range under 0.5V and low power density. Therefore, we need to increase voltage range of cobalt oxide electrode. we report here on the electrochemical properties of sol-gel-derived nanoparticulate cobalt xerogel in 1M KOH solution and aqueous polymeric gel electrolyte. In solution electrolyte, cobalt oxide electrode had over than 250F/g capacitance consisted of EDLC and pseudocapacitance. In gel electrolyte, cobalt oxide electrode had around 100F/g capacitance. This capacitance was only surface EDLC. In solution electrolyte, potassium ion as working ion reacted with both of layers easily. However, In gel electrolyte, reacted with only surface-active layer. Its very hard to reach resistive layer. So, e have studied on pretretmetn of electrode to contain working ions easily. We'll report more details.

• 한국정보처리학회:학술대회논문집
• /
• 한국정보처리학회 2020년도 춘계학술발표대회
• /
• pp.44-46
• /
• 2020

Aggregating data with an optimal delay, which is a critical problem in Wireless Sensor Networks applications, is proven as NP-hard. In this paper, we focus on optimizing the aggregation delay by presenting an idea for channel and timeslot co-scheduling data aggregation in MWSNs. The proposed scheme, which names Break and Join, maximizes the number of sensor nodes to be scheduled in a working period, so that the overall number of working periods and data collection delay are reduced.