• 대한조선학회논문집
• /
• 제47권5호
• /
• pp.657-669
• /
• 2010

Cavitation is one of the most difficult physical phenomena to understand and predict. Many experimental and computational studies have been conducted for better understanding of the phenomenon. Recently, with the rapid development of computing hardware capacity and numerical methods, considerable advancement is observed in prediction of cavitation using computational fluid dynamics. To that end, many cavitation models have been developed and reported. In the present paper, some of the distinguished cavitation models are categorized and reviewed in terms of the computational frame work and formulation of transport equations. Then those characteristics are compared with each other.

• 보건교육건강증진학회지
• /
• 제13권1호
• /
• pp.90-116
• /
• 1996

The purpose of this study is to provide basic data for the children so as to avoid any accidents and to improve their health through a sound and safe living environment with safety education established through more systematic methods. For the study, the methods used include the questionnaires for collecting data which are distributed among 273 children from 3 to 6 years old. They live in three districts of Seoul (Kangnam and Kangbuk), Kyeonggido (Munsan and Ilsan) and Incheon. The children's general characteristics are investigated and the relationship between the accident-proneness prospects and their results are analyzed assuming that children's health is expected to have an effect on their safety. The findings of the study are as follows: 1. The accident-proneness prospect (for the living safety) has significant difference in sleeping habits and physically weak conditions(p<0.05). 2. The accident-proneness prospect (for the traffic safety) has no significant difference in accordance with the children's health condition. 3. Children's reasoning power has no significant difference in accordance with their health condition. 4. Children's movement speed non-significantly differs in accordance with their health condition. 5. Children's movement stability has a significant difference in accordance with their health conditions such as history of mild disease(p<0.05) and physical work capacity(p<0.05). 6. Children's attention power has no significant difference in accordance with their health condition. 7. Children's characteristic activities show a significant difference in accordance with their health history of mild disease(p<0.05). mental health(p<0.05). eating habits(p<0.05) and others (i.e. auditory abnormality and skin desease)(p<0.05). 8. General assessment of the APP test has no significant difference in accordance with their health condition. 9. The health conditions are a significant difference in the history of mild disease in accordance with sex(p<0.05) and whole family members(p<0.001). Also there are shown significant differences. in accordance with sex(p<0.05). in physical work capacity(p<0.05). Eye sight, blood circulation and skin condition show significant differences in accordance with residence(p<0.05) and whole family members(p<0.01). and the condition of eating habits appeared significant in accordance with age(p<0.05). Also, sleeping habits and physically weak conditions shows significant differences in accordance with age(p<0.001) and housing pattern(p<0.01), and others (i.e. auditory abnormality and skin desease) show significant differences in accordance with residence (p<0.001).

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 추계학술발표대회
• /
• pp.20.1-20.1
• /
• 2011

The nano-sized quantum structure has been an attractive candidate for investigations of the fundamental physical properties and potential applications of next-generation electronic devices. Metal nano-particles form deep quantum wells between control and tunnel oxides due to a difference in work functions. The charge storage capacity of nanoparticles has led to their use in the development of nano-floating gate memory (NFGM) devices. When compared with conventional floating gate memory devices, NFGM devices offer a number of advantages that have attracted a great deal of attention: a greater inherent scalability, better endurance, a faster write/erase speed, and more processes that are compatible with conventional silicon processes. To improve the performance of NFGM, metal nanocrystals such as Au, Ag, Ni Pt, and W have been proposed due to superior density, a strong coupling with the conduction channel, a wide range of work function selectivity, and a small energy perturbation. In the present study, bismuth metal nanocrystals were self-assembled within high-k $Bi_2Mg_{2/3}Nb_{4/3}O_7$ (BMN) films grown at room temperature in Ar ambient via radio-frequency magnetron sputtering. The work function of the bismuth metal nanocrystals (4.34 eV) was important for nanocrystal-based nonvolatile memory (NVM) applications. If transparent NFGM devices can be integrated with transparent solar cells, non-volatile memory fields will open a new platform for flexible electron devices.

• 한국산림과학회지
• /
• 제87권2호
• /
• pp.121-130
• /
• 1998

별도작업에서 작업원의 작업강도를 파악하기 위하여, 체인톱을 이용한 낙엽송 간벌작업에서 작업시간과 작업량을 조사하였으며, 작업시 심박수의 변화를 조사하였다. 또한, 작업원의 최대 작업수행 능력을 평가하기 위하여 최대산소섭취량을 조사하였다. 1일 실작업시간은 6시간 6분으로 오전작업시간이 약 3시간 12분, 오후가 2시간 54분으로 나타났고, 전체작업시간 중 실작업시간의 약 90% 정도를 차지하는 것으로 나타났으며, 실작업시간 중 요소작업 의 시간비율은 이동(Movement)의 비율이 평균 26.3%로 가장 큰 값을 보였다. 작업원의 작업량을 분석하기 위하며 시간당 벌목재적을 조사한 결과 평균 $2.62m^3/hr$로 나타났다. 작업원의 작업능력을 평가하기 위하여 최대산소섭취량을 분석한 결과, 평균 $2.42{\ell}/min$($46.5m{\ell}/kg/min$)으로 나타났으며, 작업시 심박수를 바탕으로 체인톱을 이용한 낙엽송 간벌작업 중 실동시간의 작업강도를 분석한 결과, 실동시간의 심박수 증가율은 평균 93.2%로 나타났고, 작업강도지수는 평균41.9%로 나타났다.

• 한국항만학회지
• /
• 제5권2호
• /
• pp.19-37
• /
• 1991

This work aims to : establish a model of the container physical distribution system of Pusan port comprising 4 sub-systems of a navigational system, on-dock cargo handling/transfer/storage system, off-dock CY system and an in-land transport system : examine the system regarding the cargo handling capability of the port and analyse the cost of the physical distribution system. The overall findings are as follows : Firstly in the navigational system, average tonnage of the ships visiting the Busan container terminal was 33,055 GRT in 1990. The distribution of the arrival intervals of the ships' arriving at BCTOC was exponential distribution of $Y=e^{-x/5.52}$ with 95% confidence, whereas that of the ships service time was Erlangian distribution(K=4) with 95% confidence, Ships' arrival and service pattern at the terminal, therefore, was Poisson Input Erlangian Service, and ships' average waiting times was 28.55 hours In this case 8berths were required for the arriving ships to wait less than one hour. Secondly an annual container through put that can be handled by the 9cranes at the terminal was found to be 683,000 TEU in case ships waiting time is one hour and 806,000 TEU in case ships waiting is 2 hours in-port transfer capability was 913,000 TEU when berth occupancy rate(9) was 0.5. This means that there was heavy congestion in the port when considering the fact that a total amount of 1,300,000 TEU was handled in the terminal in 1990. Thirdly when the cost of port congestion was not considered optimum cargo volume to be handled by a ship at a time was 235.7 VAN. When the ships' waiting time was set at 1 hour, optimum annual cargo handling capacity at the terminal was calculated to be 386,070 VAN(609,990 TEU), whereas when the ships' waiting time was set at 2 hours, it was calculated to be 467,738 VAN(739,027 TEU). Fourthly, when the cost of port congestion was considered optimum cargo volume to be handled by a ship at a time was 314.5 VAN. When the ships' waiting time was set at I hour optimum annual cargo handling capacity at the terminal was calculated to be 388.416(613.697 TEU), whereas when the ships' waiting time was set 2 hours, it was calculated to be 462,381 VAN(730,562 TEU).

• 한국사회복지학회:학술대회논문집
• /
• 한국사회복지학회 2002년도 국제학술대회 자료집
• /
• pp.3-19
• /
• 2002

The problems and needs of families in Hong Kong are becoming more complex. Traditional family structures and functions are rapidly eroding. Moreover, family problems are further exacerbated by a growing number of socio-economic issues including rising divorce rates and extra-marital affairs. continuous family reunion migration from Mainland China, emotional and financial cost of caring for the older people and the changing economy which has pushed more families into hardship. In effect, more and more families are becoming vulnerable to risk. Traditional family services in Hong Kong are varied in mode, operation and provision, often overlapping in service boundaries with other family-oriented programs. In many instances, family service centers are stretched far beyond their capacity. As a consequence, they become too reactive, remedial and casework dominated. The University of Hong Kong Consultant Team recommended that family service programs have to protect vulnerable families and strengthen family capacities to promote maximum independence. The direction of family services is summarized as: strengthening families; child-centered, family-focused and community-based. New integrative family service centers aim at attaining the principles of promoting accessibility to users with minimum physical, psychological and administrative barriers; early identification of needs and intervention before the further deterioration of problems; integration of services cutting across program boundaries, and partnership between service providers to achieve efficient and effective use of scarce resources. Under the new model, multi-skilled teams can respond more proactively to a wide range of social needs, rather than addressing needs in isolation. To demonstrate the effectiveness of the new model, the consultant team has been commissioned by the government to evaluate the performance of these two-year pilot projects. More importantly, a coherent and family-friendly social policy should be formulated to strengthen family capacity against family-related problems.

• 대한전자공학회논문지TC
• /
• 제44권8호
• /
• pp.33-41
• /
• 2007

IEEE 802.11 DCF 채널 접근 기능은 충돌을 피하고 hidden-terminal과 exposed-terminal 문제를 회피하기 위하여 두 홈 네트워크 내에서는 단일 전송을 허락한다. 이러한 단일 전송은 전송자의 이웃 노드가 전체 왕복시간 동안 데이터 프레임을 기다리게 하며, 프레임 지연의 증가와 네트워크 처리량을 낮게 하는 결과를 초래한다. 실시간 응용들은 낮은 매체 이용, 특히 높은 네트워크 트래픽에 대해 심하게 영향을 받는다. 본 논문은 IEEE 802.11의 프레임 집합화 기술을 이용하여 기본적인 DCF 기능을 유지한 단일 전송 장애를 극복하는 새로운 방안을 제시한다. 제안한 방안은 비 간섭 동기화 슬롯에서 병렬 전송을 허용한다. 병렬 전송은 몇몇 상황에서 물리적인 전송자 감지와 랜덤 백오프 타임을 회피하며, 프레임 지연을 줄이고 매체 이용과 네트워크 용량을 증가시킨다.

• Journal of Preventive Medicine and Public Health
• /
• 제27권4호
• /
• pp.777-791
• /
• 1994

For developing the Group Health Care System, health managers' job structure were analysed in the aspects of content, amount, and process. As a trial research, data were collected by a standardized job analysis table to 6 doctors, 40 nurses, and 11 industrial hygienists of Group Health Care System. Health care managers were performing complex and intellectual jobs such as healh education for workers, managing health care, conference as well as more simple jobs like as filling diary. Especially, job was consisted of general job and health care management job in the proportion of 1:2.18. The major general job were data management related with the health statistics, and major health care management jobs were managing health care, health counselling, environmental management of working sites. Each specific jobs were required differentiated intellectual capacity, creativity, autonomy, psychic stress, and physical work; most respondents perceived that health care management jobs should require more inputs than general jobs. Additionally job satisfaction and perceived need on specific Job items were anzlysed. Results of this research, suggested through the field experiences in working sites, should be considered for improving the Group Health Care System.

• 대한인간공학회지
• /
• 제16권3호
• /
• pp.23-36
• /
• 1997

The objective of this study was to make a comparison of the oxygen consumption rates during the lifting activities and the physiological criteria of the recommended weights of RWL, AL, and MPL by NIOSH Guideline. The physical Work Capacity (PWC) based on the bicycle ergometer was 2562.71ml/min, and the one based on the treadmill was 2874.89ml/min for the college male students of Korea. Lifting activities with four different lifting frequencies(2, 5, 8, 11 lifts/min) for one lifting range from floor to 76cm height were studied. The oxygen consumption rates and the heart rates were measured or recorded while subjects were lifting the weight of RWL, AL, and MPL. The heart rates and the oxygen consumption rates increased as the frequency increased from 2 to lifts/min. However, those slightly decreased at the frequency of 11 lifts/ min. The measured oxygen consumption rates were ranging from 2.3% to 29.6% higher than the physiological criteria 620, 700, and 1000ml/min, respectively, of the RWL, AL, and MPL for all the lifting frequencies (5, 8, 11 lift/min) except 2 lifts/min. It si suggested that the physiological criteria of NIOSH Guideline should be based on the lifting PWC, which can consider the type of lifting activity and the frequency of the task, rather than using the PWC by ergometer or treadmill. The measured oxygen consumption rates were ranging from 13.26% to 40.11% higher than the values estimated using the models by Garg and Kim. From these findings it is suggested that the NIOSH Equation should not be directly applied to Korean without resonable modifications.

• 대한인간공학회지
• /
• 제18권1호
• /
• pp.1-12
• /
• 1999

The objective of this study was to investigate the metabolic energy consumption rate of the psychophysical Maximum Acceptable Weight of Loads (MAWLs) for different manual materials handling tasks. Lifting activities with four different lifting frequencies (2, 5, 8, 11 lifts/min) for a lifting range (from floor to 76cm height) were studied. The oxygen consumption rate and heart rate were measured or recorded while subjects were lifting their MAWLs. It was found that the relationship between MAWL and frequency can be described best by the exponential function with the R-sq value 0.9865 for this study. Psychophysical MAWL decreased from 22.38 to 7.48 kg, while the oxygen consumption rate with the MAWL increased from 717.8 to $1114.7m{\ell}-O_2/min$ as the frequency increased from 2 to 11 lifts/min. Heart rate also increased from 104.5 to 120.7 bpm. The ratio of oxygen consumption for the MAWL to the Physical Work Capacity (PWC) ranged from 28 to 43%. The MAWLs were greater than or equal to the Maximum Permissible Limits (MPLs) when the frequencies were higher than 8 lifts/min. It seems that the MAWLs by psychophysical approach when the frequencies were higher than 8 lifts/min tend to be overestimated from the viewpoint of the physiological criterion of the oxygen consumption rates. From these findings it is suggested that the NIOSH Guideline should not be directly applied to Korean without reasonable modifications.