• Journal of the Korean Institute of Gas
• /
• v.28 no.1
• /
• pp.11-18
• /
• 2024

If flammable liquid leaks, vapor evaporated from the pool can cause poisoning or suffocation to workers, leading to secondary accidents such as fires and explosions. To prevent such damage, ventilation facilities shall be installed when designing indoor workplaces. At this time, the behavior varies depending on the characteristics of the leaked chemical, so it is necessary to select a suitable vent location according to the material. Therefore, 3D CFD simulations were introduced to derive optimal vent position and ventilation efficiency was quantitatively evaluated by vent position. At this time, assuming a situation in which flammable liquids leak at indoor workplaces to form pools, the concentration of vapor evaporated from pools was compared to derive the optimal vent position. As a result of research on toluene with high vapor density, ventilation efficiency was confirmed to be the highest at the upper supply-lower exhaust, and it is judged that introducing it can achieve about 3.7 times ventilation effect at the same maintenance cost. Through this study, it is expected that the workplace will be able to secure workers' safety by applying simulation results and installing ventilation ports.

• Journal of the Korea Concrete Institute
• /
• v.21 no.3
• /
• pp.347-358
• /
• 2009

Recently, it is getting into a good situation for the flat-plate slab system to be applied. The flat-plate slab without beam, however, is often too weak to control deflection properly compared to other typical slab-beam structures, for which the post-tension method is generally regarded as one of best solutions. The post-tension (PT) method can effectively control deflection without increase of slab thickness. Despite this good advantage, however, the application of PT method has been very limited due to cost increase, technical problems, and lack of experiences. Therefore, in order to reduce difficulties on applying full PT method under the current domestic circumstances and to enhance constructability of PT system, this research proposed the partial PT method with top jacking anchorage applied in a part of span as need. For the top jacking anchorage system, the efficiency of deflection control shall be considered in detail because it can vary widely depending on the location of anchorage that can be placed anywhere as need, and tensile stresses induced at back of the anchorage zone also shall be examined. Therefore, in this study, analysis were performed on the efficiency of deflection control depending on the location of anchorage and on tensile stresses or forces using finite element method and strut and tie model in the proposed top jacking anchorage system. The proposed jacking system were also applied to the floor slabs at a construction site to investigate its applicability and the analysis results of slab behavior were compared to the measured values obtained from the PT slab constructed by the partial PT method. The result of this study indicates that the partial PT method can be very efficiently applied with little cost increase to control deflection and tensile stresses in the region as a need basis where problem exists.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.1
• /
• pp.305-316
• /
• 2013

To find out if modern roundabout is still effective under drivers behavior and driving conditions in Busan Metropolitan City, the effects before and after introduction of roundabout were analyzed. According to analysis on velocity profile at roundabout, velocity deviation decreased, and average vehicle speed was close to design speed. As a result, it has been confirmed that most roundabouts were properly built. In terms of traffic operation, average vehicle speed improved by 87.2% when a traffic intersection was replaced by a roundabout. therefore, it has been found out that the introduction of roundabout has a positive effect on increasing vehicle speed by reducing traffic congestion. In addition, annual benefits expected from the replacement from a traffic intersection to a roundabout were KRW 872 million as follows; KRW 410 million in traffic communication, KRW 39 million in transportation safety, KRW 255 million in energy saving, KRW 95 million in reduction of air pollution and KRW 73 million in reduction of traffic signal installation cost. In other words, if 10% (193 spots) of all traffic intersections (1,926 spots in total) in Busan City are replaced by roundabouts, the municipal authority would be able to save about KRW 168.3 billion. According to analysis on the benefits expected from the installation of roundabouts compared to the investment cost for traffic intersections, about KRW 679 million could be saved per roundabout. Considering 10% of all traffic intersections in the City of Busan, about KRW 131 billion could be saved annually. The traffic accidents in roundabout usually occur because drivers aren't aware of right-of-way rules. Once the right-of-way rules settle, the number of traffic accidents would significantly decrease. In addition, it is urgent to promote education and campaign for drivers, pedestrians and bikers on the roundabout.

• Korean Journal of Occupational Health Nursing
• /
• v.7 no.2
• /
• pp.164-176
• /
• 1998

This study deals with the current medical utilization for migrant workers and the characteristics of them. The purpose of this study is to provide the basic information to establish proper medical policy. For the study self-made questionnaire was used, which was answered by 453 migrant workers working in the area of manufacturing and non-technical work in 10 cities like Seoul, Inchon, Namyangju, Sungnam, Kwangju, Pyungchon, Kunpo, Kimpo, Masuk in Kyungki-do and Chunan in Chungchungnam-do. Besides, 303 medical records of those who had visited free medical check-up center were analyzed. The period of accumulating data is 6 months, from November 1st, 1996 to April 30th, 1997. The characteristics of migrant workers and current medical utilization are analyzed by percentage and the relation between characteristics and current medical utilization were analyzed using ${\chi}^2$-test, t-test, ANOVA. The finding of this study was as follows : 1) The number of nationality was 16. The first majority was Philippians as 32.0%. Among 16 nationalities Southeastern and Northern Asians were 48.9%, Southwestern Asian was 46.5%, the rest was 7.3%. Men were 81.0%, those who are aged from 26 to 30 were 39.0%, Graduatee from high school 92.7%, Christians 56.3%, unmarried 55.4% and salary from 600,000 Won to 800,000 Won 53.8% averaging monthly payment 669,810 Won. As for their residence, those who resided over 3 years were 31.9% and the illegal residence reached 77.4%. As for Korean language, those who speak in middle level were 5.6%. 2) As for kind of work and circumstances, manufacturing was 81.1%, 4 off-days per month 72.2% and 9-10 working hours per day 42.1%. As for accommodation, residence in fabric was 62.6% and one or two members as roommate 40.2%. 3) The characteristics of health behavior showed that 89.4% of migrant workers had 3 meals, 70.9% of them did not drink alcohol, 73.5% of them did not smoke. 4) As a characteristic of health status, 71.8% of them perceived of their health. 76.1% thought that they had no illness before coming Korea. Among them who recognized their illness, those who had problem in circulatory system was 35.3%, respiratory system ENT 19.1% and nervous system 19.1%.66.2% of those having illness had already had sickness when coming to Korea. 5) During last one month, 79.2% of them were known as ones having no illness. Among the sick, those who had problem in circulatory system was 31.6%, nervous system 23.7% and respiratory system 21.1%. 60.3% of the sick were not cured at that time. 6) Sorting the symptom of those who visited free medical check up, dental care was 24.2%, orthopedic 14.0% and digestive system 13.8%. Teethache was 34.4%, stomach problem 11.6%, upper respiratory inflammation 10.2% and back pain 5.9%. Averagely they visited free medical check up 1-2 times. According to symptom, epilepsy 25.5 times, heart and vascular disease 9 times, constipation 2.8%, neurosis 2.38 times and stomach problem 2.34 times. 7) The most frequently visited medical service by migrant workers was hospital. The most mentioned reason was good healing as 36.3%. The medical service satisfied migrant workers mostly was hospital as 64.3%. The reason of satisfaction was also good healing as 45.9%. 8) 77.2% of respondents did not spend money for medical check. Average monthly medical cost was 25,100 Won, 3.7% of income. Those who had no medical security was 73.4%. In their case, 67.7% got discount from hospital or support from working place and religious organization. 9) As for the difference of medical utilization according for the characteristics of migrant workers, legal workers and no-Korean speaker used hospital more frequently. 10) Those who were satisfied most of all with the service of hospital were female workers, hinduists and buddhists, legal workers or manufacture workers. 11) Christians, those who have 3 meals or recognize themselves as healthy ones mostly had no illness. As a result, the most of migrant workers in Korea are from Asia. They are good educated but are working in manufacturing and illegal. Their average income is under 700,000 Won which in not enough for medical cost. They have no medical security and medical fee is supported by religious organization or discounted. Considering these facts the medical policy by government is to be established.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.5-5
• /
• 2011

The research and development of hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and electric vehicle (EV) are intensified due to the energy crisis and environmental concerns. In order to meet the challenging requirements of powering HEV, PHEV and EV, the current lithium battery technology needs to be significantly improved in terms of the cost, safety, power and energy density, as well as the calendar and cycle life. One new technology being developed is the utilization of composite cathode by mixing two different types of insertion compounds [e.g., spinel $LiMn_2O_4$ and layered $LiMO_2$ (M=Ni, Co, and Mn)]. Recently, some studies on mixing two different types of cathode materials to make a composite cathode have been reported, which were aimed at reducing cost and improving self-discharge. Numata et al. reported that when stored in a sealed can together with electrolyte at $80^{\circ}C$ for 10 days, the concentrations of both HF and $Mn^{2+}$ were lower in the can containing $LiMn_2O_4$ blended with $LiNi_{0.8}Co_{0.2}O_2$ than that containing $LiMn_2O_4$ only. That reports clearly showed that this blending technique can prevent the decline in capacity caused by cycling or storage at elevated temperatures. However, not much work has been reported on the charge-discharge characteristics and related structural phase transitions for these composite cathodes. In this presentation, we will report our in situ x-ray diffraction studies on this mixed composite cathode material during charge-discharge cycling. The mixed cathodes were incorporated into in situ XRD cells with a Li foil anode, a Celgard separator, and a 1M $LiPF_6$ electrolyte in a 1 : 1 EC : DMC solvent (LP 30 from EM Industries, Inc.). For in situ XRD cell, Mylar windows were used as has been described in detail elsewhere. All of these in situ XRD spectra were collected on beam line X18A at National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory using two different detectors. One is a conventional scintillation detector with data collection at 0.02 degree in two theta angle for each step. The other is a wide angle position sensitive detector (PSD). The wavelengths used were 1.1950 ${\AA}$ for the scintillation detector and 0.9999 A for the PSD. The newly installed PSD at beam line X18A of NSLS can collect XRD patterns as short as a few minutes covering $90^{\circ}$ of two theta angles simultaneously with good signal to noise ratio. It significantly reduced the data collection time for each scan, giving us a great advantage in studying the phase transition in real time. The two theta angles of all the XRD spectra presented in this paper have been recalculated and converted to corresponding angles for ${\lambda}=1.54\;{\AA}$, which is the wavelength of conventional x-ray tube source with Cu-$k{\alpha}$ radiation, for easy comparison with data in other literatures. The structural changes of the composite cathode made by mixing spinel $LiMn_2O_4$ and layered $Li-Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ in 1 : 1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ~5.2 V vs. $Li/Li^+$, the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component only. When the cell voltage reaches at ~4.0 V vs. $Li/Li^+$, lithium extraction from the spinel $LiMn_2O_4$ component starts and becomes the major contributor for the cell capacity due to the higher rate capability of $LiMn_2O_4$. When the voltage passed 4.3 V, the major structural changes are from the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, while the $LiMn_2O_4$ component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel $LiMn_2O_4$ component, with much less changes in the layered $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research. More detailed discussion will be presented at the meeting.

• Research in Community and Public Health Nursing
• /
• v.9 no.1
• /
• pp.143-162
• /
• 1998

This is a study for the construction of nursing care based upon the Korean attitude toward medicine. Factors which were investigated include the source of nursing care, the reason for choosing care, the type of heath care chosen, the accessability of caregivers, and the desired location of death. The population examined in this study consisted of 517 adults distributed in six large cities and 191 adults from five rural communities. Data was analyzed using frequency, percent, Cronbach alpha, $X^2$ - test, t - test, F - test and scheffe post hoc contrast with an SAS program. The results of this study are summarized as follows: 1. Among sources of nursing care used, first rank rated-pharmacy(54.4), private hospital(18.2), general hospital(8.4), folk remedies in house (5.0), chinese hospital(2.8), prayer(2.8) and others(8.4), and the reasons for choosing nursing care rated 'the easiest method' (63.6), 'the best method'(15.7), 'reliable'(10.8) and 'lower cost burden'(4.6) in order of preference. 2. The type of nursing care chosen rated western medicine(6.80), chinese medicine(6.15), folk remedies(5.46), faith remedies(3.51) and divination remedies (1.41). There were significant differences in the effect recognition degree to various kinds of medicine. 3. The difference of the type of nursing care chosen according to general characteristics showed that urban residents were higher than rural community residents(t=2.15, p=0.0320) in western medicine, and urban residents, women, and singles were higher than rural community residents(t=2.04, p=0.0414), men (t= -2.89, p=0.0039), and married(t=2.50, p= 0.0126) on folk remedies. With repect to age and education those 21-30, under 20 and 31-40, graduated from college and graduate school were higher than above 51, above 61 (F = 7.76, p = 0.0001), graduated from elementary school(F=4.39, p=0.0006) on folk remedies. In other categories, rural community residents, women, younger people. Christians were higher than urban residents ( t = -2.73, p=0.0305), men(t= -4.15, p=0.0001), older people (F=2.48, p=0.0307), Catholic, Buddhist, or atheist (F= 70.18, p=0.0001) on faith remedies. Those graduated from high school and Buddhist were higher than unschooled, graduated from middle school(F=3.18, p= 0.0075), atheist, Catholic or Christian(F=18.32, p=0.0001) on divination redemies. There were significant differences concerning age and education level. 4. The accessibility of caregivers rated 'caregivers should be nearby if the patients need them' (50.0), 'caregivers must be there all day (24 hours)' (39.6), 'caregivers must be there at night only'(5.0), 'caregivers must be there during the day only'(2.6), 'caregivers always should visit during visiting hours' 0.4), 'caregivers don't need to be there at all' (1.2). The frist rank of suitable caregivers were rated as spouse(66.6), mother(24.2), daughter (3.6), daughter-in-law(1.9), and the reasons of thinking thus were rated as 'the most comfortable' (81.5), 'people should correctly with regards to family they'(7.1), 'the easiest' (5.4), 'take good care of the patient' (5.1) and 'lower cost burden' (0.4). 5. The desired location of death rated as the following: his/her house (91. 6) to the hospital(8. 4). A person going to encounter death in the hospital wanted his house(78.5) over the hospital(21.5), and a person dieing in the hospital prefered his house(52.9) over the hospital(47.1) as a funeral ceremony place. The following suggestions are made based on the above results. 1. A sampling method that enhances the re presentativeness should be used in regional and/or national related research and replicated to confirm the result of this study. 2. This study should be used to understand the Korean view of medical centers and to meet the expectations of patients in Korean nursing. 3. Research on the Korean traditional view of humans and expectations of the sick, health and illness, and health behavior, the perception of dying, the decision to heal, and the view of general medicine should continue to be conducted continuosly so that Korean nursing theory can be advanced on these concepts.

• The Korean Journal of Financial Management
• /
• v.10 no.1
• /
• pp.249-280
• /
• 1993

Recent financial theory views insurance policies as financial instruments that are traded in markets and whose prices reflect the forces of supply and demand. This article analyzes individual's insurance purchasing behavior along with capital market investment activities, which will provide a more realistic look at the tradeoff between insurance and investment in the individual's budget constraint. It is shown that the financial economic concept of insurance cost should reflect the opportunity cost of insurance premium. The author demonstrates the importance of riskless and risky financial assets in reaching an equilibrium insurance premium. In addition, the paper also investigates how the investment income could affect the four established theorems on traditional insurance literature. At the present time in Korea, the price deregulation is being debated as the most important current issue in insurance industry. In view of the results of this paper, insurance companies should recognize investment income in pricing their coverage if insurance prices are deregulated. Otherwise. price competition may force insurance companies to restrict coverage or to leave the market.

• KDI Journal of Economic Policy
• /
• v.12 no.2
• /
• pp.95-120
• /
• 1990

The underpricing of new shares of a firm that are offered to the public for the first time (initial offerings) is well known and has puzzled financial economists for a long time since it seems at odds with the optimal behavior of the owners of issuing firms. Past attempts by financial economists to explain this phenomenon have not been successful in the sense that the explanations given by them are either inconsistent with the equilibrium theory or implausible. Approaches by such authors as Welch or Allen and Faulhaber are no exceptions. In this paper, we develop a signalling model of capital investment to explain the underpricing phenomenon and also analyze the efficiency of investment. The model focuses on the information asymmetry between the owners of issuing firms and general investors. We consider a firm that has been owned and operated by a single owner and that has a profitable project but has no capital to develop it. The profit from the project depends on the capital invested in the project as well as a profitability parameter. The model also assumes that the financial market is represented by a single investor who maximizes the expected wealth. The owner has superior information as to the value of the firm to investors in the sense that it knows the true value of the parameter while investors have only a probability distribution about the parameter. The owner offers the representative investor a fraction of the ownership of the firm in return for a certain amount of investment in the firm. This offer condition is equivalent to the usual offer condition consisting of the number of issues to sell and the unit price of a share. Thus, the model is a signalling game. Using Kreps' criterion as the solution concept, we obtained an essentially unique separating equilibrium offer condition. Analysis of this separating equilibrium shows that the owner of the firm with high profitability chooses an offer condition that raises an amount of capital that is short of the amount that maximizes the potential profit from the project. It also reveals that the fraction of the ownership of the firm that the representative investor receives from the owner of the highly profitable firm in return for its investment has a value that exceeds the investment. In other words, the initial offering in the model is underpriced when the profitability of the firm is high. The source of underpricing and underinvestment is the signalling activity by the owner of the highly profitable firm who attempts to convince investors that his firm has a highly profitable project by choosing an offer condition that cannot be imitated by the owner of a firm with low profitability. Thus, we obtained two main results. First, underpricing is a result of a signalling activity by the owner of a firm with high profitability when there exists information asymmetry between the owner of the issuing firm and investors. Second, such information asymmetry also leads to underinvestment in a highly profitable project. Those results clearly show the underpricing entails underinvestment and that information asymmetry leads to a social cost as well as a private cost. The above results are quite general in the sense that they are based upon a neoclassical profit function and full rationality of economic agents. We believe that the results of this paper can be used as a basis for further research on the capital investment process. For instance, one can view the results of this paper as a subgame equilibrium in a larger game in which a firm chooses among diverse ways to raise capital. In addition, the method used in this paper can be used in analyzing a wide range of problems arising from information asymmetry that the Korean financial market faces.

• Journal of Nutrition and Health
• /
• v.52 no.3
• /
• pp.310-322
• /
• 2019

Purpose: This study examined the food purchases from e-commerce and its relation to eating behaviors or habits in adult women in Incheon and Gyeonggi. Methods: A total of 410 subjects participated in the questionnaire survey. Food purchases in e-commerce and food habits were compared according to age, marital status, and food purchase status in e-commerce of the subjects. Results: Approximately 88% of the subjects had experience of buying foods by e-commerce; more than 40% of the subjects spent less than 100,000 Won buying foods by e-commerce in the past 6 months. The major purchases were coffee and tea, instant food and frozen food, and water and beverages. The reasons for buying foods in e-commerce were cheaper price, convenience of delivery, and variety of food choices. The main factors considered for purchasing foods in e-commerce were price and quality followed by rapid and accurate delivery, and food label and information. Approximately 70% of the subjects were very satisfied or satisfied with their food purchase in e-commerce, and 96% answered that they were willing to buy food in e-commerce again. The perception on the advantages of food purchases in e-commerce was 3.6 points out of 5 and significantly lower in the over 50s and married group. The subjects with experience and high cost of food purchase in e-commerce showed significantly low scores of dietary behaviors and eating habits, which is undesirable. Conclusion: A high percentage of people purchased foods by e-commerce, and they showed undesirable eating habits, especially when the cost of purchasing foods by e-commerce is high. These results showed that purchasing foods in e-commerce may be related to consumers' food habits. Therefore, continuous attention and nutrition guidance for e-commerce consumers are needed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.3A
• /
• pp.201-209
• /
• 2010

Generally, PSC girder bridge uses total gross cross section to resist applied loads unlike reinforced concrete member. Also, it is used as short and middle span (less than 30 m) bridges due to advantages such as ease of design and construction, reduction of cost, and convenience of maintenance. But, due to recent increased public interests for environmental friendly and appearance appealing bridges all over the world, the demands for longer span bridges have been continuously increasing. This trend is shown not only in ordinary long span bridge types such as cable supported bridges but also in PSC girder bridges. In order to meet the increasing demands for new type of long span bridges, PSC hollow box girder with H-type steel as compression reinforcements is developed for bridge with a single span of more than 50 m. The developed PSC girder applies compressive prestressing at H-type compression reinforcements using unbonded PS tendon. The purpose of compressive prestressing is to recover plastic displacement of PSC girder after long term service by releasing the prestressing. The static test composed of 4 different stages in 3-point bending test is performed to verify safety of the bridge. First stage loading is applied until tensile cracks form. Then in second stage, the load is removed and the girder is unloaded. In third stage, after removal of loading, recovery of remaining plastic deformation is verified as the compressive prestressing is removed at H-type reinforcements. Then, in fourth stage, loading is continued until the girder fails. The experimental results showed that the first crack occurs at 1,615 kN with a corresponding displacement of 187.0 mm. The introduction of the additional compressive stress in the lower part of the girder from the removal of unbonded compressive prestressing of the H-type steel showed a capacity improvement of about 60% (7.7 mm) recovery of the residual deformation (18.7 mm) that occurred from load increase. By using prestressed H-type steel as compression reinforcements in the upper part of cross section, repair and rehabilitation of PSC girders are relatively easy, and the cost of maintenance is expected to decrease.