• Transactions of the Korean hydrogen and new energy society
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• v.30 no.3
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• pp.269-275
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• 2019

This study was conducted to evaluate the microbial communities in coupled system of a microbial electrolysis cell and an anaerobic digestion. Glucose, butyric acid, propionic acid and acetic acid were used as substrates. The maximum methane production and methane production rate of propionic acid respectively were $327.9{\pm}6.7mL\;CH_4/g\;COD$ and $28.3{\pm}3.1mL\;CH_4/g\;COD{\cdot}d$, which were higher than others. Microbial communities' analyses indicated that acetoclastic methangens were predominant in all systems. But the proportion of hydrogenotrophic methanogens was higher in the system using propionic acid as a substrate when compared to others. In coupled system of a microbial electrolysis cell and anaerobic digestion, the methane production was higher as the distribution of hydrogen, which was generated by substrate degradation, and proportion of hydrogenotrophic methanogens was higher.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.1
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• pp.69-76
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• 2023

An experimental study was conducted on a 4-stroke direct injection diesel engine to examine the combustion and emission characteristics of 1-octanol/diesel fuel blends. The concentration of 1-octanol in the fuel blends was 10%, 30%, and 50% by volume. Experiments were conducted by varying the engine torque from 6 Nm to 12 Nm at the same engine speed of 2,700 rpm. Results showed that the fuel conversion efficiency increased as the 1-octanol proportion increased under most experimental conditions. However, the brake specific fuel consumption increased due to the relatively low lower heating value of 1-octanol. The smoke opacity and the concentrations of NO_x and CO emissions generally decreased with brake mean effective pressure as the 1-octanol proportion increased. On the other hand, the unburned hydrocarbon concentration increased with an ascending ratio of 1-octanol.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.368-368
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• 2008

Ion implantation has been widely developed during the past decades to become a standard industrial tool. To comply with the growing needs in ion implantation, innovative technology for the control of ion beam parameters is required. Beam current, beam profile, ion fractions are of great interest when uniformity of the implant is an issue. Especially, it is important to measure the spatial distribution of beam power and also the energy distribution of accelerated ions. This energy distribution is influenced by the proportion of mass for ion in the plasma generator(ion source) and by charge exchange and dissociation within the accelerator structure and also by possible collective effects in the neutralizer which may affect the energy and divergence of ions. Hydrogen atom has been the object of a good study to investigate the energy distribution. Hydrogen ion sources typically produce multi-momentum beams consisting of atomic ion ($H^+$) and molecular ion ($H_2^+$ and $H_3^+$). In the beam injector, the molecular ions pass through a charge-exchanges gas cell and break up into atomic with one-half (from $H_2^+$) or one-third (from $H_3^+$) according to their accelerated energy. Burrell et al. have observed the Doppler shifted lines from incident $H^+$, $H_2^+$, and $H_3^+$ using a Doppler shift spectroscopy. Several authors have measured the proportion of mass for hydrogen ion and deuterium using an ion source equipped with a magnetic dipole filter. We developed an ion implanter with 50-KeV and 20-mA ion source and 100-keV accelerator tube, aiming at commercial uses. In order to measure the proportion of mass for ions, we designed a filter system which can be used to measure the ion fraction in any type of ion source. The hydrogen and helium ion species compositions are used a filter system with the two magnets configurations.

• Journal of Integrative Natural Science
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• v.16 no.4
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• pp.139-145
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• 2023

Due to changes in the distribution system and increased demand for renewable energy, interest in technology to increase the limit capacity of distributed energy grid connection using grid flexible resources is also increasing. Recently, the distribution system system is changing due to the increase in distributed power from renewable energy, and as a result, problems with the limited capacity of the distribution system, such as waiting for renewable energy to connect and increased overload, are occurring. According to the power generation facility status report provided by the Korea Power Exchange, of the total power generation capacity of 134,020 MW as of 2021, power generation capacity through new and renewable energy facilities is 24,855 MW, accounting for approximately 19%, and among them, power generation through solar power accounts for a total portion of the total. It was analyzed that the proportion of solar power generation facilities was high, accounting for 75%. In the future, the proportion of new and renewable energy power generation facilities is expected to increase, and accordingly, an efficient operation plan for the distribution system is needed. Advanced country-type NWAs that can integrate the operation and management of load characteristics for each line of the distribution system, power distribution, regional characteristics, and economic feasibility of distributed power in order to improve distribution network use efficiency without expanding distribution facilities due to the expansion of renewable energy. An integrated operating system is needed. In this study, in order to improve the efficiency of distribution network use without expanding distribution facilities due to the expansion of renewable energy, we developed a method that can integrate the operation and management of load characteristics for each line of the distribution system, power distribution, regional characteristics, and economic feasibility of distributed power. We want to develop an integrated operation system for NWAs similar to that of advanced countries.

• Korea Journal of Hospital Management
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• v.5 no.1
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• pp.105-128
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• 2000

This study was conducted to investigate the prospects and issues for the implementation of the annual salary system in Korean hospitals. Data were collected from the top management of 669 hospitals in Korea through the self-administerd questionnaires. Of the 175 respondents, 171 questionnaires were used as final data and analyzed using $X^2$ test. The results of the study are as follows. 1) It is found that 49.7% of the study hospitals are operating the annual salary system. 2) Among the hospitals which are not operating the annual salary system, 49.2% have the plan to implement the system and 44.5% have not decided yet whether they introduce the system or not. 3) The proportion of the hospitals which have the plan to implement the annual salary system within 5 years is 96.8%. 4) The proportion of the hospitals which will begin the system only with full-time physicians and middle level managers is 36.2%, while that of the hopsitals which will apply the system to all employees is 30.5%. 5) Hospital Administrators seems to prefer to 10-20% salary gap for the introduction period among the employees with same salary. 6) Most of the respondents are willing to accept the payment system based on the performance. 7) The major issues which should be dealt with before the implementation of the annual salary system are the establishment of the objectivity of performance evaluation criteria, the improvement of teamwork, and the maintenance of organizational commitment. 8) The desirable criteria for employee evaluation are found to be the mixture of the ability, job position, tenure, and the job difficulty.

• Korean System Dynamics Review
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• v.8 no.2
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• pp.235-252
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• 2007

This study focused on the analysis of the abilities and characteristics of the systems thinking for pre-service elementary teachers. Systems thinking is defined as the ability to see the world as a complex system in which one understands that everything is connected to everything else. For this study, 345 subjects carrying of the 2nd grade were selected and participated in making out the protocol developed by Sweeney and Sterman(2000) for the estimating ability of the systems thinking. As a result, the proportion of the correct answers based on the total points of view was 63%. However, the proportion of correct answer was considerably different according to the gender. The women group showed 53%, while the men group was 76%. Especially, there was a great difference in the rates of correct answer depending on their academic tracks of the humanities or natural science courses in the high school. The average rates of the correct answers for the natural science and the human science were 84 and 46%, respectively. Consequently, the ability of the systems thinking for pre-service elementary teachers is highly related with their gender and learning experience in the high school. The results of this study may contribute the practical use of the systems thinking in the area of the science education.

• Health Policy and Management
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• v.24 no.4
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• pp.357-366
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• 2014

Background: The objective of this study was to evaluate the efficiency of an emergency ambulance system and to investigate socio-economic and clinical characteristics associated with emergency ambulance service. Methods: Based on 2011 Korea health panel, unmet need and inappropriate use of emergency ambulance service were measured by Gibson in 1977. Furthermore, the factors associated with unmet need and inappropriate use of emergency ambulance service were identified by Fisher's exact tests and multiple logistic regression models. Results: Unmet need, defined as the proportion of emergency patients who clinically need ambulance transportation but do not receive it, was found to be 59.8%. Inappropriate use, defined as the proportion of emergency patient receiving ambulance care who did not clinically need it, was found to be 37.2%. There were statistically significant differences between appropriate and inappropriate groups in overall variables of socio-economic and clinical characteristics. Specifically, gender, age, relationship to household, and reasons of visiting emergency department (accident/disease) were statistically significant factors associated with appropriate use of emergency ambulance service. Conclusion: Unmet ambulance need is a useful measure for patients needs assessment, and inappropriate ambulance use is a valid criteria in judging the efficiency of emergency ambulance system. To improve and understand emergency ambulance system, unmet need and inappropriate use of emergency ambulance service should be more concerned.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.106-112
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• 2008

Modern vehicles require a high degree of refinement, including good drive ability to meet customer demands. Vehicle drive ability, which becomes a key decisive factor for marketability, is affected by many parameters such as engine control and the dynamic characteristics in drive lines. This paper focuses on the simulation of FTP-75 mode which is considered with spark timing control on transient condition. The acceleration is the most important factor for vehicle fuel economy. The retard of spark timing increases in proportion to acceleration. Likewise, bsfc(break specific fuel consumption) which is affected by spark timing also increases in proportion to acceleration. The result of simulation considered transient condition shows 0.3% of error comparing with a test on chassis-dynamometer.

• The Journal of Fisheries Business Administration
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• v.51 no.4
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• pp.137-146
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• 2020

In this study, the differences of institutional development processes of fishery products wholesale markets were compared between Korea and Japan in order to suggest improvement direction of trading system in Korea. The wholesale markets have shrunk while wholesale and distribution has been becoming larger in size in both countries. A summary of differences in the wholesale market trading systems between Korea and Japan is as follows: first, middle wholesalers play pivotal roles in wholesale transaction in Korea, and wholesale corporations take such roles in Japan. Second, most wholesale corporations take charge of listing in Korea whereas such corporations are in charge of buying in Japan. Third, Korea has high proportion of auction for transactions, in contrast to Japan with high proportion of relative transactions. Forth, Korea maintains more sales within the wholesale markers and has more small and medium customers than Japan. Finally, Korea investigates inside causes to find solutions for the decreased competitive power of the wholesale market, whereas Japan copes with the problem by searching for outside customers. To seek solutions for the decreased competitiveness of Korean fishery products wholesale markets, middle wholesalers' consignment should be limitedly allowed, and improvement direction of wholesale corporations should be investigated in the future study.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.1 no.1
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• pp.45-48
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• 1978

If two inspectors classify items in a lot into m classes, it is possible that each of them makes wrong classification in some cases, thus causing bias. Expressions have been obtained for the limits of this bias in estimating the proportion of the different classes. From the results of the classification they obtained limit for the estimates of Proportions have been worked out, based on assumption regarding the magnitudes of probabilities of misclassification. Now we suppose that $P_{ti}{\;}(t=1.2)$ is the probability that t the inspector classifies correctly an item in class $A_i$ and $q_{tji}$ is the probability that he misclassifies in $A_j$ an item actually belonging to $A_i$, therefor, $P_{ti}+ \sum\limits_{j{\neq}i}q_{tji}=1$ An estimate for the proportion $P_k$ of the class $A_k$ in the lot would be $\hat{P}_k=r_{kk}+(\frac{1}{2})\sum\limits_{j{\neq}k}r_{kj}+r_{jk}$ The % Bias in proportion $\hat{P}_k$ is $\frac{E(\hat{P}_k)-P_k}{P_k}{\times}100$