• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.95-102
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• 2023

This study aims to empirically verify the moderating effect of population drop on the relationship between demographic changes and crime decline in local cities facing population decline in Korea. The study employs changes in the population of young adults, men, elderly, foreign residents, and population movement as factors of demographic changes, including types of the city as a control variable in the research model. The rate of change in population drop is used as a moderator variable and the rate of change in crime decline as a dependent variable. Data are collected from 155 cities with declining populations from 2010 to 2022 through KOSIS, the National Statistics Portal, and information disclosure requests. Data collected are analyzed using moderated regression analysis. In the first and second stages of the analysis, they show that changes in the population of young adults, population movement, foreign people, population drop, and the type of city affect the change in crime. Moderated regression analysis shows that only the interaction terms among changes in the population of young adults, changes in population movement, and changes in the population of foreigners and the population drop affects change in crime significantly.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.127-135
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• 2013

In this study, both pressure drop and microbe-population-distribution were observed while running a novel biofilter system with improved design in which the biofilter system is composed of two, upper and lower biofilters with both equal feed-rates of up-flow and down-flow, respectively. Then they were compared with the pressure drop and microbe-population-distribution observed in a conventional biofilter of the same effective volume with unidirectional flow. The pressure drop-value of biofilter system with improved design turned out to be less at the incipient stage of run or steady-state long term operation by more than 40~80% of that of the conventional biofilter. The microbe-population-distribution was observed to be lower and higher at higher and lower column of biofilter, respectively, for both the conventional biofilter and the biofilter system with improved design. The microbe-media of waste-tire crumb showed much greater CFU counts than GAC. In the biofilter system with improved design, the $bottom{\rightarrow}up$ feeding of waste air showed greater microbe-population growth than the $top{\rightarrow}down$ feeding for both the microbe-media of waste-tire crumb and GAC. However, it was more prominent for the former than the latter. Comparing the microbe-population-distributions of both of the conventional biofilter and the biofilter system with improved design, the microbe-population of latter was distributed ca. 15 and 2.5 times more evenly for GAC and the media of waste-tire crumb, respectively, than that of former.

• Industrial Engineering and Management Systems
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• v.12 no.4
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• pp.351-358
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• 2013

This paper proposes a multiobjective model describing the trade-offs involved in selecting the locations of drop-off boxes for collecting used products and transporting these products to designated locations. We assume the following reverse flow of used products. Owners of used products (cellular phones, digital cameras, ink cartridges, etc.) take them to the nearest drop-off box when the distance is reasonably short. We also assume that owners living closer to drop-off boxes dispose of more used products than do owners living farther from drop-off boxes. Different types of used products are collected, with each type requiring its own drop-off box. A transportation destination for each product is specified. Three objectives are considered: maximizing the volume of used products collected at drop-off boxes; minimizing the cost of transporting collected products to designated locations; and minimizing the cost of allocating space for drop-off boxes. We formulate the above model as a multiobjective integer programming problem and generate the corresponding set of Pareto optimal solutions. We apply the model to an area using population data for Chofu City, Tokyo, Japan, and analyze the trade-offs between the objectives.

• Korea journal of population studies
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• v.17 no.1
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• pp.1-16
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• 1994

Since 1962, the population growth control has been one of the most important aims in the 5-Year So-cioeconomic Development Plans of Korea. The annual population growth rate has dropped to tess than 1 percent in 1990 from about 3 percents in 1960s, and projected to reach to $\ulcorner$0$\urcorner$ percent in 2021. From 2021, Korean population will decrease and the age structure will be distorted because birth rate will drop suddenly and continuously. Thus, we can consider $\ulcorner$0$\urcorner$ growth population for minimizing the prob- lems on the decreasing population. To discuss the problems caused from the changes of population size and age- sex composition, we projected three kinds of population including two kinds of $\ulcorner$0$\urcorner$ growth population under different as- sumptions. The first is the population which extended the projection of National Statistical Office up to 2090. Because the TFR is assumed and fixed as low as 1.63 after 1990, the population growth rate will be under $\ulcorner$0$\urcorner$ in 2021 and drop by about 1 percent every year from around 2050. This population trend results to old age population : 38.1 of old- age dependency ratio and 46.5 years of median age. The second is the population which the size in 2021 projected by the NOS continues after 2021. To change over from the decreasing population after 2021 to the $\ulcorner$0$\urcorner$ growth one, the TFR should be in-creased up to over 3.0 in 2040-2050, which fertility level would be too high to be accepted. The third is the population which approaches to the $\ulcorner$0$\urcorner$ growth population under the assumptions that the TFR increases from 1.63 to 2.1 in the period of 2010-2030 and then the same level continues. Although the maximum population size reaches 51, 503 thousand persons, the population will approach to the stationary population with about 42.4 million persons around 2090. In this projected population there is no more serious problems on population composition, on the rapid decrease of population, and on the increase TFR level. When the $\ulcorner$0$\urcorner$ growth population continues the problems of over population caused by the populationincrease wou]d be minimized, and the problems of unusual age composition resulted from the popula-tion decrease would not be found any more. Furthermore, when the changes of population size and composition is continuing slowly, the factors of population would effect moderately to socioeconomic development and help social changes. Therefore, with the attention of the present population changes, we should adapt new and detailde population policy which is able to get the $\ulcorner$0$\urcorner$ growth population.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4491-4503
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• 2023

This study aimed to verify and validate the transient simulation capability of the hybrid code system RAST-F for fast reactor analysis. For this purpose, control rod (CR) drop experiments involving eight separate CRs and six CR groups in the China Experimental Fast Reactor (CEFR) start-up tests were utilized to simulate the CR drop transient. The RAST-F numerical solution, including the neutron population, time-dependent reactivity, and CR worth, was compared against the measurement values obtained from two out-of-core detectors. Moreover, the time-dependent reactivity and CR worth from RAST-F were verified against the results obtained by the Monte Carlo code Serpent using continuous energy nuclear data. A code-to-code comparison between Serpent and RAST-F showed good agreement in terms of time-dependent reactivity and CR worth. The discrepancy was less than 160 pcm for reactivity and less than 110 pcm for CR worth. RAST-F solution was almost identical to the measurement data in terms of neutron population and reactivity. All the calculated CR worth results agreed with experimental results within two standard deviations of experimental uncertainty for all CRs and CR groups. This work demonstrates that the RAST-F code system can be a potential tool for analyzing time-dependent phenomena in fast reactors.

• Journal of the Korean Society of Physical Medicine
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• v.13 no.3
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• pp.133-139
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• 2018

PURPOSE: Despite the abundant literature available regarding the activity of intrinsic muscles, few studies have investigated the muscle activity of extrinsic muscles. Therefore, the present study compared the muscle activity of the peroneus longus, tibialis anterior, and abductor hallucis during short foot exercise in subjects with and without flat feet. METHODS: Twelve subjects with and without pes planus participated in this study. During the short foot exercises, muscular activity of the tibialis anterior, fibularis longus, and abductor hallucis longus were measured in both groups. To identify the effects of short foot exercises, navicular drop height was also investigated in pre and post short foot exercises. RESULTS: In a symptomatic group, the navicular drop height was significantly reduced at post measurement compared with pre-measurement. During the short foot exercise, the pes planus group showed significantly lower activities of the fibularis longus than the control group (p<.05). CONCLUSION: Similar to previous studies and clinical literature, short foot exercise was effective for alleviating navicular drop for a population with pes planus. In addition, subjects with pes planus showed decreased muscular activities of the fibularis longus, which suggests that considering extrinsic muscles such as fibularis longus is also important for rehabilitation of pes planus patients.

• Korea journal of population studies
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• v.24 no.2
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• pp.117-147
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• 2001

The main purpose of this paper is to analyze sex and age composition of the 1994 North Korean census data. First this paper describes the background information concerning the first population census ever taken in North Korea since the separation of the North and South. It utilizes the available data to explain the trend and current population status of North Korea. The focus of this research is to point out and analyze the problems in the sex and age composition of the North Korean census data. One of the most striking characteristics of the census data is that an enormous portion of the young male population was excluded from the census counts. Such omissions are strongly suggested by a incredible drop in sex ratios for the age groups of 16 to 25. In addition, the total sum of the population by age groups turns out to be substantially smaller than the total sum of the population by geographical regions. The total discrepancy amounts to 691 thousand. Along with sex ratios and age ratios, Myers indices, UN age-sex accuracy indices, indices of relative difference, and indices of dissimilarity are calculated to analyze the characteristics and accuracy of sex and age composition in the North Korean census data. Finally, this paper readjusts the sex and age composition of the 1994 census data, and attempts to produce a more accurate population of North Korea.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.116-124
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• 2022

In this study, waste air containing ethanol and hydrogen sulfide, was treated by an integrated hybrid system composed of two alternatively-operating UV/photocatalytic reactor-process and biofilter processes of a biofilter system having two units with an improved design (R reactor) and a conventional biofilter (L reactor). Both a pressure drop (△p) per unit process of the integrated hybrid system and a microbe-population-distribution of each biofilter process were observed. The △p of the UV/photocatalytic reactor process turned out very negligible. The △p of the L reactor was observed to increase continuously to 4.0~5.0 mmH₂O (i.e., 5.0~6.25 mmH₂O/m). In case of R reactor, its △p showed the one below ca. 16~20% of the △p of the L reactor. Adopting such microbes-carrying biofilter media with high porosity as waste-tire crumb media, and the improved biofilter design, contributed to △p of this study, reduced by ca. 37~50% and 40~53%, respectively, from the reported △p of conventional biofilter packed with biofilter media of the mixture (50:50) of wood chip and wood bark. In addition, the △p of R reactor in this study, reduced by ca. 80% from the reported △p of conventional biofilter packed with biofilter media of the mixture (75:25) of scoria with high porosity and compost, was mainly attributed to adopting the improved biofilter design. On the other hand, in case of L reactor, the CFU counts in its lowest column was analyzed double as much as those in any other columns. However, in case of R reactor, its CFU counts were bigger by 50% than the one of L reactor and its microbes were evenly distributed at its higher and lower columns of R_dn reactor and R_up reactor. This phenomena was attributed to an even moisture distribution of 50~55% of R reactor at its higher and lower columns. Therefore, R reactor showed superb characteristics in terms of both △p and microbe-population-distribution, compared to L reactor.

• Korea journal of population studies
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• v.33 no.2
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• pp.85-111
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• 2010

South Korea has experienced a rapid fertility decline and notable mortality improvement. As the drop in TFR was quicker and greater in terms of tempo and magnitude, it cast a new challenge of population projection - how to improve the forecasting accuracy in the country with a super-low fertility pattern. This study begin with the current status of the national population projection as implemented by Statistics Korea by comparing the 2009 interim projection with the 2006 official national population projection. Secondly, this study compare the population projection system including projection agencies, projection horizons, projection intervals, the number of projection scenarios, and the number of assumptions on fertility, mortality and international migration among super-low fertility countries. Thirdly we illustrate a stochastic population projection for Korea by transforming the population rates into one parameter series. Finally we describe the future challenges of the national population projection, and propose the projection scenarios for the 2011 official population projection. To enhance the accuracy, we suggest that Statistics Korea should update population projections more frequently or distinguish them into short-term and long-term projections. Adding more than four projection scenarios including additional types of "low-variant"fertility could show a variety of future changes. We also expect Statistics Korea topay more attention to the determination of a base population that should include both national and non-national populations. Finally we hope that Statistics Korea will find a wise way to incorporate the ideas underlying the system of stochastic population projection as part of the official national population projection.

• Korea journal of population studies
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• v.27 no.2
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• pp.35-59
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• 2004

본 연구는 우리나라의 출산율 하락 현상을 경제학적 관점에서 분석한다. 우리나라의 출산율 하락은 출산연령의 상승 및 출산여성의 고학력화를 수반하고 있다. 합계출산율의 하락을 유발하는 두 요인인 완결출산율의 하락과 출산시기의 연장 중 완결출산율은 완만히 하락하고 있는 것으로 추정되며 최근의 급속한 출산율 하락세를 설명하기에는 부족하다. 출산여성의 고학력화에 따른 출산시기의 연장은 합계출산율의 변화 방향과는 일치하나 역시 최근의 급속한 출산율 하락을 설명하기에는 충분하지 않다. 다만 이 요인은 향후 합계출산율의 반등 가능성을 시사한다. 그러므로 최근의 급속한 출산율 하락은 출산시기의 연장에 기인하였을 가능성이 높으며 그 중요한 요인은 여성 노동시장의 변화일 것으로 추정된다. 이 부분에 관한 본 연구의 분석은 충분하지 않으나 고학력 여성의 취업률 증가, 임금-연령 곡선의 상승에 의한 출산시기 지연의 가능성을 제시하였다.