• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2004년도 추계학술대회 및 정기총회
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• pp.565-565
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• 2004

Due to limitation of resources and increasing concerns about environment, reverse logistics has received growing attention in recent years. In this paper, we propose three types of reverse logistics networks based on reuse of returnable containers, materials recycling process and remanufacturing for parts reuse. First, the sender in the re-usable item network supplies containers for the recipient and orders either new containers from external supplier or returnable containers cleaned from the container depot. Second, the recycling center in the proposed recycling network collects either end of life products from customer or faulty goods from manufacturer, collected products are dismantled into materials and materials go into recycling process. Finally, the manufacturer in the proposed remanufacturing network has two alternatives for supplying parts: either ordering the required parts to external supplier or overhauling disassembled parts and bringing them back 'as new' conditions. In this product recovery environment, we build optimal order quantity models to minimize the total logistics costs related to reverse logistics network. The validity of the proposed model is investigated through comprehensive computational experiments.

• Nuclear Engineering and Technology
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• 제49권3호
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• pp.541-548
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• 2017

Uranium metal used for fabrication of fuel for research reactors in India is generally produced by magnesio-thermic reduction of $UF_4$. Performance of magnesio-thermic reaction and recovery and quality of uranium largely depends on properties of $UF_4$. As ammonium diuranate (ADU) is first product in powder form in the process flow-sheet, properties of $UF_4$ depend on properties of ADU. ADU is generally produced from uranyl nitrate solution (UNS) for natural uranium metal production and from uranyl fluoride solution (UFS) for low enriched uranium metal production. In present paper, ADU has been produced via both the routes. Variation of uranium recovery and crystal structure and composition of ADU with progress in precipitation reaction has been studied with special attention on first appearance of the precipitate Further, ADU produced by two routes have been calcined to $UO_3$, then reduced to $UO_2$ and hydroflorinated to $UF_4$. Effect of two different process routes of ADU precipitation on the characteristics of ADU, $UO_3$, $UO_2$ and $UF_4$ were studied here.

• 한국폐기물자원순환학회지
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• 제35권7호
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• pp.606-615
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• 2018

Over the past two decades, the options for solid waste management have been changing from land disposal to recycling, waste-to-energy, and incineration due to growing attention for resource and energy recovery. In addition, the reduction of greenhouse gas (GHG) emission has become an issue of concern in the waste sector because such gases often released into the atmosphere during the waste management processes (e.g., biodegradation in landfills and combustion by incineration) can contribute to climate change. In this study, the emission and reduction rates of GHGs by the municipal solid waste (MSW) management options in D city have been studied for the years 1996-2016. The emissions and reduction rates were calculated according to the Intergovernmental Panel on Climate Change guidelines and the EU Prognos method, respectively. A dramatic decrease in the waste landfilled was observed between 1996 and 2004, after which its amount has been relatively constant. Waste recycling and incineration have been increased over the decades, leading to a peak in the GHG emissions from landfills of approximately $63,323tCO_2\;eq/yr$ in 2005, while the lowest value of $35,962tCO_2\;eq/yr$ was observed in 2016. In 2016, the estimated emission rate of GHGs from incineration was $59,199tCO_2\;eq/yr$. The reduction rate by material recycling was the highest ($-164,487tCO_2\;eq/yr$) in 2016, followed by the rates by heat recovery with incineration ($-59,242tCO_2\;eq/yr$) and landfill gas recovery ($-23,922tCO_2\;eq/yr$). Moreover, the cumulative GHG reduction rate between 1996 and 2016 was $-3.46MtCO_2\;eq$, implying a very positive impact on future $CO_2$ reduction achieved by waste recycling as well as heat recovery of incineration and landfill gas recovery. This study clearly demonstrates that improved MSW management systems are positive for GHGs reduction and energy savings. These results could help the waste management decision-makers supporting the MSW recycling and energy recovery policies as well as the climate change mitigation efforts at local government level.

• Journal of Power Electronics
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• 제15권5호
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• pp.1305-1317
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• 2015

Distributed generation systems (DGSs) have been getting more and more attention in terms of renewable energy use and new generation technologies in the past decades. The self-excited induction generator (SEIG) occupies an important role in the area of energy conversion due to its low cost, robustness and simple control. Unlike synchronous generators, the SEIG has to absorb capacitive reactive power from the outer device aiming to stabilize the terminal voltage at load changes. This paper presents a novel static VAR compensator (SVC) called a magnetic energy recovery switch (MERS) to serve as a voltage controller in SEIG powered DGSs. In addition, many small scale SEIGs, instead of a single large one, are applied and devoted to promote the generation efficiency. To begin with, an expandable mathematic model based on a d-q equivalent circuit is created for parallel SEIGs. The control method of the MERS is further improved with the objective of broadening its operating range and restraining current harmonics by parameter optimization. A hybrid control strategy is developed by taking both of the stand-alone and grid-connected modes into consideration. Then simulation and experiments are carried out in the case of single and double SEIG(s) generation. Finally, the measurement results verify that the proposed DGS with SVC-MERS achieves a better stability and higher feasibility. The major advantages of the mentioned variable reactive power supplier, when compared to the STATCOM, include the adoption of a small DC capacitor, line frequency switching, simple control and less loss.

• KEPCO Journal on Electric Power and Energy
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• 제3권1호
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• pp.41-47
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• 2017

After $SF_6$, which is being used in power equipment as an insulating material, is classified as one of the 6 major greenhouse gases, the maintenance and the refinement of used $SF_6$ started to get attention. In regard to this, KEPCO Research Institute (KEPRI) is developing $SF_6$ recovery and refinement technology starting with establishing a comprehensive $SF_6$ analysis system. With the analysis system, qualitative and quantitative analyses of the purity and the impurities of $SF_6$ before and after recovery, and before and after refinement have been carried out. The analysis system is comprised of GC-DID (Gas Chromatograph -Discharge Ionization Detector) for trace impurities analysis, GC-TCD (Thermal Conductivity Detector) for analyses of $SF_6$ purity and major impurities concentration from several hundred ppm up to percent range, GC-MSD (Mass Selective Detector) for analyses of impurities not included in standard gas, FT-IR (Fourier Transform-Infrared) Spectrometer for analysis of HF and $SO_2$, and moisture analyzer for analysis of moisture below 100 ppm. With this analysis system, complete analysis method of $SF_6$ has been established. This analysis system is being used in the maintenance of power equipment and the development of $SF_6$ recovery and refinement technologies. In this paper, the analysis results of four samples - gas and liquid phase $SF_6$ samples from a $SF_6$ refinement system before and after refinement are presented.

• 대한한의학회지
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• 제27권4호
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• pp.215-224
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• 2006

Objectives : In order to apply useful data to clinical practice, we undertook this study and tried to find factors related with sequelae of facial palsy in relation with patients' age and gender distribution, past history with the disease, condition before onset, duration of recovery time, existence of remaining sequelae, types of the sequelae, and duration for sequelae to disappear. Methods : We evaluated patients' condition (fatigue, stress, chills, cold and so on), past history (diabetes mellitus, hypertension, stroke, herpes zoster, cancer and so on), duration of recovery time, types of the sequelae, age and sequelae distribution as to when the treatments were started as we examined 473 patients who were diagnosed with facial palsy, and visited the Out-patient Department of Acupuncture and Moxibustion of Bundang Oriental Medicine Hospital of Dongguk University through 2003 and 2004. Results : The sequelae of facial palsy were not significantly relevant to the signs found before facial palsy occurred(fatigue, stress, chills, and cold), or to patients' past history (hypertension, diabetes mellitus, facial palsy, herpes zoster). The duration of recovery time was within 30 days for 45.3% of the patients examined in this study, and within 90 days for 72.6%. Evaluating the existence of sequelae in relation to age, we found more in the group comprised of patients aged 50 and over than under 50. We found more sequelae in the group which is consisted of patients who had not been treated until 6 days after than within 5 days from the onset. Conclusion: Attention to sequelae will be needed for patients aged 50 and over and who were not treated until 6 days after the onset, as they had more sequelae.

• 상하수도학회지
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• 제32권1호
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• pp.1-10
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• 2018

Recently, interest in the development of alternative water resources has been increasing rapidly due to environmental pollution and depletion of water resources. In particular, seawater desalination has been attracting the most attention as alternative water resources. As seawater desalination consumes a large amount of energy due to high operating pressure, many researches have been conducted to improve energy efficiency such as energy recovery device (ERD). Consequently, this study aims to compare the energy efficiency of RO process according to ERD of isobaric type which is applied in scientific control pilot plant process of each $100m^3/day$ scale based on actual RO product water. As a result, it was confirmed that efficiency, mixing rate, and permeate conductivity were different depending on the size of the apparatus even though the same principle of the ERD was applied. It is believed that this is caused by the difference in cross-sectional area of the contacted portion for pressure transfer inside the ERD. Therefore, further study is needed to confirm the optimum conditions what is applicable to the actual process considering the correlation with other factors as well as the factors obtained from the previous experiments.

• 한국수소및신에너지학회논문집
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• 제31권2호
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• pp.210-222
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• 2020

Hydrogen is evaluated as one of new energy sources that can overcome the limitations and pollution problems of conventional fossil fuels. Although hydrogen is free from CO₂, attention is required in NOx emission and flame stability in order to use hydrogen in existing gas fuel system. This study investigates the differences in operating characteristics and its problems to be modified when the hydrogen is used as fuel for existing domestic boilers and new heat recover boilers with water spray. When the hydrogen is used in domestic boilers, the efficiency is about 6-7% lower than methane due to higher partial vapor pressure in the exhaust gas at usual operating conditions above 60℃ in combustion chamber outlet temperature. On the other hand, the heat recovery boiler with water spray (HR-B/WS-X) is expected to achieve up to 95% efficiency, which is 12% more efficient than conventional boilers. It can also significantly reduce NOx emission by lowering the flame temperature.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2021년도 추계학술대회
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• pp.132-133
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• 2021

In recent years, energy harvesting from natural sources and waste heat has been attracting more attention from researchers in response to ever-growing energy demands, high energy prices, and climate-change-mitigation purposes. It is also an important step towards future sustainable energy usages. In thermal dynamic cycles, expanders are playing as the most important equipment for waste heat recovery and energy harvesting as well. As a kind of expander, the bladeless turbine has a promising future and more widely using owning its advantages on relatively long life, good off-design performance, easy operation cleaning and maintenance, a simple structure, no blade corrosion, and low manufacturing costs. There are numerous studies about using the Tesla Turbine as a key technology for energy harvesting in a wide range of applications and conditions. They are presented to help identify technologies that have sufficient potential for applicating to our life and marine industrial engineering. This review paper, initially, presents an overview of current studies both theoretical and experimental of Tesla Turbine usage for waste heat recovery alongside its challenges and investigation on the effect of its configuration, working fluid selection as well. To conclude, future perspectives besides possible ways of transforming waste heat energy to electricity or work, which leads to circular energy, are discussed. The ambition of this paper is to act as a first-hand reference, through the well-defined possible directions, to the young researchers and senior scientists.

• 생물정신의학
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• 제27권2호
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• pp.74-83
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• 2020

Objectives Psychological resilience plays a significant role in many aspects of mental health. The aim of this study was to find an association between childhood attention deficit hyperactivity disorder (ADHD) features and adulthood psychological resilience in patients with mood disorders. Methods A total of 213 patients with mood disorders including major depressive disorder or bipolar I, II disorder and 909 healthy controls were included. We assessed childhood ADHD features using the Wender Utah Rating Scale (WURS), adulthood psychological resilience using the Connor-Davidson Resilience Scale (CD-RISC), and current depressive mood using the Beck Depression Inventory (BDI). Pearson's correlation, multiple linear regression and a mediation analyses were performed to examine the relationships between three WURS factor (impulsivity, inattention, and mood instability) scores, the BDI score, and the CD-RISC score. Results The CD-RISC score was negatively correlated with the WURS childhood inattention factor score and current BDI score in patients with mood disorders. BDI score mediated the influence of the inattention factor score on CD-RISC score among patients with mood disorders. The CD-RISC score was significantly lower in patients with mood disorders than in controls even after controlling for age, WURS scores, and the BDI score. Conclusions An evaluation of psychological resilience is important for enhancing recovery and quality of life in patients with mood disorders. When assessing psychological resilience, current depression and ADHD features in childhood, particularly inattention, should be considered.