• 방사선산업학회지
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• 제8권2호
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• pp.97-104
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• 2014

Postharvest diseases cause considerable losses to harvested fruits and vegetables worldwide. Fresh produce suspected of harboring postharvest disease must be treated to control any pathogens present. Although there are various treatments to control postharvest losses by pathogens, the current community is eager to take safer and more eco-friendly alternatives to help with human health and reduce environmental risks. Ionizing irradiation is a promising phytosanitary treatment that has a significant potential to control postharvest diseases in use worldwide. Although almost 19000 metric tons of sweet potatoes and various fruits are irradiated each year in six countries to control postharvest disease, irradiation continues to be a debate, with slow acceptance by industries. Irradiation alone is not effective as a fungicide, and an over dose affects the physical properties of irradiated products. A combination of irradiation with other treatments such as heating, biocontrol agents, chlorination, and nano Ag particles is to enhance their effectiveness. Challenges to the use of phytosanitary irradiation are an avoidance of irradiated postharvest and cost of the irradiation facilities, and thus consumers still need to be educated on the principles and benefits of irradiation and prepare an optimum economy of scale for commercial use. In this review, we evaluated the current phytosanitary irradiation, and combination with various other treatments to minimize the postharvest losses.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.223-223
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• 2015

This research evaluates cooperation in transboundary rivers with special reference to the Great Mekong Subregion (GMS) program in the Mekong River Basin. The benefit sharing approach has been deployed as a theoretical framework to analyze the extent to which the riparian states have achieved cooperation. The river basin governance led by the Mekong River Commission since 1995 has not adequately performed due to non-participation of upstream countries and the lack of law enforcement mechanism. Since the late 1980s, China has undertaken hydropower development unilaterally, thereby triggering discomfort from the Lower Mekong countries. The GMS program has led China to strengthening economic ties with the downstream countries through hydropower development as investors and developers. The program has also supported the establishment of economic corridors, and removal of physical barriers and has paved the way for cooperation in other sectors, such as the environment, agriculture, tourism and energy. There are challenges for further cooperation, including the development gaps between China and the downstream countries, political tensions and environment impacts of hydropower dams in the river basin. The Mekong River Basin shows the possibility of cooperation through benefit sharing. Sharing benefits accrued from the river and beyond the river between China and the downstream countries have enhanced economic ties, thereby consolidating cooperation each another.

• Coupled systems mechanics
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• 제3권4호
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• pp.329-344
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• 2014

In this work, quantum molecular dynamics simulations (QMD) are preformed to study the hydrogen molecules in three types of carbon nanostructures, $C_{60}$ fullerene, (5,5) and (9,0) carbon nanotubes and graphene layers. Interactions between hydrogen and the nanostructures is of importance to understand hydrogen storage for the development of hydrogen economy. The QMD method overcomes the difficulties with empirical interatomic potentials to model the interaction among hydrogen and carbon atoms in the confined geometry. In QMD, the interatomic forces are calculated by solving the Schrodinger's equation with the density functional theory (DFT) formulation, and the positions of the atomic nucleus are calculated with the Newton's second law in accordance with the Born-Oppenheimer approximation. It is found that the number of hydrogen atoms that is less than 58 can be stored in the $C_{60}$ fullerene. With larger carbon fullerenes, more hydrogen may be stored. For hydrogen molecules passing though the fullerene, a particular orientation is required to obtain least energy barrier. For carbon nanotubes and graphene, adsorption may adhere hydrogen atoms to carbon atoms. In addition, hydrogen molecules can also be stored inside the nanotubes or between the adjacent layers in graphite, multi-layer graphene.

• 한국재료학회지
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• 제29권6호
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• pp.378-384
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• 2019

Ice accumulation on Aluminum Conductor Steel Reinforced(ACSR) cable during winter is an important matter in terms of safety, economy, and efficient power supply. In this work, the ice adhesion strengths of ACSR cable oxidized during different periods(7 years oxidized and 15 years oxidized) are evaluated. At first, a plate type dry oxidation standard specimen, whose surface characteristics are similar to those of ACSR cable, is prepared. Dry oxidation standard specimens are heat-treated at $500^{\circ}C$ for 20, 60, and 120 minutes in order to obtain different degrees of oxidation. After the dry oxidation, surface properties are analyzed using contact angle analyzer, atomic force microscopy, spectrophotometer, and gloss meter. The ice adhesion strengths are measured using an ice pull-off tester. Correlations between the surface properties and the ice adhesion strength are obtained through a regression analysis indicating a Boltzmann equation. It is revealed that the ice adhesion strength of 15-year oxidized ACSR cable is approximately 8 times higher than that of ACSR-bare.

• 한국압력기기공학회 논문집
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• 제14권2호
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• pp.32-40
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• 2018

Since 2000, the frequency of earthquakes beyond the 5.0 magnitude quake has been increasing in the Korean peninsula. For instance, the 5.0-magnitude earthquake in Baekryong-do in 2003 has occurred, and recent earthquake with Gyeongju(2016) and Pohang(2017) measured respectively magnitude of 5.2 and 5.8 on the Richter scale. As results, the public concern and anxiety about earthquakes are increasing, and therefore it is necessarily required for social infrastructure to reinforce seismic design and energy production facilities directly related to the national economy and security. This study represents the analysis of seismic performance evaluation methodology such as Seismic Margin Assessment (SMA), Seismic Probabilistic Risk Assessment (SPRA), High Confidence Low Probability Failure (HCLPF) in nuclear power plants in order to develop optimal seismic performance improvement. Current methodologies to evaluate nuclear power plants are also addressed. Through review of the nuclear structure evaluation past and current trend, it contributes to be the basis for the improvement of evaluation techniques on the next generation of nuclear power plants.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.546-555
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• 2019

Since the first nuclear reactor first critical, nuclear systems has gone through four generations of history, and the fourth generation nuclear system will be truly realized in the near future. The notions of SVBR and lead-bismuth eutectic alloy coolant put forward by Russia were well received by the international nuclear science community. Lead-bismuth eutectic alloy with the ability of the better neutron economy, the low melting point, the high boiling point, the chemical inertness to water and air and other features, which was considered the most promising coolant for the 4th generation nuclear reactors. This study mainly focuses on the structural design optimization of the 4th-generation reactor coolant pump, including analysis of external characteristics, inner flow, and transient characteristic. It was found that: the reactor coolant pump with a central symmetrical dual-outlet volute structure has better radial-direction balance, the pump without guide vane has better hydraulic performance, and the pump with guide vanes has worse torsional vibration and pressure pulsation. This study serves as experience accumulation and technical support for the development of the 4th generation nuclear energy system.

• Geomechanics and Engineering
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• 제24권1호
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• pp.15-28
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• 2021

Digging well foundation has been widely used in railway bridges due to its good economy and reliability. In other instances, bridges with digging well foundation still have damage risks during earthquakes. However, there is still a lack of knowledge of lateral behavior of digging well foundation considering the soil-foundation interaction. In this study, scaled models of bridge pier-digging well foundation system are constructed for quasi-static test to investigate their lateral behaviors. The failure mechanism and responses of the soil-foundation-pier interaction system are analyzed. The testing results indicate that the digging foundations tend to rotate as a rigid body under cyclic lateral load. Moreover, the depth-width ratio of digging well foundation has a significant influence on the failure mode of the interaction system, especially on the distribution of foundation displacement and the failure of pier. The energy dissipation capacity of the interaction system is discussed by using index of the equivalent viscous damping ratio. The damping varies with the depth-width ratio changing. The equivalent stiffness of soil-digging well foundation-pier interaction system decreases with the increase of loading displacement in a nonlinear manner. The absolute values of the interaction system stiffness are significantly influenced by the depth-width ratio of the foundation.

• 한국안전학회지
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• 제36권3호
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• pp.7-14
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• 2021

Hybrid laminated Al/carbon-fiber-reinforced plastic (CFRP) composites are attracting considerable attention from industries such as aerospace and automobiles owing to their excellent specific strength and specific rigidity. However, when this material is used to fabricate high-pressure fuel storage containers subjected to repeated fatigue loads, fatigue life evaluation for the working load is regulated as an important criterion for operational safety and ease of maintenance. Among the existing evaluation methods for these vessels, the burst test and the hydraulic repeat test require expensive facilities. Thus, the present study aims to develop an improved fatigue life test for Al/CFRP laminated hybrid composites. The test specimen was manufactured using a curved mold considering the shape of a type III high-pressure storage container. The strain-life method was used for fatigue life evaluation, and the life was predicted based on the transition life. The results indicate that the more complex the CFRP stacking sequence, the longer is the transition life. This test method is expected to be useful for ensuring the fatigue safety and economy of hybrid laminate composites.

• 한국재료학회지
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• 제31권2호
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• pp.84-91
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• 2021

To cope with automobile exhaust gas regulations, ISG and charging control systems are applied to HEV vehicles for the purpose of improving fuel economy. These systems require quick charge-discharge performance of high current. Therefore, a Module of the AGM battery with high energy density and EDLC(Electric Double Layer Capacitor) with high power density are constructed to study the charging and discharging behavior. In CCA, which evaluates the starting performance at -18 ℃ & 30 ℃ with high current, EDLC contributed for about 8 sec at the beginning. At 0 ℃ CA (Charge Acceptance), the initial Charging current of the AGM/EDLC Module, is twice that of the AGM lead acid battery. To play the role of EDLC during high-current rapid charging and discharging, the condition of the AGM lead-acid battery is optimally maintained. As a result of a Standard of Battery Association of Japan (SBA) S0101 test, the service life of the Module of the AGM Lead Acid Battery/EDLC is found to improve by 2 times compared to that of the AGM Lead Acid Battery.

• 유기물자원화
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• 제29권1호
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• pp.5-17
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• 2021

본 연구는 하수슬러지 소각재에 비교적 높은 함량으로 존재하는 인을 회수하기 위한 국내외 사례를 조사한 문헌연구로서 습식방법 및 열화학적 방법에 의한 인의 회수 및 중금속 제거와 관련한 실험조건과 영향인자 등을 논의하였다. 하수슬러지 소각재의 인 회수 기술 상용화를 위해서는 인 회수과정에서 발생되는 폐수, 잔재물의 처분, 첨가 약품과 에너지 소모의 최소화 등 전체 시스템의 경제성 측면에서 소각시설과 연계한 집적처리공정이 바람직할 것으로 판단된다.