Long-term safe storage of spent nuclear fuel (SNF) determines sustainability of the current light water reactor (LWR) fleet. In the U.S., SNF is stored in stainless steel canister in dry cask storage system (DCSS) after spending several years in wet pool storage system while there is no DSCC in Republic of Korea. The SNF storage time in DSCC is expected to be multiple decades since no permanent geological repositories are identified in both countries. One limiting factor for extended storage of SNF in DSCC is chloride-induced stress corrosion cracking (CISCC) in the welded regions of the stainless steel canisters. The propensity for the occurrence of CISCC has warranted the development of the mitigation and repair technologies to ensure the safe and long-term storage for both present and new canister although no CISCC failure was reported yet. This study investigates cold spray deposition coatings of 304 L and 316 L stainless steels on prototypical stainless steel canisters such as sensitized flat and C-ring samples. The cold spray technology has been identified as the most promising approach by Extended Storage Collaboration Program (ESCP) driven by Electric Power Research Institute (EPRI). The talk includes microstructural characterization, adhesion strength measurement, residual stress evaluation, and corrosion behavior of the coated materials in boiling MgCl2 solution and electrochemical corrosion tests in NaCl solution. In addition, the capability of repair of cracks on the canister surface using the coating technology will be presented.

To dispose of spent nuclear fuel, the most promising method is disposal in a deep geological repository with a multi-barrier system. Among the multi-barrier system, canisters are used to contain the spent nuclear fuel. A role of the canister is to withstand corrosion load from the deep geological environment as possible as long. Corrosion processes consist of corroding agents transport to the canister surface and electrochemical reactions between the corroding agents and the canister surface. According to previous King’s electrochemical experiments, the mass-transport rate of corroding agents is slower than the electrochemical reaction rate with copper when the canister is surrounded by dense bentonite blocks. Therefore, the mass-transport rate is a rate-determining step for the whole corrosion process. Despite of the importance of transportation of oxidizing agents in bentonite, the transportation process was not paid attention. For example, existing models which are called continuum models assumed that the corroding agents pass through the pore in the porous medium because the continuum model does not consider the fracture networks in the bentonite. Here we develop a dualpermeability and dual-porosity model. In this model, the transport of corroding agents is considered that they pass through fracture within the porous medium. The difference between the dual-permeability and dual-porosity model is whether the corroding agents can pass through the pore. The dual-permeability model assumed that the mass-transport occurs within both fracture and porous medium. On the other hand, the dual-porosity model assumed that the mass-transport occurs only within fractures. Through both models, we found that the transport rate in the fractures is much higher than through the pores, and the canister lifetime at a point where contacting the fracture tip is much shorter than other parts when the canister lifetime is calculated by the transport-governed condition. In addition, the temperature distributions in the fracture are different compared to the existing continuum model. Our results show the effect of fractures in terms of not only corroding agents transport but also the canister lifetime. We anticipate our model to be a first step for the corrosion estimation model coupled with fracture networks.

In this paper, an approach developed by the Finnish nuclear waste management organization, Posiva, for the construction license of a geological repository was reviewed. Furthermore, a computer program based on the approach was developed. By using the computer program, the lifetime of a copper disposal canister, which was a key engineered barrier of the geological repository, was predicted under the KAERI Underground Research Tunnel (KURT) geologic conditions. The computer program was developed considering the mass transport of corroding agents, such as oxygen and sulfide, through the buffer and backfill. Shortly after the closure of the repository, the corrosion depths of a copper canister due to oxygen in the pores of the buffer and backfill were calculated. Additionally, the long-term corrosion of a copper canister due to sulfide was analyzed in two cases: intact buffer and eroded buffer. Under various conditions of the engineered barrier, the corrosion lifetimes of the copper canister due to sulfide significantly exceeded one million years. Finally, this study shows that it is necessary to carefully characterize the transmissivity of rock and sulfide concentration during site characterization to accurately predict the canister lifetime.

In the aerospace field, Carbon/Cork composites have been used for rocket propulsion systems as a light weight structural component with a high bending stiffness and high thermal insulation properties. For the fabrication of a carbon composite with a heat insulation cork part, the bonding properties between them are very important to determine the service life of the Carbon/Cork composite structure. In this study, the changes in the interfacial adhesion and mechanical properties of Carbon/Cork composites under accelerated aging conditions were investigated. The accelerated aging experiments were performed with different temperatures and humidity conditions. The properties of the aged Carbon/Cork composites were evaluated mainly with the interfacial strength. Finally, the lifetime prediction of the Carbon/Cork composites was performed with the long-term property data under accelerated conditions.

Social games where players play together with others in multiplayer mode are currently emerging and attracting attention in the media after the success of e.g. Pokemon GO. Nevertheless, little is known about the profitability of social players. Previous gaming research that has profiled different types of players has focused on games played alone, without social mechanics (cf. Vahlo et al., 2017). From a marketing perspective, it is also interesting to study the effects of merely watching game play or browsing new game ads as a mode of entertainment, and what kind of effect that has on future behaviour. Passive participation as a type of aesthetic entertainment has been acknowledged in eSports context (Seo, 2013). This paper analyses big data of a gaming company on an individual player level, including different types of single play and multiplayer gaming sessions and in-game purchase behaviour data. We compare the effects of social and non-social ingame mechanics on how individuals spend money in-game over time, frequency of play, sessions as well as the length of played sessions in minutes during the gamers’ whole lifecycle. The anonymized repository data includes gaming behaviour, in-game purchase behaviour related to the use of one specific digital game in the USA. The game can be played both alone, and with others as a team. We used structural equation modeling to analyse the behavior of 23 049 randomly selected players, who have played the game for at least one week. The data included the individual players’ total session history during their play lifecycle. Interestingly, social play with other people is a strong predictor of money spent in the long term. Social play also prompts long-term interest in the game, as friends invite and encourage each other to play with or against other virtual teams. Nevertheless, social play is not for everyone! The results help to optimize player journeys and to make strategic decisions that support long term profitability of gaming companies.

본 연구는 전남 광양시 백운산의 조릿대 개화지에서 외적 환경인자가 개화원인으로 작용하는가를 조사했다. 이를 토대로 조릿대의 개화원인, 개화양식 및 생활사 전략을 고찰했다. 조릿대 개화지와 비개화지 사이의 토양･물리적 조건･광량 차이는 없었다. 2014~17년 사이에 조릿대가 개화했던 한국과 일본 개화지의 강수량･기온은 평년치(과거 30년)와 다른 특이점을 찾을 수 없었다. 또한 대면적으로 조릿대가 꽃을 피운 후에 대부분 죽었으나 일부 조릿대 간이 다시 발생하기도 하고 일부는 죽지 않았다. 즉, 조릿대는 외적 환경인자와 상관없이 일제히 개화했으며, 대부분의 조릿대 간은 죽지만 일부는 살아남았다. 이는 조릿대 개화원인은 외적 환경인자 영향보다 생물시계에 따라 주기적으로 발현하는 특정 유전자(일명, 유전자 시계)로 촉발된다고 본다. 한편, 멀리 떨어져 있는 조릿대 개체와 동조해 꽃을 대규모로 피우며, 소규모 단독으로 여러 번 개화하기도 한다. 이것은 평생 한 번 개화하는 조릿대의 유성번식 실패 리스크를 분산하기 위한 일종의 보험시스템이라고 판단된다. 열대성 대나무･조릿대류가 온대로 분포를 넓히면서 환경 의 불확실성 증가에 따른 유성번식의 최적화를 위해 장주기 단개화성이 강화된 것으로 추정된다.

This study aims to examine how the mobile social network service experience affects value co-creation and customer lifetime value. The mobile social network service experience includes mobile convenience, social compatibility, social risk, and cognitive effort. The research hypotheses with structural equation modeling are tested. In mobile SNS context, value co-creation behaviors essentially determine customer lifetime value of mobile shopping apps. Value co-creation behaviors have received little attention in mobile shopping. The mobile SNS experience strongly influences value co-creation behaviors. This study is based on a sample of mobile SNS users nationwide in Korea. Therefore, the generalizability of the findings has to be tested. Furthermore, the study examines customer lifetime value, which is good sales predictor of mobile shopping apps. Moreover, the research model included the positive and negative determinants on mobile SNS experience. Future researches examine other use intentions of mobile SNS. Value co-creation behaviors substantially affect customer lifetime value. Mobile shopping apps should increase customer lifetime value from mobile SNS experience and value co-creation. This study shows how individual mobile SNS user provides mobile shopping apps with profit through value co-creation. This study is the first to examine how mobile SNS users enhance value co-creation and how value cocreation behaviors affect customer lifetime value of mobile SNS users.

본 연구에서는 염제거 특성을 가지는 나노여과, 역삼투 및 정삼투 폴리아마이드 TFC 삼투막의 자유부피(공극) 특성을 양전자 소멸분광법을 이용해 측정하여, 이 결과를 바탕으로 용질제거 특성을 해석해봄으로써 활성층 내 존재하는 공극 특성과 물질이동 기작과의 상관관계를 밝혀냈다. 양전자 소멸분광법으로 측정한 폴리아마이드 삼투막의 공극 크기는 약 0.48 ~ 0.62 nm (지름) 내외로, 분리막 활성층 공극의 크기와 보론 제거율은 반비례함을 확인하였다. 압력기반 여과장치에서 수투과도를 증가시켜 보론 제거 실험을 반복한 결과, 0.6 nm 내외의 상대적으로 큰 공극을 가지는 폴리아마이드 분리막에서 확산이 아닌 대류를 통한 물질이동이 주도적으로 일어남을 확인하였고, 이를 무차원수인 Peclet 수의 변화로 증명했다.

The BCBJ (Back Contact and Back Junction) or back-lit solar cell design eliminates shading loss by placing the pn junction and metal electrode contacts all on one side that faces away from the sun. However, as the electron-hole generation sites now are located very far from the pn junction, loss by minority-carrier recombination can be a significant issue. Utilizing Medici, a 2-dimensional semiconductor device simulation tool, the interdependency between the substrate thickness and the minority-carrier recombination lifetime was studied in terms of how these factors affect the solar cell power output. Qualitatively speaking, the results indicate that a very high quality substrate with a long recombination lifetime is needed to maintain the maximum power generation. The quantitative value of the recombination lifetime of minority-carriers, i.e., electrons in p-type substrates, required in the BCBJ cell is about one order of magnitude longer than that in the front-lit cell, i.e., 5 × 10−4 sec vs. 5 × 10−5 sec. Regardless of substrate thickness up to 150 μm, the power output in the BCBJ cell stays at nearly the maximum value of about 1.8 × 10−2 W·cm−2, or 18 mW·cm−2, as long as the recombination lifetime is 5 × 10−4 s or longer. The output power, however, declines steeply to as low as 10 mW·cm−2 when the recombination lifetime becomes significantly shorter than 5 × 10−4 sec. Substrate thinning is found to be not as effective as in the front-lit case in stemming the decline in the output power. In view of these results, for BCBJ applications, the substrate needs to be only mono-crystalline Si of very high quality. This bars the use of poly-crystalline Si, which is gaining wider acceptance in standard front-lit solar cells.

한국원자력환경공단에서는 국내 경수로 원전에서 발생한 사용후핵연료를 건식으로 저장하기 위하여 안전성을 최우선으로 국내/외 기술기준을 준수하여 금속겸용용기를 개발하였다. 이러한 금속용기는 50년 동안 주요 안전성요소(구조, 열제거, 격납, 임계방지, 방사선차폐 등)에 대한 건전성을 유지하고, 운영기간 중 유지보수 과정에 폐기물의 발생을 최소화 하고 이를 안전하게 관리할 수 있도록 설계하였다. 본 논문은 설계수명이 종료된 금속용기 본체 및 내/외부 구조물에 대한 방사화 평가를 통해 정량적인 방사능 재고량에 대한 정보를 제공한다. 본 논문에서는 금속용기 본체 및 구성품의 방사화 방사능 재고량은 MCNP5·ORIGEN-2 평가체계를 이용하여 계산하였으며, 각 구성품의 화학조성, 중성자속 분포, 반응률 및 저장기간 동안 중성자조사 기간을 반영하여 평가하였다. 평가결과, 설계수명 이후 10년 경과시 모든 금속재질에서 60Co의 방사능이 기타 핵종들에 비하여 가장 큰 방사능을 띄는 것으로 나타났으며, 중성자차폐체인 수지에서는 수명직후 28Al 및 24Na등의 고에 너지 감마선을 방출하는 핵종은 반감기가 짧아 0.5년 이후에는 무시할 수 있는 수준으로 나타났다. 또한, 사용후핵연료 제거 후 캐니스터 및 금속용기 본체에 대한 표면 선량률 평가결과, 상당히 낮은 값을 나타내어, 해체 시 작업자가 받는 피폭선량은 무시할 수 있는 수준으로 평가되었다. 본 평가방법은 사용후핵연료 금속겸용용기 해체 시 계획의 수립 및 해체작업 종사자의 피폭선량 예측, 방사성폐기물의 관리/재활용 등의 기본자료로 활용할 수 있을 것으로 사료된다.

The effects of coating thickness on the delamination and fracture behavior of thermal barrier coating (TBC) systems were investigated with cyclic flame thermal fatigue (FTF) and thermal shock (TS) tests. The top and bond coats of the TBCs were prepared by electron beam-physical vapor deposition and low pressure plasma spray methods, respectively, with a thickness ratio of 2:1 in the top and bond coats. The thicknesses of the top coat were 200 and 500 μm, and those of the bond coat were 100 and 250 μm. FTF tests were performed until 1140 cycles at a surface temperature of 1100 oC for a dwell time of 5 min. TS tests were also done until more than 50 % delamination or 1140 cycles with a dwell time of 60 min. After the FTF for 1140 cycles, the interface microstructures of each TBC exhibited a sound condition without cracking or delamination. In the TS, the TBCs of 200 and 500 μm were fully delaminated (> 50 %) within 171 and 440 cycles, respectively. These results enabled us to control the thickness of TBC systems and to propose an efficient coating in protecting the substrate in cyclic thermal exposure environments.

In photovoltaic power generation where minority carrier generation via light absorption is competing against minority carrier recombination, the substrate thickness and material quality are interdependent, and appropriate combination of the two variables is important in obtaining the maximum output power generation. Medici, a two-dimensional semiconductor device simulation tool, is used to investigate the interdependency in relation to the maximum power output in front-lit Si solar cells. Qualitatively, the results indicate that a high quality substrate must be thick and that a low quality substrate must be thin in order to achieve the maximum power generation in the respective materials. The dividing point is 70 μm/5 × 10−6 sec. That is, for materials with a minority carrier recombination lifetime longer than 5 × 10−6 sec, the substrate must be thicker than 70 μm, while for materials with a lifetime shorter than 5 × 10−6 sec, the substrate must be thinner than 70 μm. In substrate fabrication, the thinner the wafer, the lower the cost of material, but the higher the cost of wafer fabrication. Thus, the optimum thickness/lifetime combinations are defined in this study along with the substrate cost considerations as part of the factors to be considered in material selection.

In this empirical study, an attempt is made to show how the Customer Lifetime Value (CLV) can be computed by modeling multiple components of the customer and firm behavior. Specifically, attention will be given to modeling (1) the probability that a customer is likely to buy, (2) the quantity of purchase given that they will buy, and (3) the cost of marketing to each customer. Once the authors compute each of these inputs, they combine them to compute CLV using the net present value concept. The authors will examine multiple ways of computing purchase probabilities depending on the customer’s buying pattern. They will also discuss the estimation challenges in obtaining such inputs for computing CLV. The authors will demonstrate the implementation with a case study for a fashion retailer and what kind of managerial actions can be taken. Finally, a generalizable framework for all fashion retailers to maximize profits will be presented and discussed.

The Chlor-alkali (CA) process is a representative electrolysis system to produce valued chemicals such as chlorine gas and sodium hydroxide. Membrane cell process has been obtaining the largest market shares, because it is free from environmental issues and low chemicals purity. For the CA process, commercially available membrane materials are perfluorinated sulfonic acid ionomers (PFSAs) with high chemical resistance. Unfortunately, there are limited data associated with the relationships between membrane material parameters and CA performances. It prevents the CA membrane development to be difficult. In this study, the influences of PFSA membrane thickness are disclosed, considering their ion transport behaviors, gas evolution capability, and chemical/electrochemical resistances under CA operation conditions.

Customers are regarded as the key intangible assets of a company. It is necessary to have the capability to anticipate customer value. The study discusses the relationship among customer value anticipation, product innovativeness, and customer lifetime value from customer perspective. 178 MBA students were surveyed by questionnaire in this study. The results show that customer perceived customer value anticipation can significantly influence product innovativeness. Product innovativeness not only positively affects customer lifetime value, but also plays a partial mediating role between customer value anticipation and customer lifetime value. Both functional and emotional advertising can play a moderating role on the relationship between product innovativeness and customer lifetime value. At the end, managerial implications are discussed.

The aims of this study are to examine the lifetime and educational thought of Dasan Jeong Yak-Yong and to find the significance of meeting and Dasan's educational spirit. Dasan was born on June 16, 1762 and died on February 22, 1836. In general, his lifetime is divided into four periods : ①learning stage(1-28age), ②public service stage(28-39age), ③exile stage(40-57age), ④emancipation stage(57-75age). He systematized the philosophical foundation of practical science of the late Joseon Dynasty. An ideal image of a man to Dasan is a shepherd, who not only keeps his duties of magistrate but also is well qualified as a governor with learning and virtue, and as a teacher to lead people. Therefore, a shepherd is a practician having the whole personality of self-control first and then govern others. The spirit of governor based on practice of the self-control first and then govern others should not be looked down on as the old, and its spirit and lesson should not be overlooked in modern education. Dasan emphasized here and now and service to humanity. His aim was to educate a person to be a good father, mother, son, daughter, friend, and citizen. He believed that every person should strive for the continual development of self until excellence is achieved. The seven principles of teaching and learning which Dasan executed are as follows : ①step by step, ② major, ③fitting, ④practice, ⑤discussion, ⑥collaboration, and ⑦creative activity. It is sincerely hoped that this study on Dasan's Educational Thought will be contributed as a stepping stone of some help to those scholars and students who are interested in new teacher-education of the 21st century.