In-situ Observation and Atomistic Modelling of Early Stage Oxidation / Corrosion Behavior of Nickel Base Alloys in Nuclear Power Plants

Nuclear EngineeringAtomistic modelling and experimental observation has been conducted in order to investigate the early stage oxidation/corrosion behavior on nickel-base alloy in nuclear power plants. In order to fundamental study for the oxidation phenomena on the nickel, high resolution X-ray reflectivity is adopted. To examine the atomistic structure at the Ni(110)/NiO-liquid interface using X-ray reflectivity, the crystallinity of the Ni(110) surface is a very important parameter. To improve the surface crystallinity of Ni(110), the surface treatment by electro-polishing and sequential Ar sputtering/annealing in an ultra-high vacuum chamber is developed. After the successful surface pre-treatment, X-ray measurement at room temperature is conducted using synchrotron X-ray at advanced phonon source in US. Firstly, Crystal Truncation Rod(CTR) test for Ni(110)/NiO surface at room temperature condition in helium gas environment is conducted to obtain reference condition, and pure water is injected into the test cell to measure the water effects on the sample surface. CTR data was measurable with low errors even at lower intensity region. This CTR data also confirms that the surface pre-treatment procedure developed for Ni(110) is suitable for the surface X-ray study. According to results from helium gas environment, there are relaxed Ni layers on the Ni(110) surface with 5?? thickness and then there are stressed Ni + NiO layers on the relaxed Ni layers with 5 ??, and13?? NiO amorphous or polycrystalline layer formed on the top layer. While, the peak position and value is changed when the water is applied. In other word, the position and electron structure of Ni layer at the middle are changed due to the water contact. It can be considered that the water makes change the lattice structure of the Ni surface and NiO To investigate the chromium effect on the oxidation behavior of Ni, atomistic modelling using first principle method is conducted. Using first principles approach, It has been simulated that the atomistic diffusion of oxygen in Ni-Cr binary alloy to understand the role of chromium during the oxidation of nickel-based alloys which are versatile in a wide range of application. The activation energy of oxygen diffusion is calculated by varying the number and position of the nearest-neighbor (NN) chromium atoms relative to oxygen along the diffusion pathway. The activation energy of oxygen diffusion is found to decrease with the increase in the number of NN chromium in front of oxygen, while that increases with increase in the number of NN chromium at the back of oxygen. Therefore, in this study, the first principles calculation confirms the role of chromium as a barrier for the atomistic diffusion of oxygen in Ni-Cr binary alloy. Finally, in-situ Raman spectroscopy has been applied in order to characterize the surface oxide film of nickel-base alloy/low alloy steel dissimilar metal weld interface in simulated primary water conditions of pressurized water reactors (PWRs). In order to directly examine the oxide film in high temperature aqueous conditions, an in-situ Raman spectroscopy system has been developed by constructing a hydrothermal optical cell with direct contact immersion optics.. For the verification of the constructed Raman system, high purity NiO, NiFe2O4, Cr2O3, and NiCr2O4 powders are examined to obtain reference spectra in room temperature air environment). The specimens were exposed to typical PWR water with 1,200ppm H3BO4 and 2 ppm of LiOH at a pressure of 15MPa and 300??C. In-situ Raman spectra were collected for interfaces of as-welded/thermally aged DMW in PWR water condition at 300??C during 50hrs. Cr2O3, Fe3O4 and FeCr2O3 were measured on as-welded DMW, while FexNi1-xCr2O4 and NiFe2O4 were measured on thermally aged DMW. From the ex-situ EDS measurements, the main compositions of the oxide layer after oxidation experiment are Ni and Cr on the as-welded Alloy152 and Fe for A533Gr.B, respectively, while Ni, Cr and Fe on the both of thermally aged Alloy152 and A533Gr.B. The difference of oxidation behavior by thermal aging was found and it was caused by diffusion-assisted chemistry redistribution by thermal aging. And the thermally aged DMWope

A Study on Efficient Design of A Multimedia Conversion Module in PESMS for Social Media Services

The main contribution of this paper is to present the Platform-as-a-Service(PaaS) Environment for Social Multimedia Service (PESMS), derived fromthe Social Media Cloud Computing Service Environment. The main role ofour PESMS is to support the development of social networking services thatinclude audio, image, and video formats. In this paper, we focus in particular on the design and implementation of PESMS, including the transcoding function for processing large amounts of social media in a parallel and distributed manner. PESMS is designed to improve the quality and speed of multimedia conversions by incorporating a multimedia conversion module based on Hadoop, consisting of Hadoop Distributed File System for storing large quantities of social data and MapReduce for distributed parallel processing of these data. In this way, our PESMS has the prospect of exponentially reducing the encoding time for transcoding large numbers of image files into specific formats. To test system performance for the transcoding function, we measured the image transcoding time under a variety of experimental conditions. Based on experiments performed on a 28-node cluster, we found that our system delivered excellent performance in the image transcoding function

Morality as Social Software

The dissertation research is a project to understand morality better through the concept of ‘Social Software.’ The dissertation is, consequently, to argue that the morality in a human society functions as a form of social software in the society. The three aspects of morality as social software are discussed in detail: the evolutionary, anti-entropic, and epistemic game-theoretic aspect. We humans ‘usually’ think that, for example, (a) killing other humans without any necessary reason is morally wrong, and (b) helping other humans in need is morally right. We want to know, in this dissertation research project, why we think in such ways. Myriads of answers to this question have already been offered. We will pursue an answer that has more explanatory power and enlightening lucidity. The term, ‘Social Software’ was coined by Rohit Parikh to connote, broadly, social “procedures that structure social reality” (van Eijck and Parikh 2009, p. 2). The term can be understood, “more or less equivalently,” (Parikh 2002-1, note 2) as ‘social procedure,’ ‘social algorithm,’ or ‘social game.’ (1) The first aspect of ‘morality as social software,’ to be discussed is the evolutionary: human morality has emerged and developed further through the process of evolution; (2) the second aspect is the anti-entropic: human morality is human resistance against the universal law of entropy that tends to annihilate everything from order to disorder; (3) the third aspect is the epistemic game-theoretic: human morality is understood better by epistemic game theory, which is a combination of ‘classical game theory’ and relatively new ‘epistemic logic.’ As more specific case studies for the epistemic game-theoretic aspect, the concepts of backward induction and “the less we know, the more rational and moral,” are discussed. Finally, a thorough discussion on the naturalistic fallacy instills more philosophical rigor into the dissertation

Diversely Regularized Matrix Factorization for Accurate and Aggregately Diversified Recommendation

When recommending personalized top-$k$ items to users, how can we recommend the items diversely to them while satisfying their needs? Aggregately diversified recommender systems aim to recommend a variety of items across whole users without sacrificing the recommendation accuracy. They increase the exposure opportunities of various items, which in turn increase potential revenue of sellers as well as user satisfaction. However, it is challenging to tackle aggregate-level diversity with a matrix factorization (MF), one of the most common recommendation model, since skewed real world data lead to skewed recommendation results of MF. In this work, we propose DivMF (Diversely Regularized Matrix Factorization), a novel matrix factorization method for aggregately diversified recommendation. DivMF regularizes a score matrix of an MF model to maximize coverage and entropy of top-$k$ recommendation lists to aggregately diversify the recommendation results. We also propose an unmasking mechanism and carefully designed mi i-batch learning technique for accurate and efficient training. Extensive experiments on real-world datasets show that DivMF achieves the state-of-the-art performance in aggregately diversified recommendation.Comment: 9 pages, 7 figures, 2 table

Agricultural Drought Assessment Based on Multiple Soil Moisture Products

In this study, we evaluated three soil moisture (SM) products (Advanced Microwave Scanning Radiometer-2 [AMSR2], Advanced SCATterometer [ASCAT], and European Reanalysis Interim [ERA-interim]) across Australia in four climate zones by comparing against the Australian Water Resources Assessment-Landscape (AWRA-L) SM products from July 2012 to June 2017. The ASCAT SM indicated better performance than other SM products over Australia. To evaluate the applicability and reliability for monitoring agricultural drought, an agricultural drought index, the Soil Water Deficit Index, was estimated from three SM products and compared with three commonly-used drought indices (atmospheric water deficit [AWD], Evaporative Stress Index, and Reconnaissance Drought Index). Volumetric contingency tables were compiled to quantitatively assess the performance of agricultural drought detection using various SM products compared with the AWD. All products had reliable drought detection capability over Australia based on the results of temporal evolution and contingency tables with a mean volumetric hit index of 0.700, 0.728, and 0.787 for AMSR2, ASCAT, and ERA-interim, respectively. The slight incapability of drought detection capability of SWDI in tropical region was low due to the variation in persistence times of moisture in the atmosphere and soil. Except arid zone, in all climate zones, the reliability of SM products for drought detection followed the following order ASCAT \u3e ERA-interim \u3e AMSR2

Rain-Gauge Network Evaluations Using Spatiotemporal Correlation Structure for Semi-Mountainous Regions

A reliable network of rain gauges is a crucial component of rainfall estimation in a watershed. To provide a better evaluation method for rain-gauge networks, a new evaluation method using average inter-gauge correlation coefficients (averaged CC) for estimating an effective radius for each rain gauge was developed. In this study, averaged CCs were obtained from the values of inter-gauge correlation coefficients after choosing a minimum number of rainfall data sets as a threshold. The Nam River Basin (2400 km2) and its 24 rain gauges were selected with 8 years (2003 - 2010) rainfall data to validate a new evaluation method. In the spatial correlation coefficient fitting process for generating correlation distances, averaged CCs increased fitness accuracy (maximum 37%) in terms of coefficient of determination (R2) compared with a commonly used method (the last value of the inter-gauge correlation coefficient as the number of data sets is increased: last CC). In the evaluation of effective radii for 8 years, the robustness of the averaged CCs was supported by lower standard deviations for all rain gauges. For the optimum coverage of rainfall estimation in terms of effective radius, the Nam River Basin requires 20 rain gauges. Investigation of altitude effects presented that the effective radii were minimally influenced by the altitude of rain-gauge locations for this area

Field modulation in Na-incorporated Cu(In,Ga)Se2 (CIGS) polycrystalline films influenced by alloy-hardening and pair-annihilation probabilities

The influence of Na on Cu(In,Ga)Se2 (CIGS) solar cells was investigated. A gradient profile of the Na in the CIGS absorber layer can induce an electric field modulation and significantly strengthen the back surface field effect. This field modulation originates from a grain growth model introduced by a combination of alloy-hardening and pair-annihilation probabilities, wherein the Cu supply and Na diffusion together screen the driving force of the grain boundary motion (GBM) by alloy hardening, which indicates a specific GBM pinning by Cu and Na. The pair annihilation between the ubiquitously evolving GBMs has a coincident probability with the alloy-hardening event