Microstructure-Based Thermal Conductivity and Thermal Behavior Modeling of Nuclear Fuel UO2-BeO

The development of ceramic-ceramic composite nuclear fuels benefits from thermal modeling by providing an understanding on how fabrication variables, such as phase fractions, densities, and geometry, will determine effective thermal conductivity. Finite element method (FEM) two and three dimensional programs were used to predict the thermal conductivity of composite UO₂-BeO materials. The FEM modeling results were compared to the measured UO₂-BeO fuel sample thermal conductivities. The comparison showed that the thermal modeling was in good agreement with the measured values. These benchmarking cases with the FEM thermal modeling method successfully demonstrated the potential of the models to accurately predict the effective thermal conductivity of an enhanced thermal conductivity oxide nuclear fuel. The FEM thermal modeling was used to predict UO₂-BeO nuclear fuel thermal conductivities with different BeO percentages, and then the reactor fuel thermal behavior was analyzed using the UO₂-BeO nuclear fuel thermal conductivities and other material properties. The analysis results show significant temperature decrease for the UO₂-BeO nuclear fuel compared to the traditional UO₂ fuel, and then the safety of the reactor would be improved.     

A review of fault ride through of PV and wind renewable energies in grid codes

This paper presents a comprehensive review of fault ride through (FRT) in the grid code of 38 selected countries with an emphasis on renewable energy (REN) sources–related rules. Grid codes are the rules legislated usually by the transmission system operators (TSOs) to determine the grid integration requirements of electrical power generators. Each country establishes its grid code for satisfying the minimum required technical criteria and revises it frequently to cope with new modifications of the utility. Growing the penetration of REN sources have influenced many operational aspects of the power system such as protection, power quality, reliability, and stability. Thereupon, regulations must ensure the power system's secure and controllable operation of REN sources. FRT is one of the main parts of the grid code, and its characteristics affect the performance and rating of power system apparatus. FRT defines the performance of electric power generators during and in postfault conditions. FRT of solar photovoltaic (PV) and wind turbines (WTs) as the main REN sources of energy has great importance in the grid codes. In this paper, a comparison of FRTs in the grid code of 38 countries, including low‐voltage ride through (LVRT), zero‐voltage ride through (ZVRT), and high‐voltage ride through (HVRT) are provided and surveyed.     

Understanding the YouTube Partners and Their Data： Measurement and Analysis

User generated content,e.g.,from YouTube,the most popular online video sharing site,is one of the major sources of today＇s big data and it is crucial to understand their inherent characteristics.Recently,YouTube has started working with content providers（known as YouTube partners） to promote the users＇ watching and sharing activities.The substantial benefit is to further augment its service and monetize more videos,which is crucial to both YouTube and its partners,as well as to other providers of relevant services.In this paper,our main contribution is to analyze the massive amounts of video data from a YouTube partner＇s view.We make effective use of Insight,a new analytics service of YouTube that offers simple data analysis for partners.To provide the practical guidance from the raw Insight data,we enable more complex investigations for the inherent features that affect the popularity of the videos.Our findings facilitate YouTube partners to re-design current video publishing strategies,having more opportunities to attract more views.     

Comparison of High-Temperature Properties and Thermal Shock Resistance of Austempered Ductile Irons (ADI) with Those of Pearlitic Ductile Cast Irons

High-temperature strength and thermal shock resistance of austempered ductile iron (ADI) in high temperatures because of instability of ausferrite phase has been less interest. The aim of this study is to investigate the tensile properties of ADI and pearlitic ductile cast iron by using the short-time tensile test in high temperatures. Tensile test was conducted in temperatures of 298 K, 673 K, 873 K, and 1073 K (25 °C, 400 °C, 600 °C, and 800 °C). Thermal shock test also was conducted by using the molten lead bath at 1273 K (1000 °C). In this experiment, samples of pearlitic ductile cast iron and ADI were divided in two groups; that after immersing in the molten lead bath for 25 seconds, one group was cooled in the air and other one was quenched in the water. Results showed that strength and thermal shock resistance of ADI samples are higher than those of the pearlitic ductile cast iron.     

Multi‐expression programming based model for prediction of formation enthalpies of nitro‐energetic materials

There has been considerable interest in predicting the properties of nitro‐energetic materials to improve their performance. Not to mention insightful physical knowledge, computational‐aided molecular studies can expedite the synthesis of novel energetic materials through cost reduction labours and risky experimental tests. In this paper, quantitative structure–property relationship based on multi‐expression programming employed to correlate the formation enthalpies of frequently used nitro‐energetic materials with their molecular properties. The simple yet accurate obtained model is able to correlate the formation enthalpies of nitro‐energetic materials to their molecular structure with the accuracy comparable to experimental precision.     

Template synthesis of zinc oxide nanoparticles entrapped in the zeolite Y matrix and applying them for thermal control paint

Zinc oxide nanoparticles within faujasite zeolites have been synthesized by a procedure comprising of (i) ion-exchange of zinc ions into the zeolite, (ii) precipitation of zinc ions with sodium hydroxide within the supercage of the zeolite, and (iii) calcination. The products were characterized by XRD, SEM, TEM, EDX and FTIR techniques. The size of the ZnO particles was in the range of 24±4 nm. Finally, ZnO@zeolite was used as a pigment and its optical properties were studied.     

Improving the energy efficiency of reversible logic circuits by the combined use of adiabatic styles

One of the most prominent issues in fully adiabatic circuits is the breaking reversibility problem; i.e., non-adiabatic energy dissipation in the last stage adiabatic gates whose outputs are connected to external circuits. In this paper, we show that the breaking reversibility problem can result in significant energy dissipation. Subsequently, we propose an efficient technique to address the breaking reversibility problem, which is applicable to the usual fully adiabatic logic such as 2LAL, SCRL, and RERL. Detailed SPICE simulations are used to evaluate the proposed technique. The experimental results show that the proposed technique can considerably reduce (e.g., about 74% for RERL, 35% for 2LAL, and 17% for SCRL) the energy dissipation arising from the breaking reversibility problem.     

Robot-Assisted Needle Steering Using a Control Theoretic Approach

This paper presents a new 2D motion planner for steering flexible needles inside relatively rigid tissue. This approach uses a nonholonomic system approach, which models tissue-needle interaction, and formulates the problem as a Markov Decision Process that is solvable using infinite horizon Dynamic Programming. Unlike conventional numerical solvers such as the value iterator which inherently suffers from the curse of dimensionality for processing large-scale models, partitioned-based solvers show promising numerical performance. Given the locations of the obstacles and the targeted area, the proposed solver provides a descent solution where high spatial or angular resolution is required. As theoretically expected, it is shown how prioritized partitioning increases computational performance compared to the generic value iteration which has been used in an existing steering approach. Starting from any initial condition in the workspace, this method enables the needle to reach its target and avoid collisions with obstacles through selecting the shortest path with the least number of turning points thereby causing less trauma. In this paper, emphasis is given to the control aspects of the problem rather than to biomedical issues. Experimental results using an artificial phantom show that the method is capable of positioning the needle tip at the targeted area with an acceptable level of accuracy.