Analysis of OECD/NEA medium 1000 MWth sodium-cooled fast reactor using the Monte Carlo serpent code and ENDF/B-VIII.0 nuclear data library

This study presents a benchmark evaluation of the new ENDF/B-VIII.0 nuclear data library for the Organization for Economic Co-operation and Development/Nuclear Energy Agency Medium 1000 MWth sodium-cooled fast reactor(SFR).The study presented herein covers both SFR core types,i.e.,metallic fueled(MET-1000)and oxide fueled(MOX-1000),simulated using the continuous-energy Monte Carlo Serpent2 code.The neutronics performances of the ENDF/B-VIII.0-based simulations were compared mainly to two libraries:ENDF/B-VII.1 and JENDL-4.0.The comparison includes several neutronics parameters evaluated for the beginning and end of the cycle conditions.These parameters include the effective multiplication factor keff,total effective delayed neutron fraction beff,sodium void reactivity(DqNa),Doppler constant(DqDoppler),and control rod worth(DqCR).In addition,a sensitivity study was used to reveal the major isotope/reaction pairs contributing to the discrepancy observed in the performance of the three libraries using 33 and 44-energy-group structures.

Development of a PARCS/Serpent model for neutronics analysis of the Dalat nuclear research reactor

Cross-sectional homogenization for full-core calculations of small and complex reactor configurations,such as research reactors,has been recently recognized as an interesting and challenging topic.This paper presents the development of a PARCS/Serpent model for the neutronics analysis of a research reactor type TRIGA Mark-II loaded with Russian VVR-M2 fuel(known as the Dalat Nuclear Research Reactor or DNRR).The full-scale DNRR model and a supercell model for a shim/safety rod and its surrounding fuel bundles with the Monte Carlo code Serpent 2 were proposed to generate homogenized fewgroup cross sections for full-core diffusion calculations with PARCS.The full-scale DNRR model with Serpent 2 was also utilized as a reference to verify the PARCS/Serpent calculations.Comparison of the effective neutron multiplication factors,radial and axial core power distributions,and control rod worths showed a generally good agreement between PARCS and Serpent 2.In addition,the discrepancies between the PARCS and Serpent 2 results are also discussed.Consequently,the results indicate the applicability of the PARCS/Serpent model for further steady state and transient analyses of the DNRR.

In situ and operando infrared spectroscopy of battery systems:Progress and opportunities

In situ and operando infrared spectroscopies are powerful techniques to support the design of novel materials for batteries and the development of new battery systems.These techniques can support the study of batteries by identifying the formation of new species and monitoring electrochemical energy stability.However,few works have employed these techniques,which can be used to investigate various materials,including systems beyond lithium-ion technology,in the research of batteries.Therefore,this review presents a comprehensive overview focusing on the main contributions of in situ and operando infrared spectroscopy for lithium-ion batteries(LIBs)and other battery systems.These techniques can successfully identify the formation of species during the electrolyte reduction,electrode degradation,and the formation of the solid-electrolyte interphase(SEI)layer.From these outcomes,it is possible to conclude that this characterization approach should be employed as a protocol to overcome remaining issues in batteries,consequently supporting battery research.This review aims to be a guide on how infrared spectroscopy can contribute to monitoring battery systems and to lead researchers interested in applying this technique.

Nuclear design of an integrated small modular reactor based on the APR-1400 for RO desalination purposes

The United Arab Emirates lacks conventional water resources and relies primarily on desalination plants powered by fossil fuels to produce fresh water.Nuclear desalination is a proven technology,cost-competitive,and sustainable option capable of integrating the existing largescale desalination plants to produce both freshwater and electricity.However,Small Modular Reactors(SMRs)are promising designs with advanced simplified configurations and inherent safety features.In this study,an Integrated Desalination SMR that produces thermal energy compatible with the capacity of a fossil fuel-powered desalination plant in the UAE was designed.First,the APR-1400 reactor core was used to investigate two 150 MWthconceptual SMR core designs,core A and core B,based on two-dimensional parameters,radius,and height.Then,the CASMO-4 lattice code was used to generate homogenized few-group constants for optimized fuel assembly loading patterns.Finally,to find the best core configuration,SIMULATE-3 was used to calculate the core key physics parameters such as power distribution,reactivity coefficients,and critical boron concentration.In addition,different reflector materials were investigated to compensate for the expected high leakage of the small-sized SMR cores.The pan shape core B model(142.6132 cm diameter,100 cm height,and radially reflected by Stainless Steel)was selected as the best core configuration based on its calculated physics parameters.Core B met the design and safety criteria and indicated low total neutron leakage of 11.60%and flat power distribution with 1.50 power peaking factor.Compared to core A,it has a more negative MTC value of-6.93 pcm/°F with lower CBC.In a 2-batch scheme,the fuel is discharged at 42.25 GWd/MTU burnup after a long cycle length of 1.58 years.The core B model offers the highest specific power of 36.56 kW/kgU while utilizing the smallest heavy metal mass compared with the SMART and NuScale models.

Finite Element Analysis for Grinding and Lapping of Wire-sawn Silicon Wafers

Silicon wafers are the most widely used substrates for semiconductors. The falling price of silicon wafers has created tremendous pressure on silicon wafer manufacturers to develop cost-effective manufacturing processes. A critical issue in wafer production is the waviness induced by wire sawing. If this waviness is not removed, it will affect wafer flatness and semiconductor performance. In practice, both lapping and grinding have been used to flatten wire-sawn wafers. Although grinding is not as effective as lapping in removing waviness, it has many other advantages over lapping (such as higher throughput, fully automatic, and more benign to environment) and has great potential to reduce manufacturing cost of silicon wafers. This paper presents a finite element analysis (FEA) study on grinding and lapping of wire-sawn silicon wafers. An FEA model is first developed to simulate the waviness deformation of wire-sawn wafers in grinding and lapping processes. It is then used to explain how the waviness is removed or reduced by lapping and grinding and why the effectiveness of grinding in removing waviness is different from that of lapping. Furthermore, the model is used to study the effects of various parameters including active-grinding-zone orientation, grinding force, waviness wavelength, and waviness height on the reduction and elimination of waviness. Finally, the results of pilot experiments to verify the model are discussed.

Beyond Graphene Anode Materials for Emerging Metal Ion Batteries and Supercapacitors

Intensive research effort is currently focused on the development of efficient, reliable, and environmentally safe electrochemical energy storage systems due to the ever-increasing global energy storage demand. Li ion battery systems have been used as the primary energy storage device over the last three decades. However, low abundance and uneven distribution of lithium and cobalt in the earth crust and the associated cost of these materials, have resulted in a concerted effort to develop beyond lithium electrochemical storage systems. In the case of non-Li ion rechargeable systems, the development of electrode materials is a significant challenge, considering the larger ionic size of the metal-ions and slower kinetics. Two-dimensional(2D) materials, such as graphene, transition metal dichalcogenides, MXenes and phosphorene, have garnered significant attention recently due to their multi-faceted advantageous properties: large surface areas, high electrical and thermal conductivity, mechanical strength, etc. Consequently, the study of 2D materials as negative electrodes is of notable importance as emerging non-Li battery systems continue to generate increasing attention. Among these interesting materials, graphene has already been extensively studied and reviewed, hence this report focuses on 2D materials beyond graphene for emerging non-Li systems. We provide a comparative analysis of 2D material chemistry, structure, and performance parameters as anode materials in rechargeable batteries and supercapacitors.

OpenIFEM:A High Performance Modular Open-Source Software of the Immersed Finite Element Method for Fluid-Structure Interactions

We present a high performance modularly-built open-source software-OpenIFEM.OpenIFEM is a C++implementation of the modified immersed finite element method(mIFEM)to solve fluid-structure interaction(FSI)problems.This software is modularly built to perform multiple tasks including fluid dynamics(incompressible and slightly compressible fluid models),linear and nonlinear solid mechanics,and fully coupled fluid-structure interactions.Most of open-source software packages are restricted to certain discretization methods;some are under-tested,under-documented,and lack modularity as well as extensibility.OpenIFEM is designed and built to include a set of generic classes for users to adapt so that any fluid and solid solvers can be coupled through the FSI algorithm.In addition,the package utilizes well-developed and tested libraries.It also comes with standard test cases that serve as software and algorithm validation.The software can be built on cross-platform,i.e.,Linux,Windows,and Mac OS,using CMake.Efficient parallelization is also implemented for high-performance computing for large-sized problems.OpenIFEM is documented using Doxygen and publicly available to download on GitHub.It is expected to benefit the future development of FSI algorithms and be applied to a variety of FSI applications.

A quasi-coupled wind wave experimental framework for testing offshore wind turbine floating systems

Two sets of experiments in the St.Anthony Falls Laboratory(SAFL)wave tank facility and atmospheric wind tunnel are integrated to provide a scaled representation of a floating wind turbine under heave and pitch motions due to ocean waves.The quasi-coupling is established by controlling the turbine rotor speed to generate a thrust force mimicking steady or fluctuating wind gusts in the wave tank,and by using two actuators to oscillate a miniature turbine in the wind tunnel.Measured pitch and heave motions under varying waves are scaled down using rotor geometry and the wake meandering frequency to study the effect of the floating platform kinematics on the evolution and characteristics of the oscillating turbine wake.For a limited case of experimental conditions results provide a phenomenological and quantitative description of the floating-turbine system under variable waves and simulated wind gusts.Specifically,we demonstrate that wind gusts contribute to increase the platform pitch range,and that periodic large scale flow patches of high and low momentum flow are generated by the oscillating rotor in the turbulent boundary layer and are coherently convected through the wake.Both mechanisms could amplify the pitch response of downwind floating turbine units within the offshore power plant,in particular if the wave and/or wind forcing frequencies happen to approach the pitch natural frequency of the floating system.

回热器对制冷系统性能的影响

通过对制冷系统中回热器、蒸发器和压缩机工作过程的理论分析以及对蒸发器的热设计,定量地讨论了回热器出入口条件的改变对蒸发器尺寸、压缩机功率以及制冷系统成绩系数等的影响. 降低制冷工质在回热器出口处的过热度,可以减小蒸发器的尺寸,但由此带来的不利因素,是需要增加制冷工质的质量流量以及提高压缩机的压缩功率.

PEMFCs的膜及阴极催化层数值模拟

本文提出了一个质子交换膜燃料电池的膜和阴极催化层的一维非稳态数学模型,模型考虑了电化学反应及反应中的传质过程。本文结合算例分析了燃料电池膜及阴极催化层的性能,结果能验证燃料电池内阻理论。论文结果表明:(1)随着输出电流密度的增大,氧浓度分布不均匀性增大; (2)阴极催化层厚度减小,可提高电池输出电压; (3)电池进口处氧气摩尔浓度增大,可增加电池的输出电压。

真空钎焊多通道扁管铝蒸发器空气侧换热性能的实验研究

本文对自行设计开发的大型冷藏运输车用真空钎焊多通道扁管铝蒸发器，在干、湿工况下的空气侧换热性能进行了风洞实验研究，同时对该蒸发器的表面湿润性进行了评价。实验结果表明，该蒸发器具有良好的换热性能；湿式压降与干式压降非常接近；由于蒸发器表面采用了亲水性被覆，其前进接触角为３４°，后退接触角为零。若想用风洞获得该蒸发器湿式条件下的换热性能需制作一个小迎风面的样机。

Analysis for stress environment in the alveolar sac model

Better understanding of alveolar mechanics is very important in order to avoid lung injuries for patients undergoing mechanical ventilation for treatment of respiratory problems. The objective of this study was to investigate the alveolar mechanics for two different alveolar sac models, one based on actual geometry and the other an idealized spherical geometry using coupled fluid-solid computational analysis. Both the models were analyzed through coupled fluid-solid analysis to estimate the parameters such as pressures/ velocities and displacements/stresses under mechanical ventilation conditions. The results obtained from the fluid analysis indicate that both the alveolar geometries give similar results for pressures and velocities. However, the results obtained from coupled fluid-solid analysis indicate that the actual alveolar geometry results in smaller displacements in comparison to a spherical alveolar model. This trend is also true for stress/strain between the two models. The results presented indicate that alveolar geometry greatly affects the pressure/velocities as well as displacements and stresses/strains.

Elastoplastic Large Deformation Using Meshless Integral Method

In this paper, the meshless integral method based on the regularized boundary integral equation [1] has been extended to analyze the large deformation of elastoplastic materials. The updated Lagrangian governing integral equation is obtained from the weak form of elastoplasticity based on Green-Naghdi’s theory over a local sub-domain, and the moving least-squares approximation is used for meshless function approximation. Green-Naghdi’s theory starts with the additive decomposition of the Green-Lagrange strain into elastic and plastic parts and considers aJ2elastoplastic constitutive law that relates the Green-Lagrange strain to the second Piola-Kirchhoff stress. A simple, generalized collocation method is proposed to enforce essential boundary conditions straightforwardly and accurately, while natural boundary conditions are incorporated in the system governing equations and require no special handling. The solution algorithm for large deformation analysis is discussed in detail. Numerical examples show that meshless integral method with large deformation is accurate and robust.

A new computational approach for modeling diffusion tractography in the brain

Computational models provide additional tools for studying the brain,however,many techniques are currently disconnected from each other.There is a need for new computational approaches that span the range of physics operating in the brain.In this review paper,we offer some new perspectives on how the embedded element method can fill this gap and has the potential to connect a myriad of modeling genre.The embedded element method is a mesh superposition technique used within finite element analysis.This method allows for the incorporation of axonal fiber tracts to be explicitly represented.Here,we explore the use of the approach beyond its original goal of predicting axonal strain in brain injury.We explore the potential application of the embedded element method in areas of electrophysiology,neurodegeneration,neuropharmacology and mechanobiology.We conclude that this method has the potential to provide us with an integrated computational framework that can assist in developing improved diagnostic tools and regeneration technologies.

Wavelet Space Partitioning for Symbolic Time Series Analysis

A crucial step in symbolic time series analysis （STSA） of observed data is symbol sequence generation that relies on partitioning the phase-space of the underlying dynamical system. We present a novel partitioning method, called wavelet-space （WS） partitioning, as an alternative to symbolic false nearest neighbour （SFNN） partitioning. While the WS and SFNN partitioning methods have been demonstrated to yield comparable performance for anomaly detection on laboratory apparatuses, computation of WS partitioning is several orders of magnitude faster than that of the SFNN partitioning.

From seawater to hydrogen via direct photocatalytic vapor splitting: A review on device design and system integration

Solar-driven hydrogen production from seawater attracts great interest for its emerging role in decarbonizing global energy consumption. Given the complexity of natural seawater content, photocatalytic vapor splitting offers a low-cost and safe solution, but with a very low solar-to-hydrogen conversion efficiency. With a focus on cutting-edge photothermal–photocatalytic device design and system integration, the recent research advances on vapor splitting from seawater, as well as industrial implementations in the past decades were reviewed. In addition, the design strategies of the key processes were reviewed, including vapor temperature and pressure control during solar thermal vapor generation from seawater, capillary-fed vaporization with salt repellent, and direct photocatalytic vapor splitting for hydrogen production. Moreover, the existing laboratory-scale and industrial-scale systems, and the integration principles and remaining challenges in the future seawater-to-hydrogen technology were discussed.

The ReaxFF reactive force-field: development, applications and future directions

The reactive force-field(ReaxFF)interatomic potential is a powerful computational tool for exploring,developing and optimizing material properties.Methods based on the principles of quantum mechanics(QM),while offering valuable theoretical guidance at the electronic level,are often too computationally intense for simulations that consider the full dynamic evolution of a system.Alternatively,empirical interatomic potentials that are based on classical principles require significantly fewer computational resources,which enables simulations to better describe dynamic processes over longer timeframes and on larger scales.Such methods,however,typically require a predefined connectivity between atoms,precluding simulations that involve reactive events.The ReaxFF method was developed to help bridge this gap.Approaching the gap from the classical side,ReaxFF casts the empirical interatomic potential within a bond-order formalism,thus implicitly describing chemical bonding without expensive QM calculations.This article provides an overview of the development,application,and future directions of the ReaxFF method.

Simulation of vessel tissue remodeling with residual stress:an application to in-stent restenosis

We present a numerical procedure to model the artery wall remodeling stimulated by stenting considering varying degree of residual stresses.This framework sets up biological remodeling with the existence of residual stress.Previous studies suggest that the residual stress originates from the growth and remodeling of the premature tissue.Meanwhile,it is known that tissue remodeling can happen under mechanical loading.However,none of the existing research studies the impact of residual stress on the mechanical-driven growth of biomaterials.To fill this gap,we build a numerical framework that couples the residual stress with a growth model,and examine its impact on tissue remodeling.The proposed approach is applied to in-stent restenosis,where the tissue remodeling process is modeled with finite element method,and the residual stress is generated geometrically using open angle method.The result shows that residual stress reverses the radial distribution of stress concentration,which is ameliorated by tissue remodeling.The thickening of vessel wall tends to increase with residual stress,which links to more severe in-stent restenosis.The results demonstrate the important interplay between residual stress and tissue remodeling.The findings suggest that residual stress should be considered in the future simulation of tissue remodeling.

Effects of thermal boundary conditions on the joule heating of electrolyte in a microchannel

Joule heating effects on a slit microcharmel filled with electrolytes are comprehensively investigated with emphasis on the thermal boundary conditions. An accurate analytical expression is proposed for the electrical field and the temperature distributions due to Joule heating are numerically obtained from the energy balance equation. The results show that a thermal design based on the average electric potential difference between electrodes can cause severe underestimation of Joule heating. In addition, the parame- tric study of thermal boundary conditions gives us an insight into the best cooling scenario for microfluidic devices. Other significant thermal characteristics, including Nusselt number, thermophoretic force, and entropy generation, are discussed as well. This study will provide useful information for the optimization of a bioMEMS device in relation to the thermal aspect.

Control design of an unmanned hovercraft for agricultural applications

The efficient and precise application of agricultural materials such as fertilizer or herbicide can be greatly facilitated by autonomous operation.This is especially important under difficult conditions at remote sites.The purpose of this work is to develop an accurate nonlinear controller using a direct Lyapunov approach to ensure stability of an unmanned hovercraft prototype used for the execution of these agricultural tasks.Such a craft constitutes an underactuated system which has fewer actuators than degrees of freedom.The proposed closed loop system is simulated to demonstrate that a control law can stabilize both the actuated and unactuated degrees of freedom of the hovercraft.It is shown that the position and orientation of the hovercraft achieve high dynamic and steady performance.