Comparison of Alternative Strategies for Multilevel Optimization of Hierarchical Systems

The augmented Lagrangian penalty formulation and four different coordination strategies are used to examine the nu- merical behavior of Analytical Target Cascading (ATC) for multilevel optimization of hierarchical systems. The coordination strategies considered include augmented Lagrangian using the method of multipliers and alternating direction method of multipliers, diagonal quadratic approximation, and truncated diagonal quadratic approximation. Properties examined include computational cost and solution accuracy based on the selected values for the different parameters that appear in each formulation. The different strategies are implemented using two- and three-level decomposed example problems. While the results show the interaction between the selected ATC formulation and the values of associated parameters, they clearly highlight the impact they could have on both the solution accuracy and computational cost.

Modification Design Method for an Enveloping Hourglass Worm Gear with Consideration of Machining and Misalignment Errors

The influences of machining and misalignment errors play a very critical role in the performance of the anti-backlash double-roller enveloping hourglass worm gear(ADEHWG).However,a corresponding efficient method for eliminating or reducing these errors on the tooth profile of the ADEHWG is seldom reported.The gear engagement equation and tooth profile equation for considering six different errors that could arise from the machining and gear misalignment are derived from the theories of differential geometry and gear meshing.Also,the tooth contact analysis(TCA) is used to systematically investigate the influence of the machining and misalignment errors on the contact curves and the tooth profile by means of numerical analysis and three-dimensional solid modeling.The research results show that vertical angular misalignment of the worm wheel(Δβ) has the strongest influences while the tooth angle error(Δα) has the weakest influences on the contact curves and the tooth profile.A novel efficient approach is proposed and used to minimize the effect of the errors in manufacturing by changing the radius of the grinding wheel and the approaching point of contact.The results from the TCA and the experiment demonstrate that this tooth profile design modification method can indeed reduce the machining and misalignment errors.This modification design method is helpful in understanding the manufacturing technology of the ADEHWG.

Design of lightweight magnesium car body structure under crash and vibration constraints

Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality.In this paper,material replacement along with multidisciplinary design optimization strategy is proposed to develop a lightweight car body structure that satisfies the crash and vibration criteria while minimizing weight.Through finite element simulations,full frontal,offset frontal,and side crashes of a full car model are evaluated for peak acceleration,intrusion distance,and the internal energy absorbed by the structural parts.In addition,the first three fundamental natural frequencies are combined with the crash metrics to form the design constraints.The wall thicknesses of twenty-two parts are considered as the design variables.Latin Hypercube Sampling is used to sample the design space,while Radial Basis Function methodology is used to develop surrogate models for the selected crash responses at multiple sites as well as the first three fundamental natural frequencies.A nonlinear surrogate-based optimization problem is formulated for mass minimization under crash and vibration constraints.Using Sequential Quadratic Programming,the design optimization problem is solved with the results verified by finite element simulations.The performance of the optimum design with magnesium parts shows significant weight reduction and better performance compared to the baseline design.

Thermal Management of Vehicle Cabins,External Surfaces,and Onboard Electronics:An Overview

Reducing heat accumulation within vehicles and ensuring appropriate vehicular temperature levels can lead to enhanced vehicle fuel economy,range,reliability,longevity,passenger comfort,and safety.Advancements in vehicle thermal management remain key as new technologies,consumer demand,societal concerns,and government regulations emerge and evolve.This study summarizes several recent advances in vehicle thermal management technology and modeling,with a focus on three key areas:the cabin,electronics,and exterior components of vehicles.Cabin-related topics covered include methods for reducing thermal loads and improving heating,ventilation,and air-conditioning(HVAC)systems;and advancements in window glazing/tinting and vehicle surface treatments.For the thermal management of electronics,including batteries and insulated-gate bipolar transistors(IGBTs),active and passive cooling methods that employ heat pipes,heat sinks,jet impingement,forced convection,and phase-change materials are discussed.Finally,efforts to model and enhance the heat transfer of exterior vehicular components are reviewed while considering drag/friction forces and environmental effects.Despite advances in the field of vehicle thermal management,challenges still exist;this article provides a broad summary of the major issues,with recommendations for further study.

粉末注射成形与液相烧结科学基础的建立

就固-液-孔隙系统的流变学特性而言,粉末注射成形与液相烧结具有同样特点。粉末注射成形起始于1930年代,而金属粉末的液相烧结大体上也可溯源于同一时代。这2种工艺都对粘度和固体含量与温度的关系高度敏感,但都有所不同。因此,提出了一个包括应变速率、颗粒大小、固体含量等因素及颗粒结合程度的模型。在液相烧结中,固体在液体中的溶解度通过颗粒结合影响与时间相关的粘度。同样,在粉末注射成形中,长聚合物的缠结影响与时间相关的粘度。粉末注射成形与液相烧结二者的相似之处,在于都能够将流变学特性模型用于计算机模拟。

A generalized constitutive elasticity law for GLPD micromorphic materials, with application to the problem of a spherical shell subjected to axisymmetric loading conditions

In this work we propose to replace the GLPD hypo-elasticity law by a more rigorous generalized Hooke＇s law based on classical material symmetry characterization assumptions. This law introduces in addition to the two well- known Lame＇s moduli, five constitutive constants. An analytical solution is de- rived for the problem of a spherical shell subjected to axisymmetric loading con- ditions to illustrate the potential of the proposed generalized Hooke＇s law.

In-Situ FT-IR Investigation Methane to Syngas over of Partial Oxidation of Rh/SiO2 Catalyst

Partial oxidation of methane to syngas （POM） over Rh/SiO2 catalyst was investigated using in-situ FT-IR. When methane interacted with 1.0wt%Rh/SiO2 catalyst, it was dissociated to adsorbed hydrogen and CHx species. The adsorbed hydrogen atoms were transferred to SiO2 surface by ＂spill-over＂ and reacted with lattice oxygen to form surface -OH species. POM mechanism was investigated over Rh/SiO2 catalyst using in-situ FT-IR. It was found that CO2 was formed before CO could be detected when CH4 and O2 were introduced over the preoxidized Rh/SiO2 catalyst, whereas CO was detected before CO2 was formed over the prereduced Rh/SiO2 catalyst.

Deleterious effects of whole-body vibration on the spine:A review of in vivo,ex vivo,and in vitro models

Occupational exposure to whole-body vibration is associated with the develop-ment of musculoskeletal,neurological,and other ailments.Low back pain and other spine disorders are prevalent among those exposed to whole-body vibration in occupational and military settings.Although standards for limiting exposure to whole-body vibration have been in place for decades,there is a lack of understanding of whole-body vibration-associated risks among safety and healthcare profession-als.Consequently,disorders associated with whole-body vibration exposure remain prevalent in the workforce and military.The relationship between whole-body vibra-tion and low back pain in humans has been established largely through cohort stud-ies,for which vibration inputs that lead to symptoms are rarely,if ever,quantified.This gap in knowledge highlights the need for the development of relevant in vivo,ex vivo,and in vitro models to study such pathologies.The parameters of vibrational stimuli(eg,frequency and direction)play critical roles in such pathologies,but the specific cause-and-effect relationships between whole-body vibration and spinal pa-thologies remain mostly unknown.This paper provides a summary of whole-body vibration parameters;reviews in vivo,ex vivo,and in vitro models for spinal patholo-gies resulting from whole-body vibration;and offers suggestions to address the gaps in translating injury biomechanics data to inform clinical practice.

Damage smoothing effects in a delocalized rate sensitivity model for metals

It has been long time established that application of damage delocalization method to softening constitutive models yields numerical results that are independent of the size of the finite element. However, the prediction of real-world large and small scale problems using the delocalization method remains in its infancy. One of the drawbacks encountered is that the predicted load versus displacement curve suddenly drops, as a result of excessive smoothing of the damage. The present paper studies this unwanted effect for a delocalized plasticity/damage model for metallic materials. We use some theoretical arguments to explain the failure of the delocalized model considered, following which a simple remedy is proposed to deal with it. Future works involve the numerical implementation of the new version reproduce real-world problems.

New applications of a generalized Hooke's law for second gradient materials

We provide analytical solutions to the problems of a circular bending of a beam in plane strain and the torsion of a non-circular cross-section beam, the beams obeying a second-gradient elasticity law proposed by the author, following a previous suggestion of delrlsola et al. （2009）. The motivation was to find benchmark analytical solutions that can serve to grasp the physical foundations of second gradient elasticity laws for heterogeneous materials. The analytical solution of the circular beam problem presents the additional advantage to establish some nice properties on the unknown second gradient elastic moduli introduced by Enakoutsa （2014） model and the classical elasticity constants for both incompressible and compressible heterogeneous elastic materials. A framework to find the elastic moduli of the new model is also proposed.

Stimuli-responsive photoluminescent copper(Ⅰ) halides for scintillation, anticounterfeiting, and light-emitting diode applications

Highly sensitive stimuli-responsive luminescent materials are crucial for appli-cations in optical sensing,security,and anticounterfeiting.Here,we report two zero-dimensional(0D)copper(I)halides,(TEP)_(2)Cu_(2)Br_(4),(TEP)_(2)Cu_(4)Br_(6),and 1D(TEP)_(3)Ag_(6)Br_(9),which are comprised of isolated[Cu_(2)Br_(4)]^(2-),[Cu_(4)Br_(6)]^(2-),and[Ag_(6)Br_(9)]3-polyanions,respectively,separated by TEP^(+)(tetraethylphosphonium[TEP])cations.(TEP)_(2)Cu_(2)Br_(4) and(TEP)_(2)Cu_(4)Br_(6) demonstrate greenish-white and orange-red emissions,respectively,with near unity photoluminescence quantum yields,while(TEP)_(3)Ag_(6)Br_(9) is a poor light emitter.Optical spectroscopy mea-surements and density-functional theory calculations reveal that photoemissions of these compounds originate from self-trapped excitons due to the excited-state distor-tions in the copper(I)halide units.Crystals of Cu(I)halides are radioluminescence active at room temperature under both X-andγ-rays exposure.The light yields up to 15,800 ph/MeV under 662 keVγ-rays of ^(137)Cs suggesting their potential for scintillation applications.Remarkably,(TEP)_(2)Cu_(2)Br_(4) and(TEP)_(2)Cu_(4)Br_(6) are inter-convertible through chemical stimuli or reverse crystallization.In addition,both compounds demonstrate luminescence on-off switching upon thermal stimuli.The sensitivity of(TEP)_(2)Cu_(2)Br_(4) and(TEP)_(2)Cu_(4)Br_(6) to the chemical and thermal stimuli coupled with their ultrabright emission allows their consideration for applications such as solid-state lighting,sensing,information storage,and anticounterfeiting.

Recent progress in CFD for naval architecture and ocean engineering

An overview is provided of CFDShip-Iowa modeling, numerical methods and high performance computing （HPC）, including both current V4.5 and V5.5 and next generation V6. Examples for naval architecture highlight capability and needs. High fidelity V6 simulations for ocean engineering and fundamental physics describe increased resolution for analysis of physics of fluids. Uncertainty quantification research is overviewed as the first step towards development stochastic optimization.

Comparison of Cellular Automaton and Phase Field Models to Simulate Dendrite Growth in Hexagonal Crystals

A cellular automaton （CA）-finite element （FE） model and a phase field （PF）-FE model were used to simulate equiaxed dendritic growth during the solidification of hexagonal metals. In the CA-FE model, the conservation equations of mass and energy were solved in order to calculate the temperature field, solute concentration, and the dendritic growth morphology. CA-FE simulation results showed reasonable agreement with the previously reported experimental data on secondary dendrite arm spacing （SDAS） vs cooling rate. In the PF model, a PF variable was used to distinguish solid and liquid phases similar to the conventional PF models for solidification of pure materials. Another PF variable was considered to determine the evolution of solute concentration. Validation of both models was performed by comparing the simulation results with the analytical model developed by Lipton-Glicksman-Kurz （LGK）, showing quantitatively good agreement in the tip growth velocity at a given melt undercooling. Application to magnesium alloy AZ91 （approximated with the binary Mg-8.9 wt% AI） illustrates the difficulty of modeling dendrite growth in hexagonal systems using CA-FE regarding mesh-induced anisotropy and a better performance of PF-FE in modeling multiple arbitrarily-oriented dendrites growth.

An overview of various control benchmarks with a focus on automotive control

There exists a gap between control theory and control practice,i.e.,all control methods suggested by researchers are not implemented in real systems and,on the other hand,many important in dustrial problems are not studied in the academic research.Benchmark problems can help close this gap and provide many opportunities for members in both the controls theory and application communities.The goal is to survey and give pointers to different general controls and modeling related benchmark problems that can serve as inspiration for future benchmarks and then specifically focus the benchmark coverage on automotive control engineering application.In the paper reflections are given on how different categories of benchmark designers,benchmark solvers and third part users can benefit from providing,solving,and studying benchmark problems.The paper also collects information about several benchmark problems and gives pointers to papers than give more detailed information about different problems that have been presented.

Graph-based robot optimal path planning with bio-inspired algorithms

Recently,bio-inspired algorithms have been increasingly explored for autonomous robot path planning on grid-based maps.However,these approaches endure performance degradation as problem complexity increases,often resulting in lengthy search times to find an optimal solution.This limitation is particularly critical for real-world applications like autonomous off-road vehicles,where highquality path computation is essential for energy efficiency.To address these challenges,this paper proposes a new graph-based optimal path planning approach that leverages a sort of bio-inspired algorithm,improved seagull optimization algorithm(iSOA)for rapid path planning of autonomous robots.A modified Douglas–Peucker(mDP)algorithm is developed to approximate irregular obstacles as polygonal obstacles based on the environment image in rough terrains.The resulting mDPderived graph is then modeled using a Maklink graph theory.By applying the iSOA approach,the trajectory of an autonomous robot in the workspace is optimized.Additionally,a Bezier-curve-based smoothing approach is developed to generate safer and smoother trajectories while adhering to curvature constraints.The proposed model is validated through simulated experiments undertaken in various real-world settings,and its performance is compared with state-of-the-art algorithms.The experimental results demonstrate that the proposed model outperforms existing approaches in terms of time cost and path length.

Real-time energy optimization of HEVs under-connected environment: a benchmark problem and receding horizon-based solution

In this paper,we propose a benchmark problem for the challengers aiming to energy efficiency control of hybrid electric vehicles(HEVs)on a road with slope.Moreover,it is assumed that the targeted HEVs are in the connected environment with the obtainment of real-time information of vehicle-to-everything(V2X),including geographic information,vehicle-to-infrastructure(V2I)information and vehicle-to-vehicle(V2V)information.The provided simulator consists of an industrial-level HEV model and a traffic scenario database obtained through a commercial traffic simulator,where the running route is generated based on real-world data with slope and intersection position.The benchmark problem to be solved is the HEVs powertrain control using traffic information to fulfill fuel economy improvement while satisfying the constraints of driving safety and travel time.To show the HEV powertrain characteristics,a case study is given with the speed planning and energy management strategy.

Convection–Diffusion Model for the Prediction of Anthropogenically-Initiated Wildfire Ignition

A spatial interaction model to predict anthropogenically-initiated accidental and incendiary wildfire ignition probability is developed using fluid flow analogies for human movement patterns. Urban areas with large populations are identified as the sites of global influencing factors, and are modeled as the gravity term. The transportation corridors are identified as local influencing factors, and are modeled using fluid flow analogy as diffusion and convection terms. The model is implemented in ArcGIS, and applied for the prediction of wildfire hazard distribution in southeastern Mississippi. The model shows87 % correlation with historic data in the winter season,whereas the previously developed gravity model shows only 75 % correlation. The normalized error for convection–diffusion model predictions is about 5 % in the winter season, whereas the gravity model shows an error of 7 %.The proposed model is robust as it couples a multi-criteria behavioral pattern within a single dynamic equation to enhance predictive capability. At the same time, the proposed model is more costly than the gravity model as it requires evaluation of distance from intermodal transportation corridors, transportation corridor density, and traffic volume maps. Nonetheless, the model is developed in a modular fashion, such that either global or local terms can be neglected if required.

Porcelain insulation-defining the underlying mechanism of failure

Porcelain insulators have a long history and wide application range in power systems,but just like any other insulator,they can fail.A number of pole fires occurred on lines utilising porcelain suspension insulators.In some cases,the insulators appeared to be visually intact with no external signs of degradation or abnormal stress.This prompted a comprehensive assessment to identify the mechanism that leads to the permanent loss of insulating properties while retaining external physical characteristics.A single test is not sufficient to determine the underlying cause of conduction as results may produce contradictory conclusions.Electrical tests were able to identify samples with poor dielectric strength.Nevertheless,these same samples exhibited excellent mechanical properties.Despite successfully passing numerous porosity tests,scanning electron microscopic analysis revealed porosity and multiple microscopic punctures in the porcelain dielectric.Only upon complete dissection of samples,the conduction mechanism was revealed.This article discusses the challenges associated with establishing the root failure mechanism for the investigated porcelain insulators that allows visually sound samples to lose their insulating properties without experiencing catastrophic failure.