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shape design of arch dams under load uncertainties with robust optimization

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Frontiers of structural and Civil Engineering 2019年第4期13卷 852-862页

作者： Fengjie TAN tom LAHMER Institute of structural Mechanics Bauhaus-UniversitatWeimar D-99423Germany

Due to an increased need in hydro-electricity, water storage, and flood protection, it is assumed that a series of new dams will be build throughout the world. The focus of this paper is on the non-probabilistic-based design of new arch-type dams by applying means of robust design optimization (RDO). This type of optimization takes into account uncertainties in the loads and in the material properties of the structure. As classical procedures of probabilistic-based optimization under uncertainties, such as RDO and reliability-based design optimization (RBDO), are in general computationally expensive and rely on estimates of the system’s response variance, we will not follow a full-probabilistic approach but work with predefined confidence levels. This leads to a bi-level optimization program where the volume of the dam is optimized under the worst combination of the uncertain parameters. As a result, robust and reliable designs are obtained and the result is independent from any assumptions on stochastic properties of the random variables in the model. The optimization of an arch-type dam is realized here by a robust optimization method under load uncertainty, where hydraulic and thermal loads are considered. The load uncertainty is modeled as an ellipsoidal expression. Comparing with any traditional deterministic optimization method, which only concerns the minimum objective value and offers a solution candidate close to limit-states, the RDO method provides a robust solution against uncertainty. To reduce the computational cost, a ranking strategy and an approximation model are further involved to do a preliminary screening. By this means, the robust design can generate an improved arch dam structure that ensures both safety and serviceability during its lifetime.

关键词： arch dam shape optimization robust optimization load uncertainty approximation model

On Marx's View of Freedom

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学术界 2018年第12期 225-231页

作者： tom Rockmore Duguesne University Pittsburgh USA

This paper has briefly examined Marx's conception of freedom in modern industrial society. Even a rapid comparison indicates Marx says different things at different times.The emphasis shifts from,say,an initial view of freedom based on a quasi-Hegelian view of radical equality and even love to freedom beyond the division of labor,then later a very different view of freedom based on a shorter working day,and so on.

关键词： Marx Marx's view of freedom

维普期刊数据库

MP-PIC simulation of circulating fluidized beds using an EMMs based drag model for Geldart B particles

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Particuology 2021年第6期19卷 76-90页

作者： Timo Dymala tom Wytrwat stefan Heinrich Hamburg University of Technology Institute of Solids Process Engineering and Particle TechnologyDenickestr.1521073 HamburgGermany

In this study the multiphase particle-in-cell(MP-PIC)method is used for the simulation of two pilot-scale circulating fluidized beds(CFBs)with quartz sand belonging to Geldart’s group B as bed material.The simulations were performed using a homogeneous drag model as well as a structure dependent drag model based on the energy minimization multi-scale method(EMMs).The results are compared with experimental data from literature as well as experiments.The simulations with the EMMs based drag model show a good agreement of the time-averaged axial solids concentration,circulation rate and riser pressure drop.Furthermore,a lower grid sensitivity is observed compared to the homogeneous drag model.In contrast to the conventional drag model a dense bottom zone is predicted by the EMMs based drag model.An overprediction of the solid concentration in the dense bottom zone is presumably due to an overprediction of the cluster diameter that is calculated using an empirical cluster diameter correlation.This shows the necessity for a new meso-scale cluster correlation for the simulation of Geldart B particles.Furthermore,the results of the time-averaged radial solids concentration differ from the expectations of a core-annulus flow indicating that a mesh refinement at the walls is necessary.Finally,the importance of using a realistic particle size distribution is identified.

关键词： 3D-CFD simulation Circulating fluidized bed(CFB) Multiphase particle-in-cell method(MP-PIC) Energy minimizing multi-scale theory(EMMs) Validation study

Cost implications of increased solar penetration and time-of-use rate interactions

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Clean Energy 2020年第3期4卷 247-269页

作者： Dominique Bain tom Acker school of Earth sciences and Environmental sustainability Northern Arizona UniversityFlagstaffAZ 86011 Mechanical Engineering Northern Arizona UniversityFlagstaffAZ 86011

Electricity-grid operators are facing new challenges in matching load and generation due to increased solar generation and peak-load growth.This paper demonstrates that time-of-use(TOU)rates are an effective method to address these challenges.TOU rates use price differences to incentivize conserving electricity during peak hours and encouraging use during off-peak hours.This strategy is being used across the UsA,including in Arizona,California and Hawaii.This analysis used the production-cost model PLEXOs with an hourly resolution to explore how production costs,locational marginal prices and dispatch stacks(type of generation used to meet load)change due to changes in load shapes prompted by TOU rates and with additional solar generation.The modelling focused on implementing TOU rates at three different adoption(response)levels with and without additional solar generation in the Arizona balancing areas within a PLEXOs model.In most cases analysed,implementing TOU rates in Arizona reduced reserve shortages in the Western Interconnect and,in some cases,very substantially.This result is representative of the interactions that happen interconnection-wide,demonstrating the advantage of modelling the entire interconnection.Production costs were decreased by the additional solar generation and the load change from TOU rates,and high response levels reduced the production costs the most for high-solar-generation cases.Load change from TOU rates decreased locational marginal prices for a typical summer day but had inconsistent results on a high-load day.Additional solar generation decreased the usage of combustion turbines,combined cycles and coal-fired generation.

关键词： energy system and policy production-cost model PLEXOs time-of-use rates solar energy locational marginal price

Resilience:Lessons to be learned from safety and acceptable risk

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Journal of safety science and Resilience 2021年第4期2卷 253-257页

作者： Kosovac Anna tom McLeod Logan Faculty of Engineering and Information Technology The University of MelbourneAustralia Civil and Natural Resources Engineering The University of CanterburyNew Zealand

It is not unusual to see the concept of resilience housed in binary terms:Your city is either‘resilient’or not.In contrast,being‘safe’is widely recognized as a statement based on‘acceptable risk’where absolute safety is unattainable.so why do we treat resilience and,as an example,the idea of“Resilient Cities”as a distinct endpoint?In this paper,we argue that this mindset is not only incongruent with current understandings of safety and risk but could create a false sense of security for systems that otherwise have been judged‘resilient’.An alternative is that we can and should consider framing resilience in the same manner as we do to safety.The benefit of doing this is that we can learn from the safety literature and appreciate that,like for safety,there is no such thing as absolute resilience.Instead,we should be striving to constantly identify and reduce the risks to our systems and society.

关键词： Risk analysis safety Risk assessment Resilient Resilience Urban Cities Disaster management

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利比亚“铁面”

模型世界 2018年第12期 30-42页

作者： tomás de la Fuente

梅塞施密特Bf 110是二战最为有名的双引擎战斗机之一。它被设计成一种远程重型战斗机,然而它在不列颠之战的表现暴露了许多缺陷。由于缺乏机动性和加速性能,Bf 110跟英国单发战斗机根本无法匹敌。结果就是不仅没法给轰炸机护航,它们自... 详细信息

梅塞施密特Bf 110是二战最为有名的双引擎战斗机之一。它被设计成一种远程重型战斗机,然而它在不列颠之战的表现暴露了许多缺陷。由于缺乏机动性和加速性能,Bf 110跟英国单发战斗机根本无法匹敌。结果就是不仅没法给轰炸机护航,它们自己还得有飞机护航。但在另外一方面,Bf 110在对地攻击和夜间攻击中表现非常优秀。它的最终型号Bf 110 G-4型一直生

关键词：珐琅漆内部细节亮光漆组合度利比亚

sustainability and international chemistry collaboration

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National science Review 2021年第5期8卷 9-9页

作者： tom Welton Department of Chemistry Imperial College London Royal society of Chemistry

It is my honour to have been invited to contribute, on behalf of the Royal society of Chemistry (RsC), to this important topical issue on International Chemistry for a sustainable society. Globally,there are urgent and shared problems we need to solve to create a truly sustainable world, for everyone and for future generations. Chemistry will play a major role in achieving sustainability, whether that is in tackling air pollution in our cities,

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结合功能测试与模拟驾驶的老年人驾驶适性评估

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东南大学学报（自然科学版） 2021年第1期51卷 171-177页

作者：沈永俊谭旭 tom Brijs 东南大学交通学院南京211189 Transportation Research Institute(IMOB) Hasselt UniversityHasselt 3500Belgium

为应对老年驾驶人驾驶能力下降带来的交通安全问题并降低与其相关的事故风险,建立了可有效替代道路驾驶测试的老年人驾驶适性评估方法.对92名老年驾驶人进行了功能测试、模拟驾驶测试与道路驾驶测试,通过独立样本T检验与分层逐步Logisti... 详细信息

为应对老年驾驶人驾驶能力下降带来的交通安全问题并降低与其相关的事故风险,建立了可有效替代道路驾驶测试的老年人驾驶适性评估方法.对92名老年驾驶人进行了功能测试、模拟驾驶测试与道路驾驶测试,通过独立样本T检验与分层逐步Logistic回归确定评价指标体系,分别建立并比选了决策树、随机森林和支持向量机3种评估模型.结果表明,以对比敏感度、功能性伸展、交通标志理解以及合流变道距离等作为评价指标的支持向量机模型对驾驶适性的评估效果最好,准确率高达84.6%.该方法可以有效替代道路测试评估老年人的驾驶适性,能为其停止驾驶、调整驾驶行为、训练提升驾驶能力、使用辅助驾驶技术等提供参考.

关键词：交通安全老年驾驶人驾驶适性功能测试模拟驾驶

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size Effect of Impact Abrasive Particles on Wear and surface Hardening Behavior of High‑Manganese steel

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Acta Metallurgica sinica(English Letters) 2023年第6期36卷 906-916页

作者： Yongjin Wang Chuansongxin song Renbo song Zetian Ma tom Taylor school of Materials science and Engineering University of Science and Technology BeijingBeijing 100083China swansea University Swansea SA18EPUK

The size effect of impact abrasive particles on wear and surface hardening behavior of high-manganese steel was studied.Impact wear tests were carried out on MLD-10 tester with abrasive particle sizes of 6.0–0.75 mm,respectively.The results showed that the impact wear behavior and surface hardening mechanism of high-manganese steel were affected by the size of abrasive particles.A critical size of abrasive particle might exhibit to distinguish the impact wear behavior.When the abrasive particle size was larger than 0.75 mm,the wear mass loss generally showed a decreasing trend with the decrease of the abrasive particle size.Dislocation strengthening and mechanical twinning contributed to the good work hardening behavior.However,effective surface hardening layer could not be formed for sample tested with particle size of 0.75 mm and the wear mass loss was the highest among all the conditions.The weak hardening effect led to the sharp increase of the wear mass loss.Press-in abrasives could be observed on the wear surface when the abrasive particle size was larger than 0.75 mm.The press-in abrasives were peeled off from the wear surface and broken,leaving deep grooves and peeling pits.Material exchange with the sample would occur with the flow of abrasives.A large area of furrow was formed on the wear surface.For particle size of 0.75 mm,aggregated abrasives formed a dynamic buffer layer on the surface and the stress distribution was more even.The formation of buffer layer would lower the effect of the impact load and the work hardening effect could not be fully activated.The mutual extrusion among the abrasives,friction wheel and sample caused plastic deformation of the worn surface during impact test.The present study would help guiding to select the application field of high-manganese steel more precisely.

关键词： Abrasive particles Three-body impact wear High-manganese steel Wear mechanism surface hardening behavior