Structural composites for multifunctional applications: Current challenges and future trends

This review paper summarizes the current state-of-art and challenges for the future developments of fiber-reinforced composites for structural applications with multifunctional capabilities. After a brief analysis of the reasons of the successful incorporation of fiber-reinforced composites in many different industrial sectors, the review analyzes three critical factors that will define the future of composites. The first one is the application of novel fiber-deposition and preforming techniques together with innovative liquid moulding strategies. The second is the combination of these techniques by optimization tools based on novel multiscale modeling approaches, so fiber-reinforced composites with optimized properties can be designed and manufactured for each application. In addition, the third is the enhancement of composite applications by the incorporation of multifunctional capabilities. Among them, electrical conductivity, energy storage (structural supercapacitors and batteries) and energy harvesting (piezoelectric and solar energy) seem to be the most promising ones.     

Decision-making processes evaluation using two methodologies: field and simulation techniques

The study of information processing and human actions in complex environments requires the use of methodological tools that enable one to comprehend the complexity of context without sacrificing methodological accuracy, control of variables or results generalization. Research methods that allow the study of strategies that people use when they make decisions are, among others, field studies and simulated micro-worlds. The aim of this paper is to present the main theoretical and methodological conclusions obtained in two studies centred on decision-making processes. The authors were interested in evaluating the results obtained both in a previous field study developed with experts in process control tasks and in a simulated study with inexperienced people. In the field study, a verbal protocol technique was used, while in the simulated study a simulated dynamic task was developed which contained the main features of control process tasks. Among other factors, the authors are interested in exploring the effect of expertise with the task, the learning strategies and the ways of task solving. The results of these two studies indicate some characteristics of a good performance such as the importance of information searches; the taking into account of delays in the effects of the actions; the anticipation of possible system changes.     

Traffic engineering in ATM networks: Current trends and future issues

In this survey we present an overview of the current state-of-the-art and the future issues to be resolved for the deployment of integrated communications networks based on the Asynchronous Transfer Mode (ATM) Our presentation is from the perspective of traffic and congestion control and management issues which hold the key to the successful achievement of this deployment since it is mainly in these aspects that ATM networks differ from conventional communication networks.     

气体分离膜应用的现状和未来

考虑了气体分离膜应用和气体传递机理的各种技术．现在商业气体分离膜应用的范围包括：富氮、富氧、氢回收、从天然气中除去酸性气体(CO2和H2S)、天然气脱水和有价值的挥发有机物(VOCs)的回收．讨论了每一个应用中可用膜材料的现状和限度,及有潜在力的若干新膜的应用,如乙烯／乙烷分离和燃料电池．     

Current and future trends of additive manufacturing for chemistry applications: a review

Three-dimensional (3-D) printing, also known as additive manufacturing, refers to a method used to generate a physical object by joining materials in a layer-by-layer process from a three-dimensional virtual model. 3-D printing technology has been traditionally employed in rapid prototyping, engineering, and industrial design. More recently, new applications continue to emerge; this is because of its exceptional advantage and flexibility over the traditional manufacturing process. Unlike other conventional manufacturing methods, which are fundamentally subtractive, 3-D printing is additive and, therefore, produces less waste. This review comprehensively summarises the application of additive manufacturing technologies in chemistry, chemical synthesis, and catalysis with particular attention to the production of general laboratory hardware, analytical facilities, reaction devices, and catalytically active substances. It also focuses on new and upcoming applications such as digital chemical synthesis, automation, and robotics in a synthetic environment. While discussing the contribution of this research area in the last decade, the current, future, and economic opportunities of additive manufacturing in chemical research and material development were fully covered.

Graphical abstract

     

Mechanical sub-cooling vapor compression systems: Current status and future directions

Using mechanical sub-cooling systems to increase COP of vapor compression cycles is a known method in literature to save energy and increase efficiency. Recently, much progress has been made with respect to investigation into its different aspects that can help to put it into practice. Numerical and experimental works are considered for the purpose of highlighting this progress. These can be categorized as: a) simulation of performance characteristics resulting from different refrigerant combinations in dedicated mechanical sub-cooling systems, b) variation in performance characteristics for a vapor compression cycle using integrated mechanical sub-cooling because of fouling, c) experimental study about consequences of employing a dedicated mechanical subcooling cycle with a simple vapor compression system, and d) experimental investigation about consequences of employing a subcooler in a two-stage refrigeration cycle. Some important results are discussed. Finally, some suggestions are made to provide direction into future research in this area to help put it into practice.     

Existence and construction of translation models for stationary non-Gaussian processes

Translation models are memoryless transformations of Gaussian processes specified by their marginal distribution F and covariance function ξ. Iteration schemes are commonly used to find probability laws of Gaussian images of translation models, although these schemes may not converge since translation models do not exist for arbitrary functions F and ξ. Pairs (F,ξ) for which translation models exist are said to be consistent. Optimization algorithms are developed for constructing translation models that, for consistent pairs (F,ξ), match F and ξ, and, for inconsistent pairs (F,ξ), match F or ξ and approximate ξ or F. The resulting translation models can be used in Monte Carlo simulation studies.     

Acoustic chemometric prediction of total solids in bioslurry: A full-scale feasibility study for on-line biogas process monitoring

Dry matter is an important process control parameter in the bioconversion application field. Acoustic chemometrics, as a Process Analytical Technology (PAT) modality for quantitative characterisation of dry matter in complex bioslurry systems (biogas fermentation), has not been successful despite several earlier dedicated attempts. A full-scale feasibility study based on standard addition experiments involving natural plant biomass was conducted using multivariate calibration (Partial Least Squares Regression, PLS-R) of acoustic signatures against dry matter content (total solids, TS). Prediction performance of the optimised process implementation was evaluated using independent test set validation, with estimates of accuracy (slope of predicted vs. reference values) and precision (squared correlation coefficient, r²) of 0.94 and 0.97 respectively, with RMSEP of 0.32% w/w (RMSEP_rel = 3.86%) in the range of 5.8-10.8% w/w dry matter. Based on these excellent prediction performance measures, it is concluded that acoustic chemometrics has come of age as a full grown PAT approach for on-line monitoring of dry matter (TS) in complex bioslurry, with a promising application potential in other biomass processing industries as well.     

隐身材料和隐身混凝土的研究现状与趋势

讨论了隐身材料的隐身机理，论述了雷达隐身材料、红外隐身材料、多频谱兼容的多功能隐身材料及隐身混凝土的研究状况，并提出了这几种隐身材料的发展趋势。     

Suitability of European climate for the Asian tiger mosquito Aedes albopictus: recent trends and future scenarios

The Asian tiger mosquito (Aedes albopictus) is an invasive species that has the potential to transmit infectious diseases such as dengue and chikungunya fever. Using high-resolution observations and regional climate model scenarios for the future, we investigated the suitability of Europe for A. albopictus using both recent climate and future climate conditions. The results show that southern France, northern Italy, the northern coast of Spain, the eastern coast of the Adriatic Sea and western Turkey were climatically suitable areas for the establishment of the mosquito during the 1960–1980s. Over the last two decades, climate conditions have become more suitable for the mosquito over central northwestern Europe (Benelux, western Germany) and the Balkans, while they have become less suitable over southern Spain. Similar trends are likely in the future, with an increased risk simulated over northern Europe and slightly decreased risk over southern Europe. These distribution shifts are related to wetter and warmer conditions favouring the overwintering of A. albopictus in the north, and drier and warmer summers that might limit its southward expansion.     

Probabilistic physics-of-failure models for component reliabilities using Monte Carlo simulation and Weibull analysis: a parametric study

In reliability engineering, component failures are generally classified in one of three ways: (1) early life failures; (2) failures having random onset times; and (3) late life or ‘wear out’ failures. When the time-distribution of failures of a population of components is analysed in terms of a Weibull distribution, these failure types may be associated with shape parameters β having values <1, 1, and >1 respectively. Early life failures are frequently attributed to poor design (e.g. poor materials selection) or problems associated with manufacturing or assembly processes.

We describe a methodology for the implementation of physics-of-failure models of component lifetimes in the presence of parameter and model uncertainties. This treats uncertain parameters as random variables described by some appropriate statistical distribution, which may be sampled using Monte Carlo methods. The number of simulations required depends upon the desired accuracy of the predicted lifetime. Provided that the number of sampled variables is relatively small, an accuracy of 1–2% can be obtained using typically 1000 simulations.

The resulting collection of times-to-failure are then sorted into ascending order and fitted to a Weibull distribution to obtain a shape factor β and a characteristic life-time η.

Examples are given of the results obtained using three different models: (1) the Eyring–Peck (EP) model for corrosion of printed circuit boards; (2) a power-law corrosion growth (PCG) model which represents the progressive deterioration of oil and gas pipelines; and (3) a random shock-loading model of mechanical failure. It is shown that for any specific model the values of the Weibull shape parameters obtained may be strongly dependent on the degree of uncertainty of the underlying input parameters. Both the EP and PCG models can yield a wide range of values of β, from β>1, characteristic of wear-out behaviour, to β<1, characteristic of early-life failure, depending on the degree of dispersion of the uncertain parameters. If there is no uncertainty, a single, sharp value of the component lifetime is predicted, corresponding to the limit β=∞. In contrast, the shock-loading model is inherently random, and its predictions correspond closely to those of a constant hazard rate model, characterized by a value of β close to 1 for all finite degrees of parameter uncertainty.

The results are discussed in the context of traditional methods for reliability analysis and conventional views on the nature of early-life failures.     

Simulation of capacity and cost for the planning of future process chains

One of the most promising approaches in modern microelectronics is the introduction of 3D chip micro systems with through-silicon via (TSV) interconnections. A successful transfer of this technology from the scientific level up to the level of mass production is not least of all a matter of cost-effectiveness and profit, which is directly related to high productivity. The developed technologies therefore have to be feasible for effective mass production. In this paper we introduce a method for planning and evaluating costs in future process chains. This method goes beyond usual mostly Excel-supported solutions, as it is based on a discrete event simulation system. The simulation model is generically generated out of an XML process chain definition file and includes a sophisticated state model for machines. Multiple process scenarios are created with the help of a supporting software tool. These scenarios are investigated for achieving favourable equipment and process chain configurations as well as control strategies to support manufacturing ramp-ups.     

A comparison of models for measurable deterioration: An application to coatings on steel structures

Steel structures like bridges, tanks and pylons are exposed to outdoor weathering conditions. In order to prevent them from corrosion they are protected by organic coating systems. This paper focuses on modelling the deterioration of the organic coating layer that protects steel structures from corrosion. Only if there is sufficient knowledge of the condition of the coating on these structures, maintenance actions can be done in the most efficient way. Therefore the course of the deterioration of the coating system and its lifetime, which is also of importance for doing maintenance, have to be assessed accurately. In this paper, three different stochastic processes, viz. Brownian motion with non-linear drift, the non-stationary gamma process and a two-stage hit-and-grow physical process, are fitted to two real data sets. In this way we are the first who compare the three stochastic processes empirically on criteria such as goodness-of-fit, computational convenience and ease of implementation. The first data set is based on expert judgement; the second consists of inspection results. In the first case the model parameters are obtained by a least-squares approach, in the second case by the method of maximum likelihood. A meta-analysis is performed on the two-stage hit-and-grow model by means of fitting Brownian motion and gamma process to the outcomes of this model.     

金属凝固过程中纳米级团簇结构的形成、演变与表征研究

采用分子动力学方法对含有100万个Na原子的液态金属大系统在凝固过程中纳米级团簇结构的形成与演变进行了模拟研究。采用Honeycutt-Andersen（HA）键型指数法和原子团类型指数法（CTIM）的基本原子团表征了各种类型大团簇的结构组态。结果显示：在液态金属Na凝固过程中，与1551键型密切相关的（13364），（131102），（14248）等3种基本原子团及其组合在微观结构转变中起着最重要的作用；凝固过程中形成的纳米级大团簇结构是由大小不同的中、小团簇及各种基本原子团相互连接而成，且大团簇结构内各种基本原子团的中心原子都是相互呈单键连接或多键连接，团簇结构内呈多键结合的中心原子的数目越多，该团簇越稳定；系统中各种类型团簇结构的数目具有明显的幻数特性，与Knight等人的实验结果甚为相符。     

树脂传递模塑过程的数学描述和数值模拟进展

树脂传递模塑(resin transfer molding,RTM)过程的数值模拟对于优化工艺参数和模具设计、控制制品质量等具有重要意义.本文简述了RTM工艺的流体流动特点,介绍了RTM工艺过程数值模拟的理论基础,综述了RTM工艺过程数值模拟的发展历程,并展望了其发展趋势.     

Antioxidant capacity of spray-dried plant extracts: Experiments and simulations

The effects of different inlet air temperatures (70–150 °C) have been studied on the antioxidant retention and yields of a spray-dried bioactive solution (Hibiscus sabdariffa L.) from a Buchi B-290 spray dryer and compared with plug-flow spray drying simulations. Antioxidant retention has been tested using the Oxygen Reducing Antioxidant Capacity assay (ORAC). Experimentally, a peak yield of between 65% and 70% of the solids fed to the dryer has been found at an outlet gas temperature of 60–65 °C and an inlet air temperature of 110 °C, regardless of the batch of material or the liquid feed rate. The varying outlet gas temperatures did not significantly affect the antioxidant retention of the sample, and the simulations demonstrate that this result is due to the competing effects of increasing air temperature and decreasing water activity (at higher inlet air temperatures) on the degradation kinetics. These results suggest that it is more important to obtain greater product yields rather than minimising the degradation amount in this spray-drying situation.     

Object-oriented simulation of reciprocating compressors: Numerical verification and experimental comparison

Numerical simulation of reciprocating compressors is important for the design, development, improvement and optimization of the elements constituting the compressor circuit. In this work, an object-oriented unstructured modular numerical simulation of reciprocating compressors is presented. Pressure correction approach is applied for the resolution of tubes, chambers and compression chambers, while valve dynamics are modelled assuming a spring-mass system having single degree of freedom. The modular approach offers advantages of handling complex circuitry (e.g. parallel paths, multiple compressor chambers, etc.), coupling different simulation models for each element and adaptability to different configurations without changing the program. The code has been verified with some basic tests for assuring asymptotic behaviour to guarantee error free code and physically realistic results. Cases with different compressor configurations and working fluids (R134a, R600a and R744) have also been worked out. Numerical results are compared with experimental data and illustrative cases of multi-stage compression are also presented.     

镁合金及其成形工艺与应用状况

综述了镁合金的种类、特点及性能,全面介绍了包括塑性成形、半固态成形、RSP等在内的镁合金成形方法,并对镁合金在航空航天、汽车、3C等工业的应用历史及现状进行了概述,分析了镁合金目前存在的问题,指出了下一步研究的重点,并展望了镁合金的发展前景。     

Nosing of thin-walled hollow spheres using a die: experimental and theoretical investigation

In contrast to end forming of tubes, there is no published work that addresses the manufacturing of thin-walled hollow spheres by nosing using a die. Important characteristics of the process such as the development of plastic instability modes (local buckling), thickening of the tube-wall and occurrence of wrinkling needs to be properly studied. This paper presents a numerical and experimental investigation of the nosing of thin-walled hollow spheres using a die with the purpose of examining the process mechanics, obtaining a better understanding of the modes of deformation and establishing the formability limits in terms of the major process parameters. The paper also presents a new concept of nosing thin-walled hollow spheres that makes use of preforming stages and tube-end preparation schemes in order to successfully extend the formability limits of the process. Theoretical investigation and process development are supported by numerical predictions based on the finite element flow formulation and the overall methodology is assessed by means of experimental tests on industrial AA6060 Aluminium alloy tubes (natural aged) under laboratory-controlled conditions.     

Mixed integer simulation optimization for optimal hydraulic fracturing and production of shale gas fields

Optimal development of shale gas fields involves designing a most productive fracturing network for hydraulic stimulation processes and operating wells appropriately throughout the production time. A hydraulic fracturing network design—determining well placement, number of fracturing stages, and fracture lengths—is defined by specifying a set of integer ordered blocks to drill wells and create fractures in a discrete shale gas reservoir model. The well control variables such as bottom hole pressures or production rates for well operations are real valued. Shale gas development problems, therefore, can be mathematically formulated with mixed-integer optimization models. A shale gas reservoir simulator is used to evaluate the production performance for a hydraulic fracturing and well control plan. To find the optimal fracturing design and well operation is challenging because the problem is a mixed integer optimization problem and entails computationally expensive reservoir simulation. A dynamic simplex interpolation-based alternate subspace (DSIAS) search method is applied for mixed integer optimization problems associated with shale gas development projects. The optimization performance is demonstrated with the example case of the development of the Barnett Shale field. The optimization results of DSIAS are compared with those of a pattern search algorithm.