Critical Design Issues Research Articles

Data selection methods for Soft Sensor design based on feature extraction

Data selection is a critical issue in data-driven soft sensor design. The paper proposes a new method for data selection based on a feature extraction step, followed by data selection algorithms. The method has been applied to an industrial case study, i.e., the estimation of the quality of processed wastewater produced by a Sour Water Stripping plant working in a refinery. The paper reports the results obtained with different data selection algorithms. The comparison has been performed both by using raw data and the feature extraction phase.

How to apply mitigating actions against critical raw materials issues in mechanical design

Circular economy, sustainability and design for environment are some of the keywords that identify new formidable challenges to be faced in the next years. Raw materials have a dominant role in reaching that goal. Green energy, electric vehicles, communication, etc. depends on raw materials labeled as critical because of their economic importance coupled with high supply risk. For this reason, mitigating actions need to be used in materials selection and design such as material substitution, materials efficiency improvement and recycling. In this work, a method to implement raw materials criticality issues in materials selection for mechanical design is described according to the recent literature. The strategy is based on Ashby’s approach and the definition of the alloy criticality index quantifying the criticality per unit of mass of the material.

A Review of Automatic Vehicle Following Systems

There has been considerable interest recently in the development of connected and autonomous vehicles (CAVs). Automatic vehicle following capability is central for CAVs; in this article, we provide a review of the critical issues in the longitudinal control design for automatic vehicle following systems (AVFS) employed by CAVs. This expository review differs from others in providing a review of underlying methodologies for design of AVFS and the impact of AVFS on traffic mobility and safety.

High-Rise Social Housing in Hot-Humid Climates: Towards an ‘Airhouse’ Standard for Comfort

The pressure to provide social housing in a fast and economic way, as well as outdated regulations, constrain the design of these buildings, having serious implications for the comfort of occupants and the environment. This becomes more critical in hot-humid climates, such as Malaysia, with uniformly high temperature and humidity and low wind speeds. In its capital, Kuala Lumpur, an extensive program of construction for high-rise social housing is being carried out, however, shortly after the flats are occupied, or as soon as they can afford it, the residents fit wall mounted air conditioning units. This research started by looking at Malay vernacular architecture and the traditional strategies for ventilation and cooling. After a review of current building regulations and green tools employed in the country, two campaigns of fieldwork were carried out to assess the actual indoor and outdoor thermal and air quality conditions in the buildings, which were found to be inadequate for both the local regulations and international recommendations. The fieldwork also allowed the identification of the critical design issues to address. A ventilation and filtering ceiling system has been identified as one of the possible solutions for the current situation and has been tested through physical and computer models. The system improves comfort by reducing the air temperature, humidity, and amount of airborne particles and gases, as well as constantly providing an adequate airflow rate. It is the first attempt to develop what we have named the ‘airhouse’ standard for tropical countries.

The Economic Effects of Private Equity Buyouts: A Comment

Davis, Haltiwanger, Handley, Lerner, Lipsius, and Miranda (2019) produce an extension to the Davis et al. collection without addressing the critical research design issues raised in Ayash and Rastad (2017) and Ayash and Rastad (2018). First and foremost, the authors misrepresent their sample as specific to leveraged buyouts; it is not. We clearly illustrates this fact. Policy makers do not have an issue with venture capital and growth equity buyouts giving piles of cash to firms they acquire because of the subsequent investment in research and development, innovation, jobs and physical capital. However, policy makers cannot learn about the subject of interest, controversial leveraged buyouts, when these make up such a small portion of the sample tested in Davis et al. collection (Davis, Haltiwanger, Jarmin, Lerner, and Miranda, 2008 and Davis, Haltiwanger, Jarmin, Lerner, and Miranda, 2011 focus on employment, Davis, Haltiwanger, Jarmin, Lerner, and Miranda, 2009 presented at the World Economic Forum introduces productivity to the analysis, Davis, Haltiwanger, Handley, Jarmin, Lerner, and Miranda, 2013 brings it all together, and the final published version is Davis, Haltiwanger, Handley, Jarmin, Lerner, and Miranda, 2014). Unfortunately, these authors continue to obfuscate our understanding of the economic effects of these complex transactions due to the fact that they cannot observe leverage; they treat all buyouts as equivalent to leveraged buyouts. We therefore gladly expand our analysis to bring light to these researchers who have been in the dark for more than a decade.

A New Domain Specific Scripting Language for Automated Machine Learning Pipeline

This paper concerns on two difficulties faced by non-experts’ users in the utilization of machine learning; design of the model and the programming task for implementation. From the varieties of the machine learning algorithms, selecting the best model with the best configurations is a critical and complex design issue. In light of this situation, automated machine learning pipeline is highly beneficial. Research has proved that Genetic Programming is highly useful to find the best pipeline of an automated machine learning model. However, in respond to the implementation difficulty, there exists a limited software tool that support easy implementation for automated machine learning based on Genetic Programming. This paper presents the specifications of a domain specific scripting language for the easy development of an automated machine learning with the underlying Genetic Programming. The scripting language has a very minimal characters of codes, hence easier to understand and more concise than the Python programming language.

Building Empathy and Intercultural Citizenship through a Virtual Exchange Project

Building Empathy and Intercultural Citizenship through a Virtual Exchange Project

Numerous Clustering Techniques with Application and Limitations in Wireless Sensor Network

Wireless Sensor Network (WSN) is a very common area to work with different technology which is very useful for real time application. There are various application works with the help of WSN .some of internet of things, machine learning, big data etc. in WSN there are four basic component of WSN that is sensing unit, transceiver unit, processing unit, and storage unit. Energy is the important critical design issue in WSN. By applying clustering approach we can save the energy and attain load balancing of a network. Sensor nodes are viewed as homogeneous since the looks into in the field of WSNs have been advanced, however, a few nodes might be of various energy levels and it is draw out the lifetime of a WSN and its unwavering quality. Clustering methods are required so that sensor networks can work long time with different area. In this paper, we discussed the various clustering techniques those are helpful to maximize the lifespan of WSN.

Coverage optimization of visual sensor networks for observing 3-D objects: survey and comparison

Coverage is a basic and critical issue for design and deployment of visual sensor networks, however, the optimization problem is very challenging especially when considering coverage of three-dimensional (3-D) scenarios. This paper provides a brief survey of mainstream coverage optimization methods for visual sensor networks, including the greedy algorithm, genetic algorithm (GA), particle swarm optimization (PSO), binary integer programming (BIP) and differential evolution algorithm (DE). We provide an efficient open-source C++ implementation of these algorithms and compare their performance on a typical camera deployment problem for coverage of 3-D objects. In order to improve the computational efficiency, a parallel visual occlusion detection approach is proposed and implemented with graphic processing units (GPUs), which are then integrated into all of the aforementioned optimization approaches for a fair comparison. Evaluation results show that (1) the proposed parallel occlusion detection algorithm largely improves the computational efficiency; (2) among the five typical approaches, BIP has the best coverage performance yet with the highest time cost, and greedy algorithm is the fastest approach at the price of coverage performance; GA, PSO, and DE achieve a compromise between the performance and the time cost, while DE has better coverage performance and less time cost than PSO and GA. These results could serve as engineering guidelines and baselines for further improvement of coverage optimization algorithms.

Simulation-only experiments to mimic the effects of the reality gap in the automatic design of robot swarms

The reality gap—the discrepancy between reality and simulation—is a critical issue in the off-line automatic design of control software for robot swarms, as well as for single robots. It is understood that the reality gap manifests itself as a drop in performance: when control software generated in simulation is ported to physical robots, the performance observed is often disappointing compared with the one obtained in simulation. In this paper, we investigate whether, to observe the effects of the reality gap, it is necessary to assume that the control software is designed in a context that is simpler than the one in which it is evaluated. In the first experiment, we show that a performance drop may be observed also in an artificial, simulation-only reality gap: control software is generated on the basis of a simulation model and assessed on a second one. We will call this second model a pseudo-reality. We selected the simulation model to be used as a pseudo-reality by trial and error, so as to qualitatively replicate previously published observations made in experiments with physical robots. The results show that a performance drop occurs even if we can exclude that pseudo-reality is more complex than the simulation model used for the design. In the second experiment, we eliminate the trial-and-error selection of the first experiment by evaluating control software across multiple pseudo-realities, which are sampled around the original simulation model used for the design. The results of the second experiment confirm those of the first one and show that they do not depend on the specific pseudo-reality we previously selected by trial and error. Moreover, they suggest that one could use multiple pseudo-realities to evaluate automatic design methods and, from this simulation-only evaluation, infer their robustness to the reality gap.

Design and Testing of a New Vascular Stent with Enhanced Fatigue Life

Vascular stents could suffer from repetitive motions due to pulsatile blood pressure and daily activities. Stent fatigue resistance has thus become a critical issue for stent design. In this paper, an intriguing stent design concept aimed at enhancing the fatigue life was investigated. The concept was to re-distribute stresses more uniformly by tapering the stent strut width. Finite element models were developed to evaluate the mechanical integrity and fatigue safety factor of the stent under various loading conditions. Simulation results show that the fatigue safety factor of this novel stent design increased by 4 times that of a conventional stent. Conceptual stent prototypes were cut by a pulsed-fiber laser, followed by a series of expansions and heat treatments to gradually shape the stent to its target size. A rotating bending fatigue tester was built for this study and stent fatigue tests were conducted for proof of concept. Experimental results show that this stent design concept successfully enhanced the fatigue life as designed. Its fatigue cycle number jumped to 6∼7 times that of a conventional stent, which agreed well with the trend predicted by FEA simulations. The findings of this paper provide an excellent guide to greatly improve stent fatigue life.

Constructal Design of Elliptical Conduits for Cooling of Gas Turbine Blades with External Thermal Barrier Coating

Gas turbines (GTs) are thermal machines used to transform the energy released in combustion with a hydrocarbon into mechanical power, in order to drive a machine or generate thrust in aircraft. The critical issue in the GT design are the parts exposed to extreme mechanical and thermal conditions, e.g., the first row of turbine blades. The GT thermal efficiency is limited by the maximum temperature the blade materials can withstand without softening or creeping. Currently, the maximum operating temperature is above the softening point of the blade material thanks to techniques of ceramic coatings of low thermal conductivity, called Thermal Barrier Coating (TBC), and techniques of blade cooling. The internal cooling of blades involves conduits inside them for air that comes from a bleed in an intermediate compressor stage. The air bleeding is around 3 to 5% of the main GT flow. This air and the heat flow that it receives are not used to generate power, so it is necessary to optimize the cooling techniques in order to control the temperature using the least amount of air and minimum heat flux evacuated, for holding the GT overall efficiency high. The present work studies the internal cooling of Elemental Gas Turbine Blade (EGTB) with a fixed thickness of the TBC and the optimization of the conduit shape and position over a cross section in 2D. The optimization is carried out by exhaustive searching method based on the Constructal Theory. The optimization of the position, size, and aspect ratio of EGTBs was done for two types of standard elliptical conduits of different geometries, uniformly distributed. Two different objective functions are analyzed: minimum maximum temperature on the metal and maximum heat evacuation efficiency. The outcome of this work establishes that the use of elliptical conduits of aspect ratio 2:5 leads to improvement in the thermal performance of cooled blades. As compared with circular conduits of the same area, elliptical conduits allow transfer of a greater amount of heat; with a correct design, they enable a lower maximum temperature on the metal. Besides, the constructal designs obtained in this study for the minimum maximum relative temperature $$\tilde{T}_{\rm{max}}$$ or maximum heat evacuation efficiency ξ were not identical.

Power GaN FET boards thermal and electromagnetic optimization by FE modeling

This work deals with optimization of boards with commercial discrete power GaN FETs in applications where natural air convection is a strict constraint. In these cases, both thermal and electromagnetic behaviours are critical reliability issues for the board design, and they are modeled by Finite Element (FE) analysis, starting from literature description of the device structure, and measurements on a simple test circuit.For improved accuracy and more realistic modeling, verification and validation simulation steps are introduced, in order to evaluate the relevant error parameters for different FEM solutions.The results obtained demonstrate a good fitting with experimental and make it possible to improve board thermal characteristic. The electromagnetic simulations allow the evaluation, and possibly the reduction, of parasitic inductances for different layouts.Then, the proposed approach enables thermal and electromagnetic optimization of the layout design by simple FEM simulations, without any preliminary prototype, with time and cost saving.

Numerical Simulation of Wind Impacts on Building Blocks: Towards Sustainable Architecture Strategies

The study of wind behavior around tall buildings is a critical issue in architectural and structural design. Therefore, Tall modern buildings are extremely sensitive to the wind. Thus, the assessment of wind loads to design these buildings is essential. Monitoring the wind, which is forcing extraordinary tall buildings is highly challenging. By looking at recent constructions in Iran, it is obvious that despite the fact that constructing tall buildings is spreading, there is less concentration on environmental factors such as wind’s aerodynamic. The purpose of this study is to introduce a theoretical framework. Hence, by using CFD simulation, investigating on wind speed in various regions of the tall-triangular building have been focused. Finally, Autodesk Flow Design 2014 software is utilized to present a CFD simulation of a building model with a triangular footprint, Rounded Corner aerodynamic correction, and Set-back aerodynamic form. These simulations have been looking forward to finding out about how can aerodynamic forms affect pressure zone reduction in buildings and reduce wind flow pattern in urban regions.

Highly Improved Artificial Bee Colony Scheme to Enhance Coverage and Fault Tolerance in Sensor Networks

Wireless Sensor Networks (WSNs) consist of a large number of low-powered, low-cost and small sensors, which are communicating wirelessly with each other. Their target is to collect, process and communicate information about their surrounding environments. Due to the widespread of WSNs, fault tolerance is an important design issue to be considered. Fault tolerance refers to the ability of the system to continue operating in case of the failure of one or more nodes. There are many reasons for a node to fail in WSNs such as the failure in modules, the node out of the communication range, and due to battery depletion. Another critical design issue that needs to be considered in WSNs is the deployment issue. Nodes deployment determines the position of each node in the network. Many researchers have studied the dynamic deployment of the network in order to improve the coverage of the network using many techniques such as Artificial Ant Colony, Virtual Force (VF) and Artificial Bee Colony (ABC). This work considers both the dynamic deployment and fault tolerance issues at the same time. The goal of this work is to design an effective dynamic node deployment mechanism that recognizes the possibility of nodes failure in the future. Therefore, this paper's goal is not just to maximize the coverage area at the deployment time, but to maximize it in case of node failure as well. The proposed mechanisms will utilize Artificial Bee Colony in order to obtain an efficient solution. In this work, two schemes are proposed: the Improved Artificial Bee Colony (IABC) and the Highly Improved Artificial Bee Colony HIABC. Simulation results show that HIABC outperforms both IABC and ABC, while IABC outperforms ABC algorithm.

Health economic evaluation in orthotics and prosthetics: a systematic review protocol

BackgroundHealth economic evaluations are essential to support health care policy and investment decisions. To date, health economic evaluations in orthotics and prosthetics have focused on discrete components of an orthosis/prosthesis (e.g. a microprocessor controlled prosthetic knee joint) rather than the broader service provided by orthotist/prosthetists. As such, the contribution to orthotic/prosthetic policy and investment decisions is unclear. Whilst there are opportunities to conduct more informative health economic evaluations that describe the costs and benefits of the orthotic/prosthetic service, it is important that prospective research is informed by a critical review of the method design challenges and an understanding of how this research can be improved. The aim of this systematic review is to critically appraise the existing orthotic/prosthetic health economic evaluation literature and therefore determine evidence gaps, critical method design issues and the extent to which the literature informs orthotic/prosthetic policy and investment decisions.MethodsA comprehensive range of databases—AMED, EMBASE, MEDLINE and PsychINFO, Cumulative Index of Nursing and Allied Health Literature (CINAHL), ProQuest Nursing and Allied Health, Web of Science, Cochrane Database of Systematic Reviews (CDSR) and specialty health economic databases—will be searched using National Library of Medicine Medical Subject Headings (MeSH) terms as well as the title, abstract, and keyword terms. Search terms related to the intervention (e.g. orthosis), including variants used by varying professional disciplines (e.g. brace), will be used in preference to defining the populations that use orthotic and prosthetic services (e.g. people living with rheumatoid arthritis). Search terms related to health economic evaluations will be guided by previously developed and tested search strings and align with recommendations by the Canadian Agency for Drugs and Technologies in Health. Articles meeting the inclusion criteria will be hand-searched for relevant citations, and a forward citation search using Google Scholar will also be conducted to identify early online articles not yet indexed in traditional databases. Original research published in the English language and after 1 January 2000 will be included. The Checklist for Health Economic Evaluation Reporting Standards (CHEERS) and the Consensus on Health Economic Criteria (CHEC)-Extended list will be used to appraise the methodological quality and identify sources of bias. Data extraction and appraisal will be conducted by one reviewer independently using appraisal instrument guidelines and a content specific decision aid with exemplars. A subsequent review by a second researcher will be undertaken to confirm the accuracy of the extraction and appraisal, and a final review by a third where consensus cannot be reached. The data will be extracted to a purpose-built data extraction template with decision-making guidelines to support consistency. Where possible, the findings of the review will be reported as a meta-analysis, although the heterogeneity of the literature will likely mean a narrative review that illuminates method design issues that contribute to imprecision and variation will be more appropriate.DiscussionThis protocol has been purposefully designed to summarise the existing evidence and appraise the methodological approaches used and the quality of the health economic evaluations in orthotics and prosthetics. What we learn from this review will be used to guide further work in this area and design more rigorous health economic evaluations into the future.Systematic review registrationPROSPERO CRD42018116910.

Ground motion intensity measures for seismically isolated RC tall buildings

Seismic isolation is an effective method for realizing resilient reinforced concrete (RC) tall buildings. The selection of intensity measures (IMs) is a critical issue for a resilience-based seismic design of seismically isolated RC tall buildings. The predictive capability of IM may be affected by various factors, including structural systems, heights, seismically isolated schemes, fundamental periods, and types of ground motions. With emphasis on these factors, the predictive capability of various IMs for predicting critical engineering demand parameters (EDPs) was evaluated. To achieve these, forty-eight cases are designed based on four real engineering practices. Two sets of ground motions, particularly pulse-like near-fault ground motions, are adopted. The efficiency and sufficiency of 25 IMs in predicting four EDPs are evaluated. The IMs with high efficiency and relatively good sufficiency are identified and the corresponding sensitivities are further evaluated. The research outcome can assist in providing a useful reference for seismic design of seismically isolated RC tall buildings.

Energy-based considerations for the seismic design of ductile and dissipative glass frames

Current design standards for seismic resistant buildings provide recommendations for the advanced analysis of several structures subjected to earthquakes, but no specific details are given for structural glass systems. Compared to other constructional materials, and given the actual fail-safe design goals for earthquake resistant systems, critical design issues for glazed structures may derive from the lack of appropriate resistance but also from the limited accommodation of displacement demands. Such an outcome is strictly related to the intrinsic brittleness of glass, as well as to the typical geometrical and mechanical features of glass structures. As a result, joints and restraints can have a key role for design optimization purposes. This paper presents an energy-based analytical approach in support of the efficient design and the reliable structural performance evaluation of glass systems in seismic regions. Special care is spent for glass frames, giving evidence of their potential ductile and dissipative behaviour. More in detail, the proposed formulation takes advantage of the dissipative capacity of steel connections, for the non-linear structural analysis of seismic resistant glass frames. The reliability of the analytical method is first discussed via a practical application. Refined Finite Element (FE) numerical simulations are also presented, in support of the assessment and validation of the analytical findings. The collected results show that the combination of appropriate structural design assumptions and advanced non-linear analysis techniques can allow the achievement of highly efficient and satisfactory seismic performances of glass frames, even in the same order of other common structural systems.

Application of seismic design procedures on three modern URM buildings struck by the 2012 Emilia earthquakes: inconsistencies and improvement proposals in the European codes

The seismic performance of three modern unreinforced masonry buildings struck by the earthquake sequence of May 2012 in Emilia (Italy) has been investigated, to define the safety margins and possible critical issues in the seismic design according to the European seismic codes. The selected structures have been redesigned, applying linear and static nonlinear analyses, and verified against collapse according to both Eurocodes 6 and 8 and Italian Norms for Constructions. The design has provided inconsistent results, in particular with the application of Eurocodes, where none of the three buildings fulfilled the safety checks even at very low lateral action, although two of these structures did not attain any visible damage after the events of May 2012. The requirements of the Italian seismic code have provided, at least for static nonlinear analyses, results more in line with the actual seismic response of the buildings. The main issues and some proposals for the improvement of the codified procedures for seismic design of unreinforced masonry buildings are finally discussed.

Strategy for tuning the up-conversion intersystem crossing rates in a series of organic light-emitting diodes emitters relevant for thermally activated delayed fluorescence.

Accurate prediction on the up-conversion intersystem crossing rate (kUISC) is a critical issue for the molecular design of an efficient thermally activated delayed fluorescence (TADF) emitter, and the kUISC rate is considered to be mainly determined by the spin-orbit coupling matrix element (SOCME) and the singlet-triplet energy difference (∆EST). In the present contribution, we strategically designed a series of organic molecules, bearing an isoindole-dione core as the electron acceptor (A) unit and dinitrocarbazolyl, carbazolyl, diphenylcarbazolyl, dicarbazolyl and tercarbazolyl groups as the electron donor (D) units, respectively. Their SOCME and ∆EST values between the S1 and T1 states were calculated by the DFT and TD-DFT methodes, and the kUISC rates were estimated by using the semiclassical Marcus theory. The present studies indicate that as the π-conjugation in the D unit enhances, the ∆EST value gradually decreases, and the kUISC rate gradually increases. The molecule using tercarbazolyl as the D moiety is found to exhibit the largest kUISC in the present computations, as high as 1.22 × 106 s-1, which is of the same order of magnitude as an experimentally observed highly-efficient TADF emitter using a 4-benzoylpyridine as the A unit and the same tercarbazolyl group as the D moiety. The present results sufficiently prove the necessity of introducing strong electron-rich substituent groups when designing highly efficient TADF emitters.