Strategies For Improving Efficiency Research Articles

Efficiency Improvement Strategy for Multiple Operating Points in Doubly Fed Magnetic Geared Motor

The doubly fed magnetic geared motor, which has dual AC windings, can be operated with different frequencies in the inner and outer windings. However, the inner and outer windings have different numbers of pole pairs to meet the pole combination derived by the magnetic gearing effect, and hence undesirable space harmonic components of the magnetic flux are produced at the air gaps. These space harmonics affect the iron losses at each core, and the resultant iron loss and efficiency are varied by the frequencies of the inner and outer windings. Thus, in this paper, first, the effect of the space harmonic components of the air gap magnetic flux density in the inner stator, outer stator, and the modulating pieces is separately investigated. In addition, the iron loss characteristics of each ferromagnetic material are presented according to the frequency combinations in the inner and outer windings. Secondly, the iron loss maps and the efficiency maps according to the frequency conditions of the inner and outer windings are drawn, and the causes of the characteristic differences in each map are analyzed. Thirdly, the frequency control sequence and the roles of the inner and outer windings as the armature and field parts are changed, and the analysis of the iron loss map and efficiency map is repeated. Finally, the results in the inner-armature case and the outer-armature case are compared with each other, and the possibility of improving the overall operating efficiency over the multiple operating points by using the individual frequency control and frequency combination selection is proved.

A Novel Stochastic Two-Stage DEA Model for Evaluating Industrial Production and Waste Gas Treatment Systems

In recent decades, the high-speed development in China has caused serious air pollution in China. The present paper proposes a stochastic data envelopment analysis (DEA) model based on a general two-stage structure with comprehensively considering the randomness in both desirable and undesirable outputs to calculate the environmental efficiency of the industry system. The new proposed model is more applicable to practical system, and is applied to evaluate the performance of production and waste gas treatment in the industrial sector for China’s regions along the “One Belt and One Road” in 2015. The results show that about half of the regions along “One Belt and One Road” in China are inefficient, where the performance on waste gas treatment is significantly worse than that of industrial production. Further, the managers should take different strategies for efficiency improvement in different areas because of the obvious differences in efficiency scores, in which the regions in the southeast area should pay more attention to improving waste gas treatment efficiency while that in the northwest area need to focus on industrial production efficiency.

Theoretical studies on full-color thermally activated delayed fluorescence molecules

This work provides a detailed mechanism for exciton dynamics in D–π–A–π–D TADF molecules and strategies for further efficiency improvement.

Diesel efficiency improvement strategy

This thesis presents the author's method of analyzing the indicator diagrams of a diesel engine at idle mode, which have a two-peak nature, based on the theory of catastrophes in order to improve the operation process in this mode, and offers suggestions for improving this process.

Measuring regional differences of construction productive efficiency in China

PurposeAs one of the pillar sectors, China’s construction industry (CE) is not efficient in productivity with large regional gaps over the past decades. It is crucial for stakeholders to have insightful information on regional input of resources and output of productive efficiency for making policies and investment decisions. The purpose of this paper is to develop an efficiency measurement for the CE and explore the regional differences of construction productive efficiency across the three regions of China.Design/methodology/approachData envelopment analysis (DEA) is an objective benchmarking methodology used for measuring the performance of construction productivity. Distance friction minimization (DFM) approach, based on DEA model, is applied to identify the causes of inefficiency, sources of growth and the optimal paths to efficient frontier for regional CE. Further studies are conducted to provide insightful information for efficiency improvement, according to DFM modeling results and empirical analysis.FindingsThe results indicate that eastern region leads construction development due to strong performance of coastal provinces. Faced with decreasing supply of skilled workers in developed region, investing more on construction plants and equipment for labor savings is more efficient to the long-term productivity growth of CE in the east. For developing midland region, heavy reliance on cheap manpower should be gradually relieved by allocating more budgets to vocational training and education program to boost quality labor supply, as well as making steady investment on construction equipment and advanced technology. In underdeveloped western region, raising construction labor wages is recommended to attract more workers to meet the market demand and achieve an optimal production efficiency in the CE.Originality/valueThe findings provide insights into the causes of inefficiency, the sources of growth and the best strategies for efficiency improvement in regional CE, recommendations are made for policy making and strategic planning to enhance the overall performance of China’s construction productive efficiency.

Energy Efficiency Improvement Assessment in Africa: An Integrated Dynamic DEA Approach

In Africa, energy plays an important role in the processes of economic and sustainable development. However, inefficiency such as mismanagement of resources constrains productivity. Prior energy efficiency studies in Africa have failed to provide the paths through which energy efficiency improvement can be achieved. The current study aims to assess energy efficiency improvement among 25 selected countries in Africa. First, the dynamic slack-based measure (DSBM) data envelopment analysis (DEA) model is applied to gauge the efficiency measurement. Further, the Malmquist productivity index (MPI) is employed to investigate the energy efficiency improvement during 2006–2014. Empirically, the results from the dynamic slack-based measure (DSBM) model show that energy efficiency in Africa is generally low. Also, the findings from the MPI suggest there is no significant improvement in energy efficiency in Africa. Based on the estimated results, some energy efficiency improvement strategies are further proposed for sample countries in Africa.

The Rise of Perovskite Light-Emitting Diodes.

Recently, metal halide perovskite materials have attracted great interest in both photovoltaic and electroluminescent devices. The external quantum efficiency of the perovskite light-emitting diodes (pero-LEDs) has grown to over 20% within four years, and the operational lifetime has been improved to tens of hours. These achievements make pero-LEDs very promising technology in solid lighting and displays. In this Perspective, we first give a general introduction of the pero-LEDs; we then discuss various pero-LEDs with different cell configurations and perovskite emitting structures; to conclude, we propose some efficiency improvement strategies and development opportunities of pero-LEDs. Provided that we can continually improve efficiency and operational lifetime of pero-LEDs, we can make them more and more compatible with other mature technologies, like organic LEDs and inorganic LEDs, and then finally realize their practical application in daily life.

Variable valve actuation–based combustion control strategies for efficiency improvement and emissions control in a heavy-duty diesel engine

High nitrogen oxide levels of the conventional diesel engine combustion often requires the introduction of exhaust gas recirculation at high engine loads. This can adversely affect the smoke emissions and fuel conversion efficiency associated with a reduction of the in-cylinder air-fuel ratio (lambda). In addition, low exhaust gas temperatures at low engine loads reduce the effectiveness of aftertreatment systems necessary to meet stringent emissions regulations. These are some of the main issues encountered by current heady-duty diesel engines. In this work, variable valve actuation–based advanced combustion control strategies have been researched as means of improving upon the engine exhaust temperature, emissions, and efficiency. Experimental analysis was carried out on a single-cylinder heady-duty diesel engine equipped with a high-pressure common-rail fuel injection system, a high-pressure loop cooled exhaust gas recirculation, and a variable valve actuation system. The variable valve actuation system enables a late intake valve closing and a second intake valve opening during the exhaust stroke. The results showed that Miller cycle was an effective technology for exhaust temperature management of low engine load operations, increasing the exhaust gas temperature by 40 °C and 75 °C when running engine at 2.2 and 6 bar net indicated mean effective pressure, respectively. However, Miller cycle adversely effected carbon monoxide and unburned hydrocarbon emissions at a light load of 2.2 bar indicated mean effective pressure. This could be overcome when combining Miller cycle with a second intake valve opening strategy due to the formation of a relatively hotter in-cylinder charge induced by the presence of internal exhaust gas recirculation. This strategy also led to a significant reduction in soot emissions by 82% when compared with the baseline engine operation. Alternatively, the use of external exhaust gas recirculation and post injection on a Miller cycle operation decreased high nitrogen oxide emissions by 67% at a part load of 6 bar indicated mean effective pressure. This contributed to a reduction of 2.2% in the total fluid consumption, which takes into account the urea consumption in aftertreatment system. At a high engine load of 17 bar indicated mean effective pressure, a highly boosted Miller cycle strategy with exhaust gas recirculation increased the fuel conversion efficiency by 1.5% while reducing the total fluid consumption by 5.4%. The overall results demonstrated that advanced variable valve actuation–based combustion control strategies can control the exhaust gas temperature and engine-out emissions at low engine loads as well as improve upon the fuel conversion efficiency and total fluid consumption at high engine loads, potentially reducing the engine operational costs.

Estimation of the workload boundary in socio-technical infrastructure management systems: The case of Belgian railroads

Abstract Infrastructure systems are large-scale complex socio-technical systems that rely on humans for their safety critical decision-making activities. In the case of railroad networks, hierarchical organizations denoted as traffic control centers (TCCs) operate 24/7 in order to maintain successful network operations. Interacting social and technical factors influence TCC operational environments and thus the overall performance of the railroad system. This research presents a novel data envelopment analysis (DEA) application along with its implementation and validation by investigating the workload boundary of human performance through a case study built for the Belgian railway (INFRABEL) TCCs. We pursue two research foci. The first is to identify organizational, socio-economic, and technical factors that describe the performance environments in which TCC personnel operate. We use these factors to determine relatively homogeneous performance environments using multivariate statistical methods. The second focus is to design and implement on-site a socio-technical performance measurement framework, based on a new and unique dataset at the workstation level that is capable of considering socio-technical heterogeneity. Our approach consists of three steps. First, we apply a two-stage clustering approach to generate statistically relatively homogeneous groups. Second, we calculate meta - and in-cluster efficiency scores. Finally, we assess the validity of our results with INFRABEL. Results reveal three insights: (i) efficiency improvement strategies require further investigation based on temporal trends; (ii) disregarding performance environment heterogeneity leads to over estimation in target setting; and (iii) socio-technical system design could be informed by applying DEA, provided that, domain specific expertise is used in the model formulation.

Self-Trapped Excitons in All-Inorganic Halide Perovskites: Fundamentals, Status, and Potential Applications.

Photoluminescence is a radiative recombination process of electron-hole pairs. Self-trapped excitons (STEs), occurring in a material with soft lattice and strong electron-phonon coupling, emit photons with broad spectrum and large Stokes shift. Recently, series halide perovskites with efficient STE emission have been reported and showed promise for solid-state lighting. In this Perspective, we present an overview of various photoluminescence phenomena with the emphasis on the mechanism and characteristics of emission derived from STEs. This is followed by the introduction of STE emission in hybrid halide perovskites. We then introduce all-inorganic STE emitters and focus in particular on the mechanism of STEs in double-perovskite Cs2AgInCl6 and strategies for efficiency improvement. Finally, we summarize the current photoluminescence and electroluminescence applications of STE emitters as well as the potential in luminescent solar concentrators and provide an overview of future research opportunities.

Efficiency Analysis of Logistics Centers Dedicated to Retail Type: A Case of a Korean Distribution Company

In today’s multi-channel distribution environment, it is crucial for the competitiveness of retail stores and companies to improve efficiency of dedicated logistics centers (DLCs) servicing types of retail outlets such as large retail-stores, super supermarkets, and convenient stores. This paper derives efficiency improvement strategies for DLCs through efficiency analyses. To this end, this paper empirically analyzes the efficiency of DLCs by applying DEA (data envelopment analysis) approaches using real data from a Korean distribution company. In detail, this paper analyzes operations, finance, and service efficiencies of DLCs and performs a comparison analysis on the efficiency between DLCs. Finally, this paper discusses the analysis results considering the DLCs’ characteristics and derives managerial and operational implications.

Petri net-based scheduling strategy and energy modeling for the cylinder block remanufacturing under uncertainty

Scheduling has been extensively applied to remanufacturing for the organization of production activities, and it would directly influence the overall performance of the remanufacturing system. Since the conjunction of Petri net (PN) and artificial intelligence (AI) searching technique was demonstrated to be a promising approach to solve the scheduling problems in manufacturing systems, this study built a transition timed PN combined with heuristic A* algorithm to deal with the scheduling in remanufacturing. The PN was applied to the formulation of remanufacturing process, while the A* algorithm generated and searched for an optimal or near optimal feasible schedule through the reachability graph (RG). We took the high value-added cylinder block of engine as a research object to minimize the makespan of reprocessing a batch used components. This scheduling problem involved in batch and parallel processing machines, and the uncertain processing time and routes will complicate the scheduling problem. Three heuristics were designed to guide the search process through the RG in PN. To avoid state space explosion and select promising nodes, a new rule-based dynamic window was developed to improve the efficiency of the algorithm, and this rule was examined to outperform the conventional one. Under the determined scheduling strategy, the dynamic behavior of energy consumption rate during the processing time was simulated using PN tool, which would assist remanufacturers to develop potential strategies for energy efficiency improvement. Considering the uncertainty of processing time, the Monte Carlo simulation method was adopted to statistically analyze the distributions of makespan and total energy consumption, which would contribute to the comprehensive production scheduling and energy profile assessment for sustainable remanufacturing.

Phytoextraction of heavy metals from contaminated soil, water and atmosphere using ornamental plants: mechanisms and efficiency improvement strategies.

Accumulation of heavy metals (HMs) in soil, water and air is one of the major environmental concerns worldwide, which mainly occurs due to anthropogenic activities such as industrialization, urbanization, and mining. Conventional remediation strategies involving physical or chemical techniques are not cost-effective and/or eco-friendly, reinforcing the necessity for development of novel approaches. Phytoextraction has attracted considerable attention over the past decades and generally refers to use of plants for cleaning up environmental pollutants such as HMs. Compared to other plant types such as edible crops and medicinal plants, ornamental plants (OPs) seem to be a more viable option as they offer several advantages including cleaning up the HMs pollution, beautification of the environment, by-product generation and related economic benefits, and not generally being involved in the food/feed chain or other direct human applications. Phytoextraction ability of OPs involve diverse detoxification pathways such as enzymatic and non-enzymatic (secondary metabolites) antioxidative responses, distribution and deposition of HMs in the cell walls, vacuoles and metabolically inactive tissues, and chelation of HMs by a ligand such as phytochelatins followed by the sequestration of the metal-ligand complex into the vacuoles. The phytoextraction efficiency of OPs can be improved through chemical, microbial, soil amending, and genetic approaches, which primarily target bioavailability, uptake, and sequestration of HMs. In this review, we explore the phytoextraction potential of OPs for remediation of HMs-polluted environments, underpinning mechanisms, efficiency improvement strategies, and highlight the potential future research directions.

Fail-safe optimization of beam structures

Abstract In the current work, a fail-safe optimization of beam structures is carried out. This approach may provide an insight into the robustness of lattice structures. The use of beam elements allows a commonly used engineering approach for obtaining a fail-safe design to be applied. This consists of removing one beam element at a time and optimizing the remaining structure. At the end of the process, the maximum beam radii are used for the final design. This approach is computationally extremely expensive for lattice structures, as it requires one optimization per removed beam. In our contribution, we show that the design obtained from this approach does not actually achieve the desired fail-safe behaviour. We therefore apply a multi-model approach in which the fail-safe requirement is an optimization constraint. This is still computationally demanding and therefore, methods for reducing the number of failure cases to be considered within the optimization are discussed. Furthermore, the p-norm is applied to the stress constraints to reduce the computational effort for the gradient calculation. Reduction of failure cases and use of the p-norm have opposite effects on the conservatism of the result and therefore compensate each other to some extent. Highlights Stress constrained optimization of beam structures. Evaluation of different approaches for fail-safe design. Strategies for efficiency improvement (reducing failure cases/p-norm).

Energy Efficiency Improvement Strategies for Boilers: A Case Study in Pharmacy Industry

Energy resources are gradually scarce and expensive. Raised a gap between increasing demand and energy supply. Bridging gap of demand together with energy supply by increase energy supplies is a very costly decision. Moreover, in the industrial sector with the high cost of energy, the longer the competitiveness decreases. Energy costs in total production costs reduce the number of profits each year. The strategy to prevent these problems is by increasing the efficiency of industrial operations and equipment. Several stages of the efficiency process begin with identifying balance, energy-saving opportunities, and energy utilization. This stage is better known as an energy audit. The advanced stage of the energy audit helps identify potential energy conservation and encourages the industry to focus on efficiency and conservation and is supported by adequate financing. In the research strategy, the opportunity to save energy costs in oil boiler units is practical, sustainable and economically feasible. On the results of measurements and calculations obtained boiler efficiency of 53.67% where the factors that cause the low efficiency of this boiler are the high excess water by 17.32% and heat loss from dry exhaust gas by 42.03%. The solution is done by controlling excess air by regulating the air entering the combustion chamber. In this way, energy savings can be increased by 15%.

Plasmon-Enhanced Solar Water Splitting on Metal-Semiconductor Photocatalysts.

Photocatalytic water splitting using solar energy has been widely studied as a promising method for clean energy production. Continued efforts have been made to enhance the performance of solar-to-fuel energy conversion. The introduction of localized surface plasmon resonance (SPR) has been proposed as a promising strategy to enhance the efficiency of photocatalytic water splitting. This review presents an overview of the recent progress in the development of plasmonic photocatalysts for solar water splitting. Plasmon-enhanced mechanisms, including hot electron injection, near-field effects, and light scattering/trapping, are discussed. Furthermore, recent relevant works to discuss the emerging strategies for efficiency improvement and better understanding of the mechanisms are summarized. Finally, the perspectives of plasmonic photocatalysts for water splitting and the possible research directions are presented and discussed.

A review of energy efficient methods for all-electric ships

With stringent environmental regulations and growing concerns on energy consumption of the marine transport sector, there is a serious effort to make on board energy system more efficient. Improving fuel efficiency is conceived as a sustainable measure in terms of reducing greenhouse gas (GHG) emissions and overall marine energy use. As such, electrification of ship propulsion has been introduced as a solution for operating at higher efficiency and hence more saving fuel. However, energy efficiency in the context of marine transport is to be more stringent over time as required by International Maritime Organization (IMO). The energy performance indicators to evaluate such requirements include Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational Indicator (EEOI). Several energy efficient methods are therefore proposed to further improve fuel efficiency on board electric vessels. These involve integration of energy storage system, implementation of DC distribution, optimal power distribution and scheduling as well as various operational practices that are currently applicable for existing conventional vessels. The paper summaries the concept of ship energy efficiency in terms of the standard indicators and provide a brief review on the energy efficiency improvement strategies published in literature. The aim of the review is to analyze the methods that are potential to incorporate into the autonomous system of all-electric vessels. The results show a significant variation in reported efficiency gain and thus a combination of various methods is suggested to achieve full potential for emissions reduction.

An insight of World Health Organization (WHO) accident database by cluster analysis with self-organizing map (SOM)

ABSTRACTObjective: Road crashes are increasing every year in low- and middle-income countries compared to high-income countries, which show decreasing trends. One theory may be because of differences in enforcement of laws, vehicle safety, road standards, and many other factors. A detailed review was made of 5 death trends (total number of deaths/100,000 population and percentages of 4-wheeler, pedestrian, motorized 2/3-wheeler, bicyclist) and the underlying patterns in different countries and regions across the world. This review was done to understand the main reasons for the variances to focus on efficient improvement strategies related to future vehicle and road safety issues.Methods: A self-organizing map (SOM) technique is used to map the nonlinear relationships among different attributes. Overall, 176 countries with 44 attributes were considered from the World Health Organization's (WHO) Global Status Report on Road Traffic Crashes database. Of the 44 attributes, 5 related to accident deaths were considered as response attributes.Results: Very distinct and unique cause–effect patterns for 3 clusters were observed from SOM results. High-income countries were found to have a lower total number of deaths/100,000 population. One theory espouses that this was due to those countries maintaining high vehicle standards and policies, whereas it was quite a different situation for low-income countries. Even though helmet laws were available in Association of South East Asian Nations + 6 (ASEAN + 6) countries, the percentage of 2/3-wheeler deaths may be higher due a lack of enforcement of those laws. Percentage of deaths involving 4-wheeler vehicles was higher in certain countries in the Persian Gulf, the United States, Australia, and New Zealand. This may be due to the fact that these countries have a number of rural areas where drivers drive at highway speeds versus some lower income countries with more urban areas where drivers operate vehicles at slower speeds. Countries with a lack of laws protecting bicyclists saw higher death percentages among bicyclists. The percentage of bicyclist deaths was also higher in areas with no helmet requirement and no investment in infrastructure improvements. The percentage of pedestrian deaths was high when there was no policy to separate road users, especially in low-income African countries. Deaths can be reduced by enforcement of laws and practicing good safety standards related to road traffic.Conclusions: Future vehicle and road safety strategies should consider using advanced statistical tools like SOM to advance safety. Based on a triple-layer (vehicle, infrastructure, and society) safety approach, strict regulations and enforcement are effective measures to reduce fatalities in low- and middle-income countries. On the other hand, introduction of more advanced vehicle technologies will be useful in countries with high gross national incomes (GNIs). Hence, a proper balance of different countermeasures based on economic zones could be effective to reduce total world traffic casualties.

Crank angle-resolved exergy analysis of exhaust flows in a diesel engine from the perspective of exhaust waste energy recovery

Exhaust waste energy recovery (WER) is a critical component in the portfolio of efficiency improvement strategies being considered for internal combustion engines. This paper addresses an important existing knowledge gap by introducing a methodology for performing crank angle-resolved exergy analysis of exhaust flows from the perspective of exhaust WER in diesel engines. To this end, a single-cylinder research engine (SCRE) operating in conventional diesel combustion mode was tested at a load of 5 bar brake mean effective pressure (BMEP), speeds of 1200 and 1500 rpm, and boost pressures of 1.2, 1.5, 2, and 2.4 bar. The crank angle-resolved specific exergy and its thermal and mechanical components were calculated by combining experimental crank angle-resolved exhaust manifold pressure measurements with 1D system-level (GT-POWER) simulations. In addition, exhaust flow specific exergies in the “blowdown” and “displacement” phases of the exhaust process, the total exergy flow rates, and cumulative (time-integrated) exergy were quantified. The results obtained show that low boost pressures led to the highest crank angle-resolved specific exergy, the lowest specific mechanical exergy, and the highest specific thermal exergy. In general, the specific thermal exergy was dominant during the initial phase of the exhaust process while the specific mechanical exergy became important after peak mass flow rate was attained. Regardless of engine speed, with increasing boost pressure, the mechanical component of the cumulative exergy in the exhaust flow increased while the thermal component decreased. Consequently, the results indicate that highly boosted conditions may be more appropriate for direct WER with positive displacement expanders that leverage the mechanical component of exhaust exergy while low boost operating conditions may be better suited for other WER strategies that utilize the thermal component of exhaust exergy.

Research on R&D Resource Allocation Efficiency Improvement Strategy in China

Focusing on short board is one of the key points to push forward the structural reform of the supply side and cross the "middle income trap". At present, China's economy into a new normal, economic growth from the original "factor-driven" into "innovation-driven." R&D as the core of scientific and technological innovation activities, its input scale and output efficiency has become a measure of a country or region of science and technology and innovation ability of the important indicators. In this paper, based on the research on the efficiency of R&D resources allocation and its influencing factors at home and abroad, this paper, based on the current development trend and actual situation of China's R&D, the lack of investment in R&D, the gap between regional industry and the lack of intellectual property protection, We will improve the efficiency of R&D resource allocation by improving the quality of personnel investment, promoting regional technological innovation, carrying out domestic and foreign cooperation and strengthening government cooperation.