Academic literature on the topic 'Technical efficiency (TE)'
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Journal articles on the topic "Technical efficiency (TE)"
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Mareth, Taciana, Antônio Márcio Tavares Thomé, Luiz Felipe Scavarda, and Fernando Luiz Cyrino Oliveira. "Technical efficiency in dairy farms." International Journal of Productivity and Performance Management 66, no. 3 (March 6, 2017): 380–404. http://dx.doi.org/10.1108/ijppm-09-2015-0131.
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Purpose This systematic literature review integrates the findings of existing studies regarding technical efficiency (TE) in dairy farms. The purpose of this paper is to offer a research framework that assembles TE descriptors, a classification of previous literature that provides the basis for the synthesis and research agenda. Design/methodology/approach This paper systematically reviews 86 survey research studies using rigorous and reproducible procedures. The review is applied to published survey research. Findings The framework relates context, inputs, outputs and metrics of TE. There is no agreement among the authors on the context and determinants of TE. The main determinants of TE are geographical location, farm size, investments in veterinary care, feeding and milking practice, TE model estimation techniques, public policy, and management-related variables. This paper offers ten propositions for future research on the controversial results on the determinants of TE. The authors also explore the reasons for the discrepant results based on the Debreu-Farrell’s definition of TE, the contingency theory and the resource-based view of the firm, elucidating the literature and serving as a basis for future investigation. Implications for dairy farmers and researchers close the review. Originality/value Meta-analysis and meta-regression studies were long at the forefront of reviews in the TE of dairy farms. This paper offers a novel qualitative research synthesis with frameworks and the classification of previous literature and a research agenda, which provides a new and different perspective for analysis, by innovating over the available quantitative procedures to combine statistical results.
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Musliu, Arben, Blend Frangu, Jennie S. Popp, Nathan Kemper, and Michael Thomsen. "TECHNICAL EFFICIENCY ESTIMATION OF DAIRY FARMING IN KOSOVO." New Medit 18, no. 3 (September 15, 2019): 77–84. http://dx.doi.org/10.30682/nm1903f.
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The aim of this research paper is to assess the technical efficiency (TE) of milk production in Kosovo using the stochastic frontier analysis. Research data are collected through surveys from 100 commercially oriented dairy farmers. The study finds that TE of milk production by most of these farms is high. Using the Cobb-Douglas production function, individual measures of TE range from 0.87 to 0.98 (on a scale of 0 to 1.00) with the average being 0.95. There were 57 farms with TE greater than 0.95 and 35 farms with TE less than 0.95. In the study’s sample, female dairy farmers have roughly the same mean TE of 0.95 as male dairy farmers. The variation in milk production among the sampled farms was modeled in terms of concentrate and forage feed costs and pre-production costs. The study suggests that concentrate feed and pre-production costs can significantly influence TE of milk production among Kosovar dairy farms.
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Náglová, Zdeňka, and Marie Šimpachová Pechrová. "Technical efficiency of the food and drink industry and its determinants." Agricultural Economics (Zemědělská ekonomika) 67, No. 10 (October 26, 2021): 409–22. http://dx.doi.org/10.17221/93/2021-agricecon.
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This study focuses on evaluating the technical efficiency (TE) of food and drink companies in the Czech Republic and on finding its determinants. The analysis is based on the data of 597 firms and uses the stochastic frontier method. We have identified the key players in the market and the less effective groups of processors. Foreign-owned companies have a strong position because of a better economy, but the results showed that their efficiency is comparable with that of Czech-owned companies. The results helped confirm that the size of the company influences its TE. The lowest efficiency was observed in small companies. TE also differed among branches of the food industry. The highest efficiency was in the bakery and milk industries, and the lowest efficiency was in fruit and vegetable processing. Subsidised firms reached a significantly higher efficiency. With respect to economic results, there is still a need to improve competitiveness through investments.
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Náglová, Zdeňka, and Tamara Rudinskaya. "Factors Influencing Technical Efficiency in the EU Dairy Farms." Agriculture 11, no. 11 (November 9, 2021): 1114. http://dx.doi.org/10.3390/agriculture11111114.
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This paper aims to analyse the technical efficiency (TE) of dairy farms and find its determinants. To accomplish this problem, the Stochastic Frontier Analysis was applied. The data were obtained from the Farm Accountancy Data Network database for dairy farms (TF15-45—Specialist dairying) for 2004–2019. Dairy farms were divided into four clusters according to their physical size (number of livestock units per farm) and economic size (standard output per farm). The largest farms by physical and economic size are located in Denmark and Cyprus. The smallest, in comparison, are in Bulgaria, Croatia, Latvia, Lithuania, Austria, Poland, Romania, and Slovenia. Farms in the EU are relatively technically efficient, i.e., they use their resources efficiently to produce maximum output (production). However, they have the potential to achieve better economic results and be more competitive, as the size of farms’ is not fully optimised. The abolition of the milk quota can be considered a factor in improving technical efficiency, as the indicator is higher after the abolition. New and old member states have almost comparable technical efficiency levels (the p-value of the t-test is 0.463), with old members having slightly higher level TE. Subsidies have contradictory effects on TE. Farm efficiency with higher subsidies per cow is higher for farms with €51–100/cow. However, as subsidies increase, TE decreases. Only the group of farms with the highest subsidies has a higher TE. More diversified farms are more technically efficient than specialised farms. Milk yield did not influence the analysed indicator. The analysis results can serve the stakeholders as a tool for modelling future agricultural policy, as the European farms are very heterogenous and show different conditions and economic outcomes.
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Anang, Benjamin Tetteh, Emmanuel Owusu Dokyi, Bright Owusu Asante, and Samuel A. Donkoh. "Technical efficiency of resource-poor maize farmers in northern Ghana." Open Agriculture 7, no. 1 (January 1, 2022): 69–78. http://dx.doi.org/10.1515/opag-2022-0075.
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Abstract Farm productivity in most developing countries remains low, hence the need to enhance technical efficiency (TE) of producers. This study evaluates the TE of maize production in rural Ghana, using primary data from a survey of smallholder producers. A two-stage double bootstrap data envelopment analysis (DEA) approach was used to assess TE and its determinants. The results revealed a bias-corrected mean TE of 68% (as opposed to 81% using the traditional DEA approach). Hence, with the prevailing technology and current input levels, farmers can increase their TE of maize production by 32%. TE increased with adoption of improved varieties, weeding frequency, and herd size but decreased with producer’s age, household size, educational status, and group membership. Subsequently, these factors need to be carefully considered in targeting policies for increasing maize productivity. The study observed increased adoption of improved varieties and training in efficient methods of weed control as important measures to enhance TE of maize farmers.
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Pisulewski, Andrzej, and Jerzy Marzec. "Heterogeneity, transient and persistent technical efficiency of Polish crop farms." Spanish Journal of Agricultural Research 17, no. 1 (April 15, 2019): e0106. http://dx.doi.org/10.5424/sjar/2019171-13926.
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Accounting for heterogeneity in the measurement of farm efficiency is crucial to avoid biases related to climate and soil quality diversity in a given area. Therefore, this paper investigates the level of technical efficiency (TE) of Polish crop farms based on several stochastic frontier panel data models with different approaches to the measurement of unobserved heterogeneity, short- and long- run inefficiency. In our study, we show that ignoring farm heterogeneity can lead to underestimation of the level of TE in conventional stochastic frontier panel data models. Moreover, we have found empirically that not accounting for heterogeneity in the Generalized True Random Effects model may lead to incorrect estimates of persistent TE. The obtained results for Polish crop farms indicate that the level of transient TE (0.81) is lower than the level of persistent TE (0.88). This result suggests that Polish farms may have, for example, problems with adopting new technologies and poor managerial skills.
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Islam, Md Sariful, and Mohammed Ziaul Haider. "Poverty and technical efficiency in presence of heterogeneity in household behaviours." International Journal of Social Economics 45, no. 11 (November 5, 2018): 1490–514. http://dx.doi.org/10.1108/ijse-04-2017-0171.
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Purpose The purpose of this paper is to investigate the relationship between poverty and technical efficiency (TE) of paddy farmers in presence of their heterogeneous selling behaviours. This paper explains how such behavioural heterogeneity affects this relationship in south-western Bangladesh. Design/methodology/approach Translog production frontier model was used to estimate TE since it fitted the data set better. On the other hand, poverty indices were constructed by using P-α method. Then, multinomial logit models examined the existence of heterogeneous selling behaviours. It revealed adequate evidences in favour of behavioural heterogeneity. Finally, the authors employed a series of two stage instrumental variable regression models to relate poverty and TE with and without considering the behavioural heterogeneity. Findings The study finds that around 18, 39 and 44 per cent of households exhibit autarkic, non-wholesaling and wholesaling behaviour, respectively. Market failure due to transaction cost and credit constraints leads to emergence of such heterogeneity. Across these heterogeneous behaviours, impact of improving TE on poverty status significantly differs. Without controlling behavioural heterogeneity, TE significantly improves the poverty status of the rural farm households. However, scenario is changed after controlling this heterogeneity. After behavioural segregations, TE improves poverty status only for wholesalers. In contrary to prior expectation, it worsens the poverty situation for both autarkic and non-wholesaling households. Simultaneous failure in both credit and product market for these households might be the plausible reason behind this heterodox finding. Credit market failure compels these households to borrow from local money lenders with costlier terms. This effort might improve their TE. But, product market failure makes their additional production due to improved TE unsold. Thus, repayment of credit directly reduces their consumption expenditure. Therefore, an effort to improve TE might increase prevalence and depth of poverty when market failure exists. Henceforth, the improvement of TE appears as an effective policy instrument only when households exhibit wholesaling behaviour. Originality/value The earlier studies show the relationship between TE and poverty status but did not account behavioural heterogeneity. The authors attempt to overcome this shortcoming and show how market failure induced behavioural heterogeneity affects the effectiveness of TE on improving poverty status of farm households.
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Zhao, Linlin, Lin Zhang, and Yong Zha. "Industrial Efficiency Evaluation in China: A Nonparametric Production-Frontier Approach." Sustainability 11, no. 18 (September 13, 2019): 5019. http://dx.doi.org/10.3390/su11185019.
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An industrial system has positive and negative strategies to adapt to environmental regulations, which can be defined as natural disposability and managerial disposability. Meanwhile, the operational process of an industrial system can be divided into regular production activities and pollutant control activities. Within this, industrial system’s technical efficiency (TE) can be decomposed into economic efficiency (ECE) and environmental efficiency (ENE). On the basis of natural disposability and managerial disposability, this paper proposes static and dynamic data envelopment analysis (DEA) models to evaluate the efficiencies of industrial systems. Based on the proposed approach, TE, ECE, ENE, and Malmqusit productivity index (MPI) values were obtained simultaneously. The MPI values were further separated into the effects of static efficiency change and technical change. The proposed method was applied to assess the technical efficiencies of Chinese regional industrial systems between 2011 and 2015. Key findings are that (1) the low ENE is the main source of technical inefficiency; (2) the average static TE and ENE under natural disposability are both lower than those under managerial disposability; (3) the static efficiency change and technical change of TE are similar to those of ENE; and (4) the technical change has a significant impact on the changes in TE.
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Afrin, Sonia, Mohammed Ziaul Haider, and Md Sariful Islam. "Impact of financial inclusion on technical efficiency of paddy farmers in Bangladesh." Agricultural Finance Review 77, no. 4 (November 6, 2017): 484–505. http://dx.doi.org/10.1108/afr-06-2016-0058.
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Purpose The purpose of this paper is to investigate the impact of financial inclusion on the enhancement of paddy farmers’ technical efficiency (TE). The impact was evaluated rigorously from different dimensions which could be useful in the policy discussion for enhancing efficiency in utilizing productive resources. Design/methodology/approach A cross-sectional data of randomly selected 120 paddy farmers from Khulna district in the Southwest region of Bangladesh were collected for this study. Initially, a stochastic production frontier approach was used for estimating farmers’ TE. Thereafter, ordinary least squares and quantile regression models were applied for unveiling the existing relationship between TE and various dimensions of financial inclusion after controlling all other socio-economic characteristics. Findings The study findings revealed that farmers were around 86 percent technically efficient and amongst them, credit takers were more efficient than non-credit takers. A non-monotonic relationship between TE and amount of credit was observed where TE was maximized at amount around 20,000 Bangladeshi Taka (USD255), a medium credit in terms of its amount. In addition, credit literacy was identified as a significant factor for improving TE. Though difference in the choice of sources for accessing credit had little impact on mean TE, its effect was found significantly higher for low scored technically efficient farmers compared to high scored farmers. Practical implications The policy toward widening the coverage of financial inclusion would be more effective than providing larger amount of credit to a limited number of farmers for improving their TE. Originality/value Such an in-depth assessment of the impact of financial inclusion on TE is probably the first effort in the Khulna district of Bangladesh.
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Mareth, Taciana, Luiz Felipe Scavarda, Antonio Marcio Tavares Thomé, Fernando Luiz Cyrino Oliveira, and Tiago Wickstrom Alves. "Analysing the determinants of technical efficiency of dairy farms in Brazil." International Journal of Productivity and Performance Management 68, no. 2 (February 11, 2019): 464–81. http://dx.doi.org/10.1108/ijppm-06-2018-0234.
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PurposeThe purpose of this paper is to analyse the determinants of technical efficiency (TE) in dairy farms located in the South of Brazil, aiming for a better understanding of the topic for academics, dairy farmers and policymakers to improve the productivity and competitiveness of dairy farms.Design/methodology/approachThis study was developed using a two-stage approach. Data envelopment analysis was used to estimate the TE level and regression models to understand the factors affecting TE in dairy farms. The sample size is 253 dairy farms in the South of Brazil.FindingsThe variation in the mean TE indexes reported in the literature can be explained by the attributes of the analysed studies, including the education of the farm operator, farm size (number of cows and milk), feed and labour costs, and use of services. Additionally, the results suggest that dairy farmers in the sample could increase milk output by 50.1 per cent (level of inefficiency) on average if they improve their TE.Originality/valueThis study makes three important contributions: first, it formulates hypotheses from the previous literature’s propositions on the estimation of TE in dairy farms; second, it tests the hypotheses in an empirical study to understand the main factors affecting the TE in dairy farms of the selected municipalities in the South of Brazil; and third, it compares previous findings on the determinants of TE in dairy farms serving different stakeholders, such as researchers, farmers and government representatives, to improve the productivity and competitiveness of dairy farms.
Book chapters on the topic "Technical efficiency (TE)"
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Liote, Laurent. "Modelling for the UK’s Utility-Scale Solar Regulation Change: Lessons for Transdisciplinary Engineering in Policy Practice." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220646.
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Meeting the UK’s net-zero greenhouse gases target by 2050 requires transdisciplinary engineering, it requires efficient exchange and collaboration between engineering and social science, between engineers and policy makers within the national government. Based on ethnographic fieldwork conducted within the UK’s department for Business, Energy and Industrial Strategy (BEIS), this paper explores how technical and policy expertise were mobilized and combined in a recent change in utility-scale solar policy. Taking a model developed by BEIS’ engineering advice team in collaboration with the established renewable policy team, this paper looks at what it means to give and receive engineering advice in the context of utility-scale solar regulation. Looking at the model design process from both the engineer’s and policy advisor’s perspectives highlights how concepts of expertise, disciplinarity compatibility and opposition impact policy and outcomes. The modelling process was successful in helping the negotiation and reconciliation of technical and social concerns to enable a change in utility-scale solar regulation satisfactory to industry and constituents. By drawing on this case, this paper ends on a wider discussion about how the generation of mutual trust and development of interactional knowledge between engineers and policy advisers enables TE in policy practice.
Conference papers on the topic "Technical efficiency (TE)"
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Xu, Xinqiang, Siyi Zhou, Mark Meyers, Bahgat G. Sammakia, and Bruce Murray. "Performance Analysis of a Combination System of Concentrating PV/T Collector and TEGs." In ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73062.
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Thermoelectric modules utilize available temperature differences to generate electricity by the Seebeck effect. The current study investigates the merits of employing thermoelectrics to harvest additional electric energy instead of just cooling concentrating photovoltaic (CPV) modules by heat sinks (heat extractors). One of the attractive options to convert solar energy into electricity efficiently is to laminate TE modules between CPV modules and heat extractors to form a CPV-TE/thermal hybrid system. In order to perform an accurate estimation of the additional electrical energy harvested, a coupled field model is developed to calculate the electrical performance of TE devices, which incorporates a rigorous interfacial energy balance including the Seebeck effect, the Peltier effect, and Joule heating, and results in better predictions of the conversion capability. Moreover, a 3D multiphysics computational model for the hybrid concentrating PV-TE/thermal (CPV-TE/T) water collector system consisting of a solar concentrator, 10 serially-connected GaAs/Ge PV cells, 300 couples of bismuth telluride TE modules, and a cooling channel with heat-recovery capability, is implemented by using the commercial FE–tool COMSOL™. A conjugate heat transfer model is used, assuming laminar flow through the cooling channel. The performance and efficiencies of the hybrid system are analyzed. As compared with the traditional PV/T system, a comparable thermal efficiency and a higher 8% increase of the electrical efficiency can be observed through the PV-TE hybrid system. Additionally, with the identical convective surface area and cooling flow rate in both configurations, the PV-TE/T hybrid system yields higher PV cell temperatures but more uniform temperature distributions across the cell array, which thus eliminates the current matching problem; however, the higher cell temperatures lower the PV module’s fatigue life, which has become one of the biggest challenges in the PV-TE hybrid system.
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Wang, Guanghua, Jordi Estevadeordal, James DeLancey, Jeremy Bailey, James Kopriva, and Gregory Laskowski. "Experimental and Numerical Investigations of the Heat Transfer and Flow Field in a Trailing Edge Cooling Geometry: Part 1 — Experimental Study With IR Thermography and PIV." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43841.
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Airfoil Trailing Edge (TE) cooling is critical for turbine blade and nozzle lifing and safety. Gas turbines overall efficiency enhancement requires further increasing of the turbine inlet temperature and decreasing of cooling flow usage. This requires more advanced TE designs to meet the inherent conflicting requirements. Aerodynamic requirements of thin TE, particularly in jet engines, lead to Pressure Side (PS) cutback of the TE with a span-wise slot forming uniform cooling film over the cutback/floor region. This study focused on the PS cutback TE film effectiveness and flow field measurements of a standard geometry with t/s=0.9. The measurements were conducted in a subsonic open loop wind tunnel with a generic setup to cover different TE running conditions. IR camera is used to measure the TE coupon surface temperature distribution. The test conditions are characterized by a constant main flow Mach number with constant gas temperature. CO2 at constant temperature is used as the coolant to reach the realistic blowing ratio and density ratio. Inlet boundary layer is measured by the Particle Image Velocimerty (PIV) to characterize the TE flow conditions and study the underlying flow physics. The experimental data for 2D wall contours and laterally-averaged profiles of adiabatic film effectiveness, velocity vector field and boundary layer profiles were discussed. These data will be used to provide inlet boundary conditions and validate CFD simulations in Part 2.
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Yazawa, Kazuaki, Yee Rui Koh, and Ali Shakouri. "Analytic Optimization of Cost Effective Thermoelectric Generation on Top of Rankine Cycle." In ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73195.
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Thermoelectric (TE) generators have a potential advantage of the wide applicable temperature range by a proper selection of materials. In contrast, a steam turbine (ST) as a Rankine cycle thermodynamic generator is limited up to more or less 630 °C for the heat source. Unlike typical waste energy recovery systems, we propose a combined system placing a TE generator on top of a ST Rankine cycle generator. This system produces an additional power from the same energy source comparing to a stand-alone steam turbine system. Fuel efficiency is essential both for the economic efficiency and the ecological friendliness, especially for the global warming concern on the carbon dioxide (CO2) emission. We report our study of the overall performance of the combined system with primarily focusing on the design parameters of thermoelectric generators. The steam temperature connecting two individual generators gives a trade-off in the system design. Too much lower the temperature reduces the ST performance and too much higher the temperature reduces the temperature difference across the TE generator hence reduces the TE performance. Based on the analytic modeling, the optimum steam temperature to be designed is found near at the maximum power design of TE generator. This optimum point changes depending on the hours-of-operation. It is because the energy conversion efficiency directly connects to the fuel consumption rate. As the result, physical upper-limit temperature of steam for ST appeared to provide the best fuel economy. We also investigated the impact of improving the figure-of-merit (ZT) of TE materials. As like generic TE engines, reduction of thermal conductivity is the most influential parameter for improvement. We also discuss the cost-performance. The combined system provides the payback per power output at the initial and also provides the significantly better energy economy [$/KWh].
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Korakianitis, T., I. A. Hamakhan, M. A. Rezaienia, and A. P. S. Wheeler. "Two- and Three-Dimensional Prescribed Surface Curvature Distribution Blade Design (CIRCLE) Method for the Design of High Efficiency Turbines, Compressors, and Isolated Airfoils." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46722.
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The prescribed surface curvature distribution blade design (CIRCLE) method is presented for the design of two-dimensional (2D) and three-dimensional (3D) blades for axial compressors and turbines, and isolated blades or airfoils. The original axial turbine blade design method is improved, allowing it to use any leading-edge (LE) and trailing-edge (TE) shapes, such as circles and ellipses. The method to connect these LE and TE shapes to the remaining blade surfaces with curvature and slope of curvature continuity everywhere along the streamwise blade length, while concurrently overcoming the “wiggle” problems of higher-order polynomials is presented. This allows smooth surface pressure distributions, and easy integration of the CIRCLE method in heuristic blade-optimization methods. The method is further extended to 2D and 3D compressor blades and isolated airfoil geometries providing smooth variation of key blade parameters such as inlet and outlet flow angles, stagger angle, throat diameter, LE and TE radii etc. from hub to tip. One sample 3D turbine blade geometry is presented. The efficacy of the method is examined by redesigning select blade geometries and numerically evaluating pressure-loss reduction at design and off-design conditions from the original blades: two typical 2D turbine blades; two typical 2D compressor blades; and one typical 2D isolated airfoil blade geometries are redesigned and evaluated with this method. Further extension of the method for centrifugal or mixed-flow impeller geometries is a coordinate transformation. It is concluded that the CIRCLE method is a robust tool for the design of high-efficiency turbomachinery blades.
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Yazawa, Kazuaki, and Ali Shakouri. "Exergy Analysis and Entropy Generation Minimization of Thermoelectric Waste Heat Recovery for Electronics." In ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/ipack2011-52191.
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Energy recovery from waste heat is attracting more and more attention. All electronic systems consume electricity but only a fraction of it is used for information processing and for human interfaces, such as displays. Lots of energy is dissipated as heat. There are some discussions on waste heat recovery from the electronic systems such as laptop computers. However the efficiency of energy conversion for such utilization is not very attractive due to the maximum allowable temperature of the heat source devices. This leads to very low limits of Carnot efficiency. In contrast to thermodynamic heat engines, Brayton cycle, free piston Stirling engines, etc., authors previously reported that thermoelectric (TE) can be a cost-effective device if the TE and the heat sink are co-optimized, and if some parasitic effects could be reduced. Since the heat already exists and it is free, the additional cost and energy payback time are the key measures to evaluate the value of the energy recovery system. In this report, we will start with the optimum model of the TE power generation system. Then, theoretical maximum output, cost impact and energy payback are evaluated in the examples of electronics system. Entropy Generation Minimization (EGM) is a method already familiar in thermal management of electronics. The optimum thermoelectric waste heat recovery design is compared with the EGM approach. Exergy analysis evaluates the useful energy flow in the optimum TE system. This comprehensive analysis is used to predict the potential future impact of the TE material development, as the dimensionless figure-of-merit (ZT) is improved.
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Li, Yuefeng, Huazhao Xu, Jianhua Wang, Wei Song, Ming Wang, Taiqiu Liu, and Xu Wang. "Application of Scale Adaptive Simulation Model to Studying Cooling Characteristics of a High Pressure Turbine Blade Cutback Trailing Edge With Different Cooling Configurations." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14234.
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Abstract Effective cooling structure design in the trailing edge (TE) of a high pressure turbine (HPT) blade is essential to increase turbine efficiency and maintain structural integrity. To obtain efficient cooling structures and understand clearly cooling mechanism, this paper adopted numerical simulation methods to investigate fluid flow and cooling characteristics in detail downstream of a HPT blade TE cutback region. The effects of typical TE configurations on cutback cooling performance are investigated including three types of internal turbulators (cylindrical pin fins and elliptic pin fins arranged in streamwise and spanwise orientations), the cutback with/without land extensions and three kinds of ejection lip profiles (one straight lip shape marked as “A” and two rounded lip shapes marked as “B” and “C”, respectively). The Scale Adaptive Simulation (SAS) is implemented to study the complex unsteady mixing process downstream of the cutback under operating condition of blowing ratio M = 0.65. The results from the Shear Stress Transport (SST) k-ω model are compared as well. SAS is capable to reproduce the periodical vortex shedding phenomena and resolve the vortices coherent structures. Compared with the experimental data, SAS provides more accurate predictions in terms of laterally averaged adiabatic cooling effectiveness ηaw and discharge coefficient Cd than the SST k-ω model. On the rear part of the cutback surface, large deterioration in ηaw is predicted by SAS for all configurations, but ηaw is considerably over-predicted by the SST k-ω model except for the case of elliptic pin fins with spanwise orientation. The elliptic pin fins with streamwise orientation significantly improve ηaw at the rear part of the cutback surface over the baseline model with cylindrical pin fins and slightly increase Cd. However, the elliptic pin fins with spanwise orientation drastically reduce the ηaw and Cd. Downstream of the cutback, the coherent structures are strongly disturbed and become chaotic compared to the TE with cylindrical and streamwise oriented elliptic pin fins. The application of land extensions only causes an evident change to the coherent structure immediate downstream of the lip, and slightly improves ηaw and reduces Cd over the baseline model on the rear part of the cutback surface. Rounded lip shapes B and C also show an obvious increase in ηaw on the rear part of the cutback surface but only a minor increase in Cd compared to the straight lip shape A. The rounded lip helps the coolant diffuse into the TE cutback and reduce the intensity of mixing. Due to larger rounding radius of shape B, the cooling effectiveness predicted by shape B is slightly better than shape C.
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Leonard, Thomas, Stephen Spence, Dietmar Filsinger, and Andre Starke. "Design and Performance Analysis of Mixed Flow Turbine Rotors With Extended Blade Chord." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90389.
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Abstract Mixed flow turbines offer additional design freedom compared with conventional radial turbines. This is useful in the automotive turbocharger application to reduce rotor inertia, which can be very beneficial for the transient response of a highly-boosted downsized passenger car powertrain. A previously published study from the authors analysed a series of nine mixed flow turbine rotors with varying blade cone angle and inlet blade angle. This paper reports an extension of that study with two further mixed flow turbine rotors where the chord length of the rotor blade was extended. The aim of this work was to understand both the aerodynamic and mechanical impacts of varying the chord length, particularly for the turbocharger application where off-design performance and transient response are very important. The baseline mixed flow rotor for this study had a blade cone angle of 30° and an inlet blade angle of 30°. Two further variations were produced; one with the TE extended in the downstream direction across the entire blade span. In the second variation the chord was extended at the hub corner only, while the shroud corner of the TE remained unchanged, with the aim of achieving some aerodynamic improvement while meeting mechanical requirements. When the blade was extended at both the hub and shroud, the inertia and stress levels increased significantly and the blade eigenfrequencies reduced. There was significant improvement in peak efficiency, but the mechanical performance was unfavourable. The improvement in peak efficiency was mainly due to better exhaust diffuser performance and therefore would not be realised in most turbocharger installations. The blade that was extended at only the hub corner incurred very little additional inertia, and the centrifugal stresses and blade eigenfrequencies were improved. Consequently, it was possible to reduce the blade thickness at the TE in order to achieve a more aerodynamically optimised design. In this case, the mechanical performance was acceptable and there were efficiency improvements of up to 1.1% pts at off-design conditions, with no reduction in peak efficiency or maximum mass flow rate. Therefore, the blade that was extended only at the hub produced some improvement within acceptable mechanical limits. The flow field features were considered for the three rotor geometries to explain the changes in loss and efficiency across the operating range.
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Adjei, Richard A., Weizhe Wang, Di Peng, Yingzheng Liu, and Takahiro Bamba. "Non-Uniform Tip Clearance Effects on Turbocharger Compressor Performance." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76837.
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In most turbocharger compressors, diffusers a re designed with contractions along the passage mainly for delaying surge. The width ratio parameter, B, which defines the diffuser inlet width to diameter ratio significantly affects the losses in the diffuser. Changes to tip clearance, for example, due to the impeller rubbing the shroud casing changes the fluid flow angle at the impeller exit. The sensitivity of the absolute flow angle to the width ratio parameter has a significant influence on diffuser effectiveness and stage performance. This paper reports an investigation of tip clearance sensitivity to vaneless diffuser and stage performance of a turbocharger compressor. To assess the correlation between performance parameters and the tip clearance, Design of Experiments (DoE) was used to sample 40 design cases by changing the clearance at the leading (LE) and trailing edges (TE) of the impeller. Parameters correlation was subsequently used to determine their relationship. The key findings were that stage efficiency and pressure ratio increased linearly with decreasing LE and TE clearances having a maximum sensitivity value R = 0.7. Diffuser Cp showed a strong positive correlation for TE and a weak negative correlation for LE. Similarly, work input and diffuser loss coefficient showed an inverse relation to diffuser Cp with a maximum R value of 0.9. It was concluded that increasing the tip clearance at TE improves the diffuser effectiveness. The main source of low diffuser Cp for small tip clearances was due to higher diffusion losses as a result of flow non-uniformity when the width ratio and absolute flow angle were large. As the width ratio decreases along the passage appreciable frictional losses occur in larger tip clearance further increasing the losses. The absolute flow angle and width ratio were observed to be key to diffuser and stage performance.
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Yıldırım, Nihat, Hakan I˙s¸c¸i, and Abdullah Akpolat. "Further Evaluation of Spur Gear Tooth Profile Designs Used in Heavily Loaded Transmissions." In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47404.
Full textAbstract:
Aerospace applications require special procedures for component design and manufacturing. Spur gears of different designs, because of their simpler geometries, are used in vital units-transmissions of helicopters and alike aerospace vehicles. In this study, performances of various profile designs of previously researched low and high contact ratio spur gears with some realistic design parameters are studied. Effects of the realistic parameters of variable tooth pair stiffness, relief shape, and adjacent pitch error on Transmission Error (TE), tooth loads and root stresses are presented; composition of these parameters determines the efficiency of the gearbox assembly. Detail of minimization of tooth root stress through optimized/proper design of relief is described. More comprehensive comparison of the gear tooth profile design cases is done to be able to guide aerospace transmission designers for practical applications with realistic parameters for each of the design cases. A preference order is done among the design cases, depending on effect of some design parameters on the results such as tooth loads, tooth root stresses, TE curves and peak-to-peak TE values.
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Cai, Liu-xi, Shun-sen Wang, Juan Di, Jing-ru Mao, Zhen-ping Feng, Jun-jie Zhang, and Ya-tao Xu. "Study of Erosion Characteristics of Solid Particles in the First Reheat Stage Blades of a Supercritical Steam Turbine." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-26674.
Full textAbstract:
Reducing solid particle erosion (SPE) of blades is one of the most urgent problems for supercritical steam turbine power generation technology. Based on the erosion rate models and the particle rebound models of blade materials obtained through the accelerated erosion test under high temperature, erosion characteristics of the first reheat stage blades in a supercritical steam turbine was simulated and analyzed by three-dimension numerical simulation method in this paper. The influence of operating conditions, particle size distribution in the inlet of nozzle and axial clearance between vanes and rotating blades on the erosion distribution of cascade were explored quantitatively. Results show that: the erosion damage of the first-reheat stage stator is mainly caused by suction surface impingement from oxide particles. In designed loading condition, small and median size of particles mainly eroded the trailing edge (TE) of nozzle pressure surface, while large particles mainly impinge the leading edge (LE) of rotating blades and the TE of vane suction surface, and erosion increase along the blade height. When the turbine is running under part-load condition, particle impingement angle on stator pressure surface is basically unchanged, while impingement velocity slightly reduced. However, the amount of particles that impinge the stator TE suction side after their first-time impingement on rotor LE increase rapidly, leading to the more severe erosion damage of stator suction surface. The particle size distribution in the inlet of nozzle has a significant effect on the erosion simulation of first reheat stage blades, and the size distribution sampled in one unit may not be used to other units. When axial clearance changes, the erosion weight loss of vane pressure surface near TE is basically held constant, while the erosion weight loss in vane suction surface near TE decreases with the increase of axial clearance. For the supercritical 600MW unit simulated in this article, the anti-SPE performance and the unit efficiency can be balanced well when the axial clearance increases to 13mm. The results in this paper will provide a technology basis for reducing oxide particle erosion in the first reheat stage blades of supercritical steam turbine.
Reports on the topic "Technical efficiency (TE)"
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Bravo-Ureta, Boris E., Eric Njuki, Ana Claudia Palacios, and Lina Salazar. Agricultural Productivity in El Salvador: A Preliminary Analysis. Inter-American Development Bank, February 2022. http://dx.doi.org/10.18235/0004020.
Full textAbstract:
The need to enhance food security while reducing poverty along with the growing threat imposed by climate change clearly reveal that it is imperative to accelerate agricultural productivity growth. This paper estimates micro-level production models to identify the major factors that have contributed to productivity growth in El Salvador, including irrigation, purchased inputs, mechanization, technical assistance, and farm size, among others. The econometric framework adopted in this investigation is grounded on recent panel data stochastic production frontier methodologies. The results obtained from the estimation of these models are used to calculate Total Factor Productivity (TFP) change and to decompose such change into different factors, including technological progress, technical efficiency (TE), and economies of scale. The findings imply that efforts are needed to improve productivity in both technological progress and technical efficiency where the latter is a measurement of managerial performance. This in turn indicates that resources should be devoted to promoting the adoption and diffusion of improved technologies while enhancing managerial capabilities through agricultural extension.
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Nin Pratt, Alejandro, and Héctor Valdés Conroy. After the Boom: Agriculture in Latin America and the Caribbean. Inter-American Development Bank, December 2020. http://dx.doi.org/10.18235/0002955.
Full textAbstract:
The convergence of a favorable macroeconomic environment and high prices of primary commodities between 2000 and 2011 contributed to the best performance of agriculture in Latin America and the Caribbean (LAC) since the 1980s, with steady growth of total factor productivity (TFP) and output per worker and a reduction in the use of input per worker. The end of the upward phase of the commodity cycle in 2011 together with less favorable external markets and a deterioration of the policy environment in several countries, motivates us to revisit the situation of agriculture in LAC in recent years to analyze how these changes have affected its performance. This study applies a framework that uses index numbers together with data envelopment analysis (DEA) to estimate levels of productivity and efficiency, incorporating technical change together with technical (TE) and environmental efficiency (EE) into the decomposition of TFP. The EE index adjusts the TFP measure for pollution, treating GHG emissions as a by-product of the desired crop or livestock outputs. TFP and efficiency of crop and livestock sub-sectors was calculated for 24 LAC countries from 2000 to 2016. Our results show that the period of fast agricultural growth in LAC, driven by technical change and resource reallocation, transformed agriculture in the region leaving it in a better position to cope with the more unfavorable regional macroeconomic environment and the less dynamic global markets observed after 2011.