•An efficiency measure through reformulating the correlation, bias, ratio of variances components of NSE is presented.•The distinction between the population statistic and sampling properties was ...taken into the proposed criterion.•The proposed criterion is helpful for the design flow from hydrological frequency analysis.
Performance criteria are essential for hydrological model identification or its parameters estimation. The Kling-Gupta efficiency (KGE), which combines the three components of Nash-Sutcliffe efficiency (NSE) of model errors (i.e. correlation, bias, ratio of variances or coefficients of variation) in a more balanced way, has been widely used for calibration and evaluation hydrological models in recent years. However, the KGE does not take a reference forecasts or simulation into account and still underestimates of variability of flow time series when optimizing its value for hydrological model. In this study, we propose another performance criterion as an efficiency measure through reformulating the previous three components of NSE. Moreover, the distribution function of the new criterion was also derived to analyze uncertainties of the new criterion, which is originated from the distinction between the theoretical or population statistic and its corresponding sampling properties. The proposed criterion was tested by calibrating the “abcd” and XAJ hourly hydrological models at monthly and hourly time scales data for two different case study basins. Evaluation of the results of the case study clearly demonstrates the overall better or comparable model performances from the proposed criterion. The analysis of the uncertainties of the new criterion based on its distribution probability function suggests a rational approach to distinguish between the probabilistic properties and behavior of the theoretical statistics and the rather different sampling properties of estimators of those statistics when computed from data.
This paper proposes a novel approach for L1 performance controller design of saturated input nonlinear systems described by Takagi-Sugeno (TS) fuzzy systems. The proposed method utilizes parallel ...distributed compensation (PDC) approach to minimize the effect of persistent bounded disturbances on the system output and the design conditions are formulated in terms of linear matrix inequalities (LMIs) and a generalized eigenvalue problem (GEVP). The novelty of this paper is to design a saturated robust L1 PDC controller whose procedure comprises new techniques for both minimizing the L1 performance gain and handling actuator saturation constraint. These techniques lead to less conservative results compared to recently published papers in the viewpoint of L1 performance criterion gain as well as the control input saturation. The advantages of the proposed approach in each above-mentioned viewpoint are shown via numerical examples by comparing our results with the existing literatures. Finally, a nonlinear electromagnetic suspension (EMS) system is considered to verify the applicability and efficiency of this novel design method.
•A review on mechanical characteristics of finger mechanisms of hand prostheses.•Describing performance criteria used on artificial fingers.•Classifying the performance criteria into grasp and ...physical features.•Evaluating 28 distinct linkage-driven finger mechanisms.•Presenting key guidelines for developing an artificial finger.
Mechanical design of an artificial finger is the key factor in determining the performance of a prosthetic hand. To achieve a simple, dexterous and functional bionic hand, researchers have argued that two main requirements should be incorporated in developing an artificial finger: (i) an anthropomorphic structure and (ii) the capability of grasping objects in a stable and secure way. This paper first considers the existing body of literature on the various performance criteria used for prosthetic fingers. These criteria are classified into a) grasp and b) physical characteristics. To this end, various perspectives of existing papers on prosthetic finger's features such as shape-adaptivity, natural motion, stability, force isotropy, workspace, and weight are considered. Furthermore, existing linkage-driven fingers of hand prostheses are reviewed. For this purpose, relevant articles published between 2000 and 2019 were searched, and a total of 28 linkage-driven mechanisms from about 280 papers were selected and assessed based on the performance criteria. Finally, according to the intended use of a prosthetic hand, this paper suggests some key considerations needed for developing an anthropomorphic artificial finger.
•Mixed convection in a vented cavity having a heated cylinder is simulated.•Two counter-rotating cylinders are used as an active technique to enhance heat transfer.•The effect of the position and ...rotating speed of these cylinders on the hydrothermal index and entropy generation are detailed.•The optimal thermal performance criterion is achieved at a low Reynolds number.
In this work, hydrothermal behavior and entropy generation of a heated cylinder placed between two oppositely rotating cylinders inside a vented cavity is studied numerically using the finite volume technique. The mixed convection of a steady, 2D, and laminar flow is considered for the flow through the vented cavity. For counter-rotating cylinders, according to the center of the heated cylinder, two different vertical distances, Zy and three different horizontal distances, Zx are investigated with angular rotational speeds, Ω ranging from 0 to 15. The influence of relevant parameters on hydrothermal behavior, such as Reynolds number (100 ≤ Re ≤ 500) and Grashof number (103 ≤ Gr ≤ 106) is taken into account throughout the simulations. The numerical results are exposed in terms of various qualitative and quantitative figures. Regardless of the position of counter-rotating cylinders, results show that the optimal thermal performance criterion, ξ is achieved at low Reynolds number (Re=100) over the ranges of angular rotational speeds, Ω.
Display omitted
Forecast selection and combination are regarded as two competing alternatives. In the literature there is substantial evidence that forecast combination is beneficial, in terms of reducing the ...forecast errors, as well as mitigating modelling uncertainty as we are not forced to choose a single model. However, whether all forecasts to be combined are appropriate, or not, is typically overlooked and various weighting schemes have been proposed to lessen the impact of inappropriate forecasts. We argue that selecting a reasonable pool of forecasts is fundamental in the modelling process and in this context both forecast selection and combination can be seen as two extreme pools of forecasts. We evaluate forecast pooling approaches and find them beneficial in terms of forecast accuracy. We propose a heuristic to automatically identify forecast pools, irrespective of their source or the performance criteria, and demonstrate that in various conditions it performs at least as good as alternative pools that require additional modelling decisions and better than selection or combination.
•Forecast selection and combination assume an existing set of reasonable forecasts.•There is limited work how to construct these pools of forecasts, albeit important.•We argue that forecast selection and combination are extremes of the pooling spectrum.•We propose a model- and criterion-independent approach to construct forecast pools.•The proposed `forecast islands' improve performance and reduce computational effort.
In the present study, the cross contamination and distribution of Escherichia coli O157:H7 was investigated in fresh-cut lettuce by simulating a commercial process at a pilot plant scale with ...different initial inoculum levels. A deterministic approach was used to derive a potential Food Safety Objective (FSO) for the studied pathogen. The experimental outcomes, together with literature data, were used to develop a probabilistic exposure model for E. coli O157:H7 to elucidate potential risk management metrics, i.e., Performance Objectives (POs) and a Performance Criterion (PC) at specific process steps within the food chain of fresh-cut leafy vegetables. The proposed FSO was estimated to be −6.0 log CFU/g for E. coli O157:H7 at consumption. The experimental results indicated that the pathogen could cross contaminate most of the samples in a lot at the different contamination levels tested (1-7 log CFU/g) resulting in a homogeneous distribution of E. coli O157:H7 in fresh-cut lettuce after processing. Based on the modelling results, the average concentration estimated as PO in unprocessed lettuce should be −5.8 log CFU/g to meet the proposed FSO. On the other hand, the PO established after washing and packaging (processed lettuce) showed a lower value, with −6.8 log CFU/g E. coli O157:H7. Reduction levels during the washing or disinfection step estimated as the PC should be > 2.9 log CFU/g. The establishment of PC for the washing step, assisted by the use of disinfection process indicators (e.g., generic E. coli), could be considered as a suitable measure to reach the FSO in fresh-cut leafy vegetables. The suggested POs and PC would help food businesses and authorities to establish safety targets and corrective actions to reduce the number of potentially contaminated lettuce lots on the market, thus reducing the number of E. coli O157:H7 infections.
•The washing step resulted in homogenous contamination by E. coli O157:H7 in processed fresh-cut lettuce.•A novel model-based approach proposed to derive risk management metrics.•The estimated Food Safety Objective for E. coli O157:H7 was −6.0 log CFU/g.•Reduction levels > 2.9 log CFU/g E. coli O157:H7 in fresh-cut vegetables should be achieved during the washing step.
Solar energy can be harnessed using different evolving technologies like photovoltaic (PV), artificial photosynthesis, solar heating, solar thermal power plant, etc., whose progress depends on the ...materials in the collector. Most solar collectors use spectrally selective absorber coating with high absorptance and low emittance in the solar and at the infrared spectrum range respectively. Several efforts have been put since 1990s by different authors towards synthesizing highly efficient and thermally stable solar absorber coating for mid to high temperature applications using different deposition methods. It has been established that, the photothermal conversion efficiency of solar thermal power plant depends on the selective absorber coating with high thermal stability and excellent optical properties. This paper reviews the different types of solar absorber coatings and the current state of the art of the existing mid and high temperature absorber coatings with an emphasis on the sputter deposited coatings. A detail survey on the commercially available mid and high temperature absorber coatings with high absorptance and low emittance have been carried out. The aim of this review article is to know what has been achieved so far on the performance and thermal stability of absorber coatings especially in an air ambient. Also, the scope of performance improvement has been highlighted in this paper.
Higher levels of performance during skill acquisition predict higher levels of response maintenance, but less is known about how many observations of high levels of performance are needed to produce ...this effect of criterion levels. We analyzed two criterion‐level frequency values, or the number of observations of criterion‐level performance. We taught children with disabilities target skills to 90% accuracy observed one time or across three consecutive sessions/days. Participants required fewer sessions to meet the terminal acquisition‐performance criterion when the frequency value was set to one and response maintenance outcomes were comparable between conditions. These outcomes suggest that the frequency component of acquisition‐performance criterion is related to the efficiency of skill acquisition for participants with comparable repertoires.
In the present work, the aerodynamic design of a 10 kW horizontal axis wind turbine rotor is performed using both ideal and actual rotor theories. The obtained nonlinear blade profile is optimized in ...order to enhance the aerodynamic performance and to ease the fabricating complexity. A unique linearization approach is employed to linearize the chord and twist distribution by dividing the congruent line of both ideal and actual models into equal divisions. The points along the identical tangent line are considered as floating new blade roots, whereas the blade tip was kept fixed based on the primary design. The linear profile based on the new value of blade root is described using algebraic equations. The local element torque, capacity factor, and the annual energy production based on the Weibull distribution are adopted to determine and assess the optimal blade profile. Both CFD investigation and the FEA analysis are performed in order to evaluate both primary and optimized blades. The aerodynamic and aeroelastic comparison in terms of power output, thrust force, blade tip deflection, and the equivalent stress distribution of both blade profiles has been done over a wide range of incoming wind speeds. Results show an enhancement in the aerodynamic performance in terms of power coefficient up to (5.9%) compared to the primary blade design. Moreover, the optimized blade has shown less tip deflection by 27.92% than the primary blade at low wind speed.
□An innovative linearization approach of the chord and twist angle distributions is proposed.□The CFD and FEA analysis are conducted for both optimized and primary blade profiles.□The power coefficient of the optimized blade has improved up to 5.9% compared to the primary design.□The optimized blade shows less tip deflection by 27.92% compared to the primary blade.
The operating modes directly influence the system performance of combined cooling, heating and power (CCHP) systems. To improve the comprehensive operational performance, in this paper, based on two ...typical operating modes, i.e., following the electric load (FEL) and following the thermal load (FTL), a novel optimal operational strategy depending on an integrated performance criterion (IPC) is proposed. Using this strategy, the whole operating space of the CCHP system can be divided into several regions by one to three border surfaces determined by energy requirements and the IPC. Then the operating point of the CCHP system is located in a corresponding operating mode region to achieve improved IPC. The IPC simultaneously considers the primary energy consumption, the operational cost and the carbon dioxide emissions. The carbon tax is also included in the operational cost. A hypothetical hotel building is modeled as the reference system to evaluate the proposed strategy. Simulation results show that, for the same CCHP system of the hypothetical hotel, the IPC with the proposed strategy is better than that with the traditional strategy. The proposed strategy can reflect and balance the influences of energy requirements, energy prices and emissions effectively.
PDF
