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The measurement of power performance is an important procedure in the design verification and ongoing health monitoring of a tidal turbine. Standardised methods state that the performance should be measured relative to two independently located flow sensors, the arrangement of which is often non-trivial and necessitates additional cost. Recent interest in the usage of flow sensors mounted on the turbine has demonstrated their capabilities in profiling the rotor approach flow, but this instrument configuration is not recognised in the performance assessment standard. This study evaluates the merits of the turbine mounted configuration by measuring the performance of a tidal turbine relative to this reference and to a conventional seabed placed instrument. The turbine mounted sensor is found to provide a better reference of the free-stream conditions, evident from an improved agreement with theoretical predictions of device performance and a reduced amount of variation in the results. This new method could reduce both the costs and uncertainty associated with existing performance assessment best practices. • The power curve from a full-scale tidal turbine is measured. • Measurements from conventional seabed instrument inadequately capture turbine flows. • A new method is proposed using measurements obtained from a turbine mounted sensor. • Turbine sensor results show less variation and are in better agreement with theory. • New method reduces costs and uncertainties associated with performance assessment. [ABSTRACT FROM AUTHOR]

The measurement of power performance is an important procedure in the design verification and ongoing health monitoring of a tidal turbine. Standardised methods state that the performance should be measured relative to two independently located flow sensors, the arrangement of which is often non-trivial and necessitates additional cost. Recent interest in the usage of flow sensors mounted on the turbine has demonstrated their capabilities in profiling the rotor approach flow, but this instrument configuration is not recognised in the performance assessment standard. This study evaluates the merits of the turbine mounted configuration by measuring the performance of a tidal turbine relative to this reference and to a conventional seabed placed instrument. The turbine mounted sensor is found to provide a better reference of the free-stream conditions, evident from an improved agreement with theoretical predictions of device performance and a reduced amount of variation in the results. This new method could reduce both the costs and uncertainty associated with existing performance assessment best practices. • The power curve from a full-scale tidal turbine is measured. • Measurements from conventional seabed instrument inadequately capture turbine flows. • A new method is proposed using measurements obtained from a turbine mounted sensor. • Turbine sensor results show less variation and are in better agreement with theory. • New method reduces costs and uncertainties associated with performance assessment. [ABSTRACT FROM AUTHOR]

Organic Rankine cycles are one of the available solutions for converting low grade heat source into electrical power. However the development of plants tends to be very expansive due to the specific design of the expander. Usually, the input parameters for designing an ORC plant are the temperature and power of the heat and cold sources. They lead to the selection of a working fluid, pressures and temperatures. The expander is then designed based on the required operating parameters. Using standard turbine easily available on the market and with well known performances would allow to reduce the development and manufacturing cost. However, the ORC would have to be adapted to make the expander work in its best conditions. For a solar concentrated heat source, the temperature and power can be adapted by adjusting the concentration factor and the total area of the collector. In this paper, a given gas turbine is considered to be used as the expander of the ORC. Knowing the turbine's performances with air, the optimal operating parameters (pressure, temperature, flow rate and rotational speed) of the ORC with different fluids are sought based on similitude rules. The adaptation aims to maintain the same density evolution, inlet speed triangle and inlet Mach number with the working fluid as with air. The performance maps of the turbine are then computed with CFD simulations and showed a maximum isentropic efficiency close to the one with air, about 78%. • The potential of a given gas turbine to be used as turbo expander of an adapted solar-ORC is studied. • Simple similitude rules allow finding the best operating point for a given fluid. • The ORC parameters are adapted to use the turbine at its best operating point. • CFD simulations for SES36 and R245fa confirmed the ability of the proposed methodology. • Detailed parameters and sizing of the adapted solar ORC with parabolic through collectors are computed for SES36 and R245fa. [ABSTRACT FROM AUTHOR]

The relationship between performance and experience is non-linear, thus planning models that seek to manage workforce development through task assignment are difficult to solve. This gets even more complicated when taking into account multi-skilled workers that are capable of performing a variety of tasks. In this paper we develop a competences-based analytical model of the performance of multi-skilled workers undertaking repetitive tasks, taking into account learning and forgetting. A learning curve can be used to estimate improvement when repeating the same operation. Inverse phenomenon is forgetting, which can occur due to interruption in the production process. The Performance Evaluation Algorithm (PEA) was developed for two cases: fixed shift duration and fixed production output. The aim was to build a tool that better describes the capabilities of workers to perform repetitive tasks by binding together hierarchical competences modeled as a weighted digraph together with a learning and forgetting curve model (LFCM) to express individual learning rates. [ABSTRACT FROM AUTHOR]

Abstract: The global growth in small wind turbine (SWT) markets and in the number of SWT manufacturers has brought about an urgent need for more rigorous testing of SWTs in order to ensure safety, reliability and performance. This work presents modelling of the wind resource at the Australian National Small Wind Turbine Centre (NSWTC) test site to give insight into the scope and scheduling of power performance tests, and assess testing completion requirements for national and international SWT performance standards. Wind modelling of the long-term wind resource at the site was used to guide the NSWTC testing program and develop a tool to provide recommendations regarding suitable months for testing particular turbines. The predictions from the tool are compared to the results of testing a SOMA 1000 small wind turbine. The results indicate that current testing standards need to specify more than 10 min worth of data in each bin in order to reduce uncertainty errors in power curves, particularly at higher wind speeds and during furling and unfurling of the turbine. Furthermore, this work supports observations that there are often notable discrepancies between published SWT manufacturer power curves and test results at high wind speeds. [Copyright &y& Elsevier]

Abstract: As the penetration of wind power continuously increases, the impacts of wind power on frequency control have become of great concern. Frequency control requires real time balance between system generation and load, with system frequency deviation maintained within a certain range. Control Performance Standards (CPS) are indices for evaluating a balancing area’s frequency control performance in an interconnected system. They are important for quantifying the frequency control performance of the interconnected system and the relative distribution of frequency control responsibility among areas. Without mitigating action, the increasing wind power may inhibit a balancing area’s ability to comply with CPS due to variability in power output from wind plants and reduced system frequency response. This paper assesses the impacts of wind power on a balancing area’s frequency control characteristics and studies the wind power impacts on CPS. A two area Automatic Generation Control (AGC) model is used to verify these impacts. AGC changes the valve reference positions of units and restores system frequency to nominal values. Both theoretical study and simulation results show that CPS indices deteriorate as wind power penetration increases. Measures to improve CPS are provided. [Copyright &y& Elsevier]

Abstract: Residential energy consumption is now an important component of total energy consumption and its related emissions. In addition, this consumption has significant potential for growth in both developed and developing countries, as average incomes increase, and domestic appliance numbers rise. Reduction in this energy use may be achieved both through conservation measures, and through increased efficiency in its use. This paper focuses on energy efficiency in appliances—those many devices through which household energy is consumed. The policy instruments available to promote the uptake of more efficient devices, and issues associated with their use, are reviewed, drawing on developed country experiences to date. The instruments available are more limited than in other energy applications, and largely comprise information dissemination, forms of subsidy, and regulation. The last is commonly used in the form of minimum energy performance standards. Assessment of the three instrument types and issues with their use suggests that regulation is the most important measure—albeit with several qualifications on the manner of its use. [Copyright &y& Elsevier]

Abstract: In sub-tropical city of Hong Kong where summer is hot and humid, the usage of outdoor spaces is often hindered due to thermal discomfort. In order to improve the thermal comfort of the outdoor environment and to make urban outdoor spaces delightful places for people to use and enjoy, better understanding of the thermal perception of people is needed. This paper presents the results of an outdoor thermal comfort study conducted in Hong Kong. The findings of the study reveal that air temperature, wind speed and solar radiation intensity are influential factors in determining the thermal sensation of people outdoor. Based on our analysis, the neutral physiological equivalent temperature (PET) in summer in Hong Kong is around 28°C. Under shaded condition, a wind speed of 0.9–1.3m/s is needed for a person in light clothing to achieve neutral thermal sensation in an urban environment. This understanding can contribute towards establishing wind performance standards for thermal comfort in hot and humid tropical and sub-tropical cities. [Copyright &y& Elsevier]

Abstract: The goal of average reward reinforcement learning is to maximize the long-term average rewards of a generic system. This coincides with the design objective of the control performance standards (CPS) which were established to improve the long-term performance of an automatic generation controller (AGC) used for real-time control of interconnected power systems. In this paper, a novel R() imitation learning (R()IL) method based on the average reward optimality criterion is presented to develop an optimal AGC under the CPS. This R()IL-based AGC can operate online in real-time with high CPS compliances and fast convergence rate in the imitation pre-learning process. Its capability to learn the control behaviors of the existing AGC by observing system variations enable it to overcome the serious defect in the applicability of conventional RL controllers, in which an accurate power system model is required for the offline pre-learning process, and significantly enhance the learning efficiency and control performance for power generation control in various power system operation scenarios. [Copyright &y& Elsevier]

Abstract: This paper presents the online test and evaluation of the performance of five practical control strategies (fixed set-point control method, fixed approach control method, two near optimal strategies and one optimal strategy) for building cooling water systems to identify the best strategy for future field validation. All of these strategies were tested and evaluated in a simulated virtual environment similar to the situation when they are actually implemented in practice. A virtual building system representing the real building and its central chilling system was developed and used to test the operational performance of the system controlled by different strategies. The packages of each control strategy are separately computed by the application program of Matlab, as the control optimizers to identify the necessary control settings for the given condition based on the collected operation data. The data exchanger between the virtual building system and the control optimizer was managed by a software platform through a communication interface. The results showed that the optimal control strategy is more energy efficient and cost effective than the other strategies, and its computational cost is manageable and can satisfy the requirements of practical applications. This strategy is being implemented in a super high-rise building for field validation. [Copyright &y& Elsevier]

A new evaluation technique is presented to enable edge sensitivity analysis with respect to angular orientation and displacement errors for edges located by discrete zero-crossing operators. The technique is validated by using a Gaussian edge model and is shown to provide an effective mechanism for characterising the quality of second derivative feature detection operators in terms of quantitative measures of correctness of edge location and orientation. The technique applies a finite element interpolation to the output values of the discrete operator in order to extract sub-pixel level information about zero-crossings; in general, the displacement and orientation of a local line segment along which the line integral of the output interpolant is zero may then be readily found as the solution of a pair of simultaneous algebraic equations. A significant advantage over earlier edge sensitivity techniques is that the method does not require the use of a supplementary first derivative operator for gradient approximation. The method can therefore be used to make direct comparisons between zero-crossing operators in terms of basic performance standards without reference to particular test images; such standards are also important as they form the necessary basis for investigating the potential for the use of proxies for operator performance in relation to subsequent higher-level image processing tasks. [Copyright &y& Elsevier]

Abstract: This paper uses mixture priors for Bayesian assessment of performance. In any Bayesian performance assessment, a prior distribution for performance parameter(s) is updated based on current performance information. The performance assessment is then based on the posterior distribution for the parameter(s). This paper uses a mixture prior, a mixture of conjugate distributions, which is itself conjugate and which is useful when performance may have changed recently. The present paper illustrates the process using simple models for reliability, involving parameters such as failure rates and demand failure probabilities. When few failures are observed the resulting posterior distributions tend to resemble the priors. However, when more failures are observed, the posteriors tend to change character in a rapid nonlinear way. This behavior is arguably appropriate for many applications. Choosing realistic parameters for the mixture prior is not simple, but even the crude methods given here lead to estimators that show qualitatively good behavior in examples. [Copyright &y& Elsevier]

Abstract: This paper addresses the problem of assessing the current performance of a system, given that performance can change over time. In many problems of interest, although a significant body of historical evidence is available, current performance information is too sparse to be the sole basis for an assessment of how well the system is currently performing. Therefore, it is desirable to apply current data within a Bayesian framework, making use of a broader body of evidence. However, both noninformative priors and simple informative priors have drawbacks for this application. The present work shows that ‘mixture’ priors have relatively desirable properties for performance assessment. These properties are illustrated using a simple example in assessment of reliability performance. It is also shown that one implementation of the mixture prior (the ‘fixed-constituent model’) is formally equivalent to methods used in signal detection, statistical decision rules in medical diagnosis, and many other applications. Building on the medical analogy, the potential benefits of an integrated treatment of reliability data and inspection results are illustrated. A companion paper develops a more sophisticated implementation of the mixture prior (the ‘variable-constituent model’), and extends the treatment to more complex examples. [Copyright &y& Elsevier]

• Method to evaluate performance of a laser tracker (LT) without need for scale bar. • Method utilizes stationary targets measured from multiple LT positions. • Length uncertainty between stationary targets is reduced by fitting LT error model. • These lengths are then used as reference for laser tracker performance evaluation. • Method validated using line-of-sight interferometry. Laser trackers (LTs) are widely used for large-scale dimensional metrology. Periodic LT performance evaluation is a key aspect in ensuring measurement reliability. The existing documentary standards for LT performance evaluation require scale bars and special artifacts that are often unavailable for many LT users. A network-based method is considered in this paper as a simple and effective approach to evaluate LT performance without the need for expensive artifacts or reference instruments. In this method, a set of fixed targets are measured from different locations of the LT. The reference values for the lengths between pairs of targets are determined by incorporating the geometrical error model of the LT (i.e., the LT data from each location are corrected for systematic geometric misalignments, quantities that are also obtained from the same data), thus the LT under test is itself used to calibrate the lengths in the network. Subsequently, these length values are used as references to evaluate the LT performance. We validate this method of establishing reference lengths by comparing the values for select lengths in the network against more traditional line-of-sight interferometry. We show that the uncertainties in the reference lengths obtained in this manner are sufficiently small in comparison to the maximum permissible error (MPE) specifications so that they can be used for performance evaluation. A case study using three LTs is presented in this paper. The results obtained from that case study is also verified by a simulation based on the ASME B89.4.19 standard, showing the feasibility of the proposed network-based LT performance evaluation method. [ABSTRACT FROM AUTHOR]

High-level nuclear waste is usually immobilized into high silica glass matrix for long-term and safe disposal in the geological repository. Performance of glass forms is uncertain for the lack of standardization against a natural analogue. Thus, alteration studies were performed on the impact glass as it is surviving in a natural environment since its inception (570 ka). Further, these results were compared to laboratory induced alteration in the impact glass and Na and Ba borosilicate glass from the literature. Alteration experiments were carried out in the de-ionized water under accelerated conditions at 100 °C temperature and 17.24 bar pressure in a variable time framework. Owing to rapid dissolution of synthetic glass, Al3+, Ca2+, K+, Mg2+, Na2+ and Si4+ were released into the solution and finally secondary silicates (SS) were formed in the residue. Comparing to impact glass, a three-fold higher alteration rate is noticed in the Na and Ba borosilicate glass forms. X-ray diffraction (XRD) and scanning electron microscopic (SEM) - energy dispersive X-ray spectrometric (EDS) analyses revealed formation of secondary mineral assemblages (analcime, aragonite, illite, montmorillonite, saponite and stilbite) for both naturally and experimentally altered impact glass types. Moreover, nontronite phase was formed as a major post-alteration product in Na and Ba borosilicate glass forms. The neo-formed SS were compared to naturally derived SS from the impact glass in three time domains of (1) 570 to 5.41 ka, (2) 5.41 to 0.53 ka and (3) 0.53 to Recent Period as determined by high resolution 14C Accelerator Mass Spectroscopy (AMS). Naturally altered impact glass presents paragenetic order of saponite > calcite > montmorillonite > montmorillonite/chlorite mixed layer > siderite > chabazite > aragonite > analcime. As compared to the impact glass, synthetic glass structure is very weak and friable towards alteration. Former attended as a more reliable standard glass. Image 1 • Period of 570–5.41, 5.41–0.53 and 0.53–0 ka entailed in three alteration stages. • Na–Ba borosilicate glass forms show three folds higher alteration than impact glass. • Experimental alteration is akin to that of the natural alteration. [ABSTRACT FROM AUTHOR]

• Report on first realization of test procedures per the ASTM E3125-17 standard. • Discuss test procedures, describe measurands and test methods. • Present the test values and their uncertainties. Spherical coordinate three-dimensional (3D) imaging systems, such as Terrestrial Laser Scanners (TLS), are already used widely in different fields. Their measurement performance evaluation is a topic of active research. In 2017, the first comprehensive documentary standard describing performance evaluation methods and procedures for TLS systems, the ASTM E3125-17, was released. In this paper, we report on the first realization of the test procedures per that standard. We briefly discuss the test procedures and then describe the materials and methods used to realize the tests. We then discuss the test measurands (the quantities of interest in the testing procedure), present the test values (the measured values of the test measurands), and the test value uncertainties (uncertainties in the testing process, which is typically the uncertainty in the reference length). The work described in this paper will serve as a useful reference for understanding and implementing the ASTM E3125-17 standard. [ABSTRACT FROM AUTHOR]

• Per ASTM E3125-17, TLS performance may be evaluated using long scale bars. • We report two methods to calibrate a scale bar with sphere targets mounted on it. • The four-orientation and two-face method is to calibrate horizontal bar length. • The comparison method is proposed for calibrating bar length in any orientation. • The validation experiments for the two methods are given and discussed. A scale bar with sphere targets is one way of realizing the symmetric and asymmetric length tests to evaluate Terrestrial Laser Scanner (TLS) performance per the ASTM E3125-17 standard. The length of the scale bar is required to be known with an expanded (k = 2) uncertainty that must be at least four times smaller than the manufacturer's maximum permissible error (MPE) specification of the instrument being tested. In this paper, we propose two methods to calibrate the scale bar length using a laser tracker. The first method, which we refer to as the four-orientation and two-face (FOTF) method, is proposed for calibrating the scale bar when it is in a horizontal orientation. The other method, which we refer to as the comparison method, is proposed for calibrating the length of the scale bar in any orientation. We describe the methods, present underlying theories, discuss validation experiments, and summarize results. The two calibration methods are beneficial for the realization of the ASTM E3125-17 standard for TLS performance evaluation. [ABSTRACT FROM AUTHOR]