Performance Loss Analysis Research Articles

Preparation of M-type barium ferrite submicron absorbing powder by one-step high-temperature ball milling and its particle structure regulation

This study investigates a simple and rapid process for directly preparing M-type barium ferrite using high-temperature ball milling. By adjusting the rotation speed of the high-temperature ball milling, the morphology and size of the powder can be altered to regulate its electromagnetic properties, aiming for an overall good absorbing effect. The powder’s morphology, agglomeration properties, elemental valence states, and electromagnetic parameters were characterized using SEM, BET, XPS, EDS, and VNA. The results show that as the milling speed increases, the particle size of the M-type barium ferrite decreases, transitioning from the typical hexagonal flake particles to spherical block particles, forming a porous loose structure with richer dielectric loss mechanisms and enhanced electromagnetic wave loss capacity. Electromagnetic loss performance analysis indicates that at a milling speed of 50 rpm, the powder achieves the best electromagnetic loss of −61.16 dB at a matching thickness of 8.77 mm and a microwave absorption bandwidth of 4.1 GHz.

CsSn0.5Ge0.5I3‐Based Lead‐Free Highly Stable Perovskite Solar Cell: Numerical Modeling for Estimating Performance Ceiling

CsSn0.5Ge0.5I3 perovskite is reportedly highly stable in ambient open air, lead free, and has excellent optoelectrical properties. An inverted p–i–n solar cell device based on this mixed SnGe perovskite utilizing the reported optical and electrical characteristics of the CsSn0.5Ge0.5I3 is simulated. This theoretical device under various recombination regimes to explore the performance ceiling of CsSn0.5Ge0.5I3 is put. An optimized configuration of CsSn0.5Ge0.5I3‐based perovskite solar cell shows an efficiency of 29% under the impact of only intrinsic recombination losses such as radiative (with radiative recombination coefficient of 10−11) and Auger recombination (recombination coefficient of 10−27). When extrinsic factors are considered, such as resistance losses (series resistance as high as 2 Ω cm2 and shunt resistance as low as 1000 Ω cm2), efficiency decreases to 27.5%. The efficiency is 20% when trap‐assisted Shockley–Read–Hall recombination is considered with voltage loss (V Loss) of 0.5 V. Similarly, V Loss = 0.6 V in V OC restricts device efficiency to 15%. Finally, an efficiency waterfall chart summarizes the CsSn0.5Ge0.5I3, efficiency under different extrinsic losses, and the performance loss analysis, providing an optimal design. The results summarized here are expected to be helpful and prompt experimentalists to fabricate this stable lead‐free perovskite solar cell.

Transmission Loss Performance Analysis of Acoustic Coatings under Hydrostatic Pressure Considering Cavity Pressure

Transmission Loss Performance Analysis of Acoustic Coatings under Hydrostatic Pressure Considering Cavity Pressure

Analysis of Performance Losses Related to Shaft Angle on Fishing Boats Using the Free Running Model Test Method

Analysis of Performance Losses Related to Shaft Angle on Fishing Boats Using the Free Running Model Test Method

Analysis of Performance Losses and Degradation Mechanism in Porous La2-X NiTiO6-δ:YSZ Electrodes.

The electrode performance and degradation of 1:1 La2−xNiTiO6−δ:YSZ composites (x = 0, 0.2) has been investigated to evaluate their potential use as SOFC cathode materials by combining electrochemical impedance spectroscopy in symmetrical cell configuration under ambient air at 1173 K, XRD, electron microscopy and image processing studies. The polarisation resistance values increase notably, i.e., 0.035 and 0.058 Ωcm2 h−1 for x = 0 and 0.2 samples, respectively, after 300 h under these demanding conditions. Comparing the XRD patterns of the initial samples and after long-term exposure to high temperature, the perovskite structure is retained, although La2Zr2O7 and NiO appear as secondary phases accompanied by peak broadening, suggesting amorphization or reduction of the crystalline domains. SEM and TEM studies confirm the ex-solution of NiO with time in both phases and also prove these phases are prone to disorder. From these results, degradation in La2−xNiTiO6−δ:YSZ electrodes is due to the formation of La2Zr2O7 at the electrode–electrolyte interface and the ex-solution of NiO, which in turn results in the progressive structural amorphization of La18NiTiO6−δ phases. Both secondary phases constitute a non-conductive physical barrier that would hinder the ionic diffusion at the La2−xNiTiO6−δ:YSZ interface and oxygen access to surface active area.

Energy Harvesting Wireless Sensor Networks With Channel Estimation: Delay and Packet Loss Performance Analysis

This paper considers a single-source status monitoring system with energy harvesting in the context of applications where keeping information up-to-date is of primary interest. Specifically, a sensor node, relying on harvested energy and operating according to a harvest-then-use protocol, estimates the channel state to decide whether to perform or defer data delivery to a sink. The sink keeps track of the system status through the successfully delivered updates. To comprehensively evaluate the performance of the proposed scheme, we analytically derive the exact-closed form expressions of the packet loss probability, the age of information and the update interval metric statistics considering both constant-rate and random energy arrival processes and taking into account both the time and energy costs of sensing, transmitting and estimating the channel state. We asymptotically obtain the necessary conditions under which estimating the channel state before transmitting, despite the associated time and energy costs, allow to efficiently manage the harvested energy by avoiding erroneous transmissions and performs strictly better than transmitting without estimating the channel state. Numerical results demonstrate that in most cases, estimating the channel state before transmitting significantly reduces the packet loss probability, the age of information and the update interval of node-sink transmission.

A Comprehensive Methodology to Evaluate Losses and Process Variations in Silicon Solar Cell Manufacturing

Novel, high-throughput metrology methods are used in this paper for detailed performance loss analysis of approximately 400 industrial crystalline silicon solar cells, all coming from the same production line. The characterization sequence combines traditional global cell measurements (e.g., current–voltage, Suns- ${V}_{\text{OC}}$ ) with camera-based cell imaging of voltage distribution and power dissipation from photoluminescence and lock-in thermography, respectively. Spatial variations in current collection are visualized using a high-speed external quantum efficiency and reflectance measurement technique. A nondestructive transfer length method (TLM) measurement technique is also implemented, featuring circular TLM structures hidden within the busbars of the cells. The variance of individual loss parameters and their impact on cell performance are quantified for this large group of cells. Based on correlations performed across parameters, recombination losses in the bulk and rear surface of the cell are shown to be the primary limiting factor for the cell efficiency. The nature of these distributions and correlations provide important insights about loss mechanisms in industrial solar cells, helping to prioritize efforts for optimizing the performance of the production line. Additionally, many of the parameters extracted from these techniques can be tied back to incoming material quality issues (e.g., poor bulk carrier lifetime, nonuniform wafer doping) and to individual unit processes (e.g., texturing, phosphorus diffusion, silicon nitride deposition, metallization), allowing the data to be used directly for process control in manufacturing. All of the datasets are made available for download.

Performance loss analysis and design space optimization of perovskite solar cells

While the performance enhancement witnessed in the field of perovskite solar cells over the recent years has been impressive, a detailed analysis of various loss mechanisms is required for further performance optimization. Here, we address the same through numerical simulations of optical and electrical characteristics. We quantify various losses like optical losses (5%–6%), recombination losses (3%–4%), and resistive losses against the Auger recombination induced practical efficiency limits. Through this, we identify schemes to reduce these losses and hence lead to an increase in efficiency. In addition, we find that the optimum thickness of the perovskite (with material parameters comparable to MAPbI3-xClx and Eg = 1.55 eV) for solar cell fabrication is around 300 nm (comparable to the well-established value); however, the same could be as large as 900 nm for a trap free perovskite (∼ms as the minority carrier Shockley-Read-Hall recombination lifetime). The analyses also enable us to provide the design charts that could lead to >25% efficient perovskite solar cells on the planar structure.

Understanding the energy yield of photovoltaic modules in different climates by linear performance loss analysis of the module performance ratio

The energy yield of 15 different photovoltaic module technologies is measured during one year of operation at four locations (Germany, Italy, India, Arizona) corresponding to four different climate zones. The data are analysed in terms of a linear performance loss analysis for the module performance ratio (MPR) taking into account the influence of module temperature, low irradiance conditions, spectral and angular effects and soiling. This analysis is based on an independent characterisation of the modules in the laboratory combined with site specific data accumulated during operation. The model predicts trends of the measured MPR due to different module technologies and different locations.

Influence of Illumination on the Electrical Properties of p-(ZnMgTe/ZnTe:N)/CdTe/n-(CdTe:I)/GaAs Heterojunction Grown by Molecular Beam Epitaxy (MBE)

Heterostructure p-(ZnMgTe/ZnTe:N)/CdTe/n-(CdTe:I)/GaAs was evaporated using molecular beam epitaxy and investigated for photovoltaic energy conversion application. The electrical properties of the studied heterostructure were measured and characterized in order to understand the relevant electrical transport mechanisms. Electrical properties derived from the current–voltage (I–V) characteristics of solar cells provide essential information necessary for the analysis of performance losses and device efficiency. I–V characteristics are investigated in dark conditions and under different light intensities. All the electrical and power parameters of the heterostructure were measured, calculated and explained.

Overall Effectiveness Improvement for CNC Machine Tools

Overall effectiveness (OE) for CNC machine tools is a metric sistem for assessing the production obtained performance. To optimize OE is necessary to determine the performance indicators [1,2], identifying and correcting the non-values ​​[3,4,5]. In this paper we propose new methods for CNC machine tools OE improvement, through IFA (Information Focus Action) analysis of production losses, during milling machine Wissner Wi3020 type. Comparison of real OE diagram with the theoretical one, provides information about the real losses associated with sub-processes. Also, root-cause analysis of performance losses, leading to the generation of new ways to improve the CNC machine tools OE.

Pore Network Modeling of Gas Diffusion Layer As a Support to Better Understand Water Management in Proton Exchange Membrane Fuel Cells

PEMFC (Proton Exchange Membrane Fuel Cells) is considered as a promising solution for producing clean energy. To increase its industrial development for automotive application, performance and durability are still to be improved and cost needs to be reduced. Water management is one of the most important remaining bottlenecks to increase performance and durability of PEMFC. Nevertheless, despite numerous studies, many questions remain open and for instance it is not possible yet to propose reliable optimization of the porous layers (Gas Diffusion Layer, Active Layer…) to optimize transfers (and especially water management) in the MEA and thus increase performance and durability. One main reason is that water transfers in the MEA, and also the link between structural properties of these layers and performance, are not correctly described and understood. For instance, classical modeling used in PEMFC do not account for these structural properties despite the fact that they have a huge influence on performance. More descriptive modeling approaches have been proposed in the last years to better understand the link between structural properties of these layers and transfers in the MEA. Amongst those, Pore Network Modeling (PNM) is more and more applied to GDL. This approach, classically used for soil application, allows simulating two-phase flows in porous media taking into account local properties (Pore/Throat Size Distribution, local structure, local wettability…) which is an important progress compared to classical PEMFC modeling based on Darcy approach. This keynote lecture focuses on PNM and its application to GDL to better understand (gas and liquid) transfers in the MEA and to try and link local structural properties of GDL to the performance of PEMFC. Experimental results are presented all along the discussion either to validate the main hypothesis or to validate the PNM simulations. After a description of the PNM approach, two-phase transfers inside GDL are discussed: influence of wettability, thickness, local structure…; study of GDL degradation; role of the Micro Porous Layer (MPL); validity of classical Darçy “laws”… The two classical scenarii of water transfers in the GDL (liquid injection and/or condensation) are also discussed. The coupling between PNM and performance model, which is a step towards upscaling of PNM, is introduced by the analysis of performance loss of PEMFC as a function of hydrophobicity loss of GDL. Advanced results comparing two-phase PNM based on real 3D images of GDL and X-Ray tomography of liquid pattern inside the GDL are also presented as a step towards even more representative PNM modeling of MEA components. Finally it is shown how PNM can be extended to the Active Layers by coupling two-phase transfers to charge transfers by electrochemistry.

Performance Loss Analysis for Neglecting the Weibull Clutter Texture in Wideband Radar Spread Targets Detection

The problem of adaptive detection of spatially distributed targets or targets embedded in Weibull clutter with unknown covariance matrix is studied. At first, the texture and the speckle of Weibull clutter is researched, the texture expression is proposed base on the property of spherically invariant random vector (SIRV) , then the optimal detection statistics regards the texture of clutter as a certain function is derived, another detector regards the texture as an unknown deterministic parameter as a contrast. Next, the numerical results are presented by means of Monte Carlo simulation strategy. Assume that cells of signal components are available. Those secondary data are supposed to possess either the same covariance matrix or the same structure of the covariance matrix of the cells under test. In this context, the simulation results highlight that the performance loss of the two tests in different shaping parameter, then the influence of the Weibull clutter texture on detection performance of test is given.

Analysis of performance losses of thermal power plants in Germany – A System Dynamics model approach using data from regional climate modelling

The majority of thermal power plants of more than 300 MW use river water for cooling purposes. Increasing water and air temperatures due to climate change can significantly impact the efficiency and the power production of these power plants. In this paper we analyse these impacts by modelling selected German thermal power plant units and their respective cooling systems through dynamic simulation taking into account legal thresholds for heat discharges to river water together with climate data projections (SRES scenarios A1B, A2, and B1). Possible output and efficiency reductions in the future (2011–2040 and 2041–2070) are quantified for thermal power plants with once-through (OTC) and closed-circuit (CCC) cooling systems under current legislative framework. The model validation showed that the chosen System Dynamics approach is appropriate to analyse impacts of climate change on thermal power units. The model results indicate lowest impacts for units with CCC systems: The mean trend for CCC for the A1B scenario (2011–2070) is expected to be −0.10 MW/a and −0.33 MW/a for an OTC system. On a daily basis, the power output of all considered OTC units is reduced down to 66.4% of the nominal capacity, for a single unit even down to 32%.

Analysis of performance losses of direct methanol fuel cell with methanol tolerant PtCoRu/C cathode electrode

The long-term stability of PtCoRu/C to methanol crossover has been evaluated in a direct methanol fuel cell (DMFC) configuration. The DMFC has been subjected to continuous operation under potential step cycles. The degradation of the DMFC with PtCoRu/C has been followed by comparison of the power density curves recorded after 0, 60 and 312 h of continuous operation, and compared to that recorded for a DMFC with Pt/C. Electrochemical Impedance Spectra (EIS) were recorded directly from the DMFCs and used to identify the main degradation phenomena responsible for the loss of performance of the used fuel cell. AC impedance spectra show that the resistance of the anode reaction increases while resistance associated to the cathode reaction decreases after the long-term stability tests; however, the analysis of the power density curves unequivocally show that the performance of the DMFCs goes down during the stability tests. This apparent contradiction can be explained by taking into account the changes between the fresh and used PtCoRu/C observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. During the potential step cycles Ru dissolves form PtCoRu/C leading to Pt-enriched catalysts which are more active for the oxygen reduction reaction (lower resistance) but less tolerant to methanol (lower power density).

Diagnosis of scale up issues associated with planar solid oxide fuel cells

One of the most important challenges faced by SOFC technology towards the commercialisation lies in the issues related to scale up. In this work, root cause analysis of performance loss in scaled up (1:50) SOFC is carried out. Reduction in actual contact area (6.7% on cathode and 2.5% on the anode) between the metallic interconnects and the cell, and non-uniformity of reactant distribution, are found to play critical roles towards the poor performance of the scaled up cell. Finally, suggestions are made to sustain the performance during the scale up.

A Kind of Workflow System Performance Loss Analysis Model Based on M/G/1

A good workflow system can minimize completion time and resource capacity needs as little as possible. Therefore, workflow system performance analysis is critical for the design of workflow. Based on M/G/1 theory and combining with workflow system theory, the paper established a performance loss analysis mathematical model of workflow system and performed quantitative analysis on performance of workflow based on the model.

ANALYSIS OF PERFORMANCE LOSSES CAUSED BY THE PLANE COLLISION WITH FOREIGN OBJECTS

Analysis of performance losses caused by collision with any foreign objects provides an estimate direct and indirect economic losses and casualties caused by collision with any foreign objects, and continue to use the data to minimize economic losses, and prediction of dangerous situations and develop methods of preventing them.

The Analysis of Performance Loss with Low Platinum Loaded Cathode Catalyst Layers

An analysis of performance loss with low platinum loaded cathode catalyst layers (CCLs) was conducted. A modified 1-D calculation model in the CCL was developed in this study, where newly developed oxygen transport resistance in the direction from pores in the CCL to platinum surface (RO2,CCL-micro) and the effect of platinum oxide coverage on RO2,CCL-micro were taken into account. The analysis results indicated that the oxygen transport loss caused by RO2,CCL-micro became a dominant factor of the performance loss with the low platinum loaded CCLs.

The Analysis of Performance Loss with Low Platinum Loaded Cathode Catalyst Layers

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