Efficiency Improvement Factor Research Articles

Mechanical property identification and performance evaluation of a power take-off combined with a mechanical motion rectifier and a magnetic bistable device

The bistable mechanism has attracted lots of attention due to its potential in improving the efficiency and broadening the bandwidth of wave energy converters. However, most of existing researches are based on simplified numerical models that ignore nonlinear features of power take-off (PTO) and bistable device. Therefore, in this study, a mechanical PTO with both a mechanical motion rectifier (MMR) and a gyration magnetic bistable device (MBD) was designed and integrated into a self-reacting point absorber (SRPA). First, the gyration dynamic and bench tests were carried out to identify the mechanical properties and to explore the working principle of the PTO. Besides, the mechanical parameters of the PTO are obtained for the further analysis of the SRPA coupling dynamics. The disengagement of the MMR and the snap-through feature of the MBD were observed. As for the PTO force, the increment of the inertia moment in backside of the MMR and the electromagnetic damping increases the PTO force, while the MBD turns it more fluctuant due to its bi-stability. With regard to the MMR disengagement, the rise of the inertia moment and the drop of the electromagnetic damping expand the disengagement duration of the MMR. The result indicates the equivalent electromagnetic damping is a critical factor of efficiency improvement, and the oscillation velocity is a subordinary factor beneficial to the efficiency promotion, while the disengagement of the MMR contributes to the efficiency improvement to a limited extent. The PTO efficiency is determined by the proportion of the work done by the nonconservative force in nature. The overall efficiency of the equipment in the bench test achieves 62.9%. Then, the holistic perspective of the self-reacting point absorber integrated with the proposed PTO is given through the numerical analysis. The relatively weak bi-stability of the MBD degrades the potential barrier of the restoring force, and it is favorable to the snap-through oscillation and to promoting the energy harvesting performance of the SRPA. The proposed PTO sustains the relatively high efficiency level of the energy conversion between 50% and 70%, which manifests a good performance for the application of the wave energy utilization.

The Effect of Roughness in Absorbing Materials on Solar Air Heater Performance.

Artificial roughness on the absorber of the solar air heater (SAH) is considered to be the best passive technology for performance improvement. The roughened SAHs perform better in comparison to conventional SAHs under the same operational conditions, with some penalty of higher pumping power requirements. Thermo-hydraulic performance, based on effective efficiency, is much more appropriate to design roughened SAH, as it considers both the requirement of pumping power and useful heat gain. The shape, size, and arrangement of artificial roughness are the most important factors for the performance optimization of SAHs. The parameters of artificial roughness and operating parameters, such as the Reynolds number (Re), temperature rise parameter (ΔT/I) and insolation (I) show a combined effect on the performance of SAH. In this case study, various performance parameters of SAH have been evaluated to show the effect of distinct artificial roughness, investigated previously. Therefore, thermal efficiency, thermal efficiency improvement factor (TEIF) and the effective efficiency of various roughened absorbers of SAH have been predicted. As a result, thermal and effective efficiencies strongly depend on the roughness parameter, Re and ΔT/I. Staggered, broken arc hybrid-rib roughness shows a higher value of TEIF, thermal and effective efficiencies consistently among all other distinct roughness geometries for the ascending values of ΔT/I. This roughness shows the maximum value of effective efficiency equals 74.63% at a ΔT/I = 0.01 K·m2/W. The unique combination of parameters p/e = 10, e/Dh = 0.043 and α = 60° are observed for best performance at a ΔT/I higher than 0.00789 K·m2/W.

Quasi-Monte Carlo method for calculating X-ray scatter in CT

In this paper we transform the trajectories of X-ray as it interacts with a phantom into a high-dimensional integration problem and give the integral formula for the probability of photons emitted from the X-ray source through the phantom to reach the detector. We propose a superior algorithm called gQMCFRD, which combines GPU-based quasi-Monte Carlo (gQMC) method with forced random detection (FRD) technique to simulate this integral. QMC simulation is deterministic versions of Monte Carlo (MC) simulation, which uses deterministic low discrepancy points (such as Sobol' points) instead of the random points. By using the QMC and FRD technique, the gQMCFRD greatly increases the simulation convergence rate and efficiency. We benchmark gQMCFRD, GPU based MC tool (gMCDRR), which performs conventional simulations, a GPU-based Metropolis MC tool (gMMC), which uses the Metropolis-Hasting algorithm to sample the entire photon path from the X-ray source to the detector and gMCFRD, that uses random points for sampling against PENELOPE subroutines: MC-GPU. The results are in excellent agreement and the Efficiency Improvement Factor range 27 ∼ 37 (or 1.09 ∼ 1.16, or 0.12 ∼ 0.15, or 3.62 ∼ 3.70) by gQMCFRD (or gMCDRR, or gMMC, or gMCFRD) with comparison to MC-GPU in all cases. It shows that gQMCFRD is more effective in these cases.

Study on the Temporal and Spatial Evolution of the Total-Factor Water Efficiency in the Yangtze-River Economic Belt

Based on the SBM-Malmquist model of unexpected output, the paper estimates and decomposes the total-factor water efficiency (TFWE) of 11 provinces and cities in Yangtze-river Economic Belt from 2000 to 2017. The study finds that: (i) TWFE in the Yangtze-river Economic Belt has been significantly improved during the sample time, which has an average value of 0.70, the highest value of 0.91 in 2017 and the lowest value of 0.56 in 2006; (ii) provinces or cities from the eastern region of Yangtze-river Economic Belt including Shanghai, Zhejiang and Jiangsu, tend to have higher efficiency than the central and western regions at the same time; (iii) the index of technical change (Tech) obtained by further decomposition of the efficiency is the main contributing factor of efficiency improvement.

Sand dunes effect on the productivity of a single slope solar distiller

Access to drinking water in many parts of the globe is shrinking over the years and much of the water resources are polluted or unpurified. North Africa is facing a huge water shortage due to drought and climate change. Water desalination has become very popular and serves as solar distillation which is proving to be an economical, simple and ecological technique, especially in rural and remote areas. Significant efforts have been made by many researchers in various laboratories to increase and improve the productivity of solar greenhouse distillation. In the present work, emphasis has been placed on the study of a single slope solar distiller having as dimension 50 × 50 cm, in the thickness of the impure water is 1 cm. Natural sand dunes from the El Oued South region of Algeria have been tested as a factor of efficiency improvement. A layer of this sand was deposited on the bottom of the distiller covering the whole surface on which the submit water is emerged. The results show that the productivity of distilled water has unfortunately decreased by 1.46 times.

Principles of integration of time-oriented thinking – factor of efficiency improvement under economy digitization condition – into operating structure

The present article is substantiating the need of organization-management paradigm transition from cost (value)-based to that oriented on lead time reduction. The authors are presenting and describing basic provisions and assumptions of this approach and issuing recommendations on transition to time-oriented thinking. The paper is reflecting the impact of lead time reduction on basic indicators of economic effect and company efficiency. The authors proposed an indicator of unit (department, team, project) efficiency assessment and methods of using it.

Gain Correction for an X-ray Imaging System With a Movable Flat Panel Detector and Intrinsic Localization Crosshair.

Gain calibration for X-ray imaging systems with a movable flat panel detector and an intrinsic crosshair is a challenge due to the geometry-dependent heel effect and crosshair artifact. This study aims to develop a gain correction method for such systems by implementing the Multi-Acquisition Gain Image Correction technique. Flood field images containing crosshair and heel effect were acquired in 4 different flat panel detector positions at fixed exposure parameters. The crosshair region was automatically detected using common image processing algorithms and removed by a simple interpolation procedure, resulting in a crosshair-removed image. A large kernel-based correction was then used to remove the heel effect. Mask filters corresponding to each crosshair region were applied to the resultant heel effect-removed images to invalidate the pixels of the original crosshair region. Finally, a seamless gain map was composed with corresponding valid pixels from the processed images either by the sequential replacement or by the selective averaging techniques developed in this study. Quantitative evaluation was performed based on normalized noise power spectrum and detective quantum efficiency improvement factor for the flood field images corrected by the Multi-Acquisition Gain Image Correction-based gain maps. For comparison purposes, a single crosshair-removed gain map was also tested. As a result, it was demonstrated that the Multi-Acquisition Gain Image Correction technique achieved better image quality than the crosshair-removed technique, showing lower normalized noise power spectrum values over most of spatial frequencies. The improvement was more obvious at the priori-crosshair region of the gain map. The mean detective quantum efficiency improvement factor was 1.09 ± 0.06, 2.46 ± 0.32, and 3.34 ± 0.36 in the priori-crosshair region and 2.35 ± 0.31, 2.33 ± 0.31, and 3.09 ± 0.34 in the normal region, for crosshair-removed, Multi-Acquisition Gain Image Correction-sequential replacement, and Multi-Acquisition Gain Image Correction-selective averaging techniques, respectively. Therefore, this study indicates that the introduced Multi-Acquisition Gain Image Correction technique is an appropriate method for gain calibration of an imaging system associated with a moving flat panel detector and an intrinsic crosshair.

WE-E-18A-07: MAGIC: Multi-Acquisition Gain Image Correction for Mobile X-Ray Systems with Intrinsic Localization Crosshairs

Purpose: Gain calibration for X-ray imaging systems with movable flat panel detectors (FPD) and intrinsic crosshairs is a challenge due to the geometry dependence of the heel effect and crosshair artifact. This study aims to develop a gain correction method for such systems by implementing the multi-acquisition gain image correction (MAGIC) technique. Methods: Raw flat-field images containing crosshair shadows and heel effect were acquired in 4 different FPD positions with fixed exposure parameters. The crosshair region was automatically detected and substituted with interpolated values from nearby exposed regions, generating a conventional single-image gain-map for each FPD position. Large kernel-based correction was applied to these images to correct the heel effect. A mask filter was used to invalidate the original cross-hair regions previously filled with the interpolated values. A final, seamless gain-map was created from the processed images by either the sequential filling (SF) or selective averaging (SA) techniques developed in this study. Quantitative evaluation was performed based on detective quantum efficiency improvement factor (DQEIF) for gain-corrected images using the conventional and proposed techniques. Results: Qualitatively, the MAGIC technique was found to be more effective in eliminating crosshair artifacts compared to the conventional single-image method. The mean DQEIF over the range of frequencies from 0.5 to 3.5 mm-1 were 1.09±0.06, 2.46±0.32, and 3.34±0.36 in the crosshair-artifact region and 2.35±0.31, 2.33±0.31, and 3.09±0.34 in the normal region, for the conventional, MAGIC-SF, and MAGIC-SA techniques, respectively. Conclusion: The introduced MAGIC technique is appropriate for gain calibration of an imaging system associated with a moving FPD and an intrinsic crosshair. The technique showed advantages over a conventional single image-based technique by successfully reducing residual crosshair artifacts, and higher image quality with respect to DQE.

Reduced switching loss pulse width modulation technique for three-level diode clamped inverter

Multilevel inverters are used to reduce the harmonics and to achieve high-voltage, high-power capability but switching losses are increased because of increased device count. Switching losses can be reduced by either soft switching techniques or by modifying modulation technique employing space vector-based PWM techniques or sinusoidal PWM-based techniques. In this study, a carrier-based closed-loop control technique has been developed to reduce the switching losses based on insertion of `no switching` zone within each half cycle of fundamental wave. It effectively reduces the switching losses of three-level inverter without need of any complex mathematical expressions as involved in space vector-based techniques. An improvement of about 5` in efficiency for a switching frequency of 5`kHz is observed with proposed technique over conventional SPWM technique based on efficiency improvement factor (EIF). Simulation and experimental results are presented to validate the proposed technique.