Reverse Problem Research Articles

Single-Switch Resonant Soft-Switching Ultra-High Gain DC-DC Converter With Continuous Input Current

An ultra-high gain DC-DC converter with single-switch structure is introduced in this paper. Full soft-witching is provided by simultaneous use of quasi-resonant performance of one resonant tank and leakage inductance of a three-winding coupled inductor (CI). Adopting the secondary and tertiary windings of the CI in separated voltage multiplier cells enables the converter to provide ultra-high voltage gain. The reverse recovery problem is resolved thanks to the quasi zero current switching performance of nearly all diodes, especially output diode because of the second resonant tank, so the total electromagnetic interference is significantly reduced. Continuous input current with low ripple expands the application of the proposed converter, especially in renewable energy applications. Steady-state performance and design considerations of the introduced converter are analyzed thoroughly and compared with recently introduced converters to establish its merits. Experimental results of a 200 W prototype are given to validate its analysis and performance.

Comparison of the RAFSI and PIV method in multi-criteria decision making: application to turning processes

Multi-criteria decision-making (MCDM) methods are used in many fields so as to rank alternatives and find the best one. However, rank reversal after adding or removing an alternative can occur in using some of the methods. In this study, two methods RAFSI and PIV were compared for application of making multi-criteria decisions. They are known to be capable of avoiding rank reversal problems. Sixteen 9XC steel turning tests were performed for the experiment. Tool holder length, spindle speed, feed rate and depth of cut are parameters that vary in each test. Three criteria for evaluating the turning process consist of MRR, RE and Ra. Four methods including MEREC, ROC, RS and EQUAL were used for determining weights of the criteria. The blend of two multi-criteria decision making methods (RAFSI and PIV) with four weight-determining methods resulted in eight ranking options. This is a new approach of the study. A positive outcome was reached that all eight ranking options identified the same best test. The best experiment must ensure to have maximum MRR and minimum RE and Ra simultaneously. A detailed discussion of the ranking results in each case was also carried out. Finally, the directions and issues that need to be studied further were pointed out in this paper as well.

A high step-up Z-source-flyback converter with integrated inductors for photovoltaic applications

ABSTRACT Increasing the voltage gain by means of Z-source network will provide some features such as low-voltage stress of semiconductor devices, low duty cycle of the switch and low reverse recovery problem of output diode that leads to improve the converter performance and efficiency. The proposed converter in this paper employs a Z-source network with coupled inductors integrated with flyback converter to make it appropriate for high step-up applications. One magnetic element is used in this converter, which is its main advantage over previously introduced Z-source converters. Steady-state analysis and operation principles of the proposed converter in continuous conduction mode that leads to low current ripple, and low conductive losses for semiconductor devices due to decreasing the RMS currents are presented. In order to verify the theoretical analysis, experimental results of a prototype are provided. This converter’s high-voltage conversion ratio will result in 300 V output from 20 V input voltage source for 100 W output power.

Estimating the environmental impacts of HVDC and UHVDC lines for large-scale wind power transmission considering height-dependent wind and atmospheric stability

Due to the imbalance of China’s resources allocation, inter-provincial high voltage direct current (HVDC) transmission grid is considered to be the promising solution to solve to the large-scale wind power transmission, which could tackle the reverse regional distribution problem of energy resource and electricity load. In this contribution, a power law profile model of wind speed on embedded atmospheric stability is developed for calculating the height-dependent wind speed. The Monin-Obukhov length is introduced to determine the atmospheric stability. The ion flow environment model considering height-dependent wind speed is proposed to estimate the influence of height-dependent wind on ground-level electric field environment of DC transmission line and the iterative flux tracing method-finite difference is proposed to solve the model. It is observed that the stable, neutral and unstable atmospheric conditions have a large influence on transverse wind speed and then indirectly influence the electric field and ion current environment of DC lines. For the electromagnetic environment of the practical DC line used for the wind power transmission, the proposed model provides a reasonable agreement with measurements from a perspective of practical engineering application.

A single‐switch high‐gain DC–DC converter for photovoltaic applications

AbstractThis article presents a high‐gain DC–DC converter consisting of a quadratic boost converter and a voltage multiplier, which helps to lift up the voltage gain. The gain will be further enhanced by increasing the turn's ratio of the coupled inductor. The key features include ultrahigh gain, low voltage stress across switching devices, low input current ripple, and hence, it is preferably suitable for renewable energy applications. A passive clamp lowers the voltage stress across MOSFET, so allowing switch with lower Rds(on) reduces the system cost. Besides this, input inductor makes current continuous and reduces input current ripple. The reverse recovery problem of diodes also gets diminished with the usage of leakage energy of the coupled inductor. The operating principle with different modes of operation is also explained. Zero current switching (ZCS) turn‐on is achieved for power switch, and ZCS turn‐off is achieved for diodes, which helps to reduce the switching losses. This improves the overall system efficiency. A 250‐W prototype is built up to validate the converter.

A Multi-Stage Stochastic Programming Model for the Multi-Echelon Multi-Period Reverse Logistics Problem

Reverse logistics planning plays a crucial role in supply chain management. Stochasticity in different parameters along with time horizon can be a challenge in solving reverse logistics problems. This paper proposes a multi-stage, multi-period reverse logistics with lot sizing decisions under uncertainties. The main uncertain factors are return and demand quantities, and return quality. Moment matching method was adopted to generate a discrete set of scenarios to represent the original continuous distribution of stochastic parameters. Fast forward selection algorithm was employed to select the most representative scenarios and facilitate computational tractability. A case study was conducted and optimal solution of the recursive problem obtained by solving extensive form. Sensitivity analysis was implemented on different elements of stochastic solution. Results sow that solution of recursive problem (RP) outperforms the solution obtained from the problem with expected values of uncertain parameters (EEV).

In-situ testing method of the permeability coefficient in a coal seam based on the finite volume method and its application

The permeability coefficient in a coal seam is an important index to evaluate the efficiency of gas drainage. Accurately testing the permeability coefficient is of great significance for gas disaster prevention and gas resource utilization. The radial flow (RF) method, which is the main method for determining the permeability coefficient in Chinese coal mines, simplifies the gas flow control equation by transforming it from a nonlinear partial differential (NPD) equation to a linear one. Such a transformation changes the quantitative relationship between gas content and gas pressure, and ultimately results in the relatively small permeability coefficient calculated by the RF method. In view of the problem, based on the finite volume method and the golden section search method, a novel finite volume flow (FVF) method was proposed in this study to determine the permeability coefficient. The FVF method solves the reverse solution problem facing the NPD equation. In order to verify the FVF method, a field experiment was performed in Jiulong Coal Mine. The results show that the FVF and RF methods are both of good stability, that is, the permeability coefficients calculated by the two methods both approach stable values. However, the FVF method is superior to the RF method in predictability, operability and expansibility. Taking the data of #1 borehole on the 20th day as an example, the prediction error rate for the RF method is 1.56 times that for the FVF method. Therefore, the FVF method is more suitable for determining the permeability coefficient than the RF method. In addition, the sensitivities of seven test parameters were calculated to evaluate their effects on the permeability coefficient. Based on the findings, the equipment for permeability coefficient testing was improved. The research results lay the foundation for further promoting the accuracy of permeability coefficient measurement.

Anionic Redox Regulated via Metal-Ligand Combinations in Layered Sulfides.

The increasing demand for energy storage is calling for improvements in cathode performance. In traditional layered cathodes, the higher energy of the metal 3d over the O 2p orbital results in one-band cationic redox; capacity solely from cations cannot meet the needs for higher energy density. Emerging anionic redox chemistry is promising to access higher capacity. In recent studies, the low-lying O nonbonding 2p orbital wasdesigned to activate one-band oxygen redox, but they are still accompanied by reversibility problems like oxygen loss, irreversible cation migration, and voltage decay. Herein, by regulating the metal-ligand energy level, both extra capacities provided by anionic redox and highly reversible anionic redox process are realized in NaCr1- y Vy S2 system. The simultaneous cationic and anionic redox of Cr/V and S is observed by in situ X-ray absorption near edge structure (XANES). Under high d-p hybridization, the strong covalent interaction stabilizes the holes on the anions, prevents irreversible dimerization and cation migration, and restrains voltage hysteresis and voltage decay. The work provides a fundamental understanding of highly reversible anionic redox in layered compounds, and demonstrates the feasibility of anionic redox chemistry based on hybridized bands with d-p covalence.

Switching-Cell Buck–Boost AC–AC Converter With Common-Ground and Noninverting/Inverting Operations

This article proposes a switching-cell-based bipolar buck-boost ac-ac converter that can provide multiple modes of operation, including noninverting buck operation, noninverting boost operation, inverting buck-boost operation, and adjustable noninverting buck-boost operation with two control duty ratios. Each fundamental switching-cell in the proposed converter is composed of a unidirectional buck circuit with no short-circuit or open-circuit problems, increasing its robustness. Hence, safe commutation is naturally realized without the use of RC snubbers or soft-commutation strategies, removing the need for pulsewidth modulation deadtimes. External fast recovery diodes are utilized, avoiding the high-frequency conduction of MOSFET's body diodes and eliminating their slow reverse recovery problem and corresponding power loss. The proposed converter shares a common ground between input and output ports, offers support for reactive loads, draws continuous sinusoidal current from ac mains, and delivers a continuous output current. The converter is suitable for ac voltage regulation applications, notably as a dynamic voltage restorer, compensating extensive magnitudes of both grid voltage sags and swells. Circuit operation and analysis are provided for all the proposed modes of operation. Experimental results obtained using a 400-W laboratory-scale hardware verify the theoretical analysis.

COMPARISON OF ALGORITHMS FOR DETERMINING THE THICKNESS OF OPTICAL COATING LAYERS BASED ON THE MONOCHROMATIC MONITORING DATA

The reverse engineering problem of determining the layer thicknesses of deposited optical coatings from on-line monochromatic measurements is considered. To solve this inverse problem, non-local algorithms are proposed that use all the data accumulated during the deposition process. For the proposed algorithms, the accuracy of solving the inverse problem is compared in the presence of random and systematic errors. It is shown that in the case when the measured data contains only random errors, the best accuracy is provided by the algorithm based on minimizing the discrepancy functional. In the case of systematic errors, the advantage of one the algorithms based on minimizing the variance functionals is demonstrated. Key words: inverse problems, reverse engineering, optical coatings, thin films.

Reverse Problem to Find Right Parts Mixed Equations with the Chaplygin Operator

Reverse Problem to Find Right Parts Mixed Equations with the Chaplygin Operator

Estimating dynamic cutting forces of machine tools from measured vibrations using sparse regression with nonlinear function basis

Estimating relationships between system inputs and outputs can provide insight to system characteristics. Furthermore, with an established input-output relationship and measured output, one can estimate the corresponding input to the system. Traditionally, the relationship between input and output can be represented with transfer functions or frequency response functions. However, those functions need to be built on physical parameters, which are hard to obtain in practical systems. Also, the reverse problem of solving for the input with a known/measured output is often more difficult to solve than the forward problem. This paper aims to explore the data-driven input-output relationship between system inputs and outputs for system diagnostics, prognostics, performance prediction, and control. A data-driven relationship can provide a new way for system input estimation or output prediction. In this paper, a sparse linear regression model with nonlinear function basis is proposed for input estimation with measured outputs. The proposed method explicitly creates a nonlinear function basis for the regression relationship. A threshold-based sparse linear regression is designed to ensure sparsity. The method is tested with experimental data from a spindle testbed that simulates cutting forces within machine tools. The results show that the proposed approach can predict the input force based on the measured vibration response with high accuracy. The current model is also compared with neural networks, which is another nonlinear regression method.

A multi-objective location-routing problem model for multi-device relief logistics under uncertainty using meta-heuristic algorithm

During natural and abnormal accidents, many people are injured, and a large number of wastes and rubbish are produced, so it is necessary to collect the injured and take them to treatment centers, which must be done in the reaction phase. Also, in the recovery and reconstruction phase, since a large amount of hazardous and non-hazardous waste is produced during accidents, effective measures should be taken to collect and recycle them if necessary. Both of these cases can be considered as a reverse logistics problem. This paper investigates reverse logistics planning in the response, improvement, and reconstruction phases in earthquake conditions. Due to the nature of the problem, it is expected that we will face a multi-objective problem, and the problem condition causes the issue of uncertainty. By increasing the dimensions of the problem, the NSGA-II meta-heuristic algorithm has been used to solve the two-objective model of the problem and the result indicates that the proposed solution algorithm works well and the quality of the answer and its solution time are appropriate. The results indicate that as capacity increases, the number of distribution centers built to meet demand decreases and the distribution center constructed may be far from some shelters, leading to increased transportation costs. According to the mentioned issues, this research uses reverse logistics in the response and recovery phases. Also, information about Tehran city will be used as data for the case study.

On the origin of the anomalous sign reversal in the Hall effect in Nb thin films

We re-visit the anomalous sign reversal problem in the Hall effect of the sputtered Nb thin films. We find that the anomalous sign reversal in the Hall effect is extremely sensitive to a small tilting of the magnetic field and to the magnitude of the applied current. Large anomalous variations are also observed in the symmetric part of the transverse resistance Rxy . We suggest that the surface current loops on superconducting grains at the edges of the superconducting thin films may be responsible for the Hall sign reversal and the accompanying anomalous effects in the symmetric part of Rxy .

Innovation: Complex Geophysics in the Field of Archaeology (South Bulgarian Black Sea Coastline)

The study examines the results of complex geophysical research of threearchaeological sites located near the southern part of the Black Sea coastline in Bulgaria:Propadnalata Voda, Atiya, and Alepu. The authors discuss the use of complex geophysical methodsin archaeology depending on the objectives of archaeological research, on the one hand, and thelikely properties of the archaeological sites, on the other. As known, the methods of appliedgeophysics involve reverse geophysical problems, which do not have definitive solutions. Toovercome potential ambiguities in this regard, the study demonstrates how the complementary useof different methods makes the interpretation of the final results easier.

Parameter setting of meta-heuristic algorithms: a new hybrid method based on DEA and RSM.

The parameter setting of meta-heuristic algorithms is one of the most effective issues in the performance of meta-heuristic algorithms and is usually done experimentally which is very time-consuming. In this research, a new hybrid method for selecting the optimal parameters of meta-heuristic algorithms is presented. The proposed method is a combination of data envelopment analysis method and response surface methodology, called DSM. In addition to optimizing parameters, it also simultaneously maximizes efficiency. In this research, the hybrid DSM method has been used to set the parameters of the cuckoo optimization algorithm to optimize the standard and experimental functions of Ackley and Rastrigin. In addition to standard functions, in order to evaluate the performance of the proposed method in real problems, the parameter of reverse logistics problem for COVID-19 waste management has been adjusted using the DSM method, and the results show better performance of the DSM method in terms of solution time, number of iterations, efficiency, and accuracy of the objective function compared to other.

A Novel Full Soft-Switching High-Gain DC/DC Converter Based on Three-Winding Coupled-Inductor

In this article, a new nonisolated full soft-switching step-up dc/dc converter is introduced with a continuous input current for renewable energy applications. The use of a three-winding coupled-inductor (TWCI) along with a voltage multiplier, enables the proposed converter to enhance the voltage gain with lower turns ratios and duty cycles. Also, a lossless regenerative passive clamp circuit is employed to limit the voltage stress across the power switch. In addition to zero current switching performance at the turn-on instant of the power switch, the turn-off current value is also alleviated by adopting a quasi-resonance operation between the leakage inductor of the TWCI and middle capacitors. Moreover, the current of all diodes reaches zero with a slow slew rate, which leads to the elimination of the reverse recovery problem in the converter. Soft-switching of the power switch and all the diodes in the proposed converter significantly reduces the switching power dissipations. Therefore, the presented converter can provide a high voltage gain ratio with high efficiency. Steady-state analysis, comprehensive comparisons with other related converters, and design considerations are discussed in detail. Finally, a 160 W prototype with 200 V output voltage is demonstrated to justify the theoretical analysis.

Reverse 1-centre problem on trees under convex piecewise-linear cost function

ABSTRACT Given a network as well as a prescribed vertex s in which a facility is located, the aim of solving reverse 1-centre problems is to decrease edge lengths under a budget constraint in a way that the maximum distance between s and the other vertices is minimized. This paper considers the reverse 1-centre problem on general tree networks with weights associated to vertices under a convex piecewise-linear cost function. It is shown that the problem can be transformed into a parametric minimum cost flow problem. A polynomial time approximation scheme (PTAS) is first developed using the bisection method. Then, the problem on unweighted trees is investigated. Using sensitivity analysis, a pseudo-polynomial time algorithm is designed. Finally, a hybrid algorithm is developed to obtain an exact solution in polynomial time.

Reversibility of number-conserving 1D cellular automata: Unlocking insights into the dynamics for larger state sets

Discrete dynamical systems such as cellular automata are vastly used as models of complex physical phenomena. For this reason, the problem of reversibility of such systems is very important and recurrently taken up by researchers. Unfortunately, the study of reversibility is remarkably hard, even in the case of one-dimensional cellular automata. We propose a novel method that really supports the investigation of the reversibility of number-conserving cellular automata, i.e, cellular automata that preserve the sum of the states of all the cells upon every update. This method allows to enumerate all so-called k-ary (binary, ternary, quaternary, quinary, etc.) number-conserving cellular automata that are reversible and this for a fairly wide range of values of the parameter k.

Benders decomposition for a reverse logistics network design problem in the dairy industry

Benders decomposition for a reverse logistics network design problem in the dairy industry