Combined Scheme Research Articles

A combined compact finite difference scheme for solving the acoustic wave equation in heterogeneous media

AbstractIn this paper, we consider the development and analysis of a new explicit compact high‐order finite difference scheme for acoustic wave equation formulated in divergence form, which is widely used to describe seismic wave propagation through a heterogeneous media with variable media density and acoustic velocity. The new scheme is compact and of fourth‐order accuracy in space and second‐order accuracy in time. The compactness of the scheme is obtained by the so‐called combined finite difference method, which utilizes the boundary values of the spatial derivatives and those boundary values are obtained by one‐sided finite difference approximation. An empirical stability analysis has been conducted to obtain the Courant‐Friedrichs‐Levy (CFL) condition, which confirmed the conditional stability of the new scheme. Four numerical examples have been conducted to validate the convergence and effectiveness of the new scheme. The application of the new scheme to a realistic wave propagation problem with a Perfect Matched Layer is validated in this paper as well.

Static and multi-impact performances of RC beams strengthened with large rupture-strain FRP composites

To solve the problem of inadequate plastic deformation capacity and energy dissipation of traditional fiber-reinforced polymer (FRP) strengthened structures under impact loading, this study proposes the use of novel large-rupture-strain fiber-reinforced polymer (LRS-FRP) materials combined with different strengthening schemes to improve the impact resistance of existing structures. This study conducted three-point bending and drop hammer tests to investigate the static and dynamic behaviors of flexure-dominated LRS-FRP-strengthened beams. Experiment results showed that the end-anchored FRP strengthening system at the beam soffit significantly improved the load capacity of beams under static loading and reduced the maximum mid-span deflection under impact loading, and the ductility factor of LRS-FRP strengthened beams under static loading was 2.7 times higher than that of the carbon-FRP (CFRP) counterpart. Specimens strengthened with a mid-span LRS-FRP wrapping scheme presented improved ductility and multi-impact performance. Specimens strengthened with a combined scheme enhanced the static load capacity and ductility of by 71.9 % and 159.7 %, respectively, compared to the unstrengthened beam, and exhibited the best energy dissipation capacity (23.8 kJ) under multiple impact loads. These findings from the test investigations can facilitate design guidance and evaluation methods for strengthening schemes for RC structures under impact loading.

On an iteratively reweighted linesearch based algorithm for nonconvex composite optimization

In this paper we propose a new algorithm for solving a class of nonsmooth nonconvex problems, which is obtained by combining the iteratively reweighted scheme with a finite number of forward–backward iterations based on a linesearch procedure. The new method overcomes some limitations of linesearch forward–backward methods, since it can be applied also to minimize functions containing terms that are both nonsmooth and nonconvex. Moreover, the combined scheme can take advantage of acceleration techniques consisting in suitable selection rules for the algorithm parameters. We develop the convergence analysis of the new method within the framework of the Kurdyka–Łojasiewicz property. Finally, we present the results of a numerical experience on microscopy image super resolution, showing that the performances of our method are comparable or superior to those of other algorithms designed for this specific application.

H2 from biofuels and carriers: A concerted homo-heterogeneous kinetic model of ethanol partial oxidation and steam reforming on Rh/Al2O3

Investigating bioethanol as a renewable energy source is crucial in the context of H2-based economy. Ethanol partial oxidation and steam reforming on Rh/Al2O3 represent promising processes that have already proved to be highly tangled reacting systems.In this work, a significant step forward has been done towards the development of an engineering tool that can capture all the relevant features of the process; a combined homo-heterogeneous kinetic scheme was developed and validated against experimental data, informative of the catalytic and thermal activation of the C2-alcohol.In particular, a 36-species reduced homogeneous scheme was developed, able to capture observed trends with a limited computational load. On the other side, a macro-kinetic heterogeneous scheme with six molecular reactions (ethanol oxidative dehydrogenation, total oxidation, decomposition, dehydrogenation, steam reforming and acetaldehyde post-reforming) was tuned to accurately describe ethanol/O2 and ethanol/H2O reacting systems.

Non-Linear Signal Processing Methods for UAV Detections from a Multi-Function X-Band Radar

This article develops the applicability of non-linear processing techniques such as Compressed Sensing (CS), Principal Component Analysis (PCA), Iterative Adaptive Approach (IAA), and Multiple-input-multiple-output (MIMO) for the purpose of enhanced UAV detections using portable radar systems. The combined scheme has many advantages and the potential for better detection and classification accuracy. Some of the benefits are discussed here with a phased array platform in mind, the novel portable phased array Radar (PWR) by Agile RF Systems (ARS), which offers quadrant outputs. CS and IAA both show promising results when applied to micro-Doppler processing of radar returns owing to the sparse nature of the target Doppler frequencies. This shows promise in reducing the dwell time and increases the rate at which a volume can be interrogated. Real-time processing of target information with iterative and non-linear solutions is possible now with the advent of GPU-based graphics processing hardware. Simulations show promising results.

Detecting dengue fever in children using online Rasch analysis to develop algorithms for parents: An APP development and usability study.

Dengue fever (DF) is a significant public health concern in Asia. However, detecting the disease using traditional dichotomous criteria (i.e., absent vs present) can be extremely difficult. Convolutional neural networks (CNNs) and artificial neural networks (ANNs), due to their use of a large number of parameters for modeling, have shown the potential to improve prediction accuracy (ACC). To date, there has been no research conducted to understand item features and responses using online Rasch analysis. To verify the hypothesis that a combination of CNN, ANN, K-nearest-neighbor algorithm (KNN), and logistic regression (LR) can improve the ACC of DF prediction for children, further research is required. We extracted 19 feature variables related to DF symptoms from 177 pediatric patients, of whom 69 were diagnosed with DF. Using the RaschOnline technique for Rasch analysis, we examined 11 variables for their statistical significance in predicting the risk of DF. Based on 2 sets of data, 1 for training (80%) and the other for testing (20%), we calculated the prediction ACC by comparing the areas under the receiver operating characteristic curve (AUCs) between DF + and DF- in both sets. In the training set, we compared 2 scenarios: the combined scheme and individual algorithms. Our findings indicate that visual displays of DF data are easily interpreted using Rasch analysis; the k-nearest neighbors algorithm has a lower AUC (<0.50); LR has a relatively higher AUC (0.70); all 3 algorithms have an almost equal AUC (=0.68), which is smaller than the individual algorithms of Naive Bayes, LR in raw data, and Naive Bayes in normalized data; and we developed an app to assist parents in detecting DF in children during the dengue season. The development of an LR-based APP for the detection of DF in children has been completed. To help patients, family members, and clinicians differentiate DF from other febrile illnesses at an early stage, an 11-item model is proposed for developing the APP.

Transmission of Power and Signal Multiplex for Electric Vehicles Using Cascaded Multilevel Inverters

Abstract: P&amp;SMT, or power and signal multiplex transmission, is a method for transmitting communication signals using power electronic circuits. A three-phase cascaded multilevel inverter-based P&amp;S MT system is recommended in this investigation. By allowing communication signals to be transmitted without utilizing a Controller Area Network bus, the proposed solution can lower the wiring expense of the existing electric vehicle (EV) communication system. The system's architecture enables battery balancing discharge and motor speed management for EVs. In a simulation system proposed in MATLAB/Simulink, both power and communication signals are effectively conveyed using the combined pulse width modulation scheme and frequency shift keying approach. The maximum signal rate of the proposed system is established at 600 bits per second by analyzing the bit error rate of the sent signal.

New contributions for speed observation of asynchronous motor fed by multilevel inverter

ABSTRACT Control fulfilment of asynchronous motors requires accurate feedback of speed information. Previously, this function was attributed to mechanical sensors, however, due to the limited use restrictions, scientists have developed variety of speed observation algorithms. These latter are distinguished by their simplicity and sensitivity to machine parameter variations as well as their robustness even in a wide speed range. This paper proposes three new structures of observers in order to achieve an efficient behaviour at low and high speed. The first is a combined scheme of sliding mode observer and model reference adaptive system, the second consists in switching between the two aforementioned observers according to the operating speed, while the third consists in switching from sliding mode observer to the combined estimator. Moreover, the overall control scheme performance is enhanced by using sliding mode principle in a direct torque structure to control the motor fed by NPC multilevel inverter. Besides, a sliding mode controller is inserted in the external loop to regulate speed and provide a stable torque. To shed light on the efficiency of the proposed contributions, a critical and comparative study of simulation results has been conducted.

Concept of formation of combined transport and logistics infrastructure of Siberia, Far East and Arctic zone of Russia

This article discusses the problems and outlines a conceptual approach to the development of remote regions of Russia with large reserves of natural resources and complex geographical and climatic conditions that ensure the country's economic growth, through ensuring the transport accessibility of these regions and the growth of industry in them. The work made a conceptual justification of the need to develop cooperation of all types of transport using multimodal and intermodal transportation. Attention is drawn to the need to integrate land and water modes of transport, as well as the formation of a special combined transport scheme that combines latitudinal and meridional trunk transport directions.

Study on Stability Control Mechanism of Deep Soft Rock Roadway and Active Support Technology of Bolt-Grouting Flexible Bolt

In order to study the stability control mechanism of deep soft rock roadway and the active support technology of the anchor-grouting flexible bolt, this paper takes the west wing transportation roadway of Yuandian No. 2 Coal Mine of Huaibei Mining Co., Ltd., Huaibei, China as the research background. By analyzing the occurrence conditions and failure characteristics of the surrounding rock of the west wing transportation roadway and the structural characteristics and mechanical properties of the anchor-grouting flexible bolt, combined with the elastic–plastic and superimposed arch theory analysis, the superposition community theoretical model and the superposition joint support scheme of “bolt (cable) + anchor net + anchor-grouting flexible bolt + shotcrete support” are proposed. The reliability of the combined support scheme is analyzed by FLAC 3D numerical simulation software and field experiment. The results show that the maximum roof-to-floor convergence and two-side convergence of the west wing transportation roadway are only 30.7 mm and 27.1 mm after adopting the combined support scheme, and the deep displacement variation is within 7 mm, which can effectively maintain the stability of the roadway. The combined support scheme has a certain reference value for other similar roadways.

Combined Feature Selection Scheme for Banking Modeling

Machine learning methods have been successful in various aspects of bank lending. Banks have accumulated huge amounts of data about borrowers over the years of application. On the one hand, this made it possible to predict borrower behavior more accurately, on the other, it gave rise to the problem a problem of data redundancy, which greatly complicates the model development. Methods of feature selection, which allows to improve the quality of models, are apply to solve this problem. Feature selection methods can be divided into three main types: filters, wrappers, and embedded methods. Filters are simple and time-efficient methods that may help discover one-dimensional relations. Wrappers and embedded methods are more effective in feature selection, because they account for multi-dimensional relationships, but these methods are resource-consuming and may fail to process large samples with many features. In this article, the authors propose a combined feature selection scheme (CFSS), in which the first stages of selection use coarse filters, and on the final — wrappers for high-quality selection. This architecture lets us increase the quality of selection and reduce the time necessary to process large multi-dimensional samples, which are used in the development of industrial models. Experiments conducted by authors for four types of bank modelling tasks (survey scoring, behavioral scoring, customer response to cross-selling, and delayed debt collection) have shown that the proposed method better than classical methods containing only filters or only wrappers.

Launching Earth radiation monitoring satellites using the combined thrust

The paper considers the problem of launching satellites into the orbits for Earth radiation monitoring using the upper stage previously inserted into a reference circular orbit and equipped with a combined propulsion system, i.e. chemical rocket engines and electric rocket propulsion system (ERPS). The combined launch scheme implies formation of the intermediate orbit using the chemical rocket engines and further successive satellites insertion into the target orbits using the electric rocket propulsion system. Calculation of the satellite group launch trajectory parameters is provided, single accompanying and two more in cluster formation, to the given elliptical orbits. The spacecraft flight is approximated at the chemical rocket engines operation phase by a pulse action using the double-pulse apsidal maneuvers; and the spacecraft flight trajectory in the ERPS phase is calculated under the condition of minimizing the flight time with the Pontryagin maximum principle. The results obtained demonstrate technical feasibility of the task of launching satellites into specified orbits using the combined thrust, as well as advantages of a combined scheme for launching a payload in order to reduce flight duration compared to using the ERPS throughout the entire flight.

The first reported case of erythrodermic sarcoidosis with systemic involvement during COVID-19 vaccination.

Post-vaccinal and parainfectious activation of the immunity with subsequent development of a certain immunological/skinimmunological disease is not rare in clinical practice. This concept is mentioned in relation to molecular/antigenic mimicry. To this day, the pathogenesis of sarcoidosis and sarcoid-type reactions remains a mystery. Moreover, they can be a warning sign of changes in tissue homeostasis, whether they are infectious, noninfectious- immunological, tumor-related, etc. We present a rare form of erythrodermic sarcoidosis with massive systemic involvement (pericarditis, supraventricular tachycardia, hepatitis, iritis/iridocyclitis, pulmonary fibrosis/bihilar lymphadenopathy, and arthritis) developed after receiving the ChadOx1-S vaccine for COVID- 19. Systemic immunosuppressive therapy with Methylprednisolone was introduced according to a scheme (in a reduction mode with an initial dose of 40 mg/day intravenously) in combination with topical Pimecrolimus 1% cream twice a day. Rapid improvement of the symptoms was observed within the first two days of treatment. According to the scientific literature, the presented patient turns out to be the first case of erythrodermic sarcoidosis (with systemic involvement), described as a side effect after vaccination and/or administration of a certain medicinal form.

ANODIC PROCESSES OF URANIUM ALLOYS CONTAINING PALLADIUM AND NEODYMIUM IN 3LiCl–2KCl-UCl&lt;sub&gt;3&lt;/sub&gt; MELTS

At the reprocessing module of the pilot demonstration power complex site of the Siberian Chemical Combine, a combined technological scheme for the reprocessing of mixed nitride uranium-plutonium spent fuel consisting of pyrochemical operations, hydrometallurgical refining of uranium, plutonium and neptunium is implemented step by step. According to this scheme, the target pyrochemical reprocessing products, purified from the main mass of fission products with actinoid content not less than 99.9%, are sent for hydrometallurgical reprocessing. For pyrochemical reprocessing it is necessary to develop a technology of electrorefining of metallised spent nuclear fuel. To carry out electrolytic refining it is necessary to define processes and regimes of anodic dissolution of alloys simulating product of this head operation “metallization”. In the present work the results of investigations of processes of anodic dissolution of U–Pd and U–Pd–Nd model alloys with different concentrations of palladium and neodymium in melts based on 3LiCl–2KCl–UCl3 (10.1 wt % UCl3) at 550°C using different methods are presented. Uranium alloys containing palladium and neodymium were prepared by direct alloying of uranium metal and palladium metal powders of PdAP-1 grade, and neodymium metal (99.99%) in high-purity argon medium (99.998%). Electrochemical measurements were performed using an Autolab 302N potentiostat/halvanostat equipped with a Booster 20A high-current module. The anodic polarisation curves consist of only one oxidation wave which was attributed to the dissolution of uranium metal. Increasing the palladium content in the alloy from 1.5 to 10.0 wt %, does not affect the shape of the polarisation curves. The increase of neodymium content in the alloy from 1.0 to 10.0 wt % also does not affect the shape of polarization curves. Electrorefining parameters of uranium alloys containing palladium and neodymium were determined. The limiting current density of uranium evolution from uranium alloys containing palladium and neodymium in the electrolyte 3LiCl–2KCl–UCl3 (10.1 wt % UCl3) at 550°C was 0.4 A/cm2. It was shown that palladium does not diffuse into the melt as a result of anodic dissolution and neodymium accumulates in the electrolyte only when the alloy is refined with 10.0 wt % neodymium, which is much higher than the future real concentrations of electrotreated uranium alloy components in the technological chain of spent nuclear fuel processing.

The research about application of quasi-zero stiffness vibration isolation technology in a large vehicle-mounted optic-electronic equipment

The large vehicle-borne optic-electronic tracking equipment has the characteristics of heavy inertia, complex road condition and wide vibration spectrum. In order to solve the problem of passive broadband vibration isolation for vehicle-mounted moving platform optic-electronic equipment, a combined quasi-zero stiffness vibration isolation scheme is proposed. The vibration of the engine, generator, water cooler and the remaining vibration amplitude, frequency and Yaw of the road after passing the self-vibration isolation system of the vehicle are collected and confirmed by means of calculation simulation and field test. At the same time, the effective load of photoelectric equipment is analyzed by frequency sweeping test, and the corresponding multi-mode frequency points are obtained. According to the characteristics of the special equipment, a quasi-zero-stiffness vibration isolation system is designed to suppress the wide-frequency and high-amplitude vibration and Yaw caused by vehicle-borne vibration source, ground vibration source and resonance point of the equipment, the foundation stability of load equipment under dynamic condition is realized, which provides a condition for solving the problem of high precision and stability tracking which is greatly influenced by vibration. The vibration isolation system can realize the vibration isolation efficiency of 90% in the range of 20 Hz to 2000 Hz under the condition of 60 Km/h three-class highway with 1.5 t photoelectric load, and restrain the deflection caused by unbalance torque and vibration source offset effectively. It can be concluded that the quasi-zero stiffness vibration reduction and isolation combination design can effectively suppress the vibration of the large-scale vehicle-mounted optic-electronic equipment under the condition of moving platform.

ON THE ACCURACY OF DISCONTINUOUS GALERKIN METHOD CALCULATING GAS-DYNAMIC SHOCK WAVES

The results of a numerical calculation of gas-dynamic shock waves that arise when solving the Cauchy problem with smooth periodic initial data are presented using three variants of the DG (Discontinuous Galerkin) method, in which the solution is sought in the form of a piecewise linear discontinuous function. It is shown that the methods DG1A1 and DG1A2, for which the Cockburn limiter with parameters A1 = 1 and A2 = 2 are used for monotonization, have approximately the same accuracy in the influence areas of shocks (arising as a result of gradient catastrophes within the computational domain), while the nonmonotonic DG1 method, in which this limiter is not used, has a significantly higher accuracy in these areas, despite noticeable non-physical oscillations on shocks. With this in mind, the combined scheme obtained by the joint application of the DG1 and DG1A1 methods monotonously localizes the shocks and maintains increased accuracy in the areas of their influence.

IoT Supervised PV-HVDC Combined Wide Area Power Network Security Scheme Using Wavelet-Neuro Analysis

Power system networks are one of the most widely used methods in the real world for transferring large amounts of electrical energy from one location to another. At present, High Voltage Direct Current Transmission is preferred for long distances over hundreds of miles due to minimal power loss and transmission cost of transmission.Due to an increase in power demand, integration of renewable sources to minimise the voltage fluctuations and compensate for power loss is necessary. This is a mandatory requirement to produce sophisticated protection methods for mainly smart systems under various balanced and unbalanced fault conditions. The system protection scheme must respond as quickly as possible to protect the connected devices in a smart environment. The network must be monitored and protected under various weather conditions as well as electrical parametric problems. The proposed research work is carried on the basis of physical monitoring with the aid of the Internet-of-Things and electrical parameters calibrated with the help of wavelet analysis. A wavelet is a mathematical tool to investigate the behaviour of transient signals at different frequencies, which provides important information related to the detailed analysis of faults in power networks. The major goals of this research are to analyse faults using detailed coefficients of current signals through the bior-1.5 mother wavelet for fault identification and artificial neural network analysis for fault localization. This proposed approach furnishes an IoT supervised Photovoltaic - High Voltage Direct Current (HVDC) combined wide area power network security scheme using wavelet detailed coefficients under various types of faults with Fault-Inception-Angles.

Water hammer protection for diversion systems in front of pumps in long-distance water supply projects

For a water supply system with long-distance diversion pipelines, in addition to the water hammer problems that occur beyond pumps, the safety of the water diversion pipeline in front of pumps also deserves attention. In this study, a water hammer protection scheme combined with an overflow surge tank and a regulating valve was developed. A mathematical model of the overflow surge tank was developed, and an analytical formula for the height of the overflow surge tank was derived. Furthermore, a practical water supply project was used to evaluate the feasibility of the combined protection scheme and analyze the sensitivity of valve regulation rules. The results showed that the combined protection scheme effectively reduced the height of the surge tank, lessened the difficulties related to construction, and reduced the necessary financial investment for the project. The two-stage closing rule articulated as fast first and then slow could minimize the overflow volume of the surge tank when the power failure occurred, while the two-stage opening rule articulated as slow first and then fast could be more conducive to the safety of the water supply system when the pump started up.

Study on surrounding rock failure mechanism and rational coal pillar width of the gob‐side coal roadway under influence of intense dynamic pressure

AbstractA reasonable width of the coal pillar is very important to the surrounding rock control of the gob‐side roadway. An unreasonable width of the coal pillar will make the roadway to be located within the range of strong mining influence, leading to severe deformation of the roadway. Severe subsidence at the coal pillar side of the roof and serious coal pillar deformation are problems caused by strong dynamic pressure due to mining in the gob‐side coal roadway. This paper studies the surrounding rock instability mechanism and rational coal pillar width of the gob‐side coal roadway under the influence of intense dynamic pressure. The results show that: (1) Under the condition of large mining height, the roadway overburden is a hinged structure, and an unreasonable coal pillar width makes the gob‐side coal roadway to be located below the main roof fracture line. The rotary movement of the key block of the main roof is the main reason for the roadway deformation. (2) According to the evolution law of stress field, displacement field and plastic zone of surrounding rock of roadway under different coal pillar widths during roadway driving and mining were studied, and it is concluded that a 6‐m‐width coal pillar is the most reasonable. (3) Based on the stress distribution and plasticizing range of surrounding rock in a narrow pillar roadway, the combined support scheme of “anchor cable + grouting + single prop” is proposed and applied to engineering practice. The practice results show that the roadway deformation is well controlled, and the safe mining of the working face is realized.

A nonconvex model-based combined geometric calibration scheme for micro cone-beam CT with irregular trajectories.

Many dedicated cone-beam CT (CBCT) systems have irregular scanning trajectories. Compared with the standard CBCT calibration, accurate calibration for CBCT systems with irregular trajectories is a more complex task, since the geometric parameters for each scanning view are variable. Most of the existing calibration methods assume that the intrinsic geometric relationship of the fiducials in the phantom is precisely known, and rarely delve deeper into the issue of whether the phantom accuracy is adapted to the calibrationmodel. A high-precision phantom and a highly robust calibration model are interdependent and mutually supportive, and they are both important for calibration accuracy, especially for the high-resolution CBCT. Therefore, we propose a calibration scheme that considers both accurate phantom measurement and robust geometriccalibration. Our proposed scheme consists of two parts: (1) introducing a measurement model to acquire the accurate intrinsic geometric relationship of the fiducials in the phantom; (2) developing a highly noise-robust nonconvex model-based calibration method. The measurement model in the first part is achieved by extending our previous high-precision geometric calibration model suitable for CBCT with circular trajectories. In the second part, a novel iterative method with optimization constraints based on a back-projection model is developed to solve the geometric parameters of eachview. The simulations and real experiments show that the measurement errors of the fiducial ball bearings (BBs) are within the subpixel level. With the help of the geometric relationship of the BBs obtained by our measurement method, the classic calibration method can achieve good calibration based on far fewer BBs. All metrics obtained in simulated experiments as well as in real experiments on Micro CT systems with resolutions of 9 and 4.5 μm show that the proposed calibration method has higher calibration accuracy than the competing classic method. It is particularly worth noting that although our measurement model proves to be very accurate, the classic calibration method based on this measurement model can only achieve good calibration results when the resolution of the measurement system is close to that of the system to be calibrated, but our calibration scheme enables high-accuracy calibration even when the resolution of the system to be calibrated is twice that of the measurementsystem. The proposed combined geometrical calibration scheme does not rely on a phantom with an intricate pattern of fiducials, so it is applicable in Micro CT with high resolution. The two parts of the scheme, the "measurement model" and the "calibration model," prove to be of high accuracy. The combination of these two models can effectively improve the calibration accuracy, especially in some extremecases.