Chemical pretreatment can significantly improve the enzymatic hydrolysis efficiency of lignocellulosic biomass, thereby improving the yield of sugar materials for the production of cellulosic ethanol, but commonly used acid−base catalysts are difficult to recover and reuse. In this work, a combination method of liquid hot water (LHW) and phosphotungstic acid (PTA) pretreatment was performed to improve the saccharification efficiency of rice straw, and we attempted to evaluate the reuse effect of PTA catalysts. The rice straw was first treated with LHW at 180 °C for 90 min, and then treated with 20 mM PTA at 130 °C for 60 min. After pretreatment, the cellulose hydrolysis efficiency and glucose recovery of the rice straw increased by 201.85% and 164.25%, respectively. Glucose accounted for 96.8% of the total reducing sugar in the final enzymatic hydrolysate. After each PTA pretreatment, approximately 70.8−73.2% of the PTA catalyst could be recycled. Moreover, the catalytic activity of th... [more]

Using cascade utilization between multiple energy sources to realize multi-energy complementarity can significantly improve the economic benefits and energy utilization of integrated energy service providers. Integrated energy service providers consider the cascade utilization of energy in the regional energy system. Through the demand response management of user power loads and different qualities of heat energy, the energy loss of the system can be reduced and the energy utilization efficiency of the system can be further improved. In this paper, we creatively establish a multi-objective optimization model with the goal of a minimum total cost and minimum exergy loss, considering cross elasticity, which is solved with the constraints of equipment operation and the energy balance in the region. The calculation example proves that the implementation of energy cascade utilization and demand response management for different users, by integrated energy service providers, can effectively... [more]

Dynamic adaptive streaming over HTTP (DASH) technique, the most popular streaming method, requires a large number of hard disk drives (HDDs) to store multiple bitrate versions of many videos, consuming significant energy. A solid-state drive (SSD) can be used to cache popular videos, thus reducing HDD energy consumption by allowing I/O requests to be handled by an SSD, but this requires effective HDD power management due to limited SSD bandwidth. We propose a new SSD cache management scheme to minimize the energy consumption of a video storage system with heterogeneous HDDs. We first present a technique that caches files with the aim of saving more HDD energy as a result of I/O processing on an SSD. Based on this, we propose a new HDD power management algorithm with the goal of increasing the number of HDDs operated in low-power mode while reflecting the heterogeneous HDD power characteristics. For this purpose, it assigns a separate parameter value to each I/O task based on the ratio... [more]

The inductor inductor capacitor (LLC) resonant topology has become more popular for deployment in high power density and high-efficiency power converter applications due to its ability to maintain zero voltage switching (ZVS) over a wider input voltage range. Due to their ease of operation and acceptable accuracy, frequency domain-related analytical methods using fundamental harmonic approximation (FHA) have been frequently utilized for resonant converters. However, when the switching frequency is far from the resonant frequency, the circuit currents contain a large number of harmonics, which cannot be ignored. Therefore, the FHA is incapable of guiding the design when the LLC converter is used to operate in a wide input voltage range applications due to its inaccuracy. As a result, a precise LLC converter model is needed. Time domain analysis is a precise analytical approach for obtaining converter attributes, which supports in the optimal sizing of LLC converters. This work strives t... [more]

The pressure bleed-down/build-up (B/B) testing is enforced by the Bureau of Safty and Environmental Enforcement (BSEE) regulations in the US for gas-leaking wells with recurrent casing head annular pressure dubbed “Sustained Casing Pressure” (SCP). The bleed down test involves bleeding the pressure with a needle valve. Once the pressure reached to zero or stabilized, the valve is closedand a 24-h pressure monitoring starts. Analysis of the tests mandated by regulations involves merely a qualitative assessment of the low or high level of environmental risk measured by leak size. A quantitative analysis—based on mathematical models—has been already proposed and used for sizing cement leaks but the models give ambiguous results due to oversimplifying assumptions of the cement leak system and disregard for the testing procedure. This work addresses shortcomings of the current B/B testing and analysis methods by approaching the testing procedure as a source of useful information about the s... [more]

In this paper, driving strategy optimization for a track is proposed for an energy efficient battery electric vehicle dedicated to the Shell Eco-marathon. A measurement-based mathematical vehicle model was developed to simulate the behavior of the vehicle. The model contains complicated elements such as the vehicle’s cornering resistance and the efficiency field of the entire powertrain. The validation of the model was presented by using the collected telemetry data from the 2019 Shell Eco-marathon competition in London (UK). The evaluation of applicable powertrains was carried out before the driving strategy optimization. The optimal acceleration curve for each investigated powertrain was defined. Using the proper powertrain is a crucial part of energy efficiency, as the drive has the most significant energy demand among all components. Two tracks with different characteristics were analyzed to show the efficiency of the proposed optimization method. The optimization results are compa... [more]

Several studies have reported that the hydrothermal carbonization method (HTC) of agricultural waste is able to produce a solid residue with interesting properties for the adsorption of organic pollutants from contaminated water. This work represents a facile method to prepare hydrochar (HC) from pomegranate peels’ waste using the microwave-assisted hydrothermal carbonization method (MHTC) at 200 °C for 1 h with a mass ratio of peel to water = 1:10. Activated hydrochar (AHC) was prepared by in situ chemical activation using ZnCl2 and MHTC. Several techniques have been applied to characterize the prepared samples as FTIR, XRD, TEM and SEM. The samples were investigated for their possible use as adsorbents of methylene blue (MB) dye. The results confirm the formation of amorphous hydrochar with a porous structure. The pH of zero point charge (pHzpc) is 4.3 and 4.6 for HC and AHC samples, respectively. The maximum adsorption capacity of HC and AHC samples are 194.9 and 12.55 mg/g (i.e., m... [more]

This paper investigates how oil’s future price implies the bunker price through cointegration analysis first. A cointegration test confirms the long-run equilibrium condition of bunker and oil future prices. Based on the cointegration relationship, we construct VECM model to forecast bunker prices. In addition, we also consider ARMA, ARMAX, and VAR models for certifying whether considering the long-run equilibrium between bunker and oil future prices is helpful in prediction. One-step-ahead and four-step-ahead forecasting are considered and two out-of-sample datasets are used. The empirical results show that the increase in the value of the error correction term in the VECM model has the effect of pulling down the bunker return. VECM performs better than other models in prediction. The Crude Oil Future Contract 1 has better forecasting performance for bunker prices with VECM in the 1-step-ahead forecast, while Crude Oil Future Contract 3 performs slightly better than Crude Oil Future C... [more]

Due to high unit capacities, electric arc furnaces are among the receivers that significantly affect the power system from which they are supplied. Arc furnaces generate a number of disturbances to the power grid, including fast-changing voltage fluctuations causing the phenomenon of flickering light, asymmetry, and deformation of the voltage curve. The main issues discussed in the article are problems related to the distortion of current and voltage waveforms, resulting from the operation of electric arc furnaces. An analysis of the indices characterizing the voltage distortion recorded in the supply network of the arc furnaces is presented. The changes in the range of current and voltage waveform deformation in individual smelting phases in the arc furnace are also presented. Furthermore, the changes in the degree of deformation of the current and voltage waveforms in the individual smelting phases in an arc furnace are presented. A multi-voltage electric arc model used in computer s... [more]

Both flexoelectricity and piezoelectricity belong to the electromechanical coupling effect. While piezoelectricity only exists in materials whose crystal structure is noncentrosymmetric and a pre-polarization process is necessary for ferroelectric piezoelectric ceramics, flexoelectricity theoretically exists in all dielectric materials and does not require pre-polarization. However, this does not mean that flexoelectricity would not be affected by the pre-polarization process, considering that flexoelectricity is a polarization phenomenon. In this work, we prepared ferroelectric perovskite oxide ceramics Ba1−xCaTiO3 and revealed a strong effect of the pre-polarization process on the flexoelectric response of the ceramics, characterized by the apparent piezoelectric response measured by the point-ring method. The effective piezoelectric coefficient was separated into the one contributed by the flexoelectric(-like) response and the piezoelectric(-like) response by quasi-static d33 measur... [more]

This article reviews the results of measurement of optical properties of oil, such as polarimetry, refractometric, luminescent-bituminological research, IR-spectrometry and UV-visible-NIR spectrometry used to solve geo-bituminology development of hydrocarbon deposits. The authors pay special attention to optical research in the field of UV-visible-NIR electromagnetic radiation, the results of which allow us to estimate the residual oil reserves, separate production for each formation during the operation of multi-layer objects, determine the producing gas-oil ratio, density and content of hydrocarbons, efficiency of hydraulic fracturing, flow-reducing technologies, and injection of solvents of heavy oil sediments, etc. The published approaches to methods of optical research, which are carried out by laboratories or in-well devices, have been analyzed. This article analyzes the main advantages and disadvantages of current technologies for determining the optical properties of oil. The a... [more]

In multi-seam mining, the residual coal pillar (RCP) in the upper gob has an important influence on the layout of the roadway in the lower coal seam. At present, few papers have studied the characteristics of the surrounding rock of gob-side entry driving (GED) with different coal pillar widths under the influence of RCP. This research contributes to improving the recovery rate of the extra-thick coal seam under this condition. The main research contents were as follows: (1) The mechanical parameters of the rock and coal mass were obtained using laboratory experiments coupled with Roclab software. These parameters were substituted into the established main roof structure mechanics model to derive the breakage position of the main roof with the influence of RCP, and the rationality of the calculation results was verified by borehole-scoping. (2) Based on numerical simulation, the evolution laws of the lateral abutment stress in the lower working face at different relative distances to t... [more]

This paper aimed to research the interrelation between capital structure, corporate governance, equity ownership, and how they affect firm performance. The sample used consisted of 10 leading-energy-sector companies traded in the NYSE, most of which rank among the largest companies in the world by market capitalization, while the US-based ones are also Fortune 500 companies. Over the eleven-year period examined, from 2009 to 2019, a sampling frame of 110 data series was gathered and analyzed using panel data methodologies. The impact of the key parameters of capital structure, corporate governance, and equity ownership was tested using regression analysis (panel data method) on firm performance, measured by profitability. Our results support a significant relation among major capital structure and corporate governance parameters and firm performance, whereas no evidence was found to support a significant impact of equity ownership on the dependent variable found ascertained. Furthermor... [more]

Fractured karstic carbonate reservoirs have obvious multi-scale characteristics and severe heterogeneity due to the development of abundant karst caves and fractures with different scales. Darcy and non-Darcy flows coexist due to this property. Therefore, selecting the appropriate flow equations for different regions in the numerical simulation of fluid flows, particularly two-phase and multiphase flows, is a critical topic. This paper compares and analyses the displacement distance differences of waterfront travel using the Darcy, Forchheimer and Barree−Conway equations, as well as analyzes the influence of the Forchheimer constant, fluid viscosity, flow rate and absolute permeability on inertia action based on the Buckley−Leverett theory. The results show that the Forchheimer number/Reynolds number of water/oil two-phase flow is not a constant value and varies with water saturation, making it difficult to determine whether the inertial action should be considered solely based on thes... [more]

Detecting intrusions from the supervisory control and data acquisition (SCADA) systems is one of the most essential and challenging processes in recent times. Most of the conventional works aim to develop an efficient intrusion detection system (IDS) framework for increasing the security of SCADA against networking attacks. Nonetheless, it faces the problems of complexity in classification, requiring more time for training and testing, as well as increased misprediction results and error outputs. Hence, this research work intends to develop a novel IDS framework by implementing a combination of methodologies, such as clustering, optimization, and classification. The most popular and extensively utilized SCADA attacking datasets are taken for this system’s proposed IDS framework implementation and validation. The main contribution of this work is to accurately detect the intrusions from the given SCADA datasets with minimized computational operations and increased accuracy of classifica... [more]

The developed production of heat (steam) by Farmutil Company enables use of renewable energy from biofuel meat-bone meal which is incinerated in rotary kilns utilising vapours and odours from its production, instead of natural gas, to ensure Farmutil’s own needs for heat. The transformation of existing district heating in Piła city (currently using coal) into a fourth generation district heating system was proposed, predicting the use of heat (hot water) after combustion of biofuel meat-bone meal as district heating in the city of Piła. The maximum possible surplus amount of heat that can be produced at Farmutil exceeds the needs for the district heating demands of the city of Piła (860,200 GJ/y) by 53.2% at a meat-bone meal burning scale of 150,000 t/y. The use of 52,000 t/y of meat-bone meal for district heating production also results in an increase in incomes through the sale of hydroxyapatite ash from its combustion, amounting 1.638 million EUR/y. The closure of the coal-fired hea... [more]

Voltages of series-connected energy storage cells, such as electric double-layer capacitors (EDLCs) and lithium-ion batteries, need to be equalized to ensure years of safe operation. However, to this end, a voltage equalizer is necessary in addition to a charger, increasing the system complexity and cost. This paper proposes a family of transformerless single-switch integrated chargers that merge a charger and equalizer into a single unit, achieving a simplified system and circuit. Proposed integrated chargers are derived by stacking multiple conventional pulse width modulation (PWM) converters, such as a superbuck converter, that contain two inductors and one energy transfer capacitor. Detailed operation analyses, including an investigation on the impact of component tolerance on voltage equalization performance, are also performed. Experimental charging tests using a 12-W prototype were performed for four EDLC cells. All cells were charged with eliminating voltage imbalance and demon... [more]

Environmental protection, sustainable development, quality, and value have become the goals of societal development in the twenty-first century. As the core of environmental protection, the new energy sector has become a widespread trend. In this article, we will look at how well and how satisfied customers are with the energy market’s service. A literature review of energy sector quality and value issues was conducted. The survey was conducted in 2021 in Poland with over 2404 respondents by the CAWI survey. Additionally, it was given a qualitative analysis. In the next step, we applied selected quality management methods and tools. The results of the study clearly show that the respondents expect energy companies to become more involved in building customer−enterprise relationships. Research shows that employees of energy companies should be trained more often in the field of customer service, especially in terms of an individual approach to the customer, which has value for the custo... [more]

The design and maintenance of a reliable communication system, especially in harsh working conditions for the oil and mining industry, brings many challenges. With the use of a video transmission system, one can monitor the crew and their working environment. Broadband over power line−power line communication (BPL-PLC) seems an ideal medium for such a service, since it enables the use of the existing wired infrastructure for supplementary applications. In this paper, we perform a set of simulations for a dedicated wired medium as well as analyses of a visual data transmission system, designed to deliver video content with quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM). We investigate a set of video sequences at 480 × 270 resolution under varying network conditions, including signal-to-noise ratio (SNR) and bit error rate (BER). We perform a subjective evaluation study of video content transmitted over our simulated communication link. The re... [more]

Nowadays, several technologies for desalination processes are available and widely employed. However, they consume a considerable amount of energy and involve high capital and operating costs. Therefore, the techno-economic analysis of a system coupling different energy sources with the desalination processes is of value. The possibility of coupling a small gas turbine combined heat and power system (GT CHP) with hybrid desalination plants (HDPs) has been assessed in this study. The proposed gas turbine power generation system, based on a single-stage centrifugal compressor and an uncooled centripetal turbine, provides design simplicity and reasonable installation costs for the power generating plant. The hybrid desalination technique, based on the use of two different desalination technologies, i.e., Reverse Osmosis (RO) and a thermal desalination process, has been chosen to better exploit the electrical and thermal energy produced by the mini CHP plant. The proposed solution is numer... [more]

Traditionally, synchronous motion among multi-module permanent magnet linear synchronous motors (PMLSM) has been achieved by adopting independent power supply and control. This method, however, requires multiple drivers and has control time delays. This paper proposes a novel approach to overcome these drawbacks, in which the windings of each module connect in series. Aiming at this electrical connection, we conduct research on electromagnetic and synchronous characteristics. Firstly, a two-module PMLSM is created as a case. Secondly, accurate mathematical models considering coupling inductance for this novelty structure are established, which are essential to driving control. The synchronous characteristics of the two-module are then compared with the independent control of each module. Furthermore, this comparison is conducted under both external and no external disturbance. Finally, experimental results verify the correctness of mathematical models, and reveal that this novel techni... [more]

The technology of a pulsed detonation gun for gasification of organic waste with ultra-superheated steam has been experimentally demonstrated for the first time. Experiments were performed on natural gas conversion as well as on the gasification of liquid (waste machine oil) and solid (wood sawdust) waste by hot detonation products of natural gas−oxygen mixture at a frequency of detonation pulses f = 1 Hz. Periodic release of detonation products to a 100 L flow reactor provided a time-averaged mean temperature and pressure in the reactor at about 1200 K and 0.1 MPa. It is shown that the technology of a pulsed detonation gun can provide complete (100%) natural gas conversion to syngas containing H2 and CO with a H2/CO ratio of 1.25. During the gasification of liquid and solid wastes, the total volume fraction of combustible gases (H2, CO, and CH4) in the product syngas was 80 and 65% with H2/CO ratios of 0.8 and 0.5, respectively. Comparison of the experiments on natural gas conversion... [more]

The exploitation and utilization of coal resources are not only prone to causing water table lowering, but also produce a large amount of CO2 and coal-based solid waste. A scientific concept that employs the CO2 and solid wastes to develop filling bodies and inject them into the mined-out area, to sequestrate CO2 and mitigate the overburden migration and thus preserve the overlying aquifer, is proposed. Continuous extraction and continuous backfill (CECB) mining was selected as the mining method to meet the aforementioned objectives. Additionally, carbon dioxide mineralized filling body (CMFB) under ambient temperature and pressure was developed, with fly ash as aggregate, and CO2 gas, silicate additives and cement as accessories. The uniaxial compressive strength (UCS) and tensile strength of CMFB with various curing times and fly ash contents were tested indoors. A physical analogue simulation and FLAC3D numerical calculation were then successively implemented on the premise of deter... [more]

During the last few years, nuclear energy has received great attention due to the increase in climate change awareness. According to the Paris agreement, global temperature is to be kept below 2 °C and preferably below 1.5 °C by 2050. This approach has been substantially confirmed in the recent COP 26 in Glasgow. This research investigates the effects of integrating SMR nuclear power plants (small modular reactors) into the Nordhaus Dynamic Integrated Climate Economy (DICE) model for reducing the CO2 emissions in the atmosphere by substituting all existing fossil-fueled power plants (FPPP). The software is based on the VENSIM dynamic systems modeling platform. Simulations were carried out from the year 2019 to 2100 using 10-year increments. Several scenarios were thus simulated replacing roughly 70,000 FPPPs operating at this time in the world. Simulations indicate a CO2 reduction of approximately 12.63% relative to the initial conditions used and using 87,830 SMR core units of 80 MWe... [more]

The performance and stability of the transonic fan stage with a nonuniform inflow is a key issue in aero engine operation, and the coupling of inlet distortion and low Reynolds numbers at high altitude creates more severe challenges to aero engines. This work used computational methods to explore the performance and stability of a transonic fan stage with inlet distortion and a low Reynolds number. To investigate this issue, the transonic fan stage NASA stage 67 with a 180° total pressure distortion at a low Reynolds number was selected as the test case. Full-annulus 3D unsteady simulations were conducted to reveal the details of the flow field under coupling conditions. The computational results under different conditions were analyzed and showed that the coupling effect was not linearly stacked with single factors. The low Reynolds number in the coupling case thickened the boundary layer on the blade surface, and, on the one hand, the profile loss in the hub region increased. On the... [more]