A low material removal rate and a high tool wear rate are two major concerns among the research and development community of electric-discharge machining. From the literature, it is evident that several researchers have attempted to improve the material removal rate and minimize the tool wear rate by different means, such as parametric optimizations, powder mixing in the dielectric, induced vibrations in the electrode and/or workpiece, etc. Herein, an attempt is made to make use of a non-conventional electrode with a relief angle along with the taper angle of the machined feature and perform electric-discharge machining on D2-steel using copper as an electrode material. Preliminary level mathematical models were developed and validated for sparking the area of each non-conventional electrode’s design type. Three-stage experimentation was performed to identify the most appropriate electrode design. An approximately 70% improvement in the material removal rate, an around 45−50% reduction... [more]

Deep geothermal energy is a renewable and environmentally friendly resource, and the hot dry rock in a geothermal reservoir is subjected to thermal cycling treatment. Thermal cycling treatment can cause thermal stresses in the rock matrix and result in thermal cracking, which significantly influence the physical and mechanical properties of a rock. To investigate the influence of thermal cycling treatment on the microcrack propagation and mechanical behavior of a granite rock, a series of physical and mechanical tests were performed on nontreated and treated granite samples. The testing results show that the mass, density, and P-wave velocity of granite decrease with heating temperature and cycling time increase, while the volume of the samples increases significantly. The UCS and elastic modulus of the granite declined from 178.65 MPa and 20.09 GPa to 24.58 MPa and 3.81 GPa after treatment at 500 °C for 30 thermal cycling times, respectively. The degradation trends of the UCS and the... [more]

The water channeling of fractured carbonate rock seriously affects oil recovery, and this problem is especially serious in the Kazakh North Troyes oilfield. A conventional powder polymer plugging system needs to be hydrated ahead of time, which increases the cost and difficulty of field operation and it cannot realize large-scale plugging operations. The new emulsion polymer crosslinked system can realize rapid hydration and real-time mixing, having low base liquid viscosity and good fluidity and injectability. The results of the laboratory study show that the gelling time of HR9806 emulsion polymer and organic chromium crosslinker was 6~8 h. 0.5 wt % HR9806, which is recommended for field use with P/C ranging from 2.5 to 5.0. The emulsion polymer crosslinking system was found to be highly adaptable in reservoirs and had salinity resistance. Mineral salt and reservoir core were able to enhance the gel strength of the system but shortened the gelling time of the system by about 2 h. The... [more]

The aim of this paper was to study the suppression influence of water mist on oil pool fires, taking diesel fires and n-heptane fires as experimental objects. The effects of spray pressure and temperature on water mist suppression were examined, and an experimental platform for the suppression of water mist in a small space was set up. Their fire prevention performance and fire extinguishing mechanisms were analyzed by comparing the flame temperature and extinguishing time of diesel and n-heptane pool fire. Three types of spray pressure were set. Water mist was designed at different temperatures and design experiments were carried out for this purpose. The change process of smoke concentration, thermocouple temperature, and flame combustion under different working conditions were analyzed, and the factors affecting the fire extinguishing effect of water mist on oil pool fire were discussed. The results show that 20 °C water mist is more effective at medium and high pressure than at low... [more]

Microbial lipases are the biocatalyst of choice for the present and future because of their characteristics, including their ability to remain active as an enzyme throughout a broad pH, temperature, and substrate range. The goal of the current investigation was to find novel sources of substrates and isolates from soil contaminated by oil for the synthesis of lipase. On tributyrin media, 10 lipolytic bacterial strains that were isolated from oil-contaminated soil were grown. Using the zone of clearance, it was possible to identify the isolates with the highest activity. Following phylogenetic tree analysis, molecular characterization of the 16S rRNA sequence of the bacterial isolates revealed that it was Bacillus halotolerans (VSH 09). The enzyme was purified to near homogeneity. The enzyme activity was found to be optimum at a pH of 7.0 and a temperature of 35 °C. While Ni2+ and Cu2+ had no effect, the presence of Mg2+ and Ca2+ exhibited the highest levels of enzyme activity. At 1%, t... [more]

Polycrystalline cubic boron nitride (PCBN) tools are widely used for hard machining of various ferrous materials. The edge structure of the PCBN cutting tool greatly affects the machining performance. In this paper, dry turning experiments were conducted on gray cast iron with a PCBN chamfered tool. Both the cutting temperature and the cutting force were measured, and then the surface quality and tool wear mechanisms were analyzed in detail. It was found that the cutting temperature and cutting force increased with the increase in feed rate, depth of cut, and cutting speed. The surface roughness firstly decreased, and then increased with an increase in feed rate. The minimum surface roughness was obtained with a feed rate of 0.15 mm/r which exceeded the tool chamfer width. The PCBN tool wear mode was mainly micro notches on the rake face and micro chipping on the tool chamfer, while the adhesion wear mechanism was the main tool wear mechanism.

The combined heating and power (CHP) plants are considered one of the promising methods to support the goal of “Carbon Peak and Carbon Neutrality”. It is an important means to take heat and power load optimal dispatch (LOD) to further reduce the energy consumption of CHP plants. To achieve a better load dispatch scheme, this paper employs a potent algorithm by integrating the grey wolf optimization (GWO) algorithm and the Levy flight (i.e., Levy−GWO algorithm) to overcome premature convergence. Moreover, the constraint condition processing method is also proposed to handle the system constraints for ensuring the results within feasible zones. To confirm the effectiveness of this algorithm, it is tested on two widely used test systems (Test system I and Test system II). The accuracy of the used algorithm is proved by comparing the obtained results and reported data in other literature. Results show that the Levy−GWO algorithm can be used to obtain relatively lower power generation costs... [more]

Low permeability porous carbonate rocks occupy a certain proportion in the Middle East. Horizontal injection-production well pattern development is often adopted. Due to the influence of well type and wellbore, reservoir dynamic monitoring is mainly based on conventional daily measurement data, well test and pressure monitoring. Therefore, it is particularly important to combine well test interpretation with production dynamic analysis to diagnose the main control factors and production characteristics of this type of reservoir. In this paper, the point source function is used to obtain the pressure variation function of a horizontal well in infinite formation with upper and lower closed boundary. The difference between the horizontal well test curve of A reservoir and the typical horizontal well test curve is compared and analyzed, and the abnormal well test curve of horizontal wells is characterized by a linear flow phase with a slope of 1/3 or 1/4. The abnormal well test curve accou... [more]

Considering the uniformity of cable tension variation, in this paper, the trajectory planning problem of the exit point for a continuously reconfigurable four-cable-driven two-degrees-of-freedom (DOF) parallel mechanism was studied. Furthermore, an improved quadratic programming model-based trajectory planning method is proposed, which greatly reduces the change in cable tension and can be used to solve the problem of excessive cable tension change when the existing mechanism moves on the moving platform. First, the structural characteristics of the parallel mechanism with a fixed exit point were analyzed, and the static model was established. Considering the cable length and tension constraints, the feasible workspace of the mechanism force was solved. Then, based on the dynamic modeling, an improved quadratic programming model was used to solve the cable tension values under the typical trajectory in the force-feasible workspace. Finally, considering the influence of structural param... [more]

Regular physical activity confers health benefits and improves the general quality of life. Recently, alkaline-reduced water (ARW) consumption has garnered increasing attention in the field of sports. ARW effectively inhibits the oxidative stress generated in cells during high-intensity exercises; however, whether it exerts similar effects during exhaustive exercises remains unknown. This study was designed as a randomized, controlled, crossover, double-blind clinical trial with a single intervention of ARW intake (pH 9.5, 10 mL/kg body weight) after intense exercise. The participants were divided into two groups, wherein they consumed either purified water (PW group) or ARW (ARW group). Blood samples were collected before exercise, immediately after exercise, and 15 min after drinking water. The serum levels of oxidative stress markers and fatigue markers were determined. The results showed that ROS (p < 0.01) and NO levels (p < 0.001) were significantly decreased after ARW inta... [more]

The reduction of metal oxides by biochar is an important reaction for many biomass utilization technologies. This work investigated the temperature−programmed reduction (TPR) of NiO/Al2O3 by in situ generated biochar from citric acid pyrolysis. Firstly, NiO/Al2O3 was loaded with citric acid by impregnation and then heated from ambient temperature to 900 °C in a N2 flow. The process was on−line analyzed by the TGA−FTIR technique. Secondly, a series of intermediates was obtained and characterized by XRD, CHNO elemental analysis, and temperature programmed oxidation (TPO). Lastly, a control experiment of unsupported NiO was conducted to show the influence of Al2O3 support on the NiO reduction. Results showed that the whole heating process could be resolved into two parts that is citric acid pyrolysis and NiO reduction at a heating rate of 5 °C/min. The NiO reduction occurred above 400 °C with the biochar from citric acid pyrolysis as reductant. In the temperature−programmed reduction proc... [more]

Oxidation denitration is one of the most efficient ways to remove NOx from flue gas in a coal-fired power plant. However, this oxidation denitration produces saline solution containing a high concentration of nitrate, which needs to be well treated. In this paper, MFC was firstly used to treat the high nitrate content saline denitration solution from ozone oxidation denitration of a coal-fired power plant. The influences of chemical oxygen demand (COD) and initial nitrate concentration on the nitrate removal and electricity generation of MFC were investigated by sequencing batch mode. The results showed that using MFCs could efficiently remove nitrate from coal-fired power plant saline denitration solution with nitrate nitrogen (NO3−-N) concentration up to 1510 mg/L. The average nitrate nitrogen removal rate was as high as 248.3 mg/(L·h) at initial nitrate nitrogen concentration of 745 mg/L and COD concentration of 6.5 g/L, which was eight times as high as that of the conventional biol... [more]

Electro-hydraulic servo pump control belongs to an electro-hydraulic coupling motion control system, which involves the mutual penetration and integration of mechanical, hydraulic, electrical, control, and other disciplines, as well as the time-varying, uncertain, multisource, and multifield problems of the internal and external excitation of the system, which makes the electro-hydraulic servo pump control system have the characteristics of a complex model, strong coupling, nonlinearity, and time-variation, resulting in the low accuracy and poor dynamic characteristics of the system. This paper takes a servo motor quantitative pump hydraulic cylinder load as the main dynamic line; divides the electro-hydraulic servo pump control system into a motor pump unit, a hydraulic transmission unit and a power output unit; analyzes its electromechanical coupling characteristics, pressure flow coupling characteristics, and mechanical−hydraulic coupling characteristics, respectively; studies the m... [more]

Water injection before re-stimulation has a positive effect to mitigate the “frac hit” and increase oil production in tight reservoirs. However, the study of water injection strategy optimization has not been thoroughly investigated. Some conclusions can be found in the existing literature, but the pressure and stress distribution, fractures morphology and oil production were not considered as a whole workflow during the study. In addition, the different reservoir deficit was not considered. Although technical experience and economic benefit have been obtained in some field tests, failed cases still exist. To fill this gap, a series of numerical models are established based on a tight reservoir located in northwest China. Under the different re-stimulation timing, the pressure distribution, stress distribution, and fractures morphology after water injection of different injection/production ratios are calculated, respectively. The oil and water production are predicted. The results sho... [more]

is a traditional Chinese medicinal herbal that has been used since ancient times for its great dietary and medicinal values. Recent reports have underscored the promising cytotoxic effect of R. chingii extracts against a wide variety of cancer cells. Therefore, in the current study, we aim to explore the anticancer potential of the Rubus chingii ethanolic leaf extract (RcL-EtOH) against non-small cell lung cancer A549 cells. RcL-EtOH efficiently exerted a cytotoxic effect against A549 cells in a dose dependent manner, whilst, it exhibited non-significant toxic effects on normal murine macrophage cells, signifying its safety against normal cells. The reduced viability of A549 cells was reaffirmed by the acridine orange/ethidium bromide double staining, which confirmed the induction of apoptosis in RcL-EtOH-treated A549 cells. In addition, RcL-EtOH instigated the dissipation of mitochondrial membrane potential (ΔΨm) with mutual escalation in ROS generation in a dose-dependent manner. Fur... [more]

The application of hydrogen fuel in ORP engines makes the engine power density much higher than that of a reciprocating engine. This paper investigated the impacts of combustion characteristics, energy loss, and NOx emissions of a hydrogen-fuelled ORP engine by ignition timing over various equivalence ratios using a simulation approach based on FLUENT code without considering experiments. The simulations were conducted under the equivalence ratio of 0.5~0.9 and ignition timing of −20.8~8.3° CA before top dead centre (TDC). The engine was operated under 1000 RPM and wide-open throttle condition which was around the maximum engine torque. The results indicated that significant early ignition of the ORP engine restrained the flame development in combustion chambers due to the special relative positions of ignition systems to combustion chambers. In-cylinder pressure evolutions were insensitive to early ignition. The start of combustion was the earliest over the ignition timing of −17.3° C... [more]

The development of approaches for the non-thermal sterilization of instruments is an urgent task to ensure the safety of meat industry products, where the use of hot water leads to the formation of condensates and a deterioration in the hygienic condition of the premises. In this study, an installation for sterilizing knives was created, which works by activating aqueous salt solutions with a glow discharge. The power consumption of the installation reactor is only 125−150 Wh. The temperature rise of the sterilizing agent used is about 1.1 ± 0.2 °C/min/L. The effectiveness of the installation for plasma-activation of aqueous solutions of chloride and sodium sulfate by glow discharge (PAW) in relation to the inactivation of microorganisms, including Staphylococcus aureus, Salmonella typhimurium, Pseudomonas gessardii and L. monocytogenes, on steel surfaces was evaluated. Samples of stainless steel (parts of knives) were used in two versions (new and artificially aged). Mono- and polyspe... [more]

In order to increase the typically low equilibrium CO2 conversion to methanol using commercially proven technology, the addition of two intermediate condensation units between reaction steps is evaluated in this work. Detailed process simulations with heat integration and techno-economic analyses of methanol synthesis from green H2 and captured CO2 are presented here, comparing the proposed process with condensation steps with the conventional approach. In the new process, a CO2 single-pass conversion of 53.9% was achieved, which is significantly higher than the conversion of the conventional process (28.5%) and its equilibrium conversion (30.4%). Consequently, the total recycle stream flow was halved, which reduced reactant losses in the purge stream and the compression work of the recycle streams, lowering operating costs by 4.8% (61.2 M€·a−1). In spite of the additional number of heat exchangers and flash drums related to the intermediate condensation units, the fixed investment cos... [more]

Based on the acoustic wave finite element (AWFE) method, one can establish an AWFE method and study the influence of mechanical parameters on the shale reservoir acoustic wave propagation characteristics. The different crack characteristics and different crack multi-physical coupling phenomena are studied by using the AWFE method on shale gas reservoir cracks. To calculate the shape and position along the crack near a side borehole, the model parameters are compared with the simulation results. The reflection waveform characteristics of adjacent cracks are studied by using the AWFE method. By considering the borehole axis of symmetry, for an acoustic impedance discontinuous interface on one side of the two-dimensional axisymmetric AWFE, one can establish a borehole cross-crack and an arc cross-crack reflection interface model with the AWFE method. By processing the waveform data received by different receiving points under the same source distance, the parameters, such as the reflectio... [more]

The self-built fine water mist fire extinguishing platform studied the fire extinguishing effect of ultra-fine water mist in cold storage fires. The combustible material selected for our experiments is the cold storage insulation material—polystyrene insulation foam board. The combustion characteristics of the insulation board were studied by pyrolysis analysis. We analyzed the temperature, smoke, and other characteristics of the fire scene when a fire occurs in the cold storage and then manipulated the water mist to carry out the fire extinguishing experiment. Experiments aim to change the particle size and pressure of water mist and study the fire extinguishing efficiency of water mist under different conditions. A thorough analysis was used to determine the particle size range of fine water mist most suited for extinguishing fires in cold storage to offer a theoretical foundation for fire protection design.

For the purpose of the intensification of an industrial-scale gas-liquid process, the implementation in an alternative reactor concept is investigated at Hamburg University of Technology (TUHH) in cooperation with Ehrfeld Mikrotechnik GmbH. Existing process operation data from a bubble column hint at a mass transfer limitation of the gas-liquid reaction. In the project, a jet loop reactor (JLR) is chosen to increase the specific interfacial area between gas and liquid, and thus increase mass transfer, while keeping the reactor system mechanically simple and low-maintenance. For the investigation, a laboratory scale reactor has been designed on the basis of an existing industrial scale process and scaled according to a pilot scale reactor available at TUHH. For scaling, geometric similarity is desired, while specific energy dissipation rate and volumetric gas input are kept constant for the chosen scale-up strategy. Between the two different scales, the reactors are successfully charact... [more]

Photovoltaic systems (PV) are becoming more popular as a way to make electricity because they offer so many benefits, such as free solar irradiation to harvest and low maintenance costs. Moreover, the system is environmentally friendly because it neither emits noxious gases nor generates environmental noise. Consequently, during the operation of a PV system, the working environment is free of all types of pollution. Despite the aforementioned advantages, a photovoltaic (PV) system’s performance is significantly impacted by the fluctuation in electrical charges from the panel, such as shading conditions (PSC), weather conditions, and others, which significantly lowers the system’s efficiency. To operate the PV modules at their peak power, maximum-power point tracking (MPPT) is employed. As a result of the various peaks present during fluctuating irradiance, the P-V curves become complex. Traditional methods, such as Perturb and Observe (P and O) have also failed to monitor the Global Ma... [more]

In order to improve the operation performance of the multi-stage double-suction centrifugal pump and reduce the internal energy loss of the pump, this paper proposes a single-objective optimization design method based on the non-hierarchical response surface methodology (RSM) and the multi-island genetic algorithm (MIGA). Nine parameters, such as the blade outlet width and blade wrap angle, were used as design variables, and the optimization objective was efficiency under design conditions. In total, 149 sets of valid data were obtained under the Latin hypercube sampling method (LHS), the corresponding thresholds were set for efficiency and head, and 99 sets of valid data were obtained. A cross-validation analysis of the sieved data was carried out based on non-hierarchical RSM, global optimization of the efficiency was carried out using MIGA, and numerical verification was carried out via CFD. The research results show that compared with hierarchical RSM, non-hierarchical RSM can appr... [more]

A new experimental high-pressure setup for measuring diffusion coefficients in supercritical fluids, based on Taylor dispersion method, and using an FTIR detector to operate up to 25.0 MPa was designed and optimized. Tracer diffusivities, D12, of toluene and benzene in supercritical carbon dioxide were measured in the temperature range of 306.15−320.15 K, and pressure range of 7.5−17 MPa to evaluate the setup and experimental protocol. The effects of flow velocity, volume of the cell, absorbance at different wavenumbers on the diffusion coefficient as well as all parameters respecting the Taylor dispersion method have been analyzed. The obtained diffusion coefficients are in excellent agreement with the available literature data. The dependence of D12 on temperature, pressure, and solvent density were examined. Some correlation models based on the hydrodynamic theory were used to estimate the diffusion coefficients in supercritical carbon dioxide, which is the best agreement obtained f... [more]

To improve water vapor adsorption, this study employed oxalic acid−ethyl acetate acidic hydrolysis to modify honeycomb activated carbon and introduce hydrophilic functional groups. Scanning electron microscopy (SEM), Boehm titration, Fourier transform infrared spectroscopy (FT-IR), and an automatic surface area analyzer (BET) were used to characterize the microscopic morphology, surface functional groups, specific surface area, and pore size changes. The results showed that, when the concentration of oxalic acid is 0.0006 mol/cm3, the specific surface area is 179.06 m2/g. After hydrolysis with ethyl acetate, the original functional groups became more abundant, while the number of total acidic functional groups on the surface grew from 0.497 mmol/g to 1.437 mmol/g. The static water vapor adsorption experiments were conducted on modified activated carbon under constant temperature and humidity conditions. Compared with unmodified activated carbon, the activated carbon modified with 0.000... [more]