This paper constructs a nonlinearly parametrized hypersonic cruise vehicle model on the basis of the existing on-orbit flight data using a curve-fitting technique. The hypersonic cruise vehicle system is separated into two interconnected subsystem: an attitude subsystem with rotational dynamics and a velocity subsystem with engine dynamics. The continuous adaptive controllers are designed for two subsystems using a novel function bounding technique and appropriate coordinate transformations, respectively, which ensure the global boundedness of all signals and achieve the non-zero equilibrium point regulation of nonlinearly parametrized hypersonic vehicle systems. One of the implications of this result is that growing nonlinearities in the uncertain model of the hypersonic vehicle system may be allowed for global stabilization. A simulation result verifies the effectiveness of the proposed adaptive control scheme.

Supply chain disruptions and challenges have and will always exist, but preparing in advance and improving resilience for the upcoming consequences should be the utmost important goal. This paper explores trends that affect innovation in the technological sphere of supply chain systems. More precisely, the research is focused on Digital Twin technology applicability through other logistics IT trends and aims to research the pressing issue of ensuring the visibility and resilience of future supply chain systems. The paper’s objective is to produce a conceptual model enabling the investment assessment of the necessary IT resources. Initially, a theoretical confirmation of logistics IT trends’ relevance to supply chain systems was established. After, propositions of Digital Twin technology applications to other logistics IT trends were made, which were divided into corresponding constant multitudes of supply chain systems. Lastly, the conceptual model for the investment assessment of the... [more]

The aldol condensation of furfural and acetone is considered a promising method for the production of liquid fuel intermediates. 4-(2-furyl)-3-buten-2-one (FAc) and 1,5-di-2-furanyl-1,4-pentadien-3-one (F2Ac) are the main products of the reaction, which can go through the hydrodeoxygenation process to convert to diesel and jet fuel range fuels. Considering the present situation at the fuel-market related to crude oil shortage, the above-mentioned process seems to be a convenient path to obtain fuels in the diesel and kerosene range. This research focuses on the effect of water on the furfural conversion and product distribution during the aldol condensation. The catalyst chosen for this research was MgAl mixed oxide in molar ratio 3:1. The reaction was performed at 40 °C and 1 MPa in a continuous-flow reactor with and without water in the feedstock. The physicochemical properties of the catalyst were evaluated using different techniques. The catalyst lifetime decreased and the catalyst... [more]

Homogeneous catalysis is relevant for biodiesel fuel synthesis; however, it has the disadvantage of difficult separation of the catalyst. In the present work, heterogeneous catalysis was applied for rapeseed oil transesterification with methanol, while snail shells were used as a catalyst. CaO content in the catalyst was investigated. Transesterification reactions were carried out in a laboratory reactor, ester yield was analyzed using gas chromatography. Response surface methodology was used for process optimization. It was found that the optimum transesterification conditions when the reaction temperature is 64 °C are the following: a catalyst amount of 6.06 wt%, a methanol-to-oil molar ratio of 7.51:1, and a reaction lasting 8 h. An ester yield of 98.15 wt% was obtained under these conditions.

In order to study the gas migration in gas-bearing coal, and reasonably arrange gas drainage boreholes to improve the efficiency of gas drainage, a gas-solid coupling model is established based on the pore-fracture dual medium porous model. The solid deformation of coal body, gas seepage and diffusion, and gas adsorption and desorption are considered in this model. The COMSOL software is used to simulate the gas change in the coal matrix and coal fracture under single borehole extraction. We analyze the effective extraction range and study the migration mechanism of gas between coal fracture and borehole, coal matrix and coal fracture, and coal matrix. The effective extraction area of multi-borehole negative pressure gas extraction varies with extraction time and borehole spacing. At 140 d, the effective extraction radius is r = 1.3 m, and the spacing of boreholes is 233 r=1.5 m, 2 r=2.6 m,4 m,5 m,and 6 m, respectively. The influence of the equilateral triangle shape of three boreholes... [more]

The collision behavior and ice formation of a water droplet are affected by its falling process. In this paper, the two-phase flow of air and a water droplet at a specific temperature is adopted to investigate the processes of falling and freezing of a single water droplet. To track the air−water droplet interface and the temperature distribution, the level-set method and the non-isothermal flow coupling method are used, and the freezing model is added into the water’s control equations. The numerical results indicated that with the initial temperature at 283.15 K and the spherical shape, the water droplet changes to the shape of a straw hat at 293.15 K and a drum at 293.15 K but an oval face in freezing temperatures at 0.10 s. There is an obvious drop in the downward velocity when the water droplet falls in mild temperatures at 0.09 s. The downward velocity of the water droplet in air at sub-zero temperatures has a continuous increase during the time span from 0 s to 0.10 s. There is... [more]

Soybean bioactivity is significantly enhanced during tempeh fermentation. This study aimed to evaluate the efficacy of tempeh on colorectal cancer cells in vitro and colon precancerous lesions (aberrant crypt foci, ACF) in vivo. In the in vitro assay, tempeh water extract (WET) could inhibit the proliferation of Caco-2 cells. In the animal assay using 1,2-dimethylhydrazine (DMH)-induced Sprague−Dawley (SD) rats, 12-weeks daily feeding of tempeh could decrease the level of Clostridium perfringens in cecum contents and reduce the number of large (≥4 foci) ACF in the colon of treated rats, compared to the DMH control. By the results of TOF-MS and Edman degradation, the isolated antioxidant dipeptide, tripeptides, and tetrapeptides from WET might contain methionine, proline, and lysine. The bioactive peptides in tempeh might inhibit colon cancer by suppressing the growth of C. perfringens in the intestinal tract.

The present investigations on sealability evaluation for tubing and casing premium connections depend on the FEM with testing. This paper proposed a theoretical model to evaluate the sealability of a sphere-type premium connection based on make-up torque, which combines Hertz contact pressure and the von Mises yield criterion for calculating elastic−plastic contact pressure distribution on sealing interface and adopts the gas sealing criterion obtained from Murtagian’s experimental results for deducing gas sealing capacity. With the proposed model, the effects of additional make-up torque from the sealing interface on the sealing contact pressure distribution and key sealability parameters, including contact width, yield width, average contact pressure and gas sealing capacity, were analyzed and compared. The results show that additional make-up torque from the sealing interface closely influenced sealability parameters’ variation and gas sealing capacity. The gas sealing index based o... [more]

To solve the trajectory planning problem of the flexible manipulator under various constraints such as end-camera attitude, drive space, and obstacles during video inspection along a continuous path in narrow three-dimensional space, this paper proposes a time-optimal trajectory planning method from the initial configuration to the final configuration. The trajectory planning problem is transformed into a multi-constraint optimization problem. First, to realize continuous video inspection in an unstructured complex environment, by analyzing the geometric model of the two-segment flexible manipulator with a camera at the end, the pose constraints between the camera and the shooting surface are formulated by the space vector method, the driving constraints are formulated based on kinematics, and the obstacle constraints are formulated by space mapping. Then, a multi-constraint optimization model is constructed to generate the smooth trajectory of the drive cable of the flexible manipulat... [more]

sp. D-23 was obtained by ultraviolet-diethyl sulfate (UV-DES) compound mutagenesis from Aspergillus sp. C18 that the α-galactosidase was purified from. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and non-denaturing polyacrylamide gel electrophoresis (Native-PAGE), the purified enzyme demonstrated apparent homogeneity. The monomeric α-galactosidase’s native molecular weight was 125 kDa. The optimal temperature of α-galactosidase was 65 °C, and 75% of the initial enzyme activity could be maintained between 45 and 55 °C. Its optimal pH was 5.0 with good pH stability. After incubating for 2 h at pH 3.0−8.0, it could retain more than 80% of its original activity. Different concentrations of metal ions had different effects on the α-galactosidase activity. High concentrations of Cu2+ could strongly inhibit enzyme activity and low concentrations of Fe2+ could promote enzyme activity. Additionally, as shown by thin layer chromatography and high-performance... [more]

This study used computational fluid dynamics for low greenhouse effect refrigerant (R-513A) simulation analysis in the two-stage 150 USRT class oil-free centrifugal refrigerant compressor using integrated part load value (IPLV) and internal flow field. The compressor rotor speed and mass flow rate for the IPLV working conditions with various loads were planned using Stage 1 and Stage 2 simulations, respectively. The performance and flow field numerical simulation analyses for the two-stage centrifugal compressor is discussed. This study used Ansys-CFX software for numerical simulation analysis and the conservation form of a 3D steady-state Navier−Stokes equation set with the finite volume discretization method for computation. The computing mode produced better computing efficiency and flexible mesh setting using the k-omega (k-ω) model, which has better computational performance in the near wall boundary layer and low Reynolds number flow field (used as the turbulence model) for simul... [more]

This study was conducted in a fluidized-bed incineration plant, evaluating the formation, emission and flux of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from industrial-organic-solid-waste (IW) incineration. The results revealed that both the total (or I-TEQ) concentrations of toxic and 136 total PCDD/Fs in flue gas (FG), fly ash (FA) and bottom ash (BA)were ramped up to a higher level than those during municipal-solid-waste (MSW) incineration. A possible explanation was the chlorine (Cl) content of IW. However, the emitted PCDD/Fs in FG (FA/BA) still fulfilled the criteria. Subsequently, similar distribution patterns of PCDD/F isomers were observed in subsystems, indicating a unified formation-pathway. De novo synthesis was detected as the dominant formation-pathway of PCDD/Fs, while high-temperature and precursor syntheses were excluded. DD/DF chlorination formed PCDD/Fs to some extent. Furthermore, the mass flow chart indicated that PCDD/Fs output in primary FG w... [more]

The stability of a quadruped robot is mainly affected by the obstacles in the horizontal direction and the roughness in the vertical direction, which often leads to the robot unable to achieve the desired gait effect. In order to solve this problem, the Model Predictive Control (MPC) model and the Zero Moment Point (ZMP) method are combined, and applied to gait planning and the foot end landing control of a small quadruped robot. The tort gait of a small quadruped robot is the focus of research in this study, which simulated trajectory planning and gait stability. In addition, through comparative analysis with the corresponding experiments, the results show that the simulation results are similar to the experimental results, and the quadruped robot gait is stable. Meanwhile, it shows that the combination of the MPC model and ZMP method is feasible for gait stability control of a quadruped robot.

Food waste is a matter of deep concern as it is creating multidimensional threats to the environment. Though these are potential sources of plant nutrients, a detailed investigation has not yet been conducted. Hence, a physico-chemical characterization of non-edible food waste such as brinjal waste, potato peels, banana peels, orange peels, eggshells, cow bones, chicken bones, fish bones, and their combined waste was accomplished using FTIR, TGA, XGT-5000, CHN corder, etc. The present study revealed that plant waste samples had lower ash contents (1.36−7.79%) but higher volatile matter (72.33−80.04%), and the reverse was true in animal waste. In addition, animal waste, except eggshells (22.48%), had lower fixed carbon (1.01−2.83%). On the other hand, fruit waste was documented with higher fixed carbon (11.33−14.27%). Results also indicated that animal waste and their combined samples, except eggshells, contained more nitrogen (3.82−5.06%). The concentration of P was statistically signi... [more]

Horizontal wells with extended lateral lengths and large-scale hydraulic fracturing are a key technology for shale gas development. Lateral length is the key factor in determining the production and economic benefits of horizontal wells. Therefore, based on geology−engineering−economy integration, a method for optimizing the lateral length of shale-gas horizontal wells is established. Through fracture-shape prediction, productivity simulation and input−output analysis, the net present-value model of the technical−economic evaluation of the economic lateral length is established. A comprehensive evaluation of lateral lengths in Changning Block is then conducted. The results show that, under the current geological, engineering, and economic conditions in Changning Block, a horizontal well with a lateral length between 175 m and 3508 m is economically viable, and the optimal economic lateral length is 2000 m. The porosity and thickness of the reservoir matrix, the production time, the dri... [more]

In this study, the effect of temperature on the velocity and trajectory of a hot sphere falling in a water block was experimentally investigated. The sphere, 12 mm in diameter, was thrown through the water inside an enclosure at the ambient temperature by an electromagnetic attachment mechanism, and the particle velocity was recorded by a high-speed camera at 2000 fps. Then, using an image-processing algorithm, the real-time particle location was extracted and its velocity was measured. The results of the cold sphere falling test were compared with those obtained from the numerical solving by the governing equations. An electric heater was used to heat the sphere up to 100, 200, and 300 °C in order to investigate the effect of temperature on the sphere. The sphere was thrown upon reaching the desired temperature. By increasing the temperature, the sphere’s velocity was increased up to around 40% of the velocity of the cold sphere. Further, the sphere was thrown from a point in the vici... [more]

Several chemicals, such as pesticides and heavy metals, are frequently encountered together in environment matrices, becoming a priority concerning the prevention of their emissions, as well as their removal from the environment. In this sense, this work aimed to evaluate the effectiveness of a permeable biosorbent bio-barrier reactor (PBR) on the removal of atrazine and heavy metals (copper and zinc) from aqueous solutions. The permeable bio-barrier was built with a bacterial biofilm of R. viscosum supported on 13X zeolite. One of the aims of this work is the investigation of the toxic effects of atrazine, copper and zinc on the bacterial growth, as well as the assessment of their ability to adapt to repeated exposure to contaminants and to degrade atrazine. The growth of R. viscosum was not affected by concentrations of atrazine bellow 7 mg/L. However, copper and zinc in binary solutions were able to inhibit the growth of bacteria for all the concentrations tested (5 to 40 mg/L). The... [more]

This paper presents the circuit and control method for piezo-ceramic drives. With the proposed method, a gap is imposed in the transformer core to increase the leakage inductance. This flattens the voltage gain curve of the piezo-ceramic driver over the resonant frequency range, so voltage gain changes are insensitive to frequency changes. In addition, resonant frequency tracking and power control methods are developed, while the circuit is capable of zero-voltage soft-switching such that the circuit operation efficiency can be improved. In order to solidify the practicality of the circuit design, mathematical analysis and experimental validations have been thoroughly performed. The test results help to confirm the effectiveness of the proposed method and demonstrate its practicality in industrial applications.

Electrolysis of seawater is a promising technique to desalinate seawater and produce high-purity hydrogen production for freshwater and renewable energy, respectively. For the application of seawater electrolysis technique on a large scale, simplicity of manufacture method, repeatability of catalyst products, and stable product quality is generally required in the industry. In this work, a facile, one-step, and metal salt-free fabrication method was developed for the seawater-oxygen-evolution-active catalysts composed of CoCrFeNiMo layered double hydroxide array self-supported on CoCrFeNiMo high entropy alloy substrate. The obtained catalysts show improved performance for oxygen evolution reaction in alkaline artificial seawater solution. The best-performing sample delivered the current densities of 10, 50, and 100 mA cm−2 at low overpotentials of 260.1, 294.3, and 308.4 mV, respectively. In addition, high stability is also achieved since no degradation was observed over the chronoampe... [more]

Every year, diverse types of safety accidents cause major damage to human life and property. In particular, failure to suppress safety accidents caused by fires during the early stages can lead to large-scale accidents, which in turn can cause more serious damage than other types of accident. Therefore, this paper presents an analysis of the prevailing research trends and future directions for research on preventing safety accidents due to fire. Since fire outbreaks can occur in many types of places, the study was conducted by selecting the places and causes involved in frequent fires, using fire data from Korea. As half of these fires were found to occur in buildings, this paper presents an analysis of the causes of building fires, and then focuses on three themes: fire prevention based on fire and gas detection; fire prevention in electrical appliances; and fire prevention for next-generation electricity. In the gas detection of the first theme, the gas referred to does not denote a... [more]

The influence mechanism of the blade tip clearance (TC) of an inducer on the performance of a centrifugal pump at high speed was researched under different flow rate conditions in this work. An experiment on the pump’s external performance was carried out, and numerical calculation was also performed under four different TCs. The full characteristic performance curves, static pressure and pressure pulsation distributions of the pump were obtained. Through the research and analysis, it was found that the influence of the TC on the efficiency and the head of the centrifugal pump are related to the flow rate. Under the influence of a large flow rate, the increase in the TC is helpful to improve the efficiency and the head of the pump. The increase in the TC helps to weaken the gap jet effect on the inducer. The inlet jet of the inducer, caused by TC leakage, will form a low-pressure vortex zone at the inlet of the inducer. The splitter-bladed inducer’s pressure pulsation is affected by th... [more]

In recent years, global climate change, environmental pollution, and energy shortage have become increasingly serious [...]

γ-valerolactone can be a game-changer in the chemical industry because it could substitute fossil feedstocks in different fields. Its production is from the hydrogenation of levulinic acid or alkyl levulinates and can present some risk of thermal runaway. To the best of our knowledge, no studies evaluate the thermal stability of this production in a continuous reactor. We simulated the thermal behavior of the hydrogenation of butyl levulinate over Ru/C in a continuous stirred-tank reactor and performed a sensitivity analysis. The kinetic and thermodynamic constants from Wang et al.’s articles were used. We found that the risk of thermal stability is low for this chemical system.

Natural products are increasingly becoming part of our daily lives through their use in industry, food, as therapeutic agents, etc. To evaluate their possible applications, it is essential to characterize them chemically to explore their potential. Different techniques may be used to characterize natural products, including microextraction techniques. These techniques have been gaining popularity due to the advantages associated with their low use of organic solvents and the small amount of sample used relative to more classical sample preparation techniques. Their application in the extraction of compounds from natural products is still scarce. This manuscript intends to review the most used solid-based miniaturized sample preparation techniques applied to determining compounds in natural products. The main applications of these methodologies will be discussed, with a particular focus on natural product analysis, as well as their advantages and disadvantages over traditionally used sa... [more]

Surface location error (SLE) caused by forced vibration is a key factor to determine the quality of the finished part. When machining thin-walled structures with sculptured surfaces, the complicated milling process is significantly influenced by the vibration due to the flexibility of the part. The dynamics of the part are dominant and vary with the material removal during machining. This paper presents a prediction method of SLE considering the varying dynamics of thin-walled parts in five-axis flank milling. The in-process part is decomposed into unmachined and machined portions, which are both modelled based on the thin-plate theory. The dynamics models of the two portions are coupled using the substructure method. Coordinate transformation based on the screw theory and the general cutting dynamics model for five-axis flank milling is employed to transform the cutting force vectors and frequency response function (FRF) to the same coordinate system for the prediction of SLE. The pro... [more]