The core components of HTR mainly consist of graphite, which is an excellent solid moderating material and structure material with good irradiation performance. However, graphite is easier to be oxidized at high temperature. It is important to improve the anti-oxidation performance of graphite substrate to enhance the safety of HTR. Anti-oxidation coating has been proved that it can effectively improve the oxidation resistance of graphite substrate. The selection of coating includes the coating materials system and the preparation techniques. In addition, attention also should be paid to the anti-oxidation mechanism. SiC based coating system is most commonly used in HTR and some other coating systems such as zirconium compounds coating, noble metal coating also can be used in nuclear. However, some coating systems are not suitable in HTR because the elements contained cannot be used in high irradiation environment. The emphasis is on the antioxidant mechanism of different coating systems. Some anti-oxidation coating techniques for graphite substrate are also reviewed in this paper, such as PC, CVD, PS and slurry. Finally, the existing problems of the oxidation resistance coating are proposed and an outlook is made for the development of the protection coating system for graphite substrate used in nuclear.

To obtain flow behavior and workability of 7055 aluminium alloy during hot deformation, hot compression tests at different temperatures and strain rates are conducted. True stress-strain curves of 7055 aluminium alloy under different conditions are obtained and the flow stress increases with ascending strain rate and descending temperature. For Arrhenius constitutive equation, each material parameter is set as a constant, which will bring forth large error for predicting flow behavior. In this work, material parameters are fitted as a function of temperature or strain rate based on experimental results and a modified constitutive equation is established for more accurate prediction of flow behavior of 7055 aluminium alloy. The effects of temperature and strain rate on power dissipation and instability are analyzed to establish a processing map of 7055 aluminium alloy. The dominant deformation mechanism for microstructure evolution at different deformation conditions can be determined and high efficiency of power dissipation may be achieved from power dissipation map. Meanwhile, proper processing parameters to avoid flow instability can be easily acquired in instability map. According to the processing map, optimized processing parameters of 7055 aluminium alloy are temperature of 673–723 K and strain rate of 0.01–0.4 s⁻¹, during which its efficiency of power dissipation is over 30%. Finite element method (FEM) is used to obtain optimized parameter in hot rolling process on the basis of processing map.

Defect-based engineering of carbon nanostructures is becoming an important and powerful method to modify the electron transport properties in graphene nanoribbon FETs. In this paper, the impact of the position and symmetry of the ISTW defect on the performance of low dimensional 9AGNR double-gate graphene nanoribbon FET (DG-GNRFET) is investigated. Analyzing the transmission spectra, density of states and current-voltage characteristics shows that the defect effect on the electron transport is considerably varied depending on the positions and the orientations (the symmetric and asymmetric configuration) of the ISTW defect in the channel length. Based on the results, the asymmetric ISTW defect leads to a more controllability of the gate voltages over drain current, and drain current increases more than 5 times. The results have also confirmed the ISTW defect engineering potential on controlling the channel electrical current of DG-AGNR FET.

Finer nanoplates of silver are prepared by self-assembly on the surface of graphene, and the low-temperature sintered high conductivity ink containing the silver nanoplates is prepared. Most importantly, graphene is added to the solution before the chemical reduction reaction occurs. Firstly, it is found that silver nanoplates have self-assembly phenomenon on the surface of graphene. Secondly, the Ag nano hexagonal platelets (AgNHPs) with small particle sizes (10 nm), narrow distribution and good dispersion are prepared. Especially, smaller sizes (10 nm) and narrower particle size distribution of AgNHPs particles can be easily controlled by using this process. Finally, the conductivity of the ink is excellent. For example, when the printed patterns were sintering at 150 °C, the resistivity of the ink(GE: 0.15 g/L) reached the minimum value of 2.2×10⁻⁶ Ω·cm. And the resistivity value was 3.7×10⁻⁶ Qcm, when it was sintered at 100 °C for 30 min. The conductive ink prepared can be used for the field of printing electronics as ink-jet printing ink.

Non lubricated slide performance of functional grade copper matrix composite, fabricated using horizontal centrifuge cast technique was investigated using pin-on-disc tribo-tester. Rate of wear and friction coefficient of the inner wall thickness of hollow cylindrical cast specimen was analyzed using Taguchi based L₂₇ orthogonal array, where the percentage of graphite particles were observed higher. Variable process parameters those influenced the rate of wear directly or indirectly were: applied load (15, 25 and 35 N), slide velocity (1.5, 2.5 and 3.5 m/s) and slide distance (750, 1500 and 2250 m). Rate of wear and friction coefficient showed a proportional dependency with applied load and slide distance, whereas showing a decline during intermediate slide velocity. Signal-to-Noise ratio predicted the minimal tribo-condition, on ‘smaller-the-better’ basis. Analysis of Variance technique quantified the influence of affecting parameters, along with their interactions. Regression analysis was utilized for the validation of the experimental data. Micrographs and scanning electron microscopy exhibited the wear mechanisms and mechanically mixed layer formation during worn surfaces analysis.

With the aim of achieving a high 5-hydroxymethylfurfural (HMF) yield from glucose with H-ZSM-5 catalyst at low cost, three inexpensive biphasic reaction systems, H₂O—tetrahydrofuran (THF), H₂O—2-methyltetrahydrofuran (MeTHF) and H₂O’2-butanol, were discovered and proved to be particularly effective in promoting the formation of HMF from glucose over H-ZSM-5 zeolite. In order to determine the optimal process conditions, the effects of various experimental variables, such as reaction temperature, reaction time, catalyst dosage, volume of organic solvent, as well as inorganic salt type on glucose conversion to HMF in three systems were investigated in detail. It was found that under optimal reaction conditions, H₂O—THF, H₂O—2-butanol and H₂O—MeTHF allowed the glucose dehydration process to achieve HMF yields of up to 61%, 59%, and 50%, respectively. Moreover, in the three biphasic systems, the H-ZSM-5 catalyst was also demonstrated to maintain excellent stability. Thus, the catalytic approach proposed in this paper can be believed to have potential prospects for industrially efficient and low-cost production of HMF.

Potentially toxic metals, Cd and Pb in paddy soil, have important meanings for safety of rice. A comparison extraction of Cd and Pb with EDTA, DTPA, citric acid, and FeCl₃ and effects on soil fertility was studied. Results indicate that about 59% and 63% of soil Cd and Pb were simultaneously removed by 10 g/L EDTA at pH 5 with a soil/extractant ratio of 1:10 (W/V) for 30 min while 52% and 51% by 5 g/L DTPA. Acid extractable and reducible Cd by EDTA and DTPA contributed 58% and 53% of the removals and acid extractable and reducible Pb were about 49% and 41%, respectively. Slight changes of soil fertility, including pH, cation exchange capacity, organic matter, and soil extractable phosphorus, were observed. Extractions of citric acid and ferric chloride, however, were only efficient for Cd and the soil pH was decreased significantly. This study suggests that EDTA and DTPA can be considered as suitable agents to clean up the paddy soils contaminated with potentially toxic metals.

In this paper, the effect of sodium butyl xanthate (NaBX) adsorption on the surface of bornite at different pH on flotation was studied by adsorption kinetic and thermodynamic. The flotation results demonstrated that the recovery was the highest when pH was 9 in NaBX solution (4×10⁻⁵ mol/L). The adsorption kinetics showed the reaction of NaBX on the bornite conformed to the second order kinetic equation; it belonged to the multimolecular layer adsorption of Freundlich model; the maximum adsorption rate constant was 0.30 g/(10⁻⁶ mol·min), and the equilibrium adsorption capacity was 2.70×10⁻⁶ mol/g. Thermodynamic calculation results indicated that the adsorption process was spontaneous chemisorption, and the adsorption products of NaBX on bornite surface were cupric butyl xanthate, ferric butyl xanthate and dixanthogen, which were confirmed by infrared spectrum measurements.

The present work focuses on the influence of various parameters, i.e., the dosage of cellulase, the inoculum concentration of yeast, the fermentation temperature and the fermentation time, on the alcohol content and sensory evaluation of the low-alcoholic health drink produced from corncob in a yeast-cellulase synchronous fermentation process. The fermentation was performed by inoculating the seed solution (containing corncob powder and yeast) and cellulase into the synchronous saccharification fermentation medium. Single-factor experiments and orthogonal experiments were performed, and the optimal processing conditions were obtained based on the characterizations of alcohol content and sensory evaluation. The results show that the alcohol content and sensory evaluation of the drink can reach 6.1 vol.% and 92, respectively, when the dosage of cellulase, inoculum concentration of yeast, the fermentation temperature and the fermentation time are 15 U/g, 7%, 32 °C and 84 h, respectively.

An important problem in wireless communication networks (WCNs) is that they have a minimum number of resources, which leads to high-security threats. An approach to find and detect the attacks is the intrusion detection system (IDS). In this paper, the fuzzy lion Bayes system (FLBS) is proposed for intrusion detection mechanism. Initially, the data set is grouped into a number of clusters by the fuzzy clustering algorithm. Here, the Naive Bayes classifier is integrated with the lion optimization algorithm and the new lion naive Bayes (LNB) is created for optimally generating the probability measures. Then, the LNB model is applied to each data group, and the aggregated data is generated. After generating the aggregated data, the LNB model is applied to the aggregated data, and the abnormal nodes are identified based on the posterior probability function. The performance of the proposed FLBS system is evaluated using the KDD Cup 99 data and the comparative analysis is performed by the existing methods for the evaluation metrics accuracy and false acceptance rate (FAR). From the experimental results, it can be shown that the proposed system has the maximum performance, which shows the effectiveness of the proposed system in the intrusion detection.

The resource allocation for device-to-device (D2D) multicast communications is investigated. To achieve fair energy efficiency (EE) among different multicast groups, the max-min fairness criterion is used as the optimization criterion and the EE of D2D multicast groups are taken as the optimization objective function. The aim is to maximize the minimum EE for different D2D multicast groups under the constraints of the maximum transmit power and minimum transmit rate, which is modeled as a non-convex and mixed-integer fractional programming problem. Here, suboptimal resource allocation algorithms are proposed to solve this problem. First, channel assignment scheme is performed to assign channel to D2D multicast groups. Second, for a given channel assignment, iterative power allocation schemes with and without loss of cellular users’ rate are completed, respectively. Simulation results corroborate the convergence performance of the proposed algorithms. In addition, compared with the traditional throughput maximization algorithm, the proposed algorithms can improve the energy efficiency of the system and the fairness achieved among different multicast groups.

The understanding of crack propagation characteristics and law of rocks during the loading process is of great significance for the exploitation and support of rock engineering. In this study, the crack propagation behavior of rocks in triaxial compression tests was investigated in detail. The main conclusions were as follows: 1) According to the evolution characteristics of crack axial strain, the differential stress-strain curve of rocks under triaxial compressive condition can be divided into three phases which are linear elastic phase, crack propagation phase, post peak phase, respectively; 2) The proposed models are applied to comparison with the test data of rocks under triaxial compressive condition and different temperatures. The theoretical data calculated by the models are in good agreement with the laboratory data, indicating that the proposed model can be applied to describing the crack propagation behavior and the nonlinear properties of rocks under triaxial compressive condition; 3) The inelastic compliance and crack initiation strain in the proposed model have a decrease trend with the increase of confining pressure and temperature. Peak crack axial strain increases nonlinearly with the inelastic compliance and the increase rate increases gradually. Crack initiation strain has a linear relation with peak crack axial strain.

In the light of the problem of weak reflection signals shielded by strong reflections from the concrete surface, the detection and the recognition of hidden micro-cracks in the shield tunnel lining were studied using the orthogonal matching pursuit and the Hilbert transform(OMHT method). First, according to the matching pursuit algorithm and the strong reflection-forming mechanism, and based on the sparse representation theory, a sparse dictionary, adapted to the characteristics of the strong reflection signal, was selected, and a matching decomposition of each signal was performed so that the weak target signal submerged in the strong reflection was displayed more strongly. Second, the Hilbert transform was used to extract multiple parameters, such as the instantaneous amplitude, the instantaneous frequency, and the instantaneous phase, from the processed signal, and the ground penetrating radar (GPR) image was comprehensively analyzed and determined from multiple angles. The results show that the OMHT method can accurately weaken the effect of the strong impedance interface and effectively enhance the weak reflected signal energy of hidden micro-crack in the shield tunnel segment. The resolution of the processed GPR image is greatly improved, and the reflected signal of the hidden micro-crack is easily visible, which proves the validity and accuracy of the analysis method.

The past decade has been characterized by the development of infrastructure in the main cities in West Africa. This requires more comprehensive studies of geotechnical properties of the soil in the region with an aim of creating sustainable development. This paper examined the performance of the soil in Benin (West Africa). In this research, three objectives have been adopted in-depth on the performance characteristics of West Africans soil and aim to (i) accessing characteristics of soil types in the region; (ii) assessing the performance of these soils with 2%, 3% and 5% of lime and (iii) characterizing landslide to evaluate the damage and potential instability. The methods used to examine these objectives are experimental tests according to standard French test. The particle size test, Proctor test, and Atterberg limits test which are physical tests and the mechanical tests such as dynamic penetration test, direct shear test, and oedometer test, were used to assess the first objective. The Proctor test and California bearing ratio test were examined for the second objective and geological, environmental, social and safety study of the river bank slide were evaluated for the third objective. This paper firstly reveals the unstable and stable areas in southern Benin (West Africa) with the presence of clays soil and gives an equation for predicting the unstable and stable area, and secondly shows that the proportion of percentage lime leading to the best performances varying between 2% and 3%. Finally, this paper shows that the sliding of a bank could be the consequence of the sudden receding water recorded in a valley.

Flexural and eigen-buckling analyses for rectangular steel-concrete partially composite plates (PCPs) with interlayer slip under simply supported and clamped boundary conditions are conducted using the weak form quadrature element method (QEM). Both of the derivatives and integrals in the variational description of a problem to be solved are directly evaluated by the aid of identical numerical interpolation points in the weak form QEM. The effectiveness of the presented numerical model is validated by comparing numerical results of the weak form QEM with those from FEM or analytic solution. It can be observed that only one quadrature element is fully competent for flexural and eigen-buckling analysis of a rectangular partially composite plate with shear connection stiffness commonly used. The numerical integration order of quadrature element can be adjusted neatly to meet the convergence requirement. The quadrature element model presented here is an effective and promising tool for further analysis of steel-concrete PCPs under more general circumstances. Parametric studies on the shear connection stiffness and length-width ratio of the plate are also presented. It is shown that the flexural deflections and the critical buckling loads of PCPs are significantly affected by the shear connection stiffness when its value is within a certain range.

Rock joint shape characteristics, waviness and unevenness play essential but distinct roles in shear mechanism of rock joints. This study presents a novel method to generate virtual rock joint profiles with realistic waviness and unevenness features. Firstly, joint profiles are obtained by 3D laser scanning device. Secondly, quantification of waviness and unevenness is conducted by traditional method, including digital filtering technique and roughness parameter R_L. Thirdly, the discrete Fourier transform (DFT) method is employed to analyze the joint outlines. Two representative Fourier shape descriptors (D₃, D₈) for characterization of waviness and unevenness are suggested. Then, the inverse discrete Fourier transform (IDFT) is adopted to reconstruct the joint profiles with random values of phase angles but prescribed amplitudes controlled by D₃ and D₈. The traditional method is then applied to the reconstructed joint profiles to examine statistically the relationships between D₃ and D₈ and parameters R_L of waviness and unevenness, respectively. The results show that larger D₈ tends to result in larger waviness while higher D₃ tends to increase unevenness. Reference charts for estimation of waviness and unevenness with different pairs of D₃ and D₈ are also provided to facilitate implementation of random joint reconstruction.

Calcined ginger nuts admixed by fly ash and quartz sand (CGN-(F+S)) has been validated to be basically compatible to earthen sites as an anchor grout. Accelerated ageing tests including water stability test, temperature and humidity cycling test, soundness test and alkali resistance test are conducted with the objective to further research the property changes of CGN-(F+S) grout. Density, surface hardness, water penetration capacity, water permeability capacity, soluble salt, scanning electron microscopy (SEM) images and energy dispersive spectrometry (EDS) spectrum of these samples have been tested after accelerated ageing tests. The results show that densities of samples decrease, surface hardness, water penetration capacity and water permeability capacity of samples increase generally. Besides, soluble salt analysis, SEM and EDS results well corroborate the changes. Based on the results it can be concluded that property changes are most serious after temperature and humidity cycling test, followed by water stability, soundness and alkali resistance test in sequence. But in general, CGN-(F+S) still has good durability.

Underground mines require complex construction activities including the shaft, levels, raises, winzes and ore passes. In an underground mine based on stoping method, orebody part(s) maximizing profit should be determined. This process is called stope layout optimization (SLO) and implemented under site-specific geotechnical, operational and economic constraints. For practical purpose, the design obtained by SLO shows consecutive stopes in one path, which assists in defining the mining direction of these stopes. However, this direction may not accommodate the spatial distribution of the ore grade: if the orebody orientation and mining direction differ, the value of the mining operation may decrease. This paper proposes an approach whereby paths in the SLO are defined as decision variables to avoid the cost of mining in the wrong direction. Furthermore, in the genetic-based formulation, which accounts for orebody uncertainty, a robust cluster average design process is proposed to improve SLO’s performance regarding metal content. A case study in narrow gold vein deposit shows that the profit of an underground mining operation could be underestimated by 25%–48% if the algorithm ignores stope layout orientation.

Cantilever casting concrete arch bridge using form traveller has a broad application prospect. However, it is difficult to obtain reasonable initial cable force in construction stage. In this study, stress balance and influence matrix methods were developed to determine the initial cable force of cantilever casting concrete arch bridge. The stress balance equation and influence matrix of arch rib critical section were established, and the buckle cable force range was determined by the allowable stress of arch rib critical section. Then a group of buckle cable forces were selected and substituted into the stress balance equation, and the reasonable initial buckle cable force was determined through iteration. Based on the principle of force balance, the initial anchor cable force was determined. In an engineering application example, it is shown that the stress balance and influence matrix methods for the determination of initial cable force are feasible and reliable. The initial cable forces of arch rib segments only need to be adjusted once in the corresponding construction process, which improves the working efficiency and reduces the construction risk. It is found that the methods have great advantages for determining initial cable force in cantilever casting construction process of concrete arch bridge.

Fiber reinforced polymers (FRPs), unlike steel, are corrosion-resistant and therefore are of interest; however, their use is hindered because their brittle shear is formulated in most specifications using limited data available at the time. We aimed to predict the shear strength of concrete beams reinforced with FRP bars and without stirrups by compiling a relatively large database of 198 previously published test results (available in appendix). To model shear strength, an artificial neural network was trained by an ensemble of Levenberg-Marquardt and imperialist competitive algorithms. The results suggested superior accuracy of model compared to equations available in specifications and literature.

The study of transient heat conduction in multilayered slabs is widely used in various engineering fields. In this paper, the transient heat conduction in multilayered slabs with general boundary conditions and arbitrary heat generations is analysed. The boundary conditions are general and include various combinations of Dirichlet, Neumann or Robin boundary conditions at either surface. Moreover, arbitrary heat generations in the slabs are taken into account. The solutions are derived by basic methods, including the superposition method, separation variable method and orthogonal expansion method. The simplified double-layered analytical solution is validated by a numerical method and applied to predicting the temporal and spatial distribution of the temperature inside a landfill. It indicates the ability of the proposed analytical solutions for solving the wide range of applied transient heat conduction problems.

Cooling strength is one of the important factors affecting microstructure and properties of gas cylinders during quenching process, and reasonable water spray volume can effectively improve the quality of gas cylinders and reduce production costs. To find the optimal water spray parameters, a fluid-solid coupling model with three-phase flow was established in consideration of water-vapor conversion. The inner and outer walls of gas cylinder with the dimensions of d914 mm×38 mm×12000 mm were quenched using multi-nozzle water spray system. The internal pressure, average heat transfer coefficient (h_ave) and stress of the gas cylinder under different water spray volumes during quenching process were studied. Finally, the mathematical model was experimentally verified. The results show that both the internal pressure and h_ave increase along with the increase of spray volume. The internal pressure increases slowly first and then rapidly, but h_ave increases rapidly first and then slowly. To satisfy hardenability of gas cylinders, the minimum spray volume should not be less than 40 m³/(h·m). The results of stress indicate that water spray quenching will not cause deformation of bottle body in the range of water volume from 40 to 290 m³/(h·m).

An experimental investigation on the boiling heat transfer and frictional pressure drop of R245fa in a 7 mm horizontal micro-fin tube was performed. The results show that in terms of flow boiling heat transfer characteristics, boiling heat transfer coefficient (HTC) increases with mass velocity of R245fa, while it decreases with the increment of saturation temperature and heat flux. With the increase of vapor quality, HTC has a maximum and the corresponding vapor quality is about 0.4, which varies with the operating conditions. When vapor quality is larger than the transition point, HTC can be promoted more remarkably at higher mass velocity or lower saturation temperature. Among the four selected correlations, KANDLIKAR correlation matches with 91.6% of experimental data within the deviation range of ±25%, and the absolute mean deviation is 11.2%. Also, in terms of frictional pressure drop characteristics of flow boiling, the results of this study show that frictional pressure drop increases with mass velocity and heat flux of R245fa, while it decreases with the increment of saturation temperature. MULLER-STEINHAGEN-HECK correlation shows the best prediction accuracy for frictional pressure drop among the four widely used correlations. It covers 84.1% of experimental data within the deviation range of ±20%, and the absolute mean deviation is 10.1%.