Abstract:With the three-dimensional and multi-level development of modern naval warfare, ship/shipborne Unmanned Aerial Vehicle(UAV) landing technology has been widely studied and applied. In order to study the development status of ship/shipborne UAV landing technology and solve the key technical problems, the current literature in this field is analyzed and summarized. UAV landing technology refers to the landing technology that meets the precision requirements through ship/shipborne and UAV arresting equipment according to the process of ship/shipborne landing and the flight control system relying on the ship/shipborne and airborne guidance system. First, the development history of fixed-wing UAV recovery technology in small ships/shipborne is summarized, and the advantages and disadvantages of various recovery technologies are compared and analyzed. Second, the key technologies are expounded with emphasis on“in-flight braking recovery”and “fixed-point high-precision recovery”. Finally, the key technical problems that need to be solved in the development of fixed-wing UAV small ship landing technology are summarized, including UAV navigation system design, control system design, and other technologies. The research shows that the ship/shipborne UAV landing technology research has not formed a mature solution. There are still many technical problems to be solved. This paper provides a reference for the design of Chinas fixed wing UAV maritime recovery system.

Abstract:To overcome the non-convexity and non-differentiability of multiple eigenvalues in traditional truss topology optimization models, a unified semidefinite programming (SDP) model was established for truss topology optimization problems with various constraints. Equivalent semidefinite forms were first provided for volume, compliance, fundamental frequency, and global stability constraints. Since the stiffness matrix and the mass matrix of truss are both linear with respect to design variables, problems considering volume, compliance, and fundamental frequency constraints were reformulated as standard dual forms linear SDP. Demonstrated by the global stability constraint and the stress constraint, nonlinear semidefinite constraints and nonlinear scalar constraints were separately approximated by simpler SDP forms at the current design point, which converts the nonlinear model to a solvable approximate SDP model. An algorithm for sequentially solving the approximate problem was then introduced to deal with the nonlinear problem. When the model contains only linear semidefinite constraints, the resultant linear SDP is convex and numerically favorable. When it concerns nonlinear constraints, the sequential approximate scheme enjoys the numerical advantage of linear semidefinite forms and also maintains the ability to handle ordinary nonlinear constraints, which may contribute to a more practical design. Examples show that the proposed SDP model and algorithm could deal with various constraints in truss topology optimization, especially fundamental frequency constraints and global stability constraints with multiple eigenvalues, which verified the effectiveness of the model and the algorithm.

Abstract:Ventilated supercavity technology is an emerging technology that can improve the velocity of underwater vehicle. In order to study the maneuverability of ventilated supercavity in longitudinal plane rotation motion of the vehicle, based on the finite volume method, a three-dimensional computational model of unsteady ventilated supercavity flow was established by using VOF multiphase flow model and RNG k-e turbulence model and utilizing the numerical simulation software Fluent. By solving the Reynolds averaged Navier-Stokes equation of multiphase mixtures, the unsteady multiphase flow characteristics of the cavitator model in longitudinal plane rotation motion were analyzed. The morphological changes of the ventilated supercavity and the relationship with the pressure distribution around the supercavity were obtained under the rotating motion of the longitudinal plane. The calculation results show that the ventilated supercavity was flexed by centrifugal force during the rotary motion, and the axis of the supercavity was gradually coincident with the motion track of the vehicle. The maximum radius of the supercavity gradually decreased when it rotated downward and gradually increased when it rotated upward, and the radius of rotation had a great influence on the shape of the supercavity in the downward rotating motion. In addition, the deflection direction of the closed position of the cavity tail was different. When the bubble tail rotated downward, it drifted outward, and when the bubble tail rotated upward at a small angle, it drifted inward. Due to the centrifugal force and the reverse pressure gradient in the axial direction of the supercavity, the slenderness ratio increased significantly during the upward rotation and decreased slowly in the downward rotation process.

Abstract:To demonstrate the operational safety of the equatorial space elevator system and the mechanism of the influence of the climber moving on the system vibration characteristics, the stability of the system and the effect of the climber moving with different acceleration time and deceleration time on the system residual oscillation were studied. A rigid tether model with two-DOF was established by Lagrange method. The stability of the topological equivalent linearization system based on the small oscillation angle assumption was analyzed at the equilibrium point. Two parameters which are the time ratio of acceleration and deceleration phases with the cruise phase were introduced to study the response of the system. Results show that the system had gradual stability characteristics at the equilibrium point both inside and outside the equator plane under the condition of atmospheric damping. The motion of the climber would cause the tether to oscillate in the equatorial plane, which was mainly caused by the Coriolis force. There was always a minimum amplitude of system residual oscillation in-plane for the deceleration time ratio, which is related to the acceleration time ratio. The amplitude of system residual oscillation could be controlled in level of 10^-3degree by optimizing the deceleration time ratio, and the simulation result indicated that increasing the cruise speed and decreasing the acceleration time of the climber could shorten the time for the climber to run to the target track. Optimizing the time ratio of acceleration and deceleration phases could suppress the residual oscillation and improve the efficiency and economy of the system.

Abstract:To solve the UAV offline and online path planning problem, an adaptive cuttlefish algorithm with joint modification is proposed considering that the traditional cuttlefish algorithm may be trapped in local optimum and has low precision after long search. The regulatory mechanism combined with chaos perturbation and mutation learning is proposed to strengthen local search to improve search precision. Adaptive weight mechanism is introduced to diminish search space and ensure search efficiency. The auto filter mechanism based on individual fitness was used to adjust population diversity and to break away from local optimum. The proposed algorithm was firstly verified by tests of six benchmark functions, and then verified by path planning simulations in different environments. For offline path planning, success rate of the proposed algorithm reaches up to 100%, and paths planned by the proposed algorithm were closest to global optimum. The average track length of the proposed algorithm could be 7.3 units shorter than traditional cuttlefish algorithm, and it could reach 28.3 units shorter than particle swarm optimization. The simulation results show that the global search performance and the search precision of the proposed algorithm were significantly improved. Furthermore, as the environment became more complex, the improvement effects were more remarkable. For online path planning, the global path planning was transformed to the planning of several segmental paths, and a heuristic method was used to select the segmental goal. Simulation results show that the proposed algorithm met the real-time requirement and has high precision. The effectiveness of the proposed algorithm was further verified.

Abstract:High noise remote sensing image denoising was a difficult problem in the field of remote sensing research. In this paper, to improve the reconstruction quality of remote sensing images, an improved iterative wavelet thresholding (IWT) algorithm is proposed on the foundation of the classical compressed sensing iterative wavelet thresholding (IWT-CS) algorithm. First, an adaptive wavelet filtering operator was proposed to remove parts of image noise, which selects wavelet coefficients of the remote sensing image in the process of image sparsity transform. Second, a descending BayesShrink threshold was put forward to select the wavelet coefficients obtained again in each iteration. Finally, an improved group sparse total variation (IGSTV) method was utilized to adjust the obtained reconstructed image to further improve the reconstruction quality of the remote sensing image. The experimental result demonstrates that the proposed algorithm was superior to the IWT-CS algorithm in terms of denoising reconstruction, which could recover a high quality remote sensing image from high noise image, and the effectiveness of the proposed algorithm was validated. In addition, the proposed algorithm could effectively protect the edges, textures, and other important feature information in remote sensing image. Under low compression sampling ratio, the proposed algorithm could still obtain relatively high peak signal to noise ratio (PSNR) and visual quality. In the satellite receive station, the proposed algorithm can be directly used to reconstruct a clear remote sensing image using a small amount of received-noise remote sensing image data.

Abstract:The existing mathematical model of underwater vehicles is difficult to match the actual model with new emerging of underwater vehicles. In order to deal with modeling problem and predict space motion for new underwater vehicles, a black-box modeling method based on particle swarm optimization (PSO) and support vector machine (SVM) was proposed. Nonlinear mapping relationship between state of motion and thrusters for underwater vehicles was constructed by SVM. Optimal parameters of SVM were obtained through PSO algorithm. Then, a black-box model was established for underwater vehicles. Finally, by judging whether thrusters vary with time, space motion of a new kind of quadrotor underwater vehicle was adopted to verify the effectiveness of the proposed method. Space motion prediction results were evaluated by the root mean square error. The experimental results demonstrated that root mean square errors of the space motion prediction results were small. Space motion prediction results were in accordance with the actual space motion. The black-box model constructed by PSO and SUM was basically identical with the actual model and could effectively predict the space motion of underwater vehicles.

Abstract:With the development of micro-optical electromechanical systems, micro-lenses with adjustable focal length have become a research hotspot in the industry. In order to improve our understanding of the dynamic feature of variable-focus liquid micro-lens, a lattice Boltzmann-electrodynamic (LB-ED) method combining the lattice Boltzmann method and electrodynamic model was proposed to study the transient process of lens driven by electrowetting on dielectric (EWOD). The multi-component lattice Boltzmann method (LBM) was used to study the motion of the lens during a focusing action which is governed by Navier-Stokes equation, and then a new distribution function was introduced to calculate the electrical force. Firstly, the EWOD effect was numerically analyzed and compared with theoretical values and experimental results. Then the influence of voltage on the focal length was studied, and the dynamic process of zoom of the lens was analyzed. Finally, effects of the viscosity of the insulating liquid on the response time and stability of the lens were investigated. Results show that the change of contact angle agreed well with Loppmann-Young equation under low voltage and saturation occurred under high voltage, which indicated that the change of contact angle was consistent with the theoretical values and experimental results and verified the correctness of the numerical method. The relationship between applied voltage and focal length was established. When the voltage was switched, the contact angle changed abruptly but it cost the system some time to respond to the change in the force at the contact point. It was found that the system was in an oscillating state when the viscosity of the insulating liquid was small, and in an over-damped state when the viscosity was large. A suitable liquid viscosity could optimize the system performance.

Abstract:Delay lock loop (DLL) supported 90°phase shifters are widely used in double data rate synchronous dynamic random access memory (DDR SDRAM) to generate 90°phase-shifted clock, which achieves double data rate sampling and improves data-rate. Digitally controlled delay line (DCDL) plays a critical role in the DLL supported 90°phase shifter. To remove glitches in traditional DCDL during the process of delay adjustment, the causes of glitches generation were analyzed, and a glitch free digitally controlled delay line (GFDL) with latch and clock gating was proposed. The latch and clock gating were employed in GFDL shift digital control signals sequentially thus glitches were removed. Moreover, the proposed GFDL was used in the DLL supported 90°phase shifter to eliminate the glitches. The proposed DLL supported 90°phase shifter adopted SMIC 65 nm CMOS process with an active area of 0.018 mm² and the supply voltage of 1.2 V. HSPICE simulation results indicated that the proposed DLL supported 90° phase shifter had an operating frequency ranging from 217 MHz to 1GHz and consumed 2.8 mW at 1 GHz. The peak-to-peak and root-mean-square jitters of 90°phase-shifted clock were 17.77 ps and 5.16 ps respectively when a sine noise of 100 MHz and 30 mV was supplied. In addition, when the phase shifter track the process-voltage-temperature (PVT) variations, the outputted 90°phase-shifted clock effectively avoided glitch issues.

Abstract:Heart disease is the leading cause of death in humans, and most cardiovascular diseases are accompanied by arrhythmias. In order to realize the automatic analysis of different types of electrocardiogram (ECG) signals and recognize abnormal heart rhythm, a new classification algorithm based on deep learning was studied and proposed. Considering the characteristics of the EGG, the convolutional neural network (CNN) was used to extract the local correlation features, and the long-short term memory (LSTM) network was used to capture the long-term dependence of ECG sequence data to identify five different types of heart beats automatically. The deep learning method based on LSTM and CNN directly took the preprocessed ECG signals as the input of the network, and integrated the feature extraction and ECG classification into a single learner. In terms of the problem of imbalance, sampling by sliding window was performed on minority class data to get more training data. The effectiveness of the algorithm was evaluated with the MIT-BIH arrhythmia dataset, and the accuracy, specificity, and sensitivity of the classification results in more than 20 000 cardiac beats recorded in the test set reached 99.11%, 99.44%, and 97.27%, respectively. In addition, the operation of sliding window sampling significantly improved the sensitivity of minority class. The experimental results show that compared with the traditional methods, the parallel combination model based on LSTM and CNN did not require separate feature extraction steps and achieved better classification performance, which is suitable for wearable ECG devices and remote monitoring field.

Abstract:To improve the space comfort of manned submersible compartment, a multi-source composite evaluation method based on virtual simulation technology was proposed to evaluate the space comfort of deep-sea manned submersible compartment under strong constraints. Based on virtual simulation technology, the method combines three-dimensional digital data of manned submersible compartment space with human data of submersible to construct a digital virtual simulation model. By regarding rapid correspondence and evaluation as criterion, human comfort was divided into zones, and the space and function characteristics of manned submersible were systematically analyzed. Through acquiring human comfort zone characteristics and space constraint mapping based on human physiological characteristics, seven evaluation indicators were established. Six human factors assessment tools were combined to build a multi-source composite comfort evaluation model. The visual evaluation system of space comfort was developed by virtual simulation technology, and the feasibility of the multi-source composite evaluation method and the visual evaluation prototype system was validated by optimizing the space design of a manned submersible cabin. The research shows that different task postures seriously affected the accuracy of human comfort assessment. The narrow cabin space and the layout of equipment in cabin further increased the difficulty of job posture assessment. The composite evaluation method of spatial comfort could accurately describe the degree of spatial comfort under various postures. At the same time, the technical characteristics of multi-source and visualization improved the efficiency of evaluation of spatial design schemes and the readability of evaluation results to a certain extent.

Abstract:In order to cope with the development trend of informationization and clustering in modern battlefields, this paper studies the reentry flight time constraint in the mission of multi-hypersonic vehicles’ saturation attack, and proposes a time-controllable reentry guidance law based on the Deep Q-learning Network(DQN). Its workflow is mainly divided into three parts. First, according to the current flight state and angle of attack vs.velocity profile, the amplitude of bank angle is planned based on the prediction-correction module of longitudinal trajectory. Then the online constraint enhanced management module performs safety limiting processing the amplitude of bank angle. Finally, based on Markov Decision Process modeling of lateral flight state, the symbol planning module aims to adjust reentry flight time and to designs the corresponding deep neural network for offline training to generate the symbol of bank angle online, and then amplitude information is combined to form the final bank angle command. The comparative analysis of mutiple simulations shows that in multi-mission simulation under nominal environment, the time-controllable reentry guidance law can independently plan bank angle’s symbol online and adjust reentry flight time to meet different mission requirements without affecting guidance precision. In the Monte Carlo simulations with biased parameters, the time error can still be controlled within a reasonable range while ensuring safe and stable reentry flight. Therefore, compared with the traditional method, the reentry guidance law designed in this paper has good performance in terms of task adaptability, robustness, and time controllability, and it can effectively meet reentry mission requirements with the flight-time constraint.

Abstract:Multi-laminated drug controlled release devices are one of the most commonly used drug controlled release devices at present. In order to release the drug into human body according to the predetermined release rate, an optimization approach to achieve desired drug release behavior using multi-laminated drug controlled release devices was proposed. First, based on the idea of inverse problem, the optimization of drug release based on the multi-laminated drug controlled release devices was transformed into an initial value inverse problem of diffusion equations. Then, a modified Tikhonov regularization method was proposed by constructing a new regularizing filter based on the singular value theory of compact operators, and the convergence and the optimal asymptotic order of the regularized solution were obtained. Finally, the modified Tikhonov regularization method was applied to the optimization of the initial drug concentration distribution. For three targeted release requirements (constant release, linear decrease release, and linear increase followed by a constant release), better results could be achieved by using the optimized initial drug concentration distributions obtained by the modified Tikhonov regularization method. Numerical results demonstrate that the modified Tikhonov regularization method not only had the optimal asymptotic order, but also had a good effect on optimizing the multi-laminated controlled release device. By using the modified Tikhonov regularization method to optimize the initial concentration of the drug in the multi-laminated controlled release device, the drug release behavior of the system was basically realized as constant velocity release behavior, quasi-linear release behavior, and non-linear release behavior.

Abstract:The cracking technology by liquid CO₂ transient has been increasingly applied to rock excavation. The rapid acquisition and systematic characterization of the fragmentation distribution have important application value for rapidly evaluating the effect of liquid CO₂ transient cracking under field conditions. In order to solve the problems of incomplete information acquisition, complicated operation, and large workload, a new method is proposed in this paper that combines the UAV camera technology and the MIPS image processing technology to comprehensively and quickly obtain the broken rock feature information (area, perimeter, maximum chord length, etc.) and apply it to liquid CO₂ transients. On this basis, through the comprehensive analysis of the inhomogeneity and curvature characteristics of the block information, the fractal theory was used to describe the distribution of liquid CO₂ transient fragmentation, and the fractal dimension D was applied to quantitatively characterize the fragmentation distribution of the broken rock. The field experiment results show that the “UAV camera + MIPS image processing” technology could extract the rock block information quickly, accurately, and completely. Moreover, the fractal dimension could better characterize the distribution of split block. The larger the fractal dimension was, the higher the proportion of small pieces was, and otherwise the lower it was. This study provides a new important technical support for timely analysis and rapid adjustment of borehole scheme and corresponding technical parameters.

Abstract:In order to obtain the damage rule of anti-corrosion coating on steel structures of inland river, the erosion characteristics of anti-corrosion coating on steel structures under the condition of sand flow were studied by physical model test, the process of coating damage was analyzed, and the erosion damage model for steel structures’ coatings in inland river wharf was proposed. First of all, combined with the environmental conditions of the sandy water flow in the upper reaches of the Yangtze River, the erosion test parameters were determined, and the steel structures coated with an epoxy asphalt coating was prepared. According to similar scaling, the coating of the steel structure of the on-site dock was simulated by the sandy water flow for 4 months. Through observing the morphology after erosion damage, it was found that the model test and the field coating erosion test showed similar failure processes and damage patterns. Then, the physical model test was carried out, which focused on the relationship between the corrosion resistance of steel structures under different conditions of angle of attack, erosion time, and sediment concentration with sandy water flow. The coating of the maximum eclipse appeared in 40° angle of attack, and coating erosion quantity with -45°~90° angle of attack showed the tendency of "between big and small on both sides. During slow increase period, there was a linear correlation between the thickness and the erosion time of each impact angle. Under the condition of high sand concentration, the overall erosion amount of the coating increased exponentially with the increase of velocity of flow. Finally, based on the corrosion test results of steel structures’ anti-corrosion coating and the existing erosion theory, the erosion damage model of anti-corrosion coating was improved. The critical angle of attack of the coating at high flow rate was about 40°, which was in good agreement with the test results. The research shows that the damage law and erosion characteristics of the anti-corrosion coating on the steel structures in inland river wharf can be obtained by using the erosion test. The damage model of the hydraulic steel structures’ anti-corrosion coating can be effectively measured by the improved damage model, which provides a theoretical basis for the development of new anti-corrosion coatings.

Abstract:During the dry drilling process, wind slagging system discharges the cuttings along the annular slit of the drill at a high speed, which generates high concentration dust. In order to effectively control dust pollution during dry drilling in coal seam, the main factors that influence dust distribution were exploved and the drilling technology parameters with low dust concentration were determined. The numerical simulation of dust concentration distribution under different boundary conditions was carried out by using SolidWorks and DesignModeler to build models, using Mesh to divide the grids, using Fluent to calculate, and using CFD-Post to postprocess. Compared with field measurement of dust concentration,the simulating results basically agreed with the measured data. The result indicates that the velocity of pyramidal compressed air attenuated rapidly after the ejection from cyclic slit, and large drillings settled immediately near the orifice, while fine particles floated in the air and continued to spread with wind. Dust concentration in drilling field along the way rose sharply to a maximum value first, then dropped rapidly, and finally decreased gradually. In the horizontal direction, the dust concentration in the middle of the roadway was lower than that in the middle of the machine road, which had the highest dust concentration, and that in the center of the sidewalk was the lowest. In the vertical direction, the dust concentration distribution showed a feature that it was high in the middle and low in the upper and lower sides. The five main factors that affected the dust distribution were the wind speed in drilling field, the drill rod rotation speed, the pressure of the gas supply, the drill rod type, and the drilling type. When the wind speed was 0.5 m/s, the rotation speed was 2 r/s, and the gas pressure was 0.8 MPa, a good dust reduction effect was achieved by using outer flat drill rod to drill into the pre-drainage borehole of tilted parallel. The results can effectively guide the field operation of drilling and the development of dust control devices.

Abstract:Strain rate is an important factor affecting the mechanical properties and acoustic emission characteristics of cemented backfill. In order to study the strain rate and the acoustic emission response of cemented backfill, the acoustic emission test of cemented backfill under uniaxial compression was carried out. The strain rate and the timing characteristics of acoustic emission during loading were studied. The correlation between strain rate and acoustic emission timing characteristics as well as the intrinsic relationship between the two trends were discussed, which further revealed the crack evolution law of the cemented backfill under load. Results show that the strain rate and ringing count rate of cemented fillings had the variation trend and phase characteristics of “up→down→steady→up” in the whole process of deformation, and the correlation between them was high. The internal rupture of the cemented backfill was caused by the friction between the aggregate and the fracture evolution of the cemented material. The strain rate played a dominant role in the acoustic emission characteristics. The strain rate in the stage of plastic yield and instability, showed obvious abruptness, which could provide effective precursor information for the prediction of cemented backfill fracture. The combination of acoustic emission ringing count rate, quiet period, and expansion could better reflect the rupture of cemented backfill. The research results can lay a theoretical foundation for the study of mechanical properties of cemented backfill.

Abstract:In view of the complex nonlinear change of the compressive strength of filling cementation body caused by the chemical compound effect of different proportioning of activator in filling cementitious materials, an intelligent optimization for the mixture ratio of filling cementitious material was proposed. First, uniform design tests were carried out to obtain the compressive strength values of different activator proportions of backfill bodies. Then, improved genetic tree about dynamic adaptive exchange mutation probability and fitness competition exchange mode was used to characterize the high-precision nonlinear complex relationship between the activator material and the compressive strength of the backfill. When computing to the 49th generation, it satisfy the termination rule of the algorithm. The convergence speed was fast and the function precision was high. Finally, the constraint condition was determined and the optimization model of the proportion of activator was established. The global optimization technology of genetic algorithm was used to get the optimal ratio of the activator material to meet the strength requirements of backfill. The intelligent optimization method was utilized to study the ratio of activator for the new filling cementitious material in iron mine. The optimization show that the optimum proportion for the strength of the mine backfill was 2.91% lime, 17.39% gypsum, and 79.7% slag powder. Verification test was carried out around the optimum proportion, and results show that the compressive strength of the filling body at 7 d and 28 d reach the maximum when lime was 3%, gypsum was 17%, and slag powder was 80%, which was in accordance with the test results. Compared with 42.5 cement, the whole tailings filling cementing material could be prepared by the activator proportion prepared by the intelligent optimization method, and the cost of cementing material could be reduced by 22%.

Abstract:Proton exchange membrane fuel cell (PEMFC) is a complex system which involves multiple disciplines, and its output characteristics are affected by many factors. This paper aims to analyze the influences of working temperature, pressure, membrane water content, loading amplitude, and loading speed on its output characteristics. Based on the mathematical model of PEMFC, a voltage dynamic model that considers the electric double layer capacitance effect was established, and simulation was carried out on the Matlab/Simulink platform. Using the self-made air-cooled self-humidified DXFC-200 PEMFC and the fuel cell test system, the actual output volt-ampere curve was fitted to the model output curve, which proved the accuracy and stability of the model. On this basis, a longitudinal single-factor analysis was conducted. Besides, this study also conducted a multi-factor horizontal comparison by using an orthogonal experiment, and analyzed the impact of the operating temperature, pressure, and membrane water content on the output characteristics of the battery in low current region and high current region. Results show that the increase of the temperature, the pressure, and the water content of the membrane, and meanwhile decrease of the loading amplitude and the loading speed in a certain range could effectively improve the battery performance. In low current region, the operating temperature had a more important effect on the output characteristics of the battery. In high current region, the membrane moisture content had a more vital effect on the output characteristics of the battery. The research shows that the model can truly reflect the working characteristics of PEMFC. The study will provide theoretical support for improving battery performance, delaying battery attenuation and formulating fuel cell control strategy.

Abstract:At present, the preparation of superhydrophobic surface with fluorinating agents is not environmentally friendly. To solve this problem, a new method for fabricating fluorine-free superhydrophobic surface on aluminium alloy for drag-reduction at solid-liquid interface was proposed. First, chemical etching technology was used to fabricate micro- and nano-scale surface roughness on the substrate. Then natural rosin solution and carbon black suspension were used to modify the surface to replace traditional fluoride. In terms of characterization, scanning electron microscopy (SEM), contact angle measurement instrument, and X-ray energy spectrum analysis (EDS) were used to characterize the microstructure, surface wettability, and elemental analysis respectively. By continuously optimizing the surface structure and the concentration of the modified solution, the superhydrophobic surface with a contact angle of 155° and a rolling angle of 1.38° in the Cassie model state was achieved on the substrate. The experimental results indicated that the surface with the new method had good integrity after 80 cycles of immersion and extraction. In addition, it maintained good superhydrophobic property under continuous water drop impact at the velocity of 1.4 m/s for 3 h. Through the test of drag-reduction and scouring experiment, compared with untreated surface, the drag-reduction rate of the fluorine-free superhydrophobic surface could reach 20%~30% in the scouring velocity range of 0.5~3.5 m/s, which verified the effectiveness of the new method. The whole process is simple, cost-effective, and environmental friendly, which is conducive to large-scale production and application.

Abstract:Biomass combined heat and power (CHP) plants have higher energy efficiency than biomass power plants. They can meet the demand of heating in winter, and they are more suitable for cold regional village and town system to develop biomass energy. However, such development is limited by cost, especially operation cost, and transportation cost. In order to achieve the research purpose of improvingTo improve the transportation cost of biomass CHP plants according to rural population density data in the research area, the GIS analysis tool of network analysis, adjacent points, overlay analysis, as well as and other methods on the basis of the distribution status of different crops biomass potential are used and position and service area relying on the population distribution and biomass CHP plants’ energy demand data are determined. In the meantime, the raw material supply area of the biomass CHP plants and the transportation cost were calculated, which contains a variety of charges, fuel consumption, and traffic interference factors of the formula, and then regional scale optimization of transportation paths was obtained. Results show that biomass CHP plants are only suitable for low population density villages and towns systems according to the assumption of energy being completely self-sufficient. The supply area presented an inversed S curve pattern as rural population density increased, and transport costs presented an exponential curve pattern as rural population density increased. The overall operating efficiency of the biomass CHP plants was higher when the rural population density was not more than 65 people/km².

Abstract:To further reduce the outlet temperature of the primary water and increase the transmission capacity of the heating pipe network, the series-type supplemental fired absorption heat exchanger was used at the heat station of central heating system to replace the conventional single-segment absorption heat exchanger. In this study, with the technical constraints of feasibility of heat transfer terminal difference considered only, by analyzing the heat transfer process and thermodynamic cycle of each heat transfer component in series-type supplemental fired absorption heat exchanger, the mathematical model of the unit was established and solved by iterative numerical method, and the temperature conditions of primary water inlet, secondary water inlet and outlet satisfying the design requirements of heat exchanger station were quantitatively analyzed. The distribution rules of the minimum temperature of primary water outlet, the maximum heat supply of unit, and the heat transfer in unit were discussed. Research results show that when the temperatures of the primary water inlet was 110℃, the secondary water inlet and outlet were 60/45 ℃, the minimum temperature of the primary water outlet of the supplemental heat exchange unit was 22 ℃. The conveying capacity of the pipe network was 1.76 times of a conventional 110/60 ℃ water-to-water heat exchanger and the heat supply was twice of a conventional water-water heat exchanger. For conventional single-stage absorption heat exchangers, the primary and secondary water supply temperatures had little effects on the expansion coefficient, which was about 1.5. When the primary water inlet temperature was 100 ℃ and the secondary water inlet/outlet temperature was 69/54 ℃, the maximum expansion coefficient of the supplementary combustion absorption heat exchanger was about 3.3.

Abstract:To achieve effective removal of Dimethyl phthalate (DMP) under visible light LED (Vis-LED), N-TiO₂/Ti network catalyst was prepared on the surface of titanium mesh by one-step anodic oxidation of adding urea to electrolyte solution, and the DMP was degraded by multiple layers of N-TiO₂/Ti mesh superposed in a reactor. The N-TiO₂/Ti mesh was characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). Results show that N element mainly participated in the form of substituted nitrogen, and both surface morphology and crystal structure of the TiO₂ nanotubes were not changed. The forbidden band width of the N-TiO₂/Ti mesh calculated by the Tauc/David-Mott formula was about 2.76 eV, and the absorption band edge was extended to 449 nm, where the visible light absorption performance was significantly enhanced. After the N-TiO₂/Ti foil was equivalently stretched into 3 layers of N-TiO₂/Ti mesh, the degradation rate of DMP increased by 7.5%. When 5 layers of N-TiO₂/Ti mesh were superposed, the degradation rate of DMP tended to be stable and it increased by 25.7% compared with that of Ni-TiO₂/Ti plate. Partial acidity or alkaline was beneficial to the degradation of DMP. The addition of H₂O₂ could promote the degradation of DMP, but H₂O₂ could not effectively degrade DMP under single use and visible light irradiation.

Abstract:To investigate the influences of different energy efficiency calculation methods on the energy consumption of residential buildings, and select the appropriate method to reduce heating energy consumption, the study calculated, simulated, and comparatively analyzed energy consumption of residential buildings in 10 typical cities in severe cold and cold zones by adopting the steady-state method elaborated in ‘Design standard for energy efficiency of residential buildings in severe cold and cold zones’ and the dynamic energy consumption simulation of EnergyPlus software. Findings indicate that indexes of heat loss of building obtained from both methods were different in typical cities with varied difference ratios. Cities of high altitude, strong radiation, and greater diurnal range, namely Lhasa and Xining, had difference ratios of as high as 43.83% and 21.20%, which were followed by Yinchuan and Lanzhou, with the maximum difference ratio of 19.69% and 18.81%, respectively. Thus, by analyzing main factors concerning the difference, dynamic energy consumption simulation was recommended over steady-state method for residential building energy efficiency calculation in the abovementioned zones with a difference ratio greater than 15%. In addition, for cities such as Xi’an, Beijing, and Hailar, with a difference ratio of 10%~15%, the dynamic simulation method was also suggested to improve the accuracy of building energy efficiency design, while for other cities with a maximum difference ratio below 10%, such as Urumqi, Changchun, and Harbin, steady-state method could be adopted. The results could provide a reference for residential buildings in northern heating areas of China to choose suitable methods for engineering application in energy efficiency design.

Abstract:To explore the application of human body exergy analysis method in evaluating thermal comfort conditions of indoor environment, a more feasible method based on the definition of metabolic exergy was proposed to calculate human body metabolic exergy rate after comparison with two existing calculation methods. Then a new two-node human body exergy analysis model validated by ASHRAE thermal comfort database was proposed. Results indicate that exergy rates were more precise if the sum of warm and humid metabolic exergy rates was calculated based on clearly-defined energy metabolism by heat and moisture. The proportion of exergy consumption rate to metabolic rate was greater than that of the exergy exchange rate. The exergy exchange rate mainly consisted of convection and radiation exergy rate when the operative temperature was 25 ℃, while it consisted of evaporation and respiration exergy rate at 32 ℃. The exergy consumption rates reached extreme values at both lower and higher operative temperatures, and hence using the index alone as a thermal comfort evaluation parameter was inappropriate. It was more appropriate to consolidate exergy exchange rate with exergy consumption rate as a human body thermal comfort estimating index. The minimum values of aforementioned two terms, for a given indoor parameter, appeared at a greater outdoor air temperature and a lower outdoor relative humidity. The outdoor air temperature had a stronger impact on exergy exchange rate and exergy consumption rate than outdoor relative humidity.

Abstract:It has become a common practice to connect the gas distribution system with various gas sources. However, constituent difference of natural gas may have negative effectgs on the end users. To understand the influence of different gas constituents on the CO emission of gas cooker and avoid the damage to the indoor air quality of a large number of end-users, an experimental study on the CO emissions of gas cooker was carried out. First, the distribution of 12T natural gas constituent in China was investigated, and six groups of the original natural gas and the corresponding three-component gas were prepared by using the principle of equal Wobbe number and the conservation of hydrocarbon atom number. The CO emission of the gas cooker under each set was also tested. Then the difference between be CO emission of the original natural gas and that of the three-component gas was discussed. Different three-component gases based on Wobbe number and PN number were tested on the cooker. Results show that the CO emission of the three-component gas was equivalent to that of the original natural gas. The gas quality parameters, Wobbe number, and PN number could be used to describe the variation of CO emission of gas cookers with different gas constituents. A series of CO isoline were revealed on the PN-W diagram, which can be used to predict the CO emission of gas cooker with different gas constituents. A method to establish the CO emission limit was put forward based on the diagram. The work of this paper is of practical significance and value for ensurance indoor air quality and gas source quality management of distribution network.