Abstract:To deal with the problems of horizontal trajectory tracking control of underactuated unmanned surface vehicle (USV) in the presence of model uncertainties and unknown ocean currents, a robust nonlinear trajectory tracking controller for underactuated USV was proposed based on the backstepping method and adaptive technique. For the model uncertainties of underactuated USV, the adaptive neural network technique was employed to estimate and compensate the unknown model uncertainties. Then, the derivatives of virtual control variables were obtained by dynamic surface control method. The control law was simple in structure and easy to be realized in engineering, and it greatly reduced the complexities of the traditional backstepping method. For the disturbances of unknown time-varying currents, an observer was designed to estimate the velocity of unknown time-varying currents. Next, based on Lyapunov’s direct method, it was proved that the designed controller could ensure that the motion trajectory converged to the expected value, and that all signals of the trajectory tracking closed-loop control system were finally uniformly bounded. Lastly, under the condition of limited control input, in order to verify the tracking performance of the controller, the circular trajectory was selected as the reference trajectory. Simulations were carried out and results show that the controller could accurately track the desired trajectory and had strong robustness for model uncertainties and unknown time-varying currents. In addition, the unknown functions of the system were effectively estimated and compensated by adaptive neural network technique, which verified the effectiveness of the proposed tracking control scheme.

Abstract:The optimal design for the attitude control system of a spacecraft with on-off impulse thrusters as actuators was studied. For the spacecraft actuating a large angle rest-to-rest attitude maneuver, proper attitude control law and proper attitude commands were designed to reduce the fuel consumption of the thrusters. First, the configuration of six impulse attitude thrusters on the spacecraft was given, and a nonlinear system model to describe the large angle attitude motion of the spacecraft was established using the quaternion tool. With this model, a nonlinear PD control law was designed to steer the spacecraft in actuating large angle maneuvers, and the stability of the nonlinear attitude control system was proved by the second method of Lyapunov. Then, the allocation logic of the six impulse thrusters in the three axis attitude control system was proposed. Since the nonlinear PD control law has to be implemented with the pulse width modulation technique, three switching thresholds were introduced into the nonlinear PD control law to reduce the consumption of fuel. The switching thresholds were selected using the particle swarm optimization technique. A scheme of scheduling the quaternion command for the rest-to-rest large angle attitude maneuver was proposed by steering the Euler angles to reach their aims with uniform angular rates. The scheme was helpful for improving the transient property and reducing the fuel consumption of the control system compared with the conventional step commands. Simulation results verified the effectiveness of the control law and the scheme of scheduling the commands.

Abstract:To study the multi-cavity evolution characteristics of parallel multi-projectile water entry, the launcher that can be used for high-speed water entry in parallel was designed, and the feasibility of the system was verified by experiments. Then, based on the system, the test on parallel double-projectile water entry was carried out with different cavitator diameters and radial spacing. The high-speed photographic technology was used to collect the movement process of double-projectile water entry in parallel. Finally, the collected motion sequence images were analyzed to obtain the data of double-projectile water entry in parallel. The evolution law of double cavitation in the process of parallel water entry was obtained, which reveals the coupling evolution mechanism between the cavitation of the projectiles entering water in parallel. Results show that there were three typical phenomena of crossing, attraction, and truncation in the process of cavitation evolution of high-speed projectiles. The cavitator diameter and the radial distance of projectile were important factors affecting the coupling characteristics of double-cavity. When the radial distance of the projectiles was constant, as the diameter of the projectile cavitator decreased, the degree of coupling between the double cavitation was weakened, and the complete crossing phenomenon became a partial crossing phenomenon. Under the same cavitator diameter, with the radial distance increased, the attraction phenomenon between the shedding cavities of the projectiles was gradually weakened, while the offset amplitude of the shedding cavities increased first and then decreased with the increase of the radial distance. When there was a front-to-back distance between the double-projectile, the first projectile was prone to the truncation phenomenon. As the radial distance increased, the truncation diminished. According to the principle of independent expansion, the truncation phenomenon will also be weakened when the distance between the front and back of the projectile was reduced under the same conditions.

Abstract:To understand the influence of the dynamic strain ageing (DSA) phenomenon on the mechanical properties of GH4169 superalloy during heat treatment, experimental and modeling investigations of DSA were carried out for solid solution treated nickel-based GH4169 superalloy at elevated temperature. Uniaxial tensile tests at 620 ℃ with strain rates of 10^-2, 10^-3, and 10^-4 s^-1 were performed to characterize the DSA effect, and negative strain rate sensitivity and serrated yielding behaviours were identified. Through the use of a thermal activation based viscoplastic flow rule with the DSA effect incorporated, a one-dimensional constitutive model was established. The deformation resistance was divided into two parts, i., slip resistance and deformation resistance caused by DSA effect. Two internal variables, equivalent ageing time and waiting time, were introduced to describe the DSA effect, and a least-squares method was adopted for parameter fitting. Comparison show that the calculated results of the constitutive model were in good agreement with the experimental results. The slip resistance increased with the increase of strain rate, whereas the deformation resistance caused by DSA effect decreased with the increase of strain rate. It further indicates that the identified negative strain rate sensitivity is the result of the competition between DSA effect and normal rate effect in certain strain rate range.

Abstract:Aiming at realizing the autonomous cloud detection of remote sensing satellites for remote sensing images, improving the efficiency of autonomous target recognition, and avoiding the loss of key target information in remote sensing images with large cloud coverage that may bring about unnecessary waste of computing resources to subsequent algorithm processing, a cloud detection method was proposed based on convolutional neural network, which can achieve autonomous cloud detection with high accuracy. Firstly, a convolutional neural network was built based on the requirements of the task and the characteristics of the remote sensing image. Secondly, a large number of manually labeled remote sensing images were used to train the network, which was adjusted according to the training result until it reached a certain classification accuracy for the test image set. Finally, the captured remote sensing image was divided into hundreds of sub-images based on size, and the pre-trained network was used to predict whether the sub-images were covered by clouds. By analyzing the prediction results of all sub-images, the cloud coverage information of the original image was obtained. Taking the Landsat remote sensing images as the test object, results show that the proposed method achieved 95.3% for cloud coverage detection accuracy, 97.8% for no-cloud coverage detection accuracy, misjudgment rate of 2.58%, missing rate of 0.90%, and overall accuracy of 97.9%. With the implementation of a simple structured network and parallel computing technology, the method can be used for real-time space missions with guaranteed autonomy and robustness. The achievement of this work will provide a foundation for real-time orbit applications based on remote sensing images.

Abstract:To solve the problem of severe matching/non-matching uncertainty of hypersonic vehicles in the process of climbing, a new adaptive super-twisting sliding mode control method was proposed to suppress the matching uncertainty of the ascent phase, and the method was combined with a sliding mode differentiator to resolve the non-matching uncertainty of the ascent phase. Firstly, the sliding mode differentiator was used to estimate the derivatives of the velocity and height in the feedback linearization model to narrow the gap between the feedback linearization model and the original model. Secondly, on the basis of the traditional super-twisting sliding mode, a linear term was added to increase the convergence speed. Then, the discontinuous symbolic functions in integral terms were made continuous to ensure the smoothness of the control input, which eliminated or attenuated the chattering to a greater extent. Lastly, since the upper bound of the composite disturbance was unknown, an adaptive law was designed to ensure that the parameters were not overestimated and the initial value could be chosen to ensure the convergence speed. Simulation results show that the improved control method can meet the control requirements, and compared with the traditional super-twisting sliding mode control algorithm, the improved control method had smoother control input and faster convergence speed, which verifies the effectiveness and advancement of the proposed method.

Abstract:To solve the problems that the time resolution and measurement error of time-to-digital converter (TDC) are mutually restricted, and the single photon detection system has low working frequency and long dead time, a high-speed single photon detection system for fluorescence lifetime imaging was designed. The system integrates a 6×6 single photon avalanche diode (SPAD) array and a two-stage TDC. In this system, the SPADs are connected in parallel with each other to increase the photosensitive area. The quenching circuit could effectively reduce the detection dead time and afterpulse effect by automatically controlling the two discharge branches. Both high resolution and large dynamic range were achieved by the two-stage TDC structure, where a novel three-channel vernier structure was adopted to reduce the measurement uncertainty. The memory temporarily stored the measurement time interval in the corresponding address, and after the measurement, the UART circuit read data into the computer by the order of address. The system was simulated on the basis of TSMC 0.18 μm CMOS technology, and the overall layout area was 2 800 μm×1 800 μm. Simulation results show that the breakdown voltage of SPAD was about 11.3 V, the avalanche current was about 10^-3 A, and the dead time of quenching circuit was about 40 ns. TDC could achieve a time resolution of 30 ps and a total conversion dynamic range of 241 ns. The whole system detected two fluorescent signals at a clock frequency of 526 MHz, and the quantization error was less than 10 ps.

Abstract:To realize the estimation of gyro error by optimization-based in-motion alignment algorithm (OBA) and apply it to low precision SINS systems, a new fast in-motion alignment (FIMA) algorithm was proposed by combining the adaptive unscented Kalman filter algorithm with the OBA algorithm for SINS systems assisted by GPS. In the proposed algorithm, the relationship between the gyro constant drift and the misalignment angle was used to build the state equation, and the measurement equation was constructed by integrating the gravity acceleration and the ground speed. Since the system was nonlinear, the UKF algorithm was applied to estimate the misalignment angle and the gyro constant drift. Due to the uncertainty of measurement noise, an adaptive filtering algorithm was introduced to estimate the noise in real time. Results show that for low precision SINS systems, the proposed algorithm could converge the heading angle error to less than 3 degrees in about 15 s, and within 3 min, the heading angle error could be converged to less than 1 degree. Compared with the traditional nonlinear moving base alignment algorithm and the OBA algorithm, the proposed algorithm could realize rapid alignment under any misalignment angle. In addition, it could estimate the gyro constant drift online and compensate the misalignment angle of the system, which improved the alignment accuracy and convergence performance.

Abstract:In highly dynamic environments, there can be motion blur on the star images taken by star sensors, which will seriously affect the star spot extraction accuracy. Regarding to such issues, a method is proposed in this paper to directly extract star spots form motion blurred star images assisted by prior information. First, the prior attitude information of inertial navigation systems and star sensors was utilized to predict the coarse star spot coordinates on the motion blurred star image, which were regarded as seed points for local region growth to obtain the range of the star spots. Then, the star spot motion trajectory was estimated based on the angular velocity output of the inertial navigation system, and star spot coordinates were calculated by the centroid method. Finally, errors of the star spot coordinates were corrected according to the relationship between the star spot motion trajectory and the centroid extraction error. Simulation results show that compared with the method that extracts star spots after restoring the motion blurred star image, the proposed method can ensure high accuracy of star spot extraction and good anti-noise performance under highly dynamic environments. Besides, the proposed method can greatly reduce the processing time for motion blurred star images, which is helpful to ensure that the data update rate of star sensors is not greatly affected by highly dynamic environments.

Abstract:To overcome the obstruction of resistance moment of magnetic hinge so as to realize the reconfiguration of combination body of micro-nano satellites (CBMS), and meanwhile prevent the magnetic hinge from desorbing and reduce the impact when modules re-splicing, a compliant control method was proposed. First, the dynamic model of the multibody system under the constraint of magnetic hinge was established by using the second kind of Lagrangian equation, and the fuzzy control law of reconfiguration was designed. Then, a fuzzy regulator of quantization factors Ke and Kc was introduced into the original controller to improve the proposed control method. The method has two advantages: one is that it does not rely on the dynamic model of the system and the other is that only the module participating in reconfiguration needs to be controlled. In order to evaluate the compliance degree of reconfiguration quantitatively, two parameters were designed. Lastly, the compliance degrees of reconfiguration using the original controller and the improved controller were compared through simulations and physical experiments. The results of mathematical simulations and physical experiments on the air-bearing platform show that compared with the fuzzy controller whose quantization factors are constant, the improved control method could make the angular velocity of the module change more gently during reconfiguration, and the relative angular velocity was smaller when the modules were re-spliced, which indicates that the proposed method can achieve the target of compliant reconfiguration.

Abstract:During the terminal guidance stage of striking maneuvering targets, in order to make large caliber naval gun guided projectiles meet multiple constraints of impact angle, line of sight (LOS) angle rate measurement limitation, and actuator control saturation at the same time, an integrated guidance and control (IGC) method was proposed based on adaptive robust control and sliding mode dynamic surface. First, the IGC design model of projectile in vertical plane was constructed. Next, the extended state observer (ESO) was designed to quickly and accurately estimate the LOS angle rate and unknown disturbances, such as target maneuvering. Then, a nonsingular terminal sliding mode was designed based on adaptive exponential reaching law, so that LOS angle tracking error and LOS angle rate could converge to zero in finite time. By combining adaptive robust terms, the sliding mode dynamic surface and virtual control variable were constructed to stabilize the system and reduce the chattering of variable structure terms. Furthermore, by designing an adaptive Nussbaum gain function, the nonlinear problem of control saturation caused by canard deflection limitation was well compensated. On the basis of the Lyapunov stability theory, the finite time convergence of terminal LOS angle tracking error and LOS angle rate as well as the uniform ultimate boundedness of the system were proved. Simulation experiment shows that the proposed design method can make naval gun guided projectiles possess well guidance performance while striking targets with different maneuvering forms.

Abstract:An inflatable membrane structure derives its structural integrity from pressure difference, so as to support its self-weight and other external loads. To increase the bearing capacity of membranes, cables with more strength are added to adjust the shape and stress distribution. Form finding is critical for inflatable cable-membrane structures, and pressure difference is the key factor that influences the shape and stiffness of the inflatable structure. Based on the nonlinear finite element theory, the concept of pressure difference presetting was proposed and combined with the nodal equilibrium method for optimization. According to the design goals of airships, the form finding scheme was put forward to achieve multi-objective optimization. First, the geometric shape that satisfies the specific stress ratio between the cable and the membrane was obtained by combining the pressure difference presetting method and the nodal equilibrium method. Then, the final shape with expected volume was achieved by scaling up and down. Results show that the stress of the cable after form finding was twice as large as that before form finding, where the cable fully exerted its load-bearing effect. In addition, the stress distribution of the membrane was more uniform, and the bearing capacity of the overall structure was strengthened. The study can provide reference for solving practical engineering problems.

Abstract:To analyze the influence of different opening diameters in the upper panel of the honeycomb sandwich structure on its acoustic fatigue life, the vibro-acoustic coupling analysis was adopted in this study. First, the finite element analysis of the structure was performed to obtain low-order modes and corresponding frequencies. Next, the sound field was divided by boundary element, and a dynamic model of acoustic-structure coupling was built. In order to reduce calculation, principal component analysis was performed on the input noise load, the principal components of each order were extracted as input conditions, and the dynamic responses at each frequency and each principal component were obtained by numerical analysis. Then, the power spectral density (PSD) function of structural dangerous points was obtained by post-processing based on modal superposition. Lastly, the PSD method which combines P-M linear cumulative damage theory and probability density function was used to calculate the acoustic fatigue life of the structure. Result shows that although the structural panel opening caused the reduction of structural rigidity and the stress concentration of the hole edge, when the diameter of the opening was small, each honeycomb cell was a Helmholtz resonator. Consequently, the acoustic wave was affected by the viscosity when it propagated in the opening structure, and heat loss occurred during the propagation, which could absorb part of the acoustic energy and reduce noise. Therefore, the small open-cell structure has a positive effect on the acoustic fatigue life.

Abstract:To study and improve the traditional temporary buildings, such as wood, paper tube, bamboo, simple tents and other materials made of temporary shelters. There are some problems of temporary shelters such as weak designability, thick materials, insufficient mechanical properties and so on. In this paper, chiral honeycomb, hexagonal honeycomb, concave hexagonal honeycomb, star honeycomb and triangular honeycomb structures were fabricated by 3D printing technology. In-plane tension, out-of-plane bending and in-plane compression characteristics were tested. The results show that the chiral honeycomb structure has a large bearing capacity, and the comprehensive mechanical properties of the hexagonal honeycomb structure are better than the other four structures. This study shows that the honeycomb structure designed in this paper is superior to the traditional temporary building materials. Under certain conditions, the chiral honeycomb and hexagonal honeycomb structure prepared by using PLA material can meet the the needs of mechanical properties and design of temporary buildings after disaster, save manpower with light materials, and effectively reduce the secondary damage of temporary buildings to victims.

Abstract:To balance the exploration and exploitation in the searching process for different optimization problems and the same optimization problem in different search phases, as well as to reduce the computational cost, an adaptive mating restriction probability-based self-organizing multiobjective evolutionary algorithm (ASMEA) was proposed. Firstly, the self-organizing map (SOM) algorithm was used to establish the neighborhood relationships among the population individuals in ASMEA. The appropriate reproduction based on the above relationship is helpful to produce high quality solutions during the later period of the searching process. To reduce the computational cost of the cluster, the evolutionary algorithm was combined with SOM. At each generation, ASMEA alternately conducts the SOM training step and evolves the population. Secondly, the mating restriction probability was set to control the mating parents selected from both the neighbor population built by SOM and the whole population, so as to strengthen the exploitation and exploration respectively. Lastly, the mating restriction probability was self-adaptively updated in each generation by the utility of generation offspring based on different paternal sources in previous generations. ASMEA and five representative multiobjective evolutionary algorithms were experimented on a number of test instances. Results suggest that ASMEA performed better than the others on search quality, search efficiency, and visual comparison, which verified the ability of ASMEA to solve complicated multiobjective optimization problems.

Abstract:To protect the activity of α-tocopherol and improve its stability, α-tocopherol liposomes were prepared by using thin film hydration method with egg yolk lecithin and cholesterol as wall materials and Tween 80 as emulsifier. The effects of the mass ratio of phospholipids to cholesterol, the mass ratio of phospholipids to α-tocopherol, and the volume of absolute ethanol on the quality of liposomes were analyzed by single factor experiments with the entrapment efficiency, particle size, and Zeta potential as indexes. Based on the single factor experiments, response surface methodology was adopted to optimize the formula of α-tocopherol liposome with the entrapment efficiency of α-tocopherol as response value, and the influence of different factors on the stability of α-tocopherol liposomes was investigated. Results show that the optimum parameters for the preparation of α-tocopherol liposome were as follows: phospholipid, 280.00 mg; mass ratio of phospholipids to cholesterol, 6.22∶1; mass ratio of phospholipids to α-tocopherol, 18.70∶1; absolute ethanol, 14.65 mL. Under these conditions, the entrapment efficiency of α-tocopherol liposomes was 87.39±1.12%, the average particle size was 181.30±3.45 nm (PDI=0.201±0.013), and the Zeta potential value was -38.90±0.32 mV. The spherical structure of α-tocopherol liposomes, which has uniform size and good dispersion, was observed by electron microscope. Stability analysis results suggest that liposomes could be well stabilized at a sucrose concentration of 0.5% or less, but pH, ion concentration, heating temperature and time, as well as storage temperature and time all significantly affected the stability. The study indicates that liposomes can maintain the activity of α-tocopherol and improve its bioavailability to effectively expand the range of applications.

Abstract:To obtain an accurate and reliable prediction formula of burst pressure for pipelines, a new yield criterion was proposed to analyze the plastic failure of pipelines. By calculating the integral mean value of the apothem with variable angle, a yield criterion in the form of principal stress components was established, which is called homogenization yield criterion. The locus of the criterion on the π-plane is located in the interior of the Mises circle, and the geometric shape is a dodecagon with equal sides and unequal angles. By comparing with the experimental data of metal yielding, it showed that the rewritten formula by the Lode parameters for this criterion was a connected piecewise line, which was in good agreement with the experimental data. Based on this criterion, the stress and strain fields of a pipeline were analyzed, and an analytical solution of burst pressure for the pipeline was obtained in consideration of the strain-hardening effect of the material. Then, the main parameters that influence the burst pressure were discussed. The experimental data was compared with the burst pressure obtained based on the Tresca, Mises, and TSS yield criteria. Results showed that the prediction results of burst pressure were dependent on different yield criteria, and the results based on the proposed criterion had higher approximation to the experimental data. In addition, it was found that the geometry size of the pipeline and the strain-hardening exponent were the main factors that determine the burst pressure, and the pipeline with thicker wall or smaller diameter could bear more pressure. The results of this paper are significant to the design and evaluation of oil and gas pipelines.

Abstract:To achieve efficient resource recovery of steel slag, the effects of roller method and hot smoldering process on the basic properties of steel slag were studied by means of X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size distribution, stability, and grindability. Research indicates that the main chemical composition and phase composition of roller steel slag (RSS) and hot smoldering steel slag (HSSS) have little difference. RSS contains a large amount of dicalcium silicate (C₂S), tricalcium silicate (C₃S), and dicalcium ferrite (C₂F), and metal iron particles can be observed clearly. Compared with HSSS, the CaO content of RSS is larger, while the f-CaO content is smaller. Autoclave stability test was carried out under 2.0 MPa saturated steam, and it was found that with in the same particle size range, the stability index of RSS was higher than that of HSSS, indicating that RSS has better stability. Cement test mill was used for grinding, and the curve of specific surface area with the increase of grinding time was obtained. Results show that during the same grinding time, the specific surface area of RSS was smaller than that of HSSS. When the grinding time exceeded 70 min, the grinding efficiency of RSS tended to be gentle, while the specific surface area of HSSS increased by 15.67% when the grinding time reached 110 min, which suggests that RSS has poor grindability. Sizing experiments and crush value test show that the particle size of RSS was mostly 3-5 mm, while that of HSSS was mainly 3-10 mm, and the particle size distribution was relatively uniform. The crushing values of RSS and HSSS coarse and fine aggregates both reached the technical index of type I coarse and fine aggregates, which can thus be directly used as coarse and fine aggregates.

Abstract:To accurately calculate the filling flow rate and on-way resistance of non-Newtonian fluid filling slurry in different working conditions and to guide filling engineering practice, the flow behavior of non-Newtonian fluid filling slurry in pipeline was studied. Firstly, according to rheology and fluid mechanics theory, the flow state of filling slurry in the pipeline was analyzed, and the critical condition of laminar flow in non-Newtonian fluid pipeline transportation was determined. Then, the approximate pipe flow equation was deduced, which greatly reduced the amount of calculation and simplified the calculation process. Finally, the non-Newtonian fluid filling slurry with mass concentration of 71% and cement content of 11% was prepared from the total tailings of copper concentrator and 325 Portland cement. Loop test was carried out based on the established non-Newtonian fluid pipeline flow equation and approximate pipeline flow equation, and the yield stress τ_B, consistency coefficient K, and power exponent n were calculated by the exact solution and approximate solution, respectively. Results show that when R was 0.75 m, L was 26 m, and ΔP were 152 6,2 219, and 109 576 Pa, then Q were 119.6,3.1, and 24.3 m³/h. The τ_B solved by the exact solution in the loop test was 128.098 3 Pa, K was 0.450 6, and n was 1.109 7, while the τ_B value solved by the approximate solution was 138.965 2 Pa, K was 1.244 4, and n was 0.905 7. The comparison of 3D images drawn by equation visualization method demonstrates that the values of pipeline flow obtained by the exact solution and the approximate solution were basically the same and had similar variations, indicating the accuracy of the approximate pipeline flow equation. Therefore, the flow equation of non-Newtonian fluid pipeline is suitable for the engineering practice of non-Newtonian fluid pipeline transportation and is a strong supplement to Buckingham flow equation and Poiseuille law.

Abstract:To analyze the impact of residential form on residential energy consumption and provide suggestions for energy-saving planning, taking Harbin as the representative of winter cities, this paper investigates the influence of residential forms on residential energy consumption for heating and cooling by conducting sensitivity analysis, and offers suggestions on energy-saving planning for winter cities. Building stories, building length, space interval, and orientation were selected as the morphological parameters relating to residential energy consumption. Four residential typologies including pavilion, L-shaped, U-shaped, and slab type buildings were obtained by classifying the residential forms in Harbin. The ideal models of the four types of residential districts were formed and the energy consumption of each model was simulated by utilizing Openstudio and EnergyPlus. Aiming at figuring out the relative impact of the four examined parameters on energy consumption, the research processed the simulation data through a sensitivity analysis method using the standardized regression coefficients (SRC). Results show that the four parameters all had impact on the residential energy consumption, and the building length was the most significant parameter. Based on the results, a residential energy-saving planning strategy was proposed from the perspectives of housing type, shape coefficient, space interval, and orientation, and the parameter combinations of minimum energy consumption of multi-story and slab type residential buildings in winter cities were obtained.

Abstract:The morbidity of childhood asthma and allergic diseases has increased significantly in recent years. The indoor air quality of their dwellings and classrooms is closely related to asthma and respiratory diseases, so it is urgent to detect and analyze indoor pollutant concentration levels. Aiming to determine the concentrations of primary indoor pollutants associated with childhood asthma and allergic diseases in severe cold regions and investigate the correlation between different pollutants, the questionnaire survey about the health condition and living environment of the children about 10 years old living in Harbin was carried out, and case groups and control groups were selected for field test and comparative analysis. Results of questionnaire survey show that indoor humidity, condensation, mold, visible flow, decoration, and inhabitant smoking were closely related to childhood asthma and allergic diseases. We selected ten houses (six case groups and four control groups) and two classrooms to monitor temperature, humidity, and particulate mass concentration, collected total volatile organic compounds (TVOCs) and semi-volatile organic compounds (SVOCs), and calculated the colony counts of airborne, settled, and adherent fungi. The difference between measured parameters of case groups and control groups was analyzed, and the correlation between different parameters at sampling sites was discussed. Results show that high temperature and dryness environment might lead to childhood asthma and respiratory illnesses. The difference of PM_2.5 mass concentration between case groups and control groups was not significant (P=0.157). Children with respiratory allergic diseases were associated with SVOCs concentration in dust. There was a significant correlation between airborne fungi in living room and those in children’s bedroom (r=0.943, P=0.005), and the result was the same for adherent fungi (r=0.943, P=0.005).

Abstract:The flue gas produced by gas combustion has the characteristics of high temperature and high moisture content. The lithium bromide absorption heat pump can recover the sensible and latent heat in the flue gas, but it still requires an external driving heat source. To solve the problems of poor heat recovery capacity and low economic efficiency of such systems, this paper proposes a self-driven humid and hot flue gas waste heat recovery system. The system combines a graded flue gas heat exchanger with traditional lithium bromide absorption heat pump. The thermal model and applicability model of the system were established, and the influence of main parameters on the thermal performance and applicability of the system was analyzed. Results show that under the conditions of flue gas inlet temperature of 550 ℃ and inlet moisture content of 120 g/kg(a), the maximum heat recovery efficiency of the system was 11.6 %, and the minimum value of the heat recovery net income balance period was 5.2 a. When the expected values of the heat recovery ratio and the net income balance period were 10% and 5.5 a respectively, the applicable range of the secondary water outlet temperature was 55 ℃~64 ℃. The maximum value of the energy-saving expansion coefficient of the self-driven system was 29.7%, when the flue gas inlet temperature was high and the inlet moisture content was low, indicating that the self-driven system at this time has the most significant energy-saving capacity in contrast with the direct heat exchange scheme.

Abstract:To meet the behavioral needs of contemporary consumers, based on the “interactive design” theory, the research technologies of virtual reality and behavior simulation were applied to improve the design method of commercial buildings. First, a questionnaire survey of the interior space of commercial buildings in Milan was carried out, and the influencing factors of consumer behaviors were explained by relevance analysis via statistical software SPSS. Then, the commercial interior space in three-dimensional dynamic scene was obtained by using the virtual reality technology. Taking the signage system design of commercial space as an example, the signage system set A with single color and low brightness and single form and set B with high brightness color and different shapes were preset, and virtual dynamic scene and behavior simulation were conducted. Finally, the ResNet image recognition technology was adopted to analyze users’ visual experience and use effect. Results show that the plan layout, spatial recognition, and spatial familiarity had significant correlation with usage frequency. Visual perception was the main driving factor in choosing commercial buildings. Comparative analysis of commercial signage system shows that the mean values of the degree of confidence and the average recognition time of set B were less than those of set A, indicating that the design of bright colors and different shapes of signage system is more likely to be concerned and accepted by users. Using the interactive design method to develop commercial building design is helpful to improve the attraction of interior space of commercial buildings.

Abstract:To meet the needs of offshore wind power development in medium depth water and reduce the cost, an articulated wind turbine was designed based on articulated platform. The influence of turbulent wind on the dynamic response of the articulated wind turbine in working and extreme sea conditions was studied. The blade element momentum theory was utilized to calculate the aerodynamic load and the potential theory was applied for the simulation of wave load. Considering the coupled loads of wind, wave, and current, the instantaneous change in wet surface as well as the friction damping of the articulated joint, a calculation software was written and time domain dynamic response of the wind turbine was calculated. Based on the NPD spectrum of turbulent wind, the dynamic response of the articulated wind turbine under the loads of constant wind and turbulent wind were calculated, and the influence of turbulent wind on the dynamic response and energy efficiency of the wind turbine was analyzed. Results show that with turbulent wind, the wind wheel acceleration and the vertical pull force on the articulated joint had little change. The mean values of oscillation angle, stream-wise thrust, output power, and stream-wise thrust force on the articulated joint decreased, but the amplitudes of oscillation angle and output power increased. In addition, the low-frequency characteristics of turbulent wind could increase the low-frequency response of the system and thereby cause system resonation. In extreme climate condition, the maximum stream-wise oscillation angle of the articulated foundation increased significantly, but the turbine system still met survival requirements. Hence, turbulent wind has great influence on the dynamic response of articulated wind turbine, and it is necessarily to consider the impact of turbulent wind when analyzing the movement and strength of articulated wind turbines.

Abstract:The integrated performance simulation and genetic algorithm were adopted to optimize the design of office buildings in Xi’an, aiming at solving the problems of performance evaluation and dislocation of form design as well as the difficulty in weighing the negative correlation performance goal. Performance simulation was used to achieve the unification of architectural design elements and building performance, and genetic algorithms were applied to optimize multi-variable and multi-objectives to provide data support for program decision making. The performance optimization design framework for office buildings was established according to the logic of design, simulation, evaluation, and optimization. The performance optimization design applied to each link was formulated. Taking orientation, surface width, window-wall ratio, shading method, louver width, and louver inclination angle as variables, the individual buildings, surfaces, and details were optimized. A genetic algorithm was adopted to realize the optimization of building shape so as to improve energy consumption and light performance. A case study of an office building in Xi’an show that based on the climate characteristic quantitative energy-saving strategy, the utilization rate of passive solar energy was the highest. Taking the solar radiation gain of buildings as the target, the shape optimization result was that the long axis of the office building was in the northg-south direction and the length-width ratio was 1∶4. In the design of building surfaces, the window-wall ratios in different directions were taken as variables, the window-wall ratio in the south direction was 60%, and those in other directions were 40%. The time, light, and heat performance were excellent, so the external sunshade louvers were further optimized. Optimization results show that on the basis of the optimization of building surfaces, the total energy consumption was reduced by 3%, and the annual light exposure was reduced by 36.5%, while the percentage of all-natural lighting time in the space was not significantly decreased.

Abstract:To realize the optimal control of variable pressure difference in fan-coil unit systems, a phase plane fuzzy identification method was proposed and verified, which takes the terminal branch pressure difference of the most unfavorable thermal loop as the control variable. For fan-coil variable flow air conditioning water system, based on the heat balance equation of air conditioning room, the mathematical relations among the terminal energy difference between supply and demand, the deviation (e) between room temperature and its setpoint, and the deviation change (ec) were established. The most unfavorable thermal loop is defined as the one with the largest terminal energy difference. In the phase plane composed of e and ec, the terminal energy difference of the phase plane could be reflected by the trajectory characteristics of the phase plane connected by phase points S(e, ec). According to the fuzzy pattern recognition process, by taking the real-time tracer direction vector angle (β_i) and the room temperature deviation (e_i) as characteristic indexes, triangle function as subordinate function, and maximum subordinate degree principle as recognition criterion, the table of fuzzy recognition rules was formulated. The phase plane fuzzy identification method for the most unfavorable thermal loop was then established, and a test platform for variable flow air conditioning water system was built. The water flow of the branches was increased synchronously, and the branches that reached the balance between energy supply and demand are the most unfavorable thermal loops identified by the test. Experimental results show that the proposed method is accurate and reliable, which can be applied to identify the most unfavorable thermal loop in fan-coil unit systems.