Abstract:To overcome the disadvantages of some vector propulsion methods, such as external acurators and redundant degrees of freedom, a 2 degree-of-freedom(2-DOF) vector propulsion mechanism scheme is introduced, which is based on limited-DOF parallel mechanism and the actuator can be arranged internally. The fixed platform of the RS+2PRS mechanism can be used as the rear bulkhead of AUV, and the movable platform of the mechanism as the mounting base for the propeller. The proposed mechanism has a compact structure, high stiffness, and is well sealed. The movement decoupling analysis shows that the two independent movable parameters of the mechanism are the precession angle and the nutation angle. The nonlinear mapping model can be built between the Euler attitude angles and the driving parameters of the mechanism. The joint simulation analysis was carried out using MATLAB and ADAMS, and the experiment equipment was built. By changing the relative positions of driving components in two prismatic pairs, the 2 DOF attitude adjustment of the AUV rear propeller can be achieved, and the AUV heading and pitch angles can be adjusted rapidly. Research shows that the physical design of the propulsion mechanism is reasonable, and the attitude control algorithm is correct. This propulsion mechanism can improve the maneuverability and capability of the AUV, and this research lays a theoretical foundation for the further 2 DOF vectored thrust engineering application.

Abstract:The strapdown inertial navigation system (SINS) is a self-service navigation system widely used in military, aviation, and other fields, and the transfer alignment is one of the key technologies of SINS. The observability analysis of SINS alignment model of large misalignment angle is studied in this paper. Firstly, the nonlinear SINS error model was deduced and the error model was simplified according to the actual engineering situation. Then, based on the observability analysis method of nonlinear theory, the system observable matrix was built using the differential geometry theory, the definition of the system observable degree and the analysis method of the state variables' observable degree were given, and the method was applied to SINS nonlinear transfer alignment model under two different matching modes. Finally, the unscented Kalman filter (UKF) was designed for the SINS large misalignment angle transfer alignment simulation, and the simulation results verified the observability analysis.

Abstract:When the observed noise parameters are unknown or change with time, the performance of the traditional SLAM algorithm will decline. In this paper, an SLAM algorithm is presented based on variational Bayes noise adaptive cubature Kalman filter (VB-ACKF). The inverse Wishart distribution was used to model the observed noise parameters, and the nonlinear variational Bayes filter was utilized to estimate the joint posteriori probability of the mobile robot state and the unknown observation noise parameter. The proposed algorithm effectively solved the problem of filtering divergence of traditional filtering algorithms when the observed noise parameter was unknown or changing. Simulation results show that the positioning accuracy of VB-ACKF-SLAM algorithm was greatly improved compared with the SLAM method based on the cubature Kalman filter (CKF-SLAM), the unscented Kalman filter SLAM algorithm (UKF-SLAM), and the extended Kalman filter SLAM algorithm (EKF-SLAM) when the observed noise parameters are unknown or changing. The effectiveness of the algorithm is proved.

Abstract:To improve the analysis of fatigue multi-crack propagation problem, a method for fatigue multi-crack propagation simulation based on ordinary state-based peridynamics was established. Based on ordinary state-based peridynamics theory, a plane stress peridynamics model for fatigue crack initiation and propagation was proposed by using peridynamics fatigue theory. Due to the large amount of calculation for the peridynamics fatigue model, a parameter named “critical broken bonds number” was introduced to the model to speed up computation. The balance between computational efficiency and suitable crack path accuracy was studied with different “critical broken bonds number” based on an edge-cracked panel. Results show that the calculation was speeded up when an appropriate broken bond number was used, and the crack extention road also kept a precise shape. The fatigue crack of panel with multiple cracks was simulated by the peridynamics fatigue model with different “critical broken bonds number”, and the fatigue crack paths and a-N curve agreed well with the experimental result. Results show that fatigue crack can propagate arbitrarily by the suggested peridynamics fatigue model without setting extra crack extension criteria or preset crack routes, and it significantly improves fatigue multi-crack propagation simulation.

Abstract:To improve the lift drag ratio and motion performance of underwater gliders, combining the advanced layout of the joined-wing in aviation and the traditional underwater glider, a joined-wing underwater glider configuration is proposed, which can achieve better lift drag characteristics through optimization. First, numerical simulation of the underwater glider body was carried out, and the validity of the numerical simulation method was verified by comparing the obtained results with the experimental data. Then according to the Computational Fluid Dynamics (CFD) code, the lift drag characteristics of three layouts, the positive staggered, the negative staggered, and the combined empennage were compared and analyzed. The orthogonal layout was chosen as the basic shape of the underwater glider because of its maximum lift drag ratio. Parametric modeling of the shape of the underwater glider was thus carried out. Finally, taking the maximum lift drag ratio as the optimization objective, the Kriging surrogate model was constructed and the EGO algorithm was used to optimize the shape of the joined-wing underwater glider. Results show that the lift drag ratio of the optimized underwater glider increased by 18.42% over that of the vehicle before optimization, and 23.45% over that of the traditional underwater glider. It proved that the new type joined-wing layout has excellent lift drag characteristics in the underwater glider. The research results provide a new way of improving the gliding performance of underwater gliders.

Abstract:To improve the thermal environment comfort of the manned submersible chamber, the thermal environment characteristics of cabin thermal environment were analyzed by the thermal comfort model of predicted mean vote-predicted percentage of dissatisfied(PMV-PPD). Based on the cabin environment data of 7000-meter task, the dynamic environment characteristics of the typical task stage were analyzed, and the key data about human and environment were obtained. By calculation of PMV-PPD by Matlab and further comparison of the index, the thermal comfort dynamic characteristics and distribution characteristics were investigated. In addition, optimization analysis of cabin thermal comfort was carried out regarding two controllable factors, wind speed and clothing thermal resistance. Results show that the PMV value was constantly changing between [-2, +2], and the thermal comfort of the pre-mission was characterized by the heat. Among them, 84% of the mission stage cabin thermal comfort was poor, of which 79.69% was cold and 16% was hot. Wind speed v and clothing thermal resistance Icl were important influencing factors for the regulation of thermal comfort in airtight cabin. For the manned submersible system lack of air conditioning, when the wind speed maintained 0.5 m/s in the control thermal environment stage and clothing thermal resistance increased by 0.93~1.48 at the cooling environment stage, clothing thermal resistance could effectively improve cabin thermal comfort.

Abstract:A line readout circuit with digital outputs is presented in this paper, which is suitable for SOI diode uncooled infrared focal plane arrays. The readout channel consists of a second-order sigma-delta modulator and an output buffer. The modulator includes an integrator, a current DAC, and a comparator. With the proposed circuit desiqn which adopts direct digital guantification, traditional analog pre-amplifier circuits are no longer needed. Continuous time increment type sigma-delta modulator can be driven by weak signals, which is capable of dealing with relatively small signals outputted by SOI diodes. The readout circuit was designed and simulated with 5 V supply voltage and the readout channel width was limited below 30 μm to meet the requirement of pixel physical size. The tape-out was completed in SMIC 0.35 μm CMOS technology to further validate the effectiveness of this design. Test results show that the output noise was less than 9 μV with 60 Frame/s under room temperature, the power consumption of each channel was less than 450 μW with 5 V power supply voltage, and the area of each channel was 0.092 mm² . Compared with traditional readout circuits, the proposed circuit needs no pre-amplifier circuits nor off-chip ADC, which reduces the complexity of the system. This design can be used in low power, low noise, and high density large scale infrared imaging systems with less chip area and power consumption.

Abstract:To predict the mechanical response of IN718 alloy under various complex conditions accurately and reliably, the theoretical modeling of serrated plasticity of microsized single-crystal IN718 alloy under displacement control was carried out. Starting from the micro-compression test, a simple deformable body-spring model was proposed to further elucidate the serrated plasticity under the displacement control. Subsequently, the independent modeling elements such as strain hardening, flow rule, loading-unloading criterion, and strain burst criterion were taken into consideration. Then, a continuum constitutive model for the serrated plasticity was established. This model was used to study the compression response of IN718 micropillars with single slip and double slip orientation, respectively. The simulations produced clearly a series of visible strain bursts, loading and unloading process in micropillar plasticity, and the exhibited serrated flows are comparable with the corresponding experimental observations. The proposed continuum model for the serrated plasticity can provide a strong theoretical support for the development of the classical crystal plasticity theory in the sub-micron scale.

Abstract:Most of the existing researches on belief rule-base inference methodology focus on the problem of parameter optimization, while few on the problem that the belief rule-base system cannot operate normally due to the incomplete input information caused by the difficulty of data acquisition. In order to solve this problem, an inference method based on incomplete input is proposed. First, the precondition attributes distribution was obtained from experience or historical data using statistical method. Then, the step sampling method was used to obtain multiple candidate values for the missing precondition attribute, which was combined with other precondition attributes. Each of the inputs was inferred using the belief rule-base inference methodology. Finally, the ER algorithm was used to fuse all the input inference results. In the simulation experiment of automobile engine fault diagnosis, the method of this paper was compared with other methods. Results show that the cumulative inference error of the proposed method was obviously smaller than other methods when there was sufficient historical data. Moreover, through multiple experiments, it was found that the proposed method has good adaptability to different distributions. This method reduces the inference error on the basis of minimizing the computational complexity, and provides a new idea for the belief rule-base inference of incomplete input information.

Abstract:To achieve rapid and uniform mixing of trace samples, based on the mathematical model of “Horseshoe Transformation”, a series of operations on fluids, such as “extrusion stretching”, “curved folding”, and “inverse transformation-intersection” were carried out.Theoretical calculation show that when squeeze amplitude 0<λ <1/2 and stretch amplitude μ>2, the transformation could induce chaos flow successfully under laminar flow with low Reynolds number. Based on theoretical calculations, a mixer which consists of 4 mixing units with the effective mixing length of 13 mm was designed and manufactured. The numerical simulation results by COMSOL show that when Re≥1 and the Peclet Number Pe≥10, the chaotic flow intensity increased with the flow rate and gradually became the main factor to promote mixing. When Re=10, after passing through 4 “Horseshoe Transformation” mixing units, the concentration variance σ=0.054, and the mixing effect was nearly uniform. The visualization test of mixer chip show that the color change of the tracer photographed by the fluorescence microscope was consistent with the surface concentration cloud in the simulation result. Moreover, the mixing test of different pH value samples proved that the micromixer based on the “Horseshoe Transformation” can generate chaos flow and achieve a satisfactory mixing effect.

Abstract:For the multi-parameter, nonlinear, and real-time problem in air combat situation assessment, an approach is proposed based on a novel structure of decision tree. Ensuring the basis for the assessment of the situation includes obtaining the information of the warring parties and the state parameters of the unmanned aerial vehicle(UAV). The enemy was used as the input of the decision tree and four kinds of situation results as the output of the decision tree, which provided a theoretical basis for the rationality of the result of the UAV situation estimation. According to the state parameters that affect the attack area of the air-to-air missile, by comparing the same state parameters, the magnitude of the evaluation index value of the UAV and the enemy aircraft were obtained, and the corresponding indicators of the air combat situation classification were designed to meet the rapid response requirements of the situation assessment. The rules of the air combat situation classification were established to be inference rules of the decision tree. Finally, anti-reasoning rules were proposed for undeveloped branches in the decision tree in order to improve learning under unknown conditions. Extensive simulations, including one-to-one, one-to-two, and two-to-two air combat scenarios, show that the computing time of the proposed method was 5.39 s and its accuracy was 80%, while the computing time of the Bayesian was 11.63 s and the accuracy was 60%. The results indicate that the proposed optimal method has faster assessment speed and higher accuracy than the traditional Bayesian network.

Abstract:Uncertainty theory is mainly used to deal with indeterminacy problems based on belief degree. In order to solve the problem of the lack of testing process after fitting uncertain distributions in practical application, characteristic functions with uncertain distributions were studied and effectiveness-of-fit test method was proposed. Firstly, the characteristic function of uncertain distribution was defined, and its calculation formula was given based on the uncertain expectation value. On the basis of the formula, the characteristic functions of several typical uncertain distributions were derived. Secondly, the properties of the characteristic functions were analyzed, which laid foundation for subsequent demonstration of theories and calculation. Thirdly, according to the definition and properties of the characteristic functions, the definition of effectiveness of uncertainty distribution fitting and its judgment theorem were proposed based on the digital characteristics and shape of distribution function. Finally, two examples were given to verify the feasibility and effectiveness of the proposed method. Simulation results show that uncertainty theory and stochastic theory are different in product axiom, and it is difficult to extend the method of distribution fitting test in stochastic theory to the uncertainty theory. In addition, there is a one-to-one correspondence between the uncertainty characteristic function and the uncertainty distribution function, and the uncertainty characteristic function can be used as one of the approaches to study the uncertainty distribution fitting test.

Abstract:To identify the turn rate of fighter Zigzag maneuver under one-step randomly delayed measurements and non-Gaussian measurements noise and to achieve better tracking performance, based on the idea of joint estimation and identification and Maximum Likelihood Estimation Criteria, a joint optimization algorithm based on expectation maximization for target state estimation and turning angular identification is proposed, which takes mutual coupling between target state and turning angular velocity into account. The algorithm basically contains two parts: E-step and M-step. In the E-step, the likelihood function of particle filter was firstly reconstructed by fully taking one-step randomly delayed measurements and non-Gaussian measurements noise into account, which improves the update formula of particle weight. Meanwhile, in order to avoid particle deficiencies, the particle swarm algorithm was introduced into the reconstructed particle filter to improve the sampling process. Secondly, the idea of rejection sampling was introduced into the backward simulation particle smoother, and the termination condition for rejecting the sampling was set accordingly, thus the backward simulation particle smoother was further optimized to improve the execution efficiency of the smoothing algorithm. Lastly the smooth estimation of the target state was obtained by using the improved particle filter and backward simulation particle smoother. In the M-step, a numerical optimization algorithm was used to maximize the conditional likelihood function, and the estimation of the turning angular velocity was thus obtained for the next iteration of the algorithm. The optimized solution of the closed-loop form of the turning angular velocity was obtained by the iteration of E-step and M-step. Simulation results show that the proposed algorithm performed better in state estimation and turn rate identification than the traditional augmentation method.

Abstract:Since the directions of arrival (DOAs) of interferences change rapidly in high dynamic conditions, the traditional anti-jamming algorithm based on the linearly constrained minimum power (LCMP) criterion cannot suppress the interferences effectively, which may lead to the acquisition failure of GNSS receivers. To slove this problem, a covariance matrix taper (CMT) null widening algorithm was proposed, which can make the DOAs of interferences always in the widening nulls. Firstly, the DOAs of interferences which are unpredictable in practice were assumed to be triangular distributed. Then, the conversion relationship between the virtual covariance matrix and the real covariance matrix was obtained according to the assumption. Consequently, the virtual sample covariance matrix was derived, based on which the weight vector was acquired. Finally, the propsed algorithm was compared with the algorithms that adopt uniform distribution model and Laplace distribution model. The research results show that the proposed algorithm can widen the nulls effectively. Compared with uniform distribution model and Laplace distribution model, the proposed model achieved a superior balance between the null width and the null depth, and it had a higher array output signal to interference plus noise ratio (SINR). Moreover, software GNSS receiver was used to validate the effectiveness of the proposed algorithm.

Abstract:The noises caused by star sensor electric circuit and the complex working environment faced by the star sensor when being applied in spacecraft both have serious impact on the quality of the star image, leading to the decrease of the star centroid extraction precision. Regarding the issues above, a star centroid extraction method, which has high precision and good anti-noise performance, is presented. Firstly, a multi-window sampling adaptive threshold segmentation method was used to reduce the noise of star image. Secondly, an improved gray cross projection method was proposed for star point coarse extraction. Finally, the local region growing method and the Gaussian surface fitting were used for star centroid fine extraction. The improved gray cross projection method can solve the problems caused by star point overlap so as to quickly and accurately find the rough area of star point and provide reliable “seed” points for the local region growing method. The local region growing method can fully reserve the edge of star point, which is beneficial to improve the star centroid extraction precision. Simulation results show that the star centroid extraction accuracy of the proposed method reached 0.075 5 pixel under the simulation condition with a noise standard deviation of 2. Compared with the traditional methods such as the scanning method, the star centroid extraction accuracy of the proposed method is greatly improved with good anti-interference performance, which has significant reference value for improving the accuracy of star sensor measurement under strong noise interference conditions.

Abstract:Hypersonic vehicle is susceptible to external disturbances during maneuvering. If traditional state feedback control methods are used, the closed-loop control system can easily cause oscillations and fail to meet the precision requirements for the tracking of maneuvering flight instructions. If traditional sliding mode control methods are used, the problem of singular value will emerge in the system and the calculation process is more complicated, thus the control system is difficult to implement. In view of the above problems and considering the actual requirements of high-speed maneuvering flight control, this paper proposes a designed method of the linear parameter varying (LPV) controller based on a finite-time time-varying sliding mode and applies it to hypersonic vehicle control. First, the system was kept stable by traditional state feedback control methods without taking the external disturbances into account. Then, in the presence of perturbations, a finite-time time-varying sliding mode control law was developed by selecting a special sliding function. In order to reduce the chattering phenomenon of the system, a saturation function was introduced to replace the signed function in the control law. Theoretical derivation proved that all the signals in the closed-loop system are bounded, and the tracking error can be controlled to a small neighborhood around the origin in a predetermined time. Simulation results show that the states of the hypersonic vehicle could stably track the reference signal within a limited time, and the oscillation phenomenon of the closed-loop system was effectively suppressed. These properties verified the effectiveness of the controller presented in this paper.

Abstract:There are wide and efficient military application prospects for the vertical and/or short take-off and landing (V/STOL) aircraft. A dynamic model of V/STOL aircraft accurately reflecting the dynamic characteristics in flight simulation should be built for research on its complex flight control. By employing the principle of linear superposition and combining the mechanism modeling and empirical formula, a complete propulsion/aerodynamic force and torque model was built considering the impacts of the changing rate of gas mass flow, nonlinear and unsteady dynamic characteristics at high angle of attack, unpowered ground effect, and jet-induced effect. By applying this model, the 6-DOF nonlinear mathematic model was deducted according to the principle of rigid body dynamics and kinematics. Finally, simulation analysis provided the dynamic changes of V/STOL aircraft caused by ground effect, the jet-induced effect and the unsteady dynamic characteristics of the delta wing. Results indicate that the effect of ground effect on the dynamics of V/STOL aircraft can be ignored, while the jet-induced effect in near ground flight leads to greater lift loss that increases with the decreasing flight altitude. The unsteady dynamics of V/STOL aircraft which is derived from the hysteresis effect caused by the change of angle of attack is significant at high angle of attack and small airspeed. This model has the characteristics of clear physical meaning and simple calculation, can reflect the dynamic characteristics more accurately, and can provide help for model simplification and flight control system (FCS) design in different flight modes for the V/STOL aircraft.

Abstract:To control the system radiation risk and track the maneuvering target in clutter, a non-myopic multi-sensor scheduling policy for maneuvering target tracking is proposed. Firstly, the maneuvering target tracking accuracy in clutter was estimated by the interacting multiple model and probability data association (IMMPDA) algorithm. Secondly, the radiation cost was quantized by the emission level impact (ELI) and the posterior carmér-rao lower bound (PCRLB) was utilized to represent the target tracking performance. Then the radiation cost and the PCRLB over the future finite time horizon were predicted, respectively. Finally, considering the switching cost and the tracking accuracy constraint, a non-myopic multi-sensor scheduling policy with cost function and PCRLB was set up. The constrained scheduling problem was converted to a decision optimization problem which can be solved by a search algorithm with threshold pruning technique. Simulation results show the effectiveness of the proposed policy. Compared with the uniform cost search (UCS), the proposed search algorithm can reduce the number of nodes opened and improve the search speed with a slightly increased radiation cost. Compared with random scheduling, closest scheduling, and greedy scheduling, the proposed policy can obtain lower radiation cost while satisfying the target tracking requirement. Furthermore, the proposed policy also has the lowest switching cost, and the sensor scheduling frequency has been reduced effectively.

Abstract:Helicopter vertical descend state contains extremely dangerous vortex ring state. In order to improve the understanding of the vortex ring state, to master its aerodynamic load and flow field changes, and to provide experimental data for the corresponding numerical simulation and flight simulation, the aerodynamic load and flow field measurement test of Bo-105 rotor model under vertical descend state was conducted in Φ5 m vertical wind tunnel using helicopter vertical flight test rig and the large filed PIV measurement system. In the case of similar tip Mach number, the average thrust, average power, and wide range PIV flow field images of this rotor model under different collective pitch and descent speeds were obtained, the rotor model aerodynamic load variation was analyzed, and the flow field development process under different descent speeds was captured. The test research shows that the thrust and power decreased sharply after the vertical velocity of the rotor model dropped to 8 m/s, and the root-mean square error increased significantly. The smaller the collective pitch, the easier it was to enter vortex ring state, and the faster for the rotor model thrust to decrease with the increase of vertical descent speed. The main cause of instability of blade tip vortex structure is the vortex-pair structure. When the distance between adjacent blade tip vortices was smaller, the blade tip vortex was more unstable. The formation of vortex ring by the blade tip vortices gathering together and the dynamic evolution of the vortex ring structure were the key factors in the sudden change of rotor performance.

Abstract:Based on the bidding mechanism, an autonomous mission planning method was proposed to solve the rapid response problem of unexpected tasks in the background of multi-satellite cooperative remote sensing, which considers the limited computing resources and the weak computing power on the satellite. In order to find an optimization algorithm that satisfies the requirements of on-board autonomous mission planning and enhances the rapid response capability of the constellation of the remote sensing satellites in unexpected situations, the multi-satellite collaborative planning modeling, algorithm design, and simulation analysis were studied. First, the mathematical model of autonomous mission planning on the satellite for multi-satellite autonomous collaborative task planning was constructed. Then, in the problem solving process, a complete task planning was reasonably decomposed into three processes including invitation for bid, bidding, and evaluation. With the solving process and the corresponding constraint inspection rules designed, the multi-satellite autonomous collaborative mission planning algorithm based on bidding mechanism was obtained. Compared with commonly used intelligent optimization methods, this method can significantly reduce the computational complexity and adapt to the tight computational resource constraints on the satellite. The simulation example shows that for a typical unexpected task, the average simulation running time of the algorithm was about 1 s, the response to unexpected tasks could be completed within 40 s, and the completion rate of the original planning task was fully guaranteed, which verifies the validity and the correctness of the method.

Abstract:To explore the cause and mechanism of the disaster caused by abnormal gas emission in coal seams with low-pressure gas, the literature in this field was analyzed and summarized, and the existence of such disaster was verified by case study. Based on the fluid-solid coupling experimental system, the physical test of coal sample bearing pressure with low pressure was carried out according to the constraints and loading conditions of the engineering, and the overall stress-acoustic emission-flow experimental data and the external damage of the sample were obtained. Using UDEC software, the discrete element numerical experiments of gas-solid coupling were carried out according to the boundaries and loading conditions of the engineering, and experimental data such as stress-strain-displacement rate and internal cracking of the sample were gained. Results show that the three methods had a high consistency. With the gas pressure of 0.4 MPa, gas outburst occurred under stress-coal-gas coupling, and it generally appeared as the amount of gas emission exceeding the limit in coal mine. The unidirectional pressure load was applied under the single-degree-of-freedom boundary condition. At the early stage of the elastic deformation of the pressure-bearing coal rock, the gas flowed along initial cracks and pores at a normal steady speed. At the later stage of the elastic deformation, the initial cracks and pores were compacted and gas flowed at a slow steady speed. During the yield phase, the new fissures triggered by coal dilatancy were formed and gas flowed rapidly and unsteadily. When the coal mass bore approximately achieved ultimate load or shortly reached the peak, gas outburst disaster happened. The phenomenon of continuous decrease of gas concentration faced in the mining and excavating work under normal ventilation is a warning sign that coal seams have abnormal gas emission, and to which great importance should be attached.

Abstract:To investigate the influence law of soluble organic matter in coal on coal resistivity, briquette coals of three different metamorphic grades made of 60~80 purpose raw coal grains were selected and tested. Ethyl acetate was used as solvent to dissolve soluble organic matter in the coals at 4,8, 2,6, 0,4 h. The coals before and after dissolution were made into sample coals. The current vs. voltage curves of the sample coals were obtained at 10 ℃~90 ℃ using CHI660E electrochemical workstation and their resistivity were calculated. Based on this, the influence mechanism and rule of the soluble organic matter on coal resistivity at different temperatures were analyzed. Results show that the presence of soluble organic matter in coal increased coal resistivity for 1.31~1.74 times at temperatures from 10 ℃~90 ℃ in 0 ~24 h dissolution time. The rule that coal resistivity increased with the increase of dissolution time conforms to the Sigmoid Function relation, and coal resistivity only changed according to this rule within a certain range. Coal resistivity increasing with temperature rise exhibits parabolic rule. The ratio of coal resistivity before and after dissolution increasing with temperature rise approximately presents Lorentzian distribution with a turning point at 40 ℃~50 ℃. The sensitivity and correlation of the influence of soluble organic matter on coal resistivity gradually weakened with the increase of the degree of coal metamorphism.

Abstract:All the comminution stages of iron ore from raw ore size to the concentrate size were taken as one comminution system to research the theoretical relationship between comminution energy and particle size. Firstly, the basic theories of relationship between comminution energy and particle size of ore were analyzed to establish a theoretical model of comminution energy of iron ore. Secondly, the change patterns of comminution energy were analyzed in site investigation, and particle size distribution characteristics in each comminution stage were analyzed in indoor experiments. Lastly, the change patterns of specific energy of the comminution system were analyzed with the method of numerical fitting, and the reliability of the theoretical model of comminution energy was verified with the data of the specific energy, characteristic size, and medium size of the iron ore in each comminution stage. Results showed that the comminution energy of iron ore increased exponentially, the distribution of comminution energy was unreasonable, and the product granularity was characterized by exponential distribution, polynomial function distribution, and Langmuir power function distribution in turn along with the alteration of comminution stage in the system. There was a negative correlation function between the specific energy of the comminution system and the particle size of ore. The change rate of specific energy of the comminution system turned into a turning point when the medium size was 12 mm or the characteristic size was 25 mm. The established theoretical model of comminution energy has larger range of particle size in energy calculation compared with classical models. It can be used to fit the function formulas between specific energy of stage comminution and the size of feed and product and provides theoretical basis for the calculation of comminution energy in iron mine.

Abstract:In three-north regions of China, power regulating abilities of cogeneration units are constrained significantly by their compulsory heat outputs. Such regulation mode is one of the key reasons for the large amounts of wind curtailment in the last few years in winter. Introducing electric heating boilers and thermal energy devices are effective ways to promote wind power integration and reduce the energy consumption of district heat and power system. In order to get the optimal economic configurations of the clean heating reconstruction projects, a two-layer optimization model based on the genetic algorithms and traditional unit commitments is proposed in this paper. First, by analysing the supply and demand relationship of heat and power, a typical structure of the district energy system (DES) in northern China was given. Then, the daily net benefits were defined as the quantitative economic indexes for any reconstruction projects. Finally, the two-layer optimization model was obtained by integrating short-term dispatch models of the DES. In this model, the genetic algorithms are used to search for the most economical configuration combinations globally, and the fitness values of the population are solved by the inner linear programming. Case studies indicate that the optimal configurations of the clean heating project were affected by several factors including the heat and power demands, characteristic of the wind power outputs, and socioeconomic conditions. Although differences exist between several independent genetic optimizations, any of these solutions are good enough to meet the requirements of engineering application. In addition, although more wind power can be integrated by introducing electric heating boilers and thermal energy devices, there is no need to integrate all wind power because of the law of diminishing return.

Abstract:To solve the problems of traditional grounded kang, such as uneven temperature of kang-surface, low thermal efficiency, large exhaust heat loss, excessive indoor pollutant concentration, etc. this research puts forward a new combination of elevated kang and radiator heating system. A traditional grounded kang and the new heating system were built respectively in two same southern rooms of a new farm house in Yushu County, Jilin Province, to test the temperature of kang-surface, exhaust temperature, indoor temperature, and indoor pollutant concentration for the quantitative analysis of thermal performance of this new system. Under the same fuel consumption, the temperature standard deviation of the kang surface of the novel kang was 4.8 ℃ lower than that of the traditional ones while the temperature at the head-side was 9.4 ℃ lower. The efficiency of the heating system was 21.26% higher than that of the traditional grounded kang based on counter-balance calculation, and the indoor average temperature increased by 5.7 ℃. In addition, the CO concentration indoors decreased to the standard range. When getting the same indoor temperature, the new heating system can save 1 972.2 kg straw, which can reduce 2 603.3 kg emission of CO₂ and 1.0 kg emission of SO₂ per year. The test results show that the new system can not only solve the problems of traditional grounded kang but also improve the indoor environment significantly and has significant effect on energy saving and emission reduction. Thus, the popularization and application of this new combined operation system can reduce the heating energy consumption considerably and improve the living environment of residences in northern rural areas.

Abstract:The load of regional buildings is the orderly coupling of the loads of different type of buildings in the region, and the mastery of electrical load characteristics are the basis of regional energy planning. To analyze the characteristics of the air conditioning electrical loads of regional buildings, an analytic indices system was established from the perspectives of dynamic features, load fluctuation features, and the load coupling relationship between the individual buildings and the regional buildings. Geographic Information System was used to visualize the characteristics of the regional loads. A typical university campus was taken as an example, and the characteristics of the air-conditioning electrical loads of the buildings on this campus were analyzed. In terms of load level, research buildings and office buildings had the highest load; teaching buildings had smaller unit area load but higher daily peak load and daily average load compared with dormitory buildings.The fluctuation of the daily and weekly load was small for research buildings and dormitories, while office buildings and teaching buildings fluctuated greatly. As for the contribution of individual buildings to the regional load, research buildings, office buildings, and teaching buildings had the larger contribution to the regional peak load, while the dormitories contributed smaller. The pattern and the length of the building operation are important factors that affect the load characteristics. The regional load characteristics are related to the types and numbers of buildings, and the appropriate proportion of building types can reduce the fluctuation of the regional load. Different indices focus on different points, and the indices system developed in this paper can fully reflect the regional load characteristics and the coupling relationship with individual buildings.

Abstract:To study the characteristics of summer thermal comfort and adaptation of naturally ventilated university dormitories in Changsha, 15 naturally ventilated dormitories of two universities in Changsha are investigated in this paper. Environmental parameters were recorded, and surveys were conducted on the thermal sensation and thermal adaptation behavior of the subjects. In total, 437 research data were collected. Based on temperature frequency method and weighted linear fitting method, the relations of indoor operating temperature with clothing thermal resistance, the predicted mean thermal sensation (PMV), and the actual mean thermal sensation (MTS) were determined. Results indicate that clothing thermal resistance negatively correlated with indoor operating temperature in summer. With the increase of unit operating temperature, clothing thermal resistance reduced by 0.019 7 clo. PMV was larger than MTS, and the higher the operating temperature was, the greater the difference between the two was. The corresponding acceptable temperature ranges of the two were 24.4 ℃~28.7 ℃ and 23.8 ℃~28.9 ℃, respectively. By using adaptive PMV model, the adaptive coefficient of the naturally ventilated university dormitories in Changsha was calculated to be 0.5, which is in great discrepancy with the prescribed values given in GB/T50785—2012 “Evaluation standard for indoor thermal environment in civil buildings.” The male and female research data were studied separately.As the unit operating temperature increased, the clothing thermal resistance of male and female reduced by 0.028 8 clo and 0.016 4 clo respectively. Male feels warmer than female in summer. The neutral temperatures of male and female were 26.3 ℃ and 26.7 ℃, respectively. The acceptable temperature ranges of them were 23.8 ℃~28.7 ℃ and 24.2 ℃~29.2 ℃, respectively. This study provides reference for the studies on thermal comfort and thermal adaptation of university dormitories.