Abstract:A kind of prescribed performance based adaptive attitude tracking control scheme is discussed for flexible spacecraft attitude tracking problem with external disturbances and unmodeled dynamics. The prescribed performance method utilizes performance functions and error transformation for constraining the system tracking error within prespecified bounds to ensure desired overshoot, convergence rate, and steady-state error. Radial basis function (RBF) neural network is used to deal with the unknown dynamics caused by disturbances and flexible vibration. When considering the existence of the unknown neural network approximation error, the upper bound of the approximation error is further estimated to reduce the conservativeness in parameter selection. By using the designed adaptive laws, the prescribed performance adaptive attitude tracking control law is constructed. A simulation study on a flexible spacecraft system shows that the proposed method can compensate the influence of disturbances and flexible appendages while obtaining a fast transient process and expected attitude tracking accuracy. Compared with the method without using prescribed performance, the proposed method has obvious advantages in the convergence, tracking accuracy, and vibration suppression with lower dependence on control parameters.

Abstract:A finite-time stable guidance law is proposed to deal with the three-dimensional terminal interception impact angle constraints problem where the accelerations of target are not available. A kind of non-linear observer is designed to estimate target's accelerations with the positions and velocities information given by missile. Further theoretical analysis is introduced to prove this observer's accuracy. Then the finite-time guidance law is deduced by sliding-mode control laws and finite-time stability theory using the observer estimated values, by which the convergence of line of sight (LOS) angles in three-dimensional space to expected impact angles in finite time is guaranteed. Through analyzing the effect of observer's errors on the guidance system, it is shown that the finite-time convergence can be achieved for the engineering practice by the proposed composite guidance law. Simulation results for uniformly/non-uniformly accelerated targets and the comparison with Proportion Navigation (PN) are provided to demonstrate the effectiveness of the proposed approach. The results suggest that difficulties of finite-time three-dimensional terminal interception problem with impact angle constraints can be solved by the proposed method combining the non-linear observer of target's accelerations with the finite-time sliding-mode control laws.

Abstract:To improve the convergence rate of standard sliding mode control whose convergence rate is exponential, a robust finite-time control algorithm for satellite attitude stabilization under control torque saturation is presented. A three-stage structure finite time sliding mode with better convergence rate and steady accuracy is developed based on the Lyapunov method, and the issue that severe descent of angular velocity leads to convergence rate decline of attitude quaternion is avoided. The singularity issue is solved by using the property of Euler axis. By limiting the proportional term in control law, the control torque constraint is added into the control law. The known disturbance torque and inertia matrix uncertainty is solved by introducing the sign function. The finite-time stability is proved by a Lyapunov function, the convergence time estimation is given, and the property that the proposed controller could largely improve the convergence rate and maintain the high accuracy at steady stage is demonstrated by theoretical analysis and simulation results. This paper proves that planning angular velocity is the key to improve system performance, and the convergence rate and the system robustness could be improved by properly designing sliding mode and desired angular velocity.

Abstract:Dead-zone nonlinearities are a kind of common nonlinear characteristics of the actuator nonlinearities of spacecraft attitude control systems. They could degrade the performance, and even lead to un-stability of spacecraft attitude control systems. To solve the high precision attitude control problem for spacecraft with input dead-zone nonlinearities, this paper proposes a kind of finite time control approach. The attitude control model of the spacecraft considered in this paper is with bounded uncertainties and the information of the input dead-zone nonlinearities is only partially known. A desired attitude curve which converges to zero in the given time is introduced. A robust finite-time control algorithm is proposed based on the time-varying sliding mode approach to ensure the error between the actual attitude and the desired one keep small enough all the time. This further ensures that the actual attitude converges to the nearby of zero in the given time. By rigorous analysis, it is proved in theory that all of the signals in the closed-loop system are bounded and the attitude error can be driven into a small given neighborhood of the origin in the pre-specified time and stay there thereafter. The numerical simulation results show that the proposed control method is effective. It could guarantee that the system possesses fast state convergence speed, high control precision, and good robustness with respect to uncertainties and disturbances, so it has good potential application value in the attitude control of spacecraft.

Abstract:Flapping-wing aerial vehicle is a new type of aerial vehicle that mimics the flight mode of birds and insects. The design of airfoil parameters is crucial for improving the performance of flapping wing aerial vehicle. A numerical investigation into the effects of thickness and camber on aerodynamic performance of flapping wings during the forward flight is carried out through the solution of the two-dimensional incompressible unsteady Navier-Stokes equations using the computational fluid dynamics methods. The aerodynamic computational model with varying NACA series standard airfoil thickness and camber is built based on the observation of flying creatures. The aerodynamic forces, energy consumption, flight efficiency and flow field structure of the rigid wings with different incoming flow velocities under low Reynolds number are systematically analyzed using the finite element method coupled with the dynamic mesh method. It is found that the thrust force and energy consumption of the rigid wing with low Reynolds number decrease with increasing wing thickness at different incoming flow velocities, and the decrease in propulsive efficiency can reach as much as 15.9%. The leading edge vortex (LEV) intensity is reduced and the LEV shedding is delayed with the increase of airfoil thickness. On the other hand, the wing camber can change the wing angle of attack effectively. The positive camber can significantly improve the lift force and lifting efficiency and tilt the centerline of the wake towards the bottom right. The flapping wing with positive camber can produce large lift force during the downstroke, while the wing with negative camber can produce large thrust force during the upstroke.

Abstract:Tracking of non-cooperative maneuver target is the premise of fulfilling complex space task for geostationary-earth-orbit satellite, such as state supervising and maintenance etc. Considering propulsion efficiency, next-generation high-earth-orbit satellites prefer to adopt electric propulsion system. However, the continuous low-thrust characteristics of electric propulsion causes that the classical relative navigation tracking algorithm expectation has some bias, and there is some contradiction between the steady-state performance and the maneuvertracking response for two-stage state estimation method. To solve the rapid-tracking estimation problem of electric-propulsion maneuver target, filtering error theory is adopted to analyze the attenuation factor of the classical algorithm performance, and we obtain the evolvement characteristic of transfer matrix from maneuver acceleration to filtering information. The above evolvement characteristic can be matched by the observation matrix on the basis that detection information of target maneuver can amend the error filter. Then a kind of adaptive variable-dimension two-stage state estimation method is presented, which makes that its performance is equivalent to the classical relative-navigation tracking algorithm in the non-maneuvering interval of target and equivalent to the two-stage state estimation algorithm in the maneuver interval. Meanwhile, it has a faster tracking response. Finally, the simulation results show that for non-cooperative target the steady-state estimation performance of the proposed algorithm is consistent with that of the classical algorithm, i.e. the tracking response is four to five times faster than that of using the traditional method. For tracking of space non-cooperative maneuver target with continuous low-thrust maneuver, the new algorithm is a good exploration.

Abstract:This paper introduces the harmony search theory to propose a novel particle filter, and a visual tracking based on harmony search particle filter which can combine the current observation with history information to achieve a robust performance. Firstly, the importance sampling function is modified using such conceptions in harmony search theory as memory consideration, genetic variation, random variation and the current observation. These improve the robustness on system state transition matrix. Secondly, parameters of harmony search are optimized to balance the demand on timeliness and accuracy. Moreover, the weight of particle is compensated to further accommodate the Bayesian estimation.Simulations show that the optimized harmony search parameters are more suitable for harmony search particle filter than common parameters. Compared with classic visual tracking algorithms, the proposed algorithm demonstrates more accurate visual tracking ability under complex environments such as illumination changing and occlusion.

Abstract:To solve the contradiction between calculation speed and accuracy of Gauss Pseudo-spectral Method(GPM), a novel hp-adaptive Radau Pseudo-spectral Method(hp-RPM) is proposed for the Optimal Trajectory Planning issue in Free-Floating Space Manipulator(FFSM). Based on the multi-segment Radau Pseudo-spectral Method, the proposed method can allocate segment-numbers of total paths and the width of each sub-interval during iteration process, and configure the number of nodes in each sub-interval. By increasing the number of segment, the number of nodes and the order of polynomial can be reduced, saving the calculation speed as well. Based on the above theory, this paper first establishes the dynamic model of multi-arm FFSM system and develops a method for updating this model. Then, the continuous optimal trajectory planning problem is discretized and the design of hp-RPM is described. Finally, the hp-RPM is used to solve the trajectory planning problem of two-link FFSM system and the simulation is conducted. The result shows that the position and velocity planning curves of the two methods are similar under the same initial condition, but the error of hp-RPM at each node is obviously lower than that of the GPM. In the case of higher precision and more initial nodes, hp-RPM can effectively improve the computation speed and guarantee the accuracy simultaneously.

Abstract:Earth observation satellite often encounters unexpected situations such as finding a new target, failing to perform the original observation tasks. To improve the operation efficiency of observation satellite, and make a rapid response to the unexpected observation tasks in the absence of ground supports, researchers need to design ground-onboard joint operation mechanism for the autonomous mission planning. Firstly, aiming at the autonomous operation of imaging satellite cluster, this paper divides the problem into two parts: the ground task planning and onboard autonomous planning. Furthermore, based on full consideration of the resources of ground station and satellite, and the requirments of observation task planning, a ground-onboard joint operation mechanism of mission planning is proposed, together with the detailed operation process. The result of the distributed simulation software shows that the mechanism can carry out an effective coordination between the on-board autonomous mission planning and the ground planning. It can reflect the controller's intention, taking advantage of ground computing ability and onboard real-time flexibility to rapid response on unexpected tasks. It can solve the problem of response delay on ground to the unexpected observation tasks, limited computing resources onboard and the cooperation between onboard planning and ground planning. The research achievements can effectively improve the response ability of the remote sensing satellite to the unexpected observation mission.

Abstract:High performance aerial maneuvering target tracking is one of the core tasks of modern early warning radar. To improve the tracking performance of the probability hypothesis density(PHD)filter, a new PHD track association algorithm based on measurement partition is proposed. The traditional PHD filter cannot give the individual trajectories of each target, and the filtering efficiency will decrease drastically when there are a large number of clutters in the tracking environment. Besides, the traditional methods also have measurement mismatch problem for adjacent multi-target tracking. To solve the above problems, the measurement set at each time step can be divided into existing targets, new targets and clutter measurement subsets by the sorting ellipsoidal gate method, which targets can be updated by corresponding measurement subsets, thus reducing redundant computing time and improving computational efficiency. Furthermore, the algorithm can adjust the weight of Gaussian component when targets are close to each other, by introducing a new weight distribution scheme, thus greatly reducing the state extraction error of adjacent targets and improving adjacent targets estimation accuracy. The simulation results show that the proposed method can improve the filtering efficiency and the adjacent targets tracking accuracy.

Abstract:The high precision satellite clock error prediction is one of the key technical problems for the receiver real-time precision single point positioning technology. To find a rapid and accurate prediction method for small sample satellite clock error sequences, a optimized algorithm model PGM(1, 1) is presented based on the drawback analysis of the conventional GM(1, 1) predication model. The predication model using the latest measurement for initialization is established, followed by replacing the old information with the latest one to realize model predication. In addition, the attenuated memory recursive least squares method is adopted for weighted handling of both the old and new information. The normalized mean relative error is used as accuracy test standard for fitting coefficient optimization factors and particle swarm optimization adaptive optimization is adopted. The typical clock errors error of five GPS satellites are predicted among one day using the PGM(1, 1) model. The prediction accuracy is greatly improved with small training samples compared with the GM(1, 1) model and the second order polynomial model, which indicates that the prediction method can be applied to the accurate and rapid forecasting of satellite clock error.

Abstract:Aiming at dealing with the model validation issue for multi-output model with the mixture of random and interval inputs, a new model validation metric is proposed. Based on the probability method and interval theory, characteristics of multi-output model involving both random and interval inputs under the fixed random variables are analyzed. The new multi-output model validation metric is defined by extending the multi-output model validation method based on Mahalanobis distance (MD) under random inputs to multi-output model with the mixture of random and interval inputs. This metric provides a comparison between the MD cumulative distribution function (CDF) curves of the upper and lower bounds from model responses to which from experimental one, and meanwhile shows disagreement with model predictions and corresponding physical observations. Finally, estimation procedures are presented with a discussion of new metric properties and the correctness and effectiveness of the proposed metric are demonstrated by a numerical and an engineering case, respectively. Results show that: the new metric, on one hand, is able to measure the difference between system responses with experimental results under sufficient physical observations; and, on the other hand, can correctly differentiate models in worse or better accuracy.

Abstract:To investigate the effect of adding the winglet or enlarging the aspect ratio of the blades to the aerodynamic performance of H-VAWT, it calculated and analyzed the impaction of different designing parameters of H-VAWT to the tip loss. It based on the aerodynamic performance of the finite blade length H-VAWT, the aerodynamic performance of the related infinite blade length H-VAWT was compared with it, the related difference of aerodynamic performance got through comparing the related difference of the aerodynamic performance, the affection of different designing parameters-solidity and airfoil to the tip loss of H-VAWT was analyzed. By means of comparing the aerodynamic performance of H-VAWTs generated by different aspect ratios, the improving effect of the aspect ratio to the tip loss of H-VAWT was analyzed and concluded. The total results illustrated that: no matter how the solidity of the H-VAWT and the airfoil adopted of the H-VAWT blade was, when H-VAWT worked at high tip speed ratios(λ≥1.60), it was necessary to adopt the measures that decreasing the adverse affection of tip loss to improve the aerodynamic performance of H-VAWT; when H-VAWT had large solidity(σ≥0.96) or adopted thick airfoils, it was also necessary to add wing let or enlarge the aspect ratio of the blade to decrease the adverse affection of the tip loss; the effect of enlarging the aspect ratio to improve the aerodynamic performance of H-VAWT was finite, based on the designing requirements and the other geometry parameters' limitation, the value of aspect ratio was suitable at 5≤μ≤20.

Abstract:In the mission of approaching to a disabled tumbling target, the space will be divided into the safe zone and the unsafe zone because of the nutation of the target. During the chaser's flight in the safe zone of the target, the collision possibility between the target and the chaser should be determined to avoid the collision accident. To solve this problem, the region judgment method is used to transform the task into the position relation determination problem between the safe zone of the target and the trajectory of the chaser. By analyzing characteristics of the safe zone of the target as well as the trajectory of the chaser, both the conical safe corridor model of the target and ellipsoidal position error model of the chaser are established. As a result, the problem is further transformed into the issve of position relation determination between the cone and the ellipsoid. Through projective transformation and plane projection, the original cone and ellipsoid are transformed into a circle and an ellipse on the plane with the unchangeable position relation. Using the location criterion of plane curves, the position relation between the circle and ellipse would be determined, and then, the position relation between the cone and ellipsoid could be deduced, which is expected to determine whether the collision risk exists or not. Simulation experiment shows that this method is accurate to determine the position relation between the conical surface and the ellipsoidal surface, and it can be used to detect the collision possibility in the flight during the safe corridor of the target.

Abstract:This paper proposes a robust nonlinear control strategy based on adaptive backstepping method to cope with flight control for an air-breathing hypersonic vehicle with input saturation, parameter uncertainties and flexible effects.For the hypersonic-vehicle longitudinal control problem, the controller is designed separately for the velocity and height subsystems.An adaptation law derived from Lyapunov stability principle is adopted for the design of velocity subsystem controller to deal with engine physical limits, the stability of input saturation system is guaranteed.To improve robustness, a backstepping method with adaptive parameter online estimation is introduced to realize the stable tracking of altitude reference trajectory.By choosing a desirable inter-connect gain, the canard works in conjunction with the elevator to suppress the first-order mode under the excitation of control input and improve non-minimum phase behaviour.The derivatives of virtual control are achieved via a tracking differentiator.Based on the LaSalle-Yoshizawa theorem, the proposed control design is proved to be stable.Simulation results show the effectiveness of the control strategy despite the presence of parameter uncertainty, input saturation and aeroelastic effects.

Abstract:To meet the real time, automation, anti-concept drift and other processing requirements of pico-satellite high dimensionality telemetry data, a new cluster-based telemetry data anomaly detection method is proposed.The method contains correlative subspace search and two-phase density-based clustering processing for telemetry data.Subspace search calculates the entropy and entropy gain value to achieve low-dimensional subspace partitions of all telemetry data, to reduce the computational complexity and to avoid the occurrence of "dimension disasters".Two-phase telemetry data clustering algorithm meets the requirements of rapid anomaly detection and complex anomaly detection.In the online phase, the grid indexes are used to find single anomalies in real time, in the off-line phase, their specific features of the selected mining data are clustered to find collective anomalies.It also supports the anti-concept drift by iterative updating of normal data features and adaptive modification of the algorithm.The analysis for telemetry data of ZDPS-1A shows that in the on-line phase 10 kHz flowing data can be processed in real time and 95% of single-point anomalies can be found to meet the general needs of real-time telemetry data anomaly detection of Pico Satellite.This method adapts itself to change satellite conditions.The single cluster stays stable when the satellite rotates faster.This approach also detects an anomaly caused by attitude determination and control system's breakdown one month earlier than the current limit-checking system.The proposed algorithm solves the anomaly detection problem of telemetry data with high dimension and concept drift.It is suitable for the ground monitoring system of pico-satellite constellations.

Abstract:Currently, the most popular activation function for deep convolutional neural network is the rectified linear unit (ReLU).The ReLU activation function outputs zero for negative quadrant, inducing the death of some neurons, and remains the input data for the positive quadrant, inducing a bias shift.According to the theory that "zero means activations improving learning ability", softplus linear unit(SLU) is introduced as an adaptive activation function that can tackle with these two problems.Firstly, negative inputs are processed with the softplus function, pushing the mean of outputs of the activation function to zero and reducing the bias shift.Then, the parameters of the positive component are fixed to control vanishing gradients.Thirdly, to maintain continuity and differentiability at zero, the parameters of the negative part are updated according to the positive quadrant.Several experiments are conducted on the MNIST dataset for supervised learning with deep auto-encode networks, as well as several experiments on the CIFAR-10 dataset for unsupervised learning with deep convolutional neural networks.The experiments have shown faster convergence and better performance for image classification of SLU-based networks compared with rectified activation functions.

Abstract:Research on characteristics of helicopter rotor blade tip vortex is one of the key elements for helicopter rotor aerodynamic characteristics research.To improve the understanding of the blade tip vortex characteristics under hovering status and grasp the flow mechanism accurately, the Bo-105 rotor model hover test of tip Mach number similarity is conducted in open test section of Φ5 m vertical wind tunnel.In the same time, the hovering rotor flow filed of different collective pitches is measured elaborately with the TR-PIV measurement system, and then the detailed flow field (32 frames/circle) of this rotor is obtained.Based on the reasonable methods of the judgment of vortex center, extraction of vortex core flow parameter and fit of the vortex core model, the test results is processed and analyzed elaborately, and the evolution and development of blade tip vortex under hovering status is uncovered.The research shows that TR-PIV can catch the vortex characteristics correctly, and it will contribute to the elaborate study of rotor flow filed; using the weighted average of vorticity to calculate vortex center, it can avoid influence of shift speed on position of vortex core, and position of the vortex core accurately; using the circulation-based method, it can calculate size of vortex core and max induced velocity more reliably, and the results show that vortex core radius increases slowly and vortex core max induced velocity slowly decreases with increasing wake age; during the evolution of tip vortex, different development stages have different n parameters.

Abstract:To improve the hydrodynamic performance and gliding economy of general dish-shaped underwater vehicles, a newly flying-wing dish-shaped autonomous underwater glider has been designed in this paper.The SST (Shear Stress Transmission) flow model in the computational fluid dynamic mechanics has been used to investigate the hydrodynamic characteristics including drag coefficient, lift coefficient, moment coefficient and lift drag ratio from 0 to 21°.A good agreement is between the experimental results and the numerical results, and flying-wing dish-shaped autonomous underwater glider has more excellent hydrodynamic performance and gliding economy.In addition, the six-degree-of freedom dynamics and kinematics equations of motion has been presented based on the multi-body dynamics with considering the vary velocities of moving sliders and the pump system quality to simulate typical gliding movement characteristics.The simulation results illustrate that the flying-wing dish-shaped autonomous underwater glider has certain stability and possibility of underwater movement.

Abstract:Water-entry cavities of high-speed spinning sphere (HSS) were investigated numerically based on the volume of fluid (VOF) multiphase flow model, the k-ω model and dynamic grid technique.After analyzed and compared the published papers about the water entry, the optimum numerical models were selected, and a numerical simulation system was established suitable for HSS.The evolutionary process of cavities induced by water-entry HSS with different velocity and specific weight was discussed.The reverse lift offset phenomenon was detected during water-entry process within the depth of 0.25d.The trajectories of water-entry HSS with identical specific weight but different velocities are similar in the initial stages of entry.And the curvature of trajectories of those with larger specific weight but identical velocity gets smaller.The twice-closure phenomenon, vertical-closure and transverse-closure, was discovered during the water entry process.The closure depth, the maximum diameter and the diameter of tail-cavity increase dramatically with larger velocity, and are also affected by the specific weight.

Abstract:To realize the scale application of floating wind turbines in medium depth sea areas and solve the problem of energy shortages, viability of the new 6 MW spar-type floating offshore wind turbine (FOWT) was discussed by using Sesam software and aero-hydro-servo-elastic simulation code-FAST software.The wamit files of second-order wave force were calculated by the former and the dynamic response coupling analysis in time domain was carried out by the latter.The motion response of each DOF under different incident angles of wave and the effect of the second-order mean wave force and the second-order slow wave drift force on the motion response of the platform, mooring tension force and nacelle acceleration were researched respectively.The results showed that the yaw motion of the platform became more obvious when the incident angle of wave increased, while the other DOFs motion were affected little.The second-order slow drift wave force had a significant effect on the heave motion, and could stimulate a larger pitch motion response and induce larger mooring force.Moreover, the delta-line mooring system could avoid excessive yaw response and the maximum mooring force was below the breaking tension.Finally, the whole FOWT system had an excellent survivability in the harsh sea conditions.

Abstract:Existing experimental results showed that, for some metallic materials, nonproportional loading resulted in significantly shorter lives while no additional nonproportional cyclic hardening was observed. The equivalent strain method modified by additional hardening coefficient and nonproportionality factor cannot be used to correlate the fatigue data of these materials, which usually gives nonconservative predictions. To overcome this shortcoming, a new multiaxial low cycle fatigue life prediction model on the basis of the ASME effective strain range is proposed by introducing the fatigue life reduction factor and nonproportionality factor. The procedure was also proposed to determine the fatigue life reduction factor. A new equation is proposed to calculate the nonproportionality factor on the basis of the minimum normal strain range. Procedures to determine the minimum normal strain range are presented for the general multiaxial loadings. The proposed method is verified by the measured data of 12 kinds of nonproportional loading paths. In contrast to the existed method, the proposed one can be better used to describe the nonproportionality of the loading path. The accuracy of the proposed fatigue life prediction method is systematically checked by the experimental data found in literature for 10 different metallic materials (including 7 kinds of material showing no additional nonproportional cyclic hardening) under various constant amplitude multiaxial loading paths.

Abstract:Aiming at interactivity based on visitors' behaviors in museum buildings and depending on digital technique such as virtual reality technology, multimedia technology and informational technology, interactive museum building uses unique information exchangeable method to communicate. At first, this paper clarifies merit and demerit of methods, which can improve interactive effect to determine the superiority of video method which can track visitors' dynamic behavior on-the-spot investigation. Then taking walking path, position, duration as basic data of interactive study, this paper analyzes the behavior characteristics of three types of visitors (student groups, family-based collectives, the old in communities). Finally, this paper tries to conclude four strategies of interactive design: exploring the inevitable behaviors of visitors; visualizing sensory interaction; emphasizing connection between unit module deformation; making joint efforts to build virtual and physical environment by virtue of digital technique. Result shows that the relationship among visitors' behaviors, exhibitions and displayed space forms a dialogue on the basis of equality. On the basis of clarifying the interactive relationship among exhibition layout, streamline organization and exhibition space, and adding digital technique, interactive behaviors would strengthen the consciousness visiting, and allow visitors deepen memory of exhibition information through exploration and novelty, and could guide museum building design.

Abstract:This article clarified the quantitative relationship between the three attributes of urban building colors and the comfort of visual recognition under the haze weather to clarify the comfortably recognition threshold values of three color-appearance attributes of urban building in the hazy weather. The quantitative index could be provided to designers to choose architectural colors that effectively identify building color in both normal and abnormal weather conditions, while offering referential research methods for urban environmental color planning and evaluation in the abnormal weather. Firstly, the research experiments are based on the practical and fixed-point measurement of the three color-appearance attributes of building colors in Harbin, one of the most heavily polluted cities. The types of selected buildings are commercial and residential buildings, which make up the largest proportion of buildings in Harbin, and the research scope of haze index will be determined through experiment. Secondly, 126 color samples in total that selected by orthogonal method were evaluated on 30 subjects based on Likert scale in the laboratory. Finally, by using R language Statistics analysis, the distribution region and the changing threshold value of color attributes including hue, chroma and value could be related to the visual comfortable level of subjects. The results indicated that the values of the three color-appearance attributes of buildings could all directly affect the visual comfort level. Among those three attributes, value has the greatest influence, followed by chroma, and finally hue. Further the warm colors were more comfortable than cool color in the haze weather.

Abstract:To study the effect of urban building layout on energy consumption and to identify the key layout parameters, the simulation experiment and the sensitivity analysis method are used to simulate 200 kinds of layout in Wuhan from the perspective of reducing the solar radiation and heat gain. Firstly, the parameter combinations are created by Latin hypercube sampling (LHS). Then, 200 energy consumption models are established and calculated by R language and EnergyPlus energy consumption simulation software. Finally, the standard regression coefficient (SRC) and treed Gaussian process (TGP) global sensitivity analysis methods are implemented in order to explore the influence of the nine layout parameters of both horizontal and vertical direction on the target building energy consumption. The results show that the building layout has a significant effect on the energy consumption, the changes of 9 layout parameters would cause fluctuations in cooling, heating and total energy consumption of 15.8%, 26.8%, and 4.4%, respectively. The two sensitivity analysis results are similar. The parameter that has the greatest influence on the cooling and total energy consumption is the height of building in the western part, whose main effects are around 0.3. The least influential parameter is the width of the south, whose main effects are bellow 0.1. The dominant parameter of heating energy is the height of the south building, which can account for more than 30% of the variations of the output, and the smallest is the east building width. When the parameter value is much larger than the target building size, the influence of each parameter on energy consumption is reduced, and using the TGP sensitivity analysis is more reasonable. From the perspective of energy-saving and emissions reduction, this paper can provide theoretical basis for the urban planning and building layout.

Abstract:To improve energy saving efficiency of Tianjin office buildings, we select high-rise office tower as an example and assess the effect of geometric factors on building energy performance, also identify the most energy-efficient geometric design. A prototype model is established based on survey data. We choose 6 geometric factors according to previous studies: plane aspect ratio (length to width), orientation, floor area, floor height, window-to-wall ratio and overhang depth. Then orthogonal method and the listing method are utilized to assign DesignBuilder energy simulation experiments. The purpose of minimize building energy consumption by optimizing the above listed factors is achieved. The effect of building fabric performance on result is also taken into account by setting 2 types of building fabric: conventional fabric and passive house fabric. Results show that floor height and window-to-wall ratio constitute two main related issues, followed by floor area, plane aspect ratio and orientation, and overhang depth. The optimal solution is characterized by plane aspect ratio of 2/1, orientation of south, floor area of 1 024 m², floor height of 3.6 m, window-to-wall ratio of 0.3 and overhang depth of 300 mm. The results can serve as a reference for passive design related to geometric factors in the practice of office building design in Tianjin.

Abstract:To solve the problem of low accuracy of the results generated by building daylighting simulations under the generic sky models, this paper attempts to use the on-site measured sky luminance distribution HDR images as the light source to conduct the building daylighting / dynamic daylighting simulation and has validated the method. First, the method of measurement of sky luminance distribution via HDR image is indicated, and the image-based daydaylight lighting / dynamic daylighting simulation (IBL) and the method that uses HDR image as the light source input value in daylighting simulation are introduced and validated. The validation experiments are carried out from: 4^th to 10^th Jul. and 3^rd to 12^th Aug. 2017. The interior illuminance and luminance distribution are measured via instruments and meanwhile, the sky luminance distribution (including the exterior environment) is measured simultaneously. After comparing and analyzing the measured and simulated results, the accuracy of HDR image in measurement of sky luminance distribution and image-based daylighting simulation is validated. Finally, the pros and cons of sky mathematical model based daylighting simulation and IBL image based daylighting simulation are discussed. The results show that the sky luminance distribution could be accurately measured via HDR image, the accuracy of IBL simulation results of IBL is well performed, the the errors between simulation and measurement in one instant are concentrated focused within the range of -15%~47%, and the max error of 100 lx < UDI < 3000 lx generated from IBLimage-based dynamic simulation limits within ±25%.

Abstract:Packet multicast technology in cognitive radio ad-hoc networks (CRAN) is researched using a random network coding (RNC) based approach. A basic problem, which is termed as multi-channel single-hop wireless multicast problem (MCSHWMP), of packet multicast applications in CRAN is investigated. Definition about MCSHWMP and its 4-element tuple model were provided. A network coding based scheme framework for packet multicast applications in CRAN is described and based on which, several candidate schemes are proposed. Exploiting the broadcast nature of wireless transmissions by using RNC, necessary packet transmissions are reduced greatly. Considering opportunistic accessibility of wireless channels and heterogeneous packet reception success ratio of different wireless channels, each packet transmission is tried to maximize the packet reception gain of the receivers. Packet size to be transmitted is effectively shortened by reducing decoding information to be transmitted in the packet. Simulation results showed that, network coding based schemes can save much packet transmissions when compared with non-network coding based schemes, and the superiority of network coding based schemes is more distinctive when packet reception success ratio of wireless links is nearly but smaller than 1, in those cases, nearly 50% packet transmissions could be saved.