Optimum Profiles of Endwall Contouring for Enhanced Net Heat Flux Reduction and Aerodynamic Performance

Successfully utilized non-axisymmetric endwalls to enhance turbine efficiencies(aerodynamic and turbine inlet temperatures)by controlling the characteristics of the secondary flow in a blade passage.This is accomplished by steady-state numerical hydrodynamics and deep knowledge of the field of flow.Because of the interaction between mainstream and purge flow contributing supplementary losses in the stage,non-axisymmetric endwalls are highly susceptible to the inception of purge flow exit compared to the flat and any advantage rapidly vanishes.The conclusions reveal that the supreme endwall pattern could yield a lowering of the gross pressure loss at the design stage and is related to the size of the top-loss location being productively lowered.This has led to diminished global thermal exchange lowered in the passage of the vane alone.The reverse flow adjacent to the suction side corner of the endwall is migrated farther from the vane surface,as the deviated pressure spread on the endwall accelerates the flow and progresses the reverse flow core still downstream.The depleted association between the tornado-like vortex and the corner vortex adjacent to the suction side corner of the endwall is the dominant mechanism of control in the contoured end wall.In this publication,we show that the non-axisymmetric endwall contouring by selective numerical shape change method at most prominent locations is advantageous in lowering the thermal load in turbines to augment the net heat flux reduction as well as the aerodynamic performance using multi-objective optimization.

Bionic Design and Simulation Analysis of Energy⁃Efficient and Vibration⁃Damping Walking Mechanism

African ostrich can run for 30 min at a speed of 60 km/h in the desert,and its hindlimb has excellent energy saving and vibration damping performance.In order to realize the energy⁃efficient and vibration⁃damping design of the leg mechanism of the legged robot,the principle of engineering bionics was applied.According to the passive rebound characteristic of the intertarsal joint of the ostrich foot and the characteristic of variable output stiffness of the ostrich hindlimb,combined with the proportion and size of the structure of the ostrich hindlimb,the bionic rigid⁃flexible composite legged robot single⁃leg structure was designed.The locomotion of the bionic mechanical leg was simulated by means of ADAMS.Through the motion simulation analysis,the influence of the change of the inner spring stiffness coefficient within a certain range on the vertical acceleration of the body centroid and the motor power consumption was studied,and the optimal stiffness coefficient of the inner spring was obtained to be 200 N/mm,and it was further verified that the inner and outer spring mechanism could effectively reduce the energy consumption of the mechanical leg.Simulation results show that the inner and outer spring mechanism could effectively reduce the motor energy consumption by about 72.49%.

Self Recovery of Localization Loss for Indoor Mobile Robot

In order to solve the problem of localization loss that an autonomous mobile robot may encounter in indoor environment,an improved Monte Carlo localization algorithm is proposed in this paper.The algorithm can identify the state of the robot by real time monitoring of the mean weight changes of the particles and introduce more high weight particles through the divergent sampling function when the robot is in the state of localization loss.The observation model will make the particle set slowly approach to the real position of the robot and the new particles are then sampled to reach the position.The loss self recovery experiments of different algorithms under different experimental scenarios are presented in this paper.

Evaluation Method of Output Waveform Quality for Neutral⁃Point⁃ Clamped Three⁃Level Converter

An analytical evaluation method for output waveform quality of space vector pulse width modulation(PWM)strategies applied in neutral⁃point⁃clamped three⁃level converter(3L⁃NPC)is proposed in this paper.Low frequency error caused by neutral point voltage ripple and high frequency error introduced by space vector synthesis were both taken into account,and the unified error model of output current ripple was established.By taking continuous and discontinuous modulation strategies as examples,the unified error model was validated through Fourier analysis of the experimental results.The proposed evaluation method will be helpful for the switching sequence optimization and the modulation strategy selection.

Review:Ferromagnetism in Undoped ZrO2 Thin Films

Diluted magnetic oxides have evolved into a popular branch of materials science during the last decade. In the first few years,people attributed the ferromagnetism to the magnetic dopants. However,the observation of ferromagnetism in undoped HfO_2 thin films made it more controversial and promoted extensive research on the ferromagnetism in various undoped oxides. Both of the experimental works and theoretical studies have shown that intrinsic defects in oxide nanomaterials play a crucial role in the origin of such an unexpected ferromagnetism,in spite of some contradicting views which kind of defects is predominant. In the past several years,we have conducted systematic and thorough research on the room temperature ferromagnetism in undoped ZrO_2 thin films,and clarify some physics behind it. We firstly prepared undoped ZrO_2 thin films by different ways,such as Pulsed electron beam deposition,magnetron sputtering,and electron beam evaporation,and successfully obtained ZrO_2 thin films with different crystalline structure,in particular a pure high-temperature stabilized one,by adjusting some preparation parameters during the deposition process or post-annealing treatment. A phase-dependent ferromagnetism was then confirmed to exist in such ZrO_2 thin films. Further,we conducted exhaustive defect analysis and characterization by X-ray photoelectron spectroscopy,photoluminescence spectra,and electron paramagnetic resonance,respectively,and found the oxygen vacancy,specifically the single ionized oxygen vacancy( V_O^+),has a remarkable influence on the enhancement of ferromagnetism. Herein,we will review the work in detail on the phase-dependent and oxygen vacancy-enhanced room temperature ferromagnetism in undoped ZrO_2 thin films.

A Calibration Method of Robot Base Frame with Procrustes Analysis

In order to realize high precision industrial operations,based on the POE formula,an effective approach to calibrate the robot's actual base frame(ABF) is proposed. Due to the existence of manufacturing errors,the ABF deviates slightly from nominal base frame( NBF). Using external precision measurement,the ABF can be established only through the three dimension(3D) position of the robot's end-effector.To ensure the orthonormal constraints of rotation matrix as well as the precise solutions,Procrustes Analysis is introduced,where an optimal orthogonal matrix is solved out by the Lagrange Multiplier method and Singular Value Decomposition(SVD). Furthermore,calibration experiment on a serial 6-DOF robot is performed,where a FARO laser tracker is utilized to measure the 3D position. Finally, calibration result indicates that the positioning accuracy has been significantly improved after calibration. The calibration method is also applicable to other similar problems,such as multi-robot coordination and robot hand-eye system calibration.

Multi-objective Optimisation Design of Water Distribution Systems:Comparison of Two Evolutionary Algorithms

In order to compare two advanced multi-objective evolutionary algorithms,a multi-objective water distribution problem is formulated in this paper.The multi-objective optimization has received more attention in the water distribution system design.On the one hand the cost of water distribution system including capital,operational,and maintenance cost is mostly concerned issue by the utilities all the time;on the other hand improving the performance of water distribution systems is of equivalent importance,which is often conflicting with the previous goal.Many performance metrics of water networks are developed in recent years,including total or maximum pressure deficit,resilience,inequity,probabilistic robustness,and risk measure.In this paper,a new resilience metric based on the energy analysis of water distribution systems is proposed.Two optimization objectives are comprised of capital cost and the new resilience index.A heuristic algorithm,speedconstrained multi-objective particle swarm optimization( SMPSO) extended on the basis of the multi-objective particle swarm algorithm,is introduced to compare with another state-of-the-art heuristic algorithm,NSGA-II.The solutions are evaluated by two metrics,namely spread and hypervolume.To illustrate the capability of SMPSO to efficiently identify good designs,two benchmark problems( two-loop network and Hanoi network) are employed.From several aspects the results demonstrate that SMPSO is a competitive and potential tool to tackle with the optimization problem of complex systems.

Modeling Distortion Signals of Power Grid Based on Wiener-G Functionals

The uniform mathematical model of distortion signals in power grid has been setup with the theory of Wiener-G Functional. Firstly,the Matlab simulation models were established. Secondly,the Wiener kernel of power load was found based on the Gaussian white noise as input. And then the uniform mathematical model of the power grid signal was established according to the homogeneous of the same order of Wiener functional series. Finally,taking three typical distortion sources which are semiconductor rectifier,electric locomotive and electric arc furnace in power grid as examples,we have validated the model through the Matlab simulation and analyzed the simulation errors. The results show that the uniform mathematical model of distortion signals in power grid can approximation the actual model by growing the items of the series under the condition of the enough storage space and computing speed.

Cloud Foren:A Novel Framework for Digital Forensics in Cloud Computing

Since its birth in the early 90 's,digital forensics has been mainly focused on collecting and examining digital evidence from computers and networks that are controlled and owned by individuals or organizations.As cloud computing has recently emerged as a dominant platform for running applications and storing data,digital forensics faces well-known challenges in the cloud,such as data inaccessibility,data and service volatility,and law enforcement lacks control over the cloud.To date,very little research has been done to develop efficient theory and practice for digital forensics in the cloud.In this paper,we present a novel framework,Cloud Foren,which systematically addresses the challenges of forensics in cloud computing.Cloud Foren covers the entire process of digital forensics,from the initial point of complaint to the final point where the evidence is confirmed.The key components of Cloud Foren address some challenges,which are unique to the cloud.The proposed forensic process allows cloud forensic examiner,cloud provider,and cloud customer collaborate naturally.We use two case studies to demonstrate the applicability of Cloud Foren.We believe Cloud Foren holds great promise for more precise and automatic digital forensics in a cloud computing environment.

Design on a Multi-Sensor Integrated Attitude Determination System for Small UAVs

This paper discusses the design and implementation of a low cost multi-sensor integrated attitude determination system for small unmanned aerial vehicles( UAVs),which uses strapdown inertial navigation system( SINS) based on micro electromechanical system( MEMS) inertial sensors,commercial GPS receiver,and 3-axis magnetometer.MEMS-SINS initial attitude determination cannot be well performed for the reason that the MEMS inertial sensors biases are time-varying and poor repeatability,therefore in this paper the magnetometer and inclinometer are used to assist the MEMS-SINS initial attitude determination and MEMS inertial sensors field calibration.Furthermore,the attitude determination algorithms are presented to estimate the full attitude during GPS signal outage and non-accelerating situation.Additionally,the attitude information estimation results are compared with the reference of the non-magnetic marble platform and 3-axis turntable.Then the attitude estimation precision satisfies the requirement of attitude measurement for small UAVs during GPS signal outage and availability.Finally,the small UAV autonomous flight test results show that the low cost and real-time attitude determination system can yield continuous,reliable and effective attitude information for small UAVs.

Computer Forensics-An Essential Element of Modern IT Security

Computer forensics is the science of obtaining,preserving,and documenting evidence from computers,mobile devices as well as other digital electronic storage devices.All must be done in a manner designed to preserve the probative value of the evidence and to assure its admissibility in a legal proceeding.However,computer forensics is continually evolving as existing technologies progress and new technologies are introduced.For example,digital investigators are required to investigate content on mobile device or data stored at the cloud servers.With the popularity of computers in everyday life as well as the acceleration of cybercrime rates in recent years,computer forensics is becoming an essential element of modern IT security.This paper will cover the development of computer forensics in law enforcement and discuss the development in the latest live forensics skillsets.A number of interested areas of computer forensics will be also highlighted to explain how it can support IT security and civil / criminal investigation.

Comparison of Lattice Boltzmann Method and Monte Carlo Method for Modeling Phonon Heat Conduction

In order to investigate the applicability and performance of the Lattice Boltzmann Method( LBM) and the Monte Carlo Method( MCM) to simulate phonon heat transfer,a problem of phonon heat transfer in square geometry structures of silicon dioxide was taken as an example to compare the calculational results and analyze computational efficiency of the two methods. Moreover,this work analyzed the numerical stability for two methods. The results indicate that the MCM takes much more computation time than the LBM in the same condition. In addition,the results of the two methods have a good agreement in diffusive and diffusive-ballistic domain for investigating the phonon heat transfer. So they can be used to verify each other when the experiments of energy transport in these domains faces difficulty. In ballistic domain,duo to the random error,the temperature distribution curve from MCM is fluctuant.

Remediation of static lake water by intensified filter of dominant bacteria colony

An ecological filter is constructed for successful nitrification instead of conventional filter system. Zeolite and coal cinder compose main substrates of this micro-ecological filter. Nitrogen contamination removal process is investigated in three different systems (D system, A system and N system) contrastively. Dominant bacteria colony is applied to intensify the remedying process. The data showed that, NH4+-N removal efficiency in D system is better than those in the other two systems for zeolite absorption, nitrogen removal efficiency by nitrification increased. Functional bacterium consortium can adsorb much NH4+-N in short time. Most nitrogen removal is hastened through nitrification by abundant nitrous and nitride bacterium in dominant colony. That dominant consortium keeps high activity in long time. Phosphorus removal is improved by abundant aboriginal bacterium. Complex functional bacterium is benefit to decompose organic phosphorus and its removal.

T-S norm FNN controller based on hybrid learning algorithm

Aiming at the problems that fuzzy neural network controller has heavy computation and lag,a T-S norm Fuzzy Neural Network Control based on hybrid learning algorithm was proposed.Immune genetic algorithm (IGA) was used to optimize the parameters of membership functions (MFs) off line,and the neural network was used to adjust the parameters of MFs on line to enhance the response of the controller.Moreover,the latter network was used to adjust the fuzzy rules automatically to reduce the computation of the neural network and improve the robustness and adaptability of the controller,so that the controller can work well ever when the underwater vehicle works in hostile ocean environment.Finally,experiments were carried on " XX" mini autonomous underwater vehicle (min-AUV) in tank.The results showed that this controller has great improvement in response and overshoot,compared with the traditional controllers.

A novel mechanism based on Nash bargaining for primary system game in cognitive radios

According to the utility function and spectrum demand of the cognitive users,a novel mechanism based on Nash bargaining for primary system game was proposed under the wireless environment of Rayleigh fading.On the basis of this mechanism,we proposed a new distributed bargaining algorithm based on Nash product;then the spectrum prices and system utilities were obtained.Theoretical analysis results showed that with a close total utility to the optimal,the Nash bargaining mechanism cannot only improve the fairness between primary systems remarkably,but also reach to the stable equilibrium in finitely repeated games.Finally,simulation results were given to demonstrate the correctness of these conclusions and the efficiency of the algorithm.

Water quality and growth of phytoplankton for the Yellow River estuary reservoirs—The nutrients release from reservoir sediments

Effects of nutrients released from sediments on eutrophication in lakes and reservoirs were not well known in China. In the test, the release conditions of nitrogen and phosphorus from the sediments were observed by batch experiment. The test results revealed that the content released is correlated to the initial content of organic matter in sediments. In the Gengjing area, when the water quality of waterway, grit chamber and reservoir were compared, the water quality of the waterway was the highest, and lowered in the order of the grit chamber and the reservoir. The grit chamber could get not only fine sand removal but also the organic substance, nitrogen, phosphorus and phytoplankton, therefore it is important to operate and maintain the grit chamber to preserve the water quality of the reservoir. Due to little organic substance in sediments, ammonium nitrogen and phosphorus weren't released during the incubation. But from the absorptiometric turbidity unit (ATU) test results, although the release of ammonium concentration was very low, ammonium oxidizing and nitrite oxidizing bacteria existed in sediments.

Effectiveness-based orbital optimization for servicing spacecraft

Effectiveness-based system development is an essential technology developing concept advanced by some countries,such as the U.S.A.Making use of Analytic Hierarchy Process,this paper brings forward a methodology for orbital optimization based on effectiveness in the case of the orbital deployment for the Servicing Spacecraft(SSC),which needs to accomplish many types of tasks and whose orbit is affected by kinds of factors with contradictions in orbital parameter selection.Firstly,the possible tasks of SSC are decomposed and their degrees of importance are given by the times,probabilities,values of their applications.Then,the supporting capabilities are discussed from the viewpoint of orbit design,and the determination of their weights is put forward.Finally,the relationships between the orbital parameters and the effectiveness are established by using effective function,and three synthesizing methods for a single task and its capabilities are presented.

Experimental study on full scale light frame wood house under repeated lateral load

In order to obtain a deeper understanding of the behavior of the structure under high wind load,this paper conducted an experimental study on a full-scale L-shaped single story light frame wood house under the uniform lateral load simulated using a gasbag.The investigation involved the performance of light frame wood structure after it experienced the repeated cyclic lateral wind load as well as the performance of the structure under the ultimate lateral load.Then,the study verified that light frame wood structure can resist repeated cyclic wind loads without observable degradation in stiffness during the anticipated serve life,and recommended shear wall percent drift restriction for lateral wind load design of wood structure in serviceability limit states is 1/400 drift,and in ultimate limit states is 1/80 drift.The conclusions of this paper can be benefit for the engineering practice of the light frame wood structures in high wind load regions.

Mechanism of weld-line movement within hydroforming of tailor-welded tube

To reveal the reason of weld-line movement in hydroforming of a tailor-welded tube (TWT) with dissimilar thickness,the stress ratio of axial stress to circumferential stress is derived by mechanical analysis and analyzed between the thicker and thinner tubes,as well as the property of the axial strain. During TWT hydroforming,tensile strain along axial direction happens on the thinner tube. On the contrary,compressive strain happens on the thicker tube. Experiments are conducted to varify the weld-line movement regularity and strain distribution. It indicates that the weld-line moves from the thinner part to the thicker during TWT hydroforming. The thinning ratio of the thinner tube is bigger than that of the thicker tube,especially in the zone near weldline. Stress ratio difference between the thicker tube and the thinner tube is the main reason of weld-line movement and non-uniform thinning ratio distribution.

A general method for modified function projective synchronization

This paper investigates the modified function projective synchronization,which means that the drive system and the response system are synchronized up to a desired scale matrix of function. By the active control scheme,a general method for modified function projective synchronization is proposed. Numerical simulations on chaotic Rssler system and hyper-chaotic Chen system are presented to verify the effectiveness of the proposed scheme.