Stability analysis method considering non-parallelism:EPSE method and its application

The e-N method is widely used in transition prediction. The amplitude growth rate used in the e-N method is usually provided by the linear stability theory （LST） based on the local parallel hypothesis. Considering the non-parallelism effect, the parabolized stability equation （PSE） method lacks local characteristic of stability analysis. In this paper, a local stability analysis method considering non-parallelism is proposed, termed as EPSE since it may be considered as an expansion of the PSE method. The EPSE considers variation of the shape function in the streamwise direction. Its local characteristic is convenient for stability analysis. This paper uses the EPSE in a strong non-parallel flow and mode exchange problem. The results agree well with the PSE and the direct numerical simulation （DNS）. In addition, it is found that the growth rate is related to the normalized method in the non-parallel flow. Different results can be obtained using different normalized methods. Therefore, the normalized method must be consistent.

Optimization of Urban Ecological Network Based on MSPA-MCR Model: A Case Study of Jingzhou City

As a key carrier supporting urban ecological health and living environment quality,urban ecological network is a key focus of current urban green space research.Jingzhou City of Hubei Province is taken as the research object.Relying on GIS technology platform,MSPA method is used to analyze the landscape pattern of Jingzhou City.On this basis,the landscape connectivity evaluation method is used to accurately identify and extract the source areas with important ecological value in Jingzhou City.Then,the normalization method and weighting method are combined to create a resistance factor evaluation system to construct the resistance surface.Based on the MCR model,the ecological network of Jingzhou City is successfully constructed,and targeted spatial optimization strategies and development suggestions are proposed.

Membrane finite element method for simulating fluid flow in porous medium

A new membrane finite element method for modeling fluid flow in a porous medium is presented in order to quickly and accurately simulate the geo-membrane fabric used in civil engineering. It is based on discontinuous finite element theory, and can be easily coupled with the normal Galerkin finite element method. Based on the saturated seepage equation, the element coefficient matrix of the membrane element method is derived, and a geometric transform relation for the membrane element between a global coordinate system and a local coordinate system is obtained. A method for the determination of the fluid flux conductivity of the membrane element is presented. This method provides a basis for determining discontinuous parameters in discontinuous finite element theory. An anti-seepage problem regarding the foundation of a building is analyzed by coupling the membrane finite element method with the normal Galerkin finite element method. The analysis results demonstrate the utility and superiority of the membrane finite element method in fluid flow analysis of a porous medium.

Secrecy sum-rate analysis of massive MIMO systems under dual-threat attacks using normalization methods

Massive Multiple Input Multiple Output(MIMO)has been considered as an emerging technology to enhance the spectral and energy efficiency for the upcoming wireless communication systems.This paper derives a closedform approximation for the Ergodic Achievable Secrecy Sum-Rate(EASSR)by considering the joint impact of eavesdroppers and jammers.Two widely used linear precoding techniques,Zero-Forcing(ZF)and Maximum Ratio Transmission(MRT),were used in conjunction with matrix and vector normalization to analyze the secrecy performance.Closed-form expressions are used to explain how the secrecy performance is affected when using the ZF and MRT precoding in the eavesdropping and jamming attack models.We also analyze and compare the performances of different combinations of normalization method and precoding technique in various scenarios.From the analytical expressions and simulation results,we observe that the vector and matrix normalization perform better for the ZF precoding than for the MRT precoding in high Signal-to-Noise Ratio(SNR)scenarios.However,in low SNR,the MRT with matrix normalization outperforms the ZF with vector normalization regardless of the number of users in the system.Further,we observe that the MRT fails to serve more than two users in high SNR scenario.Numerical results obtained from Monte Carlo simulation are used to corroborate the accuracy of the asymptotic secrecy analysis.

Solving Load Flow Problems of Power System by Explicit Pseudo-Transient Continuation (E-ψtc) Method

This paper is a further study of two papers [1] and [2], which were related to Ill-Conditioned Load Flow Problems and were published by IEEE Trans. PAS. The authors of this paper have some different opinions, for example, the 11-bus system is not an ill-conditioned system. In addition, a new approach to solve Load Flow Problems, E-ψtc, is introduced. It is an explicit method;solving linear equations is not needed. It can handle very tough and very large systems. The advantage of this method has been fully proved by two examples. The authors give this new method a detailed description of how to use it to solve Load Flow Problems and successfully apply it to the 43-bus and the 11-bus systems. The authors also propose a strategy to test the reliability, and by solving gradient equations, this new method can answer if the solution exists or not.

EQUIVALENT NORMAL CURVATURE APPROACH MILLING MODEL OF MACHINING FREEFORM SURFACES

A new milling methodology with the equivalent normal curvature milling model machining freeform surfaces is proposed based on the normal curvature theorems on differential geometry. Moreover, a specialized whirlwind milling tool and a 5-axis CNC horizontal milling machine are introduced. This new milling model can efficiently enlarge the material removal volume at the tip of the whirlwind milling tool and improve the producing capacity. The machining strategy of this model is to regulate the orientation of the whirlwind milling tool relatively to the principal directions of the workpiece surface at the point of contact, so as to create a full match with collision avoidance between the workpiece surface and the symmetric rotational surface of the milling tool. The practical results show that this new milling model is an effective method in machining complex three- dimensional surfaces. This model has a good improvement on finishing machining time and scallop height in machining the freeform surfaces over other milling processes. Some actual examples for manufacturing the freeform surfaces with this new model are given.

A simple and effective model for Jones matrix to evaluate the transmission performance of Savart polariscope

Starting from the wave normal tracing treatment in the Savart polariscope that relates the Jones matrix to its transmission performance, this paper establishes a simple and effective model for the Jones matrix at an arbitrary incidence in the spatial domain. Analytical expressions of all the matrix components are determined with the consideration of all the main impact factors. This model needs only a few parameters hence it is convenient to be employed to evaluate the propagation performance of any birefringent optical system. The simulated results obtained with it demonstrate that this model gives a precise representation of the characteristic of light propagation in the Savart polariscope. This would provide useful suggestions for the design, calibration, and performance improvement of any other birefringent polarisation element and optical system.

Multiobjective maintenance optimization of the continuously monitored deterioration system

With the development of the monitoring technology,it is more and more common that the system is continuously monitored.Therefore,the research on the maintenance optimization of the continuously monitored deterioration system is important.The deterioration process of the discussed system is described by a Gamma process.The predictive maintenance is considered to be imperfect and formulated.The expected interval of two continuous preventive maintenances is derived.Then,the maintenance optimization model of the continuously monitored deterioration system is presented.In the model,the minimization of the expected operational cost per unit time and the maximization of the system availability are the optimization objectives.The improved ideal point method with the normalized objective functions is employed to solve the proposed model.The validity and sensitivity of the proposed multiobjective maintenance optimization model are analyzed by a numerical example.

Effect of Initial Stress on a Thermoelastic Functionally Graded Material with Energy Dissipation

In this paper we introduce the effect of initial stress on a magneto-thermoe- lastic functionally graded material (FGM) with Green Naghdi theory with energy dissipation. A system of PDE was obtained. The normal mode analysis method is used to convert these equations into ODE and get the analytical solution to write expressions for displacements, temperatures, stresses. Some comparisons carried out to view the initial stress influence on the field variables. Numerical results are graphed to view the influence of initial stress. Some particular cases are deduced in this study.

Improved normalization method for ductile fracture toughness determination based on dimensionless load separation principle

This study successfully deals with the inhomogeneous dimension problem of load separation assumption, which is the theoretical basis of the normalization method. According to the dimensionless load separation principle, the normalization method has been improved by intro- ducing a forcible blunting correction. With the improved normalization method, the J-resistance curves of five different metallic materials of CT and SEB specimens are estimated. The forcible blunting correction of initial crack size plays an important role in the J-resistance curve estima- tion, which is closely related to the strain hardening level of material. The higher level of strain hardening leads to a greater difference in JQ determined by different slopes of the blunting line. If the blunting line coefficient recommended by ASTM E1820-11 is used in the improved nor- realization method, it will lead to greater fracture resistance than that processed by the blunting line coefficient recommended by ISO 12135-2002. Therefore, the influence of the blunting line on the determination of JQ must be taken into full account in the fracture toughness assessment of metallic materials.

Conversion from whispered speech to normal speech using the extended bilinear transformation method

A method of conversion from whispered speech to normal speech using the extended bilinear transformation was proposed. On account of the different deviation degrees of the whisper＇s formants in different frequency bands, the spectrum of the whispered speech will be processed in the separate partitions of this paper. On the basis of this spectrum, we will establish a conversion function able to usefully convert whispered speech to normal speech. Because of the whisper＇s non-linear offset in relation to normal speech, this paper introduces an expansion factor in the bilinear transform function making it correspond more closely to the actual conversion demands of whispered speech to normal speech. The introduction of this factor takes the non-linear move of the spectrum and the compression of the formant bandwidth into consideration, thus effectively reducing the spectrum distortion distance in the conversion. The experiment results show that the conversion presented in this paper effectively improves both the sound quality and the intelligibility of whispered speech.

The impacts of evaluation indices and normalization methods on E-TOPSIS optimization of return vent height for an impinging jet ventilation system

Stratified air distribution(STRAD)systems have been intensively investigated in recent decades for their energy-saving potential and good indoor air quality performance.However,the evaluation indices used to optimize STRAD systems and the normalization methods for weight calculation vary from one research to another.This study aims to investigate the impacts of evaluation indices on the optimal return vent height of a room cooled by an impinging jet ventilation system(one type of STRAD system).The effects of several widely used normalization methods(i.e.,vector normalization,sum normalization,min-max normalization,and no normalization)on indices weights are investigated.The evaluation indices are cooling coil load(Q_(coil)),energy-saving potential(ΔQ_(coil)),mean age of air(MAA),CO_(2) mass fraction,temperature difference between the head and ankles(ΔT_(0.1-1.1)),predicted mean vote(PMV),predicted percentage of dissatisfied(PPD),and draft rate(DR).The multi-criteria optimization method is the entropy-based technique for order preference by similarity to ideal solution(E-TOPSIS).As a result,the min-max normalization method evens the weight of each index and results in unreasonable relative weights.Consequently,the raw matrix(i.e.,the normalization is omitted)is suggested for weight calculation.Among these indices,ΔT_(0.1-1.1) and PPD play critical roles.WithoutΔT_(0.1-1.1),the optimal return vent height changes from mid-level to near-floor,while without PPD,it changes to near-ceiling.Another important result is that the Q_(coil) plays the most trivial role,followed by MAA and DR.Therefore,the optimal return vent height is not determined by energy-saving performance but by performances of thermal comfort.

Normal Determinative Function Method for Judging Stability of Nonlinear Systems

This paper introduces a new method to solve Liapunov stability problems for time invariant nonlinear systems—the normal determinative function method. The topic is split into six parts: review of the construction of a V(x) function, the modified Liapunov theorem form while the derivative of V(x) is definite, polynomial features of the analytic system’s normal determinative function V(x), judgment of definitiveness for a polynomial, coefficient direct solution method and the stabilty judgment of critical nonlinear systems, and future research.

Extracting the interference components of normal modes in shallow water waveguide using singular value decomposition method

The normal mode interference characteristic in shallow water waveguide is a valu- able topic in the fields of underwater acoustic. A method for extracting the interference components of normal modes from broadband acoustic propagation data recorded by a single hy- drophone without any prior information is present in this paper. First, a Hermitian matrix is formed by the power spectral density. Second, a singular value decomposition （SVD） is performed on the Hermitian matrix to obtain the orthonormal eigenvectors, which are proportional to the interference components of normal modes. The fundamental equations of the new extracting method are derived based on normal mode and waveguide invariant theory. And the validity of the present method is verified by the numerical simulation and experimental results. In addition, the extracted results of normal-mode interference components are intended to be used for passive ranging of broadband sources.

Anti-rutting performance evaluation of modified asphalt binders: A review

Asphalt pavement inevitably suffers rutting distress induced by repeated loads under high temperatures, which can be effectively alleviated by the modification of asphalt binders.This paper summarized the asphalt modifiers for enhancing the performance of asphalt pavement at high temperatures in terms of the modifier type, additive amount and improving effect. Then, the anti-rutting performance evaluation methods of asphalt binder were introduced with details, including the ring and ball(R&B) test, the dynamic viscosity test, the zero/low shear viscosity(ZSV/LSV) test, the dynamic shear rheometer(DSR) test,the repeated creep and recovery(RCR) test, and the multiple stress creep and recovery(MSCR) test. Furthermore, the sensitivity of the evaluation method to asphalt modifier was analyzed using the normalization method. It was found that the indicators from the MSCR test could clearly reveal the influence of asphalt modifiers on high temperature performance of asphalt binder. But it still had some limitations affecting the accuracy of evaluation results, such as the number of creep-recovery cycles, the stress level and the recovery time. In addition, according to the rutting resistance improvement ratio(RRIR),the styrene-butadiene-styrene(SBS) modifier performed better in improving the rutting resistance of asphalt binder, compared with other modifiers when added within the usual dosage range.

The influence of Thomson effect and inclined loads in an electro-magneto-thermoelastic solid with voids under green-Naghdi theories

The present investigation deals with the 2-dimensional deformation in a homogeneous thermoelastic solid with voids subjected to inclined loads.The heat conduction equation is affected with the Thomson coefficient.The basic governing equations are modified by using Green-Naghdi theory of type-III.The normal mode analysis technique is used to obtain the components of stress,strain,temperature,induced magnetic field and change in volume fraction field.The variations of these quantities have been depicted graphically in the Green-Naghdi theories of type-II and III for an insulated boundary.From numerical calculations,the effect of Thomson parameter and angle of inclination on a homogeneous,isotropic,electro-magneto-thermoelastic material with voids is revealed and discussed.

The effect of gravity and inclined load in micropolar thermoelastic medium possessing cubic symmetry under G-N theory

The problem of the micropolar thermoelastic medium under(G-N)theory of both types II,III under the effect of the gravity was investigated.The normal mode analysis is used to obtain the solution of the physical quantities.Comparisons are made between the results predicted by the(G-N)theory of type II and type III in the presence and absence of gravity and for different values of the angle of inclination.©2018 Shanghai Jiaotong University.Published by Elsevier B.V.