Moment Characteristics Research Articles

A doubly stochastic rainfall model with exponentially decaying pulses

We develop a doubly stochastic point process model with exponentially decaying pulses to describe the statistical properties of the rainfall intensity process. Mathematical formulation of the point process model is described along with second-order moment characteristics of the rainfall depth and aggregated processes. The derived second-order properties of the accumulated rainfall at different aggregation levels are used in model assessment. A data analysis using 15 years of sub-hourly rainfall data from England is presented. Models with fixed and variable pulse lifetime are explored. The performance of the model is compared with that of a doubly stochastic rectangular pulse model. The proposed model fits most of the empirical rainfall properties well at sub-hourly, hourly and daily aggregation levels.

Stochastic meshfree method for elastic buckling analysis of columns

This paper proposes a probabilistic approach for the solution of elastic buckling of columns, involving uncertainties, using stochastic element free Galerkin method. In the present work, modulus of elasticity is modeled as a homogeneous random field. Karhunen-Loeve expansion and shape function method are used to represent random field and their effectiveness is compared in modeling the same in a computationally viable manner. Both Gaussian and non-Gaussian field are considered for the present study. The stochastic eigenvalue problem is solved for first and second moment characteristics of buckling load, using perturbation analysis. Numerical examples of columns with different boundary conditions are solved. Monte Carlo simulation is used as a validation tool. The obtained results are found in good agreement with those obtained by Monte Carlo simulation.

Effect of nose thickness distribution on the stall characteristics of low aspect ratio flying wing configuration at transonic flow

The wing wing-body thickness of the highly swept flying wing configuration has great influence on the shock-leading edge vortex interaction at transonic speed, which would make significant effect on the stall characteristics. The effects of the nose thickness on the stall characteristics and heading characteristic of the low aspect ratio flying wing configuration are analyzed in simulated method and the flow mechanism is also studied. The results show that to decrease the nose thickness would make the position of the first shock wave and the breakdown position move back and the shock-leading edge vortex interaction will be weakened. To make the nose move back 10% c , the first shock wave in the leeward side will move back and it can delay the vortex breakdown by an angle 4°, which makes the stall angle and available lift coefficient increase. It would significantly improve the stall characteristics and the pitching moment characteristics. To decrease the thickness in nose also can make the heading static instability margin which would improve the heading performance. This study is useful reference for the layout design and flow mechanism of the low aspect flying wing configuration.

Design of a prismatic pressure vessel: An engineering solution for non-stiffened-type vessels

This paper proposes design principles of a new concept prismatic pressure vessel that is primarily constructed of plane surfaces. These principles were compared with those of conventional pressure vessel which is primarily constructed of revolutionary surfaces. Considering structural characteristics of prismatic pressure vessel, membrane force and bending moment were calculated individually. Formulas including maximum bending moment and membrane force effects were illustrated by applying Levy's method and superposition method. For total stress at the plate of the pressure vessel, membrane force effects obtained from the shear loads of adjacent plates were included to enable to get more accurate solutions. The proposed simplified formulas for prismatic pressure vessel were suggested so that they can be applied for all dimensions and thicknesses. Case studies were conducted to verify the formulas by comparing with FEM results. By providing an overview of the stress relations of a non-stiffened type prismatic pressure vessel, the design principle of a prismatic pressure vessel shows distinctive concept to the conventional cylindrical pressure vessel. The membrane force effect studied in this research will be useful in the design of larger pressure vessels that require stiffeners.

Influence of leading edge tubercles on aerodynamic characteristics of a high aspect-ratio UAV

An experimental investigation was carried out to study the aerodynamic performance of a typical UAV whose wings were modified to incorporate tubercles on the leading edge. The aerodynamic characteristics of three configurations: a baseline (without leading edge tubercles), one with tubercles of constant wavelength and amplitude along the span (Case I) and the third with tubercles of varying amplitude and wavelength along the span (Case II) were evaluated using force measurements and surface flow visualization at Reynolds numbers (Rec¯) of 0.18 million and 0.27 million. At Rec¯=0.18 million, the wings with tubercles exhibited increased lift, stall angle and reduced drag as compared to the baseline over the range of incidences studied. Further, wing with tubercles significantly improved the aerodynamic efficiency (CL/CD) (up to 25%). At Rec¯=0.27 million, both the baseline and the modified wings exhibited identical lift characteristics, but the former had a higher drag. At both Reynolds numbers, the modified wings did not exhibit the hysteresis present in the baseline case. Additionally, the modified wings exhibited stable pitching moment characteristics even in the post stall regime. The Case II wing outperformed both the baseline and Case I wings. The results show that tubercles on the leading edge have beneficial effects especially when UAVs encounter sudden vertical gusts during operation.

Efficient Criterion To Evaluate Linear Response Theory in Optical Transitions.

The role of the Gaussian statistics on the solvation dynamics upon the photon excitation of the chromophore is deeply explored. The linear response theory for the fluorescence Stokes shift is investigated. An analytical formulism is presented to recast Stokes shift into the contributions of the equilibrium time correlation functions of the solute-solvent interactions on the excited-state surface, and the latter is further reformed and depicted by the time relaxation of the moment. As the first application of the formulism in the molecular dynamics simulations, it is verified that the efficiency of the linear response theory relies on the Gaussian characteristics of the dominant moments in terms of the Stokes shift, which is identified by the same relaxation dynamics between those moments and the linear order one. The comparisons between the above observations on the linearity of Stokes shift and the explanations in the literature are discussed. The key finding is the development of explicit criterion to measure the appropriateness of applying linear response theory.

Superconducting and Magnetic Properties of Sn-Doped EuBa2Cu3O7-δ Compound

Influence of Sn-substitution on structural, superconducting and magnetic properties of EuBa2Cu3O7-delta (Eu-123) compound was studied by X-ray diffraction and SQUID magnetic measurements. Transition process from normal to superconducting state and temperature dependences of zero field cooling and field cooling characteristics of magnetic moment and magnetization curves were measured and analysed. Samples of the nominal composition of EuBa2Cu3-xSnxO7-delta with x ranging from 0.0 to 1.5 were prepared by the solid state reaction technique. The increasing Sn-content decreases the volume of the main superconducting phase (Eu-123) and for higher Sn-contents, semiconducting tetragonal Eu3Ba3Cu6O14 (Eu-336) and Ba-Sn-O phases are the dominant ones.

Non-Destructive Detection of Wire Rope Discontinuities from Residual Magnetic Field Images Using the Hilbert-Huang Transform and Compressed Sensing.

Electromagnetic methods are commonly employed to detect wire rope discontinuities. However, determining the residual strength of wire rope based on the quantitative recognition of discontinuities remains problematic. We have designed a prototype device based on the residual magnetic field (RMF) of ferromagnetic materials, which overcomes the disadvantages associated with in-service inspections, such as large volume, inconvenient operation, low precision, and poor portability by providing a relatively small and lightweight device with improved detection precision. A novel filtering system consisting of the Hilbert-Huang transform and compressed sensing wavelet filtering is presented. Digital image processing was applied to achieve the localization and segmentation of defect RMF images. The statistical texture and invariant moment characteristics of the defect images were extracted as the input of a radial basis function neural network. Experimental results show that the RMF device can detect defects in various types of wire rope and prolong the service life of test equipment by reducing the friction between the detection device and the wire rope by accommodating a high lift-off distance.

Orbitalwise Coordination Number for Predicting Adsorption Properties of Metal Nanocatalysts.

We present the orbitalwise coordination number CN^{α} (α=s or d) as a reactivity descriptor for metal nanocatalysts. With the noble metal Au (5d^{10}6s^{1}) as a specific case, the CN^{s} computed using the two-center s-electron hopping integrals to neighboring atoms provides an accurate and robust description of the trends in CO and O adsorption energies on extended surfaces terminated with different facets and nanoparticles of varying size and shape, outperforming existing bond-counting methods. Importantly, the CN^{s} has a solid physiochemical basis via a direct connection to the moment characteristics of the projected density of states onto the s orbital of a Au adsorption site. Furthermore, the CN^{s} shows promise as a viable descriptor for predicting adsorption properties of Au alloy nanoparticles with size-dependent lattice strains and coinage metal ligands.

Wind tunnel and computational stability derivatives for a propeller-driven airplane

A comparison of wind tunnel test data with those obtained from vortex lattice-based AVL program was made for a power-off and stick-fixed model of a propeller-driven cargo airplane. For the airplane model, longitudinal and lateral-directional aerodynamics were investigated in stability-axis system. Also, experimental and computational static stability derivatives were compared. Their results agree reasonably well within the linear portion of force and moment characteristics. The comparative study should provide a benchmark for using the fast turn out computations to further improve the design of airplane.

Методика определения расчетного срока службы безбалластного пути

The problem of the scope of ballastless track superstructure (BTS) and its service life currently is urgent. Due to the high traffic density at the Test Loop of JSC VNIIZhT for a short period of time it is possible to get an idea of BTS service life with freight transport at a speed of 80 km/h and axle load of 23.5 tonnes per axle. For information on BTS service life in real conditions of high-speed up to 400 km/h and axle load to 18 tonnes it would takes several decades.To resolve this contradiction it is proposed to apply a new methodology for forecasting the estimated service life of BTS at actual high-speed traffic by the results of tests on Test Loop with using mathematical modeling.In the proposed model track vibrations are considered as vibrations of construction comprising of three endlessly long beams, the bottom of which is based on a modified Winkler base and the upper and middle rely on the elastic layer mainly having a base characteristics as Winkler base. For specific design of ballastless track it would be the rail, the concrete support plate (track concrete) and hydraulically bound layer (lean concrete) correspondingly.The calculation results are presented in the form of amplitude-frequency characteristics of the bending moments in the second layer of ballastless track structure. Given the fact that the amplitude-frequency characteristic is not dependent on the axial load, the calculations are made for the particular case when the values of the speed of 80 km/h and 300 km/h with the actual characteristics of the layers of ballastless track that is operated on the Test Loop of JSC VNIIZhT.The proposed algorithm and methodology make it possible to transfer the results of observations of the processes of degradation of tested ballastless track design, obtained at the Test Loop (st. Scherbinka), on sections of network, where installation of track of this design for mixed transport is assumed. In the future, this technique allows taking into account changes in the area of operational factors, including the effect of increasing the axial load or speed of trains on the durability of track design.

Solution Space of Bending of Tape Spring

Tape spring can be a lightweight structural member and is easy to roll-up into small volume, so that it is expected as member of deployable space structure. There have been proposed various kinds of members made of tape springs such as bi-convex booms consisting of two tape springs. The relation between the bending moment and the curvature of the tape is one of the research topics that attracts many researchers. They analyzed the relation numerically and/or experimentally, and some of them are applied to the design of deployable structures. In this paper, the bending moment of the tape spring is obtained as a function of the curvature and the change sate of the curvature, and the solution surface of the bending moment is shown for understanding of the characteristics of the bending moment of tape spring.

Prediction of influence of operating conditions and tyre design parameters on tyre cornering characteristics

Finite element (FE) tyre models are widely used for predicting tyre characteristics and dynamic properties used for vehicle dynamics simulation for CAE durability, ride comfort and handling assessment. Particularly, tyre FE simulation can be used to predict variation in tyre characteristics which would be too tedious to measure using laboratory tests, such as those due to changes in the tyre reinforcement material or structural layup. The cornering force characteristics of a tyre is one of the most influential factors in full vehicle dynamics simulation, having a significant effect on the directional control and handling stability of the vehicle. A validated FE tyre model developed using ABAQUS was used in parametric studies to determine factors affecting cornering force and aligning moment characteristics using design of experiments (DOE) method. Prediction of the cornering properties of the rolling tyre demonstrated the sensitivity of tyre cornering properties to tyre design parameters and operating conditions.

Prediction of influence of operating conditions and tyre design parameters on tyre cornering characteristics

Finite element (FE) tyre models are widely used for predicting tyre characteristics and dynamic properties used for vehicle dynamics simulation for CAE durability, ride comfort and handling assessment. Particularly, tyre FE simulation can be used to predict variation in tyre characteristics which would be too tedious to measure using laboratory tests, such as those due to changes in the tyre reinforcement material or structural layup. The cornering force characteristics of a tyre is one of the most influential factors in full vehicle dynamics simulation, having a significant effect on the directional control and handling stability of the vehicle. A validated FE tyre model developed using ABAQUS was used in parametric studies to determine factors affecting cornering force and aligning moment characteristics using design of experiments (DOE) method. Prediction of the cornering properties of the rolling tyre demonstrated the sensitivity of tyre cornering properties to tyre design parameters and operating conditions.

Object recognition with discrete orthogonal Hahn moments

In this research, we have analysed the image feature descriptive properties of discrete orthogonal Hahn moments, and proposed a new object recognition scheme with three modes of Hahn moment descriptors, global, local, and hybrid, respectively. For each mode, we have employed the four highest variances values from ten lowest order of Hahn moments to compose a four-dimensional feature vector. To clarify our new scheme of using discrete orthogonal Hahn moment characteristics, we utilised a set of 6,763 Chinese characters defined in China's national standard GB2312, with the font of song, as the testing object set. Each of the three Hahn moment modes has performed very well, while the experimental results of utilising the three Hahn moment modes are independent from each other.

Object recognition with discrete orthogonal Hahn moments

In this research, we have analysed the image feature descriptive properties of discrete orthogonal Hahn moments, and proposed a new object recognition scheme with three modes of Hahn moment descriptors, global, local, and hybrid, respectively. For each mode, we have employed the four highest variances values from ten lowest order of Hahn moments to compose a four-dimensional feature vector. To clarify our new scheme of using discrete orthogonal Hahn moment characteristics, we utilised a set of 6,763 Chinese characters defined in China's national standard GB2312, with the font of song, as the testing object set. Each of the three Hahn moment modes has performed very well, while the experimental results of utilising the three Hahn moment modes are independent from each other.

Влияние размера TCP-окна на распределение интервалов между пакетами трафика в программно-конфигурируемых сетях SDN

This work considers effect of TCP-window size on the numerical characteristics of time slots between packets. Here we researched first three initial time slot moments due to developed mathematical model utilizes them. Researches were performed on virtual experimental setup installed over physical servers by OpenNebula platform. We considered two cases including software-defined network supporting OpenFlow open protocol and conventional network without it. The first one is performed with POX controller and physical switch. Here we utilize software products tcpdump for traffic capture and Iperf for traffic generation. This work presents script providing traffic generation initiation process automation. Obtained results were imported to MS Excel. Then moment characteristics are evaluated by well-known mathematical statistics formulas.

Panel reliability assessment for FPSOs

An assessment method is developed for the panel reliability of ship-shaped Floating, Production, Storage and Offloading units (FPSO). Not only axial compressive loads but also internal and external lateral pressures are taken into account in the reliability assessment. Beam-column buckling and flexural-torsional buckling are regarded as two primary failure modes of stiffened panels. Variability of corrosion wastage and material properties are accounted for in modelling the panel’s time-dependent ultimate strength. Uncertainty of axial compressive loads induced by hull girder bending is evaluated based on probabilistic characteristics of still-water bending moment (SWBM) and vertical wave-induced bending moment (VWBM). A case study is performed to demonstrate this method and the effects of the lateral pressure, the return period of the extreme value of VWBM, the environmental severity factor, and the corrosion wastage on the panel reliability are investigated. Sensitivity measures for random variables are also carried out.

An investigation of pivotal moments in music therapy in adult mental health

A range of studies have reported that pivotal moments can occur in music therapy sessions. Four questions formed the basis for studying the pivotal moments in music therapy: 1.What are the main characteristics of pivotal moments? 2.Are there any specific aspects that help pivotal moments to emerge? 3. How do pivotal moments affect the patient’s process in therapy and life in general? 4. What is the importance of pivotal moments for the music therapist? The study was approached through completion of an extensive literature review reviewing descriptions and reports of pivotal moments from a range of fields including music therapy. Three semi-structured interviews were conducted with music therapists to provide a deeper understanding of their experience of pivotal moments, and to advance theorising about pivotal moments in music therapy. Interview data was analysed using Phenomenological Interpretative Analysis (IPA). A case study provides further support for the information gathered via the interviews and literature review. The case presents the emergence of a pivotal moment and describes its contribution within a short-term individual music therapy program with a man who has a diagnosis of schizophrenia. Pivotal moments are found to change the music therapy process and lead to a better understanding of the patient. The role of the therapist, the therapist’s qualities and basic features or techniques that support the emergence of pivotal moments, are also discussed.

Kinematics and kinetics during stair ascent in individuals with Gluteal Tendinopathy

BackgroundIndividuals with gluteal tendinopathy commonly report lateral hip pain and disability during stair ascent. This study aimed to compare kinematics and kinetics between individuals with and without gluteal tendinopathy during a step up task. Methods35 individuals with unilateral gluteal tendinopathy and 35 pain-free controls underwent three-dimensional motion analysis of stance phase during stair ascent. An analysis of covariance was performed to compare hip, pelvis and trunk kinematic and kinetic variables between groups. A K-means cluster analysis was performed to identify subgroups from the entire group (n=70) based on the characteristics of the external hip adduction moment. Finally, a Newcombe-Wilson test was performed to evaluate the relationship between group and cluster codes and a 3×2 ANOVA to investigate the differences in kinematics between groups and cluster codes. FindingsIndividuals with gluteal tendinopathy exhibited a greater hip adduction moment impulse during stair ascent (ES=0.83), greater internal rotation impulse during the first 50% stance phase (ES=0.63) and greater contralateral trunk lean throughout stance than controls (ranging from ES=0.67–0.93). Three subgroups based on hip adduction moment characteristics were identified. Individuals with GT were 4.5 times more likely to have a hip adduction moment characteristic of a large impulse and greater lateral pelvic translation at heel strike than the subgroup most likely to contain controls. InterpretationIndividuals with GT exhibit greater hip adduction moment impulse and alterations in trunk and pelvic kinematics during stair ascent. Findings provide a basis to consider frontal plane trunk and pelvic control in the management of gluteal tendinopathy.