Single-point Model Research Articles

Dynamics Modeling and Analysis of Local Fault of Rolling Element Bearing

This paper presents a nonlinear vibration model of rolling element bearings with 5 degrees of freedom based on Hertz contact theory and relevant bearing knowledge of kinematics and dynamics. The slipping of ball, oil film stiffness, and the nonlinear time-varying stiffness of the bearing are taken into consideration in the model proposed here. The single-point local fault model of rolling element bearing is introduced into the nonlinear model with 5 degrees of freedom according to the loss of the contact deformation of ball when it rolls into and out of the local fault location. The functions of spall depth corresponding to defects of different shapes are discussed separately in this paper. Then the ode solver in Matlab is adopted to perform a numerical solution on the nonlinear vibration model to simulate the vibration response of the rolling elements bearings with local fault. The simulation signals analysis results show a similar behavior and pattern to that observed in the processed experimental signals of rolling element bearings in both time domain and frequency domain which validated the nonlinear vibration model proposed here to generate typical rolling element bearings local fault signals for possible and effective fault diagnostic algorithms research.

Comparative DSC kinetics of the reaction of DGEBA with aromatic diamines IV. Iso-conversional kinetic analysis

Applying the differential scanning calorimetry, DSC, we discuss in this study the so called iso-conversional kinetics, ICK, of different epoxy–amine reactions. Single point model free methods, such as the method of Kissinger for the peak maximum temperature evolution in programmed temperature DSC regime, are applied in comparison. The dependencies of the activation energy versus degree of epoxy conversion are analyzed for the systems studied from the point of view of the probable reaction models. Important features and limitations of the ICK approach are also commented.

Real-Time Motion Generation and Control Systems for High Wheel-Legged Robot Mobility

A wheel-legged mobile robot (WLMR) has both leg and wheel structures. WLMRs have adaptability advantages because they can change locomotion methods depending on the terrain. However, the location of a WLMR's center of gravity (CoG) is very high; thus, almost all existing WLMRs move statically. In this paper, whole body motion generation and various control systems are studied to facilitate higher WLMR mobility. To this end, a zero moment point (ZMP) is introduced as a stability index. In addition, WLMRs are modeled as single point mass linear inverted pendulums. Subsequently, online CoG pattern generation methods are proposed; one is a preview control approach, and a second is an approach that realizes the desired ZMP pattern using a zero-phase low-pass filter. It is then possible to generate the desired CoG patterns more easily and faster than with a preview control approach. The CoG patterns based on the single point model are constructed via the resolved-momentum-control approach. Finally, the effectiveness of the whole body motion pattern generated by the proposed methods is validated by simulations and experiments.

A Flexible Docking Scheme Efficiently Captures the Energetics of Glycan-Cyanovirin Binding

Cyanovirin-N (CVN), a cyanobacterial lectin, exemplifies a class of antiviral agents that inhibit HIV by binding to the highly glycosylated envelope protein gp120. Here, we investigate the energetics of glycan recognition using a computationally inexpensive flexible docking approach, backbone perturbation docking (BP-Dock). We benchmarked our method using two mutants of CVN: P51G-m4-CVN, which binds dimannose with high affinity through domain B, and CVN(mutDB), in which binding to domain B has been abolished through mutation of five polar residues to small nonpolar side chains. We investigated the energetic contribution of these polar residues along with the additional position 53 by docking dimannose to single-point CVN mutant models. Analysis of the docking simulations indicated that the E41A/G and T57A mutations led to a significant decrease in binding energy scores due to rearrangements of the hydrogen-bond network that reverberated throughout the binding cavity. N42A decreased the binding score to a level comparable to that of CVN(mutDB) by affecting the integrity of the local protein structure. In contrast, N53S resulted in a high binding energy score, similar to P51G-m4-CVN. Experimental characterization of the five mutants by NMR spectroscopy confirmed the binding affinity pattern predicted by BP-Dock. Despite their mostly conserved fold and stability, E41A, E41G, and T57A displayed dissociation constants in the millimolar range. N53S showed a binding constant in the low micromolar range, similar to that observed for P51G-m4-CVN. No binding was observed for N42A. Our results show that BP-Dock is a useful tool for rapidly screening the relative binding affinity pattern of in silico-designed mutants compared with wild-type, supporting its use to design novel mutants with enhanced binding properties.

Stochastic Parameterization to Represent Variability and Extremes in Climate Modeling

Unresolved sub-grid processes, those which are too small or dissipate too quickly to be captured within a model's spatial resolution, are not adequately parameterized by conventional numerical climate models. Sub-grid heterogeneity is lost in parameterizations that quantify only the ‘bulk effect’ of sub-grid dynamics on the resolved scales. A unique solution, one unreliant on increased grid resolution, is the employment of stochastic parameterization of the sub-grid to reintroduce variability. We administer this approach in a coupled land-atmosphere model, one that combines the single-column Community Atmosphere Model (CAM-SC) and the single-point Community Land Model (CLM-SP), by incorporating a stochastic representation of sub-grid latent heat flux to force the distribution of precipitation. Sub-grid differences in surface latent heat flux arise from the mosaic of Plant Functional Types (PFT) that describe terrestrial land cover. With the introduction of a stochastic parameterization framework to affect the distribution of sub-grid PFT's, we alter the distribution of convective precipitation over regions with high PFT variability. The stochastically forced precipitation probability density functions (pdf) show lengthened tails, demonstrating the retrieval of rare events. Through model data analysis we show that the stochastic model increases both the frequency and intensity of rare events in comparison to conventional deterministic parameterization.

The Mw 7.1 Van, Eastern Turkey, earthquake 2011: two-point source modelling by iterative deconvolution and non-negative least squares

The source complexity of the Mw 7.1 (USGS) Van, Eastern Turkey, earthquake of 2011 October 23 is studied using full waveform inversions of seismic records at near-regional distances (120–220 km) and relatively low frequencies (0.05–0.15 Hz). The study relies on iterative deconvolution and on a new method in which pairs of point sources on the fault plane are systematically grid searched, and the moment-rate time functions of the two-point sources are simultaneously calculated by non-negative least-squares inversion. It is demonstrated on synthetic and real data that the wavefield in these ranges is sensitive enough to distinguish two main subevents of the Van earthquake, separated from each other by ∼10–15 km and ∼4 s. The double-event character of the Van earthquake is indicated even by a simplified single-point source model, optimally when the trial-point source is near the earthquake centroid. The simple indicators of source complexity developed in this paper are useful in practice in the first hours after an earthquake, when the source position is known only approximately and finite-fault models of slip evolution are not yet available.

Intercomponent energy transfer in incompressible homogeneous turbulence: multi-point physics and amenability to one-point closures

AbstractIntercomponent energy transfer (IET) is a direct consequence of the incompressibility-preserving action of pressure. This action of pressure is inherently non-local, and consequently its modelling must address multi-point physics. However, in second moment closures, pragmatism mandates a single-point closure model for the pressure–strain correlation, that is, the source of IET. In this study, we perform a rapid distortion analysis to demonstrate that for a given mean-flow gradient, IET is strongly dependent on fluctuation modes and critically influences the flow stability, asymptotic states and their bifurcations. The inference is that multi-point physics must be characterized and appropriately incorporated into pressure–strain correlation closures. To this end, we analyse and categorize various multi-point characteristics such as: (i) the fluctuation mode wavevector dynamics; (ii) the spectral space topology of dominant modes; and (iii) the range of IET behaviour and statistically most likely (SML) outcomes. Thence, this characterization is used to examine the validity and limitations of current one-point closures and to propose directions for improving the fidelity of future models.

The Relationship between Tectonic Subsidence and BSR of Upper Neogene in the Deep‐Water Area of the Northern Continental Slope, South China Sea

Abstract:BSR (Bottom Simulating Reflector) occurs widely in the strata since the late Miocene in the deep‐water area of the northern continental slope of South China Sea (SCS). It is an important seismic reference mark which identifies the gas hydrate and its distribution influenced by the tectonic movements. Single‐point basin modeling was conducted using 473 points in the study area. To discuss the relationships between the tectonic subsidence and BSR, the volume and rate of tectonic subsidence in each geological time have been simulated. The results show that there are three tectonic accelerate subsidence processes in the study area since the late Miocene, especially since 1.8Ma the tectonic subsidence accelerates more apparently. Since the Late Miocene to Pleistocene, the rate of tectonic subsidence in deep‐water underwent a transformation from weak to strong. The ratio of tectonic subsidence to the total subsidence was relatively high (65–70%). Through the superposition of the BSR developed areas and the contours of tectonic subsidence in this area, it was discovered that more than 80% of BSR tend to be distributed at the slope break or depression‐uplift structural transfer zone and the average tectonic subsidence rate ranges from 70 m/Ma to 125 m/Ma.

Estimating join points and modelling for multiple change point problem

In life time data analysis, it is often realistic to believe that early failures occur at one pace and afterwards at different rates. In this article, we propose a general modelling method for a continuous hazard function with multiple change points. We assume the multiple change point curve to be composed of phases that are complex functions of time. The complex functions can be represented by suitable known functions of time. We have tried four such functional combinations for different phases. We have illustrated our proposed methodology with an application to modelling lifetimes of printed circuit boards. To conclude, we have compared our models with previously developed single change point model and displayed that our models fit the data much better.

Multiattribute preference models with reference points

In the context of multiple attribute decision making, preference models making use of reference points in an ordinal way have recently been introduced in the literature. This text proposes an axiomatic analysis of such models, with a particular emphasis on the case in which there is only one reference point. Our analysis uses a general conjoint measurement model resting on the study of traces induced on attributes by the preference relation and using conditions guaranteeing that these traces are complete. Models using reference points are shown to be a particular case of this general model. The number of reference points is linked to the number of equivalence classes distinguished by the traces. When there is only one reference point, the induced traces are quite rough, distinguishing at most two distinct equivalence classes. We study the relation between the model using a single reference point and other preference models proposed in the literature, most notably models based on concordance and models based on a discrete Sugeno integral.

Use of FIB/SEM to assess the tribo-corrosion of WC/Co hardmetals in model single point abrasion experiments

This paper describes the results of experiments where single point model abrasion experiments were carried out under a range of conditions of applied load and different media. FIB/SEM revealed that in air, damage occurred by binder extrusion in conjunction with fragmentation and fracture of the tungsten carbide grains, with re-embedment of fragments of carbide in the binder phase to form surface layers of mechanically mixed material. In HCl the binder was preferentially removed leaving the WC grains unsupported leading to further fracture and breakdown of the surface of the hardmetal. FIB revealed subsurface cobalt dissolution. A cobalt–nickel binder material proved the most versatile in resisting surface degradation in both ambient air and in HCl.

A Multivariable Grey Model Based on Optimized Background Value and its Application to Subgrade Settlement Prediction

Subgrade settlement is a complex process system. Commonly used single-point prediction models can’t consider the correlation between the discrete deformation monitoring points, which doesn’t adequately reflect the overall deformation law of subgrade. A multivariable grey model (MGM(1,n)), which is an expansion of the single-point GM(1,1) model for multiple variables, is introduced to resolve the above problem. Aiming at the drawback of background value in the traditional MGM(1,n) model, the functions with non-homogeneous exponential law are used to fit the accumulated sequences for every variable, reconstruct the calculating formula of background value, and gets a new MGM(1,n) model based on optimized background value (OMGM(1,n)). A case study shows that the forecast result of the proposed model is more precise and effective than these of the single-point GM(1,1) model and the traditional MGM(1,n) model for predicting subgrade settlement.

FUNDAMENTAL ASPECTS OF EPISODIC ACCRETION CHEMISTRY EXPLORED WITH SINGLE-POINT MODELS

We explore a set of single-point chemical models to study the fundamental chemical aspects of episodic accretion in low-mass embedded protostars. Our goal is twofold: (1) to understand how the repeated heating and cooling of the envelope affects the abundances of CO and related species; and (2) to identify chemical tracers that can be used as a novel probe of the timescales and other physical aspects of episodic accretion. We develop a set of single-point models that serve as a general prescription for how the chemical composition of a protostellar envelope is altered by episodic accretion. The main effect of each accretion burst is to drive CO ice off the grains in part of the envelope. The duration of the subsequent quiescent stage (before the next burst hits) is similar to or shorter than the freeze-out timescale of CO, allowing the chemical effects of a burst to linger long after the burst has ended. We predict that the resulting excess of gas-phase CO can be observed with single-dish or interferometer facilities as evidence of an accretion burst in the past 10^3 - 10^4 yr.

Asymptotic Effect of Initial and Upstream Conditions on Turbulence

More than two decades ago the first strong experimental results appeared suggesting that turbulent flows might not be asymptotically independent of their initial (or upstream) conditions (Wygnanski et al., 1986, “On the Large-Scale Structures in Two-Dimensional Smalldeficit, Turbulent Wakes,” J. Fluid Mech., 168, pp. 31–71). And shortly thereafter the first theoretical explanations were offered as to why we came to believe something about turbulence that might not be true (George, 1989, “The Self-Preservation of Turbulent Flows and its Relation to Initial Conditions and Coherent Structures,” Advances in Turbulence, W. George and R. Arndt, eds., Hemisphere, New York, pp. 1–41). These were contrary to popular belief. It was recognized immediately that if turbulence was indeed asymptotically independent of its initial conditions, it meant that there could be no universal single point model for turbulence (George, 1989, “The Self-Preservation of Turbulent Flows and its Relation to Initial Conditions and Coherent Structures,” Advances in Turbulence, W. George and R. Arndt, eds., Hemisphere, New York, pp. 1–41; Taulbee, 1989, “Reynolds Stress Models Applied to Turbulent Jets,” Advances in Turbulence, W. George and R. Arndt, eds., Hemisphere, New York, pp. 29–73) certainly consistent with experience, but even so not easy to accept for the turbulence community. Even now the ideas of asymptotic independence still dominate most texts and teaching of turbulence. This paper reviews the substantial additional evidence - experimental, numerical and theoretical - for the asymptotic effect of initial and upstream conditions that has accumulated over the past 25 years. Also reviewed is evidence that the Kolmogorov theory for small scale turbulence is not as general as previously believed. Emphasis has been placed on the canonical turbulent flows (especially wakes, jets, and homogeneous decaying turbulence), which have been the traditional building blocks for our understanding. Some of the important outstanding issues are discussed; and implications for the future of turbulence modeling and research, especially LES and turbulence control, are also considered.

A Longitudinal Study of Nonsuicidal Self-Injury in Offspring at High Risk for Mood Disorder

To determine the demographic and clinical predictors of nonsuicidal self-injury and to examine the longitudinal relationship between nonsuicidal self-injury and suicide attempt. This was a longitudinal cohort study of the familial transmission of suicidal behavior. The sample consisted of probands with DSM-IV mood disorder (n = 212), 54.2% of whom were suicide attempters, and their offspring aged at least 10 years (n = 352), followed for a mean of 3.8 years. Personal, parental, and familial characteristics were assessed annually to identify the most parsimonious subset of these variables associated with nonsuicidal self-injury, the primary outcome. Data were collected between August 1998 and August 2007. Of 352 offspring, 7.4% (n = 26) engaged in nonsuicidal self-injury during follow-up. In the final model examining predictors at baseline, the most severe time point, and the time point prior to nonsuicidal self-injury, only predictors from the most proximal time point were significant, namely younger age (odds ratio [OR] = 0.75, P = .002), diagnosis of current major depression (OR = 5.09, P < .001), and suicidal ideation (OR = 1.46, P = .02). In 2 of the 3 single time point models, baseline nonsuicidal self-injury was the most significant predictor of nonsuicidal self-injury during follow-up. Suicide attempt was predicted by both baseline nonsuicidal self-injury and suicide attempt, but when both were included in the model, nonsuicidal self-injury was a significant predictor (OR = 7.50, P = .009), but suicide attempter was not (OR = 3.78, P = .08); offspring aggression (OR = 1.11, P = .01) predicted suicide attempt but not nonsuicidal self-injury. Parental histories of nonsuicidal self-injury, suicide attempt, and abuse were not predictive of nonsuicidal self-injury. Nonsuicidal self-injury may be an earlier manifestation of a shared diathesis with suicide attempt, consisting of depression and suicidal ideation, and that diathesis may lead to suicidal behavior in the face of greater offspring aggression and family pathology. The apparent bidirectional temporal relationship between nonsuicidal self-injury and suicide attempt may be explained by this shared diathesis.

The Isolation Effect Analysis of Base and Story Isolation System in Vertical Seismic Action

Through establishing single material point model of base isolation system and two material points model of story isolation system in vertical earthquake, the isolation effect of base and story isolation system in vertical earthquake are studied. Results show that two kinds of isolation systems cannot effectively keep apart the vertical seismic action, and the effect is amplified on the contrary, especially the position of isolation layers in story structures affect the amplification effect. Compared with the base and story isolation structures, while using the same isolation device, the former is better than the latter in isolating vertical seismic action.

An adaptive integrated algorithm for active front steering and direct yaw moment control based on direct Lyapunov method

In this article, an adaptive integrated control algorithm based on active front steering and direct yaw moment control using direct Lyapunov method is proposed. Variation of cornering stiffness is considered through adaptation laws in the algorithm to ensure robustness of the integrated controller. A simple two degrees of freedom (DOF) vehicle model is used to develop the control algorithm. To evaluate the control algorithm developed here, a nonlinear eight-DOF vehicle model along with a combined-slip tyre model and a single-point preview driver model are used. Control commands are executed through correction steering angle on front wheels and braking torque applied on one of the four wheels. Simulation of a double lane change manoeuvre using Matlab®/Simulink is used for evaluation of the control algorithm. Simulation results show that the integrated control algorithm can significantly enhance vehicle stability during emergency evasive manoeuvres on various road conditions ranging from dry asphalt to very slippery packed snow road surfaces.

Environment Canada's Experimental Numerical Weather Prediction Systems for the Vancouver 2010 Winter Olympic and Paralympic Games

The 2010 Winter Olympic and Paralympic Games took place in Vancouver, British Columbia, Canada, on 12–28 February and 12–21 March 2010, respectively. Weather forecasting presents specific challenges at the various Olympic venues, which are located in complex coastal terrain and are often characterized by tricky weather conditions, such as high winds, low visibility, and rapidly varying precipitation types and intensity. In addition to its current operational products, and in order to provide the best possible guidance and support to the Olympic Forecast Team, Environment Canada has developed several experimental numerical weather prediction systems for the games. These include 1) a regional ensemble prediction system (REPS), 2) high-resolution numerical modeling (down to 1-km horizontal grid spacing), and 3) surface modeling at the microscales (100-m grid spacing). The REPS is based on the limited-area version of the Global Environmental Multiscale model (GEM-LAM), with 20 members at 33-km horizontal grid spacing. The high-resolution models include 2.5- and 1-km grid-spacing configurations of the GEM-LAM, with improved cloud microphysics, geophysical fields, and radiation and cloud–radiation interactions. Finally, two innovative approaches are used to adapt and refine forecasts locally and to better predict surface characteristics, such as snow conditions and near-surface air temperatures. A microscale 2D surface system covers the Olympic venues with forcing from the operational regional and global models. Based on a similar strategy, a single-point model uses surface observations as forcing. The configurations of these experimental numerical weather prediction systems are described, together with some examples and verification results from the winters of 2008 and 2009 using the enhanced mesoscale observing network recently set up for the Olympics.

Structure, energetics and properties of some molecules with potent anti-HIV activity: a theoretical study

Density functional theory (DFT; B3LYP) and Hartree–Fock (HF; 3-21G, 6-31G(d) and 6-311G(d,p)) calculations with complete geometry optimisations are carried out in the ground state on five 6-aminoquinolone derivatives, which have been proved to be highly effective in inhibiting HIV replication, to study their structures, energetics and HOMO–LUMO correlation with physiological action. The gas-phase calculations and single-point polarisable continuum model water-phase calculations show that the molecules are highly effective in inhibiting HIV replication, which is in excellent agreement with the experiment. Structural features, energies, charge densities and HOMO–LUMO correlation have been found to substantiate the experimental findings. Compound 4 (pyrazine) shows some special features in DFT calculations which are not found in HF calculations. In the present series, HF results are more reliable as expected.

Influence of tyre transience on anti-lock braking

Transient tyre characteristics can have significant influence in vehicle handling, particularly in anti-lock braking system (ABS), which involves wheel speed oscillations as a result of rapid changes in wheel brake pressure. Hitherto, ABS studies have been conducted mostly with straight-line motion. Relatively simple vehicle models have been used which cannot capture the interactions between non-linear handling dynamics and tyre behaviour. This article takes such interactions into account, using a non-linear 14-degrees-of-freedom vehicle model in combination with three different single-point contact tyre models with transient characteristics. They include a stretched-string-based model, a modified stretched-string model, and a contact mass model. The particularly demanding situation of combined cornering/ABS braking is investigated. It is shown that although all tyre models are of similar bandwidth (maximum frequency ≈ 15 Hz), the simple string tyre model fails to cope with the non-linearities involved in combined braking/cornering and predicts greater braking distances than the two more enhanced tyre models.