新型阶梯式浅吃水单立柱浮式风机平台水动力分析

常规的单立柱式(Spar)风力发电机平台,在水深较浅区域工作时,结构本身受吃水限制,工作效果较差。常规Spar重心较低,具有良好的稳定性,但是由于它往往具有超过100 m的吃水,因此使其不能应用于中近海域(水深小于100 m)。可设计研究一种适用于中国东海不超过100 m水深的中近海域新型浮式风机平台以解决此问题。针对NREL 5MW风机能应用于100 m水深的情况,对50 m吃水的新型Spar(SJTU-S4)及其系泊系统进行了概念设计研究。利用商业软件建立水动力模型,进行数值仿真,同时设计缩比模型试验,在上海交通大学海洋工程国家重点实验室(SKLOE)进行水动力性能测试。结果表明,本文研究的新阶梯式浅吃水单立柱浮式风机平台在100 m水深、多种海洋波浪环境下,通过试验和仿真验证,能够具有良好的运动响应,为风机提供较好的工作条件。     

Evaluating Schmid criterion for predicting preferential locations of persistent slip markings obtained after very high cycle fatigue for polycrystalline pure copper

Very high cycle fatigue carried out on pure copper polycrystals promotes early slip markings, labelled as slip markings of types II and III, localized close to grain or twin boundaries. In this work, we focus on whether Schmid criterion can predict the preferential sites of slip markings of types II and III and identify the active slip systems. Combining observations of slip markings and polycrystalline modeling, it is shown that considering pure cubic elastic behavior, maximum resolved shear stress as a criterion for type II slip markings preferential sites is 70% reliable criterion. Concerning slip markings of type III, the reliability falls to 30%. The role of cross slip is highlighted and a scenario rationalizing the stress amplitude conditions and sites to observe early slip markings of type II or III for copper polycrystals is proposed.     

SAR of a birdcage coil with variable number of rungs at 300 MHz

The specific absorption rate produced in a rat’s brain phantom inside of quadrature birdcage coil as a function of the rung number was studied at 300 MHz. Electromagnetic field simulations and specific absorption rate and loss return responses were performed using a rat’s brain phantom weighing 100 mg. To assure optimal simulations and to evaluate coil performance, S-parameters were simulated and compared with experimentally data. Simulations showed that magnetic field uniformity improves and that electric field is increased with the number of rungs. Specific absorption rate and temperature values obtained from axial bi-dimensional maps increase as the number of rungs grows. These results corroborated very well with published data. A quadrature 16-rung birdcage coil was developed for comparison and phantom images were acquired to show its feasibility. The presented approach yields information on specific absorption rate allowing to previously develop RF coils and their possible effects on the biological sample.     

Hydrodynamic Phonon Transport Perpendicular to Diffuse-Gray Boundaries

In this paper, we examine the application of an ideal phonon-hydrodynamic material as the heat transfer medium between two diffuse-gray boundaries with a finite temperature difference. We use the integral-equation approach to solve a modified phonon Boltzmann transport equation with the displaced Bose–Einstein distribution as the equilibrium distribution between two boundaries perpendicular to the heat transfer direction. When the distance between the boundaries is smaller than the phonon normal scattering mean free path, our solution converges to the ballistic limit as expected. In the other limit, we find that, although the local thermal conductivity in the bulk of the hydrodynamic material approaches infinity, the thermal boundary resistance at the interfaces becomes dominant. Our study provides insights into both the steady-state thermal characterization of phonon-hydrodynamic materials and the practical application of phonon-hydrodynamic materials for thermal management.     

Portable spectroscopic fast neutron probe and 3He detector dead-time measurements

This paper presents dead-time calculations for the Portable Spectroscopic Fast Neutron Probe (N-Probe) using a combination of the attenuation law, MCNP (Monte Carlo N-particle Code) simulations and the assumption of ideal paralyzing and non-paralyzing dead-time models. The N-Probe contains an NE-213 liquid scintillator detector and a spherical ³He detector. For the fast neutron probe, non-paralyzing dead-time values were higher than paralyzing dead-time values, as expected. Paralyzing dead-time was calculated to be 37.6 μs and non-paralyzing dead-time was calculated to be 43.7 μs for the N-Probe liquid scintillator detector. Dead-time value for Canberra ³He neutron detector (0.5NH1/1K) was also estimated using a combination of subcritical assembly measurements and MCNP simulations. The paralyzing dead-time was estimated to be 14.5 μs, and the non-paralyzing dead-time was estimated to be 16.4 μs for ³He gas filled detector. These results are consistent with the dead-time values reported for helium detectors.     

Metrics to identify meaningful downscaling skill in WRF simulations of intense rainfall events

Dynamical downscaling attempts to provide regional detail to climate change projections that subsequently can be used as input to climate change impact models. However, unlike forecasts by numerical weather prediction models, downscaled projections cannot be tested for skill because the future of interest is decades away. Nevertheless, models can be tested in terms of how well they simulate current weather or climate, thus giving an indication of skill in representing the process of interest. Here, six configurations using different combinations of three microphysics and two planetary boundary layer schemes are assessed on their skill to simulate desired characteristics in daily rainfall fields from three two week simulations in southeast Australia; ‘desired’ meaning desirable in relation to the intended application. Of different metrics and analysis assessed, a metric based on variography analysis, summarising characteristics about spatial variability and dissimilarity, is shown to provide the most informative guidance relative to the desirable characteristics.     

Uncertainty quantification of subcritical bifurcations

Analysing and quantifying parametric uncertainties numerically is a tedious task, even more so when the system exhibits subcritical bifurcations. Here a novel interpolation based approach is presented and applied to two simple models exhibiting subcritical Hopf bifurcation. It is seen that this integrated interpolation scheme is significantly faster than traditional Monte Carlo based simulations. The advantages of using this scheme and the reason for its success compared to other uncertainty quantification schemes like Polynomial Chaos Expansion (PCE) are highlighted. The paper also discusses advantages of using an equi-probable node distribution which is seen to improve the accuracy of the proposed scheme. The probabilities of failure (POF) are defined and plotted for various operating conditions. The possibilities of extending the above scheme to experiments are also discussed.     

MPPhys—A many-particle simulation package for computational physics education

In a first course to classical mechanics elementary physical processes like elastic two-body collisions, the mass–spring model, or the gravitational two-body problem are discussed in detail. The continuation to many-body systems, however, is deferred to graduate courses although the underlying equations of motion are essentially the same and although there is a strong motivation for high-school students in particular because of the use of particle systems in computer games. The missing link between the simple and the more complex problem is a basic introduction to solve the equations of motion numerically which could be illustrated, however, by means of the Euler method. The many-particle physics simulation package MPPhys offers a platform to experiment with simple particle simulations. The aim is to give a principle idea how to implement many-particle simulations and how simulation and visualization can be combined for interactive visual explorations.     

Maxsim2—Real-time interactive simulations for computer-assisted teaching of pharmacokinetics and pharmacodynamics

We developed a computer program for use in undergraduate and graduate courses in pharmacology, pharmacokinetics and pharmacodynamics. This program can also be used in environmental and toxicological studies and preclinical simulation, to facilitate communication between modeling pharmacokineticists and project leaders or other decision-makers in the pharmaceutical industry. The program simulates the drug delivery and transport by means of (I) a six-compartment physiological pharmacokinetic flow model, (II) a system of traditional compartment models, or (III) a target-mediated drug disposition system. The program also can be used to simulate instantaneous equilibria between concentration and pharmacodynamic response, or as temporal delays between concentration and response. The latter is done by means of turnover models (indirect response models). Drug absorption, distribution, and elimination are represented by differential equations, which are described by organ and tissue volumes or other volumes of distribution, blood flows, clearance terms, and tissue-to-blood partition coefficients. The user can control and adjust these parameters by means of a slider in real time. By interactively changing the parameter values and simultaneously displaying the resulting concentration–time and/or response–time profiles, users can understand the major mechanisms that govern the disposition or the pharmacological response of the drug in the organism in real time. Schedule dependence is typically seen in clinical practice with a non-linear concentration–response relationship, and is difficult to communicate except via simulations. Here, we sought to illustrate the potential advantages of this approach in teaching pharmacology, pharmacokinetics, and pharmacodynamics to undergraduate pharmacy-, veterinary-, and medical students or to project teams in drug discovery/development.     

Model of a polymer chain twisted inside a statistical segment. Poly(3‐hexylthiophene) in chloroform solutions

A set of hydrodynamic methods in extremely dilute solutions (determination of intrinsic viscosity [η ], translational diffusion D and flotation in a centrifugal field s ) was used in the studies of conformational properties, dimensions and equilibrium rigidity of individual molecules of a series of samples of poly(3‐hexylthiophene). Absolute molecular masses M _sD were determined. The Mark–Kuhn–Houwink equations for the range of M _sD from 2240 to 15 300 g mol^?1 are given. For the first time, an analysis of conformational properties and equilibrium flexibility of poly(3‐hexylthiophene) molecules was carried out using the model of a statistical segment containing a twisted polymer chain. © 2017 Society of Chemical Industry