Projection 2 Goes Turbulent - and Fully Implicit

We describe and demonstrate both our newest projection method (fully implicit) for the incompressible Navier-Stokes equations via the finite element method and our newest turbulence model - a somewhat sophisticated nonlinear (cubic) eddy viscosity model that does not employ wall functions or normal distances to walls - the combination providing a method and a model that is each applicable in arbitrary geometry. We demonstrate both via a flow simulation past an automobile-like body at a Reynolds number of 4.3 million.     

Nonlinear model-predictive control with hysteresis compensation of an electro-pneumatic clutch for truck applications

This contribution presents two real-time capable nonlinear model-predictive control (NMPC) approaches for an electro-pneumatic clutch for heavy trucks: a centralized control approach and a cascaded one. A clutch is necessary at start-up or during gear shifts to connect or disconnect the combustion engine and the gear box. This automated actuator disburdens the driver and provides the necessary actuation force according to the large torque typically transmitted through the drive train. The force characteristic of the clutch, however, is subject to hysteresis, which is described by a generalized Bouc–Wen model and used for a feedforward hysteresis compensation in the control algorithm. The proposed NMPC-algorithm involves (i) a minimization of the difference between the desired and predicted state vector at the end of the prediction horizon and (ii) flatness-based techniques to compute desired trajectories for the complete state vector as well as the control input. The optimal control is given by an additional, minimum-norm control input that minimizes the difference between the predicted state vector and the desired one at the end of the prediction horizon. Thereby, the computation effort of the NMPC approaches can be kept relatively small, and a real-time evaluation becomes possible. A reduced-order observer estimates an effective pressure in the clutch that also accounts for an uncertain disturbance force. Thereby, a disturbance compensation and a high tracking accuracy is achievable for the piston position as controlled variable. The efficiency of the two proposed control structures is emphasized by experimental results from a dedicated test rig.     

New series of AB2‐type hyperbranched polytriazoles derived from the same polymeric intermediate: Different endcapping spacers with adjustable bulk and convenient syntheses via click chemistry under copper(I) catalysis

In this article, according to the concept of “suitable isolation group,” six new AB₂‐type polytriazoles containing azo‐chromophore moieties, derived from the same hyperbranched polymer intermediate, were successfully prepared through click reaction under copper(I) catalysis by modifying the synthetic route, in which different isolation groups in different size were introduced to the periphery of the hyperbranched polymers as end‐capping moieties. With the different end‐capping groups, these hyperbranched polymers, P1 – P6 , exhibited different solubility and processability; also, their nonlinear optical properties were modified accordingly, realizing the adjustment of the properties of hyperbranched polymers through the structural design. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Chiral crystal of a C2v‐symmetric 1,3‐diazaaulene derivative showing efficient optical second harmonic generation

Achiral nonlinear optical (NLO) chromophores 1,3‐diazaazulene derivatives, 2‐(4′‐aminophenyl)‐6‐nitro‐1,3‐diazaazulene (APNA) and 2‐(4′‐N,N‐diphenylaminophenyl)‐6‐nitro‐1,3‐diazaazulene (DPAPNA), were synthesized with high yield. Despite the moderate static first hyperpolarizabilities (β₀) for both APNA [(136 ± 5) × 10^?30 esu] and DPAPNA [(263 ± 20) × 10^?30 esu], only APNA crystal shows a powder efficiency of second harmonic generation (SHG) of 23 times that of urea. It is shown that the APNA crystallization driven cooperatively by the strong H‐bonding network and the dipolar electrostatic interactions falls into the noncentrosymmetric P2₁2₁2₁ space group, and that the helical supramolecular assembly is solely responsible for the efficient SHG response. To the contrary, the DPAPNA crystal with centrosymmetric P‐1 space group is packed with antiparalleling dimmers, and is therefore completely SHG‐inactive. 1,3‐Diazaazulene derivatives are suggested to be potent building blocks for SHG‐active chiral crystals, which are advantageous in high thermal stability, excellent near‐infrared transparency and high degree of designing flexibility. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Infrared chemical imaging: Spatial resolution evaluation and super-resolution concept

Chemical imaging systems help to solve many challenges in various scientific fields. Able to deliver rapid spatial and chemical information, modern infrared spectrometers using Focal Plane Array detectors (FPA) are of great interest. Considering conventional infrared spectrometers with a single element detector, we can consider that the diffraction-limited spatial resolution is more or less equal to the wavelength of the light (i.e. 2.5-25 μm). Unfortunately, the spatial resolution of FPA spectroscopic setup is even lower due to the detector pixel size. This becomes a real constraint when micron-sized samples are analysed. New chemometrics methods are thus of great interest to overcome such resolution drawback, while keeping our far-field infrared imaging spectrometers. The aim of the present work is to evaluate the super-resolution concept in order to increase the spatial resolution of infrared imaging spectrometers using FPA detectors. The main idea of super-resolution is the fusion of several low-resolution images of the same sample to obtain a higher-resolution image. Applying the super-resolution concept on a relatively low number of FPA acquisitions, it was possible to observe a 30% decrease in spatial resolution.     

道路约束条件下的移动机器人跟踪

为提高移动机器人的位置估计精度和跟踪效果,提出一种基于道路约束条件下的移动机器人鲁棒约束H∞滤波(CHF)跟踪算法.首先,将机器人移动的道路网络作为跟踪的约束条件,并利用当前统计模型对机器人的运动进行建模.其次,将道路约束条件作为机器人跟踪的非线性状态约束,利用最小协方差估计推导了鲁棒CHF递推方程.通过拉格朗日乘子法对非线性约束优化估计问题进行求解,并利用约束信息对CHF算法的状态更新过程进行了改进.最后,通过对CHF算法和无约束的H∞滤波算法的跟踪性能进行了对比分析和验证.仿真结果表明,该算法可以实现机器人的跟踪,且跟踪精度优于HF算法.     

Internal waves in a two‐layer system using fully nonlinear internal‐wave equations

In order to understand the nonlinear effect in a two‐layer system, fully nonlinear strongly dispersive internal‐wave equations, based on a variational principle, were proposed in this study. A simple iteration method was used to solve the internal‐wave equations in order to solve the equations stably. The applicability of the proposed numerical computation scheme was confirmed to agree with linear dispersion relation theoretically obtained from variational principle. The proposed computational scheme was also shown to reproduce internal waves including higher‐order nonlinear effect from the analysis of internal solitary waves in a two‐layer system. Furthermore, for the second‐order numerical analysis, the balance of nonlinearity and dispersion was found to be similar to the balance assumed in the KdV theory and the Boussinesq‐type equations. Copyright © 2009 John Wiley & Sons, Ltd.     

The development of recent high-power ultrasonic transducers for Near-well ultrasonic processing technology

With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers for Near-well ultrasonic processing technology are summarized. Each field application of them are also given. The purpose of this paper is to provide reference for the further development of Near-well ultrasonic processing technology.With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers for Near-well ultrasonic processing technology are summarized. Each field application of them are also given. The purpose of this paper is to provide reference for the further development of Near-well ultrasonic processing technology     

Dynamic nuclear polarization studies of nitroxyl spin probes in agarose gel using Overhauser‐enhanced magnetic resonance imaging

Agarose is a tissue‐equivalent material and its imaging characteristics similar to those of real tissues. Hence, the dynamic nuclear polarization studies of 3‐carboxy‐2,2,5,5‐tetramethyl‐pyrrolidine‐1‐oxyl (carboxy‐PROXYL) in agarose gel were carried out. The dynamic nuclear polarization parameters such as spin lattice relaxation time, longitudinal relaxivity, leakage factor, saturation parameter and coupling parameter were estimated for 2 mM carboxy‐PROXYL in phosphate‐buffered saline solution and water/agarose mixture (99 : 1). From these results, the spin probe concentration was optimized as 2 mM, and the reduction in enhancement was observed for carboxy‐PROXYL in water/agarose mixture (99 : 1) compared with phosphate‐buffered saline solution. Phantom imaging was also performed with 2 mM concentration of carboxy‐PROXYL in various concentrations of agarose gel at various radio frequency power levels. The results from the dynamic nuclear polarization measurements agree well with the phantom imaging results. These results pave the way for designing model system for human tissues suited to the biological applications of electron spin resonance/Overhauser‐enhanced magnetic resonance imaging.