Lattice Boltzmann simulations on GPUs with ESPResSo

For the dynamics of macromolecules in solution, hydrodynamic interactions mediated by the solvent molecules often play an important role, although one is not interested in the dynamics of the solvent itself. In computer simulations one can therefore save a large amount of computer time by replacing the solvent with a lattice fluid. The macromolecules are propagated by Molecular Dynamics (MD), while the fluid is governed by the fluctuating Lattice-Boltzmann (LB) equation. We present a fluctuating LB implementation for a single graphics card (GPU) coupled to a MD simulation running on conventional processors (CPUs). Particular emphasis lies on the optimization of the combined code. In our implementation, the LB update is performed in parallel with the force calculation on the CPU, which often completely hides the additional computational cost of the LB. Compared to our parallel LB implementation on a conventional quad-core CPU, the GPU LB is 50 times faster, and we show that a whole commodity cluster with Infiniband interconnnect cannot outperform a single GPU in strong scaling. The presented code is part of the open source simulation package ESPResSo ().     

Lattice Boltzmann modeling and simulation of compressible flows

In this mini-review we summarize the progress of Lattice Boltzmann (LB) modeling and simulating compressible flows in our group in recent years. Main contents include (i) Single-Relaxation-Time (SRT) LB model supplemented by additional viscosity, (ii) Multiple-Relaxation-Time (MRT) LB model, and (iii) LB study on hydrodynamic instabilities. The former two belong to improvements of physical modeling and the third belongs to simulation or application. The SRT-LB model supplemented by additional viscosity keeps the original framework of Lattice Bhatnagar-Gross-Krook (LBGK). So, it is easier and more convenient for previous SRT-LB users. The MRT-LB is a completely new framework for physical modeling. It significantly extends the range of LB applications. The cost is longer computational time. The developed SRT-LB and MRT-LB are complementary from the sides of convenience and applicability.     

Outcome of laryngeal and velopharyngeal biofeedback treatment in children and young adults: A pilot study

A relatively new management strategy for the treatment of voice disorders is the use of laryngeal (LB) and velopharyngeal biofeedback (VB). The main purpose of the present pilot study is to document the outcome of vocal and velopharyngeal performances after a well-defined LB and VB treatment. Four subjects were studied pretreatment (1 week before LB or VB treatment) and posttreatment (1 week after the LB or VB treatment). To measure and compare the effect of LB and VB, objective and subjective assessment techniques were used. Perceptual voice assessment included a perceptual rating of the voice using the GRBAS scale. Furthermore, the vocal quality in this population is modeled by means of the Dysphonia Severity Index. For the objective assessment of nasal resonance, the Nasometer and the Glatzel test were used. A perceptual evaluation of speech, the Gutzmann test, and the tests from Bzoch were used as subjective assessment techniques. Both patients selected for LB and VB treatment showed improvement of their performances. The resulting improvement, as measured by means of an objective approach, is in agreement with the perceived (auditory) improvement of voice and resonance. The use of LB and VB treatment in patients, especially in some subjects who are not responding to traditional voice or velopharyngeal therapy, must be encouraged.     

聚丁二炔Langmuir—Blodgett薄膜的光声谱研究：（Ⅰ）结构表征与光声？…

本在用Ｘ－射线小角衍射聚合与转载先后次序不同的ＰＤＡ ＬＢ膜进行结构表征的基础上,不同厚度的ＰＤＡ ＬＢ膜的光声新斩波频率效应说明,随着ＰＤＡ ＬＢ膜厚度增加,ＬＢ膜的热学性质逐渐明显。此外,还探讨了如何从ＰＤＡ ＬＢ膜的光声谱求得光声吸收系数问题,本的研究结果表明,光声谱技术是研究ＬＢ膜热学特性的有效手段。     

聚丁二炔Langmuir-Blodgett薄膜的光声谱研究(Ⅰ)结构表征与光声吸收系数

本文在用Ｘ－射线小角衍射对聚合与转载先后次序不同的ＰＤＡＬＢ膜进行结构表征的基础上,不同厚度ＰＤＡＬＢ膜的光声斩波频率效应说明,随着ＰＤＡＬＢ膜厚度增加,ＬＢ膜的热学性质逐渐明显。此外,还探讨了如何从ＰＤＡＬＢ膜的光声谱求得光声吸收系数问题,本文的研究结果表明,光声谱技术是研究ＬＢ膜热学特性的有效手段。     

复杂流动的LBGK模拟

ＬＢＧＫ方法在保留了格子气模型的一些优点的同时，克服了格子气模型的不足之处．应用ＬＢＧＫ方法，可以对更复杂的流体进行模拟．本文讨论了一种九点ＬＢＧＫ模型，并用Ｃｈａｐｍａｎ－Ｅｎｓｋｏｇ展开方法和多尺度技术证明其在二阶精度上表现为标准的Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程．用该模型对圆柱绕流和管排流动进行模拟的结果显示，该模型能较好地模拟复杂流动现象，并具有一定工程应用背景．     

Formation of thin luminescent Eu3+-LB films by in situ coordination with 2,3,5,6-tetra(2′-pyridyl)pyrazine and 1-octadecanol in pure and mixed Langmuir monolayers

The in situ complexation between 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz) molecules and europium ions at the air–liquid interface by means of mixed 1-octadecanol Langmuir films is reported. These films were transferred to solid supports by means of the Langmuir–Blodgett (LB) technique. The EDS maps attested the homogeneity of the LB films as well as the presence of the europium ions. The mixed alcohol/tppz LB film contained a larger amount of europium ions as compared to the pure octadecanol LB film. This work reports the production of a thin luminescent Eu³⁺ film containing europium ions using only alcohol molecules as ligands—an unexpected result, since it is well known that there is an occurrence of non-radiative deactivation of excited europium by hydroxyl groups. Europium ion multiple binding sites were detected from lifetime decay measurements of these films in the presence of tppz molecules.     

小牛胸腺DNA分子Langmuir-Blodgett复合膜的表面增强拉曼光谱研究

本文利用Langmuir-Blodgett(LB)技术将小牛胸腺DNA分子沉积在银基底上,测试并讨论了它的π-A等温曲线,原子力图及表面增强拉曼光谱(SERS)。通过利用LB技术,获得了DNA分子的LB复合膜的高质量的SERS。在DNA分子LB膜的表面增强拉曼光谱中,DNA的核糖和碱基腺嘌呤是吸附活性部位,它们的振动光谱得到增强。DNA的其它碱基和磷酸基团的拉曼光谱强度也明显的得到增强。分析认为DNA分子增强的拉曼光谱主要是由于LB膜的有序结构的贡献,使得SERS效应得到进一步的增强。因此利用LB技术是得到DNA的高质量SERS很好的方法。     

A study on the inclusion of body forces in the lattice Boltzmann BGK equation to recover steady-state hydrodynamics

When the lattice Boltzmann (LB) method is used to solve hydrodynamic problems containing a body force term varying in space and/or time, its modelling at the mesoscopic scale must be verified in terms of consistency in order to avoid the appearance of non-hydrodynamic error terms at the macroscopic scale. In the present work it is shown that the modelling of spatially varying steady body force terms in the LB equation must be different from the time-dependent case, when a steady-state flow solution is sought. For that, the Chapman-Enskog analysis is used to derive the LB body force model for the LB BGK equations in a steady-state flow problem. The theoretical findings are supported by numerical tests performed on two different 2D steady-state laminar flows driven by spatially varying body forces with known analytical solutions.     

半花菁／氮冠（醚）交替LB多层膜的二阶光学非线性性质

对一种新型的，具有双脂链的盘状非活性分子氮冠（醚）（ＮＣ）ＬＢ膜进行了表征。小角Ｘ射线衍射（ＳＡＸＤ）结果表明：纯ＮＣ分子可以形成非常好的ＬＢ膜有序结构。将它与活性分子半花菁（ＤＡＥＰ）制备成Ｙ型交替多层膜，由于半花菁分子的单脂链（长尾）可以镶嵌在ＮＣ分子的双脂链之间，改善了多层膜的结构有序性及稳定性，从而得到二次谐波强度随层数的变化在１￣１１６双层范围内显示出较理想的平方关系。通过二次谐波的测量     

1－苄基－9－氢富勒烯－60LB多层膜的制备及其光学非线性性质

利用π－Ａ等温线、小角Ｘ射线衍射（ＳＡＸＤ）和光学测量方法研究了一种取代富勒烯（Ｃ６０－Ｂｅ）ＬＢ膜的结构特性。纯Ｃ６０－Ｂｅ分子以体相（ｂｕｌｋｐｈａｓｅ）的形式存在于气－液界面上。氮冠（醚）（ＮＣ）分子作为隔层材料，与Ｃ６０－Ｂｅ分子相混合可以制备性能优良的ＬＢ膜。π－Ａ、吸收和小角Ｘ光衍射测量表明：这种混合膜结构的改善是由于Ｃ６０－Ｂｅ分子镶嵌在ＮＣ分子的双脂链之间造成的。通过测量三次谐波产生（ＴＨＧ）可以推出Ｃ６０－Ｂｅ的三阶非线性系数χ（３）＝２．１×１０－１１ｅｓｕ。     

Non-local closure and parallel performance of lattice Boltzmann models for some plasma physics problems

The lattice Boltzmann (LB) method is a mesoscopic approach to solving nonlinear macroscopic conservation equations. Because the LB algorithm yields a simple collide-stream sequence it has been extensively applied to Navier–Stokes flows, but its MHD counterpart is less well known in the plasma physics community. Several plasma problems that should be amenable to LB are discussed. In particular, Landau damping—a collisionless kinetic phenomenon of wave–particle interaction—can be studied by LB since non-local macroscopic closures have been generated by plasma physicists. The parallel performance of 2D LB codes for MHD are presented, including scaling performance on the Earth Simulator.     

Cole-Hopf Transformation Based Lattice Boltzmann Model for One-dimensional Burgers' Equation

In this paper,we present a Cole-Hopf transformation based lattice Boltzmann(LB) model for solving one-dimensional Burgers' equation,and compared to available LB models,the effect of nonlinear convection term can be eliminated.Through Chapman-Enskog analysis,it can be found that the converted diffusion equation based on the Cole-Hopf transformation can be recovered correctly from present LB model.Some numerical tests are also performed to validate the present LB model,and the numerical results show that,similar to previous LB models,the present model also has a second-order convergence rate in space,but it is more accurate than the previous ones.     

Fabrication and Spectroscopic Characterization of Langmuir-Blodgett Films with Luminescent Rare Earth Complexes of Long Chain Double Functional Ligands Mono-L Phthalate (L = Hexadecyl, Octadecyl and Eicosyl)

In this paper, some novel long chain amphiphillic monoester molecules were designed to afford double functions: film-formation ability and luminescent sensitization ability. Subsequently organized molecular films of rare earth complexes with these functional ligands formulated as ML2NO3 were fabricated by the Langmuir-Blodgett film (LB) technology, where RE denotes rare earth ions Eu3+, Tb3+ and Dy3+; L denotes the long chain carboxylic ligands monohexadecyl phthalate (16-Phth), monooctadecyl phthalate (18-Phth) and monoeicosyl phthalate (20-Phth). The average molecular area was obtained according to the π-A isotherms. The layer structure of the LB films was demonstrated by low-angle X-ray diffraction and the average layer spacing was determined from the Bragg equation. UV absorption intensity increases linearly with the number of LB films layers, which indicates that the LB films are homogeneously deposited. The fluorescence spectra of these LB films were quite different from those of their solid complexes. It reveals that the long chain ester ligands are suitable for the excited states of Tb3+ and Dy3+ in the LB films as well as in the solid complexes, but not match with the europium ion in the LB films.     

Ftir Studies on LB Film of Amphiphile with Schiff Base as Headgroup and Its Copper Complex

Two different ways to form monolayers and LB films (surface film and subphase film) of the complex have been used, where a novel amphiphile containing Schiff base as a headgroup was used as a ligand. the monolayer behavior at the air/water interface was characterized by π-A isotherms and two-dimensional molecular orientation of alkyl chains in LB films and thermal stability were measured by polarized and variable temperature FTIR transmission spectra, indicating that the LB film of the novel amphiphile and its copper(II) complex are very stable as well as stearic acid. Because incorporating the metal ion into the monolayer makes it more condensed, thermal stability of the LB film was enhanced. as can be compared from their structure and properties, subphase films are superior to surface films.     

酞菁铜LB薄膜复合光波导的高速双稳特性

对以有机材料酞菁铜的LB薄膜作覆盖层的K~+离子交换玻璃光波导,进行了高速光学双稳特性研究.利用比较波导的输入和输出光脉冲形状法,在532nm光波长得到开关时间为24ps的高速光学双稳特性.     

AFM investigation of polymer LB films on the alignment of ferroelectric liquid crystal

A kind of newly synthesized polyimide (PI) LB films were fabricated to align ferroelectric liquid crystal (FLC). The topologies of PI LB films treated by different imidization processes were investigated by atomic force microscopy (AFM). It is found that the imidization temperature influences the crystalline structure of the LB films and high-temperature imidized LB films can provide the energy barrier for the realization of excellent bistability, while the ultra-thinness of LB films is helpful for the quick response of the FLC cell.     

Visualization of the langmuir-blodgett film structure in liquid-crystal cells

The use of liquid-crystal (LC) cells for the visualization of the Langmuir-Blodgett (LB) film structure is described. Images appearing in LC cells upon LB film application are presented. The images are analyzed in relation to the LB film structure (application conditions) and to the relief formed by indium tin oxide (ITO) electrodes.     

Flux Limiter Lattice Boltzmann Scheme Approach to Compressible Flows with Flexible Specific-Heat Ratio and Prandtl Number

We further develop the lattice Boltzmann (LB) model [Physica A 382 (2007) 502] for compressible flows from two aspects. Firstly, we modify the Bhatnagar--Gross-Krook (BGK) collision term in the LB equation, which makes the model suitable for simulating flows with different Prandtl numbers. Secondly, the flux limiter finite difference (FLFD) scheme is employed to calculate the convection term of the LB equation, which makes the unphysical oscillations at
discontinuities be effectively suppressed and the numerical dissipations be significantly diminished. The proposed model is validated by recovering results of some well-known benchmarks, including (i) The thermal Couette flow; (ii) One- and two-dimensional Riemann problems. Good agreements are obtained
between LB results and the exact ones or previously reported solutions. The flexibility, together with the high accuracy of the new model, endows the proposed model considerable potential for tracking some long-standing problems and for investigating nonlinear nonequilibrium complex systems.