Spray granulation of Fe and C nanoparticles and their impedance match for microwave absorption

The microwave absorbents of Fe and C nanoparticles as magnetic loss and dielectric loss material respectively were composited with the polyvinyl alcohol(PVA) as binder by spray granulation method. The electromagnetic parameters of Fe and C composite particles were analyzed by vector network. The complex permittivity and magnetic permeability of Fe and C composite particles matched well with increasing C nanoparticle content, and then the microwave loss property was improved. A minimum reflection loss(RL) of -42.7 d B at 3.68 GHz for a composite with 4.6 mm in thickness can be obtained when the content ratio of the C nanoparticles, the modified Fe nanoparticles and the PVA is 21:49:30(Sample 3).     

The effect of the wetting droplets size on power consumption during drum granulation

Changes of torque during fine material (foundry dolomite) granulation in a horizontal drum granulator at changing wetting parameters were studied. The variable parameters were droplet diameter and wetting of granular material. The bed of loose material was sprayed during feeding, at a constant liquid flow rate V_l = 0.012 m³/h. The size of wetting liquid droplets was changed using different rates of air flow through pneumatic spraying nozzles in the range from V_p = 1.0 to 3.0 m³/h and applying a sprinkler which supplied (drop-wise) the liquid uniformly along the entire drum length. In each test, instantaneous values of torque on the granulator shaft were measured in 1 s time intervals. The effect of droplet size and moisture content of the bed of granular material on torque in the whole granulation cycle was estimated. It was found that bed wetting conditions had a significant influence on the nucleation and growth of agglomerates. A minimum (boundary) size of liquid droplets, at which the bed is not transformed into granulated material, depends on the total amount of liquid supplied at the wetting stage. Changes of torque during the drum granulation are a good representation of the phenomena related to the transformation of wetted feed into granulated product and can be an easy indicator of the process.The work was carried out within the project no. 4 T09C 023 22. financed by the State Committee for Scientific Research in the years 2002–2005.     

Aspects of the use of orthogonal basis functions in the element‐free Galerkin method

The element‐free Galerkin (EFG) method is probably the most widely used meshless method at present. In the EFG method, shape functions are derived from a moving least‐squares approximation using a polynomial basis, a calculation involving the inversion of a small matrix. A new implementation of the EFG method was published soon after the original where an alternative approach using an orthogonal basis was proposed to avoid matrix inversion in the formulation of the shape functions. In this paper we revisit this topic and show that the difficulties associated with the use of a polynomial basis remain present in the orthogonal case. We also show that certain terms in the derivative expressions are omitted in the new implementation of the EFG, which can lead to errors. Finally, we propose a new approach that avoids inversion while maintaining accuracy. Copyright © 2009 John Wiley & Sons, Ltd.     

Subdomain radial basis collocation method for fracture mechanics

The direct approximation of strong form using radial basis functions (RBFs), commonly called the radial basis collocation method (RBCM), has been recognized as an effective means for solving boundary value problems. Nevertheless, the non‐compactness of the RBFs precludes its application to problems with local features, such as fracture problems, among others. This work attempts to apply RBCM to fracture mechanics by introducing a domain decomposition technique with proper interface conditions. The proposed method allows (1) natural representation of discontinuity across the crack surfaces and (2) enrichment of crack‐tip solution in a local subdomain. With the proper domain decomposition and interface conditions, exponential convergence rate can be achieved while keeping the discrete system well‐conditioned. The analytical prediction and numerical results demonstrate that an optimal dimension of the near‐tip subdomain exists. The effectiveness of the proposed method is justified by the mathematical analysis and demonstrated by the numerical examples. Copyright © 2010 John Wiley & Sons, Ltd.     

The radial basis integral equation method for solving the Helmholtz equation

A meshless method for the solution of Helmholtz equation has been developed by using the radial basis integral equation method (RBIEM). The derivation of the integral equation used in the RBIEM is based on the fundamental solution of the Helmholtz equation, therefore domain integrals are not encountered in the method. The method exploits the advantage of placing the source points always in the centre of circular sub-domains in order to avoid singular or near-singular integrals. Three equations for two-dimensional (2D) or four for three-dimensional (3D) potential problems are required at each node. The first equation is the integral equation arising from the application of the Green’s identities and the remaining equations are the derivatives of the first equation with respect to space coordinates. Radial basis function (RBF) interpolation is applied in order to obtain the values of the field variable and partial derivatives at the boundary of the circular sub-domains, providing this way the boundary conditions for solution of the integral equations at the nodes (centres of circles). The accuracy and robustness of the method has been tested on some analytical solutions of the problem. Two different RBFs have been used, namely augmented thin plate spline (ATPS) in 2D and f(R)=⁴Rln(R) augmented by a second order polynomial. The latter has been found to produce more accurate results.     

Preliminary report of the discovery of a new pharmaceutical granulation process using foamed aqueous binders

Spray granulation is commonly used to improve the flow of drug formulation powders by adding liquid binders. We have discovered a new granulation process whereby liquid binders are added as aqueous foam. Initial experiments indicate that foam granulations require less binder than spray granulations, less water is added to the powder mass, rates of addition of foam can be greater than rates of addition of sprayed liquids, and foam can be added in a single batch to the surface of the powder mass for incorporation at some later stage in the process. This new process appears to have no detrimental effects on granulate, tablet, or in vitro drug dissolution properties. In addition, the elimination of spray addition reduces the complexity of the process and avoids the plugging problems associated with spray nozzles. Several formulations were successfully scaled up from laboratory scale (1.5 kg) to pilot scale (15 kg). Process control was good and there was no detrimental effect on tablet and drug dissolution properties. This paper also proposes a working hypothesis of the mechanism by which foam granulation operates.     

Synthesis of Ni and bimetallic FeNi nanopowders by microwave plasma method

Nickel nanopowders can be synthesized by microwave plasma synthesis method. The effect of the feeding rate of the precursor material to the average particle size and crystallinity was studied. FeNi bimetallic alloy nanopowders were also successfully synthesized by pre-mixing the respective precursor raw materials before feeding into the plasma reaction zone. The Ni and FeNi nanopowders were characterized by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD).     

Stage-wise characterization of the high shear granulation process by impeller torque changing rate

Fine cornstarch powders are wet granulated in a lab-scale high shear granulator. The torque required for maintaining the impeller passing through the bed with a constant rotating speed is monitored during the continuous binder addition granulation process. A new method is proposed to identify 6 stages during the granulation process based on the fraction of the positive impeller torque changing rate in a characteristic period of time. The morphologies and the behavior of the bed are found intrinsically different in the identified 6 stages. The influence of the impeller blade inclined angle on the impeller torque in each stage is initially reported. The impeller with planner 45° blades requires higher torques in Stages I and II due to the overall powder bed mass loading. The impeller with steeper 60° blades requires higher torques in Stages III and IV due to the higher collision frequencies between the blade and granules. The suitable granulation liquid binder to solid powder mass ratio can be readily identified in Stages II and III, and its range is found to increase with the increasing of the impeller rotational speed and is independent to the blade inclined angle.     

Adaptive greedy algorithms based on parameter-domain decomposition and reconstruction for the reduced basis method

The reduced basis method (RBM) empowers repeated and rapid evaluation of parametrized partial differential equations through an offline–online decomposition, a.k.a. a learning-execution process. A key feature of the method is a greedy algorithm repeatedly scanning the training set, a fine discretization of the parameter domain, to identify the next dimension of the parameter-induced solution manifold along which we expand the surrogate solution space. Although successfully applied to problems with fairly high parametric dimensions, the challenge is that this scanning cost dominates the offline cost due to it being proportional to the cardinality of the training set which is exponential with respect to the parameter dimension. In this work, we review three recent attempts in effectively delaying this curse of dimensionality, and propose two new hybrid strategies through successive refinement and multilevel maximization of the error estimate over the training set. All five offline-enhanced methods and the original greedy algorithm are tested and compared on two types of problems: the thermal block problem and the geometrically parameterized Helmholtz problem.     

Preparation and characterization of nano-NaX zeolite by microwave assisted hydrothermal method

In the present work, nano-NaX zeolite crystals were synthesized via microwave and conventional hydrothermal methods. The effects of reaction time, temperature and heating method on the characteristics of zeolite nanoparticles such as particle size, crystallinity, morphology, size distribution and surface area were investigated. The prepared NaX zeolite nanoparticles were characterized by the XRD, SEM, DLS, BET and XRF analysis. The results showed that both heating methods produced the NaX zeolite crystals with nano-in size. The microwave heating produced smaller zeolite nanoparticles with relatively narrower particle size distribution, required much shorter heating times and did not significantly change composition or crystallinity, compared with the conventional heating method. It was also observed that the time and temperature of microwave heating had significant effects on the prepared zeolite particles and the pure zeolite X nanoparticles or a mixture of zeolite X and A can be synthesized using the microwave heating method by control of the crystallization time and temperature.     

Synthesis of silver nanoparticles using N 1, N 2-diphenylbenzamidine by microwave irradiation method

Silver nanoparticles have been prepared under microwave irradiation from a solution of silver nitrate in the presence of N ¹,N ²-diphenylbenzamidine (DPBA) or simply amidine without any stabilizing agent. Different morphologies of silver colloids with charming colors could be obtained using N ¹,N ²-diphenylbenzamidine (DPBA). The structures of silver colloids were determined by TEM. UV-Vis spectroscopy was used to follow the reaction process and to characterize the optical properties of the resultant silver colloids. The influence of unconventional reducing agent on the morphology of silver was investigated.     

Subdomain radial basis collocation method for heterogeneous media

Strong form collocation in conjunction with radial basis approximation functions offer implementation simplicity and exponential convergence in solving partial differential equations. However, the smoothness and nonlocality of radial basis functions pose considerable difficulties in solving problems with local features and heterogeneity. In this work, we propose a simple subdomain strong form collocation method, in which the approximation in each subdomain is constructed separately. Proper interface conditions are then imposed on the interface. Under the subdomain strong form collocation construction, it is shown that both Neumann and Dirichlet boundary conditions should be imposed on the interface to achieve the optimum convergence. Error analysis and numerical tests consistently confirm the need to impose the optimal interface conditions. The performance of the proposed methods in dealing with heterogeneous media is also validated. Copyright © 2009 John Wiley & Sons, Ltd.     

Speed improvement of multivariate algorithms by the method of postponed basis matrix multiplication. Part III. The use of asymmetric and generalized eigenvalue equations

It is demonstrated that the method for postponed basis matrix multiplication (PBM) applied to principal component analysis can be formulated as asymmetrical and generalized eigenvalue equations.     

Weighted radial basis collocation method for boundary value problems

This work introduces the weighted radial basis collocation method for boundary value problems. We first show that the employment of least‐squares functional with quadrature rules constitutes an approximation of the direct collocation method. Standard radial basis collocation method, however, yields a larger solution error near boundaries. The residuals in the least‐squares functional associated with domain and boundary can be better balanced if the boundary collocation equations are properly weighted. The error analysis shows unbalanced errors between domain, Neumann boundary, and Dirichlet boundary least‐squares terms. A weighted least‐squares functional and the corresponding weighted radial basis collocation method are then proposed for correction of unbalanced errors. It is shown that the proposed method with properly selected weights significantly enhances the numerical solution accuracy and convergence rates. Copyright © 2006 John Wiley & Sons, Ltd.     

A quality by design approach to scale-up of high-shear wet granulation process

High-shear wet granulation is a complex process that in turn makes scale-up a challenging task. Scale-up of high-shear wet granulation process has been studied extensively in the past with various different methodologies being proposed in the literature. This review article discusses existing scale-up principles and categorizes the various approaches into two main scale-up strategies – parameter-based and attribute-based. With the advent of quality by design (QbD) principle in drug product development process, an increased emphasis toward the latter approach may be needed to ensure product robustness. In practice, a combination of both scale-up strategies is often utilized. In a QbD paradigm, there is also a need for an increased fundamental and mechanistic understanding of the process. This can be achieved either by increased experimentation that comes at higher costs, or by using modeling techniques, that are also discussed as part of this review.     

螺旋形炭纤维的吸波性能

通过气相催化裂解法分别制得了螺径约为4μm、螺距为0.5μm～0.8μm的炭纤维（简称为coils-A）和螺径为20μm左右、螺距为1μm～4μm的炭纤维（简称为coils-B）.以coils-A和coils-B为掺杂体与石蜡制成复合材料在8.2 GHz～124 GHz范围内通过反射传输系统测量其电磁参数,结果表明该等微米级螺旋形炭纤维磁损耗为零,其中coils-B的介电参数的虚部及其损耗正切值tanδε较coils-A的高.分别以coils-A和coils-B为手性掺杂体制得填充有手性材料的夹芯蜂窝板复合材料,研究发现coils-A的吸波效果较好,在10 GHz～15 GHz的范围内对电磁波的反射衰减量大于10 dB,在4.6 GHz～18 GHz 的范围内对电磁波的反射衰减量均大于5 dB,在12.4 GHz时最大的反射衰减量为18 dB,其结果与藉由电磁参数所预测的结果相反.经计算,coils-A的手性参数ξ较大.因此,手性参数ξ对于提高吸波性能的影响大于介电参数ε的影响.     

Preparing of aspirin sustained-release granules by hot-melt granulation and micro-crystal coating

In this work, aspirin (ASP) sustained granules were prepared using micro-crystal coating and hot-melt granulation, respectively. In the process of micro-crystal coating, PVP was used to form the isolation layer and then coated with either Eudragit RS/RL30D or ethyl cellulose (EC) as sustained-release layers to prepare sustained granules (the granules from this method were denoted m-cG). And in the process of hot-melt granulation, the granules were obtained with stearyl alcohol as a binder and EC as matrix material to prepare sustained granules (the granules were denoted h-mG). The in vitro release of ASP sustained-release granules was investigated by dissolution apparatus and the stability of the granules was studied. Since both methods effectively prevented the hydrolysis of ASP, the sustained granules by micro-crystal coating and hot-melt granulation were stable. However, there was a clear difference in the in vitro release of h-mG and m-cG. The h-mG was completely released in 4?h, while the m-cG with EC as sustained-release layer released 80% in 24?h and the m-cG with the Eudragit RS/RL 30?D as sustained-release layer released completely in 5?h. The results showed that micro-crystal coating was more suitable for the preparation of ASP sustained granules, and the granules with EC as sustained layer could achieve a better sustained-release effect.     

FEM-SPH耦合算法模拟铝液粒化的动态过程

针对传统基于网格方法不能有效模拟大变形问题的现状,本文引入SPH(Smoothed Particle Hydrodynamic)方法模拟液态钢渣(文中简称液渣)与粒化轮的碰撞过程.因液渣物性参数尚不完善,故以铝液代替并使用SPH方法建模,粒化轮则用FEM(Finite Element Method)建模,并通过接触算法实现FEM-SPH的耦合,研究了粒化轮转速、铝液的流速等因素对碰撞过程铝液液滴体积大小的影响.模拟结果表明:当SPH粒子承载质量为2.04×10-4kg时,粒化轮转速达到900 rad/min;粒化前铝液流速为1m/s时粒化效果较好且体积多分布在1 330~1 930 mm3;碰撞后粒子运动速度多集中在5~25 m/s.     

The theoretical basis of a method to determine the fracture energyG F of concrete

RILEM Technical Committee 50-Fracture Mechanics of Concrete, has put forward a proposal for a recommendation for the determination of the fracture energy G_F of mortar and concrete. The significance of G_F in the strength of concrete structures is discussed and it is demonstrated that G_F in some cases, for example for shear failure of beams and slabs without shear reinforcement, is a material property which may be as important as normal strength properties. For the measurements of energy absorption a three-point bend test on a notched beam has been proposed. The choice of test specimen and of evaluation method is discussed.

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Résumé La Commission Technique 50-FMC de la RILEM, Mécanique de la rupture du béton a proposé, en vue d’une recommandation, une méthode de mesure de l’énergie de rupture G_F. Les bases de cette méthode sont exposées dans le présent rapport. La rupture du béton par traction peut être décrite par deux courbes (fig. 2). La première décrit la relation contrainte/déformation relative à l’ensemble du matériau et la seconde représente la relation contrainte/déformation dans la seule zone endommagée, durant le processus de rupture. L’aire de la surface délimitée par la seconde courbe est représentative de l’énergie de rupture appelée G_F. Au moyen de courbes approximatives simplifiées, données à la figure 3, on a analysé la résistance de certaines structures dont la rupture survient par traction (fig. 4 à 6). II a été démontré que la sensibilité de la résistance par rapport aux variations des propriétés du matériau peut être déduite de ces courbes. Pour des échantillons de béton de qualités et de dimensions usuelles, la sensibilité par rapport aux variations de G_F peut être à peu près du même ordre de grandeur que celle relative aux variations de la résistance à la traction f_t. On peut donc conclure que G_F est une propriété importante du matériau qu’il conviendrait de prendre en compte dans certains types de sollicitations de structures comme par exemple la résistance au cisaillement dans les dalles. C’est la raison pour laquelle il est nécessaire de disposer d’une méthode standard pour sa détermination. La méthode d’essai proposée par la Commission Technique RILEM 50-FMC est un essai par flexion sur une poutre entaillée où l’énergie absorbée durant l’essai est mesurée. Le choix des dimensions du spécimen et l’évaluation des résultats de l’expérience sont également discutés.

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