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The effective complex permeability and permittivity spectra in composites with various ferrite volume fractions were calculated using the Bruggeman effective medium theory. The matching conditions for the maximum microwave absorption were determined by substituting the complex permeability and permittivity in the equation for the impedance matching condition. The minimum reflection loss increases from -5 to -40 dB as the ferrite volume fraction increases for [v.sub.zf] < 0.26, where single dip of minimum reflection loss was observed. However, two matching conditions were observed for [v.sub.f] [greater than or equal to] 0.26, and two minimum reflection losses shown to be about -40 dB. The results indicate that a microwave absorber with reflection loss of about -40 dB can be designed by controlling the ferrite volume fraction in MnZn ferrite-rubber composites in the frequency range 0.8-12 GHz.

• Propose two continuum FEM models to solve a granule-structure interaction problem. • Compare two FEM models with confined compression test and linked DEM-FEM model. • Produce reasonable to good agreement on the interaction behavior and load transfer. • Explore the applicability of linear FEM, porous FEM and linked DEM-FEM models. • Show the feasibility in modeling confined granule-structure interaction problems. Interaction between granular solids and confining structures is an elementary problem encountered in subsurface structural design and bulk solids storing and handling. A classic scenario is uni-axial compression of granular solids in a deformable cylindrical container. Despite being apparently simple in loading condition, the understanding of this scenario remains limited, mainly due to complex interactive deformation between the two components via frictional interfaces. This paper comparatively examines such a uni-axial compression particulate system by a laboratory experiment and two different numerical approaches, namely, continuum finite element method (FEM) and linked discrete-finite element method (linked DEM-FEM). In the continuum FEM approach, two intendedly chosen simple material models, linear elastic and porous elastic models, are attempted. The comparative study reveals that the majority of resultant characteristics show satisfactory agreement amongst the numerical predictions and the experimental measurements. The simple elastic continuum FEM models can hence be a useful alternative in modelling such problems with mild structural flexibility under a monotonic loading scenario. However, precise prediction of some characteristics, such as lateral pressure ratio, may demand more elaborated material model or parameter selection. The enhancements needed for each numerical approach in order to achieve an improved result are further discussed. [ABSTRACT FROM AUTHOR]

Presented in this paper is a tool path generation procedure for three-dimensional profile curve machining on three-axis machines, which is essential for making dies of automotive press panels. While sculptured surface machining has received a significant amount of attention, there has been very little work on profile curve machining. The most distinctive feature of profile curve machining is that the machine operator determines the exact cutter radius at the stage of numerical control (NC) machining. For this reason, profile curve machining usually makes use of the cutter radius compensation functionality of an NC controller. In this paper, four technological requirements for the profile curve machining are identified: (1) maintaining a constant machining width; (2) avoiding controller alarms; (3) avoiding unbalanced cutter wear; and (4) retaining down-milling. To satisfy these requirements, a tool path generation procedure is proposed, implemented and tested. [ABSTRACT FROM AUTHOR]

A study of the interaction between gel strength and high hydrostatic pressure (HHP) in Alaskan pollock surimi and Pacific whiting using torsions reveals HHP to enhance strain values for given temperature and pressure combination. HHP, which causes food rheological alterations, influences enzymatic functions while reducing microorganisms. HHP affects gel strength more than heat-set controls.

Torsion test, salt-soluble protein extractability and Ca++-ATPase activity were used to examine protein denaturation of frozen Pacific whiting Merluccius productus fillets stored at varying low temperature over a 10-mo period. Variation in the quality of fillets stored at lower temperatures were much less than those stored at -8 degree celsius. No major advantage over fillets stored at -20 degrees celsius, was observed for those stored at -34 and -50 degrees celsius.

This paper investigates mechanical behaviour and failure process of a 3D notched plate subjected to uni-axial tension using the discrete element method (DEM). The 3D notched plate consisted of different crystal structures, such as simple cubic (SC), body-centered cubic (BCC), face-centered cubic (FCC) and hexagonal close-packed (HCP), where constituent spheres were bonded together by contact bond. The inclination angle of the notch ranged from 0° to 90° with an increment of 15°. The aim of this study is to explore the effects of crystal packing and notch inclination angle on the mechanical responses, crack initiation and propagation, and crack paths. The proposed DEM model was first verified for the pre-cracking behaviour by the corresponding FEM calculation, and was confidently used to study the post-cracking behaviour. Numerical results reveal that the crack initiation and propagation of crystal structures depend on the crystal configuration and notch inclination angle. The loading stiffness of the four crystal structures follows the sequence of HCP > FCC > SC > BCC. The stress concentration factor shows a convex profile against notch inclination angle, with the maximum value at the notch inclination angle of 30° and the minimum value at the notch inclination angle of 90°. The SC and BCC crystal structures show a symmetric feature of crack propagation, whilst the FCC and HCP crystal structures exhibit asymmetric characteristics. In such a loading scenario, the crack initiation and propagation in all the four crystal structures are mainly dominated by the tension failure mode. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a discrete element method (DEM) model to simulate the convection phenomenon of non-spherical particles in a vibrating bed. The corresponding physical experiments were carried out in our previous study. The discrete element simulation results were validated with the experimental results. The non-spherical particles were paired particles, composed of two single beads. The proposed discrete element model adopted Hertz–Mindlin no slip contact force model to model particle collision and multi-sphere method to exactly represent the shape of paired particles. The local damping as well as contact friction and contact damping were incorporated to properly dissipate the system energy of non-spherical granular assemblies. To attain a high level quantitative validation, the important particle properties required for DEM simulation were not simply assumed but measured directly in laboratory tests. The transport properties of paired particles in a vibrated bed, involving local average velocity, local fluctuation velocity, granular temperature, fluctuation velocity distribution and self-diffusion coefficient, were analyzed. The comparison between the DEM results and experimental results was made and discussed in this paper. Both results show the convection phenomena of paired particles in a vibrating bed and the majority of transport properties show good to excellent match, thus giving a quantitative validation for the discrete element simulation of the problem studied here. This proposed discrete element model is shown to provide plausible results and can directly be applicable to realistic industrial problems comprising many non-spherical particles. [Copyright &y& Elsevier]

Abstract: This paper proposes a methodology to link the discrete element method (DEM) with the finite element analysis (FEA) to evaluate the loading of particulate solid on a contacting structure or machine. The mathematical formulation to convert the DEM boundary contact forces to the nodal forces and moments in triangular finite elements was derived based on the concept of shape function. To prove the feasibility of this proposed methodology, two numerical examples, confined compression and confined expansion of steel beads filled in a cylindrical container, were analysed. The DEM calculations for discrete steel beads were performed using the PFC3D code. The outputs from the DEM simulations were extracted and processed into ABAQUS FEA input decks by the proposed method. A finite element analysis was executed to calculate the stress distribution in the continuum steel cylinder for the two examples using a linear shell analysis. The DEM and FEA results were presented and discussed in this paper. The results show that the proposed methodology can provide an effective way to determine the stress distribution in contacting structures subjected to loading from particulate assemblies and can be applied to solve solid–structure interaction problems. The proposed methodology is not applicable to the cases where wall friction is significant. [Copyright &y& Elsevier]

1. Evidence has accumulated in mammals to support the idea that mitochondrial DNA (mtDNA) deletions and mutations might contribute to ageing and reproductive failure. White Roman geese were monitored to evaluate the effect of large-scale deletions of mtDNA in an avian species. 2. A total of 340 samples from 114 dead embryos, 111 weak goslings, and 115 normal goslings were used in this experiment. The regions of these two large-scale mtDNA deletions, ΔmtDNA6829 and ΔmtDNA6992, were between the COI and ND5 genes. A 3·6% (4 out of 111) positive sample was detected in the weak goslings. In contrast, no large-scale mitochondrial DNA deletions were detected in either the dead embryos (0 out of 114) or the normal goslings (0 out of 115). 3. Large-scale mtDNA deletions may be a factor causing weak goslings. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, Particle Tracking Velocimetry (PTV) has been extensively used to measure the translational velocity field of granular assemblies in applications such as vibrated beds, rotating drums and Couette shear cells. However, this technique has not yet been shown to be able to determine the velocity field of non-spherical particles. The aim of this paper is to develop an improved PTV technique to determine translational and rotational velocities for non-spherical particles. To prove the feasibility of this new PTV technique, it was employed to investigate the convection behaviour of non-spherical particles in a vibrated bed. In the demonstration example, paired POM particles made by gluing two single POM beads were studied. The test example was a single layer quasi-2D model. The transport properties of the paired POM particles in a vibrated bed, such as local average velocities, local fluctuation velocities, granular temperatures, fluctuation velocity distributions, self-diffusion coefficients and dimensionless convection flow rates, were evaluated from the experimental results and discussed. The developed improved PTV technique is shown to have the ability to measure more accurately the velocity field of non-spherical particulate systems. The study has demonstrated the convection phenomenon of non-spherical particles in a vibrated bed and has shown that particle rotation is significant in the vibrated granular bed. In such a granular system with convection phenomenon, the average rotational kinetic energy constitutes approximately 5.4% of the average kinetic energy and in some local regions the rotational granular temperature amounts to over 17% of the total granular temperature. [Copyright &y& Elsevier]

The polarization-nulling technique utilizes the different properties of optical signal and amplified spontaneous emission (ASE) noise for accurate monitoring of the optical-signal-to-noise ratio (OSNR) in dynamic optical networks. However, the performance of this technique is bound to be deteriorated if the signal is depolarized by polarization-mode dispersion and/or nonlinear birefringence or the ASE noise is partially polarized due to polarization-dependent loss (PDL) in the transmission link. The authors analyze these effects on the performance of the polarization-nulling technique and introduce several techniques to overcome these problems. These improved versions of the polarization-nulling techniques could monitor the OSNR with accuracy of better than plusmn1 dB, even when the differential group delay is as large as 60 ps. These techniques could also negate the effect of the signal depolarization caused by nonlinear birefringence in a highly nonlinear transmission link. The effect of the partially polarized ASE noise due to PDL is found to be not severe in most cases, as long as the PDL/span is smaller than 0.2 dB. To verify the possibility of using the polarization-nulling technique in real systems, the OSNR of the wavelength-division-multiplexed (WDM) signals transmitted through a 120-km-long aerial fiber link is measured for one week. No significant degradation in the monitoring accuracy is observed during this long-term measurement. In addition, the performance of the polarization-nulling technique in an ultralong-haul transmission link is evaluated by using a 640-km-long recirculating loop. The results show that this technique could accurately measure the OSNR in the transmission link longer than 3200 km. From these results, the authors conclude that the polarization-nulling technique is well suited for monitoring the OSNR in dynamic WDM networks [ABSTRACT FROM PUBLISHER]

Abstract: We report on the 320Gb/s (40Gb/s×8 channels) WDM transmission experiment using short-period dispersion-managed fiber. After 320-km transmission, the average Q-factor was measured to be better than 20.4dB. In addition, we compared the performances of various types of fibers in 40-Gb/s based systems. The results show that the SPDMF was robust to both the intra-channel and inter-channel nonlinearities due to its small average dispersion and large local dispersion. [Copyright &y& Elsevier]

We developed an analytical model for the statistics of polarization-dependent gain (PDG) in both copumped and counterpumped fiber Raman amplifiers (FRAs). The validity of this model was confirmed by using experimental data and numerical simulations. The results show that the PDG in a counterpumped FRA cannot be neglected since it is only about 3 times smaller than that in a copumped FRA. Using the proposed model, we also evaluated the effects of various parameters on the PDG including the wavelength difference between the signal and pump, degree-of-polarization (DOP) of pump laser, polarization-mode dispersion, and fiber loss at the pump wavelength. In addition, the proposed model was used to analyze the requirement of the DOP of pump for the suppression of PDG within 1 dB. [ABSTRACT FROM PUBLISHER]

Abstract: We demonstrate the error-free transmission of directly modulated 2.5, 10, and 40-Gb/s coarse wavelength-division-multiplexing/dense wavelength-division-multiplexing signals over negative dispersion fiber (dispersion: −2.5 ps/km/nm @ 1550 nm) without dispersion compensation. The results indicate that the metro core/access network could be implemented cost-effectively by using the proposed negative dispersion fiber and directly modulated lasers. [Copyright &y& Elsevier]

This paper discusses the evaluation of the system outage probability caused by the temperature variation and statistically distributed chromatic dispersion of optical fiber in a high-speed (>40 Gb/s) optical network. This was to identify when the tunable dispersion compensator should be used at every channel. [ABSTRACT FROM PUBLISHER]

This paper uses a finite-element model to investigate the stability of the Twin-Towers of the World Trade Center, New York for a number of different fire scenarios. This investigation does not take into account the structural damage caused by the terrorist attack. However, the fire scenarios included are based upon the likely fires that could have occurred as a result of the attack. A number of different explanations of how and why the Towers collapsed have appeared since the event. None of these however have adequately focused on the most important issue, namely ‘what structural mechanisms led to the state which triggered the collapse’. Also, quite predictably, there are significant and fundamental differences in the explanations of the WTC collapses on offer so far. A complete consensus on any detailed explanation of the definitive causes and mechanisms of the collapse of these structures is well nigh impossible given the enormous uncertainties in key data (nature of the fires, damage to fire protection, heat transfer to structural members and nature and extent of structural damage for instance). There is, however, a consensus of sorts that the fires that burned in the structures after the attack had a big part to play in this collapse. The question is how big? Taking this to the extreme, this paper poses the hypothetical question, “had there been no structural damage would the structure have survived fires of a similar magnitude”?A robust but simple computational and theoretical analysis has been carried out to answer this question. Robust because no gross assumptions have been made and varying important parameters over a wide range shows consistent behaviour supporting the overall conclusions. Simple because all results presented can be checked by any structural engineer either theoretically or using widely available structural analysis software tools. The results are illuminating and show that the structural system adopted for the Twin-Towers may have been unusually vulnerable to a major fire. The analysis results show a simple but unmistakable collapse mechanism that owes as much (or more) to the geometric thermal expansion effects as it does to the material effects of loss of strength and stiffness. The collapse mechanism discovered is a simple stability failure directly related to the effect of heating (fire). Additionally, the mechanism is not dependent upon failure of structural connections. [Copyright &y& Elsevier]

We have demonstrated an easily upgradable bidirectional passive optical network for the simultaneous transmission of wavelength-division-multiplexing channels and digital broadcast video signals. The proposed network could transmit 15 2.5-Gb/s downstream channels, 15 155-Mb/s upstream channels, and one broadcast signal consisting of more than 70 digital video channels. [ABSTRACT FROM PUBLISHER]

Investigates the interaction of quasiparticles with a barrier in fractional quantum hall. Emphasis on the bunching of quasiparticles to depend on the average dilution of the quasiparticle current; Ability of quasiparticles to go through high-potential barriers; Influence of quantum point contact for the nonlinearity of the current.

An analog fiber-optic link transporting the wireless code-division multiple-access (CDMA) signals requires a minimum dynamic range of only about 30 dB. Motivated by this relaxed requirement, we have recently proposed a passive optical network for CDMA-based microcellular communication systems. In this paper, we reviewed the basic design rules and demonstrated various networks using double-star and ring architectures. We implemented these networks by using inexpensive light sources such as a Fabry-Perot laser (for downstream) and light-emitting diodes (for upstream). The results show that these networks could support more than eight remote base stations located within ~10 km from the central base station [ABSTRACT FROM PUBLISHER]

Presents information on a study which introduced an amplitude and phase nulling with a genetic algorithm. Function of the amplitude and phase adaptive genetic algorithm; Structure of the algorithm; Scenarios of phase adaptive nulling with a genetic algorithm.