Experimental investigation on the influence of different grades of wood chips on screw feeding performance

Although basic investigations on wood chip material properties haven been carried out, only few studies deal with transport of wood chips, despite the fact that significant problems are commonly observed when feeding biomass in industrial applications. Within the work presented, basic bulk material properties were measured and experiments carried out with a system consisting of a hopper, agitator and a screw conveyor. The aim of this study was to investigate how three different wood chip grades and two blends of wood chips influence typical design parameters, such as mass flow and driving torque, of a biomass feeding system. The measured basic bulk properties are in good overall agreement with the literature. However, discrepancies were discovered between two standardized methods for determination of the bulk density. The results for the driving torque, mass flow and mass-related energy consumption showed that different grades of wood chips can alter these values considerably. Between two wood chip grades, a twice as high torque was recorded, while a third grade could not be fed due to jamming. One of the major findings of this study is that mixing a rather small amount of a high-fine content grade with the non-feedable grade of wood chips resulted in a blend which inhibited jamming during the screw feeding process.     

Modeling the dynamic properties of fibre-reinforced concrete with different coating technologies of multifilament yarns

The dynamic behaviour of fibre-reinforced, cementitious composite materials is gaining increasing interest. With respect to service life dynamic loading just under the elastic limit of the material at hand is relevant to practical applications, for the resulting (stress-)waves may be focused within regions of the heterogeneous composite material. This local overstraining of the material may lead to deterioration of the structural element. In this contribution, the effect of the set-up of the reinforcing fibres on the wave scattering behaviour is investigated. Special attention is paid to layered centric configurations of these fibres, as it occurs e. g. within textile-reinforced concrete (TRC). A mechanical model is developed and solved analytically providing an efficient and robust method to describe the dynamic behaviour of given fibre configurations. This method is needed for materials which have to be described mechanically before the manufacturing process – as it is the case for TRC. The proposed model also allows for planning experiments and thus is of additional value. It is shown that the inner structure of the fibres does influence the amplitude response spectra and consequently the proposed method also may be used for non-destructively detecting the inner structure of the multifilament yarns and other related objects.     

A decision-support system for the design and management of warehousing systems

The issue of material handling involves the design and operative control of warehousing systems (i.e., distribution centres), which allow matching vendors and demands, smoothing with seasonality, consolidating products and arranging distribution activities. Warehousing systems play a crucial role in providing efficiency and customer satisfaction. The warehouse design entails a wide set of decisions, which involve layout constraints and operative issues that seriously affect the performances and the overall logistics costs.     

High efficiency OLEDs based on anthracene derivatives: The impact of electron donating and withdrawing group on the performance of OLED

New well-defined bulky anthracene derivatives with side groups having electron donating or withdrawing properties 8a-d were synthesized. The compounds contain substituted anthracene as the central core attaching 2-(4-(2-pyridinyl)- phenyl)vinyl and 4-R-phenyl [R: H (a), OMe (b) and CF₃ (c), N(Ph)₂ (d)] groups at 9- and 10- positions. The impact of electron donating, withdrawing and neutral groups and their influence on the molecules photophysical, charge transfer (CT), triplet transfer (TT) and triplet–triplet annihilation (TTA) properties has been investigated. Based on the photophysical studies the most promising molecule (8d) has been selected and high efficiency fluorescent OLEDs with EQE at very low current efficiency reaching 7% were obtained. The value at low current density implies a Triplet Fusion (TF) contribution of 45%, very close to the maximum theoretical value of 50% when only the singlet decay channel is open to TTA, however we believe that in this case both TTA and TADF contribute to the triplet harvesting to yield high EQE values, and this mixed triplet harvesting arises through the heterogeneity of the films. At high current density a brightness of 20000 cd/m² was achieved and it is assigned partially to the material crystallisation.     

建筑实践中的材料选择

文章的重点是讨论在具体的建筑实践中材料与建筑的本质性关联,亦即与设计的意图和特征、与建筑的发生密切相关的内容。在多数实践中,设计围绕核心意图展开,在意图的指引下选择对应的材料,形成特定的特征而达到预设的目标;而另外一些实践,则是因既定材料而引发设计,甚至发展出具有持续性的工作和研究方向,如"砌筑"和"组配";材料与空间、结构、形式的同一性也成为近年来特定类型建筑实践中的某种既定追求。     

Analysis of microbending of CuZn37 brass foils based on strain gradient hardening models

Microbending experiments of brass foils were conducted and demonstrated clear size effects, i.e., the normalized bending moment increased with the reduction of foil thickness. The experiments were modeled using the classical plasticity model and three strain-gradient plasticity models. A modified Nix-Gao model was proposed to consider the number of twins across the thickness direction in strain hardening. It was found that the proposed model could better predict the normalized bending moment for both fine-grain and coarse-grain foils and the proposed equation for material intrinsic length could better capture the physics of material deformation. Furthermore, micro-hardness distributions in the bending area were measured and obvious lower-hardness region was found in the middle layer of fine-grain foils instead of coarse-grain foils. This indicates that the modified Nix-Gao model and the assumption of fully plastic bending worked better for coarse-grain foils than for fine-grain foils.     

Stress analysis of nano porous material using computed tomography images

Sintered silver materials possess an advantage that allows excellent bonding between chips and their substrate. Stress manifests as the materials resistance against external and internal forces, however during stress analysis the complex physical behavior caused by the forces and the nature of the material is often disregarded by researchers. This paper analyses the stress behavior of nano porous sintered silver in X and Y directions using finite element modelling. This study also focuses on observing the growth of the crack in samples in different directions. It is found that the occurrence of the cracks in the specimens starts at the peak stress point and the failure is observed at the largest void. It is also detected that the stress across the whole area of the model is regularly distributed in those samples which have relatively smaller voids. Thus, these samples have a better material integrity. In addition, this fact indicates that the material in these sample could hold higher levels of stress. Finally, the level of the stress and the possibility of failure in those samples that have smaller voids is found to be less than others.     

Simulation-based baggage handling system merge analysis

This paper details the investigation into the design and control of merging bottlenecks of conveyor-based baggage handling systems, encompassing the merging control algorithm and the impact of the merge’s physical layout. A methodology for the analysis of simulation model results is presented. Results show that the layout of the merge influences bag throughput and when the physical configuration is in a preferred position, input variance has no effect on bag throughput performance. These results have potential application to other material handling systems, such as those used in manufacturing and warehousing.     

A new approach of fatigue life prediction for metallic materials under multiaxial loading

Based on experimental data found in literatures, four traditionally multiaxial fatigue life criteria are analyzed and verified. It is discovered that these conventional criteria cannot reflect well the combined effect both under tension and torsion loadings for some materials, such as 6082-T6 and AlCu4Mg1, due to lack of enough consideration about the influence of stress amplitude ratio and stress level on fatigue life even under proportional loading. In order to solve this problem, a new approach of fatigue life prediction, based on the equal-life curve, is proposed and it is composed of three parts: the multiaxial fatigue life surface, a new path-dependent factor for multiaxial high-cycle fatigue and a material parameter describing material sensitivity to non-proportional loading. Finally, the precision of the presented approach is systematically checked against the experimental data found in literatures for four different materials under proportional and non-proportional loadings.     

Advances in biofilm control for food and beverage industry using organo-silane technology: A review

Cell adhesion can be a potential problem as well as a valuable tool for microbiological engineering. It can lead to biofouling, contamination of product and corrosion. On the other hand, cell adhesion is purposely employed in fermenters and bioreactors to influence reactor performance. This paper presents an overview of organo-functional silanes – their chemistry, properties, use, and the main laboratory experiments that can be of interest to the food and beverage industry. The purpose is to introduce and explore possibilities for using organo-silane combinations to enhance or reduce microbial adhesion.