A Method of Combined SHPB Technique and BP Neural Network to Study Impact Response of Materials

Abstract:  A new method combining the split Hopkinson pressure bar (SHPB) technique with the back-propagation (BP) neural network program is proposed. By this method, the treated strain wave signals become smooth with less noises induced by the transverse inertia. Moreover, the dynamic rate-dependent constitutive behaviour of materials can be identified, without any pre-assumption of a constitutive model. It is found that by taking the experimentally measured data of strain, strain rate and time as 'input' and the corresponding data of stress as 'output' of the BP neural network, the dynamic constitutive behaviour with internal damage or phase transformation evolution is easy to be identified, where the time could represent either the internal damage evolution or phase transformation process accompanied with the deformation process. It is emphasised that the data learnt by the BP neural network must include both loading and unloading processes, if the whole loading and unloading response is to be correctly predicted. The comparisons between the predictions and experimental results are in good agreement for both polyamide (PA) polymer (as an example of nonlinear viscoelastic materials) and Ti–Ni alloy (as an example of superelastic materials with stress-induced phase transformation).     

水冷热模法离心铸造大口径球铁管用管模涂料

阐述水冷热模法管模涂料的组成。说明了耐火基料，悬浮剂、粘结剂，减水剂的各自作用机理，提出了合理的涂料配方、合适的喷涂方式。     

管内材料高温放气性能的测试及应用研究

管内材料放气性能的优劣直接影响着整管的性能和寿命.本文简介了测试管内材料高温放气性能的原理、装置和方法.文中列举的几项应用实例表明,本项测试结果对产品质量控制、工艺技术改进和材料进厂检验及国产化攻关都具有指导意义.     

圆管流动的二次转捩

利用直接数值模拟方法求解N-S方程来研究空间发展的圆管转捩,计算中雷诺数Re选定为3000。在局部壁面引入的周期性吹吸(PSB)扰动作用下,圆管中首先出现了塞流结构,并向下游迁移,同时有稳定的流向条带结构形成;在塞流结构离开计算域后,随着扰动的不断发展,流向条带结构逐渐破裂失稳,圆管流动出现了第二次转捩,这是一种新的转捩形式,我们称之为“二次转捩”。     

Prebiotic synthesis of sequential peptides on the Hadean beach by a molecular engine working with nitrogen oxides as energy sources

Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry.     

一种高性能图形板的设计与实现

介绍了一种采用高性能嵌入式图形处理器、大容量双端口视频存储器、高性能查色表以及超大规模可编程逻辑器件设计的图形显示控制板的基本组成和工作原理。     

城市RBD的成长机制与产业结构演变研究——以深圳华侨城为例

深圳华侨城是一个持续成长的休闲商务中心区的典型范例.在华侨城的成长和产业变迁过程中,休闲商务的发展具有很强的影响力.从城市边缘的华侨农场逐步发展为现代化城市中心区的RBD,华侨城演变的动力直接来源于4个方面:政策导向、市场导向、所有制导向和城市化导向.     

Dual bases for spline spaces on cells

The purpose of this paper is twofold. First, we extend the basic dimension result for spline spaces on simple cells to a class of spline spaces which satisfy additional smoothness conditions at the interior vertex. This extension is useful for the study of super spline spaces. Secondly, and more importantly, we show how to choose minimal determining sets of Bézier coordinates for these spaces. These in turn are useful for constructing explicit locally supported bases for spline spaces on general triangulations.     

The application of microencapsulated phase‐change materials to nylon fabric using direct dual coating method

The fabrication of functional textiles able to provide thermal regulation and comfort for the body has attracted increasing interest in recent years. This research investigated fabric coatings containing energy absorbing, temperature stabilizing, phase‐change material microcapsules (PCMMcs), and their methods of application. Specifically, a coated fabric was directly prepared by a dual‐type coating method, in which the PCMMcs were dispersed in a polyurethane coating solution with no binder. The thermal performances of the dual‐coated samples were evaluated by differential scanning calorimetry, and their physical characteristics were examined by scanning electron microscopy, thermal vision camera, porosity, water vapor transmission rate (WVTR), and water entry pressure (WEP) analyses. Furthermore, the microclimate characteristics of the thermally enhanced fabrics were investigated under experimental conditions using a human‐clothing‐environment (HCE) simulator system. The study results confirmed the superior performance of the dual‐coated fabrics in terms of thermal regulation and body comfort, compared with those coated by the dry or wet coating method, because of the improved WEP, WVTR, and thermal performance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Neutral fitness landscapes in signalling networks

Biological and technological systems process information by means of cascades of signals. Be they interacting genes, spiking neurons or electronic transistors, information travels across these systems, producing, for each set of external conditions, an appropriate response. In technology, circuits performing specific complex tasks are designed by humans. In biology, however, design has to be ruled out, confronting us with the question of how these systems could have arisen by accumulation of small changes. The key factor is the genotype-phenotype map. With the exception of RNA folding, not much is known about the exact nature of this mapping. Here, we show that structure of the genotype-phenotype map of simple feed-forward circuits is very close to the ones found in RNA; they have a large degree of neutrality, by which a circuit can be completely rewired keeping its input-output function intact, and there is a relatively small neighbourhood of a given circuit containing almost all the phenotypes.