Measurements and statistical model calculations of activation cross-sections for 26Mg(n,α)23Ne reaction between 13.6 and 14.9 MeV neutron energies

Activation cross-sections were measured at neutron energies from 13.6 to 14.9 MeV for the reaction ²⁶Mg(n,α)²³Ne. The production of relatively short-lived activity and the spectra accumulation have been carried out by the cyclic activation method. Corrections were made for the effects of gamma-ray attenuation, random coincidence summing (pulse pile-up), dead time, and scattered low energy neutron contribution. Statistical model calculations for which the pre-equilibrium emission effects are taken into consideration were also performed. Results were compared with the previous investigations.     

Construction safety issues in Gaza Strip

Safety is considered a critical problem in developed and developing countries. The author examines the causes of accidents on building sites and the safety procedures used by local contractors in Gaza Strip. A wide range of recommendations are necessary if hazards are to be eliminated and accidents reduced. Recommendations include a suitable training programme, supervisory methods for product quality and working conditions on site, improved working conditions, a safety regulatory framework including a safety institution, standards, and penalties. La securite est consideree comme un probleme critique dans les pays industrialises et dans les pays en developpement. L'auteur examine les causes des accidents sur les chantiers de construction dans la Bande de Gaza ainsi que les procedures de securite appliquees par les entreprises locales. Pour eliminer les dangers et reduire le nombre d'accidents, il conviendrait de formuler de nombreuses recommandations portant, notamment, sur un programme de formation approprie, des methodes de suivi de la "qualito produits" et de supervision des conditions de travail sur les chantiers. Il faudrait d'ailleurs ameliorer ces conditions et definir un cadre de reglementation en matiere de securite comprenant, entre autres, la creation d'un institut de la securite, l'elaboration de normes et la mise en place d'un mecanisme de penalites.     

A Low Cost Route Optimization Scheme for Cluster-Based Proxy MIPv6 Protocol

Proxy Mobile IPv6 (PMIPv6) is a network based mobility protocol which has been designed to relieve the mobile nodes (MNs) from participating in the mobility process and to reduce the long handoff latency of the MIPv6 protocol. However, PMIPv6 incurs a long communication path due to the triangle routing problem, in which, all packets sent by MNs are obligated to pass through the local mobility anchor. Several solutions have been proposed to mitigate this issue. However, they still incur high signaling overhead to recover the Route Optimization (RO) status after handoff. In this paper, we propose a Cluster-Based RO (CBRO) scheme for the clustered architecture of the PMIPv6, in which, the Mobile Access Gateways (MAGs) are grouped into clusters with a distinguished Head MAG (HMAG) for each. In the proposed CBRO, the RO process is relied on the HMAGs to reduce the handoff latency while achieving a fast recovery of the optimized path after handoff. The proposed CBRO is evaluated analytically and compared with the basic PMIP and the current RO schemes. The obtained numerical results have shown that the proposed CBRO outperforms all other schemes in terms of signaling cost required to recover the RO status after handoff and the total cost performance metrics.     

工艺参数设置和厚度对电子束熔融加工Ti-6Al-4V合金微观结构的影响

研究了试件尺寸和工艺参数(电子束强度,扫描速度,焦点偏移量和扫描长度)对电子束熔融(EBM)加工Ti-6Al-4V合金微观结构的影响。结果表明,可以观察到EBM加工的Ti-6Al-4V合金的微观结构由原始β相的柱状晶粒组成。在柱状晶粒内部观察到典型的(α+β)结构,即魏氏体α片和在细小的α晶粒的界面上形成的杆状β相。还发现沿原始β柱状晶粒的晶界形成的α层晶界。随着试件厚度、电子束能量密度和扫描长度的增加,先前的β柱状晶粒的直径增大,并且生长的方向与加工方向一致。同时,柱状晶粒直径随着试件高度的增加而减小。随着试件厚度和电子束能量密度的增加,α片会变得更粗大。     

Progressive collapse of 2D reinforced concrete structures under sudden column removal

Once a column in building is removed due to gas explosion, vehicle impact, terrorist attack, earthquake or any natural disaster, the loading supported by removed column transfers to neighboring structural elements. If these elements are unable to resist the supplementary loading, they continue to fail, which leads to progressive collapse of building. In this paper, an efficient strategy to model and simulate the progressive collapse of multi-story reinforced concrete structure under sudden column removal is presented. The strategy is subdivided into several connected steps including failure mechanism creation, MBS dynamic analysis and dynamic contact simulation, the latter is solved by using conserving/decaying scheme to handle the stiff nonlinear dynamic equations. The effect of gravity loads, structure-ground contact, and structure-structure contact are accounted for as well. The main novelty in this study consists in the introduction of failure function, and the proper manner to control the mechanism creation of a frame until its total failure. Moreover, this contribution pertains to a very thorough investigation of progressive collapse of the structure under sudden column removal. The proposed methodology is applied to a six-story frame, and many different progressive collapse scenarios are investigated. The results illustrate the efficiency of the proposed strategy.     

Comparison of the sensory profiles of regular and reduced-fat commercial processed cheese spreads

The sensory character of 16 samples of commercial, processed cheese spread has been characterized. Samples were selected to provide information on variations both between brands and, for products differing in fat content, within brands. Products were rated for eight flavour attributes and six textural attributes by a panel of 13 professional assessors. Significant differences in both the flavour and the texture of the spreads were associated with brand. No systematic differences were found between the flavour attributes and the fat content of the spread. However, differences were revealed between spreads – classified on the basis of fat content as regular, light and ultra light – in the sensory dimensions associated with texture and mouth feel. Nevertheless, within some brands the effect of reducing fat content was minimal. This result was probably achieved by other changes in product formulation.     

Construction projects and the environment in Palestine

Continuing the series of papers on construction in Palestine, one of the most densely populated areas in the world, the author concentrates on the need for harmonized development to sustain the environment. An analysis of the Gaza seaport project demonstrates the need to educate professionals working within the construction industry on environmental issues, in particular the steps needed in carrying out the environmental impact assessment of any construction project. The author believes that further studies to increase knowledge are needed. Poursuivant sa serie d'articles sur les activites du batiment en Palestine, l'une des regions les plus peuplees au monde, l'auteur se penche ici sur la necessite d'un amenagement harmonise soucieux de l'environnement et s'inscrivant dans la duree. Suite a une analyse du projet de port: maritime a Gaza, il apparait clairement que les professionnels du secteur de la construction ont besoin d'une formation dans le domaine de la protection de l'environnement, en particulier pour la realisation d'etudes d'impact sur l'environnement de projets de construction. L'auteur estime que des etudes complementaires sont necessaires pour approfondir les connaissances en la matiere.     

Microwave preheating of anisotropic conductive adhesive films for high-speed flip chip on flex bonding

Anisotropic conductive adhesive film (ACF) can be preheated by microwave (MW) radiation in order to reduce the bonding time for flip-chip technology. Due to sluggish and nonuniform curing kinetics at the beginning of the curing reaction, thermal curing of epoxy is more time consuming. Therefore, MW radiation may be more effective, due to its uniform heating rate during the cycle. In this paper, MW preheating (for 1–4 sec) of ACF prior to final bonding has been applied to determine the electrical and mechanical performance of the bond. Powers of 80 and 240 W MW were used to study the effect of the MW preheating. A final bonding time of 6–7 sec can be used for flip chip on flex bonding instead of 10–15 sec (standard time for flip chip bonding) for MW preheating time and power used in this study. The contact resistance (as low as 0.01) is low in these samples, whereas the standard resistance is 0.017 ohm (bonded at 180°C for 10 sec without prior MW preheating). The shear forces at breakage were satisfactory (0.167–0.183 KN) for the samples bonded for 6–7 sec with MW preheating. This is very close and even higher than the standard sample (0.173 KN). For MW preheating power of 80 W and sweeping time of 2 sec, final bonding at 6 sec can also be used because of its low contact resistance (0.019 ohm). Scanning electron microscope (SEM) investigation of microjoints and fracture surface shows uneven distribution of conductive particles and thick bond lines in samples bonded for 5 sec (with MW preheating). Samples treated with MW radiation (80 W and 2–3 sec time) serve as evidence that well-distributed particles along with thin bond lines cause low contact resistance and high joint strength.     

Microscale and mesoscale discrete models for dynamic fracture of structures built of brittle material

In this work we present the discrete models for dynamic fracture of structures built of brittle materials. The models construction is based on Voronoi cell representation of the heterogeneous structure, with the beam lattice network used to model the cohesive and compressive forces between the neighboring cells. Each lattice component is a geometrically exact shear deformable beam which can describe large rigid body motion and the most salient fracture mechanisms. The latter can be represented through the corresponding form of the beam constitutive equations, which are derived either at microscale with random distribution of material properties or at a mesoscale with average deterministic values. The proposed models are also placed within the framework of dynamics, where special attention is paid to constructing the lattice network mass matrix as well as the corresponding time-stepping schemes. Numerical simulations of compression and bending tests is given to illustrate the models performance.     

基于加载算法的室内无线信道OFDM接收机的性能

本文研究了无线局域网中使信号频谱得到优化的一种简单OFDM子载波加载算法。此算法基于边缘自适应（Margin Adaptive）加载准则及其在室内无线信道上的性能。