Hydrodynamics of the initial phase of explosion

Physical and hydrodynamic processes accompanying explosions of condensed explosives and fuel–air mixtures have been considered. Wide-range equations of the state of explosion products and air have been derived. A physical model and a program code based on the equations of gas dynamics in Lagrangian representation have been developed for modeling one-dimensional hydrodynamic processes in the near zone of explosion. The described model has shown its working efficiency within a wide range of explosion energies and environmental conditions.     

Effect of different curing systems on the mechanical and physico-chemical properties of acrylonitrile butadiene rubber vulcanizates

In the present study, the effect of different curing systems including sulfur, dicumyl peroxide, dicumyl peroxide/coagent and radiation/coagent on the mechanical and physico-chemical properties of acrylonitrile butadiene rubber (NBR) was studied. In order to correlate, the effect of curing systems on rubber, the comparison was carried out at comparable value of volume fraction of rubber in swollen gel (V_r) for NBR vulcanizates. Mechanical properties like tensile strength, elongation at break, modulus, Young’s modulus, tearing strength and abrasion loss of vulcanizates have been followed up for comparison. In addition, physico-chemical properties like swelling ratio, soluble fraction, and cross-link density were investigated. On the other hand, the effects of fuel, thermogravimetric analysis, and thermal ageing have been studied.     

Mechanism of Bond Behavior of Concrete Beams Strengthened with Near-Surface-Mounted CFRP Rods

Bond tests were conducted on concrete beams strengthened with near-surface-mounted (NSM) nonprestressed and prestressed carbon fiber-reinforced polymer (CFRP) rods under static loading. In the NSM technique, the CFRP rods are placed inside precut grooves and bonded to the concrete with epoxy adhesive. Six concrete beams were tested. The test variables included presence of internal tension steel reinforcement (unreinforced and reinforced), use of NSM CFRP strengthening (nonprestressed and prestressed), and type of CFRP rod (spirally wound and sand blasted). The beams were tested statically in four-point bending. Based on the test results, the transfer length for the prestressed CFRP rod in epoxied groove was 150 and 210 mm for the sand blasted and spirally wound rods, respectively. The main failure mode was debonding between the CFRP rod and the epoxy that starts at sections close to the midspan then, as the load increases, it propagates toward the supports. At failure, the beams strengthened with a given rod type showed the same CFRP strain at sections close to the support (29% of ultimate strain for spirally wound bars and 39% of ultimate strain for sand blasted bars). A cracked section analysis was carried out and compared well with the measured results.     

Deformation twins and related softening behavior in nanocrystalline Cu–30% Zn alloy

Nanocrystalline Cu–30% Zn samples were produced by high energy ball milling at 77 K and room temperature. Cryomilled flakes were further processed by ultrahigh strain high pressure torsion (HPT) or room temperature milling to produce bulk artifact-free samples. Deformation-induced grain growth and a reduction in twin probability were observed in HPT consolidated samples. Investigations of the mechanical properties by hardness measurements and tensile tests revealed that at small grain sizes of less than ～35 nm Cu–30% Zn deviates from the classical Hall–Petch relation and the strength of nanocrsytalline Cu–30% Zn is comparable with that of nanocrystalline pure copper. High resolution transmission electron microscopy studies show a high density of finely spaced deformation nanotwins, formed due to the low stacking fault energy of 14 mJ m^–2 and low temperature severe plastic deformation. Possible softening mechanisms proposed in the literature for nanotwin copper are addressed and the twin-related softening behavior in nanotwinned Cu is extended to the Cu–30% Zn alloy based on detwinning mechanisms.     

Kinetics and mechanism of olefin methylation reactions on zeolites

Ethylene and propylene methylation rates increased linearly with olefin pressure but did not depend on dimethyl ether (DME) pressures on proton-form FER, MFI, MOR, and BEA zeolites at low conversions (<0.2%) and high DME/olefin ratios (30:1) in accordance with a mechanism that involves the zeolite surface being predominantly covered by DME-derived species reacting with olefins. Higher first-order reaction rate constants for both ethylene and propylene methylation were observed over H-BEA and H-MFI compared with H-FER and H-MOR, indicating that olefin methylation reaction cycles involved in the conversion of methanol-to-gasoline over zeolitic acids are propagated to varying extents by different framework materials. Systematically lower activation barriers and higher rate constants were observed for propylene methylation in comparison with ethylene methylation over all frameworks studied, reflecting the increased stability of reaction intermediates and activated complexes with increasing olefin substitution. A binomial distribution of d₀/d₃/d₆ in unreacted DME upon introduction of equimolar protium- and deuterium-form DME under steady-state reaction conditions of ethylene methylation over H-MFI suggests the presence and facile formation of reactive surface-bound methoxide species and the absence of C–H bond cleavage.     

A neural network model for the assessment of partners’ performance in virtual enterprises

In response to increasing international competition, enterprises have been investigating new ways of cooperating with each other to cope with today’s unpredictable market behaviour. Advanced developments in information & communication technology (ICT) enabled reliable and fast cooperation to support real-time alliances. In this context, the virtual enterprise (VE) represents an appropriate cooperation alternative and competitive advantage for the enterprises. VE is a temporary network of independent companies or enterprises that can quickly bring together a set of core competencies to take advantage of market opportunity. In this emerging business model of VE, the key to enhancing the quality of decision making in the partner companies’ performance evaluation function is to take advantage of the powerful computer-related concepts, tools and technique that have become available in the last few years. This paper attempts to introduce a neural network model, which is able to contribute to the extrapolation of the probable outcomes based on available pattern of events in a virtual enterprise. Quality, delivery and progress were selected as determinant factors effecting the performance assessment. Considering the features of partner performance assessment and neural network models, a back-propagation neural network that includes a two hidden layers was used to evaluate the partner performance.     

End‐to‐End Deep Learning Methodology for Real‐Time Traffic Network Management

This article presents a novel real‐time traffic network management system using an end‐to‐end deep learning (E2EDL) methodology. A computational learning model is trained, which allows the system to identify the time‐varying traffic congestion pattern in the network, and recommend integrated traffic management schemes to reduce this congestion. The proposed model structure captures the temporal and spatial congestion pattern correlations exhibited in the network, and associates these patterns with efficient traffic management schemes. The E2EDL traffic management system is trained using a laboratory‐generated data set consisting of pairings of prevailing traffic network conditions and efficient traffic management schemes designed to cope with these conditions. The system is applied for the US‐75 corridor in Dallas, Texas. Several experiments are conducted to examine the system performance under different traffic operational conditions. The results show that the E2EDL system achieves travel time savings comparable to those recorded for an optimization‐based traffic management system.     

室内自然通风模拟在零能耗建筑中的应用--基于零能耗太阳能住宅原型数值模拟优化设计

居住环境室内空气品质与人体健康息息相关。目前住宅的室内通风以自然通风为主,但如何通过有序的、有组织地对室内自然通风进行有效的物理环境设计,采用数值模拟分析方法进行客观评价并优化设计。以天津大学零能耗太阳能住宅原型为研究对象,针对天津地区相同室内外边界条件、不同模型下的气流组织工况,运用AIRPARK2.1模拟软件对零能耗住宅建筑室内的自然通风模式进行不同工况的模拟计算优化设计,在此基础上提出优化设计方案,以指导零能耗建筑的节能设计。     

Prioritizing barriers to successful business process re‐engineering (BPR) efforts in Saudi Arabian construction industry

Engaging in business process re‐engineering (BPR) efforts could prove to be highly rewarding for construction companies in Saudi Arabia. However, BPR is risky and could be disastrous if not properly approached. To enable sound BPR efforts and increase success chances, thorough investigation of barriers is essential. This study presents 29 barriers, with their influence (strength) on the success of BPR initiatives. Additionally, these barriers are ranked according to the ease of overcoming each. Finally, a graphical aid is provided to enable decision makers to concentrate their efforts on the most influential (strongest), yet easiest to overcome barriers. Following inadequate approach, affected people not informed, culture of construction firms, using inappropriate tools, using external consultants, undefined core processes, and fear and resistance to change are the most important barriers to successful BPR endeavours.     

What happened to Abu Dhabi’s urbanism? The question of regional integration

Neighbourhoods designed for Emirati citizens form more than 50% of Abu Dhabi’s urbanized land. As a result of planning strategies that neglect regionalism, these percentages are likely to grow in an unsustainable manner. This study traces these neighbourhoods’ morphological evolution towards the goal of identifying urban attributes that encourage cohesive growth. The analysis identifies three periods in Abu Dhabi’s neighbourhood morphology: the Inception Period (1967–1975), characterized by diversity, close-knit neighbourhoods, environmentally sensitive planning and integration with adjacent neighbourhoods and the city fabric; the Dispersion Period (1975–2007), characterized by fragmentation, massive expansion, parcel inflation and restricted integration with existing fabrics; and the Redemption Period (2007–present), characterized by nostalgic historicism, densification, parcel deflation and sparse regional integration. Neighbourhood typologies developed after the 1980s failed to conceive of physical planning at different scales. This failure led to a lack of environmental stewardship in efforts to meet citizens’ housing needs. Future development must take into account both cultural affinities and environmental effects and create effective compromises between these two priorities. Instead of relying on foreign experts, Abu Dhabi must involve local planners and academics in the construction of a new policy agenda that promotes the integration of different planning scales.