先进高强钢DP590焊缝的组织特征和力学性能改善

The effects of the welding current mode in resistance spot welding on the microstructure and mechanical properties of advanced high-strength steel dual-phase 590 (DP590) sheets were investigated. Results showed that a rough martensitic structure was formed in the weld zone of the sample welded via the single-pulsed mode, whereas the microstructure in the heat-affected zone consisted of a very rough martensitic microstructure and rough ferrite. However, using the secondary pulse mode led to the formation of tempered martensite in the weld zone. The maximum load and the energy absorption to failure of the samples with the secondary pulsed cycle were higher than those of the samples with the single-pulsed mode. Tensile shear results indicated that the secondary pulsed mode could significantly change the mode of failure upon shear tension testing. Therefore, the obtained results suggest that the use of secondary pulsed mode can improve the microstructural feature and mechanical properties of advanced high-strength steel DP590 welds.     

Developing a Cybernetics Approach to Analysing Inclusive Growth Constraints

Inclusive and sustainable economic growth supports the transformation of society towards a better quality of life and well-being. Therefore, it is crucial to diagnose the binding factors to growth. However, existing frameworks of growth diagnostics and inclusive growth analytics, which are widely used to analyse growth problems, mainly focused on a snapshot of growth constraints of a selected location at a particular point of time. Applications of these frameworks are not fully capable of addressing the dynamic nature of growth. Moreover, most existing applications of growth frameworks are mainly predictive studies, thus they do not fully support the effort of identifying the root cause of growth problem. This calls for a more comprehensive approach to diagnosing growth problems. Building upon the existing growth diagnostics and inclusive growth analytics frameworks, as well as on cybernetics and systems-based approach, we develop a cybernetics approach to analysing inclusive growth constraints. This approach enables analysis of the dynamic nature of growth, which supports the identification of growth constraint variables and mapping of their relationships, based on data gathered about the location.     

Design and Manufacture of a Wax Injection Tool for Investment Casting Using Rapid Tooling

A rapid wax injection tool of a gearbox shift fork was designed, simulated, and manufactured using rapid prototyping and rapid tooling technology to save time and cost of producing wax models used for the investment casting process. CAE simulation softwares, in particular, MoldFlow, are used to get wax injection moulding parameters such as filling parameters, temperature profiles, freeze time, speed, and pressure. The results of this research were compared with conventional wax model production methods. The criteria of such comparison were based upon parameters such as time, cost, and other related characteristics, which resulted in saving of 50% in time and 60% in cost. In this research, design, assembly, and wax injection operation of the wax tool took 10 days. Considering the fact that wax melting temperature is as low as 70℃ and injection pressure of 0.5 MPa, the tool suffers no damage due to the thermal and pressure stresses, leading to the mass production of wax models.     

不同条件下铱负载催化剂性能的比较研究

To discuss the potential role of iridium (Ir) nanoparticles loaded under atmospheric and high pressures, we prepared a series of catalysts with the same active phase but different contents of 10wt%, 20wt%, and 30wt% on gamma-alumina for decomposition of hydrazine. Under atmospheric pressure, the performance of the catalyst was better when 30wt% of the Ir nanoparticles was used with chelating agent that had greater selectivity of approximately 27%. The increase in the reaction rate from 175 to 220 h?1 at higher Ir loading (30wt%) was due to a good dispersion of high-number active phases rather than an agglomeration surface. As a satisfactory result of this investigation at high pressure, Ir catalysts with different weight percentages showed the same stability against crushing and activity with a characteristic velocity of approximately 1300 m/s.     

Evaluating the Impacts of Virtual Organization Absorption on the Quality of Urban Private Constructions; the System Dynamics Approach

Quality compliance checking of urban private constructions in Iran follows a fragmented pattern. By considering this fragmentation along with the inherent complexities of the quality compliance checking, it becomes urgent to look closer at this mechanism to find a way for making improvements. Since there is no determination to change the existing mechanism, this study discusses the use of virtual organizations as a strategy to enhance the level of quality. To this end, according to the intended approach for developing virtual organizations, this study identifies the capabilities of this type of systems in the first step. Then, this research evaluates the impacts of virtual organization absorption on the quality of urban private constructions. In this evaluation, the paper applies the system dynamics approach as the modeling tool due to its ability to address complexities and feedback structures. The resulted dynamic model needs initial values and requires functions to be able to run the simulation. In this case, the Delphi Technique is used to extract the functions and the values. After importing the resulted values and functions into the model, the focus group is used for the validation. The result of this analysis represents the positive impacts of the virtual organization absorption in the quality compliance checking mechanism. Fifty-percent improvement in the quality level of urban private constructions after a twenty-year period is one of the results, which could be considered as an indicator of virtual organization impacts.

     

Aminopeptidase N is a major receptor for the entero-pathogenic coronavirus TGEV.

Coronaviruses, like many animal viruses, are characterized by a restricted host range and tissue tropism. Transmissible gastroenteritis virus (TGEV), a major pathogen causing a fatal diarrhoea in newborn pig, replicates selectively in the differentiated enterocytes covering the villi of the small intestine. To investigate the molecular determinants of the infection, we characterized the surface molecule used by the virus for binding and entry into host cells. Here we report that aminopeptidase N, an ectoenzyme abundantly expressed at the apical membrane of the enterocytes, serves as a receptor for TGEV. Monoclonal antibodies were selected for their ability to block infection by TGEV of porcine cell lines. They recognized a brush-border membrane protein of M(r) 150K, which was identified as aminopeptidase N by amino-terminal sequencing. Two lines of evidence supported the view that the peptidase itself acts as a receptor. First, virions bound specifically to aminopeptidase N that was purified to homogeneity. Second, recombinant expression of aminopeptidase N conferred infectivity by TGEV to an otherwise non-permissive cell line.     

多元间歇精馏塔生产调度的优化

在间歇精馏塔单塔操作优化的基础上,实行多塔生产调度的优化。适当地安排各座塔的处理任务,按一定的规律交替地处理原料和中间产物,使其所需的时间为最短。本文提出的启发式优化调度方案简单易行,得到的生产调度直方图直观易读。仿真结果表明,经济效益显著,且可推广解决类似的工业生产调度问题。     

Design and Manufacture of a Wax Injection Tool for Investment Casting Using Rapid Tooling

A rapid wax injection tool of a gearbox shift fork was designed, simulated, and manufactured using rapid prototyping and rapid tooling technology to save time and cost of producing wax models used for the investment casting process. CAE simulation softwares, in particular, MoldFlow, are used to get wax injection moulding parameters such as filling parameters, temperature profiles, freeze time, speed, and pressure. The results of this research were compared with conventional wax model production methods. The criteria of such comparison were based upon parameters such as time, cost, and other related characteristics, which resulted in saving of 50% in time and 60% in cost. In this research, design, assembly, and wax injection operation of the wax tool took 10 days. Considering the fact that wax melting temperature is as low as 70°C and injection pressure of 0.5 MPa, the tool suffers no damage due to the thermal and pressure stresses, leading to the mass production of wax models.     

Similarity solutions for the mixed convection flow over a vertical plate with thermal radiation

The steady laminar boundary layer flow adjacent to a vertical plate with prescribed surface temperature immersed in an incompressible viscous fluid, where the effect of thermal radiation was taken into consideration, was investigated. The governing partial differential equations were transformed into a system of ordinary differential equations using similarity transformation, before being solved numerically by the shooting method. Both assisting and opposing buoyant flows were considered. It is found that dual solutions exist for both cases. Moreover, numerical results show that the heat transfer rate at the surface decreases in the presence of the radiation effect.