Modeling,Simulation and Control of Pulsed DE-GMA Welding Process for Joining of Aluminum to Steel

Joining of aluminum to steel has attracted significant attention from the welding research community,automotive and rail transportation industries.Many current welding methods have been developed and applied,however,they can not precisely control the heat input to work-piece,they are high costs,low efficiency and consist lots of complex welding devices,and the generated intermetallic compound layer in weld bead interface is thicker.A novel pulsed double electrode gas metal arc welding（Pulsed DE-GMAW）method is developed.To achieve a stable welding process for joining of aluminum to steel,a mathematical model of coupled arc is established,and a new control scheme that uses the average feedback arc voltage of main loop to adjust the wire feed speed to control coupled arc length is proposed and developed.Then,the impulse control simulation of coupled arc length,wire feed speed and wire extension is conducted to demonstrate the mathematical model and predict the stability of welding process by changing the distance of contact tip to work-piece（CTWD）.To prove the proposed PSO based PID control scheme’s feasibility,the rapid prototyping experimental system is setup and the bead-on-plate control experiments are conducted to join aluminum to steel.The impulse control simulation shows that the established model can accurately represent the variation of coupled arc length,wire feed speed and the average main arc voltage when the welding process is disturbed,and the developed controller has a faster response and adjustment,only runs about 0.1 s.The captured electric signals show the main arc voltage gradually closes to the supposed arc voltage by adjusting the wire feed speed in 0.8 s.The obtained typical current waveform demonstrates that the main current can be reduced by controlling the bypass current under maintaining a relative large total current.The control experiment proves the accuracy of proposed model and feasibility of new control scheme further.The beautiful and smooth weld beads are also obtained by t     

The mechanical properties of natural fibre based honeycomb core materials

This paper investigates the compression properties of square and triangular honeycomb core materials based on co-mingled flax fibre reinforced polypropylene (PP) and polylactide (PLA) polymers. Initial testing focused on investigating the sensitivity of the tensile properties of the composites to variations in processing conditions. Following this, a range of triangular and square honeycomb structures were manufactured using a simple slotting technique. These structures were tested in compression at quasi-static rates of strain and their strength and specific energy absorption characteristics were determined. Finally, a finite element analysis was undertaken to accurately predict the strength, energy-absorbing characteristics, buckling behaviour and failure modes of these natural fibre based core materials.     

当归红芪超滤物对重离子12C6+辐射肝癌细胞DNA损伤修复的影响

将人肝癌H22细胞分成4组,分别为对照组、药物组(100 mg/L)、辐射组(2 Gy)及联合组(100 mg/L药物 + 2 Gy照射),采用CCK-8法、单细胞凝胶电泳、γ-H2AX免疫荧光原位杂交技术以及Western Blotting印迹法,研究当归红芪超滤物(Radix Angelicae Sinensis and Radix Hedysari, RAS-RH)对重离子¹²C⁶⁺辐射引起人肝癌H22细胞DNA损伤修复的影响和其可能的机制。结果表明,在0～72 h和给药剂量为5～200 mg/L范围内,RAS-RH对人肝癌H22细胞的增殖抑制作用具有时间和剂量依赖性,其20%抑制浓度IC₂₀为(117.6±2.15)mg/L;单细胞凝胶电泳显示联合组头部DNA含量低于辐射组,而尾部DNA含量、尾距TM、Olive尾距OTM均高于辐射组;γ-H2AX免疫荧光原位杂交技术发现RAS-RH不增加重离子¹²C⁶⁺辐射引起的DNA损伤,但在2—12 h,DNA双链断裂的γ-H2AX foci修复作用被RAS-RH抑制,DNA损伤持续存在;Western Blotting显示RAS-RH通过下调Ku70/80及Rad51的蛋白表达,抑制γ-H2AX的聚集。以上结果说明RAS-RH对人肝癌H22细胞的辐射增敏作用可能是下调DNA损伤修复相关因子Ku70/80及Rad51的表达。     

A new approach to visualizing time-varying sensitivity indices for environmental model diagnostics across evaluation time-scales

Assessing the time-varying sensitivity of environmental models has become a common approach to understand both the value of different data periods for estimating specific parameters, and as part of a diagnostic analysis of the model structure itself (i.e. whether dominant processes are emerging in the model at the right times and over the appropriate time periods). It is not straightforward to visualize these results though, given that the window size over which the time-varying sensitivity is best integrated generally varies for different parameters. In this short communication we present a new approach to visualizing such time-varying sensitivity across time scales of integration. As a case study, we estimate first order sensitivity indices with the FAST (Fourier Amplitude Sensitivity Test) method for a typical conceptual rainfall–runoff model. The resulting plots can guide data selection for model calibration, support diagnostic model evaluation and help to define the timing and length of spot gauging campaigns in places where long-term calibration data are not yet available.     

Empirical study of open source software selection for adoption,based on software quality characteristics

Currently, open source software (OSS) products have started to become popular in the market as an alternative to traditional proprietary or closed source software. Governments and organizations are beginning to adopt OSS on a large scale and several governmental initiatives have encouraged the use of OSS in the private sector. One major issue for the government and private sector is the selection of appropriate OSS. This paper uses new internal quality characteristics for selecting OSS that can be added to the dimensions of DeLone and McLean information systems’ model. Through this study, the quality characteristics are organized in a two level hierarchy, which list characteristics and sub-characteristics that are interconnected with three main dimensions: system quality, information quality and service quality. These characteristic dimensions are tailored to the criteria having been built from literature study and standard for software quality and guidelines. This paper presents case study results of applying the proposed quality characteristic on eight different open source software that are divided between open source network tools and learning management systems.     

First-Principles Study on the (111) Surface of Half-Metallic CsN

Using the full-potential local-orbital minimum-basis method based on electronic structure calculations, we have probed the structural, electronic, and magnetic properties of the (111) surface of CsCl-type CsN. Our results indicate that bulk CsN is found to be a half-metallic ferromagnet at equilibrium lattice constant with a total spin magnetic moment of 2.0 μB per formula unit. At the same equilibrium lattice constant, the Cs-terminated (111) and N-terminated (111) surfaces preserve the half-metallic characteristics of the bulk CsN. In addition, we also show that the Cs-terminated (111) surface is energetically more stable than the N-terminated (111) surface.     

Clustering by Sorting Potential Values (CSPV): A novel potential-based clustering method

A novel clustering method called Clustering by Sorting Potential Values (CSPV) is proposed. The clustering is done in an efficient tree-growing fashion based on both the distances and the hypothetical potential values produced from the distribution of all the data points. The method is simple but is shown to be very effective in identifying different kinds of clusters. It outperforms four popular clustering methods in most of our experiments and is the only one that works for all the six studied data sets. Moreover, it is designed as a generic method which can be easily applied to different clustering problems.     

CFD analysis of the ITER first wall 06 panel. Part I: Model set-up and flow distribution

The first detailed Computational Fluid Dynamics (CFD) analysis of the FW06 panel of the ITER shielding blanket is presented in two companion papers. In this Part I we introduce the problem, define the model together with its input and discuss the results with particular reference to the hydraulics of the water coolant. The pressure drop across the panel is computed, together with the distribution of the flow among the different channels. Different design options are studied, with particular reference to the minimization of stagnation/recirculation regions.     

Water stability mechanism of silicification grouted loess

Silicification is one of the chemical stabilisation methods used in the treatment of collapsible loess soils. The water stability therein is a key parameter in the silicification of grouted loess. Based on slaking tests, permeability measurement, X-ray diffraction spectra, X-ray energy dispersive spectroscopy, and scanning electron microscopy, the water stability mechanism inherent in the CO₂-silicification grouted loess was investigated. Samples of original, compacted, and CO₂-silicification grouted loess in 30 days curing were tested. To assess the long-term water stability, CO₂-silicification grouted loess samples in 13, 19, and 24 years of curing were analysed. The study showed that the CO₂-silicification grouted loess had good water erosion resistance, no disintegration, and good water stability over time. The water stability of CO₂-silicification grouted loess depended on the strong bond strength of the grains and a low permeability. The complex physicochemical reactions among CO₂, water, alkali earth metal salts, clay minerals, and organic matter in loess produced hydrate calcium (and magnesium) silicate gels, which were mainly coated on the surface of the soil skeleton grains and original cements. A few filled in the trellis pores. The gels coated on the soil skeleton limit the hydrophilicity of clay minerals and organic matter and improve water resistance, and if coated on original cements reinforce bond strength, consequently, the water stability of CO₂-silicification grouted loess was improved.     

Determination of biomass accumulation in mixed belts of Salix,Corylus and Alnus species in combined food and energy production system

Given the energetic, demographic and the climatic challenges faced today, we designed a combined food and energy (CFE) production system integrating food, fodder and mixed belts of Salix, Alnus and Corylus sp. as bioenergy belts. The objective was to assess the shoot dry weight-stem diameter allometric relationship based on stem diameter at 10 (SD₁₀) and 55 cm (SD₅₅) from the shoot base in the mixed bioenergy belts. Allometric relations based on SD₁₀ and SD₅₅ explained 90–96% and 90–98% of the variation in shoot dry weights respectively with no differences between the destructive and the non-destructive methods. The individual stool yields varied widely among the species and within willow species with biomass yield range of 37.60–92.00 oven dry tons (ODT) ha⁻¹ in 4-year growth cycle. The biomass yield of the bioenergy belt, predicted by allometric relations was 48.84 ODT ha⁻¹ in 4-year growth cycle corresponding to 12.21 ODT ha⁻¹ year⁻¹. The relatively high biomass yield is attributed to the border effects and the ‘fertilizing effect’ of alder due to nitrogen fixation, benefitting other SWRC components. On termination of 4-year growth cycle, the bioenergy belts were harvested and the biomass yield recorded was 12.54 ODT ha⁻¹ year⁻¹, in close proximity to the biomass yield predicted by the allometric equations, lending confidence and robustness of the model for biomass yield determination in such integrated agro-ecosystem.