Experimental investigation,intelligent modeling and multi-characteristics optimization of dry WEDM process of Al–SiC metal matrix composite

Dry wire electrical discharge machining (WEDM) is an environmentally friendly modification of the oil WEDM process in which liquid dielectric is replaced by a gaseous medium. In the present work, parametric analysis has been fulfilled while dry WEDM of Al–SiC metal matrix composite. Experiments were designed and conducted based on L₂₇ Taguchi's orthogonal array to study the effect of pulse on time, pulse off time, gap voltage, discharge current, wire tension and wire feed on cutting velocity (CV) and surface roughness (SR). Firstly, a series of exploratory experiments has been conducted to identify appropriate gas and wire material based on the values of cutting velocity. After selection of best gas and best wire, they were used for later stage of experiments. Analysis of variances (ANOVA) has been performed to identify significant factors. In order to correlate relationship between process inputs and responses, an adaptive neuro-fuzzy inference system (ANFIS) has been employed to predict the process characteristics based on experimental observation. At the end, an artificial bee colony (ABC) algorithm has been associated with ANFIS models to maximize CV and minimize SR, simultaneously. Then the optimal solutions that obtained through ANFIS-ABC technique have been compared with numbers of confirmatory experiments. Results indicated that oxygen gas and brass wire guarantee superior cutting velocity. Also, according to ANOVA, pulse on time and discharge current were found to have significant effect on CV and SR. In modeling of CV and SR by ANFIS, it was resulted that the proposed method has superiority in prediction of them in the ranges of factors beyond the training condition. Also, association of ANFIS with ABC can find the optimal combination of process parameters accurately according to the confirmatory experiments.     

Mathematical model for abrasive content estimation in a pulse-electroplated abrasive microtool

A mathematical model was developed to estimate the weight percent of diamond abrasive particles incorporated in nickel binder matrix during abrasive microtool fabrication by pulse-plating process. The proposed model is based on the hypothesis that, embedment of an inert micro abrasive diamond particle on the substrate will only occur when a few nickel ions from the adsorbed ionic cloud are chemically reduced at the cathode by hydrogen ions present in the diffusion layer. Experimental verification of the model developed was performed by pulse electroplating of diamond abrasive particles on tungsten micro tool shank using an in-house built experimental setup. The predictive model developed was found to estimate diamond abrasive content in nickel binder matrix within 1–7 wt% of experimental results for different pulse-plating conditions.     

A Study of the Optimization of Sheet Metal Drawing with Active Drawbeads

An experimental study is described in which active drawbead technology is used to attempt to optimize the sheet metal forming process. Oval AA 6111-T4 panels were drawn in a series of tests using various drawbead trajectories to establish the feasibility of the approach. The selection of drawbead trajectory was shown to have a dramatic effect on maximum attainable draw depth at fracture. Increasing drawbead penetration from zero to 5 mm in the early stages of the drawing process and retracting midway through the draw resulted in a 40% increase in draw depth compared to using a fixed 5 mm penetration. In the second part of the investigation, active drawbead technology was used to study its effect on highly nonsymmetric panel forming. Drawing limit curves in terms of drawbead depth versus blankholder forces (BHF) were plotted, and different drawbead trajectories were tested to determine an optimal drawbead trajectory scheme. A corresponding finite element model was also created. The results of strain path analysis successfully support the experiments.     

Shared control of robotic friction stir welding in the presence of imperfect joint fit-up

In this paper a shared control strategy is presented that allows a skilled operator to identify irregularities that occur during robotic friction stir welding (FSW) and assist the robotic system in producing an appropriate response. Human operators are adept at identifying disturbances; however, the complexity of the friction stir welding process makes it difficult for the operator to respond. While examining the capabilities of shared control in friction stir welding, this paper focuses on responding to defects that are caused by a lack of workpiece material during butt welding, such as gaps. A compensation strategy is presented that combines the human operator's perceptual strengths with an automated procedure for adjustment of the process parameters (i.e. travel angle and plunge depth). Experiments comparing four control strategies are performed while welding 5083-H116 aluminum. Through our experiments we demonstrate that if the FSW control task is appropriately shared between the human operator and the computer control system, the weld quality (strength) can be improved (from 9 ksi to 31 ksi for a gap size of 2.5 mm) as compared with the nominal case in which no corrections are made.     

Development and characterization of microwave composite cladding

The development of cladding through microwave radiation is recently explored and very few, initial studies were reported elsewhere. In order to explore more viability of process, (EWAC (Ni based) + 20% Cr₂₃C₆ powder) composite cladding has been developed on substrate austenitic stainless steel (SS-316). The experiments were conducted in domestic microwave oven and the clad of thickness, approximate 500 m has been developed by the exposure of microwave radiation at frequency 2.45 GHz for duration of 360 s. Typical clads cross sections of composite clads showed good metallurgical bonding with the substrate by partial dilution. The back scattered electron image of clad cross section showed the reinforced chromium carbide (Cr₂₃C₆) particles are uniformly distributed and well embedded in the Ni based matrix. The developed clad is free from visible solidification cracking and has significantly less porosity which is of the order of 0.90%. The XRD pattern of the developed clad showed the presence of FeNi₃, NiSi and Cr₂₃C₆ phases. The average Vicker's microhardness of developed clad was observed as 425 ± 140 Hv.     

Simultaneous recovery of chromium and destruction of organics from LCD manufacturing process wastewater by supercritical water oxidation

The effectiveness of supercritical water oxidation (SCWO) process for the simultaneous recovery of chromium and destruction of organics from liquid crystal display (LCD) manufacturing process wastewater was investigated. The experiments were performed in an isothermal continuous-flow tubular reactor and H₂O₂ was used as an oxidant. The reaction temperatures ranged from 400 to 605 °C and the residence times ranged from 15 to 31 s at a fixed pressure of 25 MPa. The effect of temperature, oxidant concentration and residence time on chromium recovery and chemical oxygen demand (COD) conversion was investigated. The results of this study demonstrated that the SCWO process recovered chromium and decreased chemical oxygen demand up to 99.3% and 99.9%, respectively. The analyses showed that chromium are recovered as chromium oxide (α-HCrO₂ and Cr₂O₃). The SCWO process is an effective technique for simultaneously recovering chromium and for the destruction of hazardous organics in the LCD manufacturing process wastewater. Our study showed that there are two consequent reactions, chromium recovery reaction (hydrolysis) followed by the organic decomposition reaction (oxidation). The recovery of chromium can be achieved without major organic decomposition.     

The development of a microscale strain measurement system applied to sheet bulge hydroforming

Micro and multiscale sheet metal forming processes represent new and attractive solutions to many manufacturing problems. However, evaluating the strains in these products is a difficult endeavor. Larger organizations are utilizing commercially available microscale digital image correlation systems to measure the strains in microscale parts or on macroscale parts with critical microscale features. The cost of these strain measurement systems is preventing smaller research and development organizations from entering this challenging area or they are forgoing the ability to determine strains. The present paper describes the development of a method for creating microscale grids and measuring strains on microscale parts or microscale locations on larger parts. The method developed was able to measure true strains up to 0.618 for square grids that are 127 μm measured from center-to-center. Microscale strains resulting from sheet bulge hydroforming experiments using 11 mm, 5 mm, and 1 mm diameter dies were evaluated and material properties of the sheet metal were estimated based upon the strains measured in conjunction with FEA simulations and compared to analytical solutions and microscale tension tests. The material properties determined using the strains and FEM approach were consistent with the other methods.     

基于机器学习方法的小麦镉富集因子预测

应用机器学习方法解析区域土壤-小麦系统镉(Cd)富集特征有助于风险决策的准确性和科学性.基于区域调查,构建了Freundlich-type转移方程、随机森林(RF)模型和神经网络(BPNN)模型对小麦Cd富集因子(BCF-Cd)进行预测,验证不同模型的预测精度并评估其不确定性.结果表明,RF(R²=0.583)和BPNN(R²=0.490)模型预测性能均优于Freundlich转移方程(R²=0.410).重复训练结果显示RF和BPNN平均绝对误差(MAE)和均方根误差(RMSE)较为接近,但RF(R²为0.527～0.601)较BPNN(R²为0.432～0.661)模型精度和稳定性更高.特征变量重要性分析显示多重因素的共同作用导致小麦BCF-Cd的异质性,其中土壤磷(P)和锌(Zn)是影响小麦BCF-Cd变化的关键变量.参数优化可进一步提高模型精度、稳定性和泛化能力.     

改进BFO优化BPNN的自来水混凝加药预测

本文给出一种量子粒子群（QPSO）算法、改进菌群觅食（IBFO）算法优化反向传播神经网络（BPNN）的混凝投药预测模型,利用量子粒子群的个体极值与群体极值更新细菌觅食算法趋化过程中细菌位置;通过细菌协同改进趋化算子提高优化精度,结合差分算法改进繁殖算子解决部分维度退化问题,加入轮盘赌方法作为选择机制改进迁移算子来克服优化过程中优秀解消失的缺陷;进而优化BP神经网络的权值、阈值以此预测混凝剂投药量.对云南某自来水厂的数据进行离线训练和模型测试,结果表明,所提算法预测结果的均方误差（MSE）达0.0116mg/L,平均绝对误差百分比（MAPE）达1.36%,在预测精度和稳定性上优于BFO-BPNN、PSO-BPNN等模型.     

An analysis of wire manufacture using the dieless drawing method

An experimental program of a novel wire manufacturing process known as dieless drawing has been conducted. The process has the capability to effect a reduction in the diameter of a wire without the use of conventional wire drawing dies. Reduction in diameter is achieved by heating the wire, which is mechanically loaded parallel to its longitudinal axis, to a temperature that initiates plastic deformation. Both mathematical and finite element (FE) modeling of the process have been undertaken. An analysis of the wire deformation is presented and discussed. The maximum reduction in diameter achieved, effect of drawing velocity, temperature, and uniformity of resulting wire diameter are investigated. The mechanics and operational features of the experimental machine manufactured to facilitate the experimental program of dieless drawing are described. The mathematical model presented can be used to describe the occurrence of deformation during the process. This model has been validated by experiments carried out on the wire drawing machine. The primary observation from the experimental program was that uniformity of wire diameter after dieless drawing decreased with an increase in reduction ratio. Results obtained from the experimental work confirm that a complicated interdependence of the process parameters exists during the dieless drawing process.     

Carbon estimation in harvested wood products using a country-specific method: Portugal as a case study

This study aims to contribute to the ongoing international debate on the choice of approaches and methods to be used for estimating the amount of carbon that has accumulated in harvested wood products (HWP), within the context of national greenhouse gas emission inventories. A method for estimating carbon accumulation in HWP was developed and applied to three accounting approaches currently under discussion, namely: the stock-change approach, the production approach and the atmospheric-flow approach. This method is consistent with tier 3 methods suggested by the Intergovernmental Panel on Climate Change.An estimation of the carbon accumulation in HWP in Portugal for the period 1990–2000 varied between 112 and 1016 Gg C year⁻¹. The atmospheric-flow approach provided the most favourable results for the whole period, largely because Portugal acted as a net exporter of carbon. The production approach ranked second, because the HWP exported were mainly produced from domestically grown wood. The uncertainty level of the estimates was in general lower than the uncertainty level expected when using a method based on generic default data. In conclusion, a simple method such as the one developed in this study may be used to estimate carbon accumulation in HWP with acceptable uncertainty levels, provided that country-specific data are available.     

Using micro deep drawing with ironing stages to form stainless steel 304 micro cups

The needs of stainless steel 304 micro cups have been increasing tremendously due to the trend of miniaturization in medical and electronic devices, etc. For application purpose, it is highly desired to have stainless steel micro cups with high CH/OD (cup height/outer diameter) ratios. Due to the constraints of the limit draw ratio (LDR) of stainless steel 304 sheets in micro deep drawing, forming a micro cup with high CH/OD ratio at room temperature cannot be achieved by using a single stage deep drawing die. A process consisting of one micro deep drawing and two ironing stages was proposed for achieving this goal; three micro dies were designed, fabricated and used for experimental validation. A series of experiments were conducted by using the stainless steel 304 sheets of 200 μm thickness annealed at four different temperatures to understand the influence of size effects on this process for generating knowledge, know-how and technologies to form high quality stainless steel micro cups with large CH/OD ratio. No lubricant was used in this study. It was proven that the proposed process is a robust process as long as the sheets are annealed at the temperature no less than 900 °C for more than 3 min.     

Evaluation of two soil carbon models using two Kenyan long term experimental datasets

RothC and Century are two of the most widely used soil organic matter (SOM) models. However there are few examples of specific parameterisation of these models for environmental conditions in East Africa. The aim of this study was therefore, to evaluate the ability of RothC and the Century to estimate changes in soil organic carbon (SOC) resulting from varying land use/management practices for the climate and soil conditions found in Kenya. The study used climate, soils and crop data from a long term experiment (1976–2001) carried out at The Kabete site at The Kenya National Agricultural Research Laboratories (NARL, located in a semi-humid region) and data from a 13 year experiment carried out in Machang’a (Embu District, located in a semi-arid region). The NARL experiment included various fertiliser (0, 60 and 120 kg of N and P₂O₅ ha⁻¹), farmyard manure (FYM—5 and 10 t ha⁻¹) and plant residue treatments, in a variety of combinations. The Machang’a experiment involved a fertiliser (51 kg N ha⁻¹) and a FYM (0, 5 and 10 t ha⁻¹) treatment with both monocropping and intercropping. At Kabete both models showed a fair to good fit to measured data, although Century simulations for treatments with high levels of FYM were better than those without. At the Machang’a site with monocrops, both models showed a fair to good fit to measured data for all treatments. However, the fit of both models (especially RothC) to measured data for intercropping treatments at Machang’a was much poorer. Further model development for intercrop systems is recommended. Both models can be useful tools in soil C predictions, provided time series of measured soil C and crop production data are available for validating model performance against local or regional agricultural crops.     

Shrinkage and fragmentation of grasslands in the West Songnen Plain,China

In the past century, especially the past five decades, the grasslands of the West Songnen Plain, Northeast China, were rapidly converted into croplands and salinized wasteland, and experienced a fragmentation process that is still ongoing. Almost no information is available on the spatial-temporal changes of grasslands in this area. In this study, grassland cover change, agricultural reclamation and salinized wasteland expansion were investigated during the past five decades. Grassland fragmentation was studied based on four landscape metrics. The grassland cover change was detected from a time series of topographic maps from 1954, satellite images of Landsat TM in 1986, 1995, and 2000 using remote sensing and geographic information systems (GIS). In addition, the land use changes were analyzed using a transition matrix of land use types, while the driving forces were explored according to climatic changes and socioeconomic developments. The results indicated a significant decrease in grassland area. Of the 1 418 945 ha of native grassland in 1954, approximately 64% was removed by 2000, while the number of patches (NP) increased from 865 to 2035 and the mean patch size (MPS) decreased from 1640 ha to 252 ha. During the whole study period, the average annual decrease rate of grassland was 34 894 ha/year. Cropland and salinized wasteland were the two main land use types into which grassland converted. During the past decades, obvious climatic changes occurred, which supplied a favorable potential environment for agricultural development but damaged grassland productivity. On the other hand, population, GDP and livestock number increased significantly as grassland quality decreased. According to the results, the shrinkage and fragmentation of grasslands may well be explained by socioeconomic development and aided by changing climatic conditions.     

Investigation on mechanism of phosphate removal on carbonized sludge adsorbent

For the removal of phosphate (PO₄^3 -) from water, an adsorbent was prepared via carbonization of sewage sludge from a wastewater treatment plant: carbonized sludge adsorbent (CSA). The mechanism of phosphate removal was determined after studying the structure and chemical properties of the CSA and its influence on phosphate removal. The results demonstrate that phosphate adsorption by the CSA can be fitted with the pseudo second-order kinetics and Langmuir isotherm models, indicating that the adsorption is single molecular layer adsorption dominated by chemical reaction. The active sites binding phosphate on the surface are composed of mineral particles containing Si/Ca/Al/Fe. The mineral containing Ca, calcite, is the main factor responsible for phosphate removal. The phosphate removal mechanism is a complex process including crystallization via the interaction between Ca^2 + and PO₄^3 -; formation of precipitates of Ca^2 +, Al^3 +, and PO₄^3 -; and adsorption of PO₄^3 - on some recalcitrant oxides composed of Si/Al/Fe.     

Scale-up modeling of the twin roll casting process for AZ31 magnesium alloy

In the present study, a 2-D finite-element method (FEM) thermal-fluid-stress model has been developed and validated for the twin roll casting (TRC) of AZ31 magnesium alloy. The model was then used to quantify how the thermo-mechanical history experienced by the strip during TRC would change as the equipment was scaled up from a laboratory size (roll diameter = 355 mm) to a pilot scale (roll diameter = 600 mm) and to an industrial scale (roll diameter = 1150 mm) machine. The model predictions showed that the thermal history and solidification cooling rate experienced by the strip are not affected significantly by caster scale-up. However, the mechanical history experienced by the strip did change remarkably depending on the roll diameters. Casting with bigger rolls led to the development of higher stress levels at the strip surface. The roll separating force/mm width of strip was also predicted to increase significantly when the TRC was scaled to larger sizes. Using the model predicted results, the effect of both casting speed and roll diameter was integrated into an empirical equation to predict the exit temperature and the roll separating force for AZ31. Using this approach, a TRC process map was generated for AZ31 which included roll diameter and casting speed.     

Experimental continuous sludge microwave system to enhance dehydration ability and hydrogen production from anaerobic digestion of sludge

Dehydrating large amounts of sludge produced by sewage treatment plants is difficult.Microwave pretreatment can effectively and significantly improve the dewaterability and hydrogen production of sludge subjected to anaerobic digestion. The aim of this study was to investigate the effects of different microwave conditions on hydrogen production from anaerobic digestion and dewaterability of sludge. Based on an analysis of the electric field distribution, a spiral reactor was designed and a continuous microwave system was built to conduct intermittent and continuous experiments under different conditions. Settling Volume, Capillary Suction Time, particle size, and moisture content of the sludge were measured. The results show that sludge pretreatment in continuous experiments has equally remarkable dehydration performance as in intermittent experiments; the minimum moisture content was 77.29% in the intermittent experiment under a microwave power of 300 W and an exposure time of 60 sec, and that in the continuous experiment was 77.56% under a microwave power of 400 W and an exposure time of 60 sec.The peak measured by Differential Scanning Calorimeter appeared earliest under a microwave power of 600 W and an exposure time of 180 sec. The heat flux at the peak was 4.343 W/g, which is relatively small. This indicates that microwave pretreatment induced desirable effects. The maximum yield of hydrogen production was 7.967% under the conditions of microwave power of 500 W, exposure time of 120 sec, and water bath at 55°C. This research provides a theoretical and experimental basis for the development of a continuous microwave sludge-conditioning system.     

Soil C storage as affected by tillage and straw management: An assessment using field measurements and model predictions

Soil tillage and straw management are both known to affect soil organic matter dynamics. However, it is still unclear whether, or how, these two practices interact to affect soil C storage, and data from long term studies are scarce. Soil C models may help to overcome some of these problems. Here we compare direct measurements of soil C contents from a 9 year old tillage experiment to predictions made by RothC and a cohort model. Soil samples were collected from plots in an Irish winter wheat field that were exposed to either conventional (CT) or shallow non-inversion tillage (RT). Crop residue was removed from half of the RT and CT plots after harvest, allowing us to test for interactive effects between tillage practices and straw management. Within the 0–30 cm layer, soil C contents were significantly increased both by straw retention and by RT. Tillage and straw management did not interact to determine the total amount of soil C in this layer. The highest average soil C contents (68.9 ± 2.8 Mg C ha^?1) were found for the combination of RT with straw incorporation, whereas the lowest average soil C contents (57.3 ± 2.3 Mg C ha^?1) were found for CT with straw removal. We found no significant treatment effects on soil C contents at lower depths. Both models suggest that at our site, RT stimulates soil C storage largely by decreasing the decomposition of old soil C. Extrapolating our findings to the rest of Ireland, we estimate that RT will lead to C mitigation ranging from 0.18 to 1.0 Mg C ha^?1 y^?1 relative to CT, with the mitigation rate depending on the initial SOC level. However, on-farm assessments are still needed to determine whether RT management practices can be adopted under Irish conditions without detrimental effects on crop yield.     

Modeling and optimization of turning duplex stainless steels

The attractive combination of high mechanical strength, good corrosion resistance and relatively low cost has contributed to making duplex stainless steels (DSSs) one of the fastest growing groups of stainless steels. As the importance of DSSs is increasing, practical information about their successful machining is expected to be crucial. To address this industrial need, standard EN 1.4462 and super EN 1.4410 DSSs are machined under constant cutting speed multi-pass facing operations. A systematic approach which employs different modeling and optimization tools under a three phase investigation scheme has been adopted. In phase I, the effect of design variables such as cutting parameters, cutting fluids and axial length of cuts are investigated using the D-Optimal method. The mathematical models for performance characteristics such as; percentage increase in radial cutting force (%F_r), effective cutting power (P_e), maximum tool flank wear (VB_max) and chip volume ratio (R) are developed using response surface methodology (RSM). The adequacy of derived models for each cutting scenario is checked using analysis of variance (ANOVA). Parametric meta-heuristic optimization using Cuckoo search (CS) algorithm is then performed to determine the optimum design variable set for each performance. In the phase II, comprehensive experiment-based production cost and production rate models are developed. To overcome the conflict between the desire of minimizing the production cost and maximizing the production rate, compromise solutions are suggested using Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The alternatives are ranked according to their relative closeness to the ideal solution. In the phase III, expert systems based on fuzzy rule modeling approach are adopted to derive measures of machining operational sustainability called operational sustainability index (OSI). Artificial neural network (ANN) based models are developed to study the effect of design variables on computed OSIs. Cuckoo search neural network systems (CSNNS) are finally utilized to constrainedly optimize the cutting process per each cutting scenario. The most appropriate cutting setup to ensure successful turning of standard EN 1.4462 and super EN 1.4410 for each scenario is selected in accordance with conditions which give the maximum OSI.     

Simultaneous removal of arsenic and antimony from mining wastewater using granular TiO2: Batch and field column studies

Coexisting arsenic (As) and antimony (Sb) in mining wastewater is a common and great concern. On-site simultaneous removal of As and Sb from mining wastewater was achieved by using a reusable granular TiO₂ column in this study. To evaluate the accuracy of the scale-up procedure, As and Sb adsorption from wastewater was studied in both large (600 g TiO₂) and small columns (12 g TiO₂) based on the proportional diffusivity rapid small-scale column tests (PD-RSSCTs) design. The comparable As and Sb breakthrough curves obtained from small and large columns confirmed the accuracy of the PD-RSSCT theory in the design of large-scale columns. Meanwhile, the consistent As and Sb adsorption results from batch and column experiments suggested that TiO₂ adsorption for As and Sb can be predicted from bench-scale tests. Charge distribution multi-site complexation (CD-MUSIC) and one-dimensional transport modeling integrated in the PHREEQC program were performed to study the adsorption behaviors of As and Sb on the TiO₂ surface. Coexisting ions, such as Ca^2 +, Mg^2 +, and Si^4 +, play an important role in As and Sb adsorption, and the breakthrough curves were well simulated after considering the compound ion effects. The results from this study highlight the surface reactions of As and Sb on TiO₂ and provide a practical way for on-site remediation of industrial wastewater.