典型切削机床能耗模型的研究现状及发展趋势

机床作为机械制造行业的"母机",数量大、能耗高、效率低。近年来,学者们为建立精确的机床能耗模型已做大量工作。针对典型切削机床能耗的建模现状,从切削单元能耗、加工阶段整机能耗、工艺单元能耗三个层次进行综合分析。进而从节能优化、产品绿色性评估、企业资源配置、机床绿色设计四方面对机床能耗模型的应用进行论述。目前,机床能耗的建模逐渐面向高端数控机床,建模的目标性更加明确,与工业应用的结合也使得模型的实用价值不断提升。

Optimization of Abrasive Water Jet Cutting of Ductile Materials

Full factorial design of experiments was developed in order to investigate the effects of jet pressure, abrasive mixing rate, cutting feed, and plate thickness upon three response variables, surface finish of cutting wear zone, percentage proportion of striation free area, and maximum width of cut. The set of sixteen experiments was performed on each of the following two ductile materials： AISI 4340 （high strength low alloy steel, hardened to 49HRc） and Aluminum 2219. Analysis of Variance （ANOVA） was performed on experimental data in order to determine the significance of effects of different parameters on the performance measures. It was found that cutting feed and thickness were highly influential parameters, while abrasive mixing rate is influential upon surface roughness only. Strong interaction was found between jet pressure and workpiece material. Multi-criteria numerical optimization was performed in order to simultaneously maximize/minimize different combinations of performance measures.

Application of Ceramic Film as Means of Lubrication for Forming of TiSheet in a Highly Localized Deformation Process

Incremental forming is a novel die-less sheet forming process. There is a need for special means to retain lubricant at the tool/sheet interface during forming. To fulfillthe stated aim, a porous ceramic film was developed on pure Ti substrate, and it was done through an electrochemical depsition process known as plasma electrolytic oxidation. The film with preferred pore size could be realized after several attempts by varying the processing parameters. In order to characterize the film, a variety of tests including rnicrostructure, film-substrate bond strength and tribological properties tests were conducted. On-job performance of the film was also examined by forming Ti components employing a range of forming conditions. It was found that the proposed method of lubrication was effective, and the plasma eletrolytic oxidation process can be employed to fabricate films on pure Ti sheet to provide means of lubrication during incremental forming.

Influence of Integrated Nutrients on Growth, Yield and Quality of Maize (Zea mays L.)

A field experiment was conducted to evaluate the integrated nutrients effect on growth, yield and quality of maize (Zea mays L.) during spring, 2009, at the Agronomic Research Area, University of Agriculture, Faisalabad. The ex-periment was laid out in Randomized Complete Block Design (RCBD) having three replications with following treat-ments: T1 (control), T2(recommended NPK @ 200-120-125 kg ha-1), T3 [single spray of multinutrient (a solution mixture of micronutrients i.e;Zn = 2%, Fe = 1%, B = 1%, Mn = 1%, Cu = 0.2% and macronutrients N = 1%, K2O = 2%, S = 2%) @ 1.25Lha-1], T4 (recommended NPK @ 200-120-125 kg ha-1 + single spray of multinutrient @ 1.25L ha-1), T5 (recom-mended NPK @ 200-120-125 kg ha-1 + two spray of multinutrient @1.25Lha-1) and T6 (recommended NPK @ 200-120-125 kg ha-1+ three spray of multinutrient @ 1.25Lha-1).The recommended dose of NPK in addition with single spray of Multi-nutrients substationally improved all growth parameters, ear characteristics and also enhanced macronutrients use efficiency up to 11.5% which induced significant increase in grain yield as compared to control and also in the treatment where recommended dose of NPK was applied alone. The quality parameter of maize (oil contents) significantly improved by foliar application of multinutrients solution but recommended dose of fertilizer in addition to single spray of Multi-nutrients was economical.

Genotypic variation in root morphology, cotton subtending leaf physiology and fiber quality against nitrogen

Background:Nitrogen(N)is important for improving various morphological and physiological processes of cotton but their contribution to fiber quality is still lacking.Aims:The current study aimed to explore the relationship between root morphology,subtending leaf physiology,and fiber quality of contrasting N-efficient cotton genotypes in response to N.Methods:We analyzed the above parameters of CCRI 69(N-efficient)and Xinluzao-30(XLZ-30,N-inefficient)under control(2.5 mmol·L^(-1))and high N(5 mmol·L^(-1))conditions.Results:The results showed that root morphological traits were increased in CCRI-69 under control conditions than high N.Subtending leaf morphology,chlorophyll and carotenoid contents,free amino acids,and soluble proteins were higher under high N as compared with the control.However,soluble sugars,fructose,sucrose contents,and sucrose phosphate synthase were higher under control conditions than high N across the growth stages.Irrespective of the N conditions,all morphological and physiological traits of cotton subtending leaf were higher in CCRI-69 than XLZ-30.Except for fiber uniformity,fiber quality traits like fiber length,strength,micronaire,and elongation were improved under control conditions than high N.Between the genotypes,CCRI-69 had significantly higher fiber length,strength,micronaire,and elongation as compared with XLZ-30.Strong positive correlations were found between root morphology,soluble sugars,sucrose content,and sucrose phosphate synthase activity with fiber quality traits,respectively.Conclusions:These findings suggest that CCRI-69 performed better in terms of growth and fiber quality under relatively low N condition,which will help to reduce fertilizer use,the cost of production,and environmental pollution.

Plasma Surface Cu Alloyed Layer as a Lubricant on Stainless Steel Sheet:Wear Characteristics and On-job Performance in Incremental Forming

To solve the problems of poor forming and easy adhesion of the stainless steel,Cu alloyed layer on the stainless steels was prepared by the double glow plasma surface alloying technique.The experimentalresults indicated that the supersaturated copper dispersedly precipitated in grain interior and crystalboundaries and formed the vermicular structure.The tribologicaltests indicated that the friction coefficient of the Cu alloyed layer was lower than that of the stainless steels.The wear rate of stainless steelin the presence of Cu alloyed layer was approximately 2-fold lower than that in the absence of the alloyed layer.The results of the incrementalforming indicated that the ploughing phenomenon was not observed on the stainless steelin the presence of Cu alloyed layer during the incrementalforming,while the stainless steelpresented the deep ploughing.Therefore,Cu alloyed layer on stainless steelexhibited excellent self-lubrication and forming properties.

Weed Control Practices and Varying Sowing Dates Effects on Seed Production of Pearl Millet (<i>Pennisetum americanum</i>L.) under Semi-Arid Environment

Peral millet being drought tolerant has substantial potential to contribute in food security ensuring the food, fodder and nutritional value in different Asian and African countries. Susceptibility to abiotic and biotic factors and low productivity are the main reasons for decreasing productivity and area of millets. In this context, evaluation of the effect of weed control practices and varying sowing dates on grain yield of kharif season grown pearl millet (Pennisetum americanum L.) was demonstrated at post graduate agriculture research station, University of Agriculture, Faisalabad during 2015. Forage pearl millet was sown at three different sowing dates i.e. mid-June, end of June and mid-July and four weed control practices viz. weedy check (no weeding), twice hoeing at 15 and 30 days after sowing (DAS), weed control using herbicides i.e. application of Atrazine (Awax 38 SC) &#64;330 g a.i. ha-1 at 15 DAS, and twice foliar applications of 10% Sorghum water extract (Sorgaab) (at 15 and 30 DAS). The experiment was laid out in randomized complete block design (RCBD) under split plot arrangement, comprising of three replications. The treatments with varying sowing dates were randomized in main plots and weed control practices were in subplots. Results showed that the highest plant height (279.51 cm), leaf area (2777.80 cm2), fresh weight of leaves per plant (155.57 g), maximum number of grains per head (3162.0) and grain yield (3419.7 kg&middot;ha-1) were obtained in the treatment combination of 30th June sowing × twice weed hoeing (at 15 and 30 DAS) while, maximum 1000-grain weight (8.45 g) was observed in treatments where weeds were controlled by hoeing (at 15 and 30 DAS). Moreover, cultural weed control practices reduce significantly weed density, fresh and dry Wight of weeds. In sum, it is concluded that to reduce the weed-crop competition and to gain higher productivity of pearl millet, field should be weed free 20 - 45 days after sowing.

Adaptive state estimation of groundwater contaminant boundary input flux in a 2-dimensional aquifer

In many circumstances involving heat and mass transfer issues,it is considered impractical to measure the input flux and the resulting state distribution in the domain.Therefore,the need to develop techniques to provide solutions for such problems and estimate the inverse mass flux becomes imperative.Adaptive state estimator(ASE)is increasingly becoming a popular inverse estimation technique which resolves inverse problems by incorporating the semi-Markovian concept into a Bayesian estimation technique,thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters.The ASE is particularly designed for a system that encompasses independent unknowns and/or random switching of input and measurement biases.The present study describes the scheme to estimate the groundwater input contaminant flux and its transient distribution in a conjectural two-dimensional aquifer by means of ASE,which in particular is because of its unique ability to efficiently handle the process noise giving an estimation of keeping the relative error range within 10%in 2-dimensional problems.Numerical simulation results show that the proposed estimator presents decent estimation performance for both smoothly and abruptly varying input flux scenarios.Results also show that ASE enjoys a better estimation performance than its competitor,Recursive Least Square Estimator(RLSE)due to its larger error tolerance in greater process noise regimes.ASE's inherent deficiency of being slower than the RLSE,resulting from the complexity of algorithm,was also noticed.The chosen input scenarios are tested to calculate the effect of input area and both estimators show improved results with an increase in input flux area especially as sensors are moved closer to the assumed input location.

Recent advances in multipactor physics and mitigation

Recent progress made in the prediction,characterisation,and mitigation of multipactor discharge is reviewed for single‐and two‐surface geometries.First,an overview of basic concepts including secondary electron emission,electron kinetics under the force law,multipactor susceptibility,and saturation mechanisms is provided,followed by a discus-sion on multipactor mitigation strategies.These strategies are categorised into two broad areas–mitigation by engineered devices and engineered radio frequency(rf)fields.Each approach is useful in different applications.Recent advances in multipactor physics and engineering during the past decade,such as novel multipactor prediction methods,un-derstanding space charge effects,schemes for controlling multipacting particle trajec-tories,frequency domain analysis,high frequency effects,and impact on rf signal quality are presented.In addition to vacuum electron multipaction,multipactor‐induced ioni-zation breakdown is also reviewed,and the recent advances are summarised.

Experimental study on the meso-scale milling of tungsten carbide WC-17.5Co with PCD end mills

Tungsten carbide is a material that is very difficult to cut,mainly owing to its extreme wear resistance.Its high value of yield strength,accompanied by extreme brittleness,renders its machinability extremely poor,with most tools failing.Even when cutting with tool materials of the highest quality,its mode of cutting is mainly brittle and marred by material cracking.The ductile mode of cutting is possible only at micro leveIs of depth of cut and feed rate.This study aims to investigate the possibility of milling the carbide material at a meso-scale using polycrystaline diamond(PCD)end mills.A series of end milling experiments were performed to study the effects of cutting speed,feed per tooth,and axial depth of cut on performance measures such as cutting forces,surface roughness,and tool wear.To characterize the wear of PCD tools,a new approach to measuring the level of damage sustained by the faces of the cutter's teeth is presented.Analyses of the experimental data show that the effects of all the cutting parameters on the three performance measures are significant.The major damage mode of the PCD end mills is.found to be the intermittent micro-chipping.The progress of tool damage saw a long,stable,and steady period sandwiched between two short,abrupt,and intermittent periods.Cutting forces and surface roughness are found to rise with increments in the three cutting parameters,although the latter shows signs of reduction during the initial increase in cutting speed only.The results of this study find that an acceptable surface quality(average roughness Ra<0.2μm)and tool life(cutting length L>600mm)can be obtained under the conditions of the given cutting parameters.It indicates that milling with PCD tools at a meso-scale is a suitable machining method for tungsten carbides.

Analysis of Classical Encryption Techniques in Cloud Computing

Cloud computing has become a significant computing model in the IT industry. In this emerging model,computing resources such as software, hardware, networking, and storage can be accessed anywhere in the world on a pay-per-use basis. However, storing sensitive data on un-trusted servers is a challenging issue for this model. To guarantee confidentiality and proper access control of outsourced sensitive data, classical encryption techniques are used. However, such access control schemes are not feasible in cloud computing because of their lack of flexibility, scalability, and fine-grained access control. Instead, Attribute-Based Encryption（ABE） techniques are used in the cloud. This paper extensively surveys all ABE schemes and creates a comparison table for the key criteria for these schemes in cloud applications.