Nonlinear error control of five-axis machining singular region

Aiming at the singular problem of large nonlinear error caused by the extreme change of rotation in five axis NC machining of complex surface. An optimization algorithm of tool path in singular region is proposed. Taking a-c double turntable five axis linkage NC machine tool as an example, firstly, the mathematical models of tool local milling ability, machining bandwidth and tool axis inclination are established. Based on the two constraint models, the mechanism of singularity and the size of singular region are analyzed, and it is proposed to adjust the side angle with the tool contact as the rotation center to avoid the singular region. The modified tool axis vector that does not meet the accuracy is interpolated recursively according to the interpolation principle. This method solves the problem of large nonlinear error caused by the extreme rotation of the rotating axis in the singular region on the basis of meeting the requirement of no curvature interference. At the same time, the processing bandwidth before and after modification is guaranteed to remain unchanged. Simulation results show that the algorithm can effectively detect the singular region and improve the machining quality in the singular region

The Chan-Vese Model With Elastica and Landmark Constraints for Image Segmentation

In order to completely separate objects with large sections of occluded boundaries in an image, we devise a new variational level set model for image segmentation combining the Chan-Vese model with elastica and landmark constraints. For computational efficiency, we design its Augmented Lagrangian Method (ALM) or Alternating Direction Method of Multiplier (ADMM) method by introducing some auxiliary variables, Lagrange multipliers, and penalty parameters. In each loop of alternating iterative optimization, the sub-problems of minimization can be easily solved via the Gauss-Seidel iterative method and generalized soft thresholding formulas with projection, respectively. Numerical experiments show that the proposed model can not only recover larger broken boundaries but can also improve segmentation efficiency, as well as decrease the dependence of segmentation on parameter tuning and initialization

Optimization method for complex surface partitioning and cutting parameters in 5-axis machining

For complex surfaces with variable geometric features and high processing requirements, the current stage still uses more conservative machining cutting parameters to generate five-axis machining tool positions, which inevitably leads to some parts not to obtain the best cutting state, and the generated machining tool positions are poorly adapted, so it will produce a great processing deformation error seriously affects the surface quality. In addition, conservative cutting parameters applied to different geometric features of the surface area is very likely to induce dramatic changes in the machining process cutting forces and machine motion parameters, resulting in uneven distribution of machining errors and local super poor, seriously affecting the quality of machining. In five-axis machining, due to the introduction of two rotary axes, the tool vector can be rotated arbitrarily in the spatial domain. When machining complex surfaces, the distance between the tool center coordinates and the oscillation center or rotation center of the five-axis machine will change with the curvature of the surface. surface quality. Therefore, the optimization of tool cutting parameters in 5-axis simultaneous machining is a technical bottleneck that needs to be solved urgently

Release characteristics of sediment phosphorus in all fractions of West Lake, Hang Zhou, China

The release characteristics of sediment phosphorus (P) in all fractions under varying environmental factors: P concentration in overlying water, light, pH, temperature and agitation intensity in shallow city lake West Lake, Hang Zhou, China were investigated. The release quantity and release rate of sediment P in the distilled water were significantly higher than that of lake water, and the maximum release quantity of sediment P in irradiated conditions was lower than that without irradiation. P release from the sediments occurred in both acidic and alkaline conditions, acidic condition was more favorable, and neutral condition was the least favorable. The released amount of each P forms changed variously with the temperature increasing, and various P fractions content in the sediment decreased sharply comparing to static conditions after strong disturbing. The logarithm values of released amount of sediment P were linear with the logarithm values of time, and the fitted release kinetics curves could be described well by exponent kinetic model: lnq = b + klnt. The results showed that the extent of P in all fractions release from West Lake sediment were affected variously by the environmental factors, and the sediment was unstable, at risk of releasing P to West lake. (C) 2016 Elsevier B.V. All rights reserved.</p

Synergistic removal effect of P in sediment of all fractions by combining the modified bentonite granules and submerged macrophyte

The removal efficiency of sediment phosphorus (P) with the in-situ synergistic effect of modified bentonite granules( MBG) and Vallisneria spiralis (V. spiralis) in West Lake, Hangzhou, China was investigated for the first time in the study. CMBG-Na10-450 (nitrification (10% Na2CO3)-calcination (450 degrees C) combined modification) was prepared and characterized, and the removal effects of sediment P of all fractions with CMBG-Na10-450 and V. spiralis in combination and separately were evaluated in batch experiments. Results showed that CMBG-Na10-450 could promote the growth of V. spiralis, and the residual P of the sediment not adsorbed on CMBG-Na10-450 was changed through root oxygenation and nutrition allocation, and then enhanced the extra P adsorption on CMBG-Na10-450. The combination of MBG and V. spiralis exhibited a synergistic removal effect higher than the summation of MBG and V. spiralis applied separately. The results of microcosm experiments showed that the combination of CMBG-Na10-450 and V. spiralis enhanced the function of P metabolism by increasing the special genus that belongs to the family Erysipelotrichaceae. (C) 2018 Elsevier B.V. All rights reserved.</p

EFFECT OF A PHOTOCATALYTIC COMPOSITE COUPLED WITH POTAMOGETOR CRISPUS ON CONTROL SEDIMENT PHOSPHORUS

The treatment efficiency of phosphorus (P) in a sediment with the joint action of a new photocatalytic composite Sr-TiO2/PCFM and submerged macrophyte was studied for the first time in Donghu Lake. Wuhan, China. The results showed that Sr-TiO2/PCFM prepared by the sol-gel process exhibited a strong photocatalytic capacity. The dosage of Sr-TiO2/PCFM, irradiation, operation temperature, reaction time and pH were the principal factors affecting the removal of each sediment P forms by Sr-TiO2/PCFM. The synergistic effect of Sr-TiO2/PCFM and submerged macrophyte Potamogetor crispus on the sediment P under irradiation and control conditions showed that the removal rates of each P form have been further enhanced after irradiation. The unity of Sr-TiO2/PCFM and Potamogeton crispus plays a more important role in removing the sedimental P than the summation of Sr-TiO2/PCFM and Potamogeton crispus used separately under the irradiation conditions. The results suggested that the united technology of Sr-TiO2/PCFM and submerged macrophyte could be further applied to the treatment of endogenous P pollution in eutrophic lakes

Effects of Chinese Cooking Methods on the Content and Speciation of Selenium in Selenium Bio-Fortified Cereals and Soybeans

Cereals and soybeans are the main food sources for the majority of Chinese. This study evaluated the effects of four common cooking methods including steaming, boiling, frying, and milking on selenium (Se) content and speciation in seven selenium bio-fortified cereals and soybeans samples. The Se concentrations in the selected samples ranged from 0.91 to 110.8 mg/kg and selenomethionine (SeMet) was detected to be the main Se species. Total Se loss was less than 8.1% during the processes of cooking except milking, while 49.1% of the total Se was lost in milking soybean for soy milk due to high level of Se in residuals. It was estimated that about 13.5, 24.0, 3.1, and 46.9% of SeMet were lost during the processes of steaming, boiling, frying, and milking, respectively. Meanwhile, selenocystine (SeCys2) and methylselenocysteine (SeMeCys) were lost completely from the boiled cereals. Hence, steaming and frying were recommended to cook Se-biofortified cereals in order to minimize the loss of Se

Investigation on the adsorption of phosphorus in all fractions from sediment by modified maifanite

Sediment phosphorus (P) removal is crucial for the control of eutrophication, and the in-situ adsorption is an essential technique. In this study, modified maifanite (MMF) prepared by acidification, alkalization, salinization, calcination and combined modifications, respectively, were first applied to treat sediment P. The morphology and microstructure of MMF samples were characterized by X-ray fluorescence (XRF), Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET). Various adsorption parameters were tested, such as dosage of maifanite, time, operation pH and temperature. The adsorption mechanisms were also investigated and discussed. Results showed that CMMF-H2.5-400 (2.5 mol/L H2SO4 and calcined at 400 degrees C) exhibited the highest P adsorption capacity. Thus, it was selected as the in-situ adsorbent material to control the internal P loading. Under the optimal conditions of dynamic experiments, the adsorption rates of TP, IP, OP, Fe/Al-P and Ca-P by CMMF-H2.5-400 were 37.22%, 44.41%, 25.54%, 26.09% and 60.34%, respectively. The adsorption mechanisms analysis revealed that the adsorption of P onto CMMF-H2.5-400 mainly by ligand exchange. Results of this work indicated that the modification treatment could improve the adsorption capacity of maifanite, and CMMF-H2.5-400 could be further applied to eutrophication treatment