Applied Mechanics and Materials Vols. 496-500

Abstract: Water jet incremental sheet metal forming (WJISMF) is a new technology of sheet metal forming , a five-axis forming machine tool was designed ,with regard to research in this area is still in its infancy. Plenty of experiments was designed to study how to choose the reasonable molding process parameters. In addition, a spiral track instead of a contour track to solve the problem of surface depression was presented, and an example of processing was given to verify the advantages of the spiral track. Details of the use of UGCAM to generate spiral trajectory are descriped, the method is of universal significance. In addition, a vertical wall cylinder is formed through multi-step forming.

Abstract: The β-O-4 type model compound guaiacylglycerol-β-guaiacyl ether was treated with a Violuric acid (VIO) mediated electrochemical delignification system. GC-MS analysis were used to investigate the changes of chemical structure of β-O-4 type model compound during reaction. Mechanism of this electrochemical delignification was also explored. Results indicated that the electrochemical oxidation by VIO as a mediator had strong oxidation capability on degradation of β-O-4 type model compound. After degradation, a series of aromatic compounds containing single benzene ring, furan compounds and aliphatic compounds with small molecule were produced. From their structures, the following reactions were caused by electrochemical oxidation: ether-bond cleavage, C_α-C_β cleavage and benzene ring cleavage. Corrsequently, this work provides a comprehensive information on electrochemical oxidation delignification system that could be applied to industrial nonpollution bleaching.

Abstract: Hydrogen peroxide production via cathodic reduction of oxygen on self-made gas diffusion electrode was investigated in an undivided electrochemical system. The effects of mass ratio between graphite and PTFE in cathode, the calcination temperature, current density, pH, and plate distance on hydrogen peroxide generation were discussed. The results showed that the self-made gas diffusion cathode had high catalyze capacity for production of hydrogen peroxide using cathodic oxygen-reducing reaction. The hydrogen peroxide concentration could reach 80.52 mg·L^{- 1} within 2 h. The optimal conditions for this system are as follows: mass ratio of graphite to PTFE in cathode, 21, calcination temperature, 300 °C, current density,4.69mA/cm^2, pH 13.0, and the distance between anode and cathode, 8cm. The high concentration of hydrogen peroxide generated gives a promising application of this novel gas diffusion electrode system in pulp bleaching and waste-water treatment.

Abstract: Although Apocynum leaves have been used for the treatment of cardiovascular diseases, the study on active compounds of Apocynum venetum L. is little. In this paper,high performance liquid chromatography with mass spectrometry (HPLC-MS) were used for the active ingredient in qualitative analysis of Apocynum leaves, based on the information of the mass spectrum molecular ion peak [M-and some characteristic fragment ions, and combined with UV spectral characteristics we initially speculated that Apocynum leaves water extract isolated to 10 components.

Abstract: Dry strength additives play an important roll in papermaking process. In this work, we aimed at analyzing the performance of poly vinyl alcohols (PVA) and PVA & cationic starch (CS), as dry strength additives, on the properties of high-yield pulp (HYP). Various dosages of PVA were applied on HYP under various conditions and the corresponding pulp properties were evaluated. It was observed that PVA increased the strength properties of the HYP significantly, and the enhanced strength properties can be kept even after refining, which gave a promising application of this method in conventional pulping process. The best conditions of PVA for dosage, pH, pulp consistency and time was 20 mg/g, 6.0, 3% and 10 min, respectively. The application of CS, combined with PVA, can further improve the final physical strength properties of HYP. The results obtained from using PVA & CS were more effective than those obtained from using only PVA.

Abstract: The layer-by-layer deposition technique was adopted in this paper to improve the physical strength properties of alkaline peroxide mechanical pulp (APMP). The cationic starch (CS), anionic polyacryamide (APAM) and cationic polyacryamide (CPAM) were chosen and used to build-up polyelectrolyte multilayers on surface of APMP fibers. The improvements of physical strength of pulp through adsorption of different polyelectrolyte onto fibers were discussed and compared. The results showed that when the APMP fibers were treated with CPAM, the breaking length and burst index were 53% and 83% respectively, higher than that of untreated pulp. The optimal treatment conditions are 60 mgCPAM/g pulp, 1.5% pulp concentration and 9min treatment time. The pulp deposited by CPAM-APAM polyelectrolyte multilayer gave a highest physical strength compared with pulp with other multilayer deposition such as CS-APAM. At the whole beating degree range investigated in this paper, the CPAM-APAM deposition on fiber surface can improve the physical strength properties significantly, especially when the beating degree is at 40^oSR. In addition, the improvement of physical strength can be remained even after pulp refining.

Abstract: Alkali hydrolysis was used as a method of decomposing hemicellulose in corn stalk in this paper. The effects of NaOH concentration, hydrolysis time and hydrolysis temperature in the pretreatment on the degradation of hemicellulose in corn stalk were investigated. In addition, the yields of reducing-sugar and alkali hydrolysis corn stalk were discussed. The experimental results showed that the process of alkali hydrolysis had positive effect on the removal of hemicellulose in corn stalk and the whole process almost finished in 3h. The maximum reducing-sugar yield was 7.2% by the pretreatment with 20% NaOH for 6 h at 90°C, and 6.6% under the condition of 15% NaOH for 3h at 90°C, which was slightly lower than the maximum reducing-sugar yield, but the alkali charge and hydrolysis time dramatically reduced. So it was clarified that the best pretreatment condition was 15% NaOH for 3h at 90°C, and also this method is easy to applied in the alkaline pulping process.

Abstract: The violuric acid mediated chemical delignification system has a high delignification efficiency for pulp fibers and high delignification selectivity. The process conditions and effectiveness were carried out.The kinetics of electrochemical delignification has been investigated using the violuric acid (VIO) as the mediator. The reaction orders with respect to delignification, concentration of VIO and voltage of electrolytic cell were determined experimentally, which were dependent on the reaction conditions. The kinetic equation of electrochemical delignification and estimation function of kappa number were obtained respectively as follows: - dK/dt = A e-[VI^1.031[^2.197K^6.25 , E=16.2KJ/mol, K(t)={2.89×10^-7+5.25k [VI^1.031[^2.197t}^-0.19.

Abstract: The removal of Cr (VI) from aqueous solution is paying more and more attention due to the higher concern of environmental influence of this ion. In this paper, the biodegradable cellulosic fibers were modified with the grafting reaction to introduce the amide groups onto the fibers. In the grafting reaction, the toluene diisocyanate was firstly grafted on the surface of natural fibers, and then the 3-Chloro-2-hydroxypropyltrimethylammonium chloride (HPTMAC), as a high efficiency trapping agent of Cr (VI), was introduced through the condensation reaction. The modified fibers was characterized by infrared spectroscopy (IR) and elemental analysis. The modified fibers were applied to adsorb chromium (VI) ion from aqueous solution. The adsorption capability of the modified fibers was evaluated under different pH, time and temperature. The optimal adsorption conditions were obtained. The results showed that the grafted fibers had high efficient adsorption of chromium (VI) ion.

Abstract: According to the characteristics of solidification process of air cushion continuous casting, and on the basis of continuum model for binary solid-liquid phase change system, a set of equations which include continuity, momentum conservation, energy conservation and solute conservation ones are established. Furthermore, a coupled solution method of the set of equations, in which controlled-volume finite difference method is used and developed. The effects of some typical parameters such as billet diameter, casting speed and the second cooling on the solidification behavior are studied, and some meaningful results, which are significant to the technique optimizing of the air cushion continuous casting, are obtained.