Water-atomized Fe-Ni-Mo steel powder, was utilized as base powder for designing powder mixtures for warm pressing. The warm pressing and sintering behaviours of the powder mixtures were studied. The results show that, compared with the pressing at room temperature, the green density gain by warm pressing is within a range of 0.10–0.19 g/cm3 and reduction in spring back is 30%–40% of the ambient, and maximum green density of 7.32 g/cm3 at 735 MPa is obtained as the graphite mass fraction is 0.8%. It was found that sintered densities of the compacts were reduced slightly due to releasing of elastic stress stored in the compacts during sintering. The warm pressing of steel powders gives evidence for substituting the traditional double pressing and double sintering process.
With OLYMPUS PMG3 metallograph, an abnormal three-layer gradient structure, i. e. coarse grain zone, binder enrichment zone and normal structure zone from surface to inner, was observed in Cr3C2 based cemented carbide. In the binder enrichment zone, three different shapes of anomalous coarse carbides were observed. It is shown that the transverse rupture strength can be raised remarkably, up 20.7% from the alloy with abnormal gradient structure by removing the abnormal gradient structure. The results suggested that the abnormal gradient structure in the surface, especially the anomalous coarse carbides in the binder enrichment zone is the main reason for the lower strength
It is practical, economic and sometimes essential to derive rules or conclusions by performing lesser runs of experiments. In this part, a methodology based on 2f factorial design was brought up to derive guidelines to simulate growth curve and production of sugars by Spirulina (Arthrospira) maxima. The growth curve or accumulation process of sugars was idealized by sets of straight lines limited by phase transfers of growth or accumulation of sugars. Normal analyses of the critical values of the transfers were used to derive their linear relationships with the initial conditions of the experimental factors. These linear functions were called guidelines and were used to simulate the growth curve or accumulation of sugars. Generalization of the guideline technique was determined by the kinetic limitation of nutrient nitrogen or sulfur that was dependent upon their stoichiometric deficiency directly derived from their initial values in the medium. This method uses the initial conditions of culture and does not need measurements of concentrations of nitrate, sulfate and pigments during cultivation. It is a practical and useful alternative way to trace and predict approximately the growth curve and production of sugars by S. maxima.
The mechanism of additive ZC-1 for catalyzing combustion of coke breeze in sintering of iron ore fines was studied by using X-ray Diffraction, TGA and GC(Gas Chromatographer), by which energy saving was achieved on sinter pot test. The results show that the distance between cleavage planes is enlarged and the π-electrons are re-distributed because of the insertion of cations/molecules of ZC-1 into the cleavage planes of carbon, resulting in the weakening of C-C bond, improving the adsorption of oxygen and lowering the activation energy of gasification of carbon from 25.8 kJ/mol to 18.9 kJ/mol, and the burning rate being increased and combustion residual reduced, all of which can lead to lower solid fuel consumption. Compared with the sintering test without addition of additives, the solid fuel consumption is reduced by 16.0%, meanwhile, the rate of finished sinter, the output of finished sinter and the tumbling index are increased by 2.03%, 7.0% and 3.71%, respectively, with incorporating 0.2% of additive ZC-1 in the sintering mixture, which is in agreement with the catalyzing mechanism of ZC-1.
Two new chiral stationary phases, 2,3-di-O-acetyl-6-O-trimethylsilyl-β-cyclodextrin (DATBCD) and 2, 6-di-O-trimethylsilyl-3-O-acetyl-β-cyclodextrin (DTABCD), were synthesized, their structures were identified by means of infrared and NMR spectra. Capillary columns were coated with the two stationary phases by dynamic method. The chromatographic properties, and enantiomers separation, such as ketone, esters, alcohols and olefines, were investigated on the silylated and acetylated β-cyclodextrin stationary phases. The experimental results show that the silylated and acetylated β-cyclodextrins are suitable to be used as capillary gas chromatographic stationary phases, the relative polarity of DATBCD and DTABCD stationary phases is respectively 4143 and 3928, the column efficiencies are respectively 3084 and 4198, and DATBCD is of stronger enantioselectivity than DTABCD, capacity factor of the first eluted enantiomer (k1) and separation factor(α)of α-phenylethanol on DATBCD stationary phase are respectively 8.23 and 1.019.
The synthetic method of nickel borate acylate (NBA), a kind of rubber-steel cord adhesion promoter (AP), through nickel carbonate, borate and mixed carboxylic acid was studied. The preparation of nickel carbonate could be performed through reaction of nickel sulfate with sodium carbonate in aqueous solution, in which fractional conversion of nickel was more than 99.9%. The mixed nickel carboxylate was prepared by the reaction of nickel carbonate with isooctanoic acid and acetic acid, under strong stirring for 2 h, the mole ratio of these chemicals were 1:1:1.1 respectively, and water should be removed completely by adding of inert organic solvent after reaction was finished so as to avoid hydrolysis of tributyl borate in the second reaction. NBA was synthesized by reaction of mixed nickel carboxylate with tributyl borate under strong stirring at 200–250 °C for 6 h. By detection and comparison with 680C product from Manobond Company of England, the NBA synthesized through isooctanoic acid and tributyl borate was very similar to product 680C in IR data, 300% fixed extension strength, tensile strength, hardness and cure curve, and was slightly lower than those of product 680C in tensile failure extensibility and hot air aging. The experimental results show that the prepared NBA can be used as rubber-steel cord AP.
Upgrade and separation of Co from solution with low-grade Co were studied. In the solution, the content of Co is about 1 g·L−1, while that of Ni, Zn, Mn, Mg, Si and Ca is 0.145, 1.108, 0.119, 6.672, 0.026 and 0.200 g·L−1, respectively. After absorbed with absorbent G − 1, the content of Co in the solution is less than 1 mg·L−1, the average loss rate of Co is 0.07%, while the average loss rate of Mg is 67.92%. It is demonstrated that the absorbent has selectivity to absorb Co. After the absorbent was eluted with HCl at room temperature, the solution with higher content of Co was obtained. Through being evaporated and concentrated, the contant of Co in the solution can be upgraded to 26.6 g·L−1. At the same time, most of Si, Mg is removed, the total recovery of Co can reach as high as 98.7%. The content of Pb, Ni, Cu, Zn, Mn in the discharge solution is 1.00, 0.26, 0.21, 0.09, 0.15 mg·L−1, respectively, and the discharge solution can reach the national discharge standard. CoCl2 solid can be obtained and can reach chemical purity.
Regarding flowing granular media as weak transverse isotropic media, the phase velocity expressions of wave P, wave SH and wave SV were deduced, the propagation characteristics of waves in flowing granular media were analyzed. The experiments show that vibration has great influence on granular fluidity. The wavefront of wave P is elliptic or closely elliptic, the wavefront of wave SH is elliptic, and the wavefront of wave SV is not elliptic. Wave propagation in the granular flowing field attenuates layer after layer. The theory and experiment both substantiate that the density difference is the key factor which leads to the attenuation of vibrating energy. In terms of characteristics of wave propagation one can deduce that vibrating waves have less influence on flowability of granules when the amplitude and frequency are small. However, when the amplitude and frequency increase gradually, the eccentricity of ellipsoid, the viscosity resistance and inner friction among granules, and shear intensity of granules decrease, and the loosening coefficient of granules increases, which shows the granules have better flowability.
A two-phase model of rock was proposed in order to investigate the mechanism of brittle fracture due to uniaxial compression, in which rock was considered to be a composite material consisting of hard grains and colloids. The stress state in colloid region near grains was calculated using Finite Element Method (FEM). The influence of the tensile stresses on the crack initiation and failure process of brittle rock subjected to uniaxial compression was investigated by numerical experiments. The FE results show that tensile stresses are induced easily in the neighboring area of hard grains with the maximum value near grain boundaries. The distribution of tensile stresses depends on the relative position of hard grains. The cracks initiated just near the boundary area of hard grains, which was governed by tensile stress. These results clearly reveal the micro-fracture mechanism of brittle rock loaded by uniaxial compression. It can be concluded that the failure mode of brittle rock under uniaxial compression is still tensile fracture from the point view of microstructure. However, since the wide colloid region is still under compressive stress state, further propagation of boundary cracks through this region obviously needs more external load, thus causing the uniaxial compressive strength of rock much higher than its tensile strength obtained via Brazilian (splitting) experiment.
The mobile IPv6 proposed by the IETF aims at providing mobility support on the next generation Internet. First, the authors described the basic principle of mobile IPv6 in brief and analyzed the advantages and disadvantages of it, presented a new idea of allocating a specific address space for mobile node (MN) and developed a new extension header and two ICMP message types for mobile IPv6. Lastly the authors proposed an optimization strategy for mobile IPv6 based on these extensions of protocol, which has the following advantages: 1) It is more convenient to manage the MNs because MN can be judged from its IP address; 2) When the correspondent node (CN) is not actively communicating with a MN, the MN and its home agent (HA) need not send Binding Update to the CN, and the CN need not send Binding Request to the MN. Only when the CN really wants to send a packet to the MN, will the CN voluntarily send a MN Discovery Request message to acquire the MN’s care-of address. In this way, the transmission of Binding Update and Binding Request is greatly reduced, consequently the network overhead is also decreased; 3) While sending packets, the CN simply uses a MN Home Address Extension Header without using IPinIP encapsulation and routing header, which can reduce the redundant information in the packet and the message delay; 4) All the packets sent by the CN can be directly routed to the MN and the triangle routing can be completely avoided. By using these protocol extensions, the overhead of the network is greatly reduced and the network quality of services (QoS) is improved.
The purpose of this work is to propose a scheme to stabilize the predictive control systems in the practical stability sense. In the paper, the authors dealt with a general discrete predictive control system xj+1|t=f(xj|t, uj|t) by using the Lyapunov direct method combining with receding-horizon control technique, and presented a new condition to guarantee the practical stabilization of the systems. With the proposed results, one can design the optimal controllers easily to practically stabilize the predictive control systems.
A quasi-physical algorithm was proposed for solving the linear separation problem of point set in n-dimensional space. The original idea of the quasi-physical algorithm is to find an equivalent physical world for the primitive mathematical problem and to observe the vivid images of the motion of matter in it so as to be inspired to obtain an algorithm for solving the mathematical problem. In this work, the electrostatics with two kinds of matter is found to be the equivalent physical world. As a result, the proposed algorithm is evidently more efficient and robust than the famous LMS algorithm and ETL algorithm. The efficiency of the quasiphysical algorithm is about 10 – 50 times of the LMS algorithm’s for representative instances. A typical Boolean-valued instance shows that it is hard for ETL algorithm but very easy for the quasi-physical algorithm. In this instance, point set A and B is {000, 010, 011, 111} and {001, 100}, respectively.
In order to get an insight into the thermal characteristic and to evaluate the thermal reliability of the “System in Packaging” (SIP), a new solution of electronics packaging, a heat transfer model of SIP was developed to predict the heat dissipation capacity and to investigate the effect of different factors on the temperature distribution in the electronics. The affecting parameters under consideration include the thermophysical properties of the substrates, the coefficient of convection heat transfer, the thickness of the chip, and the density of power dissipation. ALGOR, a kind of finite element analysis software, was used to do the model simulation. Based on the simulation and analysis of the heat conduction and convection resistance, criteria for the thermal design were established and possible measurement for enhancing power dissipation was provided. The results show that the heat transfer model provides a new and effective way to the thermal design and thermal analysis of SIP and to the mechanical analysis for the further investigation of SIP.
The qualitative behavior of solutions for a generalized Gause-type predator-prey system was studied. A large number of biological and bioeconomic models are special cases of this system. The system was investigated in the region D={(x, y)|x>0, y>0} because of the biological meaning of the system. The authors derived some sufficient conditions for the boundedness of the solutions and the existence of limit cycles of the system, which ensure that the system has at least one limit cycle. The theory of limit sets of autonomous plane systems and the theorem of cycle field of Poincare-Bendixson are efficiently employed in the research. The main results and their consequences presented not only generalize some known results, but also improve some corresponding results of other authors.