浅析大冶铁矿东露天截排水系统

详细介绍了大冶铁矿东露天所采用的截水排水系统和该矿多年截排水方面的经验 ,对深凹露天矿的截排水提出了一些值得注意的问题     

Temperature distribution in an array of moving cracks acting as heat sinks

The temperature distribution in a periodic array of parallel cracks acting as heat sinks is studied for the case of stationary crack motion by use of the Wiener–Hopf method. The problem arises in the investigation of cracks propagating into solid material, where the stresses driving crack motion are caused by heat transfer from the solid through the crack surfaces. The solution is given in terms of Fourier integrals involving infinite products. The heat-flux distribution in the vicinity of the crack tips is computed analytically from the high wavenumber asymptotics. Numerical solutions of the temperature distribution are presented for several values of the Biot and Péclet number, and the effect of varying these parameters is discussed qualitatively.     

Short Chain Fatty Acids Alter HEp-2 Cell Association and Invasion by Stationary Growth Phase Salmonella Typhimurium

ABSTRACT: We examined the ability of stationary phase Salmonella typhimurium to adhere and invade cultured HEp-2 cells after growth in broth supplemented with acetate, propionate, butyrate, or a mixture of the three short chain fatty acids (SCFA). At pH 6, all concentrations, except 25 and 50 mM butyrate, reduced cell-association of S. typhimurium when compared to controls, while at pH 7 only 100 mM concentrations of acetate and butyrate reduced cell-association significantly. Invasion percentages were greater for S. typhimurium grown at an initial pH of 6 with 25 mM acetate when compared to controls, SCFA mixture, and all other single SCFA concentration combinations. At pH 7, invasion was greater with either the SCFA mixture or 25 or 50 mM acetate than with control and all other single SCFA concentration combinations.     

Liquid crystalline properties of cholesteric elastomers based on a mesogenic monomer containing menthyl groups

A new chiral mesogenic monomer (M_LC) based on menthyl groups and the corresponding cholesteric elastomers (LCE₁–LCE₃) were prepared. Their chemical structures and purity were characterized by Fourier transform infrared, nuclear magnetic resonance and elemental analyses. The liquid crystalline properties were investigated by differential scanning calorimetry, polarizing optical microscopy, thermogravimetric analysis and X‐ray diffraction. The selective reflection of light for M_LC was characterized with ultraviolet/visible/near infrared. The effect of the content of crosslinking units on the liquid crystalline behaviour of LCE₁–LCE₃ is discussed. The experimental results show that the chiral monomer and the corresponding elastomers containing menthyl groups can show mesomorphism when a flexible linkage chain is inserted between the mesogenic core and the bulky terminal menthyl fragments to reduce the steric effect. M_LC exhibited a chiral smectic C phase, a cholesteric phase and a cubic blue phase. LCE₁–LCE₃ with a low content of crosslinking units showed a cholesteric phase because of the introduction of the nematic crosslinking unit. With increasing content of crosslinking units, the corresponding glass transition temperature increased, while the clearing temperature decreased. Thermogravimetric analysis showed that LCE₁–LCE₃ have good thermal stability. Copyright © 2012 Society of Chemical Industry     

Comparison of Heavy Metal Removal from Chemically Interactive and Non-Interactive Solid Phases by the CEHIXM Process

A laboratory study was conducted to compare the removal of heavy metals from chemically interactive and non-interactive solid phases using coupled electric-hydraulic gradient assisted by ion exchange medium (CEHIXM) process. The removal of primarily four heavy metals Pb, Cd, Zn, and Mn from the contaminated sources was investigated. Experiments were conducted at a constant electric field of 50 V DC for both the solid phases and with constant hydraulic flow-rates of 10 cm³/min for chemically non-interactive solid phase and 4 cm³/min for chemically interactive solid phase. As much as 93% of Pb, 97% of Cd, 98% of Zn, and 94% of Mn were removed after 100 hours of the processing from chemically non-interactive solid phase. About 72% of Pb, 85% of Cd, 81% of Zn, and 77% of Mn were removed after 100 hours of the processing and about 90% of Pb, 96% of Cd, 93% of Zn, and 91% of Mn were removed after 200 hours of the processing from chemically interactive solid phase. Metal removal percentage was always higher for chemically non-interactive solid phase than that of chemically interactive solid phase. Chemically interactive solid phase required prolonged experiment duration to achieve compatible metal removal. The two solid phases did not follow quite the same order of metal removal. The order of removal was Zn > Cd > Mn > Pb for chemically non-interactive solid phase and Cd > Zn > Mn > Pb for chemically interactive solid phase.     

Stochastic Stability in a Model of Drilling

A random perturbation of a dynamical system serving as a model for the drilling process is studied. For this perturbation the existence of absolutely continuous stationary distributions is proved. It is shown that these distributions tend to a unique absolutely continuous invariant probability of the nonperturbed system as the magnitude of perturbation tends to zero.     

High-energy X-ray diffraction study on the temperature-dependent mechanical stability of retained austenite in low-alloyed TRIP steels

The stability of the retained austenite has been studied in situ in low-alloyed transformation-induced-plasticity (TRIP) steels using high-energy X-ray diffraction during tensile tests at variable temperatures down to 153 K. A detailed powder diffraction analysis has been performed to probe the austenite-to-martensite transformation by characterizing the evolution of the phase fraction, load partitioning and texture of the constituent phases simultaneously. Our results show that at lower temperatures the mechanically induced austenite transformation is significantly enhanced and extends over a wider deformation range, resulting in a higher elongation at fracture. Low carbon content grains transform first, leading to an initial increase in average carbon concentration of the remaining austenite. Later the carbon content saturates while the austenite still continues to transform. In the elastic regime the probed {h k l} planes develop different strains reflecting the elastic anisotropy of the constituent phases. The observed texture evolution indicates that the austenite grains oriented with the {2 0 0} plane along the loading direction are transformed preferentially as they show the highest resolved shear stress. For increasing degrees of plastic deformation the combined preferential transformation and grain rotation results in the standard deformation texture for austenite with the {1 1 1} component along the loading direction. The mechanical stability of retained austenite in TRIP steel is found to be a complex interplay between carbon concentration in the austenite, grain orientation, load partitioning and temperature.     

Comparison study of a chiral stationary phase based on cellulose derivatives prepared by “grafting from” and “grafting to” methods

Chiral stationary phase (CSP) with cellulose derivatives was synthesized using the “grafting from” and “grafting to” methods. The “grafting to” method involves the bonding of a preformed end‐functionalized polymer to reactive surface amine groups on the silica gel. The “grafting from” involves the immobilization of initiator onto the aminated silica gel followed by atom transfer radical polymerization (ATRP) to generate the chiral polymer chains. The successful preparation of the CSP with cellulose derivatives prepared by ATRP was confirmed by FE‐SEM, XPS, EA, and thermal analysis. The chiral resolution of the CSP with cellulose derivatives was evaluated by high‐performance liquid chromatography using 10 racemates with various mobile phases that consisted of hexane/alcohol, hexane/THF, and hexane/chloroform. Furthermore, the CSP with cellulose derivatives prepared by “grafting from” and “grafting to” were compared and discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Chiral copolymers of (R)‐N‐(1‐phenylethyl) methacrylamide and 2‐hydroxyethyl methacrylate: copolymerization characteristics and chiroptical properties

The aim of this investigation was the copolymerization of a chiral monomer, (R)‐N‐(1‐phenylethyl) methacrylamide, with an achiral monomer, 2‐hydroxyethyl methacrylate (HEMA). The copolymerization characteristics as well as the chiroptical properties (optical rotation and circular dichroism) and their variation with copolymer composition and temperature are discussed. The copolymers are statistical and enriched in HEMA. The monomer reactivity ratio of the chiral monomer (r₁) is 0.133 whereas that of HEMA (r₂) is 1.042 based on the Kelen–Tudos method. The sequence of consecutive chiral monomer units predominates for a feed composition between 0.5 and 0.9 (mole fraction). On the other hand, the sequence of HEMA is uniform and it predominates for a feed composition of around 0.5 (mole fraction). The chiroptical properties of the copolymers do not vary linearly with the content of chiral units in the copolymers. The optical rotation and circular dichroism attain optimum values above 30–40 mol% of chiral monomer units in the copolymers. However, the circular dichroism of the copolymers varies linearly with the temperature. The chiral monomer being a more bulky structure is less reactive than HEMA. The nonlinear variation of chiroptical properties of the copolymers with the content of chiral units may be due to the secondary interaction in the copolymers associated with the hydrogen bonding involving the amide linkage (CONH) present in the pendant chromophore of the chiral monomer as well as the hydroxyl pendant group of HEMA and also the aromatic π–π interaction. Copyright © 2009 Society of Chemical Industry