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Field cultivation practices affected soil temperature that influenced the crop development of winter crops. This study was undertaken to determine the effects of different mulch materials, tillage depths and planting methods on spike differentiation of winter wheat ( Triticum aestivum L.). The field experiment was consisted of three tests: (i) polythene mulch, straw mulch and no mulch; (ii) ridge planting and furrow planting; (iii) conventional tillage and shallow tillage. The results showed that soil temperature was affected by different practices. The higher soil temperature under polythene mulch resulted in the earlier initiation of spike differentiation, while straw mulch decreased soil temperature in spring that delayed the initiation compared with the non-mulch treatment. The spike initiation under ridge planting started earlier than that of furrow planting. Reduced tillage delayed the initiation compared with the conventional tillage. Duration of spike differentiation lasted longer under earlier starting of initiation that increased the grain numbers per spike. Other yield component characters were not affected by soil temperature. It was concluded that in the North China Plain where grain-filling duration of winter wheat was limited, agricultural practices that increased soil temperature in spring were favorable for grain production.
Abstract
Low-temperature positron lifetime and Doppler broadening measurements were made in MgO crystals containing D– or H– ions in order to investigate the temperature dependence of the positron trapping by D– and H– ions and elucidate the possible formation of PsD (PsH) states. Positrons are trapped at D– and H– ions once the oxygen vacancies, which are more effective positron traps, are eliminated by annealing the crystals at high temperatures in a reducing atmosphere. From the temperature dependence of the annihilation parameters the positron trapping coefficients for D– and H– centers were shown to increase with temperature between 100–300 K. The lifetime of the PsD (PsH) state is (650±30) ps and temperature independent. The dissociation rate of the PsD (PsH) state into D (H) and Ps is also temperature independent. No isotopic effect was observed.
Abstract
DSC and TG-DTA techniques were used to investigate micro-sized silver powder particles and the adsorption of ethyl cellulose on these particles in a solution of ethyl acetate. The apparent specific heat of the silver particles was determined, and the kinetics of temperature-programmed desorption (TPD) of these adsorbed silver particles was investigated. Results show that the apparent specific heat and desorption kinetic parameters obtained by thermal analysis techniques could be used to characterize certain physico-chemical properties of such a particulate system.
Abstract
According to the theoretical basis of thermokinetics, the integral and differential thermokinetic equations of opposing reactions have been derived, and a novel thermokinetic research method, the characteristic parameter method for opposing reactions which taking place in a batch conduction calorimeter under isothermal condition, has been proposed in this paper. Only needing the characteristic thermoanalytical data corresponding to tm and 2tm from the same curve, the rate constants of forward and backward reactions and equilibrium constant can be calculated simultaneously with this method. In order to test the validity of this method, the proton-transfer reactions of nitroethane with ammonia at 15 and 25°C, and with trihydroxymethyl aminomethane (Tris) at 15 and 30°C have been studied, respectively. The results of rate constants and equilibrium constants calculated with this method are in agreement with those in the literature. Therefore, the characteristic parameter method for opposing reaction is believed to be correct.
Testing of some dynamic kinetic equations
Part III. Zero-order reaction
The acid-catalysed iodination of acetone in aqueous solution was used to test three dynamic kinetic equations. The Freeman and Carroll treatment yields the most satisfactory results.
Abstract
A novel thermokinetic research method for determination of rate constants of simple-order reaction in batch conduction calorimeter under isothermal condition, the characteristic parameter method, is proposed in this paper. Only needing the characteristic time parameter tm obtained from the measured thermoanalytical curve, the kinetic parameters of reactions studied can be calculated conveniently with this method. The saponifications of ethyl propionate and ethyl acetate in aqueous ethanol solvent, the polymerization of acrylamide in aqueous solution, the ring opening reaction of epichlorohydrin with hydrobromic acid have been studied. The experimental results indicate that the characteristic parameter method for simple-order reaction is correct.
Testing of some dynamic kinetic equations
Part II. Second-order reaction
The conversion of ammonium cyanate into urea in aqueous solution was used to test three dynamic kinetic methods. It is concluded that the Freeman and Carroll method is the most satisfactory.
Abstract
The concentration of radionuclides in environmental samples and the environmental radiation level (including cosmic rays) was monitored on Spratly Islets in South China Sea prior to the commercial operation of nearby Chinese nuclear power plants. Samples of coral sand, sea food, vegetation, water, and accumulated fallout on the islet were obtained and measured for radioactivity. Except for some exposure originating from minute amounts of60Co and137Cs, the radiation background is mainly emitted from naturally occurring radionuclides. Radiation levels including beta, gamma, and neutron on the islet have also monitored. Gamma dose rates for outdoor exposure averaged approximately 0.09 
Sv/h; the neutron dose rate was about 0.003 Sv/h. Automatic radiation surveillance and a routine sampling program on the Spratly Islets are viewed as essential to provide an early warning in the Far East in case of a nuclear emergency.
Abstract
This research investigated the influence of binary solutions of benzene and methanol for their vapor flammability characteristics. The different mixing ratios (100/0, 75/25, 50/50, 25/75 and 0/100 vol%) samples were injected into a 20-liter spherical explosion vessel under various initial temperatures (100, 150 and 200C) to study their flammability behaviors. According to the experimental results, the flammability diagram of mixtures can be completely illustrated and combined with specific safety-related properties such as lower explosion limit (LEL), upper explosion limit (UEL), minimum oxygen concentration (MOC), maximum explosion overpressure (P max), and gas or vapor deflagration index (K g). The experimental results showed that the UEL, P max and K g all increased with the temperature, pressure and oxygen concentration, whereas there was no significant variation on the part of LEL. The results can provide specific information on fire and explosion hazards for related industries.
