Feasibility study on 1.6 μm continuous-wave modulation laser absorption spectrometer system for measurement of global CO2 concentration from a satellite

A feasibility study is carried out on a 1.6 μm continuous-wave modulation laser absorption spectrometer system for measurement of global CO(2)concentration from a satellite. The studies are performed for wavelength selection and both systematic and random error analyses. The systematic error in the differential absorption optical depth (DAOD) is mainly caused by the temperature estimation error, surface pressure estimation error, altitude estimation error, and ON wavelength instability. The systematic errors caused by unwanted backscattering from background aerosols and dust aerosols can be reduced to less than 0.26% by using a modulation frequency of around 200 kHz, when backscatter coefficients of these unwanted backscattering have a simple profile on altitude. The influence of backscattering from cirrus clouds is much larger than that of dust aerosols. The transmission power required to reduce the random error in the DAOD to 0.26% is determined by the signal-to-noise ratio and the carrier-to-noise ratio calculations. For a satellite altitude of 400 km and receiving aperture diameter of 1 m, the required transmission power is approximately 18 W and 70 W when albedo is 0.31 and 0.08, respectively; the total measurement time in this case is 4 s, which corresponds to a horizontal resolution of 28 km.     

Oxidation behavior of copper nanoparticles at low temperature

A mass gain for copper nanoparticles with a mean diameter of 20 nm in a 20% oxygen-nitrogen atmosphere was measured at 150-300 °C using thermogravimetry (TG). The mass gain equilibrium of the copper particles differed at each temperature, and a threshold temperature was recorded. Oxide products, consisting mainly of Cu₂O, formed on the copper nanoparticles below the threshold temperature. Above the threshold temperature, there was an initial, and drastic, formation of Cu₂O, which then changed to CuO. The activation energy for the oxidation of the copper nanoparticles that could be calculated from the rate of the mass gain was an indication of the nano-effect of the copper nanoparticles.     

Effects of stimulus information and number of stimuli on sequential dependencies in absolute identification.

Three absolute identification experiments examined the effects on sequential dependencies of 2 factors: stimulus information and the number of stimuli used. Data were analyzed by multivariate information analysis. In Exp 1 with 5 university studentswith experience in absolute identification experiments, the stimulus modality was pure tone frequency under masking and no-masking conditions and 4, 6 10, and 16 tones were used. In Exp 2 with 5 university students, luminance levels of light circles were used as stimuli and number of luminance levels was 10 or 16. In Exp 3 with 6 university students, the stimuli were pointer positions along a horizontal line and they were presented either within a small or a large range to manipulate the stimulus information available. Results show that the sequential dependencies became larger as the stimulus information was decreased and as the number of stimuli was increased. Results are discussed in the context of models of sequential dependencies. Results of a multiple regression analysis on the data were compared with those of the information analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

SAW气体传感器的转换机制

讨论了在SAW气体的传感器中把化学信号(气体浓度)转换成物理信号(SAW相速度变化)的机制以及将它们彼此分离开来的方法.     

浅谈入世后我国农产品质量安全和标准体系建设

<正> 随着农业发展进入新的阶段,农产品质量安全已成为制约我国农业和农村经济发展的突出问题。特别是WTO成立以来,伴随着农产品贸易的自由进程,传统的关税壁垒作用在逐步减弱,以控制农产品质量安全为中心的技术性壁垒的作用在逐步加强,围绕农产品质量安全而产生的贸易摩擦乃至争端呈增长趋势。我国加入WTO之后,无论是农产品的国内市场,还是面对国际农产品贸易,都不可避免地要被卷入这场新的国际角逐。     

Concentration distribution of antioxidant additive BHT in polypropylene after heating

The concentration distribution of an antioxidant 2,6-di-tert-butyl-p-cresol (BHT) in the polypropylene (PP) after heating the film containing BHT for a long period of time in succession was studied with use of the rolled film method. The film of 0.003 cm in thickness containing uniformly 710 mg kg^?1 of BHT was wound tightly around a glass tube. At the beginning, BHT was distributed uniformly in all layers, and after a given time of the heat treatment at 70–100°C, a remarkable alteration of the concentration distribution of BHT in PP took place. The relations between BHT concentration and the distance from the surface were shown by parabolic curves after heating. The BHT concentration was always kept at almost zero concentration at the surface layer of the rolled film. Assuming that the diffusion obeys Fick's law, the diffusion coefficients at 70, 80, 90, and 100°C were estimated to be 1.05, 4.17, 8.69, and 24.7 × 10^?9 cm² s^?1, respectively. The activation energy was calculated as 105 kJ mol^?1.     

Thermal decomposition of aluminium hydroxycarboxylates—lactate,citrate and tartrate

The thermal transformation of anhydrous alumina obtained by the decomposition of the lactate, citrate and tartrate of aluminium has been examined by thermal analysis(TGA and DTA), infrared spectrophotometry and X-ray diffraction study. It is found that under an atmosphere of air the thermal decomposition of aluminium hydroxycarboxylates to anhydrous amorphous alumina, which transforms to α-alumina via γ-, δ- and θ-aluminas, proceeds as follows for Al[CH₃CH(OH)COO]₃, the decomposition of skeleton and the combustion of its decomposition products; for Al[CH₂C(OH)CH₂(COO)₃] and Al₂{[CH(OH)COO]₂}₃, dehydroxylation, decomposition of skeleton and the combustion of its decomposition products.