温室气体变化数值模拟试验中全球降水和温度变化的迟滞效应

利用耦合气候模式(GFDL-CM2.1)研究变动气候背景下全球平均降水和温度的变化。不同情景CO2 强迫试验表明, 降水变化存在明显的迟滞效应。全球平均降水与地表温度的变化存在显著的线性关系, 但是降水同时也受到CO2 浓度的直接影响。在CO2 增加又恢复的试验中, 降水变化滞后于地表温度变化, 出现降水 “迟滞效应”。在CO2 增加过程中, 温室效应增强会立即导致大气长波吸收增强, 大气获得的净辐射能量增加, 为维持大气能量收支平衡, 地面向上潜热通量受到抑制, 形成CO2 增加对降水的抑制效应。随之而来的温度上升则主要引起大气层顶出射长波辐射以及大气对地表的长波回辐射增加, 大气净辐射能量减少, 地面潜热通量增加, 从而引起降水的增加。在CO2 减少过程中, 情况正好相反, 温室效应减弱会增加降水, 而温度降低会减少降水。温度和CO2 对降水的不同影响决定了降水的迟滞效应。     

CO2浓度增加对西北太平洋热带风暴气候特征的影响

为了研究CO2浓度变化对西北太平洋热带风暴气候特征的影响,采用全球大气海洋耦合环流模式GFDL CM2.1 3个CO2排放情景下的数值试验资料,提出了适合模式的识别模式热带风暴的标准,并采用NCEP再分析资料和年鉴资料检验了标准的合理性,分析了模式热带风暴在CO2浓度增加后气候特征的变化.结果表明,所提标准是合理的,所识别的模式热带风暴在暖心平均结构等方面与NCEP热带风暴平均结构相似性高;CO2浓度增加后,模式热带风暴频数减少,强度增强,强热带风暴增多,主要源地和活动地区西移,季节分布和持续时间的分布形势没有明显变化.     

Nonlinear optical properties of Eu<Subscript>2</Subscript>O<Subscript>3</Subscript> doped 5ZnO-20Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>-75TeO<Subscript>2</Subscript> glasses

The third-order optical nonlinearities, including third-order nonlinear susceptibility X^(3), nonlinear refractive index (n2) and temporal response, were measured with forward DFWM using Nd:YAG mode-locked pulse laser. The results show that Eu203 doped 5ZnO-20Nb2O5-75TeO2 glasses have large n2 and ultra-fast temporal response. Raman spectra show that Eu2O3 dopant induces the changes in the local structure of glasses. The higher the dopant concentration, the larger the nonlinear refractive n2 and the faster the temporal response. The enhancement on the third-order optical nonlinearities can be attributed to the deformation of the electronic clouds in [TeO4] enhanced by Eu2O3 dopant.     

Climate as the dominant control on C<Subscript>3</Subscript> and C<Subscript>4</Subscript> plant abundance in the Loess Plateau: Organic carbon isotope evidence from the last glacial-interglacial loess-soil sequences

Two modes of photosynthesis predominate in terres-REPORTS trial plants: the C3 and C4 modes[1]. The C3 mode is used by all of trees, bushes, and cold season grasses. The C4 mode is used by the most of tropical and warm season grasses. They are disadvantaged relative to C3 plants at high CO2/O2 ratios because of the additional energy ex-pense needed to concentrate CO2 in the bundle-sheath cells. At low CO2/O2, however, C4 plants can achieve a relatively high quantum yield by suppressin…     

Chemical quenching and inhibition of positronium in Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The pore structure of Cr2O3/Al2O3 catalysts and the surface chemical properties of these pores were characterized by positron lifetime and coincidence Doppler broadening (CDB) measurements. Four lifetime components could be resolved from the positron lifetime spectrum, with two long lifetime components and two short lifetime components. The two long lifetimes τ4 and τ3 are attributed to ortho-positronium (o-Ps) annihilation in large pores and microvoids, respectively. With increasing Cr2O3 content, both τ4 and its intensity I4 show sharp decrease, while τ3 and its intensity I3 keep nearly unchanged. The Doppler broadening S parameters also show sharp decrease with increasing Cr2O3 content. Detailed analysis of the CDB spectrum reveals that the parapositronium (p-Ps) intensity also decreases with increasing Cr2O3 content. This indicates that the change of o-Ps lifetime τ4 is due to the chemical quenching by Cr2O3 but not spin-conversion of positronium. The decrease of o-Ps intensity I4 indicates that Cr2O3 also inhibits positronium formation.     

Improved and excellent CO sensing properties of Cu-doped TiO<Subscript>2</Subscript> nanofibers

Cu-doped TiO2 nanofibers with an average diameter of about 80 nm are synthesized through an electrospinning method. Both anatase and rutile crystallographic structures are found in the fibers based on XRD results. Compared with pure TiO2 nanofibers, the Cu-doped TiO2 nanofibers exhibit improved CO sensing properties at 300°C. The sensitivity of Cu-doped TiO2 nanofibers is up to 3 when the sensor is exposed to 5 ppm CO, and the response and recovery times are about 4 and 8 s, respectively. Good selectivity i...     

Preparation and radar-absorbing properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript>/Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/Yb<Subscript>2</Subscript>O<Subscript>3</Subscript> composite powder

Al₂O₃/TiO₂/Fe₂O₃/Yb₂O₃ composite powder was synthesized via the sol-gel method. The structure, morphology, and radar-absorption properties of the composite powder were characterized by transmission electron microscopy, X-ray diffraction analysis and RF impedance analysis. The results show that two types of particles exist in the composite powder. One is irregular flakes (100-200 nm) and the other is spherical Al₂O₃ particles (smaller than 80 nm). Electromagnetic wave attenuation is mostly achieved by dielectric loss. The maximum value of the dissipation factor reaches 0.76 (at 15.68 GHz) in the frequency range of 2-18 GHz. The electromagnetic absorption of waves covers 2-18 GHz with the matching thicknesses of 1.5-4.5 mm. The absorption peak shifts to the lower-frequency area with increasing matching thickness. The effective absorption band covers the frequency range of 2.16-9.76 GHz, and the maximum absorption peak reaches -20.18 dB with a matching thickness of 3.5 mm at a frequency of 3.52 GHz.     

Preparation and upconversion luminescence of YVO<Subscript>4</Subscript>:Er<Subscript>3+</Subscript>, Yb<Subscript>3+</Subscript>

YVO₄:Er³⁺, Yb³⁺ with varying Yb³⁺ concentrations were prepared by a precipitation method. The results of X-ray diffraction (XRD) show that all the samples have a tetragonal zircon structure; the calculated average crystallite sizes are in the range of 14–22 nm. The lattice constants and cell volume of the samples decrease slightly with the increase in Yb³⁺ concentration. The upconversion luminescence spectra of all the samples were studied under 980 nm laser excitation. The strong green emission is observed, which is attributed to the ²H_11/2 → ⁴I_15/2 and ⁴S_3/2→⁴I_15/2 transitions of Er³⁺, and the red emission peaks in 650–675 nm can be ignored. The emission intensity for the sample depends on the Yb³⁺ concentration. These results reveal that the upconversion processes of YVO₄:Er³⁺, Yb³⁺ are related to the structure and the doping Yb³⁺ concentration of the sample.     

Transparent organic light-emitting diodes based on Cs<Subscript>2</Subscript>CO<Subscript>3</Subscript>:Ag/Ag composite cathode

The transparent organic light-emitting diodes (TOLEDs) based on Cs 2 CO 3:Ag/Ag composite cathode are reported in this paper.They show higher efficiency and better stability than the control devices with the Cs 2 CO 3 /Ag cathode.The devices are highly transparent,and show total efficiencies from both sides of the devices comparable with conventional bottom-emitting devices.The electroluminescence (EL) spectrum from the cathode side of the device is closer to the photoluminescence (PL) spectrum of the light...     

GCMs模式在黄河源区的适用性分析

利用黄河源区24个气象站1961～1990年的月平均气温、最高气温、最低气温、月降水资料和IPCC 提供的5个全球海气耦合模式(CCC,CCSR,CSIRO,GFDL,HADL)的模拟结果,采用多年平均、不均匀系数、绝对变化幅度等统计特征,验证分析了各个模式对黄河源区降水和气温的模拟效果.结果表明:各个模式在降水和气温2个方面的模拟效果均不相同,如GFDL模式对降水的模拟效果最好,GFDL和HADL模式对气温的模拟效果较好;若同时考虑降水、气温2个方面的模拟效果,GFDL模式要略优于其他模式.     

鸡蛋水解产物对酸性,碱性溶液中碳钢阳极过程的影响

通过测定碳钢在含有不同浓度鸡蛋水解产物的２ｍｏｌ／Ｌ盐酸、２ｍｏｌ／Ｌ硫酸、２ｍｏｌ／Ｌ碳酸铵溶液中的阳极极化曲线，研究了碳钢在不同介质中的阳极过程，发现鸡蛋水解产物对在酸性、碱性溶液中的碳钢皆有明显的缓蚀作用．在ＨＣｌ溶液及（ＮＨ４）２ＣＯ３溶液中，鸡蛋水解产物的最佳浓度为２．０％，在Ｈ２ＳＯ４溶液中，鸡蛋水解产物的最佳浓度为１．０％，并对鸡蛋水解产物的缓蚀性能进行了理论探讨     

Gene product expression of cyclin D<Subscript>2</Subscript> and p16 during the transition from cardiac myocyte hyperplasia to hypertrophy

The current study was to investigate mRNA expression of cyclin D₂ and p16 during the transition from cardiac myocyte hyperplasia to hypertrophy. Cultured cardiac myocytes (CM) and fibroblasts (FC) obtained from 1-day-old Sparague-Dawley rats were used in this study. We have determined (1) hyperplasia by cell growth curve and fluorescence activated cell sorting (FACS); and (2) ultrastructure by electron microscope observation; and (3) expresions of cyclin D₂ mRNA and p16 mRNA by using in situ hybridization and image analysis. The results were shown (1) Results of cell growth curve and FACS analysis showed CM could proliferate in the first 3 cultured days (4 days in postnatal development). But the ability decreased quickly, concomitant with the differentiation. (2) The ultrastructure of CM showed the large amount of myofilaments and mitochondrion and FC showed moderate amount of rough endoplasmic reticulum. (3) The expression of cyclin D₂ mRNA in 3−, 4−, 5−day CM group was 0.89 times (p<0.05), 0.80 times (p<0.05) and 0.56 times (p<0.01) of that in 1-day group respectively. P16 mRNA in 2−, 3−, 4−, 5−day CM group were 1.63 times (p<0.01), 1.72 times (p<0.01), 1.99 times (p<0.01) and 2.84 times (p<0.01) of that in 1−day group respectively. It can be concluded that cultured neonatal rat cardiac myocytes could proliferate during the first 3 cultured days, but the ability of proliferation decreased, from the fourth day, concomitant with differentiation. Cyclin D₂ and p16 have the key roles during the transition from myocyte hyperplasia to hypertrophy. Biography: Zhang Yu-xia (1974-), female, Master, research direction: cardiovascular pathology.     

Micro-arc oxidization fabrication and ethanol sensing performance of Fe-doped TiO<Subscript>2</Subscript> thin films

In-situ pure TiO₂ and Fe-doped TiO₂ thin films were synthesized on Ti plates via the micro-arc oxidation (MAO) technique. The as-fabricated anatase TiO₂ thin film-based conductometric sensors were employed to measure the gas sensitivity to ethanol. The results showed that Fe ions could be easily introduced into the MAO-TiO₂ thin films by adding precursor K₄(FeCN)₆·3H₂O into the Na₃PO₄ electrolyte. The amount of doped Fe ions increased almost linearly with the concentration of K₄(FeCN)₆·3H₂O increasing, eventually affecting the ethanol sensing performances of TiO₂ thin films. It was found that the enhanced sensor signals obtained had an optimal concentration of Fe dopant (1.28at%), by which the maximal gas sensor signal to 1000 ppm ethanol was estimated to be 7.91 at 275°C. The response time was generally reduced by doped Fe ions, which could be ascribed to the increase of oxygen vacancies caused by Fe³⁺ substituting for Ti⁴⁺.     

Study of droplet size and velocity of fuel containing CO2 spray by means of PDA

Injection of fuel containing CO2 has potential to reduce NOx and soot emissions in a diesel engine. This paper presents an experimental study on the spray characteristics of fuel containing CO2 as measured by phase doppler anemometry (PDA). Experiments were performed under atmospheric conditions on diesel hole-type nozzles at constant injection pressure. Effects of CO2 concentration in diesel fuel on the spray pattern, droplet size and velocity were measured. Experimental results show that fuel atomization will improve greatly when the concentration of dissolved CO2 in the fuel exceeds the critical value. The axial and radial velocity of the fuel spray containing CO2 is larger than that of conventional diesel fuel spray near the nozzle exit due to flash boiling phenomena. Downstream of the spray, the radial velocity and droplet size of fuel containing CO2 is much more uniform and smaller than that of pure diesel spray. It is attributed to the greatly enhanced liquid-gas mixing resulting from flash separation of CO2 from the liquid. New insight into the atomization of the fuel containing CO2 was obtained and a possible mechanism to explain the phenomena was proposed. The method may be developed into a new technique for controlling diesel combustion and exhaust emis-sions.     

Up-conversion luminescence of Er^3＋ doped and Er^3＋/Yb^3＋ co-doped YTaO4

The synthesis and up-conversion luminescent properties of YTaO4：Er^3＋ and YTaO4：Er^3＋/Yb^3＋ are reported for the first time. According to the measurement results of up-conversion spectra, Yb^3＋ co-doping can remarkably enhance the green （^2H11/2/^4S3/2→^4I15/2） and red （^4F9/2→^4I15/2） emissions, but depress the infrared emission （^4I9/2→^4I15/2）. With the increase of the Yb^3＋ concentration, the intensity of green emission increases, after that, when the Yb^3＋ concentration increases continuously, the intensity of green emission decreases, while those of the red and infrared emissions increase and decrease alternately. In addition, the up-conversion mechanisms of Er^3＋ doped and Er^3＋/Yb^3＋ co-doped YTaO4 are also discussed. It is found that the transform of up-conversion mechanism from two-step energy transfer to cooperating sensitization takes place when Yb^3＋ concentration is increased up to 12 mol%. With the further increase of Yb^3＋ concentration, the energy-back-transfer gradually becomes the dominant up-conversion mechanism, which results in the quenching of the green emission and slight increasing of the red and infrared emissions.     

Effect of TiO<Subscript>2</Subscript> on the viscosity and structure of low-fluoride slag used for electroslag remelting of Ti-containing steels

The viscosity of CaF₂-CaO-Al₂O₃-MgO-(TiO₂) slag was measured using a rotating crucible viscometer. Raman spectroscopy analysis was performed to correlate the viscosity to slag structure. The viscosity of the slag was found to decrease with increasing TiO₂ content in the slag from 0 to 9.73wt%. The activation energy decreased from 95.16 kJ/mol to 79.40 kJ/mol with increasing TiO₂ content in the slag. The introduction of TiO₂ into the slag played a destructive role in Al-O-Al structural units and Q4 units by forming simpler structural units of Q2 and Ti₂O₆4- chain. The amount of Al-O-Al significantly decreased with increasing TiO₂ content. The relative fraction of Q4 units in the[AlO₄]5--tetrahedral units shows a decreasing trend, whereas the relative fraction of Q2 units and Ti₂O₆4- chain increases with increasing TiO₂ content accordingly. Consequently, the polymerization degree of the slag decreases with increasing TiO₂ content. The variation in slag structure is consistent with the change in measured viscosity.     

Effect of reinforcement content on the adhesive wear behavior of Cu10Sn5Ni/Si3N4 composites produced by stir casting

The main objective of this paper was to fabricate Cu10Sn5Ni alloy and its composites reinforced with various contents of Si₃N₄ particles (5wt%, 10wt%, and 15wt%) and to investigate their dry sliding wear behavior using a pin-on-disk tribometer. Microstructural examinations of the specimens revealed a uniform dispersion of Si₃N₄ particles in the copper matrix. Wear experiments were performed for all combinations of parameters, such as load (10, 20, and 30 N), sliding distance (500, 1000, and 1500 m), and sliding velocity (1, 2, and 3 m/s), for the alloy and the composites. The results revealed that wear rate increased with increasing load and increasing sliding distance, whereas the wear rate decreased and then increased with increasing sliding velocity. The primary wear mechanism encountered at low loads was mild adhesive wear, whereas that at high loads was severe delamination wear. An oxide layer was formed at low velocities, whereas a combination of shear and plastic deformation occurred at high velocities. The mechanism at short sliding distances was ploughing action of Si₃N₄ particles, which act as protrusions; by contrast, at long sliding distances, direct metal-metal contact occurred. Among the investigated samples, the Cu/10wt% Si₃N₄ composite exhibited the best wear resistance at a load of 10 N, a velocity of 2 m/s, and a sliding distance of 500 m.     

Effect of NaNO<Subscript>3</Subscript> concentration on anodic electrochemical behavior on the Sb surface in NaOH solution

The effect of NaNO₃ concentration on the anodic electrochemical behavior of antimony in 4 M NaOH solution was investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses. The mechanism of NO₃- concentration effect on the anodic electrochemical behavior of antimony was proposed, and its availability was confirmed by experimental results. The effect of NaNO₃ on the anodic behavior of antimony in NaOH solution can be interpreted as a stepwise formation of different antimony compounds with different NaNO₃ concentrations. Metallic antimony is apt to be oxidized into Sb₂O₃ within the NaNO₃ concentration range of 0-0.48 M. NaSbO₃ can be found on the antimony surface when the NaNO₃ concentration increases gradually. Insoluable NaSbO₃ inhibits the anodic oxidation of antimony due to its shielding effect on the mass transport of the reactants and products. Surface morphology and composition were analyzed by X-ray photoelectron spectroscopy (XPS), scanning electronic microscopy (SEM), and electron dispersion spectroscopy (EDS) analyses. Results indicate that the anodic oxidation layer is composed of Sb₂O₃, NaSbO₃, and Sb. The atomic proportion of antimony in the form of NaSbO₃ increases with increasing NaNO₃ concentration due to the powerful oxidizing property of NaNO₃.     

Microwave absorption properties of SiC@SiO2@Fe3O4 hybrids in the 2-18 GHz range

To enhance the microwave absorption performance of silicon carbide nanowires (SiCNWs), SiO₂ nanoshells with a thickness of approximately 2 nm and Fe₃O₄ nanoparticles were grown on the surface of SiCNWs to form SiC@SiO₂@Fe₃O₄ hybrids. The microwave absorption performance of the SiC@SiO₂@Fe₃O₄ hybrids with different thicknesses was investigated in the frequency range from 2 to 18 GHz using a free-space antenna-based system. The results indicate that SiC@SiO₂@Fe₃O₄ hybrids exhibit improved microwave absorption. In particular, in the case of an SiC@SiO₂ to iron(Ⅲ) acetylacetonate mass ratio of 1:3, the microwave absorption with an absorber of 2-mm thickness exhibited a minimum reflection loss of -39.58 dB at 12.24 GHz. With respect to the enhanced microwave absorption mechanism, the Fe₃O₄ nanoparticles coated on SiC@SiO₂ nanowires are proposed to balance the permeability and permittivity of the materials, contributing to the microwave attenuation.     

Synthesis and characterization of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> prepared from atmospheric pressure acid leach liquors of nickel laterite ores

A chemical precipitation-thermal decomposition method was developed to synthesize Co₃O₄ nanoparticles using cobalt liquor obtained from the atmospheric pressure acid leaching process of nickel laterite ores. The effects of the precursor reaction temperature, the concentration of Co2+, and the calcination temperature on the specific surface area, morphology, and the electrochemical behavior of the obtained Co₃O₄ particles were investigated. The precursor basic cobaltous carbonate and cobaltosic oxide products were characterized and analyzed by Fourier transform infrared spectroscopy, thermogravimetric differential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, specific surface area analysis, and electrochemical analysis. The results indicate that the specific surface area of the Co₃O₄ particles with a diameter of 30 nm, which were obtained under the optimum conditions of a precursor reaction temperature of 30℃, 0.25 mol/L Co2+, and a calcination temperature of 350℃, was 48.89 m2/g. Electrodes fabricated using Co₃O₄ nanoparticles exhibited good electrochemical properties, with a specific capacitance of 216.3 F/g at a scan rate of 100 mV/s.