高海拔隧道出渣过程CO分布分析及需风量研究

为解决高海拔施工隧道出渣过程的排气排放物污染,改善通风排污效果,基于海拔环境参数变化和紊流扩散理论,构建了高海拔隧道气体扩散模型.以海拔3200 m的川藏铁路某隧道为研究背景,对洞内的环境参数和CO分布进行测定,利用SolidWorks和ANSYS建立施工隧道掌子面出渣模型,采用Fluent中的组分输运方程,对不同海拔高度的有害气体运移规律和质量分数分布进行动态模拟.结果表明,隧道中内燃机械作业时,在靠近工作面迎头位置,CO分布不均匀,极差值较大.在靠近隧道出口方向,CO分布逐渐趋于平稳.CO质量分数随海拔的升高而增加,而CO质量浓度却呈相反的变化趋势.从0 m到6 km,CO质量分数上升了96％;由于环境参数变化对CO质量浓度影响的权重大于CO排放量,导致CO质量浓度下降了18％.在保证隧道内CO质量分数不变的条件下,需风量随海拔高度呈非线性增加.根据得到的需风量计算模型,在海拔3200 m时,需风量约为4.95 m3/(kW·min).     

Synthesis of few layer single crystal graphene grains on platinum by chemical vapour deposition

The present competition of graphene electronics demands an ef fi cient route which produces high quality and large area graphene. Chemical vapour deposition technique, where hydrocarbons dissociate in to active carbon species and form graphene layer on the desired metal catalyst via nucleation is considered as the most suitable method. In this study, single layer graphene with the presence of few layer single crystal graphene grains were grown on Pt foil via chemical vapour deposition. The higher growth temperature changes the surface morphology of the Pt foil so a delicate process of hydrogen bubbling was used to peel off graphene from Pt foil samples with the mechanical support of photoresist and further transferred to Si O2/Si substrates for analysis. Optical microscopy of the graphene transferred samples showed the regions of single layer along with different oriented graphene domains. Two type of interlayer stacking sequences, Bernal and twisted, were observed in the graphene grains.The presence of different stacking sequences in the graphene layers in fl uence the electronic and optical properties; in Bernal stacking the band gap can be tunable and in twisted stacking the overall sheet resistance can be reduced. Grain boundaries of Pt provides low energy sites to the carbon species, therefore the nucleation of grains are more at the boundaries. The stacking order and the number of layers in grains were seen more clearly with scanning electron microscopy. Raman spectroscopy showed high quality graphene samples due to very small D peak. 2D Raman peak for single layer graphene showed full width half maximum(FWHM) value of 30 cm-1. At points A, B and C, Bernal stacked grain showed FWHM values of 51.22, 58.45 and 64.72 cm-1, while twisted stacked grain showed the FWHM values of 27.26, 28.83 and 20.99 cm-1,respectively. FWHM values of 2D peak of Bernal stacked grain showed an increase of 20–30 cm-1 as compare to single layer graphene which showed its dispersive nature and con fi rmed Bernal sequence. On the other hand, the slightest decrease in FWHM values of 2D peak in twisted grain comparing to single layer con fi rmed the twisted sequence of grains. Atomic force microscopy analysis showed an increasing trend in grain height pro fi le with an increase in the number of layers.     

DSC analyses of static and dynamic precipitation of an Al–Mg–Si–Cu aluminum alloy

In the present investigation, both static and dynamic precipitations of an Al–Mg–Si–Cu aluminum alloy after solid-solution treatment(SST)were comparatively analyzed using differential scanning calorimetry(DSC). Dynamic aging was performed in the SST alloy through equal channel angular pressing(ECAP) at different temperatures of room temperature, 110, 170, 191 and 300 1C. For comparison, static artificial aging was conducted in the SST alloy at 191 1C with two aging times of 4 and 10 h. The DSC analyses reveal that the dynamic precipitation has occurred in the ECAPed samples, while the activation energies associated with the strengthening precipitates in the dynamic samples are considerably higher than the energies in the SST and static aged samples. The higher activation energies are probably attributed to the smaller grains and higher dislocation density developed after ECAP. The results in the present investigation allow the prediction of the type of the dynamic precipitates to influence the strength of the ultrafine grained alloy during ECAP at various temperatures.     

Plant microremains provide direct evidence for the functions of stone knives from the Lajia site,northwestern China

A large number of stone knives have been recovered from Neolithic archaeological sites in East Asia. However, direct evidence regarding the functions of the stone knives has been scarce, and hence, their functions have remained controversial. In this study, we recovered and analysed ancient starch grains and phytoliths from residues adhering to stone knives excavated from the Lajia site, Qinghai Province, northwest China, thus providing direct evidence for the functions of the knives. Our anal- yses were based on the following： （1） an assemblage of 278 identifiable starch grains, representing grains from the stems of foxtail millet （Setaria italica） and broomcorn millet （Panicum miliaceum） （65.1% of the total） and the stems of Hordeum and Triticum species （3.6 % of the total）, and （2） an assemblage of 361 identifiable phytoliths, the majority of which were from the stems and leaves of plants such as Panicoideae and related taxa （96 % of the total）. Our study demonstrates that one of the functions of the stone knives was the harvesting crops. In addition, a few starch grains from food legumes and roots （3.4 % of the total） indicate that the stone knives were also likely used to process, peel and cut some foods.     

A molecular cryptography model based on structures of DNA self-assembly

With the progress of DNA computing, DNA- based cryptography becomes an emerging interdisciplinary research field. In this paper, we present a novel DNA cryptography that takes advantage of DNA self assembled structure. Making use of the toehold strands recognition and strand displacement, the bit-wise exclusive-or （XOR） operation is carried out to fulfill the information encryption and decryption in the form of a one-time-pad. The security of this system mainly comes from the physical isolation and specificity of DNA molecules. The system is con- structed by using complex DNA self-assembly, in which technique of fluorescent detection is utilized to implement the signal processing. In the proposed DNA cryptography, the XOR operation at each bit is carried out individually, thus the encryption and decryption process could be con- ducted in a massive, parallel way. This work may dem- onstrate that DNA cryptography has the great potential applications in the field of inRwmation security.     

Synthesis and characterization of cerium sulfide thin film

Cerium sulfide(Cex Sy)polycrystalline thin film is coated with chemical bath deposition on substrates(commercial glass).Transmittance,absorption,optical band gap and refractive index are examined by using UV/VIS.Spectrum.The hexagonal form is observed in the structural properties in XRD.The structural and optical properties of cerium sulfide thin films are analyzed at different p H.SEM and EDX analyses are made for surface analysis and elemental ratio in films.It is observed that some properties of films changed with different p H values.In this study,the focus is on the observed changes in the properties of films.The p H values were scanned at 6–10.The optical band gap changed with p H between 3.40 to 3.60 e V.In addition,the film thickness changed with p H at 411 nm to 880 nm.     

New bisexual form of Cavernocypris subterranea (Wolf, 1920) (Crustacea, Ostracoda) from Idaho

Males of Cavernocypris subterranea were found for the first time in an Idaho spring. The bisexual form is described on soft body parts and valves. The genus Cavernocypris now includes 2 bisexual and 1 parthenogenteic species.     

Correlation,entropy, and information transfer in black hole radiation

Since the discovery of Hawking radiation, its consistency with quantum theory has been widely questioned. In the widely described picture, irrespective of what initial state a black hole starts with before collapsing, it eventually evolves into a thermal state of Hawking radiations after the black hole is exhausted. This scenario violates the principle of unitarity as required for quantum mechanics and leads to the acclaimed ‘‘information loss paradox'. This paradox has become an obstacle or a reversed touchstone for any possible theory to unify the gravity and quantum mechanics. Based on the results from Hawking radiation as tunneling, we recently show that Hawking radiations can carry off all information about the collapsed matter in a black hole. After discovering the existence of information-carrying correlation, we show in great detail that entropy is conserved for Hawking radiation based on standard probability theory and statistics. We claim that information previously considered lost remains hidden inside Hawking radiation. More specifically, it is encoded into correlations between Hawking radiations. Our study thus establishes harmony between Hawking radiation and the unitarity of quantum mechanics, which establishes the basis for a significant milestone toward resolving the long-standing information loss paradox. The paper provides a brief review of the exciting development on Hawking radiation. In addition to summarize our own work on this subject, we compare and address other related studies.     

Conservation status of the threatened, insular San Jose brush rabbit ( Sylvilagus mansuetus )

The conservation status and distribution of the insular endemic San Jose brush rabbit ( Sylvilagus mansuetus ), as well as threats to its population viability, were determined through surveys undertaken since 1995 on San José Island in the Gulf of California, Mexico. Sylvilagus mansuetus is restricted to a specific desert habitat found in the southwestern coastal plains of the island. Vegetation in this habitat is composed primarily of 7 plant species. The extent of rabbit occurrence is only 20 km 2 , and the population density estimate in the most optimal habitat is 25–35 individuals · km –2 . To our knowledge, the San Jose brush rabbit possesses the smallest distribution among all lagomorph species. Sylvilagus mansuetus is threatened by a population of feral cats and by human activities, including illegal hunting, development of a tourist area, and a salt mine. Human activities, even over a short time frame, could severely impact this restricted area and endanger the survival of this species. Recommended management includes removing cats and conducting additional research on the rabbit’s life history and ecology. Se determinó el estado de conservación y la distribución del conejo de San José ( Sylvilagus mansuetus ), una especie insular endémica, mediante muestreos que se han llevado a cabo desde 1995 en la isla de San José en el Mar de Cortés, México. Sylvilagus mansuetus quedó restringido a un tipo específico de hábitat desértico en la llanura costera suroccidental de la isla, donde predominan 7 especies de plantas. La extensión de la especie es de sólo 20 km 2 , y la densidad de la población en el hábitat óptimo se estimó entre 25 y 35 individuos · km –2 . Hasta donde conocemos, el conejo de San José tiene el área de distribución más pequeña de todas las especies de lagomorfos. Sylvilagus mansuetus se ve amenazado por una población de gatos ferales y por actividades humanas tales como la caza ilegal, el turismo y la operación de una mina de sal. Las actividades humanas podrían tener un impacto severo en esta área restringida y podrían poner en peligro la supervivencia de esta especie dentro de poco tiempo. Algunas acciones recomendables para el manejo de la especie incluyen el eliminar los gatos y llevar a cabo estudios adicionales para obtener más detalles sobre la biología y ecología del conejo a fin de mejorar su conservación.