Atomic layer deposition on Pd nanocrystals for forming Pd-TiO2 interface toward enhanced CO oxidation

Pd typically exhibits relatively low catalytic activity in CO oxidation, as CO is apt to be adsorbed on Pd to poison the surface for O2 activation. In this Letter, we report that this limitation can be overcome by integrating Pd with TiO2. The TiO2 was coated on Pd nanocubes with a controllable thickness using atomic layer deposition (ALD) method. Given the different work functions of TiO2 and Pd, the electrons in TiO2 semiconductor will flow toward Pd. With the electron density increased on Pd, the adsorption of CO to Pd will be weakened while the oxygen activation can be facilitated. Meanwhile, the interface-confined sites at Pd-TiO2 may further enhance the oxygen activation. As the species adsorption and activation are strongly correlated with electron density, the performance of Pd-TiO2 in CO oxidation turns out to depend on the TiO2 thickness, which determines the number of transferred electrons, within a certain range (<1.8 nm). This work provides a new strategy for enhancing catalytic performance through tailoring charge densities in hybrid catalysts.     

基于霍尔三维模型的雾霾治理对策研究

运用霍尔三维结构的基本理论,构建雾霾治理对策的三维结构模型。从时间维、逻辑维和知识维对雾霾的治理对策进行划分,构建"三元主体"模型,探讨政府、企业和个人三大主体在雾霾治理各个阶段中的相互作用,对推动雾霾治理研究具有重要的指导作用。     

内蒙古地区4种林分类型UVB屏蔽效应研究

选取内蒙古大兴安岭地区和呼和浩特市兴安落叶松、油松、樟子松和白杆4种典型针叶林,利用PC-2型太阳辐射记录仪进行UVB辐射日进程测定,以获得4种典型性针叶林的UVB屏蔽效应;对4种林分UVB屏蔽效率与枝下高、郁闭度等冠层特征因子进行相关分析.结果表明,(1)4种林分对UVB辐射均产生显著消减作用,其屏蔽效应分别为:落叶松(91.2%)、白杆(90.2%)、油松(88.9%)、樟子松(88.2%);但林分类型和时间段的不同对UVB的屏蔽效应均无显著影响.(2)UVB屏蔽效应与林分郁闭度呈正相关关系,相关系数0.635,与冠层呈负相关关系,相关系数0.966,而与林分平均树高,平均枝下高相关性不显著.     

B2O3对高铝钢连铸保护渣理化性能的影响

高铝钢连铸过程中,为了避免或减轻钢液中Al与保护渣中SiO2发生反应,设计了低SiO2、高Al2O3含量的高铝钢连铸保护渣,通过添加适量的酸性氧化物B2O3协调熔渣酸碱性,利用实验分析了B2O3含量对高铝钢保护渣熔融特性、黏度特性及渣膜传热特性的影响。结果表明,B2O3含量在4%～10%时,随着B2O3含量增加,保护渣熔化温度、黏度、黏流活化能均降低,渣膜热流密度增加;保护渣的等温转变曲线(TTT曲线)向孕育时间增加的方向移动,晶体生长速率降低;实验条件下,增加B2O3含量可抑制保护渣中CaF2的析出。     

基于扩散模型的ZnO/p-Si异质结伏安特性研究

为了揭示ZnO/p-Si异质结的导电机理,基于p-n结扩散模型和Anderson扩散模型推导了ZnO/p-Si异质结在理想情况下的伏安特性,并分析了掺杂浓度、工作温度以及能带补偿的影响.结果表明:当正向偏压超过势垒高度时,界面两边多数载流子由耗尽变为堆积,形成反向势垒,对异质结的正向电流起阻碍作用;当外加正向电压等于内...     

Response of the northwestern Pacific upper water δ~(13)C to the last deglacial ventilation of the deep Southern Ocean

The deglacial δ~13C minimum events that originated from the ventilation of the deep Southern Ocean around Antarctica, have been recorded in a range of marine sediments from the southern to tropical oceans in late Pleistocene. However, the broad δ~13C minimum event was also reported as far as to the northern middle latitudes, in northwestern Pacific marginal sea areas, during the last deglaciation. In the northwestern Pacific, forcing from the northern high latitudes is strongly expressed, while the records of in- fluence from the southern high latitudes are few. The Kuroshio Source Region (KSR) forms a boundary between the northwestern Pacific and the southern, tropical Pacific. So, high-resolution planktonic foraminiferal records in core MD06-3054 from the KSR are well positioned to identify signals from the southern hemisphere in the northwestern Pacific. Planktonic foraminiferal tests from the upper 1030 cm of the core were subject to AMS14C, carbon and oxygen isotopic measurements. A negative excursion was found to occur from about 20.0-6.0 ka BP in δ~13C records of both surface (Globigerinoides ruber) and subsurface (Pulleni- atina obliquiloculata) dwellers, but the overall trends of the two curves have reversed since 26.5 ka BP. Moreover, the δ~13C rec- ord of G. ruber (the surface dweller) shows a robust link to the record of atmospheric CO2, and its changes precede the records of P. obliquiloculata (the subsurface dweller). According to the hydrologic conditions, the broad δ~13C minimum event recorded in the KSR is also a response to the increasing ventilation of the deep Southern Ocean around Antarctica during the last deglaciation. The inconsistency between the records of the surface and subsurface dwellers was possibly caused by the ways that the low δ~13C signal was transmitted. Subsurface water primarily received the low δ~13C signal from the Antarctic Intermediate Water (AAIW), whereas the surface water was probably mainly impacted by atmospheric CO2 in the KSR. The records from the KSR confirm the deduction that the broad δ~13C minimum event in the Okinawa Trough was due to the impact of tropical Pacific surface water dur- ing the last deglaciation, and suggest that signals from the southern high latitudes also can be delivered to the northern middle latitudes.     

手指口述安全管理方法的探讨

大多数煤矿生产事故是由于人的不安全行为造成的,通过执行"手指口述"方法,可以使员工对自己的操作行为以及作业环境的安全状态进行确认,通过提高员工自主管理和互助保安意识,保证操作过程安全可靠,消除生产事故隐患,从而可以提高安全管理水平,促进矿井安全生产.     

Genome sequence and analysis of the tuber crop potato

Potato (Solanum tuberosum L.) is the world's most important non-grain food crop and is central to global food security. It is clonally propagated, highly heterozygous, autotetraploid, and suffers acute inbreeding depression. Here we use a homozygous doubled-monoploid potato clone to sequence and assemble 86% of the 844-megabase genome. We predict 39,031 protein-coding genes and present evidence for at least two genome duplication events indicative of a palaeopolyploid origin. As the first genome sequence of an asterid, the potato genome reveals 2,642 genes specific to this large angiosperm clade. We also sequenced a heterozygous diploid clone and show that gene presence/absence variants and other potentially deleterious mutations occur frequently and are a likely cause of inbreeding depression. Gene family expansion, tissue-specific expression and recruitment of genes to new pathways contributed to the evolution of tuber development. The potato genome sequence provides a platform for genetic improvement of this vital crop.     

高海拔地区室内富氧浓度安全试验研究

室内富氧可以改善人在高海拔地区的缺氧状况,同时也会带来火灾危险,室内富氧的安全控制已成为重要的研究课题.文章对高海拔地区室内环境富氧条件下滤纸的燃烧速度和安全富氧浓度上限进行了试验研究,并对高海拔地区的富氧安全问题进行了分析.结果表明,在不同海拔地区,室内环境维持相同的氧分压时,滤纸的燃烧速度会随着海拔的升高而显著增加,如果不考虑当地的海拔高度而只以氧分压作为参考会带来火灾危险,但存在富氧的安全氧浓度上限,该氧浓度上限值与环境压力的关系为Y=27.91×exp(-P/44.78)+20.09;海拔不同,富氧到安全氧浓度上限时所对应的相当海拔也不同,该相当海拔与实际海拔的关系为H’=-0.68841+0.63893H+0.0048H2;在海拔高度低于5.55km的地区,通过对室内环境富氧可以安全地将相当海拔降低到3km以下.     

基于DCS的管道输送实验系统设计

针对油气储运工程专业实验教学与科研的需要,设计开发了一套以DCS为核心的管道输送实验系统。该系统技术先进、自动化程度高、组态灵活,可模拟长输管道运行工况,实现从泵到泵、从罐到罐、旁接油罐等多种输送工艺,具有丰富多样的实验功能;并可用于专业实习、课程设计、毕业设计和研究生培养等。