Silicon-based micro direct methanol fuel cell with an N-inputs-N-outputs anode flow pattern

A micro direct methanol fuel cell(μDMFC) is suitable for use in notebook computers,mobile phones,and other digital products.To resolve the poor mass-transport efficiency problem in the anode flow channel,this paper presents an N-inputs-N-outputs parallel flow pattern with rectangular convexes to reinforce methanol mass transport and reduce concentration polarization.The simulation results show that the N-inputs-N-outputs parallel flow channels with the rectangle convexes improve the performance.μDMFCs,which have four anode flow patterns,are fabricated using MEMS(microelectromechanical systems) technology.The experimental results show that the μDMFC with the rectangle convexes has a performance better than previously reported systems,and has a peak power density of 19.96 mW/cm2.The simulation and experimental results are in good agreement.     

我国东北地区黄土堆积的磁性地层年代与古气候变化

我国东北地区有较广泛的黄土分布, 是环境变化的重要地质记录. 长期以来, 由于缺乏可靠的年代学证据, 对这里黄土沉积及其记录的古气候变化了解不多. 在广泛野外踏勘的基础上, 对具有代表性的科尔沁沙地南缘牛样子沟和平安村黄土剖面进行了磁性地层与光释光年代等测试, 结果表明, 牛样子沟剖面的B/M 界限位于深度27 m 处, 平安村剖面处于布容正极性期. 基于光释光年龄和磁性地层年代计算的黄土沉积速率外推, 科尔沁沙地南缘的黄土堆积应早于1.0 Ma. 黄土是半干旱环境下的粉尘堆积, 指示东北地区的半干旱气候至少在早更新世晚期已经开始. 这里黄土开始堆积的年代对应于中更新世全球气候转型, 可能为全球气候变冷驱动了亚洲内陆干旱化和较快粉尘堆积的假说提供了证据.     

Metamorphic solid salt (KCl-NaCl) in quartzo-feldspathic polyphase inclusions in the Sulu ultrahigh-pressure eclogite

Unusual polyphase inclusions of K-feldspar+quartz+titanite+solid salt and K-feldspar+albite+quartz+epidote with textures similar to the other K-feldspar+quartz inclusions were found in omphacite grains from the Sulu ultrahigh pressure (UHP) eclogites. One of these inclusions contain square to round solid salt inclusions of KCl-NaCl composition. Such a mineral assemblage within K-feldspar-bearing inclusions hosted by UHP metamorphic phases suggests that (1) potassium granitic melts enriched in Cl components were presented during UHP metamorphism or at the early stage of rapid exhumation of deeply subducted continental slab; (2) they were resulted from reactions between the incoming granitic melts and quartz (or coesite); and (3) solid salt inclusions of NaCl-KCl were derived from dehydration and desiccation of Cl-bearing melts. Our new observations further demonstrate that during the tectonic evolution of UHP rocks, fertile components within deeply subducted continental materials could undergo partial melting, leading to the formation of Cl-bearing potassium granitic melts and substantial migration of fluid-conservative elements (e.g. Ti, Hf) within the UHP slab.     

An experimental study of premixed laminar methane/oxygen/argon flames doped with hydrogen at low pressure with synchrotron photoionization

Laminar premixed stoichiometric methane/hydrogen/oxygen/argon flames were investigated with tunable synchrotron vacuum ultraviolet （VUV） photoionizaUon and molecular-beam sampling mass spectrometry techniques. The methane/hydrogen fuel blends with hydrogen volumetric fraction of 0, 20%, 40%, 60% and 80% were studied. All observed flame species, including stable intermediates and radicals in the flames, were detected by measuring photoionization mass spectra and photoionization efficiency （PIE） spectra. Mole fraction profiles of major species and intermediates were derived by scanning burner at some selected photon energies near ionization thresholds. The influence of hydrogen addition on mole fraction of major species and intermediates was analyzed. The results show that the major species mole fraction of CO, CO2 and CH4 decreases with the increase of hydrogen fraction. The mole fraction of intermediates measured in this experiment decreases remarkably with the increase of hydrogen fraction. This would be due to the increase of H and OH radicals by hydrogen addition and the high diffusivity and activity of H radical promoting the chemical reaction. In addition, the increase of H/C ratio with the increase of hydrogen fraction also leads to the decrease of the mole fraction of carbon-related intermediates and contributes to the decrease of unburned and incomplete combustion products.     

Preparation of aluminum borate whisker reinforced aluminum phosphate wave-transparent materials

Aluminum borate whisker/aluminum phosphates composites were prepared with normal pressure sintering, It was found that the aluminum borate whisker was effective to suppress the crystallization of aluminum phosphates in the aluminum borate whisker/aluminum phosphates composites and contributed to the improvement of the mechanical properties. After sintered at 1050℃ for 1 h, the flexural strength of the composites with 30 vol% aluminum borate whisker addition reached 215.3 MPa. The dielectric constant and loss tangent of the composites were 4.23 and 0.0024 at 10 GHz.     

Characterization and fine mapping of an early senescence mutant （es-t） in Oryza sativa L.

An es-t (early senescence-temporary) mutant, produced by ethylene methylsulfonate treatment of strain Nipponbare, was identified in rice. The leaves of es-t appeared yellow at the seedling stage, and had decreased chlorophyll content. Rust spots were found during growth in es-t, especially at the leaf margin and tip. The plants showed a typical early-senescence phenotype at the milky stage. The leaf surface of es-t appeared smoother than wild-type leaves under a scanning electron microscope, because the lea...     

声悬浮条件下Ag-Cu共晶合金的无容器凝固研究

采用声悬浮技术结合激光加热,实现了Ag-Cu共晶合金的无容器熔化与凝固,并通过CMOS图像分析与数值计算,研究了声悬浮过程中合金熔体的温度场分布特性.由于声辐射压作用,合金熔体在声悬浮条件下呈现扁球或圆饼形,表面温度沿赤道点到极点方向升高.凝固样品表面出现涟漪状波纹,统计分析发现,该表面波纹出现在大变形(a/b>2.1)的样品上.波纹中心为共晶形核点,且波纹传播方向与共晶生长方向相同.分析表明,表面形核以及形核后辐射推移的固液界面是形成表面波纹的先决条件.声场的增强能够促进悬浮样品在表面形核.     

Heat treatment and associated early modern human behaviors in the Late Paleolithic at the Shuidonggou site

Unearthed artifacts and cultural relics from the Shuidonggou site revealed extensive information and insights regarding the activities of early modern humans.A series of experimental research and physical analysis suggest that stone artifacts from Locality 2 and Locality 12 have undergone heat treatment.The utilization ratio and knapping properties of raw materials were consequently enhanced.Heat treatment technology reflects the production capacities and the survival strategies in the Upper Paleolithic period.This discovery indicates the earliest existence of this technology in the East Asia and thus confirms a wider geographic distribution of this technology which provides new perspectives and evidence for understanding the associated early modern human behaviors.     

重质有机资源热解过程中的自由基化学

热解是煤炭、油页岩、重油、生物质以及有机废物等重质有机资源生产燃料和化学品过程中的重要步骤，不仅存在于非催化过程，也存在于催化过程。热解工艺有很多种，但其化学反应主体是自由基机理。针对文献在自由基机理这个宽泛概念下缺乏对自由基反应内涵的认识的现状，作者团队自2007年起开展了对煤、油页岩、重油、生物质等热解过程中的自由基行为研究，明确了文献中的一些不确切推论，形成了系统性认识，逐步建立了热解过程中的自由基化学体系。本文将介绍这些研究的主要进展，包括活性自由基与稳定自由基的确定、赋存状态及在热解过程中的作用、稳定自由基与缩聚反应和积炭的关系、催化剂积炭的形态与稳定自由基的关系、自由基诱导热解与反应调控等等。     

Geochronologic and petrochemical evidence for the genetic link between the Maomaogou nepheline syenites and the Emeishan large igneous province

The Maomaogou nepheline syenite is located at the inner zone of the Emeishan large igneous province and exhibits intrusive contact with the Emeishan basalts. SHRIMP U-Pb dating on zircons from this syenite yields an age of 261.6±4.4 Ma, in agreement with the age of the Panzhihua layered intrusion and the eruption age of the Emeishan basalts as constrained by stratigraphic data. Geochemical data fur-ther suggest that the Maomaogou syenite has a source analogue to the Emeishan basalt, and may have been formed by partial melting of gabbroic cumulates underplated in the lower crust. As s result, tem-poral and spatial relationships and petrogenetic constraints provide evidence for the genetic link be-tween basalts, mafic/ultramafic and intermediate/acidic intrusives in the Panxi area.