Permafrost science and secondary education: direct involvement of teachers and students in field research

Permafrost and periglacial geomorphology are absent from the science curriculum in most secondary schools in the United States. This is an unfortunate situation given the recent increases in development and environmental concerns in northern latitudes and high-mountain areas, and the interesting examples of basic scientific principles found in the history of research on periglacial geomorphology and permafrost. In 1997 and 1998, a University of Delaware research group studying permafrost and periglacial geomorphology in northern Alaska participated in the National Science Foundation's (NSF) Teachers Experiencing the Antarctic and Arctic (TEA) Program. In each of these years, a high school teacher and a student traveled as part of the research team to the North Slope of Alaska. They learned about the landscape, collected active-layer thickness and temperature measurements, and assisted in data analysis. Results from studies of active-layer thickness variability and ground temperature contributed to a series of long-term observations and international research on the impacts of global climate change. Since their expeditions, the teachers have shared their experiences with their classrooms and communities in several ways, including public lectures and the Internet. Classroom activities are available to the public through the TEA web site (http://tea.rice.edu). This experience may heighten public awareness of permafrost and contribute to it becoming a useful part of the secondary curriculum.     

活动断裂的变形特征及其大地震复发周期的估算

活动断裂是晚更新世10~12万年以来一直在活动, 现在正在活动, 未来一定时期内仍会发生活动的各类断裂。活动断裂控制着大地震的发生,是不同类型地震的发震构造。从活动断裂的变形特征来看,不同性质的活动断裂具有不同的发震构造模型,研究这些问题对认识强震的发震条件,划分潜在的震源区或地震危险区,评估发震构造和发震地点具有重要的意义。基于国内外对不同类型活动断裂的认识,结合近10年来在青藏高原地区对活动断裂的研究,总结了活动断裂的基本变形特征和对大地震复发周期估算的认识。研究表明,东昆仑断裂库塞湖段类似2001年Ms 8.1级大地震的强震复发周期为250～350年,阿尔金断裂康西瓦段类似Ms 7.4大地震的强震复发周期为370～500年,而在青藏高原东缘的龙门山地区,类似2008年5月12日Ms 8.0汶川大地震的强震复发周期为3000～6000年。这些结果可能暗示着走滑断裂大地震的复发周期远短于逆冲断裂大地震的长复发周期,这是值得高度重视和深入研究的新课题。     

AM／FM／GIS领域应用与应用发展

AM／FM（Automatic Mapping／Facility Management）是一种设备和生产技术管理的计算机图文交互系统,建立在GIS基础上的AM／FM系统为AM／FM／GIS系统,被广泛应用于城市公用事业的信息化管理中。随着GIS技术的不断发展以及人们对AM／FM技术认识的不断加深,AM／FM／GIS的应用领域正在不断拓展。AM／FM／GIS必将成为城市公用事业领域进行科学管理的现代化工具。     

基于GML/WebGIS的空间数据集成研究

GIS的迅速发展和广泛应用导致了空间数据多源性的产生,为数据综合利用和共享带来不便.GML被许多公司接受和采用,由此为空间数据的集成和共享提供了有利的数据交换基础,使用GML存储和发布空间数据,将非常有利于WebGIS的发展和应用.     

一种改进的道路匹配算法

针对遗传算法在道路匹配时出现的平行路段匹配跳跃问题,利用距离角度拟合法进行改进.将矢量地图与影像地图叠加作为底图进行辅助判断,避免了导航中单一使用矢量数据信息量不足的情况.实验表明,改进后的算法解决了地图矢量数据不完整时产生的误匹配问题;同时在弯道、U形转弯处、交叉路口、平行路段等处都具有较好的匹配准确度.     

企业创新网络与多维邻近性关系研究述评

创新是引领经济发展的第一动力,企业创新网络相关研究近来受到经济地理学者的高度关注,纵观当前国内外企业创新网络相关研究文献,企业创新网络研究经历了从定性研究向定量研究转变的过程,尤其是基于专利或论文数据刻画创新网络结构特征成为当前研究的热点,然而企业创新网络结构形成的内在机制仍不够深入,不少学者引入多维邻近性框架用于解析企业创新网络形成的重要视角。本文正是基于这一背景,从企业创新网络的影响因素、演化动力及机理、典型案例企业创新网络三个方面梳理了当前经济地理学者的研究热点,并重点基于多维邻近性视角评述了企业创新网络运行机理。研究发现,众多邻近性中,地理、认知和组织邻近对企业创新合作具有较为重要的促进作用,在未来研究中还需加强最佳邻近尺度、不同邻近性替代或互补作用和重要性排序等问题的相关研究。     

泥蚶(Tegillarca granosa)重组铁蛋白富集锰铁后的磁学性质解析

利用埋栖性双壳类生物泥蚶(Tegillarca granosa)重组铁蛋白富集锰铁的性质,在不同锰铁浓度下制备Fe-铁蛋白和Mn-铁蛋白磁性纳米颗粒,通过扫描电镜观察高、中和低三个浓度下制备Fe-铁蛋白和Mn-铁蛋白磁性纳米颗粒的表面形貌,通过PPMS综合物性测量系统测定Fe-铁蛋白和Mn-铁蛋白磁性纳米颗粒的磁学性质。结果显示,在低浓度(0.1mmol/L)锰铁制备的Fe-铁蛋白和Mn-铁蛋白磁性纳米颗粒粒径均一,分散性好;发现Fe-铁蛋白和Mn-铁蛋白的磁滞回线均表现为超顺磁性,且随着重组铁蛋白对锰铁富集量的增加,磁性强度随之增大,增加速率逐渐减小。通过本实验探索高、中和低三个浓度下制备Fe-铁蛋白和Mn-铁蛋白磁性纳米颗粒的磁化强度变化规律,为Fe-铁蛋白和Mn-铁蛋白磁性纳米颗粒的应用提供数据支持。     

Gaseous electron multiplier gain characteristics using low-pressure Ar/CO<Subscript>2</Subscript>

Gaseous Electron Multiplier detectors, or GEMs, show promise for use on space-based X-ray missions. Operating pressure strongly affects the gain of the detector and must be optimized for best performance. We have measured the gain characteristics of a GEM detector at various pressures below atmosphere using a mixture of Ar:CO₂ with the goal of maximizing gain to push GEM capabilities to the lowest energies possible. This paper discusses our tests, results, and their implications for choosing a detector pressure. We found that at any operating pressure the detector voltage can be adjusted to achieve roughly the same maximum gain prior to the onset of electrical discharges. We also find that the gain varies substantially by spatial location across the detector, but this variation is insensitive to changes in pressure allowing it to be calibrated and corrected if necessary. The detector pressure can therefore be optimized in the interest of other performance parameters such as leak rate, window stress, power requirements, or quantum efficiency without concern for negatively affecting the gain. These results can inform the choice of operating pressure and voltage for GEMs used onboard future space missions.     

Seismic retrofit of low‐rise steel buildings in Canada using rocking steel braced frames

This article examines the use of rocking steel braced frames for the retrofit of existing seismically deficient steel building structures. Rocking is also used to achieve superior seismic performance to reduce repair costs and disruption time after earthquakes. The study focuses on low‐rise buildings for which re‐centring is solely provided by gravity loads rather than added post‐tensioning elements. Friction energy dissipative (ED) devices are used to control drifts. The system is applied to 2‐storey and 3‐storey structures located in 2 seismically active regions of Canada. Firm ground and soft soil conditions are considered. The seismic performance of the retrofit scheme is evaluated using nonlinear dynamic analysis and ASCE 41‐13. For all structures, rocking permits to achieve immediate occupancy performance under 2% in 50 years seismic hazard if the braces and their connections at the building's top storeys are strengthened to resist amplified forces due to higher mode response. Base shears are also increased due to higher modes. Impact at column bases upon rocking induces magnified column forces and vertical response in the gravity system. Friction ED is found more effective for drift control than systems with ring springs or bars yielding in tension. Drifts are sufficiently small to achieve position retention performance for most nonstructural components. Horizontal accelerations are generally lower than predicted from ASCE 41 for regular nonrocking structures. Vertical accelerations in the gravity framing directly connected to the rocking frame are however higher than those predicted for ordinary structures. Vertical ground motions have limited effect on frame response.     

Integrated geophysical exploration in onshore frontier basins

Faced with the challenge of rapidly screening a huge expanse of frontier exploration acreage, often characterized by sparse vintage data, it is our experience that a combination of appropriate air- and ground-based geophysical techniques contributes positively to the exploration value chain. Airborne gravity gradiometry in conjunction with conventional gravity and magnetic data, as well as geological knowledge, add significant value to the screening process. This combination can subsequently assist in optimizing the location of the more time-consuming and expensive seismic programme. In addition, analysis and inversion of passive seismic data have also proven useful in providing depth to basement estimates, and results derived from all the techniques investigated have been consistent within several study areas. Following initial tests, where the data were independently analysed and cross-checked for consistency (including comparisons with active source seismic data and well data, when available), the company now routinely adopts the integration of these techniques in our frontier exploration acreage to support sedimentary basin delineation and mapping. This allows the optimal positioning and focussing of the higher spend and higher footprint programmes, such as active reflection seismic.