Politics, geological past, and the future of earth

From the 1940s, new technologies, like carbon dating, ice- and sea-core drilling, and pollen analysis not only vastly expanded time horizons in geophysical and climatological research, but also pinpointed past events on a newly historical timescale. Using natural proxy indicators, these studies brought to light a series of globally disruptive events in geological time, for example, volcanic eruptions of previously unknown scale and types that had also an impact on the Earth’s climate. The past became discrete. Knowing more about the past also meant knowing more about possible futures, given that some catastrophic events have occurred repeatedly or have become increasingly predictable with the help of computer modeling. This meant that scientists' claims about the future of the earth increasingly came to interfere with politics and with traditional economic planning. The paper argues that the “new” past has come to weigh in two ways on the present and the future. First, it dwarfed the human time scale, thus in-creasing the challenge of dealing with heterogeneous time scales. Second, prehis-toric past events came to take on political significance. The deep past became part of political history, and thus of politics

Effects of Scratching Parameters on Fabrication of Polymer Nanostructures in Atomic Force Microscope Tapping Mode

AbstractThe nano scratching with an oscillating Atomic Force Microscopy (AFM) tip in tapping mode is called as the dynamic ploughing. The tip is vibrated in a high frequency and scratches the surface which is similar to the conventional vibration-assistant machining process. In the present study, the dynamic ploughing technique is utilized to scratch PolymethylMethacrylate (PMMA) polymer surfaces forming nanostructures with a commercial AFM system and two kinds of cantilevers. Effects of scratching parameters of the dynamic ploughing including scratching velocity, driving amplitude, pitch and the cantilever's elastic constant on the machined results are studied in detail. Finally nano ring structures with different radius are achieved successfully.Video abstrac

BES3 time of flight monitoring system

A Time of Flight monitoring system has been developed for BES3. The light source is a 442-443 nm laser diode, which is stable and provides a pulse width as narrow as 50 ps and a peak power as large as 2.6 W. Two optical-fiber bundles with a total of 512 optical fibers, including spares, are used to distribute the light pulses to the Time of Flight counters. The design, operation, and performance of the system are described.Comment: 8 pages 16 figures, submitted to NI

Long-term measurements of particle number size distributions and the relationships with air mass history and source apportionment in the summer of Beijing

A series of long-term and temporary measurements were conducted to study the improvement of air quality in Beijing during the Olympic Games period (8–24 August 2008). To evaluate actions taken to improve the air quality, comparisons of particle number and volume size distributions of August 2008 and 2004–2007 were performed. The total particle number and volume concentrations were 14 000 cm−3 and 37 μm−3 cm−3 in August of 2008, respectively. These were reductions of 41% and 35% compared with mean values of August 2004–2007. A cluster analysis on air mass history and source apportionment were performed, exploring reasons for the reduction of particle concentrations. Back trajectories were classified into five major clusters. Air masses from the south direction are always associated with pollution events during the summertime in Beijing. In August 2008, the frequency of air mass arriving from the south was 1.3 times higher compared to the average of the previous years, which however did not result in elevated particle volume concentrations in Beijing. Therefore, the reduced particle number and volume concentrations during the 2008 Beijing Olympic Games cannot be only explained by meteorological conditions. Four factors were found influencing particle concentrations using a positive matrix factorization (PMF) model. They were identified as local and remote traffic emissions, combustion sources as well as secondary transformation. The reductions of the four sources were calculated to 47%, 44%, 43% and 30%, respectively. The significant reductions of particle number and volume concentrations may attribute to actions taken, focusing on primary emissions, especially related to the traffic and combustion sources

From double Lie groupoids to local Lie 2-groupoids

We apply the bar construction to the nerve of a double Lie groupoid to obtain a local Lie 2-groupoid. As an application, we recover Haefliger's fundamental groupoid from the fundamental double groupoid of a Lie groupoid. In the case of a symplectic double groupoid, we study the induced closed 2-form on the associated local Lie 2-groupoid, which leads us to propose a definition of a symplectic 2-groupoid.Comment: 23 pages, a few minor changes, including a correction to Lemma 6.

Studies of Static and Dynamic Characteristics of the EDM Machine Based on the ANSYS Workbench

The static and dynamic characteristics of the EDM machine as the main machining unit directlyinfluence the machining accuracy and stability. For a particular type of the EDM machine, the three-dimensional model was built with SolidWorks and the finite element method was employed with the ANSYS Workbench to analyze the static and dynamic characteristics of the machine. The results show that the stiffness of the ram and vertical guide (Z-axis) in the Y and Z directions is the weak side of the machine. The analytical method is proved to be effective for the optimization of the machine design.Установлено, что точность и стабильность обработки зависят от статических и динамических характеристик электроэрозионного станка как основного станочного модуля. Для электроэрозионного станка определенного типа с помощью программного комплекса SolidWorks была построена трехмерная модель, а для анализа его статических и динамических характеристик использовали метод конечных элементов в комбинации с программным комплексом ANSYS. Результаты показывают, что жесткость ползуна и вертикальной направляющей (ось Z) в направлениях Y и Z слабая сторона станка. Доказано, что аналитический метод является эффективным средством оптимизации его конструкции