WEC-透空式防波堤集成装置能量转换效率研究

基于成本共享理念的波浪能发电装置(WEC)的开发与设计为降低建设成本提供了新的研究思路,应用计算流体力学方法对在透空箱式防波堤前附加垂荡浮子的集成装置进行数值模拟研究,主要研究了流体黏性和非线性PTO系统以及浮子形状对此类集成装置能量转换效率的影响。结果表明,此类集成装置可以获得较高的波能捕获宽度比(CWR),最高可达0.7,可以较好地利用反射波波能。共振区间上受黏性影响较大,相比于线性无黏理论解,CWR下降明显;实现了2种非线性PTO系统的模拟,有待于进一步的优化未获得更高的CWR值;浮子形状优化效果明显,采用圆底形浮子受黏性影响更小,可以获得更大的CWR值。此种集成模型的模拟和研究可以为新型防波堤设计和现有防波堤的改造提供思路和参考。     

A comparison between mesospheric wind measurements made near Christchurch (44°S, 173°E) using the high resolution doppler imager (HRDI) and a medium frequency (MF) radar

We report on the comparison of winds measured by a medium frequency (MF) radar near Christchurch, New Zealand, and by the high resolution doppler imager (HRDI). Previous comparisons have demonstrated that there can be significant differences in the winds obtained by the two techniques, and our results are no different. However, these data show relatively good agreement in the meridional direction, but large differences in the zonal direction, where the radar is regularly measuring the zonal wind as too easterly. To do the comparison, overpasses from the satellite must be obtained when it is close to the radar site. The radar data are averaged in time around the overpass because we know the radars sample phenomena which have spatial and temporal scales which make them invisible to HRDI. There are a limited number of overpass comparisons which limit our confidence in these results, but a detailed analysis of these data show that the proximity of the overpass is often an important factor in the differences obtained. Other factors examined include the influence of the local time of the overpass, and the amount of radar data averaged around the overpass time.     

Ground clutter cancellation in incoherent radars: solutions for EISCAT Svalbard radar

Incoherent scatter radars measure ionosphere parameters using modified Thomson scatter from free electrons in the target (see e.g. Hagfors, 1997). The integrated cross section of the ionospheric scatterers is extremely small and the measurements can easily be disturbed by signals returned by unwanted targets. Ground clutter signals, entering via the antenna side lobes, can render measurements at the nearest target ranges totally impossible. The EISCAT Svalbard Radar (ESR), which started measurements in 1996, suffers from severe ground clutter and the ionosphere cannot be measured in any simple manner at ranges less than about 120–150 km, depending on the modulation employed. If the target and clutter signals have different, and clearly identifiable, properties then, in principle, there are always ways to eliminate the clutter. In incoherent scatter measurements, differences in the coherence times of the wanted and unwanted signals can be used for clutter cancellation. The clutter cancellation must be applied to all modulations, usually alternating codes in modern experiments, used for shorter ranges. Excellent results have been obtained at the ESR using a simple pulse-to-pulse clutter subtraction method, but there are also other possibilities.     

Stream-scanning laser system, electric sensing counter and settling grain size analysis: a comparison using reference materials and marine sediments

Surface and deep-sea core sediments and two sets of standards were measured by three different techniques — Galai Cis-1 laser system, Coulter Counter TA II, and Micromeritics SediGraph 5000D — in order to compare the Galai results with the other two. The differences between the three types of measuring device turned out to be greater in sediments than in standards, and were attributed to the physical properties, shape, density and composition of the particles (complexity of the matrix). Comparison of moment statistics showed that the Galai determines coarser grain sizes than the Coulter and finer than the SediGraph, particularly as regards analysis of surface sediments. The relationships between Galai and SediGraph were estimated using analysis of variation/residuals within individual intervals. The analysis showed a higher variability of residuals for the coarser fractions (8–16 μm and 16–32 μm) with respect to the finer (2–4 μm and 4–8 μm) fractions. The <2 μm SediGraph fraction, with a cut-off at 0.49 μm, showed good correspondence with the <2.5 μm Galai analysis.     

黄土坡滑坡的发育历史: 坠覆-滑坡-改造

长江三峡库区巴东新县城黄土坡是否为古滑坡、滑坡的范围有多大、新滑坡与古滑坡的关系如何等, 还存在着不同认识.基于大量的野外观察资料, 提出了坠覆-滑坡-改造多阶段变形、失稳的斜坡演化模式.认为黄土坡在滑坡以前经历了长期的坠覆作用, 坠覆包括了倾倒和深层蠕变两种基本的斜坡变形型式; 坠覆的基础上发生了滑坡, 造成了台阶状地貌、构造面线与基岩不协调及滑动角砾岩带等现象; 滑坡形成后受水文、地貌等条件的影响, 长期经历着小规模滑坡的叠加改造, 1995年发生的两次滑坡仍是进一步改造的结果.黄土坡坠覆-滑坡-改造这一有机联系的岩质斜坡变形过程的建立, 使得关于黄土坡的一些重大问题有了比较明确的认识, 这也为构造学解决斜坡研究中的一些问题提供了一个典范.      

塔木察格盆地南贝尔凹陷东次凹构造转换带与油气成藏关系

塔木察格盆地位于蒙古国东部,与中国的海拉尔盆地同属一个盆地,为叠置于兴蒙造山带之上的拉张一挤压型中新生代陆相断陷盆地.南贝尔凹陷位于海拉尔一塔木察格盆地中部断陷带的中部,面积为3 200 km2.南贝尔凹陷东次凹南一北洼槽构造转换带位于南贝尔凹陷东次凹中部,为反向聚敛叠覆型构造转换带,是重要的含油气构造带.转换带对油气...     

Two suggested configurations for the Chinese space telescope

China will establish a 2-meter space-based astronomical telescope. Its main science goals are performing a sky survey for research about dark matter and dark energy, and high resolution observations. Some experts suggest that this space telescope should be installed inside the Chinese space station. In accord with this suggestion we put forward our first configuration, i.e., to adopt a coud′e system for this telescope.This coud′e system comes from the Chinese 2.16 m telescope's coud′e system, which includes a relay mirror so that excellent image quality can be obtained. In our second configuration, we suggest that the whole space telescope fly freely as an independent satellite outside the space station. When it needs servicing, for example, changing instruments, refilling refrigerant or propellant, etc., this space telescope can fly near or even dock with the core space station. Although some space stations have had accompanying satellites, the one we propose is a space telescope that will be much larger than other accompanying satellites in terms of weight and volume. On the basis of the second configuration, we also put forward the following idea: the space station can be composed of several large independent modules if necessary.     

The WMAP data and results

The Wilkinson Microwave Anisotropy Probe (WMAP) science team has released results from the first year of operation at the Earth–Sun L₂ Lagrange point. The maps are consistent with previous observations but have much better sensitivity and angular resolution than the COBE DMR maps, and much better calibration accuracy and sky coverage than ground-based and balloon-borne experiments. The angular power spectra from these ground-based and balloon-borne experiments are consistent within their systematic and statistical uncertainties with the WMAP results. WMAP detected the large angular-scale correlation between the temperature and polarization anisotropies of the CMB caused by electron scattering since the Universe became reionized after the “Dark Ages”, giving a value for the electron scattering optical depth of 0.17 ± 0.04. The simplest ΛCDM model with n=1 and Ω_tot=1 fixed provides an adequate fit to the WMAP data and gives parameters which are consistent with determinations of the Hubble constant and observations of the accelerating Universe using supernovae. The time-ordered data, maps, and power spectra from WMAP can be found at http://lambda.gsfc.nasa.gov along with 13 papers by the WMAP science team describing the results in detail.     

Cipher, A Polarimeter Telescope Concept for Hard X-Ray Astronomy

The polarisation of astrophysical source emission in the energy range from a few tens of keV up to the MeV region is an almost unexplored field of high-energy astrophysics. Till date, polarimetry in astrophysics–in the energy domain from hard X-rays up to soft γ-rays–has not been pursued due to the difficulties involved in obtaining sufficient sensitivity. Indeed for those few instruments that are capable of performing this type of measurement (e.g. the COMPTEL instrument on the Compton Gamma-ray Observatory and the IBIS instrument on INTEGRAL), polarimetry itself plays a secondary role in the mission objectives, as the efficiencies (0.5% and 10% maximum, respectively) and polarimetric Q factors (0.1 and 0.3, respectively) are relatively limited. In order to perform efficient polarimetric measurements for hard X-ray and soft gamma-ray sources, with an instrument of relatively robust and simple design, a CdTe based telescope (CIPHER: Coded Imager and Polarimeter for High Energy Radiation) is under study. This instrument is based on a thick (10 mm) CdTe position-sensitive spectrometer comprising four modules of 32 × 32 individual pixels, each with a surface area of 2 × 2 mm² (about 160 cm² total detection area). The polarimetric performance and design optimisation of the CIPHER detection surface have been studied by use of a Monte Carlo code. This detector, due to its intrinsic geometry, can allow efficient polarimetric measurements to be made between 100 keV and 1 MeV. In order to predict the polarimetric performance and to optimise the design and concept of the CIPHER detection plane, a Monte Carlo code based on GEANT4 library modules was developed to simulate the detector behaviour under a polarised photon flux. The Compton double event efficiency, as well bi-dimensional double event distribution maps and the corresponding polarimetric modulation factor will be presented and discussed. Modulation Q factors better than 0.50 and double event total efficiencies greater than 10% were calculated in the energy range between 100 keV and 1 MeV. Herein we will present and discuss the general problems that affect polarimetric measurements in space, such as the inclination of the source with respect to the telescope optical axis and background radiation. Q factor calculations for several beam inclinations as well as for background together with simulated astronomical sources will be presented and discussed.