升温氧化过程煤表面介观特征和分形参数研究

将原子力显微镜（AFM）用于煤表面结构研究,提出介观尺度下煤表面结构研究方法. 得出基于分形理论和AFM观测结果计算分形维数D的方法.实验分析证明,煤表面有明显的分形特征,在煤样的升温氧化过程中,分形维数随温度的升高趋于增大.     

Estimation of forest volumes by integrating Landsat TM imagery and forest inventory data

Accurate information about forest volumes is essential for forest management planning. The survey interval of the Forest Resource Inventory of China (FRIC) is too long to meet the demand for timely decision-making required for forest protection, management, and utilization. Analysis of satellite imagery provides good potential for more frequent reporting of forest parameters. In this study, we describe an application of the k-nearest neighbors (kNN) method to Landsat TM imagery for improving estimation of forest volumes. Several spectral features were tested and compared in forest volume estimations, including normalized difference vegetation index, environmental vegetation index, and the combination of the spectral features. The combined index resulted in the most accurate volume estimations. The kNN estimator and the combined index were then used in forest volume estimation. The estimation error (RMSE) of the total volume was 44.2%, much lower than those for Larix forest (the RMSE was 51.7%) and those for the Korean pine and broadleaved forests (the estimation errors were over 71.7% and 88.19%, respectively). This preliminary study demonstrates the potential of forest volume estimations with remote sensing data to provide useful information for forest management if only limited ground information is available.     

A database framework of digital forestry towards sustainable forestry development in China

Six forestry scientific and technological projects being actualized in China were the implementations of ecological construction and security, development of forestry biological technique and fine variety cultivation, protection and utilization of forest biological germplasm resources, development of forestry bio-industry and digital forestry, and construction of forestry innovation ability. Among them, digital forestry was an effective measure to improve the ability of forestry innovation, to realize resources sharing, and to develop sustainable forestry. Spatial database of digital forestry should be constructed according to the criteria and index system of forest sustainable management. Based on analyzing the status and advances of China’s digital forestry construction, a database framework of digital forestry towards sustainable forestry development was studied and established preparatorily. The database was divided into four layers as theory layer, system layer, status layer, and parameter layer. It was concluded that during the process of digital forestry platform construction, the relative social, economic, and politic data should be considered and collected, which meant that the database should represent not only the current forestry development, but also the social, politic, and economic situations. Constructing China’s digital forestry information platform under full utilization of idea and index system for sustainable forest management was urgent and important.     

论全球化供应链管理的延迟运作战略的应用——基于惠普(HP)和戴尔(DELL)公司的成功案例

在介绍延迟运作理论的基础上,结合惠普、戴尔两大公司根据自身的具体条件和特点实施延迟运作战略的案例分析,介绍了其成功运用的供应链运作战略,分析了全球化供应链管理中实施延迟运作战略的条件,指出了延迟运作战略在21世纪全球化供应链管理中的巨大作用。     

国家电网安监[2005]83号中绝缘工器具的若干问题

国家电网公司国家电网安监[2005]83号发布的《国家电网公司电力安全工作规程(变电站和发电厂电气部分、电力线路部分)(试行)》文件中对电力绝缘工器具有若干规定是错误的或不准确的,因此有必要对新安规绝缘工器具的规定进行探讨。     

DTM320／580型磨煤机传动齿轮轴断裂原因分析及防范措施

介绍了DTM580/320型磨煤机传动齿轮轴断裂的情况,并进行了分析;找到了断裂的原因,提出了防范措施。     

多线性Littlewood-paley算子在一类Block-hardy空间上的加权有界性

定义一类与L ittlewood-paley算子相关的多线性算子,它是L ittlewood-paley算子的交换子的推广.然后利用Hardy空间的原子分解和B lock空间的块分解方法引入一类B lock-hardy空间,并由此证明这类与L ittlewood-paley算子相关联的多线性算子在上述B lock-hardy空间上的加权有界性.     

A miniature UWB planar monopole antenna with 5-GHz band-rejection filter and the time-domain characteristics

A planar monopole antenna with a staircase shape and small volume (25/spl times/26/spl times/1 mm/sup 3/) is proposed in this paper. With the use of a half-bowtie radiating element, the staircase-shape, and a modified ground plane structure, the proposed antenna has a very wide impedance bandwidth measured at about 11.6 GHz (2.9-14.5 GHz, bandwidth ratio about 1:5) below VSWR 2 including the WLAN band notched in the vicinity of 5 GHz. An omnidirectional radiation pattern is obtained. The group delay which is an indication of linearity between two proposed antennas is less than 1 ns. The electrical characteristics in terms of frequency and time domains and physical ones of the proposed antenna make it attractive for use in ultrawideband (UWB) systems.     

Operation, system architectures, and physical Layer design considerations of distributed MAC protocols for UWB

Impulse-based ultra wideband (I-UWB) is an attractive radio technology for large ad hoc and sensor networks due to its robustness to harmful multipath effects, sub-centimeter ranging ability, simple hardware, and low radiated power. To scale to large sizes, networks often implement distributed medium access control (MAC) protocols. However, most MAC protocols for I-UWB are centralized, and they target small wireless personal area networks and cellular networks. We propose three distributed MAC protocols suitable for I-UWB. Two multichannel protocols, called multichannel pulse sense multiple access (M-PSMA) and multichannel ALOHA achieve high aggregate throughput. A busy-signal protocol, called busy-signal multiple access (BSMA), reduces the energy wasted from re-transmitted packets. This paper describes the three protocols in terms of the protocol's operation, the supporting system architecture, and the I-UWB physical layer. Physical layer simulations confirm the feasibility of implementing the proposed systems and also provide parameters for network simulations. Network simulations show that the throughput of M-PSMA exceeds that of a centralized time-division multiple-access protocol and that the energy efficiency of BSMA far surpasses that of other distributed protocols.     

Parallel optical transmitter module using angled fibers and a V-grooved silicon optical bench for VCSEL array

We propose an advanced structure of optical subassembly (OSA) for packaging of the vertical-cavity surface-emitting laser (VCSEL) array, using (111) facet mirror of the V-groove ends formed in a silicon optical bench (SiOB) and angled fiber apertures. The feature of our OSA can provide a low optical crosstalk between neighboring channels, a low feedback reflection, and a large misalignment tolerance along the V-groove. We describe the optimized design of fiber angle, VCSEL position, and fiber position. The fabricated OSA structure consists of 12 channels of angled fiber array, 54.7/spl deg/ V-grooves, Au-coated mirrors on (111) end facet of the V-grooves, and flip-chip-bonded VCSEL array on a SiOB. In this structure, the beam emitted from the VCSEL is deflected at the 54.7/spl deg/ mirror of (111) end facet and propagated into the angled fiber. The angled fiber array was polished by 57/spl deg/. Fabricated OSAs showed a coupling efficiency of 30%-50% that is 25 times larger than that obtained from an OSA with a vertically flat fiber array. Our OSA showed large misalignment tolerance of about 90 /spl mu/m along the longitudinal direction in the V-groove. We fabricated a parallel optical transmitter module using the OSA and demonstrated 12 channels /spl times/2.5 Gb/s data transmission with a clear eye diagram.