钢结构自支撑法安装实践探讨——厦门园博园月光环工程

月光环为厦门园艺博览会上的景点之一,四面环水,取海上升明月意境。月光环主体结构为环行高耸钢管网架结构,由钢管和钢管鼓节点组成,各杆件和节点的空间关系复杂,定位困难;施工现场四面环水,安装作业难度大。介绍了月光环工程钢结构制作和结构自支撑安装施工方案。

Stability margin of the quadruped bionic robot with spinning gait

Spinning gait is valuable for quadruped robot,which can be used to avoid obstacles quickly for robot walking in unstructured environment. A kind of bionic flexible body is presented for quadruped robot to perform the spinning gait. The spinning gait can be achieved by coordinated movement of body laterally bending and legs swing,which can improve the mobility of robot walking in the unstructured environments. The coordinated movement relationship between the body and the leg mechanism is presented. The stability of quadruped robot with spinning gait is analyzed based on the center of gravity( COG) projection method. The effect of different body bending angle on the stability of quadruped robot with spinning gait is mainly studied. For the quadruped robot walking with spinning gait,during one spinning gait cycle,the supporting polygon and the trajectory of COG projection point under different body bending angle are calculated. Finally,the stability margin of quadruped robot with spinning gait under different body bending angle is determined,which can be used to evaluate reasonableness of spinning gait parameters.

Authorization Administration in a Distributed Multi-application Environment

To meet the authorization administration requirements in a distributedcomputer network environment, this paper extends the role-based access control model with multipleapplication dimensions and establishes a new access control model ED-RBAC(Extended Role Based AccessControl Model) for the distributed environment. We propose an extendable hierarchical authorizationassignment framework and design effective role-registeringi role-applying and role-assigningprotocol with symmetric and asymmetric cryptographic systems. The model can be used to simplifyauthorization administration in a distributed environment with multiple applications.

Characterization of heavy petroleum fraction by positive-ion electrospray ionization FT-ICR mass spectrometry and collision induced dissociation: Bond dissociation behavior and aromatic ring architecture of basic nitrogen compounds

This paper examined the bond dissociation behavior and aromatic ring architecture of basic nitrogen compounds in Sudan heavy petroleum fraction. Both broadband and quadrupole isolation modes positive-ion electrospray ionization （ESI） Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS） coupled with collision induced dissociation （CID） tech- niques were used to characterize a low sulfur crude oil derived vacuum residuum （VR）. The appropriate CID operating condi- tion was selected by comparing the molecular weight distributions of the basic nitrogen compounds under various CID operat- ing conditions. Both odd- and even-electron fragment ions were observed from the mass spectrum, indicating that the hetero- lyric and homolytic bond cleavages occurred simultaneously during the CID process. The odd-electron fragment ions were predominant in each class species, indicating preferential heterolytic bond cleavages. At the optimal CID condition, the alkyl groups decomposed deeply and just left the aromatic cores of the nitrogen compounds. No Significant variation in double bond equivalent （DBE） value was observed between the fragment and parent ions, revealing that the domination of single core structure.

Hydrodynamics in a Circulating Fluidized Bed with Annular Furnace and Six Parallel Cyclones

Systematic measurements were conducted on a cold CFB with annular furnace and six parallel cyclones to study gas-solids flow in the annular furnace and flow non-uniformity among six cyclones. The results show that axial solids holdup in the annular furnace decreases exponentially with height, similar to the conventional rectangular furnace. The uniform transverse distribution of solids holdup suggests a good gas-solids mixing in the annular furnace. The annular furnace presents the core/double-annulus flow structure, and it results in enhanced gas-solids back-mixing than the conventional core/annulus flow structure. The gas-solids flow of the inner wall-layer and the outer wall-layer is very close at most part of the furnace height, and the wall-layer thickness decreases with height. Flow non-uniformity exists among six parallel cyclones in the annular furnace CFB. But non-uniform distribution of solids circulating rates and cyclone pressure drops show no regularity, and the flow non-uniformity is no larger than the CFBs with conventional furnace. Under typical operating conditions, the relative deviation of six solids circulating rates is 8.0%.