Effect of Fog and Clouds on the Image Quality in Millimeter Communications

The effect of fog and clouds in millimeter communication is discussed, and the attenuation caused by fog and clouds is reviewed. Signal-to-noise ratio (SNR) of image is derived using relating models of fog and clouds attenuation. According to the relation of image quality and its signal-to-noise ratio, the system behavior is forecasted theoretically. It is shown that the signal-to-noise ratio of receiver at certain transmitter power is inverse with radio wave frequency, from about 70dB at 10GHz to 48dB for fog and 49dB for clouds. The image quality of received signal at certain transmitter power is inverse with radio wave frequency, from about 7 grade at 10GHz to 5.27 grade for fog and 5.37 grade for clouds. The above calculated results are consistent with experimental results.     

A model for evaluation and administration of security inobject-oriented databases

The integration of object-oriented programming concepts with databases is one of the most significant advances in the evolution of database systems. Many aspects of such a combination have been studied, but there are few models to provide security for this richly structured information. We develop an authorization model for object-oriented databases. This model consists of a set of policies, a structure for authorization rules, and algorithms to evaluate access requests against the authorization rules. User access policies are based on the concept of inherited authorization applied along the class structure hierarchy. We propose also a set of administrative policies that allow the control of user access and its decentralization. Finally, we study the effect of class structuring changes on authorization     

Effects of multiple weak interactions on the binding of phenolic compounds by polymeric adsorbents

To investigate the effects of multiple weak interactions on the binding of phenolic compounds by polymeric adsorbents, macroporous polystyrene (PS) resin and PS‐based adsorbents with different hydrogen‐bond acceptor atoms (PS CH₂( OCH₂CH₂)_n OCH₃, n = 0, 1, 2, and 3, denoted as PS‐EG₀, PS‐EG₁, PS‐EG₂, and PS‐EG₃) were prepared. The phenol adsorption strength order on these adsorbents was PS/PS‐EG₀ < PS‐EG₁ < PS‐EG₂ < PS‐EG₃, indicating that the adsorption on PS and PS‐EG₀ was driven by hydrophobic and π–π interactions, and the adsorption on PS‐EG₁, PS‐EG₂, and PS‐EG₃ was driven by a hydrogen bond in addition to hydrophobic and π–π interactions. PS‐EG₂ may adsorb a second phenol molecule on each binding site and PS‐EG₃ may adsorb second and third ones. The adsorption strength of resorcinol increased in the order of PS, PS‐EG₁, and PS‐EG₂, indicating that the adsorption was driven by 0, 1, and 2 hydrogen bonds in addition to hydrophobic and π–π interactions. Similarly, the adsorption of phloroglucinol on PS, PS‐EG₁, PS‐EG₂, and PS‐EG₃ was driven by 0, 1, 2, and 3 hydrogen bonds in addition to hydrophobic and π–π interactions because the adsorption strength increased in this order. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4652–4658, 2006     

Computation of Microwave Attenuation on Coplanar Waveguide with Conformal ADI-FDTD Method

A novel Conformal Finite-Difference Time-Domain based on Alternating-Direction Implicit Method(ADI-CFDTD) used to calculate the microwave attenuation on coplanar waveguide(CPW) with complicated cross-section up to 200GHz is presented. This ADI-CFDTD algorithm is the combination of conformal algorithm dealing with the deformed cell with ADI-FDTD, and has unconditionally stable. The difference equations are derived from the Faraday's and Ampere's law. To validate its accuracy and efficiency, as an example, a CPW fabricated on lithium niobate is proposed. Numerical results demonstrate that this new ADI-CFDTD algorithm has more accuracy than that of quasi-static and CFDTD and shows good agreement with experiment data. When frequency is up to millimeter wave band the radiation loss is not negligible in total power loss.     

Study on the Intelligent System of Gear Pitch Deviation Measurement and Analysis

The intelligent controlling and data process of pitch error measurement is proposed. The whole system takes C++ as the development tool and takes advantages of object-oriented and visualization, having the advantages of easy operation and humanistic interface. In the meanwhile, the system can be complemented and improved according to the demand of user, having certain independence. The research of the system provides an efficient and reliable way to measure and analyze the gear pitch, which can be referenced in the future research.     

Transient aspects of inner wall temperatures at different spatial positions in fluidized bed evaporators

In this work, the instantaneous data of inner wall temperatures obtained at given axial positions but for different heated tubes or at various axial positions but at the same heated tube in a tube-bank fluidized bed evaporator with a vapor–liquid–solid external natural circulation flow were analyzed by employing linear and nonlinear time series analysis methods, including correlation dimension and Kolmogorov entropy analyses besides time domain, power spectrum and autocorrelation analyses. It is found that nonlinear characteristics of the wall temperature time series vary with spatial position in the evaporator at given operation conditions, and thus the multi-phase flow boiling behavior. However, the signals obtained at given axial position but different heated tubes in the evaporator exhibit more similar nonlinear evolution behavior, and those measured in the same heated tube but at different axial heights in the evaporator undergo more distinct nonlinear dynamic behavior. Multi-scale phenomena in different spatial positions are also found and discussed. These transient aspects of inner wall temperatures are closely related to the average holdup of solid particles and motion of vapor bubbles in vapor–liquid–solid flow. These results can provide some valuable information on the system modeling and controlling from the point of view of nonlinearity.     

Effects of chemical and plasma surface treatments on the O2-annealed Ni/Au contact to p-Gan

The effects of boiling Aqua Regia (AQ), N₂/Cl₂ plasma followed by AQ and O₂ plasma followed by AQ surface treatments prior to Ni/Au (20 nm/20 nm) metallization to p-GaN:Mg (∼ 3 × 10¹⁷ cm^− 3) have been investigated. N₂/Cl₂ plasma was employed in a bid to lower the Ga/N and O/Ga ratios of the GaN surface to improve the contact properties to p-GaN, while O₂ plasma was employed as an alternative to incorporate O into the Ni/Au system. Results show that a low Ga/N ratio does not necessarily correspond to a better contact. The positive effect of O₂ over N₂ anneal is observed only for the AQ-treated sample, although the mechanisms responsible for its positive effect: NiO formation and Ni/Au layer-reversal were observed for all O₂-annealed contacts. We conclude that the effect of O₂ anneal on the Ni/Au contact is dependant on the p-GaN surface prior to metallization.     

Influence of Shaping Condition on Etherification Performance of Hβ Zeolite

Etherification reaction of FCC light gasoline over Hβ zeolite was investigated to decrease the light olefins in motor gasoline while enhancing octane. Etherification activity of several molecular sieve catalysts for FCC light gasoline was studied in a fixed-bed reactor. The influence of pore-enlarging agent (PEG) with different molecular weight, binder (γ-Al₂O₃), and peptizing agent (HNO₃) in the shaping process on etherification activity of Hβ zeolite was studied. The impregnating ways of precursor of oxides and the order of extruding and impregnating were also investigated. The results show that the activity of extruded Hβ zeolite before impregnating precursor of oxides is higher than the reverse order. The best shaping condition obtained was PEG-4000 10%, γ-Al₂O₃ 20%, and HNO₃ 10%. At the optimal reaction condition, the conversion of tert-olefins reached the peak. 62.93%, the yield of TAME, is also high and the technology can be applied to industry as well.     

数据处理系统性能评价的简单理论模型

提出了一个简单的理论模型．旨在为数据处理系统的性能评价提出一个理论框架．以此框架为基础，可形成实用的简单评估方法．该模型只含两个参数，它们是统计量，可用统计方法确定．