钢制阻拦索与合成纤维制阻拦索性能分析

航母阻拦索是舰载机着舰时与阻拦装置接触的关键部件,是舰载机的"生命线",目前国内外航母多采用液压式阻拦装置,使用的是钢制阻拦索。为了满足舰载机重量范围更大的要求,人们将目光投向合成纤维制阻拦索,希望能成为新型阻拦索。对钢制阻拦索及合成纤维制阻拦索的结构特点及检测方法进行分析,针对舰载机着舰的对中及偏心情况,基于波动传载理论建立数学模型,对钢制阻拦索的应变载荷及合成纤维制阻拦索的拉伸力进行对比计算分析。研究结果表明:钢制阻拦索具有良好的抗拉强度及抗冲击能力,而合成纤维制阻拦索具有良好的强度重量比及柔性,较强的抗弯曲及抗冲击能力,在阻拦过程中受偏心程度的影响较小。

Soft Sensor for Ammonia Concentration at the Ammonia Converter Outlet Based on an Improved Group Search Optimization and BP Neural Network

The ammonia synthesis reactor is the core unit in the whole ammonia synthesis production. The ammonia concentration at the ammonia converter outlet is a significant process variable, which reflects directly the production efficiency. However, it is hard to be measured reliably online in real applications. In this paper, a soft sensor based on BP neural network (BPNN) is applied to estimate the ammonia concentration. A modified group search optimization with nearest neighborhood (GSO-NH) is proposed to optimize the weights and thresholds of BPNN. GSO-NH is integrated with BPNN to build a soft sensor model. Finally, the soft sensor model based on BPNN and GSO-NH (GSO-NH-NN) is used to infer the outlet ammonia concentration in a real-world application. Three other modeling methods are applied for comparison with GSO-NH-NN. The results show that the soft sensor based on GSO-NH-NN has a good prediction performance with high accuracy. Moreover, the GSO-NH-NN also provides good generalization ability to other modeling problems in ammonia synthesis production.

Deriving Changjiang coastal zone wind from C-band SAR and its application to salinity simulation

Wind plays an important role in hydrodynamic processes such as the expansion of Changjiang （Yangtze） River Diluted Water （CDW）, and shelf circulation in the Changjiang estuary. Thus, it is essential to include wind in the numerical simulation of these phenomena. Synthetic aperture radar （SAR） with high resolution and wide spatial coverage is valuable for measuring spatially inhomogeneous ocean surface wind fields. We have collected 87 ERS-2 SAR images with wind-induced streaks that cover the Cbangjiang coastal area, to verify and improve the validity of wind direction retrieval using the 2D fast Fourier transform method. We then used these wind directions as inputs to derive SAR wind speeds using the C-band model. To demonstrate the applicability of the algorithms, we validated the SAR-retrieved wind fields using QuikSCAT measurements and the atmospheric Weather Research Forecasting model. In general, we found good agreement between the datasets, indicating the reliability and applicability of SAR- retrieved algorithms under different atmospheric conditions. We investigated the main error sources of this process, and conducted sensitivity analyses to estimate the wind speed errors caused by the effect of speckle, uncertainties in wind direction, and inaccuracies in the normalized radar cross section. Finally, we used the SAR-retrieved wind fields to simulate the salinity distribution off the Changjiang estuary. The findings of this study will be valuable for wind resource assessment and the development of future numerical ocean models based on SAR images.

Determination of reasonable finished state of self-anchored suspension bridges

A systematic and generic procedure for the determination of the reasonable finished state of self-anchored suspension bridges is proposed, the realization of which is mainly through adjustment of the hanger tensions. The initial hanger tensions are first obtained through an iterative analysis by combining the girder-tower-only finite element(FE) model with the analytical program for shape finding of the spatial cable system. These initial hanger tensions, together with the corresponding cable coordinates and internal forces, are then included into the FE model of the total bridge system, the nonlinear analysis of which involves the optimization technique. Calculations are repeated until the optimization algorithm converges to the most optimal hanger tensions(i.e. the desired reasonable finished bridge state). The "temperature rigid arm" is introduced to offset the unavoidable initial deformations of the girder and tower, which are due to the huge axial forces originated from the main cable. Moreover, by changing the stiffness coefficient K in the girder-tower-only FE model, the stiffness proportion of the main girder, the tower or the cable subsystem in the whole structural system could be adjusted according to the design intentions. The effectiveness of the proposed method is examined and demonstrated by one simple tutorial example and one self-anchored suspension bridge.

Study of the Influence of a Young Synthetic Leachate on the Hydromechanical Properties of a Swelling Clay

Despite the developments of sectors which aim at valorizing recyclable materials, landfills remain essential in integrated waste management. The construction of such infrastructures is an engineering challenge that must be proven over the long term. The purpose of this study is to understand the modification of the hydromechanical properties of bottom liners of landfills that may occur during their exploitation under leachate action. To do so, on the basis of its parameters of nature, a swelling clay from Burkina Faso is selected from soils of seven localities in Burkina Faso （West Africa）. Laboratory tests carried out with distilled water and then with a young synthetic leachate show a degradation of the permeability of this clay from 2.42 × 10^-10 m/s to 1.01 × 10^-9 m/s. In addition, leachate leads to an inhibition of the swelling and a remarkable increase of its compressibility, inducing significant settlement. With the increase in permeability, the primary consolidation settlement is increasing faster. Changes in the hydromechanical behavior can be attributed to the clays mineralogy, mainly cation exchange and the development of the diffuse double layer.

Study on engineering audit based on Valuation

in the bill of quantities mode, audit department how to perform the function of supervision, control the cost of the project, to improve the infrastructure investment efficiency to have the important meaning. This article from the valuation list elements of engineering audit mode based solutions, engineering audit under BOQ valuation mode is put forward from the audit information management, engineering contract claim, audit personnel quality etc..

T-QoS-aware based parallel ant colony algorithm for services composition

In order to make cloud users get credible, high-quality composition of services, the trust quality of service aware(TQoS-aware) based parallel ant colony algorithm is proposed. Our approach takes the service credibility as the weight of the quality of service, then calculates the trust service quality T-QoS for each service, making the service composition situated in a credible environment. Through the establishment on a per-service T-QoS initialization pheromone matrix, we can reduce the colony's initial search time. By modifying the pheromone updating rules and introducing two ant colonies to search from different angles in parallel,we can avoid falling into the local optimal solution, and quickly find the optimal combination of global solutions. Experiments show that our approach can combine high-quality services and the improvement of the operational success rate. Also, the convergence rate and the accuracy of optimal combination are improved.

Mortality weighting-based method for aggregate urban air risk assessment

This paper deals with a mortality-weighted synthetic evaluation （MWSE） method for evaluating urban air risk. Sulphur dioxide （SO2）, nitrogen oxide （NOx）, and particulate matter （PMl0） were used as pollution indices. The urban area of Hangzhou, China is divided into 756 grid cells, with a resolution of 1 km× 1 km, and is evaluated using the MWSE and the air quality index （AQI）, a widely-used method to evaluate ambient air quality and air risk. In an evaluation of one day in April 2004, the surface areas categorized as levels Ⅰ and Ⅲ, as defined by the integrated air risk evaluation, were 27.3% and 3.3% lower, respectively, than grades Ⅰ and Ⅲ defined by the AQI evaluation. Meanwhile, the areas classified as level Ⅱ or above level Ⅲ by the integrated air risk evaluation were 55.1% and 101. 1% higher, respectively, than grade Ⅱ or above grade Ⅲ when using the AQI evaluation. From this comparison, we find that the MWSE method is more sensitive than the AQI method. The AQI method uses a single index to assess integrated air quality and is therefore unable to evaluate integrated air risks due to multiple pollutants. The MWSE method overcomes this problem, providing improved accuracy in air risk assessment.