Preparation of Bio-beads and Their Atrazine Degradation Characteristics

Screened atrazine-mineralizing bacterium-Pseudomonas W4 was embedded inside an improved PVA- H<,3>BO<,3> embedment matrix to make bio-beads to degrade atrazine. The atrazine degradation characteristics were stu- died. The preparation procedure of bio-beads was as follows: (1) preparing a mixture of 100, 12.5, 10, 1.5 and 1 g/L PVA, bentonite(Ca), activated carbon powder, sodium alginate and centrifuged Pseudomonas W4 bacterium, respec- tively; (2) the mixture was dropped into a gently stirred cross linker solution(pH=6.7) and cured at 10 ℃ for 24 h. The optimal atrazine degradation conditions by bio-beads were as follows: pH=7, the auxiliary carbon source was glucose, and the concentration of glucose was greater than 325 mg/L. The bio-beads demonstrated stronger tolerance ability than the free microorganism to the increase of PCBs, hydrogen ion and hydroxide ion. SEM images show the uniform distribution of the microorganism inside bio-beads and the porous cross-linked structure of bio-beads which provides excellent mass transfer capacity.     

太原一电厂六期锅炉柱脚固定新方案的确立和实施

太原一电厂１３号锅炉柱脚施工中,采用了取消埋设地脚螺栓的定位方法,缩短了工期,提高了效益,取得良好效果。     

A methodological approach for finite element modeling of pretensioned concrete members at the release of pretensioning

This paper presents a methodological approach for finite element simulation of pretensioned concrete members. The three-dimensional analysis presented in this paper involves a rectangular [150 mm (6 in.) tall × 150 mm (6 in.) wide × 2440 mm (96 in.) long] concrete member hosting one 15-mm (0.6 in.) diameter 7-wire low-relaxation Grade 1860 MPa (270 ksi) prestressing strand. The finite element models are divided into two general classifications: (i) concentrically pretensioned, and (ii) eccentrically pretensioned. The finite element models are analyzed based on elastoplastic material behaviors as well as mesh sensitivity. Two approaches are examined for finite element modeling of the pretensioned concrete specimens: (i) the extrusion technique utilizing friction-based contact simulations, and (ii) the embedment technique simulating equivalent responses while being a computationally less expensive solution. A comparative analysis is presented to measure the validity as well as accuracy of the findings by the finite element techniques against the commonly used closed-form solutions based on elastic beam theory. The validity of the finite element approach is further verified by comparative analysis of the analytical data against the experimental findings. The paper concludes that the embedment technique provides an accurate and numerically efficient alternative in comparison with the extrusion method for the simulation of the pretensioned concrete members. While the extrusion technique provides more detailed information corresponding to the regions located immediately around the prestressing strands, including the interface overstresses and bond slippage, the embedment technique appears to have the ability to simulate the overall response of the concrete members with comparable accuracy.     

高层建筑基础埋置深度不足时的结构设计

本文结合工程实例,针对高层建筑不满足基础埋置深度的情况,对小,中,大震工况下桩基的抗压、抗拉和水平承载力进行验算,确认主体结构在地震作用和水平风荷载作用下满足整体倾覆验算需采取的措施。     

浅谈输电线钢管杆的设计

本文对输电线钢管杆设计中的材料选择、杆段连接形式、横担连接形式和地脚螺栓形式及锚固长度等各方面进行了介绍,以期指出输电线路钢管杆设计中的关键点,为工程建设提供参考。     

Lateral and Upward Soil-Pipeline Interactions in Sand for Deep Embedment Conditions

The soil–pipeline interactions in sand under lateral and upward movements are investigated with particular attention to the peak forces exerted on the pipe. The analytical solutions for estimating the peak forces are summarized and it is shown that, for deep embedment condition, there is large uncertainty in the true values since the bounds established by the analytical solutions are large. In order to find the solution for the peak force and to investigate its transition from shallow to deep failure mechanism, finite element analyses of lateral and upward pipe movements are performed for different embedment conditions. Two different soil models (Mohr–Coulomb and Nor–Sand models) are used for the simulations. The accuracy of the analysis is first examined by simulating experimental tank tests. The analysis is further extended to deeper embedment ratios of as large as 100. The obtained finite element results are used to construct a design chart for deep embedded pipelines.     

高店双曲拱坝原型观测系统设置及蓄水前观测资料分析

简述高店水库工程双曲拱坝观测仪器的布置、选型及埋设施工情况,并对大坝在蓄水前所取得的观测资料进行了初步分析,为掌握大坝施工期的运行性态及工程的后期运行管理提供了依据,可供类似工程借鉴.     

Scanning electron microscopic observations on deembedded biological tissue sections: Comparison of different fixatives and embedding materials

Conventional plant histological specimens fixed in formalin-acetic acid-alcohol, chromic acid-acetic acid-formaldehyde, or glutaraldehyde-osmium and embedded in either paraffin or plastic are examined as possible rapid methods for providing an alternative image of cellular structure by using scanning electron microscopy. Using the mitotic figures of actively growing onion root tips as a study specimen, the organization of the nucleus and spindle apparatus is reasonably well preserved as compared with isolated mitotic spindles and studies of mitosis in endosperm tissue. Relief of internal structure in this technique is obtained through the coagulant nature of the fixative. Used judiciously, this technique can reveal aspects of the three-dimensional nature of internal tissue structure that may otherwise be difficult to discern.     

Effect of Surface Heave on Response of Partially Embedded Pipelines on Clay

The as-laid embedment of an on-bottom pipeline strongly influences the resulting thermal insulation, and the resistance to subsequent axial and lateral movement of the pipeline. Reliable assessment of these parameters is essential for the design of offshore pipelines. Static vertical penetration of a pipe into a soft clay seabed—which can be modeled as an undrained process—causes heave of soil on each side of the pipeline. The heaved soil contributes to the vertical penetration resistance and the horizontal capacity. This paper describes a series of large deformation finite-element analyses of pipe penetration, supported by a simple analytical assessment of the heave process. The conventional bearing capacity approach to the analysis of pipe penetration is reviewed, and modifications for the effects of soil weight and heave are presented. It is shown that in soft soil conditions—which are typical for deep water—the soil self-weight contributes a significant portion of the vertical penetration resistance and horizontal capacity. If heave is neglected, the soil weight leads to a vertical force due to buoyancy, based on Archimedes’ principle. When heave is considered, the soil weight contributes an additional component of vertical load, exceeding simple buoyancy, due to the distorted geometry of the soil surface. Archimedes’ principle does not apply. The finite-element analyses, benchmarked against rigorous plasticity solutions, are used to calibrate simple expressions for predicting static vertical pipe penetration, and the resulting horizontal capacity. These simple solutions allow the conventional bearing capacity approach to be used in a manner which correctly accounts for the effects of soil self-weight and heave. An approximate solution for predicting the “local” pipe embedment—relative to the raised soil level immediately adjacent to the pipe—is derived. The local embedment significantly exceeds the nominal embedment relative to the original soil surface. This effect counteracts the tendency for heave to reduce the embedment by raising the penetration resistance.