混凝土坝基防渗帷幕体老化的基本模式及识别指标

采用综合分析方法,对混凝土坝基防渗帷幕体的老化模式以及识别指标进行了系统的探讨。基于相对防渗效率,把帷幕体老化分为相对稳定型、缓慢变化型以及阶段性变化型3种基本模式;在分析时段内,不同的模式具有不同的防渗效率。用于识别帷幕体老化的指标有3类:第一类为渗流的微观动态要素,包括析钙量、TDS值、pH值、无机质和有机质等,可用于揭示帷幕体的老化机制;第二类为渗流的宏观动态要素,包括扬压力、排水量等,可用于判断帷幕体的老化程度及其基本模式;第三类为数值分析指标,包括饱和指数和渗漏水源比例系数等,可用于量化分析帷幕体的老化过程。3类指标的识别有助于构建混凝土坝基防渗帷幕体老化评估体系。     

Exploiting Bayesian networks for fault isolation: A diagnostic case study of diesel fuel injection system

Fault isolation is known to be a challenging problem in machinery troubleshooting. It is not only because the isolation of multiple faults contains considerable number of uncertainties due to the strong correlation and coupling between different faults, but often massive prior knowledge is needed as well. This paper presents a Bayesian network-based approach for fault isolation in the presence of the uncertainties. Various faults and symptoms are parameterized using state variables, or the so-called nodes in Bayesian networks (BNs). Probabilistically causality between a fault and a symptom and its quantization are described respectively by a directed edge and conditional probability. To reduce the qualitative and quantitative knowledge needed, particular considerations are given to the simplification of Bayesian networks structures and conditional probability expressions using rough sets and noisy-OR/MAX model, respectively. By adopting the simplified approach, symptoms under multiple-fault are decoupled into the ones under every single fault, while the quantity of the conditional probabilities is simplified into the linear form of the faults quantity. Prior knowledge needed in Bayesian network-based diagnostic model is reduced significantly, which decreases the complexity in establishing and applying this diagnosis model. The computational efficiency is improved accordingly in the simplified BN model, after eliminating the redundant symptoms. The fault isolation methodology is illustrated through an example of diesel engine fuel injection system to verify the developed model.     

Optimal load rating-based inspection planning of corroded steel girders using Markov decision process

Steel girder bridges are vulnerable to corrosion. To maintain their safety above a predefined target level, the load rating can be computed from the inspection results and guide the following maintenance actions. Optimizing inspection and maintenance based on load ratings has substantial practical and economic relevance. Load rating-based strategies can be categorized based on whether the inspection interval and replacement criteria are fixed or flexible. Existing studies focus on fixed inspection intervals throughout the service life. In general, their results are not optimal for inspection planning. To reduce life-cycle cost, aged steel girders may be inspected and repaired in an adaptive manner. To this end, a method based on Markov decision process (MDP) is proposed to compare the life-cycle cost of four load rating-based policies (i.e. uniform or adaptive non-uniform inspection interval, and fixed or adaptive replacement threshold). Load rating-based inspection planning is formulated as MDP and the optimal plans are obtained using dynamic programming. The conventional approach to discretize states cannot accurately approximate the non-stationary deterioration process, while state augmentation is successful in doing this but will increase computational cost. A comparison of two approaches is made to investigate their effects on life-cycle cost. A bridge girder under corrosion attack is used as an illustrative example. The results show that the load rating-based plan with an adaptive non-uniform inspection interval and fixed replacement threshold obtained using the state augmentation technique can be near-optimal.     

柴油发动机高压共轨燃油喷射技术研究

本本文介绍了柴油机电控燃油喷射技术的发展历程。阐述柴油机高压共轨电控燃油喷射系统的基本组成、工作原理、特点及未来研究方向。     

Inductive modulation on P-glycoprotein and cytochrome 3A by resveratrol,a constituent of grapes

Resveratrol has been reported to show various beneficial pharmacological effects. Nowadays, resveratrol dietary supplement (RDS) is available in the market. Cyclosporin (CsA), a probe drug of P-glycoprotein (P-gp) and cytochrome P450 3A4 (CYP3A4), is an important immunosuppressant. This study investigated the effect of coadministration of RDS on CsA pharmacokinetics.     

Soot oxidation kinetics under pressurized conditions

The oxidation kinetics, under different pressures, of soot samples obtained from different liquid fuels and two standards (a commercial black carbon sample and a reference diesel soot) was studied. Soot samples were generated in a flat-flame, premixed burner under heavily-sooting conditions and captured on a water-cooled stabilization plate located above the burner surface. The collected soot was oxidized using a high-pressure thermogravimetric analyzer (HTGA). TGA operation was optimized to reduce mass transfer effects by adjusting the oxidizer flow rate and initial sample mass. Further corrections for mass transfer were accomplished by computing the effectiveness factors for intraparticle, interparticle, and external mass transfer. Two pressures were evaluated (1 and 10 atm) and O₂ concentration was varied between 10 and 21%.     

Experimental and numerical investigation of intermittent drying of timber

Intermittent drying may be of interest in the future to address energy issues. Such drying conditions are also likely to help stress relaxation through mechanosorptive creep. The influence of applying oscillations of temperature and relative humidity during the drying of beech timber on time and drying stresses is discussed in the paper by means of nonsymmetrical and loaded drying. Experimental data were used to validate a numerical model in the case of intermittent drying. The model was then used to perform a numerical investigation of the possibility of using an intermittent energy source to dry wood.     

Limitation of cracking in AAC masonry under the window zone

The article describes the results of tests on the impact of reinforcement on the appearance of cracks and on the manner of damage to masonry under the window zone. Masonry made of Autoclaved Aerated Concrete units with thin layer mortar was tested. Eight unreinforced test specimens (two series) and four series of test specimens (12 specimens) with reinforcement in the bed joints were subject to testing. Two types of reinforcement were used in the tests. It is demonstrated that the reinforcement has a significant impact on the level of cracking stress and propagation of cracks. It was found that when a pillar is correctly designed, cracks should not occur in the masonry under the window zone.     

低压投煤技术在壳牌煤气化装置中的应用

壳牌煤气化装置低压投煤开车技术要求开工烧嘴在较低热负荷情况下的运行时间尽可能短,且气化炉压力在0.1～0.5 MPa（原设计为0.8～1.0 MPa）时就投用煤烧嘴,并通过煤烧嘴的运行来为气化炉升温升压,直至装置满负荷运行。分析了壳牌煤气化装置采用高压投煤开车存在的主要问题及其原因;对比了高压投煤和低压投煤的运行情况;...