The effect of traffic data source on deterioration rates of heavy-duty flexible pavements

The purpose of this study is to assess the effect of traffic data source (estimated vs. actual) on predicted progression rates of roughness and rutting for heavy-duty flexible pavements of rural freeways. Progression rates are predicted using calibrated HDM-4 models. The assessment is performed in terms of variations in maintenance intervention timing associated with the variations in progression rates. Time series pavement condition data (covering 3–5 years) have been collected for 7 sections of rural freeways for use in calibrating HDM-4 deterioration models. They range in length from 10 to 60.8 km and cover different traffic volumes, climate zones and subgrade soil types. For these sections, estimated annual average daily traffic (AADT), growth factors and assumed loading have been extracted from relevant database. Only six segments of these sections have Weigh-in-Motion (WIM) sites so relevant actual AADT, growth factors and axle load distributions have been extracted from WIM reports. The results of running the calibrated HDM-4 deterioration models using different traffic data show that actual traffic data from WIM sites result in higher rates of deterioration to that of estimated data for four sites, resulting in earlier intervention timing and higher present value agency cost. The other two sites have lower rates with actual data due to lower traffic loading than estimated.     

Predictive association of metal–organic systems in the solid-state: the molecular electrostatic potential based approach

Designing crystalline solids with improved properties or performances remains a challenging task, despite great strides that have been made within the field of crystal engineering since its birth several decades ago. Herein, we are bringing examples that illustrate recent successes in taking supramolecular synthetic guidelines from the organic crystal engineering and adjusting those to metal-containing systems, particularly to the lower-dimensional ones. The versatility of calculated molecular electrostatic potential (MEP) as a new crystal engineering tool is demonstrated.     

读懂衡器的最大允许误差

本文主要讨论衡器的检定分度数能否大于传感器的最大检定分度数nmax,这是一直困扰大家和争论不休的问题。作者由分析最大允许误差mpe本质入手,指出mpe是人为规定的误差,不是传感器实际的物理特性。通过理论分析得出的对单只传感器的衡器,n≤nmax和v≥vmin的误差限原则是不能违背的。对于四只传感器的衡器,不受上述误差限原则限制。     

Prices

Assessed or estimated prices and values for the major types of crude oils traded on spot markets. Updated on a monthly basis. Official sales prices (except as otherwise noted) and are generally market-related, subject in some cases to retroactive adjustment. Updated on a monthly basis.     

大学生信守社会主义核心价值观“三自”理性演进论——基于主体能动价值的实现

依据马克思主义哲学观对人的主体能动价值实现的条件，联系高校对大学生社会主义核心价值观培育的实践，尊重、培育、强化大学生信守社会主义核心价值观的主体性就应当基于其主体能动价值的实现，应当尊重、培育、强化自为、自觉、自由的“三自”理性的能动性，使之信守社会主义核心价值观的“三自”理性能动性向着由高校引领的方向演进。     

Multiple models decentralized coordinated control of doubly fed induction generator

In this paper, a multiple model optimal tracking control (MOTC) design method for the double fed induction generator (DFIG) using correlative measured technique is proposed. The DFIG is represented by a third-order model, where electro-magnetic transients of stator are neglected. By using the correlative measured technique, the correlative measured matrix (CMM) of wind power system is obtained firstly. Then, a nonstandard state space equation of DFIG is obtained with the correlative measured vectors (CMVs), which reflect interactions between the DFIGs and grid. In order to cope with nonlinearities and continuous variation in the operating points, a multiple model design method is proposed in the discrete domain. The obtained control law, synthesized by using Bayesian probability, only depends on the local measured parameters. Hence, the MOTC can be regarded as a decentralized coordinated control, which can simplify the control structure and improve the transient stability of DFIG. To illustrate the effectiveness of the proposed MOTC strategy, simulations on a hybrid wind thermal power (HWTP) system are performed. The results show that the proposed MOTC strategy can provide acceptable performance throughout the whole operating region. Comparing to the conventional PID control, transient stability, damping, and fault ride-through capability of DFIG with the proposed MOTC design method have been improved effectively.     

爆炸能分配比值对爆炸应力波峰值的影响

为评价膨胀能Ｅｂ在破岩过程中的作用，进行了爆炸应力波的测定实验，研究了冲击能（Ｅｓ）与膨胀能（Ｅｂ）分配比值的变化对爆炸应力波峰值的影响。实验结果表明，随着Ｅｓ／Ｅｂ比值的增大，原生爆炸应力波的峰值随之增大，而次生爆炸应力波的峰值则相应减小。     

牙轮钻头直径的计算

采用求极值来计算才轮钻头的直径，给出了牙轮钻头直径的计算公式，并分别对有移轴及无移轴牙轮钻头直径的计算进行了分析。     

在缓倾斜煤层中推广综采放顶煤技术浅析

对综采放顶煤技术在缓倾斜煤层中的应用进行科学理论上的分析 ,对放顶煤液压支架的选择进行合理的论证 ,对顶煤冒落的采煤过程进行论述     

受动压影响巷道围岩稳定性浅析

分析了静压及动压作用下巷道围岩的稳定性特点 ,并论述了动压作用下巷道围岩控制原理与技术。