Carbonation behaviour of recycled aggregate concrete

This paper reviews the effect of incorporating recycled aggregates, sourced from construction and demolition waste, on the carbonation behaviour of concrete. It identifies various influencing aspects related to the use of recycled aggregates, such as replacement level, size and origin, as well as the influence of curing conditions, use of chemical admixtures and additions, on carbonation over a long period of time. A statistical analysis on the effect of introducing increasing amounts of recycled aggregates on the carbonation depth and coefficient of accelerated carbonation is presented. This paper also presents the use of existing methodologies to estimate the required accelerated carbonation resistance of a reinforced recycled aggregate concrete exposed to natural carbonation conditions with the use of accelerated carbonation tests. Results show clear increasing carbonation depths with increasing replacement levels when recycled aggregate concrete mixes are made with a similar mix design to that of the control natural aggregate concrete. The relationship between the compressive strength and coefficients of accelerated carbonation is similar between the control concrete and the recycled aggregate concrete mixes.     

基于多源信息探查中小尺度土地利用变化:内蒙古乌审旗案例研究

以Landsat 8 OLI/TM5数据、DEM数据、ISODATA分类结果等构建多源数据集,采用CART决策树方法提取乌审旗2005年、2010年和2015年三期土地利用数据。基于"3S"技术,利用此三期土地利用数据对研究区2005年~2015年土地利用变化特征进行时空变化分析。结果表明:(1)CART决策树分类图的精度分别为86.5%、88%、91.5%,较监督分类精度有所提高,可用于本次土地利用变化研究分析;(2)乌审旗主要的土地利用类型为草地、未利用地和林地;2005年~2015年水域、林地和建设用地的面积均持续上升;耕地与未利用地均先以较快的速度增加后以较快的速度减少,整体为增加趋势;草地面积则先以较快的速度降低,后以较慢的速度增长;(3)未利用地及草地的转化比例占研究区所有土地利用类型转化比例的80.38%,说明未利用地和草地是乌审旗境内极为重要的土地利用现象;(4)2005年~2010年土地利用综合程度减小,而2010年~2015年土地利用综合程度呈现上升趋势。总体来看,2005年~2015年土地利用程度综合指数整体有所增大,说明乌审旗的土地利用正处于发展时期。     

Pedestrian self-reports of factors influencing the use of pedestrian bridges

The study was designed to find out factors that influence use/non-use of pedestrian bridges. The use rate of five pedestrian bridges was observed in the central business district (CBD) of Ankara. After the observations, a survey was conducted among pedestrians using those bridges and crossing contrary to safe practice under them at street level (n=408). In the present data, the use rate of pedestrian bridges varied from 6 to 63%. The frequent use of the bridge when crossing the road concerned, and seeing bridge use as time saving and safe in general were positively related to respondents' bridge use. Frequent visits to CBD decreased the likelihood of using the bridge. Other factors accounted only for a small proportion of variance in bridge use. The study suggests that bridge use or non-use is a habit and not coincidental behaviour. For increasing the pedestrians' bridge use, escalators seem to be a good solution, but traffic signals under a bridge may deteriorate the use rate. In addition, increasing the number of legs leading to the bridge may not increase the use rate. The use rate is likely to improve, if the safety benefits and convenience of using the bridge without considerable time loss are clearly visible to pedestrians.     

Electrical Resistance of CdSe and CdTe at Elevated Temperatures and Pressures

The electrical resistance of polycrystalline CdSe and CdTe was measured as a function of temperature (up to 560 K) and pressure (up to 5.5 GPa). The resistance change across the phase transition and the transition onset pressure were found to decrease linearly with increasing temperature. The band gap of the low-pressure phases of CdSe and CdTe decreases with increasing pressure. The rapid reduction in the resistance change with increasing temperature restricts the use of CdSe and CdTe as high-temperature pressure calibration standards.     

桩锚支护结构在深基坑中的应用

近年来随着我国城市建设的迅速发展,高层建筑物越来越多,由于城市用地的有限性,使得高层建筑不断向地下空间发展,需要进行基坑的开挖,随着基坑开挖深度的增大就要求对基坑进行支护。本文结合工程实例,根据桩锚支护结构的特点,以及该工程的地质条件和周围环境,对本工程基坑开挖进行了可行性和稳定性分析,并对桩锚在工程中的应用进行了探讨。     

Investigation of the effect of barium-based additive on smoke and NOx emissions of a diesel engine fueled with conventional and biodiesel fuels

Clean Technologies and Environmental Policy - Nowadays, increasing energy demand and environmental and air pollution issues have spread the use of alternative fuels such as biodiesel in diesel...     

Decreasing Input Losses of Laser Radiation in Single-Mode Fiber Light Guides

It is shown that use of an anisotropic fiber-optic insert for increasing the efficiency of the connection of an injection laser to a single-mode optical fiber is promising.     

Formational bounds of link prediction in collaboration networks

Scientometrics - With an ever increasing number of academic conferences being offered and a growing concern regarding the appearance of “predatory conferencing”, the optimal use of...     

The Possibility of the Ionization and Acceleration Layer Shifting outside the Magnetic Poles Plane in a Morozov Stationary Plasma Thruster

Technical Physics Letters - Requirements for stationary Morozov plasma thrusters are increasing due to the expansion of their use. Therefore, attempts are made to improve the organization of...     

A Phase-Tuned Oscillating Transducer with Positive Phase Feedback

A new method is proposed for increasing the sensitivity of a phase oscillator transducer by the use of positive phase feedback; the algorithm is described. Basic characteristics are given.     

Molecular architectures for electrocatalytic amplification of oligonucleotide hybridization

In this work, we describe a new platform suitable for electrocatalytic amplification of oligonucleotide hybridization based on the use of supramolecular bioconjugates incorporating ferrocene-labeled streptavidin. Our goals were aimed at designing a biosensing platform which could support highly reproducible and stable electrocatalytic amplification with maximum efficiency. The use of nonlabeled streptavidin as an underlying layer promotes a major improvement on the characteristics of the amplified electrochemical signal. In addition, the electrocatalytic current can be easily amplified by tuning the concentration of electron donor species in solution. Because of the fact that the redox labels are bioconjugated to the DNA strands, increasing the ionic strength does not lead to the loss of redox labels. More importantly, increasing the concentration of donors only involves the magnification of the signal without implying the permeation of donors (thus reducing the efficient electrocatalysis). This approach represents a major improvement on the use of electrocatalytically amplified DNA-sensing platforms, thus overcoming any possible limitation in connection with the reproducibility and reliability of this well-established method.     

Influence of the Pressure and Composition of the Fuel Mixture on its Ignition by a Subcritical Streamer Discharge

Journal of Engineering Physics and Thermophysics - Based on the data of a physical experiment, the possibility of increasing the efficiency of combustion of fuel in power plants with the use of a...     

More screen operation than calling: The results of observing cyclists' behaviour while using mobile phones

Operating a mobile telephone while riding a bicycle is fairly common practice in the Netherlands, yet it is unknown if this use is stable or increasing. As such, whether the prevalence of mobile phone use while cycling has changed over the past five years was studied via on-road observation. In addition the impact of mobile phone use on lateral position, i.e. distance from the front wheel to the curb, was also examined to see if it compared to the results seen in previous experimental studies.     

A compact computer program for calculating buckling stresses and natural frequencies of vibration of prismatic plate assemblies

Low cost and increasing capability favour the use of mini-computers as design tools. The 336 statement Fortran program which is listed and explained was developed to use such small computers efficiently. It calculates the buckling stresses, or the natural frequencies of vibration, of prismatic assemblies of longitudinally compressed isotropic plates. Various refinements have been used to keep the array requirements very small, including the ability to handle sub-structures very flexibly and to use radial and tangential axes to define polygonal sub-structures or structures.     

油田电泵井套管杂散电流腐蚀排流设计及应用

为加强对油田电泵井套管的腐蚀控制,通过室内模拟交流杂散电流腐蚀试验,考察了交流杂散电流对电泵井套管的腐蚀性.结果表明:试样腐蚀速率随着电压的增加而增大,随介质电阻率的增大而减小,电泵井套管的腐蚀存在杂散电流腐蚀及土壤电化学腐蚀的双重强腐蚀.该区域土壤具有较强的腐蚀性,虽然杂散电流并不连续,但可加剧土壤电化学腐蚀.确定采用排流保护法并设计了牺牲阳极排流方案来控制腐蚀.现场测试表明,管地电位波动范围由措施前的124.0 mV减少至27.1 mV,管地电位可负移至一850.0mV(相对饱和硫酸铜参比电极),保护率为78.1%,达到了石油行业标准规定的防腐蚀要求.     

中央空调水系统二管制与四管制问题的探讨

探讨了大、中型中央空调水系统四管制的优越性，分析了四管制系统相对于二管制系统所需增加的投资费用，提出了四管制空调水系统的适用范围。     

Methods of Checking Piezoelectric Vibration Sensors in Situ

Some methods for periodically checking piezoelectric vibration sensors in situ are considered. The use of the substitution method is analyzed and possible ways of increasing the metrological reliability and authenticity of such periodic checks are discussed.     

The specification and installation of alumina ceramics in industry

The increasing cost of maintenance and loss of production caused by downtime of expensive capital equipment has meant that wear is now not just considered a fact of life. Engineers are becoming familiar with alternative materials such as polymers and ceramics and realising the potential in these areas. Ceramics have found an increasing market in industrial and process plant This paper will consider the use of alumina in engineering applications and discuss the selection, specification and installation of alumina ceramics.     

Microwave Initiated Self-Propagating High-Temperature Synthesis of SiC

The use of microwave energy to initiate self-propagating, high-temperature synthesis (SHS) of Si + graphite mixtures has been investigated. The results indicate that, unlike with conventional ignition techniques, green densities in excess of 80% of theoretical can be ignited and the combustion wavefront can be crudely controlled. It was found that the induction time for ignition increased with increasing green density and that a higher microwave power level was required with the denser green pellets to achieve the same ignition time. Combustion front velocity increased with green density. The degree of densification was found to decrease with increasing green density. For a given green density, the degree of densification increased with increasing microwave power. The product contained a significant proportion of ultrafine (36–72 nm diameter) SiC whiskers; despite this, final densities as high as 83.6% of theoretical could be obtained without the use of applied pressure. This compares with the 50% densities obtained via conventional ignition techniques.     

Preparation and characterization of PEG–PPG–PEG copolymer/pregelatinized starch blends for use as resorbable bone hemostatic wax

In this study, polymer blends between PEG–PPG–PEG copolymer mixtures and pregelatinized starch at various compositions ranging from 0 to 3 % by weight were prepared and evaluated for potential use as novel resorbable bone hemostatic wax. It was found that the prepared samples had sufficient smearability for use as a bone wax. An addition of pregelatinized starch increased the hardness, smoothness and consistency of the texture while decreasing the adherence to glove. Thermal analysis indicated that the heat of fusion slightly decreased with increasing pregelatinized starch content. Compressive stiffness tended to decrease with increasing starch content for concentrations lower than 20 %, but re-increased at higher starch levels. In contrast, adherence deformation increased initially, but then decreased with increasing starch content. This behavior was related to the dependence of softening or reinforcing effect on the level of starch concentration in the samples. Adherence load and energy decreased with the addition of pregelatinized starch implying the decrease in adhesiveness of the samples. Furthermore, increasing the pregelatized starch amount also increased the liquid sealing duration of the samples at both 23 and 37 °C. Cytotoxicity tests against osteoblasts using a MTT assay revealed that the all the prepared samples and their raw materials did not show any cytotoxic potential. Formulations containing pregelatinized starch content between 20 and 30 % were found to show optimized performance.