Quantifying Field-Test Behavior for Rating Steel Girder Bridges

Field testing is valuable for evaluating existing bridges. It allows the owner to reduce the conservatism of analytical rating methods and safely rate the bridge for higher loads. Many factors not considered in design contribute to the response of a tested bridge. Several of these, like actual load distribution and additional stiffness from curbs and railings, are welcome benefits that can be used to increase load ratings. However, there are also contributions from bearing restraint forces and unintended composite action that may not be reliable during the bridge's service life. These factors tending to increase the load capacity need to be separated and quantified so that the bridge owner can: (1) confirm the origin of the useable benefit; and (2) remove the unwanted contributions. Presented are procedures for load rating steel girder bridges through field testing. A systematic approach is presented to separate and quantify the contributions from various effects. Therefore, the responsible engineer can remove the unwanted contributions and justify an experimental load rating. The procedures are demonstrated for a three-span steel girder bridge.     

Soluble Microbial Products in ABR Treating Low-Strength Wastewater

The chemical composition, molecular weight (MW) distribution, and biodegradability (both aerobic and anaerobic) of soluble microbial products (SMPs) in an anaerobic baffled reactor (ABR) treating low-strength wastewater were investigated. The effect of various process parameters on the production of SMPs was also examined. Results indicated that high MW (>300 kDa) compounds were produced in the middle compartments of the reactor and formed 22% of the effluent chemical oxygen demand (COD). This fraction was found to be 86% degradable under aerobic conditions but only 4% under anaerobic conditions. Low MW (<1 kDa) material represented the highest portion (36%) of the effluent COD and was mainly found in the first compartment of the ABR and in the effluent. This fraction was more easily degraded under anaerobic conditions (33%) than aerobic conditions (17%). Analysis of a hydrolyzed sample of the high MW fraction revealed the presence of several sugars and volatile fatty acids. Therefore, it was concluded that the high MW material contains heteropolysaccharides. Nuclear magnetic resonance analysis of the low MW fraction revealed the possible presence of alcohol, carboxylate, and aromatic chemical groups. SMP production increased with increasing hydraulic retention time (HRT), probably due to enhanced biomass decay at high HRTs, and also increased with decreasing temperature, probably due to increased stress on the biomass and a reduced metabolism of the SMP at low temperatures. Finally, SMP production in an ABR containing higher levels of initial biomass concentration was greater than for an ABR operating at the same conditions but with lower levels of initial biomass.     

IMPROVEMENT OF STIFF-MUD CLAYS THROUGH PH CONTROL *

Clays, when given a correct alkali treatment, show a marked improvement in working qualities. They become more plastic, require less power to extrude the clay through the die, and, when dried, have greater strength and are less pervious to water. The tendency of clays to laminate is reduced. The fired ware is stronger and has a lower moisture absorption. Both acid and calcareous clays are susceptible to improvement by this process. The amount of reagents must be carefully controlled by p_H measurement for best results. The method of testing for p_H. and the limits within which the two type clays must be held are described.     

STUDIES ON BEER HAZE FORMATION. 1. GAS CHROMATOGRAPHIC PROFILES OF BEER: POLYAMIDE RESIN ADSORBATES*

A methanol-soluble fraction of beer-Nylon 66 adsorbates has been examined by gas chromatography using enhanced volatilities afforded by trimethylsilylation. Mass spectrometry was used to assign structures to several profile components which included fatty acids, residual wort carbohydrates and phenols. The latter comprised free acids, the most prominent being p-hydroxy-cinnamic and ferulic acids, catechins, a catechin glycoside, dicatechin and condensed biflavans. Flavonoids were not observed. The profiles can be used to gain information, which has hitherto been unavailable from paper and thin layer chromatographic studies, on the relative concentrations of adsorbate components. PVP-adsorbate profiles contained the same phenols as were observed in the Nylon profiles.     

Correction to: 3D APT and NOE CEST-MRI of healthy volunteers and patients with non-enhancing glioma at 3 T

Magnetic Resonance Materials in Physics, Biology and Medicine -     

Defect Activity in Lead Halide Perovskites

The presence of various types of chemical interactions in metal‐halide perovskite semiconductors gives them a characteristic “soft” fluctuating structure, prone to a wide set of defects. Understanding of the nature of defects and their photochemistry is summarized, which leverages the cooperative action of density functional theory investigations and accurate experimental design. This knowledge is used to describe how defect activity determines the macroscopic properties of the material and related devices. Finally, a discussion of the open questions provides a path towards achieving an educated prediction of device operation, necessary to engineer reliable devices.     

Who finds value in news comment communities? An analysis of the influence of individual user,perceived news site quality,and site type factors

User commenting forums are a ubiquitous interactive feature offered by news organizations. Despite their popularity, research has generally failed to investigate extent to which news readers themselves find any redeeming value in news comment communities and, therein, the factors that serve as antecedents to such value perceptions. In light of this gap in the literature, this study set out to determine the factors associated with news community value. Using a sample of over 500 news consumers, we explored the impact of individual user, site quality, and site type factors. The results suggested that perceived news community value was highest among those with high levels of self-efficacy and those who use the Internet for civic purposes. The data indicated also that value perceptions were highest for those news sites that were understood to be interactive and aesthetically pleasing. Finally, perceived news community value was highest on sites that were both non-traditional and non-partisan in nature.     

Sources of variation in multi-centre brain MTR histogram studies: body-coil transmission eliminates inter-centre differences

Object: 1. Identify sources of variation affecting Magnetisation Transfer Ratio (MTR) histogram reproducibility between-centres. 2. Demonstrate complete elimination of inter-centre difference. Materials and methods: Six principle sources of variation were summarised and analysed. These are:the imager coil used for radiofrequency (RF) transmission, imager stability, the shape and other parameters describing the Magnetisation Transfer (MT) pulse, the MT sequence used (including its parameters), the image segmentation methodology, and the histogram generation technique. Transmit field nonuniformity and B1 errors are often the largest factors. PLUMB (Peak Location Uniformity in MTR histograms of the Brain) plots are a convenient way of visualising differences. Five multi-centres studies were undertaken to investigate and minimise differences. Results: Transmission using a body coil, with a close-fitting array of surface coils for reception, gave the best uniformity. Differences between two centres, having MR imagers from different manufacturers, were completely eliminated by using body coil excitation, making a small adjustment to the MT pulse flip angle, and carrying out segmentation at a single centre. Histograms and their peak location and height values were indistinguishable. Conclusions: Body coil excitation is preferred for multi-centre studies. Analysis (segmentation and histogram generation) should ideally be carried out at a single site.     

Monte carlo study of mobility in Si devices with -based oxides

HfO₂-based high-κ dielectrics are among the most likely candidates to replace SiO₂ and the currently favoured oxinitride in the next generation of MOSFETs. High-κ materials allow the use of a thicker gate dielectric, maintaining the gate capacitance with reduced gate leakage. However, they lead to a fundamental mobility degradation due to the coupling of carriers to surface soft (low-energy) optical phonons. Comparing the vertical field dependence of the mobility for HfO₂ and SiO₂, the severe degradation in mobility in the presence of high-κ becomes evident. The introduction of a SiO₂ interfacial layer between the channel and the HfO₂ mitigates this degradation, by increasing the effective distance between the carriers and the SO phonons, thus decreasing the interaction strength, this does though lead to an increase in the equivalent oxide thickness (EOT) of the gate dielectric. The material of choice for the first commercial introduction of high-κ gate stacks is Hafnium Silicate (Si_xHf_1-xO₂). This alloy stands up better to the processing challenges and as a result suffers less from dielectric fluctuations. We show that as the fraction of Hf increases within the alloy, the inversion layer mobility is shown to decrease due to the corresponding decrease in the energy of the surface optical phonons and increase in the dielectric constant of the oxide.