Quantum Hall Effect across Graphene Grain Boundary

Charge carrier scattering at grain boundaries (GBs) in a chemical vapor deposition (CVD) graphene reduces the carrier mobility and degrades the performance of the graphene device, which is expected to affect the quantum Hall effect (QHE). This study investigated the influence of individual GBs on the QH state at different stitching angles of the GB in a monolayer CVD graphene. The measured voltage probes of the equipotential line in the QH state showed that the longitudinal resistance (Rxx) was affected by the scattering of the GB only in the low carrier concentration region, and the standard QHE of a monolayer graphene was observed regardless of the stitching angle of the GB. In addition, a controlled device with an added metal bar placed in the middle of the Hall bar configuration was introduced. Despite the fact that the equipotential lines in the controlled device were broken by the additional metal bar, only the Rxx was affected by nonzero resistance, whereas the Hall resistance (Rxy) revealed the well-quantized plateaus in the QH state. Thus, our study clarifies the effect of individual GBs on the QH states of graphenes.

Determining the impact of sensor orientation on moisture content measurements in eastern white pine

As buildings become more airtight and insulated, the movement and accumulation of moisture within building envelopes become paramount in determining its resiliency. Current methods for quantifying the moisture content (MC) of wood species involve the measurement of electrical resistance between two installed electrodes and the use of existing empirical correlations to evaluate the MC. However, these correlations do not adequately consider the impact of sensor orientation within wall assemblies. The objective of this paper is to determine the impact of MC readings within a wood sample due to sensor orientation. A total of 126 eastern white pine samples were tested with electrodes placed along the grain of the wood (longitudinal), across the grain of the wood (tangential), and in a diamond pattern, using six different fasteners as electrodes. The samples were placed in a controlled environmental chamber until steady state was achieved at approximately 18% MC. Electrical resistances of the samples were measured in both directions at temperatures ranging from -10°C to 40°C. It was found that the tangential-to-longitudinal resistance ratio is 1.1-1.35 depending on the electrode type.

Integrated Geophysical and Hydrogeochemical Characterization and Assessment of Groundwater Studies in Adum West Area of Benue State,Nigeria

Integration of geophysical and hydrogeochemical methods has been scientifically proven to be useful in vulnerability study and groundwater characterization. Subsurface geoelectric parameters such as resistivity and thickness obtained from geophysical method (Vertical Electrical Sounding VES) was used to determine aquifers vulnerability, longitudinal resistance (ρL) and transverse unit resistance (Rt). Thirty four water samples were collected from groundwater sources for physicochemical analysis.Estimated results from longitudinal conductance (S), (Rt) and (ρL) showed that the values ranges from 0.03 to 2.5mhos, 103.64 to 1964417.8 Ω/m2 and 215.41 to 65731.68 Ω-m respectively. Result from S suggested that 50 % of groundwater is considered to be vulnerable to contamination from the earth surface, while the remaining 50 % is considered to be slightly vulnerable to surface contamination. Further findings obtained from hydrogeochemical analysis such as Gibb’s and Chadba plots revealed that groundwater is highly influenced by rock water interaction,groundwater is classified to be Na+ + HCO3¯, Ca2+ + Mg2++ HCO3¯ , Na+ + Cl¯ and Ca2+ + Mg2+ + Cl¯ water type. Deduction from Soltan classification suggested that groundwater is classified to be of Na+ ˗ HCO3¯ and Na+ ˗ SO4 2¯ water type. Results obtained from Ec and pH suggested that the values were below WHO permissible limit, while result obtained from TDS showed that at some sampling points TDS values were above WHO limit. Based on pH value obtained groundwater within the study area fell within slightly basic to acidic.

Research on the longitudinal mechanical behaviours of subway turnouts of large slope under train braking force

To study subway turnouts’ adaptability to steep gradients, a finite element model of a metro No. 9 simple turnout was established. The main works include: (1) The train’s most unfavourable loading condition was modelled. (2) The turnout’s longitudinal displacement and stress were analysed with different gradients under the train braking load, temperature change load and a combination of the two, to determine the structure’s safety and stability under the most unfavourable working conditions. (3) The turnout structure’s cumulative longitudinal deformation under reciprocating load was studied. Both a fastener longitudinal resistance-displacement experiment under reciprocating load and a numerical simulation of No. 9 turnout modelled by the finite element modelling software, ANSYS, were carried out to study the gradient’s influence on the turnout’s longitudinal mechanical characteristics. (1) The turnout’s longitudinal displacement and stress increase linearly with an increase in gradient and temperature change, both of which are unfavourable to the turnout structure. As the gradient increases from 0‰ to 30‰, the longitudinal stress and displacement increase by more than 10%. (2) The turnout’s rail strength and displacement on a 30‰ slope under the most unfavourable load conditions are within the specification limitations. (3) Under reciprocating load, the fastener longitudinal stiffness decreases and the maximum and residual longitudinal displacement of the switch rail increase; an increased gradient intensifies these effects on the turnout.

Indoor simulation test research on cumulative longitudinal displacement of rail based on force and displacement sensors data collection

The train sometimes needs to brake frequently on the turnout, although the braking force does not exceed the limit resistance of fastener, cumulative displacement of rail occurs because of the long-term effect of the train brakes, thus, the relationship between the cumulative displacement of rail and the number of train braking actions should be explored. Aiming at the spring bar type III fastener, a 1:1 physical indoor simulation test was carried out, and an electromagnetic relay device was used to simulate the train load, force, and displacement sensors for data collection. Then a single load no more than the maximum resistance of fastener was applied to the rail end to explore the relationship between the number of loads and the rail cumulative deformation. The rail longitudinal cumulative displacement changes linearly in positive correlation with the number of load actions, and increases faster when the number of load actions is small. As the number of repeated loads increases, the above-mentioned relationship approximately and credibly obeys the power function distribution. Repeatedly applying load no more than the maximum longitudinal resistance of fastener to the rail, the existence of the rail cumulative displacement caused by frequent train braking can be demonstrated, and the relationship curve between the rail displacement and the number of loads can be obtained. Applying the fitting formula, the rail displacement after a specific number of loading times can be attained, and then referring to specific codes, we can determine whether it will exceed the safety limit.

Novel Analytical Model of Stress Concentration around Broken Fibers of Unidirectional Composite Plate

During the fiber fracture of unidirectional composite a distribution of stress around the neighbored fibers happens, this mechanism is called the local redistribution efforts. Referring to the "shear lag" method, the researches wanted to predict the stress concentration in the surrounding area of broken fibers as well as the longitudinal resistance of the unidirectional composite which presents a fiber breaking. The goal of this paper is to develop a new probabilistic model of unidirectional composite plate to calculate the stress concentration at the broken fibers and their neighboring fiber intact. The "shear lag" method has been generalized to see the broken fibers interference on the stress concentration factor variation of surrounding sound fibers.

Longitudinal sliding resistance characteristics of the WJ-8 conventional resistance fastner

In this paper, the longitudinal resistance and displacement of the WJ-8 conventional resistance fastener under vertical and torque loadings were experimentally conducted and the relationship between longitudinal resistance and displacement was established. To validate the experimental results, numerical simulation using a finite-element model of the fastener was established to obtain the longitudinal resistance variation of the conventional-resistance. Results of the analysis show that both results of the experiment and simulation are in agreements. Furthermore, the skid resistance frictional coefficient of the fastener system under the vertical load was studied and its variation rule under both vertical and torque loads was obtained. The longitudinal sliding resistance of fasteners under different torques and/or vertical loads followed a linear trend. Under load and no-load conditions, the skid-resistance frictional coefficient of the fastener system varied significantly.

Электроосаждение металлов на p-Si из водных электролитов

The features of electrochemical deposition of metal coatings on hole silicon are presented, and the properties of the obtained metal layers are measured. The dependence of the thickness of the depleted region and the internal voltage drop in it on the composition of the electrolyte and the type of precipitated metal was investigated. The effect of current density and electrolyte composition on the properties of precipitation is proved. By selection of the electrolyte pretreatment and the deposition mode, metal precipitates with acceptable adhesion and low longitudinal resistance were obtained.