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Anchor bolts play a crucial role in supporting the power cables of the overhead catenary system (OCS) in underground train tunnels. With exposure to humid conditions and water seepage in the tunnel from wet weathers, the anchor bolts can experience corrosion and damage at an accelerated rate. As anchor bolts are embedded into the concrete tunnel, and their conditions are unknown without proper inspection of their internal bodies. This paper aims to propose an inspection process to allow technicians to perform ultrasonic testing (UT) on anchor bolts during scheduled maintenance works in the tunnel. Experimental studies using ultrasonic waves were carried out on the anchor bolts of different integrity conditions. Analytical studies conducted were then used to determine the tolerance level and decision matrix to categorize the different conditions of anchor bolts. The outcome of this study shows that there is a feasible approach to perform UT inspections on the anchor bolts.

A thermal conduction measurement device was fabricated, consisting of a silicon dioxide membrane with integrated thermal sensors (Pt resistance heater/thermometer and Pt–Au thermocouples) using MEMS technology. Heat transfer between the heated device and a number of unused atomic force microscope and scanning thermal microscope probes was measured. Changes in thermal conduction related to changes in the tip shape resulting from initial contact were observed. The sensors were fabricated by electron beam lithography and lift-off followed by local subtractive processing of a Pt–Au multilayer to form Pt heater–resistance thermometer elements and Pt–Au thermocouples. Thermal isolation from the silicon substrate was provided by dry release of the supporting 50 nm thick SiO2 membrane using an isotropic SF6 inductively coupled plasma etch. The high thermal isolation of the sample combined with the sensitivity of the temperature sensors used allowed the detection of thermal conduction between the tip and the sample with high precision. The measured temperature range of the Pt resistor was 293–643 K. The measured thermal resistance of the membrane was 3 × 105 K/W in air and 1.44 × 106 K/W in vacuum. The tip contact resistance was measured with a noise level of 0.3g0 T at room temperature, where g0 is the thermal resistance quantum.

International audience; We propose an approach for the characterization of scanning thermal microscopy (SThM) probe response using a sample with silicon dioxide steps. The chessboard-like sample provides a series of nine surfaces made of the same material, with identical roughness, but consisting of different thicknesses of silica layers standing on a single silicon wafer. The nine regions have different effective thermal conductivities, allowing calibration of SThM probes within a given set of surface conditions. A key benefit is the possibility of comparing the spatial resolution and the sensitivity to vertical inhomogeneities of the sample for different probes. A model is provided to determine the thermal contact area and contact thermal resistance from the experimental data. The results underline that ballistic heat conduction can be significant in crystalline substrates below the top thin films, especially for film thicknesses lower than 200 nm and effective thermal contact radius lower than 200 nm. They also highlight the sensitivity of SThM to ultrathin films, as well as the substrate below micrometric films under in-air conditions but not when in vacuum. This work advances quantitative nanometer-scale thermal metrology, where usual photothermal methods are more difficult to implement.

This paper presents a review of a standalone and grid-connected hybrid renewable energy system (HRES) to supply AC loads. The configuration of the HRESs and interfacing power converters for connecting the energy sources to the AC bus is extensively discussed. An overview of the control concepts in an HRES and the application of the appropriate control schemes for system stabilization, effective injection of high quality power and proper load sharing are discussed. The different approaches for HRES design and control strategies for power converters in the recently published literature are also briefly addressed. Finally, this paper highlights the future developments in HRESs to increase the utilization of power generated from renewable energy sources (RESs).

We report the response of sub-micron epitaxial graphene Hall devices to localized and inhomogeneous magnetic field produced by an MFM tip. We analyze the magneto-transport properties of epitaxial graphene and report the independent contribution of magnetic and electric fields in the measured transverse voltage maps with respect to the lateral and vertical position of the tip. A finite element model has also been developed to support the experimental results.

High cost of renewable energy systems has led to its slow adoption in many countries. Hence, it is vital to select an appropriate size of the system in order to reduce the cost and excess energy produced as well as to maximize the available resources. The sizing of hybrid system must satisfy the LPSP (Loss of Power Supply Probability) which determines the ability of the system to meet the load requirements. Once the lowest configurations are determined, the cost of the system must then be taken into consideration to determine the system with the lowest cost. The optimization methodology proposed in this paper uses the ANFIS (Adaptive Neuro-Fuzzy Inference System) to model the PV and wind sources. The algorithm developed is compared to HOMER (Hybrid Optimization Model for Electric Renewables) and HOGA (Hybrid Optimization by Genetic Algorithms) software and the results demonstrate an accuracy of 96% for PV and wind. The optimized system is simulated in PSCAD/EMTDC and the results show that low excess energy is achieved. The optimized system is also able to supply power to the load without any renewable sources for a longer period, while conforming to the desired LPSP.

Environmental concern over the use of conventional sources has reached an alarming stage, thus alternatives sources is imminent. Renewable sources such as wind and solar has gain popularity and demand over the last decade. These sources suffer from certain deficiencies when used alone. Power produced from these sources depends very much on the weather condition. Thus, combination of these sources had shown excellent potential as complementary option to generate power. This paper investigates the performance of micro scale solar-wind-battery scheme for a residential load in Malaysia. Real wind speed, solar radiation and temperature have been obtained from the Malaysian Meteorological Department and will be used as the parameters for this study. The outcome presented in this paper show potential and viability in using hybrid system to sustain residential load in Malaysia.

As renewable technologies are technologically matured, hybrid renewable energy system is promising to replace conventional fossil fuel distributed power generation. This paper proposes a photovoltaic/wind based hybrid power system connected to a common bus with battery storage and conventional backup source to supply a telecommunication load. The proposed hybrid power system model is modeled in PSCAD/EMTDC platform. Several operating modes have been developed based on the Malaysian climate condition for the overall power management strategies to enhance the hybrid power system efficiency. Response of the hybrid system towards a practical load profile and weather data is analyzed and discussed. The paper shows the hybrid system with the proposed modes of operation is able to supply power continuously to the load.

We have performed sensitivity mapping of graphene Hall devices with the width of 0.6–15 μm operating in the diffusive regime under non-uniform, local magnetic and electric fields induced by a scanning metallic magnetic probe. The transverse voltage was recorded, while tuning the magnitude and orientation of the bias current, the probe-sample distance, and orientation of the probe magnetization. A strong two-fold symmetry pattern has been observed, as a consequence of capacitive coupling between the probe and the sample. The effect is particularly pronounced in small devices (

The present paper investigates the influence of localized magnetic and electric fields, produced by a magnetic scanning tip, on the response of high-mobility two-dimensional electron gas in a Hall bar geometry. We have developed a comprehensive numerical model, validated it by experiment and found the optimal design for magnetic sensing and limitation of perturbing effects due to electric field. This approach can be straightforwardly extended to the design of sensors for the detection of charged magnetic nanoparticles.