The capability of ultrafiltrated alkaline and organosolv oil palm (Elaeis guineensis) fronds lignin as green corrosion inhibitor for mild steel in 0.5 M HCl solution

The inhibitive effect of ultrafiltrated oil palm fronds (OPF) lignins on the corrosion of mild steel in 0.5 M HCl solution has been investigated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP) and weight loss measurement. The presence of smaller lignin fractions reduces remarkably the corrosion rate of mild steel. The highest corrosion inhibition efficiency for all ultrafiltrated lignins were attained at maximum concentration of 500 ppm (IE_P.Soda: 87% > IE_P.Organosolv: 83% > IE_P.Kraft: 81%). The results from this corrosion test clearly reveal that all ultrafiltrated lignins behaved as a mixed-type inhibitor with predominant anodic (organosolv lignin) or cathodic (alkaline lignin) effectiveness. It was deduced that the inhibition process was spontaneous and the inhibitors were mainly physically adsorbed onto the mild steel surface.     

Mechanical impedance-based technique for steel structural corrosion damage detection

The electromechanical impedance (EMI) technique has gained acceptance for structural health monitoring, due to its merits of model-free, high frequency detection and fast response features. This paper presents an innovative mechanical impedance-based technique to monitor the development of corrosion damage on steel structure, which is different from the traditional admittance (inverse of impedance)-based EMI technique. Firstly, structural mechanical impedance (SMI) which directly manifests the structural properties is theoretically deprived. Secondly, by measuring the raw admittance signature, the sensitivity of SMI is investigated in the experiment of steel structural corrosion damage conducted within 117 days. Finally, the corrosion damage quantification is also discussed by calculating the root mean square deviation (RMSD) index. The results indicate that structural mechanical impedance is sensitive to corrosion damage but the detecting range is limited. The real part of SMI can be adopted for an effective indicator of steel structural corrosion damage. The proposed technique is found to be effective in steel structural corrosion damage detection.     

Electrochemical Impedance Spectroscopy: Insights for fretting corrosion experiments

Using Electrochemical Impedance Spectroscopy (EIS), in the tribocorrosion field, especially in fretting corrosion, is new. The key point of this work is using EIS. The influence of ionic strength (I_c) and a model protein, albumin, on passive layer behavior was studied. At cathodic applied potential, E=−400 mV(SCE), fretting leads to an increase of corrosion current, without albumin. The current drop increases with the ionic strength. With albumin of 20 g L⁻¹, I is constant whatever the ionic strength: albumin acts as a corrosion inhibitor. Thanks to EIS, the degradation of passive layer due to fretting-corrosion is assessed by the fall of Polarization Resistance (R_p) and exponent of constant phase element (n), and the rise of constant phase element (Q).     

Continuous accurate pH measurements of human GI tract using a digital pH-ISFET sensor inside a wireless capsule

This paper describes the design and implementation of a reliable, low-power pH-ISFET sensor inside a wireless diagnostic capsule for monitoring the pH of the human gastrointestinal (GI) tract. The sensitive element of the pH sensing device was an ion-sensitive FET (ISFET) with a threshold voltage that varies by concentration of hydrogen ions. An Ag/AgCl reference electrode that was surrounded by gel (mixed KCl) was applied in this pH-sensing device. An application-specific integrated circuit (ASIC) that is designed by a very large scale integration (VLSI) architecture was used as the interface between the pH sensing device and a wireless transceiver. Experimental results demonstrated that the pH sensitivity and operating range of the pH sensing device was 44.94 mV/pH and 1–11 pH; the device is linear. With the 18-bit Analog/Digital converter (ADC) module in the ASIC, the resolution could achieve 11,780 bits/pH. Moreover, the power dissipation of the pH-sensing device was only 0.048 mW while working in intermittent mode (duty cycle = 20%). Results from human experiments showed that this pH sensing device can work reliably for 136 h, and the pH data of sampled from the human GI tract can be received by a portable data recorder outside the human body in real time.     

The pore water pressure sensor based on Sagnac interferometer with polarization-maintaining photonic crystal fiber for the geotechnical engineering

The pore water pressure sensors with the six-hole suspended-core polarization-maintaining photonic crystal fiber (SC-PM-PCF) and commercial polarization-maintaining photonic crystal fiber (PM-PCF) are designed based Sagnac interferometer and calibrated in the laboratory. According to the theoretical analysis and calibration results, the transmission spectrum is very sensitive to the pore water pressure. It is found that the wavelength of the spectrum has a good linear relationship with variances of the surrounding pore water pressure, and the coefficient of wavelength–pressure of the commercial PM-PCF is 304.41 kPa/nm with the length of 35 cm as the sensing element while the coefficient of the SC-PM-PCF is 254.75 kPa/nm with the length of 100 cm. Finally, the two PM-PCF sensors are applied and compared with the conventional Pore water Pressure Transducers (PPTs) in a physical model test. It is found that measurements of the PM-PCF sensors are in good agreement with the results measured by the conventional PPTs.     

High-precision and high-speed positioning of 100 G linear synchronous motor

The present paper describes a moving permanent magnet linear synchronous motor (MPM LSM) that can move with an acceleration above 100 G (=980 m/s²), and is also capable of high-precision and high-speed positioning. The MPM LSM consists of a mover including permanent magnets and a double-sided electromagnet stator. It can produce a thrust of 4.56 × 10³ N and has a working range wider than 1 m. The MPM LSM mover is improved for light weight and is driven using a suitable phase lead for flux weakening. The combination of the improved mover and the suitable phase lead provides motion at an acceleration above 100 G and a velocity above 12 m/s. The positioning characteristics of the improved MPM LSM are examined using a controller with two suitable phase lead functions. The control system shows a positioning accuracy and a positioning resolution of 500 nm, which is similar to the vibration amplitude of the sensor output in open loop. In 300-mm step positioning, the improved MPM LSM shows an acceleration above 660 m/s² and a velocity above 8.3 m/s. It takes less than 101 ms to reduce the positioning error to less than 5 μm. The temperature rise during positioning is also examined experimentally. Continuous positioning for longer than 30 minutes increases the temperature of the MPM LSM, but by less than 6 °C.     

Feasibility assessment of magnetic resonance-thermometry on pancreas undergoing laser ablation: Sensitivity analysis of three sequences

Laser ablation (LA) is a minimally invasive technique for the treatment of tumors as an alternative to surgical resection. The light absorbed by tissue is converted into heat, and causes irreversible cell damage when temperatures higher than 60 °C are reached. The knowledge in real time of temperature may be particularly beneficial for adjusting laser settings applied during treatment and to be notified in real time about its end-point. As a consequence, several techniques for temperature monitoring within the tissue have been investigated along the last decades. In the field of LA, particularly attractive are non-invasive methods. Among these techniques, thermometry based on the analysis of Magnetic Resonance Imaging (MR-thermometry) has gaining large acceptance in this field. MR-thermometry allows estimating the temperature variation thanks to the thermal dependence of several MRI parameters, among others the most promising are T₁ relaxation time, and proton resonance frequency shift.The aim of this study is to assess the sensitivity of MRI thermometry using three T₁-weighted sequences (i.e., Inversion Recovery Turbo-FLASH, IRTF, Saturation Recovery Turbo-FLASH, SRTF, and FLASH) using an 1.5-T MR scanner on healthy swine pancreases undergoing LA. The reference temperature was measured by MRI-compatible fiber optic sensors (fiber Bragg grating sensors). The sensitivity of the proposed techniques was estimated and compared. The thermal sensitivity of the three sequences was −1.47 ± 0.08 °C⁻¹, −0.95 ± 0.05 °C⁻¹, and −0.56 ± 0.04 °C⁻¹ for IRTF, SRTF and FLASH, respectively. Results show that the proposed technique may be adequate for temperature monitoring during LA.     

Silver nanoparticles/polymethacrylic acid (AgNPs/PMA) hybrid nanocomposites-modified electrodes for the electrochemical detection of nitrate ions

AgNPs/PMA hybrid nanocomposite materials with different Ag loadings have been synthesized using a simple chemical route assisted by UV irradiation. The hybrid composites were characterized by means of SEM and TEM, UV–vis spectroscopy and XPS. The as synthesized hybrid samples, composed of small Ag nanoparticles (AgNPs) embedded within the PMA (poly-methacrylic-acid) matrix, have been used to modify the working electrode of disposable screen printed carbon electrodes (SPCEs). It has been observed that hybrid composite with the lowest Ag loading forms dendritic silver structures on the surface of working electrode, whereas at higher loadings massive structures were formed. The electrocatalytic properties of the AgNPs/PMA/SPCEs were investigated toward the reduction of nitrate at neutral pH. Based on these modified electrodes, both voltammetric and amperometric sensors were developed for the electrochemical sensing of nitrate. Voltammetric sensor showed a wide linear range (0–20 mM) and high sensitivity (130 μA mM⁻¹ cm⁻²).     

Realization of coaxial reference air-lines as high frequency capacitance standard at CSIR-NPL

The reported work has been carried out in the direction of establishment of metrological traceability of capacitance up to 200 MHz at CSIR-NPL. In this perspective, the set of seven coaxial reference air-lines (Type 900-LZ series) exhibiting capacitance values varying from 2 pF to 20 pF have been realized as a capacitance standard at high frequency (1 MHz–200 MHz). This is principally achieved with reference to the SI base units of the meter and the second. The standard value of capacitance of each of the reference air-line has been computed up to 1000 MHz by employing transmission line theory. The reference capacitance value of each of these air-lines has also been measured at 1 kHz which thereafter extrapolated up to 1000 MHz using resonance technique. RF impedance analyzer has been calibrated up to 200 MHz for capacitance using computed capacitance of reference air-lines as standard. The reported work will be helpful in establishing the calibration services for low value of capacitance standards in a frequency range from 1 MHz to 200 MHz at CSIR-NPL. The work will also bridge the gap between LF and RF impedance metrology.     

Large stroke and high precision positioning using iron–gallium alloy (Galfenol) based multi-DOF impact drive mechanism

A miniature-positioning device with a large stroke motion has attracted more and more attentions in these years because of the intensive development in precision engineering. In this paper, we have achieved the large stroke actuating and the high precision positioning, as well as realized a multi-degree-of-freedom in-plane motion using the developed Galfenol impact drive mechanism (IDM) actuator. In order to enhance the system robustness, two pieces of U-shape Galfenol (iron–gallium alloy) have been employed as the driving elements with a bias magnetic field contributed by a permanent magnet to generate the swing motion that amplifies the propelling inertia force. The current amplitude modulation has been applied in the precision positioning of the actuator under the quasi-static condition because of the motion step-size fineness. The results show that the actuator is able to achieve a sub-micrometer positioning accuracy that has reached the measurement limit of our setup. Meanwhile, the frequency modulation method has been explored in the large stroke actuation with a high motion speed. We have found out that this design is capable of achieving an accurate positioning without the frequency modulation because of the intrinsic fine step-size of the actuator. In addition, a rectangular in-plane motion has been realized with the image-based control for the multi-degree-of-freedom positioning. The actuator has an inductive impedance with a resistance of 3.796 Ω and an inductance of 0.4697 mH. Under the present driving ratings, the power consumption is smaller than 1.97 W while the reactive power can be ignored. Moreover, the experimental load analysis indicates that the design can achieve a maximum carry-load-to-weight ratio of 6.5.     

Precision design and control of a flexure-based roll-to-roll printing system

This paper presents the design, characterization, and control of a flexure-based roll-to-roll (R2R) printing system that achieves nanometer level precision and repeatability. The R2R system includes an unwinding/rewinding module, a web guide mechanism, and a core positioning stage consisting of two monolithic compliant X–Y stages that control the position/force of the print roller. During the printing process, capacitance probes, eddy current sensors and load cells are used to monitor the displacements of the flexure stage and contact force in real time. Control strategies, including decoupling, PID, and cascade control, have been implemented to decouple the cross-axis and cross-stage motion coupling effect and improve the overall precision and dynamic performance. In actual printing processes, the contact force and roller position can be uniformly controlled within ±0.05 N and ±200 nm respectively across a 4 in. wide PET web. To demonstrate the performance, a positive microcontact printing (MCP) process is adapted to the R2R system, printing various fine metal patterns, e.g., optical gratings and electrodes, in a continuous fashion.     

Design,calibration and tests of versatile low frequency impedance analyser based on ARM microcontroller

Numerous simple impedance analysers based on the microcontroller (μC) and dedicated impedance converter integrated circuits (IC) were reported recently. In many applications sophisticated analogue circuitry has to be appended to enhance the measurement possibilities or to circumvent the limitations. In this paper the impedance analyser IMP-STM32 based solely on the μC and general purpose operational and instrumentation amplifiers is presented. It uses the internal DAC and ADCs in the μC to generate the excitation and to measure the response of the measured object. It also uses the external analogue circuits to condition the excitation signal and measure voltage and current. The magnitudes and phase shifts of voltage and current are evaluated using the three parameter sine fitting algorithm allowing for fast low-frequency impedance measurements. The calibration procedure of completed device is presented as well as the tests of its accuracy. The device allowed for measurements at frequency range between 1 mHz and 100 kHz in 1 Ω to 1 GΩ impedance range with 1% accuracy. IMP-STM32 was also compared to the Agilent 4294A precision impedance analyser. In the middle of the impedance ranges (1 Ω to 300 kΩ) the discrepancies between the two were less than 0.2%.     

Triboelectrochemical behaviour of a Si3N4–TiN ceramic composite and a titanium alloy commonly used in biomedical applications

In this paper the corrosion and tribocorrosion behaviour of a traditional metallic biomaterial (Ti6Al4V) and a Si₃N₄/TiN (SN/TiN) ceramic composite are studied and compared during exposures to 1% NaCl and 1% NaCl + 1% lactic acid solutions.Electrochemical impedance spectroscopy (EIS) data collected on Ti6Al4V in both neutral and acidic solution have been interpreted on the basis of a double layer surface oxide film, which is completely removed from the wear track during the sliding tests. Under these conditions, the impedance of the depassivated region dominates the overall electrode impedance.Previous EIS tests performed on SN/TiN evidence that even this material exposed to neutral solution is covered by a double layer film, while a porous monolayer film forms in acid solution. Under pure corrosion conditions, SN/TiN exhibits corrosion rates which are quite comparable to those measured on Ti6Al4V. During tribocorrosion tests the EIS response of the ceramic material does not change much. Its corrosion rates are two orders of magnitude lower than those measured on Ti6Al4V.Profilometer analysis shows that on both materials most of overall tribocorrosion damage is due to mechanical wear.The tests suggest that SN/TiN is a promising biomaterials for applications where sliding conditions occur.     

Impedance plethysmography as a tool for assessing exertion-related blood flow changes in the lower limbs in healthy subjects

Impedance plethysmography, also known as the impedance test, the blood flow test, or impedance phlebography, is a non-invasive test that measures blood flow in the vessels of the peripheral vascular system by monitoring changes in electrical resistance (impedance) to detect deep thrombosis (blood clots or thrombophlebitis).The aim of our study was to use this technique for assessing changes in blood flow in the lower limbs in healthy subjects wearing protective footwear while walking.The test was performed on a group of 30 professional firefighters (age 30.7 ± 4.5, BMI 25.1 ± 3). Blood flow was monitored in the peripheral vascular system of the lower limbs during walking on a treadmill. The testing protocol consisted of the following three phases: warm-up, exercise, and rest.In order to identify differences between the three phases of the study, analysis of variance (ANOVA) with repeated measures was conducted. The statistically significant parameters of blood flow in the lower limbs were the impedance ratio (IR) (p < 0.001), slope ratio (SR) (p < 0.001), crest width (CW) (p < 0.001), and alternative blood flow (ABF) (p < 0.001). All of them showed an upward trend.The study confirmed the validity of impedance plethysmography as a non-invasive technique for measuring blood flow changes in the lower limbs in healthy subjects, especially under non-steady-state conditions, such as walking. This technique provides valuable quantitative data.Therefore, impedance plethysmography may be considered a reliable research method enabling evaluation of local blood flow in healthy subjects under different conditions.     

Investigation of GPS positioning accuracy during the seasonal variation

The aim of this study is to investigate the accuracy of GPS (Global Positioning System) positioning determined by GPS measurements carried out during the seasonal variations. The observations have been analyzed to determine how the accuracy of derived relative positions of GPS stations depends on the baseline length, the duration of observing session and the seasonal variations.For this purpose, we selected three days of each month in 2009 from the GPS observations made in the Marmara Continuous GPS Network (MAGNET). The GPS observations were processed in the ITRF 2005 reference frame using the Bernese 5.0 GPS software. The baseline length varies between 6 km and 237 km, session duration varies between 4 h and 24 h. Seasonal variation effects on the accuracy of coordinate components were analyzed. Our results showed that seasonal variation is a significant factor for determining the accuracy of GPS measurements. Also, increasing the observation period hardly improves the horizontal positioning accuracy while improving the vertical positioning accuracy.     

Effect of heat treatment on the structure,cavitation erosion and erosion–corrosion behavior of Fe-based amorphous coatings

In this study, high-velocity oxygen-fuel sprayed amorphous coatings have been heat treated at various temperatures to form microstructures with crystalline phases. The structure, micro-hardness, cavitation erosion resistance and erosion–corrosion resistance of these coatings are compared. Crystalline phases are discovered in the coatings after heat treatments at 650 °C and 750 °C. The coating heat treated at 750 °C exhibits the poorest cavitation erosion resistance in 3.5 wt% NaCl solution among all coatings due to the degraded corrosion resistance. However, the hardness of the crystallized coating can reach 1000 Hv and the erosion–corrosion resistance of the heat treated coating is better than the untreated one.     

Miniaturized liquid film sensor (MLFS) for two phase flow measurements in square microchannels with high spatial resolution

Two miniaturized liquid film sensors (MLFS) based on electrical conductance measurement have been developed and tested. The sensors are non-intrusive and produced with materials and technologies fully compatible and integrable with standard microfluidics. They consist of a line of 20 electrodes with a purpose-designed shape, flush against the wall, covering a total length of 5.00 and 6.68 mm. The governing electronics achieve 10 kHz of time resolution. The electrode spacing of the two sensors is 230 μm and 330 μm, which allows measurements of liquid films up to 150 μm and 400 μm for sensors MLFS_A and MLFS_B, respectively. The sensor characteristics were obtained by imposing static liquid films of known thickness on top of the actual sensor. Further dynamic measurements of concurrent air-water flow in a horizontal microchannel were performed. The line of electrodes is placed across the flow direction with an angle of 3.53° from the direction of flow, allowing for a spatial resolution perpendicular to the flow of 14.2 μm for sensor MLFS_A and 20.5 μm for sensor MLFS_B. The high time and spatial resolution allows for fast and accurate detection of the presence of bubbles, and even measurement of film thickness and bubble velocity. Further information, such as the bubble shape, can be gathered based on the shape of the liquid layer underneath the bubble, which is particularly important for heat transfer studies in microchannels.     

Corrosion measurement of Sn–Zn lead-free solders in 6 M KOH solution

The corrosion measurements of Sn–Zn alloys with varying Zn contents from 0 wt.% to 12 wt.% were investigated in a 6 M KOH solution. The corrosion parameters of this series of materials, which include open circuit potential, galvanic corrosion current, corrosion potential, and corrosion current, were studied. The Sn–Zn alloys initially revealed an activity similar with that of pure Zn in this 6 M KOH solution. The alloy activity became more inert when the corrosion analysis was prolonged. In addition, phase and morphological analyses results confirmed the formation of mixed corrosion products on the surface after polarisation.     

Failure of gas turbine blades

The first-stage blades of a gas turbine had suffered a severe deterioration after around 10 500 h service. The expected service life was 40 000 h. Failure analysis (visual observations, studies by optical microscopy, scanning electron microscopy (SEM), SEM back-scattered electron (SEM-BSE), EDX, X-ray diffraction (XRD) and dimensional metrology) has been carried out. Blades, manufactured in the nickel superalloy CMSX-4, lost the protective coatings from their tips due to wear. Unprotected surfaces suffered high-temperature hot corrosion (Type-I corrosion). It is concluded that failure was mainly caused by an uneven clearance (out-of-line) between rotor and lining.     

Online monitoring of wire breaks in prestressed concrete cylinder pipe utilising fibre Bragg grating sensors

With steel prestressing wires tensioned around core, Prestressed Concrete Cylinder Pipe (PCCP) is a high-strength composite pipe designed for large-diameter water propagation and distribution. However, some PCCPs may fail after a certain time of service due to corrosion and deterioration. Real-time health monitoring of wire breaks is essential to assess the condition and avoid catastrophic failures of PCCPs. In this paper, a novel approach based on Fibre Bragg Grating (FBG) sensing technology, is presented to monitor and locate wire breaks in PCCP lines. FBG vibration sensors are utilised to capture the signals of wire break activities in the pipeline and obtain their locations. The online monitoring system and localization principle of wire break activities are described. Preliminary experiments were carried out on PCCPs with an inner diameter of 2 m, which were filled with pressurized water. Experimental results indicate that the wire break activity can be detected and located effectively by FBG sensors. The detection error of wire break locations is analysed. With unique features, the proposed non-destructive method is expected to be used for the online monitoring of wire break activities in long term for the condition assessment and performance prediction of PCCP lines.