Possibility Of On-line Monitoring Research Articles

DISPERSION OF LAMB WAVES IN MULTILAYER STRUCTURES

Low cost, the possibility of online monitoring and high sensitivity distinguish the method of structural monitoring using Lamb waves from other available methods. Structural analysis based on Lamb waves in heterogeneous materials requires fundamental knowledge of the behavior of Lamb waves in such materials. This basic knowledge is critical for signal processing in determining possible damage that can be detected by the propagating wave. Recently, Lamb wave methods have been used to simultaneously survey large areas of composite structures. However, such methods are more complex than traditional ultrasonic testing because Lamb waves have dispersive characteristics, namely, the wave speed varies depending on the frequency, modes and thickness of the plates. Experimentally measured group velocities of Lamb waves in composite materials with anisotropic characteristics do not coincide with theoretical group velocities, which are calculated using the dispersion equation of Lamb waves. This discrepancy arises because in anisotropic materials there is an angle between the direction of the group velocity and the direction of the phase velocity. This work investigates the propagation characteristics of Lamb waves in composites, focusing on group velocity and characteristic wave curves. For symmetric laminates, a robust method is proposed by imposing boundary conditions on the mid-plane and top surface to separate symmetric and antisymmetric wave modes. The dispersive and anisotropic behavior of Lamb waves in two different types of symmetrical laminates is theoretically studied in detail. The dispersion of Lamb waves was studied for 10 symmetric and asymmetric modes. It is shown that only fundamental modes are not characterized by a cutoff frequency, which indicates the interaction of fundamental modes with composite layers in the low-frequency range. A high level of group velocity dispersion was discovered for the SH0 and S0 modes. It is concluded that in isotropic laminates, dispersion is characteristic of symmetric modes. It is shown that the frequency dependence of the group velocity of Lamb waves of laminar composites can be represented in polynomial form.

Address Fiber Optical Sensor for Relative Humidity Measuring in a Switchgear

A number of governing documents and by-laws of the Russian Federation, branch ministries, departments and companies have introduced the use of measuring relative air humidity, elements insulation, and SF6 into operation and maintenance process of complete switchgear. A wide range of high-precision laboratory instruments has been developed to implement these measurements. However, as a rule, these are scheduled measurements to be carried out once or twice a quarter, although the constant on-line monitoring of humidity is concerned in both the production and scientific circles of the energy industry. The possibility of on-line monitoring appeared with the advent of fiber-optic object-based passive networks for collecting information and the possibility of forming interrogation channels in them, which is provided for by the development of the Smart Grid Plus concept. Fiber optic sensors, single in their physical layer structure with passive optical networks, are highly robust and resistant to high electromagnetic fields, typical of those generated in a switchgear, and are designed to operate in harsh environments. Among their broad class, fiber optic sensors on Bragg gratings, which differ from others by direct measurement methods, have significant advantages. In particular, an increase or decrease in relative humidity will lead to a corresponding change in the wavelength of the sensing source reflected from the grating, which can be measured with an accuracy of sixth place from its absolute value.This paper proposes to consider a two-element sensor of relative humidity of a parallel structure, which differs from the existing ones by using address fiber Bragg gratings made in SMF-28 fiber. One of the gratings has a polyimide-replaced quartz shell, synthesized using a reductant fiber coating, and a completely multiplicative response to temperature and deformation caused by humidity. The second grating is recorded in a standard fiber and responds only to temperature. It is possible to include an additional third grating with a partially etched cladding, which can be used for refract metric measurements of the amount of condensed moisture on the elements of a complete switchgear. All the gratings are identical, have, as a rule, the same Bragg wavelength after manipulating their claddings, but they have differing unique addresses, which are formed by recording two transparency windows in each of the gratings with different difference frequency space. The transparency windows correspond to phase p-shifts symmetrically located at the same distance from the center of each grating. The structure obtained makes it possible to record information of the measurement conversion at the said difference frequencies in the radio range, which significantly increases the speed of relative humidity measurements and their accuracy by an order of magnitude more. In addition to what has been said, it is possible to note the capability for building a network of these sensors in series arranged in switchgear devices, with a different radiofrequency address group being used in each of them.

Microfluidics Era in Chemistry Field: A Review

By miniaturizing the reactor dimension, microfluidic devices are attracting world attention and starting the microfluidic era, especially in the chemistry field because they offer great advantages such as rapid processes, small amount of the required reagents, low risk, ease and accurate control, portable and possibility of online monitoring. Because of that, microfluidic devices have been massively investigated and applied for the real application of human life. This review summarizes the up-to-date microfluidic research works including continuous-flow, droplet-based, open-system, paper-based and digital microfluidic devices. The brief fabrication technique of those microfluidic devices, as well as their potential application for particles separation, solvent extraction, nanoparticle fabrication, qualitative and quantitative analysis, environmental monitoring, drug delivery, biochemical assay and so on, are discussed. Recent perspectives of the microfluidics as a lab-on-chip or micro total analysis system device and organ-on-chip are also introduced.

An innovative laboratory characterization: hydrogen interaction with X60 pipeline steel

Corrosion is evaluated to be one of the most important cause for pipeline failures. Given the serious consequences of these events in terms of human safety, environmental preservation and cost saving, it is evident that on-field corrosion control could have a fundamental role. The aim of the present work was to meet this need with preliminary feasibility study to develop a test procedure, characterized at the same time by non-invasive approach and scientific rigor, to evaluate the possibility of on-line monitoring and assess the integrity of a pipeline during its operation. The experimental campaign was performed on a HSLA Steel X60, characterized by a ferritic microstructure with fine grains and ultimate tensile strength equal to 520MPa. The hydrogen interaction with steel was investigated by means of an advanced equipment based on an innovative high sensitivity hydrogen gas sensor. The following types of investigations were carried out [1]: - Various permeation tests were performed with reference to EN ISO 17081:2014 increasing test temperature from 10°C to 60°C. - Afterwards a series of Hydrogen Induced Cracking nucleation tests was performed with reference to ASTM STP 692:0. - Finally, permeation concept was applied in an innovative way to Hydrogen Induced Cracking nucleation phenomena.

Simultaneous estimation of vitamin K1 and heparin with low limit of detection using cascaded channels fiber optic surface plasmon resonance

We report an approach for the simultaneous estimation of vitamin K1 (VK1) and heparin via cascaded channel multianalyte sensing probe employing fiber optic surface plasmon resonance technique. Cladding from two well separated portions of the fiber is removed and are respectively coated with thin films of silver (channel-1) and copper (channel-2). The nanohybrid of multiwalled carbon nanotube in chitosan is fabricated over silver layer for the sensing of VK1 whereas core shell nanostructure of polybrene@ZnO is coated over copper layer for the sensing of heparin. Spectral interrogation method is used for the characterization of the sensor. Analyte selectivity of both the channels is performed by carrying out experiments using independent solutions of VK1 and heparin. Experiments performed on the solution of the mixture of VK1 and heparin show red shifts in both the channels on changing the concentration of both the analytes in the mixture. The operating range of both VK1 and heparin is from 0 to 10−3g/l. The limit of detection of the sensor is 2.66×10−4µg/l and 2.88×10−4µg/l for VK1 and heparin respectively which are lower than the reported ones. The additional advantages of the present sensor are low cost, possibility of online monitoring and remote sensing.

A novel approach for simultaneous sensing of urea and glucose by SPR based optical fiber multianalyte sensor

A novel design is presented for the sensing of urea and glucose simultaneously by surface plasmon resonance (SPR) based optical fiber multianalyte sensor using gel entrapment technique in a fluid for biomedical applications. Sensing surfaces are prepared by coating of different metals and high index dielectric over-layers (silver and silicon in channel 1 and copper and tin-oxide in channel 2) over two small and well separated unclad portions of an optical fiber. Enzymes urease and glucose oxidase are immobilized over respective surfaces using gel entrapment method for the sensing of urea and glucose, respectively. Wavelength interrogation technique is used for the calibration of the sensor. The concentration of urea and glucose are selected in the range 0-180 mM and 0-260 mg dl(-1), respectively, to mimic the physiological range of urea and glucose in human blood. Mixed solutions of urea and glucose with varying concentrations are prepared in buffer solution for the calibration of the sensor. The resonance wavelengths are determined corresponding to two channels responding independently to the interaction of analytes in solution on sensing channels. It is observed that the resonance wavelengths in the case of both the sensing channels decrease with the increasing concentrations of urea and glucose in solutions. The sensor gives 8.51 nm and 13.04 nm total shifts in resonance wavelength for 0 mM to 180 mM urea and 0 mg dl(-1) to 260 mg dl(-1) glucose concentrations in a sample, respectively. The advantages of the present sensor are cascaded design with multiple sensing channels on a single platform, inexpensive, simultaneous sensing of two parameters, possibility of online monitoring and remote sensing.

Online monitoring and assessment of emerging risk in conventional industrial plants: possible way to implement integrated risk management approach and KPI’s

Existing methodologies and practices do not provide enough possibility for online monitoring and assessment of emerging risks occurring as a result of a change in technology, product, operating conditions, as well as in organization of activities in conventional industrial plants. Typical today’s off and online methods and corresponding software packages are used as risk assessment methods, while various risk aspects (such as: process risks, process equipment integrity risks, organizational risks, and health and environmental risks) are being assessed and treated independently. However, it is clear that risk assessment and making decisions in line with that has to be based on information collected from different (independent) sources in online mode. Also, the fact that additional risks in operations may occur due to unexpected changes in technology, accidents or unexpected process equipment degradation should be taken into account. When monitoring and process management systems are being designed and developed, only the process aspect and process risk are usually analyzed, while other risk aspects are not taken into account (like health and environmental risks). A new approach, to be presented in this paper, provides a possibility of online monitoring and assessment of risks (e.g. in petrochemical industry, power industry, etc.).

Optical fiber sensor for the detection of tetracycline using surface plasmon resonance and molecular imprinting

We present a simple and highly selective optical fiber sensor for the detection of tetracycline in foodstuffs by using the combination of surface plasmon resonance (SPR) and a molecular imprinted polymer (MIP) matrix. The sensor is fabricated first by coating a thin film of silver metal over the unclad portion of an optical fiber, and then preparing a molecular imprinting of the target molecules over the metal coated region. The MIP creates several binding sites/nano-cavities which have the complementary shape and functional groups of the target molecules on its surface. The sensor works on the wavelength modulation scheme in which the shift in resonance wavelength is measured with respect to the change in tetracycline concentration. Two kinds of tetracycline, tetracycline hydrochloride (TC) and oxy-tetracycline hydrochloride (OTC) have been selected as the imprinting molecules because these possess similar structures. The presence of tetracycline samples in the vicinity of the sensing region causes the interaction between binding sites and target molecules which results in the change in the dielectric properties of the sensing surface, causing the shift in the SPR spectrum towards the red region. The selectivity of the sensor for dissimilar compounds, and cross-selectivity between TC and OTC, has been tested. The reusability of the sensor has also been checked. The present sensor is suitable for commercialization for the detection of tetracycline in food as it has several advantageous features such as low cost, ease of handling, a miniaturized probe, fast response, high selectivity, reusability and the possibility of online monitoring and remote sensing.

A sensitive microsystem as biosensor for cell growth monitoring and antibiotic testing

Standard bacterial tests such as growth inhibition tests are the only convenient investigation method to detect the impacts of water soluble drugs, e.g. antibiotics, on bacteria. State of the art methods for determining the inhibiting effect of toxic components are cumbersome, because they are for parallelization not feasible. The principle of these inhibition tests is the detection of cell numbers by measuring the optical density. With this time-consuming and complicate method only endpoint detection and no monitoring of cell growth is possible, which is obviously a drawback. Furthermore, colored and turbid components cannot be tested. A new microsystem is introduced in this paper overcoming the mention problems. A continuously working conductivity sensor system for high throughput application is developed. With this miniaturized system a reduction of sample volume from 50 ml down to 12 μl becomes possible. An additional advantage is the possibility of online monitoring during biological tests and cell growth detection in high turbid or colored samples, which could not be investigated before. The sensor system is calibrated for growth inhibition of Pseudomonas putida, tested with antibiotics.