Analysis of AC-DC Converter Circuit Performance With Difference Piezoelectric Transducer Array Connection

This research presents a simulation analysis for the AC-DC converter circuit with a different configurations of the array connection of the piezoelectric sensor. The selection of AC-DC converter circuits is full wave bridge rectifier (FWBR), parallel SSHI (P-SSHI) and parallel voltage multiplier (PVM) with array configuration variation in series (S), parallel (P), series-parallel (SP) and parallel-series (PS). The system optimizes with different load configurations ranging from 10 kΩ to 1 MΩ. The best configuration of AC-DC converter with an appropriate array piezoelectric connection producing the optimum output of harvested power is presented. According to the simulation results, the harvested power produced by using P-SSHI converter connected with 3 parallel piezoelectric transducer array was 85.9% higher than for PVM and 15.88% higher than FWBR

Preliminary study of KNN thin films doped by rare-earths for sensor applications

ABSTRACT -Among ferroelectrics systems, potassium sodium niobate (KNN) has drawn much attention due to a clear-cut advantage of high piezoelectric and ferroelectric performances. The volatility of alkaline element (K,Na) is detrimental to the stoichiometry of KNN, contributing to the formation of intrinsic defects. Thus, the primary goal of this study is to design a solution to overcome the volatility issue of KNN. Introduction of rare-earth cations in the host KNN could reduce the vacancies in KNN. Currently, three arrays of dopants were integrated into KNN. In this preliminary work, a sol-gel technique was employed to produce a thin film that can be utilized later in the sensor applications. The structural and electrical properties were characterized using Raman spectroscopy and 2-point probe equipment, respectively. The typical Raman spectra of KNN thin films were shifted towards lower or higher wavenumbers depending on the cations deficiencies or redundancies. The conductivity of thin films was found to be increased as the dopant concentration was increased

A framework for Operational Security Metrics Development for industrial control environment

Security metrics are very crucial towards providing insights when measuring security states and susceptibilities in industrial operational environments. Obtaining practical security metrics depend on effective security metrics development approaches. To be effective, a security metrics development framework should be scope-definitive, objective-oriented, reliable, simple, adaptable, and repeatable (SORSAR). A framework for Operational Security Metrics Development (OSMD) for industry control environments is presented, which combines concepts and characteristics from existing approaches. It also adds the new characteristic of adaptability. The OSMD framework is broken down into three phases of: target definition, objective definition, and metrics synthesis. A case study scenario is used to demonstrate an instance of how to implement and apply the proposed framework to demonstrate its usability and workability. Expert elicitation has also be used to consolidate the validity of the proposed framework. Both validation approaches have helped to show that the proposed framework can help create effective and efficient ICS-centric security metrics taxonomy that can be used to evaluate capabilities or vulnerabilities. The understanding from this can help enhance security assurance within industrial operational environments

The simulation analysis of piezoelectric transducer with multi-array configuration

Low frequency energy harvesting using piezoelectric is one of promising method on harvesting energy from a free source. This method offered powering low load and remote device application. However, due to its nature which is inconsistency in providing the magnitude of input, specifically in low frequency harvesting, better solution to stable up and increase the converted output is explored widely. There are a few parameter that influences in the piezoelectric output generation. These parameter includes the type of piezoelectric, piezoelectric array configuration, AC-DC converter and etc. The types of the piezoelectric used in this project are the circular piezoelectric. When there is a force (motion) exerted on the piezoelectric disk, electrical charge was produced which initiated the energy conversion. In this research, the configuration of array connection for piezoelectric were investigated. The system is tested with different load configuration in a range of 10 kΩ to 1 MΩ. The design and development of the piezoelectric array variant were series (S), parallel(P), series parallel (SP) and parallel-series (PS). The observation emphasized on finding the best types of piezoelectric array configuration in producing optimum output of the harvested power. The simulation part consists of designing, simulating and analysing the result are done by using PSIM software. For validation of the simulation result, the implementation design of the hardware prototype that supplies pressure to piezoelectric have been done. In conclusion, a proper implementation of piezoelectric array configuration will produce optimum power output which can fulfil the minimum requirement of energy for powering low load device

Revealing the role of kapok fibre as bio-template for In-situ construction of C-doped g-C3N4@C, N co-doped TiO2 core-shell heterojunction photocatalyst and its photocatalytic hydrogen production performance

For the first time, C-doped g-C3N4@C, N co-doped TiO2 core-shell heterojunction photocatalyst was successfully prepared by an in-situ one-pot hydrothermal bio-template approach, assisted by calcination treatment at 500 °C. Kapok fibre was used as a bio-templates and in-situ C doping in g-C3N4 and TiO2 during the formation of core-shell heterojunction photocatalyst. Moreover, the used of urea as g-C3N4-precursor also contribute to band-gap narrowing by an in-situ carbon and nitrogen doping in TiO2. Various characterisation techniques were employed to understand the effect TiO2 precursor concentration on the evolution of core-shell nanostructure heterojunction photocatalyst that can affect and boost the catalytic activity. The detailed understanding of the concurrent growth of C-doped g-C3N4 (CCN) and C, N co-doped TiO2 mechanism, as well as the formation of core-shell nanostructures heterojunction formation, are also proposed in this study. Our finding indicated that the bio-template core-shell nanostructure heterojunction photocatalysts showed a dramatic increase in photoinduced electron-hole separation efficiency as demonstrated by the photoelectrochemical and photoluminescence analyses. The enhancement in photogenerated charge carrier separation and narrower band gap resulted in superior photocatalytic activities with the highest rate of hydrogen production was recorded by CCN/T-1.5 sample (625.5 μmol h−1 g−1) in methanol aqueous solution. The well-developed interconnected heterojunction formation with appropriate CCN and TiO2 contents in core-shell nanoarchitectures system is a prime factor for the future design of a highly efficient visible-light-driven photocatalyst

Influence of yttrium dopant on the structure and electrical conductivity of potassium sodium niobate thin films

KNN thin films with diverse yttrium concentration (mol % = 0, 0.1, 0.3, 0.5, 0.7 and 0.9) were fabricated using sol-gel spin coating technique. Doped KNN revealed that Y3+ was successfully doped into the ABO3 perovskite lattice without changing the phase formation of KNN. The thickness of the deposited layer of KNN produced with increasing dopant concentration was determined to be 200 nm with dense and well-defined grains. Afterwards, the vibrational bonding and conductivity of KNN films with diverse yttrium concentration were identified according to the charge compensation mechanism. At high dopant concentration of > 0.5 mol %, O-Nb-O bonding was asymmetric and became distorted due to B-site occupancy by yttrium dopant. Further investigation revealed that charge compensation mechanism was shifted by increasing doping concentration. As a result, yttrium-doped KNN became semi-conductive at low yttrium concentration. Meanwhile, at high concentration, yttrium-doped KNN became an insulator and underwent ionic compensatio

Optimizing the processing conditions of sodium potassium niobate thin films prepared by sol-gel spin coating technique

In the present study, potassium sodium niobate (KNN) thin films were synthesized by means of sol-gel spin coating method. Along with the synthesis, the effects of annealing temperature and various number of coating layers on both the structural and electrical properties were looked into. The results of the study revealed that the annealing temperature had a great impact on the properties of KNN. In addition, the XRD diffractograms and texture coefficient of the synthesized films confirmed that a highly oriented orthorhombic perovskite structure was obtained at 650 °C, whereas at a relatively higher temperature (700 °C), a spurious phase of K4Nb6O17 was evolved. In addition, the growth of KNN at 650 °C exhibited a reasonable resistivity value for piezoelectric applications. Looking into the results, it was discovered that the KNN thin films also found to be dependent on a number of coating layers. Field emission scanning electron microscopy (FESEM) showed that KNN with five coating layers was highly crystalline, cracks-free, and had significantly more homogenous surface morphology and the size of grains being uniform, the resistivity of KNN thin films improved with the increasing number of coating layers i.e., up to fiv

Enhancement of visible light photocatalytichydrogen evolution by bio-mimetic c-dopedgraphitic carbon nitride

Bio-mimetic C-doped graphitic carbon nitride (g-C3N4)with mesoporous microtubular structure has been prepared by a simple chemical wet bio-template impregnation approach (direct impregnation and hydrothermal impregnation)using urea as a precursor and kapok fibre as bio-template and in-situ carbon dopant. Our finding indicated that the hydrothermal impregnation had induced more in-situ C-doping in g-C3N4 as compared to the direct impregnation approach. The introduction of in-situ C doping in the g-C3N4 and the mesoporous microtubular structure remarkably enhanced light-harvesting capability up to near infrared regions. The photocurrent measurement and electrochemical impedance spectroscopy (EIS)analysis suggested that the bio-template C-doped g-C3N4 exhibits a superior photoinduced electron-hole pairs separation efficiency due to C doping and mesoporous microtubular structure significantly promotes excellent conductivity and electron redistribution in the sample. C-doped graphitic carbon nitride sample prepared by the hydrothermal (HB/g-C3N4)approach exhibits excellent photocatalytic hydrogen production with an H2 production rate of 216.8 μmol h−1 g−1 which was a 1.3 and 2.9 improvement over C-doped graphitic carbon nitride prepared by direct impregnation (DB/g-C3N4)and pristine g-C3N4, respectively. This study provides new insights into the development of low-cost and sustainable photocatalysts for photocatalytic hydrogen production

Enhanced gas separation performance using carbon membranes containing nanocrystalline cellulose and BTDA-TDI/MDI polyimide

This paper presents the derivation of carbon membranes from BTDA-TDI/MDI polyimide (PI) prepared via a dip-coating technique on an inorganic tubular support surface, followed by a heat treatment (stabilization and carbonization) under N2 gas flow. In order to enhance the gas separation performance of the resultant carbon membrane, a synthesized nanocrystalline cellulose (NCC) using tissue paper as an additive was added into the dope solution at various carbonization temperatures of 600, 700, 800, and 900 °C. The NCC was prepared by extracting the unprinted area of a newspaper and was processed as an additive in the polymer solution. The chemical structure, morphological structure, and gas permeation properties of the resultant membrane were analyzed. Special attention was given to the physicochemical characteristics of the resulting PI/NCC-based carbon membrane and its corresponding gas permeation properties. Pure gas permeation tests were performed using CO2, CH4, O2, and N2 at room temperature. The gas permeation data demonstrated that the carbon membrane exhibited an excellent performance compared to the polymeric membrane. Enhancement in both gas permeance and selectivity were observed in the NCC-containing carbon membranes prepared at carbonization temperature of 800 °C, with the CO2/CH4 selectivity of 68.2 ± 3.3, the CO2/N2 selectivity of 66.3 ± 2.2, and the O2/N2 selectivity of 9.3 ± 2.5, with respect to the neat carbon membrane. By manipulating various carbonization temperatures, carbon membranes with different structures and properties were obtained

Enhancement in photocatalytic degradation of methylene blue by LaFeO3-GO integrated photocatalyst-adsorbents under visible light irradiation

Perovskite LaFeO3 photocatalyst prepared by using sol-gel glucose method was assembled on graphene oxide sheets to produce integrated photocatalyst-adsorbents (IPCA) and investigated as photocatalyst for the degradation of methylene blue under visible light irradiation. The prepared photocatalyst was characterized by FTIR, XRD, FESEM, BET specific surface area measurement, TEM/HRTEM and UV-Vis spectroscopy analysis. The FTIR, FESEM and TEM analysis has suggested that the photocatalyst LaFeO3 has been successfully embedded at the surface of the graphene oxide (GO) sheets due to a strong interaction between the photocatalyst and the adsorbents matrix. Methylene blue degradation shows that IPCA possesses higher photodegradation kinetics compared to bare LaFeO3 photocatalyst. The resultant photocatalyst also possesses magnetic properties which can overcome the difficulty in recollecting and removal of photocatalyst suspension in water after photocatalytic treatment