Voltage Scanning Research Articles

Tensegrity Modelling and the High Toughness of Spider Dragline Silk.

This work establishes a tensegrity model of spider dragline silk. Tensegrity systems are ubiquitous in nature, being able to capture the mechanics of biological shapes through simple and effective modes of deformation via extension and contraction. Guided by quantitative microstructural characterization via air plasma etching and low voltage scanning electron microscopy, we report that this model is able to capture experimentally observed phenomena such as the Poisson effect, tensile stress-strain response, and fibre toughness. This is achieved by accounting for spider silks’ hierarchical organization into microfibrils with radially variable properties. Each fibril is described as a chain of polypeptide tensegrity units formed by crystalline granules operating under compression, which are connected to each other by amorphous links acting under tension. Our results demonstrate, for the first time, that a radial variability in the ductility of tensegrity chains is responsible for high fibre toughness, a defining and desirable feature of spider silk. Based on this model, a discussion about the use of graded tensegrity structures for the optimal design of next-generation biomimetic fibres is presented.

Soliton-Dependent Electronic Transport across Bilayer Graphene Domain Wall.

Layer-stacking domain wall in bilayer graphene is one type of topological defects that can greatly affect the electronic properties of bilayer graphene and therefore lead to nontrivial transport behaviors. An outstanding question on the layer stacking domain wall is how the electrons hop between two adjacent stacking domains. Here we report the first experimental observation of electronic transport across bilayer graphene domain walls by combining near-field infrared nanoscopy and scanning voltage microscopy techniques. We observe markedly different electron transport behaviors across the tensile- and shear-type domain walls. The tensile-type domain wall is highly reflective of low-energy incident electrons, but becomes more transparent when the electron density and the Fermi energy are increased by electrostatic gating. In contrast, the shear-type domain wall is always highly transparent at different gate voltages. Such soliton-dependent electronic transport can open up new routes to engineer novel nanoelectronic devices based on layer-stacking domain walls in bilayer graphene.

Effects of exponentially decaying and growing concentrations on particle size distribution from a scanning mobility particle sizer

A scanning mobility particle sizer (SMPS) is one of the most widely used instruments to obtain size distribution for atmospheric particles. In an SMPS measurement, a voltage scanning process on a d...

Derivatization assisted LC-p-MRM-MS with high CID voltage for rapid analysis of brassinosteroids

In this study, a derivatization-assisted pseudo-multiple reaction monitoring with high CID voltage (HV-p-MRM) strategy was proposed for the analysis of brassinosteroids (BRs) by liquid chromatography-triple quadrupole mass spectrometry (LC-QqQ MS). The concept of the HV-p-MRM strategy was proposed on the basis of an assumption that the precursor ion of analyte is stable in collision cell and less prone to fragmentation at high CID voltage, while co-existing ions (impurity) of easy fragmentation can break down into smaller fragment ions. In such case, by increasing the CID voltage, the co-existing ions that are introduced due to the low resolution of the quadrupole 1 (Q1) can be filtered out by quadrupole 3 (Q3), while the stable precursor ion of analyte will pass through Q3, thereby that the signal-to-noise ratio (S/N) of the analysis can be improved. As a proof-of-concept study, BRs were derivatized with rhodamine B-boronic acid (RhB-BA) and then the derivatives were used to investigate their variations in MS signal, background noise, and S/N upon the CID voltage and MS scanning resolution. The results showed that S/N of these derivatives can be improved in HV-p-MRM mode. To further demonstrate the feasibility of HV-p-MRM strategy, a RhB-BA derivatization assisted LC-HV-p-MRM-MS method was developed for the analysis of BRs. Using this method, rapid and sensitive determination of BRs in different organs of rape flower was achieved. It can be expected that HV-p-MRM may be suitable for the analytes that are stable or can be converted into compounds of high stability in collision cell at high CID voltage.

Study of Structural, Electrical and Optical Properties of (200)-Oriented CdTe Thin Films Depending on the Post-deposition Low Temperature

Cadmium telluride nanoparticles (CdTe NPs) have been synthesized by a sonochemical technique, deposited on glass and quartz glass at 100°C and 2.7 × 10−6 kPa and then studied by analyzing the x-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–Vis), current–voltage test (I–V) and scanning electron microscopy (SEM). The XRD results indicated the formation of a strong preferential (200) orientation of CdTe with a cubic zinc-blende structure on both substrates. In order to show the effect of heating on the structure and optical properties of the prepared thin films, they were annealed at temperatures of 50°C, 70°C and 100°C for 1 h. It was found that the grain size in this orientation increases with the increase of the temperature. In addition, the obtained optical band gap energies by UV–Vis measurements were in the range of 1.46–1.53 eV. The electrical properties of the prepared films were observed to increase with annealing using I–V measurements. The thin films were also found to be uniform with a small particle size, as revealed by SEM.

Development of a new nanoparticle sizer equipped with a 12-channel multi-port differential mobility analyzer and multi-condensation particle counters

Abstract. Measuring particle size distributions precisely is an important concern in addressing environmental and human health-related issues. To measure particle size distributions, a scanning mobility particle sizer (SMPS) is often used. However, it is difficult to analyze particle size distributions under fast-changing concentration conditions because the SMPS cannot respond fast enough to reflect current conditions due to the time necessary for voltage scanning. In this research, we developed a new nanoparticle sizer (NPS), which consists of a multi-port differential mobility analyzer (MP-DMA) with 12 sampling ports and multi-condensation particle counters (M-CPCs) that simultaneously measure concentrations of particles classified by the sampling ports. The M-CPC can completely condense particles larger than 10 nm, and the total particle concentrations measured by each CPC in the M-CPCs and an electrometer were in agreement up to 20 000 no.cm-3. We conducted size distribution measurements under steady-state conditions using an aerosol generator and under unsteady conditions by switching the aerosol supply on or off. The data obtained by the NPS corresponded closely to the SMPS measurement data for the steady-state particle concentration case. In addition, the NPS could successfully capture the changes in particle size distribution under fast-changing particle concentration conditions. Finally, we present NPS measurement results of size distributions in a common situation (cooking) as an exemplary real-world application.

Improved voltage scanning method for maximum power point under partial shadow conditions

This paper proposes a novel maximum power point tracking (MPPT) algorithm with global search. The algorithm combines global voltage sweep and incremental conductance method, and introduces a Judging factor as a criterion for global voltage scanning. The Judging factor is compared with the threshold and the scan step size is selected based on the result. Take a large step when far from the peak. When approaches the peak, uses the incremental conductance method to find the local extrema and store it, then continues scanning. When the output power is close to zero, the scan is complete, Comparing all local extrema points then the global maximum power point will be found by this algorithm. Matlab simulation results show that the algorithm can find the global maximum and the search speed is fast.

Scanning tunneling microscopy of the tetraphenylporphyrin thin films on a graphite single-crystal substrate

Features of the surface topography of a tetraphenylporphyrin film on a graphite single crystal (HOPG) substrate and the local current-voltage characteristics were studied using a scanning tunneling microscope under ambient conditions. STM images of surface were acquired on a scale from a few nanometers to 4 micrometers. Local tunnelling current-voltage characteristics in different ranges of bias voltage and in different directions of voltage scanning can have hysteresis due to the hopping electron conductivity in porphyrin.

A Global Maximum Power Point Tracking Algorithm for Photovoltaic Systems Under Partially Shaded Conditions Using Modified Maximum Power Trapezium Method

In this article, a modified maximum power trapezium (MPT) method for global maximum power point tracking of photovoltaic (PV) systems under partially shaded conditions (PSCs) is proposed. Compared with the traditional MPT method, the proposed method introduces a variable current range lower bound by utilizing the monotonic output characteristics of the PV array. Moreover, considering the influence of the initial operating point of the PV array on the scanning path under dynamic PSCs, a judgment mechanism for the initial voltage is added in the modified method. The proposed method guarantees that the global maximum power point is tracked accurately with a smaller voltage scanning range and shorter tracking time under all conditions. Furthermore, the excellent performance of the proposed method has been verified by both simulation and experimental results.

Effects of noises on curve fitting to the I–V characteristics of retarding filed analyzers

Retarding filed analyzers (RFAs) measure the ion velocity distribution in edge plasmas, leading to an estimate of the ion temperature and space potential through curve fitting. This paper describes the bi-directional RFA detector installed on the Experimental Advanced Superconducting Tokamak for edge plasma parameter measurements. The paper also describes a technique to compensate for a known induced noise using a dummy signal line and a method to reconstruct the I–V curve from the scanning voltage signal and the resultant ion current waveform. Fitting to experimental data and numerical simulations show that the I–V curve reconstruction method serves for both smoothing and induction noise compensation purposes.

System for Measuring Emittance Characteristics of Ion Sources

The article presents the results of the development of a system for measuring emittance characteristics of ion sources studied at the IAP NAS of Ukraine with the aim of obtaining the ion beams with a high brightness. The emittance measurement system is based on the scheme of an electrostatic scanner and consists of two main parts: the scanner, which moves in the direction perpendicular to the beam axis using a stepper motor, and the electronic system of control, processing and data acquisition. The electronic system contains a Raspberry pi 3B microcomputer, precision DAC/ADCs, the high-voltage amplifier of a scanning voltage up to ±500 V on deflection plates of the scanner and a wide range current integrator. The determination of the emittance consists in measuring the ion beam intensity distribution when the scanner moves along the x-coordinate and the electrostatic scanning along the x´ angle. The obtained two-dimensional data array allows determining the main characteristics of ion beam: geometric 90% emittance, the root mean square (rms) emittance, the Twiss parameters and phase ellipse of rms emittance, the beam current profile and the angle current density distribution. To test the performance and functionality of the system, the emittance characteristics of the penning type ion source were measured. The working gas was helium, and the beam energy varied within 7–15 keV. At 13 keV of beam energy the following emittances of the He+ ions beam was obtained: 90% emittance is 30 π∙mm∙mrad, rms emittance is 8.4 mm∙mrad, and the normalized rms emittance is equal to 0.022 mm∙mrad. The developed system for measuring the emittance of the ion beams is characterized by a short measurement time of 10-15 minutes.

Establishing Sequence of Inkjet Printer, Laser Printer and Writing Ink Strokes using Scanning Electron Microscopy (SEM)

The aim of the present study is to determine the sequence of laser printer, inkjet printer, and writing ink (ball point pen ink, gel pen ink, pilot pen ink and fountain pen ink) strokes using a low voltage (1kV) scanning electron microscope (SEM). Intersections were prepared using an inkjet printer, laser printer, and writing instruments on copier paper. About 1cm2 of intersection was cut using scissors and mounted to the probe stage of the SEM using double-sided tape. Each sample was analyzed at different operating parameters. The results were evaluated on the basis of continuity and iscontinuity of strokes at intersection point. It was possible to determine the correct sequence of printer strokes versus other writing instruments’ strokes; inkjet printer stroke versus fountain and pilot pen ink stroke; however, inconclusive results were obtained in the case of inkjet printer strokes versus ball point pen and gel pen ink strokes. The ffectiveness of this technique was determined by analyzing the exact sequence of blind samples. An SEM could be used as mplimentary tool with other optical methods to examine the sequence of strokes.

Efficient Anti-solvent-free Spin-Coated and Printed Sn-Perovskite Solar Cells with Crystal-Based Precursor Solutions

Summary Tin-based perovskite solar cells (PSCs), with more consummate optical band gaps, lower exciton-binding energies, and higher charge-carrier mobility, have not attracted tremendous research efforts compared with the lead-based ones that have a record power conversion efficiency (PCE) of 24.2%. The major challenges for Sn-based research are significantly low open-circuit voltage, poor reproducibility, and environmental instability. It has been identified that the oxidation processes take place during the preparation of precursor solutions and fabrication of films, due to the low redox potential of the stannous absorption layer. Herein, we propose two strategies of crystal-resolving and recrystallization technology to reduce the oxidation process. As a result, PCEs of 8.9% (active area of 0.04 cm2) and 5.5% (active area = 1.01 cm2) are attained using the inverted p-i-n structure, which will lead to a revival of lead-free PSC research.

Imaging low-dimensional nanostructures by very low voltage scanning electron microscopy: ultra-shallow topography and depth-tunable material contrast

We demonstrate the implications of very low voltage operation (<1 kV) of a scanning electron microscope for imaging low-dimensional nanostructures where standard voltages (2–5 kV) involve a beam penetration depth comparable to the cross-section of the nanostructures. In this common situation, image sharpness, contrast quality and resolution are severely limited by emission of secondary electrons far from the primary beam incidence point. Oppositely, very low voltage operation allows reducing the beam-specimen interaction to an extremely narrow and shallow region around the incidence point, enabling high-resolution and ultra-shallow topographic contrast imaging by high-angle backscattered electrons detection on the one hand, and depth-tunable material contrast imaging by low-angle backscattered electrons detection on the other. We describe the performance of these imaging approaches on silicon nanowires obtained by the vapor-liquid-solid mechanism. Our experimental results, supported by Monte Carlo simulations of backscattered electrons emission from the nanowires, reveal the self-assembly of gold-silica core-shell nanostructures at the nanowire tips without any ad-hoc thermal oxidation step. This result demonstrates the capacity of very low voltage operation to provide optimum sharpness, contrast and resolution in low-dimensional nanostructures and to gather information about nanoscaled core-shell conformations otherwise impossible to obtain by standard scanning electron microscopy alone.

A Fast GMPPT Algorithm Based on PV Characteristic for Partial Shading Conditions

Photovoltaic (PV) modules experience some partial shading conditions (PSC) due to some various factors. In that kind of a condition, a few maximum power points (MPPs) possibly appear on the power-voltage (P-V) curve, which increases the tracking difficulties. It is known that maximum power point tracking (MPPT) may not be realized by hill climbing (HC) based conventional MPPT algorithms under PSCs. In this context, this paper presents a novel micro converter based algorithm that was developed by using P-V characteristics of PV modules. Unlike voltage or duty ratio scanning techniques, this paper introduces a new deciding method to determine the correct global MPP (GMPP) region. For this, the proposed method uses some duty ratios that were calculated corresponding to each MPP region. Thus, the initialization of duty ratio is done properly, which results in high tracking speed and accurate tracking of the GMPP. The other advantages of the proposed algorithm are structural simplicity, less computational burden, and ease of implementation with a basic microcontroller. The simulation results show that this algorithm has fast tracking capability and it manages to track GMPP for PSCs correctly, since it includes an artificial scanning procedure. Single ended primary inductance converter (SEPIC) is built in order to validate the proposed global maximum power point tracking (GMPPT) algorithm. The performance of the proposed GMPPT technique is verified by experimental studies. The results show that the proposed GMPPT technique is fast by up to five times than an adaptive full scanning strategy and improved IC algorithm. Furthermore, the proposed algorithm can be commercially used in micro converters, since it is compatible with small number of bypass diodes in a module.

Estimation of dielectric constant by using mirror effect

An experimental-theoretical investigation has been presented in this paper to study of the ion mirror effect on the Poly Methyl Methacrylate (PMMA) sample, and how to control this effect and use it as an analytical tool for imaging in practical field was presented. This means creating a deeper understanding of the characteristics of ions beam related to the mirror effect. As a result, a mathematical relation for the beam properties of the sample surface has been adopted and realistic physical concepts must be constructed. Where the study of the effect of some parameters on the ion mirror effect was submitted, and these parameters are: the trapped charge quantity on the sample surface and acceleration voltage in the imaging process, a distance of work and irradiation area.The purpose of this study is to achieve a measurement of dielectric constant by using the mirror effect. Where a mathematical relation was derived to estimate the dielectric constant for any of insulating material by using the mirror effect, where it gave good results that correspond to a good extent with the practical results. This was done by knowing the scanning voltage for the disappearance of the mirror effect as well as measuring the Coulomb diameter for each scanning voltage.

Cardiac CT: why, when, and how : Update 2019.

The aim of this study was to review established and emerging techniques of cardiac computed tomography (CT) and their clinical applications with aspecial emphasis on new techniques, recent trials, and guidelines. Cardiac CT has made great strides in recent years to become an ever more robust and safe imaging technique. The improvements in spatial and temporal resolution are equally important as the substantial reduction in radiation exposure, which has been achieved through prospective ECG-triggering, low tube voltage scanning, tube current modulation, and iterative reconstruction techniques. CT-derived fractional flow reserve and CT myocardial perfusion imaging are novel, investigational techniques to assess the hemodynamic significance of coronary stenosis. In asymptomatic patients at risk for coronary artery disease, CT coronary artery calcium scoring is useful to assess cardiovascular risk and guide the intensity of risk factor modification. Coronary CT angiography is an excellent noninvasive test to rule out obstructive coronary artery disease in patients with stable chest pain. In acute chest pain with normal ECG and normal cardiac enzymes, cardiac CT can safely rule out acute coronary syndrome although its benefit and role in this indication remains controversial. Cardiac CT is the established standard for planning transcatheter aortic valve implantation and-increasingly-minimally invasive mitral valve procedures. Our review makes practical recommendations on when and how to perform cardiac CT and provides templates for structured reporting of cardiac CT examinations.

Preface to the special issue on electrochemical energy storage discussed at the NZEE conference 2018 in Czech Republic

This paper describes fabrication and characterization of a hybrid nanostructure comprised of multi-walled carbon nanotubes (MWCNTs) on reduced graphene oxide (r-GO) via layer by layer (LBL) assembly. This structure was prepared by vacuum filtration and heat-treated at 500 °C. The morphology of the sample was investigated by field emission electron microscopy (FE-SEM). The crystalline structure and chemical composition were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Cyclic voltammetry (CV) curve of MWCNTs/r-GO hybrid film appeared close to that of an ideal double layer capacitor, in quasi-rectangular shape. The current density gradually increased with increasing voltage scanning rate, exceeding 20 A/g at a scan rate of 500 mV/s. Accordingly, the specific capacitance decreased with the increase of the voltage scanning rate as expected. Electrochemical performance of this hybrid film indicates that it can further improve supercapacitor electrodes.

Using collision-induced dissociation to constrain sensitivity of ammonia chemical ionization mass spectrometry ( CIMS) to oxygenated volatile organic compounds.

Chemical ionization mass spectrometry (CIMS) instruments routinely detect hundreds of oxidized organic compounds in the atmosphere. A major limitation of these instruments is the uncertainty in their sensitivity to many of the detected ions. We describe the development of a new high-resolution time-of-flight chemical ionization mass spectrometer that operates in one of two ionization modes: using either ammonium ion ligand-switching reactions such as for CIMS or proton transfer reactions such as for protontransfer-reaction mass spectrometer (PTR-MS). Switching between the modes can be done within 2min. The CIMS mode of the new instrument has sensitivities of up to 67 000 dcps ppbv-1 (duty-cycle-corrected ion counts per second per part per billion by volume) and detection limits between 1 and 60 pptv at 2σ for a 1 s integration time for numerous oxygenated volatile organic compounds. We present a mass spectrometric voltage scanning procedure based on collision-induced dissociation that allows us to determine the stability of ammonium-organic ions detected by the CIMS instrument. Using this procedure, we can effectively constrain the sensitivity of the ammonia chemical ionization mass spectrometer to a wide range of detected oxidized volatile organic compounds for which no calibration standards exist. We demonstrate the application of this procedure by quantifying the composition of secondary organic aerosols in a series of laboratory experiments.

MWCNTs/r-GO hybrid films fabricated by layer by layer assembly for supercapacitor electrodes

Abstract This paper describes fabrication and characterization of a hybrid nanostructure comprised of multi-walled carbon nanotubes (MWCNTs) on reduced graphene oxide (r-GO) via layer by layer (LBL) assembly. This structure was prepared by vacuum filtration and heat-treated at 500 °C. The morphology of the sample was investigated by field emission electron microscopy (FE-SEM). The crystalline structure and chemical composition were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Cyclic voltammetry (CV) curve of MWCNTs/r-GO hybrid film appeared close to that of an ideal double layer capacitor, in quasi-rectangular shape. The current density gradually increased with increasing voltage scanning rate, exceeding 20 A/g at a scan rate of 500 mV/s. Accordingly, the specific capacitance decreased with the increase of the voltage scanning rate as expected. Electrochemical performance of this hybrid film indicates that it can further improve supercapacitor electrodes.