Rising Edge Research Articles

Effects of Viscosity and Refractive Index on the Emission and Diffusion Properties of Alexa Fluor 405 Using Fluorescence Correlation and Lifetime Spectroscopies

Fluorescence Correlation Spectroscopy (FCS) studies of the interaction of polymers or proteins in solution are strongly affected by the viscosity and refractive index of the medium, and the effects are likely to be more significant with the use of short wavelength excitation (e.g., 405 nm diode lasers). Failing to account for these issues can lead to incorrect measurement of average size, conformational changes, and dynamic behaviour of polymers and proteins. Steady-state, time-resolved, and FCS measurements of Alexa 405 in glycerol:water mixtures were performed to determine its suitability for FCS measurements with 405 nm excitation. The effects of the refractive index and viscosity on the diffusion coefficient and photophysical parameters (lifetime and relative quantum yield) of the fluorophore were determined. Alexa 405 lifetime decreased from 3.55 ns in water to 3.25 ns in a 50:50 glycerol:water mixture, while its diffusion coefficient dropped from 333 ± 16 to 44 ± 1 µm2s- 1. Lifetime data collected from micromolar solutions of Alexa 405 did however also suggest that as solvent polarity decreased, aggregates (excimers) were formed as evidenced by the appearance of a rising edge in the decay plots. The interdependence between lifetime, refractive index, and diffusion coefficient could be accurately fitted by a simple polynomial function indicating that the probe is well behaved and predictable in the glycerol:water model system. Overall, Alexa 405 is a most promising and reliable probe for FCS measurement using violet laser diode excitation sources.

A Pulse Shaper for Control of Electro-Optical Modulators

Abstract—A compact pulse shaper described here for controlling broadband electro-optical modulators is capable of operating at frequencies from 0 to 1.5 MHz and allows the generation of control pulses with voltages up to 300 V or more and rise and fall edges of ~35 ns. The small dimensions of the shaper make it possible to combine it with an electro-optic modulator into a single unit, which significantly reduces parasitic electromagnetic radiation.

Waveform analysis of a large-area superconducting nanowire single photon detector

Superconducting nanowire single photon detectors (SNSPDs) are typically used as single-mode-fiber-coupled single-pixel detectors, but large area detectors are increasingly critical for applications ranging from microscopy to free-space quantum communications. However, the long meander-line length of such large-area SNSPDs results in a proportionately large kinetic inductance that affects the waveform generated by the device. Here, we explore changes in the rising edge of the readout pulse for a single-pixel large-area SNSPD as a function of the optical spot size on the detector and compare to the rising edge of the dark-count waveform. We observe a bimodal distribution of bright-count rise times and show that the probability of a slow rise time increases in the limit of large spot sizes, indicative of a position sensitive response. Additionally, in the limit of low bias currents, the dark-count readout pulse is most similar to the large spot-size bright-count readout pulse, which suggests that dark counts arise from locations spanning the device. These results are consistent with a simple model of traveling microwave modes excited by single photons incident at varying positions along the length of the nanowire.

Improving transient magnetorheological response of magnetorheological elastomer by incorporating CIP@FeNi particles

The transient magnetorheological response of magnetorheological elastomer (MRE) is critical to the control system in its applications. Overlong magnetorheological response time will prolong the control time delay of whole application system, which will lead to the degradation of control accuracy and timeliness, or even bring unwanted results. Therefore, it is particularly important to improve the transient magnetorheological response property of MRE for enhancing control efficiency of system. To this end, this paper synthesized a kind of new magnetic filler particle, carbonyl iron powder (CIP)@FeNi, which possesses Fe–Ni nano-flakes on its surface. Vibrating sample magnetometer test results showed that CIP@FeNi possessed superior magnetization under low magnetic field when compared with CIP. By partially replacement of CIP with CIP@FeNi, new dimorphic MREs were prepared. The influence of CIP@FeNi content on both of the transient magnetorheological response and magnetorheological mechanical properties of MRE were experimentally studied. Results indicated that CIP@FeNi is efficacious for improving the response velocity of MRE. In the rise edge, characteristic response time shows obvious decrease trend with increasing content of CIP@FeNi. In addition, at CIP@FeNi content of 2 vol% and 4 vol%, the doped CIP@FeNi can also enhance the magnetorheological property of MRE. This study provides a novel and effective way to improve the transient magnetorheological response property of MRE, which is of great significance for improving the control efficiency of MRE devices.

Development of a High Peak Voltage Picoseconds Avalanche Transistor Based Marx Bank Circuit

Avalanche transistor-based Marx bank circuit (MBC) is widely used to generate high voltage nanosecond pulses with high amplitude, high repetition rate, fast rise time, and low jitter. Researchers have tried to modify the circuit structure by using parallel or series avalanche transistors to increase peak power. However, in this work, the detailed process of analyzing and designing a compact Marx generator using avalanche transistors will be described. The purpose of this article is to report our experimental observations on the mechanism of operation of the MBCs. By studying the influence of amplitude and pulse width of the trigger circuit, a Gaussian pulse with a rising edge of 160 ps, full width at half maximum (FWHM) of 660 ps, and amplitude of 5000 V are obtained. The design improves the output voltage and pulse repetition frequency (PRF) effectively while reducing the use of the number of transistors. Based on the conventional principles of avalanche transistors and Marx circuit, a list of useful and interesting conclusions obtained from experiments will be reported.

A Novel Design of High Performance Low Power Phase-Frequency Detector for CMOS PLL Frequency Synthesizer

A high performance low power phase frequency detector is designed and simulated. The various different parameters of the circuit are obtained through various type of simulations. We worked mainly upon the power dissipation, power supply, input frequency range and its area. The proposed PFD will have the locking capability i.e. to lock at the edges either on the rising or falling edge w.r.t the reference and the feedback signal. The proposed design will have the very high performance and ultra-low phase noise. It has the added advantage of low cost and the compact size. The primary objective is to design a low power phase frequency detector for CMOS PLL Frequency Synthesizer using lows power technique. The pass transistor logic is used in the circuit to eliminate the reset path. By this change of the path the operating frequency and operating speed both are increased in the proposed design. The input Frequency can be taken up to 5 gigahertz. The power supply is taken to be 1 V. The proposed PFD design will have a less number of transistors and also a low consumption of power. The output pulses of the PFD at phase difference of 0, 0, п/2, п, 3п/2, 2п will have its average voltage as 0, VDD and VDD/2. The proposed phase detector will perfectly detect the phase difference between two signals so that the harmonics problem can be minimized. The proposed design is having its operating frequency as 5GHz over the conventional one which has its frequency as 800MHz. Power dissipation in the proposed design is reduced due to less number of transistors used as compared with the conventional one. The operating region has become much wider for proposed design as it is having operating frequency much higher than that of the conventional one the proposed PFD will increase the locking capability on the both rise and fall edge w.r.t. the reference and the feedback signal. The input Frequency can be taken up to 5 gigahertz. The power supply is taken to be 1 V. The proposed PFD circuit will have a less number of transistors and also a low consumption of power 7.14 mW.

Selective amplification of the chirped attosecond pulses produced from relativistic electron mirrors

AbstractIn this paper, the generation of relativistic electron mirrors (REMs) and the reflection of an ultra-short laser off this mirrors are discussed, applying two-dimensional particle-in-cell (2D-PIC) simulations. REMs with ultra-high acceleration and expanding velocity can be produced from a solid nanofoil illuminated normally by an ultra-intense femtosecond laser pulse with a sharp rising edge. Chirped attosecond pulse can be produced through the reflection of a counter-propagating probe laser off the accelerating REM. In the electron moving frame, the plasma frequency of the REM keeps decreasing due to its rapidly expanding. The laser frequency, on the contrary, keeps increasing due to the acceleration of REM and the relativistic Doppler shift from the lab frame to the electron moving frame. Within an ultra-short time interval, the two frequencies will be equal in the electron moving frame, which leads the resonance between laser and REM. The reflected radiation near this interval and the corresponding spectra will be amplified due to the resonance. Through adjusting the arriving time of the probe laser, certain part of the reflected field could be selectively amplified or depressed, leading to the selectively adjusting of the corresponding spectra.

All-fiber phase modulator and switch based on local surface plasmon resonance effect of the gold nanoparticles embedded in gel membrane.

All-fiber modulators and switches have drawn great interest in the photonics domain, and they are applied in viable photonic and optoelectronic devices. In this work, with the assistance of an agarose membrane, aspherical gold nanoparticles are embedded on the surface of the microfiber treated with the piranha solution. An all-fiber Mach-Zehnder interferometer was used to realize a low-cost, low-loss, and conveniently prepared all-fiber phase modulator. By taking advantage of the local surface plasmon resonance effect of gold nanoparticles embedded in the agarose membrane, under the excitation of near-infrared region light, the gold nanoparticles were excited to change the effective refractive index of one arm of the Mach-Zehnder interferometer. A maximum phase shift of ∼6π at 1550 nm was obtained from the device. In addition, an all-optical switch was achieved with a rising edge time of 47 ms and falling edge time of 14 ms. The proposed all-fiber modulator and switch based on the local surface plasmon resonance effect of gold nanoparticles embedded in agarose membrane will provide great potential in all-optical fiber systems.

Fluid simulation model and analysis of partial discharge characteristics of tip defects

The tip discharge is modeled and the micro discharge characteristics are studied. The hydrodynamic model of tip discharge in transformer oil is established. The development process of streamer discharge under pulse voltage is analyzed. The distribution of space charge density and space electric field under different pulse voltage amplitude and rising edge is obtained. The numerical results show that: with the increase of applied voltage amplitude, the average velocity of streamer development changes more significantly with the same discharge spacing; the steeper the rising edge pulse is, the faster the average discharge development speed is and the larger the discharge radius is. At the same time, according to the change law of streamer morphology development under AC voltage, the discharge frequency is less, the amplitude is higher, and the phase distribution is narrow when the applied voltage is positive half cycle. When the applied voltage is negative half cycle, the discharge times are more and the phase distribution is wide, and the tip discharge has obvious polarity effect.

Study on inertial characteristics of photoresistors in a physical workshop

The article describes a measuring complex based on the 32-bit STM32F103VET6 microcontroller for studying the lux-ampere (light), frequency and inertial characteristics of a photoresistor with different laws of recombination of nonequilibrium charge carriers arising under the influence of light. The developed complex is connected to a personal computer (smartphone) and allows to analyze the rise and fall edges of the photoresistor current, as well as to determine the lifetime of excess charge carriers at different illumination levels. Unlike traditional methods for measuring the parameters of photoresistors operating in a dynamic mode, the proposed measuring complex does not use an oscilloscope and a separate modulator of the luminous flux (generator or light interrupter), this made it possible to significantly reduce the size and cost of the complex, as well as automate the measurement process. To determine the frequency response of the photoresistor, it is proposed to use a frequency synthesizer, which allows, together with a digital-to-analog converter of the microcontroller, to form an amplitude-modulated light flux of the required frequency and modulation depth. The complex described in the work can be connected to the Internet using a Wi-Fi module based on an ESP8266 microcontroller, which allows conducting research in a remote mode. It is also possible to determine the parameters of the photoresistor at different values of the load resistance.

Development of a five-stage solid-state linear transformer driver.

In this paper, the development of a five-stage solid-state linear transformer driver (LTD) is described. Each stage consists of eight compact pulse generating modules and a magnetic core. The pulse generating modules contain a multilayer-ceramic-capacitor-based pulse-forming network (PFN) and an insulated-gate bipolar transistor (IGBT) switch array, as well as magnetic switches, which are used to speed up the pulse front. To prevent damage from the reverse voltage to the IGBT switch, a reverse voltage absorption circuit was added to the PFN. For this study, a larger cross-sectional core with improved output characteristics was adopted. The developed five-stage LTD has the advantages of long life, low jitter, fast rising edge, and so on. The device can provide a 35 kV, 119 ns, 4.3 kA square pulse train with a maximum frequency of 50 Hz. On this basis, a 50-stage LTD of output 500 kV, which would serve as a high-power microwave driver source, is under development.

Layout and performance of HPK prototype LGAD sensors for the High-Granularity Timing Detector

The High-Granularity Timing Detector is a detector proposed for the ATLAS Phase II upgrade. The detector, based on the Low-Gain Avalanche Detector (LGAD) technology, will cover the pseudo-rapidity region of 2.4<|η|<4.0 with two end caps on each side and a total area of 6.4 m2. The timing performance can be improved by implanting an internal gain layer that can produce signals with a fast rising edge. It significantly improves the signal-to-noise ratio. The required average timing resolution per track for a minimum ionizing particle is 30 ps at the start and 50 ps at the end of the HL-LHC operation. This is achieved with several layers of LGAD. The innermost region of the detector would accumulate a 1MeV neutron-equivalent fluence up to 2.5× 1015 neq/cm2 including a safety factor of 1.5 before being replaced during the scheduled shutdowns. The addition of this new detector is expected to play an important role in the mitigation of high pile-ups at the HL-LHC. The layout and performance of the various versions of LGAD prototypes produced by Hamamatsu (HPK) have been studied by the ATLAS Collaboration. The breakdown voltages, depletion voltages, inter-pad gaps, collected charge as well as the time resolution have been measured and the production yield of large size sensors has been evaluated.

Estimation of Machine Parameters in Superconducting Transformer using Differential Evolution

To analyze the inrush current in a superconducting transformer, the machine parameters for the transformer were estimated from the measured current using a search algorithm. To address the large rising edge error in estimations performed using a genetic algorithm (GA), a differential evolution (DE) was used in this study. As a result, the estimated time was reduced to about 1/10 that obtained with GA, and the evaluation value indicating the difference between the measured value and the estimated value was reduced to about 1/2. Thus, it was possible to estimate with higher accuracy by using DE.

Selective amplification of the chirped attosecond pulses produced from relativistic electron mirrors

AbstractIn this paper, the generation of relativistic electron mirrors (REM) and the reflection of an ultra-short laser off the mirrors are discussed, applying two-dimension particle-in-cell simulations. REMs with ultra-high acceleration and expanding velocity can be produced from a solid nanofoil illuminated normally by an ultra-intense femtosecond laser pulse with a sharp rising edge. Chirped attosecond pulse can be produced through the reflection of a counter-propagating probe laser off the accelerating REM. In the electron moving frame, the plasma frequency of the REM keeps decreasing due to its rapid expansion. The laser frequency, on the contrary, keeps increasing due to the acceleration of REM and the relativistic Doppler shift from the lab frame to the electron moving frame. Within an ultra-short time interval, the two frequencies will be equal in the electron moving frame, which leads to the resonance between laser and REM. The reflected radiation near this interval and corresponding spectra will be amplified due to the resonance. Through adjusting the arriving time of the probe laser, a certain part of the reflected field could be selectively amplified or depressed, leading to the selective adjustment of the corresponding spectra.

Magnetoacoustic position imaging for liquid metal in animal interstitial structure**Project supported by the National Natural Science Foundation of China (Grant Nos. 61771448, 61427806, and 51937010), the National Key Research and Development Program of China (Grant No. 2018YFC0115200), and the Natural Science Fund from the Chinese Academy of Sciences (Grant Nos. ZDKYYQ20190002 and YJKYYQ20190005).

Magnetoacoustic tomography with magnetic induction (MAT-MI), as a new kind of in-vivo imaging method, has potential application value in interstitial fluid research. In this paper, we propose the application of MAT-MI with liquid metal serving as a tracer of the interstitial structure to study its fluid behavior, and use it to implement the positional imaging of the spatial distribution of liquid metal. Owing to the particularity of liquid metal magnetoacoustic pressure (MAP) signals, we propose an envelope analysis method to extract the rising edge of the amplitude envelope of the detected waveform as effective position data. And for the first time, we propose the method of superpositing pixel matrix to achieve the position imaging of liquid metal. Finally, the positional imaging of the liquid metal sample embedded in the gel is achieved to have relatively accurate results. This study provides a method of effectively extracting data and implementing the position imaging for liquid metal in the interstitial structure in the frame of MAT-MI.

Theoretical Analysis of Fe K-Edge XANES on Iron Pentacarbonyl.

Iron pentacarbonyl (Fe(CO)5) is a versatile material that is utilized as an inhibitor of flame, shows soot suppressibility, and is used as a precursor for focused electron-beam-induced deposition (FEBID). X-ray absorption near-edge structure (XANES) of the K edge, which is a powerful technique for monitoring the oxidation states and coordination environment of metal sites, can be used to gain insight into Fe(CO)5-related reaction mechanisms in in situ experiments. We use a finite difference method (FDM) and molecular-orbital-based time-dependent density functional theory (TDDFT) calculations to clarify the Fe K-edge XANES features of Fe(CO)5. The two pre-edge peaks P1 and P2 are mainly the Fe(1s) → Fe–C(σ*) and Fe(1s) → Fe–C(π*) transitions, respectively. When the geometry transformed from D3h to C4v symmetry, a ∼30% decrease of the pre-edge P2 intensity was observed in the simulated spectra. This implies that the π bonding of Fe and CO is sensitive to changes in geometry. The following rising edge and white line regions are assigned to the Fe(1s) → Fe(4p)(mixing C(2p)) transitions. Our results may provide useful information to interpret XANES spectra variations of in situ reactions of metal–CO or similar compounds with π acceptor ligandlike metal–CN complexes.

Polarity effect of PD in oil-pressboard insulation under highly uneven electric field

The polarity effect of the partial discharge (PD) in oil-pressboard (oil-PB) insulation under a highly non-uniform electric field is remarkable. For intensive analysis of the characteristics and mechanisms of this polarity effect, a non-uniform electric field was simulated by a needle-plate model with oil-PB composite insulation. The PD statistical features, PD pattern and PD pulse were studied via pulse current method, the charge distribution was simulated on the basis of hydrodynamic drift-diffusion model and bipolar charge transport model, and the cause of the polarity effect was analysed based on the PD mechanism which is quantificationally explained via a PD circuit model. It was found that the average apparent discharge amplitude and PD repetition rate of the neg-PD are higher; the average equivalent frequency and equivalent time of neg-PD are higher and lower respectively; the pos-PD pulse is unimodal and the neg-PD pulse is oscillating with some secondary discharges at AC voltage or a back discharge at DC voltage; and the neg-PD pulse has a narrower width owning to the fast rising edge and falling edge. The PD current pulse in the coupling loop is essentially caused by the charging process of the streamer-shorted defect. The cause of the polarity effect is that the positive streamer evolves slowly and can puncture the entire oil gap with an energy-concentrated channel, whereas the negative streamer with a diffused channel evolves faster but cannot puncture the entire oil gap.

A Rising Edge-Based Detection Algorithm for MIMO Molecular Communication

In this letter, we propose a low-complexity detection algorithm for multi-input-multi-output (MIMO) molecular communication (MC). By virtue of a rising edge in received signals, this detection algorithm is capable of recovering the information bits in MIMO-MC systems. From an engineering point of view, this algorithm can significantly eliminate the impact of inter-symbol interference. It has also proven itself useful for dealing with the received signal from the MIMO-MC testbed with sufficiently low bit error rate (BER) or even an error-free performance. Moreover, in terms of BER performance, this algorithm outperforms existing detection algorithms for single-input single-output MC systems.

Methodology for Digital Synthesis of Deterministic and Random Jitter Generation on Rising or Falling Edges of Data Pattern

Jitter is becoming an important factor in high-speed serial link and integrated circuits (ICs). Generating controllable jitter plays a crucial role in simulating the test environment of high-data links, evaluating the performance of IC, preventing jitter in high-speed serial link, and even testing the synchronous trigger circuit. In this paper, a digital synthesis for jitter generation and a logical combination method for selecting jitter on the rising edge or falling edge of a data pattern are presented. Precisely controllable jitter is generated by digital synthesis, including sinusoidal period jitter, rectangular period jitter, duty cycle distortion (DCD) jitter, and adjustable random jitter. Additionally, the validity and accuracy of the proposed method were demonstrated by hardware experiments, where the jitter frequency had an accuracy of ±30 ppm and the jitter amplitude had a step of 2 ps.

Control Strategy to Generate PWM Signals with Stability Analysis for Dual Input Power Converter System

The prime role of a renewable resource based DC hybrid power system is, to maintain the output voltage constant with higher efficiency. In order to achieve this the duty cycles of the converter switches are dynamically controlled. Multiple input single output (MISO) converter uses separate controller for adjusting the duty cycle, this complicates the design and implementation of the system. Hence, to overcome this limitation a centralized controller is used. The control strategy depends on the pattern of gating signals given to the converter switches. When independent controller is employed, then gating signals of any pattern can be used to drive the switches. However, if a single controller is used, and then a definite pattern is very much essential otherwise, the output voltage and efficiency gets affected. In this paper, an attempt is made to validate and evaluate the performance parameters of MISO converter with two pattern of gating signals; they are synchronized and unsynchronized pulses at their rising edge. The control strategy focusses on the generation of these gating pulses. PID controller is tuned appropriately to determine the gains to achieve the stability of the proposed converter. The dual input power converter validated to show how the PWM pattern affects the efficiency, ripple and regulation of the converter. Using MATLAB SIMULINK platform the simulation of the proposed concept with dual input converter in closed loop is validated. Simulation results proves that synchronized pulses gives DC efficiency of 87% at designed output of 12V output. Converter with unsynchronized PWM pulses operates at lesser efficiency of 75% and the output voltage is of 10V.