DC Voltage Signal Research Articles

A low-cost optical transducer utilizing common electronics components for the gold nanoparticle-based immunosensing application

We developed a cost-effective and convenient optical transducing platform for use in gold nanoparticle-based immunosensing applications. Two types of gold nanoparticles were prepared and used as optical signaling probes: spherical gold nanoparticles (GNPs) exhibiting maximal absorbance at 519nm and gold nanorods (GNRs) exhibiting maximal absorbance at 620nm. Common components used in electronics, including two types of laser diodes (λmax=532- and 635-nm), solar cells, and a multimeter, were reassembled to construct the optical transducing platform. Under the condition in which the emission spectra of lasers and the absorption spectra of gold nanoparticles are matched, laser intensity is decreased. In the designed transducing system, these changes in light intensity are directly indicated as alterations in the DC voltage signal. Based on this principle, we demonstrated the immunosensing applicability of the optical transducing platform. As model immunoreaction pairs, we used anti-mouse IgG/mouse IgG and anti-human IgG/human IgG; superparamagnetic microparticles (MPs) were conjugated with capture antibodies (anti-mouse IgG and anti-human IgG) and the GNPs and GNRs were conjugated with the target mouse IgG and human IgG (model antigens). When the capture antibody-modified MPs and the optical probes mixed in the platform's reaction channel, the optical probes bound to the MPs through an affinity-based reaction. Under a magnetic field, the biospecifically conjugated MP/GNP and MP/GNR complexes could be localized in the reaction channel. Consequently, the amounts of the GNPs and GNRs remaining in the solution were inversely proportional to the rate of the MP/GNP and MP/GNR reactions, and could be registered as DC voltage signals. Based on these results, we expect the novel transducing system and immunosensing strategy presented herein to be applied in practical optical immunosensing performed using key disease markers and their antibodies.

The Design of the Elevator Remote Monitoring System Based on GSM

To solve the sudden of the operational failure of the elevator, uncertainties of the failure and the lower reliability duo to maintenance personnel non-standard operation, we design and implement a system of the elevator secure remote monitoring which based on GSM wireless communications. The terminal of the system regards GSM wireless communication module as a main control unit, which meanwhile has the reliable wireless five-party call subsystem and UPS function. The system, mainly through a wide range of AC and DC voltage signal acquisition unit and RFID radio frequency module monitors the elevator’s various of state, and records maintenance personnel’s information. All information transmitted by GPRS and display in the terminal. Experiments show that this system is stable and reliable and has a good compatibility, which truly achieves the real-time of the failure information feedback, reduces the blindness of the troubleshooting, and has a broad market.

Noise activated dc signal sensor based on chaotic Chua circuit

The noise activated dc voltage signal sensor based on Chua’s electronic circuit made from standard electronic components and operating in the chaotic regime where two single scroll attractors coexist is proposed. The crossings between attractors are driven only by the Gaussian noise. The unknown dc target signal is detected and measured via the monitoring of the residence time proportion the sensor stays in one of the two attractors. The dependence of the output time proportion on the input dc target signal voltage and the noise intensity were obtained performing computer simulations. The optimal noise intensity range for detection is indicated and the dependence of the measurement error on the observation time in this range is obtained. The nearly linear output–input relation for the optimal noise level is found.

Design and optimization of piezoelectric impact-based micro wind energy harvester for wireless sensor network

The purpose of the current study is to design and optimize a piezoelectric impact-based micro wind energy harvester (PIMWEH) as a power source for wireless sensor networks. First, using new PIMWEH design, numerical simulation, and experimental comparison analysis, we determined the most durable PIMWEH shape for application as a power source of WSNs. The experimental results show that the optimized PIMWEH generated 2.8mW (RMS value) and did not crack within 40h. Second, to supply power for sensor operation, we performed an experiment using a rectifying circuit, an AC–DC converter, and an electrical charger. The experimental results show a pure DC voltage signal of 3.3V, and the output power was 1.0mW (3.1mW/cm3). A charging energy of 0.845J was obtained in 24min. Third, we calculated the efficiency of the PIMWEH to evaluate its performance. Using a three-step energy conversion process (using wind turbine, PZT, and LTC3588-1), an overall PIMWEH power conversion efficiency of 3.2% was obtained. For one day, the PIMWEH could supply power that is 6263–25055 times the power requirement of a commercialized ZigBee transmission. In addition, transmitting signals at intervals from 3.4 to 13s was made possible.

Abnormal spin-pumping effect at Pt/NiFe interface by an oxidation of ferromagnet

The Inverse Spin Hall Effect (ISHE) voltage induced by spin-pumping was measured in Pt/[nonoxidized or oxidized NiFe] samples. The spectrum shape of the DC voltage signal was well-reproduced by simple Lorentzian functions, which were consistent with the prediction of ISHE in Pt/nonoxidized NiFe sample. On the other hand, the voltage signal from the Pt/oxidized NiFe was significantly decreased in accordance with abnormal ferromagnetic resonance (FMR) behavior. The origin of the ISHE voltage degradation was investigated by the FMR spectrum and X-ray photoelectron spectroscopy (XPS) analyses. The spin-pumping was suppressed by the oxidation of NiFe layer and deficient Pt/NiFe interface. The well-defined ferromagnet and clear interface with a normal spin mixing conductance were experimentally demonstrated to be reasonable spin-pumping.

A single-ended fault location method for segmented HVDC transmission line

This paper presents a single-ended traveling wave-based fault location method for segmented high voltage DC (HVDC) transmission lines; an overhead line combined with an underground cable. DC transient voltage and current signals at the sending-end of the overhead line are assumed to be available. Discrete Wavelet Transformation (DWT) is then applied to the DC voltage and current signals. The wavelet energies of voltage and current transients over 16ms (i.e. 1-cyle in 60-Hz frequency) are calculated and then normalized. The normalized energies are used as the input to a binary Support Vector Machine (SVM) classifier for faulty section identification (underground cable or overhead line). Once the faulty section is identified, the faulty-half is determined by comparing polarity of the first two current traveling waves. Bewley diagrams are finally observed for the traveling wave pattern and the wavelet coefficients squared of DC voltage are used to locate the fault. The transient voltage and current for different fault locations are simulated using the ATP software. MATLAB is used to process the simulated transients and apply the proposed method. The performance of the proposed method is evaluated for different fault locations and fault resistances. The impacts of non-linear high impedance faults (NLHIF) and cable aging are also studied.

Double resonance response in nonlinear magnetic vortex dynamics

We present experimental evidences for the dynamical bifurcation behavior of ac-driven magnetic vortex core gyration in a ferromagnetic disk. The dynamical bifurcation, i.e., appearance and disappearance of two stable dynamical states in the vortex gyration, occurring as the amplitude of the driving Oersted field increases to ${B}_{Oe}>{B}_{Oe}^{cr}$, manifests itself in a double resonance response in the dependence of homodyne the dc-voltage signal on the frequency $\ensuremath{\omega}$ of the applied microwave current. We find that the frequency range $\ensuremath{\delta}\ensuremath{\omega}$ between the two resonance features strongly increases with the excitation power. Our analysis based on the model of a low dissipative nonlinear oscillator subject to a resonant alternating force is in good agreement with the experimental results. This allows us to determine quantitatively key parameters of magnetic vortex dynamics, i.e., the critical value of the driving Oersted field ${B}_{Oe}^{cr}$ for nonlinear dynamics to occur, the resonant frequency, and the quality factor as well as damping of the magnetic vortex gyration.

Study on Electrical Automation with Design of the PWM Signal Generator Based on MSP430

The PWM signal generator, in which the DC voltage, sine AC or arbitrary waveform signal can be the base wave to control the duty cycle, is designed in this paper. The high-speed comparator modulates the two signals, one is the base wave signal generated by MSP430F169 and the other one is the PWM modulated wave signal generated by the voltage controlled oscillator, and then generates the PWM signal. The frequency of the PWM signal can be regulated, the frequency and waveform of the base wave can be programmed and the three-phase SPWM signal can be generated. The PWM signal generator can be applied in the field of converting technology in power electronics and electrical automation.

Spintronic microwave imaging

By using an on-chip microwave sensor employing spintronic and spin caloritronic principles, a spintronic technique has been developed for microwave imaging. This novel technique allows microwave fields to be directly rectified on chip into dc voltage signals. This imaging technique does not require complicated and expensive microwave systems to operate, yet it can still electrically detect scattered microwave fields accurately enough to image embedded defects and hidden objects. By varying the experimental setup, apparatuses based on spintronic sensors have been developed for achieving both near- and far-field imaging (at microwave frequencies) as well as for performing on-chip dielectric analysis.

Microwave reflection imaging using a magnetic tunnel junction based spintronic microwave sensor

A far-field microwave imaging technique has been developed using a spintronic sensor based on a magnetic tunnel junction (MTJ). Such a sensor can directly rectify a microwave field into a dc voltage signal using the Seebeck effect. Thanks to the high conversion efficiency of the microwave rectification in MTJs, the microwave power sensitivity of the spintronic sensor is on the order of 1–10 mV/mW. This high sensitivity allows the sensor to directly measure the coherent spatial scattered microwave field distribution, which gives it the ability to non-destructively detect hidden objects down to a few wavelengths in size.

Nondestructive two-dimensional phase imaging of embedded defects via on-chip spintronic sensor

A microwave near field phase imaging technique has been achieved by an on-chip spintronic sensor. The sensor directly rectifies a microwave field into a dc voltage signal by employing the spintronic principle, in which the relative phase between microwave electric and magnetic fields plays an important role. By manipulating the relative phase, the sensor can nondestructively detect embedded defects of subwavelength size.

Charge pumping by magnetization dynamics in magnetic and semimagnetic tunnel junctions with interfacial Rashba or bulk extrinsic spin-orbit coupling

We develop a time-dependent nonequilibrium Green function (NEGF) approach to the problem of spin pumping by precessing magnetization in one of the ferromagnetic layers within F$|$I$|$F magnetic tunnel junctions (MTJs) or F$|$I$|$N semi-MTJs in the presence of intrinsic Rashba spin-orbit coupling (SOC) at the F$|$I interface or the extrinsic SOC in the bulk of F layers of finite thickness (F, ferromagnet; N, normal metal; I, insulating barrier). To express the time-averaged pumped charge current, or the corresponding dc voltage signal in an open circuit, we construct a novel solution to double-time-Fourier-transformed NEGF equations. The two energy arguments of NEGFs in this representation are connected by the Floquet theorem describing multiphoton emission and absorption processes. Within this fully quantum-mechanical treatment of the conduction electrons, we find that (i) only in the presence of the interfacial Rashba SOC, the nonzero dc pumping voltage ${V}_{\mathrm{pump}}$ in F$|$I$|$N junctions can emerge at the adiabatic level (i.e., proportional to the microwave frequency), which could explain recent experiments on microwave-driven semi-MTJs [T. Moriyama et al., Phys. Rev. Lett. 100, 067602 (2008)]; (ii) a unique signature of this charge pumping phenomenon, where the Rashba SOC within the precessing F layer participates in the pumping process, is a ${V}_{\mathrm{pump}}$ that changes sign as the function of the precession cone angle; (iii) unlike conventional spin pumping in MTJs in the absence of any SOC, where one emitted or absorbed microwave photon is sufficient to match the exact solution in the frame rotating with the magnetization, the presence of the Rashba SOC requires taking into account up to 10 photons in order to reach the asymptotic value of pumped charge current; (iv) the disorder within F$|$I$|$F MTJs can enhance ${V}_{\mathrm{pump}}$ in the quasiballistic transport regime; and (v) the extrinsic SOC in F$|$I$|$F MTJs causes spin relaxation and eventually the decay of ${V}_{\mathrm{pump}}$, which becomes negligible when the ratio of F layer thickness to the spin-diffusion length is around five. Our formalism can also be applied to charge and spin propagation in any noninteracting open quantum system that is brought out of equilibrium by time-dependent periodic external fields of arbitrary strength or frequency.

The Design of Power Supply and Distribution Real-Time Monitoring System Based on PXI Bus for Telemetering System

Telemetering power supply and distribution system is an important part of the telemetry system. Arming at a telemetering power supply and distribution system, this paper adopts digital multimeter and multiplex switch based on PXI bus to realize 32-channel power supply and distribution DC voltage signal acquisition, storage, real-time monitoring and analysis, and also automatic data interpretation. The system consists of PXI host, multiplex switch, digital multimeter, interface unit, a control software and so on, which has the advantages of high precision, high efficiency, easy to operate, and has been used successfully in the test of a telemetry system.

The Research on Inductive Gas Rotameter Transmission System

The glass tube rotameter is usually used only for site instructions, without remote transmission. In this paper, the inductance sensor detects the float's displacement, with the coil around the inner tube, core installed on the float. As a result, the displacement of the float caused by the flow can reflect the inductor changes. It turns the inductance changes to voltage amplitude changes through the three-point capacitance oscillator circuit, and we can get the DC voltage signal by filtering the sine wave through high-frequency filter circuit. After sampling process in AD converter, the output voltage can be measured. Based on the relationship between voltage and inductance, and inductance and flow, we can program in the MSP430 to get flow. The realization of non-electrify electrometric measurement by transforming float displacement changes to inductance changes improves the measurement accuracy, and achieves the remote transmission by precision current transmitter.

The liquid nitrogen fill level meter for the AGATA triple cluster detector

A novel liquid nitrogen fill level meter has been put into operation for the all-position dewar of the triple cluster detector of the Advanced GAmma Tracking Array. The new device is based on a capacitance measurement between a metallic cylindrical tube inside the dewar and the inner wall of the cryostat. The fill level dependent capacitance is converted by a C/ V-transducer into a DC voltage signal. Direct monitoring of the LN 2 level inside the detector dewar has been performed with several AGATA detectors at various inclinations and rotation angles of the detector axis. The time-dependent LN 2 consumption is an additional quantity used to survey the status of the cryostat. Supplementary results are the investigations of the LN 2 consumption and the heat loss of the detector during different modes of operation.

Tunnel-barrier-enhanced dc voltage signals induced by magnetization dynamics in magnetic tunnel junctions

We theoretically study the recently observed tunnel-barrier-enhanced dc voltage signals generated by magnetization precession in magnetic tunnel junctions. While the spin pumping is suppressed by the high tunneling impedance, two complementary processes are predicted to result in a sizable voltage generation in ferromagnet $(\text{F})|\text{insulator}\phantom{\rule{0.3em}{0ex}}(\text{I})|\text{normal}\phantom{\rule{0.3em}{0ex}}\text{metal}\phantom{\rule{0.3em}{0ex}}(\text{N})$ and $\text{F}|\text{I}|\text{F}$ junctions with one ferromagnet being resonantly excited. Magnetic dynamics in $\text{F}|\text{I}|\text{F}$ systems induce a robust charge pumping, translating into voltage in open circuits. In addition, dynamics in a single ferromagnetic layer develop longitudinal spin accumulation inside the ferromagnet. A tunnel barrier then acts as a nonintrusive probe that converts the spin accumulation into a measurable voltage. Neither of the proposed mechanisms suffers from spin relaxation, which is typically fast on the scale of the exponentially slow tunneling rates. The longitudinal spin-accumulation buildup, however, is very sensitive to the phenomenological ingredients of the spin-relaxation picture.

Study on estimation of rotor position of self-sensing active magnetic bearings

The self-sensing principle of self-sensing active magnetic bearings(SSAMBs) is introduced, and a self-sensing configuration based on the current amplitude modulation is explored. The inductance coefficient is the function of rotor displacement, so the voltage of the electromagnetic coil is the function of rotor displacement too. Add a high-frequency signal to the input of linear power amplifier for amplitude modulation, and then let the coil voltage go through the syntony circuit to extract the high-frequency voltage signal containing the displacement signal and perform demodulation. After commutating the demodulated voltage signal, the pulsed DC voltage signal is gained. Lastly, through the lowpass, the smooth DC voltage signal reflecting the rotor displacement is gained. Convert this signal to feedback signal to control the rotor position. Simulations are completed, and the results show that this system is successful in sensing the rotor position and this approach is feasible.

Data reduction in the ITMS system through a data acquisition model with self-adaptive sampling rate

Long pulse or steady state operation of fusion experiments require data acquisition and processing systems that reduce the volume of data involved. The availability of self-adaptive sampling rate systems and the use of real-time lossless data compression techniques can help solve these problems. The former is important for continuous adaptation of sampling frequency for experimental requirements. The latter allows the maintenance of continuous digitization under limited memory conditions. This can be achieved by permanent transmission of compressed data to other systems. The compacted transfer ensures the use of minimum bandwidth. This paper presents an implementation based on intelligent test and measurement system (ITMS), a data acquisition system architecture with multiprocessing capabilities that permits it to adapt the system's sampling frequency throughout the experiment. The sampling rate can be controlled depending on the experiment's specific requirements by using an external dc voltage signal or by defining user events through software. The system takes advantage of the high processing capabilities of the ITMS platform to implement a data reduction mechanism based in lossless data compression algorithms which are themselves based in periodic deltas.

Properties of vortex propagation in a niobium film with spacing-graded density of pinning sites

The vortex propagation has been investigated in Nb superconductors with one dimension spacing-graded density of submicrometer-scaled holes in this research. A rectification effect can be discerned because the applied ac is transformed into a net dc voltage. These results demonstrate that the rectification is mainly characterized by the asymmetric pinning landscape and the rectified voltage depends considerably on temperature and the amplitude of applied ac. The dc voltage increases steeply up to the maximum value and then decreases to zero dc voltage with the increase of ac. The shape of peaks in the dc voltage signal become steeper and move to higher applied ac regime with the decrease of temperature.

Current-driven ferromagnetic resonance, mechanical torques, and rotary motion in magnetic nanostructures

We study theoretically the detection and possible utilization of electric current-induced mechanical torques in ferromagnetic--normal-metal heterostructures generated by spin-flip scattering or the absorption of transverse spin currents by a ferromagnet. To this end, we analyze the dc voltage signals over a spin valve driven by an ac current. In agreement with recent studies, this ``rectification,'' measured as a function of ac frequency and applied magnetic field, contains important information on the magnetostatics and magnetodynamics. Subsequently, we show that the vibrations excited by spin-transfer to the lattice can be detected as a splitting of the dc voltage resonance. Finally, we propose a concept for a spin-transfer-driven electric nanomotor based on integrating metallic nanowires with carbon nanotubes, in which the current-induced torques generate a rotary motion.