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Recording both Electromyographic (EMG) and temporo-mandibular joint (TMJ) sounds using surface (SEMG) and intramuscular electrodes can prove to be extremely beneficial for both dental research and clinics. SEMG can provide a comprehensive overview, while needle EMG can be used to analyze the functioning of a specific muscle or muscle component. Amplifiers should have various power level options and a flat frequency response. When using needle electrodes for EMG recording, it is crucial to have a sampling rate of at least 10,000 Hz to capture the necessary waveforms. [ABSTRACT FROM AUTHOR]

For heat assisted magnetic recording (HAMR) media development, measurement of erasure temperature (Te) is interesting and important for practical HAMR testing and applications. Here, we present an investigation on Te measurements of L10 ordered FePt granular HAMR media made using a Laser Heating (LH) method on a home-built HAMR write test system versus that from a bulk heating approach. The HAMR write test system provides HAMR writing, micro-MOKE (magneto- optical Kerr effect) signal detection, and MOKE imaging functions at the same testing spot in one single system. Magnetic force microscopy (MFM) and magnetic Kerr microscopy observations of the scanning laser induced degradation/erasure/demagnetization of the pre-recorded magnetic patterns on disk media (over a wide area of a few hundreds of μm2) show that the magnetic (MFM and Kerr signal) amplitude of the pre-recorded magnetic patterns decreases slowly with increasing laser power (Pw) (/temperature rise) for Pw≲66 mW and then drops sharply to nearly zero for Pw⩾~72 mW (the laser power corresponding to complete thermal erasure when the media temperature is ~Te). It was further found that this trend of magnetic amplitude reduction with increased Pw is similar to that from magnetic amplitude decrease of pre-recorded magnetic patterns with increased bulk heating temperature. The temperature for complete erasure at laser power, Pw=72 mW for the LH method, corresponds therefore to ~650K (≈Te) for the bulk heating methods. Besides fast measurement, LH (as a comparable and viable approach for erasure measurement) is dynamic, localized, and has time scales closer to practical HAMR situation. [ABSTRACT FROM AUTHOR]

Parametric transformers are magnetic components which employ a variable inductance to generate parametric oscillations in a secondary resonant tank. Power conversion with parametric transformer can provide constant output voltage regulation, short‐circuit protection, input over‐voltage and under‐voltage protection, and bidirectional filtering. In spite of these benefits, parametric transformers did only experience small scientific attention during the 1970s. Due to the low energy density and low efficiency of the topologies developed at the time, parametric transformers were discarded in favour of the more common power converters based on the magnetic amplifier. In spite of the great developments in power semiconductors, magnetic amplifier control still remains a competitive option in present‐day power electronic applications benefiting from its high robustness. This publication presents a new topology of parametric transformer based on permanent magnet (PM)‐inductors, presenting higher efficiency and higher energy density. Finite element method magnetics simulations are used to analyse the variable inductance mechanisms. A physical prototype is developed and tested empirically in an AC/DC power converter. The prototype verifies all the mentioned benefits of parametric power conversion, and presents an efficiency and energy density equivalent to presently employed solutions for voltage regulation, using power semiconductor magnetic amplifiers. [ABSTRACT FROM AUTHOR]

We have investigated characteristics of THz waves generated by using a regenerative amplifier in InN micropyramids. Our experimental results indicate that when the density of the micropyramids becomes sufficiently high, the THz output power is dramatically enhanced. In comparison, the PL intensity stays more or less a constant regardless of the density. By measuring the dependences of the THz output power and polarization on the incident angle and pump polarization angle, we have deduced the contributions to the THz output powers from optical rectification and photocurrent surge. [ABSTRACT FROM AUTHOR]

Cooperative interactions of signal transduction and environmental noise are investigated with a coupled hormone system, in which selective explicit internal signal stochastic resonance (EISSR) is observed. More specifically, the large peak of a period-2 oscillation (i.e., a strong signal) is greatly amplified by the environmental noise while the small peak (i.e., a weak signal) does not exhibit cooperative interactions with noise. The EISSR phenomenon could be controlled by adjusting the frequency or amplitude of an external signal and a critical amplitude for external signal is found. Significantly, the maximal signal-to-noise ratio increases almost linearly with the increment of control parameter, despite that the magnitude of the large peak is decreased. In addition, the noise does not alter the fundamental frequencies of the strong signal and the weak signal, which implicates that the system can keep its intrinsic oscillatory state and resist the effect of environmental fluctuations. [ABSTRACT FROM AUTHOR]

Disclination loops threaded on a polymeric fiber with planar axial anchoring are shown to be sensitive to magnetic fields. In particular, a homogeneous magnetic field oblique to the fiber drives translation of disclination loops along it. The velocity of translation depends on the intensity of the field and on the angle between the field and the fiber. It is shown experimentally that an inhomogeneous magnetic field of an appropriate geometry can act as a trap for disclination loops. When such a magnetic trap is translated along the fiber, it drags the loop with it and therefore acts as magnetic tweezers. Theoretical model of the translational stability of disclination loops in magnetic fields is proposed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pre-equalization corrects eddy current effects from pulsed field gradients. • Total experiment time is significantly reduced compared to previous correction method. • Pre-equalized, motion-sensitized pulse sequences produce accurate velocity maps. Abstract Eddy currents caused by pulsed field gradients in magnetic resonance measurements of high-speed flow cause the magnetic field gradient amplitude waveform experienced by the sample to be different from the waveform demanded of the magnetic field gradient amplifiers. By measuring and using the system impulse response, pre-equalization magnetic field gradient waveform correction can be used to counteract the resulting errors in measured signal phase at the cost of minimal additional experimental time. The effectiveness of the pre-equalization method of magnetic field gradient waveform correction is tested with a motion-sensitized (pulsed field gradient) version of the SPRITE imaging pulse sequence which requires extreme gradient slew rates in excess of 1000 T/m/s in a 6.7-cm-bore set of gradient windings. Pre-equalized, motion-sensitized SPRITE is used to create velocity maps of high-speed (c. 4 m/s) water flow through a pipe constriction. [ABSTRACT FROM AUTHOR]

The manifestations of the three laws of thermodynamics are explored in a model of an irreversible quantum heat engine. The engine is composed of a three-level system simultaneously coupled to hot and cold heat baths, and driven by an oscillating external field. General quantum heat baths are considered, which are weakly coupled to the three-level system. The work reservoir is modeled by a classical electro-magnetic field of arbitrary intensity, which is driving the three-level system. The first law of thermodynamics is related to the rate of change of energy obtained from the quantum master equation in the Heisenberg picture. The fluxes of the thermodynamic heat and work are then directly related to the expectation values of quantum observables. An analysis of the standard quantum master equation for the amplifier, first introduced by Lamb, is shown to be thermodynamically inconsistent when strong driving fields are used. A generalized master equation is rigorously derived, starting from the underlying quantum dynamics, which includes relaxation terms that explicitly depend upon the field. For weak fields the generalized master equation reduces to the standard equation. In very intense fields the amplifier splits into two heat engines. One engine accelerates as the field intensifies, while the other slows down and eventually switches direction to become a heat pump. The relative weight of the slower engine increases with the field intensity, leading to a maximum in power as a function of the field intensity. The amplifier is shown to go through four ‘‘phases’’ as the driving field is intensified, throughout all of which the second law of thermodynamics is generally satisfied. One phase corresponds to a ‘‘refrigeration window’’ which allows for the extraction of heat out of a cold bath of temperatures down to the absolute zero. This window disappears at absolute zero, which is conjectured to be a dynamical... [ABSTRACT FROM AUTHOR]

The article provides an overview of the rise of ASynchronous OPtical Sampling (ASOPS) technology as multiphysics measurement standard. It mentions that the ASOPS systems are fitted with ultrafast lasers as the frequencies cannot be generated having standard transductors. The system of ASOPS can go beyond the picosecond ultrasonics and obtain more from raw data such as critical mechanical parameters or thermal information.

This paper proposes and analyzes the design philosophies of the single-phase main exciter (ME) for an aircraft wound-rotor synchronous machine and investigates its operating characteristics in both generating and starting modes. The fundamental structure and starting–generating system are discussed. The load features of single-phase ME are summarized. The ME has the characteristics of linear current amplifier and approximately constant current source the generating mode, which can be used in the wide range of working temperature. Detailed waveforms and finite-element analysis verify that excitation current $I_{\mathrm {ef}}$ is almost irrelevant to speed but in direct proportion to frequency in the starting mode. Besides, simulated data indicate that the energy transferring efficiency between ME stator and rotor can reach about 55% by the single-phase ac excitation method. Finally, the experimental verification is carried out, and the simulated and experimental data and waveforms of single-phase ME agree well with each other. [ABSTRACT FROM AUTHOR]

Abstract Two three-dimensional metal-organic frameworks {CdNa 2 (H 2 O) 2 (DMF)[(ML) 2 Na(H 2 O) 2 ]}·6H 2 O (L = C 22 H 18 N 2 O 6 ; M = Ni 1 , Cu 2) based on carboxylate-functionalized salen ligands were successfully synthesized by one-step synthesis of reacting 1,2-cyclohexanediamine- N , N ′-bis-(3-carboxylsalicylide) (H 4 L) with metal acetate. Both of them were characterized by single-crystal X-ray diffraction, powder X-ray diffraction (XPRD), elemental analysis, TG analysis, IR and UV–visible spectroscopy. X-ray Single-crystal structural analysis reveals that compounds 1 and 2 are isostructural, which display a 3D porous framework constructed by infinite [CdNa 2 (H 2 O) 2 (DMF)(COO) 4 ] n chains as nodes and [(ML) 2 Na(H 2 O) 2 ] (M = Ni 1 , Cu 2) units as linkers. They present the first examples of metal-salen-based MOFs constructed by heterometallic inorganic node. In addition, magnetic studies indicate that ferromagnetic interactions exist in compound 1. Graphical abstract Two metal-organic frameworks 1 and 2 based on carboxylate-functionalized salen ligands were successfully obtained by one-step synthesis. 1 and 2 are isostructural, which display a porous framework constructed by infinite [CdNa 2 (H 2 O) 2 (DMF)(COO) 4 ] n chains as nodes and [(ML) 2 Na(H 2 O) 2 ] (M = Ni 1 , Cu 2) units as linkers. Unlabelled Image Highlights • Compounds 1 and 2 present the first examples of metal-salen-based MOFs constructed by heterometallic inorganic node. • Compounds 1 and 2 were obtained by one-step synthesis without the preparation of “metalloligand” in advance. • Magnetic studies indicate that ferromagnetic interactions exist in compound 1. [ABSTRACT FROM AUTHOR]

Abstract: A new wideband 0.18‐μm SiGe BiCMOS power amplifier (PA) operating from 16.5 to 25.5 GHz is presented. The PA consists of a drive amplifier and two main amplifiers integrated through lumped‐element Wilkinson power divider and combiner. The PA exploits the advantages of both HBT and NMOS characteristics in a cascode topology in addition to floating the NMOS body to achieve good gain, output power, power‐aided efficiency (PAE), and linearity. The developed PA has relatively flat saturated output power (Psat) of 18.5‐20.8 dBm, output 1‐dB compression point (OP1dB) of 15.1‐18.1 dBm, 13.5‐23% maximum PAE, and gain of 19.5 ±1.5 dB across 16.5‐25.5 GHz. At 24 GHz, the PA achieves Psat, OP1dB, maximum PAE, and gain of 20.8 dBm, 18.1 dBm, 23%, and 20 dB, respectively. [ABSTRACT FROM AUTHOR]

A wireless deep-subwavelength metamaterial architecture is proposed, modeled and demonstrated for a high-resolution magnetic resonance imaging (HR-MRI) application that is miniaturized to be resonant at approximately λ 0 /1500 dimensions. The proposed structure has the adjustable resonance frequency from 65 MHz to 5.5 GHz for the sub-cm footprint area (8 mm × 8 mm for this study) and provides a quality factor (Q-factor) of approximately 80 in free space for 123 MHz of operation. This structure consists of a cross-via metallized partial-double-layer metamaterial, sandwiching a dielectric thin film; this structure strongly localizes the electric field in this film and has a highly capacitive metal overlay that allows for a wide range of frequency adjustment. Although the achieved resonance frequencies enable a large number of applications, as a proof-of-concept demonstration, we experimentally showed the operation of this wireless metastructure in HR-MRI to highlight its precise frequency adjustment and signal-to-noise-ratio (SNR) improvement capabilities. The proposed metamaterial was found to maintains high Q-factors despite loading with a body-mimicking lossy phantom. The experimental results indicated that the proposed metastructure can be used as an SNR-enhancing device offering 15-fold SNR enhancements that allows for imaging of objects as small as 200 μm in diameter in its vicinity, at an unprecedented level of resolution at the given DC field using standard head coils. As a result of its deep-subwavelength miniaturization accompanied by reasonable Q-factor with outstanding resonance frequency adjustment capability, this class of metastructure is proved to be an excellent candidate for in vivo medical applications. [ABSTRACT FROM AUTHOR]

We present simulations of magnetized astrophysical shocks taking into account the interplay between the thermal plasma of the shock and suprathermal particles. Such interaction is depicted by combining a grid-based magnetohydrodynamics description of the thermal fluid with particle in cell techniques devoted to the dynamics of suprathermal particles. This approach, which incorporates the use of adaptive mesh refinement features, is potentially a key to simulate astrophysical systems on spatial scales that are beyond the reach of pure particle-in-cell simulations. We consider in this study non-relativistic shocks with various Alfvénic Mach numbers and magnetic field obliquity. We recover all the features of both magnetic field amplification and particle acceleration from previous studies when the magnetic field is parallel to the normal to the shock. In contrast with previous particle-in-cell-hybrid simulations, we find that particle acceleration and magnetic field amplification also occur when the magnetic field is oblique to the normal to the shock but on larger time-scales than in the parallel case. We show that in our simulations, the suprathermal particles are experiencing acceleration thanks to a pre-heating process of the particle similar to a shock drift acceleration leading to the corrugation of the shock front. Such oscillations of the shock front and the magnetic field locally help the particles to enter the upstream region and to initiate a non-resonant streaming instability and finally to induce diffuse particle acceleration. [ABSTRACT FROM AUTHOR]

Focuses on a study on thermomagnetic phenomena in exchange-coupled trilayers (ECTL) at the basic of a magnetic amplification of the super-resolution signal used for magneto-optical storage. T-induced phase transition in exchange-coupled bilayers (ECDL); T-induced changes of magnetization reversal in ECDL and ECTL; Conclusions.

Capacitive input couplers based on a 50 Ω coaxial transmission line are frequently used to transmit RF power to superconducting (SC) resonators operating in CW mode. It is well known that coaxial transmission lines are prone to multipacting phenomenon in a wide range of RF power level and operating frequency. The Facility for Rare Isotope Beams (FRIB) being constructed at Michigan State University includes two types of quarter wave SC resonators (QWR) operating at 80.5 MHz and two types of half wave SC resonators (HWR) operating at 322 MHz. As was reported in ref. [1] a capacitive input coupler used with HWRs was experiencing strong multipacting that resulted in a long conditioning time prior the cavity testing at design levels of accelerating fields. We have developed an insert into 50 Ω coaxial transmission line that provides opportunity to bias the RF coupler antenna and protect the amplifier from the bias potential in the case of breakdown in DC isolation. Two of such devices have been built and are currently used for the off-line testing of 8 HWRs installed in the cryomodule. [ABSTRACT FROM AUTHOR]

A Digital Loudspeaker Array (DLA) is an electro-mechanical transductor which receives a numerical signal as input data and allows the analogical conversion directly in the air. We designed PZT actuated membranes in order to obtain the highest acoustic pressure as possible. We built 256-MEMS-membranes DLAs using a generic PZT technology and digital acoustic reconstructions of the sound have been already demonstrated using our MEMS-DLA. In this paper, using FEM simulations, we evidence that residual stresses are responsible of the high distortion level measured on our demonstrators. A stress compensated technology was established using FEM approach. Acoustic characterization of stress compensated demonstrators proves distortion decreased and validates our hypothesis. [ABSTRACT FROM AUTHOR]

This paper proposes a technique suitable for on-chip tuning of digitally-tunable positive-feedback operational transconductor amplifiers in a continuous-time sigma-delta modulator (CT-SDM) with active-RC integrator stages. The work we present relies on phase shift and offset measurement of individual active-RC integrator stages output using comparators to estimate output conductance, DC-gain, and common mode level of the differential output signals. The tuning methodology aims to tune the integrator stages to achieve sufficient DC-gain as required by the SDM. We present experimental results to confirm the correlation of our integrator phase and output offset detection technique with the operational transconductance amplifier (OTA) DC gain. We employ this technique in a tuning process of two digitally-tunable OTA chips implemented in complementary metal-oxide semiconductor 180 nm process configured in a second-order CT-SDM circuit with discrete components. The tuning algorithm results in a measured signal-to-noise and distortion ratio (SNDR) of 46.97 dB, which is close to the maximum SNDR of 47.83 dB achievable across a subset of the digitally-tunable OTA code space. High-speed operation of the CT-SDM and tuning circuitry has been verified through circuit simulations. [ABSTRACT FROM AUTHOR]

This paper reports a single-chip solution for the implementation of radiation-tolerant CMOS front-end electronics (FEE) for applications requiring the acquisition of base-band sensor signals. The FEE has been designed in a 0.35~\mu \text m CMOS process, and implements a set of parallel conversion channels with high levels of configurability to adapt the resolution, conversion rate, as well as the dynamic input range for the required application. Each conversion channel has been designed with a fully-differential implementation of a configurable-gain instrumentation amplifier, followed by an also configurable dual-slope ADC (DS ADC) up to 16 bits. The ASIC also incorporates precise thermal monitoring, sensor conditioning and error detection functionalities to ensure proper operation in extreme environments. Experimental results confirm that the proposed topologies, in conjunction with the applied radiation-hardening techniques, are reliable enough to be used without loss in the performance in environments with an extended temperature range (between −25 and 125 °C) and a total dose beyond 300 krad. [ABSTRACT FROM PUBLISHER]

To increase the effective actuation stroke of piezoelectric stack actuators and giant magnetostrictive actuators, displacement amplifiers are usually employed to provide mechanical amplification. In this work, a novel symmetric two-stage lever-type amplifier called tensural displacement amplifier is proposed, in which all the flexural hinges are loaded in tension and bending rather than compression and bending when deflected. The tensural displacement amplifier does not have the potential problems buckling may cause because all the compliant members are loaded in tension. In addition, the proposed amplifier exhibits higher lateral frequency when deflected due to the stress stiffening effects of the tensural hinges. The kinetostatic model for the tensural displacement amplifier was established, based on which an amplifier whose amplification ratio exceeds 40 was designed. The amplification ratio of the design was further verified by the finite element model and prototype test. [ABSTRACT FROM AUTHOR]

This article presents a magnetic amplifier-based power flow controller as a new approach to control power flow based on a magnetically saturated reactor concept. The magnetic amplifier-based power flow controller uses the magnetic field as control medium to decrease the operating energy losses and increase system reliability. By providing continuous impedance, the magnetic amplifier-based power flow controller can suppress the inter-area oscillation and improve the system stability. A model of magnetic amplifier-based power flow controller is built and verified by lab experiments. A control strategy implementing the magnetic amplifier-based power flow controller is proposed to demonstrate the application of this new device to damp low-frequency oscillation in an interconnected power system. A comparative analysis of the controller's performance is carried out and incorporated with various input signals and multiple loading conditions. The simulations are conducted by power systems CAD (PSCAD, Manitoba Hydro International Ltd., Winnipeg, Canada). The results show the effectiveness of the controller in damping inter-area oscillations. [ABSTRACT FROM AUTHOR]

This paper presents an improved model for the prediction of bandwidth enhancement factor (BWEF) in an inductively tuned common source amplifier. In this model, we have included the effect of drain-source channel resistance of field effect transistor along with load inductance and output capacitance on BWEF of the amplifier. A frequency domain analysis of the model is performed and a closed-form expression is derived for BWEF of the amplifier. A prototype common source amplifier is designed and tested. The BWEF of amplifier is obtained from the measured frequency response as a function of drain current and load inductance. In the present work, we have clearly demonstrated that inclusion of drain-source channel resistance in the proposed model helps to estimate the BWEF, which is accurate to less than 5% as compared to the measured results. [ABSTRACT FROM AUTHOR]

Polarization shift keying (PolSK) is a digital modulation technique using the state of polarization of an electromagnetic wave as the signalling quantity. PolSK comes from fibre communications, where the channel offers two orthogonal states of polarization. This article develops on the idea to adapt this technology to satellite communications, where similar channel conditions exist. For this purpose, a digital PolSK modem was implemented on a programmable logic board. A proposal for constellation design as well as thoughts on synchronization of PolSK over satellite is presented. The modem was used to demonstrate a 16-state Polarization Shift Keying link over a commercial satellite in Ku band. Measurements have been conducted in a back-to-back setup on intermediate frequency and on a Ku band transponder simulator to assess the impact of path-length differences, carrier recovery and non-linearity. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The first attempt is made at applying the method of atomic force microscopy (AFM) for determining the molecular mechanisms of intracellular signalization with the participation of Na, K-ATPhase playing an important role of a signal transductor (amplifier). The AFM method combined with the organotypic cultivation makes it possible to obtain quantitative information on the Young moduli of living neurons and cells subjected to the action of very low concentrations of ouabain. This substance is known to trigger in this case the intracellular signalization processes by transferring a molecular signal to the genome of a cell. The cell response is manifested in a sharp intensification of protein synthesis accompanied by a rearrangement of the cytoskeleton and activation of enzyme signal pathways in a cytosol. AFM measurements of the images of the cell surface relief are performed using the PeakForce quantitative nanomechanical properties mapping PeakForce QNM mode. The Young moduli of control neurons and of sensory neurons under the action of ouabain are measured simultaneously. It is found that the activation of the signal-transducing function of Na, K-ATPhase triggers intracellular signal cascades, which increase the cell stiffness. The application of the AFM method in further studies of the mechanisms of intracellular molecular processes appears as promising. Its combination with inhibitory analysis will clarify the role of individual molecules (e.g., a number of ferments) in regulation of growth and development of living organisms. [ABSTRACT FROM AUTHOR]

The influence of the interfacial Dzyaloshinskii-Moriya interaction (IDMI) on the parametric amplification of spin waves propagating in ultrathin ferromagnetic film is considered theoretically. It is shown that the IDMI changes the relation between the group velocities of the signal and idler spin waves in a parametric amplifier, which may result in the complete vanishing of the reversed idler wave. In the optimized case, the idler spin wave does not propagate from the pumping region at all, which increases the efficiency of the amplification of the signal wave and suppresses the spurious impact of the idler waves on neighboring spin-wave processing devices. [ABSTRACT FROM AUTHOR]

The concept of the magnetic amplifier, a common electromagnetic device in electronic applications in the past, has seldom been used in power systems. The magnetic amplifier-based power-flow controller (MAPFC), an innovative low-cost device that adopts the idea of the magnetic amplifier for power-flow control applications, is introduced in this paper. The uniqueness of MAPFC is in the use of the magnetization of the ferromagnetic core, shared by an ac and a dc winding, as the medium to control the ac winding reactance inserted in series with the transmission line to be controlled. Large power flow in the line can be regulated by the small dc input to the dc winding. A project on the R&D of an MAPFC has been funded by the U.S. Department of Energy (DOE) and conducted by the Oak Ridge National Laboratory (ORNL), the University of Tennessee-Knoxville, and Waukesha Electric Systems, Inc. since early 2012. Findings from the project are presented along with some results obtained in a laboratory environment. [ABSTRACT FROM AUTHOR]

The unbalanced magnetic pull (UMP) often occurs in different kinds of electrical machines. In induction motors, UMP is usually caused by air-gap eccentricity, which is generally divided into static eccentricity, dynamic eccentricity, mixed eccentricity, and inclined eccentricity, also known as rotor misalignment. However, it has been verified that the curved dynamic eccentricity always occurs to some extent where the shaft in the majority of large electrical machines is bent, such as submersible motors. The curved dynamic eccentricity is defined as a condition in which the degree of dynamic eccentricity varies along the axial direction, and the eccentricity in the middle part of the motor is larger than that of the ends. Therefore, this paper presents a new method to calculate the UMP in cage induction motors, considering the curved dynamic eccentricity. Finite-element method is adopted for verification. [ABSTRACT FROM AUTHOR]

A new single Miller capacitor for frequency compensation of three-stage amplifier is proposed in this paper. In this scheme, a differential stage in which its negative and positive inputs are connected to the output and input nodes of third stage with a cascade capacitor forms the compensation block of a conventional three-stage amplifier. Analysis shows that this configuration significantly improves the frequency domain performances of total circuit such as phase margin (PM) and gain-bandwidth product (GBW) with just a very small amount of compensation capacitor. A three-stage amplifier has been simulated with and without a differential feedback path in a 0.18 µm complementary metal-oxide-semiconductor (CMOS). The simulated amplifier with a 100 pF capacitive load achieved more than 9 MHz GBW and 83° PM while the compensation is less than 0.2% of load capacitor. An amplifier based on conventional nested Miller compensation can just achieve less than 0.23 MHz GBW with the same load, while using more than 100 pF as compensation capacitor. So this method shows an improvement of a factor of 40 in GBW and reduction of a factor of 550 in the size of compensation capacitor. It is a suitable strategy for ON-CHIP compensation in comparison to other methods. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper describes a novel broad band Spatial Power Combiner (SPC) Amplifier based on Square Coaxial (Squarax) Transmission Line (TL), able to tolerate the Thermo-Mechanical effects due to the transistor heating. In the proposed SPC, Fin Line to microstrip transitions (FLuS) are inserted into the Squarax TL, in order to connect many Monolithic Microwave Integrated Circuit (MMIC) Solid State Power Amplifier (SSPA) while maintaining an easy integration. The proposed structure has some advantages over the traditional SPC's. The Squarax SPC geometry allows the feeding of a higher number of MMIC than in a Waveguide SPC, and its straight profile allows to connect simple and low-cost square or rectangular heat-sink devices with high thermal dissipation attitude. Conversely, coaxial SPC needs apposite circular heat-sinkers that requires expensive custom production. Squarax structure ensures high power outputs and small sizes, together with theoretical DC frequency cut-off. In this work, a 16 cards Squarax SPC in the operative bandwidth 4-18 GHz has been designed, able to account for 32 MMIC SSPA's. The design Electromagnetic and Thermo-structural simulation of the proposed device are shown. [ABSTRACT FROM AUTHOR]

Direct measurements of the vector turbulent emf in a driven two-vortex flow of liquid sodium were performed in the Madison Dynamo Experiment [K. Rahbarnia et al., Astrophys. J. 759, 80 (2012)]. The measured turbulent emf is anti-parallel with the mean current and is almost entirely described by an enhanced resistivity, which increases the threshold for a kinematic dynamo. We have demonstrated that this enhanced resistivity can be mitigated by eliminating the largest-scale eddies through the introduction of baffles. By tailoring the flow to reduce large-scale components and control the helical pitch, we have reduced the power required to drive the impellers, doubled the magnetic flux generated by differential rotation, and increased the decay time of externally applied magnetic fields. Despite these improvements, the flows remain sub-critical to the dynamo instability due to the reemergence of turbulent fluctuations at high flow speeds. [ABSTRACT FROM AUTHOR]

A advanced analysis of the existing models of the switching choke is made. An improved model of the switching choke, which takes into account the non-linearity and the ambiguity of the magnetization characteristic of its core, is offered. Numerical simulation of transient processes in a magnetic pulse generator with a key in the charging circuit is produced. Graphs of electrical and magnetic characteristics of the process are received. The modes of its operation at different load resistances and parameters of the bias circuit are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, compensation of the dc-side voltage harmonics of a medium-voltage (MV) 12-pulse ac/dc converter is achieved using a series active power filter (APF). The output voltage harmonics are dependent on the converter firing delay angles and, consequently, on the specific power locus followed by the ac/dc converter. This power locus ensures minimum fifth and seventh harmonics (total rms) in the input current which provides minimum input current total harmonic distortion when the reactive power is less than 0.5 p.u. The series APF is connected between the load and the converter output via a magnetic amplifier to eliminate the dc current from the APF inverter, thus reducing inverter losses. Voltage harmonic compensation using a series APF, with and without a magnetic amplifier, is examined with both resistive and inductive loads. The simulation results for compensating a 3.3-kV MV 12-pulse converter system are experimentally verified using a scaled prototype 12-pulse converter with a series APF. [ABSTRACT FROM PUBLISHER]

The design and technology of magnetic semiconductor elements of wireless magnetoresistive microsystems for magnetic field measurements are proposed and the results of the investigations of a highly sensitivity magnetoresistive converter with magnetic field concentrators are presented. The characteristics of the developed measuring amplifier for operation with a signal from a low-resistance magnetoresistive bridge with a certain unbalance value are reported. The technology for fabricating magnetic semiconductor ICs based on thin-film magnetoresistive structures is described. [ABSTRACT FROM AUTHOR]

The Doppler modulation system is a principal part of a Mössbauer spectrometer. It includes the Doppler modulator (velocity transducer) and a control system (the modulator driver) which consists of a function generator that produces a reference signal by which the vibrator can be controlled and the error correction circuit that corrects the motion of the vibrator according to the reference signal. The motion of the driver must be identical to the preferred wave shape for the operation of the spectrometer. The aim of the present article is to design and test a low cost lab-built modulator velocity driver for a Mössbauer spectrometer to be used in the constant acceleration (triangular) mode of operation, although it can be used in the other operational modes. A triangular wave is stored in RAM. The axis of the vibrator carries two coils, one for the driving signal and the other for the pickup signal which gives the shape of the motion of the driver (i.e., the actual motion of the source). The stored reference triangular wave is compared with the one from the pickup coil and the difference between them gives an error signal. The error signal will be zero if the motion of the vibrator is identical to that of the stored wave. This error signal is added to the driving pulse in a suitable phase and amplitude in order to obtain a source motion with minimized deviation from its correct value. [ABSTRACT FROM AUTHOR]

In this study, porous suspended ceramsite with a specific density close to that of water was prepared by high-temperature calcination using fly ash, feldspar, calcite, fired talc and kaolin as the raw materials. The ceramsite was modified by activated carbon/Fe3O4magnetic composites. The optimum modification conditions determined by methylene blue adsorption experiment were: KOH/glucose ratio of 1.5:1, carbonization temperature of 400°C, activation temperature of 850°C, activation time of 1 h, and Fe3O4/KOH+glucose ratio of 1:10. The results demonstrated that the adsorption capacity of the modified ceramsite for methylene blue was significantly higher than that of the unmodified ones. The presence of the composites did not lead to significant decrease in the mechanical properties of the modified ceramsite. Moreover, the modified ceramsite showed good resistance towards acid and alkali. The modified ceramsite can be used as biocarrier and adsorbent for a wide range of contaminants in water and can subsequently be removed from the medium by a simple magnetic procedure. [ABSTRACT FROM PUBLISHER]

We study the ternary clathrate Pr3Pd20Si6 in specific heat and ac susceptibility measurements on a high-quality single crystal, distinguishing antiferromagnetic and antiferroquadnipolar ordering, as well as a hitherto unknown magnetic low-temperature transition. The specific heat shows the direct involvement of nuclear spin degrees of freedom in the antiferromagnetic ordering, which is well supported by our calculation of the hyperfine level scheme without adjustable parameters. Pr3Pd20Si6 is, therefore, one of the rare materials where the nuclear moments are involved in the formation of the magnetic ground state. [ABSTRACT FROM AUTHOR]

A high linearity down-conversion mixer for the application of the fourth generation (4G) mobile communication systems is presented. The presented 2.3 to 5.8GHz broadband mixer adopts current-reused and bulk-controlled techniques. The linearized transconductor stage is composed of the CMOS amplifiers and the bulk-controlled compensation (BCC) transistors. The bulk-controlled voltage is applied to adjust the threshold voltage of the BCC transistor. Thus, the equivalent third-order intermodulation (IM3) term of the CMOS amplifiers and the BCC transistors can be mitigated so as to improve the linearity. Furthermore, the current-reused architecture enhances the conversion gain of the proposed mixer and compensates the loss caused by the shunt feedback matching network. The presented mixer consumes 4.8mA from a 1.5 V power supply. The measurement results of the mixer exhibit the maximum power conversion gain of 11.3 dB. The input third-order intercept point (IIP3) of 4.7 dBm over the entire 2.3{5.8GHz band is observed. [ABSTRACT FROM AUTHOR]

A self-consistent kinetic-theory based method of analysing the small-signal amplification of a transverse magnetic (TM) mode of a circular cylindrical waveguide linearly interacting with an annular beam of gyrating electrons in a gyrotravelling wave tube (TWT) configuration is presented. When the cyclotron-resonance condition is enforced over the entire frequency range by allowing the gyro-radius and the relativistic factor to be frequency-dependent for a constant value of the axial electron speed chosen to coincide with the reciprocal of the TM-mode phase speed at a particular frequency, the initial growth rate of the interacting TM wave is seen to exhibits a shallow minimum close to, but shifted to the right of, that frequency. The growth-rate curve, however, exhibits two maxima on either side of the minimum, a sharp but large maximum to the left and a broad but a smaller maximum to the right. A gyro-TWT designed by choosing the amplifier parameters (none of them varying any longer with frequency) in such a way as to place the broad maximum of the growth-rate curve at the design frequency is shown to be capable of operation over a wide band of frequencies around the design frequency coupled with a decent value of small-signal gain and negligible frequency distortion. [ABSTRACT FROM AUTHOR]

In this paper, we discuss a few techniques that allow an effective reduction of the background noise and/or the reduction of the measurement time when performing voltage noise measurements by employing a number of nominally identical voltage amplifiers with negligible equivalent input current noise. It is demonstrated in particular that, if N\ (N > 2) voltage amplifiers are connected to the device under test and if the properties of cross-correlation among all N acquisition channels connected to the output of each amplifier are exploited, the time required for obtaining a given accuracy is reduced by a factor N(N - 1)/2 with respect to the conventional setup for cross-correlation that employs only two channels. From another point of view, the effective background noise is reduced for constant measurement time. Such a factor can be further increased if amplifier paralleling is also employed for reducing the equivalent input voltage noise for each channel. Measurements on two different setups employing up to four channels and up to eight channels are presented that confirm the expected reduction factors in measurement times. [ABSTRACT FROM AUTHOR]

We present experiments on decelerating and trapping ammonia molecules using a combination of a Stark decelerator and a traveling wave decelerator. In the traveling wave decelerator, a moving potential is created by a series of ring-shaped electrodes to which oscillating high voltages (HV) are applied. By lowering the frequency of the applied voltages, the molecules confined in the moving trap are decelerated and brought to a standstill. As the molecules are confined in a true 3D well, this kind of deceleration has practically no losses, resulting in a great improvement on the usual Stark deceleration techniques. The necessary voltages are generated by amplifying the output of an arbitrary wave generator using fast HV amplifiers, giving us great control over the trapped molecules. We illustrate this by experiments in which we adiabatically cool trapped NH3 and ND3 molecules and resonantly excite their motion. [ABSTRACT FROM AUTHOR]

In this paper, new principles for designing low-radiation microwave circuits with single-stub impedance transformers are developed and a design flowchart for perfecting these principles is provided. The single-stub microstrip impedance transformers are widely used in microwave circuits and usually become the main radiation sources of these circuits. The developed principles show that the characteristic line impedance of a short-circuited (open-circuited) shunt stub should be high (low). In addition, if the shunt stub is open-circuited, using dual shunt open stubs can further reduce radiation; nevertheless, using dual shunt short stubs should be avoided due to additional via-current radiation. In most transformers, a high-impedance series line is recommended. Obeying the proposed principles, the radiation from a well-designed impedance transformer can be suppressed for more than 5 dB in contrast to that from the transformer using only \50- \Omega microstrip lines. Six microstrip amplifiers are demonstrated, adopting various representative impedance transformers, but with the same RF performance at 1.5 GHz. The measured and simulated radiation characteristics all support the proposed principles. This work is the first study on the radiation minimization of such microwave circuits. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Scalp-derived human somatosensory evoked potentials (SEPs) contain high-frequency oscillations (600Hz; ‘sigma-burst’) reflecting concomitant bursts of spike responses in primary somatosensory cortex that repeat regularly at 600Hz. Notably, recent human intracranial SEP have revealed also 1kHz responses (‘kappa-burst’), possibly reflecting non-rhythmic spiking summed over multiple cells (MUA: multi-unit activity). However, the non-invasive detection of EEG signals at 1kHz typical for spikes has always been limited by noise contributions from both, amplifier and body/electrode interface. Accordingly, we developed a low-noise recording set-up optimised to map non-invasively 1kHz SEP components. Methods: SEP were recorded upon 4Hz left median nerve stimulation in 6 healthy human subjects. Scalp potentials were acquired inside an electrically and magnetically shielded room using low-noise custom-made amplifiers. Furthermore, in order to reduce thermal Johnson noise contributions from the sensor/skin interface, electrode impedances were adjusted to ⩽1kΩ. Responses averaged after repeated presentation of the stimulus (n =4000 trials) were evaluated by spatio-temporal pattern analyses in complementary spectral bands. Results: Three distinct spectral components were identified: N20 (<100Hz), sigma-burst (450–750Hz), and kappa-burst (850–1200Hz). The two high-frequency bursts (sigma, kappa) exhibited distinct and partially independent spatiotemporal evolutions, indicating subcortical as well as several cortical generators. Conclusions: Using a dedicated low-noise set-up, human SEP ‘kappa-bursts’ at 1kHz can be non-invasively detected and their scalp distribution be mapped. Their topographies indicate a set of subcortical/cortical generators, at least partially distinct from the topography of the 600Hz sigma-bursts described previously. Significance: The non-invasive detection and surface mapping of 1kHz EEG signals presented here provides an essential step towards non-invasive monitoring of multi-unit spike activity. [Copyright &y& Elsevier]

We have performed a case study on the use of magnetic amplitude inversion in imaging volcanic rocks that are burled in a sedimentary basin and have strong remanent magnetization. The application arises in exploration for natural gas hosted in volcanic rocks in basin environments. The weak anomaly associated with the volcanic units and the presence of remanent magnetization therein pose major challenges in the magnetic interpretation. We first use a Wiener filter based on an ensemble analysis to examine the depth characteristics of the anomalies, and then we use an inversion-based signal separation to extract the anomaly for final interpretation. We apply an amplitude inversion method to recover the distribution of effective susceptibility in the absence of the knowledge about the total magnetization direction. The result effectively identifies the volcanic rock units at large depths and the imaged distribution of these units is consistent with information from drillholes and local geology. [ABSTRACT FROM AUTHOR]

The evolution of structures associated with mirror modes during their flow in the Earth's magnetosheath is studied. The fact that the related magnetic fluctuations can take distinct shapes, from deep holes to high peaks, has been assessed in previous works on the observational, modeling and numerical points of view. In this paper we present an analytical model for the flow lines and velocity magnitude inside the magnetosheath. This model is used to interpret almost 10 years of Cluster observations of mirror structures: by back tracking each isolated observation to the shock, the "age", or flow time, of these structures is determined together with the geometry of the shock. Using this flow time the evolutionary path of the structures may be studied with respect to different quantities: the distance to mirror threshold, the amplitude of mirror fluctuations and the skewness of the magnetic amplitude distribution as a marker of the shape of the structures. These behaviours are confronted to numerical simulations which confirm the dynamical perspective gained from the association of the statistical analysis and the analytical model: magnetic peaks are mostly formed just behind the shock and are quickly overwhelmed by magnetic holes as the plasma conditions get more mirror stable. The amplitude of the fluctuations are found to saturate before the skewness vanishes, i.e. when both structures quantitatively balance each other, which typically occurs after a flow time of 100-200 s in the Earth's magnetosheath. Comparison with other astrophysical contexts is discussed. [ABSTRACT FROM AUTHOR]