High Frequency Impulse Research Articles

Repeated Horizontal Jumping is a Feasible Exercise Countermeasure for Microgravity

Astronauts who spend prolonged time in microgravity on the International Space Station can experience a significant reduction in physical fitness. Jumping exercises represent a potential solution to this problem as the European Space Agency has demonstrated that the deconditioning effect of long-term bed-rest can be countered with around four minutes per day of jumping. The purpose of this study was to evaluate if repeated jumping is possible in microgravity and if the transmission of impact forces and vibration to the aircraft can be minimised. Five subjects performed repeated jumping on a custom jump sled both in microgravity during a parabolic flight campaign and in normal gravitational conditions. Forces expressed by the user and transmitted to the aircraft were quantified using a bespoke instrumentation system. These results show, for the first time, that repeated horizontal jumping is possible in microgravity, and that force transmission can be minimised by using a custom supine jump sled. The peak effective ground reaction force experienced by the user was sensitive to both the style of jumping used and resistance employed. These results open the door to the next generation of exercise countermeasures for deep space exploration. In particular, we have qualified the High Frequency Impulse for Microgravity (HIFIm) exercise device to a Technology Readiness Level of 6 making it a leading candidate to replace the Advanced Resistive Exercise Device (ARED) which has been in service since 2009.

High-Frequency Impulse Modeling and Longitudinal Insulation Analysis of Bifilar Superconducting Coil

Bifilar coil is one of the most applicable structures used for resistive-type superconducting fault current limiter. However, the turn-to-turn (longitudinal) insulation of the bifilar coil under lightning and switching impulse is rather different from the conventional pancake coil. The longitudinal insulation is characterized as the distributed circuit of the coil under high-frequency excitation, and the capacitance, inductance, and resistance parameters are solved by finite element model. The influence of those resistance, inductance and capacitance (RLC) parameters on the accuracy of the model is analyzed, and two samples of one bifilar pancake coil and two series connected bifilar coils are fabricated for high-frequency impulse voltage testing. The experimental results are consistent with the simulation results. The initial voltage distribution and impulse response of two samples are calculated under standard lightning impulse. In the initial voltage distribution calculation, the interturn channels of one bifilar coil and two series-connected bifilar coils are subjected to a maximum voltage of 1 and 0.5 times the lightning impulse voltage.

Phase evolution of Mo-W-Cu alloy rapid prepared by spark plasma sintering

In this paper, a novel Mo-W-Cu alloy with the relative density of 94%, fine microstructure, good electrical conductivity and hardness is prepared at a low temperature (800 °C) in a short time (5 min) under the combined action of discharge plasma, high frequency impulse, electric field and hot pressed sintering. The phase evolution and the phase structure of new phases are discussed based on the comprehensive analysis of XRD and TEM. The results show that Mo-W-Cu alloy consists of W, Mo, Cu phase and the new phases including Mo-W ordered phase at the Mo/W interface, Cu0.4W0.6 intermetallic compound at the W/Cu interface and Mo-Cu solid solution at the Mo/Cu interface. All of the new phases are BCC structure. The type of new phases obtained in this experiment is consistent with the calculation results based on the theory of Hume-Rothery, the correction theory of solid solution formation, and the theory of electronegativity. This presented research is expected to provide reference for the further research of Mo-W-Cu alloy.

Investigation of Archeological Caves in Israel Using High-Frequency Impulse Electric Prospecting

The archeological site of Machpelah Temple (Cave of the Patriarchs), Israel, was studied. At the moment, the first stage of investigations is finished: it included the study of a certain part inside the temple proper. New high-frequency impulse sounding hardware was applied, and its depth and spatial resolution of physical inhomogeneities exceeded the capabilities of existing electromagnetic prospecting methods by an order of magnitude.

Investigation of Archaeological Caves in Israel Using the High-Frequency Impulse Electric Prospecting

Investigation of Archaeological Caves in Israel Using the High-Frequency Impulse Electric Prospecting

High frequency impulse ground penetrating radar application in assessment of interlayer connections

Ground Penetrating Radar (GPR) technique is commonly used in the nondestructive evaluation of pavement structures. In particular, this method is used to estimate thicknesses of pavement layers as well as it can be utilized in advanced studies of pavement structures. The device presented in this paper comprise the high frequency impulse antennas that allow for investigating the interlayer zones in terms of their electromagnetic properties (e.g. dielectric constant). In some cases these electromagnetic responses can be suitable in the assessment of layer bonding in the pavement structure. This paper discusses the assessment of the quality of asphalt pavement interlayer bonding with the use of high frequency GPR techniques. The preliminary laboratory measurements were performed using an impulse antenna in the zero-offset configuration combined with the large-scale models simulating an idealized horizontal delamination. These measurements allowed to estimate the antenna sensitivity to detect interlayer connection under dry and wet conditions. Analysis of collected results led to formulating practical conclusions regarding critical limitations of the measuring system and adequate methods of signal processing and interpretation. The field investigations consisted of the GPR measurements along selected road sections and collection of the core samples at the locations associated with the specific reflexes. Inspection of the cores provided some real insights into the structure of different delaminations associated with characteristic reflexes. Analysis showed the reflection properties are able to expresses some important features of the interlayer zone, such as delaminations, presence of alien material at the interface, insufficient compaction occurring at the base of layer, and water penetration.

Fatigue damage in fieldshapers used during electromagnetic forming and welding processes at high frequency impulse current

Fieldshapers used in electromagnetic forming and welding processes are prone to have fatigue damage. During each test, impulse current passes through the coil that induces an eddy current cycle and a cyclic Lorentz force on the fieldshaper. Thus, the failure of the fieldshapers during service is associated with the cyclic loading conditions during a decaying high frequency electric current pulse. Repetition of the current pulse that causes the damage and eventually results in a failure which is similar to that occurs during a fatigue problem. Therefore, firstly mechanical and fatigue properties of the new material proposed for the fieldshaper (Siclanic alloy) were characterized. Then various fatigue loading cases with input voltages of 6–8.5 kV were investigated to predict the influence of dynamic cyclic loading on the fatigue damage. This study provides a clear understanding of the fatigue damage due to electromagnetic loading and establishes a linear correlation to predict the life cycle for an input electric current. The predicted fatigue damage locations are also in good agreement with the crack formation and their distribution on the filed shapers used in service.

A novel high symmetry interlocking micro-architecture design for polymer composites with improved mechanical properties

Development and design of novel materials based on their micro-structural arrangements are being intensely investigated due to their wide range of real and potential applications. One of the key objectives of such design is to achieve multiple properties, which are often competing in nature (such as high stiffness-high damping, high strength-high toughness etc.), within a single composite material. In the present work we propose a novel interlocking micro-architecture design to achieve high symmetry in a plane within a composite. The present study shows that constraining a very low volume fraction of high damping polymer within this micro-architecture, together with a stiff polymer, results in a simultaneously high stiffness and high damping polymer composite. The proposed micro-architecture design possesses high symmetry that is not commonly found in fiber-reinforced polymer composites. The interlocking feature avoids use of extra adhesives for holding two adjacent building blocks. Finite element simulations are performed by considering the micro-architecture made of two widely used polymeric materials such as polymethyl methacrylate (PMMA as the stiffer building block) and polyurethane (PU as the soft viscous material). Our numerical predictions show remarkable stiffness and damping properties for the design over a wide range of frequencies. Simulations are also performed considering contact between two polymer interfaces to establish the fact that the geometric interlocking works well without any use of adhesive for holding the blocks together. Further simulations are performed under high frequency impulse pressure loading to study dynamic wave propagation through the micro-architecture that shows the near-isotropic response of the proposed micro-architecture.

Hybrid modeling and auralization for complex structures

When a design is too complex for direct computer simulation, a hybrid physical/computer model can be an effective tool. Such was the case of the concert stage for Grand Junction Park in Westfield, Indiana. The stage façade comprises an opus spicatum of 6x6-inch stone caps on square aluminum tubing. In addition to the dramatic look, the complicated surface provides an opportunity to control diffusion, reflection and absorption. But the effect that the irregular 6-inch tier construction would have on the stage acoustics was a troubling unknown. With nearly 10,000 closely-packed surfaces—each with dimensions straddling audible wavelengths—direct computer modeling and auralization of the pavilion’s acoustics was felt to be unreliable. Therefore, a 1/12th scale physical model was built and used to obtain high frequency impulse responses for the design. Post processing of the responses showed a dip in the frequency response, most notably for the flute section as heard at the conductor’s position. Additional post processing was used to create auralizations of a 25-piece orchestra to demonstrate the level of the effect. This presentation will describe in detail the hybrid modeling and auralization used for this project, the results of the testing, and the recommendations made to the architect.

Formation of High-Frequency Impulses in a High-Power Magnetotherapeutic Apparatus

We describe here a novel method for forming magnetic field impulses for a high-power medical magnetotherapy apparatus. We present a block diagram of the apparatus for forming magnetic field impulses with specified parameters: rate of impulse rising front, impulse frequency, and magnetic field induction amplitude. The characteristics of solenoids are given, along with calculations of various device parameters.

TPT-Dance&Actions : un corpus multimodal d’activités humaines

TPT-Dance&Actions : un corpus multimodal d’activités humaines

Application of Ground Penetrating Radar in Tunnel Concrete Lining Quality Detection

Ground Penetrating Radar is a method using high frequency impulse electromagnetic wave to detect underground media distribution. It has been gradually widely used as it has the advantage of high accuracy, fast and nondestructive respecting to the conventional method such as visual measurement and confirmation with drilling hole. In the tunnel construction process, it is easy occurred that the quality problem of insufficient lining thickness, the distance of steel arch centering too large and the concrete disengaging. The work achieved in this paper based on the project of LongSheng tunnel and its conclusion and suggestion has important practical engineering significance.

Formation of Nonbranched Positive Streamer With High-Frequency Impulse Voltage in Atmospheric Air

Formation of Nonbranched Positive Streamer With High-Frequency Impulse Voltage in Atmospheric Air

A Method for Calculating the Maximal Temperature of Single Grain though Analyzing the Grinding Temperature Signal

In the present study, grinding temperature was measured by using a foil thermocouple when granite was ground by SiC wheel. De-noised the temperature signals with soft threshold method base on wavelet transform was conducted to analyze the grinding process. Energy partition to workpiece was estimated to be about 10%~30% by matching the measured temperature to analytically value. The number of active grains was determined by counting the high frequency impulses in the measured temperature signals. The ratio of active grains to total grains was about 4.5%~6.1%. Based on the results, a formula was deduced for calculating the temperature of single grain in the grinding process.

3D time-domain spectral elements for stress waves modelling

Elastic stress waves induced by piezoelectric transducers are extensively used for damage detection purposes. Induced high frequency impulse signals cause that stress wave modelling by the finite element method is inefficient. Instead, numerical model based on the time-domain spectral element method has been developed to simulate stress wave propagation in metallic structures induced by the piezoelectric transducers. The model solves the coupled electromechanical field equations simultaneously in three-dimensional case. Visualisation of the propagating elastic waves generated by the actuator of different shapes and properties has been performed.

20 GHz Wavelet Generator Using a Gated Tunnel Diode

We demonstrate the use of a GaAs-AlGaAs gated tunnel diode (GTD) in an ultra-wideband (UWB) wavelet generator. An inductor is integrated to form an oscillator circuit, which is driven by the negative differential conductance property of a GTD. It is demonstrated that as the gate tunes the magnitude of the output conductance, the oscillator may be switched on and off, creating short RF pulses. The shortest pulses generated are 500 ps long, the highest output power for the free running oscillator is -4.1 dBm, and the highest oscillation frequency is 22 GHz. Analytical expressions based on the van der Pol equation describing the pulse length and amplitude are presented. This technique is applicable for high frequency impulse radio UWB implementations.

Verhalten von Titan-Mittelohrimplantaten bei 1,5 und 3 Tesla Feldstärke in der Magnetresonanztomographie

Investigations into the MRI compatibility of middle ear implants made from titanium alloys with 1.5 and 3.0 tesla MRI systems which are frequently used for imaging diagnostics. 17 different middle ear (ME) implants (ossicular replacement prosthesis (ORP) and ventilation tubes) made from titanium were tested in vitro. Potential warming was determined via an MRI-compatible fibre optic temperature sensor under the influence of sequences with high-level high frequency impulses. An assessment of the attractive force of the implants was carried out placed on a Petri dish under vibration and floating on rubber-sponge (RS) in a water bath. No significant warming of the implants was observed with any of the used sequences at either 3 or 1.5 Tesla field strength (TF). With 3 TF, all 17 implants changed their position on the surface of the water and moved at a slow speed (0.0004-0.0014 m/s) towards the magnetic field. With 1.5 TF, the tested ME implants moved at a maximum speed of 0.0002 m/s and in the case of the ventilation tubes at 0.0005 m/s. No warming occurred in any of the tested middle ear implants at either 1.5 or 3 TF. The attractive forces exerted through the static magnetic field were overall low at 1.5 and 3 TF, indicating that no dislocation is to be expected if intraoperative anchoring is correctly conducted. Nevertheless, the indication for examination at 3 TF should be carefully considered due to the anatomically sensitive region.

Impulse buying: the role of affect, social influence, and subjective wellbeing

PurposeThe purpose of this research is to examine predictors of impulse buying. Although moderate levels of impulse buying can be pleasant and gratifying, recent theoretical work suggests that chronic, high frequency impulse buying has a compulsive element and can function as a form of escape from negative affective states, depression, and low self‐esteem.Design/methodology/approachThe present research empirically tests a theoretical model of impulse buying by examining the associations between chronic impulse buying tendencies and subjective wellbeing, affect, susceptibility to interpersonal influence, and self‐esteem.FindingsResults indicate that the cognitive facet of impulse buying, associated with a lack of planning in relation to purchase decisions, is negatively associated with subjective wellbeing. The affective facet of impulse buying, associated with feelings of excitement and an overpowering urge to buy, is linked to negative affect and susceptibility to interpersonal influence.Practical implicationsGiven the link to negative emotions and potentially harmful consequences, impulse buying may be viewed as problematic consumer behavior. Reductions in problematic impulse buying could be addressed through public policy or social marketing.Originality/valueThis study validates and extends the Verplanken et al. model by examining the relationship between impulse buying and other psychological constructs (i.e. subjective wellbeing, positive and negative affect, social influence, and self‐esteem).

Multiple information fusion and quality classification of aluminum alloy resistance spot welding

Resistance spot welding quality real-time monitoring of aluminum alloy is realized by distributed multiple-sensor synchronous collection system and the related data processing software is also developed by using LABVIEW graphical language.The results show that the endo-expulsion in spot welding is related to the notching curve of voltage and electrode displacement signal.Moreover,there is a correlation between the high frequency impulse amplitude and duration of the electrode pressure signal and the expulsion strength index,and three characteristics simultaneously or separately occur according to the expulsion strength index in spot welding. Resistance spot welding quality can be reflected by nine characteristics of high signal-to-noise ratio,and they become the base of on-line quality classification of aluminum alloy spot welding in future.Furthermore,using principal component analysis may implement the information fusion and data compression.The percentage of spot welding quality classification accuracy can reach 98%.

A spectrally formulated finite element for wave propagation analysis in functionally graded beams

In this paper, spectral finite element method is employed to analyse the wave propagation behavior in a functionally graded (FG) beam subjected to high frequency impulse loading, which can be either thermal or mechanical. A new spectrally formulated element that has three degrees of freedom per node (based upon the first order shear deformation theory) is developed, which has an exact dynamic stiffness matrix, obtained by exactly solving the homogeneous part of the governing equations in the frequency domain. The element takes into account the variation of thermal and mechanical properties along its depth, which can be modeled either by explicit distribution law like the power law and the exponential law or by rule of mixture as used in composite. Ability of the element in capturing the essential wave propagation behavior other than predicting the propagating shear mode (which appears only at high frequency and is present only in higher order beam theories), is demonstrated. Propagation of stress wave and smoothing of depthwise stress distribution with time is presented. Dependence of cut-off frequency and maximum stress gradient on material properties and FG material (FGM) content is studied. The results are compared with the 2D plane stress FE and 1D Beam FE formulation. The versatility of the method is further demonstrated through the response of FG beam due to short duration highly transient temperature loading.