Two-point Measurement Research Articles

Response of the far scrape-off layer plasma to strong gas puffing in the high poloidal beta configuration of the QUEST spherical tokamak

The response of the far scrape-off layer (far-SOL) to strong gas puffing (SGP), and its role as the boundary condition for core plasma, are investigated using a two-point Langmuir probe measurement in the high poloidal beta configuration in the QUEST spherical tokamak. The temperature and heat flux behave in an opposite way in the far-SOL and end-plate region after SGP, although SGP increases the density globally. The apparent density decay time in the far-SOL area is much longer than that in the core. Significant co-current flow is driven solely by the electron cyclotron wave in the far-SOL flow. Sheared flow is also observed in the perpendicular velocity profile during the recovered current flat-top phase, and such flow profiles are flattened by SGP. These flow profiles are attributed not only to drift-driven flow but also to transport-driven flow, the sink effect on the end-plate, and the balance of the neutral particle source.

Reliability of the two-point measurement of the spatial correlation length from Gaussian-shaped fluctuating signals in fusion-grade plasmas

A statistical method for the estimation of the spatial correlation lengths of Gaussian-shaped fluctuating signals with two measurement points is examined to quantitatively evaluate its reliability (variance) and accuracy (bias error). The standard deviation of the correlation value is analytically derived for randomly distributed Gaussian shaped fluctuations satisfying stationarity and homogeneity, allowing us to evaluate, as a function of fluctuation-to-noise ratios, the sizes of averaging time windows and the ratios of the distance between the two measurement points to the true correlation length, and the goodness of the two-point measurement for estimating the spatial correlation length. Analytic results are confirmed with numerically generated synthetic data and real experimental data obtained with the KSTAR beam emission spectroscopy diagnostic. Our results can be applied to Gaussian-shaped fluctuating signals where a correlation length must be measured with only two measurement points.

An Experimental Study of Pile-Supported OWC-Type Breakwaters: Energy Extraction and Vortex-Induced Energy Loss

Integrating wave energy converters with breakwaters is a promising concept for wave energy utilization. On the basis of fulfilling the wave protection demands, pile-supported Oscillating Water Column (OWC)-type breakwaters can also meet the local needs of electricity far from the lands. In the present study, the wave energy extraction and vortex-induced energy loss of pile-supported OWC-type breakwaters were analyzed based on a two-point measurement method. The importance of energy extraction and vortex-induced energy loss on the wave energy dissipation of pile-supported OWC-type breakwaters were experimentally investigated. It was found that the trends of energy extraction and vortex-induced energy loss were generally correlated. The effects of the pneumatic damping induced by top opening affected the vortex-induced energy loss more than the energy extraction. Results showed that a larger pneumatic damping was preferable for the purpose of increasing energy extraction, whereas for a smaller pneumatic damping the vortex-induced energy loss was more important to the energy dissipation. With increasing draft, the energy extraction decreased, but the vortex-induced energy loss complementally contributed to the total energy dissipation and made the energy dissipation at the same level as that for a shallower draft.

Large-amplitude flapping of an inverted flag in a uniform steady flow – a vortex-induced vibration

The dynamics of a cantilevered elastic sheet, with a uniform steady flow impinging on its clamped end, have been studied widely and provide insight into the stability of flags and biological phenomena. Recent measurements by Kimet al.(J. Fluid Mech., vol. 736, 2013, R1) show that reversing the sheet’s orientation, with the flow impinging on its free edge, dramatically alters its dynamics. In contrast to the conventional flag, which exhibits (small-amplitude) flutter above a critical flow speed, the inverted flag displays large-amplitude flapping over a finite band of flow speeds. The physical mechanisms giving rise to this flapping phenomenon are currently unknown. In this article, we use a combination of mathematical theory, scaling analysis and measurement to establish that this large-amplitude flapping motion is a vortex-induced vibration. Onset of flapping is shown mathematically to be due to divergence instability, verifying previous speculation based on a two-point measurement. Reducing the sheet’s aspect ratio (height/length) increases the critical flow speed for divergence and ultimately eliminates flapping. The flapping motion is associated with a separated flow – detailed measurements and scaling analysis show that it exhibits the required features of a vortex-induced vibration. Flapping is found to be periodic predominantly, with a transition to chaos as flow speed increases. Cessation of flapping occurs at higher speeds – increased damping reduces the flow speed range where flapping is observed, as required. These findings have implications for leaf motion and other biological processes, such as the dynamics of hair follicles, because they also can present an inverted-flag configuration.

Morphological and Electrical Characterization of MWCNT Papers and Pellets.

Six types of commercially available multiwall carbon nanotube soot were obtained and prepared into buckypapers by pellet pressing and by filtration into a paper. These samples were evaluated with respect to thickness, compressibility and electrical conductivity. DC conductivity results by two-point and four-point (van der Pauw) measurement methods as a function of preparation parameters are presented. Topology was investigated qualitatively by way of scanning electron microscopy and helium ion microscopy and from this, some generalizations about the nanotube structural properties and manufacturing technique with respect to conductivity are given.

A Newly Advanced Anti-Vibration Pad With a Phase Balancer Designed by Analysis of Washing Machine Behaviors

Abstract This study proposed an anti-vibration pad with a phase balancer that helps reduce wood floor vibrations from a washing machine as well as the vibrations of the machine itself. When a washing machine is installed just on anti-vibration pads, the floor vibrations can be reduced, but consequently the machine’s left–right vibrations become more violent. Accordingly, in order to identify the mechanism by which anti-vibration pads generate left-right vibrations in washing machines, the present study proposed a two-point measurement method that can determine vertical washing machine vibrations and phase differences. In addition, we proposed an optimal phase balancer designed by a finite element analysis-based response surface method for reducing vibrations using a phase difference. As a result, the anti-vibration pad with a phase balancer, when applied to washing machines, greatly contributed to simultaneously reducing the actual vibrations of washing machines and the vibration transfer to the floor.

In Operando Electrochemical-Acoustic Time-of-Flight Analysis: Correlating Physical Dynamics within Batteries to States of Charge and Health

Recently, advances in the mechanical understanding of electrochemical energy storage devices, based investigations of stress/strain, have yielded significant improvements in battery materials, designs, and management systems. To date, however, the field has lacked a non-invasive method for monitoring these complex mechanics within in practical cells. Here, we demonstrate a simple electrochemical-acoustic model and experiment as the basis for a potentially universal in operando, field-deployable tool for determining the mechanical evolution, state-of-charge (SOC) and state-of-health (SOH) of any closed battery. This technique, which we call Electrochemical Acoustic Time of Flight (EAToF) analysis, was tested against several off-the-shelf lithium ion and alkaline batteries and a general phenomenon was observed: that the behavior of sound passing through the cells correlated strongly to its SOC and SOH. Regardless of the chemistry, the density distribution within a battery must change as a function of its SOC, and the bulk moduli of the anode and cathode change as well. These shifts, in turn, directly influence the behavior of sound passing through the cells. Overall, a one- or two-point acoustic measurement can be related to the interaction of a pressure wave at multiple discrete interfaces within a battery, which in turn provides insights into state of charge, state of health, and mechanical evolution/degradation. This work, which is unique to the literature, provides new physical insights into the physical dynamics within batteries. With this EAToF technique, we propose a framework relating changes in sound speed within the cell, via changes in electrode densities and moduli, to SOC and SOH measurements in a manner that can be readily embedded into battery management systems. Figure 1

Force-penetration curves of a button bit generated during impact penetration into rock

To improve the performance and efficiency of percussion rock drills, it is essential to understand the impact penetration behavior of a bit drilling into rock. However, little knowledge to date has been published about the penetration behavior of the button bit, which is commonly used for hard rock. In this study, the impact penetration behavior of the button bit was investigated in laboratory tests. An impact penetration tester built from the same components used in an actual rock drill was developed and used in single-blow impact penetration tests. Unnatural fluctuations were observed in the force-penetration curves calculated using a two-point strain measurement method, which were probably due to not only the difference in rod stress as measured at two points on the rod, but also to the mismatch between the actual bit and the calculation model. A data correction method, in which the bit force calculated in a free end test is subtracted from that in the impact penetration test, was proposed using a numerical simulation. The method was applied to the measured rod stress, and force-penetration curves with a button bit were obtained from more than 40 impact penetration tests. Graph curves showed that peak force, initial slope and elastic penetration increased, while the maximum and final penetrations decreased with an increase in the secant slope. The crushing and elastic strain energies changed, but the sum of the energies was constant with an increase in the secant slope. The variations in the force-penetration curves are caused by the contact conditions between the bit and rock, the rock properties, and damage to the rock caused with each blow, not by the test conditions. The findings of this study will contribute to progress in the performance and efficiency of percussive rock drilling.

Trajectory phases of a quantum dot model

We present a thermodynamic formalism to study the trajectories of charge transport through a quantum dot coupled to two leads in the resonant-level model. We show that a close analogue of equilibrium phase transitions exists for the statistics of transferred charge; by tuning an appropriate ‘counting field’, crossovers to different trajectory phases are possible. Our description reveals a mapping between the statistics of a given device and current measurements over a range of devices with different dot–lead coupling strengths. Furthermore insight into features of the trajectory phases are found by studying the occupation of the dot conditioned on the transported charge between the leads; this is calculated from first principles using a trajectory biased two-point projective measurement scheme.

Moments of work in the two-point measurement protocol for a driven open quantum system

We study the distribution of work induced by the two-point measurement protocol for a driven open quantum system. We first derive a general form for the generating function of work for the total system, bearing in mind that the Hamiltonian does not necessarily commute with its time derivative. Using this result we then study the first few moments of work by using the master equation of the reduced system, invoking approximations similar to the ones made in the microscopic derivation of the reduced density matrix. Our results show that, already in the third moment of work, correction terms appear that involve commutators between the Hamiltonian and its time derivative. To demonstrate the importance of these terms, we consider a sinusoidally, weakly driven and weakly coupled open two-level quantum system, and indeed find that already in the third moment of work the correction terms are significant. We also compare our results to those obtained with the quantum jump method and find a good agreement.

Universal departure from Johnson-Nyquist relation caused by limited resolution

Exploiting the two-point measurement statistics, we propose a quantum measurement scheme of current with limited resolution of electron counting. Our scheme is equivalent to the full counting statistics in the long-time measurement with the ideal resolution, but is theoretically extended to take into account the resolution limit of actual measurement devices. Applying our scheme to a resonant level model, we show that the limited resolution of current measurement gives rise to a positive excess noise, which leads to a deviation from the Johnson-Nyquist relation. The deviation exhibits universal single-parameter scaling with the scaling variable $Q\ensuremath{\equiv}{S}_{\mathrm{M}}/{S}_{0}$, which represents the degree of the insufficiency of the resolution. Here, ${S}_{0}$ is the intrinsic noise, and ${S}_{\mathrm{M}}$ is the positive quantity that has the same dimension as ${S}_{0}$ and is defined solely by the measurement scheme. For the lack of the ideal resolution, the deviation emerges for $Q<1$ as $2exp[\ensuremath{-}{(2\ensuremath{\pi})}^{2}/Q]$ having an essential singularity at $Q=0$, which followed by the square root dependence $\sqrt{Q/4\ensuremath{\pi}}$ for $Q\ensuremath{\gg}1$. Our findings offer an explanation for the anomalous enhancement of noise temperature observed in Johnson noise thermometry.

Recovery of complex valued objects from two-point intensity correlation measurement

We propose and experimentally demonstrate a technique for the recovery of the wavefront from spatially fluctuating fields using the two point intensity correlation, i.e., fourth order correlation. Assuming spatial ergodicity and Gaussian statistics for the speckle field, we connect the fourth order correlation to the modulus of the corresponding second order correlation. The idea is to retrieve the complex coherence function and consequently the wavefront using the off-axis holography. Application of this technique is demonstrated in the reconstruction of complex field of the object lying behind a weak scatterer. Experimental results of recovery of the complex field of phase objects “vortices” with three values of topological charges are presented.

Influence of Emitted Electrons on the Method for Direct Measurement of Condensate Resistance

Electrical resistance of the vacuum-deposited condensate has non-linear relation to the condensate film thickness. Therefore, there exists a need for experiments to study applicability of the non-invasive method for condensate resistance measurement and to identify parameters by measuring condensate resistance directly. By using two-point measurement probes, this study analyses the influence of electrons emitted in the process of evaporator electronic emission on the method for direct measurement of condensate resistance. DOI: http://dx.doi.org/10.5755/j01.eee.20.2.6379

Apparent electrical conductivity (ECa) as a surrogate for neutron probe counts to measure soil moisture content in heavy clay soils (Vertosols)

Site-specific measurements of the apparent electrical conductivity (ECa) of soil using the EM38 were correlated with near-simultaneous neutron probe readings over periods of moisture extraction by an irrigated cotton crop. Thirty sites were monitored from three ECa zones within a 96-ha field of grey Vertosol soil 30 km west of Moree, New South Wales, Australia. This study differs from previous approaches by reporting the effect on ECa of a wetting front (irrigation) reaching a single ECa measurement point in a field and by using polyethylene neutron probe access tubes so that the EM38 could be operated directly over the same site measured by a neutron probe. We report strong correlations (r = 0.94) between neutron probe counts (CRR) averaged to a depth of 40 or 60 cm and ECa from an EM38 held in the vertical mode 20 cm above the soil surface. All combinations of EM sensor height (0–1.2 m) to neutron probe measurement depth (0.2–1.4 m) returned correlations >0.85. The relationship between CCR and ECa was linear for the purposes of estimating water content over a range of background ECa levels. More critical modelling suggested a slight curve (logarithmic model) fitted best. The range of surface-surveyed ECa from the start of irrigation (refill point) to fully irrigated (full point) was ~27 mS m–1 for this Vertosol, where surface ECa readings typically ranged from 50 to 200 mS m–1. We suggest that the calibration of ECa to CRR might be effected by a two-point measurement of the soil, namely at both upper (field capacity) and lower (wilting point) ECa values, and a site-specific calibration template generated by extending these point measures to whole-field surveys.

Demonstration of two-point velocity measurement using diffraction grating elements for integrated multi-point differential laser Doppler velocimeter

We have proposed a configuration of an integrated multi-point differential laser Doppler velocimeter (LDV) using arrayed waveguide gratings (AWGs) as grating elements. This paper demonstrates two-point velocity measurement using the proposed configuration with diffraction grating elements. An experiment was conducted using a free-space optical setup with bulk diffraction gratings instead of AWGs. The experimental results indicate that velocities at different positions can be measured using the proposed configuration. The measured separation of the two measurement positions was about 20.5mm, about 11% of the working distance.

SMS fiber structure for temperature measurement using an OTDR

A singlemode-multimode-singlemode (SMS) fiber structure for temperature measurement using an optical time domain reflectometer (OTDR)-based interrogation system is proposed. A temperature measurement range of 40 °C–195 °C with a resolution of 0.12 °C and a linearity of 0.992 could be achieved for the multimode fiber (MMF) graded index with a length of 60 mm. It was also demonstrated that two-point temperature measurement with two SMS fiber structures as temperature sensors could be made. The proposed temperature measurement system offered a high resolution and also benefited from a simple configuration with a capability of multi-point temperature measurement.

Two-Point Measurement of High-Frequency Density Fluctuations by Reflectometry in GAMMA 10

To study the detailed radial structure of the Alfvén ion-cyclotron (AIC) waves excited in the GAMMA10 central cell, we upgraded the previously used reflectometer system so as to measure radially separated two density fluctuations simultaneously. Successful application of the new reflectometer system reveals existence of non-trivial radial structure of the AIC waves; from the core to about a half plasma radius, the density fluctuations arising from the AIC waves have common phase relationship, while in the external region, they have opposite phase relation with that of the core.

Validity of the Water Hammer Formula for Determining Regional Aortic Pulse Wave Velocity: Comparison of One-Point and Two-Point (Foot-to-Foot) Measurements Using a Multisensor Catheter in Human

Lack of high-fidelity simultaneous measurements of pressure and flow velocity in the aorta has impeded the direct validation of the water-hammer formula for estimating regional aortic pulse wave velocity (AO-PWV1) and has restricted the study of the change of beat-to-beat AO-PWV1 under varying physiological conditions in man. Aortic pulse wave velocity was derived using two methods in 15 normotensive subjects: 1) the conventional two-point (foot-to-foot) method (AO-PWV2) and 2) a one-point method (AO-PWV1) in which the pressure velocity-loop (PV-loop) was analyzed based on the water hammer formula using simultaneous measurements of flow velocity (Vm) and pressure (Pm) at the same site in the proximal aorta using a multisensor catheter. AO-PWV1 was calculated from the slope of the linear regression line between Pm and Vm where wave reflection (Pb) was at a minimum in early systole in the PV-loop using the water hammer formula, PWV1 = (Pm/Vm)/ρ, where ρ is the blood density. AO-PWV2 was calculated using the conventional two-point measurement method as the distance/traveling time of the wave between 2 sites for measuring P in the proximal aorta. Beat-to-beat alterations of AO-PWV1 in relationship to aortic pressure and linearity of the initial part of the PV-loop during a Valsalva maneuver were also assessed in one subject. The initial part of the loop became steeper in association with the beat-to-beat increase in diastolic pressure in phase 4 during the Valsalva maneuver. The linearity of the initial part of the PV-loop was maintained consistently during the maneuver. Flow velocity vs. pressure in the proximal aorta was highly linear during early systole, with Pearson's coefficients ranging from 0.9954 to 0.9998. The average values of AO-PWV1 and AO-PWV2 were 6.3 ± 1.2 and 6.7 ± 1.3 m/s, respectively. The regression line of AO-PWV1 on AO-PWV2 was y = 0.95x + 0.68 (r = 0.93, p <0.001). This study concluded that the water-hammer formula (one-point method) provides a reliable and conventional estimate of beat-to-beat aortic regional pulse wave velocity consistently regardless of the changes in physiological states in human clinically. (English Translation of J Jpn Coll Angiol 2011; 51: 215-221).

Comprehensive characterization of Cu-rich Cu(In,Ga)Se2 absorbers prepared by one-step sputtering process

The characteristics of the Cu-rich Cu(In,Ga)Se2 (CIGS) films prepared by one-step sputtering process from a single quaternary target have been studied. The influences of working pressure, substrate temperature, Mo back contact, and KCN treatment on the properties of CIGS films were investigated. Target stability has been in-situ monitored by using optical emission spectroscopy. Obvious compositional change due to the KCN effect was observed, while only slight variation was caused by working pressure. We found the preferred orientation and crystallinity of one-step sputtered CIGS films were affected by the working pressure and substrate temperature when CIGS were directly deposited on the glass substrates. However, for the device fabrication, Mo back contacts dominated the growth behavior of CIGS films and induced better crystallinity with larger CIGS grain sizes. To explore the electrical properties of CIGS films on Mo back contacts, we developed a simple two-point probe measurement to examine the conductive channels within CIGS films before the device fabrication. Finally, one-step sputtered CIGS devices showed the efficiency of more than 8% at the working pressure of 0.4–2.7Pa with KCN treatment.

Solution derived ZnO:Al films with low resistivity

ZnO:Al thin films were prepared via chemical solution deposition, using 2-butoxyethanol as an alternative for 2-methoxyethanol, which is more commonly used, but acutely toxic. The precursor solutions can be readily spin coated. The phase, morphology, electrical and optical properties of the deposited films are investigated, by XRD (X-ray diffraction), scanning electron microscopy, a two-point contact measurement and UV–vis spectrophotometry respectively. This way, the effect of this solvent is investigated. The films are deposited on borosilicate glass substrates and were found to be continuous and smooth. XRD measurements show a highly preferential c-axis orientation. The effects of the thermal treatment profile and Al dopant concentration are studied with respect to the obtained electrical properties. Optimally, the electrical resistivity was lowered to 6.5×10−3Ωcm after annealing at 450°C in a 95% He/5% H2 atmosphere.