Journal articles: 'Multi-hole probe'

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Johansen, Espen S., Othon K. Rediniotis, and Greg Jones. "The Compressible Calibration of Miniature Multi-Hole Probes." Journal of Fluids Engineering 123, no. 1 (September 6, 2000): 128–38. http://dx.doi.org/10.1115/1.1334377.

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This work presents the development of a data reduction algorithm for non-nulling, multihole pressure probes in compressible, subsonic flowfields. The algorithm is able to reduce data from any 5- or 7-hole probe and generate very accurate predictions of the velocity magnitude and direction, total and static pressures, Mach and Reynolds number and fluid properties like the density and viscosity. The algorithm utilizes a database of calibration data and a local least-squares interpolation technique. It has been tested on four novel miniature 7-hole probes that have been calibrated at NASA Langley Flow Modeling and Control Branch for the entire subsonic regime. Each of the probes had a conical tip with diameter of 1.65 mm. Excellent prediction capabilities are demonstrated with maximum errors in angle prediction less than 0.6 degrees and maximum errors in velocity prediction less than 1 percent, both with 99 percent confidence.

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Yasa, Tolga, and Guillermo Paniagua. "Robust procedure for multi-hole probe data processing." Flow Measurement and Instrumentation 26 (August 2012): 46–54. http://dx.doi.org/10.1016/j.flowmeasinst.2012.03.004.

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Calmer, Radiance, Gregory C. Roberts, Jana Preissler, Kevin J. Sanchez, Solène Derrien, and Colin O'Dowd. "Vertical wind velocity measurements using a five-hole probe with remotely piloted aircraft to study aerosol–cloud interactions." Atmospheric Measurement Techniques 11, no. 5 (May 3, 2018): 2583–99. http://dx.doi.org/10.5194/amt-11-2583-2018.

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Abstract. The importance of vertical wind velocities (in particular positive vertical wind velocities or updrafts) in atmospheric science has motivated the need to deploy multi-hole probes developed for manned aircraft in small remotely piloted aircraft (RPA). In atmospheric research, lightweight RPAs (< 2.5 kg) are now able to accurately measure atmospheric wind vectors, even in a cloud, which provides essential observing tools for understanding aerosol–cloud interactions. The European project BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) focuses on these specific interactions. In particular, vertical wind velocity at cloud base is a key parameter for studying aerosol–cloud interactions. To measure the three components of wind, a RPA is equipped with a five-hole probe, pressure sensors, and an inertial navigation system (INS). The five-hole probe is calibrated on a multi-axis platform, and the probe–INS system is validated in a wind tunnel. Once mounted on a RPA, power spectral density (PSD) functions and turbulent kinetic energy (TKE) derived from the five-hole probe are compared with sonic anemometers on a meteorological mast. During a BACCHUS field campaign at Mace Head Atmospheric Research Station (Ireland), a fleet of RPAs was deployed to profile the atmosphere and complement ground-based and satellite observations of physical and chemical properties of aerosols, clouds, and meteorological state parameters. The five-hole probe was flown on straight-and-level legs to measure vertical wind velocities within clouds. The vertical velocity measurements from the RPA are validated with vertical velocities derived from a ground-based cloud radar by showing that both measurements yield model-simulated cloud droplet number concentrations within 10 %. The updraft velocity distributions illustrate distinct relationships between vertical cloud fields in different meteorological conditions.

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Nieto Muro, Pablo, Florian M. Heckmeier, Sean Jenkins, and Christian Breitsamter. "Development of an Analytic Convection Model for a Heated Multi-Hole Probe for Aircraft Applications." Sensors 21, no. 18 (September 16, 2021): 6218. http://dx.doi.org/10.3390/s21186218.

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Ice accretion or icing is a well-known phenomenon that entails a risk for the correct functioning of an aircraft. One of the areas more vulnerable to icing is the air data measuring system. This paper studies the icing protection offered by a heating system installed inside a multi-hole probe. The problem is initially solved analytically, creating a tool that can be used in order to predict the heating performance depending on the flying conditions. Later, the performance of the real system is investigated with a heated five-hole probe prototype in a wind tunnel experiment. The measured results are compared with the predictions made by the analytical model. Last, the icing protection provided by the system is estimated with respect to flying altitude and speed. As a result, a prediction tool that can be used in order to make quick icing risk predictions for straight cylindrical probes is delivered. Furthermore, the study provides some understanding about how parameters like altitude and air speed affect the occurrence of ice accretion.

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Chen, Jie, Zhiwei Shi, Mengbei Zhou, Kangli Li, Min Fan, Kun Zhang, and Haining Dong. "Modeling and simulation of UAV static soaring based on multi-hole probe." AIP Advances 11, no. 7 (July 1, 2021): 075309. http://dx.doi.org/10.1063/5.0055276.

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Kim, Sung-Hyun, Young-Jin Kang, Rho-Shin Myong, Tae-Hwan Cho, Young-Min Park, and In-Ho Choi. "Calibration of a Five-Hole Multi-Function Probe for Helicopter Air Data Sensors." International Journal of Aeronautical and Space Sciences 10, no. 2 (November 30, 2009): 43–51. http://dx.doi.org/10.5139/ijass.2009.10.2.043.

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Rediniotis, O. K., and G. Chrysanthakopoulos. "Application of Neural Networks and Fuzzy Logic to the Calibration of the Seven-Hole Probe." Journal of Fluids Engineering 120, no. 1 (March 1, 1998): 95–101. http://dx.doi.org/10.1115/1.2819670.

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The theory and techniques of Artificial Neural Networks (ANN) and Fuzzy Logic Systems (FLS) are applied toward the formulation of accurate and wide-range calibration methods for such flow-diagnostics instruments as multi-hole probes. Besides introducing new calibration techniques, part of the work’s objective is to: (a) apply fuzzy-logic methods to identify systems whose behavior is described in a “crisp” rather than a “linguistic” framework and (b) compare the two approaches, i.e., neural network versus fuzzy logic approach, and their potential as universal approximators. For the ANN approach, several network configurations were tried. A Multi-Layer Perceptron with a 2-node input layer, a 4-node output layer and a 7-node hidden/middle layer, performed the best. For the FLS approach, a system with center average defuzzifier, product-inference rule, singleton fuzzifier, and Gaussian membership functions was employed. The Fuzzy Logic System seemed to outperform the Neural Network/Multi-Layer Perceptron.

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Baskaran, Subbiah, Narayanan Ramachandran, and David Noever. "Probabilistic and Other Neural Nets in Multi-Hole Probe Calibration and Flow Angularity Pattern Recognition." Pattern Analysis & Applications 2, no. 1 (April 1999): 92–98. http://dx.doi.org/10.1007/s100440050018.

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Al-Ghussain, Loiy, and Sean C. C. Bailey. "An approach to minimize aircraft motion bias in multi-hole probe wind measurements made by small unmanned aerial systems." Atmospheric Measurement Techniques 14, no. 1 (January 11, 2021): 173–84. http://dx.doi.org/10.5194/amt-14-173-2021.

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Abstract. A multi-hole probe mounted on an aircraft provides the air velocity vector relative to the aircraft, requiring knowledge of the aircraft spatial orientation (e.g., Euler angles), translational velocity and angular velocity to translate this information to an Earth-based reference frame and determine the wind vector. As the relative velocity of the aircraft is typically an order of magnitude higher than the wind velocity, the extracted wind velocity is very sensitive to multiple sources of error including misalignment of the probe and aircraft coordinate system axes, sensor error and misalignment in time of the probe and aircraft orientation measurements in addition to aerodynamic distortion of the velocity field by the aircraft. Here, we present an approach which can be applied after a flight to identify and correct biases which may be introduced into the final wind measurement. The approach was validated using a ground reference, different aircraft and the same aircraft at different times. The results indicate a significant reduction in wind velocity variance at frequencies which correspond to aircraft motion.

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Rautenberg, Alexander, Martin Graf, Norman Wildmann, Andreas Platis, and Jens Bange. "Reviewing Wind Measurement Approaches for Fixed-Wing Unmanned Aircraft." Atmosphere 9, no. 11 (October 28, 2018): 422. http://dx.doi.org/10.3390/atmos9110422.

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One of the biggest challenges in probing the atmospheric boundary layer with small unmanned aerial vehicles is the turbulent 3D wind vector measurement. Several approaches have been developed to estimate the wind vector without using multi-hole flow probes. This study compares commonly used wind speed and direction estimation algorithms with the direct 3D wind vector measurement using multi-hole probes. This was done using the data of a fully equipped system and by applying several algorithms to the same data set. To cover as many aspects as possible, a wide range of meteorological conditions and common flight patterns were considered in this comparison. The results from the five-hole probe measurements were compared to the pitot tube algorithm, which only requires a pitot-static tube and a standard inertial navigation system measuring aircraft attitude (Euler angles), while the position is measured with global navigation satellite systems. Even less complex is the so-called no-flow-sensor algorithm, which only requires a global navigation satellite system to estimate wind speed and wind direction. These algorithms require temporal averaging. Two averaging periods were applied in order to see the influence and show the limitations of each algorithm. For a window of 4 min, both simplifications work well, especially with the pitot-static tube measurement. When reducing the averaging period to 1 min and thereby increasing the temporal resolution, it becomes evident that only circular flight patterns with full racetracks inside the averaging window are applicable for the no-flow-sensor algorithm and that the additional flow information from the pitot-static tube improves precision significantly.

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Hirotani, Tomonari, Makoto Ueno, Masashi Shigemi, Hiroshi Wakai, and Toru Iwata. "Measurement Accuracy Improvement of the Pitot Probe with Multi-Hole Pyramidal Head at High Altitude Condition." JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 53, no. 618 (2005): 325–29. http://dx.doi.org/10.2322/jjsass.53.325.

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12

Cai, X., T. Ning, F. Niu, G. Wu, and Y. Song. "Investigation of wet steam flow in a 300 MW direct air-cooling steam turbine. Part 1: Measurement principles, probe, and wetness." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 223, no. 5 (April 24, 2009): 625–34. http://dx.doi.org/10.1243/09576509jpe690.

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The direct air-cooling steam turbines have been operated more and more in the north of China. The backpressure of a turbine is affected easily with weather and varies very often in a short time. The variation of backpressure in a larger range from about 10 to 60 kPa causes many problems in design and operation of the turbine. To study the properties of the wet steam flow in the low pressure direct air-cooling steam turbine, an optical—pneumatic probe was developed based on the multi-wavelength light extinction and four-hole wedge probe. Measurements with this probe in a 300 MW direct air-cooling turbine were carried out. The measured local wetness, total wetness of exhaust steam, size distribution of fine droplets, and their profiles along the blade height are presented. The measured cylinder efficiency and total wetness agree well with the results obtained by the thermal performance tests.

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13

Lien, S. J., and N. A. Ahmed. "An examination of suitability of multi-hole pressure probe technique for skin friction measurement in turbulent flow." Flow Measurement and Instrumentation 22, no. 3 (June 2011): 153–64. http://dx.doi.org/10.1016/j.flowmeasinst.2011.01.004.

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14

Traub, L. W., B. Moeller, and S. F. Galls. "Alleviation of pitch-up on delta wings using distributed porosity." Aeronautical Journal 103, no. 1025 (July 1999): 339–47. http://dx.doi.org/10.1017/s000192400006471x.

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Abstract An experimental investigation was undertaken to determine the effectiveness of distributed surface porosity for the alleviation of pitch-up on a delta wing. Tests were undertaken using a 65° sweep delta wing with distributed porosity evaluated at various locations on the wing. Force balance, on and off surface flow visualisation and flow field surveys using a multi-hole probe were undertaken. The data shows that distributed porosity applied along the wing leading edge at the apex is effective in eliminating pitch-up whilst incurring a minimal performance cost. Trailing edge porosity generally degraded performance.

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Haggard, Daryl. "Advances from Recent Multi-wavelength Campaigns on Sgr A*." Proceedings of the International Astronomical Union 11, S322 (July 2016): 1–10. http://dx.doi.org/10.1017/s1743921316012217.

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AbstractSagittarius A* is the closest example of a supermassive black hole and our proximity allows us to detect emission from its accretion flow in the radio, submillimeter, near IR, and X-ray regimes. Ambitious monitoring campaigns have yielded rich multi-wavelength, time-resolved data that have the power to probe the physical processes underlying Sgr A*’s quiescent and flare emission. Here, I review the status of Sgr A* X-ray monitoring campaigns from the Chandra X-ray Observatory (also XMM Newton, and Swift), and efforts to coordinate these with observations across the electromagnetic spectrum. I also discuss how these observations constrain models for Sgr A*’s variability, which range from tidal disruption of asteroids to gravitational lensing to collimated outflows to magnetic reconnection.

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Han, Fenghui, Zhe Wang, Yijun Mao, Yiyun Zhang, and Jiajian Tan. "Large-Scale Flow Measurements and Analysis for Radial Inlets of Industrial Centrifugal Compressors Based on Multi-hole Probe System." International Journal of Precision Engineering and Manufacturing 20, no. 1 (January 2019): 79–92. http://dx.doi.org/10.1007/s12541-019-00036-w.

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17

Shi, Jun-Feng, Feng Deng, Li-Zhi Xiao, Hua-Bing Liu, Feng-Qin Ma, Meng-Ying Wang, Rui-Dong Zhao, Shi-Wen Chen, Jian-Jun Zhang, and Chun-Ming Xiong. "A proposed NMR solution for multi-phase flow fluid detection." Petroleum Science 16, no. 5 (September 25, 2019): 1148–58. http://dx.doi.org/10.1007/s12182-019-00367-3.

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Abstract In the petroleum industry, detection of multi-phase fluid flow is very important in both surface and down-hole measurements. Accurate measurement of high rate of water or gas multi-phase flow has always been an academic and industrial focus. NMR is an efficient and accurate technique for the detection of fluids; it is widely used in the determination of fluid compositions and properties. This paper is aimed to quantitatively detect multi-phase flow in oil and gas wells and pipelines and to propose an innovative method for online nuclear magnetic resonance (NMR) detection. The online NMR data acquisition, processing and interpretation methods are proposed to fill the blank of traditional methods. A full-bore straight tube design without pressure drop, a Halbach magnet structure design with zero magnetic leakage outside the probe, a separate antenna structure design without flowing effects on NMR measurement and automatic control technology will achieve unattended operation. Through the innovation of this work, the application of NMR for the real-time and quantitative detection of multi-phase flow in oil and gas wells and pipelines can be implemented.

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Thompson, M., S. Watkins, C. White, and J. Holmes. "Span-wise wind fluctuations in open terrain as applicable to small flying craft." Aeronautical Journal 115, no. 1173 (November 2011): 693–701. http://dx.doi.org/10.1017/s0001924000006412.

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Abstract Micro air vehicles (MAVs) are typically of low mass and moment of inertia and have flight speeds comparable to birds and the larger insects. Such craft traverse the lower levels of the atmospheric boundary layer (ABL) which is a significantly different environment than that experienced by larger manned aircraft, which spend the majority of their time in relatively clean air and fly at speeds significantly higher than typical wind speeds in the ABL. Here a new series of measurements dedicated to understanding spatial and temporal velocity fields that MAVs experience are presented. Atmospheric wind measurements were taken by sampling four multi-hole dynamic pressure probes spanned perpendicular to the oncoming wind at spans of between 0·014m and up to 0·45m. It was noted that the variation of both longitudinal velocity and flow pitch angle against spacing followed a fractional power law and as such large variations were present even for the smallest inter-probe separations. This effect is thought to explain the increasing piloting difficulties experienced in maintaining good roll control for decreasing scales of craft.

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ARZANO, MICHELE, ALIOSCIA HAMMA, and SIMONE SEVERINI. "HIDDEN ENTANGLEMENT AND UNITARITY AT THE PLANCK SCALE." Modern Physics Letters A 25, no. 06 (February 28, 2010): 437–45. http://dx.doi.org/10.1142/s0217732310032603.

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Attempts to go beyond the framework of local quantum field theory include scenarios in which the action of external symmetries on the quantum fields Hilbert space is deformed. We show how the Fock spaces of such theories exhibit a richer structure in their multi-particle sectors. When the deformation scale is proportional to the Planck energy, such new structure leads to the emergence of a "planckian" mode-entanglement, invisible to an observer that cannot probe the Planck scale. To the same observer, certain unitary processes would appear non-unitary. We show how entanglement transfer to the additional degrees of freedom can provide a potential way out of the black hole information paradox.

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Bian, Xingyuan, Junning Cui, Yesheng Lu, and Jiubin Tan. "Ultraprecision Diameter Measurement of Small Holes with Large Depth-To-Diameter Ratios Based on Spherical Scattering Electrical-Field Probing." Applied Sciences 9, no. 2 (January 10, 2019): 242. http://dx.doi.org/10.3390/app9020242.

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In order to solve the difficulty of precision measurement of small hole diameters with large depth-to-diameter ratios, a new measurement method based on spherical scattering electrical-field probing (SSEP) was developed. A spherical scattering electrical field with identical sensing characteristics in arbitrary spatial directions was formed to convert the micro gap between the probing-ball and the part being measured into an electrical signal. 3D non-contact probing, nanometer resolution, and approximate point probing—which are key properties for high measurement precision and large measurable depth-to-diameter ratios—were achieved. A specially designed hole diameter measuring machine (HDMM) was developed, and key techniques, including laser interferometry for macro displacement measurement of the probe, multi-degree-of-freedom adjustment of hole attitude, and measurement process planning, are described. Experiments were carried out using the HDMM and a probing sensor with a ϕ3-mm probing ball and a 150-mm-long stylus to verify the performance of the probing sensor and the measuring machine. The experimental results indicate that the resolution of the probing sensor was as small as 1 nm, and the expanded uncertainty of measurement result was 0.2 μm (k = 2) when a ϕ20-mm ring gauge standard was measured.

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Subathra, P., S. Sivagurunathan, and N. Ramaraj. "Detection and Prevention of Single and Cooperative Black Hole Attacks in Mobile Ad Hoc Networks." International Journal of Business Data Communications and Networking 6, no. 1 (January 2010): 38–57. http://dx.doi.org/10.4018/jbdcn.2010010103.

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A Mobile Ad hoc Network (MANET) is a collection of wireless computers (nodes) communicating over multi-hop paths, without infrastructures such as base stations and access points. Nodes must cooperate to provide necessary network functionalities. The Dynamic Source Routing (DSR) protocol is a principal routing protocol in MANET, where security can be compromised by a “Black Hole” attack. In this attack, a malicious node claims to have the shortest path to the destination and attracts all traffic and drops all packets sent for forwarding, leading to performance degradation in the network. The situation becomes even more severe when two or more nodes cooperate and perform an attack called the “Cooperative Black Hole” attack. This article proposes a solution based on probing to identify and prevent such attacks. The proposed solution discovers a secure route between the source and destination by identifying and isolating both single and cooperative black holes, making the MANET resistant against such attacks. Simulation results show that the protocol provides better security and performance in terms of detection time, packet delivery ratio and false negative probability in comparison with trust and probe based schemes.

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Djerourou, Samira, Mourad Djebli, and Mohamed Ouchabane. "Plasma parameters of RF capacitively coupled discharge: comparative study between a plane cathode and a large hole dimensions multi-hollow cathode." European Physical Journal Applied Physics 85, no. 1 (January 2019): 10801. http://dx.doi.org/10.1051/epjap/2019180193.

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This work deals with a comparative study of plasma discharge generated by two geometrical configurations of cathodes through an investigation of their plasma parameters. A large hole diameter and depth (D = 40 mm, W = 50 mm) multi-hollow (MH) cathode compared with a plane (PL) cathode are presented for argon capacitively coupled radiofrequency discharge. The electrical characteristics of MH and PL cathodes have been measured in terms of the self-bias voltage (Vdc) while the Langmuir probe was used to measure electron density (ne) and electron temperature (Te) for a wide range of gas pressure (60–400 mTorr) and incident power (50–300 W). It is found that the hollow cathode effect (HCE) is optimum at 60 mTorr with 220 mTorr as a critical gas pressure for which a transition from HCE to insufficient HCE is seen. The electron temperature varies from 3 to 5 eV in the case of MH and PL cathodes with respect to incident power and gas pressure.

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Harmatys, Wiktor, Adam Gąska, Piotr Gąska, Maciej Gruza, and Jerzy A. Sładek. "Assessment of Background Illumination Influence on Accuracy of Measurements Performed on Optical Coordinate Measuring Machine Equipped with Video Probe." Sensors 21, no. 7 (April 3, 2021): 2509. http://dx.doi.org/10.3390/s21072509.

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Currently the Coordinate Measuring Technique is facing new challenges both in terms of used methodology and a speed of measurement. More and more often modern optical systems or multisensor systems replace classic solutions. Measurement performed using the optical system is more vulnerable to incorrect points acquisition due to such factors as an inadequate focus or parameters of applied illumination. This article examines the effect of an increasing illumination on the measurement result. A glass reference plate with marked circles and a hole plate standard were used for the measurements performed on a multi-sensor machine Zeiss O’ Inspect 442. The experiment consisted of measurements of standard objects with different values of the backlight at the maximum magnification. Such approach allows to assess the influence of controlled parameter on errors of diameter and form measurements as well as an uncertainty of measurements by determination of ellipses of point repeatability. The analysis of the obtained results shows that increasing backlight mainly affects the result of the diameter measurement.

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Pratley, L., M. Johnston-Hollitt, S. Dehghan, and M. Sun. "Using radio jets of PKS J0334-3900 to probe the intra-cluster medium in A3135." Proceedings of the International Astronomical Union 10, S313 (September 2014): 301–2. http://dx.doi.org/10.1017/s1743921315002379.

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AbstractWe present a multi-wavelength study of the radio galaxy PKS J0334-3900, which resides at the centre of Abell 3135. Using Australia Telescope Compact Array (ATCA) observations at 1.4, 2.5, 4.6 & 8.6 GHz, we performed a detailed analysis of PKS J0334-3900. The morphology and spectral indices give physical parameters that constrain the dynamical history of the galaxy, which we use to produce a simulation of PKS J0334-3900. This simulation shows that the morphology can be generated by a wind in the intracluster medium (ICM), orbital motion caused by a companion galaxy, and precession of the black hole (BH).Additionally, ATCA polarisation data was used to obtain rotation measure values along the line of sight to PKS J0334-3900. Using our simulation we are able to infer the distance between the jets along the line of sight to be 154 ± 16 kpc, which when combined with the difference in rotation measure between the jets provides a novel new way to estimate the average magnetic field within the cluster. A lower limit to the cluster magnetic field was calculated to be 0.09±0.03 μG. We have shown that different techniques can be applied to observations of jets in galaxies to infer information on cluster environments.

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Yang, Jun, Zsolt Paragi, Emanuele Nardini, Willem A. Baan, Lulu Fan, Prashanth Mohan, Eskil Varenius, and Tao An. "The nearby extreme accretion and feedback system PDS 456: finding a complex radio-emitting nucleus." Monthly Notices of the Royal Astronomical Society 500, no. 2 (August 17, 2020): 2620–26. http://dx.doi.org/10.1093/mnras/staa2445.

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ABSTRACT When a black hole accretes close to the Eddington limit, the astrophysical jet is often accompanied by radiatively driven, wide-aperture and mildly relativistic winds. Powerful winds can produce significant non-thermal radio emission via shocks. Among the nearby critical accretion quasars, PDS 456 has a very massive black hole (about 1 billion solar masses), shows a significant star-forming activity (about 70 solar masses per year), and hosts exceptionally energetic X-ray winds (power up to 20 per cent of the Eddington luminosity). To probe the radio activity in this extreme accretion and feedback system, we performed very long baseline interferometric (VLBI) observations of PDS 456 at 1.66 GHz with the European VLBI Network and the enhanced Multi-Element Remotely Linked Interferometry Network. We find a rarely seen complex radio-emitting nucleus consisting of a collimated jet and an extended non-thermal radio emission region. The diffuse emission region has a size of about 360 pc and a radio luminosity about three times higher than that of the nearby extreme starburst galaxy Arp 220. The powerful nuclear radio activity could result either from a relic jet with a peculiar geometry (nearly along the line of sight) or more likely from diffuse shocks formed naturally by the existing high-speed winds impacting on high-density star-forming regions.

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RAUE, M., L. STAWARZ, D. MAZIN, P. COLIN, C. M. HUI, M. BEILICKE, W. MCCONVILLE, et al. "THE 2010 M 87 VHE FLARE AND ITS ORIGIN: THE MULTI-WAVELENGTH PICTURE." International Journal of Modern Physics: Conference Series 08 (January 2012): 184–89. http://dx.doi.org/10.1142/s2010194512004588.

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The giant radio galaxy M 87, with its proximity (16 Mpc) and its very massive black hole ((3-6) × 109 M⊙), provides a unique laboratory to investigate very high energy (E>100 GeV; VHE) gamma-ray emission from active galactic nuclei and, thereby, probe particle acceleration to relativistic energies near supermassive black holes (SMBH) and in relativistic jets. M 87 has been established as a VHE γ-ray emitter since 2005. The VHE γ-ray emission displays strong variability on timescales as short as a day. In 2008, a rise in the 43 GHz Very Long Baseline Array (VLBA) radio emission of the innermost region (core; extension of < 100 R s ; Schwarzschild radii) was found to coincide with a flaring activity at VHE. This had been interpreted as a strong indication that the VHE emission is produced in the direct vicinity of the SMBH. In 2010 a flare at VHE was again detected triggering further multi-wavelength (MWL) observations with the VLBA, Chandra, and other instruments. At the same time, M 87 was also observed with the Fermi-LAT telescope at MeV/GeV energies, the European VLBI Network (EVN), and the Liverpool Telescope (LT). Here, preliminary results from the 2010 campaign will be reported.

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van der A, R. J., M. A. F. Allaart, and H. J. Eskes. "Multi sensor reanalysis of total ozone." Atmospheric Chemistry and Physics Discussions 10, no. 4 (April 28, 2010): 11401–48. http://dx.doi.org/10.5194/acpd-10-11401-2010.

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Abstract. A single coherent total ozone dataset, called the Multi Sensor Reanalysis (MSR), has been created from all available ozone column data measured by polar orbiting satellites in the near-ultraviolet Huggins band in the last thirty years. Fourteen total ozone satellite retrieval datasets from the instruments TOMS (on the satellites Nimbus-7 and Earth Probe), SBUV (Nimbus-7, NOAA-9, NOAA-11 and NOAA-16), GOME (ERS-2), SCIAMACHY (Envisat), OMI (EOS-Aura), and GOME-2 (Metop-A) have been used in the MSR. As first step a bias correction scheme is applied to all satellite observations, based on independent ground-based total ozone data from the World Ozone and Ultraviolet Data Center. The correction is a function of solar zenith angle, viewing angle, time (trend), and stratospheric temperature. As second step data assimilation was applied to create a global dataset of total ozone analyses. The data assimilation method is a sub-optimal implementation of the Kalman filter technique, and is based on a chemical transport model driven by ECMWF meteorological fields. The chemical transport model provides a detailed description of (stratospheric) transport and uses parameterisations for gas-phase and ozone hole chemistry. The MSR dataset results from a 30-year data assimilation run with the 14 corrected satellite datasets as input, and is available on a grid of 1×1½ degrees with a sample frequency of 6 h for the complete time period (1978–2008). The Observation-minus-Analysis (OmA) statistics show that the bias of the MSR analyses is less than 1 percent with an RMS standard deviation of about 2 percent as compared to the corrected satellite observations used.

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van der A, R. J., M. A. F. Allaart, and H. J. Eskes. "Multi sensor reanalysis of total ozone." Atmospheric Chemistry and Physics 10, no. 22 (November 30, 2010): 11277–94. http://dx.doi.org/10.5194/acp-10-11277-2010.

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Abstract. A single coherent total ozone dataset, called the Multi Sensor Reanalysis (MSR), has been created from all available ozone column data measured by polar orbiting satellites in the near-ultraviolet Huggins band in the last thirty years. Fourteen total ozone satellite retrieval datasets from the instruments TOMS (on the satellites Nimbus-7 and Earth Probe), SBUV (Nimbus-7, NOAA-9, NOAA-11 and NOAA-16), GOME (ERS-2), SCIAMACHY (Envisat), OMI (EOS-Aura), and GOME-2 (Metop-A) have been used in the MSR. As first step a bias correction scheme is applied to all satellite observations, based on independent ground-based total ozone data from the World Ozone and Ultraviolet Data Center. The correction is a function of solar zenith angle, viewing angle, time (trend), and effective ozone temperature. As second step data assimilation was applied to create a global dataset of total ozone analyses. The data assimilation method is a sub-optimal implementation of the Kalman filter technique, and is based on a chemical transport model driven by ECMWF meteorological fields. The chemical transport model provides a detailed description of (stratospheric) transport and uses parameterisations for gas-phase and ozone hole chemistry. The MSR dataset results from a 30-year data assimilation run with the 14 corrected satellite datasets as input, and is available on a grid of 1× 1 1/2° with a sample frequency of 6 h for the complete time period (1978–2008). The Observation-minus-Analysis (OmA) statistics show that the bias of the MSR analyses is less than 1% with an RMS standard deviation of about 2% as compared to the corrected satellite observations used.

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Lien, Amy, Takanori Sakamoto, Neil Gehrels, David Palmer, and Carlo Graziani. "Trigger Simulations for GRB Detection with the Swift Burst Alert Telescope." Proceedings of the International Astronomical Union 7, S279 (April 2011): 347–48. http://dx.doi.org/10.1017/s1743921312013282.

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AbstractUnderstanding the intrinsic cosmic long gamma-ray burst (GRB) rate is essential in many aspects of astrophysics and cosmology, such as revealing the connection between GRBs, supernovae (SNe), and stellar evolution. Swift, a multi-wavelength space telescope, is quickly expanding the GRB category by observing hundreds of GRBs and their redshifts. However, it remains difficult to determine the intrinsic GRB rate due to the complex trigger algorithm adopted by Swift. Current studies of the GRB rate usually approximate the Swift trigger algorithm by a single detection threshold. Nevertheless, unlike the previously flown GRB instruments, Swift has over 500 trigger criteria based on count rates and additional thresholds for localization. To investigate possible systematic biases and further explore the intrinsic GRB rate as a function of redshift and the GRB luminosity function, we adopt a Monte Carlo approach by simulating all trigger criteria used by Swift. A precise estimation of the intrinsic GRB rate is important to reveal the GRB origins and their relation to the black-hole forming SNe. Additionally, the GRB rate at high redshifts provides a strong probe of the star formation history in the early universe, which is hard to measure directly through other methods.

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Biswas, A. K., Ashoke K. Raman, and A. N. Mullick. "A Numerical Simulation of Turbulent Flow through a Curved Duct." Mapana - Journal of Sciences 11, no. 3 (August 21, 2012): 169–78. http://dx.doi.org/10.12723/mjs.22.11.

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This paper presents the comparison the results of an experimental work with a numerical work keeping the geometry of the test duct and inlet boundary conditions unaltered. The numerical simulation is validated with the experimental results based on the wall y+ approach for different turbulence models suited for this type of geometry. The experimental work is carried out at mass averaged mean velocity of 40m/s with the measurement of total pressure by a pre-calibrated multi-hole pressure probe and the results presented in the form of a pressure contours in 2-D. For validation of the numerical results Standard k-ε, k-ω and Reynolds Stress Model (RSM) are used to solve the closure problem. The turbulence models are investigated in the commercial CFD code of Fluent using y+ value as guidance in selecting the appropriate grid configuration and turbulence model. Based on the wall y+ values for different turbulence models, it is concluded in the present study that the mesh resolving the fully turbulent region is sufficiently accurate in terms of qualitative features and RSM turbulence model predicts the best results while comparing with the experimental results.

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Moskalets, Michael. "Auto- versus Cross-Correlation Noise in Periodically Driven Quantum Coherent Conductors." Entropy 23, no. 4 (March 25, 2021): 393. http://dx.doi.org/10.3390/e23040393.

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Expressing currents and their fluctuations at the terminals of a multi-probe conductor in terms of the wave functions of carriers injected into the Fermi sea provides new insight into the physics of electric currents. This approach helps us to identify two physically different contributions to shot noise. In the quantum coherent regime, when current is carried by non-overlapping wave packets, the product of current fluctuations in different leads, the cross-correlation noise, is determined solely by the duration of the wave packet. In contrast, the square of the current fluctuations in one lead, the autocorrelation noise, is additionally determined by the coherence of the wave packet, which is associated with the spread of the wave packet in energy. The two contributions can be addressed separately in the weak back-scattering regime, when the autocorrelation noise depends only on the coherence. Analysis of shot noise in terms of these contributions allows us, in particular, to predict that no individual traveling particles with a real wave function, such as Majorana fermions, can be created in the Fermi sea in a clean manner, that is, without accompanying electron–hole pairs.

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Wyrzykowski, Łukasz, and Ilya Mandel. "Constraining the masses of microlensing black holes and the mass gap with Gaia DR2." Astronomy & Astrophysics 636 (April 2020): A20. http://dx.doi.org/10.1051/0004-6361/201935842.

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Context. Gravitational microlensing is sensitive to compact-object lenses in the Milky Way, including white dwarfs, neutron stars, or black holes, and could potentially probe a wide range of stellar-remnant masses. However, the mass of the lens can be determined only in very limited cases, due to missing information on both source and lens distances and their proper motions. Aims. Our aim is to improve the mass estimates in the annual parallax microlensing events found in the eight years of OGLE-III observations towards the Galactic Bulge with the use of Gaia Data Release 2 (DR2). Methods. We use Gaia DR2 data on distances and proper motions of non-blended sources and recompute the masses of lenses in parallax events. We also identify new events in that sample which are likely to have dark lenses; the total number of such events is now 18. Results. The derived distribution of masses of dark lenses is consistent with a continuous distribution of stellar-remnant masses. A mass gap between neutron star and black hole masses in the range between 2 and 5 solar masses is not favoured by our data, unless black holes receive natal kicks above 20−80 km s−1. We present eight candidates for objects with masses within the putative mass gap, including a spectacular multi-peak parallax event with mass of 2.4−1.3+1.9 M⊙ located just at 600 pc. The absence of an observational mass gap between neutron stars and black holes, or conversely the evidence of black hole natal kicks if a mass gap is assumed, can inform future supernova modelling efforts.

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Qiu, Jane. "South China Sea: the gateway to China's deep-sea ambitions." National Science Review 4, no. 4 (July 1, 2017): 658–63. http://dx.doi.org/10.1093/nsr/nwx107.

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Abstract For most parts of its history, China has largely turned its back on ocean exploration. Even after it started oceanographic research in the 1950s, the focus was mostly on coastal and offshore waters. But this changed a decade ago when the country began to invest heavily on deep-sea research—resulting in the launch in 2011 of its first multi-disciplinary deep-sea research programme called the South China Sea (SCS)-Deep to probe the mystery of this marginal sea. Covering an area of 3.5 million square kilometres and with a maximum depth of 5500 metres, SCS occupies a scientifically interesting position between the world's highest mountains, the Himalayas, and the deepest point on Earth, the Mariana Trench in the western Pacific Ocean. In a forum organized by National Science Review at the Annual Conference of the South China Sea-Deep Programme held in January in Shanghai, a panel of scientists explained what China's deep-sea ambitions are, why SCS is a fantastic natural laboratory, the importance of international collaboration, what China needs to do to develop cutting-edge marine technologies and how SCS could be an ideal platform for regional cooperation. Nianzhi Jiao an ecologist at Xiamen University, Xiamen, China Dongxiao Wang a physical oceanographer at South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China Jian Lin a marine geophysicist at Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA, and South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China Pinxian Wang a paleoceanographer at Tongji University, Shanghai, China Jiwei Tian a physical oceanographer at Ocean University of China, Qingdao, China Aiqun Zhang chief engineer at the Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China

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Frost, A. J., R. D. Oudmaijer, W. J. de Wit, and S. L. Lumsden. "Unveiling the traits of massive young stellar objects through a multi-scale survey." Astronomy & Astrophysics 648 (April 2021): A62. http://dx.doi.org/10.1051/0004-6361/202039748.

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Context. The rarity and deeply embedded nature of young massive stars has limited the understanding of the formation of stars with masses larger than 8 M⊙. Previous work has shown that complementing spectral energy distributions with interferometric and imaging data can probe the circumstellar environments of massive young stellar objects (MYSOs) well. However, complex studies of single objects often use different approaches in their analysis. Therefore the results of these studies cannot be directly compared. Aims. This work aims to obtain the physical characteristics of a sample of MYSOs at ~0.01″ scales, at ~0.1″ scales, and as a whole, which enables us to compare the characteristics of the sources. Methods. We apply the same multi-scale method and analysis to a sample of MYSOs. High-resolution interferometric data (MIDI/VLTI), near-diffraction-limited imaging data (VISIR/VLT, COMICS/Subaru), and a multi-wavelength spectral energy distribution are combined. By fitting simulated observables derived from 2.5D radiative transfer models of disk-outflow-envelope systems to our observations, the properties of the MYSOs are constrained. Results. We find that the observables of all the MYSOs can be reproduced by models with disk-outflow-envelope geometries, analogous to the Class I geometry associated with low-mass protostars. The characteristics of the envelopes and the cavities within them are very similar across our sample. On the other hand, the disks seem to differ between the objects, in particular with regards to what we interpret as evidence of complex structures and inner holes. Conclusions. The MYSOs of this sample have similar large-scale geometries, but variance is observed among their disk properties. This is comparable to the morphologies observed for low-mass young stellar objects. A strong correlation is found between the luminosity of the central MYSO and the size of the transition disk-like inner hole for the MYSOs, implying that photoevaporation or the presence of binary companions may be the cause.

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Ng, Cherry. "Conducting the deepest all-sky pulsar survey ever: the all-sky High Time Resolution Universe survey." Proceedings of the International Astronomical Union 8, S291 (August 2012): 53–56. http://dx.doi.org/10.1017/s1743921312023137.

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AbstractThe extreme conditions found in and around pulsars make them fantastic natural laboratories, providing insights to a rich variety of fundamental physics and astronomy. To discover more pulsars we have begun the High Time Resolution Universe (HTRU) survey: a blind survey of the northern sky with the 100-m Effelsberg radio telescope in Germany and a twin survey of the southern sky with the 64-m Parkes radio telescope in Australia. The HTRU is an international collaboration with expertise shared among the MPIfR in Germany, ATNF/CASS and Swinburne University of Technology in Australia, University of Manchester in the UK and INAF in Italy. The HTRU survey uses multi-beam receivers and backends constructed with recent advancements in technology, providing unprecedentedly high time and frequency resolution, allowing us to probe deeper into the Galaxy than ever before. While a general overview of HTRU has been given by Keith at this conference, here we focus on three further aspects of HTRU discoveries and highlights. These include the ‘Diamond-planet pulsar’ binary J1719-1438 and a second similar system recently discovered. In addition, we provide specifications of the HTRU-North survey and an update of its status. In the last section we give an overview of the search for highly-accelerated binaries in the Galactic plane region. We discuss the computational challenges arising from the processing of the petabyte-sized HTRU survey data. We present an innovative segmented search technique which aims to increase our chances of discovering highly accelerated relativistic binary systems, potentially including pulsar-black-hole binaries.

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OKANO, Masahisa, Fumitaka MATANO, Tsunehiro SEKIMOTO, and Hiroyuki KATAYAMA. "EXPERIMENTAL STUDY ON THE HYDRAULIC CHARACTERISTICS OF THE MULTI-HOLE SUCTION PIPE." PROCEEDINGS OF HYDRAULIC ENGINEERING 48 (2004): 1393–98. http://dx.doi.org/10.2208/prohe.48.1393.

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Kurtz, Anthony D. "Ultra miniature multi-hole probes having high frequency response." Journal of the Acoustical Society of America 126, no. 1 (2009): 517. http://dx.doi.org/10.1121/1.3182981.

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Garcia-Basabe, Yunier, Denis Ceolin, Aldo J. G. Zarbin, Lucimara S. Roman, and Maria Luiza M. Rocco. "Ultrafast interface charge transfer dynamics on P3HT/MWCNT nanocomposites probed by resonant Auger spectroscopy." RSC Advances 8, no. 46 (2018): 26416–22. http://dx.doi.org/10.1039/c8ra04629h.

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Ghosh, Anindya, David M. Birch, and Olaf Marxen. "Neural-Network-Based Sensor Data Fusion for Multi-Hole Fluid Velocity Probes." IEEE Sensors Journal 20, no. 10 (May 15, 2020): 5398–405. http://dx.doi.org/10.1109/jsen.2020.2969286.

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Kavic, Michael J., Djordje Minic, and John Simonetti. "Quantum gravity and BH-NS binaries." International Journal of Modern Physics D 27, no. 14 (October 2018): 1847007. http://dx.doi.org/10.1142/s0218271818470077.

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We argue that the Black Hole-Neutron Star (BH-NS) binaries are the natural astrophysical probes of quantum gravity in the context of the new era of multi-messenger astronomy. In particular, we discuss the observable effect of enhanced BH mass loss in a BH-NS binary, due to the presence of an additional length scale tied to the intrinsic noncommutativity of quantum spacetime in quantum gravity.

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Heckmeier, Florian M., Daniel Iglesias, Stefanie Kreft, Sascha Kienitz, and Christian Breitsamter. "Development of unsteady multi-hole pressure probes based on fiber-optic pressure sensors." Engineering Research Express 1, no. 2 (October 31, 2019): 025023. http://dx.doi.org/10.1088/2631-8695/ab4f0d.

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Menu, J., R. van Boekel, T. Henning, M. Benisty, C. J. Chandler, H. Linz, C. Waelkens, et al. "TW Hydrae: multi-wavelength interferometry of a transition disk." Proceedings of the International Astronomical Union 8, S299 (June 2013): 104–8. http://dx.doi.org/10.1017/s1743921313008016.

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AbstractFor over a decade, the structure of the inner “hole” in the transition disk around TW Hydrae has been a subject of debate. To probe the innermost regions of the protoplanetary disk, observations at the highest possible spatial resolution are required. We present new interferometric data of TW Hya from near-infrared to millimeter wavelengths. We confront existing models of the disk structure with the complete data set and develop a new, detailed radiative-transfer model. This model is characterized by: 1) a spatial separation of the largest grains from the small disk grains; and 2) a smooth inner rim structure, rather than a sharp disk edge.

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Tomaszewski, Adam, Tomasz Przybylinski, and Marcin Lackowski. "Experimental and Numerical Analysis of Multi-Hole Orifice Flow Meter: Investigation of the Relationship between Pressure Drop and Mass Flow Rate." Sensors 20, no. 24 (December 18, 2020): 7281. http://dx.doi.org/10.3390/s20247281.

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The paper presents the results of the experimental and numerical analysis of a six-hole orifice flow meter. The experiments were performed on humid air in a 100 mm diameter duct. The aim of this research was to investigate the mass flow and pressure drop dependency in an orifice of a predetermined shape and to compare the results obtained with computational formulas recommended in the ISO 5167-2 standard for a single-hole orifice flow meter. The experiments and calculations were performed on several multi-hole orifice geometries with different contraction coefficient in a wide range of Reynolds numbers. The pressure was probed immediately upstream and downstream of the orifice. The flow coefficient determined for the six-hole orifice flow meter investigated was compared with the flow coefficient of conventional single-hole orifice with the same contraction coefficient. The results from computational formulas for single-hole orifice from ISO 5167 are also included in the paper. During some experiments, an obstacle has been introduced in the duct at variable distance upstream from the orifice. The effect of the thus generated velocity field disturbance on the measured pressure drop was then investigated. Numerical simulation of the flow with the presence of the obstacle was also performed and compared with experimental data.

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Nikpey Somehsaraei, Homam, Magnus Hölle, Herwart Hönen, and Mohsen Assadi. "A novel approach based on artificial neural network for calibration of multi-hole pressure probes." Flow Measurement and Instrumentation 73 (June 2020): 101739. http://dx.doi.org/10.1016/j.flowmeasinst.2020.101739.

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LEVINSON, AMIR. "JETS ON ALL SCALES." International Journal of Modern Physics D 19, no. 06 (June 2010): 649–57. http://dx.doi.org/10.1142/s0218271810016919.

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A brief overview of jets and their central drivers is presented, with a focus on accreting black hole systems. In particular, scaling relations that elucidate some basic properties of the engines are derived, and the implications for the associated outflows are discussed. The kinematics and dynamics of relativistic jets in various systems and the dissipation of their bulk energy is considered, with an emphasis on consequences of recent observations. Also considered is the interaction of the jets with their environment. Comments on multi-messenger probes are made at the end.

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Allaz, Julien M., Michael L. Williams, Michael J. Jercinovic, Karsten Goemann, and John Donovan. "Multipoint Background Analysis: Gaining Precision and Accuracy in Microprobe Trace Element Analysis." Microscopy and Microanalysis 25, no. 1 (February 2019): 30–46. http://dx.doi.org/10.1017/s1431927618015660.

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AbstractElectron microprobe trace element analysis is a significant challenge. Due to the low net intensity of peak measurements, the accuracy and precision of such analyses relies critically on background measurements, and on the accuracy of any pertinent peak interference corrections. A linear regression between two points selected at appropriate background positions is a classical approach for electron probe microanalysis (EPMA). However, this approach neglects the accurate assessment of background curvature (exponential or polynomial), and the presence of background interferences, a hole in the background, or an absorption edge can dramatically affect the results if underestimated or ignored. The acquisition of a quantitative wavelength-dispersive spectrometry (WDS) scan over the spectral region of interest remains a reasonable option to determine the background intensity and curvature from a fitted regression of background portions of the scan, but this technique can be time consuming and retains an element of subjectivity, as the analyst has to select areas in the scan which appear to represent background. This paper presents a new multi-point background (MPB) method whereby the background intensity is determined from up to 24 background measurements from wavelength positions on either side of analytical lines. This method improves the accuracy and precision of trace element analysis in a complex matrix through careful regression of the background shape, and can be used to characterize the background over a large spectral region covering several elements to be analyzed. The overall efficiency improves as systematic WDS scanning is not required to assess background interferences. The method is less subjective compared to methods that rely on WDS scanning, including selection of two interpolation points based on WDS scans, because “true” backgrounds are selected through an exclusion method of possible erroneous backgrounds. The first validation of the MPB method involves blank testing to ensure the method can accurately measure the absence of an element. The second validation involves the analysis of U-Th-Pb in several monazite reference materials of known isotopic age. The impetus for the MPB method came from efforts to refine EPMA monazite U-Th-Pb dating, where it was recognized that background errors resulting from interference or strong background curvature could result in errors of several tens of millions of years on the calculated date. Results obtained on monazite reference materials using two different microprobes, a Cameca SX-100 Ultrachron and a JEOL JXA-8230, yield excellent agreement with ages obtained by isotopic methods (Thermal Ionization Mass Spectrometry [TIMS], Sensitive High-Resolution Ion MicroProbe [SHRIMP], or Secondary Ion Mass Spectrometry [SIMS]). Finally, the MPB method can be used to model the background over a large spectrometer range to improve the accuracy of background measurement of minor and trace elements acquired on a same spectrometer, a method called the shared background measurement. This latter significantly improves the accuracy of minor and trace element analysis in complex matrices, as demonstrated by the analysis of Rare Earth Elements (REE) in REE-silicates and phosphates and of trace elements in scheelite.

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Zhang, Huabin, Shouwei Zuo, Mei Qiu, Sibo Wang, Yongfan Zhang, Jing Zhang, and Xiong Wen (David) Lou. "Direct probing of atomically dispersed Ru species over multi-edged TiO2 for highly efficient photocatalytic hydrogen evolution." Science Advances 6, no. 39 (September 2020): eabb9823. http://dx.doi.org/10.1126/sciadv.abb9823.

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A cocatalyst is necessary for boosting the electron-hole separation efficiency and accelerating the reaction kinetics of semiconductors. As a result, it is of critical importance to in situ track the structural evolution of the cocatalyst during the photocatalytic process, but it remains very challenging. Here, atomically dispersed Ru atoms are decorated over multi-edged TiO2 spheres for photocatalytic hydrogen evolution. Experimental results not only demonstrate that the photogenerated electrons can be effectively transferred to the isolated Ru atoms for hydrogen evolution but also imply that the TiO2 architecture with multi-edges might facilitate the charge separation and transport. The change in valence and the evolution of electronic structure of Ru sites are well probed during the photocatalytic process. Specifically, the optimized catalyst produces the hydrogen evolution rate of 7.2 mmol g−1 hour−1, which is much higher than that of Pt-based cocatalyst systems and among the highest reported values.

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Wildmann, N., S. Ravi, and J. Bange. "Towards higher accuracy and better frequency response with standard multi-hole probes in turbulence measurement with remotely piloted aircraft (RPA)." Atmospheric Measurement Techniques 7, no. 4 (April 22, 2014): 1027–41. http://dx.doi.org/10.5194/amt-7-1027-2014.

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Abstract. This study deals with the problem of turbulence measurement with small remotely piloted aircraft (RPA). It shows how multi-hole probes (MHPs) can be used to measure fluctuating parts of the airflow in flight up to 20 Hz. Accurate measurement of the transient wind in the outdoor environment is needed for the estimation of the 3-D wind vector as well as turbulent fluxes of heat, momentum, water vapour, etc. In comparison to an established MHP system, experiments were done to show how developments of the system setup can improve data quality. The study includes a re-evaluation of the pneumatic tubing setup, the conversion from pressures to airspeed, the pressure transducers, and the data acquisition system. In each of these fields, the steps that were taken lead to significant improvements. A spectral analysis of airspeed data obtained in flight tests shows the capability of the system to measure atmospheric turbulence up to the desired frequency range.

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Wildmann, N., S. Ravi, and J. Bange. "Towards higher accuracy and better frequency response with standard multi-hole probes in turbulence measurement with Remotely Piloted Aircraft (RPA)." Atmospheric Measurement Techniques Discussions 6, no. 6 (November 14, 2013): 9783–818. http://dx.doi.org/10.5194/amtd-6-9783-2013.

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Abstract. This study deals with the problem of turbulence measurement with small remotely piloted aircraft (RPA). It shows how multi-hole probes (MHPs) can be used to measure fluctuating parts of the airflow in flight up to 20 Hz. Accurate measurement of the transient wind in the outdoor environment is needed for the estimation of the 3-D wind vector as well as fluxes of heat, momentum, water vapour, etc. In comparison to an established MHP system, experiments were done to show how developments of the system setup can improve data quality. The study includes a re-evaluation of the pneumatic tubing setup, the conversion from pressures to airspeed, the pressure transducers, and the data acquisition system. In each of these fields, the steps that were taken lead to significant improvements. A spectral analysis of airspeed data obtained in flight tests shows the capability of the system to measure atmospheric turbulence up to the desired frequency range.

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Zach, Alexander, Walter Kasparek, Carsten Lechte, Burkhard Plaum, Francesco Monaco, Harald Schütz, Jörg Stober, Hiroshi Idei, and Thomas Hirth. "In-situ real-time monitoring of spurious modes in HE11 transmission lines using multi-hole couplers in miter bends." EPJ Web of Conferences 203 (2019): 04018. http://dx.doi.org/10.1051/epjconf/201920304018.

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Transmission of high-power millimeter waves for ECRH is often realised with oversized corrugated circular waveguides. Coupling from the gyrotron source to the waveguide is typically done via matching mirrors in free space. Small alignment errors of the system lead to the excitation of higher-order modes inside the waveguide beside the main transmission mode HE11. Those modes have comparably higher losses and can in worst case result in local fields exceeding the breakdown limit of the medium inside the waveguide. For alignment control over the whole pulse duration of the gyrotron, a set of hole-array couplers placed into a miter bend mirror probes the field inside the waveguide. The arrays are designed to detect the marker modes for beam oﬀset and tilt (LP(e=o)11 )as well as for beam waist mismatch (LP02). In addition, a main mode coupler sensitive mostly for the HE11 content is used as a power monitor. By maximizing the signal of the power monitor and minimizing the content of marker modes, a first-order optimization of the coupling from free space to the waveguide can be achieved. Signal processing of the 140 GHz information is done at kHz range after downmixing, using a frequency shifted part of the power monitor signal. As the measurement system is placed in a miter bend mirror, it can also be easily installed at various locations along the transmission line to check for possible misalignments of the waveguide connections between miter bends. Simulation and low power experimental results will be shown.

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Journal articles on the topic 'Multi-hole probe'

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