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1
Wang, Yong Qing, Na Chong, Li Mei Dong, Yu Jun Tang i Hai Jun Song. "Study on Electronic Excitation Temperature of Argon Plasma Using Low Pressure Micro-ICP Excitation Source". Advanced Materials Research 383-390 (listopad 2011): 1844–48. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.1844.
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Electronic excitation temperature is an important indicator of the spectrometer excitation source. This work experimented self-made micro-ICP excitation spectroscopy based on PCB technology, and detected 17 spectral lines in 690~860 nm of argon atom. 763.51 nm and 772.42 nm spectral lines whose wavelengths are close to were used to calculate electronic excitation temperature of argon excited by micro-ICP, and results show in 1600~3000 K. Experimental test data shows effects of argon gas pressure on electronic excitation temperature that in 20~210 Pa electronic excitation temperature increases with pressure on the whole. When argon pressure is greater than 220 Pa, plasma flame flickers and the electronic excitation temperature shows greater fluctuation; Experimental test shows effects of RF power on electronic excitation temperature that in 3~23 W electronic excitation temperature gradually increases with RF power. Causes of electronic excitation temperature with pressure, RF power variation are analyzed.
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Allen, G. Mark, i David M. Coleman. "Characterization of a Dual Inductively Coupled Plasma Atomic Emission Source". Applied Spectroscopy 41, nr 3 (marzec 1987): 381–87. http://dx.doi.org/10.1366/0003702874449039.
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A dual inductively copuled plasma atomic emission spectroscopic system is described. This new analytical discharge segregates the normally integrated processes of sampling and spectral excitation associated with atomic emission sources. A low-power, low-argon-flow, radio-frequency plasma is used as a sampling device to create gaseous species from liquid and solid samples which are subsequently transported to a second plasma for excitation. Design and construction of instrumentation and associated operational parameters are reviewed. Comparisons of the sampling and the excitation plasmas include spatial emission profiles, linear calibration plots, signal-to-background ratios, and analytical detection limits. Use of the dual ICP for direct analysis of particulates (coal fly ash and firebrick) is demonstrated.
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Abolmasov, P. K., S. N. Fabrika i O. N. Sholukhova. "The optical counterpart of the ultraluminous X-ray source NGC6946 ULX-1". Proceedings of the International Astronomical Union 2, S238 (sierpień 2006): 229–32. http://dx.doi.org/10.1017/s1743921307005029.
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AbstractWe present a study of a peculiar nebula MF16 associated with an Ultraluminous X-ray Source NGC6946 ULX-1. We use integral-field and long-slit spectral data obtained with the 6-m telescope (Russia). The nebula was for a long time considered powered by strong shocks enhancing both high-excitation and low-excitation lines. However, kinematical properties point to rather moderate expansion rates (VS ∼ 100÷200 km s−1). The total power of the emission-line source exceeds by one or two orders of magnitude the power observed expansion rate can provide, that points towards the existence of an additional source of excitation and ionization. Using CLOUDY96.01 photoionization code we derive the properties of the photoionizing source. Its total UV/EUV luminosity must be about 1040 erg/s.
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Zhou, Fen Ping, Yang Jiao i Hui Juan Duan. "Design of Excitation Source for Ultrasonic Guided Waves Based on DDS Technology". Advanced Materials Research 1049-1050 (październik 2014): 674–77. http://dx.doi.org/10.4028/www.scientific.net/amr.1049-1050.674.
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According to the characteristics of ultrasonic guided wave inspection, An exciting power, used for exciting ultrasonic guided waves in pipeline is designed based on DDS and FPGA. The excitation source consists of FPGA, D/A conversion circuit, a low-pass filter circuit and power amplifier circuit. Constructing DDS based on FPGA as the controller and signal generator. Filter circuit and power amplifier circuit are designed in this paper. The experiment results show that the excitation source can have high voltage and high frequency output capability, and can generate desired signal type with a good accuracy to fit the requirements in practice. It can be conveniently used for pipeline ultrasonic guided wave detection.
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Leonard, James D., Gen Katagiri i Terry L. Gustafson. "Quasi-Continuous Generation of 211-nm Excitation for Resonance Raman Spectroscopy". Applied Spectroscopy 48, nr 4 (kwiecień 1994): 489–92. http://dx.doi.org/10.1366/000370294775268901.
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We demonstrate the generation of 211-nm radiation using sum frequency mixing of the second and third harmonics of a cw mode-locked Nd: YLF laser operating at 76 MHz as an excitation source for resonance Raman spectroscopy. Owing to the relatively low peak power (∼4 W) but high average power (∼8 mW), we obtain good-quality spectra with relatively short collection times. In order to demonstrate the utility of this source, we have obtained the Raman spectra of several biological molecules and an inorganic molecule, ruthenium trisbipyridine, using 211-nm excitation.
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Wang, Yong Qing, Na Chong, Rong Xia Sun, Ying Chang Zhou i Wen Jun Chen. "Study on Start Burning Performance of Micro-ICP Using Stereo Spiral Coil". Advanced Materials Research 383-390 (listopad 2011): 390–94. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.390.
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According to the problem of low energy utilization of plane spiral coil used in micro-ICP, a kind of micro stereo helical coil was designed. Made 24 different structural parameters of stereo spiral coil whose diameter range 3~10 mm. Using comprehensive experimental method tested different parameters’ coils inspire argon plasma. In 13.56MHz RF power, relationships between argon pressure, coil turns, coil diameter and combustion /maintaining power of micro-ICP excitation source were tested. From spectrometer observed 17 argon emission spectrum in 690~860 nm. Spectral lines intensity influenced by RF power and work pressure. Experiments proved that micro-ICP excitation source using stereo helical coil is feasible. It can form Ar plasma and inspire Ar spectral lines.
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Xie, Xinying, Kaiqi Chen, Zhichao Zhou, Wei Jiang, Yuqi Wang, Sisi Wang, Zhihe Xia i Man Wong. "P‐1.4: Oxygen‐Plasma Induced Generation of Mobile Charge Carriers in Indium‐Tin‐Zinc Oxide". SID Symposium Digest of Technical Papers 54, S1 (kwiecień 2023): 448–50. http://dx.doi.org/10.1002/sdtp.16328.
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Mobile charge carriers can be generated in indium‐tinzinc oxide (ITZO) covered with a silicon oxide layer when subjected to an oxygen plasma treatment. The resulting resistivity is sensitive to the thickness of the cover oxide, the plasma excitation power, and the treatment time. With 280 nm of cover oxide and 10 mins of treatment, a low resistivity of 1.2 mΩ∙cm can be obtained in a plasma biased with a radio frequency excitation power of 100 W and an inductively coupled plasma excitation power of 2000 W. The treatment has been deployed to form the source/drain regions of a self‐aligned, top‐gate ITZO thin‐film transistor.
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Deng, Yujia, Wen Zeng, Xiaoming Jiang i Xiandeng Hou. "Portable photochemical vapor generation-microwave plasma optical emission spectrometer". Journal of Analytical Atomic Spectrometry 35, nr 7 (2020): 1316–19. http://dx.doi.org/10.1039/d0ja00104j.
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A low power microwave plasma torch as an excitation source was combined with a photochemical vapor generator (PVG) and a miniaturized charge-coupled device to construct a portable optical emission spectrometer.
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Higashino, Kohta, Naoki Okamura, Teruyoshi Sasayama i Takashi Yoshida. "Application of square-wave inverter in excitation system for magnetic nanoparticle tomography". AIP Advances 12, nr 3 (1.03.2022): 035012. http://dx.doi.org/10.1063/9.0000266.
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To collect the signals of magnetic nanoparticles (MNPs) at a distance from a magnetic nanoparticle tomography, a strong ac magnetic field should be generated by applying a high current to the excitation coil. To this end, sinusoidal excitation using a linear amplifier-type ac power source has been applied to the tomography. Although this source can provide a high-quality sinusoidal voltage, its low power efficiency is not suitable for generating the required high current. To overcome this limitation, we use an H-bridge voltage source inverter to achieve high efficiency by generating a square-wave voltage. However, the third harmonic component in the square wave, undermines the acquisition of MNP signals. Thus, we suppress the third harmonic by shifting the switching phase of the inverter transistors. As a result, the third harmonic in the excitation current is reduced to less than one-tenth of that obtained after conventional suppression. We verify the distribution of MNP signals at depths up to 50 mm using the proposed excitation approach. The results demonstrate the effectiveness of the proposed approach based on square-wave inverter excitation for magnetic nanoparticle tomography.
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Bodduluri, Mani Teja, Torben Dankwort, Thomas Lisec, Sven Grünzig, Anmol Khare, Minhaz Ahmed i Björn Gojdka. "Fully Integrated High-Performance MEMS Energy Harvester for Mechanical and Contactless Magnetic Excitation in Resonance and at Low Frequencies". Micromachines 13, nr 6 (30.05.2022): 863. http://dx.doi.org/10.3390/mi13060863.
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Energy harvesting and storage is highly demanded to enhance the lifetime of autonomous systems, such as IoT sensor nodes, avoiding costly and time-consuming battery replacement. However, cost efficient and small-scale energy harvesting systems with reasonable power output are still subjects of current development. In this work, we present a mechanically and magnetically excitable MEMS vibrational piezoelectric energy harvester featuring wafer-level integrated rare-earth micromagnets. The latter enable harvesting of energy efficiently both in resonance and from low-g, low-frequency mechanical energy sources. Under rotational magnetic excitation at frequencies below 50 Hz, RMS power output up to 74.11 µW is demonstrated in frequency up-conversion. Magnetic excitation in resonance results in open-circuit voltages > 9 V and RMS power output up to 139.39 µW. For purely mechanical excitation, the powder-based integration process allows the realization of high-density and thus compact proof masses in the cantilever design. Accordingly, the device achieves 24.75 µW power output under mechanical excitation of 0.75 g at resonance. The ability to load a capacitance of 2.8 µF at 2.5 V within 30 s is demonstrated, facilitating a custom design low-power ASIC.
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Fisher, W. G., E. A. Wachter, Fred E. Lytle, Michael Armas i Colin Seaton. "Source-Corrected Two-Photon Excited Fluorescence Measurements between 700 and 880 nm". Applied Spectroscopy 52, nr 4 (kwiecień 1998): 536–45. http://dx.doi.org/10.1366/0003702981944085.
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Passively mode-locked titanium:sapphire (Ti:S) lasers are capable of generating a high-frequency train of transform-limited subpico-second pulses, producing peak powers near 105 W at moderate average powers. The low energy per pulse (<20 nJ) permits low fluence levels to be maintained in tightly focused beams, reducing the possibility of saturating fluorescence transitions. These properties, combined with a wavelength tunability from approximately 700 nm to 1 μm, provide excellent opportunities for studying simultaneous two-photon excitation (TPE). However, pulse formation is very sensitive to a variety of intracavity parameters, including group velocity dispersion compensation, which leads to wavelength-dependent pulse profiles as the wavelength is scanned. This wavelength dependence can seriously distort band shapes and apparent peak heights during collection of two-photon spectral data. Since two-photon excited fluorescence is proportional to the product of the peak and average powers, it is not possible to obtain source-independent spectra by using average power correction schemes alone. Continuous-wave, single-mode lasers can be used to generate source-independent two-photon data, but these sources are four to five orders of magnitude less efficient than the mode-locked Ti:S laser and are not practical for general two-photon measurements. Hence, a continuous-wave, single-mode Ti:S laser has been used to collect a source-independent excitation spectrum for the laser dye Coumarin 480. This spectrum may be used to correct data collected with multimode sources; this possibility is demonstrated by using a simple ratiometric method to collect accurate TPE spectra with the mode-locked Ti:S laser. An approximate value of the two-photon cross section for Coumarin 480 is also given.
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Streli, Christina, P. Wobrauschek, H. Aiginger, W. Ladisich i R. Rieder. "Total Reflection Xrf of Light Elements Using Various Excitation Sources". Advances in X-ray Analysis 37 (1993): 577–83. http://dx.doi.org/10.1154/s0376030800016128.
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AbstractTotal Reflection X-Ray Fluorescence Analysis (TXRF) has been proved to be well suited for the energy dispersive analysis of light elements using a special spectrometer, which is equipped with an energy dispersive detector having all properties for the detection of low energy radiation. The detection of the light elements is strongly influenced by the excitation source which should provide a large number of photons with energies near the K-absorption edge of these elements (0.2 - 3 keV). Various standard tubes with Be-window as well as a homemade windowless tube are compared, all differing in focal size, total power and anode material. Optimized excitation conditions are provided by synchrotron radiation meeting all requirements for excellent excitation of light elements in total reflection geometry such as high brilliance and ideal spectral distribution specially in the low energy region. A comparison of excitation with X-ray tubes as well as with synchrotron radiation is shown. Detection limits of 200 fg for Mg have been obtained with synchrotron radiation.
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Beliy, V. B. "ANALYSIS OF OVERVOLTAGE POSSIBILITY ON THE EXCITATION WINDING OF A SYNCHRONOUS GENERATOR OF AUTONOMOUS POWER SUPPLY SYSTEM IN CASE OF EXTERNAL SYMMETRICAL SHORT CIRCUIT". Vestnik Altajskogo gosudarstvennogo agrarnogo universiteta, nr 11 (2021): 112–15. http://dx.doi.org/10.53083/1996-4277-2021-205-11-112-115.
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Reliable supply of consumers with electric energy largely depends on the reliability of power source function-ing. In the context of this paper it depends on synchronous generators operating in autonomous power supply sys-tems. In contrast to the power plant generators which are part of power systems and are protected from the loads by sufficiently large resistances, power supply systems withautonomous generators are characterized by rather low resistances. Abrupt changes in the supply load parameters, their own transient and emergency modes, for example, short circuits at the generator terminals, forcing excitation, etc. may lead to various failures in the synchronous gener-ator operation. This paper discusses the possibility of over-voltage in the valve excitation system of a synchronous generator with external three-phase short circuits. On the basis of analytical expressions describing the physical pro-cesses occurring in the excitation system of synchronous generators, the conditions for the occurrence of overvolt-ages are identified
14
Wang, Chuang, Zhen Wang, Weiguo Yan, Hongkun Li i Chunli Yang. "Study on Characteristics of the Vibration and Noise of High-Power Scroll Compressor". Shock and Vibration 2021 (9.09.2021): 1–17. http://dx.doi.org/10.1155/2021/5953133.
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With the rapid development of a high-power scroll compressor (HSC), the dynamic performance of a scroll compressor has an important impact on the vibration and noise of the whole compressor. So, the dynamic characteristics and structural acoustic radiation characteristics of HSC under dynamic excitation are studied by simulation and experiment in this paper. Firstly, the dynamic simulation model of HSC is established to analyze the time-domain and frequency-domain characteristics of bearing excitation and upper support excitation. At the same time, the finite element models of housing, upper support, and lower support are constructed to analyze the transient dynamic response of housing under the excitation source. Based on the vibration displacement of the housing surface, the prediction model of the housing radiated noise is also established, and then the radiated noise of the housing surface and the noise spectrum of the standardized test points are analyzed. Finally, the accuracy of the prediction model is verified by acoustic experiments. The experimental results show that the vibration and radiation noise of the housing can be accurately predicted by reasonable modeling to calculate the gas force and approximate the actual gas load. The vibration of the housing coupling system is the main source of the vibration characteristics of the HSC. The conclusions of the study can provide a reference for the low noise design of the HSC.
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Kou, Zi Ming, Chun Yue Lu, Juan Wu i Hui Xian Zhang. "A New Hydraulic Excitation Mode with Liquid-Filled Pipe". Advanced Materials Research 279 (lipiec 2011): 280–86. http://dx.doi.org/10.4028/www.scientific.net/amr.279.280.
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The current vibration modes, whether inertial vibration or hydraulic vibration, have some problems such as large power consumption and low energy utilization rate. A new low energy hydraulic excitation mode is presented. This mode takes the high-pressured pipe as the new excitation source. Periodic pressure pulsation generated by wave exciter makes the pipe vibrating. The vibration mode of pipe with fluid-structure interaction is established and solved with numerical method. The modal analysis and the simulation of the vibration have been carried out. An experimental platform is built to verify that the new hydraulic vibration can be exploited.
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Burge, Leah E., i Murray S. Korman. "Photoacoustic LED imaging apparatus using a low-cost system". Journal of the Acoustical Society of America 151, nr 4 (kwiecień 2022): A249. http://dx.doi.org/10.1121/10.0011223.
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The use of compact and cost-effective visible light emitting diodes (LEDs) as an alternative to Q-switched lasers, the conventional photoacoustic excitation source, has been explored for vascular imaging applications [T. J. Allen and P. C. Beard, “Light emitting diodes as an excitation source for biomedical photo-acoustics,” Proc. SPIE 8581, 85811F (2013)]. This research motivated our work. Experiments used a 619 nm LED (Luminus SST-90-R-F11-HH100) pulsed for 450 ns with period 34 ms utilizing a pulse generator, MOSFET driver and power MOSFET switch, discharging a bank of capacitors (990 μ F) with 36 A peak current. A pair of 2.5 cm diameter aspherical acrylic lens focused the LED—with an emitting area of 3mm × 3 mm—onto the surface of a vertical capillary tube (1.19 mm ID, 1.75 mm OD) filled with 5% McCormick Green food coloring or 5% Higgins India Ink and placed in the 10 cc acrylic water tank. An Olympus emersion transducer (1.27 cm diameter circular plane array, 1 MHz with 0.4MHz bandwidth) was amplified using four home-made low noise amplifiers (87 dB overall gain, 0.5–30 MHz bandwidth). An Agilent DSO 7014 B oscilloscope recorded the photoacoustic signal pulse averaging 8196 trials.
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Stefan, John T., i Alexander G. Kosovichev. "Analysis and Modeling of High-frequency Emission and Deep Seismic Sources of Sunquakes". Astrophysical Journal Letters 937, nr 2 (27.09.2022): L26. http://dx.doi.org/10.3847/2041-8213/ac8f92.
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Abstract Recent work published by Lindsey et al. find evidence for a deep and compact seismic source for the sunquake associated with the 2011 July 30 M9.3 flare, as well as seismic emission extending up to 10 mHz. We examine the sunquake independently, and a possible wave front is found in the 8 mHz band, though no wave front is easily discernible in the 10 mHz band. Additionally, we perform numerical simulations of seismic excitation modeled with the reported parameters and changes in the power spectra with increasing depth of the excitation source are examined. It is found that the peak frequency decreases for increasing depths, but a shallow minimum is indicated between z = 0 and z = −840 km. Analysis of the suspected wave front of the M9.3 sunquake finds that the power spectrum of the reported seismic emission is close to that of background oscillations, though with a peak frequency noticeably lower than the background peak. Additionally, it is found that the amplitude of the source estimated by Lindsey et al. is too low to produce the observed wave front.
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Choi, Yo-Seb, Suk-Yoon Hong, Jee-Hun Song, Hyun-Wung Kwon i Jee-Hwoon Kang. "Power transformer excitation force estimation for load noise reduction using experimental apparatus based on beamforming theory". Noise Control Engineering Journal 70, nr 1 (1.01.2022): 77–89. http://dx.doi.org/10.3397/1/37706.
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To comply with noise regulations in residential areas, low-noise electrical transformers must be developed. However, it is difficult to accurately reflect the frequency characteristics of the transformer, which have a large influence on the noise produced, because the high voltage and current make it impossible to experimentally measure the internal excitation forces involved. In this paper, we propose a new method using an experimental apparatus for estimating the internal excitation forces experienced by transformers whose results accurately reflect the actual frequency characteristics of the transformer. To estimate the excitation force, the pressure distribution data outside the enclosure of a transformer was experimentally measured by the experimental apparatus based on a beamforming method, and the transfer function from the excitation source to the noise radiation was derived numerically. The excitation force was then derived using the pressure distribution data and transfer function. Based on the estimated excitation force, the contribution of each vibration transmission path was derived using transfer path analysis with integrated transfer function matrix as a basis for creating an effective noise reduction plan. The noise reduction plan based on our method was able to reduce transformer noise sufficiently to meet the noise standard set in standard transformer export contracts.
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Chen, Tunan, Fengxiang Ma, Yue Zhao, Zhenghai Liao, Zongjia Qiu i Guoqiang Zhang. "Cantilever enhanced based photoacoustic detection of SF6 decomposition component SO2 using UV LED". Sensor Review 42, nr 1 (13.01.2022): 70–75. http://dx.doi.org/10.1108/sr-12-2020-0292.
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Purpose This paper aims to establish a photoacoustic detection system for SO2 using UV-LED and testify its feasibility for sensitive measurement. The work in this paper can avoid potential crossover interference in infrared (IR) range and also balance the capability and cost of feasible excitation for photoacoustic detection system. Design/methodology/approach In this experimental work, a cantilever-enhanced–based photoacoustic SO2 detection system using an ultraviolet (UV) LED light source with a light power of 4 mW as the excitation was established. Findings A feasible photoacoustic detection system for SO2 using UV-LED was established. Experimental results demonstrate that the detection limit of the system can reach the level of 0.667 ppm, which can serve as a reference for the application of PAS in insulation fault diagnosis. Originality/value This work investigated the potential of using ultraviolet photoacoustic spectroscopy to detect trace SO2, which provided an ideal replacement of infrared-laser-based detection system. In this paper, a photoacoustic detection system using LED with a low light power was established. Low light power requirement can expand the options of light sources accordingly. In this paper, the absorption characteristics of SO2 in the presented detection system and ultraviolet range were studied. And the detection limit of the presented system was given. Both of which can provide reference to SO2 detection in ambient SF6.
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Wang, Kemeng, Yangfan Gu, Yongchang Lu, Jianqiang Gu i Weili Zhang. "Terahertz radiation enhancement in gallium arsenide nano-hole array under low power optical pump". Applied Physics Letters 121, nr 7 (15.08.2022): 071703. http://dx.doi.org/10.1063/5.0099288.
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Though accelerating photocarriers by the semiconductor surface electric field is the simplest way to generate broadband terahertz pulses, the weak THz power under low optical pump hinders its application in these compact systems. Here, we report a ⟨100⟩ semi-insulating gallium arsenide nano-hole array under above-the-bandgap excitation, which boosts terahertz emission power up to 5.75 folds of bare gallium arsenide with a 32 mW pump. The nano-structured array lifts the absorption of the optical pump and localizes the photocarriers near the surface of gallium arsenide, benefiting the transient photocurrents and thus the THz power. Interestingly, the enhancement is poorly related to the terahertz frequency, and the power difference of the emitted THz wave under the TE and TM pumps is greatly smoothed. In addition, the THz emission enhancement of the nanoscale hole arrays favors a low-power pump. The demonstration shown here provides a potential route for advancing the weak THz power of surface emission, which will promote the application of the surface emitting THz source in the practical THz systems employing compact femtosecond lasers.
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Wang, Jie, Mostafa R. A. Nabawy, Andrea Cioncolini, Alistair Revell i Samuel Weigert. "Planform Geometry and Excitation Effects of PVDF-Based Vibration Energy Harvesters". Energies 14, nr 1 (3.01.2021): 211. http://dx.doi.org/10.3390/en14010211.
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In the present paper, we report a systematic investigation of planform geometry and excitation level effects on the dynamics and power generation characteristics of polyvinylidene difluoride (PVDF)-based cantilevered vibration energy harvesters. Piezoelectric vibration energy harvesters provide a promising energy harvesting solution for widespread use of wireless sensors in remote locations. Highly flexible PVDF polymers offer resonant frequencies at suitable range for harvesting mechanical energy within low-frequency applications, though information on the efficient sizing of these devices is currently limited. We test the response of a set of eight harvesters to typical vibration sources excitation levels in the range 0.2–0.6 g. This set comprises four widths and two lengths, incrementing each time by a factor of two. The selected range of dimensions is sufficient to identify optimal power output versus width for both lengths tested. This optimal width value depends on excitation amplitude in such a way that narrower harvesters are more suited for small excitations, whereas wider harvesters perform better upon experiencing large excitations. Non-linear effects present in longer harvesters are demonstrated to significantly reduce performance, which motivates the selection of planform dimensions inside the linear range. Finally, we explore the correlation of performance with various geometric quantities in order to inform future design studies and highlight the value of using the second moment of planform area to measure harvester efficiency in terms of power density. This points towards the use of harvesters with non-rectangular planform area for optimal performance.
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Liu, Gui Lin, Xin Li Song i Wei Song. "Analysis on Coordination of Loss of Excitation Protection, Out-of-Step Protection and Out-of-Step Splitting". Advanced Materials Research 971-973 (czerwiec 2014): 398–401. http://dx.doi.org/10.4028/www.scientific.net/amr.971-973.398.
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In units’ grid-related protection, loss of excitation protection and out-of-step protection are very important to ensure the stable running of grid. If both can realize the right coordination when unit occur a phenomenon of low excitation, it can improve the level of power source coordinated with grid. However, there is a problem in the coordination of both. Propose an idea to solve the problem based on power angle. Besides, out-of-step protection and out-of-step splitting exists a coordination relation according to the location of out-of-step oscillation center. In order to prevent the collapse of grid and protect units, it is necessary to cut off out-of-step lines and units correctly. Summarize the reasonable coordination relation between both by theory analysis and research.
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Nikishechkin, Anatolij. "To the question of constructing measuring devices based on fluxgate sensors". MATEC Web of Conferences 298 (2019): 00048. http://dx.doi.org/10.1051/matecconf/201929800048.
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The article discusses the issues of feeding fluxgates from compact, low-power generators built on AND-NOT logic elements. The frequency of such generators depends on the magnitude of the measured magnetic field strength. This gives reason to consider the possibility of using frequency as a useful signal. The article discusses the issues of feeding fluxgates from compact, low-power generators built on AND-NOT logic elements. The frequency of such generators depends on the magnitude of the measured magnetic field strength. This gives reason to consider the possibility of using frequency as a useful signal. The article proposes to use modulated rectangular voltage pulses, that is, pulses with high-frequency filling, to power a fluxgate. Then, under the influence of the measured magnetic field, the filling frequency changes, according to which the magnitude of the intensity is determined, and the frequency of the modulating voltage corresponding to the passport frequency of the fluxgate remains constant. In this case, it becomes possible to increase the deviation of the filling frequency due to the use of the released output winding of the fluxgate as an additional element of the generator. It was also experimentally established that in order to increase the voltage on the excitation winding of the fluxgate and, as a consequence, to increase its sensitivity, it is advisable to power through the D-trigger, which makes it possible to obtain bipolar voltage on the excitation winding. In addition, it is necessary to use resonance phenomena (at the frequency of the modeling voltage) in the serial circuit “connecting capacitors - excitation coil of a fluxgate”, which allows increasing the voltage on the excitation winding without increasing the voltage of the power source.
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König, Karsten. "Two-Photon near Infrared Excitation in Living Cells". Journal of Near Infrared Spectroscopy 5, nr 1 (styczeń 1997): 27–34. http://dx.doi.org/10.1255/jnirs.97.
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Non-linear effects due to two-photon near infrared (NIR) excitation of endogenous and exogenous cellular chromophores allow novel techniques in tissue, cell and biomolecule diagnostics, as well as in intracellular micromanipulation (e.g. intracellular photochemistry). Two-photon NIR excitation may also result in cell damage effects. The high photon intensities (1024 photons cm−2 s−1) required for non-resonant two-photon excitation can be achieved by diffraction-limited focusing of continuous wave (cw) laser beams (cw microbeams) with powers in the mW range. For example, NIR traps (“laser tweezers”) used as force transducers and micromanipulation tools in cellular and molecular biology are sources of two-photon excitation. NIR traps can induce two-photon excited visible fluorescence and, in the case of <800 nm-traps, UVA-like cell damage. Multimode cw microbeams may enhance non-linear effects due to longitudinal mode-beating. To perform high scan rate two-photon fluorescence imaging, the application of ultrashort laser pulses of moderate peak power but low average power (pulsed microbeams) is required. In NIR femtosecond microscopes, non-destructive imaging of two-photon excited fluorophores in various human and culture cells was demonstrated for <2 mW average powers, <200 mW peak powers and 400 GW cm−2 intensities (700–800 nm, ∼150 fs, ∼100 MHz). However, higher average power levels may result in failed cell reproduction and cell death due to intracellular optical breakdown. In addition, destructive transient local heating and μN force generation may occur.
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Godin, Oleg A., i Iosif M. Fuks. "Transmission of acoustic-gravity waves through gas–liquid interfaces". Journal of Fluid Mechanics 709 (10.08.2012): 313–40. http://dx.doi.org/10.1017/jfm.2012.336.
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AbstractIt was demonstrated recently that gas–liquid interfaces, which are usually almost perfect reflectors of acoustic waves, become anomalously transparent, and the power flux in the wave transmitted into the gas increases dramatically, when a compact sound source in the liquid approaches the interface within a fraction of the wavelength (Godin, Phys. Rev. Lett., vol. 97, 2006b, 164301). Powerful underwater explosions and certain natural sources, such as underwater landslides, generate very low-frequency waves in water and air, for which fluid buoyancy and compressibility simultaneously serve as restoring forces. In this paper, analysis of sound transmission through gas–liquid interfaces is extended to acoustic-gravity waves (AGWs) and applied to the air–water interface. It is found that, as for sound, the interface becomes anomalously transparent for sufficiently shallow compact sources of AGWs. Depending on the source type, the increase of a wave power flux into gas due to diffraction effects can reach several orders of magnitude. The physical mechanisms responsible for the anomalous transparency are discussed. Excitation of an interface wave by a point source in the liquid is shown to be an important channel of AGW transmission into the gas, which has no counterpart in the case of sound.
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Benson, Ronda L., Koichi Iwata, William L. Weaver i Terry L. Gustafson. "Improvements in the Generation of Quasi-Continuous, Tunable Ultraviolet Excitation for Raman Spectroscopy: Applications to Drug/Nucleotide Interactions". Applied Spectroscopy 46, nr 2 (luty 1992): 240–45. http://dx.doi.org/10.1366/0003702924125591.
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We demonstrate the generation of quasi-continuous ultraviolet excitation at wavelengths shorter than 240 nm using the frequency-doubled output of a synchronously pumped picosecond dye laser operating in the region of 420 nm. Owing to the relatively low peak power but high average power of the system, we obtain high-quality resonance Raman spectra at wavelengths as short as 209 nm. We apply the source to the study of the binding of anticancer drugs to DNA. In particular, we compare the binding of cis-diamminedichloroplatinum (II) (cisplatin) and cis-diammine-1, 1-cyclobutane dicarboxylate platinum (II) (carboplatin) to certain mononucleotides.
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Balakrishnan, Gurusamy, Ying Hu, Steen Brøndsted Nielsen i Thomas G. Spiro. "Tunable kHz Deep Ultraviolet (193–210 nm) Laser for Raman Applications". Applied Spectroscopy 59, nr 6 (czerwiec 2005): 776–81. http://dx.doi.org/10.1366/0003702054280702.
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The performance characteristics of a kilohertz solid-state laser source for ultraviolet Raman spectroscopy are described. Deep ultraviolet (UV) excitation in the 193–210 nm region is provided by mixing of the fundamental and third harmonics of a Ti–sapphire laser, which is pumped by the second harmonic of a Q-Switched Nd–YLF laser. The combination of tunability, narrow linewidth, high average power, good stability, and kilohertz repetition rate makes this laser suitable for deep UV resonance Raman applications. The short pulse duration (∼20 ns) permits nanosecond time resolution in pump–probe applications. The low peak power and high data rate provide artifact-free spectra with a high signal-to-noise ratio. UV Raman cross-section and Raman excitation profiles are reported for gaseous O2 (relative to N2), aqueous ClO4−, tyrosine, phenylalanine, tryptophan, histidine, and hemoglobin excited between 193 nm and 210 nm to illustrate laser performance.
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Duan, Yixiang, Xiaoguang Du, Yimu Li i Qinhan Jin. "Characterization of a Modified, Low-Power Argon Microwave Plasma Torch (MPT) as an Atomization Cell for Atomic Fluorescence Spectrometry". Applied Spectroscopy 49, nr 8 (sierpień 1995): 1079–85. http://dx.doi.org/10.1366/0003702953965128.
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A microwave plasma torch (MPT) has been newly modified and used as an atomization cell for atomic fluorescence spectrometry (AFS). The analytical performance of the MPT-AFS system has been characterized with hollow cathode lamps (HCLs) working in the pulsed mode as an excitation source and a pneumatic nebulizer for aqueous sample introduction. The method exhibits a relatively large dynamic range over at least three orders of magnitude in concentration and fairly good precision in a range from 0.42% (Zn) to 4.9% (Ag). It was found that observation height, microwave power, and plasma support-gas flow rate have an important influence on the performance of MPT-AFS. The detection limits obtained by the new MPT-AFS system are in a range from 0.25 (Cd) to 121 (As) ng/mL for ten elements examined. A comparison of MPT-AFS with other plasma AFS approaches suggests several advantages of the MPT source as an atomizer for AFS.
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Mohan, Manoj Kumar Chandra, Sang Kyun Shim, June Key Lee, Nakwon Jang, Naesung Lee i Wael Z. Tawfik. "Optimized Aluminum Reflector for Enhancement of UVC Cathodoluminescence Based-AlGaN Materials with Carbon Nanotube Field Emitters". Molecules 26, nr 13 (30.06.2021): 4025. http://dx.doi.org/10.3390/molecules26134025.
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The far ultraviolet C (UVC) light sources based on carbon nanotube (CNT) field emitters as excitation sources have become promising light sources for sterilization, disinfection, and water purification. However, the low light extraction efficiency of UVC–CNT light sources still hinders the practical application of these structures. Herein, we report an optimized aluminum (Al) reflector to enhance the light extraction efficiency of UVC–CNT light sources. Optical analysis of UVC-CNT light sources covered by the Al reflectors with various thicknesses ranging from 30 to 150 nm was performed to realize the optimized reflector. The UVC-CNT light sources exhibit the highest light extraction efficiency when the Al reflector layer has an optimized thickness of 100 nm. For comparison, the cathodoluminescence (CL) spectra were recorded for UVC–CNT light sources with and without the optimized Al reflector. The measured light output power and the estimated power efficiency of the UVC–CNT light-source-tube with Al reflector were enhanced by about 27 times over the reference. This enhancement is mainly attributed to the outstanding reflection effect of the Al reflector.
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Fang, Yuan Yuan, Guo Hong Zhang, Ya Fan Li i Peng Zhe Qi. "Design of Vibration Isolation Device for Ship Power Equipment and Investigation on its Dynamic Properties". Applied Mechanics and Materials 496-500 (styczeń 2014): 1129–33. http://dx.doi.org/10.4028/www.scientific.net/amm.496-500.1129.
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Mechanical noise caused by power equipment vibration is the main source of underwater radiated noise of the ship, and vibration isolation and noise reduction of ship equipment has been widely concerned. Therefore,a vibration isolation system designed for four sets of auxiliary engine of ship cabin was investigated in the paper, aimed to further reveal the influence of various parameters including floating raft shell thickness, excitation source, and different ship hull and installation platform thickness on the vibration level difference of system. The results obtained from numerical analysis using MSC software and experiment indicate that one-dimensional spring element simplified can properly simulate the actual rubber vibration isolator on low frequency bands, and increasing thickness of flat, hull and platform can improve the effect of vibration isolation obviously.
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Niu, B., i N. Olhoff. "Minimization of vibration power transmission from rotating machinery to a flexible supporting plate". International Journal of Structural Stability and Dynamics 14, nr 03 (16.02.2014): 1350068. http://dx.doi.org/10.1142/s0219455413500685.
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This paper deals with the problem of optimum design of a foundation for rotating machinery with a view to minimize vibration transmission from a machine source to its supporting structure. The problem of analysis and optimization of the installation systems of machinery has been extensively researched on the assumption of a rigid supporting structure. The design based on a rigid supporting structure model is reasonable for the installation of machinery in many real engineering situations. However, this rigid support based model may not be appropriate for the problem studied herein where the machinery is to be installed on a relatively flexible supporting plate. Thus, a generalized mathematical model of mobility power flow is developed in this paper, with a rotating machine as vibration source, resilient mounts as isolator, and a flexible supporting plate as receiver. The objective of minimizing vibration transmission is realized by optimization of stiffness coefficients of resilient mounts with a constraint on the vibration level of the machine. The design objective is chosen as the minimization of the power flow transmitted to the flexible supporting plate through the resilient mounts at the excitation frequency of the machinery. Both a single excitation frequency and a range of excitation frequencies are considered. A gradient-based mathematical programing method is selected for its advantage of efficiently solving the current type of optimization problem with multiple mounts and multi-degree-of-freedom vibration transmission. The sensitivities of the objective and the constraint functions with respect to the design variables are derived analytically. The design and performance of the optimized machinery foundation is illustrated and discussed using several numerical examples. The optimized mounting system is suitable for the installation case of a rotating machine with a low or medium service speed on a flexible supporting plate structure.
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Nazari, P., M. L. van Gelder, E. F. van Dishoeck, B. Tabone, M. L. R. van ’t Hoff, N. F. W. Ligterink, H. Beuther i in. "Complex organic molecules in low-mass protostars on Solar System scales". Astronomy & Astrophysics 650 (czerwiec 2021): A150. http://dx.doi.org/10.1051/0004-6361/202039996.
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Context. The chemical inventory of planets is determined by the physical and chemical processes that govern the early phases of star formation. Nitrogen-bearing species are of interest as many provide crucial precursors in the formation of life-related matter. Aims. The aim is to investigate nitrogen-bearing complex organic molecules towards two deeply embedded Class 0 low-mass protostars (Perseus B1-c and Serpens S68N) at millimetre wavelengths with the Atacama Large Millimeter/submillimeter Array (ALMA). Next, the results of the detected nitrogen-bearing species are compared with those of oxygen-bearing species for the same and other sources. The similarities and differences are used as further input to investigate the underlying formation pathways. Methods. ALMA observations of B1-c and S68N in Band 6 (~1 mm) and Band 5 (~2 mm) are studied at ~0.5′′ resolution, complemented by Band 3 (~3 mm) data in a ~2.5′′ beam. The spectra are analysed for nitrogen-bearing species using the CASSIS spectral analysis tool, and the column densities and excitation temperatures are determined. A toy model is developed to investigate the effect of source structure on the molecular emission. Results. Formamide (NH2CHO), ethyl cyanide (C2H5CN), isocyanic acid (HNCO, HN13CO, DNCO), and methyl cyanide (CH3CN, CH2DCN, and CHD2CN) are identified towards the investigated sources. Their abundances relative to CH3OH and HNCO are similar for the two sources, with column densities that are typically an order of magnitude lower than those of oxygen-bearing species. The largest variations, of an order of magnitude, are seen for NH2CHO abundance ratios with respect to HNCO and CH3OH and do not correlate with the protostellar luminosity. In addition, within uncertainties, the nitrogen-bearing species have similar excitation temperatures to those of oxygen-bearing species (~100–300 K). The measured excitation temperatures are larger than the sublimation temperatures for the respective species. Conclusions. The similarity of most abundances with respect to HNCO for the investigated sources, including those of CH2DCN and CHD2CN, hints at a shared chemical history, especially the high D-to-H ratio in cold regions prior to star formation. However, some of the variations in abundances may reflect the sensitivity of the chemistry to local conditions such as temperature (e.g. NH2CHO), while others may arise from differences in the emitting areas of the molecules linked to their different binding energies in the ice. The excitation temperatures likely reflect the mass-weighted kinetic temperature of a gas that follows a power law structure. The two sources discussed in this work add to the small number of sources that have been subjected to such a detailed chemical analysis on Solar System scales. Future data from the James Webb Space Telescope will allow a direct comparison between the ice and gas abundances of both smaller and larger nitrogen-bearing species.
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Guo, Zhe, Hanxian Fang i Farideh Honary. "The Generation of ULF/ELF/VLF Waves in the Ionosphere by Modulated Heating". Universe 7, nr 2 (29.01.2021): 29. http://dx.doi.org/10.3390/universe7020029.
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One of the most important effects of ionospheric modification by high power, high frequency (HF) waves is the generation of ultra low frequency/extremely low frequency/very low frequency (ULF/ELF/VLF) waves by modulated heating. This paper reviews the scientific achievements of the past five decades regarding the main mechanisms of excitation of ULF/ELF/VLF waves and discusses their characteristics, such as their electrojet dependency, the location of the source region, continuous and discontinuous waves, the number of HF arrays, and the suitable range of the modulation frequency for different proposed mechanisms. Finally, the outlook for future research in this area is presented.
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Özçelik, Mehmet Ali. "Operating the Induction Motor as a Generator Mode by Supplying DC Voltage and Investigation of the End Voltage Depending on the Excitation Current and RPM". International Journal of Energy Research 2023 (24.07.2023): 1–8. http://dx.doi.org/10.1155/2023/9967218.
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Asynchronous or induction machines are among the leading devices in the electrical industry. They are well suited for motor and production applications with power ratings from a few kilowatts to megawatts. In addition, their use in renewable energy systems, especially in wind conversion systems, is increasing daily due to their advantages, such as low cost, brushless, and robust structure. In this work, the operation of a three-phase asynchronous motor with a winding rotor as an alternator, the variation of the voltage produced depending on the excitation current by keeping the number of revolutions constant, and the interpretation of the voltage produced according to the number of revolutions by keeping the excitation current constant have been investigated. The variation of the terminal voltage in ohmic, inductive, and capacitive loads has been experimentally investigated by observing the source voltage providing the rotational speed and excitation current constant.
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Lavrinovica, I., A. Supe i J. Porins. "Experimental Measurement of Erbium-Doped Optical Fibre Charecteristics for Edfa Performance Optimization". Latvian Journal of Physics and Technical Sciences 56, nr 2 (1.04.2019): 33–41. http://dx.doi.org/10.2478/lpts-2019-0011.
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Abstract The paper presents experimental study of the major erbium-doped fibre amplifier (EDFA) features such as gain at low signal and gain saturation by an application of different erbium-doped optical fibres (EDFs). The main objective of the research is to estimate how the performance of EDFA varies depending on the length of doped fibre, pumping configuration scheme, as well as excitation source power. It is shown that a high gain coefficient of 16–20 dB can be practically achieved.
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Smilek, Jan, i Zdenek Hadas. "Experimental evaluation of Tusi couple based energy harvester for scavenging power from human motion". MATEC Web of Conferences 211 (2018): 05004. http://dx.doi.org/10.1051/matecconf/201821105004.
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This paper deals with the experimental performance evaluation of the prototype of a novel inertial energy harvester based on Tusi couple mechanism. The harvester was developed as an autonomous power source for environments with very low frequency and magnitude of mechanical vibrations available. The experiments were conducted using human body during different activities as a source of mechanical excitation, with the prospect of using the harvester for powering up future wearable electronic devices. Four different locations on a single measurement specimen were picked for the harvester placement - back of the head, belt, wrist and ankle. Measurements in each location comprised of walking on a straight and level path at natural speed, walking up and down the stairs, jumping, running, and location-specific activities that were expected to provide significant output power. The measured average output power of the device with dimensions 50x50x20 mm on empirically selected 2 kΩ electrical load reached up to 6.5 mW, obtained with the device attached to the ankle while shaking the leg.
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Lundberg, Karl-Ola. "An Alternative Method for Measurement of Airborne Sound Insulation". Building Acoustics 8, nr 1 (marzec 2001): 57–74. http://dx.doi.org/10.1260/1351010011501731.
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A method for determination of the transmission coefficient from Complex Modulation Transfer Functions CMTF:s based on measured impulse-responses is shown. In the method a separate measurement of the equivalent sound absorption area is not needed in contrast to in the standardised measurement. By averaging over a number of estimates of the impulse-response the influence of background noise can be reduced substantially, implying that low-power sources can be used. A model for the power balance in the receiving room with time-varying power is considered. In the model the quotient of the receiving room intensity and the source room intensity has one pole, which is proportional to the equivalent sound absorption area in the receiving room, and a gain, proportional to the transmission coefficient. In the physical system the power can be time-varied by letting the system excitation signal consist of random noise modulated with a deterministic time-varying function. However, since the ensemble average of the squared response is proportional to the squared impulse-response convolved with the squared modulating function, random excitation is avoided and replaced by impulse-response measurements. The quotient of intensities in the model is in the physical system a quotient of CMTF:s. Experiments are carried out in an airborne sound insulation laboratory. For comparison, standardised measurements are also carried out. It is found that the presented method gives as result comparatively small transmission coefficients, though the relative differences are small. By refining the power balance model by introducing an energy propagation time delay, and selecting an appropriate delay, the differences were diminished.
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Ma, Chengjian, Yang Liu i Changyu Shen. "Phase-Extraction-Based MFL Testing for Subsurface Defect in Ferromagnetic Steel Plate". Sensors 22, nr 9 (26.04.2022): 3322. http://dx.doi.org/10.3390/s22093322.
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Magnetic flux leakage (MFL) based on phase extraction for detecting the subsurface defects in ferromagnetic steel plate was investigated. The relationship between electromagnetic field phase and the subsurface defect was analyzed. Low-frequency alternating current (AC) excitation source and high-power magnetizer arrangement with Hall sensor were used to increase the skin depth of the MFL. Experiments results showed that 12 mm deep subsurface defect can be detected by using the phase extraction means, which is about two times higher than that by using the amplitude method.
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Balthazar, José Manoel, Reyolando Manoel Lopes Rabelo da Fonseca Brasil i F. J. Garzeri. "On Non-Ideal Simple Portal Frame Structural Model: Experimental Results under a Non-Ideal Excitation". Applied Mechanics and Materials 1-2 (wrzesień 2004): 51–58. http://dx.doi.org/10.4028/www.scientific.net/amm.1-2.51.
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We present measurements of the non-linear oscillations of a portal frame foundation for a non-ideal motor. We consider a three-time redundant structure with two columns, clamped in their bases and a horizontal beam. An electrical unbalanced motor is mounted at mid span of the beam. Two non-linear phenomena are studied: a) mode saturation and energy transfer between modes; b)interaction between high amplitude motions of the structure and the rotation regime of a real limited power motor. The dynamic characteristics of the structure were chosen to have one-to-two internal resonance between the anti-symmetrical mode (sway motions) and the first symmetrical mode natural frequencies. As the excitation frequency reaches near resonance conditions with the 2nd natural frequency, the amplitude of this mode grows up to a certain level and then it saturates. The surplus energy pumped into the system is transferred to the sway mode, which experiences a sudden increase in its amplitude. Energy is transformed from low amplitude high frequency motion into high amplitude low frequency motion. Such a transformation is potentially dangerous. We consider the fact that real motors, such as the one used in this study, have limited power output. In this case, this energy source is said to be non-ideal, in contrast to the ideal source whose amplitude and frequency are independent of the motion of the structure. Our experimental research detected the Sommerfeld Effect: as the motor accelerates to reach near resonant conditions, a considerable part of its output energy is consumed to generate large amplitude motions of the structure and not to increase its own angular speed. For certain parameters of the system, the motor can get stuck at resonance not having enough power to reach higher rotation regimes. If some more power is available, jump phenomena may occur from near resonance to considerably higher motor speed regimes, no stable motions being possible between these two.
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Xie, Liming, Feng Tian, Jun Liu i Hao Chen. "Analysis on the Causes of Cracking at the Last Stage Blade of the Low-pressure Rotor in thermal power plant". E3S Web of Conferences 165 (2020): 06010. http://dx.doi.org/10.1051/e3sconf/202016506010.
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Transverse cracking occurred in the blade body of the last stage of the low pressure rotor of a 200MW unit in a thermal power plant. The causes of blade cracking were analyzed by means of macro morphology, SEM, microstructure, mechanical properties, chemical composition and energy spectrum analysis. The results show that the corrosive Cl- accumulates on leaves, and then combined action of tensile stress is formed with the static load and dynamic load during the blade operation, and the stress corrosion microcracks had been conceived in the Cl- corrosion region. Under the long period cyclic excitation stress of the blade during the rotor rotation at high speed, the crack source extends in fatigue mode, finally resulting in cracking.
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Rittmann, Johannes, Markus Rahammer, Niels Holtmann i Marc Kreutzbruck. "A mobile nondestructive testing (NDT) system for fast detection of impact damage in fiber-reinforced plastics (FRP)". Journal of Sensors and Sensor Systems 9, nr 1 (11.02.2020): 43–50. http://dx.doi.org/10.5194/jsss-9-43-2020.
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Abstract. Impact damage in fiber-reinforced plastics, such as carbon-fiber-reinforced plastics (CFRP) and glass-fiber-reinforced plastics (GFRP), involves high challenges to nondestructive testing (NDT). The anisotropic material structure significantly complicates the interpretation of results in conventional testing. Resonant frequency sweep thermography (RFST) based on local defect resonance combined with well-known ultrasonic thermography enables the fast and simple detection of relevant impact damages. RFST utilizes frequency sweep excitation in the low- and mid-kilohertz range to activate defect resonances with low acoustical power of a few megawatts. Resonances of defects amplify the acoustic vibration amplitude by more than 1 order of magnitude and lead to a significant enhancement of the corresponding thermal signal. This is based on both crack friction and/or visco-elastic heating and can be detected at the part surface by an infrared camera. The defect detection threshold depends on excitation power and the distance between the defect and the ultrasonic source. For this new NDT approach, a first prototype system in the form of a tripod with an integrated infrared (IR) camera and ultrasonic excitation was developed. It stands out due to its simple handling and flexible applications. Augmented reality assists the inspector to interpret the results and mark the defect by projecting the evaluated test result onto the part surface. In this article, the first results from a series of impact damages in CFRP of varying impact energies and crack sizes are presented.
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Che Mustapha, Nurul Arfah, A. H. M. Zahirul Alam, Sheroz Khan i Amelia Wong Azman. "EFFICIENT CAPACITANCE SENSING FOR WIRELESS HEALTH MONITORING SYSTEM". IIUM Engineering Journal 17, nr 2 (30.11.2016): 21–29. http://dx.doi.org/10.31436/iiumej.v17i2.609.
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This paper presents a low power capacitance to voltage converter (CVC) circuit using two differential amplifier circuits, two Schottky rectifier diodes constructed in symmetrical manner and combined with instrumentation amplifier circuits. The differential capacitance to voltage simulation work has been realized with cheap discrete components. Combination energy from solar, vibration and heat is expected to be used to source the capacitance circuit. Constant dc voltage of 3 V has been used to source the CVC circuit in this work. It is found by the simulation, the converter circuit consumes 3.9 mW of total power, operates at 40 kHz using 400 mV excitation signal. The circuit is able to detect changes of capacitance from 4 – 12.5 pF using reference capacitance of 5 pF. Sensitivity of 0.132 mV for 1 fF capacitance change has been observed in the circuit. This circuit is suitable for wireless health monitoring system.
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Keenan, Mary, Eileen T. Meyer, Markos Georganopoulos, Karthik Reddy i Omar J. French. "The relativistic jet dichotomy and the end of the blazar sequence". Monthly Notices of the Royal Astronomical Society 505, nr 4 (28.04.2021): 4726–45. http://dx.doi.org/10.1093/mnras/stab1182.
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ABSTRACT Our understanding of the unification of jetted AGN has evolved greatly as jet samples have increased in size. Here, based on the largest-ever sample of over 2000 well-sampled jet spectral energy distributions, we examine the synchrotron peak frequency – peak luminosity plane, and find little evidence for the anticorrelation known as the blazar sequence. Instead, we find strong evidence for a dichotomy in jets, between those associated with efficient or ‘quasar-mode’ accretion (strong/type II jets) and those associated with inefficient accretion (weak/type I jets). Type II jets include those hosted by high-excitation radio galaxies, flat-spectrum radio quasars (FSRQ), and most low-frequency-peaked BL Lac objects. Type I jets include those hosted by low-excitation radio galaxies and blazars with synchrotron peak frequency above 1015 Hz (nearly all BL Lac objects). We have derived estimates of the total jet power for over 1000 of our sources from low-frequency radio observations, and find that the jet dichotomy does not correspond to a division in jet power. Rather, type II jets are produced at all observed jet powers, down to the lowest levels in our sample, while type I jets range from very low to moderately high jet powers, with a clear upper bound at L 300MHz ∼1043 erg s−1. The range of jet power in each class matches exactly what is expected for efficient (i.e. a few to 100 % Eddington) or inefficient ( <0.5% Eddington) accretion on to black holes ranging in mass from $10^7{\, {\rm to}\,}10^{9.5}\, {\rm M}_\odot$.
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Pierce, J. C. S., C. N. Tadhunter i R. Morganti. "The radio properties of high-excitation radio galaxies with intermediate radio powers". Monthly Notices of the Royal Astronomical Society 494, nr 2 (24.02.2020): 2053–67. http://dx.doi.org/10.1093/mnras/staa531.
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ABSTRACT In the past decade, high-sensitivity radio surveys have revealed that the local radio active galactic nucleus population is dominated by moderate-to-low power sources with emission that is compact on galaxy scales. High-excitation radio galaxies (HERGs) with intermediate radio powers (22.5 < log (L1.4 GHz) < 25.0 W Hz−1) form an important sub-group of this population, since there is strong evidence that they also drive multiphase outflows on the scales of galaxy bulges. Here, we present high-resolution Very Large Array observations at 1.5, 4.5, and 7.5 GHz of a sample of 16 such HERGs in the local universe (z < 0.1), conducted in order to investigate the morphology, extent, and spectra of their radio emission in detail, down to sub-kpc scales. We find that the majority (56 per cent) have unresolved structures at the limiting angular resolution of the observations (∼0.3 arcsec). Although similar in the compactness of their radio structures, these sources have steep radio spectra and host galaxy properties that distinguish them from local low-excitation radio galaxies that are unresolved on similar scales. The remaining sources exhibit extended radio structures with projected diameters ∼1.4–19.0 kpc and a variety of morphologies: three double-lobed; two large-scale diffuse; one jetted and ‘S-shaped’; one undetermined. Only 19 per cent of the sample therefore exhibit the double-lobed/edge-brightened structures often associated with their counterparts at high and low radio powers: radio-powerful HERGs and Seyfert galaxies, respectively. Additional high-resolution observations are required to investigate this further, and to probe the ≲300 pc scales on which some Seyfert galaxies show extended structures.
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Rahmani, Amir Reza, Steve Bryant, Chun Huh, Alex Athey, Mohsen Ahmadian, Jiuping Chen i Michael Wilt. "Crosswell Magnetic Sensing of Superparamagnetic Nanoparticles for Subsurface Applications". SPE Journal 20, nr 05 (20.10.2015): 1067–82. http://dx.doi.org/10.2118/166140-pa.
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Summary Stable dispersions of superparamagnetic nanoparticles that are already in use in biomedicine as image-enhancing agents also have potential use in subsurface applications. Surface-coated nanoparticles are capable of flowing through micron-sized pores across long distances in a reservoir, with modest retention in rock. These particles change the magnetic permeability of the flooded region, and thus one can use them to enhance images of the flood. In this paper, we model the propagation of a “ferrofluid” slug in a reservoir and its response to a crosswell magnetic tomography system. This approach to monitoring fluid movement within a reservoir is built on established electromagnetic (EM) conductivity-monitoring technology. In this work, however, we investigate the contrast between injected and resident fluids when they have different magnetic permeabilities. Specifically, we highlight the magnetic response at low frequency to the magnetic excitations generated by a vertical magnetic dipole source positioned at the injection well. At these frequencies, the induction effect is small, the casing effect is manageable, the crosswell response originates purely from the magnetic contrast in the formation, and changes in fluid conductivities are irrelevant. The sensitivity of the measurements to the magnetic slug is highest when the slug is closest to the source or receivers and lower when the slug is midway in the interwell region. At low frequencies, the magnetic response of the ferrofluid slug is largely independent of frequency. As expected for the conductive slug, the sensitivity of the inductive measurements is negligible at low frequencies whereas significant levels of detectability result at higher frequencies. We demonstrate sensitivity to the vertical boundaries of the slug by shifting the vertical position of the excitation source relative to the magnetic slug. The slug geometry plays a key role in determining the magnetic response. With a fixed volume of ferrofluid, there is an optimum slug geometry that results in the maximum magnetic response. Hydrodynamic dispersion of the slug has negligible effect on the magnetic response during early stages of the waterflood. As the slug travels farther into the formation, however, dispersion reduces the concentration of nanoparticles, and the spatial contributions of the magnetic measurements are more diffuse. We illustrate how these low-frequency excitation behaviors are consistent with the quasistatic magnetic dipole physics. The fact that the progress of the magnetic slug can be detected at very early stages of the flood, that the traveling slug's vertical boundaries can be identified at low frequencies, and that the magnetic nanoparticles can be sensed well before the actual arrival of the slug at the observer well provide significant value of the use of the magnetic-contrast agents in crosswell EM tomography.
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Duan, Rujiao, Xuyun Yang, Yonggang Qi i Zhe Liu. "Design of a precise current source with adjustable frequency for AC-FSM". Journal of Physics: Conference Series 2290, nr 1 (1.06.2022): 012039. http://dx.doi.org/10.1088/1742-6596/2290/1/012039.
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Abstract AC-FSM is a new technology of external monitoring the internal corrosion for oil and gas pipelines. The current source stability of the FSM equipment is one of the important factors affecting the monitoring accuracy. According to the equipment requirements, a precision current source with adjustable frequency is designed. With C8051MCU as the control core, DAC conversion and differential amplifier are used to control the frequency and the current amount. The experiment shows that the output of excitation power supply has good consistency, the changing range was less than 0.3 %. When the temperature changes, under the condition of low frequency 5Hz, the change of current is less than 0.5 %, under the condition of high frequency 102Hz, the change of current is less than 0.4 %, which avoids the influence of temperature drift. This equipment is suitable for the long period operation of oil and gas pipelines in the field.
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Swapna, M. S., i S. Sankararaman. "Low-power CW laser-assisted synthesis of plasmonic aluminium nanoparticles using low duty cycle optical chopper". Canadian Journal of Physics 100, nr 3 (marzec 2022): 145–51. http://dx.doi.org/10.1139/cjp-2021-0042.
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This paper reports continuous wave (CW) laser-assisted synthesis of plasmonic aluminium nanoparticles (ANPs) by drastically reducing the laser power density from the existing 105 W/cm2 to 9 W/cm2 using a specially designed ultralow duty cycle chopper. The aluminium target is subjected to laser irradiation by keeping it in a liquid medium maintained at a specific temperature. The effect of chopping frequencies (F), temperatures (T), and surfactant-glucose (C) on the formation of ANPs are investigated through field emission scanning electron microscopic and UV-visible spectroscopic analyses. The energy required for the ejection of ANPs from the target is obtained from the optical source, thermal source, and the molecular collision due to convection current. The purity of the nanoparticle is determined from energy dispersive spectroscopic analysis. The analysis reveals that ANPs of sizes in the range 20–50 nm are formed when F = 30 Hz, T = 60 °C, and C = 18 mg/cc, exhibiting excellent ageing stability. The photoluminescence spectrum, power spectrum, and CIE analyses for the excitations at 350 nm and 390 nm indicate the emission to be blue, suggesting that it is a suitable fluorescence material for UV-plasmonics.
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Ali, Hassan, Erwan Sulaiman, Zamri Omar, M. F. Omar i Faisal Amin. "2D-FEA Based Design and Performance Analysis of Low Weight Segmented Rotor HE-FSM for Light Weight Aircrafts". International Journal of Engineering & Technology 7, nr 2.23 (20.04.2018): 152. http://dx.doi.org/10.14419/ijet.v7i2.23.11905.
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All electric aircraft (AEA), is one of the main intentions of the aerospace industry for future. Where electrical machines are capable to provide high torque density and are dominant for the feasibility of direct drive electrical driving force for aircraft applications. Besides, low weight and high torque capabilities, the best candidate solution should also inherently fault tolerant for aircraft applications. For these reasons, a new sort of machine has been familiarized and published in last decade know as flux switching machine (FSM). FSMs contain all excitation sources on stator side with robust rotor structure. According to the type of excitation, FSMs are characterized into three types such as permanent magnet PM FSM, field excitation FE FSM and hybrid excitation HE FSM. PM FSM and FE FSM use PM and FE coil for their excitation sources respectively, whereas both PM and FE coil is used in HE-FSM for excitation. Subsequently, these machines have shown high torque to weight ratios and high efficiency during research in the last decade. Therefore in this paper, a new structure of 12S-8P HE-FSM with segmental rotor has been proposed and analyzed. The proposed segmented HE-FSM has the simple structure using only three PMs and three FECs. The proposed structure is analyzed using commercial 2D FEA package, JMAG-designer ver. 14.0. This paper presents the coil test analysis of segmented HE-FSM to confirm the working principle. Besides, cogging torque, flux strengthening, torque vs current densities and power vs current densities have been analyzed and presented.
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Seltzer, M. D., i R. B. Green. "Direct Laser Ionization in Analytically Useful Flames". Applied Spectroscopy 43, nr 2 (luty 1989): 257–63. http://dx.doi.org/10.1366/0003702894203165.
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Direct laser ionization (DLI) proceeds by resonant excitation of analyte followed by photoionization of the excited-state atoms. Photoionization is accomplished with the use of off-resonant radiation, which is usually obtained from the dye laser pumping source. DLI has been shown to enhance ionization yields, relative to laser-enhanced ionization (LEI), in low-temperature atom reservoirs where collisional ionization is inefficient. In the present study, DLI has been demonstrated in high-temperature, analytically useful flames, with similar results. DLI detection limits and spectral interferences, as well as the effects of photoionizing laser power on ionization yield, have been evaluated.
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Benamimour, Tariq, Amar Bentounsi i Hind Djeghloud. "Study of Wind Turbine based Variable Reluctance Generator using Hybrid FEMM-MATLAB Modeling". International Journal of Electrical and Computer Engineering (IJECE) 7, nr 1 (1.02.2017): 1. http://dx.doi.org/10.11591/ijece.v7i1.pp1-11.
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Based on exhaustive review of the state of the art of the electric generators fitted to Wind Energy Conversion System (WECS), this study is focused on an innovative machine that is a Variable Reluctance Generator (VRG). Indeed, its simple and rugged structure (low cost), its high torque at low speed (gearless), its fault-tolerance (lowest maintenance), allow it to be a potential candidate for a small wind power application at variable wind speed. For better accuracy, a finite element model of a studied doubly salient VRG is developed using open source software FEMM to identify the electromagnetic characteristics such as linkage flux, torque or inductance versus rotor position and stator excitation. The obtained data are then transferred into look-up tables of MATLAB/Simulink to perform various simulations. Performance of the proposed wind power system is analyzed for several parameters and results are discussed.