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  • AIP Publishing  (15)
  • 1
    In: AIP Advances, AIP Publishing, Vol. 11, No. 8 ( 2021-08-01)
    Abstract: In the field of plasma diagnosis, the measurement of the distribution function is significant because the distribution function is the basis for the use of plasma kinetic theory and it is the prerequisite for analyzing many physical phenomena, such as Landau damping (wave-particle resonance phenomenon) and ion sheath. Theoretical analysis and a large number of experiments have proved that plasma components do not obey Boltzmann–Gibbs statistics and can be well described by nonextensive statistical mechanics. The field of nonextensive electric probe has also made great progress, and the invention of the nonextensive single electric probes has developed and strengthened the power of plasma diagnostics. The nonextensive electric probe can not only measure the electron nonextensive parameter of plasma that cannot be measured by traditional probes but can also measure more accurate plasma parameters that can also be measured by traditional probes, such as Te, Φp, ne, Φf, and αqFe. However, diagnosing the plasma distribution function by the nonextensive electric probe has not been thoroughly and systematically analyzed and discussed. Here, we show the measurement of the plasma distribution function with a nonextensive single electric probe. This work expands the diagnostic capabilities of the nonextensive single electric probe. We utilize the nonextensive single electric probe theory to analyze the experimental data points of the I–V curve, measure the plasma electron distribution function fvx, and display the distribution curve (figure f-vx), and we also measure the plasma parameters of qFe, Te, Φp, ne, Φf, αqFe, etc. The proposed method provides a new approach to the diagnosis of the plasma distribution function and contributes to a more accurate and comprehensive grasp of plasma, which creates better conditions for us to take advantage of plasma. These initial results illustrate the potential of the nonextensive electric probe in the field of plasma diagnosis and, more generally, in accelerating the progress of fusion-energy science and helping to understand complex physical systems.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 2583909-3
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  • 2
    In: AIP Advances, AIP Publishing, Vol. 12, No. 9 ( 2022-09-01)
    Abstract: It is very important to monitor pH values. In this paper, we fabricated an all-solid-state AlGaN/GaN-based ion-sensitive heterostructure field effect transistor (ISHFET) pH sensor microprobe. The microprobe could facilitate measurement of pH values. The microprobe was fabricated by packaging the pH sensor microprobe chip into a 21 G medical needle. The performance of the integrated pH sensor microprobe was evaluated in pH range of 4–9.18. A sensitivity of 143.57 µA/pH can be achieved using the pH sensor microprobe with a width to length ratio of 4.2 at a drain–source voltage of 0.5 V. The pH sensor microprobe keeps a similar current when the pH values of solutions are the same. A response time of 1 s can be achieved when no neutralization reaction occurs. The pH sensor microprobe can accurately measure pH of solutions under 0.1M interfering ions. This probe-type AlGaN/GaN-based ISHFET pH sensor may be used in medicine or biology, especially in the detection of pH of biological fluid, blood, and some precious biological samples.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2583909-3
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  • 3
    Online Resource
    Online Resource
    AIP Publishing ; 2018
    In:  Physics of Fluids Vol. 30, No. 10 ( 2018-10-01)
    In: Physics of Fluids, AIP Publishing, Vol. 30, No. 10 ( 2018-10-01)
    Abstract: A numerical study was performed to investigate the detailed effects of activation energy Ea on the oblique detonation wave surface instability. Numerical simulations were performed using an ideal reactive flow model given by the inviscid Euler equations with one-step irreversible Arrhenius reaction kinetics. The numerical results demonstrate two types of unstable structures following the initial smooth surface after detonation initiation. One exhibits by a “saw-tooth” reactive front and the other exhibits by a “keystone” feature. To quantify the destabilization processes, two characteristic length scales, L1 and L2, are defined statistically to be the length of the smooth detonation surface before the appearance of instabilities and the length of the unstable surface before the first cellular structure with the onset of right-running transverse waves, respectively. Their dependence on Ea was simulated and analyzed. In general, both lengths decrease with increasing Ea, making the surface more unstable. However, with increasing Ea, the high temperature sensitivity of the mixture causes an abrupt explosion in the initiation region, introducing a high overdriven surface and suppressing the instability. With the balance between the destabilizing effect of Ea and the stabilizing effect of increasing overdrive factor, both L1 and L2 are found to approach a near-constant value in the high Ea limit.
    Type of Medium: Online Resource
    ISSN: 1070-6631 , 1089-7666
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 1472743-2
    detail.hit.zdb_id: 241528-8
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  • 4
    Online Resource
    Online Resource
    AIP Publishing ; 2019
    In:  Physics of Fluids Vol. 31, No. 2 ( 2019-02-01)
    In: Physics of Fluids, AIP Publishing, Vol. 31, No. 2 ( 2019-02-01)
    Abstract: Stoichiometric acetylene-oxygen mixtures diluted by argon are widely used in normal detonation waves but have not yet been used in oblique detonation waves (ODWs). The present study simulates ODWs in acetylene-oxygen-argon mixtures, with a dilution ratio Φ = 50%-90%, using the reactive Euler equations with a detailed chemistry model, and describes the characteristics of acetylene ODWs. Similar to ODWs in hydrogen-air mixtures, the transition from the oblique shock wave to ODW may be either abrupt or smooth and the effects of Φ are investigated with a variable incident Mach number M0. When M0 changes between 8 and 10, the transition is abrupt in the case of Φ = 50%, while it is smooth in the case of Φ = 90%. In the case of Φ = 70%, a high M0 corresponds to a smooth transition, while a low M0 corresponds to an abrupt transition. A further study on the initiation mechanism was performed by comparing the numerical initiation length with the length obtained via the constant-volume combustion calculation, which demonstrated that the initiation is kinetic-controlled in the cases of Φ = 70% and 90%, but wave-controlled in the case of Φ = 50% with M0 below 8.5. Moreover, an initiation structure featured by two-shock in the product was observed for the first time, and its formation mechanism is qualitatively discussed and compared to hydrogen ODWs.
    Type of Medium: Online Resource
    ISSN: 1070-6631 , 1089-7666
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 1472743-2
    detail.hit.zdb_id: 241528-8
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  • 5
    In: AIP Advances, AIP Publishing, Vol. 8, No. 11 ( 2018-11), p. 115106-
    Type of Medium: Online Resource
    ISSN: 2158-3226
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 2583909-3
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  • 6
    In: AIP Advances, AIP Publishing, Vol. 10, No. 4 ( 2020-04-01)
    Abstract: The capacitance and the series resistance are two main factors which determine the cut-off frequency of Schottky barrier diodes (SBDs) for their application in millimeter-wave and terahertz regions. The junction capacitance is closely related to the anode dimension of a SBD. Reducing the anode size can effectively decrease the junction capacitance, but it will increase the series resistance and the difficulty of the device manufacturing process is also increased. In this paper, an AlGaN/GaN based air-bridge structure planar SBD with a half through-hole is investigated. The half through-hole was formed on the center of a circular anode by inductively coupled plasma etching to the unintentional doping-GaN channel layer. The capacitance formed by the anode metal and the two-dimensional electron gas at the AlGaN/GaN interface is effectively reduced under the condition of holding the metal area of anode. The total capacitance of the 20 μm-radius anode SBD with a 19.95 μm-radius half through-hole dramatically decreases from 2.32 pF of the device without the half through-hole to 21.5 fF. In addition, since the current is mainly distributed at the edge of the circular anode, the series resistance is only slightly increased. The cut-off frequency of the air-bridge planar SBD with a 20 μm-radius anode and a 19.95 μm-radius half through-hole was 114.1 GHz. To reduce the size of the anode and optimize the ohmic contact, the cut-off frequency could be further improved.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2583909-3
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  • 7
    In: Journal of Applied Physics, AIP Publishing, Vol. 126, No. 8 ( 2019-08-28)
    Abstract: Benefiting from their minimally or noninvasive nature, thermal therapies are becoming increasingly important in tumor treatment, in which real-time monitoring of in vivo temperature based on ultrasonic imaging has shown great promise. In this work, an improved dynamic frame selection algorithm and a modified adaptive filtering method were combined with a thermal expansion model, and in vivo temperature monitoring with improved accuracy was achieved. The ultimate aim being the use of thermometry in the thermal treatment of hypertension, experiments targeting the perirenal fat of living pigs were carried out, in which microwaves were applied as a heat source at different power levels. By comparing the echo shift of the ultrasound (US) and the temperature—sensed via a thermocouple—a constant temperature evaluation coefficient was determined. As the tissue was raised to 6.4, 9.8, and 19.3 °C above its base temperature, the root-mean-square evaluation error (ɛrms) was about 0.3, 0.5, and 0.8 °C, respectively. High precision and a high signal-to-noise ratio can help US thermometry play a more important role in monitoring the application of thermal therapies.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 8
    Online Resource
    Online Resource
    AIP Publishing ; 2020
    In:  Physics of Fluids Vol. 32, No. 4 ( 2020-04-01)
    In: Physics of Fluids, AIP Publishing, Vol. 32, No. 4 ( 2020-04-01)
    Abstract: Oblique detonation waves (ODWs) have been studied widely as the basis of detonation-based hypersonic engines, but there are few studies on ODWs in a confined space. This study simulates ODW reflection on a solid wall before an outward turning corner for a simplified combustor–nozzle flow based on a two-step kinetic model. Numerical results reveal three types of ODW structures: stable, critical, and unstable. When the reflection occurs at the turning point, the stable ODW structure remains almost the same as before reflection. When the wave reflects at the wall before the turning point, either the critical structure or the unstable structure arises, which has never been investigated before. Both structures have the same initial two-section detonation surface: but the critical one becomes stationary at a certain position, while the unstable one keeps traveling upstream. By adjusting the location of the expansion wave and degree of the turning angle, the difference of the two structures is attributed to the thermal choking appearing only in the unstable structure. The thermal choking is achieved by the merging of subsonic zones, whose dependence on the various parameters is discussed.
    Type of Medium: Online Resource
    ISSN: 1070-6631 , 1089-7666
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 1472743-2
    detail.hit.zdb_id: 241528-8
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  • 9
    Online Resource
    Online Resource
    AIP Publishing ; 2020
    In:  Physics of Fluids Vol. 32, No. 11 ( 2020-11-01)
    In: Physics of Fluids, AIP Publishing, Vol. 32, No. 11 ( 2020-11-01)
    Abstract: Previous studies of a high-speed blunt projectile in a combustible mixture found two oscillating unsteady combustion modes induced by the curved shock, referred to as high- and low-frequency modes. A new unsteady combustion mode is observed in the present study. The frequency reaches approximately twice the high frequency and is referred to as the super-high frequency to maintain consistency with the terminology used in previous works. The super-high-frequency mode appears in cases of a small sphere diameter, and with a proper diameter, an intermediate mode arises with the co-existence of both high and the super-high frequencies. An analysis of pressure and temperature gradients along the stagnation streamline attributes the oscillation of combustion to the interaction of compression and entropy waves between the shock and flame front. If the compression/entropy waves affect the flame front of the next cycle, the high-frequency mode arises; this is consistent with the results of previous works. However, weakened compression/entropy waves in cases of a small sphere diameter only affect the flame front of every other cycle, leading to the super-high-frequency mode.
    Type of Medium: Online Resource
    ISSN: 1070-6631 , 1089-7666
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 1472743-2
    detail.hit.zdb_id: 241528-8
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  • 10
    Online Resource
    Online Resource
    AIP Publishing ; 2014
    In:  Chaos: An Interdisciplinary Journal of Nonlinear Science Vol. 24, No. 3 ( 2014-09-01)
    In: Chaos: An Interdisciplinary Journal of Nonlinear Science, AIP Publishing, Vol. 24, No. 3 ( 2014-09-01)
    Abstract: Experimental studies have shown that neuron population located in the basal ganglia of parkinsonian primates can exhibit characteristic firings with certain firing rates differing from normal brain activities. Motivated by recent experimental findings, we investigate the effects of various stimulation paradigms on the firing rates of parkinsonism based on the proposed dynamical models. Our results show that the closed-loop deep brain stimulation is superior in ameliorating the firing behaviors of the parkinsonism, and other control strategies have similar effects according to the observation of electrophysiological experiments. In addition, in conformity to physiological experiments, we found that there exists optimal delay of input in the closed-loop GPtrain|M1 paradigm, where more normal behaviors can be obtained. More interestingly, we observed that W-shaped curves of the firing rates always appear as stimulus delay varies. We furthermore verify the robustness of the obtained results by studying three pallidal discharge rates of the parkinsonism based on the conductance-based model, as well as the integrate-and-fire-or-burst model. Finally, we show that short-term plasticity can improve the firing rates and optimize the control effects on parkinsonism. Our conclusions may give more theoretical insight into Parkinson's disease studies.
    Type of Medium: Online Resource
    ISSN: 1054-1500 , 1089-7682
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2014
    detail.hit.zdb_id: 1472677-4
    SSG: 11
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