Journal articles: 'Radiative proce'

1

Yang, Guangwei, Jianying Li, Jiangjun Yang, and Zijian Xing. "Dual-band slot microstrip patch antennas with dual-radiation modes for wireless communication." International Journal of Microwave and Wireless Technologies 12, no. 2 (July 31, 2019): 155–62. http://dx.doi.org/10.1017/s1759078719001065.

Full text

Abstract:

AbstractIn this paper, a novel compact dual-band microstrip patch antenna with dual-radiation modes is investigated. The proposed antenna consists of a rectangular ground plane, a U-shaped feed probe, and an H-shaped slot radiating patch. By adjusting the size of these structures, a dual-band antenna can be obtained. In the low-frequency band, the antenna can radiate one radiation beam with high gain. In the high-frequency band, the antenna can achieve monopole-like radiation pattern. Therefore, an antenna prototype is fabricated and measured for validation. Good agreement between the simulated and measured results is observed in this paper. The antenna's operating frequency ranges are 3.6–3.85 GHz in the low-frequency band and 5.1–6.1 GHz in the high-frequency band with the reflection coefficient less than −10 dB. At 3.7 GHz, the antenna radiate one beam with 8.8 dBi realized gain. At 5.5 GHz, it exhibits dual-radiation beams directed to −48 and 48° with 5.6 and 5.5 dBi realized gain in the xoz-plane and −48 and 48° with 2.9 and 3.0 dBi realized gain in the yoz-plane. Therefore, the proposed antenna is a good candidate for wireless communication systems.

APA, Harvard, Vancouver, ISO, and other styles

2

BALUGIN, N. V., B. A. FOMIN, A. D. LYKOV, and V. A. YUSHKOV. "ESTIMATION OF STRATOSPHERIC AEROSOL EFFECTS ON STRATOSPHERIC RADIATION BUDGET ACCORDING TO OPTICAL BALLOON BACKSCATTER PROBE AND RADIATION MODELING." Meteorologiya i Gidrologiya, no. 10 (October 2022): 121–29. http://dx.doi.org/10.52002/0130-2906-2022-10-121-129.

Full text

Abstract:

A method for evaluating stratospheric aerosol effects on the stratospheric radiation budget according to balloon sounding with an optical aerosol backscatter probe is presented. It is shown for the sounding in the equatorial zone under conditions of perturbed aerosol filling of the stratosphere that observed changes in the composition of stratospheric aerosol lead to significant changes (2-3-fold) in radiative heating. The evaluation technique is based on using the radiative (line-by-line and Monte Carlo) model of solar radiation transfer and can be especially useful in case of episodical perturbations of the stratospheric aerosol layer resulting from anthropogenic and natural disasters accompanied by aerosol emissions.

APA, Harvard, Vancouver, ISO, and other styles

3

Chaulagain, U., C. Stehlé, P. Barroso, M. Kozlova, J. Nejdl, F. Suzuki Vidal, and J. Larour. "Target Design for XUV Probing of Radiative Shock Experiments." Journal of Nepal Physical Society 6, no. 1 (August 6, 2020): 30–41. http://dx.doi.org/10.3126/jnphyssoc.v6i1.30514.

Full text

Abstract:

Radiative shocks are strong shocks characterized by plasma at a high temperature emitting an important fraction of its energy as radiation. Radiative shocks are commonly found in many astrophysical systems and are templates of radiative hydrodynamic flows, which can be studied experimentally using high-power lasers. This is not only important in the context of laboratory astrophysics but also to benchmark numerical studies. We present details on the design of experiments on radiative shocks in xenon gas performed at the kJ scale PALS laser facility. It includes technical specifications for the tube targets design and numerical studies with the 1-D radiative hydrodynamics code MULTI. Emphasis is given to the technical feasibility of an XUV imaging diagnostic with a 21 nm (~58 eV) probing beam, which allows to probe simultaneously the post-shock and the precursor region ahead of the shock. The novel design of the target together with the improved X-ray optics and XUV source allow to show both the dense post-shock structure and the precursor of the radiative shock.

APA, Harvard, Vancouver, ISO, and other styles

4

Coffing, Shane X., Chris L. Fryer, Harry F. Robey, Christopher J. Fontes, Suzannah R. Wood, Pawel M. Kozlowski, Heather M. Johns, et al. "Inferring the temperature profile of the radiative shock in the COAX experiment with shock radiography, Dante, and spectral temperature diagnostics." Physics of Plasmas 29, no. 8 (August 2022): 083302. http://dx.doi.org/10.1063/5.0081167.

Full text

Abstract:

Predicting and modeling the behavior of experiments with radiation waves propagating through low-density foams require a detailed quantification of the numerous uncertainties present. In regimes where a prominent radiative shock is produced, key dynamical features include the shock position, temperature, and curvature and the spatial distribution and temperature of the corresponding supersonic radiation wave. The COAX experimental platform is designed to constrain numerical models of such a radiative shock propagating through a low-density foam by employing radiography for spatial and shock information, Dante for characterizing the x-ray flux from the indirectly driven target, and a novel spectral diagnostic designed to probe the temperature profile of the wave. In this work, we model COAX with parameterized 2D simulations and a Hohlraum-laser modeling package to study uncertainties in diagnosing the experiment. The inferred temperature profile of the COAX radiation transport experiments has been shown to differ from simulations more than expected from drive uncertainties that have been constrained by simultaneous soft x-ray flux and radiography measurements.

APA, Harvard, Vancouver, ISO, and other styles

5

Tiranov, Alexey, Vasiliki Angelopoulou, Cornelis Jacobus van Diepen, Björn Schrinski, Oliver August Dall’Alba Sandberg, Ying Wang, Leonardo Midolo, et al. "Collective super- and subradiant dynamics between distant optical quantum emitters." Science 379, no. 6630 (January 27, 2023): 389–93. http://dx.doi.org/10.1126/science.ade9324.

Full text

Abstract:

Photon emission is the hallmark of light-matter interaction and the foundation of photonic quantum science, enabling advanced sources for quantum communication and computing. Although single-emitter radiation can be tailored by the photonic environment, the introduction of multiple emitters extends this picture. A fundamental challenge, however, is that the radiative dipole-dipole coupling rapidly decays with spatial separation, typically within a fraction of the optical wavelength. We realize distant dipole-dipole radiative coupling with pairs of solid-state optical quantum emitters embedded in a nanophotonic waveguide. We dynamically probe the collective response and identify both super- and subradiant emission as well as means to control the dynamics by proper excitation techniques. Our work constitutes a foundational step toward multiemitter applications for scalable quantum-information processing.

APA, Harvard, Vancouver, ISO, and other styles

6

Keeler, Jason M., Brian F. Jewett, Robert M. Rauber, Greg M. McFarquhar, Roy M. Rasmussen, Lulin Xue, Changhai Liu, and Gregory Thompson. "Dynamics of Cloud-Top Generating Cells in Winter Cyclones. Part I: Idealized Simulations in the Context of Field Observations." Journal of the Atmospheric Sciences 73, no. 4 (February 24, 2016): 1507–27. http://dx.doi.org/10.1175/jas-d-15-0126.1.

Full text

Abstract:

Abstract This paper assesses the influence of radiative forcing and latent heating on the development and maintenance of cloud-top generating cells (GCs) in high-resolution idealized Weather Research and Forecasting Model simulations with initial conditions representative of the vertical structure of a cyclone observed during the Profiling of Winter Storms campaign. Simulated GC kinematics, structure, and ice mass are shown to compare well quantitatively with Wyoming Cloud Radar, cloud probe, and other observations. Sensitivity to radiative forcing was assessed in simulations with longwave-only (nighttime), longwave-and-shortwave (daytime), and no-radiation parameterizations. The domain-averaged longwave cooling rate exceeded 0.50 K h−1 near cloud top, with maxima greater than 2.00 K h−1 atop GCs. Shortwave warming was weaker by comparison, with domain-averaged values of 0.10–0.20 K h−1 and maxima of 0.50 K h−1 atop GCs. The stabilizing influence of cloud-top shortwave warming was evident in the daytime simulation’s vertical velocity spectrum, with 1% of the updrafts in the 6.0–8.0-km layer exceeding 1.20 m s−1, compared to 1.80 m s−1 for the nighttime simulation. GCs regenerate in simulations with radiative forcing after the initial instability is released but do not persist when radiation is not parameterized, demonstrating that radiative forcing is critical to GC maintenance under the thermodynamic and vertical wind shear conditions in this cyclone. GCs are characterized by high ice supersaturation (RHice > 150%) and latent heating rates frequently in excess of 2.00 K h−1 collocated with vertical velocity maxima. Ice precipitation mixing ratio maxima of greater than 0.15 g kg−1 were common within GCs in the daytime and nighttime simulations.

APA, Harvard, Vancouver, ISO, and other styles

7

Akdagli, Ali, and Abdurrahim Toktas. "Design of wideband orthogonal MIMO antenna with improved correlation using a parasitic element for mobile handsets." International Journal of Microwave and Wireless Technologies 8, no. 1 (September 15, 2014): 109–15. http://dx.doi.org/10.1017/s1759078714001263.

Full text

Abstract:

In this paper, a novel design of compact wideband multiple-input multiple-output (MIMO) antenna operating over a frequency range of 1.8–4.0 GHz at 10 dB is presented for mobile terminals. The MIMO antenna design consists of two symmetrical and orthogonal radiating elements with a small size of 15.5 × 16.5 mm2 printed on the corners of a mobile circuit board. The radiating element is composed of four meandered monopole branches with a strip-line fed by a probe. By triangularly trimming the corners of the common ground plane beneath the radiating elements, not only the mutual coupling is reduced, but also impedance bandwidth is increased. Although, the antenna in this form has sufficient correlation level between the radiating elements for MIMO operation, a novel design of plus-shaped parasitic element is inserted to the ground plane between those radiating elements in order to further enhance the isolation. The performance of the MIMO antenna is investigated in terms of s-parameters, radiation pattern, gain, envelope correlation coefficient (ECC), and total active reflection coefficient (TARC), and is verified through the measurements. The results demonstrate that the proposed MIMO antenna has good characteristics of wideband, isolation, gain, radiation pattern, and is compatible with LTE, WiMAX, and WLAN, besides it is small, compact, and embeddable in mobile terminals.

APA, Harvard, Vancouver, ISO, and other styles

8

Savard, N., G. Fubiani, and M. Dehnel. "Comparison of Langmuir probe and optical emission spectroscopy on a volume-cusp filament ion source using helium." Review of Scientific Instruments 93, no. 10 (October 1, 2022): 103303. http://dx.doi.org/10.1063/5.0092156.

Full text

Abstract:

D-Pace has a Penning ion source that runs with helium for studies of α-particle production. We want to study its plasma properties as a function of varying operational parameters, which results in varied output ion beam characteristics. In order to diagnose the ion source plasma, a collisional-radiative code for helium to be used with optical emission spectroscopy measurements is developed. This has the advantage of being non-invasive, which allows for measurements using the emitted light from the plasma. This collisional-radiative code is shown to compare well with the Yacora on the Web model developed at IPP-Garching, and improves upon it with the addition of radiation trapping. Furthermore, the sensitivity of this model to the inclusion of additional excited state populations and non-Maxwellian electron energy distribution functions is investigated. It is shown that non-Maxwellian distributions can significantly affect spectroscopy measurements. This diagnostic is benchmarked to Langmuir probe measurements on the TRIUMF-licensed volume-cusp ion source to determine whether it can replicate the measured electron density and electron temperature as a function of varied operational parameters. The operational parameters are helium gas flow (10–40 SCCM), arc voltage (100–200 V), and arc current (1–5 A). The measured plasma properties, while different in absolute value, have similar trends for each operational parameter except when varying arc voltage. It is shown that this mismatch as a function of arc voltage is likely due to high energy non-Maxwellian electrons from the cathode sheath, which are not included within the collisional-radiative model.

APA, Harvard, Vancouver, ISO, and other styles

9

Calvagna, Chiara, Andrea Azelio Mencaglia, Iacopo Osticioli, Daniele Ciofini, and Salvatore Siano. "Novel Probe for Thermally Controlled Raman Spectroscopy Using Online IR Sensing and Emissivity Measurements." Sensors 22, no. 7 (March 31, 2022): 2680. http://dx.doi.org/10.3390/s22072680.

Full text

Abstract:

Temperature rise during Raman spectroscopy can induce chemical alterations of the material under analysis and seriously affect its characterization. Thus, such photothermal side effects can represent a serious problem to be carefully controlled in order to safeguard the integrity of the material and its spectral features. In this work, an innovative probe for thermally controlled portable Raman spectroscopy (exc. 785 nm) equipped with infrared sensing lines was developed. It included an infrared source and two thermopile sensors, which allowed to perform real-time measurements of the local emissivity of the material surface under laser excitation. The emissivity, which is needed in order to monitor the temperature of the irradiated surface through infrared radiation measurements, represents the complementary component of the reflectance in the radiative energy balance. Thus, total reflectance, temperature measurements and Raman spectroscopy were integrated in the present probe. After independently assessing the reliability of the former in order to derive the emissivity of variety of materials, the probe was successfully applied on pigments, paint layers, and a painting on canvas. The results achieved evidence the significant exploitation potential of the novel tool.

APA, Harvard, Vancouver, ISO, and other styles

10

Johnston, Christopher O., Brian R. Hollis, and Kenneth Sutton. "Radiative Heating Methodology for the Huygens Probe." Journal of Spacecraft and Rockets 44, no. 5 (September 2007): 993–1002. http://dx.doi.org/10.2514/1.26424.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Poklonski, N. A., S. A. Vyrko, A. T. Vlassov, A. I. Siahlo, and S. V. Ratkevich. "Model of Electromagnetic Emitter Based on a Stream of Single Electrons inside Curved Carbon Nanotube." Devices and Methods of Measurements 9, no. 4 (December 17, 2018): 288–95. http://dx.doi.org/10.21122/2220-9506-2018-9-4-288-295.

Full text

Abstract:

The problems of elaboration and application of microand nanometer sized antennas for the generation and reception of electromagnetic radiation is still relevant in both fundamental and applied aspects. With decreasing antenna size, the frequency of electromagnetic radiation increases, and its power decreases. To increase the radiation power, the periodic (in space) electrodynamic structures are used. The aim of the work is to find the possibility of application of injection and (quasi)ballistic drift of single electrons inside curved carbon nanotubes for emission of electromagnetic waves in the microwave range and to determine the parameters of the radiating system that affect the radiation power.By the calculation within the framework of classical electrodynamics it is shown the possibility in principle of generation of electromagnetic radiation of the gigahertz range by a stream of single electrons inside a hollow curved dielectric carbon nanotube.It was found that the spectrum and power of this radiation can be controlled by varying the electron flux density, length and curvature of the hollow nanotube.The results of the work can be applied for elaboration of a microminiature emitter of microwave electromagnetic radiation based on a curved carbon nanotube in the engineering of contactless probe microscopy.

APA, Harvard, Vancouver, ISO, and other styles

12

Zhang, Lulu, Luis C. Ho, and Aigen Li. "Evidence That Shocks Destroy Small PAH Molecules in Low-luminosity Active Galactic Nuclei." Astrophysical Journal 939, no. 1 (October 28, 2022): 22. http://dx.doi.org/10.3847/1538-4357/ac930f.

Full text

Abstract:

Abstract We combined mapping-mode mid-infrared Spitzer spectra with complementary infrared imaging to perform a spatially resolved study of polycyclic aromatic hydrocarbon (PAH) emission from the central regions of 66 nearby galaxies, roughly evenly divided into star-forming systems and low-luminosity active galactic nuclei (AGNs). In conjunction with similar measurements available for quasars, we aim to understand the physical properties of PAHs across a broad range of black hole accretion power, with the goal of identifying observational diagnostics that can be used to probe the effect of AGNs on the host galaxy. Whereas the PAH emission correlates tightly with far-ultraviolet luminosity in star-forming regions, the spatially resolved regions of AGNs tend to be PAH deficient. Moreover, AGN regions exhibit on average smaller PAH 6.2 μm/7.7 μm and larger PAH 11.3 μm/7.7 μm band ratios. Although the current data are highly restrictive, they suggest that these anomalous PAH band ratios cannot be explained by the effects of the AGN radiation field alone. Instead, they hint that small grains may be destroyed by the combined effects of radiative processes and shocks, which are plausibly linked to jets and outflows preferentially associated with highly sub-Eddington, radiatively inefficient AGNs. While quasars also present a PAH deficit and unusual PAH band ratios, their characteristics differ in detail compared to those observed in more weakly accreting AGNs, a possible indicator of fundamental differences in their modes of energy feedback.

APA, Harvard, Vancouver, ISO, and other styles

13

Alexanian, Arik G., Nikolay S. Aramyan, Romen P. Grigoryan, Ashot M. Khachatrian, Lenrik A. Matevossian, and Arsham S. Yeremyan. "On the Optical Memory of a Thin-Film pInSb-nCdTe Heterojunction Obtained by Laser Pulsed Deposition." MRS Proceedings 692 (2001): H9.38.1—H9.38.6. http://dx.doi.org/10.1557/proc-692-h9.38.1.

Full text

Abstract:

AbstractThin film pInSb-nCdTe heterojunctions (HJs) were produced using pulsed laser deposition (PLD) technique and their photoelectric properties were studied for various thickness of the CdTe layer at nitrogen temperature and under a background radiation the photo-EMF for which was around 1.5 mV. At radiative excitation of the HJ a photo-EMF is observed, which persists when the excitation is turned off. The optical memory (OM) effect is observed in an idling regime and in a wide spectral range: (0.37–1.37)μm with “recording” (0.37–0.575)μm, (0.75–1.37)μm, and “clearing” (0.575–0.75)μm sub-regions. The maximum OM signal is observed at λ=0.575μm while the minimum is at λ=0.768μm. In the spectral dependence of the OM signal at direct and reverse scanning of monochromatic irradiation an hysteresis is observed which is evident for the OM effect. The time dependence of OM signal is investigated at λ=0.575μm and at various intensities of the radiation source. Here, an effect of saturation is clearly observed, and the time during which the OM signal runs up to saturation, depends strongly on the incident light flow power and decreases drastically as the latter is increased. The external bias applied to the HJ enhances the OM on 2 orders over its value in the idling regime. The OM signal persists for a time period no less than 105 sec, either with or without an external bias. The actually obtained values of “recording” sensitivity and the “recording” time are U=0.66 μJ/mm2 and τ=10−4 sec., respectively. The OM signal reaches its maximal value as the thickness of CdTe layer increases (up to d=0.45 μm). It is shown that the investigated HJ possess the property of integration of the radiation.

APA, Harvard, Vancouver, ISO, and other styles

14

Di Menza, Laurent, Claire Michaut, and Océane Saincir. "Diffusion approximation in a radiative transfer model for astrophysical flows." ESAIM: Proceedings and Surveys 64 (2018): 78–92. http://dx.doi.org/10.1051/proc/201864078.

Full text

Abstract:

In this work, we present the diffusion approximation model for radiative transfer when we deal with optically thick astrophysical flows. Since the initial model is high CPU time demanding when dealing with its numerical approximation, solving this simpler system can provide a low cost strategy for the simulation of radiative media. We then use a finite-volume algorithm coupled with an implicit scheme for radiative contributions to solve this simplified system. Numerical experiments in the one-dimensional and two dimensional cases are presented to validate our numerical strategy and to prove the relevance of this asymptotic model.

APA, Harvard, Vancouver, ISO, and other styles

15

Matsumoto, Kosei, Takao Nakagawa, Keiichi Wada, Shunsuke Baba, Shusuke Onishi, Taisei Uzuo, Naoki Isobe, and Yuki Kudoh. "Probing Dynamics and Thermal Properties Inside Molecular Tori with CO Rovibrational Absorption Lines." Astrophysical Journal 934, no. 1 (July 1, 2022): 25. http://dx.doi.org/10.3847/1538-4357/ac755f.

Full text

Abstract:

Abstract A recent hydrodynamic model, the radiation-driven fountain model (Wada et al. 2016), presented a dynamical picture that active galactic nuclei (AGNs) tori sustain their geometrical thickness by gas circulation around AGNs, and previous papers have confirmed that this picture is consistent with multiwavelength observations of nearby Seyfert galaxies. Recent near-infrared observations implied that CO rovibrational absorption lines (ΔJ = ± 1, v = 0 − 1, λ ∼ 4.7 μm) could probe the physical properties of the inside tori. However, the origin of the CO absorption lines has been under debate. In this paper, we investigate the origin of the absorption lines and conditions for detecting them by performing line radiative transfer calculations based on the radiation-driven fountain model. We find that CO rovibrational absorption lines are detected at inclination angles θ obs = 50°–80°. At the inclination angle θ obs = 77°, we observe multi-velocity components: inflow (v LOS = 30 km s−1), systemic (v LOS = 0 km s−1), and outflows (v LOS = −75, − 95, and −105 km s−1). The inflow and outflow components (v LOS = 30 and −95 km s−1) are collisionally excited at the excitation temperatures of 186 and 380 K up to J = 12 and 4, respectively. The inflow and outflow components originate from the accreting gas on the equatorial plane at 1.5 pc from the AGN center and the outflowing gas driven by AGN radiation pressure at 1.0 pc, respectively. These results suggest that CO rovibrational absorption lines can provide us with the velocities and kinetic temperatures of the inflow and outflow in the inner few parsec region of AGN tori, and the observations can probe the gas circulation inside the tori.

APA, Harvard, Vancouver, ISO, and other styles

16

Liu, Jin-Ku, Xi-Lai Zhao, Chen-Xin Zhang, and Zan-Yang Wang. "A Novel Low Axis Ratio Double-Circularly Polarized Microstrip Antenna." International Journal of Antennas and Propagation 2022 (April 13, 2022): 1–7. http://dx.doi.org/10.1155/2022/8947697.

Full text

Abstract:

This article presents a dual circular polarization (CP) microstrip antenna, emitting electromagnetic waves above and below the substrate, which is fed by the double L-probe. Selecting the L-probe feed increases the bandwidth of the antenna, and different probes control the rotation of CP. The antenna could radiate two polarized waves of the same amplitude and vertical through two square radiation patches; meanwhile, adjusting the phase difference between both waves to 90° will produce a CP wave in the far-field. The simulation and measurement results show that the antenna is in 4.3–4.8 GHz band with S11<−10 dB, S22<−10 dB, and AR<3 dB. Furthermore, a lower axis ratio could be obtained in this work compared with similar antennas of the same type.

APA, Harvard, Vancouver, ISO, and other styles

17

Lévis, K., A. Ittipiboon, and A. Petosa. "Probe radiation cancellation in wideband probe-fed microstrip arrays." Electronics Letters 36, no. 7 (2000): 606. http://dx.doi.org/10.1049/el:20000513.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

KOBAYASHI, Mitsutoshi, Terutake HAYASHI, and Yasuhiro TAKAYA. "D31 Evaluation of Unstable Behavior in Micro-probe Trapped by Optical Radiation Pressure(Nano/micro measurement and intelligent instruments)." Proceedings of International Conference on Leading Edge Manufacturing in 21st century : LEM21 2009.5 (2009): 777–80. http://dx.doi.org/10.1299/jsmelem.2009.5.777.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Chiaramonti, Ann N., Luis Miaja-Avila, Paul T. Blanchard, David R. Diercks, Brian P. Gorman, and Norman A. Sanford. "A Three-Dimensional Atom Probe Microscope Incorporating a Wavelength-Tuneable Femtosecond-Pulsed Coherent Extreme Ultraviolet Light Source." MRS Advances 4, no. 44-45 (2019): 2367–75. http://dx.doi.org/10.1557/adv.2019.296.

Full text

Abstract:

ABSTRACTPulsed coherent extreme ultraviolet (EUV) radiation is a potential alternative to pulsed near-ultraviolet (NUV) wavelengths for atom probe tomography. EUV radiation has the benefit of high absorption within the first few nm of the sample surface for elements across the entire periodic table. In addition, EUV radiation may also offer athermal field ion emission pathways through direct photoionization or core-hole Auger decay processes, which are not possible with the (much lower) photon energies used in conventional NUV laser-pulsed atom probe. We report preliminary results from what we believe to be the world’s first EUV radiation-pulsed atom probe microscope. The instrument consists of a femtosecond-pulsed, coherent EUV radiation source interfaced to a local electrode atom probe tomograph by means of a vacuum manifold beamline. EUV photon-assisted field ion emission (of substrate atoms) has been demonstrated on various insulating, semiconducting, and metallic specimens. Select examples are shown.

APA, Harvard, Vancouver, ISO, and other styles

20

Marin, F. "Modeling optical and UV polarization of AGNs." Astronomy & Astrophysics 615 (July 2018): A171. http://dx.doi.org/10.1051/0004-6361/201833225.

Full text

Abstract:

Context. One of the main challenges for polarimetric observations of active galactic nuclei (AGN) is to properly estimate the amount of parasitic light that contaminates the polarization signal. Removing this unpolarized flux is a complex task that has only been achieved in a couple of objects. Aims. In this fifth paper of the series, we present a new version of the Monte Carlo code STOKES that accounts for dilution by interstellar polarization and host starlight in radiative transfer modeling. Methods. We upgraded our code by including spectral energy distribution (SED) templates for a set of representative host galaxies. The unpolarized light emitted by those hosts alters the observer polarization while being coherently radiatively coupled to the AGN structure. We also included in our analysis tool a routine that may add, depending on the user’s objectives, an interstellar component. Results. Using a generic AGN model, we illustrate how interstellar polarization and starlight dilution impact the observed polarimetric signal of AGN. We applied our code to NGC 1068, an archetypal edge-on AGN and demonstrate that STOKES can reproduce its SED, the expected wavelength-dependent polarimetric signatures, and the observed high-angular resolution polarimetric maps. Using the flexibility of the code, we derived several intrinsic parameters such as the system inclination and the torus opening angle. Conclusions. The new version of our publicly available code now allows observers to better prepare their observations, interpret their data and simulate the three-dimensional geometry and physics of AGN in order to probe unresolved structures. Additionally, the radiative interaction between the host and the AGN can be used to probe the co-evolution of the system.

APA, Harvard, Vancouver, ISO, and other styles

21

Salmi, Tuomo, Valery F. Suleimanov, Joonas Nättilä, and Juri Poutanen. "Magnetospheric return-current-heated atmospheres of rotation-powered millisecond pulsars." Astronomy & Astrophysics 641 (September 2020): A15. http://dx.doi.org/10.1051/0004-6361/202037824.

Full text

Abstract:

We computed accurate atmosphere models of rotation-powered millisecond pulsars in which the polar caps of a neutron star (NS) are externally heated by magnetospheric return currents. The external ram pressure, energy losses, and stopping depth of the penetrating charged particles were computed self-consistently with the atmosphere model, instead of assuming a simplified deep-heated atmosphere in radiative equilibrium. We used exact Compton scattering formalism to model the properties of the emergent X-ray radiation. The deep-heating approximation was found to be valid only if most of the heat originates from ultra-relativistic bombarding particles with Lorentz factors of γ ≳ 100. In the opposite regime, the atmosphere attains a distinct two-layer structure with an overheated optically thin skin on top of an optically thick cool plasma. The overheated skin strongly modifies the emergent radiation: It produces a Compton-upscattered high-energy tail in the spectrum and alters the radiation beaming pattern from limb darkening to limb brightening for emitted hard X-rays. This kind of drastic change in the emission properties can have a significant impact on the inferred NS pulse profile parameters as performed, for example, by Neutron star Interior Composition ExploreR. Finally, the connection between the energy distribution of the return current particles and the atmosphere emission properties offers a new tool to probe the exact physics of pulsar magnetospheres.

APA, Harvard, Vancouver, ISO, and other styles

22

Сапрыкин, Э. Г. "Инверсия вклада изотопа малой относительной концентрации в суммарный коэффициент поглощения смеси изотопов неона на переходе 3s-=SUB=-2-=/SUB=--2p-=SUB=-4-=/SUB=-." Журнал технической физики 127, no. 8 (2019): 179. http://dx.doi.org/10.21883/os.2019.08.48027.122-18.

Full text

Abstract:

AbstractAbsorption of probe laser radiation by a mixture of even isotopes of neon in a gas discharge plasma is investigated by the method of magnetic scanning of 3 s _2–2 p _4 transition. The contours of absorption lines of isotopes are resolved by means of numerical modeling. It is discovered that, upon decrease in relative concentration of one of the isotopes, its contribution to absorption is replaced by gain. The effect is found to be caused by radiative transfer of excitation energy between atoms of different kinds in the absence of a difference in level energies (the process known as optical pumping). The effect of this mechanism turned out to be substantial for the upper level transitions from which to the ground state are allowed while being absent for the lower level of the transition from which such transitions are forbidden although other decay channels are available.

APA, Harvard, Vancouver, ISO, and other styles

23

GIEBELS, BERRIE. "VERY HIGH ENERGY GAMMA-RAY MEASUREMENTS OF BLAZARS." International Journal of Modern Physics D 17, no. 09 (September 2008): 1431–41. http://dx.doi.org/10.1142/s0218271808013005.

Full text

Abstract:

The origin of γ-rays emitted by blazars is widely attributed to radiative cooling of the most energetic particles in a relativistic flow, which itself is thought to originate from the surroundings of a supermassive black hole. The linkage between the accreting gas, the black hole, jet formation, and the observed radiation from the jet, are still very difficult to establish. The most energetic γ-rays are likely to be produced close to the comptonizing particles acceleration zone, and are therefore a unique probe of the underlying physical mechanisms at play. This report contains a review of the status of the field of Very High Energy (VHE) γ-ray astronomy, in the light of measurements from the current generation of Atmospheric Čerenkov Telescopes (ACTs), which have dramatically changed our view of blazars over the last years, and given us new insights about the blazar phenomenon.

APA, Harvard, Vancouver, ISO, and other styles

24

Yoshiura, Shintaro, Jack L. B. Line, Kenji Kubota, Kenji Hasegawa, and Keitaro Takahashi. "Foreground mitigation strategy for measuring the 21 cm-LAE cross-correlation." Proceedings of the International Astronomical Union 12, S333 (October 2017): 292–95. http://dx.doi.org/10.1017/s1743921317011152.

Full text

Abstract:

AbstractThe cross power spectrum of the 21 cm signal and Lyman-α emitters (LAEs) is a probe of the Epoch of Reionization. Astrophysical foregrounds do not correlate with the LAE distribution, though the foregrounds contribute to the error. To study the impact of foregrounds on the measurement, we assume realistic observation by the Murchison Widefield Array using a catalogue of radio galaxies, a LAE survey by the Subaru Hyper Supreme-Cam and the redshift of LAEs is determined by the Prime Focus Spectrograph. The HI distribution is estimated from a radiative transfer simulation with models based on results of radiation hydrodynamics simulation. Using these models, we found that the error of cross power spectrum is dominated by foreground terms. Furthermore, we estimate the effects of foreground removal, and find 99% of the foreground removal is required to detect the 21 cm-LAE signal at k ∼ 0.4 h Mpc−1.

APA, Harvard, Vancouver, ISO, and other styles

25

Saajasto, Mika, Mika Juvela, Charlène Lefèvre, Laurent Pagani, and Nathalie Ysard. "Multi-wavelength observations and modelling of a quiescent cloud LDN1512." Astronomy & Astrophysics 647 (March 2021): A109. http://dx.doi.org/10.1051/0004-6361/202038401.

Full text

Abstract:

Context. Light scattering at near-infrared (NIR) wavelengths has been used to study the optical properties of the interstellar dust grains, but these studies are limited by the assumptions on the strength of the radiation field. On the other hand, thermal dust emission can be used to constrain the properties of the radiation field, although this is hampered by uncertainty about the dust emissivity. Aims. Combining light scattering and emission studies allows us to probe the properties of the dust grains in detail. We wish to study if current dust models allow us to model a molecular cloud simultaneously in the NIR and far-infrared (FIR) wavelengths and compare the results with observations. Our aim is to place constraints on the properties of the dust grains and the strength of the radiation field. Methods. We present computations of dust emission and scattered light of a quiescent molecular cloud LDN1512. We use NIR observations covering the J, H, and KS bands, and FIR observations between 250 and 500 μm from the Herschel space telescope. We constructed radiative transfer models for LDN1512 that include an anisotropic radiation field and a three-dimensional cloud model. Results. We are able to reproduce the observed FIR observations, with a radiation field derived from the DIRBE observations, with all of the tested dust models. However, with the same density distribution and the assumed radiation field, the models fail to reproduce the observed NIR scattering in all cases except for models that take into account dust evolution via coagulation and mantle formation. The intensity from the diffuse interstellar medium like, dust models can be increased to match the observed one by reducing the derived density, increasing the intensity of the background sky and the strength of the radiation field between factors from two to three. We find that the column densities derived from our radiative transfer modelling can differ by a factor of up to two, compared to the column densities derived from the observations with modified blackbody fits. The discrepancy in the column densities is likely caused because of a temperature difference between a modified blackbody fit and the real spectra. The difference between the fitted temperature and the true temperature could be as high as ΔT = +1.5 K. Conclusions. We show that the observed dust emission can be reproduced with several different assumptions about the properties of the dust grains. However, in order to reproduce the observed scattered surface brightness, dust evolution must be taken into account.

APA, Harvard, Vancouver, ISO, and other styles

26

Kim, Rinah, Sang Bin Lee, Jae Wook Kim, and Joo Hyun Moon. "Development and Comparison of Fiber-Optic Beta Radiation Sensors with Different Diameters of Their Sensing Probes." Journal of Sensors 2017 (2017): 1–5. http://dx.doi.org/10.1155/2017/1452765.

Full text

Abstract:

A fiber-optic radiation sensor (FORS) was developed for remote and real-time measurements of beta radiation from radioactive-contaminated soil. The sensing probe consisted of a bundle of organic scintillators and a mixture of epoxy resin to improve the detection efficiency. The measurement system consisted of a sensing probe with an aluminium foil reflector, a transmitting plastic optical fiber, and a light-measuring system comprising a photomultiplier tube, a preamplifier, a multichannel analyzer, and a laptop computer. Several sensing probes, whose dead-end diameters were 26 mm (bundle type I), 36 mm (bundle type II), and 46 mm (bundle type III), were prepared and characterized to identify the best sensing probe in terms of its radiation detection efficiency. The reproducibility of the FORS for the measurement of beta radiation was confirmed using a χ2-test. The measurements showed that the FORS sensing probe with a diameter 46 mm has the best detection performance.

APA, Harvard, Vancouver, ISO, and other styles

27

Al-Helal, Ibrahim, Abdullah Alsadon, Mohamed Shady, Abdullah Ibrahim, and Ahmed Abdel-Ghany. "Diffusion Characteristics of Solar Beams Radiation Transmitting through Greenhouse Covers in Arid Climates." Energies 13, no. 2 (January 18, 2020): 472. http://dx.doi.org/10.3390/en13020472.

Full text

Abstract:

In hot and sunny regions, extensive solar radiation transmitted into greenhouses makes it essential to select a greenhouse cover with specific characteristics. Reflection and diffusion are the most important properties of covers for reducing solar heating load and scattering solar beams for better growth of plants. Three types of plastic films that are commonly used for covering greenhouses in arid climate were selected for this study. These were reflective-diffusive (RDF), diffusive (DF), and locally produced (CF) films. The films were used to cover three identical twin-span greenhouse models; the radiation components, air temperature (Ti), and relative humidity (RHi) were measured in each model. Transmission of solar radiation through each cover was characterized by determining: (i) The beam that is diffused during transmission, and (ii) the unscattered beam that is transmitted directly through the film. The results show that the diffuse radiation transmitted through the DF, RDF, and CF covers was enhanced, respectively by 77%, 85%, and 109% as a result of diffusing 34%, 33%, and 43% of the transmitted beam radiation by the DF, RDF, and CF covers, respectively during transmission. The diffusive nature of the tested covers increased the ratio of diffuse to direct beam radiation (D/B) from 0.3 outside the greenhouse to 0.77, 0.69, and 0.95 inside a greenhouse covered with DF, RDF, and CF, respectively. At around noon, the CF cover decreased Ti by about 5–10 °C and increased RHi by about 3%–5% compared to those under the DF and RDF covers. However, DF and RDF covers showed almost similar effects in Ti and RHi. The low-price CF cover showed higher diffusive-radiative properties than DF and RDF covers and can serve effectively in arid climate as an alternative covering material.

APA, Harvard, Vancouver, ISO, and other styles

28

Habibi, Zakaria. "Homogenization of a Conductive-Radiative Heat Transfer Problem." ESAIM: Proceedings 35 (March 2012): 228–33. http://dx.doi.org/10.1051/proc/201235019.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Joulain, K., J. P. Mulet, R. Carminati, and J. J. Greffet. "Nanoscale radiative heating of a sample with a probe." Journal of Magnetism and Magnetic Materials 249, no. 3 (September 2002): 462–65. http://dx.doi.org/10.1016/s0304-8853(02)00472-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Gladstone, D. J., X. Q. Lu, J. L. Humm, H. F. Bowman, and L. M. Chin. "A miniature MOSFET radiation dosimeter probe." Medical Physics 21, no. 11 (November 1994): 1721–28. http://dx.doi.org/10.1118/1.597214.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

den Outer, P. N., A. van Dijk, H. Slaper, A. V. Lindfors, H. De Backer, A. F. Bais, U. Feister, T. Koskela, and W. Josefsson. "Correcting spaceborne reflectivity measurements for application in solar ultraviolet radiation levels calculations at ground level." Atmospheric Measurement Techniques Discussions 5, no. 1 (January 4, 2012): 61–96. http://dx.doi.org/10.5194/amtd-5-61-2012.

Full text

Abstract:

Abstract. The Lambertian Equivalent Reflection (LER) produced by satellite-carried instruments is used to determine cloud effects on ground level UltraViolet (UV) radiation. The focus is on data use from consecutive operating instruments: the Total Ozone Mapping Spectrometers (TOMS) flown on Nimbus 7 from 1979 to 1992, TOMS on Earth Probe from 1996 to 2005, and the Ozone Monitoring Instrument (OMI) flown on Aura since 2004. The LER data produced by TOMS on Earth Probe is only included until 2002. The possibility to use the Radiative Cloud Fraction (RCF)-product of OMI is also investigated. A comparison is made with cloud effects inferred from ground-based pyranometer measurements at over 83 World Radiation Data Centre stations. Modelled UV irradiances utilizing LER data are compared with measurements of UV irradiances at eight European low elevation stations. The LER data set of the two TOMS instruments shows a consistent agreement, and the required corrections are of low percentage i.e. 2–3%. In contrast, the LER data of OMI requires correction of 7–10%, and a solar angle dependency therein is more pronounced. These corrections were inferred from a comparison with pyranometer data, and tested using the UV measurements. The RCF product of OMI requires a large correction but can then be implemented as a cloud effect proxy. However, a major drawback of RCF is the large number of clipped data, i.e. 18%, and results are not better than those obtained with the corrected LER product of OMI. The average reduction of UV radiation due to clouds for all sites together indicate a small trend: a diminishing cloudiness, in line with ground-based UV observations. Uncorrected implementation of LER would have indicated the opposite. An optimal field of view of 1.25° was established for LER data to calculate UV radiations levels. The corresponding area can be traversed within 5–7 h at the average wind speeds found for the West European continent.

APA, Harvard, Vancouver, ISO, and other styles

32

Tiwari, Rakesh N., Prabhakar Singh, and Binod Kumar Kanaujia. "Bandwidth enhancement using modified L-probe fed slotted patch antenna for WLAN and UMTS applications." International Journal of Microwave and Wireless Technologies 11, no. 3 (December 3, 2018): 302–12. http://dx.doi.org/10.1017/s175907871800154x.

Full text

Abstract:

AbstractIn this paper, two different radiating structures fed with modified L-probe, are reported using a circuit theory concept. The proposed antennas are operating in wireless local area network (WLAN) and universal mobile telecommunications system (UMTS) frequency bands. In the first design, an E-shaped patch is studied to increase the bandwidth. It is observed that the bandwidth is directly proportional to notch dimensions. In the second design, E-shaped patch is modified to reduce the antenna size up to 30% with high bandwidth. In the first design, measured bandwidth and gain achieved are 32.68% (1.92–2.67 GHz) and 8.43 dBi while in second design it is 34.19% (1.94–2.74 GHz) and 8.39 dBi, respectively. Radiation patterns for both the antennas are symmetrical and broadside in nature. The proposed antennas are fabricated and measured results compare well with the theoretical and simulated results.

APA, Harvard, Vancouver, ISO, and other styles

33

Liu, Hua, Xue Chen, Zhongcan Chen, Caobing Wei, Zuo Chen, Jiang Wang, Yanjun Duan, Nan Ren, Jian Li, and Xingzhou Zhang. "Optimal Experimental Design for Inverse Identification of Conductive and Radiative Properties of Participating Medium." Energies 14, no. 20 (October 13, 2021): 6593. http://dx.doi.org/10.3390/en14206593.

Full text

Abstract:

The conductive and radiative properties of participating medium can be estimated by solving an inverse problem that combines transient temperature measurements and a forward model to predict the coupled conductive and radiative heat transfer. The procedure, as well as the estimates of parameters, are not only affected by the measurement noise that intrinsically exists in the experiment, but are also influenced by the known model parameters that are used as necessary inputs to solve the forward problem. In the present study, a stochastic Cramér–Rao bound (sCRB)-based error analysis method was employed for estimation of the errors of the retrieved conductive and radiative properties in an inverse identification process. The method took into account both the uncertainties of the experimental noise and the uncertain model parameter errors. Moreover, we applied the method to design the optimal location of the temperature probe, and to predict the relative error contribution of different error sources for combined conductive and radiative inverse problems. The results show that the proposed methodology is able to determine, a priori, the errors of the retrieved parameters, and that the accuracy of the retrieved parameters can be improved by setting the temperature probe at an optimal sensor position.

APA, Harvard, Vancouver, ISO, and other styles

34

Liu, Hua, Xue Chen, Zhongcan Chen, Caobing Wei, Zuo Chen, Jiang Wang, Yanjun Duan, Nan Ren, Jian Li, and Xingzhou Zhang. "Optimal Experimental Design for Inverse Identification of Conductive and Radiative Properties of Participating Medium." Energies 14, no. 20 (October 13, 2021): 6593. http://dx.doi.org/10.3390/en14206593.

Full text

Abstract:

The conductive and radiative properties of participating medium can be estimated by solving an inverse problem that combines transient temperature measurements and a forward model to predict the coupled conductive and radiative heat transfer. The procedure, as well as the estimates of parameters, are not only affected by the measurement noise that intrinsically exists in the experiment, but are also influenced by the known model parameters that are used as necessary inputs to solve the forward problem. In the present study, a stochastic Cramér–Rao bound (sCRB)-based error analysis method was employed for estimation of the errors of the retrieved conductive and radiative properties in an inverse identification process. The method took into account both the uncertainties of the experimental noise and the uncertain model parameter errors. Moreover, we applied the method to design the optimal location of the temperature probe, and to predict the relative error contribution of different error sources for combined conductive and radiative inverse problems. The results show that the proposed methodology is able to determine, a priori, the errors of the retrieved parameters, and that the accuracy of the retrieved parameters can be improved by setting the temperature probe at an optimal sensor position.

APA, Harvard, Vancouver, ISO, and other styles

35

Паршков, О. М. "Короткие импульсы нормальных мод электромагнитно индуцированной прозрачности." Журнал технической физики 126, no. 4 (2019): 483. http://dx.doi.org/10.21883/os.2019.04.47520.304-18.

Full text

Abstract:

AbstractThe process of propagation of short probe pulses of electromagnetically induced transparency has been analyzed theoretically in the case of elliptically polarized control radiation. As a model of a resonant medium, a Λ scheme of quantum transitions between the $$^{3}{{P}_{0}}$$ , $$^{3}P_{1}^{0}$$ , and $$^{3}{{P}_{2}}$$ degenerate levels of the ^208Pb isotope has been used. The situation in which the probe radiation is rather weak compared to the control radiation has been examined. In this case, the field of the probe pulse can be represented as a sum of the fields of two elliptically polarized pulses that propagate in the medium independently of one another without changing their polarization state, which makes it possible to interpret them as nonstationary normal modes. Numerical simulation has shown that the structure of normal modes depends on the ratio of the width of the spectrum of the input probe pulse to the Doppler frequency broadening of the quantum transition that is resonant to the probe field. If this ratio is small, each mode in the medium is a single pulse similar to the input probe pulse. Under these conditions, the propagation of each normal mode in the medium can be fairly well characterized by the group velocity depending on the intensity and the state of polarization of the control radiation. As this ratio increases, normal modes in the medium initially acquire the shape of a regular decaying train of pulses, and then their structure becomes chaotic. The described evolution is accompanied by an increase in the energy absorption of the probe radiation by the medium and by a significant deterioration in the applicability of the notion of group velocity for describing the propagation process of normal modes.

APA, Harvard, Vancouver, ISO, and other styles

36

Arslan, A., A. K. Razzouk, and F. Al-Ain. "The performance and radiation exposure of some neutron probes in measuring the water content of the topsoil layer." Soil Research 35, no. 6 (1997): 1397. http://dx.doi.org/10.1071/s96111.

Full text

Abstract:

The use of neutron scattering technique for determining the soil surface water content is not popular due to the radiation escaping from the soil surface and the large errors in measurement. To compare the radiation exposure and the performance of different techniques statistically, 3 sites were selected. Five different neutron probe models and different adaptors were used with the depth probes. Exposure to neutrons and γ radiations, at various distances from the probes, were determined. In situ calibration curves were determined using different models of depth probes with a Solo surface reflector block, CPN surface adaptor, and different numbers of plastic Teflon parallelepiped, as well as surface Troxler 3401-B probes. Depth neutron probe readings increased with increasing number of Teflon plastic blocks deposited on the soil surface. The intercept of the straight line regression analysis of CR (count ratio, surface count over standard count) u. percentage water content on a volume basis decreased with increasing number of blocks deposited on the soil surface at all sites. The determination coefficient values of any depth probe with a Solo surface reflector or a block of 4·8 cm thickness were higher than those of a Troxler 3401-B surface probe or CPN 503 depth probe with its surface adaptor. The least exposure to radiation was with a depth probe with surface reflectors. This study proves the possibility of measuring the moisture content of the soil surface by using a depth neutron probe with a block laid on the surface, without danger of receiving the threshold dose of radiation.

APA, Harvard, Vancouver, ISO, and other styles

37

Xiao, Lian, Yue Wang, Yi Huang, Teckneng Wong, and Handong Sun. "Self-trapped exciton emission from carbon dots investigated by polarization anisotropy of photoluminescence and photoexcitation." Nanoscale 9, no. 34 (2017): 12637–46. http://dx.doi.org/10.1039/c7nr03913a.

Full text

Abstract:

We provide clear evidence that C-dot emission originates from radiative recombination of self-trapped excitons. We also probe the momentum evolution dynamics and evaluate the decay process of the photoexcited hot carriers.

APA, Harvard, Vancouver, ISO, and other styles

38

Liu, Neng-Wu, Lei Zhu, and Wai-Wa Choi. "A printed wide-beamwidth circularly polarized antenna via two pairs of radiating slots placed in a square contour." International Journal of Microwave and Wireless Technologies 9, no. 3 (August 1, 2016): 649–56. http://dx.doi.org/10.1017/s1759078716000246.

Full text

Abstract:

A low-profile circularly polarized (CP) slot antenna to achieve a wide axial-ratio (AR) beamwidth is proposed in this paper. The radiating patch consists of two orthogonal pairs of parallel slots etched symmetrically onto a ground plane. Firstly, our theoretical study demonstrates that the CP radiation can be satisfactorily achieved at the broadside, when the vertical and horizontal paired-slots are excited in the same amplitude with 90° phase difference. Secondly, the principle of CP radiation of the proposed antenna on an infinite ground plane is described. Through analyzing the spacing between two parallel slots, the |Eθ| and |Eφ| radiation patterns can be made approximately identical with each other over a large angle range. As such, the slot antenna achieves a wide AR beamwidth. After that, the 3 dB AR beamwidth with respect to the size of a finite ground plane is investigated to constitute a practical CP antenna on a finite ground plane. In final, the proposed CP antenna with a 1–4 probe-to-microstrip feeding network is designed and fabricated on a finite ground plane of a dielectric substrate. Measured results are shown to be in good agreement with the simulated ones about the gain, reflection coefficient, AR bandwidth, and radiation patterns. Most importantly, a wide 3 dB AR beamwidth of 126° and low-profile property with the height of 0.036λ0 are achieved.

APA, Harvard, Vancouver, ISO, and other styles

39

Petosa, A., A. Ittipiboon, and N. Gagnon. "Suppression of unwanted probe radiation in wideband probe-fed microstrip patches." Electronics Letters 35, no. 5 (1999): 355. http://dx.doi.org/10.1049/el:19990269.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Hoppert, Jeffrey B., Ioannis N. Miaoulis, and Peter Y. Wong. "Numerical Modeling of Radiative Properties of Patterned Wafers with Sub-Micron Features." MRS Proceedings 429 (1996). http://dx.doi.org/10.1557/proc-429-51.

Full text

Abstract:

AbstractDecreasing feature sizes in the microelectronics industry have led to numerous processing problems with thin film semiconductors. Non-uniform temperature distributions, due to microscale radiation effects on the radiative properties of the thin film structures, are responsible for wafer defects. These microscale radiation effects become significant as pattern spacing and film thicknesses reach the same order of magnitude as the wavelengths of the heat-source radiation. A numerical model has been developed in which normal emissivities for patterned wafers are calculated, using an effective index of refraction technique. In this study various patterns at temperatures critical to the thermal processing are examined.

APA, Harvard, Vancouver, ISO, and other styles

41

Cui, Longji, Wonho Jeong, Víctor Fernández-Hurtado, Johannes Feist, Francisco J. García-Vidal, Juan Carlos Cuevas, Edgar Meyhofer, and Pramod Reddy. "Study of radiative heat transfer in Ångström- and nanometre-sized gaps." Nature Communications 8, no. 1 (February 15, 2017). http://dx.doi.org/10.1038/ncomms14479.

Full text

Abstract:

Abstract Radiative heat transfer in Ångström- and nanometre-sized gaps is of great interest because of both its technological importance and open questions regarding the physics of energy transfer in this regime. Here we report studies of radiative heat transfer in few Å to 5 nm gap sizes, performed under ultrahigh vacuum conditions between a Au-coated probe featuring embedded nanoscale thermocouples and a heated planar Au substrate that were both subjected to various surface-cleaning procedures. By drawing on the apparent tunnelling barrier height as a signature of cleanliness, we found that upon systematically cleaning via a plasma or locally pushing the tip into the substrate by a few nanometres, the observed radiative conductances decreased from unexpectedly large values to extremely small ones—below the detection limit of our probe—as expected from our computational results. Our results show that it is possible to avoid the confounding effects of surface contamination and systematically study thermal radiation in Ångström- and nanometre-sized gaps.

APA, Harvard, Vancouver, ISO, and other styles

42

Wong, Peter Y., and Ioannis N. Miaoulis. "Thermal-Radiation Absorption Characteristics of Patterned Wafers During Rapid Thermal Processing." MRS Proceedings 342 (1994). http://dx.doi.org/10.1557/proc-342-395.

Full text

Abstract:

ABSTRACTMicroscale radiation effects are responsible for the dependence of absorption and temperature distributions on the geometry of the layering structures and the spectral characteristics of the heat source. The effect of patterned wafers, which may contain several different structures and materials, on the wafer absorption characteristics are investigated for rapid thermal processing. A numerical model to determine the thermal radiative absorptivity of the wafer for different structures and materials is presented for different heating conditions. The resulting transient effects are determined numerically for different rapid thermal processes. The changes in radiative properties for rapid thermal annealing and chemical vapor deposition are investigated for patterned wafers.

APA, Harvard, Vancouver, ISO, and other styles

43

DeWitt, D. P., F. Y. Sorrell, and J. K. Elliott. "Temperature Measurement Issues in Rapid Thermal Processing." MRS Proceedings 470 (1997). http://dx.doi.org/10.1557/proc-470-3.

Full text

Abstract:

ABSTRACTReliable radiometrie temperature measurement has been a major challenge in making rapid thermal processing (RTP) more widely accepted. In order to meet road map requirements involving temperature uncertainty, uniformity and control, new techniques must be demonstrated and/or existing measurement methods must be substantially improved. Critical aspects of radiometrie methods for temperature measurement are centered about the topics: radiative and optical properties of the wafers including layered systems, surface roughness effects, and reflected irradiation from lamp banks and chamber walls. The systematic method for inferring temperature is rooted in the measurement equation which relates the radiometer output to the exitent spectral radiance from the target which reaches the detector and prescribes the roles that emissivity variability and stray radiation have on the result. An overview is provided on the knowledge base for optical and thermal radiative properties. Methods for reducing emissivity and stray radiation effects are summarized. Calibration procedures necessary to assure that the in-chamber or local temperature scale is traceable to the International Temperature Scale (ITS-90) are discussed. The issues which can impact improved temperature measurement practice are summarized.

APA, Harvard, Vancouver, ISO, and other styles

44

Yunovich, A. E., V. E. Kudryashov, A. N. Turkin, M. Leroux, and S. Dalmasso. "Tunnel radiation in the luminescence spectra of GaN-based heterostructures." MRS Proceedings 743 (2002). http://dx.doi.org/10.1557/proc-743-l11.4.

Full text

Abstract:

ABSTRACTTunnel effects in luminescence spectra and electrical properties of LEDs based on InGaN/GaN-heterostructures made by different technological groups were studied. The tunnel radiation in a spectral region of 1.9 - 2.7 eV predominates at low currents (J<0.2 mA). The position of the tunnel luminescence maximum orħħωmax is approximately equal to the voltage U, orħħωmax = eU. The low energy spectral band is described by the theory of tunnel radiative recombination. Tunnel recombination mechanisms in GaN-based heterostructures are caused by high electric fields in the active InGaN/GaN - MQW layers. The energy diagram of the structures is analyzed. The probability of tunnel radiation is higher due to piezoelectric fields in InGaN quantum wells. The tunnel radiation spectral band was not observed in the more effective LEDs with modulated doped MQWs. The spectra of GaN-based LEDs are compared with tunnel radiation spectra of GaAs-, InP- and GaSb- based LEDs. The equation: orħħωmax = eU describes experimental data in various semiconductors in the range 0.5–2.7 eV.

APA, Harvard, Vancouver, ISO, and other styles

45

Duley, W. W., and G. Kinsman. "Excimer Laser Interaction with Metals." MRS Proceedings 285 (January 1, 1992). http://dx.doi.org/10.1557/proc-285-145.

Full text

Abstract:

ABSTRACTExcimer laser radiation may be used to process metal surfaces in a variety of novel ways. The simplest of these involves the use of UV laser pulses for ablation. Ablation occurs as the result of both vaporization and hydrodynamical effects. Experimental data related to these processes will be discussed. In addition, it will be shown how specific irradiation regimes can yield metal surfaces with unique radiative properties.

APA, Harvard, Vancouver, ISO, and other styles

46

Kim, Yong Sung, and Shawn-Yu Lin. "Wavelength Selective Emitting Materials Using High-Temperature Photonic Structures." MRS Proceedings 1162 (2009). http://dx.doi.org/10.1557/proc-1162-j02-03.

Full text

Abstract:

AbstractRecently, wavelength selective emitting materials have attracted extensive interest due to their potential of high optical-to-electricity conversion efficiency for thermal photovoltaic (TPV) cells and realizing high efficient incandescent light sources. A substantial increase in spectral control over thermal radiation and photon recycling can accomplish this objective by the development of high-temperature photonic structures (HTPS) that simultaneously suppress unwanted radiation and enhance emission in a desirable wavelength range. In this paper, we shall review the properties of HTPS as a wavelength selective emitter, the radiative energy transfer relation in real devices, and photon recycling scheme using wavelength selective filters.

APA, Harvard, Vancouver, ISO, and other styles

47

Im, J. S., C. K. Chen, C. V. Thompson, M. W. Geis, and H. Tomita. "Liquid-Solid Interface Morphologies and Defect Structures in Zone-Melting-Recrystallized Silicon-On-Insulator Films." MRS Proceedings 107 (1987). http://dx.doi.org/10.1557/proc-107-169.

Full text

Abstract:

AbstractIn-situ optical microscopy has been used to observe liquid-solid interface morphologies during zone-melting recrystallization of silicon-on-insulator films. These morphologies have been correlated with the defect morphologies of the recrystallized films. Stable cellular solidification fronts, which are obtained at low zone velocities if the radiation intensity gradient in the interfacial region is small, yield subboundary free films. We suggest that under these experimental conditions the interface morphology is primarily the result of radiative heating rather than constitutional supercooling.

APA, Harvard, Vancouver, ISO, and other styles

48

Crawford, M. H., J. Han, M. A. Banas, S. M. Myers, G. A. Petersen, and J. J. Figiel. "Optical Spectroscopy of Ingan Epilayers in the Low Indium Composition Regime." MRS Proceedings 595 (1999). http://dx.doi.org/10.1557/proc-595-f99w11.41.

Full text

Abstract:

AbstractPhotoluminescence (PL) spectroscopy was carried out on a series of Si-doped bulk InGaN films in the low indium (In) composition regime. Room temperature PL showed a factor of 25 increase in integrated intensity as the In composition was increased from 0 to 0.07. Temperature dependent PL data was fit to an Arrhenius equation to reveal an increasing activation energy for thermal quenching of the PL intensity as the In composition is increased. Time resolved PL measurements revealed that only the sample with highest In ( x=0.07) showed a strong spectral variation in decay time across the T=4K PL resonance, indicative of recombination from localized states at low temperatures. The decay times at room temperature were non-radiatively dominated for all films, and the room temperature (non-radiative) decay times increased with increasing In, from 50-230 psec for x=0-0.07. Our data demonstrate that non-radiative recombination is less effective with increasing In composition.

APA, Harvard, Vancouver, ISO, and other styles

49

Timans, P. J. "The Role of Thermal Radiative Properties of Semiconductor Wafers in Rapid Thermal Processing." MRS Proceedings 429 (1996). http://dx.doi.org/10.1557/proc-429-3.

Full text

Abstract:

AbstractRapid thermal processing (RTP) has become a key technology in the fabrication of advanced semiconductor devices. As RTP becomes the accepted technique for an increasingly wide range of processes in device fabrication, the understanding of the basic physics of radiation heat transfer in RTP systems is also being extended rapidly. This paper illustrates the use of optical models for prediction of the thermal radiative properties of semiconductor wafers. Such calculations can be used to address many of the key issues of interest in RTP, including questions concerning temperature measurement and process repeatability.

APA, Harvard, Vancouver, ISO, and other styles

50

Tada, Haruna, Seth E. Mann, Ioannis N. Miaoulis, and Peter Y. Wong. "Microscale Radiative Effects in Complex Microstructures of Iridescent Butterfly Wing Scales." MRS Proceedings 489 (1997). http://dx.doi.org/10.1557/proc-489-173.

Full text

Abstract:

AbstractThe cellular microstructure of insect scales can be detailed intricately with threedimensional structures and multiple thin-film layers. In butterflies, iridescent scales can reflect bright colors through thin-film interference and other optical phenomena; the balance of radiation is absorbed for thermoregulatory purposes. Results of numerical and experimental investigations into the function, properties, and structure of these scales are presented. Of particular interest are the numerical modeling of the microscale radiative effects in the scales, determining the optical properties of the biological material, and the cellular development of thin-film structures.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Radiative proce'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles