Hydrogen has been inferred to occur in enhanced concentrations within permanently shadowed regions and, hence, the coldest areas of the lunar poles. The Lunar Crater Observation and Sensing Satellite ...(LCROSS) mission was designed to detect hydrogen-bearing volatiles directly. Neutron flux measurements of the Moon's south polar region from the Lunar Exploration Neutron Detector (LEND) on the Lunar Reconnaissance Orbiter (LRO) spacecraft were used to select the optimal impact site for LCROSS. LEND data show several regions where the epithermal neutron flux from the surface is suppressed, which is indicative of enhanced hydrogen content. These regions are not spatially coincident with permanently shadowed regions of the Moon. The LCROSS impact site inside the Cabeus crater demonstrates the highest hydrogen concentration in the lunar south polar region, corresponding to an estimated content of 0.5 to 4.0% water ice by weight, depending on the thickness of any overlying dry regolith layer. The distribution of hydrogen across the region is consistent with buried water ice from cometary impacts, hydrogen implantation from the solar wind, and/or other as yet unknown sources.
The description of Dynamic Albedo of Neutrons (DAN) experiment is presented, as a part of the NASA’s Mars Science Laboratory mission onboard the mars rover Curiosity. The instrument DAN includes ...Pulsing Neutron Generator (PNG) producing pulses of 14.1 MeV neutrons for irradiation of subsurface material below the rover, and Detectors and Electronics (DE) unit, which operates the instrument itself and measures the die-away time profiles of epithermal and thermal neutrons following each neutron pulse. It is shown that the DAN investigation will measure a content of hydrogen along the path of the MSL rover, and it will also provide information about a depth distribution of hydrogen at 10–20 regions selected for the detailed studies and sampling analysis.
Surface Emitting Quantum-Cascade Ring Laser Babichev, A. V.; Kolodeznyi, E. S.; Gladyshev, A. G. ...
Semiconductors (Woodbury, N.Y.),
07/2021, Letnik:
55, Številka:
7
Journal Article
Recenzirano
Quantum-cascade lasers with surface emission of radiation by means of a grating formed in the upper waveguide cladding layers by ion-beam milling are fabricated and studied. The active region of the ...laser heterostructure is based on the In
0.53
Ga
0.47
As/Al
0.48
In
0.52
As alloy alloys and uses a design with two-phonon resonance emptying of the lower level in the cascade. Room-temperature lasing near 7.9 μm is demonstrated for a laser with a ring-cavity diameter of 191 μm. The mode spacing in the lasing spectra corresponds to whispering-gallery modes.
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Microcapsules consisting of only a gelatin shell, a gelatin shell with magnetite, and a gelatin shell filled with ozonated water (ozonated water in the microcapsule core was adsorbed by activated ...carbon), a gelatin shell treated with ozone, a gelatin shell with ozone-treated magnetite, and a gelatin shell containing magnetite and ozonated water were obtained by simple coacervation method. The effectiveness of using aqueous emulsions of the shells as production lubricants and coolants during cutting in turning operations on a 16K20 screw-cutting lathe using side cutters made of high-speed R6M5 steel was investigated. The set of processed materials included 12Kh18N10Т stainless steel, 40Kh chromium steel, and VT5-1 and VT-6 titanium alloys. The introduction of ozone into the composition of microcapsules is shown to increase the period of normal wear of the cutting tool. In addition, the duration of the initial wear-out period increases. It was revealed that the wear resistance of cutting tools increased most strongly if microcapsules with gelatin shells filled with magnetite and ozonated water are used. The increase in the wear resistance of a cutting tool can be explained by the formation of lubricant films at the interface between the tool and the material being processed; the films may include metal polymers and complex compounds of atomic iron, covering surface irregularities that are sterically inaccessible to metal polymers. Based on this hypothesis, an approach has been proposed, which enables predicting the potential effectiveness of production lubricants and coolants using quantum chemistry methods.
The results of studying a ring surface-emitting quantum-cascade laser with radiation emission through a textured layer formed in the layers of the upper cladding of the waveguide by ultrahigh-vacuum ...ion-beam milling are presented. The far-field profile shows that the radiation is emitted through windows with a textured layer in the range of angles ~63°–75° to the surface normal.
The isomeric ratios in neutron capture reactions, induced by thermal, resonant and mixed thermal-resonant neutrons on
108
Pd and
110
Pd nuclei have been measured by the activation method. The data ...analysis and necessary corrections as the self-absorption and summing cascade effects were made in gamma rays radioactivity measurements to improve the precision of the isomeric ratio determination. The results were discussed and compared with those in the existing literature. The isomeric ratios in
108
Pd(n, γ)
109m,g
Pd and
110
Pd(n, γ)
111m,g
Pd reactions, induced by mixed thermal-resonant neutrons as well as in
110
Pd(n, γ)
111m,g
Pd reaction, induced by resonant neutron are first measurements.
This article reviews aspects of the simulation modeling of a cascade of hydropower plants (HPPs) in the AnyLogic software package. The authors analyzed simulation approaches for the analysis of HPP ...hydrological and electrical operating modes and presented basic rules for creating a model in the software package. The work presents a detailed description of the modeling process for the selected object under study, describes the influence of meteorological factors on the operation mode of the cascade, considers daily and seasonal changes in the load schedule in the power system, and implements a prognosis of the required parameters (water consumption, consumer power, and load schedule configuration). The paper presents mathematical equations that describe the relationship between cascade parameters and technological and mode restrictions imposed on the operation of the plants. The developed simulation model can be used for the analysis of current processes in the power system, short-term and long-term predictions, and solving the mode optimization issues of the regime.
The results of studies of 7.5–8.0 μm range surface-emitting ring quantum-cascade lasers are presented. A second- order diffraction grating with a calculated coupling coefficient of ~9 cm
–1
is formed ...on the entire surface of the ring cavity by focused ion beam milling. Surface-emitting lasing at room temperature near 7.75 μm with a threshold current density of ~8 kA/cm
2
and an outer radius of the ring cavity of 202 μm is demonstrated. The results of studying the intensity distribution in the far-field near the normal to the surface showed the presence of two maxima. It is shown that the implemented coupling coefficient is not sufficient to ensure single-mode lasing in the studied ring quantum-cascade lasers.
The results of studies of ring quantum-cascade lasers with surface emission due to a second-order grating formed in the top cladding layers are presented. Surface emission near 7.85 μm with a low ...threshold current density (3.8 kA/cm
2
), in comparison with ridge quantum-cascade lasers of the same cavity length is demonstrated. The results of measurements of the intensity distribution of the near and far fields at different pumping levels are presented. The estimated value of the angle of beam extraction relative to the surface normal is in the range 5.7°–6.7°.
Single-mode lasing of quantum-cascade lasers with a distributed Bragg reflector formed by ion-beam etching in layers of the upper waveguide cladding is demonstrated. The active region is formed based ...on an In
0.53
Ga
0.47
As/Al
0.48
In
0.52
As solid-alloy heteropair with two-phonon depletion of the lower level in the cascade. Single-mode lasing at a temperature of 280 K corresponds to the emission wavelength of 7.74 μm, and the side-mode suppression ratio is 24 dB.
