We present results of a spectral survey towards a dense molecular condensation and young stellar objects (YSOs) projected on the border of the HII region RCW 120 and discuss emission of 20 molecules ...which produce the brightest lines. The survey was performed with the APEX telescope in the frequency range 200 -- 260 GHz. We provide evidences for two outflows in the dense gas. The first one is powered by the RCW 120 S2 YSO and oriented along the line of sight. The second outflow around RCW 120 S1 is aligned almost perpendicular to the line of sight. We show that area with bright emission of CH\(_3\)OH, CH\(_3\)CCH and CH\(_3\)CN are organised into an onion-like structure where CH\(_3\)CN traces warmer regions around the YSOs than the other molecules. Methanol seems to be released to the gas phase by shock waves in the vicinity of the outflows while thermal evaporation still does not work towards the YSOs. We find only a single manifestation of the UV radiation to the molecules, namely, enhanced abundances of small hydrocarbons CCH and c-C\(_3\)H\(_2\) in the photo-dissociation region.
The results of SEST millimeter observations of the molecular cloud G345.01+1.79 are presented. Spectra of CH3OH, SO2, SiO, HCO, CO, CS, CS, HCN, and DCN lines have been obtained. Mapping of the cloud ...in CH3OH, SiO, and CS lines indicates that the maximum integrated intensity in the SiO and CS lines and in low-excitation CH3OH transitions coincide with the northern group of methanol masers, while the corresponding maximum for high-excitation CH3OH transitions coincides with the southern methanol-maser group. The physical parameters are estimated from the quasi-thermal CH3OH lines under the large-velocity-gradient approximation, and their distribution on the sky derived. The density and temperature are higher toward the southern group of methanol masers than in the northern group. This may indicate that star formation is in an earlier stage of evolution in the northern than toward the southern group. A maser component can be distinguished in 14 (of 71) CH3OH lines. We have detected for the first time weak, probably maser, emission in the CH3OH lines at 148.11, 231.28, 165.05, 165.06, and 165.07 GHz. A blue wing is clearly visible in the CH3OH, SiO, CO, and SO2 lines. The emission in this wing is probably associated with a compact source whose velocity is characteristic of the CH3OH maser emission in the southern group of masers.
Observations of the molecular cloud G1.6-0.025 in the 2^sub K^-1^sub K^ and J^sub 0^-J^sub -1^ E series and 5^sub -1^-4^sub 0^ E line of CH^sub 3^OH, the (2-1) and (3-2) lines of SiO, and the 7^sub ...-7^-6^sub -6^ line of HNCO are described. Maps of the previously observed extended cloud with V^sub lsr^50 km/s and high-velocity clump with V^sub lsr^160 km/s, as well as a newly detected clump with V^sub lsr^0 km/s, have been obtained. The extended cloud and high-velocity clump have a nonuniform structure. The linewidths associated with all the objects are between 20 and 35 km/s, as is typical of clouds of the Galactic center. In some directions, emission at velocities from 40 to 160 km/s and from -10 to +75 km/s is observed at the clump boundaries, testifying to a connection between the extended cloud and the high-velocity clump and clump at V^sub lsr^0 km/s. Compact maser sources are probaby contributing appreciably to the emission of the extended cloud in the 5^sub -1^-4^sub 0^ E CH^sub 3^OH line. Non-LTE modeling of the methanol emission shows that the extended cloud and high-velocity clump have a relatively low hydrogen density (<10^sup 4^ cm^sup -3^). The specific column density of methanol in the extended cloud exceeds 6×10^sup 8^ cm^sup -3^s, and is 4×10^sup 8^-6×10^sup 9^ cm^sup -3^s in the high-velocity clump. The kinetic temperatures of the extended cloud and high-velocity clump are estimated to be <80 K and 150-200 K, respectively. Possible mechanisms that can explain the link between the extended cloud with V^sub lsr^50 km/s and the clumps with V^sub lsr^0 km/s and 160 km/s are briefly discussed.PUBLICATION ABSTRACT
The precedence constrained traveling salesman (TSP-PC), also known as sequential ordering problem (SOP), consists of finding an optimal tour that satisfies the namesake constraints. Mixed ...integer-linear programming works well with the 'lightly constrained' TSP-PCs, close to asymmetric TSP, as well as the with the 'heavily constrained' (Gouveia, Ruthmair, 2015). Dynamic programming (DP) works well with the heavily constrained (Salii, 2019). However, judging by the open TSPLIB SOP instances, the worst for any method are the 'medium'.
We implement a parallel Morin-Marsten branch-and-bound scheme for DP (DPBB). We show how the lower bound heuristic parameterizes DPBB's worst-case complexity and DPBB 'inherits' the abstract travel cost aggregation feature of the DP, permitting its direct use with both the conventional and bottleneck TSP-PC.
The scheme was tested on TSPLIB instances, with best known upper bounds (TSP-PC), or those found by restricted DP (Bottleneck TSP-PC), and lower bounds from a greedy-type heuristic. Our OPENMP-based parallel implementation achieved 20-fold speedup for larger instances. We close the long-standing
kro124p.4.sop
(conventional TSP-PC) and both
kro124p.4.sop
and
ry48p.2.sop
(Bottleneck TSP-PC).
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
We study molecular emission in a massive condensation at the border of the HII region RCW 120, paying particular attention to the Core 1 and Core 2 objects, the most massive fragments of the ...condensation found previously by ALMA. The latter fragment was previously suggested to host a high-mass analogue of Class 0 young stellar object. We present spectra of molecular emission in the 1 mm range made with the APEX telescope. We detect CH\(_3\)OH and C\(^{34}\)S lines in Core 1 and Core 2. The CH\(_3\)CN series and the SO\(_2\) lines are only found in Core 2. We estimate gas physical parameters using methanol lines and obtain gas temperature less than 100 K in both regions. Molecular hydrogen number density in Core 2 is in the range of \(10^5-10^7\) cm\(^{-3}\) and is more uncertain in Core 1. However, the detection of the CH\(_3\)CN lines corresponding to highly excited transitions (\(E_{\rm u}> 400\)~K) in Core~2 indicates that the region contains hot gas, while the abundances of CH\(_3\)OH, CS, SO\(_2\) and CH\(_3\)CN are quite low for a hot core stage. We propose that Core 2 is in the warm-up phase prior to the establishing of the hot gas chemistry. We suggest that Core 2 is in the beginning of the hot core stage. There are no detected CH\(_3\)CN lines in Core 1, therefore, it might be on an even less evolved evolutionary stage.
Photovoltaic converters of high-power (λ = 800–860 nm, ELR = 150–550 W/cm2) laser radiation (PhotoVoltaic Laser Power Converters – PVLPCs) based on AlGaAs/GaAs heterostructures grown by metalorganic ...vapor-phase epitaxy have been developed. To increase the output voltage, the space charge region of p-GaAs/n-AlхGa1-хAs heterojunction was shifted to the n-AlхGa1-хAs wide-gap layer with a gradual “x”. The technology for embedding a rear reflector based on TiOx/SiO2/Ag into the photovoltaic converter structure by “transferring” the heterostructure to a supporting substrate and the method of bonding to form a monolithic structure of the PVLPC has been elaborated. To operate the heterostructures at an increased power density of laser radiation, they have been designed to eliminate possible potential barriers at the heterointerfaces and the frontal contact topology with a high density of the metal grid (50 μm and 125 μm contact pitch are under consideration) has been employed. PVLPCs with efficiency of 62% were obtained at the power density of monochromatic radiation (λ = 850 nm) ELR = 170 W/cm2. The finger pitch of 50 μm allows keeping efficiency more than 56% even with a fivefold increase in laser radiation (up to ELR = 500 W/cm2).
•AlGaAs/GaAs photovoltaic converters of high-power laser radiation were grown by MOVPE.•p-GaAs/n-AlGaAs heterojunction is used for decreasing injection current.•Carrier lifetime is increased with rear reflector for "inverted" heterostructure.•Optimal front contact pitch for both high laser power and for high SR is developed.•PVLPC efficiency doesn't fall below 56% for laser power up to 0.5 kW/cm2 (62% max.eff).
Laser power converters (LPCs) based on InxGa1-xAs/GaAs metamorphic heterostructure grown by MOVPE have been investigated. Both direct study of transmission electron microscopy images and analysis of ...the dark I–V curves at a low photogenerated current have shown the absence of the effect of threading dislocations from the metamorphic buffer on the LPC parameters. It has been shown, according to the “voltage” and “current” invariants that voltage loss in all investigated LPCs evidences the good quality of p-n junctions for the operating mode of high power laser radiation conversion. It has been also demonstrated that the method of saturation current approximation with current invariant allows obtaining the limit voltage losses irrespective of photogenerated current. Band-gap and thickness of the InGaAs LPCs have been adjusted using spectral characteristics. Fundamental losses (thermal and resistive) and ways to minimize them have been discussed. As a result, LPCs based on In0.23Ga0.77As have demonstrated the laser conversion efficiency (λ = 1064 nm) of more than 50% with maintaining the efficiency of more than 48% up to 13 W/cm2.
•InxGa1-xAs/GaAs metamorphic laser power convertors (LPCs) were created by MOVPE.•Threading dislocations from step graded buffer do not affect the I–V characteristics.•LPC voltage loss has been estimated by voltage and current invariants.•Structure design optimized for quantum efficiency increase at wavelength of 1064 nm.•LPCs have demonstrated laser conversion efficiency (1064 nm) of more than 50%.
ABSTRACT
We present results of the investigations of the properties of the methanol J1 –J0 A−+ line series motivated by the recent serendipitous detection of the maser emission in the 141 – 140 A−+ ...line at 349 GHz in S255IR-SMA1 soon after the accretion burst. The study includes further observations of several lines of this series in S255IR with the SMA, a mini-survey of methanol lines in the 0.8-mm range towards a sample of bright 6.7-GHz methanol maser sources with the IRAM 30-m telescope, and theoretical modelling. We found that the maser component of the 141 – 140 A−+ line in S255IR decayed by more than order of magnitude in comparison with that in 2016. No clear sign of maser emission is observed in other lines of this series in the SMA observations except the 71 – 70 A−+ line where an additional bright component is detected at the velocity of the maser emission observed earlier in the 141 – 140 A−+ line. Our LVG model constrains the ranges of the physical parameters that match the observed emission intensities. No obvious maser emission in the J1 – J0 A−+ lines was detected in the mini-survey of the 6.7-GHz methanol maser sources, though one component in NGC 7538 may represent a weak maser. In general, the maser effect in the J1 – J0 A−+ lines may serve as a tracer of rather hot environments and in particular luminosity flaring events during high-mass star formation.
The effect of positioning of the In
0.8
Ga
0.2
As quantum dots (QDs) array in the
i
-region of the solar cell (SC) on its photogenerated current and dark saturation currents, which determine the ...device operating voltage, have been investigated. It was found out that the indicated photoelectric characteristics depend on the location of the QD array relative to the electric field of the
p–n
junction. The displacement of the QD array to the boundary of the weakly doped base leads to a decrease in the photogenerated current. But at the same time, the voltage drop effect, which is well-known for nanoheterostructural SC, is minimal.
The H II region RCW120 is a well-known object, which is often considered as a target to verify theoretical models of gas and dust dynamics in the interstellar medium. However, the exact geometry of ...RCW120 is still a matter of debate. In this work, we analyse observational data on molecular emission in RCW120 and show that 13CO(2-1) and C18O(2-1) lines are fitted by a 2D model representing a ring-like face-on structure. The changing of the C18O(3-2) line profile from double-peaked to single-peaked from the dense molecular Condensation 1 might be a signature of stalled expansion in this direction. In order to explain a self-absorption dip of the 13CO(2-1) and 13CO(3-2) lines, we suggest that RCW120 is surrounded by a diffuse molecular cloud, and find confirmation of this cloud on a map of interstellar extinction. Optically thick 13CO(2-1) emission and the infrared 8 um PAH band form a neutral envelope of the H II region resembling a ring, while the envelope breaks into separate clumps on images made with optically thin C18O(2-1) line and far-infrared dust emission.
