The problem of route optimization with realistic constraints is becoming extremely relevant in the face of global urban population growth. While we are aware of approaches that theoretically provide ...an exact optimal solution, their application becomes challenging as the problem size increases because of exponential complexity. We investigate the Capacitated Vehicle Routing Problem with Time Windows (CVRPTW) and compare solutions obtaining by exact solver SCIP 1 with heuristic algorithms such as LKH, 2-OPT, 3-OPT 2, the OR-Tools framework 3, and the deep learning model JAMPR 4. We demonstrate that for problem of size 50 deep learning and classical heuristic solutions became close to SCIP exact solution but requires less time. Additionally for problems with size 100, SCIP exact methods ~13 times slower that neural and classical heuristics with the same route cost and on ~50% worse for the first feasible solution on the same time. To conduct experiments, we developed the Smart Routes platform for solving route optimization problems, which includes exact, heuristic, and deep learning models, and facilitates convenient integration of custom algorithms and datasets.
It is established experimentally that noticeable changes in the
I
–
V
characteristics and low-frequency noise in 4
H
-SiC
pin
diodes irradiated by electrons with an energy of 0.9 MeV are observed ...after doses of Φ ≥ 1.4 × 10
15
cm
–2
. The currents in the forward and reverse branches of the
I
–
V
characteristics vary nonmonotonically at voltages lower than 2 V with increasing dose, which is explained by the interaction between the excited electronic subsystem and metastable defects. In this case, a steady increase in the ideality factor and the series resistance of diodes in the region of exponential growth of the
I
–
V
characteristics at voltages exceeding 2 V is observed. The reliable operation of microwave devices with low-noise 4
H
-SiC
pin
diodes under conditions of electron irradiation is possible up to a cumulative dose of Φ ≤ 10
15
cm
–2
. In microwave devices, the level of low-frequency noise in which is irrelevant but the stabile regime of parameters is of importance, the dose can be increased to Φ ≈ 8 × 10
15
cm
–2
.
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► The texture of Ni catalysts supported on porous Ni with MgO underlayer was studied. ► In reduced Ni catalysts phases of Ni and solid solution of NiO in MgO were observed. ► A ...considerable part of nickel crystallites is epitaxially bound with MgO. ► The activity of Ni catalysts decreased slightly after 100 h of testing in POM. ► No carbon deposition was detected by TEM in tested samples.
The phase composition and texture of nickel catalysts supported on ribbon porous nickel with a magnesium oxide underlayer were investigated by X-ray diffraction, low-temperature nitrogen adsorption, and electron microscopy combined with energy dispersive X-ray microanalysis. The MgO underlayer was obtained by impregnation the porous nickel with a Mg(NO
3)
2 solution followed by calcination at 550
°C; nickel was supported additionally by impregnation with a Ni(NO
3)
2 solution followed by calcination at 450
°C. In the supported reduced nickel catalysts (800–900
°C, H
2) the phases of Ni and a solid solution of NiO in MgO were observed; a considerable part of nickel crystallites was epitaxially bound with MgO. The partial oxidation of methane to synthesis gas (800
°С, O
2/C
=
0.65, GHSV
=
127 L/g
h) over porous nickel based catalysts was studied. The activity of initial nickel support decreased considerably during the partial oxidation of methane; the value of methane conversion decreased slightly after 100
h of testing on the supported nickel catalysts.
The paper discusses the features of machining of a compressor blade airfoil. The problem of airfoil deformations under the action of residual stresses that negatively affect the accuracy of the ...relative position of the airfoil relative to the blade root is discussed. Methods of compensating for the effect of permanent deformations on the accuracy in blade machining and the impossibility of using this approach when the compressor blade is included in the duplex mode technology of electrochemical machining are specified. The analysis of the pattern of electrochemical machining of the blade airfoil with adjustment of the auxiliary technological base developed by the authors and the use of segmented electrodes showed the effectiveness of its use in order to compensate for airfoil deformations. We suggest measuring the interelectrode gaps in the machining chamber after refixturing the base in order to reduce the total machining time. We also suggest using the modernized electrochemical machining scheme when designing a CNC machine for the machining of a blade airfoil.
Based on data from the SWIFT, INTEGRAL, MAXI/ISS orbital observatories, and the ground-based RTT-150 telescope, we have investigated the broadband (from the optical to the hard X-ray bands) spectrum ...of the X-ray nova MAXI J1828-249 and its evolution during the outburst of the source in 2013–2014. The optical and infrared emissions from the nova are shown to be largely determined by the extension of the power-law component responsible for the hard X-ray emission. The contribution from the outer cold regions of the accretion disk, even if the X-ray heating of its surface is taken into account, turns out to be moderate during the source’s “high” state (when a soft blackbody emission component is observed in the X-ray spectrum) and is virtually absent during its “low” (“hard”) state. This result suggests that much of the optical and infrared emissions from such systems originates in the same region of main energy release where their hard X-ray emission is formed. This can be the Compton or synchro-Compton radiation from a high-temperature plasma in the central accretion disk region puffed up by instabilities, the synchrotron radiation from a hot corona above the disk, or the synchrotron radiation from its relativistic jets.
We consider the project of a sub-gigawatt free-electron laser (FEL) in the THz range based on a high-current electron beam proposed in 2020 by a scientific collaboration team from G. I.Budker ...Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences (BINP SB RAS, Novosibirsk) and the Institute of Applied Physics of the Russian Academy of Sciences (Nizhny Novgorod). A new generation of linear induction accelerators (LIA) with a kiloampere current level and an energy of up to 10 MeV, which are capable of forming beams with a high current density and low normalized emittance, is developed at the BINP SB RAS and can be used as a source of an electron beam for such a FEL generator. The objective of our research is to develop and create a FEL generator producing pulses of coherent radiation in the THz range with a sub-GW power level and a record-breaking energy content in a pulse of about 10–100 J. Combination of a high current density of the beam and its long pulse duration (about 100 ns) together with a small spread in the longitudinal electron velocities of the beam opens up the possibility of implementing the FEL scheme in two different types of oversized electrodynamic systems. The first is based on a two-mirror Bragg resonator, in which waves are reflected due to the coupling of the traveling and quasi-critical waves on a corrugated surface. In the second type of the electrodynamic system, a quasi-optical resonator based on the Talbot effect is used. According to the theory, the simulation results, and the data of the cold experiments, both schemes make it possible to ensure a stable regime of narrow-band generation of THz radiation under the conditions of significant cavity oversize, i.e., the ratio of the cavity diameter and the radiation wavelength (ϕ/⋋ > 30–40). The main structural elements of the developed section of the FEL generator and their design parameters are discussed within the framework of this article. When developing the magnetic system of this section, we calculated the time dependence of the spatial configurations of pulsed magnetic field in a helix undulator with a period of d = 10 cm and a length of 2 m, as well as in the solenoid of a quasi-homogeneous magnetic field of the same length intended for compression of the beam cross section before its input in the vacuum channel of the FEL section and for consequent transport of the beam inside it. The presented results of modeling and testing of the manufactured elements for the FEL section will become the basis for the design of a high power FEL generator operated in the frequency range from 0.3 to 1.2 THz.
The problem of route optimization with realistic constraints is becoming extremely relevant in the face of global urban population growth. While we are aware of approaches that theoretically provide ...an exact optimal solution, their application becomes challenging as the problem size increases because of exponential complexity. We investigate the Capacitated Vehicle Routing Problem with Time Windows (CVRPTW) and compare solutions obtaining by exact solver SCIP 1 with heuristic algorithms such as LKH, 2-OPT, 3-OPT 2, the OR-Tools framework 3, and the deep learning model JAMPR 4. We demonstrate that for problem of size 50 deep learning and classical heuristic solutions became close to SCIP exact solution but requires less time. Additionally for problems with size 100, SCIP exact methods ∼ 13 times slower that neural and classical heuristics with the same route cost and on ∼ 50% worse for the first feasible solution on the same time. To conduct experiments, we developed the Smart Routes platform for solving route optimization problems, which includes exact, heuristic, and deep learning models, and facilitates convenient integration of custom algorithms and datasets.
Tamoxifen therapy results in endometrial thickening in some patients with hormone-sensitive breast cancer (HSBC). The data on the impact of polymorphic variants of the CYP2D6 gene encoding the CYP2D6 ...enzyme of the cytochrome P450 family on the efficacy and safety of treatment with tamoxifen are controversial. A prospective cohort study was aimed to explore the association of CYP2D6*3, *4, *6 polymorphisms with the risk of endometrial thickness during adjuvant tamoxifen therapy for HSBC. A total of 145 patients with resectable HSBC, who received 20 mg of oral tamoxifen per day, were enrolled. The CYP2D6*3, *4, *6 polymorphisms were identified by real-time PCR. Endometrial thickness was measured by ultrasonography after 3, 6 and 9 months of endocrine therapy. The study showed that endometrial hyportrophy was more often found in patients having no alternative alleles after 3 months of follow-up (40% against 23.2% in the group of “poor” metabolizers; p = 0.034). Meta-analysis of all follow-up periods has revealed that “normal” metabolizers show a significantly higher rate of endometrial thickness than “poor” metabolizers (OR = 1.88; 95% CI = 1.27–2.79; p = 0.002). A lack of significant differences in indicators of the state of endometrium between groups of patients with different CYD2D6 genotypes and menopausal status requires further investigation.
We show that the set of observational characteristics for low-mass X-ray binaries in the optical and X-ray bands can be explained in terms of the model of an optically thick accretion disk with an ...atmosphere irradiated by a central X-ray source. We show that this set of observational data can be successfully used to measure the orbital inclination of a binary, the geometric parameters of its accretion disk, and the reprocessing time of X-emission to optical one. For the burster GS 1826-238, a low-mass X-ray binary with a neutron star, we have estimated the binary inclination and the thickness of the disk atmosphere at the outer edge from the mean optical flux and the amplitude of periodic modulations in the optical light curve:
i
= 62.5° ± 5.5° and
H
d
/
R
d
= 0.145 ± 0.009. The optical response time of the binary to an X-ray burst disagrees with the geometric delay in the propagation of X-ray photons in the binary. We believe that this points to a finite X-ray reprocessing/reradiation time, 1.0 s ≲
τ
repr
≲ 2.2 s, in the hot atmosphere above the accretion disk.
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