Journal of Experimental and Theoretical Physics最新文献

This study investigates the performance of a gas sensor based on composites of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] (TFB) polymer and graphene (Gr) for the detection of nitrogen dioxide (NO₂) and hydrogen sulfide (H₂S). The sensor was fabricated by spin-coating mixtures of TFB and Gr at various volume ratios onto glass substrates with aluminum electrodes. The structural and morphological properties of the films were characterized using X-ray diffraction (XRD) and atomic force microscopy (AFM). The gas sensing performance was evaluated at different operating temperatures (50–200°C). The results demonstrate that the sensor’s performance is highly dependent on the TFB:Gr mixing ratio and temperature. The optimum sensitivity for NO₂, an oxidizing gas, was 64.4%, achieved at a 5 : 1 mixing ratio and an operating temperature of 150°C. In contrast, the highest sensitivity for H₂S, a reducing gas, was 60%, observed at a 5 : 1 ratio and 100°C. The TFB:Gr composite sensor exhibits superior performance for NO₂ detection at elevated temperatures, with the 5 : 1 ratio providing an optimal balance between the polymer’s gas interaction sites and graphene’s conductive pathways.

This paper presents a machine-learning methodology for solving the inverse radiation problem in turbulent hydrocarbon-fuel flames. A multilayer perceptron (MLP) is trained to map spectral radiance measurements, obtained along a discrete set of ray paths at selected wavenumbers, onto four scalar parameters characterizing the thermochemical state of the flame cross-section: the axial mixture fraction, a jet-radius parameter, the mixture-fraction variance coefficient, and a reaction-progress variable. Training sets are generated by jointly applying the Schlichting profile for the mixture fraction, gas-dynamic parameter calculations, and a spectral radiation model based on the statistical narrow-band (SNB) method. The network is trained using the quasi-Newton BFGS optimizer. On the resulting test set, the mean prediction error does not exceed 1%; verification against the full numerical solution of the Navier–Stokes equations in ANSYS Fluent confirms accurate recovery of temperature and species mass-fraction profiles at distances of 15–30 m from the nozzle exit. Limitations of the method near the nozzle and directions for further research are discussed.

The paper develops a method for calculating the neutron yield in a photoneutron source. The effect of an external magnetic field applied to an accelerated electron beam on the specific neutron yield is analyzed. The 1.5-dimensional modeling of electron beam acceleration in an electromagnetic wave field is performed. The main characteristics of the charged particle beam are obtained based on the results of the calculation. The results of the electron energy and neutron fluence calculations are in good agreement with the experimental data obtained in similar studies.

We present a theoretical investigation of two-mode squeezing and bipartite entanglement in the nondegenerate sum-frequency generation (NSFG) process, based on a second-order Hamiltonian under the short-time approximation. Both first- and second-order amplitude squeezing are shown to depend strongly on the coherent input amplitudes, nonlinear coupling strength, and relative phase. Asymmetric input configurations, especially those with enhanced signal-mode intensity, substantially enhance squeezing and deepen nonclassicality. In particular, second-order quadrature squeezing proves highly sensitive to phase and amplitude imbalances, making it a robust probe of higher-order quantum correlations. Entanglement is assessed using the Duan inseparability criterion and both variants of the Hillery–Zubairy (HZ) criteria. Under coherent excitation, the Duan condition approaches the separability threshold, indicating notable entanglement. Both HZ-1 and HZ-2 reveal bipartite entanglement under suitable field configurations, with HZ-2 displaying greater sensitivity at higher field intensities. The entanglement primarily resides in the pump modes, which symmetrically engage in the nonlinear interaction. These findings highlight the critical role of field asymmetry and higher-order effects in quantum-state engineering, establishing NSFG as a promising, tunable platform for generating nonclassical light in integrated photonics and continuous-variable quantum technologies.

This work investigates self-absorption effects in two-dimensional high-intensity discharge (2D HID) lamps with particular emphasis on mercury (Hg) and thallium (Tl) emission lines. Special attention is devoted to the Tl 535 nm resonance line and selected Hg transitions, both strongly affected by optical thickness and radiative trapping phenomena under high-pressure plasma conditions. A two-dimensional radiative transfer model based on the discrete ordinates method (DOM) is employed to simulate the spectral intensity distribution inside the arc tube. The model accounts for spatial variations in temperature, particle density, and absorption coefficients under local thermodynamic equilibrium (LTE) assumptions. Results show that self-absorption significantly modifies the spectral line profiles, leading to central reversal, line broadening, and intensity redistribution depending on radial and axial plasma positions. The strongest self-absorption effects are observed in cold peripheral regions where ground-state particle densities are high, whereas the hot plasma core remains comparatively optically thinner. The study further demonstrates that Hg and Tl resonance lines exhibit different sensitivities to temperature gradients and optical thickness due to their distinct spectroscopic properties. Implications for optical emission spectroscopy (OES), plasma diagnostics, and line-ratio methods are discussed. The present analysis highlights the importance of accurate multidimensional radiative transfer modeling for understanding spectral distortions and optimizing the performance and luminous efficiency of HID lamps.

This paper proposes a new method for estimating the elastic modulus of protective polymer coatings based on standard tensile tests on three-layer strip specimens. The proposed method derives the coating’s elastic modulus from a comparison of experimental elastic modulus values obtained for the base material (08 PS steel) and the effective elastic modulus for specimens coated with the studied coatings. The differences between these values are 10–15%. In this case, the accuracy of estimating the coating’s elastic modulus largely depends on the accuracy of stress and strain determination during testing of the material specimens, which were measured using ZWICK Z100 precision equipment and mechanical testing methods. Using this equipment, tensile tests were performed on four protective polymer coatings applied to the specimen surfaces. The elastic modulus values of the coatings were calculated using the rule of mixtures. For two modifications of the studied coatings, the elastic modulus values were obtained from four-point bending tests. It was shown that both methods yield similar values for the elastic modulus of the coatings.

This study presents the design and numerical simulation of a CW operation solid-state Nd:YAG laser operating at a wavelength of 1064 nm. The laser system was modeled and optimized using ASLD simulation software to analyze the resonator configuration, pumping geometry, and output characteristics. The proposed system employs an Nd:YAG crystal rod with a radius of 3 mm, a length of 100 mm, and a doping concentration of 1%, which is longitudinally cooled to enhance thermal stability. A plane-parallel optical resonator composed of two flat mirrors with a reflectivity of 90% was implemented to ensure stable laser operation. The laser medium was pumped using diode light optics combined with cylindrical reflectors and elliptical elements, allowing efficient absorption and uniform distribution of pump energy within the crystal. Ray-tracing analysis confirmed that the pump light is concentrated near the center of the gain medium, thereby improving excitation efficiency. Dynamic mode analysis was utilized to investigate the temporal behavior and beam quality of the laser output. The simulation results indicate that the proposed system achieves high output power with rapid transient response, reaching steady-state operation within approximately 0.6 ms. Furthermore, the output beam exhibits a uniform spatial profile and stable amplitude, demonstrating high beam quality and excellent resonator stability. The findings of this study highlight the effectiveness of the proposed design in producing stable laser output. The developed simulation model provides a reliable platform for optimizing solid-state Nd:YAG laser systems and can support future experimental implementation for scientific and industrial.

This investigation elucidates the wavelength-dependent development of plasma and the kinetics of structural fragmentation in laser-induced paracetamol (C₈H₉NO₂) polymorphs plasma, thereby establishing a predictive framework for organic laser-induced breakdown spectroscopy (LIBS) diagnostics. Ablation plumes were meticulously generated using both the fundamental (λ = 1064 nm) and second-harmonic (λ = 532 nm) Nd:YAG laser regimes across a calibrated energy range of 100–300 mJ. Spectroscopic analysis reveals a significant mechanistic divergence: the 532 nm photon flux (2.33 eV) induces a photolytic multi-photon ionization (MPI) mechanism, triggering rapid electron cascading that increases densities to 4.46 × 10¹⁷ cm^–3. This process results in sudden optical saturation and localized thermal stabilization (10 420–10 670 K) through inverse Bremsstrahlung core shielding. In contrast, the 1064 nm pathway (1.17 eV) promotes a mass-dominant pyrolytic avalanche and phase explosion, characterized by consistent, unsaturated thermodynamic scaling (8390–11050 K) accompanied by pronounced spatial expansion gradients. These thermal anomalies induce pronounced ex-situ peripheral recombination chemistry at elevated infrared energies, as evidenced by a significant CN/C I radical emission spike (2.05). All operational parameters strictly conform to the McWhirter criterion, thereby confirming the validity of local thermodynamic equilibrium (LTE). The integration of these discrete electronic, thermal, and molecular topologies into a comprehensive multidimensional phase transition map provides a robust ontological framework for high-precision quantitative spectroscopy of complex pharmaceutical matrices.

The compatibility of ghost modes in quadratic gravity with the second law of thermodynamics of black holes is investigated. A bilayer architecture of the protection is proposed. The first (basic) layer is the Anselmi fakeon rule, in which a ghost possesses zero physical degrees of freedom on the mass surface and cannot be thermolyzed. The second layer is a model-independent estimate of thermal and spatial suppression, which serves as a verification of stability in the case when the fakeon rule cannot be generalized rigorously to curved backgrounds. Two independent mechanisms (Boltzmann suppression (exp ( - {{m}_{{{text{gh}}}}}{text{/}}{{T}_{{H}}})) and Yukawa suppression (exp ( - {{m}_{{{text{gh}}}}}{{r}_{H}}))) jointly guarantee that ratio ({text{|}}{{dot {S}}_{{{text{gh}}}}}{text{/}}{{dot {S}}_{{{text{mat}}}}}{text{|}}) does not exceed (C{{(m{text{/}}{{T}_{{H}}})}^{{5/2}}}exp ( - m{text{/}}{{T}_{{H}}})) in any diffeomorphic-invariant theory with a massive ghost. For the spectral causality theory with ({{m}_{{{text{gh}}}}} = 2.69) meV and black holes of stellar masses, this estimate gives suppression by hundreds million orders. It has been shown that a Schwarzschild black hole is the worst case among stationary solutions (Kerr, Reissner–Nordström, Kerr–Newman), and de Sitter cosmological horizon is suppressed even more strongly. Critical mass, ({{M}_{{{text{crit}}}}} = M_{{{text{Pl}}}}^{2}{text{/}}(8pi {{m}_{{{text{gh}}}}})), below which ghost effects become significant, is determined and minimal mass ({{M}_{{min }}}) of a black hole, for which there is no gravity trap surface on the horizon, is obtained. It is shown that ({{M}_{{min }}}{text{/}}{{M}_{{{text{crit}}}}} = 7)–13 so that the ghost activity domain is empty at the Yukawa approximation level. The results are applied to five observable black holes and to analysis of the Dong–Wall entropy. Three (fakeon, Lie–Wick, and physical) interpretations of a ghost are considered and the model comparison with other approaches to quadratic gravity is performed.

Efficient thermal management is essential for ensuring the safety, performance, and longevity of lithium-ion battery systems. This study investigates the thermal behavior of a battery module under direct liquid cooling using computational fluid dynamics (CFD) model. The model was employed to evaluate the effects of coolant type, flow velocity, and inlet temperature on temperature distribution and overall cooling performance. Four working fluids (deionized water, ethylene glycol, mineral oil, and Novec 7300) were comparatively analyzed. Deionized water achieves the lowest maximum temperature due to its high thermal conductivity and specific heat capacity, while Novec 7300 shows the weakest cooling capability. Increasing coolant velocity effectively reduces peak temperature by enhancing convective heat transfer, whereas lowering inlet temperature decreases the overall temperature level with limited impact on temperature uniformity. The results further reveal a trade-off between peak temperature reduction and temperature uniformity, indicating that stronger cooling may induce larger thermal gradients. Therefore, thermal management design should balance cooling capacity and uniformity. Overall, selecting a coolant with superior thermophysical properties is more effective than solely adjusting operating parameters.