Longitudinal Channel Research Articles

Flight test evaluation of trim tab stabilisation system on a PZL-130 orlik aircraft

Purpose The paper presents the results of the final phase of the project, namely flight tests, aimed at developing a stabilisation system utilizing trim tabs for the PZL-130 Orlik turboprop military trainer aircraft. Design/methodology/approach The proposed flight stabilisation system was developed using modern techniques of model-based design, automatic code generation and software and hardware-in-the-loop testing. The project progressed to the flight testing stage, enabling the assessment of the control system’s quality and its final calibration. Findings Analysis of the results obtained during flight tests confirmed the high quality of the stabilisation system. Specifically, the anticipated accuracy of both longitudinal and lateral channel stabilisation was achieved. Originality/value The proposed flight stabilisation system, utilizing trim tabs, offers several advantages over classic automatic flight systems in terms of weight, energy consumption, structural simplicity and obviates the need for primary control modifications on the aircraft. It was developed using modern techniques of model-based design, automatic code generation and hardware-in-the-loop simulations.

Automatic Landing Control for Fixed-Wing UAV in Longitudinal Channel Based on Deep Reinforcement Learning

The objective is to address the control problem associated with the landing process of unmanned aerial vehicles (UAVs), with a particular focus on fixed-wing UAVs. The Proportional–Integral–Derivative (PID) controller is a widely used control method, which requires the tuning of its parameters to account for the specific characteristics of the landing environment and the potential for external disturbances. In contrast, neural networks can be modeled to operate under given inputs, allowing for a more precise control strategy. In light of these considerations, a control system based on reinforcement learning is put forth, which is integrated with the conventional PID guidance law to facilitate the autonomous landing of fixed-wing UAVs and the automated tuning of PID parameters through the use of a Deep Q-learning Network (DQN). A traditional PID control system is constructed based on a fixed-wing UAV dynamics model, with the flight state being discretized. The landing problem is transformed into a Markov Decision Process (MDP), and the reward function is designed in accordance with the landing conditions and the UAV’s attitude, respectively. The state vectors are fed into the neural network framework, and the optimized PID parameters are output by the reinforcement learning algorithm. The optimal policy is obtained through the training of the network, which enables the automatic adjustment of parameters and the optimization of the traditional PID control system. Furthermore, the efficacy of the control algorithms in actual scenarios is validated through the simulation of UAV state vector perturbations and ideal gliding curves. The results demonstrate that the controller modified by the DQN network exhibits a markedly superior convergence effect and maneuverability compared to the unmodified traditional controller.

Formation condition for concave-bank deposition in the meanders of the Middle Yangtze River and its application

In what kind of meanders concave-bank deposition (CBD) can occur remains an open question. This study investigated the characteristics and major influencing factors of CBD in the meanders of the Middle Yangtze River (MYR), and proposed a formation condition for CBD. Concave-bank deposition occurred in 10 of 23 meanders in the MYR, including two types: counter point bar (CPB) and concave-bank bench (CBB). CPB occurred in both mildly-curved and sharp bends, while CBB only occurred in sharp bends. Hydrodynamic conditions and sediment supply are two major factors controlling the formation of CBD. The incoming sediment load remained in an amount of 0.68 × 108 t/y at Jianli and 0.77 × 108 t/y at Luoshan after Three Gorges Project operation, therefore, CBD development was not limited by a lack of sediment and instead is mainly dependent on the hydrodynamic conditions in the MYR. Flow separation zones were observed in the typical CBD-type bends of the MYR, which indicated that CBD was the result of flow separation or recirculation. An adverse longitudinal water surface gradient is the necessary condition for the formation of concave-bank flow separation. Therefore, a formation condition for CBD was proposed based on this assumption, which considered the combined effects of channel resistance, riverbed slope, channel widening, and curvature. CBD happens when the channel widening and curvature terms are greater than the channel resistance and longitudinal channel slope terms. The proposed condition was verified based on the data of the 23 bends in the MYR and 26 bends in 12 other rivers. The results indicated that more than 85% of the bends were correctly identified. Therefore, the proposed formation condition provided considerably high accuracy.

Inspection of numerical and fractional CMC and water-based hybrid nanofluid with power law and non-singular kernel: A fractal approach

A number of thermal devices might benefit from the usage of nanofluids in solar power. In this research, the idea of MHD mixed convective hybrid nanofluids including grapheme oxide (GO) and molybdenum disulfide (MoS2) nanoparticles with water (H2O) and Carboxymethyl Cellulose (CMC) as base fluids in a perpendicular channel to analyze the heat transfer of the flowing fluid with the help of recent definition of fractional derivatives namely Fractal fractional derivative. The problem is expressed as PDEs with beginning and boundary conditions, and it is analyzed analytically using the Laplace transform method. The velocity, temperature, and concentration measurements are also shown in series for their appropriate Laplace inverse. Delays in parameters like nanoparticle volume sharing rate have a significant influence on these techniques. Skin friction, Nusselt, and Sherwood numbers are computed for the longitudinal channel's left and right walls, and the necessary numerical results are presented in tabular format. As a result, it is discovered that the rate of heat transfer reduces as the volume percentage of nanoparticles and the Fractal time fractional value rise. Furthermore, when comparing nanofluids, water-based (H2O + GO + MoS2) hybrid nanofluids have a greater influence on governed model than (CMC + GO + MoS2)-based hybrid nanofluids.

Controllable propagation of waveguide mode in multi-channel photonic crystal waveguide

In this paper, we introduce a new method to realize the separation of waveguide modes in photonic crystal waveguides by controlling the position and polarization of the dipole sources. Our study shows that the waveguide modes in the transversal channel and longitudinal channel can be manipulated, respectively, by the dipole sources placed within the corresponding channels. Based on this discovery, we may further adjust the dipole sources in the transversal (longitudinal) channel individually and separate the zeroth order and the first order modes to propagate towards the preassigned channels. Compared with the former schemes to realize the mode separation by changing the structure, our method is more intuitive, convenient, and flexible.

Analysis and Design of Bat-Like Flapping-Wing Aircraft

As the only flying mammal in nature, bats have superb flight skills and aerodynamic characteristics that have been the subject of research by scholars from all over the world. In recent years, the research on bionic flapping-wing aircraft has made good progress. However, such research mostly uses birds or insects as the research objects, and there are few studies on bat-imitating flapping-wing aircraft. This paper combines the characteristics of bats’ flexible wings to model and analyze the aerodynamic theory and parameters of the flexible wings of bat-like flapping aircraft. The longitudinal dynamic and kinematic model design of bat-like flapping aircraft is based on the pitch angle of LQR. In terms of height control, the controller uses energy control methods to complete the closed-loop longitudinal channel control of the bat-like flapping aircraft. Finally, this study performed the simulation and flight experimentation of the designed bat-like flapping aircraft, demonstrating the correctness of this system.

Research and Optimization of Four Serpentine-Wave Flow Fields in PEMFC

The layout of the cathode flow field largely determines the net output power of the proton exchange membrane fuel cell (PEMFC). To make the normal mass transfer effect best, the longitudinal channel was waved based on four serpentine flow channels, and the effects of sag depth and longitudinal channel width on the output efficiency of the cell were explored. The results show that the wave channel design systematically enhances the forced convection between adjacent channels, which can prevent a large zone of oxygen starvation zone at the outlet of the channel. The increase of the normal velocity in the gas transmission process will inevitably induce a significant enhancement of the mass transfer effect and obtain a higher current density in the reaction zone. For the longitudinal channel width, it is found that increasing its size in the effective range can greatly reduce the channel pressure drop without reducing the output power, thereby improving the overall efficiency. When the sag depth and longitudinal channel width gradient are 0.6 mm and 0.2 mm respectively, PEMFC can obtain the best comprehensive performance.

Study on heat transfer performance of cold plate with grid channel

The utilization of cold plate radiators as a prevalent method for indirect liquid cooling has been extensively investigated and implemented in server cooling systems. However, there is a lack of comprehensive study on the application of this technology at the chip size, indicating a need for more development and exploration in this area. A proposal was made for a grid-channel chip cold plate heat sink to facilitate the dissipation of heat from a chip. tests were conducted to investigate the impact of the flow rate of the cold plate and the layout of the inlet and outlet on various thermal parameters, including the average temperature, maximum temperature, thermal resistance, and uniformity coefficient of the cold plate. The tests were specifically conducted under a chip power of 150W, and the accuracy of the simulation was confirmed through the use of FLUENT. The findings indicate that the cold plate effectively regulates the temperature of the chip, ensuring it remains below 85 °C throughout all experimental groups. In contrast to the single in single out configuration, the single-in multiple-out layout exhibits a higher degree of temperature uniformity within the cold plate. Nevertheless, it is important to note that augmenting the quantity of exits does not guarantee an improvement in heat transfer efficiency. This outcome is contingent upon the presence of a longitudinal flow channel shared by the outlet and intake, as well as the dispersion characteristics of the outlet. Enhancing the dispersion of the exit can significantly enhance the thermal transfer efficiency of the cold plate. Furthermore, a strategy for adjusting the aperture of the orifice is proposed as a solution to address the challenges related to flow uniformity and the issue of high pressure drop in the cold plate.

Nonlinear and Nonreciprocal Transport Effects in Untwinned Thin Films of Ferromagnetic Weyl Metal SrRuO3

The identification of distinct charge transport features, deriving from nontrivial bulk band and surface states, has been a challenging subject in the field of topological systems. In topological Dirac and Weyl semimetals, nontrivial conical bands with Fermi-arc surface states give rise to negative longitudinal magnetoresistance due to chiral anomaly effect and unusual thickness dependent quantum oscillation from Weyl-orbit effect, which were demonstrated recently in experiments. In this work, we report the experimental observations of large nonlinear and nonreciprocal transport effects for both longitudinal and transverse channels in an untwinned Weyl metal of SrRuO3 thin film grown on a SrTiO3 substrate. From rigorous measurements with bias current applied along various directions with respect to the crystalline principal axes, the magnitude of nonlinear Hall signals from the transverse channel exhibits a simple sinα dependence at low temperatures, where α is the angle between bias current direction and orthorhombic [001]o, reaching a maximum when current is along orthorhombic [11¯0]o. On the contrary, the magnitude of nonlinear and nonreciprocal signals in the longitudinal channel attains a maximum for bias current along [001]o, and it vanishes for bias current along [11¯0]o. The observed α-dependent nonlinear and nonreciprocal signals in longitudinal and transverse channels reveal a magnetic Weyl phase with an effective Berry curvature dipole along [11¯0]o from surface states, accompanied by 1D chiral edge modes along [001]o. Published by the American Physical Society 2024

Study of crosshead-guided lubrication systems for hydraulic fracturing plunger pumps

Efficient extraction of hard-to-recover hydrocarbon reserves requires impressive expenditures on the use of advanced technologies and energy-intensive equipment. Hydraulic fracturing technologies require the use of high-pressure pumps (105 and 138 MPa), and this determines the use of plunger pumps in these conditions. To relieve the radial load on the plunger seals, a crosshead layout of the drive part is used. The goal is to investigate crosshead (guide) load distribution throughout the crankcase and also the oil distribution in the crosshead-guide gap to find the most efficient design. The methods of simulation modeling of the kinematics of the crosshead and connecting rod group with the use of modal analysis were applied for the study. The analysis was performed taking into account the elastic properties of the crosshead, seal and connecting rod. The Reynolds-Stokes-Halerkin finite element method (R-SGFEM) with sliding boundary conditions was used to model and study hydrodynamic lubrication. A study was conducted for three types of oil channels on the crosshead: one longitudinal channel at the apex, one longitudinal channel and two transverse channels, one longitudinal channel and three transverse channels. Load distribution graphs were obtained for the contact area with respect to the oil-feeding hole in the guide. The obtained data make it possible to understand the nature of the crosshead sliding on the guide and evaluate the possibility of providing the hydrostatic mode in the friction knot at different types of the lubricant supply into the contact zone. The study showed one of the causes of increased wear of the bottom guide of the crosshead, which consists in insufficient non-drying ability of the lubricating layer and allowed to determine the parameters for further research and optimization of the node design.

(Invited) Mechanical Stress Simulations for Advanced Logic Devices

Novel transistor concepts are continuously being investigated to scale beyond FinFETs and nanosheets. One such architecture is the Complementary FET (CFET), consisting of an NFET and a PFET fabricated on top of each other [1-4], offering increased device density thanks to its stacking. However, additional challenges arise, such as significantly complicated processing and higher complexity of the connections between devices. Another concern lies in the optimization of the device performance by incorporating mechanical channel strain: in particular for the top-channel device it is challenging to employ traditional stressors efficiently, as it is largely disconnected from the substrate underneath. The purpose of this study is to study whether a CFET technology, and especially its top-channel device can be properly stressed. To this end, a TCAD process simulation flow that mimics the relevant steps for stress modeling has been built using Sentaurus-Process [5].An example of a quarter-structure of the simulated CFET at the end of the simulation (after channel release) is shown in Fig. 1. The device has a gate length of 14nm, a fin-like silicon channel both for the top and bottom device (5nm width, 30nm height), and fully strained source/drain (S/D) epitaxial layers in the bottom and top devices. For the top (NFET) device, the source/drain epi does not fill up all available space but consists rather of a thin layer grown against the sidewalls of the device, as observed experimentally. Tungsten contacts are added to connect the devices, and a thin oxide layer is present in the source/drain regions to isolate the top from the bottom device.Fig. 2 shows the longitudinal channel stress in the channels for a varying composition of the top-channel S/D epi. A large compressive (i.e. negative) stress is generated in the bottom PFET channels, thanks to the strained Si0.5Ge0.5 bottom S/D epi. On the other hand, the channel stress in the top channel is much smaller and becomes more tensile (positive) for higher Ge% in the top S/D. This opposite trend from traditional S/D’s was reported for nanowires in [6] and can be explained by the fact that the top S/D does not fill up the available space, which leads also to a large reduction in absolute channel stress. Another observation from Fig. 2 is that the stress in the bottom channel is independent of the composition in the top S/D, indicating that the devices are mechanically decoupled. Fig. 3 plots the channel stress in the structure after various steps of the simulation, showing that a small channel stress is generated after S/D etch by the presence of the sacrificial layer (Si0.75Ge0.25) between the channels. Furthermore, dummy gate removal tends to increase the absolute channel stress. Finally, the bottom S/D epi growth does not affect the top-channel stress, again confirming the mechanical decoupling of both channels to first order. Fig. 4 shows how the channel stress is affected for an intrinsic tensile stress of 2GPa in the tungsten or oxide isolation between the devices. Tungsten is a rather ineffective stressor due to its high stiffness: less than 200MPa tensile top-channel stress is generated by a stressed tungsten in its S/D’s. For the bottom device, the effect is even smaller due to the increased distance between the bottom-tungsten and the channel. The oxide isolation proves to be a more efficient stressor for the top channel, leading to about 1GPa additional tensile stress which is concentrated at the bottom of the channel.The presentation will highlight the importance of other stress components besides longitudinal stress. Furthermore, whereas the results in Figs. 1-4 were obtained for fin-like (vertically elongated) devices, a CFET technology can also be built using nanosheet (horizontally elongated) channels. It will be shown that changing towards this type of channels leads to a significant change of the stressor effectiveness in CFET technologies. These insights will help us to continue improving the device performance in advanced transistor architectures like CFETs.

An improved dynamic model identification method for small unmanned helicopter

PurposeThe purpose of this paper is to introduce an improved system identification method for small unmanned helicopters combining adaptive ant colony optimization algorithm and Levy’s method and to solve the problem of low model prediction accuracy caused by low-frequency domain curve fitting in the small unmanned helicopter frequency domain parameter identification method.Design/methodology/approachThis method uses the Levy method to obtain the initial parameters of the fitting model, uses the global optimization characteristics of the adaptive ant colony algorithm and the advantages of avoiding the “premature” phenomenon to optimize the initial parameters and finally obtains a small unmanned helicopter through computational optimization Kinetic models under lateral channel and longitudinal channel.FindingsThe algorithm is verified by flight test data. The verification results show that the established dynamic model has high identification accuracy and can accurately reflect the dynamic characteristics of small unmanned helicopter flight.Originality/valueThis paper presents a novel and improved frequency domain identification method for small unmanned helicopters. Compared with the conventional method, this method improves the identification accuracy and reduces the identification error.

Direct assessment of the hydraulic structure of the plate boundary at the toe of the Nankai accretionary prism

SUMMARY The Nankai Trough is a locus of slow slip, low-frequency earthquakes, and large magnitude (Mw > 8) earthquakes. It is usually assumed that high pore pressure contributes substantially to earthquake dynamics. Hence, a thorough understanding of the hydraulic regime of the Nankai accretionary prism is needed to understand this diversity of behaviours. We focus on the toe of the accretionary prism by studying data from Hole C0024A, part of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) project, that intersected the décollement at 813 m below seafloor (mbsf) about 3 km away from the trench. We contribute to this understanding by innovatively integrating drilling and logging data to derive high-resolution hydraulic profiles along the borehole. A quantitative re-analysis of the variation in the downhole annular pressure monitored during drilling show localized fluid flow from the formation to the borehole in excess of 0.05 m3 s−1, especially in the damage zones at the footwall of the décollement. To validate the fluid flow profile, pore pressure was estimated independently from empirical relationships between pore pressure, porosity and P-wave velocity, obtained from consolidation experiments and Eaton-type methods based on drilling or sonic velocity data. The formation fluids are becoming significantly overpressurized with depth in the few hundred metres above décollement. The hydraulic profile suggests that the core of the décollement acts as a barrier inhibiting upward fluid convection, whereas the damage zone acts as an efficient longitudinal channel able to diffuse high pressure from the deeper part of the subduction.

Skin-Attachable Ink-Dispenser-Printed Paper Fluidic Sensor Patch for Colorimetric Sweat Analysis.

In situ analysis of sweat biomarkers potentially provides noninvasive lifestyle monitoring and early diagnosis. Quantitative detection of sweat rate is crucial for thermoregulation and preventing heat injuries. Here, a skin-attachable paper fluidic patch is reported for in situ colorimetric sensing of multiple sweat markers (pH, glucose, lactate, and uric acid) with concurrent sweat rate tracking. Two sets of fluidic patterns-multiplexed detection zones and a longitudinal sweat rate channel-are directly printed by an automated ink dispenser from a specially developed ceramic-based ink. The ceramic ink thermal-cures into an impervious barrier, confining sweat within the channels. The ceramic-ink-printed boundary achieves higher pattern resolution, prevents fluid leakage, attains pattern thermal stability, and resistant to organic solvents. The cellulose matrix of the detection zones is modified with nanoparticles to improve the color homogeneity and sweat sensor sensitivity. The sweat rate channel is made moisture sensitive by incorporating a metal-salt-based dye. The change in saturation/color of the detection zones and/or channels upon sweat addition can be visually detected or quantified by a smartphone camera. A cost-effective way is provided to fabricate paper fluidic sensor patches, successfully demonstrating on-body multiplexed evaluation of sweat analytes. Such skin wearables offer on-site analysis, meaningful to an increasingly health-conscious population.

Experimental Study on the Longitudinal Mechanical Behavior of Shield Tunnel in Soft-Hard Uneven Strata and the Reinforcement Effect of Longitudinal Channel Steel

This paper investigates the longitudinal behavior and failure pattern of shield tunnel, as well as the reinforcement mechanism of longitudinal channel steel, using reduced-scale tunnel models assembled with 24 lining rings. The longitudinal behavior of the shield tunnel and the reinforcement effect are discussed in terms of vertical deformation, joint deformation, and concrete cracking. The results indicate that the shield tunnel without reinforcement longitudinally deforms in a “bending and dislocation” mode, with the failure pattern dominated by bending deformation. In contrast, the failure pattern of the shield tunnel reinforced by channel steels is characterized by brittle shearing dislocation fracture of the circumferential joint. The load at which damage occurs in the reinforced tunnel model is 1.74 times and 2.04 times that of the non-reinforced staggered and straight jointed tunnels. The reinforcement reduces the horizontal convergence discrepancy of lining rings above the soft foundation spring and the adjacent lining rings, which improves the overall integrity of the tunnel structure.

Steady-state forms of channel profiles shaped by debris flow and fluvial processes

Abstract. Debris flows regularly traverse bedrock channels that dissect steep landscapes, but our understanding of bedrock erosion by debris flows and their impact on steepland morphology is still rudimentary. Quantitative models of steep bedrock channel networks are based on geomorphic transport laws designed to represent erosion by water-dominated flows. To quantify the impact of debris flow erosion on steep channel network form, it is first necessary to develop methods to estimate spatial variations in bulk debris flow properties (e.g., flow depth, velocity) throughout the channel network that can be integrated into landscape evolution models. Here, we propose and evaluate two methods to estimate spatial variations in bulk debris flow properties along the length of a channel profile. We incorporate both methods into a model designed to simulate the evolution of longitudinal channel profiles that evolve in response to debris flow and fluvial processes. To explore this model framework, we propose a general family of debris flow erosion laws where erosion rate is a function of debris flow depth and channel slope. Model results indicate that erosion by debris flows can explain the occurrence of a scaling break in the slope–area curve at low-drainage areas and that upper-network channel morphology may be useful for inferring catchment-averaged erosion rates in quasi-steady landscapes. Validating specific forms of a debris flow incision law, however, would require more detailed model–data comparisons in specific landscapes where input parameters and channel morphometry can be better constrained. Results improve our ability to interpret topographic signals within steep channel networks and identify observational targets critical for constraining a debris flow incision law.

Inversion of Late Miocene uplift history from the transient Daxia River landscape, NE Tibetan Plateau

The mechanisms of the upward and outward growth of the Tibetan Plateau are crucial for understanding the geodynamic significance of Cenozoic continental collisions. Northeastern Tibet has been suggested as one of the youngest deforming and uplifting margins surrounding the plateau. The existence of fluvial knickpoints and low-relief topographic surfaces along the Yellow River and its tributaries indicate the transience of the landscape in response to active tectonic uplift. Therefore, the uplift history of the North Eastern Tibetan Plateau (NETP) can be potentially inverted from the disequilibrium channel profiles of the Yellow River and its tributaries. The West Qinling Fault (WQF) is part of the geomorphological and topographic boundaries of the NETP. Its uplift history helps to clarify the deformation history of the Tibetan Plateau. In this study, the focus was on the Daxia River (one of the Yellow River tributaries) to identify the distribution of peneplain surfaces and knickpoints, and to present a linear inversion on the fluvial longitudinal profiles for the relative uplift history of the West Qinling. We obtained a relative uplift history with two pulses of change in the uplift rates at ∼5 and ∼2 Ma. Rates of relative uplift maintained low values during the Late Miocene, then slowly increased from 0.1 to 0.2 mm a −1 after ∼5 Ma and suddenly jumped to 0.3 mm a −1 at ∼2 Ma, consistent with recent findings on the deformation records in the NE Tibetan Plateau. We suggest that (1) the Late Miocene–Pliocene landscape evolution was driven by both tectonics and climate change and (2) inversion of the transient longitudinal channel profiles, if applied, may provide broader insights into the upward and outward growth patterns of the NE Tibetan Plateau. Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

A new approach to simulate watershed sediment graphs

Soil loss management requires reliable data for assessing the conditions prevailing in a watershed. Suspended sediment concentration (SSC) is one of the indicators of soil loss, and its data and associated properties are essential for integrated watershed management. However, until now, practical methods for estimating the temporal variation of SSC at the watershed scale, i.e., a sediment graph (SG), using measured data have been given less attention. Therefore, the current study was planned to simulate the SG through conceptual modeling of the soil erosion process and sediment yield. The Galazchai Watershed in West Azerbaijan Province, Iran, was selected as a case study. In this regard, the isochrone histograms were initially prepared using two methods of the longitudinal channel profile and spatially distributed travel time. Soil erosion was calculated in each isochrone segment using the Revised Universal Soil Loss Equation (RUSLE), applying the lumped and cellular automata approach. The soil erosion between isochrones was subsequently routed using the Hadley, WaTEM/SEDEM, and newly modified U.S. Forest Service methods. The last method was developed based on seven standardized variables for the current research. Synthetic SGs were ultimately derived from 12 different combinations of the study methods. The modeling performance was assessed using 38 storm events collected over several years. The base time, time to peak, peak value, and total sediment load of the simulated and observed SGs were evaluated using relative error. Comparison based on the evaluation indicators indicated better performance of the combination of the spatially distributed travel time method, cellular automata, and modified U.S. Forest Service method with the coefficient of efficiency and the normalized coefficient of efficiency varying from −1.16 to 0.99 and from 0.32 to 0.99 for the calibration and validation stages, respectively. However, none of the models were simulating satisfactorily the entire sediment graphs.

Interactions of omega mesons in nuclear matter and with nuclei

In-medium interactions of omega -mesons in infinite nuclear matter and finite nuclei are investigated in a microscopic approach, focused on the particle-hole excitations of the medium involving nucleonic NN^{-1} and N^*N^{-1} modes, where N^* denotes a nucleon resonance. The nuclear polarization tensors include relativistic mean-field dynamics by self–consistent scalar and vector fields. The resulting self-energies are transmitted to finite nuclei in local density approximation. Real and imaginary parts of longitudinal and transversal self-energies are discussed. The relation of the present approach to meson cloud models is addressed and an ambiguity is pointed out. Applications to recent data on the in–medium width of omega mesons scattered on a Niobium target serve to determine unknown N^*Nomega in-medium coupling constants. The data are well described by N^*N^{-1} self–energies containing S–wave and P-wave N^* resonances. Exploratory investigations, however, show that the spectroscopic composition of self-energies depends crucially on the near-threshold properties of the width which at present is known only within large error bars. The calculations predict the prevalence of transversal self–energies, implying that vector current conservation is still maintained in the nuclear medium by slightly more than 90%. Schrödinger-equivalent potentials are derived and scattering lengths and effective range parameters are extracted for the longitudinal and transversal channel. Longitudinal and transversal spectral distributions are discussed and the dependencies on momentum and nuclear density are investigated. Schrödinger-type omega +{}^{93}Nb optical potentials are constructed. Low-energy parameters are determined, are used to study the pole structure of the S-matrix at threshold. The effective range expansion of the omega-nucleus K-matrix led to a omega +{}^{93}Nb bound states with binding energy Re(varepsilon _B)=-448 keV but of width Gamma _B=4445 keV.

Composite welds reinforced in volume with lanthanides

Under the conditions of dynamic impact of high‑speed clusters of powdered micro‑particles on the volume zone of welding between 110G13 and St.10 steel plates, longitudinal strengthening channel elements are formed, and rare earth elements such as lanthanum and cerium are also synthesized.