Cross Section Distribution Research Articles

Broadband one-dimensional range profiles characteristic of rough surface in terahertz band

<sec>The one-dimensional (1D) range profile is an important back scattering characteristic of objective, which reveals the longitudinal distribution of radar cross section (RCS) along the detection beam. Since the shape and posture can be reflected by the 1D range profile, it is of great significance in military to determine the target orientation, velocity and whether it is armed. In this paper, broadband terahertz 1D-range-profile measurement system is built based on the time-domain spectroscopy (TDS) system. It is in bistatic configuration (bistatic angle of 9°) and the signal-to-noise ratio (SNR) is 34.5 dB, with a gold mirror used as a reflector. Benefiting from the ultrashort terahertz pulse width (full pulse width of 0.52 ps), the bandwidth covers the frequency range from 0.1 THz to 2.5 THz (peaked at 0.9 THz), corresponding to the range resolution on a submillimeter scale.</sec><sec>Firstly, the 1D range profiles of several objects in different shapes are measured, including the step, cylinder, step cone and their combination, which indicates that the geometric profile of the target in the detection direction is adequate to identify the shape feature of the target and proves the reliability of the 1D range profile measuring system based on TDS. Secondly, aluminum plates with different surface roughness in a range of 0–25 μm are also characterized. The Kirchhoff approximation theory and small perturbation method (SPM) are introduced to illustrate the characteristics of broadband terahertz 1D range profile related to the surface roughness of target. It is found that the scattering characteristic of metal object in the terahertz range is sensitive to surface roughness. If the surface roughness of the object is larger, the peak intensity of the 1D range profile will be weaker and the echo signal pulse width becomes wider. The rule is also applicable for the cases with different incident angles. Furthermore, it is revealed that the time delay of the 1D range profile in the bistatic system is related to the rotation direction of the target, which is useful in estimating the posture of the target. In summary, the characteristics of 1D range profile for metal objects relating to shape, surface roughness and posture are studied. The conclusions have certain guiding significance for the target detection and recognition of terahertz radar.</sec>

Optimization of the flue gas-flow controlling devices of the electrostatic precipitator of unit A4 in TPP "Nikola Tesla"

Homogeneity of the flue gas-flow through the chamber of an electrostatic precipitator is one of the basic influencing parameter on dedusting efficiency. This paper presents results of a multiobjective optimization study of the flue gas controlling devices of electrostatic precipitator of 324 MWe lignite fired Unit A4 of TPP "Nikola Tesla" in Serbia. The aim was to achieve better flow homogeneity in the cross-section of the precipitator compared to the original design. Additional constraints were to maintain the minimum as possible overall weight of the proposed design as well as pressure drop through the precipitator. Numerical simulations based on CFD were used to investigate dependence of the velocity distribution in the ducts and precipitator?s chamber with respect to the geometrical parameters of tested concepts of turning blades. A series of 22 detailed full-scale numerical models of the precipitator with different concepts of turning vanes designs were developed. Assessment of the flow field uniformity for each tested design was performed based on the analysis of several homogeneity parameters calculated for selected vertical cross-sections of the precipitator. After the reconstruction according to optimized design, results of measurements confirmed significant improvements of the velocity distribution in the vertical cross-sections of the precipitator, increase of dedusting efficiency and reduction of PM emission.

Comparison of binding energy from Atomic Mass Evaluation (AME-2020) with statistical model calculations

Realistic model calculations are fundamental to any physical problem. The statistical model continues to remain one of the important theoretical basis formalism in the nuclear reaction and structure field, which is based on the theory of compound nuclei. In this work, we have compared the recently measured binding energies from The Atomic Mass Evaluation 2020 with statistical model calculation. This comparison becomes very important from the fact that code calculates everything from excitation energy Q-value of reaction to cross-sections based on binding energy and is used frequently by nuclear research communities throughout the world. We have given a brief explanation of how code calculates and comparison of calculated Binding energy with recently measured binding energies from The Atomic Mass Evaluation 2020. A total of 254 stable nuclides binding energies are compared. Statistical model calculations are presented for spin distribution of fusion cross-section for different diffusive parameters for two different reactions are shown and nuclear level density using different formalisms are also presented

The Neutron Scattering Cross Section and Angular Distribution Measurement Program at LANL

Neutron scattering cross sections and angular distributions are leading terms in descriptions of neutron transport through any system. Despite the fundamental importance of nuclear data on these quantities, significant gaps in understanding and lack of experimental data persist in heavier elements and down to lighter structural materials, such as iron and aluminum. Recent measurements on carbon have also shown definitive proof that the neutron angular distribution can change with respect to the emission angle of γ-rays from inelastic scattering, thereby complicating γ-tagged measurements of inelastic neutron scattering. In this work, we describe the emerging program at Los Alamos National Laboratory for measurements of neutron scattering cross sections and neutron, γ-ray, and correlated n-γ angular distributions utilizing liquid scintillator detectors and the Correlated Gamma-Neutron Array for Scattering (CoGNAC) of CLYC scintillators. Currently, these detectors are operated simultaneously with the in-progress array of CLYC detectors in an inverted position, and data analysis techniques are being developed to span scattering measurements from light nuclei up through actinides. Preliminary results for measurements on 12C, 27Al, and 56Fe are presented here with a description of the analysis methods applied and anticipated capabilities of the full-scale detection system.

Effect of correlation between cross sections and angular distributions in nuclear data of 63Cu on estimation of uncertainty of neutron penetration

Uncertainty in neutron reaction rates after penetrating a 608mm-thick copper benchmark experiment performed by the FNS facility of JAEA was estimated based on two different kinds of the Total Monte Carlo methods under random sampling methodology. 500 random nuclear data files were generated for 63Cu by the T6 code system with perturbing underlying model parameters. In the first method, these files were used directly to yield processed library preserving all the correlations among different physical quantities. In the second method, the random files populated by T6 were used but the angular distribution data were kept fixed to the non-perturbed nominal ones. It was found that the two methods gave the same neutron reaction rate after the 608 mm penetration of a copper, however uncertainty of the second method was larger than that of the first method. It shows that the correlation between total cross section and angular distribution of elastic scattering at 0 degree, which stems from Wick’s inequality, affects uncertainty of the calculated neutron reaction rate. The result is consistent with the case of 28Si on deep penetration of thick concrete problem previously reported by the authors. It could be concluded that the uncertainty obtained by using the covariance files given in the ENDF-6 format may not give correct results for the uncertainty of neutron penetration calculation.

Heterogeneous Beliefs and the Phillips Curve

We establish a set of novel empirical facts concerning cross-section distributions of inflation expectations reported in surveys. Almost all the variation in expectations about their mean may be summarized via three factors we call disagreement, skew, and shape. We adopt a functional principal component regression approach to estimating forward-looking models of inflation that exploits the heterogeneity present in individual-level data. By using survey information more effectively, our approach reveals an enhanced role for expectations in inflation dynamics that is robust to lagged inflation, trend inflation, and supply factors. Our findings hold in similar form across two major economies.

Native Electrospray Ionization of Multi-Domain Proteins via a Bead Ejection Mechanism.

Native ion mobility mass spectrometry is potentially useful for the biophysical characterization of proteins, as the electrospray charge state distribution and the collision cross section distribution depend on their solution conformation. We examine here the charging and gas-phase conformation of multi-domain therapeutic proteins comprising globular domains tethered by disordered linkers. The charge and collision cross section distributions are multimodal, suggesting several conformations in solution, as confirmed by solution hydrogen/deuterium exchange. The most intriguing question is the ionization mechanism of these structures: a fraction of the population does not follow the charged residue mechanism but cannot ionize by pure chain ejection either. We deduce that a hybrid mechanism is possible, wherein globular domains are ejected one at a time from a parent droplet. The charge vs solvent accessible surface area correlations of denatured and intrinsically disordered proteins are also compatible with this "bead ejection mechanism", which we propose as a general tenet of biomolecule electrospray.

Assessment of fire exposure on the load bearing capacity of basement storey walls

This paper presents the numerical modelling of the fire exposure on structural element and its static analysis taking account of the material properties reduction due to elevated temperature.
 The reinforced concrete wall of basement storey was subjected to one side fire exposure.
 Advanced calculation methods were used to assess the fire exposure on the structural element as most reliable and approximate to fire test results. Thermal analysis was performed with LIRA-CAD software by the simulating of three main heat-transfer ways: thermal conductivity, convection and radiation. As a result of the thermal analysis, temperature distribution in the concrete and reinforcement parts of the structural element cross-section was obtained. The thermal analysis of the wall structural element was performed for 120 minutes in standard fire exposure. Reduction factors for the strength of concrete and reinforcement steel were determined based on the temperature distribution in the wall structural element cross-section. The cross-section is divided into a number of parallel zones of equal thickness where the mean temperature and the corresponding mean compressive strength is assessed according to the Zone method procedure. The fire damaged zone of thickness az at the fire exposed sides and reduced cross-section were obtained.
 Static analysis of the wall load-bearing capa-city was performed using the procedure applicable for normal temperature design. The Deformation method for normal temperature design taking to account concrete deformation was used. The Deformation method for normal design taken to account concrete deformation at every step of iteration was used. The reduced load-bearing capacity of the fire damaged wall taking into account residual concrete strength was calculated and relevant load-bearing capacity diagrams were determined.

Structural Fire Analysis of Beams and Slabs Using ANSYS and FEAST Software Program

In recent years, building fire has become more frequent event and fire accidents have increased all over the world. Major problem with fire is it provides very less time to handle the situation and due to elevated temperature, reduction in strength of structural member with increase in fire exposure time has been observed. To evaluate this reduced strength of structural members and design for fire load, it is necessary to have the parameters such as fire load, fire exposure time and temperature variation across the structural members. In this paper, evaluation of fire load, equivalent time of exposure and temperature distribution of beams and slabs using finite element analysis software FEAST and ANSYS has been done. For temperature variation, transient heat thermal analysis, in which temperature is increasing continuously over the time, is used. For this analysis, beams and slabs are exposed to surface fire on different surfaces and the temperature distribution of cross section has been evaluated. The results are compared and found to be matching with the European Standard procedure.

Optimization of Ti-6Al-4V ring rolling process by FE simulation using RSM

Ring rolling is a process to manufacture seamless rings. The process is characterised by high non-linearity, asymmetry, unsteady state and non-uniformities in plastic strain and temperature distribution in the ring cross-section. Inhomogeneities in distribution of plastic strain and temperature have significant effects on deformation behavior, microstructure and mechanical properties. Fishtail defect, one of the form defects, is also a major concern. In this study, a reliable coupled 3D thermo-mechanical finite element model of the ring rolling process was developed using dynamic explicit code in ABAQUS/Explicit environment. Nine simulations with different combinations of feed rate and rotational speed were ascertained using Central Composite Design (CCD). CCD model is an integral part of Response Surface Methodology (RSM). Strain and temperature heterogeneities and fishtail defect were predicted using the simulated models. Coefficient of Variation (CoV) was introduced as a heterogeneity index for strain and temperature analysis. The fishtail coefficient was used to quantify fishtail defect. ANOVA was carried to find out the significant factors and interactions affecting the ring rolling process. Feed rate was found to be the only significant factor in the range of parameters studied. Multi-response optimization was performed to find out the feed rate at which the process is most optimized with an aim to minimize both strain and temperature heterogeneity and fishtail defect. Feed rate of 1.61 mm/s was found to be the most optimized process parameter.

Structure and production mechanism of the enigmatic X(3872) in high-energy hadronic reactions

We calculate the total cross section and transverse momentum distributions for the production of the enigmatic chi _{c1}(3872) (or X(3872)) assuming different scenarios: c bar{c} state and D^{0*} {bar{D}}^0 + D^0 {bar{D}}^{0*} molecule. The derivative of the c bar{c} wave function needed in the first scenario is taken from a potential model calculations. Compared to earlier calculations of molecular state we include not only single parton scattering (SPS) but also double parton scattering (DPS) contributions. The latter one seems to give smaller contribution than the SPS one. The upper limit for the DPS production of chi _{c1}(3872) is much below the CMS data. We compare results of our calculations with existing experimental data of CMS, ATLAS and LHCb collaborations. Reasonable cross sections can be obtained in either c bar{c} or molecular D {bar{D}}^* scenarios for X(3872), provided one takes into account both directly produced D^0, bar{D}^0, as well as D^0, bar{D}^0 from the decay of D^*. However arguments related to the lifetime of D^* suggest that the latter component is not active.

Influence of a pinhole diameter on the experimental determination of critical power for femtosecond filamentation in air.

Filamentation of intense femtosecond laser pulses in optical media has attracted great attention due to its various unique characteristics and potential applications. It is an important task to determine the critical power for the filamentation especially in many applications, which can be obtained by evaluating the transmitted pulse energy through a pinhole located in the filamentation region as a function of input laser energy. The pinhole diameter is very crucial to the measurement. However, there is no report on the experimental determination of critical power for filamentation in air by using the pinhole method and the influence of the pinhole diameter on the determination. In this paper, we numerically and experimentally investigate the influence of pinhole diameter on the determination of the filamentation critical power. The obtained critical power tends to a reasonable value as the decrease of the pinhole diameter, because the transmitted energy through the pinhole with a smaller diameter is more sensitive to the change of energy distribution in the beam cross section during the beginning process of filamentation. Under our experimental condition, the pinhole diameter as small as ∼50 µm is applicable to be used to determine the critical power for filamentation of femtosecond laser pulses in air.

Magnetic neutron scattering from spherical nanoparticles with Néel surface anisotropy: atomistic simulations.

A dilute ensemble of randomly oriented non-interacting spherical nanomagnets is considered, and its magnetization structure and ensuing neutron scattering response are investigated by numerically solving the Landau-Lifshitz equation. Taking into account the isotropic exchange interaction, an external magnetic field, a uniaxial magnetic anisotropy for the particle core, and in particular the Néel surface anisotropy, the magnetic small-angle neutron scattering cross section and pair-distance distribution function are calculated from the obtained equilibrium spin structures. The numerical results are compared with the well known analytical expressions for uniformly magnetized particles and provide guidance to the experimentalist. In addition, the effect of a particle-size distribution function is modelled.

Effect of active cooling on the thermal effect of electromagnetic rail under single launch mode

In order to investigate the influence of active cooling on the rail thermal effect of electromagnetic gun under single launch mode, characteristics of the peak temperature, cross-section current density and temperature distribution, axial temperature distribution of rail with and without active cooling are simulated. In addition, the time-varying characteristics of the rail axial temperature distribution, the temperature time-varying characteristic in different temperature parts on the rail and the influence of the cooling water flow velocity on the temperature in different temperature parts are experimentally studied. The results show that during the launch, there is almost no difference between the rail peak temperature and its location with and without active cooling, and the peak temperature is basically located at the initial position of the armature. Without active cooling, the rail axial temperature distribution shows a trend of higher at the gun tail and lower at the gun muzzle. The current density and temperature distribution of rail cross-section show a trend of higher on the rail inner side and lower on the rail outer side, and the diffusion of heat lags behind the diffusion of current. Under the action of active cooling, the rail peak temperature will move to the muzzle along the armature moving direction, and there is a “thermal inversion” phenomenon. The rail cross-section temperature drops faster, and the lowest temperature region appears near the middle cooling channel. Active cooling has different effects on rail temperature in different temperature parts. In the high-temperature part, the rail temperature decreases monotonically with the increase of cooling water flow velocity, increasing the water velocity can accelerate the decline of rail temperature. In the middle-temperature parts, the variation trend of rail temperature is different with different water flow velocities. At low water velocity, the rail temperature increases gradually. When the water flow velocity is greater than 0.75 m/s, the phenomenon of “thermal inversion” will occur. i.e., the rail temperature increases first and then decreases. In the low-temperature part, “thermal inversion” will occur at different flow velocities, that is, the rail temperature increases first and then decreases. When the water flow velocity is greater than 1.0 m/s, the improvement of rail cooling effect will no longer be obvious. It is suggested that the appropriate water flow velocity is 0.75–1.0 m/s under the present experimental conditions.

Current Distribution and Kinetic Inductance of Coplanar Waveguide Transmission Lines

Analysis of superconducting circuits requires knowledge of current density distribution in the film cross section. This article aims to investigate the current density distribution in superconducting coplanar waveguides (SCPWs), a basic component with increasing use in microwave integrated circuits. In this regard, first, the CPW is mapped to a pair of parallel plates and the vector potential is described through the Green's function concept. Then, based on the Green's function and utilizing London's second equation, an integral equation is formed which yields the current density distribution. The procedure is verified by COMSOL Multiphysics software. Examining the current density for several SCPWs shows that as the gap is reduced, the SCPW experiences much more current density especially at the edges. Based on the proposed procedure, the kinetic inductance of SCPW is examined, which is another focus of the article. In this article, for several CPWs with different aspect ratios, the kinetic inductance is evaluated and discussed. Results show that as the ratio is increased, the kinetic inductance is decreased.

An analysis of crystallographic texture and residual stresses of aluminium alloy RSA-501 after selected processes of twist extrusion (TE)

This study presents the residual stress analysis for the twist extrusion (TE) process after the experiment and numerical simulation and the analysis of the crystallographic texture changes and changes in hardness before and after the TE process for an RSA-501 aluminium alloy (Al; Mg5%; Mn1.5%; Sc0.8%; Zr0.4%).Crystallographic textures were obtained with the PANAlytical Empyrean X-ray diffractometer. The stresses were measured by applying the X-ray method with the use of using the PROTO iXRD diffractometer.The use of severe plastic deformation processes in the mass of the material leads to a significant change difference in the stress distribution in the workpiece and a change in texture compared to the reference material. The stress distribution in the sample cross-section and stress values varied and depended on the stage of the twisting process to which the surface was subjected. The highest stress (about 600 MPa) appears at the peaks of the front surface when exiting the twist area die TE. Higher stress values at the edges of the specimen are caused by friction (deformation) of the material against the die surface. The TE process strengthened the highest crystallographic texture background level was 49%.The conducted tests and the obtained results allow the determination of the process parameters and critical areas of the sample by carrying out a numerical simulation.Microhardness increases due to the TE process and the largest values were observed at the edges. This phenomenon is confirmed by the numerical simulation results presented in this paper.

Next-to-next-to-leading order QCD corrections to Wbb¯ production at the LHC

The authors compute the next-to-next-to-leading order (NNLO) QCD corrections to the production of a W-boson in association with a bottom- quark pair at hadron colliders. This calculation is the very first $2$ \ensuremath{\rightarrow} $3$ process with a massive external particle to be studied at such a perturbative order. The authors present numerical results for the cross section and differential distributions for this process at the LHC with 8 TeV center-of-mass energy.

Hydrodynamic characteristics of grass swale runoff in Guanzhong area of Loess Plateau, Northwest China.

Grass swale has been widely used in sponge city construction, which can effectively improve the urban ecological environment. To explore the regulation mechanism of runoff in grass swale, runoff scouring experiment was carried out to study the hydrodynamic characteristics of runoff and the distribution of cross-section velocity under the combined conditions of five slopes (1%, 2%, 3%, 4%, 5%) and five scour flows (20, 30, 40, 50, 60 L·min-1). With the increases of flow rate and slope, flow velocity, Reynolds number and Froude number all increased gradually, while the Manning roughness coefficient and Darcy-Weisbach friction coefficient decreased gradually. The velocity (V) could be expressed as a power function V=0.3387Q0.555S0.6601 of flow rate (Q) and slope (S). The variation ranges of Reynolds number and Froude number were 1160.95-6596.82 and 0.17-1.21, respectively. The runoff flow patterns were all turbulent. The flow pattern was greatly affected by the slope. When flow rate and slope were small, they had great influence on friction coefficient. Under the experimental conditions, the Darcy-Weisbach friction coefficient was negatively correlated with Reynolds number. The velocity distribution of cross-section showed symmetrical distribution on both sides of the center. The maximum velocity point was located at the center of water surface. With the increases of flow rate and slope, the velocity contours of cross section gradually became dense and the gradient of the velocity change increased. Our results provide a theoretical basis for the design, application and hydraulic calculation of grass swale in the construction of sponge cities in loess areas, and reveal the runoff regulation mechanism by analyzing the hydraulic characteristics of grass swale runoff.

GLTC: A Metro Passenger Identification Method Across AFC Data and Sparse WiFi Data

In this paper, we investigate an efficient way for identifying passengers in a metro system across two heterogeneous but complementary trajectory data sources: AFC data recording two points per trip about when and where a passenger enters or leaves the metro system, and WiFi data recording a few points passed by a passenger in the way of some of his/her trips. The identification result can help us to complete individuals’ mobility, and benefits to lots of services, e.g., individual route choice analysis, epidemic case detecting and so on. The problem is similar to calculate the similarity between two trajectories from two data sources, where a trajectory refers to a sequence of points where a passenger appeared in a metro system on observed days. However, due to the small location space in a metro network, large number of passengers with similar travel pattern, and so on, there are lots of trip overlaps or point co-occurrences between different passengers. That results in a large number of passengers mismatched by existing trajectory similarity measurement. To address the problem, this paper proposes a novel global-local correlation based trajectory similarity measurement GLTC. Specifically, GLTC first extracts all overlapping trip pairs of two trajectories by considering the spatiotemporal inclusions from global level. Then it gets the similarity by aggregating each overlapping trip pair’s local similarity, which is calculated by considering some data-driven insights helpful to uniquely identify a passenger (e.g., uneven passenger flow distribution in different cross-sections of a metro network, the number of trips in same travel pattern of a trajectory, and so on). We evaluate GLTC based on real-world data, and the experimental result shows that GLTC outperforms other baselines.

Numerical investigation and entropy generation for flow boiling evaporation in U-bend tube heat exchanger with elliptical and circular cross-sections

• Entropy generation for flow boiling in a U-bend tube heat exchanger with the elliptical and circular cross-section. • Effect of mass velocities on entropy generation for flow boiling a in a U-bend tube heat exchanger. • Local entropy generation for flow boiling along the Length of the U-bend tube heat exchanger. • Effect of the bend on the flow pattern in the U-bend tube heat exchanger with an elliptical and circular cross-section. This paper presents the numerical analysis of entropy generation of two-phase flow boiling in a U-bend tube heat exchanger with the elliptical and circular cross-sections of the same hydraulic diameter for oriented downward flow. The entropy generation criterion due to pressure drop and heat transfer irreversibilities was utilized to measure the quality of energy transfer in the heat exchanger. For the purpose of comparison, the same geometrical parameters were used. The computations were implemented using computational fluid dynamics code for the operating parameters such as mass velocities ranging from 100 to 500 kg/m 2 s with respect to vapour qualities from 0.1 to 0.9 and a constant uniform heat flux of 10 kW/m 2 imposed on the tube’s outer surface. The results reveal that the U-bend tube heat exchanger with the elliptical cross-section performs better than the circular cross-section due to the lower entropy generations obtained in the elliptical cross-section compared to the circular cross-section. The effect of bend on liquid and vapour phase distribution in circular and elliptical cross-sections was illustrated by the flow pattern, just before and after the bend. The flow patterns formed after the bend were quite different from the ones formed before the bend. For the elliptical and circular cross-sections, the flow patterns were observed to be almost the same with the fluids taking the shape of the cross-section. The numerical calculations were validated and found to be consistent with what was found in the open literature.