Cylindrical Source Research Articles

A new laser welding method of two transparent plastic parts based on reflector assisted method

It is a challenging work to joint two transparent plastic parts using traditional laser welding because the absorptivity of transparent plastic on short wavelength (800–1000 nm) laser energy is very low. During the laser welding of two transparent plastic parts, although laser absorber and long wavelength (1600–2000 nm) laser can obtain the high-strength weld joint, the problems of unattractive weld joint or pollution will occur when laser absorber is used, and the laser energy utilization coefficient is about 70% when long wavelength laser energy is used. To address this issue, this paper proposes a new production method for the absorber-free laser welding of two transparent plastic parts based on reflector assisted method. From three-dimensional thermal model, it can be found that the simulation data of the modified Gauss cylindrical body heat source show better agreement with the experimental result than those of Gauss surface heat source and Rotary-Gauss body heat source. In addition, for the same the weld joint width on the contact surface, the reflector assisted laser welding method can decrease the laser energy consumption by about 20%. Moreover, the maximum shear force of weld joint can be up to 1315 N. Under the same process parameters, the reflector assisted method can increase the shear strength of weld joint by 15.3%. Hence, the reflector assisted method has good application and promotion value in laser welding two transparent plastic parts.

Study of the matrix composition effect on gamma spectrometry analysis using Monte Carlo simulation: application for soil to crop transfer factor determination

Abstract Self-absorption effect has a significant impact on gamma spectrometry measurement for the highly precise determination of the radionuclides activity. Among the main factors affecting the self-absorption effect especially at low gamma energies is the matrix composition of the sample. For this purpose, we studied the matrix composition effect on the self-absorption correction for plant and soil matrices using a Monte Carlo simulation model, composed of High Purity Germanium (HPGe) detector and a cylindrical geometry source. The simulated configuration model was validated by comparison of simulated full energy peak efficiency (FEPE) values with the experimental ones using a standard radioactive solution, covering large interval gamma energies in the range of 59.54–1836.12 keV. The results show that the FEPE values of low gamma energies are affected by the matrix composition, where in the soil matrix the FEPEs decreased by 36% and only by 1% in the plant matrix. The Monte Carlo results were applied in order to accurately calculate the transfer factor of the environmental radionuclides 226Ra, 232Th and 40K from soils to several crops, mustard, artichoke and fennel through their specific activities.

Sound field separation technique for nonplanar sources based on field prediction by using statistically optimized near-field acoustic holography

For the sound field of cylindrical or compact sources, the current sound field separation technique (FST) based on statistically optimized near-field acoustic holography (SONAH) uses planar wave for separation, and the effects of different wave functions have not yet been studied. However, the non-conformal problem between the hologram surface and the sound sources commonly has a risk of accuracy reduction. Here, an FST for nonplanar sources based on SONAH is proposed to solve this problem. First, considering that field prediction of near-field acoustic holography will attenuate errors, noise immunity of the FST is effectively improved in a noisy environment by moving the reconstruction surface to the prediction area. Subsequently, the appropriate conformal wave function is determined by combining the shape of the sound source and is substituted into the improved method in the first step to separate the free-field sound pressure. Finally, simulations, experiments using loudspeakers, and a cylindrical experiment platform prove the effectiveness of the proposed method, which can greatly improve the adaptability and reliability of the FST in nonplanar sound sources in mechanical systems.

A comprehensive investigation of PCM based annular thermoelectric generator for energy recovery: Energy conversion characteristics and performance evaluation

Annular thermoelectric generators (ATEG) are increasingly attracting attention and are pivotal in thermal energy recovery due to their unique characteristics, which can be perfectly adapted to cylindrical heat sources. Considering the efficient thermal management and power generation of thermoelectric generator (TEG), phase change material (PCM) can be integrated with the cold side of TEG as a favourable cooling medium to meet its functional requirements. However, previous studies have focused on the intrinsic connection between flat-plat TEG and PCM, while the impact of PCM on ATEG has not been systematically explored. In the present study, an annular thermoelectric generator with PCM (ATEG-PCM) under a pulsed heat source is proposed, and its dynamic characteristics and energy distribution are evaluated. The effects of PCM parameters such as height, latent heat and melting temperature are comprehensively explored from multi-index, including PCM temperature, liquid fraction, temperature difference, output power, energy and exergy efficiencies. Furthermore, a comparative investigation of ATEG-PCM, PCM-ATEG where PCM is applied on the hot side, and ATEG without PCM is further carried out to clarify the coupled mechanism of PCM on thermal management and power generation enhancement of ATEG. The results indicate that the energy efficiency of ATEG-PCM has saturated at PCM height of 10 mm to 12 mm, while the exergy efficiency merely slightly increases. Especially, the PCM melting temperature merely affects the time at which PCM initiates to change from solid state to liquid state, without affecting the total energy efficiency of ATEG-PCM. Furthermore, the comparison analysis determines that ATEG-PCM deserves more attention, judging by thermal management and power generation. This work not only contributes to the understanding of the coupling mechanisms between PCM and ATEG but also provides a research direction for energy recovery in PCM based ATEG hybrid system.

Investigation of Fludioxonil Reduction Using Non-Thermal Atmospheric Plasma through Experimental Simulation

In this study, the effect of non-thermal atmospheric plasma (NTAP) treatment on the reduction of residual fludioxonil (C12H6F2N2O2, 4-(2,2-difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile) was investigated through experimental simulation. Fludioxonil is known for its high residual concentration on fruits and vegetables. To simulate residual fludioxonil reduction in the storage location prior to consumption of fruits or vegetables by consumers, we designed an experimental setup utilizing a gas distribution system and a cylindrical dielectric barrier discharge (DBD) plasma source. A cylindrical DBD plasma source was adopted to produce the plasma activated chemical species (O3). To evaluate the effect of plasma treatment on the reduction of residual fludioxonil, experiments were performed under three different conditions: varying concentrations and treatment times of O3, as well as the surface roughness of microscope slide glass. Based on the results, 10 min plasma treatment with an O3 concentration of 11.89 μL/L, which showed a 58.5% reduction rate, is recommended. The O3 concentration has a higher priority than the treatment time for reduction rates of residual fludioxonil.

Detecting pipeline leakage using active distributed temperature Sensing: Theoretical modeling and experimental verification

This paper presents a feasibility study on leak detection of buried pipelines using the active distributed temperature sensing (ADTS) method. The proposed solution involves the use of actively heated fiber optic (AHFO) cables arranged parallel to the pipelines, allowing for changes in the thermal properties of the surrounding soil to be captured and correlated with leakage accidents. This problem was modeled as an infinite cylindrical or linear heat source buried in porous media with seepage flowing inside. AHFO sensors were designed to verify the proposed method through scale-reduced model tests. The fiber optic temperature sensing technology based on optical frequency domain reflectometry (OFDR) was used to continuously monitor temperature profiles. The test results demonstrate that the ADTS solution has greatly improved the accuracy of passive temperature sensing methods. The feasibility of the solution was evaluated regarding different levels of leakage estimation, namely, identification, location, and quantification. This paper presents the first attempt to monitor the infiltration process associated with pipeline leaks using the AHFO-OFDR technique, which is a reliable method for structural health monitoring of underground pipelines.

Laser welding simulation of large-scale assembly module of stainless steel side-wall

Due to the advantageous characteristics of laser welding technology, it is being increasingly used for constructing stainless steel rail vehicles. It can improve the appearance of a vehicle, enable designs with a relatively high degree of flatness, and ensure higher-quality connections between different parts of a vehicle. Moreover, it can improve the strength and stiffness of the components of the vehicle. In this study, a large-scale assembly module of a stainless steel side-wall was considered as the research object. The combined heat source model of a Gaussian heat source and a cylindrical volume heat source was used to obtain the heat source parameters of laser welding to match the experimental data. Based on the thermal cycle curve method (TCCM), the influence of the number of weld segments and mesh divisions of the local model on the efficiency and accuracy of laser welding simulations was investigated. Thereafter, the research results were applied to the welding simulation of the whole side-wall module. The shape of the molten pool obtained using the combined heat source was closer to that of the experiments (error < 10%), demonstrating the accuracy and effectiveness of the developed the heat source model for laser welding simulation. For local model laser welding using the TCCM, a coarse mesh was used, and the weld was divided into four segments, and highly accurate results were obtained. This calculation time was only 5.97% of that of a moving heat source in case of the thermo-elastic-plastic method (TEPM). Residual stress and welding deformation of the stainless steel side-wall module were calculated according to actual process parameters and the results of local model simulation. Residual stress was discontinuously distributed at the weld segments, and it only slightly influenced the overall stress distribution. The maximum residual stress (462.15 MPa) occurred at the weld of the large crossbeam. Welding eight small and two large crossbeams influenced the deformation change and the maximum deformation (1.26 mm) appeared in the middle position of the left side-wall. The findings of this study show that the TCCM has high calculation accuracy and is sufficiently economical for predicting laser welding of large structures.

Establishing zone of influence (ZOI) for cylindrical heat source in dry sand

ABSTRACT Safe, proper design and installation of several thermo-active structures necessitate establishing zone of extent of heat migration in soil mass. This zone is termed as ‘zone of influence’, ZOI, and its determination is imperative to avoid unwanted situations, which could be threat to the surrounding structures. This is where in-situ monitoring of the temperatures in the near- and far-field would be quite prudent, however would be an expensive exercise. Therefore, COMSOL Multiphysics® was employed to determine the ZOI. Nevertheless, the relative efficiency of these tools in yielding the ZOI remains a big question, and requires results from experiments to validate. Hence, an attempt was made in this study to establish the ZOI of cylindrical heat source, which replicates geothermal energy pile in dry sands, by adopting novel experimental methodology. ZOI has been established for cylindrical heat source experimentally and numerically. Furthermore, unique mathematical equation has been developed by using regression analysis.

Mapping the weak field limit of scalar-Gauss-Bonnet gravity

We derive the weak field limit of scalar-Gauss-Bonnet theory and place novel bounds on the parameter space using terrestrial and space-based experiments. In order to analyze the theory in the context of a wide range of experiments, we compute the deviations from Einstein gravity around source masses with planar, cylindrical, and spherical symmetry. We find a correction to the Newtonian potential around spherical and cylindrical sources that can be larger than PPN corrections sufficiently close to the source. We use this to improve on laboratory constraints on the scalar-Gauss-Bonnet coupling parameter $\Lambda$ by two orders of magnitude. Present laboratory and Solar System bounds reported here are superseded by tests deriving from black holes.

Alpha dose modeling in diffusing alpha-emitters radiation therapy-Part I: single-seed calculations in one and two dimensions.

Diffusing alpha-emitters Radiation Therapy ("DaRT") is a new method, presently in clinical trials, which allows treating solid tumors by alpha particles. DaRT relies on interstitial seeds carrying μCi-level 224 Ra activity below their surface, which release a chain of short-lived alpha emitters that spread throughout the tumor volume primarily by diffusion. Alpha dose calculations in DaRT are based on describing the transport of alpha emitting atoms, requiring new modelingtechniques. A previous study introduced a simplified framework, the "Diffusion-Leakage (DL) model", for DaRT alpha dose calculations, and employed it to a point source, as a basic building block of arbitrary configurations of line sources. The aim of this work, which is divided into two parts, is to extend the model to realistic seed geometries (in Part I), and to employ single-seed calculations to study the properties of DaRT seed lattices (Part II). Such calculations can serve as a pragmatic guide for treatment planning in future clinicaltrials. We derive a closed-form asymptotic solution for an infinitely long cylindrical source, and extend it to an approximate time-dependent expression that assumes a uniform temporal profile at all radial distances from the source. We then develop a finite-element one-dimensional numerical scheme for a complete time-dependent solution of this geometry and validate it against the closed-form expressions. Finally, we discuss a two-dimensional axisymmetric scheme for a complete time-dependent solution for a seed of finite diameter and length. Different solutions are compared over the relevant parameter space, providing guidelines on their usability and limitations. We show that approximating the seed as a finite line source comprised of point-like segments significantly underestimates the correct alpha dose, as predicted by the full two-dimensional calculation. The time-dependent one-dimensional solution is shown to coincide to sub-percent-level with the two-dimensional calculation in the seed midplane, and maintains an accuracy of a few percent up to ∼2mm from the seed edge. For actual treatment plans, the full two-dimensional solution should be used to generate dose lookup tables, similarly to the TG-43 format employed in conventional brachytherapy. Given the accuracy of the one-dimensional solution up to ∼2mm from the seed edge it can be used for efficient parametric studies of DaRT seedlattices.

Influence of Cluster Sources on the Growth Mechanisms and Chemical Composition of Bimetallic Nanoparticles

Metal nanoparticles are omnipresent in today’s applied and fundamental research. Both wet-chemical as well as physical procedures for their fabrication are well-established, where the latter is of particular interest as they supply surfactant-free particles. Particle growth has been investigated for several decades, but due to its complexity, involving kinetic and dynamic processes on various length and time scales, often only phenomenological rules of thumb are available. In this study, we report on bimetallic AgAu nanoparticles and demonstrate how the additional degree of freedom of the chemical composition can be used to derive information about how and where the particles grow, depending on two different cluster source types (hollow magnetron vs laser vaporization). The chemical composition is quantified on the single-particle level using electron-induced X-ray spectroscopy (STEM-EDS) and shows significant differences for the two fabrication routes. Based on molecular dynamics and Monte Carlo simulations, we derive that for hollow cylindrical sources both the mean particle size and the chemical composition are determined within the plasma region, where particles not only grow but also evaporate low-boiling silver. The comparably large plasma plays a decisive role here, as opposed to planar magnetron or laser vaporization sources, where no such evaporation is observed. These results shed light into the complex cluster growth and help understanding and optimizing nanoscale fabrication processes.

Оценка мощности дозы гамма-излучения от контейнера с РАО

Assessment of personnel exposure from various operations performed inside radioactive waste (RW) storage facilities is seen as an essential task under the safety assessment of such storage facilities. However, radiation scattered from the structures inside the premises of RW storage facilities is often not taken into account in the assessment of personnel exposure doses. Characteristics of the radiation field from RW containers have been calculated under a few studies. For example, the radiation fields were calculated based on some engineering approaches and the Monte Carlo method using specialized software. This paper focuses on the Monte Carlo calculations of the gamma radiation dose rate from a volumetric cylindrical source located in a RW storage facility. The study evaluates the contributions of scattered radiation from the walls, floor and ceiling of a storage premise to the absorbed dose also considering the case of a flooded floor. The paper compares the calculated radiation dose rates with those evaluated by integrating the source volume for axisymmetric geometries with no account taken of scattered radiation. The calculations show that depending on the distance from the source if no scattered radiation from all the wall, floor and ceiling structures of a storage facility is accounted for, the dose rate may be underestimated by up to two times.

Numerical Simulation of Temperature Field and Melt Pool Characteristics of CP-Ti Manufactured by Laser Powder Bed Fusion

A coupled heat source model that combined a Gauss surface heat source with a Gauss cylindrical volumetric heat source was introduced to simulate temperature field distribution and melt pool characteristics using a finite element simulation (FEM) method for the deep and narrow melt pools formed in laser powder bed fusion (L-PBF) aiming at commercial pure titanium (CP-Ti). For comparison, the same simulations using the Gauss surface heat source model and the double ellipsoid heat source model were also performed. The simulated melt pool geometries using the coupled heat source model match well with the measurements, with an average error of 1% for the melt pool depth and 7% for the width. Based on the single-track experimental results, it was found by comparing the simulated results from the three heat source models that the coupled heat source model had better accuracy than the other two. Then, the temperature field and the melt pool geometries of CP-Ti fabricated at different laser power levels from 300 W to 500 W and scanning speeds from 600 mm/s to 4000 mm/s were simulated. According to the simulated maximum temperature and geometries of the melt pool, a suitable process parameters map for CP-Ti was obtained. The reported experimental results agree well with the simulated map. The coupled heat source model is more accurate and applicable for the deep and narrow melt pools formed during L-PBF.

Industrially deposited hard and damage resistant W-B-C coatings

The article presents composition-dependent structural and mechanical properties of sputter-deposited W-B-C coatings. The industrial batch-coater employs a cylindrical sputter source fitted with a segmented target composed of tungsten, boron carbide, and carbon segments. Stationary and single-axis rotation depositions are carried out to understand the differences between laboratory-like and industrial preparation of the coatings. The W-B-C coatings are studied over a broad range of chemical compositions. Coatings are mainly amorphous, but at specific chemical compositions, they tend to form the short-range ordered tungsten borides or nanocrystalline cubic tungsten carbide. The amorphous coatings exhibit high hardness (24 GPa), high elastic modulus (440 GPa), no residual stress, and outperform the TiN and AlCrN in the damage resistance determined by the instrumental indentation test.

Multi-photon time-of-flight MLEM application for the positronium imaging in J-PET

Abstract We develop a positronium imaging method for the Jagiellonian PET (J-PET) scanners based on the time-of-flight maximum likelihood expectation maximisation (TOF MLEM). The system matrix elements are calculated on-the-fly for the coincidences comprising two annihilation and one de-excitation photons that originate from the ortho-positronium (o-Ps) decay. Using the Geant4 library, a Monte Carlo simulation was conducted for four cylindrical 22Na sources of β+ decay with diverse o-Ps mean lifetimes, placed symmetrically inside the two JPET prototypes. The estimated time differences between the annihilation and the positron emission were aggregated into histograms (one per voxel), updated by the weights of the activities reconstructed by TOF MLEM. The simulations were restricted to include only the o-Ps decays into back-to-back photons, allowing a linear fitting model to be employed for the estimation of the mean lifetime from each histogram built in the log scale. To suppress the noise, the exclusion of voxels with activity below 2% – 10% of the peak was studied. The estimated o-Ps mean lifetimes were consistent with the simulation and distributed quasi -uniformly at high MLEM iterations. The proposed positronium imaging technique can be further upgraded to include various correction factors, as well as be modified according to realistic o-Ps decay models.

Sensitivity analysis of boehmite alumina nanofluid in a novel cylindrical heat sink with hybrid helical-straight minichannels using the taguchi method and statistical analysis

In the present study, heat transfer, fluid flow characteristics and entropy generation of boehmite alumina nanofluid in a cylindrical heat sink with hybrid helical-straight minichannels are simulated and examined numerically. Attention is focused to determine the influential design factors and the optimal levels for output parameters. The design factors are selected at four levels including the helix angle of minichannels, the Reynolds number, the helical length ratio, the nanoparticles shape and the volume fraction of nanoparticles. Sensitivity analysis of design factors was carried out using the Taguchi method with L16 orthogonal array and statistical analysis of variance (ANOVA). The Nusselt number (Nu), the Fanning friction factor (f), the total hydrothermal performance factor (JF), the rate of entropy generation (Sgen), and the entropy generation number (Ns), are selected as the output parameters. The obtained results revealed that the helix angle of minichannels and the Reynolds number play a vital role in Nu, JF, and Sgen, with the sum of the contribution ratios of the two factors 82.57%, 68.16%, and 81.97%, respectively. Also, the helix angle of minichannels has a 50.67% contribution in Ns. The optimized model is improved by 94.5%, 37.5%, 84%, 63.4%, and 64.1% for Nu, f, JF, Sgen, and Ns, respectively, compared with the original model. Two optimal combinations for JF and Sgen are acquired as A2B3C1D4E4 and A1B3C4D4E4, respectively. Overall, the hybrid helical-straight minichannel with boehmite alumina nanofluid can be beneficial as a preferred cooling for the cylindrical heat sources.

Thermal investigations on eccentric sleeve grinding of fibre reinforced composites

Thermal driven damages are one of the major concerns while machining fibre reinforced polymer (FRP) composites. Though cutting of fibre-matrix system using abrasive grains exhibited promising outcomes, conventional surface grinding (CSG) still poses the barriers of undesired surface damages on FRPs. High magnitudes of grinding forces due to continuous interaction of cutting edges, particularly at higher levels of depths of cut, leads to successive accumulation of heat flux in CSG and thereby, the thermal damages on fibre-matrix system may get enhanced. Eccentric Sleeve Grinding (ESG) is a unique grinding strategy proposed for FRPs, which adopts a progressive-intermittent cutting scheme capable of reducing grinding temperature and thermally triggered damages. Main focus of this paper is to investigate the thermal aspects of eccentric sleeve grinding and develop an analytical model for grinding temperature in ESG. Considering the unique cutting scheme followed by abrasive grains during their interaction with FRP, a progressively distributed-moving heat source model is introduced. The model is capable of predicting grinding temperature on FRP surfaces, during CSG as well as ESG at various grinding conditions, and thereby illustrates the merits of proposed ESG scheme. A thermal flux model using a cylindrical surface source is also introduced to study the temperature generated at the grinding wheel during its interaction with FRP. This paper also presents an attempt of 3D grinding simulation, both in ESG and CSG mode, with realistic modelling of CFRP and grinding wheel using Composite Modeler in ABAQUS. Thorough experimental investigation, incorporating the measurement of grinding force and temperature, is also covered to demonstrate ESG process and its thermal performance on Carbon Fibre Reinforced Polymer (CFRP) composites. 30 % and 10 % reduction, respectively, in average and peak grinding temperature during ESG of CFRP and subsequent reduction in thermal damages opens great avenues for industrial applications.

General framework for calculating irradiance distributions of symmetric surface sources.

Symmetries in system modeling can be exploited to obtain analytical results on the system behavior and to speed up computations using the symmetric model. This work explores the use of symmetries in radiant surfaces for calculating the induced irradiance distributions by developing a general mathematical expression. The obtained model is applied to flat, cylindrical, and spherical sources to obtain explicit expressions. An experimental evaluation of the flat source is carried out and compared with a traditional point source, and the obtained procedure for the flat scenario is compared with the direct integration approach, which shows an improvement in the computation time of at least two orders of magnitude with a relative root mean square error of less than 10%. The results show that the proposed approach enhances short-range predictions for extended sources. To demonstrate the impact of this in optical wireless communications we have outlined a few applications.

Semi-analytical modeling of large-scale water tank for seasonal thermal storage applications

Buildings consume large amount of energy for cooling in summer and heating in winter. A renewable energy-based district heating using seasonal thermal storage can better serve for a lower carbon space heating for buildings. The research objective is to propose a first semi-analytical model of large-scale water tank storage as an efficient and flexible tool for further development of TES. A new idea of “three-zone method” is proposed for detailed heat and mass flow inside water storage with least increase in computational burden and better capture of internal non-uniform thermal distribution. All three modes of charging, discharging and standby are modeled separately with high flexibility. A modified finite cylindrical source model for TES was proposed, for the first time, for transient heat transfer in the ground, which is inspired by analytical model of ground source heat pump. A complete comparison was made between the new semi-analytical model and validated reference data, which shows a good match in temperature profile in different locations. This study will pave a way for a further systematical study on seasonal thermal storage.

Cylindrical partially coherent scalar sources.

Partially coherent scalar sources with cylindrical symmetry radiating outwards are introduced. Homogeneous cross-spectral densities are shown to possess angularly modulated Hankel modes, whose amplitudes are subject to a filtering process during propagation. Simple criteria for treating such sources are given. For the case of an incoherent cylinder, the number of effective modes is found and spatial coherence is shown to appear in the radiated light. The radial coherence of the radiated field is then examined. Non-homogeneous cylindrical sources are also introduced.