PosgenPy: An Automated and Reproducible Approach to Assessing the Validity of Cluster Search Parameters in Atom Probe Tomography Datasets

One of the main capabilities of atom probe tomography (APT) is the ability to not only identify but also characterize early stages of precipitation at length scales that are not achievable by other techniques. One of the most popular methods to identify nanoscale clustering in APT data, based on the density-based spatial clustering of applications with noise (DBSCAN), is used extensively in many branches of research. However, it is common that not all of the steps leading to the selection of certain parameters used in the analysis are reported. Without knowing the rationale behind parameter selection, it may be difficult to compare cluster parameters obtained by different researchers. In this work, a simple open-source tool, PosgenPy, is used to justify cluster search parameter selection via providing a systematic sweep through parameter values with multiple randomizations to minimize a false-positive cluster ratio. The tool is applied to several different microstructures: a simulated material system and two experimental datasets from a low-alloy steel . The analyses show how values for the various parameters can be selected to ensure that the calculated cluster number density and cluster composition are accurate.

Numerical modeling of bulk flow on a pelletizing disc in different rotational regimes

Pelletizing processes are used in various industries to agglomerate fine materials. Investigation of this process is important for optimizing corresponding equipment and machines. In this article the particle-based discrete element method is used to simulate the particle behavior of a dry material on an inclined rotating disc (pelletizing disc). The process is modelled in different rotation regimes and by varying the inclination angle of the disc. Qualitative model verification is performed by a comparison of numerical simulations with experimental data. Contact data is used to analyze the flow mode of the simulated material and for detecting critical rotation speeds.

A generalized stress correction scheme for the MEB rheology: impact on the fracture angles and deformations

A generalized damage parameterization is developed for the Maxwell Elasto-Brittle (MEB) rheology that reduces the growth of residual errors associated with the correction of super-critical stresses. In the generalized stress correction, a decohesive stress tensor is used to bring the super-critical stresses back on the yield curve based on any correction path. The sensitivity of the simulated material behaviour to the magnitude of the decohesive stress tensor is investigated in uniaxial compression simulations. Results show that while the decohesive stress tensor influences the short-term fracture deformation and orientation, the long-term post-fracture behaviour remains unchanged. Divergence first occurs when the elastic response is dominant followed by post-fracture shear and convergence when the viscous response dominates – contrary to laboratory experiment of granular flow and satellite imagery in the Arctic. The post-fracture deformations are shown to be dissociated from the fracture process itself, an important difference with classical Viscous Plastic (VP) models. Using the generalized damage parameterization together with a stress correction path normal to the yield curve brings the simulated fracture angles closer to observations (from 40–50° to 35–45°, compared to 20–30° in observations) and reduces the growth of errors sufficiently for the production of longer-term simulations.

EDM process through mathematical model

<span>EDM is a well-established hole machining option with various advantages due to non-contact characteristics of the process. However, knowledge about the process is not enough for its more improvements. Exprimenal studies are costly and time consuming because of the complex nature of process. Therefore, process modeling is a good alternative to reduce the experimental expense related to the technology. This paper studys EDM process through mathematical model, which includes the precise insight into the interactive behavior of EDM system. The ignition, discharge and recovery phases of the model have been developed through MATLABs time domain analysis. Simulation result shows good agreement with expected profile of EDM spark. To verify the model, simulated material removal rates (MRRs) from series of simulation are compared with the experimental ones reported by previous researcher. Ability of the model to predict the dynamic behavior profile of the EDM system is successfully confirmed by low average percentage error in predicting MRR.</span>

Non-destructive testing of arbitrarily shaped refractive objects with millimetre-wave synthetic aperture radar imaging

Millimetre-wave (mmW) imaging is an emerging technique for non-destructive testing. Since many polymers are transparent in this frequency range, mmW imaging is an attractive means in the testing of polymer devices, and images of relatively high resolution are possible. This contribution presents an algorithm for the precise imaging of arbitrarily shaped dielectric objects. The reconstruction algorithm is capable of automatically detecting the object's contour, followed by a material-sensitive reconstruction of the object's interior. As an example we examined a polyethylene device with simulated material defects, which could be depicted precisely.

Optimalisasi Geometri Wedge pada Pesawat Teleterapi 60Co

<p class="AbstractEnglish"><strong>Abstract</strong>: In RSUD Dr. Moewardi available wedge angle of 15°, 30°, 45°, and 60°. This research simulates with Monte Carlo N-Particle eXtended Version (MCNPX) computer software to determine the geometry of the wedge that produces the isodose angle of 20°, which is hoped to be applied to therapy of organ tilt of 20 ° in some cases of cervical cancer. In simulation obtained the value of the wedge factor of isodose angle of 20° and distribution of dose rate. The simulated material of wedge is Lead-Antimony Alloy. Verification of the simulation result was done by measuring the wedge factor of angle of 30° and 60°, the simulation result was validated with result of measurement experiment on ⁶⁰Co teletherapy in RSUD Dr. Moewardi Surakarta. The relative error between simulation and measurement experiment of wedge angle of 30° is 8.84% and angle of 60° is 4.35%. The relative error is small to convince the researcher to develop a simulation at an isodose angle of about 20°. From the simulation results obtained isodose angle 20.3° of Lead-Antimony Alloy material with geometry is length 16 cm, width 14.9 cm, thick 0.83 cm, the value of the angle α of 3.2°. Wedge factor of isodose angle of 20.3 ° is (0.68 ± 0.01). Wedge isodose angle of 20.3° if used in therapy in an organ tilt about 20 ° gives dose rate enough uniform.</p><p class="KeywordsEngish"> </p><p class="AbstrakIndonesia"><strong>Abstrak </strong><strong>:</strong>. Di RSUD Dr. Moewardi tersedia <em>wedge </em>untuk sudut 15°, 30°, 45°, dan 60°. Penelitian ini mensimulasikan dengan software computer <em>Monte Carlo N-Particle eXtended Version</em> (MCNPX) untuk menentukan geometri <em>wedge </em>yang menghasilkan sudut isodosis 20°, dimana diharapkan dapat diaplikasikan pada terapi organ dengan kemiringan 20° di beberapa kasus kanker serviks. Besaran yang diperoleh dari simulasi adalah nilai faktor transmisi <em>wedge </em>sudut isodosis 20° dan distribusi laju dosis serap penggunaan <em>wedge </em>tersebut. Bahan <em>wedge</em> yang disimulasikan adalah <em>Lead-Antimony Alloy</em>. Verifikasi hasil simulasi dilakukan dengan pengukuran faktor <em>wedge</em> pada sudut isodosis 30° dan 60°, hasil simulasi divalidasi dengan hasil pengukuran langsung pada pesawat teleterapi ⁶⁰Co di RSUD Dr. Moewardi Surakarta. Kesalahan antara simulasi dan pengukuran langsung pada isodosis sudut 30° adalah 8,84 % dan pada sudut 60° adalah 4,35 %. Kesalahan relatif tersebut cukup kecil sehingga meyakinkan peneliti untuk menyusun simulasi pada sudut sekitar 20°. Dari hasil simulasi diperoleh isodosis sudut 20,3° dari bahan <em>Lead-Antimony Alloy</em><em> </em>dengan geometri yaitu panjangnya 16 cm, lebarnya 14,9 cm, tebalnya 0,83 cm, nilai sudut α sebesar 3,2°. Faktor <em>wedge</em> sudut 20,3° sebesar (0,68 ± 0,01). <em>Wedge</em><em> </em>sudut isodosis<em> </em>20,3° bila digunakan dalam terapi pada organ dengan kemiringan 20° memberikan laju dosis yang cukup seragam.<strong></strong></p><p class="KataKunci"> </p>

Influence of the Residual Stress on Mechanical Properties of Ductile Materials by Simulating Small Punch Test

This paper describes an approach to identify the influence of mechanical properties of the materials under the condition of containing residual stress. The numerical method of simulating small punch test (SPT) is used to determine the material response under loading. The simulated material behavior of the specimen is based on the ductile elastoplastic damage theory of Gurson, Tvergaard and Needleman (GTN). The residual stress can be prefabricated on the specimen by loading and unloading. By comparing the original specimen with the specimen contains residual stress, the change of the mechanical properties of the materials can be studied. The results of simulation indicate that the material properties decrease with the increase of the residual stress.

Validation of Simulated Material Flow in Aluminium Hot Extrusion with a Novel Visualisation Method

Commonly used visualisation methods for observing material flow during extrusion are either labor intensive, prone to loss of the tracer pattern or subject to different flow behaviour than occurs in practice. A novel visualisation method using a copper mesh inlay and computer tomography was developed and used to visualise the flow behaviour of partially extruded EN AW-6082 aluminum billets. In parallel with the physical experiments, a finite element (FE) model was developed and compared with the experiments. The material flow was readily observable from the computer tomography images and the FE model data closely matched the experimental results.

Use of Simulated Thermal Cues for Material Discrimination and Identification with a Multi-Fingered Display

Thermal cues provide information about the thermal properties of an object held in the hand. These cues can be simulated in a thermal display and used to assist in identifying the object. Two experiments were conducted using a thermal display that simulated the cues associated with contact with different materials. The thermal contact model was based on a semi-infinite body model that included thermal contact resistance and blood perfusion. Its performance was evaluated in two experiments, the first of which involved discriminating between simulated materials, and in the second, subjects were required to identify simulated materials based on the thermal cues presented to one, three, or five fingers. The results from the first experiment indicated that when the temperature profile associated with contact with a real material is presented to the finger, subjects can use this cue to discriminate between simulated materials. Their performance on this task is comparable to that achieved with real materials with similar thermal properties. In the second experiment, the accuracy with which subjects identified a simulated material based on thermal cues improved as the number of fingers stimulated increased, suggesting that spatial summation of cold occurs when the area stimulated is noncontiguous. However, most of the improvement in identifying materials occurred when the display presented thermal cues to three as compared to one finger, with little further enhancement in performance when five fingers were stimulated. These results indicate that thermal displays can be used effectively to present information about the material composition of objects in virtual environments.