Single-Grain Virtualization for Contact Behavior Analysis on Sand

A methodology for virtualizing irregularly shaped grains is described here. The principle, largely inspired by computed tomography, is simple and accessible because only the three-dimensional (3D) outline of the grain is required. The volumetric object is obtained by reconstructing the planar projections of the grain acquired at different angles of rotation using a standard camera. Depending on the lens system, the resolution of the images can be as good as a few microns. A numerical representation of the real grain can be obtained by meshing the 3D image. The influence of grain morphology on the contact behavior of quartz sand is investigated here as an application of this novel technique. Numerical simulations using a finite-element model were carried out to reproduce the experimental data from normal compression single-grain tests. The results show the contribution of the initial grain rearrangement on the normal force-displacement response and its strong dependency on the shape of the grain. This study demonstrates that particle shape is a critical parameter for calibration of the contact behavior of sand

Numerical modelling of rough particle contacts subject to normal and tangential loading

Our understanding of the mechanics of contact behaviour for interacting particles has been developed mostly assumingthat surfaces are smooth. However,real particlesof interest inengineering science are generally rough. While recent studies have considered the influence of roughness on the normal force-displacement relationship, surface roughness was quantified using only a single scalar measure, disregardingthe topology of the surface. There are some conflicting arguments concerning the effect of roughness on the tangential or shear force-displacement relationship. In this study,optical interferometry data are used to generate the surface topology for input into a 3D finite element model. This model is used to investigate the sensitivity of the normal force-displacement response to thesurfacetopology by considering differentsurfaces with similar overall roughness values. The effect of surface roughness on the tangential force-displacement relationshipand the influence of loading history are also explored. The results indicate that quantifying roughness using a single value, such as the root mean square height of roughness, Sq, is insufficient to predict the effect of roughness upon stiffness. It is also shown that in the absenceof interlocking,rough particle surfaces exhibit a lower frictional resistance in comparison with equivalent smooth surfaces

An Area-Optimized Chip of Ant Colony Algorithm Design in Hardware Platform Using the Address-Based Method

The ant colony algorithm is a nature-inspired algorithm highly used for solving many complex problems and finding optimal solutions; however, the algorithm has a major flaw and that is the vast amount of calculations and if the proper correction algorithm and architectural design are not provided, it will lead to the increasing use of hardware platform due to the high volume of operations; and perhaps at higher scales, it causes the chip area not to work because of the high number of problems; hence, the purpose of this paper is to save the hardware platform as far as possible and use it optimally through providing a particular algorithm running on a reconfigurable chip driven by the address-based method, so that the comparison of synthesis operations with the similar works shows significant improvements as much as 1/3 times greater than the other similar hardware methods.DOI:http://dx.doi.org/10.11591/ijece.v4i6.692

Stress and input energy analyses of shearing a particle bed under a centrifugal field

Effective shearing of fine powders for surface modification and dry coating requires a compressed powder bed to prevent aeration. A device known as Mechanofusion® provides the necessary conditions using a centrifugal field, under which submicron particles are coated onto coarser host particles by shearing under great compressive forces at very high strain rates. This creates composite powders with enhanced properties, such as good flowability, surface functional effects, etc. Understanding the dynamics of particle motion, required level of shear stresses and input energy is a prerequisite for process optimisation. Here, numerical simulation by the Discrete Element Method is carried out, analysing features which are otherwise difficult to obtain by experimental work, e.g. the determination of the thickness of the zone in which particles experience shearing strains, as necessary for functional effect, compressive forces on particles, and input energy. Correlations are proposed for the energy input requirement and stresses experienced by the device as a function of rotational speed

Evaluating the effectiveness of using visual stimuli methods on architecture students’ design creativity

Background and Objectives: During design process, images as visual stimuli are significant tools in reaching creative design ideas. So this issue has resulted in conducting extensive studies in the field of educational technology on the methods of using visual stimuli as an educational tool. Since the visual stimuli can be categorized based on their similarity to the design problem or their quality (clear, ambiguous), in some of the studies, the impact of various types of visual stimuli on students’ design creativity has been examined. The level of students is another factor which could have an influence on students’ creativity when they were using visual stimuli. Also, in some studies, the relationship between the type of the design task and the visual stimuli has been investigated.  However, there is no comprehensive evaluation of the effectiveness of these methods in the field of architecture design education. As a result, the purpose of the present research is examining the effectiveness of the methods of using visual stimuli in design training.    Methods: In the present study, first, a framework for using visual stimuli based on previous studies was suggested which consisted of two sections: in the first section, the relationship between different types of visual stimuli and different aspects of creativity was determined; the second section, the factors influencing the methods of using the visual stimuli by the students were determined that consisted of students’ level, the type of the design task, and the design problem. Then,the methodofpeer review was applied to evaluate the effectiveness of the methods of using the visual stimuli in the design training. As a result, expert teachers in architecture from Iran and the United States evaluated the compiled text. In this regard, the teachers’ opinions were recorded through interviews and then their opinions were written and analyzed by a qualitative coding method. Peer review as the method of analysis was applied to investigate the validity of those methods. First participants’ ideas were gathered by interview. All their utterances were audio recorded and transcribed. In the next step the data were analyzed by a qualitative coding method. So the utterances of the participants were segmented based on different sections. Then, in the next stage, their content were codified in terms of validation, similar experience; criticism or suggestions. Findings: The opinions of the expert teachers were examined according to two sections of methods of using visual stimuli and also the effective conditions for using them in design education. Besides confirming the methods related to the types of stimulus and design task, the participants also provided numerous educational experiences on the proper interpretation of various types of stimuli. In the second section, besides confirming the impact of the students’ level, and the type of the design problem, some of the teachers offered criticisms and suggestions regarding the classifications of these problems. Conclusion: The results of peer review, besides confirming the methods of using visual stimuli, provide approaches that can improve the effectiveness of the methods of using visual stimuli in design education. Moreover, the expert teachers offered criticisms and suggestions regarding some problems and also added some suggestions. For example, the visual stimulus which has more similarity to the design problem has more effect on students’ design creativity than those images which have less similarity to the design problem.  Or when using the ambiguous sketches related to the expert designers, the way they use their sketches and the stages through which these sketches are transformed into the final idea should be taken into consideration and these processes should also be taught to the students. In other words, students need to know how expert designers transform those ambiguous images to final design solution. Also, categorizing the design problems into formal and functional has ambiguities and other methods of categorization should be used.   The results of analyzing the opinions of the expert teachers can be used for future research besides the development of the subject. ===================================================================================== COPYRIGHTS  ©2021 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.  ====================================================================================

Exploring the micro-to-macro response of granular soils with real particle shapes via \u1d741\u1d46a\u1d47b-aided DEM analyses

This contribution provides high fidelity images of real granular materials with the aid of X-ray micro computed tomography (μCT ), and employs a multi-sphere approximation to reconstruct non-spherical particles. Through the discrete element method (DEM) simulations on granular samples composed of these non-spherical clumps, the effect of particle shape on the macroscopic mechanical response and microscopic soil fabric evolution is examined for sheared soil assemblies under triaxial loading conditions. Simulation results indicate that materials with more irregular particles tend to show higher shear resistance in both peak and critical stresses, while more sphere-like materials tend to exhibit lower void ratio and mean coordination number values under isotropic loading conditions and in the critical state. The proposed critical state parameters for describing the sensitivity of the mean coordination number to confining pressures are larger as particles become more irregular. At a microscopic level of observation, more irregular materials appear to exhibit higher fabric anisotropy in terms of contact normal and particle orientation in the critical state. The critical stress ratio determined through experimental and simulation results are found to be linearly linked to the shape-weighted fabric anisotropy index

Characterisation of gas-atomised metal powders used in binder jet 3D printing

A comprehensive characterisation study has been undertaken to examine the flowability and spreadability of two distinct types of gas-atomised metal powders used in Binder Jet 3D printing technology. The experimental characterisation encompasses an analysis of the physical properties of individual particles as well as the flow behaviour of bulk powder. The data gathered from individual particle analysis are subsequently employed in numerical simulations of roller spreading by Discrete Element Method (DEM) to gain valuable insights into the intricate interplay between powder attributes and its spreading characteristics. The findings reveal that employing bulk characterisation tests, such as shear cell tests and compressibility indices, results in contradictory outcomes. Moreover, the spreadability data derived from the DEM simulations do not exhibit a strong correlation with the results obtained from the characterisation of the bulk powder. These results underscore that the flowability of the powder may not necessarily serve as an accurate measure of its spreadability when applied in thin layers for additive manufacturing. This study further establishes a crucial connection between the intrinsic properties of individual particles and the collective behaviour of particles within the bulk material

Effect of opium consumption on cardiovascular diseases – a cross- sectional study based on data of Rafsanjan cohort study

Background: There are differences of opinion about the beneficial or detrimental effects of opium consumption on cardiovascular diseases (CVDs). So, we aimed to study the association between opium use and CVDs. Methods: We used data obtained from the Rafsanjan Cohort Study (RCS), as a part of the prospective epidemiological research studies in IrAN (PERSIAN), with detailed, validated data on opium consumption and some other exposures. A total of 10,000 adults were enrolled in the study. Logistic regression models were used to assess the possible relationships of opium consumption with the prevalence of ischemic heart diseases (IHD) and myocardial infarction (MI). Results: In this study, 9990 participants in the baseline phase of the Rafsanjan adult cohort study were included according to their completed questionnaire. Among all participants, 870 and 296 individuals were found to suffer from IHD and MI, respectively. Opium consumption was found to be relatively high in the RCS participants, especially in men (men = 2150 and women = 228). Opium use was associated with a higher odds of IHD and MI, with the adjusted odds ratios (95% CI) of 1.51 (1.22–1.86) and 1.79 (1.31–2.45), respectively. Also, dose-response increases were observed with the highest odds ratios in the 4th quartile for MI and IHD (p-values for trend < 0.001). Increased odds were observed for the two main methods of opium consumption, i.e. oral and smoking, but oral administration had higher odds ratio. Conclusions: Opium consumption is associated with the increased odds of both IHD and MI diseases

Serum liver enzymes and diabetes from the Rafsanjan cohort study

Background: We evaluated the relation between ALT, AST, GGT and ALP with diabetes in the Rafsanjan Cohort Study. Materials and methods: The present study is a cross-sectional research including 9991 adults participated via sampling. We used data obtained from the Rafsanjan Cohort Study (RCS), as a part of the prospective epidemiological research studies in IrAN (PERSIAN). Elevated serum levels of ALT, AST, GGT and ALP were defined according to the reference range of the laboratory in the cohort center. Serum liver enzymes levels within the normal range were categorized into quartiles, and their relationship with diabetes was evaluated by logistic regressions. Findings: In present study, elevated serum levels of ALT, AST, GGT, and ALP were associated with increased odds of diabetes (adjusted ORs: 1.81, 95%CI 1.51-2.17; 1.75, 95%CI 1.32-2.32; 1.77, 95%CI 1.50-2.08; 1.60, 95%CI 1.35-1.90 respectively). Also, in subjects with normal levels of ALT, GGT and ALP, a dose-response increase was shown for diabetes. Conclusion: Elevated levels of ALT, AST, GGT and ALP are related to a higher odds of diabetes. Also, increased levels of ALT, GGT and ALP even within normal range were independently related with the increased odds of diabetes. These results indicated the potential of elevated liver enzymes as biomarkers for the possible presence of diabetes