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The purpose of this paper is to examine several calibration techniques that have been developed to determine the discrete element method (DEM) parameters for slow and rapid unconfined flow of granular conical pile formation. This paper also aims to discuss some of the methods currently employed to scale particle properties to reduce computational resources and time to solve large DEM models.

DEM models have been calibrated against simple bench‐scale experimental results to examine the validity of selected parameters for the contact, material and mechanical models to simulate the dynamic and static behaviour of cohesionless polyethylene pellets. Methods to determine quantifiable single particle parameters such as static friction and the coefficient of restitution have been highlighted. Numerical and experimental granular pile formation has been investigated using different slumping and pouring techniques to examine the dependency of the type of flow mechanism on the DEM parameters.

The proposed methods can provide cost effective and simple techniques to determine suitable input parameters for DEM models. Rolling friction and particle shape representation has shown to have a significant influence on the bulk flow characteristics via a sensitivity analysis and needs to be accessed based on the environmental conditions.

This paper describes several effective known and novel methodologies to characterise granular materials that are needed to accurately model granular flow using the DEM to provide valuable quantitative data. For the DEM to be a viable predictive tool in industrial applications which often contain huge quantities of particles with random particle shapes and irregular properties, quick and validated techniques to “tune” DEM models are necessary.

The purpose of this work is to discuss high-strength concrete mix proportioning optimization. In this study, the three parameters (W/B ratio), coarse aggregate maximum size (D_max) and superplasticizer dosage (Sp%) were considered.

A full factorial design with three factors and two levels was carried out. The statistical analysis and analysis of variance of statistical models were made easier with the aid of JMP7 software. The generated models explain how each parameter affects the mechanical compressive strength at 28 days (Cs28) and slump, and they have an excellent determination coefficient (R² = 0.99). For each high-strength concrete (HSC) mixture, the slump was measured four times: at 0 min, 20 min, 40 min and 60 min.

The results show that HSC6 (0.35(W/B), 12.5(D_max), 1.4(Sp%)) is the best HSC mixture, with a (Cs28) of 71.84 MPa, a slump of 22 cm, and slump loss of 3.5 cm in 60 min.

Quantifying the impact of high-strength concrete mix components from a small number of experiments is made achievable by combining two methods: the Dreux-Gorisse method and the full factorial design approach. It's possible to tune the mix proportioning of the high-strength concrete for the desired slump and compressive mechanical strength thanks to the created statistical models.

The purpose of this paper is to establish a new dynamic coupled discrete-element contact model used for investigating fresh concrete with different grades and different motion states, and demonstrate its correctness and reliability according to the rheological property results of flow fresh concrete in different working states through simulating the slump process and mixing process.

To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength. The fluid-like fresh concrete is modelled as a two-phase fluid consisting of mortar and aggregate. Depending on the contact forms of the aggregate and mortar, the model is of one of the five types, namely, Hertz–Mindlin, pendular LB contact, funicular mucous contact, capillary LB contact or slurry lift/drag contact.

To verify the accuracy of this contact model, concrete slump and cross-vane rheometer tests are simulated using the traditional LB model and dynamic coupled contact model, for five concrete strengths. Finally, by comparing the simulation results from the two different contact models with experimental data, it is found that those from the proposed contact model are closer to the experimental data.

This contact model could be used to address issues such as (a) the mixing, transportation and pumping of fresh concrete, (b) deeper research and discussion on the influence of fresh concrete on the dynamic performance of agitated-transport vehicles, (c) the behaviour of fresh concrete in mixing tanks and (d) the abrasion of concrete pumping pipes.

To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength.

12 mil pitch processing is achievable with solder paste. It may also be the limit of solder paste printing technology, mainly due to the scooping problem associated with thin stencils. With decreasing pitch size, both smear and insufficiency rate increase. Tapering of stencil aperture helps thick stencil prints, but has an adverse effect on thin stencil printing. Apertures with orientation parallel to squeegee movement result in a higher print defect rate. Overall, the use of fine powders is the most effective means to meet most challenges. It helps in achieving high performance in printability, tack and non‐slump, with acceptable trade‐offs in rheology and tack time. Solder balling may be the primary drawback. The problem may be resolved by using inert reflow atmosphere or via flux chemistry improvements. A metal load of 90.5 to 91% seems to be the optimum for most properties.

Reflow soldering in a controlled O₂ atmosphere will lead to practical benefits in the wetting behaviour of solder pastes. The required O₂ level and its control depend on the solder paste used and the solderability of the materials to be joined. For a typical application with either fine‐pitch technology, multiple soldering or low residue solder paste, a lack of O₂ control can cause soldering problems. Fine‐pitch solder pastes today still do not show an optimum slump behaviour, which is absolutely necessary to avoid bridging between IC leads and to reduce the formation of solder balls during reflow. Using a low O₂ atmosphere to reduce these defects can make a difference, but an improved slump behaviour through predrying of the applied solder paste at 50°C or in a low pressure environment will be more effective. Spread of solder is in general better at lower O₂ levels, but substantial improvements are only achieved if low residue pastes with low activation levels are reflowed. Even when the low residue paste is compatible with reflow in air, there is still a significant difference found between 20 and 200 ppm O₂. Reflow systems which show variations up to 500 ppm in the preheat zones during loading, while maintaining 50ppm in the peak zone, will show non‐wetting or dewetting when a 100 ppm O₂ solder paste is used. The visual cleanliness of solder joints is significantly improved at lower O₂ levels because the flux residue will be distributed differently over the solder joints. Bridging is initially determined by the slump behaviour of the paste and the alignment of the paste pattern to the pads and the leads, but when the paste of adjacent pads slumps together before reflow, the tendency for the solder to pull back is influenced by the oxygen level. Wetting and spread of the solder on the lands are then an essential factor. All the proven benefits of a low O₂ level are not worth the money spent on nitrogen if the consumption necessary to obtain the properly controlled O₂ level is very high. When solderability or the solder defect level not an issue the benefits may not represent a value higher than the cost of the nitrogen consumed.

This paper aims to clarify the relationship between corporate capital investments and business cycles. Specifically, a major purpose of this paper is to investigate whether there are inherent differences in corporate investment patterns and whether the stock market exhibits different reactions to the value relevance of capital expenditures across different business conditions.

The authors use pooled ordinary least square regressions with archival stock price data and financial data from CRSP and Compustat. The authors regress buy and hold returns on the main test variables and control variables that are identified to be related to the investment literature.

This paper provides empirical evidence that US firms’ capital expenditures are more value relevant to capital market participants during expansionary business cycles and, conversely, less value relevant during contractionary business cycles. This evidence validates previous literature that has found the information content of capital expenditures to be uncertain and cyclical in nature.

The main limitation of this paper, as with other work dealing with stock returns and archived financial data, is that the authors try to match stock returns with contemporaneous financial data in an association study context. The precise mapping in this methodology is always challenging and has been questioned in the literature.

This paper has various implications for capital market participants. Capital expenditures are good news for investors, but they will make a better investment when firms make capital investments during an expansionary period. Creditors deciding whether to extend credit to firms would benefit from more accurate information on the viability of long-term investment. The results also suggest to creditors that an excessive number of loans during the contractionary period may be suboptimal because firms’ returns on capital investment are smaller in that period than in the expansionary period.

Given the valuation of implications of long-term capital investments across different business conditions, this paper sheds light on asset allocations for mutual funds, institutional investors who are entrusted with investors’ investments including retirement funds.

This paper fulfils an identified need to study how capital investments are valued differently across different business conditions.

The durability of concrete containing recycled aggregates, sourced from concrete specimens that have been tested in laboratory testing facilities, remains understudied. This paper aims to present the results of experiments investigating the effect of incorporating such type of concrete waste on the strength and durability-related properties of concrete.

A total of 77 concrete cylinders sized Ø100 × 200 mm with varying amount of recycled concrete aggregate (RCA) (0%–100% by volume, at 25% increments) and maximum aggregate size (12.5, 19.0 and 25.0 mm) were fabricated and tested for slump, compressive strength, sorptivity and electrical resistivity. Disk-shaped specimens, 50-mm thick, were cut from the original cylinders for sorptivity and resistivity tests. Analysis of variance and post hoc test were conducted to detect statistical variability among the data.

Compared to regular concrete, a reduction of slump (by 18.6%), strength (15.1%), secondary sorptivity (31.5%) and resistivity (17.0%) were observed from concrete containing 100% RCA. Statistical analyses indicate that these differences are significant. In general, an aggregate size of 19 mm was found to produce the optimum value of slump, compressive strength and sorptivity in regular and RCA-added concrete.

The results of this study suggest that comparable properties of normal concrete were still achieved by replacing 25% of coarse aggregate volume with 19-mm RCA, which was processed from laboratory-tested concrete samples. Therefore, such material can be considered as a potential and sustainable alternative to crushed gravel for use in light or nonstructural concrete construction.

This study deals with three major topics: (1) the developed generations of 3D concrete printers, (2) the mix design approach for cement-based materials and (3) laboratory testing.

The big question is how to approach and follow the trend of 3D concrete printing technology with limited conditions such as printers, technology issues and budget. Therefore, this research focused on dealing with prominent issues, including printing equipment, mixed proportion design approaches and laboratory testing methods will be presented and analyzed.

The details of three printing equipment, including a printhead, a small-scale 3D printer, a 3D concrete printer and the printing process related to Simplify and Mach3 software, will be revealed. Secondly, the classification and efficient process will be given according to the mixture proportion design method proposed. Thirdly, laboratory testing will be conducted, including extrudability, buildability and printability. Finally, some highlight conclusions are given based on the appearance and quality of the samples printed.

Research has been carried out with cement-based materials and 3D concrete printer which adopted the screw extruders.

Mix design proportion method via coefficient and slump value proposed by the authors is a relatively effective and convenient method; the rheological properties, printing process and geometry of a sample are the most significant factors that decide the success of the printing work.

Additive manufacturing, widely known as 3D printing, has recently drawn the attention of researchers worldwide for a few decades. Thanks to its capability to transform a drawing into an object, the idea of 3D printing has also attracted the attention of engineers, architects and investors.

(1) Mix design proportion via coefficient and slump value proposed by the authors is a relatively effective and convenient method that can be implemented simply at the laboratory or the site. (2) The ranges of coefficients by weight of the water, sand and PP fibers to binder are (0.27–0.3), (0.6–1.0) and around 0.3, respectively. The maximum sand size was smaller than 2.5 mm, and the small amount of PP fibers enhanced the quality and significantly reduced the printed samples' shrinkage. (3) The printability is affected by mix proportion and the relationship between nozzle printing speed parameter and extrusion speed of motor turning. (4) The chosen layer height recommended smaller than 0.83 times nozzle diameter is reasonable and improves adhesions and buildability. (5) The printing open time of the concrete mixture of (12–15) minutes is a barrel to promote 3D concrete printing technology and needs improvement.

This study aims on a broad review of Concrete's Rheological Properties. The Concrete is a commonly used engineering material because of its exquisite mechanical interpretation, but the addition of constituent amounts has significant effects on the concrete’s fresh properties. The workability of the concrete mixture is a short-term property, but it is anticipated to affect the concrete’s long-term property.

In this review, the concrete and workability definition; concrete’s rheology models like Bingham model, thixotropy model, H-B model and modified Bingham model; obtained rheological parameters of concrete; the effect of constituent’s rheological properties, which includes cement and aggregates; and the concrete’s rheological properties such as consistency, mobility, compatibility, workability and stability were studied in detail.

Also, this review study has detailed the constituents and concrete’s rheological properties effects. Moreover, it exhibits the relationship between yield stress and plastic viscosity in concrete’s rheological behavior. Hence, several methods have been reviewed, and performance has been noted. In that, the abrasion resistance concrete has attained the maximum compressive strength of 73.6 Mpa; the thixotropy approach has gained the lowest plastic viscosity at 22 Pa.s; and the model coaxial cylinder has recorded the lowest stress rate at 8 Pa.

This paper especially describes the possible strategies to constrain improper prediction of concrete’s rheological properties that make the workability and rheological behavior prediction simpler and more accurate. From this, future guidelines can afford for prediction of concrete rheological behavior by implementing novel enhancing numerical techniques and exploring the finest process to evaluate the workability.

The rheology of solder paste significantly affects the qualities of stencil printing, tack and slump performance. This paper describes a series of tests performed on solder paste to investigate and determine the rheological properties of a group of solder pastes and fluxes, and the correlation of those properties with paste performance prior to reflow. Data indicate that: the incidence of print defects are proportional to the material’s compliant qualities (J1 and J2) and are inversely proportional to the elastic properties (G¢/G¢¢ and recovery) and meta‐rigidity (yield stress); slump resistance is proportional to elastic properties (recovery), solid characteristics (stress [G¢ = G¢¢]), and rigidity (|G*|); and that high elastic properties (recovery), low compliance (J1 and J2), and low solid characteristics (stress [G¢ = G¢¢]) are required in order to achieve high tack value. Good correlation between fluxes and solder pastes were observed for yield stress and recovery only, suggesting that those two properties are primarily dictated by fluxes.