Research on Shear Behavior of Sand–Structure Interface Based on Monotonic and Cyclic Tests

In order to study the shear behavior of the interface between sand and structure, a series of shear tests were carried out using an HJ-1 ring shear apparatus (Nanjing, China). First, through the monotonic shear tests, the loose sand and dense sand were sheared at the steel interface with different roughnesses. The results showed that when the interface was relatively smooth, the shear stress–shear displacement curves of loose sand and dense sand both exhibit strain hardening characteristics. When the interface was rough, the dense sand showed strain softening. The initial shear stiffness of the sand–steel interface increased with the increase in normal stress, interface roughness, or sand relative density. Then, considering the influence of initial shear stress, through the cyclic shear test, this work analyzed the shape of the loading and unloading curves and the development law of cumulative normal deformation, and discussed the change of loading and unloading shear stiffness under different stress level amplitudes and the residual deformation generated during the cycle. The research results showed that loose sand and dense sand generally shrunk in volume during the cycle. The initial loading process was similar to the case of static loading. In the later dynamic loading process, the shear shrinkage per cycle was relatively small and continued to develop. Additionally, it was found that the unloading stiffness of the sand–steel interface is always greater than the initial loading stiffness. As the number of cycles increases, the loading stiffness increases, and it may eventually approach the unloading stiffness.

Experimental study on flexural strengthening of reinforced concrete beams with U-shaped steel under secondary load

This study proposes a new method to strengthen reinforced concrete (RC) beams with U-shaped steel, which can achieve rapid construction and great improvement in the flexural performance of RC beams. To investigate the influence of secondary load defined as newly applied loads after strengthening on the strengthening effect, a total of nine specimens were tested under four-point bending, including a reference beam, a strengthened beam under initial load, and seven strengthened beams under secondary load. The initial loading degree, the thickness of the bottom plate, and the height of the steel box were the main variables considered in this study. Testing results showed that compared with the reference beam, the flexural performance of strengthened beams was significantly enhanced, indicating the good joint performance of the U-shaped steel and the RC beams. Among the three main variables, the initial loading degree was found to have a minimal effect on the flexural performance while the thickness of the bottom plate and the height of the steel box had considerable influence, with the latter having a more pronounced effect. Testing results also showed that most of the strengthened beams experienced flexural failures, which were reflected by steel web peeling and buckling, and concrete crushing. Moreover, a formula was derived for calculating the flexural capacity of strengthened beams under secondary load. The results from the derived formula were found to be in good agreement with those from experiments.

Comparison between 5 mg and 10 mg warfarin loading doses therapy in cardiac care unit patients at Elobied Hospital, Elobied City- Sudan

Background and objectives: Warfarin sodium therapy is usually initiated with a loading dose to reduce the time needed to reach the target international normalized ratio (INR). The right initial dose of warfarin is controversial. This study aimed to determine the best initial dose of warfarin in terms of safety and efficacy. Patients and methods: This is a prospective hospital-based study. Fifty-nine patients who were admitted to the coronary care unit with clinical indication for warfarin were assigned to use the initial dose of warfarin 5 mg or 10 mg with the target INR of 2-3. An ethical clearance was obtained from the state ministry of health. A written consent was taken from each patient. An INR was measured at baseline and then after 72 hours. The data were then collected using a data sheet including age, gender, baseline INR, initial dose of warfarin, INR after 72 hours and whether the patient developed bleeding or not. Patients on Aspirin and other non-steroidal anti-inflammatory drugs were excluded. The data were analyzed using SPSS version 18. Results: A total number of 59 patients were enrolled in the study. In this series, 59% of patients were females. The mean age of patients was 56 years. Five mg loading dose was used in 35 of patients (59%) while 10 mg was used in 24 patients (41%). The mean INR after 72 hours was 2.8 for those with the initial dose of 5 mg. For those with the initial loading dose of 10 mg the mean INR after 72 hours was 3.2. Minor bleeding occurred in three patients, two of them used the initial loading dose of 5mg and only one patient from the group of 10mg. Conclusion: From this study, it seems that 5 mg loading dose of warfarin is reasonable and cost effective; nevertheless, 10mg initial loading dose is not associated with increased risk of bleeding.

Analysis of the mixing of solid particles in the slant cone and ploughshare mixers via Discrete Element Method (DEM)

Discrete element method (DEM) was employed to characterize the mixing of the solid particles in two different types of the powder blenders. In the first part of this study, DEM was used to investigate the effects of initial loading, drum speed, fill level, and agitator speed on the mixing efficiency of a slant cone mixer. DEM simulation results were in good agreement with the experimentally determined data, both qualitatively and quantitatively. In the second part of this study, DEM was employed to characterize the mixing of the solid particles in a Ploughshare mixer. To validate the model, the simulation results were compared to the positron emission particle tracking (PEPT) data reported in the literature. The validated DEM was then utilized to calculate the mixing index as a function of the initial loading, plough rotational speed, fill level, and particle size for a ploughshare mixer.

Analysis of the mixing of solid particles in the slant cone and ploughshare mixers via Discrete Element Method (DEM)

Discrete element method (DEM) was employed to characterize the mixing of the solid particles in two different types of the powder blenders. In the first part of this study, DEM was used to investigate the effects of initial loading, drum speed, fill level, and agitator speed on the mixing efficiency of a slant cone mixer. DEM simulation results were in good agreement with the experimentally determined data, both qualitatively and quantitatively. In the second part of this study, DEM was employed to characterize the mixing of the solid particles in a Ploughshare mixer. To validate the model, the simulation results were compared to the positron emission particle tracking (PEPT) data reported in the literature. The validated DEM was then utilized to calculate the mixing index as a function of the initial loading, plough rotational speed, fill level, and particle size for a ploughshare mixer.

Evaluation of Blood Coagulation Parameters and ADMA, NO, IL-6, and IL-18 Serum Levels in Patients with Neovascular AMD before, during, and after the Initial Loading Phase of Intravitreal Aflibercept

We evaluated the effect of intravitreal injections of aflibercept (IVA) on blood coagulation parameters including prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin time (TT), as well as asymmetric dimethylarginine (ADMA), nitric oxide (NO), interleukin 6 (IL-6), and interleukin 18 (IL-18) serum levels in patients with neovascular AMD (nAMD). Twenty-two eyes of 22 patients with nAMD were included. Parameters were evaluated before and 2–3 days after the first IVA injection, and then immediately before and 2–3 days after the third IVA injection. We revealed prolongation of the TT after the initial loading phase of IVA (p = 0.041) and a significant increase in IL-18 serum concentration immediately before the third IVA administration compared to baseline (p = 0.037). There were no statistically significant differences of other parameters and PT, APTT, ADMA, NO, and IL-6 values remained within the normal range at each of the time points of the study. Our results suggest that repeated IVA administration may affect the common blood coagulation pathway, which manifests as a prolongation of the TT value. Furthermore, we showed a significant increase in serum concentration of the pro-inflammatory cytokineIL-18during the initial loading phase of IVA.

Fractional derivative modeling of time-varying viscosity materials considering initial loading ramp in real experiments

The fractional derivative models with time-varying viscosity have been used in characterizing creep or relaxation properties of different viscoelastic material, and many combination models were presented using the Boltzmann superposition principle. However, those models defined as initial ones in this manuscript usually ignored the initial loading ramp, and the ideal-loading condition is commonly assumed as a step function in modeling. The real-loading conditions of tested samples are usually a ramp load followed by constant stress or strain. The difference in loading conditions between the theoretical modeling and experimental procedure strongly influences the models’ rheological property characterization and parameter determination. It is especially the case for the fractional derivative model due to its memory or history-dependent characters, even though the ramp time is short compared with the total experimental time. An application example of the Maxwell model with time-varying viscosity Scott–Blair model (TVSM) shows that the initial loading ramp has a strong influence. To solve this problem, the authors propose modified models of TVSM based on real-loading conditions. The relative errors between initial and modified models are presented. In addition, a history-dependent optimization algorithm for parameter determination is proposed. Three sets of polymer experimental data are employed to suggest that the fitting results of models disregarding initial ramp loads are unreliable. The modified model should be used for characterizing rheological behavior, as this leads to obtaining the best fitting results even for a short experimental time.