bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Flow Separation Characteristics in a Pump as Turbines Impeller Under the Best Efficiency Point Condition
Authors: Lin Tong , Li Xiaojun , Zhu Zuchao , Xie Renhua , Lin Yanpi
Published: January 2021

The impeller, which is the main energy conversion component of a pump as turbine (PAT), is designed for pumping mode, and its internal flow characteristics are quite complicated even at the best efficiency point (BEP) of the turbine mode. This study aims to investigate the flow separation characteristics in a PAT impeller under the BEP condition by numerical method. The hydraulic performance and transient pressure characteristics of PAT predicted numerically were verified through experimentation. The surface friction lines and flow topological structure were applied to diagnose the flow separation at the surface of the blade. The relationship between flow topological structure and vortex in the impeller and static pressure at the blade were analyzed. Analysis results show that the backflow and open flow separation are observed significantly in the leading region and near the shroud of the trailing region of suction side. The passage vortex always appears near the spiral node. The saddle point and spiral node correspond to the peak position of adverse pressure and the lowest position between two peak values of the static pressure of the blade, respectively. The inflow conditions of blade and shape of the trailing edge significantly influence the flow separations in the impeller.
Tensile Response of a Flexible Pipe With an Incomplete Tensile Armor Layer
Authors: Zhu Xiaohua , Lei Qinglong , Meng Yu , Cui Xiaoxuan
Published: January 2021

Unbonded flexible pipes are widely utilized in the exploitation of offshore oil and gas resources. They are connected to two of the most critical types of system: floating production platforms and underwater production systems. However, if some tensile armor wires are substituted by cables or broken, the tensile armor layer will be incomplete, which seriously reduces the safety and reliability of the flexible pipe. In the present study, models of a flexible pipe with a complete tensile layer and with the tensile layer partially missing were established. The error for the tensile stiffness obtained by the finite element model of an intact flexible pipe was only 1% compared with experimental results. Because the load borne by the inner tensile armor layer is larger under tension than that borne by the outer tensile armor layer, the loss of inner tensile armor wires has a greater impact on the tensile properties. The maximum axial elongation of the flexible pipe increases with the number of missing inner tensile armor wires as a cubic polynomial. If the distribution of the missing armor wires is too dense, a stress concentration and local bending may occur, which will reduce the tensile strength of the flexible pipe.
Multi-Objective Optimal Design of an Active Aeroelastic Cascade Control System for an Aircraft Wing With a Leading and Trailing Control Surface
Authors: Chen Yuekun , Sardahi Yousef
Published: January 2021

This paper presents a multi-objective optimal design of cascade controllers applied to an aircraft wing with a leading and trailing control surface driven by electromagnetic actuators (EMAs). The design of the control system is decoupled into an inner (slave or secondary) and outer (master or primary) control algorithm. The master control algorithm is applied to the dynamics of the wing and its ailerons while two salve control loops are designed for the two EMAs. Then, a multi-objective and optimal design of the control algorithms is carried out. Three objectives are considered : 1) the speed of response of the slave controlled system must be faster than that of the master one, 2) the controlled system must be robust against external upsets, and 3) optimal energy consumption. The multi-objective optimization problem (MOP) is solved by the non-dominated sorting genetic algorithm (NSGA-II), which is one of the widely algorithms in solving MOPs. The setup parameters of the primary and secondary control algorithms are tuned during the optimization and the design objectives are evaluated. The solution of the MOP is a set of optimal cascade controllers that represent the trade-offs among the design objectives. Computer simulations show that the design objectives are achieved. However, some of the optimal solutions are practically in-feasible because they respond poorly to external disturbances. Presented study may become the basis for multi-objective optimal design of active aeroelastic control systems.
Speed Trajectory Generation for Energy-Efficient Connected and Automated Vehicles
Authors: Jan Lung En , Zhao Junfeng , Aoki Shunsuke , Bhat Anand , Chang Chen-Fang , Rajkumar Ragunathan (Raj)
Published: January 2021

Connected and automated vehicles (CAVs) have real-time knowledge of the immediate driving environment, actions to be taken in the near future and information from the cloud. This knowledge, referred to as preview information, enables CAVs to drive safely, but can also be used to minimize fuel consumption. Such fuel-efficient transportation has the potential to reduce aggregate fuel consumption by billions of gallons of gas every year in the U.S. alone. In this paper, we propose a planning framework for use in CAVs with the goal of generating fuel-efficient vehicle trajectories. By utilizing on-board sensor data and vehicle-to-infrastructure (V2I) communications, we leverage the computational power of CAVs to generate eco-friendly vehicle trajectories. The planner uses an eco-driver model and a predictive cost-based search to determine the optimal speed profile for use by a CAV. To evaluate the performance of the planner, we introduce a co-simulation environment consisting of a CAV simulator, Matlab/Simulink and a CAV software platform called the InfoRich Eco-Autonomous Driving (iREAD) system. The planner is evaluated in various urban traffic scenarios based on real-world road network models provided by the National Renewable Energy Laboratory (NREL). Simulations show an average savings of 14.5% in fuel consumption with a corresponding increase of 2% in travel time using our method.
Advanced Dynamics Analysis of a Drilling Roller Reamer As a Rigid Multibody System
Authors: Adewuya Opeyemi
Published: January 2021

The roller-reamer tool is typically installed in an oil and gas well bottom hole drilling assembly (BHA) to ream or smoothen out rough, gouging and scored wellbore surfaces left from the drill bit cutting action. The rotational dynamics of the roller-reamer functionally combines reaming and stabilizing action as it is constrained to rotate in circular wellbores. The relative velocity method developed for dynamics analysis of planetary gears is first used to obtain the Newtonian velocity and acceleration equations, then with use of the Extended Hamilton’s principle, derive Lagrange equations of motion. Published works of dynamics simulations from numerical models typically idealize drillstrings as series of connected non-linear Euler-Bernoulli beam elements representing various components of a drillstring, for instance, stabilizers and roller reamers are modeled as point contacts. This idealization and lumped parameter model approximations of potential sources of dynamics dysfunction such as roller-reamers mask understanding of their behavior and opportunities for design improvements and further application optimization. Of particular interest in this work is comparison between the torque magnitudes generated by the drilling stabilizer and the roller-reamer. Phase portraits of angular velocity versus displacement — proxy for torque generated — from numerical simulations for torque-free, precession modes in oversized wellbores and applied external load states, offer insights into downhole operating dynamics of an essential component of oil and gas well bottom hole assembly (BHA) drilling assemblies.
Frequency-Amplitude Response of Subharmonic Resonance of One-Third Order of Electrostatically Actuated MEMS Circular Plates
Authors: Caruntu Dumitru I. , Beatriz Julio , Martinez Miguel
Published: January 2021

This work deals with the subharmonic resonance of one-third order of electrostatically actuated clamped MEMS circular plate resonators. The system consists of flexible MEMS circular plate parallel to a ground plate actuated only by AC voltage. Hard excitations due to large enough AC voltage of frequency near three-halves of the natural frequency of the MEMS plate resonator lead it into a subharmonic resonance. The partial differential equation describing the motion of the resonator is nondimensionalized and two reduced order models are developed. The first one consists of a one mode of vibration model which is solved using the Method of Multiple Scales (MMS). The frequency-amplitude response (bifurcation diagram) is predicted. Hard excitations were modeled by keeping the first term of the Taylor polynomial of the electrostatic force as a large term and the rest of them as small terms. The second model uses two modes of vibration, and it is solved through numerical integration. This produces time responses of the resonator. Both methods show a zero-amplitude steady-state stable branch for the entire range of resonant frequencies. Also, two branches, one unstable and one stable, with a saddle node bifurcation point are predicted for non-zero steady state amplitudes. One can notice that non-zero steady state amplitudes can be reached only from large enough initial amplitudes. Both methods are in agreement for amplitudes up to 0.7 of the gap. The effect of damping and voltage on the frequency response are reported. As the damping increases, the saddle-node bifurcation point and consequently the non-zero steady-state branches are shifted to larger amplitudes. As the voltage increases, the saddle-node bifurcation point and the non-zero branches are shifted to lower amplitudes and lower frequency.
Modeling Thermal Effects in DC-Motors Using Pseudo-Bond Graphs
Authors: Clemen Layne , Beckerman Alex
Published: January 2021

Motor selection is important in all mechatronic systems. This requires understanding how motor performance degrades as a function of system temperature. In this paper, bond graphs are used to develop two simple motor models that captures this performance degradation, specifically by modeling the changes in system resistance and the motor constant as a function of system temperature. In the first system, the entire motor is assumed to be one thermal mass while in the second, the rotor and stator are modeled as two thermal masses separated by an air gap. The calculation of system temperatures allow for relevant system parameters to be represented more accurately over long periods of operation. Either model is readily integrated into models of larger mechatronic systems, a task made more simple through the use of bond graphs. The results presented in this paper will help future engineers to appropriately size motors for mechatronic systems based on such considerations as steady state temperature response, low versus high load conditions, and ambient operating conditions.
Dynamic Prediction-Based Optical Localization of a Robot During Continuous Movement
Authors: Greenberg Jason N. , Tan Xiaobo
Published: January 2021

Localization of mobile robots is essential for navigation and data collection. This work presents an optical localization scheme for mobile robots during the robot’s continuous movement, despite that only one bearing angle can be captured at a time. In particular, this paper significantly improves upon our previous works where the robot has to pause its movement in order to acquire the two bearing angle measurements needed for position determination. The latter restriction forces the robot to work in a stop-and-go mode, which constrains the robot’s mobilitty. The proposed scheme exploits the velocity prediction from Kalman filtering, to properly correlate two consecutive measurements of bearing angles with respect to the base nodes (beacons) to produce location measurement. The proposed solution is evaluated in simulation and its advantage is demonstrated through the comparison with the traditional approach where the two consecutive angle measurements are directly used to compute the location.
Design, Modeling, and Identification of an Experimental Liquid-Level Control System: Enabling Research in Fault Diagnosis
Authors: Workneh Hilina T. , Raptis Ioannis A.
Published: January 2021

In this work we address the design and analysis challenge of a laboratory benchmark system, suited for testing and comparing model-based fault diagnosis algorithms. The motivation is the democratization of research in fault diagnosis, which is hindered by the lack of accessible data from real-world systems. A liquid-level control system with three interconnected storage tanks was selected for the physical process. The fault modes under consideration — liquid leak at the tanks — were planted in a manner that their impact can be measured and quantified. Commercially available sensing, actuating, and data acquisition electronic components were used for interfacing the monitoring unit (cyber part) with the process (physical part). A detailed description of the first-principles mathematical modeling is provided for deriving the state-space equations of the physical process. System identification, using elementary least-squares estimation, was performed to estimate the parameters of the parametric model using input/output data. The validation of the identified dynamic model and its agreement with the collected data showcase the capabilities of the proposed system for testing and comparing model-based fault diagnosis algorithms.
Contrast agent shell properties effects on heat deposition in bubble enhanced high intensity focused ultrasound
Authors: Gnanaskandan Aswin , Hsiao Chao-Tsung , Chahine Georges
Published: January 2021

The effects of the viscoelastic shell properties of ultrasound contrast agents on heat deposition in bubble enhanced high intensity focused ultrasound (HIFU) are studied numerically using a model that solves the ultrasound acoustic field and the multi-bubble dynamics. The propagation of the nonlinear acoustic waves in the test medium is modeled using the compressible Navier-Stokes equations in a fixed Eulerian grid, while the microbubbles are modeled as discrete flow singularities, which are tracked in a Lagrangian fashion. These two models are intimately coupled such that both the acoustic field and the bubbles influence each other at each time step. The resulting temperature rise in the field is then calculated by solving a heat transfer equation applied over a much longer time scale than the computed high frequency dynamics. Three shell models for the contrast agent are considered, and the effect of each of these models on the heat deposition at the focus is studied. The differences obtained in the bubble dynamics results between the shell models are discussed. The importance of modeling the elasticity of the shell is addressed by comparing the results between Newtonian and non-Newtonian shell models. Next, a parametric study varying the shell properties is carried out, and the relative roles of the shell viscosity and elasticity in affecting the heat deposition are discussed. These observations are then used to give recommendations for the design of innovative contrast agents, specifically for the purpose of obtaining higher heat deposition in bubble enhanced HIFU.
Concurrent Validity and Reliability of a Handheld Dynamometer in Measuring Isometric Shoulder Rotational Strength
Authors: Chen Bin , Liu Lifen , Bin Chen Lincoln , Cao Xianxin , Han Peng , Wang Chenhao , Qi Qi
Published: January 2021

Context: Measuring isometric shoulder rotational strength is clinically important for evaluating motor disability in athletes with shoulder injuries. Recent evidence suggests that handheld dynamometry may provide a low-cost and portable method for the clinical assessment of isometric shoulder strength. Objective: To investigate the concurrent validity and the intrarater and interrater reliability of handheld dynamometry for measuring isometric shoulder rotational strength. Design: Cross-sectional study. Setting: Biomechanics laboratory. Participants: Thirty-nine young, healthy participants. Main Outcome Measures: The peak isometric strength of the internal rotators and external rotators, measured by handheld dynamometry (in newton) and isokinetic dynamometry (in newton meter). Interventions: Maximal isometric shoulder rotational strength was measured as participants lay supine with 90° shoulder abduction, neutral rotation, 90° elbow flexion, and forearm pronation. Measurements were performed independently by 2 different physiotherapists and in 3 different sessions to evaluate interrater and intrarater reliability. The data obtained by handheld dynamometry were compared with those obtained by isokinetic testing to evaluate concurrent validity. Results: The intraclass correlation coefficients for interrater reliability in measuring maximum isometric shoulder external and internal rotation strength were .914 (95% confidence interval [CI], .842–.954) and .842 (95% CI, .720–.914), respectively. The intrarater reliability values of the method for measuring maximal shoulder external and internal rotation strength were 0.865 (95% CI, 0.757–0.927) and 0.901 (95% CI, 0.820–0.947), respectively. The Pearson correlation coefficients between the handheld and isokinetic dynamometer measurements were .792 (95% CI, .575–.905) for external rotation strength and .664 (95% CI, .419–.839) for internal rotation strength. Conclusions: The handheld dynamometer showed good to excellent reliability and moderate to good validity in measuring maximum isometric shoulder rotational strength. Therefore, handheld dynamometry could be acceptable for health and sports professionals in field situations to evaluate maximum isometric shoulder rotational strength.
OXA-181-Like Carbapenemases in Klebsiella pneumoniae ST14, ST15, ST23, ST48, and ST231 from Septicemic Neonates: Coexistence with NDM-5, Resistome, Transmissibility, and Genome Diversity
Authors: Naha Sharmi , Sands Kirsty , Mukherjee Subhankar , Saha Bijan , Dutta Shanta , Basu Sulagna
Published: January 2021

Neonatal sepsis is a leading cause of neonatal mortality in low- and middle-income countries (LMICs). Treatment of sepsis in this vulnerable population is dependent on antimicrobials, and resistance to these life-saving antimicrobials is worrisome.
Supplemental Material: Anisovolumetric weathering in granitic saprolite controlled by climate and erosion rates
Authors: Riebe Clifford , al. et
Published: January 2021

Supplemental methods and Tables S1–S4.
Six-year incidence and systemic associations of retinopathy in a multi-ethnic Asian population without diabetes
Authors: Gupta Preeti , Lamoureux Ecosse Luc , Sabanayagam Charumathi , Tham Yih-Chung , Tan Gavin , Cheng Ching-Yu , Wong Tien Yin , Cheung Ning
Published: January 2021

Purpose

We described the 6-year incidence and changes of retinopathy, and their associated risk factors in a multi-ethnic Asian population without diabetes.

Methods

We included 4374 participants with non-diabetes from a population-based cohort, the Singapore Epidemiology of Eye Disease Study, with gradable retinal photographs at baseline and 6-year follow-up visit. Retinopathy was assessed according to the modified Airlie House classification system.

Results

Over the 6-year period, the cumulative rates were 2.5% (106/4279) for retinopathy incidence, 1.0% (1/95) for retinopathy progression and 68.4% (65/95) for retinopathy regression. In multivariable analysis, higher diastolic blood pressure (DBP) (risk ratio (RR)=1.02; 95% CI: 1.00 to 1.04; per 10 mm Hg increase in DBP) and wider retinal arteriolar calibre (RR=1.36; 95% CI: 1.13 to 1.63; per SD increase in central retinal artery equivalent) were associated with higher risk of incident retinopathy, while higher level of high-density lipoprotein (HDL) was associated with lower risk of incident retinopathy (RR=0.56; 95% CI: 0.32 to 0.99; per mmol/L increase in HDL). Compared with Chinese, Malays were more likely to have retinopathy regression (RR=1.63; 95% CI: 1.20 to 2.22), while overweight (RR=0.47; 95% CI: 0.26 to 0.84) and higher glycosylated haemoglobin (HbA1c) level (RR=0.58; 95% CI: 0.37 to 0.93; per per cent increase in HbA1c) were associated with lower likelihood of retinopathy regression.

Conclusion

Risk of developing retinopathy in Asians without diabetes is generally low. However, regression of retinopathy over time is common, suggesting that these retinopathy signs may reflect subclinical reversible microvascular dysfunction. Several metabolic risk factors are associated with incidence or regression of retinopathy, suggesting that good metabolic control may still be important in the management of non-diabetic retinopathy.
Activated intestinal muscle cells promote preadipocyte migration: a novel mechanism for creeping fat formation in Crohn’s disease
Authors: Mao Ren , Doyon Genevieve , Gordon Ilyssa O , Li Jiannan , Lin Sinan , Wang Jie , Le Thi Hong Nga , Elias Michael , Kurada Satya , Southern Brian , Olman Mitchell , Chen Minhu , Zhao Shuai , Dejanovic Dina , Chandra Jyotsna , Mukherjee Pranab K , West Gail , Van Wagoner David R , Fiocchi Claudio , Rieder Florian
Published: January 2021

Objective

Creeping fat, the wrapping of mesenteric fat around the bowel wall, is a typical feature of Crohn’s disease, and is associated with stricture formation and bowel obstruction. How creeping fat forms is unknown, and we interrogated potential mechanisms using novel intestinal tissue and cell interaction systems.

Design

Tissues from normal, UC, non-strictured and strictured Crohn’s disease intestinal specimens were obtained. The muscularis propria matrisome was determined via proteomics. Mesenteric fat explants, primary human preadipocytes and adipocytes were used in multiple ex vivo and in vitro cell migration systems on muscularis propria muscle cell derived or native extracellular matrix. Functional experiments included integrin characterisation via flow cytometry and their inhibition with specific blocking antibodies and chemicals.

Results

Crohn’s disease muscularis propria cells produced an extracellular matrix scaffold which is in direct spatial and functional contact with the immediately overlaid creeping fat. The scaffold contained multiple proteins, but only fibronectin production was singularly upregulated by transforming growth factor-β1. The muscle cell-derived matrix triggered migration of preadipocytes out of mesenteric fat, fibronectin being the dominant factor responsible for their migration. Blockade of α5β1 on the preadipocyte surface inhibited their migration out of mesenteric fat and on 3D decellularised intestinal tissue extracellular matrix.

Conclusion

Crohn’s disease creeping fat appears to result from the migration of preadipocytes out of mesenteric fat and differentiation into adipocytes in response to an increased production of fibronectin by activated muscularis propria cells. These new mechanistic insights may lead to novel approaches for prevention of creeping fat-associated stricture formation.
Electromagnetic fields, 5G and health: what about the precautionary principle?
Authors: Frank John William
Published: January 2021

New fifth generation (5G) telecommunications systems, now being rolled out globally, have become the subject of a fierce controversy. Some health protection agencies and their scientific advisory committees have concluded that there is no conclusive scientific evidence of harm. Several recent reviews by independent scientists, however, suggest that there is significant uncertainty on this question, with rapidly emerging evidence of potentially harmful biological effects from radio frequency electromagnetic field (RF-EMF) exposures, at the levels 5G roll-out will entail. This essay identifies four relevant sources of scientific uncertainty and concern: (1) lack of clarity about precisely what technology is included in 5G; (2) a rapidly accumulating body of laboratory studies documenting disruptive in vitro and in vivo effects of RF-EMFs—but one with many gaps in it; (3) an almost total lack (as yet) of high-quality epidemiological studies of adverse human health effects from 5G EMF exposure specifically, but rapidly emerging epidemiological evidence of such effects from past generations of RF-EMF exposure; (4) persistent allegations that some national telecommunications regulatory authorities do not base their RF-EMF safety policies on the latest science, related to unmanaged conflicts of interest. The author, an experienced epidemiologist, concludes that one cannot dismiss the growing health concerns about RF-EMFs, especially in an era when higher population levels of exposure are occurring widely, due to the spatially dense transmitters which 5G systems require. Based on the precautionary principle, the author echoes the calls of others for a moratorium on the further roll-out of 5G systems globally, pending more conclusive research on their safety.
Study of incident drag response of the Hyperloop pod based on change in aerodynamic brake plate orientation
Authors: Mahmud Shadman , Adnan Adib , Khan Shahnoor Shamim , Rahman Md. Hamidur
Published: January 2021

The concept of the Hyperloop has received significant attention, with expectations of it becoming a revolutionary and potentially the fastest mode of land transportation on the planet. The low-pressure tube through which the pod travels at expected speeds close to Mach 1.0, presents a unique case among other transport models, and braking of the pod is of critical importance if passenger safety protocols are to be maintained. The high-speed flow around the pod exerts high adverse pressure gradients on the pod surface, resulting in boundary layer separation, increasing drag, and affecting the acceleration of the pod. Numerical simulations have shown that the placement of an aerodynamic brake plate on the pod surface at the point at which boundary layer separation occurs provides the necessary drag required for safe deceleration. This study aimed to find the best angle for the aerodynamic brake positioned at a fixed point on the pod, allowing for the maximum generation of drag, using numerical simulations. After various trials, it was observed that angling the brake 15° backwards while increasing its length to keep the incident brake profile constant, the drag value obtained was the highest.
The variational method, backreactions, and the absorption probability in Wald type problems
Authors: Düztaş Koray
Published: January 2021

We argue that the variational method in Wald type thought experiments, involves order of magnitude problems when one imposes the fact that $$\delta M$$

δ
M

is inherently a first order quantity itself. One observes that the contribution of the second order perturbations is actually of the fourth order. Therefore backreactions have to be explicitly calculated. Here, we re-consider the overspinning problem for Kerr–Newman black holes interacting with test fields. We calculate the backreaction effects due to the induced increase in the angular velocity of the event horizon, which brings a partial solution to the overspinning problem. To bring an ultimate solution, we argue that the absorption probability should be taken into account in Wald type problems where black holes interact with test fields. This fundamentally alters the course of the analysis of the thought experiments. Due to the fact that a small fraction of the challenging modes is absorbed by the black holes, overspinning is prevented for both nearly extremal and extremal cases. Some extreme cases are easily fixed by backreaction effects. The arguments do not apply to the generic overspinning by fermionic fields for which the absorption probability is positive definite.
Resonant cavity enhanced waveguide transmission for high-efficiency Terahertz polarization beam splitter
Authors: Jiao Xiao-Fei , Zhang Zi-Heng , Xu Yun , Song Guo-Feng
Published: January 2021

In this study, a design for the high-efficiency transmissive terahertz polarization beam splitter is proposed. Based on the metal–insulator–metal waveguide array structure, it is found that the phase change between the transverse-electric (TE) and transverse-magnetic (TM) modes of terahertz wave transmission depends greatly on the medium width. According to this phenomenon, our designed devices can achieve polarization splitting of TE and TM modes in the frequency range 0.8–2.4 THz, and the transmittance can be maintained above 85%. In addition, through judicious design, polarization splittings with 93% transmittance at 1 THz and 95% transmittance at 1.5 THz are obtained, and polarization splitting at different angles is achieved according to variable periods. Compared with the traditional polarization beam splitter, this design has the advantages of adjustable frequency, high efficiency, and easy integration, thus having potential application in terahertz optical systems.
Adaptive strategies to conduct participant-centric structured virtual group discussions for postgraduate students in the wake of the COVID-19 pandemic
Authors: Kaur Simran , Bir Megha , Chandran Dinu S. , Deepak Kishore Kumar
Published: January 2021

In the wake of COVID-19, the postgraduate activities in physiology were shifted from live (face-to-face teaching) to virtual mode. This transition posed a challenge to postgraduate students and faculty moderators, especially for participant-centric group discussion, wherein face-to-face interaction contributes significantly to active learner engagement. To bridge the gap between live group discussion (GD) and virtual GD in the conventional format (VGD), we implemented an innovative yet feasible multistep approach of conducting structured virtual group discussion (sVGD). It involved priming of students during the preparatory phase and incorporation of the Tuckman model of group dynamics, which consists of sequential substages of forming, storming, norming, and performing into the virtual format. Unsupervised synchronous and asynchronous, as well as supervised synchronous interactions within and in between the minigroups in a structured way, led to active engagement of students with one another and the moderator, despite the constraints imposed by the virtual format. After establishing the feasibility of the approach during the first GD (sVGD-1), sVGD-2 was conducted, further refining the approach, and feedback was obtained from the postgraduate students. Pre-GD feedback revealed that the live session was preferred over virtual for the conduct of GD, whereas both live GD and sVGD were perceived to be more effective than VGD in the post-GD feedback. Such pedagogical innovations may also help to address the challenges posed in traditional teaching across the undergraduate and postgraduate courses in medical education and beyond during such unforeseeable circumstances.
Biomechanics without Borders: Teaching Biomechanics in Brazil and South Africa
Authors: Bayne Helen , Albertus Yumna , Breen Sarah , Green Andrew , de Andrade André Gustavo , Kramer Mark , Carpes Felipe P.
Published: January 2021

The “Biomechanics without Borders: Teaching Biomechanics in Brazil and South Africa” involved academics from different countries combining efforts to improve remote education. In addition to the live discussions, the event resulted in the availability of online content to help academic staffs improve teaching strategies in the field of human movement sciences.
A Comparison between Two Different Remineralizing Agents against White Spot Lesions: An In Vitro Study
Authors: Alsubhi Hassan , Gabbani Mohammad , Alsolami Abdulsalam , Alosaimi Mohammed , Abuljadayel Jameel , Taju Waleed , Bukhari Omair
Published: January 2021

Enamel demineralization and white-spot lesions (WSLs) around the orthodontic brackets are common clinical complications after orthodontic fixed appliance therapy. WSLs form mainly due to plaque deposition around the brackets during the orthodontic treatment period. This study was designed to compare and evaluate the efficacy of two different remineralization agents on WSLs, which are “Clinpro 5000 and Colgate Sensitive Pro-Relief”. 27 caries-free human premolar teeth were collected after extraction for orthodontic purposes. The crowns were set in acrylic resin, and the entire surfaces were coated with nail varnish apart from an area of 4 × 4 mm on the buccal surface. The surface microhardness (SMH) was measured using the Vickers microhardness testing machine at baseline, after demineralization, and after treatment. Then, the different SMH values were statistically analyzed using mixed-effects linear regression. All samples were immersed in demineralizing solution for ten days to create WSLs, and then the teeth were allocated randomly into one of the three groups: Group 1 (control group-immersed in artificial saliva), Group 2 (treated with Colgate sensitive Pro-Relief toothpaste), and Group 3 (Clinpro 5000 toothpaste). Cycles of treatment were done for 5 minutes every 12 hours for 14 days. The samples were stored in freshly prepared artificial saliva between cycles. The mixed-effects model was used to quantify the effect of different remineralization agents. All statistics were computed using STATA software (version14.1; Stata, College Station, TX). All statistical tests were two-tailed and interpreted at the 0.05 significance level. Both agents improved the surface hardness. Clinpro 5000 improved the surface hardness by 12.7 (

P

value 0.012), and Colgate Sensitive Pro-Relief improved surface hardness by 18.2 (

P

value <0.0001), However when both treatments are compared with each other, there was no statistical significance among them. When compared to the control group, both treatments “Clinpro™ 5000 and Colgate Sensitive Pro-Relief” have significantly improved enamel’s SMH.
The Scale Effect of Coarse‐Grained Materials by Triaxial Test Simulation
Authors: Ai Xiaotao , Wang Guangjin , Kong Xiangyun , Cui Bo , Hu Bin , Ma Hongling
Published: January 2021

The scale effect is an unavoidable problem in the laboratory test of coarse‐grained materials. By combining the self‐developed cellular automaton program with laboratory experiments, a method of simulating the triaxial test of coarse‐grained materials was proposed in this paper, and a triaxial test numerical specimen that can characterize the discontinuous, nonuniform, and heterogeneous characteristics of bulk geotechnical materials was established. The parallel grading method was adopted to create six grading curves for numerical simulation based on one in situ grading curve. The failure process and the scale effect on the strength and deformation of coarse‐grained materials were analyzed and discussed. The results showed that under the same confining pressure, the peak stress and initial deformation modulus Ei increased with the increase of the maximum particle size dmax, while the degree of shear shrinkage and Poisson’s ration υ decreased. As the confining pressure increased, the scale effect of coarse‐grained materials would be magnified. If particle breakage and migration were assumed to be neglected, the internal friction angle φ and dmax would be roughly proportional, the cohesive force c fluctuated with the increase of dmax, and the empirical relations between dmax and c and φ were established, respectively, which provides a reference for estimating the actual shear strength parameters of coarse‐grained materials on‐site. The research results can provide a way of thinking for the study of the scale effect of coarse‐grained materials and also have certain reference significance for inferring the strength parameters of the original‐graded coarse‐grained materials.
Spheroidization and Coarsening of Eutectic Si Particles in Al‐Si‐Based Alloys
Authors: Ibrahim Mohamed , Abdelaziz Mohamed , Samuel Agnes , Doty Herbert , Samuel Fawzy
Published: January 2021

The present study was carried out on three Al‐Si cast alloys viz., 319, 356, and 413 alloys, solidified at 8°C/s. Samples from 319 and 413 alloys were solution heat‐treated at 510°C, whereas samples from 356 alloy were solutionized at 550°C, for up to 1200 h. The results reveal that complete spheroidization of eutectic Si particles in terms of achieving individual spherical particles cannot be achieved in most Al‐Si‐Cu‐Mg alloys even after a solutionizing time of 1200 h which contradicts with the existing theory. Addition of Sr to Cu‐free 356 alloy could lead to complete spheroidization after 1200 h at 550°C if the alloy was solidified at 8°C/s. Besides the dissolution theory of Ostwald, coarsening of Si particles can as well take place by impingement, fusion, and agglomeration. Increasing the Si content makes it difficult to achieve spheroidization, i.e., fragmentation and coarsening. Results obtained from observations of deeply etched samples (3D) contradict those obtained from polished samples (2D).
On Topological Indices for New Classes of Benes Network
Authors: Hussain Aftab , Numan Muhammad , Naz Nafisa , Butt Saad Ihsan , Aslam Adnan , Fahad Asfand
Published: January 2021

Topological indices (TIs) transform a molecular graph into a number. The TIs are a vital tool for quantitative structure activity relationship (QSAR) and quantity structure property relationship (QSPR). In this paper, we constructed two classes of Benes network: horizontal cylindrical Benes network

HCB

r

and vertical cylindrical Benes network obtained by identification of vertices of first rows with last row and first column with last column of Benes network, respectively. We derive analytical close formulas for general Randić connectivity index, general Zagreb, first and the second Zagreb (and multiplicative Zagreb), general sum connectivity, atom-bond connectivity (

VCB

r

), and geometric arithmetic

ABC

index of the two classes of Benes networks. Also, the fourth version of

GA

and the fifth version of

ABC

indices are computed for these classes of networks.
Optimal Selection Method for Sweet Spots in Low-Permeability Multilayered Reservoirs
Authors: Bai Xiangwu , Li Zhiping , Lai Fengpeng
Published: January 2021

Low-permeability oil reservoirs account for more than two-thirds of China’s proven reserves, and most of them are multilayered; the traditional sweet spots focus on single-layered reservoirs. The sweet spots of low-permeability reservoirs have two meanings: the geologically superior reservoir and the beneficial development of the reservoir. In this study, a concept of reservoir stratification coefficient is proposed to evaluate the characteristics of multilayered reservoirs, and three indicators are proposed, namely, reservoir stratification coefficient, energy storage coefficient, and stratigraphic coefficient, as the indicators of sweet spots of multilayered reservoirs. The three indicators are combined into a single indicator using a weighted approach, and the sweet spots can be identified based on the combined indicator. The Xiliu A area of the North China oilfield was selected for a case study. According to the structural, sedimentary, and reservoir characteristics of the block, combined with the development and production conditions, the Sha 3 Member I oil group was selected as the study object of sweet spots of the low-permeability reservoir. The results show that the reservoir stratification coefficient, energy storage coefficient, and stratigraphic coefficient proposed in this study are effective indicators for the preferential selection of sweet spots, which can reflect the longitudinal heterogeneity, energy storage size, and flow capacity of multilayered reservoirs. After a comparative analysis with actual blocks, it was found that the results obtained using the method are consistent with the actual capacity of the reservoir. The production capacity is high. The evaluation effect is ideal, and the applicability is good. Thus, this study provides a new technical method for the evaluation of similar multilayered reservoirs. The findings of this study can help for a better understanding of the development and production conditions and optimization basis of low-permeability reservoirs.
Effects of Sediment Dredging on Nutrient Release and Eutrophication in the Gate-Controlled Estuary of Northern Taihu Lake
Authors: Chen Xi , Wang Yanhua , Sun Tian , Huang Yu , Chen Yan , Zhang Mingli , Ye Chun
Published: January 2021

Estuarine zones are regarded as the ecotones connecting the rivers and lakes. Sediment dredging is a conventional treatment technology that is widely used to remove the internal loading in estuarine zones worldwide. However, what is the characteristic of nutrient release in the gate-controlled estuary and how long this practice is effective are still unclear. Hence, sediment and water samples were collected from dredged and undredged regions around the gate-controlled estuary of northern Taihu Lake for laboratory experiments, in which they were subjected to different temperatures, depths, and disturbance levels. The total nitrogen (TN) and total phosphorus (TP) concentrations of the dredged region were lower than those from the undredged region under stable hydrodynamic conditions. A high dynamic release rate (R) of nutrients in the dredged sediments (RTN = 164.75 mg/m2·d and RTP = 5.83 mg/m2·d) existed under dynamic release conditions (stirring speeds: 90 and 120 r/min). The effect of disturbance and temperature on release rate and nutrient form was completely different for the static and dynamic release cases. The nutrient loads from dynamic release were 4–17 times greater than those from static release. For unstable hydrodynamic conditions, the release rate from the bottom sediment exceeded that from the surface sediment in the undredged region. These results indicated that, under stable hydrodynamic conditions, dredging improves long-term water quality. However, dredging alone in unstable hydrodynamic conditions may not remove the potential risk of internal release in the long term. Specific ecological and engineering measures should be combined with dredging practice to restore estuary habitats and minimize the release of internal pollutants.
Analysis of Bianchi Type V Holographic Dark Energy Models in General Relativity and Lyra’s Geometry
Authors: Gusu Daba Meshesha , Santhi M. Vijaya
Published: January 2021

In this paper, we analyze anisotropic and homogeneous Bianchi type V spacetime in the presence of dark matter and holographic dark energy model components in the framework of general relativity and Lyra’s geometry. The solutions of differential equation fields have been obtained by considering two specific cases, namely, the expansion scalar

θ

in the model is proportional to the shear scalar

σ

and the average scale factor taken as hybrid expansion form. The solutions for field equations are obtained in general relativity and Lyra’s geometry. The energy density of dark matter in both natures was obtained and compared so that the energy density of dark matter in general relativity is slightly different from the energy density of dark matter in Lyra’s geometry. A similar behavior occurred in case of pressure and EoS parameter of holographic dark energy model in respective frameworks. Also, it is concluded that the physical parameters such as the average Hubble parameter, spatial volume, anisotropy parameter, expansion scalar, and shear scalar are the same in both frameworks. Moreover, it is observed that the gauge function

β

t

is a decreasing function of cosmic time in Lyra’s geometry, and for late times, the gauge function

β

t

converges to zero and Lyra’s geometry reduces to general relativity in all respects. Finally, we conclude that our models are a close resemblance to the

Λ

CDM cosmological model in late times and consistent with the recent observations of cosmological data.
Effect of Micronization on Panax notoginseng: In Vitro Dissolution and In Vivo Bioavailability Evaluations
Authors: Liang Xiao , Xu Guobing , Li Zhenbao , Xuan Zihua , Zhao Hongsu , Peng Daiyin , Gui Shuangying
Published: January 2021

Panax notoginseng (PN) has become the most widely used dietary supplement and herbal in Asian countries. The effect of micronization on PN is not entirely clear. The aim of this study was to investigate the effects of particle size of Panax notoginseng powder (PNP) and the potential to improve the bioavailability. The results showed that particle size reduction significantly changed the Panax notoginseng saponins (PNS) in vitro dissolution and in vivo pharmacokinetics. The size of the Panax notoginseng powder (PNP) ranges from 60 to 214 μm. The surface morphology and thermal properties of PNP were extensively characterized, and these changes in physicochemical properties of PNP provide a better understanding of the in vitro and in vivo release behaviors of PNS. The in vitro studies demonstrated that the dissolution of PNS and particle size were nonlinear (dose- and size-dependent). The pharmacokinetics parameters of PNP in rats were determined by UHPLC-MS/MS. Powder 4 (90.38 ± 8.28 μm) showed significantly higher AUC0-T values in plasma

P
<
0.05

. In addition, we also investigated the influence of the hydrothermal treatment of PNP. The results showed that the PNS in vitro release and in vivo bioavailability of PNP pretreatment at 40°C were the highest. This suggests that PNP with a particle size of around 90 μm and heat pretreatment at 40°C would be beneficial. These results provided an experimental basis, and it was beneficial to choose an appropriate particle size and hydrothermal temperature when PNP was used in clinical treatment.
Herb-Induced Liver Injury by Cimicifuga racemosa and Thuja occidentalis Herbal Medications for Fertility
Authors: Patel Rohan , Alavi Fareeha , Ortega Susel , Matela Ajsza
Published: January 2021

Herb-induced liver injury (HILI) is often an underreported sequela for many herbal remedies due to the lack of safety measurements involving these supplements. Cimicifuga racemosa and Thuja occidentalis are two herbal medications commonly used by women for fertility purposes. Many herbal preparations of these two supplements do not specify the risks behind their individual usage. We present a case of a 40-year-old woman who developed acute liver injury after concomitant use of these two products assessed for causality using the updated RUCAM. Upon a detailed investigation, the patient did not have evidence of underlying liver disease or any other risk factors to explain her presentation. After discontinuation of both herbal supplements, the patient had complete resolution of her symptoms and a significant improvement of transaminitis. This report highlights the importance of potential risk of hepatotoxicity induced by concomitant use of Cimicifuga racemosa and Thuja occidentalis.