ABSTRACT
Fibrous electrodes are a promising alternative to conventional particle-based lithium-ion battery electrodes. In this contribution, we propose an efficient computational approach for the modeling and simulation of electrochemical phenomena taking place in fibrous electrodes during battery charge/discharge processes. Since each fiber is explicitly modeled by means of a dimensionally reduced embedded fiber model, the framework enables simulations in a three-dimensional setting with relatively modest discretization and computational requirements compared to simulations with fully resolved fiber discretizations. The approach is applied to electrodes with high volume fractions of high aspect ratio fibers. Various local and global quantities are analyzed and results are compared to those obtained with the standard finite element method and the pseudo-2D model.
ABSTRACT
Background and aim: Ischemic heart diseases lead to numerous deaths worldwide. Prevention, rapid diagnosis and treatment are principal strategies in controlling mortality due to coronary artery diseases (CAD). Considering variety of options, finding suitable diagnostic modality for each patient has been controversial for long times. Exercise treadmill test (ETT) is a well-known and old modality compared to radionuclide scintigraphy. In this study we aimed to assess if heart rate recovery (HRR) and exercise capacity (EC) in ETT can predict perfusion defects in 99mTc-MIBI SPECT myocardial perfusion imaging (MPI). Materials and methods: In this cross-sectional, descriptive-analytic study, we enrolled 254 patients referred for MPI to nuclear medicine department of Afshar or Shahid Sadoughi Hospital, Yazd, Iran. All patients underwent ETT and MPI. HRR and EC in ETT plus abnormal perfusion findings in MPI along with patient's history and demographic information were recorded in a questionnaire. Finally, all data were analyzed using SPSS ver.22 software. Results: Based on our results, 161 (63.4%) of patients were men. Half of patients were diagnosed with hypertension. 45% were diagnosed with diabetes, 41% had hyperlipidemia and 8.3% were smokers. Based on our findings, 18.1% of patients had abnormal MPI results. Our analytic results indicated that there is no statistically significant association between transient RV visualization, transient ischemic dilation or lung to heart ratio with 1st and 2nd minute HRR and EC. Conclusion: Considering lack of association between ETT indices and MPI findings, it seems that ETT is not adequately sensitive in predicting perfusion defects in MPI. Thus, it seems logical in some cases to ignore expenses of MPI and suggest it to patients before ETT based on clinical judgement.
ABSTRACT
Calcium phosphate cements (CPCs) have been widely used during the past decades as biocompatible bone substitution in maxillofacial, oral and orthopedic surgery. CPCs are injectable and are chemically resemblant to the mineral phase of native bone. Nevertheless, their low fracture toughness and high brittleness reduce their clinical applicability to weakly loaded bones. Reinforcement of CPC matrix with polymeric fibers can overcome these mechanical drawbacks and significantly enhance their toughness and strength. Such fiber-reinforced calcium phosphate cements (FRCPCs) have the potential to act as advanced bone substitute in load-bearing anatomical sites. This work achieves integrated experimental and numerical characterization of the mechanical properties of FRCPCs under bending and tensile loading. To this end, a 3-D numerical gradient enhanced damage model combined with a dimensionally-reduced fiber model are employed to develop a computational model for material characterization and to simulate the failure process of fiber-reinforced CPC matrix based on experimental data. In addition, an advanced interfacial constitutive law, derived from micromechanical pull-out tests, is used to represent the interaction between the polymeric fiber and CPC matrix. The presented computational model is successfully validated with the experimental results and offers a firm basis for further investigations on the development of numerical and experimental analysis of fiber-reinforced bone cements.
