Finite element modelling and characterization of 3D cellular microstructures for the design of a cementless biomimetic porous hip stem

Mehboob, Hassan,Tarlochan, Faris,Mehboob, Ali,Chang, Seung-Hwan Elsevier 2018 Materials & Design Vol.149 No.-

<P><B>Abstract</B></P> <P>Titanium porous cellular microstructures are commonly used in bone mimetic implants. The orientations of the internal strut architectures of these microstructures affect the mechanical performance under various loads; however, poor architectural designs may result in their failure. Three-dimensional (3D) finite element models of cubic, diamond, and body-centered cubic (BCC) geometries were constructed with 1<B>–</B>4 numbers of unit cells and 4–10-mm unit cell size. Mechanical testing of the finite models of the cubic, diamond, and BCC structures with porosities of 20–90% was performed under compression, bending, and torsional loads. The BCC structure showed moderate and relatively isotropic mechanical properties compared with those of the diamond and cubic structures. A design space for a BCC porous structure with a porosity of 40–65% was estimated to model a complete porous stem to mimic the bone properties. Furthermore, the stems with the determined porous mechanical properties of the BCC microstructures with 20–90% porosities were tested under physiological loading conditions. It was found that a porosity of 47.3% of the BCC structure exhibits the closest stiffness (469N/mm) to an intact bone (422N/mm). This was predicted by our suggested design space of the porosity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bioinspired 3D FE models of porous cellular structures with cubic, diamond, and body centered cubic geometries were constructed. </LI> <LI> Mathematical simplified relationship for porosity calculation was derived with less than 6% error between theoretical and CAD models. </LI> <LI> 20–90% porous cellular structures were tested under compression, bending and torsional loads. </LI> <LI> Gibson and Ashby and regression models were utilized to correlate the mechanical properties from FEA results. </LI> <LI> A design space of BCC porous structure with porosity of 40–65% was determined and 47.3% porous stem gave the similar stiffness to the bone. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Application of composites to orthopedic prostheses for effective bone healing: A review

Mehboob, H.,Chang, S.H. Applied Science Publishers ; Elsevier 2014 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.118 No.-

This paper aims to provide useful and practical information on the design of composite prostheses for healing bone fractures and describes the material properties of living tissues such as cartilage, structural materials and loading conditions according to various cases, and modeling techniques for the simulation of tissue differentiation during bone healing. In addition, the present review paper provides an overview of composite materials for the design of prostheses and highlights the merits of using composites. The history and recent trends in fixation methods and types, types of materials used for prostheses, loading conditions, mechano-regulation theories, and modeling techniques for finite element analyses to estimate the healing of bone fractures are also introduced. The healing process of bone fractures is fully influenced by the biomechanical characteristics of an orthopedic prosthesis and the injured bone such as fracture configurations, prosthesis shape, material properties, and degradation rate of the material. The appropriate parameters are highlighted for the optimal design of composite prostheses to heal bone fractures successfully.

Analysis of activated colloidal crud in advanced and modular reactor under pump coastdown with kinetic corrosion

Mehboob Khurram,Al-Zahrani Yahya A. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.12

The analysis of rapid flow transients in Reactor Coolant Pumps (RCP) is essential for a reactor safety study. An accurate and precise analysis of the RCP coastdown is necessary for the reactor design. The coastdown of RCP affects the coolant temperature and the colloidal crud in the primary coolant. A realistic and kinetic model has been used to investigate the behavior of activated colloidal crud in the primary coolant and steam generator that solves the pump speed analytically. The analytic solution of the non-dimensional flow rate has been determined by the energy ratio b. The kinetic energy of the coolant fluid and the kinetic energy stored in the rotating parts of a pump are two essential parameters in the form of b. Under normal operation, the pump's speed and moment of inertia are constant. However, in a coastdown situation, kinetic damping in the interval has been implemented. A dynamic model ACCP-SMART has been developed for System Integrated Modular and Advanced Reactor (SMART) to investigate the corrosion due to activated colloidal crud. The Fickian diffusion model has been implemented as the reference corrosion model for the constituent component of the primary loop of the SMART reactor. The activated colloidal crud activity in the primary coolant and steam generator of the SMART reactor has been studied for different equilibrium corrosion rates, linear increase in corrosion rate, and dynamic RCP coastdown situation energy ratio b. The coolant specific activity of SMART reactor equilibrium corrosion (4.0 mg s1 ) has been found 9.63 103 mCi cm3 , 3.53 103 mC cm3 , 2.39 102 mC cm3 , 8.10 103 mC cm3 , 6.77 103 mC cm3 , 4.95 104 mC cm3 , 1.19 103 mC cm3 , and 7.87 104 mC cm3 for 24Na, 54Mn, 56Mn, 59Fe, 58Co, 60Co, 99Mo, and 51Cr which are 14.95%, 5.48%, 37.08%, 12.57%, 10.51%, 0.77%, 18.50%, and 0.12% respectively. For linear and exponential coastdown with a constant corrosion rate, the total coolant and steam generator activity approaches a higher saturation value than the normal values. The coolant and steam generator activity changes considerably with kinetic corrosion rate, equilibrium corrosion, growth of corrosion rate (DC/Dt), and RCP coastdown situations. The effect of the RCP coastdown on the specific activity of the steam generators is smeared by linearly rising corrosion rates, equilibrium corrosion, and rapid coasting down of the RCP. However, the time taken to reach the saturation activity is also influenced by the slope of corrosion rate, coastdown situation, equilibrium corrosion rate, and energy ratio b.

Effect of air plasma treatment on mechanical properties of bioactive composites for medical application: Composite preparation and characterization

Mehboob, Hassan,Bae, Ji-Hun,Han, Min-Gu,Chang, Seung-Hwan Elsevier 2016 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.143 No.-

<P><B>Abstract</B></P> <P>The aim of this study was to fabricate unidirectional bio-glass fibers (BGF) (13-93)-reinforced polylactic acid (PLA) composites with improved mechanical properties for a bone plate to heal the weight-bearing long-bone fractures. Various exposure times of air plasma (30, 60, 90 and 120s) on BGF fibers were studied, and the most suitable conditions were determined for the fabrication of the BGF/PLA composite. Mechanical properties, microscopic characteristics, <I>in vitro</I> degradation and the bioactivity of the BGF/PLA composites were evaluated. Fatigue life of 30s plasma treated composites completed 1 million cycles when actual loading conditions (10–20% body weight) were used. 30s plasma treated specimens showed increase in tensile strength, flexural strength and interlaminar shear strength as 31%, 13.5% and 33%, respectively. The SEM image of fractured surface of 30s plasma treated composite suggested that the failure was shifted to the PLA which is evidence of superior bonding between fiber and PLA matrix. Moreover, a bone-like calcium-phosphate layer was precipitated on the surface of degraded composite that is essential for bone healing.</P>

Biofilm Formation and Indole-3-Acetic Acid Production by Two Rhizospheric Unicellular Cyanobacteria

( Mehboob Ahmed ),( Lucas J Stal ),( Shahida Hasnain ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.8

Microorganisms that live in the rhizosphere play a pivotal role in the functioning and maintenance of soil ecosystems. The study of rhizospheric cyanobacteria has been hampered by the difficulty to culture and maintain them in the laboratory. The present work investigated the production of the plant hormone indole-3-acetic acid (IAA) and the potential of biofilm formation on the rhizoplane of pea plants by two cyanobacterial strains, isolated from rice rhizosphere. The unicellular cyanobacteria Chroococcidiopsis sp. MMG-5 and Synechocystis sp. MMG-8 that were isolated from a rice rhizosphere, were investigated. Production of IAA by Chroococcidiopsis sp. MMG-5 and Synechocystis sp. MMG-8 was measured under experimental conditions (pH and light). The bioactivity of the cyanobacterial auxin was demonstrated through the alteration of the rooting pattern of Pisum sativum seedlings. The increase in the concentration of L-tryptophan and the time that this amino acid was present in the medium resulted in a significant enhancement of the synthesis of IAA (r > 0.900 at p = 0.01). There was also a significant correlation between the concentration of IAA in the supernatant of the cyanobacteria cultures and the root length and number of the pea seedlings. Observations made by confocal laser scanning microscopy revealed the presence of cyanobacteria on the surface of the roots and also provided evidence for the penetration of the cyanobacteria in the endorhizosphere. We show that the synthesis of IAA by Chroococcidiopsis sp. MMG-5 and Synechocystis sp. MMG-8 occurs under different environmental conditions and that the auxin is important for the development of the seedling roots and for establishing an intimate symbiosis between cyanobacteria and host plants.

Quantification of in-containment fission products source term for 1000MWe PWR under loss of coolant accident

Mehboob, Khurram,Park, Kwangheon,Khan, Rehan Elsevier 2015 Annals of nuclear energy Vol.75 No.-

<P><B>Abstract</B></P> <P>The aim of this work is the modeling and simulation of in-containment fission products (FPs) quantification and behavior under loss of coolant accident (LOCA) in terms of NUREG-1465 key aspects. For this purpose, a kinetic model has been developed to determine the quantification and behavior of in-containment source term after loss of coolant accident for typical 1000MWe PWR. A more realistic approach of continuous release of fission products from damaged core has been implemented with coolant retention. The simulation for in-containment fission product quantification influenced by containment atmosphere and containment system response has been carried out. Dramatic results have been obtained upon comparison study of fission product behaviors with different computational values. Moreover a contradiction in mixing rate (<I>w<SUB>x</SUB> </I>) value has been observed with a factor of 10 in comparison with Saeed et al. (2012).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Kinetic modeling for in-containment fission product activity. </LI> <LI> Modeling and simulation of in-containment source term after LOCA. </LI> <LI> Quantification of airborne in-containment activity. </LI> <LI> BURNUP activity calculation and comparison with literature. </LI> <LI> Study the effect of ESFs and coolant retention with mixing rate. </LI> </UL> </P>

Enhancing the performance of all-vanadium redox flow batteries by decorating carbon felt electrodes with SnO₂ nanoparticles

Mehboob, Sheeraz,Ali, Ghulam,Shin, Hyun-Jin,Hwang, Jinyeon,Abbas, Saleem,Chung, Kyung Yoon,Ha, Heung Yong Elsevier 2018 APPLIED ENERGY Vol.229 No.-

<P><B>Abstract</B></P> <P>An all-vanadium redox flow battery (VRFB) is an attractive candidate as an electrochemical energy storage system that uses conversion technology for applications that range from those requiring only a few kilowatts to those that must perform on a megawatt scale. Issues to be resolved, however, include problems with increasing the rates of charge/discharge (due to an increase in overpotentials) and cycling stability (due to the irreversibility of redox reactions at the electrodes as well as crossover of the vanadium species) that have prevented a broader market penetration of VRFB systems. One of the strategies to overcome these problems may be the introduction of electrocatalysts to the electrode surface to improve the reaction kinetics of the positive and negative redox couples, thus enabling the achievement of higher levels of power density. Therefore, carbon felt electrodes decorated with SnO<SUB>2</SUB> nanoparticles were evaluated in this study. The performance of VRFBs at a high current density of 150 mA cm<SUP>−2</SUP> with SnO<SUB>2</SUB>-deposited carbon felts returned an energy efficiency of 77.3%, with a corresponding increase in discharge capacity of 23.7% over a pristine electrode. Cycling stability of the system was also improved almost 2.7-fold compared with that of a pristine electrode at 50 mA cm<SUP>−2</SUP>. The electrocatalytic activity of SnO<SUB>2</SUB> nanoparticles facilitates a reduction in the overpotentials, which enables charge/discharge reactions at faster rates, which was confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. Furthermore, confirmation of the formation of clusters of SnO<SUB>2</SUB> nanocrystals as well as their chemical and physical stability after cycling (as probed by various characterization techniques including synchrotron-based X-ray absorption) supports their feasibility as a stable, efficient and cost-effective electrocatalyst for use in VRFB systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Carbon felt is deposited with clusters of SnO<SUB>2</SUB> nanoparticles (3–5 nm). </LI> <LI> The SnO<SUB>2</SUB>-deposited carbon felt exhibits energy efficiency of 77.3% at 150 mA cm<SUP>−2</SUP>. </LI> <LI> Impact of SnO<SUB>2</SUB> electrocatalyst on improvement of cycling stability is also focused. </LI> <LI> Stability of electrocatalyst is probed by synchrotron radiations-based techniques. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Excellent electrocatalytic effects of tin through in situ electrodeposition on the performance of all-vanadium redox flow batteries

Mehboob, Sheeraz,Mehmood, Asad,Lee, Ju-Young,Shin, Hyun-Jin,Hwang, Jinyeon,Abbas, Saleem,Ha, Heung Yong The Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.33

<▼1><P>The impact on the performance of all-vanadium redox flow batteries by tin as an electrocatalyst through <I>in situ</I> electrodeposition is investigated.</P></▼1><▼2><P>This work unfolds novel electrocatalytic effects of tin for all-vanadium redox flow batteries (VRFBs). By the introduction of Sn<SUP>2+</SUP> ions into the electrolyte, tin nanoparticles are <I>in situ</I> electrodeposited on a carbon felt electrode. The effectiveness of the two tin species (Sn<SUP>2+</SUP> and Sn<SUP>4+</SUP>) as well as their impact on the kinetics of cathode (VO2<SUP>2+</SUP>/VO2<SUP>+</SUP>) and anode (V<SUP>3+</SUP>/V<SUP>2+</SUP>) half-reactions are also evaluated comprehensively. Cyclic voltammetry reflects the excellent improvement in reaction kinetics, particularly for the anode half-reaction (<I>i.e.</I> V<SUP>3+</SUP>/V<SUP>2+</SUP> reduction) by reducing its peak potential separation from 1011 to 589 mV, owing to the deposition of tin nanoparticles in its vicinity. The electrocatalytic effects of tin cause a significant improvement in key performance parameters of voltage efficiency, energy efficiency (EE), specific discharge capacity, discharge energy density and cycling stability for VRFBs. The VRFBs employing Sn<SUP>2+</SUP> ions in the anolyte exhibit an EE of 77.3% at a high current density of 150 mA cm<SUP>−2</SUP> while the corresponding specific discharge capacity and discharge energy density are increased by 26.2 and 32.0%, respectively, as compared to the pristine system. Thus, electrolyte utilization is also increased at faster charge/discharge rates due to the reduction of overpotentials. Various characterization techniques confirm the deposition and effectiveness of tin at the electrodes. EIS studies reveal remarkable acceleration in the charge transfer process for the V<SUP>3+</SUP>/V<SUP>2+</SUP> redox couple which is considered as a performance limiting reaction for VRFBs nowadays. Therefore, the convenience in its application coupled with effectiveness for VRFBs, makes tin a commercially feasible electrocatalyst for this technology.</P></▼2>

Effect of composite bone plates on callus generation and healing of fractured tibia with different screw configurations

Mehboob, Ali,Chang, Seung-Hwan Elsevier 2018 Composites science and technology Vol.167 No.-

<P><B>Abstract</B></P> <P>In this paper, finite element analysis of a fractured tibia with a glass/polypropylene composite implant is introduced. A rejection coefficient algorithm (for callus development) that is sensitive to interfragmentary movement is programmed, calibrated (using experimental <I>in vivo</I> statistics), and successfully implemented on a 3D fractured tibia model. A biphasic mechano-regulation algorithm is implemented to verify healing status under five different screw configurations (C1–C5) using glass/polypropylene composite bone plates and the development of tissue phenotypes in calluses is estimated. A 300% increase in circumferential callus volume is obtained when using the composite bone plate. Furthermore, the C5 configuration of the composite bone plate results in a maximum interfragmentary movement of 4.33% on day one with faster and stronger healing through 95% of bone growth during the final day of healing.</P>

Biomechanical simulation of healing process of fractured femoral shaft applied by composite intramedullary nails according to fracture configuration

Mehboob, Ali,Chang, Seung-Hwan ELSEVIER (APPLIED SCIENCE) 2018 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.185 No.-

<P><B>Abstract</B></P> <P>Flexible composite implants are receiving increased attention in this modern era of orthopedics for the stabilization of long bone fractures because they facilitate tissue development in calluses. An endochondral ossification process involves generation of calluses, and it is well known that this significantly affects the stabilization and healing of the broken bones. Therefore, the exact configuration of callus formation is highly important for the accurate simulation of bone healing. In this study, finite element analysis was performed to estimate the external callus shape by using the rejection coefficient (RC) algorithm. Regarding the application of a fractured femur by an intramedullary (IM) nail, the bone healing simulation was conducted by employing the biphasic mechano-regulation algorithm according to the fracture type (transverse (0°) and oblique (35°)), fracture location (proximal, medial, and distal ends), and nail property. The simulation results revealed that a glass/polypropylene fabric composite (Twintex [0]<SUB>2nT</SUB>) IM nail, which has the similar Young’s modulus to the cortical bone, provided the most appropriate bio-mechanical environment for bone healing.</P>