Displaying publications 41 - 60 of 91 in total

Abstract:
Sort:
  1. Physicochemical characterization of kappa-carrageenan (Euchema cottoni) based films incorporated with various plant oils
    R NFN, Nur Hanani ZA
    Carbohydr Polym, 2017 Feb 10;157:1479-1487.
    PMID: 27987859 DOI: 10.1016/j.carbpol.2016.11.026
    This study investigated the effects of different types of plant oil (olive oil, corn oil, soybean oil and sunflower oil) on the physical and mechanical properties of kappa-carrageenan films from Euchema cottoni species. The incorporation of plant oils increased the film thickness significantly (P<0.05). However, the moisture content, solubility and tensile strength of films decreased significantly (P<0.05) as plant oils were added. The incorporation of plant oils also contributed to a plasticizing effect, whereby the values for elongation at break increased significantly (P<0.05), from 22.3% to 108.8%. Higher oil content also led to carrageenan films with lower opacity, which contradicted with previous studies. In conclusion, the plant oils used in this research significantly improved film properties, thus demonstrating the potential of these materials to be used as food packaging films and coatings.
    Matched MeSH terms: Mechanical Phenomena
  2. Fulltext Simulation of passive exotendon assistive device for agricultural harvesting task
    Chan YS, Teo YX, Gouwanda D, Nurzaman SG, Gopalai AA
    Phys Eng Sci Med, 2023 Dec;46(4):1375-1386.
    PMID: 37493930 DOI: 10.1007/s13246-023-01305-9
    This study proposes and investigates the feasibility of the passive assistive device to assist agricultural harvesting task and reduce the Musculoskeletal Disorder (MSD) risk of harvesters using computational musculoskeletal modelling and simulations. Several passive assistive devices comprised of elastic exotendon, which acts in parallel with different back muscles (rectus abdominis, longissimus, and iliocostalis), were designed and modelled. These passive assistive devices were integrated individually into the musculoskeletal model to provide passive support for the harvesting task. The muscle activation, muscle force, and joint moment were computed with biomechanical simulations for unassisted and assisted motions. The simulation results demonstrated that passive assistive devices reduced muscle activation, muscle force, and joint moment, particularly when the devices were attached to the iliocostalis and rectus abdominis. It was also discovered that assisting the longissimus muscle can alleviate the workload by distributing a portion of it to the rectus abdominis. The findings in this study support the feasibility of adopting passive assistive devices to reduce the MSD risk of the harvesters during agricultural harvesting. These findings can provide valuable insights to the engineers and designers of physical assistive devices on which muscle(s) to assist during agricultural harvesting.
    Matched MeSH terms: Mechanical Phenomena
  3. Fulltext The influence of chemical surface modification of kenaf fiber using hydrogen peroxide on the mechanical properties of biodegradable kenaf fiber/poly(lactic acid) composites
    Razak NI, Ibrahim NA, Zainuddin N, Rayung M, Saad WZ
    Molecules, 2014;19(3):2957-68.
    PMID: 24609017 DOI: 10.3390/molecules19032957
    Bleaching treatment of kenaf fiber was performed in alkaline medium containing hydrogen peroxide solution maintained at pH 11 and 80 °C for 60 min. The bleached kenaf fiber was analyzed using Fourier Transform Infrared (FTIR) and X-ray Diffraction (XRD) analysis. The bleached kenaf fiber was then compounded with poly-(lactic acid) (PLA) via a melt blending method. The mechanical (tensile, flexural and impact) performance of the product was tested. The fiber treatment improved the mechanical properties of PLA/bleached kenaf fiber composites. Scanning electron micrograph (SEM) morphological analysis showed improvement of the interfacial adhesion between the fiber surface and polymer matrix.
    Matched MeSH terms: Mechanical Phenomena*
  4. Mechanical compression controls the biosynthesis of human osteoarthritic chondrocytes in vitro
    Chong PP, Panjavarnam P, Ahmad WNHW, Chan CK, Abbas AA, Merican AM, et al.
    Clin Biomech (Bristol, Avon), 2020 10;79:105178.
    PMID: 32988676 DOI: 10.1016/j.clinbiomech.2020.105178
    BACKGROUND: Cartilage damage, which can potentially lead to osteoarthritis, is a leading cause of morbidity in the elderly population. Chondrocytes are sensitive to mechanical stimuli and their matrix-protein synthesis may be altered when chondrocytes experience a variety of in vivo loadings. Therefore, a study was conducted to evaluate the biosynthesis of isolated osteoarthritic chondrocytes which subjected to compression with varying dynamic compressive strains and loading durations.

    METHODS: The proximal tibia was resected as a single osteochondral unit during total knee replacement from patients (N = 10). The osteoarthritic chondrocytes were isolated from the osteochondral units, and characterized using reverse transcriptase-polymerase chain reaction. The isolated osteoarthritic chondrocytes were cultured and embedded in agarose, and then subjected to 10% and 20% uniaxial dynamic compression up to 8-days using a bioreactor. The morphological features and changes in the osteoarthritic chondrocytes upon compression were evaluated using scanning electron microscopy. Safranin O was used to detect the presence of cartilage matrix proteoglycan expression while quantitative analysis was conducted by measuring type VI collagen using an immunohistochemistry and fluorescence intensity assay.

    FINDINGS: Gene expression analysis indicated that the isolated osteoarthritic chondrocytes expressed chondrocyte-specific markers, including BGN, CD90 and HSPG-2. Moreover, the compressed osteoarthritic chondrocytes showed a more intense and broader deposition of proteoglycan and type VI collagen than control. The expression of type VI collagen was directly proportional to the duration of compression in which 8-days compression was significantly higher than 4-days compression. The 20% compression showed significantly higher intensity compared to 10% compression in 4- and 8-days.

    INTERPRETATION: The biosynthetic activity of human chondrocytes from osteoarthritic joints can be enhanced using selected compression regimes.

    Matched MeSH terms: Biomechanical Phenomena; Mechanical Phenomena*
  5. The use of salt-coating to improve textural, mechanical, cooking and sensory properties of air-dried yellow alkaline noodles
    Yeoh SY, Lubowa M, Tan TC, Murad M, Mat Easa A
    Food Chem, 2020 Dec 15;333:127425.
    PMID: 32683254 DOI: 10.1016/j.foodchem.2020.127425
    Zero-salted yellow alkaline noodles (YAN) were immersed in solutions of resistant starch HYLON™ VII (HC) or fruit coating Semperfresh™ (SC) containing a range of salt (NaCl) between 10 and 30% (w/v). The objective was to evaluate the effect of salt-coatings on the textural, handling, cooking, and sensory properties of YAN. Increasing salt in the coatings caused a reduction in optimum cooking time, cooking loss and increase in cooking yield. The mechanical and textural parameters, sensory hardness, springiness and overall sensory acceptability of the salt-coated noodles however decreased with increasing salt application. HC-Na10 and SC-Na10 showed the highest textural and mechanical parameters, sensory hardness and springiness. The differences in the parameters were attributed mainly to the water absorption properties of starch that was affected by salt application. Thus, the quality of salt-coated noodles was dependent mainly on the amounts of salt applied in the coatings rather than on the types of coatings used.
    Matched MeSH terms: Mechanical Phenomena*
  6. Enhancement of thermal, mechanical and physical properties of polyamide 12 composites via hybridization of ceramics for bone replacement
    Abdullah AM, Mohamad D, Rahim TNAT, Akil HM, Rajion ZA
    Mater Sci Eng C Mater Biol Appl, 2019 Jun;99:719-725.
    PMID: 30889745 DOI: 10.1016/j.msec.2019.02.007
    This study reports the influence of ZrO2/β-TCP hybridization on the thermal, mechanical, and physical properties of polyamide 12 composites to be suited for bone replacement. Amount of 15 wt% of nano-ZrO2 along with 5,10,15,20 and 25 wt% of micro-β-TCP was compounded with polyamide 12 via a twin-screw extruder. The hybrid ZrO2/β-TCP filled polyamide 12 exhibited higher thermal, mechanical and physical properties in comparison to unfilled polyamide 12 at certain filler loading; which is attributed to the homogenous dispersion of ZrO2/β-TCP fillers particle in polyamide 12 matrix. The hybrid ZrO2/β-TCP filled PA 12 demonstrated an increment of tensile strength by up to 1%, tensile modulus of 38%, flexural strength of 15%, flexural modulus of 45%, and surface roughness value of 93%, as compared to unfilled PA 12. With enhanced thermal, mechanical and physical properties, the newly developed hybrid ZrO2/β-TCP filled PA 12 could be potentially utilized for bone replacement.
    Matched MeSH terms: Mechanical Phenomena*
  7. Thermal, mechanical, and physical properties of seaweed/sugar palm fibre reinforced thermoplastic sugar palm Starch/Agar hybrid composites
    Jumaidin R, Sapuan SM, Jawaid M, Ishak MR, Sahari J
    Int J Biol Macromol, 2017 Apr;97:606-615.
    PMID: 28109810 DOI: 10.1016/j.ijbiomac.2017.01.079
    The aim of this research is to investigate the effect of sugar palm fibre (SPF) on the mechanical, thermal and physical properties of seaweed/thermoplastic sugar palm starch agar (TPSA) composites. Hybridized seaweed/SPF filler at weight ratio of 25:75, 50:50 and 75:25 were prepared using TPSA as a matrix. Mechanical, thermal and physical properties of hybrid composites were carried out. Obtained results indicated that hybrid composites display improved tensile and flexural properties accompanied with lower impact resistance. The highest tensile (17.74MPa) and flexural strength (31.24MPa) was obtained from hybrid composite with 50:50 ratio of seaweed/SPF. Good fibre-matrix bonding was evident in the scanning electron microscopy (SEM) micrograph of the hybrid composites' tensile fracture. Fourier transform infrared spectroscopy (FT-IR) analysis showed increase in intermolecular hydrogen bonding following the addition of SPF. Thermal stability of hybrid composites was enhanced, indicated by a higher onset degradation temperature (259°C) for 25:75 seaweed/SPF composites than the individual seaweed composites (253°C). Water absorption, thickness swelling, water solubility, and soil burial tests showed higher water and biodegradation resistance of the hybrid composites. Overall, the hybridization of SPF with seaweed/TPSA composites enhances the properties of the biocomposites for short-life application; that is, disposable tray, plate, etc.
    Matched MeSH terms: Mechanical Phenomena*
  8. Prediction of damage formation in hip arthroplasties by finite element analysis using computed tomography images
    Abdullah AH, Todo M, Nakashima Y
    Med Eng Phys, 2017 06;44:8-15.
    PMID: 28373012 DOI: 10.1016/j.medengphy.2017.03.006
    Femoral bone fracture is one of the main causes for the failure of hip arthroplasties (HA). Being subjected to abrupt and high impact forces in daily activities may lead to complex loading configuration such as bending and sideway falls. The objective of this study is to predict the risk of femoral bone fractures in total hip arthroplasty (THA) and resurfacing hip arthroplasty (RHA). A computed tomography (CT) based on finite element analysis was conducted to demonstrate damage formation in a three dimensional model of HAs. The inhomogeneous model of femoral bone was constructed from a 79 year old female patient with hip osteoarthritis complication. Two different femoral components were modeled with titanium alloy and cobalt chromium and inserted into the femoral bones to present THA and RHA models respectively. The analysis included six configurations, which exhibited various loading and boundary conditions, including axial compression, torsion, lateral bending, stance and two types of falling configurations. The applied hip loadings were normalized to body weight (BW) and accumulated from 1 BW to 3 BW. Predictions of damage formation in the femoral models were discussed as the resulting tensile failure as well as the compressive yielding and failure elements. The results indicate that loading directions can forecast the pattern and location of fractures at varying magnitudes of loading. Lateral bending configuration experienced the highest damage formation in both THA and RHA models. Femoral neck and trochanteric regions were in a common location in the RHA model in most configurations, while the predicted fracture locations in THA differed as per the Vancouver classification.
    Matched MeSH terms: Mechanical Phenomena*
  9. Torque and mechanomyogram relationships during electrically-evoked isometric quadriceps contractions in persons with spinal cord injury
    Ibitoye MO, Hamzaid NA, Hasnan N, Abdul Wahab AK, Islam MA, Kean VS, et al.
    Med Eng Phys, 2016 Aug;38(8):767-75.
    PMID: 27289541 DOI: 10.1016/j.medengphy.2016.05.012
    The interaction between muscle contractions and joint loading produces torques necessary for movements during activities of daily living. However, during neuromuscular electrical stimulation (NMES)-evoked contractions in persons with spinal cord injury (SCI), a simple and reliable proxy of torque at the muscle level has been minimally investigated. Thus, the purpose of this study was to investigate the relationships between muscle mechanomyographic (MMG) characteristics and NMES-evoked isometric quadriceps torques in persons with motor complete SCI. Six SCI participants with lesion levels below C4 [(mean (SD) age, 39.2 (7.9) year; stature, 1.71 (0.05) m; and body mass, 69.3 (12.9) kg)] performed randomly ordered NMES-evoked isometric leg muscle contractions at 30°, 60° and 90° knee flexion angles on an isokinetic dynamometer. MMG signals were detected by an accelerometer-based vibromyographic sensor placed over the belly of rectus femoris muscle. The relationship between MMG root mean square (MMG-RMS) and NMES-evoked torque revealed a very high association (R(2)=0.91 at 30°; R(2)=0.98 at 60°; and R(2)=0.97 at 90° knee angles; P<0.001). MMG peak-to-peak (MMG-PTP) and stimulation intensity were less well related (R(2)=0.63 at 30°; R(2)=0.67 at 60°; and R(2)=0.45 at 90° knee angles), although were still significantly associated (P≤0.006). Test-retest interclass correlation coefficients (ICC) for the dependent variables ranged from 0.82 to 0.97 for NMES-evoked torque, between 0.65 and 0.79 for MMG-RMS, and from 0.67 to 0.73 for MMG-PTP. Their standard error of measurements (SEM) ranged between 10.1% and 31.6% (of mean values) for torque, MMG-RMS and MMG-PTP. The MMG peak frequency (MMG-PF) of 30Hz approximated the stimulation frequency, indicating NMES-evoked motor unit firing rate. The results demonstrated knee angle differences in the MMG-RMS versus NMES-isometric torque relationship, but a similar torque related pattern for MMG-PF. These findings suggested that MMG was well associated with torque production, reliably tracking the motor unit recruitment pattern during NMES-evoked muscle contractions. The strong positive relationship between MMG signal and NMES-evoked torque production suggested that the MMG might be deployed as a direct proxy for muscle torque or fatigue measurement during leg exercise and functional movements in the SCI population.
    Matched MeSH terms: Biomechanical Phenomena; Mechanical Phenomena*
  10. New polyurethane nanocomposites based on soya oil
    Mohammed IA, Abd Khadir NK, Jaffar Al-Mulla EA
    J Oleo Sci, 2014;63(2):193-200.
    PMID: 24420063
    New polyurethane (PU) nanocomposites were prepared from a dispersion of 0 - 5% montmorillonite (MMT) clay with isocyanate and soya oil polyol that was synthesized via transesterification of triglycerides to reduce petroleum dependence. FT-IR spectra indicate the presence of hydrogen bonding between nanoclay and the polymer matrix, whereas the exfoliated structure of clay layers was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Optical microscopy, mechanical and thermal analyses were done to investigate significant improvement of the nanocomposites. The results showed PU-3% nanoclay (NC) showed optimum results in mechanical properties such as tensile and flexural strength but the lowest in impact strength.
    Matched MeSH terms: Mechanical Phenomena
  11. Dental implants from functionally graded materials
    Mehrali M, Shirazi FS, Mehrali M, Metselaar HS, Kadri NA, Osman NA
    J Biomed Mater Res A, 2013 Oct;101(10):3046-57.
    PMID: 23754641 DOI: 10.1002/jbm.a.34588
    Functionally graded material (FGM) is a heterogeneous composite material including a number of constituents that exhibit a compositional gradient from one surface of the material to the other subsequently, resulting in a material with continuously varying properties in the thickness direction. FGMs are gaining attention for biomedical applications, especially for implants, owing to their reported superior composition. Dental implants can be functionally graded to create an optimized mechanical behavior and achieve the intended biocompatibility and osseointegration improvement. This review presents a comprehensive summary of biomaterials and manufacturing techniques researchers employ throughout the world. Generally, FGM and FGM porous biomaterials are more difficult to fabricate than uniform or homogenous biomaterials. Therefore, our discussion is intended to give the readers about successful and obstacles fabrication of FGM and porous FGM in dental implants that will bring state-of-the-art technology to the bedside and develop quality of life and present standards of care.
    Matched MeSH terms: Mechanical Phenomena
  12. Fulltext The Effect of Welding Current and Electrode Force on the Heat Input, Weld Diameter, and Physical and Mechanical Properties of SS316L/Ti6Al4V Dissimilar Resistance Spot Welding with Aluminum Interlayer
    Taufiqurrahman I, Ahmad A, Mustapha M, Lenggo Ginta T, Ady Farizan Haryoko L, Ahmed Shozib I
    Materials (Basel), 2021 Feb 27;14(5).
    PMID: 33673716 DOI: 10.3390/ma14051129
    Welding parameters obviously determine the joint quality during the resistance spot welding process. This study aimed to investigate the effect of welding current and electrode force on the heat input and the physical and mechanical properties of a SS316L and Ti6Al4V joint with an aluminum interlayer. The weld current values used in this study were 11, 12, and 13 kA, while the electrode force values were 3, 4, and 5 kN. Welding time and holding time remained constant at 30 cycles. The study revealed that, as the welding current and electrode force increased, the generated heat input increased significantly. The highest tensile-shear load was recorded at 8.71 kN using 11 kA of weld current and 3 kN of electrode force. The physical properties examined the formation of a brittle fracture and several weld defects on the high current welded joint. The increase in weld current also increased the weld diameter. The microstructure analysis revealed no phase transformation on the SS316L interface; instead, the significant grain growth occurred. The phase transformation has occurred on the Ti6Al4V interface. The intermetallic compound layer was also investigated in detail using the EDX (Energy Dispersive X-Ray) and XRD (X-Ray Diffraction) analyses. It was also found that both stainless steel and titanium alloy have their own fusion zone, which is indicated by the highest microhardness value.
    Matched MeSH terms: Mechanical Phenomena
  13. Friction at nanopillared polymer surfaces beyond Amontons' laws: Stick-slip amplitude coefficient (SSAC) and multiparametric nanotribological properties
    Ishak MI, Dobryden I, Martin Claesson P, Briscoe WH, Su B
    J Colloid Interface Sci, 2021 Feb 01;583:414-424.
    PMID: 33011410 DOI: 10.1016/j.jcis.2020.09.038
    Frictional and nanomechanical properties of nanostructured polymer surfaces are important to their technological and biomedical applications. In this work, poly(ethylene terephthalate) (PET) surfaces with a periodic distribution of well-defined nanopillars were fabricated through an anodization/embossing process. The apparent surface energy of the nanopillared surfaces was evaluated using the Fowkes acid-base approach, and the surface morphology was characterized using scanning electron microscope (SEM) and atomic force microscope (AFM). The normal and lateral forces between a silica microparticle and these surfaces were quantified using colloidal probe atomic force microscopy (CP-AFM). The friction-load relationship followed Amonton's first law, and the friction coefficient appeared to scale linearly with the nanopillar height. Furthermore, all the nanopillared surfaces showed pronounced frictional instabilities compared to the smooth sliding friction loop on the flat control. Performing the stick-slip amplitude coefficient (SSAC) analysis, we found a correlation between the frictional instabilities and the nanopillars density, pull-off force and work of adhesion. We have summarised the dependence of the nanotribological properties on such nanopillared surfaces on five relevant parameters, i.e. pull-off force fp, Amontons' friction coefficient μ, RMS roughness Rq, stick-slip amplitude friction coefficient SSAC, and work of adhesion between the substrate and water Wadh in a radar chart. Whilst demonstrating the complexity of the frictional behaviour of nanopillared polymer surfaces, our results show that analyses of multiparametric nanotribological properties of nanostructured surfaces should go beyond classic Amontons' laws, with the SSAC more representative of the frictional properties compared to the friction coefficient.
    Matched MeSH terms: Mechanical Phenomena
  14. Effect of magnetic field on nano-magnetite composite exhibits in ion-adsorption
    Lo FF, Kow KW, Kung F, Ahamed F, Kiew PL, Yeap SP, et al.
    Sci Total Environ, 2021 Aug 01;780:146337.
    PMID: 33770606 DOI: 10.1016/j.scitotenv.2021.146337
    Nano-magnetites are widely researched for its potential as an excellent adsorbent in many applications. However, the efficiency of the nano-magnetites are hindered by their tendency to agglomerate. In this work, we dispersed and embedded the nano-magnetites in a porous silica gel matrix to form a nanocomposite to reduce the extent of agglomeration and to enhance the adsorption performance. Our experimental results showed that the removal efficiency of Cu2+ ion has improved by 46% (22.4 ± 2.2%) on the nano-magnetite-silica-gel (NMSG) nanocomposite as compared to pure nano-magnetites (15.3 ± 0.6%). The adsorption capacity is further enhanced by 39% (from 11.2 ± 1.1 to 15.6 ± 1.6 mg/g) by subjecting the NMSG to a magnetic field prior to adsorption. We infer that the magnetic field aligned the magnetic domains within the nano-magnetites, resulting in an increased Lorentz force during adsorption. Similar alignment of magnetic domains is near to impossible in pure nano-magnetites due to severe agglomeration. We further found that the adsorption capacity of the NMSG can be manipulated with an external magnetic field by varying the strength and the configurations of the field. Equipped with proper process design, our finding has great potentials in processes that involve ion-adsorptions, for example, NMSG can: (i) replace/reduce chemical dosing in controlling adsorption kinetics, (ii) replace/reduce complex chemicals required in ion-chromatography columns, and (iii) reduce wastage of nano-adsorbents by immobilizing it in a porous matrix.
    Matched MeSH terms: Mechanical Phenomena
  15. Fulltext Microstructural behavior of magnetorheological elastomer undergoing durability evaluation by stress relaxation
    Johari MAF, Mazlan SA, Nasef MM, Ubaidillah U, Nordin NA, Aziz SAA, et al.
    Sci Rep, 2021 May 25;11(1):10936.
    PMID: 34035434 DOI: 10.1038/s41598-021-90484-0
    The widespread use of magnetorheological elastomer (MRE) materials in various applications has yet to be limited due to the fact that there are substantial deficiencies in current experimental and theoretical research on its microstructural durability behavior. In this study, MRE composed of silicon rubber (SR) and 70 wt% of micron-sized carbonyl iron particles (CIP) was prepared and subjected to stress relaxation evaluation by torsional shear load. The microstructure and particle distribution of the obtained MRE was evaluated by a field emission scanning electron microscopy (FESEM). The influence of constant low strain at 0.01% is the continuing concern within the linear viscoelastic (LVE) region of MRE. Stress relaxation plays a significant role in the life cycle of MRE and revealed that storage modulus was reduced by 8.7%, normal force has weakened by 27%, and stress performance was reduced by 6.88% along approximately 84,000 s test duration time. This time scale was the longest ever reported being undertaken in the MRE stress relaxation study. Novel micro-mechanisms that responsible for the depleted performance of MRE was obtained by microstructurally observation using FESEM and in-phase mode of atomic force microscope (AFM). Attempts have been made to correlate strain localization produced by stress relaxation, with molecular deformation in MRE amorphous matrix. Exceptional attention was focused on the development of molecular slippage, disentanglement, microplasticity, microphase separation, and shear bands. The relation between these microstructural phenomena and the viscoelastic properties of MRE was diffusely defined and discussed. The presented MRE is homogeneous with uniform distribution of CIP. The most significant recent developments of systematic correlation between the effects of microstructural deformation and durability performance of MRE under stress relaxation has been observed and evaluated.
    Matched MeSH terms: Mechanical Phenomena
  16. Fulltext Comparison of Orthodontic Bracket Debonding Force and Bracket Failure Pattern on Different Teeth In Vivo by a Prototype Debonding Device
    Ahmed T, Rahman NA, Alam MK
    Biomed Res Int, 2021;2021:6663683.
    PMID: 33959664 DOI: 10.1155/2021/6663683
    Objective: To compare the orthodontic bracket debonding force and assess the bracket failure pattern clinically between different teeth by a validated prototype debonding device. Materials and Method. Thirteen (13) patients at the end of comprehensive fixed orthodontic treatment, awaiting for bracket removal, were selected from the list. A total of 260 brackets from the central incisor to the second premolar in both jaws were debonded by a single clinician using a validated prototype debonding device equipped with a force sensitive resistor (FSR). Mean bracket debonding forces were specified to ten (10) groups of teeth. Following debonding, Intraoral microphotographs of the teeth were taken by the same clinician to assess the bracket failure pattern using a 4-point scale of adhesive remnant index (ARI). Statistical analysis included one-way ANOVA with post hoc Tukey HSD and independent sample t-test to compare in vivo bracket debonding force, Cohen's kappa (κ), and a nonparametric Kruskal-Wallis test for the reliability and the assessment of ARI scoring.

    Results: A significant difference (p < 0.001) of mean debonding force was found between different types of teeth in vivo. Clinically, ARI scores were not significantly different (p = 0.921) between different groups, but overall higher scores were predominant.

    Conclusion: Bracket debonding force should be measured on the same tooth from the same arch as the significant difference of mean debonding force exists between similar teeth of the upper and lower arches. The insignificant bracket failure pattern with higher ARI scores confirms less enamel damage irrespective of tooth types.

    Matched MeSH terms: Mechanical Phenomena
  17. Fulltext Propionic Anhydride Modification of Cellulosic Kenaf Fibre Enhancement with Bionanocarbon in Nanobiocomposites
    Rizal S, Mistar EM, Oyekanmi AA, H P S AK, Alfatah T, Olaiya NG, et al.
    Molecules, 2021 Jul 13;26(14).
    PMID: 34299524 DOI: 10.3390/molecules26144248
    The use of chemical modification of cellulosic fibre is applied in order to increase the hydrophobicity, hence improving the compatibility between the fibre and matrix bonding. In this study, the effect of propionic anhydride modification of kenaf fibre was investigated to determine the role of bionanocarbon from oil palm shell agricultural wastes in the improvement of the functional properties of bionanocomposites. The vinyl esters reinforced with unmodified and propionic anhydride modified kenaf fibres bio nanocomposites were prepared using 0, 1, 3, 5 wt% of bio-nanocarbon. Characterisation of the fabricated bionanocomposite was carried out using FESEM, TEM, FT-IR and TGA to investigate the morphological analysis, surface properties, functional and thermal analyses, respectively. Mechanical performance of bionanocomposites was evaluated according to standard methods. The chemical modification of cellulosic fibre with the incorporation of bionanocarbon in the matrix exhibited high enhancement of the tensile, flexural, and impact strengths, for approximately 63.91%, 49.61% and 54.82%, respectively. The morphological, structural and functional analyses revealed that better compatibility of the modified fibre-matrix interaction was achieved at 3% bionanocarbon loading, which indicated improved properties of the bionanocomposite. The nanocomposites exhibited high degradation temperature which signified good thermal stability properties. The improved properties of the bionanocomposite were attributed to the effect of the surface modification and bionanocarbon enhancement of the fibre-matrix networks.
    Matched MeSH terms: Mechanical Phenomena
  18. Mass attenuation coefficient of tannin-added Rhizophora spp. particleboards at 16.59-25.56 keV photons, and 137Cs and 60Co gamma energies
    Yusof MFM, Hamid PNKA, Tajuddin AA, Hashim R, Bauk S, Isa NM, et al.
    Radiol Phys Technol, 2017 Sep;10(3):331-339.
    PMID: 28718054 DOI: 10.1007/s12194-017-0408-3
    The aim of this study was to determine the suitability of tannin-added Rhizophora spp. particleboards as phantom materials in the application of low- and high-energy photons. The tannin-added Rhizophora spp. particleboards and density plug phantoms were created with a target density of 1.0 g/cm3. The elemental composition and effective atomic number of the particleboards were measured using energy dispersive X-ray analysis. The mass attenuation coefficient of the particleboards for low-energy photons were measured using the attenuation of X-ray fluorescence. The mass attenuation coefficients of high-energy photons were measured using the attenuation of 137Cs and 60Co gamma energies. The results were compared to the calculated value of water using XCOM calculations. The results showed that the effective atomic number and mass attenuation coefficients of tannin-added Rhizophora spp. particleboards were similar to those of water, indicating the suitability of tannin-added Rhizophora spp. particleboards as phantom materials for low- and high-energy photons.
    Matched MeSH terms: Mechanical Phenomena
  19. Effects of plasticizers on the physicochemical properties of kappa-carrageenan films extracted from Eucheuma cottonii
    Ili Balqis AM, Nor Khaizura MAR, Russly AR, Nur Hanani ZA
    Int J Biol Macromol, 2017 Oct;103:721-732.
    PMID: 28528954 DOI: 10.1016/j.ijbiomac.2017.05.105
    The physicochemical properties of κ-carrageenan films extracted from Eucheuma cottonii (E. cottonii) incorporated with different concentrations and types of plasticizers were studied. Glycerol, sorbitol, and polyethylene glycol-300 (PEG-300) in the range of 10-60% were used as plasticizers. The results showed that the thickness and moisture content (MC) of films increased significantly (p≤0.05) with the increase in plasticizer concentration. Sorbitol-plasticized films had the lowest values. Sorbitol-plasticized films have better mechanical properties and the lowest water vapor permeability (WVP), solubility and water uptake ratio (WUR) compared with glycerol and PEG-plasticized films (p≤0.05). Fourier transform infrared (FTIR) spectra showed the intermolecular reactions between κ-carrageenan and the plasticizers in the films. Scanning electron microscopy (SEM) observations indicated that sorbitol-plasticized films have a compact structure, even at the highest concentration. The melting temperature (Tm) of films decreased (p≤0.05) with an increase in the plasticizer concentration. Here, the glycerol-plasticized films had the lowest values. X-ray diffraction (XRD) showed broad and narrow peaks of the un-plasticized κ-carrageenan film at 2θ=20.0° and 2θ=8.4°, respectively. The intensity of the broad peak increased and the narrow peak disappeared as the concentration of plasticizers increased. In conclusion, films from E. cottonii successfully produced with sorbitol as the plasticizer exhibited good physical properties as packaging films.
    Matched MeSH terms: Mechanical Phenomena
  20. Analysis of laser sintered materials using finite element method
    AHMAD SHAHIR BIN JAMALUDIN, ABDULLAH BIN YASSIN
    Sains Malaysiana, 2013;42:1727-1733.
    Invention of milling combined laser sintering system (MLSS) is able to reduce the mould manufacturing time and improve the mould accuracy. Thus, more study is needed to increase the understanding for the laser sintered material machining characteristic to gain benefit from the invention of MLSS. This paper clarified the analysis of laser sintered material machinability with the application of Finite Element Method (FEM). Mild steel AISI1055 was applied in developing the Finite Element model in this study due to its popularity in machinability test and adequate level of data availability. 2D orthogonal cutting was employed on edge design tools with updated Lagrangian coupled thermo mechanical plane strain model. Adaptive meshing, tool edge radius and various types of friction models were assigned to obtain efficient simulations and precise cutting results. Cutting force and cutting-edge temperature estimated by Finite Element Method are validated against corresponding experimental values by previous researchers. In the study, cutting force increases when radial depth increases and lowest error acquired when the shear friction factor of 0.8 was applied. Machining simulation for laser sintered materials estimated lower cutting force compared with mild steel AISI1055 due to lower Young modulus. Higher cutting temperature estimated for machining simulation laser sintered material compared with machining simulation mild steel AISI1055 due to its low thermal conductivity.
    Matched MeSH terms: Mechanical Phenomena
Related Terms
Filters
Contact Us

Please provide feedback to Administrator ([email protected])

External Links