Displaying publications 21 - 40 of 66 in total

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  1. Finite element analysis of different surgical approaches in various occlusal loading locations for zygomatic implant placement for the treatment of atrophic maxillae
    Ishak MI, Abdul Kadir MR, Sulaiman E, Abu Kasim NH
    Int J Oral Maxillofac Surg, 2012 Sep;41(9):1077-89.
    PMID: 22575179 DOI: 10.1016/j.ijom.2012.04.010
    The aim of this study was to compare two different types of surgical approaches, intrasinus and extramaxillary, for the placement of zygomatic implants to treat atrophic maxillae. A computational finite element simulation was used to analyze the strength of implant anchorage for both approaches in various occlusal loading locations. Three-dimensional models of the craniofacial structures surrounding a region of interest, soft tissue and framework were developed using computed tomography image datasets. The implants were modelled using computer-aided design software. The bone was assumed to be linear isotropic with a stiffness of 13.4 GPa, and the implants were assumed to be made of titanium with a stiffness of 110 GPa. Masseter forces of 300 N were applied at the zygomatic arch, and occlusal loads of 150 N were applied vertically onto the framework surface at different locations. The intrasinus approach demonstrated more satisfactory results and could be a viable treatment option. The extramaxillary approach could also be recommended as a reasonable treatment option, provided some improvements are made to address the cantilever effects seen with that approach.
    Matched MeSH terms: Computer-Aided Design*
  2. Design and fabrication of scaffolds for anatomic bone reconstruction
    Hollister SJ, Lin CY, Lin CY, Schek RD, Taboas JM, Flanagan CL, et al.
    Med J Malaysia, 2004 May;59 Suppl B:131-2.
    PMID: 15468853
    Matched MeSH terms: Computer-Aided Design*
  3. Particle swarm optimization on threshold exponential gain of stimulated Brillouin scattering in single mode fibers
    Al-Asadi HA, Al-Mansoori MH, Hitam S, Saripan MI, Mahdi MA
    Opt Express, 2011 Jan 31;19(3):1842-53.
    PMID: 21368999 DOI: 10.1364/OE.19.001842
    We implement a particle swarm optimization (PSO) algorithm to characterize stimulated Brillouin scattering phenomena in optical fibers. The explicit and strong dependence of the threshold exponential gain on the numerical aperture, the pump laser wavelength and the optical loss coefficient are presented. The proposed PSO model is also evaluated with the localized, nonfluctuating source model and the distributed (non-localized) fluctuating source model. Using our model, for fiber lengths from 1 km to 29 km, the calculated threshold exponential gain of stimulated Brillouin scattering is gradually decreased from 17.4 to 14.6 respectively. The theoretical results of Brillouin threshold power predicted by the proposed PSO model show a good agreement with the experimental results for different fiber lengths from 1 km to 12 km.
    Matched MeSH terms: Computer-Aided Design
  4. Simplified ASE correction algorithm for variable gain-flattened erbium-doped fiber amplifier
    Mahdi MA, Sheih SJ, Adikan FR
    Opt Express, 2009 Jun 08;17(12):10069-75.
    PMID: 19506658
    We demonstrate a simplified algorithm to manifest the contribution of amplified spontaneous emission in variable gain-flattened Erbium-doped fiber amplifier (EDFA). The detected signal power at the input and output ports of EDFA comprises of both signal and noise. The generated amplified spontaneous emission from EDFA cannot be differentiated by photodetector which leads to underestimation of the targeted gain value. This gain penalty must be taken into consideration in order to obtain the accurate gain level. By taking the average gain penalty within the dynamic gain range, the targeted output power is set higher than the desired level. Thus, the errors are significantly reduced to less than 0.15 dB from 15 dB to 30 dB desired gain values.
    Matched MeSH terms: Computer-Aided Design
  5. Axial contraction in etched optical fiber due to internal stress reduction
    Lim KS, Yang HZ, Chong WY, Cheong YK, Lim CH, Ali NM, et al.
    Opt Express, 2013 Feb 11;21(3):2551-62.
    PMID: 23481713 DOI: 10.1364/OE.21.002551
    When an optical fiber is dipped in an etching solution, the internal stress profile in the fiber varies with the fiber diameter. We observed a physical contraction as much as 0.2% in the fiber axial dimension when the fiber was reduced from its original diameter to ~6 µm through analysis using high resolution microscope images of the grating period of an etched FBG at different fiber diameters. This axial contraction is related to the varying axial stress profile in the fiber when the fiber diameter is reduced. On top of that, the refractive index of fiber core increases with reducing fiber diameter due to stress-optic effect. The calculated index increment is as much as 1.8 × 10(-3) at the center of fiber core after the diameter is reduced down to ~6 µm. In comparison with the conventional model that assumes constant grating period and neglects the variation in stress-induced index change in fiber core, our proposed model indicates a discrepancy as much as 3nm in Bragg wavelength at a fiber diameter of ~6 µm.
    Matched MeSH terms: Computer-Aided Design
  6. Low-cost low-tech obstacle pushing/gliding wheelchair accessory
    Jalal Abdullah S, Shaikh Mohammed J
    Disabil Rehabil Assist Technol, 2019 11;14(8):849-858.
    PMID: 30556753 DOI: 10.1080/17483107.2018.1539130
    Purpose: Some wheelchair users continue to struggle in maneuvering a wheelchair and navigating through manual doors. Several smart wheelchairs and robotic manipulators were developed to minimize such challenges facing disabled people. Disappointingly, a majority of these high-tech solutions are restricted to laboratories and are not extensively available as commercial products. Previously, a low-tech wheelchair accessory (arc-shaped with many wheels) for pushing doors was modelled and simulated. This work demonstrates the fabrication and testing of the first-generation prototype of the accessory.Materials and methods: The accessory has side portions with a straight arrangement of wheels and a front portion with a straight-arc-straight arrangement of wheels. The accessory was fabricated using conventional manufacturing, off-the-shelf components, and 3D printed ABS fasteners. Stress analysis simulations were done for the fasteners that attach the front accessory to the wheelchair frame. The proof-of-concept of the prototype installed onto a powered wheelchair was tested with a door and an obstacle, each with ∼50 N resistance force.Results: Prototype tests demonstrate the ability of the accessory along with the mechanical robustness of the 3D printed fasteners to push open doors allowing easy navigation through doors and to push/glide against obstacles. The accessory is foldable and detachable.Conclusion: The low-cost of the accessory makes it affordable to many users intending to improve their quality of life. The current study provides an engineering perspective of the accessory, and a clinical perspective is crucial. Other potential applications of the wheelchair accessory include use with scooters, walkers and stretchers.Implications for rehabilitationLow-cost, low-tech accessory is foldable and detachable.Accessory is effective for pushing doors and pushing/gliding against obstacles.Protective nature of the front accessory could prove highly beneficial to some wheelchair users.
    Matched MeSH terms: Computer-Aided Design
  7. Fulltext Design and development of 3d face mask clips for hijab
    Ahmad Sofian, Shminan, Rehman, Ullah Khan, Wan Norizan, Wan Hashim, Iswandy, Jamaludin
    Journal of Cognitive Sciences & Human Development, 2020;6(2):52-62.
    MyJurnal
    The world has suffered from a critical shortage of Personal Protective Equipment (PPE) (Riva et al., 2007) during the pandemic of Covid-19 for medical staffs, the front liners. Like the whole world, Malaysia also imposed the stay-at-home and Movement Control Order (MCO) to break the chain of infections and flatten the curve of cases. The supply of PPE became a challenge during the lock down. There have been joined efforts from various parties stepping up, with different ways to help the production process of these key equipment but mostly focus on PPTs for male. Another challenge was face mask for Muslim lady health workers who wear hijab. This paper is about how to overcome these challenges and designed a novel face mask clip for hijab, using 3D printing. The face mask clip is for wearing a mask over hijab and is designed by generating a 3D digital file using computer-aided design (Hourcade, Bullock-Rest, & Hansen, 2012) software. Then the 3D design was converted to Standard Tessellation Language (STL) format, for the use of 3D printing systems. Then the design was split into layers for precise printing. The clips were tested by the staff in faculty of Cognitive Sciences and Human Development, Universiti Malaysia Sarawak. Feedbacks were collected by an online survey using the modified System Usability Scale. The participants reported that the clips are very comfortable and easy to use.
    Matched MeSH terms: Computer-Aided Design
  8. Fulltext The Study of Drag Reduction on Ships Inspired by Simplified Shark Skin Imitation
    Ibrahim MD, Amran SNA, Yunos YS, Rahman MRA, Mohtar MZ, Wong LK, et al.
    Appl Bionics Biomech, 2018;2018:7854321.
    PMID: 29853998 DOI: 10.1155/2018/7854321
    The skin of a fast swimming shark reveals riblet structures that help reduce the shark's skin friction drag, enhancing its efficiency and speed while moving in the water. Inspired by the structure of the shark skin denticles, our team has carried out a study as an effort in improving the hydrodynamic design of marine vessels through hull design modification which was inspired by this riblet structure of shark skin denticle. Our study covers on macroscaled design modification. This is an attempt to propose an alternative for a better economical and practical modification to obtain a more optimum cruising characteristics for marine vessels. The models used for this study are constructed using computer-aided design (CAD) software, and computational fluid dynamic (CFD) simulations are then carried out to predict the effectiveness of the hydrodynamic effects of the biomimetic shark skins on those models. Interestingly, the numerical calculated results obtained show that the presence of biomimetic shark skin implemented on the vessels give about 3.75% reduction of drag coefficient as well as reducing up to 3.89% in drag force experienced by the vessels. Theoretically, as force drag can be reduced, it can lead to a more efficient vessel with a better cruising speed. This will give better impact to shipping or marine industries around the world. However, it can be suggested that an experimental procedure is best to be conducted to verify the numerical result that has been obtained for further improvement on this research.
    Matched MeSH terms: Computer-Aided Design
  9. Fulltext Development and performance of a new prosthesis system using ultrasonic sensor for wrist movements: a preliminary study
    Abd Razak NA, Abu Osman NA, Gholizadeh H, Ali S
    Biomed Eng Online, 2014 Apr 23;13:49.
    PMID: 24755242 DOI: 10.1186/1475-925X-13-49
    BACKGROUND: The design and performance of a new development prosthesis system known as biomechatronics wrist prosthesis is presented in this paper. The prosthesis system was implemented by replacing the Bowden tension cable of body powered prosthesis system using two ultrasonic sensors, two servo motors and microcontroller inside the prosthesis hand for transradial user.

    METHODS: The system components and hand prototypes involve the anthropometry, CAD design and prototyping, biomechatronics engineering together with the prosthetics. The modeler construction of the system develop allows the ultrasonic sensors that are placed on the shoulder to generate the wrist movement of the prosthesis. The kinematics of wrist movement, which are the pronation/supination and flexion/extension were tested using the motion analysis and general motion of human hand were compared. The study also evaluated the require degree of detection for the input of the ultrasonic sensor to generate the wrist movements.

    RESULTS: The values collected by the vicon motion analysis for biomechatronics prosthesis system were reliable to do the common tasks in daily life. The degree of the head needed to bend to give the full input wave was about 45°-55° of rotation or about 14 cm-16 cm. The biomechatronics wrist prosthesis gave higher degree of rotation to do the daily tasks but did not achieve the maximum degree of rotation.

    CONCLUSION: The new development of using sensor and actuator in generating the wrist movements will be interesting for used list in medicine, robotics technology, rehabilitations, prosthetics and orthotics.

    Matched MeSH terms: Computer-Aided Design
  10. Fulltext Analysis and optimization of spiral circular inductive coupling link for bio-implanted applications on air and within human tissue
    Mutashar S, Hannan MA, Samad SA, Hussain A
    Sensors (Basel), 2014;14(7):11522-41.
    PMID: 24984057 DOI: 10.3390/s140711522
    The use of wireless communication using inductive links to transfer data and power to implantable microsystems to stimulate and monitor nerves and muscles is increasing. This paper deals with the development of the theoretical analysis and optimization of an inductive link based on coupling and on spiral circular coil geometry. The coil dimensions offer 22 mm of mutual distance in air. However, at 6 mm of distance, the coils offer a power transmission efficiency of 80% in the optimum case and 73% in the worst case via low input impedance, whereas, transmission efficiency is 45% and 32%, respectively, via high input impedance. The simulations were performed in air and with two types of simulated human biological tissues such as dry and wet-skin using a depth of 6 mm. The performance results expound that the combined magnitude of the electric field components surrounding the external coil is approximately 98% of that in air, and for an internal coil, it is approximately 50%, respectively. It can be seen that the gain surrounding coils is almost constant and confirms the omnidirectional pattern associated with such loop antennas which reduces the effect of non-alignment between the two coils. The results also show that the specific absorption rate (SAR) and power loss within the tissue are lower than that of the standard level. Thus, the tissue will not be damaged anymore.
    Matched MeSH terms: Computer-Aided Design*
  11. Fulltext Comparative study of popular objective functions for damping power system oscillations in multimachine system
    Islam NN, Hannan MA, Shareef H, Mohamed A, Salam MA
    ScientificWorldJournal, 2014;2014:549094.
    PMID: 24977210 DOI: 10.1155/2014/549094
    Power oscillation damping controller is designed in linearized model with heuristic optimization techniques. Selection of the objective function is very crucial for damping controller design by optimization algorithms. In this research, comparative analysis has been carried out to evaluate the effectiveness of popular objective functions used in power system oscillation damping. Two-stage lead-lag damping controller by means of power system stabilizers is optimized using differential search algorithm for different objective functions. Linearized model simulations are performed to compare the dominant mode's performance and then the nonlinear model is continued to evaluate the damping performance over power system oscillations. All the simulations are conducted in two-area four-machine power system to bring a detailed analysis. Investigated results proved that multiobjective D-shaped function is an effective objective function in terms of moving unstable and lightly damped electromechanical modes into stable region. Thus, D-shape function ultimately improves overall system damping and concurrently enhances power system reliability.
    Matched MeSH terms: Computer-Aided Design*
  12. Fulltext Development of simple designs of multitip probe diagnostic systems for RF plasma characterization
    Naz MY, Shukrullah S, Ghaffar A, Rehman NU
    ScientificWorldJournal, 2014;2014:279868.
    PMID: 24683326 DOI: 10.1155/2014/279868
    Multitip probes are very useful diagnostics for analyzing and controlling the physical phenomena occurring in low temperature discharge plasmas. However, DC biased probes often fail to perform well in processing plasmas. The objective of the work was to deduce simple designs of DC biased multitip probes for parametric study of radio frequency plasmas. For this purpose, symmetric double probe, asymmetric double probe, and symmetric triple probe diagnostic systems and their driving circuits were designed and tested in an inductively coupled plasma (ICP) generated by a 13.56 MHz radio frequency (RF) source. Using I-V characteristics of these probes, electron temperature, electron number density, and ion saturation current was measured as a function of input power and filling gas pressure. An increasing trend was noticed in electron temperature and electron number density for increasing input RF power whilst a decreasing trend was evident in these parameters when measured against filling gas pressure. In addition, the electron energy probability function (EEPF) was also studied by using an asymmetric double probe. These studies confirmed the non-Maxwellian nature of the EEPF and the presence of two groups of the energetic electrons at low filling gas pressures.
    Matched MeSH terms: Computer-Aided Design*
  13. Reflection spectra of etched FBGs under the influence of axial contraction and stress-induced index change
    Yang HZ, Lim KS, Qiao XG, Chong WY, Cheong YK, Lim WH, et al.
    Opt Express, 2013 Jun 17;21(12):14808-15.
    PMID: 23787668 DOI: 10.1364/OE.21.014808
    We present a new theoretical model for the broadband reflection spectra of etched FBGs which includes the effects of axial contraction and stress-induced index change. The reflection spectra of the etched FBGs with several different taper profiles are simulated based on the proposed model. In our observation, decaying exponential profile produces a broadband reflection spectrum with good uniformity over the range of 1540-1560 nm. An etched FBG with similar taper profile is fabricated and the experimental result shows good agreement with the theoretical model.
    Matched MeSH terms: Computer-Aided Design*
  14. Analytical analysis of second-order Stokes wave in Brillouin ring fiber laser
    Al-Asadi HA, Abu Bakar MH, Al-Mansoori MH, Adikan FR, Mahdi MA
    Opt Express, 2011 Dec 5;19(25):25741-8.
    PMID: 22273966 DOI: 10.1364/OE.19.025741
    This paper details a theoretical modeling of Brillouin ring fiber laser which incorporates the interaction between multiple Brillouin Stokes signals. The ring cavity was pumped at several Brillouin pump (BP) powers and the output was measured through an optical coupler with various coupling ratios. The first-order Brillouin Stokes signal was saturated with the presence of the second-order Stokes signal in the cavity as a result of energy transfer between them. The outcome of the study found that the optimum point for the first-order Stokes wave performance is at laser power reduction of 10%. Resultantly, at the optimum output coupling ratio of 90%, the BFL was able to produce 19.2 mW output power at BP power and Brillouin threshold power of 60 and 21.3 mW respectively. The findings also exhibited the feasibility of the theoretical models application to ring-type Brillouin fiber laser of various design parameters.
    Matched MeSH terms: Computer-Aided Design*
  15. Evaluation of the marginal fit of a zirconia ceramic computer-aided machined (CAM) crown system
    Baig MR, Tan KB, Nicholls JI
    J Prosthet Dent, 2010 Oct;104(4):216-27.
    PMID: 20875526 DOI: 10.1016/S0022-3913(10)60128-X
    The marginal fit of crowns is a concern for clinicians, and there is no conclusive evidence of any one margin configuration yielding better results than others in terms of marginal fit.
    Matched MeSH terms: Computer-Aided Design*
  16. Effect of CAD-CAM porcelain veneers thickness on their cemented color
    Omar H, Atta O, El-Mowafy O, Khan SA
    J Dent, 2010;38 Suppl 2:e95-9.
    PMID: 20493232 DOI: 10.1016/j.jdent.2010.05.006
    To determine the effect of thickness of porcelain veneers constructed from CAD-CAM on their final color when two resin cements were used.
    Matched MeSH terms: Computer-Aided Design*
  17. Low energy, low latency and high speed array divider circuit using a shannon theorem based adder cell
    Senthilpari C, Diwakar K, Singh AK
    Recent Pat Nanotechnol, 2009;3(1):61-72.
    PMID: 19149756
    The paper discuss the design of 1-bit full adder circuit using Shannon theorem. This proposed full adder circuit is used as one of the circuit component for implementation of Non- Restoring and Restoring divider circuits. The proposed adder and divider schematics are designed by using DSCH2 CAD tool and their layouts are generated by Microwind 3 VLSI CAD tool. The divider circuits are designed by using standard CMOS 0.35 microm feature size and corresponding power supply 3.5 V. The parameters analyses are carried out by BSIM 4 analysis. We have compared the simulated results of the Shannon based divider circuit with CPL and CMOS adder cell based divider circuits. We have further compared the results with published results and observed that the proposed adder cell based divider circuit dissipates lower power, gives faster response, lower latency, low EPI and high throughput.
    Matched MeSH terms: Computer-Aided Design*
  18. Analysis of coupling efficiency on hemispherical fiber lens by method of lines
    Lambak Z, Abdul Rahman F, Mokhtar MR, Tengku IA
    Opt Express, 2009 Feb 16;17(4):2926-37.
    PMID: 19219196
    The method of lines (MoL) has been developed to study coupling efficiency on hemispherical lens. In this paper, the physical shape of the lens is approximated by cascading a number of straight waveguide segments. The perfectly matched layer (PML) is applied as an absorber for the MoL to reduce numerical reflection in the simulation region. Analysis is done by calculating coupling efficiency at the plane of integration where the coupling efficiency is an overlap integral between laser diode field and fiber field. The result of coupling efficiency in this analysis is compared to the experiment and ABCD matrix. It is found that MoL gives good result accuracy.
    Matched MeSH terms: Computer-Aided Design*
  19. Tunable range enhancement of Brillouin-erbium fiber laser utilizing Brillouin pump pre-amplification technique
    Al-Mansoori MH, Mahdi MA
    Opt Express, 2008 May 26;16(11):7649-54.
    PMID: 18545472
    We demonstrate an enhanced multiwavelength L-band Brillouin-erbium fiber laser (BEFL), in which the Brillouin pump is pre-amplified before entering the single-mode fiber. The Brillouin pump pre-amplification provided by the Erbium-doped fiber has created higher intensity of Brillouin Stokes line generated in the single-mode fiber that leads to the homogenous gain saturation. Thus the built-up of self-lasing cavity modes is suppressed in a wider wavelength range. In contrary to the conventional linear-cavity BEFL, the number of output channels is enhanced within the same tuning range.
    Matched MeSH terms: Computer-Aided Design*
  20. Fulltext Fit Accuracy of Removable Partial Denture Frameworks Fabricated with CAD/CAM, Rapid Prototyping, and Conventional Techniques: A Systematic Review
    Ahmed N, Abbasi MS, Haider S, Ahmed N, Habib SR, Altamash S, et al.
    Biomed Res Int, 2021;2021:3194433.
    PMID: 34532499 DOI: 10.1155/2021/3194433
    Objective: Analyzing and comparing the fit and accuracy of removable partial denture (RPDs) frameworks fabricated with CAD/CAM and rapid prototyping methods with conventional techniques.

    Materials and Methods: The present systematic review was carried out according to PRISMA guidelines. The search was carried out on PubMed/MEDLINE, Cochrane collaboration, Science direct, and Scopus scientific engines using selected MeSH keywords. The articles fulfilling the predefined selection criteria based on the fit and accuracy of removable partial denture (RPD) frameworks constructed from digital workflow (CAD/CAM; rapid prototyping) and conventional techniques were included.

    Results: Nine full-text articles comprising 6 in vitro and 3 in vivo studies were included in this review. The digital RPDs were fabricated in all articles by CAD/CAM selective laser sintering and selective laser melting techniques. The articles that have used CAD/CAM and rapid prototyping technique demonstrated better fit and accuracy as compared to the RPDs fabricated through conventional techniques. The least gaps between the framework and cast (41.677 ± 15.546 μm) were found in RPDs constructed through digital CAD/CAM systems.

    Conclusion: A better accuracy was achieved using CAD/CAM and rapid prototyping techniques. The RPD frameworks fabricated by CAD/CAM and rapid prototyping techniques had clinically acceptable fit, superior precision, and better accuracy than conventionally fabricated RPD frameworks.

    Matched MeSH terms: Computer-Aided Design/trends
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