Displaying publications 1 - 20 of 31 in total

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  1. Mohamad, D., Ibrahim, S.Z.
    MyJurnal
    Fuzzy set with similarity measure approaches are known to be effective in handling imprecise and
    subjective information to solve decision making problems. Many methods have been introduced based on these two concepts. However, most methods do not take into account the reliability factor of the imprecise information in the evaluation process. In 2010, Zadeh coined the idea of Z-number that has the ability to consider the reliability factor or the level of confidence of human’s information expression. Since then, some decision-making methods have included this concept. In this paper, we present a new fuzzy decision making procedure by integrating the Jaccard similarity measure with Z-number to solve a multi criteria decision making problem. The conversion method of the Z-number based linguistic value to trapezoidal fuzzy numbers is used and the Jaccard similarity measure of the expected intervals of trapezoidal fuzzy numbers is applied to obtain the final decision. The feasibility of the methodology is demonstrated by investigating the preference factors that could influence customers to buy their preferred choice of car. The proposed methodology is applicable to solving decision making with a fuzzy environment to achieve a reliable and optimal decision.
  2. Azlisham, N.A.F., Abdul Rahman, F.S., Mohamad, D.
    MyJurnal
    The objective of the present study is to evaluate the effect of incorporation of 3- acetylcoumarin (3-AC), an antibacterial agent, on the mechanical and surface morphology of glass ionomer cement (GIC). A conventional GIC, Fuji II LC, was used as a control. 3-AC was incorporated into GIC during its manipulation at percentage of 2% and 5% (wt/wt). Flexural strength of the specimens were analysed using Shimadzu AGX-Plus while morphological evaluation of the specimens were observed using Scanning Electron Microscope (SEM). Oneway analysis (ANOVA) with post-hoc Bonferroni multiple-range test was used to determine the significant differences among the groups. Statistically, the incorporation of 2% (wt/wt) of 3-AC into GIC showed a significantly lower flexural strength (p
  3. Mokhtar, M., Shuib, A., Mohamad, D.
    MyJurnal
    Portfolio optimisation is one of the most crucial issues in investment decision-making and has received considerable attention from researchers and practitioners. Traditionally, the portfolio optimisation models are formulated based on the assumption that investors have complete information on the distribution of random returns. However, in real life case, this is not possible since decisions have to be made under uncertainty. This paper deals with a fuzzy portfolio optimisation problem in which returns and turnover rates of securities are represented by fuzzy variables. A goal programming model is proposed to optimise three objectives: maximisation of portfolio return, maximisation of liquidity and minimisation of the portfolio risk. The cardinality constraints, floor and ceiling constraints are also taken into consideration. Finally, a numerical experiment using real data is conducted to demonstrate the applicability of the model.
  4. Mohamad, D., Hanif, H.M., Dom, R.M.
    MyJurnal
    Complexity has been discussed in decision making, computational, task complexity, activity network,
    supply chain, imaging, project management and mechanical. This paper reviews the definition of
    complexity and the preliminary-related definitions of complexity index in decision making. It proposes
    a complexity index for decision making, its properties, and implementation.
  5. Mohamad, D., Young, R.J., Mann, A.B., Watts, D.C.
    MyJurnal
    The aim of the study was to evaluate post-polymerization of resin composite by measuring NanoHardness (H), Young’s Modulus (E) and Degree of Conversion (DC) using nanoindentation and Micro-Raman spectroscopy. For this purpose a computer-controlled NanoIndenter™ and a Renishaw 1000 Raman Spectrometer fitted with an Olympus microscope attachment, operated at 638 nm, were used. A light-activated resin composite was used in this study, (Z250, 3MESPE). Sub-groups (n=3) of specimens were irradiated for 20, 30, 40 s. All samples for nanoindentation were polished metallographically and typically 50 nanoindentations were performed per specimen. After curing and polishing, half of the samples were tested immediately (Group 1); the others after being stored dry at 37 °C for 7 days (Group 2) to allow scope for postpolymerization. H values ranged from 1.08 to 1.40 GPa for Group 1, and from 1.64 to1.71 GPa for Group 2. E values in Group 1 ranged from 19.60 to 19.94 GPa and for Group 2, from 21.42 to 22.05 GPa. DC values ranged from 55 to 66.39%, and 60.90 to 66.47% for Group 1 and Group 2 respectively. All values obtained shown significant different between Groups 1 and 2 (p
  6. Abd Rahman, R., Mohamad, D., Ab Ghani, Z., Hasan, H., Abdullah, N.A.
    MyJurnal
    The objective of the study was to asses the adhesion of Streptococcus mutans on nanofilled and microfilled composite resin and glass ionomer cement restorative materials. Glass ionomer cements; KetacTM N100 (nanofilled) and Fuji IITM LC (microfilled) and composite resins; FiltekTM Z350 (nanofilled) and FiltekTM Z250 (microhybrid) were packed in acrylic mould of 2 mm thickness and 5 mm diameter. All samples were light-cured and polished with Sof-Lex discs. All materials were cultured with the exponential phase of S. mutans cultivation. Surface roughness values were assessed using Atomic Force Microscope (AFM, Ambios, USA) at time intervals (7hrs, 24 hrs, 7 days, 14 days and 21 days). The morphology of S. mutans on materials was observed after 24 hour incubation of S. mutan on materials under Scanning Electron Microscope (SEM, Quanta FEG 450). Within groups, results showed that both nanofilled materials had lower surface roughness and less adhesion of S. mutans compared to microfilled materials. This study would enhance the clinical knowledge especially in aesthetic area and improve the longevity of the dental restoration.
  7. Saddki N, Sukerman N, Mohamad D
    Malays J Med Sci, 2017 Mar;24(1):59-68.
    PMID: 28381929 DOI: 10.21315/mjms2017.24.1.7
    BACKGROUND: This study investigated the association of emotional intelligence (EI) and other factors with perceived stress (PS) in undergraduate dental students.

    METHODS: A total of 234 undergraduate dental students at the School of Dental Sciences, Universiti Sains Malaysia (USM), in the academic year of 2009/2010, participated in this cross-sectional study. Self-administered questionnaires, the Assessing Emotions Scale and the Perceived Stress Scale (PSS-10), were used to evaluate EI and PS, respectively.

    RESULTS: The mean EI score was 121.2 (SD 11.85). The scores were significantly higher in females than males, and in students who chose dentistry based on their own interest rather than in those who were motivated by others to study dentistry. The mean PSS-10 score was 21.2 (SD 5.08). Pearson correlation analysis indicated a significant inverse relationship between EI and PSS-10 scores (r = -0.337). Multi-variable regression analysis also indicated a significant negative linear association between EI and PSS-10 scores (b = -0.156, 95% CI: -0.207, -0.104). PSS-10 scores were significantly higher for students who were in the clinical years rather than the preclinical years.

    CONCLUSIONS: This study of USM undergraduate dental students shows that a low EI, female sex, and being in the clinical years were significant predictors of PS.
  8. Mohamad D, Suppian R, Mohd Nor N
    Hum Vaccin Immunother, 2014;10(7):1880-6.
    PMID: 25424796 DOI: 10.4161/hv.28695
    Macrophage phagocytosis is the first line of defense of the innate immune system against malaria parasite infection. This study evaluated the immunomodulatory effects of BCG and recombinant BCG (rBCG) strains expressing the C-terminus of the merozoite surface protein-1 (MSP-1C) of Plasmodium falciparum on mouse macrophage cell line J774A.1 in the presence or absence of lipopolysaccharide (LPS) or LPS + IFN-γ. The rBCG strain significantly enhanced phagocytic activity, production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, nitric oxide (NO), and inducible nitric oxide synthase (iNOS) as compared with parental BCG strain, and these activities increased in the presence of LPS and LPS+IFN-γ. Furthermore, the rBCG strain also significantly reduced the macrophage viability as well as the rBCG growth suggesting the involvement of macrophage apoptosis. Taken together, these data indicate that the rBCG strain has an immunomodulatory effect on macrophages, thus strengthen the rational use of rBCG to control malaria infection.
  9. Salman A, Jaafar M, Mohamad D, Malik S
    Environ Sci Pollut Res Int, 2021 Aug;28(31):42945-42958.
    PMID: 33834332 DOI: 10.1007/s11356-021-13609-y
    Located in one of the famous natural and cultural tourist destinations of northern Malaysia, Penang Hill serves as an ideal destination for both local and international tourists. The objective of this study was to understand and explore key stakeholders perspectives to enhance management for the aim of conservation, economic development, and recreation in Penang Hill. Data was collected from three key stakeholders of Penang Hill using semi-structured in-depth interviews. Stakeholders showed robust interests in environmental protection, cultural conservation, economic activities, awareness, and empowerment. This paper concludes by stating that Penang Hill is under strong management, and stakeholders are continuously engaged in the destination. The management authority collaborates with the key stakeholders of Penang Hill and incorporates their interests and viewpoint to ensure the ecotourism process goes smoothly and Penang Hill becomes one of the top ecotourism destinations.
  10. Salman A, Jaafar M, Mohamad D, Khoshkam M
    Environ Dev Sustain, 2022 Jun 27.
    PMID: 35789745 DOI: 10.1007/s10668-022-02488-z
    Ecotourism offers several economic, environmental, and cultural benefits; however, even after all these years, achieving ecotourism sustainability is still complex because of multiple stakeholders with diversified interests and influence. This study focused on the multiple stakeholders' complexity and management for achieving sustainable ecotourism in Penang Hill in Malaysia. Understanding the existence of multiple stakeholders with varying interests and their respective power of influence is critical for a tourism destination to be sustainable. This study aimed to create a multi-stakeholder management framework and understand stakeholder management's mediating role toward ecotourism sustainability in Penang Hill. Data were collected from Penang Hill key stakeholders and analyzed using SmartPLS and fuzzy-set Qualitative Comparative Analysis (fsQCA). The findings revealed that stakeholder management plays a significant mediating role in achieving ecotourism sustainability. Stakeholders' interests and their level of influence should be understood to develop engagement, empowerment, and monitoring strategies for managing stakeholders. Thus, the study contributes by validating the results through symmetric and asymmetric techniques, offering solutions to the emerging issues during the Covid-19 pandemic, and recommending policy changes. Lastly, the study also extends prior literature by displaying the mediating role played by stakeholder management on ecotourism sustainability, comparing indirect and total effects on stakeholder management support for achieving sustainable ecotourism in Penang Hill.
  11. Hussein TA, Bakar WZ, Ghani ZA, Mohamad D
    J Conserv Dent, 2014 Nov;17(6):531-5.
    PMID: 25506139 DOI: 10.4103/0972-0707.144585
    To investigate the effect of acidic solution on surface roughness and microleakage of tooth-colored restorative materials.
  12. Alkawaz MH, Basori AH, Mohamad D, Mohamed F
    ScientificWorldJournal, 2014;2014:367013.
    PMID: 25136663 DOI: 10.1155/2014/367013
    Generating extreme appearances such as scared awaiting sweating while happy fit for tears (cry) and blushing (anger and happiness) is the key issue in achieving the high quality facial animation. The effects of sweat, tears, and colors are integrated into a single animation model to create realistic facial expressions of 3D avatar. The physical properties of muscles, emotions, or the fluid properties with sweating and tears initiators are incorporated. The action units (AUs) of facial action coding system are merged with autonomous AUs to create expressions including sadness, anger with blushing, happiness with blushing, and fear. Fluid effects such as sweat and tears are simulated using the particle system and smoothed-particle hydrodynamics (SPH) methods which are combined with facial animation technique to produce complex facial expressions. The effects of oxygenation of the facial skin color appearance are measured using the pulse oximeter system and the 3D skin analyzer. The result shows that virtual human facial expression is enhanced by mimicking actual sweating and tears simulations for all extreme expressions. The proposed method has contribution towards the development of facial animation industry and game as well as computer graphics.
  13. Rahim TN, Mohamad D, Md Akil H, Ab Rahman I
    Dent Mater, 2012 Jun;28(6):e63-70.
    PMID: 22480722 DOI: 10.1016/j.dental.2012.03.011
    To determine the diffusion coefficient, water sorption and solubility of various types of restorative dental composites and to evaluate the effect of acidic media (orange juice and coke) on their characteristics.
  14. Musa M, Ponnuraj KT, Mohamad D, Rahman IA
    Nanotechnology, 2013 Jan 11;24(1):015105.
    PMID: 23221152 DOI: 10.1088/0957-4484/24/1/015105
    Nanocomposite is used as a dental filling to restore the affected tooth, especially in dental caries. The dental nanocomposite (KelFil) for tooth restoration used in this study was produced by the School of Dental Sciences, Universiti Sains Malaysia, Malaysia and is incorporated with monodispersed, spherical nanosilica fillers. The aim of the study was to determine the genotoxic effect of KelFil using in vitro genotoxicity tests. The cytotoxicity and genotoxicity of KelFil was evaluated using MTT assay, comet assay and chromosome aberration tests with or without the addition of a metabolic activation system (S9 mix), using the human lung fibroblast cell line (MRC-5). Concurrent negative and positive controls were included. In the comet assay, no comet formation was found in the KelFil groups. There was a significant difference in tail moment between KelFil groups and positive control (p < 0.05). Similarly, no significant aberrations in chromosomes were noticed in KelFil groups. The mitotic indices of treatment groups and negative control were significantly different from positive controls. Hence, it can be concluded that the locally produced dental restoration nanocomposite (KelFil) is non-genotoxic under the present test conditions.
  15. Ab-Ghani Z, Jaafar W, Foo SF, Ariffin Z, Mohamad D
    J Conserv Dent, 2015 Sep-Oct;18(5):355-9.
    PMID: 26430296 DOI: 10.4103/0972-0707.164028
    To evaluate the shear bond strength between the dentin substrate and computer-aided design and computer-aided manufacturing feldspathic ceramic and nano resin ceramics blocks cemented with resin cement.
  16. Qadri GW, Noor SN, Mohamad D
    Pediatr Dent, 2009 Sep-Oct;31(5):389-94.
    PMID: 19947133
    The purpose of this study was to evaluate the effects of different repairing techniques of a fractured sealant on microleakage in vitro.
  17. Abbas N, Mohamad D, Abdullah AH, Saba T, Al-Rodhaan M, Al-Dhelaan A
    Pak J Pharm Sci, 2015 Sep;28(5):1801-6.
    PMID: 26408877
    The Leukocytes are differentiated from each other on the basis of their nuclei, demanded in many Medical studies, especially in all types of Leukemia by the Hematologists to note the disorder caused by specific type of Leukocyte. Leukemia is a life threatening disease. The work for diagnosing is manually carried out by the Hematologists involving much labor, time and human errors. The problems mentioned are easily addressed through computer vision techniques, but still accuracy and efficiency are demanded in terms of the basic and challenging step segmentation of Leukocyte's nuclei. The underlying study proposed better method in terms of accuracy and efficiency by designing a dynamic convolution filter for boosting low intensity values in the separated green channel of an RGB image and suppressing the high values in the same channel. The high values in the green channel become 255 (background) while the nuclei always have low values in the green channel and thus clearly appear as foreground. The proposed technique is tested on 365 images achieving an overall accuracy of 95.89%, while improving the efficiency by 10%. The proposed technique achieved its targets in a realistic way by improving the accuracy as well as the efficiency and both are highly required in the area.
  18. Bakhori SKM, Mahmud S, Mohamad D, Masudi SM, Seeni A
    Mater Sci Eng C Mater Biol Appl, 2019 Jul;100:645-654.
    PMID: 30948101 DOI: 10.1016/j.msec.2019.03.034
    Zinc oxide eugenol (ZOE) cements are generally made up of 80%-90% ZnO powder while the remaining content consists of eugenol bonding resin. ZnO structure plays a major role in the morphology and mechanical properties of ZOE. In this study, we investigated the effects of different particle sizes/shapes of ZnO particles on the surface and mechanical properties of ZOE. Three samples were prepared namely ZnO-Ax, ZnO-B and ZnO-K. The crystallite sizes calculated from XRD were 37.76 nm (ZnO-Ax), 39.46 nm (ZnO-B) and 42.20 nm (ZnO-K) while the average particle sizes obtained by DLS were 21.11nm (ZnO-Ax), 56.73 nm (ZnO-B) and 2012 nm (ZnO-K). Results revealed that the compressive strengths of ZOE-Ax and ZOE-B were improved by 87.92% and 57.16%, respectively, relative to that of commercial ZOE-K. Vickers hardness test demonstrated that the hardness of ZOE-Ax and ZOE-B also increased by 74.9% and 31.1%, respectively. The ZnO-Ax nanostructure possessed a small average particle size (21.11 nm), a homogeneous size distribution (DLS) and an oxygen-rich surface (from EDS and elemental mapping). Meanwhile, ZnO-B exhibited a slightly larger average particle size of 56.73 nm compared with that of other samples. Sample ZnO-Ax demonstrated the highest compressive strength which was attributed to its large particle surface area (21.11 nm particle size) that provided a large contact area and greater interfacial (or interlock) bonding capability if compared to that of ZnO-K sample (2012 nm particle size).
  19. Abdullah AM, Rahim TNAT, Hamad WNFW, Mohamad D, Akil HM, Rajion ZA
    Dent Mater, 2018 11;34(11):e309-e316.
    PMID: 30268678 DOI: 10.1016/j.dental.2018.09.006
    OBJECTIVE: To compare the mechanical and biological properties of newly developed hybrid ceramics filled and unfilled polyamide 12 (PA 12) for craniofacial reconstruction via a fused deposition modelling (FDM) framework.

    METHODS: 15wt% of zirconia (ZrO2) as well as 30, 35, and 40wt% of beta-tricalcium phosphate (β-TCP) were compounded with PA 12, followed by the fabrication of filament feedstocks using a single screw extruder. The fabricated filament feedstocks were used to print the impact specimens. The melt flow rate, tensile properties of fabricated filament feedstocks, and 3D printed impact properties of the specimens were assessed using melt flow indexer, universal testing machine, and Izod pendulum tester, respectively. The microstructure of selected filament feedstocks and broken impact specimens were analysed using a field emission scanning electron microscope and universal testing machine. Human periodontal ligament fibroblast cells (HPdLF) were used to evaluate the cytotoxicity of the materials by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid) (MTT) assay.

    RESULTS: Hybrid ceramics filled PA 12 indicated sufficient flowability for FDM 3D printing. The tensile strength of hybrid ceramics filled PA 12 filament feedstocks slightly reduced as compared to unfilled PA 12. However, the tensile modulus and impact strength of hybrid ceramics filled PA 12 increased by 8%-31% and 98%-181%, respectively. A significant increase was also detected in the cell viability of the developed composites at concentrations of 12.5, 25, 50 and 100mg/ml.

    SIGNIFICANCE: The newly developed hybrid ceramics filled PA 12 filament feedstock with improved properties is suitable for an FDM-based 3D printer, which enables the creation of patient-specific craniofacial implant at a lower cost to serve low-income patients.

  20. 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.
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