Displaying publications 121 - 140 of 157 in total

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  1. Fulltext Identification and Characterization of Macrophomina phaseolina Causing Leaf Blight on White Spider Lilies (Crinum asiaticum and Hymenocallis littoralis) in Malaysia
    Huda-Shakirah AR, Kee YJ, Hafifi ABM, Mohamad Azni NN, Zakaria L, Mohd MH
    Mycobiology, 2019;47(4):408-414.
    PMID: 32010462 DOI: 10.1080/12298093.2019.1682448
    Crinum asiaticum and Hymenocallis littoralis, commonly known as spider lilies are bulbous perennial and herbaceous plants that widely planted in Malaysia as ornamental. During 2015-2016, symptom of leaf blight was noticed on the hosts from several locations in Penang. The symptom appeared as irregular brown to reddish lesions surrounded by yellow halos. As the disease progressed, the infected leaves became blighted, dried, and fell off with the presence of black microsclerotia and pycnidia on the lesions parts. The present study was conducted to investigate the causal pathogen of leaf blight on C. asiaticum and H. littoralis. Based on morphological characteristics and DNA sequences of internal transcribed spacer (ITS) region and translation elongation factor 1-alpha (TEF1-α) gene, the causal pathogen was identified as Macrophomina phaseolina. Phylogenetic analysis of combined dataset of ITS and TEF1-α grouped the isolates studied with other isolates of M. phaseolina from GenBank. The grouping of the isolates was supported by 96% bootstrap value. Pathogenicity test proved the role of the fungus in causing leaf blight on both hosts.
  2. An improved simplified rules Fuzzy Logic Speed Controller method applied for induction motor drive
    Talib MHN, Ibrahim Z, Abd Rahim N, Zulhani R, Nordin N, Farah N, et al.
    ISA Trans, 2020 Oct;105:230-239.
    PMID: 32475537 DOI: 10.1016/j.isatra.2020.05.040
    Fuzzy Logic Speed Controller (FLSC) has been widely used for motor drive due to its robustness and its non-reliance to real plant parameters. However, it is computationally expensive to be implemented in real-time and prone to the fuzzy rules' selection error which results in the failure of the drive's system. This paper proposes an improved simplified rules method for Fuzzy Logic Speed Controller (FLSC) based on the significant crisp output calculations to address these issues. A systematic procedure for the fuzzy rules reduction process is first described. Then, a comprehensive evaluation of the activated crisp output data is presented to determine the fuzzy dominant rules. Based on the proposed method, the number of rules was significantly reduced by 72%. The simplified FLSC rule is tested on the Induction Motor (IM) drives system in which the real-time implementation was carried out in the dSPACE DS1103 controller environment. The simulation and experimental results based on the proposed FLSC have proved the workability of the simplified rules without degrading the motor performance.
  3. Fulltext Diaporthe species causing stem gray blight of red-fleshed dragon fruit (Hylocereus polyrhizus) in Malaysia
    Huda-Shakirah AR, Kee YJ, Wong KL, Zakaria L, Mohd MH
    Sci Rep, 2021 02 16;11(1):3907.
    PMID: 33594187 DOI: 10.1038/s41598-021-83551-z
    This study aimed to characterize the new fungal disease on the stem of red-fleshed dragon fruit (Hylocereus polyrhizus) in Malaysia, which is known as gray blight through morphological, molecular and pathogenicity analyses. Nine fungal isolates were isolated from nine blighted stems of H. polyrhizus. Based on morphological characteristics, DNA sequences and phylogeny (ITS, TEF1-α, and β-tubulin), the fungal isolates were identified as Diaporthe arecae, D. eugeniae, D. hongkongensis, D. phaseolorum, and D. tectonendophytica. Six isolates recovered from the Cameron Highlands, Pahang belonged to D. eugeniae (DF1 and DF3), D. hongkongensis (DF9), D. phaseolorum (DF2 and DF12), and D. tectonendophytica (DF7), whereas three isolates from Bukit Kor, Terengganu were recognized as D. arecae (DFP3), D. eugeniae (DFP4), and D. tectonendophytica (DFP2). Diaporthe eugeniae and D. tectonendophytica were found in both Pahang and Terengganu, D. phaseolorum and D. hongkongensis in Pahang, whereas D. arecae only in Terengganu. The role of the Diaporthe isolates in causing stem gray blight of H. polyrhizus was confirmed. To date, only D. phaseolorum has been previously reported on Hylocereus undatus. This is the first report on D. arecae, D. eugeniae, D. hongkongensis, D. phaseolorum, and D. tectonendophytica causing stem gray blight of H. polyrhizus worldwide.
  4. Distribution and assessment of heavy metal contents in surface sediments of the western Sunda Shelf
    Zhang H, Liu S, Wu K, Cui J, Zhu A, Zhang Y, et al.
    Mar Pollut Bull, 2021 Jul;168:112433.
    PMID: 33962084 DOI: 10.1016/j.marpolbul.2021.112433
    The heavy metal contents (Cr, Cu, Zn, Cd, Pb, Hg, and As) of 88 surface sediment samples from the western Sunda Shelf were analyzed to determine their spatial distribution patterns and contamination status. The results demonstrated that high enrichment regions of heavy metals were focused in the Kelantan, Pahang, and Ambat river estuaries, and deep water regions of the study area. These high enrichment regions were mainly controlled by riverine inputs and their hydrodynamic conditions. The enrichment factor (EF), geoaccumulation index (Igeo), and potential ecological risk index (PERI) were used to assess heavy metal accumulation. The results indicated that the study area was not significantly contaminated overall at the time of the study; however, Cd, As, and Hg were at levels corresponding to moderate contamination at many stations located in the Pahang River estuary, Kelantan River estuary, and north-eastern region of the study area, primarily because of anthropogenic activities.
  5. Relationship of selective complement markers with schizophrenia
    Mohd Asyraf AJ, Nour El Huda AR, Hanisah MN, Norsidah KZ, Norlelawati AT
    J Neuroimmunol, 2022 02 15;363:577793.
    PMID: 34990981 DOI: 10.1016/j.jneuroim.2021.577793
    Immune system dysregulation may be involved in schizophrenia, but biomarker studies have thus far reported inconsistent findings. The relationship of plasma levels of complement markers C3 and C4, with schizophrenia, sociodemographic and clinico-psychological factors were here studied in 183 patients and 212 controls. C3 and C4 levels were significantly higher in the patients and in subjects with elevated C-reactive protein (CRP), and positively correlated with body mass index (BMI) (p 
  6. Factors influencing Malaysian public attitudes to agro-biotechnology
    Amin L, Ahmad J, Jahi JM, Nor AR, Osman M, Mahadi NM
    Public Underst Sci, 2011 Sep;20(5):674-89.
    PMID: 22164706
    Despite considerable research in advanced countries on public perceptions of and attitudes to modern biotechnology, limited effort has been geared towards developing a structural model of public attitudes to modern biotechnology. The purpose of this paper is to identify the relevant factors influencing public attitudes towards genetically modified (GM) soybean, and to analyze the relationship between all the attitudinal factors. A survey was carried out on 1,017 respondents from various stakeholder groups in the Klang Valley region. Results of the survey have confirmed that attitudes towards complex issues such as biotechnology should be seen as a multifaceted process. The most important factors predicting support for GM soybean are the specific application-linked perceptions about the benefits, acceptance of risk and moral concern while risk and familiarity are significant predictors of benefit and risk acceptance. Attitudes towards GM soybean are also predicted by several general classes of attitude.
  7. Extensive facial and orbital infantile hemangiomas associated with high intraocular pressure
    Shatriah I, Norazizah MA, Wan-Hitam WH, Wong AR, Yunus R, Leo SW
    Pediatr Dermatol, 2013 Jan-Feb;30(1):151-4.
    PMID: 22329437 DOI: 10.1111/j.1525-1470.2011.01618.x
    High intraocular pressure is a rare ophthalmic condition associated with infantile hemangiomas that involves the orbit, eyelid, or both. Here, we describe a patient with extensive facial and orbital infantile hemangiomas associated with high intraocular pressure in the affected eye. The prompt management of this challenging condition is essential.
  8. Lateral rectus myositis mimicking an abducens nerve palsy in a pregnant woman
    Haslinda AR, Shatriah I, Azhany Y, Nik-Ahmad-Zuky NL, Yunus R
    Ophthalmic Plast Reconstr Surg, 2013 3 28;30(1):e13-5.
    PMID: 23531952 DOI: 10.1097/IOP.0b013e31828957ae
    Myositis is a rare unknown inflammatory disorder of the skeletal muscle tissue. Generalized inflammatory myopathies, polymyositis, and dermatomyositis have been reported during pregnancy. Isolated orbital myositis in pregnancy has not been previously described in the literature. The authors report a case of left isolated orbital myositis in a primigravida at 38 weeks gestation affecting the patient's left lateral rectus muscle. MRI of the orbit was consistent with the diagnosis. She showed remarkable clinical improvement with oral corticosteroids therapy.
  9. Endothelial nitric oxide synthase G894T gene polymorphism and response to skin reactive hyperemia
    Rasool AH, Ghazali DM, Abdullah H, Halim AS, Wong AR
    Microvasc Res, 2009 Sep;78(2):230-4.
    PMID: 19481100 DOI: 10.1016/j.mvr.2009.05.005
    Post occlusive skin reactive hyperemia (PORH) is a tool used to assess microcirculation. Endothelial nitric oxide synthase (eNOS) mediates nitric oxide (NO) production; polymorphism of the eNOS gene may affect response to the PORH process. This study aims to determine whether eNOS G894T gene polymorphism affects response to skin PORH. 230 normotensive male and females between 18 and 40 years participated in this cross-sectional study. 170 subjects were of the homozygous GG genotype, whereas 60 were of the GT genotype. Skin PORH was performed by occlusion of the upper arm at 200 mm Hg for 3 min. Skin perfusion and temperature were monitored before, during and after occlusion release using the laser Doppler fluximetry. There were no significant differences between genotypes in their baseline blood pressure, serum cholesterol, BMI and age. Maximum change in perfusion after occlusion release (PORHmax) for the GG and GT genotypes were not significantly different at 50.15+/-1.29 vs. 47.92+/-2.17 AU; ANCOVA, p=0.351. Peak perfusion (PORHpeak) were also not significantly different between the two genotypes (61.23+/-1.36 vs. 57.72+/-2.32 AU; p=0.169). Minimum baseline perfusion were however higher in the GG compared to the GT genotype (10.83+/-0.29 vs. 9.61+/-0.50, p=0.029). We conclude that microvascular reactivity, assessed by change in perfusion after temporary ischemia was not significantly different between the GG and GT genotypes of the eNOS G894T gene. eNOS 894T allele carriers however, have lower baseline perfusion compared to the homozygous G894 allele carrier.
  10. Characterization of alkanes, hopanes, and polycyclic aromatic hydrocarbons (PAHs) in tar-balls collected from the East Coast of Peninsular Malaysia
    Chandru K, Zakaria MP, Anita S, Shahbazi A, Sakari M, Bahry PS, et al.
    Mar Pollut Bull, 2008 May;56(5):950-62.
    PMID: 18328505 DOI: 10.1016/j.marpolbul.2008.01.028
    The East Coast of Peninsular Malaysia faces the South China Sea and is vulnerable to oil pollution because of intense petroleum production activities in the area. The South China Sea is also a favored route for supertankers carrying crude oil to the Far East. Consequently, oil spills can occur, causing pollution and contamination in the surrounding areas. Residual oil spills stranded on coastal beaches usually end up as tar-balls. Elucidating the sources of tar-balls using a molecular marker approach is essential in assessing environmental impacts and perhaps settling legal liabilities for affected parties. This study utilizes a multimodal molecular marker approach through the use of diagnostic ratios of alkanes, hopanes, and polycyclic aromatic hydrocarbons (PAHs) to determine the source, distribution and weathering of tar-balls. Hopane ratios (e.g., C29/C30, and summation C31-C35/C30 ratios) were used to identify the sources of tar-balls. The weathering effects were distinguished by using alkanes, namely the unresolved complex mixture (UCM) and low molecular weight/high molecular weight (L/H) ratios. Similarly, PAHs were also used for the determination of weathering processes undergone by the tar-balls. This multimodal molecular marker gave a very strong indication of the sources of tar-balls in this study. For example, 16 out of 17 samples originated from South East Asian Crude Oil (SEACO) with one sample from Merang, Terengganu originating from North Sea Oil (Troll). The TRME-2 sample may have come from a supertanker's ballast water discharge. The second possibility is that the tar-ball may have been transported via oceanographic currents. All 'weathered' sample characterizations were based on the presence of UCM and other ratios. The multimodal molecular marker approach applied in this study has enabled us to partially understand the transport behavior of tar-balls in the marine environment and has revealed insights into the weathering process of tar-balls.
  11. Fulltext Abnormal microvascular reactivity with hypercholesterolaemia in pregnancy
    Rasool AH, Abdul Rahman AS, Abd Ghaffar NA, Nik Mahmood NM, Wong AR
    Malays J Med Sci, 2010 Oct;17(4):14-9.
    PMID: 22135556 MyJurnal
    Post-occlusive skin reactive hyperaemia (PORH) is a model used to assess microvascular reactivity. This study aims to compare PORH response among pregnant hypercholesterolaemic patients with age and gestational age-matched controls.
  12. Fulltext Colonies in engineered articular cartilage express superior differentiation
    Selvaratnam L, Abd Rahim S, Kamarul T, Chan KY, Sureshan S, Penafort R, et al.
    Med J Malaysia, 2005 Jul;60 Suppl C:49-52.
    PMID: 16381284
    In view of poor regeneration potential of the articular cartilage, in-vitro engineering of cartilage tissue offers a promising option for progressive joint disease. This study aims to develop a biologically engineered articular cartilage for autologous transplantation. The initial work involved determination of chondrocyte yield and viability, and morphological analysis. Cartilage was harvested from the knee, hip and shoulder joints of adult New Zealand white rabbits and chondrocytes were isolated by enzymatic digestion of the extra-cellular matrix before serial cultivation in DMEM/Ham's F12 media as monolayer cultures. No differences were noted in cell yield. Although chondrocytes viability was optimal (>93%) following harvest from native cartilage, their viability tended to be lowered on passaging. Chondrocytes aggregated in isogenous colonies comprising ovoid cells with intimate intracellular contacts and readily exhibited Safranin-O positive matrix; features typically associated with articular cartilage in-vivo. However, chondrocytes also existed concurrently in scattered bipolar/multipolar forms lacking Safranin-O expression. Therefore, early data demonstrated successful serial culture of adult chondrocytes with differentiated morphology seen in established chondrocyte colonies synthesizing matrix proteoglycans.
  13. Synchronous primary malignancies of papillary thyroid carcinoma and Hodgkin lymphoma: Interventions and outcome
    Abd Rahim A, Muhammad R, Ismail F, Wong YP, Che Abdul Aziz R, Chong GY, et al.
    Malays J Pathol, 2023 Aug;45(2):275-283.
    PMID: 37658537
    Thyroid carcinoma is uncommon. Papillary thyroid carcinoma (PTC) represents the majority of differentiated thyroid carcinoma and is a recognised complication of prior exposure to ionizing radiation. Even more uncommon is the synchronous occurrence of PTC with Hodgkin lymphoma (HL) as multiple primary malignancies. We report a 33-year-old mother of three who developed asymptomatic thyroid nodule for four years, and neck swelling for the recent ten months. She denied constitutional symptoms or B symptoms, and thyroid profiles were normal. Initially, metastatic thyroid cancer was suspected based on ultrasound scan findings of enlarged left thyroid gland and enlarged supraclavicular lymph nodes (LN). However, fine needle aspiration examinations of the thyroid nodule were inconclusive, and the supraclavicular LN was suspicious of HL. Computerised tomography scan detected a large mass at the thyroid glands and lymphadenopathies in the mediastinal, hilar, subcarinal and axilla with dimensions up to 6 cm. Left hemi-thyroidectomy with left supraclavicular LN biopsy revealed PTC in the left thyroid lobe measuring 38 x 25 x 18 mm, and the left supraclavicular LN was not definitive of HL. Completion thyroidectomy on the right side, bilateral central neck dissection and excision biopsy of the right supraclavicular LN revealed the presence of HL in the right supraclavicular LN, and both HL and metastatic PTC in right central LN. After multidisciplinary discussions, the patient received chemotherapy at four weeks postoperatively and achieved complete remission. This report highlights the importance of patient-centered approach and multidisciplinary consensus within lack of established guidelines, given rarity of the case.
  14. Fulltext Knowledge, acceptance and concerns regarding COVID-19 vaccination among pregnant women on the east coast of Peninsular Malaysia: A cross-sectional study
    Farhana AH, Afendi NR, Che Hashim NAH, Ismail AA, Zon EM, Rahimah AR
    Malays Fam Physician, 2024;19:29.
    PMID: 39011293 DOI: 10.51866/oa.533
    INTRODUCTION: This prospective cross-sectional study, conducted from 1 April 2022 to 31 October 2022, aimed to assess the knowledge, acceptance and concerns regarding COVID-19 vaccination among pregnant women visiting the Obstetrics and Gynaecology Department of Hospital Universiti Sains Malaysia.

    METHODS: The study included all pregnant women aged >18 years. Sociodemographic data, information related to COVID-19 and vaccination and information on the knowledge, acceptance and concerns regarding COVID-19 vaccination were collected using a validated questionnaire.

    RESULTS: Out of 420 eligible pregnant women, 412 participated in the study, yielding a response rate of 98.1%. Of the respondents, 97.1% had received a COVID-19 vaccine, while 2.9% had not. Approximately 85.2% demonstrated a good understanding of COVID-19 vaccination. Among those vaccinated, 76.8% based their decision on recommendations from healthcare providers or the Ministry of Health. Among those unvaccinated, 91.7% believed that COVID-19 vaccines could harm their pregnancy and baby. Although 51% of the respondents expressed concerns about vaccine safety, 202 still chose to be vaccinated, indicating a willingness to prioritise their health despite apprehensions.

    CONCLUSION: The study found no significant link between acceptance and good knowledge of COVID-19 vaccination. However, income and prior COVID-19 booster vaccination were strongly associated with acceptance. Despite safety concerns, 97.1% of the respondents had received a COVID-19 vaccine. This emphasises the importance of providing comprehensive information and addressing concerns to support informed decision-making among pregnant women. Healthcare providers play a vital role in guiding them through this crucial decision-making process.

  15. Fulltext Factors of Never Screened with Faecal Occult Blood Test in Public Primary Care Facilities
    Sazali MF, Syed Abdul Rahim SS, Avoi R, Hassan MR, Hayati F, Azhar ZI, et al.
    Asian Pac J Cancer Prev, 2021 Jan 01;22(1):163-169.
    PMID: 33507695 DOI: 10.31557/APJCP.2021.22.1.163
    BACKGROUND: Colorectal cancer (CRC) is still a major public health threat. In the effort to reduce CRC incidence and mortality, faecal occult blood test (FOBT) is currently the screening tools used for early detection of CRC. However, the uptake of FOBT screening is less than promising. This study aims to identify the prevalence and predictors of Never Screened with FOBT (NS-FOBT).

    METHODS: A cross sectional study was conducted in five health clinics under Kota Kinabalu district, Sabah, Malaysia Borneo involving 162 attendees with age of 50 years old and above. A validated self-administered questionnaire was used to collect the data. Multiple logistic regression analysis was used to determine the predictors of NS-FOBT.

    RESULTS: The prevalence of NS-FOBT was 85.8% (n=139). Important predictors of NS-FOBT were age (aOR: 0.922; 95% CI: 0.855, 0.995; p=0.035), Bumiputera ethnicity (vs Non Bumiputera; aOR: 4.285; 95% CI: 1.384, 13.263; p=0.012), knowledge score (aOR: 0.921; 95% CI: 0.856, 0.99; p=0.027), and attitude score (aOR: 0.801; 95% CI: 0.702, 0.913; p=0.001).

    CONCLUSION: There is high prevalence of NS-FOBT. Age, ethnicity, knowledge, and attitude were important predictors of NS-FOBT. Strategies are needed to improve FOBT screening rate among the public. Socio-culturally tailored health promotion strategies as well as strengthening the communication, collaboration, and education to enhance the role of family physician is vital in improving the CRC prevention and care.

  16. Gender disparity in the prescription of secondary prevention medications in a Malaysian primary care clinic
    Baharudin N, Ahmad Roslan AM, Mohamed Yassin MS, Ramli AS, Zainal Abidin ANI, Sahar NH, et al.
    Malays Fam Physician, 2021 Jul 22;16(2):37-44.
    PMID: 34386162 DOI: 10.51866/oa1080
    Introduction: Cardiovascular disease is the leading cause of death worldwide. Despite the proven benefit of secondary prevention medications (SPMs), their utilisation remains suboptimal in many countries. This study aimed to assess the use of SPMs in a Malaysian primary care clinic and factors associated with it.

    Methods: A retrospective review of electronic medical records was conducted to assess the prescription of SPMs among patients with coronary artery disease who attended the clinic between 1st January 2018 and 31st December 2018. Prescriptions of SPMs were documented in numbers and percentages. Multiple logistic regressions were used to analyse factors associated with the prescription of SPMs.

    Results: Of the 662 patients included in the study, 99.1% were prescribed statins, 97% antiplatelets, 81.7% angiotensin-converting enzyme (ACE)-inhibitors or angiotensin II receptor blockers (ARBs), and 78.7% beta-blockers. Male patients were more likely to be prescribed statins (OR = 8.584, 95% CI: 1.431 - 51.510) and antiplatelets (OR = 6.818, 95% CI: 2.294 - 20.257). Another significant factor for antiplatelets prescription was having diabetes (OR = 3.318, 95% CI: 1.148 - 9.590). Having hypertension was associated with ACE-inhibitors or ARBs prescription (OR = 4.008, 95% CI: 2.522 - 6.370).

    Conclusion: Although the majority of patients received SPMs, there were significant disparities for some SPMs prescriptions among female patients. As these medications are widely available in the Malaysian primary care setting, steps should be taken to ensure that these medications are prescribed equally for all eligible patients.

  17. Fulltext Tool Wear and Surface Evaluation in Drilling Fly Ash Geopolymer Using HSS, HSS-Co, and HSS-TiN Cutting Tools
    Ghazali MF, Abdullah MMAB, Abd Rahim SZ, Gondro J, Pietrusiewicz P, Garus S, et al.
    Materials (Basel), 2021 Mar 26;14(7).
    PMID: 33810517 DOI: 10.3390/ma14071628
    This paper reports on the potential use of geopolymer in the drilling process, with respect to tool wear and surface roughness. The objectives of this research are to analyze the tool life of three different economy-grade drill bit uncoated; high-speed steel (HSS), HSS coated with TiN (HSS-TiN), and HSS-cobalt (HSS-Co) in the drilling of geopolymer and to investigate the effect of spindle speed towards the tool life and surface roughness. It was found that, based on the range of parameters set in this experiment, the spindle speed is directly proportional to the tool wear and inversely proportional to surface roughness. It was also observed that HSS-Co produced the lowest value of surface roughness compared to HSS-TiN and uncoated HSS and therefore is the most favorable tool to be used for drilling the material. For HSS, HSS coated with TiN, and HSS-Co, only the drilling with the spindle speed of 100 rpm was able to drill 15 holes without surpassing the maximum tool wear of 0.10 mm. HSS-Co exhibits the greatest tool life by showing the lowest value of flank wear and produce a better surface finish to the sample by a low value of surface roughness value (Ra). This finding explains that geopolymer is possible to be drilled, and therefore, ranges of cutting tools and parameters suggested can be a guideline for researchers and manufacturers to drill geopolymer for further applications.
  18. Fulltext Warpage Optimisation on the Moulded Part with Straight Drilled and Conformal Cooling Channels Using Response Surface Methodology (RSM), Glowworm Swarm Optimisation (GSO) and Genetic Algorithm (GA) Optimisation Approaches
    Mohd Hanid MH, Abd Rahim SZ, Gondro J, Sharif S, Al Bakri Abdullah MM, Zain AM, et al.
    Materials (Basel), 2021 Mar 10;14(6).
    PMID: 33802032 DOI: 10.3390/ma14061326
    It is quite challenging to control both quality and productivity of products produced using injection molding process. Although many previous researchers have used different types of optimisation approaches to obtain the best configuration of parameters setting to control the quality of the molded part, optimisation approaches in maximising the performance of cooling channels to enhance the process productivity by decreasing the mould cycle time remain lacking. In this study, optimisation approaches namely Response Surface Methodology (RSM), Genetic Algorithm (GA) and Glowworm Swarm Optimisation (GSO) were employed on front panel housing moulded using Acrylonitrile Butadiene Styrene (ABS). Each optimisation method was analysed for both straight drilled and Milled Groove Square Shape (MGSS) conformal cooling channel moulds. Results from experimental works showed that, the performance of MGSS conformal cooling channels could be enhanced by employing the optimisation approach. Therefore, this research provides useful scientific knowledge and an alternative solution for the plastic injection moulding industry to improve the quality of moulded parts in terms of deformation using the proposed optimisation approaches in the used of conformal cooling channels mould.
  19. Fulltext Hybrid Mold: Comparative Study of Rapid and Hard Tooling for Injection Molding Application Using Metal Epoxy Composite (MEC)
    Hussin R, Sharif S, Nabiałek M, Zamree Abd Rahim S, Khushairi MTM, Suhaimi MA, et al.
    Materials (Basel), 2021 Feb 01;14(3).
    PMID: 33535504 DOI: 10.3390/ma14030665
    The mold-making industry is currently facing several challenges, including new competitors in the market as well as the increasing demand for a low volume of precision moldings. The purpose of this research is to appraise a new formulation of Metal Epoxy Composite (MEC) materials as a mold insert. The fabrication of mold inserts using MEC provided commercial opportunities and an alternative rapid tooling method for injection molding application. It is hypothesized that the addition of filler particles such as brass and copper powders would be able to further increase mold performance such as compression strength and thermal properties, which are essential in the production of plastic parts for the new product development. This study involved four phases, which are epoxy matrix design, material properties characterization, mold design, and finally the fabrication of the mold insert. Epoxy resins filled with brass (EB) and copper (EC) powders were mixed separately into 10 wt% until 30 wt% of the mass composition ratio. Control factors such as degassing time, curing temperature, and mixing time to increase physical and mechanical properties were optimized using the Response Surface Method (RSM). The study provided optimum parameters for mixing epoxy resin with fillers, where the degassing time was found to be the critical factor with 35.91%, followed by curing temperature with 3.53% and mixing time with 2.08%. The mold inserts were fabricated for EB and EC at 30 wt% based on the optimization outcome from RSM and statistical ANOVA results. It was also revealed that the EC mold insert offers better cycle time compared to EB mold insert material.
  20. Fulltext Optimisation of Shrinkage and Strength on Thick Plate Part Using Recycled LDPE Materials
    Roslan N, Abd Rahim SZ, Abdellah AE, Abdullah MMAB, Błoch K, Pietrusiewicz P, et al.
    Materials (Basel), 2021 Apr 05;14(7).
    PMID: 33916414 DOI: 10.3390/ma14071795
    Achieving good quality of products from plastic injection moulding processes is very challenging, since the process comprises many affecting parameters. Common defects such as warpage are hard to avoid, and the defective parts will eventually go to waste, leading to unnecessary costs to the manufacturer. The use of recycled material from postindustrial waste has been studied by a few researchers. However, the application of an optimisation method by which to optimise processing parameters to mould parts using recycled materials remains lacking. In this study, Response Surface Methodology (RSM) and Particle Swarm Optimisation (PSO) methods were conducted on thick plate parts moulded using virgin and recycled low-density polyethylene (LDPE) materials (100:0, 70:30, 60:40 and 50:50; virgin to recycle material ratios) to find the optimal input parameters for each of the material ratios. Shrinkage in the x and y directions increased in correlation with the recycled ratio, compared to virgin material. Meanwhile, the tensile strength of the thick plate part continued to decrease when the recycled ratio increased. R30 (70:30) had the optimum shrinkage in the x direction with respect to R0 (100:0) material where the shrinkage increased by 24.49% (RSM) and 33.20% (PSO). On the other hand, the shrinkage in the y direction for R30 material increased by 4.48% (RSM) and decreased by 2.67% (PSO), while the tensile strength of R30 (70:30) material decreased by 0.51% (RSM) and 2.68% (PSO) as compared to R0 (100:0) material. Validation tests indicated that the optimal setting of processing parameter suggested by PSO and RSM for R0 (100:0), R30 (70:30), R40 (60:40) and R50 (50:50) was less than 10%.
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