Kesan lapisan berliang dan nisbah keluasan plat berlubang terhadap ciri akustik serabut sabut kelapa sebagai bahan penyerap bunyi

Penyelidikan ini dilakukan untuk mengkaji ciri akustik serabut sabut kelapa yang berpotensi digunakan sebagai bahan penyerap bunyi. Untuk meningkatkan ciri akustik serabut sabut kelapa pada frekuensi rendah, lapisan berliang digunakan di bahagian depan atau belakang bertujuan untuk meningkatkan nilai galangan permukaan. Bahan selanjutnya dilapisi dengan plat berlubang dengan nisbah keluasan yang berbeza. Sampel diuji mengikut piawaian antarabangsa ASTM E 1050-98 untuk menentukan pekali penyerapan bunyi. Daripada hasil uji kaji, plat 1 mm berlubang yang diperbuat daripada kepingan aluminium yang melapisi serabut sabut kelapa, didapati bahawa nilai maksimum pekali penyerapan bunyi berada pada frekuensi antara 2750 Hz hingga 2825 Hz iaitu dengan nilai 0.97. Nilai nisbah keluasan plat berlubang memberikan pengaruh penurunan pekali penyerapan bunyi pada frekuensi tinggi. Penurunan nilai pekali penyerapan bunyi terjadi apabila plat berlubang mempunyai nilai nisbah keluasan di bawah 0.22. Akan tetapi, penggunaan plat berlubang boleh meningkatkan prestasi penyerapan bunyi serabut sabut kelapa pada frekuensi rendah. Kesepakatan yang baik diperoleh daripada keputusan uji kaji dan analisis dengan pendekatan rangkaian elektrik setara yang digunakan untuk menghitung nilai pekali penyerapan bunyi. Ini menunjukkan bahawa pendekatan rangkaian elektrik setara boleh digunakan untuk merancang dan mengoptimumkan ciri akustik serabut sabut sebagai bahan penyerap buny

Penggunaan kaedah aliran angin untuk mengatasi masalah kecacatan produk plastik

Kecacatan produk plastik adalah satu mimpi ngeri untuk setiap pekerja di sektor pengilangan proses pengacuan suntikan. Kecacatan produk seperti produk tidak penuh (short mould), kesan terbakar (burn mark), lebihan (flashing), kesan melengkung (warping), kesan gelombong udara (bubble) dan sebagainya. Aliran angin (air vent) adalah satu saluran atau longkang yang dibuat pada permukaan acuan, di tengah batang ejektor, di celah sambungan blok di dalam acuan atau ditempat-tempat yang sesuai. Aliran ini dibuat semasa proses pemasangan acuan baru atau selepas acuan dipasang atau semasa acuan sedang dijalankan mengikut kesesuaian keperluan. Kedudukan serta saiz aliran angin ditentukan mengikut analisa perjalanan bahan mentah (menggunakan software seperti Moldflow) ataupun berdasarkan pengalaman pembuat acuan ataupun menggunakan kaedah cuba dan guna (trial and error) yang biasa dilakukan setelah produk mengalami masalah. Jika kadar masa yang diambil adalah kurang dari masa yang diperlukan semasa bahan leburan dimasukkan (S2 >S1), maka ia boleh dikatakan udara tidak dapat dilepaskan semasa bahan leburan dimasukkan ke dalam rongga acuan.Maka ini akan menghasilkan produk yang mempunyai masalah. Kajian dijalankan secara rujukan kertas ilmiah dan empat(4)kes secara praktikal diberikan. Selepas pengubahsuaian untuk setiap kes yang dibentangkan, banyak kebaikan yang diperolehi dari segi masa dan jumlah kecacatan yang dihasilkan. Tetapi proses ini hanya dapat dikekalkan jika pembersihkanacuan dan jangka hayat untuk penyelengaraan minor haruslah dilakukan untuk mengelakan saluran aliran angin (air vent)dari tertutup. Dari segi kos operasi pula kadar penurunan jumlah produk yang cacat berkurangan dengan ketara sekalididalam kes pengubahsuaian penambahbaikan

Parameter optimization: effect of humidity and fabrication process on flexural

Biocomposite from kenaf reinforced polylactic acid (Kenaf/PLA) has the potential to replace a synthetic reinforcement and matrix in polymer composite applications. Kenaf is well known as a natural fiber that can be replaced with synthetic fiber and reinforced with synthetic resin, whether thermoset or thermoplastic. An increase in environmental impact drives increased usage of a biodegradable polymer such as PLA in the application of biocomposite. However, moisture uptake from the humidity and elevated temperature exposure during fabrication of composite is mostly a factor that affects the properties of biocomposite. Therefore, this study aims to optimize the factors consisting of humidity exposure, temperature and time holding during hot press using the design of experiment (DOE) by Box-Behnken Design (BBD) approach. The kenaf/PLA was exposed to the humidity range from 40% up to 80% before undergoing composite fabrication. Then produce the composite using a hot press molding where the parameter consists of elevated temperature (range from 160 o C up to 200 o C) and time holding (range from 3 minutes up to 10 minutes) that possibly affects the mechanical properties of kenaf/PLA. These three factors were evaluated based on optimizing maximum results on flexural properties, where all the combination factors were assessed using DOE. Using analysis of variance (ANOVA) revealed that humidity exposure and hot press temperature are essential factors affecting kenaf/PLA flexural strength. The results indicated that the selected humidity and hot press parameters were 40 %RH, 160 o C press molding temperature, and a 3-minute heating duration for optimal flexural strength. The parameter will obtain 111.61 MPa of flexural strength. Implementing the chosen factor can produce the kenaf/PLA biocomposite with an optimum flexural strength of 111.61 MPa

Tensile and flexural properties of kenaf reinforced polylactic acid under heat effect

Biocomposite is a combination of natural reinforcement and natural matrix material consisting of kenaf reinforced with polylactic acid (PLA), where its mechanical properties will be affected when exposed to heat. This research investigates the effect of exposure of biocomposites to different temperatures on the mechanical properties of biocomposites, consisting of tensile and flexural properties. Before producing the sample, kenaf in the form of one-way yarn is conditioned with 40% RH humidity, and then the sample is produced using hot compression molding techniques by combining kenaf with PLA. Tensile and bending tests carried out in a heating chamber with the heat were studied using a Universal Testing Machine (UTM). The choice of heat temperature depends on the glass transition temperature of polylactic acid, where the study temperature ranges from 25 oC to 65 oC. From the results of the study, it was found that the maximum bending strength and modulus (117 MPa, 5.8 GPa) and the maximum tensile strength and modulus (59 MPa, 3.2 GPa) were both obtained at low temperatures (25 oC). While the modulus value decreases significantly at 55 oC, the tensile and flexural properties both show a steady decrease with increasing temperature. Therefore, the presence of temperature has a significant effect on the tensile and flexural properties of kenaf-reinforced PLA biocomposites. When it is exposed to high temperatures, the mechanical quality deteriorates, and the risk of failure increases. Failure is caused by poor reinforcement and matrix bonding caused by the degradation of natural fiber properties of kenaf and the level of PLA plastic deformation

Pemilihan parameter utama pengacuan suntikan dalam pemprosesan polimer: ulasan ilmiah

Sistem suntikan menjadi nadi utama di dalam proses Pengacuan Suntikan, di mana ia merangkumi pelbagai faktor yang perlu dikawal dan diselaraskan. Sistem kawalan ini merangkumi parameter yang dikategorikan sebagai empat parameter utama: tekanan, suhu, masa, dan jarak. Tekanan Suntikan adalah tekanan yang diperlukan untuk menggerakan bahan leburan polimer ke dalam acuan. Tekanan Pegangan adalah fasa selepas fasa tekanan suntikan. Suhu Barel mengandungi empat zon suhu pada unit suntikan yang terdiri daripada zon belakang, zon tengah, zon depan, dan zon muncung. Suhu acuan biasanya digunakan ketika proses penyejukkan bahan plastik selepas ia disuntik ke dalam acuan yang mempunyai saluran air penyejuk. Sejumlah 40 kertas penyelidikan telah dikaji dan diringkaskan berdasarkan kepada parameter yang digunakan di dalam penganalisaan. Kebanyakan penyelidik mengamalkan kaedah Taguchi dalam kaedah penyelidikan mereka. Dari analisa, terdapat empat parameter yang kerap digunakan iaitu Suhu Barel, Suhu Acuan, Tekanan Suntikan dan Tekanan Pegangan dalam usaha untuk menghasilkan produk, menambahbaikan produk agar lebih berkualiti atau menaikkan kadar kekuatan maksimum produk. Kertas kerja ini adalah ulasan ilmiah semua parameter utama yang terlibat dalam proses pengacuan suntikan tersebut

Studies on Flame Retardants on Malaysian Coir Fiber

In this study to the effect of the utilization of urea and diammonium phosphate as fire retardant on Malaysian coir fiber was evaluated. Flammability and thermogravimetric analysis (TGA) tests were used to evaluate the fire retardancy. Weight loss and percentage of mass residue were used as a measure from the results of flammability and TGA, respectively. The results revealed the effectiveness of using urea and diammonium phosphate as fire retardant for Malaysian coir fiber. However, for the samples treated with retardant high concentration the weight loss is not significant with the time of dipping treatment. This indicates that the just dip application for the fire retardant of higher concentration is sufficient

Bleed or clot? managing bleeding in post thrombolysis patient with massive pulmonary embolism who underwent recent major cancer surgery

A 51-year-old lady with invasive left breast cancer had a syncopal attack following acute chest pain on day 1 post-mastectomy. She was hypotensive and her electrocardiogram showed ST elevation at anterior leads. She had received systemic thrombolysis therapy with an excellent initial symptomatic response and ECG resolution. However, echocardiogram and computed-tomography pulmonary angiogram later showed evidence of massive pulmonary embolism. The treatment was complicated with significant bleeding from the surgical site which required a total of 11 units of packed cells, 4 units of fresh frozen plasma, 4 units of platelet, 6 units of cryoprecipitate and prothrombin complex concentrate; in order to control the bleeding along with local compression. As the haemostasis was achieved, anticoagulation was cautiously initiated, initially with unfractionated heparin followed by low-molecular-weight heparin. Eventually, she received rivaroxaban to complete her course of treatment. She made an excellent recovery on follow-up review and is planned for further treatment for her breast cancer. This case portrayed the complexity of managing a concurrent event of massive thrombosis and significant bleeding, which required a diligent assessment of both risks to ensure the best patient’s outcome

ECONOMIC ANALYSIS OF A GRID CONNECTED SOLAR HYDROGEN PV SYSTEM

The grid connected solar hydrogen energy system has been developed in order to investigate the performance under the local climate conditions. The grid connected solar hydrogen energy system (GCSHES) have the capability of overcoming the problems that occur on the grid connected power system (GCPS) when there is a black-out of grid electricity. Moreover, stand alone power system (SAPS) requires batteries, and larger hydrogen tank capacity is required for higher energy generation. An experimental GCSHES has been setup and tested. The GCSHES consists of subsystems photovoltaic (PV) array with 40 PV module with its capacity of 5000 Wp, inverter capacity (6000W), electrolyzer, hydrogen tank and fuel cell (500 W). The monthly efficiency and performance of PV array is 12.7% and 26%, while the efficiency and performance of inverter is 95.1% and 98%, respectively. The techno-economical analysis indicated that the pay back period of this system is 18 years

PERFORMANCE OF A GRID CONNECTED SOLAR HYDROGEN PV SYSTEM IN MALAYSIA

In this project, an experimental grid connected solar hydrogen energy system (GCSHES) has been setup and tested. The important element of GCSHES is that it has the capability of overcoming the problems that occur on the grid connected power system (GCPS) when there is no electricity. The system will converts the electric energy-generated from a PV module into hydrogen. The polymer electrode fuel cell generates electricity using the hydrogen stored in the storage tank. The GCSHES consists of a subsystems photovoltaic array, inverter, electrolyser, hydrogen tank and fuel cell. It has been found that the monthly efficiency and performance of PV array is 12.7% and 26%, and for inverter is 95.1% and 98%, respectively. The efficiency of electrolyzer subsystem and fuel cell is 51% and 25%, respectively. The results have shown that GCSHES gave a very good performance and can effectively be used in Malaysian climate conditions for renewable energy generations

Influence of the oblique fin arrangement on the fluid flow and thermal performance of liquid cold plate

Electric vehicle (EV) is advancing as the transportation industry and the demand is expanding globally. The use of liquid cold plate (LCP) in EV battery is more effective in providing the desire temperature rather than using the conventional air cooling. The use of straight fins is being switched to oblique-shape fins to assist disruption of the thermal boundary layer development. The arrangement of fins in the LCP also will affect the performance of it cooling the battery. Three different arrangement of the oblique fin are developed to enhance the fluid flow and heat transfer performance. The LCP contains three arrangements of oblique fin namely as inline, incline and loureved. Experimental and numerical results reveal the good aggrement where the Nusselt number is enhanced with the louvered arrangement. Among three arrangements, loureved obtained the lowest surface temperature of the battery followed by inline and incline. It also found that Nusselt number increases as the Reynolds number increases. The LCP is able to maintain the average surface temperature of the battery below permitted working temperature of 50 °C. This shows that the present LCP with oblique fin could be a promising method for EV battery thermal management. Keywords: Liquid cold plate, Oblique fin, Heat transfer, Electric vehicl