Effect of waste plaster of Paris on physical and mechanical properties of ceramic pottery body

Over the years, millions tonnes of waste plaster of Paris (POP) were generated and disposed in landfills or most of the time was dumped directly into the environment without any treatments, makes it as one of the environmental issues. Therefore, a new alternative is required to convert the wastes POP into useful materials and marketable to minimize the environmental impact. In the early stage, this study focused on the characterization of the raw material used through particle size analysis, thermal analysis, and identification of its purity. Then, the slip casting technique and standard American Society for Test and Materials (ASTM) was respectively used to fabricate and characterize all of the pottery samples. In the second stage, the ceramic pottery body was fabricated using different composition of waste POP, started from 0 wt.% until 12 wt.%. The samples obtained were analysed through viscosity test and its green body was observed. The results showed that the samples with compositions of 0 to 10 wt.% of waste POP were the only samples that can be used in this study. The analysis on the effects of particle sizes ranging from 25 to 73 μm and sintering temperatures ranging from 950 to 1050 °C on the physical and mechanical properties of the fabricated ceramic pottery body, respectively, were then determined in the third and fourth stage of this study. The physical properties were reported in terms of shrinkage, porosity, and density values; whereas, the mechanical properties were reported in terms of the value of modulus of rupture (MOR). The result showed that a dense and a high strength of ceramic pottery can be produced by using a finer size of particle of 25 μm and at a high sintering temperature of 1050 °C, based on the low porosity value, the high density value, MOR and also the controllable value of shrinkage. Therefore, it can be concluded that the waste POP can be successfully used as a filler to enhance the properties of ceramic pottery body

Acoustical characteristic of empty fruit bunch (EFB) fibre with influence of sodium hydroxide treatment time and decay lifespan

Research on natural fibres has gain much interest in recent years due to the sustaibability and avaibility in which demand for green renewable reinforced composites. Natural fibres can be considered as the alternative way to replace the synthetic fibre as well as to implement the sustainability of the materials. However, the natural fibre also has its own disadvantage which is the ability to maintain the quality of absorption due to the lack of information and research on the acoustic application. Thus, in this research, the untreated and treated Empty Fruit Bunch (EFB) fibre was investigated as control unit and the standard used for sound absorption test was ISO 10534-2 and ASTM E1050-98. The EFB has undergone a chemical modification process known as alkali treatment using sodium hydroxide (NaOH). Five parameters were chosen for the alkali treatment process which is the fiber immersion time (at 1 hour until 5 hours) with fixed alkali treatment concentration of 6% NaOH. Cross sectional area of the fibre was measured using Leica stereo video analyser. The results from the test show EFB fibre gives positive value of sound absorption from mid to high frequency which is from 2000 Hz to 5000 Hz. The best sound absorption is performed by the 1 hour of treated fibre with a maximum sound absorption coefficient (α) nearly 1 at 2500 Hz and with thickness of 50 mm. The Noise Reduction Coefficient (NRC) for the 1 hour treated fibre is 0.53. As for decay lifespan, the sound absorptions performance was slightly decreased from 0.68 to 0.55 within 5 to 20 months. This result indicates that the treated EFB are highly absorptive material and it is recommended to become as a natural base for acoustical absorption material

Effect of waste plaster of Paris on physical and mechanical properties of ceramic pottery body

Over the years, millions tonnes of waste plaster of Paris (POP) were generated and disposed in landfills or most of the time was dumped directly into the environment without any treatments, makes it as one of the environmental issues. Therefore, a new alternative is required to convert the wastes POP into useful materials and marketable to minimize the environmental impact. In the early stage, this study focused on the characterization of the raw material used through particle size analysis, thermal analysis, and identification of its purity. Then, the slip casting technique and standard American Society for Test and Materials (ASTM) was respectively used to fabricate and characterize all of the pottery samples. In the second stage, the ceramic pottery body was fabricated using different composition of waste POP, started from 0 wt.% until 12 wt.%. The samples obtained were analysed through viscosity test and its green body was observed. The results showed that the samples with compositions of 0 to 10 wt.% of waste POP were the only samples that can be used in this study. The analysis on the effects of particle sizes ranging from 25 to 73 μm and sintering temperatures ranging from 950 to 1050 °C on the physical and mechanical properties of the fabricated ceramic pottery body, respectively, were then determined in the third and fourth stage of this study. The physical properties were reported in terms of shrinkage, porosity, and density values; whereas, the mechanical properties were reported in terms of the value of modulus of rupture (MOR). The result showed that a dense and a high strength of ceramic pottery can be produced by using a finer size of particle of 25 μm and at a high sintering temperature of 1050 °C, based on the low porosity value, the high density value, MOR and also the controllable value of shrinkage. Therefore, it can be concluded that the waste POP can be successfully used as a filler to enhance the properties of ceramic pottery body

A review of grouper (Epinephelus suillus) fry production research in Malaysia

Research on grouper (Epinephelus suillus) fry production in captivity has been carried out in Malaysia since 1986 at Tanjung Demong Marine Finfish Production and Research Centre (TDMFPRC) but the breakthrough was only achieved four years later in 1990. Eggs were obtained through natural and induced spawning in tanks. Natural spawning of grouper in captivity seldom occurred and was unpredictable. However induced spawnings were successfully carried out by injecting human chorionic gonadotropin (hCG) intramuscularly at a dose of 500-1000 IU/kg fish. The results from several trials on larval rearing conducted since 1989 until recently showed that larvae obtained from natural spawnings survived longer with some reaching the juvenile stage. The highest recorded survival rate of 43 days posthatch (32.5 mm total length) was 12.1% at 28-32 °C water temperature. On the other hand, 100% mortality usually occurred in larvae obtained from induced spawning 7 days after hatching. The major constraints of grouper fry production in Malaysia are lack of male spawners, inconsistent and unpredictable natural spawning, small quantity of eggs released every spawning day, poor fertilization and hatching rate, weak hatchlings, and high mortality rate at the early stages of larval development. The latter is probably due mainly to problems on initial feeding

Modelling of advanced submicron gate InGaAs/InAIAs pHEMTS and RTD devices for very high frequency applications

InP based InAlAs/InGaAs pseudomorphic High Electron Mobility Transistors (pHEMTs) have shown outstanding performances, which makes them prominent in high frequency mm-wave and submillimeter-wave applications. However, conventional InGaAs/InAlAs pHEMTs have major drawbacks, i.e., very low breakdown voltage and high gate leakage current. These disadvantages degrade device performance, especially in Monolithic Microwave Integrated Circuit (MMIC) low noise amplifiers (LNAs). The optimisation of InAlAs/InGaAs epilayer structures through advanced bandgap engineering together with gate length reduction from 1 m into deep sub-μm regime is the key solution to enabled high breakdown and ultra-high speed, low noise pHEMT devices to be fabricated. Concurrently, device modelling plays a vital role in the design and analysis of pHEMT device and circuit performance. Physical modeling becomes essential to fully characterise and understand the underlying physical phenomenon of the device, while empirical modelling is significant in circuit design and predicts device’s characteristic performance. In this research, the main objectives to accurately model the DC and RF characteristics of the two-dimensional (2D) physical modelling for sub-μm gate length for strained channel InAlAs/InGaAs/InP pHEMT has been accomplished and developed in ATLAS Silvaco. All modelled devices were optimised and validated by experimental devices which were fabricated at the University of Manchester; the sub-micrometer devices were developed with T-gate using I-line optical lithography. The underlying device physics insight are gained, i.e, the effects of changes to the device’s physical structure, theoretical concepts and its general operation, hence a reliable pHEMT model is obtained. The kink anomalies in I-V characteristics was reproduced and the 2D simulation results demonstrate an outstanding agreement with measured DC and RF characteristics. The aims to develop linear and nonlinear models for sub-μm transistors and their implementation in MMIC LNA design is achieved with the 0.25 m In0.7Ga0.3As/In0.52Al0.48As/InP pHEMT. An accurate technique for the extraction of empirical models for the fabricated active devices has been developed and optimised using Advance Design System (ADS) software which demonstrate excellent agreement between experimental and modelled DC and RF data. A precise models for MMIC passive devices have also been obtained and incorporated in the proposed design for a single and double stage MMIC LNAs in C- and X-band frequency. The single stage LNA is designed to achieve maximum gain ranging from 9 to 13 dB over the band of operation while the gain is increased between 20 dB and 26 dB for the double stage LNA designs. A noise figure of less than 1.2 dB and 2 dB is expected respectively, for the C- and X-band LNA designed while retaining stability across the entire frequency bands. Although the RF performance of pHEMT is being vigorously pushed towards terahertz region, novel devices such as Resonant Tunnelling Diode (RTD) are needed to support future ultra-high speed, high frequency applications especially when it comes to THz frequencies. Hence, the study of physical modelling is extended to quantum modelling of an advanced In0.8Ga0.2As/AlAs RTD device to effectively model both large size and submicron RTD using Silvaco’s ATLAS software to reproduce the peak current density, peak-to-valley-current ratio (PVCR), and negative differential resistance (NDR) voltage range. The simple one-dimensional physical modelling for the RTD devices is optimised to achieve an excellent match with the fabricated RTD devices with variations in the spacer thickness, barrier thickness, quantum well thickness and doping concentration

Pemilihan kerjaya di kalangan pelajar-pelajar pendidikan khas aliran teknik dan vokasional : satu tinjauan

Kajian ini bertujuan untuk mengenalpasti ciri-ciri pemilihan keijaya yang menjadi pilihan para pelajar pendidikan khas aliran Teknik dan Vokasional. Selain daripada itu juga, kajian ini dilakukan adalah untuk mendapatkan corak atau pola pemilihan keijaya yang dilakukan oleh pelajar-pelajar Pendidikan Khas berdasarkan keadaan keluarga dan keadaan pekeijaan itu sendiri. Walaubagaimanapun, kajian ini juga dilakukan untuk mengenalpasti keijaya yang menjadi pilihan pelajar-pelajar Pendidikan Khas aliran Teknik dan Vokasional. Kajian ini dijalankan di sebuah sekolah sahaja iaitu Sekolah Menengah Pendidikan Khas Vokasional, Seksyen 17, Shah Alam, Selangor. Seramai 50 orang pelajar tingkatan lima yang terdiri dari pelbagai bidang kursus telah dipilih sebagai sampel kajian ini. Data yang diperolehi dianalisis menggunakan SPSS (Statistical Package For Social Science) versi 10.0. Pengkaji menggunakan kaedah soal selidik dan hasil dapatan dianalisis dalam bentuk skor min dan peratusan. Hasil kajian menunjukkan bahawa ciri kerjaya yang boleh membantu masyarakat atau dapat memberi bantuan amal amat digemari oleh pelajarpelajar pendidikan khas ini. Keputusan kajian juga menunjukkan keadaan keluarga dan keadaan pekeijaan itu sendiri boleh menentukan corak pemilihan kerjaya bagi pelajar-pelajar istimewa ini. Selain daripada itu juga, hasil kajian menunjukkan pekerjaan yang berunsur kreatif adalah yang paling ramai digemari oleh mereka. Melalui kajian ini, akan membolehkan kita merangka satu program yang lebih tersusun dan berterusan bagi membantu mereka secara lebih berkesan dalam pemilihan kerjaya

Transmission properties of acousto optic material

Laser beam can be modulated by acousto optic modulator using a suitable acousto optic material. UV-VIS Spectrophotometer was utilized to investigate the transmission spectrum of two non linear acousto optic materials that are lithium niobate and fused quartz. From the spectrum it shows that transmittance for fused quartz and lithium niobate were 90% and 68% respectively. The absorption coefficient ? is calculated and plotted versus photon energy. It was found that ? increases linearly with photon energy in the range of 3.50 eV to 4.0 eV for fused quartz and 3.15 eV to 4.0 eV for lithium niobate. The estimated optical energy band gap was 2.97 eV for lithium niobate and 3.69 for fused quartz. From the transmission properties obtained in this study, it can be summarized that fused quartz is a better choice to be an acousto optic material

Laser beam modulation by an acousto optic mode locker

Nazariahmatdaud2006the characterization of beam modulation by acousto-optic mode locker is reported. Hene laser was employed as a source. Acousto-optic mode locker (aoml) was used to convert the continuous beam to become pulsed. Radio frequency signal provided an acoustic source to the aoml. The signal was amplified using a power amplifier. A pulse generator was utilized to regulate the frequency of the signal. The frequency and the power of the amplifier were varied to characterize the modulated beam. The hene laser beam was modulated into a periodic signal. The pulse width of the modulated signal was found to increase linearly with the rf pulse width. The modulated signal intensity was also found to vary linearly with rf drive power_laserbeammodulationbya

Hubungan di antara status Sosio Ekonomi (SSE) keluarga dengan pencapaian akademk : satu kajian ke at as pelajar aliran teknikal di Sekolah Menengah Teknik Negeri Sembilan

Kajian ini bertujuan untuk melihat hubungan di antara status sosio ekonomi (SSE) keluarga dengan pencapaian akademik di kalangan pelajar aliran teknikal. Kajian ini dijalankan ke atas pelajar tingkatan empat aliran teknikal di lima buah Sekolah Menengah Teknik di Negeri Sembilan iaitu Sekolah Menengah Teknik Tuanku Jaafar, Sekolah Menengah Teknik Juasseh, Sekolah Menengah Teknik Pertanian Rembau, Sekolah Menengah Teknik Ampangan dan Sekolah Menengah Teknik Port Dicksoa Seramai 350 orang pelajar terlibat dalam kajian ini dan dipilih secara rawak mudah. Analisis regresi mudah dan regresi berbilang digunakan untuk melihat hubungan di antara pembolehubah yang dikaji. Keseluruhan data kajian telah dianahsis menggunakan perisian Statistical Packages for the Social Sciences (SPSS) versi 11.5 dengan membuat pengiraan peratusan dan regresi. Dapatan kajian menunjukkan secara majoritinya, SSE mempunyai hubungan yang signifikan dengan tahap pencapaian akademik pelajar. Dengan itu dapat dirumuskan bahawa SSE mempengaruhi tahap pencapaian akademik pelajar aliran teknikal. Beberapa cadangan dikemukakan untuk panduan kajian selanjutnya