Preliminary design of a test rig for combining passive nonlinear isolation with active control

Resilient elements are typically used to isolate delicate equipment from a vibrating host structure. Conventionally, these isolators are designed to operate in their linear region, but more recently nonlinear isolators have been employed to increase the frequency over which vibration isolation can be achieved. Another way of improving the performance of an isolator has been to use active control in conjunction with a passive linear system. The work presented in this paper concerns the development of an experimental rig for vibration isolation and is motivated by the intention to combine the advantages of passive nonlinear isolation with active control.The structure consists of a mass suspended on four tensioned wires to form a single-degree-of-freedom system. The nonlinear stiffness of the wires is such that the system behaves like a hardening Duffing oscillator. Firstly, a static analysis is carried out, both analytically and experimentally, where the nonlinearity of the system is determined by the tension, length, cross-sectional area and Young’s modulus of the wires. For the dynamic analysis, harmonic base excitation is considered. The magnitude of the base displacement is fixed for all excitation frequencies and the level of nonlinearity is adjusted by varying the tension in the wires, a higher tension leading to a milder system nonlinearity. Finally, the motion transmissibility of the system is measured and appears to agree with the theoretical result. The rig forms a suitable platform for subsequent incorporation of an active control system for combining the benefits of passive nonlinear isolation with, for example, skyhook damping

Kualiti pengalaman pembelajaran pelajar-pelajar sarjana muda kejuruteraan elektrik di Kolej Universiti Teknologi Tun Hussein Onn (KUiTTHO) dari aspek pembelajaran kognitif, psikomotor dan afektif

Pembelajaran kognitif, psikomotor dan afektif merupakan pembelajaran yang perlu ditekankan dalam konteks pengajaran dan pembelajaran di institusiinstitusi pengajian tinggi. Ketiga-tiga aspek pembelajaran tersebut amat penting bagi melahirkan graduan yang mempunyai ketrampilan yang tinggi dari segi kreativiti, berinovatif, berkaliber, berkompetensi serta mempunyai motivasi kendiri yang tinggi. Kajian ini adalah satu kajian untuk menilai kualiti pengalaman pembelajaran pelajar-pelajar Saijana Muda Kejuruteraan Elektrik di KUiTTHO. Kajian ini meninjau pengalaman pembelajaran di dalam kelas dan di makmal/bengkel dari aspek pembelajaran kognitif, psikomotor dan afektif. Responden terdiri daripada empat puluh orang pelajar Saijana Muda Kejuruteraan Elektrik semester akhir yang dipilih secara rawak. Instrumen yang digunakan dalam kajian ini ialah jenis soal selidik di mana penilaian dilakukan berdasarkan persepsi responden terhadap pengalaman pembelajaran yang ditempuhi sepanjang pengajiannya serta menjalankan sesi temubual dengan beberapa orang responden. Data-data yang dikumpulkan, dianalisis menggunakan SPSS version 11.0 yang melibatkan skor min dan sisihan piawai. Dapatan kajian menunjukkan kualiti keseluruhan pengalaman pembelajaran pelajar adalah di tahap sederhana (skor min = 3.49). Bagi pengalaman pembelajaran di dalam kelas dan makmal, kualitinya adalah di tahap sederhana (skor min = 3.31 dan 3.67 masing-masing). Sementara kualiti keseluruhan pengalaman pembelajaran dari aspek kognitif, psikomotor dan afektif juga berada di tahap sederhana (skor min = 3.50, 3.39 dan 3.57 masing-masing). Oleh itu, berdasarkan kualiti pengalaman pembelajaran pelajar yang sederhana ini, pengkaji telah membina satu produk cadangan iaitu Sistem Senarai Semak Kualiti Pengajaran dan Pembelajaran bagi membantu pihak pengurusan akademik KUiTTHO meningkatkan kualiti pengajaran dan pembelajaran dari ketiga-tiga aspek kognitif, psikomotor dan afektif

Sensor material characterisation for magnetometer application

Pengukuran dan gangguan medan magnet arus terus dan arus ulang-alik memerlukan penderia medan magnet yang mempunyai kepekaan yang tinggi dan stabil. Untuk menghasilkan penderia tersebut, ciri-ciri bahan magnet yang baik telah dikenalpasti. Beberapa jenis bahan magnet yang berbeza telah digunakan untuk mengkaji ciri-ciri dan kesannya terhadap medan magnet. Teras gelang yang diperbuat daripada bahan-bahan magnet tersebut direkabentuk dengan dimensi yang sama bagi membolehkan perbandingan dibuat dengan mudah. Selain itu, rod tunggal dan berkembar juga telah digunakan sebagai teras penderia fluxgate, untuk melihat prestasi setiap jenis penderia tersebut. Kedua-dua penderia tersebut telah diuji dengan menggunakan dua sumber bahan magnet iaitu bar magnet tetap dan solenoid dengan diameter dawai yang berbeza. Isyarat keluaran bagi setiap penderia fluxgate seterusnya diproses bagi mengenalpasti hubungannya dengan ketumpatan medan magnet

Sintesis Absolut Asimetrik Baru

New absolute asymmetric syntheses have been found. Eugenol based-acetylenes monomers have been synthesized, corresponding three compounds and one unknown compound. Two compounds are crystal chiral (1 and 2) and one (3) not. Polymerization of chiral crystal and not were different although the structure is same. After recrystalization polymerization of 1 and 2 compare with 3 also different. This is one example of new absolute asymmetric synthesis

Formulation of refined, bleached and deodorised palm stearin with zinc dialkyl-dithiophosphate additive and its tribological performance

Vegetable oils have recently received worldwide attention for their use as a lubricant base stock that has numerous advantages, including their environmental friendliness. In this study, a refined, bleached and deodorised palm stearin was selected as the base lubricant, and its friction and wear performance were investigated with a pin-on-disk tribotester. The effect of zinc dialkyl-dithiophosphate (ZDDP) additive in concentrations of 1wt%, 3wt% and 5wt% on friction and wear performance were evaluated. Commercial semi-synthetic oil SAE 15W50 was used for comparison purposes. The experiments were conducted at a sliding speed of 1.5 m/s under a normal force of 9.81 N for 60 min. Results show that an increase in ZDDP concentrations improved both friction reduction and wear performance of the lubricant. The coefficient of friction (COF) of RBD palm stearin was reduced approximately at 71% when 5wt% of ZDDP was added and it shows that the friction reduction performance of PS+5wt% (COF=0.039) was comparable to SAE 15W50 (COF=0.035). While, wear coefficient of RBD palm stearin was reduced significantly from 2.08 × 10−3 to 8.89 × 10−5 when 5wt% ZDDP additive was added and it shows that the wear performance of PS+5wt% was better than that of SAE 15W50, 1.94 × 10−4. Further analysis of the wear worn surface with a high-resolution optical microscope was also conducted with a surface profilometer to examine the metallurgy of the pin surface and the roughness of the pin

A study of the effect of palm oil as MQL lubricant on high speed drilling of titanium alloys

The main objective was to study the potency of MQL palm oil (MQLPO) as a lubricant in the high speed drilling of Ti–6Al–4V. For the comparison, MQL synthetic ester (MQLSE), air blow and flood conditions were selected. Uniform flank wear, micro-chipping, thermal cracking and flaking were the dominant tool failure modes. It was found that MQLSE and MQLPO gave comparable performance with the flood conditions. In addition, MQLPO outperformed MQLSE on the cutting forces, temperature, power and specific cutting energy. This shows that palm oil can be used as a viable alternative to synthetic ester for MQL lubricant

Manual pengajaran berteraskan teknologi kejuruteraan

Kajian dijalankan untuk membangunkan manual pengajaran bagi subjek berteraskan teknologi kejuruteraan. Ia merupakan panduan kepada pensyarah untuk membangunkan pengajaran dan pembelajaran bagi subjek berteraskan teknologi kejuruteraan secara sistematik. Kaedah ini akan dapat membantu pensyarah untuk melaksanakan pengajaran secara tersusun, berkesan dan efisien. Manual ini membincangkan keperluan, reka bentuk, perancangan dan pembangunan manual. Manual pengajaran dibangunkan untuk memenuhi tujuan program teknologi kejuruteraan iaitu operasi kemahiran dan aplikasi kejuruteraan serta kemahiran analitikal untuk menyelesaikan masalah menggunakan teori, prosedur dan teknologi terkini. Kaedah kajian yang digunakan ialah secara kualitatif. Dapatan kajian diambil melalui kaedah temubual dan semakan dokumen. Hasil penyelidikan mendapati manual pengajaran sesuai dan penting dalam perlaksanaan program dan aktivitiaktiviti pengajaran dan pembelajaran yang berteraskan teknologi kejuruteraan

Analisis Spektrum Suara Manusia Berdasarkan Jenis Kelamin (Gender) dan Kelompok Umur Menggunakan Komputer

Research on analysis of human voice spectrum based on gender and age group has been conducted. To record the human voice, it was used a microphone and a computer equipped with a software called “Praat” as a substitute for spectrum analyzer. From the voice spectra, it was obtained the fundamental frequency (pitch) and formant. The sample of the human voice was recorded based on the male and women voice which divided into age group such as children aged 8-11 years, adult 19-23 years and elderly aged above 50 years. In this research, it was used 3 pieces of said, namely “Universitas Riau”, “Selamat Datang” and “Mari Berjuang”. The result of this research indicated that pitch of male was lower than that of women. In general, the relationship between pitch and age showed that the pitch decreases as the age increases. For male, the pitch decreases very significantly from 245,8 Hz to 124,6 Hz as the age increases from children to elderly, while for women the decrease of pitch was linear with small slope. The average formant value for boys is a little bit higher than that of girls which is 525 Hz and 512 Hz respectively. In general, the value of first formant (F1) decreases as the age of human increases

Optimization of Pulsed Nd:YAG Laser Melting of Gray Cast Iron At Different Spot Sizes for Enhanced Surface Properties

This paper presents a laser surface modification process of gray cast iron using different laser spot size with an aims to eliminate graphite phase and achieve minimum surface roughness and maximum depth of molten zone and microhardness properties. The laser processing was conducted using JK300HPS Nd:YAG twin lamp laser source pulse TEM 00 mode, 50 W average power, 1064 nm wavelength and different laser spot sizes of 1.0 mm, 1.2 mm, 1.4 mm and 1.7 mm. Three controlled parameter were peak power (Pp), pulse repetition frequency (PRF) and traverse speed (v). Increasing spot size the parameter setting where peak power is increased and pulse repetition frequency and traverse speed is decreased. The modified surface of laser surface melting was characterized for metallographic study, surface roughness and hardness. Metallographic study and surface morphology were conducted using optical microscope while hardness properties were measured using Vickers scale. Surface roughness was measured using a 2D stylus profilometer. From metallographic study, the graphite phase was totally eliminated from the molten zone and formed white zone. This phenomenon affected hardness properties of the modified surface where maximum hardness of 955.8 HV0.1 achieved. Optimization of laser surface modification was conducted for minimum surface roughness and maximum depth of modified layer and hardness properties. From the optimization, the higher desirability is 0.902. The highest depth of molten zone obtain from spot size 1.4 mm at 132 µm and the highest hardness is 989 HV0.1 at laser’s spot size 1.0 mm. The surface roughness increased when the spot size increased from 3.10 µm to 7.31 µm. These finding indicate potential application of enhanced gray cast iron in high wear resistance automotive components such as cylinder liner and break disc

Penghasilan modul pembelajaran lukisan kejuruteraan berbantukan komputer

Perkembangan teknologi maklumat dalam dunia pendidikan tidak lagi boleh dinafikan pada masa kini. Keperluan yang meningkat dalam sistem pembelajaran dan pengajaran memerlukan mereka yang terlibat memberi sepenuh tumpuan terhadap mata pelajaran bagi mencapai matlamat. Untuk tujuan ini Modul Pembelajaran Lukisan Kejuruteraan berbantukan Komputer dihasilkan bagi membantu memudahkan pelajar dalam mata pelajaran Lukisan kejuruteraan. Statistik deskriptif digunakan dalam mengumpul dan menganalisis data. Secara keseluruhannya dari hasil kajian, menunjukkan para pelajar memberikan maklum balas yang positif terhadap modul ini. Semua responden memberi tindak balas positif terhadap modul dari segi mesra pengguna, isi kandungan, motivasi dan daya kognitif. Hasil dari kajian ini, didapati bahawa kebanyakan pelajar berminat terhadap Modul Pembelajaran Lukisan Kejuruteraan Berbantukan Komputer. Walau bagaimanapun masih terdapat beberapa aspek yang perlu diperbaiki untuk memantapkan modul ini