Experimental Analysis to Evaluate the Effect of Dynamic Absorber / M. Azhan Anuar...[et al.]

Passive Dynamic Absorber (PDA) is a mechanical device used to tackle unwanted vibration resonance within the operational frequency of the system. Theoretically, resonance can be avoided if the excitation (operating) frequency is far away from the natural frequencies of the structures. Hence, it is important to identify the structural natural frequencies, to ensure this condition did not occur. In this study, an experimental main system is designed and fabricated and then, tested using Operational Modal Analysis (OMA) to obtain the natural frequency. PDAs are developed based on Dunkley Method (DM) and Randy Fox Method (RFM) and applied to the main vibrating system. Frequency Response Function (FRF) for both models is obtained using OMA and its effectiveness is evaluated. It is shown that the PDA reduces the magnitude of FRF of the main system at the selected resonance frequency and splitting it into two new resonance frequencies. Hence, it can be predicted that the vibration can be effectively suppressed at a specific frequency when the PDA is attached to the main system. This study enables verification of the effectiveness of dynamic absorber to tackle resonance problem. In future, these results will be helpful to evaluate the performance of PDA based on DM and RFM methods

Performance Evaluation of Dynamic Absorbers Based on Randy Fox and Dunkerley Methods / Syafirah A. Samat ...[et al.]

Dynamic Absorber (DA) application is the method used to avoid resonance in a vibrating system. In practice, many types of DA are utilized such as active and passive DA and it depends on the cost and environmental conditions. Designers/ engineers select DA parameters and model the absorber before it is implemented and tested to the main system. Hence, it will be beneficial to have tools or templates for fast and effective selection of DA. This paper will discuss the selection parameters of a passive DA based on templates derived from Dunkerley Method (DM) and Randy Fox Method (RFM) and its accuracy is verified experimentally. It is observed that in this case, DA has reduced the vibration amplitude significantly. Furthermore, the results show the RFM absorber has performed better than the DM absorber. This study enables verification of the effectiveness of DA to tackle resonant problems. In the future, these GUI templates could be helpful for industrial application with vibrating problems

Improper Technique of Eye Drop Instillation Leading to Corneal Ulcer in a Visually Impaired Glaucoma Patient / Azhan A … [et al.]

We report a case of visually impaired glaucoma patient with long term use of topical glaucoma medications presented with a corneal ulcer due to the improper technique of eye drop instillation. A 70-year-old gentleman with advanced primary open angle glaucoma (POAG) on his right eye and absolute glaucoma on his left eye, presented with painful redness and purulent discharge of the right eye for two weeks. He was using four types of topical glaucoma medication on his right eye since failed trabeculectomy two years ago. His right eye vision was 6/24 and painless blindness of the left eye before the presentation. He was administering all the medications himself despite his current vision status. Right eye examination showed visual acuity of 3/60 with clinical features of corneal ulcer. During the observation of his eye drop instillation technique, he consistently touched the tip of the bottle to his right cornea. The corneal contact area corresponded to the corneal ulcer area and size. In addition to this, the culture result obtained from both corneal ulcer and the bottles’ tips yielded similar microorganism which was Staphylococcus aureus. After an intensive course of topical antibiotics treatment, the corneal ulcer healed with a scar and the vision improved to 6/24 from 3/60. Although this incident is rare, it is crucial for the treating physicians to address the issue properly and co-manage these patients with pharmacists and nursing staffs as well as to seek support from the caretakers to prevent this blinding complication

Magnetic characterisation using approximation method (APM) of BaFe12 0 19 derived from millscale / R. S. Azis … [et al.]

This paper describes a new method for measuring the magnetic properties of hexagonal Barium ferrite using approximation method (APM) theory. The sample was prepared by recycling the waste steel product from Malaysian steel factories. Using a Curie temperature separation technique, the wustite, FeO contained in the millscale was separated by this new technique using de-ionized water at 90°CI 100°C in the presence of IT external field. The wustite was then oxidized in the air at 400°C/500°C/600°C for 10 hours. An XRD phase analysis showed that a very high percentage of Fe20 3 was present in the final powder preparation. A conventional processing method was then done to prepare hexagonal BaFe'20'9 pallet shaped samples. Analysis of samples was done on grain size, saturation magnetization, coercive force and remanence. The magnetic properties were measured using approximation method (APM) theory. The high remanence 20000e, 20000e saturation magnetisation and 15000e coercive force of sample derived from millscale shows that this technique used has a high percentage for magnetic properties measurement in the future

Dynamic magnetic properties of mn doped YBa2Cu3O7_δ superconducting ceramics / S. A. Halim … [et al.]

AC complex susceptibility, X = X' + i X", measurements were done on the YBa2Cu3O7_δ superconducting samples doped with Mn at Y, Ba and Cu sites Y123 with nominal starting composition (x = 0.02 and 0.1). The data of X' shows that the coupling of the grains in samples that doped at Cu site are weaker than that samples doped at Y and Ba sites as shown by using the Ambegaokar-Baratoff equation 10 = 1.57 x 108Tc2-/( Tc-Tej), the calculated values of Josephson current, 10 where 1o(in y > l0(in Ba) > 10(in Cu) due to the weakening of the grain's coupling. This observation is supported by the intrinsic coupling loss, Tp obtained from X" that shows a bigger shift of the intergranular coupling peak, Tp, towards lower temperature in Mn doping at Cu site as compared to the doping in Ba and Y sites. Hence the effect of doping is obvious at higher concentration for all samples. Analysis based on the sensitivity of the data of dx'/dT versus temperature furnished further information on the two step transition related to the coupling of the grains in all systems

Luminescence spectra of TeO ₂-PbO-Li ₂O doped Nd ₂O ₃ glass

A tellurite glass of TeO 2-PbO-Li 2O doped with Nd 2O 3 has been successfully fabricated by using the conventional melt-quenched technique. The absorption and emission spectroscopy have been identified using UV-VIS-NIR and photoluminescence spectrometer, respectively. From the spectroscopy, ten significant spectra have been observed in the region of 400-900 nm. The absorption wavelength centered at 585 nm attributed to 4I 9/2 → 4G 5/2 transition is the predominant wavelength to be used as the excitation wavelength. Emission spectra have been determined by using 585 nm excitation wavelength at room temperature. From the emission spectra, seven distinctive upconversion bands contributed from Nd 3+ were observed in the region of 400-1500 nm. It was found that the bands were centered at 450 nm ( 4G 11/2 → 4I 9/2), 485 nm ( 4G 11/2 → 4I 11/2), 605 nm ( 4G 11/2 → 4I 15/2), 665 nm ( 4G 7/2 → 4I 13/2), 880 nm ( 4F 3/2 → 4I 9/2), 1062 nm ( 4F 3/2 → 4I 11/2) and 1340 nm ( 4F 3/2 → 4I 11/2), respectively. These emission bands showed the possibility of visible and near infrared emission spectra

Spectroscopic Properties of Rare Earth Ion Doped TeO2-B2O3-PbO Glass

This work focuses on the spectroscopic study of RE3+ ion, namely, trivalent neodymium (Nd3+) doped lead borotellurite glass with a composition of TeO2-B2O3-PbO. The glass sample has been prepared by conventional melt-quenching technique. The density, molar volume and optical energy band gap of these glasses have been measured. The refractive index, molar refraction and polarizability of oxide ion have been calculated by using Lorentz-Lorentz relations. The absorption spectra are recorded using UV-Vis-NIR spectrometer in the range of 200-900 nm.</jats:p

Effect of Ba and Zn doping in Bi2Pb0.6Sr2Ca2Cu3Oδ superconductors using ac susceptibility measurements

Ac complex susceptibility, χ = χ′ - iχ″, measurements were done on the samples doped with barium and zinc (Bi2Pb0.6Sr2Ca2-xMxCu3Oδ, M = Ba, Zn and x = 0.02 and 0.10). The data of χ′ shows that coupling of the grains in Zn-doped samples are weaker than that of Ba-doped samples and hence it could be concluded that Zn-doped samples are dominated by the S-I-S type of weak links, whereas the Ba doped samples are dominated by the S-N-S weak links. Calculated values of I0 is three times higher in the Ba doped samples such that the values of Josephson coupling energy, Ej is four times that of Zn doped samples. Analysis based on the sensitivity of the data of dχ′(T)/dT versus temperature furnished further information on the two-step transitions related to the coupling of the grains in both systems

The Structural Properties of Trivalent Rare Earth Ions (Er3+) Doped Borotellurite Glass

Six samples of borotellurite glasses with system (80-x)TeO2- 10B2O3 - 10PbO - xEr2O3 (x=0.0, 0.5, 1.0, 1.5, 2.0, 2.5 mol%) have been prepared by using the conventional melt-quenching method. Some basic physical parameters such as density and molar volume were measured. The result reveals that the density and molar volume increases with the increases of mol% of Er2O3. The amorphous nature of the glass has been characterized using X-ray Diffraction (XRD) and all glasses are found to be amorphous in nature. The structure was analysed by FTIR spectroscopy. The FTIR spectra were recorded at room temperature in the frequency range from 650 to 4000  cm-1 using Attenuated Total Reflectance (ATR) method. From the IR results, the absorption bands were found to be in the range 667-669 cm-1, 710-712 cm-1, 880-887 cm-1, 981-997 cm-1 and 1190-1204 cm-1 which correspond to the stretching and bending vibrations mode. The absorption peaks around 1386-1388 cm-1 and 3741-3748 cm-1 which ascribed to the hydroxyl-metal bond and hydroxyl-hydrogen bond stretching vibration also have been observed. The FTIR results demonstrate that the existing of erbium in the composition leads to good structural properties thus creating potential for this glass in laser applications.</jats:p