Comprehensive study on structural and optical properties of Tm2O3 doped zinc silicate based glass–ceramics

In this research, Tm2O3 doped zinc silicate based glass–ceramics were prepared by using conventional melt-quenching method and has been successfully derived from ZnO-WRHA glasses with control heat treatment process. The formation of zinc silicate phase affected by heat treatment process was investigated using X-ray diffraction. Fourier transform infrared reflection spectroscopy (FTIR) analysis was used to determine the crystallization of Zn2SiO4 in the glass matrix. FTIR analysis showed the appearance of Zn2SiO4 and SiO2 bands that supported the formation of Zn2SiO4 crystal phase in the glass matrix. The optical absorption and energy band gap of the glass and glass–ceramics was investigated using UV–Vis spectroscopy. The absorption edge shows the movement towards longer wavelength with increasing heat treatment temperature. Besides, the energy band gap decreased with the progression of heat treatment. This ability to enhance optical properties in glass–ceramics was expected to have bright future in the opto-electronics devices

Exploring the Effects of Alternate Auditory Attention Tasks on Electromotility of Cochlear Outer Hair Cells in Healthy Normal Hearing Adults

Background and Aim: There is limited study on the role of rostral efferent auditory pathway on Outer Hair Cell (OHC) activity. We investigated the effect of integrating alternate auditory attention (ALAUDIN©) tasks with White Noise (WN) and its reliability using contralateral suppression of Transient Evoked Otoacoustic Emission (TEOAE). Methods: This study was conducted at the Audiology Clinic, Universiti Kebangsaan Malaysia, with fifty normal-hearing adults. All subjects underwent standard audiological testing to ensure normal hearing, middle ear, and cochlear function. Contralateral suppressors with and without attention tasks were delivered randomly to the non-test ear while simultaneously measuring TEOAE amplitude in the test ear to investigate the effect of auditory attention on OHC electromotility. Suppressors with and without attention refer to the combination of a 1000 Hz tone and speech stimulus embedded in WN and WN alone, respectively. Subsequently, the difference in TEOAE amplitude during the presence and absence of suppressors was calculated, and thus suppression magnitude was determined. Results: Intraclass correlation revealed that 4 suppressors produced high reliability. In paired sample t-tests, the tasks significantly reduced the amplitude of the TEOAE in the right ear compared to the left ear (p0.05). Descriptively, females showed greater TEOAE suppression. Conclusion: This study demonstrated that directing ALAUDIN© tasks to one ear can affect OHC electromotility, as evidenced by TEOAE amplitude changes, but it did not impact the overall suppression magnitude. Additionally, it hinted at potential gender differences in TEOAE suppression, warranting further investigation

Crystallization behavior of low-cost biphasic hydroxyapatite/β-tricalcium phosphate ceramic at high sintering temperatures derived from high potential calcium waste sources

This paper reported the formation of biphasic hydroxyapatite, (HA) and β-tricalcium phosphate, (β-TCP) sintered at various sintering temperature from waste material. The phase stability of HA ceramic was investigated by imposing the high sintering temperature in order to study the transformation of the single phase of HA to biphasic HA/β-TCP ceramic. The evolution microstructure of HA and biphasic HA/β-TCP ceramic was studied at various sintering temperature reach up to 1400 °C. The single phase of HA was observed from 200 to 1200 °C and the secondary phase β-TCP appears due to the decomposition of partial HA at 1300-1400 °C. The optimum temperature for a single phase of HA was identified after sintering at 1200 °C to produce HA with high mechanical hardness about 5.11 GPa. This is clearly related to the phase stability and morphology of HA. The particles size of HA as-synthesized were recorded in nano range scale at ∼9 to 20 nm. However, the average particle sizes become larger and compact between ∼0.21 and ∼3.3 μm from 600 to 1200 °C. Thus, the sintering temperature gives an impact on the phase stability, microstructure and microhardness of HA derived from high potential waste sources

Optical band gap and photoluminescence studies of Eu3+-doped zinc silicate derived from waste rice husks

In this study, investigation on photoluminescence and optical properties of europium doped zinc silicate (Zn2SiO4:Eu3+) glass ceramics derived from white rice husk ash as potential silica source have been done. Undoped and 3 wt. % of europium doped zinc silicate were prepared by solid state method and sintered at 600–1000 °C for 2 h. XRD analysis revealed the phase formation of amorphous, α or β-Zn2SiO4:Eu3+ phases of the glass and glass ceramic samples. FESEM results show the samples were irregular in shapes but well connected and formed large grain crystallites as sintering temperatures increases. The optical band gap values for undoped samples are increasing from 2.97 eV to 3.39 eV respectively. Meanwhile, the optical band gap values for 3 wt. % Eu3+ doped samples decrease from 4.14 eV to 2.62 eV and increase again to 3.71 eV as sintering temperature increases. PL analysis concludes that the red emission exhibited corresponding to 5D0 → 7F2 electron configuration at 612 nm while excitation spectra was found at 400 nm attributed to 7F0 → 5L6 transition. As conclusion, Eu3+ doped Zn2SiO4 glasses has potential as glass host phosphor which can be used for optical devices such as plasma display panels (PDPs) and cathode ray tubes

Isoprene hotspots at the Western Coast of Antarctic Peninsula during MASEC′16

Isoprene (C5H8) plays an important role in the formation of surface ozone (O3) and the secondary organic aerosol (SOA) which contributed to the climate change. This study aims to determine hourly distribution of tropospheric isoprene over the Western Coast of Antarctic Peninsula (WCAP) during the Malaysian Antarctic Scientific Expedition Cruise 2016 (MASEC′16). In-situ measurements of isoprene were taken using a custom-built gas chromatography with photoionization detector, known as iDirac. Biological parameters such as chlorophyll a (chl-a) and particulate organic carbon (POC) were compared to the in-situ isoprene measurements. Significant positive correlation was observed between isoprene and POC concentrations (r2 = 0.67, p < 0.001), but not between isoprene and chl-a. The hotspots of isoprene over maritime Antarctic were then were investigated using NAME dispersion model reanalysis. Measurements showed that isoprene mixing ratio were the highest over region of King George Island, Deception Island and Booth Island with values of ∼5.0, ∼0.9 and ∼5.2 ppb, respectively. Backward trajectory analysis showed that air masses may have lifted the isoprene emitted by marine algae. We believe our findings provide valuable data set of isoprene estimation over the under sampled WCAP

Effect of cobalt oxide on optical and dielectric properties of willemite-based glass-ceramics using white rice husk ash as silica source

Nowadays, researchers are interested in the production of willemite (Zn2SiO4) since it has good phosphor properties in optoelectronic applications. However, still lack of study in the fabrication of cobalt oxide (Co3O4) doped willemite based glass-ceramics (Zn2SiO4: Co2+) derive from white rice husk ash (WRHA). The Zn2SiO4: Co2+ were fabricated based empirical formula of (Co3O4)y[(ZnO)0.55(WRHA)0.45]1-y where y = 0.0, 0.1, 0.5, 1.0 wt.% heat-treated at 700-950 °C using melt-quenching technique. This research focuses on the effect of heat treatment and effect of Co3O4 doping on the physical, structural, optical, and dielectric properties of Zn2SiO4: Co2+ . The densities of undoped-Zn2SiO4 and Zn2SiO4: Co2+ increased from 3.4138 to 3.4659 g/cm3 as dopant increases, also the linear shrinkage increased from 6.23 to 6.92% when dopant increased. X-ray Diffraction (XRD) shows the formation of β−Zn2SiO4 at 750 ℃, then achieve stable state of α-Zn2SiO4 at 950 ℃. Meanwhile, the crystallite size was increased from 74.47 to 74.68 nm then decreased to 73.18 nm as dopant increased. Field Emission Scanning Electron Microscopy (FESEM) shows no obvious changes as the dopant increased. However, at 950 ℃, Zn2SiO4: 0.5 wt.% Co2+ and Zn2SiO4: 1.0 wt.% Co2+ showed a larger grain and less porosity compared to other samples. Fourier Transform Infrared (FTIR) spectroscopy showed eight significant vibrational bands of Zn2SiO4 at 750- 950 ℃ for both undoped and doped samples. The presence of SiO4 and ZnO4 bands in the FTIR absorption spectrum prove the formation of Zn2SiO4. The absorption spectra of UV-Visible were recorded in the range of 220-800 nm and the absorption band of undoped- Zn2SiO4 shifted to lower wavelengths (370 and 349 nm) at 900 and 950 ℃ respectively. When Co3O4 was introduced to Zn2SiO4 two absorption spectra occurred which is at 450 -700 nm and ~325 nm attributed to 4A2 → 4T1 ( 4P) transitions. The optical band gap was increased as dopants were introduced to Zn2SiO4 from ~4.09 eV to 4.57 eV then decreased to 4.29 eV. Photoluminescence spectroscopy (PL) showed blue emissions at ~420, ~444, ~464 and ~485 nm and green emission at ~525 nm under 325 nm excitation which attributed to the transition of Co2+ from 4A2 → 4T1( 4P). Besides, the dielectric constant increased from 4.84047 to 5.52423 when Co3O4 increase due to enhancement of the crystallinity and decrement of the polarization at higher temperatures. The dielectric loss remained low with the increase of dopant and AC conductivity showed each sample has different range of frequency cut-off which is at ~1.2, ~1.7, ~1.3 and ~1.4 GHz for undoped-Zn2SiO4, Zn2SiO4: Co2+ at 0.1, 0.5 and 1.0 wt.% respectively. The differences of frequency cut-off might occur due to the difference in ability of each sample to transport the electron when electric field is applied. In conclusion, the ability of the Zn2SiO4: Co2+ to exhibit blue emission and able to operate at higher frequency, also low loss makes it suitable to be used as a phosphor material in optoelectronic applications

A Study on Optical Properties of Zinc Silicate Glass-Ceramics as a Host for Green Phosphor

For the very first time, a study on the crystallization growth of zinc silicate glass and glass-ceramics was done, in which white rice husk ash (WRHA) was used as the silicon source. In this study, zinc silicate glass was fabricated by using melt&ndash;quenching methods based on the composition (ZnO)0.55(WRHA)0.45, where zinc oxide (ZnO) and white rice husk ash were used as the raw materials. The control crystallization technique was used in which the sample was sintered at 700&ndash;950 &deg;C; then, the physical, structural, and optical properties of the glass and glass-ceramics were investigated by using a densitometer, linear shrinkage, X-ray diffraction (XRD), Fourier transform infrared radiation (FTIR), field-emission scanning electron microscopy (FESEM), and photoluminescence spectroscopy (PL). The density and linear shrinkage increased as the crystallinity increased and the XRD results showed the progression of the crystal formation, in which the sample was still in an amorphous state at 27 &deg;C and 700 &deg;C; the crystalline phase started at 750 &deg;C. Based on the FTIR spectra, all samples showed sharpened absorption bands as the sintering temperature was increased, and the FESEM image showed the progression of crystal growth, indicating the formation of zinc silicate glass-ceramics. Lastly, the PL spectra emitted three emission peaks, at 529, 570, and 682 nm for the green, yellow, and red emission, respectively

Manipulation of safety training practices on organizational safety performance: an evidence in Malaysia's automotive industry

This paper aims to investigate the role of safety training practices to safety performance in Malaysia’s automotive industry. This study adopts a non-experimental type research which employs questionnaire as the method of collecting data. The measurement tool undertaken in the data collection is Safety Performance Scale that developed by Wu et al. (2007). A total of 696 employees from Malaysia automotive manufacturing and assembly plants are selected as the respondents of this study. The selection of respondents is made using systematic sampling design. Data of the study are then analyzed using canonical correlation analysis. The finding of the study highlights that safety training practices plays a significant influence to an organization’s safety performance (r 2 = 0.631, p <0.001)

The mediating effects of work-related attitudes in the relationship between psychological strain and job performance among Malaysian technical workers

This paper aims to investigate the effect of psychological strain on job performance among technical workers in Malaysia. In addition, this paper also tests the mediating effects of work-related attitudes, such as job satisfaction, affective commitment and turnover intentions in the relationships between psychological strain and job performance among technical workers in Malaysia. This study uses a non-experimental type research which employs questionnaire as the method of collecting data. A total of 429 technical workers from a large Telecommunication industry in Malaysia are selected as the respondents of this study. The selection of respondents is made using simple random sampling design. Data of the study are then analyzed using structural equation modeling. The result of the study indicates that psychological strain is related to job performance. The result also highlights that job satisfaction, affective commitment and turnover intentions function as mediator in the relationships between psychological strain and job performance

Deep' as a learning approach in inspiring creative and innovative minds among postgraduate students in research university

This paper investigates the level of deep learning approach among research university (RU) postgraduate students in Universiti Teknologi Malaysia (UTM). It is believed that deep approach may foster students to become competent, creative and versatile professionals in order to adapt with on-going challenge for a research university such as UTM. In specific, this paper aims to determine the level of deep learning approaches adopted by postgraduate students and to identify whether the approach is associated with demographic factors (age, gender, main streams, mode of study and working experience). Participants included 354 postgraduate students from different faculties in UTM whereas questionnaires were distributed via email and through designated contact person. The One-Way Analysis of Variance (ANOVA) revealed that there were significant differences on the usage of deep learning approach across age and years of working experience. Significance was not seen between deep learning on gender, main streams and mode of study. Our investigation suggests that deep approach to learning should be included in their academics, however the suggestion is tailored according on the tasks given to the students. Hence, we concluded that further investigation could be carried out on the effect of learning environment towards students dynamic in learning. (C) 2012 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Asia Pacific Business Innovation and Technology Management Societ