24 research outputs found
Dielectric Properties of Oil Palm Mesocarp at Various Stages of Maturity
Dielectric properties at frequencies from 10⁻² to 10⁶ Hz and 0.2 to 20 GHz of
mashed mesocarp of oil palm fruits at various stages of maturity are presented. The study
includes the variation of dielectric constant, ɛ" and dielectric loss, ɛ" with moisture
content ranging from 40 to 100% (wet basis). Measurement of the dielectric properties
was done by using open-ended coaxial line probe and automated network analyzer for
high frequency and spectrum analyzer for low frequency. The accuracy of the
measurement is about 5% for dielectric constant, ɛ" and 3% for dielectric loss, ɛ".
Results of measurements demonstrate a good relationship between dielectric properties of
the mesocarp and moisture content or maturity of the fruit and also close to the values
predicted by dielectric mixture models especially at frequencies above 3 GHz. At 10
GHz the difference between predicted and measured values are within 5%.
Results of measurement also show that the ac ionic conductivity dominated in the
region less than 3 GHz while above 3 GHz the dipole orientation of water molecules becomes dominant. Such a crossover in the form of dielectric loss from conductive loss to
the dipole orientation about 2 GHz was observed. The effect of ac ionic conductivity is
higher in young fruit and decreasing as a degree of maturity increases.
Permittivity of oil palm mesocarp over the frequency range was found to increase
with moisture content. A significant variation of ɛ' and ɛ" with maturity at 0.2 GHz
and 10 GHz respectively make it suitable to form a maturity index as suggested by
Nelson et al. With moisture content ranging from 25% to 85%, the ɛ' at 2 GHz varies
from 11 to 61 and the ɛ" varies from 2.1 to 24.6 at 10 GHz. Based on the above values
the permittivity-based maturity index for young and fully ripe fruits are 1 and 0.3
respectively
PERFORMANCE COMPARISON BETWEEN ANALYTICAL ANALYSIS AND NUMERICAL SIMULATIONS FOR AVERAGE SOLITON SYSTEM
This paper presents the comparison between analytical results and computer simu lated results showing the performance of soliton transmission in optical fibre optics . A study of average soliton systems with 50 km amplifier spacing is presented both analytically and numerically. The effect of modifying the existing rule of thumb formulae is presented in terms of a design diagram. Th is is then compared to the numerical simu lations. A series of design diagram with Gordon-Haus (GH) jitter, signal to noise ratio (SNR) and soliton collapse limited transmission is also introduced
The generation of dual wavelength pulse fiber laser using fiber bragg grating
A stable simple generation of dual wavelength pulse fiber laser on experimental method is proposed and demonstrated by using Figure eight circuit diagram. The generation of dual wavelength pulse fiber laser was proposed using fiber Bragg gratings (FBGs) with two different central wavelengths which are 1550 nm and 1560 nm. At 600 mA (27.78 dBm) of laser diode, the stability of dual wavelength pulse fiber laser appears on 1550 nm and 1560 nm with the respective peak powers of -54.03 dBm and -58.00 dBm. The wavelength spacing of the spectrum is about 10 nm while the signal noise to ratio (SNR) for both peaks are about 8.23 dBm and 9.67 dBm. In addition, the repetition rate is 2.878 MHz with corresponding pulse spacing of about 0.5 μs, is recorded
Metadiscourse in the academic writing of local and international students at a university in Malaysia
This study examines the use of metadiscourse markers among 50 Malaysian and 50
Arab Pre-University students. The findings of this study indicated that there was a
significant difference in the use of metadiscourse markers between Malaysian and Arab
Pre-University students {χ2 (1, n = 100) = 7.17, p-value is .007} where the use of
metadiscourse markers among Malaysian Pre-University students was substantially
higher than that of the Arab Pre-University students. In the use of interactive markers,
the results showed significant differences between Malaysian and Arab Pre-University
students in the use of transitions, evidential and code glosses. Additionally, in the use of
interactional markers, Malaysian and Arab students differed in their use of hedges,
engagement markers and self-mentions. These variances in the frequency and forms of
metadiscourse markers utilized by the students could be attributed to the diverse
cultural backgrounds of the two groups of students. It is therefore suggested that
English language teachers integrate and incorporate cultural elements in their lessons
with regard to metadiscourse markers
Engineering properties of ring shaped polytheylene terephthalate (RPET) fiber self-compacting concrete
Polyethylene terephthalate (PET) bottles are plastic containers that are typically
discarded, and thus, cause environmental pollution. To solve this problem, PET bottles
are recycled in concrete. Previous studies have mostly used PET with straight or
irregularly shaped fibers. It has been shown that PET has a weak interfacial bond with
cement paste in the pullout load because of the lamellar shape of fibers. Therefore, ringshaped
PET (RPET) fibers are introduced in this study to overcome the limitations of
traditional straight, lamellar, or irregularly shaped fibers. RPET fibers are mainly
designed with a special shape to mobilize fiber yielding rather than fiber pullout. RPET
fibers are made directly from waste bottles. The diameter of RPET bottles is fixed at 60 ±
5 mm. The width of RPET fibers is fixed at 5, 7.5, or 10 mm and designated as RPET-5,
RPET-7.5, and RPET-10 respectively. This study mainly determines the optimum water–
binder ratio and fiber content of RPET fiber concrete (FC) through self-compacting, as
well as through compressive, tensile, and toughness strength tests. A water–binder ratio
of 0.55 and working ranges from 0.25% to 1% of fiber content are successfully accepted
for all sizes of RPET fibers. Result of the pullout test shows that RPET fiber interfacial
bond strength ranges from 0.502 MPa to 0.519 MPa for RPET-5 fiber, from 0.507 MPa
to 0.529 MPa for RPET-7.5 fiber, and from 0.516 MPa to 0.540 MPa for RPET-10 fiber.
This study presented that the compressive and tensile strength of RPET fiber exhibited an
increase of 17.3% and 35.7%, respectively compared to normal concrete. RPET FC shows
improvement in first crack load for flexural toughness strength of RPET FC with increase
of 24.5% compared to normal concrete specimen. Moreover, 156 FC cylinders were used
to develop new equations for predicting the compressive and tensile strengths of RPET
FC via multiple regression analysis. Two equations are obtained. These equations are
included in calculating compressive and tensile strength of RPET FC limited up to 28
days In conclusion, incorporating RPET fibers when recycling waste PET bottles in
concrete produces FC with An improvement performance comparable to that of normal
concrete
Saturable absorption measurement of platinum as saturable absorber by using twin detector method based on mode-locked fiber laser
This paper illustrates the absorption measurement of Pt as saturable absorber (SA) by using mode-locked fiber laser system. The SA is fabricated by depositing 10 nm of Pt on the fiber ferrules using sputtering method. The absorption measurement of Pt is characterised by employing a balanced twin detector method based on mode-locked fiber laser with central wavelength of 1532.25 nm, repetition rate of 2.833 MHz and pulse duration of 34.3 ns. The Pt-SA produce modulation depth of 21.9% and saturation intensity of 21.6 MW cm-2
Generation of four-wave mixing in a highly non-linear optical fiber using a tunable dual wavelength fiber laser source
In this paper, we demonstrate a Four Wave Mixing (FWM) effect in a highly nonlinear single mode optical fiber. A tunable dual-wavelength fiber laser is used to provide the pump and signal probe to generate partially degenerate FWM. Calculations using coupled differential equations and experimental results in the generation of FWM were analyzed. We observed that FWM conversion efficiency depends more significantly on the wavelength detuning between pump and signal wavelength as compared to zerodispersion wavelength. The tunability is achieved using an arrayed waveguide grating which provides different wavelength combinations of the dual-wavelength fiber laser output and can be tuned from 1530.47nm to 1548.61nm with a spacing of 100GHz. The highly nonlinear fiber has a nonlinear coefficient, γ of 10.8 W-1km-1 . Hence, to achieve higher FWM output power the pump power of the dual wavelength fiber laser has to be higher than that of the signal probe. The optimum measured values of pump and signal power are +13.3dBm and +5dBm respectively, limited buy the current experimental setup
Passively mode-locked fiber laser by utilizing TTG film on a D-shaped fiber as a saturable absorber
In this paper, we propose a mode-locked fiber laser by utilizing single layer Trivial Transfer Graphene film (TTGF) as a saturable absorber (SA). The SA was deposited on the top of a side-polished D-shaped fiber. The SA was then integrated in the ring cavity configuration, with a clockwise light propagation. Three distinctive 2 m erbium doped fibers (EDFs) those are Metro-Gain15 EDF, Iso-Gain6 EDF and Iso-Gain12 EDF were used as gain media, interchangeable in the experiment. From the results, the Metro-Gain15 EDF gives the most proficient gain medium on generating a passively mode-locked fiber laser. The Metro-Gain15 Erbium doped mode-locked Laser was successfully producing ultrashort pulse with 8 nm spectral band-width, 13 MHz of repetition rate and 915 fs pulse duration. These outcomes demonstrated that TTGF deposited on the D-shaped fiber is a suitable component as an SA to produce a stable output passively mode-locked fiber laser for many optical fiber applications
Passively Q-Switched pulse erbium doped fiber laser using Antimony (III) Telluride (Sb2Te3) thin film as saturable absorber
This paper demonstrates on an antimony telluride (Sb2Te3) thin film sandwiched between two fiber ferrule as saturable absorber for Qswitched pulsed Erbium doped fiber (EDF) laser. The saturable absorber is fabricated by dissolving Antimony (III) Telluride powder into PVA solution and dry in the ambient temperature for 48 hours. Then, 1 mm2 x 1 mm2 Sb2Te3-PVA film based saturable absorber is sandwiched in between FC/PC ferrule for Q-switched laser generation. The modulation depth of the Sb2Te3 is measured as 28.01% with input intensity 0.02 MW/cm2 . The developed passive saturable absorber integrated in EDF laser in ring cavity and the characterised pulse is with repetition rates of 30.21 kHz, shortest pulse width of 3.26 µs and signal-noise-ratio (SNR) of 42 dB. The maximum output pulse energy is achieved at pump power 69.5 mW with 29.5 nJ and the output power 0.89 mW
Graphite saturable absorber for Q switched fiber laser
This paper reported a successful demonstration on Q-switched fiber laser by using graphite as saturable absorber (SA). The graphite is deposited on the fiber ferrule through a simple mechanical exfoliation method. The modulation depth of the graphite SA is 19.2% with a saturation intensity of 85 MW/cm². The maximum achievable pulse repetition rates and pulse width are 42.41 kHz and 3.40 μs respec-tively. Meanwhile, its optical signal-to-noise ratio is about 50.81 dB. The Q-switched pulses have the maximum pulse energy of 5.84 nJ. These outcomes demonstrated that a stable output of passively Q-switched fiber laser is produced and can be applied for various optical fiber applications