Abstract: This paper presents a 0.13-µm Complementary Metal-Oxide Semiconductor (CMOS) vector modulator for beamforming system. The vector modulator features a 360° phase and gain range of -10 dB to 10 dB with a root mean square phase and amplitude error of only 2.2° and 0.45 dB, respectively. These features make it a suitable for wireless backhaul system in the 5 GHz industrial, scientific, and medical (ISM) bands. It draws a current of 20.4 mA from a 1.2 V supply. The total chip size is 1.87x1.34 mm².
Abstract: In this paper, a CMOS vector modulator designed for wireless backhaul system based on 802.11ac is presented. A poly phase filter and sign select switches yield two orthogonal signal paths. Two variable gain amplifiers with strongly reduced phase shift of only ±5 ° are used to weight these paths. It has a phase control range of 360 ° and a gain range of -10 dB to 10 dB. The current drawn from a 1.2 V supply amounts 20.4 mA. Using a 0.13 mm technology, the chip die area amounts 1.47x0.75 mm².
Abstract: The properties of hollow sandcrete blocks produced in
Minna, Nigeria are presented. Sandcrete block is made of cement,
water and sand binded together in certain mix proportions. For the
purpose of this work, fifty (50) commercial sandcrete block industries
were visited in Minna, Nigeria to obtain block samples and
aggregates used for the manufacture, and to take inventory of the mix
composition and the production process. Sieve analysis tests were
conduction on the soil sample from various block industries to
ascertain their quality to be used for block making. The mix ratios
were also investigated. Five (5) nine inches (9’’ or 225mm) blocks
were obtained from each block industry and tested for dimensional
compliance and compressive strength. The results of the soil test
shows that the grading fall within the limit for natural aggregate and
can easily are used to obtain workable mix. Physical examinations of
the block sizes show slight deviation from the standard requirement
in NIS 87:2000. Compressive strength of hollow sandcrete blocks in
range of 0.12 N/mm2 to 0.54 N/mm2 was obtained which is below the
recommendable value of 3.45 N/mm2 for load bearing hollow
sandcrete blocks. This indicates that these blocks are below the
standard for load-bearing sandcrete blocks and cannot be used as load
bearing walling units. The mix composition also indicated low
cement content resulting in low compressive strength. Most of the
commercial block industries visited does not take curing very serious.
Water were only sprinkled ones or twice before the blocks were
stacked and made readily available for sale. It is recommended that a
mix ratio of 1:4 to 1:6 should be used for the production of sandcrete
blocks and proper curing practice should be adhered. Blocks should
also be cured for 14 days before making them available for
consumers.
Abstract: This paper presents two types of microstrip bandpass
filter (BPF) at microwave frequencies. The first one is a tunable BPF
using planar patch resonators based on a varactor diode. The filter is
formed by a triple mode circular patch resonator with two pairs of
slots, in which the varactor diodes are connected. Indeed, this filter is
initially centered at 2.4 GHz; the center frequency of the tunable
patch filter could be tuned up to 1.8 GHz simultaneously with the
bandwidth, reaching high tuning ranges. Lossless simulations were
compared to those considering the substrate dielectric, conductor
losses and the equivalent electrical circuit model of the tuning
element in order to assess their effects. Within these variations,
simulation results showed insertion loss better than 2 dB and return
loss better than 10 dB over the passband. The second structure is a
BPF for ultra-wideband (UWB) applications based on multiple-mode
resonator (MMR) and rectangular-shaped defected ground structure
(DGS). This filter, which is compact size of 25.2 x 3.8 mm2, provides
in the pass band an insertion loss of 0.57 dB and a return loss greater
than 12 dB. The proposed filters presents good performances and the
simulation results are in satisfactory agreement with the
experimentation ones reported elsewhere.
Abstract: Artificial intelligence applications are commonly used
in industry in many fields in parallel with the developments in the
computer technology. In this study, a fire room was prepared for the
resistance of wooden construction elements and with the mechanism
here, the experiments of polished materials were carried out. By
utilizing from the experimental data, an artificial neural network
(ANN) was modelled in order to evaluate the final cross sections of
the wooden samples remaining from the fire. In modelling,
experimental data obtained from the fire room were used. In the
developed system, the first weight of samples (ws-gr), preliminary
cross-section (pcs-mm2), fire time (ft-minute), and fire temperature
(t-oC) as input parameters and final cross-section (fcs-mm2) as output
parameter were taken. When the results obtained from ANN and
experimental data are compared after making statistical analyses, the
data of two groups are determined to be coherent and seen to have no
meaning difference between them. As a result, it is seen that ANN
can be safely used in determining cross sections of wooden materials
after fire and it prevents many disadvantages.
Abstract: This work reports the potential of using Palm Kernel
(PK) ash and shell as a partial substitute for Portland Cement (PC)
and coarse aggregate in the development of mortar and concrete. PK
ash and shell are agro-waste materials from palm oil mills, the
disposal of PK ash and shell is an environmental problem of concern.
The PK ash has pozzolanic properties that enables it as a partial
replacement for cement and also plays an important role in the
strength and durability of concrete, its use in concrete will alleviate
the increasing challenges of scarcity and high cost of cement. In order
to investigate the PC replacement potential of PK ash, three types of
PK ash were produced at varying temperature (350-750C) and they
were used to replace up to 50% PC. The PK shell was used to replace
up to 100% coarse aggregate in order to study its aggregate
replacement potential. The testing programme included material
characterisation, the determination of compressive strength, tensile
splitting strength and chemical durability in aggressive sulfatebearing
exposure conditions. The 90 day compressive results showed
a significant strength gain (up to 26.2 N/mm2). The Portland cement
and conventional coarse aggregate has significantly higher influence
in the strength gain compared to the equivalent PK ash and PK shell.
The chemical durability results demonstrated that after a prolonged
period of exposure, significant strength losses in all the concretes
were observed. This phenomenon is explained, due to lower change
in concrete morphology and inhibition of reaction species and the
final disruption of the aggregate cement paste matrix.
Abstract: This paper presents a novel fractal antenna structure
proposed for UWB (Ultra – Wideband) applications. The frequency
band 3.1-10.6GHz released by FCC (Federal Communication
Commission) as the commercial operation of UWB has been chosen
as frequency range for this antenna based on coplanar waveguide
(CPW) feed and circular shapes fulfilled according to fractal
geometry. The proposed antenna is validated and designed by using
an FR4 substrate with overall area of 34x43 mm2. The simulated
results performed by CST-Microwave Studio and compared by ADS
(Advanced Design System) show good matching input impedance
with return loss less than -10dB between 2.9 GHz and 11 GHz.
Abstract: This work presents a new planar multiband antenna
based on fractal geometry. This structure is optimized and validated
into simulation by using CST-MW Studio. To feed this antenna we
have used a CPW line which makes it easy to be incorporated with
integrated circuits. The simulation results presents a good matching
input impedance and radiation pattern in the GSM band at 900 MHz
and ISM band at 2.4 GHz. The final structure is a dual band fractal
antenna with 70 x 70 mm² as a total area by using an FR4 substrate.
Abstract: Bamboo is extensively used in construction industry.
Low durability of bamboo due to fungus infestation and termites
attack under storage puts certain constrains for it usage as modern
structural material. Looking at many chemical formulations for
bamboo treatment leading to severe harmful environment effects,
research on eco-friendly preservatives for bamboo treatment has been
initiated world-over. In the present studies, eco-friendly preservative
for bamboo treatment has been developed. To validate its application
for structural purposes, investigation of effect of treatment on
compressive strength has been investigated. Neemoil (25%)
integrated with copper naphthenate (0.3%) on dilution with kerosene
oil impregnated into bamboo culm at 2 bar pressure, has shown
weight loss of only 3.15% in soil block analysis method. The results
from compressive strength analysis using HEICO Automatic
Compression Testing Machine reveal that preservative treatment has
not altered the structural properties of bamboo culms. Compressive
strength of control (11.72 N/mm2) and above treated samples (11.71
N/mm2) was found to be comparable.
Abstract: In this paper we make a temperature investigations in
two type of superposed crimped connections using experimental
determinations. All the samples use 8 copper wire 7.1 x 3 mm2
crimped by two methods: the first method uses one crimp indents and
the second is a proposed method with two crimp indents. The ferrule
is a parallel one. We study the influence of number and position of
crimp indents. The samples are heated in A.C. current at different
current values until steady state heating regime. After obtaining of
temperature values, we compare them and present the conclusion.
Abstract: Transesterification reactions free of catalyst between
roasted chicken fat with methanol were carried out in a batch reactor
in order to produce biodiesel to temperatures from 120°C to 140°C.
Parameters related to the transesterification reactions, including
temperature, time and the molar ratio of chicken fat to methanol also
investigated. The maximum yield of the reaction was of 98% under
conditions of 140°C, 4 h of reaction time and a molar ratio of chicken
fat to methanol of 1:31. The biodiesel thus obtained exhibited a
viscosity of 6.3 mm2/s and a density of 895.9 kg/m3. The results
showed this process can be right choice to produce biodiesel since
this process does not use any catalyst. Therefore, the steps of
neutralization and washing are avoided, indispensables in the case of
the alkaline catalysis.
Abstract: We present the design of Analog front end (AFE) low noise pre-amplifier implemented in a high voltage 0.18-µm CMOS technology for a three dimensional ultrasound bio microscope (3D UBM) application. The fabricated chip has 4X16 pre-amplifiers implemented to interface a 2-D array of high frequency capacitive micro-machined ultrasound transducers (CMUT). Core AFE cell consists of a high-voltage pulser in the transmit path, and a low-noise transimpedance amplifier in the receive path. Proposed system offers a high image resolution by the use of high frequency CMUTs with associated high performance imaging electronics integrated together. Performance requirements and the design methods of the high bandwidth transimpedance amplifier are described in the paper. A single cell of transimpedance (TIA) amplifier and the bias circuit occupies a silicon area of 250X380 µm2 and the full chip occupies a total silicon area of 10x6.8 mm².
Abstract: Service life of existing reinforced concrete (RC)
structures in coastal towns of Sabah has been affected very much.
Concrete crack, spalling of concrete cover and reinforcement rusting
of RC buildings are seen even within 5 years of construction in
Sabah. Hence, in this study a new mix design of concrete grout was
developed using locally available materials and investigated under
two curing conditions and workability, compressive strength,
Accelerated Mortar Bar Test (AMBT), water absorption, volume of
permeable voids (VPV), Sorptivity and 90-days salt ponding test
were conducted. The compressive strength of concrete grout at the
age 90 days was found to be 44.49 N/mm2 under water curing. It was
observed that the percentage of mortar bar length change was below
1% for developed concrete grout. The water absorption of the
concrete grout was in between the range of 0.88 % to 3.60 % under
two different curing up to the age 90 days. It was also observed that
the VPV of concrete was in the range of 0 % to 9.75 and 2.44% to
13.05% under water curing and site curing respectively. It was found
that the Sorptivity of the concrete grout under water curing at the age
of 28 days is 0.211mm/√min and at the age 90 day are 0.067
mm/√min. The chloride content decreased greatly, 90% after a depth
of 15 mm. It was noticed that the site cured samples showed higher
chloride contents near surface compared to water cured samples.
This investigation suggested that the developed mix design of
concrete grout using locally available construction materials can be
used for crack repairing of existing RC structures in Sabah.
Abstract: In this paper, a planar antenna for UWB applications
has been proposed. The antenna consists of a square patch, a partial
ground plane and a slot on the ground plane. The proposed antenna is
easy to be integrated with microwave circuitry for low manufacturing
cost. The flat type antenna has a compact structure and the total size
is 14.5×14.5mm2. The result shows that the impedance bandwidth
(VSWR≤ 2) of the proposed antenna is 12.49 GHz (2.95 to 15.44
GHz), which is equivalent to 135.8%. Details of the proposed
compact planar UWB antenna design is presented and discussed.
Abstract: We present a dual-band (Cellular & PCS) dual-path
zero-IF receiver for CDMA2000 diversity, monitoring and
simultaneous-GPS. The secondary path is a SAW-less diversity
CDMA receiver which can be also used for advanced features like
monitoring when supported with an additional external VCO. A GPS
receiver is integrated with its dedicated VCO allowing simultaneous
positioning during a cellular call. The circuit is implemented in a
0.25μm 40GHz-fT BiCMOS process and uses a HVQFN 56-pin
package. It consumes a maximum 300mW from a 2.8V supply in
dual-modes. The chip area is 12.8mm2.
Abstract: Investigations of the unimolecular decomposition of
vinyl ethyl ether (VEE), vinyl propyl ether (VPE) and vinyl butyl
ether (VBE) have shown that activation of the molecule of a ether
results in formation of a cyclic construction - the transition state (TS),
which may lead to the displacement of the thermodynamic
equilibrium towards the reaction products. The TS is obtained by
applying energy minimization relative to the ground state of an ether
under the program MM2 when taking into account the hydrogen bond
formation between a hydrogen atom of alkyl residue and the extreme
atom of carbon of the vinyl group. The dissociation of TS up to the
products is studied by energy minimization procedure using the
mathematical program Gaussian. The obtained calculation data for
VEE testify that the decomposition of this ether may be conditioned
by hydrogen bond formation for two possible versions: when α- or β-
hydrogen atoms of the ethyl group are bound to carbon atom of the
vinyl group. Applying the same calculation methods to other ethers
(VPE and VBE) it is shown that only in the case of hydrogen bonding
between α-hydrogen atom of the alkyl residue and the extreme atom
of carbon of the vinyl group (αH---C) results in decay of theses
ethers.
Abstract: Attempt was made to improve certain characteristics of bio-oil derived from palm kernel pyrolysis by blending it with diesel fuel and alcohols. Two types of alcohol, ethanol or butanol, was used as cosolvent to stabilize the phase of ternary systems. Phase behaviors and basic fuel properties of palm kernel bio-oildiesel- alcohol systems were investigated in this study. Alcohol types showed a significant influence on the phase characteristics with palm kernel bio-oil-diesel-butanol system giving larger soluble area than that of palm kernel bio-oil-diesel-ethanol system. For fuel properties, blended fuels showed superior properties including lower values of density (~860 kg/m3 at 25°C), viscosity (~4.12 mm2/s at 40°C), carbon residue (1.02-2.53 wt%), ash (0.018-0.034 wt%) and pour point (
Abstract: The prediction of transmembrane helical segments
(TMHs) in membrane proteins is an important field in the
bioinformatics research. In this paper, a method based on discrete
wavelet transform (DWT) has been developed to predict the number
and location of TMHs in membrane proteins. PDB coded as 1F88 was
chosen as an example to describe the prediction of the number and
location of TMHs in membrane proteins by using this method. One
group of test data sets that contain total 19 protein sequences was
utilized to access the effect of this method. Compared with the
prediction results of DAS, PRED-TMR2, SOSUI, HMMTOP2.0 and
TMHMM2.0, the obtained results indicate that the presented method
has higher prediction accuracy.
Abstract: Bentonitic material from South Aswan, Egypt was evaluated in terms of mineral-ogy and chemical composition as bleaching clay in refining of transformer oil before and after acid activation and thermal treatment followed by acid leaching using HCl and H2SO4 for different contact times. Structural modification and refining power of bento-nite were investigated during modification by means of X-ray diffraction and infrared spectroscopy. The results revealed that the activated bentonite could be used for refining of transformer oil. The oil parameters such as; dielectric strength, viscosity and flash point had been improved. The dielectric breakdown strength of used oil increased from 29 kV for used oil treated with unactivated bentonite to 74 kV after treatment with activated bentonite. Kinematic Viscosity changed from 19 to 11 mm2 /s after treatment with activated bentonite. However, flash point achieved 149 ºC.
Abstract: The composite materials were prepared by sawdust, cassava starch and natural rubber latex (NR). The mixtures of 15%w/v gelatinized cassava starch and 15%w/v PVOH were used as the binder of these composite materials. The concentrated rubber latex was added to the mixtures. They were mixed rigorously to the treated sawdust in the ratio of 70:30 until achive uniform dispersion. The batters were subjected to the hot compression moulding at the temperature of 160°C and 3,000 psi pressure for 5 min. The experimental results showed that the mechanical properties of composite materials, which contained the gelatinized cassava starch and PVOH in the ratio of 2:1, 20% NR latex by weight of the dry starch and treated sawdust with 5%NaOH or 1% BPO, were the best. It contributed the maximal compression strength (341.10 + 26.11 N), puncture resistance (8.79 + 0.98 N/mm2) and flexural strength (3.99 + 0.72N/mm2). It is also found that the physicochemical and mechanical properties of composites strongly depends on the interface quality of sawdust, cassava starch and NR latex.