Monthly and Diurnal Variability of Rain Rate and Rain Attenuation during the Monsoon Period in Malaysia

Rain is the major source of attenuation for microwave propagation above 10 GHz. In tropical and equatorial regions where the rain intensity is higher, designing a terrestrial and earth-to-satellite microwave links is very critical and challenging at these frequencies. This paper presents the preliminary results of rain effects in a 23 GHz terrestrial point-to-point communication link 1.3km long. The experimental test bed had been set up at Skudai, Johor Bahru, Malaysia. In this area, a monsoon equatorial climate prevails and the rainfall rate can reach values well above 100mm/h with significant monthly and diurnal variability. Hence, it is necessary to implement a mitigation technique for maintaining an adequate radio link performance for the action of very heavy rain. Since we now know that the ULPC (Up Link Power Control) cannot guarantee the desired performance, a solution based on frequency band diversity is proposed in this paper. Here, a secondary radio link operating in a frequency not affected by rain (C band for instance) is placed parallel with the main link. Under no rain or light rain conditions, the secondary link carries without priority radio signals. When there is an outage of the main link due to rain, the secondary link assumes the priority traffic. The outcome of the research shows a solution for higher operating frequencies during rainy events

EXPERIMENTAL ANALYSIS ON THE PHOTOVOLTAICTHERMAL SOLAR COLLECTOR WITH COMPOUND PARABOLIC CONCENTRATOR USING PHASE CHANGE MATERIAL-TOWARDS SOLAR ENERGY UTILIZATION

In this study, the performance of a photovoltaic-thermal solar collector with compound parabolic collector for clear day in winter and summer season was investigated. Phase change material storage unit, compound parabolic collector unit, photovoltaic thermal unit were integrated into one piece to reduce the area to get higher performance and better concentration ratio. The performance of water flow rate, heat removal factor, amount of energy storage of the collector in winter season and comparison of temperature variation, total generated energy, performance factor in summer season by varying different parameters were evaluated. Water flow rate increases up to 0.004 kg/s corresponding to the thermal efficiency of around 42%. Heat removal factor for thermal collector was in the range of 0.94-0.96, which indicates better energy gain of the system and effective outlet water temperature was found 55 0C in winter season. The total generated thermal energy 1500W and maximum performance factor of a collector was 0.0135 kW-1m2 in summer season. Finally total efficiency of a collector varies from 58% -68% in summer season

Genome wide association mapping of grain arsenic, copper, molybdenum and zinc in rice (Oryza sativa L.) grown at four international field sites

Peer reviewedPublisher PD

Rice grain cadmium concentrations in the global supply-chain

One of cadmium’s major exposure routes to humans is through rice consumption. The concentrations of cadmium in the global polished (white), market rice supply-chain were assessed in 2270 samples, purchased from retailers across 32 countries, encompassing 6 continents. It was found on a global basis that East Africa had the lowest cadmium with a median for both Malawi and Tanzania at 4.9 μg/kg, an order of magnitude lower than the highest country, China with a median at 69.3 μg/kg. The Americas were typically low in cadmium, but the Indian sub-continent was universally elevated. In particular certain regions of Bangladesh had high cadmium, that when combined with the high daily consumption rate of rice of that country, leads to high cadmium exposures. Concentrations of cadmium were compared to the European Standard for polished rice of 200 μg/kg and 5% of the global supply-chain exceeded this threshold. For the stricter standard of 40 μg/kg for processed infant foods, for which rice can comprise up to 100% by composition (such as rice porridges, puffed rice cereal and cakes), 25% of rice would not be suitable for making pure rice baby foods. Given that rice is also elevated in inorganic arsenic, the only region of the world where both inorganic arsenic and cadmium were low in grain was East Africa

Energy efficient modulation technique on 10Gb/s coherent detection optical OFDM

The performance of energy efficiency in a radio-over-fiber system utilizing M-QAM (quadrature amplitude modulation), OOK (On-Off-keying) and M-PAM (Pulse amplitude modulation) is highlighted. The performance of single channel CO-OFDM and with 10GHz channels pacing at 10-Gb/s data rate is shown through the optisystem for different modulation schemes and different fiber lengths at different receiving power levels. The experimented results have been achieved over 100km, 400km, 600km and 1000 km distances to study the effect of power consumption at the receiver end with different modulation schemes. In short distance PAM performs quite well and 16 QAM has worst results. In long distance OOK obtain the highest receive power and high order QAM receive the lowest power for the same distance. In middle range 600km, OOK is better and 128QAM has high loss 16QAM & PAM was almost same performance. To increase BER performance of M-QAM, amplifier power should increase trade off but noise level and signal quality also has to maintain. Furthermore, the simulation results expose that the transmission length increased and also the receive power level decreased for fiber attenuation, dispersion and low power of the laser. The results show the relationship of transmission distance and receive power level, and between bit error rate and optical signal to noise ratio (OSNR)

A Wideband Circularly-Polarized Spiral Antenna for CubeSat Application

In this paper, a wideband circularly-polarized spiral antenna is proposed to be used for CubeSat application. The antenna covers two of CubeSat frequencies; the S-band (2.2 GHz) and X-band (8 GHz). The proposed antenna belongs to the wideband and frequency-independent antenna category, which are known to provide a constant radiation pattern, impedance and polarization throughout the whole bandwidth. The performance of the spiral is compared in two different conditions; in free space and above a ground plane with a separation distance of λ/4 at the operating frequency of 2.2 GHz and 8 GHz. The spiral above the ground plane exhibits a unidirectional radiation and higher gain with an increase of 26.6% (2.2 GHz) to 34.6% (8 GHz) than the free space spiral. Moreover, the return loss also managed to stay within the ideal limit of S11<-10dB (-19.528 dB at 2.2 GHz, and -21.92 dB at 8 GHz) and exhibits circularly-polarized radiation with low axial ratio<3 dB (0.78 dB at 2.2 GHz, and 0.89 dB at 8 GHz)