Momona Ethiopian Journal of Science

Comparative Study of Antireflection Coating Materials for Solar Thermal Collectors

Fana Filli — 2018-06-07

Locally available absorber and antireflection coating materials for solar thermal collectors have been assessed and tested for performance compared to ordinary commercial black paint used in solar water heaters and solar cookers. Absorber plates made of aluminum and iron sheet metals coated with blackboard paint, commercial black paint, and black ABRO spray were prepared. These materials were tested for thermal performance on a natural circulation flat plate solar water heater and plastic bottles. Comparison has been made separately for both absorber material and coating materials which showed that the iron sheet and black ABRO spray to have the highest absorptance. On a clear sky radiation of 973.5W/m2, a maximum stagnation temperature of 99.2°C and 107.5°C is achieved on the black ABRO spray painted aluminum sheet metal and iron sheet metal respectively. This is because ABRO black paint has the highest absorptance for wavelengths of below 2.5μm and low thermal emittance for wavelengths above 2.5μm. During the testing of solar water heaters, an increase in temperature of 14.9°C at the outlet from absorber plate and 7.5°C at the surface of storage tanker has been achieved when using ABRO black spray. This is attributed to the highest absorptance for wave lengths of below 2.5μm and low thermal emittance for wave lengths above 2.5μm of ABRO black paint. As can be concluded, iron sheet metal which is cheap and easily available is best for solar thermal applications and provides significant benefit in cost reduction. Furthermore, the cost for ABRO black paint is similar to other coating materials and it can easily be applied on the surface of absorber materials.

Steam-based Charging-Discharging of a PCM Heat Storage

Asfafaw H. Tesfay — 2018-06-07

Latent heat storage and efficient heat transport technology helps to utilize the intermittent solar energy for continuous and near isothermal applications. However, many latent heat storages face challenges of storage charging, heat retaining, and discharging the stored heat. This paper tries to address the challenges of heat transportation and storage charging-discharging issues. The heat transportation from the receiver over some distance, from outside to the kitchen, is carried out with a stainless pipeline and water as heat transfer fluids. However, the charging-discharging process is carried by conduction method with the help of fins. In addition, the stored heat is retained for about one-two days by using aerogel insulation. The latent heat is stored in a phase change material (PCM), nitrate salt (mixture of 60%NaNO3 and 40%KNO3), which melts at 222ºC and has 109 J/g specific heat of fusion. The storage has the capacity of storing up to 250ºC heat and supply this heat isothermally during baking in the liquid-solid phase transition. However, the sensible heat stored in the solid and liquid form of the PCM is used to perform additional applications that do not require uniform heat which includes bread baking, kita (large pancake) baking and water boiling. The low thermal conductivity of PCM is enhanced by using extended aluminum fins that are attached to the baking plate and extruded inward to the storage. In this paper, two-phase loop thermosyphon of steam is used to manage the long distance heat transportation required between the receiver (outside) and the storage (inside a house). The steam in the thermosyphon flow has restricted to a maximum working temperature of 250ºC. Steam is selected for its highest heat capacity, availability and stable nature. It carries heat from the collector focus point and condenses in a coiled pipe imbedded in aluminum plate placed on top of the storage. Many fins are solidly attached to this plate to conduct the heat down to the PCM inside the storage during charging. This design configuration avoids pressure development inside the PCM storage and the charging-discharging temperature is recorded in three zones (top, middle and bottom) of the storage. The experimental and numerical results show that the heat transportation, retention and charging-discharging methods are effective.

Polypropylene Nano-composites at High Strain Rate Impacts: Characterization, Failure Modes, and Modeling

Shishay Amare Gebremeskel — 2018-06-07

As a major challenge, development of light-weight fibre reinforced polymer (FRP) composite body armour, characterization of candidate matrix polymers at high strain rate impact is the focus in this research. Polypropylene (PP) and the nano-composites with 1-5% by weight of NC (nanoclay) platelets are the candidates considered. In the characterization phase, high strain rate impact and quasi-static loading tests were performed to figure out the limiting (failure) responses. Comparison between the material systems is, subsequently, made to nominate one matrix configuration. Enhancements of mechanical properties with increase in weight percentage of the nanoparticles are observed at both quasi-static and dynamic loadings. Observations of dispersed imposed failure modes, development of novel model for failure modulus and evaluation of peak strength values are also attempted.

Simulation of Phase Meter Using TINA Software

Chaudhari A. J — 2018-06-07

The use of a circuit simulator is more and more crucial in designing electrical and electronic gadgets. This technique makes it possible to obtain results when the hardware is unavailable or very costly. Simulations are widely used in the industry hence it is necessary to use it astutely. Authors tried to study an important concept about “Squaring a Signal” and further it is extended to design and simulation of phase meter. Squaring a sinusoidal lead doubling its frequency and adding the dc component. In this study squaring sine wave with frequency of 5KHz gives a negative cosine wave with frequency 10KHz along with a dc term of 2V. TINA software is used for this study. TINA software has ability to perform DC analysis, AC analysis and transient analysis. Transient analysis calculates the circuit response to various input waveforms. Results are analyzed using transient analysis for sinusoidal input.

Radiological Impacts of Natural Radioactivity in Locally Produced Tobacco Products in Ibadan, Oyo State, Nigeria

Akinyose F. C — 2018-06-07

Radionuclides are found naturally in air, water and soil. They are even found in vegetation, consumer products and in human body. Everyone on the planet is exposed to some background level of ionizing radiation through external exposures that occurs as a result of irradiation, and internal exposures that occurs as a result of ingestion and inhalation. Studies have shown that tobacco contains minute quantities of radioisotopes from uranium and thorium-decay series which are radioactive and carcinogenic. Tobacco product increases both external and internal exposure due to these radioisotopes. In fact, tobacco products have been considered to be one of the most significant causes of lung cancer. Owing to the large-scale consumption of tobacco in Nigeria at the present time, locally produced tobacco products in Nigeria were collected from the market and the naturally-occurring 238U and 232Th decay series, as well as non-series decay 40K in these products were measured using γ-ray spectrometer. The radiological impacts of the radionuclides in these products were assessed from their specific activities. The average values of the absorbed dose rate were 19.72 and 17.59 nGy h-1 for snuff and cigarette products respectively. The average values of the effective doses due to daily inhalation of smoke by consumers from one wrap of snuff and one stick of cigarette products is 592.32 and 66.62 μSv yr-1 respectively. Similarly, the values of the radium equivalent activity index for snuff and cigarette samples were 40.95 and 38.95 Bq kg-1 respectively. Also the external radiation hazard index were 0.12 and 0.11 for snuff and cigarette samples respectively while the internal radiation hazard index were 0.17 and 0.15 for the two samples respectively. The average excess lifetime cancer risk (x 10-3) values for daily inhalation of smoke from one wrap of snuff and one (1) stick of cigarette were 2.07 and 0.23 x 10-3 respectively. The estimated values of some of these parameters were found to be lower than the recommended limit by UNSCEAR (2000). However, the effective dose poses a serious health risk to addicted consumers of the product when three (3) or more wraps of snuff and one (1) or more packs of cigarette products are consumed daily. The mean excess lifetime cancer risks values estimated were also much higher than the recommended limits by UNSCEAR (2000). This then makes the risk of suffering cancer and other radiation injuries to be high.

Explicit Pre A*-algebra

Habtu Alemayehu — 2018-06-07

This manuscript is a study on Birkhoff centre of a Pre-A*-algebra. In fact, it is proved that Birkhoff centre of a Pre A*-algebra is also a Pre A*-algebra and identified that the centre of Birkhoff centre of a Pre A*-algebra is a Boolean algebra.

Indirect Estimation of Selected Measures of Fertility and Marital Fertility from Information on CWR (0-9): An Application to India /States /Districts

Krishna Murthy Ponnapalli — 2018-06-07

Fertility is one of the important components of population change, the other two being mortality and migration. When vital statistical data on number of births is readily available it is estimated directly using various direct measures of fertility such as the crude birth rate (CBR). When the information on number of births is not directly available, fertility is measured using the census information on child woman ratios (CWR) of various types. CWR has several limitations, but gained importance with the attempts made by Rele in 1963, and followed by several other researchers such as Hauer and his co-authors in 2013 deriving TFR from it. In the present study yet another attempt is made to use CWRs to derive not only TFR but also other summary indicators such as the TMFR. A set of simple mathematical formula have been used to estimate the fertility and marital fertility using the CWR of the ages 0-9. The 2011 census age-sex data of districts in India was used to derive a set of fertility estimates for total, rural and urban areas of all districts. Further, these estimates of 2011 have been compared with the estimates of 2011 earlier made by Guilmoto and Rajan to analyse the robustness of the estimates.

Effects of Indole-3-Acetic Acid on the Growth Parameters of Citrullus lanatus (Thunberg) Matsum and Nakai

Ogwu M. C — 2018-06-07

Effects of Indole-3-Acid (IAA) on Citrullus lanatus plant height, leaf number, branching and flower production were studied in order to evaluate the optimum concentrations required for growth and development. Foliar application using five different concentrations [1, 5, 10, 20 and 0 ppm IAA] was conducted twice at two weeks interval. The results suggest that as IAA concentration increases, plant height decreases with an optimum concentration of 5 ppm IAA. Mean plant height was also significantly different. More so, optimum concentration for leaf production and branching varied with varietal difference. Results obtained for number of branching suggest that 1 ppm IAA is optimum for variety A and 10 ppm is optimum for varieties B, C and D. Although flower production was poor during the study, high flower production is recorded for plants in 20 ppm IAA at 6 weeks after planting for all the varieties. This work establishes the inducing effects of different IAA concentration, which may be exploited for the commercial production of C. lanatus.

Effect of Rhamnus prinoide (Gesho) Intercropping in Wheat Field on Soil Nutrient and Moisture in the Drylands of North Ethiopia

Destaalem Gebremeskel — 2018-06-07

Rhamnus prinoide (Gesho) intercropping is a common practice with significant socioeconomic and ecological importance in Ganta-afoshum district. However, this practice is not well explored so far, especially from the perspective of its impact on sustainable land management while land degradation and low productivity is a challenge in the district. The objective of this study was to examine the effect of R. prinoide intercropping on soil nutrient and moisture. The study was conducted in Ganta-afoshum district, eastern zone of Tigray regional state where smallholder farmers practice R. prinoide intercropping. Soil samples were taken from farmland with dense, medium and sparse density of R. prinoide intercropping and from farmland without trees as a control for analysis. The density of the trees significantly affected the soil bulk density (P<0.05). Soil moisture content significantly increased with increasing soil depth and by the interaction effects of soil depth and density (P<0.05). Soil nitrogen concentration significantly influenced by the density and soil depth (P<0.05). Soil phosphorus and potassium concentration significantly affected by soil depth (P<0.05). Lower mean soil pH values were observed for soils under the farm with dense trees as compared to soils in open farm. Overall, the enhancing and exploitative effects of R. prinoide intercropping on soil nutrient and moisture is minimal. This could be the reason for being practiced and maintained by most farmers.

Effect of NPK and Blended Fertilizer Application on Nutrient Uptake and Use Efficiency of Selected Sorghum (Sorghum bicolor (L.) Moench) Varieties Under Rain-fed Condition in Sheraro District, Northern Ethiopia

Redai Weldegebriel — 2018-06-07

Sorghum (Sorghum bicolor (L.) Moench) is an important cereal crop and stable food for the semi-arid small scale farming communities in the third world. Even though, it is highly adapted to different agro-ecological conditions, its yield is constrained by different factors including declining soil fertility and improper utilization of fertilizer. Results of the research conducted in Shire-Mytsebri Agricultural Research Center at Sheraro sub-site during the main cropping season of 2016 are presented in the paper. The aim was to investigate the effect of NPK; and blended fertilizer on nitrogen, phosphorus, and potassium uptake; and nutrient use efficiency of selected sorghum varieties. The treatments are comprised of factorial combination of ten levels of fertilizers including the recently recommended [N, P, Blanket recommendation (NP), NPK, NPS, NPKS, NPKSZn, NPKSZnB, NPKSZnB (after Agricultural Transformation Agency, ATA) and Control (0)]. Two sorghum varieties (Melkam and Dekeba) were tested in a Factorial Randomized Complete Block Design with three replications. The data were computed using four agronomic indices, which are commonly used to describe nutrient (N, P and K) uptake and use efficiency. The results indicate that there is a significant interaction effect of fertilizer treatments and sorghum varieties on majority of the parameters studied. Application of NPKSZn blended fertilizer significantly enhanced nutrient uptake and use efficiency. The highest total N (78.70 kg ha-1), P (51.19 kgha-1) and K (74 kg ha-1) uptake and use efficiency in Melkam variety treated by fertilizer contained NPKSZn brought higher yield (5541 kg ha-1). Increasing uptake of the major nutrient elements ensured ample nutrient availability for normal growth and high yield of sorghum. Thus, application of macronutrients in combination with micronutrients increased sorghum yield and concomitantly improved N, P and K uptake, and nutrient use efficiency for the sorghum varieties used in the study. Therefore, it is recommended that in the study area and other similar areas blended fertilizer 41N-46P-13.7K-9.25S-1.72Zn kg ha-1 be used to achieve higher yields.