Ethiopian Journal of Science and Sustainable Development

16-21

Authors: Tole Fikadu Aga

In the realm of calculating trigonometric functions, computing the tangent function with a high degree of accuracy and precision without using scientific calculators has been an area of interest and importance. However, the manual determination of trigonometric values presents a formidable challenge, demanding careful attention to detail and the application of rigorous techniques. In this article, a set of formulas that enable the computation of tangent function values without resorting to scientific calculators are presented. The proposed formulas generate results that exhibit a remarkably high level of accuracy and precision, reproducible up to three decimal places. They are applicable within the degree intervals of 0 -21o, 21-45o and 45-90o. For angles larger than 90 degrees, the unit circle definition of the function was utilized. The paper provides detailed and comprehensive mathematical derivations for each formula corresponding to their respective intervals and conducts a thorough comparison of the obtained results with the pre-existing tangent function values through the utilization of a tabular method of comparison. Considering the high degree of accuracy and precision exhibited by these formulas, their practical adoption by both students and teachers at all levels of academic pursuits are recommended. Overall, the formulas proposed have the potential to facilitate mathematical calculations and scientific research by providing more accurate and efficient means of calculating tangent function values.

30-41

Authors: Yilfashewa Seyoum Mekuria, Chala Mosisa Hunduma, Solomon Molla, Getinet Tesfaye

attainment at Haramaya University. A comprehensive analysis was conducted, aligning the university's faculty promotion criteria with the recent Ministry of Education (MoE) standard, with a specific focus on research output. The research methodology comprised a meticulous examination of university records/archival research, including minutes documented by the university's appointment, promotion, and scholarship committee. In addition, the study enriched its insights through in-depth interviews with faculty members. The investigation explored academic promotion, gender dynamics, and the differentiation between native and expatriate faculty. The findings underscored certain disparities, particularly in terms of fields of study, nationality, and gender. A notable discrepancy was observed, with a higher proportion of male faculty members attaining promotions, a phenomenon more pronounced at elevated academic ranks such as Associate Professor and Full Professor. To address these disparities and nurture a more inclusive research environment, Haramaya university promotion policy may partially help as most of the values is given to publication, which was already fixed by the guideline prepared by Ethiopian MoE. A call for transparent promotion standards, robust mentorship programs, and focused support for women in research and leadership roles emerge as a means to bridge the gender gap in staff promotions. Furthermore, additional research and analysis must be undertaken to attain a more profound understanding of the factors influencing publishing trends, facilitate staff promotions, and ultimately advance the promotion of academic excellence.

58-69

Authors: Afework Alemayehu, Taye Negussie, Pietro Toggia

In a wider qualitative study concerned with corruption crimes in Ethiopia, there are only 16 which are about tender/contract corruption crimes. This study dealt only with these corruption crimes, based on court case files in which defendants were found guilty. The crimes were committed as medium or top level government and private organizations’ officials competed for livelihood goals. To corruptly increase own income or profit, the officials used authority and qualification, manipulated bureaucratic rules, regulations and decisions. They further exploited the free market (money) economy in which items of exchange are not delivered immediately; illegal means of earning the ‘charming’ money or owning other valuable assets remains unquestioned, self-control and ethical concerns have been minimized. The criminals owned properties contrary to socially approved ways while the high monetary values the crimes involved- one to several millions- implied that the criminals reaped huge amounts of kickbacks. The article further argues that these corruption crimes, though committed for economic benefits, could not be considered economic actions. To minimize tender/contract corruption crimes, it is recommended to reward public officials with “secure existence” by means of salaries regularly revised in accordance with inflation and corruption controlling coercive laws at least partially redirected to social sanctions.

85-97

Authors: Olugbenga Orisasona, Kolawole Emmanuel Ajani, Bamidele Oluwarotimi Omitoyin, Omotola Jenyo-Oni, Elijah Friday Osho, Kazeem Oladeji Kareem, Traore Youssouf, Abimbola Olumide Adekanmbi

Aquaculture production can be boosted with enhanced feed efficiency, growth and disease resistance using probiotics. In this study, the effects of Lactobacillus fermentum (LF) probiotic on growth, intestine, immune competence of Oreochromis niloticus, and the resistance to virulent Aeromonas hydrophila were investigated. A basal (LF1) diet (35% crude protein) was formulated and five treatments with L. fermentum included at 1 x 103 cfu/g (LF2), 1 x 105 cfu/g (LF3), 1 x 107 cfu/g (LF4), 1 x 109 cfu/g (LF5) and 1 x 1011 cfu/g (LF6). The six diets were each allotted to three groups of Oreochromis niloticus (1.85±0.01g mean weight) for 90 days. After which fish were injected with A. hydrophilia, fed and observed for 15 days. At the end of the 90 days, LF diets fed fish had higher (p<0.05) mean weight gain. Feed conversion ratio and specific growth rate were superior in fish fed LF3 and LF4. Villi height was significantly high in LF3, while microbial loads were more in the guts of fish fed probiotics. Blood packed cell volume and haemoglobin increased significantly in the groups fed LF. Hydrogen peroxide and malondialdehyde reduced significantly (p<0.05) in the liver and kidney of fish fed L. fermentum, while glutathione transferase and glutathione peroxidase activities were increased. The challenge test with virulent Aeromonas hydrophila showed improved resistance in fish fed probiotic. Thus, the study disclosed improved growth performance, enhanced health status and better survival with the supplementation of Lactobacillus fermentum in the diets of Oreochromis niloticus.

16-22

Authors: J. B. Yerima, Dunama William, S. D. Najoji, Alkali Babangida, and S. C. Ezike

An exact current density-voltage (J-V) equation of an effective and applicable solar cell is intrinsically implicit, which requires iterative computations to obtain the fill factor and the peak power point. A simple explicit power law J-V model was applied to 14 dye-sensitized solar cells. The model permits an easy prediction of the entire J-V curve, highest power point, and fill factor from four simple measurements of the bias points corresponding to Voc, ~0.6Voc, Jsc, and ~0.6Jsc, where Voc is the open circuit voltage and Jsc is the short circuit current density. Also, the model gives a closed-form description of the J-V curve, maximum power point, and fill factor (FF) in terms of the physical parameters of the single exponential model. The results show that all the model parameters are regular, unlike previous findings that reported parameter irregularities of varying degrees. Furthermore, the DSSCs are grouped into two classes as good or bad based on their FF values such that 12 (86%) with 0.45<

36-46

Authors: Alemu Disassa Mulleta

Organizational communication in general and superior-subordinate communication, in particular, are among the factors that determine the level of employees’ work engagement. Though there are studies across the world, this issue has not been addressed at least in the context of the current study. The purpose of this study was, therefore, to examine the association between organizational communication and employee work engagement. To this end, quantitative data were collected from 302 participants including 47 managers and 255 non-manager staff of Adama Science and Technology University using standardized Likert scales. Results of the study show that superior-subordinate communication and the opportunity to communicate with the upper manager have a statistically significant moderate positive association with employee work engagement. Nevertheless, results of standard regression analysis revealed that only positive superior communication has significantly contributed to the variation in the level of employee work engagement. Implications of the study include the need to strengthen and maintain positive superior communication while addressing other variables which could affect employee work engagement.

60-73

Authors: Hadish Teklehaimanot Gebru, Neeraj Gupta, Ramesh Babu Nallamothu

compression test engine were explored using Jatropha curcas as a feedstock for biodiesel production. Two-step techniques, esterification and transesterification, were employed to create biodiesel with diesel fuel-like properties. In the first phase of esterification process, the molar ratio of methanol to the parent oil Jatropha curcas was 1:6, and 1% volume of sulfuric acid was added. The mixture temperature was maintained at 65 degrees Celsius, and the magnetic stirrer on the hotplate was adjusted to 600 rpm. At this point, the acid value decreased from 4.6mg-KOH/g-oil to 1mg-KOH/g-oil. During the second transesterification procedure, the catalysts were sodium hydroxide pellets and analytical-grade methanol at the same stirring speed and mixture temperature for 25 minutes. The emission as well as performance characteristics of biodiesel-diesel blends containing various mixing ratios were studied. The test samples B20, and B100 produced less carbon monoxide and hydrocarbon as compared to the baseline diesel fuel, and the power, and torque outputs of B20 were superior to all blends. The unexpected conclusion of the study was that increasing the blend's biodiesel component increases braking power and torque while decreasing brake-specific fuel consumption.

97-104

Authors: Sisay Negash, Yenesaw Anmaw

Soil infertility constraints and low soil pH are the predominant problems to barley production and productivity in the highland regions of Ethiopia. In reaction to this, the experiment was carried out in highland areas of Semen Ari district with low soil pH to determine the effects of split application of lime on soil pH and grain yield of barley from 2018 to 2020 for three cropping years. Six treatments were used for this experiment as control (no inputs); 200 kg ha-1 of NPKSZnB + 94 kg ha-1 of urea top-dressed; lime applied at once (7.6 t ha-1); two splits or 50% (1st and 2nd years); three splits or 33% (1st, 2nd and 3rd years); two splits or 50% (1st and 3rd years). The RCBD design within three replications was employed to arrange treatments. The result of soil analysis after lime application revealed that it improved available phosphorus and raised the soil pH, but decreased the exchangeable acidity compared to control treatments. Among the treatments, lime application in two splits (1st and 3rd years) gave the maximum grain yield (3061.5 kg ha-1) of barley significantly, whereas the minimum yield was obtained from the control (untreated plot). The maximum grain yield in the third year was obtained from the application of two splits or 50% (1st and 3rd years) which were statistically non-significant with the application of three splits or 33% in each year (1st, 2nd and 3rd years) and two splits or 50% (1st and 2nd years). Thus, to enhance soil fertility status and obtain better barley grain yield, farmers must undertake the use of a split application of lime with inorganic fertilizer rather than a sole application of inorganic fertilizer. It suggested that, depending on the accessibility of lime and affordability of barley producers, farmers in the study area could use the above application frequencies with recommended inorganic fertilizers (69N and 46P2O5). Further investigation should be done on plant nutrient uptake, nutrient use efficiency and optimization.

7-19

Authors: Tewabech Temesgen Mekonnen, Moges Admasie Mengstie, Fasika Kebede Shewareged

Anaerobic digestion process is one of the non-thermal technologies of energy recovery to meet the ever-growing energy demand of rural areas in developing countries, particularly Ethiopia, in a green way. The aim of the present study was to investigate the effectiveness and performance characteristics of anaerobic digestion of calabash waste mixed in selected ratios with donkey and sheep dung for biogas production. Production of biogas from calabash waste, mixed with donkey and sheep dung in ratios 1:1, 2:1, 3:1, and 4:1 by mass, was investigated in a 45 L plastic container using a retention period of 20 days and within the mesophilic temperature range. The average biogas yield was significantly (P≤ 0.05) influenced by the different mixing ratios of calabash waste with dung. The composition of gas generated from each ratio ranged (from 67.41-63.81)% CH4, (33.00-26.01)%, CO2, (1.06-0.40)% CO, (3.00-0.07)% H2O, (0.06-0.02)% NH4,(0.90-0.05)% N, (0.72-0.02)% H, (0.98-0.09) % O2, and (0.006-0.001) % H2S. The average biogas yield was 13.5, 11.6, 10.7, and 7.8L respectively for 1:1, 2:1, 3:1, and 4:1 mixing ratios when calabash waste was mixed with sheep dung. On mixing calabash waste with donkey dung, the average biogas yield increased to 16.2, 15.5, 12.6, and 9.8L respectively for 1:1, 2:1, 3:1, and 4:1 mixing ratios. The results show that mixing both dungs with calabash waste in a ratio of 1:1 by mass-produced the highest biogas volumes, and higher in donkey dung. The reason behind this is that higher mixing ratios meant a higher quantity of waste in the mixture which also implied increased lignin content, and this made digestion activities more difficult for the microbes. Reduction in digestion activities of the methanogen bacteria resulted in lower biogas yield. The result of the present study has shown that anaerobic digestion from calabash waste, mixed with donkey and sheep dung in ratios 1:1, 2:1, 3:1, and 4:1 by mass can form a renewable energy that is comfortable and environmentally friendly. This energy production process is found to be an easy way of replacing fossil fuels

28-37

Authors: Achalu Chimdi

Soil phosphorus is an essential plant nutrient, and its insufficiency severely limits crop yields. However, its adsorption study plays a vital role in devising appropriate soil phosphorus, “P”, management practices for its use proficiency. This study was initiated to evaluate phosphorous adsorption characteristics and kinetics of soil of three different land uses. A representative topsoil samples (0-20 cm) depth from the forest, grazing, and cultivated lands were collected and weighed 1g of composited soil samples were equilibrated in 20 ml of 0.01 M CaCl2 solution containing KH2PO4 at rates of( 0, 5, 25, 100, 150 and 250) mg P L-1 for assessment of Langmuir adsorption isotherm using batch type experiment. Then, the equilibration time was deduced from the kinetic experiment and fixed at 5 hours. The textural class of soils of forest land was clayey loam, whereas that of grazing and cultivated lands was clayey. Soil pH values under the three land uses were found to be strongly acidic. The experimental soils differed considerably in sorption characteristics under the three land uses. The highest mean value of the product of biding energy and sorption maximum (Kqmax) was recorded in the soil of cultivated land (1.08 Lmg-1) followed by forest land soil (0.7313 Lmg-1), while the lowest was recorded for the soil of grazing land (0.672 Lmg-1), indicating considerable variation soil phosphorus adsorption characteristics under three land-uses. The value of the regression equation (R2) indicated that higher values (R2 > 0.9864) have better soil binding strength than the others. Thus, the good fitness of the model was ascertained by witnessing the R2 values. The kinetic data showed that the values of concentration of soil “P” adsorbed (qe) under the three land uses were closer and the R2 values were comparably lower and almost analogous for the pseudo 1st order kinetic model than the pseudo 2nd order model. Soil “P” sorption kinetics was fast in the first 120 minutes and then showed no change with the increase of the contact time.

49-60

Authors: Aliyu Nesru, Achalu Chimdi, Wondwosen Tena

The study was initiated to assess the level of soil acidity and lime requirement of four types of land uses (forest lands, grazing lands, cultivated lands, and Eucalyptus tree plantation) and in replications from 0-20 cm soil depth. Lime requirement was evaluated by exchangeable acidity and buffer solution methods. The data were analyzed by SAS software, version 9.1. The study revealed that soils of cultivated and Eucalyptus lands were very strongly acidic with mean of pH 4.8 and 5.0, whereas soils of grazing lands were strongly acidic with pH 5.5 and forest lands were moderately acidic with pH 5.7and 5.6 in both kebeles, respectively. Meaningfully higher pH, OM, TN, CEC, exchangeable Ca2+, and Mg2+ were noted under forest lands as compared to the remaining land uses. However, meaningfully lower exchangeable acidity (EA) (1.06) and percentage acid saturation (PAS) (5.18) were obtained in the forest lands than in the other land uses. Significantly higher available P (2.54) was noted in the grazing land, followed by natural forest (1.77) land for Berchernamocheya kebele, and higher available P was recorded under forest (2.50), followed by grazing land (2.37) for Badnayegor kebele. Significantly higher exchangeable K+ (1.29) and Na+ (0.63) were observed in grazing land for Badnayegor and Berchernamocheya Kebeles, respectively. The results of the lime requirement revealed that using the SMP buffer solution method recorded 4.1-11.3 t/ha while using the exchangeable acidity method recorded 1.3-6.7 t/ha across the land uses for both kebeles. Based on lime requirement determination methods, the amount of lime required highly varies among the land uses. The investigation showed that soil acidification is a serious problem in the study areas. Thus, integrated land management needs to be practiced to overcome the problem of soil acidification and achieve sustainable agricultural production.