Evaluation of a concrete–graphite hybrid mixture for low-cost thermal energy storage material

The intermittent nature of solar energy is a drawback to its wide use in the absence of solar radiation. Therefore, there is the need for some forms of thermal storage. The objective of this study is to develop a hybrid mixture of a thermal storage material, which can be employed in medium-temperature-concentrated solar power plants. A concrete-graphite mixture sensible thermal storage material for applications up to 400°C for use with solar collectors was evaluated. Comparisons were made to determine the charging and discharging characteristics, thermal storage capabilities as well as costs between concrete only and a mixture of concrete and graphite. A mixture of expanded graphite and concrete was prepared and tested. The hybrid material exhibited fast charging and slow discharging for the same volume of thermal storage. The hybrid material showed an improved thermal storage capacity in a ratio of 1.625:1 to concrete and thus reduces the space requirements. Also, results from the study revealed that when the costs of space requirements and the costs of using a hybrid material are compared, the hybrid material is expensive and only desirable in cases where there are space limitationsMechanical and Industrial Engineerin

Ripening stage and drying method affecting colour and quality attributes of Ziziphus mauritiana fruits in Zimbabwe

Ziziphus mauritiana Lamk. (Ber) fruit is harvested at different stages of ripening in the Zambezi valley of Zimbabwe. We hypothesize that the organoleptic quality attributes of fruits depend on post-harvestdrying method and ripening stage at harvest. This study was carried out to evaluate the effect of different stages of ripening on the quality of Z. mauritiana fruits during drying. The fruits were graded into green, yellowish-brown and brown categories and these formed the treatments. Some of these fruits were blanched before drying for 1, 2 and 3 weeks under the solar dryer and the open sun drying methods. The green fruits lost significantly (

Fostering Active Learning in an International Joint Classroom: A Case Study

Engaging students in an international online setting that is interdisciplinary and culturally diverse is a challenge. A joint classroom between German and Ugandan universities used a formative assessment approach paired with active learning elements to foster individual and peer learning in an international virtual setting. A survey at three different times across the semester explored students’ perceptions towards the value of the active learning activities and evaluated how perceptions changed over time. Overall, students enjoyed the diverse active learning activities and perceived value toward their success in class. This was more pronounced and unidirectional for individual tasks than it was for group work. In addition to the findings of the structured survey, observation and feedback indicated that other elements contributed to effective course delivery. These included clear and frequent communication to the students from the primary instructor, prompt feedback from the instructor on graded exercises, such as a reflective learning diary and ungraded quizzes, and student confidence that sincere effort would achieve a good grade

Genetic progress achieved in bean breeding in Uganda

Several cultivars of common bean (Phaseolus vulgaris L.) have been released in Uganda over a period of five decades, but the genetic gain to selection in respect of yield and agronomic characteristics has not been determined. This study was conducted to estimate the gain in selection over the 1960 - 2016 period, of common bean breeding in Uganda. Twenty nine bush and eleven climbing type cultivars were evaluated for yield and yield components, in three locations, during 2017B and 2018A cropping seasons. The study was carried out at the National Crop Resources Research Institute (NaCCRI), Nakabango Research Institute in central and Kwachwekano Zonal Agriculture Research Institute in southwestern Uganda. The design used was a randomised complete blocks with three replicates for the climbing types; and a 3x10 Alpha lattice design with three replicates for bush types. Significant differences (P<0.001) were recorded among cultivars for most traits in both bush and climbers, except seed number per pod (NSP). The range of genetic gain in grain yield was between 1,505 to 2,418 kg ha-1 for bush type cultivars, and 1,641 to 2,687 kg ha-1 for the climbing types. Yield has increased by16.3 and 26.3 kg ha-1 per year for bush and climbers, respectively; with a relative gain of 1.27%/year for bush types and 1.54%/year for the climbing types. Biomass yield and harvest index explained most of the variation in grain yield and number of pods per plant in climbing types. Among climbing types, biomass yield was significantly and positively correlated with grain yield per plant and grain yield per ha (P<0.05, and r= 0.87) and with grain yield per ha (P<0.01 r = 0.98) for bush types, biomass yield was significantly and positively correlated with grain yield per plant (P<0.05, and r= 0.59) and with grain yield per ha (P<0.01 r = 0.80) and harvest index (P<0.5 r = 0.80)

Blanching and drying period affect moisture loss and vitamin C content in Ziziphus mauritiana (Lamk.)

Wider utilization of Ziziphus mauritania (Lamk) Ber fruits in sub-Saharan Africa is hindered by the rapid deterioration of the fresh fruits and darkening of sun-dried fruits. This study was undertaken to determine the effect of pre-drying treatment, drying method and the subsequent duration of storage on the quality attributes of Z. mauritiana fruits harvested from the Zambezi Valley. The vitamin C content was high at the beginning of the drying period and progressively decreased as the drying increased, and was lowest at three weeks for all drying methods. Effect of drying method was not significant (P > 0.05). The purity (chroma) and lightness (value) of fruit colour decreased (P < 0.001) with increasing drying duration irrespective of the drying method. Blanching fruits before drying significantly (P< 0.001) decreased the colour chroma of the fruits (6.4) in comparison with non-blanched fruits (6.6). Further work to determine the causes of darkening in drying Z. mauritiana fruits and sensory evaluations to determine the level of darkening that is acceptable to consumers is warranted

Multiaxial Fatigue Assessment of Friction Stir Welded Tubular Joints of Al 6082-T6

The present paper addresses the problem of designing aluminium friction stir (FS) welded joints against multiaxial fatigue. After developing a bespoke FS welding technology suitable for joining aluminium tubes, some one hundred welded tubular specimens of Al 6082-T6 were tested under pure axial, pure torsional and biaxial tension-torsion loading. The influence was explored of two independent variables, namely the proportional or nonproportional nature of the biaxial loading and the effect of axial and torsional non-zero mean stresses. The experimental results were re-analysed using the Modified Wöhler Curve Method (MWCM), with this bi-parametrical critical plane approach being applied in terms of nominal stresses, notch stresses, and also the Point Method. The validation exercise carried out using these experimental data demonstrated that the MWCM is applicable to prediction of the fatigue lives for these FS welded joints, with its use resulting in life estimates that fall within the uniaxial and torsional calibration scatter bands. The approach proposed in the present paper offers, for the first time, a complete solution to the problem of designing tubular FS welded joints against multiaxial fatigue loading

Marker-Assisted Selection for Biotic Stress Resistance in Peanut

Peanut is the second-most important legume grown worldwide. Cultivated peanut is a disomic tetraploid, 2n—4x—40, with limited genetic diversity due to a genetic bottleneck in formation of the polyploid from ancestors A. duranensis and A. ipaensis. Consequently, resistance_to biotic stresses is limited in the cultigen; however, wild species possess strong resistances. Transfer o f these resistances is hindered by differences o f ploidy, but production o f synthetic amphidiploids, coupled with use o f molecular markers, enables efficient gene transfer. Marker maps have been made from interspecific crosses, and SSR-based maps from cultivated parents have been developed recently. At least 410 resistance gene analogues have been identified. The first markers for biotic stress tolerance were for root-knot nematode resistance and introgressed from one A. cardenasii chromosome. These and improved markers have been used for marker-assisted backcrossing, contributing to release of three cultivars. Additional QTLs have been identified since. Early and late leafspots cause significant yield losses worldwide, and resistance depends on multiple genes. Using interspecific populations, five resistance QTLs for early leafspot were identified using greenhouse inoculations, and five QTLs for late leafspot were identified using detached leaf assays. Using cultivated species populations, 28 QTLs were identified for LLS resistance; all but one were minor QTLs; the major QTL was donated by an interspecific introgression line parent. Rust often occurs alongside leafspots, and rust resistance was characterized as one major QTL, plus several smaller QTLs. Marker-assisted backcrossing o f this major QTL has been performed into different populations. QTLs for resistance to other biotic stresses have been identified, namely to groundnut rosette virus, Sclerotinia blight, afiatoxin contamination, aphids, and tomato spotted wilt virus. Marker-assisted breeding is still in early stages, and development o f more rapid and inexpensive markers from transcriptome and genome sequencing is expected to accelerate progress

Effect of Two Formulations of Sufentrazone on Weed Control in Tobacco (Nicotiana Tabacum L)

Field studies were done to compare the weed control efficacy of a wettable granular formulation (Authority 75 WG) and a suspension concentrate formulation (Authority 48 SC) of the herbicide sulfentrazone. A 6 x 2 factorial experiment was laid out in a split plot design to evaluate the effect of the two herbicides on the weed control efficacy in tobacco. The first factor was herbicide which had 6 levels and the second factor was weeding which had 2 levels. One rate of the wettable granular formulation at 0.225 kg/ha, four different rates of the suspension concentrate formulation at 0.165, 185, 0.205 and 0.225 kg a.i. /ha and the untreated control were tested. These were split into two weeding levels (weedy and weed free). The weed free plots were weeded every other week for 12 weeks beginning two weeks after transplanting tobacco. The treatments were combined to give 6 treatments for each main plot. These were replicated four times. This work reported efficacy data from the weedy plots. Weed counts were measured at 4 and 8 weeks after transplanting (WAP) and weed dry-mass at 8WAP. Results show that both formulations at all tested rates poorly controlled broadleaf and grass weeds while nutsedge control was excellent. This study showed that the rates used were too low to effectively control grasses and broadleaved weeds while they were adequate for control of nutsedge. We therefore suggest that this material fills an important niche as a nutsedge material with post emergent nutsedge control. Further work should look at herbicide mixtures in order to improve grass and broadleaf control

Effect of Moringa Extract on Growth and Yield of Tomato

Trials were carried out to evaluate the effect of Moringa oleifera leaf extract as a growth hormone on growth and yield of tomato (Lycopersicon esculentumL var. Rodade). In the greenhouse, five treatments were used: the control, where only water was added (M0), second control where ethanol 80 % was added (ME), moringa extract applied once at 2 weeks from emergence (M1), moringa extract applied at 2 and 4 weeks from emergence (M2), and moringa extract applied every 2 weeks to maturity,starting from two weeks from germination (M3).The same treatments were adopted in the field except the ME which was considered unnecessary after observing the results of the greenhouse experiment. Results showed that moringa extract increased growth and yield of tomato in both greenhouse and field. Moringa extract significantly increased above ground dry matter yield (DM), root dry matter weight and plant height for the crop. Yields obtained at MI, M2 and M3 were increasing in ascending order from M1. The study recommends the application of extract at M3