Analytical study of heat and mass transfer effects on unsteady Casson fluid flow over an oscillating plate with thermal and solutal boundary conditions

In this study, the impacts of heat and mass transfer characteristics on an isotropic incompressible Casson fluid flow over an oscillatory plate with the incidences of solutal and thermal boundary conditions have been investigated. Exact solutions of the fundamental equations governing the fluid flow are determined by using the Laplace transform technique. Numerical results based on analytical solutions are presented in graphical and tabular illustrations to clarify the behaviors of the fluid. Most interestingly, both fluid velocity and species concentration increase with an increment of mass transfer coefficient, whereas the fluid velocity diminishes as oscillating frequency increases near the surface of the plate. This happens due to the presence of high fluctuation of the plate in the flow system. Finally, this investigation is helpful to the scientific community, and the obtained results can be used as benchmark solutions for solving nonlinear flow governing problems fully via various numerical methods.     

Status and Potential of Spate Irrigation in Ethiopia

This article discusses spate irrigation in Ethiopia and aims to take stock of the current status of spate irrigation development. It summarizes experiences so far and formulates a number of recommendations on the development of this upcoming resource management system. It argues that raised weirs are useful mainly in areas where a large head for spate flow diversion is required, but that traditional earthen structures with conical stone/gabion reinforcements are cost-effective and technically adequate for floodwater distribution and management. It contends that the practical successes of sediment settling ponds (gravel traps) are at best mixed. Even where a small basin is justified, it can only ever trap a small proportion of the incoming sediment load. It is better to allow large floods with excessive sediment load (>100,000 ppm) to by-pass upstream intakes to be diverted lower down the system, and provide additional livelihood opportunities in downstream areas in the form of rangeland and agro-forestry development. This is particularly useful in the lowlands of Ethiopia with large pastoral community where spate irrigation is yet to make in-roads. The article further explains that water rights in spate are different from the sharing and allocation of perennial flows—they are dynamic and respond to a situation that differs from year to year as well as within a year and that a certain degree of inequity among users is inevitable. Keeping the command area compact can ensure two or more irrigation turns and this can highly increase productivity as crops are no longer in the ‘stress zone’. To transform spate irrigation in Ethiopia from subsistence to a business-oriented production system, the article proposes the promotion of cash crops including pulses and oil seeds as well as encouraging investors to go for bio-fuel development and agro-forestry in the lowland areas where huge potential exist. To avoid vehement conflicts that may arise among the settled agricultural and pastoral communities due to the implementation of the business-oriented production system, the traditional rights of the pastoral communities must be respected and their rangeland and water resources be safeguarded. For maximum yield, soil moisture conservation measures such as pre-irrigation land preparation, deep ploughing and mulching are essential as is the conjunctive use of spate flow and groundwater. Last, but most important, the article emphasizes that farmers need to be placed at the heart of any spate irrigation development programme as primary beneficiaries, managers and operators as well as part of the decision making institution.     

Thermal radiation and inclined magnetic field effects on MHD flow past a linearly accelerated inclined plate in a porous medium with variable temperature

An analysis of unsteady MHD natural convective flow, transfer of mass, and radiation past linearly accelerated slanted plate inserted in an immersed permeable medium with uniform permeability, variable temperature, and concentration within the sight of a slanted magnetic field has been done. The novelty of the current examination is to analyze the effect of a slanted magnetic field on the flow phenomena with heat source/sink and destructive reaction for linearly accelerated slanted plate. The governing equations have been solved by using Laplace transform strategy. The estimations of flow velocity, concentration, and temperature are exhibited graphically, while local skin friction, mass, and heat transfer rates are put on view in tabular form for different values of relevant stream parameters. It is fascinating to observe that the raise of inclination angle of an applied magnetic field diminishes both velocity profiles and local skin friction.     

Hybritus: a password strength checker by ensemble learning from the query feedbacks of websites

Password authentication is vulnerable to dictionary attacks.Password strength measurement helps users to choose hard-to-guess passwords and enhance the security of systems based on password authentication.Although there are many password strength metrics and tools,none of them produces an objective measurement with inconsistent policies and different dictionaries.In this work,we analyzed the password policies and checkers of top 100 popular websites that are selected from Alexa rankings.The checkers are inconsistent and thus they may label the same password as different strength labels,because each checker is sensitive to its configuration,e.g.,the algorithm used and the training data.Attackers are empowered to exploit the above vulnerabilities to crack the protected systems more easily.As such,single metrics or local training data are not enough to build a robust and secure password checker.Based on these observations,we proposed Hybritus that integrates different websites'strategies and views into a global and robust model of the attackers with multiple layer perceptron(MLP)neural networks.Our data set is comprised of more than 3.3 million passwords taken from the leaked,transformed and randomly generated dictionaries.The data set were sent to 10 website checkers to get the feedbacks on the strength of passwords labeled as strong,medium and weak.Then we used the features of passwords generated by term frequency-inverse document frequency to train and test Hybritus.The experimental results show that the accuracy of passwords strength checking can be as high as 97.7%and over 94%even if it was trained with only ten thousand passwords.User study shows that Hybritus is usable as well as secure.     

Incidences of aligned magnetic field on unsteady MHD flow past a parabolic accelerated inclined plate in a porous medium

An exact analysis of a radiative hydromagnetic flow behavior over a tilted parabolic plate through a permeable medium along with variable species concentration and fluid temperature in the presence of a slanted magnetic field parameter, chemical reaction, and heat generation has been carried out in this study. Closed-form analytical benchmark solutions for flow-governing equations are obtained by using the Laplace transform method. Thereafter, the incidences of different important physical entities on the nondimensional velocity field, temperature distribution, and species concentration are presented using graphs, whereas impacts of various physical entities on wall shear stress, heat and mass transfer rates are presented in tables. It is worth noting that an increase in the magnetic field and its inclination angle causes the reduction in the fluid velocity. However, wall shear stress increases with the increase of magnetic field and its inclination angle. The novel results in this article can be used to improve quicker cooling and producing miniaturized heat flow systems with upgraded efficiency and cost-effectiveness.     

Exploiting locally available resources for food and nutritional security enhancement: wild fruits diversity, potential and state of exploitation in the Amhara region of Ethiopia

This paper features the composition of wild fruits, their exploitation and their potential contribution to improved food and nutritional security in three districts of the Amhara region of Ethiopia. Data were gathered through structured, semi-structured and key-informant interviews which were administered to the heads of 92 randomly chosen households. Focus group discussions and direct field explorations by the researchers were also undertaken. The results revealed that altogether 44 wild fruit species are available for use in the study areas. The fruits are rich in valuable nutrients and are accessible year-round with significant overlap at times of acute food and nutrient scarcity. Nevertheless, owing to the peoples’ cereal-based dietary habits, cultural perceptions and attitudes, the current state of fruit utilization is very low. Consequently, the potential nutritional contribution of wild fruits to the people’s diets remains largely unexploited. In order to remedy this situation, a wider and sustained acceptance of wild fruits as important dietary components must be fostered.

Simultaneous Determination of Alkaloids in Green Coffee Beans from Ethiopia: Chemometric Evaluation of Geographical Origin

The alkaloid compositions of 99 green coffee (Coffea arabica L.) bean samples comprising eight varieties (Harar, Jimma, Kaffa, Wollega, Sidama, Yirgachefe, Benishangul and Finoteselam) from the major production regions of Ethiopia were investigated. High performance liquid chromatography was applied for the simultaneous determination of four coffee alkaloids in the aqueous extracts of the beans. The limits of detection for the method were established as 13 mg kg^?1 for trigonelline, 7 mg kg^?1 for theobromine, 8.5 mg kg^?1 for caffeine and 4 mg kg^?1 for theophylline in the dry coffee beans. Theophylline was not detected in any of the samples. The determined concentrations (% w/w dry coffee beans) ranged from 0.98 to 1.32 % for trigonelline, 0.0048 to 0.0094 % for theobromine and 0.87 to 1.38 % for caffeine. The concentrations of the alkaloids varied significantly, depending on the geographical origin of the beans. Theobromine was not detected in coffee beans from the East (Harar coffees), and its absence in samples can be used to ascertain whether the coffee originates from this region. Coffee beans from the Northwest were characterized by higher concentrations of caffeine. Application of linear discriminant analysis provided 75 % correct classification of samples into the respective production regions, with a 74 % prediction success rate. The moderate classification efficiency obtained when using alkaloid data demonstrates the potential of using this class of compounds in discriminant models for determination of the geographical origin of green coffee beans from Ethiopia.     

Inorganic heterogeneous catalysts for biodiesel production from vegetable oils

Biofuels are renewable solutions to replace the ever dwindling energy reserves and environmentally pollutant fossil liquid fuels when they are produced from low cost sustainable feedstocks. Biodiesel is mainly produced from vegetable oils or animal fats by the method of transesterification reaction using catalysts. Homogeneous catalysts are conventionally used for biodiesel production. Unfortunately, homogeneous catalysts are associated with problems which might increase the cost of production due to separation steps and emission of waste water. Inorganic heterogeneous catalysts are potentially low cost and can solve many of the problems encountered in homogeneous catalysts. Many solid acid and base inorganic catalysts have been studied for the transesterification of various vegetables oils. The work of many researchers on the development of active, tolerant to water and free fatty acids (FFA), as well as stable inorganic catalysts for biodiesel production from vegetable oils are reviewed and discussed.     

Temporal analysis of dual phase‐lag double‐diffusive MHD flow within a porous microchannel with chemical reaction

A novel investigation is carried out to capture the transient effects of a dual phase‐lag (DPL) model for combined heat and mass transfer magnetohydrodynamic (MHD) flow within a porous microchannel in the presence of Dufour effects and homogenous first‐order chemical reaction. The governing equations for the fluid flow problem are solved using the Laplace transform method, which is a powerful technique for solving partial differential equations. Its inversion is done by using the INVLAP subroutine of MATLAB. The numerical values of fluid velocity, fluid temperature, and species concentration are demonstrated graphically and those of skin friction, heat transfer rate, and mass transfer rate are presented through tables. It is for the first time that the actual time gap between the DPL model, the Cattaneo‐Vernotte model, and the classical Fourier?s model has been deciphered and the results unique to the DPL model are presented. We observe a clear difference between the DPL and the other two models at a dimensionless time , which gradually diminishes as time progresses, and all models coincide together at , that is, where a steady state temperature is reached. An important contribution of this study lies in discovering the time‐bound effects of the phase‐lag parameters of the DPL model on fluid temperature, species concentration, and fluid velocity and support them by physical justification. A similar discussion is provided for all other flow parameters. The results conveyed through this study would undoubtedly help researchers to advance the design of mechanical systems in microdevices involving MHD flow in porous media.