Experimental and numerical investigations of free convection heat transfer in solar oven

The use of solar energy for baking, heating or drying represents a sustainable way of solar energy applications with negligible negative effects. Solar oven is an alternative to conventional oven that rely heavily on coal and wood or Electric oven that uses the power from the National grid of which the end users have little or no control. Since the Solar oven uses no fuel and it cost nothing to run, it use are widely promoted especially in situations where minimum fuel consumption or fire risks are considered highly important. As useful as the Solar Oven proved, it major setback in the area of applications has been its future sustainability. For the use of Solar Oven/Cookers to be sustained in the future, the design and development of solar oven must rely on sound analytical tools. Therefore, this work focused on the design and development of the solar oven. To test the performance of the Small Solar Oven a 5000cm3 beaker of water was put into the Oven and the temperature of the water was found to reach 810C after about 3hrs under an average ambient temperature of 300C. On no load test, the oven reached a maximum temperature of 112oC in 6hrs. In order to carry out the parametric studies and improve the performance of the Solar Oven, Mathematical models were developed and solved by using Characteristics-Based Split (CBS) Finite Element Method. The Model results were compared with the Experimental results and a good agreement ware found between the two results

Leveraging agrigenomics" for crop improvement"

Modern biotechnologies have dramatically reshaped the crop improvement research during the past decade. Biotechniques have become indispensable for efficient and effective development of new knowledge, processes, and products. IITA's biotechnology, strategized as three major themes― genomics, transgenics, and diagnostics, is directed toward the genetic improvement of staple food crops of Africa, such as cooking-banana, plantain, cassava, yam, and cowpea. This section provides some insights and progress in this program

Perceived Parental Monitoring on Adolescence Premarital Sexual Behavior in Pontianak City, Indonesia

Inadaquate parental monitoring is widely recognized as a risk factor for the development of child and adolescent conduct problems, including early premarital sexual behavior. Previous studies examining parental monitoring have largely effect to adolescents premarital sexual behavior. Parental monitoring is the most important and effective factor to prevent early adolescents sexual activity. This paper examines the role of perceived parental monitoring in adolescent\u27s premarital sexual behavior (study on Adolescent\u27s Junior High School in Pontianak). A cross-sectional study and proportionated random sampling was conducted among 402 adolescents of junior high school at six subdistricts in Pontianak. SEM analyses was conducted using SMART-PLS. Result of path analysis revealed that parental knowledge (r = 0.389) and parental-adolescence relationship (r = 0.334) had a strong influence on parental monitoring. Then, parental monitoring had a significant indirect relationship with adolescent premarital sexual behavior through attitudes about premarital sexual (path coefficient = 0.063), and attitudes about premarital sexual and intention to sexual behaviour (path coefficient = 0.03). Parental monitoring can act as protective factor in early adolescent premarital sexual behavior. Therefore, risk reduction interventions with adolescents should include their parents to learn about monitoring skill and develop skill that will allow them to buffer negative influences

Performance Enhancement of Wideband Reflectarray Antennas Embedded on Paper Substrate Materials

This research presents an innovative solution to address the bandwidth limitation of microstrip reflectarray antennas. Organic substrate materials with controlled compositions have been characterized to be employed as substrate materials for microstrip reflectarrays. The three proposed materials show low dielectric permittivity values of 1.81, 1.64 and 1.84 along with loss tangents of 0.053, 0.047 and 0.057 respectively. The proposed substrate materials have been verified by modelling reflectarray unit elements in CST MWS and measured using a waveguide simulator technique. The comparison between measured and simulated results show a good agreement with promising broadband performance of 312, 340 and 207 MHz for S1, S2 and S3 substrate materials respectively

Design and analysis of dual U slot reflectarray antenna for X-band applications

A novel design of a dual frequency single layer reflectarray antenna is presented for X-band frequency applications. Dual U slots embedded on conventional rectangular microstrip reflectarray have been designed to attain a dual frequency operation. A detailed analysis of the effect on surface current distributions with the introduction of dual U slots is presented. Moreover a parametric study on the variation of significant dimensions of the design have been carried out and analysed thoroughly using a commercially available CST computer model. Proposed design configurations were fabricated above a 0.508 mm thick substrate of Rogers Duroid 5880. The dual U slot configuration offers a significant dual frequency behavior at 8.54 and 11.56 GHz with 10% bandwidth improvement of 47 and 56 MHz with a reflection loss of -4.54 and 4.11 dB respectively

Design and analysis of dual U slot reflectarray antenna for X-band applications

A novel design of a dual frequency single layer reflectarray antenna is presented for X-band frequency applications. Dual U slots embedded on conventional rectangular microstrip reflectarray have been designed to attain a dual frequency operation. A detailed analysis of the effect on surface current distributions with the introduction of dual U slots is presented. Moreover a parametric study on the variation of significant dimensions of the design have been carried out and analysed thoroughly using a commercially available CST computer model. Proposed design configurations were fabricated above a 0.508 mm thick substrate of Rogers Duroid 5880. The dual U slot configuration offers a significant dual frequency behavior at 8.54 and 11.56 GHz with 10% bandwidth improvement of 47 and 56 MHz with a reflection loss of -4.54 and 4.11 dB respectively

Energy utilization models of cattle grazing in oil palm plantations II. validations of models

This study showed that models of energy utilization (EU) developed for grazing cattle in oil palm plantations is valid as the simulated results shows an agreement with actual data of calves and cows body weight changes collected from Brahman x Kedah-Kelantan herd on Pengeli Timor Plantation. Simulation runs on EU models demonstrated that the growth pattern of male and female calves and the weight changes of cows are similar and showed slight variation from the actual data but with no significant difference (p>0.05). Parameter values such as metabolizability (q), fry matter digestibility (DMD) of herbage and voluntary intake of grazing cattle (NIG) and faecal output/body weight ratio (F) of the animals which were collected from the field are essential in bearing the pattern of body weight changes of the calves production system. The EU models is suitable for determining the metabolizable energy requirements and to predict the production of grazing cattle according to quality of the feed on offer

Reflectarray Antenna with Radar Cross-Section Reduction

This paper presents the design of a low RCS reflectarray at 8.52 GHz by replacing the solid metal sheet behind the antenna with a band stop frequency selective surface. A 50 element linear array of omni-directional elements was used to simulate the far field pattern of a reflectarray with f/D=0.325 in the plane of the elements to assess the effect of an imperfect aperture distribution on the gain and sidelobe levels. It is found that the reflection loss variation across the aperture does not have a significant effect on the radiation pattern of the antenna, because for the layout that was studied, only a few of resonant loops were predicted to give a significantly different loss than the others in the array. Simulated and measured results show that the ‘in-band’ reflection phase response of the structure with metal ground plane and with a periodic FSS ground plane is very similar, however the periodic ground plane reduces the ‘out of band’ reflectivity by more than 4 dB, thereby decreasing its RCS profile to these signals

Response of FBG-bonded graphene plate at different applied stress location

In this study, the response of a FBG-bonded-graphene plate at different applied stress location is demonstrated. The sensing element utilized for this purpose is a 35.9-mm FBG sensor bonded onto the surface of a graphene plate. The lateral displacement is changed with corresponding increase or decrease in the FBG’s curvature. The change in center wavelength of the reflected spectrum is almost linear, without a significant hysteresis effect. It was also observed that the sensitivity of the FBG changes for location of applied stress. Likewise, the area under the reflection curve is observed to increase with increase in strain level, indicating an increase total power reflected. This is verified by an increase in the voltage output as observed from the oscilloscope