In this study,Cu_(0.25)Ni_(0.5)Zn_(0.25)Fe_(2-x)Nd_(x)O_(4)(0.000≤x≤0.100,andΔx=0.025)spinel ferrites were synthesized using the auto-combustion method to investigate the influence of neodymium(Nd^(3+))substitution...In this study,Cu_(0.25)Ni_(0.5)Zn_(0.25)Fe_(2-x)Nd_(x)O_(4)(0.000≤x≤0.100,andΔx=0.025)spinel ferrites were synthesized using the auto-combustion method to investigate the influence of neodymium(Nd^(3+))substitution on their structural,optical,dielectric,and magnetic properties.X-ray diffraction result confirms the formation of a face-centered cubic spinel structure,with the average crystallite size decreasing from 39 to 15 nm as Nd^(3+)concentration increases.Fourier transform infrared spectroscopy reveals characteristic absorption bands,affirming the spinel structure.Dielectric measurements over a broad frequency range show a higher dielectric constant and lower dielectric loss,indicating potential suitability for energy-efficient electronic applications.Magnetic analysis using a vibrating sample magnetometer demonstrates soft magnetic behavior,with saturation magnetization decreasing from82.69 to 66.80 emu/g and a tunable ratio(0.0221-0.0068)of remnant magnetization to saturation magnetization depending on Nd^(3+)content.In situ ultrasonic studies provides phase transition temperature(Curie temperature,T_(c))values ranging from 516 to 489 K,highlighting thermal stability and magnetic phase transition behavior.Furthermore,reflection loss measurements in the X-band frequency range(8-12 GHz)confirm the excellent electromagnetic interference shielding and radar absorption capabilities of Cu_(0.25)Ni_(0.5)Zn_(0.25)Fe_(2-x)Nd_(x)O_(4)spinel ferrites.These findings underscore the potential of Nd^(3+)-doped Cu-Ni-Zn spinel ferrites for advanced technological applications,including electronic devices,thermal sensors,and electromagnetic wave absorbers.展开更多
Spinels are an emerging class of advanced technological materials for spintronic,energy harvesting,and water-splitting applications.In this work,we explored the electronic,magnetic,optical,and transport properties of ...Spinels are an emerging class of advanced technological materials for spintronic,energy harvesting,and water-splitting applications.In this work,we explored the electronic,magnetic,optical,and transport properties of CaCe_(2)(S/Se)_(4)by density functional theory based on the Wien2k code.The energy released during optimization in ferromagnetic and antiferromagnetic states confirms that the ferromagnetic state is stable,which is further verified by negative formation energy.Heisenberg model and density of states report the Curie temperature and spin polarization.Half metallic ferromagnetism(HMF)regarding hybridization,crystal fields,exchange ene rgies,and double exchange mechanisms is discussed.The transfer of magnetic moments from Ce to Ca and S/Se and interstitial sites ensure the role of spin of electrons rather than clustering.Mo reover,the optical prope rties are addressed by dielectric constants,absorption,refraction,and optical loss.The first absorption peaks exist in infrared zone;others fall in visible to ultraviolet zones.The spin-up(↑)and spin-down(↓)channel thermoelectric factors combine and report the performance by conductivities,Seebeck coefficient,and power factor.Therefore,the studied materials'optical and thermoelectric behaviours will allow researchers to realize them for technological applications.展开更多
The degradation kinetics of polypropylene(PP)composites reinforced with titanium dioxide(TiO_(2))microparticles were investigated using various kinetic models.The composites were prepared through a twin-screw extrusio...The degradation kinetics of polypropylene(PP)composites reinforced with titanium dioxide(TiO_(2))microparticles were investigated using various kinetic models.The composites were prepared through a twin-screw extrusion process by varying the filler loading up to 30 wt%.The thermal degradation studies were conducted by using a thermogravimetric analyzer(TGA)at four different heating rates.The activation energies of the degradation of the composites were calculated using different model equations such as Friedman,Kissinger-Akahira-Sunnose(KAS),Ozawa-Flynn,Wall(OFW),and Starink.The Horowitz and Metzger method revealed an increasing trend in activation energy with higher filler loadings,attributed to enhanced barrier properties,improved dispersion,increased thermal stability,and the formation of protective layers.The Coats-Redfern method indicated a transition in the thermal degradation mechanism from the contracting sphere model to the contracting cylinder model with the incorporation of TiO_(2).The Criado model highlighted a shift from the Avrami–Erofeev equation(A_(2) mechanism)to the power law-contracting cylinder mechanism(R_(2))in PP/TiO_(2)composites,driven by improved nucleation and growth,filler-matrix interactions,and barrier effects.These findings demonstrate that the incorporation of TiO_(2)particles significantly enhances the thermal stability and alters the degradation mechanisms of PP composites,providing valuable insights for the development of advanced composite materials with improved thermal properties.展开更多
U-Pb ages of detrital zircons were newly dated for 4 Archean sandstones from the Pilbara craton in Australia, Wyoming craton in North America, and Kaapvaal craton in Africa. By using the present results with previousl...U-Pb ages of detrital zircons were newly dated for 4 Archean sandstones from the Pilbara craton in Australia, Wyoming craton in North America, and Kaapvaal craton in Africa. By using the present results with previously published data, we compiled the age spectra of detrital zircons for 2.9, 2.6, 2.3,1.0, and0.6 Ga sandstones and modern river sands in order to document the secular change in age structure of continental crusts through time. The results demonstrated the following episodes in the history of continental crust：（1） low growth rate of the continents due to the short cycle in production/destruction of granitic crust during the Neoarchean to Paleoproterozoic（2.9-23 Ga）,（2） net increase in volume of the continents during Paleo-to Mesoproterozoic（2.3-1.0 Ga）, and（3） net decrease in volume of the continents during the Neoproterozoic and Phanerozoic（after 1.0 Ga）. In the Archean and Paleoproterozoic, the embryonic continents were smaller than the modern continents, probably owing to the relatively rapid production and destruction of continental crust. This is indeed reflected in the heterogeneous crustal age structure of modern continents that usually have relatively small amount of Archean crusts with respect to the post-Archean ones. During the Mesoproterozoic, plural continents amalgamated into larger ones comparable to modern continental blocks in size. Relatively older crusts were preserved in continental interiors, whereas younger crusts were accreted along continental peripheries.In addition to continental arc magmatism, the direct accretion of intra-oceanic island arc around continental peripheries also became important for net continental growth. Since 1.0 Ga, total volume of continents has decreased, and this appears consistent with on-going phenomena along modern active arc-trench system with dominant tectonic erosion and/or arc subduction. Subduction of a huge amount of granitic crusts into the mantle through time is suggested, and this requires re-consideration of the mantle composition and heterogeneity.展开更多
The study examines the impact of variability in rainfall characteristics on maize yield in a tropical setting. The study design involves the collection and analyses of data on rainfall characteristics and maize yield ...The study examines the impact of variability in rainfall characteristics on maize yield in a tropical setting. The study design involves the collection and analyses of data on rainfall characteristics and maize yield at Gboko LGA in Benue State, Nigeria. The methodology adopted is the use of archival data on rainfall and maize yield for 30 years, collected from the Agro-Meteorological Unit and Farm Department of Akperan Orshi College of Agriculture, Yandev (AOCAY). The data was analyzed using mean, correlation and regression analysis to establish cause and effect relationship between rainfall characteristics and maize yield at the study area. The result of the correlation analysis showed that rain days and rainfall amount had strong positive relationship (r = 0.747 and r = 0.599, respectively) with maize yield. It was also observed that the rainfall characteristics jointly contributed 67.4% in explaining the variations in the yield of maize per hectare. The study concludes with the development of a model for predicting maize yield in Gboko LGA. The study also recommended the application of irrigation technology, use of appropriate management practices that ensured moisture conservation and improved crop species with shorter growing periods/less moisture consumption as adaptive measures to the changing rainfall pattern within the study area.展开更多
This paper reports on the assessment of the quality and quantity of castor oil from castor seeds collected from different regions in Tanzania. The castor seeds from Arusha, Dar es Salaam, Dodoma, Iringa, Kagera and Mo...This paper reports on the assessment of the quality and quantity of castor oil from castor seeds collected from different regions in Tanzania. The castor seeds from Arusha, Dar es Salaam, Dodoma, Iringa, Kagera and Morogoro regions in Tanzania were extracted by Soxhlet method using n-hexane and the oil yields were determined. The yields were 52.78%, 49.95%, 47.89%, 44.23%, 43.71% and 43.69% for Dodoma, Arusha, Iringa, Morogoro, Kagera and Dar es Salaam respectively. The physico-chemical parameters that were determined were refractive index (1.468 - 1.473), pH 5.7- 6.3, viscosity (0.943 - 0.954), specific gravity (165.50 - 187.46 mg KOH/g Oil), saponification value (76.68 - 80 mg KOH/g Oil), iodine value (76.68 - 80.12 g I2/100 g Oil), acid value (0.44 - 1.97 mg NaOH/g Oil), free fatty acid (0.22 - 0.99) and peroxide value (10.79 - 13.73). Fatty acid profile of castor oil was analysed using Shimadzu GCMS and ricinoleic acid ranged from 83.5% to 92.3% of the total fatty acids in the castor oils.展开更多
Grain boundary activity in nanocrystalline Al under an indenter is studied by using a multiscale method. It is found that grain boundaries and twin boundaries can be transformed into each other by emitting and absorbi...Grain boundary activity in nanocrystalline Al under an indenter is studied by using a multiscale method. It is found that grain boundaries and twin boundaries can be transformed into each other by emitting and absorbing dislocations. The transition processes might result in grain coarsening and refinement events. Dislocation reflection generated by a piece of stable grain boundary is also observed, because of the complex local atomic structure within the nanocrystalline Al. This implies that nanocrystalline metals might improve their internal structural stability with the help of some special local grain boundaries.展开更多
The effects of stacking fault energy,unstable stacking fault energy,and unstable twinning fault energy on the fracture behavior of nanocrystalline Ni are studied via quasicontinuum simulations.Two semi-empirical poten...The effects of stacking fault energy,unstable stacking fault energy,and unstable twinning fault energy on the fracture behavior of nanocrystalline Ni are studied via quasicontinuum simulations.Two semi-empirical potentials for Ni are used to vary the values of these generalized planar fault energies.When the above three energies are reduced,a brittle-to-ductile transition of the fracture behavior is observed.In the model with higher generalized planar fault energies,a nanocrack proceeds along a grain boundary,while in the model with lower energies,the tip of the nanocrack becomes blunt.A greater twinning tendency is also observed in the more ductile model.These results indicate that the fracture toughness of nanocrystalline face-centered-cubic metals and alloys might be efficiently improved by controlling the generalized planar fault energies.展开更多
Climate change has become a serious global challenge. Developing countries are the worst affected due to poor response mechanism to associated disasters. This study examined the application of the indigenous knowledge...Climate change has become a serious global challenge. Developing countries are the worst affected due to poor response mechanism to associated disasters. This study examined the application of the indigenous knowledge (IK) methods to predict the changes in seasonal rainfall. The study used data collected through individual interviews using a structured questionnaire. The study found vegetation changes (i.e. shading off leaves, excessive branching);changes in animal behavior (i.e. eating soil, restlessness), and other atmospheric indicators (i.e. changes in wind, color of stars and moon, earthquake, migrating of birds, swarming of bees, cold windy mornings and warm nights) being used to observe and monitor the changes in rainfall over the season. The study recommends a more detailed study to validate the IK and integrate it with the scientific knowledge so as to reduce local farmers’ vulnerability, increase resilience and strengthen their adaptive capacity to cope with climate change effects.展开更多
The insecticidal effect of four dosage rates of three botanicals namely Jatropha curcas,Heliathus annus and Cocos nucifera was tested on the maize weevil Sitophilus zeamais Mots..This is done for the purpose of findin...The insecticidal effect of four dosage rates of three botanicals namely Jatropha curcas,Heliathus annus and Cocos nucifera was tested on the maize weevil Sitophilus zeamais Mots..This is done for the purpose of finding a replacement for conventional insecticides which has been found to be harmful to man.The seed oil was applied topically at the rate of 0.1,0.2,0.3 and 0.4 mL per insect.There were a total of 20 insects per Petri-dish.There were four replicates per treatment.Insect mortality was recorded on 12 hourly basis for 48 hours.The results of insects treated with all dosage rates of C.nucifera showed a significantly higher mortality when compared with the control.In the case ofH.annus,insect mortality ranged from 40-100,70-100,60-100 and 80-100%and for J.curcas the result ranged from 0.0-100,40-100,80-100 and 80-100%for rates of 0.1,0.2,0.3 and 0.4 mL,respectively,from 12 hrs to 48 hrs post application.The control experiment remained at 0%level throughout the period of the experiments.展开更多
The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector ...The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector diffraction theory. Here we report a new method used to generate a needle of transversely polarized light beam with sub diffraction beam size of 0.366A that propagates without divergence over a long distance of about 22A in free space. We also expect that such a light needle of transversely polarized beam may find its applications in utilizing optical materials or instruments responsive to the transversal field only.展开更多
Mineral deposit mapping is very essential for sustainable and eco-friendly exploitation of natural resources.The Kingdom of Saudi Arabia has abundant natural resources such as natural gas,oil and minerals.It reserves ...Mineral deposit mapping is very essential for sustainable and eco-friendly exploitation of natural resources.The Kingdom of Saudi Arabia has abundant natural resources such as natural gas,oil and minerals.It reserves high quantity of minerals such as phosphates,bauxites,copper,gold and other industrial minerals.The red soil regions located in Hail and Qassim provinces of Saudi Arabia have rich amount of bauxite(major aluminum ore)deposits.In order to initiate the focus on mapping of mineral deposits along this area,standardized hyper-spectral analysis has been carried out by using Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER)satellite data.The spectral signature of gibbsite(major element in bauxite)samples is analyzed with reference to the spectral features of gibbsite in the visible near infrared and short-wave infrared bands electromagnetic spectrum.Advanced hyper-spectral transformations such as minimum noise fraction function and pixel purity index have been performed to identify the target end-member.The existence of the mineral is confirmed by comparing the spectral signatures of the endmember with the predefined spectral plots of ASTER and United States Geological Survey spectral libraries.Finally,the end-members are mapped and their abundance is estimated in 0–1 scale.The study has opened up new areas for mapping of bauxite deposits in the area and leads to eco-friendly exploitation of natural resources.It also validates the high potential of ASTER multispectral satellite data for the exploration and mapping of mineral resources.展开更多
Based on the vector diffraction theory, the effect of complex phase filters on intensity distribution of a radially polarized multi Gaussian beam in the focal region of high NA lens is theoretically investigated. It i...Based on the vector diffraction theory, the effect of complex phase filters on intensity distribution of a radially polarized multi Gaussian beam in the focal region of high NA lens is theoretically investigated. It is observed that a properly designed multi belt complex phase filter can generate subwavelength novel focal patterns including splitting of focal spots and generation of multiple focal spot segments such as eight, six and four focal spots along the optical axis are obtained. We expect that such an investigation is useful for optical manipulation and material processing, multiple high refractive index particle trapping technologies.展开更多
In this paper, we approach the problem of obtaining approximate solution of second-order initial value problems by converting it to an optimization problem. It is assumed that the solution can be approximated by a pol...In this paper, we approach the problem of obtaining approximate solution of second-order initial value problems by converting it to an optimization problem. It is assumed that the solution can be approximated by a polynomial. The coefficients of the polynomial are then optimized using simulated annealing technique. Numerical examples with good results show the accuracy of the proposed approach compared with some existing methods.展开更多
We propose a new approach for generating a multiple focal spot segment of subwavelength size, by tight focusing of a phase modulated radially polarized Laguerre Bessel Gaussian beam. The focusing properties are invest...We propose a new approach for generating a multiple focal spot segment of subwavelength size, by tight focusing of a phase modulated radially polarized Laguerre Bessel Gaussian beam. The focusing properties are investigated theoretically by .vector diffraction theory. We observe that the focal segment with multiple focal structures is separated with different axial distances and a super long dark channel can be generated by properly tuning the phase of the incident radially polarized Laguerre Bessel Gaussian beam. We presume that such multiple focal patterns and high intense beam may find applications in atom optics, optical manipulations and multiple optical trapping.展开更多
The study investigated constraints of women farmers access to ICTs for agricultural information in Oyo State.A total of 120 respondents were sampled.Data were retrieved using interview schedule and were analysed using...The study investigated constraints of women farmers access to ICTs for agricultural information in Oyo State.A total of 120 respondents were sampled.Data were retrieved using interview schedule and were analysed using descriptive and inferential statistics.Statistics reveal respondents average age,average household size and average monthly income as x=45.8,x=10.6 and x=₦7,800.34 respectively,majority(86.7%)were married,58.3%representing respondents with primary education.Mobile phone(x=0.98)was the most available among the respondents while poor ICTs infrastructure(x=1.55)and difficulty in the utilization of ICTs gadgets(x=1.62)ranked highest as constraints access to ICTs for agricultural information.Significant relationship existed between respondents average monthly income(r=0.492,p=0.000),educational level(χ^(2)=4.726,p=0.021)and the constraints access to ICTs for agricultural information.Scaling up the ICTs infrastructure base around farming clusters and capacity building like training on ICTs to access agricultural information retrieval is advocated for women farmers.展开更多
Chemical bath deposition technique has been used to deposit Ni-doped Sb2S3 thin films onto glass substrate. Doping was carried out by adding 1, 3 and 5 wt% of Ni. Bath temperature was kept as 10℃ and films were annea...Chemical bath deposition technique has been used to deposit Ni-doped Sb2S3 thin films onto glass substrate. Doping was carried out by adding 1, 3 and 5 wt% of Ni. Bath temperature was kept as 10℃ and films were annealed at 250℃ under vacuum. Polycrystalline nature of films with an orthorhombic phase was analyzed by X-ray diffraction technique. Scanning electron microscopy was used for morphological study which shows that grains are spherical. Optical measurements using transmittance data indicated that films have a direct band gap of 1.00 - 2.60 eV with an absorption coefficient of ~104 cm<sup>-1</sup> in visible range. The average value of electrical conductivity was calculated as 1.66, 1.11 and 1.06 (Ω·cm)<sup>-1</sup> for as-deposited films and 1.90, 2.08 and 1.15 (Ω·cm)<sup>-1</sup> for annealed films while refractive indices were found as 2.18 - 3.38 and 1.91 - 3.74 respectively. The obtained films can be used for solar cell applications due to their good absorbing properties like higher absorption coefficient and refractive index values.展开更多
Rainfall is crucial for many applications e.g. agriculture, health, water resources, energy among many others. However, quantitative rainfall estimation is normally a challenge especially in areas with sparse rain gau...Rainfall is crucial for many applications e.g. agriculture, health, water resources, energy among many others. However, quantitative rainfall estimation is normally a challenge especially in areas with sparse rain gauge network. This has introduced uncertainties in rainfall projections by climate models. This study evaluates the performance of three representative concentration pathways, RCP i.e. 4.5, 6.0 and 8.5 over Uganda using the Weather Research and Forecasting (WRF) model. It evaluates the model output using observed daily rain gauge data over the period 2006-2018 using Pearson correlation;relative root mean square error;relative mean error and skill scores (accuracy). It also evaluates the potential improvement in the performance of the WRF model with respective RCPs by applying bias correction. The bias correction is carried out using the quantile mapping method. A poor correlation with observed rainfall is generally found (-0.4 to +0.4);error magnitudes in the ranges of 1 to 3.5 times the long-term mean are observed. The RCPs presented different performances over different areas suggesting that no one RCP is universally valid. Application of bias correction did not produce realistic improvement in performance. Largely, the RCPs underestimated rainfall over the study area suggesting that the projected rainfall cases under these RCPs could be seriously underestimated. However, the study found RCP8.5 with slightly better performance and is thus recommended. Due to the general weak performance of the RCPs, the study recommends re-evaluating the assumptions under the RCPs for different regions or attempt to improve them using data assimilation.展开更多
The significance of the thermophysical properties of Tetra hybrid nanofluid in enhancing heat transmission in various applications like heat exchangers, automobiles, and solar storage cannot be overstated. These featu...The significance of the thermophysical properties of Tetra hybrid nanofluid in enhancing heat transmission in various applications like heat exchangers, automobiles, and solar storage cannot be overstated. These features can be tampered with when nanoparticles are been introduced into the base fluid to produce an improved heat carrier fluid for the system. This study investigates the impact of temperature-dependent properties on the movement of TiO2-SiO2-ZnO-Fe2O3/PAO Tetra hybrid nanofluid along a vertical porous surface with suction. The system of governing Partial Differential Equations (PDEs) was formulated and transformed into the system of coupled nonlinear third-order Ordinary Differential Equations (ODEs) by similarity techniques. The resulting ODEs were solved numerically using the shooting method and fourth order Runge-Kutta method with the aid of Maple 18.0 software. Using numerical and statistical methods, the study analyzes velocity, temperature profiles, skin friction coefficient, and Nusselt number. It was found that as the variable thermal conductivity parameter upsurges both the skin friction coefficient and Nusselt number intensify at the rate of 0.011697519 and 8.043581616 respectively. This study underscores the vital role of Tetra hybrid nanofluid’s thermophysical properties in improving heat transmission for diverse appli cations. By manipulating nanoparticles within the base fluid, the heat carrier fluid’s efficiency can be enhanced, critical for industries like automotive and enewable energy. These insights inform the design of more efficient heat exchange systems, advancing sustainability and performance in real-world scenarios.展开更多
基金Princess Nourah bint Abdulrahman University Researchers Supporting Project(No.PNURSP2025R479)。
文摘In this study,Cu_(0.25)Ni_(0.5)Zn_(0.25)Fe_(2-x)Nd_(x)O_(4)(0.000≤x≤0.100,andΔx=0.025)spinel ferrites were synthesized using the auto-combustion method to investigate the influence of neodymium(Nd^(3+))substitution on their structural,optical,dielectric,and magnetic properties.X-ray diffraction result confirms the formation of a face-centered cubic spinel structure,with the average crystallite size decreasing from 39 to 15 nm as Nd^(3+)concentration increases.Fourier transform infrared spectroscopy reveals characteristic absorption bands,affirming the spinel structure.Dielectric measurements over a broad frequency range show a higher dielectric constant and lower dielectric loss,indicating potential suitability for energy-efficient electronic applications.Magnetic analysis using a vibrating sample magnetometer demonstrates soft magnetic behavior,with saturation magnetization decreasing from82.69 to 66.80 emu/g and a tunable ratio(0.0221-0.0068)of remnant magnetization to saturation magnetization depending on Nd^(3+)content.In situ ultrasonic studies provides phase transition temperature(Curie temperature,T_(c))values ranging from 516 to 489 K,highlighting thermal stability and magnetic phase transition behavior.Furthermore,reflection loss measurements in the X-band frequency range(8-12 GHz)confirm the excellent electromagnetic interference shielding and radar absorption capabilities of Cu_(0.25)Ni_(0.5)Zn_(0.25)Fe_(2-x)Nd_(x)O_(4)spinel ferrites.These findings underscore the potential of Nd^(3+)-doped Cu-Ni-Zn spinel ferrites for advanced technological applications,including electronic devices,thermal sensors,and electromagnetic wave absorbers.
基金the Deanship of Research and Graduate Studies at King Khalid University,Saudi Arabia for funding this work through Large Research Project under grant number RGP2/630/45。
文摘Spinels are an emerging class of advanced technological materials for spintronic,energy harvesting,and water-splitting applications.In this work,we explored the electronic,magnetic,optical,and transport properties of CaCe_(2)(S/Se)_(4)by density functional theory based on the Wien2k code.The energy released during optimization in ferromagnetic and antiferromagnetic states confirms that the ferromagnetic state is stable,which is further verified by negative formation energy.Heisenberg model and density of states report the Curie temperature and spin polarization.Half metallic ferromagnetism(HMF)regarding hybridization,crystal fields,exchange ene rgies,and double exchange mechanisms is discussed.The transfer of magnetic moments from Ce to Ca and S/Se and interstitial sites ensure the role of spin of electrons rather than clustering.Mo reover,the optical prope rties are addressed by dielectric constants,absorption,refraction,and optical loss.The first absorption peaks exist in infrared zone;others fall in visible to ultraviolet zones.The spin-up(↑)and spin-down(↓)channel thermoelectric factors combine and report the performance by conductivities,Seebeck coefficient,and power factor.Therefore,the studied materials'optical and thermoelectric behaviours will allow researchers to realize them for technological applications.
文摘The degradation kinetics of polypropylene(PP)composites reinforced with titanium dioxide(TiO_(2))microparticles were investigated using various kinetic models.The composites were prepared through a twin-screw extrusion process by varying the filler loading up to 30 wt%.The thermal degradation studies were conducted by using a thermogravimetric analyzer(TGA)at four different heating rates.The activation energies of the degradation of the composites were calculated using different model equations such as Friedman,Kissinger-Akahira-Sunnose(KAS),Ozawa-Flynn,Wall(OFW),and Starink.The Horowitz and Metzger method revealed an increasing trend in activation energy with higher filler loadings,attributed to enhanced barrier properties,improved dispersion,increased thermal stability,and the formation of protective layers.The Coats-Redfern method indicated a transition in the thermal degradation mechanism from the contracting sphere model to the contracting cylinder model with the incorporation of TiO_(2).The Criado model highlighted a shift from the Avrami–Erofeev equation(A_(2) mechanism)to the power law-contracting cylinder mechanism(R_(2))in PP/TiO_(2)composites,driven by improved nucleation and growth,filler-matrix interactions,and barrier effects.These findings demonstrate that the incorporation of TiO_(2)particles significantly enhances the thermal stability and alters the degradation mechanisms of PP composites,providing valuable insights for the development of advanced composite materials with improved thermal properties.
基金supported by Japan Society of Promotion of Science (JSPS KAKENHI Grants-in-Aid for Scientific Research Grant Nos. 23224012, 26106002, and 26106005) from the Japanese Ministry of Education, Science, Sports, Technology, and Culture
文摘U-Pb ages of detrital zircons were newly dated for 4 Archean sandstones from the Pilbara craton in Australia, Wyoming craton in North America, and Kaapvaal craton in Africa. By using the present results with previously published data, we compiled the age spectra of detrital zircons for 2.9, 2.6, 2.3,1.0, and0.6 Ga sandstones and modern river sands in order to document the secular change in age structure of continental crusts through time. The results demonstrated the following episodes in the history of continental crust：（1） low growth rate of the continents due to the short cycle in production/destruction of granitic crust during the Neoarchean to Paleoproterozoic（2.9-23 Ga）,（2） net increase in volume of the continents during Paleo-to Mesoproterozoic（2.3-1.0 Ga）, and（3） net decrease in volume of the continents during the Neoproterozoic and Phanerozoic（after 1.0 Ga）. In the Archean and Paleoproterozoic, the embryonic continents were smaller than the modern continents, probably owing to the relatively rapid production and destruction of continental crust. This is indeed reflected in the heterogeneous crustal age structure of modern continents that usually have relatively small amount of Archean crusts with respect to the post-Archean ones. During the Mesoproterozoic, plural continents amalgamated into larger ones comparable to modern continental blocks in size. Relatively older crusts were preserved in continental interiors, whereas younger crusts were accreted along continental peripheries.In addition to continental arc magmatism, the direct accretion of intra-oceanic island arc around continental peripheries also became important for net continental growth. Since 1.0 Ga, total volume of continents has decreased, and this appears consistent with on-going phenomena along modern active arc-trench system with dominant tectonic erosion and/or arc subduction. Subduction of a huge amount of granitic crusts into the mantle through time is suggested, and this requires re-consideration of the mantle composition and heterogeneity.
文摘The study examines the impact of variability in rainfall characteristics on maize yield in a tropical setting. The study design involves the collection and analyses of data on rainfall characteristics and maize yield at Gboko LGA in Benue State, Nigeria. The methodology adopted is the use of archival data on rainfall and maize yield for 30 years, collected from the Agro-Meteorological Unit and Farm Department of Akperan Orshi College of Agriculture, Yandev (AOCAY). The data was analyzed using mean, correlation and regression analysis to establish cause and effect relationship between rainfall characteristics and maize yield at the study area. The result of the correlation analysis showed that rain days and rainfall amount had strong positive relationship (r = 0.747 and r = 0.599, respectively) with maize yield. It was also observed that the rainfall characteristics jointly contributed 67.4% in explaining the variations in the yield of maize per hectare. The study concludes with the development of a model for predicting maize yield in Gboko LGA. The study also recommended the application of irrigation technology, use of appropriate management practices that ensured moisture conservation and improved crop species with shorter growing periods/less moisture consumption as adaptive measures to the changing rainfall pattern within the study area.
文摘This paper reports on the assessment of the quality and quantity of castor oil from castor seeds collected from different regions in Tanzania. The castor seeds from Arusha, Dar es Salaam, Dodoma, Iringa, Kagera and Morogoro regions in Tanzania were extracted by Soxhlet method using n-hexane and the oil yields were determined. The yields were 52.78%, 49.95%, 47.89%, 44.23%, 43.71% and 43.69% for Dodoma, Arusha, Iringa, Morogoro, Kagera and Dar es Salaam respectively. The physico-chemical parameters that were determined were refractive index (1.468 - 1.473), pH 5.7- 6.3, viscosity (0.943 - 0.954), specific gravity (165.50 - 187.46 mg KOH/g Oil), saponification value (76.68 - 80 mg KOH/g Oil), iodine value (76.68 - 80.12 g I2/100 g Oil), acid value (0.44 - 1.97 mg NaOH/g Oil), free fatty acid (0.22 - 0.99) and peroxide value (10.79 - 13.73). Fatty acid profile of castor oil was analysed using Shimadzu GCMS and ricinoleic acid ranged from 83.5% to 92.3% of the total fatty acids in the castor oils.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No. 2011CB606403)
文摘Grain boundary activity in nanocrystalline Al under an indenter is studied by using a multiscale method. It is found that grain boundaries and twin boundaries can be transformed into each other by emitting and absorbing dislocations. The transition processes might result in grain coarsening and refinement events. Dislocation reflection generated by a piece of stable grain boundary is also observed, because of the complex local atomic structure within the nanocrystalline Al. This implies that nanocrystalline metals might improve their internal structural stability with the help of some special local grain boundaries.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB606403)
文摘The effects of stacking fault energy,unstable stacking fault energy,and unstable twinning fault energy on the fracture behavior of nanocrystalline Ni are studied via quasicontinuum simulations.Two semi-empirical potentials for Ni are used to vary the values of these generalized planar fault energies.When the above three energies are reduced,a brittle-to-ductile transition of the fracture behavior is observed.In the model with higher generalized planar fault energies,a nanocrack proceeds along a grain boundary,while in the model with lower energies,the tip of the nanocrack becomes blunt.A greater twinning tendency is also observed in the more ductile model.These results indicate that the fracture toughness of nanocrystalline face-centered-cubic metals and alloys might be efficiently improved by controlling the generalized planar fault energies.
文摘Climate change has become a serious global challenge. Developing countries are the worst affected due to poor response mechanism to associated disasters. This study examined the application of the indigenous knowledge (IK) methods to predict the changes in seasonal rainfall. The study used data collected through individual interviews using a structured questionnaire. The study found vegetation changes (i.e. shading off leaves, excessive branching);changes in animal behavior (i.e. eating soil, restlessness), and other atmospheric indicators (i.e. changes in wind, color of stars and moon, earthquake, migrating of birds, swarming of bees, cold windy mornings and warm nights) being used to observe and monitor the changes in rainfall over the season. The study recommends a more detailed study to validate the IK and integrate it with the scientific knowledge so as to reduce local farmers’ vulnerability, increase resilience and strengthen their adaptive capacity to cope with climate change effects.
文摘The insecticidal effect of four dosage rates of three botanicals namely Jatropha curcas,Heliathus annus and Cocos nucifera was tested on the maize weevil Sitophilus zeamais Mots..This is done for the purpose of finding a replacement for conventional insecticides which has been found to be harmful to man.The seed oil was applied topically at the rate of 0.1,0.2,0.3 and 0.4 mL per insect.There were a total of 20 insects per Petri-dish.There were four replicates per treatment.Insect mortality was recorded on 12 hourly basis for 48 hours.The results of insects treated with all dosage rates of C.nucifera showed a significantly higher mortality when compared with the control.In the case ofH.annus,insect mortality ranged from 40-100,70-100,60-100 and 80-100%and for J.curcas the result ranged from 0.0-100,40-100,80-100 and 80-100%for rates of 0.1,0.2,0.3 and 0.4 mL,respectively,from 12 hrs to 48 hrs post application.The control experiment remained at 0%level throughout the period of the experiments.
文摘The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector diffraction theory. Here we report a new method used to generate a needle of transversely polarized light beam with sub diffraction beam size of 0.366A that propagates without divergence over a long distance of about 22A in free space. We also expect that such a light needle of transversely polarized beam may find its applications in utilizing optical materials or instruments responsive to the transversal field only.
文摘Mineral deposit mapping is very essential for sustainable and eco-friendly exploitation of natural resources.The Kingdom of Saudi Arabia has abundant natural resources such as natural gas,oil and minerals.It reserves high quantity of minerals such as phosphates,bauxites,copper,gold and other industrial minerals.The red soil regions located in Hail and Qassim provinces of Saudi Arabia have rich amount of bauxite(major aluminum ore)deposits.In order to initiate the focus on mapping of mineral deposits along this area,standardized hyper-spectral analysis has been carried out by using Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER)satellite data.The spectral signature of gibbsite(major element in bauxite)samples is analyzed with reference to the spectral features of gibbsite in the visible near infrared and short-wave infrared bands electromagnetic spectrum.Advanced hyper-spectral transformations such as minimum noise fraction function and pixel purity index have been performed to identify the target end-member.The existence of the mineral is confirmed by comparing the spectral signatures of the endmember with the predefined spectral plots of ASTER and United States Geological Survey spectral libraries.Finally,the end-members are mapped and their abundance is estimated in 0–1 scale.The study has opened up new areas for mapping of bauxite deposits in the area and leads to eco-friendly exploitation of natural resources.It also validates the high potential of ASTER multispectral satellite data for the exploration and mapping of mineral resources.
文摘Based on the vector diffraction theory, the effect of complex phase filters on intensity distribution of a radially polarized multi Gaussian beam in the focal region of high NA lens is theoretically investigated. It is observed that a properly designed multi belt complex phase filter can generate subwavelength novel focal patterns including splitting of focal spots and generation of multiple focal spot segments such as eight, six and four focal spots along the optical axis are obtained. We expect that such an investigation is useful for optical manipulation and material processing, multiple high refractive index particle trapping technologies.
文摘In this paper, we approach the problem of obtaining approximate solution of second-order initial value problems by converting it to an optimization problem. It is assumed that the solution can be approximated by a polynomial. The coefficients of the polynomial are then optimized using simulated annealing technique. Numerical examples with good results show the accuracy of the proposed approach compared with some existing methods.
文摘We propose a new approach for generating a multiple focal spot segment of subwavelength size, by tight focusing of a phase modulated radially polarized Laguerre Bessel Gaussian beam. The focusing properties are investigated theoretically by .vector diffraction theory. We observe that the focal segment with multiple focal structures is separated with different axial distances and a super long dark channel can be generated by properly tuning the phase of the incident radially polarized Laguerre Bessel Gaussian beam. We presume that such multiple focal patterns and high intense beam may find applications in atom optics, optical manipulations and multiple optical trapping.
文摘The study investigated constraints of women farmers access to ICTs for agricultural information in Oyo State.A total of 120 respondents were sampled.Data were retrieved using interview schedule and were analysed using descriptive and inferential statistics.Statistics reveal respondents average age,average household size and average monthly income as x=45.8,x=10.6 and x=₦7,800.34 respectively,majority(86.7%)were married,58.3%representing respondents with primary education.Mobile phone(x=0.98)was the most available among the respondents while poor ICTs infrastructure(x=1.55)and difficulty in the utilization of ICTs gadgets(x=1.62)ranked highest as constraints access to ICTs for agricultural information.Significant relationship existed between respondents average monthly income(r=0.492,p=0.000),educational level(χ^(2)=4.726,p=0.021)and the constraints access to ICTs for agricultural information.Scaling up the ICTs infrastructure base around farming clusters and capacity building like training on ICTs to access agricultural information retrieval is advocated for women farmers.
文摘Chemical bath deposition technique has been used to deposit Ni-doped Sb2S3 thin films onto glass substrate. Doping was carried out by adding 1, 3 and 5 wt% of Ni. Bath temperature was kept as 10℃ and films were annealed at 250℃ under vacuum. Polycrystalline nature of films with an orthorhombic phase was analyzed by X-ray diffraction technique. Scanning electron microscopy was used for morphological study which shows that grains are spherical. Optical measurements using transmittance data indicated that films have a direct band gap of 1.00 - 2.60 eV with an absorption coefficient of ~104 cm<sup>-1</sup> in visible range. The average value of electrical conductivity was calculated as 1.66, 1.11 and 1.06 (Ω·cm)<sup>-1</sup> for as-deposited films and 1.90, 2.08 and 1.15 (Ω·cm)<sup>-1</sup> for annealed films while refractive indices were found as 2.18 - 3.38 and 1.91 - 3.74 respectively. The obtained films can be used for solar cell applications due to their good absorbing properties like higher absorption coefficient and refractive index values.
文摘Rainfall is crucial for many applications e.g. agriculture, health, water resources, energy among many others. However, quantitative rainfall estimation is normally a challenge especially in areas with sparse rain gauge network. This has introduced uncertainties in rainfall projections by climate models. This study evaluates the performance of three representative concentration pathways, RCP i.e. 4.5, 6.0 and 8.5 over Uganda using the Weather Research and Forecasting (WRF) model. It evaluates the model output using observed daily rain gauge data over the period 2006-2018 using Pearson correlation;relative root mean square error;relative mean error and skill scores (accuracy). It also evaluates the potential improvement in the performance of the WRF model with respective RCPs by applying bias correction. The bias correction is carried out using the quantile mapping method. A poor correlation with observed rainfall is generally found (-0.4 to +0.4);error magnitudes in the ranges of 1 to 3.5 times the long-term mean are observed. The RCPs presented different performances over different areas suggesting that no one RCP is universally valid. Application of bias correction did not produce realistic improvement in performance. Largely, the RCPs underestimated rainfall over the study area suggesting that the projected rainfall cases under these RCPs could be seriously underestimated. However, the study found RCP8.5 with slightly better performance and is thus recommended. Due to the general weak performance of the RCPs, the study recommends re-evaluating the assumptions under the RCPs for different regions or attempt to improve them using data assimilation.
文摘The significance of the thermophysical properties of Tetra hybrid nanofluid in enhancing heat transmission in various applications like heat exchangers, automobiles, and solar storage cannot be overstated. These features can be tampered with when nanoparticles are been introduced into the base fluid to produce an improved heat carrier fluid for the system. This study investigates the impact of temperature-dependent properties on the movement of TiO2-SiO2-ZnO-Fe2O3/PAO Tetra hybrid nanofluid along a vertical porous surface with suction. The system of governing Partial Differential Equations (PDEs) was formulated and transformed into the system of coupled nonlinear third-order Ordinary Differential Equations (ODEs) by similarity techniques. The resulting ODEs were solved numerically using the shooting method and fourth order Runge-Kutta method with the aid of Maple 18.0 software. Using numerical and statistical methods, the study analyzes velocity, temperature profiles, skin friction coefficient, and Nusselt number. It was found that as the variable thermal conductivity parameter upsurges both the skin friction coefficient and Nusselt number intensify at the rate of 0.011697519 and 8.043581616 respectively. This study underscores the vital role of Tetra hybrid nanofluid’s thermophysical properties in improving heat transmission for diverse appli cations. By manipulating nanoparticles within the base fluid, the heat carrier fluid’s efficiency can be enhanced, critical for industries like automotive and enewable energy. These insights inform the design of more efficient heat exchange systems, advancing sustainability and performance in real-world scenarios.
