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 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 po...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
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
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
This paper evaluates the skills of physical Parameterization schemes in simulating extreme rainfall events over Dar es Salaam Region, Tanzania using the Weather Research and Forecasting (WRF) model. The model skill is...This paper evaluates the skills of physical Parameterization schemes in simulating extreme rainfall events over Dar es Salaam Region, Tanzania using the Weather Research and Forecasting (WRF) model. The model skill is determined during the 21 December 2011 flooding event. Ten sensitivity experiments have been conducted using Cumulus, Convective and Planetary boundary layer schemes to find the best combination and optimize the WRF model for the study area for heavy rainfall events. Model simulation results were verified against observed data using standard statistical tests. The model simulations show encouraging and better statistical results with the combination of Kain-Fritsch cumulus parameterization scheme, Lin microphysics scheme and Asymmetric Convection Model 2 (ACM2) planetary boundary scheme than any other combinations of physical parameterization schemes over Dar es Salaam region.展开更多
Unlike other balistids, grey triggerfish Batistes capriscus occur in social groups in subtropical reef assemblages andhave been noted to cooperate in capturing large crustacean prey. The objective of this study were t...Unlike other balistids, grey triggerfish Batistes capriscus occur in social groups in subtropical reef assemblages andhave been noted to cooperate in capturing large crustacean prey. The objective of this study were to determine the structure ofdominance hierarchies of these social groups and the factors that influence hierarchies of wild-caught grey triggerfish in a naturalisticsetting. From observations of four groups of triggerfish (n - 19 fish) in both dyad and group (4-5 fish) settings, we providea description of triggerfish behaviors and coloration patterns and an explanation of the social context in which suites of behaviorsare used by dominant, middle-ranking, and subordinate fish. Sixteen behaviors and nine coloration patterns were noted forgrey triggerfish. Grey triggerfish groups form linear hierarchies in both dyads and groups as measured by Landau's Index ofLinearity (h = 1.0 for Groups 1, 3, and 4 and h = 0.95 for Group 2 in dyads; h = 1.0 for all groups in group settings). Dyadic hierarchies,however, were not necessarily good predictors of the hierarchies found in larger group settings, as they only predictedtwo of the four group hierarchies. Sex played no role in influencing status or behavior. Size had the greatest influence on dominancestatus, with larger fish being more dominant than smaller fish. An individual's dominance ranking influenced both bodycoloration and posture. These results suggest that color patterns and body postures may also be used by observers as an indicatorof an individual's social status in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
This investigative study is focused on the impact of wavelet on traditional forecasting time-series models,which significantly shows the usage of wavelet algorithms.Wavelet Decomposition(WD)algorithm has been combined...This investigative study is focused on the impact of wavelet on traditional forecasting time-series models,which significantly shows the usage of wavelet algorithms.Wavelet Decomposition(WD)algorithm has been combined with various traditional forecasting time-series models,such as Least Square Support Vector Machine(LSSVM),Artificial Neural Network(ANN)and Multivariate Adaptive Regression Splines(MARS)and their effects are examined in terms of the statistical estimations.The WD has been used as a mathematical application in traditional forecast modelling to collect periodically measured parameters,which has yielded tremendous constructive outcomes.Further,it is observed that the wavelet combined models are classy compared to the various time series models in terms of performance basis.Therefore,combining wavelet forecasting models has yielded much better results.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
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 the last decade, Daubechies’ wavelets have been successfully used in many signal processing paradigms. The construction of these wavelets via two channel perfect reconstruction filter bank requires the identificat...In the last decade, Daubechies’ wavelets have been successfully used in many signal processing paradigms. The construction of these wavelets via two channel perfect reconstruction filter bank requires the identification of necessary conditions that the coefficients of the filters and the roots of binomial polynomials associated with them should exhibit. In this paper, orthogonal and Biorthogonal Daubechies families of wavelets are considered and their filters are derived. In particular, the Biorthogonal wavelets Bior3.5, Bior3.9 and Bior6.8 are examined and the zeros distribution of their polynomials associated filters are located. We also examine the locations of these zeros of the filters associated with the two orthogonal wavelets db6 and db8.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
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
The threat to human, fauna and flora life posed by pollution due to gas flaring cannot be over-emphasized. Gas flared often resulted in some environmental degradation, one of such influence is soil pollution and poor ...The threat to human, fauna and flora life posed by pollution due to gas flaring cannot be over-emphasized. Gas flared often resulted in some environmental degradation, one of such influence is soil pollution and poor crop yield. This study examined the effect of gas flaring on soil and cassava productivity in Ebedei, Ukwuani LGA, Delta State. For the purpose of data collection, five (5) experimental sites were systematically selected around the flare site in Ebedei and a control site at Obiaruku. Soil samples were collected at surface 0 - 10 cm and 10 - 20 cm at distance of 50 m, 100 m, 150 m, 200 m and 250 m apart respectively away from the bund wall of the flare. The data generated were analysed using multiple regression and paired t-test analyses. The study revealed that the soils found in Ebedei have high composition of sand and soil temperature and are acidic. The soil electrical conductivity, Phosphorous, Nitrogen, Potassium and Sodium were very low. More so, the yield of cassava increases with a corresponding increase in distances from flare site. The first hypothesis revealed that there is significant variation in soil nutrients as distance increases from gas flare sites. This is evident from F value of 234.99 which is greater than the critical table value of 4.39. Furthermore, as flare distance increases, so also the organic carbon, electrical conductivity and Nitrogen increase. The second hypothesis revealed that there is a significant difference in cassava yield at gas-flared area and the non-flared area which is evident at t (6.032) is greater than the critical table (1.895) at P 0.05. It is therefore recommended that Government and FEPA should enact environmental Policies and revisit and review existing environmental and oil drilling laws in Nigeria with a view of updating them to international and environmental friendly standards.展开更多
One-dimensional photonic crystals (1D PhCs) have a unique ability to control the propagation of light waves, however certain classes of 1D oxides remain relatively unexplored for use as PhCs. Specifically, there has n...One-dimensional photonic crystals (1D PhCs) have a unique ability to control the propagation of light waves, however certain classes of 1D oxides remain relatively unexplored for use as PhCs. Specifically, there has not been a comparative study of the three different 1D PhC structures to compare the influence of layer thickness, number, and refractive index on the ability of the PhCs to control light transmission. Herein, we use the transfer matrix method (TMM) to theoretically examine the transmission of 1D PhCs composed of layers of TiO<sub>2</sub>/SiO<sub>2</sub>, TiO<sub>2</sub>/SnO<sub>2</sub>, SiO<sub>2</sub>/SnO<sub>2</sub>, and combinations of the three with various top and bottom layer thicknesses to cover a substantial region of the electromagnetic spectrum (UV to NIR). With increasing layer numbers for TiO<sub>2</sub>/SiO<sub>2</sub> and SiO<sub>2</sub>/SnO<sub>2</sub>, the edges became sharper and wider and the photonic bandgap width increased. Moreover, we demonstrated that PhCs with significantly thick TiO<sub>2</sub>/SiO<sub>2</sub> layers had a high transmittance for a wide bandgap, allowing for wide-band optical filter applications. These different PhC architectures could enable a variety of applications, depending on the properties needed.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
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
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.
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This paper evaluates the skills of physical Parameterization schemes in simulating extreme rainfall events over Dar es Salaam Region, Tanzania using the Weather Research and Forecasting (WRF) model. The model skill is determined during the 21 December 2011 flooding event. Ten sensitivity experiments have been conducted using Cumulus, Convective and Planetary boundary layer schemes to find the best combination and optimize the WRF model for the study area for heavy rainfall events. Model simulation results were verified against observed data using standard statistical tests. The model simulations show encouraging and better statistical results with the combination of Kain-Fritsch cumulus parameterization scheme, Lin microphysics scheme and Asymmetric Convection Model 2 (ACM2) planetary boundary scheme than any other combinations of physical parameterization schemes over Dar es Salaam region.
基金funded by a Research Enhancement Grant to KLL from Southwest Texas State University, San Marcos,TX, USA
文摘Unlike other balistids, grey triggerfish Batistes capriscus occur in social groups in subtropical reef assemblages andhave been noted to cooperate in capturing large crustacean prey. The objective of this study were to determine the structure ofdominance hierarchies of these social groups and the factors that influence hierarchies of wild-caught grey triggerfish in a naturalisticsetting. From observations of four groups of triggerfish (n - 19 fish) in both dyad and group (4-5 fish) settings, we providea description of triggerfish behaviors and coloration patterns and an explanation of the social context in which suites of behaviorsare used by dominant, middle-ranking, and subordinate fish. Sixteen behaviors and nine coloration patterns were noted forgrey triggerfish. Grey triggerfish groups form linear hierarchies in both dyads and groups as measured by Landau's Index ofLinearity (h = 1.0 for Groups 1, 3, and 4 and h = 0.95 for Group 2 in dyads; h = 1.0 for all groups in group settings). Dyadic hierarchies,however, were not necessarily good predictors of the hierarchies found in larger group settings, as they only predictedtwo of the four group hierarchies. Sex played no role in influencing status or behavior. Size had the greatest influence on dominancestatus, with larger fish being more dominant than smaller fish. An individual's dominance ranking influenced both bodycoloration and posture. These results suggest that color patterns and body postures may also be used by observers as an indicatorof an individual's social status in
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This investigative study is focused on the impact of wavelet on traditional forecasting time-series models,which significantly shows the usage of wavelet algorithms.Wavelet Decomposition(WD)algorithm has been combined with various traditional forecasting time-series models,such as Least Square Support Vector Machine(LSSVM),Artificial Neural Network(ANN)and Multivariate Adaptive Regression Splines(MARS)and their effects are examined in terms of the statistical estimations.The WD has been used as a mathematical application in traditional forecast modelling to collect periodically measured parameters,which has yielded tremendous constructive outcomes.Further,it is observed that the wavelet combined models are classy compared to the various time series models in terms of performance basis.Therefore,combining wavelet forecasting models has yielded much better results.
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.
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 the last decade, Daubechies’ wavelets have been successfully used in many signal processing paradigms. The construction of these wavelets via two channel perfect reconstruction filter bank requires the identification of necessary conditions that the coefficients of the filters and the roots of binomial polynomials associated with them should exhibit. In this paper, orthogonal and Biorthogonal Daubechies families of wavelets are considered and their filters are derived. In particular, the Biorthogonal wavelets Bior3.5, Bior3.9 and Bior6.8 are examined and the zeros distribution of their polynomials associated filters are located. We also examine the locations of these zeros of the filters associated with the two orthogonal wavelets db6 and db8.
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.
文摘The threat to human, fauna and flora life posed by pollution due to gas flaring cannot be over-emphasized. Gas flared often resulted in some environmental degradation, one of such influence is soil pollution and poor crop yield. This study examined the effect of gas flaring on soil and cassava productivity in Ebedei, Ukwuani LGA, Delta State. For the purpose of data collection, five (5) experimental sites were systematically selected around the flare site in Ebedei and a control site at Obiaruku. Soil samples were collected at surface 0 - 10 cm and 10 - 20 cm at distance of 50 m, 100 m, 150 m, 200 m and 250 m apart respectively away from the bund wall of the flare. The data generated were analysed using multiple regression and paired t-test analyses. The study revealed that the soils found in Ebedei have high composition of sand and soil temperature and are acidic. The soil electrical conductivity, Phosphorous, Nitrogen, Potassium and Sodium were very low. More so, the yield of cassava increases with a corresponding increase in distances from flare site. The first hypothesis revealed that there is significant variation in soil nutrients as distance increases from gas flare sites. This is evident from F value of 234.99 which is greater than the critical table value of 4.39. Furthermore, as flare distance increases, so also the organic carbon, electrical conductivity and Nitrogen increase. The second hypothesis revealed that there is a significant difference in cassava yield at gas-flared area and the non-flared area which is evident at t (6.032) is greater than the critical table (1.895) at P 0.05. It is therefore recommended that Government and FEPA should enact environmental Policies and revisit and review existing environmental and oil drilling laws in Nigeria with a view of updating them to international and environmental friendly standards.
文摘One-dimensional photonic crystals (1D PhCs) have a unique ability to control the propagation of light waves, however certain classes of 1D oxides remain relatively unexplored for use as PhCs. Specifically, there has not been a comparative study of the three different 1D PhC structures to compare the influence of layer thickness, number, and refractive index on the ability of the PhCs to control light transmission. Herein, we use the transfer matrix method (TMM) to theoretically examine the transmission of 1D PhCs composed of layers of TiO<sub>2</sub>/SiO<sub>2</sub>, TiO<sub>2</sub>/SnO<sub>2</sub>, SiO<sub>2</sub>/SnO<sub>2</sub>, and combinations of the three with various top and bottom layer thicknesses to cover a substantial region of the electromagnetic spectrum (UV to NIR). With increasing layer numbers for TiO<sub>2</sub>/SiO<sub>2</sub> and SiO<sub>2</sub>/SnO<sub>2</sub>, the edges became sharper and wider and the photonic bandgap width increased. Moreover, we demonstrated that PhCs with significantly thick TiO<sub>2</sub>/SiO<sub>2</sub> layers had a high transmittance for a wide bandgap, allowing for wide-band optical filter applications. These different PhC architectures could enable a variety of applications, depending on the properties needed.
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.