Utilizing biomaterials for every conceivable purpose area, such as automobiles, sporting goods, medical, civil, and textile industries, is the aim of the research field. Applications of Natural Fiber (NF) reinforced polymer composites in structural and tribological engineering are rapidly expanding. For the first time in this work, Prosopis juliflora bark and two different types of NF (jute and kenaf) were reinforced with polyester matrix by the hand layup method. The objective of the work is to determine the wear performance and viscoelastic properties of the new hybrid bio-composite. Under dry contact conditions, the tribological performance of the proposed hybrid composite material was evaluated using a range of process parameters, including sliding distance (1000-2000 m), applied load (10-50 N), and sliding velocity (1-5 m/s). The wear behaviour of the fabricated NF composite was greatly enhanced (17.5 x10-8 mm3 /N-mm) by the higher composition of kenaf fibers has been observed. The dynamic mechanical analysis (DMA) showed that the manufactured composites had high storage modulus (4.1 GPa) and loss modulus (3.8 GPA). SEM was used to investigate and propose a potential wear mechanism for the developed composites by evaluating the exterior geomorphology of samples after wear tests. AFM provided details on the fiber surface properties of hybrid composites.

Abstract: An experiment was conducted to standardize the critical boron level in soil and leaf samples of coconut palms grown in a typical Entisol of the Onattukara region of Kerala, India. Graded levels of boron as borax were applied at 0, 6, 12, 18 and 24 g per palm per year in four split doses. The critical boron level in soil and leaves was standardized using the following methods: the Cate and Nelson graphical (CN) method, the Mistcherlich equation (ME), and the quadratic plateau response (QP) method. In the CN method, the critical level of boron in soil and leaves was 0.48 mg kg-1 and 11.5 mg kg-1, respectively. In the ME model, the critical boron level in soil and leaves was 0.46 mg kg-1 and 7.55 mg kg-1, respectively. In the QP response curve, the critical level of boron in soil was estimated to be 0.87 mg kg-1, and in the leaf, the critical level was found to be 13.27 mg kg-1. Because the level estimated via the graphical method and by the Mistcherlich equation is similar with regard to the soil boron, 0.48 mg kg-1 can be considered as the critical boron level in soil. Regarding the critical boron level in the leaf, values estimated via the CN method and the QP response curve are in proximity, and, hence, the critical boron level in leaf is 13.27 mg kg-1. These results suggest that the application of 160 g of borax in four split doses when the levels of boron in soil and leaves fall below the estimated critical values for better use efficiency.

Foram estudadas as correlações lineares simples, múltiplas e não-lineares entre os parâmetros erosividade da chuva, da enxurrada e da chuva-enxurrada e as perdas de solo provocadas por chuvas erosivas num Luvissolo. Os dados correspondentes ao período de 1986-1990 foram obtidos na estação experimental de Sumé (PB), pertencente à Universidade Federal da Paraíba - UFPB. Para determinar os parâmetros erosividade da chuva, da enxurrada e da chuva-enxurrada, foram analisadas chuvas individuais registradas em 136 pluviogramas. O volume de enxurrada isolado ou em combinação com características da chuva contribuiu, de forma significativa, para melhorar a estimativa das perdas de solo de chuvas individuais. Os parâmetros erosividade da chuva-enxurrada a(Vu α I30)b; a(Vu α I5)b; a(EIA)b e da enxurrada a(Vu)b foram os melhores estimadores das perdas de solo para chuvas individuais. Dentre os parâmetros da erosividade da chuva, os que melhor se correlacionaram com as perdas de solo foram aqueles que incluíram o produto do volume da chuva pela intensidade máxima em trinta minutos a(VrI30).

Simple linear, multiple linear and nonlinear correlations between rainfall, runoff and rainfall-runoff erosivity parameters were studied, as well as soil losses caused by erosive rainfall on a Haplargids. Data were obtained in the period from 1986 to 1990 at the Experimental Station in Sumé, which belongs to the Universidade Federal da Paraíba - UFPB, Paraíba State, Brazil. Individual rainfalls registered in 136 rain gauges were analyzed for the determination of rainfall, runoff and rainfall-runoff erosivity parameters. The runoff volume, single or combined with rainfall characteristics improved the estimated soil losses of individual rainfall significantly. The erosivity parameters for rainfall-runoff a(Vu α I30)b; a(Vu α I5)b; a(EIA)b and runoff a(Vu)b were best fit to estimate soil losses caused by individual storms. The rainfall erosivity parameters that included the product of rainfall volume at a maximum intensity for thirty minutes (VrI30) were the ones that correlated best with soil losses.

Foram estudados os efeitos do desmatamento da caatinga sobre as perdas de solo e água provocadas por chuvas erosivas num Luvissolo. Os dados relativos aos anos de 1983-1990 foram obtidos na Estação Experimental de Sumé (PB), pertencente à Universidade Federal da Paraíba - UFPB. Os tratamentos consistiram de duas parcelas desmatadas, uma parcela com caatinga nativa, uma parcela com caatinga nova, duas macroparcelas com caatinga nativa e duas macroparcelas desmatadas. Nas parcelas desmatadas, as perdas de solo foram de 61,7 e 47,7 t ha-1 e as perdas de água de 224,2 e 241,0 mm. A parcela com caatinga nativa, quando comparada com a parcela desmatada, reduziu a perda de solo em cerca de 98% e a perda de água em torno de 73%. Nas macroparcelas desmatadas foram observadas perdas anuais de solo de 31 e 26 t ha-1 e de água de 151,3 e 131,5 mm. Nas macroparcelas com caatinga, houve uma redução de aproximadamente 99% das perdas de solo e 90% das perdas de água, em relação às macroparcelas desmatadas.

The effects of native semiarid vegetation deforestation on soil and water losses caused by erosive rainfall in Haplargid were studied. The data covering the period of 1983-1990 were obtained from the Experimental Station of Sumé (Paraíba, from Brazil) of the Universidade Federal da Paraíba (UFPB). The treatments consisted of two deforested runoff plots, two runoff plots with native semiarid vegetation, two deforested watersheds and two watersheds with native semiarid vegetation. The deforested runoff plots, had soil losses of 61.7 and 47.7 t ha-1and water losses of 224.2 and 241.0 mm, respectively. When compared with the deforested runoff plots, the runoff plots with native semiarid vegetation reduced the soil losses in about 98% and the water losses in about 73%. The deforested macro runoff plots contributed with soil losses of 31.0 and 26.0 t ha-1 and water losses of 151.3 and 131.5 mm, respectively. In the macro runoff plots with native semiarid vegetation, there was a reduction of approximately 99% of soil losses and 90% of water losses, compared to the deforested macro runoff plots.

Foram estudadas correlações lineares simples entre os parâmetros erosividade da chuva e da enxurrada e as perdas de solo provocadas por chuvas erosivas num solo Bruno Não-Cálcico Vértico. Os dados correspondentes aos anos de 1986-1990 foram obtidos na estação experimental de Sumé (PB), pertencente à Universidade Federal da Paraíba-UFPB. Os parâmetros erosividade da chuva e da enxurrada estudados foram: (a) altura total da chuva (P), em mm; (b) intensidades máximas (In), ocorridas nos tempos de 5; 10; 15; 20; 25; 30; 35; 40; 45; 50; 55; 60 e 120 minutos, respectivamente, em mm h-1; (c) energia cinética total, pelo método de Wischmeier e Smith (Ec) e pelo método de Wagner e Massambani (EcW), em MJ ha-1; (d) somatório da energia cinética de intensidades superior a 10 mm h-1 (Ec > 10 e EcW > 10) em MJ ha-1; (e) somatório da energia cinética de intensidades superior a 25 mm h-1 (Ec > 25 e EcW > 25), em MJ ha-1; (f) produtos da energia cinética total pelas intensidades máximas de chuva em intervalos crescentes de tempo (EIn), ou seja: EI5; EI10; EI15; EI20; EI25; EI30; EIW30; EI35; EI40; EI45; EI50; EI55; EI60 e EI120, em MJ mm ha-1 h-1; (g) produtos da altura total da chuva pelas intensidades máximas das chuvas em intervalos crescentes de tempo (PIn), ou seja: PI5; PI10; PI15; PI20; PI25; PI30; PI35; PI40; PI45; PI50; PI55; PI60 e PI120, em mm² h-1, e (h) volume de enxurrada (Vu), em m³. O parâmetro volume de enxurrada (Vu) foi o que melhor estimou (r = 0,812) as perdas de solo em Sumé (PB). Dentre os parâmetros erosividade da chuva, o que melhor se correlacionou com as perdas de solo foi o parâmetro PI25 (r = 0,753). As equações de Wischmeier & Smith e de Wagner & Massambani, utilizadas no cálculo da energia cinética total da chuva, apresentaram o mesmo grau de precisão na estimativa das perdas de solo.

Simple linear correlations among runoff and rainfall erosivity parameters and soil losses caused by erosivity rainfall in Haplargids were studied. Data related to 1986-1990 were obtained in the Experimental Station at Sumé-Brazil. The rainfall erosivity parameters were the following: a) total height of the rainfall (P) in mm; b) maximum intensity (In): I5; I10; I15; I20; I25; I30; I35; I40; I45; I50; I55; I60 and I120 minutes in mm h-1, respectively; c) total kinetic energy by the Wischmeier & Smith's and by the Wagner & Massambani's methods in MJ ha-1 (KE and KEW); d) kinetic energy of intensities higher than 10 mm h-1 (KE > 10 and KEW > 10) in MJ ha-1; e) kinetic energy of intensities higher than 25 mm h-1 (KE > 25 e KEW > 25) in MJ ha-1; f) total kinetic energy products by maximum intensities rainfall (EIn): EI5, EI10; EI15; EI20; EI25; EI30 EIW30; EI35; EI40; EI45; EI50; EI55; EI60 and EI120 in MJ mm ha-1h-1, respectively; g) total height of rainfall products by maximum intensity rainfall (PIn): PI5, PI10, PI15; PI20; PI25; PI30; PI35; PI40; PI45; PI50; PI55; PI60 and PI120 in mm² h-1, respectively; and h) runoff volume (Vu) in m³. The runoff erosivity parameter (Vu) best estimated (r = 0.812) the soil losses in Sumé-PB. Among rainfall erosivity parameters, the PI25 type (r = 0.753) was best correlated with soil losses. The Wischmeier & Smith's and the Wagner & Massambani's equations used to calculate the total kinetic energy rainfall presented the same degree of precision in estimating soil losses.