Geometric Diameter Research Articles

Heat transfer of suspended carbon nanotube yarn to gases

We investigate the pressure dependence of heat transfer to ambient gases for a suspended carbon nanotube yarn. The heat transport of the yarn including the heat exchange with surrounding gases is investigated using a simple one-dimensional heat transport model under Joule heating of the yarn. It is revealed that the effective diameter of the yarn for heat exchange is much smaller than the geometrical diameter of the yarn. This smaller effective diameter for heat exchange should contribute to realizing higher sensitivity and sensing over a wider range of pressures for heat-exchange-type vacuum gauges and flow sensors.

Hand preference is selectively related to common and internal carotid arterial asymmetry

ABSTRACTThis study documents relationships between handedness and carotid arterial asymmetries. The article is divided into two sections, considering first geometric (n = 195) and then haemodynamic (n = 228) asymmetries. In the geometric study, diameters, lengths, and angles of the common carotid arteries in left and right-handed participants were measured using computed tomography angiography scans. Resistance to blood flow was calculated according to Poiseuille’s formula. In the haemodynamic study, peak systolic and end-diastolic velocity, vessel diameter, and volume flow rate of the common, internal, and external carotid arteries were measured in left and right-handed participants, using Doppler ultrasonography. The findings reveal for the first time that the extracranial arteries supplying the cerebral hemispheres are asymmetrical in a direction that increases blood flow to the hemisphere dominant for handedness. Significant handedness interactions were identified in arterial length, diameter, resistance to blood flow, velocity and flow volume rate (p < .001). Arterial resistance and volume flow rates significantly predicted hand preference and proficiency. Our findings reveal a vascular correlate of handedness, but causality cannot be determined from this study alone. These asymmetries appear to be independent of aortic arch anomalies, suggesting a top-down, possibly demand-driven, pattern of development.

EFFECT OF RELATION BETWEEN MOISTURE CONTENT AND TERMINAL VELOCITY ON WHEAT AND BARLEY GRAINS

Terminal velocity (TV) is one of the important aerodynamic properties of materials, including seeds of agricultural crops that are necessary to design of pneumatic conveying systems, fluidized bed dryer and cleaning the product from foreign materials. Among the properties, terminal velocity is very important. This investigation aimed to provide database about the physical properties (length, width, thickness, volume, percent of sphericity, geometric diameter, arithmetic diameter, transverse surface area and flat surface area) and terminal velocity of crop grains at different moisture contents. Two different grains crop were tested such as wheat grains (Sakha 93-variety) and barley (Giza 130-variety). The wheat and barley grains were tested at different moisture contents of 9, 11, 13, 15 and 17 %. The main results in this study can be summarized as follows: -Length, width, and thickness for wheat grains were 6.18, 2.80 and 2.21 mm respectively. Meanwhile, length, width, and thickness for barley grains were 9.85, 2.49 and 3.52 mm respectively. -Volumes for wheat and barley were 30.52 and 45.2 mm3 respectively. -Percents of sphericity for wheat and barley were 62.75 and 44.87% respectively. -Geometric and arithmetic diameters for wheat and barley were 3.88, 4,21 and 4.42, 5.29 mm respectively. -By increasing moisture content of all grains, the terminal velocity increased in general. The highest terminal velocities were 8.53 and 7.8 m/ s for wheat and barley grains respectively at moisture content of 17 %. Meanwhile, the lowest terminal velocities were 7.8 and 6.98 m/ s for wheat and barley grains respectively at moisture content of 9 %.

Measurement of true ileal phosphorus digestibility in meat and bone meal for broiler chickens using the direct method

The aim of the present study was to determine the true ileal phosphorus (P) digestibility in meat and bone meal (MBM) for broiler chickens using the direct method. Four MBM samples (coded as MBM-1, MBM-2, MBM-3 and MBM-4) were obtained and analysed for nutrient composition, particle size distribution and bone to soft tissue ratio. The total P concentration of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 38, 60, 60 and 41g/kg, respectively. The corresponding geometric mean particle diameter and bone to soft tissue ratio were 0.866, 0.622, 0.875 and 0.781mm, and 1:1.49, 1:0.98, 1:0.92 and 1:1.35, respectively. Five experimental diets, including four diets with similar P concentration (4.4g/kg) from each MBM and a P-free diet, were developed. Meat and bone meal served as the sole source of P in the MBM diets. Titanium dioxide (3g/kg) was incorporated in all diets as an indigestible marker. Each experimental diet was randomly allotted to six replicate cages (eight birds per cage) and offered from day 28–31 posthatch. Apparent ileal P digestibility was calculated by the indicator method and basal ileal endogenous P losses, determined following the feeding of the P-free diet, were used to calculate the true ileal P digestibility. Basal ileal endogenous P losses were determined to be 354mg/kg dry matter intake. True ileal P digestibility coefficients of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 0.623, 0.617, 0.615 and 0.444, respectively. True ileal P digestibility of MBM-1, MBM-2 and MBM-3 were similar (P>0.05) and higher (P<0.05) than that of MBM-4. The present findings suggest that the direct method may be considered for use in the determination of true P digestibility in feed ingredients for poultry, but further studies are clearly needed to validate this possibility. The present data also suggest that the general assumption that P in MBM is highly available is not valid.

Effect of sugarcane waste in the control of interrill erosion

The cultivation of sugarcane uses different cropping systems that result in varying quantities of crop waste, this may influence soil erosion. The objective of this study was to evaluate the loss of soil and water, the infiltration rate, and soil surface roughness in an area cultivated with sugarcane (Saccharum spp.). Six treatments with different levels of plant waste were evaluated: sugarcane without plant waste; sugarcane with 4.0 Mg ha-1 of waste; sugarcane with 8.0 Mg ha-1 of waste; sugarcane with 12.0 Mg ha-1 of waste; sugarcane with 16.0 Mg ha-1 of waste; and burned sugarcane. The treatments were arranged in a randomized block design with four replications, totalling 24 experimental plots. As soil depth increased, there is reduction in macroporosity, total soil porosity, organic carbon content, mean geometric diameter and weighted mean diameter of the soil aggregates, whereas the bulk density of the soil displays the opposite trend. The presence of sugarcane waste on the soil surface increases the time required for the initiation of surface runoff. Sugarcane waste does not alter soil surface roughness, and at the minimum amount of waste administered (4 Mg ha-1) reduces losses of soil and water and increases the infiltration rate. The lack of soil surface coverage after harvesting the sugarcane contributes to soil and water loss, and reduces the rate of stable infiltration of water into the soil.

Caracterização e quantificação de dejetos de poedeiras alimentadas com milho de diferentes granulometrias

Este trabalho foi desenvolvido com o objetivo de avaliar os efeitos de diferentes graus de moagem do milho sobre a caracterização e quantificação dos dejetos de poedeiras semipesadas. Para isso, foram utilizadas 128 aves da linhagem Hisex Brown (poedeiras semipesadas) com 30 semanas de idade, durante o período de 112 dias (quatro ciclos de 28 dias). As aves foram distribuídas em um delineamento experimental inteiramente casualizado, com quatro tratamentos, quatro repetições e oito aves por unidade experimental. Os tratamentos consistiram de quatro rações com diferentes graus de moagem (mm): 2,0 (diâmetro geométrico médio - DGM= 565 μm); 4,0 (DGM= 620 μm); 6,0 (DGM= 781 μm) e 8,0 (DGM= 1085 μm). As variáveis analisadas foram: produção de dejetos (kg.ave.dia-1), matéria seca (kg e %), porcentagens de fósforo e nitrogênio nos dejetos, e coeficiente de resíduo (kg). Os dados foram submetidos à análise de regressão polinomial (p

The effect of symmetrical perforated holes on the turbulent heat transfer in the static mixer with modified Kenics segments

The numerical simulation on forced convective heat transfer of water in the modified Kenics static mixer (MKSM) was investigated by the three-dimensional turbulent and steady incompressible flow of computational fluid dynamics (CFD). The conservation equations were solved by using finite volume method (FVM) and the SIMPLEC algorithm scheme in ANSYS Fluent 16.1. The simulation results of Nusselt number and the friction factor in MKSM have a good agreement with the literature results. The effects of Reynolds number, perforated diameter, perforated spacing, and segment number on the heat transfer are evaluated in the range of Re=2000–20,000 under uniform heat tube wall temperature conditions. The Nusselt number increases gradually with increasing Re. Furthermore, both the values and deviations of Nusselt number for different perforated diameter accord with an antisymmetrical tendency at the critical Re=11,000. It could be seen that the Nusselt number and the friction factor are not sensitive to the increasing perforated spacing within a given perforated diameter. In view of thermal performance factor, the geometrical diameter and spacing of two symmetrical perforated holes are optimized. The MKSM with d/W=0.3 and s/W=0.6 have the best performance with the consideration of both heat transfer rate and friction loss compared to the others. Thermal performance factor decreases gradually with increasing Re which indicated that the modified Kenics segments are more effective for heat transfer in lower Re. The local and global synergies between secondary flow and temperature fields have been investigated through field synergy principle.

Rice grain discoloration effect on physical properties and head rice yield in three rice cultivars

Rice grain discoloration is a complex disease which develops by a range of micro-organisms. Effects of fungal agents such as Alternaria sp., Curvularia sp., Cladosporium spp., Bipolaris spp. on the physical properties and head rice yield (HRY) were examined during the cropping season 2013-2014. The experiment was conducted in factorial design with two factors; three rice cultivars of Hashemi, Gohar and Khazar, and two grain disease severity levels (high and low) based on a randomised complete design with four replications. In order to attain high disease severity level, water was sprayed at the heading stage of the crop. The grains axial dimensions, geometric and arithmetic mean diameters, sphericity, surface area, volume, slenderness ratio, 1000-grain weight, as well as HRY were measured at a moisture content of 9% (wet basis). The average of length, width, thickness, surface area, volume and 1000-grain weight at the high disease severity were found to be 7.64, 2.04, 1.67 mm, 20.375 mm2, 13.796 mm3 and 2...

Hydraulic characterization of diesel engine single-hole injectors

Due to world trend on the emission regulations and greater demand of fuel economy, the research on advanced diesel injector designs is a key factor for the next generation diesel engines. For that reason, it is well established that understanding the effects of the nozzle geometry on the spray development, fuel–air mixing, combustion and pollutants formation is of crucial importance to achieve these goals. In the present research, the influence of the injector nozzle geometry on the internal flow characteristics is studied. For this purpose, ten single-hole diesel injectors differing in the orifices degree of conicity (five cylindrical, five conical) but with similar nozzle flow capacity have been characterized geometrically (measurements of nozzle outlet section) and hydraulically. The mass flow and momentum flux rates have been measured for a wide range of experimental conditions. Special attention is given to study the cavitation phenomenon since the cylindrically-shaped nozzle orifices are expected to propitiate cavitation due to abrupt changes in flow direction. The study has been carried out with two different fuels: n-dodecane and commercial diesel, thereby the effect of the fuel properties is also analyzed. The results show that the measured nozzle outlet diameters are higher than the nominal specification for both nozzle types. As expected, the onset of cavitation on the cylindrical nozzles has been identified causing a reduction on the injected mass for all tested conditions. The effective diameter for the cylindrical nozzles have been found to be around 175μm (geometrical diameter ≈212μm) and around 185μm (geometrical diameter ≈191μm) for the conical ones. Finally, the higher density of diesel with respect to n-dodecane have resulted on mass flow rates around 8% over the n-dodecane values for the same test conditions.

Physical Properties of Cucurbita Ficifolia Seed and Functional Properties of Whole and Defatted Meal

The aim of this research was to describe some physical properties of Cucurbita ficifolia seeds and evaluate the effect of defatting on C. ficifolia seed meal functional properties. Geometric diameter was 8.05 mm, arithmetic diameter was 10.61 mm, sphericity was 45.36%, aspect ratio was 64.29%, surface area was 204.08 mm2, volume was 187.44 mm3, true density was 0.51 Kg/m3, porosity was 31.81% and hardness was 6.23 N. Defatted C. ficifolia seed meal presented a content of protein (70.36 g/100 g) and carbohydrates (13.18 g/100 g). The defatted meal had higher water absorption capacity (2.94 g H2O/g sample), water solubility capacity (34.08 %), oil absorption capacity (2.97 g oil /g sample), emulsifying capacity (24.93%), foaming capacity (30.33%) and better foam stability (from 20 to 60 min) than the whole meal. The high protein content of defatted seed meal, suggests its use as a natural alternative ingredient in numerous food industry applications.

Edge activators and a polycationic polymer enhance the formulation of porous voriconazole nanoagglomerate for the use as a dry powder inhaler

Purpose: Voriconazole has both low aqueous solubility and stability. We hypothesize that designing voriconazole in the form of a nano powder inhaler at a geometric diameter within 1–5 μm will enhance its stability and solubility. Therefore, we prepared nanoagglomerates of voriconazole which will collapse in the lungs to reform the nanoparticles.Method: The nanoparticles were formulated using both stearic acid and sodium deoxycholate as edge activators. Osmogenic polycation polyethyleneimine (PEI) was used to form agglomerates of controllable size.Results: Voriconazole nanoparticles and agglomerates showed a significant higher cumulative drug release than the pure powder (p < 0.05) with R2 = 0.95. Small-sized particles were formed (353 nm), while their zeta potential was −30.7 mV. The agglomerates were 2.7 μm in size and their zeta potential was −20.9 mV. The formation of porous agglomerates was confirmed using a transmission electron microscope. Cascade impactor was used to evaluate the aerodynamic properties of the nanoparticles and the agglomerates. The aerodynamic characterization of the nanoparticles and the agglomerates resulted in a significant smaller mass median aerodynamic diameter (MMAD) (p < 0.05) and higher fine particle dose (FPD) (p < 0.01), fine particle fraction (FPF) (p < 0.01), and total emitted dose (TED) (p < 0.01) than the pure powder.Conclusion: The results suggest that using the combination of edge activators and diluted polycationic polymer solution provides porous voriconazole nanoagglomerates in a respirable range, which is proved successful in enhancing both the deposition and the dissolution of water insoluble-drugs in the lung.

Measurement of true ileal calcium digestibility in meat and bone meal for broiler chickens using the direct method

The objective of the study that is presented herein was to determine the true ileal calcium (Ca) digestibility in meat and bone meal (MBM) for broiler chickens using the direct method. Four MBM samples (coded as MBM-1, MBM-2, MBM-3 and MBM-4) were obtained and analyzed for nutrient composition, particle size distribution and bone to soft tissue ratio. The Ca concentrations of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 71, 118, 114 and 81 g/kg, respectively. The corresponding geometric mean particle diameters and bone to soft tissue ratios were 0.866, 0.622, 0.875 and 0.781 mm, and 1:1.49, 1:0.98, 1:0.92 and 1:1.35, respectively. Five experimental diets, including four diets with similar Ca concentration (8.3 g/kg) from each MBM and a Ca and phosphorus-free diet, were developed. Meat and bone meal served as the sole source of Ca in the MBM diets. Titanium dioxide (3 g/kg) was incorporated in all diets as an indigestible marker. Each experimental diet was randomly allotted to six replicate cages (eight birds per cage) and offered from d 28 to 31 post-hatch. Apparent ileal Ca digestibility was calculated by the indicator method and corrected for ileal endogenous Ca losses to determine the true ileal Ca digestibility. Ileal endogenous Ca losses were determined to be 88 mg/kg dry matter intake. True ileal Ca digestibility coefficients of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 0.560, 0.446, 0.517 and 0.413, respectively. True Ca digestibility of MBM-1 was higher (P < 0.05) than MBM-2 and MBM-4 but similar (P > 0.05) to that of MBM-3. True Ca digestibility of MBM-2 was similar (P > 0.05) to MBM-3 and MBM-4, while that of MBM-3 was higher (P < 0.05) than MBM-4. These results demonstrated that the direct method can be used for the determination of true Ca digestibility in feed ingredients and that Ca in MBM is not highly available as often assumed. The variability in true Ca digestibility of MBM samples could not be attributed to Ca content, percentage bones or particle size.

AN ATOMIZER TO GENERATE MONODISPERSE DROPLETS FROM HIGH VAPOR PRESSURE LIQUIDS

This work describes an atomizer capable of generating monodisperse droplets of high vapor pressure liquids such as HFA227ea and HFA134a. This atomizer is expected to be a useful tool in future fundamental explorations of the mechanics of these highly dynamic aerosols. Hydrofluoroalkanes (HFAs) are the most common propellants in metered dose inhalers (MDIs), which are themselves the most common delivery method for pulmonary disease medications. As a result of the high vapor pressure of these fluids, generation of monodisperse droplets and their study are not possible with previously existing monodisperse atomizers due to fluid flashing when exposed to ambient conditions. The new atomizer uses a piezoelectric transducer to disintegrate the propellant jet, a cooling circuit with a low-temperature limit of −30°C to reduce propellant vapor pressure, and a high-pressure feed system (up to 2.7 MPa) to keep the propellant in the liquid phase, thereby avoiding flash atomization. In the current setup, the diameter of the generated droplets was monitored with a laser scattering system (using Fraunhofer diffraction theory) to optimize the operating parameters of the setup (for example, the actuation frequency and amplitude of the piezoelectric transducer). This monitoring system allowed for the measurement of droplet geometric diameter, spacing, and velocity. The capabilities of the atomizer for generating monodisperse droplets are demonstrated by a case study in which monodisperse dry particles of beclomethasone dipropionate (BDP) are generated using a solution of BDP, ethanol co-solvent, and HFA134a propellant.

Bond evaluation of steel bolts for concrete subjected to impact loading

The presented study deals with steel bolts for concrete subjected to impact loading. Impact loading induced by the Schmidt hammer was used to assess the quality of bond between the anchor bolt and the surrounding concrete. The effect of impact loading on the load-carrying capacity of 8, 10 and 12 mm diameter bolts with a constant embedment length and concrete strength was studied. Concrete quality, anchor alignment, diameter and water ingress were also taken into consideration. An analytical model is presented which takes into account the interfacial bonding between the bolt and surrounding concrete matrix, bolt geometric shape, diameter, alignment and embedment length. The comparisons between theoretical and experimental results revealed that the analytical model was capable to predict the maximum load carrying capacity and pull-out mechanism of the anchor bolts. From the presented results and discussion, it was found that the bond performance of the bolts and hidden defects can be identified by imparting impact energy. The proposed model can be used by engineers and researchers to judge the quality of the bond between bolt and surrounding concrete and for predicting their peak load carrying capacity and displacement of various types of anchor bolts.

Influence of physical properties of Jatropha curcas L. seeds on shelling performance using a modified disc mill

The objective of this study was to investigate the effect of physical characteristics of different size classes of J. curcas seeds on shelling performance using a modified disc mill. The seeds were grouped into four size classes using sieves with hole diameters of 8, 9, 10 and 12mm. Length, breadth, width, arithmetic and geometric diameter, bulk and solid density, and surface area were significantly different at p≤0.01. No significant differences were found in terms of sphericity and moisture content. Smaller seed size lead to higher porosity and percentage of shells. Rupture force was examined along length (L), width (W), and breadth (B) axes. A prototype of a disc mill was re-engineered and optimized. The preferential orientation of the seeds passing the mill was in the vertical direction. Optimum setting of rotational speed and aperture between the discs of the mill were strongly related to seed breadth. As the output fractions, dust, shells, fragmented kernels and full kernels could be separated pneumatically. Meanwhile, partially-shelled and unshelled seeds could only be separated manually by visual inspection. Under optimum conditions, the shelling efficiency for the four size classes was determined as 81.0, 83.5, 83.7, and 84.6%, respectively. Compared with results from unsorted seeds, pre-sorting the seeds significantly reduced the amount of partially-shelled and unshelled seeds at p≤0.01. The maximum capacity of the machine was estimated as 131.5kg/h which resulted in the lowest energy consumption of 0.002kWh/kg.

Seasonal variability in aerosol, CCN and their relationship observed at a high altitude site in Western Ghats

Atmospheric aerosols which serve as cloud condensation nuclei (CCN) are key elements of the hydrological cycle and climate. In the present work, aerosol–CCN variability and their relationship have been studied for the first time at Mahabaleshwar, a high altitude (1348 m AMSL) site in Western Ghats, using one year (June 2012–May 2013) of observations. Present study has been done in two sections in which first temporal variability (diurnal and seasonal) of aerosol and CCN has been analyzed. Later CCN to aerosol ratio and other microphysical properties have been investigated along with detail discussion on possible sources of aerosol. First part, i.e., diurnal variation in aerosol and CCN concentration has shown relatively higher values during early morning hours in monsoon season whereas in winter and pre-monsoon it was higher in the evening hours. Seasonal mean variation in aerosol and CCN (SS above 0.6 %) has shown higher (less) in monsoon (winter) season. Temporal variation reveals dominance of fine-mode aerosol during monsoon season over the study region. In the second part temporal variation of activation ratio, k value (exponent of CCN super-saturation spectra) and geometric mean aerosol diameter have been analyzed. Variation of activation ratio showed the ratio is higher in monsoon especially for SS 0.6–1 %. The analysis also showed high k value during monsoon season as compared to other seasons (pre-monsoon and winter) which may be due to dominance of hygroscopic aerosols in the maritime air masses from Arabian Sea and biogenic aerosol emissions from the wet forest. Analyzed mean aerosol diameter is much smaller during monsoon season with less variability compared to other seasons. Overall analysis showed that aerosol and CCN concentration was higher over this high altitude site despite of dominant sink processes such as cloud scavenging and washout mechanisms indicating local emissions and biogenic Volatile Organic Compounds (BVOC) emissions from wet forest as major sources.

Production of well dispersible single walled carbon nanotubes via a “floating catalyst”-method

In this paper, we present a unique process chain for the production of single-walled carbon nanotubes (SWCNT) and document the relationship between the process parameters in gas phase production, the dispersibility of SWCNTs in aqueous solutions of sodium cholate and their properties. SWCNTs were prepared by a “floating catalyst” method using a solution of ferrocene in ethanol as precursor. Production rates in the range from 5 to 20mg/h were achieved by using an optimized riser reactor design, which enables reduction of undesired wall-sticking of the catalyst particles and SWCNTs. Products featuring iron catalyst contents less than 30wt% were obtained for low precursor concentrations in combination with short residence time in the reactor. Transmission electron microscopy (TEM) and statistical Raman analyses of the products reveal that the SWCNTs exhibit a diameter distribution ranging from 0.5 to 2.0nm. Processing conditions, including precursor concentration, residence time, etc. were found to have only a slight impact on the mean geometric SWCNT diameter. Sonication based post-processing of the as-prepared SWCNTs in aqueous solutions of sodium cholate leads to an effective individualization of SWCNTs as proven by atomic force microscopy (AFM), 3D fluorescence spectroscopy, and by multi-wavelength analytical ultracentrifugation (AUC). Overall, the dispersibility of the non-purified SWCNTs in a 2wt% aqueous solution of sodium cholate increases as the ferrocene partial pressure is decreased and, in turn, the catalyst concentration is reduced in the gas phase. Statistical Raman spectroscopy performed with the SWCNTs reveals that more than 75% of the produced carbon species are SWCNTs and that about 2/3 are semiconducting.

Development of low density azithromycin-loaded polycaprolactone microparticles for pulmonary delivery

Context: The development of low-density polymeric microparticles may be a useful approach to deliver antibiotics such as azithromycin into the lung.Objective: The aim of this study was to develop azithromycin-loaded low density polycaprolactone microparticles by the double emulsion/solvent evaporation method.Materials and methods: Microparticles were prepared and characterized according to their physicochemical properties, drug loading, and drug release profiles. A full 23 factorial design was used to evaluate the effect of some independent variables on the drug loading and aerodynamic diameter of the particles. An in silico pulmonary deposition model was used to predict the lung deposition profiles for the formulations.Results and discussion: The resulting particles presented drug loading up to 23.1% (wt%) and mean geometric diameters varying from 4.0 µm to 15.4 µm. Bulk and tapped densities were low, resulting in good or excellent flow properties. SEM images showed spherical particles with a smooth surface. However, hollow inner structures were observed, which may explain the low values of bulk density. The estimated aerodynamic diameters ranged from 2.3 µm to 8.9 µm. The in silico pulmonary deposition profiles indicated, for some formulations, that a significant fraction of the particles would be deposited in the deeper lung regions.Conclusions: Statistical analysis demonstrated that not only drug loading but also the aerodynamic diameter of the microparticles is greatly affected by the preparation conditions. Overall, the results indicated that the low-density azithromycin-loaded microparticles with a relatively high respirable fraction may be obtained for the local treatment of lung infections.

Performance Evaluation of Pedotransfer Functions to Predict Field Capacity and Permanent Wilting Point Using UNSODA and HYPRES Datasets

Using basic soil properties could save time and costs in determining field capacity (FC) and permanent wilting point (PWP). The objectives of this study were to investigate the relationship between FC and PWP and basic soil properties, develop two new equations for estimating FC and PWP, and evaluating their performance as compared to some existing pedotransfer functions (PTFs) in predicting FC and PWP. For this purpose, 210 soil samples of UNSODA dataset and 45 soil samples of HYPRES dataset were used for development and validation of the PTF, respectively. Graphical exploration of relations between soil texture component, geometric mean particle-size diameter (dg), bulk density (BD), and organic matter (OM) with FC and/or PWP showed that relations of FC was nonlinearly related to percentage of clay (positive) and dg (negative) and relations of PWP was linearly and nonlinearly related to percentage of clay (positive) and dg (negative), respectively. Based on standardized independent variable weight (W), dg showed the highest influence on FC (W = 0.81), followed by percentage of clay (W = 0.70), OM and BD (W = 0.49). PWP was primarily affected by percentage of clay (W = 0.89) and dg (W = 0.64), whereas BD and OM with Wof 0.30 were less effective. The two new functions suggested and evaluated for predicting FC and PWP had root mean squares error (RMSE) of 0.06 and 0.02 m3 m−3, geometric mean error (GMER) 1.03 and 1.10 m3 m−3 and Akaike's information criterion (AIC) of −262 and −349, respectively. As such, their prediction performance was higher than that of other FC and PWP PTFs found in literature.

CARBONO ORGÂNICO TOTAL E AGREGAÇÃO DO SOLO EM SISTEMA DE PLANTIO DIRETO AGROECOLÓGICO E CONVENCIONAL DE CEBOLA

Decorrente dos sistemas de manejo empregados no solo, como o sistema de preparo convencional (SPC) versus o sistema de plantio direto de hortaliças (SPDH), modificações nos atributos edáficos ocorrem; por exemplo, nos índices de agregação do solo e seu teor de carbono orgânico total (COT). Objetivaram-se quantificar os teores de COT e avaliar os índices de agregação do solo e a distribuição dos agregados por classes de diâmetro sob cultivo de cebola em SPDH e SPC, comparados a uma área de mata adjacente em Ituporanga, SC. Os tratamentos constituíram-se da semeadura de plantas de cobertura, solteiras e consorciadas, em SPDH: vegetação espontânea (VE); 100 % aveia; 100 % centeio; 100 % nabo-forrageiro; consórcio de nabo-forrageiro (14 %) e centeio (86 %); e consórcio de nabo-forrageiro (14 %) e aveia (86 %). Adicionalmente, foram avaliadas uma área de cultivo de cebola em SPC por ±37 anos e uma área de mata (floresta secundária; ±30 anos), ambas adjacentes ao experimento. Em setembro de 2013, cinco anos após a implantação dos tratamentos com plantas de cobertura, foram coletadas amostras indeformadas do solo nas camadas de 0-5, 5-10 e 10-20 cm e separados os agregados para avaliar a estabilidade via úmida. Nos agregados, foi quantificado o COT; após a separação em classes de diâmetro (8,00 mm&gt;Ø≥0,105 mm), calcularam-se o diâmetro médio ponderado (DMP) e o geométrico (DMG) dos agregados; a distribuição deles em macroagregados (Ø≥2,0 mm), mesoagregados (2,0&gt;Ø≥0,25 mm) e microagregados (Ø&lt;0,25 mm); e o seu índice de sensibilidade (IS). Os dados foram submetidos à análise de variância e de componentes principais (ACP). Os maiores teores de COT foram encontrados na área de mata (52,83; 37,77; e 26,70 g kg-1, respectivamente para 0-5, 5-10 e 10-20 cm); e os menores, no SPC (18,23 g kg-1, 0-5 cm). Os tratamentos com plantas de cobertura, solteiras ou consorciadas, não apresentaram diferenças entre si (p≤0,05) para o COT, nem em relação à área testemunha (VE). O SPC apresentou os menores índices de DMP (3,425; 3,573; e 3,401 mm), DMG (2,438; 2,682; e 2,541 mm) e IS (0,77; 0,79; e 0,81), nas três camadas avaliadas. Para o DMP e DMG, não foram verificadas diferenças (p≤0,05) entre tratamentos no SPDH; porém, esses índices foram superiores aos do SPC; os de DMP, iguais aos da área de mata; e os de DMG, maiores na camada de 0-5 e 5-10 cm. Na camada de 10-20 cm, no SPDH, o tratamento com nabo-forrageiro apresentou maiores valores de DMP (4,520 mm), DMG (4,284 mm) e IS (1,07). Em relação à distribuição dos agregados por classes de diâmetro, o SPC evidenciou, respectivamente, os menores (14,22; 14,75; e 13,86 g) e maiores (4,94; 3,44; e 3,52 g/3,0; 3,0; e 3,76 g) valores para macro e meso/microagregados, enquanto o SPDH demonstrou maiores valores de macroagregados (médias de 19,90; 20,48; e 18,56 g) em comparação à mata (16,0; 16,31; e 15,47 g) e ao SPC (14,22; 14,75; e 13,86 g) nas três camadas avaliadas. O uso de plantas de cobertura, solteiras ou consorciadas, em SPD de cebola foi eficiente para recuperar e aumentar os teores de COT e os índices de DMP, DMG e IS em relação ao SPC; e, em comparação à área de mata, aumentou o DMG (0-5 e 5-10 cm). O nabo-forrageiro aumentou a agregação do solo (DMG e IS) na camada de 10-20 cm em relação aos demais tratamentos com plantas de cobertura. A ACP evidenciou a perda de COT e o aumento dos meso e microagregados no SPC, assim como a substituição do SPC por SPDH com plantas de cobertura elevou a formação de macroagregados estáveis em água, com posterior aumento do DMP, DMG e IS.