Hot-air drying of purslane (Portulaca oleracea L.)

Drying characteristics of purslane was experimentally studied in a cabinet dryer. The experimental drying data were fitted best to Modified Henderson and Pabis and Midilli et al. models apart from other models to predict the drying kinetics. The effective moisture diffusivity varied from 1.12 × 10^?9 to 3.60 × 10^?9 m²/s over the temperature range studied and activation energy was 53.65 kJ/mol.     

Effects of timber skidding on chemical characteristics of herbaceous cover, forest floor and topsoil on skidroad in an oak (Quercus petrea L.) forest

This paper examines the effects of timber harvesting by skidding on some soil properties (sand, silt, clay, pH, organic carbon, bulk density and compaction), herbaceous cover (unit mass) and forest floor (unit weight) properties. Also N (%), P, K, Na, Ca, Mg, Fe, Zn, Cu and Mn (ppm) were determined in all herbaceous cover, forest floor and two soil depth (0–5 cm and 5–10 cm) on skidroad of an oak (Quercus petrea L.) stand in Istanbul Belgrad Forest – Turkey. In this study, obtained results are; the forest floor and the herbaceous cover amount on the skidroad have been found considerably lower than undisturbed area. There were some crucial changes in the characteristics of the soil which has been investigated down to 10 cm depth. Soil bulk density was found quite high in the samples taken from the skidroad subject to compaction compared to the ones on the undisturbed area. Nevertheless, no important difference had been detected between the skidroad and the undisturbed area at both soil depths in terms of organic carbon contents. Moreover, the soil acidity (pH) values showed noteworthy differences in the analysis of soil samples taken from both soil depths on the skidroad and on the undisturbed area. Fe and Cu contents of herbaceous samples on skidroad were significantly higher than undisturbed area. Forest floor on skidroad had significantly higher K content, and significantly lower Zn, Mn and N content compared to undisturbed area. P, Fe, Zn and Mn contents were found significantly lower in 0–5 cm soil depth on skidroad than undisturbed area. In 5–10 cm soil depth, concentrations of N, P, Fe, Zn and Mn were significantly lower, while Mg and Cu contents were significantly higher than undisturbed area. Results indicate that long-term harvest using skidding techniques on these sites had adversely affected soil cation concentrations, physical soil conditions and mass of herbaceous cover and forest floor.     

TG-DSC method applied to drying characteristics and heat requirement of cotton stalk during drying

Drying characteristics of cotton stalk were investigated at four temperatures (60, 80, 100 and 120?°C) using a simultaneous thermal analyzer (TG-DSC). Heat requirements of cotton stalk during drying were calculated ranging from 189 to 406?kJ/kg. Consequently, Midilli-Kucuk model showed the best fit to experimental drying data. The values of effective diffusivity ranged from 4.38?×?10^?9 to 8.15?×?10^?9?m²/s, and the activation energy was calculated to be 11.6?kJ/mol.     

Thin-layer drying characteristics of sweet potato slices and mathematical modelling

The effect of blanching and drying temperature (50, 60 and 70°C) on drying kinetics and rehydration ratio of sweet potatoes was investigated. It was observed that both the drying temperature and blanching affected the drying time and rehydration ratio. The logarithmic model showed the best fit to experimental drying data. The values of effective moisture diffusivity and activation energy ranged from 9.32 × 10⁻¹¹ to 1.75 × 10⁻¹⁰ m²/s, and 22.7–23.2 kJ/mol, respectively.     

Wettability and impact dynamics of water droplets on rice (Oryza sativa L.) leaves

A displacement-shifted approach is introduced to the vision-based particle tracking velocimetry (VB-PTV) technique described in Lei et al. (Exp Fluids 53(5):1251–1268, 2012), using translational and angular displacements. The particle matching algorithm in VB-PTV is based on a proximity matrix, G _ij , which favors short distance particle matches over long distance matches. By modifying the formula used in constructing G _ij , particles that lie at the expected location of the match are favored. Two displacement-shifted methods are introduced: the first of which relies on particle image velocimetry estimates of particle displacements and the second of which relies on both the expected displacement and direction of the correct match to construct the proximity matrix. These displacement-shifted algorithms improve performance in high gradient (0.3 px/px and above), high displacement flows (upwards of 20 pixels), broadening the range of flows for which VB-PTV can be used. RMS errors in PTV results are reduced by 33 % or more when these displacement-shifted algorithms are made to the VB-PTV algorithm which is used to process Oseen vortex images. Experimental images of shear layer and the wake region of vortex shedding were used to verify the performances of the proposed methods, and the results are in agreement with the synthetic tests.     

Rheology of milled black cumin (Nigella sativa L.)

Black cumin (Nigella sativa L.) paste is a local food in the Middle East, which is produced from dehulled black cumin seeds. The rheological properties of a commercial black cumin paste in the temperature range of 5-40 °C have been studied. Shear-thinning flow behavior with a yield stress was observed for the samples tested. The Herschel-Bulkley model described well the flow curves of the black cumin pastes at different temperatures. It was found that the yield stress, the consistency coefficient, and the flow behavior index decrease with temperature. As far as the effect of steady shearing on the rheological properties of black cumin paste is concerned, the structural kinetic approach was used to predict the thixotropic behavior. It was found that the thixotropic behavior of black cumin paste increases with increasing shear rate and is mitigated by increasing temperature. The completely destructed black cumin paste flow curves were also measured after subjecting the samples to a high shear rate for 2 h. The flow curves of the completely destructed samples were modeled well by the Herschel-Bulkley model. A comparison between the fresh and the completely destructed black cumin paste results at different temperatures revealed that there was a systematic difference, such that the completely destructed paste showed lower yield stress and flow behavior index, and showed a greater consistency coefficient.     

Dehydration characteristics and mathematical modelling of lemon slices drying undergoing oven treatment

In this study, the effect of drying temperature on drying behaviour and mass transfer parameters of lemon slices was investigated. The drying experiments were conducted in a laboratory air ventilated oven dryer at temperatures of 50, 60 and 75 °C. It was observed that the drying temperature affected the drying time and drying rate significantly. Drying rate curves revealed that the process at the temperature levels taken place in the falling rate period entirely. The usefulness of eight thin layer models to simulate the drying kinetics was evaluated and the Midilli and Kucuk model showed the best fit to experimental drying curves. The effective moisture diffusivity was determined on the basis of Fick’s second law and obtained to be 1.62 × 10^?11, 3.25 × 10^?11 and 8.11 × 10^?11 m² s^?1 for the temperatures of 50, 60 and 75 °C, respectively. The activation energy and Arrhenius constant were calculated to be 60.08 kJ mol^?1 and 0.08511 m² s^?1, respectively. The average value of convective mass transfer coefficient for the drying temperatures of 50, 60 and 75 °C was calculated to be 5.71 × 10^?7, 1.62 × 10^?6 and 2.53 × 10^?6 m s^?1, respectively.     

Effect of wetting and drying on soil physical properties

Agricultural soils are subject to seasonal wetting and drying cycles. Effect of drying stress, as influenced by one cycle of wetting and drying, on physical properties of a clay–loam soil was investigated in the laboratory. The physical properties studied were soil bulk density, cone penetration resistance, shear strength, adhesion and aggregate size and stability. Three drying stress treatments were made by wetting air-dried soil of initial moisture content of 12% (on dry weight basis) to three different higher moisture contents, namely 27, 33 and 40%, and then drying each of them back to their original moisture content of 12%. Thus, the soil was subjected to three different degrees of drying stress. The results showed that the soil strength indicated by cone penetration resistance and cohesion, and soil aggregate size, increased with the degree of drying stress. However, the soil bulk density did not change significantly with the drying stress.     

Drying characteristics of garlic (Allium sativum L) slices in a convective hot air dryer

The effects of drying temperatures on the drying kinetics of garlic slices were investigated using a cabinet-type dryer. The experimental drying data were fitted best to the Page and Modified Page models apart from other theoretical models to predict the drying kinetics. The effective moisture diffusivities varied from 4.214 × 10^?10 to 2.221 × 10^?10 m² s^?1 over the temperature range studied, and activation energy was 30.582 kJ mol^?1.     

Effects of actuator nonlinearity on aeroelastic characteristics of a control fin

The influences of actuator nonlinearities on actuator dynamics and the aeroelastic characteristics of a control fin were investigated by using iterative V-g methods in subsonic flows; in addition, the doublet-hybrid method (DHM) was used to calculate unsteady aerodynamic forces. The changes of actuator dynamics induced by nonlinearities, such as backlash or freeplay, and the variations of flutter boundaries due to the changes of actuator dynamics were observed. Results show that the aeroelastic characteristics can be significantly dependent on actuator dynamics. Thus, the actuator nonlinearities may play an important role in the nonlinear aeroelastic characteristics of an aeroelastic system. The present results also indicate that it is necessary to seriously consider the influence of actuator dynamics on the flutter characteristics at the design stage of actuators to prevent aeroelastic instabilities of aircraft or missiles.     

Effects of ultrahigh vacuum on the response characteristics of strain gages

Strain gages are extensively used in spacesimulation research; yet, little if any information has been reported about the environmental effects on the gage installations themselves. Since ultrahigh vacuum affects the physical and chemical properties of materials, one may expect that the response characteristics of strain-gage installations will also be affected. A study was initiated to determine the behavior of a number of strain-gage installations subjected to ultrahigh-vacuum environments. This paper presents the results of the first phase of the program. The gages and adhesives were selected to provide optimum chance for failure in order to establish a time parameter for following tests and, more importantly, to verify the extent and nature of failure possible under the environmental test conditions. Data were obtained on a number of strain-gage-per-formance characteristics. The performances of the gage installations varied widely being dependent in part upon gage and adhesive composition, whether a gage was used as an active or inactive device, and the level of strain to which a gage was subjected. Detailed pre- and post-test examinations showed that there was little permanent damage to any of the installations.     

Effects of chamber temperature and pressure on the characteristics of high speed diesel jets

This study is an investigation into the effects of temperature and pressure within a test chamber on the dynamic characteristics of injected supersonic diesel fuel jets. These jets were generated by the impact of a projectile driven by a horizontal single stage powder gun. A high speed video camera and a shadowgraph optical system were used to capture their dynamic characteristics. The test chamber had controlled air conditions of temperature and pressure up to 150 °C and 8.2 bar, respectively. It was found experimentally that, at the highest temperature, a maximum jet velocity of around 1,500 m/s was obtained. At this temperature, a narrow pointed jet appeared while at the highest pressure, a thick, blunt headed jet was obtained. Strong shock waves were generated in both cases at the jet head. For analytical prediction, equations of jet tip velocity and penetration from the work of Dent and of Hiroyasu were employed to describe the dynamic characteristics of the experiments at a standard condition of 1 bar, 30 °C. These analytical predictions show reasonable agreement to the experimental results, the experimental trend differing in slope because of the effect of the pressure, density fluctuation of the injection and the shock wave phenomena occurring during the jet generation process.