Kc Values Research Articles

Variations of crop coefficient and its influencing factors in an arid advective cropland of northwest China

Understanding the variation and magnitude of crop coefficient (Kc) is important for accurate determination of crop evapotranspiration and water use. In this study, we calculated Kc in an irrigated maize field with ground mulching by eddy covariance evapotranspiration measurements during the whole growing periods in 2009 and 2010 in an arid region of northwest China. A semi-empirical practical approach for estimating Kc was proposed by introducing the dynamic fraction of canopy cover and incorporating the effect of leaf senescence as a function of days after sowing. The contribution of arid advection of sensible heat resulting from irrigation to Kc and the response of Kc to canopy conductance (Gc) were investigated. The averaged values of daily Kc were lower than typical values obtained previously without mulching due to decreasing effect of mulching on Kc, with 0.82 and 0.80 for the 2 years, respectively. The maximum average Kc occurred at the heading stage, with 1.21 and 1.04 for the 2 years, respectively. The difference of Kc was attributed to the difference of leaf area index. The semi-empirical practical approach could well estimate the variations of Kc, thus could be a robust and useful tool for the practical users and water managers. The contributions to daily Kc from the arid advection were 4.4–28.0% of the measured Kc. The Gc had stronger control on daily Kc at the early and later stages than at the middle stage. When Gc, leaf area index and relative soil extractable water were lower than the respective threshold values of 20 mm s−1, 3.0 m2 m−2 and 0.5, the daily Kc increased significantly with the increase of the three factors, and almost remained constant when the three factors were beyond the threshold values. These results are helpful for quantifying contributions of individual factors to Kc, and subsequently improving water management practices according to Kc. Copyright © 2014 John Wiley & Sons, Ltd.

Determination of the Water Requirement and Kc Values of Sugarcane at Different Crop Growth Stages by Lysimetric Method

The water requirement of sugarcane was studied in a lysimeter set up at the Sugarcane Research and Seed Farm, Pyinmana, Mandalay Division, Myanmar. Sugarcane variety Phil 74/64 and grass (locally called Wun be sa; Echinochloa colona L.) were used. Daily crop water uptakes for both cane and grass were recorded from the lysimeter and the crop coefficient (Kc value) was re-derived. Sugarcane crop evapotranspiration or crop water uptake was also determined using the Penman–Monteith (FAO) method from daily weather data gathered from the nearby agrometerological station. The total sugarcane water consumption in the lysimeter study was 1369.84 mm year−1 and the average sugarcane yield was 173.29 t ha−1. Water use efficiency in the lysimeter study was 12.65 t cane ML−1 (0.13 t mm−1). The locally determined Kc values were 0.53, 0.81, 1.25, and 1.27 for initial, development, mid and late sugarcane growth stages, respectively.

Self-organization principles in the formation of multiporphyrin complexes and "semiconductor quantum dot-porphyrin" nanoassemblies

In this paper, we review several aspects of molecular recognition (based on non-covalent binding interactions) occurring between meso-pyridyl substituted tetrapyrrole extra-ligands and chemical dimers of tetrapyrrolic macrocycles containing central Zn ions and spacers of various nature and flexibility. Experimental results obtained by us earlier are analyzed using a novel approach (based on steady-state absorption/fluorescence measurements) for the evaluation of complexation constants KC for the formation of porphyrin triads. It was found that KC values [ KC ~ (0.5 – 70) × 106 M-1] show noticeable dependence on the structural parameters of the interacting subunits as well as on the solvent nature. The same self-assembly approach has been used to attach meso-pyridyl substituted porphyrins to the surface of semiconductor CdSe / ZnS quantum dots (QD). It was comparatively found that in contrast to self-assembled porphyrin triads, the formation of "QD-porphyrin" nanoassemblies takes place in competition with surface stabilizing tri-n-octyl phosphine oxide (TOPO) ligand molecules and attached porphyrin molecules. It manifests in a temporal dynamics of QD photoluminescence caused by ligand exchange, TOPO layer reorganization, QD surface reconstruction, solvent properties. It was shown that the sensitivity of QD surface morphology to attached organic ligands (e.g. porphyrins) provides an opportunity to control the dynamics and pathways of the exciton relaxation in "QD-dye" nanoassemblies by changing the structure and electronic properties of these ligands.

Assessment of aquatic plants evapotranspiration for secondary agriculture drains (case study: Edfina drain, Egypt)

This research was set in order to estimate aquatic plants evapotranspiration, (ET) in Edfina drain, Nile Delta, Egypt, which had an in-stream treatment wetland that was taken as a case study. A simple field scale approach is presented to measure drain water evaporation and water consumption of five aquatic plants, cultivated in floating tanks. Plants ET, (ETp) values were obtained by measuring the daily quantity of water required to renovate the tank’s initial volume. Crop coefficients (Kc) were obtained and water loss from the drain wetland was calculated due to evaporation and plants cells ETp. Results presented values of ETp and Kc which were controlled by plant leaf area and growing stage. The major ETp was for Hyacinth followed by Cattail, Reeds, Torpedo grass, and then duckweeds. All ETp values exceeded twice the adjacent non-vegetated water evaporation. The obtained Kc values referenced to the drain water evaporation were almost twice the Kc values of FAO Penman–Monteith ET, due to the landscape effects, as hot dry air can cause extra heat input and water loss. Total losses from in-stream treatment series of pond, 4 plants reaches and open disinfection zone did not exceed 0.55% of drain discharge.

Electronic structures and selective fluoride sensing features of Os(bpy)2(HL(2-)) and [{Os(bpy)2}2(μ-HL(2-))](2+) (H3L: 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid).

The article deals with the newly designed mononuclear and asymmetric dinuclear osmium(ii) complexes Os(II)(bpy)2(HL(2-)) (1) and [(bpy)2Os(II)(μ-HL(2-))Os(II)(bpy)2](Cl)2 ([2](Cl)2)/[(bpy)2Os(II)(μ-HL(2-))Os(II)(bpy)2](ClO4)2 ([2](ClO4)2), respectively, (H3L = 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid and bpy = 2,2'-bipyridine). The identity of 1 has been established by its single crystal X-ray structure. The ligand (HL(2-))-based primary oxidation process (E, 0.23 V versus SCE) along with the partial metal contribution (∼20%) in 1 has been revealed by the ligand-dominated HOMO of 1 (HL(2-): 88%, Os: 8%), as well as by the Mulliken spin density distribution of 1(+) (HL(2-): 0.878, Os: 0.220). Accordingly, 1(+) exhibits a free radical type EPR at 77 K with a partial metal-based anisotropic feature (g1 = 2.127, g2 = 2.096, g3 = 2.046; <g> = 2.089; Δg = 0.08). (1)H-NMR of the dinuclear 2(2+) in CDCl3 suggests an intimate mixture of two diastereomeric forms in a 1 : 1 ratio. The DFT-supported predominantly Os(ii)/Os(iii)-based couples of asymmetric 2(2+) at 0.24 V and 0.50 V versus SCE result in a comproportionation constant (Kc) value of 8.2 × 10(4). The class I mixed valent state of 2(3+) (S = 1/2) has, however, been corroborated by the Mulliken spin density distribution of Os1: 0.887, Os2: 0.005, HL(2-): 0.117, as well as by the absence of a low-energy IVCT (intervalence charge transfer) band in the near-IR region (up to 2000 nm). The appreciable spin accumulation on the bridge in 2(3+) or 2(4+) (S = 1, Os1: 0.915, Os2: 0.811 and HL(2-): 0.275) implies a mixed electronic structural form of [(bpy)2Os(III)(μ-HL(2-))Os(II)(bpy)2](3+)(major)/[(bpy)2Os(II)(μ-HL˙(-))Os(II)(bpy)2](3+)(minor) or [(bpy)2Os(III)(μ-HL(2-))Os(III)(bpy)2](4+)(major)/[(bpy)2Os(III)(μ-HL˙(-))Os(II)(bpy)2](4+) (minor), respectively. The mixed valent {Os(III)(μ-HL(2-))Os(II)} state in 2(3+), however, fails to show EPR at 77 K due to the rapid spin relaxation process. The DFT-supported bpy-based two reductions for both 1(+) and 2(2+) appear in the potential range of -1.5 V to -1.8 V versus SCE. The electronic transitions in 1(n) and 2(n) are assigned by the TD-DFT calculations. Furthermore, the potential anion sensing features of 1 and 2(2+)via the involvement of the available N-H proton in the framework of coordinated HL(2-) have been evaluated by different experimental investigations, in conjunction with the DFT calculations, using a wide variety of anions such as F(-), Cl(-), Br(-), I(-), OAc(-), SCN(-), HSO4(-) and H2PO4(-). This, however, establishes that both 1 and 2(2+) are equally efficient in recognising the F(-) ion selectively, with log K values of 6.83 and 5.89, respectively.

Towards Optical Monitoring of Vanadium Redox Flow Batteries (VRFBs): An Investigation of the Underlying Spectroscopy

The UV-visible spectra of VIII-VII electrolytes in 3 mol dm−3 H2SO4 showed a linear relationship of absorbance to mole fraction but those of VIV-VV electrolytes did not. At all wavelengths, VIV-VV mixtures showed excess absorbance over that expected for a linear combination of the components. Plots of excess absorbance Aex against mole fraction f of VIV were found to be symmetrical parabolas that reach a peak at a mole fraction f = 0.5. Excess absorbance is attributed to a strongly absorbing 1:1 mixed-valence complex, V2O33+, in equilibrium with VO2+ and VO2+. Based on this, an expression is derived that relates Aex to f and from this it is shown that when KcC < 1 (where Kc is the equilibrium constant and C is the total vanadium concentration), Aex should vary linearly with f(1 – f). Experimentally, plots of Aex versus f(1 – f) showed excellent linearity through the origin at all wavelengths, thus confirming the model. An excess molar extinction coefficient ɛex and an alternative excess absorbance parameter p are defined. Values of p and approximate values of Kc and ɛex were estimated; the spectrum of V2O33+ is plotted as its approximate molar extinction coefficient.

Effect of deficit irrigation and mulching on consumptive use and yield of potato in gypsiferous soil under drip irrigation.

In order to determine the effect of the lack of irrigation and mulch in water consumption use and yield of potatoes under gypsiferous soil conditions in spring season in 2013 at experimental station of soil and water resources department, college of Agriculture, Tikrit university. The experimental design was split plot in three replicates. The main plots were irrigation treatment (I), and sub plots were no mulch (C1) and mulch with wheat straw (C2). The treatments were as follows: for no mulch full irrigation (control), C1I1, the deficit irrigation treatment included omitting two irrigations at vegetative growth C1I2, tuber initiation C1I3 and tuber bulking and maturation C1I4. For the mulch, The treatments were (C2I1, C2I2, C2I3 and C2I4) for four treatments, respectively. The mulch was spread on the soil surface of 12 ton ha-1. Potato tubers, Rudolph variety were planted on 3-2-2013 for spring season and harvested on 20-6-2013. Reached values ​​ ETa for potato was (345 and 338 mm/season) for full irrigation with the no mulch and the mulch, respectively. Whears the values of ETa for deficit irrigations were reduced to (419-428 mm/season) for the no mulch, and (326-330 mm/season) for the mulch conditions. The value of the Reference ET0 estimated using the equation Penman- Monteith adjusted higher than the rate of ETa values ​​in the cases of no mulch and mulch (688, 426 and 330 mm/season) respectively. Mulch treatment caused higher water saving as compared with no mulch conditions. The amounts reached (22.3, 22.9, 22.3 and 22.1%) for full irrigation, and deficit irrigation in vegetative growth, tuber initiation and tuber bulking and maturation, respectively. Maximum value of KC was 1.1 in full and deficit irrigation treatments under no mulch compared with 0.84 for full irrigation under mulch conditions. significant decrease in tuber yield was found in deficit irrigation vegetative growth and tuber initiation stage with mulch. The yield was (12.6 and 12.3 ton ha-1) respectively compared with (14.0 ton ha-1) for full irrigation. On the other hand, deficit irrigation showed no effect on yield in tuber bulking stage. The non mulch treatment showed the same behavior, No significant differences in yield was found for no mulch (13.2 ton ha-1) and mulch (14.5 ton ha-1).

Increasing Water Use Efficiency in Husk Tomato (&amp;lt;i&amp;gt;Physalis ixocarpa&amp;lt;/i&amp;gt; Brot) Production in Tabasco, Mexico with Improved Irrigation Water Management

Husk tomato production technology was developed utilizing plastic sheeting and drip irrigation based on the results of reference evapotranspiration and crop coefficients (Kc) proposed at different phenological stages. The objectives of this study were as follows: 1) to evaluate the effect of plastic sheeting on the yield of husk tomato fruit with drip irrigation based on crop evapotranspiration; 2) to validate the use of drip irrigation technology and plastic sheeting in husk tomato production using demonstration plots; and 3) to determine the profitability and economic viability of the product in the domestic market. The proposed Kc values were 0.25, 0.71 and 0.56 in the initial, intermediate and final stage of crop development, respectively. Irrigation rates ranged from 2.5 to 6 mm·day-1, which was equivalent to an irrigation time of 0.6 to 2.5 hr. Soil moisture tension was monitored with tensiometers at depths of 15 and 30 cm in a loamy eutricfluvisol. The use of plastic sheeting increased husk tomato yield by 56.2% and water productivity by 63.5% under drip irrigation conditions when basing irrigation levels on crop evapotranspiration. Soil matrix potential varied between depths of 15 and 30 cm based on irrigation or rainfall amounts and the use of plastic sheeting with values being higher when the plastic sheeting was used. The husk tomato fruit yield in validation plots was 46 and 54.6 t·ha-1 with water use efficiencies ranging from 16.1 to 19.1 kg·m-3. These results exceeded the national average of 14 t·ha-1 and water use efficiency of 2.54 kg·m-3. With this new technology, a cost benefit ratio of 3.6 is obtained, which represents an economically profitable margin for farmers in the region.

LOW COST PVC HYDRAULIC WEIGHING LYSIMETER FOR MEASUREMENT OF CROP EVAPOTRANSPIRATION

Lysimeters are used for measurement of crop evapotranspiration (ETc), which in turn is used for effective crop water management. Though weighing type lysimeters with sophisticated electronic or mechanical weighing systems are the best devices for measurement of ETc, they are quite expensive. Therefore, a study was undertaken at the Indian Institute of Technology Kharagpur to develop a low cost weighing type lysimeter. The developed lysimeter consisted of a circular PVC (Polyvinyl Chloride) tank of 1 m diameter and 0.60 m height and an insulated heliflex PVC pipe of 10 cm diameter, serving as the load cell. Two adjacent holes were made on this pipe, which were fitted with two tubes; one was connected to a manometer and the other was used to fill the heliflex pipe with water. The lysimeter was used to determine the crop coefficients of a chili crop (Capsicum annuum L). Daily reference evapotranspiration (ETo) was computed using the FAO Penman-Monteith method. Crop coefficients (Kc) were estimated at different growth stages of chili crop, using the lysimeter measured actual ET and the estimated ETo. The Kc values for initial, crop development and reproductive stages were found to be 0.41, 0.72 and 0.78 respectively. The performance of the lysimeter was evaluated by comparing the ETc measured through manometric deflection of the hydraulic weighing lysimeter, with that of measured ETc using soil moisture data recorded by neutron probe. The regression analysis between the two methods of measurement of crop evapotranspiration gave a correlation coefficient of 0.93, indicating potential for the low cost PVC hydraulic weighing lysimeter’s use in the developing and under developed countries. The sensitivity of the lysimeter for 5° manometer angle was found to be 0.45 mm of water.

Determination of an efficient irrigation schedule for the cultivation of rose cv. Freedom under greenhouse conditions in Colombia

An experiment on rose (Rosa sp.) cv. Freedom was performed in a greenhouse on the Bogota Plateau, Colombia, to identify an efficient irrigation regime for this crop. The tested treatments were based on three irrigation doses, applying different fractions of the estimated crop evapotranspiration (ETc), calculated using a class A evaporation tank: i) 100% ETc (ETc100), ii) 80% ETc (ETc80) and iii) 70% ETc (ETc70). During the entire experimental period, from mid-May to early September, the crop had a constant production of floral stems. In all of the irrigation treatments, the soil and plant water status were monitored using tensiometers and the midday stem water potential, respectively (ystem). In the fully irrigated roses, the actual water use was determined using a drainage lysimeter in order to obtain the local crop coefficients (Kc) by means of a water balance. From June to August, the obtained monthly Kc values varied between 1.10 and 1.26. Compared to the ETc100 treatment, 14.5 and 21.8% less water was applied in treatments ETc80 and ETc70, respectively. Despite this fact, no statistically significant differences were found among the treatments for rose production or quality. Finally, in the more irrigated roses, tight relationships between the stem water potential and vapor pressure deficit were obtained. The reported base-line equations can be used for predicting the optimum rose plant water status, depending on the environmental conditions. Overall, the reported results can be used for an efficient irritation schedule for rose crops under greenhouse conditions, using the local Kc and direct determinations of plant water status corrected for the evaporative demand.

Determination of Water Requirement and Crop Coefficient for Sorghum (&lt;i&gt;Sorghum bicolor L&lt;/i&gt;.) at Melkassa, Ethiopia

Knowledge of crop evapotranspiration (ETc), the combined process of evaporation and plant transpiration, is important in agriculture for scheduling farm operations and designing and managing irrigation and drainage systems. Development of crop coefficient (Kc) can enhance crop evapotranspiration (ETc) estimates in specific crop growth stages. However, locally determined Kc information is not available for many important crops in Ethiopia. This research was, therefore, conducted to determine growth stage specific Kc and crop water use for sorghum (Sorghum bicolor L.) var. Gambella-1107 at the Melkassa Agricultural Research Center which is located in a semi arid climate zone in Ethiopia. Drainage type lysimeter was used to measure Gambella-1107 crop water use under water balance system on a clay loam soil and local weather data were used to determine the reference evapotranspiration (ETo). Crop coefficient was developed from measured ETc and ETo calculated using weather data. The growth stages of the crop were assessed as the seasonal change of plant height (pH), leaf area (LA) and leaf area index (LAI). The yield obtained was 5.3 t ha-1 and the measured LAI were 0.2, 4.2, 4.9 and 1.6 at the initial, development, midseason and late season stages, respectively. The maximum LAI was achieved when the plants reach their maximum height at mid-season stage with high crop evapotranspiration due to leaf enlargement that increases transpiration. The measured ETc values were 53.8, 138.5, 214.4, and 94.0 mm during the initial, development, midseason and late-season stages, respectively, and the seasonal total value was 500.7 mm. The calculated Kc values for the crop were 0.45, 0.83, 1.18 and 0.78 during the initial, development, mid-season and late-season stages, respectively. These values were greater than those reported in FAO publication for sorghum varieties which could be a result of soil, climate and crop genetic differences. This suggests the need for developing site-specific Kc values for proper irrigation management.

MÉTODO DE PULSO DE CALOR Y FLUJO DE SAVIA PARA MEDIRLA TRANSPIRACIÓN EN EL CULTIVO DE CACAO

The heat pulse method is used for determining transpiration based on the amount of water flowing within the stem of perennial crops such as cacao. The objectives of this study were to determine hourly transpiration from a sap flow meter and estimate crop coefficients (Kc) at different stages of development in order to determine crop water requirements. It is concluded that the heat pulse method and sap flow reasonably estimate the transpiration of cacao trees and properly detect flow direction. Transpiration in cacao varies from 10 to 40 liters per day, in a 10-year-old tree during the irrigation requirement period. The Kc values estimated with shade trees during their growth and development vary from 0.6 to 0.7 in the months of February to May, when irrigation is required due to the water deficit that occurs according to the crop water balance.

Evaluation of clear-sky conditions in high altitude sites

The correct assessment of cloud conditions in any site is important for determining the characteristics of solar resource availability. The criterion proposed by Iqbal has been widely used for this purpose, through the classification of the daily clearness index Kt. However, evidence was found to suggest that this criterion may not be applicable to data measured in high altitude sites, because partially cloudy days are incorrectly classified as clear-sky days. This paper analyzes the cloudiness state of the sky by observing the values of the clearness index Kt and the clear-sky index Kc. These indices were obtained from reliable global solar irradiance data measured over a year in three places of Argentina located at different altitudes (25, 1200 and 3700 m.a.s.l). ESRA and ARG-P models were used to estimate daily clear-sky global solar irradiation values Hc. They also reveal that the most probable value of Kc which corresponds to an actual clear-sky day of a particular location and time depends on the model used to estimate the clear-sky global solar radiation values. Thus, it was confirmed that, unlike the index Kc, the Iqbal's criterion does not correctly classify the cloud cover status from data measured in high altitude sites (>1000 m.a.s.l.).

Evapotranspiration and crop coefficient for watermelon grown under plastic mulched conditions in sub-tropical Florida

Evapotranspiration (ETc) fluxes from plastic mulch production systems are different than open field production systems and require quantification of ETc for plastic mulch environment. A 3-year study was conducted to quantify bi-weekly ETc and develop a crop coefficient (Kc) for drip-irrigated watermelon grown with plastic mulch in sub-tropical Florida using four large drainage lysimeters. The average seasonal ETc was 278mm (min=244mm and max=344mm). Variability in ETc was mainly influenced by rainfall, especially during the initial growth period when it was high. The initial, mid-season, and late season Kc values were 0.65, 1.01, and 0.71, respectively. The initial Kc was considerably higher than literature values. This finding was mainly due to high soil moisture at the beginning of the growing season resulting from surface application of water for plastic mulched raised bed preparation and additional wetting from rainfall that increased evaporative flux. The Kc values were statistically higher (p=0.008) than FAO-56, which underestimated ETc by 30%. A polynomial model was developed to predict Kc as a function of days after transplanting. To improve the ETc estimates for the first two bi-weekly periods when the large area of bare and wet soil results in significantly higher evaporation, a multivariate model (r2=0.78) was developed to predict the Kc as a function of rainfall and relative humidity. The model can be used to adjust Kc, and therefore ETc, for the initial stages when evaporation accounts for most of ETc and is sensitive to frequency of wetting. Use of Kc values from this study will help improve the accuracy of ETc estimates for drip-irrigated watermelon in subtropical Florida and elsewhere with similar environmental condition.

Studies on the mechanical properties of glycine lithium chloride NLO single crystal

The microhardness study reveals the mechanical strength of the grown crystal. The Vicker’s and Knoop hardness studies were performed to understand the mechanical behavior of the glycine lithium chloride crystals. The Vicker’s and Knoop microhardness numbers (HV and HK) for the crystal were found for different loads. It is found that these numbers increase with an increase in the load. The Mayer’s index (n) was found to be greater than 1.6 predicting a soft-material nature. The fracture toughness value (Kc), was determined from the measurements of the crack length. The brittleness indices (Bi) were found for the grown crystals. Using Wooster’s empirical relation, the elastic stiffness constant (C11) was calculated from the Vicker’s hardness values at different loads. The Young’s modulus was also calculated from Knoop microhardness values. Key words: Microhardness number, Mayer’s index, fracture toughness, brittleness indices, elastic stiffness coefficient, Young’s modulus.

Experimental study of the flow field induced by a resonating piezoelectric flapping wing

Flexible plate structures with integrated piezoelectric patches offer interesting possibilities when considered as actuation mechanisms for energy harvesting devices, cooling devices and propulsion devices of micro-aerial vehicles. Most of the studies reported in literature are based on the assumption of a 2D aerodynamic flow. However, the flow behind a finite span wing is significantly more complex than that of an infinite span wing. In order to corroborate this statement, the present experimental study contains high-speed particle image velocimetry measurements performed on a piezoelectric finite span wing oscillating in air, at 84.8 Hz. The paper focuses on the situation of low Keulegan–Carpenter numbers (KC < 3). The dimensionless KC number describes the relative importance of the drag forces over inertia forces for objects that oscillate in a fluid flow at rest. The evolution of the unsteady vortex structures near the plate is characterized for different conditions. This allows a better understanding of the unsteady aerodynamics of flapping flight. The accomplished experimental data analysis has shown that the flow phenomena are strongly dependent on the KC values.

Tuned liquid dampers with a Keulegan–Carpenter number-dependent screen drag coefficient

The amplitude-dependent damping associated with a tuned liquid damper (TLD) equipped with slat-type screens produces a device that performs optimally at a targeted response amplitude. Increasing the slat height produces a screen whose drag coefficient is dependent on the Keulegan–Carpenter number (KC), which may improve the TLD performance. This new type of TLD is modeled as an equivalent mechanical model with damping that is dependent on both KC and the response amplitude. An experimental shake table testing program is undertaken to study the influence of KC on the TLD response and to validate the model. A power fit is performed on the experimentally determined screen drag coefficient and KC values to express the drag coefficient as a function of KC and the steady flow drag coefficient. Predicted frequency response plots of sloshing forces and energy dissipation per cycle are in agreement with experimental results. A structure–TLD system model is developed to theoretically study the performance of this new TLD. Nonlinear shallow water wave theory is used to validate the output of the mechanical model. Results indicate that a KC-dependent screen drag coefficient produces a more robust TLD whose performance is maintained over a broader range of structural response amplitudes.

Consumptive water use and crop coefficients of irrigated sunflower

In semi-arid environments, the use of irrigation is necessary for sunflower production to reach its maximum potential. The aim of this study was to quantify the consumptive water use and crop coefficients of irrigated sunflower (Helianthus annuus L.) without soil water limitations during two growing seasons. The experimental work was conducted in the lysimeter facilities located in Albacete (Central Spain). A weighing lysimeter with an overall resolution of 250 g was used to measure the daily sunflower evapotranspiration throughout the growing season under sprinkler irrigation. The lysimeter container was 2.3 m × 2.7 m × 1.7 m deep, with an approximate total weight of 14.5 Mg. Daily ET c values were calculated as the difference between lysimeter mass losses and lysimeter mass gains divided by the lysimeter area. In the lysimeter, sprinkler irrigation was applied to replace cumulative ET c, thus maintaining non-limiting soil water conditions. Seasonal lysimeter ET c was 619 mm in 2009 and 576 mm in 2011. The higher ET c value in 2009 was due to earlier planting and a longer growing season with the maximum cover coinciding with the maximum ET o period. For the two study years, maximum average K c values reached values of approximately 1.10 and 1.20, respectively, during mid-season stage and coincided with maximum ground cover values of 75 and 88 %, respectively. The dual crop coefficient approach was used to separate crop transpiration (K cb) from soil evaporation (K e). As the crop canopy expanded, K cb values increased while the K e values decreased. The seasonal evaporation component was estimated to be about 25 % of ET c. Linear relationships were found between the lysimeter K cb and the canopy ground cover (f c) for the each season, and a single relationship that related K cb to growing degree-days was established allowing extrapolation of our results to other environments.

The equilibrium between metallic titanium and titanium ions in LiCl–KCl melts

Abstract The equilibrium between metallic titanium and titanium ions (Ti2+, Ti3+) dissolved in LiCl–KCl melts and the influence of the electrolyte composition on the equilibrium were investigated. The accurate concentrations of titanium ions had been obtained based on a reliable approach for taking samples. Furthermore, accurate values of the equilibrium constants were calculated by the best-fitting method under the consideration of the TiOCl dissolution. The influence of the electrolyte composition on the equilibrium was evaluated by determining the equilibrium constant Kc between titanium metal and titanium ions in LiCl–KCl melts with different concentration of LiCl. It was shown that LiCl could affect the equilibrium and the Kc values decreased with the increase of concentration of LiCl.

Determination of maize crop coefficients in humid climate regime using the eddy covariance technique

Italy is one of the most important maize producers in the EU, and the Po Valley plain in northern Italy is the largest maize area in the country, with over 1millionha planted. Water consumption for maize is very high because the crop covers almost 30% of the agricultural land of the plain and is irrigated mainly by border irrigation. Conversion to more efficient methods is currently under discussion for many areas. Whatever the irrigation method adopted, an accurate knowledge of maize irrigation requirements is essential to improving irrigation scheduling and water use planning on a regional scale. The FAO-56 “single crop coefficient” procedure is currently the most widely used procedure for the estimation of crop irrigation requirements. However, in the last 15 years, many authors have shown that FAO-56 crop coefficients, even if adjusted to account for local conditions (climate, soil, irrigation and crop management), may differ by up to ±40% from experimentally determined values. In this study, Kc was derived as the ratio of the actual crop evapotranspiration in well-watered conditions (ETc), as measured by the eddy covariance technique at two maize fields over three years, to the reference crop evapotranspiration ETo. The crop cycle length ranged from 136 to 146 days, depending on the year and the harvesting date, and the accumulated growing degrees-days (GDD) varied from 1590 to 1730°C for silage and grain maize, respectively. The average locally developed Kc values for initial, middle and late growing seasons were 0.33, 0.99 and 0.89–0.35 (the Kc-end value depends on the harvesting time). The experimental Kc-mid was 15% lower than the FAO-56 value adjusted for local conditions. Average seasonal ETc values were 430 and 400mm for grain and silage second-crop maize, respectively