Variation Of ET Research Articles

Climate Change and Vegetation Greening Jointly Promote the Increase in Evapotranspiration in the Jing River Basin

Within the Earth’s terrestrial environment, evapotranspiration significantly contributes to the hydrological cycle, accounting for around 80% of the precipitation on landmasses to be reintroduced into the atmosphere. This mechanism profoundly affects the distribution and availability of surface water resources throughout the ecosystem. Gaining insight into the factors influencing local evapotranspiration fluctuations in response to varying climatic and vegetative scenarios is crucial for effective water management strategies and rehabilitating ecosystem resilience. To this end, our study focuses on the Jing River Basin in the Loess Plateau, utilizing multi-source remote sensing data and climatic information to investigate the spatiotemporal dynamics of evapotranspiration from 1984 to 2018 through the application of the Priestley–Taylor Jet Propulsion Laboratory (PT-JPL) model. Our research results indicate a general ascending tendency in evapotranspiration across the investigated region, demonstrating a notably discernible escalation at a pace of approximately 3.11 mm/year (p < 0.01), with an annual vegetation ET volume reaching 533.88 mm. Across different vegetation types in the Jing River Basin between 1984 and 2018, the mean yearly ET was observed to be highest in forests (572.88 mm), followed by croplands (564.74 mm), shrublands (536.43 mm), and grasslands (503.42 mm). The leaf area index (LAI) demonstrated the strongest partial correlation with ET (r = 0.35) and contributed the most significantly to the variation in ET within the Jing River Basin (0.41 mm/year). Additionally, LAI indirectly influences ET through its impact on vapor pressure deficit (VPD), precipitation (Pre), and temperature (Temp). Radiation is found to govern most ET changes across the region, while radiation and precipitation notably affected ET by modulating air temperature. In summary, these radiant energy changes directly affect the evaporation rate and total evapotranspiration of surface water. It provides important support for understanding how evapotranspiration in the Jing River Basin is adjusting to climate change and increased vegetation cover. These findings serve as a theoretical foundation for devising sustainable vegetation restoration strategies to optimize water resource utilization within the region.

Spatio-temporal variation of evapotranspiration and its linkage with environmental factors in the largest freshwater lake wetland in China

Study regionPoyang lake wetland Study focusEvapotranspiration (ET) is a critical parameter in the hydrologic and energy budget, and it is important for understanding spatio-temporal variations in ET in large lake wetlands. Monthly ET in the Poyang Lake wetland during 2008–2017 was estimated by the remote sensing ET retrieval model based on a Nonparametric approach (RS-NP). And the spatio-temporal variation of ET and the influencing factors were analyzed. New hydrological insights for the regionThe validation revealed the usefulness of the RS-NP model in a moist region and yielded a relative error of 6 % (12 %) in the wet (dry) season. Temporally, the average yearly ET was 884 mm with ET/P (precipitation) of 55 %− 65 %. The monthly ET/P ratio increased significantly from 40 %− 50 % from January to May to 90 %− 130 % from July to October. ET in June was lower by over 20 % than that in May and July with the lowest ET/P value (33 %). Spatially, relatively larger and lower ET occurred in the northern and southern parts, respectively. The main factors affecting ET variability were downwelling shortwave radiation (∼2/3 contribution) and water area (∼1/3 contribution) at the monthly scale. Precipitation and surface temperature dominantly controlled the hysteresis effects with a lag of one month and regulated LE monthly variations. This study improves our understanding of complicated water-atmosphere interactions and their linkages with environmental factors in large lake systems.

Conformational Dependence of Triplet Energies in Rotationally Hindered N- and S-Heterocyclic Dimers: New Design and Measurement Rules for High Triplet Energy OLED Host Materials.

A series of four heterocyclic dimers has been synthesized, with twisted geometries imposed across the central linking bond by ortho‐alkoxy chains. These include two isomeric bicarbazoles, a bis(dibenzothiophene‐S,S‐dioxide) and a bis(thioxanthene‐S,S‐dioxide). Spectroscopic and electrochemical methods, supported by density functional theory, have given detailed insights into how para‐ vs. meta‐ vs. broken conjugation, and electron‐rich vs. electron‐poor heterocycles impact the HOMO–LUMO gap and singlet and triplet energies. Crucially for applications as OLED hosts, the triplet energy (E T) of these molecules was found to vary significantly between dilute polymer films and neat films, related to conformational demands of the molecules in the solid state. One of the bicarbazole species shows a variation in E T of 0.24 eV in the different media—sufficiently large to “make‐or‐break” an OLED device—with similar discrepancies found between neat films and frozen solution measurements of other previously reported OLED hosts. From consolidated optical and optoelectronic investigations of different host/dopant combinations, we identify that only the lower E T values measured in neat films give a reliable indicator of host/guest compatibility. This work also provides new molecular design rules for obtaining very high E T materials and controlling their HOMO and LUMO energies.

Spatiotemporal variation of actual evapotranspiration and its response to changes of major meteorological factors over China using multi-source data

Abstract Evapotranspiration (ET) is an important component of the water and energy cycle. To obtain more accurate actual ET estimation, three commonly used actual ET products (i.e., GLEAM, GLDAS, and SSEBop) are merged by the simple Taylor skill score fusion method. Validation results show that the merged actual ET data exhibits better correlation with eddy-covariance ET observation than single-source ET data. Based on the merged ET, the spatiotemporal variations of ET over China and their links to changes of three meteorological factors, i.e., precipitation, air temperature (Ta), and shortwave radiation (Rs), are analyzed. During 2003–2016, there is a general upward trend in ET with an increase rate of 1.6 mm/year over China. ET increases very significantly in northeastern China, the southern coastal region, and the northwestern corner of China, whereas it decreases significantly in Huang-Huai-Hai Plain. There is a clear spatial pattern of the relationship between ET and its driving factors, i.e., the variation of ET in the humid southeast is dominated by Ta and Rs; in the semi-humid and semi-arid zone, the variation of ET is controlled mainly by precipitation, followed by Ta; and in arid northwestern China, the variation of ET is controlled mainly by precipitation.

(Invited) Electrical Activity of Extended Defects in III-V Semiconductors

The electrical activity of a defect in a semiconductor material is usually expressed in terms of the Shockley-Read-Hall (SRH) theory which provides an expression for the generation or recombination lifetime. Along the same lines, one can calculate the leakage current generated by a single defect in the depletion region of a junction, as shown in Fig. 1 [1]. It is clear that for III-V based ternary alloys, like the InxGa1-xAs system, the generation current depends proportionally on the intrinsic carrier concentration ni (see equation in Fig. 1). However, equally important is also the variation of the defect energy level ET as a function of the In content x: for ET pinned to the intrinsic Fermi level Ei(x), the leakage current will follow ni. On the other hand, when ET is pinned to either the valence or conduction band, the leakage current will decrease exponentially with the difference |ET-Ei| [2]. It is thus important to derive the variation of ET with alloy composition x for a certain type of defect and to establish what could be consideredas a kind of Vegard’s law for specific deep levels. In addition, when integrating III-V compounds on a silicon CMOS platform, extended defects will be inevitably introduced [3]; for a sufficiently high density, they will govern the reverse current [3,4]. It is thus of vital importance to study the electrical parameters of extended defects in III-V-on-silicon materials and their evolution with composition x. The aim of the this work is to review what is known about the electrical activity of extended defects in InxGa1-xAs-based hetero-epitaxial layers. Results will be described about a combined p-n diode current-voltage (I-V) and lifetime analysis on a set of nearly strain-free layers where x=0.53 with varying densities of extended defects [5]. Based on this, it is demonstrated that for an extended defect density exceeding ~2×107 cm-2 the SRH lifetime becomes dominated by a near mid-gap trap level, associated with them. A detailed Deep-Level Transient Spectroscopy (DLTS) analysis provides further information about the electrical activity of these extended defects and confirms the presence of a dominant electron trap. The corresponding activation energy is represented in Fig. 2 versus x and compared with available literature data. In addition, it is shown that this deep level indeed belongs to an extended defect, based on the electron capture behavior, varying approximately logarithmically with the capture time [4]. Moreover, it can be shown that the electron traps belong to a one-dimensional band-of-states, associated with a ‘perfect’ extended defect. According to Fig. 2, this level appears to follow approximately Ei(x), so that it will dominate the leakage current of a p-n junction over a wide composition range, at least up to 0.53, when present in a sufficient density. Moreover, the defects will become more efficient leakage centers for increasing x. Finally, the implications of the band-like nature of the energy states of extended defects on the carrier generation/recombination will be discussed. [1] J. Vanhellemont and E. Simoen, J. Electrochem. Soc, 154, H572 (2007). [2] E. Simoen, J. Lauwaert and H. Vrielinck, Semiconductors and Semimetals, Eds. L. Romano, V. Privitera and C. Jagadish, 91, pp. 205-250, Elsevier 2015. [3] E. Simoen, “Impact of defects on the performance of high-mobility semiconductor devices”, In: High Mobility Materials for CMOS Applications, Ed. N. Collaert, Elsevier, Ch. 5, July 2018. [4] C. Claeys et al., ECS J. Solid State Sci. and Technol., 5, P3149 (2016). [5] P.-C. Hsu et al., J. Appl. Phys., 124, 165707 (2018). Figure 1

Analysis of Changes in Reference Evapotranspiration, Pan Evaporation, and Actual Evapotranspiration and Their Influencing Factors in the North China Plain During 1998–2005

AbstractEvapotranspiration (ET) plays an important role in both energy and water balances. Determining changes in the different types of ET and their influencing factors under climate change is crucial to fully understand the mechanisms controlling ET and regional water cycles. Based on ET and meteorological data measured during 1998–2005 at the Yucheng Comprehensive Experimental Station of the Chinese Academy of Sciences, the variation of reference ET (ET0), pan evaporation (Epan), and lysimeter ET (the actual ET, Elys) were estimated. Together with a Mann‐Kendall trend test, correlation and sensitivity analyses were conducted to determine the effects of climatic factors, crop coefficients (Kc), and leaf area index (LAI) on different types of ET. During 1998–2005, precipitation presented an upward trend at all time scales, and average temperature (Ta), minimum temperature (Tmin), relative humidity, Epan, and ET0 exhibited downward trends. Elys displayed a downward trend at the daily scale and an upward trend at monthly and annual scales. The correlation analysis indicated that Epan and Elys were significantly positively correlated with all climatic factors except precipitation and relative humidity. The sensitivity analysis revealed that except for relative humidity, the influence of the other climatic factors on ET0 was positive. The highest sensitivity was found for relative humidity, followed by Ta, maximum temperature (Tmax), and Tmin. An analysis of the influence of Kc and LAI on the actual ET indicated that with an increase of Kc and LAI, the actual water demand of crops also displayed an upward trend.

Combining biophysical parameters, spectral indices and multivariate hyperspectral models for estimating yield and water productivity of spring wheat across different agronomic practices.

Manipulating plant densities under different irrigation rates can have a significant impact on grain yield and water use efficiency by exerting positive or negative effects on ET. Whereas traditional spectral reflectance indices (SRIs) have been used to assess biophysical parameters and yield, the potential of multivariate models has little been investigated to estimate these parameters under multiple agronomic practices. Therefore, both simple indices and multivariate models (partial least square regression (PLSR) and support vector machines (SVR)) obtained from hyperspectral reflectance data were compared for their applicability for assessing the biophysical parameters in a field experiment involving different combinations of three irrigation rates (1.00, 0.75, and 0.50 ET) and five plant densities (D1: 150, D2: 250, D3: 350, D4: 450, and D5: 550 seeds m-2) in order to improve productivity and water use efficiency of wheat. Results show that the highest values for green leaf area, aboveground biomass, and grain yield were obtained from the combination of D3 or D4 with 1.00 ET, while the combination of 0.75 ET and D3 was the best treatment for achieving the highest values for water use efficiency. Wheat yield response factor (ky) was acceptable when the 0.75 ET was combined with D2, D3, or D4 or when the 0.50 ET was combined with D2 or D3, as the ky values of these combinations were less than or around one. The production function indicated that about 75% grain yield variation could be attributed to the variation in seasonal ET. Results also show that the performance of the SRIs fluctuated when regressions were analyzed for each irrigation rate or plant density specifically, or when the data of all irrigation rates or plant densities were combined. Most of the SRIs failed to assess biophysical parameters under specific irrigation rates and some specific plant densities, but performance improved substantially for combined data of irrigation rates and some specific plant densities. PLSR and SVR produced more accurate estimations of biophysical parameters than SRIs under specific irrigation rates and plant densities. In conclusion, hyperspectral data are useful for predicting and monitoring yield and water productivity of spring wheat across multiple agronomic practices.

Spatial‐Temporal Patterns of Evapotranspiration Along an Elevation Gradient on Mount Gongga, Southwest China

AbstractEvapotranspiration (ET) is a crucial component of the hydrological cycle in terrestrial ecosystems, but estimating ET in mountainous regions is challenging. In this study, the performance of a generalized nonlinear formulation of the complementary principle while estimating daily ET was evaluated, and the spatial‐temporal variation of ET was analyzed across four vegetation types along an elevation gradient on Mount Gongga, Southwest China. The values of the calibrated Priestley and Taylor coefficients for each of the four sites ranged from 0.98 to 1.13. The correlation coefficients between the estimated and observed daily actual evapotranspiration for each of the four sites ranged from 0.71 to 0.92. A markedly asymmetrical complementary relationship existed among the four studied sites, and the values showed less scattered during the wet season. The annual ET rates were 779.12, 781.63, 701.77, and 625.17 mm/yr in the broadleaf forest (BLF), broadleaf and coniferous mixed forest (BCF), coniferous forest (CF), and shrub land (SL), respectively, and showed a decreasing trend of 9.72 mm per 100 m along the elevation gradient. After recalibration of the seasonal αe values, the estimated annual ET rates increased and were closer to the observed values in BLF and BCF. The results indicate that daily ET in mountainous areas can be estimated using the generalized nonlinear formulation of the complementary relationship together with routine meteorological data alone, but seasonal changes in αe values should be taken into consideration in forests with deciduous trees.

Discordant Voting Processes on Finite Graphs

We consider an asynchronous voting process on graphs which we call discordant voting, and which can be described as follows. Initially each vertex holds one of two opinions, red or blue say. Neighbouring vertices with different opinions interact pairwise. After an interaction both vertices have the same colour. The quantity of interest is T, the time to reach consensus, i.e. the number of interactions needed for all vertices have the same colour. An edge whose endpoint colours differ (i.e. one vertex is coloured red and the other one blue) is said to be discordant. A vertex is discordant if its is incident with a discordant edge. In discordant voting, all interactions are based on discordant edges. Because the voting process is asynchronous there are several ways to update the colours of the interacting vertices. Push: Pick a random discordant vertex and push its colour to a random discordant neighbour. Pull: Pick a random discordant vertex and pull the colour of a random discordant neighbour. Oblivious: Pick a random endpoint of a random discordant edge and push the colour to the other end point. We show that ET, the expected time to reach consensus, depends strongly on the underlying graph and the update rule. For connected graphs on n vertices, and an initial half red, half blue colouring the following hold. For oblivious voting, ET = n2/4 independent of the underlying graph. For the complete graph Kn, the push protocol has ET = =(n log n), whereas the pull protocol has ET = =(2n). For the cycle Cn all three protocols have ET = =(n2). For the star graph however, the pull protocol has ET = O(n2), whereas the push protocol is slower with ET = =(n2 log n). The wide variation in ET for the pull protocol is to be contrasted with the well known model of synchronous pull voting, for which ET = O(n) on many classes of expanders.

Estimation of forest evapotranspiration over Uttarakhand hills, India

Potential evapotranspiration (PET) in the Uttarakhand forests has been estimated using the Modified Prestly-Taylor Method [1]. The estimated PET has been used to determine the actual evapotranspiration (AET) based on the limitation in available water (soil moisture) on the ground. The required meteorological data used in the estimation of ET is obtained from field measurements at three forest sites which includes Deodar (Cedrus deodara), Pine (Pinus roxburghii) and Oak (Quercus spp.) forests located within an area of five km radius in the district Tehri Garhwal. The meteorological data including daily sun shine hours, humidity, air temperature and soil moisture for one year from July, 2005 to June, 2006 were recorded and used in the estimation of ET. The daily average ET was highly influenced by the sunshine hours and soil moisture. A significant seasonal variation in the ET is observed. The results of seasonal variation in ET can be used as an indicator of possible forest fire events and helpful in prevention and management of forest fire in the hilly areas of Uttarakhand state of India.

Impacts of climate variability on reference evapotranspiration over 58 years in the Haihe river basin of north China

Abstract Physically, evaporative demand is driven by net radiation ( R n ), vapour pressure ( e a ), wind speed ( u 2 ), and air temperature ( T a ), each of which changes over time. By analyzing temporal variations in reference evapotranspiration (ET 0 ), improved understanding of the impacts of climate change on hydrological processes can be obtained. In this study, variations in ET 0 over 58 years (1950–2007) at 34 stations in the Haihe river basin of China were analyzed. ET 0 was calculated by the FAO Penman–Monteith formula. Calculation of Kendall rank coefficient was done by analyzing the annual and seasonal trends in ET 0 derived from its dependent climate variables. Inverse distance weighting (IDW) was used to analyze the spatial variation in annual and seasonal ET 0 , and in each climate variable. An attribution analysis was performed to quantify the contribution of each input variable to ET 0 variation. The results showed that ET 0 gradually decreased in the whole basin over the 58 years at a rate of −1.0 mm yr −2 , at the same time, R n , u 2 and precipitation also decreased. Changes in ET 0 were attributed to the variations in net radiation (−0.9 mm yr −2 ), vapour pressure (−0.5 mm yr −2 ), wind speed (−1.3 mm yr −2 ) and air temperature (1.7 mm yr −2 ). Looking at all data on a month by month basis, we found that T a had a positive effect on dET 0 /d t (the derivative of reference evapotranspiration to time) and R n and u 2 had negative effects on dET 0 /d t . While changes in air temperature were found to produce a large increase in dET 0 /d t , changes in other key variables each reduced rates, resulting in an overall negative trend in dET 0 /d t .

Evapotranspiration and crop coefficient for a temperate desert steppe ecosystem using eddy covariance in Inner Mongolia, China

AbstractEvapotranspiration (ET), which links water, energy and the carbon cycle in terrestrial ecosystems, is an important eco‐hydrological process, especially in arid and semi‐arid regions. To determine the crop coefficient (Kc) over a 2‐year period for a temperate desert steppe in Inner Mongolia, China, ET was measured using the eddy covariance method and the reference evapotranspiration (ET0) was estimated from site meteorological data. The results showed that the seasonal variation of ET differed on an annual timescale between the 2 consecutive years, exhibiting a multi‐peak curve in 2008 and a single peak in 2009. The mean daily Kc values were 0·15 and 0·17 in 2 years, varying from 0·009 to 0·75 in 2008 and from 0·005 to 0·58 in 2009. The 5‐day moving average for Kc values was mainly affected by SWC10cm and Rn, and the regression coefficients (R2) were 58·9 and 69·5%, respectively. These results will aid in making accurate and quantitative assessments of the vulnerability of the sparse vegetation to climate change. Copyright © 2011 John Wiley & Sons, Ltd.

Role of irrigation and mulch on yield, evapotranspiration rate and water use pattern of tomato (Lycopersicon esculentum L.)

▶ Two irrigations under CPE 50 resulted 9 Mg ha −1 yield increment compare to rainfed condition. The same was 12 Mg ha −1 more under five irrigations treatment. Thus, additional three irrigations amounting 90 mm enhanced the yield by only 3 Mg ha −1 . Therefore under limited water, irrigation application with moderate (CPE 50 ) level is highly desirable instead of high frequency (CPE 25 ) irrigation. Under such cases the additional three irrigations can be employed to bring out more (1.5 times) land under irrigation with 52 Mg ha −1 more yield. ▶ Among different mulches, RSM and WPM significantly increase yield to the tune of around 7 Mg ha −1 compare to NM condition. On the other hand black polythene mulch has the capacity to increase fruit yield by 16 Mg ha −1 in expense of less water compare to NM condition. So BPM could be a good management option for tomato cultivation in the Lower Gangetic Plain of eastern India. ▶ There was a close interaction between irrigation frequency and actual evapotranspiration rate (ET R ). Thus, interval between two consecutive irrigations greatly influenced the ET R value. Increase in irrigation frequency promoted more unproductive loss of water by surface evaporation. The same was decreased with the decrease in frequency of irrigation. Maximum ET rate occur under bare soil condition, which minimized by different mulches in the order of RSM > BPM > WPM. ▶ The highest WUE value (21.6 kg m −3 ) was noted when two irrigations was applied (CPE 50 ) and the same was at the lowest point when five irrigations were supplied to the crop. Among different mulches the values were in the order of BPM > RSM > WPM > NM. ▶ Finally it can be concluded that, under water scarce situation adoption of deficit irrigation clubbed with black polyethylene mulch can be a good option for utilizing water resource most efficiently without significant decrease in yield. Irrigation management strategy invites the quantification of crop response to irrigation frequencies. Conventionally, mulches increase the yield and water use efficiency (WUE) to a great extent by augmenting the water status in the root zone profile. A field study was carried out during the winter season (November–March) of 2003–2004 and 2004–2005 at the Central Research Farm of Bidhan Chandra Krishi Viswavidyalaya (Latitude 22°58′N, Longitude 88°31′E and altitude 9.75 m amsl), Gayeshpur, India, to evaluate the effect of irrigation frequencies and mulches on evapotranspiration rate from tomato crop field as well as leaf area index (LAI), fruit yield and WUE of the crop. The experiment was laid out in a split-plot design where three irrigation treatments {rainfed (RF); CPE 50 and CPE 25 where irrigation was given at 50 and 25 mm of cumulative pan evaporation (CPE)} were kept in the main plots and the subplots contained four mulch managements {no mulch (NM), rice straw mulch (RSM), white polyethylene mulch (WPM) and black polyethylene mulch (BPM)}. Under CPE 25 , tomato crop recorded significantly higher leaf area index (LAI) over CPE 50 and rainfed condition. LAI value under BPM was 9–30% more over other mulches. Maximum variation of LAI among different treatments was recorded at 60 days after transplanting (DAT). Fruit yield under CPE 25 was 39.4 Mg ha −1 ; a reduction of 7 and 30% has been obtained under CPE 50 and RF condition. The use of mulch increased 23–57% yield in comparison to NM condition. Actual evapotranspiration rate (ET R ) was 1.82 mm day −1 under CPE 25 and declined by 15 and 31% under CPE 50 and RF condition, respectively. The variation of ET R among different mulches became more prominent under maximum water stressed (RF) condition, whereas the variation was negligible under CPE 25 frequency. Irrespective of mulching WUE was highest under moderately wet (CPE 50 ) soil environment. Among different mulches, BPM was responsible for attaining the highest WUE value (25.1 kg m −3 ), which declined by 22, 21 and 39% under WPM, RSM and NM, respectively.

Modeling cherry orchard evapotranspiration based on an improved dual-source model

Abstract The partitioning of canopy transpiration (Ec) and soil evaporation (Es) is often important to estimate evapotranspiration for hydrologic, ecologic, forest, and agricultural applications. Although Shuttleworth–Wallace (SW) model can estimate the partitioning of Ec and Es, some parameters due to the complicated model structure are not easily obtained. Therefore, this has limited the further development of SW model. In this study, an improved dual-source model (SSW) was proposed for ET estimation. This simpler model structure with less parameters than SW model can estimate Ec and Es, separately, and only requires conventional meteorological data. The estimations of Ec and Es for the observation period were consistent with the data measured from sap flow and micro-lysimeter, respectively, in a commercial cherry orchard in Beijing, China. Also daily ET estimated from the SSW, SW, and Penman–Monteith (PM) model were compared and analyzed. The results showed there was a small difference between SSW and SW model, but their accuracy were both higher than PM model's, and the root mean square error (RMSE) was 0.641, 0.613 and 0.955 mm/day, respectively. Sensitivity analysis for SSW model showed that the variation of ET was less than 2% when parameters varied in the range of ±20%. So, the SSW model is not only simple but also high accurate and stable, and it appears suitable to estimate cherry orchard ET.

Influence of irrigation frequencies and phosphate fertilization on actual evapotranspiration rate, yield and water use pattern of rajmash ( Phaseolus vulgaris L.)

The hypothesis was tested, whether soil wetness and phosphorus status could regulate the evapotranspiration rate (ET R), which is of special interest in the lower Gangetic Plain. Rajmash was grown during November–February of 2003–2004 and 2004–2005 on a sandy loam soil, and was irrigated when cumulative pan evaporation (CPE) attained the value of 33 mm (CPE 33); 44 mm (CPE 44) and 66 mm (CPE 66). Four levels of phosphate application were 0 kg P 2O 5 ha −1 (P 0); 30 kg P 2O 5 ha −1 (P 30); 60 kg P 2O 5 ha −1 (P 60) and 90 kg P 2O 5 ha −1 (P 90). Seed yield under CPE 33 was 1.37 Mg ha −1 and reduced by 18% and 35%, respectively under CPE 44 and CPE 66. Continuous increasing trend in yield was recorded with an increase in phosphate level (PL). Irrespective of growth stages, similar trends were recorded for leaf area index (LAI). Maximum variation in LAI among the treatments was recorded at 60 days after sowing. On average, actual ET R was 1.37 mm day −1 under CPE 33 and declined by 13% and 16% under CPE 44 and CPE 66, respectively. Variation in ET R under different PL was highest under CPE 33 and lowest under CPE 44. Except P 90, irrespective of PL, highest value of water use efficiency (WUE) was obtained under CPE 44. However, magnitude of net evapotranspiration efficiency (WUE ET) and irrigation efficiency (WUE I) attained the highest level under CPE 33 regime. All water use indices showed an increasing trend with the increase in phosphate level from 0 to 90 kg ha −1. Impact of phosphorus on various parameters was pronounced under CPE 33.

Advanced modelling of GaN/AlGaN HEMT devices with field plate

AbstractIn this paper we carry out detailed study and numerical modelling of the operation of the GaN/AlGaN High Electron Mobility Transistor (HEMT) with Field Plate (FP) optimisation. The FP has the effect of smoothing the potential gradient along the HEMT channel near the gate edge on the drain side, resulting in the enhancement of the breakdown voltage. We show that the main effect of the FP is a substantial decrease in the longitudinal component of the field EL, along with little variation of the normal component ET. In addition to the main peak of the EL field at the gate edge, there is a secondary peak under the FP edge which grows rapidly with drain bias and eventually surpasses the first. The appearance of the second peak should be taken into account in optimising of the HEMT design. The I‐V characteristics of the FP‐gated device remain practically the same as those of a device without a FP. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Survival, starvation, and activity in Heterorhabditis megidis (Nematoda: Heterorhabditidae)

Infective juveniles (IJs) of entomopathogenic nematodes do not feed but have ample stored energy reserves and can survive for several months in soil or in water. Intraspecific variation in survival of Heterorhabditis megidis has been observed for eight isolates of H. megidis stored in water at 20 °C for up to 14 weeks with the 50% survival time (ST 50 ) ranging from 5.6 to 12.5 weeks. How important physical and behavioral attributes were in explaining this variation in survival was explored using stepwise regression. Included in the analysis were: initial energy reserves (measured by image analysis densitometry), size (area and length) the time at which 50% of energy reserves were depleted (ET 50 ), and motility (head movements/min in week 0). Energy depletion rate, ET 50 , is an important predictor of survival, explaining 93.8% of the variation in ST 50 among isolates. Energy depletion rate was highest in the first week, a time at which H. megidis IJs were spontaneously active during storage. By week 5, when IJs had begun to die, some individuals had completely depleted their energy reserves, supporting the hypothesis that death was a result of starvation. In a second stepwise regression, performed to explore what factors contribute to variation in rate of energy depletion, motility accounted for 60.1% of the variation in ET 50 . With the inclusion of initial energy reserves, length, and area, 88.5% of the variation was accounted for. We conclude that intraspecific variation in survival of H. megidis in water is due largely to variation in rates of depletion of energy reserves, which in turn is strongly associated with levels of locomotory activity.

Correlation of bispectral index with end-tidal sevoflurane concentration and age in infants and children

The bispectral index (BIS) has been evaluated as a tool for measuring depth of anaesthesia, but the use of BIS in a paediatric population is still controversial. This study was designed to evaluate the correlation of BIS with end-tidal sevoflurane concentration and age in infants and children. Eighty-one patients undergoing elective urology surgery were allocated into three age groups; 6 months to 2 yr (n=28), 3-7 yr (n=33), and 8-12 yr (n=20). Sevoflurane was administered to achieve steady-state end-tidal sevoflurane concentrations (ET(sevo)) of 2.0, 3.0, and 4.0%; these were achieved consecutively either from the lowest or from the highest concentration. The BIS (version XP) was monitored continuously. In all three groups, BIS decreased significantly when ET(sevo) increased from 2.0 to 3.0% but there was a paradoxical increase in BIS values when ET(sevo) increased from 3.0 to 4.0%. The non-linear regression analysis showed a significant correlation between BIS and age at each ET(sevo). The younger patients showed the higher BIS values. In children aged 6 months to 12 yr, the BIS increased paradoxically as ET(sevo) increased from 3.0 to 4.0%. BIS values showed a wide variation in the same ET(sevo) and the age itself was considered to be a factor affecting the BIS values.

Influence of welding parameters on microstructures and mechanical properties of electron beam welded aluminium–lithium plates

The present work focused on the welding characteristics of electron beam welding (EBW) in 8090 Al–Li plates, evaluated in terms of strength or toughness degradation in post-weld impact and bending tests with loading rates of 103, 10-1, and 10-4 s-1. The influence of welding parameters, such as welding power, welding speed, and electron beam focus position, on the post-weld microstructures, porosity, and mechanical properties were examined. Although the joint efficiency for the maximum flexure strength (Fp ), or tensile strength, can be as high as 85–90%, the joint efficiency for the fracture absorption energy (Et ) was only 20–40%, a level usually unsuitable for applications. It was found that changing the welding power and speed by a factor of 3 resulted in significant variation in Et but only minor variation in Fp . Changing the welding focus position had little effect on post- weld mechanical properties. The abundant grain boundary precipitates in the welded specimens were thought to be the main cause of the degraded post-weld properties. Other microstructural factors included the δ′ precipitate and grain sizes. The volume fraction of porosity did not play any decisive role owing to the small size (<0·3 mm), low quantity (1–2%), and spherical shape of the EBW induced pores. Finally, given the same post-weld microstructures, the toughness degradation of the EBW specimens was worst under high rate impact loading.

Optimization of furrow irrigation schedules, designs and net return to water

A seasonal furrow irrigation model consisting of irrigation scheduling and kinematic-wave-based hydraulic submodels was modified to incorporate an economic optimization submodel. The model used a systematic simulation technique to optimize furrow irrigation schedules and designs assuming 80% irrigation adequacy at cutoff time. The irrigation schedules and designs were optimized for the homogeneous and heterogeneous infiltration under the mean and observed ET o (grass reference crop ET) conditions. The optimal management allowable depletion (MAD) level changed with the variation in ET o condition, and with the consideration of spatial and temporal (seasonal) variability in infiltration characteristics. Irrigation design changed with both infiltration conditions and MAD level. Infiltration variability did not influence the bean yield. However, the return to water decreased when spatial variability in infiltration conditions was considered. Using mean ET o resulted in slightly higher yield and net return to water as compared to using observed ET o. A small variation in daily mean ET o values with respect to daily observed ET o values caused a change in both irrigation schedules and designs. Therefore, mean ET o cannot be used to forecast irrigation schedules and designs at the beginning of crop season. The net return to water increased (1.7 to 3.6%), and the seasonal inflow, losses, and bean yield decreased in the case of variable interval scheduling (holding MAD constant) as compared to the fixed interval scheduling (MAD varies).