Nitrogen availability to maize as affected by fertilizer application and soil type in the Tanzanian highlands

Enhancing crop production by maintaining a proper synchrony between soil nitrogen (N) and crop N demand remains a challenge, especially in under-studied tropical soils of Sub-Saharan Africa (SSA). For two consecutive cropping seasons (2013–2015), we monitored the fluctuation of soil inorganic N and its availability to maize in the Tanzanian highlands. Different urea-N rates (0–150 kg N ha^?1; split into two dressings) were applied to two soil types (TZi, sandy Alfisols; and TZm, clayey Andisols). In the early growing season, soil mineralized N was exposed to the leaching risk due to small crop N demand. In the second N application (major N supply accounting for two-thirds of the total N), applied urea was more efficient in increasing soil inorganic N availability at TZm than at TZi. Such effect of soil type could be the main contributor to the higher yield at TZm (up to 4.4 Mg ha^?1) than that at TZi (up to 2.6 Mg ha^?1) under the same N rate. The best-fitted linear-plateau model indicated that the soil inorganic N availability (0–0.3 m) at the tasseling stage largely accounted for the final yield. Further, yields at TZi were still limited by N availability at the tasseling stage due to fast depletion of applied-N, whereas yields plateaued at TZm once N availability was above 67 kg N ha^?1. Our results provided a valuable reference for designing the N management to increase yield, while minimizing the potentially adverse losses of N to the environment, in different agro-ecological zones in SSA.     

HEAT TRANSFER CHARACTERISTICS AT EVAPORATING WATER SURFACE IN LAMINAR STREAM OF SUPERHEATED STEAM

ABSTRACT

The heat transfer characteristics at a horizontal evaporating water surface exposed to a laminar stream of superheated stenm, which is a radiation participating real gas, have been investigated and compared to those of a hot air flow by means of a real-time laser holographic inter ferometry. Water surface temperatures and temperature profiles within the laminar boundary layer were measured precisely under adiabatic evaporation conditions. Temperature gradients at the water surface were determined and local Nusselt numbers were estimated. Those experimental results were compared to the analytical results obtained by solving the laminar boundary equations. It can be concluded here that both temperature profiles within the laminar boundary layer and heat transfer characteristics at the evaporating water surface in superheated steam stream are quite different from those in hot air flow due to an influence of gas radiation from superheated steam.     

Living ring-opening polymerization of ɛ-caprolactone with combinations of tert-butyllithium and bilky aluminium phenoxides

Summary The polymerization of ɛ-caprolactone (ɛ-CL) with a combination of tert-butyllithium (t-BuLi) and bis(2,6-di-t-butylphenoxy)methylaluminum [MeAl(ODBP)₂] in toluene at 0°C proceeded in a living manner to give polymers with narrow molecular weight distributions (MWD) within a few minutes, while the polymerization with t-BuLi alone gave a polymer with much broader MWD. The yield of the polymer did not reach 100 % at the Al/Li ratio of 5, because the excess MeAl(ODBP)₂ coordinates with ɛ-CL to protect it from the attack by the propagating species. The polymerization with t-BuLi/EtAl(ODBP)₂ gave polymers in quantitative yields regardless of Al/Li ratio, and also narrower MWD even for higher molecular weight polymers. Received: 1 August 2000/Accepted: 11 August 2000     

Synthesis and photoluminescence properties of fluorine-containing poly(phenylene vinylene) bearing hexafluorocyclopentene-fused phenanthrene unit

The intramolecular oxidative photocyclization of 1,2-diarylhexafluorocyclopentene ( 1 ) under light irradiation (λ = 365 nm) provided hexafluorocyclopentene-fused phenanthrene with formyl groups ( 2 ) in moderate yield. The copolymerization of 2 with tetraethyl(2,5-bis(dodecyloxy)-1,4-phenylene)bis(methylene)diphosphonate by the Horner–Wadsworth–Emmons reaction gave a fluorine-containing poly(phenylene vinylene), Polymer-2, in 41% yield. For comparison, a diphenylethene-type copolymer, Polymer-1, was also prepared analogously. The number-average molecular weights of Polymer-1 and Polymer-2 were 8900 and 3300 g mol^?1, respectively. The copolymers showed high thermal stability, as revealed by their thermogravimetric analysis. UV–visible spectra of the copolymers in CHCl₃ showed π–π* transition peaks at around 420 nm, and the peaks shifted to longer wavelengths by ca 10 nm for samples in film form. The photoluminescence spectra of Polymer-1 and Polymer-2 exhibited peaks at 542 and 560 nm in CHCl₃, respectively, whereas the photoluminescence intensity of Polymer-2 was very low in the solid state, presumably owing to the partial aggregation of the polymer molecules. © 2021 Society of Industrial Chemistry.     

Effect of Pu-rich agglomerates in MOX fuel on reactivity analysis of light water reactor MOX core physics experiments

The effect of Pu-rich agglomerates in U-Pu mixed oxide (MOX) on the reactivity analysis of light water reactor MOX core physics experiments was studied with the continuous-energy Monte Carlo calculation code MVP II. First, the following three different models were compared in the analysis of a representative unit cell of a MOX core tested at the KRITZ reactor: a Lattice model where Pu-rich agglomerates were assumed to exist in a fixed pitch, a statistical geometry (STG) model of MVP II, and a Random model where the random distribution of Pu-rich agglomerates was directly modeled. Since the three models gave comparable results, the STG model was used in parametric calculations to systematically understand the reactivity effect depending on the characteristics of Pu-rich agglomerates. In addition, the selected unit cells composing the MOX cores and one representing MOX core tested at the EOLE criticality facility were analyzed with the measured characteristics of Pu-rich agglomerates in MOX fuel. Consequently, the reactivity differences between the calculations assuming the homogeneous Pu distributions and those considering Pu-rich agglomerates were less than 0.0005 Δk/k/k', indicating that the effect of Pu-rich agglomerates was small on the reactivity analysis of the MOX cores tested in the EOLE facility.     

A function to provide neutron spectrum produced from the 9Be + p reaction with protons of energy below 12 MeV

A function to give the total neutron production cross section, angular distribution, and energy spectrum via the ⁹Be + p reaction has been created by fitting experimental data to characterize compact neutron sources with thick Be targets bombarded by protons with energy below 12 MeV. To examine the suitability of the function, calculations of the angle-dependent neutron energy spectra produced in thick Be targets with 4- and 12-MeV protons using the function were compared with corresponding experiments and calculations using the nuclear data libraries of ENDF/B-VII.0 and JENDL4.0/HE. The function was in better agreement with the experiments than the calculations using the libraries except for at backward angles. The ¹¹⁵In(n,n’)^115mIn reaction rates calculated using GEANT4 with source neutrons given by both the function and ENDF/B-VII.0 were compared with that measured at the RIKEN Accelerator-Driven Compact Neutron Source to evaluate the neutron spectrum above 1 MeV. The function slightly overestimated the measurement by 14% and the calculation with ENDF/B-VII.0 underestimated by 35%. It was concluded that the function can be applied in compact neutron source designs.     

A unified approach for numerical calculation of space-dependent kinetic equation

A unified numerical method based on the factorization approach is developed to solve the space-dependent neutron kinetic equation. Various numerical methods for solving the space-dependent kinetic equation have been developed so far. These methods can be classified into two categories, i.e., the direct and the factorization methods. The factorization method is known as an effective numerical method. In the present study, a new factorization method named the multigrid amplitude function (MAF) method is developed. Unlike the improved quasi-static (IQS) method, an independent amplitude function is assigned for each spatial region and energy group in the MAF method. The MAF method is a generalization of conventional methods, e.g., the frequency transform, IQS, and Theta methods. To evaluate the amplitude function in the MAF method, the time-dependent coarse-mesh finite difference (TCMFD) method is developed. The MAF method is implemented into a space-dependent kinetic code on the basis of the analytical polynomial nodal method. In order to verify the effectiveness of the MAF method, the TWIGL, Langenbuch, Maurer, and Werner (LMW), and Laboratorium für Reaktorregelung and Anlagensicherung (LRA) benchmark problems are analyzed. The calculation results show the effectiveness of the present method.     

Effects of dose rate change under irradiation on hardening and microstructural evolution in A533B steel

Iron-ion irradiations were carried out for 0.09wt%Cu A533B steel specimens at 290°C to investigate effects of dose rate change during irradiation; the irradiations consisted of the base irradiation (with an unchanged dose rate) and an additional one with changed dose rates from 1 to 50 times that of the base one. Nano-indentation hardness measurements showed that the increase in hardness was higher for lower dose rate of the base irradiation. A similar trend was identified during the additional irradiation. Transmission electron microscope (TEM) and three-dimensional atom probe (3DAP) analyses were carried out for the quantitative characterization of defect features. Mn/Ni/Si/Cu-enriched clusters and dislocation loops were observed in all specimens. The increase in hardness mainly depended on the formation of the solute atom clusters. The square root of the volume fraction of the solute atom clusters provided a good correlation with the increase in hardness. The effects of dose rate and dose rate change during irradiation were explained by the formation of solute atom clusters.     

Preservation of transmission probabilities in the method of characteristics

An efficient calculation scheme for the method of characteristics, which allows coarser ray separation width, is newly proposed. Effective lengths of characteristics lines are evaluated from the viewpoint of preservation of transmission probability in the present method. The effective lengths to preserve transmission probabilities can be rigorously estimated through detailed numerical integrations. However, calculation and storage of all effective lengths is inefficient since the transmission probabilities depend on many parameters such as azimuthal angle, polar angle, position of characteristics line, and total cross section. To resolve this issue, in this paper, the analytical equations for the effective lengths are derived from an assumption that distribution function of actual characteristics lengths can be expressed by a linear function. The new approach introduced in this paper is named as transmission probability preservation through linear approximation (TPPL). Verification results indicate that accurate results can be obtained by the TPPL even if ray separation width becomes coarse.