Lower Sublayer Research Articles

CURRENT TRENDS IN THE DEVELOPMENT OF AGRICULTURAL SYSTEMS IN THE UDMURT REPUBLIC

Minimisation of soil tillage is one of the defining trends in the development of agriculture. It allows for a significant reduction in agrotechnical operations in crop cultivation, thereby reducing the technological load on soils, energy, and labour inputs in production and increasing soil resistance to erosion processes. Minimum tillage effectively promotes the restoration of potential and adequate soil fertility and aligns with the principles of adaptive landscape agriculture. Despite numerous positive aspects of minimum tillage, its implementation in production is restrained by certain drawbacks: worsening of crop phytosanitary conditions, increased plough layer density, differentiation of the plough layer by agrochemical and agrophysical indicators, and more. To assess the possibility of implementing minimum tillage in the soil and climatic conditions of the Udmurt Republic, long-term field experiments have been conducted at the Udmurt Research Institute of Agriculture since 1980. Both positive and negative aspects of three types of primary soil tillage have been identified. Moldboard ploughing, throughout the observation period, compared to other types of tillage, provided the highest crop yield (by 0.15 0.50 t per hectare or 5.6 17.5%) and energy efficiency coefficient (by 1.9 16.7%). No-till soil treatment proved to be the most environmentally friendly, increasing the organic matter content in the 0-10 cm layer by 8.1 11.5%. However, it led to a strong differentiation of the plough layer into two sub-layers: 0-10 and 10-20 cm. The lower sub-layer was characterised by higher density and lower content of mineral nutrients and humus. In most cases, combined tillage showed intermediate results. Further scientific research is needed to develop agrotechnologies with more significant minimisation of soil tillage.

The Hummocky Patches and Associated Sediment Dynamics Over an Accretional Intertidal Flat

Tidal flat system is composed of multiple sub-scale geomorphological units. We found a new mesoscale geomorphological unit on sand-mud mixed intertidal zone along China coast, which was defined as hummocky patches. Hummock patches are most developed in middle tidal flat, with horizontal magnitude of 10–20 m and vertical magnitude of ∼15 cm. Hummocky patches significantly influence local sediment transport, thus affect morphological evolution of tidal flats. In order to understand the formation and development mechanisms of hummocky patches, we collected hydrodynamics, topography, sediment properties, and substrate erosion thresholds data through an in-situ field observation covering a spring-neap tidal cycle over an accretional intertidal flat in Jiangsu, China. We found that sediment characteristics including sorting coefficient (σ: measuring the uniformity of sediment particles) and silt/clay/organic matter/water content are essentially different between hummocky patches and nearby seabed, which leads to spatially varied substrate erosion resistance. The measured erosion thresholds for patches are two times higher comparing to surrounding seabed sediment, which provides foundation for the formation of hummocky patches. Under the impact of periodical tidal currents and waves, surrounding seabed experiences considerably more erosion than patch area, which finally develops to hummocky patches. Therefore, hydrodynamic forces drive the formation and development of patches. The erosion resistance of patches decreases vertically from seabed surface to sublayer, causing initial erosion in the lower sublayer, followed by a mass collapse of the seabed surface layer. Hummocky patches are commonly found in middle tidal zone and their sizes decrease to the shore as tidal currents and waves attenuate with shoreward propagation. Hummocky patches have distinct seasonal variations, which only appear in summer and autumn when wind waves are comparatively lower than winter and spring. We infer the reason is that the strong hydrodynamics caused by winter storms cause larger bottom shear stress than the erosion threshold of hummocky patches, leading to destruction of hummocky patches and a smooth tidal flat surface. This study shed new insight on the knowledge of mesoscale geomorphological units and their formation and development in intertidal flats, which provides crucial information for developing more realistic tidal flat sediment transport and morphological models.

Aerodynamic Characteristics Over Fine-Grained Gravel Surfaces in a Wind Tunnel

Gravels can protect soil from wind erosion, however, there is little known about the effects of fine-grained gravel on aerodynamic characteristics of the near-surface airflow. Drag coefficient, wind-speed gradient, and turbulent transfer coefficient over different coverages of gravel surfaces were investigated in a compact boundary-layer wind tunnel. The drag coefficient of the fine-grained gravel surface reached the maximum value at 15% coverage and then tended to stabilize at gravel coverage 20% and greater. At a height of 4 cm, near-surface airflow on gravel surfaces can be divided clearly into upper and lower sublayers, defined as the inertial and roughness sublayers, respectively. The coefficient of variation of wind speed over gravel surfaces in the roughness sublayer was 8.6 times that in the inertial sublayer, indicating a greater effect of gravel coverage on wind-speed fluctuations in the lower layer. At a height of 4 cm, wind-speed fluctuations under the observed wind speeds were independent of changes in gravel coverage. In addition, an energy-exchange region, where sand particles can absorb more energy from the surrounding airflow, was found between the roughness and inertial sublayers, enhancing the erosional state of wind-blown sand. This finding can be applied to evaluate the aerodynamic stability of the gravel surface in the Gobi Desert and provide a theoretical basis for elucidation of the vertical distributions of wind-blown sand flux.

High-Rate Growth of Bicrystal ZnO Films on a Rhombohedral Sapphire Plane

A method for growing bicrystal ZnO films using the specific features of magnetron sputtering and the orienting effect of a rhombohedral sapphire plane is proposed. It is shown that the successive application of two deposition regimes (~2 and ~16 nm/s) leads to the formation of a bicrystal film with the (110)-oriented lower sublayer and the (002)-oriented upper sublayer. Recrystallization annealing at 1000°C for 10 h does not affect the upper (002)-oriented layer and induces stress relaxation in the lower (110)-oriented layer.

Chemistry of intermediate layer water-oil emulsion formation

The paper considers the problem of accumulation and disposal of oil sludge including a resistant water-oil emulsion, oil sludge classification and treatment methods are presented. Detailed studies have revealed that stability giving to the emulsion system consisting of two immiscible liquids requires presence of the third component which performs function of a stabilizer. These stabilizers create boundary adsorption films which are a structural and mechanical barrier to contact and coalescence dispersed water globules. The structure of intermediate layer and lower sublayer is considered, the reasons for their formation are determined.

Matrix Synthesis of Graphene on a Diamond Surface and Its Simulation

A quantum-chemical simulation is performed for the transformation of the upper sublayer of carbon atoms in the lattice of single-crystal diamond into a flat graphene lattice under the influence of the atoms of a molten copper film on the diamond surface. It is established that the stable system configuration corresponds to the thermally activated motion of carbon atoms in the lower sublayer of the interface diamond layer to the position of graphene, i.e., at the same level as the atoms of the upper sublayer. The energy gain in comparison to the noninteracting subsystems of the copper and diamond atoms is approximately 0.7 eV per atom of the lower sublayer. The maximum size of the resulting graphene film is estimated and a possible mechanism for its rupture is considered.

Estimating the Evaporation from Irrigation Canals in Northwestern China Using the Double-Deck Surface Air Layer Model

The evaporation from irrigation canals was estimated by the aerodynamic method based on the double-deck surface air layer model (called “DSAL model” for short hereafter). The DSAL model describes the surface air layer over a canal as a composite air layer with two sublayers, the lower sublayer and the upper sublayer. The lower sublayer is a few tens of centimeters thick and formed by the flowing water, in which there is no advection; the upper sublayer is over the lower sublayer and formed by the surface wind. The results were compared to those obtained by the heat balance method; field experiments were conducted in the middle reaches of the Heihe River in northwestern China. Results showed that cumulative evaporation instances estimated by the DSAL model were equal in order of magnitude to those by the heat balance method on observed days during the daytime (0700~1900 BST). We infer from these experimental results that the evaporation loss in transport in this region is of the order of one percent at most.

Field-effect transistor with nanowire channel based on heterogeneously doped SOI

The article presents production methods and test results of field-effect transistor based on silicon nanowire made of heterogeneously arsenic-doped silicon on insulator (SOI). Dopant concentration has been varied over the depth of the silicon layer with a depth of 100 nm from higher than 1020 cm−3 to about 1017 cm−3. The field-effect transistor was manufactured from SOI using electron beam lithography and reactive ion etching. The upper highly conducting part of silicon layer has been used as a substrate for input electrodes and contact pads. The lower sublayer has been used for the formation of semiconductor nanowire. The current-voltage and gate characteristics of the transistor have been measured at 77 and 300 K. The possibility of using a field-effect transistor based on silicon nanowire as a highly sensitive local field-effect and charge sensor with nanometric spatial resolution for application in various fields of physics, technology and medicine has been analyzed.

Density inhomogeneity in ferroelectric thin films

Structural investigations of Pb(Zr,Ti)O3 (PZT) ferroelectric thin films derived by chemical solution deposition on Pt∕TiOx electrode stacks were performed using grazing incidence x-ray specular reflectivity of synchrotron radiation and transmission electron microscopy. A density inhomogeneity, i.e., a sublayer structure, in the PZT thin films was observed; the upper PZT sublayer had a lower density and the lower sublayer had a higher density. The influence of the density inhomogeneity, as a possible extrinsic contribution to size effects in ferroelectric thin films, was discussed.

The Structure of the Near-Neutral Atmospheric Surface Layer

Abstract Recent observational data (turbulence variables by sonic anemometers and three-dimensional flow pattern by Doppler lidar), obtained during the Cooperative Atmosphere Surface Exchange Study field campaign in October 1999 (CASES-99), show evidence of a layered structure of the near-neutral surface layer: (i) the eddy surface layer (ESL), which is the lower sublayer where blocking of impinging eddies is the dominating mechanism; and (ii) the shear surface layer (SSL), which is an intermediate sublayer, where shear affects the isotropy of turbulence. The origin of the eddies impinging from aloft (probably from the SSL) down to the ESL is preliminarily addressed in this study, since the Doppler lidar data show evidence of linearly organized eddies embedded in the surface layer (i.e., about 100-m vertical extent) and horizontally spaced by about 300 m. This is consistent with theories predicting that the primary mechanism of eddy motion in high Reynolds number wall layers is “top-down.” The layered str...

Studies on interfacial and crystalline structures of spin valve multilayers

Spin valves of high quality were fabricated by a two-step deposition procedure. Lower sublayers (i.e., buffer layer Ta/free layer NiFe/inter layer Cu) are deposited at a lower argon pressure, which promoted formation of strong (111) textures, smooth interfaces and dense Cu film, and upper sublayers (i.e., pinned layer NiFe/pinning layer Fe/Mn/cover Ta) are deposited at a higher pressure, which promoted small grains and less diffusive interface. The independent control of the magnetoresistance, the ferromagnetic interlayer coupling, and exchange biasing was achieved by improving the interfacial and crystalline structures of the spin valves.

Otozamites ornatussp. nov., a new bennettitalean leaf species from Patagonia, Argentina

Leaves of Otozamites ornatus sp. nov., belonging to the order Bennettitales, have been studied using light microscopy and scanning and transmission electron microscopy of their cuticles. The leaves occur in the Baqueró Formation (Lower Cretaceous) of Santa Cruz Province, Argentina. Cuticular analysis of the leaves has determined the presence of a very ornamented abaxial epidermis with an alveolar ultrastructure in its lower sub-layer and sunken stomata protected by papillate subsidiary cells. The presence of these complicated epidermal structures are directly or indirectly associated with water stress, such as hot, dry, exposed sites that developed in this region of Patagonia towards the end of the Mesozoic.

Hydromechanical boundary layers over a coral reef

Three hydrodynamic boundary layers were measured over a coral reef, dominated by Porites compressa and Montipora verrucosa corals, in Kaneohe Bay, Hawaii. These measurements were used to evaluate the applicability of present models describing boundary layers and to define the range in which processes governed by them takes place. The Diffusion Boundary Layer (DBL), related to diffusion-limited processes such as respiration and photosynthesis, was thicker over M. verrucosa than over P. compressa (2.00 ± 0.6 and 1.42 ± 0.4 mm, respectively). The Momentum Boundary Layer (MBL), controlling water movement in the proximity of the sessile organisms, was thicker over M. verrucosa than over P. compressa as well (97 ± 27 and 58 ± 24 mm, respectively), corresponding to the stronger requirement for water motion by the former, and was thicker by an order of magnitude than the DBL. The Benthic Boundary Layer (BBL), controlling the interactions of the reef with the open sea waters, was found to be more than 1 m thick and was characterized by a roughness height of 31 cm and a shear velocity ( u *) of 0.42 cm s −1. The BBL was composed of three distinguished segments, a lower sublayer with slow water motion throughout its height, an inner sublayer up to the height of the coral knolls, and a fully developed outer BBL. This structure of the BBL suggests that: (1) sedimentation at the lower segment of the BBL is contributing to the patchy structure of this reef; and (2) high corals colonies increase sedimentation while reducing water motion and food supply from lower colonies located within the lower and middle segments of the BBL.

Daytime Boundary Layer Evolution in a Deep Valley. Part I: Observations in the Ina Valley

Abstract The development process of the daytime boundary layer under fair weather and weak synoptic wind conditions was observed in the Ina Valley, a deep two-dimensional valley in Japan. The daytime boundary layer over the bottom of the valley consisted of two sublayers. The lower sublayer is a turbulent mixed layer that reached to heights of 500–1000 m above the surface. The upper sublayer is formed by the local subsidence, which is part of the thermally induced cross-valley circulation, remaining a slightly stable stratification during the daytime. The specific humidity did not become vertically uniform in the upper sublayer due to the weakness of the turbulent mixing. The heating rate of the boundary layer was larger over the valley bottom while smaller over the mountainous areas. The observed results suggest that the thermally induced cross-valley circulation (e.g., upslope flow along the side slopes) plays a role in the heat transport from the mountainous regions to the central part of the valley. T...

Separated flow over a backward-facing step whose height is much greater than the thickness of the lower sublayer of the interaction zone

Separated flow over a backward-facing step whose height is much greater than the thickness of the lower sublayer of the interaction zone