Evaluation of Profiles of Standard Deviation of Vertical Wind in the Urban Area of Rome: Performances of Monin–Obukhov Similarity Theory Using Different Scaling Variables

The parametrizations of meteorological variables provided by the Monin–Obukhov similarity theory (MOST) is of major importance for pollutant dispersion assessment. However, the complex flow pattern that characterizes the urban areas limits the applicability of the MOST. In this work, the performance of different existing parametrizations of the standard deviation of vertical wind velocity were tested in the city of Rome. Results were compared with experimental data acquired by a sonic detection and ranging (SODAR) and a sonic anemometer. Different scaling variables estimated from the anemometer data by considering two coordinate systems—one aligned with the geodetic reference frame and the other following the flow streamlines—were used to evaluate the effects of flow distortion due to the presence of buildings. Results suggest that the MOST parametrizations perform better if the scaling variables obtained using the coordinate system following the flow streamlines are used. This estimation of the scaling variables would make it possible to overcome the difficulties in conducting measurements of turbulent fluxes, either at different altitudes or even in the constant flux layer.

Ohmic contacts to n-type and p-type gallium antimonide whiskers

The ohmic contacts to the n-type conductivity gallium antimonide whiskers were created due to a current pulse shaper. It was established that I–V characteristics of GaSb whiskers at low temperatures are linear, regardless of the direction of current transmission. That allows using the investigated techniques to create electrical contacts and study their electrophysical characteristics. GaSb samples with a diameter of 12 μm and 20 μm were studied at temperatures 4.2 K and 77 K. A slide table with bath and microfurnace was made for welding ohmic contacts to GaSb whiskers. Gold microwire with a diameter of 30 μm was used as a contact material. The melting was carried out under the flux layer. It was revealed that the fusion is one of the most suitable methods for creating contacts to the whiskers grown by gas transport reactions.

Off-line urban building energy model reproducibility against ‘observed’ anthropogenic heat and electricity consumption

<p>Here we verify an off-line urban building energy model (CM-BEM) against ‘observed’ anthropogenic heat and electricity consumption at Tokyo (Yoyogi) residential area. Anthropogenic heat (Q<sub>F</sub>) due to electricity air-conditioning (AC) use (Q<sub>F, AC</sub>) is estimated by continuous simultaneous observations of atmospheric O<sub>2</sub>, CO<sub>2</sub> and turbulent CO<sub>2</sub> and heat fluxes. Here we explain the outline of how to estimate Q<sub>F, AC</sub>. (1) The O<sub>2</sub>:CO<sub>2</sub> exchange ratio (oxidation ratio, OR) is used for the partitioning of CO<sub>2</sub> into emissions from gas fuels and gasoline (see detail in Ishidoya et al. 2020), which allow estimating Q<sub>F</sub> from gas fuels and gasoline (Q<sub>F, gas</sub> and Q<sub>F, traffic</sub>), respectively. (2) Total Q<sub>F</sub> is estimated by turbulent heat fluxes and net radiation observations using a heat balance equation within the constant flux layer. Finally (3) the Q<sub>F, AC</sub> is estimated by ‘Total Q<sub>F</sub> – (Q<sub>F, gas</sub> + Q<sub>F, traffic</sub>)’. This estimation allows verifying directly simulated Q<sub>F, AC</sub> by the CM-BEM. Our aim is an improvement of the CM-BEM to develop more realistic Q<sub>F</sub> and CO<sub>2</sub> inventory data. Here we compare simulated Q<sub>F, AC</sub>, electricity consumption, and turbulent heat fluxes against observations during winter (Jan-Feb 2017) and summer (July-Aug 2018) seasons at Tokyo. Our results will be reported at the conference.</p><p>Ref.</p><p>Ishidoya et al. 2020: Consumption of atmospheric O<sub>2</sub> in an urban area of Tokyo, Japan derived from continuous observations of O<sub>2</sub> and CO<sub>2</sub> concentrations and CO<sub>2</sub> flux. Atmospheric Chemistry and Physics Discussions. under review.</p>

Tubes’ Rupture at Faulty Fusion of Welding Seam

In the straight-seam tubes, the appearance of defects in the area of the welding seam welded under the flux layer and the seam geometry are closely related to the technology and metallurgy of welding process. Possible defects are the pores, incisions, slag inclusions and cracks. The pores can appear in different shapes, with different distribution and in different amounts during the solidification of welding seam. When molten metal solidifies, the gas bubbles can come to the surface or remain inside the metal. The incisions may occur due to the fact that the juncture is not completely filled. Such incisions, passing most often along the edge of welding seam, are explained by the discrepancy between the amount of metal deposited per unit of time and the volume of the juncture. The occurrence of the slag inclusions is determined by the metallurgical reactions between the slag and the drop, separating from the end of the electrode, as well as the bath of molten metal. The cracks differ depending on the size, the nature of location and the causes. There are the macro-cracks and micro-cracks, the hot and cold cracks. In this paper the critical in-tube pressure, at which the destruction of tube occurs at the partial faulty fusion of the tube’s welding seam, is obtained. The results can be used in the diagnosis of the causes of the destruction of the steel large-diameter tubes of the main gas-oil tube-lines.

Effect of TIG-Welding on the Structure and Mechanical Properties of the Pseudo-β Titanium Alloy VT19 Welded Joints

Analysis of the TIG-welding impact on the structure and mechanical properties of pseudo-β titanium alloy VT19 welded joints, obtained with different welding speed, different filler wire amount in welded joint, with and without flux layer. Microstructure of obtained welded joints were investigated. Using welded joints microsections approximate amount of β-phase in different parts of welds have been obtained. Mechanical properties of the obtained welded joints were analyzed and dependency of tensile strength and amount of β-phase were build.

Large-Eddy Simulation Study of Log Laws in a Neutral Ekman Boundary Layer

The characteristics of wind profiles in a neutral atmospheric boundary layer and their dependence on the geostrophic wind speed Ug, Coriolis parameter f, and surface roughness length z0 are examined utilizing large-eddy simulations. These simulations produce a constant momentum flux layer and a log-law layer above the surface characterized by a logarithmic increase of wind speed with height. The von Kármán constant derived from the mean wind profile is around 0.4 over a wide range of control parameters. The depths of the simulated boundary layer, constant-flux layer, and surface log-law layer tend to increase with the wind speed and decrease with an increasing Coriolis parameter. Immediately above the surface log-law layer, a second log-law layer has been identified from these simulations. The depth of this upper log-law layer is comparable to its counterpart in the surface layer, and the wind speed can be scaled as , as opposed to just in the surface log-law layer, implying that in addition to surface processes, the upper log-law layer is also influenced by Earth’s rotation and large-scale conditions. Here is the friction velocity at the surface, and h is the boundary layer depth. An analytical model is proposed to assist in the interpretation of the log laws in a typical Ekman boundary layer. The physics and implications of the upper log-law layer are discussed.

Winds near the Surface of Waves: Observations and Modeling

The concept of a constant-flux layer is usually employed for vertical profiling of the wind measured at some elevation near the ocean surface. The surface waves, however, modify the balance of turbulent stresses very near the surface, and therefore such extrapolations can introduce significant biases. This is particularly true for buoy measurements in extreme conditions, when the anemometer mast is within the wave boundary layer (WBL) or even below the wave crests. In this paper, field data and a WBL model are used to investigate such biases. It is shown that near the surface the turbulent stresses are less than those obtained by extrapolation using the logarithmic-layer assumption, and the mean wind speeds very near the surface, based on Lake George field observations, are up to 5% larger. The behavior is then simulated by means of a WBL model coupled with nonlinear waves, which confirmed the observations and revealed further details of complex behaviors at the wind-wave boundary layer.