Aims. We study the ability of magnetic helicity expulsion to alleviate catastrophic α-quenching in mean field dynamos in two– dimensional spherical wedge domains. Methods. Motivated by the physical state of the outer regions of the Sun, we consider α2Ω mean field models with a dynamical α quenching. We include two mechanisms which have the potential to facilitate helicity expulsion, namely adve...

The production of electrical energy from renewable sources has, in recent years, increased significantly with wind generation as the predominant technology. This development is expected to continue in the near future. However, the integration of such stochastic and intermittent power sources into the existing power system implies a higher ratio of non-dispatchable generation which, in turn, lea...

Pulsed ionospheric flows (PIFs) in the cusp footprint have been observed by the SuperDARN radars with periods between a few minutes and several tens of minutes. PIFs are believed to be a consequence of the interplanetary magnetic field (IMF) reconnection with the magnetospheric magnetic field on the dayside magnetopause, ionospheric signatures of flux transfer events (FTEs). The quasiperiodic P...

The singular values associated with optimally growing perturbations to stationary and time-dependent solutions for the general circulation in an ocean basin provide a measure of the rate at which solutions with nearby initial conditions begin to diverge, and hence, a measure of the predictability of the flow. In this paper, the singular vectors and singular values of stationary and evolving exa...

This paper describes an advanced multi-scale weather modeling system, WRF–RTFDDA–LES, designed to simulate synoptic scale ( 2000 km) to smalland micro-scale ( 100 m) circulations of real weather in wind farms on simultaneous nested grids. This modeling system is built upon the National Center for Atmospheric Research (NCAR) community Weather Research and Forecasting (WRF) model. WRF has been en...

X線 回折 法 に よる結 晶構 造 解 析 は,大 き さ0 .1 ~1mmの 単 結 晶 が あ れ ば ,原 子 の三 次 元 配 列 を 決 定 す る こ とが で き,原 子 間 距 離,結 合 角,配 位 数 な どの化 学 結 合 に 関 す る知 識 が 直 接 得 られ る非 常 に 優 れ た 方法 で あ る。 結 晶構 造 を決 定 す る過 程 は,次 の二 つ の段 階 に分 け られ る。 第1は ,単 結 晶 を 選 んで ワイ セ ンベ ル グ写 真 法 な どに よ って 晶 系,格 子 定 数,空 間 群 を 決 め,比 重 測 定 に よ って 単 位 格 子 内 の 化 学 単 位 数 を 決 定 す る過程 で あ る。 第2は,単 結 晶 のX線 回 折 強 度 か ら各原 子 の座 標 を 決 定 す る過 程 で あ る。 こ の過...

A novel method of heating wind tunnel flows to strong thermal stratifications is described. Variable electric heating is employed to create user-selectable temperature profiles in steady, uniform mean flow. Linear temperature gradients of up to 200~ (V/iisfil~i frequencies of 2.5 rad s1) can be sustained. The performance of the facility is discussed in the context of continuouslystratified grid...

Statically stable atmospheric flows are characterized by weak and highly anisotropic turbulence, gravity waves, instabilities, and meandering motions that are not observed in neutral or unstable flows. These features complicate both modeling and measurements in stable boundary layers. Nevertheless, these flows remain of considerable importance for a variety of problems including nighttime flow ...

in this study, aerodynamic characteristics of a circular cylinder in an axial flow have been investigated numerically and experimentally. the model has been considered as a cylinder with truncated nose and fineness ratio of 3 (length to diameter ratio of 3). the investigation involves a series of wind tunnel measurements, flow visualization, and numerical simulation. we used different mach numb...

Aerodynamic, load, flow-visualization, and inflow measurements have been made on a 10-m, three-bladed, downwind, horizontal-axis wind turbine ( HAWT). A video camera mounted on the rotor was used to record night­ time and daytime video images of tufts attached to the low-pressure side of a constant-chord, zero-twist blade. Load measurements were made using strain gages mounted at every 10% of t...