Experimental study of vibrations of a steel beam in order to determine the damping coefficients of the material based on the idea of the limit transition using a laser vibrometer

Данная работа посвящена экспериментальным исследованиям консольной балки, разработке методики проведения измерений колебаний в среде на основе измерений в воздухе и жидкости (воде). Измерение амплитудно-частотных характеристик производится с помощью лазерного виброметра: “Polytec High Speed Laser Vibrometer HSV2001, Polytec GmbH, Germany”. Для снятия показаний в экспериментах ис-пользовалась программа «Рolytec vibrometer software» (Polytec High Speed Laser Vibrometer HSV2001, Polytec GmbH, Germany). Обработка экспериментальных данных и построение графиков проводились с помощью программы «Microsoft Excel» с включением в нее фрагментов собственного программного обеспечения. Главной конечной целью является определение коэффициентов демпфирования материала колеблющейся конструкции. При этом используется идея предельного перехода. Методика является оригинальной. Ее оригинальность заключается в использовании новой идеи предельного перехода и выполнении экспериментов на базе виброметра (Polytec High Speed Laser Vibrometer HSV2001). Полученные на основе экспериментальных исследований результаты также являются оригинальными. Методика создана для практического применения и позволяет определять амплитудно-частотные характеристики систем, колеблющихся в различных жидкостях и состоящих из различных материалов. This paper is devoted to experimental studies of the cantilever beam, the development of methods for measuring vibrations in the medium based on measurements in air and liquid (water). The amplitude-frequency characteristics are measured using a laser vibrometer: “Polytec High Speed Laser Vibrometer HSV2001, Polytec GmbH, Germany”. To take readings in the experiments, the program "Polytec vibrometer software" (Polytec High Speed Laser Vibrometer HSV2001, Polytec GmbH, Germany) was used. The processing of experimental data and the construction of graphs were carried out using the Microsoft Excel program with the inclusion of fragments of its own software. The main ultimate goal is to determine the damping coefficients of the material of the oscillating structure. In this case, the idea of a limit transition is used. The technique is original. Its originality lies in the use of a new idea of the limit transition and performing experiments based on a vibrometer (Polytec High Speed Laser Vibrometer HSV2001). The results obtained on the basis of experimental studies are also original. The method is designed for practical application and allows to determine the amplitude-frequency characteristics of systems that oscillate in different fluids and consist of different materials.

Comparison of spatiotemporal carbon, nitrogen and phosphorus burial in two plateau lacustrine sediments: Implication for N and P control

The long-term accumulation, burial and release of nutrients, such as carbon (C), nitrogen (N) and phosphorus (P) in lacustrine sediments are responsible for the global lake eutrophication. Interpretation of the spatiotemporal sedimentary record of nutrients (C, N and P) in contrasting trophic level of lakes is helpful for understanding the evolutionary process of water eutrophication. Based on the radiochronology of 210Pbex and 137Cs, a comparative study of spatial and temporal concentrations, burial of total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP), the sources of organic matter were conducted using sediment cores from two plateau lakes Dianchi (DC) and Fuxian (FX) of SW China. Results showed that concentrations and burial of C, N and P in sediments of DC, a shallow hypertrophic lake with the maximum depth of 5.8 m, were both higher than those in FX, an oligotrophic deep lake with the maximum depth of 155.0 m. For both lakes the molar ratio of TOC/TN increased in the sediments moving from north to south. The values of TOC/TN molar ratios increased over time in DC and was higher than in FX. The extremely high values of TOC/TN appeared in the central and southern parts of FX, indicating the impacts of accumulation effect and sediment focusing in the deeper region and indirect supplement from the Lake Xingyun (XY), an adjoining lake connected with FX via the Gehe River. Time-integrated sources identification in DC indicated the contribution of allochthonous sources was dominant over the past few decades, which contributed to the increased trophic level of the lake. The comparison of relationships of carbon accumulation rates (CAR), nitrogen accumulation rates (NAR) and phosphorous accumulation rates (PAR), the ratios of N/P and the utilizations of N and P fertilizer between DC and FX implied that both of N and P inputs should be limited for reducing the trophic level, but N control was predominant in comparison with P for both lakes. The results indicated that caution is required in plateau lakes to limit transition from oligotrophic to eutrophic in these lakes.

Prediction of intrinsic topological superconductivity in Mn-doped GeTe monolayer from first-principles

The recent discovery of topological superconductors (TSCs) has sparked enormous interest. The realization of TSC requires a delicate tuning of multiple microscopic parameters, which remains a great challenge. Here, we develop a first-principles approach to quantify realistic conditions of TSC by solving self-consistently Bogoliubov-de Gennes equation based on a Wannier function construction of band structure, in presence of Rashba spin-orbit coupling, Zeeman splitting and electron-phonon coupling. We further demonstrate the power of this method by predicting the Mn-doped GeTe (Ge1-xMnxTe) monolayer—a well-known dilute magnetic semiconductor showing superconductivity under hole doping—to be a Class D TSC with Chern number of −1 and chiral Majorana edge modes. By constructing a first-principles phase diagram in the parameter space of temperature and Mn concentration, we propose the TSC phase can be induced at a lower-limit transition temperature of ~40 mK and the Mn concentration of x~0.015%. Our approach can be generally applied to TSCs with a phonon-mediated pairing, providing useful guidance for future experiments.