Swing Characteristics and Vibration Feature of Tower Cranes under Compound Working Condition

The swing behaviour of tower cranes under compound working conditions is closely related to construction safety and structural health. This paper presents dynamic models and simulated them for parameter analysis to understand tower cranes’ dynamic characteristics and vibration features under compound working conditions. The parameters contain payload mass, rope length, lifting acceleration, slewing acceleration, luffing acceleration, and initial angle. For the lifting-luffing coupling motion (LLCM) and lifting-slewing coupling motion (LSCM) of the tower crane, the D’Alembert principle provides a theoretical basis for the derivation of system dynamics equations. The spatial swing angle description of the crane payload includes the time-domain response and frequency-domain response, which uses a dynamic model. The result shows that the mass has little effect on the spatial swing angle. The value of the lifting acceleration is stable at 0.004 m/s2 to 0.01 m/s2. Peak value (PV), root mean square value (RMS), root mean square frequency (RMSF), and frequency standard deviation (RVF) present the best sensitivity to changes in the spatial swing angle response. When PV of angles θ and β increases by tens of thousands of times in the LLCM, PV can reflect the phenomenon of angle divergence. The skewness value (SV) increases by 3422% at the severe swing angle performance in the LSCM. The swing angle regularity with the compound working conditions can provide theoretical guidance for eliminating structural vibration.

Investigation of 6S 1/2–8S 1/2 two-photon transition of cesium atoms by a single 822 nm laser

We experimentally investigate the 6S 1/2–8S 1/2 two-photon transition in cesium vapor by a single laser. A blue (455.5 and 459.3 nm) fluorescence signal is observed as a result of 822.5 nm laser beams illuminating the Cs vapor with a counter-propagating configuration. The dependences of the fluorescence intensity on the polarization combinations of the laser beams, laser power and vapor temperature are studied to obtain optimal experimental parameters. The frequency difference between the two hyperfine components of 4158 (7) MHz is measured with a Fabry–Perot interferometer as a frequency reference. Such a large spectral isolation and the insensitivity to the Earth’s magnetic field enable the 6S 1/2–8S 1/2 transition to be a stable frequency standard candidate for a frequency-doubled 1644 nm laser in the U-band window for quantum telecommunication.

Er:fiber-based femtosecond frequency comb stabilized to an Yb+ single-ion optical frequency standard

An erbium fiber-based femtosecond optical frequency comb stabilized to an Yb+ single-ion optical frequency standard was created. For the first time, a combination of an extra-cavity acousto-optic frequency modulator with fiber outputs and an intracavity electro-optic phase modulator based on a KTP crystal were used to stabilize offset frequency and one of the optical components of the Er:fiber femtosecond comb. As a result a locking bandwidth of 30 kHz for the optical comb offset frequency has been obtained. It is shown that the relative instability introduced by the stabilization and measurement systems into the output radio frequencies (in addition to the instability of the reference optical signal) is no worse than 5 × 10−14 for averaging times of 1 s and 2 × 10−16 for averaging times of 400 s.

The use of digital data processing to improve the metrological characteristics of the rubidium frequency standard

The necessity of improving the metrological characteristics of a quantum frequency standard when determining the coordinates of an object on the Earth’s surface or long-term transmission of large amounts of data in satellite communication systems is substantiated. A new algorithm for digital processing of optical signals in the frequency standard is proposed. The results of experimental studies of the metrological characteristics of a quantum frequency standard based on rubidium atoms - 87 are presented

Single-step alkaline etching of deep silicon cavities for chip-scale atomic clock technology

This paper presents the results of experiments on the development of the technology of MEMS alkali vapor cells for a miniature quantum frequency standard. The classical design of a two-chamber silicon cell containing an optical chamber, shallow filtration channels and a technical container for a solid-state alkali source was implemented in a single-step process of wet anisotropic silicon etching. To prevent the destruction of the filtration channels during etching of the through silicon cavities, the shapes of the compensating structures at the convex corners of the silicon nitride mask were calculated and the composition of the silicon etchant was experimentally found. The experiments results were used in the manufacture of chip-scale atomic clock cells containing vapors of 87Rb or 133Cs isotopes in the neon atmosphere.

Modified quantum frequency standard on Hg-199 ions

The world around us depends on devices capable of producing or maintaining a signal with an extreme precision. Quantum frequency standards are the answer to this problem. This article presents a modified version of newly developed quantum frequency standard based on trapping Hg-199 ions by magnetic field. The new prototype was developed a while ago and now it was modified due to algorithm improvements and renewed digital hardware, analog and digital circuitry being reordered. Results for Allan deviation show 3 % improvement for long-term frequency stability and more than 5 % for short-term stability

Features of the formation of the frequency of the microwave excitation signal in the quantum frequency standard on rubidium atoms - 87

The article discusses the main disadvantages of the current design of a quantum frequency standard based on rubidium-87 atoms. The main disadvantages of the current design of the quantum frequency standard on rubidium-87 atoms are considered. It is noted that the processes associated with light shifts in the optical part contribute to the greatest instability in the long-term operation of the quantum frequency standard. A solution is proposed to improve the design of the rubidium standard. A forecast for improving its metrological characteristics is presented. The results of experimental investigations are presented.

Leadership capacity and organizational citizenship behavior in educational institutions

In this research, it is aimed to examine the leadership capacity and organizational citizenship levels belong to the teachers working in some schools and the relationship between them. Relational survey design was used in this research. In the 2019-2020 academic year, 4025 teachers working in some primary, secondary and high school levels in the central districts of Uşak province constitute the study group of this research. In this study, the study titled “The adaptation of the leadership capacity scale (Olkö) in schools into Turkish: a validity and reliability study”, which was adapted into Turkish, was used to determine the level of organizational citizenship. For analyzing of the data obtained from the participants, arithmetic mean percentage, frequency, standard deviation values ​​were calculated. In the study linear regression analysis and pearson correlation analysis were used. Considering the results of the analysis of this research; the average perception of teachers' leadership capacity behaviors is moderate. Again, according to the results of the research; perception of organizational citizenship behavior on average belonging to teachers is at a "high" level. According to teachers' perceptions, a low, but positive and significant relationship has been found between school leadership capacity and organizational citizenship behavior. Leadership capacity is a significant predictor of organizational citizenship behaviors.

ENHANCING DIGITAL LITERACY OF SENIOR CITIZENS

As information and communication technology (ICT) becomes part of our life, we need to understand how to effectively use it. Especially, when internet can be reached by all, money transaction and buying products/services through online platform becomes normal. Because of this, digital technology can help to complete our needs. This research, thus, aims to analyze senior citizens behavior and to enhance their digital literacy. Population of this research is Thai senior citizens who are aged 60 and over. 35 samples are selected using purposive sampling method. Then data has been collected using questionnaire via online platform. Statistics used in this research include average, mean, frequency, standard deviation, and t-test. The results show that senior customers often use digital technology when they transfer money to another account and purchase products online. The product/service they brought normally is household goods, food, and drink. After the seniors learn how to use digital technology from our instructional media, they have increased a digital literacy rate significantly at statistical level of .01.