Determination method of the structure size interval of dynamic similar models for predicting vibration characteristics of the isotropic sandwich plates

A method is studied for determining the structure size interval of dynamic similar models of the isotropic sandwich plates. Firstly, a comparison between the two theories of plates, the Resineer theory and the Hoff theory, is conducted, including their governing equations and the ANSYS analytic solutions of frequency. The Resineer theory is chosen as the basic theory of this paper finally. Secondly, the scaling laws between the model and prototype of isotropic sandwich plate are established by combining the dimensional analysis and governing analysis. Both complete and incomplete geometric similarity conditions are discussed. Thirdly, the determination method of the structure size interval of the models is proposed. The nature vibration mode keeps the same and the nature frequency and harmonic response keep in proportion with the prototype of the sandwich plate. At last, the flow step of the intervals determination method is given

Study of the structure size interval of incomplete geometrically similitude model of the elastic thin plates

To design the similitude test model having the same nature characteristics with the prototype of the elastic thin plates, an innovative method of confirm the structure size applicable interval of distorted (incomplete geometrically) similar model was proposed. Firstly, the complete scaling laws and the distortion scaling laws between the model and its prototype were established by using the governing equation analysis. Then, under the study of the structure size applicable interval which kept the same first-order nature characteristic (nature frequency and vibration mode), through the research of the vibration mode control interval (each order of the mode keep the same) and the predict interval of frequency, the method of structure size applicable interval of distorted similar model was obtained, which they were in different orders with the same nature characteristic. Finally, the proposed calculation method is verified by experiment

Experimental study on vibration behavior of rotating manipulator in the process of scramming

In order to study the vibration behavior of rotating manipulator in the process of scramming, an experimental test is conducted on the vibration behavior during the process on different initial and measuring conditions. Through the experimental test, the vibration behavior exists two impact phenomena, which are found in the scramming process, and the feature extraction of the two impact phenomena is investigated. The dynamics parameters of the rotating manipulator are identified and hammer experiment is done to verify the dynamics parameters. With these parameters, an envelope model of the second impact response is established, and the applicability of the model is validated by experiments. The method of pasting damping layer on the surface of manipulator is employed to inhibit the vibration which is caused by the first impact. Via the experimental verification, the damping layer takes a certain effect on the vibration elimination

Quantifying effects of cold acclimation and delayed springtime photosynthesis resumption in northern ecosystems.

Land carbon dynamics in temperate and boreal ecosystems are sensitive to environmental change. Accurately simulating gross primary productivity (GPP) and its seasonality is key for reliable carbon cycle projections. However, significant biases have been found in early spring GPP simulations of northern forests, where observations often suggest a later resumption of photosynthetic activity than predicted by models. Here, we used eddy covariance-based GPP estimates from 39 forest sites that differ by their climate and dominant plant functional types. We used a mechanistic and an empirical light use efficiency (LUE) model to investigate the magnitude and environmental controls of delayed springtime photosynthesis resumption (DSPR) across sites. We found DSPR reduced ecosystem LUE by 30-70% at many, but not all site-years during spring. A significant depression of LUE was found not only in coniferous but also at deciduous forests and was related to combined high radiation and low minimum temperatures. By embedding cold-acclimation effects on LUE that considers the delayed effects of minimum temperatures, initial model bias in simulated springtime GPP was effectively resolved. This provides an approach to improve GPP estimates by considering physiological acclimation and enables more reliable simulations of photosynthesis in northern forests and projections in a warming climate

Accurate prediction approach of dynamic characteristics for a rotating thin walled annular plate considering the centrifugal stress requirement

In allusion to the problem that experimental results of similitude models of a rotating turbine disc predict dynamic characteristics of the prototype, the accurate design method of dynamic similitude models of a rotating thin walled annular plate is investigated by considering the centrifugal stress requirement. The vibration differential equation is employed to deduce geometrically complete scaling laws of dynamic frequency and centrifugal stress. In order to determine accurate distorted scaling laws of dynamic frequency, the sensitivity analysis and determination principle are used. For distorted scaling laws of centrifugal stress, the average approach of candidate distorted scaling laws is proposed, and its mathematical form is simple. Furthermore, the numerical validation indicates that distorted scaling laws can predict dynamic characteristics of the prototype and reflect the strength conditions or even failures of a prototype with good accuracy, and applicable intervals of the distorted scaling law are calculated. Finally, an acceptable procedure of the similitude design method of a rotating thin walled annular plate is provided, which guides to the design of test models considering centrifugal stress requirement

Experimental study on vibration behavior of rotating manipulator in the process of scramming

In order to study the vibration behavior of rotating manipulator in the process of scramming, an experimental test is conducted on the vibration behavior during the process on different initial and measuring conditions. Through the experimental test, the vibration behavior exists two impact phenomena, which are found in the scramming process, and the feature extraction of the two impact phenomena is investigated. The dynamics parameters of the rotating manipulator are identified and hammer experiment is done to verify the dynamics parameters. With these parameters, an envelope model of the second impact response is established, and the applicability of the model is validated by experiments. The method of pasting damping layer on the surface of manipulator is employed to inhibit the vibration which is caused by the first impact. Via the experimental verification, the damping layer takes a certain effect on the vibration elimination

Study of the structure size interval of incomplete geometrically similitude model of the elastic thin plates

To design the similitude test model having the same nature characteristics with the prototype of the elastic thin plates, an innovative method of confirm the structure size applicable interval of distorted (incomplete geometrically) similar model was proposed. Firstly, the complete scaling laws and the distortion scaling laws between the model and its prototype were established by using the governing equation analysis. Then, under the study of the structure size applicable interval which kept the same first-order nature characteristic (nature frequency and vibration mode), through the research of the vibration mode control interval (each order of the mode keep the same) and the predict interval of frequency, the method of structure size applicable interval of distorted similar model was obtained, which they were in different orders with the same nature characteristic. Finally, the proposed calculation method is verified by experiment

SALI: A Scalable Adaptive Learned Index Framework based on Probability Models

The growth in data storage capacity and the increasing demands for high performance have created several challenges for concurrent indexing structures. One promising solution is learned indexes, which use a learning-based approach to fit the distribution of stored data and predictively locate target keys, significantly improving lookup performance. Despite their advantages, prevailing learned indexes exhibit constraints and encounter issues of scalability on multi-core data storage. This paper introduces SALI, the Scalable Adaptive Learned Index framework, which incorporates two strategies aimed at achieving high scalability, improving efficiency, and enhancing the robustness of the learned index. Firstly, a set of node-evolving strategies is defined to enable the learned index to adapt to various workload skews and enhance its concurrency performance in such scenarios. Secondly, a lightweight strategy is proposed to maintain statistical information within the learned index, with the goal of further improving the scalability of the index. Furthermore, to validate their effectiveness, SALI applied the two strategies mentioned above to the learned index structure that utilizes fine-grained write locks, known as LIPP. The experimental results have demonstrated that SALI significantly enhances the insertion throughput with 64 threads by an average of 2.04x compared to the second-best learned index. Furthermore, SALI accomplishes a lookup throughput similar to that of LIPP+.Comment: Accepted by Conference SIGMOD 24, June 09-15, 2024, Santiago, Chil

On the FRB Luminosity Function – – II. Event Rate Density

The luminosity function of Fast Radio Bursts (FRBs), defined as the event rate per unit cosmic co-moving volume per unit luminosity, may help to reveal the possible origins of FRBs and design the optimal searching strategy. With the Bayesian modelling, we measure the FRB luminosity function using 46 known FRBs. Our Bayesian framework self-consistently models the selection effects, including the survey sensitivity, the telescope beam response, and the electron distributions from Milky Way/ the host galaxy/ local environment of FRBs. Different from the previous companion paper, we pay attention to the FRB event rate density and model the event counts of FRB surveys based on the Poisson statistics. Assuming a Schechter luminosity function form, we infer (at the 95 per cent confidence level) that the characteristic FRB event rate density at the upper cut-off luminosity L∗=2.9+11.9−1.7×1044ergs−1 is ϕ∗=339+1074−313Gpc−3yr−1, the power-law index is α=−1.79+0.31−0.35, and the lower cut-off luminosity is L0≤9.1×1041ergs−1. The event rate density of FRBs is found to be 3.5+5.7−2.4×104Gpc−3yr−1 above 1042ergs−1⁠, 5.0+3.2−2.3×103Gpc−3yr−1 above 1043ergs−1, and 3.7+3.5−2.0×102Gpc−3yr 1 above 1044ergs−1. As a result, we find that, for searches conducted at 1.4 GHz, the optimal diameter of single-dish radio telescopes to detect FRBs is 30–40 m. The possible astrophysical implications of the measured event rate density are also discussed in the current paper