A novel method to determine the coupling scaling laws of vibration characteristics for rotor-bearing systems

The purpose of this article is to study the coupling effects of support stiffness on geometric scaling factor powers of the rotor-bearing system and predict vibration characteristics of a prototype by scaled models accurately. Associated to the least-squares–based similitude method, the discrete iteration method proposed evaluates the estimated scaling laws under variable (instable) powers and further broadens the restriction of boundary conditions in scaling laws, which is the main finding in this article. The discrete iteration method does not need to establish a physical model but directly uses input and output parameters to establish output scaling laws. The complete scaled model and geometric distorted model are selected as study cases to prove the effectiveness and accuracy of the discrete iteration method. The vibration characteristics of the rotor-bearing system are obtained by the finite element method with validation by experimental test for the natural characteristics. The comparison between the prediction results and those without the discrete iteration method shows that discrete iteration method can significantly improve the accuracy for predicting the prototype.

Vietnamese lives matter… Image of democracy in US cinematography (on the example of Vietnam war’s theme)

The article is devoted to the image of democracy in US cinematography through the theme of Vietnam war. Special attention is paid to the phases of the image development proposed by Jean Baudrillard. The author made the conclusion that the image of democracy in American cinema offers a distorted model of US intervention, in which the images of the aggressor and the victims replace each other, as well as the concept of democracy, which does not allow the fact of lawlessness and violation of the rights of citizens of any nationality or country.

Distorted mental spatial representation of multi-level buildings - Humans are biased towards equilateral shapes of height and width

A distorted model of a familiar multi-level building with a systematic overestimation of the height was demonstrated earlier in psychophysical and real world navigational tasks. In the current study we further investigated this phenomenon with a tablet-based application. Participants were asked to adjust height and width of the presented buildings to best match their memory of the dimensional ratio. The estimation errors between adjusted and true height-width ratios were analyzed. Additionally, familiarity with respect to in- and outside of the building as well as demographic data were acquired. A total of 142 subjects aged 21 to 90 years from the cities of Bern and Munich were tested. Major results were: (1) a median overestimation of the height of the multi-level buildings of 11%; (2) estimation errors were significantly less if the particular building was unknown to participants; (3) in contrast, the height of tower-like buildings was underestimated; (4) the height of long, flat shaped buildings was overestimated. (5) Further features, such as the architectonical complexity were critical. Overall, our internal models of large multi-level buildings are distorted due to multiple factors including geometric features and memory effects demonstrating that such individual models are not rigid but plastic with consequences for spatial orientation and navigation.

Study on model design and dynamic similitude relations of vibro-acoustic experiment for elastic cavity

Coupling between aero-acoustic noise and structural vibration under high-speed open cavity flow-induced oscillation may bring about severe random vibration of the structure, and even cause structure to fatigue destruction, which threatens the flight safety. Carrying out the research on vibro-acoustic experiments of scaled down model is an effective means to clarify the effects of high-intensity noise of cavity on structural vibration. Therefore, in allusion to the vibro-acoustic experiments of cavity in wind tunnel, taking typical elastic cavity as the research object, dimensional analysis and finite element method were adopted to establish the similitude relations of structural inherent characteristics and dynamics for distorted model, and verifying the proposed similitude relations by means of experiments and numerical simulation. Research shows that, according to the analysis of scale-down model, the established similitude relations can accurately simulate the structural dynamic characteristics of actual model, which provides theoretic guidance for structural design and vibro-acoustic experiments of scaled down elastic cavity model.

A parameterized Doppler distorted matching model for periodic fault identification in locomotive bearing

The locomotive bearings support the whole weight of the train under the high speed and its continuous running is a key factor of the train safety. The collected Doppler distorted signal greatly increases the difficulties in detecting the whelmed fault information. To overcome this disadvantage, a novel Doppler distorted correlation matching model using the single side Laplace wavelet and acoustic theories is constructed to recognize the bearing fault-related impulse intervals. The parameterized Doppler distorted model is assessed by the correlation coefficient with the bearing fault signal in waveform. The optimal Doppler distorted model, that is the Doppler distorted correlation matching model which matches the fault component in the acoustic signal could be used for identifying the fault impulse interval. Then, the bearing fault can be successfully detected from the parameters of the Doppler distorted correlation matching model due to its maximum similarity to the real signal. Except for the simulation study, the proposed model is also employed to match the fault components in some real acoustic bearing fault signals. The recognized fault impulse period in the Doppler distorted correlation matching model’s initial model keep in good accordance with the correct fault impacts, which represent the locomotive bearing fault characteristics.

Similitudes for the structural response of flexural plates

This article presents an investigation into exact and distorted similitudes and the related scaling laws for the analysis of the dynamic response of rectangular flexural plates. The response of a given model in similitude is determined from a generalization of the modal approach, which allows the use the mode shapes and natural frequencies in order to establish scaling laws. Analytical models of simply supported rectangular plates are used to produce both the original and distorted model responses. Some highlights about the distribution of the natural frequencies, the forced response and the energy response are given. The results show that, with the proposed methodology, it is possible to reproduce with good confidence the response of the reference plate, even if distorted models are used.