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The supercritical design of tail rotor drive shaft has attracted more attention in helicopter design due to its high power–weight ratio and low maintenance cost. However, there exists excessive vibration when the shaft passes through the critical frequency. Dry friction damper is the equipment applied to the drive shaft to suppress the excessive vibration. In order to figure out the damping mechanism of the dry friction damper and improve the damping efficiency, the dynamic model of the shaft/damper system is established based on the Jeffcott rotor model.

The typical frequency response of the system is studied through bifurcation diagrams, amplitude-frequency characteristic curves and waterfall frequency response spectrum. The typical transient responses under frequency sweeps are also obtained.

The results show that the response of the system changes from periodic no-rub motion to quasi-periodic rub-impact motion, and then to synchronous full annular rub-impact, and finally, back to periodic no-rub motion. The slip of the rub-impact ring improves the stability of the system. Besides, the effects of the system parameters including critical dry friction force, rub-impact friction coefficient, initial clearance on the stability and the vibration damping capacity are studied. It is observed that the stability changes significantly varying the three parameters respectively. The vibration damping capacity is mainly affected by the critical dry friction force and the initial clearance.

Presented results provide guidance for the design of the dry friction damper.

The front bearing mount structure in an aero engine has been severely loaded under the fan blade off (FBO) event since imbalance forces at high amplitude but low frequency is transformed to the engine front mount structure. The bearing mount structural forces are estimated by an integrated implicit-explicit analysis process of whole engine model of an aero engine. Since there are many dependent factors which are governing those predicted loads, experimental evidence on FBO is becoming necessary to validate the model used for the load prediction which is more expensive and also time consuming. This paper aims to discuss the above mentioned issues.

The current paper deals with the high impact but low probability nature of FBO load prediction on the bearing mount structure by stochastic approach which could be replaced for FBO experiments which is highly essential for current economic conditions. Several influential factors on the predicted loads have been chosen in the stochastic model and sensitive analysis has also been performed to bring down the variation involved in the predicted load.

The predicted load by proposed stochastic model is then compared with the experimental results. The conclusion on the predicted load with various dependent influential factors is matching well with certain value of damage factor from planned FBO test event.

Limitation of this paper could be that it does not cover with range of load amplitude and is only applicable for civil small and medium engines.

The high amplitude but low frequency load pattern is assessed with impact condition by stochastic model.

Combining experimental and probabilistic load prediction was never done before and read across from previous engine test program could be effectively performed with stochastic model approach.

Face contact has a strong impact on the service life of non-contacting gas face seals; the current research which mainly focuses on the face contact had appeared during the startup or shutdown operation. This paper aims to present a closed-form contact model of a gas face seal during the opened operation.

Referring to the axial rub-impact model of rotor dynamics, a closed-form contact model is developed under a nonparallel plane contact condition that corresponds to the local face contact of sealing rings arising from some disturbances during the opened operation. The closed-form contact model and a direct numerical contact model are performed on Gaussian surfaces to compare the contact behavior.

The closed-form contact model is in a good agreement with the direct numerical contact model. However, the closed-form contact model cannot involve the influence of grooves on the sealing ends. The error is eliminated in some other types of gas face seals such as coned gas face seals. Besides non-contacting face seals, the closed-form model can be applied to the axial rub impact of rotor dynamics.

A closed-form contact model of a gas face seal is established during the opened operation. The closed-form contact model is validated by a direct numerical contact model. The closed-form contact model also suits for axial rub-impact of rotor dynamics.

The stability of exchange rates facilitates international trade, diminishes portfolio risk, and ensures that economic policies are effective. The war in Ukraine is showing that the European financial system is still fragile to external shocks. This paper examines the consequences of the Russian invasion of Ukraine on five Euro exchange rates. The final goal is to empirically test whether the ruble caused the euro to depreciate with the Russian invasion of Ukraine.

The exchange rates analyzed are Euro/Russian Ruble, Euro/US Dollar, Euro/Japanese Yen, Euro/British Pound, and Euro/Chinese Yuan. The data collected are daily and cover the period from November 1, 2021, to May 1, 2022. In this context, the changes in the FX rates reflect two months of the ongoing war in Ukraine. The FX rates used in the study contain 137 observations indicating five months of daily series.

The results from impulse response function, variance decomposition, SVAR, and VECM indicate that the EUR/RUB significantly influenced the Euro devaluation. On the other side, the FX rates used in our work altogether hold long-run cointegration. The situation is different in the short run, where only EUR/RUB, EUR/USD, and EUR/CNY possess significant relations with other parities.

The Ruble is not among hard currencies, but its position strengthened during this period due to the importance of Russian gas to the Eurozone. The results indicate that even weak currencies can be influential depending on the geopolitical and economic situation. To this end, diversification remains a valid concept not only in portfolio construction but also for the preservation of the national economy.

The application of synthetic dyestuffs in the dyeing and printing industries has been criticized because of the introduction of contaminants into the environment. With time, the increasing international awareness of environment and ecology preservation has led to the industry’s attention towards natural dyes and their efficient usage compared to synthetic counterparts. Because the need for “Green” goods and services are rising public awareness, this paper aims to use a banana bio-resource waste to dye cotton fabric.

Factorial design with three variables, including parts of a banana plant, combination of alkalis and application temperature at three different levels, was studied to identify a significant correlation between the effect of these variables on the colour strength and fastnesses of the dyed cotton fabrics.

Dyeing samples achieved with various parts of banana are found to offer significant colour strength and a good wash and rub fastness. Experimental design analysis helped to formulate a standard workable dyeing recipe with the minimum use of resources exhibiting reasonably good wash and rub fastness.

This dyeing technique is novel and can be found useful for partially replacing synthetic dyes with natural colourants possessing good washing and rubbing fastness.

Proposing a new type of water-lubricated thrust bearing meets the load-bearing requirements of high-power shaft-less rim driven thrusters.

The designs were tested by establishing a bearing thermal-fluid-magnetic comprehensive simulation model and developing bearing fluid film force and magnetic simulation. Lubrication performance tests were carried out on the bearing test rig.

The Halbach array of magnet blocks is able to reach the maximum magnetic force. The material of sheath can help increase the magnetism. The magnetism is able to reduce wear during low-speed and the start-stop phase, while the eddy current loss at high speeds will lead to a decrease in magnetic force. The experiment found that the bearing was more stable at low speeds and would not demagnetize due to the temperature rise, but it is necessary to pay attention to the running stability at high speeds to prevent rubbing and impact.

An innovative combination of hydrodynamic pressure and permanent magnetic repulsion was observed to form a magnetic-liquid double suspension bearing with large bearing capacity.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2020-0295

The purpose of this paper is to study the influence of pivot stiffness on the dynamic characteristics of tilting-pad journal bearings (TPJBs) and the stability of the bearing-rotor system.

A theoretical numerical model is established, and the influences of pivot stiffness on TPJBs and a bearing-rotor system are analyzed. Then, two kinds of pivot structures with different stiffness are designed and the vibration characteristics are tested on the vertical rotor bearing test bench.

The pivot stiffness has an obvious effect on the dynamic characteristics of the TPJBs and the stability of the bearing-rotor system. As a result of appropriate pivot stiffness, the critical speed and the vibration amplification factor can be reduced, the logarithmic decay rate and the stability of the rotor system can be effectively increased. While the journal whirl orbit is smoother and the rubbing is obviously reduced when the bearings have flexible pivots.

The influence of pivot stiffness on TPJBs and a vertical rotor-bearing system is studied by theoretical and experimental methods.

The purpose of this study is to successfully apply ultrasonic waves for the quick extraction of flax seed gum from flaxseed hull or whole seed and compare it to the standard technique of extraction.

The effect of the heating source, extracted time, temperature and pH of extracted solution on the extraction was studied. The obtained gum is subsequently used for silk screen printing on cotton, linen and viscous fabrics. Rheological properties and viscosity of the printing paste were scrutinized in the current study to get a better insight into this important polysaccharide. The output of this effort aimed to specify the parameters of the processes for printing textiles to serve in women’s fashion clothes by applying innovated handmade combinations of Islamic art motives using a quick and affordable method. Seven designs are executed, and inspiring from them, seven fashion designs of ladies’ clothes were designed virtually by Clo 3D software.

The result recorded that the new gum has excellent printing properties. In addition, they have better rheological properties, viscosity, chromatic strength and fastness qualities, all of which could help them in commercial production.

Flaxseed and three different fabric types (Cotton, Linen and Viscous) were used.

Synthesis of a new biodegradable thickener from a natural resource, namely, flaxseed, by applying new technology to save time, water and energy.

Synthesis of eco-friendly biodegradable thickener and used in textile printing alternative to the synthetic thickener.

The paper investigates the advantages of graphical mapping of national research publication and citation profiles from scientific fields in order to provide additional information with respect to research performance. By means of multi‐dimensional scaling techniques national social science profiles from seventeen OECD countries and two periods, 1989‐1993 and 1994‐1998, are mapped, each profile represented by a vector of either publication volumes or citation values for nine social science fields. Aside from demonstrating the developments of publication volumes and citedness ranges as well as patterns, the graphical maps display clusters and similarities of national profiles over time. Combined with international rankings of averaged national impact factors (NIF) relative to the average world impact of field (WIF) for the same number of fields and periods, the graphical display supplies additional otherwise concealed information of the differences in research patterns between countries – even when the NIFs are quite similar. The analyses show that low Pearson correlation coefficients can be applied to flag extraordinary instances of either high or low national citation impacts during a period. Most importantly, the graphical maps make a strong case for adjusting or tuning the baseline impact to the actual national publication profiles when comparing NIFs of different countries. A new indicator, the Tuned Citation Impact Index (TCII) is proposed. It is constructed from the amount of expected citations a country ought to have received in each research field aggregated over its true profile. Common baseline profiles, like those of the world or EU, are consequently not regarded as the ideal benchmark. In the case illustrated by the journal publications of the social sciences the paper verifies the hypothesis that a dominant central cluster exists consisting of the large Anglo‐American countries: USA, Canada and the UK. A further hypothesis, that the smaller northern EU countries with English as the second language are located together and close to the central cluster on the publication maps is only partly satisfied in the second period. A third hypothesis, that countries located near the central cluster on the citation maps may hold high(er) NIFs is falsified.

Early fault detection of bearing plays an increasingly important role in the operation of rotating machinery. Based on the properties of early fault signal of bearing, this paper aims to describe a novel hybrid early fault detection method of bearings.

In adaptive variational mode decomposition (AVMD), an adaptive strategy is proposed to select the optimal decomposition level K of variational mode decomposition. Then, a criterion based on envelope entropy is applied to select the optimal intrinsic mode functions (OIMF), which contains most useful fault information. Afterwards, local tangent space alignment (LTSA) is used to denoising of OIMF. The envelope spectrum of the OIMF is used to analyze the fault frequency, thereby detecting the fault. Experiments are conducted in a simulated signal and two experimental vibration signals of bearings to verify the effect of the new method.

The results show that the proposed method yields a good capability of detecting bearing fault at an early stage. The new method can extract more useful information and can reduce noise, which can provide better detection accuracy compared with the other two methods.

An adaptive strategy based on center frequency is proposed to select the optimal decomposition level of variational mode decomposition. Envelope entropy is used to fault feature selection. Combining the advantage of the AVMD-envelope entropy and LTSA, which suits the nature of the early fault signal. So, the proposed method has better detection accuracy, which provides a good alternative for early fault detection of bearings.