Principal Axes Research Articles

Analysis of High-Speed Rotor Vibration Failure Due to Sudden Angular Deformation of Bolt Joints

As the efficiency of advanced aero engines improves, the operational speed of their rotors increases. This heightened operational speed makes the rotor dynamics highly sensitive to changes in the rotor’s mass asymmetry state, or unbalance state. During the use of a dual-spool turbofan engine, when its supercritical high-pressure rotor (HPR) exceeds a certain operational speed, the rotor’s vibration spikes and continues to increase with the operational speed until it drops sharply near the maximum operational speed. Analysis of the bolt joints in the faulty rotor reveals various phenomena such as joint interface damage, changes in bolt loosening torque distribution, and alterations in rotor initial unbalance. This paper proposes that at high operational speeds, the bolt joint of the HPR undergoes sudden angular deformation, resulting in the slanting of the principal axis of inertia of the turbine disk. This slant leads to changes in the unbalanced state of the HPR. The additional unbalance causes a sudden rotational inertia load excitation, triggering the rotor vibration failure. Subsequently, a rotor dynamic model that incorporates the angular deformation of the joints is established to simulate how this joint deformation influences the dynamic response of the rotor. The simulation results align well with the observed failure phenomenon and validate the proposed failure mechanism. Finally, troubleshooting measures are proposed and implemented in the faulty engine, effectively mitigating the vibration fault.

A study on the landscape and cultural space of Yulin City, China

Urban growth in China over the past 40 years has increased sharply. Following a modernist approach during this period, the historic urban cultural landscape was neglected. Recently, in response, scholars have been investigating alternative approaches whose conceptual roots spring from traditional Chinese urban planning. The theory of the ‘Science of Human Settlement Environment’ has emerged as a framework for exploring this direction. This research, drawing upon literary records, historic city maps, and field investigations, builds on this approach. Yulin City, initially developed as a high-ranking military city during the Ming Dynasty, drew upon the characteristics of the existing landscape and traditional Chinese planning strategies for its design. Noting the relationship of the city’s layout to its surrounding Shan-Shui (Mountain-Water), the development of its principal axis, the influence of the Tuo Mountain spiritual space, and the definition of the city wall, greater insight into traditional Chinese planning can be learned.

Discrete Element Simple Shear Test Considering Particle Shape

The particle shape has significant effects on the slip and rotation of particles in the shear of geomaterials, which is an important factor in the deformation and strength of geomaterials. This paper employed particle flow code (PFC3D) to simulate the simple shear test, and ellipsoidal particles with different aspect ratios were prepared to study the effects of particle shape on the mechanical behavior and fabric evolution of granular materials under complex stress paths. The numerical results show that the particle shape has a significant effect on the peak strength, dilatancy, non-coaxiality, and other mechanical properties of granular materials. The contact fabric evolves from orthotropy to transverse isotropy under the principal stress axes rotation. This paper will provide a reference for natural granular materials with different shapes in the study of mechanical behavior and the micro-constitutive model.

TECTONIC STRESSES IN THE CHERSKY FAULT ZONE (BAIKAL RIFT SYSTEM

Based on the kinematic and structural-paragenetic approaches, there were performed the reconstructions of tectonic stresses in the Chersky fault zone. Rank analysis as applied to specialized mapping of fault zones was made for heterochronous rock complexes: Paleozoic, Upper Oligocene – Lower Pliocene and Upper Pliocene – Quaternary. There are distinguished three regional stress fields: Pre-Cenozoic compressive stress field with the NW-SE striking principal axis and two Cenozoic tensile stress fields with different axial orientations. The Cenozoic tensile stress field with a sub-meridionally striking minimum compression axis may be an earlier occurrence because it was found to exist in the Paleozoic and Oligocene – Early Pliocene rocks, and the tensile stress field, with the NW-SE axial orientation, may be later occurrence as reconstructed for all rock complexes including Quaternary pebbles. No evidence was found of tectonic shear stresses within the studied segment of the Chersky fault zone. Consideration is being given to probable reasons for the absence of residual shear deformations in the region and to the problems in the study of hierarchy of the upper crustal tectonic stresses.

Seasonal dynamics of water circulation and exchange flows in a shallow lagoon-inlet-coastal ocean system

A wave–current coupled, unstructured-grid, three-dimensional hydrodynamic model was applied to investigate the seasonal dynamics of the Maryland Coastal Bays system. The model's performance was validated successfully against hydrodynamic observations from the spring to fall of 2014, and the driving forces of water circulation and exchange flows were discussed. Results indicate that seasonal dynamics are primarily controlled by tides, modulated by winds, waves, and density variations, and regulated by the inlet orientation and geometry. Seasonal circulation in the surface layer is stronger than that near the bottom. The strong coastal circulation, net outflows via inlets, and the clockwise movements in the southern Isle of Wight Bay are primarily controlled by tides. The directional alignment between winds and the bay's principal axis and inlet orientation are key to the seasonal circulation and exchange flows in Sinepuxent Bay and via inlets. Wave-induced effects are comparable to tides in particular regions (e.g., reaching 30 cm/s in Isle of Wight Bay), and much larger than those caused by density variations overall. Additional numerical experiments indicate that spatial variations in salinity are mainly responsible for the density-induced circulation (e.g., 6 cm/s at the mouth of Newport River in Newport Bay). Further analysis indicates that the net exchange flows vary from the surface to bottom layers (e.g., different magnitudes or transporting directions) both in the lagoon and via the paired inlets. This work is beneficial to coastal communities and numerical modelers in understanding the dynamics of shallow lagoon-inlet-coastal ocean systems at a seasonal timescale.

Three-dimensional spatial stress state of highway subgrade under vehicle load: experimental evidence and evaluation model

ABSTRACT In this study, field tests of highway subgrade dynamic response were conducted using a self-developed regular dodecahedron soil pressure sensor (RDSPS). The RDSPS can be used to quantify the total stress of the subgrade soil element. The effects of different axle loads, speeds, and vehicle types on the dynamic response of the subgrade were investigated. The spatial distribution law of the vertical dynamic stress of the highway subgrade was examined. An estimation model for the vertical dynamic stress and the influence depth of vehicle load was developed. The results suggest that, under the action of a moving traffic load, the principal stress axis continues to rotate. Both vehicle speed and axle load have an impact on the dynamic response of the subgrade; however, for newly built highways, the impact of the vehicle axle load on the dynamic stress is more significant. The vertical dynamic stress increases linearly with the speed or axle load of the vehicle. The attenuation law of the vertical dynamic stress caused by different types of vehicles on the subgrade along the depth direction is basically consistent, and the attenuation speed changes from fast to slow, with the fastest attenuation rate in the base layer.

Sustainability‐oriented innovation in retailing

AbstractSustainability‐oriented innovation in services has recently been raising interest among academics and professionals. The present research has a dual objective. The first is to develop a scale that captures the notion of sustainability‐oriented innovation in retailing (SOI‐r) from the consumer's perspective. A sequential process is carried out to purge and retain 17 items which synergistically measure SOI‐r. We use quantitative research, adopting an exploratory‐descriptive approach on a total sample of 510 customers of commercial food establishments. The principal axis factor analysis shows six factors: product innovation, marketing innovation, relational innovation, economic sustainability, social sustainability, and environmental sustainability. The second objective is to develop an index using importance‐performance map analysis, which allows analysis of the level of development of the six dimensions identified in SOI‐r and areas for their improvement. The results are compared across food retail formats (hypermarkets, supermarkets, and discount stores) and recommendations are made at a strategic level.

Experimental study on strain accumulation characteristics of saturated remolded loess under pure rotation of the principal stress axis

The study conducted a pure rotation test of 720° for saturated remolded Q2 loess under principal stress axis (PSA) rotation when deviatoric stress and the intermediate principal stress ratio are different, also paying attention to examining the changes of strain accumulation and pore pressure of such loess. According to the test, as the PSA rotates continuously, the pore water pressure exhibited by saturated remolded loess presents a normal cyclic accumulation elevation, and under the same deviatoric stress conditions, the pore water pressure accumulation trend of different principal stress ratios is the same; however, the magnitude is different. The increment of pore water pressure becomes smaller as the number of cycles increases. When the deviatoric stress level is low, the material hardening is in a cyclic stable state, the strain component remains stable with the continuous rotation of the PSA, and the strain path area is reduced, together with a stable final size. In case of higher deviatoric stress, the material strength cycle becomes weaker and the strain component accumulates slowly as the PSA (the spiral line of the strain path) continuously rotates in the γzθ−(ϵz−ϵθ) plane, and gradually expands until failure. The increased intermediate principal stress is accompanied by accelerated strain development speed and advanced failure.

Labor unit culture and attitudes toward supporting vaginal birth-The Swedish version of the labor culture survey (S-LCS)-Psychometric properties.

In order to evaluate interventions aimed at reducing cesarean births, care practitioners' attitudes are important to measure. The Labor Culture Survey (LCS) is a scale that measures individual and unit attitudes towards supporting vaginal birth. As no equivalent scale exists in Sweden, the aim was to translate, adapt, and validate the LCS and to investigate whether there were differences in attitudes toward supporting vaginal birth between maternity care practitioners. A cross-sectional study including midwives, physicians, and nurse assistants working with intrapartum care in five labor wards in Sweden. The original LCS was translated into Swedish, and six context-specific items were developed for the Swedish setting (SLCS). The translation was tested for face validity. Psychometric analysis was conducted using exploratory factor analysis with principal component analysis, parallel analysis, and principal axis factoring. Reliability was estimated using Cronbach's alpha. One-way ANOVA and Tukey HSD were calculated to analyze differences in attitudes between professions on the subscales of the S-LCS. A total of 539 midwives, physicians, and nurse assistants participated. The final S-LCS showed a five-factor solution with the following subscales: Best Practices to reduce cesarean overuse, Unpredictability of vaginal birth, Unit Microculture, Maternal Agency, and Organizational Oversight. Chronbach alpha values varied from 0.60 to 0.83. Midwives were more supportive towards vaginal birth and less fearful of potential consequences of vaginal birth compared with physicians. The S-LCS demonstrated satisfactory psychometric properties for use in Swedish maternity care. Further work to improve the scale should include additional items reflecting the subscale Maternal Agency.

Predicting cognitive decline in a low-dimensional representation of brain morphology

Identifying early signs of neurodegeneration due to Alzheimer’s disease (AD) is a necessary first step towards preventing cognitive decline. Individual cortical thickness measures, available after processing anatomical magnetic resonance imaging (MRI), are sensitive markers of neurodegeneration. However, normal aging cortical decline and high inter-individual variability complicate the comparison and statistical determination of the impact of AD-related neurodegeneration on trajectories. In this paper, we computed trajectories in a 2D representation of a 62-dimensional manifold of individual cortical thickness measures. To compute this representation, we used a novel, nonlinear dimension reduction algorithm called Uniform Manifold Approximation and Projection (UMAP). We trained two embeddings, one on cortical thickness measurements of 6237 cognitively healthy participants aged 18–100 years old and the other on 233 mild cognitively impaired (MCI) and AD participants from the longitudinal database, the Alzheimer’s Disease Neuroimaging Initiative database (ADNI). Each participant had multiple visits (n ge 2), one year apart. The first embedding’s principal axis was shown to be positively associated (r = 0.65) with participants’ age. Data from ADNI is projected into these 2D spaces. After clustering the data, average trajectories between clusters were shown to be significantly different between MCI and AD subjects. Moreover, some clusters and trajectories between clusters were more prone to host AD subjects. This study was able to differentiate AD and MCI subjects based on their trajectory in a 2D space with an AUC of 0.80 with 10-fold cross-validation.

Psychometric evaluation of a contemporary version of the drug and drug problems perception questionnaire

BackgroundMore than 20 years ago, the Drug and Drug Problems Perception Questionnaire (DDPPQ) was developed to examine healthcare providers’ attitudes and perceptions towards individuals who use drugs. In alignment with recommended terminology respectful of this patient population, the 20-item measure was revised using person-centered language. Therefore, this study aimed to examine the psychometric properties of the person-centered DDPPQ (PC-DDPPQ) version among undergraduate nursing students. MethodsExploratory and confirmatory factor analyses were used to examine the PC-DDPPQ factor structure using a cross-sectional design. A convenience sample of 400 students from two nursing schools located in the Northeast and Mid-Atlantic regions of the US participated in the study. The sample (N = 400) was divided equally between the exploratory factor analysis (EFA) and the confirmatory factor analysis (CFA). ResultsAfter applying principal axis factoring (PAF) with oblique (Promax) rotation, the EFA yielded a five-factor, 20-item structure that explained 70.0% of the variance. The CFA revealed that the final model, derived from the EFA, which yielded a 19-item, five-factor structure adequately fit the data (Comparative Fit Index (CFI) = 0.959, the Tucker-Lewis Index (TLI) = 0.951 and Root Mean Square Error of Approximation (RMSEA) = 0.058). ConclusionsExcept for one item (item #14), the five-factor structure aligned with the original 20-item version. This study contributes to promoting the use of a more appropriate and less stigmatizing language among healthcare providers working with patients who use drugs.

A theory of pitch for the hydrodynamic properties of molecules, helices, and achiral swimmers at low Reynolds number.

We present a theory for pitch, a matrix property that is linked to the coupling of rotational and translational motion of rigid bodies at low Reynolds numbers. The pitch matrix is a geometric property of objects in contact with a surrounding fluid, and it can be decomposed into three principal axes of pitch and their associated moments of pitch. The moments of pitch predict the translational motion in a direction parallel to each pitch axis when the object is rotated around that axis and can be used to explain translational drift, particularly for rotating helices. We also provide a symmetrized boundary element model for blocks of the resistance tensor, allowing calculation of the pitch matrix for arbitrary rigid bodies. We analyze a range of chiral objects, including chiral molecules and helices. Chiral objects with a Cn symmetry axis with n > 2 show additional symmetries in their pitch matrices. We also show that some achiral objects have non-vanishing pitch matrices, and we use this result to explain recent observations of achiral microswimmers. We also discuss the small but non-zero pitch of Lord Kelvin's isotropic helicoid.

Investigating the Dimensions of Mind Perception

Mind perception is the ability to infer the presence of a mind in other beings or non-living things (e.g., a tree, an animal, a robot) and make judgements about what "kind" of mind that being possesses. Research has shown that there is a dimensionality to the schema of mind perception, though the number of dimensions is debated. The present study aimed to explore the dimensions via a mind perception scale that measures participants’ perceptions of mental capacities (n = 181). The data was highly suited for factor analysis, so principal axis factoring and multiple criteria were used to find the retained factors. Findings suggest a two-dimensional model of mind perception, supporting the field’s landmark study by Gray et al. (2007).

Fitting the Light Curve of 1I/‘Oumuamua with a Nonprincipal Axis Rotational Model and Outgassing Torques

In this paper, we investigate the nonprincipal axis (NPA) rotational state of 1I/‘Oumuamua—the first interstellar object discovered traversing the inner solar system—from its photometric light curve. Building upon Mashchenko, we develop a model which incorporates NPA rotation and Sun-induced, time-varying outgassing torques to generate synthetic light curves of the object. The model neglects tidal forces, which are negligible compared to outgassing torques over the distances at which ‘Oumuamua was observed. We implement an optimization scheme that incorporates the NPA rotation model to calculate the initial rotation state of the object. We find that an NPA rotation state with an average period of 〈P〉 ≃ 7.34 hr best reproduces the photometric data. The discrepancy between this period and previous estimates is due to continuous period modulation induced by outgassing torques in the rotational model, as well as different periods being used. The best fit to the 2017 October data does not reproduce the 2017 November data (although the later measurements are too sparse to fit). The light curve is consistent with there being no secular evolution of the angular momentum, which is somewhat in tension with the empirical correlations between nuclear spin-up and cometary outgassing. The complex rotation of ‘Oumuamua may be the result of primordial rotation about the smallest principal axis if (i) the object experienced hypervolatile outgassing and (ii) our idealized outgassing model is accurate.

Cultural Insights into Pakistan: Development and Validation of Perceived Cultural Logic Scale

Dignity, honor, and face culture is a new and different normative script for behavior in social interaction and negotiations. The main objective of the study was to develop and validate a theoretical model to measure the cultural logic of dignity, honor, and face culture. The study was configured in three phases using samples from different Universities in Pakistan with an age range of 18-25. In phase A, items were developed using a literature review and Thematic Analysis of data obtained through focused group discussions and interviews. Phase B was comprised of scale development in which the factor structure of the scale was confirmed using Principal Axis Factoring on the sample of N=348 emerging adults. In phase C, the measure was further subjected to confirmatory factor analysis, reliability, and validity procedures (N= 422). It was established through CFA that the measure had construct validity. Coefficient alpha ranged from .93 to .95. Validity of the measure was established through Average Variance Extracted (AVE= .64-.73), Maximum Variance Extracted (MSV= .02-.10) Fornell - Lacker Criterion and Hetro-trait Mono-trait criteria. Overall results indicated that the Perceived Cultural Logic Scale is a self-report, psychometrically sound, and comprehensive measure comprised of 23 items that can be used to evaluate the perception of cultural logic among emerging adults.

Mathematics Attitude of Future Teachers of Stem Subjects

Aim. This paper presents research aimed at testing the mathematical self-efficacy of mathematics and computer science student teachers. The aim of the presented phase of the research was to verify the effectiveness of the chosen research instrument after translation into Czech, its applicability within the specific environment of the preparation of future teachers and the design of a shorter version of the questionnaire. Methods. 97 students of the first and second year of Bachelor's degree studies at the Faculty of Education of Charles University, specialising in mathematics and computer science, were interviewed either in a single-subject form or in combination with a second subject. Subsequently, the data was processed and evaluated using quantitative methods. Results. The results confirmed that the test, even when translated into Czech, fully met the claim of high reliability (Cronbach's Alpha = 0.965). Using the Principal Axis Factoring method with Varimax with Kaiser Normalisation in 11 iterations, convergence to the four basic components, which were characterised as Motivation and Enjoyment, Anxiety, Self-confidence and Value, was achieved. Conclusion. The research has shown that the chosen research instrument, the ATMI questionnaire, is fully functional after translation into English and use in the environment of preparation of future mathematics and science teachers. The first measurement data also confirms that attitudes towards mathematics are very different among future mathematics and science teachers. It also confirmed the assumption that the questionnaire has the potential to identify students who have problematic attitudes towards mathematics and are therefore at risk of dropping out.

Anomalous tumbling of colloidal ellipsoids in Poiseuille flows.

Shear flows cause aspherical colloidal particles to tumble so that their orientations trace out complex trajectories known as Jeffery orbits. The Jeffery orbit of a prolate ellipsoid is predicted to align the particle's principal axis preferentially in the plane transverse to the axis of shear. Holographic microscopy measurements reveal instead that colloidal ellipsoids' trajectories in Poiseuille flows strongly favor an orientation inclined by roughly π/8 relative to this plane. This anomalous observation is consistent with at least two previous reports of colloidal rods and dimers of colloidal spheres in Poiseuille flow and therefore appears to be a generic, yet unexplained feature of colloidal transport at low Reynolds numbers.

A phylogenetically-conserved axis of thalamocortical connectivity in the human brain

The thalamus enables key sensory, motor, emotive, and cognitive processes via connections to the cortex. These projection patterns are traditionally considered to originate from discrete thalamic nuclei, however recent work showing gradients of molecular and connectivity features in the thalamus suggests the organisation of thalamocortical connections occurs along a continuous dimension. By performing a joint decomposition of densely sampled gene expression and non-invasive diffusion tractography in the adult human thalamus, we define a principal axis of genetic and connectomic variation along a medial-lateral thalamic gradient. Projections along this axis correspond to an anterior-posterior cortical pattern and are aligned with electrophysiological properties of the cortex. The medial-lateral axis demonstrates phylogenetic conservation, reflects transitions in neuronal subtypes, and shows associations with neurodevelopment and common brain disorders. This study provides evidence for a supra-nuclear axis of thalamocortical organisation characterised by a graded transition in molecular properties and anatomical connectivity.

Analysis of the effect of the translational-rotational coupling on the pseudo-diffusion along the molecular axes of meta-cresol: A molecular dynamics analysis

We investigate the dynamical properties (translation and rotation) of the glass-forming liquid meta-cresol by molecular dynamics simulations. This system is investigated at 9 temperatures between 230 K and 400 K, encompassing the liquid and glassy states of meta-cresol. In order to get insight into the coupling between the translational and rotational motions, the centre of mass velocity autocorrelation function is calculated along the principal axes of meta-cresol. We show that the time behaviour of the velocity and angular velocity is connected to the change in the local structure occurring upon the glass transition. Indeed, the long-time negative region in the velocity autocorrelations is associated with a caging effect while the occurrence of a short time negative region in these functions is considered as a signature of hydrogen bonding interactions. By studying, the centre of mass velocity of meta-cresol in the molecular frame, the translation and rotation coupling was directly evidenced. The time evolution of the translational-rotational coupling is evaluated from the difference ΔαRTC(t) between the velocity autocorrelation function calculated with respect to the molecular frame (where α stands for the three axes of the local cartesian frame fixed to the individual molecule, x, y, and z) of the meta-cresol molecule and that of the same function calculated in the frame of the hypothesis that there is no statistical correlation between the translational and rotational motions. The positive regions of ΔαRTC(t) indicate an occurrence of a cooperative effect, which means that the each of the two motions is realized in the favour of the other. Conversely, negative regions indicate that the rotation and translation motions are anti-cooperative. Our results show that a strong coupling between translation and rotation occurs along the × axis that is perpendicular to the ring of meta-cresol molecule, and also along which the hydrogen bond is established.

Figure Rotation of IllustrisTNG Halos

We use the TNG50 and TNG50 dark matter (DM)-only simulations from the IllustrisTNG simulation suite to conduct an updated survey of halo figure rotation in the presence of baryons. We develop a novel methodology to detect coherent figure rotation about an arbitrary axis and for arbitrary durations, and we apply it to a catalog of 1577 DM halos from the DM-only run and 1396 DM halos from the DM+baryons (DM+B) run that are free of major mergers. Figure rotation was detected in 94% of DM-only halos and 82% of the DM+B halos. The pattern speeds of rotations lasting ≳1h −1 Gyr were log-normally distributed with medians of 0.25 h km s−1 kpc−1 for DM-only in agreement with past results, but 14% higher at 0.29 h km s−1 kpc−1 in the DM+B halos. We find that rotation axes are typically aligned with the halo minor or major axis in 57% of DM-only halos and in 62% of DM+B halos. The remaining rotation axes were not strongly aligned with any principal axis but typically lie in the plane containing the halo minor and major axes. Longer-lived rotations showed greater alignment with the halo minor axis in both simulations. Our results show that, in the presence of baryons, figure rotation is marginally less common, shorter-lived, faster, and better aligned with the minor axis than in DM-only halos. This updated understanding will be consequential for future efforts to constrain figure rotation in the Milky Way dark halo using the morphology and kinematics of tidal streams.