Non-conventional Behavior Research Articles

Nonconventional Fluorescent Non‐Isocyanate Polyurethane Foams for Multipurpose Sensing Applications

Fluorescent foams with interconnected pores are attractive for the detection and quantification of various products. However, many fluorescent probes are suffering from aggregation‐caused fluorescence quenching in their solid/aggregated state, are costly, and/or not straightforward to incorporate in foams, limiting their utility for this application. Herein, non‐isocyanate polyurethane foams, prepared by the simple water‐induced self‐blowing process, present a nonconventional fluorescence behaviour, i.e. they are intrinsically fluorescent with a multicolor emission without requiring ex‐situ traditional fluorescent probes. These foams demonstrate utility for capturing‐sensing gaseous formaldehyde (an emblematic indoor air pollutant), as well as for detecting and quantifying various metal ions (Fe2+, Cu2+, Fe3+, Hg2+). They are also able to selectively sense tetracycline antibiotic in a ratiometric way with a high sensitivity. By exploiting the unique multicolor photoluminescent foam properties, a smartphone‐compatible device is used for the facile antibiotic quantification. This nonconventional fluorescence behaviour is discussed experimentally and theoretically, and is mainly based on clusteroluminescence originating from multiple hydrogen bonding and hetero‐atomic sub‐luminophores, thus from aggregation‐induced emission luminogens that are naturally present in the foams. This work illustrates that easily accessible non‐conventional fluorescent NIPU foams characterized by a modular emission wavelength have an enormous potential for multiple substrates detection and quantification.

Nonconventional Fluorescent Non‐Isocyanate Polyurethane Foams for Multipurpose Sensing Applications

Fluorescent foams with interconnected pores are attractive for the detection and quantification of various products. However, many fluorescent probes are suffering from aggregation‐caused fluorescence quenching in their solid/aggregated state, are costly, and/or not straightforward to incorporate in foams, limiting their utility for this application. Herein, non‐isocyanate polyurethane foams, prepared by the simple water‐induced self‐blowing process, present a nonconventional fluorescence behaviour, i.e. they are intrinsically fluorescent with a multicolor emission without requiring ex‐situ traditional fluorescent probes. These foams demonstrate utility for capturing‐sensing gaseous formaldehyde (an emblematic indoor air pollutant), as well as for detecting and quantifying various metal ions (Fe2+, Cu2+, Fe3+, Hg2+). They are also able to selectively sense tetracycline antibiotic in a ratiometric way with a high sensitivity. By exploiting the unique multicolor photoluminescent foam properties, a smartphone‐compatible device is used for the facile antibiotic quantification. This nonconventional fluorescence behaviour is discussed experimentally and theoretically, and is mainly based on clusteroluminescence originating from multiple hydrogen bonding and hetero‐atomic sub‐luminophores, thus from aggregation‐induced emission luminogens that are naturally present in the foams. This work illustrates that easily accessible non‐conventional fluorescent NIPU foams characterized by a modular emission wavelength have an enormous potential for multiple substrates detection and quantification.

Improved microwave dielectric properties of LaZn1/2Ti1/2O3 through Y3+ substitution

LaZn1/2Ti1/2O3 is a double perovskite with promising microwave dielectric properties for applications towards dielectric resonators and antennas. Its dielectric properties can be enhanced through the substitution of suitable ions in either A- or B-sites. In this paper, we report a significant improvement in the quality factor (Q) by substituting Y3+ in the La site with a marginal reduction in dielectric constant (εr). A single phase is confirmed in XRD indicating the formation of La1-xYxZn1/2Ti1/2O3 (0 ≤ x ≤ 0.25) solid solutions. The substitution results in an expansion of lattice along the b direction while there is a contraction in both a and c directions, leading to a reduction in unit cell volume. The dielectric constant, εr, is observed to reduce from 33.4 to 29.6 due to the polarizability of A-site atoms. The temperature coefficient of resonant frequency (τf) increases with an increase in x which does not appear to correlate with reducing tolerance factor (t). This non-conventional behaviour of τf in this perovskite based solid solutions brings bond valence of O site (VO) into picture. VO appears to show competing effect on τf. The non-monotonic behaviour is observed in Q×f with a maximum value of 41,400 GHz at x = 0.15 and a sharp decline for x > 0.15. This observation is correlated with variations in the A-site bond valence (VA) and a long-range ordering (LRO) of B-site ions. LRO is associated with Ag mode at 710 cm−1 in the Raman spectra. The low frequency (< 250 cm−1) Raman modes shift to a higher frequency with the increase in Y3+. Y3+ substitution also induces lattice distortion which is discussed in terms of variations in FWHM and relative intensity of the Raman modes.

Non-conventional resonant behavior of an unconfined magnetic domain wall in a permalloy strip

The resonant dynamic of a magnetic domain wall in a permalloy microstrip has been investigated using an innovative experimental setup that enables a simultaneous measurement of the ferromagnetic resonance and the magnetoresistance. The resonance frequency associated with the presence of the magnetic domain wall increases linearly with the external magnetic field in the range of fields where the domain wall is present in the microstrip. This linear behavior is unusual in a domain wall and not related to the standard resonant modes of a magnetic domain wall, such as breathing, twisting, or translational modes. The slope of this linear dependency is 1.38 GHz/mT, which is an incredibly large value and allows the detection of very small changes in the external magnetic field. This linear behavior opens a path for developing a highly tunable radio frequency oscillator or a magnetic sensing device where the presence of an external field is detected via small variations in the resonant frequency of the domain wall.

Media Influence on Intergenerational Attitudes toward Non-Conventional Sexual Behaviors in Contemporary China: Evidence from Chinese General Social Survey

Objective Within the context of rapid sociocultural transformation in Chinese society over recent decades, exploring intergenerational disparities in attitudes toward non-conventional sexual behaviors holds sociological significance. Employing a methodology akin to cultivation analysis, this study focuses on the potential influence of television and the internet in narrowing or widening attitudinal disparities between distinct age groups. This is achieved by comparing heavy users of these media to individuals with light media consumption. Materials and Methods In the present study, we utilized the 2017 wave of the Chinese General Social Survey, a dataset that is representative of the national demographic of China. Our objective was to explore the potential influence of both traditional media (TV) and new media (the internet) consumption on the attitudes of Chinese adults toward three forms of non-conventional sexual behavior, namely premarital, extramarital, and same-sex behaviors. Results Firstly, compared to television, the internet is more likely to contribute to the liberalization of sexual attitudes, though this influence is age sensitive. Secondly, regarding the attitudes toward premarital sex and same sex behaviors, television tends to sustain or create consensus across different generations, whereas the internet tends to widen attitudinal gaps. Lastly, probably due to the moralized nature of extramarital sex in the Chinese context, both television and the internet maintain or produce the conservative consensus, though heavy television viewing could widen the attitudinal gap between young people and the other two age groups. Discussion and Conclusion Our study reveals that for premarital sex and same-sex behaviors, heavy television viewing tends to foster or sustain intergenerational consensus, while frequent internet usage tends to augment intergenerational divergence or erode intergenerational agreements. However, the media’s impact on intergenerational differences in attitudes toward extramarital sex exhibits distinctive features, likely stemming from the deeply moralized nature of extramarital affairs within Chinese society. To conclude, by conducting a comparative examination of various media landscapes, our research offers a mediated perspective that aids in comprehending the disparities in attitudes toward sexual behaviors across different generations in contemporary China.

Uncovering the hidden structure: A study on the feasibility of induction thermography for fiber orientation analysis in CFRP composites using 2D-FFT

The induction heating process elicits a heating response in a carbon fiber reinforced polymer (CFRP) composite distinctly different from those in metal. Prior work in our lab and elsewhere has established that the intensity and spatial distribution of the heating patterns are governed by the fiber orientations in each layer and the degree of electrical contact between layers. Based on more extensive work on this non-conventional heating behavior, we show that the analysis of induction heating patterns enables the characterization of the fiber orientations and stacking order within the material. In the first step, 2D Fast Fourier Transform (2D-FFT) is used to extract the fiber orientations from the spatial characteristics of the heating pattern recorded with an infrared camera. In the next step, the extracted fiber orientation is used to design bandpass filters to carry out the inverse 2D-FFT and obtain the layer stacking order. Our findings demonstrate that this approach can accurately identify the layer orientations (maximum error of 6o) and the stacking sequence in quasi-isotropic CFRP laminates with up to 12 layers. We believe that the proposed approach has the potential as a valuable nondestructive, non-contact tool for large-area inspection and quality control in manufacturing fiber-reinforced composites.

Beyond behavior: the penitence congruity effect among children

The penitence congruity effect observed in adults suggests that people may assess wrongdoers more leniently when they exhibit guilt and deontological beliefs. It means that judgments about one’s morality are influenced not only by their actions but also by their expressed moral emotions and beliefs. To determine whether children also exhibit this effect, we studied N = 250 children aged 10 and 11. We presented them with six vignettes: four depicting morally questionable actions (cheating on an exam, lying about homework, fighting with another student, stealing money found in a school hallway) and two displaying socially undesirable behaviors (attending school in pajamas, being late to school). Children also received information about the wrongdoer’s emotions (presence or absence of guilt) and beliefs (deontological stance or its absence) or were provided with no additional information on emotions or beliefs. Participants were then asked to assess a wrongdoer’s morality for each story. Our findings not only confirm the presence of the penitence congruity effect in children but also demonstrate its applicability to non-conventional behaviors. Specifically, when a wrongdoer expresses guilt and acknowledges wrongdoing, children are more lenient in their evaluations than in the control condition when no insights into the wrongdoer’s emotions or beliefs are provided. The results align with the person-centered theory, which posits that individuals assess overall character rather than isolated actions, considering all available information about the person in question. The findings hold potential applications, e.g., in moral education.

Widening of working temperature range in Mn5-xCuxGe3 (x = 0.1 and 0.3) magnetocaloric compounds by compositional tuning

This study presents the effect of Cu doping on the fundamental properties, magnetocaloric effect, and critical behavior of Mn5Ge3 system. Mn5-xCuxGe3 compounds with x = 0.1 and 0.3 conform D88-hexagonal structure. The unit cell volume decreases, and MnI-MnI distance increases with Cu content. This modifies the exchange interaction and impacts Curie temperature and saturation magnetization accordingly. The critical exponents β and γ of x = 0.1 compound are of 3D Ising class, while the x = 0.3 compound shows non-conventional behavior with its γ lying within the 3D Ising framework and β lying between 3D XY and Heisenberg classes. Both the compounds have extended-type spin interactions, and the decay of the exchange integrals has been calculated. Mn5-xCuxGe3 compounds clearly outperform most materials of Mn5Ge3 class in terms of the magnetocaloric effect. They show an appreciable reversible isothermal entropy change across a wide temperature span with a large relative cooling power near the room temperature effect. These compounds can be combined with other suitable Mn5Ge3 materials and used in ‘active magnetic regenerative (AMR)’ systems as layered refrigerants for more efficient magnetocaloric cooling.

Q-dependent electron-phonon coupling induced phonon softening and non-conventional critical behavior in the CDW superconductor LaPt2Si2

This paper reports the first experimental observation of phonons and their softening on single crystalline LaPt2Si2 via inelastic neutron scattering. From the temperature dependence of the phonon frequency in close proximity to the charge density wave (CDW) q-vector, we obtain a CDW transition temperature of TCDW = 230 K and a critical exponent β = 0.28 ± 0.03. This value is suggestive of a non-conventional critical behavior for the CDW phase transition in LaPt2Si2, compatible with a scenario of CDW discommensuration (DC). The DC would be caused by the existence of two CDWs in this material, propagating separately in the non equivalent (Si1–Pt2–Si1) and (Pt1–Si2–Pt1) layers, respectively, with transition temperatures TCDW−1 = 230 K and TCDW−2 = 110 K. A strong q-dependence of the electron-phonon coupling has been identified as the driving mechanism for the CDW transition at TCDW−1 = 230 K while a CDW with 3-dimensional character, and Fermi surface quasi-nesting as a driving mechanism, is suggested for the transition at TCDW−2 = 110 K. Our results clarify some aspects of the CDW transition in LaPt2Si2 which have been so far misinterpreted by both theoretical predictions and experimental observations and give direct insight into its actual temperature dependence.

Field-Theoretic Renormalization Group in Models of Growth Processes, Surface Roughening and Non-Linear Diffusion in Random Environment: Mobilis in Mobili

This paper is concerned with intriguing possibilities for non-conventional critical behavior that arise when a nearly critical strongly non-equilibrium system is subjected to chaotic or turbulent motion of the environment. We briefly explain the connection between the critical behavior theory and the quantum field theory that allows the application of the powerful methods of the latter to the study of stochastic systems. Then, we use the results of our recent research to illustrate several interesting effects of turbulent environment on the non-equilibrium critical behavior. Specifically, we couple the Kazantsev–Kraichnan “rapid-change” velocity ensemble that describes the environment to the three different stochastic models: the Kardar–Parisi–Zhang equation with time-independent random noise for randomly growing surface, the Hwa–Kardar model of a “running sandpile” and the generalized Pavlik model of non-linear diffusion with infinite number of coupling constants. Using field-theoretic renormalization group analysis, we show that the effect can be quite significant leading to the emergence of induced non-linearity or making the original anisotropic scaling appear only through certain “dimensional transmutation”.

Internal Migration and Cohabitation in China: A Mixed-method Study

Migration occurs at earlier ages, lasts for long periods, and profoundly shapes migrants’ experiences of cohabitation. We use a mixed-method approach based on the 2012 China Family Panel Studies and 127 in-depth interviews. To address potential selection bias, we estimated the treatment effects of migration based on propensity score matching. Results show that migrants, particularly rural-origin migrants with longer migration duration, are more likely to cohabit than their non-migrant counterparts. Qualitative interviews reveal the main underlying mechanisms: more liberal attitudes and less parental supervision in the receiving communities, a desire to vet potential partners in the absence of background knowledge, and economic barriers to marriage that make cohabitation an attractive buffer. Although migrants may cohabit as a sub-optimal option due to life instabilities and financial pressures, cohabitation also reflects a newly gained autonomy in their private lives, attributable to the liberal mindsets toward nonconventional family behaviors in the receiving communities.

Experimental validation of nonextensive statistical field theory: Applications to manganites

In this Letter we validate experimentally the nonextensive statistical field theory, a new general field-theoretic approach introduced recently in the literature. With such an approach, we are capable of computing the critical properties of nonextensive systems undergoing continuous phase transitions, belonging to the new generalized O(N)q universality class. We compare the nonextensive critical indices values evaluated from the theory with those already obtained in literature through experiments for various distinct manganites presenting nonconventional critical behavior. The agreement is satisfactory, whose relative errors are <5% for the most of manganites employed and as better as |1−q|<1 which is the limit of validity of the theory. We present the physical interpretation of the experimental results and of the theory through the general physical interpretation of the q-parameter.

(Invited, Digital Presentation) Understanding the Self-Assembly of Polymer-Grafted Nanocrystals

Combination of inorganic nanocrystals (NCs) and polymeric materials is promising for the design of novel functional materials due to their complementary properties. For the preparation of such hybrid nanomaterials with tailored functionalities, it is important to precisely control their nanostructures since material properties of NCs strongly depend not only on the morphology of each NC building block, but also their assembled packing symmetries. In this talk, I will present precise control of polystyrene-grafted Au NC (Au@PS) superlattice symmetry, which shows non-conventional assembly behavior compared to short alkyl chain-coated NCs. Au@PS NCs were synthesized by ligand exchange using thiol-terminated PS with various molecular weights (M n). The Au@PS particles were self-assembled through liquid-air interface self-assembly process. Transmission electron microscopy images and grazing incidence small-angle X-ray scattering data indicated long-range ordered Au@PS superlattices. In particular, symmetry transitions from hexagonal close packing (hcp) to body centered cubic (bcc) symmetry were found as M n of PS increases or diameter of NCs decreases. We tried to understand the structural transitions by proposing “effective softness” model, which considers concentrated polymer brushes around NC surface as part of “hard core.” Finally, I will show how these polymer-grafted NCs can be self-assembled with block copolymers for the development of colloidal hybrid particles with stimuli-responsive photoluminescence behavior, which have great potential for the applications in smart material systems.

Dimensional transmutation and nonconventional scaling behavior in a model of self-organized criticality

This paper addresses two unusual scaling regimes (types of critical behavior) predicted by the field-theoretic renormalization group analysis for a self-organized critical system with turbulent motion of the environment. The system is modeled by the anisotropic stochastic equation for a “running sandpile” introduced by Hwa and Kardar in [Phys. Rev. Lett. 62, 1813 (1989)]. The turbulent motion is described by the isotropic Kazantsev–Kraichnan “rapid-change” velocity ensemble for an incompressible fluid. The original Hwa–Kardar equation allows for independent scaling of the spatial coordinates [Formula: see text] (the coordinate along the preferred dimension) and [Formula: see text] (the coordinates in the orthogonal subspace to the preferred direction) that becomes impossible once the isotropic velocity ensemble is coupled to the equation. However, it is found that one of the regimes of the system’s critical behavior (the one where the isotropic turbulent motion is irrelevant) recovers the anisotropic scaling through “dimensional transmutation.” The latter manifests as a dimensionless ratio acquiring nontrivial canonical dimension. The critical regime where both the velocity ensemble and the nonlinearity of the Hwa–Kardar equation are relevant simultaneously is also characterized by “atypical” scaling. While the ordinary scaling with fixed IR irrelevant parameters is impossible in this regime, the “restricted” scaling where the times, the coordinates, and the dimensionless ratio are scaled becomes possible. This result brings to mind scaling hypotheses modifications (Stell’s weak scaling or Fisher’s generalized scaling) for systems with significantly different characteristic scales.

Study on the mechanical properties of CFRP composite auxetic structures consist of corrugated sheets and tubes

In recent years, auxetic (negative Poisson's ratio) structures have attracted great attention because of their non-conventional behaviour. However, auxetic structures are usually characterized by low stiffness, which limits their application. Once, their stiffness can be improved, their application field will be significantly broadened. In addition, most auxetic structures are difficult to be produced due to their complex geometries. To solve these two problems, high-performance carbon fibre reinforced polymer (CFRP) composites are used to manufacture an auxetic structure consist of corrugated sheets and tubes. The mechanical properties of the composite auxetic structure consist of corrugated sheets and tubes (CorTube) are studied by experiments, finite element simulation and theory analysis. The results show that, the composite CorTube structures display obvious negative Poisson's ratio effect in large compression strain range, and the auxetic characteristics of the composite CorTube structures become more notable with the increase of the compression strain. The stiffness of the structure depends on the thickness of the corrugated sheets in small strain stage, while the material parameters of the tubes plays determining role in large strain stage. Finally, the deformation characteristics and failure modes of the CorTube during the compression process are discussed.

Imidazolidinyl urea reinforced polyacrylamide hydrogels through the formation of multiple hydrogen bonds

Hydrogels with outstanding mechanical characteristics, remoldability, and self-healability possess vast potentials in biomedical applications and flexible sensors. However, it is still difficult to prepare hydrogels with integrated mechanical characteristics straightforwardly. Herein, we proposed to introduce a hydrogen bonding reinforced factor, imidazolidinyl urea (IU), to the polymerization of acrylamide for the construction of multi-functional hydrogels in one pot. There are multiple hydrogen bonding donors and receptors in IU, which can interact with polyacrylamide through multiple hydrogen bonds to form the hydrogel networks. The break strength, fracture elongation, and compressive strength of the IU-included hydrogels could be adjusted in the range of 18.8–23.8 kPa, 305%–560%, and 2.0–3.9 MPa, respectively. The hydrogels featured outstanding fatigue resistance, and the obvious loss of compressive strength was not observed even after 50 cycles of loading-unloading under 85% strain. Moreover, the IU-based hydrogels not only showed promising self-healing and remodeling abilities but also exhibited nonconventional emission behaviors. Our work offers a facile strategy for the construction of multi‑hydrogen bond crosslinked hydrogels and may inspire researchers to explore new supramolecular systems using the hydrogen bonding reinforced factor (IU).

Stress peaks, stiffening and back-flow in bilayer poro-elastic metamaterials

In the present work, we present a linear poroelastic model for a quasi-static oscillating bilayer beam made by two thick strata in perfect bond at their interface, characterized by different elastic moduli and permeability, both directly influenced by porosity. The solution is built up by considering the structure as a three-dimensional object and is obtained analytically for the full coupling of mass balance and mechanical equations, by imposing weak boundary conditions on the sole forces emerging at the lateral outermost surfaces, neglecting the inertial effects. After verifying the accuracy of the solution by comparing theoretical outcomes and numerical results from Finite Element simulations, ad hoc sensitivity analyses were then carried out in order to investigate the effects on the stress distribution and fluid flow due to prescribed inhomogeneities related to variations of material and geometrical parameters across the beam thickness, by keeping constant the total volume of the porous solid skeleton and applying self-equilibrated and oscillating in time axial forces and bending moments at two opposite sides of the structure. Some dynamic analyses were also performed to highlight proper periods and frequencies ranges where pulse loadings ensured the quasi-static response of the system, however discussing interferences due to transient regimes for selected cases on the basis of numerical analyses. Finally, we show that, by playing with ratios between elastic moduli, thickness and porosity of the two layers, a number of counterintuitive or even non-conventional behaviors can be observed, which give rise to unexpected back-flow phenomena and anomalous fluid content distributions, as well as to stress peaks kindled by moving the layer interface and overall stiffening that could be all exploited for the design of new multi-objective poroelastic metamaterials.

Effects of W/ WO3-x junction on synaptic characteristics of W/WO3-x/ITO memristor

Abstract Two tungsten/tungsten oxide/Indium–Tin Oxide (W/WO3-x/ITO) memristors were fabricated for studying comparatively the effects of W/WO3-x junction on their synaptic performances, in which one is ohmic (Ohm-type device) and the other is rectified (Rec-type device). The characterization results show that Ohm-type device exhibits rich synaptic properties, including the controllable synapse weight update by adjusting the input pulse amplitude, interval, and number, as well as the transformation from the paired-pulse facilitation (PPF) to the paired-pulse depression (PPD) by only changing the pulse width. However, the Rec-type device manifests the nonconventional synaptic behavior and the bowknot-shaped I–V curves. The fitting of I–V curves by the various carrier transport modes demonstrates the bulk mechanism for the Ohm-type device and Schottky mechanism for the Rec-type device. Therefore, we suggest that oxygen vacancy injection and migration in WO3-x layer lead to the presence of synaptic properties in the Ohm-type device, while the rectified W/WO3-x junction and the variable conductance of WO3-x layer lead to the nonconventional synaptic properties and bowknot-shaped I–V curves. This report revealed the complexity of memristors, and emphasizing the necessity to carefully select the material combination and design the device structures for realizing the synaptic properties.

Turbulence Quantification in Supercritical Nitrogen Injection: An Analysis of Turbulence Models

In Liquid Rocket Engines, higher combustion efficiencies come at the cost of the propellants exceeding their critical point conditions and entering the supercritical domain. The term fluid is used because, under these conditions, there is no longer a clear distinction between a liquid and a gas phase. The non-conventional behavior of thermophysical properties makes the modeling of supercritical fluid flows a most challenging task. In the present work, a RANS computational method following an incompressible but variable density approach is devised on which the performance of several turbulence models is compared in conjunction with a high accuracy multi-parameter equation of state. Also, a suitable methodology to describe transport properties accounting for dense fluid corrections is applied. The results are validated against experimental data, becoming clear that there is no trend between turbulence model complexity and the quality of the produced results. For several instances, one- and two- equation turbulence models produce similar and better results than those of Large Eddy Simulation (LES). Finally, considerations about the applicability of the tested turbulence models in supercritical simulations are given based on the results and the structural nature of each model.&#x0D; Keywords: Supercritial fluids, RANS turbulence modeling, Liquid rocket engines

Investigation on Sensorless Estimating Method and Characteristics of Friction for Ball Screw System

In this study, a novel sensorless method is developed to estimate the friction in a ball screw system using asynchronous experimental data for a worktable position (WP) and the servo motor torque current (SMTC), which is collected by the FOCAS library functions from a FANUC digital control system. The corresponding time stamps are retrieved by a high-resolution performance counter in Windows. The fluctuations in friction over the whole travel distance of the worktable (WTDOW) are analyzed using a piecewise polynomial fitting algorithm to extract the instantaneous average friction value (IAFV) and the friction fluctuating signal (FFS). The IAFVs can describe the effect of the WP and the pitch errors of the shaft on the friction. The FFT results of the FFS show that the friction depends on the rolling tool, the pitch of the shaft and the refeeding of the balls in the ball screw and linear ball rail guides. The experimental results show that the estimated friction can capture the characteristic spectra of the FFS. The effects of the feed velocity and direction, the effects of the WP on the IAFV, and the frequencies and amplitudes of the significant FFT components are discussed. The nonuniform pitch errors of the shaft impact the repeatability of the IAFVs at a given WP. The variations in the mean value of the IAFVs with the feed velocity for tests at a fixed WP show nonconventional Stribeck behavior. These results also demonstrate that the friction force varies with the WP, which is not captured by Stribeck characteristics. This study provides an effective method to evaluate the performance of a ball screw system and to predict the friction in that system without the use of sensors.