Theoretical Strengths Research Articles

Reframing Sexual Health for Black Girls and Women in HIV/STI Prevention Work: Highlighting the Role of Identity and Interpersonal Relationships.

While Black girls and women are disproportionately impacted by sexual health disparities, there continues to be an overwhelming focus on individual risk behaviors within prevention initiatives, which offers a fragmented narrative of the multidimensional nature of risk and plausibly limits effectiveness of prevention programs and attenuates reductions in disparities. Because sexual health is experienced within an individual’s beliefs/values, interpersonal relationships, and behaviors and reflects larger social and cultural systems, it is important to critically examine common theories used to inform HIV/STI prevention interventions for Black women and girls. To fill this gap in the literature, we critique two commonly used theories in HIV/STI prevention interventions, namely the social cognitive theory and the theory of gender and power, by highlighting theoretical and practical strengths and weaknesses. We propose research implications that incorporate key strengths of the two theories while adding new concepts grounded in the intersectionality theory. The overall goal is to introduce a more comprehensive conceptual model that is reflective of and applicable to the multidimensional sexual experiences of Black girls and women within the evolving definition of sexual health and behavior.

Theoretical and Numerical Analysis of the Fatigue Strength of Mechanical Material and Part under Uniaxial Stress

To characterize the fatigue strength of mechanical material and part, a methodology combining the fatigue damage theory with the numerical simulation is proposed under three types of uniaxial loads. The equal-life fatigue curve of a shaft is used for the theoretical and numerical analysis of fatigue damage. Its theoretical fatigue strengths under different loadings are gained through theory equations. Utilizing the mean stress correction method, the stress distribution and fatigue life of the shaft are obtained through the collaborative simulation of ANSYS and nCode software. Consequently, the resultant fatigue lives are all within the value band of basic cycle number as demanded in practice, implying the correction and validation of theory analysis. The proposed strategy provides a new pathway and perspective for the analysis of fatigue damage.

Achieving cylindrical duct modes generation in spinning mode synthesizer via a least-square identification of the global calibration factor

Spinning Mode Synthesizer is an effective engine noise test rig for aero-engine noise propagation and radiation research. Spinning mode generation is realized through amplitude modulation and phase shift between individual loudspeakers. The target spinning mode is not the primary mode. It is even submerged in the undesired modes due to the system error of artificial source generators, especially the magnitude and phase mismatch of loudspeakers. In this paper, a global calibration factor is used to minimize the effect of loudspeaker nonuniformity in mode generation. The mode generation process of the calibrated system is mainly divided into two steps. The first step is to identify the calibration factors of individual loudspeakers with an optimized microphone array, which is used primarily for mode analysis. No particular error sensor or additional devices is used in the measurement. The theoretical complex source strengths are multiplied by the calibration factor to calibrate artificial source generators. The second step is to carry out mode generation experiments using the calibrated system, and Radial Mode Analysis is used to analyze the mode components in the duct. A spinning mode synthesizer with three axially spaced rows of loudspeakers is introduced, and each row consists of 12 excitation units. The maximum controllable circumferential mode order is m = 9, and the maximum controllable radial mode order is n = 2. It has been proven that the calibrated system can generate the target mode more precisely, and the mode coefficient signal-to-noise ratio (SNRA) of any propagable mode is greater than 10 dB in the operating frequency range.

Moral sensitivity in business: A revised measure

In order to manage ethical challenges in organizations and the workplace, moral sensitivity (MS)—the ability to identify and ascribe importance to moral issues when they arise in the workplace—is seen as the key prerequisite by researchers and professionals. However, despite the importance of MS, satisfactory reliable and valid measures to assess this competence are to date lacking. The present research tests the psychometric qualities of a revised MS measure for the business domain (R-MSB) that is designed to assess individual differences in moral and business-related value sensitivity. We present three different analyses with two heterogeneous samples of Swiss and German employees (total N = 1168). The first two studies provide good evidence of the measures’ factorial structure, its construct, and criteria-related validity. The third study examines how affective and empathic responses are associated with MS and business sensitivity (BS). The results support the view that empathic responsiveness enhances MS. The instrument’s theoretical and practical strengths, limitations, and avenues for future research are discussed.

Effect of silver co-doping on luminescence of the Pr3+-doped lithium tetraborate glass

Spectroscopic and luminescent properties of the Pr-doped and Pr–Ag co-doped borate glasses with Li2B4O7 (Li2O–2B2O3) composition are studied and discussed. Experimental and theoretical oscillator strengths (fexp and ftheor), phenomenological parameters (Ω2, Ω4, Ω6), radiative properties (Arad, β, τrad), and quantum efficiencies (η) of the Pr3+ luminescence were calculated basing on the obtained experimental results and Judd–Ofelt theory. Most intense band of the Pr3+ luminescence is peaked at 601 nm (1D2 → 3H4 transition). Presence of the isolated Ag+ (4d10, 1S0) ions, small non-plasmonic Ag aggregates (Agmn+ nanoclusters), and plasmonic Ag metallic nanoparticles in the Li2B4O7:Pr,Ag glass was proposed basing on analysis of the photoluminescence and optical absorption spectra. Observed enhancement of luminescence intensity and increasing of stimulated emission cross-section and quantum efficiency of luminescence in the Li2B4O7:Pr,Ag glass is explained by energy transfer from Ag species to the Pr3+ ions as wells local-field effect induced by Ag nanoparticles.

Interface modulation mechanism of alloying elements on the interface interaction and mechanical properties of graphene/copper composites

The interface doping with transition metal elements (TM = Ti, Cr, Co, Ni) has been experimentally proved to be an effective pathway to improve the weak interface bonding of graphene/copper (Gr/Cu) composites. In this paper, the microscopic influencing mechanism of TM doping on the interface interaction and mechanical properties of Gr/Cu was investigated by the first-principles calculations. The sandwich model with graphene embedded in Cu matrix was adopted here to simulate the TM-doped interfaces. It is revealed that the introduction of TM doping elements can significantly improve the work of separation, which relates to the electronegativity difference between TM and Cu elements based on the analysis of the interface electronic structure. Then, the mechanical properties of the clean and TM-doped interfaces were studied by the rigid stretching and the relaxed stretching. We found that, in rigid case, the theoretical tensile strengths of different interfaces are positively correlated with the work of separation, and the electronegativity is also a main factor affecting the mechanical properties. Furthermore, a fitting function containing the element electronegativity was applied to get the stress–strain relationship curve, and the quantitative relationship between the interface bonding and mechanical properties determined in this work can be served as a favorable support for the experimental design of Gr/Cu composites.

Rurality and Crises of Democracy: What Can Rural Sociology Offer the Present Moment?*

AbstractThis article discusses the growing political divide in the United States and how ideological polarization has increasingly assumed spatial dimensions, as rural areas have become strongly associated with Republican support, and urban areas have become associated with strong Democratic support. In the context of the recent Trump administration, marked not only by authoritarian tendencies, ethno‐nationalism, and hostility towards democratic institutions, but its denouement represented by the U.S. Capitol insurrection on January 6th, 2021 and the weeks that followed, what are the implications for growing spatialized civic and political divides, and indeed for democracy itself? I discuss several main approaches taken by social scientists to explain the relationship between spatial and political divides in the United States, including those that focus on shifting political geographies, cultural factors, economic anxiety, and racial resentment. Then, pointing to several recent exemplars, I identify theoretical, methodological, and perspectival strengths that the discipline of rural sociology can and should engage in developing explanatory frameworks for better understanding these social and spatial shifts – shifts that are simultaneously crises of democracy and crises of epistemology.

Managing COVID-19 in workplaces – a theoretical framework for integral employees’ health

PurposeThe purpose of this paper is to develop a framework on how to deal with stressors emerging from the COVID-19 outbreak. The theoretical framework aims to explain pandemic-related stressors and potential ways to prevent them, considering a wide range of interacting factors at individual, team and organizational levels to ensure their employees’ health.Design/methodology/approachThe authors drew on an integrative literature review to identify pandemic-related stressors influenceable by the organization and gathered solution approaches to counteract them. Popular psychological stress theories served as a theoretical base for the framework.FindingsThe authors based the framework on an integration of the transactional stress theory (Lazarus and Folkman, 1984) and the job demands resources model (Schaufeli and Bakker, 2004), focusing on their respective theoretical strengths. The final framework offers a solid orientation for scholars regarding the introduction of holistic and strategic measures in coping with pandemic-related stressors. A section describing possibilities for practitioners’ use of the framework has been integrated.Originality/valueTo the best of the authors’ knowledge, this study is the first to offer a framework on how to handle COVID-19-related stressors in the workplace by implementing teamwide and companywide measures.

Proposals for Determining the Relative Deformations Design Value of ε<sub>b3</sub> Concrete in Volumetric Deformation Conditions

The article presents the studies’ results on the deformability and strength of reinforced concrete racks reinforced with composite materials with the characteristics stretching beyond the limits established by the norms of Russia, namely: the λh structures flexibility exceeding the value 15, the ratio of the cross-section sides equal to 1.5 and the eccentricity of the load application e0 exceeding 0.1h. The results of the tested racks calculations are analyzed according to BC 164.1325800.2014, which in some cases confirmed the inexpediency of using composite materials. However, according to the results of our experiment, an increase in the strength of a number of racks with the characteristics that go beyond the recommended standards was found. The purpose of this study is to check the methodology for calculating Russian norms for the compressed reinforced concrete elements, the parameters of which are outside the limits recommended by the norms, to develop proposals for improving the calculation based on the obtained experimental data and to determine the concrete deformability effect on the change in bearing capacity. The article discusses flexible struts, reinforced with composite materials, located in the transverse direction. The experimental data results on the deformability of concrete and the strength of struts reinforced in the transverse direction are presented. The calculation methodology, compiled in accordance with Russian standards, the calculation results of which are the theoretical values ​​of the deformability of concrete and the strength of the racks, is considered. After comparison, a significant underestimation of the theoretical strengths and a mismatch in the struts’ concrete deformations were revealed. It was found that the change in compressive deformations of concrete depends on the external composite reinforcement. Theoretical values , calculated according to the current standards, have significant discrepancies with the experimental ones. Based on the experiments’ results analysis, in the methodology of norms for calculating the ultimate compressive deformations of concrete the suggestions that take into account the type and percentage of composite reinforcement and ensure a good agreement between experimental and theoretical values have been made. After the introduction of the coefficient into normative calculation, new data on the theoretical strength of the struts were obtained, which showed significantly better convergence with the experimental data.

Spectroscopic analysis of Nd3+-doped cadmium-vanadate invert glasses for near-infrared laser applications

Nd3+ activated CdO-V2O5 invert glasses were synthesized by the well-stablished melt quenching technique, using starting proportions of 95.0 and 5.0 mol% of CdO and V2O5, respectively. The XRD patterns revealed that the glass system remains amorphous up to 4.0 mol% of Nd3+. Such fact was mainly attributed to the low V2O5 content, which avoided the segregation of additional phases. The minimal addition of 0.1 mol% of Nd3+ reduced the direct and indirect glass bandgap energies from 2.79 to 2.66 eV, and from 2.48 to 2.13 eV, respectively. For higher Nd3+ contents, the bandgap energy was recovered, reaching values of 2.78 and 2.40 eV for direct and indirect allowed transitions, respectively. This fact was associated with a Burstein-Moss like effect, observed in semiconductors highly doped. The tail of the absorption edge revealed that the Urbach energy systematically grows with the addition of Nd3+, because of the creation of localized states into the bandgap. The Judd-Ofelt (JO) parameters obtained by least-square method from the experimental and theoretical oscillator strengths, were found in the Ω2 = 5.24-11.04 × 10−20 cm2, Ω4 = 2.26-4.47 × 10−20 cm2, and Ω6 = 2.85-6.28 × 10−20 cm2 range. Such values are close to those reported in other popular glass systems. The stimulated emission cross-section peak (σp) values calculated for the glass sample doped with 2.0 mol% resulted to be 0.26 × 10−20 cm2 (Nd3+: 4F3/2 → 4I9/2) and 0.81 × 10−20 cm2 (Nd3+: 4F3/2 → 4I11/2). The Nd3+ emission spectra, recorded upon 585 nm excitation (Nd3+: 4I9/2 → 4G5/2 + 2G7/2), showed the near-infrared Nd3+ emission bands at 881 nm (Nd3+: 4F3/2 → 4I9/2), 1063 nm (Nd3+: 4F3/2 → 4I11/2) and 1341 nm (Nd3+: 4F3/2 → 4I13/2), being dominated for that coming from the Nd3+: 4F3/2 → 4I11/2 transition. The overall emission reached the optimum intensity at 2.0 mol% of Nd3+, with a maximum quantum efficiency (ηQE) of 0.23. From the emission spectra important laser parameters such as gain bandwidth (σEMI(λp) × Δλem) and optical gain (σEMI(λp) × τR), were determined for the sample with the highest ηQE value. The σEMI(λp) × Δλem values resulted to be 11.3 and 32.0 × 10−27 cm3 for the Nd3+: 4F3/2 → 4I9/2, 11/2 transitions, respectively. The σEMI(λp) × τR parameter values were 11.1 and 35.3 × 10−25 cm2s for Nd3+: 4F3/2 → 4I9/2,11/2 transitions, respectively. The Inokuti-Hirayama model suggested that the Nd3+ cross-relaxation process might be dominated by an electric dipole-dipole interaction, inside Nd3+-Nd3+ clusters.

On the effects of temperature on tensile behavior of carbon fiber reinforced epoxy laminates

As a highly promising lightweight material, carbon fiber reinforced plastics (CFRP) composites have been widely used in aerospace, marine and automotive industries, which could expose to low or high thermal environments with varying material properties. This study investigated the effects of temperature variation ranging from −30 °C to 160 °C on tensile properties of CFRP experimentally and theoretically. The specimens were prepared using thermo-forming technology; and the glass transition temperatures of epoxy resins were measured by dynamic mechanical analysis (DMA). Digital image correlation (DIC) technique was used to capture the variation in strain and damage fields. By means of scanning electron microscopy (SEM), the failure mechanisms, delamination and resin softening, were identified by scrutinizing the images of fracture areas subject to different temperatures. The two-parameter Weibull analysis was conducted to evaluate the theoretical tensile strengths from relatively discrete data. The obtained Weibull parameters are considered useful for the reliability analysis of CFRP structures. It is found that the tensile strength decreases with the increase of temperature in a nonlinear fashion, which can be modeled in terms of a tanh function by correlating with the temperature-dependent experimental data. The study is anticipated to provide fundamental understanding and a predictive tool for mechanical strength of composite structures operating under different thermal conditions.

Judd-Ofelt, radiative properties of Sm3+ ions doped PVA+PEG complex polymer films from spectral analysis

A trivalent rare earth ion Sm3+ (1-5 mol %) doped Poly (vinyl alcohol) (PVA) and Poly (ethylene glycol) (PEG) complex polymer blends were synthesized by using solution casting technique. The spectroscopic characteristics behaviour and Judd-Ofelt (J-O) intensity parameters, oscillatory strengths and radiative properties of the prepared polymer blends were investigated with the help of optical absorption and photoluminescence spectral studies. Well defined UV-VIS-NIR optical absorption bands pertaining Sm3+ ions are observed in optical absorption spectrum and these bands has been assigned to their respective electronic transitions. The theoretical oscillatory strengths (f cal) and Judd-Ofelt (J-O) network framing theory were adopted to evaluate J-O intensity parameters Ω λ (λ=2,4,6) from the experimental oscillatory strengths (f exp). The covalent characteristic nature of the Sm3+ ions with surrounding ligands within the host polymer matrix was confirmed through bonding parameter (δ). The coordinated environment of Sm3+ ions and the key significant J-O intensity parameters are used for calculation of spectroscopic radiative properties. Photoluminescence spectrum is obtained and the highly intensified emission peak is observed for the transition 4G5/2→6H7/2 at 595 nm under 401 nm excitation wavelengths. The CIE colour coordinate diagram shows that the present complex polymer films incorporated with Sm3+ ions are acting as perfect and highly stable material for active reddish-orange emissions.

Experimental transition probabilities and oscillator strengths of doubly ionised krypton in the ultraviolet region

We report 62 new experimentally obtained transition probabilities (oscillator strengths) for doubly ionized krypton within the ultraviolet wavelength region (213 – 362) nm. The transition probabilities were obtained combining measured intensities of spectral lines emitted by a plasma generated in a low-pressure pulsed arc with theoretical oscillator strengths of 12 lines used as a reference. The plasma temperature ranged from 26,200 to 29,200 K and the electron density was in the range (1.7−3.2)×1022 m−3.

High pressure lattice dynamics and stress-strain responses of LaIn3 and LaTl3

A detailed study of the ground state structure, non-zero elastic constants, high pressure lattice dynamics as well as theoretical tensile and shear strengths of the cubic intermetallic compounds LaIn3 and LaTl3 with AuCu3 (L12)-type has been made through first-principles. The optimized equilibrium crystal constants, cell volumes, bulk modulus and its pressure derivative, and single-crystalline elastic constants are in fair agreement with available experimental data and other calculations. More importantly, high pressure phonon spectrum, total and partial phonon densities of states in LaIn3 and LaTl3 up to 10 GPa are reported by employing Density Functional Perturbation Theory (DFPT), and the present results have demonstrated that both systems are dynamically stability up to 10 GPa. The differences between the dynamical properties of LaIn3 and LaTl3 have also been discussed systematically. Additionally, the tensile and shear stress-strain responses and the theoretical strengths of LaIn3 and LaTl3 are further calculated, we have found that LaIn3 exhibits larger tensile and shear strengths than LaTl3. These investigations are expected to provide beneficial references for further exploring the physical properties of rare earth compounds.

Dislocation-mediated shear amorphization in boron carbide.

The failure of superhard materials is often associated with stress-induced amorphization. However, the underlying mechanisms of the structural evolution remain largely unknown. Here, we report the experimental measurements of the onset of shear amorphization in single-crystal boron carbide by nanoindentation and transmission electron microscopy. We verified that rate-dependent loading discontinuity, i.e., pop-in, in nanoindentation load-displacement curves results from the formation of nanosized amorphous bands via shear amorphization. Stochastic analysis of the pop-in events reveals an exceptionally small activation volume, slow nucleation rate, and lower activation energy of the shear amorphization, suggesting that the high-pressure structural transition is activated and initiated by dislocation nucleation. This dislocation-mediated amorphization has important implications in understanding the failure mechanisms of superhard materials at stresses far below their theoretical strengths.

A Simplified Design Method for Lateral–Torsional Buckling of GFRP Pultruded I-Beams

This paper provides a simplified design approach for estimating the lateral–torsional buckling (LTB) strength of the pultruded glass fiber-reinforced polymer (GFRP) composite I-beams. A detailed finite element (FE) model based on ABAQUS incorporating more realistic parameters for pultruded GFRP I-beam is developed and verified against the test results available in the relevant literature. After achieving a reliable FE model (through high degree of accuracy in the numerical validation), detailed parametric studies were undertaken by varying the section geometries as well as the span of pultruded I-beams. The selection of the sectional dimensions was based on the composite manuals available in the market, to ensure ease in the practical application of the outcomes of this study. In this analysis, simply supported beam with a uniform bending moment is considered. In accordance with the results of the FE parametric analysis, the accuracy of the theoretical LTB strengths predicted by the equations proposed for pultruded GFRP beams available in the literature is assessed. This comparison indicates that the existing method results in an over-conservative LTB strength estimates for pultruded GFRP I-beams, especially in the low and medium slenderness range. This is primarily due to a comparatively lesser impact of section imperfections on LTB resistance than high slenderness range. Therefore, to address this shortcoming, new simplified design formulations were proposed to have high accuracy of the LTB strength predictions for pultruded GFRP I-beams especially in the low and medium slenderness range. The proposed equations have been provided that might aid the structural engineers in economically designing the pultruded GFRP I-beams in the future.

The same old story – or not? How storytelling can support inclusive local energy policy

Local energy policy agendas require commonly defined desirable future visions and collective agenda-setting to spur collaborative action. However, methods designed for multi-stakeholder engagement often do not sufficiently open up deliberative processes to all voices, and efforts to envision desired futures built from current local energy challenges are usually designed by and oriented towards specialists. With this paper, we aimed to explore how the theoretical strengths of storytelling for supporting local policy processes play out in practice. We contrast what the literature states about the potential of storytelling for solving complex challenges and facilitating collaborative processes to the lessons learnt from actually using storytelling in a set of 17 multi-stakeholder workshops across 17 European countries run as part of the H2020 SHAPE ENERGY project. The workshops were each designed around a tangible local energy policy challenge. We found storytelling has unique strengths in terms of enabling significant (un)learning regarding stakeholder relationships, allowing participants to step into others’ perspectives, keeping hold of diversity, and the use of ‘we’ in stories leading to concrete future initiatives. We also note specific learnings about when these outcomes may not be achieved, for example due to fears, traditions, hierarchical structures, as well as the need for sufficient time for planning, facilitator training and stakeholder invitations. We conclude that as an innovative, playful and flexible methodology, storytelling can undoubtedly be a valuable additional tool for policymakers where there is a desire for deliberative stakeholder involvement, and appetite to tailor approaches to local contexts.

Flexural behaviour of cover plated CFS built-up beams composed of lipped channels: Comparison of test and design strengths

Built-up members are efficient in developing adequate resistance against large load demands, and their efficiency largely depends on how adequately the built-up sections are designed. This paper discusses the flexural behaviour of cover plated cold-formed steel (CFS) built-up beams made up of lipped channels. Lipped channels were placed at an adequate distance in the back-to-back arrangement and were connected at the flanges with self-drilling screws by means of cover plates, on both the tension as well as the compression faces. Simply supported end conditions were adopted in all the specimens. Both three-point loading as well as four-point loading was considered to study the influence of moment gradient and constant moment loading of theses built-up beam specimens. The sectional compactness of the channel section and the aspect ratio of the built-up section were varied to assess the behavioural effect in the specimens with respect to the variations incorporated. This study deals with the tests conducted to generate the test data. Prior to the testing of the specimens, tensile coupon tests were carried out as per the relevant standards to acquire the actual material properties of the steel used for the specimen fabrication. Both the European code as well as the North American Standards were used for developing the theoretical strengths and were compared with the test results.

Performance evaluation of reinforced concrete beams with corroded web reinforcement: Experimental and theoretical study

This study investigated the effect of corroded web reinforcement on the shear behavior of reinforced concrete (RC) beams. In this study, nine shear-critical RC beams were cast and tested. Six of these beams were corroded stirrups, while the remaining three beams were uncorroded stirrups serving as control samples. An accelerated corrosion technique was employed to corrode the stirrups in the beams. After the accelerated corrosion process, the beams were tested in three-point bending over a simply supported span. The shear span-to-depth ratio was kept constant at 3 for all beam specimens. The effects of the corrosion level, the type of steel stirrups (smooth or deformed), and the stirrup diameter were considered in the tests. The corrosion damage could easily be observed in the form of rust stains and corrosion cracks, which developed parallel to the stirrups. The beams with higher corrosion levels showed a reduction in their shear capacities. This reduction was more apparent in the beams with deformed steel stirrups. The shear capacities of the test beams were analyzed using a theoretical model that considers the effects of corrosion of the stirrups. The results of the analysis showed a good correlation between the experimental and theoretical shear strengths of the beam specimens.

Bimodality of incipient plastic strength in face-centered cubic high-entropy alloys

ABSTRACT Spherical tip nanoindentation experiments on two typical face-centered cubic high-entropy alloys (HEAs), CoCrFeNi and CoCrFeMnNi in as-solutionized and aged conditions were performed using tips of two different radii. Large datasets of the strength at the first pop-in were obtained and their statistical nature were analyzed to gain insights into the micromechanisms responsible for the onset of incipient plasticity in HEAs that are notionally monophasic. In all the cases examined, the probability density distributions were bimodal in nature. The deconvoluted distributions were utilized to estimate the activation volumes of the underlying deformation mechanisms. They show that when the probed material's volume is relatively small, heterogeneous dislocation nucleation aided by monovacancies occurs at lower indentation stresses; this followed by homogeneous dislocation nucleation at high loads, resulting in strengths corresponding to the theoretical strengths. When a substantially larger volume is sampled, by using a larger radius tip, either the preexisting dislocation mediated ones at low stresses or vacancy cluster /grain boundary aided heterogeneous dislocations nucleation at higher stresses become dominant. Increasing the chemical short-range order in the alloy via high temperature aging leads to overall strengthening of the alloy by enhancing stress required for the homogeneous dislocation nucleation. Implications of such plurality of mechanisms with overlapping strength distributions at HEA's disposal in imparting high strength-ductility combinations are discussed.