Significant Stress Relief Research Articles

Measurement of Stress Relief during Scented Cosmetic Product Application Using a Mood Questionnaire, Stress Hormone Levels and Brain Activation

Nowadays, consumers’ well-being plays a decisive role in the purchase of cosmetic products. Although factors influencing consumers’ well-being are very subjective, companies strive to develop their products in such a way that a positive effect is likely. Therefore, methods are required to objectively explore and scientifically prove the product’s performance on humans. In this placebo-controlled study, a method was developed to evaluate relaxation or stress relief associated with one olfactory ingredient of a cosmetic product (face cream). Our experimental protocol included product testing in 25 healthy females, while an emotion questionnaire, analysis of saliva samples regarding the concentration of the hormones cortisol and α-amylase and mobile EEG measurement for quantification of the alpha brain waves before and after stress induction were conducted. It was shown that with this experimental design, the sample with the ingredient produced significant stress relief, as evidenced by significantly less negative emotion, significantly lowered cortisol levels and showed a trend towards a significant increase in alpha activity compared to placebo application. Our data provide evidence that this method is suitable for analyzing the differences between the two samples. In the future, this method can be utilized in the current or a further optimized form to evaluate the psychophysiological effects of cosmetic products on humans.

Strata movement and fracture evolution characteristics in adjacent seam mining

The mining-induced stress distribution and fracture characteristics of overlying strata in the lower coal seams are different from those in single coal seam mining. Based on the distribution of the mining-induced fracture elliptical parabolic zone in a single coal seam, the dynamic distribution equation is deduced for the mining-induced fracture elliptical parabolic zone in two short coal seams through theoretical analysis. Combined with physical experiment and numerical simulation, a study has been made on the characteristics of overlying strata deformation, displacement, and mining-induced fracture evolution in the single coal seam and its lower coal seam mining. The results show that high stress concentrations occurred near the coal pillars at the upper coal floor on both sides after mining, and the overlying strata subsidence of the upper coal seam is 155.70% of the intermediate strata after superimposed mining, with the upper and lower coal floor showing significant stress relief. Under the influence of the two mining actions, the overlying strata of the upper coal seam have more fully developed fractures. The fracture density increases with the advance distance, the position of caving zone and fracture zone continues to develop upward, and the compaction zone further compacts; the fracture zone presents the distribution of the superimposed mining elliptical paraboloid zone. FLAC3D was used to simulate superposition of two layers of coal mining; the strata displacement and stress distribution nephograms were obtained as well, with the result that the floor stress release could reach up to 14.87 MPa under the influence of mining of two adjacent seams. This indicates that the pressure relief degree of the floor under the influence of two mining operations is obviously higher than that under one mining operation. The fracture distribution obtained by numerical simulation is basically consistent with the physical simulation and the superimposed mining elliptical paraboloid zone.

Inhomogeneous Bonding in Low-TemperatureSoldering: Brief Review

Thermal stresses [1-4] in solder joint interconnections (see, e.g., [5]) used in electronic and photonic packaging are proportional to the thermal contraction mismatch strains T [3-9]. Here  is the effective coefficient of thermal expansion (CTE) mismatch between the soldered materials (the chip or the package to their substrates), and T is the change in temperature from the elevated manufacturing (bonding/fabrication/solder ing) temperature, at which, because of the interaction of shrinkage and stressrelaxation processes, the induced stresses are next-to-zero, to the low, room, testing or operation, temperature, at which the induced stresses are the highest. Clearly, these stresses are lower for lower soldering temperatures, and therefore there is an obvious incentive for using low temperature solders. What is less obvious is that significant stress relief in solder joints can be achieved also by employing, for the same materials and the same thermal mismatch strain T, inhomogeneous bonds [10-19], when, e.g., a solder material with a high soldering temperature and/or with a high Young’s/shear modulus is employed in the mid-portion of the assembly, where the stresses in this material are low (at the mid-cross-section of the assembly these stresses, distributed in an anti-symmetric fashion, are always zero), and a low-melting-point solder and/or a solder with a lower modulus is employed at the assembly’s peripheral portions, where the interfacial shearing and peeling thermal stresses are the highest. Ultimately, when only the elevated stresses, and not heat transfer considerations, are viewed to be critical, even assemblies bonded at the ends only are viable [16,17].

Molecular dynamics simulations of internal stress evolution in ultrathin amorphous carbon films subjected to thermal annealing

The evolution of internal stress in ultrathin amorphous carbon (a-C) films is a complex physical process that is difficult to experimentally analyze due to the very small film thickness (a few nanometers) and the lack of instruments that can perform spatiotemporal stress measurements at sub-nanometer resolutions. Even more challenging is the elucidation of the correlation between internal stress, film activated, and temperature. Molecular dynamics (MD) provides potent computational capability for tracking structural changes activated by stress and temperature at the atomic level. Consequently, the aim of this study was to perform a comprehensive MD analysis that elucidates the origin of internal stress in sub-2-nm-thick a-C films grown on single-crystal silicon under optimal deposition energy conditions and explore its dependence on prevalent structural features (e.g., hybridization state) and temperature. The physical mechanisms of a-C film growth and stress built-up under deposition conditions of energetic particle bombardment and stress relief due to thermal annealing are interpreted in the context of MD results. Simulations of film growth illuminate the correlation between film stress and energy of incident carbon atoms. A significant stress relief occurs mainly in the bulk layer of the multilayered a-C film structure at a critical annealing temperature, which continues to intensify with the further increase of temperature. Simulations of time-dependent variation of stress through the film thickness reveal that the stress relief is a very fast process that accelerates with the increase of temperature. The results of this study provide insight into the spatial and temporal variation of internal stress in ultrathin a-C films due to structure and temperature effects and the film stress-structure interdependence.

Effect of mesoporous silica nanoparticles-based nano-fragrance on the central nervous system.

Fragrances are widely used in our daily lives and can make us feel happy. However, traditional aromatic products release fragrance quickly and have a strong aroma. This not only worsens our scenting experience, but also severely shortens the useful life of fragrance products. In this study, nano‐fragrances based on mesoporous silica nanoparticles with great encapsulation efficiency and slow‐release function were designed and prepared. In addition, this nano‐fragrances are applied to wallpapers. Open field tests showed that this nano‐fragrance had significant stress relief and anti‐depressant effects.

Predicted Thermal Stress in a Multileg Thermoelectric Module (TEM) Design

A physically meaningful analytical (mathematical) model is developed for the prediction of the interfacial shearing thermal stress in an assembly comprised of two identical components, which are subjected to different temperatures. The bonding system is comprised of a plurality of identical columnlike supports located at equal distances (spaces) from each other. The model is developed in application to a thermoelectric module (TEM) design where bonding is provided by multiple thermoelectric material supports (legs). We show that thinner (dimension in the horizontal direction) and longer (dimension in the vertical direction) TEM legs could result in a significant stress relief, and that such a relief could be achieved even if shorter legs are employed, as long as they are thin and the spacing between them is significant. It is imperative, of course, that if thin legs are employed for lower stresses, there is still enough interfacial “real estate,” so that the adhesive strength of the assembly is not compromised. On the other hand, owing to a lower stress level in an assembly with thin legs and large spacing, assurance of its interfacial strength is less of a challenge than for a conventional assembly with stiff, thick, and closely positioned legs. We show also that the thermal stresses not only in conventional TEM designs (using Be2Te3 as the thermoelectric material, and Sn-Sb solder), but also in the future high-power (and high operating temperatures) TEM design (using Si or SiGe as the thermoelectric material and Gold100 as the appropriate solder), might be low enough, so that the short- and long-term reliability of the TEM structure could still be assured. We have found, however, that thin-and-long legs should be considered for lower stresses, but not to an extent that appreciable bending deformations of the legs become possible. Future work will include, but might not be limited to, the finite-element computations and to experimental evaluations (e.g., shear-off testing) of the stress-at-failure for the TEMs of interest.

Deformation characteristics of a 38 m deep excavation in soft clay

To meet the increasing demand for underground space for economical development and infrastructural needs, more and more deep excavations have been constructed in Shanghai. In this paper, field performance of a 38 m deep multistrutted excavation in Shanghai soft clay is reported. The deep excavation was retained by a 65 m deep diaphragm wall. Inclinometers as well as settlement and heave markers were installed to monitor the performance of the deep excavation. This project provides an unusual opportunity to study the differential heaves of center columns and diaphragm walls during excavation. Because of the significant stress relief resulting from the 38 m deep excavation, maximum heaves of the center column and diaphragm wall panel were about 30 and 16 mm, respectively. The measured ratio δp/H (heave/final excavation depth) of column is less than 0.1% whereas the observed δp/H of the diaphragm wall panel is about 0.04%. The maximum distortion between the column and the diaphragm wall panel is smaller than 1/500, which is within the limit range proposed by Bjerrum in 1963. Owing to careful construction control, stiff strutting system, and compaction grouting, the measured lateral wall deflections and ground settlements at this site are generally smaller than other shallower excavations in soft clays in Shanghai, Singapore, and Taipei.

Annealing Ni nanocrystalline on WC–Co

The effects of annealing temperature on nanocrystalline sputter-deposited Ni thin films (500 nm) deposited on WC–Co (4 wt.%) were investigated. Special attention was focused on quantitative evaluation of residual stress and Ni diffusion into the WC–Co, after heat treatment, from 873 to 1273 K. The estimated level of residual stress, as measured by X-ray diffraction, is around −1.3 ± 0.1 GPa for the as-deposited film, whereas after annealing at 1273 K it decreases significantly. Atomic force microscopy shows that high annealing temperature results into an exponential increase of the roughness. An intermixing between the nanocrystalline Ni and the Co from WC substrate occurs, as it is revealed by quantitative depth-resolved Rutherford backscattering spectrometry analysis and also supported by X-ray photoelectron spectroscopy. We ascribe a significant stress relief with the increasing annealing temperature to the diffusion process. The understanding of this process is particularly important in WC–Co parts with the surface treated with Ni in order to improve the maximum surface service temperature.

The plugging behaviour of driven and jacked piles in sand

A series of model pile tests have been performed in the geotechnical centrifuge at the University of Western Australia to study the plugging behaviour of piles in sand. Open and sleeve-ended piles have been driven and jacked by a miniature pile driving actuator into silica flour of varying densities. The progression of the soil column has been measured during installation and static loading. It was found that the plug length increased with increasing relative density during driving and decreased with increasing relative density during jacking. During installation, the jacked piles exhibited a greater tendency to plug than the driven piles. Piles fitted with an internal driving shoe provided significant stress relief within the soil plug during jacking, leading to longer plug lengths compared with internally flush piles. All static load tests at high embedments behaved in a completely plugged manner. An analysis of the plug capacity is conducted and a model for the variation of the earth pressure coefficient inside the pile is proposed. Differential base pressure on the pile annulus and the internal soil plug is postulated and validated by means of the experimental data.

Fabrication and Microstructures of MoSi2 Reinforced–Si3N4 Matrix Composites

Details of the fabrication and microstructures of hot‐pressed MoSi2 reinforced–Si3N4 matrix composites were investigated as a function of MoSi2 phase size and volume fraction, and amount of MgO densification aid. No reactions were observed between MoSi2 and Si3N4 at the fabrication temperature of 1750°C. Composite microstructures varied from particle–matrix to cermet morphologies with increasing MoSi2 phase content. The MgO densification aid was present only in the Si3N4 phase. An amorphous glassy phase was observed at the MoSi2–Si3N4 phase boundaries, the extent of which decreased with decreased MgO level. No general microcracking was observed in the MoSi2–Si3N4 composites, despite the presence of a substantial thermal expansion mismatch between the MoSi2 and Si3N4 phases. The critical MoSi2 particle diameter for microcracking was calculated to be 3 μm. MoSi2 particles as large as 20 μm resulted in no composite microcracking; this indicated that significant stress relief occurred in these composites, probably because of plastic deformation of the MoSi2 phase.

Magnetostriction and thin-film stress in high magnetization magnetically soft FeTaN thin films

Domain structures in thin-film heads can be significantly influenced by magnetoelastic anisotropy. In this study we have undertaken systematic measurements of magnetostriction and stress in as-deposited and annealed states in FeN and FeTaN single-layer thin films with varying nitrogen contents. Magnetostriction was positive for FeN films, increased with increasing nitrogen content, and shifted toward negative values after annealing. Stress in as-deposited FeN films was tensile and decreased (became more compressive) with increasing nitrogen content. Annealing the FeN films resulted in significant stress relief. By contrast, magnetostriction was found to be negative for simple FeTa (zero nitrogen) and increased linearly with increasing nitrogen content to positive values. The magnetostriction in FeTaN did not change significantly after annealing at 200 and 250 °C. FeTaN film stresses were compressive in the as-deposited state and increased in magnitude (became more compressive) with increasing nitrogen content. After annealing these stresses were relieved slightly. Ta has been found to be very effective in enhancing the thermal stability of the FeN films.

An estimate of rebound potential of the Shaftesbury shales at a damsite in British Columbia

The hydraulic structures of the proposed site C hydroelectric project in northeastern British Columbia would require deep excavations in Lower Cretaceous Shaftesbury shales. A significant stress relief would occur over most of the area to be occupied by the structures. Concerns about the magnitude and rate of time-dependent rebound and their impacts on project design, construction, and operation have been addressed. A review was made of several important case histories of other major projects constructed on Prairie shales. The properties of those shales were compared with the Shaftesbury shales. Long-term testing to establish the shale swelling characteristics was performed. Analyses were then made to evaluate potential elastic and time-dependent rebounds of the project area. A procedure for computing stress changes and time-dependent deformations due to the unloading effect of excavation followed by structural loading was developed. The procedure is useful in determining differential rebound that would occur in areas of steep topography or significant variations in the distribution of structural loads. Key words : rebound, shales, dam, swelling properties, swelling pressure, stress relief, deep excavations.

Thermal relief of stresses in sputtered refractory metals and compounds

Abstract The compressive stresses in sputtered films produced with ion bombardment can be very high, increasing hardness, bending substrates, and causing adhesion failure. The thermal relief of the lattice strains produced by these stresses in chromium, molybdenum and TiN films made with bombardment from unbalanced magnetrons was studied using X-ray diffraction in films deposited at various temperatures. Significant thermal stress relief was observed during deposition for all materials, even at quite low temperatures. The lattice strain data for chromium and molybdenum were observed to overlay one another upon plotting against deposition temperature normalized by the melting temperature. The results for TiN show significant stress relief in (111) oriented crystallites, and small stresses in (200) oriented crystallites.

Stress Relief in Solder Joints Due to the Application of a Flex Circuit

A stress analysis model is developed to assess the stresses in solder joints caused by thermal contraction mismatch between a low expansion flex-circuit (FC) and a high expansion rigid substrate. It is shown that application of low expansion FCs can result in significant stress relief for solder joints. This is due to the fact that the force acting on a joint cannot exceed the buckling force for the adjacent portion of the FC. It is shown that the strains in solder joints interconnecting FCs to rigid substrates can be made very small, thereby resulting in a substantially longer fatigue life of the interconnection. In the executed example these strains are about two orders of magnitude smaller, than in the case of a rigid board. The obtained results can be utilized as guidance in physical design of assemblies with FCs.