Initial Compression Research Articles

Quality of life study in patients with nodular and multinodular forms of euthyroid goiter

Objective. To study and estimate the quality of life in patients with nodular and multinodular forms of euthyroid goiter prior to the surgery and in different postoperative periods.
 Materials and methods. The method of random study was used to examine 100 patients with nodular and multinodular forms of euthyroid goiter, who were treated at Perm Regional Treatment and Diagnostic Center Center of Hepatic and Endocrine Surgery in 20092017. To study patients quality of life, SF-36 survey was used. The quality of life indices were assessed prior to the surgery, 1 and 6 days after the surgery as well as 3 and 6 postoperative months.
 Results. The quality of life in patients with nodular and multinodular forms of euthyroid goiter is subjected to the influence of not only preoperative factors but also factors, occurring in both early and long-term postoperative periods. Special attention is to be paid to psychological factors of the preoperative period. Three and six months after the surgery, patients with initial compression of cicatricial deformity of the neck organs had improved psychoemotional indices.
 Conclusions. Studying of the quality of life permits to estimate the efficiency of surgical treatment in patients with thyroid diseases. Relative decrease in the quality of life indices among patients with nodular and multinodular forms of euthyroid goiter are most evidently manifested in the early postoperative period. In case of favorable course of the postoperative period, improvement of physical activity is observed in 5 days, psychological in six months. Six months later, the quality of life indices in patients with both forms of goiter did not differ from those in the comparison group.

Energy evolution of brittle granite under different loading rates

The mechanisms for rock failure involve instability, where an energy exchange and transformation occurs between the rock and an external energy source. Few studies have been conducted on rock failure characteristics in terms of the energy evolution under different loading rates. This study investigated the damage resulting from brittle granite failure under loading rates of 0.001, 0.005, 0.01, and 0.05 mm/s from the energy perspective. The results showed that the elastic and scattered strain energies absorbed in the initial compression phase were small. The elastic strain energy absorbed in the rock elasticity stage was mainly stored in the form of elastic energy, and the rate of increase for the scattered energy was less than those for the total strain energy and elastic strain energy. In the dilatation and breaking stage, the scattered energy increased sharply, elastic energy was rapidly released, and rock bursting accompanied the breaking. The loading rate increased from 0.001 mm/s to 0.05 mm/s, total strain energy increased by 91%, elastic energy increased by 48%, and spread energy increased by 184%. At the first stage of loading, the damage variable of the rock mass was small. With an increase in the loading rate, the damage variable of the rock sample gradually increased. When the stress reached its peak value, the damage variable rapidly increased. Under the same stress, a greater loading rate resulted in a greater change in the damage variable.

Compaction effects on permeability of spherical packing

PurposeThe purpose of this paper is to investigate the evolution of the permeability of spherical packing during cold compaction by pore-scale modeling.Design/methodology/approachThe discrete element method (DEM) is used to generate spherical packing structure under different compressive pressures and the Lattice Boltzmann method (LBM) is adopted to calculate the permeability of each spherical assembly.FindingsIt is found that the decrease of the porosity is the main reason of the reduction in permeability in the initial compression stage, but its influence becomes insufficient in the late compression stages. Besides, two empirical formulas are obtained, which describe the relation between the permeability and the equivalent mean diameter and the variation of normalized permeability with compressive pressure, respectively.Research limitations/implicationsIn this study, the authors study the spherical particles and ignore the non-spherical effects. Besides, the classical contact model, the linear-spring-damping model, is used in DEM, so the plastic deformation cannot be considered.Originality/valueThe DEM and the LBM are well combined to study the compaction effects on permeability of spherical packing. Two simple expressions of the spherical packing structure with uniform diameter distribution are given for the first time.

Improvement on Curve Negotiation Performance of Suspended Monorail Vehicle Considering Flexible Guideway

This work presents the investigation and improvement on curve negotiation performance of suspended monorail vehicle considering a flexible guideway. First, a spatial train–guideway interaction model of suspended monorail system (SMS) is established based on the secondary development of ANSYS software. Then, the dynamic analysis of the train over the flexible curved guideway is conducted, and the curve negotiation performance of the vehicle and the guideway vibration feature are revealed. Subsequently, several crucial design parameters that significantly influence the curve negotiation performance of the vehicle are found, and their influences on the train–guideway dynamic responses are systematically investigated. Finally, by comprehensively considering the dynamic indexes of the vehicle–guideway system, the optimal ranges of these crucial design parameters are obtained. Results show that decreasing the radial stiffness of guiding tyre can effectively reduce the lateral vibration levels of vehicle and guideway, but it would increase the lateral displacements of the bogie and hanging beam; and the radial stiffness is finally suggested to be around 1[Formula: see text]kN/mm by comprehensively considering all dynamic indexes. Increasing the initial compression displacement of guiding tyre can well limit the lateral displacements of the bogie and the hanging beam, thus enhancing the train running safety; however, it would intensify the vehicle-guideway lateral vibration level; especially, the optimal initial compression displacement of guiding tyre is related to its radial stiffness characteristics. To ensure a good curve negotiation performance of vehicle and guideway vibration level, the stiffness of the anti-roll torsion bar and the initial gradient angle of the installed trapezoid four-link suspended device are suggested to be 1.0[Formula: see text]MNm/rad and 65–[Formula: see text], respectively.

Effect of some feed filament parameters and weave on compressional properties of air-jet textured yarn fabrics

The influence of some feed filament parameters and weave on compression and recovery behaviour of air-jet textured yarn fabrics has been studied and compared with their corresponding parent yarn fabrics. Fabric low load compression-recovery behaviour has been analysed by defining initial thickness, compression parameter, recovery parameter and resiliency. Fabrics made from coarser yarn (larger total yarn dtex) have higher initial thickness and compression parameter while lower recovery parameter and resiliency, as compared to fabrics made from finer yarn. Fabrics are woven with two woven structures, namely plain and twill weave to assess the effect of fabric structure on compression and recovery behaviour of the fabrics. Twill woven fabrics exhibit a higher value of all compressional parameters compared to their equivalent plain woven fabrics. Parent yarn fabrics exhibit a low value of all compressional properties, irrespective of change in any feed yarn characteristics as compared to their equivalent textured yarn fabrics.

An analytical study on the morphology of buckle-delamination under large compression and boundary undulation

Spontaneous formation of various buckle-delamination patterns originates from complex interaction between buckles and delamination. However the impact of large compression and delamination boundary undulation on the morphology of buckle-delamination remains a challenge especially from an analytical approach. Here, a nonlinear solution based on the Föppl–von Kármán (FvK) plate theory for buckle-delamination is derived by using a coordinate transformation technique in combination with perturbation series based on Koiter expansion. The analytical results validated by finite element simulations (FEM) show that the sequential sectional profile of straight-sided (SS) blister with asymmetric secondary buckling instability exhibits a butterfly shape dependent on the compression amplitude even when the delamination boundary is straight. Besides, the wavelength for SS blister after the instability drastically changes with the compression amplitude, which is coincident with the experimental results. Our analysis further demonstrates that the elastic energy of the wavy-sided blister can be significantly lower than that of the SS blister even when the initial equi-biaxial compression is a little larger than the Euler buckling stress, significantly lower than the critical stress for secondary buckling instability of SS blisters. This result indicates an alternative mechanism that formation of telephone-cord blister may proceed first by an undulation instability of the delamination boundary.

The compression specificity of plant tissue.

The aim of this study was to determine the compression characteristics of nonhomogeneous plant materials with a complex morphological structure (beetroots, celery roots, and potato tubers), to compare the analyzed samples with the compression characteristics of reference materials (homogeneous isotropic structural materials: steel coil spring and vulcanized rubber), and to determine the influence of the compression rate on stress in compressed samples. Structural materials and plant materials clearly differed in compression characteristics. Excluding the short initial compression phase, the compression curves for the steel coil spring and vulcanized rubber were straight parallel lines, and the higher the crosshead speed, the higher the lines' location in the diagram. In tests conducted on plant materials, the rate of changes in compression force increased throughout the experiment with an increase in crosshead speed. The greatest variations in compression force resulting from differences in crosshead speed were observed in potato samples. The apparent retardation times determined in the developed rheological model ranged from 0.079 s for the steel coil spring to 6.863 s for potatoes.

Dynamics of Hermite–Gaussian beams in the linear and nonlocal nonlinear fractional Schrödinger equations

We analytically and numerically investigated the dynamics of the Hermite–Gaussian (HG) beams in linear and nonlocal nonlinear fractional Schrödinger equations (SEs), in both one and two dimensions. In the linear regime, HG beams on the order of n>1 were observed to undergo an initial compression phase before they split into two sub-beams. The sub-beams were saddle-shaped; the separation between them linearly increased with the propagation distance. Due to their nonlinear propagation dynamics, HG beams quite unexpectedly followed a zigzag trajectory in the real space, which corresponds to a modulated anharmonic oscillation in the momentum space. Although the beam was well localized during propagation, it still broadened and may become unstable. In the two-dimensional case, a superposition of HG beams showed a linear evolution similar to that in the one-dimensional case; however, because of orbital angular momentum, the beams in two dimensions exhibited incomplete rotation during propagation. In the nonlinear regime, the superposed HG input beam first evolved in the real space into a filiform structure and then into an annular structure, with periodic inversion and variable rotation.

Mechanical behavior and microstructures of aluminum processed by low strain amplitude multi-directional confined forging

Severe Plastic Deformation (SPD) leads to grain refinement and strengthening of metals. Among the many SPD processing methods, Multi-Directional Forging (MDF) is the only one where in-situ material stress–strain curves can be obtained. These are adequate only for specimens re-machined after each compression step, thus avoiding problems connected to specimen shape distortions; re-machining involves complex, expensive and time consuming procedures. This difficulty has been circumvented using confined plane strain compressions, where the strain path, however, differs from that in simple, unconfined free compression. A new processing method involving, for each processing step, an initial free simple compression followed by a confined compression (Multi-Directional Confined Forging – MDCF) is proposed, eliminating the specimen re-machining. Strengthening by MDF depends on strain amplitude; low strain amplitude MDF (LSA-MDF) leads to lower work hardening of the material than high strain amplitude MDF, as well as to limited softening and to an increase in the residual work hardening capacity of material previously deformed monotonically or in successive deformation steps with high strain amplitudes. This supplies a highly desired enhanced uniform elongation of the material after SPD. It is shown that Low Strain Amplitude Multi-Directional Confined Forging (LSA-MDCF) of aluminum leads to adequate stress–strain curves up to the contact of the specimen with the confining die walls, as well as to microstructures very similar to those obtained using free compressions with re-machined specimens. This processing route is simpler, faster and cheaper than LSA-MDF with re-machined samples, and thus emerges as a more practical MDF route.

Anomalous lattice stiffening in tungsten tetraboride solid solutions with manganese under compression

Tungsten tetraboride (WB4)-based solid solutions represent one of the most promising superhard metal candidates; however, their underlying hardening mechanisms have not yet been fully understood. Here, we explore the lattice compressibility of WB4 binary solid solutions with different manganese (Mn) concentrations using high-pressure x-ray diffraction (XRD) up to 52 GPa. Under initial compression, the lattices of low and high Mn-doped WB4 alloys (i.e. W0.96Mn0.04B4 and W0.84Mn0.16B4) are shown to be more and less compressible than pure WB4, respectively. Then, a c-axis softening is found to occur above 39 GPa in WB4, consistent with previous results. However, an anomalous sudden a-axis stiffening is revealed at ~36 GPa in W0.96Mn0.04B4, along with suppression of c-axis softening observed in WB4. Furthermore, upon Mn addition, a simultaneous stiffening of a- and c-axes is demonstrated in W0.84Mn0.16B4 at ~37 GPa. Speculation on the possible relationship between this anomalous stiffening and the combined effects of valence-electron concentration (VEC) and atomic size mismatch is also included to understand the origin of the nearly identical hardness enhancement in those two solid solutions compared to WB4. Our findings emphasize the importance of accurate bonding and structure manipulation via solute atoms to best optimize the hardness of WB4 solid solutions.

Geostatistics of strength, modeling and GIS mapping of soil properties for residential purpose for Sulaimani City soils, Kurdistan Region, Iraq

The main objective of the present study is to measure the soil properties of the study area, Sulaimani City (35° 33′ 26″ N 45° 26′ 08″ E) and their spatial variability. A combination of conventional analytical methods and geostatistical methods were used to analyze the data for spatial variability. This study was focused on the correlations between the physical and mechanical properties and geostatistical analysis of the Sulaimani City soils based on the experimental data and the data collected from various research studies. The study was also focused on presenting the Atterberg limits, and the mechanical properties such as undrained shear strength of extruded soils using ArcGIS mapping. A total of 85 boreholes with depth up to 6 m underground were drilled and the physical and mechanical properties of the soils were tested. The index properties, compressibility properties, free swelling, and compressive strength of the soils were investigated and quantified with over 1000 data records collected from the literature. The field-tested data were compared with the data from literature and qualified using Vipulanandan correlation model. Using the mean, standard deviation, and coefficient of variation, the parameters of soils properties such as density (γ), index properties, swelling index, initial void ratio, compression index (Cc) and undrained shear strength (Su) properties were also studied. Undrained shear strength (Su) of Sulaimani City soils varied from 10 to 119 kPa and quantified very well as a function of liquid limit, plasticity index, moisture content and dry density using the experimental data and data collected from the literature. Statistical analyses and ArcGIS zonation maps based on soil type are presented. Thus, these data are speedily available and can be valuable and provide suggestions for engineers and planners.

Effect of Density on Consolidation and Creep Parameters of Clay

Effect of density on consolidation and creep parameters of a clay soil was investigated using a soil classified according to Unified Soil Classification System (USCS) as Clay of High plasticity (CH) and composing majorly of secondary minerals, including montmorillonite. The air-dried soil was compacted at five different compaction energy levels (Reduced Standard Proctor compaction energy, Standard Proctor compaction energy, West African compaction energy, Reduced Modified Proctor compaction energy, and Modified Proctor compaction energy). Specimens for consolidation tests were molded at the five different compaction energy levels (densities). The consolidation parameters (initial void ratio, compression index, and preconsolidation pressure) were observed to be empirically related to the compaction energy. The creep parameters (i.e. primary compression index, secondary compression index, and magnitude of creep) were observed to increase with increases in loading to 387kN/m2, after which the values decreased. Curves resulting from these relationships were observed to increase with increases in compaction energy level and tent towards straight line at Modified Proctor compaction energy. Maximum magnitude of creep estimated for three years was observed to reduce from 455.5 mm at Reduced Standard Proctor compaction energy through 268 mm at West African compaction energy to 247.4 mm at Modified Proctor compaction energy levels.

Pressure-Induced Remarkable Enhancement of Self-Trapped Exciton Emission in One-Dimensional CsCu2I3 with Tetrahedral Units.

Self-trapped exciton (STE) emissions derived from inorganic octahedral units make metal halide perovskites promising photoluminescence materials for light-emitting applications. However, there is still little understanding of the intrinsic STE emissions in metal halide perovskites or derivatives with nonoctahedral units. In this work, via high pressure compression, remarkable STE emission enhancement is, for the first time, realized in one-dimensional CsCu2I3 crystals with {CuCl4} tetrahedral units. The intertetrahedral distortionis believed to induce the slight emission enhancement of the ambient phase under initial compression. Notably, the obvious structural distortions of both inter- and intratetrahedra are responsible for the significant emission enhancement of the high pressure phase. This work not only sheds light on the structure-optical property relationships of tetrahedron-based halide complexes, but also may provide guidance for the design and fabrication of highly luminescent metal halides.

Numerical simulation of the operation of the disc shredder

The purpose of the work is to model the performance of the disk grain shredder by numerical methods of determining the performance of the device and its components, and to establish the existing trends in the influence of the size of the initial particles on the components of the shredder performance. The increase in the initial particle size leads to an increase in the initial angular velocity of the particle movement, which increases as the particle is compressed, while the increase in particle size does not significantly reduce the productivity of the shredder due to the worsening conditions of particle capture by the disks as they increase in size. The increase in the initial spring compression force ensures a reduction in the thickness of the resulting flattened particles and at the same time reduces the productivity.

Mechanical Characteristics and Failure Mechanism of Siltstone with Different Joint Thickness

The mechanics of rock mass is significantly affected by joints, but many existing studies of jointed rocks make simplifications that do not consider the joint thickness. To further study the influence of joint thickness on rock mechanics (mechanical properties, failure mechanism, damage model, etc.), we fabricated jointed siltstone specimens with different joint thickness (5, 10, 15, and 20 mm) and the specimens were subjected to uniaxial compression tests. The effects of joint thickness on the uniaxial compression strength (UCS), the strain at UCS, the elastic modulus, and the stress‐strain curves were thus analyzed. For the stress‐strain curve, with rising joint thickness, the upper concave in the initial compression stage intensified, the slope of the stress‐strain in the elastic stage decreased, and the sudden stress drop after peak strength became more obvious. Both the peak compression strength and the elastic modulus gradually decreased with rising joint thickness, but a positive correlation was found between the strain at UCS and the joint thickness.

Mechanical Behavior and Energy Evolution of Sandstone considering Slenderness Ratio Effect

To study the influence of slenderness ratio effect on the mechanical behavior, acoustic emission properties, and energy evolution of sandstone, the uniaxial compression tests coupled with acoustic emission technology are carried out at different slenderness ratios D (0.5, 1.0, 1.5, 2.0, 3.0). The results show that a logarithmic function relationship is observed between the peak strength, the peak strain, and the elastic modulus with slenderness ratio. The failure patterns of the tested sandstone varied significantly with the increasing slenderness ratio. When the slenderness ratio, D, is lower than 1.5, complex failures and multiple shear planes are formed, while simple failures and single shear planes are generated at D larger than 1.5. Besides, the AE ringing counts are more obvious with a higher slenderness ratio, D, at the initial compression stage due to the greater body volume and more defects in the sandstone. The energy evolution curves and energy ratio distribution curves can be divided into four stages, corresponding to the stress‐strain curves.

The influence of the parameters of hot drawing of MgCa alloys wires on the mechanical properties that determine the applicability of the material as a high strength biodegradable surgical thread

Magnesium alloys with calcium are some of the promising materials for creating soluble surgical threads. The recommended daily intake of magnesium in the human body is 375-500 mg, calcium - 800 mg. Other candidates as a material for surgical sutures are zinc and iron. For them, this parameter is 6.5–11 mg and 6–20 mg, respectively. Thus, in terms of the permissible content in the body, magnesium-calcium alloys compare favorably with other materials. However, these alloys have low ductility in the cold state and low deformability during drawing.The paper proposes to obtain wire from MgCa0.7, MgCa0.9 alloys by hot drawing. Moreover, the drawing process consists of deformation of the metal in the heated die and recrystallization during the movement of the workpiece. These processes allow us to control the microstructure of the finished wire to obtain the necessary ductility.The theoretical part of the work was to develop a mathematical model of the hot drawing process, taking into account the dependence of the flow stress on deformation, temperature, and strain rate, as well as recrystallization processes. To calibrate the model of flow stresses, experiments in the GLEEBLE machine were carried out to compress the sample under various thermomechanical conditions. To calibrate the recrystallization model, the initial compression of the sample to a strain of 0.1–0.3 and the subsequent registration of stress relaxation was carried out. The resulting material models were implemented in the FEM model of hot drawing. It made it possible to calculate the range of permissible parameters of the drawing and determine the optimal values of the speed and temperature of the drawing.The experimental part of the work consisted of a three-pass wire drawing with an initial diameter of 1.8 mm to a final diameter of 1.5 mm at various temperatures: 350°C, 400°C and 440°C. After the drawing was completed, the microstructure and mechanical properties of the wire were analyzed. The maximum elongation of the wire was observed for the maximum temperature (440°C) and amounted to 20% with Tensile Strength (TS) 230 MPa, which is sufficient to use the material as a thread.An in vitro corrosion tests showed that an increase in the temperature of deformation and annealing leads to accelerated corrosion. Thus, the data obtained allowed us to find a compromise between the strength, ductility, and corrosion rate of a MgCa magnesium alloys wire.

Investigation of mechanical properties and microstructural behavior of 7050 aluminium alloy by multi directional forging technique

Multi directional forging (MDF) is a process of severe plastic deformation used to produce fine grained bulk materials. In the present study, 7050 Aluminium alloy is used due to its wider applications in the field of aerospace industry particularly for making blade stringers. During experimentation, As-cast alloy samples were subjected to solutionizing heat treatment at 400 °C for 20 h to remove segregation effects and undergone multidirectional forging at ambient warmth for different equivalent strains. The mechanical properties such as Vickers’s hardness and compression tests were done on processed and unprocessed samples. The microstructural characterization was done using optical microscopy. It was observed that initial compression strength was increased from 505 MPa to 586 MPa and hardness was increased from 141 Vickers hardness number (VHN) to 182 Vickers hardness number (VHN) due to refinement of grains from 60 µm to 10 µm. It was found that solutionizing heat treatment reduces the defects like porosity which was developed during casting process. In the present work, more emphasis is given on the improvement of mechanical properties and microstructure of as-cast alloys that are multi-directionally forged.

Modelling Unsaturated Soil Response Beyond Residual Suction State via Vapor-Pressure Controlled Triaxial Testing

Most of the previous research has been focused on developing and validating constitutive models to predict response of unsaturated soils in low-medium suction range. However, there is a scarcity of efforts in developing soil models to simulate its mechanical response in high suction range, particularly above the residual suction. This article presents a new constitutive model introducing net stress and suction as two independent variables. Furthermore, non-associative flow rule incorporating modified stress-dilatancy relationship to take unsaturated state into account is introduced to improve the model results in low-medium to high suction range. The essential soil model parameters are calibrated using suction-controlled triaxial test results for predictions of compacted silty sand response at high values of total suction above residual suction. Preliminary simulations show that proposed model can reasonably simulate the post-peak strain softening response obtained from suction-controlled CTC tests above residual suction value with reasonable accuracy. Although, the proposed model captures initial compression followed by dilation volumetric response with reasonable accuracy, it needs some improvements to be able to capture volumetric response accurately over entire suction range.

Influence of photobiomodulation on pain perception during initial orthodontic tooth movement

Abstract Introduction Laser in low intensity (LLI) has been used to reduce the discomfort and pain that is triggered by the forces applied during orthodontic treatment. Objective To evaluate the effect of LLI application in the pain perception of periodontal ligament initial compression, during orthodontic tooth movement; and to compare the effect of this therapy between men and women. Material and method The sample consisted of 30 volunteers, who needed orthodontic band placement on mandibular first molars. After insertion of the elastic separators, LLI was applied to the mesial and distal apical region (wavelength 808nm, energy 2J, time 20s and fluency of 8.32J/cm2) and at three points on the root region (wavelength 808nm, energy 1J, time 10s and fluency of 4.16J/cm2) of the first molar (irradiated side) and compared to the contralateral first molar (non-irradiated side), in three time intervals: 0hs, 24hs and 48hs. Pain perception was evaluated by the Visual Analog Scale (VAS), at 0hs, 24hs and 48hs after insertion, with significance of 5%. Result The pain level was observed to be significantly lower (p<0.05) on the irradiated side, irrespective of gender and time. Women presented a significantly higher pain level (p<0.05) than men, irrespective of time and side. There were no significant differences between the time intervals (p>0.05). Conclusion It was concluded that LLI reduced the perception of initial pain in patients in whom compression of the periodontal ligament was promoted by elastic separation, and that women had a greater perception of pain sensitivity in the time intervals studied.