Normal Compression Research Articles

Varicose Veins Treatment Using Automated Stockings

This work presents a home based automated temporary treatment for patient healthcare to be made easier. Varicose veins are veins that are twisted and bulging. Varicose veins can form near the surface of the skin (superficial veins). Varicose veins most commonly affect the veins in the legs. The proposed system consists of a wearable device with vibrating motors connected to an ESP32. Here pressure sensors are used to measure variation of blood pressure in the upper and lower region of the body and if the reading of pressure is higher in the lower region compared to the upper region, then it will activate the motor to give in the exercise to subtle pain and the block of blood in the nerves. This exercise is also given in a periodic time interval without waiting until pressure variation is observed. These automated stockings will also behave as a normal compression stocking when vibration is not applied. In simple words the new designed stocking can perform in 3 ways. The signal acquired from the pressure sensor is processed by ESP32. This in turn activates the motor(to provide periodic vibrations). Patients will be able to receive rapid temporary therapy if this rehabilitation system is implemented.

Chemo-mechanical behaviour of non-expansive clays accounting for salinity effects

Changes in the chemistry of the pore fluid are known to have an impact on the hydro-mechanical behaviour of clays. Experimental evidence collected in recent decades has led to the formulation of constitutive chemo-mechanical models for expansive soils used in engineering practice for the containment of pollution, such as bentonite. Less attention has been paid to modelling the chemo-mechanical behaviour of non-expansive clays, which are less frequently used for geoenvironmental applications, but equally exposed to chemical changes. Key differences between the impact of salinity on the fabric of expansive and non-expansive clays are pointed out. At the macroscopic scale, an increase in salinity causes a translation of the normal compression line of non-expansive clays to higher void ratios, which in some cases is also accompanied by an increase in compressibility. The opposite occurs for expansive clays. Such experimental evidence provides the basis for a chemo-mechanical model formulated in the frame of elasto-plasticity with generalised hardening, whose yield surface expands with pore fluid concentration. The model is validated against experimental results, both original and from the literature. Simulation results compare very well with those of tests performed on reconstituted, compacted and intact samples.

Roughness and humidity effects on contact, friction, and contact plasticity revealed by micromechanical testing and analysis

Understanding the effects of surface roughness, surface lubrication, and environmental conditions on inter-particle contact mechanics is important for a broad range of applications of granular materials. In this paper, a new micromechanical testing apparatus was developed and used to characterize smooth and rough soda lime glass particles in carefully controlled dry, humid, and lubricated environments during normal compression and shearing. From surface profilometry measurements and digital image correlation, we observed a humidity independent correlation between hysteresis, contact plasticity, and surface roughness in normal compression tests. From analysis of shear test data, we observed an increase in friction with increasing surface roughness, contact hold times, and water lubrication. Our work highlights roughness and environmental effects on contact and friction of silicate materials.

The Impact of Surface Water Seepage on Seismicity and Rockbursting in Mines

Retrospective analysis of data obtained from long-term monitoring of technogenic seismicity and rockbursts at the Apatitovy Tsirk and the Rasvumchorr Plateau deposits (Russia) showed that there is a significant (by 50% or more) increase in the number of geodynamic events during spring snowmelt periods. An upswing of seismic activity within this rock massif occurs when following conditions are true: water reserve in the snow cover on the deposit area is more than 3 × 108 m3; snowmelt period exceeds 40 days; increase in water ingress rates continues for over 5 days and total water inflow volume exceeds the previous daily measurements by at least a factor of 2. Seismic activity of the massif starts to intensify after the snowmelt develops momentum. Major induced earthquakes occurred in the years when these conditions were met (for example, in 2005 there was a magnitude 2.3 earthquake; in 2009, M = 1.6 earthquake), and more than 1000 seismic events were recorded during the snowmelt period. It has been established that when mining reaches the depths of more than 500 m, seismic events during infiltration of atmospheric precipitation begin to occur from a depth of 100–200 m and are recorded to depths of about 900 m. A possible controlling factor of the seismic activation is the reactivation of tectonic faults, which occurs under conditions of the critically stressed state of the massif, due to a decrease in their normal compression during infiltration. Retrospective analysis of the factors contributing to a strong rockburst (K = 10–11) in 1990 at a bauxite mine in the South Urals shows that prior to this disaster there was an inrush of the Ai River waters into the mine workings through a large tectonic disturbance, which has not been previously taken into account when analyzing the mechanism of this geodynamic event. The intrusion of water into the fault located in the field of regional stresses and subsequent partial relief of its fault plane from normal stresses could have triggered the rockburst with fault-slip mechanism. The study of the relationship between amount of precipitation and the degree of water encroachment into the field, on the one hand, and seismicity, on the other hand, is needed to draw up recommendations on improving geodynamic and environmental safety of mining regions in order to ensure their sustainable development.

Mechanical and microstructural properties of iron tailings

Due to the importance of their handling and the consequent negative impacts on humans and the environment as well as limited understanding of their mechanics, detailed investigations on the mechanical and microstructural properties of tailings are very crucial. Studying tailings is very important in the geotechnical engineering, engineering geology and geomechanics community worldwide because of the need for deeper and better understanding of their behaviour for safer design and construction of tailings dams. The following findings were obtained: (a) The grading characteristics are a function of the degree of sorting by sedimentation during discharge. (b) The fabrics of the iron tailings are heterogeneous and isotropic. (c) Chromium and copper are the significant heavy metals that can have adverse effects on human. (d) There are non-convergent curves and no unique normal compression lines. (e) The transitional mode of behaviour results from heterogeneous fabrics, which shows that the behaviour of iron tailings depends on the initial state. (f) The particles of iron tailings are angular, and the angularity of particle shapes increases slightly with vertical effective stresses. (g) The non-convergent behaviour cannot be attributed to preferential particle breakage.

On-Skin Flexible Pressure Sensor with High Sensitivity for Portable Pulse Monitoring.

Radial artery pulse pressure contains abundant cardiovascular physiological and pathological information, which plays an important role in clinical diagnosis of traditional Chinese medical science. However, many photoelectric sensors and pressure sensors will lose a large number of waveform features in monitoring pulse, which will make it difficult for doctors to precisely evaluate the patients’ health. In this letter, we proposed an on-skin flexible pressure sensor for monitoring radial artery pulse. The sensor consists of the MXene (Ti3C2Tx)-coated nonwoven fabrics (n-WFs) sensitive layer and laser-engraved interdigital copper electrodes. Benefiting from substantially increased conductive paths between fibers and electrodes during normal compression, the sensor obtains high sensitivity (3.187 kPa−1), fast response time (15 ms), low detection limit (11.1 Pa), and long-term durability (20,000 cycles). Furthermore, a flexible processing circuit was connected with the sensor mounted on wrist radial artery, achieving wirelessly precise monitoring of the pulse on smart phones in real time. Compared with the commercial flexible pressure sensor, our sensor successfully captures weak systolic peak precisely, showing its great clinical potential and commercial value.

Outcomes from a tertiary care center using a catheter thrombectomy system for managing acute iliofemoral deep vein thrombosis

ObjectiveThe aim of the present study was to report a large, single-center experience using the ClotTriever thrombectomy system (Inari Medical, Irvine, CA) for the management of acute iliofemoral (IF) deep vein thrombosis (DVT). One limitation of all endovascular devices for the treatment of acute IF-DVT has been the inability to completely remove all acute thrombus and the need for adjunctive thrombolysis with its attendant risk of bleeding complications. MethodsA single-center retrospective review of consecutive patients with acute IF-DVT treated with the ClotTriever thrombectomy system (Inari Medical) is reported. Procedural efficacy was evaluated by an independent core imaging laboratory (Syntactx, New York, NY). Both procedural and in-hospital safety were assessed during the index hospitalization. The treated vein patency was assessed using duplex ultrasound at 30 days after the procedure. ResultsA total of 96 patients were included in the present retrospective review, 40 of whom (40%) had contraindications to thrombolytic therapy. In terms of efficacy, 93 patients (97%) had ≥75% thrombus removal. During the index hospitalization, two patients (2%) had experienced a symptomatic pulmonary embolus. However, no mortality, major bleeding, or device-related complications had occurred in the study population. Of the 96 patients, 64 had undergone duplex ultrasound at 30 days after the procedure. Of the 64 patients, 62 had normal flow (97%), 53 (83%) had normal compressibility, and 11 (17%) had partial compressibility. ConclusionsThe ClotTriever thrombectomy catheter was both safe and effective in our cohort of patients with acute IF-DVT outside a randomized clinical trial.

Effect of Lateral Stress on the Mechanical Properties of Rock Fracture and Its Implication on the Stability of Underground Oil Storage Caverns

It is of great significance to study the mechanical properties of rock fracture for the stability of rock engineering projects. The mechanical properties, including the normal compression and shear properties of rock fracture, are studied by a series of shear tests considering the effect of lateral stress using the self-developed true triaxial test apparatus. The test results show that the initial normal stiffness and the maximum normal closure value of rock fracture increase with the increase of lateral stress, and the peak shear strength and the peak dilatancy angle increase with the increase of lateral stress, whereas the peak shear displacement decreases with the increase of lateral stress. Considering the effect of lateral stress, the improved normal loading model, peak shear strength model and peak dilatancy angle model of rock fracture are established. Using the equivalent parameters of rock fracture obtained based on the test, the hydro-mechanical coupling analysis considering lateral stress is carried out for an underground water sealed oil storage cavern project. It can be concluded that with the increase of lateral stress, the displacement of surrounding rock decreases, and the surrounding rock tends to be more stable.

Localization of TSH-secreting pituitary adenoma using 11C-methionine image subtraction

BackgroundPituitary adenomas (PA) affect ~ 1:1200 of the population and can cause a wide range of symptoms due to hormone over-secretion, loss of normal pituitary gland function and/or compression of visual pathways, resulting in significantly impaired quality of life. Surgery is potentially curative if the location of the adenoma can be determined. However, standard structural (anatomical) imaging, in the form of MRI, is unable to locate all tumors, especially microadenomas (< 1 cm diameter). In such cases, functional imaging [11C-methionine PET/CT (Met-PET)] can facilitate tumor detection, although may be inconclusive when the adenoma is less metabolically active. We, therefore, explored whether subtraction imaging, comparing findings between two Met-PET scans with medical therapy-induced suppression of tumor activity in the intervening period, could increase confidence in adenoma localization. In addition, we assessed whether normalization to a reference region improved consistency of pituitary gland signal in healthy volunteers who underwent two Met-PET scans without medical suppression.ResultsWe found that the mean percentage differences in maximum pituitary uptake between two Met-PET scans in healthy volunteers were 2.4% for (SUVr) [cerebellum], 8.8% for SUVr [pons], 5.2% for SUVr [gray matter] and 23.1% for the SUVbw [no region]. Laterality, as measured by contrast–noise ratio (CNR), indicated the correct location of the adenoma in all three image types with mean CNR values of 6.2, 8.1 and 11.1 for SUVbw, SUVbwSub and SUVrSub [cerebellum], respectively. Subtraction imaging improved CNR in 60% and 100% of patients when using images generated from SUVbw [no region] and SUVr [cerebellum] scans compared to standard clinical SUVbw imaging.ConclusionsMet-PET scans should be normalized to the cerebellum to minimize the effects of physiological variation in pituitary gland uptake of 11C-methionine, especially when comparing serial imaging. Subtraction imaging following endocrine suppression of tumor function improved lateralization of PA when compared with single time point clinical Met-PET but, importantly, only if the images were normalized to the cerebellum prior to subtraction.

The role of creep in geopressure development

This study developed a one-dimensional numerical model of sedimentation and compaction based on the equivalent isochrone framework to investigate the impact of creep on geopressure during burial. In this framework, the void ratio is a function of effective stress and strain rate; the change in void ratio is the same with each order of magnitude decrease in strain rate at a constant effective stress. We simulated lower void ratio and higher overpressure when creep was included compared to cases where no creep was present and void ratio is only a function of effective stress. Creep causes apparent overconsolidation. The apparent overconsolidation ratio is used to quantify the magnitude of creep; this is the vertical distance from the normal compression curve in a void ratio v. effective stress plot. The magnitude of creep depends on the loading rate, and increases with depth at sites with low sedimentation rates. These findings bridge the gap between laboratory and field observations on rock compression behaviours. For example, it provides one explanation why laboratory-derived compression curves have a higher void ratio at a given effective stress. In addition, it suggests under what conditions the rock will behave elastically. Thematic collection: This article is part of the Geopressure collection available at: https://www.lyellcollection.org/cc/geopressure

Modeling the shearing behavior of discontinuous rock mass incorporating dilation of joint aperture

The shearing characteristics of rock joints govern the mechanical performance of discontinuous rock masses. The present study investigated the normal compression and shear behavior of rock joints through cyclic compression tests and direct shear tests. The irreversible relationship between the normal stress and the normal closure was confirmed by cyclic compression tests on rock joints. An elastoplastic model was proposed incorporating the aperture variation. A modified version of the critical state framework was developed for modeling the shearing and dilation behavior. Specifically, the initial state of the rock joints was determined according to the stress history. The proposed model for the mechanical behavior of rock joints was validated by predicting the experimental results. A parameter analysis was also performed to highlight the difference in the shear behavior of the rock joints due to the difference in the initial apertures.

Preparation process and compression mechanics of carbon fiber reinforced plastics negative Poisson’s ratio structure (CFRP + NPRS)

Negative Poisson’s ratio structures (NPRS) have been extensively studied as a meta-mechanical structure. However, NPRS fabricated by laminated carbon fiber reinforced plastics (CFRP) are rarely reported. To study the compression mechanics of carbon fiber reinforced plastics negative Poisson’s ratio structure (CFRP + NPRS), a detailed preparation process of NPRS was developed, and six types of re-entrant cell structures were prepared. The quasi-static compression experiments were conducted by using the full-field strain measurement and analysis system. Combining the macroscopic and microscopic experimental features of cell structures, the compression deformation mechanism, failure modes, and the relationship to their mechanical behaviors were discussed. Further, the stiffness, strength, and specific energy absorption (SEA) were explored. The results show that the out-of-plane normal compression of cell structure results in progressive failure, which has the highest stiffness, strength and SEA. The in-plane compression realizes the negative Poisson’s ratio effect of compression-contraction. The failure types include cracking, delamination, shear and bending fracture, and interface debonding. As a conclusion, the strength of adhesion interface will induce the deformation mode. CFRP + NPRS has potential engineering applications in lightweight cushioning energy-absorption situations.

Modeling of the PHEMA-gelatin scaffold enriched with graphene oxide utilizing finite element method for bone tissue engineering

The development of computer-aided facilities has contributed to the optimization of tissue engineering techniques due to the reduction in necessary practical assessments and the removal of animal or human-related ethical issues. Herein, a bone scaffold based on poly (2-hydroxyethyl methacrylate) (PHEMA), gelatin and graphene oxide (GO), was simulated by SOLIDWORKS and ABAQUS under a normal compression force using finite element method (FEM). Concerning the mechanotransduction impact, GO could support the stability of the structure and reduce the possibility of the failure resulting in the integrity and durability of the scaffold efficiency which would be beneficial for osteogenic differentiation.

Experimental and numerical analysis on mode II fracture toughness of CFRP adhesive joints using a nonlinear cohesive/friction coupled model

In this work, a nonlinear cohesive/friction coupled model was proposed by combining experiments and numerical simulations for mode II fracture analysis of hybrid carbon nanofillers toughened carbon fiber composite bonded joints. First, end-notched flexure tests were performed to investigate the toughening effects of multi-walled carbon nanotubes (MWCNTs) and graphene nanoplates (GNPs) hybrids modified adhesive on mode II fracture toughness of adhesive joints. Testing results show that 0.75 wt% MWCNTs/GNPs hybrid has an improvement of 45% compared to pure adhesive. Secondly, a phenomenological progressive rising friction model was introduced into an exponential cohesive zone model for delamination analysis of adhesive layer under shear and normal compression loadings. Finally, the proposed model was implemented in ABAQUS/Explicit via user subroutine VUMAT and model parameters were determined by fitting experimental results of end-notched flexure tests for adhesive joints.

The Thermally Grown Oxide Thickness and Substrate Film Coefficient Effect on Residual Stresses within Thermal Barrier System

Aims: This work is to give a further insight into the residual stress distribution within APS TBC system within TBC system by coupled thermo-mechanic finite element analysis. Background: Thermal barrier coatings are a typical example of ceramic-metal system. Thermal stress could be produced in the thermal barrier coatings on account of the difference in coefficient of thermal expansion between the ceramic and metal and poses a serious threat to the performance and lifetime of the thermal barrier coatings. Objective: Many previous studies used out-of-plane stresses to estimate the delamination of the bond-coat/TGO and TGO/top-coat interfaces. However, in the present work, normal and tangential stresses under thermal-mechanic coupling analysis are adopted to investigate the interface delamination Methods: A thermo-mechanic coupled model comprised of a top-coat, thermally grown oxide, bond-coat, and substrate, is built for the stress evolution within the thermal barrier coatings using finite element method. The thermal conduction is carried out inside the thermal barrier coating model according to Fourier's law, with the temperature gradient forming in the model. Results: The top-coat is subjected to tensile stresses around the peak, with the stress magnitudes decreasing with the oxide thickness. Normal tension acts across the oxide/bond-coat interface around the peak while normal compression acts around the valley. Their magnitudes are dependent on the oxide thickness but are not so sensitive to the substrate surface heat transfer coefficient Conclusion: The TC/TGO interface might be subjected to tensile or compressive stresses around the peak, which depends on the TGO thickness. The TGO/BC interface is subjected to tensile stresses around the peak and compressive stresses around the valley, the magnitudes of which increase with the TGO thickness. The influence of substrate film coefficient on the stress across the TGO/BC interface is not so significant. Discussion: The thermo-mechanic coupled model is employed to analyze the top-coat stress, bond-coat plastic strain and interface stress. Simultaneously, a parametric study is performed on the effect of thermally grown oxide thickness and substrate surface heat transfer coefficient on the above mechanical responses.

Mechanical strength and band alignment of BAs/GaN heterojunction polar interfaces: A first-principles calculation study

Recently, GaN-on-BAs has been synthesized and demonstrated as a promising architecture for efficient thermal management in GaN based high-power electronic devices with remarkably reduced thermal boundary resistance compared to that of GaN-on-diamond. In this paper, we report studies on ideal strengths and band alignments for polar BAs/GaN heterojunctions and superlattices using first-principles calculations. The results show that under normal compression, all BAs/GaN interface configurations show much higher compressive stiffness compared to that in bulk GaN [0001] direction, with the GaN softening during its structural transformation under compression markedly suppressed, which improves protection of the electronic properties under external impacts. The natural band alignments of the mismatched BAs/GaN heterojunctions are calculated by a three-step approach. Most of the heterojunction and all the superlattice interfaces show type-II staggered band offsets. Large polarization built-in electric fields are predicated in superlattice with repeatedly positive- and negative-charged N-As and Ga-B interfaces, producing a saw-tooth like dipole potential, which can effectively separate electrons and holes to different interfaces, desirable for the photocatalytic processes. Our research shows that BAs/GaN heterojunction can not only provide a much-needed alternative to GaN-on-diamond heat dissipation system in future designing of high-power electronic devices, but also offers possibilities of applications in photovoltaic and photocatalytic devices as a type-II semiconductor heterojunction or superlattice.

Discrete element modelling of normal compression of clay

The discrete element method (DEM) has only rarely been used to simulate clay, due to difficulties in modelling clay particle shape and capturing the various particle interactions. This paper presents a new approach to simulate clay in three dimensions using DEM, featuring realistic particle shape and a new straightforward interaction law, which is able to reproduce all well-known characteristic platelet interactions. By varying the interactions between the platelets (including both the ‘edges’ and ‘faces’), it is possible to account for a range of environmental conditions. Simple sedimentation and one-dimensional compression tests are presented, which correctly reproduce the expected behaviour, confirming the validity of the model. Particle-scale analysis reveals the influence of the platelet interactions on the bulk behaviour, and it is also shown that platelet aggregation appears to lead to a fractal distribution of aggregated ‘stack’ sizes as a means of space filling.

Study on test set-ups for determining the failure characterisation in masonry components

This paper presents experimental studies and detailed micro-modelling on test set-ups to determine the strength and failure mechanism of brick masonry components. Experimental studies include compressive strength tests of masonry units, red clay brick masonry triplet tests and Z-shaped flexural bond tests. Failure mechanisms for masonry relates not only to mortar and brick material properties, but also to the bond strength between the brick and mortar. A contact law based on the cohesive zone model and Coulomb's law was used to describe the fracture behaviour of mortar joints. Numerical studies are based on the interface cohesive model for mixed modes I and II. Tests were evaluated numerically using the Benzeggagh–Kenane mixed mode criterion. The results obtained from finite-element (FE) simulation showed the reliability of computational modelling approaches for masonry bed joint behaviour. Finally, a parametric study on masonry triplet under various compression stresses was carried out by using the FE simulation. The results indicate that an increase in normal compression stress leads to an increase in shear bond strength of masonry.

Reversible anomia and cerebral venous thrombosis: a case report and review of the literature

BackgroundCerebral venous thrombosis is a rare form of venous stroke with diverse clinical manifestations. Word-finding difficulty (anomia) is rarely reported in patients with cerebral venous thrombosis.Case presentationWe report a 30-year-old right-handed Ethiopian female patient, who presented with global headache associated with a new onset word-finding difficulty of 2 weeks duration. The headache was not responsive to over-the-counter medications. She reported blurring of vision and nausea. Two months previously, she gave birth to a dead fetus. On neurological assessment, the patient was fully conscious and oriented, with a Glasgow coma score of 15/15, and cranial nerves, motor, and sensory examinations were unremarkable. Examination of fundus showed grade 2 papilledema bilaterally. Language assessment showed normal fluency, compression, naming, reading, and repetition. Naming was assessed using a 60 second word generating test, which indicated anomia. Brain magnetic resonance imaging showed left temporoparietal ischemia, magnetic resonance venography showed thrombosis of the left transverse, sigmoid sinus, and corresponding cortical veins. She was started on warfarin 5 mg daily for 6 months and showed significant resolution of symptoms, including the anomia.ConclusionThe present case describes a young female patient with reversible anomia as a complication of cerebral venous thrombosis. The case also highlights the importance of timely diagnosis and treatment of cerebral venous thrombosis for a benign prognosis.

Study of the strength limit of the bark of a plum tree trunk under the action of normal compression

Purpose. Reduction of damage to trunks of tree bark due to substantiation of the parameters of the harvesting technique using the method of determining the strength limit of tree bark in field conditions during research and the device for its implementation. Methods. Standardized and improved methods of determining the strength limit of tree bark under normal load were used, as well as the basic provisions for conducting laboratory and field experiments. Results. During field research, the developed method of determining the strength limit of tree bark was applied. It was established that highly elastic deformation of the bark does not affect the functional properties of phloem, phelloderm and cambium, i.e. after removing the load, the bark is completely restored, and irreversible plastic deformation leads to the death of bark fibers. The transition to the region of plastic deformation is marked by a sharp increase in the rate of deformation at a constant rate of load application, i.e. the strength limit of the crust is overcome and the flow fluidity phase. To implement the improved method, the developed device was used to determine the strength limit of the crust under normal compression, which made it possible to substantiate the parameters of the overlays of working organs and modes of operation of shakers of fruit-harvesting means and machines during development. Conclusions. The proposed method and device made it possible to determine the bark strength limit during normal compression in the field without damaging the tree bark. It was established that for plum orchard trees with diameters of 50–200 mm, it is 0.68–1.74 MPa and depends on the thickness of the cork tissue, which increases with the age of the tree. The method of implementing the method and the device is universal, therefore it is advisable to use it during field tests to determine the limit of bark strength for other fruit and nut trees. Keywords: method, instrument, tree bark, normal pressure, strength limit.