Polyvinyl Chloride Tubes Research Articles

Evaluation of the sieve analysis effect on the efficiency of PVC waste as sand replacement in concrete mixtures

Recycling materials has become an immerging tendency as a way for preserving natural resources. The waste disposal of polymeric materials has a significant impact on the environment and public health through their practical application in civil engineering constructions. The current experimental study aims to investigate the possibility of using polyvinyl chloride (PVC) waste in concrete and also to evaluate the PVC concrete properties in comparison with ordinary concrete (OC). This investigation research involves reusing the left-over PVC tube wastes and their incorporation in concrete. Three different replacement ratios (5%, 10% and 15%) of natural sand by polyvinyl chloride were considered, taking into account two different sizes (fine and fiber) of polymeric wastes. The effects of each incorporated PVC waste on the compressive strength, and tensile strength were studied. The fresh properties of concrete were investigated by conducting a slump test. The results revealed a decrease in the workability of the fresh PVC concrete compared to ordinary concrete. It was observed that the concrete made with fiber PVC shows a lower workability (decrease of 54%) in comparison with the first one which contains fine PVC aggregates. The concrete made with fiber PVC aggregates improves the compressive strength up to 23.5%. This latter increased simultaneously with increasing the replacement ratio of PVC waste. However, the increase of fine PVC waste content caused a decrease in compressive strength till 21%. The test results also revealed that the concrete mixes with high fiber and moderate fine PVC ratios enhanced the concrete mechanical performance.

Digital twins for the rapid startup of manufacturing processes: a case study in PVC tube extrusion

In this work, a soft sensor–based digital twin (DT) was developed to reduce the startup time in manufacturing plastic tubes and enable real-time product quality monitoring, i.e., the weight per unit length and the inner and outer diameters of the tube. An experimental campaign was conducted on a real tube extrusion line using three polyvinyl chloride (PVC) compounds and different process conditions, and machine learning regression algorithms were trained and tested to create the models of the extruder and the extrusion die the DT is based on. The characterization of the considered material, whose properties were given as input to the digital models, was carried out according to a procedure based only on the data collected by the production line. The DT was tested for the startup of the production of a single-layer tube and allowed to achieve the specified customer requirements (thickness and weight) in a few minutes. The proposed solution thus proved to be a valuable tool for reducing the setup time, thus increasing the efficiency of the process.

Structural behavior of concrete filled double-skin PVC tubular columns confined by plain PVC sockets

Abstract The behavior of concrete-filled double-skin poly vinyl chloride (PVC) tubular columns confined by plain PVC sockets is studied in this research. The plastic pipes have been used with concrete as columns. PVC has several advantages as it is inexpensive, light weight for construction, and decrease in the time taken for construction. Thus it can be used as an alternative to metal in various applications in which the maintenance cost is increased and the corrosion is reduced. This study is an experimental work on four groups of composite hollow PVC columns, each group containing three different samples. The effects of several parameters are studied, including slenderness ratio, compactness ratio, compressive strength, and confinement ratio. The experimental results show that stiffness, strength, as well as the ductility of composite columns of different loadings were considerably influenced by all these parameters. An increase in loading carrying capacity by about 40.4% was noticed as slenderness ratio decreased from 20 to 12 and about 21.1% as compactness ratio decreased from 50 to 25. Besides, the rate of increase in load capacity was about 96.6% as compressive strength increased from 33 to 54 MPa. For the case of variation of confinement ratio from 25 to 75%, the increase in the axial load capacity was about 56.7%. The main benefit of this type of column is the interaction between PVC tube and concrete. Besides, restriction of concrete by tube results in the delay of local buckling so that the concrete strength is enlarged by the effect of confining provided by the tube.

Structural Performance of Strengthening of High-Performance Geopolymer Concrete Columns Utilizing Different Confinement Materials: Experimental and Numerical Study

The objective of this study was to investigate the effectiveness of different confinement materials in strengthening geopolymer concrete (GP) columns subjected to axial compression loading. This research encompassed both experimental and numerical analyses. The experimental phase involved testing seven circular GP columns, while the numerical phase involved developing 3D finite element (FE) models using ABAQUS software. The primary focus of this study was to assess the impact of using outer and inner steel tubes, as well as an outer polyvinyl chloride (PVC) tube and a carbon-fiber-reinforced polymer (CFRP) sheet. To validate the FE models, the experimental results were utilized for comparison. The findings of this study revealed that the outer steel tube provided superior confinement effects on the GP column’s concrete core compared to the PVC tube and CFRP sheet. The axial capacities of the columns confined with steel, PVC, and CFRP materials were observed to increase by 254.7%, 43.2%, and 186%, respectively, in comparison to the control specimens. Furthermore, the utilization of all confinement materials significantly enhanced the absorbed energy and ductility of the columns. The FE models demonstrated a reasonably close match to the experimental results in terms of load–displacement curves and deformation patterns. This correspondence between the numerical predictions and experimental data confirmed the reliability of the FE models and their suitability for generating further predictions. In summary, this study contributes to the field by exploring the efficacy of various confinement materials in strengthening GP columns. The results highlight the superior performance of the outer steel tube and demonstrate the positive influence of PVC and CFRP materials on enhancing the structural behavior of the columns. The validation of the FE models further supports their reliability and their potential for future predictions in similar scenarios.

Change of dexmedetomidine and midazolam concentrations by simultaneous injection in an in vitro extracorporeal circuit.

Patient sedation and analgesia are vital for safety and comfort during extracorporeal membrane oxygenation (ECMO). However, adsorption by the circuit may alter drug pharmaco-kinetics and remains poorly characterized. This study is the first to examine the concentrations of DEX and MDZ in the presence of drug-drug interactions using an in vitro extracorporeal circuit system that incorporates a polymer-coated polyvinyl chloride tube, but not a membrane oxygenator. Nine in vitro extracorporeal circuits were prepared using polymer-coated PVC tubing. Once the circuits were primed and running, either a single drug or two drugs were injected as boluses into the circuit with three circuits per drug. Drug samples were drawn following injection at 2, 5, 15, 30, 60, and 120min and at 4, 12, and 24h. They were then analyzed using high-performance liquid chromatography with mass spectrometry. When compared with an injection of DEX alone, the combination of DEX and MDZ is highly changed, with DEX and MDZ affecting the availability of free drugs in the circuit. The change of DEX and MDZ concentrations was confirmed by a combination of both drugs as compared with either single-infusion DEX or MDZ in an in vitro extracorporeal circuit. Drug-drug interactions developed between DEX and MDZ through albumin in an extracorporeal circuit; as a result, the unbounded drugs might change in the circuit.

Toxic or not toxic? The specifications of the standard ISO 10993-5 are not explicit enough to yield comparable results in the cytotoxicity assessment of an identical medical device.

Medical device manufacturers are obliged to prove the biocompatibility of their products when they come into contact with the human body. The requirements for the biological evaluation of medical devices are specified by the international standard series ISO 10993. Part five of this series describes the performance of in vitro cytotoxicity tests. This test evaluates the effects of medical device use on cell health. The existence of the specific standard suggests that the tests will produce reliable and comparable results. However, the ISO 10993-5 offers wide latitude in the test specifications. In the past, we noticed inconsistencies of the results from different laboratories. To determine if the specifications of the standard ISO 10993-5 are explicit to ensure the comparability of test results and, if not, identify potential influencing factors. An interlaboratory comparison was conducted for the in vitro cytotoxicity test according to ISO 10993-5. Fifty-two international laboratories evaluated the cytotoxicity for two unknown samples. One was polyethylene (PE) tubing, which is expected to be non-cytotoxic and the other was polyvinyl chloride (PVC) tubing, for which a cytotoxic potential was presumed. All laboratories were asked to perform an elution test with predefined extraction specifications. The other test parameters were freely chosen by the laboratories according to the guidelines set by the standard. To our surprise only 58 percent of the participating laboratories identified the cytotoxic potential of both materials as expected. Particularly for PVC a considerable variation of the results between the laboratories was observed [mean = 43 ± 30 (SD), min = 0, max = 100]. We showed that ten percent serum supplementation to the extraction medium, as well as longer incubation of the cells with the extract, greatly increased the test sensitivity for PVC. The results clearly show that the specifications set by the ISO 10993-5 are not explicit enough to obtain comparable results for an identical medical device. To set requirements that ensure reliable cytotoxicity assessments, further research will be necessary to identify the best test conditions for specific materials and/or devices and the standard needs to be revised accordingly.

P37: Development of a Large Diameter In Vitro Flow Loop Thrombogenicity Test System

Purpose: To accommodate a wide range of medical device sizes for in vitro thrombogenicity testing, a larger flow loop system using 9.5 mm inner diameter (ID) tubing was developed and evaluated based on the 6.4 mm ID system that we previously used. Methods: Four cardiopulmonary bypass roller pumps were used concurrently to drive four different flow loops constructed with 9.5 mm ID polyvinyl chloride (PVC) tubing. To ensure that the four pumps produced a consistent blood flow rate (around 530 mL/min), a simplified dynamic roller-occlusion method was developed and applied. ACDA-anticoagulated bovine blood from live donors was obtained commercially, shipped overnight, and used within 24-36 hours of the blood draw. Immediately before starting each flow loop test, the blood was recalcified and heparinized to a donor-specific concentration (0.5 – 0.8 U/mL). The donor-specific heparin level was selected based on an established static pre-test and verified by an initial flow loop test with the following acceptance criteria: thrombus surface coverages of ≤10% on the negative control (PTFE) and ≥50% on the positive control (latex) materials, and platelet (PLT) reduction of ≤30% for the negative control and ≥90% for the positive control. For the dynamic testing, the heparinized blood was recirculated at 20 rpm for 1 hour at room temperature through each PVC tubing loop containing a test material. Six materials (3.2 mm OD, 12 cm long) with different thrombogenic potentials were assessed: negative control polytetrafluoroethylene (PTFE), positive control latex, BUNA rubber, silicone, abraded PTFE, and 3D printed nylon. Thrombogenicity potentials of the test materials were evaluated after the recirculation by measuring the thrombus surface coverage on test materials and platelet count reduction in the blood samples. Results: The in vitro flow loop test system effectively differentiated the known thrombogenic materials (latex, BUNA) from the historically thromboresistant PTFE (p<0.05 for PLT count reduction and thrombus surface coverage, Figure 1). Additionally, the 3D printed nylon and silicone test samples were shown to have an intermediate thrombogenicity level with significantly less thrombus surface coverage and PLT count reduction than latex and BUNA, but significantly more thrombus surface coverage than the PTFE (p<0.05). While the average PLT count reductions for the 3D printed nylon and silicone were also greater than that of PTFE, the differences were not statistically significant. Conclusion: The preliminary data suggest that the 9.5 mm ID test system is capable of differentiating materials of varying thrombogenicity potentials, and the different pumps can produce consistent results when appropriate occlusion settings are used. This system will be further investigated in an ASTM interlaboratory study to develop standardized best practices for performing in vitro dynamic thrombogenicity testing of medical devices and materials.Figure 1. A) Platelet count reduction, and B) Thrombus surface coverage on test material after 1 hour blood recirculation at room temperature. Data are shown as a mean ± standard error. n=4 for all materials, except BUNA and silicone (n=3). *p<0.05.

Axial compression test on concrete columns hybrid strengthened with CFRP/CPVC tube and ECC cladding layers

Existing research proved that the confinement of fiber-reinforced polymer (FRP) and commercially available chlorinated polyvinyl chloride (CPVC) tubes can considerably improve the strength and ductility of concrete columns. Meanwhile, engineered cementitious composite (ECC), as a kind of high-ductility and high-energy absorbing material, can effectively improve the ductility of concrete columns. In this study, a novel hybrid system was proposed, including the hybrid confinement of carbon fiber-reinforced polymer (CFRP) and CPVC, and an inner ECC layer. Its compressive behavior was explored by the axial compression test, and the effects of the number of CFRP layers, the diameter of the CPVC tubes, and the net spacing of the CFRP strips were considered as the test variables. The test results showed that CFRP-CPVC confinement can significantly improve the peak strength and corresponding strain of cylinders, and the inner ECC layer can enhance the relative ductility. Compared to the diameter of the CPVC tube and the net spacing of CFRP strips, thicker CFRP layers and full CFRP wrapping noticeably improved the loading capacity of the specimens. Finally, a theoretical model was given for predicting the peak axial stress of the specimens, which can provide a reference for designing the hybrid strengthening system.

Effect of Temperature on Thrombogenicity Testing of Biomaterials in an In Vitro Dynamic Flow Loop System.

To develop and standardize a reliable in vitro dynamic thrombogenicity test protocol, the key test parameters that could impact thrombus formation need to be investigated and understood. In this study, we evaluated the effect of temperature on the thrombogenic responses (thrombus surface coverage, thrombus weight, and platelet count reduction) of various materials using an in vitro blood flow loop test system. Whole blood from live sheep and cow donors was used to assess four materials with varying thrombogenic potentials: negative-control polytetrafluoroethylene (PTFE), positive-control latex, silicone, and high-density polyethylene (HDPE). Blood, heparinized to a donor-specific concentration, was recirculated through a polyvinyl chloride tubing loop containing the test material at room temperature (22-24°C) for 1 hour, or at 37°C for 1 or 2 hours. The flow loop system could effectively differentiate a thrombogenic material (latex) from the other materials for both test temperatures and blood species ( p < 0.05). However, compared with 37°C, testing at room temperature appeared to have slightly better sensitivity in differentiating silicone (intermediate thrombogenic potential) from the relatively thromboresistant materials (PTFE and HDPE, p < 0.05). These data suggest that testing at room temperature may be a viable option for dynamic thrombogenicity assessment of biomaterials and medical devices.

Upcycling poly(vinyl chloride) waste tubes: Studies of thermal stability and kinetics of films made of waste polyvinylchloride tube at the initial steps of degradation

AbstractPolyvinylchloride (PVC) tubing products almost have replaced cast iron sewer and piping systems for water and wastewater collections; it also replaced metal and wood in window frames in construction. PVC has a high value, and its resin production continues to grow yearly at a considerable rate. Availability of the disposed or postconsumer PVC (wPVC) mimics a pseudo‐renewable resource of wPVC, which creates many upcycling, recycling, and downcycling that result in many economic opportunities, besides reducing its burden on the environment while saving energy. This work presents the thermal characteristics of a film made of wPVC (wPVCf). Six samples of wPVCf were analyzed by its own heating, rate appropriate for kinetics properties evaluation, using a thermogravimetric analysis (TGA) instrument. The isoconversional degradation energy barrier (Ea,α) values were evaluated by applying 14 kinetic models, f(α), to the TGA data assuming that the degradation process follows a pseudo‐single component model. The values of Eα,α obtained from all models for each given α value were close to each other with a standard deviation of less than 0.1 kJ mol−1 indicating the validity of the method. The results were consistent with the kinetics data reported in the literature for pure PVC.

Using analytical and data-driven methods to develop a soft-sensor for flow rate monitoring in tube extrusion

In manufacturing polyvinyl chloride (PVC) tubes, the required thickness and weight depend on the extruder flow rate. The extruder setup can be very time-consuming and inefficient since it requires adjusting the screw rotational speed by trial & error, as the relation between the flow rate and the rotational speed is not known a priori. Furthermore, it is also affected by the material properties, the melt temperature, and the pressure drop in the die. Direct measuring the flow rate or the tube thickness would require expensive gravimetric dosers or X-ray systems, respectively. Therefore, a soft-sensor was developed to monitor tube thickness and its weight per unit length. Two alternative approaches are proposed to predict the extruder flow rate under wall slip conditions: one is based on a developed analytical model and one on data-driven algorithms. Results show that machine learning regression models can achieve high predictive performance (a relative error of 1.2% using a Support Vector Regressor).

Evaluation of improved transvenous heartworm extraction brush in dogs with caval syndrome.

Heartworm infection in dogs is caused by Dirofilaria immitis and common in shelter animals and outdoors dogs. Caval syndrome can develop with severe infection and physical heartworm removal is essential with heartworm burdens. In this study, we used an improved transvenous heartworm extraction brush, which was expected to cause less cardiovascular damage and allow easier manipulation. This study aims to evaluate efficacy of this improved transvenous heartworm extraction brush. The brush was designed to improve upon the limitations of the previous brush-type devices. The brush was made of a polyvinyl chloride tube and threads of polyamides or polyglyconates. Metal material was inserted at the front tip for easy visualization under fluoroscopy. The eight dogs diagnosed with caval syndrome with large numbers of heartworms and pulmonary hypertension were used in this study. The removal procedure began with the dissection of the subcutaneous tissue around the right jugular vein. The device was inserted through the jugular vein. After insertion, the tube was rotated to catch the heartworms and extracted with the heartworms hanging on the threads. The procedure was repeated several times. Lastly, jugular vein and skin sutures were made. Adulticidal therapy was administered after heartworm removal. The mean number of removed heartworms was 10.5 ± 4.24 and mean number of remaining heartworms was 0.63 ± 1.06. Total procedure time was 72.63 ± 51.36. Except for three cases, heartworms were not detected on ultrasonography after the procedure. No procedure-related side effects were observed within the 1- to 2-mon. An improved transvenous heartworm extraction brush is efficient for heartworm removal in dogs with caval syndrome.

Synthesis of nanocomposites reduced graphene oxide-silver nanoparticles prepared by hydrothermal technique using sodium borohydride as a reductor for photocatalytic degradation of Pb ions in aqueous solution

Heavy metals are pollutants that are harmful to living things and the environment can be degraded by microbes or understood by other living things so that they can cause health problems. One of the heavy metals that is often found in wastewater is lead. Lead is widely used in the manufacture of batteries, metal products such as ammunition, cable coatings, Polyvinyl Chloride (PVC) tubing, solder, chemicals and dyes This use causes humans to be exposed to large amounts of lead. One method to deal with lead pollution is to use photocatalysts. Photocatalysts react with heavy metals and reduce them so that the level of toxicity becomes lower than before through photocatalytic reactions. In this study, synthesis of reduced graphene oxide/silver nanoparticle nanoparticles was performed by facile hydrothermal methods for photocatalytic degradation of Pb ion. The characterization results indicate that the synthesis has been successfully carried out. The successful result of rGO/AgNPs nanocomposites synthesis was proved by several techniques such as X-ray diffraction analysis, Raman, UV-Vis spectroscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray analysis (EDX). This indicates the presence of these groups in the graphene oxide and rGO/AgNPs samples, respectively. The resulting rGO/AgNPs nanocomposite has an absorbance peak at a wavelength of 267 nm. The diffraction peaks for nanocomposites rGO/AgNPs and their Miller indices were 38.08° (111), 44.16° (200), 64.44° (220), and 77.44° (311). The Raman spectra of rGO/AgNPs exhibits D bands at 1334,13 with intensity of 630,60 cm−1 and G band at 1594,61 with intensity of 477,29 cm−1. The ID/IG ratio rGO/AgNPs-NaBH4 is ~1,32. Furthermore, the photocatalytic activity test results showed that the rGO/AgNPs nanocomposite was able to reduce Pb2+ to Pb with a maximum exposure time of 1.5 hours

Physicochemical Characterization of Dembi Reservoir Water for Suitability of Fish Production, Southwest Ethiopia.

Reservoir water physicochemical characteristics provide important information about water suitability for fish production. Accordingly, the study aimed to characterize the physicochemical characteristics of Dembi reservoir water for sustainable fish production. The study was conducted in Dembi reservoir during the dry season. Water samples were collected in triplicate from selected 10 sampling sites of the reservoir water using manually prepared water sampler made from polyvinyl chloride (PVC) tube. The depth integrated sampling technique was employed to take water samples for all physicochemical characteristics analysis. From the selected 14 physicochemical characteristics, four (temperature, electrical conductivity, pH, and dissolved oxygen) were tested onsite using a multisystem HQ4d electronic meter (probe), whereas the rest 10 water quality characteristics were tested in the laboratory. The result showed that the current average depth of the dam was 5.6 ± 1.61 m. The overall mean values of the water quality characteristics at different sites of the reservoir were as follows: turbidity (26.4 ± 0.44 FTU), total hardness (22.2 ± 0.51 mgL-1), NO3 (5.4 ± 0.48 mgL-1), NO2 (0.3 ± 0.11 mgL-1), NH4 (2.1 ± 0.06 mgL-1), PO4 -3 (1.7 ± 0.27 mgL-1), total alkalinity (52.5 ± 0.91 mgL-1), and BOD5 (2.7 ± 0.24 mgL-1). There was a significant difference (p < 0.05) in all physicochemical characteristics among 10 sampling sites of the reservoir water. The recorded values of all physicochemical characteristics, except NO2, NH4, and PO4 -3, were found within the recommended standard limit for fish production. The change in reservoir water depth and increase in nutrients shows the presence of sediment siltation and nutrient enrichment. Therefore, proper watershed management practices and waste management should be carried out for sustainable water quality maintenance and fish production.

Heating of Large Endovascular Stents and Stent Grafts in Magnetic Particle Imaging—Influence of Measurement Parameters and Isocenter Distance

PurposeMagnetic particle imaging (MPI) is a tomographic imaging modality with the potential for cardiovascular applications. In this context, the extent to which stents are heated should be estimated from safety perspective. Furthermore, the influence of the measurement parameters and stent distance to the isocenter of the MPI scanner on stent heating were evaluated.Materials and MethodsNine different endovascular stents and stent grafts were tested in polyvinyl-chloride tubes. The stents had diameters from 10 to 31 mm, lengths between 25 and 100 mm and were made from stainless steel, nitinol or cobalt-chromium. The temperature differences were recorded with fiber-optic thermometers. All measurements were performed in a preclinical commercial MPI scanner. The measurement parameters were varied (drive field strengths: 3, 6, 9, 12 mT and selection field gradients: 0, 1.25 and 2.5 T/m). Furthermore, measurements with different distances to the scanner’s isocenter were performed (100 to 0 mm).ResultsAll stents showed heating (maximum 53.1 K, minimum 4.6 K). The stent diameter directly correlated with the temperature increase. The drive field strength influenced the heating of the stents, whereas the selection field gradient had no detectable impact. The heating of the stents decreased with increasing distance from the scanner’s isocenter and thus correlated with the loss of the scanner’s magnetic field.ConclusionStents can cause potentially harmful heating in MPI. In addition to the stent diameter and design, the drive field strength and the distance to the MPI scanner’s isocenter must be kept in mind as influencing parameters.

Comparison of a polyvinyl chloride tube with a wire-reinforced tube for tracheal intubation through the SaCoVLM video laryngeal mask airway: protocol for a randomised controlled study

IntroductionThe SaCoVLM is a new type of video intubating laryngeal mask airway (LMA), and it is the first LMA to realise continuous visual monitoring. There is a lack of studies...

Study of Behaviour of Short Concrete Columns Confined with PVC Tube under Uniaxial Load

An experimental investigation has been carried out to evaluate the effectiveness of Polyvinyl chloride (PVC) confinements in short plain circular concrete columns. The experimental part is conducted using different PVC tube diameters (110, 160, 220, and 250 mm) with two types of confinement strategies (fully and confined with the cut ends). The results are validated with unconfined samples (control samples). The test results showed that using external confinement of concrete columns by PVC tubes enhances the ultimate load capacity of the short columns. For fully confined samples, the enhancement ratio ranges between 5% and 8.3%, and from 4.16% to 15% for samples with cut ends. Furthermore, the confining of PVC pipes with the cut ends (CCC) has a more considerable effect on load capacity for all diameters except the ones with 250 mm, where the samples with full confinement (Cc) carried a bigger load than those with cutting ends. Finally, a numerical simulation of samples is carried out by the finite element (FE) model using the ABAQUS software. For all scenarios, the results of the numerical analysis showed considerable similarity to the experimental results, with R2 of 0.95 indicating the high linearity between the actual and simulated compressive strength values. Moreover, the FE induces fewer simulated errors with a relative error (RE) ranging from 0.16% to 6% for all scenarios.

Behaviour of lump-grout material filled PVC tubular column under uniaxial compression

The hybrid structural form made of the polyvinyl chloride (PVC) and lump-grout (LG) material, termed LGFPT column, was developed as the alternative standing support for deep underground mines. To explore the mechanical response of this structural form under the uniaxial compression, various critical parameters (i.e., the water-to-powder ratio of the cementitious grout material, length-to-diameter ratio of the PVC tube, loading mode and loading speed) were investigated. Test results showed that the LGFPT column had an excellent ductility (>30% of the column length) associated with the strain hardening behaviour. Compared to its counterparts, the effect of the water-to-powder ratio of the grout material is most significant when the peak load of the LGFPT is evaluated. In parallel, the compressive behaviour of the cementitious grout material-filled PVC tubular (GFPT) column was investigated. When the ultimate axial compressive strength of the LGFPT and the GFPT are compared, the strength of the LGFPT was not significantly affected, although the cementitious grout material consumption of which has been reduced about 50% in volume. As a family member of the standing support systems, the LGFPT is an ideal candidate to be used in underground mines attributed to its cost-effective and environmentally-friendly.

Axial behavior of circular CFST encased seawater sea-sand concrete filled PVC/GFRP tube columns

In order to directly apply seawater and sea sand in construction without desalination, a new type of circular concrete-filled steel tube (CFST) encased prefabricated seawater sea-sand concrete filled Polyvinyl Chloride (PVC)/Glass Fiber Reinforced Polymer (GFRP) tube column was proposed. 24 short columns were tested under uniaxial loads and the test parameters included types of inner tubes, seawater sea-sand concrete replacement ratios, concrete strength, the wrapping area of Carbon Fiber Reinforced Polymer (CFRP) strips and the thickness of inner tube. Moreover, the effects of the parameters on bearing capacity, ductility, stiffness, and strain responses were discussed. The results indicate that the bearing capacity and the strength index of specimens with PVC tube wrapped with CFRP strips and GFRP tube as the inner tube was significantly improved, and the improvement level increased as the wrapping area of CFRP strips or the thickness of GFRP tube increased. The increase in the concrete strength can also improve the bearing capacity and stiffness. In addition, an analytical model was proposed for the composite column with PVC tube wrapped with CFRP strips or GFRP tube as the inner tube.

КОНТРОЛЬ ПАРАМЕТРОВ ТЕМПЕРАТУРНОГО РАСПРЕДЕЛЕНИЯ В ПРЕДПЛЕЧЬЕ ЧЕЛОВЕКА ПРИ ПРОЦЕДУРЕ УВЧ-ГИПЕРТЕРМИИ МЕТОДАМИ ПАССИВНОЙ АКУСТИЧЕСКОЙ ТЕРМОМЕТРИИ И ИНФРАКРАСНОЙ ТЕРМОГРАФИИ

In this work we performed UHF heating with an electromagnetic field of frequency 40.68 MHz and power of 30 W on human forearms and phantoms made of plastisol with simulated blood flow at physiotherapeutic doses of 10, 15 and 20 minutes. Thermal acoustic radiation of heated objects measured with a multichannel acoustothermograph with a bandwidth of 1.6-2.5 MHz, an integration time of 10 C, and a threshold sensitivity of 0.2 K. Additionally, the surface temperature of the forearm measured by infrared thermometry and the internal temperature of the phantom by an electronic thermometer. We obtained data about temperature distribution patterns in the human forearm and in the plastisol phantom. Blood flow in the phantoms was simulated by copper, aluminum and polyvinyl chloride tubes, through which water from a thermostat was passed. Comparison of cooling rates of different types of phantoms showed that the thermal properties of the phantom with aluminum tubes were the closest to the soft tissues of the human forearm. The data of objective control do not agree with the subjective sensations of the subjects, but agree well with each other, which confirms the necessity and shows the possibility of objective assessment of temperature distribution parameters in the soft tissues of the human body during hyperthermia during UHF-physiotherapy.