Gradual Increase In Strength Research Articles

Clinical application research of intelligent monitoring system for knee rehabilitation: a randomized controlled trial

BackgroundThis study investigates the effectiveness of a self-developed intelligent monitoring system for home-based knee rehabilitation following total knee arthroplasty (TKA).MethodsIn this randomized controlled trial, 120 patients undergoing TKA were divided using random digit allocation. Preoperative and one-month postoperative assessments of knee function, quality of life, and isometric knee extension strength were conducted with the Intelligent Monitoring System. Patients received group-specific rehabilitation instructions pre-discharge and performed exercises for one month.ResultsChanges in isometric knee extensor strength on the affected side within one month post-surgery for the brace-monitored rehabilitation group showed a significant decrease three days after surgery compared to one day before surgery. Subsequent measurements taken at postoperative days 5, 7, 14, and 21 indicated a gradual increase in strength, although these increases did not reach statistical significance when compared with previous measurements. One month post-surgery, all groups demonstrated significant improvements in knee joint function and mobility compared to pre-surgery levels. Notably, the brace-monitored group showed statistically significant improvements in 36-Item Short-Form Health Survey (SF-36) scores over the conventional rehabilitation group.ConclusionsThe Intelligent Monitoring System provides effective real-time monitoring and guidance for home-based knee rehabilitation post-TKA. It significantly enhances knee joint function, isometric knee extension strength, and quality of life shortly after surgery compared to traditional rehabilitation methods. This system offers a promising approach for improving postoperative recovery in TKA patients.Trial registrationThis study was approved by the Medical Ethics Committee of Xiangya Hospital, Central South University (Ethics Approval Number 202209008-2). It was registered with the China Clinical Trial Registry, a primary registry of the World Health Organization’s International Clinical Trials Registry Platform (Registration Number ChiCTR2300068852).

Improving interfacial strength at room and elevated temperatures in ultrasonic welding of pure titanium: Interlayer-induced phase transformation and concentrated plastic deformation

Ultrasonic welding (USW) of Titanium (Ti) sheets presents several challenges, notably crack formation due to sliding friction. To overcome this problem, the present study applied USW to pure α-Ti sheets both with and without different interlayer metals (Al, Ni, and Fe). Al interlayer improved the strength at room temperature significantly to cause base metal fracture (1700 N) by inducing concentrated plastic deformation, facilitating bonding with Ti while minimizing damage. However, its strength decreased significantly at 150–300 °C, suggesting the limitation of using Al interlayer at elevated temperatures. Conversely, the Ni and Fe interlayers led to a two-phase strength development. This enhancement was due to β-phase transformation, which reduces the interfacial defects and generates a more pronounced β-stabilization effect. The Ni interlayer, which has a higher β-transus point (765 °C) and lower molybdenum equivalency, required a higher welding energy (1800 J) and longer diffusion time into Ti, resulting in a gradual increase in strength due to a slower β-Ti transformation. On the other hand, the Fe interlayer with a lower β-transus point relative to Ti (595 °C) achieved peak strength at a lower welding energy of 1200 J. Both Fe and Ni interlayers displayed only a slight decrease in strength (1500–1600 N) at 300 °C with base metal fracture, revealing better joint performance at higher temperatures. These insights suggest a strategical interlayer selection based on the operation temperature, where Al interlayers were advantageous for low-energy welding at room temperature application, Fe and Ni interlayers offer sufficient strength at elevated temperatures by facilitating the β-Ti formation.

CARACTERÍSTICAS DO CONSUMO DE ENERGIA DOS JOGADORES DE BASQUETE COM DIFERENTES INTENSIDADES DE TREINAMENTO

ABSTRACT Introduction: In competitive basketball sports, athletes must repeatedly perform movements of maximum intensity quickly, followed by rest. A training mode called high-intensity interval training (HIIT) has the same characteristics. Objective: Explore basketball players’ energy supply characteristics and training changes under different exercise intensities. Methods: The effects of different recovery methods in the intermittent period on exercise capacity and aerobic metabolic energy supply of young male basketball players during high-intensity intermittent interval training (HIIT) were presented. Results: Increased aerobic energy production during HIIT was closely related to the acceleration of kinetics. However, although the time to exhaustion, a parameter characterizing exercise capacity, increased by 3.5% and 4.6%, respectively, in the HIITa group compared to HIITs and HIITp, there was no significant difference. After analyzing each group for the 30s, a gradual increase in strength was noticed. Conclusion: The use of HIIT as training is an important way to improve the physical performance of athletes. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Comparison of calcium aluminate cements on hydration and strength development at different initial curing regimes

This paper examines the influence of CA2 (monocalcium dialuminate, CaAl4O7) in calcium aluminate cement (CAC) on strength development relevant to conversion reaction in the hydration process. to ensure the different phase compositions at early ages, a curing temperature of 5 and 65 °C was applied to fabricating cement paste with two types of CAC for the first 24 h. The hydration behavior of the specimen was investigated by isothermal calorimetry, X-ray diffraction, and thermogravimetry. Simultaneously, the development of pore structure was analyzed by mercury intrusion porosimetry. The results showed that CAC containing CA2 exhibits a gradual increase in strength with no drop during test periods, regardless of initial temperature, while the typical CAC paste treated at 5 °C suffers from a strength loss due to conversion. The performance of refractory CAC may arise from CA2 hydration, producing amounts of crystalline gibbsite and thus mitigating/restricting the transformation of metastable hydrates into stable ones in order to preserve their chemical balance in the cement matrix. This phenomenon could be supported by a variation in hydrate composition and pore volume derived from the present works. However, conversion reaction should be verified in the temperature-fluctuated environment and over long-term stability in future work.

Effect of the deformation temperature on the deformation behavior of a Cu-Cr-Zr alloy

The mechanical properties and deformation behavior of a Cu-Cr-Zr alloy after solution treatment (ST) or aging (ST+AT) and equal channel angular pressing (ECAP) at elevated temperature were investigated. ECAP at elevated temperature led to strengthening and degradation of plasticity compared with the initial state. The deformation behavior of the alloy after 1 and 2 ECAP passes at 200 °C was almost the same. An increase in ECAP temperature promoted uniform strain and plasticity. An increase in the number of ECAP led to a gradual increase in strength. YS and UTS in ST+AT condition were higher than in ST samples regardless of the ECAP temperature and the number of passes. The maximum values of YS and UTS were obtained after 4 ECAP passes at 400 °C and achieved 525 MPa and 600 MPa in ST and 570 MPa and 650 MPa in ST+AT condition, respectively. The effect of deformation strain and ECAP temperature on work hardening rate and recovery were discussed in terms of the Voce equitation.

A special band structure perpendicular to the basal planes formed in a magnesium alloy during hot-rolling process

Special band structures were observed in original matrix of AZ31 alloy during hot-rolling process. They were always perpendicular to basal planes, formed by intersecting of a⃑+c⃑ slip on prismatic plane with basal dislocations. The misorientation gradient was much higher across band area than locally inside. Such bands showed straight morphology at low rolling strain range, which effectively strengthened the material by reducing the mean free path of slipping dislocations on basal plane in original matrix, without evident loss in ductility. On further strain, the bands structures became more severely deformed, which lead to a gradual increase in strength and a quick drop in ductility.

Seat strength in rear body block tests

ABSTRACTPurpose: This study collected and analyzed available testing of motor vehicle seat strength in rearward loading by a body block simulating the torso of an occupant. The data were grouped by single recliner, dual recliner, and all belts to seat (ABTS) seats.Methods: The strength of seats to rearward loading has been evaluated with body block testing from 1964 to 2008. The database of available tests includes 217 single recliner, 65 dual recliner, and 18 ABTS seats. The trends in seat strength were determined by linear regression and differences between seat types were evaluated by Student's t-test. The average peak moment and force supported by the seat was determined by decade of vehicle model year (MY).Results: Single recliner seats were used in motor vehicles in the 1960s to 1970s. The average strength was 918 ± 224 Nm (n = 26) in the 1960s and 1,069 ± 293 Nm (n = 65) in the 1980s. There has been a gradual increase in strength over time. Dual recliner seats started to phase into vehicles in the late 1980s. By the 2000s, the average strength of single recliner seats increased to 1,501 ± 335 Nm (n = 14) and dual recliner seats to 2,302 ± 699 Nm (n = 26). Dual recliner seats are significantly stronger than single recliner seats for each decade of comparison (P < .001). The average strength of ABTS seats was 4,395 ± 1,185 in-lb for 1989–2004 MY seats (n = 18). ABTS seats are significantly stronger than single or dual recliner seats (P < .001). The trend in ABTS strength is decreasing with time and converging toward that of dual recliner seats.Conclusions: Body block testing is an quantitative means of evaluating the strength of seats for occupant loading in rear impacts. There has been an increase in conventional seat strength over the past 50 years. By the 2000s, most seats are 1,700–3,400 Nm moment strength. However, the safety of a seat is more complex than its strength and depends on many other factors.

Effects of Elevated Temperature on Concrete with Recycled Coarse Aggregates

This paper discusses the effects of heating temperatures of 200°C, 400°C and 600°C each for 2 hours at a heating rate of 2.5°C/min on concrete with the content of Natural Coarse Aggregates (NCA) partially replaced with Recycled Coarse Aggregates (RCA), obtained from demolished building in the ratio of 0%, 15% and 30%.There was an initial drop in strength from 100°C to 200°C which is suspected to be due to the relatively weak interfacial bond between the RCA and the hardened paste within the concrete matrix;a gradual increase in strength continued from 200°C to 450°C and steady drop occurred again as it approached 600°C.With replacement proportion of 0%, 15% and 30% of NCA and exposure to peak temperature of 600°C, a relative concrete strength of 23.6MPa, 25.3MPa and 22.2MPa respectively can be achieved for 28 days curing age. Furthermore, RAC with 15% NCA replacement when exposed to optimum temperature of 450°C yielded high compressive strength comparable to that of control specimen (normal concrete). In addition, for all concrete samples only slight surface hairline cracks were noticed as the temperature approached 400°C. Thus, the RAC demonstrated behavior just like normal concrete and may be considered fit for structural use.

Improvement of Geotechnical Characteristics of Clay Soils Using Lime

This study presents the results of an experimental work carried out to investigate the effects of treatment of fine bentonite clay using various contents of lime. Tests conducted verified substantial changes and significant improvement in physical and mechanical characteristics of the clay. Techniques including ultrasonic tests and unconfined compression were utilized for a series of lime content (0%,2%, 4% and 6%) for variable curing times. The studied clay soils revealed that lime treated clays get changed and improved with regard to particular geotechnical characteristics due to cation exchanges, particle rearrangements and pozzolanic reactions. The analysis of ultrasonic tests and compressive strength showed a process of gradual increase in strength and compactness of the reaction products over time. For an optimum dose and extended curing time, the stabilized soil acts as a rock.

Novel method of screw extrusion for fabricating Al/Mg (macro-) composites from aluminum alloy 6063 and magnesium granules

A novel method of screw extrusion was used for producing a bimetal composite Al/Mg from granules containing aluminium alloy 6063 (AA6063) and commercial pure magnesium. Up to 12.5% (mass fraction) pure magnesium was added to the aluminium alloy. In general, the material consisted of a fine grained microstructure. In addition to the phases originating from the input materials, intermetallic phases were observed as islands consisting of the Al2Mg3 phase surrounded by γ-Mg17Al12, throughout the microstructure. The mechanical properties of the extruded material showed a gradual increase in strength with increasing the addition of Mg. The highest registered UTS, well above 350 MPa, was observed for the material containing 10% Mg. Examinations of the fracture surfaces indicated that increasing the magnesium content led to a higher degree of brittle fracture and a gradual change of the fracture micro-mechanisms. The optimization of the post-extrusion processing conditions is still ongoing.

Effect of Different Forms of CaO on the Properties of Cement-Based Materials Containing High Content of GGBFS

The effects of different forms of CaO on performances of cementitious binders containing 50 wt. % GGBFS powder are studied using compressive strength testing, hydration heat and X-ray diffraction measuring, microstructure measuring, and deformation testing. Results show that, the use of analytical-grade CaO or calcined CaO expansive clinker produces a higher mechanical strength than analytical-grade Ca (OH)2for mortar samples. The mortar containing analytical-grade CaO or calcined CaO expansive clinker shows a strength increase higher than the reference before 14 days of curing, but a litter lower than the reference after 28 days. With the increase of curing age, the diffraction peaks of Ca (OH)2gradually weaken, while those of C-S-H and hydrotalcite gradually increase, contributing to a gradual increase in strength of GGBFS pastes. Compared to analytical-grade CaO, the expansive process of calcined CaO expansive clinker matches better to the deformation history of mortar containing large content of GGBFS. This work is of great significance to explore the potential use of different forms of CaO as an alternative activator for GGBFS.

Thermal and mechanical properties of ultrahigh molecular weight polyethylene/high-density polyethylene/polyethylene glycol blends

Abstract Blends of ultrahigh molecular weight polyethylene (UHMWPE) with high-density polyethylene (HDPE) provide adequate mechanical properties for biomedical application. In this study, the mechanical and thermal properties of UHMWPE/HDPE blends with the addition of polyethylene glycol (PEG) prepared via single-screw extruder nanomixer were investigated. The UHMWPE/HDPE blends exhibit a gradual increase in strength, modulus, and impact strength over pure polymers, suggesting synergism in the polymer blends. The elastic and flexural modulus was increased at the expense of tensile, flexural, and impact strength for the blends containing PEG. The degradation temperature of UHMWPE was improved with the incorporation of HDPE due to good thermal stability of HDPE. HDPE improved the dispersibility of PEG in matrix, consequently reduced the surface area available for the kinetic effects, and reduced the degradation temperature. The morphology analysis confirmed the miscibility between UHMWPE and HDPE and the changes in polymer structure with the presence of PEG modify the thermal behavior of the blends. The mechanical properties of the blends that are underlying values for the design of implant material show the potential used as biomedical devices.

Mechanical Properties and Microstructures of Al-Fe Alloys Processed by High-Pressure Torsion

Al-Fe alloys in the form of thin disks 10 mm in diameter, with Fe nominal weight fractions of 0.5, 1, 2, and 5 pct, were extracted from bulk-extruded rods and processed by high-pressure torsion (HPT). A group of these bulk samples was processed in an as-received state, whereas another group was annealed at 773 K (500 °C) for a period of 1 hour, prior to the application of HPT. An additional set of samples was prepared by mixing high-purity powders with similar Fe contents and consolidated directly in the HPT facility. The samples were processed up to 10 revolutions. Vickers microhardness, tensile strength, and elongation to failure were evaluated for all cases along with observations of the Al matrix by transmission electron microscopy (TEM). Basic characterization of the microstructures was carried out by X-ray diffraction (XRD) and optical microscopy (OM). Significant strengthening with ductility retained was achieved in the bulk samples as a consequence of grain refinement and dispersion of intermetallic phases. Powder samples had a more gradual increase in strength but increased ductility as a result of the imposed strain.

A gradual rather than abrupt increase in soil strength gives better root penetration of strong layers

The purpose of this paper is to test the hypothesis that gradual rather than abrupt increases in strength lead to increased root penetration of strong layers. This was tested experimentally in a model system with multi-layered wax discs with a total thickness of up to 6 mm that either increased in strength with depth, or decreased in strength with depth. Strength was varied by altering the proportions of hard paraffin wax and white soft paraffin. Multi-layered wax discs consisted of three layers, each 1.5 or 2 mm thick, to give a disc thickness of either 4.5 or 6 mm. ‘Test’ wax discs had a 40% hard wax layer above a 60% wax layer, which was above an 80% wax layer. This led to a gradual increase in strength as roots encountered the disc from the sand growing medium. In ‘control’ discs, the order was reversed so that 80% wax was encountered immediately below the sand. These treatments were used to challenge roots of the rice cvs. Azucena and Bala. Compared with the control, the test layers increased root penetration of Azucena from a mean of 5.9 root axes to 12.4, while penetration of Bala was increased from 0.5 to 5.6. These results show that there was increased root penetration when roots encountered a gradual increase in strength rather than a sudden increase in strength. This was explored further with numerical simulations of stress distributions at the tips of roots. These simulations indicated that gradual rather than abrupt increases in strength decreased stress concentration at the root tip, consistent with the experimental results.

Investigation of the post-hardening reaction in glass-ionomer cements based on poly(vinyl phosphonic acid)

In this study the behaviour of two PVPA-based glass-ionomer cements was investigated. The first cement was prepared from PVPA homopolymer and glass, together with a reaction modifier. In the second cement a modified version of the polymer was used instead of the homopolymer. The modification was achieved by the treatment of the polymer with a small quantity of zinc fluoride. The effect of ageing under different conditions on the strength, mass and volume of the cements was determined. The ZnF2-containing system behaved in a fairly straightforward manner, showing a gradual increase in strength with time (up to 3 months) that was similar to glass-ionomer cements based on poly(acrylic acid). By contrast the unmodified material did not increase in strength with time, a feature that was attributed to extensive crosslinking of the material, causing it to become more brittle and hence more sensitive to defects in the specimens. With regard to the effect on mass and volume, both types of cement behaved like typical set glass-ionomers, displaying a sensitivity to dessication but little, if any, sensitivity to aqueous media.

Effect of Heat Treatment on Strength of Clays

The main objective of this investigation was to understand the strength development of clays below fusion or vitrification temperatures of 900°C. The other objective was to establish threshold temperatures to produce a satisfactory construction material from clayey sediments from the Western Beaufort Sea for shore protection of artificial islands with minimum expense of thermal energy. Studies were, therefore, conducted using kaolinite, bentonite, and a clayey sediment from the Beaufort Sea. Unconfined-compressive-strength tests were conducted on clay samples heat treated from 110 to 700°C. Furthermore, to understand the factors responsible for strength-development-thermogravimetric studies and pore-size analysis, using mercury porosimetry, were also conducted. A gradual increase in strength was obtained with an increase in firing temperature. However, substantial and permanent increase in strength occurred only after dehydroxylation of all the clays studied; Clay samples heated to temperatures above dehydroxylation became resistant to disintegration upon immersion in water. Results indicate that the clayey sediments from Western Beaufort Sea have to be heat treated to about 600°C to produce granular material for use as a fill or shore-protection material for artificial islands.

A Population Discriminant in M-Dwarf Spectra

The CaH bands in the λ 6385 region of the spectra of M dwarfs have long been known; they become visible in the late K's and show a gradual increase in strength to later types. However, Greenstein and Eggen have noted that there is a substantial strengthening of all the hydride bands, including CaH, in high-velocity dwarfs (notably G95-59), and one of us (W.P.B.) has also seen this effect in suitable Warner and Swasey Observatory objective-prism plates of the rather low-velocity subdwarfs Ross 730 and 731. In a recent southern-hemisphere survey with the Curtiss Schmidt, Smethells has discovered nearly 200 late K and early M dwarfs, for all of which estimates of CaH-band strength were made. He found a considerable variation of the CaH-band strength in stars of the same (TiO-band) spectral type, and a slight tendency for the CaH/TiO band ratio to increase with increasing tangential velocity. A fuller account of this work will appear elsewhere.

Force measurements in screw fixation

An entire range of screw sizes and types from one manufacturer (Synthes, Switzerland) along with two experimental sizes were tested in bovine cancellous bone to measure torque of insertion, screwdriver pressure, axial compression generated by the screw, screw breaking strength and efficacy of various head types. The results showed a gradual increase in strength as diameter increased. Maximal axial compression peaked at 5.0 mm. The hexagonal shaped imbus head proved superior to the Phillips type.