Experimental and Modeling Studies on the Stress Relaxation Behaviour of Ti-6Al-4V Alloy

The transient mechanical behavior of materials during stress relaxation has evoked interest in manufacturing applications because of the effect of stress relaxation on formability enhancement. However, most of the previous studies have focused on advanced high strength steels and aluminum alloys. Limited transient stress relaxation studies have been conducted on titanium alloys in order to understand the influence of stress relaxation on forming behavior. Titanium alloys are widely used in aerospace components because of their high strength to weight ratios and excellent fatigue strengths. However, room temperature formability of Ti alloys is an important concern, which restricts their widespread use in various applications. To address these challenges, the present study is aimed to understand the role of transient stress relaxation on formability of Ti alloys. Toward this end, stress relaxation of a dual phase titanium alloy (Ti-6Al-4V) has been investigated experimentally. Stress relaxation tests were performed by interrupting uniaxial tensile tests in the uniform deformation regime for a pre-defined strain and hold time after which tests were continued monotonically until fracture. Single step, room temperature stress relaxation experiments were performed systematically to study the effect of hold time, pre-strain, and strain rate on mechanical properties. The stress relaxation phenomenon was found to contribute positively to the ductility improvement. The mechanisms responsible for enhancing the formability are discussed. The experimentally obtained stress vs. time data were analyzed using a advanced constitutive model for stress relaxation available in literature.

Lumbopelvic-Hip Complex Contribution During Lower Extremity Screening Tests in Elite Figure Skaters

ABSTRACT Context: Figure skating requires power and stability for take-off and landing from multi-rotational jumps and various on-ice skills. Repetitive forces may cause overuse injuries distally making lumbopelvic-hip endurance, strength, and neuromuscular control imperative. Objective: The purpose was to compare lumbopelvic-hip endurance and neuromuscular control in elite figure skaters between sex and limbs using common screening tests. Design: Cross-sectional study. Setting: U.S. Olympic and Paralympic Training Center. Participants: Forty elite figure skaters (23.2±4.3 years, 169.1±12.2 cm, 20F, 40R landing limb) performed the Y-balance test, single leg squat (SLS), single leg squat jump (SLSJ), and unilateral hip bridge endurance test. Main Outcome Measures: Normalized reach difference (% of leg length) and composite scores (((Anterior + Posteromedial + Posterolateral)/Limb length x 3) x100) were calculated for Y-balance test. Skaters held the unilateral hip bridge until failure with a maximum allotted time of 120s. Participants performed 5 SLS and SLSJ, barefooted with the contralateral limb held behind them to mimic a landing position. Both tests were scored by the number of times the patella moved medially to the first ray (medial knee displacement (MKD)). MANOVA with post-hoc independent t-tests were performed between groups and sex. Paired t-tests were used to analyze limb differences. Results: Females had a larger composite Y-balance score (R:+10.8, p=.002; L:+10.5, p=.001) and hip bridge hold time (R:+26.4 sec, p=.004; L:+28.2 sec, p=.002) on both limbs compared to males. Males held the hip bridge longer on their landing limb. During the SLS and SLSJ, 6 skaters performed worse on their non-landing limb during the SLS, and 11 skaters had no MKD with either test. Conclusions: Females performed better on the Y-balance and unilateral hip bridge tests. Increased MKD for some skaters in the SLS and SLSJ may indicate hip abductor weaknesses. Understanding proximal lumbopelvic-hip variables during take-off and landing may elucidate contributing factors to distal overuse injuries.

A Study on a Modified Model for the Hold Time of a Clean Extinguishing Agent

When estimating the theoretical hold time of a Clean Extinguishing Agent (CEA), the hold time is predicted using a leakage exponent and leakage characteristics that are measured through an Enclosure Integrity Test (EIT). In particular, the leakage exponent n is conventionally applied as 0.5, but recently, a variable exponent has been applied through measurement (approximately 0.48 to 0.85). When variable n is applied, the hold time varies greatly depending on the size of n. Therefore, in this study, a modified theoretical model for the hold time of a CEA is proposed to improve the accuracy of the hold time depending on the leakage exponent n. The modified theoretical model applies a different analysis of the inflow and outflow volumetric flow, and the results enable a more accurate hold time prediction. The modified theoretical equation shows an improvement of up to 8.6% for outflow volumetric flow V˙o and a maximum improvement of approximately 10.7% for hold time th.

ESTIMATION OF RESIDUAL SOLVENTS IN NETUPITANT API BY HEADSPACE GAS CHROMATOGRAPHY

Objective: Residual solvents are undesirable components present in Active Pharmaceutical Ingredients (API), excipients, or drug products. To meet the specific quality-based requirements, the presence of these solvents in pharmaceutical products should be monitored to ensure their safety. The main objective of this work is to develop a new method for the determination of residual solvents in netupitant API by an HS-GC method with an FID detector. Methods: An automated headspace GC method has been developed and validated for the estimation of the residual solvents-N-methyl pyrrolidine, xylene, toluene, and N, N Dimethylacetamide in netupitant API. The samples were dissolved in dimethyl sulfoxide and the equilibrium headspace gas was formed at 80 ᵒC, which was analyzed using a DB-624 column (30m*0.53 mm, 3.00 µm) with an injector and detector temperature set at 160 ᵒC and 230 ᵒC, respectively. The initial oven temperature was set at 60 ᵒC for 5 min and programmed at a rate of 10 ᵒC/min to the final temperature of 150 ᵒC, with a hold time of 5 min by maintaining the flow rate of 4.0 ml/min with a split ratio of 1:10, and total run time of 20 min. Nitrogen was used as carrier gas. The method developed was validated as per International Conference for Harmonization (ICH) guidelines for repeatability, linearity, range, ruggedness, detection limit, quantification limit, and recovery studies. Results: The linearity range selected was 50-350µg/ml and the correlation coefficient(γ2) values for all the solvents were found to be>0.99; recovery studies values were in a range of 90-110% and %RSD values were also found to be not more than 10 for the solvents. Conclusion: A novel, accurate, sensitive, and simple method was described for estimating residual solvents in Netupitant API by Headspace Gas Chromatography (HS-GC) coupled with a Flame Ionization Detector (FID). Excellent results have been observed for all the validated parameters with good peak resolution and lesser retention times.

Neck Pain and Disability: Are They Related to Dysfunctional Breathing and Stress?

Purpose: People with neck pain are likely to have negative respiratory findings. The purpose of this study was to investigate the relationship between neck pain and dysfunctional breathing and to examine their relationship to stress. Method: This cross-sectional study included 49 participants with neck pain and 49 age- and sex-matched controls. We measured neck pain using the numeric rating scale (NRS); neck disability using the Neck Disability Index (NDI); dysfunctional breathing using the Nijmegen Questionnaire (NQ), Self-Evaluation of Breathing Questionnaire (SEBQ), breath hold time, and respiratory rate (RR); and stress using the Perceived Stress Scale (PSS). Results:Participants with neck pain scored higher on the NQ ( p < 0.001) and the SEBQ ( p < 0.001) than controls. NQ and SEBQ scores correlated moderately with NDI scores ( r > 0.50; 95% CI: 0.25, 0.68 and 0.33, 0.73, respectively) and PSS scores ( r > 0.50; 95% CI: 0.29, 0.78 and 0.31, 0.73, respectively). SEBQ scores showed a fair correlation with NRS scores and RR a fair correlation with NDI scores. Conclusions: Participants with neck pain had more dysfunctional breathing symptoms than participants without neck pain, and dysfunctional breathing was correlated with increased neck disability and increased stress. The NQ and SEBQ can be useful in assessing dysfunctional breathing in patients with neck pain.

Six Weeks Effects of Dynamic Neuromuscular Stabilization (DNS) Training in Obese Postpartum Women With Low Back Pain: A Randomized Controlled Trial

Background: The worldwide prevalence of obesity and low back pain (LBP) has recently dramatically increased and is mainly indicated among postpartum women, leading to a range of adverse health consequences. Objective: This study aimed to investigate the effects of 6 weeks of Dynamic Neuromuscular Stabilization training (DNS) in obese postpartum women with LBP. Method: This was a pretest-posttest study design. The study was conducted with 40 obese postpartum women with LBP randomized to receive DNS ( n = 20) or General Exercise (GE, n = 20) 6 times a week for 6 weeks. The data were gathered before and after the 6-week intervention. Results: Forty participants completed the study (mean ± SD, age 29.30 ± 3.77 years; weight 88.10 ± 6.09 kg; height 165.40 ± 6.31 cm; and BMI, 32.19 ± 1.07 kg/m2). The overall group-by-time interaction was significant for Numeric Pain-Rating Scale, Modified Oswestry Disability Questionnaire, Fear-Avoidance Beliefs Questionnaire, Inspiration and Expiration Breath Hold Time, and Respiratory Rate outcomes. The global rating of change was significantly different between groups ( p < .05). The rate of improvement was higher in the DNS group compared to the GE group in all 6 tests. Conclusion: The present study confirms that DNS is applicable in obese postpartum women with LBP and effectively improved NPRS, MODQ, FABQ, BHT, and RR. It is clinically suggested that DNS is imperative based on ideal ontogenetic patterns to attain optimal results for obese postpartum women with LBP.

The Influence of an 8-Week Training Program with Small-Sided Games on the Anaerobic Capacity of Junior Football Players

"ABSTRACT. Introduction. The level of development of anaerobic capacity at footballers requires the achievement of sporting performance. Objective. The study analyses whether the anaerobic capacity is developed as a result of the participation of the athletes in a training program with small-sided football games. Methods. A group of 40 athletes aged 16-18 years old were grouped in two equal teams, named: experimental group (EG) and control group (CG). During the period of the study, which was between 5.01.2021 – 27.02. 2021, the two groups were exposed to different training programs: the EG in a smallsided football games training program and the CG in a classic way. The following technology was used: Hosand GT.a – to measure HR – and the WittyGateMicrogate2 system for timing of the stress sample. Subjects took the YYIRTL1 sample. SPSS program, variant 23 was used for statistical analysis of the data. Results. The results taken in the initial test (IT) between the two groups had no statistical significance in YYIRTL1 field sample was concerned, but there could be noticed significant differences in the final test (FT) for the parameter indicating the hold time in the anaerobic zone>81%HRmax (U = 67.50, N1 = 20, N2 = 20, twotailed p = .000336, d = 1.46). Conclusions. The study shows that the anaerobic capacity of subjects has developed through the implementation of an 8-week period program where small-sided football games have been used."

Effect of Scapular Retraction Exercise on Shoulder Alignment, Pulmonary Function and Aerobic Capacity in Subjects with Forward Shoulder Posture

Background: Forward shoulder posture is identified when the acromion process is most anteriorly positioned when compared with the position of mastoid process, which is characterized by acromion protraction infront of the line of gravity as well as protraction, downward rotation and anterior tilt of scapula. It is one of the common postural abnormality that accounts for 60% of shoulder abnormalities, with an incidence of 75% in the right side and 66% in left side. The study aims to find the effect of scapular retraction exercises on shoulder alignment, pulmonary function and aerobic capacity in subjects with forward shoulder posture. Methods: The study was conducted on 14 subjects with FSP within the age group of 18 to 25. Scapular retraction exercises were given to the subjects for a duration of 3 weeks. Pre and post test values of scapular index, chest expansion, incentive spirometry and six minute walk test was taken. Results: Subjects showed statistically significant differences with a mean difference of 0.7(cm) for scapular index right, 0.68(cm) for scapular index left, 0.59(cm) for upper chest expansion, 1.21(secs) for inspiratory hold time using incentive spirometry and 6.79(m) for aerobic capacity (p<0.05, CI =95%). Pre and post mean scores of scapular index, chest expansion, inspiratory hold time and 6 minute walk test reveals that scapular retraction exercises has a positive impact on improving shoulder alignment, pulmonary function, and aerobic capacity Conclusion: Scapular retraction exercises is effective in improving shoulder alignment, pulmonary function and aerobic capacity in subjects with Forward shoulder posture KEY WORDS: Forward shoulder posture, rounded shoulder, pulmonary function, aerobic capacity, scapular retraction exercises, lung volume.

Vibration damping capacity of deep cryogenic treated AISI 4140 steel shaft supported by rolling element bearings

The main objective of the present study is to experimentally investigate and figure out the effect of deep cryogenic treatment in improving dynamic behaviors in terms of damping of a rotating shaft supported by rolling element bearings. An AISI 4140 steel for rotating shafts was selected for the experiments because it is the most widely used material in most industries for a wide range of applications such as machinery components, crankshafts, motor shafts, axle shafts, and railway locomotive traction motor shafts. Untreated, conventionally heat treated, deep cryogenic treated, and deep cryogenic treated and tempered shafts were used for the experiments to observe damping behavior changes of the shafts. Deep cryogenic treated and deep cryogenic treated and tempered shafts were cooled from pre-tempering temperature to -140 °C and held for tempering hold times of 12, 24, 36, and 48 hours. So, ten sets of shafts were employed for the experiment. The vibration data was captured for each of the shafts for five different shaft running speeds 600, 1200, 1800, 2400 and 3000 rpm. The results showed that damping ability of the deep cryogenic treated shaft at a hold time of 36 hours was superior to that of the others shafts.

A Variation-aware Hold Time Fixing Methodology for Single Flux Quantum Logic Circuits

Single flux quantum (SFQ) logic is a promising technology to replace complementary metal-oxide-semiconductor logic for future exa-scale supercomputing but requires the development of reliable EDA tools that are tailored to the unique characteristics of SFQ circuits, including the need for active splitters to support fanout and clocked logic gates. This article is the first work to present a physical design methodology for inserting hold buffers in SFQ circuits. Our approach is variation-aware, uses common path pessimism removal and incremental placement to minimize the overhead of timing fixes, and can trade off layout area and timing yield. Compared to a previously proposed approach using fixed hold time margins, Monte Carlo simulations show that, averaging across 10 ISCAS’85 benchmark circuits, our proposed method can reduce the number of inserted hold buffers by 8.4% with a 6.2% improvement in timing yield and by 21.9% with a 1.7% improvement in timing yield.