Hasil untuk "cond-mat.soft"

Micheál J. Cahill, J. Oliver, J. Cronin et al.

Abstract Cahill, MJ, Oliver, JL, Cronin, JB, Clark, KP, Cross, MR, and Lloyd, RS. Sled-push load-velocity profiling and implications for sprint training prescription in young athletes. J Strength Cond Res 35(11): 3084–3089, 2021—Resisted sled pushing is a popular method of sprint-specific training; however, little evidence exists to support the prescription of resistive loads in young athletes. The purpose of this study was to determine the reliability and linearity of the force-velocity relationship during sled pushing, as well as the amount of between-athlete variation in the load required to cause a decrement in maximal velocity (Vdec) of 25, 50, and 75%. Ninety (n = 90) high school, male athletes (age 16.9 ± 0.9 years) were recruited for the study. All subjects performed 1 unresisted and 3 sled-push sprints with increasing resistance. Maximal velocity was measured with a radar gun during each sprint and the load-velocity (LV) relationship established for each subject. A subset of 16 subjects examined the reliability of sled pushing on 3 separate occasions. For all individual subjects, the LV relationship was highly linear (r > 0.96). The slope of the LV relationship was found to be reliable (coefficient of variation [CV] = 3.1%), with the loads that cause a decrement in velocity of 25, 50, and 75% also found to be reliable (CVs = <5%). However, there was large between-subject variation (95% confidence interval) in the load that caused a given Vdec, with loads of 23–42% body mass (%BM) causing a Vdec of 25%, 45–85 %BM causing a Vdec of 50%, and 69–131 %BM causing a Vdec of 75%. The Vdec method can be reliably used to prescribe sled-push loads in young athletes, but practitioners should be aware that the load required to cause a given Vdec is highly individualized.

A. J. Scala, C. Sanna, Edoardo Signorini

Abstract Recently, Blanco-Chacón proved the equivalence between the Ring Learning With Errors and Polynomial Learning With Errors problems for some families of cyclotomic number fields by giving some upper bounds for the condition number Cond(Vn) of the Vandermonde matrix Vn associated to the nth cyclotomic polynomial. We prove some results on the singular values of Vn and, in particular, we determine Cond(Vn) for n = 2kpℓ, where k, ℓ ≥ 0 are integers and p is an odd prime number.

S. Chowdhury, T. Husain

In this research, multivariate statistical analysis was performed on twenty water quality parameters (WQP) collected on tri-monthly basis (four times/year) from 441 drinking water sources in Newfoundland and Labrador (NL), Canada for 18 years (1999-2016). The WQP included alkalinity (Alk), color (Col), conductivity (Cond), hardness (Hard), pH, total dissolved solids (TDS), turbidity (Turb), bromide (Br), calcium (Ca), chloride (Cl), fluoride (F), potassium (K), sodium (Na), sulfate (SO4), dissolved organic carbon (DOC), ammonia (NH3), nitrate (NO3), Kjeldahl nitrogen (N), total phosphorus (P) and magnesium (Mg). The assessment was conducted on surface water (SWS) and groundwater (GWS) sources separately. In SWS and GWS, number of samples analyzed for each WQP were in the ranges of 3434-6057 and 1915-1919 respectively. Averages of DOC and pH showed increasing trends (SWS: DOC = 0.0722 mg/L/year; pH = 0.0375 units/year; GWS: DOC = 0.0491 mg/L/year; pH = 0.0441 units/year) while the other WQP showed variable characteristics, which could increase treatment cost and deteriorate tap water quality. Strong correlations were observed for Ca-Hard (r = 0.97-0.98), TDS-Cond (r = 0.91-0.99) and Na-Cl (r = 0.87-0.96). In SWS, Alk had stronger correlations with Cond, Hard, pH, TDS, Ca and Mg (r = 0.62-0.94) than GWS (r = 0.56-0.63). Principal Component Analysis revealed separate clusters for DOC-Col, Na-Cl, TDS-Cond, Ca-Alk and Mg-Hard, indicating that these WQP moved together. In SWS and GWS, six principal components were significant (eigenvalue ≥ 1.0), and explained 74.8% and 72.9% of overall variances respectively. In Factor Analysis, six varifactors explained 73.4% and 70.5% of total variances in SWS and GWS respectively. For SWS and GWS, eleven and ten WQP, respectively explained these variances, indicating 45% and 50% data reduction respectively. The findings can assist in controlling water quality through monitoring reduced number of WQP, which is likely to minimize the monitoring cost.

C. Latella, Daniel J. van den Hoek, W. Teo

Latella, C, van den Hoek, D, and Teo, WP. Differences in strength performance between novice and elite athletes: Evidence from powerlifters. J Strength Cond Res XX(X): 000-000, 2018-Strength forms an integral part of many sports. In particular, powerlifting success is determined solely by maximal strength, providing a unique opportunity to investigate the differences and potential factors influencing novice and elite competitors. We evaluated performance from 2,137 competitors between local (LOC), national (NAT), and international (INT) competitions. Results were analyzed by using the total (TOT) competition score within weight classes and age categories. Cohen's d effect sizes and 95% confidence intervals were used to detect differences within categories between LOC, NAT, and INT competitions. The coefficient of variation (CV) was used to determine the absolute variability. A moderate to large increase in performance was observed for all weight classes between LOC and NAT (men; d = 0.76, women; d = 1.09). No meaningful differences were observed between LOC and NAT, and NAT and INT when compared using age. No meaningful differences were observed between NAT to INT competitions when compared using weight classes. The CV was not different across competition level (CV = 17.4-22.9%) categories. Several internal (athlete) and external (environmental) factors are likely to explain these findings. Therefore, factors such as training experience, performance variability, body composition, anthropometric characteristics, and competition pressure that may influence strength performance should also be considered in both training phases and during competition. Collectively, the results offer novel information regarding the difference in strength performance between novice, subelite, and elite strength athletes. Strength and conditioning professionals should consider these factors when working with various athletes where maximal strength is an important determinant of success.

D. Dobrosielski, Kyle M. Leppert, N. Knuth et al.

X. Freixa, N. Bellera, J. Ortiz-Perez et al.

Naoki Ikeda, T. Ryushi

Ikeda, N and Ryushi, T. Effects of 6-week static stretching of knee extensors on flexibility, muscle strength, jump performance, and muscle endurance. J Strength Cond Res XX(X): 000-000, 2018-The purpose of this study was to evaluate the changes in flexibility and muscular performance after stretching training for 6 weeks. Twelve healthy young men were assigned to a stretching group and 13 to a control group. The participants of the stretching group performed static stretching of knee extensors for 6 weeks. Knee flexion range of motion (KFROM), leg extension strength, rate of force development (RFD) in leg extension, jump performance (squat and countermovement jump height, and index of rebound jump), and strength decrement index of 50 repetitions of isokinetic knee extension (muscle endurance) were measured before and after the interventions. In the stretching group, KFROM significantly increased from 145.2 ± 17.3 to 158.7 ± 6.3° (p < 0.05), whereas RFD significantly improved from 10,173 ± 2,401 to 11,883 ± 2,494 N·s (p < 0.05). By contrast, leg extension strength and jump performance of each jump type did not improve significantly. Furthermore, muscle endurance decreased significantly. All variables remained unchanged in the control group. In conclusion, 6 weeks of stretching training of knee extensors improved KFROM and RFD in leg extension, but not leg extension strength and jump performance; moreover, muscle endurance decreased. These findings indicate that this stretching training protocol can be used by athletes in sports who require high flexibility and those who require high-power exertion.

Alex T. Coyle, R. Spragg, Armen N. Amirkhanian et al.

L. Wallace, Katie Slattery, A. Coutts

A. Zagatto, W. R. Beck, C. Gobatto

A. Dellal, Stephen V. Hill-Haas, C. Lago‐Peñas et al.

B. C. Nairn, C. Sutherland, Janessa D M Drake

Fernaz Narin Nur, Selina Sharmin, Md. Ahsan Habib et al.

In directional wireless sensor networks (DSNs), sensor nodes with directional antennas provide extended network lifetime and better coverage performance. However, one of the key challenges of directional nodes is to discover their neighbors due to difficulty in achieving synchronization among their directed transmissions and receptions. Existing solutions suffer from high discovery latency and poor percentage of neighbor discovery either due to lack of proper coordination or centralized management of the discovery operation. In this work, we develop a collaborative neighbor discovery (COND) mechanism for DSNs. Each COND node polls to directly discover its neighbors in a distributed way and collaborates with the already discovered nodes so as to allow indirect discovery. It helps to increase the neighbor discovery performance significantly. A Markov chain-based analytical model is developed to quantify theoretical performances of the proposed COND system. The performance of the COND system is evaluated in Network Simulator Version 3, and simulation results reveal that it greatly reduces the discovery latency and increases neighbor discovery ratio compared to state-of-the-art approaches.

G. Mangine, Kevin Huet, Cassie M. Williamson et al.

Abstract Mangine, GT, Huet, K, Williamson, C, Bechke, E, Serafini, P, Bender, D, Hudy, J, and Townsend, J. A resisted sprint improves rate of force development during a 20-m sprint in athletes. J Strength Cond Res 32(6): 1531–1537, 2018—This study examined the effect of a resisted sprint on 20-m sprinting kinetics. After a standardized warm-up, 23 (male = 10, female = 13) Division I basketball players completed 3 maximal 20-m sprint trials while tethered to a robotic resistance device. The first sprint (S1) used the minimal, necessary resistance (1 kg) to detect peak (PK) and average (AVG) sprinting power (P), velocity (V), and force (F); peak rate of force production (RFD) was also calculated. The second sprint (S2) was completed against a load equal to approximately 5% of the athlete's body mass. Minimal resistance (1 kg) was again used for the final sprint (S3). Approximately 4–9 minutes of rest was allotted between each sprint. Separate analyses of variance with repeated measures revealed significant (p ⩽ 0.05) main effects for all sprinting kinetic measures except VPK (p = 0.067). Compared with S1, increased (p < 0.006) 20-m sprint time (3.4 ± 4.9%), PAVG (115.9 ± 33.2%), PPK (65.7 ± 23.7%), FAVG (134.1 ± 34.5%), FPK (65.3 ± 16.2%), and RFD (71.8 ± 22.2%) along with decreased (p < 0.001) stride length (−21 ± 15.3%) and VAVG (−6.6 ± 4.6%) were observed during S2. During S3, only RFD was improved (5.2 ± 7.1%, p < 0.001) compared with S1. In conclusion, completing a short, resisted sprint with a load equating to 5% of body mass before a short sprint (∼20-meters) does not seem to affect sprinting time or kinetics. However, it does appear to enhance RFD.

James L. Nuzzo, J. Anning, Jessica Scharfenberg

J. Krieger

T. Sattler, D. Sekulić, V. Hadžić et al.

J. Abt, J. Oliver, T. Nagai et al.

E. Jeckelmann

In their Comment (see cond-mat/0301237), Sandvik, Sengupta, and Campbell present some numerical evidences to support the existence of an extended bond-order-wave (BOW) phase at couplings (U,V) weaker than a tricritical point (U_t,V_t) in the ground state phase diagram of the one-dimensional half-filled U-V Hubbard model. They claim that their results do not agree with the phase diagram proposed in my Letter (cond-mat/0204244), which shows a BOW phase for couplings stronger than the critical point only. However, I argue here that their results are not conclusive and do not refute the phase diagram described in the Letter.

A. Drăgulescu, V. Yakovenko

In this short paper, we overview and extend the results of our papers cond-mat/0001432, cond-mat/0008305, and cond-mat/0103544, where we use an analogy with statistical physics to describe probability distributions of money, income, and wealth in society. By making a detailed quantitative comparison with the available statistical data, we show that these distributions are described by simple exponential and power-law functions.