The dynamic stability is studied for thin-walled structural elements with variable stiffness subjected to periodically alternating axial force in this paper. Here, the VARIATION STIFFUESS means that it changes with periodically alternating axial force as for nonlinear geometry STIFFUESS matrix of thin-walled member. Damping is considered and the governing equations are expressed in terms of a system of two second-order differential equations of the Mathieu type, with periodic coefficients. MATLAB package is used to determine the stability boundary. Numerical example is presented for the dynamic stability boundary of a simply supported beam with I-shaped cross section. Comparison is made with finite element analysis. Considered damping, some conclusions are drawn out: Excited zone of thin-walled member is continuous, the dynamic instability is highly dominant in the first region while the second and third instability regions are of much less practical importance; The larger the ratio of damp, the less the dynamic instability region; The larger the ratio of damp, the more time dependent components of the load wanted, absorption of damping is commonly of no effect to prevent parametrically excited vibration from dynamic instability; Parametrically excited vibration considering damping is much more different from damped forced vibration in nature.

This paper reports an experimental investigation involving 29 rock cores obtained from 6 boreholes drilled to various depths, up to 67.00m, in a major construction site in the United Arab Emirates as part of a ground investigation. The tested rock materials included sandstone, mudstone and calcarenite.The rock cores were prepared and tested to determine the unconfined compressive strength and the full axial and diametric stress-strain relationship using strain gauges. The deformability measurements were carried out according to the suggested methods for rock testing ISRM [1].The secant modulus and Poisson's ratio were determined from the average slope of the axial and circumferential stress-strain curve at 50% of the ultimate compressive strength. The unconfined compressive strength of the majority of the cores was found to be in the range 0.5 to 8.7Mpa,which is traditionally associated with weak rocks. A reasonable correlation between the compressive strength, secant modulus and Ultrasonic Pulse Velocity was found. However, no relationship between the axial and diametric stiffness was revealed. The testing programme highlighted the difficulties in preparing, testing and interpreting the test results of such weak rock materials.

A characteriation of continuity of the p-L-VARIATION function is given and the Helly’s selection principle for LBV(p) functions is established. A characterization of the inclusion of Waterman-Shiba classes into classes of functions with given integral modulus of continuity is given. A useful estimate on modulus of VARIATION of functions of class LBV(p) is found.

Multivariate control charts such as Hotelling's T2 and X2 are commonly used for monitoring several related quality characteristics. These control charts use correlation structure that exists between quality characteristics in an attempt to improve monitoring. The purpose of this article is to discuss some issues related to the G chart proposed by Levinson et al. [9] for detecting shifts in the process variance-covariance matrix. They use a G statistic which is distributed as a chi-square with p(p+1)/2 degrees of freedom where p denotes the number of variables under study. The authors show through simulation that the chi-square distribution only holds for certain cases. The results could be important to practitioners who use G chart for monitoring purposes.

Background: Treatment recommendations for trapeziometacarpal (TMC) arthrosis are highly variable from surgeon to surgeon. This study addressed the influence of viewing radiographs on a decision to offer surgery for TMC arthrosis. Methods: In an online survey, 92 hand surgeons viewed clinical scenarios and were asked if they would offer surgery to 30 patients with TMC arthrosis. Forty-two observers were randomly assigned to review clinical information alone and 50 to review clinical information as well as radiographs. The degree of limitation of daily activities, time since diagnosis, prior treatment, pain with grind, crepitation with grind, and metacarpal adduction with metacarpophalangeal hyperextension were randomized for each patient scenario to determine the influence of these factors on offers of surgery. A cross-classified binary logistic multilevel regression analysis identified factors associated with surgeon offer of surgery. Results: Surgeons were more likely to offer surgery when they viewed radiographs (42% vs. 32%, P = 0. 01). Other factors associated VARIATION in offer of surgery included greater limitation of daily activities, symptoms for a year, prior splint or injection, deformity of the metacarpophalangeal joint. Factors not associated included limb dominance, prominence of the TMC joint, crepitation with the grind test, and pinch and grip strength. Conclusion: Surgeons that view radiographs are more likely to offer surgery to people with TMC arthrosis. Surgeons are also more likely to offer surgery when people do not adapt with time and nonoperative treatment. Given the notable influence of surgeon bias, and the potential for surgeon and patient impatience with the adaptation process, methods for increasing patient participation in the decision-making process merit additional attention and study.