Study on semi-active control of mega-sub controlled structure by MR damper subject to random wind loads

The recently proposed mega-sub controlled structure （MSCS）, a new type of structure associated with the design and construction of super-tall buildings, has attracted the attention of designers for use in enhancing the control effectiveness in mega-frame buildings. In this paper, a dynamic equation and method to assemble parameter matrixes for a mega-sub controlled structure under random wind loads is presented. Semi-active control using magnetorheological dampers for the MSCS under random wind loads is investigated, and is compared with a corresponding system without dampers. A parametric study of the relative stiffness ratio and relative mass ratio between the mega-frame and the substructures, as well as the additional column stiffness ratio that influences the response control effectiveness of the MSCS, is discussed. The studies reveal, for the first time, that different control mechanisms exist. The results indicate that the proposed structure employing semi-active control can offer an effective control mechanism. Guidelines for selecting parameters are provided based on the analytical study.

Relationship between Neutrophil-to-Lymphocyte Ratio and Pulse Wave Velocity in Young Patients with Systemic Lupus Erythematosus

Background： The incidence of atherosclerosis-related myocardial infarction can be as much as 50-fold greater in young patients with systemic lupus e~,thematosus （SLE） than in age-matched controls. There are several explanations for this phenomenon, all of which result in a chronic state of low-grade inflammation. Recently, the neutrophil-to-lynlphocyte ratio （NLR） has been proposed as a useliil biomarker of inflammation. Pulse wave velocity （PWV） is a reliable indicator of vascular damage and atherosclerosis. There is a paucity of data concerning the relationship between NLR and atherosclerosis as measured by PWV in patients with SLE. This study aimed to verify whether there is a positive correlation between NLR and PWV and to explore factors that influence PWV in young SLE patients. Methods： A total of 90 female patients with SLE were enrolled in this cross-sectional investigation. Traditional and nontraditional cardiovascular risk factors were assessed on the same day that brachial-ankle PWV （baPWV） was examined. The patients were divided into three groups according to their mean baPWV values： patients whose mean baPWV value was lower than the first tertile were placed in Group 1 ： patients whose mean baPWV value was between the first tertile and the second tertile were placed in Group 2： and patients whose mean baPWV value was higher than the second tertile were placed in Group 3. SPSS 20.0 was used to perform all statistical analyses in this study. Both univariate linear regression and multivariate regression models were utilized to analyze the association between NLR and arterial stiffness. Results： Systolic blood pressure, diastolic blood presstire （DBP）. and triglycerides were all significantly different among Groups 1,2, and 3 （ 111.90 ± 12.85 mmHg vs. 114.60 ± 12.88 mmHg vs. 129.43 ±16.21 mmHg, P 〈 0.001 ： 68.77 ± 8.63 mmHg vs. 71.87 ± 9.77 mmHg vs. 82.57 ± 14.89 mmHg, P 〈 0.001 ; and 1.44 [0.91-2.47] mmol/L vs. 0.98 [0.78-1.26] mmol/L vs. 2.20 [0.94-3.66] mmol/L P = 0.030： respectively）, as were creatinine （57.50 [52.00-69.00] mmol/L vs. 55.50 [49.00-64.00] mmol/L vs. 64.00 [56.00-86.00] mmol/L P = 0.045） and blood urea nitrogen （4.27 [3.79-6.22] mmol/L vs. 4.16 [3.47-4.84] mmol/L vs. 5.88 [4.04-8.19] mmol/L, P = 0.011 ）. NLRs were significantly different among Groups 1, 2, and 3 （2.16 [1.56-3.42] vs. 3.12 [1.91-4.19] vs. 5.29 [2.63-7.25], P = 0.001）. N LR, together with DBP and the SLE disease activity index, independently predicts PWV. Conclusions： This study demonstrated that there was a positive correlation between NLR and PWV. Moreover, we found that disease activity and DBP were also positively correlated with PWV.

Discrete element modeling of the effect of particle size distribution on the small strain stiffness of granular soils

Discrete element modeling was used to investigate the effect of particle size distribution on the small strain shear stiffness of granular soils and explore the fundamental mechanism controlling this small strain shear stiffness at the particle level. The results indicate that the mean particle size has a negligible effect on the small strain shear modulus. The observed increase of the shear modulus with increasing particle size is caused by a scale effect. It is suggested that the ratio of sample size to the mean particle size should be larger than 11.5 to avoid this possible scale effect. At the same confining pressure and void ratio, the small strain shear modulus decreases as the coefficient of uniformity of the soil increases. The Poisson＇s ratio decreases with decreasing void ratio and increasing confining pressure instead of being constant as is commonly assumed. Microscopic analyses indicate that the small strain shear stiffness and Poisson＇s ratio depend uniquely on the soil＇s coordination number.

Fatigue crack propagation of new aluminum lithium alloy bonded with titanium alloy strap

A new type of aluminum lithium alloy （Al–Li alloy） Al–Li–S–4 was investigated by test in this paper. Alloy plate of 400 mm · 140 mm · 6 mm with single edge notch was made into samples bonded with Ti–6Al–4V alloy （Ti alloy） strap by FM 94 film adhesive after the surface was treated. Fatigue crack growth of samples was investigated under cyclic loading with stress ratio （R） of 0.1 and load amplitude constant. The results show that Al–Li alloy plate bonded with Ti alloy strap could retard fatigue crack propagation. Retardation effect is related with width and thickness of strap. Flaws have an observable effect on crack propagation direction.