Numerical study of wind profiles over simplified water waves

Cao, Shuyang,Zhang, Enzhen,Sun, Liming,Cao, Jinxin Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.3

Vertical profiles of mean and fluctuating wind velocities over water waves were studied, by performing Large-Eddy Simulations (LES) on a fully developed turbulent boundary layer over simplified water waves. The water waves were simplified to two-dimensional, periodic and non-evolving. Different wave steepness defined by $a/{\lambda}$ (a : wave amplitude; ${\lambda}$ : wavelength) and wave age defined by $c/U_b$ (c: phase velocity of the wave; $U_b$ : bulk velocity of the air) were considered, in order to elaborate the characteristics of mean and fluctuating wind profiles. Results shows that, compared to a static wave, a moving wave plays a lesser aerodynamic role as roughness as it moves downstream slower or a little faster than air, and plays more aerodynamic roles when it moves downstream much faster than air or moves in the opposite direction to air. The changes of gradient height, power law index, roughness length and friction velocity with wave age and wave amplitude are presented, which shed light on the wind characteristics over real sea surfaces for wind engineering applications.

Numerical study of wind profiles over simplified water waves

Shuyang Cao,Enzhen Zhang,Liming Sun,Jinxin Cao 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.3

Vertical profiles of mean and fluctuating wind velocities over water waves were studied, by performing Large-Eddy Simulations (LES) on a fully developed turbulent boundary layer over simplified water waves. The water waves were simplified to two-dimensional, periodic and non-evolving. Different wave steepness defined by a /λ ( a : wave amplitude; λ : wavelength) and wave age defined by c/Ub (c: phase velocity of the wave; Ub : bulk velocity of the air) were considered, in order to elaborate the characteristics of mean and fluctuating wind profiles. Results shows that, compared to a static wave, a moving wave plays a lesser aerodynamic role as roughness as it moves downstream slower or a little faster than air, and plays more aerodynamic roles when it moves downstream much faster than air or moves in the opposite direction to air. The changes of gradient height, power law index, roughness length and friction velocity with wave age and wave amplitude are presented, which shed light on the wind characteristics over real sea surfaces for wind engineering applications.

Case Study on Rock Support Technology for Roadways Based on Characteristics of Plastic Area

Chao Yuan,Liming Cao,Wenjun Wang,Lei Fan,Cong Huang 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.2

Rocks surrounding deep, high-stress roadways typically undergo a vicious cycle of destruction → repair → re-destruction → re-repair over a long time. This article uses the roadway restoration project of Pingmei Mine No. 6 (400 m underground) as research object. Starting from the plastic area, the characteristics of the distribution of rock surrounding the circular roadway are analyzed, and the influence of the side pressure coefficient, cohesive force, inside friction angle, support strength, and roadway radius on the plastic area is studied. Four types of distribution patterns were observed in rocks surrounding the plastic area of the roadway: round, oval, rounded rectangle, and butterfly. The side pressure coefficient, cohesive force, and inside friction angle affected the distribution and range of rocks surrounding the plastic area of the roadway. The support radius of the roadway and the support strength of its face did not change the distribution of the plastic area, but only affected its size. Therefore, to maintain the long-term stability of weak and broken roadways, the strength of the surrounding rocks must be increased, and roadway renovation should be avoided as it affects the distribution of the plastic area and reduces its scope. Engineering practice has shown that the “anchor net spray + hollow grouting anchor cable” technology for the combined, step-by-step repair and support of roadways, with a hollow grouting anchor cable as core, can suppress the distribution and scope of the plastic area to guarantee safe and long-term use of the roadway.

Frequency and magnetic properties in the range of 10 kHz to 100 MHz for nanocrystal Fe -Co alloy

Yongsheng Liu,Jincang Zhang,Liming Yu,Guangqiang Jia,Yufeng Zhang,Xinyan Wang,Shixun Cao 한국물리학회 2004 Current Applied Physics Vol.4 No.5

Fe-based soft magnetic alloy with Co-doping was fabricated by high-energy milling. The X-ray diraction (XRD) results exhibita single phased structure,which could be regarded as BCC-like FeCo solid solution,was formed. Moreover,it has also been demonstrated that a nanocrystalline FeCo alloy was obtained and the evaluated grain sizes were about 712 nm. The frequency dependence of the initial permeability and magnetic losses,as well as DC-magnetization measurements,was systematically studiedthen. The results show that thefn (fn is the frequency when the curve of the No.n sample has a minimum value) shifts to the higherfrequency with the increasing Co content in the range of 10 kHz to 100 MHz,while the magnetic losses of the samples decrease withthe increasing Co content at the high frequency (800 kHz to 20 MHz). The Co-doping increases the cut-o frequencies of thesamples and makes the initial permeability to keep a constant value in a wider frequency range. The corresponding peak value of theinitial permeability as function of Co-doping concentration turns to the region of low Co concentration. For the long milling time,the loss apparently decreases beyond 1 MHz.

Effect of fabrication conditions on I-V properties for ZnO varistor with high concentration additives by sol-gel technique

Jincang Zhang,Shixun Cao,Ruiying Zhang,Liming Yu,Chao Jing 한국물리학회 2005 Current Applied Physics Vol.5 No.4

Polycrystalline nano-grain-boundary multi-doping ZnO-based nonlinear varistors with higher concentration additives have beenfabricated by solgel and standard solid-state reaction method, of which the best sample has a very high threshold voltage ofEb ¼ 3300 V/mm. The eect of sintering processes, sintering temperature and sintering time, and that of additive concentration ofBi2O3 on Eb of the samples are systematically investigated. The results show that the great merit of solgel method is its highthreshold voltage obtained by a lower sintering temperature than the solid-state reaction method. The present work also shows thatve phases including solid-state sintering, rich Bi liquid phase formation and ZnO as well as other additive dissolution, ZnO graingrowth, the secondary phase sucient formation and evolution have been experienced at dierent sintering temperatures. The holetype defect and nonhomogeneity of the microstructure will lead to the decrease of threshold voltage, i.e., the grain size and thehomogeneity of the material will be important factors and directly aect the characteristic of the varistor. The sintering charac-teristic and the inuence of Bi2O3 content on the threshold voltage are also discussed..

Extreme Value Prediction of Traffic Loads Using the Average Conditional Exceedance Rate Method

Liping Zhang,Jianqing Bu,Liming Zhou,Wenlong Cao,Cunbao Zhao,Wei Chai 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.12

An efficient prediction of the extreme value of traffic loads is crucial for the structural design, reliability evaluation, maintenance planning, and further life-cycle cost analysis of bridges. In this work, a novel method is proposed for predicting the appropriate extreme traffic load distribution. Specifically, the average conditional exceedance rate (ACER) statistical model is estimated from the historical traffic loads which was collected through a weigh-in-motion system installed in toll stations. The basic idea of the ACER approach lies in the introduction of a cascade of conditioning approximations and the average exceedance rate to capture the dependence effects and obtain the data tail, the trend features of which are fitted with a similar Gumbel distribution function and extrapolated to the concerned level. An illustration case dealing with traffic loads using the ACER strategy is presented, the extreme value and confidence interval (CI) in any return period can be predicted by application of this approach. Furthermore, the peaks-over-threshold (POT) method based on the asymptotic extreme theory is also applied to illustrate the advantages of the ACER method. The ACER method has advantages in analyzing extreme traffic loads, with good robustness and the ability to handle extreme value prediction for different sampling strategies, it also can produce more accurate confidence intervals and predicts consistent extreme values. The study results are expected to help accurately determine traffic loads and ensure safety in bridge engineering.

Fe-curcumin Nanozyme-Mediated Immunosuppression and Anti-inflammation in Experimental Autoimmune Uveitis

Zhengxuan Jiang,Kun Liang,Xiang Gao,Fan Cao,Guangqi An,Siyu Gui,Weiwei Tang,Liping Du,Liming Tao,Xianwen Wang 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background EAU is an inflammatory disease usually characterized by autoinflammation and autoimmunity and is aggravated by excessive generation of ROS. Conventional hormone therapy often has more adverse effects. It is urgent to find a therapeutic drug with higher efficiency and fewer adverse effects. Methods We developed an Fe-curcumin nanozyme in which natural antioxidants coordinate with Fe3+ to form nanoparticles with excellent solubility for directing anti-inflammatory and ROS scavenging effects to treat EAU. Several experiments were used to detect the characteristics of nanozymes. EAU model rats were used to detect the abilities of decreasing autoinflammation and autoimmunity. PBMCs were used to detect the ability to inhibit cell proliferation. Results Free radical scavenging experiments showed that nanozymes decreased the level of free radicals at low concentrations. In vitro and in vivo experiments revealed that the group treated with Fe-curcumin nanozymes had lower inflammatory reactions and ROS levels than the control group, as reflected by the downregulated levels of several critical inflammatory cytokines, such as IFN-γ, IL-17, and TNF-α; decreased H2O2 release; inhibited proliferation of Th1 and Th17 cells; and alleviated pathological changes in the eye. Importantly, the Fe-curcumin nanozyme was detected in the retina using Prussian blue staining. Additionally, Fe-curcumin nanozyme is noncytotoxic when directing these biological activities. Conclusion This study has demonstrated the feasibility of using the Fe-curcumin nanozyme as a nanodrug to inhibit inflammatory reactions and scavenge ROS in the treatment of EAU, indicating that it may serve as a promising therapeutic agent in clinical treatment.