Hierarchical Life-Cycle Design of Concrete Structures

Concrete structures’ service life lasts decades. In order to deal with all the probable degradations and deteriorations in the whole life span, the concept of concrete structures’ Life-Cycle Design was introduced into China in the 1980s. However, until this day, Life-Cycle Design is still more of a concept to most structure designers and engineers, rather than a practical method. This paper provides a hierarchical method for concrete structures’ Life-Cycle Design, in which the design process is divided into five levels. Safety should be the fundamental requirements for all concrete structures, so as to guarantee a reliable quality. For structures located in severe environments, durability design is necessary so as to ensure the designed service life. Further, when specific economic requirements are set for concrete structures, life-cycle cost (LCC) should be considered carefully in selecting the optimal scheme. Besides, those concrete structures designed to be environmental-friendly should also take into account the specific environmental assessment criteria. Nowadays, user-friendly schemes have attracted increasing attention too; therefore, customers’ demands should also be fully involved in the design process. Considering all the design levels mentioned above, diverse designing criteria are provided accordingly. This paper also uses a road bridge member which exposed to chloride attack in marine environment as an example to illustrate this hierarchical design method. Using the life-cycle-based hierarchical design method, a probable scheme that is safe, durable, economic, environmental friendly, and user friendly is provided

Simulation for field emission images of micrometer-long SWCNTs

The electron distribution of open-ended single-walled carbon nanotubes with chirality indexes (7,0) and (5,5) in the field emission conditions was calculated via a multi-scaled algorithm. The field emission images were produced numerically. It was found that the emission patterns change with the applied macroscopic field. Especially, the symmetry of the emission pattern of the (7,0) carbon nanotube is breaking in the lower field but the breaking is less obvious in the higher field. The enlargement factor increases with the applied macroscopic field.Comment: 8 pages, 4 figure

Global Well-Posedness and Long Time Decay of Fractional Navier-Stokes Equations in Fourier-Besov Spaces

We study the Cauchy problem of the fractional Navier-Stokes equations in critical Fourier-Besov spaces FB˙p,q1-2β+3/p′. Some properties of Fourier-Besov spaces have been discussed, and we prove a general global well-posedness result which covers some recent works in classical Navier-Stokes equations. Particularly, our result is suitable for the critical case β=1/2. Moreover, we prove the long time decay of the global solutions in Fourier-Besov spaces

Atomic decoration for improving the efficiency of field electron emission of carbon nanotubes

The field electron emission from the single-walled carbon nanotubes with their open ends terminated by -BH, -NH, and -O has been simulated. The apex-vacuum barrier and the emission current have been calculated. It has been found that -BH and -NH suppress the apex-vacuum barrier significantly and lead to higher emission current in contrast to the -O terminated structure in the same applied field. The calculated binding energy implies that the carbon nanotubes terminated with -BH and -NH are more stable than those saturated by oxygen atoms or by hydrogen atoms.Comment: 8 pages, 9 figures, LaTeX; content changed, typos corrected, references adde

Screening effects on field emission from arrays of (5,5) carbon nanotubes: Quantum-mechanical simulation

The simulation of field electron emission from arrays of micrometer-long open-ended (5, 5) carbon nanotubes is performed in the framework of quantum theory of many electrons. It is found that the applied external field is strongly screened when the spacing distance is shorter than the length of the carbon nanotubes. The optimal spacing distance is two to three times of the nanotube length, slightly depending on the applied external fields. The electric screening can be described by a factor that is a exponential function of the ratio of the spacing distance to the length of the carbon nanotubes. For a given length, the field enhancement factor decreases sharply as the screening factor larger than 0.05. The simulation implies that the thickness of the array should be larger than a value but it does not help the emission much by increasing the thickness a great deal

Calycosin regulates glucocorticoid-induced apoptosis via Nrf2/ARE signaling in MC3T3-E1 cells

Purpose: To determine the anti-osteoporotic effect of calycosin (CA) and investigate the mechanism involved.Methods: To establish a cell model of osteoporosis, MC3T3-E1 cells were treated with dexamethasone (DEX). Subsequently, the levels of accumulated reactive oxygen species (ROS) and subsequent apoptotic cell death (using flow cytometry) were determined. Relevant mRNA and protein expression levels were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunoblot respectively.Results: CA reduced the apoptosis and accumulation of ROS in DEX-treated cells. DEX induced the expression of caspase-3/-8/-9 in the cleavage of poly ADP-ribose polymerase (PARP), whereas CA treatment decreased expression levels of caspase-3/-8/-9 and PARP. In addition, DEX treatment significantly suppressed the expression of nuclear factor-erythroid 2-related factor 2 (Nrf2) as well as its downstream targets, viz, heme oxygenase-1 and quinone oxidoreductase-1. Interestingly, CA treatment reversed this suppressive effect. It was also found that Nrf2 small interfering RNA effectively inhibited the protective effects of CA against DEX-induced ROS overproduction as well as apoptosis.Conclusion: CA attenuates the cytotoxicity of DEX via inhibition of the generation of ROS and promotion of Nrf2 expression. These findings offer novel insights into a molecular approach to the treatment of glucocorticoid-induced osteoporosis via the application of natural compounds.Keywords: Calycosin, Osteoporosis, Nrf2, Antioxidant response elements, Apoptosi

Parallel STEPS: Large Scale Stochastic Spatial Reaction-Diffusion Simulation with High Performance Computers

Stochastic, spatial reaction-diffusion simulations have been widely used in systems biology and computational neuroscience. However, the increasing scale and complexity of models and morphologies have exceeded the capacity of any serial implementation. This led to the development of parallel solutions that benefit from the boost in performance of modern supercomputers. In this paper, we describe an MPI-based, parallel operator-splitting implementation for stochastic spatial reaction-diffusion simulations with irregular tetrahedral meshes. The performance of our implementation is first examined and analyzed with simulations of a simple model. We then demonstrate its application to real-world research by simulating the reaction-diffusion components of a published calcium burst model in both Purkinje neuron sub-branch and full dendrite morphologies. Simulation results indicate that our implementation is capable of achieving super-linear speedup for balanced loading simulations with reasonable molecule density and mesh quality. In the best scenario, a parallel simulation with 2,000 processes runs more than 3,600 times faster than its serial SSA counterpart, and achieves more than 20-fold speedup relative to parallel simulation with 100 processes. In a more realistic scenario with dynamic calcium influx and data recording, the parallel simulation with 1,000 processes and no load balancing is still 500 times faster than the conventional serial SSA simulation