Crack analysis of concrete beams based on pseudo-discrete crack model

Crack widths are important considerations in both serviceability and durability design of concrete structures and should be evaluated to ensure compliance with design limits. However, existing empirical formulas for maximum crack width prediction are discrepant with each other, and they cannot reveal key information such as crack number and crack spacing. To obtain such information, finite element analysis has to be adopted. However, conventional finite element analysis has its limits in carrying out crack analysis. Particularly, the common smeared crack models, which do not realistically reflect bond-slip of reinforcing bars, would not give correct crack widths. In contrast, the discrete crack models are difficult to apply because of the need to adaptively generate discrete crack elements according to the cracks formed during the loading process. In this paper, a pseudo-discrete crack model is developed for finite element implementation. The conventional smeared crack model is transformed and reformulated, and a novel crack queuing algorithm is introduced for crack analysis. The method has been applied to analyse concrete beams in the literature. It is demonstrated that the computational results of crack number, spacing and widths agree closely with the measured results

Acculturation and Bicultural Efficacy Effects on Chinese American Immigrants’ Diabetes and Health Management

The primary goal of this study was to examine effects of bicultural efficacy, or perceived confidence in dealing with bicultural acculturation stressors, on type 2 diabetes management and health for first-generation, Cantonese-speaking, Chinese American immigrants (N=162) recruited for a larger community-based diabetes intervention study (Chesla et al., 2013). The current study also tested whether a new Bicultural Efficacy in Health Management (BEFF-HM) scale is a more robust predictor of diabetes and health outcomes than proxy (years in the U.S.) and general acculturation measures. Hierarchical regression analyses of cross-sectional data revealed that high BEFF-HM was significantly related to positive outcomes on five of six diabetes and health measures as hypothesized after accounting for participant characteristics, proxy and general acculturation measures, and social support. Proxy and general acculturation measures failed to predict any study outcome supporting our secondary hypothesis that BEFF-HM is a better predictor of Chinese American immigrants’ diabetes and health management. An immigrant-focused research approach advances understanding of acculturation and bicultural efficacy effects on health by identifying key acculturation domains for study

Decoherence and dephasing errors caused by D.C. Stark effect in rapid ion transport

We investigate the error due to D.C. Stark effect for quantum information processing for trapped ion quantum computers using the scalable architecture proposed in J. Res. Natl. Inst. Stan. 103, 259 (1998) and Nature 417, 709 (2002). As the operation speed increases, dephasing and decoherence due to the D.C. Stark effect becomes prominent as a large electric field is applied for transporting ions rapidly. We estimate the relative significance of the decoherence and dephasing effects and find that the latter is dominant. We find that the minimum possible of dephasing is quadratic in the time of flight, and an inverse cubic in the operational time scale. From these relations, we obtain the operational speed-range at which the shifts caused by D.C. Stark effect, no matter follow which trajectory the ion is transported, are no longer negligible. Without phase correction, the maximum speed a qubit can be transferred across a 100 micron-long trap, without excessive error, in about 10 ns for Calcium ion and 50 ps for Beryllium ion. In practice, the accumulated error is difficult to be tracked and calculated, our work gives an estimation to the range of speed limit imposed by D.C. Stark effect.Comment: 7 pages, 1 figure. v2: Title is changed in this version to make our argument more focused. Introduction is rewritten. A new section IV is added to make our point more prominent. v3: Title is changed to make our argument more specific. Abstract, introduction, and summary are revise

An algorithm for series expansions based on hierarchical rate equations

We propose a computational method to obtain series expansions in powers of time for general dynamical systems described by a set of hierarchical rate equations. The method is generally applicable to problems in both equilibrium and nonequilibrium statistical mechanics such as random sequential adsorption, diffusion-reaction dynamics, and Ising dynamics. New result of random sequential adsorption of dimers on a square lattice is presented.Comment: LaTeX, 9 pages including 1 figur

Secondary organic aerosol (SOA) formation from reaction of isoprene with nitrate radicals (NO_3)

Secondary organic aerosol (SOA) formation from the reaction of isoprene with nitrate radicals (NO3) is investigated in the Caltech indoor chambers. Experiments are performed in the dark and under dry conditions (RH<10%) using N2O5 as a source of NO3 radicals. For an initial isoprene concentration of 18.4 to 101.6 ppb, the SOA yield (defined as the ratio of the mass of organic aerosol formed to the mass of parent hydrocarbon reacted) ranges from 4.3% to 23.8%. By examining the time evolutions of gas-phase intermediate products and aerosol volume in real time, we are able to constrain the chemistry that leads to the formation of low-volatility products. Although the formation of ROOR from the reaction of two peroxy radicals (RO2) has generally been considered as a minor channel, based on the gas-phase and aerosol-phase data it appears that RO2+RO2 reaction (self reaction or cross-reaction) in the gas phase yielding ROOR products is a dominant SOA formation pathway. A wide array of organic nitrates and peroxides are identified in the aerosol formed and mechanisms for SOA formation are proposed. Using a uniform SOA yield of 10% (corresponding to Mo≅10 μg m−3), it is estimated that ~2 to 3 Tg yr−1 of SOA results from isoprene + NO3. The extent to which the results from this study can be applied to conditions in the atmosphere depends on the fate of peroxy radicals (i.e. the relative importance of RO2+RO2 versus RO2+NO3 reactions) in the nighttime troposphere

A flexible system for scheduling drivers

A substantial part of the operating costs of public transport is attributable to drivers, whose efficient use therefore is important. The compilation of optimal work packages is difficult, being NP-hard. In practice, algorithmic advances and enhanced computing power have led to significant progress in achieving better schedules. However, differences in labor practices among modes of transport and operating companies make production of a truly general system with acceptable performance a difficult proposition. TRACS II has overcome these difficulties, being used with success by a substantial number of bus and train operators. Many theoretical aspects of the system have been published previously. This paper shows for the first time how theory and practice have been brought together, explaining the many features which have been added to the algorithmic kernel to provide a user-friendly and adaptable system designed to provide maximum flexibility in practice. We discuss the extent to which users have been involved in system development, leading to many practical successes, and we summarize some recent achievements