In situ study of the mechanical properties of airborne haze particles

Particulate pollution has raised serious concerns regarding its potential impacts on human health in developing countries. However, much less attention has been paid to the threat of haze particles to machinery and industry. By employing a state-of-the-art in situ scanning electron microscope compression testing technique, we demonstrate that iron-rich and fly ash haze particles, which account for nearly 70% of the total micron-sized spherical haze particles, are strong enough to generate abrasive damage to most engineering alloys, and therefore can generate significant scratch damage to moving contacting surfaces in high precision machineries. Our finding calls for preventive measures to protect against haze related threat.National Basic Research Program of China (973 Program) (Grant 2012CB619402)National 111 Project of China (Grant B06025)National Science Foundation (U.S.) (Grants DMR-1120901 and DMR-1410636)National Natural Science Foundation (China) (Grants 51231005, 51471128 and 51321003

Human Streptococcus suis Outbreak, Sichuan, China

Streptococcus suis outbreak was associated with exposure to sick or dead pigs

Variability of Bio-Clinical Parameters in Chinese-Origin Rhesus Macaques Infected with Simian Immunodeficiency Virus: A Nonhuman Primate AIDS Model

BACKGROUND: Although Chinese-origin Rhesus macaques (Ch RhMs) infected with simian immunodeficiency virus (SIV) have been used for many years to evaluate the efficacy of AIDS vaccines and therapeutics, the bio-clinical variability of such a nonhuman primate AIDS model was so far not established. METHODOLOGY/PRINCIPAL FINDINGS: By randomizing 150 (78 male and 72 female) Ch RhMs with diverse MHC class I alleles into 3 groups (50 animals per group) challenged with intrarectal (i.r.) SIVmac239, intravenous (i.v.) SIVmac239, or i.v. SIVmac251, we evaluated variability in bio-clinical endpoints for 118 weeks. All SIV-challenged Ch RhMs became seropositive for SIV during 1-2 weeks. Plasma viral load (VL) peaked at weeks 1-2 and then declined to set-point levels as from week 5. The set-point VL was 30 fold higher in SIVmac239 (i.r. or i.v.)-infected than in SIVmac251 (i.v.)-infected animals. This difference in plasma VL increased overtime (>100 fold as from week 68). The rates of progression to AIDS or death were more rapid in SIVmac239 (i.r. or i.v.)-infected than in SIVmac251 (i.v.)-infected animals. No significant difference in bio-clinical endpoints was observed in animals challenged with i.r. or i.v. SIVmac239. The variability (standard deviation) in peak/set-point VL was nearly one-half lower in animals infected with SIVmac239 (i.r. or i.v.) than in those infected with SIVmac251 (i.v.), allowing that the same treatment-related difference can be detected with one-half fewer animals using SIVmac239 than using SIVmac251. CONCLUSION/SIGNIFICANCE: These results provide solid estimates of variability in bio-clinical endpoints needed when designing studies using the Ch RhM SIV model and contribute to the improving quality and standardization of preclinical studies

Kinematic Chain Equivalent Method for Tube Model and Elastodynamic Optimization for Parallel Mechanism Based on Matrix Structural Analysis

The platforms of parallel mechanisms usually suffer vibration loads. In these cases, structure elastodynamic analysis and elastodynamic optimization of parallel mechanisms are important. A tube structure is very common for parallel mechanisms. This work establishes the model of a tube structure based on matrix structural analysis. The kinematic pair equivalent method is used to simulate the surface contact between the inner and outer tubes. The corresponding mass and stiffness matrices are derived through the strain energy minimization method. The reconfigurable legged lunar lander has been used as an example to verify the effectiveness of this method. By adding the mechanism configuration to the optimization process, the equivalent static load method and the desirability approach are combined and modified. A procedure for the multi-objective elastodynamic optimization of parallel mechanisms is proposed. The optimization procedure is implemented on the lander and the results show a reduction in mass and an increase in natural frequency

NuBot: A Magnetic Adhesion Robot with Passive Suspension to Inspect the Steel Lining

Abstract The steel lining of huge facilities is a significant structure, which experiences extreme environments and needs to be inspected periodically after manufacture. However, due to the complexity (crisscross welds, curved surface, etc.) of their inside environments, high demands for stable adhesion and curvature adaptability are put forward. This paper presents a novel wheeled magnetic adhesion robot with passive suspension applied in nuclear power containment called NuBot, and mainly focuses on the following aspects: (1) proposing the wheeled locomotion suspension to adapt the robot to the uneven surface; (2) implementing the parameter optimization of NuBot. A comprehensive optimization model is established, and global optimal dimensions are properly chosen from performance atlases; (3) determining the normalization factor and actual dimensional parameters by constraints of the steel lining environment; (4) structure design of the overall robot and the magnetic wheels are completed. Experiments show that the robot can achieve precise locomotion on both strong and weak magnetic walls with various inclination angles, and can stably cross the 5 mm weld seam. Besides, its maximum payload capacity reaches 3.6 kg. Results show that the NuBot designed by the proposed systematic method has good comprehensive capabilities of surface-adaptability, adhesion stability, and payload. Besides, the robot can be applied in more ferromagnetic environments and the design method offers guidance for similar wheeled robots with passive suspension

Irradiation damage of single crystal, coarse-grained, and nanograined copper under helium bombardment at 450 °C

The irradiation damage behaviors of single crystal (SC), coarse-grained (CG), and nanograined (NG) copper (Cu) films were investigated under Helium (He) ion implantation at 450 °C with different ion fluences. In irradiated SC films, plenty of cavities are nucleated, and some of them preferentially formed on growth defects or dislocation lines. In the irradiated CG Cu, cavities formed both in grain interior and along grain boundaries; obvious void-denuded zones can be identified near grain boundaries. In contrast, irradiation-induced cavities in NG Cu were observed mainly gathering along grain boundaries with much less cavities in the grain interiors. The grains in irradiated NG Cu are significantly coarsened. The number density and average radius of cavities in NG Cu was smaller than that in irradiated SC Cu and CG Cu. These experiments indicate that grain boundaries are efficient sinks for irradiation-induced vacancies and highlight the important role of reducing grain size in suppressing radiation-induced void swelling.United States. Dept. of Energy. Office of Basic Energy Sciences (Center for Materials in Irradiation and Mechanical Extremes. Award 2008LANL 1026

Metal. Int.

In this paper, the basic sintering characteristics of common fluxes (quicklime, limestone, dolomite and serpentine) were examined in details with micro-sintering method by measuring the mineralization capacity, liquid generation capacity, consolidation strength of iron ores and fluxes with different particle sizes, then the difference and influencing law were analyzed. Based on the fundamental study, sintering pot tests with different particle size of fluxes were carried out, and the reducibility and mineralogical morphology of sinters were further investigated. The results show that: (1)With the particle size of fluxes decreasing, the mineralization capacity and liquid phase generation capacity of iron ore fines and flux increased. But different from other fluxes, with the particle size of limestone decreasing, the pores in sinter affected the consolidation strength of sample. (2)The decrease of flux particle size went against the productivity of sinter, but when the particle size of quicklime, dolomite and especially that of serpentine decreased, the sinter strength, production yield, reducibility and mineralogical morphology of sinter were improved, and the coke consumption decreased. However, the particle size of limestone decreased affected the quality of the sinter negatively. (3)The refinement of quicklime, dolomite and especially of serpentine could improve the properties of sinter and decrease energy consumption greatly without considering the productivity.In this paper, the basic sintering characteristics of common fluxes (quicklime, limestone, dolomite and serpentine) were examined in details with micro-sintering method by measuring the mineralization capacity, liquid generation capacity, consolidation strength of iron ores and fluxes with different particle sizes, then the difference and influencing law were analyzed. Based on the fundamental study, sintering pot tests with different particle size of fluxes were carried out, and the reducibility and mineralogical morphology of sinters were further investigated. The results show that: (1)With the particle size of fluxes decreasing, the mineralization capacity and liquid phase generation capacity of iron ore fines and flux increased. But different from other fluxes, with the particle size of limestone decreasing, the pores in sinter affected the consolidation strength of sample. (2)The decrease of flux particle size went against the productivity of sinter, but when the particle size of quicklime, dolomite and especially that of serpentine decreased, the sinter strength, production yield, reducibility and mineralogical morphology of sinter were improved, and the coke consumption decreased. However, the particle size of limestone decreased affected the quality of the sinter negatively. (3)The refinement of quicklime, dolomite and especially of serpentine could improve the properties of sinter and decrease energy consumption greatly without considering the productivity