비만아 부모의 돌봄 경험: q 방법론

By 27 February 2020, the outbreak of coronavirus disease 2019 (COVID-19) caused 82 623 confirmed cases and 2858 deaths globally, more than severe acute respiratory syndrome (SARS) (8273 cases, 775 deaths) and Middle East respiratory syndrome (MERS) (1139 cases, 431 deaths) caused in 2003 and 2013, respectively. COVID-19 has spread to 46 countries internationally. Total fatality rate of COVID-19 is estimated at 3.46% by far based on published data from the Chinese Center for Disease Control and Prevention (China CDC). Average incubation period of COVID-19 is around 6.4 days, ranges from 0 to 24 days. The basic reproductive number (R0 ) of COVID-19 ranges from 2 to 3.5 at the early phase regardless of different prediction models, which is higher than SARS and MERS. A study from China CDC showed majority of patients (80.9%) were considered asymptomatic or mild pneumonia but released large amounts of viruses at the early phase of infection, which posed enormous challenges for containing the spread of COVID-19. Nosocomial transmission was another severe problem. A total of 3019 health workers were infected by 12 February 2020, which accounted for 3.83% of total number of infections, and extremely burdened the health system, especially in Wuhan. Limited epidemiological and clinical data suggest that the disease spectrum of COVID-19 may differ from SARS or MERS. We summarize latest literatures on genetic, epidemiological, and clinical features of COVID-19 in comparison to SARS and MERS and emphasize special measures on diagnosis and potential interventions. This review will improve our understanding of the unique features of COVID-19 and enhance our control measures in the future.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmv.25748

Unique epidemiological and clinical features of the emerging 2019 novel coronavirus pneumonia (COVID-19) implicate special control measures.

A review of techniques, advances and outstanding issues in numerical modelling for rock mechanics and rock engineering

The Mohr–Coulomb (M–C) fracture criterion is revisited with an objective of describing ductile fracture of isotropic crack-free solids. This criterion has been extensively used in rock and soil mechanics as it correctly accounts for the effects of hydrostatic pressure as well as the Lode angle parameter. It turns out that these two parameters, which are critical for characterizing fracture of geo-materials, also control fracture of ductile metals (Bai and Wierzbicki 2008; Xue 2007; Barsoum 2006; Wilkins et al. 1980). The local form of the M–C criterion is transformed/extended to the spherical coordinate system, where the axes are the equivalent strain to fracture $${\bar \varepsilon_f}$$
 , the stress triaxiality η, and the normalized Lode angle parameter $${\bar \theta}$$
 . For a proportional loading, the fracture surface is shown to be an asymmetric function of $${\bar \theta}$$
 . A detailed parametric study is performed to demonstrate the effect of model parameters on the fracture locus. It was found that the M–C fracture locus predicts almost exactly the exponential decay of the material ductility with stress triaxiality, which is in accord with theoretical analysis of Rice and Tracey (1969) and the empirical equation of Hancock and Mackenzie (1976), Johnson and Cook (1985). The M–C criterion also predicts a form of Lode angle dependence which is close to parabolic. Test results of two materials, 2024-T351 aluminum alloy and TRIP RA-K40/70 (TRIP690) high strength steel sheets, are used to calibrate and validate the proposed M–C fracture model. Another advantage of the M–C fracture model is that it predicts uniquely the orientation of the fracture surface. It is shown that the direction cosines of the unit normal vector to the fracture surface are functions of the “friction” coefficient in the M–C criterion. The phenomenological and physical sound M–C criterion has a great potential to be used as an engineering tool for predicting ductile fracture.

Application of extended Mohr–Coulomb criterion to ductile fracture

The purpose of this review is to discuss the development and the state of the art in dynamic testing techniques and dynamic mechanical behaviour of rock materials. The review begins by briefly introducing the history of rock dynamics and explaining the significance of studying these issues. Loading techniques commonly used for both intermediate and high strain rate tests and measurement techniques for dynamic stress and deformation are critically assessed in Sects. 2 and 3. In Sect. 4, methods of dynamic testing and estimation to obtain stress–strain curves at high strain rate are summarized, followed by an in-depth description of various dynamic mechanical properties (e.g. uniaxial and triaxial compressive strength, tensile strength, shear strength and fracture toughness) and corresponding fracture behaviour. Some influencing rock structural features (i.e. microstructure, size and shape) and testing conditions (i.e. confining pressure, temperature and water saturation) are considered, ending with some popular semi-empirical rate-dependent equations for the enhancement of dynamic mechanical properties. Section 5 discusses physical mechanisms of strain rate effects. Section 6 describes phenomenological and mechanically based rate-dependent constitutive models established from the knowledge of the stress–strain behaviour and physical mechanisms. Section 7 presents dynamic fracture criteria for quasi-brittle materials. Finally, a brief summary and some aspects of prospective research are presented.

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A Review of Dynamic Experimental Techniques and Mechanical Behaviour of Rock Materials

SINOROCK2004 Paper 2B 05Identification of dynamic rock properties using a genetic algorithm

Online detection of bioaerosols based on the light-induced fluorescence (LIF) technique is still challenging due to the complexity of bioaerosols and the external/internal mixing with nonbiological fluorescent compositions. Although many lab studies have measured the fluorescence properties of the biological and nonbiological materials, there is still a scarcity of knowledge of the sources of fluorescent aerosol particles (FAP) in the ambient atmosphere. Here, we fill this gap by combining the online measurement of an LIF-based instrument (wideband integrated bioaerosol sensor, WIBS, 0.8-20 μm) with the measurements of typical biological matter and the compositions related to major nonbiological FAP from May to July in the megacity Beijing. We find that fungal spores and pollen are widely observed in all types of FAP using a WIBS. Bacteria are suggested to be associated with the fine mode FAP (excitation/emission: 280 nm/310-400 nm; 0.8-3 μm). The FL-B and -BC particles (emission in 420-650 nm) contributing the most to FAP are strongly associated with humic-like substances, dust, burning and combustion emissions, and secondary organic aerosols (SOA). This study provides a guide for interpreting individual FAP measured by LIF instruments and points to the applicability of online LIF instruments to characterize nonbiological compositions including SOA.

Biological and Nonbiological Sources of Fluorescent Aerosol Particles in the Urban Atmosphere.

Sonic wave tests have been conducted in the construction site of Ling'ao Nuclear Power Station(LNPS)in Guangdong Province,China.Based on the change rate of sound wave speed before and after blasting,damage zone size of surrounding rock has been determined.On the other hand,a statistics-based damage variable of rock mass has been proposed based on micromechanics.Damage zone size of rock mass under blasting is thus studied using a hybrid LS-DYNA and FLAC3D scheme.It is reported that the numerical simulation results agree well with the site monitoring results,and the damage threshold for the rock in site of LNPS,Dc ri,is 0.2.The variation of damage zone size with charge weight has been analyzed by numerical simulations.It is observed that the rock damage zone size increases with charge weight.Damage zone depth of rock mass under blasting is less than damage zone radius.The damage zone radius is approximately 3 times of the damage zone depth.

Study on damage characteristics of rock mass under blasting load in ling'ao nuclear power station,guangdong province

The failure of infilled rock joints can be divided into interface damage and filling damage,which one dominates depends on the stress conditions of the two parts.When the filling was damaged,its plane stress state was analyzed.A theoretical shear strength formula was obtained and the effects of normal stress and filling thickness were studied.With the increase of normal stress the shear strength of infilled rock joints increases first and then decreases,but the influence of filling thickness is not obvious.Some direct shear tests of infilled rock joints were also carried out.The results show that the shear strength is related to the failure modes of the joints,and under the same mode it is independent of filling thickness.

Fracture mechanism and experiment of infilled rock joints

Multiscale modelling has great advantages by simulating material behaviours on one level using information from another level. The popular multiscale methodology couples the atomistic/meso particle model with the continuum model (e.g., multiscale model by coupling molecular dynamics and finite element analysis). In this paper, a new multiscale method is proposed using the numerical manifold method (NMM) and its micro extension particle manifold method (PMM). Due to the same mathematical and mechanical scheme NMM and PMM adopt, their multiscale coupling has a uniform framework and does not need special treatment at the multiscale boundary. The proposed method has an advantage over PMM in presenting the material’s micro structure and failure description. It also saves the computational resource by using NMM to present the macro part. In the paper, the multiscale methodology is presented with some numerical demonstrations. It is proven that this novel multiscale manifold method is a good tool for analysis of...

Jian Zhao

Papers

SINOROCK2004 Paper 2B 05Identification of dynamic rock properties using a genetic algorithm

Biological and Nonbiological Sources of Fluorescent Aerosol Particles in the Urban Atmosphere.

Study on damage characteristics of rock mass under blasting load in ling'ao nuclear power station,guangdong province

Fracture mechanism and experiment of infilled rock joints

A multiscale manifold method using particle representations of the physical domain