Strength assessment of stiffened blast walls in offshore installations under explosions

Offshore installations are exposed to hydrocarbon explosions and/or fire accidents. Especially, explosions lead to serious damages to human, safety, and environment. To minimise and prevent the damage from explosions, blast walls are generally installed in oil and gas production structures. Typical blast walls are classified into flat, corrugated, and stiffened types. Among them, corrugated blast walls are frequently used for reasons such as construction, cost, and energy absorption. However, it has been known that a corrugated type of blast wall buckles between the web and flange under the explosion loads, and loses its stiffness. It means that the buckling phenomenon of a blast wall is closely related to the structural strength. This study investigates on the structural characteristics of a blast wall under quasi-static and dynamic (explosion) loads with or without a flat-plated stiffener. Finally, it can be concluded that the flat type of stiffeners are located at the buckling region to delay the buckling and improve the strength of blast walls

Teleconnections: Summer Monsoon over Korea and India

This study investigates the relationship between the summer monsoon rainfall over Korea and India, by using correlation analysis and Singular Value Decomposition (SVD). Results reveal that summer monsoon rainfall over Korea is negatively (significant at the 99 level) correlated with the rainfall over the northwest and central parts of India. In addition, coupled spatial modes between the rainfall over Korea and India have been identified by the SVD analysis. The squared covariance fraction explained by the first mode is 70 and the correlation coefficient between the time coefficients of the two fields is significant at the 99 level, indicating that the coupled mode reflects a large part of the interaction between the summer monsoon rainfall over Korea and India. The first mode clearly demonstrates the existence of a significant negative correlation between the rainfall over the northwest and central parts of India and the rainfall over Korea. Possible mechanisms of this correlation are investigated by analyzing the variation of upper-level atmospheric circulation associated with the Tibetan high using NCEP / NCAR Reanalysis data

Relationship between Soviet snow and Korean rainfall

In this study the statistical relationship between winter-spring Soviet snow depth and summer monsoon rainfall over South Korea has been investigated by lag correlation correlation coefficients and composite analysis. Data for the 1966-95 period are used. Results reveal that the winter/springtime snow depth over western Eurasia (over Kazakhstan) is negatively related, whereas the snow depth over eastern Eurasia (over Manchuria-eastern Siberia) is positively related with Korean monsoon rainfall. The dipole correlation pattern suggests that heavy snow over eastern Eurasia and light snow over western Eurasia is favourable, whereas the reverse situation is unfavourable for monsoon activity over South Korea. The NCEP-NCAR re-analyses data reveal that the dipole correlation configuration is indicative of a mid-latitude long-wave pattern with an anomalous ridge over north Asia during the winter prior to a weak Korean monsoon and an anomalous trough prior to a strong monsoon. The re-analyses data further suggest that the position, shape, and strength of the summertime North Pacific subtropical high and the low-level jet over the East Asian sector could be considerably influenced by the snow distribution over Eurasia

Post-Stenotic Recirculating Flow May Cause Hemodynamic Perforator Infarction

Background and Purpose The primary mechanism underlying paramedian pontine infarction (PPI) is atheroma obliterating the perforators. Here, we encountered a patient with PPI in the post-stenotic area of basilar artery (BA) without a plaque, shown, by high-resolution magnetic resonance imaging (HR-MRI). We performed an experiment using a 3D-printed BA model and a particle image velocimetry (PIV) to explore the hemodynamic property of the post-stenotic area and the mechanism of PPI. Methods 3D-model of a BA stenosis was reconstructed with silicone compound using a 3D printer based on the source image of HR-MRI. Working fluid seeded with fluorescence particles was used and the velocity of those particles was measured horizontally and vertically. Furthermore, microtubules were inserted into the posterior aspect of the model to measure the flow rates of perforators (pre- and post-stenotic areas). The flow rates were compared between the microtubules. Results A recirculating flow was observed from the post-stenotic area in both directions forming a spiral shape. The velocity of the flow in these regions of recirculation was about one-tenth that of the flow in other regions. The location of recirculating flow well corresponded with the area with low-signal intensity at the time-of-flight magnetic resonance angiography and the location of PPI. Finally, the flow rate through the microtubule inserted into the post-stenotic area was significantly decreased comparing to others (P<0.001). Conclusions Perforator infarction may be caused by a hemodynamic mechanism altered by stenosis that induces a recirculation flow. 3D-printed modeling and PIV are helpful understanding the hemodynamics of intracranial stenosis.114Ysciescopu

Porohyperelastic anatomical models for hydrocephalus and idiopathic intracranial hypertension

This is the accepted manuscript of a paper published in the Journal of Neurosurgery, Published online February 6, 2015; DOI: 10.3171/2014.12.JNS14516.OBJECT Brain deformation can be seen in hydrocephalus and idiopathic intracranial hypertension (IIH) via medical images. The phenomenology of local effects, brain shift, and raised intracranial pressure and herniation are textbook concepts. However, there are still uncertainties regarding the specific processes that occur when brain tissue is subject to the mechanical stress of different temporal and spatial profiles of the 2 neurological disorders. Moreover, recent studies suggest that IIH and hydrocephalus may be diseases with opposite pathogenesis. Nevertheless, the similarities and differences between the 2 subjects have not been thoroughly investigated. METHODS An anatomical porohyperelastic finite element model was used to assess the brain tissue responses associated with hydrocephalus and IIH. The same set of boundary conditions, with the exception of brain loading for development of the transmantle pressure gradient, was applied for the 2 models. The distribution of stress and strain during tissue distortion is described by the mechanical parameters. RESULTS The results of both the hydrocephalus and IIH models correlated with pathological characteristics. For the hydrocephalus model, periventricular edema was associated with the presence of positive volumetric strain and void ratio in the lateral ventricle horns. By contrast, the IIH model revealed edema across the cerebral mantle, including the centrum semiovale, with a positive void ratio and volumetric strain. CONCLUSIONS The model simulates all the clinical features in correlation with the MR images obtained in patients with hydrocephalus and IIH, thus providing support for the role of the transmantle pressure gradient and capillary CSF absorption in CSF-related brain deformation. The finite element methods can be used for a better understanding of the pathophysiological mechanisms of neurological disorders associated with parenchymal volumetric fluctuation.Dr. M. Czosnyka is a consultant for J&J (Codman), and has received payment for lectures from Integra Lifescience. This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRFK) funded by the Ministry of Science, ICT, & Future Planning (2013R1A1A1004827); and the International Research & Development Program of the NRFK funded by the Ministry of Education, Science, and Technology of Korea (Grant No. 2014K1A3A1A21001366)

Genetic Comparison of Stemness of Human Umbilical Cord and Dental Pulp

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Methods for determining the optimal arrangement of water deluge systems on offshore installations

Offshore installations are prone to fire and/or explosion accidents. Fires have particularly serious consequences due to their high temperatures and heat flux, which affect humans, structures and environments alike. Due to the hydrocarbon explosions caused by delayed ignition following gas dispersion, fires can be the result of immediate ignition after gas release. Accordingly, it can be difficult to decrease their frequency, which is an element of risk (risk=frequency×consequence), using an active protection system (APS) such as gas detectors capable of shutting down the operation. Thus, it is more efficient to reduce the consequence using a passive protection system (PSS) such as water spray. It is important to decide the number and location of water deluge systems, thus the aim of this study is to introduce a new procedure for optimising the locations of water deluge systems using the water deluge location index (WLI) proposed herein. The locations of water deluge systems are thus optimised based on the results of credible fire scenarios using a three-dimensional computational fluid dynamics (CFD) tool. The effects of water spray and the effectiveness of the WLI are investigated in comparison with uniformly distributed sprays

Direct Evidence for Dominant Bond-directional Interactions in a Honeycomb Lattice Iridate Na2IrO3

Heisenberg interactions are ubiquitous in magnetic materials and have been prevailing in modeling and designing quantum magnets. Bond-directional interactions offer a novel alternative to Heisenberg exchange and provide the building blocks of the Kitaev model, which has a quantum spin liquid (QSL) as its exact ground state. Honeycomb iridates, A2IrO3 (A=Na,Li), offer potential realizations of the Kitaev model, and their reported magnetic behaviors may be interpreted within the Kitaev framework. However, the extent of their relevance to the Kitaev model remains unclear, as evidence for bond-directional interactions remains indirect or conjectural. Here, we present direct evidence for dominant bond-directional interactions in antiferromagnetic Na2IrO3 and show that they lead to strong magnetic frustration. Diffuse magnetic x-ray scattering reveals broken spin-rotational symmetry even above Neel temperature, with the three spin components exhibiting nano-scale correlations along distinct crystallographic directions. This spin-space and real-space entanglement directly manifests the bond-directional interactions, provides the missing link to Kitaev physics in honeycomb iridates, and establishes a new design strategy toward frustrated magnetism.Comment: Nature Physics, accepted (2015