420 research outputs found
Large scale physical model testing on the ultimate strength of a steel stiffened plate structure under cyclic compressive loading
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Large scale physical model testing on the ultimate compressive strength of a steel stiffened plate structure at cryogenic condition
Ship structures are typical examples of large plated structures which are made of large number of structural elements composed into system structures to be strong enough, while keeping the structural weight at minimum, to survive varying loads arising from cargo (e.g. weight and cryogenic condition due to LNG cargo), waves, winds or other environmental conditions (e.g. cold temperature due to Arctic operation). The design of ship structures are today designed based on limit states which are defined by the description of a condition for which a particular structural member or an entire structure would fail to perform the function designated beforehand. Four types of limit states are relevant, namely SLS (serviceability limit state), ULS (ultimate limit state), FLS (fatigue limit state) and ALS (accidental limit state). At the preliminary design stage, structural scantlings and materials of ship structures are determined based on the ULS, and ultimately other types of limit states are integrated to ensure so that the different parts of a ship structure will meet safety requirements and survive environmental and operational conditions during the life time period of some 25 years. \ua0The stiffened plate structures in the bottom, the deck and the side-shell are the most important parts of a ship in association with a ship’s integrity, safety and survivability. The design criteria for determining the scantlings of stiffened plate structures are the ultimate limit states (or ultimate strength). If applied loads exceed the ultimate strength then the stiffened plate structures fail to perform the function, leading to total loss of the ship. Therefore, it is of vital importance to accurately and efficiently compute the ultimate strength of stiffened plate structures. The behavior of stiffened plate structures until and after the ultimate strength is reached is highly nonlinear involving geometric nonlinearities (e.g. buckling and large deflection) and material nonlinearities (e.g. yielding, plasticity and material failure or fracture). Various types of collapse modes, including overall buckling collapse, beam-column type collapse, web buckling induced collapse and flexural-torsional buckling induced collapse, are relevant. Today\u27s large merchant ship structures are made of different grades of steel materials that should meet specific requirements for yield strength, ductility, brittleness, ultimate tensile strength resistance to corrosion in association with operational and environmental conditions.\ua0\ua0As of today, the ultimate strength of stiffened plate structures has been studied and applied in room temperature conditions. However, ships now operate in Arctic region at cold temperatures as climate change causes Arctic ice to melt at an alarming rate. A shipping company MAERSK recently navigates a 200m long container ship through the Arctic waters for the first time without the help of icebreakers. The average ambient temperature in Arctic region during winter season is -40 deg. C and the lowest temperature is reportedly -68 deg. C. Furthermore, the number of LNG-fueled ships is increasing in terms of resolving the issues associated with CO2 emissions. LNG-fueled ships need to have LNG fuel tanks in a large size, and hazards of LNG leakage always exist. The temperature of LNG is -163 deg. C. The collapse behavior of ship stiffened plate structures is vulnerable to cold temperatures or cryogenic condition in association with catastrophic failure, leading to total loss of ships that can affect personnel, assets and the environment, where brittle facture must be playing a significant role on the ultimate strength behavior. Theoretical methods are almost impossible to apply for computing such a highly nonlinear behavior of ship stiffened plate structures involving buckling, yielding and brittle fracture. Advanced computational models should be developed for that purpose. However, it is highly demanding to obtain physical model test database which shall be used to validate the accuracy and applicability of the advanced computational models.\ua0The purpose of the present study is to obtain physical model test database on the ultimate strength characteristics of ship stiffened plate structures subject to extreme loads and cold temperatures (due to LNG leakage). Physical model testing on a large scale ship stiffened plate structure is undertaken at cryogenic condition (-160 deg. C). Elastic-plastic large deflection behavior of the test model under axial compressive loads is measured until and after the ultimate strength is reached. Material properties at cryogenic temperature are tested in separate material experiments. Details of the test database are documented
A Case of Hypereosinophilic Syndrome with Bladder Involvement in a 7-Year-Old Boy
Hypereosinophilic syndrome (HES) is characterized by the presense of hypereosinophilia with evidence of target organ damage. We report a patient diagnosed with eosinophilic cystitis and HES. A 7 year old boy had hematuria, dysuria, and increased urinary frequency for 1 day. Laboratory examinations revealed hypereosinophilia (eosinophils, 2,058/µL), hematuria, and proteinuria. Abdominal sonography revealed diffuse and severe wall thickening of the bladder. The patient was treated initially with antibiotics. However, his symptoms did not improve after 7 days. A computed tomography scan demonstrated severe wall thickening of the bladder and the hypereosinophilia persisted (eosinophils, 2,985/µL). The patient complained of chest discomfort, dyspnea, epigastric pain, and vomiting on hospital day 10. Parasitic, allergic, malignancy, rheumatologic, and immune workups revealed no abnormal findings. Chest X-rays, electrocardiography, and a pulmonary function test were normal; however, the hypereosinophilia was aggravated (eosinophils, 3,934/µL). Oral deflazacort was administered. A cystoscopic biopsy showed chronic inflammation with eosinophilic infiltration. The patient’s respiratory, gastrointestinal, and urinary symptoms improved after 6 days of steroids, and he was discharged. The eosinophil count decreased dramatically (182/µL). The hypereosinophilia waxed and waned for 7 months, and the oral steroids were tapered and stopped. This case describes a patient diagnosed with eosinophilic cystitis and HES
Report on the Observation of a Dark morph Tree Sparrow (Passer montanus) in Daejeon Metropolitan City
AbstractOn March 16th, 2010, at 13:35, a single count of dark morph tree sparrow (Passer montanus) was observed for approximately 15 minutes while it was resting with approximately 30 ordinary tree sparrows at a terrace land on water (east longitude 127°21′31.4”, north latitude 36°18′20.2”) under Gasuwon Bridge (Gasuwongyo) of Gasuwon-dong, Seo-gu in Daejeon Metropolitan City. Dark morph tree sparrow has not been observed in nature for 16 years since its observation in Pyeongtaek-gun of Gyeonggi-do by the Korean Avian Association in 1994
Electric field control of nonvolatile four-state magnetization at room temperature
We find the realization of large converse magnetoelectric (ME) effects at
room temperature in a multiferroic hexaferrite
BaSrCoFeO single crystal, in which rapid
change of electric polarization in low magnetic fields (about 5 mT) is coined
to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then
reaches up to 0.62 /f.u. in an electric field of 1.14 MV/m. We find
further that four ME states induced by different ME poling exhibit unique,
nonvolatile magnetization versus electric field curves, which can be
approximately described by an effective free energy with a distinct set of ME
coefficients
Realization of giant magnetoelectricity in helimagnets
We show that low field magnetoelectric (ME) properties of helimagnets
Ba0.5Sr1.5Zn2(Fe1-xAlx)12O22 can be efficiently tailored by Al-substitution
level. As x increases, the critical magnetic field for switching electric
polarization is systematically reduced from ~1 T down to ~1 mT, and the ME
susceptibility is greatly enhanced to reach a giant value of 2.0 x 10^4 ps/m at
an optimum x = 0.08. We find that control of nontrivial orbital moment in the
octahedral Fe sites through the Al-substitution is crucial for fine tuning of
magnetic anisotropy and obtaining the conspicuously improved ME
characteristics
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