In the present paper, the 100-year history of break-in-two accidents is reviewed considering the technological developments relevant to these events. The chronology starts from the epoch making ...break-in-two accident of torpedo-boat destroyer “Cobra” (1901), where Biles (1905) examined the elastic stress and deformation induced in a ship hull by hogging and sagging conditions based on the experiments using a destroyer ”Wolf,” while the ultimate bending strength was experimentally investigated by Kell (1931, 1940) using two destroyers.
Then, we shall proceed to review the brittle fracture of all-welded ships during the World War II, and serious damages of bulk carriers and ore carriers experienced from the late 60s to the early 80s. In the 90s, another problem “substandard ships” had emerged, which had lead IACS to make the so-called “Common Structural Rules (CSRs)” for oil tankers and bulk carriers, while IMO implemented “Goal Based Standards (GBSs)” for new construction of oil tankers and bulk carriers in SOLAS conventions. Lastly, we shall consider the break-in-two accidents of large container ships, where discussions are made how to investigate the causes of the accidents by using the numerical tools for the evaluation of wave-induced loads and ultimate strength.
Having reviewed the chronology, one may understand what have been learned in the last 100 years, and also what to be further studied in the structural design against ultimate hull-girder failures in the future.
•The chronology of critical break-in-two accidents of ships are presented over the last 100 years.•Break-in-two accidents occurred in relation to innovative designs responding to societal needs. They are categorized into•Excessive light weight structures of high-speed destroyers (1900-1940),•Brittle fracture of all-welded ships (WWII- 1950),•Rapid up-sizing of cargo-specific ships (1970s-1980s), and•Structural failures of substandard ships (1990s-2000s).•Very recently, hogging failures have emerged for large container ships.•Precise evaluations of strength of the double bottom and the slam-induced whipping moment are of urgent needs.•Structural failures of substandard ships seem to be reduced in the 2010s.•Re-analysis based on the present data is necessary to evaluate the effectiveness of countermeasures to aged ships.
In order to prevent the initiation of a brittle crack in a marine structure, fatigue crack propagation from potentially hazardous embedded weld defects must be evaluated under the realistic seaway ...loading using certain clustered loading patterns. We first simulate the fatigue crack propagation under the random sequence of clustered loading so-called storm model. The numerical simulation is carried out by a method considering the plastic wake on the crack surfaces, which may cause the retardation effects after high amplitude of loading. Furthermore, fatigue crack propagation under the effect of slam-induced whipping stress is examined by a series of experiments using CT specimens and by simulations.
The aims of this study were to observe the behavior of composite and formation of gaps during and immediately after light polymerization using swept source optical coherence tomography (OCT) and to ...compare the interfacial integrity of adhesives in cavities through 3-dimensional (3D) image analysis. Forty tapered cylindrical cavities (4-mm diameter, 2-mm depth) were prepared in bovine incisors and restored using Bond Force (BF), Scotchbond Universal Adhesive (SBU), OptiBond XTR (XTR), or Clearfil SE Bond 2 (SE2), followed by Estelite Flow Quick flowable composite. Real-time imaging was performed at the center of restoration by the OCT system (laser center wavelength: 1,330 nm; frequency: 30 KHz) during and up to 10 min after light curing. The 3D scanning was performed 0, 1, 3, 5, and 10 min after light curing. The percentages of sealed enamel and dentin interface area (E%, D%) were calculated using Amira software. In real-time videos, the initial gaps appeared as a bright scattered area mainly on dentin floor and rapidly progressed along the cavity floor. The timing, rate, and extent of gap formation were different among the specimens. From 3D visualization, gap progress could be seen on both enamel and dentin even after irradiation; furthermore, typical toroidal gap patterns appeared at the dentin floor of BF and SBU. XTR and SE2 showed nearly perfect sealing performance on the dentin floor up to the 10 min that images were recorded. From quantitative analysis, SE2 and XTR showed significantly higher E% and D% than other groups. SBU showed the smallest E% and BF showed a significantly smaller D% than other groups (P < 0.05). In conclusion, real-time observation of composite placement and 3D quantification of interfacial gaps were implemented within the experimental limitations. Interfacial gap formation during polymerization of the composite depended on the adhesive system used. The formed gaps continued to propagate after composite light curing finished.
The aim of this study was to nondestructively analyze enamel crack behavior on different areas of teeth using 3D swept source-optical coherence tomography (SS-OCT). Ten freshly extracted human teeth ...of each type on each arch (n = 80 teeth) were inspected for enamel crack patterns on functional, contact and nonfunctional, or noncontact areas using 3D SS-OCT. The predominant crack pattern for each location on each specimen was noted and analyzed. The OCT observations were validated by direct observations of sectioned specimens under confocal laser scanning microscopy (CLSM). Cracks appeared as bright lines with SS-OCT, with 3 crack patterns identified: Type I – superficial horizontal cracks; Type II – vertically (occluso-gingival) oriented cracks; and Type III – hybrid or complicated cracks, a combination of a Type I and Type III cracks, which may or may not be confluent with each other. Type II cracks were predominant on noncontacting surfaces of incisors and canines and nonfunctional cusps of posterior teeth. Type I and III cracks were predominant on the contacting surfaces of incisors, cusps of canines, and functional cusps of posterior teeth. Cracks originating from the dental-enamel junction and enamel tufts, crack deflections, and the initiation of new cracks within the enamel (internal cracks) were observed as bright areas. CLSM observations corroborated the SS-OCT findings. We found that crack pattern, tooth type, and the location of the crack on the tooth exhibited a strong correlation. We show that the use of 3D SS-OCT permits for the nondestructive 3D imaging and analysis of enamel crack behavior in whole human teeth in vitro. 3D SS-OCT possesses potential for use in clinical studies for the analysis of enamel crack behavior.
The objective of this study was to estimate the strength and deformability of corroded steel plates under quasi-static uniaxial tension. In order to accurately simulate this problem, we first ...estimated the true stress-strain relationship of a flat steel plate by introducing a vision sensor system to the deformation measurements in tensile tests. The measured true stress-stain relationship was then applied to a series of nonlinear implicit three-dimensional finite element analyses using commercial code LS-DYNA. The strength and deformability of steel plates with various pit sizes, degrees of pitting intensity, and general corrosion were estimated both experimentally and numerically. The failure strain in relation to the finite element mesh size used in the analyses was clarified. Two different steels having yield ratios of 0.657 and 0.841 were prepared to examine the material effects on corrosion damage. The strength and deformability did not show a clear dependence on the yield ratios of the present two materials, whereas a clear dependence was shown with respect to the surface configuration such as the minimum cross-sectional area of the specimens, the maximum depth of the pit cusp from the mean corrosion diminution level, and pitting patterns. Empirical formulae for the reduction of deformability and the reduction of energy absorption of pitted plates were proposed which may be useful in strength assessment when examining the structural integrity of aged corroded structures.
Recent advances in the field of optics have enabled accurate and localized measurement of optical properties of biological substrates. This work aimed to elucidate the relationship between the local ...refractive index (n) and mineral content (MC) of enamel and dentin. De- and remineralized lesions in bovine enamel and dentin blocks were sectioned into 300- to 400-µm-thick slices, and placed on a metal plate to capture images of sound, de- and remineralized regions transversely by optical coherence tomography. Mean n at each depth level of the lesion (20- or 40-µm steps for enamel or dentin) was measured by the optical path length-matching method and used to plot n through lesion depth. The specimens were further polished and processed for transverse microradiography for analysis of MC. The n and MC ranged from 1.52 to 1.63 and 50 to 87 (vol.%) in enamel, and from 1.43 to 1.57 and 11 to 48 (vol.%) in dentin, respectively. Strong, positive linear correlations were found between n and MC (Pearson's r = 0.95 and 0.91 for de- and remineralized enamel, and r = 0.94 and 0.91 for dentin, respectively, p < 0.001). Experimental data were validated with a theoretical calculation of n from MC. De- and remineralization of enamel and dentin resulted in measurable changes of n, and, in turn, MC changes of the tissue could be estimated with good accuracy from this long-known optical property by the new analytical approach. Compositional changes of enamel crystallites after remineralization affect n.
Background and Objective
Diagnosis is a crucial step in periodontal treatment. The aim of this study was to evaluate the effectiveness of optical coherence tomography (OCT) for observation and ...determination of periodontal tissue profiles in vivo.
Material and Methods
In experiment 1, refractive indices of purified water, porcine gingiva and human gingiva at 1330 nm were determined for the analysis of OCT images of periodontal tissues. In experiment 2, OCT examination was performed in the midlabial apico‐coronal plane of mandibular anteriors in 30 Asian volunteers with healthy gingiva. Sulcus depth was measured on intra‐oral photographs taken during probing. In the OCT images, the gingival, epithelial and connective tissue thickness, and the position of alveolar bone crest were determined and finally, the biologic width was measured.
Results
Refractive indices of purified water, porcine gingiva and human gingiva were 1.335, 1.393 and 1.397, respectively. Cross‐sectional images of gingival epithelium, connective tissue and alveolar bone were depicted in real‐time. The sulcular and junctional epithelium could be visualized occasionally. Laser penetration and reflection were limited to a certain depth with an approximate maximal imaging depth capability of 1.5 mm and OCT images of the periodontal structure were not clear in some cases. The average maximal thickness of gingiva and epithelium and biologic width at the mandibular anteriors were 1.06 ± 0.21, 0.49 ± 0.15 and 2.09 ± 0.60 mm, respectively.
Conclusion
OCT has promise for non‐invasive observation of the periodontal tissue profile in detail and measurement of internal periodontal structures including biologic width in the anterior region.
Backgrounds
The World Health Organization has published the Integrated Care for Older People, ICOPE handbook Guidance on person-centred assessment and pathways in primary care. This is an integrated ...individual care tool focused on the individual and healthy ageing. The ICOPE tool proposes step by step, a screening, a fine assessment, the development of a personalized care plan, its implementation and follow up and finally the consideration of the caregivers and community. The new Geroscience field is focusing on preventing age-related diseases, and should now investigate with the ICOPE tool the optimal maintenance of intrinsic capacity (IC) through mobility, cognition, psychology, vitality, hearing and vision. This article aims to present this new tool and to presents its innovative implementation at the Toulouse University Hospital through the INSPIRE study. We believe that the ICOPE integrated care program will also be a pragmatic way to maintain cognitive functions and detect early Alzheimer.
Objectives
The main objective of the INSPIRE study is to build a Bio-resource Research Platform for Healthy Ageing gathering biological, clinical and digital resources in order to identify markers of ageing, age-related diseases and IC evolution. The study will be also testing the implementation and follow up of the ICOPE tool.
Methods
The Inspire Platform will gather clinical data and bio-specimens from 1000 subjects in the Occitania Region, of different ages (from 30 years and over) over 10 years. Data will be collected annually. Using the ICOPE tool IC domains will be monitored every 4 months. Once IC decline is identified, participants will have a thorough clinical assessment and blood sampling to investigate the response of markers of ageing at the time of decline. The French ethic committee approved the study.
Results
The Inspire platform aims to develop an integrative approach to promote novel new technologies for the assessment and monitoring of functional capacities.
Abstract
MHPS and MHI suggest HP/IP/LP separate casing and one bearing/rotor (one bearing between two casings) type steam turbine. To design this type of shaft arrangement, journal bearing that ...supports high specific load with superior oil film static and dynamic characteristics is demanded. In this paper, it is shown that 610 mm diameter direct lubricated two pads bearing which can operate at high specific load has been developed. Also, it is confirmed that its good bearing characteristics in full scale test.
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