Actual Cross-section Research Articles

Full-Section Deformation Monitoring of High-Altitude Fault Tunnels Based on Three-Dimensional Laser Scanning Technology.

In traditional tunnel monitoring, the characteristic points of an object within a tunnel are measured to obtain information about the object. Considering the limitations of the traditional method in measuring the complex surface structure of tunnels, such as limited monitoring points, a long measurement period, and low precision, this study introduces an approach that uses three-dimensional (3D) laser scanning for monitoring tunnel cross-section deformation. Using this approach, the soft surrounding rock of a high-altitude ultralong tunnel was taken as the monitoring object. The test tunnel was first scanned using a 3D laser scanner, and the collected data were processed. The internal structural data of the tunnel were subsequently compared with its actual contour lines and the data of its primary branch and secondary lining on different dates. The results indicate that the arch roof of the tunnel tended to be stable within a certain time range when the positions of the primary branch and secondary lining were at different measuring points with different pile numbers. The deformation of the pile number on the left and right sides did not generally exceed 0.02 m, except at a few measuring points. A comparison between the actual cross section of the initial branch and that of the designed section showed that the actual elevation of the arch of the initial branch of the tunnel was greater than its designed elevation by no more than 0.3 m. Hence, through this study, a convenient and practical method is presented for monitoring deformation in complex curved tunnel structures.

Understanding ac losses in CORC cables of YBCO superconducting tapes by numerical simulations

Alternating current (ac) losses in conductor-on-rounded-core (CORC) cables of YBCO high-temperature superconducting (HTS) tapes are a significant challenge in HTS power applications. This study employs two finite element analysis (FEA) models to investigate the contributions from different ac loss components and provide approaches for reducing ac losses in cables. An FEA model based on the T-A formulation treats the cross section of thin superconducting layers as 1D lines and, therefore, only can predict the ac loss generated by the perpendicular magnetic field. In contrast, the model based on H-formulation can be performed on the actual 2D rectangular cross section HTS tapes to provide the total ac losses generated by magnetic fluxes penetrating from both the edges and surfaces of HTS tapes, although this model requires more computing time and memory. The 1D and 2D simulation models were validated by cross comparing the results from both models and by comparing sub-section and full cross section models. Subsequently, two models relate cable design and operational parameters to the surface and edge losses of a two-layer CORC cable by considering the (1) relative contributions of edge and surface losses to the overall ac losses; (2) effect of the current distribution between inner and outer HTS layers on ac losses; (3) impact of the tape alignment on ac losses in each HTS layer; (4) influence of the thickness of HTS layers on ac losses; (5) effect of size and number of inter-tape gaps on ac losses; and (6) contribution frequency on the ac losses. The research results given in this paper are therefore not only valuable to suggest strategies for reducing ac loss in multi-layer cables but also for developing more accurate and effective methods to calculate ac loss in CORC HTS cables.

Long bones under three-point bending: The role of special feed on bone’s mechanical properties

Osteoporosis is a bone disease that causes a reduction in bone mineral density and microarchitecture, and subsequently in bone strength. It is estimated that millions of people suffer from some type of osteoporosis. Ιn this study, a quantitative comparison of two different types of enriched diet, i.e., with sesame oil and tahini, was made, in order to assess the effect of these particular types of feed on the strength of rat bones. The experimental procedure was based on a well-documented model for rats’ femoral bones, which underwent three-point bending test. After the fracture of each bone, one of the two fragments was embedded in resin and the bone-resin construct was, then, photographed with a stereoscope. As a next step, the photo was inserted in commercially available CAD software and the actual cross section of the fractured bone was drawn. Taking advantage of the accurate calculation of the geometric characteristics of the cross section, the maximum bending stress, the parasitic shear stress and the equivalent von Mises stress were determined. The results of the study revealed that both sesame oil and tahini seem to be beneficial for the femur bone with sesame oil to be the most beneficial one. In addition, the study pointed out the necessity of using the accurate cross section of the bone rather than any kind of approximate configuration.

Experimental verification of efficacy of pBCT in terms of physical and biological aspects

Proton–boron capture therapy (pBCT) has recently attracted attention as a method for enhancing the efficacy of proton therapy. In pBCT, boron-accumulated cancer cells are irradiated with protons to induce the p +11B→ 3α reaction. The biological efficacy of pBCT has been confirmed by cell-based experiments. However, the actual 3α reaction cross section is relatively small, and the number of α particles produced by this reaction is known to be significantly less than that in the primary proton beam. Therefore, the effectiveness of pBCT has not been theoretically elucidated, and its physical origin and biological effects remain controversial. Consequently, in this study, we sought to clarify these mechanisms by verifying their physical and biological aspects. First, we explored the possibility that other α-particle production channels as alternatives to the 3α reaction were the cause of the pBCT effect. The results suggested the existence of other α-particle production reaction channels, as predicted by theoretical calculations. However, these cross sections were not large enough to support the effectiveness of pBCT. Thus, to investigate the efficacy of pBCT, including biochemical factors that are not limited to α-particle production, experiments were performed to measure the cell viability during proton irradiation. The measurements used boronophenylalanine (BPA) and sodium borocaptate (BSH), which are two boron delivery agents used in boron neutron capture therapy (BNCT). However, no significant changes were observed with respect to the conventional proton therapy. Based on these results, the biological efficacy of pBCT remained unconfirmed under our experimental conditions, and the effectiveness of pBCT needs to be carefully discussed in the future.

結晶相の形状不均一性を考慮した結晶性ポリマの寸法依存性に関する分子鎖塑性FEM解析

Crystalline polymers may show different deformation responses depending on size of crystalline phase with respect to that of specimen. In the previous report, experimental stress-strain curves are numerically reproduced by the molecular chain plasticity FE analysis using a unit cell with hexagonal crystalline phases. However, there are some problems that the shape of crystalline phase in the unit cell is not always 6-fold symmetrical in the actual two-dimensional cross section of PP and the effect of the shape heterogeneity of crystalline phases on deformation responses has not been clarified. In the present report, the authors change the shape of some crystalline phase in the unit cell from hexagon to square and attempt to conduct the molecular chain plasticity FE analysis for amorphous phase and crystal plasticity FE analysis for crystalline one. Furthermore, the effect of shape heterogeneity of crystalline phases on deformation responses is investigated by comparing the results for unit cells with different heterogeneity.

Acoustic scattering reduction of elliptical targets via pentamode near-cloaking based on transformation acoustics in elliptic coordinates

Cloaks for underwater applications designed for actual submarine acoustic stealth are still far from the technological advancement needed for being put in practice. Several challenges need to be overcome such as dealing with weight or non-axisymmetric shapes. In this paper, we introduce the use of elliptical coordinates to define quasi-symmetric transformations to retrieve the material properties of pentamode cloaks for elliptical shaped targets, along with a quantifiable approximation introduced by the rotation tensor being different from the identity. This is done analytically adopting transformation theory, in an attempt to generalize the usual approach for axisymmetric cloaks, with the aim of dealing with shapes closer to those of the actual cross section of a submarine. With respect to existing techniques for dealing with arbitrarily shaped pentamode cloaks, the introduced technique allows for a priori control on the principal directions of anisotropy and for enlarged design space in terms of possible combinations of material property distributions for the same geometry of the problem.

On the Shapes of Interstellar Grains: Modeling Infrared Extinction and Polarization by Spheroids and Continuous Distributions of Ellipsoids

Abstract Although interstellar grains are known to be aspherical, their actual shapes remain poorly constrained. We assess whether three continuous distributions of ellipsoids (CDEs) from the literature are suitable for describing the shapes of interstellar grains. Randomly selected shapes from each distribution are shown as illustrations. The often-used Bohren–Huffman CDE includes a very large fraction of extreme shapes: fully 10% of random draws have axial ratio a 3/a 1 > 19.7, and 5% have a 3/a 1 > 33. The CDE2 distribution includes a much smaller fraction of extreme shapes, and appears to be the most realistic. For each of the three CDEs considered, we derive shape-averaged cross sections for extinction and polarization in the Rayleigh limit. Finally, we describe a method for “synthesizing” a dielectric function for an assumed shape or shape distribution if the actual absorption cross sections per grain volume in the Rayleigh limit are known from observations. This synthetic dielectric function predicts the wavelength dependence of polarization, which can then be compared to observations to constrain the grain shape.

An investigation on viscoelastic characteristics of 3D-printed FDM components using RVE numerical analysis

Fused deposition modelling (FDM) has emerged as an economical additive manufacturing method having the potential to fabricate functional components. Dynamic behaviour of FDM components is of great interest while designing and printing them for functional applications. This paper presents a methodology to describe the dynamic characteristics of FDM, combining the features of thermoplastic material and build parameters adopted in fabrication. The viscoelastic characteristics of thermoplastic filament induce time–temperature dependence in FDM components. The viscoelastic characteristic of the polymer is determined by dynamical mechanical analysis. Layer height is a significant build parameter that determines void geometry even in 100% infill printing, that influences mechanical properties of these additive manufactured components. Dynamic response of FDM 3D-printed parts is highly dependent on viscoelastic characteristics of polymer filaments and build parameters associated with printing. In the study, micro-scale models representing the features of actual cross section morphology with different layer heights are identified as representative volume element (RVE) models. Harmonic analysis is conducted on the RVE models using polymer material data approximated with generalized Maxwell model to determine the dynamic characteristics of the FDM print. The numerical analysis reveals orthotropic viscoelastic nature with maximum stiffness along the direction of filament deposition (raster) direction followed by transverse and vertical directions. A drastic reduction in the FDM component stiffness was observed at lower straining rates. The characteristics determined on RVE can be homogenized to the entire structure based on its print conditions and can be used for designing functional components.

The characteristic analysis of temperature sensor based on a fabricated microstructure fiber by digital image processing technique and finite element method

A temperature sensor based on a Sagnac interferometer by the actual microstructure fiber (MSF) selectively filled with ethanol has been designed in this paper. We obtained the vectorized cross-section of MSF using the method of the digital image processing technique and the finite element method. This method can model the actual cross section structure of MSF rapidly by gray scale processing, filtering, threshold, and edge detection and be applied to the calculation and simulation of the actual MSF perfectly. The air holes on both sides of the core were filled with ethanol to improve the birefringence of the MSF. The simulation result showed that the dip wavelength in transmission spectrum has a blue-shift when the temperature increasing. The average sensitivity can be up to 1 nm °C−1 as the temperature rises from 25 °C to 75 °C. It can be tested in a wide temperature range, which plays a profound role in practical application.

Origin and Quantification of Increased Core Loss in MnZn Ferrite Plates of a Multi-Gap Inductor

Inductors realized with high permeable MnZn ferrite require, unlike iron-powder cores with an inherent dis-tributed gap, a discrete air gap in the magnetic circuit to prevent saturation of the core material and/or tune the inductance value. This large discrete gap can be divided into several partial gaps in order to reduce the air gap stray field and consequently the proximity losses in the winding. The multi-gap core, realized by stacking several thin ferrite plates and inserting a non-magnetic spacer material between the plates, however, exhibits a substan-tial increase in core losses which cannot be explained from the intrinsic properties of the ferrite. In this paper, a comprehensive overview of the scientific literature regarding machining induced core losses in ferrite, dating back to the early 1970s, is provided which suggests that the observed excess core losses could be attributed to a deterioration of ferrite properties in the surface layer of the plates caused by mechanical stress exerted during machining. However, in a first experimental analysis no structural evidence for a deteriorated layer close to the surface is identified by means of Scanning Electron Microscopy (SEM). Therefore, in a next step, a new calorimetric measurement setup based on temperature rise monitoring is proposed in this paper in order to quantify and differentiate between core losses associated with the bulk and the surface of the ferrite plates and therefore to pinpoint the measured excess core loss to shallow layers of ferrite with deteriorated magnetic performance. Electrical measurement of the surface related core losses utilizing the widely accepted two-winding wattmeter method with reactive power compensation is outlined in the appendix but was not employed in this work due to comparably low measurement accuracy. By means of the proposed measurement technique, the bulk and surface core loss density of the MnZn ferrite material 3F4 from FerroxCube was determined for sinusoidal flux density amplitude varying from 75 mT up to 200 mT and excitation frequencies ranging from 200 kHz to 1 MHz. The measured core loss densities (W/cm 3 ) show good agreement with the Steinmetz model provided by the manufacturer validating the proposed calorimetric core loss measurement technique. The measured surface loss density (W/cm 2 ) can also be well predicted with a Steinmetz model, whereby the frequency exponent α in the surface is slightly smaller and the flux density exponent β is slightly larger compared to the Steinmetz parameter of the bulk ferrite. It is shown that the ratio between surface and bulk core losses of a composite core assembled from individual plates is only a function of plate thickness and does not depend on the actual cross section area. Critical plate thickness is then defined to be reached when the total power loss in the composite core has doubled compared to a solid (single-piece) core sample. This new quantity provides a very helpful figure for multi-gap inductor designs. Besides the deteriorated surface layers, several other mechanisms potentially contributing to increased core losses in multi-gap inductors were identified and are finally discussed in the appendix of this paper: flux crowding in the core due to tolerances and imperfections in machining and assembly; deterioration of ferrite properties due to pressure buildup in the stack of plates during the curing of the employed epoxy resin; ohmic loss in the ferrite associated with the current flowing in the conduction path provided by the low impedance of the ferrite material at high frequencies and the parasitic capacitance between winding and the ferrite core.

Gaussian process regression to predict the morphology of friction-stir-welded aluminum/copper lap joints

The joining of materials with different or even competing properties is of high industrial interest regarding resource-efficient production. Friction stir welding (FSW) has been employed to create high-quality joints of dissimilar material combinations. Many studies report both metallurgical bonding and form-fit to be the relevant joining mechanisms. While metallurgical bonding is driven by interdiffusion and occurs in almost every case, form-fit can only appear if the interface is deformed. The hooks of the deformed interface cause interlocking; however, they also result in an increased stress concentration. Hence, the hooking can either enhance or reduce the joint strength depending on their geometries. This study demonstrates an approach to predict the morphology of the cross-sectional interfacial area of friction-stir-welded multi-material joints. Image processing was used to convert cross sections of aluminum/copper lap joints into binary b/w images. Using Gaussian process regression, a data-driven model of the interfacial area’s morphology was constructed based on 13 data sets. The applicability of the resulting Gaussian process model was tested for seven data sets by comparing the algorithm’s morphological predictions with cross sections welded with test parameters that were not used for training. This allows to estimate, which joining mechanism is relevant or dominant for the overall joint strength. The predicted results agreed well with the actual cross sections. Recesses as well as hooks at the interfacial area were successfully predicted even for a limited number of training data. To enhance the space of possible uses of the model for subsequent applications (e.g., simulation of fracture mechanics), more input parameters can be implemented into the model.

Study on AZ91D chip for injection molding (2nd Report, Effect of dimension on effective thermal conductivity after consolidation)

The purpose of this study is to propose an effective model to estimate the effective thermal conductivity of compacts made from magnesium alloy particles, considering the effects of particle size, temperature and pressure. In order to investigate the influence of the particle size, six kinds of particles were prepared in which the cross sectional area was different. The test particles made from AZ91D were poured into a compression vessel and then a given pressure was applied to the piston of vessel for six hours under constant temperature condition. After compression, effective thermal conductivity of compacts were measured by steady state comparative-longitudinal heat flow method. The numerical calculation considering two-dimensional steady heat conduction was also conducted by using the actual cross section of compacts. Test results showed that the effective thermal conductivity of compacts were increased with increase of applied pressure and temperature elevation. Calculation results also revealed that by considering the actual cross section of compacts, the effective thermal conductivity could be well estimated when filling fraction is lower than 0.8. However, when filling fraction is exceed 0.8, the effect of thermal contact resistance between particles on thermal conductivity is not negligible. The experimental equation of effective thermal conductivity of compacts was determined to discuss the effects of cross sectional area of particles.

Two-Photon Spectra of Chlorophylls and Carotenoid-Tetrapyrrole Dyads.

We present a direct comparison of two-photon spectra of various carotenoid-tetrapyrrole dyads and phthalocyanines (Pc) as well as chlorophylls (Chl) in the spectral range between 950 and 1360 nm, corresponding to one-photon spectra between 475 and 680 nm. For carotenoids (Car) with 8, 9, or 10 conjugated double bonds, the two-photon absorption cross section of states below the optical allowed carotenoid S2 is at least about 3-10 times higher than that of Pc or chlorophyll a and b at 550/1100 nm. A quantitative comparison of spectra from Pc with and without carotenoids of eight and nine conjugated double bonds confirms energy transfer from optically forbidden carotenoid states to Pc in these dyads. When considering that less than 100% efficient energy transfer reduces the two-photon contribution of the carotenoids in the spectra, the actual Car two-photon cross sections relative to Chl/Pc are even higher than a factor of 3-10. In addition, strong spectroscopic two-photon signatures at energies below the optical allowed carotenoid S2 state support the presence of additional optical forbidden carotenoid states such as S*, Sx, or, alternatively, contributions from higher vibronic or hot S1 states dominating two-photon spectra or energy transfer from the carotenoids. The onset of these states is shifted about 1500-3500 cm-1 to lower energies in comparison to the S2 states. Our data provides evidence that two-photon excitation of the carotenoid S*, Sx, or hot S1 states results in energy transfer to tetrapyrroles or chlorophylls similar to that observed with the Car S1 two-photon excitation.

Numerical Modeling of Seismic Site Effects in a Shallow Alluvial Basin of the Northern Apennines (Italy)

Research Article| September 25, 2017 Numerical Modeling of Seismic Site Effects in a Shallow Alluvial Basin of the Northern Apennines (Italy) Claudia Madiai; Claudia Madiai aDipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Firenze, via Santa Marta 3, 50139 Florence, Italy, claudia.madiai@unifi.it Search for other works by this author on: GSW Google Scholar Johann Facciorusso; Johann Facciorusso aDipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Firenze, via Santa Marta 3, 50139 Florence, Italy, claudia.madiai@unifi.it Search for other works by this author on: GSW Google Scholar Elisa Gargini Elisa Gargini aDipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Firenze, via Santa Marta 3, 50139 Florence, Italy, claudia.madiai@unifi.it Search for other works by this author on: GSW Google Scholar Author and Article Information Claudia Madiai aDipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Firenze, via Santa Marta 3, 50139 Florence, Italy, claudia.madiai@unifi.it Johann Facciorusso aDipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Firenze, via Santa Marta 3, 50139 Florence, Italy, claudia.madiai@unifi.it Elisa Gargini aDipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Firenze, via Santa Marta 3, 50139 Florence, Italy, claudia.madiai@unifi.it Publisher: Seismological Society of America First Online: 27 Sep 2017 Online Issn: 1943-3573 Print Issn: 0037-1106 Bulletin of the Seismological Society of America (2017) 107 (5): 2094–2105. https://doi.org/10.1785/0120160293 Article history First Online: 27 Sep 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Claudia Madiai, Johann Facciorusso, Elisa Gargini; Numerical Modeling of Seismic Site Effects in a Shallow Alluvial Basin of the Northern Apennines (Italy). Bulletin of the Seismological Society of America 2017;; 107 (5): 2094–2105. doi: https://doi.org/10.1785/0120160293 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search Abstract The main purpose of this work is to investigate the basin‐edge effects on a cross section of an alluvial basin in the northern Apennines (Italy) and to compare the results with those obtained by applying existing approximate criteria to account for valley effects in cases of simple geometrical and stratigraphic conditions. The combined influence of geometry and layering of the basin was evaluated by performing 1D and 2D numerical analyses. The examined site is located in one of the highest seismicity zones of Tuscany. Geological, geophysical, and geotechnical information is obtained from extensive surveys carried out in the area as part of a pioneering Italian project (1998–2004) promoted and supported by the Regional Government of Tuscany to address microzoning studies on an urban scale. Five actual accelerometric signals were adopted in the analyses, consistent with a site reference spectrum defined according to Italian building code. To estimate the additional valley effects on the ground surface of the basin, numerical results from a 2D model were compared with the corresponding 1D numerical results obtained for an isolated soil column at the same location. A large number of vertical soil profiles were analyzed along the cross section, and different types of amplification factors were computed with reference to both peak ground accelerations and elastic response spectra. The results obtained were compared with those of existing approximate approaches for estimating basin effects on basic geometric and geological conditions (sine‐ or trapezoidal‐shaped valley, homogeneous soil deposits), fitting the actual cross section by a simplified symmetrical trapezoidal scheme. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Estimation of hysteretic losses for MgB2 tapes under the operating conditions of a generator

Hysteretic losses in the MgB2 wound superconducting coils of a 550 kW synchronous hybrid scaled generator were estimated as part of the European project SUPRAPOWER led by the Spanish Fundación Tecnalia Research & Innovation. Particular interest was given to the losses caused by the magnetic flux ripples in the rotor coils originating from the conventional stator during nominal operation. To compute these losses, a 2D finite element analysis was conducted and Maxwell’s equations written in the H-formulation were solved considering the nonlinear material properties of the conductor materials. The modeled tapes are made of multiple MgB2 filaments embedded in a Ni matrix and soldered to a high purity copper strip and insulated with Dacron braid. Three geometrical models of single tape cross sections of decreasing complexity were studied: (1) the first model reproduced closely the actual cross section obtained from tape micrographs. (2) The second model was obtained from the computed elasto-plastic deformation of a round Ni wire. (3) The third model was based on a simplified cross section with the superconducting filaments bundled in a single elliptical bulky structure. The last geometry allowed the validation of the modeling technique by comparing numerical losses with results from well-established analytical expressions. Additionally, the following cases of filament transpositions of the multi-filamentary tape were studied: no transposition, partial and full transposition; thereby improving understanding of the relevance of the tape fabrication process on the magnitude of the determination of ac losses. Finally, choosing the right level of geometrical detail, the following operational regimes of the machine and its impact on individual superconducting tape losses in the rotor were studied: bias-dc current, ramping current under ramping background field and magnetic flux ripples under dc background current and field.

Capturing spiral radial growth of conifers using the superellipse to model tree-ring geometric shape.

Tree-rings are often assumed to approximate a circular shape when estimating forest productivity and carbon dynamics. However, tree rings are rarely, if ever, circular, thereby possibly resulting in under- or over-estimation in forest productivity and carbon sequestration. Given the crucial role played by tree ring data in assessing forest productivity and carbon storage within a context of global change, it is particularly important that mathematical models adequately render cross-sectional area increment derived from tree rings. We modeled the geometric shape of tree rings using the superellipse equation and checked its validation based on the theoretical simulation and six actual cross sections collected from three conifers. We found that the superellipse better describes the geometric shape of tree rings than the circle commonly used. We showed that a spiral growth trend exists on the radial section over time, which might be closely related to spiral grain along the longitudinal axis. The superellipse generally had higher accuracy than the circle in predicting the basal area increment, resulting in an improved estimate for the basal area. The superellipse may allow better assessing forest productivity and carbon storage in terrestrial forest ecosystems.

Improved Nuclear Inputs for Nuclear Model Codes Based on the Gogny Interaction

The need for cross sections far from the valley of stability, for applications such as nuclear astrophysics or future nuclear facilities, challenges the robustness as well as the predictive power of nuclear reaction models. Traditionally, cross section predictions rely on more or less phenomenological approaches, depending on parameters adjusted to generally scarce experimental data or deduced for systematic relations. While such predictions are expected to be reliable for nuclei not too far from the experimentally accessible regions, they are clearly questionable when dealing with exotic nuclei. To improve the predictive power of nuclear model codes, one should use more fundamental approaches, relying on sound physical bases, when determining the nuclear inputs (ingredients) required by the reaction model. Thanks to the high computer power available today, all these major ingredients have been microscopically or semi-microscopically determined, starting from the information provided by a Skyrme effective (and efficient) nucleon-nucleon interaction. These microscopic inputs have shown their ability to compete with the traditional classical methods as such, but also when they are used in actual nuclear cross sections calculations. We will discuss the current efforts made to improve the predictive power of such microscopic inputs using a more coherent nucleon-nucleon interaction, namely the finite-range Gogny force.

Prediction of Burst in Flexible Pipes

Usually when a large internal fluid pressure acts on the inner walls of flexible pipes, the carcass layer is not loaded, as the first internal pressure resistance is given by the internal polymeric layer that transmits almost all the loading to the metallic pressure armor layer. The last one must be designed to ensure that the flexible pipe will not fail when loaded by a defined value of internal pressure. This paper presents three different numerical models and an analytical nonlinear model for determining the maximum internal pressure loading withstood by a flexible pipe without burst. The first of the numerical models is a ring approximation for the helically rolled pressure layer, considering its actual cross section profile. The second one is a full model for the same structure, considering the pressure layer laying angle and the cross section as built. The last numerical model is a two-dimensional (2D) simplified version, considering the pressure layer as an equivalent ring. The first two numerical models consider contact nonlinearities and a nonlinear elastic-plastic material model for the pressure layer. The analytical model considers the pressure armor layer as an equivalent ring, taking into account geometrical and material nonlinear behaviors. Assumptions and results for each model are compared and discussed. The failure event and the corresponding stress state are commented.

Measurement of Complex Permittivity of Cylindrical Objects in the E-Plane of a Rectangular Waveguide

Remote sensing of dielectric properties is used for numerous applications such as the field evaluation of soil water, salinity, or the organic matter content. The objective of this study is to measure dielectric properties of cylindrical shaped samples for the previously specified applications. The proposed method employs an analytical approach for determining the complex permittivity of cylindrical dielectric objects placed in the E-plane of a rectangular waveguide. The overall procedure is based on the measurement of reflection and transmission coefficients of the test specimen by placing it inside a section of rectangular waveguide. The reconstruction of dielectric properties of the test sample from the measured scattering coefficients is carried out using the newly proposed closed-form expressions, which are derived by transforming the actual circular cross section of the cylindrical sample into the equivalent multilayered rectangular cross sections. The dielectric properties of a number of specimens, including typical plastics and vegetation samples, are determined using the proposed approach. The typical error in the reconstruction of the dielectric constant of these samples having moderate permittivity values is found to be less than 5%.

현장조사와 침투모형시험을 통한 방조제 침투특성 연구

본 연구는 다층지반으로 구성된 방조제의 침투변화에 따른 안정성을 검토하기 위하여 현장조사와 역해석 방법으로 투수계수와 침투수량을 결정하고, 제체의 변형량과 유실량 측정을 위하여 침투모형시험을 수행하여 가장 합리적인 수치해석 방법을 결정하였다. 검토결과 방조제는 다층지반구조물로 투수계수 차이에 의해 바닥보호공과 성토체 경계부에서 유실이 발생하고 이로 인해 방조제의 변형이 발생한다는 것을 예측할 수 있었다. 한편 침투모형 시험에 대한 수치해석결과 한계유속에 의한 방법은 실측치가 해석값보다 작게 나왔으나 그 경향이 유사하여 실제 단면에 적용 가능할 것으로 판단되었다. The purpose of this study is to decide the permeability and the rate of flow in a way of both site investigation and backward analysis and the most reasonable numerical analysis by performing a seepage model test for measuring the deformation swept volume of the embankment body in order to review a stability of the sea dyke being composed of multi-layers depending on variation of infiltration. As a result of the review, it could be forecasted that sweeping loss would be taken place at the boundary between bed protection works and embankment materials of the sea dyke due to a permeability difference of the multi-layered bed foundation structures and the sea dyke deformation would be occurred as a result thereby. As result of a numerical analysis for the seepage model test, it could be observed that critical velocity method was found to be smaller than the numerical analysis value but its tendency was similar and therefore it was judged that this method could be applied for the actual cross section.