• Advances in aircraft and spacecraft science
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• v.7 no.3
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• pp.251-269
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• 2020

Euclid is an optical/near-infrared survey mission of the European Space Agency (ESA) to investigate the nature of dark energy, dark matter and gravity by observing the geometry of the Universe and the formation of structures over cosmological timescales. The Euclid spacecraft mechanical architecture comprises the Payload Module (PLM) and the Service Module (SVM) connected by an interface structure designed to maximize thermal and mechanical decoupling. This paper shortly illustrates the mechanical system of the spacecraft and the mechanical verification philosophy which is based on the Structural and Thermal Model (STM), built at flight standard for structure and thermal qualification and the Proto Flight Model (PFM), used to complete the qualification programme. It will be submitted to a proto-flight test approach and it will be suitable for launch and flight operations. Within the overall verification approach crucial mechanical tests have been successfully performed (2018) on the SVM platform and on the sunshield (SSH) subsystem: the SVM platform static test, the SSH structure modal survey test and the SSH sine vibration qualification test. The paper reports the objectives and the main results of these tests.

• Structural Engineering and Mechanics
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• v.10 no.1
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• pp.37-51
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• 2000

Identification of damage location based on modal measurement is an important problem in structural health monitoring. The damage index method that attempts to evaluate the changes in modal strain energy distribution has been found to be effective under certain circumstances. In this paper two damage index methods using bending strain energy and shear strain energy have been evaluated for numerous cases at different locations and degrees of damage. The objective is to evaluate the feasibility of the damage index method to localize the damage on large span concrete bridge. Finite element models were used as the test structures. Finally this method was used to predict the damage location in an actual structure, using the results of a modal survey from a large concrete bridge.

• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.11
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• pp.1291-1299
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• 2003

In order to design the better brassiere in terms of appearance and functions, various parameters of the materials should be considered; in this study, fatigue properties and subjective sensation of wing materials and its relation to the preference for a brassiere was investigated. After the survey of commercially available products, five elastic fabrics such as cotton, Modal, polyester, nylon, and Tactel, all of which contain 10% polyurethane, were chosen as specimens. Fabric growth were determined to evaluate fatigue properties. Qmax was determined to evaluate the warm-cool feeling. For the sensory test, semantic differential scale which contains 15 adjectives were developed. Fatigue properties were very similar at the 20% elongation irrespective of the duration of tension, but at 40% and 100% elongation, man made fabric showed less growth than cellulose fabrics. The factor analysis showed four factors such as sense of warmth, smoothness, weight and elasticity. Preference of the specimens was ranked in the order of Tactel>Modal>cotton>nylon>polyester.

• Computational Structural Engineering
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• v.5 no.4
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• pp.93-102
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• 1992

The design of reactor internals requires the accurate vibration characteristics of each component for subsequent dynamic structural response analyses. For Korean standard nuclear power plant some modifications on the Control Element Assembly shroud from the reference design have been made, Since the shroud is complex in geometry having an array of vertical round tubes and webs in a square grid pattern, and being tied down by preloaded tie rods into position, it is planned to perform a vibration measurement program consisting of both experimental and analytical modal studies upon that component. The shroud modal testing was performed on the low frequency global survey to measure the first several modes. The analysis using the finite element model was also performed for the as-tested conditions. The natural frequencies and mode shapes from both test and analysis have been acquired and compared to be in good agreement. It is concluded that finite element model generated is good enough to be used in the design for the dynamic response analysis under various loading conditions.

• Smart Structures and Systems
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• v.15 no.3
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• pp.665-682
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• 2015

Structural identification or St-Id is 'the parametric correlation of structural response characteristics predicted by a mathematical model with analogous characteristics derived from experimental measurements'. This paper describes a St-Id exercise on Humber Bridge that adopted a novel two-stage approach to first calibrate and then validate a mathematical model. This model was then used to predict effects of wind and temperature loads on global static deformation that would be practically impossible to observe. The first stage of the process was an ambient vibration survey in 2008 that used operational modal analysis to estimate a set of modes classified as vertical, torsional or lateral. In the more recent second stage a finite element model (FEM) was developed with an appropriate level of refinement to provide a corresponding set of modal properties. A series of manual adjustments to modal parameters such as cable tension and bearing stiffness resulted in a FEM that produced excellent correspondence for vertical and torsional modes, along with correspondence for the lower frequency lateral modes. In the third stage traffic, wind and temperature data along with deformation measurements from a sparse structural health monitoring system installed in 2011 were compared with equivalent predictions from the partially validated FEM. The match of static response between FEM and SHM data proved good enough for the FEM to be used to predict the un-measurable global deformed shape of the bridge due to vehicle and temperature effects but the FEM had limited capability to reproduce static effects of wind. In addition the FEM was used to show internal forces due to a heavy vehicle to to estimate the worst-case bearing movements under extreme combinations of wind, traffic and temperature loads. The paper shows that in this case, but with limitations, such a two-stage FEM calibration/validation process can be an effective tool for performance prognosis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.692-700
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• 2014

In this work, satellite FE (finite element) model updating for the prediction of the effect of micro-vibration is described. In the case of satellites launched in low earth orbit, high agility and more mission accomplishments are required by the customer in order to procure many images from satellites. To achieve the goal, many mechanisms, including high capacity wheels and antennas with multi-axis gimbals have been widely adopted, but they become a source of micro-vibration which could significantly deteriorate the quality of images. To investigate the effect due to the micro-vibration in orbit on the ground, a prediction is conducted through an integrated model coupling the measured jitter sources with FE (finite element) model. Before prediction, the FE model is updated to match simulation results with the modal survey test. Subsequently, the quality of FE model is evaluated in terms of frequency deviation error, the resemblance of mode shapes and FRFs (frequency response functions) between test and analysis.

• Journal of Korean Society of Transportation
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• v.30 no.4
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• pp.85-94
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• 2012

Modern freight transport pursues not only the reduction of logistic costs but also aims at green logistics and efficient shipments. In order to accomplish these goals, various policies regarding the multimodal shipment and stopover to logistic facilities have widely been made. Such situation requires changes in existing methods for analyzing freight demand. However, the reality is that a reliable freight demand forecast is limited, since in the transport research field there is no robust freight demand model that can accommodate transshipments at logistic facilities. This study suggested a novel method to analyze freight demand, which can consider transshipments in multi-modal networks. Also, the applicability of this method was discussed through an example test.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.14-22
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• 2011

This study is to estimate delay time model of signalized intersection by using travel data of Bus Information System. BIS, which applies the advanced information technology to an existing bus system, has been developing and operating in many cities. However, even though some useful traffic informations have been collected from BIS operation, utilization of real-time data to the traffic operation has not been promoted due to the inhomogeneity of modal speeds. Accordingly, in this study, a fundamental research is performed for traffic controls in urban areas and providing a traffic information throughout a methodology for estimating delay time using the data from BIS was developed. This delay time model setting bus travel time excluding service time of a bus stop as explanatory variables was constructed as a regression model, and the coefficient of determination of a linear regression model most highly appeared as 0.826. As a result of performing T-test with field survey values and model estimation values for verifying constructed models statistically, it was analyzed to be statistically significant in a confidence level of 95%.

• Journal of Korean Society of Transportation
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• v.17 no.5
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• pp.19-32
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• 1999

In this study, the trip characteristics of workers in the city are systematically analyzed. The trip behaviors and socioeconomic characteristics of workers are analyzed using Person Trip Survey Data of 1988 and 1992 in Taegu Metropolitan area. With the results of behavioral analyses, the daily travel pattern of workers is shown as one tour contained two trips and it is relatively simple and stable. Also the rate using the same mode in a day is Presented as high ratio. So, it can be explained that the choice of worker\`s first trip is fixed his/her travel mode for his/her daily travel mode. Based on these analyses, the mode choice model for workers is developed by applying the Multi-nominal Logit Model with the choice set of bus, taxi, and car. The explanatory variables of this model include sex, age, auto, travel time, and cost. Empirical tests of the model show encouraging results. After that, the temporal transferability of the model is examined by the Pairwise t-test and five indexes far the model of 1988 and 1992. The results of examination are satisfied with each significance level of the explanatory variables and five indexes. Therefore. it can be concluded that the temporal transferability of this model developed in this study is resonable.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.26-33
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• 2005

Inversion of multi-mode surface-wave phase velocity for shallow engineering site investigation has received much attention in recent years. A sensitivity analysis and inversion of both synthetic and field data demonstrates the greater effectiveness of this method over employing the fundamental mode alone. Perturbation of thickness and shear-wave velocity parameters in multi-modal Rayleigh wave phase velocities revealed that the sensitivities of higher modes: (a) concentrate in different frequency bands, and (b) are greater than the fundamental mode for deeper parameters. These observations suggest that multi-mode phase velocity inversion can provide better parameter discrimination and imaging of deep structure, especially with a velocity reversal, than can inversion of fundamental mode data alone. An inversion of the theoretical phase velocities in a model with a low velocity layer at 20 m depth can only image the soft layer when the first higher mode is incorporated. This is especially important when the lowest measurable frequency is only 6 Hz. Field tests were conducted at sites surveyed by borehole and PS logging. At the first site, an array microtremor survey, often used for deep geological surveying in Japan, was used to survey the soil down to 35 m depth. At the second site, linear multichannel spreads with a sledgehammer source were recorded, for an investigation down to 12 m depth. The f-k power spectrum method was applied for dispersion analysis, and velocities up to the second higher mode were observed in each test. The multi-mode inversion results agree well with PS logs, but models estimated from the fundamental mode alone show f large underestimation of the depth to shallow soft layers below artificial fill.