• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.11
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• pp.1119-1126
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• 2007

In this paper, the dynamic stability of a cracked cantilever pipe conveying fluid with tip mass is investigated. The pipe is modelled by the Euler-Bernoulli beam theory in which rotatory inertia and shear deformation effects are ignored. The equation of motion is derived by the energy expressions using extended Hamilton's Principle. The crack section is represented by a local flexibility matrix connecting two undamaged pipe segments. The influence of the crack severity, the position of crack, the mass ratio, and a tip mass on the stability of a cantilever pipe conveying fluid are studied by the numerical method. Besides, the critical flow velocity and the stability maps of the pipe system as a function of mass ratios($\beta$) for the changing each parameter are obtained.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.10
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• pp.1002-1009
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• 2007

In this paper, the dynamic stability of a cracked simply supported pipe conveying fluid with an attached mass is investigated. Also, the effect of attached mass on the dynamic stability of a simply supported pipe conveying fluid is presented for the different positions and depth of the crack. Based on the Euler-Bernouli beam theory, the equation of motion can be constructed by the energy expressions using extended Hamilton's principle. The crack section is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of a fracture and to be always opened during the vibrations. Finally, the critical flow velocities and stability maps of the pipe conveying fluid are obtained by changing the attached mass and crack severity.

• Structural Engineering and Mechanics
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• v.54 no.4
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• pp.711-723
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• 2015

This study investigates the identification of added mass and its location in the glass fiber reinforced polymer (GFRP) beam structures. The main emphasis of this paper is to ascertain the importance of inclusion of rotational degrees of freedom (dofs) in the introduction of added mass or damage identification. Two identification indices that include the rotational dofs have been introduced in this paper: the modal force index (MFI) and the modal rotational curvature index (MRCI). The MFI amplifies damage signature using undamaged numerical stiffness matrix which is related to changes in the altered mode shapes from the original mode shapes. The MRCI is obtained by using a higher derivative of rotational mode shapes. Experimental and numerical results are compared with the existing methods leading to a conclusion that the contributions of the rotational modes play a key role in the identification of added mass. The authors believe that the similar results are likely in the case of damage identification also.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.99-107
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• 2008

In this paper, the stability of a cracked cantilever Timoshenko beam with a tip mass subjected to follower force is investigated. In addition, an analysis of the flutter instability(flutter critical follower force) and a critical natural frequency of a cracked cantilever Euler / Timoshenko beam with a tip mass subjected to a follower force is presented. The vibration analysis on such cracked beam is conducted to identify the critical follower force for flutter instability based on the variation of the first two resonant frequencies of the beam. Therefore, the effect of the crack's intensity, location and a tip mass on the flutter follower force is studied. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations.

• Mass Spectrometry Letters
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• v.9 no.1
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• pp.1-16
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• 2018

Microfluidic technologies hold high promise and emerge as a potential molecular tool to facilitate the progress of fundamental and applied biomedical researches by enabling miniaturization and upgrading current biological research tools. In this review, we summarize the state of the art of existing microfluidic technologies and its' application for characterizing biophysical properties of individual cells. Microfluidic devices offer significant advantages and ability to handle in integrating sample processes, minimizing sample and reagent volumes, and increased analysis speed. Therefore, we first present the basic concepts and summarize several achievements in new coupling between microfluidic devices and mass spectrometers. Secondly, we discuss the recent applications of microfluidic chips in various biological research field including cellular and molecular level. Finally, we present the current challenge of microfluidic technologies and future perspective in this study field.

• Mass Spectrometry Letters
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• v.12 no.1
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• pp.26-30
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• 2021

The impurity concentration is a crucial parameter for semiconductor thin films. Evaluating the impurity distribution in silicon thin film is another challenge. In this study, we have investigated the doping concentration of boron in silicon thin film using time of flight secondary ion mass spectrometry in dynamic mode of operation. Boron doped silicon film was grown on i) p-type silicon wafer and ii) borosilicate glass using hot wire chemical vapor deposition technique for possible applications in optoelectronic devices. Using well-tuned SIMS measurement recipe, we have detected the boron counts 101~104 along with the silicon matrix element. The secondary ion beam sputtering area, sputtering duration and mass analyser analysing duration were used as key variables for the tuning of the recipe. The quantitative analysis of counts to concentration conversion was done following standard relative sensitivity factor. The concentration of boron in silicon was determined 1017~1021 atoms/㎤. The technique will be useful for evaluating distributions of various dopants (arsenic, phosphorous, bismuth etc.) in silicon thin film efficiently.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.45-54
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• 1991

The closed forms of mass matrix with rotational inertia matrix are developed for free vibration analysis in space structures containing linearing tapered members with cross section of thin-walled tube. The exact displacement functions are used for formulating mass matrix. The very small slopes of the tapered member are used in usual practice, such that the series expansion forms of these are also developed to avoid numerical failure in vibration analysis. Significant improvements of accuracy and efficiency of free vibration analysis are achieved by using the mass matrices developed in this study. Frequencies of free vibration of tapered members are compared with solutions based upon stepped representation of beam element.

• Journal of Engineering Education Research
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• v.9 no.3
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• pp.49-61
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• 2006

The objective of this study was to propose a new framework for the creative engineering in the product family design coursework. The idea of product family design is a good solution to fulfill customer's requirements and to respond quickly for the technology change. Mass customization based on product family and product platform is a new paradigm with variety and customization through flexibility and quick responsiveness. In this study, the subjects of product family, product platform, product family map, platform leveraging strategy, morphological matrix and module based product family design were reviewed and presented. A new idea generation scheme utilizing SCAMPER method was combined with the morphological matrix approach. For the effective product family and platform design, creative efforts and approaches were utilized and implemented in the coursework process. This will help students to develop creative thinking and approaches in the engineering problem solving.

• Journal of Soil and Groundwater Environment
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• v.13 no.6
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• pp.40-49
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• 2008

Matrix diffusion from planar fractures was studied mathematically and through physical model experiments. Mathematical models were developed to simulate diffusion from 2D and 3D instantaneous disk sources and a 3D continuous disk source. The models were based on analytical solutions previously developed by Carslaw and Jaeger (1959). The mathematical simulations indicated that the 2D scenario produces significantly different results from the 3D scenario, the time for mass disappearance is significantly larger for continuous sources than for instantaneous sources, the normalized concentration generally decreased over time for instantaneous sources while it increased over time for continuous sources, diffusion rates decrease significantly over time and space, and the normalized mass loss from the source zone never reaches 1 for continuous sources due to the semi-infinite integral. The simulations also showed that disappearance times increase exponentially with increasing source radii and matrix porosity, and decrease with increasing aqueous-phase NAPL solubilities.

• Food Science and Biotechnology
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• v.18 no.1
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• pp.113-117
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• 2009

A method was developed using enhanced liquid chromatography coupled with electrospray ionization mass spectrometry for the analysis and quantitation of 2 main potato glycoalkaloids, $\alpha$-chaconine, and $\alpha$-solanine, without any pre-concentration or derivatisation steps. Calibration curves generated by this technique exhibited a linear dynamic range from 0.025 to $50{\mu}g/mL$ and from 0.05 to $50{\mu}g/mL$ for $\alpha$-chaconine and $\alpha$-solanine, respectively. Matrix effects were evaluated by comparing calibration curves measured in matrix-matched and solvent-based systems. Ion suppression due to matrix effects was weak and extraction recoveries of 88 to 114% were obtained in different sample matrices spiked with analyte concentrations ranging from 15 to $35{\mu}g/mL$. Potatoes that had been genetically modified to tolerate glufosinate contained the same glycoalkaloid levels as their non-transgenic counterpart. We suggest complementing compositional comparison assessment strategy by validating quantitative analytical methods for the toxic glycoalkaloids in potato plants.