• 한국소음진동공학회논문집
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• 제15권1호
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• pp.72-80
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• 2005

Recent studies have dealt with brake squeal in terms of the coupled vibration of brake component parts. In this paper, we assemble the mode models derived from FE analysis of the individual components of the drum brake system into the system model by considering the friction interaction of the lining and drum at the interface. The validity of the component models are backed up by the experimental confirmation work. By scrutinizing the real parts of the complex eigen-values of the system, the unstable modes, which may be strong candidate sources of squeal noise, are identified. Mode participation factors are calculated to examine the modal coupling mechanism. The model predictions for the unstable frequencies pointed well the actual squeal noise frequencies measured through field test. Sensitivity analysis is also performed to identify parametric dependency trend of the unstable modes, which would indicate the direction for the squeal noise reduction design. Finally, reduction of the squeal noise tendency through shape modification is tried.

• 한국해양공학회지
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• 제17권4호
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• pp.31-36
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• 2003

In case of this thick rolling-steel for a multistory building, a large oil-drilling structure, a large vessel, a bridge and so on, Lamella Tearing around the welded joint zone is the most serious problems. In order to prevent Lamella Tearing, not only is choice of material important, but also the comprehensive investigation for the structural design and the construction. The Lamella Tearing that is a staircase-shape occurs due to the contraction stress to the thickness direction of the plate and has the character that the cracks progress along the elongated inclusion by rolling. In general, because cracks occur at the heat affected zone and around HAZ, it is necessary to establish the safety and the confidence of the welded structure to restrain the welding defect such as Lamella Tearing. The mechanical approaches are the easier and more economical than the approaches of the material and the construction method. In addition, the appropriate welding profile and the optimum welding condition contribute toward the improvement of the productivity and influence on the standardization of the manufacturing technology.

• Structural Engineering and Mechanics
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• 제63권1호
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• pp.37-46
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• 2017

This paper is concerned with the numerical study on the resonance response of a rigid spar-type floating platform in coupled heave and pitch motion. Spar-type floating platforms, widely used for supporting the offshore structures, offer an economic advantage but those exhibit the dynamically high sensitivity to external excitations due to their shape at the same time. Hence, the investigation of their dynamic responses, particularly at resonance, is prerequisite for the design of spar-type floating platforms which secure the dynamic stability. Spar-type floating platform in 2-D surface wave is assumed to be a rigid body having 2-DOFs, and its coupled dynamic equations are analytically derived using the geometric and kinematic relations. The motion-variance of the metacentric height and the moment of inertia of floating platform are taken into consideration, and the hydrodynamic interaction between the wave and platform motions is reflected into the hydrodynamic force and moment and the frequency-dependent added masses. The coupled nonlinear equations governing the heave and pitch motions are solved by the RK4 method, and the frequency responses are obtained by the digital Fourier transform. Through the numerical experiments to the wave frequency, the resonance responses and the coupling in resonance between heave and pitch motions are investigated in time and frequency domains.

• ETRI Journal
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• 제38권2호
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• pp.217-226
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• 2016

We propose an architecture that reduces the power consumption and active area of such a modulator through a reduction in the number of active components and a simplification of the topology. The proposed architecture reduces the power consumption and active area by reducing the number of active components and simplifying the modulator topology. A novel second-order loop filter that uses a single operational amplifier resonator reduces the number of active elements and enhances the controllability of the transfer function. A trapezoidal-shape half-delayed return-to-zero feedback DAC eliminates the loop-delay compensation circuitry and improves pulse-delay sensitivity. These simple features of the modulator allow higher frequency operation and more design flexibility. Implemented in a 130 nm CMOS technology, the prototype modulator occupies an active area of $0.098mm^2$ and consumes 5.23 mW power from a 1.2 V supply. It achieves a dynamic range of 62 dB and a peak SNDR of 60.95 dB over a 15 MHz signal bandwidth with a sampling frequency of 780 MHz. The figure-of-merit of the modulator is 191 fJ/conversion-step.

• Structural Monitoring and Maintenance
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• 제3권3호
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• pp.297-314
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• 2016

As the study of internal corrosion of pipeline need a large number of experiments as well as long time, so there is a need for new computational technique to expand the spectrum of the results and to save time. The present work represents a new non-destructive evaluation (NDE) technique for detecting the internal corrosion inside pipeline by evaluating the dielectric properties of steel pipe at room temperature by using electrical capacitance sensor (ECS), then predict the effect of pipeline environment temperature (${\theta}$) on the corrosion rates by designing an efficient artificial neural network (ANN) architecture. ECS consists of number of electrodes mounted on the outer surface of pipeline, the sensor shape, electrode configuration, and the number of electrodes that comprise three key elements of two dimensional capacitance sensors are illustrated. The variation in the dielectric signatures was employed to design electrical capacitance sensor (ECS) with high sensitivity to detect such defects. The rules of 24-electrode sensor parameters such as capacitance, capacitance change, and change rate of capacitance are discussed by ANSYS and MATLAB, which are combined to simulate sensor characteristic. A feed-forward neural network (FFNN) structure are applied, trained and tested to predict the finite element (FE) results of corrosion rates under room temperature, and then used the trained FFNN to predict corrosion rates at different temperature using MATLAB neural network toolbox. The FE results are in excellent agreement with an FFNN results, thus validating the accuracy and reliability of the proposed technique and leads to better understanding of the corrosion mechanism under different pipeline environmental temperature.

• 센서학회지
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• 제26권6호
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• pp.379-385
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• 2017

In this study, an amperometric non-enzymatic glucose sensor was developed on the surface of a glassy carbon electrode by simply drop-casting the synthesized homogeneous suspension of hexagonal boron nitride (h-BN) nanosheets with a copper metal-organic framework (Cu-MOF) composite. Comprehensive analytical methods, including field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), cyclic voltammetry, electrochemical impedance spectroscopy, and amperometry, were used to investigate the surface and electrochemical characteristics of the h-BN-Cu-MOF composite. The FE-SEM, FT-IR, and XRD results showed that the h-BN-Cu-MOF composite was formed successfully and exhibited a good porous structure. The electrochemical results showed a sensor sensitivity of $18.1{\mu}A{\mu}M^{-1}cm^{-2}$ with a dynamic linearity range of $10-900{\mu}M$ glucose and a detection limit of $5.5{\mu}M$ glucose with a rapid turnaround time (less than 2 min). Additionally, the developed sensor exhibited satisfactory anti-interference ability against dopamine, ascorbic acid, uric acid, urea, and nitrate, and thus, can be applied to the design and development of non-enzymatic glucose sensors.

• Wind and Structures
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• 제28권5호
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• pp.331-345
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• 2019

Long-span bridge decks are often shaped as streamlined to improve the aerodynamic performance of the deck. There are a number of important shaping parameters for a streamlined bridge deck. Their effects on aerodynamics should be well understood for shaping the bridge deck efficiently and for facilitating the bridge deck design procedure. This study examined the effect of various shaping parameters such as the bottom plate slope, width ratio and side ratio on aerodynamic responses of single box streamlined bridge decks by employing unsteady RANS simulation. Steady state responses and flow field were analyzed in detail for wide range of bottom plate slopes, width and side ratios. Then for a particular deck shape Reynolds number effect was investigated by varying its value from $1.65{\times}10^4$ to $25{\times}10^4$. The aerodynamic response showed very high sensitivity to the considered shaping parameters and exhibited high aerodynamic performance for a particular combination of shaping parameters.

• 센서학회지
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• 제33권3호
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• pp.173-178
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• 2024

Development of pressure sensors for harsh environments with high pressure, humidity, and temperature is essential for many applications in the aerospace, marine, and automobile industries. However, existing materials such as polymers, adhesives, and semiconductors are not suitable for these conditions and require materials that are less sensitive to the external environment. This study proposed a pressure sensor that could withstand harsh environments and had high durability and precision. The sensor comprised a piezoresistor pattern and an insulating film directly formed on a stainless-steel membrane. To achieve the highest sensitivity, a pattern design method was proposed that considered the stress distribution in a circular membrane using finite element analysis. The manufacturing process involved depositing and etching a dielectric insulating film and metal piezoresistive material, resulting in a device with high linearity and slight hysteresis in the range of a maximum of 40 atm. The simplicity and effectiveness of this sensor render it a promising candidate for various applications in extreme environments.

• 대한의생명과학회지
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• 제30권3호
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• pp.131-136
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• 2024

In this investigation, a novel design for a well-plate structure was created to optimize antigen-antibody reactions. The main objective during the development process was to enhance the internal structure of the well plate and increase the surface area. To improve efficiency, the newly designed well-plate was conical in shape and featured internal protrusions, or fins, which increased the surface area per unit volume by 1.45 times compared to standard plates. The performance of the newly developed well plate was assessed using a sandwich CLEIA system, which demonstrated a detection limit approximately 2.5 times better than that of commercial products. Additionally, the coefficient of variation (CV%) was superior to that of commercial products, with inter-assay CV(%) ≤ 11 and intra-assay CV(%) ≤ 9, compared with inter-assay CV(%) ≤ 15 and intra-assay CV(%) ≤ 10 for commercial products. Furthermore, the newly designed well plate demonstrated higher reaction efficiency, even with smaller sample volumes (25~50 µL) compared to the 50~100 µL typically required by commercial well plates. The incorporation of fine patterns increases the number of active sites available for interaction with the samples, thereby significantly enhancing the reaction sensitivity and overall performance.

• 한국실내디자인학회논문집
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• 제21권1호
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• pp.68-77
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• 2012

Appreciating the aspect of modem architecture requires not only the comprehension of the nature of design and architects' ways of thinking and expression but also observers' views on buildings and their perceptive/cognitive stages. This calls for an in-depth study on the "system of phenomenological perceptions" that works as a new architectural experience system. The system of phenomenological perceptions makes it possible to specify the individual process of understanding architecture, that is, hands-on experiences, participations, feelings, perceptions, and cognition. The value of user experience and cognition has been emphasized by philosophical and aesthetical concepts as well. Therefore, in order to better appreciate the modern architecture, this study suggests theoretical consideration to "orientation and event" that are crucial elements in understanding a phenomenological view and materializing actual space formation. This offers the cognitive system with which we analyze modem architecture and comprehensive expressional methods. In other words, this study contemplates the system of phenomenological perceptions from an existential spatial perspective by structurizing the system of the orientation and the event in order to segmentalize users' current locations, potential directions, the relations with spaces, continual vie'wpoints as well as buildings' functions and interior and exterior division. The system of phenomenological perceptions helps understand and systemize modern architecture through a system based on relations between sensation, perception, cognition, sensitivity, and rationality. This creates a new cognitive system employing the concept of the orientation and the event, which is different from a normal cognitive system basing on the sense of vision. When observers appreciate space, they tend to relate the space to a certain event and to remember their experiences in it. During the process, they draw borders of the space in which the event takes place and give shape to their experiences including actions, movements, cognition and sensation. The process leads to the formation of "placeness," and here, the concept of the orientation comes in as the location and the center of the placeness. This study proves that a determined orientation coupled with individual experience and events settles the place ness; detailed elements in the cognitive system have close relations with one another; the orientation, actions, events, and places are the factors that materialize observers' architectural experience.