• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2082-2087
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• 2004

In this study, the variation of spark plug location in the combustion chamber was investigated for the sake of emission characteristics from SI engine by using PDA valve. The swirl is ong of the important parameters that effects emission characteristics. PDA valve has been used to satisfy the requirements of sufficient swirl generation to improve combustion and emission reduction to effect on flow profile on a combustion chamber. Especially, the variation of spark plug location have an important effect to analyze exhaust gas and the early flame propagative process. Therefore, this test is forced that injection timing, spark timing and intake air motion govern the stable combustion. From the results, it showed that the variable spark plug location and PDA valve can be reduced exhaust gas.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.282-287
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• 1996

The non-linear torsional vibrations of the propulsion shafting system with viscous damper are considered. The motion is modeled by non-linear differential equations of second order. the equivalent system is modeled by two mass softening system with Duffing's oscillator. The steady state response of a equivalent system is analyzed for primary resonance only. Harmonic balance method as a non-linear vibration analysis technique is used. Jump phenomena are explained. The primary unstable region obtained by the Mathieu equation is investigated. Both theoretical and measured results of the propulsion shafting system are compared with and evaluated. As a result of comparisons with both data, it was confirmed that Duffing's oscillator can be used as a analysis method in the modeling of the propulsion shafting system attached viscous damper with non-linear stiffness.

• Bulletin of the Society of Naval Architects of Korea
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• v.13 no.3
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• pp.1-9
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• 1976

A numerical method for solving the boundary-value problem related to potential flows with a free surface and an experimental work are introduced in this paper. The forced heaving motion of cylinders with arbitrary shapes in water of finite depth are Considered here. The Fredholm integral equation of the first kind is employed in determining strengths of singularities distributed on the body surface. And the results obtained by the present method for the case of a heaving circular cylinder on water of finite depth agree well with existing results of earlier investigators.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.155-163
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• 1996

This paper presents vibration and position tracking control of a smart structure using shape memory alloy(SMA) actuators. A governing equation of motion of the proposed structure is obtained via Hamilton's princeple. The dynamic characteristics of the SMA actuator are experimentally identified and incorporated with the governing equation to furnish a control system model. Subsequently, a sliding mode controller which has inherent robustness to external disturbances is formulated on the basis of the sliding mode conplacement, and also for the position tracking control of desired trajectories with low-frequency sine and square waves.

• Structural Engineering and Mechanics
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• v.90 no.4
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• pp.403-415
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• 2024

We looked at how the damping qualities of epoxy composites changed when different amounts of graphite nanoplatelets (GNP) were added, from 0% to 6% by weight. A mix of free and forced vibration tests helped us find the key GNP content that makes the damper ability better the most. We also created a Representative Volume Element (RVE) model to guess how the alloys would behave mechanically and checked these models against testing data. An Artificial Neural Network (ANN) was also used to guess how these compounds would react to motion. With proper hyperparameter tweaking, the ANN model showed good correlation (R²=0.98) with actual data, indicating its ability to predict complex material behavior. Combining these methods shows how GNPs impact epoxy composite mechanical properties and how machine learning might improve material design. We show how adding GNPs to epoxy composites may considerably reduce vibration. These materials may be used in industries that value vibration damping.

• Structural Engineering and Mechanics
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• v.89 no.6
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• pp.549-556
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• 2024

A serial pendulum dynamic vibration absorber (DVA) was designed to suppress the vibration of two degrees of freedom (Two-DOF) structure model. The optimal DVA parameters are selected using a genetic algorithm (GA) by minimizing the fitness function formulated from the system's frequency response function (FRF). Two fitness function criteria, using one and two target frequency ranges, were utilized to calculate the optimal DVA parameters. The optimized serial pendulum DVA parameters were used to reduce structural vibration under free and forced excitation conditions. The simulation study found that the serial pendulum DVA can effectively reduce the vibration response for a small excitation amplitude. However, the DVA performance decreases for a large excitation amplitude due to the nonlinearity of pendulum motion, and the percentage of vibration response attenuation is smaller than that obtained using a small excitation amplitude.

• Journal of Chest Surgery
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• v.29 no.9
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• pp.1017-1022
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• 1996

Patients with fractured ribs necessarily suffer from severe chest ain, which prevents coughing, deep breathing and bronchial toilette, cause atelectasis and pulmonary shunting. Relief of chest pain is benecial to patients, providing consort and facilitating physiotherapy and effective expectoration. We compared the efficacy of pain relief be!ween continuous epidural analgesia and conventional intramlrscular analgesia in 20 patients with fractured ribs. Among 20 patients, epidural analgesia was done or 10 patients(experimental group) and the remainder ten received intramuscular analgesia(control group). The pain and ROM(range of motion) scores, vital sign, PaO2, forced vital capacity(FVC) and forced expiratory volume for 1 second(FEVI) were checked on immediate admission and 12, 24 hours, third, fifth, and seventh day after starting of continuous epidural block. The pain and ROM scores were decreased and the PaO2, FRC and FEVI were significantly increased in experimental group. The side effects of epidural analgesia were mild and reversible. With th se result, we can suggest that epidural analgesia is more effective for pain relief and restoration of pulmonary mechanics in patients with fractured ribs.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.1
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• pp.73-81
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• 2002

This study is performed to evaluate and design the vibration characteristics of the onboard machinery with resilient mountings. To reduce the vibration revel of onboard machinery with resilient mountings, it is important to evaluate and, if necessary modify vibration characteristics of the resilient mountings. In this study we have developed a program to calculate natural frequencies of the machinery with resilient mountings, forced vibration levels due to internal excitation force of the machinery itself and external excitation forces of the main engine and the propeller, and the force and motion transmissibility of the resilient mountings. The developed program can be also applied to optimal design of the resilient mountings for obtaining a target natural frequency and for achieving a minimum forced vibration level at the center of gravity of the machinery.

• The Korean Journal of Pain
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• v.9 no.1
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• pp.135-139
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• 1996

Intercostal nerve blockade with local anesthetics has been used extensively in the past to provide pain relief following thoracotomy. Its popularity fell, for a period, probably due to increasing use of epidural analgesia. More recently, interest has focused on intercostal nerve block with the introduction of variously sited catheters. Two epidural catheters were placed under direct vision, in the intercostal spaces just above and below the wound by feeding the catheters posteriorly from the wound edges, superficial to the parietal pleura. Bupivacaine 0.25%. Was infused continuously at a rate of 5 ml/hour through each of the two intercostal catheters. Each catheter was primed with 10 ml/hour through each of the two intercostal catheters. Each catheter was primed with 10 ml of 0.25% bupivacaine. Postoperative vital signs resembled preoperation data. Arterial carbon dioxide pressure ($PaCO_2$) was unchanged and arterial oxygen pressure ($PaO_2$) was increased during two days after surgery because oxygen was administered at 21/min. Forced vital capacities (FVC) and forced expiratory volume in 1 second ($FEV_1$) were decreased the day of operation but restored to preoperative value from second operation day. VAS were increased on operation day but decreased from second operation day. Motion range of arms were not impaired. We concluded that continuous intercostal nerve block through catheters placed during thoracotomy in the adjacent intercostal spaces is a simple and effective method for management of the post-thoracotomy pain.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.4
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• pp.395-404
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• 2000

A damage detection and assessment algorithm is developed by measuring accelerations at limited locations of a structure under forced vibrations. The developed algorithm applies a time-domain system identification (SI) method that identifies a structure by solving a linearly constrained nonlinear optimization problem for optimal structural parameters. An equation error of the dynamic equilibrium of motion is minimized to estimate optimal parameters. An adaptive parameter grouping scheme is applied to localize damaged members with sparse measured accelerations. Damage is assessed in a statistical manner by applying a time-windowing technique to the measured time history of acceleration. Displacements and velocities at the measured degrees of freedom (DOF) are computed by integrating the measured accelerations. The displacements at the unmeasured DOF are estimated as additional unknowns to the unknown structural parameters, and the corresponding velocities and accelerations we computed by a numerical differentiation. A numerical simulation study with a truss structure is carried out to examine the efficiency of the algorithm. A data perturbation scheme is applied to determine the thresholds lot damage indices and to compute the damage possibility of each member.