• Journal of Power System Engineering
• /
• v.18 no.6
• /
• pp.180-185
• /
• 2014

Due to the larger and high-speed vessels recently constructed, output and speed of the engines for propulsion or power generation is increasing. These high-power and high-speed engine of the ship is becoming as a major contributor causing excessive noise and vibration. Other fittings as well as equipment installed on board, it makes equipment failure or other defect by resonance. This causes a lot of M/H(Man Hour) for repairs and the reliability of the company is invading even be negative because the clients give much comment. Thus, it's being studied for any fittings installed on board to maintain the safe operation and to prevent any problem during the performance in any operating conditions. In this study, it was investigated to solve these problems for the supports of the various fittings for easy installation-related support that each type of intensity and shape and manufacturing method using structural analysis program(DNV Nauticus Hull 3D Beam). Namely, it would be applied to the very large crude carriers in consideration of mechanics of materials of the support equipment by providing the fact that dynamics analysis of the structural characteristics of the equipment and the support of the production installation is easy and productivity can be high standards for geometry and thereby to simplify the analysis task to design changes at the same time and to minimize the reinforcement for the supports.

• Tribology and Lubricants
• /
• v.31 no.6
• /
• pp.302-307
• /
• 2015

The use of turbocharger in internal combustion engines has increased as it is a key components for improving system efficiency without increasing engine size. Because of increasing demand, many studies have evaluated rotordynamic performance so as to increase rotation speed. This paper presents a linear and nonlinear analysis model for a turbocharger rotor supported by a floating ring bearing. We constructed rotor model by using the finite element method and approximated bearings as being infinitely short. In the linear model, we considered fluid film force as stiffness and damping element. In nonlinear analysis, calculation of the fluid film force involved solving the time dependent Reynolds equation. We verified the developed model by comparing the results to those of previous research. The analysis results show that there are four unstable modes, which are rigid body modes combining ring and rotor motion. As the rotating speed increases, the logarithmic decrement shows that certain unstable modes goes into the stable area or the stable mode goes into the unstable area. These unstable modes appear as sub-synchronous vibrations in nonlinear analysis. In nonlinear analysis frequency jump phenomenon demonstrated in several experimental studies appears. The analysis results also showed that frequency jump phenomenon occurs when the vibration mode changes and the sequence of unstable mode matches the linear analysis result. However, the natural frequency predicted using linear analysis differs from those obtained using nonlinear analysis.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.128-128
• /
• 2000

박막의 탄성 특성을 평가하는 방법으로 nano-indentation, Brillouin light scattering measurement, ultrasonic surface wave measurement, bulge test, vibration membrane method 등 여러 가지가 제시되어 왔다. 이러한 방법들은 필름의 두께가 일정 두께 이상이 되어야 정확한 측정이 가능한 방법으로 매우 얇은 박막에서도 탄성특성을 평가할 수 있는 freehang, bridge 방법이 제시되었으며, 이 방법은 간단한 식각 공정을 통해 매우 얇은 박막에도 적용시킬 수 있다는 장점을 가지고 있다. 본 연구에서는 아주 얇은 박막에서도 탄성특성을 평가할 수 있는 freehang 방법을 이용하여 순수한 Diamond-like carbon (DLC) 필름과 Sidl 첨가된 DLC 필름의 탄성 특성을 평가하고자 한다. 실험에서 사용한 필름은 rf-PACVD 장비를 이용하여 증착하였다. 이때 전극과 플라즈마 사이의 바이어스 음전압은 -400 Vb로 합성압력은 10mTorr로 고정하였다. 사용한 반응 가스는 벤젠(C6H6), 그리고 벤젠과 희석된 실렌(SiH4 : H2 = 10 : 90)이며, 희석된 실렌의 첨가량을 조절하여 필름 내에 일정량의 Si을 함유시켰다. 각각의 조건에서 증착시간을 조절하여 필름의 두께를 변화시켰으며, KOH(5.6mol) 용액을 이용하여 습식 식각을 함으로써 freehang을 제작하였다. 이때 식각액에 의한 DLC 필름의 손상은 관찰되지 않았다. 필름의 잔류 응력을 측정하기 위해 200$\pm$10 혹은 100$\pm$5$\mu\textrm{m}$ 두께의 얇은 (100) Si wafer를 5$\times$50 mm2의 strip 형태로 절단하여 사용하였다. 필름의 압축 잔류 응력에 의해 발생한 필름/기판 복합체의 곡률은 laser 반사법과 $\alpha$-step profiler를 이용하여 측정하였으며, 이 결과를 Brenner 등에 유도된 식을 이용하여 잔류 응력을 계산하였다. 또한 제작된 frddhang은 광학 현미경과 전자주사현미경에 의해 관찰되었다. 이렇게 제작된 freehang을 이용하여 필름이 기판에 부착되기 위해 필요한 변형률을 측정하고, 독립적으로 측정된 필름의 잔류 응력을 박막의 응력-변형률 관계식에 적용하여 biaxial elastic modulus, E/(1-v)를 구할 수 있었다. 측정 결과 필름의 잔류 응력과 biaxial elastic modulus는 필름의 두께가 감소함에 따라 감소하는 경향을 나타냈으며, 같은 두께의 필름인 경우, 식각 깊이에 따른 biaxial elastic modulus 의 변화를 통해 최적의 식각 깊이를 알 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.2
• /
• pp.201-206
• /
• 2011

A spacer grid assembly is one of the most important structural components of the nuclear fuel assembly of a pressurized water reactor (PWR), and it affects the performance of the fuel assembly. The primary design requirement is that the mechanical integrity of the fuel rod should be maintained by the spacer grid assembly during the operation of the reactor. It was known that fretting damage to the fuel rod can be reduced by adjusting the relative moving displacement between the fuel rod and its support. In this study, we used the finite element method to evaluate the characteristics of a sliding support designed to reduce fretting damage of fuel rods.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.7
• /
• pp.711-716
• /
• 2012

The purpose of this study was to investigate how the modulation method affects the effectiveness of eliciting tactile sensations by electrical stimulation. Two methods were employed and the results were compared and analyzed; pulse amplitude modulation (PAM) and pulse width modulation (PWM). Thirty-five healthy subjects participated in the experiments to measure the stimulation intensity that began to elicit a tactile sensation - activation threshold (AT). Constant-current monophasic rectangular pulse trains were employed, and the stimulation intensity was varied from zero until the subject felt any uncomfortable sensation. The step size of the stimulation intensity was 100nC/pulse. After each experiment, the subject described the sensation both quantitatively and qualitatively. The two modulation methods did not make a significant difference as far as the AT values were concerned, but most of the subjects showed 'intra-individual' consistency. Also, it was confirmed that our range of the stimulation parameters enabled us to obtain three major tactile sensations; tickling, pressure and vibration. The results suggested that the stimulation parameters and the modulation type should be selected for each individual and that selective electrical stimulation of the mechanoreceptors needs more diversified researches on the electrode design, multi-channel stimulation protocol, waveforms of the pulse train, etc.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.12
• /
• pp.1434-1440
• /
• 2011

In this paper, we assessed muscular activities of lower limbs and foot pressure for car and bus drivers according to operating three electronic pedals that we developed. To analyze drivers' physical exhaustion, muscular fatigue of lower limbs was evaluated. Eleven car drivers and six urban bus drivers were participated in this experiment. The virtual driving system was used for the real driving environment. The virtual driving system was comprised of a spring seat, a steering wheel, pedals (clutch, excel and brake pedals), a manual transmission and a virtual driving simulation. For the real vibration like situation on the road, six degree of freedom motion base system was used. Measured muscles were rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA) and gastrocnemius (Gn) muscles. For the quantitative muscular activities, integrated electromyography (IEMG) was analyzed. Muscular fatigues also were analyzed through the analysis of the median frequency. In addition, foot pressures were analyzed and compared through the peak and averaged pressure during the operating three developed electronic pedals. The experiments are conducted with total 17 drivers, 11 general public and 6 drivers. As a result of the analysis, electromyogram and fatigue analysis through intermediate frequency reduction for pedal-1 more efficient than other pedals. And foot pressure also was decreased. Consequently, we suggested the most efficient pedal and method to minimize the amount of cumulative fatigue.

• Applied Chemistry for Engineering
• /
• v.19 no.3
• /
• pp.345-350
• /
• 2008

Polymer Impregnated Concrete (PIC) prepared from Ordinary Portland Cement Concrete (OPC) has excellent mechanical properties as well as physico-chemical properties. For the manufacturing of PIC, drying process of basis concrete (precast concrete), impregnation process with evacuation system and ultrasonic vibration system, polymerization process of monomers are essential. Modified microwave reactor using magnetron was used for polymerization of styrene/MMA (1 : 1) impregnated in pore volume of basis concrete. From the experimental results, the degree of polymerization increased up to 30% and more homogeneous PIC was prepared as compared to the conventional thermal method. Also the mechanical strengths increased more than 400% ($800{\sim}1200kg_f/cm^2$) and the resistance for corrosion to acids was improved up to 25%. AIBN and BPO as initiators for polymerization were used at the concentration less than 1%. Optimum conditions for polymerization were obtained at the frequency of microwave of 400 W and 2450 MHz, and optimum reaction temperature was $120^{\circ}C$ at an atmospheric pressure.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
• /
• v.21 no.2
• /
• pp.133-138
• /
• 2010

Background and Objectives : High-speed imaging can be useful in studies of linguistic and artistic singing styles, and laryngeal examination of patients with voice disorders, particularly in irregular vocal fold vibrations. In this study, we introduce new laryngeal imaging systems which are commercially available high speed cameras connected with a laryngoscope. Materials and Method : The laryngeal images were captured from three different types of cameras. First, the adapter was made to connect with laryngoscope and Casio EX-F1 to capture the images using $2{\times}150$ Watt Halogen light source (EndoSTROB) at speeds of 1,200 tps (frame per second)($336{\times}96$). Second, Phantom Miro ex4 was used to capture the digital laryngeal images using Xenon Nova light source 175 Watt (STORZ) at speeds of 1,920 fps ($512{\times}384$). Finally, laryngeal images were captured using MotionXtra N-4 with 250 Watt halogen lamp (Olympus CLH-250) light source at speeds of 2,000tps ($384{\times}400$) by connecting with laryngoscope. All images were transformed into the Kymograph using KIPS (Kay's image processing Software) of Kay Pentex Inc. Results: Casio EX-F1 was too small to adjust the focus and screen size was diminished once the images were captured despite of high resolution images. High quality of color images could be obtained with Phantom Miro ex4 whereas good black and white images from Motion Xtra N-4 Despite of some limitations of illumination problems, limited recording time capacity, and time consuming procedures in Phantom Miro ex4 and Motion Xtra N-4, those portable devices provided high resolution images. Conclusion : All those high speed cameras could capture the laryngeal images by connecting with laryngoscope. High resolution images were able to be captured at the fixed position under the good lightness. Accordingly, these techniques could be applicable to observe the vocal fold vibration properties in the clinical practice.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.11
• /
• pp.4468-4472
• /
• 2010

SiOC films made by the inductively coupled plasma chemical vapor deposition were researched the relationship between the dielectric constant and the chemical shift. SiOC film obtained by plasma method had the main Si-O-C bond with the molecule vibration mode in the range of $930{\sim}1230\;cm^{-1}$ which consists of C-O and Si-O bonds related to the cross link formation according to the dissociation and recombination. The C-O bond originated from the elongation effect by the neighboring highly electron negative oxygen atoms at terminal C-H bond in Si-$CH_3$ of $1270cm^{-1}$. However, the Si-O bond was formed from the second ionic sites recombined after the dissociation of Si-$CH_3$ of $1270cm^{-1}$. The increase of the Si-O bond induced the redshift as the shift of peak in FTIR spectra because of the increase of right shoulder in main bond. These results mean that SiOC films become more stable and stronger than SiOC film with dominant C-O bond. So it was researched that the roughness was also decreased due to the high degree of amorphous structure at SiOC film with the redshift after annealing.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.6 no.4
• /
• pp.1-6
• /
• 2002

The structural safety required in general design is to be proved with safety factors provided for structural members in elastic range. But, for the safety requirement in the earthquake resistant design, a specific ductile failure mechanism in plastic range should be verified according to the structural configuration. Therefore such verifications should be done in the preliminary design stage by comparing various design alternatives. In the main design stage only a confirmation of the ductile failure mechanism is required. In this study typical roadway bridges are selected and analysis models are presented for the preliminary and main design. For the two models, vibration periods and mode shapes are compared and the multi-mode spectrum method is applied to determine failure mechanisms. The failure mechanisms obtained with the two models are compared to check the properness of the model used for the preliminary design, which may well be used as an earthquake resistant analysis model in practice.