• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.351-352
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• 2009

On-demand ejection of ultra-fine droplets that uses both electrohydrodynamic (EHD) force and mechanical actuation is presented. The liquid meniscus was controlled by a piezoelectric actuator and droplets were ejected by EHD force. Through these effects, it was possible to obtain a high operational jetting frequency of 5kHz with a short delay-time (about 50 us) when compared with existing on-demand EHD jetting methods, such as the pulsating jet mode (3-10 msec) and the pulsed-voltage cone-jet mode(3.6 msec). Also, we obtained ultra-fine droplets at a volume that was at the femto-liter level simultaneously. The jetting characteristics were examined for both hydrophobicity and hydrophilicity of the surface of a capillary.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.127-132
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• 2014

Micro/nano-injection molding is one of the main processing techniques for polymer micro-fabrication. Most of the difficulties encountered in polymer micro-molding are caused by the demolding, rather than the filling of molds. Therefore, studying the demolding process is vitally important for manufacturing polymer replicas. The most important parameters are the thermal stress, friction and adhesion forces, and mechanical strength of the resist. In this research, we determinedthe effects of the processing conditions on the ejection force for cases involving two common thermoplastic polymers. The results showed that the processing conditions noticeably influenced the ejection force.

• Journal of the Ergonomics Society of Korea
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• v.11 no.1
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• pp.67-79
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• 1992

Cardiac systolic time intervals (STLs) and Heather index (HI) were used to access changes in left ventricular function of six male subjects exposed to postural changes,$0^{\circ}C$, ${\pm}2^{\circ}C$, ${\pm}45^{\circ}C$, ${\pm}90^{\circ}C$, Significant prolongation of the pre-ejection period (PEP) and PEP/ LVET ratio, shortening of the left ventricular ejection time (LVET), STI, HI and $1/PEP^{2}$were observed during exposure to both $+45^{\circ}C $ and $+90^{\circ}C $But the values measured during $-45^{\circ}C $ and$-90^{\circ}C $ were reversed. Changes in fluid shift, filling volume, preload, after load and sympathetic activities may account for the observed findings. Early response of cardiac foctions was recorded using impedance cardiography. This method is very simple but accurate. Thus it will be useful in this aerospace and work physiology. In conclusion, STIs appear to provide reliable noninvasive method for examining changes of cardiac function during exposure to postural changes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.237-240
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• 1999

The elastic stress analysis of the die for helical gear forging has been calculated by using the nodal force at the final stage obtained from the rigid-plastic finite element analysis. In order to obtain more precise gear products. the elastic analysis of the die after release of punch and the elastic spring-back analysis of product after ejection have been performed and the final dimension of the computational product has been in good agreement with that of the experimental product.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1947-1950
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• 2008

Printing technology is a very useful method in the several process of industrial fabrication due to noncontact and fast pattern generation. To make micro pattern, we investigate the electrostatic induced inkjet printer head for micro droplet generation and drop-on-demand jetting. In order to achieve the drop-on-demand micro droplet ejection by the electrostatic induced inkjet printer head, the pulsed DC voltage is supplied. In order to find optimal pulse conditions, we tested jetting performance for various bias and pulse voltages for drop-on-demand ejection. In this result, we have successful drop-on-demand operation and micro patterning. Therefore, our novel electrostatic induced inkjet head printing system will be applied industrial area comparing conventional printing technology.

• Korean Journal of Veterinary Research
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• v.47 no.1
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• pp.99-102
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• 2007

A 3-year-old, intact female, Shih-tzu dog was presented with a 15-day history of vomiting,depression, and anorexia. On physical examination, systolic ejection murmurs with precordial thril atthe left heart base were detected. A diagnosis of congenital pulmonic stenosis (PS) was made mainlyfrom the thoracic radiography, electrocardiography, and echocardiography. On complete blood counts andconfirmed that main pulmonary artery was tremendously buldged and electrocardiography was suggestiveof severe right ventricular hypertrophy. Echocardiographic findings revealed the pulmonic valve stenosiscontaining valvular dysplasia and poststenotic dilation. On Doppler echocardiography, ejection velocityof the lesion accounted for 3.38 m/sec, meaning mild velocity through the stenotic area. The dog'sproblem and resulted in death. However, there has been no reliable relation between PS and CRF. Primarymalformation of pulmonic valve was confirmed at necropsy after death.

• Journal of Powder Materials
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• v.25 no.2
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• pp.99-103
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• 2018

Spherical monosized pure aluminum (Al) particles are successfully fabricated by the pulsated orifice ejection method (POEM). The surface reaction between Al and the graphite crucible is investigated by analysing the microstructure and chemical composition of the materials. No significant chemical reaction occurs between Al and the graphite owing to the crystalline Al oxide (${\gamma}-Al_2O_3$) layer generated in the initial state. The ${\gamma}-Al_2O_3$ layer is clearly observed in all regions between the Al particles and graphite via transmission electron microscopy and confirmed by the selected area diffraction pattern. The morphology of the ${\gamma}-Al_2O_3$ layer perfectly follows the surface morphology of the graphite crucible, which showed nanoscale roughness. This implies that molten Al could not directly contact graphite even though the surface of the crucible became rough to some extent. However, this passivation phenomenon allowed the successful fabrication of monosized pure Al particles. Therefore, POEM is a useful process at least to manufacture monosized pure Al particles.

• Laser Solutions
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• v.3 no.3
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• pp.39-45
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• 2000

The volume and depth of the craters produced on silicon samples during high power laser ablation show a strong nonlinear change as the laser irradiance increases across a threshold value, approximately 2.2$\times$10$\^$10/ W/㎠. Time-resolved shadowgraph images of the ablation plume reveal the ejection of large particulates from the sample for laser irradiance above the threshold, with a time delay of about 300-400 ㎱. The numerically estimated thickness of the superheated liquid layer, considering the transformation of liquid metal into liquid dielectric near the critical state, agrees with the measured agrees with crater depths. It is suggested that a phase explosion of the deep superheated liquid layer near the critical state is responsible for the measured sudden increase of crater volume and the ejection of large particulates.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.1
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• pp.28-38
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• 2009

Numerical simulation is performed for microdroplet deposition on a pre-patterned micro-structure. The liquid-air interface is tracked by a level-set method, which is improved by incorporating a sharp-interface modeling technique for accurately enforcing the matching conditions at the liquid-gas interface and the no-slip condition at the fluid-solid interface. The method is further extended to treat the contact angle condition at an immersed solid surface. The present computation of a patterning process using microdroplet ejection demonstrates that the multiphase characteristics between the liquid-gas-solid phases can be used to improve the patterning accuracy.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.39.1-39.1
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• 2011

Coronal mass ejection (CME) plasmas have been observed in EUV and X-ray passbands as well as in white light. Mass of CME has been determined using polarized brightness observed by the Large Angle and Spectrometric Coronagraph Experiment (LASCO) on board Solar and Heliospheric Observatory (SOHO). Therefore, this mass obtained from the LASCO observation indicates the total CME mass. However, the mass of CME plasma in different temperatures can be determined in EUV and X-ray passbands using observations by SOHO/EIT, STEREO/EUVI, and Hinode/XRT. Prominence/CME plasmas have been observed as absorption or emission features in EUV and X-ray passbands. The absorption features provide a lower limit to cold mass. In addition, the emission features provide an upper limit to the mass of plasmas in temperature ranges of EUV and X-ray. We determine the mass constraints using the emission measure obtained by assuming the prominence/CME structures. This work will address the mass constraints of hot and cold plasmas in CMEs, comparing to total CME mass.