• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.505-508
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• 2006

An electrostatic ink jet head can be used for manufacturing processes of large display systems and printed circuit boards (PCB) as well as inkjet printers because an electrostatic field provides an external force which can be manipulated to control sizes of droplets. The existing printing methods such as thermal bubble and piezo inkjet heads have shown difficulties to control the ejection of the droplets for printing applications. Thus, the new inkjet head using the electrostatic force has been proposed in this study. In order to prove the theory of the developed electrostatic ink jet head, the applicable and basic theory has been studied using distilled water and water with sodium dodecyl surfate (SDS). Also, a numerical analysis has been performed to calculate the intensity of the electrostatic field using the Maxwell's equation. Furthermore, experiments have been carried out using a downward glass capillary with outside diameter of $500{\mu}m$. The gravity, surface tension, and electrostatic force have been analyzed with high voltages of 0 to 5kV. It has been observed that the droplet size decreases and the frequency of the droplet formation and the velocity of the droplet ejection increase with increasing the intensity of the electrostatic field. The results of the experiments have shown good agreement with those of numerical analysis.

• Imaging Science in Dentistry
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• v.32 no.2
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• pp.99-105
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• 2002

Purpose: To evaluate the diagnostic accuracy of transcranial radiographs and magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ) in the assessment of osseous changes of the condylar head and articular eminence. Materials and Methods: Osseous changes of the TMJ were evaluated in forty-three patients. Osseous changes of the condylar head and articular eminence were observed in 41 joints and 64 joints, respectively on transcranial radiographs, and 48 joints and 59 joints, respectively on MRI. Results: The flattening, sclerosis, erosion, and osteophyte formation of the condylar heads were observed in 36.6%, 43.9%, 12.2%, and 7.3%, respectively on transcranial radiographs compared with 35.4%, 20.8%, 37.5%, and 6.3%, respectively on MRI. While, the flattening, sclerosis, and erosion of the articular eminences were observed in 26.6%, 67.2%, and 6.2%, respectively on transcranial radiographs compared with 32.2%, 59.3%, and 8.5%, respectively on MRI. Conclusion: There were no statistical differences between transcranial radiographs and MRI scans in the detection of osseous changes of the TMJ. However, MRI scans were superior to the transcranial radiographs in the detection of erosion of the condylar head (p<0.01).

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.128-133
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• 2007

An electrostatic inkjet head can be used for manufacturing processes of large display systems and printed circuit boards (PCB) as well as inkjet printers because an electrostatic field provides an external force which can be manipulated to control sizes of droplets. The existing printing methods such as thermal bubble and piezo inkjet heads have shown difficulties to control the ejection of the droplets for printing applications. Thus, the new inkjet head has been proposed using the electrostatic force. A numerical analysis has been performed to calculate the intensity of the electrostatic field using the Maxwell's equation. Also, experiments have been carried out to investigate the droplet movement using a downward capillary with outside diameter of $500{\mu}m$. Gravity, surface tension, and electrostatic force have been analyzed with high voltages for a drop-on-demand ejection. It has been observed that the droplet size decreases and the frequency of the droplet formation and the velocity of the droplet ejection increase with increasing the intensity of the electrostatic field using high-speed camera.

• Journal of The Korean Astronomical Society
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• v.41 no.5
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• pp.139-145
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• 2008

The molecular cloud, embedding AFGL 2591, has a "head-and-tail" structure with a total mass of ${\sim}\;1800\;M_{\odot}$, about half of the mass (${\sim}\;900\;M_{\odot}$) in the head (size ${\sim}\;1.2\;pc$ in diameter), and another half in the envelope (${\sim}\;3.5\;pc$ in the east-west direction). We found a new cloud in the direction toward north-east from AFGL 2591 (projected distance ${\sim}\;2.4\;pc$), which is probably associated with the AFGL 2591 cloud. The $^{12}CO$ spectrum clearly shows a blue-shifted high-velocity wing at around the velocity $-20\;{\sim}\;-10\;km\;s^{-1}$, but it is not clear whether this high-velocity component has a bipolar nature in our observations. The observed CN spectra also show blue-shifted wing component but the existence of the red-shifted component is not clear, either. In some CN and HCN spectra, the highvelocity components appear as a different velocity component, not a broad line-wing component. The dense cores, traced by CN and HCN, exist in the 'head' of the AFGL 2591 cloud with an elongated morphology roughly in the north-south direction with a size of about 0.5 pc. The abundance ratio between CN and HCN is found to be about 2 - 3 within the observed region, which may suggest a possibility that this core is being affected by the embedded YSOs or by possible shocks from outside.

• Journal of the Semiconductor & Display Technology
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• v.23 no.2
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• pp.65-70
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• 2024

Using a computational fluid dynamics(CFD) simulation tool, we have provided a coating guideline for slot-die coating with a double layer slot die head. We have analyzed the fluid dynamics in terms of the coating speed, flow rate ratio, and viscosity ratio, which are critical for the stability of coating meniscus. We have identified the common coating defects such as break-up, air entrainment, and leakage by varying the coating speeds. The flow rate ratio is the critical parameter determining the wet film thickness of the top and bottom layers. It is shown that when the flow rate ratio exceeds or equals 1.8, air entrainment occurs due to insufficient hydraulic pressure in the bottom layer, even though the total flow rate remains constant. Furthermore, we have found that the flow of the bottom layer is significantly affected by the viscosity of top layer. The viscosity ratio of 4 or higher obstructs the flow of the bottom layer due to the increased hydraulic resistance, resulting in leakage. Finally, we have demonstrated that as the viscosity ratio increases from 0.1 to 10, the maximum coating speed rises from 0.4 mm/s to 1.6 mm/s, and the minimum wet film thickness decreases from 800 ㎛ to 200 ㎛.

• Hip & pelvis
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• v.34 no.3
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• pp.177-184
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• 2022

This study aimed to analyse the initial results of five patients with symptomatic osteochondral lesions (OCL) and femoroacetabular impingement (FAI) who were treated successfully with osteochondral autologous transfer (OAT) and femoral neck osteochondroplasty (OCP) through surgical dislocation of the hip. Five patients with FAI and OCL of the femoral head who underwent surgery between 2015-2018 were studied retrospectively. All patients had a grade IV OCL, and the median defect size was 2 cm2 (interquartile range [IQR], 2-2). At the final follow-up, the modified Harris hip score showed a median value of 94 (IQR, 91-95) (P=0.04). Pain evaluation using the visual analogue scale showed a median value of 1 (IQR, 1-2) (P=0.04). Adequate graft union and healthy formation of the chondral surface were observed by magnetic resonance imaging. Although the procedure is demanding, the combination of OAT and femoral neck OCP appears to be an effective alternative in young patients.

• ETRI Journal
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• v.34 no.6
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• pp.922-931
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• 2012

With the increasing demands for mobile wireless sensor networks in recent years, designing an energy-efficient clustering and routing protocol has become very important. This paper provides an analytical model to evaluate the power consumption of a mobile sensor node. Based on this, a clustering algorithm is designed to optimize the energy efficiency during cluster head formation. A genetic algorithm technique is employed to find the near-optimal threshold for residual energy below which a node has to give up its role of being the cluster head. This clustering algorithm along with a hybrid routing concept is applied as the near-optimal energy-efficient routing technique to increase the overall efficiency of the network. Compared to the mobile low energy adaptive clustering hierarchy protocol, the simulation studies reveal that the energy-efficient routing technique produces a longer network lifetime and achieves better energy efficiency.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.5
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• pp.197-205
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• 1996

The flow characteristics of five different 4-valve cylinder heads were investigated in a steady flow rig using laser-Doppler velocimetry. The tumble flow of each head with pentroof combustion chamber was quantified by nondimensional tumble number using a tumble adaptor. The formation of tumbling vortex was examined in an optical single-cylinder engine which has windows for in-cylinder LDV measurements. Tumble vortex ratio was estimated from the tumble flow measurement. The four-valve cylinder heads with pent-roof combustion chamber showed the tumble vortex from the intake process, which was investigated in the steady flow test. The tumble adaptor which converts the tumble into swirl flow was found to be feasible in predicting the tumble flow in the real engine. The tumble strength in the steady flow test coincides with that in the real engine experiment within 15%. It was found that the steady flow test on the four-valve cylinder heads provides the tip for a better design of cylinder head.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1400-1403
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• 2007

The 3DP(three dimensional printing) technology is one of the SFF(solid freeform fabrication) technologies which has recently come into a spotlight due to its suitability to various field. A manufacturing process of product is using many pattern formation technology. The 3DP technology uses multi nozzle that can fabricate three dimensional object of high speed and accuracy. In this paper, we introduce a development of the office type solid freeform fabrication system. This system is used UV resin and multi-piezo head.

• Korean Journal of Head & Neck Oncology
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• v.26 no.1
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• pp.30-32
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• 2010

Tracheo-gastric fistula is a very rare late complication of total laryngopharyngoesophagectomy with gastric pull-up procedure. It usually occurs after transhiatal esophagectomy, but it has only rarely been reported after total laryngopharyngoesophagectomy with gastric pull-up procedure. Chronic irritation and gastric ulcer may be the cause of tracheogastric fistula. To prevent fistula formation, active management of gastric ulcer and avoidance of mucosal irritation are necessary. We report a case of a tracheogastric fistula which occurred two years after total laryngopharyngoesophagectomy with gastric pull-up procedure that maybe occurred by chronic irritation and gastric ulcer.