• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.271-271
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• 2012

Many studies have been investigated on high density plasma source (Electron Cyclotron Resonance, Inductively Coupled Plasma, Helicon plasma) for large area source after It is announced that productivity of plasma process depends on plasma density. In this presentation, we will propose the new concept of the multiple source, which consists of a parallel connection of ICP sources and helicon plasma sources. For plasma uniformity, equivalent power (especially, equivalent current in ICP & Helicon) should distribute on each source. We design power feeding line as coaxial transmission line with same length of ground line in each source for equivalent power distribution. And we confirm the equivalent power distribution with simulation and experimental result. Based on basic study, we develop the plasma source for oxidation in semiconductor process. we will discuss the relationship between the processing parameters (With or WithOut magnet, operating pressure, input power ). In ICP, plasma density uniformity is uniform. In ICP with magnet (or Helicon) plasma density is not uniform. As a result, new design (magnet arrangement and gas distributor and etc..) are needed for uniform plasma density in ICP with magnet and Helicon.

• Journal of Magnetics
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• v.21 no.3
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• pp.387-392
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• 2016

Lower flux leakage designs have become important in the development of microspeakers used in thin and miniaturized mobile phones. We propose four methods to reduce the flux leakage of the magnetic circuit in a microspeaker. Optimization was performed based on the proposed approach by using the response surface method. Electromagnetic analyses were conducted using the finite element method. Experimental results are in good agreement with the simulated results obtained in one degree-of-freedom analysis from 100 to 5 kHz. Both the simulated and experimental results confirm that one of the proposed methods is much more effective in reducing flux leakage than the other methods. In the optimized method, compared with a default approach, the average radial flux density in the air gap decreased only by 5.5%, the maximum flux leakage was reduced by 28.6%, and the acoustic performance at primary resonance decreased by 0.45 dB, which gap is indiscernible to the human ear.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.405-412
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• 1999

Meta! Halide Discharge(]\1HD) Iamps have good color rendition, long life and good focusing capability but h have flickers bv acoustic resonances. We have designed the electronic ballast for reducing acoustic resonances in high pressure discharge tube. The ballast consists of main two parts, the first part is a half-bridge inverter to make a square wave form a and the st'Cond part is a flyback converter to combine the low frequency and high frequency component. As a r result of this study, we conclude that MHD lamps of 70 watt 따c very well light(D without acoustic resonance p phenomena by the elestronic ballast.

• Mass Spectrometry Letters
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• v.3 no.2
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• pp.43-46
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• 2012

In this study, comprehensive two dimension gas chromatography (2D GC-MS) and 15 T Fourier transform ion cyclotron resonance mass spectrometry (15T FT-ICR MS) connected to atmospheric pressure photo ionization (APPI) have been combined to obtain detailed chemical composition of a diesel oil sample. With 2D GC-MS, compounds with aliphatic alkyl, saturated cyclic ring(s), and one aromatic ring structures were mainly identified. Sensitivity toward aromatic compounds with more than two aromatic rings was low with 2D GC-MS. In contrast, aromatic compounds containing up to four benzene rings were identified by APPI FT-ICR MS. Relatively smaller abundance of cyclic ring compounds were found but no aliphatic alkyl compounds were observed by APPI FT-ICR MS. The data presented in this study clearly shows that 2D GC-MS and 15T FT-ICR MS provides different aspect of an oil sample and hence they have to be considered as complementary techniques to each other for more complete understanding of oil samples.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.780-785
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• 2005

Vibration has been severly increased at the branch pipe of main steam header since the commercial operation of a nuclear power plant. Intense broad band disturbance flow at the discontinuous region such as elbow, valve or heather generates the acoustical pulsation which is propagated through the piping system. The pulsation becomes the source of low frequency vibration at piping system. If it coincide with natural frequency of the pipe system, excessive vibration is made. High level vibration due to the pressure pulsation related to high dynamic stress, and ultimately, to failure probability affects fatally the reliability and confidence of plant piping system. This paper discusses vibration effect for the branch pipe system due to acoustical pulsations by broad band disturbance flow at the large main steam header in 7nn nuclear power plant. The exciting sources and response or the piping system are investigated by using on site measurements and analytical approaches. It is identified that excessive vibration is caused by acoustical pulsations of 1.3Hz, 4.4Hz and 6.6Hz transferred from main steam header, which are coincided with fundamental natural frequencies of the piping structure. The energy absorbing restraints with additional stiffness were installed to reduce excessive vibration.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.54-62
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• 2009

The purpose of this study is to develop a piezo injector driver for common-rail direct injection diesel engines. In this research, we analyzed the electrical and mechanical characteristics of the piezo actuator through experiments. Current flow and charging voltage of the piezo injector are controlled by the PWM signal of variable duty ratio in order to realize both fast response and low peak current. The optimal switching duty ratio was designed by modeling and analyzing of the piezo driver circuit. In order to avoid resonance and unacceptably long settling time, appropriate frequency range of the PWM signal was derived based on the driver circuit model. The developed injector driver was validated by experiments under various fuel rail pressure, injection duration, and charging voltage.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.9
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• pp.972-981
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• 2008

The blower which is installed in a FCEV(fuel cell electric vehicle) may cause noise due to misalignment and unbalance of mechanical components that rotate at high speed. One of the key points in efforts to minimize the noise radiation from a blower is the knowledge of the main radiating component and the relation between the surface vibration of a blower and the sound pressure. In this research, the blower model is developed based on FEM(finite element method). FE(finite element) model is reliable by correlation of frequencies and MAC(modal assurance criterion) values between EMA(experimental modal analysis) and FEA(finite element analysis). This model is applied to predict the vibration of a blower by using inverse force identification method and predict the radiating noise by using BEM(boundary element method). Comparing the frequencies of resonance and those mode shapes between EMA and FEA, a structural modification of the FE model is evaluated for reducing the parameters of the blower noise.

• Journal of Korean Neurosurgical Society
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• v.52 no.3
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• pp.246-249
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• 2012

Intracranial extraskeletal myxoid chondrosarcoma is extremely rare, with only seven patients previously reported. We present a case report of a 21-year-old woman admitted for weakness in her right extremities and symptoms of increased intracranial pressure. Magnetic resonance imaging (MRI) revealed hydrocephalus and a well-enhanced large mass around her left thalamus. A left parietal craniotomy and a cortisectomy at the superior parietal lobule were performed. Total surgical resection was also performed, and pathology results confirmed an extraskeletal myxoid chondrosarcoma. Postoperative MRI showed no residual tumor, and the patient underwent radiotherapy. After six months of radiotherapy, the patient's headache and weakness had improved to grade IV. This malignant tumor showed high rates of recurrence in previous reports. We here report another occurrence of this highly malignant and rare tumor in a patient treated using total surgical excision and adjuvant radiotherapy.

• Journal of Korean Neurosurgical Society
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• v.53 no.2
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• pp.112-114
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• 2013

Bilateral abducens nerve palsy related to ruptured aneurysm of the anterior communicating artery (ACoA) has only been reported in four patients. Three cases were treated by surgical clipping. No report has described the clinical course of the isolated bilateral abducens nerve palsy following ruptured ACoA aneurysm obliterated with coil. A 32-year-old man was transferred to our institution after three days of diplopia, dizziness and headache after the onset of a 5-minute generalized tonic-clonic seizure. Computed tomographic angiography revealed an aneurysm of the ACoA. Magnetic resonance imaging showed focal intraventricular hemorrhage without brain stem abnormalities including infarction or space-occupying lesion. Endovascular coil embolization was conducted to obliterate an aneurysmal sac followed by lumbar cerebrospinal fluid (CSF) drainage. Bilateral paresis of abducens nerve completely recovered 9 weeks after ictus. In conclusion, isolated bilateral abducens nerve palsy associated with ruptured ACoA aneurysm may be resolved successfully by coil embolization and lumbar CSF drainage without directly relieving cerebrospinal fluid pressure by opening Lillequist's membrane and prepontine cistern.

• Journal of Chest Surgery
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• v.28 no.5
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• pp.491-494
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• 1995

A fibroma arising in the right ventricle outflow tract of a 14 month-old infant was successfully removed. The patient was first seen because of shortness of breath and tachycardia. Pertinent clinical and laboratory findings included a grade II/VI systolic murmur, blood pressure of 120/60 mmHg, slight cardiomegaly on chest X-ray, a mass obstructing the outflow tract of the right ventricle on echocardiography and magnetic resonance imaging. On october 30,1992, under cardiopulmonary bypass, a 4cm x 3cm x 3cm tumor was resected from the right ventricular outflow tract, together with a portion of the ventricular wall. Histologically, it was diagnosis as a fibroma. The patient was sent home on the 6th postoperative day following an uneventful recovery form the operation. Although cardiac fibroma is the second most common cardiac tumor in infancy and childhood, it is usually found in the left ventricle and one arising in the right ventricle is considered rare. Although it is a benign tumor, it could produce a severe cardiac dysfunction and even sudden death, depending on its size and location. With the advance in diagnostic techniques and operative management, there is a renewed interest in the early detection and operative removal of these tumors. The case herein presented is the first such case successfully managed and reported in the Korean literature.