• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.939-942
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• 2007

Vacuum cleaner is a close life product that can remove various dusts from our surroundings. However well vacuum cleaner clean our environments, many people are looking away from it, due to its loud noise. Its noise causes a big trouble in the usual life, for example, catch calls, TV watching and discussing etc. To reduce these inconveniences, noise reduction methods and systematic design of low noise vacuum cleaner are studied in this paper. At first, sound quality investigation is performed to get the noise level and quality that make people TV watching and catch calls available. Based on the European and domestic customer SQ survey result, sound power, peak noise level and target sound spectrum guideline are studied and introduced. As a second, precise product sound spectrums are designed into each part based on the sound quality result. Fan-motor, brush, mainbody, cyclone spectrums are decided to get the final target sound based on the contribution level. Fan-motor is the major noise source of vacuum cleaner. Specially, its peak sound, RPM peak and BPF Peak, cause the people nervous. To reduce these peak sounds, high rotating impeller and diffuser are focused due to its interaction. A lot of experimental and numerical tests, operation points are investigated and optimization of flow path area between diffusers is performed. As a bagless device, cyclones are one of the major noise sources of vacuum cleaner. To reduce its noise, previous research is used and adopted well. Brush is the most difficult part to reduce noise. Its noise sources are all comes from aero-acoustic phenomena. Numerical analysis helps the understanding of flow structure and pattern, and a lot of experimental test are performed to reduce the noise. Gaps between the carpet and brush are optimized and flow paths are re-designed to lower the noise. Reduction is performed with keeping the cleaning efficiency and handling power together and much reduction of noise is acquired. With all above parts, main-body design is studied. To do a systematic design, configuration design developments technique is introduced from airplane design and evolved with each component design. As a first configuration, fan-motor installation position is investigated and 10 configuration ideas are developed and tested. As a second step, reduced size and compressed configuration candidates are tested and evaluated by a lot of major factor. Noise, power, mass production availability, size, flow path are evaluated together. If noise reduction configuration results in other performance degrade, the noise reduction configuration is ineffective. As a third configuration, cyclones are introduced and the size is reduced one more time and fourth, fifth, sixth, seventh configuration are evolved with size and design image with noise and other performance indexes. Finally we can get a overall much noise level reduction configuration. All above investigations are adopted into vacuum cleaner design and final customer satisfaction tests in Europe are performed. 1st grade sound quality and lowest noise level of bagless vacuum cleaner are achieved.

• Journal of Biomedical Engineering Research
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• v.28 no.1
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• pp.46-54
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• 2007

Objective: The first aim of this study is to determine the effects of acupuncture on the autonomic nervous system (ANS) via Heart Rate (HR) and Pupil Size (PS), and to compare the effects of acupuncture on the subjects' ANS when they are in a sitting position with the effects when they are in a supine position. Methods: Ten healthy male subjects were randomized to receive either verum acupuncture stimulation in a sitting position (SitV), verum acupuncture stimulation in a supine position (SupV), sham acupuncture stimulation in a sitting position (SitS), and sham acupuncture stimulation in a supine position (SupS). Acupuncture stimulation was applied to Neguan point (PC6) on the forearm. The subject's electrocardiogram (ECG) and pupil size were recorded continuously from 5 min before stimulation to 12 min after stimulation. Results: Verum and sham acupuncture stimulation were found to have reduced heart rate (p<0.01) and to have increased pupil size (p<0.01) in all the subjects. But when the reduction in HR and the increment in PS after verum acupuncture stimulation (both sitting and supine position) were compared with those after sham acupuncture stimulation, it was found that the reduction in HR (74.48 and 73.47 bpm, p<0.063) and the increment of PS (7.32 and, 6.10 mm, p<0.001) after verum acupuncture stimulation were greater than those after sham acupuncture stimulation, and that the corresponding values were statistically significant. In addition, at the baseline, it was found that the subjects had a larger PS and a faster HR in a sitting position than when they did so in a supine position. And then the reduction and increment ratio in the subject's HR and PS when they underwent acupuncture stimulation in a sitting position was significantly different from the reduction and increment in their HR and PS when they underwent the procedure in a supine position-i.e., the reduction ratio in HR was greater when they underwent the procedure in a sitting position, and such reduction ratio was statistically significant (p<0.05). As for the increment in PS, it was greater when the subjects underwent the procedure in a supine position, and such increment was significant (p<0.05). Conclusion: Manual acupuncture stimulation on Neguan point (PC6) has more significant influence on the autonomic nervous system rather than sham acupuncture (tactile stimulation). And the position-induced different states of ANS have different influence on the acupuncture effect.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.476-481
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• 1991

This paper investigates the relationship between the two problems, supervisor reduction and observation function (projection) design, which arise in supervisory control of DEDS. It is shown through an example that a reduced supervisor of minimal size does not necessarily result in a maximal projection when a projection design method which uses the transition structure of a supervisor is applied. Also, if an L-realizable projection P is available and if a supervisor has a special structural feature, a cover C for supervisor reduction can be easily obtained. By investigating the control-compatibility of states of the reduced supervisor based on C, we can also check maximality of P in a simple manner.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1058-1061
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• 2002

This paper presents the method of low power optimization considering the glitch reduction in CMOS circuits. Our algorithm utilizes the information of MOS size, the load capacitance of fan-out, and input slew to calculate the output waveform by using the linear signal model. Therefore, the accurate waveform of glitch can be obtained for estimation of power dissipation caused by glitches. Our algorithm is applied to ISCAS’85 benchmark circuits and experimental results show 23% glitch reduction and 11% total power reduction.

• Membrane Journal
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• v.22 no.5
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• pp.332-341
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• 2012

We studied the effects of induction of natural convection instability flow (NCIF) according to the gravitational orientation (inclined angle) of the membrane cell on the reduction of membrane fouling in the constant-flow ultrafiltration (UF) of colloidal silica solutions. Five colloidal silica solutions with different silica size (average size = 7, 12, 22, 50 nm and 78 nm) were used as UF test solutions. The silica particles in colloidal solutions form cakes on the membrane surface thereby causing severe membrane fouling. The constant-flow UF performance according to the gravitational orientation of the membrane cell (from $0^{\circ}$ to $180^{\circ}$ inclined angle), was examined in an unstirred dead-end cell. We evaluate the effects of NCIF on the suppression of fouling formation by measuring the variation of transmembrane pressure (TMP) and the increase of critical flux by using the flux-stepping method. In the constant-flow dead-end UF for the smaller size (7, 12 nm and 22 nm) silica colloidal solutions, changing the gravitational orientation (inclined angle) of the membrane cell above the $30^{\circ}$ angle induces NCIF in the membrane module. This induced NCIF enhances back transport of the deposited silica solutes away from the membrane surface, therefore gives for the reduction of TMP. But in the constant-flow UF for the more larger size (50 nm and 78 nm) silica colloidal solutions, NCIF effects are not appearing. The critical flux is increased as increasing the module angle and decreasing the silica size. Those results show that the intesity of NCIF occurrence in membrane module is more higher as increasing the module angle and decreasing the silica size.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.10-16
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• 2016

This work investigates the size and dispersion characteristics of silver nanoparticles synthesized by a liquid phase reduction method using PAA. The experimental variables were the molecular weight and doses of the PAA, reducing agent, dispersant, and organic solvent (ethanol-acetone). UV-visible spectrophotometer results confirm the formation of the silver particles, and SEM indicates size in the nanometer range. As the ultrasonication time increases, there is a tendency toward smaller agglomerates of nanoparticles. The agglomerates were dispersed into 1-5 agglomerates of particles by ultrasonication for 3 hours or more. Relatively spherical nanoparticles were produced with a completely homogeneous dispersion and size of 49.56-85.75 nm by ultrasonication using BYK-192, a dispersant containing copolymer with a pigment affinic group. The average size of the silver nanoparticles was increased to 36.82, 50.66, and 56.06 nm with increasing molecular weight of PAA. Also, the size of the nanoparticles increased with the capping of PAA on the surfaces of the nanoparticles when increasing the amount of PAA. The addition of hydrazine as a reducing agent produced relatively small particles because many nuclei were created by the reduction reaction. The ethanol-acetone solvent helped with the regular arrangement of the silver nanoparticles.

• Journal of Powder Materials
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• v.4 no.2
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• pp.106-112
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• 1997

$Cu-Al_20_3 $ composite powders were prepared by hydrogen reduction of $Cu^{2+}$ from ammoniacal copper sulfate solution on alumina core using autoclave. The copper reduction rate and the properties of copper layer were investigated using Scanning Electron Microscope(SEM), X-ray diffractometer, size and chemical analyzers. The reduction rate of $Cu^{2+}$ showed the maximum value when the molar ratio of [$NH_3$]/[$Cu^{2+}$] was 2. In order to prevent the agglomeration of Cu powder and ethane reduction rate, $Fe^{2+}$ and anthraquinone which act as catalysis were added in the solution. Catalysis was effectively chanced with the addition of two elemerts at a time. Optimum conditions obtained in this study were hydrogen reduction temperature of 205$^{\cire}C$, stirring speed of 500 rpm and hydrogen partial pressure of 300 psi. Obtained $Cu-Al_20_3 $ composite Powders were found to have the uniform and continuous copper coating layer of nodule shape with 3~5 $\mu$m thickness.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.137-142
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• 2004

The aim of this study is to investigate the characteristics and quantity of the noise reduction by floor coverings. The characteristics on the reduction of the lightweight impact sound level by floor coverings is as follows. The insulation level attained by floor coverings tends to be smaller in actual buildings than in public laboratories. The reduction of the impact sound level to the tape is similar to the method of adhesives. For this reason, the reduction of impact sound level by floor coverings in public laboratories can be utilized to tape. And the reduction of impact sound level by floor coverings is not influenced by the size of specimen except the specific frequency.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.3
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• pp.191-194
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• 2003

Macroglossia can cause dentomusculoskeletal deformities, instability of orthodontic and orthognathic surgical treatment, and create masticatory, speech and airway management problems. To determine whether a reduction glossectomy is necessary, it will important to identify the signs and symptoms of macroglossia. Development of dentoskeletal changes directly related with tongue size, such as an anterior open bite or a Angle Class III malocclusion tendency, would indicate that reduction glossectomy may be beneficial. For reduction glossectomy, several techniques have been reported. However, in most techniques the tip of tongue is removed. So its excision causes the loss of most mobile and sensitive portion of the tongue, and creates ankylosed, globular tongue. To avoid such problems, central tongue reduction technique have been proposed. This article will introduce central tongue reduction for anterior openbite case associated with macroglossia.

• Journal of Powder Materials
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• v.25 no.5
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• pp.390-394
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• 2018

Metallic tantalum powder is manufactured by reducing tantalum oxide ($Ta_2O_5$) with magnesium gas at 1,073-1,223 K in a reactor under argon gas. The high thermodynamic stability of magnesium oxide makes the reduction reaction from tantalum oxide into tantalum powder possible. The microstructure after the reduction reaction has the form of a mixture of tantalum and magnesium oxide, and the latter could be entirely eliminated by dissolving in weak hydrochloric acid. The powder size in SEM microstructure for the tantalum powder increases after acid leaching in the range of 50-300 nm, and its internal crystallite sizes are observed to be 11.5 to 24.7 nm with increasing reduction temperatures. Moreover, the optimized reduction temperature is found to be 1,173 K as the minimum oxygen concentration is approximately 1.3 wt.%.