• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.152-159
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• 2001

In this paper it is intended to set-up a sound model of the 60,000rpm 100kW prototype APU gas turbine rotor-bearing system, and particularly to investigate the influences of the tie shaft on the rotordynamic characteristics of the entire APU gas turbine rotor-bearing system, employing the dual shaft model. Firstly, a mock-up APU rotor has been constructed to test and verify the model. Analytical natural frequency results have agreed with the corresponding modal test ones to within 5% difference. Then, the rotordynamic characteristics of the prototype APU rotorbearing system have been investigated. Natural vibration and unbalance response analyses results have shown that the inner tie shaft resonance can cause high enough vibration of the outer main rotor shaft. This could be a concern as the rotor journals operate on very thin air film at high speed. It is concluded as a conservative design practice that the inner tie shaft should be explicitly modeled in the rotordynamic analysis of the APU rotor-bearing system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.347-351
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• 1997

A micromachined piezoelectic cantilever transducer,which works both as a microphone and as a microspeaker,has been fabricated and tested. The 2000*2000*3.mu.m .sap2. cantilever has oxide(ZnO)piezoelectric thin film on a supporting layer of low-pressure chemical-vapor-deposited(LPCVD)low-stress siliconnitride. A highlight of the fabrication process which may also be relevant for other micromachined stuctures is the technique for producing a flat,multilayer cantilever. The measured microphone sensitivity is fairly constant at 2 mV/.mu.bar in the low frequency range and rise to 20 mV/.mu.bar at the lowest resonant frequency of 890 Hz. The 2 mV/.mu.bar sensitivity is the highest report to data for a microphone with a micromachined diaphragm. When measured into a 2 cm/sap3 coupler with 4V (zero-park)drive,the microspeaker output sound pressure level(SPL) is 75 dB at 890 Hz. It increases to approximately 100dB SPL at 4.8kHz with 6V(zero-park)drive. The measured microphone frequency response agrees well with the results of an ABAQUS simulation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.7
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• pp.499-507
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• 2003

This paper presents a method for active noise control (ANC) in a duct by using a ring-tyPe smart foam. The ring-type smart foam consists of an elastic porous material of lining shape and a PVDF film embedded In the material. The PVDF element acts as a secondary sound source to reduce the noise. Active noise control using a ring-type smart foam is only effective locally because of the way to excite radially. To enlarge the quiet zone, the duct Is lined with additional acoustic foam between the smart foam and the error microphone. When cancellation path ks optimized by the LMS/RLS algorithm, the computation power is reduced while control performance Is maintained. The filtered-x LMS algorithm is used to minimize the error signal.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.37-44
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• 2002

The dynamic behavior of rotor-bearing system has been investigated using finite element method. A procedure is presented for dynamic modeling of rotor-bearing system which consists of shaft elements, rigid disk, flexible bearing and support structure. A finite element model including the effects of rotary inertia, shear deformation, gyroscopic moments is developed. Linear stiffness and damping coefficients are calculated for 2 lobe sleeve bearing. The whirl frequency, mode shape, stability and unbalance response of rotor system including effects of bearing coefficient and support structures are calculated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.45-46
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• 2005

The piezoelectric ZnO thin films were deposited onto Al/Si substrate in order to figure out the crystalline and the residual stress of deposited films. As the $Ar/O_2$ gas ratio is increased, c-axis orientation of deposited films is significantly enhanced and also the residual stresses of ZnO films are all compressive. They are decreased from -1.2 GPa to -950 MPa as the $Ar/O_2$ gas ratio is increased. A diaphragm-based piezoelectric microspeaker fabricated on ONO films shows about 14 mPa output pressure at 1 kHz with $8V_{peak-to-peak}$.

• Journal of Sensor Science and Technology
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• v.25 no.6
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• pp.412-417
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• 2016

Scent display is used mainly to augment immersion, reality and emotion, besides provide more tension and suggestion. However, this paper pay attention to effect of smells as ambient media, and propose a notification service using scents without sound and vibration when a user has new mail, test message and phone call. And we designed a scent service platform and API function for easy application of scent notification service. We demonstrated feasibility by experiment using smart phone and self-producted scent device.

• Journal of Sensor Science and Technology
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• v.30 no.5
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• pp.273-278
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• 2021

Here, we studied the change in the mechanical stiffness of a diaphragm according to the corrugation pattern. The diaphragm consists of a silicon oxide and nitride double layer; a corrugation pattern was formed by dry etching, and the diaphragm was released by wet etching. The fabrication of the thin film was verified using focused ion beam and scanning electron microscopy images. The mechanical stiffness of the diaphragm was obtained by measuring the surface vibration using a laser Doppler vibrometer while applying external sound pressure. Flat squares, diaphragms with square corrugations, and circular corrugation patterns were measured and compared. The stiffness of the diaphragm with a corrugation structure was found to be smaller than that without a corrugation structure; in particular, circular corrugation showed a better effect because of the high symmetry. Furthermore, the effect of corrugation was theoretically predicted. The proposed corrugated diaphragm showed comparable flexibility with the state-of-the-art MEMS microphone diaphragm.

• The Journal of the Korea Contents Association
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• v.14 no.4
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• pp.110-122
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• 2014

Korea's film industry has been growing over the last 10 years, and there has been much attention to the antecedents of film box office sales both academic and business communities. So far, previous research which explained success factors of film or movie mainly focused on 3 stages, production, distribution and screening. However, these 3 steps are heavily vertically integrated in Korea's firm industry unlike United States. Almost 130% of movie theaters are multiplex chain and operated by film production companies such as CJ and Lotte Entertainment In this situation, film sales are likely to he affected by movie theaters own facilities or location factors rather than movie contents. Based. on resource-based view and S-C-P paradigm, the authors examined "whether movie theater's facilities factors and trade area factors such as accessibility, competitive situation, and population have effect to movie theater's sales revenues. The results showed that the average occupancy of theater is the most important factor to movie theaters sales in both large and small cities. In large cities, movie theater's facilities factors which included vibration seat special sound system, premium movie theater, VIP lounge are relatively important than trade area factors. In contrast, in small cities, location factors and accessibility are the most important factors to movie theaters sales. We discuss the managerial and theoretical implication for the results and the specific limitations are suggested at the end of the paper.

• Journal of Digital Convergence
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• v.15 no.9
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• pp.453-461
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• 2017

The video image in the movie has become more spectacular than ever, and the expression area and the subject have been infinitely expanded, but it can not be said that the range of imagination has expanded. Instead, the 60s and 70s, which were the epochs of popular culture, The film that implements the artististic visual style and expression style of the artist. Stanley Kubrick's "Clockwork Orange", which has been pursuing technological perfection and experimental style, was created using traditional video grammar and gained a great repercussion with outstanding material and high artistic expression technique at that time. These techniques have led audiences to rational observation through irony, rather than emotional sympathy for the situation, for extreme violence and sensational films. This is because the purpose of the director was not to be in technological perfection but to reveal the contradictions of the real society and to reflect on the meaning of the existence of society itself. These creative traditional visual grammar and expression methods are a good visual style that enables the intentionally transmitted message to be transmitted more intensely and effectively, and the artistic depth can be created at the same time by unconsciously perceiving the meaning present on the back to the audience.

• Imaging Science in Dentistry
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• v.30 no.4
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• pp.265-274
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• 2000

Purpose: The aims of the present study are to determine the optimum compression rate in terms of file size reduction and diagnostic quality of the images after compression and evaluate the transmission speed of original or each compressed image. Materials and Methods: The material consisted of 24 extracted human premolars and molars. The occlusal surfaces and proximal surfaces of the teeth had a clinical disease spectrum that ranged from sound to varying degrees of fissure discoloration and cavitation. The images from Digora system were exported in TIFF and the images from conventional intraoral film were scanned and digitalized in TIFF by Nikon SF-200 scanner (Nikon, Japan). And six compression factors were chosen and applied on the basis of the results from a pilot study. The total number of images to be assessed were 336. Three radiologists assessed the occlusal and proximal surfaces of the teeth with 5-rank scale. Finally diagnosed as either sound or carious lesion by one expert oral pathologist. And sensitivity, specificity and k value for diagnostic agreement was calculated. Also the area (Az) values under the ROC curve were calculated and paired t-test and oneway ANOVA test was performed. Thereafter, transmission time of the image files of the each compression level was compared with that of the original image files. Results: No significant difference was found between original and the corresponding images up to 7% (1 : 14) compression ratio for both the occlusal and proximal caries (p<0.05). JPEG3 (1 : 14) image files are transmitted fast more than 10 times, maintained diagnostic information in image, compared with original image files. Conclusion: 1 : 14 compressed image file may be used instead of the original image and reduce storage needs and transmission time.