• The Journal of the Acoustical Society of Korea
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• v.14 no.5
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• pp.29-35
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• 1995

Nonlinear distortion arising from the nonlinear movement of the loudspeaker diaphragm degradates the tone quality. The distortion is, in low frequency range, mainly caused by nonlinear characteristics of the suspension stiffness and the force factor. In this paper, the nonlinear suspension stiffness and the nonlinear force factor are modeled to the quadratic functions and a method is proposed to determine their coefficients. An additional mass to the diaphragm moved the quiescent point of the diaphragm and uncoupled the stiffness and the force factor. This made it possible to deter mine the coefficients of the nonlinear suspension stiffness by measuring the resonance frequencies at several quiescent points. The coefficients of the nonlinear force factor are then determined by fitting the curve which is calculated from the waveforms of input voltage and input current, and the displacement of the diaphragm at resonance frequency.

• The Journal of the Acoustical Society of Korea
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• v.14 no.5
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• pp.94-101
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• 1995

In this paper, a new vocal cords model, called a four-mass model, is proposed for a hoarse speech mechanism. Pathological changes of vocal cords cause hoarse speech and glottal waveform reflects motion states of vocal cords. From these facts, we assumed that the morbid vocal cords be dissymmetric and take the four-mass type. The glottal waveforms and the model parameters of normal and hoarse speech signals are analyzed, and some relations bet ween the model parameters and the hoarse pathology are discussed. Experimental results show that the new research method of hoarse speech can reveal relations between the acoustic features of hoarse speech and the hoarse pathology, and be used to diagnose laryngeal diseases and to improve tone quality of hoarse speech.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.8
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• pp.55-64
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• 1999

In this paper, new gamut-mapping algorithm (GMA) that utilizes variable anchor points (center of gravity on the luminance axis) is proposed. The proposed algorithm increases luminance range, which is reduced from conventional gamut mapping toward an anchor point. In this process, this algorithm utilizes multiple anchor points with constant slopes to both reduce a sudden color change on the gamut boundary of the printer and to maintain a uniform color change during the mapping process. Accordingly, the proposed algorithm can reproduce high quality images with low-cost color devices.

• Journal of the Korea Furniture Society
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• v.24 no.4
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• pp.345-349
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• 2013

Yellow poplar is well known commercial hardwood species in the world because of its availability, rapid growth, large size, excellent form, early natural pruning, and the good working quality of the wood. Therefore, yellow poplar (Liriodendron tulipifera L.) has been adopted in South Korea for decades ago, and its cultivating the saplings and silvicultural system have been studied. However, yellow poplar is still embroiled in controversy for utilization of use and worth. This species has not only advantages such as lower weight, light color, and higher machinability and bending processing, but also has disadvantages which are bad smell and different colors on heartwood and sapwood. In this study, the objective was that use of yellow poplar board as furniture materials by drying and painting process. Thirty years old yellow poplar was cut and dried for 7 days by high-frequency dryness. Adjustment of color tone to walnut color was conducted with multiple colorants and various number of spread times. Uniform color of yellow poplar on heartwood and sapwood was accomplished by applying 1 time stain (green), 2 times transparent primer, 1 time middle-painting (walnut), and 2 times top-painting (walnut) in sequentially. The painted yellow poplar board was used to manufacture table and dressing table. During the furniture manufacture process, no critical issues were occurred on part of jointing and painting. This painting method may be useful data for future use of yellow poplar as furniture materials.

• Speech Sciences
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• v.2
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• pp.25-44
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• 1997

When listening the various speech synthesis systems developed and being used in our country, we find that though the quality of these systems has improved, they lack naturalness. Moreover, since the voice color of these systems are limited to only one recorded speech DB, it is necessary to record another speech DB to create different voice colors. 'Voice Color' is an abstract concept that characterizes voice personality. So speech synthesis systems need a voice color control function to create various voices. The aim of this study is to examine several factors of voice color control rules for the text-to-speech system which makes natural and various voice types for the sounding of synthetic speech. In order to find such rules from natural speech, glottal source parameters and frequency characteristics of the vocal tract for several voice colors have been studied. In this paper voice colors were catalogued as: deep, sonorous, thick, soft, harsh, high tone, shrill, and weak. For the voice source model, the LF-model was used and for the frequency characteristics of vocal tract, the formant frequencies, bandwidths, and amplitudes were used. These acoustic parameters were tested through multiple regression analysis to achieve the general relation between these parameters and voice colors.

• Clinical and Experimental Pediatrics
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• v.59 no.9
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• pp.347-354
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• 2016

An apparent life-threatening event (ALTE) is defined as the combination of clinical presentations such as apnea, marked change in skin and muscle tone, gagging, or choking. It is a frightening event, and it predominantly occurs during infancy at a mean age of 1-3 months. The causes of ALTE are categorized into problems that are: gastrointestinal (50%), neurological (30%), respiratory (20%), cardiovascular (5%), metabolic and endocrine (2%-5%), or others such as child abuse. Up to 50% of ALTEs are idiopathic, where the cause cannot be diagnosed. Infants with an ALTE are often asymptomatic at hospital and there is no standard workup protocol for ALTE. Therefore, a detailed initial history and physical examination are important to determine the extent of the medical evaluation and treatment. Regardless of the cause of an ALTE, all infants with an ALTE should require hospitalization and continuous cardiorespiratory monitoring and evaluation for at least 24 hours. The natural course of ALTEs has seemed benign, and the outcome is generally associated with the affected infants' underlying disease. In conclusion, systemic diagnostic evaluation and adequate treatment increases the survival and quality of life for most affected infants.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.3
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• pp.37-43
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• 2009

In this paper, we proposed that a novel method base on a binary image that technique is proposed for data hiding into binary images and halftone image. A binary image is bitmap image and halftone is composed by two-tone value in a limited region in an image. For this reason, it is not easy to hide messages in binary images. PWLC is a new method to hide a message in binary images. However, it yields images of unacceptable quality, unless you should change very few of it. Therefore, in order to solve this problem, we used run-length method into binary images. That is, we find a proper region to hide messages. In this paper, we proposed new method to hide messages in binary images. In addition, we proved that our algorithm is better than PWLC through the experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.873-876
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• 2008

Although Permeable concrete is resently used as a pavement at a parking lot, a public squre and a bicycle road, we use without enough examining. most the maintenance of quality for Permeable concrete is only dealt with strength and color tone. also, there is not yet enough fundamental data about dynamical properties for strength, rate of void and water permeability. even when it is applied to at the scene, it is been a matter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.620-628
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• 2005

Spatial control of sound is essential to deliver better sound to the listener's position in space. As it can be experienced in many listening environments, the quality of sound can not be manifested over every position in a hall. This motivates us to control sound in a region we select. The primary focus of the developed method has to do with the brightness and contrast of acoustic image in space. In particular, the acoustic brightness control seeks a way to increase loudness of sound over a chosen area, and the contrast control aims to enhance loudness difference between two neighboring regions. This enables us to make two different kinds of zone - the zone of quiet and the zone of loud sound - at the same time. The other perspective of this study is on the direction of sound. It is shown that we can control the direction of perceived sound source by focusing acoustic energy in wavenumber domain. To begin with, the proposed approaches are formulated for pure-tone case. Then the control methods are extended to a more general case, where the excitation signal has broadband spectrum. In order to control the broadband signal in time domain, an inverse filter design problem is defined and solved in frequency domain. Numerical and experimental results obtained in various conditions certainly validate that the acoustic brightness, acoustic contrast, direction of wave front can be manipulated for some finite region in space and time.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.460-466
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• 2003

The aeroacoustic characteristics and noise reduction method of a centrifugal fan for a bagless vacuum cleaner were studied. The major noise source of vacuum cleaner is the centrifugal fan. The impeller of the fan rotates over 30000 rpm and generates very high-level piercing noise. It was found that the dominant noise source of the fan is generated from the aerodynamic interaction between the highly rotating impeller and stationary diffuser. In order to reduce the high tonal sound generated from the aerodynamic interaction between the impeller and diffuser, tapered impeller was carefully designed and tested. The trailing edge of the tapered impeller was inclined and this reduces the flow interactions between the rotating impeller and the stationary diffuser because of some phase shift. The static efficiency of the new impeller is slightly lower than the conventional one. The overall SPL is reduced about 3.6 dBA. The SPL of blade passing frequency(BPF) is reduced about 6 dBA and the $2^{nd}$ BPF is reduced about 20 dBA. The vacuum cleaner with the tapered impeller has lower noise level than that of the previous impeller and the strong tonal sound was dramatically reduced.