• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.32-42
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• 2013

We study the gap effect on detonating high explosives using numerical simulation. The characteristic acoustic impedance theory is applied to understand the reflection and transmission phenomena associated with gap test of high explosives and solid propellants. A block of charge with embedded multiple gaps is detonated at one end to understand the ensuing detonation propagation through pores and non uniformity of the tested material. A high-order multimaterial simulation provides a meaningful insight into how material interface dynamics affect the ignition response of energetic materials under a shock loading.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.1
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• pp.78-82
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• 2019

This paper addressed the spectrum of ultrasonic waves produced by arc and/or coronal discharge inside the switchboard. Portable ultrasound sensors are useful for detecting discharge phenomena, such as coronal means in electrical systems. However, a typical handheld ultrasound detector has a disadvantage of determining the type of problem by listening to the sound characteristics and predicting the results, as a result of the determination of whether a discharge is present. Therefore, a new method of analysis is required to distinguish ultrasonic characteristics. In this paper, we published an ultrasound analysis case study to visualize the sound of ultrasonic waves measured with ultrasonic sensors. From the results of the experiment, it was possible to detect coronal discharge and serial arc discharge without interference by the ultrasonic detection system.

• The Journal of the Acoustical Society of Korea
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• v.27 no.6
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• pp.303-308
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• 2008

The purpose of the present study is to investigate that word frequency has significant influence on noun definitions in Korean. The experimental group was 80 students from Elementary school, Middle school, High school and University. They rated familiarity and wrote definitions for nouns. Noun definitions were analyzed with semantic categories such as "use/purpose," "description," "association/relation," "partial explanation," "explanation," "error," "partial explanation-attribute," "partial explanation-specific class," "partial explanation-nonspecific class," "explanation-specific class," "explanation-nonspecific class." As a result, they showed familiarity for high-frequency nouns. "EXPL" categories that use class terms or critical attributes were used more frequently in definitions of high-frequency nouns compared with low-frequency nouns. They increased with age and errors decreased with age. Word frequency had a significant influence on noun definitions.

• The Journal of the Acoustical Society of Korea
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• v.31 no.4
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• pp.235-243
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• 2012

This paper studies characteristics and causes of sound, and many others by distinguishing passivity and activity of the cases of a dog vocalizing human's words. As a result of the previous cases of vocalization of human's words, the dog was able to understand characteristics of a host's voice and imitate the sound using his own vocal organs. This is the case of passive vocalization accompanied by temporary voice imitation without a function of communication. On the contrary, as a consequence of the recently reported case in which a dog vocalizes such words as "Um-ma" and "Nu-na-ya," it shows the vocalization pattern clearly distinguished from the prior cases. The given dog repeatedly vocalizes pertaining words in an active manner according to circumstances and plays a role of fundamental communication and interaction with its host. The reason why the dog can vocalize the man's words actively is determined to be that the dog has a high level of intelligence and intimacy with its host, that people react actively to its pertaining pronunciation, and so forth. The following results can be used for the study that investigates animals' sound with vocalization possibility and language learning feasibility.

• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.321-327
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• 2019

The purpose of this study is paper is to improve the flow performance and to reduce the aerodynamic noise of air discharge system consisting of a centrifugal fan, ducts and a housing for the clothes dryer. Using computational fluid dynamics and acoustic analogy based on FW-H (Ffowcs-Williams and Hawkings) Eq., air flow field and acoustic fields of the air discharge system are investigated. To optimize aerodynamic performance and aerodynamic noise, the response surface method is employed. The two factors central composite design using the inflow and outflow angles of fan blades is adopted. The devised optimum design shows the reduction of turbulent kinetic energy in the ducts and the housing of the system, and as a result, the improved flow rate and reduce noise is confirmed. Finally, the experment using the proto-type manufactured usign the optimum design shows the increase of flow rate by 4.2 %.

• Science of Emotion and Sensibility
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• v.13 no.1
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• pp.121-128
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• 2010

This study is to analyze change of connectivity between brain positions caused by relaxation through EEG coherence. EEG spectrum analysis method has been used to analyze brain activity when relaxation was experienced. However, the spectrum analysis method has a limit that could not observe interactive reaction between brain-functional positions. Therefore, coherence between positions was analyzed to observe connectivity between the measurement positions in this study. Through the method, the reaction of the central nervous system caused by the emotion change was observed. Twenty-four undergraduates of both genders(12 males and 12 females) were asked to close their eyes and listen to the sound. During experiment, EEG was measured at eight positions. The eight positions were F3, F4, T3, T4, P3, P4, O1, and O2 in accordance with International 10-20 system. The sounds with white noise and without were used for relaxation experience. Subjective emotion was measured to verify whether or not they felt relaxation. Subjective emotion of participants were analyzed by ANOVA method(Analysis of Variance). In the result, it was proved that relaxation was subjectively evoked when participants heard sound. Accordingly, it was proved that relaxation could be enhanced by the mixed white noise. EEG coherence between the measurement positions was analyzed. T-test was performed to find its significant difference between relaxation and not-relaxation. In the results of EEG coherence, connectivity with occipital lobes has been increased with relaxation, and connectivity with parietal lobes has been increased with non-relaxed state. Therefore, brain connectivity has shown different pattern between relaxed emotion and non-relaxed emotion.

• Science of Emotion and Sensibility
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• v.16 no.1
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• pp.117-124
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• 2013

This study examined that how precisely MFCC, LPC, energy, and pitch related parameters of the speech data, which have been used mainly for voice recognition system could predict the vocal emotion categories as well as dimensions of vocal emotion. 110 college students participated in this experiment. For more realistic emotional response, we used well defined emotion-inducing stimuli. This study analyzed the relationship between the parameters of MFCC, LPC, energy, and pitch of the speech data and four emotional dimensions (valence, arousal, intensity, and potency). Because dimensional approach is more useful for realistic emotion classification. It results in the best vocal cue parameters for predicting each of dimensions by stepwise multiple regression analysis. Emotion categorizing accuracy analyzed by LDA is 62.7%, and four dimension regression models are statistically significant, p<.001. Consequently, this result showed the possibility that the parameters could also be applied to spontaneous vocal emotion recognition.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.449-454
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• 1998

전립선 비대증 및 각종 고형암 조직을 제거하기 위해 이용되는 고강도 집속형 초음파 시스템은 초음파의 조직에 대한 열 효과를 이용한다. 이 경우 수MPa의 고 압력 초음파를 사용하기 때문에 수술시 초음파에 의한 조직내의 공동 현상이 수반되고 이로 인해 초음파의 집속 효과가 감소하게 된다. 본 논문에서는 초음파 공동 현상을 억제하기 위하여 초음파의 주파수 특성을 고려하였다. 초음파의 크기는 일정하게 유지하면서 증가하는 주파수로 변조된 초음파와 비선형 고저파 (nonlinear harmonics) 성분을 포함한 왜곡된 초음파에 대한 기포의 반응을 Gilmore 기포 모델을 이용하여 관찰하였다. 초음파의 주파수 변조는 10 $\mu\textrm{s}$ 동안 초기 주파수 1 MHz부터 시작하여 7 MHz까지 선형적으로 증가하도록 하였다. 파형을 왜곡시키는 고저파 성분의 크기는 주파수에 역 비례 하도록 하였다. 초음파의 기본 주파수는 1 MHz로 하였고, 압력은 0.1 MPa과 1 MPa의 두 경우를 고려하였다. 초기 기포의 반경은 1 $\mu\textrm{m}$으로 하였고, 기포 주위의 유체는 물로 가정하였다. 시뮬레이션 결과로부터, 주파수를 변조시키거나 파형을 왜곡시킨 초음파에 대한 기포의 진동은, 동일한 압력의 정현파에 대한 경우 보다 작은 것으로 나타났다. 주파수 변조된 초음파에 반응한 기포의 진동은 압력이 낮을 때 (0.1 MPa), 변조된 주파수가 기포의 공진 주파수인 3 MHz 부근에서 최대치를 보이다가 이후 급격히 감소하는 경향을 보였다. 반면, 압력이 높아지면 (1 MPa) 기포의 진동은 주파수의 증가와 함께 감소하다가 3 MHz 이상으로 변조 될 경우, 유의한 변화를 보이지 않는 것으로 나타났다. 이 결과는 초음파의 적절한 주파수 성분 조절로 초음파 공동 현상을 일정 수준 억제할 수 있음을 시사한다. 고려가 수반되어야 할 것으로 보인다. 다음 내용을 정리해 보고자 한다.리해 보고자 한다.rc$ 구입할 때 중점적으로 살펴보는 사항은 신선도와 순수재래종 여부, 위생상태였다. 한편 소비자가 언제나 구입할 수 없다는 의견이 85.2%나 되어 원활한 공급과 시장조성이 아직 정착되지 않고 있었다. $\bigcirc$ 현재 유통되고 있는 재래종닭은 소비자 대부분이 잡종으로 인식하고 있었으며, 재래종과 일반육계와의 구별은 깃털색, 피부색, 정강이색등 외관상으로 구별하고 있었다. 체중에 대한 반응은 너무 작다는 의견이었고, 식품으로의 인식도는 비교적 고급식품으로 인식하고 있다. $\bigcirc$ 재래종닭고기의 브랜드화에 대한 견해는 젊고 소득이 높은 계층에서 브랜드화의 필요성을 강조하고 있다. $\bigcirc$ 재래종달걀의 소비형태는 대부분의 소비자가 좋아하였으나 아직 먹어보지 못한 응답자가 많았다. 재래종달걀의 맛에 대해서는 고소하고 독특하여 차별성을 느끼고 있었다. $\bigcirc$ 재래종달걀의 구입장소는 계란판매점(축협.농협), 슈퍼, 백화점, 재래닭 사육 농장등 다양하였으며 포장단위는 10개를 가장 선호하였고, 포장재료는 종이, 플라스틱, 짚의 순으로 좋아하였다. $\bigcirc$ 달걀의 가격은 200원정도를 적정하다고 하였으며, 크기는 (평균 52g)는 가장 적당하다고 인식하고 있으며, 난각색은 대부분의 응답자가 갈색을 선호하였다. $\bigcirc$ 재래종달걀의 구입시 애로사항은 믿을수 없고, 구입장소를 몰라서, 값이 싸다 등이었고, 앞으로 신뢰할 수 있고 위생적인 생산 및 유통체계가 확립될 경우 더 많이 소비하겠다는 의견이었다. $\bigcirc$ 재래닭 판매업소(식당)의 판매형태는 66.7%인 대부분

• The Journal of the Acoustical Society of Korea
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• v.16 no.2
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• pp.89-94
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• 1997

A new type SO$_2$ gas sensor with a particular inorganic thin film on SAW devices was developed. The sensor consisted of twin SAW oscillators of the center frequency of 54 MHz fabricated on the LiTaO$_3$ piezoelectric single crystal. One delay line of the sensor was coated with a CdS thin film that selectively adsorbed and desorbed SO$_2$, while the other was uncoated for use as a stable reference. Deposition of the CdS thin film was carried out by the spray pyrolysis method using an ultrasonic nozzle. The sensor could measure the concentration in air less than 0.25 parts per million of SO$_2$. Stability of the sensor turned out to be as good as less than 20ppm, recovery time after each measurement was as short as 5 minutes. Repeatability of the measurement was confirmed through so many reiterated experiments. Hence, the SAW sensor developed through this work showed promising performance as a microsensing tool of SO$_2$. Further work required to improve the performance of the sensor includes enhancement of the reactivity of the CdS thin film with SO$_2$ through appropriate dopant addition, an increase of the center frequency of the SAW device.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.13-16
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• 2014

We have surveyed on significant progress in recent developments of accelerator-based pulsed X-ray sources has offered the opportunity for time-resolved studies on fast structure dynamics on the nanometer scale. The required and currently available techniques for time resolved X-ray diffraction measurements using the third-generation synchrotron radiation sources are summarized. Ultrafast X-ray experimental techniques are discussed for femtosecond studies at future synchrotron radiation sources.