• Title/Summary/Keyword: Sound Power

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Numerical and experimental analysis of aerodynamics and aeroacoustics of high-speed train using compressible Large Eddy Simulation (압축성 대와류모사를 이용한 고속열차의 공력 및 공력소음의 수치적/실험적 분석)

  • Kwongi Lee;Cheolung Cheong;Jaehwan Kim;Minseung Jung
    • The Journal of the Acoustical Society of Korea
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    • v.43 no.1
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    • pp.95-102
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    • 2024
  • Due to technological advances, the cruising speed of high-speed trains is increasing, and aerodynamic noise generated from the flow outside the train has been an important consideration in the design stage. To accurately predict the flow-induced noise, high-resolution generation of sound sources in the near field and low-dissipation of sound propagation in the far field are required. This should be accompanied by a numerical grid and time resolution that can properly consider both temporal and spatial scales for each component of the real high-speed train. To overcome these challenges, this research simultaneously calculates the external flow and acoustic fields of five high-speed train cars of real-scale and at operational running speeds using a threedimensional unsteady Large Eddy Simulation technique. To verify the numerical analysis, the measurements of the wall pressure fluctuation and numerical results are compared. The Ffowcs Williams and Hawking equation is used to predict the acoustic power radiated from the high-speed train. This research is expected to contribute to noise reduction based on the analysis of the aerodynamic noise generation mechanism of high-speed trains.

Effect of Diffuser Locations on the Room Acoustical Parameters in 1:25 Scale Model Hall (1:25 축소모형 홀에서 확산체의 설치부위에 따른 실내 음향지표의 변화)

  • Kim, Yong-Hee;Seo, Choon-Ki;Lee, Hye-Mi;Jeon, Jin-Yong
    • The Journal of the Acoustical Society of Korea
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    • v.31 no.3
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    • pp.115-128
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    • 2012
  • This paper investigates the effects of diffuser on the acoustical parameters in music hall with consideration of the result of scattering coefficient measurement. A scale model hall of 600 seats with orchestra shell was used for experiments. The materials of 1:50 scale model was chosen through absorption coefficient measurement based on ISO 354. The model was matched to the computer simulation model in terms of reverberation time. In order to evaluate the effect of diffuser location, the measurements were accomplished with and without diffusers according to 7 configurations by diffuser-installed region; sidewall, balcony front, ceiling and so on. The following acoustical parameters were extracted from each measurement case; Reverberation time (RT), Early decay time (EDT), Clarity (C80), Center time (Ts), Sound strength (G) and Temporal diffusion (TD) from the auto-correlation function (ACF) of impulse responses. As a result, the absorption power and diffusion power were increased with number of diffusers. Accordingly RT, EDT and G were decreased by diffuser and the redirection of reflections was occurred briskly. Averaged TD was 6.05 to 6.30 by measurement cases. RT was found to be the most related factor to diffusion power (R = 0.94). The correlation between TD and EDT was high (R = 0.73). In addition, the effects of diffuser-installed location were discussed in terms of acoustical parameter variation.

The Public Television Crisis and the Mutation of the Public Sphere in Neo-liberalism (신자유주의 시대 공영방송의 위기와 공공영역의 변화)

  • Lee, Sang-Hoon
    • Korean journal of communication and information
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    • v.57
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    • pp.250-266
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    • 2012
  • In neo-liberalism, the change-value of the market and of the machandise based on the individual as the consumer dominate the public sphere, and the capital power encroach on it. with the technological revolution. At the same time the public sphere as such represent the media sphere, which is more and more subordinate, and have no choice but to do to the governmental authority having political power privatized. The private usage of reason in the public sphere is carried out at the structual level. How can we call such a space in which the private usage of reason is generalized and dominant as the public sphere? And so now, we sound out the possibility of the public sphere such as a new space of the universality where the public usage of reason can be realized without any limits and with free. So, when we imagine the proletarian public sphere, in which co-exist the divers private interests, as a new public sphere capable to be constructed, we can address a question as follow. What is the caracteristic of the proletarian public sphere in modern society?, Is the public community able to be formed and realized in such space? How would have the proletarian public sphere the carateristics of the publis sphere? What is the attribute of the community that the proletarian public sphere would make, and what is its force of emancipation? The power is no longer stable and static. Rather, it is reconstructed and reorganized in the divers phases of the everyday life. It is the reason why we put on the order of the day the proletarian public sphere as alternative public space, which would be a place of divers hegemonic representation. And now, we are aware of the beginning of thses changes.

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Wearable Computers

  • Cho, Gil-Soo;Barfield, Woodrow;Baird, Kevin
    • Fiber Technology and Industry
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    • v.2 no.4
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    • pp.490-508
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    • 1998
  • One of the latest fields of research in the area of output devices is tactual display devices [13,31]. These tactual or haptic devices allow the user to receive haptic feedback output from a variety of sources. This allows the user to actually feel virtual objects and manipulate them by touch. This is an emerging technology and will be instrumental in enhancing the realism of wearable augmented environments for certain applications. Tactual displays have previously been used for scientific visualization in virtual environments by chemists and engineers to improve perception and understanding of force fields and of world models populated with the impenetrable. In addition to tactual displays, the use of wearable audio displays that allow sound to be spatialized are being developed. With wearable computers, designers will soon be able to pair spatialized sound to virtual representations of objects when appropriate to make the wearable computer experience even more realistic to the user. Furthermore, as the number and complexity of wearable computing applications continues to grow, there will be increasing needs for systems that are faster, lighter, and have higher resolution displays. Better networking technology will also need to be developed to allow all users of wearable computers to have high bandwidth connections for real time information gathering and collaboration. In addition to the technology advances that make users need to wear computers in everyday life, there is also the desire to have users want to wear their computers. In order to do this, wearable computing needs to be unobtrusive and socially acceptable. By making wearables smaller and lighter, or actually embedding them in clothing, users can conceal them easily and wear them comfortably. The military is currently working on the development of the Personal Information Carrier (PIC) or digital dog tag. The PIC is a small electronic storage device containing medical information about the wearer. While old military dog tags contained only 5 lines of information, the digital tags may contain volumes of multi-media information including medical history, X-rays, and cardiograms. Using hand held devices in the field, medics would be able to call this information up in real time for better treatment. A fully functional transmittable device is still years off, but this technology once developed in the military, could be adapted tp civilian users and provide ant information, medical or otherwise, in a portable, not obstructive, and fashionable way. Another future device that could increase safety and well being of its users is the nose on-a-chip developed by the Oak Ridge National Lab in Tennessee. This tiny digital silicon chip about the size of a dime, is capable of 'smelling' natural gas leaks in stoves, heaters, and other appliances. It can also detect dangerous levels of carbon monoxide. This device can also be configured to notify the fire department when a leak is detected. This nose chip should be commercially available within 2 years, and is inexpensive, requires low power, and is very sensitive. Along with gas detection capabilities, this device may someday also be configured to detect smoke and other harmful gases. By embedding this chip into workers uniforms, name tags, etc., this could be a lifesaving computational accessory. In addition to the future safety technology soon to be available as accessories are devices that are for entertainment and security. The LCI computer group is developing a Smartpen, that electronically verifies a user's signature. With the increase in credit card use and the rise in forgeries, is the need for commercial industries to constantly verify signatures. This Smartpen writes like a normal pen but uses sensors to detect the motion of the pen as the user signs their name to authenticate the signature. This computational accessory should be available in 1999, and would bring increased peace of mind to consumers and vendors alike. In the entertainment domain, Panasonic is creating the first portable hand-held DVD player. This device weight less than 3 pounds and has a screen about 6' across. The color LCD has the same 16:9 aspect ratio of a cinema screen and supports a high resolution of 280,000 pixels and stereo sound. The player can play standard DVD movies and has a hour battery life for mobile use. To summarize, in this paper we presented concepts related to the design and use of wearable computers with extensions to smart spaces. For some time, researchers in telerobotics have used computer graphics to enhance remote scenes. Recent advances in augmented reality displays make it possible to enhance the user's local environment with 'information'. As shown in this paper, there are many application areas for this technology such as medicine, manufacturing, training, and recreation. Wearable computers allow a much closer association of information with the user. By embedding sensors in the wearable to allow it to see what the user sees, hear what the user hears, sense the user's physical state, and analyze what the user is typing, an intelligent agent may be able to analyze what the user is doing and try to predict the resources he will need next or in the near future. Using this information, the agent may download files, reserve communications bandwidth, post reminders, or automatically send updates to colleagues to help facilitate the user's daily interactions. This intelligent wearable computer would be able to act as a personal assistant, who is always around, knows the user's personal preferences and tastes, and tries to streamline interactions with the rest of the world.

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Self-Powered Smart Jump-Rope to Transform an Intensive Physical Activity into Electricity-Generating Fun Experience (고강도의 줄넘기 운동을 지속 가능하고 즐거운 경험으로 만들기 위한 에너지 자립형 스마트 줄넘기)

  • Jo, Jonghyun;Yeo, Jungjin;Park, Heajeong;Ryu, Munho;Yang, Yoonseok
    • Journal of the HCI Society of Korea
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    • v.9 no.2
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    • pp.13-21
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    • 2014
  • Jump-rope is a simple and effective exercise, but its intensive exercise load and monotonous pattern make it difficult to perform consistent workout. On the other hand, jumping rope accompanies large amount of kinetic energy which can be converted into electrical energy. In this study, we designed and implemented a self-powered jump-rope which can support the low-power embedded Bluetooth system inside it. The embedded system wirelessly transmits the acceleration data measured during jumping-rope exercise to a smartphone. We also developed a smartphone app which can count the number of jumps and provide real-time feedback with sound and animated graphic effects in a game context. Pilot test using the prototype smart jump-rope verified that it can be useful to motivation for the jump-rope exercise and make the exercise more effective by providing users with precise information about their exercise. We expect that the developed self-powered jump-rope will change the exercise from an intensive physical activity into electricity-generating fun experience combined with smartphone game, which maximize the benefit of the consistent jump-rope exercise.

Thermal distribution change in polyvinyl alcohol gel caused by focused ultrasound (폴리비닐알코올 젤의 집속초음파에 의한 온도분포 변화)

  • Kim, Jungsoon;Kim, Moojoon
    • The Journal of the Acoustical Society of Korea
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    • v.39 no.6
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    • pp.576-584
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    • 2020
  • In order to obtain basic information for using polyvinyl alcohol (PVA) gel as a tissue mimicking phantom for temperature visualization, the temperature change characteristics due to the focused ultrasound were examined for different concentration of PVA. To obtain the basic acoustic characteristics, the speed of sound, the attenuation coefficient, and the density depending on the PVA concentration were measured, and the thermodynamic characteristics, such as thermal conductivity and heat capacity, were measured. The range of temperature rising in the vicinity of the focal point due to the focused ultrasound was observed using a thermochromic film that changes color at 30 degree or more, and the discolored area was obtained by image processing of the recorded image. As the concentration of PVA increases in the given range of 2 wt% ~ 16 wt%, the area that rises above 30 degree inside the gel increases linearly. It is confirmed that the discolored area increases as the power applied to the focused ultrasonic transducer increases. These results showed good agreement with the simulation results using the finite element method.

Design of Signal Processing Circuit for Semi-implantable Middle Ear Hearing Device with Bellows Transducer (벨로즈형 진동체를 갖는 반이식형 인공중이용 신호처리회로 설계)

  • Kim, Jong Hoon;Shin, Dong Ho;Seong, Ki Woong;Cho, Jin-Ho
    • Journal of rehabilitation welfare engineering & assistive technology
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    • v.11 no.1
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    • pp.63-71
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    • 2017
  • In this paper, a signal processing circuit for semi-implantable middle ear hearing device is designed using the TCBT which is recently proposed for a new middle ear transducer that can be implanted at round window of cochlea. The designed semi-implantable hearing device transmits digital sound signal from external device located at behind the ear to the internal device implanted under the skin using inductive coupling link methods with high efficiency. The coils and signal processing circuits are designed and implemented considering the total transmission and reception distance including skin thickness of temporal bone for the semi-implantable hearing device. And also, to improve the data transmission efficiency, the output circuits which can supply sufficient signal power is designed. In order to confirm operation of semi-implantable hearing device using inductive coupling link, the circuit analysis was performed using PSpice, and the performance was verified by implementing a signal processing board of an available size.

Intelligibility Enhancement of Multimedia Contents Using Spectral Shaping (스펙트럼 성형기법을 이용한 멀티미디어 콘텐츠의 명료도 향상)

  • Ji, Youna;Park, Young-cheol;Hwang, Young-su
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.11
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    • pp.82-88
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    • 2016
  • In this paper, we propose an intelligibility enhancement algorithm for multimedia contents using spectral shaping. The dialogue signals is essential to understand the plot of audio-visual media contents such as movie and TV. However, the non-dialogue components as like sound effects and background music often degrade the dialogue clarity. To overcome this problem, this paper tries to improves the dialogue clarity of audio soundtracks which contain important cues for the visual scenes. In the proposed method, the dialogue components are first detected by soft masker based on speech presence probability (SPP) which is widely used in speech enhancement field. Then, extracted dialogue signals are applied to the spectral shaping method. It reallocate the spectral-temporal energy of speech to enhanced the intelligibility. The total energy is maintained as unchanged via a loudness normalization process to prevent saturation. The algorithm was evaluated using the modeled and real movie soundtracks and it was shown that the proposed algorithm enhances the dialogue clarity while preserving the total audio power.

Genetically Optimized Self-Organizing Polynomial Neural Networks (진화론적 최적 자기구성 다항식 뉴럴 네트워크)

  • 박호성;박병준;장성환;오성권
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.53 no.1
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    • pp.40-49
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    • 2004
  • In this paper, we propose a new architecture of Genetic Algorithms(GAs)-based Self-Organizing Polynomial Neural Networks(SOPNN), discuss a comprehensive design methodology and carry out a series of numeric experiments. The conventional SOPNN is based on the extended Group Method of Data Handling(GMDH) method and utilized the polynomial order (viz. linear, quadratic, and modified quadratic) as well as the number of node inputs fixed (selected in advance by designer) at Polynomial Neurons (or nodes) located in each layer through a growth process of the network. Moreover it does not guarantee that the SOPNN generated through learning has the optimal network architecture. But the proposed GA-based SOPNN enable the architecture to be a structurally more optimized network, and to be much more flexible and preferable neural network than the conventional SOPNN. In order to generate the structurally optimized SOPNN, GA-based design procedure at each stage (layer) of SOPNN leads to the selection of preferred nodes (or PNs) with optimal parameters- such as the number of input variables, input variables, and the order of the polynomial-available within SOPNN. An aggregate performance index with a weighting factor is proposed in order to achieve a sound balance between approximation and generalization (predictive) abilities of the model. A detailed design procedure is discussed in detail. To evaluate the performance of the GA-based SOPNN, the model is experimented with using two time series data (gas furnace and NOx emission process data of gas turbine power plant). A comparative analysis shows that the proposed GA-based SOPNN is model with higher accuracy as well as more superb predictive capability than other intelligent models presented previously.

A STUDY OF ANALGESIC EFFECT ON PULP INDUCED BY PULSED Nd : YAG LASER (Pulsed Nd ; YGA 레이저의 치수마취효과에 관한 연구)

  • Kim, Do-Hyeong;Lee, Chang-Seop;Lee, Sang-Ho
    • Journal of the korean academy of Pediatric Dentistry
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    • v.24 no.1
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    • pp.301-312
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    • 1997
  • The purpose of this study was to evaluate the analgesic effect on pulp induced by pulsed Nd : YAG laser according to the power density, irradiated time and the method of application (Non-contact vs contact) in vivo. Experiments were carried out on 90 volunteers who have sound 4 canines. Each canine was grouped by the intensity and the time of irradiation of pulsed Nd : YAG laser was measured. Mean EPT response(units) was measured at 5 min, 30 min, and 60 min after irradiation with various intensity(1.5-3W, 15-30Hz), irradiated time (1.5min, 3min), and application method (Non-contact and contact). The results were as follows: 1. 5 minutes after irradiation, the mean EPT response(units) was increased by 32 % in the non-contact method and by 35% in the contact method of application. Which showed significant difference in mean EPT response(units) compared to not-lased canine in each groups(P<0.05). 2. The mean EPT response(units) with irradiating condition according to the various laser intensity, and the irradiation time stastically did not show significant difference in each groups as time elapsed. 3. There was no significant difference between the non-contact and contact method in the mean EPT response(units). 4. The mean EPT response(units) returned to the baseline value within 30 miuntes. In regard to the above results, the analgesic effect on pulp induced by pulsed Nd : YAG laser resulted a slight increase of pulpal pain threshold, but it was not as high as to replace the role of drug analgesia as whole. This technique can be used for inducing pulpal analgesia as adjunct to other pain control methods and is needed to develop better analgesic effects.

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