• The Journal of the Acoustical Society of Korea
• /
• v.34 no.2
• /
• pp.146-156
• /
• 2015

This study investigated how the location of sound absorptive materials and sound diffusers affects the acoustic performance of small auditoriums. It was conducted for a standard model established with the averaged dimension of 36 auditoriums which had opened since 2000 in Daehak-ro, Seoul. In this study, the installation area of finishing materials was calculated upon a back wall which had the smallest installation effective area of finishing materials. To analyze the changes of acoustic performance according to installation location of finishing materials, experiments were carried out using the 1/10 down scale models for 8 cases which were made by classifying the installation location of ceiling and side wall into the front, middle and rear part.The used acoustic parameters were reverberation time (RT), early decay time (EDT), clarity (C80), definition (D50) and speech transmission index (STI). In result, the index related to the amount of reverberant sound (RT, EDT) showed the great changes when evaluating it through just noticeable difference (JND), but the one related to clarity (C80, D50, STI) hardly indicated the changes. In case to obtain short reverberation time, it was most effective to control reverberation time through the side walls when installing sound absorptive and diffusive materials, and side wall front was the location which could get the shortest reverberation time.

• International Journal of Automotive Technology
• /
• v.7 no.3
• /
• pp.289-294
• /
• 2006

Better fundamental understanding of the interactions between the in-cylinder flows and combustion process is an important requirement for further improvement in the fuel economy and emissions of internal combustion(IC) engines. Flow near a spark plug at the time of ignition plays an important role for early flame kernel development(EFKD). Velocity data measurements in this study were made with a two-component laser Doppler velocimetry(LDV) near a spark plug in a single cylinder optical spark ignition(SI) engine with a heart-shaped combustion chamber. LDV velocity data were collected on an individual cycle basis under wide-open motored conditions with an engine speed of 1,000rpm. This study examines and compares the flow fields as interpreted through ensemble, cyclic and discrete wavelet transformation(DWT) analysis. The energy distributions in the non-stationary engine flows are also investigated over crank angle phase and frequency through continuous wavelet transformation(CWT) for a position near a spark plug. Wavelet analysis is appropriate for analyzing the flow fields in engines because it gives information about the transient events in a time and frequency plane. The results of CWT analysis are provided and compared with the mean flows of DWT first decomposition level for all cycles at a position. Low frequency high energy found with CWT corresponds well with the peak locations of the mean velocity. The high frequency flows caused by the intake jet gradually decay as the piston approaches the bottom dead center(BDC).

• Phonetics and Speech Sciences
• /
• v.1 no.4
• /
• pp.105-109
• /
• 2009

This thesis describes the method for well voice announcement using the TTS(Text-To-Speech) technology in the shop music broadcasting service. Offering a high quality TTS sound service for each shop requires a great expense. According to a report on the architectural acoustics the room acoustic indexes such as reverberation time and early decay time are closely connected with a subjective awareness about acoustics. By using the result the customers will be able to recognize better the voice announcement by applying sound effect to speech files made by TTS. The result of an aural comprehension examination has shown better about almost all of the parameters by applying reverb effect to TTS sound.

• The Journal of the Acoustical Society of Korea
• /
• v.37 no.5
• /
• pp.349-355
• /
• 2018

A large number of parameters have been defined in order to describe and to evaluate the acoustical propeTies in rooms. Reverberation time is an impoTant characteristic of conceT halls, theaters and studios, etc. Over the years, a number of different methods for measuring the reverberation time have been developed, the most common being: the interrupted noise method, the integrated impulse response method, and the method of recording the room response to an impulsive source. However, the reverberation time can be changed by the measurement method, sound source and microphone. Therefore, it is difficult to accurately measure the reverberation time in a room. In this paper, it will be analyzed the interpretation method of the reverberation time and discussed the limitations.

• Research in Plant Disease
• /
• v.6 no.1
• /
• pp.23-26
• /
• 2000

Effects of infection time of the clubroot pathogen, Plasmodiophora brassicae, on yield loss of Spring-sown Chinese cabbage plants were examined in field experiments. Yield loss of Chinese cabbage plants increased as the infection time becomes early. Plants infected at 20 days after transplanting or earlier were completely killed before harvest, and those infected at 30 days after transplanting were healthy in appearance but their head weights were reduced to 59% with poor commodity value. The plants infected 40 days after transplanting were not affected in yield. Development of root hairs in diseased plants was greatly reduced as the infection progressed, and root length was reduced to 1/2 to 1/3 of that of healthy plants. root galls were first developed 20 days after inoculation and rapidly enlarged to reach the peak in size 20 days from initial development, and decayed thereafter. Development and decay of root galls tended to be faster at later season as air temperature became high, regardless of the infection time. Diseased plants started to wilt approximately 10 days after root gall development. Root galls began to decay 10 days after initial plant wilting, and then were completely rotten within following 10 days. Based on the results, root gall development stages on spring-sown Chinese cabbage plants could be grouped into 20 days of root gall enlargement period, and 10 days of root gall decay period, followed by survival period in soil.

• Journal of Korean Society of Forest Science
• /
• v.40 no.1
• /
• pp.57-62
• /
• 1978

This study was carried out to determine the proper transplanting time of Platanus occidentalis L. (plane tree, sycamore) with 5 to 6 cm and 25 to 30 cm in diameter of breast height at the forest nursery of Chonnam National University in 1977. For that purpose, the experiment of the time of transplantation, and the moisture content and soluble sugar were analysed. The results are as follows: 1. Both its rooting and growth were slightly different in the period of January to early April (before bud-break), but remarkably declined after its bud-break (mid-April to May). 2. And also, its moisture content and soluble sugar were slightly different (January to early April), but, on the other hand, considerably increased in the content of moisture and sharply decreased in soluble sugar after bud-break (mid-April to May). 3. In comparision with healthy trees, rooting and growth of trees infected with Cankers were unusually retarded and its moisture content and soluble sugar were much less. 4. The proper time to plant sycamore was recognized to be the period of November to March, since the higher amounts of soluble sugar and the lesser amounts of moisture in that period. 5. The sudden exposure to the sun of the boles of diseased and wounded trees could be in death in case of sun-scald on the side of south-west. 6. Pruning wounds should be treated with an antiseptic, as soon as they are made, to prevent entrance of decay or disease while the wound is healing. 7. The wound and sun-scald can be presented by covering the trunk with straw ropes before transplantations.

• Proceedings of the IEEK Conference
• /
• 2005.11a
• /
• pp.447-450
• /
• 2005

Multi-channel artificial reverberation algorithm to control perceived direction and distance is described in this paper. In conventional algorithms using IIR filters, reverberation time is the only parameter to be controlled. Moreover, since the convolution-based conventional algorithms apply only same impulse responses, but not considering sound localization, it was not realistic enough. The new algorithm proposed in this paper utilizes early reflections segmented according to the azimuth from which direct sound comes and controls perceived direction by panning the direct sound, and controls perceived distance by adjusting Energy Decay Curve (EDC) of reverberation and gain of the direct sound. In addition, the algorithm enhances Listener Envelopment(LEV) to make late reverberation incoherent among channels.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.40 no.1
• /
• pp.44-51
• /
• 1995

This investigation was conducted to determine the effect of the optimum planting date and place for good seed production on growth variation, grain yields, different of variety, infection of seed by fungi, and seed germination and vigor after room storage. Early maturity Korean soybean variety, Keunolkong, and introduced vegetable soybean variety, Fukura-edamame, were planted at field of YAES. and high cool land of Sajapyong in Milyang（altitude, 850m） on May 15 （early）, June 15 （mid.）, and July 15 （late） in 1991. The emergence and vegetative period gradually increased in the early planting date. The grain yield, seed weight, pod number, healthy grain yield also increased when Keunolkong was planted on early date. The healthy seed rate, Keunolkong increased in the early planting date, whereas that of Fukura also increased in the late planting date. Infection ratio of grain to phomopsis seed decay （Phomopsis spp. ' Diaporthe phaseolorum） in Fukura steadily increased in the early planting date. Infection ratio of grain to purple seed stain （Cercospora kikuchii） generally increased in the mid and late planting date. The seed germination and seedling vigor after room storage from five to six months gradually increased in the late planting date. And seed germination of Fukura rapidly decreased in the early planting date. Therefore, the optimum planting date for good seed production in early maturity vegetable soybean was June 15 in terms of harvesting time avoid a high temprature and humidity.

• Journal of Bio-Environment Control
• /
• v.17 no.2
• /
• pp.143-149
• /
• 2008

The effects of fruit bagging time, bag kinds, and plant oil treatment on fruit cracking, pathogenic decay, and quality in grapevines were studied. The occurrence of cracking fruit was not affect by bag kinds in 'Campbell Early'. But, bitter rot occurrence in 'Campbell Early' and occurrence of cracking fruit and bitter rot in 'Wase Campbell Early' decreased effectively compared the ones of conventional bag, window bag, calcium coated bag to non-bagging. The cracking fruit occurrence of and 'Kyoho' decreased significantly by bagging to each before July 5 of 'Campbell Early' and before June 29 and July 5 of 'Kyoho' grapevines. The cracking fruit and bitter rot occurrence by plant oil treatment decreased significantly in 'Wase Campbell Early', and increased calcium of fruit skin in 'Campbell Early'. The soluble solids in fruits were much reduced by window bag and the Hunter b value in fruit skin was reduced by calcium coated bag. Accordingly, treatment of Ca-coated bag and plant oil was become judgment to reduction effect of cracking fruit.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.5
• /
• pp.429-436
• /
• 2012

In concert halls and auditoriums, acoustic reflector and stage enclosure is one of the main factors on the room and stage acoustic characteristics. As a stage enclosure and acoustic reflector honey comb based light-weight reflector is widely used, because it is easy to install. However, there was not enough research on the surface density effect on room and stage acoustics. In this study, sound absorption coefficient tests on three kinds of wooden acoustic reflectors with different surface density were conducted. Surface density of acoustic reflector was changed from 11 kg/$m^2$ to 41 kg/$m^2$. For the low frequency excitation, sub-woofer was used with omnidirectional loud-speaker simultaneously. From the experiments, it was found that sound absorption coefficient below 250 Hz band was decrease by the increment of surface density. In order to check the influence of the surface density on room and stage acoustic parameters, room acoustic simulation was conducted with sound absorption coefficients, which were tested in reverberation chamber. By the increment of surface density of acoustic reflector, RT(reverberation time) and EDT(early decay time) were increased. Also, ST(stage support) was improved in low frequency bands.