• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.3
• /
• pp.340-349
• /
• 2016

A coupled room system consists of adjacent rooms and apertures where the sound energy is exchanged between the two rooms. Acoustically, a coupled room system shows a non-exponential decay profile. Most of the related researches have been to analyze the acoustic properties of two-room coupled system so far whereas three-room coupled system were seldom studied. In this regard, this paper aims to analyse the distribution of sound pressure level, sound decay curve of three-room coupled system and sound energy flow between them by using the acoustic diffusion model and to further verify them through experiments. Firstly, the sound pressure level distribution and mean sound pressure level in the steady-state condition are analyzed at various frequencies and source locations. Good agreements are observed in both experiments and analysis results. Secondly, two double slope effect quantifiers of sound attenuation, LDT/EDT and LDT/T10 are compared at various frequencies and for different source locations. The result indicates that LDT/T10, less affected by the early reflection patterns than LDT/EDT, is more suitable to the analysis and experiments of a multi-slope sound decay curve. Lastly, the sound energy flow in each room is analyzed based on the acoustic diffusion model. After the early decay stage, the sound energy is observed to flow from the room with a long reverberation time to the room with a short one.

• Journal of the Korean Wood Science and Technology
• /
• v.29 no.3
• /
• pp.1-13
• /
• 2001

Compression, lateral, and opposite woods in the stem and branch of rimu (Dacrydium cupressinum Lamb.), a softwood species indigenous to New Zealand, were described and compared in the anatomical aspects. Qualitatively, growth rings were wide in the compression wood, intermediate in the lateral wood, and narrow in the opposite wood. Tracheid transition from early wood to late wood was very gradual in the compression wood but was more abrupt in both the lateral and opposite woods. When viewed transversely, compression wood tracheids showed a roundish outline except at the growth ring boundary but lateral and opposite wood tracheids were angular to rectangular in outline. Intercellular spaces were occasionally detected in the compression wood except in the late wood at the growth ring boundary but were absent from both the lateral and opposite woods. Slit-like extensions of the bordered pit openings caused by the location of pit apertures within short and narrow helical grooves were observed in the compression wood tracheids but not in the opposite or lateral wood tracheids. In the compression wood tracheids, fine striations in the form of fine checks or grooves were observed on the lumen surfaces and the innermost $S_3$ layer of secondary wall was absent. In the tracheids of lateral and opposite woods, the $S_3$ layer was sometimes absent but occasionally highly developed. Cross-field pits in the compression wood appeared to be piceoid due to slit-like pit apertures but those in the lateral and opposite wood tracheids showed cupressoid to taxodioid. Quantitatively, compression wood tracheids were somewhat shorter than those of opposite or lateral wood in stem but not different from the opposite or lateral wood tracheids in branch. The walls were thicker in the compression wood than in the lateral or opposite wood. Uniseriate rays in the compression wood were fewer than in the lateral or opposite wood.

• Korean Journal of Optics and Photonics
• /
• v.15 no.5
• /
• pp.443-448
• /
• 2004

We realized the national standard of the candela, one of the SI units, by using two photometers with the spectral responsivity measured in reference to the absolute cryogenic radiometer. The external apertures of the photometers were fabricated using a diamond turning machine, and measured in terms of area with uncertainty of 0.05 %(k = 1). The candela is realized using a 1 kW FEL lamp and the characterized photometers on an optical bench. The uncertainty is budgeted to be 0.25 %(k = 1) considering the uncertainty of the spectral responsivity and the response uniformity of the detectors, the area of the external apertures, the color temperature of the lamp, and the positioning reproducibility of the photometers and the lamp. We verified the realized scale by comparing with the scale of National Institute of Standards and Technology, USA. They coincided with each other within 0.1%.

• Korean Journal of Plant Taxonomy
• /
• v.41 no.2
• /
• pp.108-112
• /
• 2011

The pollen of 5 taxa on Korean Oldenlandia L. was investigated by LM and SEM. The pollen grains were monads, $20.7-36.0{\mu}$m in polar length, with an equatorial diameter of $21.0-38.4{\mu}m$. The pollen shapes were oblate-spheroidal or spherical (P/E ratio 0.93-1.00). The apertures numbered 3-7 in number, colporate in shape, with a colpus length of $4.2-20.4{\mu}m$ and a colpus width of $2.6-3.4{\mu}m$. The sexine was $0.9-2.4{\mu}m$ in terms of its thickness, the surface pattern was reticulate, scabrate or neither. Based on these results, the size of the pollen grain, the number of apertures, and the surface pattern of the sexine were all useful for an interspecific classification. The genus Neanotis, established via the pollen characteristics, was thought to be reviewed in its entity regarding the continuous variation of generic characteristics.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.12 no.6
• /
• pp.989-996
• /
• 2017

The proposed directional pencil beam antenna consists of a waveguide feeder with bended elliptical conductor plate feed and a parabolic curved reflector. Two rectangular apertures located at the broad wall near the end of the feed waveguide inserted from behind the reflector are located at the focus of the reflector and emit electromagnetic energy with bended elliptical conductor plate. This plate is designed to reflect electromagnetic energy primarily and to face the main reflector. The two rectangular apertures located at the waveguide end have inwardly protruding tabs for impedance matching of the antenna system, the shape of the tabs is a truncated oval. The proposed parabolic reflector antenna has a diameter of 400 mm and a focal length of 134.23 mm. The antenna gain is 33.68 dBi at the center frequency of 16.5 GHz, the beam width is $3.3^{\circ}$ and the reflection loss is -15 dB. Using the HFSS-IE, simulation results are performed to validate the proposed antennas.

• Geomechanics and Engineering
• /
• v.21 no.4
• /
• pp.357-369
• /
• 2020

Different from the conventional planar fracture and simplified Newton model, for power-law slurries with a lower water-cement ratio commonly used in grouting engineering, flow model in geological rough fractures is built based on ten standard profiles from Barton (1977) in this study. The numerical algorithm is validated by experimental results. The flow mechanism, grout superiority, and water plugging of pseudo plastic slurry are revealed. The representations of hydraulic grouting properties for JRCs are obtained. The results show that effective plugging is based on the mechanical mechanisms of the fluctuant structural surface and higher viscosity at the middle of the fissure. The formulas of grouting parameters are always variable with the roughness and shear movement, which play a key role in grouting. The roughness can only be neglected after reaching a threshold. Grouting pressure increases with increasing roughness and has variable responses for different apertures within standard profiles. The whole process can be divided into three stationary zones and three transition zones, and there is a mutation region (10 < JRCs < 14) in smaller geological fractures. The fitting equations of different JRCs are obtained of power-law models satisfying the condition of -2 < coefficient < 0. The effects of small apertures and moderate to larger roughness (JRCs > 10.8) on the permeability of surfaces cannot be underestimated. The determination of grouting parameters depends on the slurry groutability in terms of its weakest link with discontinuous streamlines. For grouting water plugging, the water-cement ratio, grouting pressure and grouting additives should be determined by combining the flow conditions and the apparent widths of the main fracture and rough surface. This study provides a calculation method of grouting parameters for variable cement-based slurries. And the findings can help for better understanding of fluid flow and diffusion in geological fractures.

• The Korean Journal of Nuclear Medicine
• /
• v.39 no.6
• /
• pp.445-455
• /
• 2005

Purpose: We developed an animal SPECT system using clinical Philips ARGUS scintillation camera and pinhole collimator with specially manufactured small apertures. In this study, we evaluated the physical characteristics of this system and biological feasibility for animal experiments. Materials and Methods: Rotating station for small animals using a step motor and operating software were developed. Pinhole inserts with small apertures (diameter of 0.5, 1.0, and 2.0 mm) were manufactured and physical parameters including planar spatial resolution and sensitivity and reconstructed resolution were measured for some apertures. In order to measure the size of the usable field of view according to the distance from the focal point, manufactured multiple line sources separated with the same distance were scanned and numbers of lines within the field of view were counted. Using a Tc-99m line source with 0.5 mm diameter and 12 mm length placed in the exact center of field of view, planar spatial resolution according to the distance was measured. Calibration factor to obtain FWHM values in 'mm' unit was calculated from the planar image of two separated line sources. Te-99m point source with i mm diameter was used for the measurement of system sensitivity. In addition, SPECT data of micro phantom with cold and hot line inserts and rat brain after intravenous injection of [I-123]FP-CIT were acquired and reconstructed using filtered back protection reconstruction algorithm for pinhole collimator. Results: Size of usable field of view was proportional to the distance from the focal point and their relationship could be fitted into a linear equation (y=1.4x+0.5, x: distance). System sensitivity and planar spatial resolution at 3 cm measured using 1.0 mm aperture was 71 cps/MBq and 1.24 mm, respectively. In the SPECT image of rat brain with [I-123]FP-CIT acquired using 1.0 mm aperture, the distribution of dopamine transporter in the striatum was well identified in each hemisphere. Conclusion: We verified that this new animal SPECT system with the Phlilps ARGUS scanner and small apertures had sufficient performance for small animal imaging.

• Journal of Korean Society of Forest Science
• /
• v.99 no.5
• /
• pp.663-672
• /
• 2010

The pollen morphology of eleven species and three forms of the genus Rhododendron (Ericaceae) in Korea was examined using light, scanning electron and transmission electron microscopy. The pollen grains are grouped in permanent tetrahedral tetrads; viscin threads are present on the tetrads. The hexacolporate tetrads are of tricolporate monads whereby the apertures form in pairs at six points in the tetrad. The exine sculpture pattern is rugulate, scabrate or verrucate on mesocolpium but psilate, rugulate or microscabrate around the aperture on apocolpium. The exine of Korean Rhododendron pollen consists of tectum, columella, foot layer and endexine. The surface of viscin threads is more or less smooth. The threads are sometimes tangled together and occasionally divided into strands. Six types are recognized based on the pollen morphology. The types are: (1) Micranthum-type (rugulate mesocolpium and psilate apcolpium), (2) Tomentosum-type (rugulate mesocolpium and apocolpium), (3) Aureum-type (scabrate mesocolpium and rugulate apocolpium), (4) Brachycarpum-type (scabrate mesocolpium and rod shaped-microscabrate apocolpium), (5) Schlippenbachiitype (scabrate mesocolpium and round-microscabrate apocolpium) and (6) Weyrichii-type (verrucate mesocolpium).

• ETRI Journal
• /
• v.24 no.6
• /
• pp.429-434
• /
• 2002

This paper investigates the effect of a corrugated aperture on a common-mode current traveling along a penetrating wire. Computational results illustrate that the corrugated aperture acts as a filter, significantly reducing the common-mode current on the wire. This effect causes a reduction of radiated emission from cables passing through apertures on shielding enclosures. To predict and analyze the characteristics of the common-mode current on a straight wire passing through a corrugated aperture with cylindrical symmetry, the finite-difference time-domain (FDTD) method is applied.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.2 no.3
• /
• pp.60-66
• /
• 1991

In this paper, circula and rectangular apertures arranged with triangular and rectangular lattices and having a certain thickness are considered for eddective electromagnctic wave shielding when the plane wave is incident normally to the perfectly conductingmaterrial. The shielding effectiveness is represented by the transmitted power which can be obtained by reflection and transmission coefficients using Floquet mode representation.