• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.4
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• pp.423-430
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• 2011

The most satisfactory split-beam transducer for fish sizing maintains a wide bearing angle region for correct fish tracking without interference from side lobes and lower sensitivity to fish echoes outside of the main lobe region to correctly measure the angular location of free-swimming fishes in the sound beam. To evaluate the performance of an experimentally developed 50 kHz split-beam transducer, the angular location of a target was derived from the electrical phase difference between the resultant signals for the pair of transducer quadrants in the horizontal and vertical planes consisting of 32 transducer elements. The electrical phase difference was calculated by cross-spectral density analysis for the signals from the pair of receiving transducer quadrants, and the directivity correction factor for a developed split-beam transducer was estimated as the fourth-order polynomial of the off-axis beam angle for the angular location of the target. The experimental results demonstrate that the distance between the acoustic centers for the pair of receiving transducer quadrants can be controlled to less than one wavelength by optimization with amplitude-weighting transformers, and a smaller center spacing provides a range of greater angular location for tracking of a fish target. In particular, a side lobe level of -25.2 dB and an intercenter spacing of $0.96\lambda$($\lambda$= wavelength) obtained in this study suggest that the angular location of fish targets distributing within a range of approximately ${\pm}28^{\circ}$ without interference from side lobes can be measured.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.183-186
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• 2001

• Journal of Korean Society of Steel Construction
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• v.28 no.1
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• pp.53-64
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• 2016

The double split tee connection, a type of beam-to-column moment connection, exhibits different behavioral characteristics according to changes in the thickness of the T-stub flange, the gauge distance of the high-strength bolt, and the number and diameter of high-strength bolts. In general, the double split tee connection is idealized and designed so that a T-stub fastened to the top and bottom supports a flexural moment, and a shear tab supports a shear force. However, if the double split tee connection is applied to low-and medium-rise steel structures, the size of the beam member becomes small, and thus the shear tab cannot be bolted to the web of a beam. In this regard, this study was conducted to propose connection details to ensure that the double split tee connection with a geometric shape can display sufficient shear resisting capacity. To this end, experiments were conducted using full-scale specimens for the double split tee connection.

• Steel and Composite Structures
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• v.15 no.3
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• pp.247-266
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• 2013

This paper presents a comparison of results obtained by a newly developed numerical model for predicting the behaviour of structures under fire with experimental study carried out on heated and simply supported steel beam elements. A newly developed numerical model consists of three submodels: 3D beam model designed for calculating the inner forces in the structure, 2D model designed for calculation of stress and strain distribution over the cross section, including the section stiffness, and 3D transient nonlinear heat transfer model that is capable of calculating the temperature distribution along the structure, and the distribution over the cross section as well. Predictions of the calculated temperatures and vertical deflections obtained by the numerical model are compared with the results of the inhouse experiment in which steel beam element under load was heated for 90 minutes.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.40 no.1
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• pp.11-16
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• 2014

Objectives: The aim of this study was to evaluate the pattern of lingual split line when performing a bilateral sagittal split osteotomy (BSSO) for asymmetric prognathism. This was accomplished with the use of cone-beam computed tomography (CBCT) and three-dimensional (3D) software program. Materials and Methods: The study group was comprised of 40 patients (20 males and 20 females) with asymmetric prognathism, who underwent BSSO (80 splits; n=80) from January 2012 through June 2013. We observed the pattern of lingual split line using CBCT data and image analysis program. The deviated side was compared to the contralateral side in each patient. To analyze the contributing factors to the split pattern, we observed the position of the lateral cortical bone cut end and measured the thickness of the ramus that surrounds the mandibular lingula. Results: The lingual split patterns were classified into five types. The true "Hunsuck" line was 60.00% (n=48), and the bad split was 7.50% (n=6). Ramal thickness surrounding the lingual was $5.55{\pm}1.07$ mm (deviated) and $5.66{\pm}1.34$ mm (contralateral) (P =0.409). The position of the lateral cortical bone cut end was classified into three types: A, lingual; B, inferior; C, buccal. Type A comprised 66.25% (n=53), Type B comprised 22.50% (n=18), and Type C comprised 11.25% (n=9). Conclusion: In asymmetric prognathism patients, there were no differences in the ramal thickness between the deviated side and the contralateral side. Furthermore, no differences were found in the lingual split pattern. The lingual split pattern correlated with the position of the lateral cortical bone cut end. In addition, the 3D-CT reformation was a useful tool for evaluating the surgical results of BSSO of the mandible.

• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.5
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• pp.554-559
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• 2003

A newly developed contact angle measurement instrument by laser beam projection allows for rapid and direct determination of contact angles. The instrument may have a possibility to characterize newly developed nano-fibers. When the laser beam impinges on an edge of an interface of liquid and solid, projected beam were split across and made two straight lines on a tangent screen. From the result, it could measure the contact angle directly by reading the angle between two split beams. The purpose of this study was to prove reliability and reproducibility of the contact angle measurement instrument by laser beam projection compare to the conventional one by microscope through the comparative experiment and questionnaire. Test samples were selected by consideration of hydrophilic and hydrophobic, such as nylon 6 and polypropylene, respectively. The laser contact angle measurement has accurate, fast and convenient method to measure contact angle, and it can be a unique method to characterize nano-fibers.

• Journal of Korean Dental Science
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• v.14 no.2
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• pp.110-117
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• 2021

Purpose: The purpose of this article is to study the relationship of unintentionally extended split in the distal segment during the bilateral sagittal split ramus osteotomy (BSSRO) and skeletal relapse. Materials and Methods: Twenty patients with mandibular prognathism were divided into two groups according to whether or not unintentionally extended split had occurred. Cone-beam computed tomography images were taken before surgery (T0), immediately after surgery (T1), and postoperatively at 6 months (T2). The stability was evaluated by measuring the change of Nasion perpendicular-Pogonion (N-Pog) distance. Result: Both groups showed mild advancement of Pog during follow-up. In both groups, the condyle head rotated inward and moved posterioinferiorly after surgery, but tended to return to their original position during follow-up. Conclusion: There was no statistically significant difference between the two groups in mandible position. Moreover, the condylar position was stable. If it is difficult to proceed reduction of the unintentionally extended split, careful inspection should be performed to prevent subsequent complications during follow-up.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.4
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• pp.318-324
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• 2016

Commercial split beam echosounder (ES70) installed on a krill fishing vessel was calibrated in order to utilize it in estimating biomass of Antarctic krill (Euphausia superba). The method of calibration was to analyze the difference between the bottom backscattering strength of the commercial split beam echosounder (i.e. ES70) and the scientific echosounder (i.e. EK60) at one of transects near South Shetland Islands designated by CCAMLR. 38 kHz and 120 kHz were used for the calibration, and krill swarm signal levels obtained from multi frequencies, was examined to verify the calibration result. The analysis result indicated possibility of calibration by bottom backscattering strength, since the proportion of krill swarm signals within 2 dB < $S_{V\;120\;kHz-38\;kHz}$ < 12 dB (i.e. a common $S_{V\;120\;kHz-38\;kHz}$ range of 38 kHz and 120 kHz to be an indicator of Antarctic krill) over the total acoustic signals were 26.95% and 92.04%, respectively before and after the calibration.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.2
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• pp.173-183
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• 2010

In a split beam echo sounder, the transducer design needs to have minimal side lobes because the angular position and level of the side lobes establishes the usable signal level and phase angle limits for determining target strength. In order to suppress effectively the generation of unwanted side lobes in the directivity pattern of split beam transducer, the spacing and size of the transducer elements need to be controlled less than half of a wavelength. With this purpose, a 50 kHz tonpilz type transducer with a half-wavelength diameter in relation to the development of a split beam transducer was designed using the equivalent circuit model, and the underwater performance characteristics were measured and analyzed. From the in-air and in-water impedance responses, the measured value of the electro-acoustic conversion efficiency for the designed transducer was 51.6%. A maximum transmitting voltage response (TVR) value of 172.25dB re $1{\mu}Pa/V$ at 1m was achieved at 52.92kHz with a specially designed matching network and the quality factor was 10.3 with the transmitting bandwidth of 5.14kHz. A maximum receiving sensitivity (SRT) of -183.57dB re $1V/{\mu}Pa$ was measured at 51.45kHz and the receiving bandwidth at -3dB was 1.71kHz. These results suggest that the designed tonpilz type transducer can be effectively used in the development of a split beam transducer for a 50kHz fish sizing echo sounder.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.1-7
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• 2021

A computer simulation was performed to study the effectiveness of temperature on the type of laser heat source in the context of the heterogeneous welding of aluminum and copper materials. Three different types of heat sources were used in the computer simulation: 1) Single Beam Straight Scan, 2) Single Beam Wobble Scan, and 3) Dual Beam Straight Scan. Among these sources, dual beam straight scan was found to be the most effective from the viewpoint of heat source control. Because the difference between the melting temperatures of copper and aluminum is approximately 400℃, a clear separation of heating temperature was required, and the dual beam straight scan provided superior controllability in this regard. When using the dual beam, the temperature of the 90:10 split was considerably easier to control than that of the 50:50 split. The optimal offset was calculated to be 4 mm off to the copper side, where the melting temperature and thermal conductivity were higher. In this manner, computer simulation was effectively used for determining the optimal laser beam hear source control without performing an actual laser welding experiment.