• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.35-45
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• 2005

TR-E2 configuration designed by Bell Textron was tested in KARI 1-m wind tunnel. To explore aerodynamic characteristics for the given configuration, a $12\%$ scaled model was fabricated and tested. Wind tunnel test for TR-E2 had been performed by changing the incidence angles of wing and deflection angles of control surfaces. Test result showed that the lower wing incidence angle has more favorable lift to drag ratio compared with original design. Longitudinal and directional characteristics of TR-E2 were found to be stable for the pitch and yaw motions. However, the lateral stability of TR-E2 is not stable for certain control surface deflection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7C
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• pp.554-561
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• 2008

For the tone reservation (TR) scheme in orthogonal frequency division multiplexing (OFDM), there exists a trade-off between peak to average power ration (PAPR) reduction performance and data transmission rate. While PRT set is fixed in the conventional TR scheme, the proposed scheme adaptively select the PRT set according to the PAPR of the input OFDM symbol. It is shown that the PAPR reduction performance of the proposed scheme is better than that of the conventional scheme when the data transmission rate is the same.

• ETRI Journal
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• v.38 no.6
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• pp.1124-1134
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• 2016

The tone reservation method is one of the most effective pre-distortion methods for peak-to-average power ratio reduction in orthogonal frequency division multiplexing (OFDM) systems. Its direct application to OFDM systems with offset quadrature amplitude modulation (OQAM) is, however, not effective. In this paper, two novel TR-based methods are proposed, specifically designed for OFDM/OQAM systems by taking into consideration the overlapping nature of OQAM signals. These two methods have different approaches to the generation of the peak-cancelling signal. The first one (overlapped scaling tone reservation) generates the peak-cancelling signal using a least squares approximation algorithm with possible adjacent symbol overlap; the second one (multi-kernel tone reservation) generates the peak-cancelling signal by using multiple impulse-like time domain kernels. It is shown by simulation that, when used in OFDM/OQAM systems, the proposed methods can provide better performance than the direct application of the existing controlled clipping tone reservation method, and even outperform the multi-block tone reservation method.

• PNF and Movement
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• v.19 no.2
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• pp.215-223
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• 2021

Purpose: This study aimed to compare the contraction ratios of the abdominal muscles and the preferential activation ratios of the transversus abdominis muscle (TrA) during the abdominal drawing-in maneuver (ADIM) in the hook-lying, sitting, and standing positions. Methods: This study included 30 healthy participants. The thicknesses of the TrA, internal oblique muscle (IO), and external oblique muscle (EO) were measured at rest and during the ADIM in the hook-lying, sitting, and standing positions using B-mode ultrasound imaging. The contraction ratios of these muscles and the preferential activation ratios of the TrA were calculated for each position. Results: The contraction ratio of the TrA and preferential activation ratio of the TrA during the ADIM in the hook-lying position were significantly higher than those in the sitting and standing positions (p < 0.05). The contraction ratio of the TrA during the ADIM in the sitting position was significantly higher than that in the standing position (p < 0.05). Conclusion: The hook-lying position tended to facilitate TrA activity better than the sitting position. Furthermore, the sitting position tended to facilitate TrA activity better than the standing position. These findings suggest that the ADIM in the hook-lying position should be implemented before that in the sitting position and that the ADIM in the sitting position should be implemented before that in the standing position.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.295-305
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• 2005

To improve the aerodynamic effciency of TR-E2, a new configuration so called TR-E2Sl was introduced. TR-2251 is composed of different wing airfoil section and T-tail shape compared with TR-E2. Wind tunnel test for TR-EBS1 had been performed by changing the incidence angles of wing and deflection angles of control surfaces such as elevator and rudder. Also the on/off effect of ventral fin attached underneath of AFT fuselage was tested. Test result showed that variations of wing incidence angle did not cause any severe differences in aerodynamic characteristics. Longitudinal and directional characteristics of TR-E2S1 show stable for the pitch and yaw motions. However, the lateral stability of TR-E2S1 is not stable for a certain control surface deflection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5C
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• pp.540-547
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• 2009

In this paper, we propose a transceiver structure that can effectively improve BER(Bit Error Rate) performance for TR-UWB (Transmitted Reference Ultra Wide Band) systems based on impulse radio. Unlike coherent UWB systems that are too complex for practical implementation while having good BER performances, the complexity of the TR-UWB systems is quite low since they transmit data with the corresponding reference signals and demodulate the data through correlation using these received signals. However, the BER performance in the conventional TR-UWB systems is affected by SNR (Signal-to-Noise Ratio) of the reference templates used in the correlator. To this end, we propose a receiver structure that can effectively improve the BER performance by increasing the SNR of reference templates. Simulation results reveal that the proposed scheme achieves significant BER improvement as compared to the conventional TR-UWB systems.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.95-104
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• 2016

Flexural strength of concrete ground slab reinforced with steel fiber is evaluated using the equivalent flexural strength ratio of steel fiber reinforced concrete based on the yield line theory. Recently, the European standard specifies that the tensile performance of the steel fiber reinforced concrete be evaluated directly from the residual flexural strength after the cracking of concrete. Thus, in the study, an experiment was carried out to evaluate the conventional equivalent flexural strength ratio and the residual flexural strength of the steel fiber reinforced concrete. Then the design flexural strength was investigated according to the location of a point load, based on the ratio of the radius of contact area of the load to the radius of relative stiffness. Design flexural capacity obtained from ACI 360R-10 was smaller than that from TR 34 (2003 & 2013). In addition, TR 34 (2013), which evaluates the design flexural capacity based on the residual flexural strength, showed slightly smaller value than TR 34 (2003).

• PNF and Movement
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• v.13 no.1
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• pp.25-30
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• 2015

Purpose: The aim of this study was to examine the effects of abdominal muscle contraction thickness using real-time ultrasound imaging while applying an abdominal draw-in maneuver (ADIM) and pelvic floor muscle contraction (PFC) to low back pain patients and healthy subjects. Methods: The subjects were 21 young adults; a group of 10 low back pain patients and a control group of 11 healthy subjects. Measurements were made with the subjects on a pillow in a supine position, with the knee joints flexed at 60 degrees. While the two groups conducted ADIM and PFC, their transverse abdominal muscle (TrA), internal abdominal oblique muscle (IO), and external abdominal oblique muscle (EO) thicknesses were measured using an ultrasound imaging system. Result: The TrA muscle contraction thickness ratio during PFC and ADIM was significantly lower in the low back pain group than in the healthy group (p<0.05). The EO muscle contraction thickness ratio during ADIM was also significantly lower in the low back pain group than in the healthy group. The healthy group's muscle contraction thickness ratio was significantly lower during PFC than during ADIM in the TrA, IO, and EO (p<0.05). The low back pain group's muscle contraction thickness ratio was lower during PFC than during ADIM in the TrA, IO, and EO, but the difference was not statistically significant. Conclusion: The results of this study indicate that oral direction during ADIM induced an appropriate contraction of the TrA. Therefore, the procedure reported here may be applied during rehabilitation for appropriate contraction of the TrA.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.817-824
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• 2019

We propose an ATR (Adaptive Tone Reservation) scheme based on clipping noise for PAPR (Peak-to-Average Power Ratio) reduction of OFDM (Orthogonal Frequency Division Multiplexing) signals. The proposed scheme is composed of three steps: clipping, tone selection, and TR procedures. In the first step, the peak samples in the IFFT (Inverse Fast Fourier Transform) outputs are scaled down by clipping. In the second step, the sub-carrier position where the power of the clipping noise is the maximum, is selected. Finally, the generic TR procedure is performed. Simulation results show that the proposed scheme does not require all the possible combinations for the original TR procedures, while maintaining the PAPR reduction performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.81-89
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• 2009

We propose a D-ATR UWB (Differential-Average Transmitted Reference Ultra Wide Band) system based on impulse radio. The TR-UWB systems including traditional TR (Transmitted Reference) and ATR (Average TR), exhibit a problem of reduced data rate, since reference signals are additionally transmitted. To tackle this issue, the transmitter of the proposed D-ATR system employs a differential coding like the conventional D-TR system. In addition, the receiver of the proposed system has the structure that can improve signal-to-noise ratio of the reference template used in the correlation process, by recursively averaging the received reference signals like the conventional ATR system. The simulation results in the IEEE 802.15.4a UWB multipath channel models reveal that the proposed D-ATR system achieves much better bit error rate performance as compared to the conventional D- TR system.