• Macromolecular Research
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• v.15 no.2
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• pp.109-113
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• 2007

The surface molecular motion of monodisperse polystyrene (PS) films was examined using scanning vis-coelasticity microscopy (SVM) in conjunction with lateral force microscopy (LFM). The dynamic storage modulus, E', and loss tangent, $tan\delta$, at a PS film surface with number-average molecular weights, $M_n$, smaller than 30 k were found to be smaller and larger than those for the bulk sample, even at room temperature, meaning that the PS surface is in a glass-rubber transition or fully rubbery sate at this temperature when the $M_n$ is small. In order to quantitatively elucidate the dynamics of the molecular motion at the PS surface, SVM and LFM measurements were performed at various temperatures. The glass transition temperature, $T_g$, at the surface was found to be markedly lower than the bulk $T_g$, and this discrepancy between the surface and bulk became larger with decreasing $M_n$. Such an intensive activation of the thermal molecular motion at the PS surfaces can be explained in terms of an excess free volume in the vicinity of the film surface induced by the preferential segregation of the chain end groups.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.277-280
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• 2000

수중환경에서 표적의 탐지 성능을 향상시키기 위하여 능동 소나에서는 높은 시간-대역폭곱의 파형들을 사용하며 대표적인 것으로 LFM 펄스를 들 수 있다 LFM 펄스를 사용하여 표적까지의 거리와 표적의 속도를 추정하는 방법으로는 모호함수를 사용하는 방법과 deconvolution 방법 및 FR-기반 기법 등이 있다. 이러한 기법중 모호함수 사용 방법과 deconvolution 방법은 능동 소나의 운용 주파수 대역에서 많은 연산량이 요구되므로 실제 시스템에 적용하기에는 제약을 받는다. 그리고 다른 기법에 비해 적은 연산량을 가지는 FFT-기반 상관관계 기법은 실제 시스템에 적용이 가능하지만 다중경로에 의한 성능 저하를 가지고 있다. 본 논문에서는 적은 연산량을 가지는 FFT-기반 기법을 보완하여 다중경로에 적용 가능한 새로운 탐지기를 제안한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.125-133
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• 2016

As one of solutions to pursue the efficient use of spectrum resource, we proposed the methodology for the co-channel multi-site radar operations with the synchronous GPS clock. The proposed algorithm, based on a quasi orthogonal property, find a candidate set of the time shifted linear frequency modulation(TSLFM) signals with the minimum acceptable level of the correlation among selected TSLFM signals. To check suggested algorithm, numerical analysis for several radars operating in the same channel with a sawtooth waveform has been performed by using range-Doppler processing for the given system parameters, and computational results are presented and examined in terms of range profile and doppler shift for a targets with velocity and distance. Simulated results have a good agreement with assumed target distance and its velocity, within the error of resolution.

• Nutrition Research and Practice
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• v.4 no.3
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• pp.196-202
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• 2010

To investigate the neuroprotective effects of bovine colostrums (BC), we evaluate the ability of consuming BC after focal brain ischemia/reperfusion injury rat model to reduce serum cytokine levels and infarct volume, and improve neurological outcome. Sprague-Dawley rats were randomly divided into 4 groups; one sham operation and three experimental groups. In the experimental groups, MCA occlusion (2 h) and subsequent reperfusion (O/R) were induced with regional cerebral blood flow monitoring. One hour after MCAO/R and once daily during the experiment, the experimental group received BC while the other groups received 0.9% saline or low fat milk (LFM) orally. Seven days later, serum pro-inflammatory cytokine (IL-$1{\beta}$, IL-6, and TNF-${\alpha}$) and anti-inflammatory cytokine (IL-10) levels were assessed. Also, the infarct volume was assessed by using a computerized image analysis system. Behavioral function was also assessed using a modified neurologic severity score and corner turn test during the experiment. Rats receiving BC after focal brain I/R showed a significant reduction (-26%/-22%) in infarct volume compared to LFM/saline rats, respectively (P < 0.05). Serum IL-$1{\beta}$, IL-6, and TNF-${\alpha}$ levels were decreased significantly in rats receiving BC compared to LFM/saline rats (P < 0.05). In behavioral tests, daily BC intake showed consistent and significant improvement of neurological deficits for 7 days after MCAO/R. BC ingestion after focal brain ischemia/reperfusion injury may prevent brain injury by reducing serum pro-inflammatory cytokine levels and brain infarct volume in a rat model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.6
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• pp.661-670
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• 2013

In this paper, we propose the measurement techniques of mixed waveform. Mixed waveform has phase-continuous periodic waveform with fixed frequency signal and Linear Frequency Modulation(LFM) signal. This waveform is generated from a compact radar transmitter with frequency synthesizer and high power amplifier. Frequency synthesizer generates various signal waveform with continuos phase and high power amplifier amplify transmitting signal. First, we describe a compact radar transmitter with the phase-continuos signal and then verify the distortion characteristic of pulse compression by the mismatch of LFM waveform. Second, we describe three kinds of measurement techniques for measuring LFM waveform. These techniques include methods using signal analyzer, signal source analyzer and new methods using RF mixer and phase shifter. Finally, we verify the accuracy of the measurement technique from the pulse compression result of receiving signal.

• The Journal of the Acoustical Society of Korea
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• v.26 no.2
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• pp.87-94
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• 2007

In active sonar system, aspect angle and length of a target can be estimated by calculating the cross-correlation between left and right split-beams of a LFM(Linear Frequency Modulated) signal. However, high-resolution performances in bearing and range are required to estimate the information of a remote target. Because a certain higher sampling frequency than the Nyquist sampling frequency is required in this performance, an over-sampling process through interpolation method should be required. However, real-time implementation of split-beam processing with over-sampled split-beam outputs on a COTS(commercial off-the-shelf) DSP platform limits its performance because of given throughput and memory capacity. This paper proposes a cumulative processing algorithm for split-beam processing to solve the problems. The performance of the proposed method was verified through some simulation tests. Also, the proposed method was implemented as a real-time system using an ADSP-TS101.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.446-460
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• 2022

In this paper, we propose an algorithm to improve target detection rate degradation due to direct blast in a bi-static sonar systems with high duty cycle using an adaptive filters. It is very important to suppress the direct blast in the aforementioned sonar systems because it has a fatal effect on the actual system operation. In this paper, the performance was evaluated by applying the Normalized Least Mean Square (NLMS) and Recursive Least Square (RLS) algorithms to the simulation and sea experimental data. The beam signals of the target and direct blast bearings were used as the input and desired signals, respectively. By optimizing the difference between the two signals, the direct blast is removed and only the target signal is remained. As a result of evaluating the results of the matched filter in the simulation, it was confirmed that the direct blast was removed to the noise level in both Linear Frequency Modultated (LFM) and Generalized Sinusoidal Frequency Modulated (GSFM), and in the case of GSFM, the target sidelobe decreased by more than 20 dB, thereby improving performance. In the sea experiment, it was confirmed that the LFM reduced the level of the transmitted direct wave by 10 dB, the GSFM reduced the level of the transmitted direct wave by about 4 dB, and the side lobe of the target decreased by about 4 dB, thereby improving the performance.

• Journal of Internet Computing and Services
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• v.6 no.4
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• pp.47-58
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• 2005

There are two major type of flash memory products, namely, NAND-type and NOR-type flash memory. NOR-type flash memory is generally deployed as ROM BIOS code storage because if offers Byte I/O and fast read operation. However, NOR-type flash memory is more expensive than NAND-type flash memory in terms of the cost per byte ratio, and hence NAND type flash memory is more widely used as large data storage such as embedded Linux file systems. In this paper, we designed an efficient flash memory file system based an Embedded system and presented to make up for reduced to Swapping a weak System Performance to flash file system using NAND-type flash memory, then proposed Swapping algorithm insured to an Execution time. Based on Implementation and simulation studies, Then, We improved performance bases on NAND-type flash memory to the requirement of the embedded system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.754-756
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• 2013

The modern Electronic Warfare Receivers are required to the current radar technologies like the Low Probability of Intercept(LPI) radars to avoid detection. LPI radars have features of intra-pulse modulation differ from existing radar signals. This features require counterworks such as signal confirmation and identification. Hence this paper presents a study on intra-pulse modulation recognition. The proposed method automatically recognizes intra-pulse modulation types such as LFM and NLFM using classifiers extracted from the features of each intra-pulse modulation. Several simulations are also conducted and the simulation results indicate the performance of the given method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.11
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• pp.949-958
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• 2016

This paper presents the new development result of the multi-band, the multi-mode SDR(Software Defined Radar) platform. The SDR hardware platform is implemented by using the reconfigurable multi-band RF transceiver and antenna modules of S, X, and K-bands, and a programmable signal processing module. The SDR software platform is implemented by using the multi-mode waveform generation of CW, Pulse, FMCW, and LFM Chirp as well as the adaptable algorithm library of signal processing and open API software modules. Through the integrated test of the SDR platform, the operational performance was verified in real-time. Also, through the field-application test, the ground target and air-vehicle drone target were successfully detected and their test results were presented.