• 한국산업융합학회 논문집
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• 제6권1호
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• pp.81-86
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• 2003

For the simultaneous removal of $SO_2$/NOx from an iron-ore sintering plant, industrial plasma experiments have been conducted with a flue gas flow rate of $5,000Nm^3/hr$. The maximum 40kW power using the magnetic pulse compression (MPC) system generates a peak value of 100-150kV pulse voltage with its risetime of 200nsec and full width at half maximum (FWHM) of 500nsec, and with a frequency <300Hz. The plasma reactor module adopts a wire-plate structure with a gap of 200-400mm ID between plates. Initial concentrations of $SO_2$ and NOx were around 100-150ppm, respectively in the presence of 15% $O_2$ and <10% $H_2O$. Various reaction parameters such as specific energy ($Whr/Nm^3$), $NH_3$ injection with corona discharge, flow rate and injection of hydrocarbons were investigated for $SO_2$/NOx removal characteristics. About 90/65% of $SO_2$/NOx were simultaneously removed with a specific energy of $3.0Whr/Nm^3$ when both $NH_3$ and hydrocarbons were injected. Practical implications that the pilot-scale plasma results provide are further discussed.

• Geomechanics and Engineering
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• 제23권4호
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• pp.339-349
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• 2020

This study investigates the feasibility of using the results of the UPV (ultrasonic pulse velocity) test to assess the UCS (unconfined compressive strength) of unsaturated soil. A series of laboratory tests was conducted on samples of unsaturated lateritic soils of northern Taiwan. Specifically, the unconfined compressive test was combined with the pressure plate test to obtain the unconfined compressive strength and its matric suction (s) of the samples. Soil samples were first compacted at the designated water content and subsequently subjected to the wetting process for saturation and the following drying process to its target suction using the apparatus developed by the authors. The correlations among the UCS, s and UPV were studied. The test results show that both the UCS and UPV significantly increased with the matric suction regardless of the initial compaction condition, but neither the UCS nor UPV obviously varied when the matric suction was less than the air-entry value. In addition, the UCS approximately linearly increased with increasing UPV. According to the investigation of the test results, simplified methods to estimate the UCS using the UPV or matric suction were established. Furthermore, an empirical formula of the matric suction calculated from the UPV was proposed. From the comparison between the predicted values and the test results, the MAPE values of UCS were 4.52-9.98% and were less than 10%, and the MAPE value of matric suction was 17.3% and in the range of 10-20%. Thus, the established formulas have good forecasting accuracy and may be applied to the stability analysis of the unsaturated soil slope. However, further study is warranted for validation.

• Journal of the Optical Society of Korea
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• 제18권3호
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• pp.207-216
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• 2014

In this work, we report detailed numerical analysis of the near-elliptic core index-guiding triangular-lattice and square-lattice photonic crystal fiber (PCFs); where we numerically characterize the birefringence, single mode, cut-off behavior and group velocity dispersion and effective area properties. By varying geometry and examining the modal field profile we find that for the same relative values of $d/{\Lambda}$, triangular-lattice PCFs show higher birefringence whereas the square-lattice PCFs show a wider range of single-mode operation. Square-lattice PCF was found to be endlessly single-mode for higher air-filling fraction ($d/{\Lambda}$). Dispersion comparison between the two structures reveal that we need smaller lengths of triangular-lattice PCF for dispersion compensation whereas PCFs with square-lattice with nearer relative dispersion slope (RDS) can better compensate the broadband dispersion. Square-lattice PCFs show zero dispersion wavelength (ZDW) red-shifted, making it preferable for mid-IR supercontinuum generation (SCG) with highly non-linear chalcogenide material. Square-lattice PCFs show higher dispersion slope that leads to compression of the broadband, thus accumulating more power in the pulse. On the other hand, triangular-lattice PCF with flat dispersion profile can generate broader SCG. Square-lattice PCF with low Group Velocity Dispersion (GVD) at the anomalous dispersion corresponds to higher dispersion length ($L_D$) and higher degree of solitonic interaction. The effective area of square-lattice PCF is always greater than its triangular-lattice counterpart making it better suited for high power applications. We have also performed a comparison of the dispersion properties of between the symmetric-core and asymmetric-core triangular-lattice PCF. While we need smaller length of symmetric-core PCF for dispersion compensation, broadband dispersion compensation can be performed with asymmetric-core PCF. Mid-Infrared (IR) SCG can be better performed with asymmetric core PCF with compressed and high power pulse, while wider range of SCG can be performed with symmetric core PCF. Thus, this study will be extremely useful for designing/realizing fiber towards a custom application around these characteristics.

• Fibers and Polymers
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• 제7권4호
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• pp.450-456
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• 2006

The objectives of this study were to investigate physiological and psychological responses to the rustling sound of Korean traditional silk fabrics and to figure out objective measurements such as sound parameters and mechanical properties determining the human responses. Five different traditional silk fabrics were selected by cluster analysis and their sound characteristics were observed in terms of FFT spectra and some calculated sound parameters including level pressure of total sound (LPT), Zwicker's psychoacoustic parameters - loudness(Z), sharpness(Z), roughness(Z), and fluctuation strength(Z), and sound color factors such as ${\Delta}L\;and\;{\Delta}f$. As physiological signals, the ratio of low frequency to high frequency (LF/HF) from the power spectrum of heart rate variability, pulse volume (PV), heart rate (HR), and skin conductance level (SCL) evoked by the fabric sounds were measured from thirty participants. Also, seven aspects of psychological state including softness, loudness, sharpness, roughness, clearness, highness, and pleasantness were evaluated when each sound was presented. The traditional silk fabric sounds were likely to be felt as soft and pleasant rather than clear and high, which seemed to evoke less change of both LF/HF and SCL indicating a negative sensation than other fabrics previously reported. As fluctuation strength(Z) were higher and bending rigidity (B) values lower, the fabrics tended to be perceived as sounding softer, which resulted in increase of PV changes. The higher LPT was concerned with higher rating for subjective loudness so that HR was more increased. Also, compression linearity (LC) affected subjective pleasantness positively, which caused less changes of HR. Therefore, we concluded that such objective measurements as LPT, fluctuation strength(Z), bending rigidity (B), and compression linearity (LC) were significant factors affecting physiological and psychological responses to the sounds of Korean traditional silk fabrics.

• 방송공학회논문지
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• 제13권5호
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• pp.612-621
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• 2008

이용 가능한 데이터 영역과 전송전력 등 다양한 제한 요소들로 인하여 지그비 통신의 기술규격에는 음성통신에 대한 기준 사양이 포함되지 않았다. 본 논문에서는 지그비의 기반인 IEEE 802.15.4 표준에 적용하기 위한 음성부호화 기법이 제시된다. 여기서는 높은 압축율과 파형 복구능력이 우수한 파형부호기의 실현이 필수적이다. 이를 위하여 제시된 방법에서는 다단 이산 웨이블릿변환과 두 가지 펄스부호변조로 구성된 이진부호기가 사용된다. 이론적인 분석과 실내 무선 환경에서의 모의실험 결과 2단 웨이블릿변환을 적용한 경우가 압축율과 음성신호 복구능력 면에서 가장 적합한 것으로 판단된다. 직선전파경로 성분이 지배적인 경우 제시된 방법은 중간 정도의 신호 대 잡음비에서도 만족스러운 복구능력을 가진다. 따라서 제시된 음성부호화 방법은 향후 지그비를 이용한 음성통신의 표준 선정에 참고 가능한 기술이 될 수 있을 것으로 사료된다.

• 한국자기학회지
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• 제19권1호
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• pp.5-11
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• 2009

Explosive Magnetic Generator of Frequency(EMGF)는 고폭화약의 폭발을 이용하여 화약의 폭발 에너지를 전자기 에너지로 변환 시키면서 초고주파의 강한 전자파를 발생시키는 효율적인 방법으로 연구되고 있다. 이 때 발생하는 전자파의 물리적 원인은 현재까지 명확하게 규명되어 있지 않은데, 단순한 시변 등가회로 해석만으로는 이러한 고주파 발진을 설명하기 어려운 것으로 알려져 있다. 이 논문에서는 기존에 널리 받아 들여 지고 있는 지수 감소적인 시변 인덕턴스 변화 모델에 대해서 자장압축효과를 고려한 유한요소 해석을 통해 문제점을 분석하고 보다 정확한 인덕턴스 변화 모델의 경향성에 대해서 제시하고자 한다. 그리고 이렇게 제시된 새로운 인덕턴스 변화 모델을 사용한 EMGF 출력 시뮬레이션을 통해 새로운 인덕턴스 변화 모델이 출력에 미치는 영향을 분석한다.

• 한국항행학회논문지
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• 제6권2호
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• pp.97-103
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• 2002

고해상도 영상레이다에서 초광대역 파형 처리기술은 정밀 표적 식별을 위해서 매우 중요하다. 본 논문에서는 영상 레이다의 거리 분해능을 초 고해상도로 향상시킬 수 있는 방법으로서, 송신 펄스의 첩 변조 파형을 모듈방식으로 확장하여 광대역의 송신 파형을 얻을 수 있는 레이다 첩 파형 설계 기법에 대하여 논한다. 먼저 디지털 첩 신호발생 원리와 광대역 첩 신호 파형을 얻기 위한 신호대역 연결 및 분리 기법을 제시한다. 그리고, 영상 레이다의 거리 해상도 성능분석을 위하여 발생시킨 광대역 신호 파형 발생과 복원과정을 시뮬레이션을 통하여 성능 결과를 제시한다.

• 한국통신학회논문지
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• 제39A권2호
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• pp.109-116
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• 2014

본 논문에서는 기상 레이다의 효율적 주파수 사용을 위해 직교 파형과 간섭 제거 기술을 이용한 주파수 재사용 기술을 제안하였다. 주파수 공유로 발생한 레이다간 간섭 영향을 줄이기 위해 직교 코드 시퀀스 간 상호 상관 최대값이 가장 작은 조합으로 선택하였으며, 잔여 간섭 성분 제거를 위해 CLEAN 알고리즘을 사용하였다. 전산 모의 실험 결과 재사용 기술 적용 후에도 성능 요구 조건을 만족하는 것으로 나타남으로써 현행 S 밴드 기상 레이다의 점유 주파수 8개를 1개로 줄일 수 있어 신규 주파수 확보 가능성 제시하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1993년도 춘계학술대회논문집; 한국과학연구소, 21 May 1993
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• pp.147-147
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• 1993

All types of dynamic excitation, periodical, pulse or transient in vertical, horizontal or all three directions can be effectively reduced by vibration isolation systems. Typical elements for vibration isolation control are spring units consisting of a group of helical compression springs. In all cases of shock, transient or random excitation energy absorbing dampers have to be added to the spring units in order to reduce system response in the frequency range near the natural frequency of the isolation system. The same isolation system of spring units and viscos-dampers has been used since 1979 for passive protection of buildings and structures has been proved to by very advantageous for vibration and structure borne noise control. Not only because of high vertical flexibility of the spring units, compared for example with typical rubber or neoprene mounts out also because of the horizontal of flexibility, which can be adapted by modifying the spring dimensions to nearly every requirement. It is just normal to use the same basic elements for passive isolation as for active isolation.

• 한국음향학회지
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• 제20권5호
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• pp.92-99
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• 2001

1999년 10월에 수행한 한국 동해 중북부 해역의 토모그래피 실험은 저주파수음원을 블라디보스톡 부근의 대륙붕 해역에 위치시켰고 수직선배열 수신기를 울릉도 부근에 고정시켜 원거리 음향 신호의 변화특성을 파악코저하였다. 음원은 위상 변조된 신호이며 울릉도 부근해역의 수직선배열 수신기를 이용하여 자료를 수집하였다. 수신된 자료에 대해 도달시간 및 그 변화를 파악하였다. 이를 위해 위상 변조된 신호를 복조하였으며 특성을 파악하기 위해 도달시간 확산 및 상관성 분석을 수행하였다. 분석결과 단주기성 변화가 존재하고 있으며 이는 내부파에 의한 매질의 수직 변동에 의한 영향이라 할 수 있다.