• Bulletin of the Korean Chemical Society
• /
• 제23권4호
• /
• pp.580-586
• /
• 2002

We investigated the effect of ionic component on crystalline morphology development during isothermal annealing in a sodium neutralized sulfonated poly(ethylene terephthalate) ionomer (Ion-PET) by time-resolved small-angle x-ray scattering (TR-SAX S) using synchrotron radiation. At early stage in Ion-PET, SAXS intensity at a low annealing temperature (Ta = 120 $^{\circ}C)$ decreased monotonously with scattering angle for a while. Then SAXS profile showed a peak and the peak position progressively moved to wider angles with isothermal annealing time. Finally, the peak intensity decreased, shifting the peak angle to wider angle. It is revealed that ionic aggregates (multiplets structure) of several nm, calculated by Debye-Bueche plot, are formed at early stage. They seem to accelerate the crystallization rate and make fine crystallites without spherulite formation (supported by optical microscopy observation). From decrease of peak intensity in SAXS,it is suggested that new lamellae are inserted between the preformed lamellae so that the concentration of ionic multiplets in amorphous region decreases to lower the electron density difference between lamellar crystal and amorphous region. In addition, analysis on the annealing at a high temperature (Ta = 210 $^{\circ}C)$ by optical microscopy, light scattering and transmission electron microscopy shows a formation of spherulite, no ionic aggregates, the retarded crystallization rate and a high level of lamellar orientation.

• 한국멀티미디어학회논문지
• /
• 제15권5호
• /
• pp.639-650
• /
• 2012

Tsai 등은 2009년에 예측 코딩과 히스토그램 이동 기법을 이용한 가역 은닉 방법을 제안하였다. Tsai 등의 방법은 비밀 정보를 숨길 수 있는 양을 향상시키기 위해 예측 코딩을 이용하고, 히스토그램을 두 개 생성하였다. 하지만, 예측 코딩은 삽입과정에서 기준 픽셀이 사용되지 않고, 히스토그램을 두 개로 나누는 방법은 한 블록마다 두 쌍의 최대값과 최소값이 생성되기 때문에 기존 히스토그램 이동 기법보다 많은 양의 추가 전송 데이터가 발생하게 된다. 이러한 문제점을 해결하기 위해 본 논문에서는 모듈러 연산과 히스토그램 이동에 기반한 새로운 가역 정보 은닉 기법을 제안한다. 실험결과를 통해 제안한 방법의 비밀 정보를 숨길 수 있는 양은 Tsai 등의 방법보다 28% 증가 하면서도 추가 전송 데이터의 양은 71% 감소하는 것을 볼 수 있었다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 추계학술대회논문집
• /
• pp.431-434
• /
• 2005

Generally, noise in a reciprocating compressor is attributed to the driving force of a pump. However, close examination shows that the noise heard by customers finally results from radiation of a shell in a compressor, the noise caused by both transmission through a shell and resonance with the natural frequency of a shell. Therefore, the peak frequencies contributing to the overall level of a compressor' noise are closely concerned with vibration of a shell. That's why radiated noise by vibration can be reduced by changing the mode of a shell and by shifting the peak frequencies to other ranges, which are not globally related with the overall noise level. In this paper, the main peak frequencies are analyzed to reduce the radiated noise of a shell, and the vibration characteristics of a shell are examined through Frequency Response Function and Finite Element Analysis. Moreover, the Operational Deflection Shape for a shell is measured with consideration of real driving force of a pump. Finally, the optimum position on a shell, closely related to the main peak frequencies, is found, and the overall noise level caused by radiated noise of a shell is noticeably reduced by mass or stiffness modification of the position.

• 대한전자공학회논문지SP
• /
• 제47권2호
• /
• pp.51-60
• /
• 2010

본 논문에서는 백색광 위상천이 간섭계에서 향상된 3차원 형상 정보를 보다 빠르게 얻을 수 있는 새로운 방법을 제안한다. 백색광 위상천이 간섭계는 초정밀 제품의 형상 측정에 사용되는 유용한 방법이다. 첫째, 가시도 함수를 포함하는 간섭신호로부터 3차원 높이 정보를 신속하게 계산할 수 있는 가시도 유효 검출 구간 설정 방법을 제안한다. 둘째, 기존의 백색광 위상천이 간섭계에서 발생하는 전역 기울어짐 현상을 해결하기 위하여 바닥면 데이터 자동 추출 방법과 이를 이용한 최소 제곱 근사화 기반의 바닥 평변 추정 방법을 제안한다. 셋째, 높이의 변화가 큰 경계영역에서의 형상 왜곡인 bat-wing effect를 제거하기 위한 적응 필터 방법을 제안한다. 실험을 통해 제안하는 방법이 기존의 백색광 위상천이 간섭법의 성능을 보다 향상시킴을 보인다.

• 대한물리치료과학회지
• /
• 제11권4호
• /
• pp.29-37
• /
• 2004

Measurements of plantar pressure provide an indication of foot and ankle function during gait and other functional activities because the foot and ankle provide necessary support and flexibility for weight bearing and weight shifting while people are performing these activities. Plantar pressure is being increasingly used in both research and clinical practice to measure the effects of various footwear and physical therapy intervention. The influence of walking speed and ground inclination on plantar pressure parameters However has not been evaluated in detail. So, in this study to determine the effect of changes in walking speed and ground inclination on plantar pressure treadmills with different walking speeds and inclination were used. Plantar pressure parameters were measured with the Parotec system using the walking and running in 20 healthy participants(10 male, 10 female) aged $20{\sim}28$(mean 22.22, S.D.2.26 years) when slow walking and running. The result of this study with increased die walking speed, the peak pressure of 1st, 5th metatarsal head and total contact time and impulse total at the forefoot was affected by walking speed; however, die peak pressure, contact time and impulse total at the forefoot was not affected by ground inclination.

• 한국음향학회지
• /
• 제34권2호
• /
• pp.157-162
• /
• 2015

본 논문은 MCLT(Modulated complex lapped transform) 피크쌍 기반의 강인한 해시 함수를 이용한 오디오 핑거프린팅을 제안한다. 기존 방식의 오디오 핑거프린팅은 시간-스케일, 피치-이동, 이퀄라이제이션과 같은 다양한 왜곡이 발생했을 때, 강인한 핑거프린트를 추출하지 못한다는 문제점이 있다. 이를 해결하기 위해 본 논문에서는 MCLT 스펙트럼, 현저한 피크검색을 위한 적응적 문턱값 방식, 개선된 해시 함수를 이용하여 잡음과 왜곡 환경 강인한 오디오 핑거프린팅을 추출하였다. 실험결과 제안된 방식이 잡음과 왜곡 환경에서 보다 강인한 핑거프린팅을 추출할 수 있으며 매칭 인식률을 향상 시키는 것을 보여준다.

• ETRI Journal
• /
• 제46권2호
• /
• pp.227-237
• /
• 2024

This study proposes a novel, conditionally applied neural network technique to reduce the overall peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) system while maintaining an acceptable bit error rate (BER) level. The main purpose of the proposed scheme is to adjust only those subcarriers whose peaks exceed a given threshold. In this respect, the developed C-ANN algorithm suppresses only the peaks of the targeted subcarriers by slightly shifting the locations of their corresponding frequency samples without affecting their phase orientations. In turn, this achieves a reasonable system performance by sustaining a tolerable BER. For practical reasons and to cover a wide range of application scenarios, the threshold for the subcarrier peaks was chosen to be proportional to the saturation level of the nonlinear power amplifier used to pass the generated OFDM blocks. Consequently, the optimal values of the factor controlling the peak threshold were obtained that satisfy both reasonable PAPR reduction and acceptable BER levels. Furthermore, the proposed system does not require a recovery process at the receiver, thus making the computational process less complex. The simulation results show that the proposed system model performed satisfactorily, attaining both low PAPR and BER for specific application settings using comparatively fewer computations.

• The Korean Journal of Ecology
• /
• 제18권2호
• /
• pp.243-253
• /
• 1995

Seral changes in environmental factors and recovery of soil fertility during abandoned field succession after shifting cultivation were investigated in eastern Kangwon-Do, Korea. Relative light intensity of herb and shrub layer decreased gradually until 50 years and increased slightly thereafter. Amount of litter and nutrients derived from it were depicted as a parabola form showing the gradual increment during the first 50 years and slight decrease thereafter. Organic matter, pH value, total-N and Mg of soil were plotted as an early depletion-mid pinnacle form showing the extrems depletion during the first 10 years, abrupt increase in about 20 or 50 years and gradual decrease thereafter. Ca, Al, Mn and Na of soil were depicted as a pinnacle form showing the peak in about 20 or 50 years. Thickness and field capacity of soil increased gradually, but K and total-P did not show any tendency as succession proceeded. The soil fertility, overall capacity of soil nutrients and water for plant growth, was plotted as the early depletion-mid pinnacle form.

• Journal of the Optical Society of Korea
• /
• 제17권5호
• /
• pp.415-422
• /
• 2013

White-light phase-shifting interferometry (WLPSI) is widely recognized as a standard method to measure shapes with high resolution over a long distance. In practical applications, WLPSI, however, is associated with some degree of ambiguity of its phase, which occurs due to a phase delay, which is the offset between the phase of the fringes and the fringe envelope peak position. In this paper, a new algorithm is proposed for the determination of a fringe order suitable for samples in which the phase delay mainly occurs due to noise, diffraction and a steep angle. The concepts of the decouple factor and the connectivity are introduced and a method for calculating the decouple factor and the connectivity is developed. With the phase-unwrapping procedure which considers these values, it is demonstrated that our algorithm determines the correct fringe order. To verify the performance of the algorithm, a simulation was performed with the virtual step height under noise. Some specimens such as step height standard and a column spacer with a steep angle are also measured with a Mirau interference microscope, after which the algorithm is shown to be effective and robust.

• Journal of Ecology and Environment
• /
• 제29권3호
• /
• pp.227-235
• /
• 2006

강원도 평창군 일대에서 화전 후 묵밭의 식생 천이에 따른 식생 구조의 발달 과정과 종다양성의 변화를 조사하였다. 방치 후 경과 년 수에 따라 최상층부의 키는 초기에 빠르게 증가하고 후기에 안정화하는 경향을 나타내었다. 10, 20, 50 및 80 년차 묵밭에서 최상층부 식생의 키는 각각 4, 8, 18 및 18 m이었다. 교목층, 아교목층, 관목층 및 초본층의 4층 구조를 갖춘 완전한 형태의 숲으로 발달하기까지는 방치 후 약 35년이 경과해야 하는 것으로 추정되었다. 방치 후 경과 년 수에 따라 식생치 Ivc는 로그 함수적으로 그리고 식생치 Hcl은 직선적으로 증가하는 경향이 있었다. 묵밭의 식생천이에서 종다양성은 천이 중기인 $10{\sim}20$년차에서 최고로 증가한 다음 이후 점차 감소하는 경향을 나타내었다. 본 조사지에서 종다양성은 균등도보다 종풍부도와 매우 밀접한 상관을 나타내었다. 대부분의 목본은 개망초-쑥 단계인 $2{\sim}6$년차에 정착이 이루어져 시간 경과에 따라 이들의 우점도가 변화함으로써 Egler (1954)의 초기 종조성 모델을 따르는 것으로 확인되었다.