• 한국항공우주학회지
• /
• 제34권4호
• /
• pp.47-52
• /
• 2006

불규칙 혼합잡음의 등가 ARMA 모델 표현을 사용하여 자이로의 불규칙 혼합잡음을 고려하는 보조항법시스템 칼만필터 설계 방법을 제안한다. 필터 설계 절차는 먼저 보조항법 시스템에 사용되는 필터는 간접 되먹임 칼만필터임을 고려하여 등가 ARMA 모델로 표현된 자이로 불규칙 잡음의 시간 차분을 구한다. 다음으로 시간 차분된 ARMA 모델을 상태 방정식으로 표현하는데 AR과 MA 차수에 따라 두 가지로 나누어진다. 먼저 AR 차수가 큰 경우 가제어 혹은 가관측 특이형태를 사용한다. MA 차수가 큰 경우에는 몇 단계 이후의 예측치를 상태변수로 하는 상태방정식을 사용하는데, 이때 자이로 출력을 보상하는 값에 따라 다시 고차수 필터와 저차수 필터로 구분된다. 마지막으로 자이로 불규칙 잡음을 보조항법시스템 칼만필터에 포함시켜 최종적인 필터 모델을 얻는다. 시뮬레이션 결과를 통하여 제안된 고차수 및 저차수 필터 모두 혼합잡음을 백색잡음으로 간주한 기존의 필터보다 항법오차를 감소시킬 수 있음을 보임으로써 그 효용성을 제시한다.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2007년도 춘계종합학술대회
• /
• pp.739-742
• /
• 2007

다양한 매체를 통해 전달되는 멀티미디어 정보신호를 처리하는 과정에서 시스템 내 외부적인 원인에 의해 잡음이 발생하고 있으며, 이러한 잡음은 정보신호에 대한 인지도를 저하시킨다. 따라서 잡음을 제거하고 신호를 복원하기 위한 많은 연구들이 진행되고 있으며, 최근에는 레이브렛의 시간-주파수 국부성을 이용한 잡음제거 방법들이 많은 응용분야에 적용되고 있다. 한편, 두 개의 웨이브렛 기저가 힐버트 변환쌍을 형성하도록 설계될 때, 웨이브렛은 신호의 특징을 검출하기 위해 보다 효과적으로 적용될 수 있다. 따라서 본 논문에서는 잡음에 의해 훼손된 신호를 복원하기 위해, 웨이브렛의 힐버트 변환쌍을 이용한 잡음제거 알고리즘을 제안하였다.

• 음성과학
• /
• 제11권2호
• /
• pp.105-117
• /
• 2004

Recently, many scholars have emphasized the importance of English listening ability for smoother communication. Most audio materials, however, were recorded in a quiet sound-proof booth. Therefore, students who have spent so much time listening to the ideal audio materials are expected to have difficulty communicating with native speakers in the real life. In this study, we examined how well thirty three Korean university students and five native speakers will repeat the recorded English sentences under noise and speed conditions. The subjects' production was scored by listening to each recorded sentence and counting the number of words correctly produced and determined the percent ratios of correctly produced words to the total words in each sentence. Results showed that the student group correctly repeated around 65% of all the words in each sentence while the native speakers demonstrated almost perfect match. It seemed that the students had difficulty perceiving and repeating function words in various conditions. Also, high-proficiency student group outperformed the low-proficiency student group particularly in their repetition of function words. In addition, the student subjects' accuracy of repetition remarkably dropped when the normal sentences were both sped up and mixed with noise. Finally, it was observed that the Korean students' percent correct ratio fell down as the stimulus sentence became longer.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2013년도 추계학술대회
• /
• pp.265-267
• /
• 2013

에지는 물체의 여러가지 중요한 정보를 포함하고 있다. 이러한 에지는 많은 분야에서 응용되고 있으며, 기존의 에지 검출 방법에는 마스크를 이용하는 방법 등이 있다. 이러한 기존의 에지 검출 방법들은 구현이 간단하다. 그러나, 고정된 마스크를 이용하므로 복합 잡음 환경에서의 에지 검출 특성은 다소 미흡하다. 따라서 기존의 에지 검출 방법들의 단점을 보완하기 위하여, 본 논문에서는 국부 마스크의 표준편차 및 잡음 제거를 이용한 에지 검출 알고리즘을 제안하였다.

• Journal of Audiology & Otology
• /
• 제25권1호
• /
• pp.22-26
• /
• 2021

Background and Objectives: Music listening has a concomitant effect on structural and functional organization of the brain. It helps in relaxation, mind training and neural strengthening. In relation to it, the present study was aimed to find the effect of Carnatic music listening training (MLT) on speech in noise performance in adults. Subjects and Methods: A total of 28 participants (40-70 years) were recruited in the study. Based on randomized control trial, they were divided into intervention and control group. Intervention group underwent a short-term MLT. Quick Speech-in-Noise in Kannada was used as an outcome measure. Results: Results were analysed using mixed method analysis of variance (ANOVA) and repeated measures ANOVA. There was a significant difference between intervention and control group post MLT. The results of the second continuum revealed no statistically significant difference between post training and follow-up scores in both the groups. Conclusions: In conclusion short-term MLT resulted in betterment of speech in noise performance. MLT can be hence used as a viable tool in formal auditory training for better prognosis.

• 대한청각학회지
• /
• 제25권1호
• /
• pp.22-26
• /
• 2021

Background and Objectives: Music listening has a concomitant effect on structural and functional organization of the brain. It helps in relaxation, mind training and neural strengthening. In relation to it, the present study was aimed to find the effect of Carnatic music listening training (MLT) on speech in noise performance in adults. Subjects and Methods: A total of 28 participants (40-70 years) were recruited in the study. Based on randomized control trial, they were divided into intervention and control group. Intervention group underwent a short-term MLT. Quick Speech-in-Noise in Kannada was used as an outcome measure. Results: Results were analysed using mixed method analysis of variance (ANOVA) and repeated measures ANOVA. There was a significant difference between intervention and control group post MLT. The results of the second continuum revealed no statistically significant difference between post training and follow-up scores in both the groups. Conclusions: In conclusion short-term MLT resulted in betterment of speech in noise performance. MLT can be hence used as a viable tool in formal auditory training for better prognosis.

• 한국수소및신에너지학회논문집
• /
• 제19권1호
• /
• pp.26-34
• /
• 2008

This study presents an aerodynamic design and an experimental performance test of a turbo air compressor consisted of mixed-flow impeller and curved diffuser for the PEM fuel cell vehicle application. Many studies compare the efficiency, cost or noise level of high-pressure and low-pressure operation of PEM fuel cell systems. Pressure ratio 2.2:1 is considered as design target The goal of compressor design is to enlarge the flow margin of compressor from surge to choke mass flow rate to cover the operational envelope of FCV. Large-scale rig test is performed to evaluate the compressor performance and to compare the effects of compressor exit pipe volume to stall or surge characteristics. The results show that the mixed-flow compressor designed has large flow margin, and the flow margin of compressor configuration with small exit volume is larger than that with large exit volume.

• Journal of Advanced Marine Engineering and Technology
• /
• 제28권7호
• /
• pp.1082-1091
• /
• 2004

Analyzed Parametrically was an internal combustion engine combined with gas turbine the cycle of which is splitted into compression side cylinder and expansion side one, and heat adding of which is during constant volume pressure, temperature process. The advantages of each measures were analyzed by means of thermal cycle diagram. The thermal efficiency of partial load cutting off firstly isothermal heat adding and secondly isobaric heat adding also was analyzed The authors suggested some potentials about the performance as for thermal efficiency, mean effective pressure and reducing emissions and noise supposed were the operating parameter of the engine set to some values and were some problems solved.

• ETRI Journal
• /
• 제33권2호
• /
• pp.287-290
• /
• 2011

We consider a two-hop multiple-relay network implemented with opportunistic decode-and-forward cooperative strategy, where the first hop and second hop links experience different fading (Rayleigh and Rician). We derive the exact expressions of end-to-end outage probability and analyze the approximate results in high signal-to-noise ratio region. The analysis shows that the same diversity order can be achieved even in different mixed fading environments. Simulation results are provided to verify our analysis.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 D
• /
• pp.2531-2533
• /
• 2001

This paper describes a low noise and high efficiency analog-digital switching mixed mode battery charger for production facilities of Li-Ion batteries. The requirements for battery chargers for production facilities are very strict. The accuracy of output voltage and output current should be below 0.1% with very low ripple current. Therefore analog type linear regulators are widely used for battery charger in spite of their inefficiency and bulkiness. We combined linear regulator as a voltage source with digital switching converter as a dependent current source. Low current ripple and high accuracy are obtained by linear regulator while high efficiency is achieved by digital switching converter. Experimental results show that proposed method has 0.1% ripple and 90% efficiency at an output current of 1A for a battery voltage of 4V.