• Computers and Concrete
• /
• 제33권5호
• /
• pp.559-572
• /
• 2024

Problems of under-sized dams (small dams with large basin area) could get worse under the global warming condition. This study evaluates the possible change of these problems with the Namgang Dam, an under-sized dam in Korea. For this purpose, first, this study simulates the dam inflow data using a rainfall-runoff model, which are then used as input for the reservoir operation. As a result, daily dam storage, dam release, and dam water supply are derived and compared for both past observed period (1973~2022) and future simulated period (2006~2099) based on the global warming scenarios. Summarizing the results are as follows. First, the inflow rate in the future is expected to be increased significantly. The maximum inflow could be twice of that observed in the past. As a result, it is also expected that the frequency of the water level reaching the high level is increasing. Also, the amount and frequency of dam release are to be increased in the future period. More seriously, this increase is expected to be concentrated on rather extreme cases with large dam release volume. Simply, the condition for flood protection in the downstream of the Namgang Dam is becoming worse and worse. Ironically, the severity of water shortage problem is also expected to become much worse. As the most extreme case, the frequency of no water supply was zero in the observed period, but in the future period, it becomes once every five years. Both the maximum consecutive shortage days and the total shortage volume are expected to become more than twice in the future period. To prevent or mitigate this coming problem of an under-sized dam, the only countermeasure at this moment seems to be its redevelopment. Simply a bigger dam with larger dam reservoir can handle this adverse effect more easily.

• 전기전자학회논문지
• /
• 제27권4호
• /
• pp.472-476
• /
• 2023

피치 혹은 기본 주파수는 음성 신호의 주요 특성 인자이며 음성 부호화, 음성인식, 화자인식 등의 다양한 음성 관련 응용에 활용된다. 본 논문에서는 기본 주파수의 역수인 음성의 피치 주기를 추정하기 위해서 음성 신호의 변곡점을 이용한다. 변곡점은 국소적인 최대값, 최소값 혹은 신호의 기울기가 변하는 지점으로 정의된다. 음성 신호는 저역통과 필터로 먼저 전처리되어 고주파 성분이 제거된다. 이를 통해 불필요한 변곡점들이 제거되며, 피치 주기 추정에 유용한 국소적인 최대값만을 변곡점 검출법을 이용하여 추출한다. 얻어진 변곡점 간의 시간 간격을 측정하여 피치 주기를 추정하며, 그 역수로 기본 주파수 추정치를 얻는다. 기존의 피치 추정 방법은 음성이 국소적으로 시불변이라는 가정하에 음성을 블록 단위로 처리하여 블록당 피치 주기를 구하지만, 제안된 방법은 음성을 샘플 단위로 처리하여 변곡점을 검출하며, 그 결과 피치 주기를 시간 경과에 따라 얻게 되어 음성의 시변성이 반영된 기본 주파수 추정치를 얻는다. 컴퓨터 모의실험으로 기본 주파수 추정기로서 제안된 방법의 유용성을 볼 수 있다.

• 부모자녀건강학회지
• /
• 제3권1호
• /
• pp.46-59
• /
• 2000

The purpose of this study is to determine whether the NCASA (Nursing Child Assessment Sleep/Activity Record) would be suitable to evaluate and to provide the basic resources for a Korean model of sleep/activity patterns during the first 6 months Korean infants' lives and to provide a basis for nursing intervention for mothers of early infants. The subjects of this study were 94 normal infants from birth to 6 months of age who visited the postpartum care center and two general hospitals located in Pusan from February 1 to April 28, 2000. The method of data collection was through convenient sampling. The instrument of this study was the NCASA translated by the Korean parent Child Health Academic Association. The collected data were analysed by mean, standard deviation, frequency percentage and ANOVA, Post Hoc test by use of SPSS/PC. The conclusions obtained from this study are summarized as follows: 1. The mean amount of daytime sleep was 8.06 hours. The mean amount of nighttime sleep was 6.31 hours. The mean amount of total daily sleep was 14.37 hours. The mean of the longest sleep period was 5.20 hours. The mean regularity of daytime sleep was 25.84%. The mean regularity of nighttime sleep was 77.69%. The mean regularity of total daily sleep was 42.60%. The mean frequency of nighttime wakenings was 2.33 times. 2. The mean amount of daytime activity was 8.25 hours. The mean amount of nighttime activity was 1.39 hours. The mean amount of daily total activity was 9.64 hours. The mean of the longest activity period was 3.80 hours The mean frequency of daytime feeding was 5.69 times. The mean frequency of nighttime feeding was 2.08 times. The mean frequency of total daily feeding was 7.74 times. The mean frequency regularity of feeding was 54.62%. The mean frequency of wakenings was 5.14 times. The mean frequency of crying was 1.90 times. 3. According to an analysis of sleep patterns based on an infant's age, there were some significant differences in the following factors: amount of daytime sleep(p<.001), amount of night time sleep(p<.05), amount of total daily sleep (p<.001), longest sleep period(p<.001), regularity of daytime sleep(p<.001), regularity of nighttime sleep(p<.01), regularity of total daily sleep(p<.001), frequency of nighttime wakenings(p<.001). 4. According to an analysis of activity patterns based on an infant's age, there were some significant differences in the following factors: amount of daytime activity(p<.001), amount of nighttime activity(p<.01), amount of total daily activity(p<.001), longest activity period(p<.05), frequency of nighttime feeding(p<.01), frequency of wakenings(p<.001). 5. The mean amount of a mother's day time was 16.30 hours. The mean amount of a mother's night time was 7.70 hours. In conclusion, the initial irregular sleeping and activity patterns of the early infant became regurized as the infant grew older and estabilished firmer patterns of sleeping and of activity.

• 한국지진공학회논문집
• /
• 제20권7_spc호
• /
• pp.503-508
• /
• 2016

In this study, effectiveness of seismic retrofitting methods using passive damping devices was investigated through numerical analyses of short-period structures under earthquakes which have short-duration and high-frequency impulse characteristics similar to Geyongju earthquakes. Displacement spectra of elastic systems and ductility demand of inelastic systems were evaluated by increasing viscous or friction damping. The damping devices could reduce responses of the structures with shorter structural period than 0.2s. The earthquakes similar to impulse load did not induce the responses of the structures with longer period than 0.4s, and the effects of the damping devices which generates damping forces proportional to structural responses became insignificant.

• 한국콘텐츠학회논문지
• /
• 제9권12호
• /
• pp.826-835
• /
• 2009

이 연구의 목적은 시큐리티요원들의 여가유형에 따른 여가제약과 참가의 관계를 규명하는데 있다. 이 연구는 2009년 서울소재 14개소 민간경비회사를 모집단으로 설정한 다음, 유의표집법을 이용하여 최종분석에 사용된 사례 수는 총 387명이다. 설문지의 신뢰도는 Cronbach's $\alpha$값이 .673이상으로 나타났다. 결론은 다음과 같다. 첫째, 성별에 따라서는 여성 집단에서 개인적, 시간적 제약이 높으며, 연령에 따라서는 26-30세 집단에서 시간적 제약, 36세 이상의 집단에서 주변 의식적 제약이 높다. 학력에 따라서는 고졸 이하 집단에서 주변 의식적, 대인적 제약, 전문대졸 집단에서는 구조적 제약이 높으며, 월수입에 따라서는 100만원 미만의 집단에서 주변 의식적, 구조적, 개인적, 대인적 제약이 높다. 직위에 따라서는 팀장급에서 주변 의식적, 구조적, 개인적, 시간적 제약이 높으며, 근무형태에 따라서는 신변보호원 집단이 개인적 제약, 기계경비원 집단에서는 주변 의식적, 구조적, 시간적 제약, 그리고 기타 사무직에서 대인적 제약이 높다. 둘째, 취미 교양 활동의 경우 시간적 제약이 많을수록 참가빈도, 구조적 제약이 많을수록 참가기간, 개인적 제약이 많을 수록 참가강도는 감소한다. 반면, 시간적 제약이 많음에도 참가강도는 증가한다. 놀이 오락 활동의 경우 주변 의식적 제약이 많음에도 참가빈도 및 기간, 개인적 제약이 많음에도 참가기간이 증가한 반면, 구조적 제약이 많을수록 참가빈도 및 기간은 감소한다. 관람 감상 활동의 경우 대인적 제약이 많음에도 참가빈도 및 기간, 시간적 제약이 많음에도 참가기간은 증가한 반면, 구조적 제약이 많을수록 참가빈도 및 기간은 감소한다.

• 한국항공우주학회지
• /
• 제34권4호
• /
• pp.25-32
• /
• 2006

현대의 고성능 전투기는 공력성능 및 조종성능의 향상을 위하여 대부분 세로축 방향으로 항공기를 불안정하게 설계하는 정안정성 완화(Relaxed Static Stability) 개념을 채택하고 있다. 비행제어법칙의 설계 작업은 불안정하게 설계된 항공기에 안정성(Stability)을 부여하고, 주어진 비행임무에 대하여 만족스런 조종성능(Controllability)을 발휘할 수 있도록 비행성능을 조작하는 일련의 과정이다. 항공기의 세로축 운동은 장주기 및 단주기 운동이라는 2개의 감쇠진동 모드가 중첩되어 있다고 간주한다. 전투기에서 세로축 제어법칙설계는 장주기 모드가 설계대상으로 고려되지 않으며, 미 군사규격인 MIL-F-8785C에 정의되어 있는 단주기 모드(Short Period Mode)의 요구조건을 이용하여 주파수와 감쇠비를 최적화한다. 이 때, 제어법칙이 포함된 고차시스템을 저차 등가시스템으로 등가 시켜 판별한다. 현재까지 항공기의 단주기 운동 특성에 관한 연구는 활발하게 진행되어 왔으나, 장주기 운동 특성에 관한 연구는 그렇지 못하였다. 본 논문에서는 T-50 훈련기의 장주기 모드 운동 특성을 분석하기 위해 선형 및 비선형해석을 수행하였으며, 받음각제한기 및 자동 피치자세각 트림 명령이 세로축 운동에 미치는 영향성을 분석하였다.

• Interaction and multiscale mechanics
• /
• 제5권3호
• /
• pp.169-185
• /
• 2012

The concrete bridge is likely to produce fatigue cracks during long period of service due to the moving vehicular loads and the degeneration of materials. This paper deals with the time-frequency analysis of a coupled bridge-vehicle system. The bridge is modeled as an Euler beam with breathing cracks. The vehicle is represented by a two-axle vehicle model. The equation of motion of the coupled bridge-vehicle system is established using the finite element method, and the Newmark direct integration method is adopted to calculate the dynamic responses of the system. The effect of breathing cracks on the dynamic responses of the bridge is investigated. The time-frequency characteristics of the responses are analyzed using both the Hilbert-Huang transform and wavelet transform. The results of time-frequency analysis indicate that complicated non-linear and non-stationary features will appear due to the breathing effect of the cracks.

• 한국환경과학회지
• /
• 제24권7호
• /
• pp.851-864
• /
• 2015

This study analyzed the climate regime shift using statistical change-point analysis on the time-series tropical cyclone (TC) frequency that affected Japan in July to September. The result showed that there was a significant change in 1995 and since then, it showed a trend of rapidly decreasing frequency. To determine the reason for this, differences between 1995 to 2012 (9512) period and 1978 to 1994 (7894) period were analayzed. First, regarding TC genesis, TCs during the 9512 period showed a characteristic of genesis from the southeast quadrant of the tropical and subtropical western North Pacific and TCs during the 7894 period showed their genesis from the northwest quadrant. Regarding a TC track, TCs in the 7894 period had a strong trend of moving from the far east sea of the Philippines via the East China Sea to the mid-latitude region in East Asia while TCs in the 9512 period showed a trend of moving from the Philippines toward the southern part of China westward. Thus, TC intensity in the 7894 period, which can absorb sufficient energy from the sea as they moved a long distance over the sea, was stronger than that of 9512. Large-scale environments were analyzed to determine the cause of such difference in TC activity occurred between two periods. During the 9512 period, anomalous cold and dry anticyclones were developed strongly in the East Asia continent. As a result, Korea and Japan were affected by the anomalous northerlies thereby preventing TCs in this period from moving toward the mid-latitude region in East Asia. Instead, anomalous easterlies (anomalous trade wind) were developed in the tropical western Pacific so that a high passage frequency from the Philippine to the south China region along the anomalous steering flows was revealed. The characteristics of the anomalous cold and dry anticyclone developed in the East Asia continent were also confirmed by the analysis of air temperature, relative humidity and sensible heat net flux showing that most regions in East Asia had negative values.

• 전기의세계
• /
• 제30권5호
• /
• pp.291-296
• /
• 1981

In the paper, in order to get the characteristics of the saccadic and the smooth pursuit movements of the oculomotor systems, a revised stochastic sampled data model suggested by Young et. al. was simulated and analyzed by using the MIMIC language. The results are summerized as follows; (1) The predictability to the sinusoidal inputs increased as the input frequency increased, but at the frequency of 1.0[Hz] the prediction started to decrease. (2) The responses of the system drifted when the system was open-looped. (3) The responses showed the transient state during the first period of the input waves, and then moved into the steady state.

• Journal of Ship and Ocean Technology
• /
• 제9권2호
• /
• pp.21-28
• /
• 2005

Recently moored offshore vessels like as FPSO(Floating Production Storage Offloading) are frequently deployed in seas for a long time. For successful operation, the motion behavior of such a vessel in waves must be clarified in advance either theoretically or experimentally. It is of particular interest to examine the behavior, when swells are superposed to seas with different incident angle. Such a situation is actually reported in some offshore oilfield. In this paper, the motion of a FPSO in irregular waves including swells is studied in time domain. Hydrodynamic coefficients and wave forces are calculated in frequency domain using three-dimensional singularity distribution method. Time memory function and added mass at infinite frequency are derived by Fourier transform utilizing hydrodynamic damping coefficients. In the process, the numerical accuracy of added mass at infinite frequency is carefully examined in association with free decay simulations. It is found from numerical simulations that swells significantly affect the vertical motion of FPSO mainly because of their longer period compared to the ordinary sea waves. In particular, the roll motion is largely amplified because the dominant period of swell is closer to the roll natural period than that of seas.