• 한국농공학회지
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• 제17권3호
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• pp.3795-3814
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• 1975

The purpoes of this thesis is to study the effect of the variation of the beginning date of the suspension of irrigation and the length of intermittent suspension period of irrigation in the paddy field on the growth and yield of rice, so as the provide a critical limit of saving irrigation water and an irrigation method to prevent drough damage in rice cultivation. In this experiment, the rice variety adopted was NONGRIM No.29. There were seven main test plot, each test plot having a different beginning date of the suspension of irrigation. A main test plot was susdivided into five small test plots, each having a different length of the suspension period of irrigation. The results obtained in this experiment are summarized as follows: 1. The number of tillers is controlled by the treatment of the suspension of irrigation, its beginning date being early of late. The reductive effects of beginning dates of suspension upon the number of tillers. investigated on July 30, are about 84% for the treatment suspended on July 8, 87% on July 12, and 92% on July 19, respectively, in comparison with the standard plot. However. the suspenion treatments after the foregoing dates does not affect the control of their numbers. On the other hand, the lengths of intermittent suspension periods influence highly on the number of tillers to be restrained considerably, the decrease ratio ranging from 91% to 80% Both treatments on dates and periods are so intermingled that the restraining effects of suspension periods become greater as the dates of its beginning are earlier. 2. The elongation of plant hieghts also restrained considerably by the longer periods and earlier dates of suspension treatments of irrigation. Especially, the effects of the lengths of suspension periods become more serious. 3. Heading dates are delayed by two to five days through the suspension treatments of irrigation. However, the heading stage ends almost on the same day without relation to the differences between the irrigation suspension treatments. In the test plot where the suspension date of irrigation comes after the young panicle forming stage, the heading stage ends one or two days later than in the standard test plot. 4. Both culm lengths and panicle lengths show significant differences in their values, i.e., their lengths are shorter, as the begining dates of irrigation suspension are earlier and the suspension periods are longer. 5. The earlier the beginning date and the longer the period of irrigation suspension, the less is the number of panicles per hill in comparison with the standard plot. 6. The earlier the beginning date and the longer the period of irrigation suspension, the higher is the significant difference in the number of kernels per panicle in comparison with that in the standard test plot, i.e., the less is the number of kernels per panicle. 7. The earlier the beginning date and the longer the period of irrigation suspension, the lighter are the weights of rough rice and straws per hill in comparison with those in the standard plot.

• Journal of Korean Dental Science
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• 제8권2호
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• pp.65-73
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• 2015

Purpose: Parathyroid hormone (PTH) therapy has drawn attention, as an alternative to anti-resorptive drugs since PTH accelerates bone density by anabolic action. The purpose of this study was to identify the effect of intermittent PTH administration on jaw bones of rat undergone bilateral ovariectomy. Materials and Methods: Nine female Sprague-Dawley rats were divided into three groups. PTH group was ovariectomized (OVX) to induce osteoporosis and PTH $30{\mu}g/kg$ was administered 1 week after the surgery. In OVX group, ovariectomy was performed and only vehicle was administered by subcutaneous injection 3 times per week. Control group was subjected to sham surgery. The animals were sacrificed 8 weeks after the surgery and specimens were obtained from ilium and upper and lower jaw bones. Histological investigation was carried out by using an optical microscope and micro-computed tomography was taken to examine structural property changes in each bone sample. Result: In the ilium, the bone volume ratio (bone volume/total volume, BV/TV) of PTH, OVX and control groups was $53.75%{\pm}7.57%$, $50.61%{\pm}12.89%$, $76.20%{\pm}5.92%$ (P=0.061) and bone mineral density (BMD) was $1.12{\pm}0.09$, $0.88{\pm}0.48$, $1.38{\pm}0.07g/cm^3$ (P=0.061). In the mandible, BV/TV of PTH, OVX and control groups was $64.60%{\pm}12.17%$, $58.26%{\pm}9.63%$, $67.54%{\pm}14.74%$(P=0.670) and BMD was $1.21{\pm}0.17$, $1.19{\pm}0.13$, $1.27{\pm}0.18g/cm^3$ (P=0.587). In the maxilla, BV/TV of PTH, OVX and control groups was $61.19%{\pm}8.92%$, $52.50%{\pm}11.22%$, $64.60%{\pm}12.17%$ (P=0.430) and BMD was $1.20{\pm}0.11$, $1.11{\pm}0.16$, $1.21{\pm}0.17g/cm^3$ (P=0.561). No statistically significant difference was found in any variables in all groups. Histological observation revealed that the ilium in OVX group demonstrated sparsely formed trabecular bones compared with other groups. However, upper and lower trabecular bones did not present significant differences. Conclusion: Intermittent administration of PTH appears to affect the microstructure of rat jaw bones, but statistical significance was not found. However, the measurements in this study partly implicated the possible anabolic effect of PTH in vivo.

• Geomechanics and Engineering
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• 제13권3호
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• pp.431-446
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• 2017

Rock bridges in rock masses would increase the bearing capacity of Non-persistent discontinuities. In this paper the effect of ratio of rock bridge surface to joint surface, rock bridge shape and normal load on failure behaviour of intermittent rock joint were investigated. A total of 42 various models with dimensions of $15cm{\times}15cm{\times}15cm$ of plaster specimens were fabricated simulating the open joints possessing rock bridge. The introduced rock bridges have various continuities in shear surface. The area of the rock bridge was $45cm^2$ and $90cm^2$ out of the total fixed area of $225cm^2$ respectively. The fabricated specimens were subjected to shear tests under normal loads of 0.5 MPa, 2 MPa and 4 MPa in order to investigate the shear mechanism of rock bridge. The results indicated that the failure pattern and the failure mechanism were affected by two parameters; i.e., the ratio of joint surface to rock bridge surface and normal load. So that increasing in joint area in front of the rock bridge changes the shear failure mode to tensile failure mode. Also the tensile failure change to shear failure by increasing the normal load.

• 전기학회논문지
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• 제57권3호
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• pp.494-500
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• 2008

This paper presents the analyzed result of the series arc fault current by using the discrete wavelet transform. The series arcing is caused by a loose connection in series with the load circuit. The series arc current is limited to a moderate value by the resistance of the device connected to the circuit, such as an appliance or a lighting system. The amount of energy in the sparks from the series arcing is less than in the case of parallel arcing but only a few amps are enough to be a fire hazard. Therefore, it is hard to detect the distinctive difference between a normal current and a intermittent arc current. This paper, presents the variation of the ratio of peak values and RMS values of the series arc fault current, and proposes the novel series arc fault detecting method by using the discrete wavelet transform. Loads such as a CFL lamp, a vacuum cleaner, a personal computer, and a television, which has the very similar normal current with the arc current, were selected to confirm the novel method.

• 한국미생물·생명공학회지
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• 제23권2호
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• pp.220-228
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• 1995

For polyhydroxyalkanoic acid (PHA) production, several microorganisms were isolated from sewage sludge. One of them, GB-77 strain, was chosen from its PHB/HV copolymer production on only fructose without cosubstrate. The isolated strain GB-77 was identified as the genus Alcaligenes. Optimal temperature and pH for cell growth were 36C and 6.8. Optimal medium composition was 10 g/l of fructose and 5 g/l of polypeptone, 1 $\times$ 10$^{-2}$M Na$^{2}$HP0$^{4}$, 1.3 $\times$ 10$^{-2}$M KH$^{2}$PO$^{4}$. To investigate the optimal condition for polyhydroxyalkanoic acid production two-stage culture technique was used; first stage for cell growth and second stage for PHA production on unbalanced growth conditions. Optimal conditions for high PHA production were C/N ratio 50, temperature 36$\circ$C and pH 6.8. To overcome fructose inhibition on cell growth, intermittent feeding fed-batch culture technique was used. Total cell concentration was 17.4 g/l with 9.1 g/l of PHA. The purified PHA was identified PHB/HV copolymer by NMR analysis.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.35-41
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• 2003

Propagation speeds of turbulent premixed flames have been measured in a pulsed-flame flow reactor which generates flames propagating in nearly isotropic turbulent flow field with U'/$S_L$ ranging from 1.2 to 5.3. The measurement involved a high-speed digital imaging at 1000 frames/second to capture the flame propagation motion. In addition to the flame speed measurements, flame perimeter ratio was measured for comparison. The observed flame propagation speed is high ranging from 5 to 20 times the laminar flame speed for the range of U'/$S_L$. The flames observed at extreme equivalence ratios exhibit intermittent propagation in that only a small fraction of ignited flame kernel resulted in full propagation of the flame. Also, at low equivalence ratios the flame speed decreased substantially even at high turbulence intensities.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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• pp.1223-1236
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• 2014

With the extension of wireless technology, vehicular ad hoc networks provide important services for the dissemination of general data and emergency warnings. However, since, the vehicle topology frequently changes from a dense to a sparse network depending on the speed of the moving vehicles and the time of day, vehicular ad hoc networks require a protocol that can facilitate the efficient and reliable dissemination of emergency messages in a highly mobile environment under dense or intermittent vehicular connectivity. Therefore, this paper proposes a new vehicular broadcast protocol, called BL-CAST, that can operate effectively in both dense and sparse network scenarios. As a low overhead multi-hop broadcast protocol, BL-CAST does not rely on the periodic exchange of beacons for updating location information. Instead, the location information of a vehicle is included in a broadcast message to identify the last rebroadcasting vehicle in an intermittently connected network. Simulation results show that BL-CAST outperforms the DV-CAST protocol in terms of the end-to-end delay, message delivery ratio and network overhead.

• 대기
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• 제29권5호
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• pp.615-626
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• 2019

To find any effects of precipitation climate on the forecast verification methods, we processed the hourly records of precipitation over South Korea. We examined their relationship between the climate and the methods of verification. Precipitation is an intermittent process in South Korea, generally less than an hour or so. Percentile ratio of precipitation period against the entire period of the records is only 14% in the hourly amounts of precipitation. The value of the forecast verification indices heavily depends on the climate of rainfall. The direct comparison of the index values might force us to have a mistaken appraisal on the level of the forecast capability of a weather forecast center. The size of the samples for verification is not crucial as long as it is large enough to satisfy statistical stability. Our conclusion is still temporal rather than conclusive. We may need the amount of precipitation per minute for the confirmation of the present results.

• 한국항공우주학회지
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• 제35권5호
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• pp.426-437
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• 2007

초음속 흡입구는 설계점에서 안정된 작동을 보이지만 탈설계점에서는 흔히 버즈라고 불리는 공력 불안정성에 직면하게 되고, 결과적으로 현저한 엔진 성능의 저하를 초래하게 된다. 버즈의 일반적인 특성을 파악하기 위해 1단 꺽임각을 갖는 외부 압축식 축대칭 흡입구를 이용하여 실험적, 수치적 연구를 수행하였다. 본 연구를 통해, 흡입구 목에서 박리에 의한 흡입구 질식이 버즈의 주요 원인임을 밝힘으로써 버즈 현상의 메커니즘을 파악하였다. 여러 면적비율에 따라 간헐적 버즈와 연속적 버즈가 관찰되었고 그 천이과정이 파악되었다. 면적비율이 감소할수록 버즈 주파수가 증가하였으나, 각 면적비율에서 흡입구 내 모든 위치의 압력 진동 주파수는 동일한 특성을 갖는다.

• 대한전자공학회논문지
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• 제19권6호
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• pp.84-90
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• 1982

본 논물에서는 HCDM(hybrid companding delta modulation)을 사용하여 음성을 부호화할 때, 음성의 간헐성을 이용하여 전송속도를 줄이거나 잡음에 대한 신호비(SQNR)을 증가시키는 연구를 하였다. 음성부분과 묵음(silence)부분을 식별하는 판별기를 이용하여 음성의 묵음부분을 검출하며, 이때 음성부분에 대해서는 HCDM 부호화를 행한다. 음성을 5msec 간격으로 검사하여, 그때 검출되는 묵음부분에 대해서는 그 구간이 묵음이라는 정도만을 전송하며, 수신단에서는 이 정보를 이용하여 묵음부불을 재생한다. 그런데 HCDM 부호기는 2진 신호를 일정한 속도로 또 동기적으로 전송하기 때문에, 버퍼 (buffer)를 사용해야 하며 또한 그것을 효율적으로 제어해야 한다. 음성을 부호화할 때, 묵음검출 기능을 이용하는 HCDM 부호기를 사용하면, 재래의 HCDM 보다 잡음에 대한 신호비를 6dB 만큼 증가시킬 수 있거나, 전송속도를 1/3가량 줄일 수 있다.In this paper we exploit the use of the intermittent property of speech to reduce the transmission rate or to increase signal-to-quantization noise ratio (SQNR) in coding speech by hybrid companding data modulation (HCDM). In this scheme we detect silence in speech by a speech/silence discriminator. HCDM coding is done only for speech portion. For silence that is detected in evert block of 5 ms, only the information indicating that the Since the HCDM coder transmits bina교 signal synchronously at a fixed rate, the use of a buffer and its efficient control is essential. By using the HCDM with silence detection in coding speech, we could improve SONR by as much as 6 dB over the conventional HCDM or reduce the transmission rate by one third of the HCDM rate.