• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.501-506
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• 2002

The unbonded prestressed concrete(PSC) members exhibit very different structural behavior from that of bonded PSC members because of having different tendon stress increment. Recently, AASHTO changed the provision of ultimate tendon stress with unbonded tendons, because some researches tried to improve the provision of ultimate tendon stress with unbonded tendons. The purpose of the present study is to compare various Codes with the ultimate failure stresses of prestressing(PS) steels for the unbonded PSC members. To this end, Some national Codes have been collected and analyzed. A series of major influencing variables have been included in the analysis. It was found that the span-depth ratio, neutral axis depth-effective depth ratio, concrete compressive strength, effective prestress, and prestressing steel ratio have great influence on the ultimate failure stress of PS steel in unbonded PSC members. The Comparison indicates that existing formulas including ACI and domestic Code's equations shows some unwarranties. The present study allows more realistic analysis and design of prestressed concrete structures with internal unbonded tendons.

• 한국농공학회논문집
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• 제48권2호
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• pp.69-76
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• 2006

Fallow paddy areas have been increased due to the import of cheap agricultural product, and the unbalance between farming cost and rice price since 1990. The increasing fallow paddy area needs to be protected from the devastation by weed breeding for the re-cultivation. In this study, two fallow paddy fields managed with different water depth were selected for monitoring and analysing of water quality, water balance and plant body change. The managed fallow paddy fields were more effective in water quality purification and plants growth control than non-managed fallow paddy fields. And the fallow paddy field managed with some degree of water depth was the most effective field in terms of weed control.

• 한국지반공학회논문집
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• 제22권1호
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• pp.25-34
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• 2006

본 연구에서는 비교적 높은 초기 유효응력을 가진 지반구조물의 액상화연구에 사용된 동적 원심모형실힘결과를 이용하여 유효응력모델검증에 관한 연구를 수행하였다. 원심모형 지반은 최대 유효응력 380kPa를 가진 충분히 포화된 느슨한 Nevada 모래 지반으로 구성되었으며, 수치해석에서는 1차원의 기둥형태로 가정하였다. 수치해석에 이용한 두 종류의 원심모형실험에서는 상당한 깊이(37m 및 22m)까지도 액상화가 발생하였으나, 깊이에 따른 액상화발생 경향은 경험적 액상화 평가방법과 상반된 결과를 보였다. 즉, 원심모형실험에서 계측된 과잉간극수압을 기준으로 해석하였을 때, 액상화는 모형지반의 윗부분에서 먼저 발생한 후 점차적으로 아랫부분으로 이동함을 알았다. 이와 같은 실험결과는 수치해석에서 비교적 잘 예측된 것으로 판단되었다 원심모형 지반의 초기 포화도와 원심력 증가에 따른 지반의 상대밀도 증가가 액상화모형실험의 수치해석에서 중요한 역할을 함을 알 수 있었다.

• 한국수자원학회논문집
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• 제31권3호
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• pp.269-277
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• 1998

본 연구에서는 수리실험을 실시하여 만곡부의 흐름특성과 만곡부에서의 교각 주위 국부세굴형상, 최대 국부세굴심 등을 분석하였다. 또한, 기존의 세굴보호공법 중 원환에 의한 보호공법을 만곡부에 적용하여 세굴감소효과를 분석하였다. 180' 만곡수로에 대해 이동상 실험결과 본 실험조건에서는 최대 횡방향 하상경사가 150' 단면에서 발생하였으며, 원환에 의한 세굴감소효과는 유로 직선부에서 최대 40%, 만곡부에서는 150' 단면 외측의 경우 최대 44%의 감소효과를 보였다. 폭이 교각폭에 2배인 원환에 대하여 실험한 결과, 유로 직선부에서는 원환을 .02h(여기서 h는 수심)만큼 하상저면에 설치하였을 때 가장 효과적이었으며, 유로 만곡부에서는 0.1h 만큼 하상저면에 설치하였을 때 가장 효과적이었다.

• 한국농공학회논문집
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• 제63권3호
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• pp.75-85
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• 2021

This study evaluated variations in the paddy rice water demand based on the continuous changing in rice transplanting period and ponding depth at the four study paddy fields, which represent typical rice producing regions in Korea. Total 7 scenarios on rice transplanting periods were applied while minimum ponding depth of 0 and 20 mm were applied in accordance with maximum ponding depth ranging from 40 mm to 100 mm with 20 mm interval. The weather data from 2013 to 2019 was also considered. The results indicated that the highest rice water demand occurred at high temperature and low rainfall region. Increased rice transplanting periods showed higher rice water demand. The rice water demand for 51 transplanting days closely matched with the actual irrigation water supply. In case of ponding depth, the results showed that the minimum ponding depth had a proportional relationship with rice water demand, while maximum ponding depth showed the contrary results. Minimum ponding depth had a greater impact on rice water demand than the maximum ponding depth. Therefore, these results suggest that increasing the rice transplanting period, which reflects the current practice is desirable for a reliable estimation of rice water demand.

• International Journal of Internet, Broadcasting and Communication
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• 제16권2호
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• pp.169-178
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• 2024

This study aimed to investigate the effects of water depth and speed on the activation of lower muscles during squat exercises, utilizing electromyography(EMG). It involved ten male participants in there. Participants performed 30 squats over a minute at a speed of 60bpm and maximum speed squats until exhaustion within a minute. The Integrated electromyography(iEMG) readings for the rectus femoris showed statistically significant differences due to water depth and speed, with a significant interaction effect between depth and speed during squat exercises. The iEMG readings for the biceps femoris also showed statistically significant differences, with a significant interaction effect between depth and speed during squat exercises. The iEMG readings for the gastrocnemius showed statistically significant differences according to water depth and speed. However, the interaction effect of water depth and speed during squat exercises did not show a statistically significant difference. In contrast, the iEMG readings for the tibialis anterior demonstrated statistically significant differences, with a statistically significant interaction effect during squats. These findings suggest that water depth and speed positively influence the activation patterns of lower muscles. Therefore, appropriately tailored aquatic exercises based on water depth for individuals with musculoskeletal discomfort, including the elderly or those with physical impairments, can effectively reduce physical strain and enhance balance, as well as physical and perceptual aspects. It is concluded that such exercises could provide a safer and more effective method of exercise compared to ground-based alternatives.

• Journal of Computational Design and Engineering
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• 제3권3호
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• pp.191-197
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• 2016

Since 3D measurement technologies have been widely used in manufacturing industries edge detection in a depth image plays an important role in computer vision applications. In this paper, we have proposed an edge detection process in a depth image based on the image based smoothing and morphological operations. In this method we have used the principle of Median filtering, which has a renowned feature for edge preservation properties. The edge detection was done based on Canny Edge detection principle and was improvised with morphological operations, which are represented as combinations of erosion and dilation. Later, we compared our results with some existing methods and exhibited that this method produced better results. However, this method works in multiframe applications with effective framerates. Thus this technique will aid to detect edges robustly from depth images and contribute to promote applications in depth images such as object detection, object segmentation, etc.

• 한국농공학회지
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• 제17권4호
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• pp.3991-4000
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• 1975

It is the aim of this study to investigate the influence of the factors in the sprayer nozzle for the travelling distance and to get nozzle design data in relation to the nozz1e with and without swirl plate. The factors of sprayer nozzle are composed of the spraying pressure, the helical angle of swirl plate, the helical groove depth of swirl plate, the distance of vortex chamber the slope of nozz1e cap, the curvature of nozzle cap and the hole diameter of nozz1e cap. The travelling distance and the size of sprayed particle are experimeted indoors by the factorial arrange-ment according to the 5 each level of the above factors. The results of this stupy are summarized as follows; 1. In the nozzle with swirl p1ate there were remarkable significance among factors each other, while without swirl plate were no significance. 2. The helical angle and groove depth in the nozzle with swirl plate were the highest effective factors. The effect of helical angle was very remarked in the quadratic curve with minium value. 3. The correlation betweenthe travelling distance and the sprayed particle size was no high and under 250 micron in the case with swirl plate, and there was higher correlation in the case without swirl plate. 4. The new ideal development of the swirl plate using of the most effective helical angle and groove depth will probably show the possiblities to make effective travelling distance over 8 meters and more over and to make average particle diameter under 300 micron.

• 한국농공학회논문집
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• 제51권1호
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• pp.33-39
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• 2009

A number of fallow paddies field continues to increase because of adverse agricultural circumstance such as upsurge income of foreign products, increase of labor costs in local community, imbalance between productivity and profitability etc. Such fallow paddies are necessary to be protected against weeds and trees. If fallow paddies are not managed, it will be devastated and needed cost for re-cultivation. Therefore, management of gradually increased fallow paddy fields should be conducted. In this study, the effect of plants growth inhibition and water quality purification through the control of flood in fallow paddy were examined in an experimental field. The managed and unmanaged fallow paddies through the control of water depth were constructed in the experimental field. The monitoring was conducted from 2005 to 2007. As the result, the managed fallow paddies were more effective than the unmanaged ones on the growth inhibition and water purification. In addition, when the fallow paddy is managed with regular water depth, it was the most effective in the plants growth inhibition.

• Journal of Periodontal and Implant Science
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• 제39권3호
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• pp.375-381
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• 2009

Purpose: Root resection can be a valuable procedure when the tooth in question has a high strategic value. The prognosis of root resection has been well documented in previous studies, but the results focused on the palatal root resection have not been discussed in depth. I represent here the short term effectiveness of palatal root resection of maxillary first molars. Methods: Palatal root resection was performed on maxillary first molars of three patients. All the palatal roots were floating state on the radiographic finding and showed full probing depth and purulent exudation at initial examination. Reduction of palatal cusp and occlusal table was performed concomitantly. Endodontic therapy was completed after root resection. Results: Compromised maxillary first molars were treated successfully by palatal root resection in 3 cases. The mobility of resected tooth was decreased a little bit. The probing pocket depth of remaining buccal roots was not increased compared to initial depth. All the patients satisfied with comfort and cost effective results and the fact they could save their natural teeth. Conclusions: Within the above results, palatal root resection is an effective procedure treating compromised maxillary first molar showing advanced palatal bone loss to root apex with or without pulp involvement when proper case selection is performed.