Earticle

이 연구는 수중 외발젓기 운동 시 수심과 속도에 따른 하지근과 몸통근의 근활성도를 분석하여 균형을 유지하기 위한 근육 간 협응 기전과 수중에서 평형성 훈련 시 기초자료를 제공하고자 하였다. 연구대상자는 저항운동 경력 6개월 이상의 남자 대학생 9명을 선정하였으며, 3가지 수심과 속도조건에 따라 수중 외발젓기 운동을 총 9회 실시하였다. 운동 중 하지근과 몸통근의 근전도를 측정하였으며, 측정된 변인들은 반복측정 이원변량분석으로 분석하였다. 그 결과 젓는발 의 속도가 빨라질수록 하지근과 몸통근에서 근활성도가 유의하게 높게 나타났으며(p=.001), (p=.019, p=.001), 한편 수심 조건에서는 수심이 낮아질수록 디딤발 종아리 근육의 근활성도가 유의하게 높게 나타났고(p=019, p=.001), 배곧 은근은 허리수심에서 근활성도가 유의하게 높게 나타났다(p=.043). 따라서 이 연구는 수중에서 평형성 향상을 위한 운 동 시 동작의 속도를 증가시켜 운동의 강도를 조절할 수 있을것으로 판단되며, 한편 수심에 따라서는 발목 주변 근육의 강화를 위해 단계적으로 수심을 낮추는 것이 효과적이고, 몸통 주변 근육의 강화를 위해서는 허리수심이 가장 적합할 것으로 판단된다.

The purpose of this study was to analyze muscle activity of lower extremity and trunk muscles according to water depth and speed during single leg swing aquatic exercise, and to provide a mechanism for intermuscular coordination to maintain balance and basic data for balance training in water. The subjects of this study were 9 males with more than 6 months of resistance training experience, and a total of 9 experiment were performed according to 3 water depths and speed conditions. EMG was measured during exercise and the measured variables were analyzed with Repeated measurements two-way ANOVA. As a result, as the speed of rowing foot increased, the muscle activity was significantly higher in the lower extremity and trunk muscles(p=.001), (p=.019, p=.001). On the other hand, the lower the water depth, the higher the calf muscle activity of the stepping foot(p=019, p=.001), and the higher the rectus abdominis muscle activity at the waist(p=.043). Therefore, this study is thought to be able to control intensity of exercise by increasing the speed during exercise to improve balance in water, and in the water depth condition, it is appropriate to gradually lower the water depth for training the muscles around the ankle, and it is judged that the waist depth is the most suitable for training the trunk muscles.

본 연구는 마이크로 사이펀 수차의 성능에 블레이드 수가 미치는 영향을 실험적으로 분석하였다. 블레이드 수는 2개에서 6개까지 변화시켰으며, 수로의 유입 유속, 상부 수조의 수심, 회전 속도, 토크, 전류, 전압 등의 주요 성능 지표를 동일한 조건에서 측정하였다. 그 결과, 블레이드 수가 2개에서 5개로 증가함에 따라 상부 수조의 수심은 상승하고 유입 유속은 감소하는 경향을 보였다. 이 범위 내에서 전압, 회전 속도, 토크, 전류는 전반적으로 증가하는 추세를 나타냈다. 그러나 블레이드 수가 5개를 초과할 경우 성능 향상이 둔화했으며, 블레이드 수가 5개일 때 수차의 전기 출력이 최적화되는 것으로 나타났다.

This study experimentally investigates the effect of the number of blades on the performance of a micro siphon turbine. The number of blades was varied from two to six, and key performance indicators such as inlet flow velocity at the channel, water depth in the upper tank, rotational speed, torque, current, and voltage were measured under the same conditions. The results show that as the number of blades increased from two to five, the water depth in the upper tank rose, while the inlet flow velocity decreased. During this range, voltage, rotational speed, torque, and current generally exhibited increasing trends. However, beyond five blades, performance gains diminished, indicating that the turbine's electrical output was optimized when equipped with five blades.

본 연구는 물새의 주요서식지인 한강의 물리적 구조 변화특성에 대한 시계열적분석을 실시함으로써 향후 물새서식지 복원 등 관리를 위한 기초자료를 구축하고자 하였다. 분석은 한강 전체 497.5km 중 서울 시내를 관통하는 구간인 상류부 팔당대교에서부 터 하류부 행주대교까지 총 41.5km을 대상으로 하였고, 1975년을 기준하여 한강의 제외지를 대상으로 하였다. 토지이용분석 결과, 1975년에는 퇴적지(22.7%), 수면(20.7%)을 포함하여 주변으로 시가화지역(16.9%), 밭(16.2%), 논(15.9%)이 주요 유형이 었는데, 이후 대부분 지역의 토지이용을 위해 하천권역 내부로 간선도로가 조성되었고 수면 확대를 위해 수중보가 건설되면서 1985년에는 하천의 역할을 상실한 제내지(51.7%)가 급격히 증가하였다. 수면(32.8%)의 증가 또한 두드러졌으며, 제방의 축조와 수중보 조성 이후에는 토지이용의 급격한 변화보다는 조금씩 이용지역의 면적이 늘어나고 상대적으로 자연지역이 줄어드는 경향을 보였다. 2005년에는 제내지가 차지하는 비율이 57.7%까지 증가하였으며 수면은 33.3%로 증가하였다. 호안길이 는 2005년 기준 1975년 대비 10.9% 감소하였으며, 자연호안의 길이는 91.5% 감소하였다. 반면 수심은 1.46m 증가한 것으로 분석되었다. 지난 30년간의 한강의 물리적 구조 변화의 흐름을 종합하면 1980년대 이전까지는 대규모 건설공사로 인한 수변구역의 축소와 수면부의 확장이 주로 진행되었으며 이후에는 호안의 인공화가 주로 진행된 흐름을 확인할 수 있었다. 서식처 측면에서 한강은 과거 다양한 서식환경을 유지하던 곳에서, 현재는 소수 물새류를 위한 단순한 서식지로 변화되어 서식처 다양성을 위한 적극적 개선이 필요한 것으로 판단되었다.

This study aims to set up the basic data to manage the waterfowl habitat through the analysis of the changes of physical structure according to the time series of Hangang(Riv.) as water birds' habitat. Study area was 41.5km in length from Paldang bridge to Hangju bridge. during total length of 497.52km and horizontal boundary was based on the protected lowland in year 1975. As the analysis result of land use from the center of water to adjacent road to the river, ratio of year 1975 was in order of sedimentary land(22.7%), surface water(20.7%), built-up area(16.9%), field(16.2%), paddy field(15.9%), and afterwards most of the areas were changed through the construction of arterial highway and submerged weir in order to use Hangang(Riv.). In year 1985, the area ratio of protected lowland(57.8%) and surface water(32.8%) dramatically increased. After construction of river bank the recreational areas continually increased and relatively natural areas decreased. In year 2005, the area ratio of protected lowland was enlarged to 57.6% and surface water also to 33.3%. While the length of both riversides and naturalness decreased by 10.9%, 91.5% respectively in year 2005 compared to year 1975, the depth of water increased by 1.46m. Comprehensively, the flow of changes by physical structure in Hangang(Riv.) for 30 years was divided into two periods. The main characteristics in the first period were decrease of riverside area and enlargement of the surface water through the massive construction before middle of year 1980, and afterwards revetments were intensively artificialized with changes of land use for amusement area. In terms of water fowl habitat, Hangang(Riv.) which previously had various types of habitat condition was changed into simplified habitat for few of species, and the active improvement apporach was needed for habitat diversity.

본 연구는 중량식 수위계 개발을 위한 기초 실험이다. 무게추는 밀도 1.1–1.35g/cm3의 PVC(Polyvinyl Chloride)를 이용하여 다양한 크기의 원통형으로 제작하였다. 무게추의 직경은 5, 6, 7 그리고 8cm로 여러 종류이며, 무게추의 길이는 20cm와 30cm 2종류이다. 무게추의 중량은 로드셀을 이용하여 측정하였 으며, 증가한 수심에 대해 반대로 감소하는 중량변화의 관계를 조사하였다. 또한, 무게추와 외부케이스 사이의 간격 조정을 통해, 물의 표면장력 72.75dyne/cm(20℃)에 의한 중량관측의 오류가 작용하지 않는 거리를 확인하였다. 결론적으로, 무게추의 직경이 크고, 높이가 작을수록 수심과의 상관성이 좋다는 사실을 확인하였다. 또한 무게추 오염 및 제작 정밀도를 고려할 때 무게추와 외부케이스의 간격은 1cm 이상의 여유 공간이 필요하다고 판단하였다. 부력식 침수심계는 최대한 무게추 직경을 줄이고, 외부 케이스와의 충분한 간격이 필요하다.

This study is one of the basic experiments for the development of a weight type water level gauge. The weights are made of polyvinyl chloride (PVC) with a density of 1.1-1.35 g/cm3, in cylindrical shapes of different sizes. The weights come in different diameters: 5, 6, 7, and 8 centimeters, and two different lengths: 20 and 30 centimeters. The weight of the weights was measured using a load cell and the inverse relationship of weight change with increasing depth was investigated. Also, by adjusting the gap between the weight and the outer casing, the distance at which the error in the weight observation due to the surface tension of water of 72.75 dyne/cm (20℃) was not affected was determined. In conclusion, we found that the larger the diameter of the weight and the smaller the height, the better the correlation with the water depth. Also, considering contamination of the PVC weight and manufacturing precision, it was determined that the space between the PVC weight and the external case required more than 1cm. A buoyancy type water level gauge requires the smallest possible weight diameter and sufficient clearance.

When the PDD (percentage depth dose) in the megavoltage beams is measured in the water phantom, the polarity and ionrecombination effects of ionization chambers with depth in water are not usually taken into consideration. We try toinvestigate if those variations with depth should be taken into consideration or could be ignored for the thimble type semi-flex ionization chamber (PTW 31010TM, SN 1551). According to the recommendation of IAEA TRS-398, the 4 representativedepths of ds, dmax, d90and d50were used for the electron beams. For the photon beams, the 4 depths were arbitrarily chosenfor the photon beams, which were ds, dmax, d10and d20. For the high energy photon beam both polarity and ion recombinationfactors of the chamber with depth in water gives the good agreements within the maximum ±0.2%, while the Cpols withdepth came within the maximum ± 0.4% and the CIRs within the maximum ±0.6% in every electron beam used. This studyshows that PDI (percentage depth ionization) could be a good approximation to PDD for the chamber used.

호소에서 취수되는 상수원수의 수질은 수심에 따라 수질이 서로 다르게 나타날 수 있으며 이때 가장 좋은 수질을 가진 수심으로부터 물을 취수할 수 있다면 정수비용의 절감뿐 아니라 수돗물의 안전성을 더 높일 수 있을 것이다. 호소에서는 조류발생, 강우, 수층전도 등의 원인으로 이상수질이 나타날 수 있고 이에 대한 대응조치의 일환으로 수심선택 취수가 실 시되고 있다. 본 연구에서는 이러한 선택취수는 취수장의 조류증가, 탁도증가, 망간증가 시에 적용 가능한 것으로 나타났 다. 또한 취수수심 선택과 연관된 탁도, EC, Chl-a 등 14개 항목들을 설정하여 각각에 대한 판단기준의 책정뿐 아니라 이 들 전체를 상호 연계시켜 본 연구에서 마련한 룰 기반 시스템은 최적의 취수수심 선택 시에 유용한 의사결정도구가 될 수 있다

The water quality of raw water taken from lakes can vary depending on the water depth, and if water can be intaked from the water depth with the best water quality, it will not only reduce the cost of water purification but also increase the safety of tap water. In lakes, abnormal water quality can occur due to algal occur, rainfall, and water layer turn-over, and as a countermeasure for these problems, water depth-selective intake is being implemented. In this study, it was found that this selective intake can be applied when algae, turbidity and manganese increase in the raw water. In addition, in this study, 14 items such as turbidity, EC, Chl-a, etc. related to the selection of water intake depth were set, the criteria for each item were established, and a rule-based system was developed by interconnecting all items. Therefore, the system can be a useful decision-making tool for choosing the optimal water depth.

서울역사박물관에서 소장하고 있는 운현궁 석조수조의 재질은 미세층리와 여러 조의 점토질 세맥이 발달된 석회질 대리암이다. 이 수조에는 전면에 걸쳐 균열이 나타나며 흑색변색이 심하여 보존처리가 필수적이다. 수조에서 나타나는 수평 및 수직방향의 균열은 상대적으로 결합력이 낮은 층리부분과 세맥이 형성된 곳에 집중적으로 발달되어 있다. 수조 표면을 변색시킨 물질은 유기물의 침착과 고사로 인해 발생한 탄소성분으로 밝혀졌다. 초음파 측정결과, 운현궁수조를 구성하는 암석의 물성은 약한풍화단계(SW)로 나타났으나 전체적인 표면 풍화는 구성광물의 입상분해가 발생할 정도로 심각하다. 또한 이 수조의 안정성에 가장 큰 위협요인인 33조에 달하는 균열의 깊이는 석조의 최대 두께인 60cm를 완전히 관통한 것도 있으며, 최소깊이는 9mm로 산출되었다. 점토질 세맥을 따라 발생한 균열중에는 수조의 외벽과 내벽을 관통한 개방형 균열도 있으며 층리를 따라 생성된 균열은 대부분 20~30mm의 심도를 나타내었다. 이 결과는 운형궁수조의 장기적인 보존관리에 중요한 자료로 활용될 것이다.

The Unhyungung Water Container in the possession of the Seoul Museum of History in Korea is consisted of a calcareous marble developed laminated bedding and numerous argillaceous veinlets. This monument should need to conservation treatment because of black discoloration and seriously numerous cracks. Vertical and horizontal cracks in the monument are developed following stratification and argillaceous veinlets that are relatively low coherence between the rock materials. We have proved that the material inducing discoloration on the surface is carbon which is formed by deposited organic matters. As the result of the ultrasonic measurements, although highly surface weathering degree, the physical properties of the Unhyungung Water Container is confirmed slightly weathered state. The depths of cracks in the monument are calculated at maximum 60mm in some cracks completely penetrating into the wall and at minimum 9mm in the other crack. The cracks, developed following veinlet, are revealed that there penetrate from an outer wall to an inside wall for the monument. And most depths of cracks, developed following stratification, are calculated 20 to 30mm. This result will offer a significant data for conservation of the Unhyungung Water Container.

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.

This study aimed to investigate the immediate physiological responses, including heart rate, blood pressure, and rate pressure product (RPP), following squat exercises performed at three water depths (ground, knee depth, waist depth) and two speed conditions (60bpm speed, Max speed). The participants consisted of 10 men in their 20s with over 6 months of resistance exercise experience. For the 60bpm speed squats, participants performed 30 repetitions in 1 minute at a rate of 2 seconds per repetition, while for Max speed squats, they performed at Max speed without a set limit on the number of repetitions for 1 minute. All experiments were conducted with a random assignment. The study results showed that immediately after the aquatic squat exercise, the average heart rate, blood pressure, and cardiac load were higher in the order of knee depth, ground level, and waist depth at both 60bpm speed and Max Speed. At 60bpm speed, the heart rate was higher in the order of ground level, knee depth, and waist depth. Overall, exercise in an aquatic environment was considered to impose relatively lower physical burden compared to land-based exercise. Therefore, it is suggested that depending on individual fitness levels and exercise goals, appropriately combining aquatic exercise, which imposes lower immediate physiological burden, and land-based exercise may lead to safer and more effective exercise methods.

The purpose of this study was to investigate the difference in the number of repetitions and the change in electromyographic response during the maximum speed squat exercise according to the depth conditions and the maximum speed squat exercise according to the time of each depth. Ten men in their 20s were selected as subjects and the maximum speed squat was performed for one minute in three environmental conditions (ground, knee depth, waist depth). We found that the number of repetitions according to the depth of water showed a significant difference, and as a result of the post-mortem comparison, the number of repetitions was higher in the ground condition and the knee depth than in the waist depth. And the muscle activity of rectus abdominis, erector spinae, rectus femoris, biceps femoris was increased during ground squat exercise, activity of all muscle was decreased during knee depth squat exercise, and activity of rectus abdominis, erector spinae, biceps femoris, tibialis anterior, gastrocnemius was decreased during waist depth squat. In conclusion, muscle activity of lower extremities during squat exercise in underwater environment can be lowered as the depth of water is deep due to buoyancy, but muscle activity of trunk muscles can be increased rather due to the effect of viscosity and drag.

이 연구는 수심에 따른 공기소모량의 변화를 인간의 특성 및 이론값과의 비교·분석하였다. 실험 결과는 다음과 같다. 첫째, 실험대상자 A·B는 수심에 따라 각각 비슷한 상승률을 보였다. 둘째, 실험대상자 C는 수중 25m에서 공기 소모량의 상승률이 유의하게 높게 나타났는데, 그 이유는 깊은 수심의 수압에 신체가 민감하게 반응하여, 호흡이 다 른 참여자보다 다소 빨라 공기소모량을 증가시킨 것으로 보인다. 셋째, 실험대상자 D·E는 공기소모량이 전반적으로 유의하게 낮게 나타났다. 이는 D와 E의 연령이 각각 37세, 35세로 실험대상자 중 가장 젊고, 체력이 강건하며, 군 복 무 당시 해상의 심해 잠수경험이 풍부하여 나타난 결과로 보인다. 넷째, 실험대상자 분당 평균 공기소모량은 수면과 비교하여 수중 5m는 약 1.45배, 수중 10m는 약 1.85배, 수중 20m는 약 2.8배로 분당 공기소모량이 증가하였다. 이는 구조대원 각자의 경험과 체력, 신체가 수중에서 적응하는 정도의 차이, 그리고 수중 호흡법이 달라서 나타난 결과로 보인다. 마지막으로 실험 평균값과 이론값의 차이는 실험대상자 구조대원 5명 각자의 경험과 체력, 신체가 수중에서 적응하는 정도의 차이 및 수중 호흡법에 따라 이론값보다 많거나 적게 공기를 소모하여서 나타난 결과로 보인다.

This study compared and analyzed the change of air consumption according to water depth with human characteristics and theoretical values. The experimental results are as follows. First, subjects A and B showed similar rise rates depending on the water depth. Second, subject C had a significantly higher rate of increase in air consumption at 25m underwater because the body responded sensitively to deep water pressure, which increased air consumption because breathing was faster than other participants. Third, the subjects D and E showed significantly lower overall air consumption. D and E were 37 and 35 years of age, respectively, the youngest, strongest and most experienced in deep sea diving at the time of military service. Fourth, the average air consumption per minute of the test subjects increased from 5m in water to 1.45 times, 10m in water to 1.85 times, and 20m in water to 2.8 times. This seems to be a result of different experiences, physical fitness, the degree of adaptation of the body to underwater, and different breathing techniques. Lastly, the difference between the experimental average value and the theoretical value appears to be the result of using more or less air than the theoretical value depending on the experiences and physical strength of each of the 5 rescuers, the degree of adaptation of the body underwater, and the method of underwater breathing.

The high rate algal ponds (HRAP) powered and mixed by a paddlewheel have been widely used for over 50 years to culture microalgae for the production of various products. Since light incidence is limited to the surface, water depth can affect microalgal growth in HRAP. To investigate the effect of water depth on microalgal growth, a mixed microalgal culture constituting three major strains of microalgae including Chlorella sp., Scenedesmus sp., and Stigeoclonium sp. (CSS), was grown at different water depths (20, 30, and 40 cm) in the HRAP, respectively. The HRAP with 20cm of water depth had about 38% higher biomass productivity per unit area ($6.16{\pm}0.33g{\cdot}m^{-2}{\cdot}d^{-1}$) and required lower nutrients and energy consumption than the other water depths. Specifically, the algal biomass of HRAP under 20cm of water depth had higher settleability through larger floc size (83.6% settleability within 5 min). These results indicate that water depth can affect the harvesting process as well as cultivation of microalgae. Therefore, we conclude that water depth is an important parameter in HRAP design for mass cultivation of microalgae.

This study introduces the navigational environment database(DB) compiling water depth, sediment type and marine managed areas (MMAs) in coastal waters of South Korea. The water depth and sediment data were constructed by combining their sparse points of electronic navigation chart and survey data with high spatial resolution using the inverse distance weighting and natural neighbor interpolation method included in ArcGIS. The MMAs were integrated based on all shapefiles provided by several government agencies using ArcGIS because the areas should be used in an emergency case of ship. To test the validity of the constructed DB, we conducted a test application for grounding and anchoring zones using a ship accident case. The result revealed each area of possible grounding candidates and anchorages is calculated and displayed properly, excluding obstacle places.

This paper describes the design and implementation of a practical underwater positioning system, which is applicable for shallow water depth conditions. In this paper, two strategies are used to enhance the navigation performance. First, a low-cost acoustic-ranging-based precise navigation solution for shallow water is designed. Then, the outlier rejection algorithm is introduced by designing a velocity gate. The acoustic-ranging-based navigation is implemented by modifying the long base line solution. To enhance the tracking precision, the outlier rejection algorithm is introduced. The performance of the developed approach is evaluated using experiments. The results demonstrate that precise shallow water depth navigation can be implemented using the suggested approaches.

A potential flow approach is used to develop a method and an associated computer program for floating marine structures of general configuration in wave of all water depths with arbitrary heading. It computes the total force distributions and six degrees-of-freedom motion. The hydrodynamic-force equations and derived become identical under certain assumptions to the equations commonly used by the offshore industry, and the two methods are compared in detail. The computed motions of all six degree agree quite well with model-scale and full-scale experimental data for two typical semisubmersible drilling rigs in finite-depth water. Also the presented motion computations are more accurate than a previous work by the second approach. The present computations use experimentally validated or determined values of frequency-dependent hydrodynamic coefficients with the effects of the free surface and both finite and infinite water depths. The present method generates sufficient computation accuracy to use for practical design applications.

The aim of this study is to develop a simplified formula for added mass coefficients of a two-dimensional floating body moving vertically in a finite water depth. Floating bodies with various sectional areas may represent simplified structure sections transformed by Lewis form, and can be used for floating body motion analysis using strip theory or another relevant method. Since the added mass of a floating body varies with wave frequency and water depth, a correction factor is developed to take these effects into account. Using a developed two-dimensional numerical wave tank technique, the reference added masses are calculated for various water depths at high frequency, and used them as basis values to formulate the correction factors. To verify the effectiveness of the developed formulas, the predicted heave added mass coefficients for various wetted body sections and wave frequencies are compared with numerical results from the Numerical Wave Tank (NWT) technique.