• Korean Chemical Engineering Research
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• 제59권2호
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• pp.276-280
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• 2021

왕복 요동 교반조의 액체 표면에서의 산소 전달 속도에 대해 연구하였다. 왕복 요동 교반조의 소요 동력은 선회요동 교반조와는 달리 요동 주파수에 비례하지 않았으며, 교반조 내의 유동양상이 선회요동의 선회류와는 다른 좌우 물결류인 관계로 어떤 진동수에서 갑자기 액면이 크게 흔들리며 움직이는 양상을 보이며. 3 s-1 이상의 요동 주파수부터는 소요 동력이 선회요동 교반조보다 적어지는 등 요동 주파수가 소요 동력에 미치는 영향은 매우 복잡하였지만, 생성되는 회전류의 범위에서의 왕복 요동 교반조 소요 동력은 회전 요동 교반조에 대해 보고된 식으로 상관시킬 수 있었다. 왕복요동 교반조에서의 kLa (물질이동 용량계수) 역시 교반 소요 동력이 단순한 형태로 소비되지 않았기 때문에 주파수의 증가에 따라 선형으로 증가하는 선회요동 교반조의 kLa와는 달리 복잡한 형태로 증가하였다. 왕복요동 교반의 kLa가 선회요동 교반의 kLa 보다 컸으며, kLa 값이 커질수록 그 차이도 급격히 커졌다. 결과적으로 왕복 요동에서의 산소 전달 속도는 회전 요동보다 컸으며, 단위 부피당 소요 동력과 상관시킬 수 있었다.

• Fisheries and Aquatic Sciences
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• 제18권3호
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• pp.325-332
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• 2015

An active stimulating method for juvenile fishes to drive escaping from mesh of the codend was examined by shaking canvas in the bottom trawl followed by shrimp beam trawl. Field fishing trials by a bottom trawl were carried out between the Geomoondo and Jejudo in west of South sea, Korea by conver-net methods to examine the effect on the reduction of juvenile fish as a discard catch by generating a shaking movement of the codend using two pieces of asymmetrical semi-circular canvas. The mean period of the shaking motion with the round canvas was 10-15 s, and the range of amplitude as a vertical depth change was up to 0.4-0.6 m when towing speed 3.4-4.3 k't as estimated by peak event analysis. The escape rate of juvenile fish in conver-net by total juvenile bycatch (codend and cover-net) in 14 trials increased from 20% in a steady codend to 34% using a shaking codend in the bottom trawl, while the marketing catch or total bycatch was similar between steady and shaking cod ends. There was no difference in the body size of the fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction actually up to 18% using an active stimulating device, although further experiments are needed to increase an effective shaking motion of the codend in amplitude and period for more bycatch reduction.

• Fisheries and Aquatic Sciences
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• 제16권3호
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• pp.211-220
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• 2013

A shaking motion could be used to improve fish escapement from a cod-end net by creating a sieving effect over the swept volume or by disturbing the optomotor response of the fish. In this study, a perpendicular shaking motion was generated in a towed cod-end net by a circular canvas attached to the end of the codend, which formed a biased cap-like shape. This concept was tested by using a model in a flow tank and by towing a prototype cod-end during sea trials. For the model tests, the amplitude of the shaking motion was $0.6{\pm}0.1$ times the rear diameter of the cod-end, and the period of the shaking motion was $2.6{\pm}0.1$ s at a flow velocity of 0.6 or 0.8 m/s. In the sea trials, the amplitude was $0.5{\pm}0.2$ times the rear diameter of the cod-end, and the period of the shaking motion was $7{\pm}4$ s at towing speeds of 1.2 or 1.7 m/s. Thus, the shaking amplitude during the sea trials was equal to or less than that observed in the tank tests, and the shaking period was twice as long. The shaking motion described by the amplitude and period could be an effective means to stimulate fish escapement from cod-end during fishing operations considering the response of the fish.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.556-560
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• 2007

In this paper, the research results for the improvement of tracking performance of a hydraulic shaking table are presented. A servo-hydraulic shaking table is not only highly nonlinear but also has a lot of time delay. In addition, the shaking table, which consists of multi axial hydraulic actuators, is a MIMO system coupled by kinematics and dynamics of each other's actuators. And it is demanded for the shaking table to track arbitrary trajectories up to high frequency even at the extreme situations such as substantial external loads and large disturbances. For this purpose, an iterative feed-forward control based on the inverse of a measured frequency response function is used for the shaking table. To solve the dynamic coupling, a pressure feedback control as numerical damping is used. It is shown through numerical simulations that the tracking performance of shaking table is improved up to 100Hz.

• Smart Structures and Systems
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• 제13권1호
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• pp.137-154
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• 2014

Servohydraulic shaking tables are being increasingly used in the field of earthquake engineering. They play a critical role in the advancement of the research state and remain one of the valuable tools for seismic testing. Recently, the National Earthquake Engineering Research Center, CGS, has acquired a 6.1m x 6.1 m shaking table system which has a six degree-of-freedom testing capability. The maximum specimen mass that can be tested on the shaking table is 60 t. This facility is designed specially for testing a complete civil engineering structures, substructures and structural elements up to collapse or ultimate limit states. It can also be used for qualification testing of industrial equipments. The current paper presents the main findings of the experimental shake-down characterization testing of the CGS shaking table. The test program carried out in this study included random white noise and harmonic tests. These tests were performed along each of the six degrees of freedom, three translations and three rotations. This investigation provides fundamental parameters that are required and essential while elaborating a realistic model of the CGS shaking table. Also presented in this paper, is the numerical model of the shaking table that was established and validated.

• 수산해양기술연구
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• 제50권3호
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• pp.342-350
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• 2014

An active stimulating device, such as a fluttering net or canvas attached to the end of a cod end generating a shaking motion, could help to encourage the escape of juvenile fish positioned passively near the net. Field fishing trials using a shrimp beam trawl were carried out to examine the effect on the reduction of juvenile fish or other discard catch by generating a shaking movement of the cod end using an unbiased cap-like round canvas. The mean period of the shaking motion with the round canvas was ~14 s, and the mean amplitude was 0.4 m as measured by peak event analysis and the global wavelet method. The bycatch of juvenile fish in 14 trials decreased by ~30% and by ~25% using a steady cod end for the total bycatch using a shaking cod end in the shrimp beam trawl, while the marketing catch was similar between steady and shaking cod ends. There was no difference in the body size of the shrimp or fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction using an active stimulating device, although more detailed studies are needed.

• Korean Chemical Engineering Research
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• 제53권2호
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• pp.174-180
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• 2015

8자 진동교반조에 대해 실험적으로 유동상태를 관찰하여 혼합 가시화, 소요동력, 고-액 및 기-액 물질이동에 대한 여러가지의 특성을 측정하였다. 진동수가 증가하면 유동상태, 혼합시간 소요동력 및 물질이동계수는 규칙적으로 변하지 않으므로 조작조건의 선정이 중요하다. 어떤 진동수에서라도 Fr = 0.095 이상에서는 실험적으로 명확하게 되었다. 이때 교반조내 유체는 선회류형으로 되어 혼합에 적합한 상태가 되고, 8자 진동교반에서의 최적 조작범위는 왕복 진동교반 보다도 넓었다. 8자 진동교반과 기존의 선회진동교반내의 고-액간 물질이동계수는 완전히 같은 식으로 상관되었다. 또한 기-액간 물질이동용량계수도 기존의 선회진동교반에서의 식과 같은 형태의 상관식으로 나타났다.

• 한국환경보건학회지
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• 제26권3호
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• pp.81-85
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• 2000

In order to reduce emission of air pollutants from spot incineration, it is required to develope the combustion chamber of small wastes incinerator having combustion efficiency. The characteristics of combustion of the incinerator with combustion chamber having tangential angels with surface of 45$^{\circ}$of air supply nozzles were studied in accordance with non-grate, fixed-grate and shaking-grate in the combustion chamber. Combustion conditions were evaluated with combustion efficiency, emission of hazardous gases, temperatures, ignition loss of ash and so on. Combustion efficiencies were shown 73.9% for non-gate, 81.1% for fixed-grate and 89.0% for shaking-grate. Emissions of CO were revealed 6.52 ppm for non-grate, 273 ppm for fixed-grate and 224 for shaking-grate. Comprehensively evaluated, combustion conditions got better in order of shaking-grate, fixed-grate and non-grate. This study suggests that small wastes incinerator should have shaking-or fixed-grate in combustion chamber to get better combustion condition even though at expensive cost of manufacturing.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.1-4
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• 2008

본 조사연구는 건축물의 진동대 실험을 이용한 국내의 연구 상황을 조사한 것이다. 진동대 성능을 나타내는 항목을 소개하고, 국내의 2m ${\times}$ 2m 크기를 초과하는 진동대 실험실을 조사, 정리 하였으며 국내의 진동대 실험을 통한 논문을 정리하였다. 본 조사를 통해 추후 지진공학 연구에 진동대 실험이 좀 더 활발하게 사용되는데 보탬이 될 것을 기대한다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 2차
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• pp.38-44
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• 2010

Shaking table tests were performed to reproduce the dynamic behavior of estuary barrage and its subbase soil which can be potentially damaged during earthquake loading. For understanding the vibration effect to the ground during earthquake, the model was formulated with 1/300 scale of prototype estuary barrage and subbase soil. Scott and Iai(1989) proposed the law of the similarity for similar experimental conditions. The laboratory model shaking table test was conducted under the vibration condition of simulated earthquake of 0.154g. The horizontal displacement on the structure was measured during the shaking table test. The pore water pressure was also monitored for the underground layers of soil. The field horizontal displacement and the pore water pressure can be predicted by using the results of the laboratory shaking table test.