• Title/Summary/Keyword: bottom velocity

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Strength and durability characteristics of bricks made using coal bottom and coal fly ash

  • Ashish, Deepankar Kumar;Verma, Surender Kumar;Singh, Joginder;Sharma, Namesh
    • Advances in concrete construction
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    • v.6 no.4
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    • pp.407-422
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    • 2018
  • The study evaluates properties of brick having coal ash and explores the possibility of utilization of coal bottom ash and coal fly ash as an alternative raw material in the production of coal ash bricks. Lower cement content was used in the investigations to attain appropriate strength and prohibit high carbon content that is cause of environmental pollution. The samples use up to 7% of cement whereas sand was replaced with bottom ash. Bricks were tested for compressive strength, modulus of rupture, ultrasonic pulse velocity (UPV), water absorption and durability. The results showed mix proportions of bottom ash, fly ash and cement as 1:1:0.15 i.e., M-15 achieved optimum values. The coal ash bricks were well bonded with mortar and could be feasible alternative to conventional bricks thus can contribute towards sustainable development.

Least Squares Velocity Estimation of a Mobile Robot Using a Regular Polygonal Array of Optical Mice (정다각형 배열의 광 마우스를 이용한 이동 로봇의 최소 자승 속도 추정)

  • Kim, Sung-Bok;Jeong, Il-Hwa;Lee, Sang-Hyup
    • Journal of Institute of Control, Robotics and Systems
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    • v.13 no.10
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    • pp.978-982
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    • 2007
  • This paper presents the velocity estimation of a mobile robot using a regular polygonal array of optical mice that are installed at the bottom of a mobile robot. First, the basic principle of the proposed velocity estimation method is explained. Second, the velocity kinematics from a mobile robot to an array of optical mice is derived as an overdetermined linear system. Third, for a given set of optical mouse readings, the mobile robot velocity is estimated based on the least squares solution to the obtained system. Finally, simulation results are given to demonstrate the validity of the proposed velocity estimation method.

Robust Velocity Estimation of an Omnidirectional Mobile Robot Using a Polygonal Array of Optical Mice

  • Kim, Sung-Bok;Lee, Sang-Hyup
    • International Journal of Control, Automation, and Systems
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    • v.6 no.5
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    • pp.713-721
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    • 2008
  • This paper presents the robust velocity estimation of an omnidirectional mobile robot using a polygonal array of optical mice that are installed at the bottom of the mobile robot. First, the velocity kinematics from a mobile robot to an array of optical mice is derived as an overdetermined linear system. The least squares velocity estimate of a mobile robot is then obtained, which becomes the same as the simple average for a regular polygonal arrangement of optical mice. Next, several practical issues that need be addressed for the use of the least squares mobile robot velocity estimation using optical mice are investigated, which include measurement noises, partial malfunctions, and imperfect installation. Finally, experimental results with different number of optical mice and under different floor surface conditions are given to demonstrate the validity and performance of the proposed least squares mobile robot velocity estimation method.

Concrete Target Size Effect on Projectile Penetration (침투시험에서의 콘크리트 표적크기 영향 분석)

  • Kim, Seokbong;Yoo, Yohan
    • Journal of the Korea Institute of Military Science and Technology
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    • v.18 no.2
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    • pp.154-159
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    • 2015
  • This paper deals with the effect of concrete target size on penetration of projectiles. We investigated the penetration depth and residual velocity of projectiles using the 2-D axial symmetric model. Most analysis were conducted with 13 kg projectile (striking velocity: 456.4 m/s) and concrete target with compressive strength of 39 MPa. This paper provided penetration depth (or residual velocity) versus ratio D/d (target diameter, D and projectile diameter, d). When the bottom of concrete cylinder was constrained, penetration depth converged to limit depth more than the ratio D/d of 36. The residual velocity of projectile with thin concrete target were investigated. The residual velocity was converged to specific velocity more than the ratio D/d of 16.

Linear Spectral Method for Simulating the Generation of Regular Waves by a Moving Bottom in a 3-dimensional Space (3차원 공간에서 바닥의 움직임에 의한 규칙파의 생성을 모의할 수 있는 선형 스펙트럼법)

  • Jae-Sang Jung;Changhoon Lee
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.36 no.2
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    • pp.70-79
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    • 2024
  • In this study, we introduce a linear spectral method capable of simulating wave generation and transformation caused by a moving bottom in a 3-dimensional space. The governing equations are linear dynamic free-surface boundary conditions and linear kinematic free-surface boundary conditions, which are solved in Fourier space. Solved velocity potential and free-surface displacement should satisfy continuity equation and kinematic bottom boundary condition. For numerical analysis, a 4th order Runge-Kutta method was utilized to analyze the time integral. The results obtained in Fourier space can be converted into velocity potential and free-surface displacement in a real space using inverse Fourier transform. Regular waves generated by various types of moving bottoms were simulated with the linear spectral method. Additionally, obliquely generated regular waves using specified bottom movements were simulated. The results obtained from the spectral method were compared to analytical solutions, showing good agreement between the two.

Relationship between Rock Quality Designation and Blasting Vibration Constant "K" & Decay Constant "n" by Bottom Blasting Pattern (바닥발파에서 암질지수(RQD)와 발파진동상수 K, n의 관계)

  • 천병식;오민열
    • Geotechnical Engineering
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    • v.11 no.3
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    • pp.55-68
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    • 1995
  • This paper is the analysis of the relationship between RQD and decay constant, blasting vi bration constant of cube root scaling and square root scaling, through experimental blast ins test in subway construction for excavation of shaft hole by bottom blasting. The magnitude of particle velocity is largely effected by the distance from blasting source, the maximum charge per delay and the properties of ground. In order to verify the effects of ground properties on blast-induced vibration, the relation-ship between magnitude of blasting vibration and Rock Quality Disignation which stands for joint property was studied. The results of test are verified that blasting vibration constant "K" and the absolute value("n") of decay constant relatively increse as RQD increased. According to the result, it can be predict the particle velocity by the blast -induced vibration in bottom blasting pattern.om blasting pattern.

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The Distribution and Behaviors of Suspended Matters in Seomjin River Estuary - Compared with Rainy and Wet Season - (섬진강하구에서 부유물질의 분포와 거동 - 풍수기와 평수기의 비교 -)

  • Kim, Seok-Yun;Lee, Byoung Kwan
    • Journal of Korean Society on Water Environment
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    • v.25 no.6
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    • pp.935-942
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    • 2009
  • During period of the rainy season of spring tide Aug. 2005, the suspended sediment transport rate from Seomjin River increased ten times as high as neap tide of low river discharge. During ebb tide of high terrestrial input, the grain size of suspended particles of both surface and bottom layer of the water column, showed a uni-modal distribution with a dominant peak at coarse fraction, which suggests a characteristic development of floc-sized particles of low mean effective density. On the contrary, the particles supplied toward upstream of Seomjin river from Gwangyang Bay during flood tide showed a bi-modal distribution with a secondary peak at finer fraction, possibly due to the resuspension and the deflocculation associated with the increased shear velocity at near bottom. Break-up of large flocs is also suggested by the increased mean effective density. However, settling velocity was lower during flood tide because of smaller grain size. Thus, net deposition of suspended sediment is expected at within Gwangyang Bay instead of upstream of Seomjin River, even though suspended sediment transport rate at near bottom water was three times higher than that at surface water during flood tide.

Tilt variation and wake turbulence in the otter board of a bottom trawl during fishing operations

  • KIM, Yong-Hae
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.53 no.4
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    • pp.337-348
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    • 2017
  • The tension of warp from trawler and sea-floor contact can generate tilt and wake turbulence around otter boards. Preliminary measurements of otter board tilt and 3-D flow velocity during bottom trawl operations were taken using a vector instrument to investigate the effects of wake turbulence at the trailing edge of the otter board. Tilt data (i.e., yaw, pitch, and roll) at 1 Hz and flow data (velocities in the towing, lateral, and vertical directions) at 16 Hz were analyzed to determine their periods and amplitudes using global wavelet and peak event analyses. The mean period (${\pm}standard$ deviation) of the tilt from the peak event analysis ($5{\pm}2s$) was longer or double than that of flow velocity ($3{\pm}2s$). The two periods also had a significant linear relationship. The turbulence rate of flow was 30-50% at the trailing edge and was closely related to roll deviation. The frequency of phase difference ratios (i.e., peak time differences between tilts and flow periods) was significantly different from random occurrence in two trials, possibly due to side tidal effects. However, in the other trials, flow peaks were random, as shown by the even peak times between tilts and flows. Future studies should focus on reducing tilt variation, wake turbulence, and bottom contact to stabilize otter board motion.

Quantitative Analysis of the Swimming Movements of Flatfish Reacting to the Ground Gear of Bottom Trawls

  • Kim, Yong-Hae;Wardle Clem S.
    • Fisheries and Aquatic Sciences
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    • v.9 no.4
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    • pp.167-174
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    • 2006
  • Two typical responses have been documented for flatfish when they encounter the ground gear of bottom trawls: herding response and falling back response. These two responses were analyzed from video recordings of fish and were characterized by time sequences for four parameters: swimming speed, angular velocity, acceleration, and distance between the fish and the ground gear. When flatfish displayed the falling-back response, absolute values of the three swimming parameters and their deviations were significantly higher than those during the herding response. However, the swimming parameters were not dependent on the distance between the flatfish and the ground gear, regardless of which response occurred. The dominant periods for most of the movement parameters ranged from 2.0 to 3.7 s, except that no periodicity was observed for swimming speed or angular velocity during the falling-back response. However, variations in the four parameters during the falling -back response revealed greater irregularity in periodicity and higher amplitudes. This complex behavior is best described as a chaos phenomenon' and is discussed as the building block for a model predicting the responses of flatfish to ground gear as part of the general understanding of the fish capture process.

Measurement and Analysis on the Mixing Flows in a Tank with a Bottom Agitator using a Hybrid Volume Measurement Technique (하이브리드 볼륨측정법에 의한 하부교반 탱크내 혼합유동 측정 및 해석)

  • Doh, Deog Hee;Lee, Chang Jae;Baek, Tae Sil
    • Journal of the Korean Society of Visualization
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    • v.10 no.3
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    • pp.42-47
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    • 2012
  • Experimental data for the flows in a mixing tank with a bottom agitator are useful for the validation of CFD commercial code. A hybrid volume PIV measurement technique was constructed to measure the flows inside of the mixing tank. The measurement system consists of three cameras. An agitator was installed at the bottom of the tank and it rotates clockwise and counterclockwise. Using the constructed measurement system, instantaneous vector fields were obtained. A phase averaging technique was adopted for the measured instantaneous three-dimensional velocity vector fields. Turbulent properties were evaluated from the instantaneous vector fields.