• Journal of Korea Water Resources Association
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• v.42 no.8
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• pp.619-629
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• 2009

The objective of this study is to estimate bed-resistance in gravel-bed rivers using the equivalent roughness height($k_s$). We calculated the friction factor(f) with the measured data from 8 domestic gravel-bed rivers and investigated the size distributions of the bed materials. The averaged $k_s$ in each cross-section, which is determined under the hypothesis that the vertical velocity distribution follows the logarithmic law, is compared with the reach $k_s$ which is calculated with the cumulative grain diameter distribution curve of bed materials. Moreover, the applicability of existing formulae, such as Strickler type equations, is examined by comparing with Manning's n value converted from the $k_s$. According to the results, the reach $k_s$ proves to be a good indicator of representative characteristic of bed materials in a reach, and the Manning's n based on the reach $k_s$ is appropriate for practical estimation of the bed-resistance, for RMS errors between calculated and measured Manning's n is less than 0.003. The correlation between the $k_s$ and specified bed-material size($D_i$) is very low, so it is difficult to select a proper one among the existing empirical equations.

• Journal of Biosystems Engineering
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• v.37 no.3
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• pp.155-165
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• 2012

This study was performed to offer the data for design of the seedling bed transfer equipment to make the automation of working process in a plant factory. The seedling bed transfer equipment pushing the seedling bed with bearing wheels on the rail for interconnecting each working process by a pneumatic cylinder was made and examined. The examined transfer force to push the seedling bed with a weight of 178.9 N by the pneumatic cylinder with length of 60 cm and section area of 5 $cm^2$ was measured by experiments. The examined transfer forces was compared with theoretical ones calculated by the theoretical formula derived from dynamic system analysis according to the number of the seedling bed and pushing speed of the pneumatic cylinder head at no load. The transfer function of the equipment with the input variable as the pushing speed $V_{h0}$(m/s) and the output variable as the transfer force f(t)(N) was represented as $F(s)=(V_{h0}/k)(s+B/M)/(s(s^2+Bs/M+1/(kM))$ where M(kg), k(m/N) and B(Ns/m) are the mass of the bed, the compression coefficient of the pneumatic cylinder and the dynamic friction coefficient between the seedling bed and the rail, respectively. The examined transfer force curves and the theoretical ones were represented similar wave forms as to use the theoretical formular to design the device for the seedling bed transfer. The condition of no vibration of the transfer force curve was $kB^2>4M$. The condition of transferring the bed by the repeatable impact and vibration force according to difference of transfer distance of the pneumatic cylinder head from that of the bed was as $Ce^{-\frac{3{\pi}D}{2\omega}}<-1$, where ${\omega}=\sqrt{\frac{1}{kM}-\frac{B^2}{4M^2}}$, $C=\{\frac{\frac{B}{2M}-\frac{1}{kB}}{\omega}\}$, $D=\frac{B}{2M}$. The examined mean peak transfer force represented 4 times of the stead state transfer force. Therefore it seemed that the transfer force of the pneumatic cylinder required for design of the push device was 4Bv where v is the pushing speed.

• Korean Journal of Agricultural Science
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• v.5 no.2
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• pp.49-55
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• 1978

In order to get healthy seedling of rice suitable for rice transplanter, the growing characteristics of the seedling grown under different growing days and sowing densities were invesigated and the results obtained were summarized as follows; In the 20 days old seedling, the difference of growing state of seed ling and its characteristics between the two types of nursery bed was not found, but for the 30 days old seedling, both of the crop growth rate and the relative growth rate on the band-type nursery bed appeared higher than those on the mat-type nursery bed. And also, "the dry weight, the content of cardohydrate and the ratio of dry weight to plant height of the seedling grown on the band-type nursery bed were much higher than those on the mat-type nursery bed, however the amount of difference of seedling characteristics between two types of nursery bed was decreased for 40 days old seedling and leaf number was not increased. The amount of the seedling growth was increased with less density of sowing and for the difference between the higher and the less density, the difference getting bigger with the longer nursery days. The maximum density of sowing was approximately 200cc per nursery case on the band-type nursery bed and 250cc per nursery case on the mat-type nursery bed. It was seemed that the growing uniformity of the seedling grown on the mat-type nursery bed was better than that on the band- type nursery bed, As the coefficient of variation of the plant height and the leaf numbers of the seedling grown on the band- type nursery bed was higher than that on the mat-type nursery bed.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.7
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• pp.746-751
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• 2006

In this study, drying and carbonization experiment was conducted in a fluidized bed reactor according to the variations in gas velocity, particle size, and reactor temperature. As a result, the weight loss rates of sludge by drying in the fixed bed and fluidized bed type dryer showed that drying in the fluidized bed was about 6 times faster than drying in the fixed bed, and the weight loss rates of sludge by carbonization in the fixed bed and fluidized bed type reactor showed that carbonization in the fluidized bed was about 4 times faster than drying in the fixed bed. This implies that carbonization in the fluidized bed was completed within 10 minutes. Although the amount of char decreased with the increase of carboniration temperature, the amount of char became similar at upper 873K. Also, the amount of char decreased with increasing gas velocity. Consequently, it could be efficient that slow fluidization should be maintained within the range of fluidization in case of fluidized carbonization of sewage sludge at 873K.

• Journal of Korea Water Resources Association
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• v.35 no.1
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• pp.77-90
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• 2002

The condition of initial movement for the river bed revetment using rip rap is a limit condition beyond which the lining is progressively destroyed as the separate elements are removed by the flow. In the case of the river bed revetment using mattress, however, after the initial movement the containment offered by the mesh remains. A new situation of equilibrium with a deformed river bed revetment using mattress is obtained, allowing it to withstand more severe conditions without compromising the resistance and without further bed deformation. Shield's coefficient for the river bed revetment using mattress is twice the value of that for the river bed revetment using rip rap. This means that with the same hydraulic behavior conditions, the average dimension of the rocks to be used in the river bed revetment using mattress is half that of the river bed revetment using rip rap rock. When the same size rocks are used the allowable velocity for the river bed revetment using mattress is more than twice, even as much as 3 or 4 times that for the river bed revetment using rip rap.

• Korean Journal of Food Science and Technology
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• v.41 no.1
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• pp.27-31
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• 2009

Top spray-drying method is frequently utilized for flavor encapsulation, but the top spray-dried products frequently suffer from high losses of volatile flavor as the result of a high processing temperature (150-$300^{\circ}C$). In an effort to solve these problems, a low-temperature fluidized-bed granulating method was utilized to encapsulate the flavor. For the encapsulation of sesame oil, oil-in-water emulsions of sesame oil and a mixture of maltodextrin, modified starch, gum arabic, and gellan gum were bottom-sprayed at milder temperatures (70-$100^{\circ}C$) using a fluidized-bed granulator. Sesame oil extracts from microcapsules were obtained via a simultaneous distillation/extraction technique, and the retention of volatile flavor compounds was analyzed via a gas chromatography-mass spectrometry. The retention of volatile flavors of sesame oil per se, spray-dried and fluidized-bed granulated microcapsules after 3-day-storage at $37^{\circ}C$ were 0.8%, 37.2%, and 42.0%, respectively. In addition, the low-temperature fluidized-bed granulation showed higher encapsulation yield and sensory preferences for the application of commercial products (beef rice porridge), as compared to spray drying.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.140-144
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• 1996

Trickle bed를 이용하여 고분가 촉매에 의한 용존산소 제거반응을 수행하였다. 고분자 촉매는 폴리스티렌-디비닐 벤젠의 공중합체로 이루어진 담체를 제조하여 백금 용액을 함침시킨 후 수소로 환원하여 제조하였다. trickle bed는 수소 및 산소로 포화되어 있는 물을 향류식으로 접촉할 수 있도록 설계하였다. 이 경우는 액상 실험 장치와 달리 포화기가 없기 때문에 장치는 비교적 단순하였으나 컬럼내에 축적되는 액상의 축적이 중요한 운전변수로 나타났다. trickle bed에서의 용존산소 제거 거동을 semi-empirical relation으로 나타내어 실험치와 비교한 결과 예측된 모델과 매우 잘 일치하는 것으로 나타났다.

• Journal of the Korean Society of Combustion
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• v.14 no.3
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• pp.1-15
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• 2009

The circulating fluidized bed (CFB) boiler has some problems to scale up. Several engineering solutions have been proposed by a few suppliers which had advanced CFB technology. Large-scale CFB design concepts from different suppliers were reviewed and compared. Points of the hydrodynamic and heat recovery were summarized and discussed for developing the guideline of the large-scale circulating fluidized bed boilers.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.1
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• pp.107-110
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• 1982

Fixed bed drying method was selected to reduce the initial drying time of squid and the effects of drying air temperature and bed height on the drying rate were investigated, with following results. 1. The drying rate in the fixed bed dryer was faster than that of natural convection type dryer heated indirectly and that of hot air dryer heated directly. 2, Shirai-equation was applicable to squid being dried. Using the equation, drying rate constant obtained was as shown in table 1.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.297-300
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• 2002

Semi-two dimension numerical models were applied to study on the hydraulic and sedimentologic characteristics of upstream and downstream channel section in Dal stream. The feature of this paper is (1) to analyse the effects of bed changes by sediment transport formulas, (2) to analyse the effects of bed changes by stream tube. The simulation results of Meyer-peter and Muller formula for long-term bed changes are good when compared to the measured data.