• Transactions of Materials Processing
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• v.9 no.4
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• pp.389-394
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• 2000

The studies on gram size refinement for rheocast processing of hypereutectic Al-18%Si alloys have been investigated in the present study. To increase the efficiency of mechanical stirring, sieve type stirrer are newly designed and implemented for rheocasting of hypereutectic Al-18%Si alloy. Mechanical stirring of semi-solid slurry by using sieve type mechanical stirrer results in morphological changes of the primary Si particles, from angular rod shape to near spherical shape and uniform distribution of proeutectic Si. The remarkable spheroidization of Primary Si Particles and distributional uniformity of proeutectic Si show well the efficiency of sieve type mechanical stirring method which can accelerate the coalescence-fracture-wear of the individual particles by strong turbulent flow between lattices during rotation of sieve type stirrer.

• The KIPS Transactions:PartA
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• v.8A no.1
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• pp.36-41
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• 2001

In this paper, we first design an parallel quadratic sieve algorithm for factoring method. We then present parallel factoring algorithm for factoring a large odd integer by repeatedly using the parallel quadratic sieve algorithm based on the divide-and-conquer strategy on SIMD machines with DMM. We show that this algorithm is optimal in view of the product of time and processor numbers.

• Journal of Biosystems Engineering
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• v.6 no.2
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• pp.33-47
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• 1982

To modernize the conventional rice post production technology and reduce grain losses, a transition toward the wet-paddy threshing system has been strongly demanded. The head-feeding type thresher with pneumatic separation has been used dominantly for threshing dried-paddy, but some adverse effects in separation performance for threshing wet-paddy is encounterred. In order to solve the problems, the development of thresher with an additional oscillating sieve to the conventional pneumatic separation has been recommanded. This study was intended to evaluate the separating performance of thresher with oscillating sieve which was attached additionally to the conventional auto-thresher equipped with separation system of blower and suction fan. For different feed rates and rice varieties, wet-and dry-material were tested with threshers attached with and without oscillating sieve. Results of the study are summarized as follows: 1. When the feed rates were 480 and 640 kg/hr, there was no statistically significant difference in power reqirements between the threshers with and without an additional sieve device for both dry-and wet-threshing. However, when the feed rate was 960 kg/hr, power requirements of thresher without sieve were greater for wet-paddy threshing than the thresher with the additional sieve separator by about 20% points. 2. With additional oscillating sieve device, the ratios of total weights of whole grains including grains with branch let and damaged grains to the total output did not show statistical difference among the feed rates. However, with pneumatic separation the ratio was decreased as the level of feed rate increased. 3. The total amount of grains with branchlet (including broken panicle) increased with the moisture content. For both the wet-and dry-material threshing with the additional oscillating sieve, the percent of grains with branchlet to the total output decreased greatly as the feed rate increased. 4. The output of the damaged grains increased as moisture content decreased. Especially, for the dry-paddy threshing, the additional sieve separating device produced more damaged grains than the pneumatic separation at all feed rates. 5. Generally, for dry paddy threshing, the separating performance of the thresher with the additional sieve device was better at all feed rates, showing greater difference with increasing feed rates. 6. Separating losses were greater with the pneumatic than sieve separation for both the wet-and dry-threshing. 7. The overall comparison of separating performance of threshers tested with and without an additional sieve device showed that the former was more effective than the latter for the dry-material threshing. However, for the wet-paddy threshing, the separation performance with a sieve device was better than the pneumatic only when the feed rate was high.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.301-310
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• 2013

For analyzing sand grain size, a specialized high-priced instrument has been used, such as sieve shaker, video camera, laser particle size analyzer, and microscope. Among these, the sieve shaker is commonly used because it is not only cheaper than others but also provides reasonable accuracy. However, it takes a long time and makes lots of dust and noise. In this study, a cheaper and easier method which can replace the sieve shaker is proposed. By using a commercial flat-bed scanner and a darkroom box, the sand size distribution can be analyzed. The darkroom box makes sand images clear and protects the glass of the scanner from being scratched. Comparison between the present method and sieve analysis shows that the present method not only has an accuracy comparable to the sieve analysis but also can save time and effort.

• Bulletin of the Korean Mathematical Society
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• v.53 no.1
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• pp.1-20
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• 2016

The general number field sieve (GNFS) is asymptotically the fastest known factoring algorithm. One of the most important steps of GNFS is to select a good polynomial pair. A standard way of polynomial selection (being used in factoring RSA challenge numbers) is to select a nonlinear polynomial for algebraic sieving and a linear polynomial for rational sieving. There is another method called a nonlinear method which selects two polynomials of the same degree greater than one. In this paper, we generalize Montgomery's method [12] using geometric progression (GP) (mod N) to construct a pair of nonlinear polynomials. We also introduce GP of length d + k with $1{\leq}k{\leq}d-1$ and show that we can construct polynomials of degree d having common root (mod N), where the number of such polynomials and the size of the coefficients can be precisely determined.

• Journal of the Korean Society of Visualization
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• v.15 no.3
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• pp.34-40
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• 2017

Within fractionating devices existing in separation and purification industries, sieve trays are widely used as tower internals and their choice is due to economical attractiveness. While operating a trayed distillation tower weeping phenomenon has a critical effect on the efficiency, in this case study a weeping phenomenon was undertaken by means of numerical model in a rectangular sieve tray. Eulerian-Eulerian Computational Fluid Dynamics (CFD) method was used and the obtained CFD results are in a good agreement with the experimental data in terms of weeping rate and pressure drop.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.57-58
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• 2015

In this research the processing method of Desulfurized Plaster is changed to cyclotomy, 0.3mm sieve analysis and 500℃ heat exposure, and by changing the mix rate of the binding agent to 0~20%, it was applied to mortar that used cyclic aggregate and blast furnace slag for testing. The test results showed that the flow decreased in the order of cyclotomy, high heat exposure, and sieve analysis according to the mix rate of FGD, and while the air volume decreased for cyclotomy, it was shown to have almost no effect on sieve analysis and high heat exposure. The setting time accelerated as the mixing rate of FGD increased, and the compression strength increased as the mixing rate of FGD increased and especially showed a high trend with cyclotomy and sieve analysis.

• Membrane Journal
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• v.29 no.4
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• pp.202-215
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• 2019

Molecular sieve membranes separate molecules based on their size and/or shape and have been of high interest, due to their potentially high energy efficiency and high selectivity. Zeolite MFI membrane is one of the most-studied molecular sieve membranes and has affected following studies on other molecular sieve membranes. This review discusses the technical developments on the control of morphology, microstructure, and defect of MFI membranes, which have significantly improved xylene isomer separation performances. These include crystal morphology control, effective secondary growth, seed coating method, crystal orientation control, heteroatom doping, and defect healing method.

• Journal of The Geomorphological Association of Korea
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• v.27 no.2
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• pp.19-28
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• 2020

Grain size analysis is the most basic procedure for identifying the origin, transport and sedimentation processes of sediments, and is widely used in geomorphology and sedimentology. Traditionally, grain size was determined by a sieve-pippette method, but the use of automated analyzers is increasing in recent years. These analyzers have many advantages over traditional techniques, but the measurement results are not always the same. It is still difficult to solve the pretreatment problem such as incomplete diffusion and residual organic matter, and inappropriate results may be obtained. This study compared image-based grain size analysis and sieve analysis to verify its statistical reliability, and conducted experiments to enhance the measurement accuracy using shape parameters. The results showed that the image-based analysis overestimated the grain size of sand dunes by about 7% compared to the sieve analysis, but the two measurements were not statistically different. In addition, by using shape parameters, such as aspect ratio, sphericity, and convexity, improved statistics were obtained compared to the original data. Using the morphological properties of the individual grains is a complementary method to the incomplete pretreatment of the grain size analysis process, and at the same time, it will contribute to improving the accuracy and reliability of the results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.6
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• pp.164-172
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• 2023

The grain size distribution of sand provides crucial information for understanding coastal erosion and sediment deposition. The commonly used sieve analysis for grain size distribution analysis has limitations such as time-consuming processes and the inability to obtain information about individual particle shapes and colors. In this study, we propose a grain size distribution analysis method using smartphone digital images, which is simpler and more efficient than the sieve analysis method. During the image analysis process, we effectively detect particles from relatively low-resolution smartphone digital images by extracting particle boundaries through image gradient calculation. Using samples collected from four beaches in Gyeongsangbuk-do, we compare and validate the proposed boundary extraction image analysis method with the analysis method that does not extract boundaries, against sieve analysis results. The proposed method shows an average error rate of 8.21% at D₅₀, exhibiting a 65% lower error compared to the method without boundary extraction. Therefore, grain size distribution analysis using smartphone digital images is convenient, efficient, and demonstrated accuracy comparable to sieve analysis.