• ETRI Journal
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• v.41 no.5
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• pp.658-669
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• 2019

For dual-channel time-frequency (TF) overlapped signals with low sparsity in underdetermined blind source separation (UBSS), this paper proposes an effective method based on interval probability to estimate and expand the types of mixing matrices. First, the detection of TF single-source points (TF-SSP) is used to improve the TF sparsity of each source. For more distinguishability, as the ratios of the coefficients from different columns of the mixing matrix are close, a local peak-detection mechanism based on interval probability (LPIP) is proposed. LPIP utilizes uniform subintervals to optimize and classify the TF coefficient ratios of the detected TF-SSP effectively in the case of a high level of TF overlap among sources and reduces the TF interference points and redundant signal features greatly to enhance the estimation accuracy. The simulation results show that under both noiseless and noisy cases, the proposed method performs better than the selected mainstream traditional methods, has good robustness, and has low algorithm complexity.

• Composites Research
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• v.29 no.4
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• pp.223-229
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• 2016

SiC nanoparticles were used to increase flexural properties of polymer matrix. This study was to manufacture huge concentration SiC nanoparticle/epoxy composites and to evaluate the dispersion. During mixing SiC nanoparticle and epoxy, 20 wt% SiC nanoparticle in total composites was used with both stirrer and sonication equipment together. Mixing speed and dispersion were improved with the method by using both stirrer and sonication equipment at the same time via mechanical test and FE-SEM. Based on the results, modeling of SiC nanoparticle dispersion could be established. Ultimately, unidirectional carbon fiber reinforced composites was manufactured using 20 wt% SiC nanoparticle/epoxy. Mechanical property of CFRP using dual stirrer and sonication mixing method was better than composites by single sonication mixing method.

• Resources Recycling
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• v.24 no.6
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• pp.61-68
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• 2015

In this study, the strength properties of NHL based mortar with blending basalt fiber were investigated. In the first step, it was evaluated that physical properties of NHL based mortar according to mixing method of four types of basalt fiber and then mixing method of one type was selected. As a result of assessment, it showed that the physical properties with mixing method of dry blending were better than that of wet blending and mixing method that basalt fiber pre-mixed with NHL for 5 min in a blender was selected and water and aggregate were finally added. Secondly, the investigation of blending fiber length on the compressive and flexural strength for basalt fiber reinforced NHL based mortars was carried out. The compressive strength was decreased with adding fiber, and the flexural strength was increased more than plain mortar. In the case of adding 6 mm fiber, the compressive and flexural strength were improved more than that of others.

• The KSFM Journal of Fluid Machinery
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• v.7 no.6 s.27
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• pp.15-20
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• 2004

Numerical analysis of the partial admission turbine in the KARI turbopump has been performed. Flow field of the partial admission turbine is intrinsically unsteady and three dimensional. To avoid heavy computational efforts, the frozen rotor method is adopted in computation and compared with the mixing plane approach. The frozen rotor method can represent the variation of a flow field along the circumferential direction of rotor blades, which have the different relative positions to the nozzle with one another. It also illustrates the wake loss mechanism starting from the lip of a nozzle, which is not captured in the mixing plane method. The frozen rotor method has proven to be an efficient tool for the design of a partial admission turbine.

• Korean Journal of Mathematics
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• v.4 no.1
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• pp.17-30
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• 1996

In ergodic theory cutting and stacking constructions have been used to obtain a variety of important examples of transformations on the unit interval. We examine the example constructed by J. von Neumann and Kakutani and then apply the method used in the construction of Chacon's transformation to make examples that are weakly mixing but not mixing.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.1
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• pp.47-53
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• 2016

The electrolyte wetting phenomena occurring in the electrode of lithium-ion battery was studied using lattice Boltzmann method (LBM). Recently, lithium-ion batteries are being mixed with small particles on the active material to increase the capacity and energy density during the electrode design stage. The change to the mixing ratio may influence the wettability of electrolyte. In this study, the changes in electrolyte distribution and saturation were investigated according to various mixing ratios of active material. We found that the variations in mixing ratio of active material affect the wetting mechanism, and result in changes to the wetting speed and wettability of electrolyte.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.63-70
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• 2006

Due to the small size and weight of micro aerial vehicle (MAV), only miniaturized MEMS type sensors are applicable for MAV autonomous flight system. In this paper, we propose a accelerometer and gyro mixing algorithm to improve an attitude performance of MEMS type sensors. The performance of the proposed mixing algorithm is compared with the performance of fuzzy-based mixing algorithm through simulation. The simulation results show that the attitude compensation method through the attitude compensation has better performance than the fuzzy-based mixing method for MAV attitude estimation.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.119-122
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• 2009

The gravel compaction pile method has been used as a soft foundation improvement method because bearing capacity and discharge capacity is excellent. But the discharge capacity decreased when the clogging was generated because the clay penetrate into a void of gravel compaction pile. Accordingly, the purpose of this study is to reduce the clogging generation in gravel compaction pile constructing in the soft ground and take a step to minimize a void of gravel compaction pile. And the proper mixing ratio was determined with the large scale direct shear test performed to get strength and permeability with mixing ratio of crushed stone and sand(100:0, 90:10, 85:15, 80:20, 75:25). As a result of the test, it was showed that internal friction angle was the highest at 85:15 mixing ratio of crushed stone and sand and we can make sure a tendency of internal friction angle's decrease when the mixing ratio of crushed stone and sand passed 15%.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.309-312
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• 2006

Effective mixing is an important problem in microfluidics for chemical and biomechanical applications. In this study, the influences of the Reynolds number and the oscillating frequency on mixing characteristics of micro-stirrer are studied in a microchannel with single stirrer. The influence of fluid inertial effects in an active mixer is first discussed. It is found that the stirring effects by stirrer oscillation are promptly attenuated at low Reynolds number, which makes greatly difficult the rapid mixing. As the inertial effects are increased, the chaotic advection is generated and then developed. The mixing phase is finally developed some mushroom shaped structure. And the mixing efficiency is also studied as a function of the oscillating frequency. We found that the mixing efficiency does not always increase with higher oscillating frequency of stirrer. Consequently, we found the functional relation between the optimal frequency of a stirrer and the Reynolds number.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.49-55
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• 2007

The quality of chaotic mixing in three-dimensional micro channel flow has been numerically studied using Fractional-step method (FSM) and particle tracking techniques such as $Poincar{\acute{e}}$ section and Lyapunov exponents. The flow was driven by pressure distribution and the chaotic mixing was generated by applying alternating current to electrodes embedded on the bottom wall at a first half period and on the top wall at a second half period. The equations governing the velocity and concentration distributions were solved using FSM based on Finite Volume approach. Results showed that the mixing quality depended significantly on the modulation period. The modulation period for the best mixing performance was determined based on the mixing index for various initial conditions of concentration distribution. The optimal values of modulation period obtained by the particle tracking techniques were compared with those from the solution of concentration distribution equation using FSM and CFX software and the comparison showed their good match.