• Journal of Advanced Navigation Technology
• /
• v.21 no.5
• /
• pp.450-458
• /
• 2017

This paper presents dynamic modelling and simulation study on attitude/altitude control of an insect-mimicking flapping micro aerial vehicle during hovering. Mathematical modelling consists of three parts: simplified flapping kinematics, flapping-wing aerodynamics, and six degree of freedom dynamics. Attitude stabilization is accomplished through linear quadratic regulator based on the linearized model of the time-varying nonlinear system, and altitude control is designed in the outer loop using PID control. The performance of the proposed controller is verified through numerical simulation where attitude stabilization and altitude control is done for hovering. In addition, it is confirmed that the attitude channel by periodic control is marginally stable against periodic pitching moment caused by flapping.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.42 no.5
• /
• pp.951-958
• /
• 2017

In an attack context, the adversary wants to retrieve the message from the intercepted noisy bit stream without any prior knowledge of the channel codes used. The process of finding out the code parameters such as code length, dimension, and generator, for this purpose, is called the blind recognition of channel codes or the reconstruction of channel codes. In this paper, we suggest an improved algorithm of the blind recovery of rate k/n convolutional encoders in a noisy environment. The suggested algorithm improves the existing algorithm by Marazin, et. al. by evaluating the threshold value through the estimation of the channel error probability of the BSC. By applying the soft decision method by Shaojing, et. al., we considerably enhance the success rate of the channel reconstruction.

• Journal of Distribution Research
• /
• v.12 no.3
• /
• pp.91-109
• /
• 2007

This paper intends to examine the antecedents to the ex-post supply price cut which is typical retailer's unfair trade practices from three perspectives such as market power, efficiency, and retailer's tendency. For the empirical research, we analyzed manufacturer's 79 key account managers who have traded with domestic discount stores. As a result, the harder a retailer tries to increase sales and margin simultaneously, the more the retailer tends to use the ex-post supply price cut against manufacturers. In addition, the most frequent pattern of ex-post supply price cut occurs after retailer's discount at discretion. Finally, we suggest this research's implications, limitations of this research with future research directions.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.9
• /
• pp.773-780
• /
• 2015

In this paper, the structural integrity for a cylindrical vehicle in subsonic environments is verified. In order to confirm static structural safety for the cylindrical vehicle in extreme maneuver condition, the structure analysis and full-scale static structure test are carried out. The commercial finite element codes, MSC. Patran/Nastran is used for numerical simulation. The full-scale static structure test equipment consists of the counterbalance system, loading system and data acquisition system. Besides, the dynamic characteristics for the cylindrical vehicle are reviewed by performing an impact hammer test.

• Journal of Microbiology and Biotechnology
• /
• v.23 no.4
• /
• pp.459-466
• /
• 2013

The lactic acid bacterium Streptococcus thermophilus is widely used as a starter culture for the production of dairy products. Whole-genome sequencing is expected to utilize the genetic basis behind the metabolic functioning of lactic acid bacterium (LAB), for development of their use in biotechnological and probiotic applications. We sequenced the whole genome of Streptococcus thermophilus MTCC 5461, the strain isolated from a curd source, by 454 GS-FLX titanium and Ion Torrent PGM. We performed comparative genome analysis using the local BLAST and RDP for 16S rDNA comparison and by the RAST server for functional comparison against the published genome sequence of Streptococcus thermophilus CNRZ 1066. The whole genome size of S. thermophilus MTCC 5461 is of 1.73Mb size with a GC content of 39.3%. Streptococcal virulence-related genes are either inactivated or absent in the strain. The genome possesses coding sequences for features important for a probiotic organism such as adhesion, acid tolerance, bacteriocin production, and lactose utilization, which was found to be conserved among the strains MTCC 5461 and CNRZ 1066. Biochemical analysis revealed the utilization of 17 sugars by the bacterium, where the presence of genes encoding enzymes involved in metabolism for 16 of these 17 sugars were confirmed in the genome. This study supports the facts that the strain MTCC 5461 is nonpathogenic and harbors essential features that can be exploited for its probiotic potential.

• Journal of the Korea Society for Simulation
• /
• v.25 no.1
• /
• pp.1-9
• /
• 2016

This study focuses on the air to air missile control fin planform optimization for the minimizing hinge moment with the considering phenomena of fluid and structure simultaneously. The fluid-structure interaction method is applied for the fluid and structure phenomena simulation of the control fins. A transient-loosely coupled method is used for the fluid-structure interaction simulation because it is suited for using each fluid and structure dedicated simulation software. Searching global optimization point is required many re-calculation therefore in this study, a mathematical model is applied for rapidly calculation. The face centered central composite method is used for generating design points and the 2nd polynomial response surface is sued for generating mathematical model. Global optimization is performed by using the generic algorithm. An objective function is the minimizing travel distance of the center of pressure between Mach 0.7 and 2.0 condition. Finally, the objective function of optimized planform is reduced 7.5% than the baseline planform with satisfying constrained conditions.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.20 no.6
• /
• pp.743-751
• /
• 2017

To evaluate the structural integrity of the helicopter radome, we performed bird strike analysis using SPH (Smoothed Particle Hydrodynamics) technique. Since the SPH method is a meshfree method, there is no phenomenon such as mesh tangling and it is suitable to predict the dispersion behavior of debris and debris cloud generated by high-speed impact. In order to observe the scattering direction of fractured bolts, the analysis were performed under the condition that the fracture occurs at the proof load. As a result of bird strike analysis, there is no secondary damage as well as the damage due to, the dispersion behavior of the bird model, and the scattering of the fractured bolts and radome. From the additional analysis that were performed to determine the actual bolt fracture, only plastic deformation is predicted since the maximum stress of the bolt does not exceed the ultimate stress.

• Journal of Microbiology and Biotechnology
• /
• v.30 no.9
• /
• pp.1430-1435
• /
• 2020

Bacterial cellulose (BC) has outstanding physical and chemical properties, including high crystallinity, moisture retention, and tensile strength. Currently, the major producer of BC is Komagataeibacter xylinus. However, due to limited tools of expression, this host is difficult to engineer metabolically to improve BC productivity. In this study, a regulated expression system for K. xylinus with synthetic ribosome binding site (RBS) was developed and used to engineer a BC biosynthesis pathway. A synthetic RBS library was constructed using green fluorescent protein (GFP) as a reporter, and three synthetic RBSs (R4, R15, and R6) with different strengths were successfully isolated by fluorescence-activated cell sorting (FACS). Using synthetic RBS, we optimized the expression of three homologous genes responsible for BC production, pgm, galU, and ndp, and thereby greatly increased it under both static and shaking culture conditions. The final titer of BC under static and shaking conditions was 5.28 and 3.67 g/l, respectively. Our findings demonstrate that reinforced metabolic flux towards BC through quantitative gene expression represents a practical strategy for the improvement of BC productivity.

• Korean Journal of Plant Tissue Culture
• /
• v.24 no.3
• /
• pp.175-181
• /
• 1997

Plants were regenerated from hypocotyl protoplast culture of cabbage (F$_1$hybrid Green Challenger) and were transplanted on fields. The ploidy level of regenerated and seed-grown plants was measured by flow cytometry. In total 125 regenerated plant, diploid (2n), tetraploid(4n), and mixoploid (2n+4n) were 72.8%, 25.6%, and 1.6%, respectively. Most of the regenerated plants had normal phenotype, whereas several plane showed abnormal phenotype such as heavy leaf incision, savoy, and wave. The regenerated plants with abnormal phenotype and different ploidy level were analysed by isozyme and RAPD, but no significant difference was found.

• Steel and Composite Structures
• /
• v.25 no.6
• /
• pp.693-704
• /
• 2017

In this research, a simple hyperbolic shear deformation theory is developed and applied for the bending, vibration and buckling of powerly graded material (PGM) sandwich plate with various boundary conditions. The displacement field of the present model is selected based on a hyperbolic variation in the in-plane displacements across the plate's thickness. By splitting the deflection into the bending and shear parts, the number of unknowns and equations of motion of the present formulation is reduced and hence makes them simple to use. Equations of motion are obtained from Hamilton's principle. Numerical results for the natural frequencies, deflections and critical buckling loads of several types of powerly graded sandwich plates under various boundary conditions are presented. The accuracy of the present formulation is demonstrated by comparing the computed results with those available in the literature. As conclusion, this theory is as accurate as other theories available in the literature and so it becomes more attractive due to smaller number of unknowns.