• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.1
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• pp.102-107
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• 2021

This paper discusses the containment control problem for multi-agent systems with input saturations. The goal of the containment control is to obtain swarming behavior by driving follower agents into the convex hull which is spanned by multiple leader agents. This paper considers multiple leader agents moving at the same constant speed. Then, to solve the containment problem for moving leaders, we propose a PI-based distributed control algorithm. We next analyze the convergence of follower agents to the desired positions. Specifically, we apply the integral-type Lyapunov function to take into account the saturation nonlinearity. Then, based on Lasalle's Invariance Principle, we show that the asymptotic convergence of error states to zero for any positive constant gains. Finally, numerical examples with the static and moving leaders are provided to validate the theoretical results.

• Journal of Ocean Engineering and Technology
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• v.35 no.1
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• pp.38-49
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• 2021

Slug flow is the most common multi-phase flow encountered in oil and gas industry. In this study, the hydrodynamic features of flow in pipes investigated numerically using computational fluid dynamic (CFD) simulations for the effect of slug flow on the vertical and bent pipeline. The compressible Reynold averaged Navier-Stokes (RANS) equation was used as the governing equation, with the volume of fluid (VOF) method to capture the outline of the bubble in a pipeline. The simulations were tested for the grid and time step convergence, and validated with the experimental and theoretical results for the main hydrodynamic characteristics of the Taylor bubble, i.e., bubble shape, terminal velocity of bubble, and the liquid film velocity. The slug flow was simulated with various air and water injection velocities in the pipeline. The simulations revealed the effect of slug flow as the pressure occurring in the wall of the pipeline. The peak pressure and pressure oscillations were observed, and those magnitudes and trends were compared with the change in air and water injection velocities. The mechanism of the peak pressures was studied in relation with the change in bubble length, and the maximum peak pressures were investigated for the different positions and velocities of the air and water in the pipeline. The pressure oscillations were investigated in comparison with the bubble length in the pipe and the oscillation was provided with the application of damping. The pressures were compared with the case of a bent pipe, and a 1.5 times higher pressures was observed due to the compression of the bubbles at the corner of the bent. These findings can be used as a basic data for further studies and designs on pipeline systems with multi-phase flow.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.7
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• pp.866-872
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• 2020

Indoor location-based services provide a service based on the distance between an object and a person. Recently, indoor location-based services are often implemented using inexpensive depth sensors such as Kinect. The depth sensor provides a function to measure the position of a person, but the position of an object must be acquired manually using a tool. To acquire a 3D position of an object, it requires 3D interaction, which is difficult to a general user. GUI(Graphical User Interface) is relatively easy to a general user but it is hard to gather a 3D position. This study proposes the Interactive LOcation Context Authoring Toolkit(ILOCAT), which enables a general user to easily acquire a 3D position of an object in real space using GUI. This paper describes the interaction design and implementation of ILOCAT.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.4
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• pp.357-367
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• 2021

This paper studies the simulations of active airframe vibration controls for the Sikorsky X2 helicopter with a lift-offset coaxial rotor. The 4P hub vibratory loads of the X2TD rotor are obtained from the previous work using a rotorcraft comprehensive analysis code, CAMRAD II. The finite element analysis software, MSC.NASTRAN, is used to model the structural dynamics of the X2TD airframe and to analyze the 4P vibration responses of the airframe. A simulation study using Active Vibration Control System(AVCS) with Fx-LMS algorithm to reduce the airframe vibrations is conducted. The present AVCS is modeled using MATLAB Simulink. When AVCS is applied to the X2TD airframe at 250 knots, the 4P longitudinal and vertical vibration responses at the specified airframe positions, such as the pilot seat, co-pilot seat, engine deck, and prop gearbox, are reduced by 30.65 ~ 94.12 %.

• Korean Journal of Agricultural Science
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• v.48 no.2
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• pp.283-297
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• 2021

Investigation of genetic diversity and molecular characterization in high yielding rice varieties is important for their identification. The experiment was conducted during 2016 - 2017 to analyse the genetic diversity of fifteen high yielding rice varieties in Bangladesh by using random amplification of polymorphic DNA (RAPD) markers. Polymorphism was revealed in 12 RAPD primers out of 30, whereas no other reaction was detected on the remaining 18 primers. The 40 out of 45 bands (88.89%) polymorphics were produced by the primers and ranged from 50 to 100%. The maximum number of polymorphic bands was produced by the primer OPB-18 whereas the lowest number of polymorphic bands belonged to OPC-12. The genetic similarity coefficients were determined with the RAPD data, which ranged from 0.47 to 0.94. The unweighted paired group of arithmetic means (UPGMA) dendrogram presented the studied rice varieties into two major clusters. Moreover, the value of Nei's genetic diversity is 0.26 and the Shanon information index is 0.41. The study produced distinct positions, suggesting that the genotypes were different from each other. The results indicated that these markers could be efficient for comparing the genetic relationships, patterns of variation, and measurement of genetic distance among rice varieties. Considering all of these results, RAPD analysis is found to be an effective tool for estimating the genetic diversity of different rice varieties. The outcomes of this research may contribute to the germplasm data of rice accessions and a future breeding program of rice genotypes.

• Bulletin of the Korean Chemical Society
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• v.6 no.4
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• pp.202-206
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• 1985

The crystal structure of The crystal structure of $Ag^+$-Exchanged Zeolite A, $Ag_{4.6}Na_{7.4}-A$, dehydrated, treated with $H_2$, and evacuated, all at $350^{\circ}C$, has been determined by single crystal x-ray diffraction methods in the cubic space group Pm3m at $24(1)^{\circ}C;$ a = $12.208(2)\AA.$ The structure was refined to the final error indices R1 = 0.088 and R2 (weighted) = 0.069 using 194 independent reflections for which II_0$ > $3{\sigma}(I_0)$. On threefold axes near the centers of 6-oxygen rings, $7.4 Na^+$ ions and $0.6 Ag^+$ ions are found. Two non-equivalent 8-ring $Ag^+$ ions are found off the 8-ring planes, each containing about $0.6 Ag^+$ ions. Three non-equivalent Ag atom positions are found in the large cavity, each containing about 0.6 Ag atoms. This crystallographic analysis may be interpreted to indicate that $0.6 (Ag_6)^{3+}$ clusters are present in each large cavity. This cluster may be viewed as a nearly linear trisilver molecule $(Ag_3)^0$ (bond lengths, 2.92 and 2.94 $\AA;$ angle, $153^{\circ})$ stabilized by the coordination of each atom to a Ag^+$ ion at 3.30, 3.33, and 3.43 $\AA$, respectively. In addition, one of the silver atoms approaches all of the 0(1) oxygens of a 4-ring at $2.76\AA.$ Altogether $7.4 Na^+$ ions, $1.8 Ag^+$ ions, and 1.8 Ag atoms are located per unit cell. The remaining $1.0 Ag^+$ ion has been reduced and has migrated out of the zeolite framework to form silver crystallites on the surface of the zeolite single crystal.

• Bulletin of the Korean Chemical Society
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• v.10 no.3
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• pp.234-238
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• 1989

The crystal structure of partially $Ag^+$-exchanged zeolite A, $Ag_{3.2}Na_{8.8}$-A, vacuum dehydrated at $360^{\circ}C$ and then exposed to 0.1 torr of cesium vapor for 12 hours at $250^{\circ}C$ has been determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m (a = 12.262(2)${\AA})\;at\;21(1)^{\circ}C$. The structure was refined to the final error indexes $R_1=0.068\;and\;R_2=0.072$ by using 338 reflections for which $I_o\;>\;3{\sigma}(I_o)$ and the composition of unit cell is $Ag_{3.2}Cs_{8.8}-A.\;3\;Cs^+$ ions lie on the centers of the 8-rings at sites of D4h symmetry. Two crystallographycally different 6-ring $Cs^+$ ions were found: 1.5 $Cs^+$ ions at Cs(2) are located inside of sodalite cavity and 4.3 $Cs^+$ ions at Cs(3) are located in the large cavity. The fractional occupancies observed at Cs(2) and Cs(3) indicate that the existence of at least three types of unit cells with regard to the 6-ring $Cs^+$ ions. For example, 50% of unit cells may have two $Cs^+$ ions at Cs(2) and 4 $Cs^+$ ions at Cs(3). 30% of unit cells may have one Cs+ ion at Cs(2) and 5 $Cs^+$ ions at Cs(3). The remaining 20% would have one $Cs^+$ ion at Cs(2) and 4 $Cs^+$ ions at Cs(3). On threefold axes of the unit cell two non-equivalent Ag atom positions are found in the large cavity, each containing 0.64 and 1.92 Ag atoms, respectively. A crystallographic analysis may be interpreted to indicate that 0.64 $(Ag_5)^+$ clusters are present in each large cavity. This cluster may be viewed as a tetrasilver molecule $(Ag_4)^0$(bond length, 2.84${\AA}$) stabilized by the coordination of one $Ag^+$ ion.

• Bulletin of the Korean Chemical Society
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• v.13 no.4
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• pp.363-367
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• 1992

The crystal structure of (1,3,6,9,11,14-hexaazatricycol[12.2.1.$1^{6,9}$]octadecane)copper(Ⅱ) perchlorate, Cu($C_{12}H_{26}N_6$)$(ClO_4)_2$, has been determined by the X-ray diffraction methods. The crystal data are as follows: Mr=516.9, triclinic, ${\alpha}=8.572\;(2)$, b=8.499 (3), c=15.204 (3) ${\AA}$, ${\alpha}=80.42\;(5),\;{\beta}=73.57\;(3),\;{\gamma}=69.82\;(4)^{\circ},\;V=994.2\;{\AA}^3,\;D_C=1.726\;gcm^{-3}$, space group $P{\tilde{1}},\;Z=2,\;{\mu}=21.27\;cm^{-1}&, F(000)=534 and T=297 K. The structure was solved by direct methods and refined by full-matrix least-squares methods to and R value of 0.081 for 1608 observed reflections measured with graphite-mono-chromated Mo Ka radiation on a diffractometer. There are two independent complexes in the unit cell. The two copper ions lie at the special positions (1/2, 0, 0) and (0, 1/2, 1/2)and each complex possesses crystallographic center of symmetry. Each Cu ion is coordinated to four nitrogen donors if the hexaazamacrotricyclic ligand and weakly interacts with two oxygen atoms of the perchlorate ions to form a tetragonally distorted octahedral coordination geometry. The Cu_N (sec), Cu_N(tert) and Cu_O coordination distances are 1.985 (14), 2.055 (14) and 2.757 (13) ${\AA}$ for the complex A and 1.996 (10), 2.040 (11) and 2.660 (13) ${\AA}$ for the complex B, respectively. The macrocycles in the two independent cations assume a similar conformation with the average r.m.s. deviation of 0.073 ${\AA}$. Two 1,3-diazacyclopentane ring moieties of the hexaazamacrotricyclic ligand are placed oppositely and almost perpendicularly to the square coordination plane of the ruffled 14-membered macrocycle. The secondary N atoms are hydrogen-bonded to the perchlorate O atoms with distances of 3.017 (23) and 3.025 (19) ${\AA}$ for the complexes A and B, respectively.

• Archives of Orthopedic and Sports Physical Therapy
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• v.14 no.2
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• pp.33-44
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• 2018

Purpose: The primary purpose of this study was to investigate the effects of cervical stabilization exercise (CSE) on hamstring flexibility in patients with neck pain. A secondary purpose of this study was to investigate the effects of cervical range of motion (CROM) and craniovertebral angle (CVA). Methods: This study was a single-blind, randomized, comparative trial. Twenty patients were allocated into either the cranio-cervical flexion exercise (CCFE) group or the CSE group. Before and after the intervention, we measured straight leg raise (SLR), popliteal angle (PA), CROM, and CVA in the sitting and standing positions. Fisher's exact test, the Mann-Whitney test, and Wilcoxon's signed-rank test were used to analyze our data. Results: Both groups showed significant improvements in the value of SLR, PA, cervical extension, cervical rotation, and CVA in the standing position (both, p<.05) after intervention. However, only the CSE group showed significant improvements in cervical right lateral flexion (z=-2.209; p<.01) and cervical left lateral flexion (z=-2.537; p<.05) after intervention. The CSF group showed more significant improvements in SLR, PA, both cervical lateral flexions, and both cervical rotations than the CCFE group. Conclusions: The results of this study will guide future research in identifying the effectiveness of CSE. In conclusion, it can be inferred that CSE has a positive effect on SLR, PA, CROM, and CVA in the standing position in patients with chronic neck pain.

• Journal of English Language & Literature
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• v.64 no.3
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• pp.453-468
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• 2018

Nat Turner's rebellion in 1831 was considered pre Civil War South's most dreadful nightmare due to the merciless murder of white slave owner victims. The motive of vengeance has been emphasized as that of Turner's notorious black preacher religious fanaticism. However, the recent film, The Birth of a Nation (2016) directed by Nate Parker, utilized the identical title of a film (1915) directed by D. W. Griffith. Providing limited evidence, information about the rebellion in Thomas Gray's pamphlet The Confessions of Nat Turner (1831), was the only accessible historical source for the factual event of the slaves' rebellion. In addition, William Styron's The Confessions of Turner (1967), a fictionalized biography, also examined Turner's life in the harshness of slavery. Although these two texts deal with the personal level of Nat Turner's rage and religious enthusiasm, both provide only fractured parts of the motive of vengeance. Strikingly, Parker's film interrogates the ideology of "victims," as well as the hierarchical term of "confessions," with their different positions between whites and blacks. More specifically, Parker's film offers discursive fields of proslavery arguments regarding biblical interpretations in addition to external visualization of slaves' inner emotional lives. The film demonstrates how the institution of slavery allowed slaves to be exploited, beaten, raped, through interrogating the problematic image of the "contested hero" Nat Turner. In contrast to the traditional image of blacks' bloody rebellion, the film underlines the absurdity of certain Biblical misinterpretations. It furthermore implies how the 1915 film manipulated proslavery propaganda in America.