• Honam Mathematical Journal
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• v.40 no.4
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• pp.749-763
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• 2018

In this paper firstly, It was studied almost paraholomorphic vector field with respect to almost para-Nordenian structure ($F^S$, g) and the purity conditions of the Sasakian metric is investigate with respect to almost para complex structure F on cotangent bundle. Secondly, we obtained the integrability conditions of almost paracomplex structure F by calculating the Nijenhuis tensors of F of type (1, 1) on $^CT(M_n)$. Finally, the Tachibana operator ${\phi}_{\varphi}$ applied to $^Sg$ according to F and the Vishnevskii operators (${\psi}_{\varphi}$-operator) applied to the vertical and horizontal lifts with respect to F on cotangent bundle.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.725-731
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• 2006

A novel design of frequency multiplier using a feedforward technique and a defected ground structure(DGS) is proposed. The feedforward loop in the proposed frequency multiplier suppresses the fundamental component $(f_0)$, the dumb-bell or spiral shaped DGS diminish unwanted harmonics such as second, third and fourth. Due to the combination of the feedforward structure and the DGS, only the multiplied frequency component$(2f_0,\;3f_0,\;4f_0)$ appears at the output port and the other unwanted components are suppressed excellently. The frequency multiplier is designed at 1 GHz $(f_0)$, by the proposed technique and measured. The measured output power of $2f_0,\;3f_0$ and $4f_0$ is -2.59 dBm, -5.36dBm and -4.57dBm, respectively, when the input power is 0dBm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.9
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• pp.49-54
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• 2008

In this paper, the power added efficiency(PAE) of class F power amplifier is improved by applying a new Photonic Bandgap (PBG) structure on the output of amplifier. The proposed spiral PBG structure is a two-dimensional (2-D) periodic lattice patterned on a dielectric slab that does not require nonplanar fabrication process. This structure bas higher suppression performance at second harmonic. Also, It has a sharp skirt property. This new PBG structure can be applied with class F power amplifier for efficiency improvement. We obtained the PAE of 73.62 % for CDMA applications, and the PAE performance is improved as much as 6.2 % compared with that of a conventional class F power amplifier.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.2
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• pp.81-86
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• 2007

In this paper, the Power Added Efficiency (PAE) and linearity of class-F PA has been improved by using the PBG structure and the application of EER structure, simultaneously. The adaptive bias control circuit has been employed to improve the PAE through the application of EER structure. The PBG structure has been adapted for improving the Linearity by suppressing the harmonics on the output of amplifier. The PAE and the 3rd Inter-Modulation Distortion (IMD) has improved 34.56%, 10.66 dB, compared with those of the conventional Doherty amplifier, respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.745-749
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• 2001

The rigid body properties of a structure may be estimated easily if the mass-line of the structure could be taken exactly. However, the exact mass-line cannot be obtained experimentally. In the past years, the modal analysis for which the structure is mounted on the flexible supporter is frequently used to acquire the mass-line. Unfortunately, it is difficult not only to mount the structure but also to decouple the coupled 6 dof mode. If the structure is pended by very long and flexible rope to act free, the rigid-body modes influenced by the rope will be eliminated and the improved mass-line will be obtained. In this paper, the method using the mass-line of F.R.F. for rigid body in free-condition is suggested. The robustness of the suggested method was tested and verified numerically. The experimental results also showed a good agreement with the true value.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.11a
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• pp.101-105
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• 2002

FRP(Fiber glass reinforced plastics) is compound with materials, which are created to combine each other materials, of which nature of mechanical and chemical are different. Even though the weight and the thickness are identic, its physical figure of characteristic changes with consisting of lay-up and work situation. It is also a method of creating after manufacturing of mould. It has feature that manufacturing of FRP runs parallel design of material with design of structure simultaneously. The rule of FRP structure is distinguished from the length of a ship and it is hard to catch the feature of structure mechanics due to identical formula and figure used for it regardless of the shape of a ship or the speed. This studying, basing on a small FRP ship, will show te fundamental data needed to design of structure analysing the feature of intensity with direction, the method of Lay-up, and the characteristic of materials of FRP.

• Smart Structures and Systems
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• v.21 no.6
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• pp.777-791
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• 2018

This paper discusses the shape control of deformable mirrors for Adaptive Optics in the dynamic range. The phenomenon of control-structure interaction appears when the mirror becomes large, lowering the natural frequencies $f_i$, and the control bandwidth $f_c$ increases to improve the performance, so that the condition $f_c{\ll}f_i$ is no longer satisfied. In this case, the control system tends to amplify the response of the flexible modes and the system may become unstable. The main parameters controlling the phenomenon are the frequency ratio $f_c/f_i$ and the structural damping ${\zeta}$. Robustness tests are developed which allow to evaluate a lower bound of the stability margin. Various passive and active strategies for damping augmentation are proposed and tested in simulation.

• Journal of IKEEE
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• v.28 no.1
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• pp.110-115
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• 2024

This paper analyzed the V_th (Threshold Voltage) variations in 3D NAND Flash memory with tapered O/N/O (Oxide/Nitride/Oxide) structure and O/N/F (Oxide/Nitride/Ferroelectric) structure, where the blocking oxide is replaced by ferroelectric material. With a tapering angle of 0°, the O/N/F structure exhibits lower resistance compared to the O/N/O structure, resulting in reduced V_th variations in both the upper and lower regions of the WL (Word Line). Tapered 3D NAND Flash memory shows a decrease in channel area and an increase in channel resistance as it moves from the upper to the lower WL. Consequently, as the tapering angle increases, the V_th decreases in the upper WL and increases in the lower WL. The tapered O/N/F structure, influenced by V_fe proportional to the channel radius, leads to a greater reduction in V_th in the upper WL compared to the O/N/O structure. Additionally, the lower WL in the O/N/F structure experiences a greater increase in V_th compared to the O/N/O structure, resulting in larger V_th variations with increasing tapering angles.

• Journal of the Korean Chemical Society
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• v.41 no.4
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• pp.175-179
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• 1997

Luminescence of $Eu^{3+}$ has been studied in $Sr_{2-2x}Eu_xK_xSnO_4$ with two-dimensional $K_2NiF_4$ structure. The $^5D_o$ → $^7F_o$$Eu^{3+}$ ion represents the J=0 → J=0 transition which is forbidden by a Judd-Ofelt selection rule for electric dipole transition in 4f shell of $Eu^{3+}$ ions. However, the emission line of $^5D_o$ → $^7F_o$$Eu^{3+}$ emission spectra of Sr2-2xEuxKxSnO4$Sr_{2-2x}Eu_xK_xSnO_4$structure around $Eu^{3+}$ ions.

• Journal of Sericultural and Entomological Science
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• v.36 no.1
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• pp.30-36
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• 1994

choChorion(egg-shell) morphology of the F1 hybrid between Bombyx mori and Bombyx mandarina has been observed by scanning electrom microscope and chorion protein was analyzed by electrophoresis. The chorion surface structure of F1 hybrids in the lateral(flat) region was similar to that of maternal line. The F1 hybrids chorion was found to have basically a three layer structure. The middle and inner layer were very much like those of the Bombyx mandarina and Bombyx mori. There were many conic pillar structures in the outer layer of the F1 hybrid, which was similar to Bombyx mandarina. This conic pillar structure had a thin cover layer was more clear in the dorsal and ventral side of the F1 hybrid chorion. The conic pillar structure of Bombyx mandarina was found to be dominant in F1 hybrid chorion irrespective of their maternal line. Major components of chorion protein were analyzed by two-dimensional electrophoresis and found to have isoelectric points in the range of pH 4.0-6.5 and molecular weight 10 to 50 kd. F1 hybrid chorion protein components related directly to those of the maternal line. The conic pillar structure was dominat characteristic and it was present in all F1 hybrid.