• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.1
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• pp.280-294
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• 2023

Unmanned aerial vehicles (UAVs) and millimeter-wave frequencies play key roles in supporting 5G wireless communication systems. They expand the field of wireless communication by increasing the data capacities of communication systems and supporting high data rates. However, short wavelengths, owing to the high millimeter-wave frequencies can cause problems, such as signal attenuation and path loss. To address these limitations, research on high directional beamforming technologies continue to garner interest. Furthermore, owing to the mobility of the UAVs, it is essential to track the beam angle accurately to obtain full beamforming gain. This study presents a beam tracking method based on the unscented Kalman filter using hybrid beamforming. The simulation results reveal that the proposed beam tracking scheme improves the overall performance in terms of the mean-squared error and spectral efficiency. In addition, by expanding analog beamforming to hybrid beamforming, the proposed algorithm can be used even in multi-user and multi-stream environments to increase data capacity, thereby increasing utilization in new-radio multiple-input multiple-output orthogonal frequency-division multiplexing systems.

• KIEAE Journal
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• v.8 no.1
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• pp.93-98
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• 2008

As high rise buildings and large span spatial structures are constructed, new composite members and construction techniques are continuously developed. Wide flange steel beam can be easily constructed but the fire proofing protection is necessary and the cost is high. Nowadays environmental pollution of structures is becoming a big issue. The material of fire proofing protection is not allowed to use for structural members in several countries because it cab be a cause of environment pollution. Composite beam is a new hybrid beam system which is not needed a fire proofing protection process. Composite beam has better construction capacity than that of RC system and has more economic advantages than that of wide flange steel beam. In this paper, structural design guide lines of composite beam were provided to apply design and construction.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.43-50
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• 2007

We have investigated the electro-optical characteristics and reliability of LEDs with the Indium-Tin-Oxide (ITO) electrodes formed by different deposition methods: electron beam evaporation, sputtering, and hybrid method of electron beam evaporation and subsequent sputtering. The deposition method of the ITO electrode has significant influence on the electro-optical characteristics and reliability of LEDs. The LEDs with the ITO electrodes formed by sputtering and electron beam evaporation have problems caused by sputtering damage and increased electrical resistance, respectively, and the problems have been solved by the hybrid method.

• Structural Engineering and Mechanics
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• v.88 no.5
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• pp.481-492
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• 2023

The past earthquakes revealed the importance of the design of moment-resisting reinforced concrete framed structures with ductile behavior. Due to seismic activity, failures in framed structures are widespread in beam-column joints. Hence, the joints must be designed to possess sufficient strength and stiffness. This paper investigates the effects of fibers on the ductility of hybrid fiber reinforced self-compacting concrete (HFRSCC) when subjected to seismic actions; overcoming bottlenecks at the beam-column joints has been studied by adding low modulus sisal fiber and high modulus steel fiber. For this, the optimized dose of hooked end steel fiber content (1.5%) was kept constant, and the sisal fiber content was varied at the rate of 0.1%, up to 0.3%. The seismic performance parameters, such as load-displacement behavior, ductility, energy absorption capacity, stiffness degradation, and energy dissipation capacity, were studied. The ductility factor and the cumulative energy dissipation capacity of the hybrid fiber (steel fiber, 1.5% and sisal fiber, 0.2%) added beam-column joint specimen is 100% and 121% greater than the control specimen, respectively. And also the stiffness of the hybrid fiber reinforced specimen is 100% higher than the control specimen. Thus, the test results showed that adding hybrid fibers instead of mono fibers could significantly enhance the seismic performance parameters. Therefore, the hybrid fiber reinforced concrete with 1.5% steel and 0.2% sisal fiber can be effectively used to design structures in seismic-prone areas.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.459-468
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• 2015

In this paper, we consider an uplink multiuser hybrid beamforming system where an access point (AP) communicates with multiple users simultaneously. The performance of the uplink multiuser hybrid beamforming system depends on the effective channel which is given by the product of the channel matrix and the analog beams. Therefore, to maximize the performance, we need to obtain the channel information and then select the analog beams appropriately by using the acquired channel information. In this paper, we propose the channel estimation method and low complexity analog beam selection algorithm for the uplink multiuser hybrid beamforming system. Additionally, our analysis shows that the proposed low complexity analog beam selection algorithm provides much less complexity than the optimum analog beam selection algorithm. From the numerical results, we confirm that the proposed low complexity analog beam selection algorithm has little performance degradation in spite of much less complexity than the optimum analog beam selection algorithm under the equal system configuration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1279-1290
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• 2007

In this paper, a cylindrical hybrid antenna which is spatially fed by an off-set linear feed array is described to form complex beam patterns. The linear feed array consists of twelve micro-strip patch elements and forms a flat-topped beam pattern with a beam-width of $90^{\circ}$ in the horizontal plane. The vertical curve on the cylindrical reflector with the linear feed array is shaped in order to form a cosecant beam pattern within the range of $-5^{\circ}$ to $-25^{\circ}$ in the vertical plane. To form complex beam patterns, the hybrid antenna with cylindrical reflector aperture of $140{\times}50\;cm$ was designed and fabricated to be operated within the IMT 2000 service band, and also electrical performances of the antenna were measured and analyzed.

• Journal of Korean Society of Steel Construction
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• v.28 no.3
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• pp.151-162
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• 2016

This study developed the shape of low depth new shape high performance hybrid composite beam which is taken strengths and compensated the defect of composite beam and hybrid beam. Also, this study performed the monotonic test to evaluate the bending performance of Low depth shape by creating 12 bending specimens. Bending performance test result showed that capacity of the beam was increased stably. Also, it is possible to apply the existing evaluation equation(KBC 2009) of composite beam. Mechanical properties and structural performance of materials are considered when high-strength steel ($F_y=650MPa$) is applied to the bottom plate.

• Journal of KSNVE
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• v.10 no.3
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• pp.437-443
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• 2000

The optimal design problem for increasing dynamic stiffness using hybrid model which composed of original detailed BIW(body in white) and impinged beam elements is investigated. Using the characteristics of the beam elements and design sensitivity analysis this approach utilizes an optimization technique to determine the optimal section properties of beam elements. The constraint is to increase the first natural frequency by five percent compared with original one. The results show that the first torsion and bending natural frequencies are increased by five percent using hybrid model and optimization. These results indicate that this optimization method can be employed to enhance the dynamic stiffness of vehicle body structure in design concept stage.

• Journal of Mechanical Science and Technology
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• v.19 no.3
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• pp.811-819
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• 2005

In this study, we present a new efficient hybrid-mixed composite laminated curved beam element. The present element, which is based on the Hellinger-Reissner variational principle and the first-order shear deformation lamination theory, employs consistent stress parameters corresponding to cubic displacement polynomials with additional nodeless degrees in order to resolve the numerical difficulties due to the spurious constraints. The stress parameters are eliminated and the nodeless degrees are condensed out to obtain the ($6{\times}6$) element stiffness matrix. The present study also incorporates the straightforward prediction of interlaminar stresses from equilibrium equations. Several numerical examples confirm the superior behavior of the present composite laminated curved beam element.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.76-79
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• 2005

Bending deformation and energy absorption characteristics of aluminum-composite hybrid tube beams have been analyzed for improvement in the bending performance of aluminum space frame by using experimental tests combined with theoretical and finite element analyses. Hybrid tube beams composed of glass fabric/epoxy layer wrapped around on aluminum tube were made in autoclave with the recommended curing cycle. Basic properties of aluminum material used for initial input data of the finite element simulation and theoretical analysis were obtained from the true stress-true strain curve of specimen which had bean extracted from the Al tube beam. A modified theoretical model was developed to predict the resistance to the collapse of hybrid tube beams subjected to a bending load. Theoretical moment-rotation angle curves of hybrid tube beams were in good agreement with experimental ones, which was comparable to the results obtained from finite element simulation. Hybrid tube beams strengthened by composite layer on the whole web and flange showed an excellent bending strength and energy absorption capability.