• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.12
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• pp.1060-1068
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• 2011

In this paper, Current-Mode Class-D(CMCD) RF Power Amplifier(PA) is designed and implemented at 900 MHz. Conventional CMCD PA has output parallel resonator to reconstruct a fundamental frequency component of the output signal. However the resonator can be removed by connecting inverse class-F PAs because even-harmonic components can be removed by CMCD PA's push-pull structure. Using load-pull, inverse class-F PA with GaN transistors is designed, and CMCD PA with the inverse class-F PA is implemented. The CMCD PA has 64.5 % drain efficiency, 34.2 dBm output power. Comparing with the drain efficiency of a CMCD PA with parallel resonator, the CMCD with the inverse class-F technology has 13.6 % improved drain efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.679-688
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• 2010

The major objective of the present study is to extend the applications of inverse analysis to more realistic engineering fields with a complex combustion process rather than the traditional simple heat-transfer problems. In order to do this, the unknown initial mass fractions of $CH_4/O_2$ are estimated from the temperature measurement data by inverse analysis in the practical diffusion-controlled turbulent combustion problem. In order to ensure efficient inverse analysis, the repulsive particle swarm optimization (RPSO) method, which belongs to the class of stochastic evolutionary global optimization methods, is implemented as an inverse solver. Based on this study, it is expected that useful information can be obtained when inverse analysis is used in the diagnosis, design, or optimization of real combustion systems involving unknown parameters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.158-164
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• 2006

In this paper, we proposed a new algorithm of the inverse scattering for the reconstruction of unknown dielectric scatterers using the finite-difference time-domain method and the design sensitivity analysis. We introduced the design sensitivity analysis based on the gradient information for the fast convergence of the reconstruction. By introducing the adjoint variable method for the efficient calculation, we derived the adjoint variable equation. As an optimal algorithm, we used the steepest descent method and reconstructed the dielectric targets using the iterative estimation. To verify our algorithm, we will show the numerical examples for the two-dimensional $TM^2$ cases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5389-5396
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• 2012

In this paper, an optimized residual data decoder architecture is proposed to improve the performance in H.264/AVC. The proposed architecture is an integrated architecture that combined parallel inverse transform architecture and parallel inverse quantization architecture with common operation units applied new inverse quantization equations. The equations without division operation can reduce execution time and quantity of operation for inverse quantization process. The common operation unit uses multiplier and left shifter for the equations. The inverse quantization architecture with four common operation units can reduce execution cycle of inverse quantization to one cycle. The inverse transform architecture consists of eight inverse transform operation units. Therefore, the architecture can reduce the execution cycle of inverse transform to one cycle. Because inverse quantization operation and inverse transform operation are concurrency, the execution cycle of inverse transform and inverse quantization operation for one $4{\times}4$ block is one cycle. The proposed architecture is synthesized using Magnachip 0.18um CMOS technology. The gate count and the critical path delay of the architecture are 21.9k and 5.5ns, respectively. The throughput of the architecture can achieve 2.89Gpixels/sec at the maximum clock frequency of 181MHz. As the result of measuring the performance of the proposed architecture using the extracted data from JM 9.4, the execution cycle of the proposed architecture is about 88.5% less than that of the existing designs.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.187-193
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• 2002

Since the bus is regarded as the one of the most public transportation systems, research on the safety and facilities of the bus has been increased actively in recent years. In this paper, we concern the design of the bus door mechanism that is composed of many linkages and actuators(or motors). In particular, the folding door mechanism is representative system installed in most of urban buses. To design the folding door mechanism, we construct the kinematic and dynamic analysis model fur computer simulation. Also, the dynamic analysis is accomplished by both direct dynamics and inverse dynamics. Since the folding door mechanism has many design variables, the analysis program is developed to perceive kinematic and dynamic characteristics according to the design variables and simulation conditions.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.4
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• pp.206-215
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• 2016

Delta parallel robots are now widely used for high-speed applications. However, typical Delta robots, such as ABB Flexpicker suffer from rotating axis with passive prismatic joint subjected to critical speed and so requiring careful maintenance. In this paper, a novel 4-DOF high-speed parallel robot with four legs is presented, which consists of three legs with 90 degree arrangement for translational motions and one remaining leg with rack & pinion gears for rotational motion. The inverse kinematics, velocity, acceleration, statics, and inverse dynamics have been analyzed. From the workspace analysis and inverse dynamics simulation for 0.43 sec cycle time, the 4-axis parallel robot prototype with 12kg payload has been designed. In the future research, computed torque control methods will be developed for the prototype.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.94-97
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• 2001

An inverse finite element approach is employed for more capability to design the optimum blank shape from the desired final shape with small amount of computation time and effort. For multi-stage deep-drawing processes, numerical analysis is extremely difficult to carry out due to its complexities and convergence problem as well as tremendous computation time. In this paper, multi-stage finite element inverse analysis is applied to multi-stage rectangular cup drawing processes to calculate intermediate blank shapes and strain distributions in each stages. Deformation history of the previous stage is considered in the computation. Finite element patches are used to describe arbitrary intermediate sliding constraint surfaces.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.158-161
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• 2000

An inverse finite element approach is employed for more capability to design the optimum blank shape from the desired final shape with small amount of computation time and effort. For multi-stage deep-drawing processes, numerical analysis is extremely difficult to carry out due to its complexities and convergence problem as well as tremendous computation time. In this paper, multi-stage finite element inverse analysis is applied to multi-stage rectangular cup drawing processes to calculate intermediate blank shapes and strain distributions in each stages. Finite element patches are used to describe arbitrary intermediate sliding constraint surfaces.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.5
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• pp.747-755
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• 1990

In this paper, we presented a method of constructing a multiplier and an inverse element generator over finite field GF(3**m). We proposed the multiplication method using a descending order arithmetics of mod F(X) to perform the multiplication and mod F(X) arithmetics at the same time. The proposed multiplier is composed of following parts. 1) multiplication part, 2) data assortment generation part and 5) multiplication processing part. Also the inverse element generator is constructed with following parts. 1) multiplier, 2) group of output registers Rs, 3) multiplication and cube selection gate Gl, 4) Ri term sequential selection part. 5) cube processing part and 6) descending order mod F(X) generation part. Especially, the proposed multiplier and inverse element generator give regularity, expansibility and modularity of circuit design.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.12
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• pp.1670-1679
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• 1995

In this paper, an optimal variable structure controller with a multilayer neural inverse identifier is proposed. A multilayer neural network with error back propagation learning algorithm is used for construction the neural inverse identifier which is an observer of the external disturbances and the parameter variations of the system. The variable structure controller with the multilayer neural inverse identifier not only needs a small part of a priori knowledge of the bounds of external disturbances and parameter variations but also alleviates the chattering magnitude of the control input. Also, an optimal sliding line is designed by the optimal linear regulator technique and an integrator is introduced for solving the reaching phase problem. Computer simulation results show that the proposed approach gives the effective control results by reducing the chattering magnitude of control input.