• Smart Structures and Systems
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• 제30권3호
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• pp.245-253
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• 2022

A two-layer beam consisting of an elastoplastic layer and a functional layer made of shape memory alloy (SMA) TiNi is considered. Constitutive relations for SMA are set by a microstructural model capable to calculate strain increment produced by arbitrary increments of stress and temperature. This model exploits the approximation of small strains. The equations to calculate the variations of the strain and the internal variables are based on the experimentally registered temperature kinetics of the martensitic transformations with an account of the crystallographic features of the transformation and the laws of equilibrium thermodynamics. Stress and phase distributions over the beam height are calculated by steps, by solving on each step the boundary-value problem for given increments of the bending moment (or curvature) and the tensile force (or relative elongation). Simplifying Bernoulli's hypotheses are applied. The temperature is considered homogeneous. The first stage of the numerical experiment is modeling of preliminary deformation of the beam by bending or stretching at a temperature corresponding to the martensitic state of the SMA layer. The second stage simulates heating and subsequent cooling across the temperature interval of the martensitic transformation. The curvature variation depends both on the total thickness of the beam and on the ratio of the layer's thicknesses.

• ETRI Journal
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• 제45권5호
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• pp.795-810
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• 2023

Unmanned aerial vehicles (UAV) and ground vehicles (UGV) require advanced video analytics for various tasks, such as moving object detection and segmentation; this has led to increasing demands for these methods. We propose a zero-shot video object segmentation method specifically designed for UAV and UGV applications that focuses on the discovery of moving objects in challenging scenarios. This method employs a background memory model that enables training from sparse annotations along the time axis, utilizing temporal modeling of the background to detect moving objects effectively. The proposed method addresses the limitations of the existing state-of-the-art methods for detecting salient objects within images, regardless of their movements. In particular, our method achieved mean J and F values of 82.7 and 81.2 on the DAVIS'16, respectively. We also conducted extensive ablation studies that highlighted the contributions of various input compositions and combinations of datasets used for training. In future developments, we will integrate the proposed method with additional systems, such as tracking and obstacle avoidance functionalities.

• Smart Structures and Systems
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• 제2권4호
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• pp.357-363
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• 2006

Equations describing deformation defects, damage accumulation, and fracture condition have been suggested. Analytical and numerical solutions have been obtained for defects produced by a shear in a fixed direction. Under cyclic loading the number of cycles to failure well fits the empirical Koffin-Manson law. The developed model is expanded to the case of the micro-plastic deformation, which accompanies martensite accommodation in shape memory alloys. Damage of a shape memory specimen has been calculated for two regimes of loading: a constant stress and cyclic variation of temperature across the interval of martensitic transformations, and at a constant temperature corresponding to the pseudoelastic state and cyclic variation of stress. The obtained results are in a good qualitative agreement with available experimental data.

• Transactions on Electrical and Electronic Materials
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• 제15권1호
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• pp.37-40
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• 2014

A novel memory is reported, in which $Ge_2Sb_2Te_5$ (GST) has been used as a floating gate. The threshold voltage was shifted due to the phase transition of the GST layer, and the hysteretic behavior is opposite to that arising from charge trapping. Finite Element Modeling (FEM) was adapted, and a new simulation program was developed using c-interpreter, in order to analyze the small shift of threshold voltage. The results show that GST undergoes a partial phase transformation during the process of RESET or SET operation. A large $V_{TH}$ shift was observed when the thickness of the GST layer was scaled down from 50 nm to 25 nm. The novel 1 transistor PCM (1TPCM) can achieve a faster write time, maintaining a smaller cell size.

• Nuclear Engineering and Technology
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• 제29권6호
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• pp.433-443
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• 1997

In this work, an analytic approach to the dependability of software in the operational phase is suggested with special attention to the hardware fault effects on the software behavior : The hardware faults considered are memory faults and the dependability measure in question is the reliability. The model is based on the simple reliability theory and the graph theory which represents the software with graph composed of nodes and arcs. Through proper transformation, the graph can be reduced to a simple two-node graph and the software reliability is derived from this graph. Using this model, we predict the reliability of an application software in the digital system (ILS) in the nuclear power plant and show the sensitivity of the software reliability to the major physical parameters which affect the software failure in the normal operation phase. We also found that the effects of the hardware faults on the software failure should be considered for predicting the software dependability accurately in operation phase, especially for the software which is executed frequently. This modeling method is particularly attractive for the medium size programs such as the microprocessor-based nuclear safety logic program.

• Journal of Communications and Networks
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• 제16권4호
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• pp.436-446
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• 2014

The high intensity of research and modeling in fields of mathematics, physics, biology and chemistry requires new computing resources. For the big computational complexity of such tasks computing time is large and costly. The most efficient way to increase efficiency is to adopt parallel principles. Purpose of this paper is to present the issue of parallel computing with emphasis on the analysis of parallel systems, the impact of communication delays on their efficiency and on overall execution time. Paper focuses is on finite algorithms for solving systems of linear equations, namely the matrix manipulation (Gauss elimination method, GEM). Algorithms are designed for architectures with shared memory (open multiprocessing, openMP), distributed-memory (message passing interface, MPI) and for their combination (MPI + openMP). The properties of the algorithms were analytically determined and they were experimentally verified. The conclusions are drawn for theory and practice.

• ETRI Journal
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• 제28권3호
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• pp.347-354
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• 2006

The characteristic variation of 3-dimensional (3-D) solenoid-type embedded inductors is investigated. Four different structures of a 3-D inductor are fabricated by using a low-temperature co-fired ceramic (LTCC) process, and their s-parameters are measured between 50 MHz and 5 GHz. The circuit model parameters of each building block are optimized and extracted using the partial element equivalent circuit method and an HSPICE circuit simulator. Based on the model parameters, the characteristics of the test structures such as self-resonant frequency, inductance, and quality (Q) factor are analyzed, and predictive modeling is applied to the structures composed of a combination of the modeled building blocks. In addition, characteristic variations of the 3-D inductors with different structures using extracted building blocks are also investigated. This approach can provide a characteristic estimation of 3-D solenoid embedded inductors for structural variations.

• 한국전기전자재료학회논문지
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• 제13권3호
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• pp.200-205
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• 2000

This paper describes the structure modeling and operation characteristics of MFMIS(metal-ferroelectric-metal-insulator-semiconductor) device using the Tsuprem4 which is a semiconductor device tool by Avanti. MFMIS device is being studied for nonvolatile memory application at various semiconductor laboratory but it is difficult to fabricate and analyze MFMIS devices using the semiconductor simulation tool: Tsuprem4, medici and etc. So the new library and new materials parameters for adjusting ferroelectric material and platinum electrodes in the tools are studied. In this paper structural model and operation characteristics of MFMIS devices are measured, which can be easily adopted to analysis of MFMIS device for nonvolatile memory device application.

• 통합자연과학논문집
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• 제11권4호
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• pp.204-208
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• 2018

Comparison of different optimizer performance in photovoltaic power modeling using artificial neural deep learning techniques is described in this paper. Six different deep learning optimizers are tested for Long-Short-Term Memory networks in this study. The optimizers are namely Adam, Stochastic Gradient Descent, Root Mean Square Propagation, Adaptive Gradient, and some variants such as Adamax and Nadam. For comparing the optimization techniques, high and low fluctuated photovoltaic power output are examined and the power output is real data obtained from the site at Mokpo university. Using Python Keras version, we have developed the prediction program for the performance evaluation of the optimizations. The prediction error results of each optimizer in both high and low power cases shows that the Adam has better performance compared to the other optimizers.

• 한국전자파학회논문지
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• 제19권11호
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• pp.1254-1264
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• 2008

본 논문에서는 RF 전력 증폭기의 메모리 효과 모델링의 정확성을 향상시키기 위한 확장된 메모리 다항식 모델을 제안하고 검증하였다. 볼테라 커널 중에서 대각행렬의 성분만을 고려하는 기본적인 메모리 다항식 기반의 모델의 정확성을 향상시키기 위하여 지연차수가 다른 성분들에 의한 교차항을 추가하여 확장 모델을 구성하였다. 제안된 확장 메모리 다항식의 복잡성을 메모리리스 모델, 메모리 다항식 모델과 비교하였다. 확장된 모델을 이용하여 비선형 관계식을 행렬식으로 표현한 후, 최소 자승법(least square method)을 이용하여 변수를 추출하는 모델링 기법을 제시하였다. 또한, 제안된 기법과 간접 학습 방식을 이용하여 디지털 사전 왜곡기를 구현하기 위한 디지털 사전 왜곡부 구현 방안 및 디지털 신호 처리(DSP) 방식을 제시하였다. 제안된 모델의 성능을 검증하기 위하여 2.3 GHz 대역의 WiBro 신호를 인가한 10 W급 GaN HEMT 전력 증폭기와 30W급 LDMOS 전력 증폭기에 대하여 모델의 정확도를 비교 검토하였으며, 10W GaN HEMT 전력 증폭기에 대하여 제안된 모델을 이용하는 간접 학습 방식에 기반한 디지털 사전 왜곡기를 적용하여 인접 채널 간섭비(ACPR) 성능을 검증하였다. 제안한 모델은 메모리 다항식에 비하여 모델의 정확성을 향상시키고 10 W GaN HEMT에 대하여 디지털 사전 왜곡기 적용시 기존 방식에 비하여 3차 비선형 영역에서 평균 3 dB의 ACPR 성능 향상을 보여주었다.