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Naqvi Furqan Ul Hassan,Naqvi Furqan Ul Hassan,Kim Tae Heon,Ahn Chang Won,Hwang Younghun 한국물리학회 2022 Current Applied Physics Vol.44 No.-
Structural and vibrational characteristics of methylammonium(MA) halide perovskite MAPbBr3-xClx single crystals (x = 0–3) were investigated by using powder X-ray diffraction and Raman scattering experiments. The lattice constant in the cubic phase obtained from powder X-ray diffraction peaks at room temperature showed nearly a linear dependence as a function of composition. On the other hand, some of the Raman mode frequencies obtained from single crystals exhibited substantial changes in both frequency shifts and half widths over the investigated composition range. Especially, the MA torsional mode showed a significant change from 325 to 485 cm 1 and mode splitting as Cl was replaced by Br. This mode splitting was more clearly seen at low temperatures reflecting the symmetry lowering of the local structure. The contrast between the linear change in the lattice constant and the substantial change in the vibrational frequencies and half widths of the MA torsional mode in the intermediate composition range indicates the local heterogeneous environment for the MA cations caused by the substitutional disorder.
Furqan Ul Hassan Naqvi,Jae-Hyeon Ko,Ki-Soo Lim 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.4
The elastic constants of tetragonal tungsten-bronze lead barium niobate, Pb(1-x)BaxNb2O6 with x = 0.5, were determined under poled and unpoled conditions by using Brillouin spectroscopy. The elastic constant C11 was larger than C33 similar to other ferroelectric tungsten-bronze systems. The C11 did not show any appreciable change between the poled and unpoled conditions while the C33 increased from 117 to 173 GPa upon poling the sample. This substantial change was attributed to the higher density of domain walls and the polar nanoregions in the unpoled condition and the resulting strong coupling between the longitudinal acoustic waves propagating along the polar c-axis and the one-dimensional order parameter aligned along the same direction. This elastic anisotropy associated with the dimensionality affected the acoustic damping and the central peak behaviors.
Furqan Abid,Wonhoi Kim,Junho Lee,Seoji Lee 한국지능정보시스템학회 2023 한국지능정보시스템학회 학술대회논문집 Vol.2023 No.10
Object recognition is one of the critical tasks for an autonomous agent. Previous studies mostly dealt with object detection for traffic agents such as cars, bicycles, and buses while the detection of road obstacles remained unatꠓtended. Obstacles on the road must also be detected to avoid collisions and ensure a high level of safety. In this paper, we introduce a novel image dataset with annotation for both categories. We report a preliminary dataset containing 7, 500 images with annotations for 7, 7 classes for the traffic agents and the road obstacles each. We further provide the detection results on a fine-tuned Yolov5 model. Our results suggest that the trained model is capable of running in real-time with a runtime of 17ms and a mean Average Precision of 0.728 on Jetson AGX Orin. In the future, we aim to collect an image dataset from our small mobility platform for better generalization to the real-world environment.
Model Analysis of fringe-projection-based 3D Measurement Systems using Real-time 3D Virtual Scanner
Furqan Ullah(펄칸 울라),Kang Park(박강) (사)한국CDE학회 2012 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2012 No.2
This paper presents a real-time 3D virtual scanning system based on fringe projection technique. In this system, four models of 3D measurement systems are evaluated based on collimating and perspective projections. Once the intensity variations of the projected fringe pattern are captured using a perspective camera, the wrapped phase is obtained by performing the phase-shifting technique. However, the obtained phase is in the range of [-π, +π] along with discontinuities. In order to unwrap it to obtain a continuous phase map, a conventional phase-unwrapping algorithm is used. Experimental and theoretical inspection of the phase-to-coordinate relation for all four cases is presented. Nonlinear system models are proposed for the collimating projection and finally, the coordinate acquisition, reconstruction, and display processes are performed in the real-time virtual environment, and results are presented to verify the proposed approaches.
Development of Fuzzy Logic based battery charging algorithm for Photovoltaic system
Furqan Asghar,Muhammad Talha,Sung Ho Kim 한국지능시스템학회 2015 한국지능시스템학회 학술발표 논문집 Vol.25 No.1
Due to the severity of the environmental pollution and global energy crisis, the photovoltaic system has become one of the most important renewable energy sources. For efficient and dynamic use of this energy source, Rechargeable batteries are widely used in stand-alone PV systems to store the surplus energy and supply this stored energy to the load in case of low renewable energy production. In this study, MPPT based photovoltaic battery charging system is proposed for Li-ion batteries using CC-CV technique and charging mechanism is effectively controlled by fuzzy logic system. CC mode is used initially to fasten the charging mechanism while CV mode is used later to avoid the battery overcharging. Buck converter is used to regulate the voltages for charging purposes whereas fuzzy logic control system is used to regulate the PID gains to determine the optimal gain value for battery charging in CC-CV modes according to PV system variant output power. Research work is being done to make charging system performance more efficient and energetic. Therefore, efficient Simulink model for PV based battery charging system is proposed and some simulation study is carried out to verify the feasibility of the proposed scheme. Simulation result showed that proposed system can overcome the disturbance of external environmental changes, and achieve fast charging than conventional charging systems.
Comparative Study of Three Fault Diagnostic Methods for Three Phase Inverter with Induction Motor
Furqan Asghar,Muhammad Talha,Sung Ho Kim 한국지능시스템학회 2017 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.17 No.4
In recent times, inverters are considered as the basic building block in an electrical drive system used widely in many industrial drive applications. However, the reliability of these inverters is mainly affected by the failure of power electronic switches. Various faults in inverter may influence the system operation by unexpected maintenance, which increases the cost factor and reduce overall efficiency. In this paper, comparative study of three different fault detection and diagnosis systems for three phase inverter is presented. The basic purpose of these fault detection and diagnosis systems is to detect single or multiple faults efficiently. These techniques rely on the neural network for fault detection and diagnosis by using Clarke transformed two-dimensional features extraction, three-dimensional features extraction and features extraction using discrete wavelet transform (DWT) with a different number of features in each technique. Several features are extracted using different mechanisms and used in the neural network as input for fault detection and diagnosis. Furthermore, a simulation study is carried out to analyze the fault detection and diagnosis response of these techniques. Also, a comparative study has been performed by considering fault detection time and accuracy. Comparison results prove the supremacy of three-dimensional feature extraction technique over other two techniques as it can detect and diagnose single, double and triple faults in a single cycle with high accuracy as compared to other two techniques multi-cycles detection.
Range-view (RV) Based Semantic Segmentation of Outdoor Point Cloud with Data Augmentation
Furqan Abid,Dong He,Jong-Hwan Kim 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11
Semantic segmentation is a critical task in scene understanding of autonomous driving. Because of the irregular and sparse structure of outdoor point clouds, semantic segmentation for point clouds has received a lot of attention from both academia and industry. In this paper, we propose an approach that combines data augmentation for point clouds and lightweight 2D semantic segmentation network. The data augmentation technique produces a balanced dataset for training by interpolating more samples of object classes. The 2D deep layer aggregation network is then employed to train a semantic segmentation model on above augmented dataset to achieve better performance while costing less memory. We benchmark our model on the NuScenes dataset against RangeNet++. Our experiments demonstrate a +1.8% rise in mIoU and an over 6-fold reduction in trainable parameters compared to the baseline.
프린지 투영법을 이용한 실시간 3D 구강 내 스캐너의 개발
Furqan Ullah,이건수(Gunn Soo Lee),박강(Kang Park) (사)한국CDE학회 2012 한국CDE학회 논문집 Vol.17 No.3
Real-time three-dimensional shape measurement is becoming increasingly important in various fields, including medical sciences, high-technology industry, and microscale measurements. However, there are not so many 3D profile tools specially designed for specifically narrow space, for example, to scan the tooth shape of a human jaw. In this paper, a real-time 3D intraoral scanner is proposed for the measurement of tooth profile in the mouth cavity. The proposed system comprises a laser diode beam, a micro charge-coupled device, a graticule, a piezoelectric transducer, a set of optical lenses, and a polhemus device sensor. The phase-shifting technique is used along with an accurate calibration method for the measurement of the tooth profile. Experimental and theoretical inspection of the phase-to-coordinate relation is presented. In addition, a nonlinear system model is developed for collimating illumination that gives the more accurate mathematical representation of the system, thus improves the shape measurement accuracy. Experiment results are presented to verify the feasibility and performance of the developed system. The experimental results indicate that overall measurement error accuracy can be controlled within 0.4 ㎜ with a variability of ±0.01.