Daegu Gyeongbuk Institute of Science and Technology
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Manufacturing strategies for highly sensitive and self-powered piezoelectric and triboelectric tactile sensors
Full text linkPiezoelectric and triboelectric effects are of growing interest for facilitating high-sensitivity and self-powered tactile sensor applications. The working principles of piezoelectric and triboelectric nanogenerators provide strategies for enhancing output voltage signals to achieve high sensitivity. Increasing the piezoelectric constant and surface triboelectric charge density are key factors in this enhancement. Methods such as annealing processes, doping techniques, grain orientation controls, crystallinity controls, and composite structures can effectively enhance the piezoelectric constant. For increasing triboelectric output, surface plasma treatment, charge injection, microstructuring, control of dielectric constant, and structural modification are effective methods. The fabrication methods present significant opportunities in tactile sensor applications. This review article summarizes the overall piezoelectric and triboelectric fabrication processes from materials to device aspects. It highlights applications in pressure touch, bending, texture, distance, and material recognition sensors. The conclusion section addresses challenges and research opportunities, such as limited flexibility, stretchability, decoupling from multi-stimuli, multifunctional sensors, and data processingTRUEsci
Enhanced performance of solution-processed organic light-emitting diodes with TEMPOL derivatives
No full textThis study reports novel solution-processed 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL)-derivative organic compounds in a widely employed hole-injection/transport poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) layer. The TEMPOL-derived organic dopants, synthesized via a one-step chemical procedure, exhibited distinctive molecular dipole characteristics and electrical conductivities. The green organic light-emitting diodes (OLEDs) with a 4-benzene sulfonyl-2,2,6,6-tetramethyl-1-piperidenyloxy radical (TBS)-doped PEDOT:PSS layer exhibited a maximum power efficiency (PEmax) of 25.58 lm W−1, maximum external quantum efficiency (EQEmax) of 12.19 %, and maximum current efficiency (CEmax) of 40.85 cd A−1, demonstrating significant improvements compared with the pristine PEDOT:PSS layer-based device. The PEmax (16.18 lm W−1), EQEmax (10.67 %), and CEmax (37.01 cd A−1) were obtained with fiber OLEDs under same conditions. This enhancement in OLED performance can be attributed to the decreased hole-injection barrier at the anode and emissive layer interfaces. © 2024 Elsevier B.V.FALSEscopu
Compact Posture Control System for Jumping Robot Using an Air Reaction Wheel
No full textIn this article, we propose a novel balance control method called air reaction wheel (ARW) for a small-scale legged jumping robot, which can generate high torque while being compact and lightweight. The ARW generates torque in the same direction through the combination of the torque induced by pushing the air, and the moment of inertia of ARW with the angular acceleration of the motor, resulting in high torque performance while being lighter and more compact than conventional balance control mechanisms. To validate the torque performance of the ARW, we conduct dynamic analysis and computational fluid dynamics simulations of the ARW and utilize a central composite face model to find the optimal shape for generating high torque. Furthermore, we verify that the proposed method generates high torque while being compact and lightweight compared to the conventional methods through theoretical analysis and comparative experiments on the ARW and existing mechanisms regarding torque performance. Finally, we conducted jump and landing experiments by attaching the optimized ARW model to a jumping robot, and through experimental results, we verified that the proposed mechanism contributes to stable jumping and landing. IEEEFALSEsciescopu
Training techniques and enhanced kinematic modeling for extended range twisted string actuators
No full textAs a linear actuator, the twisted string actuator (TSA) offers ease of miniaturization, flexibility, and the capability to exert a strong actuation force, due to its large gear ratio. Owing to these characteristics, TSA has recently gained attention as a suitable small actuator for wearable devices, and surgical robots. However, the operating range relative to its size has been reported as limited. This study aims to overcome this limitation by extending the operating range of TSA using the coiling phase, following the twisting phase. To achieve this, we first analyze the training process to effectively mitigate the irregular overlapping phenomena in the coiling stage of TSA, considering the hysteresis and the training effect of TSA under different loads. Second, we address the limitations of conventional TSA kinematic models and propose an improved kinematic model for the extended operating range of TSA. Specifically, this study presents the precise transition points between the twisting and coiling phases of TSA and proposes enhanced analytical models for each phase. Finally, through various experiments, we validate the proposed training process and kinematic model for extended TSA operation. It is expected that the proposed training process and kinematic model for TSA will enable precise actuation within the extended operating range, facilitating a wider array of applications. © 2024 Elsevier LtdFALSEsciescopu
APPARATUS AND METHOD FOR SUPPRESSING NOISE IN ULTRASOUND IMAGE BASED ON DEEP-LEARNING NETWORK WITHOUT REFERENCE DATA
No full text본 개시의 일 실시 예에 따른 초음파 영상의 스페클 저감 방법은 프로세서에 의해, 스페클 패턴이 포함된 제1 초음파 영상을 제공 받는 단계 및 프로세서에 의해, 제1 초음파 영상을 딥러닝 기반의 학습 모델에 입력하여 스페클 패턴의 적어도 일부가 저감된 제2 초음파 영상을 획득하는 단계를 포함하고, 학습 모델은 스페클 패턴이 포함된 서로 다른 초음파 영상이 각각 입력 및 레이블(label)로 구성된 훈련 데이터로 훈련된 학습 모델일 수 있다
Fabrication and characterization of lead lanthanum zirconate titanate ceramic-based fully transparent piezoelectric loudspeakers for next-generation electronic devices
No full textTransparency is a critical attribute of next-generation electronic devices; this ensures unobstructed visibility while maintaining device functionality. Traditional electromagnetic coils are opaque, and piezoelectric materials with high optical transparency, low power consumption, and rapid responses are required when preparing innovative transparent electronics. In this study, we developed lead lanthanum zirconate titanate (PLZT) ceramics with excellent transparency (PLZT S1 = 65 %, PLZT S2 = 42 % at 550 nm) and piezoelectric properties (PLZT S1 = 180 pC/N, PLZT S2 = 470 pC/N). An indium tin oxide (ITO)-coated PLZT ceramic (PLZT S2) was used to create a fully transparent transducer with a glass diaphragm. This delivered outstanding sound output, attaining 105 dB at the resonance frequency (5.6 kHz) at an input of only 5 Vpp. To demonstrate the versatility of PLZT in terms of transparent electronic applications, PLZT transducers were placed on a desiccator wall; this showcased their capacity to emit a warning sound without compromising visibility when gas leaked inside the desiccator. An ITO-coated PLZT disc was employed to fabricate a loudspeaker with a polyethylene terephthalate (PET) diaphragm; this produced sounds from 30 dB to 68 dB across the entire voice frequency spectrum (500 Hz–8 kHz) with an input of 10 Vpp. This loudspeaker meets the demands of next-generation transparent electronics; optical visibility and high-quality sound reproduction are assured without any compromise in terms of sound quality or visual transparency. © 2024 Elsevier B.V.FALSEsciescopu
Machine Learning-Enhanced Skull-Universal Acoustic Hologram for Efficient Transcranial Ultrasound Neuromodulation Across Varied Rodent Skulls
No full textUltrasound neuromodulation (UNM) has gained significant interest in brain science due to its non-invasive nature, precision, and deep brain stimulation capabilities. However, the skull poses challenges along the acoustic path, leading to beam distortion and necessitating effective acoustic aberration correction. Acoustic holograms used with single-element ultrasound transducers offer a promising solution by enabling both aberration correction and multi-focal stimulation. A major limitation, however, is that hologram lenses designed for specific skulls may not perform well on other skulls, requiring multiple custom lenses for scaled studies. To address this, we introduce the Skull-Universal Acoustic Hologram (SUAH), which enables efficient transcranial UNM across various skull types. Our hologram generation framework integrates a physics-based acoustic hologram, differentiable acoustic simulation in heterogeneous media, and a gradient accumulation technique. SUAH, trained on a range of rodent skull shapes, demonstrated remarkable generalizability and robustness, even outperforming the Skull-Specific Acoustic Hologram (SSAH). Through comprehensive analyses, we showed that SUAH performs exceptionally well - even when trained on smaller datasets - significantly outperforming training based on individual skulls. In conclusion, SUAH shows promise as a scalable, versatile, and accurate tool for ultrasound neuromodulation, representing a significant advancement over conventional single-skull hologram lenses. Its ability to adapt to different skull types without the need for multiple custom lenses has the potential to greatly facilitate research in ultrasound neuromodulation. © IEEE.FALSEsciescopu
ELECTRONIC DEVICE AND CONTROLLING METHOD OF ELECTRONIC DEVICE
No full text전자 장치 및 전자 장치의 제어 방법이 개시된다. 본 개시에 따른 전자 장치의 제어 방법은 제1 데이터를 획득하는 단계, 제1 데이터에 결측된 제1 센싱 값이 포함되면, 제1 데이터가 획득된 시점 이전에 센서를 통해 획득된 데이터에 포함된 센싱 값들 중 제1 센싱 값에 대응되는 복수의 센싱 값을 데이터의 시간적 보간을 수행하도록 학습된 제1 신경망 모델에 입력하여, 제1 센싱 값이 시간적으로 보간된 제1 보간 값을 획득하는 단계, 제1 데이터에 포함된 센싱 값들 중 제1 센싱 값 주변의 영역에 포함된 복수의 센싱 값을 데이터의 공간적 보간을 수행하도록 학습된 제2 신경망 모델에 입력하여, 제1 센싱 값이 공간적으로 보간된 제2 보간 값을 획득하는 단계 및 제1 보간 값 및 제2 보간 값의 가중합 연산 결과에 따라 제3 보간 값을 획득하는 단계를 포함한다
SDN기반 예측 링크 캐싱을 통한 동적 네트워크 지연 시간 감소
No full textSoftware-Defined Networking, Mobile node, Predictive Forwarding Rule Caching, Dynamic Network Optimization, Unmanned Swarm NodeIn recent mission-critical environments like industry and military settings, the use of unmanned vehicles is increasing. In these settings, a ground control system (GCS) and nodes such as unmanned ground vehicles (UGVs) and unmanned aerial vehicles (UAVs) are included. The GCS and nodes transmit control data to manage unmanned vehicle operations and sensor data that provide details about real-world conditions. If disruptions or delays occur in data transmission during the interaction among these components, it may negatively impact mission performance. In dynamic networks, path calculations are performed in a distributed approach. However, this method generates significant network traffic as each node individually communicates to identify new routes. The increased traffic causes internal interference, which leads to delays in communication and potential data loss. In contrast, software-defined networking (SDN) offers a centralized approach that calculates paths for all nodes from a single central point, thereby reducing network traffic. However, speed of generating new routes remains independent of whether the approach is centralized, so SDN does not always guarantee faster results. As a result, even in an SDN framework, creating new routes as quickly as possible remains a critical challenge.
This paper introduces a caching technique for forwarding rules based on predicted link states in SDN, named the caches routing information in mobile SDN optimized network (CRIMSON) algorithm. The CRIMSON algorithm detects network link state changes caused by node mobility and caches new forwarding rules in advance based on expected topology changes. We evaluate the performance of CRIMSON by comparing the amount of internal traffic and end-to-end communication latency in dynamic networks. Simulation results demonstrate that CRIMSON generates less internal traffic compared to the proactive mode. Additionally, CRIMSON reduces end-to-end latency by an average of 88.96% and 59.49% compared to conventional reactive and proactive methods, respectively. The results indicate CRIMSON, an SDN method for storing forwarding rules based on predicted link states can contribute to stable mission performance by reducing latency in dynamic networks.
Keywords: Software-Defined Networking, Mobile node, Predictive Forwarding Rule Caching, Dynamic Network Optimization, Unmanned Swarm Node|최근 산업 및 군사와 같은 미션 크리티컬 환경에서 무인 차량의 사용이 증가하고 있다. 이러한 환경에서는 ground control system (GCS)과 unmanned ground vehicles (UGV), unmanned aerial vehicles (UAV) 와 같은 노드들이 포함된다. GCS와 노드는 무인 차량의 작동을 관리하기 위한 제어 데이터와 실제 환경에 대한 세부 정보를 제공하는 센서 데이터를 전송한다. 이러한 구성 요소 간의 상호작용 중 데이터 전송에 방해나 지연이 발생하면 임무 수행에 부정적인 영향을 미칠 수 있다. 동적 네트워크에서는 경로 계산이 분산 방식으로 수행된다. 그러나 이 방식은 각 노드가 새로운 경로를 식별하기 위해 개별적으로 통신함에 따라 상당한 네트워크 트래픽을 발생시킨다. 이러한 트래픽 증가는 내부 간섭을 초래하여 통신 지연과 데이터 손실로 이어질 수 있다. 반면, software-defined networking (SDN)은 모든 노드의 경로를 중앙의 단일 지점에서 계산하는 중앙집중식 접근 방식을 제공하여 네트워크 트래픽을 줄일 수 있다. 하지만 새로운 경로를 생성하는 속도는 중앙집중식 접근 방식인지 여부와 무관하므로 SDN이 항상 더 빠른 결과를 보장하지는 않는다. 따라서 SDN 프레임워크 내에서도 가능한 한 빠르게 새로운 경로를 생성하는 것은 여전히 중요한 과제로 남아있다.
본 논문에서는 SDN에서 예측된 링크 상태를 기반으로 포워딩룰을 캐싱하는 기술인 CRIMSON(Caches Routing Information in Mobile SDN Optimized Network) 알고리즘을 소개한다. CRIMSON 알고리즘은 노드 이동으로 인해 발생하는 네트워크 링크 상태 변화를 감지하고, 예상되는 토폴로지 변화를 기반으로 새로운 전달 규칙을 사전에 캐싱한다. 우리는 동적 네트워크에서 내부 트래픽 양과 종단 간 통신 지연 시간을 비교하여 CRIMSON의 성능을 평가한다. 시뮬레이션 결과, CRIMSON은 사전 대응형(proactive) 방식과 비교했을 때 내부 트래픽이 더 적게 발생함을 보여준다. 또한, CRIMSON은 기존의 반응형(reactive) 및 사전 대응형(proactive) 방식과 비교하여 종단 간 지연 시간을 각각 평균 88.96%와 59.49% 줄이는 것으로 나타났다. 해당 결과는 예측된 링크 상태를 기반으로 전달 규칙을 저장하는 SDN 방식인 CRIMSON이 동적 네트워크에서 지연을 줄임으로써 안정적인 임무 수행에 기여할 수 있음을 나타낸다.
핵심어: Software-Defined Networking, Mobile node, Predictive Forwarding Rule Caching, Dynamic Network Optimization, Unmanned Swarm NodeList of contents
Abstract i
List of contents ii
List of tables iii
List of figures vi
Ⅰ. INTRODUCTION 1
Ⅱ. RELATED WORK 4
Ⅲ. BACKGROUND 6
3.1 SDN overview 6
3.2 Link layer discovery protocol (LLDP) 7
3.3 Dynamic network 8
3.4 Graph form representation 8
3.5 Shortest path algorithm 9
3.6 Forwarding rule installation method 10
3.6.1 Reactive mode 10
3.6.2 Proactive mode 10
3.7 Caching effect 10
3.8 Confusion matrix 11
Ⅳ. SYSTEM MODEL 13
4.1 Simulation environments 13
4.1.1 Simulation setting 13
4.1.2 UAV modeling 13
4.2 Proactive mode in SDN 14
4.3 Scenario 14
4.3.1 Link change detection 14
4.3.2 Predicting change link status 15
4.3.3 Caching updated forwarding rule 15
4.4 The entire environment 16
Ⅴ. PROPOSED ALGORITHM (CRIMSON) 17
5.1 Link change detection and node prediction location calculation 17
5.2 Generating adjacency matrices and processing data 18
5.3 Update forwarding rule based on predicted link status 19
Ⅵ. VALIDATION 21
6.1 Common setup 21
6.2 Find the best threshold value 22
6.2.1 Simulation setup 22
6.2.2 Simulation results 22
6.3 Analysis of network latency 23
6.3.1 Simulation setup 24
6.3.2 Simulation results 24
6.4 Analysis of LLDP packets 25
6.4.1 Simulation setup 25
6.4.2 Simulation results 25
6.5 Comparison of network latency by bandwidth 26
6.5.1 Simulation setup 26
6.5.2 Simulation results 27
Ⅶ. CONCLUSION 29
REFERENCES 30
SUMMARY (KOREAN) 35MasterdCollectio
