Electromagnetic Compatibility Research in Wire Harnesses and CAN Transceivers

This dissertation develops methods how to design wire harnesses reducing common mode components and to analyze the conversion from differential mode to common mode. The three chapters presented are design methods how to figure out the impact of the common-mode components, not only describe the test results but provide important insight as to how the design related to radiated emissions. In the first chapter of this dissertation, the method designing wire harnesses has been presented to match the electrical balance of the circuit board (PCB). This is accomplished via calculating the current division factor (CDF) of the wire harnesses and the PCB, which provides us with the electrical balance of a transmission line. To reduce the amount of common-mode currents induced on the harness, matching the imbalance of the wire harness to the imbalance of its source and termination is essential. The second chapter explores Controller Area Network (CAN) characteristics. Unintentional common-mode components of the CAN transceivers are analyzed and evaluated to determine how much common-mode voltage they produce in various circumstances. The final chapter provide valuable understanding such that ground proximity impacts on the common-mode currents of wire harnesses. The electrical balance change of the wire harness depending on the distance from ground structures is highlighted. It is also analyzed that losing the ground wire impacts on the common-mode excitation

Solution-processed near-infrared Cu(In,Ga)(S,Se)(2) photodetectors with enhanced chalcopyrite crystallization and bandgap grading structure via potassium incorporation

Although solution-processed Cu(In,Ga)(S,Se)(2) (CIGS) absorber layers can potentially enable the low-cost and large-area production of highly stable electronic devices, they have rarely been applied in photodetector applications. In this work, we present a near-infrared photodetector functioning at 980 nm based on solution-processed CIGS with a potassium-induced bandgap grading structure and chalcopyrite grain growth. The incorporation of potassium in the CIGS film promotes Se uptake in the bulk of the film during the chalcogenization process, resulting in a bandgap grading structure with a wide space charge region that allows improved light absorption in the near-infrared region and charge carrier separation. Also, increasing the Se penetration in the potassium-incorporated CIGS film leads to the enhancement of chalcopyrite crystalline grain growth, increasing charge carrier mobility. Under the reverse bias condition, associated with hole tunneling from the ZnO interlayer, the increasing carrier mobility of potassium-incorporated CIGS photodetector improved photosensitivity and particularly external quantum efficiency more than 100% at low light intensity. The responsivity and detectivity of the potassium-incorporated CIGS photodetector reach 1.87 A W-1 and 6.45 x 10(10) Jones, respectively, and the - 3 dB bandwidth of the device extends to 10.5 kHz under 980 nm near-infrared light

The Performance of Relay-Enhanced Cellular OFDMA-TDD Network for Mobile Broadband Wireless Services

A multihop relay (MR) and repeater are useful means for improving system throughput and coverage in a cellular mobile packet access system, as the carrier-to-interference ratio can be improved when deploying them in a heavily shadowed region. In this paper, we report on our investigation of bandwidth efficiency and the associated service outage performance for different relay scenarios, using system level simulation for a cellular Orthogonal Frequency Division Multiple Access-Time Division Duplexing (OFDMA-TDD) system. We have demonstrated that network throughput gain by typical optical repeaters, which have a simple amplify-and-forwarding capability in a full-duplexing mode, could be minimal in open space subject to cochannel interference from all repeaters in the neighboring cells. This is true, even though they are generally useful for warranting the outage performance with a multiple order of combining gain, especially in the destructive area, for example, basements or indoors with heavy wall attenuation, that naturally shields interference. Meanwhile, we show that multihop relays increase the average system capacity (almost doubling the system throughput) by fully reusing the frequency in every relay station, while improving the per-user data rate in the cell edges or improving the outage performance in the heavily shadowed areas.</p

The Performance of Relay-Enhanced Cellular OFDMA-TDD Network for Mobile Broadband Wireless Services

A multihop relay (MR) and repeater are useful means for improving system throughput and coverage in a cellular mobile packet access system, as the carrier-to-interference ratio can be improved when deploying them in a heavily shadowed region. In this paper, we report on our investigation of bandwidth efficiency and the associated service outage performance for different relay scenarios, using system level simulation for a cellular Orthogonal Frequency Division Multiple Access-Time Division Duplexing (OFDMA-TDD) system. We have demonstrated that network throughput gain by typical optical repeaters, which have a simple amplify-and-forwarding capability in a full-duplexing mode, could be minimal in open space subject to cochannel interference from all repeaters in the neighboring cells. This is true, even though they are generally useful for warranting the outage performance with a multiple order of combining gain, especially in the destructive area, for example, basements or indoors with heavy wall attenuation, that naturally shields interference. Meanwhile, we show that multihop relays increase the average system capacity (almost doubling the system throughput) by fully reusing the frequency in every relay station, while improving the per-user data rate in the cell edges or improving the outage performance in the heavily shadowed areas

Radiological Safety Assessment of Transporting Radioactive Wastes to the Gyeongju Disposal Facility in Korea

A radiological safety assessment study was performed for the transportation of low level radioactive wastes which are temporarily stored in Korea Atomic Energy Research Institute (KAERI), Daejeon, Korea. We considered two kinds of wastes: (1) operation wastes generated from the routine operation of facilities; and (2) decommissioning wastes generated from the decommissioning of a research reactor in KAERI. The important part of the radiological safety assessment is related to the exposure dose assessment for the incident-free (normal) transportation of wastes, i.e., the radiation exposure of transport personnel, radiation workers for loading and unloading of radioactive waste drums, and the general public. The effective doses were estimated based on the detailed information on the transportation plan and on the radiological characteristics of waste packages. We also estimated radiological risks and the effective doses for the general public resulting from accidents such as an impact and a fire caused by the impact during the transportation. According to the results, the effective doses for transport personnel, radiation workers, and the general public are far below the regulatory limits. Therefore, we can secure safety from the viewpoint of radiological safety for all situations during the transportation of radioactive wastes which have been stored temporarily in KAERI

Multilayer WSe2/MoS2 Heterojunction Phototransistors through Periodically Arrayed Nanopore Structures for Bandgap Engineering

While 2D transition metal dichalcogenides (TMDs) are promising building blocks for various optoelectronic applications, limitations remain for multilayered TMD-based photodetectors: an indirect bandgap and a short carrier lifetime by strongly bound excitons. Accordingly, multilayered TMDs with a direct bandgap and an enhanced carrier lifetime are required for the development of various optoelectronic devices. Here, periodically arrayed nanopore structures (PANS) are proposed for improving the efficiency of multilayered p-WSe2/n-MoS2 phototransistors. Density functional theory calculations as well as photoluminescence and time-resolved photoluminescence measurements are performed to characterize the photodetector figures of merit of multilayered p-WSe2/n-MoS2 heterostructures with PANS. The characteristics of the heterojunction devices with PANS reveal an enhanced responsivity and detectivity measured under 405 nm laser excitation, which at 1.7 × 104 A W−1 and 1.7 × 1013 Jones are almost two orders of magnitude higher than those of pristine devices, 3.6 × 102 A W−1 and 3.6 × 1011 Jones, respectively. Such enhanced optical properties of WSe2/MoS2 heterojunctions with PANS represent a significant step toward next-generation optoelectronic applications. © 2022 Wiley-VCH GmbH1

Probing Optical Multi-Level Memory Effects in Single Core-Shell Quantum Dots and Application Through 2D-0D Hybrid Inverters

Challenges in the development of a multi-level memory (MM) device for multinary arithmetic computers have posed an obstacle to low-power, ultra-high-speed operation. For the effective transfer of a huge amount of data between arithmetic and storage devices, optical communication technology represents a compelling solution. Here, by replicating a floating gate architecture with CdSe/ZnS type-I core/shell quantum dots (QDs), a 2D–0D hybrid optical multi-level memory (OMM) device operated is demonstrated by laser pulses. In the device, laser pulses create linear optically trapped currents with MM characteristics, while conversely, voltage pulses reset all the trapped currents at once. Assuming electron transfer via the energy band alignment between MoS2 and CdSe, the study also establishes the mechanism of the OMM effect. Analysis of the designed device led to a new hypothesis that charge transfer is difficult for laterally adjacent QDs facing a double ZnS shell, which is tested by separately stimulating different positions on the 2D–0D hybrid structure with finely focused laser pulses. Results indicate that each laser pulse induced independent MM characteristics in the 2D–0D hybrid architecture. Based on this phenomenon, we propose a MM inverter to produce MM effects, such as programming and erasing, solely through the use of laser pulses. Finally, the feasibility of a fully optically-controlled intelligent system based on the proposed OMM inverters is evaluated through a CIFAR-10 pattern recognition task using a convolutional neural network. © 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.TRU

Chiroptical Synaptic Heterojunction Phototransistors Based on Self‐Assembled Nanohelix of π‐Conjugated Molecules for Direct Noise‐Reduced Detection of Circularly Polarized Light

Abstract High‐performance chiroptical synaptic phototransistors are successfully demonstrated using heterojunctions composed of a self‐assembled nanohelix of a π‐conjugated molecule and a metal oxide semiconductor. To impart strong chiroptical activity to the device, a diketopyrrolopyrrole‐based π‐conjugated molecule decorated with chiral glutamic acid is newly synthesized; this molecule is capable of supramolecular self‐assembly through noncovalent intermolecular interactions. In particular, nanohelix formed by intertwinded fibers with strong and stable chiroptical activity in a solid‐film state are obtained through hydrogen‐bonding‐driven, gelation‐assisted self‐assembly. Phototransistors based on interfacial charge transfer at the heterojunction from the chiroptical nanohelix to the metal oxide semiconductor show excellent chiroptical detection with a high photocurrent dissymmetry factor of 1.97 and a high photoresponsivity of 218 A W−1. The chiroptical phototransistor demonstrates photonic synapse‐like, time‐dependent photocurrent generation, along with persistent photoconductivity, which is attributed to the interfacial charge trapping. Through the advantage of synaptic functionality, a trained convolutional neural network successfully recognizes noise‐reduced circularly polarized images of handwritten alphabetic characters with better than 89.7% accuracy