56016 research outputs found
Sort by
Secure Precoding for Future Wireless Communication Systems
Get PDFDepartment of Electrical EngineeringPhysical layer security has emerged a flourishing strategy to protect confidential information from eavesdroppers with lower computational complexity compared to cryptography. Secure precoding is a promising transmission method of physical layer security to improve security by exploiting an intrinsic attribute of wireless communications. The main goal of the secure precoding is to maximize secrecy rate in multi-input and multi-output (MIMO) systems with the presence of eavesdroppers. Unfortunately, there exists no optimal solution, and also solving the secrecy rate maximization problem becomes more challenging as networks involve a multi-user (MU) and multi-eavesdropper (ME) scenario because of its non-smoothness and non-convexity. In this thesis, I proposed a novel secure precoding algorithm for downlink MU-MIMO systems under ME threat to enhance the secrecy rate, and provide subsequent analyses for realizing ultra-reliable low latency communications (URLLC). By incorporating strong security, communication reliability, and latency, a multi-objective optimization problem is investigated in the finite blocklength (FBL) regime. The derived optimization problem aims to maximize the secrecy rate by designing a secure precoder, while simultaneously minimizing both the maximum error probability and the rate of information leakage. The proposed FBL-based optimization algorithm provides the significantly improved tradeoff among the security, the error probability, and information leakage rate. Therefore, the proposed algorithms can offer significantly improved security for future wireless communication systems.clos
????????? ????????? ?????? ????????? ???????????? ?????? ?????? ???
Get PDFDepartment of Computer Science and EngineeringThe existing network performance measurement tools are limited to measuring end-host latency within the scope of the TCP layer or network latency. This limitation hinders the detailed analysis of latency occurring at various points within each component of the network protocol stack. Therefore, this thesis presents eBPF-ELEMENT as a solution to address the aforementioned issues. eBPF-ELEMENT utilizes eBPF (extended Berkeley Packet Filter) and XDP (Express Data Path) to overcome the limita- tions and challenges associated with implementing a real-time fine-grained latency measurement tool for large-scale systems. eBPF-ELEMENT provides a versatile framework that enables detailed mea- surement of network performance within servers and across server boundaries and offers network per- formance metrics, including per-layer latency, packet loss rate, throughput, and system performance metrics, including CPU and memory utilization. Thereby, eBPF-ELEMENT enables holistic system performance measurement and analysis and provides abundant information for troubleshooting different network issues in large-scale systems.clos
Design Strategy of Photo-Electrode to Improve Photo-Energy Conversion for Dye Sensitized Solar Cells
No full textDepartment of Chemistryclos
Triplet Energy Engineering of Organic and Organoplatinum(II) Compounds for Stable Optoelectronic Devices
No full textDepartment of Chemistryclos
Roles of ambient temperature and relative humidity on the relationship between fine particulate matter and gaseous pollutants in the largest industrial city of Ulsan, South Korea
No full textAlthough meteorological conditions play a significant role in air pollution, research on their effects on the relationship between air pollutants is limited. In this study, trends of six criteria air pollutants were investigated from 15 air quality monitoring stations (AQMSs) in Ulsan, a multi-industrial city in South Korea, during 2015-2019. Unlike CO and O-3, SO2, NO2, PM10, and PM2.5 showed statistically significant decreasing trends over the period. The companion relationship between PM2.5 and gaseous pollutants was evaluated by their correlations [R (PM2.5-GPs)]. R (PM2.5-NO2) was relatively high at almost all AQMSs, whereas high R (PM2.5-SO2) was observed near the petrochemical industrial complex, suggesting a great influence of local emissions (vehicles and industries). R (PM2.5-CO) and the standardized regression coefficients of CO obtained from the multiple linear regression model were the highest, indicating that combustion processes may significantly contribute to PM2.5. The effect of temperature (T) was more apparent on R (PM2.5-GPs) than that of relative humidity, with significant values under T > 15 & DEG;C. Moreover, R (PM2.5-O-3) was positive at the T range of 12-18 & DEG;C, suggesting that reducing GPs emitted by industrial facilities during May-June may control PM2.5 and O-3 in Ulsan. The methodology demonstrated in this study can be further used for a better understanding of the influences of environmental factors on the secondary PM2.5 formation from gaseous precursors and the R (PM2.5-O-3)
Conservation implications of elucidating the Korean wolf taxonomic ambiguity through whole-genome sequencing
No full textThe taxonomic status of the now likely extirpated Korean Peninsula wolf has been extensively debated, with some arguing it represents an independent wolf lineage, Canis coreanus. To investigate the Korean wolf's genetic affiliations and taxonomic status, we sequenced and analysed the genomes of a Korean wolf dated to the beginning of the 20th century, and a captive wolf originally from the Pyongyang Central Zoo. Our results indicated that the Korean wolf bears similar genetic ancestry to other regional East Asian populations, therefore suggesting it is not a distinct taxonomic lineage. We identified regional patterns of wolf population structure and admixture in East Asia with potential conservation consequences in the Korean Peninsula and on a regional scale. We find that the Korean wolf has similar genomic diversity and inbreeding to other East Asian wolves. Finally, we show that, in contrast to the historical sample, the captive wolf is genetically more similar to wolves from the Tibetan Plateau; hence, Korean wolf conservation programmes might not benefit from the inclusion of this specimen
Framework for rapid characterization of fresh properties of cementitious materials using point cloud and machine learning
No full textThis study presents a framework that utilizes point cloud analysis and machine learning to automate and accelerate the characterization of fresh properties of cementitious materials. The framework collects point cloud data using a depth camera and extracts diameter, height, and curvature information through post-processing techniques. Data augmentation technique is used to generate new data for ANN training based on nonlinear correlations between these parameters and experimentally determined fresh properties. The developed framework is validated through additional experimental results and shows high prediction accuracy, offering a rapid and effective approach for characterizing fresh properties of cementitious materials
Advancements and Challenges in the Carbon Fiber-Reinforced Polymer (CFRP) Trimming Process
No full textIn this review, we comprehensively examine the carbon fiber-reinforced polymer (CFRP) trimming process, covering both conventional machining techniques and novel approaches. We explore various methods, including conventional cutting, laser beam machining, robot arm machining, electrical discharge machining, and ultrasonic machining; we assess their respective strengths and limitations in the fabrication of CFRP components. We evaluate the effectiveness of each approach with respect to accuracy, surface integrity, defect occurrence, and productivity. Moreover, we explore the latest advancements and emerging trends in CFRP trimming processes, emphasizing the potential for improved efficiency and quality. The insights from this review support an in-depth understanding of the benefits and limitations of various trimming methods, providing valuable guidance for researchers and industry professionals in the selection of an optimal approach for CFRP component production
Liver dECM-Gelatin Composite Bioink for Precise 3D Printing of Highly Functional Liver Tissues
No full textIn recent studies, liver decellularized extracellular matrix (dECM)-based bioinks have gained significant attention for their excellent compatibility with hepatocytes. However, their low printability limits the fabrication of highly functional liver tissue. In this study, a new liver dECM-gelatin composite bioink (dECM gBioink) was developed to overcome this limitation. The dECM gBioink was prepared by incorporating a viscous gelatin mixture into the liver dECM material. The novel dECM gBioink showed 2.44 and 10.71 times higher bioprinting resolution and compressive modulus, respectively, than a traditional dECM bioink. In addition, the new bioink enabled stable stacking with 20 or more layers, whereas a structure printed with the traditional dECM bioink collapsed. Moreover, the proposed dECM gBioink exhibited excellent hepatocyte and endothelial cell compatibility. At last, the liver lobule mimetic structure was successfully fabricated with a precisely patterned endothelial cell cord-like pattern and primary hepatocytes using the dECM gBioink. The fabricated lobule structure exhibited excellent hepatic functionalities and dose-dependent responses to hepatotoxic drugs. These results demonstrated that the gelatin mixture can significantly improve the printability and mechanical properties of the liver dECM materials while maintaining good cytocompatibility. This novel liver dECM gBioink with enhanced 3D printability and resolution can be used as an advanced tool for engineering highly functional liver tissues
