Cheongju University

The automotive drivetrain is a critical component for power transmission in vehicles, and its importance is self-evident. It is responsible for efficiently and smoothly transferring engine power to the wheels, directly affecting the vehicle’s acceleration performance, driving stability, and safety; it is an indispensable component for ensuring normal vehicle operation. Among these components, the transmission is a key part of the automotive drivetrain. However, metal failure currently occurs in vehicle transmissions, which directly affects the vehicle’s service life and performance. Shot peening is a cold-working surface-hardening process that uses high-speed shots to impact the surface of the material, causing plastic deformation and generating residual compressive stress, thereby enhancing the component’s fatigue strength. To better elucidate the influence of shot peening on the performance of vehicle transmission gears, this paper reviews recent phenomena and mechanisms of gear failure, introduces several novel shot peening techniques, analyzes the effects of different shot peening parameters on residual stresses, and focuses on investigating the mechanism by which residual stresses affect the high-cycle fatigue life of gears under bending load (pulsating cycle) conditions. Finally, the paper discusses methods for inspecting metal surface integrity. This paper provides a theoretical basis for future research on extending the service life of automotive transmission gears.

This study explores how media framing of housing policies influences public perceptions of housing tax policy. Using a quasi-experimental design, this study analyzes the impact of exposure to media tones-whether critical or supportive-on individuals' attitudes toward a housing tax increase policy in South Korea. Political belief and taxpayer status serve as major determinants of opinions on housing tax increase policies, but media framing also plays a moderating role in shaping these policy attitudes. In general, taxpayers and politically conservative respondents tended to be less supportive of the housing tax increase policy compared to non-taxpayers and liberals, respectively. Interestingly, taxpayers who encountered critical media coverage exhibited even lower support, whereas supportive media coverage slightly increased their acceptance. Moreover, among the group exposed to both critical and supportive media frames, the differences in policy attitudes based on progressive or conservative political orientation and taxpayer status were significantly reduced, indicating the importance of balanced media literacy in shaping public opinion on policy issues. The findings of this study enhance the understanding of media influence in housing policy debates and provide valuable insights for policymakers and the public.

Rechargeable lithium-ion batteries are extensively used in various applications, such as smartphones and laptops; however, their stability and safety are significant factors that influence their development. To address these concerns, research efforts have focused on developing poly(ethylene oxide) (PEO)-based solid polymer electrolytes. However, practical PEO applications are limited because PEO exhibits an inherently low ionic conductivity at room temperature. This study investigated the effects of a conventional EC/DEC liquid electrolyte and the ionic liquid Pyr14TFSI, which are two distinct plasticizers, on the ionic conductivity, thermal stability, and electrochemical performance of a crosslinked LiTFSI-Pyr14TFSI-PEO polymer matrix in conjunction with an LiFePO4 cathode. The system with the EC/DEC-plasticized electrolyte exhibited enhanced ionic conductivity and a high lithium-ion transference number, thereby facilitating efficient ion mobility. In contrast, the Pyr14TFSIplasticized electrolyte system exhibited a broader electrochemical stability window and superior interfacial compatibility. As a result, the Pyr14TFSI-based system delivered an exceptional discharge capacity retention of 165 mAh g- 1 after 100 cycles at 0.1C and 25 degrees C, surpassing the EC/DEC-plasticized counterpart (131 mAh g-1). These findings highlight that the collective contributions of optimized ion transport dynamics, stable electrode-electrolyte interfaces, and enhanced electrolyte robustness are decisive in governing electrochemical performance. Overall, this work demonstrates the synergistic potential of combining molecular and ionic plasticizers to overcome the intrinsic limitations of conventional PEO-based electrolytes, offering a viable route toward the development of safe, high-performance all-solid-state lithium batteries.

Large-scale wireless sensor networks (WSNs), consisting of hundreds to thousands of sensor nodes, are vulnerable to malicious threats such as sinkhole attacks. While several frameworks for simulating WSNs have been proposed to defend against malicious threats, existing simulators have limitations when it comes to configuring large-scale environments, modeling sinkhole attacks, and building standardized attack datasets. These difficulties hinder the development of effective attack detection and defense mechanisms. To overcome these limitations, this paper proposes PyWSNSim, a component-centric Python-based simulation framework to simulate and analyze sinkhole attacks in large-scale WSNs. PyWSNSim provides scalability for environment parameters, routing protocols, and attack models in a sensor network. The proposed framework transforms the behavior of the network in various sinkhole attack scenarios into a dataset. This dataset not only guarantees the reproducibility of attacks but is also utilized as a training dataset for machine learning-based network threat detection models.

ABSTRACT Composite polymer electrolytes (CPEs) are promising for all‐solid‐state sodium metal batteries but suffer from low ionic conductivity, which stems from limited Na‐salt dissociation and narrow polymer amorphous domains, as well as sluggish ion transport caused by discontinuous composite interfacial charge‐transfer paths, and poor electrode/electrolyte interfacial stability. This study proposes an original molecular interface engineering strategy: inorganic Zr 4+ induces organic phase reconstruction to build continuous high‐speed ion channels, simultaneously accelerating Na‐salt dissociation and reducing ion migration energy barriers. Zr 4+ directs the oriented reorganization of polar groups (─C≡N) to alleviate Na‐metal anode interfacial passivation, facilitate NaF/Na 3 N‐rich stable solid electrolyte interphase formation, and enable uniform Na deposition. Moreover, Zr─N═C metal‐ligand coordination at the organic/inorganic interface induces interfacial electronic coupling and charge redistribution, promoting fast Na + migration along continuous coordination pathways. The developed CPEs, denoted as polyacrylonitrile‐metal organic framework@polyethylene oxide‐Na[N(SO 2 CF 3 ) 2 ] (PM@PN), show a synergistic interface‐bulk effect that significantly enhances electrolyte performance, as evidenced by a reduced apparent activation energy of 0.027 eV (derived from Vogel–Tammann–Fulcher, VTF fitting above T m ), an enhanced ionic conductivity of 3.52 × 10 −4 S cm −1 , and a Na + transference number of 0.67 at 60°C, along with an expanded electrochemical window of 5.06 V. The Na|PM@PN|Na symmetric cell demonstrates 0.56 mA cm −2 critical current density and stable Na deposition/stripping over 700 h at 0.4 mA cm −2 . Additionally, the assembled Na 3 V 2 (PO 4 ) 3 |PM@PN|Na full cell maintains 93.99% capacity retention after 200 cycles at 0.1 C, confirming PM@PN's applicability in advanced all‐solid‐state sodium metal batteries.