Korea Testing Certification

Abstract. To enhance the dynamic performance and stability of high-speed railway vehicles, this study investigates the vibration attenuation mechanism of the transverse secondary inertial suspension System (TSISS). Based on vehicle–track coupled dynamics, models were established for a conventional suspension (Condition S1: parallel spring–damper) and four TSISS configurations (Condition S2: parallel inerter–spring–damper); an inerter in series with a damper, parallel to the air spring (Condition S3); an inerter in series with a spring, parallel to the air spring–damper (Condition S4); and a parallel spring–damper unit in series with an inerter, all parallel to the air spring (Condition S5). The analysis focuses on the response distribution of sensitive wavelengths under track irregularity excitations and their impact on ride comfort. Results indicate distinct frequency domain characteristics: Conditions S2 and S4 show sensitivity to short wavelengths (peaking around 20 m), improving ride quality indices by 11 % and 8 % over S1, respectively. Conversely, Conditions S3 and S5 target the longwave range, yielding improvements of 14 % and 28 %. Validated by coherence function analysis, Condition S5 significantly suppresses longwave irregularities (40–150 m), with a response peak near 105 m. Notably, with inertance set between 500 and 1000 kg, Condition S5 achieves a ride quality index of approximately 2.75 and substantially reduces lateral acceleration, demonstrating superior ride comfort.

A significant amount of frictional heat is generated during the braking process of mine-used monorail cranes under heavy-load and low-speed creeping (or reciprocating speed regulation) conditions, causing thermal softening and performance degradation of the brake pads. Thus, investigating the tribological evolution mechanism is necessary to ensure reliable braking in deep underground environments. In this paper, full-scale tribological testing technology is applied to the brake system, and the friction and wear characteristics of copper-based powder metallurgy (P/M) brake pads under complex hygrothermal environments are studied. A physical experimental model coupling normal load, sliding speed, and humidity is established using a custom-designed open-structure reciprocating tester, revealing the “load weakening effect” under dry conditions and the “dual regulation mechanism” of mixed lubrication and cooling flushing under high humidity. Then, a surrogate prediction model of friction coefficient and wear rate, with respect to the operating parameters, is constructed based on Central Composite Design (CCD) and Response Surface Methodology (RSM). The reliability of the model under non-linear working conditions is estimated based on Analysis of Variance (ANOVA) and blind tests. The results indicate that the model possesses high prediction accuracy (relative error < 5%), and the feasibility of utilizing the high-humidity environment to enhance wear resistance and stability is verified.

This study draws on socio-technical transition theory to examine how multi-actor dynamics among producers, consumers, and the media within an experimental niche—Korea’s regulatory sandbox—shape policy responsiveness and the regulatory speed of governmental responses to emerging technologies, thereby influencing socio-technical transitions. We construct a longitudinal dataset of 2136 sandbox approvals between 2019 and 2025 and 1374 cases in which related legal or administrative adjustments have been completed. Changes in actor couplings before and after sandbox approval are first assessed using Pearson correlation analysis, while temporal lead–lag relationships are identified via vector autoregression (VAR) and Granger causality tests. Building on these dynamic analyses, the study subsequently investigates the determinants of regulatory response speed using ordered logistic regression, incorporating government policy orientation (progressive vs. conservative) as a moderating variable. The results show, first, that the strong producer–consumer coupling observed prior to sandbox approval weakens afterwards, whereas the consumer–media linkage becomes substantially stronger. Second, the time-series analysis of technologies within the regulatory sandbox reveals a typical technology-push pattern and a self-reinforcing feedback loop. Specifically, producer activity initiates the signal sequence, preceding consumer reactions; subsequently, media coverage significantly drives consumer engagement, and the resulting increase in consumer attention, in turn, stimulates further media coverage. Third, in the ordered logit model, media activity accelerates legal and regulatory reform, whereas consumer activity acts as a delaying factor, with producer activity showing no significant direct effect. Finally, government policy orientation systematically moderates the magnitude and direction of these effects. Overall, the study proposes an actor-centered mechanism in which learning generated in the sandbox is externalized through consumer–media channels and translated into regulatory pacing. Based on these findings, we derive practical implications for firms and regulators regarding proactive media engagement, transparent use of evidence, institutionalized channels for consumer input, and robust feedback standards that support sustainable commercialization of emerging technologies.

Contamination by foodborne pathogens has become a serious threat to human health and has caused significant economic losses. As a protective barrier, food packaging can protect food from bacteria, ultraviolet rays, and other external factors. Among these, antibacterial silver food packaging shows great potential for extending food shelf life and controlling foodborne pathogen contamination due to its excellent antibacterial and barrier properties. This paper offers a comprehensive review of recent progress in the application of antibacterial silver nanomaterials in food packaging. In addition to an overview of the various synthesis methods for antibacterial silver nanomaterials, the green synthesis of silver nanoparticles (AgNPs) and the synthesis of Ag-based nanomaterials are highlighted. Furthermore, two main antimicrobial mechanisms of AgNPs and the effects of AgNPs on the properties of packaging are also discussed in detail. Subsequently, we also explore the application of various types of antibacterial silver food packaging for vegetable, fruit, and meat preservation, with a focus on highlighting the potential of smart food packaging for food safety applications. Finally, the future prospects and development of silver-based nanomaterials for antibacterial food packaging are discussed, and the challenges that need to be addressed in the application of silver-based nanomaterials to ensure safety and reliability are outlined. Overall, antibacterial silver food packaging is emerging as a new and effective means of preserving food.

The mode I interlaminar fracture toughness, G IC , of unidirectional fiber-reinforced polymer matrix composite laminates was determined using the double cantilever beam (DCB) specimens. To ensure real-time correspondence with the growing crack length, load and displacement, the Digital Image Correlation (DIC) technology, a non-contact optical measurement technique, was selected for the fracture toughness tests in this paper. In addition, fracture toughness calculation programs were used to accelerate data processing.The results indicated that the DIC technology was reliable compared with the traditional technology (magnifying glass). The G I C values obtained from all the three calculation methods (CC, MBT and MCC method) differed by no more than 3%. The SEM analysis showed that the crack propagation occurred along the fiber-matrix interface, resulting in plastic cracking and microcracks in the matrix. The observed intact fiber bundles indicated the matrix-dominated cracking in crack propagation, with localized fiber fracture at high stress and a small amount of fiber bridging during separation.