Speaking is a key aspect of language learning and an important measure of learners’ proficiencies. On November 19, 2022, the first-ever speaking section of the Korean Language Proficiency Test (TOPIK) was conducted. An analysis of the test results revealed that a significant number of test-takers were Chinese learners. This study aims to examine the TOPIK speaking test by conducting surveys and interviews with 24 Chinese learners of Korean to explore their perceptions of ‘Korean speaking,’ ‘Korean speaking classes,’ and the ‘TOPIK speaking evaluation.’ Based on the findings, the study seeks to propose effective strategies for improving Korean speaking education. The significance of this study can be summarized in three key points. First, it highlights the specific perceptions of Chinese Korean learners regarding Korean speaking, speaking classes, and the TOPIK speaking test. Second, it provides valuable insights into how Korean speaking education can be improved for Chinese learners through an analysis of the TOPIK speaking test. Finally, the proposed educational strategies can be practically applied in the field of Korean language education, benefiting both teaching and learning.

Capacitive deionization (CDI) represents a novel technology for the desalination and purification of seawater. Selecting the appropriate electrode material is crucial, with carbon electrodes frequently employed owing to their high specific surface area, extensive porous structure, and environmentally sustainable nature. This study presents a nitrogen-doped porous carbon, derived from household waste, which demonstrates outstanding electrochemical and desalination performance. The purified chitosan was mixed with a specific ratio of CaCO3 and carbonized at 800 °C to produce chitosan porous carbon (CPC-T). To verify the role of the templating agent, its performance was compared with chitosan porous carbon (CPC) prepared by direct carbonization. CPC-T possesses more mesoporous structures (31.25%), shortening ion transport pathways and significantly enhancing charge transfer rates. The nitrogen-rich doping (8.65 at%) provides numerous active sites and excellent conductivity, making it highly appropriate for capacitive deionization applications. Compared to CPC prepared without a templating agent, CPC-T has a higher specific capacitance (101.5 F g− 1 at a scan rate of 2 mV s− 1) and good cycling stability. The CDI cell made from it exhibits a salt adsorption capacity (SAC) of 25.8 mg g− 1 for 500 mg L− 1 NaCl solution at an applied voltage of 1.4 V, retaining 88% capacity after 50 adsorption–desorption cycles, demonstrating excellent desalination regeneration performance. Additionally, among different concentrations of salt solutions, the CPC-T material shows the best desalination performance for the test solution at a concentration of 500 mg L− 1. For different solute ions, the CDI cell with this material as the electrode exhibits excellent desalination performance for Ca2+, with a SAC value of up to 34.02 mg g− 1. This is a self-doped porous carbon material that significantly outperforms traditional carbon-based materials.

This paper evaluates the effect of two kinds of recycled coarse aggregate with different sized particles on the performance of concrete. The test program is introduced, which investigated the compressive strength, axial compressive strength, the mass loss rate of concrete specimens after a freeze-thaw cycle and dynamic elasticity modulus change. The results show that the mechanical properties of the concrete decreased when it was prepared with recycled aggregate having the same size as that of the natural aggregates. The strength of the concrete with large-size recycled aggregate increased, and then decreased as the blend proportion rose above 50%. The strength of concrete incorporating oversized recycled aggregates exhibited a trend of rising and then falling with increasing mixing ratio. The 28-day compressive strength reached 45Mpa when the mixing amount was 50%. The durability of the large-size recycled aggregate was also found to improve compared with the freezing and thawing cycle experiments. These results provide a reference for research on the performance of recycled aggregate concrete.