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Yukyeong Jung,Jae Ho Han,Seokyu Choi,Jae Hee Lee 한국청각언어재활학회 2021 Audiology and Speech Research Vol.17 No.4
Purpose: This study aimed to measure the test-retest reliability of the Korean Matrix sentence-in-noise test in a sound-field testing condition. Methods: Fifty-five listeners with normal hearing participated. The sound-field speech-in-noise test was administered with a front loudspeaker by presenting noise at a fixed level (65 dB SPL) while adaptively adjusting the sentence level based on the listener’s response. The speech reception thresholds (SRTs) corresponding to 50% sentence-in-noise intelligibility were obtained using speech-shaped noise (SSN), International Collegium of Rehabilitative Audiology (ICRA) noise, and International Speech Test Signal (ISTS) noise. For the test-retest reliability, each subject was tested twice in a 2-week interval. The test-retest reliabilities were judged by the intraclass correlation coefficient (ICC), the minimal detectable change (MDC) values, and Bland-Altman plots. Results: The test-retest reliabilities of the Korean Matrix sentence test were good (ICC, 0.84~0.86) across SSN, ICRA, ISTS noises. The MDC was 0.92 dB SNR for SSN and 2.83 and 2.98 dB SNR for ICRA and ISTS, indicating the random measurement error varied across the types of noise. Conclusion: The Korean Matrix sentence-in-noise test can be used as a reliable tool to assess speech-in-noise intelligibility in sound-field testing condition. Further study across various sessions would strengthen the present finding.
Yukyeong Lee,김은성,Sangeun Park,Jeong Min Park,Jae Bok Seol,Hyoung Seop Kim,이태경,Hyokyung Sung,Jung Gi Kim 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.1
Process optimization of additively manufactured Ti–6Al–4V alloy is an important aspect of the production of engineered,high-performance parts for the aerospace and medical industries. In this study, the microstructural evolution and mechanicalproperties of direct energy deposition processed Ti–6Al–4V alloy were investigated using diferent processing parameters. Experimental analyses revealed that the line energy density corresponding to the processing parameters of the direct energydeposition process infuences the properties of additively manufactured Ti–6Al–4V alloy. First, an optimal line energydensity limits the incidence and size of voids resulting from a lack of fusion to enhance both alloy strength and ductility. Second, an excessively high energy density induces the coarsening of prior-β grains to impair both alloy strength with theHall–Petch relationship and alloy ductility due to the plastic deformation instability caused by the limited number of grains. These results indicate that both the extent of fusion and prior-β grain size afect the mechanical properties of additivelymanufactured Ti–6Al–4V alloy. Moreover, the results demonstrate the utility of the line energy density-based approach indetermining the optimal processing parameters for realizing high-performance materials.
RF 플라즈마 처리법에 기반한 기계적 밀링된 Zr 분말의 구형화에 따른 특성 변화
이유경,최미선,박언병,오정석,남태현,김정기,Lee, Yukyeong,Choi, Mi-Sun,Park, Eon Byeong,Oh, Jeong Seok,Nam, Taehyun,Kim, Jung Gi 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.2
Powder quality, including high flowability and spherical shape, determines the properties of additively manufactured products. Therefore, the cheap production of high-quality powders is critical in additive manufacturing. Radio frequency plasma treatment is an effective method to fabricate spherical powders by melting the surface of irregularly shaped powders; in the present work, mechanically milled Zr powders are spheroidized by radio frequency plasma treatment and their properties are compared with those of commercial Zircaloy-2 alloy powder. Spherical Zr particles are successfully fabricated by plasma treatment, although their flowability and impurity contents are poorer than those of the commercial Zircaloy-2 alloy powder. This result shows that radio-frequency plasma treatment with mechanically milled powders requires further research and development for manufacturing low-cost powders for additive manufacturing.