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Estimation and Measurement of Forward Propagated Ultrasonic Fields in Layered Fluid Media
Ha, Kang-Lyeol,Kim, Moo-Joon,Hyun, Byung-Gook The Acoustical Society of Korea 2000 韓國音響學會誌 Vol.19 No.e2
The forward propagated ultrasonic fields resulting from a circular plane or a concave transducer in layered fluid media as well as in homogeneous water are theoretically estimated by the angular spectrum method(ASMJ) combined with Rayleigh-Sommerfeld diffraction theory(RSDT), and measured by a precision 3-D scanning system with a needle-point hydrophone. To make the aliasing error negligible on the 2-D FFT in the theoretical estimation, the spatial discretization in the ASM are carefully considered for optimal selection of spatial sampling intervals and the size of discretization area. It is shown that the estimated fields agree reasonably with the measured ones.
Effects of Mechanical Milling on the Carbothermal Reduction of Oxide of WC/Co Hardmetal Scrap
이길근,Gook-Hyun Ha 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.2
The effects of mechanical milling on the carbothermal reduction of oxidized WC/Co hardmetal scrap with solid carbon were examined. Mixed powders were manufactured by milling the WC/Co hard metal scrap oxide and carbon powder in either a tumbler-ball mill or a planetary-ball mill. The milling type affected the carbothermal reduction of the oxide owing to the differing collision energies (mechanical milling energies) in the mills. The hardmetal scrap oxide powder (WO3, CoWO4) milled at high energy was more greatly reduced and at a lower temperature than that milled at lower mechanical energy. The formation of WC by the carburization reaction with solid carbon reached completion at a lower temperature after higher-energy milling than after lower-energy milling. The WC/Co composite particles synthesized by the combined oxidationmechanical milling-carbothermal reduction process were smaller when the initial powder was milled at higher mechanical energy.
정현철,이우철,김태오,이창원,류수형,이수봉,곽임수,나하연,송상헌,이현국 대한내과학회 1999 대한내과학회지 Vol.56 No.3
Acute focal bacterial nephritis is a part of urinary tract infection and a special form of acute pyelonephritis. In most cases, it is treated well by antimicrobial therapy without severe complications. Unusual cases have been reported that renal failure and or chronic granulomatous interstitial nephritis was combined with acute focal bacterial nephritis. We describe a case of acute reanl failure complicated by acute focal bacterial nephritis in 30-year-old male. He was admitted to this hospital owing to fever, chilling, right flank pain. On admission, BUN and creatinine were 29 mg/dl, 1.8 mg/dl. Urinalysis showed leukocyturia, & bactriuria. Urine culture revealed E. coli over us. Abdominal CT and ultrasonography was represented focal hypodense area and diffuse renal enlargement so we could diagnose acute focal bacterial nephritis. The patient was improved with antimicrobial therapy and hydration. In conclusion, this case shows the possibility that unusual complication such as acute reanl failure can be happensed in acute focal bacterial nephritis in continum with acute pyelonephritis
초음파 유량계에 사용되는 초음파 진동자 특성향상에 관한 연구
현병국(Byung-Gook Hyun),황상윤(Shang-Yoon Hwang),안용관(Yong-Kwan Ahn),박성하(Sung-Ha Park) 한국유체기계학회 2001 유체기계 연구개발 발표회 논문집 Vol.- No.-
For the piezoelectric vibrator, PZT, in a general transmit-receive sensor using the ultrasonic flowmeter, the characteristics of frequency response relating to the backing materials were analyzed with the Mason equivalent circuit for design, and the sensitivity of fabricated transducer relating to the matching materials was measured and discussed. The results those were measured in water for the transmit-receive characteristics of each transducer can be applied to the flowmeter sensor.