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An Experimental Study of the Nozzle Lip Thickness Effect on Supersonic Jet Screech Tones
Aoki Toshiyuki,Kweon Yong-Hun,Miyazato Yoshiaki,Kim Heuy-Dong,Setoguchi Toshiaki The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.4
It is well known that screech tones of supersonic jet are generated by a feedback loop driven by the instability waves. Near the nozzle lip where the supersonic jet mixing layer is receptive to external excitation, acoustic disturbances impinging on this area excite the instability waves. This fact implies that the nozzle lip thickness can influence the screech tones of supersonic jet. The objective of the present study is to experimentally investigate the effect of nozzle-lip thickness on screech tones of supersonic jets issuing from a convergent-divergent nozzle. A baffle plate was installed at the nozzle exit to change the nozzle-lip thickness. Detailed acoustic measurement and flow visualization were made to specify the screech tones. The results obtained obviously show that nozzle-lip thickness significantly affects the screech tones of supersonic jet, strongly depending on whether the jet at the nozzle exit is over-expanded or under-expanded.
An Experimental Study of the Nozzle Lip Thickness Effect on Supersonic Jet Screech Tones
Toshiyuki Aoki,Yong-Hun Kweon,Yoshiaki Miyazato,Heuy-Dong Kim,Toshiaki Setoguchi 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.4
It is well known that screech tones of supersonic jet are generated by a feedback loop driven by the instability waves. Near the nozzle lip where the supersonic jet mixing layer is receptive to external excitation, acoustic disturbances impinging on this area excite the instability waves. This fact implies that the nozzle lip thickness can influence the screech tones of supersonic jet. The objective of the present study is to experimentally investigate the effect of nozzle-lip thickness on screech tones of supersonic jets issuing from a convergent-divergent nozzle. A baffle plate was installed at the nozzle exit to change the nozzle-lip thickness. Detailed acoustic measurement and flow visualization were made to specify the screech tones. The results obtained obviously show that nozzle-lip thickness significantly affects the screech tones of supersonic jet, strongly depending on whether the jet at the nozzle exit is over-expanded or under-expanded.
Development of State-Based Squeak and an Examination of Its Effect on Robot Programming Education
( Hiroyuki Aoki ),( Jamee Kim ),( Yukio Idosaka ),( Toshiyuki Kamada ),( Susumu Kanemune ),( Wongyu Lee ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.11
Robot programming often sparks students` interest in programming, but it is not easy for them to program both procedure and reactivity of robot movements that are essential requirements. In this study, we reviewed in detail a new programming language, State-Based Squeak. It allows novice students to implement both procedure and reactivity of robots easily. The effect of this new language on robot programming education was also examined using a group of 28 middle school students. According to the results of analyzing the students` understanding of programming, reading and programming abilities the group that used State-Based Squeak (the experimental group) showed a higher completion ratio than the other (control) group. The significance of this study is that a robot programming language has been developed that addresses the concepts of both procedure and reactivity in such a way that middle school students can more easily learn how to program robots, something that is often difficult to attempt even for professional programmers.
권용훈(Yonghun Kweon),임채민(Chaemin Lim),靑木俊之(Toshiyuki Aoki),김희동(Heuydong Kim) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
The present paper describes an experimental work to investigate a transonic resonance in supersonic jet that is discharged from a convergent-divergent nozzle with a design Mach number of 2.0. Whenthe conver-gent-divergent nozzle runs at low nozzle pressure ratios, the shock wave occurs within the divergent section of the nozzle. The transonic resonance of a jet flow is generated by an emission of strong acoustic tones due to the unsteadiness of the shock. In the present study, the nozzle pressure ratio is varied to obtain the super-sonic jets which are operated in the range between 1.0 and 7.8. A high-quality Schlieren optical system is used to visualize the flow field of supersonic jets. In order to specify the flow resonance of a jet, acoustic measure-ments are performed to obtain the overall sound pressure level and noise spectra. The acoustic characteristicsof transonic resonance are compared with those of jet screech tones. The results obtained show that the transonic resonance is different in characteristics from jet screech tones. It is also found that unlike screech frequency, the transonic resonance frequency somewhat increases with increasing the nozzle pressure ratio, and the transonic resonance takes place in two stages.
Eiji Kondo,Tsutomu Tabata,Nao Suzuki,Daisuke Aoki,Hideaki Yahata,Yoshio Kotera,Osamu Tokuyama,Keiichi Fujiwara,Eizo Kimura,Fumitoshi Terauchi,Toshiyuki Sumi,Aikou Okamoto,Nobuo Yaegashi,Takayuki Enomo 대한부인종양학회 2020 Journal of Gynecologic Oncology Vol.31 No.6
Objective: In this study we sought to investigate the clinical factors that affect post progression survival (PPS) in patients with recurrent or persistent clear cell carcinoma (CCC). We utilized the JGOG3017/Gynecological Cancer InterGroup data to compare paclitaxel pluscarboplatin (TC) and irinotecan plus cisplatin (CPT-P) in the treatment of stages I to IV CCC. Methods: We enrolled 166 patients with recurrent or persistent CCC and assessed the impactof variables, including platinum sensitivity, treatment arm, crossover chemotherapy, primarystage, residual tumor at primary surgery, performance status, ethnicity, and tumor reductionsurgery at recurrence on the median of PPS in patients with recurrent or persistent CCC. Results: A total of 77 patients received TC, and 89 patients received CPT-P. The median PPSfor patients with platinum-resistant disease was 10.9 months, compared with 18.8 monthsfor patients with platinum-sensitive disease (hazard ratio [HR]=1.88; 95% confidence interval[CI]=1.30–2.72; log-rank p<0.001). In the multivariate analysis, the platinum sensitivity(resistant vs. sensitivity; HR=1.60; p=0.027) and primary stage (p=0.009) were identified asindependent predictors of prognosis factors for PPS in recurrent or persistent CCC. Conclusions: Our findings revealed that platinum sensitivity and primary stage are clinicalfactors that significantly affect PPS in patients with recurrent or persistent CCC as well as other histologic subtypes of ovarian cancer. PPS in patients with recurrent CCC shouldestablish the basis for future clinical trials in this population.
권영훈(Yong-Hun KWEON),靑木俊之(Toshiyuki AOKI),김희동(Heuy-Dong KIM) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Supersonic jet issuing from a nozzle invariably cause high-frequency noises. These consist of three<br/> principal components ; the turbulent mixing noise, the broadband shock-associated noise, and the screech tone.<br/> In present study, it was experimentally investigated to the effect of nozzle lip thickness on the characteristics<br/> of supersonic jet noise. The convergent-divergent nozzle of a design Mach number 2.0 was used in<br/> experiment. With three different nozzle-lip thicknesses, the jet pressure ratio was varied in the range between<br/> 2.0 and 12.0. Acoustic measurements were conducted by microphones in an anechoic room, and the major<br/> structures of the supersonic jets were visualized by a Schlieren optical system to investigate the effect of<br/> nozzle lip thickness. The measured results show that the characteristics of supersonic jet noise, such as overall<br/> sound pressure level (OASPL) and screech frequency, strongly depend upon the thickness of nozzle-lip.
반사판이 초음속 제트 유동장에 미치는 영향에 관한 실험적 연구
권용훈(Yonghun Kweon),임채민(Chaemin Lim),靑木俊之(Toshiyuki Aoki),김희동(Heuydong Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The present study describes an experimental work to investigate the effect of a reflector on the flow-field of the supersonic jet issuing from a convergent-divergent nozzle. A reflector is placed in the exit of nozzle and its size is varied. A high-quality Schlieren optical system is used to visualize the flow-field of supersonic jet with and without a reflector. Pitot pressure measurement is also carried out to specify the supersonic jet with and without a reflector. The results obtained clearly show that the strength of the supersonic jet oscillation increases as the reflector is installed. It is also found that the placement of a reflector substantially reduces the supersonic length.
곽종호(Jong-Ho GWAK),권용훈(Yong-Hun KWEON),木俊之(Toshiyuki AOKI),김희동(Heuy-Dong KIM) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The effects of absorbing materials on the characteristics of supersonic jet noise were experimentally investigated using a convergent-divergent nozzle with a design Mach number of 2.0. Overall sound pressure levels (OASPL) and noise spectra were obtained at far-field locations. Schlieren optical system was used to visualize the flow-fields of supersonic jets. In order to investigate the effect of absorbing materials, baffle plates of different materials (metal, grass wool and polyurethane foam) were installed at the exit of the nozzle. Experiment was carried out over a wide range of nozzle pressure ratios from 2.0 and 18.0, which corresponds to over- and under-expanded conditions. The results obtained show that the screech tone amplitude and the overall sound pressure level reduce by using the baffle plates of absorbing materials, compared with the metal baffle plate. It is also found that the characteristics of supersonic jet noise are strongly dependent on the size of baffle plate.