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Measurement of Axisymmetric-Wave Speed in a Pipe by Using Piezoelectric Cylindrical Transducers
Hwang, Kyo-Kwang,Kim, Jin-Oh The Acoustical Society of Korea 2004 韓國音響學會誌 Vol.23 No.e1
This paper presents an experimental technique to generate and detect axisymmetric longitudinal waves in a pipe by using piezoelectric cylindrical transducers. Radial pulses transmitted by one transducer have propagated in two opposite directions along the pipe, and other two transducers have received the propagating waves. The difference of the transit times measured for the waves in two paths of known distance difference has yielded the phase speed of the wave propagation. Wave speed has been measured in an empty pipe and in a water-filled pipe.
Switching of Photonic Crystal Lasers by Graphene
Hwang, Min-Soo,Kim, Ha-Reem,Kim, Kyoung-Ho,Jeong, Kwang-Yong,Park, Jin-Sung,Choi, Jae-Hyuck,Kang, Ju-Hyung,Lee, Jung Min,Park, Won Il,Song, Jung-Hwan,Seo, Min-Kyo,Park, Hong-Gyu American Chemical Society 2017 NANO LETTERS Vol.17 No.3
<P>Unique features of graphene have motivated the development of graphene-integrated photonic devices. In particular, the electrical tunability of graphene loss enables high-speed modulation of light and tuning of cavity resonances in graphene-integrated waveguides and cavities. However, efficient control of light emission such as lasing, using graphene, remains a challenge. In this work, we demonstrate on/off switching of single- and double-cavity photonic crystal lasers by electrical gating of a monolayer graphene sheet on top of photonic crystal cavities. The optical loss of graphene was controlled by varying the gate voltage V-g, with the ion gel atop the graphene sheet. First, the fundamental properties of graphene were investigated through the transmittance measurement and numerical simulations. Next, optically pumped lasing was demonstrated for a graphene-integrated single photonic crystal cavity at V-g below-0.6 V, exhibiting a low lasing threshold of -4801 mu W, whereas lasing was not observed at V-g above -0.6 V owing to the intrinsic optical loss of graphene. Changing quality factor of the graphene-integrated photonic crystal cavity enables or disables the lasing operation. Moreover, in the double-cavity photonic crystal lasers with graphene, switching of individual cavities with separate graphene sheets was achieved, and these two lasing actions were controlled independently despite the close distance of -2.2 mu m between adjacent cavities. We believe that our simple and practical approach for switching in graphene-integrated active photonic devices will pave the way toward designing high-contrast and ultracompact photonic integrated circuits.</P>
Choi, Kwang Sik,Hwang, Moon Ok,Kim, Dae Joong,Lee, Chong Kyo,Moon, Aeree,Han, Beom Seok 한국응용약물학회 1993 Biomolecules & Therapeutics(구 응용약물학회지) Vol.1 No.2
The possible tumor-promoting activities of sodium chloride (NaCl) and dimethyl itaconate (DMI), one of the quinone reductase inducers, were examined on stomach of male Wistar rats treated with N-methylN-nitro-N-nitrosoguanidine (MNNG). Administrations of NaCl and DMI after the initiation by MNNG resulted in various sized masses in the rat forestomach. Histopathologic studies showed that the combination of NaCl and DMI made an enhancing effect on the MNNG-induced carcinogenesis, resulting in papilloma in 5 weeks and squamous cell carcinoma in 20 weeks in submucosal area of forestomach. We also used an in vivo shortterm method for evaluating possible tumor-promoting activity with ornithine decarboxylase (ODC) as a marker. The markable inductions of the ODC activities by MNNG, NaCl, and DMI were found in the pyloric mucosa of rat stomach in time-dependent manners. A single administration of MNNG induced ODC activity up to 288 pmol CO₂/hr/mg protein at 24 hr after the administration. NaCl caused induction of ODC with a maximum of 179 pmol CO-2/hr/mg protein at 8 hr after the administration. ODC was induced up to 539 pmol CO₂/hr/mg protein at 16 hr after the administration of DMI. Additional treatment of NaCl and NaCl plus DMI caused 2 fold and 7 fold increases, respectively, in the ODC activity of the MNNG-alone group at 24 hr after the administration. These results suggest that NaCl and DMI have promoting activities in the rat gastric carcinogenesis initiated by MNNG.
추교영(Kyo Young Choo),최명규(Myung Gyu Choi),최황(Hwang Choi),이동수(Dong Soo Lee),김진일(Jin Il Kim),김성수(Sung Soo Kim),방춘상(Choon Sang Bhang),박수헌(Soo Heon Park),김재광(Jae Kwang Kim),한석원(Sok Won Han),최규용(Kyu Yong Cho 대한소화기기능성질환·운동학회 2000 Journal of Neurogastroenterology and Motility (JNM Vol.6 No.1
N/A Background/Aims: Chronic gastrointestinal (GI) symptoms are believed to be common in the general population, but there is a lack of data from Korea. The aim of this study was to es1imate the prevalence of chronic gastrointestinal symptoms in a rural community in Korea by using the Bowel Symptom Questionnaire (BSQ), which was based on the multinational diagnotic Rome criteria for functional bowel disorders, as a measure of GI symptoms. Methods: A cross-sectional survey, using a reliable and valid questionnaire based on the fulfillment of the Rome criteria, was performed in a densely populated district in a Korean rural community on the residents aged l8-69 yr (mean 48±14 yr). 95,5% responded (n=420). All respondents were interviewed at their home or offices by a team of interviewers. Results: Two thirds of Korean rural residents experience gastrointestinal symptoms and one fifth of them visit a clinic or hospital at least once a year. Prevalences of weekly heartburn, gastroesophageal reflux disease, dyspepsia, irritable bowel syndrome (IBS), and chronic constipation were 5.2% (95% confidence interval [CI], 3.l-7.4, 2.6% (95% Cl, 1.1-4.2), 15.5% (95% CI, 11.9-19.0), 8.6% (95% CI, 3.8-11,3), and 24.3% (95% CI, 20.1-28.5) respectively. The prevalence of dyspepsia was 25%, taking medication usage into consideration. Ulcer-like dyspepsia (11.2%) was the most common subtype and 40% of the subjects with dyspepsia were classified into more than one subtype of dyspesia. There was an overlap between subjects with IBS and dypepsia with 6.1% of dypeptics having IBS and ll,l% of IBS patients having dypepsia. Conclusions: The prevalence of GERD was low in Korea compared with that of the Western countries. The prevalences of dyspepsia and IBS were similar to those of the Western countries. The most common gastrointestinal symptom in a rural community in Korea is dyspepsia, (Korean Journal of Castrointestinal Motility 2000;6:31-43)