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Response spectrum analysis considering non-classical damping in the base-isolated benchmark building
Huating Chen,Ping Tan,Haitao Ma,Fulin Zhou 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.64 No.4
An isolated building, composed of superstructure and isolation system which have very different damping properties, is typically non-classical damping system. This results in inapplicability of traditional response spectrum method for isolated buildings. A multidimensional response spectrum method based on complex mode superposition is herein introduced, which properly takes into account the non-classical damping feature in the structure and a new method is developed to estimate velocity spectra from the commonly used displacement or pseudo-acceleration spectra based on random vibration theory. The error of forced decoupling method, an approximated approach, is discussed in the viewpoint of energy transfer. From the baseisolated benchmark model, as a numerical example, application of the procedure is illustrated companying with comparison study of time-history method, forced decoupling method and the proposed method. The results show that the proposed method is valid, while forced decoupling approach can’t reflect the characteristics of isolated buildings and may lead to insecurity of structures.
Generalized complex mode superposition approach for non-classically damped systems
Huating Chen,Yanhui Liu,Ping Tan 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.3
Passive control technologies are commonly used in several areas to suppress structural vibrations by the addition of supplementary damping, and some modal damping may be heavy beyond critical damping even for regular structures with energy dissipation devices. The design of passive control structures is typically based on (complex) mode superposition approaches. However, the conventional mode superposition approach is predominantly applied to cases of under-critical damping. Moreover, when any modal damping ratio is equal or close to 1.0, the system becomes defective, i.e., a complete set of eigenvectors cannot be obtained such that some well-known algorithms for the quadratic eigenvalue problem are invalid. In this paper, a generalized complex mode superposition method that is suitable for under-critical, critical and over-critical damping is proposed and expressed in a unified form for structural displacement, velocity and acceleration responses. In the new method, the conventional algorithm for the eigenvalue problem is still valid, even though the system becomes defective due to critical modal damping. Based on the modal truncation error analysis, modal corrected methods for displacement and acceleration responses are developed to approximately consider the contribution of the truncated higher modes. Finally, the implementation of the proposed methods is presented through two numerical examples, and the effectiveness is investigated. The results also show that over-critically damped modes have a significant impact on structural responses. This study is a development of the original complex mode superposition method and can be applied well to dynamic analyses of non-classically damped systems.
Cultural Factors Influencing Functional Gastrointestinal Disorders in the East
( Kee-huat Chuah ),( Sanjiv Mahadeva ) 대한소화기기능성질환·운동학회(구 대한소화관운동학회) 2018 Journal of Neurogastroenterology and Motility (JNM Vol.24 No.4
Culture forms an integral aspect of environmental factors which influences disease presentation and clinical outcomes in functional gastrointestinal disorders (FGIDs). In this review, the role of culture in FGIDs in the East is briefly explored with regards to symptom presentation and diagnostic issues, lifestyle and cultural habits, epidemiology, and healthcare seeking behavior. In both functional dyspepsia and irritable bowel syndrome, symptom presentation and disease sub-typing in Asians are known to differ from their Western counterparts, possibly relating to cultural dietary practices and from cultural perception of symptoms. Dietary patterns, together with defecating practices are explored as factors contributing to a lower prevalence of constipation in the East. An urban-rural difference in the prevalence of FGIDs in Asia is attributed to a change in dietary patterns in rapidly developing urban communities, together with an increased level of psychological morbidity. Lastly, cultural attitudes towards traditional/local remedies, variation in healthcare systems, anxiety regarding organic disease, and religious practices have been shown to influence healthcare seeking behavior among FGID patients in the East. (J Neurogastroenterol Motil 2018;24:536-543)
Basal and Acetazolamide Brain Perfusion SPECT in Internal Carotid Artery Stenosis
Teck Huat Wong,Qaid Ahmed Shagera,류현지,하승균,이동수 대한핵의학회 2020 핵의학 분자영상 Vol.54 No.1
Internal carotid artery (ICA) stenosis including Moyamoya disease needs revascularization when hemodynamic insufficiency is validated. Vascular reserve impairment was the key to find the indication for endarterectomy/bypass surgery in the atherosclerotic ICA stenosis and to determine the indication, treatment effect, and prognosis in Moyamoya diseases. Vascular reserve was quantitatively assessed by 1-day split-dose I-123 IMP basal/acetazolamide SPECT in Japan or by Tc-99m HMPAO SPECT in other countries using qualitative or semi-quantitative method. We summarized the development of 1-day basal/ acetazolamide brain perfusion SPECT for ICA stenosis, both quantitative and qualitative methods, and theirmethodological issues regarding (1) acquisition protocol; (2) qualitative assessment, either visual or deep learning-based; (3) clinical use for atherosclerotic ICA steno-occlusive diseases and mostly Moyamoya diseases; and (4) their impact on the choice of treatment options. Trials to use CT perfusion or perfusion MRI using contrast materials or arterial spin labeling were briefly discussed in their endeavor to use basal studies alone to replace acetazolamide-challenge SPECT. Theoretical and practical issues imply that basal perfusion evaluation, no matter how much sophisticated, will not disclose vascular reserve. Acetazolamide rarely causes serious adverse reactions but included fatality, and now, we need to monitor patients closely in acetazolamide-challenge studies.
Ng, Boon Huat,Rozita, AM,Adlinda, A,Lee, Wei Ching,Zamaniah, WI Wan Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.9
Background: Positive para-aortic lymph node (PALN) at diagnosis in cervical cancer patients confers an unfavorable prognosis. This study reviewed the outcomes of extended field radiotherapy (EFRT) and concurrent chemotherapy with extended field RT (CCEFRT) in patients with positive PALN at diagnosis. Materials and Methods: Medical records of 407 cervical cancer patients between 1st January 2002 to 31st December 2012 were reviewed. Some 32 cases with positive PALN were identified to have received definitive extended field radiotherapy with or without chemotherapy. Treatment outcomes, clinicopathological factors affecting survival and radiotherapy related acute and late effects were analyzed. Results: Totals of 13 and 19 patients underwent EFRT and CCEFRT respectively during the period of review. The median follow-up was 70 months. The 5-year overall survival (OS) was 40% for patients who underwent CCEFRT as compared to 18% for patients who had EFRT alone, with median survival sof 29 months and 13 months, respectively. The 5-years progression free survival (PFS) for patients who underwent CCEFRT was 32% and 18% for those who had EFRT. Median PFS were 18 months and 12 months, respectively. Overall treatment time (OTT) less than 8 weeks reduced risk of death by 81% (HR=0.19). Acute side effects were documented in 69.7% and 89.5% of patients who underwent EFRT and CCEFRT, respectively. Four patients (12.5%) developed radiotherapy late toxicity and there was no treatment-related death observed. Conclusions: CCEFRT is associated with higher 5-years OS and median OS compared to EFRT and with tolerable level of acute and late toxicities in selected patients with cervical cancer and PALN metastasis.
Functionalization of Multi-Walled Carbon Nanotubes with Poly(2-ethyl-2-oxazoline)
Tan, Soon Huat,Goak, Jeung Choon,Lee, Naesung,Kim, Jeong-Yeol,Hong, Sung Chul WILEY-VCH Verlag 2007 Macromolecular symposia Vol.249 No.1
<P>Multi-walled carbon nanotubes (MWCNTs) were successfully functionalized with water-soluble poly(2-ethyl-2-oxazoline) (PEOX) through a polymer wrapping process. Pristine MWCNTs were first treated with nitric acid (HNO<SUB>3</SUB>) at 120 °C for 24 hours. The resulting carboxylated MWCNTs were then mixed with 10 wt.% PEOX in ethanol, followed by sonication using a horn-type sonicator for 30 min and stirring at room temperature for 24 hours. Thereafter, unreacted free polymer was washed out repeatedly by centrifugation with an excess amount of ethanol. Scanning electron microscopy exhibited that the diameter of MWCNTs increased approximately by 10 nm after the functionalization of MWCNT with PEOX. Thermogravimetric analysis showed that approximately 15 wt.% polymer was incorporated in the functionalized MWCNTs. The functionalized MWCNTs gave excellent and stable dispersion in water as well as other organic solvents such as ethanol and DMF.</P>