Biomedical subjects

Chi-Hung Huang

Publications and source records attributed to Chi-Hung Huang.

7 recordsLinked to original sources

PubMed2006

Transverse vibration analysis for piezoceramic rectangular plates using Ritz's method with equivalent constants.

The transverse vibration of piezoceramic rectangular thin plates is investigated theoretically and experimentally using the Ritz's method incorporated with the defined equivalent constants. The equivalent constants are derived by comparing the characteristic equations of transverse resonant frequencies between isotropic and piezoceramic disks. By replacing the Poisson's ratio and flexural rigidity with the equivalent constants, the well-known Ritz's method can be used to investigate the transverse vibration of piezoceramic rectangular plates. Two different types of boundary conditions-clamped-free-free-free (CFFF) and clamped-free-clamped-free (CFCF)-are analyzed in this paper. For the experimental measurement, two optical techniques-amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV)-are used to validate the analytical results. Both the transverse vibration modes and resonant frequencies of piezoceramic rectangular plates are obtained by the AF-ESPI method. Numerical calculations using the finite-element method (FEM) are performed, and the results are compared with the theoretical analysis and experimental measurements. Excellent agreements are obtained for results of both resonant frequencies and mode shapes. According to the theoretical calculations with different equivalent Poisson's ratios, resonant frequency variations versus aspect ratios ranging from 0.1 to 10 also are discussed for the first several modes in the work.

Journal Article↗

PubMed2005

Is guidewire exchange a better approach for subclavian vein re-catheterization for chronic hemodialysis patients?

BACKGROUND: The objectives of this study were to compare outcomes and survival rates of subclavian vein re-catheterization through guide wire exchange (GWE) or de novo insertion (DN). MATERIALS AND METHODS: The study was conducted in a retrospective manner. Medical records of 36 patients who received percutaneous subclavian vein re-catheterization for hemodialysis in our institution during the period from April 1, 2001 to September 30, 2004 were reviewed. All patients had at least 2 catheter insertions records in our institute. Incidences of adverse events (infection, thrombosis) were compared between GWE and DN groups using x2 test. Predictors for adverse event occurrences were analyzed using logistic regression models. Cox proportional hazard model was used to investigate the predictors for adverse event-free catheter days. Kaplan-Meire survival curves were computed and compared using log rank test. RESULTS: Information were generated from 98 catheters (41 from DN, 57 from GWE groups). The average catheter usage was 2.8+/-0.9 devices per patient and the mean catheter-indwelling-day was 125.4+/-129.5 days in this cohort. We found GWE group had significantly lower thrombosis rate (49.1% vs. 85.4% for DN group, P<0.000) in general. Surgical approach was a significant risk factors for catheter thrombosis (GWE vs. DN, odds ratio=0.261, P=0.05). The actuarial survival rates for GWE were > or =30 days, 85.4%; > or =60 days, 75.5%; > or =90 days, 64.5%; > or =180 days, 44.3%. The actuarial survival rates for DN were > or =30 days, 70.7%; > or =60 days, 58.5%; > or =90 days, 34.2%; > or =180 days, 18.4%. GWE group catheters had significantly higher catheter survival rates (P=0.0009). Mahukar catheter (hazard ratio 0.514, P=0.03), non-shock (hazard ratio 3.358, P=0.04), and older age (hazard ratio 0.958, P=0.026) were predictors of adverse event-free remaining catheter days. CONCLUSION: We suggest that GWE might be a favorable option over DN insertion when revised subclavian vein catheterization is inevitable. GWE can be performed repeatedly without compromising catheter outcomes.

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PubMed2005

Theoretical, numerical, and experimental investigation on resonant vibrations of piezoceramic annular disks.

In this study, vibration characteristics of thin piezoceramic annular disks with stress-free boundary conditions are investigated by theoretical analysis, numerical simulation, and experimental measurement. The nonaxisymmetric, out-of-plane (transverse), and axisymmetric in-plane (tangential and radial extensional) vibration modes are discussed in detail in terms of resonant frequencies, mode shapes, and electrical currents. Two optical techniques, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), as well as the electrical impedance measurement are used to validate the analytical results. Both theoretical and experimental results indicate that the transverse and tangential vibration modes cannot be determined by the impedance analysis; hence, only resonant frequencies of extensional vibration modes are presented from the impedance analyzer. The LDV system is used to measure the resonant frequencies of transverse vibrations. However, both the transverse and extensional vibration modes and resonant frequencies of piezoceramic annular disks are obtained by the AF-ESPI method, and the interferometric fringes are produced instantly by a video recording system. Numerical results obtained by finite-element calculations are compared with those from theoretical analysis and experimental measurements. It is shown that the theoretical predictions of resonant frequencies and the corresponding mode shapes agree well with the experimental results. Good agreement between the predicted and measured electrical impedance also is found. The dependence of resonant frequencies and dynamic electromechanical coupling coefficients on the inner-to-outer radius ratio also is analyzed and discussed in this study.

Journal Article↗

PubMed2005

Resonant vibration investigations for piezoceramic disks and annuli by using the equivalent constant method.

This paper presents the equivalent constant method to investigate the transverse vibration of piezoceramic disks and annuli. By comparing the characteristic equations of resonant frequencies between isotropic and piezoceramic disks, the named equivalent Poisson's ratio v is derived, then the transverse vibration characteristic equation can be expressed as a single formulation for these two materials. To verify this method, characteristic equations of transverse vibration for piezoceramic disks and annuli with many different boundary conditions are discussed and calculated for resonant frequencies. Numerical calculations based on the finite-element method (FEM) also are performed, and the results agree rather well with the theoretical predictions. With the aid of the relations between frequency parameter and equivalent Poisson's ratio in explicit form, the other application of equivalent Poisson's ratio is the inverse evaluation of material constants. The laser Doppler vibrometer (LDV) and impedance analyzer are used to experimentally obtain the resonant frequencies of transverse and radial extensional vibrations, respectively. By the experimental results for the traction-free piezoceramic disk, the planar Poisson's ratio v(p) and planar electromechanical coupling coefficient k(p) are determined.

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PubMed2005

Free vibration analysis of the piezoceramic bimorph with theoretical and experimental investigation.

This paper investigates the vibration characteristics of an asymmetric, three-layered piezoceramic circular bimorph under traction-free boundary conditions by applying the electroelasticity and Kirchhoff plate theory. The asymmetric, three-layered bimorph consists of an isotropic shim layer and two piezoceramic layers of equal thickness and same polarization. Two optical techniques, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are used to validate the theoretical analysis. The resonant frequencies of the piezoceramic bimorph also are measured by an impedance analyzer. Both theoretical and experimental results indicate that the transverse vibration modes cannot be measured by impedance analysis, and only resonant frequencies of extensional vibration modes are present. However, transverse vibration modes of the piezoceramic bimorph can be obtained by the AF-ESPI and LDV measurements. The numerical calculations also are obtained using the finite-element method (FEM), and the results agree comparatively well with the theoretical analysis and experimental measurements. According to the theoretical calculation, the variations in resonant frequencies and effective coupling factors versus the various layer-thickness ratios also are investigated in this work.

Journal Article↗

PubMed2004

Theoretical analysis and experimental measurement for resonant vibration of piezoceramic circular plates.

Based on the electroelastic theory for piezoelectric plates, the vibration characteristics of piezoceramic disks with free-boundary conditions are investigated in this work by theoretical analysis, numerical simulation, and experimental measurement. The resonance of thin piezoceramic disks is classified into three types of vibration modes: transverse, tangential, and radial extensional modes. All of these modes are investigated in detail. Two optical techniques, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are used to validate the theoretical analysis. Because the clear fringe patterns are shown only at resonant frequencies, both the resonant frequencies and the corresponding mode shapes are obtained experimentally at the same time by the proposed AF-ESPI method. Good quality of the interferometric fringe patterns for both the transverse and extensional vibration mode shapes are demonstrated. The resonant frequencies of the piezoceramic disk also are measured by the conventional impedance analysis. Both theoretical and experimental results indicate that the transverse and tangential vibration modes cannot be measured by the impedance analysis, and only the resonant frequencies of extensional vibration modes can be obtained. Numerical calculations based on the finite element method also are performed, and the results are compared with the theoretical analysis and experimental measurements. It is shown that the finite element method (FEM) calculations and the experimental results agree fairly well for the resonant frequencies and mode shapes. The resonant frequencies and mode shapes predicted by theoretical analysis and calculated by finite element method are in good agreement, and the difference of resonant frequencies for both results with the thickness-to-diameter (h/D) ratios, ranging from 0.01 to 0.1, are presented.

Journal Article↗

PubMed2003

Coronary stent graft for hypertrophic obstructive cardiomyopathy combined with coronary artery disease.

Percutaneous transluminal coronary angioplasty and stenting are established therapeutic modalities for coronary artery disease (CAD). Percutaneous transluminal septal myocardial ablation has become increasingly important for the treatment of symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM). We report a case of HOCM combined with CAD involving the left anterior descending coronary artery. Coronary stent graft implantation was performed with uneventful recovery. Coronary stent graft implantation may be beneficial in selected cases of symptomatic HOCM combined with CAD.

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