Mao-Kuen Kuo | National Taiwan University (original) (raw)

Papers by Mao-Kuen Kuo

Nanomaterials, Dec 24, 2023

Elsevier eBooks, 1989

Transient response on the surface of an elastic half-space due to a finite rectangular fault is i... more Transient response on the surface of an elastic half-space due to a finite rectangular fault is investigated. In this paper, the case of shear fault motions in a horizontal plane is considered. In the analysis, the solution due to a quadrantal fault is first derived. The superposition of four quadrantal faults then leads to a desired finite rectangular fault. The crucial steps of the analysis are the direct application of the one-sided Laplace transform and the double two-sided Laplace transform over the time variable t and spatial variables x and y, respectively. Then the generalized ray theory is employed to take into account the free surface effect. The extended Cagniard-de Hoop method is subsequently applied to invert the integral transforms. The final solution consists of a number of finite range integration plus some contributions from poles. Numerical results of the ground acceleration due to several different fault motions are presented and compared. The procedure can easily be extended to faults with arbitrary dip.

Springer eBooks, 1991

The transient elastodynamic stress intensity factors of a sub-surface semi-infinite crack in an e... more The transient elastodynamic stress intensity factors of a sub-surface semi-infinite crack in an elastic half plane are analyzed. The crack is subjected to an incident SH wave initially, and some time later a screw dislocation emitting from a point located away from the crack tip. The crucial steps in the analysis are the direct application of integral transforms together with the Wiener-Hopf technique. Exact expressions are obtained for the resulting mode-Ill stress intensity factors as functions of time. The solution is constructed as a series. Each term in the solution series can be interpreted as the contribution of waves that have reflected at the free surface of half-plane different times. The first two terms in the series for the stress intensity factor history are then computed. The results are exact for the time interval from initial loading until the first wave scattered at the crack tip is reflected twice at the free surface of the half-plane and returns to the crack tip. Numerical results show that the smaller the emitting angle (and/or the smaller the emitting speed) of the dislocation is, the larger shielding effect to the crack.

International Journal of Solids and Structures, 1991

ABSTRACT

Proceedings of SPIE, Feb 10, 2011

ABSTRACT This paper investigates the differences between the fully coupled and the semi-coupled p... more ABSTRACT This paper investigates the differences between the fully coupled and the semi-coupled piezoelectric models for determining strain fields, piezoelectric potentials and optical properties of wurtzite InGaN quantum dots (QDs) in three different shapes. Through the calculations, we show that the relative difference of the x-component strain inside the dot remains almost unchanged regardless of the shapes and the sizes of the dot. On the other hand, a large relative difference for the z-component strain is obtained with the use of the semi-coupled model. We also find that the semi-coupled model clearly overestimates the piezoelectric potential, and the transition energy difference increased with increases in the dot size and indium composition. Consequently, the semi-coupled model causes a great amount of distortion in predicting the optical properties of InGaN QDs. It is thus evident that the fully coupled model for calculating the electromechanical fields and optical properties of InGaN QDs may be more appropriate according to our numerical examples.

Applied Physics Letters, Jun 18, 2012

In this study, the Purcell effect for CdSe/ZnS quantum dots emission coupled to a silver nanowire... more In this study, the Purcell effect for CdSe/ZnS quantum dots emission coupled to a silver nanowire cavity was investigated. We manipulated the interaction between colloidal quantum dots (QDs) and an Ag NW in the presence of a metallic tip. When a metal tip approaches the Ag NW, the Ag surface plasmon mode could be lifted away from the metallic NW so that a low optical loss could still be obtained. This work demonstrates enhancement of the spatial coupling between the plasmonic mode and light sources and reduction in metal Ohmic losses, resulting in an enhanced Purcell effect and coupling efficiency accompanied with increased fluorescence intensity.

2016 IEEE 16th International Conference on Nanotechnology (IEEE-NANO), 2016

Light-driven self-assembly of two coupled gold nanorods (GNRs) was studied theoretically. We anal... more Light-driven self-assembly of two coupled gold nanorods (GNRs) was studied theoretically. We analyzed the optical forces and torques on both GNRs. Our results show that due to the plasmon-mediated light-matter interaction two adjacent GNRs could coalesce in the end-to-end or side-by-side manner, depending on the wavelength and their initial configurations.

North-holland Series in Applied Mathematics and Mechanics, 1989

The diffraction of elastic waves by a crack tip is investigated for the case that cohesive tracti... more The diffraction of elastic waves by a crack tip is investigated for the case that cohesive tractions on the crack faces in the immediate vicinity of the crack tip have not been completely released. In this paper it is assumed that such residual cohesive tractions are proportional to the local crack-opening displacement. This assumption is equivalent to a spring-constrained near-tip zone. The crack is subjected to normal incidence of a longitudinal wave. For the time interval before signals from the other crack tip arrive, approximate expressions have been obtained for the spring tractions and the elastodynamic scattering field. The results are valid for the case of small range of constraints and small spring constant. In this approximation, the spring tractions are reduced to a separable form of a time dependence multiplied by a space dependence. The space dependence is found first. The time dependence is then expressed in a form of perturbation series for small in terms of powers o...

The transient elastodynamic stress intensity factors (SIF) of a sub-surface semi-infinite crack i... more The transient elastodynamic stress intensity factors (SIF) of a sub-surface semi-infinite crack in an elastic half plane are analyzed. The crack is parallel to the surface of the half plane where a pair of anti-plane force are acting at a fixed position on the crack faces. Exact expressions are obtained for the mode-III SIF as functions of time. The results are exact for the time interval from initial loading until the first wave scattered at the crack tip is reflected three times at the surface of half plane and returns to the crack tip.

Journal of Quantitative Spectroscopy and Radiative Transfer, 2016

This study theoretically examines a spinning gold nanoparticle (GNP) driven by circularly polariz... more This study theoretically examines a spinning gold nanoparticle (GNP) driven by circularly polarized (CP) plane waves. The wavelength-dependent optical torques which were exerted on three different shapes of GNPs (spherical, prolate and oblate spheroidal) were analyzed by utilizing Mie theory for the former and the multiple multipole method for the latter two, respectively. Numerical results show that both the absorbed and scattered photons contribute to optical torques in most cases. For the case that the CP wave is incident along the long axis of an oblate spheroid or the short axis of a prolate one, the scattering effect in optical torque is more pronounced than the absorption one. This phenomenon is significant especially when the wavelength of the CP wave is close to the longitudinal surface plasmon resonance band of the GNP. In contrast, when the CP wave is incident along the axes of revolution of these shapes of GNPs, the ratio of optical torque to absorption power is directly proportional to the wavelength. Moreover, this ratio is independent of the size and even the aspect ratio of GNPs. This result suggests that only the absorbed photons contribute to optical torques, but not the scattered ones, due to the conservation of angular momentum for cases of rotational symmetry.

Journal of Mechanics, 2022

Nanomaterials, 2022

In this work, we studied the initiated plasmonic nanobubbles and the follow-up microbubble in gol... more In this work, we studied the initiated plasmonic nanobubbles and the follow-up microbubble in gold nanorod (GNR) colloidal solution induced by a pulsed laser. Owing to the surface plasmon resonance (SPR)-enhanced photothermal effect of GNR, several nanobubbles are initiated at the beginning of illumination and then to trigger the optical breakdown of water at the focal spot of a laser beam. Consequently, microbubble generation is facilitated; the threshold of pulsed laser energy is significantly reduced for the generation of microbubbles in water with the aid of GNRs. We used a probing He-Ne laser with a photodetector and an ultrasonic transducer to measure and investigate the dynamic formations of nanobubbles and the follow-up microbubble in GNR colloids. Two wavelengths (700 nm and 980 nm) of pulsed laser beams are used to irradiate two kinds of dilute GNR colloids with different longitudinal SPRs (718 nm and 966 nm). By characterizing the optical and photoacoustic signals, three ...

The conversion of a helical surface plasmon polariton (SPP) creeping out of a circular nanohole i... more The conversion of a helical surface plasmon polariton (SPP) creeping out of a circular nanohole in a thick metal (Ag or Au) film into a spiral (Hankel type) SPP outward propagating at the film's interface is studied theoretically. The dispersion relations of SPPs of various modes in a nanohole, calculated from a transcendental equation, show that the propagation length of an SPP of mode 1 is much larger than the other modes in a specific frequency band, which is dependent on the nanohole size. In this band, the streamlines of the Poynting vector (energy flux) of mode-1 SPP in nanohole exhibit helixes; the surface component of the energy flux is perpendicular to the phase front of the SPP. Numerical results show that, after a helical SPP tunnels through a nanohole, most of the energy flux fans out at the outlet as a dipole radiation. The spatial phase distribution of E z above the interface indicates that the transmission light carries orbital angular momentum with a topological charge of 1. Additionally, a part of the helical SPP creeping along the edge of an outlet naturally converts into a spiral (Hankel type of order 1) SPP outward propagating at the film's interface; both SPPs have the same handedness. Moreover, the interferences of multi SPPs generating from two nanoholes and even from a two-dimensional nanohole array are also related to the spiral SPP.

Plasmonics, 2011

ABSTRACT We present a theoretical study on plasmonic enhancement of molecular fluorescence near a... more ABSTRACT We present a theoretical study on plasmonic enhancement of molecular fluorescence near a nanocomposite, Ag nanoshell (Ag-NS) coated by a gain medium of molecule-doped SiO2 layer. We use an average enhancement factor (AEF), which considers contributions from all possible orientations and locations of molecules in the silica layer to estimate the overall performance of Ag-NS@SiO2 at specific excitation and emission wavelengths. Our results on the AEF reveal that Ag-NS@SiO2 is a dual-band enhancer on the spontaneous emission of the gain medium; one is a narrowband in a shorter wavelength regime (quadrupole mode) and the other is a broadband in a longer wavelength regime (dipole mode). These two bands are tunable by adjusting the core size and the thickness of the Ag shell. Due to this merit, Ag-NS@SiO2 has great potentials to enhance Forster resonance energy transfer between a donor and a corresponding acceptor with large Stokes shifts.

Ultrasonics, 1998

Four distinct algorithms to locate the crack tip of a surface-breaking crack using only the arriv... more Four distinct algorithms to locate the crack tip of a surface-breaking crack using only the arrival time information of the first diffracted waves are described and compared. To illustrate these algorithms, a line crack in a half-plane is considered. The first two algorithms are based mainly on elementary geometric arguments, where the crack tip is formulated as the intersecting point of two ellipses (algorithm 1) and/or three circles (algorithm 2). The other two algorithms are formulated as optimization problems, where cost functions based upon the arrival time data of diffracted waves are constructed. The unknown crack tip coordinates are then determined by minimizing the cost functions through the Lagrange multiplier method (algorithm 3) or the simplex method (algorithm 4). In the numerical experiments, the exact arrival times are superimposed by Gaussian error with different levels to simulate the real extracted arrival times from experimental signals. The numerical optimization method (algorithm 4) is found to have the best performance with respect to noise, as well as for accuracy. Moreover, the recovery of the crack length is much more robust than the orientation and depth.

Optics Express, 2010

Average enhancement factor (AEF) of a coreshell (Ag@SiO 2) on the fluorescence of molecules doped... more Average enhancement factor (AEF) of a coreshell (Ag@SiO 2) on the fluorescence of molecules doped within the silica shell is proposed and studied to estimate the overall performance of a large number of coreshells. Using Mie theory and dyadic Green's functions, the enhancement factor (EF) of a coreshell is first calculated for any arbitrarily oriented and located electric dipole embedded in the shell. AEF is then obtained by averaging the individual EF over all possible orientations and positions of the electric dipoles. AEF of a FITC-doped coreshell (radius of Ag core: 25 nm, thickness of shell: 15 nm) irradiated by a laser of 488 nm for FITC's emission at 518 nm is 2.406. It is much smaller than the maximum EF (30.114) of a coreshell containing a single molecule with a radial orientation at its optimal position. For Alexa 430-doped coreshell excited at 428 nm, AEF is 12.34 at the emission of 538 nm.

Journal of Elasticity, 1993

Static three-dimensional stress intensity factors of a semi-infinite plane crack are investigated... more Static three-dimensional stress intensity factors of a semi-infinite plane crack are investigated in this paper. The deformations are caused by a pair of normal and tangential point forces acting on the crack faces but located away from the crack front. Cases of symmetric and anti-symmetric loadings with respect to the crack plane are both considered. Analytic solutions are obtained by the application of Fourier transforms together with the Wiener-Hopf technique. The formulation departs significantly from the Papkovich-Neuber formulation used in previous works. This alternative formulation reduces the complexity of the calculations involved and has the same potential in regard to the elastodynamic problem. Several misprints in previous works are also noted.