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Chern-Sheng Lin,Jen Min Tsai,Kai-Sheng Chen,Yun-Long Lay,Nin-Chun Chang 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
In this paper an automatic optical inspection system for the advanced fiber coupler assembly manufacturing process is presented. Coupling efficiency variations were compared with axial displacement. The main standard components of light peak fiber couplerswere used in the experiment to determine the corresponding offset and position of the optimal optical coupling efficiency in order toachieve a positioning effect. This study used the parameters of lens curvature, focal length and light source for validation using opticaldesign software. An infrared CCD camera was used to extract the coupled light spot images. The curve fitting method and couplingsimulation database were used for image processing and to calculate optimal coupling efficiency. Under optimal coupling efficiency,the minimum amount of movement of the translation stages was used to calculate the offset of each axle or the coupling efficiencywhen tilted. Moreover, a coupling efficiency database was established. The optical axle center offset in the alignment was calculatedby comparing the data in the database. Finally, the optical axle center offset or tilt direction was identified through the program toachieve the position of optimal coupling efficiency.
ON THE ENTIRE SERIES WITH FINITE LOGARITHMIC ORDER
Chern, Peter Tien-Yu,Kim, In-Soo The Honam Mathematical Society 2011 호남수학학술지 Vol.33 No.3
We deal with a kind of impossible decomposition of some entire functions in terms of a certain form.
Chern-Hwa Chen,Cheng-Hsin Chang,Yuh-Yi Lin 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.16 No.2
A wind tunnel test of a scaled-down model and field measurement were effective methods for elucidating the aerodynamic behavior of a chimney under a wind load. Therefore, the relationship between the results of the wind tunnel test and the field measurement had to be determined. Accordingly, the set-up and testing method in the wind tunnel had to be modified from the field measurement to simulate the real behavior of a chimney under the wind flow with a larger Reynolds number. It enabled the results of the wind tunnel tests to be correlated with the field measurement. The model surface roughness and different turbulence intensity flows were added to the test. The simulated results of the wind tunnel test agreed with the full-scale measurements in the mean surface pressure distribution behavior.
Fermionic spin liquid analysis of the paramagnetic state in volborthite
Chern, Li Ern,Schaffer, Robert,Sorn, Sopheak,Kim, Yong Baek American Physical Society 2017 Physical Review B Vol.96 No.16
<P>Recently, thermal Hall effect has been observed in the paramagnetic state of volborthite, which consists of distorted kagome layers with S = 1/2 local moments. Despite the appearance of magnetic order below 1 K, the response to external magnetic field and unusual properties of the paramagnetic state above 1 K suggest possible realization of exotic quantum phases. Motivated by these discoveries, we investigate possible spin liquid phases with fermionic spinon excitations in a nonsymmorphic version of the kagome lattice, which belongs to the two-dimensional crystallographic group p2gg. This nonsymmorphic structure is consistent with the spin model obtained in the density functional theory calculation. Using projective symmetry group analysis and fermionic parton mean field theory, we identify twelve distinct Z(2) spin liquid states, four of which are found to have correspondence in the eight Schwinger boson spin liquid states we classified earlier. We focus on the four fermionic states with bosonic counterpart and find that the spectrum of their corresponding root U(1) states features spinon Fermi surface. The existence of spinon Fermi surface in candidate spin liquid states may offer a possible explanation of the finite thermal Hall conductivity observed in volborthite.</P>
Chern, Li Ern,Hwang, Kyusung,Mizoguchi, Tomonari,Huh, Yejin,Kim, Yong Baek American Physical Society 2017 Physical Review B Vol.96 No.3
<P>The Kagome-lattice-based material, volborthite, Cu3V2O7(OH)(2) center dot 2H(2)O, has been considered as a promising platform for discovery of unusual quantum ground states due to the frustrated nature of spin interaction. We explore possible quantum spin liquid and magnetically ordered phases in a two-dimensional nonsymmorphic lattice, which is described by the plane group p2gg, consistent with the spatial anisotropy of the spin model derived from density functional theory (DFT) for volborthite. Using the projective symmetry group (PSG) analysis and Schwinger boson mean field theory, we classify possible spin liquid phases with bosonic spinons and investigate magnetically ordered phases connected to such states. It is shown, in general, that only translationally invariant mean field spin liquid ansatzes are allowed in two-dimensional nonsymmorphic lattices. We study the mean field phase diagram of the DFT-derived spin model and find that possible quantum spin liquid phases are connected to two types of magnetically ordered phases, a coplanar incommensurate (q, 0) spiral order as the ground state and a closely competing coplanar commensurate (pi, pi) spin density wave order. In addition, periodicity enhancement of the two-spinon continuum, a consequence of symmetry fractionalization, is found in the spin liquid state connected to the (pi, pi) spin density wave order. We discuss relevance of these results to recent and future experiments on volborthite.</P>
THE ASYMPTOTIC STABILITY OF SOME INTEGRODIFFERENTIAL EQUATIONS
Chern, Jann-Long,Huang, Shu-Zhu Korean Mathematical Society 2000 대한수학회보 Vol.37 No.2
In this paper we consider two delay equations with in-finite delay. We will give two sufficient conditions for the positive and zero equilibriums of these equations to be a global attractor respectively.
Instantaneous Frequency Estimation with Modified Trench`s Method
Chern, Shiunn Jang,Tsai, Lin Chung 대한전자공학회 1994 ISPACS:Intelligent Signal Processing and Communica Vol.1 No.1
In this paper, a new algorithm for instantaneous frequency estimation (IFE) is developed. The modified Trench's method along with the Bauer-Fike theorem is proposed for solving the principal eigenvalues of the Hermitian Toeplitz autocorrelation matrix for IFE. Here for IFE, first, the modified Trench's method is employed for solving the principal eigenvalues of the autocorrelation matrix formed by the initial block of data with length N. When a new data is received, the Bauer-Fike theorem is then applied to update the new eigenvalues based on the previous obtained eigenvalues. The advantage of this approach is that each individual eigenvalue can be updated independently Therefore, it can be implemented by the parallel structure such that the computation time can be reduced. From the simulation results, we found that. the presented method can resolve two chirped signal with close center frequencies.
ON THE UNIQUENESS FOR ENTIRE FUNCTIONS
Chern, Peter Tien-Yu,Kim, Jong-Jin,Kim, In-Su The Honam Mathematical Society 2007 호남수학학술지 Vol.29 No.4
We establish two uniqueness theorems for non-constant entire functions which extends results of J. S. Hwang in J. Math. Anal. and its Appl. Vol. 37 (1972) 452-456.
Chen, Chern-Hwa,Chang, Cheng-Hsin,Lin, Yuh-Yi Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.16 No.2
A wind tunnel test of a scaled-down model and field measurement were effective methods for elucidating the aerodynamic behavior of a chimney under a wind load. Therefore, the relationship between the results of the wind tunnel test and the field measurement had to be determined. Accordingly, the set-up and testing method in the wind tunnel had to be modified from the field measurement to simulate the real behavior of a chimney under the wind flow with a larger Reynolds number. It enabled the results of the wind tunnel tests to be correlated with the field measurement. The model surface roughness and different turbulence intensity flows were added to the test. The simulated results of the wind tunnel test agreed with the full-scale measurements in the mean surface pressure distribution behavior.