Due to the mismatch in the coefficients of thermal expansion of slicon chip and the surrounding plastic encapsulation materials, the induced thermal stress is the main cause for die and encapsulant rupture. The corner...Due to the mismatch in the coefficients of thermal expansion of slicon chip and the surrounding plastic encapsulation materials, the induced thermal stress is the main cause for die and encapsulant rupture. The corner geometry is simplified as the semi_infinite wedge. Then the two_dimensional thermal stress distribution around the corner was obtained explicitly. Based on the stress calculation, the strain energy density factor criterion is used to evaluate the strength of the structure, which can not only give the critical condition for the stresses, but also determine the direction of fracture initiation around the corner.展开更多
It is reported that simple beam structure used for FBG tuning can cause FBG chirping. A novel tuning method utilizing the clamped beam structure under pure bending is introduced. In this paper, we experimentally and t...It is reported that simple beam structure used for FBG tuning can cause FBG chirping. A novel tuning method utilizing the clamped beam structure under pure bending is introduced. In this paper, we experimentally and theoretically demonstrate that new method can tune the Bragg wavelength without chirp. Further integration of this package can be used for FBG athermal/MEMS packaging.展开更多
Energy levels and emission line wavelengths of high-Z materials are useful for impurity diagnostics due to their potential application in the next generation fusion devices.For this purpose,we have calculated the fine...Energy levels and emission line wavelengths of high-Z materials are useful for impurity diagnostics due to their potential application in the next generation fusion devices.For this purpose,we have calculated the fine structural energies of the 67 levels belonging to the 1s 2,1s2l,1s3l,1s4l,1s5l,and 1s6l configurations of Kr XXXV using GRASP（general purpose relativistic atomic structure package） code.Additionally,we have reported the transition probabilities,oscillator strengths,line strengths,and transition wavelengths for some electric dipole（E1） transitions among these levels.We predict new energy levels and radiative rates,which have not been reported experimentally or theoretically,forming the basis for future experimental work.展开更多
Effects of tilt angles of reflective cup structure and phosphor surface geometries on light extraction efficiency and angular color uniformity （ACU） of phosphor converted light emitting diodes （pcLED） are investig...Effects of tilt angles of reflective cup structure and phosphor surface geometries on light extraction efficiency and angular color uniformity （ACU） of phosphor converted light emitting diodes （pcLED） are investigated by Monte Carlo ray-tracing simulations. It is found that tilt angles of reflective cup and phosphor surface geometries affect the light extraction efficiency and the ACU distinctly. When the tilt angle varied from 60° to 15°, the light extraction efficiency of LED can achieve the improvements of 13.87%, 18.25% and 14.79% respectively, when the phosphor surface geometry is concave, flat and convex, respectively. It is also found the variety law of phosphor concentrations with the change of tilt angles and phosphor surface geometries to maintain a fixed correlated color temperature （CCT）.展开更多
文摘Due to the mismatch in the coefficients of thermal expansion of slicon chip and the surrounding plastic encapsulation materials, the induced thermal stress is the main cause for die and encapsulant rupture. The corner geometry is simplified as the semi_infinite wedge. Then the two_dimensional thermal stress distribution around the corner was obtained explicitly. Based on the stress calculation, the strain energy density factor criterion is used to evaluate the strength of the structure, which can not only give the critical condition for the stresses, but also determine the direction of fracture initiation around the corner.
文摘It is reported that simple beam structure used for FBG tuning can cause FBG chirping. A novel tuning method utilizing the clamped beam structure under pure bending is introduced. In this paper, we experimentally and theoretically demonstrate that new method can tune the Bragg wavelength without chirp. Further integration of this package can be used for FBG athermal/MEMS packaging.
文摘Energy levels and emission line wavelengths of high-Z materials are useful for impurity diagnostics due to their potential application in the next generation fusion devices.For this purpose,we have calculated the fine structural energies of the 67 levels belonging to the 1s 2,1s2l,1s3l,1s4l,1s5l,and 1s6l configurations of Kr XXXV using GRASP（general purpose relativistic atomic structure package） code.Additionally,we have reported the transition probabilities,oscillator strengths,line strengths,and transition wavelengths for some electric dipole（E1） transitions among these levels.We predict new energy levels and radiative rates,which have not been reported experimentally or theoretically,forming the basis for future experimental work.
基金The authors would like to acknowledge the financial support in part from the Major State Basic Research Development Program of the Ministry of Science and Technology of China （No. 2011CB013105）, and in part by the National Natural Science Foundation of China （Grant No. 2011AA03A109）.
文摘Effects of tilt angles of reflective cup structure and phosphor surface geometries on light extraction efficiency and angular color uniformity （ACU） of phosphor converted light emitting diodes （pcLED） are investigated by Monte Carlo ray-tracing simulations. It is found that tilt angles of reflective cup and phosphor surface geometries affect the light extraction efficiency and the ACU distinctly. When the tilt angle varied from 60° to 15°, the light extraction efficiency of LED can achieve the improvements of 13.87%, 18.25% and 14.79% respectively, when the phosphor surface geometry is concave, flat and convex, respectively. It is also found the variety law of phosphor concentrations with the change of tilt angles and phosphor surface geometries to maintain a fixed correlated color temperature （CCT）.
