[show abstract][hide abstract] ABSTRACT: In this research, we propose an analytical method to control the period and the clarity of the beat in a slightly asymmetric
ring. The concept of a simple equivalent ring is applied, i.e. a slightly asymmetric ring with known modal data is modeled
as an equivalent circular ring with one or multiple point masses, which has the same modal data as that of the original ring.
By using the equivalent ring model, the optimal beat tuning is achieved by adding a 2nd point mass in order to obtain the required period and clarity in the beating vibration. The results obtained from the analytical
method are compared with those obtained from finite element analysis(FEA) and the validity of the proposed method is verified.
The proposed method can be effectively used to predict the mode pair and control the beat property in bell-type structures.
KeywordsAsymmetric ring-Beat tuning
Journal of Mechanical Science and Technology 01/2007; 21(8):1226-1234. · 1.09 Impact Factor
[show abstract][hide abstract] ABSTRACT: We demonstrate room-temperature low-threshold-current lasing action from electrically driven wavelength-scale high-quality photonic crystal lasers having large spontaneous emission factors by solving the theoretical and technical constraints laid upon by the additional requirement of the current injection. The ultrasmall cavity is electrically pulse pumped through a submicron-size semiconductor “wire” at the center of the mode with minimal degradation of the quality factor. In addition, to better utilize the low mobility of the hole, we employ a doping structure that is inverted from the conventional semiconductors. Rich lasing actions and their various characteristics are experimentally measured in the single-cell and three-cell photonic crystal cavities. Several relevant measurements are compared with three-dimensional finite-difference time-domain computations based on the actual fabricated structural parameters. The electrically driven photonic crystal laser, which is a small step toward a “practical” form of the single photon source, represents a meaningful achievement in the field of photonic crystal devices and photonic integrated circuits as well as of great interest to the quantum electrodynamics and quantum information communities.
IEEE Journal of Quantum Electronics 10/2005; · 1.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: We have successfully integrated 8M bits Localized ONO Memory (LONOM) for the embedded nonvolatile memory using 0.13um standard logic process with 5-level Cu metallization. which has a small cell size of 0.276UM and the simplest cell array structure. Without any special algorithm, the localized storage layer of the LONOM can satisfy the essential features for an embedded memory solution, such as low program current. disturb-free read operation and good endurance characteristics. The read speed is as high as 60MHz at V<sub>cc</sub>=0.9V, 85°C and the current consumption is lower than 5mA at Vcc = 1.4V.
[show abstract][hide abstract] ABSTRACT: A new Local SONOS structure has been proposed for an embedded NVM cell in 0.13 μm standard CMOS logic process. The localized storage silicon nitride layer of Local SONOS cell provides the essential properties for the embedded NVM such as the complete erase, low program current, and high on cell current from the low threshold voltage. The entire embedded memory solution has been realized with 0.276 μm<sup>2</sup> Local SONOS NVM cell, which has 20 μs program and 2 ms erase speed under 5.5 V bias condition, and good reliability without the special algorithms and cell array modifications.
[show abstract][hide abstract] ABSTRACT: EXECUTIVE SUMMARY In the treatment of municipal solid waste, the ratio of landfill, incineration and recycling was 23.6%, 18.6%, and 57.8%, respectively in 2007 which was shown high recycling ratio in Korea. However, the landfill ratio has been decreased sharply, and that of incineration and recycling have been increased. As a result, in 2008 the amount of incineration ash reached to 555 thousand tons in which the quantities of bottom ash and fly ash were 466 and 89 thousand tons, respectively. The bottom ash showed 84% of ash produced. Currently only about 10% of total bottom ash was recycled in Korea, mostly for bricks, tiles and blocks in the construction area. Thus, the recycling ratio of bottom ash should be increased in Korea instead of landfill. The bottom ash containing glass, ceramic, iron has high recycling feasibility through stabilization. However, pretreatment technology for heavy metal in bottom and fly ash are needed. The purpose of this study is to evaluate the stabilization of heavy metals with the change of moisture contents for stable recycling of bottom and fly ash generated from MSWI process. Bottom ash samples used in this study were taken from municipal solid waste incinerator located in the north side of Seoul, Korea. The experiment of aging treatment was carried out in lab-scale containers (390mm x 305mm x 220mm). The pH of bottom ash was about 12.57. The particle size distribution of bottom ash was shown in the range of 1-5 mm. The moisture content of bottom ash was adjusted 0 to 25% with particle size distribution. The bottom ash and fly ash were tested in different conditions for the stabilization ability through aging process. The effect of water addition was evaluated at room temperature during 3 months. Leaching concentration of heavy metals with aging time analyzed for Pb, Cu. The results showed that the leaching concentration of Pb, one of the main heavy metals was decreased dramatically, and addition of water to improve moisture condition could enhance the stabilization efficiency compared with that in the air condition. The optimum moisture content of MSWI bottom and fly ash was shown about 20%.