• IEIE Transactions on Smart Processing and Computing
• /
• v.4 no.3
• /
• pp.141-144
• /
• 2015

A broadband radio frequency synthesizer for multi-band, multi-standard mobile DTV tuners is proposed, it's loop bandwidth can be calibrated to optimize integrated phase noise performance without the problem of phase noise peaking. For this purpose, we proposed a new third-order scalable loop filter and a scalable charge pump circuit to minimize the variation in phase margin during calibration. The prototype phase-lock loop is fabricated in 180nm complementary metal-oxide semiconductor shows that it effectively prevents phase noise peaking from growing while the loop bandwidth increases by up to three times.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.5 no.1
• /
• pp.17-22
• /
• 2000

The separation of tryptophan enantiomers was carried out with medium-pressure liquid chromatography using BSA (bovine serum albumin)-bonded silica as a chiral stationary phase. The influence of various experimental factors such as pH and ionic strength of mobile phase, separation temperature, and the presence of organic additives on the resolution was studied. In order to expand this system to preparative scale, the loadability of sample and the stability of stationary phase for repeated use were also examined. The separation of tryptophan enantiomers was successful with this system. The data indicated that a higher separation factor (a) was obtained at a higher pH and lower temperature and ionic strength in mobile phase. Addition of organic additives (acetonitrile and 2-propanol) in mobile phase contributed to reduce the retention time of L-tryptophan. About $30\%$ of the separation factor was reduced after 80 days of repeated use.

• Journal of the Korean Society for Heat Treatment
• /
• v.18 no.6
• /
• pp.362-368
• /
• 2005

Formation and thermal stability of a quasicrystalline phases in Al-Fe-Mo alloys were investigated by means of melt-spinning process and subsequent heat treatment test. Thermal decomposition and phase transformation process of the as-spun alloys were studied using X-ray diffraction and electron microscopy. The melt-spun Al-Fe-Mo alloys contained an icosahedral quasicrystalline phase with a quasilattice constant of 0.457 nm. Icosahedral phase formed at a composition of $Al_{82.5}Fe_{14}Mo_{3.5}$ as a metastable phase during rapid solidification was transformed into the stable crystalline phases, cubic 1/0 approximant and monoclinic ${\lambda}$-phase, upon heating. A metastable icosahedral and cubic(a = 0.93 nm) phases in as-spun $Al_{65}Fe_{20}Mo_{15}$ alloy were decomposed into two cubic(a = 0.62, 0.31 nm) phases by heat treatment.

• Electrical & Electronic Materials
• /
• v.7 no.5
• /
• pp.417-424
• /
• 1994

PbNb$_{2}$O$_{6}$ piezoelectric ceramics have good properties, but the applications of them have been limited due to the problems of microstructures. In the present study, effects of additives on the phase stability, microstructure, and electrical proper-ties of ferroetectric phase were investigated. La$_{2}$O$_{3}$, Nd$_{2}$O$_{3}$ and Sm$_{2}$O$_{3}$ were added with the amounts of 1, 3, 5 mol% respectively. The results showed that single orthorhombic(ferroelectric phase) phase compared with the mixed phase of pure PbNb2O6 was obtained. In the case of 5 mol% Nd$_{2}$O$_{3}$ addition, relative density of >95% and dense microstructure with -2.mu.m grain size were obtained.d.

• Current Optics and Photonics
• /
• v.7 no.5
• /
• pp.557-561
• /
• 2023

Ultralow-noise soliton pulse generation over a wider Fourier frequency range is highly desirable for many high-precision applications. Here, we realize a low-phase-noise soliton pulse generation by transferring the low phase noise of a mode-locked laser to a silica microcomb. A 21.956-GHz and a 9.9167-GHz Kerr soliton combs are synchronized to a 2-GHz and a 2.5-GHz mode-locked laser through a fractional optoelectronic phase-locked loop, respectively. The phase noise of the microcomb was suppressed by up to ~40 dB at 1-Hz Fourier frequency. This result provides a simple method for low-phase-noise soliton pulse generation, thereby facilitating extensive applications.

• Nuclear Engineering and Technology
• /
• v.54 no.7
• /
• pp.2427-2434
• /
• 2022

Series of unequal quantity Nd/Ce co-doped ceramic nuclear waste forms, (Gd, Nd)₂(Zr, Ce)₂O₇, were prepared to tailor its ordered pyrochlore or disordered fluorite structure. The phase transition, microtopography, and elemental composition of the ceramic samples were systematically investigated, especially the effect of order-disorder structure on the chemical stability. It was confirmed that unequal quantity of Nd/Ce could synchronously replace the Gd/Zr-sites of Gd₂Zr₂O₇. And the phase transition of order-disorder structure could be successfully tailored by regulating the average cationic radius ratio of (Gd, Nd)₂(Zr, Ce)₂O₇ series. The elements of Gd, Nd, Zr, and Ce are uniformly distributed in the ordered or disordered structures. The MCC-1 leaching results showed that (Gd, Nd)₂(Zr, Ce)₂O₇ pyrochlore ceramic nuclear waste forms had excellent chemical stability, whose elements' normalized leaching rates were as low as 10^-4-10^-7 g·m^-2·d^-1 after 7 days. In particular, the chemical stability of disordered structure was superior to that of ordered structure. It was proposed that the force constant and the closest packing were changed with the structure transformation resulting the chemical stability difference.

• International Journal of Control, Automation, and Systems
• /
• v.6 no.3
• /
• pp.460-466
• /
• 2008

This paper deals with the stability analysis of a missile guidance loop employing an integrated proportional navigation guidance law. The missile guidance loop is formulated as a closed-loop control system consisting of a linear time-invariant feed-forward block and a time-varying feedback gain. Based on the circle criterion, we have defined the concept of absolute stability margins and obtained the gain and phase margins for the system assuming 1 st order missile/autopilot dynamics. The correlation between the absolute stability margins and the margins derived from the frozen system analysis is also discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.04b
• /
• pp.490-496
• /
• 1995

A four-legged mobile robot can move on the plain terrain with mobility and stability, but if there exist any obstacles on the terrain of the motion direction, it takes extra times for a mobile robot to cross those obstacles and the stability should be considered during motion. The main objevtive is the study of a quadruped which can cross obstacles with better mobility, stability and fuel economy than any other wheeled or tracked vehicles. Vertical step, isolated wall and ditch are the basic obstacles and by understanding those three cases perfectly, a quadruped can move on any mixed rough terrain as 4-legged animal moves. Each leg of a determine the crossing capability in a static analysis. A quadruped can be simplified with links and joints. By applying the research method, a quadruped can determine the control procedures as soon as it receives the terrain informations from scanner and finally can be moved as animals move with mobility and stability.

• Proceedings of the KSME Conference
• /
• 2001.06b
• /
• pp.301-306
• /
• 2001

In this paper, we developed a quadruped walking robot, FRAMIX-T, with insectile leg mechanism and we inspected the efficiency of it in detail. In robotics, the legs of insect type are appropriate for the stability and the agile movement. So we first performed a gait analysis using duty factor, stride, phase etc., and analyzed the stability margin to improve the stability of robot. On the basis of this research, we planned the wave gait suitable for FRAMIX-T and performed a walking experiment. From this result, we proved the high efficiency using insectile leg mechanism and the possibility of walking with improved stability and mobility.

• Steel and Composite Structures
• /
• v.41 no.6
• /
• pp.775-785
• /
• 2021

Analysis of nonlinear stability behaviors of composite magneto-electro-elastic (MEE) nano-scale shells have been represented in this reaserch. The shell is assumed to be under a transverse mechanical load. Composite MEE material has been produced form piezoelectric and magnetic ingradients in which the material charactristics may be varied according to the percentages of the ingradients. The governing equations including scale effects have been developed in the framework of nonlocal elasticity. It has been demonstrated that nonlinear stability behaviors of MEE nano-sized shells in electrical-magnetic fields rely on the percentages of the ingradients. Also, the efficacy of nonlocality parameter, magnetic intensities and electrical voltages on stability loads of the nanoshells have been researched.