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A NEW MEAN VALUE RELATED TO D. H. LEHMER'S PROBLEM AND KLOOSTERMAN SUMS
Han, Di,Zhang, Wenpeng Korean Mathematical Society 2015 대한수학회보 Vol.52 No.1
Let q > 1 be an odd integer and c be a fixed integer with (c, q) = 1. For each integer a with $1{\leq}a{\leq}q-1$, it is clear that the exists one and only one b with $0{\leq}b{\leq}q-1$ such that $ab{\equiv}c$ (mod q). Let N(c, q) denote the number of all solutions of the congruence equation $ab{\equiv}c$ (mod q) for $1{\leq}a$, $b{\leq}q-1$ in which a and $\bar{b}$ are of opposite parity, where $\bar{b}$ is defined by the congruence equation $b\bar{b}{\equiv}1$ (modq). The main purpose of this paper is using the mean value theorem of Dirichlet L-functions to study the mean value properties of a summation involving $(N(c,q)-\frac{1}{2}{\phi}(q))$ and Kloosterman sums, and give a sharper asymptotic formula for it.
Di Han,Bulent Sarlioglu 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6
Gallium nitride (GaN)-based power switching devices, such as high-electron-mobility transistors (HEMT), provide significant performance improvements in terms of faster switching speed, zero reverse recovery, and lower on-state resistance compared with conventional silicon (Si) metal–oxide–semiconductor field-effect transistors (MOSFET). These benefits of GaN HEMTs further lead to low loss, high switching frequency, and high power density converters. Through simulation and experimentation, this research thoroughly contributes to the understanding of performance characterization including the efficiency, loss distribution, and thermal behavior of a 160-W GaN-based synchronous boost converter under various output voltage, load current, and switching frequency operations, as compared with the state-of-the-art Si technology. Original suggestions on design considerations to optimize the GaN converter performance are also provided.
Han, Di,Sarlioglu, Bulent The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6
Gallium nitride (GaN)-based power switching devices, such as high-electron-mobility transistors (HEMT), provide significant performance improvements in terms of faster switching speed, zero reverse recovery, and lower on-state resistance compared with conventional silicon (Si) metal-oxide-semiconductor field-effect transistors (MOSFET). These benefits of GaN HEMTs further lead to low loss, high switching frequency, and high power density converters. Through simulation and experimentation, this research thoroughly contributes to the understanding of performance characterization including the efficiency, loss distribution, and thermal behavior of a 160-W GaN-based synchronous boost converter under various output voltage, load current, and switching frequency operations, as compared with the state-of-the-art Si technology. Original suggestions on design considerations to optimize the GaN converter performance are also provided.
A new mean value related to D. H. Lehmer's problem and Kloosterman sums
Di Han,Wenpeng Zhang 대한수학회 2015 대한수학회보 Vol.52 No.1
Let $q>1$ be an odd integer and $c$ be a fixed integer with $(c, q)=1$. For each integer $a$ with $1\le a \leq q-1$, it is clear that there exists one and only one $b$ with $0\leq b \leq q-1$ such that $ab \equiv c $ (mod $q$). Let $N(c, q)$ denote the number of all solutions of the congruence equation $ab \equiv c$ (mod $q$) for $1 \le a, b \leq q-1$ in which $a$ and $\overline{b}$ are of opposite parity, where $\overline{b}$ is defined by the congruence equation $b\overline{b}\equiv 1$ $(\bmod q)$. The main purpose of this paper is using the mean value theorem of Dirichlet $L$-functions to study the mean value properties of a summation involving $\left(N(c, q)-\frac{1}{2}\phi(q)\right)$ and Kloosterman sums, and give a sharper asymptotic formula for it.
High-Speed and Low-Voltage-Driven Shift Register With Self-Aligned Coplanar a-IGZO TFTs
Di Geng,Dong Han Kang,Man Ju Seok,Mativenga, M.,Jin Jang IEEE 2012 IEEE electron device letters Vol.33 No.7
<P>We report a high-speed and low-voltage-driven shift register utilizing self-aligned coplanar amorphous-indium-gallium-zinc-oxide thin-film transistors (a -IGZO TFTs). The a-IGZO TFTs exhibit field-effect mobility, threshold voltage, and gate-voltage swing of 24.7 cm<SUP>2</SUP>/V·s, 0.2 V, and 118 mV/dec, respectively. The rise and fall times of the shift register at the supply voltage (<I>V</I><SUB>DD</SUB>) of 1 V are 8 and 7 μs, respectively, and the output pulse is free from distortion or ripple. For a <I>V</I><SUB>DD</SUB> of 15 V, the clock frequency of the shift register approaches 500 kHz, making it applicable to high-resolution active-matrix displays.</P>
A Seamless Constraint Model of Multi-Scale Representation of Geographical Information
Di Chen,Han Yue,Xinyan Zhu 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.8
At present, it has become a hot issue to provide a multi-representation mechanism and build multi-scale spatial databases in the field of GIS. Meanwhile, an inevitable problem is how to evaluate and preserve the consistency of multi-scale spatial data. In this paper, we introduce the concepts of homonymous points and homonymous entities based on innate characteristics of spatial data and put forward a seamless constraint model of multi-scale representation of geographic information that involves time, geometry, spatial relations and semantic characteristics. According to this model, a consistency assessment method has been implemented by computing similarities between vector data at three different scales. The main contributions of this paper are the proposal of a consistency constraint model and assessment system of multi-scale spatial data.
Di Geng,Dong Han Kang,Jin Jang IEEE 2011 IEEE electron device letters Vol.32 No.6
<P>We report the fabrication of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with a bottom-gate inverted-staggered structure with an etch stopper formed by a self-aligned process using back-side UV exposure. In addition to reduction in process complexity, the gate-to-source capacitance of an a-IGZO TFT is significantly reduced, resulting in fast TFT circuits. The fabricated TFT exhibits a field-effect mobility value of 42.59 cm<SUP>2</SUP>/V·s , a threshold voltage of 6.1 V, and a gate voltage swing of 374 mV/dec. An 11-stage ring oscillator made of TFTs shows a propagation delay time of 56 ns/stage at 25 V.</P>