Fu Zhongqian

Epidemic spread in weighted scale-free networks

We investigate the detailed epidemic spreading process in scale-free networks with link weights that denote familiarity between two individuals. It is found that the spreading velocity reaches a peak quickly then decays in a power-law form. Numerical study exhibits that the nodes with larger strength is preferential to be infected, but the hierarchical dynamics are not clearly found, which is different from the well-known result in the unweighed network case. In addition, also by numerical study, we demonstrate that larger dispersion of weight of networks results in slower spreading, which indicates that epidemic spreads more quickly on unweighted scale-free networks than on weighted scale-free networks with the same condition.In this letter, we investigate the detailed epidemic spreading process in scale-free networks with links weights that denote familiarity between two individuals and find that spreading velocity reaches a peak quickly then decays in a power-law form. Numerical study exhibits that the nodes with larger strength is preferential to be infected, but the hierarchical dynamics are not clearly found, which is different from the well-known result in unweighed network case. In addition, also by numerical study, we demonstrate that larger dispersion of weight of networks results in slower spreading, which indicates that epidemic spreads more quickly on unweighted scale-free networks than on weighted scale-free networks with the same condition.

Epidemic dynamics on complex networks

Abstract Recently, motivated by the pioneer work in revealing the small-world effect and scale-free property of various real-life networks, many scientists devote themselves to studying complex networks. One of the ultimate goals is to understand how the topological structures affect the dynamics upon networks. In this paper, we give a brief review on the studies of epidemic dynamics on complex networks, including by description of classical epidemic models, the epidemic spread on small-world and scale-free networks, and network immunization. Finally, perspectives and some interesting problems are proposed. * Supported National Natural Science Foundation of China (Grant Nos. 70471033, 10472116, and 70271070), and the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20020358009)

A 1.8 V LDO voltage regulator with foldback current limit and thermal protection

This paper introduces the design of a l.8 V low dropout voltage regulator (LDO) and a foldback current limit circuit which limits the output current to 3 mA when load over-current occurs. The LDO was implemented in a 0.18 μm CMOS technology. The measured result reveals that the LDOs power supply rejection (PSR) is about −58 dB and −54 dB at 20 Hz and 1 kHz respectively, the response time is 4 μs and the quiescent current is 20 μA. The designed LDO regulator can work with a supply voltage down to 2.0 V with a drop-out voltage of 200 mV at a maximum load current of 240 mA.

Networks Emerging from the Competition of Pullulation and Decrepitude

In real-world network evolution, the aging effect is universal. We propose a microscopic model for aging networks, which suggests that the activity of a vertex is the result of the competition of two factors: pullulation and decrepitude. By incorporating the pullulation factor into previous models of aging networks, both the global and individual aging effect curves in our model are single peaked, which agrees with the empirical data well. This model can generate networks with scale-free degree distribution, large clustering coefficient and small average distance when the decrepitude intensity is small and the network size not very large. The results of our model show that pullulation may be one of the most important factors affecting the structure and function of aging networks and should not be neglected at all.

A 0.18 μm CMOS inductorless complementary-noise-canceling-LNA for TV tuner applications

This paper presents an inductorless complementary-noise-canceling LNA (CNCLNA) for TV tuners. The CNCLNA exploits single-to-differential topology, which consists of a common gate stage and a common source stage. The complementary topology can save power and improve the noise figure. Linearity is also enhanced by employing a multiple gated transistors technique. The chip is implemented in SMIC 0.18 μm CMOS technology. Measurement shows that the proposed CNCLNA achieves 13.5–16 dB voltage gain from 50 to 860 MHz, the noise figure is below 4.5 dB and has a minimum value of 2.9 dB, and the best P1dB is −7.5 dBm at 860 MHz. The core consumes 6 mA current with a supply voltage of 1.8 V, while the core area is only 0.2 × 0.2 mm2.

A digitally controlled power amplifier with neutralization capacitors for Zigbee™ applications

This paper presents a single chip CMOS power amplifier with neutralization capacitors for Zigbee™ system according to IEEE 802.15.4. A novel structure with digital interface is adopted, which allows the output power of a PA to be controlled by baseband signal directly, so there is no need for DAC. The neutralization capacitors will increase reverse isolation. The chip is implemented in SMIC 0.18 μm CMOS technology. Measurement shows that the proposed power amplifier has a 13.5 dB power gain, 3.48 dBm output power and 35.1% PAE at P1dB point. The core area is 0.73 × 0.55 mm2.

An energy detection receiver for non-coherent IR-UWB

A non-coherent receiver for impulse radio ultra-wide band (IR-UWB) is presented. The proposed receiver front-end consists of a high gain LNA, a high frequency detector and an intermediate frequency (IF) amplifier to amplify the recovered signal and drive an external test instrument. To meet the requirements of high gain and a low noise figure (NF) under moderate power consumption for the LNA, capacitor cross coupled (CCC) and current reuse techniques were adopted. The detector consists of a squarer and an integrator. The overall circuit consumes 41.2 mA current with a supply voltage of 1.8 V at a 400 MHz pulse rate. The resulting energy efficiency is 0.19 nJ/pulse. A chip prototype is implemented in 0.18-?m CMOS. The die area is 2.1 ? 1.4 mm2 and the active area is 1.7 ? 0.98 mm2.

High performance QVCO design with series coupling in CMOS technology

A high performance quadrature voltage-controlled oscillator (QVCO) is presented. It has been fabricated in SMIC 0.18 μm CMOS technology with top thick metal. The proposed QVCO employed cascade serial coupling for in phase and quadrature phase signal generation. Source degeneration capacitance is added to the NMOS differential pair to suppress their flicker noise from up-conversion to close in phase noise. A dedicated low noise and high power supply rejection low drop out regulator is used to supply this QVCO. The measured phase noise of the proposed QVCO achieves phase noise of −123.3 dBc/Hz at an offset frequency of 1 MHz from the carrier of 4.78 GHz, while the QVCO core circuit and LDO draw 6 mA from a 1.8 V supply. The QVCO can operate from 4.09 to 4.87 GHz (17.5%). Measured tuning gain of the QVCO (Kvco) spans from 44.5 to 66.7 MHz/V The chip area excluding the pads and ESD protection circuit is 0.41 mm2.

A low power high gain UWB LNA in 0.18-μm CMOS

A low power high gain differential UWB low noise amplifier (LNA) operating at 3–5 GHz is presented. A common gate input stage is used for wideband input matching; capacitor cross coupling (CCC) and current reuse techniques are combined to achieve high gain under low power consumption. The prototypes fabricated in 0.18-μm CMOS achieve a peak power gain of 17.5 dB with a –3 dB bandwidth of 2.8–5 GHz, a measured minimum noise figure (NF) of 3.35 dB and –12.6 dBm input-referred compression point at 5 GHz, while drawing 4.4 mA from a 1.8 V supply. The peak power gain is 14 dB under a 4.5 mW power consumption (3 mA from a 1.5 V supply). The proposed differential LNA occupies an area of 1.01 mm2 including test pads.

Reinforcement Based Fuzzy Neural Network Control with Automatic Rule Generation

A reinforcemen-based fuzzy neural network control with automatic rule generation (RBFNNC) is proposed. A set of optimized fuzzy control rules can be automatically generated through reinforcement learning based on the state variables of object system. RBFNNC was applied to a cart-pole balancing system and simulation result shows significant improvements on the rule generation.