Advanced Materials Research Vols. 712-715

Abstract: With the previous proposed G/G/1 model, this paper analyzed the throughput expression in an unsaturated 802.11e one-hop ad hoc network. The expression is validated and the throughput performance is discussed by the simulations. The throughput expression derived in this paper will provide a way to analyze the impact of major QoS specific features on the throughput and hence can improve the performance of the network.

Abstract: This paper presents a method based on statistical approach which known as Taguchi method. This method is used to optimize power dissipations and gain in a two-stage op-amp. Standard L₂₇ which uses three factors and two outputs is chosen to optimize power and gain in the circuit. Simulation of the circuit has been implemented by using Mentor Graphics DA-IC. From the simulation, the results showed that total power dissipation has decreased from 3.9643 mW to 1.0345 mW. The percentage of power reduction is 73.9%. The overall gain also has been improved from 22 dB to 45.49 dB. The percentage of increment gain in two-stage op-amp is 56%.

Abstract: based on the analyzing the characteristic of BiCMOS circuits and theory of transmission voltage-switches, we proposed a general structure of binary BiCMOS circuit based on NPN-NPN feedback driver circuit. Then we designed binary BiCMOS master-slave JK flip-flop circuit and transmission gate D flip-flop circuit base on the general structure of NPN-NPN feedback driver circuit. With using HSPICE simulation, the results show that the circuits have the correct logical function. The proposed driver circuits can be used in the design of BiCMOS sequential circuits.

Abstract: Linear encoder as an important displacement measurement device has been widely used in manufacturing industry. The accuracy of linear encoder is based on the precision of its scales. In this article, the manufacturing process of the scales based on photolithography process and etching process was discussed in order to explain the opening ratio variation. A mathematical model was derived to analyze the effects of opening ratio variation on the waveform of output signal. The result shows that the waveform of the signal is cut off in comparison with the ideal waveform, and the magnitude of the output signal is changed.

Abstract: The fabrication and operation of a new thick film type of limiting current oxygen sensor is demonstrated that utilizes YSZ as oxygen ion conducting solid electrolytes and La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ +60% YSZ as dense diffusion barrier. The oxygen sensor shows a near linear response between 0 to 10ppm O₂ in argon at 973K.

Abstract: Using software of ANSYS, natural convection formed by point heat source in square and cylinder chambers were simulated numerically. The velocity field of different shape chambers was compared. The simulated results of velocity field show that, with regard to easy to produce convection, cylinder chamber is better than square one. Based on cylinder chamber, the diameter and length of cylinder chamber were set. Every technical parameter of tilt sensors with this structure all reached practical requirement.

Abstract: There exist some mobile node localization algoriths in wireless sensor netwok,which require high computation and specialized hardware and high node large density of beacon nodes.The Monte Carlo localization method has been studied and an improved Monte Carlo node localization has been proposed. Predicting the trajectory of the node by interpolation and combing sampling box to sampling. The method can improve the efficiency of sampling and accuracy. The simulation results show that the method has achieved good localization accuracy.

Abstract: At present, the effective technical means for air quality forecast and air pollution control is imperative for China environment utilities because of the increasing and serious environment pollution problems. In this paper, we discuss an air quality monitoring scenario which utilizes the wireless sensor network (WSN) to monitor the air quality of the transportation, industry and residential areas. Using the WSN, it is possible to deploy a large number of sensor nodes randomly distributed throughout the monitored area to capture environmental information of CO₂, NO, NO₂ and total suspended particulates. To achieve this goal, a special WSNs architecture is proposed, where the sensor nodes and coordinator nodes are designed by using ZigBee-based prototype wireless network, using GPRS to transmit the data from coordinator node to monitoring center, and designing the monitoring center server accessed from remote terminals through internet. In addition, the open source software (OSS) is proposed to design the database and website of the server. The designed air quality monitoring system reduces the cost of network installation and maintenance and provides a data delivery service for the air quality monitoring service in a timely and reliable manner.

Abstract: Grounding electrode electromagnetic flowmeter can reduce the loss of the measurement signal,and the conductivity lower medium can be measured if the area of the grounding electrode was increased. However, if the grounding electrode area is increased, the measurement signal will be reduced. The weight function theory of electromagnetic flow meter shows that the reason is the distribution of electromagnetic flow meter weight functions is changed by the grounding electrode, lead to the induced electromotive force every point of media in the pipeline contribution to the measuring electrode is changed. the weight function of the electromagnetic flowmeter which possesses one or two grounding electrodes was analyzed respectively, get the law of electromagnetic flowmeter output signal decreases with the increase of the grounding electrode area. Finally, the relationship of the electromagnetic flowmeter output signal and the ground electrode diameter accounted for measuring the ratio of the pipe been demonstrated. This theory and method has a certain significance to research and development grounding electrode electromagnetic flowmeter.

Abstract: The influence of quadrature phase shift caused by angular misalignment on the measurement accuracy of two moiré linear encoders is analyzed. A mathematical model of quadrature phase-shift error is derived. The model is employed to analyze the quadrature phase-shift error in lateral-moiré-fringe-based and Vernier-moiré-fringe-based linear encoders respectively, and comparisons are carried out. The results show the nonlinearity of the quadrature phase-shift error and the relative insensitivity of the Vernier-moiré-fringe-based linear encoders to the angular misalignment.