Applied Mechanics and Materials Vols. 128-129

Abstract: The conventional method to measure the tracking accuracy of antenna is based on the boresight tower. But the accuracy of this method is not very high because the result is easy to be disturbed by reflecting electromagnetic wave from ground, surrounding buildings and terrains under low elevation in measuring. And a boresight tower and a lot of corresponding equipments are needed in this method. It costs both time and money. This paper presents a new method of using precise geostationary satellite orbit to measure the tracking accuracy. It is easy to operate. Moreover, the accuracy of this method is higher than the conventional one. The feasibility of the new method is validated in comparison with the conventional one, so it can be used in the construction and maintenance of ground stations.

Abstract: During the design process of Internal Combustion (IC) engine, what is often taken into consideration is the temperature of the important heated parts. The temperature distributions are the primary causes of thermal fatigue in the engine. A combined experimental and analytical approach was followed in this work to study temperature distributions of gasoline engine under steady-state and transient operation condition. Experimental studies were conducted to measure temperatures under a series of steady-state and transient operating conditions. A comparison of the steady-state and transient measurements has been made and the character of transient temperature distributions is concluded. Subsequently, a calculation analysis was conducted to predict the detailed temperature distributions. Solid-Fluid whole conjugated heat transfer method is applied in the numerical calculation, which can take the mutual influence both the fluid flow and the heat transfer into account. The predicted temperatures met well with the measurements. Furthermore, the predicted location of coolant boiling phenomena in the water jacket can be made certain. This can give some suggests for the further observation experiment of boiling heat transfer.

Abstract: In this paper, a novel and efficient Dempster-Shafer (D-S) evidence theory multi-node spectrum sensing based on double threshold judgment is proposed. A specific coordinate operation of D-S theory and double threshold judgment is discussed. It defines the uncertain area in double threshold detection, controls the application range of D-S theory and obtains the final detection results by drawing a clear line between data decision and information fusion. A better performance and higher sensing efficiency in a low signal-to-noise ratio is resulted according to the simulations.

Abstract: A designed network control system of multi mobile robot is presented. It is based on wireless distribution system. One or more mobile robot and some other devices are connected via wireless network to form a network control system. More than one wireless node is provided in order to realize distribution wireless network and extend the coverage range. The hierarchy control structure is used in the robot control system. It is optimized by the features of the network control system especially in time delay. By testing the time delay in different network environment, the performance of the whole control system can be proved.

Abstract: Multi-user detection (MUD) is used to control multiple access interference (MAI) and promote system performance and capacity, which is one of the key technology for CDMA system. Independent component analysis (ICA) aims to recover a set of unknown mutually independent source signals from theirs observed mixtures without knowledge of the mixing coefficients. FastICA, one of the ICA methods, has been successfully applied in various fields. But the classical FastICA does not converge quickly. In multi-user detection of direct sequence code division multiple access (DS-CDMA) system, we proposes an Improved-FastICA algorithm to reduce multiple access interference (MAI). The improved-FastICA algorithm uses a new Fifth-order Newton iterative method to estimate the negentropy. The experimental results show that the improved algorithm has the advantages of smaller bit error rate than traditional algorithm. The Improved-FastICA is more suitable for applications in DS-CDMA system.

Abstract: The cipher algorithms are categorized by block cipher, stream cipher and HASH, and they are weighed in faithful transmission which is known as independent condition. In faithful transmission, the ciphers are studied because of their root cipher. Intelligent application of ciphers is a direction that uses Bayesian model of cognition science. Bayesian inference is a rational engine for solving such problems within a probabilistic framework, and consequently is the heart of most probabilistic models of weighing the ciphers. The approach of this paper is that ciphers, which are considered as a suitable weight cipher to kinds of networks, are ranged based on root ciphers. This paper shows the other kinds of transformation among the different cipher algorithms themselves.

Abstract: According to the topology of Wireless Mesh Sensor Networks (abbreviate to WMSN), and the channel access strategy of alternately listening/sleeping scheme, this paper study a neighbor-based adaptive listening/sleeping mechanism for WMSN. Based on the theory of queuing, the paper designed an algorithm named neighbor-based listening and sleeping algorithm (abbreviate to NLS) which can adaptively arrange the duty cycle of transmission frame. On the account of three typical topology for WMSN and consider the neighbor number of Mesh routers and sensor nodes, the performance of proposed scheme are simulated and studied under NS-2. The study results show that the combination of the WSN and WMN can be constructed to achieve full interconnection of heterogeneous mesh topology network. Application of queuing theory to establish the WMSN network multi-hop data transmission model can dynamically adjust listening time of different nodes. Using NLS algorithm, the throughput, delay and energy-efficiency of WMSN network are all improved to some extent.

Abstract: In this paper, we study the node deployment in long narrow area of wireless sensor networks. Currently, studies on node deployment of wireless sensor networks mostly concentrated in two-dimensional flat area and three-dimensional space area which are complicated or inapplicable for long narrow area. The significant difference of node deployment between long narrow area and two-dimensional area is that the nodes in two-dimensional monitored area can be deployed anywhere, while the nodes in long narrow area can only be deployed by side with the environmental constraints. Considering the coverage, connectivity and reliability, we give out the densities and numbers of needed nodes in node deployment scheme for both 1-connected cover and k-connected cover in long narrow area covered completely by sensor networks.

Abstract: Monitoring oil quality on-line has become an important issue in today’s military, transportation and manufacturing industries. Although laboratory analysis procedures are comprehensive and detailed, they do not provide the timely information about oil for the aircraft health management. Condition monitoring is a preventive maintenance tool which has been used for over 50 years. In this paper we discuss several aircraft oil analysis methods and instruments or sensors. A new methodology of the aircraft oil health management is presented. It can assist realizing autonomous maintenance and dramatically reduce maintenance costs through the data integration from individual oil monitoring sensors. It offers a more comprehensive figure of the whole situation and a more accurate evaluation of the system condition. Therefore the aircraft safety will be greatly improved.

Abstract: A kind of optical fiber radiation pyrometer based on the theory of color comparison temperature measurement is designed in order to get the precise temperature on the appearance of work pieces during the process of plasma hot machining. In this article, the advantage of temperature measurement by optical fiber, the building of mathematic module for colorimetric temperature measurement, the application of key technology during the process of system building and the methods of reducing the interference is described in detail. The data calibrated and tested in blackbody furnace is given out. The results show that the precision of temperature measurement could reach to 0.5%. It is repetitiveness is well enough.