Papers by Keyword: Signal Strength

Abstract: Fatigue crack of the precast reinforced concrete beam under repetition loading is vital to be examined. Reinforced concrete structures exposed to excessive repetition loading could lead to the failure of the structures. In order to examine the active fatigue crack, the reinforced concrete beams were subjected to three-point repetition maximum loading. Eight phases of maximum fatigue loading with sinusoidal wave, frequency of 1 Hz and 5000 cycles for each phase were performed on the reinforced concrete beams. The inspection was carried out with visual observation of the crack pattern and acoustic emission technique for each load phase. The signal strength of acoustic emission was investigated. It is found that the signal strength of acoustic emission and crack pattern of the reinforced concrete beam subjected to repetition loadings showed promising results for structural health monitoring.

Abstract: Nowadays the wireless communication networks are the bigger part in the communication area. It is very important to choose the best place for the wireless nodes. To support the placement of these devices I wanted to create a signal strength measurement system that I implemented on ZigBee platform with GPS positioning.

Abstract: In this paper, the research topic is that the expert experience is established by the size of the measured signal strength of wireless sensor networks and put the strength of the actual collection of historical data into the neural network model. In order to get the minimize error we use the errors to modify the weights and threshold of the neural network links. We compare the differences of hidden layer neural network and the experimental results. We set up a wireless sensor networks environment to collect the measurement values of signal strength (RSSI) and develop an indoor positioning system.

Abstract: In this paper the authors present the localization system which uses triangulation and trilateration to position mobile robot in the two-dimensional space. Distance was measured with the strength of radio signal emitted by devices of existing communication network, which were constructed by the authors. To get the actual distance in the function of radio signal strength the calibration curve, which was set empirically, made from the spline of linear functions was used. Research in this paper can be divided into two parts: the quality tests of communication and the localization using radio waves. Quantity measure of the correctly transmitted frames showed that the communication network works with the credibility of 80%, which is good result for the radio waves. Outcome of the localization quality showed that the position error did not surpass 1.7 m, which is a good result compared to the error of a typical GPS receiver is 15 m. Summing up, the localization system proposed by the authors is working well. Furthermore the test showed that triangulation and trilateration are universal methods of positioning and they can be used in other systems. Additionally the test indicated that the accuracy can by increased by using devices with a better signal strength measure.

Abstract: The purpose of this study is to find out the AE characteristics and fracture mechanisms through AE signal analysis for the weldment, PWHT specimen and basemetal of the pressure vessel steel. Charpy sized specimens were taken from the multi-passed weld block. Specimens were given to four point bend and AE tests. Lots of AE signals were emitted from the weldment compared with the basemetal and PWHT specimen. Besides, amplitude for the weldment was the largest, followed by PWHT specimen and basemetal and more AE counts for the weldment were emitted in the process of deformation. Lots of microcracks around the notch for the weldment were formed so that more AE signals were produced. In addition, second phase particle such as MgO for the basemetal acts as AE source. However, in case of weldment, debonding mechanisms between matrix and hard oxides which are formed during welding in air attributed to the emission of AE signals and softened particles for the PWHT specimen cause to produce the low level AE signals.

Abstract: The purpose of this study is to find out the method to detect AE signals at around the notch tip and to evaluate the AE signal characteristics for the basemetal, PWHT(post weld heat treatment) and weldment specimens of SA-516 steel during bend test. AE signals were produced in the process of plastic deformation. AE signal strength and amplitude of the weldment was the strongest, followed by PWHT specimen and basemetal. More AE signals were produced from the weldment because of the oxides, and discontinuous mechanical properties. The stronger AE signal strength, amplitude and more AE event counts for the weldment were shown.