Yin Zhouping

High Probability Impulse Noise-Removing Algorithm Based on Mathematical Morphology

A novel filter based on mathematical morphology for high probability impulse noise removal is presented. First, an impulse noise detector using mathematical residues is proposed to identify pixels that are contaminated by the salt or pepper noise. Then the image is restored using specialized open-close sequence algorithms that apply only to the noisy pixels. Finally, black and white blocks that degrade the quality of the image will be recovered by a block smart erase method. Experimental results demonstrate that the proposed filter outperforms a number of existing algorithms and is particularly effective for the very highly corrupted images

Morphology characterization and influential mechanism analysis of electrospun micro/nano-fiber

Electrospinning attracts more eyes of scientists with the continuous rapid development of nanotechnology. The key problem in application is to improve the controllability of electrospinning parameters, such as material parameters, processing parameters and environmental factors, which would affect the morphology and consistency of electrospun fibers. In this paper, the effects of material and process parameters, including molecular weight, concentration, applied voltage, electrode spacing, diameter of nozzle, and topography of electrospun polyoxyethylene (PEO) fibers are experimentally investigated. The results show that the evolution of the morphology experienced from spherical particle to fiber with beads, and to fiber with the concentration of PEO from 4% to 8% increasingly. The fiber with beads structure changed into uniform and smooth fibers with molecular weight of PEO from the 4×105 to 6×105. When the molecular weight of PEO further added, the morphology of PEO fibers is started to become uneven and jagged structure. When the conductivity of PEO rises from 151 to 355 μs/cm, the diameter is nearly five times thicker. As the applied voltage (25–30 kV) is increased, the diameter and spindle beads are increased at first and then decreased. With electrode spacing (15–25 cm) rising, PEO fibers become fine, but with more spindle beads. As nozzle diameter was increased from the 160 to 600 μm, the fibers is uniform and smooth at first, then form bonding structures. These results are able to guide the electrospinning technology in the biomedical, nano-devices and nano-manufacturing and other fields.

A Comparative Study on the Performance of the RFID Tag Collision Resolution Protocols

One of the key issues that affect the universal application of RFID system is the collision caused by that multiple tags try to transmit their data simultaneously through the air interface. Although frame slot ALOHA based and splitting tree based collision resolution protocols are widely adopted, for the resolution of different number of tags, these protocols and their variants perform differently. The performance evaluation and comparison of these protocols are seldom researched and reported. In this paper, the time and message complexity of some typical collision resolution protocols are evaluated and compared through theoretical analysis and computation. Results indicate that the splitting tree based protocols, especially the k-ary tree protocol, perform much better than the frame slot ALOHA protocols, and it is difficult for the frame slot ALOHA protocols to resolve the collision happened in dense RFID tag environment.

QTS ALOHA: A Hybrid Collision Resolution Protocol for Dense RFID Networks

The performances of the frame slotted ALOHA based and tree based protocols are unsatisfactory in resolving the collision occurring in dense RFID networks made up of hundreds or even thousands RFID tags. QTS ALOHA, a hybrid collision resolution protocol which combines both the query tree protocol and the dynamic frame slotted ALOHA protocols, is proposed to achieve the rapid identification of a large amount memory-less RFID tags. For the identification of a group of tags, based on the data already collected, the population of tags in the group is estimated, and according to the identification accuracy required by the application system, the group of tags may be split into multiple subgroups through some binary suffix strings, dynamic slotted ALOHA protocol is performed to identify tags and collect data in the group or subgroups. This collision resolution process is performed repeatedly until the required identification accuracy is achieved. Numeric simulation verifies that this hybrid protocol outperforms othr protocols in frames and slots consumed to identify different number of tags, keeps a high throughput in each identification frame, and is especially suitable for the collision resolution in dense memory-less passive RFID networks.

Reflow profile optimization of μBGA solder joints considering reflow temperature and time coupling

Purpose – The purpose of this paper is to present a novel reflow profile optimization method using mechanical reliability estimation of micro‐ball grid array (μBGA) solder joints, based on the heating factor, Qη is introduced, where the coupling effect of reflow temperature and time on the mechanical reliability of μBGA joints is considered.Design/methodology/approach – The method presented is actualized through vibration fatigue tests. First, a two‐parameter Weibull distribution is used to model the collected data of vibration fatigue lifetime for different Qη. After that, two explicit functions are deduced in a unified mathematic expression form, which give an intuitionistic description of the mean time to failure and reliability of solder joints against induced variable Qη, thus revealing definitely the effect of Qη on the mechanical fatigue lifetime of solder joints suffering from cyclic vibration loading. Finally, for a specified reliability goal, how to choose proper Qη values, based an improved Gol...

Edge Detection of the Low Contrast Welded Joint Image Corrupted by Noise

To extract the edges from the low-contrast welded joint image corrupted by noise, the morphological filter is firstly proposed to remove the noise from the image. Then the improved fuzzy edge detection (FED) algorithm is adopted to realize the multi-level fuzzy enhancement of the filtered image and extract the edges from the enhanced image using multi-directional edge detection operator. Experimental results demonstrate that the improved FED algorithm can extract the continuous and thin edges and remove the false edges from the image, which leads to its better performance than the Sobel operator, Canny operator, traditional FED algorithm and fast FED algorithm.

Mechanical reliability estimation for μBGA solder joints based on heating factor Q η

A novel method of mechanical reliability analysis on vibration fatigue failure of muBGA solder joints, based on the heating factor Qeta, is introduced. Firstly, a two-parameter weibull distribution is used to model the collected data of vibration fatigue lifetime for different Qeta. After that, two explicit functions are deduced in a unified mathematic expression form, which give an intuitionistic description of the MTTF and reliability of solder joints against induced variable Qeta, thus revealing definitely the effect of Qeta on the mechanical fatigue lifetime of solder joints suffering from cyclic vibration loading. Numerical analysis and calculation are performed. The results show that the solder joints reflowed at Qeta near 500 have higher reliable, and those reflowed farther away this optimal process parameter have less reliability.

A comparative study on the splitting tree based protocols for RFID tag identification

Collision caused by that multiple RFID tags try to transmit their identifiers through the shared wireless communication channel simultaneously is one of the key issues that affect the ubiquitous adoption of RFID system. In this paper, based on the stochastic distribution model, a simple but efficient tag population estimation method is suggested to work in the splitting tree collision resolution protocol, and the estimation accuracy is also discussed. Based on tag population estimation, the group of RFID tags to be identified is divided into multiple subgroups to be resolved in following slots. This group splitting process is performed recursively until that in each subgroup, there is zero or one tag, so all subgroups can be resolved and all tags can be identified. The performances of different splitting tree protocols are evaluated and some useful conclusions are achieved.

Stochastical Model and Performance Analysis of Frequency Radio Identification

RFID (Radio Frequency Identification) can assign a unique digital identifier to each physical item, and provide an efficient, cheap and contactless method for gathering the information of the physical items to enable their automatic tracking and tracing(Finkenzeller 2003). RFID technology serves as the back stone of the “Internet of Things”(Engels 2001), and is reviewed as a main enabler of the upcoming “Pervasive Computing”(Stanford 2003). RFID systems have been widely adopted in quite a lot applications, ranged from “smart box” to world-wide logistics management systems. A typical RFID system is consisted of some RFID tags, one or more RFID readers and the backend information system. Each RFID tag holds a unique identifier and is attached to a physical item. RFID reader is used to collect the identifiers stored in the RFID tags located in its vicinity and is often connected with the backend information system. During identification, The RFID reader asks the RFID tags to modulate their binary identifiers into signals and transmit these signals back to the reader through the air interface, which is a wireless communication channel for the RFID tag and reader to exchange information. Afterwards, The RFID reader sends the data gathered to the backend information system for further processing and dispatching to various applications. One of the main issues that affect the universal deployment and application of the RFID system is the collisions occurred during RFID tag identification(Wu 2006). The simultaneous modulated signals broadcasted by the RFID reader and transmitted from the RFID tags will interfere in the air interface, in which case, what the receivers can get is only a collision signal but no useful information. Collisions occurred in the RFID system can be categorized as the reader-reader, reader-tag and tag-tag collisions(Shih 2006). When two or more RFID readers try to broadcast messages through the air interface simultaneously, reader-reader collision occurs. Due to that they are often connected with the computer system and can be equipped with enough resource to monitor the air interface, RFID readers can detect the collision and coordinate with each other in advance. Reader-reader collision can be avoided and resolved completely with some deliberate designed protocols, such as the ColorWav(Waldrop 2003) and others(Leong 2006).

A Hybrid Collision Resolution Protocol for Passive RFID Tag Identification

Wireless communication channel collision of RFID system is a key issue that affects the pervasive application of the system, especially for passive RFID system due to the constrained communication ability and energy supply of tags. The collision resolution protocols suggested can be categorized into deterministic tree based protocols and probabilistic frame slot ALOHA based protocols. A hybrid protocol, which combines the query tree protocol and dynamic framed slotted ALOHA protocol, is presented here. In this protocol, at the beginning of each identification frame, the reader broadcasts a query command message which contains a suffix string and integer to indicate a frame size used in this frame to all tags in its vicinity, and every tag whose data match the specified suffix string randomly selects a slot in the frame to transmit its data to the reader. After each round, based on the different occupying situation of slots, the reader re-estimates the number of tags in its range, and according to the identification accuracy required, decides whether to split the group of tags to be identified into sub-groups or not, and adjust the suffix string and select a suitable frame size for the command messages of the following frames. Through this repeated identification and division process, the RFID tags can be identified within a number of frames. Some key factors that influence the efficiency of the identification are also discussed based on binomial distribution model. Three methods for the tag population estimation are examined and their accuracies are compared, and the optimum frame size for the identification of different number of tags is given in consideration of the throughput and efficiency. To verify the performance of the hybrid protocol, a numeric simulation is performed, in which 100 groups of SGTIN-96 encoded tags are generated randomly. Simulation shows that this hybrid protocol outperforms other frame slot ALOHA based collision resolution protocols, especially when there are a large number of RFID tags to be identified. The overall throughput of the hybrid protocol is kept around 34.8% when there are more than 40 tags, near the theoretical maximum value 36.8%. A linear relationship between the number of tags and the total frames and slots required is also observed in the numeric simulation.