Search

the reliability of solder joint under drop impact is a crucial research area due to the smaller and higher density. The test standard for board level has been published by JEDEC in detail. Based on JEDEC board level drop test standard, the square board with four symmetry component is designed in this paper. The structure size of test board is 0.5mm×121mm×121mm. The distance of the center component to the center of test board is 15mm. The first six modal frequency is 23.56Hz, 136.37Hz, 138.53Hz, 165.98Hz, 346.35Hz and 394.56Hz respectively. This Design benefits for the board level drop life of solder joint statistics analysis. And the 0.5mm thickness design can be used as replacement test board to analyze the failure mechanism of solder joint under relative high drop impact level.

An active disturbance rejection control (ADRC) technique based on adaptive differential evolution (ADE) algorithm and an improved PID control strategy were proposed so as to solve the problem of self-balancing control and steering control for two-wheeled self-balancing robot. By using Lagrange formula, the nonholonomic dynamic mathematical model was derived based on the nonholonomic dynamic Routh equation of generalized coordinates. For self-balancing control, an ADRC strategy whose parameters were adjusted by means of ADE algorithm was designed. For steering control, a PID control strategy combined with tracking differentiator (TD) was designed. The dynamic model of the whole robot was built through Adams software by applying virtual prototype technology. Finally, co-simulations using both Matlab/Simulink and Adams were carried on. The co-simulation results showed that the supposed control strategy could achieve self-balancing and steering operation effectively with the performance of fast adjusting speed, high accuracy and strong robustness as well.

The reliability of Sn-0.3Ag-0.7Cu (SAC0307) and Sn-1.0Ag-0.5Cu (SAC105) solder joint under drop impact were researched. SAC0307 have a finer Ag3Sn precipitates, thinner IMC layer, and high fraction of primary β-Sn phase than SAC 105. The average IMC thickness of SAC 0307 is 2.9µm and SAC105 is 3.7µm. Both SAC0307 and SAC105 has a similar failure mode. The failed samples were categorized into four modes: (1) the whole crack through the IMC layer, (2) bonging pad fracture, (3) the crack initiate from IMC layer and propagate through void, (4) the crack initiate from IMC layer and voids, propagate through IMC and bulk solder. The conditional probability density distribution surface (CPDDS) revealed that the SAC0307 solder joint showed better performance than those of SAC 105 under drop impact. The scattering of SAC0307 drop times large than SAC105.

Recently, a new-style agricultural industry, pollution-purifying agriculture (PPA) or contamination-purifying agriculture (CPA), is proposed and carried out in China. Combination and development from established on the base of environmental engineering technological principles and methods, PPA focus on the eutrophication removing and aquatic ecosystem remediation by using the advanced constructed wetland system and modern agricultural techniques. High value farm produce, such as vegetable, is provided in the process of controlling pollutant discharge to the environment by the constructed wetland system. The advantages of such an industry are obvious. First and foremost, there would be positive effect in environmental quality. Moreover, the products which were provided by constructed wetland system would increase the incoming of the involvers and help to maintain the running of contamination-purifying system. In this article, the concept and characters of PPA were introduced; the researches and development in PPA related field were reviewed; the prospects, chances and challenges of PPA in China were discussed.

The thermal fatigue and mechanical fatigue are the two main failure modes for board level solder joint in SMT. The comparison investigation of thermal fatigue and mechanical fatigue behavior of solder joint are carried out by experimental method in this study. The surface mounted test PCB is used and two kinds of solder materials, including SAC305 and Sn37Pb, are considered. It is shown that lead-free solder joint (SAC305) has a longer thermal fatigue lifetime, but a shorter mechanical fatigue lifetime than traditional eutectic lead-tin solder. Moreover, the inelastic strain (including creep and plastic strain) evolutions of solder joint during thermal and mechanical fatigue procedure are analyzed by FEM individually. It shows that the creep and plastic strain in mechanical fatigue procedure is different from those in thermal fatigue.

Workflow patterns contain basic features of business process, and describe activities and their execution ordering through different constructors, which permit flow of execution control. Pi-calculus, as a kind of process algebra, can be applied in business process modeling. In this paper, we introduced a formal semantics for workflow patterns, which is based on the Pi-calculus, to investigate some workflow patterns.

In SMT, the investigation on solder joint's failure is always very important. Thermal fatigue is the main failure form for solder joint in SMT. In this paper the failure process of solder joint in SMT was investigated by both electrical resistance measurement method and crack observation method together. The characteristics of electrical resistance value variation of lead-tin and lead-free solder (SAC305) joint during thermal fatigue test were obtained. And at the same time the crack propagation in solder joint was observed. According to this, the failure rules of lead-tin and lead-free solder joint were compared. And by FEM, the relationship between electrical resistance value variation and crack propagation of solder joint during thermal fatigue test was studied, through which an criterion based on electrical resistance value variation for solder joint's failure during thermal fatigue test could be obtained from experience. It was shown from experimental results that the lead-free solder (SAC305) joint had a higher resistibility from thermal fatigue than the traditional lead-tin eutectic solder joint. And the criterion based on electrical resistance value variation was built up from the experimental and simulation results.

Listeria monocytogenes (LM) is a bacterial foodborne pathogen responsible for listeriosis, an illness characterized by encephalitis, septicaemia , and meningitis. One of the best ways to detect and confrim the pathogen is through the detection of one of the virulence factors, listeriolysin O (LLO) produced by the microorganism. LLO is absolutely required for virulence by L. monocytogenes, and is found only in virulent strains of the species. This paper focuses on the electrical detection methods used to detect the LLO toxin gene in food products or organism. A new and simple electrochemical approach for hybridisation detection without the labelling the target DNA is described. The coupling of DNA electrochemical sensors have specialities of quick detection and cheapness and have the potential of the quantitative evaluation of the hlyA gene of Listeria monocytogenes. The electrochemical sensor was obtained by immobilizing single-stranded oligonucleotides onto gold electrodes through mercaptan of the DNA bases using N- hydroxysulfosuccinimide (NHS) and N-(3-dimethylamion)propyl-N'-ethyl carbodiimidehydrochloride (EDC) as activation. The hybridization reaction that occurred on the electrode surface was evidenced by cyclic voltammetry (CV) analysis - using as [Co(phen)3](C1O4)3 indicator. The covalently immobilized single-stranded DNA could selectively hybridize with its complementary DNA in solution to form double-stranded DNA on the gold surface. A significant increase of the peak current of cyclic voltammetry (CV) upon the hybridization of immobilized ssDNA with PCR amplification products in the solution was observed. This peak current change was used to monitor the amount of PCR amplification products. Factors such as DNA target concentration and hybridization conditions determining the sensitivity of the electrochemical assay were investigated.

A novel assay for the cyclic voltammetry (CV) detection of PCR amplification to using electrochemical DNA biosensor was reported. The coupling of DNA electrochemical sensors have specialities of quick detection and cheapness and have the potential of the quantitative evaluation of the PCR amplification. The electrochemical sensor was obtained by immobilizing single-stranded oligonucleotides onto gold electrodes through mercaptan of the DNA bases using N-hydroxysulfosuccinimide (NHS) and N-(3-dimethylamion)propyl-N'-ethyl carbodiimidehydrochloride (EDC) as activation. The hybridization reaction that occurred on the electrode surface was evidenced by cyclic voltammetry (CV) analysis-using as [Co(phen)3](ClO4)3 indicator. The covalently immobilized single- stranded DNA could selectively hybridize with its complementary DNA in solution to form double-stranded DNA on the gold surface. A significant increase of the peak current of cyclic voltammetry (CV) upon the hybridization of immobilized ssDNA with PCR amplification products in the solution was observed. This peak current change was used to monitor the amount of PCR amplification products. Factors such as DNA target concentration and hybridization conditions determining the sensitivity of the electrochemical assay were investigated.