关注BGA器件重新植球的可靠性问题

作为新一代面阵列封装器件，BGA封装器件其固有的特点是用焊料合金取代了易损的引脚，从而可以确保具有良好的机械、电气，以及具有良好热耗散的互连，同时也是一项可以实现高密度纽装的方式。在实际应用过程中可能会遇到对BGA器件进行重新植球操作，那么这是否会对BGA器件本体可靠性带来影响？本文着重介绍了对BGA器件实施重新植球对可靠性方面影响的研究。

Complete decoupling rebalance loop design of a micromachined electrostatically suspended gyroscope

A micromachined electrostatically suspended gyroscope(MESG)based on UV-LIGA microfabrication process was introduced.By close-loop control,the suspended rotor is kept in null position and through the torque rebalance loop,in which the output control voltages reflects the input angular velocity,a dual-axis input angular velocity can be measured simultaneously.First,the system model of MESG was established by dynamic analysis based on the torque analysis.Then,the rebalance loop under ideal condition is designed using modern control technique.The performance of the designed decoupling rebalance loop was compared with that of conventional proportional integral differential(PID)rebalance loop combined with the compensation loop.In order to realize the decoupling of the output voltages,a compensated decoupling matrix and its difference equation were presented and realized by a digital decoupling method employing digital signal processor(DSP).It was confirmed that the controller could realize the complete decoupling and improve the performance of the gyroscope,which includes merits of fast response speed,low overshoot and good dynamic performance,as the simulation results shown.At last,the circuit and digital realization scheme were given.

Portfolio Construction for Value Appreciation

Background: While working as risk consultants at Barra in 1990’s, the first two authors decided to start collaborating on a research project with its first paper titled “Application of Volatility in Portfolio Construction” [1]. The third author was then a risk manager of a financial institution which was a client of Barra’s. Bringing his expertise in portfolio risk management, he joined the research team. Aim: The core of this paper lies in the construction of an investment portfolio with a main objective of value appreciation while examining its tracking error [1]-[3], a risk measurement with reference to a benchmark [1] [4]. The authors believe, while tracking error measurement is a common tool for portfolio risk management, total risk measurement is more important. The management goal is to minimize drawbacks using the technique of risk budgeting. These topics will be discussed in future research papers.

Gas-propelled nanomotors alleviate colitis through the regulation of intestinal immunoenvironment-hematopexis-microbiota circuits

The progression of ulcerative colitis(UC)is associated with immunologic derangement,intestinal hemorrhage,and microbiota imbalance.While traditional medications mainly focus on mitigating inflammation,it remains challenging to address multiple symptoms.Here,a versatile gas-propelled nanomotor was constructed by mild fusion of post-ultrasonic CaO_(2) nanospheres with Cu_(2)O nanoblocks.The resulting CaO_(2)–Cu_(2)O possessed a desirable diameter(291.3 nm)and a uniform size distribution.It could be efficiently internalized by colonic epithelial cells and macrophages,scavenge intracellular reactive oxygen/nitrogen species,and alleviate immune reactions by pro-polarizing macrophages to the anti-inflammatory M2 phenotype.This nanomotor was found to penetrate through the mucus barrier and accumulate in the colitis mucosa due to the driving force of the generated oxygen bubbles.Rectal administration of CaO_(2)–Cu_(2)O could stanch the bleeding,repair the disrupted colonic epithelial layer,and reduce the inflammatory responses through its interaction with the genes relevant to blood coagulation,anti-oxidation,wound healing,and anti-inflammation.Impressively,it restored intestinal microbiota balance by elevating the proportions of beneficial bacteria(e.g.,Odoribacter and Bifidobacterium)and decreasing the abundances of harmful bacteria(e.g.,Prevotellaceae and Helicobacter).Our gas-driven CaO_(2)–Cu_(2)O offers a promising therapeutic platform for robust treatment of UC via the rectal route.

Recurrent breakdown and rebalance of segregation distortion in the genomes: battle for the transmission advantage

Mendel’s laws state that each of the two alleles would segregate during gamete formation and show the same transmission ratio in the next generation.However,an unexpected biased allele transmission was first detected in Drosophila a century ago,and was subsequently observed in other animals,plants,and microorganisms.Such segregation distortion(SD)shows substantial effects in population structure and fitness of the progenies,which would ultimately lead to reproductive isolation and speciation.Here,we trace the early investigations on the violation of Mendelian genetic principle,which appears as a wideexistence phenomenon rather than a case of exception.The occurence of SD in the whole genome was observed in a number of plant species at the single-and multi-locus level.Biased transmission ratio might occur at meiosis stage due to asymmetric movement of the chromosome;transmission ratio advantage is also caused by interaction and battle between the alleles from respective genomes at the genetic and molecular level.The origin of a SD system is likely to be determined by coevolution of the killer and protector via recurrent breakdown or rebalance loop.These updated understandings also promote genetic improvement of hybrid crops.

Utilization of mechanical compression as a disinfestation technique for Hessian fly(Mayetiola destructor(say))in timothy hay:Field test

Baled timothy hay underwent testing at a hay processing plant in Canada to determine if mechanical compression(rebaling)could be used as a disinfestation protocol for Hessian fly(Mayetiola destructor(Say))puparia.Pressure sensitive films were randomly placed throughout the hay material,on the chamber walls,and in different orientations,to assess the hay compaction unit’s ability to induce the required pressure to crash a Hessian fly puparium in the hay.Attached to the pressure films were organdy cages containing wheat seedlings infested with Hessian fly puparia.The variables which were tested included the hold time(0.5 and 2.0 s),applied pressure(10.34 and 12.41 MPa),and timothy hay quality(low-moisture first cut,high-moisture first cut and high-moisture second cut hay).A total of 36 tests were conducted.For each test,10 Hessian fly cages and 10 pressure sensitive films were used.Each test cage contained approximately 168.56 Hessian fly puparia,translating into a total Hessian fly count of 60681 for the entire field test.Analysis of the pressure sensitive films showed that 100%of the hay experienced at least 200 kPa(29 psi)of pressure.Following the 75-day post experiment emergence period,0.0066%of the puparia survived,which may be due to the fact that the emerged puparia might have not been crushed and not subjected to a pressure of at least 20.6 kPa.The applied pressures affected Hessian fly emergence by considerably reducing the number of puparia that emerged.However,Hessian fly emerged from one of the cages in two tests.Most of the Hessian fly puparia were destroyed irrespective of the applied pressure,hold time or hay quality.