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.

The Power Shift： National Anxiety, Territorial Dispute, and Trans-Regional Cooperation in Asia and the US Role

＂Power Shift＂ is used as the emerging Asia （emerging China and India） and declining US, European Union （EU） and Japan in the contemporary world. In parallel, it is used as raising territorial disputes and Xenophobia in Asia and Europe, especially in East Asia, Japan, China, and Korea. However, Asian economic development and high economic growth rate attracts the US and the EU to Asian region, not a conflict, and it demands Asian stable development, rather than unstable territorial disputes. Angas Maddison Statistics, International Monetary Fund （IMF） and World Bank also shows that China will surpass the USA by Purchasing power parity （PPP） based Gross domestic product （GDP） economically in 2015. The world of the 21st century is not unilateral, but multilateral or multipolar system, and the sift is already starting from the American continent to the Asian continent. How does it ensure the Asian stability and how does it guarantee the collaboration and prosperity between Asian countries and the world？ And how does the United States uses Asian pivot and Asian rebalance strategy？ The analysis of these policies are extremely important for considering the future of the world system. In this article, the author investigates the rise and fall of the great powers in the transition era, and develops economics, knowledge and science technology in the near future. Especially the author investigates the importance of making networks of the think-tanks, and to strengthen the relationship between nation states and regions under the conflict and antagonism.

China＇s Economic Reform and Its Prospects

China＇s economy can be characterized as having two correlated imbalances, i.e. imbalances in its domestic and international economic structures. It would be very difficult to identify a causal relationship between the two imbalances. In any case, this is an outcome of the past few decades. The same situation can also befound in other countries. Where are China＇s economy and its reform heading towards？ At the macro-level, the econmnic policies guiding China＇s economy and its performance are closely related to the two imbalances. One thing is for certain： world economic equilibrium will help balance various economies including China. But the world economy cannot automatically balance itself. Various economies must restore their balance before equilibrium can be achieved at the global level. For individual countries, balancing their domestic economy is what they can concentrate on. In other words, China needs to rely on its own efforts to achieve internal economic balance through reform. Internal econontic balance will promote sustainable development and contribute to the world economic balance. The questhm is where will such internal balance come from？ How can China achieve an internal rebalance？

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.

Delicate Balance of Power in the Asia-Pacific:The Obama Administration's Strategic Rebalance and the Transformation of US-China Relationship

The rise of China has transformed the global power balance and made the US-China relationship increasingly strategic and complicated.While some Americans are anxious about what China’s great power aspiration means for US interests,many Chinese are concerned about the US intention to keep China down.In this context,many in Beijing believe that the Obama administration’s strategic rebalance toward the Asia-Pacific is bent on hindering China’s rise as a great power.To what extent is the strategic rebalance about China?Is it part of the US strategy to contain China’s rise?Can the US and China function in relative power equality and build a balance of power to maintain peace and stability in the Asia-Pacific?Seeking answers to these important questions,this article argues that the strategic rebalance is a continuation of the long-standing struggle of the US to define its interests in the region.China remains a centerpiece in the rebalance not only because building a cooperative relationship with China is the key for its success,but also because the rebalance has to address the rapidly shifting balance of power in the region where China has emerged as an ever-more influential power.It is in US interests to work with its partners as well as China to construct a regional order based on the balance of power,and rules and institutions capable of allowing China to grow and be secured but not use its new might arbitrarily.

A novel robust design method for the sense mode of a MEMS vibratory gyroscope based on fuzzy reliability and Taguchi design

This paper proposes a novel robust design method for the sense mode of a MEMS vibratory gyroscope based on fuzzy reliability and Taguchi design. The principles of fuzzy reliability and Taguchi design are both introduced and described in detail. Experimental results demonstrate that the signal to noise ratio of the robust design scheme is better than those of the other experimental schemes.Over the full temperature range from -40 to 80°C, the temperature sensitivities of phase margin, gain margin, sensitivity margin,the maximum amplitude of open loop system, bandwidth of closed loop system, and the performance function of the robust design system are all smaller than those of the original design system. Meanwhile, the temperature sensitivity of the bandwidth of the robust design system is improved to 126 from 1075 ppm/°C. Moreover, the bias drift over the full temperature range of the robust design system is improved to 61°/h from 179°/h.

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.