Remarks on the Formulation of the Cosmological Constant/Dark Energy Problems

Associated with the cosmic acceleration are the old and new cosmological constant problems, recently put into the more general context of the dark energy problem. In broad terms, the old problem is related to an unexpected order of magnitude of this component while the new problem is related to this magnitude being of the same order of the matter energy density during the present epoch of cosmic evolution. Current plans to measure the equation of state or density parameters certainly constitute an important approach; however, as we discuss, this approach is faced with serious feasibility challenges and is limited in the type of conclusive answers it could provide. Therefore, is it really too early to seek actively for new tests and approaches to these problems? In view of the difficulty of this endeavor, we argue in this work that a good place to start is by questioning some of the assumptions underlying the formulation of these problems and finding new ways to put this questioning to the test. First, we calculate how much fine tuning the cosmic coincidence problem represents. Next, we discuss the potential of some cosmological probes such as weak gravitational lensing to identify novel tests to probe dark energy questions and assumptions and provide an example of consistency tests. Then, motivated by some theorems in General Relativity, we discuss if the full identification of the cosmological constant with vacuum energy is unquestionable. We discuss some implications of the simplest solution for the principles of General Relativity. Also, we point out the relevance of experiments at the interface of astrophysics and quantum field theory, such as the Casimir effect in gravitational and cosmological contexts. We conclude that challenging some of the assumptions underlying the cosmological constant problems and putting them to the test may prove useful and necessary to make progress on these questions.     

Improvement of corrosion properties of microarc oxidation coating on magnesium alloy by optimizing current density parameters

The microstructure, composition and corrosion performance of oxide coatings formed on AM60B alloy using microarc oxidation techniques at different waveforms of applied current densities were investigated within this study. It is found that the use of optimizing current density waveforms, i.e. decaying freely current density in the later stage and stepped decreasing current density, significantly improved the microstructure of oxide coatings compared with the constant current density mode, which are connected with changes in behaviors of spark discharges on the surface in oxidation process. The optimal waveform of current density is showed to be decaying freely current density in the later stage, which results in sealing the originally formed large micropores. The optimisation of the microstructure results in a significant improvement of the corrosion resistance of oxide coating.     

35 W集成控制型HID镇流器的设计

设计了一种基于集成芯片控制的HID灯镇流器。该镇流器集成了对恒功率、电流采样、温度补偿、斜坡补偿部分的控制,同时改进了采样电路,有效提高了调制信号的占空比。镇流器电路拓扑结构简单,降低了成本,效率达到80.3%,可靠性高,无声谐振现象。     

交互式多模型在警戒类雷达跟踪中的应用研究

用CV模型、CA模型、Singer模型以及"当前"统计模型两两交互的多模型算法来处理某警戒雷达的两条航迹,并且把其仿真得出的一系列结果与目前常用的处理航迹滤波的Kalman(Singer模型)算法进行比较。研究了对不同的飞行轨迹选择什么样的模型组合可以最大提高滤波的精度,讨论了模型的优选问题。     

Fast Multiplication on Elliptic Curves over Small Fields of Characteristic Two

We discuss new algorithms for multiplying points on elliptic curves defined over small finite fields of characteristic two. This algorithm is an extension of previous results by Koblitz, Meier, and Staffelbach. Experimental results show that the new methods can give a running time improvement of up to 50 % compared with the ordinary binary algorithm for multiplication. Finally, we present a table of elliptic curves, which are well suited for elliptic curve public key cryptosystems, and for which the new algorithm can be used. Received 14 January 1997 and revised 4 September 1997     

几种复合传输线特性阻抗的计算

本文就高速光电器件微波封装提出了有希望的几种复合传输线（微带＋共面线，屏蔽微带＋共面线，微带＋不对称共面线），采用边界元法计算了它们的特性阻抗，给出了几组有工程价值的计算曲线，并讨论了实验结果。     

InAs／InP_（0．7）Sb_（0．3）热电子晶体管的电流增益及最高收集极电压

分析ＩｎＡｓ／ＩｎＰ（０．７）Ｓｂ（０．３）热电子晶体管的电流增益β及最高收集极电压Ｖ（ＣＭ）。计算结果表明，β超过２０，Ｖ（ＣＭ）接近１．５Ｖ。     

Mean reversion in the current account of forty-eight african countries: Evidence from the Panel SURADF test

Here, the Panel seemingly unrelated regressions augmented Dickey-Fuller test (SURADF) test, first introduced and advanced by Breuer et al. [Misleading inferences from panel unit-root tests with an illustration from purchasing power parity, Rev. Int. Econ. 9(3) (2001) 482-493], is used to investigate the mean-reverting behavior of the current account of 48 African countries during the 1980-2004 periods. The empirical results from numerous panel-based unit root tests, conducted earlier, indicated that the current account of each of these countries is stationary; however, when Breuer et al.'s (2001) Panel SURADF test is conducted, it is found that a unit root exists in the current account of 11 of the countries studied. These results have one extremely important policy implication for the 48 African countries studied: the current account deficit of most is sustainable, and thus signifying that those nations should have no incentive to default on their international debt.     

In0.53Ga0.47As／InP异质结光电二极管的深能级

采用深能级瞬态谱仪（ＤＬＴＳ）测定了Ｉｎ０．５３Ｇａ０．４７Ａｓ／ＩｎＰ异质结光电二极管的ＤＬＴＳ谱。发现存在一电子陷阱，该陷阱能级位于导带底以下０．４４ｅＶ处，能级密度为３．１０×１０１３ｃｍ－３，电子俘获截面为１．７２×１０－１２ｃｍ－２。由于深能级的存在，导致了该器件存在一种新的“暗电流”──“深能级协助隧穿电流”。     

InP表面等离子体CVD淀积SiO2膜的界面结构及C—V特性

报道了以正硅酸乙酯（ＴＥＯＳ）为源，采用等离子体增强化学汽相淀积（ＰＥＣＶＤ）技术在ＩｎＰ表面低温生长ＳｉＯ２钝化膜。对ＳｉＯ２／ＩｎＰ界面态进行了Ｘ射线光谱（ＸＰＳ）分析和Ｃ－Ｖ特性研究。