Forecasting the 23 and 24 solar cycles on the basis of MGM spectrum

A new method of nonlinear spectral analysis (called the method of global minimum: MGM), based on the best presentation (in sense of minimal squares) of a given time data set as a sum of sinusoids whose frequencies, amplitudes and phases are to be determined, has been used to find periodicities in annual Wolf sunspot numbers (W) during the period 1700–1995. The possible future behaviour of the 11-year solar cycle (based on an extrapolation of the calculated model) is also presented. The main characteristics of the 23^rd solar cycle are as follows: the W maximum occurs about 2004, with a peak of nearly 220. An unusually large value of W will occur during the 23^rd cycle, which should be characterised by the longest maximum, specifically, W will be greater than 100 during the 11-year period from 1997 to 2007. The first sharp rise will occur during the period 1996–1998, the second sharp during 2002–2004. The main features of the 24 year cycle are as follows: the next minimum in W, associated with the 24^th solar cycle, should occur in the year 2008 and the maximum in 2014. W is expected to peak at about 180. The minimum value for the 25^th year cycle is expected to occur in the year 2019. It is shown that the accuracy of these predictions depends, first of all, on the extrapolation of the hyperlong harmonic of the calculated polyharmonic model fit of observed annual sunspot numbers during the period 1700–1995. The error bars in the definition of the maximum and minimum epochs can be as large as two years.     

EUV emission from normal galaxies

Using data from the Wide Field Camera EUV all-sky survey, we have established upper limits to the EUV flux from a sample of 30 bright, nearby, non-active spiral galaxies. These galaxies were chosen to be those most likely to be detected in the EUV on the basis of (i) low interstellar absorption within our own galaxy, (ii) brightness in other wavebands, (iii) high star formation activity, and (iv) proximity. The derived EUV upper limits are restrictive, and establish for the first time that the EUV flux escaping from galaxies does not constitute a major component of their bolometric luminosity, and in particular that it cannot be the sink for the energy injected into the interstellar medium by supernova explosions, as had been suggested following the failure to detect this power in the X-ray band.     

The INFRARED SPACE OBSERVATORY (ISO)

The INFRARED SPACE OBSERVATORY (ISO), a project of the European Space Agency (ESA), will make various astronomical observations in the wavelength range of 2 to 200 μm. Two-thirds of its observing time will be available to guest observers via the traditional route of proposal submission. ISO will be launched in 1995 by an Ariane 4 from Kourou (Guyana) and be brought into a very elongated orbit with a 24hr period of which 16 hr can be used for astronomical observations. The payload module is essentially a large cryostat with a tank that will be filled with over 2000 litres of superfluid helium to keep the instruments cold (2 to 4 K) during an expected lifetime of 18 months. Inside the dewar, there is a Ritchey-Chretien telescope with a primary mirror of diameter 60cm. Four instruments, each provided by a different PI consortium, share the ISO focal plane. These instruments are : a photometer, a camera and two spectrometers — one for the wavelength range 2–45 μm and the other for 45–180 μm.     

Senrad: an advanced wideband air-surveillance radar

The generic characteristics and performance of an experimental long-range air-surveillance radar, known at the Naval Research Laboratory as Senrad, is described. Its distinguishing feature is that it can operate with simultaneous transmissions over a very wide bandwidth-from 850 to 1400 MHz. The technology and type of experimental radar equipment employed are discussed and examples are given of its performance capabilities obtained by means of very wideband operation. The unusually wide bandwidth of this radar allows 1) improved detection and tracking performance because of the absence of the nulls that are common in the antenna elevation radiation-pattern of a single-frequency radar; 2) moving target indication (MTI) without loss of targets due to blind speeds and without the need for multiple PRFs (pulse repetition frequencies); 3) accurate height finding with a fan-beam radar by taking advantage of the multipath time difference as a function of target height; 4) a form of limited target recognition based on high range-resolution; and 5) a reduction of the effectiveness of electronic countermeasures that can seriously degrade more narrowband radars     

Reconfigurable NDI controller using inertial sensor failuredetection & isolation

A modified derivation of nonlinear dynamic inversion provides the theoretical underpinnings for a reconfigurable control law for aircraft that have suffered combinations of actuator failures, missing effector surfaces, and aerodynamic changes. The approach makes use of acceleration feedback to extract information pertaining to any aerodynamic change and thus does not require a complete aerodynamic model of the aircraft. The control law does require feedback of effector positions to accommodate actuator dynamics. Both accelerometer and rate gyro failure detection and isolation (FDI) systems are implemented, allowing up to three independent failures for each FDI system as long as they are in different axes. Nonlinear simulation results show that the FDI systems improve the robustness to accelerometer/rate gyro uncertainties. An advanced tailless aircraft model is used to demonstrate the concepts. The simulation includes accelerometer and rate gyro noise and bias, failures due to accelerometers, rate gyros, and actuators, and modeled missing surfaces that cause airplane aerodynamic changes     

Paramecium--a model system for studying cellular graviperception.

Experiments under varied gravitational accelerations as well as in density-adjusted media showed that sensation of gravity in protists may be linked to the known principles of mechanosensation. Paramecium, a ciliate with clear graviresponses (gravitaxis and gravikinesis) is an ideal model system to prove this hypothesis since the ciliary activity and thus the swimming behaviour is controlled by the membrane potential. It has also been assumed that the cytoplasmic mass causes a distinct stimulation of the bipolarly distributed mechano-sensitive K+ and Ca2+ ion channels in the plasma membrane in dependence of the spatial orientation of the cell. In order to prove this hypothesis, different channel blockers are currently under investigation. Gadolinium did not inhibit gravitaxis in Paramecium, showing that it does not specifically block gravireceptors. Further studies concentrated on the question of whether second messengers are involved in the gravity signal transduction chain. Exposure to 5 g for up to 10 min led to a significant increase in cAMP.     

褶皱结构成形时的形状偏差计算

解决了褶皱结构成形时相邻的平行四边形平面元素之间连接区棱的修圆半径值预测问题。把毛坯模拟成薄板，定义了平行四边形平面元素的边界条件，采用能量法导出挠度和力函数的非线性微分方程组，利用积分－差分法实现其数值解，并提供计算结果和分析应力－应变场。采用的计算方法可用于研究毛坯的刚度参数和工艺参数对褶皱结构的形状影响。     

Broadening of Fe X (6374 Å) profiles above the limb in a coronal hole

Profiles of the visible Fe X (6374 Å) coronal emission line as a function of height above the limb were obtained out to 1.16 solar radii in a coronal hole using the NSO/Sacramento Peak Observatory Coronagraph, Universal Spectrograph and a CCD camera. These are the first coronal line profiles obtained as a function of height in a coronal hole from the ground. Analysis of the line widths suggests a large component of nonthermal broadening which increases with height ranging from 40 to 60 km/s, depending upon the assumed temperature or thermal component of the profile.     

Global Response of Martian Plasma Environment to an Interplanetary Structure: From Ena and Plasma Observations at Mars

As a part of the global plasma environment study of Mars and its response to the solar wind, we have analyzed a peculiar case of the subsolar energetic neutral atom (ENA) jet observed on June 7, 2004 by the Neutral Particle Detector (NPD) on board the Mars Express satellite. The “subsolar ENA jet” is generated by the interaction between the solar wind and the Martian exosphere, and is one of the most intense sources of ENA flux observed in the vicinity of Mars. On June 7, 2004 (orbit 485 of Mars Express), the NPD observed a very intense subsolar ENA jet, which then abruptly decreased within ∼10 sec followed by quasi-periodic (∼1 min) flux variations. Simultaneously, the plasma sensors detected a solar wind structure, which was most likely an interplanetary shock surface. The abrupt decrease of the ENA flux and the quasi-periodic flux variations can be understood in the framework of the global response of the Martian plasma obstacle to the interplanetary shock. The generation region of the subsolar ENA jet was pushed towards the planet by the interplanetary shock; and therefore, Mars Express went out of the ENA jet region. Associated global vibrations of the Martian plasma obstacle may have been the cause of the quasi-periodic flux variations of the ENA flux at the spacecraft location.     

Rationale for the development of the UK defence standards forsafety-critical computer software

Changes in the procurement environment and developments in technology that will require the adoption of new development certification procedures within the next few years are examined. Characteristics of safety-critical computer systems and the safety problems posed by digital computers are described. The way in which the changes have influenced the preparation of the new draft defence standards offered for public debate in the UK prior to their formal adoption by the Ministry of Defence is discussed. Principle features of the future safety-critical systems policy are outlined. The use of Ada for safety-critical software is considered