ASTROCULTURE (TM) root metabolism and cytochemical analysis.

Physiology of the root system is dependent upon oxygen availability and tissue respiration. During hypoxia nutrient and water acquisition may be inhibited, thus affecting the overall biochemical and physiological status of the plant. For the Astroculture (TM) plant growth hardware, the availability of oxygen in the root zone was measured by examining the changes in alcohol dehydrogenase (ADH) activity within the root tissue. ADH activity is a sensitive biochemical indicator of hypoxic conditions in plants and was measured in both spaceflight and control roots. In addition to the biochemical enzyme assays, localization of ADH in the root tissue was examined cytochemically. The results of these analyses showed that ADH activity increased significantly as a result of spaceflight exposure. Enzyme activity increased 248% to 304% in dwarf wheat when compared with the ground controls and Brassica showed increases between 334% and 579% when compared with day zero controls. Cytochemical staining revealed no differences in ADH tissue localization in any of the dwarf wheat treatments. These results show the importance of considering root system oxygenation in designing and building nutrient delivery hardware for spaceflight plant cultivation and confirm previous reports of an ADH response associated with spaceflight exposure.     

Spatial Metaphors of Web Use

When the web became popular, people had to develop ways to talk and think about it. In the mid-1990s, we analyzed spatial language in “web talk.” We found that people described pages as places, and search as motion, both passive and active motion. Here we investigate web talk nearly two decades later. Our analysis reveals that some spatial language has stayed the same, and some has changed. Of special interest is how far fewer motion verbs are used nowadays. We argue that people naturally produce spatial metaphors when talking about new technological domains, and that over time, the most useful elements persist.     

Towards the use of large eddy simulation in engineering

This paper reviews some important aspects of Large Eddy Simulation (LES) as applied to engineering flows. We first summarize the present status of modeling in incompressible, compressible and reacting multi-phase flows, with a view towards the overall formalism instead of the intrinsic details of different subgrid models. On the basis of the assumed requirements on future LES, expected to handle full-scale flows and reacting flows with detailed chemistry, we discuss some potentially interesting LES methods for the future. These methods are exclusively based on multi-scale modeling, in which simplified equations are solved within each LES cell, instead of semi-empirical modeling based on the resolved flow scales only. After that we outline a few flows studied by LES at the Swedish Defense Research Agency—FOI, which form the basis for the subsequent discussion of validation and verification, and quality management, being of increasing importance for practical engineering flows. Next we summarize some practical aspects of LES of engineering applications, many of which being crucial to the successful use of LES, and being of increasing importance for engineering flows. Finally, a view of the future use of LES in engineering is presented, which is based primarily on the evolutionary use of LES during the last decade in the fields of hydrodynamics and combustion.     

Plasma sheet oscillations and their relation to substorm development: Cluster and double star TC1 case study

We examined two consecutive plasma sheet oscillation and dipolarization events observed by Cluster in the magnetotail, which are associated with a pseudo-breakup and a small substorm monitored by the IMAGE spacecraft. Energy input from the solar wind and an associated enhancement of the cross-tail current lead to current sheet thinning and plasma sheet oscillations of 3–5 min periods, while the pseudo-breakups occur during the loading phase within a spatially limited area, accompanied by a localized dipolarization observed by DSP TC1 or GOES 12. That is, the so-called “growth phase” is a preferable condition for both pseudo-breakup and plasma sheet oscillations in the near-Earth magnetotail. One of the plasma sheet oscillation events occurs before the pseudo-breakup, whereas the other takes place after pseudo-breakup. Thus there is no causal relationship between the plasma sheet oscillation events and pseudo-breakup. As for the contribution to the subsequent small substorm, the onset of the small substorm took place where the preceding plasma sheet oscillations can reach the region.     

Theory of LDV Tracking Systems

The application of frequency-tracking systems to the analysis of laser doppler velocimeter (LDV) signals degraded by background noise has been studied both theoretically and experimentally. Expressions are derived for both the correlation function and the expected value of the phase derivative in the general case of noise off center from the Doppler frequency, and these results are specialized to specific cases of practical interest. Laboratory measurements of output signal-to-noise ratio (SNR) and dc error, for varying input SNR and noise center frequency offset, show good agreement with the theoretical predictions.     

Hierarchical path computation approach for large graphs

Time is a critical factor in several path planning problems such as flood emergency rescue operations, escape planning from fires and chemical warfare agents dispersed in large buildings, evacuation from urban areas during natural disasters such as earthquakes, and military personnel movement. We propose a hierarchical path planning algorithm (HIPLA) for real time path planning problems where the computational time is of critical significance. The main idea of HIPLA is to significantly reduce the search space for path computation by searching in a high-level abstraction graph, whose nodes are associated with precomputed risk estimates. The cumulative risk associated with all nodes along a path determines the quality of a path. We present a detailed experimental analysis of HIPLA by comparing it with two well-known approaches viz., shortest path algorithm (SPAH) [1] and Dijkstra's algorithm with pruning [2] for large node-weighted graphs.     

Wake vortex characteristics of transport aircraft

The flow and flight physics of wake vortex systems has been intensively investigated concentrating on a large variety of aspects. This paper gives a brief overview on past and present wake vortex research activities such as early studies, integrated programs, model and flight tests, numerical investigations, fundamental physical aspects and alleviation strategies. Then, detailed results of the properties of the wake near field and extended near field are presented addressing typical length and time scales and especially turbulence quantities. Progressing from the near field to the far field wake instability mechanisms are explained along with their relevance for wake vortex decay. Characteristic quantities are given for the short and long wave instabilities associated with vortex merging and wakes consisting of two and four trailing vortices. A non-dimensional frequency parameter is introduced to classify the main instability types. Means for wake vortex alleviation are described aimed at influencing the wake vortex turbulence field or triggering and amplifying the inherent instabilities. The methods discussed include passive means such as the effects of spoilers, differential flap setting and four-vortex systems and active means using oscillating flaps or auxiliary devices.     

Space-based societal applications—Relevance in developing countries

Space technology has the vast potential for addressing a variety of societal problems of the developing countries, particularly in the areas of communication, education and health sectors, land and water resources management, disaster management and weather forecasting. Both remote sensing and communication technologies can be used to achieve this goal.With its primary emphasis on application of space technology, on an end-to-end basis, towards national development, the Indian Space Programme has distinguished itself as one of the most cost-effective and development-oriented space programmes in the world.Developing nations are faced with the enormous task of carrying development-oriented education to the masses at the lower strata of their societies. One important feature of these populations is their large number and the spread over vast and remote areas of these nations, making the reaching out to them a difficult task. Satellite communication (Satcom) technology offers the unique capability of simultaneously reaching out to very large numbers, spread over vast areas, including the remote corners of the country. It is a strong tool to support development education. India has been amongst the first few nations to explore and put to use the Satcom technology for education and development-oriented services to the rural masses.Most of the developing countries have inadequate infrastructure to provide proper medical care to the rural population. Availability of specialist doctors in rural areas is a major bottleneck. Use of Satcom and information technology to connect rural clinics to urban hospitals through telemedicine systems is one of the solutions; and India has embarked upon an effective satellite-based telemedicine programme.Space technology is also useful in disaster warning and management related applications. Use of satellite systems and beacons for locating the distressed units on land, sea or air is well known to us. Indian Space Research Organisation (ISRO) is already a part of the International initiative called Satellite Aided Search and Rescue System.The programme to set up satellite-based Village Resource Centres (VRCs) across India, for providing a variety of services relevant to the rural communities, is also a unique societal application of space technology. The VRCs are envisaged as single window delivery mechanism for a variety of space-based products and services, such as tele-education; telemedicine; information on natural resources for planning and development at local level; interactive advisories on agriculture, fisheries, land and water resources management, livestock management, etc.; interactive vocational training towards alternative livelihood; e-governance; weather information; etc.This paper describes the various possibilities and potentials of Satcom and Remote Sensing technologies for societal applications. The initiatives taken by Indian Space Research Organisation in this direction are highlighted.     

Optimization of transfers under constraints on the thrust direction: I

Transfers with a low thrust are considered under constraints imposed on the thrust vector direction. These constraints can be caused by peculiarities of the attitude control system and the mode of stabilization of a spacecraft, and, in the general case, they are functions of the time and state vector. The constraints specified by equalities and inequalities are investigated. It is shown that the optimal thrust is directed along the projection of the Lawden’s primer vector onto the restricting set.