Micro-Satellite Structure Fracture Investigation techniques

Mounting accuracy of satellite payload and
ADCS (attitude determination and control subsystem) seats
is one of the requirements to achieve the satellite mission
with satisfactory performance. Deviation of the position of
the mounting seat for Multi-Band-Earth-Imager (MBEI) is
caused by cracks in the plate of the basis unit and bracket
for attachment of MBEI. These cracks were detected during
inspection of the satellite strength mock-up after vibration
testing for air transportation phase. Most probable reason of
the cracking is fatigue damage as strength mock-up
structure was subjected to prolonged vibration loading
during various loading cases. Total vibration duration
during testing is about 56 hours. In order to study the
cracking reasons, finite element modeling of the structural
parts of the basis unit including MBEI bracket and
instrument MBEI is subjected to harmonic response to
simulate vibration loading for the case of air transportation.
Numerical results are compared with the experimental ones,
and mechanical design of the basis-plate unit is modified

A micro-mechanics damage approach for fatigue of composite materials

A new model for fatigue damage evolution of polymer matrix composites (PMC) is presented. The model is based on a combination of an orthotropic damage model and an isotropic fatigue evolution model. The orthotropic damage model is used to predict the orthotropic damage evolution within a single cycle. The isotropic fatigue model is used to predict the magnitude of fatigue damage accumulated as a function of the number of cycles. This approach facilitates the determination of model parameters since the orthotropic damage model parameters can be determined from available data from quasi-static-loading tests. Then, limited amount of fatigue data is needed to adjust the fatigue evolution model. The combination of these two models provides a compromise between efficiency and accuracy. Decomposition of the state variables down to the constituent scale is accomplished by micro-mechanics. Phenomenological damage evolution models are then postulated for each constituent and for the micro-structural interaction among them. Model parameters are determined from available experimental data. Comparison between model predictions and additional experimental data is presented.

Thermal Deformation Analysis of Micro satellite Structure

Mounting accuracy of satellite payload and ADCS (attitude determination and control subsystem) seats is one of the requirements to achieve the satellite mission with acceptable performance. Components of mounting inaccuracy are technological inaccuracies, residual plastic deformations after loading (during transportation and orbital insertion), elastic deformations, and thermal deformations during orbital operation. This paper focuses on estimation of thermal deformations of satellite structure. Thermal analysis is executed by applying finite-difference method (IDEAS) and temperature profile for satellite components case is evaluated. Then, Perform thermal finite-element analysis applying the finite-difference model results as boundary conditions; and calculate the resultant thermal strain. Next, applying the resultant thermal strain, perform finite-element structure analysis to evaluate structure deformations at the payload and ADCS equipments seats.

Phenomenology and system engineering of micro- and nano-antenna FPA sensors for detection of concealed weapons and improvised explosive devices

The ability of millimetre wave and terahertz systems to penetrate clothing is well known. The fact that the transmission of clothing and the reflectivity of the body vary as a function of frequency is less so. Several instruments have now been developed to exploit this capability. The choice of operating frequency, however, has often been associated with the maturity and the cost of the enabling technology rather than a sound systems engineering approach. Top level user and systems requirements have been derived to inform the development of design concepts. Emerging micro and nano technology concepts have been reviewed and we have demonstrated how these can be evaluated against these requirements by simulation using OpenFx. Openfx is an open source suite of 3D tools for modeling, animation and visualization which has been modified for use at millimeter waves. © 2012 SPIE.

Using solute/ micro organism comparative tracer testing to investigate hydrogeological heterogeneity in a fluvioglacial sand and gravel aquifer.

Groundwater drawn from fluvioglacial sand and gravel aquifers form the principal source of drinking water in many part of central Western Europe. High population densities and widespread organic agriculture in these same areas constitute hazards that may impact the microbiological quality of many potable supplies. Tracer testing comparing two similarly sized bacteria (E.coli and P. putida) and the smaller bacteriophage (H40/1) with the response of non-reactive solute tracer (uranine) at the decametre scale revealed that all tracers broke through up to 100 times more quickly than anticipated using conventional rules of thumb. All microbiological tracer responses were less disperse than the solute, although bacterial peak relative concentrations consistently exceeded those of the solute tracer at one sampling location reflecting exclusion processes influencing micro biological tracer migration. Relative recoveries of H40/1 and E.coli proved consistent at both monitoring wells, while responses of H40/1 and P.putida differed. Examination of exposures of the upper reaches of the aquifer in nearby sand and gravel quarries revealed the aquifer to consist of laterally extensive layers of open framework (OW) gravel enveloped in finer grained gravelly sand. Granulometric analysis of these deposits suggested that the OW gravel was up to two orders of magnitude more permeable than the surrounding deposits giving rise to the preferential flow paths. By contrast fine grained lenses of silty sand within the OW gravels are suspected to play an important role in the exclusion processes that permit solutes to access them but exclude larger micro organisms.

An exploration of the attitudes and strategic responses of soleproprietor micro-enterprises in adopting information and communication technology

This article analyses longitudinal case-based research exploring the attitudes and strategic responses of micro-enterprise owners in adopting information and communication technology (ICT). In so doing, it contributes to the limited literature on micro-enterprise ICT adoption, with a particular focus on sole proprietors. It provides a basis for widening the theoretical base of the literature pertaining to ICT adoption on two levels. First, a framework is developed which integrates the findings to illustrate the relationships between attitudes towards ICT adoption, endogenous and exogenous influencers of these attitudes and subsequent strategic response in ICT adoption. Second, building upon this framework the article reveals the unique challenges, opportunities and implications of ICT adoption for sole-proprietor micro-enterprises. © The Author(s) 2012

Micro-scale biopitting by endolithic lichen and their role in meso-scale solution basin development on limestone

Data are reported demonstrating the potential role of microscale morphologies, induced by endolithic lichen communities, specifically Verrucaria baldensis, in the initiation and development of mesoscale solution basin formation on limestone in the Burren, Co. Clare. A biophysical model is proposed outlining the different microscale stages leading to solution basin initiation with a progression from initial lichen colonisation and growth, associated biopitting followed by biopit coalescence to form biotroughs, their subsequent enlargement and eventual incipient solution basin formation. This model provides one explanation for solution basin development as this end state may also be achieved through simple solutional means without biological input. The complexity of interactions at the rock / lichen interface are identified with emphasis on the spatial and temporal variability of these underlining the point that, as with macro-topographies at the landscape scale, rock surface micro-topographies also reflect historical weathering legacies.

Micro-Environmental monitoring of temperature and moisture changes in building stone

The monitoring of temperature and moisture changes in response to different micro-environment of building stones is essential to understand the material behaviour and the degradation mechanisms. From a practical point of view, having a continuous and detailed understanding of micro-environmental changes in building stones helps to assist in their maintenance and repair strategies. Temperature within the stone is usually monitored by means of thermistors, whereas wide ranges of techniques are available for monitoring the moisture. In the case of concrete an electrical resistance method has previously been used as an inexpensive tool for monitoring moisture changes. This paper describes the adaptation of this technique and describes its further development for monitoring moisture movement in building stones.
In this study a block of limestone was subjected to intermittent infrared radiation with programmed cycles of ambient temperature, rainfall and wind conditions in an automated climatic chamber. The temperature and moisture changes at different depths within the stone were monitored by means of bead thermistors and electrical resistance sensors. This experiment has helped to understand the thermal conductivity and moisture transport from surface into deeper parts of the stone at different simulated extreme climatic conditions. Results indicated that variations in external ambient conditions could substantially affect the moisture transport and temperature profile within the micro-environment of building stones and hence they could have a significant impact on stone decay.

Micro-environmental conditions modulate protein secretion and infectivity of the Trichinella spiralis L1 larva

After digestion of infected meat the free L1 of Trichinella spp. penetrate the intestinal mucosa where they moult to the mature adult stage. We have used proteomics to identify changes in protein secretion during in vitro culture of free T. spiralis muscle larvae under different environmental conditions, and to correlate these changes with their infectivity in mice. Muscle larvae were cultured in different media (RPMI-1640, C-199 and HBSS) under conditions of anaerobiosis, microaerobiosis and in 5% CO(2) at 37 degrees C. Following incubation the larval excretory/secretory proteins were analysed by two-dimensional gel electrophoresis and the larvae were used to orally infect naïve CD1 mice. For all culture media tested, infectivity of the L1 was preserved following incubation in anaerobic conditions. In contrast, the infectivity of worms cultured in nutrient-rich media was almost completely abolished in both microaerobiosis and in the presence of 5% CO(2). Some infectivity was retained in poor or reduced culture media. Comparative analysis of larval infectivity and protein secretion showed that loss of infectivity correlated with the appearance of non-tyvelosylated proteins that in turn may be related to the onset of moulting.

Micro-organic compounds in the Humber rivers

The concentrations of a range of micro-organic compounds in the Humber rivers have been measured at weekly intervals over a period of 1 year. The compounds include the triazine herbicides (simazine, atrazine, propazine, desmetryn and prometryn), selected organophosphorus insecticides (fenitrothion, malathion and parathion), phenylurea (chlorotoluron, diuron, isoproturon and linuron) and phenoxyacid herbicides (2,4-D, MCPA, MCPB and mecoprop), phenol derivatives (phenol, 2-ethylphenol, 2-chlorophenol, 4-nitrophenol, 2-methylphenol, 4-ethylphenol and 2,4-dichlorophenol), organochlorine insecticides (HEOD, DDT, TDE, DDE, HCB, alpha-BHC and lindane), PCB's and some synthetic pyrethroid insecticides (cis/trans-permethrin, fenvalerate and cypermethrin). The results indicate the high frequency of occurrence of many compounds in the southern Humber rivers Aire, Calder, Trent and Don compared with the more occasional concentrations found in the upland rivers with catchments dominated by low intensity agriculture. The more water soluble herbicides, atrazine, simazine, isoproturon and diuron are detected frequently in the southern rivers with the highest concentrations and abundance in the rivers Aire, Calder and Trent. The most abundant phenolic compound is 2,4-dichlorophenol usually occurring at concentrations <1 mu g/l. The organochlorine insecticides and PCB's are generally at concentrations <0.01 mu g/l, cis/trans-permethrin are the only synthetic pyrethroids detected and these are found in the rivers Aire and Calder at about equal concentrations of between 0.01 and 0.11 mu g/l. The results of the occurrence of simazine and atrazine in the rivers Trent, Don and Aire illustrate peaks in concentration in the spring and then later in the year during the early autumn coinciding with the first major storm after the summer. In the rivers Trent and Don, the annual exports (March 1994-95) of atrazine are lower than for simazine whereas in the R. Calder the yield of atrazine is higher than for simazine suggesting differences in use in these catchments. The maximum triazine concentration observed, i.e. 8 mu g/l of atrazine in the R. Calder, could have inhibiting effects on the phytoplankton and algal growth, although because of the transient nature of the peaks, recovery is expected to be rapid. The only other compounds measured at concentrations likely to produce detrimental ecotoxicological effects are cis/trans permethrin in the rivers Aire and Calder. (C) 1997 Elsevier Science B.V.

Numbered-up gas-liquid micro/milli channels reactor with modular flow distributor

Gas-liquid processing in microreactors remains mostly restricted to the laboratory scale due to the complexity and expenditure needed for an adequate numbering-up with a uniform flow distribution. Here, the numbering-up is presented for multi-phase (gas-liquid) flow in microreactor suitable for a production capacity of kg/h. Based on the barrier channels concept, the barrier-based micro/milli reactor (BMMR) is designed and fabricated to deliver flow non-uniformity of less than 10%. The BMMR consists of eight parallel channels all operated in the Taylor flow regime and with a liquid flow rate up to 150. mL/min. The quality of the flow distribution is reported by studying two aspects. The first aspect is the influence of different viscosities, surface tensions and flow rates. The second aspect is the influence of modularity by testing three different reaction channels type: (1) square channels fabricated in a stainless steel plate, (2) square channels fabricated in a glass plate, and (3) circular channels (capillaries) made of stainless steel. Additionally, the BMMR is compared to that of a single channel regard the slug and bubble lengths and bubble generation frequency. The results pave the ground for bringing multi-phase flow in microreactor one step closer for large scale production via numbering-up. © 2012 Elsevier B.V.