Development and modification of National Instruments Data Acquisition hardware for use in the centrifuge environment

This paper details the modification of a commercial data acquisition system for use in a geotech-nical centrifuge. As with many ‘off-the-shelf’ components put into service within the harsh high stress centri-fuge environment, they are not originally conceived to operate under these extreme conditions and thus it is not uncommon for high failure rates to occur in standard hardware items. In many cases successful modification can be implemented to strengthen standard components to enhance their robustness and operation. In this re-spect, this paper reports on difficulties experienced in the operation of a National Instruments PXI chassis sys-tem and its failure in the high gravity environment. Specific problems identified relate to fragility of the cooling fan systems that generate fault conditions that trigger auto shut down sequence of the chassis. A bespoke solution is developed and documented that has been successfully implemented to circumnavigate and mitigate fan failures

Centrifuge Health Monitoring of the 50gTon beam centrifuge at the University of Sheffield

In order to fully understand scientific test data it is crucial that we first understand the back-ground centrifuge operational environment and its variation with time and centrifugal acceleration. For exam-ple, changes in ambient air temperature or relative humidity in the centrifuge chamber during operation can have a significant impact on the evaporation levels of water from the surface of a clay model. It is vital to un-derstand these temporal changes in order to mitigate drying out of the soil surface as this would have a detrimental impact on model performance. This paper details the development of a centrifuge health monitoring system capable of measuring environmental parameters over natural seasonal variations of the laboratory environment but also during test conditions. The results of a series of preliminary tests of different duration, acceleration and configuration are discussed to demonstrate the significant changes that occur in the scientific environment during operation

Development of a 25ton consolidation press at the Centre for Energy and Infrastructure Ground Research

1d consolidation frame has been designed and manufactured at the Centre for Energy and Infrastructure Ground Research (CEIGR), University of Sheffield. The consolidation frame allows static consolidation of soil beds. This system comprises of a 25 ton rated press that can accommodate a range of centrifuge payload strong box configurations. The consolidation force is delivered via a hydraulic piston rated to deliver 80 kN force at 10bar supply pressure with a stroke of 500mm. A series of vertical draw-wire transducers are implemented which monitor consolidation settlement. Combined with pore pressure transducers, the user can measure the pore water pressure at the top and at the bottom of the clay sample. A bespoke LabVIEW VI visual display is implemented which offers visual/graphical feedback to the user on the range of sensor information and a live update of consolidation progress; it also incorporates data entry to capture test specific in-formation

Development of deep Vs profiles and site periods for the Canterbury region

Recent field investigations were carried out to define the shear wave velocity (VS) profile and site periods across the Canterbury region, supplementing earlier efforts in urban Christchurch. Active source surface wave testing, ambient wave field (passive) and H/V spectral ratio methods were used to characterise the soil profile in the region. H/V spectral ratio peaks indicate site periods in the range of 5-7 seconds across much of the Canterbury Plains, broadly consistent with those based on a 1D velocity model for the region. Site periods decrease rapidly in the vicinity of the Canterbury foothills and the Banks Peninsula outcrops. In Christchurch, the Riccarton Gravels result in a significant mode of vibration that has a much shorter period than the site period of the entire soil column down to basement rock

Performance of refractory alloy-clad fuel pins

This paper discusses objectives and basic design of two fuel-cladding tests being conducted in support of SP-100 technology development. Two of the current space nuclear power concepts use conventional pin type designs, where a coolant removes the heat from the core and transports it to an out-of-core energy conversion system. An extensive irradiation testing program was conducted in the 1950's and 1960's to develop fuel pins for space nuclear reactors. The program emphasized refractory metal clad uranium nitride (UN), uranium carbide (UC), uranium oxide (UO/sub 2/), and metal matrix fuels (UCZr and BeO-UO/sub 2/). Based on this earlier work, studies presented here show that UN and UO/sub 2/ fuels in conjunction with several refractory metal cladding materials demonstrated high potential for meeting space reactor requirements and that UC could serve as an alternative but higher risk fuel

Gammakennis voor de groene ruimte; evaluatie van onderzoeksprogramma 314 Mens en draagvlak in de groene ruimte

Voor een evaluatie van programma 314 zijn drie onderzoeksvragen geformuleerd. 1 Welke prestaties heeft programma 314 geleverd en welke leerpunten kunnen worden opgetekend voor programma 376 (Mens, economie en groene ruimte)? 2 Wat is de doorwerking geweest van kennisproducten in de voorbereiding, besluitvorming en uitvoering van het beleid voor de groene ruimte en hoe kan deze doorwerking op middellange termijn vergroot worden? 3 Wat is de toekomstige vraag naar gammaonderzoek voor de groene ruimte en in welke richtingen moeten de investeringen in onderzoek gaan? Dit rapport bundelt een aantal producten uit het evaluatieproject: onderzoeksverslagen over de aanbodkant (vraag 1), de doorwerking van onderzoek naar de praktijk (vraag 2) en de behoefte aan gammakennis aan de vraagkant (vraag 3). Tevens omvat het twee adviezen die zijn uitgebracht over korte- en middellangetermijnonderzoek en een notitie met aanbevelingen voor onderzoekers en het onderzoeksmanagement van Alterra en LEI

Non-geometric flux vacua, S-duality and algebraic geometry

The four dimensional gauged supergravities descending from non-geometric string compactifications involve a wide class of flux objects which are needed to make the theory invariant under duality transformations at the effective level. Additionally, complex algebraic conditions involving these fluxes arise from Bianchi identities and tadpole cancellations in the effective theory. In this work we study a simple T and S-duality invariant gauged supergravity, that of a type IIB string compactified on a $T^6/(Z_2 x Z_2)$ orientifold with O3/O7-planes. We build upon the results of recent works and develop a systematic method for solving all the flux constraints based on the algebra structure underlying the fluxes. Starting with the T-duality invariant supergravity, we find that the fluxes needed to restore S-duality can be simply implemented as linear deformations of the gauge subalgebra by an element of its second cohomology class. Algebraic geometry techniques are extensively used to solve these constraints and supersymmetric vacua, centering our attention on Minkowski solutions, become systematically computable and are also provided to clarify the methods.Comment: 47 pages, 10 tables, typos corrected, Accepted for Publication in Journal of High Energy Physic

ISO Spectroscopy of Young Stellar Objects

Observations of gas-phase and solid-state species toward young stellar objects (YSOs) with the spectrometers on board the Infrared Space Observatory are reviewed. The excitation and abundances of the atoms and molecules are sensitive to the changing physical conditions during star-formation. In the cold outer envelopes around YSOs, interstellar ices contain a significant fraction of the heavy element abundances, in particular oxygen. Different ice phases can be distinguished, and evidence is found for heating and segregation of the ices in more evolved objects. The inner warm envelopes around YSOs are probed through absorption and emission of gas-phase molecules, including CO, CO_2, CH_4 and H_2O. An overview of the wealth of observations on gas-phase H_2O in star-forming regions is presented. Gas/solid ratios are determined, which provide information on the importance of gas-grain chemistry and high temperature gas-phase reactions. The line ratios of molecules such as H_2, CO and H_2O are powerful probes to constrain the physical parameters of the gas. Together with atomic and ionic lines such as [0 I] 63 µm, [S I] 25 µm and (Si II] 35 µm, they can also be used to distinguish between photon- and shock-heated gas. Finally, spectroscopic data on circumstellar disks around young stars are mentioned. The results are discussed in the context of the physical and chemical evolution of YSOs