Cavitation-induced ignition of cryogenic hydrogen-oxygen fluids

The Challenger disaster and purposeful experiments with liquid hydrogen (H2) and oxygen (Ox) tanks demonstrated that cryogenic H2/Ox fluids always self-ignite in the process of their mixing. Here we propose a cavitation-induced self-ignition mechanism that may be realized under these conditions. In one possible scenario, self-ignition is caused by the strong shock waves generated by the collapse of pure Ox vapor bubble near the surface of the Ox liquid that may initiate detonation of the gaseous H2/Ox mixture adjacent to the gas-liquid interface. This effect is further enhanced by H2/Ox combustion inside the collapsing bubble in the presence of admixed H2 gas

Measurements of magnetic circuit characteristics for comprehension of intrinsic magnetic properties of materials from surface inspection

A transfer function is presented for calculating magnetic field and flux density inside a test material as a result of surface measurement. By considering flux leakage, we introduce a parameter η, called the leakage coefficient, which can be experimentally determined. It is introduced into the equations to make the transfer function more practical. The distribution of field inside a test material is then discussed in accordance with a surfacemagnetic charge model

When to invest in carbon capture and storage technology in the presence of uncertainty: A mathematical model

We present a model for determining analytically the critical threshold for investment in carbon capture and storage technology in a region where carbon costs are volatile and assuming the cost of investment decreases. We first study a deterministic model with quite general dependence on carbon price and then analyse the effect of carbon price volatility on the optimal investment decision by solving a Bellman equation with an infinite planning horizon. We find that increasing the expected carbon price volatility increases the critical investment threshold and that adoption of this technology is not optimal at current prices, in agreement with other works. However, reducing carbon price volatility by switching from carbon permits to taxes or by introducing a carbon floor as in Great Britain would accelerate the optimal adoption of this technology. Our deterministic model provides a good description of this decision problem

Magnetomechanical effect in nickel and cobalt

The change in magnetization as a result of applied uniaxial stress has been measured in nickel and cobalt. Both tensile and compressive stresses were applied up to 125 MPa. Magnetostriction and anhysteretic magnetization as a function of stress were also measured. The change in magnetization with stress depended on the applied stress and the displacement between the prevailing magnetization and anhysteretic. At the loop tips, nickel showed a +6 mT (compression) and −6 mT (tension) magnetization change while cobalt displayed a +15 mT (compression) and −15 mT (tension) magnetization change. At remanence,nickel decreased in magnetization by 45 mT under either sign of stress, while cobalt decreased by 20 mT also under either sign of stress. Magnetomechanical changes in magnetization near the loop tips were mostly reversible, while at remanence the magnetomechanical change was predominately irreversible. Cobalt generally displayed larger changes in magnetization with stress than nickel at locations close to the loop tips, while the converse was true at locations near remanence. The results confirm the hypothesis that the magnetomechanical effect(dM/dσ) depends on the displacement between the anhysteretic and prevailing magnetization

Finite element analysis of the influence of a fatigue crack on magnetic properties of steel

Fatigue can affect the magnetic properties of materials due to microstructural changes. Previous investigations have shown that several structure sensitive magnetic properties, such as coercivityHc and remanenceBr, changed systematically as a result of fatigue. When approaching failure the accumulated changes in microstructure resulted in the occurrence of fatigue cracks and the magnetic properties showed dramatic changes which mainly resulted from the geometrical changes in samples due to the cracks. It was found that the remanenceBr followed the changes in stress, while the coercivityHc sometimes showed different trends. In this article the influence of the size and the position of a fatigue crack on magnetic field and magnetic induction were studied using finite element modeling. Models were constructed to simulate the geometry of the test sample and sensor. It was found that, for a given coil current in the exciting coil, the magnetic induction was mainly determined by the geometry of the crack, while the magnetic field was influenced by both the size and the position of the crack

MARC-60 and Propulsion System Collaboration Status Meeting

No abstract availabl

When to invest in carbon capture and storage technology in the presence of uncertainty: a mathematical model. ESRI WP461, July 2013

We present a model for determining analytically the critical threshold for investment in carbon capture and storage technology in a region where carbon costs are volatile and assuming the cost of investment decreases. We first study a deterministic model with quite general dependence on carbon price and then analyse the effect of carbon price volatility on the optimal investment decision by solving a Bellman equation with an infinite planning horizon. We find that increasing the expected carbon price volatility increases the critical investment threshold and that adoption of this technology is not optimal at current prices, in agreement with other works. However, reducing carbon price volatility by switching from carbon permits to taxes or by introducing a carbon floor as in Great Britain would accelerate the optimal adoption of this technology. Our deterministic model provides a good description of this decision problem

MRI and Neuropsychological Correlates of Carbon Monoxide Exposure: A Case Report

A 45-year-old woman experienced long-term, chronic exposure to carbon monoxide in the restaurant kitchen where she was employed as a cook. After returning to the restaurant after 5 days off work, she noticed that her symptoms returned immediately; she then aired out the room and called the gas company. Approximately 6 hr after a leak was detected, the patient went to the hospital, where her carboxyhemoglobin was found to be within normal limits and results of a neurologic examination were described as normal. Based on her symptoms, the patient believed she had been exposed to CO for at least 1 year before the leak was discovered. Initially, she experienced flu-like symptoms, which eventually resolved. At the time of her first neuropsychological evaluation (17 months after the exposure was identified), her persisting complaints included difficulties in reading, writing, speaking and word retrieval. The test results were consistent with secondary frontal lobe dysfunction associated with subcortical disorders such as those seen after CO exposure. Results of a subsequent neuropsychological examination (29 months postexposure) showed slight improvement in performance, but her performance was still consistent with mild frontal/subcortical dysfunction. Although the initial screening of a brain magnetic resonance image (MRI) performed 15 months after the exposure was interpreted as being within normal limits, two subsequent blind reviews of the same scans identified multiple bilateral lesions in the basal ganglia, which were consistent with chronic CO exposure. We present this case as an example of the utility of MRI and neuropsychological examinations in detecting central nervous system dysfunction secondary to CO exposure