Frequency response in short thermocouple wires

Theoretical expressions are derived for the steady state frequency response of a thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for a nonuniform wire with unequal material properties and wire diameters across the junction. The amplitude ratio at low frequency omega approaches 0 agrees with the results of Scadron and Warshawsky (1952) for a steady state temperature distribution. Moreover, the frequency response for a nonuniform wire in the limit of infinite length l approaches infinity is shown to reduce to a simple expression that is analogous to the classic first order solution for a thermocouple wire with uniform properties. Theoretical expressions are also derived for the steady state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire and a two material wire with unequal material properties across the junction. For the case of a one material supported wire, an exact solution is derived which compares favorably with an approximate expression that only matches temperatures at the support junction. Moreover, for the case of a two material supported wire, an analytical expression is derived that closely correlates numerical results. Experimental measurements are made for the steady state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire (type K) and a two material wire (type T) with unequal material properties across the junction. The data for the amplitude ratio and phase angle are correlated to within 10 pct. with the theoretical predictions of Forney and Fralick (1991). This is accomplished by choosing a natural frequency omega sub n for the wire data to correlate the first order response at large gas temperature frequencies. It is found that a large bead size, however, will increase the amplitude ratio at low frequencies but decrease the natural frequency of the wire. The phase angle data are also distorted for imperfect junctions

Numerical investigation of high-pressure combustion in rocket engines using Flamelet/Progress-variable models

The present paper deals with the numerical study of high pressure LOx/H2 or LOx/hydrocarbon combustion for propulsion systems. The present research effort is driven by the continued interest in achieving low cost, reliable access to space and more recently, by the renewed interest in hypersonic transportation systems capable of reducing time-to-destination. Moreover, combustion at high pressure has been assumed as a key issue to achieve better propulsive performance and lower environmental impact, as long as the replacement of hydrogen with a hydrocarbon, to reduce the costs related to ground operations and increase flexibility. The current work provides a model for the numerical simulation of high- pressure turbulent combustion employing detailed chemistry description, embedded in a RANS equations solver with a Low Reynolds number k-omega turbulence model. The model used to study such a combustion phenomenon is an extension of the standard flamelet-progress-variable (FPV) turbulent combustion model combined with a Reynolds Averaged Navier-Stokes equation Solver (RANS). In the FPV model, all of the thermo-chemical quantities are evaluated by evolving the mixture fraction Z and a progress variable C. When using a turbulence model in conjunction with FPV model, a probability density function (PDF) is required to evaluate statistical averages of chemical quantities. The choice of such PDF must be a compromise between computational costs and accuracy level. State- of-the-art FPV models are built presuming the functional shape of the joint PDF of Z and C in order to evaluate Favre-averages of thermodynamic quantities. The model here proposed evaluates the most probable joint distribution of Z and C without any assumption on their behavior.Comment: presented at AIAA Scitech 201

Measurement of frequency response in short thermocouple wires

Experimental measurements are made for the steady-state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire (type K) and a two material wire (type T) with unequal material properties across the junction. The data for the amplitude ratio and phase angle are correlated to within 10 percent with the theoretical predictions of Fralick and Forney (1991). This is accomplished by choosing a natural frequency omega(sub n) for the wire data to correlate the first order response at large gas temperature frequencies. It is found that a large bead size, however, will increase the amplitude ratio at low frequencies but decreas the natural frequency of the wire. The phase angle data are also distorted for imperfect junctions

Frequency response of a supported thermocouple wire: Effects of axial conduction

Theoretical expressions are derived for the steady-state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire and a two material wire with unequal material properties across the junction. For the case of a one material supported wire, an exact solution is derived which compares favorably with an approximate expression that only matches temperatures at the support junction. Moreover, for the case of a two material supported wire, an analytical expression is derived that closely correlates numerical results. Experimental data were taken with a type K supported thermocouple. The test thermocouple was constructed with dimensions to demonstrate the effects of axial heat conduction assuming constant physical properties across the junction

Existence of Integral mm-Varifolds minimizing ∫∣A∣p\int |A|^p and ∫∣H∣p\int |H|^p, p>mp>m, in Riemannian Manifolds

We prove existence and partial regularity of integral rectifiable $m$-dimensional varifolds minimizing functionals of the type $\int |H|^p$ and $\int |A|^p$ in a given Riemannian $n$-dimensional manifold $(N,g)$, $2\leq mm$, under suitable assumptions on $N$ (in the end of the paper we give many examples of such ambient manifolds). To this aim we introduce the following new tools: some monotonicity formulas for varifolds in $\mathbb{R}^S$ involving $\int |H|^p$, to avoid degeneracy of the minimizer, and a sort of isoperimetric inequality to bound the mass in terms of the mentioned functionals.Comment: 33 pages; this second submission corresponds to the published version of the paper, minor typos are fixe

'What is this corpus about?': Using topic modelling to explore a specialised corpus

This paper introduces topic modelling, a machine learning technique that automatically identifies 'topics' in a given corpus. The paper illustrates its use in the exploration of a corpus of academic English. It first offers the intuitive explanation of the underlying mechanism of topic modelling and describes the procedure for building a model, including the decisions involved in the model-building process. The paper then explores the model. A topic in topic models is characterised by a set of co-occurring words, and we will demonstrate that such topics bring us rich insights into the nature of a corpus. As exemplary tasks, this paper identifies the prominent topics in different parts of papers, investigates the chronological change of a journal, and reveals different types of papers in the journal. The paper further compares topic modelling to two more traditional techniques in corpus linguistics, semantic annotation and keywords analysis, and highlights the strengths of topic modelling.We believe that topic modelling is particularly useful in the initial exploration of a corpus

Common genetic variants of fetal hemoglobin modify hematological phenotypes in MDS/MPN/Myeloma patients receiving cytotoxic drugs

Genetic studies identify common variants within the HBS1L-MYB intergenic region (HMIP), BCL11A, and Xmn1-HBG2 as associated with elevated fetal hemoglobin (HbF) levels and other clinically important human hematological traits. Recent studies suggest HbF is a predictor of outcome in MDS/AML patients receiving decitabine. We assessed effects of HbF genetic variants on hematological traits in myeloproliferative neoplasm (MPN), myelodysplastic syndrome (MDS) and myeloma on HbF-inducing therapy to determine potential for variants predicting treatment response. Seven common HbF variants at HMIP, BCL11A, Xmn1-HGB2 loci were genotyped in 89 patients with MPN on Hydroxyurea (HU), myeloma on Lenalidomide, and MDS on Azacytidine. HbF genetic association was seen with rs9494142 (HMIP) in MPN on HU (p = 0.04) and rs1427407 (BCL11A) in myeloma on Lenalidomide (p = 0.002). HMIP variants rs9494142 and rs6920211 influenced baseline platelets (p = 0.04) and hemoglobin treatment response (p = 0.02). rs1427407 (BCL11A) was significantly associated with increased platelets (p = 0.04) negating thrombocytopenic tendency of Lenalidomide. These HbF variants showed significantly discordant minor allele frequencies in MDS/MPN/myeloma compared to wider European population data. This small study findings together suggest the implication of these variants in treatment response and disease biology in MDS/MPN/myeloma warranting larger prospective genotype-phenotype association studies

Is social support associated with hypertension control among Ghanaian migrants in Europe and non-migrants in Ghana? The RODAM study

Hypertension (HTN) control is crucial in preventing HTN-related complications such as stroke and coronary heart disease. Yet, HTN control remains suboptimal particularly among sub-Saharan African (SSA) populations partly due to poor self-management. Self-management of HTN is influenced by social support, but the evidence on the role of social support on HTN control particularly among SSA populations is limited. This study assessed the association between multiple proxies for social support and HTN control among Ghanaians resident in Ghana and Europe. The Research on Obesity and Diabetes among African Migrants (RODAM) study participants with HTN and who self-reported HTN (n = 1327) were included in this analysis. Logistic regression was used to assess the association between proxies of social support and HTN control (SBP < 140 mmHg and DBP < 90 mmHg) with adjustments for age and socioeconomic status (SES). Among Ghanaian males in both Europe and Ghana, cohabiting with more than two persons was associated with increased odds of having HTN controlled. Male hypertensive patients cohabiting with ≥ 5 persons had the highest odds of having HTN controlled after adjustment for age and SES (OR 0.30; 95% CI 0.16–0.57; 0.60; 0.34–1.04, respectively). This association was not observed among females. Relationship status, frequency of religious activity attendance and satisfaction with social support did not show any significant association with HTN control. Our study shows that cohabitation is significantly associated with HTN control but in males only. The other proxies for social support appeared not to be associated with HTN control. Involving persons living with Ghanaian men with HTN in the treatment process may help to improve adherence to HTN treatment. Further research is needed to explore in-depth, how these social support proxies could contribute to improved HTN control among SSA populations

B Cells Migrate into Remote Brain Areas and Support Neurogenesis and Functional Recovery after Focal Stroke in Mice

Lymphocytes infiltrate the stroke core and penumbra and often exacerbate cellular injury. B cells, however, are lymphocytes that do not contribute to acute pathology but can support recovery. B cell adoptive transfer to mice reduced infarct volumes 3 and 7 d after transient middle cerebral artery occlusion (tMCAo), independent of changing immune populations in recipient mice. Testing a direct neurotrophic effect, B cells cocultured with mixed cortical cells protected neurons and maintained dendritic arborization after oxygen-glucose deprivation. Whole-brain volumetric serial two-photon tomography (STPT) and a custom-developed image analysis pipeline visualized and quantified poststroke B cell diapedesis throughout the brain, including remote areas supporting functional recovery. Stroke induced significant bilateral B cell diapedesis into remote brain regions regulating motor and cognitive functions and neurogenesis (e.g., dentate gyrus, hypothalamus, olfactory areas, cerebellum) in the whole-brain datasets. To confirm a mechanistic role for B cells in functional recovery, rituximab was given to human CD20+ (hCD20+) transgenic mice to continuously deplete hCD20+-expressing B cells following tMCAo. These mice experienced delayed motor recovery, impaired spatial memory, and increased anxiety through 8 wk poststroke compared to wild type (WT) littermates also receiving rituximab. B cell depletion reduced stroke-induced hippocampal neurogenesis and cell survival. Thus, B cell diapedesis occurred in areas remote to the infarct that mediated motor and cognitive recovery. Understanding the role of B cells in neuronal health and disease-based plasticity is critical for developing effective immune-based therapies for protection against diseases that involve recruitment of peripheral immune cells into the injured brain