Are Engineered Geothermal Energy Systems a Viable Solution for Arctic Off-Grid Communities? A Techno-Economic Study

Deep geothermal energy sources harvested by circulating fluids in engineered geothermal energy systems can be a solution for diesel-based northern Canadian communities. However, poor knowledge of relevant geology and thermo-hydro-mechanical data introduces significant uncertainty in numerical simulations. Here, a first-order assessment was undertaken following a “what-if” approach to help design an engineered geothermal energy system for each of the uncertain scenarios. Each possibility meets the thermal energy needs of the community, keeping the water losses, the reservoir flow impedance and the thermal drawdown within predefined targets. Additionally, the levelized cost of energy was evaluated using the Monte Carlo method to deal with the uncertainty of the inputs and assess their influence on the output response. Hydraulically stimulated geothermal reservoirs of potential commercial interest were simulated in this work. In fact, the probability of providing heating energy at a lower cost than the business-as-usual scenario with oil furnaces ranges between 8 and 92%. Although the results of this work are speculative and subject to uncertainty, geothermal energy seems a potentially viable alternative solution to help in the energy transition of remote northern communities.

A review of variable-impedance acoustic liner concepts developed at NASA

This paper presents results attained in the NASA Langley Research Center test rigs using concepts for which the impedance varies over the surface of the liner. These liners are typically designed for significant sound absorption over a wide frequency range, but it is also possible to tune the design to achieve increased absorption at selected frequencies. A brief review is provided regarding a number of variable-impedance concepts. The first is a modified version of a conventional two-layer liner, in which the embedded septum location and acoustic properties are different for adjacent core chambers. Two concepts employ core chambers with different lengths, one with bent chambers to allow packaging within a limited volume, and the other with shared inlet ports to reduce the surface porosity. The last employs a perforated facesheet in which the hole diameter and porosity are varied over the surface of the liner. Data acquired in the NASA normal incidence and grazing flow impedance tubes are used to demonstrate the capabilities of these concepts. Impedance prediction models are also presented for comparison with these measured data.

Impedance eduction for uniform and multizone acoustic liners

This paper presents results for five uniform and two multizone liners based on data acquired in the NASA Langley Grazing Flow Impedance Tube. Two methods, Prony and CHE, are used to educe the impedance spectra for each of these liners for many test conditions. The Prony method is efficient and generally provides accurate results for uniform liners, but is not well suited for multizone liners. The CHE method supports assessment of both uniform and multizone liners, but is much more computationally expensive. The results from these liners demonstrate the efficacy of both eduction methods, but also clearly demonstrate that sufficient attenuation is required to support accurate impedance eduction. For the liners considered in this study, the data indicate approximately 3 dB attenuation is needed for each zone of a multizone liner in order to ensure quality impedance eduction results. This study was conducted in response to two acoustic liner research challenges in support of a collaboration of multiple national laboratories under the International Forum for Aviation Research.

Doppler Assessment of the Uterine Arteries for the Definition of Pubertal Onset in Girls

Pelvic ultrasonography (US) is a quick, non-invasive and low-cost method, and doppler analysis facilitates assessment of flow impedance measurement in the uterine vascular tree. The pulsatility index (PI) reflects blood flow impedance in the vessel distal to the sampling point and has been suggested as a parameter to define pubertal development. In order to evaluate the PI and US measurements of uterus and ovaries in girls with different pubertal stages, we performed a cross-sectional study in girls with normal pubertal development. US and Doppler assessed PI of the uterine arteries (defined as the difference between the peak systolic flow and end-diastolic flow divided by the mean maximum flow velocity), endometrial thickness, uterine and ovarian volumes were evaluated. All the US exams were performed with the same equipment by the same radiologist. Clinical data such as the age of menarche, pubarche and thelarche were recorded. Statistical analyses were performed in SPSS, with ANOVA test, Spearman correlation and ROC curve with Youden. One hundred and sixty-nine girls aged 5-16 years (mean 11.3 ± 1.8) who performed two hundred and two pelvic US were included (Tanner 1=20%, Tanner 2=22%, Tanner 3=23%, Tanner 4=17%, Tanner 5=17%). Mean age of thelarche, pubarche and menarche were 11.1 ± 1.8, 10.2 ± 1.2 and 12.2 ± 1.1 years respectively. Prepubertal girls (Tanner 1) had mean PI significantly higher than girls in initial puberty (Tanner 2 and 3 grouped) and in late puberty (Tanner 4 and 5 grouped), respectively 6.5 ± 2.27 vs. 4.15 ± 1.55 vs. 2.82 ± 1.06, p<0.001 for all the comparisons. ROC curve analysis demonstrated that the PI is able to identify the onset of puberty with an area under the curve of 0.80 ± 0.04, P<0.001, and a cutoff point of IP=5.05 presented a sensitivity of 0.77 and a specificity of 0.80 to identify the onset of puberty. When we combined the cutoffs of IP <5.05 plus uterine volume >3.75 cm³, we found a sensitivity of 0.72 and specificity of 0.90 to detect puberty. We identified a strong negative correlation between PI and uterine volume (rs=-0.72, p<0.001) and a moderate negative correlation with endometrial thickness (rs=-0.68, p<0.001) and right (rs=-0.60, p<0.001) and left (rs=-0.59, p<0.001) ovarian volumes. In conclusion, we found a significant reduction of the PI during pubertal development, reflecting a progressive increase in blood flow to the uterus, which can be a valuable non-invasive and highly specific tool to confirm the onset of puberty.

Role of uterine artery Doppler in assessment of unexplained infertility

Background The study aimed to compare the values of uterine artery Doppler indices including resistance index (RI), pulsatility index (PI), and systolic/diastolic (S/D) ratios in fertile female and female with unexplained infertility and investigate their association with unexplained infertility. This study included 70 women divided into two groups. Study group included 40 women with unexplained infertility and control group included 30 fertile women. Results The mean ages of study and control groups were 26.9 and 28.5 years respectively. In infertile group, the mean values of uterine arteries resistance index (RI), pulsatility index (PI), and systolic/diastolic (S/D) ratios were 0.9, 2.9, and 8.0 respectively. In the fertile control group, mean RI and PI values and S/D ratio were 0.6, 1.5, and 2.7 respectively. There was statistically significant difference as regards RI, PI, and S/D ratios between study and control groups. The best cut off values of RI, PI, and S/D ratios for predicting increased uterine blood flow impedance were more than 0.67, 1.95, and 3 respectively with sensitivity of 100%, 95%, and 100% respectively, specificity of 96.7%, 86.7%, and 96.7% respectively, and diagnostic accuracy of 98.6%, 91.42%, and 98.57% respectively. Conclusion Uterine artery Doppler indices mean values were higher in unexplained infertility women than fertile women. Uterine artery Doppler indices have high sensitivity and specificity for diagnosis of high uterine blood flow impedance. High uterine blood flow impedance diagnosed by uterine artery Doppler may contribute in the etiology of unexplained infertility. Uterine artery Doppler should be included in investigation of unexplained infertility.