Influence of film cooling hole angles and geometries on aerodynamic loss and net heat flux reduction

Turbine design engineers have to ensure that film cooling can provide sufficient protection to turbine blades from the hot mainstream gas, while keeping the losses low. Film cooling hole design parameters include inclination angle (α), compound angle (β ), hole inlet geometry and hole exit geometry. The influence of these parameters on aerodynamic loss and net heat flux reduction is investigated, with loss being the primary focus. Low-speed flat plate experiments have been conducted at momentum flux ratios of IR = 0.16, 0.64 and 1.44. The film cooling aerodynamic mixing loss, generated by the mixing of mainstream and coolant, can be quantified using a three-dimensional analytical model that has been previously reported by the authors. The model suggests that for the same flow conditions, the aerodynamic mixing loss is the same for holes with different α and β but with the same angle between the mainstream and coolant flow directions (angle κ). This relationship is assessed through experiments by testing two sets of cylindrical holes with different α and β : one set with κ = 35°, another set with κ = 60°. The data confirm the stated relationship between α, β, κ and the aerodynamic mixing loss. The results show that the designer should minimise κ to obtain the lowest loss, but maximise β to achieve the best heat transfer performance. A suggestion on improving the loss model is also given. Five different hole geometries (α =35.0°, β =0°) were also tested: cylindrical hole, trenched hole, fan-shaped hole, D-Fan and SD-Fan. The D-Fan and the SD-Fan have similar hole exits to the fan-shaped hole but their hole inlets are laterally expanded. The external mixing loss and the loss generated inside the hole are compared. It was found that the D-Fan and the SD-Fan have the lowest loss. This is attributed to their laterally expanded hole inlets, which lead to significant reduction in the loss generated inside the holes. As a result, the loss of these geometries is ≈ 50 % of the loss of the fan-shaped hole at IR = 0.64 and 1.44. Copyright © 2011 by ASME.

High-precision digital lock-in measurements of critical current and AC loss in HTS 2G-Tapes

Application of High Temperature Superconducting (HTS) has been increasingly popular since the new superconducting materials were discovered. This paper presents a new high-precision digital lock-in measurement technique which is used for measuring critical current and AC loss of the 2nd Generation HTS tape. Using a lock-in amplifier and nano-voltage meter, we can resolve signals at nano-volt level, while using a specially designed compensation coil we can cancel out inductive by adjusting the coil inductance. Furthermore, a finer correction for the inductive component can be achieved by adjusting the reference phase of the lock-in amplifier. The critical current and AC loss measurement algorithms and hardware layout are described and analyzed, and results for both numerical and experimental data under varieties of frequencies are presented. © 2008 SICE.

AC loss estimation of HTS armature windings for electric machines

This paper studies 2G high-temperature superconducting (HTS) coils for electric machine armature windings, using finite element method (FEM) and H formulation. A FEM model for 2G HTS racetrack coil is built in COMSOL, and is well validated by comparing calculated ac loss with experimental measurements. The FEM model is used to calculate transport loss in HTS armature windings, using air-cored design. We find that distributed winding used in conventional machine design is an effective way to reduce transport loss of HTS armature winding, in terms of air-cored design. Based on our study, we give suggestions on the design of low loss HTS armature winding. © 2002-2011 IEEE.

Influence of film cooling hole angles and geometries on aerodynamic loss and net heat flux reduction

Turbine design engineers have to ensure that film cooling can provide sufficient protection to turbine blades from the hot mainstream gas, while keeping the losses low. Film cooling hole design parameters include inclination angle (a), compound angle (b), hole inlet geometry, and hole exit geometry. The influence of these parameters on aerodynamic loss and net heat flux reduction is investigated, with loss being the primary focus. Low-speed flat plate experiments have been conducted at momentum flux ratios of IR=0.16, 0.64, and 1.44. The film cooling aerodynamic mixing loss, generated by the mixing of mainstream and coolant, can be quantified using a three-dimensional analytical model that has been previously reported by the authors. The model suggests that for the same flow conditions, the aerodynamic mixing loss is the same for holes with different a and b but with the same angle between the mainstream and coolant flow directions (angle k). This relationship is assessed through experiments by testing two sets of cylindrical holes with different a and b: one set with k=35 deg, and another set with k=60 deg. The data confirm the stated relationship between α, β, k and the aerodynamic mixing loss. The results show that the designer should minimize k to obtain the lowest loss, but maximize b to achieve the best heat transfer performance. A suggestion on improving the loss model is also given. Five different hole geometries (α=35.0 deg, β=0 deg) were also tested: cylindrical hole, trenched hole, fan-shaped hole, D-Fan, and SD-Fan. The D-Fan and the SD-Fan have similar hole exits to the fan-shaped hole but their hole inlets are laterally expanded. The external mixing loss and the loss generated inside the hole are compared. It was found that the D-Fan and the SD-Fan have the lowest loss. This is attributed to their laterally expanded hole inlets, which lead to significant reduction in the loss generated inside the holes. As a result, the loss of these geometries is≈50% of the loss of the fan-shaped hole at IR=0.64 and 1.44. © 2013 by ASME.

Demonstration of multi-casting in a 1 × 9 LCOS wavelength selective switch

A multi-functional 1 × 9 wavelength selective switch based on liquid crystal on silicon (LCOS) spatial light modulator technology and anamorphic optics was tested at a channel spacing of 100 and 200 GHz, including dynamic data measurements on both single beam deflection and multi-casting to two ports. The multi-casting holograms were optimized using a modified Gerchberg-Saxton routine to design the core hologram, followed by a simulated annealing routine to reduce crosstalk at non-switched ports. The effect of clamping the magnitude of phase changes between neighboring pixels during optimization was investigated, with experimental results for multi-casting to two ports resulting in a signal insertion loss of-7.6 dB normalized to single port deflection, a uniformity of ±0.6%, and a worst case crosstalk of-19.4 dB, which can all be improved further by using a better anti-reflection coating on the LCOS SLM coverplate and other measures. © 2013 IEEE.

Cooperation of Mtmr8 with PI3K Regulates Actin Filament Modeling and Muscle Development in Zebrafish

Background: It has been shown that mutations in at least four myotubularin family genes (MTM1, MTMR1, 2 and 13) are causative for human neuromuscular disorders. However, the pathway and regulative mechanism remain unknown. Methodology/Principal Findings: Here, we reported a new role for Mtmr8 in neuromuscular development of zebrafish. Firstly, we cloned and characterized zebrafish Mtmr8, and revealed the expression pattern predominantly in the eye field and somites during early somitogenesis. Using morpholino knockdown, then, we observed that loss-of-function of Mtmr8 led to defects in somitogenesis. Subsequently, the possible underlying mechanism and signal pathway were examined. We first checked the Akt phosphorylation, and observed an increase of Akt phosphorylation in the morphant embryos. Furthermore, we studied the PH/G domain function within Mtmr8. Although the PH/G domain deletion by itself did not result in embryonic defect, addition of PI3K inhibitor LY294002 did give a defective phenotype in the PH/G deletion morphants, indicating that the PH/G domain was essential for Mtmr8's function. Moreover, we investigated the cooperation of Mtmr8 with PI3K in actin filament modeling and muscle development, and found that both Mtmr8-MO1 and Mtmr8-MO2+LY294002 led to the disorganization of the actin cytoskeleton. In addition, we revealed a possible participation of Mtmr8 in the Hedgehog pathway, and cell transplantation experiments showed that Mtmr8 worked in a non-cell autonomous manner in actin modeling. Conclusion/Significance: The above data indicate that a conserved functional cooperation of Mtmr8 with PI3K regulates actin filament modeling and muscle development in zebrafish, and reveal a possible participation of Mtmr8 in the Hedgehog pathway. Therefore, this work provides a new clue to study the physiological function of MTM family members.

Signal bandwidth of general N x N multimode interference couplers

Analytical expression of signal bandwidth of general straight and tapered N x N multimode interference (MMI) couplers is presented. The signal bandwidth is characterized as a function of mode relative energy, mode propagation delay time, and mode pulse broadening in the multimode section of MMI coupler. The model is used to evaluate the signal bandwidth of specific couplers. Results indicate that the signal bandwidth decreases seriously with the increase of channel number and channel guide space. Compared with the straight MMI coupler, the tapered MMI coupler has an improved signal bandwidth.

Investigation of vertical radiation loss for whispering-gallery modes in 3-D microresonators by FDTD simulation

The vertical radiation loss of three-dimensional (3-D) microresonators is investigated by 3-D finite-difference time-domain (FDTD) simulation. The simulation shows that the vertical radiation causes an important loss in the microresonators with weak waveguiding, and result in decrease of the quality factors (Q-factors) of whispering-gallery (WG) modes. Through the simulation, we find that TM-like modes have much weaker vertical radiation loss than TE-like modes. High Q-factor TM-like modes are observed in the 3-D microresonators with weak vertical waveguiding, but the Q-factors of TE-like modes decrease greatly.

Measurement of Cavity Loss and Quasi-Fermi-Level Separation for Fabry-Perot Semiconductor Lasers

A fitting process is used to measure the cavity loss and the quasi-Fermi-level separation for Fabry- Perot semiconductor lasers. From the amplified spontaneous emission (ASE) spectrum, the gain spectrum and single-pass ASE obtained by the Cassidy method are applied in the fitting process. For a 1550nm quantum well InGaAsP ridge waveguide laser, the cavity loss of about ～24cm~(-1) is obtained.

Design of Topas photonic bandgap fiber with high birefringence and low confinement loss

A highly birefringent hollow-core photonic bandgap fiber based on Topas cyclic olefin copolymer is designed. The rhombic hollow-core with rounded corners is formed by omitting four central air holes of the cladding structure. The guided modes, birefringence and confinement loss of the fiber are investigated by using the full-vector finite element method. A high phase birefringence of the order of 10(-3), a group birefringence of the order of 10(-2) and confinement loss less than 0.1 dB/km are obtained at the central wavelength (1.55 mu m) range of the bandgap for fiber with seven rings of air holes in the cladding region. (C) 2010 Elsevier B.V. All rights reserved.

Analysis of arable land loss and its impact on rural sustainability in Southern Jiangsu Province of China

Rapid urbanization and industrialization in southern Jiangsu Province have consumed a huge amount of arable land. Through comparative analysis of land cover maps derived from TM images in 1990, 2000 and 2006, we identified the trend of arable land loss. It is found that most arable land is lost to urbanization and rural settlements development. Urban settlements, rural settlements, and industrial park-mine-transport land increased, respectively, by 87 997 ha (174.65%), 81 041 ha (104.52%), and 12 692 ha (397.99%) from 1990 to 2006. Most of the source (e.g., change from) land covers are rice paddy fields and dryland. These two covers contributed to newly urbanized areas by 37.12% and 73.52% during 1990-2000, and 46.39% and 38.86% during 2000-2006. However, the loss of arable land is weakly correlated with ecological service value, per capita net income of farmers, but positively with grain yield for some counties. Most areas in the study site have a low arable land depletion rate and a high potential for sustainable development. More attention should be directed at those counties that have a high depletion rate but a low potential for sustainable development. Rural settlements should be controlled and rationalized through legislative measures to achieve harmonious development between urban and rural areas, and sustainable development for rural areas with a minimal impact on the ecoenvironment. (C) 2009 Elsevier Ltd. All rights reserved.

Volumetric consequences of particle loss by grading entropy.

Chemical and biological processes, such as dissolution in gypsiferous sands and biodegradation in waste refuse, result in mass or particle loss, which in turn lead to changes in solid and void phase volumes and grading. Data on phase volume and grading changes have been obtained from oedometric dissolution tests on sand–salt mixtures. Phase volume changes are defined by a (dissolution-induced) void volume change parameter (Λ). Grading changes are interpreted using grading entropy coordinates, which allow a grading curve to be depicted as a single data point and changes in grading as a vector quantity rather than a family of distribution curves. By combining Λ contours with pre- to post-dissolution grading entropy coordinate paths, an innovative interpretation of the volumetric consequences of particle loss is obtained. Paths associated with small soluble particles, the loss of which triggers relatively little settlement but large increase in void ratio, track parallel to the Λ contours. Paths associated with the loss of larger particles, which can destabilise the sand skeleton, tend to track across the Λ contours.

BMP signaling in the development of the mouse esophagus and forestomach.

The stratification and differentiation of the epidermis are known to involve the precise control of multiple signaling pathways. By contrast, little is known about the development of the mouse esophagus and forestomach, which are composed of a stratified squamous epithelium. Based on prior work in the skin, we hypothesized that bone morphogenetic protein (BMP) signaling is a central player. To test this hypothesis, we first used a BMP reporter mouse line harboring a BRE-lacZ allele, along with in situ hybridization to localize transcripts for BMP signaling components, including various antagonists. We then exploited a Shh-Cre allele that drives recombination in the embryonic foregut epithelium to generate gain- or loss-of-function models for the Bmpr1a (Alk3) receptor. In gain-of-function (Shh-Cre;Rosa26(CAG-loxpstoploxp-caBmprIa)) embryos, high levels of ectopic BMP signaling stall the transition from simple columnar to multilayered undifferentiated epithelium in the esophagus and forestomach. In loss-of-function experiments, conditional deletion of the BMP receptor in Shh-Cre;Bmpr1a(flox/flox) embryos allows the formation of a multilayered squamous epithelium but this fails to differentiate, as shown by the absence of expression of the suprabasal markers loricrin and involucrin. Together, these findings suggest multiple roles for BMP signaling in the developing esophagus and forestomach.

Correlates of poor health among orphans and abandoned children in less wealthy countries: the importance of caregiver health.

BACKGROUND: More than 153 million children worldwide have been orphaned by the loss of one or both parents, and millions more have been abandoned. We investigated relationships between the health of orphaned and abandoned children (OAC) and child, caregiver, and household characteristics among randomly selected OAC in five countries. METHODOLOGY: Using a two-stage random sampling strategy in 6 study areas in Cambodia, Ethiopia, India, Kenya, and Tanzania, the Positive Outcomes for Orphans (POFO) study identified 1,480 community-living OAC ages 6 to 12. Detailed interviews were conducted with 1,305 primary caregivers at baseline and after 6 and 12 months. Multivariable logistic regression models describe associations between the characteristics of children, caregivers, and households and child health outcomes: fair or poor child health; fever, cough, or diarrhea within the past two weeks; illness in the past 6 months; and fair or poor health on at least two assessments. PRINCIPAL FINDINGS: Across the six study areas, 23% of OAC were reported to be in fair or poor health; 19%, 18%, and 2% had fever, cough, or diarrhea, respectively, within the past two weeks; 55% had illnesses within the past 6 months; and 23% were in fair or poor health on at least two assessments. Female gender, suspected HIV infection, experiences of potentially traumatic events, including the loss of both parents, urban residence, eating fewer than 3 meals per day, and low caregiver involvement were associated with poorer child health outcomes. Particularly strong associations were observed between child health measures and the health of their primary caregivers. CONCLUSIONS: Poor caregiver health is a strong signal for poor health of OAC. Strategies to support OAC should target the caregiver-child dyad. Steps to ensure food security, foster gender equality, and prevent and treat traumatic events are needed.

The liver kinase B1 is a central regulator of T cell development, activation, and metabolism.

T cell activation leads to engagement of cellular metabolic pathways necessary to support cell proliferation and function. However, our understanding of the signal transduction pathways that regulate metabolism and their impact on T cell function remains limited. The liver kinase B1 (LKB1) is a serine/threonine kinase that links cellular metabolism with cell growth and proliferation. In this study, we demonstrate that LKB1 is a critical regulator of T cell development, viability, activation, and metabolism. T cell-specific ablation of the gene that encodes LKB1 resulted in blocked thymocyte development and a reduction in peripheral T cells. LKB1-deficient T cells exhibited defects in cell proliferation and viability and altered glycolytic and lipid metabolism. Interestingly, loss of LKB1 promoted increased T cell activation and inflammatory cytokine production by both CD4(+) and CD8(+) T cells. Activation of the AMP-activated protein kinase (AMPK) was decreased in LKB1-deficient T cells. AMPK was found to mediate a subset of LKB1 functions in T lymphocytes, as mice lacking the α1 subunit of AMPK displayed similar defects in T cell activation, metabolism, and inflammatory cytokine production, but normal T cell development and peripheral T cell homeostasis. LKB1- and AMPKα1-deficient T cells each displayed elevated mammalian target of rapamycin complex 1 signaling and IFN-γ production that could be reversed by rapamycin treatment. Our data highlight a central role for LKB1 in T cell activation, viability, and metabolism and suggest that LKB1-AMPK signaling negatively regulates T cell effector function through regulation of mammalian target of rapamycin activity.