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This paper demonstrates the improvement of a low temperature natural gas (LTNG) mechanism for simulating fuel ignition and combustion emissions under engine-like conditions. The LTNG mechanism was compared and validated in both the simplified zero-dimensional (0D)/one-dimensional (1D) reactors and three-dimensional (3D) engine models. In a 0D premixed constant volume reactor, the LTNG mechanism can more accurately predict the ignition delay than the well-developed GRI-3.0 natural gas mechanism, when the temperature is lower than 1300 K, compared to the experimental data. The results also indicate that the LTNG mechanism can well predict the formation of important carbon-containing gaseous species, such as acetylene and carbon dioxide, and nitrogen oxides emissions under typical engine conditions with and without technologies that implement low temperature combustion. In a 3D computational fluid dynamic model with a range of temperatures and pressures, the matched ignition delay curves from the numerical simulation and the experimental measurements indicate that the LTNG mechanism can improve the prediction of natural gas ignition and combustion compared to the GRI-3.0 mechanism. A further validation conducted in a direct-injection natural gas engine ignited by a hot surface illustrates the reliability of the LTNG mechanism for predicting natural gas ignition and combustion inside compression ignition engines.

International audience; The study of cold or obscured, red astrophysical sources can significantly benefit from adaptive optics (AO) systems employing infrared (IR) wavefront sensors. One particular area is the study of exoplanets around M-dwarf stars and planet formation within protoplanetary disks in star-forming regions. Such objects are faint at visible wavelengths but bright enough in the IR to be used as a natural guide star for the AO system. Doing the wavefront sensing at IR wavelengths enables high-resolution AO correction for such science cases, with the potential to reach the contrasts required for direct imaging of exoplanets. To this end, a new near-infrared pyramid wavefront sensor (PyWFS) has been added to the Keck II AO system, extending the performance of the facility AO system for the study of faint red objects. We present the Keck II PyWFS, which represents a number of firsts, including the first PyWFS installed on a segmented telescope and the first use of an IR PyWFS on a 10-m class telescope. We discuss the scientific and technological advantages offered by IR wavefront sensing and present the design and commissioning of the Keck PyWFS. In particular, we report on the performance of the Selex Avalanche Photodiode for HgCdTe InfraRed Array detector used for the PyWFS and highlight the novelty of this wavefront sensor in terms of the performance for faint red objects and the improvement in contrast. The system has been commissioned for science with the vortex coronagraph in the NIRC2 IR science instrument and is being commissioned alongside a new fiber injection unit for NIRSPEC. We present the first science verification of the system-to facilitate the study of exoplanets around M-type stars.

Performance and emissions experiments were conducted on a compression-ignition direct-injected natural gas engine (DING) equipped with a shielded glow plug ignition assist system. Tests were conducted at three different intake pressures (34.5 kPag, 68.9 kPag, 103.4 kPag), and four nominal (targeted) equivalence ratios (0.2, 0.3, 0.4, 0.5). CH4, NOx, CO and PM emissions were measured and analyzed, showing that emissions levels are influenced by the DING engine’s combustion modes and intake pressure. Premixed combustion which dominates at low equivalence ratios resulted in higher levels of CH4 and NOx emissions, while mixing-controlled combustion, which develops at higher equivalence ratios, resulted in elevated CO and PM levels. Higher intake pressure was found to improve all emissions levels. The most significant effect was the reduction of PM and CO emissions due to improved fuel charge mixing and air entrainment that results from a pressure-driven momentum increase of the engine’s air swirl field. Brake specific emissions and fuel consumption were estimated and compared against levels reported in the literature for dual-fuel port-injection, and High-Pressure Direct-Injection (HPDI) natural gas engines. The most significant finding was that the DING engine exhibits lower fuel consumption and PM emissions levels when compared to values reported in the literature for HPDI engines. The PM emissions advantage was attributed to a higher proportion of premixed combustion and the absence of a diesel pilot in DING engine operation. Lastly, PM size distributions were analyzed, showing that the DING engine produces PM that is smaller than PM of a conventional diesel engine, but similar to the PM reported in the literature for HPDI engines.

The results of a previous study, part 1, showed that use of a shield can improve the thermal performance of a glow plug, and thereby reduce ignition time. However, the part 1 study also found that use of a simple shield with only one circular opening can delay flame propagation out of the shield. The conclusions of that study suggested that there is scope for further improvements of the shield design, especially the shield opening geometry. Accordingly, this article presents the results of computational studies investigating the influence of multi-opening shield designs on natural gas ignition characteristics in glow plug–assisted compression–ignition engines. Two types of multi-opening glow plug shield, consisting of four small circular openings distributed in either diamond-pattern or square-pattern arrangements, were employed. The simulated results demonstrated that both multi-opening shields can not only increase glow plug surface temperature, but also increase the residence time of fuel mixture adjacent to the glow plug surface in the early injection stage, resulting in a faster ignition than the single-opening shield. Furthermore, the diamond-pattern multi-opening glow plug shield provides a faster or comparable flame propagation path back to combustion chamber, compared to single-opening glow plug shield, while the square-pattern multi-opening glow plug shield delays the flame propagation under several specific engine conditions. Compared to the single-opening glow plug shield, the overall natural gas ignition delays are further reduced by 6%–44% when using the diamond-pattern multi-opening glow plug shield, while the square-pattern multi-opening glow plug shield is only able to reduce the natural gas ignition delay under a few specific conditions.

This article presents the results of computational studies investigating the ignition of high-pressure natural gas jets in a compression-ignition engine with glow plug ignition assist. The simulation was conducted using a KIVA-3V-based three-dimensional engine model, along with an improved fuel injector model, a detailed cut-off glow plug shield model and a modified two-step methane reaction mechanism, to simulate the natural gas injection and ignition. The simulated results demonstrate the significance of using a shield for the glow plug. Compared to an unshielded (bare) glow plug, the shield not only reduces the heat loss from the hot glow plug surface to the cold intake air charge and the cold injected gas jet but also traps the fuel mixture to increase its residence time adjacent to the hot surface. Over a representative range of heavy-duty diesel engine operating conditions, a shielded glow plug greatly improves the natural gas engine performance and provides reliable ignition, while an unshielded glow plug can only be optimized for specific conditions. The understanding of glow plug shield behavior gained from the simulations suggests avenues for improved shield designs that would yield further reduced ignition delays.

Use of a shielded glow plug (GP) for ignition assist enables operation of direct-injection engines on 100% natural gas. The shield improves ignition performance by reducing GP cooling from impinging intake air and injected natural gas jets and by trapping mixture adjacent to the hot surface thereby increasing residence time. After ignition, flame must propagate out of the shield to consume fuel in the combustion chamber. The number, size, and position of openings in the GP shield determines the path of flame propagation from the shield. This study computationally investigated the performance of a shield with multiple openings arranged in a diamond pattern compared to a basic single-opening shield. A KIVA-3V based engine model coupled with the CANTERA kinetics package was used and incorporated a multi-step phenomenological soot model to predict the formation of soot particles. The results illustrate that the new multi-opening shield has significant influence on both the flow of injected fuel into the shield and the flame propagation out of the shield. The multi-opening shield design reduces the fuel flow into the shield during injection and improves fuel distribution within the shield compared to the single-opening shield. With the multi-opening shield, the initial flame propagating out moves towards the combustion chamber wall to consume the adjacent fuel jets before spreading in the swirl direction. Both shields result in comparable pressure rise, but the multi-opening shield reduces overall soot emissions by 46.6%, with similar methane emissions, compared to the single-opening shield.

This paper studies the influences of different fuel injection strategies on flame propagation and combustion characteristics in a glow plug assisted direct-injection natural gas engine. Our previously existing version of the KIVA-3V CFD code incorporates a model of internal flows in the gaseous fuel injector and also a detailed model of the glow plug and its shield. This study was conducted by using the KIVA-3V code with added improved emissions models, including a detailed kinetic chemical model and a modified phenomenological soot model. In the simulation, a low temperature natural gas mechanism is selected to estimate the gaseous species, and acetylene was chosen as the key species to model the soot formation. The simulation indicated that the fuel injection duration, injector nozzle size and injection angle can affect the natural gas combustion characteristics. Generally, shorter injection duration reduces both peak cylinder pressure and emissions in the natural gas engine; however, the natural gas flame propagation cannot be maintained once the injected fuel mass is lower than a limit. The simulation also reveals that the injector nozzle size highly affects the natural gas combustion by inducing diffusion combustion for a small diameter nozzle and partially premixed combustion for a large diameter nozzle. Compared to a large nozzle, a small nozzle results in a faster pressure rise with more engine emissions and lower combustion efficiency. The fuel injection angle can influence natural gas combustion characteristics by affecting the flame propagation out of the glow plug shield in the initial combustion stage.

One of the goals of high-contrast imaging is to reach contrasts of 10^(-10) at small inner working angles to directly image Earth-like exoplanets around solar-type stars. In most imaging systems, a deformable mirror (DM) in the pupil plane can correct for phase errors but surface errors in out-of-pupil optics get coupled into amplitude errors which can only be controlled with a second, out of pupil, DM. Furthermore, correcting static errors introduced by the optics can take up valuable DM stroke. Thus, minimizing the wavefront error within the system is critical to reaching high contrast levels. For example, the High Contrast Spectroscopy for Segmented Telescopes Testbed (HCST) in the Exoplanet Technologoy lab at Caltech aims to develop exoplanet imaging technologies down to small inner working angles (< 3λ/D) which requires an RMS wavefront error of less than 10 nm per optic to achieve a contrast of 10^(−5) with the DM flattened. While aligning HCST, it was determined that despite the excellent surface quality of all the optics, the mounts were introducing significant wavefront errors. Here we assess the effect of mount-induced wavefront errors that can rapidly consume the wavefront budget of a high-contrast system. We also present the method used to mitigate this effect within HCST such that a mean contrast of 6 × 10^(-6) from 3-10λ/D was achieved with a vortex coronagraph and flattened DM.

A near-infrared, high order pyramid wavefront sensor will be implemented on the Keck telescope, with the aim of providing high resolution adaptive optics correction for the study of exoplanets around M-type stars and planet formation in obscured star forming regions. The pyramid wavefront sensor is designed to support adaptive optics correction of the light to an imaging vortex coronagraph and to a fiber injection unit that will feed a spectrograph. We present the opto-mechanical design of the near-infrared pyramid wavefront sensor, the optical performance, and the alignment strategy. The challenges of designing the assembly, as well as a fiber injection unit, to fit into the limited available space on the Keck adaptive optics bench, will also be discussed., Adaptive Optics Systems VI, June 10-15, 2018, Austin, TX, USA, Series: Proceedings of SPIE; no. 10703

Imaging Earth-like exoplanets with future space telescopes will require a coronagraph instrument that is capable of creating a dark zone in the starlight at the image plane that is ten orders of magnitude fainter than the off-axis image of the host star. What is more, the coronagraph must simultaneously provide a stable dark zone and high throughput over the angular separations that correspond to habitable zones around nearby Sun-like stars (~10-100 milliarcseconds). Since the pupils of most large-aperture space telescope architectures are likely to be obstructed by secondary mirrors, spider support structures, and gaps between mirror segments, the coronagraph optics must also be specially tailored to passively suppress starlight diffracted from the obstructions and discontinuities in the telescope pupil. Here, we demonstrate an apodized vortex coronagraph optimized for an off-axis segmented telescope on the new High Contrast Spectroscopy Testbed for Segmented Telescopes (HCST) at Caltech. The coronagraph consists of a microdot apodizer, a liquid crystal vortex phase mask in the focal plane, and a Lyot stop. The microdot apodizer is an AR-coated glass window with 10um gold microdots to be used in reflection around lambda=800nm. We describe the HCST optical system; the apodizer optimization, fabrication, and metrology procedures; and present end-to-end testbed results of the coronagraph coupled with a 32x32 Boston Micromachines deformable mirror for wavefront control. We aim to achieve a dark zone 10^-7 times fainter than the simulated host star over a wavelength range of 800±40nm in Spring 2018. Finally, we will outline future plans to demonstrate coronagraph concepts for centrally obscured telescopes.

The High Contrast Spectroscopy Testbed for Segmented Telescopes (HCST) at Caltech is aimed at filling gaps in technology for future exoplanet imagers and providing the U.S. community with an academic facility to test components and techniques for high contrast imaging with future segmented ground-based telescope (TMT, E-ELT) and space-based telescopes (HabEx, LUVOIR). The HCST will be able to simulate segmented telescope geometries up to 1021 hexagonal segments and time-varying external wavefront disturbances. It also contains a wavefront corrector module based on two deformable mirrors followed by a classical 3-plane single-stage corona- graph (entrance apodizer, focal-plane mask, Lyot stop) and a science instrument. The back-end instrument will consist of an imaging detector and a high-resolution spectrograph, which is a unique feature of the HCST. The spectrograph instrument will utilize spectral information to characterize simulated planets at the photon-noise limit, measure the chromaticity of new optimized coronagraph and wavefront control concepts, and test the overall scientific functions of high-resolution spectrographs on future segmented telescopes.

Natural gas direct injection (DI) and glow plug ignition assist technologies were implemented in a single-cylinder, compression-ignition optical research engine. Initial experiments studied the effects of injector and glow plug shield geometry on ignition quality. Injector and shield geometric effects were found to be significant, with only two of 20 tested geometric combinations resulting in reproducible ignition. Of the two successful combinations, the combination with 0 deg injector angle and 60 deg shield angle was found to result in shorter ignition delay and was selected for further testing. Further experiments explored the effects of the overall equivalence ratio (controlled by injection duration) and intake pressure on ignition delay and combustion performance. Ignition delay was measured to be in the range of 1.6–2.0 ms. Equivalence ratio was found to have little to no effect on the ignition delay. Higher intake pressure was shown to increase ignition delay due to the effect of swirl momentum on fuel jet development, air entrainment, and jet deflection away from optimal contact with the glow plug ignition source. Analysis of combustion was carried out by examination of the rate of heat release (ROHR) profiles. ROHR profiles were consistent with two distinct modes of combustion: premixed mode at all test conditions, and a mixing-controlled mode that only appeared at higher equivalence ratios following premixed combustion.

This paper presents a numerical study on fuel injection, ignition, and combustion in a direct-injection natural gas (DING) engine with ignition assisted by a shielded glow plug (GP). The shield geometry is investigated by employing different sizes of elliptical shield opening and changing the position of the shield opening. The results simulated by KIVA-3V indicated that fuel ignition and combustion is very sensitive to the relative angle between the fuel injection and the shield opening, and the use of an elliptical opening for the glow plug shield can reduce ignition delay by 0.1–0.2 ms for several specific combinations of the injection angle and shield opening size, compared to a circular shield opening. In addition, the numerical results also revealed that the natural gas ignition and flame propagation will be delayed by lowering a circular shield opening from the fuel jet center plane, due to the blocking effect of the shield to the fuel mixture, and hence, it will reduce the DING engine performance by causing a longer ignition delay.

Nine experts on Cold War history offer commentaries about John Lewis Gaddis's Pulitzer Prize-winning biography of George F. Kennan, the first head of the U.S. State Department's Policy Planning Staff. The commentators come from several countries and offer a wide range of perspectives about Gaddis's George F. Kennan: An American Life, published by Penguin Books in 2011. Although most of the commentators express highly favorable assessments of the book, they also raise numerous points of criticism. Two of the commentators, Barton J. Bernstein and Anders Stephanson, present extended critiques of Gaddis's biography. The forum concludes with a reply by Gaddis to all the commentaries, especially those by Bernstein and Stephanson.

Canada has become the newest country to establish a special office within its foreign policy institutions dedicated to advancing the cause of religious freedom around the world. On February 19, 2013, at an Ahmadiyya Muslim Jama'at in Toronto, Ontario, Canadian Prime Minister Stephen Harper officially announced the establishment of Canada's Office of Religious Freedom (ORF) and the appointment of its first ambassador, Dr. Andrew P.W. Bennett. By its own admission, Canada borrowed the idea of an Office of Religious Freedom from the United States. Yet the origins and development of the concept of religious freedom in Canada are notably different from the United States.

This paper presents a numerical study on fuel injection, ignition and combustion in a direct-injection natural gas (DING) engine with ignition assisted by a shielded glow plug (GP). The shield geometry is investigated by employing different sizes of elliptical shield opening and changing the position of the shield opening. The results simulated by KIVA-3V indicated that fuel ignition and combustion is very sensitive to the relative angle between the fuel injection and the shield opening, and the use of an elliptical opening for the glow plug shield can reduce ignition delay by 0.1∼0.2ms for several specific combinations of the injection angle and shield opening size, compared to a circular shield opening. In addition, the numerical results also revealed that the natural gas ignition and flame propagation will be delayed by lowering a circular shield opening from the fuel jet center plane, due to the blocking effect of the shield to the fuel mixture, and hence it will reduce the DING performance by causing a longer ignition delay.

Static Zernike phase-contrast plates have been used extensively in microscopy for half a century and, more recently, in optical telescopes for wavefront sensing. A dynamic Zernike wavefront sensor (WFS) with four phase shifts, for reducing error due to spurious light and eliminating other asynchronous noise, has been proposed for use in adaptive optics. Here, we propose adapting this method for co-phasing the primary mirror of a segmented space telescope. In order to extend the dynamic range of the WFS, which has a maximum range of +/ − λ/2, a phase- contrast plate with multiple steps, both positive and negative, has been developed such that errors as large as +/ − 10λ can be sensed. The manufacturing tolerances have been incorporated into simulations, which demonstrate that performance impacts are minimal. We show that the addition of this small optical plate along with a high precision linear translation stage at the prime focus of a telescope and pupil viewing capability can provide extremely accurate segment phasing with a simple white-light fringe fitting algorithm and a closed-loop controller. The original focal-plane geometry of a centro-symmetric phase shifting element is replaced with a much less constrained shape, such as a slot. Also, a dedicated pupil imager is not strictly required; an existing pupil sampler such as a Shack-Hartmann (SH) WFS can be used just as effectively, allowing simultaneous detection of wavefront errors using both intensity and spot positions on the SH-WFS. This could lead to an efficient synergy between Zernike and SH-WFS, enabling segment phasing in conjunction with high-dynamic range sensing.

Many micro-combined heat and power (micro-CHP) technologies have emerged in the residential market in the recent years. However, the selection of a particular micro-CHP system for an application and investigating the trade-offs between micro-CHP and centralized power remain a problem. The present analysis compares three micro-CHP systems on the basis of energy, exergy, and marginal efficiencies. The systems feature different energy conversion technologies: Stirling engine (WhisperGen), spark-ignition internal combustion (IC) engine (FreeWatt), and polymer electrolyte fuel cell (PEFC) (EBARA Ballard). These systems are fueled by natural gas and produce power and heat for residential applications. The analysis suggests that the IC system provides the highest energy and exergy efficiencies at higher heat use (ηenergy = 76.7%, ηexergy = 57.2%, and f = 0.71), while the PEFC operates at higher energy and exergy efficiencies at lower heat use (ηenergy > 29.0%, ηexergy > 32.0%, and f > 0.00). The PEFC system exhi...

This article reviews the principal experimental methods currently available to simultaneously measure all the terms of the velocity gradient tensor of turbulent flows. These methods have been available only for a little more than 20 years. They have provided access to the most fundamental and defining properties of turbulence. The methods include small, multisensor, hot-wire probes that provide single-location, time-resolved measurements of the tensor and various optical arrangements, most of which provide the tensor information over a larger spatial extent but, in most cases, without resolution in time. Data-reduction algorithms, spatial-resolution issues, and the use of Taylor's hypothesis are addressed in evaluating the accuracy of the various methods.

Concern with climate change and energy security has generated interest in both cogeneration and biofuels. This experimental study examines the performance of a residential microcogeneration system based on a Stirling engine fueled by diesel and biodiesel. Run on diesel, the system achieves a power efficiency of 11.7% and a heat efficiency of 78.7%. The corresponding efficiencies for the system, when run on biodiesel, are slightly lower at 11.5% and 77.5%, respectively. Particulate emissions for biodiesel are 69.2 mg/kWh, an order of magnitude higher than that of diesel (2.3 mg/kWh). The total unburned hydrocarbon emissions for biodiesel are higher than those of diesel. Emissions of carbon monoxide, nitrogen dioxide, methane, acetylene, ethylene, formaldehyde, and acetaldehyde are comparable between diesel and biodiesel, but nitric oxide emissions for diesel are observed to be higher at 151 ppm compared to those for biodiesel (117 ppm). The difference in the performance of the system is generally attribute...

A numerical study of ignition and combustion in a glow plug (GP) assisted direct-injection natural gas (DING) engine is presented in this paper. The glow plug is shielded and the shield design is an important part of the combustion system development. The results simulated by KIVA-3V indicated that the ignition delay (ID) predicted by an in-cylinder pressure rise was different from that based on a temperature rise, attributed to the additional time required to burn more fuel to obtain a detectable pressure rise in the combustion chamber. This time difference for the ignition delay estimation can be 0.5 ms, which is significant relative to an ignition delay value of less than 2 ms. To further evaluate the time difference between the two different methods of ignition delay determination, sensitivity studies were conducted by changing the glow plug temperature, and rotating the glow plug shield opening angle towards the fuel jets. The results indicated that the ID method time difference varied from 0.3 to 0.8 ms for different combustion chamber configurations. In addition, this study also investigated the influences of different glow plug shield parameters on the natural gas ignition and combustion characteristics, by modifying the air gap between the glow plug and its shield, and by changing the shield opening size. The computational results indicated that a bigger air gap inside the shield can delay gas ignition, and a smaller shield opening can block the flame propagation for some specific fuel injection angles.Copyright © 2015 by ASME

Most endodontists use ultrasonic instruments for retrograde root-end cavity preparations even though they have been found to produce cracks. In this laboratory study, thirty-six randomly chosen roots had root-end cavity preparations made with the Waterlase laser and only one questionable intra-canal crack was found. It was concluded that the Waterlase laser when used to make endodontic root-end cavity preparations produces either no cracks, or a very low percentage (2.8%) of cracks.

High-dispersion coronagraphy (HDC) optimally combines high contrast imaging techniques such as adaptive optics/wavefront control plus coronagraphy to high spectral resolution spectroscopy. HDC is a critical pathway towards fully characterizing exoplanet atmospheres across a broad range of masses from giant gaseous planets down to Earth-like planets. In addition to determining the molecular composition of exoplanet atmospheres, HDC also enables Doppler mapping of atmosphere inhomogeneities (temperature, clouds, wind), as well as precise measurements of exoplanet rotational velocities. Here, we demonstrate an innovative concept for injecting the directly-imaged planet light into a single-mode fiber, linking a high-contrast adaptively-corrected coronagraph to a high-resolution spectrograph (diffraction-limited or not). Our laboratory demonstration includes three key milestones: close-to-theoretical injection efficiency, accurate pointing and tracking, on-fiber coherent modulation and speckle nulling of spurious starlight signal coupling into the fiber. Using the extreme modal selectivity of single-mode fibers, we also demonstrated speckle suppression gains that outperform conventional image-based speckle nulling by at least two orders of magnitude., Comment: 10 pages, 7 figures, accepted by ApJ

Natural gas requires some form of ignition assist in order to autoignite in the time available in a compression ignition engine. Ignition assist using a glow plug — a heated surface — was investigated using an apparatus that consists of an optically accessible constant volume combustion bomb coupled to a single cylinder CFR engine through the spark plug port. Previous studies have shown the dominant effect of fuel injection pattern and glow plug shield geometry on ignition delay, combustion rate, and fuel utilization with 1–3 fuel jets. New work has been carried out to evaluate the ability of a shielded glow plug to ignite a full nine jet symmetrical fuel injection pattern. The sensitivity of ignition delay and fuel utilization to fuel injector angular alignment relative to the glow plug, glow plug shield opening angle, and glow plug power was analyzed using in-cylinder pressure data and exhaust hydrocarbon emissions concentrations. Two glow plugs, one conventional metallic and one ceramic, and two fuel injector nozzle orifice sizes were evaluated for their effect on ignition delay. The ignition and flame propagation process was observed using high speed images. Glow plug power was shown to have a dominant effect on ignition delay and fuel utilization, with a secondary effect from fuel injector angle and glow plug opening angle. The ceramic glow plug was shown to provide superior ignition assist while consuming less power than the metallic glow plug. The larger fuel injector nozzle size increased ignition delay times, likely due to increased convective cooling of the glow plug surface from the larger gas jet. Acquired images show that the smaller fuel injector orifice size created a flammable path in two distinct areas; along the periphery of the fuel jets and between the fuel jets. The higher mass flow rate and subsequent increased mixing of the larger fuel jets created flammable paths throughout the entirety of the combustion chamber.Copyright © 2014 by ASME

The Gemini Planet Imager (GPI) entered on-sky commissioning phase, and had its First Light at the Gemini South telescope in November 2013. Meanwhile, the fast loops for atmospheric correction of the Extreme Adaptive Optics (XAO) system have been closed on many dozen stars at different magnitudes (I=4-8), elevation angles and a variety of seeing conditions, and a stable loop performance was achieved from the beginning. Ultimate contrast performance requires a very low residual wavefront error (design goal 60 nm RMS), and optimization of the planet finding instrument on different ends has just begun to deepen and widen its dark hole region. Laboratory raw contrast benchmarks are in the order of 10-6 or smaller. In the telescope environment and in standard operations new challenges are faced (changing gravity, temperature, vibrations) that are tackled by a variety of techniques such as Kalman filtering, open-loop models to keep alignment to within 5 mas, speckle nulling, and a calibration unit (CAL). The CAL unit was especially designed by the Jet Propulsion Laboratory to control slowly varying wavefront errors at the focal plane of the apodized Lyot coronagraph by the means of two wavefront sensors: 1) a 7x7 low order Shack-Hartmann SH wavefront sensor (LOWFS), and 2) a special Mach-Zehnder interferometer for mid-order spatial frequencies (HOWFS) - atypical in that the beam is split in the focal plane via a pinhole but recombined in the pupil plane with a beamsplitter. The original design goal aimed for sensing and correcting on a level of a few nm which is extremely challenging in a telescope environment. This paper focuses on non-common path low order wavefront correction as achieved through the CAL unit on sky. We will present the obtained results as well as explain challenges that we are facing., Adaptive Optics Systems IV, June 22-27, 2014, Series: Proceedings of SPIE; no. 9148

The Gemini Planet Imager (GPI) is a facility extreme-AO high-contrast instrument – optimized solely for study of faint companions – on the Gemini telescope. It combines a high-order MEMS AO system (1493 active actuators), an apodized pupil Lyot coronagraph, a high-accuracy IR post-coronagraph wavefront sensor, and a near-infrared integral field spectrograph. GPI incorporates several other novel features such as ultra-high quality optics, a spatially-filtered wavefront sensor, and new calibration techniques. GPI had first light in November 2013. This paper presnets results of first-light and performance verification and optimization and shows early science results including extrasolar planet spectra and polarimetric detection of the HR4696A disk. GPI is now achieving contrasts approaching 10-6 at 0.5” in 30 minute exposures.

The recent introduction of cryotherapy and radiofrequency ablation of liver metastasis has expanded the indications for treatment. As technology has advanced, a percutaneous approach has been developed. Percutaneous treatment, however, requires accurate preoperative imaging. From 1993 to 1999, 179 patients underwent operative exploration for treatment of suspected hepatic metastases from colorectal carcinoma. One hundred seventy-seven patients were staged by preoperative CT, two patients were staged by MRI, and complete data were available in 176. Hepatic tumor count by preoperative imaging was compared to intraoperative tumor count obtained by inspection, palpation, ultrasonographic examination using a 3.5/7.5 MHz T probe, and careful gross sectioning of the resected specimen. Post hoc analysis was performed on 35 CT scans by two radiologists who specialize in abdominal CT. These radiologists were blinded to the intraoperative findings. Their interpretations were compared to the intraoperative counts and to each other. Thirty-four (19%) of 179 patients were deemed untreatable at operation because of unsuspected overwhelming liver involvement in 11 (6%) or extrahepatic metastases in 23 (13%). For the group, CT was accurate in 80 patients (45%), showed more lesions than were found in 16 (9%), and showed fewer metastases than were found in 80 (45%). When the preoperative scan predicted a solitary metastasis, it was correct in 45 (65%) of 69 patients and underestimated disease in 24 (35%). In the post hoc analysis, the mean numbers of lesions reported by the two radiologists did not differ from the mean number of tumors found; however, the radiologists' counts agreed on 16 (59%) and disagreed on 11 (41%) of the scans. The accuracy of CT decreased with increasing numbers of lesions. Regardless of the type of preoperative imaging, intraoperative findings altered the course of the operation in 96 (55%) of 176 patients. Preoperative imaging is not sufficiently accurate to permit adequate percutaneous treatment of hepatic metastases from colorectal carcinoma.

To make improvements in spark ignition engine fuel economy and emissions, a better fundamental understanding of the interaction between the in-cylinder flows and the combustion process is needed. The influence of in-cylinder flows on the natural gas combustion process in configurations representative of light duty vehicle spark ignition engines is investigated here. This investigation focuses on the influence of the mean and turbulent flow fields on the flame kernel development. The flow was characterised using two-component laser Doppler velocimetry and the mass burn rate was calculated from the measured in-cylinder pressure. Results from a single cylinder V6 production engine, modified to run on a single cylinder and to allow optical access, are reported. The discrete wavelet transform (DWT) is used to show the energy cascade process in the non-stationary engine flow field over crank degree and frequency. Specifically, the preferential breakup of vortex structures as the expansion stroke begins was observed. The DWT is also used to show how the flow field evolution influences the early stages of the natural gas combustion process. Turbulence scales smaller than 1.5 mm were found to increase the early mass burn rate. Larger scales were found to act as an energy source for the smaller scales, thereby indirectly influencing the combustion process.

LDV measurements are commonly made in spark ignition engines to investigate the interaction between the flow field and the combustion process. To achieve high LDV data rates relatively large quantities of seed particles must be introduced into the engine intake flow. Based on the measurement of the characteristic engine operating parameters, it was determined that the introduction of TiO2 seed particles into an optical L-head research engine fuelled by natural gas at stoichiometric and lean conditions did not significantly influence the combustion process.

This paper examines velocity averaging within Spark-Ignition (SI) engines, a non-stationary system. Comparison is made between the mean and turbulence velocities found from (a) Ensemble, (b) Cyclic and (c) Wavelet-based averaging. The various methods of extracting turbulence within this flow system result in qualitatively similar average velocities; however, there are significant differences in the turbulence velocities and spectral content of the flow field based on the definition used. The differing interpretation of turbulence results in a subjectivity to the physical understanding of the flows. The experience in extracting coherent structures in stationary turbulence suggests that wavelet analysis offers a unique insight that has applicability for engine studies.

An experiment was conducted to evaluate the potential for reduced exhaust emissions and improved efficiency, by way of lean-burn engine fuelling with hydrogen supplemented natural gas (Hythane). The emissions and efficiency of the Hythane fuel (15 percent hydrogen, 85 percent natural gas by volume), were compared to the emissions and efficiency of pure natural gas using a turbocharged, spark ignition, 3.1 L, V-6 engine. The feasibility of heavy duty engine fueling with Hythane was assessed through testing conducted at engine speed and load combinations typical of heavy-duty engine operation. Comparison of the efficiency and emissions at MBT spark timing revealed that Hythane fueling of the test engine resulted in consistently lower brake specific energy consumption and emissions of total hydrocarbons (THC), carbon monoxide (CO), and carbon dioxide (CO2), at a given equivalence ratio. There was no clear trend with respect to MBT oxides of nitrogen (NOx) emissions. It was also discovered that an improved NOx-THC tradeoff resulted when Hythane was used to fuel the test engine. Consequently, Hythane engine operating parameters can be adjusted to achieve a concurrent reduction in NOx and THC emissions relative to natural gas fueling.

Here we present two simple concepts to make the vortex coronagraph (VC) immune to heavily obscured apertures. The multi-stage VC (MSVC) uses the ability of the vortex to move light in and out of apertures through multiple VC in series to restore the nominal attenuation capability of the charge 2 vortex regardless of the aperture obscurations. The ring-apodized VC (RAVC) is a one-stage apodizer exploiting the VC Lyot-plane amplitude distribution in order to perfectly null the diffraction from any central obscuration size, and for any vortex topological charge. In this paper, we also emphasize the complementarity and similarities of the RAVC to the recently proposed Active Compensation of Aperture Discontinuities (ACAD, L. Pueyo et al. 2013, these proceedings) and more finely optimized shaped-pupil-like apodizations (A. Carlotti et al. 2013, these proceedings). This paper ends with a brief discussion about the trade-offs these techniques offer in the framework of the Extremely Large Telescopes (ELT) and the Astrophysics Focused Telescope Assets (AFTA).

We have built and commissioned a prototype agitated non-circular core fiber scrambler for precision spectroscopic radial velocity measurements in the near-infrared H band. We have collected the first on-sky performance and modal noise tests of these novel fibers in the near-infrared at H and K bands using the CSHELL spectrograph at the NASA InfraRed Telescope Facility (IRTF). We discuss the design behind our novel reverse injection of a red laser for co-alignment of star-light with the fiber tip via a corner cube and visible camera. We summarize the practical details involved in the construction of the fiber scrambler, and the mechanical agitation of the fiber at the telescope. We present radial velocity measurements of a bright standard star taken with and without the fiber scrambler to quantify the relative improvement in the obtainable blaze function stability, the line spread function stability, and the resulting radial velocity precision. We assess the feasibility of applying this illumination stabilization technique to the next generation of near-infrared spectrographs such as iSHELL on IRTF and an upgraded NIRSPEC at Keck. Our results may also be applied in the visible for smaller core diameter fibers where fiber modal noise is a significant factor, such as behind an adaptive optics system or on a small < 1 meter class telescope such as is being pursued by the MINERVA and LCOGT collaborations., Proceedings of the SPIE Optics and Photonics Conference "Techniques and Instrumentation for Detection of Exoplanets VI" held in San Diego, CA, August 25-29, 2013

We present a new instrument, the "Stellar Double Coronagraph" (SDC), a flexible coronagraphic platform. Designed for Palomar Observatory's 200" Hale telescope, its two focal and pupil planes allow for a number of different observing configurations, including multiple vortex coronagraphs in series for improved contrast at small angles. We describe the motivation, design, observing modes, wavefront control approaches, data reduction pipeline, and early science results. We also discuss future directions for the instrument., Comment: 25 pages, 12 figures. Correspondence welcome. The published work is open access and differs trivially from the version posted here. The published version may be found at http://iopscience.iop.org/article/10.1088/1538-3873/128/965/075003/meta

The separate effects on heat transfer of 1) piston crown surface finish and 2) the use of a metal based thermal barrier coating (MTBC) on the piston crown of a spark ignition (SI) engine were quantified through experimental analysis in a single cylinder CFR engine. Measured engine parameters such as power, fuel consumption, emissions and cylinder pressure were used to identify the effects of the coating and its surface finish. Two piston coatings were tested: a baseline copper coating and a metal-based thermal barrier coating. Each coating was tested at multiple surface finishes. Tests showed that reducing surface roughness of both coatings increased in-cylinder temperature and pressure as a result of reduced heat transfer through the piston crown. For both coatings, this resulted in small improvements (∼3%) in power and fuel consumption, while also having a measurable effect on emissions. Oxides of nitrogen emissions increased while total hydrocarbon emissions generally decreased as a result of polishing. The polished coatings were also seen to increase in-cylinder peak pressures and burn rates. Improvements attributed to the TBC were found to be small, but statistically significant. At an equivalent surface finish, the MTBC-coated piston produced slightly higher power output and peak pressures. Hydrocarbon emissions were also seen to be significantly higher for the MTBC-coated piston due to its porosity. The effectiveness of the coating was found to be highly dependent on surface finish.

Direct injection natural gas (DING) engines offer the advantages of high thermal efficiency and high power output compared to spark ignition natural gas engines. Injected natural gas requires some form of ignition assist in order to ignite in the time available in a diesel engine combustion chamber. A glow plug — a heated surface — is one form of ignition assist. Simple experiments show that the thickness of the heat penetration layer of a glow plug is very small (≈10−5 m) within the time scale of the ignition preparation period (1–2 ms). Meanwhile, the theoretical analyses reveal that only a very thin layer of the surrounding gases (in micrometer scale) can be heated to high temperature to achieve spontaneous ignition. A discretized glow plug model and virtual gas sub-layer model have been developed for CFD modeling of glow plug ignition and combustion for DING diesel engines. In this paper, CFD modeling results are presented. The results were obtained using a KIVA3 code modified to include the above mentioned new developed models. Natural gas ignition over a bare glow plug was simulated. The results were validated against experiments. Simulation of natural gas ignition over a shielded glow plug was also carried out and the results illustrate the necessity of using a shield. This paper shows the success of the discretized glow plug model working together with the virtual gas sub-layer model for modeling glow plug assisted natural gas direct injection engines. The modeling can aid in the design of injection and ignition systems for glow plug assisted DING engines.

Utilization of biogas is attractive from a greenhouse gas standpoint since it is carbon neutral due to the use of renewable resources. One source of biogas is anaerobic digestors. The biogas produced could be used to power IC engine-generator sets to produce electric power and heat on farms and in rural and northern communities. Use of local energy sources is particularly attractive in remote regions where liquid fuels must be shipped in via difficult terrain. Whatever the fuel, the engine must meet stringent exhaust emission standards. Biogas is typically used in spark ignition engines, where stoichiometric engine operation coupled to a three-way catalyst is a proven technology for achieving low emissions. An appropriate three-way catalyst was selected on the basis of tests with natural gas. A flow mixing system was used to create simulated biogas mixtures consisting of varying concentrations of methane, carbon dioxide, hydrogen and nitrogen. The effectiveness of the catalyst in achieving low emissions when the engine was fueled by the various simulated biogas mixtures was assessed.Copyright © 2012 by ASME

Small-angle coronagraphy is technically and scientifically appealing because it enables the use of smaller telescopes, allows covering wider wavelength ranges, and potentially increases the yield and completeness of circumstellar environment - exoplanets and disks - detection and characterization campaigns. However, opening up this new parameter space is challenging. Here we will review the four posts of high contrast imaging and their intricate interactions at very small angles (within the first 4 resolution elements from the star). The four posts are: choice of coronagraph, optimized wavefront control, observing strategy, and post-processing methods. After detailing each of the four foundations, we will present the lessons learned from the 10+ years of operations of zeroth and first-generation adaptive optics systems. We will then tentatively show how informative the current integration of second-generation adaptive optics system is, and which lessons can already be drawn from this fresh experience. Then, we will review the current state of the art, by presenting world record contrasts obtained in the framework of technological demonstrations for space-based exoplanet imaging and characterization mission concepts. Finally, we will conclude by emphasizing the importance of the cross-breeding between techniques developed for both ground-based and space-based projects, which is relevant for future high contrast imaging instruments and facilities in space or on the ground., Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, July 1-6, 2012, Amsterdam, Netherlands, Series: Proceedings of SPIE

Glow plugs are a possible ignition source for direct injected natural gas engines. This ignition assistance application is much different than the cold start assist function for which most glow plugs have been designed. In the cold start application, the glow plug is simply heating the air in the cylinder. In the cycle-by-cycle ignition assist application, the glow plug needs to achieve high surface temperatures at specific times in the engine cycle to provide a localized source of ignition. Whereas a simple lumped heat capacitance model is a satisfactory representation of the glow plug for the air heating situation, a much more complex situation exists for hot surface ignition. Simple measurements and theoretical analysis show that the thickness of the heat penetration layer is small within the time scale of the ignition preparation period (1–2 ms). The experiments and analysis were used to develop a discretized representation of the glow plug domain. A simplified heat transfer model, incorporating both convection and radiation losses, was developed for the discretized representation to compute heat transfer to and from the surrounding gas. A scheme for coupling the glow plug model to the surrounding gas computational domain in the KIVA-3V engine simulation code was also developed. The glow plug model successfully simulates the natural gas ignition process for a direct-injection natural gas engine. As well, it can provide detailed information on the local glow plug surface temperature distribution, which can aid in the design of more reliable glow plugs.

Exoplanet imaging is driving a race to higher contrast imaging, both from earth and from space. Next-generation instruments such as the Gemini Planet Imager (GPI) and SPHERE are designed to achieve contrast ratios of 10 -6 - 10 -7 this requires very good wavefront correction and coronagraphic control of diffraction. GPI is a facility instrument, now in integration and test, with first light on the 8-m Gemini South telescope expected by the middle of 2012. It combines a 1700 subaperture AO system using a MEMS deformable mirror, an apodized-pupil Lyot coronagraph, a high-accuracy IR interferometric wavefront calibration system, and a nearinfrared integral field spectrograph to allow detection and characterization of self-luminous extrasolar planets at planet/star contrast ratios of 10 -7. In this paper we will discuss the status of the integration and test now taking place at the University of Santa Cruz California. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)., Astronomical Adaptive Optics Systems and Applications IV, August 21-24, 2011, San Diego, CA, USA, Series: Proceedings of SPIE

The Vector Vortex Coronagraph (VVC) is one of the most attractive new-generation coronagraphs for ground- and space-based exoplanet imaging/characterization instruments, as recently demonstrated on sky at Palomar and in the laboratory at JPL, and Hokkaido University. Manufacturing technologies for devices covering wavelength ranges from the optical to the mid-infrared, have been maturing quickly. We will review the current status of technology developments supported by NASA in the USA (Jet Propulsion Laboratory-California Institute of Technology, University of Arizona, JDSU and BEAMCo), Europe (University of Li`ege, Observatoire de Paris- Meudon, University of Uppsala) and Japan (Hokkaido University, and Photonics Lattice Inc.), using liquid crystal polymers, subwavelength gratings, and photonics crystals, respectively. We will then browse concrete perspectives for the use of the VVC on upcoming ground-based facilities with or without (extreme) adaptive optics, extremely large ground-based telescopes, and space-based internal coronagraphs.

A 4-8m diameter telescope carrying a coronagraph instrument is a leading candidate for an anticipated flagship mission to detect and characterize Earth-size exoplanets in the 2020s.1 Many candidate coronagraph instruments have been proposed, and one is close to meeting some of the principal requirements for that mission. But the telescope and instrument will need exquisite stability and precise control of the incoming wavefront to enable detection of faint companions (10 -10 of the star) at an angular separation of 2-4 Airy radii. In particular, wavefront errors cause speckles in the image, and variations in those speckles can confound the exoplanet detection. This challenge is compounded by the background light from zodiacal dust around our Sun and the target star, which limits the speed with which we can estimate and correct the speckles. We are working on developing coherent speckle detection techniques that will allow rapid calibration of speckles on the science detector, allowing subtraction in post-processing or correction with deformable mirrors. The expected speed improvement allows a much quicker timeline for measurement & calibration, which reduces the required telescope stability requirement and eases both the flight system design and the challenge of ground testing. We will describe the experiments and summarize progress to date.

The optical vortex coronagraph has great potential for enabling high-contrast observations very close to bright stars, and thus for reducing the size of space telescopes needed for exoplanet characterization missions. Here we discuss several recent developments in optical vortex coronagraphy. In particular, we describe multi-stage vortex configurations that allow the use of on-axis telescopes for high-contrast coronagraphy, and also enable the direct measurement of the amplitudes and phases of focal plane speckles. We also briefly describe recent laboratory demonstrations of the optical properties of the dual-stage vortex, and of the broadband performance of single stage vortex masks. Indeed, the demonstrated performance of the vector vortex phase masks already in hand, ≈ 10^(-8), is approximately that needed for an initial coronagraphic mission, such as an exoplanet explorer, aimed at detecting exozodiacal light and jovian exoplanets.

The Proton Exchange Membrane (PEM) fuel cell is an attractive energy conversion device that can provide efficient and clean electrical energy. However, limitations in water management can deleteriously affect its conversion efficiency. Overcoming this technological challenge is essential. In this paper, two design methodologies, biomimetic design and TRIZ, were used to find potential solutions to this water management problem. Each design method produced two potential solutions. We found biomimetic design to have more potential for bias by the designer’s prior knowledge of biology. This bias can serve to either hinder or help the design process. A notable finding is that biomimetic design and TRIZ can be considered mutually inclusive in the potential solutions generated in this study. This suggests that either design method could have been used to produce the same solutions.

A feasibility study has been conducted for an organic Rankine cycle (ORC) system coupled to the exhaust of a Diesel engine generator. The objective of this study was to determine the possible electrical generation of the ORC using the exhaust gas of a 78 kW diesel engine as its energy input. A thermodynamic model was developed to predict the possible electricity generation of the ORC. Using this model it was determined that the preferred working fluid for the ORC was R245ca. The calculated maximum ORC thermal efficiency was 14.3%. The net electrical power generated from the ORC was 5.36 kWe. The ORC would require no additional fuel and would not generate any additional emissions. The most cost-effective and simple means to develop a small packaged ORC system is to high volume production HVAC system components. An ORC system consisting of air conditioning system components, including a scroll expander, yielded a projected ORC efficiency of 10.7%, and a net electrical power of 4.02 kWe. The total capital cost of the ORC system was $2,140 CAD. Three engine usage scenarios were developed, with the time to payback of the initial capital cost of the ORC ranging from 12.8 to 0.58 years, depending on low or high usage.

Injected natural gas requires some form of ignition assist in order to ignite in the time available in a diesel engine combustion chamber. A glow plug — a heated surface — is one form of ignition assist. Ignition by glow plug results in a single site of ignition from which the flame must propagate to other jets in the ignition pattern. The goal of this work was to determine what factors affect how the flame propagates from this initial ignition site to the remaining unburned mixture. The combustion of natural gas jets under diesel engine conditions was studied over a range of temperatures with a glow plug shield using a CFR engine as a rapid compression device. The results showed that of all the factors considered it is the inter-related geometries of the injection pattern, combustion chamber, and glow plug shield that are most dominant in controlling combustion rates and fuel utilization, because those factors determine the distribution of fuel in the combustion chamber. Ignition of adjacent gas jets requires a flammable path between jets, which is achieved: 1) through mixing between the entrainment regions of adjacent jets and 2) through mixing along the cylinder wall of adjacent jets that are spreading along the wall. Ignition by either of both of these pathways can provide high fuel utilization and combustion rates and low combustion variability. Autoignition of an adjacent jet due to heat release from ignition of the first jet was not observed in these experiments with two jets.Copyright © 2011 by ASME

The organic Rankine cycle (ORC) is a power generating technology that can enable the utilization of waste heat to generate electric power from different sources, including geothermal hot springs, other power generating technologies, and industrial applications. There is a significant technical challenge in producing financially viable ORC plants, due to the high costs associated with custom heat exchange components and turbo-machinery. In the last few years, however, packaged systems have been developed from commercially available refrigeration systems, which significantly reduce cost. The goal of this project was to evaluate the feasibility of generating electricity using the waste heat from industrial air compression equipment. A simulation program was written to model the thermodynamics of the ORC. Several potential working fluids were surveyed and ranked based on their applicability to the industrial operating conditions. In particular, refrigerant R-236fa has been determined to be the most appropriate working fluid. The decision was made by weighing its thermal properties, as well as environmental and health considerations. Two types of heat rejection technology were considered, namely water-cooling and air-cooling, with emphasis on the effect of ambient conditions on ORC performance. It is concluded that water-cooling can be used for a plant located in Ontario, Canada, with the possibility of utilizing air-cooling during the cooler seasons of the year. An installation cost of U.S. $1,300/kW is feasible, yielding a simple payback period of 6.35 years. The results of this research project encourage further work to be done on this application of waste heat recovery.Copyright © 2011 by ASME

The goal of a large (25 m) submillimeter telescope with high aperture efficiencies up to frequencies of ~ 1 THz requires a wavefront sensor able to measure the telescope surface figure to an accuracy of order 1 micron, better than has been achieved to date in the millimeter/submillimeter (MSM) regime. On the other hand, the recent availability of largeformat submillimeter detector arrays suggests that new techniques can be applied. In particular, using submillimeter focal plane arrays, variants of interferometric pupil-plane wavefront sensing techniques familiar from the optical/infrared (OIR) regime could perhaps be applied profitably in the MSM. However, while many possibilities can in principle be considered, many of these possibilities would be unwieldy in the MSM, because of the need for large off-axis reflective optical elements, and the consequent sizeable optical layout. However, the overall size of an interferometer can be minimized by making use of a common-path interferometer. Here we thus consider the applicability to MSM wavefront sensing of a rather simple common-path pupil-plane interferometer, specifically a scanning version of the fixed-phase phase-contrast interferometers described in different contexts by Zernicke 1 and Dicke 2 . Both transmissive and reflective solutions for the needed phase shifting interferometers are possible, but here we focus on the reflective case as a proof of principle. Such a common-path phase-shifting interferometer has several potential advantages: relative simplicity, compactness, ease of manufacturability, reduced systematic effects, and high accuracy.