A Rapidly Moving Shell in the Orion Nebula

A well-resolved elliptical shell in the inner Orion Nebula has been investigated by monochromatic imaging plus high- and low-resolution spectroscopy. We find that it is of low ionization and the two bright ends are moving at -39 and -49 km/s with respect to OMC-1. There is no central object, even in the infrared J bandpass although H2 emission indicates a possible association with the nearby very young pre-main-sequence star J&W 352, which is one of the youngest pre-main-sequence stars in the inner Orion Nebula. Many of the characteristics of this object (low ionization, blue shift) are like those of the Herbig-Haro objects, although the symmetric form would make it an unusual member of that class

High velocity flows, shocks in the star forming H II region: The Orion Nebula

We have studied the high velocity flows and related shock phenomena in the Orion Nebula. Hubble Space Telescope WF/PC and WFPC2 images have been used in morphological studies and proper motion studies of the objects of interest. The high spectral resolution echelle slit spectra have been obtained for the central Orion Nebula in order to study both high velocity flows associated with compact objects and large scale high velocity systems. A group of Herbig-Haro objects located to the north of the Trapezium cluster have been studied in detail. Their morphology, proper motions and motions along the line of sight have been investigated. A bow shock model has been applied to predict the emission line profiles of bow shocks and the resultant line profiles were compared with the observed spectra. The comparison was successful except there is a discrepancy for one of the objects. The possible origin and evolution of this group of objects have been discussed. Two Herbig-Haro objects(HH203/HH204) in the vicinity of \theta\sp2A have also been studied both through the HST images and slit spectra. The possible nature of HH203 was suggested by comparing the emission line image with bow shock model predicted emission in inhomogeneous density environment. The spectra of Knot C has been presented and the nature of this object was discussed. We also reported the discovery of a Herbig-Haro like object-HH269, which is located to the southwest of the Trapezium cluster. A slit spectra mapping of the vicinity of the Trapezium cluster and HH202 have been done. The high velocity flows associated with several "proplyds" have been studied. A 1\sp\prime diameter "receding disk" near the Trapezium cluster was found in (OIII) line spectra. A couple of complicated extended high velocity systems were found near HH202. The spectra of this region were presented

Study of inner region of the Orion nebula using the Hubble Space Telescope

Narrow band filter images of the inner Orion nebula were taken by the the Hubble Space Telescope WF/PC in 1990 and 1991. Two data sets were reduced and astrometric solutions were obtained for the two fields with good accuracy. The three major emission line filters for the 1991 data were calibrated into absolute energy units. The continuum contribution was removed from the images, and the $\rm H\alpha$ contribution was removed from the (NII) images. Calibration constants were found to differ from predicted prelaunch values, and possible explanations were investigated. VLA and HST images of two compact sources near the center of the Orion Nebula were compared. The VLA and HST images are similar when the two are scaled to the same units. VLA images show a higher concentration of surface brightness, reflecting its better resolution; whereas, the HST images, due to greater sensitivity of the HST, showed extended cometary form. The positions of three Herbig-Haro objects on HST images were compared with ground based observations at various wavelengths. The basic agreement between these positional observations can be used to analyze the structure of these sources, because of the different excitation mechanism for each source

Evaluation of BESS Management Strategies for Grid Primary and Enhanced Frequency Response

Maintaining the electrical power system frequency is becoming a severe challenge due to the increasing penetration of renewable generation schemes, which are highly dynamic and intermittent. System operators are investigating ways of solving this problem. The battery energy storage system (BESS) with a proper control strategy can be a suitable candidate to assist in regulating frequency. However, there are only a few reported specifications and management strategies for the use of BESS to assist the grid. This paper investigates the feasibility of two published frequency reserve strategies, and Primary Frequency Response (PFR) and Enhanced Frequency Response (EFR). A Lithium-ion (Li-ion) battery model is developed for this study. The battery cell model has been previously experimentally tested and dynamically assessed. The cell model is then expanded to a representative BESS of suitable size for future distributed power systems using published data for larger scale battery systems. This paper investigates the performance of BESS when battery terminal voltage variation, current, internal resistance and SoC when subject to PFR and EFR power demands. Four different energy management strategies are compared and alternative battery size and configuration analyzed. In addition, battery performance following existing strategies in real running conditions is examined and discussed in the paper

RSR_1.5 of ICP and CICP algorithms in two steps on US-MERGE and US-SNAP datasets.

<p>RSR_1.5 of ICP and CICP algorithms in two steps on US-MERGE and US-SNAP datasets.</p

Comparison of ICP (dark) and CICP (light) in two steps with (a) average LMSD and (b) LMAXD on US-MERGE and US-SNAP datasets.

<p>An asterisk in (a) and (b) indicates statistically significant (<i>p</i> < 0.05) reduction in average LMSD or LMAXD from ICP to CICP.</p

RSR_1.5 and computation time with the same configuration for different feature-based algorithms on US-MERGE and US-SNAP datasets.

<p>RSR_1.5 and computation time with the same configuration for different feature-based algorithms on US-MERGE and US-SNAP datasets.</p

Overview of proposed TACICP algorithm for carotid image registration.

<p>The segmented 2D contours from images are the only inputs for our algorithm. Centerline and surface features are generated automatically from contours for two steps. The final output of the registration is a transformation composed by the rigid transformation <i>T</i>_rigid from rigid initialization step and the thin-plate-spline transformation <i>T</i>_TPS from non-rigid refinement step.</p