Assessing the effectiveness of multi-touch interfaces for DP operation

Navigating a vessel using dynamic positioning (DP) systems close to offshore installations is a challenge. The operator's only possibility of manipulating the system is through its interface, which can be categorized as the physical appearance of the equipment and the visualization of the system. Are there possibilities of interaction between the operator and the system that can reduce strain and cognitive load during DP operations? Can parts of the system (e.g. displays) be physically brought closer to the user to enhance the feeling of control when operating the system? Can these changes make DP operations more efficient and safe? These questions inspired this research project, which investigates the use of multi-touch and hand gestures known from consumer products to directly manipulate the visualization of a vessel in the 3D scene of a DP system. Usability methodologies and evaluation techniques that are widely used in consumer market research were used to investigate how these interaction techniques, which are new to the maritime domain, could make interaction with the DP system more efficient and transparent both during standard and safety-critical operations. After investigating which gestures felt natural to use by running user tests with a paper prototype, the gestures were implemented into a Rolls-Royce DP system and tested in a static environment. The results showed that the test participants performed significantly faster using direct gesture manipulation compared to using traditional button/menu interaction. To support the results from these tests, further tests were carried out. The purpose is to investigate how gestures are performed in a moving environment, using a motion platform to simulate rough sea conditions. The key results and lessons learned from a collection of four user experiments, together with a discussion of the choice of evaluation techniques will be discussed in this paper

Design concepts for bioreactors in space

Microbial food sources are becoming viable and more efficient alternatives to conventional food sources especially in the context of Closed Ecological Life Support Systems (CELSS) in space habitats. Since bioreactor designs for terrestrial operation will not readily apply to conditions of microgravity, there is an urgent need to learn about the differences. These differences cannot be easily estimated due to the complex nature of the mass transport and mixing mechanisms in fermenters. Therefore, a systematic and expeditious experimental program must be undertaken to obtain the engineering data necessary to lay down the foundations of designing bioreactors for microgravity. Two bioreactor design concepts presented represent two dissimilar approaches to grappling with the absence of gravity in space habitats and deserve to be tested for adoption as important components of the life support function aboard spacecrafts, space stations and other extra-terrestrial habitats

Design concepts for bioreactors in space

Microbial food sources are becoming viable and more efficient alternatives to conventional food sources, especially in the context of closed ecological life support systems (CELSS) in space habitats. Two bioreactor design concepts presented represent two dissimilar approaches to grappling with the absence of gravity in space habitats and deserve to be tested for adoption as important components of the life support function aboard spacecraft, space stations and other extra-terrestrial habitats

RMS Radio Source Contributions to the Microwave Sky

Cross-correlations of the WMAP full sky K, Ka, Q, V, and W band maps with the 1.4 GHz NVSS source count map and the HEAO I A2 2-10 keV full sky X-ray flux map are used to constrain rms fluctuations due to unresolved microwave sources in the WMAP frequency range. In the Q band (40.7 GHz), a lower limit, taking account of only those fluctuations correlated with the 1.4 GHz radio source counts and X-ray flux, corresponds to an rms Rayleigh-Jeans temperature of ~ 2 microKelvin for a solid angle of one square degree. The correlated fluctuations at the other bands are consistent with a beta = -2.1 +- 0.4 frequency spectrum. Using the rms fluctuations of the X-ray flux and radio source counts, and the cross-correlation of these two quantities as a guide, the above lower limit leads to a plausible estimate of ~ 5 microKelvin for Q-band rms fluctuations in one square degree. This value is similar to that implied by the excess, small angular scale fluctuations observed in the Q band by WMAP, and is consistent with estimates made by extrapolating low-frquency source counts.Comment: 17 pages, 8 figures, submitted to Ap

Optically Faint Microjansky Radio Sources

We report on the identifications of radio sources from our survey of the Hubble Deep Field and the SSA13 fields, both of which comprise the deepest radio surveys to date at 1.4 GHz and 8.5 GHz respectively. About 80% of the microjansky radio sources are associated with moderate redshift starburst galaxies or AGNs within the I magnitude range of 17 to 24 with a median of I = 22 mag. Thirty-one (20%) of the radio sources are: 1) fainter than $I>$25 mag, with two objects in the HDF $I_{AB}>$28.5, 2) often identified with very red objects $I-K>$4, and 3) not significantly different in radio properties than the brighter objects. We suggest that most of these objects are associated with heavily obscured starburst galaxies with redshifts between 1 and 3. However, other mechanisms are discussed and cannot be ruled out with the present observations.Comment: to appear in Astrophysical Journal Letters, 3 figures, 1 tabl

The Evolution of Radio Galaxies at Intermediate Redshift

We describe a new estimate of the radio galaxy 1.4 GHz luminosity function and its evolution at intermediate redshifts (z~0.4). Photometric redshifts and color selection have been used to select Bj<23.5 early-type galaxies from the Panoramic Deep Fields, a multicolor survey of two 25 sq deg fields. Approximately 230 radio galaxies have then been selected by matching early-type galaxies with NVSS radio sources brighter than 5 mJy. Estimates of the 1.4 GHz luminosity function of radio galaxies measure significant evolution over the observed redshift range. For an Omega_M=1 cosmology the evolution of the radio power is consistent with luminosity evolution where P(z)=P(0)(1+z)^{k_L} and 3<k_L<5. The observed evolution is similar to that observed for UVX and X-ray selected AGN and is consistent with the same physical process being responsible for the optical and radio luminosity evolution of AGN.Comment: 26 pages, 9 Figures, Accepted for Publication in A

A necklace of Wulff shapes

In a probabilistic model of a film over a disordered substrate, Monte-Carlo simulations show that the film hangs from peaks of the substrate. The film profile is well approximated by a necklace of Wulff shapes. Such a necklace can be obtained as the infimum of a collection of Wulff shapes resting on the substrate. When the random substrate is given by iid heights with exponential distribution, we prove estimates on the probability density of the resulting peaks, at small density

Age Problem in the Holographic Dark Energy Model

In this note, we test the original holographic dark energy model with some old high redshift objects. The main idea is very simple: the universe cannot be younger than its constituents. We find that the original holographic dark energy model can be ruled out, unless a lower Hubble constant is taken.Comment: 12 pages, 3 tables, 3 figures, revtex4; v2: accepted for publication in Phys. Rev. D; v3: published versio

Keck Spectroscopy of Faint 3<z<8 Lyman Break Galaxies:- Evidence for a Declining Fraction of Emission Line Sources In the Redshift Range 6<z<8

Using deep Keck spectroscopy of Lyman break galaxies selected from infrared imaging data taken with WFC3/IR onboard the Hubble Space Telescope, we present new evidence for a reversal in the redshift-dependent fraction of star forming galaxies with detectable Lyman alpha emission in the redshift range 6.3 < z < 8.8. Our earlier surveys with the DEIMOS spectrograph demonstrated a significant increase with redshift in the fraction of line emitting galaxies over the interval 4 < z < 6, particularly for intrinsically faint systems which dominate the luminosity density. Using the longer wavelength sensitivities of LRIS and NIRSPEC, we have targeted 19 Lyman break galaxies selected using recent WFC3/IR data whose photometric redshifts are in the range 6.3 < z < 8.8 and which span a wide range of intrinsic luminosities. Our spectroscopic exposures typically reach a 5-sigma sensitivity of < 50 A for the rest-frame equivalent width (EW) of Lyman alpha emission. Despite the high fraction of emitters seen only a few hundred million years later, we find only 2 convincing and 1 possible line emitter in our more distant sample. Combining with published data on a further 7 sources obtained using FORS2 on the ESO VLT, and assuming continuity in the trends found at lower redshift, we discuss the significance of this apparent reversal in the redshift-dependent Lyman alpha fraction in the context of our range in continuum luminosity. Assuming all the targeted sources are at their photometric redshift and our assumptions about the Lyman alpha EW distribution are correct, we would expect to find so few emitters in less than 1% of the realizations drawn from our lower redshift samples. Our new results provide further support for the suggestion that, at the redshifts now being probed spectroscopically, we are entering the era where the intergalactic medium is partially neutral.Comment: 8 pages, 5 figures, Accepted to ApJ 10/1/1