Nacelle design

The external cowlings of engine nacelles on large turbofan powered aircraft are good candidates for application of natural laminar flow. These nacelles usually have shorter characteristic lengths than other candidate surfaces such as wings and fuselages and therefore have lower characteristic Reynolds numbers. A conceptive figure of the natural flow nacelle (NLF) is shown. On the typical nacelle the flow accelerates to a curvature induced velocity peak near the lip and then decelerates over the remainder of the nacelle length. Transition occurs near the start of the deceleration, so turbulent flow with high friction coefficient exists over most of the nacelle length. On the other hand, the NLF nacelle is contoured to have an accelerating flow over most of its length, so transition is delayed, and a relatively lower friction drag exists over most of the nacelle. The motivation for development of the LFN is a potential 40 to 50 percent reduction in nacelle friction drag

Pengembangan Model Penguatan Lembaga Pertanian sebagai Prime Mover Pembangunan Kawasan Daerah Penyangga Pembangunan (Dpp) Destinasi Wisata Kintamani Bali

Tujuan pokok penelitian ini mengembangkan model prime mover sektor pertanian argo di daerah penyangga pembangunan (DPP) destinasi wisata Kintamani untuk penguatan dan pemberdayaan para petani agro berbasis kewilayahan dan berbasis penguatan kelembagaan lokal di Kecamatan Kintamani Kabupaten Bangli. Penelitian ini menggunakan desain penelitian dan pengembangan (R&D) dengan metode kuantitatif IG (Indeks Gravitasi) untuk melihat derajat keterkaitan aktivitas ekonomi antara DPP dan desa sekitarnya, CDSF (Cobb-Douglas Stochastic Frontier) untuk melihat tingkat efisiensi teknis yang mencerminkan sejauhmana kegiatan produksi sektor dominan di DPP mencapai titik optimumnya, serta metode EL (Ekonometrik Logit) untuk mengetahui adakah fragmentasi produksi DPP dengan desa sekitarnya. Dalam penyusunan desain pola pengembangan ekonomi di DPP mengacu pada temuan studi pendahuluan dan trending analysis terkait dengan keunggulan potensi, permasalahan yang paling urgen, dan peluang usaha di masing-masing wilayah. Produk penelitian ini adalah : (1) peta permasalahan dan produksi dominan petani agro, (2) peta kelembagaan petani agro, (3) model pelembagaan petani agro, (4) draft model prime mover sektor pertanian agro terhadap pengembangan destinasi wisata, dan (5) artikel ilmiah (jurnal terakreditasi). Hasil penelitian menunjukkan bahwa : (1) berdasarkan data Dinas Pariwisata Kabupaten Bangli Provinsi Bali, yaitu : Desa Batur Selatan, desa Songan A, desa Songan B,dan desa Kedisan. Secara umum lembaga-lembaga social kemasyarakatan yang ada di semua desa tersebut hamper sama,hanya struktur organisasinya yang sedikit berbeda, yang disesuaikan dengan kebutuhan dan kebiasaan masyarakat setempat. (2) lembaga social dan budaya yang terdapat di desa-desa kawasan agrowisata Kintamani, pada umumnya adalah : sekehe teruna teruni, kelompok tani, gabungan kelompok tani, sekehe jogged, sekehe santi, sekehe tabuh, sekehe payus, sekehe rejang,sekehe manyi, sekehe baris, sekehe pruguh, sekehe gong, sekehe gambuh, lembaga perkreditan desa, desa adat, prajuru desa adat, koperasi unti desa,kelompok penyakap,dan kelompok peternak. (3) pada desa-desa kawasan agrowisata di Kintamani, terdapat lahan yang masih cukup besar untuk dimaksimalkan pemanfaatannya, yakni berkisar antara 10 sampai 100 hektar di setiap desanya. Namun, berdasarkan hasil survey di lapangan, hanya sebagian kecil dari lahan tersebut yang merupakan milik penduduk setempat. (4) potensi kawasan Kintamani pada dasarnya bersandar pada keindahan alam dan modalitas social budaya masyarakat itu sendiri. (5) masih ditemukan berbagai kendala yang dihadapi oleh masyarakat desa kawasan agrowisata pada umumnya dan petani pada khusnya, terutama pada aspek-aspek khusus, seperti: aturan desa dan pengelolaan lembaga sosial dan budaya desa, luas dan kepemilikan lahan, system permodalan, pemanfaatan sumber daya, dan system penjualan

Dumb-bell galaxies in southern clusters: Catalog and preliminary statistical results

The dominant galaxy of a rich cluster is often an object whose formation and evolution is closely connected to the dynamics of the cluster itself. Hoessel (1980) and Schneider et al. (1983) estimate that 50 percent of the dominant galaxies are either of the dumb-bell type or have companions at projected distances less than 20 kpc, which is far in excess of the number expected from chance projection (see also Rood and Leir 1979). Presently there is no complete sample of these objects, with the exception of the listing of dumb-bell galaxies in BM type I and I-II clusters in the Abell statistical sample of Rood and Leir (1979). Recent dynamical studies of dumb-bell galaxies in clusters (Valentijn and Casertano, 1988) still suffer from inhomogeneity of the sample. The fact that it is a mixture of optically and radio selected objects may have introduced an unknown biases, for instance if the probability of radio emission is enhanced by the presence of close companions (Stocke, 1978, Heckman et al. 1985, Vettolani and Gregorini 1988) a bias could be present in their velocity distribution. However, this situation is bound to improve: a new sample of Abell clusters in the Southern Hemisphere has been constructed (Abell et al., 1988 hereafter ACO), which has several advantages over the original northern catalog. The plate material (IIIaJ plates) is of better quality and reaches fainter magnitudes. This makes it possible to classify the cluster types with a higher degree of accuracy, as well as to fainter magnitudes. The authors therefore decided to reconsider the whole problem constructing a new sample of dumb-bell galaxies homogeneously selected from the ACO survey. Details of the classification criteria are given

Large Merger Recoils and Spin Flips From Generic Black-Hole Binaries

We report the first results from evolutions of a generic black-hole binary, i.e. a binary containing unequal mass black holes with misaligned spins. Our configuration, which has a mass ratio of 2:1, consists of an initially non-spinning hole orbiting a larger, rapidly spinning hole (specific spin a/m = 0.885), with the spin direction oriented -45 degrees with respect to the orbital plane. We track the inspiral and merger for ~2 orbits and find that the remnant receives a substantial kick of 454 km/s, more than twice as large as the maximum kick from non-spinning binaries. The remnant spin direction is flipped by 103 degrees with respect to the initial spin direction of the larger hole. We performed a second run with anti-aligned spins, a/m = +-0.5 lying in the orbital plane that produces a kick of 1830 km/s off the orbital plane. This value scales to nearly 4000 km/s for maximally spinning holes. Such a large recoil velocity opens the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy.Comment: 4 pages. Accepted for publication in ApJ

The ATESP 5 GHz radio survey. II. Physical properties of the faint radio population

One of the most debated issues about sub-mJy radio sources, which are responsible for the steepening of the 1.4 GHz source counts, is the origin of their radio emission. Particularly interesting is the possibility of combining radio spectral index information with other observational properties to assess whether the sources are triggered by star formation or nuclear activity. The aim of this work is to study the optical and near infrared properties of a complete sample of 131 radio sources with S>0.4 mJy, observed at both 1.4 and 5 GHz as part of the ATESP radio survey. We use deep multi-colour (UBVRIJK) images, mostly taken in the framework of the ESO Deep Public Survey, to optically identify and derive photometric redshifts for the ATESP radio sources. Deep optical coverage and extensive colour information are available for 3/4 of the region covered by the radio sample. Typical depths of the images are U~25, B~26, V~25.4, R~25.5, I~24.3, 19.5<K_s<20.2, J<22.2. Optical/near infrared counterparts are found for ~78% (66/85) of the radio sources in the region covered by the deep multi-colour imaging, and for 56 of these reliable estimates of the redshift and type are derived. We find that many of the sources with flat radio spectra are characterised by high radio-to-optical ratios (R>1000), typical of classical powerful radio galaxies and quasars. Flat-spectrum sources with low R values are preferentially identified with early type galaxies, where the radio emission is most probably triggered by low-luminosity active galactic nuclei. Considering both early type galaxies and quasars as sources with an active nucleus, such sources largely dominate our sample (78%). Flat-spectrum sources associated with early type galaxies are quite compact (d<10-30 kpc), suggesting core-dominated radio emission.Comment: 15 pages, 13 figures, accepted for pubblication in A&

The ATESP Radio Survey II. The Source Catalogue

This paper is part of a series reporting the results of the Australia Telescope ESO Slice Project (ATESP) radio survey obtained at 1400 MHz with the Australia Telescope Compact Array (ATCA) over the region covered by the ESO Slice Project (ESP) galaxy redshift survey. The survey consists of 16 radio mosaics with ~8"x14" resolution and uniform sensitivity (1sigma noise level ~79 microJy) over the whole area of the ESP redshift survey (~26 sq. degrees at decl. -40 degr). Here we present the catalogue derived from the ATESP survey. We detected 2960 distinct radio sources down to a flux density limit of ~0.5 mJy (6sigma), 1402 being sub-mJy sources. We describe in detail the procedure followed for the source extraction and parameterization. The internal accuracy of the source parameters was tested with Monte Carlo simulations and possible systematic effects (e.g. bandwidth smearing) have been quantified.Comment: 14 pages, 14 Postscript figures, Accepted for publication in A&A Suppl. Corrected typos and added Journal Referenc

Status report on a natural laminar-flow nacelle flight experiment

The natural laminar flow (NLF) nacelle experiment is part of a drag reduction production program, and has the dual objectives of studying the extent of NLF on full scale nacelles in a flight environment and the effect of acoustic disturbance on the location of transition on the nacelle surface. The experiment is being conducted in two phases: (1) an NLF fairing was flown on a full scale Citation nacelle to develop the experiment technique and establish feasibility; (2) full scale, flow through, NLF nacelles located below the right wing of an experimental NASA OV-1 aircraft are evaluated. The measurements of most interest are the static pressure distribution and transition location on the nacelle surface, and the fluctuating pressure levels associated with the noise sources. Data are collected in combinations of acoustic frequencies and sound pressure levels. The results of phase 2 tests to date indicate that on shape GE2, natural laminar flow was maintained as far aft as the afterbody joint at 50 percent of the nacelle length. An aft facing step at this joint caused premature transition at this station. No change was observed in the transition pattern when the noise sources were operated

X-ray-emitting Atmospheres of B2 Radio Galaxies

We report ROSAT PSPC spatial and spectral analysis of the eight B2 radio galaxies NGC 315, NGC 326, 4C 35.03, B2 0326+39, NGC 2484, B2 1040+31, B2 1855+37, and 3C 449, expected to be representative of the class of low-power radio galaxies. Multiple X-ray components are present in each, and the gas components have a wide range of linear sizes and follow an extrapolation of the cluster X-ray luminosity/temperature correlation, implying that there is no relationship between the presence of a radio galaxy and the gas fraction of the environment. No large-scale cooling flows are found. There is no correlation of radio-galaxy size with the scale or density of the X-ray atmosphere. This suggests that it is processes on scales less than those of the overall gaseous environments which are the major influence on radio-source dynamics. The intergalactic medium is usually sufficient to confine the outer parts of the radio structures, in some cases even to within 5 kpc of the core. In the case of NGC 315, an extrapolation suggests that the pressure of the atmosphere may match the minimum pressure in the radio source over a factor of about 40 in linear size (a factor of about 1600 in pressure).Comment: 34 pages, including 10 figures, using aasms4.sty To appear in the Ap

Multifrequency VLA observations of the FR I radio galaxy 3C 31: morphology, spectrum and magnetic field

We present high-quality VLA images of the FR I radio galaxy 3C 31 in the frequency range 1365 to 8440 MHz with angular resolutions from 0.25 to 40 arcsec. Our new images reveal complex, well resolved filamentary substructure in the radio jets and tails. We also use these images to explore the spectral structure of 3C 31 on large and small scales. We infer the apparent magnetic field structure by correcting for Faraday rotation. Some of the intensity substructure in the jets is clearly related to structure in their apparent magnetic field: there are arcs of emission where the degree of linear polarization increases, with the apparent magnetic field parallel to the ridges of the arcs. The spectral indices are significantly steeper (0.62) within 7 arcsec of the nucleus than between 7 and 50 arcsec (0.52 - 0.57). The spectra of the jet edges are also slightly flatter than the average for their surroundings. At larger distances, the jets are clearly delimited from surrounding larger-scale emission both by their flatter radio spectra and by sharp brightness gradients. The spectral index of 0.62 in the first 7 arcsec of 3C 31's jets is very close to that found in other FR I galaxies where their jets first brighten in the radio and where X-ray synchrotron emission is most prominent. Farther from the nucleus, where the spectra flatten, X-ray emission is fainter relative to the radio. The brightest X-ray emission from FR I jets is therefore not associated with the flattest radio spectra, but with a particle-acceleration process whose characteristic energy index is 2.24. The spectral flattening with distance from the nucleus occurs where our relativistic jet models require deceleration, and the flatter-spectra at the jet edges may be associated with transverse velocity shear. (Slightly abridged)Comment: 17 pages, 13 figures, accepted for publication in MNRA