221 research outputs found
Aspek-Aspek Pertimbangan dalam Perencanaan Pelestarian Kawasan Pusaka (Heritage)
Konservasi atau pelestarian dengan lingkup kawasan harus mempertimbangkan banyak hal yang terkait. Apalagi jika ternyata kawasan tersebut juga sekaligus merupakan lokasi yang menjadi destinasi kawasan wisata dan juga merupakan permukiman yang masih dihuni dan hidup sepanjang waktu. Artikel ini akan membahas aspek-aspek yang mempengaruhi pertimbangan dalam meren-canakan penataan kawasan yang memiliki nilai pusaka atau heritage, sekaligus sebagai kawasan destinasi wisata dan masih dihuni atau masih ada penduduk yang bermukim di kawasan tersebut. Aspek-aspek pertimbangan perencanaan penataan coba dimunculkan dengan menjaring pendapat responden berdasarkan metode penelitian kualitatif dengan Analisis Data Teks. Dari hasil analisis data teks diperoleh kategori-kategori jawaban yang bisa dikelompokkan sehingga diperoleh bebe-rapa aspek yang dapat dijadikan pertimbangan utama dalam menentukan penataan kawasan pusaka. Aspek-aspek tersebut yaitu pertimbangan yang terintegrasi dari: (1) prinsip-prinsip pelestarian atau konservasi, (2) kaidah-kaidah perancangan kota, dan (3) persyaratan atau kriteria obyek destinasi wisata
Good covers are algorithmically unrecognizable
A good cover in R^d is a collection of open contractible sets in R^d such
that the intersection of any subcollection is either contractible or empty.
Motivated by an analogy with convex sets, intersection patterns of good covers
were studied intensively. Our main result is that intersection patterns of good
covers are algorithmically unrecognizable.
More precisely, the intersection pattern of a good cover can be stored in a
simplicial complex called nerve which records which subfamilies of the good
cover intersect. A simplicial complex is topologically d-representable if it is
isomorphic to the nerve of a good cover in R^d. We prove that it is
algorithmically undecidable whether a given simplicial complex is topologically
d-representable for any fixed d \geq 5. The result remains also valid if we
replace good covers with acyclic covers or with covers by open d-balls.
As an auxiliary result we prove that if a simplicial complex is PL embeddable
into R^d, then it is topologically d-representable. We also supply this result
with showing that if a "sufficiently fine" subdivision of a k-dimensional
complex is d-representable and k \leq (2d-3)/3, then the complex is PL
embeddable into R^d.Comment: 22 pages, 5 figures; result extended also to acyclic covers in
version
Cosmic cookery : making a stereoscopic 3D animated movie.
This paper describes our experience making a short stereoscopic movie visualizing the development of structure in
the universe during the 13.7 billion years from the Big Bang to the present day. Aimed at a general audience for
the Royal Society's 2005 Summer Science Exhibition, the movie illustrates how the latest cosmological theories
based on dark matter and dark energy are capable of producing structures as complex as spiral galaxies and
allows the viewer to directly compare observations from the real universe with theoretical results. 3D is an
inherent feature of the cosmology data sets and stereoscopic visualization provides a natural way to present the
images to the viewer, in addition to allowing researchers to visualize these vast, complex data sets.
The presentation of the movie used passive, linearly polarized projection onto a 2m wide screen but it was
also required to playback on a Sharp RD3D display and in anaglyph projection at venues without dedicated
stereoscopic display equipment. Additionally lenticular prints were made from key images in the movie. We
discuss the following technical challenges during the stereoscopic production process; 1) Controlling the depth
presentation, 2) Editing the stereoscopic sequences, 3) Generating compressed movies in display speci¯c formats.
We conclude that the generation of high quality stereoscopic movie content using desktop tools and equipment
is feasible. This does require careful quality control and manual intervention but we believe these overheads
are worthwhile when presenting inherently 3D data as the result is signi¯cantly increased impact and better
understanding of complex 3D scenes
Bounding Helly numbers via Betti numbers
We show that very weak topological assumptions are enough to ensure the
existence of a Helly-type theorem. More precisely, we show that for any
non-negative integers and there exists an integer such that
the following holds. If is a finite family of subsets of such that for any
and every
then has Helly number at most . Here
denotes the reduced -Betti numbers (with singular homology). These
topological conditions are sharp: not controlling any of these first Betti numbers allow for families with unbounded Helly number.
Our proofs combine homological non-embeddability results with a Ramsey-based
approach to build, given an arbitrary simplicial complex , some well-behaved
chain map .Comment: 29 pages, 8 figure
Analogues of the central point theorem for families with -intersection property in
In this paper we consider families of compact convex sets in
such that any subfamily of size at most has a nonempty intersection. We
prove some analogues of the central point theorem and Tverberg's theorem for
such families
Convexity in partial cubes: the hull number
We prove that the combinatorial optimization problem of determining the hull
number of a partial cube is NP-complete. This makes partial cubes the minimal
graph class for which NP-completeness of this problem is known and improves
some earlier results in the literature.
On the other hand we provide a polynomial-time algorithm to determine the
hull number of planar partial cube quadrangulations.
Instances of the hull number problem for partial cubes described include
poset dimension and hitting sets for interiors of curves in the plane.
To obtain the above results, we investigate convexity in partial cubes and
characterize these graphs in terms of their lattice of convex subgraphs,
improving a theorem of Handa. Furthermore we provide a topological
representation theorem for planar partial cubes, generalizing a result of
Fukuda and Handa about rank three oriented matroids.Comment: 19 pages, 4 figure
Mock galaxy redshift catalogues from simulations: implications for Pan-STARRS1
We describe a method for constructing mock galaxy catalogues which are well
suited for use in conjunction with large photometric surveys. We use the
semi-analytic galaxy formation model of Bower et al. implemented in the
Millennium simulation. We apply our method to the specific case of the surveys
soon to commence with PS1, the first of 4 telescopes planned for the Pan-STARRS
system. PS1 has 5 photometric bands (grizy), and will carry out an all-sky 3pi
survey and a medium deep survey (MDS) over 84 sq.deg. We calculate the expected
magnitude limits for extended sources in the two surveys. We find that, after 3
years, the 3pi survey will have detected over 10^8 galaxies in all 5 bands, 10
million of which will lie at redshift z>0.9, while the MDS will have detected
over 10^7 galaxies with 0.5 million lying at z>2. These numbers at least double
if detection in the shallowest band, y is not required. We then evaluate the
accuracy of photometric redshifts estimated using an off-the-shelf photo-z
code. With the grizy bands alone it is possible to achieve an accuracy in the
3pi survey of Delta z/(1+z)~0.06 for 0.25<z<0.8, which could be reduced by
about 15% using near infrared photometry from the UKIDDS survey, but would
increase by about 25% for the deeper sample without the y band photometry. For
the MDS an accuracy of Delta z/(1+z)~0.05 is achievable for 0.02<z<1.5 using
grizy. A dramatic improvement in accuracy is possible by selecting only red
galaxies. In this case, Delta z/(1+z)~0.02-0.04 is achievable for ~100 million
galaxies at 0.4<z<1.1 in the 3pi survey and for 30 million galaxies in the MDS
at 0.4<z<2. We investigate the effect of using photo-z in the estimate of the
baryonic acoustic oscillation scale. We find that PS1 will achieve a similar
accuracy in this estimate as a spectroscopic survey of 20 million galaxies.Comment: 23 pages, 18 figures, accepted by MNRA
Subtidal macrozoobenthos communities from northern Chile during and post El Niño 1997–1998
Despite a large amount of climatic and oceanographic information dealing with the recurring climate phenomenon El Niño (EN) and its well known impact on diversity of marine benthic communities, most published data are rather descriptive and consequently our understanding of the underlying mechanisms and processes that drive community structure during EN are still very scarce. In this study, we address two questions on the effects of EN on macrozoobenthic communities: (1) how does EN affect species diversity of the communities in northern Chile? and (2) is EN a phenomenon that restarts community assembling processes by affecting species interactions in northern Chile? To answer these questions, we compared species diversity and co-occurrence patterns of soft-bottoms macrozoobenthos communities from the continental shelf off northern Chile during (March 1998) and after (September 1998) the strong EN event 1997–1998. The methods used varied from species diversity and species co-occurrence analyses to multivariate ordination methods.
Our results indicate that EN positively affects diversity of macrozoobenthos communities in the study area, increasing the species richness and diversity and decreasing the species dominance. EN represents a strong disturbance that affects species interactions that rule the species assembling processes in shallow-water, sea-bottom environments
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