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	Differential geometry and topology Article, Differentialgeometryandtopology Information (Site not responding. Last check: 2007-10-27)
		The apparatus of differential geometry is that of calculus on manifolds: this includes the study of manifolds, tangent bundles, cotangent bundles, differential forms, exterior derivatives, integrals of p-forms over p-dimensional submanifolds and Stokes' theorem, wedgeproducts, and Lie derivatives.
		One definition of the tangent space is as the dualspace to the linear space of all functions which are zero at that point, divided by the space of functions which are zero andhave a first derivative of zero at that point.
		A vector field is a function from a manifold to the disjoint union ofits tangent spaces (this union is itself a manifold known as the tangentbundle), such that at each point, the value is an element of the tangent space at that point.
	www.anoca.org /space/manifold/differential_geometry_and_topology.html (920 words)

	Encyclopedia :: encyclopedia : Cotangent (Site not responding. Last check: 2007-10-27)
		In differential geometry, the cotangent bundle of a manifold is the vector bundle of all the cotangent spaces at every point in the manifold.
		All cotangent spaces have the same dimension, equal to the dimension of the manifold.
		All the cotangent spaces of a manifold can be "glued together" to form a new differentiable manifold of twice the dimension, the cotangent bundle of the manifold.
	www.hallencyclopedia.com /Cotangent (1210 words)

	Lefebvre Absolute Abstract Differential Space, Bo Grönlund 1993
		Absolute space is the opposite of the space of a secular life, that is freed from politico-religious space, from the space of signs of death and of non-body.
		Abstract space (the space produced by capitalism) means the disintegration and self-destruction of the town and of urban space.
		Abstract space is that space where the tendency to homogenisation exercises its pressure and its repression with the means at its disposal: a semantic void abolishes former meanings (without, for all that, standing in the way of the growing complexity of the world and its multiplicity of messages, codes and operations.
	hjem.get2net.dk /gronlund/Absolute_space_etc.html (7630 words)

	Space Shuttle program - Wikipedia, the free encyclopedia
		According to the Vision for Space Exploration, use of the Space Shuttle will be focused on completing assembly of the ISS in 2010 (more specifically, the construction completion of the ISS), after which it will be replaced by the Crew Exploration Vehicle (CEV).
		It was delivered to Kennedy Space Center on March 25, 1979, and was first launched on April 12, 1981—the 20th anniversary of Yuri Gagarin's space flight—with a crew of two.
		Since the Space Shuttle Columbia disaster in 2003, the ISS has been operating on a skeleton crew of two and is currently being serviced primarily by Russian space vehicles.
	en.wikipedia.org /wiki/Space_shuttle (7397 words)

	Diffeology - Wikipedia, the free encyclopedia
		The concept was first introduced by Kuo Tsaï Chen in the 1970s, under the name "differential spaces", then rediscovered by Souriau in the 1980s and later refined by many people.
		If Y is a subset of the diffeological space X, then Y is itself a diffeological space in a natural way: the plots of Y are those plots of X whose images are subsets of Y.
		The relationship between smooth manifolds and diffeological spaces is analogous to the relationship between topological manifolds and topological spaces.
	en.wikipedia.org /wiki/Differential_space (661 words)

	1-Differential GPS Explained
		Differential correction techniques are used to enhance the quality of location data gathered using global positioning system (GPS) receivers.
		Differential correction can be applied in real-time directly in the field or when postprocessing data in the office.
		The underlying premise of differential GPS (DGPS) requires that a GPS receiver, known as the base station, be set up on a precisely known location.
	www.esri.com /news/arcuser/0103/differential1of2.html (930 words)

	Differentials
		Spaces of differentials of function fields can be created and the differentials belonging to them manipulated.
		A vector space and the isomorphism from this space to the space of differentials of the first kind (holomorphic differentials) of F/k.
		The operations on differentials are inherited from the vector space structure of the space of differentials.
	www.umich.edu /~gpcc/scs/magma/text697.htm (782 words)

	Apparatus and method for receiving differential space-time block code invention
		The apparatus for receiving a differential STBC includes a detector for detecting a symbol from a received differential STBC using a trellis diagram and a Viterbi algorithm, a deinterleaver for deinterleaving the detected symbol, and a decoder for decoding a signal deinterleaved by the deinterleaver.
		When a differential signal is encoded, the improved differential STBC schemes normalize a current symbol using the power of a previously transmitted symbol, thereby allowing decoding at a reception end even when a symbol amplitude changes.
		However, unlike general differential STBC schemes, in the improved differential STBC schemes, the reception end should be informed of a squared sum of channel coefficients, i.e., a value corresponding to the power of the channel coefficients.
	www.freshpatents.com /Apparatus-and-method-for-receiving-differential-space-time-block-code-dt20060706ptan20060146964.php (1622 words)

	Why Differential Forms? FS_PB
		The importance of the Cartan concept resides with the fact that differential forms are well defined objects with respect to Functional Substitution and the PullBack (FS_PB for short) relative to C1 differentiable maps from an initial variety of variables to a final state or variety of variables.
		The coefficients of differential forms are either anti-symmetric co-variant tensors, or tensor densities, the most useful of field structures used to describe physical systems.
		Construct a differential form on (meaning in terms of the variables of) the final state, and then by functional substitution and use of the Jacobian map construct the well defined functional form of the tensor coefficients of the differential form on the initial state.
	www.uh.edu /~rkiehn/ed3/ed3fre1.htm (440 words)

	Urbanity & Aesthetics on Lefebvre, Bo Grönlund
		To human beings it is social space that is the crucial space, and both natural space and mental space have to be seen in relation to social space.
		I read it mainly as the unconscious, non-verbalised, direct relation to space and the space that humans express themselves in, conscious or not, while conceived space is the constructed space for which people in power (including planners, many architects, scientists, etc.) is mainly responsible.
		To me 'Lived Space' and 'Differential Space' are essential dimensions that have to be related to the earlier mentioned concept of 'the urban', 'urban centrality' or 'urbanity' to develop it further, not the least as we might be entering a new epoque with the advent of 'The Information Age'.....
	hjem.get2net.dk /gronlund/Lefebvreindlaeg_21_3_97v2.html (1535 words)

	Noncoherent Receivers for Differential Space-Time Modulation
		It is shown that the performance of the previously proposed conventional differential detection (DD) receiver is satisfactory only for very slow flat fading channels.
		R. Schober, W. Gerstacker and J. Huber, "Decision-feedback differential detection of MDPSK for flat Rayleigh fading channels", IEEE Trans.
		L. Lampe and R. Schober, "Iterative decision-feedback differential demodulation of bit-interleaved coded MDPSK for flat Rayleigh fading channels", IEEE Trans.
	www.comsoc.org /comm/private/2002/may/768_50comm05-schober.html (854 words)

	Grassmannian
		In mathematics, a Grassmannian is the space of all k-dimensional subspaces of an n-dimensional vector space V, often denoted G
		a topological space, homogeneous space, differential manifold or algebraic variety), and notice that up to appropriate isomorphisms, we have a well-defined geometric object for the given pair (n,k).
		Supposing first that K is the real number or complex number field, the easiest approach to Grassmannians is probably to consider them as homogeneous spaces.
	www.brainyencyclopedia.com /encyclopedia/g/gr/grassmannian.html (604 words)

	[No title]
		For case b), with unitary space time codes, the objective is to maximize the diversity gain which is the rank of the matrix in (10) and to maximize the coding advantage which is given in (10).
		A simple suboptimal differential demodulator that estimates the message matrix using only the last two received blocks is derived.
		However, in Section III-B, in the derivation of the differential demodulator, it is assumed that the channel is constant for all the observations.
	www.ece.osu.edu /ips/links/hughes.txt (794 words)

	Vector (spatial) (Site not responding. Last check: 2007-10-27)
		Alternatively, it can be defined in a coordinate-free fashion via a tangent space of a three-dimensional manifold in the language of differential geometry.
		A spatial vector is a special case of a tensor and is also analogous to a four-vector in relativity (and is sometimes therefore called a three-vector in reference to the three spatial dimensions, although this term also has another meaning for p-vectors of differential geometry).
		In differential geometry, the term vector usually refers to quantities that are closely related to tangent spaces of a differentiable manifold (assumed to be three-dimensional and equipped with a positive definite Riemannian metric).
	www.freedownloadsoft.com /info/vector-spatial-.html (1829 words)

	Differential Space-Time Modulation Schemes (ResearchIndex) (Site not responding. Last check: 2007-10-27)
		Abstract: Differential space-time modulation (DSTM) schemes were recently proposed to fully exploit the receive and transmit antenna diversities without the need for channel state information.
		DSTM is attractive in fast flat fading channels since accurate channel estimation is difficult to achieve.
		44 A differential detection scheme for transmit diversity (context) - Tarokh, Jafarkhani - 2000
	citeseer.ist.psu.edu /642582.html (319 words)

	Cayley Differential Unitary Space-Time Codes (Site not responding. Last check: 2007-10-27)
		Abstract: One method for communicating with multiple antennas is to encode the transmitted data differentially using unitary matrices at the transmitter, and to decode differentially without knowing the channel coefficients at the receiver.
		Since channel knowledge is not required at the receiver, differential schemes are ideal for use on wireless links where channel tracking is undesirable or infeasible, either because of rapid changes in the channel characteristics or because of limited system resources.
		The codes are named for their use of the Cayley transform, which maps the highly nonlinear Stiefel manifold of unitary matrices to the linear space of skew-Hermitian matrices.
	mars.bell-labs.com /papers/cayley (245 words)

	Differential Unitary Space-Time Modulation (Site not responding. Last check: 2007-10-27)
		Abstract: We present a framework for differential modulation with multiple antennas across a continuously fading channel, where neither the transmitter nor the receiver knows the fading coefficients.
		The framework can be seen as a natural extension of standard differential phase shift keying (DPSK) commonly used in single-antenna unknown-channel systems.
		As a special case, we introduce a class of diagonal signals where only one antenna is active at any time, and show how these signals may be used to achieve full transmitter diversity and low probability of error.
	cm.bell-labs.com /who/wim/papers/dust (287 words)

	LI Kwok Hung
		C Ling, K H Li and Alex C Kot, "Noncoherent Sequence Detection of Differential Space-Time Modulation," I EEE Transactions on Information Theory, USA, vol.
		C Ling, K H Li and Alex C Kot, "On Decision-Feedback Detection of Differential Space-Time Modulation in Continuous Fading," I EEE Transactions on Communications, USA, Vol.
		C Ling, W H Mow, K H Li and Alex C Kot, "Multiple-Antenna Differential Lattice Decoding," I EEE Journal on Selected Areas in Communications, USA, Vol.
	www.ntu.edu.sg /eee/eee5/cv/ekhli.htm (379 words)

	Dwyer Instruments - Space-saving differential pressure switch gauge
		THE Series MP Mini-Photohelic differential pressure switch gauge from Dwyer Instruments combines the Minihelic 11 differential pressure gauge with two SPDT switching set points.
		It is designed to measure and control positive, negative or differential pressures consisting of non-combustible and non-corrosive gases.
		Switching status is visible by LED indicators located on the front and the rear of the gauge.
	www.ferret.com.au /articles/6F/0C01A86F.asp (154 words)

	Comet Seminars: Differential Unitary Space-Time Modulation (Site not responding. Last check: 2007-10-27)
		We propose a generalization of standard differential phase-shift keying (DPSK) to multiple-antenna wireless communication.
		DPSK is commonly used for single-antenna mobile wireless communication on an unknown rapidly-fading channel.
		Using multiple transmitter antennas at the basestation, we propose a differential modulation scheme that promises large performance and diversity gains over standard DPSK when communicating with a mobile.
	www.comet.columbia.edu /activities/seminars/fall99/abs-hochwald.html (74 words)

	Techniques for High Altitude Platform System Capacity Enhancement (Site not responding. Last check: 2007-10-27)
		Whilst this may be feasible when the channel is quasi-static and flat, it is difficult and costly to estimate channel properties accurately for fast fading channels when CSI varies very frequently.
		It is much more appropriate to design modulation and coding schemes that do not require estimation of the channel at the transmitter or receiver by using differential coding techniques.
		A primary intention of the project is to find ways of generating more efficient modulation and coding techniques to further improve system performance and reduced computational complexity.
	www.elec.york.ac.uk /comms/projects/lingyangsong.html (143 words)

	Publications of Lutz Lampe
		Iterative Decision-Feedback Differential Demodulation of Bit-Interleaved Coded MDPSK for Flat Rayleigh Fading Channels.
		Channel Capacity of Fading Channels for Differentially Encoded Transmission.
		Differential Phase Shift Keying with Constellation Expansion Diversity.
	www.ece.ubc.ca /~lampe/publicat.html (1600 words)

	[No title] (Site not responding. Last check: 2007-10-27)
		It can provide the maximal Diversity product and diversity sum for some values of L, and outperform other existent code at various values of L. Thus it is chosen as the constellation for the following scheme.
		The problem of differential space-time modulation can, in some sense, be considered as the higher-dimension counterpart of DPSK.
		On the other hand, if part of the information is embedded differentially in the change of the levels, the further away the layers are set apart and the smaller the inner layer energy is, the less error it will incur in the recovery of this part of the information.
	www.eecis.udel.edu /~hzhang/DataCompression/Presentation04172001.ppt (1473 words)

	Space Weather Data and Products
		See the Information page for notices, copyright information, SEC credit statement, troubleshooting tips, and a glossary of terms.
		Also see Non-SEC Sources of Space Weather Data.
		Daily Space Weather Indices ---10cm solar radio flux; SWO sunspot number, area, and new regions; GOES x-ray background flux; and x-ray and optical flare counts, GOES proton and electron flux; neutron monitor % of background; Fredericksburg, Boulder, College, and est.
	www.sec.noaa.gov /Data (359 words)

	Receiver Concepts for Differential Space-Time (ResearchIndex) (Site not responding. Last check: 2007-10-27)
		Abstract: This paper addresses receiver structures for unitary differential space-time modulation schemes, where channel coefficients are modelled as complex Gaussian-distributed random variables and where only second-order statistics about channel coefficients are available at the receiver.
		Specifically, we derive the maximum-likelihood (ML) receiver for flat timevarying channels.
		68 Differential space-time modulation (context) - Hughes - 2000
	citeseer.ist.psu.edu /664866.html (298 words)

	- free online file hosting and storage directory - All the Free Space
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	www.all-the-free-space.com (634 words)

	Citebase - Realization of the Three-dimensional Quantum Euclidean Space by Differential Operators
		Realization of the Three-dimensional Quantum Euclidean Space by Differential Operators
		The three-dimensional quantum Euclidean space is an example of a non-commutative space that is obtained from Euclidean space by q-deformation.
		In this paper it is shown, that this algebra can be realized by differential operators acting on C
	citebase.eprints.org /cgi-bin/citations?id=oai:arXiv.org:math/0006179 (182 words)

	Spacetransportation.org Science Directory
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