ppxscal/embedding_network huggingface dataset:
New architectural parameters derived from micro-MRI for the prediction of trabecular bone strength
Authors: Felix W. Wehrli, Scott N. Hwang, Hee Kwon Song
Venue: Technology and Health Care (1998)

This article reviews recent progress in magnetic resonance microimaging of cancellous bone in vitro and in vivo from the perspective of the authors laboratory. It is shown that in particular in vivo the key technical prerequisites to satisfy are: (i) achieving sufficient signal-to-noise ratio (SNR) to allow for adequate spatial resolution; (ii) the image processing algorithms have to be robust enough to provide accurate structural information in the limited spatial resolution regime, i.e., in the presence of inevitable partial volume blurring and noise. The practical lower limit of voxel size in vivo was found to be about 6\times 10^{-3} mm3 in the radius, and about 10^{-4} mm3 for small specimens in vitro with state-of-the-art equipment and scan times of 10 and 30 minutes, resp., and {\rm SNR}\sim 10. Finally, data are presented highlighting the potential of these methods for predicting the bones elastic modulus in vitro and fracture risk in vivo.
On the Asymptotic and Numerical Solution of Linear Ordinary Differential Equations
Authors: A. B. Olde Daalhuis, F. W. J. Olver
Venue: SIAM Review (1998)

An investigation is made of the nature of asymptotic solutions of homogeneous linear differential equations of arbitrary order in the neighborhood of a singularity of unit rank. We introduce a classification of the solutions into two types, explicit and implicit. For the former there exists a sector on which the solution is dominated by all independent solutions as the singularity is approached. No such sector exists for implicit solutions. In consequence, the two types of solution have different uniqueness properties. Another difference is that error bounds for the asymptotic expansions of explicit solutions are generally stronger than those for implicit solutions.We also investigate the computation of the solutions by numerical integration of the differential equation. It is shown that it is the exception rather than the rule for the integration process to be stable, particularly so for implicit solutions. To overcome these instabilities we develop boundary-value methods, complete with error analysis.Numerical examples illustrate the computation of both explicit and implicit solutions, and also the associated Stokes multipliers.
Applications of the polynomial s-power basis in geometry processing
Authors: Javier Sánchez-Reyes
Venue: ACM Transactions on Graphics (TOG) (2000)

We propose a unified methodology to tackle geometry processing operations admitting explicit algebraic expressions. This new approach is based on representing and manipulating polynomials algebraically in a recently basis, the symmetric analogue of the power form (s-power basis for brevity), so called because it is associated with a &ldquo;Hermite two-point expansion&rdquo; instead of a Taylor expansion. Given the expression of a polynomial in this basis over the unit interval u &egr;[0, 1], degree reduction is trivally obtained by truncation, which yields the He many terms as desired of the corresponding Hermite interpolant and build &ldquo;s-power series,&rdquo; akin to Taylor series. Applications include computing integral approximations of rational polynomials, or approximations of offset curves.
Style machines
Authors: Matthew Brand, Aaron Hertzmann
Venue: Proceedings of the 27th annual conference on Computer graphics and interactive techniques (2000)

We approach the problem of stylistic motion synthesis by learning motion patterns from a highly varied set of motion capture sequences. Each sequence may have a distinct choreography, performed in a distinct sytle. Learning identifies common choreographic elements across sequences, the different styles in which each element is performed, and a small number of stylistic degrees of freedom which span the many variations in the dataset. The learned model can synthesize novel motion data in any interpolation or extrapolation of styles. For example, it can convert novice ballet motions into the more graceful modern dance of an expert. The model can also be driven by video, by scripts or even by noise to generate new choreography and synthesize virtual motion-capture in many styles.
A scalable front-end architecture for fast instruction delivery
Authors: Glenn Reinman, Todd Austin, Brad Calder
Venue: ACM SIGARCH Computer Architecture News (1999)

In the pursuit of instruction-level parallelism, significant demands are placed on a processor's instruction delivery mechanism. Delivering the performance necessary to meet future processor execution targets requires that the performance of the instruction delivery mechanism scale with the execution core. Attaining these targets is a challenging task due to I-cache misses, branch mispredictions, and taken branches in the instruction stream. To further complicate matters, a VLSI interconnect scaling trend is materializing that further limits the performance of front-end designs in future generation process technologies.To counter these challenges, we present a fetch architecture that permits a faster cycle time than previous designs and scales better with future process technologies. Our design, called the Fetch Target Buffer, is a multi-level fetch block-oriented predictor. We decouple the FTB from the instruction fetch and decode pipelines to afford it the fastest clock possible. Through cycle-based simulation and circuit-level delay analysis, we find that our multi-level FTB design is capable of delivering instructions 25% faster than the best single-level BTB-based pipeline configuration. Moreover, we show that our design scales better to future process technologies than traditional single-level designs.
Long-Time-Step Methods for Oscillatory Differential Equations
Authors: B. García-Archilla, J. M. Sanz-Serna, R. D. Skeel
Venue: SIAM Journal on Scientific Computing (1999)

Considered are numerical integration schemes for nondissipative dynamical systems in which multiple time scales are present. It is assumed that one can do an explicit separation of the RHS "forces" into fast forces and slow forces such that (i) the fast forces contain the high frequency part of the solution, (ii) the fast forces are conservative, and (iii) the reduced problem consisting only of the fast forces can be integrated much more cheaply than the full problem. The fast forces are allowed to have low frequency components. Particular applications for which the schemes are intended include N-body problems (for which most of the forces are slow) and nonlinear wave phenomena (for which the fast forces can be propagated by spectral methods). The assumption of cheap integration of fast forces implies that the overall cost of integration is primarily determined by the step size used to sample the slow forces. A long-time-step method is one in which this step size exceeds half the period of the fastest normal mode present in the full system. An existing method that comes close to qualifying is the "impulse" method, also known as Verlet-I and r-RESPA. It is shown that it might fail, though, for a couple of reasons. First, it suffers a serious loss of accuracy if the step size is near a multiple of the period of a normal mode, and, second, it is unstable if the step size is near a multiple of half the period of a normal mode. Proposed in this paper is a "mollified" impulse method having an error bound that is independent of the frequency of the fast forces. It is also shown to possess superior stability properties. Theoretical results are supplemented by numerical experiments. The method is efficient and reasonably easy to implement.
Asymptotic-Induced Domain Decomposition Methods for Kinetic and Drift Diffusion Semiconductor Equations
Authors: Axel Klar
Venue: SIAM Journal on Scientific Computing (1998)

This paper deals with domain decomposition methods for kinetic and drift diffusion semiconductor equations. In particular accurate coupling conditions at the interface between the kinetic and drift diffusion domain are given. The cases of slight and strong nonequilibrium situations at the interface are considered and numerical examples are shown.
Evolutionary features of genomes as disclosed by comparative analysis of complete genome sequences (abstract only)
Authors: Takashi Gojobori, T. Daniel Andrews, Takeshi Itoh
Venue: Proceedings of the fourth annual international conference on Computational molecular biology (2000)

Our comparisons of complete genome sequences revealed that the genome structures have been extensively shuffled among eubacteria, particularly when the orders of orthologous genes were examined. Moreover, archaebacterial and eukaryotic genome structures were found to be unstable, too, as were the cases of eubacteria. We then turned our attention to operon structures, which were expected to be well conserved during evolution because of their regulatory importance. Surprisingly enough, however, we found that even within operons, gene orders have not been conserved, with exception to only a few cases such as ribosomal operons. When we reconstructed the ancestral genome structure of eubacteria and archaebacteria, and examined the relative instability of the genome structures among eubacteria, we found that there were differences in the degree of the genome instability among the examined species. The genome instability appears to be correlated with the number of insertion sequences. Interestingly enough, the intensity of the intrastrand bias of nucleotide composition (G-C skew) was found to be affected by the genome instability, implying that accumulation of strand-specific mutations depends heavily upon the stability of a genome. These findings imply that the gene orders have not been essential for survival of microbes in long-term evolution, and that the evolutionary instability of the genome structures is an intrinsic nature common to eubacteria, archaebacteria and eukaryotes. For eukaryotic genomes, we found that a lot of gene fusion events might have happened in the early evolution of eukaryotes so as to compensate for the loss of bacterial operon structures. The evolutionary instability of the genome structures can be one of the most important factors in understanding the evolutionary processes of the genome evolution.
Urp: a luminous-tangible workbench for urban planning and design
Authors: John Underkoffler, Hiroshi Ishii
Venue: Proceedings of the SIGCHI conference on Human factors in computing systems: the CHI is the limit (1999)

We introduce a system for urban planning - called Urp -that integrates functions addressing a broad range of the fields concerns into a single, physically based workbench setting. The I/O Bulb infrastructure on which the application is based allows physical architectural models placed on an ordinary table surface to cast shadows accurate for arbitrary times of day; to throw reflections off glass facade surfaces; to affect a real-time and visually coincident simulation of pedestrian-level windflow; and so on. We then use comparisons among Urp and several earlier I/O Bulb applications as the basis for an understanding of luminous-tangible interactions, which result whenever an interface distributes meaning and functionality between physical objects and visual information projectively coupled to those objects. Finally, we briefly discuss two issues common to all such systems, offering them as informal thought-tools for the design and analysis of luminous-tangible interfaces.
Some remarks on variable independence, closure, and orthographic dimension in constraint databases
Authors: Leonid Libkin
Venue: ACM SIGMOD Record (1999)

The notion of variable independence was introduced by Chomicki, Goldin, and Kuper in their PODS'96 paper as a means of adding a limited form of aggregation to constraint query languages while retaining the closure property. Later, Grumbach, Rigoux and Segoufin showed in their ICDT'99 paper that variable independence and a related notion of orthographic dimension are useful tools for optimizing constraint queries. However, several results in those papers are incorrect as stated. As the notions of variable independence and orthographic dimension appear to be important for implementing constraint database prototypes, I explain in this short note the problems with the above mentioned papers and outline a solution for aggregate closure.
Performance evaluation of packet data services over cellular voice networks
Authors: Young Yong Kim, San-qi Li
Venue: Wireless Networks (1999)

In this paper we develop a Markov chain modeling framework for throughput/delay analysis of data services over cellular voice networks, using the dynamic channel stealing method. Effective approximation techniques are also proposed and verified for simplification of modeling analysis. Our study identifies the average voice call holding time as the dominant factor to affect data delay performance. Especially in heavy load conditions, namely when the number of free voice channels becomes momentarily less, the data users will experience large network access delay in the range of several minutes or longer on average. The study also reveals that the data delay performance deteriorates as the number of voice channels increases at a fixed voice call blocking probability, due to increased voice trunking efficiency. We also examine the data performance improvement by using the priority data access scheme and speech silence detection technique.
A Second Degree Method for Nonlinear Inverse Problems
Authors: F. Hettlich, W. Rundell
Venue: SIAM Journal on Numerical Analysis (1999)

The paper is concerned with the solution of nonlinear ill-posed problems by methods that utilize the second derivative. A general predictor-corrector approach is developed; one which avoids solving quadratic equations during the iteration process. Combining regularization of each iteration step with an adequate stopping condition leads to a general regularization scheme for nonlinear equations. Possible implementations and discussion of the performance of this method are illustrated by applications to some well-known inverse problems.
Internet service performance failure detection
Authors: Amy Ward, Peter Glynn, Kathy Richardson
Venue: ACM SIGMETRICS Performance Evaluation Review (1998)

The increasing complexity of computer networks and our increasing dependence on them means enforcing reliability requirements is both more challenging and more critical. The expansion of network services to include both traditional interconnect services and user-oriented services such as the web and email has guaranteed both the increased complexity of networks and the increased importance of their performance. The first step toward increasing reliability is early detection of network performance failures. Here we consider the applicability of statistical model frameworks under the most general assumptions possible. Using measurements from corporate proxy servers, we test the framework against real world failures. The results of these experiments show we can detect failures, but with some tradeoff questions. The pull is in the warning time: either we miss early warning signs or we report some false warnings. Finally, we offer insight into the problem of failure diagnosis.
Automatic discovery of language models for text databases
Authors: Jamie Callan, Margaret Connell, Aiqun Du
Venue: ACM SIGMOD Record (1999)

The proliferation of text databases within large organizations and on the Internet makes it difficult for a person to know which databases to search. Given language models that describe the contents of each database, a database selection algorithm such as GIOSS can provide assistance by automatically selecting appropriate databases for an information need. Current practice is that each database provides its language model upon request, but this cooperative approach has important limitations. This paper demonstrates that cooperation is not required. Instead, the database selection service can construct its own language models by sampling database contents via the normal process of running queries and retrieving documents. Although random sampling is not possible, it can be approximated with carefully selected queries. This sampling approach avoids the limitations that characterize the cooperative approach, and also enables additional capabilities. Experimental results demonstrate that accurate language models can be learned from a relatively small number of queries and documents.
A Loop Transformation Algorithm for Communication Overlapping
Authors: Kazuaki Ishizaki, Hideaki Komatsu, Toshio Nakatani
Venue: International Journal of Parallel Programming (2000)

Overlapping communication with computation is a well-known approach to improving performance. Previous research has focused on optimizations performed by the programmer. This paper presents a compiler algorithm that automatically determines the appropriate loop indices of a given nested loop and applies loop interchange and tiling in order to overlap communication with computation. The algorithm avoids generating redundant communication by providing a framework for combining information on data dependence, communication, and reuse. It also describes a method of generating messages to exchange data between processors for tiled loops on distributed memory machines. The algorithm has been implemented in our High Performance Fortran (HPF) compiler, and experimental results have shown its effectiveness on distributed memory machines, such as the RISC System/6000 Scalable POWERparallel System. This paper also discusses the architectural problems of efficient optimization.
Finite Element Methods of Least-Squares Type
Authors: Pavel B. Bochev, Max D. Gunzburger
Venue: SIAM Review (1998)

We consider the application of least-squares variational principles to the numerical solution of partial differential equations. Our main focus is on the development of least-squares finite element methods for elliptic boundary value problems arising in fields such as fluid flows, linear elasticity, and convection-diffusion. For many of these problems, least-squares principles offer numerous theoretical and computational advantages in the algorithmic design and implementation of corresponding finite element methods that are not present in standard Galerkin discretizations. Most notably, the use of least-squares principles leads to symmetric and positive definite algebraic problems and allows us to circumvent stability conditions such as the inf-sup condition arising in mixed methods for the Stokes and Navier--Stokes equations. As a result, application of least-squares principles has led to the development of robust and efficient finite element methods for a large class of problems of practical importance.
Choices in server-side programming: a comparative programming exercise
Authors: Robert G. Brown, Willi Hahn
Venue: Proceedings of the conference on APL '99 : On track to the 21st century: On track to the 21st century (1999)

One of the fastest growing and changing fields for software developers is in writing applications that are used across the "World Wide Web", which is in turn a client-server system that runs on the Internet. Servers, known by name, can be accessed over the Internet, and a protocol, known as HTTP (Hypertext Transfer Protocol) is used to send requests to servers for text, images (still and moving), audio, and other information. A very large amount of business will be conducted this way, now and in the future, having grown from almost nothing only 5 years ago. Application development on the Web is largely a matter of writing programs that are executed by the server, and we're going to focus our attention on two programming and operating environments that can be used to deliver server-side software.We would like to show how APL can be used to develop programs that run on the server, and we will contrast it with another means of developing and delivering server-side programs. It is not our goal to deliver any judgment about whether or not one system is "better" than the other (we believe that any such statement would be simplistic to the point of being misleading); we intend only to share the results of our experience, help the reader understand what technologies that are available, and assist in making an informed choice if participation in a project of this nature is part of what the reader does.
Fast Approximation Algorithms on Maxcut, k-Coloring, and k-Color Ordering for VLSI Applications
Authors: Jun-Dong Cho, Salil Raje, Majid Sarrafzadeh
Venue: IEEE Transactions on Computers (1998)

There are a number of VLSI problems that have a common structure. We investigate such a structure that leads to a unified approach for three independent VLSI layout problems: partitioning, placement, and via minimization. Along the line, we first propose a linear-time approximation algorithm on maxcut and two closely related problems: k-coloring and maximal k-color ordering problem. The k-coloring is a generalization of the maxcut and the maximal k-color ordering is a generalization of the k-coloring. For a graph G with e edges and n vertices, our maxcut approximation algorithm runs in O(e + n) sequential time yielding a node-balanced maxcut with size at least (w(E) + w(E)/n)/2, improving the time complexity of O(e log e) known before. Building on the proposed maxcut technique and employing a height-balanced binary decomposition, we devise an O((e + n)log k) time algorithm for the k-coloring problem which always finds a k-partition of vertices such that the number of bad (or "defected") edges does not exceed (w(E)/k)((n$-$ 1)/n)log k, thus improving both the time complexity O(enk) and the bound e/k known before. The other related problem is the maximal k-color ordering problem that has been an open problem [16]. We show the problem is NP-complete, then present an approximation algorithm building on our k-coloring structure. A performance bound on maximal k-color ordering cost, 2kw(E)/3 is attained in O(ek) time. The solution quality of this algorithm is also tested experimentally and found to be effective.
Learning and Design of Principal Curves
Authors: Balázs Kégl, Adam Krzyzak, Tamás Linder, Kenneth Zeger
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (2000)

Principal curves have been defined as ¿self-consistent¿ smooth curves which pass through the ¿middle¿ of a d-dimensional probability distribution or data cloud. They give a summary of the data and also serve as an efficient feature extraction tool. We take a new approach by defining principal curves as continuous curves of a given length which minimize the expected squared distance between the curve and points of the space randomly chosen according to a given distribution. The new definition makes it possible to theoretically analyze principal curve learning from training data and it also leads to a new practical construction. Our theoretical learning scheme chooses a curve from a class of polygonal lines with $k$ segments and with a given total length to minimize the average squared distance over $n$ training points drawn independently. Convergence properties of this learning scheme are analyzed and a practical version of this theoretical algorithm is implemented. In each iteration of the algorithm, a new vertex is added to the polygonal line and the positions of the vertices are updated so that they minimize a penalized squared distance criterion. Simulation results demonstrate that the new algorithm compares favorably with previous methods, both in terms of performance and computational complexity, and is more robust to varying data models.