27097783
Four new BIBDs with block size seven
Abstract Hanani (1989) has proved that there exists a B (7, 3; v ) for all positive integers v ≡ 1 or 7 (mod 14) with 7 possible exceptions. We show that such designs exist for 4 of these values.
12880164
Packings and coverings of the complete directed multigraph with 3- and 4-circuits
Abstract Let λDK v denote the complete directed multigraph with v vertices, where any two distinct vertices x and y are joined by λ arcs ( x , y ) and λ arcs ( y , x ). By a k -circuit we mean a directed cycle of length k . In this paper, we consider the problem of finding maximal packings and minimal coverings of λDK v with k -circuits. In particular, we completely determine the packing number and covering number for the cases k = 3 and 4.
29194002
On the existence of perfect Mendelsohn designs with k = 7 and lambda even
Abstract Let v, k and λ be positive integers. A ( v, k , λ)- Mendelsohn design (briefly ( v, k , λ)-MD) is a pair ( X ,B) where X is a v -set (of points ) andBis a collection of cyclically ordered k -subsets of X (called blocks ) such that every ordered pair of points of X are consecutive in exactly λ blocks of B. A set of k distinct elements { a 1 , a 2 , ..., a k } is said to be cyclically ordered by a 1 a 2 a k a 1 and the pair a i , a i + t are said to be t -part in a cyclic k -tuple ( a 1 , a 2 ,..., a k ) where i + t is taken modulo k . If for all t = 1, 2,..., k − 1, every ordered pair of points of X are t -apart in exactly λ blocks of B, then the ( v, k , λ)-MD is called perfect and is denoted briefly by ( v, k , λ)-PMD. A necessary condition for the existence of a ( v, k , λ)-PMD is λ v ( v −1)≡0 (mod k ). In this paper, we shall be concerned mostly with the case k = 7 and λ even. It will be shown that the necessary condition for the existence of a v , 7, λ)-PMD, namely λ v ( v −1)≡0 (mod 7), is also sufficient for all even λ ⪖ 16, with at most 29 possible exceptions for the pair ( v , λ) where λ is even and λ v ≡0 or 1 (mod 7) for the existence of a ( v , 7, 1)-PMD is also sufficient for all v ⪖ 421 with at most 40 possible exceptions below this value, which improves the earlier results.
18873920
Signal Sets From Functions With Optimum Nonlinearity
Signal sets with the best correlation property are desirable in code-division multiple-access (CDMA) systems. In this paper, the construction of Wootters and Fields for mutually unbiased bases is extended into a generic construction of signal sets using planar functions. Then, specific classes of planar functions and almost bent functions are employed to obtain (q2+q,q) signal sets. The signal sets derived from planar functions are optimal with respect to the Levenstein bound, and those obtained from almost bent functions nearly meet the Levenstein bound. The signal sets constructed in this paper could have a very small alphabet size, and have applications in synchronous DS-CDMA systems, where the number of users is greater than the signal space dimension or the spreading factor
11507660
Existence of perfect Mendelsohn designs with k=5 and lambda>1
Abstract Let υ, k , and λ be positive integers. A (υ, k , λ )- Mendelsohn design (briefly (υ, k , λ )-MD) is a pair ( X , B ) where X is a υ-set (of points ) and B is a collection of cyclically ordered k -subsets of X (called blocks ) such that every ordered pair of points of X are consecutive in exactly λ blocks of B . A set of k distinct elements { a 1 , a 2 ,…, a k } is said to be cyclically ordered by a 1 a 2 a k a 1 and the pair a i , a i + t is said to be t -apart in cyclic k -tuple ( a 1 , a 2 ,…, a k ) where i + t is taken modulo k . It for all t =1,2,…, k -1, every ordered pair of points of X is t -apart in exactly λ blocks of B , then the (υ, k , λ )-MD is called a perfect design and is denoted briefly by (υ, k , λ )-PMD. In this paper, we shall be concerned mainly with the case where k =5 and λ >1. It will be shown that the necessary condition for the existence of a (υ, 5, λ )-PMD, namely, λv ( υ -1)≡0 (mod 5), is also sufficient for λ >1 with the possible exception of pairs (υ, λ ) where λ =5 and υ =18 and 28.
5254546
Constructions for Perfect 5-Deletion-Correcting Codes of Length$7$
There are two kinds of perfect (k-t)-deletion-correcting codes with words of length k over an alphabet of size v, those where the coordinates may be equal and those where all coordinates must be different. We call these two kinds of codes T*(t,k,v)-codes and T(t,k,v)-codes respectively. Both a T*(t,k,v)-code and a T(t,k,v)-code are capable of correcting any combination of up to (k-t) deletions and insertions of letters occurred in transmission of codewords. In this correspondence, we consider constructions for the codes from directed designs. By means of these constructions, the existence of a T(2,7,v)-code is settled for all positive integers v with the exception of 68 values of v; T*(2,7,v)-codes are constructed for all integers vges2350. A large number of explicit constructions for T*(2,7,v)-codes with v<2350 are also presented
14742588
Reducing Complexity of Software Deployment with Delta Configuration
Deploying a modern software service usually involves installing several software components, and configuring these components properly to realize the complex interdependencies between them. This process, which accounts for a significant portion of information technology (IT) cost, is complex and error-prone. In this paper, we propose delta configuration - an approach that reduces the cost of software deployment by eliminating a large number of choices on parameter values that administrators have to make during deployment. In delta configuration, the complex software stack of a distributed service is first installed and tested in a test environment. The resulting software images are then captured and used for deployment in production environments. To deploy a software service, we only need to copy these pre-configured software images into a production environment and modify them to account for the difference between the test environment and a production environment. We have implemented a prototype system that achieves software deployment using delta configuration of the configuration state captured inside virtual machines. We perform a case study to demonstrate that our scheme leads to substantial reduction in complexity for the customer, over the traditional software deployment method.
109716942
A nanoscale nonvolatile memory device made from RbAg4I5 solid electrolyte grown on a Si substrate
A nanoscale nonvolatile memory device made from RbAg"4I"5 solid electrolyte has been made directly on a Si substrate with lateral size scaled down to 100nm. By applying voltages with different polarity, the device could be switched between high- and low-resistance states. The ratio between the high and low resistances could reach ~10^3, and the low-resistance state showed rectifying diode characteristics. The configured resistances remained nonvolatile after switching, and the device could be switched repeatedly for ~10^3 times. Our results show that the nanoscale nonvolatile memory device can be integrated directly with Si-based circuit and can be potentially used for high-density memory application.
7184753
Speech separation algorithms for multiple speaker environments
Conventional speaker identification and speech recognition algorithms do not perform well if there are multiple speakers in the background. For high performance speaker identification and speech recognition applications in multiple speaker environments, a speech separation stage is essential. Here we summarize the implementation of three speech separation techniques. Advantages and disadvantages of each method are highlighted, as no single method can work under all situations. Stand-alone software prototypes for these methods have been developed and evaluated.
26570649
Constrained mesh optimization on boundary
This paper presents a new mesh optimization approach aiming to improve the mesh quality on the boundary. The existing mesh untangling and smoothing algorithms (Vachal et al. in J Comput Phys 196: 627–644, 2004; Knupp in J Numer Methods Eng 48: 1165–1185, 2002), which have been proved to work well to interior mesh optimization, are enhanced by adding constrains of surface and curve shape functions that approximate the boundary geometry from the finite element mesh. The enhanced constrained optimization guarantees that the boundary nodes to be optimized always move on the approximated boundary. A dual-grid hexahedral meshing method is used to generate sample meshes for testing the proposed mesh optimization approach. As complementary treatments to the mesh optimization, appropriate mesh topology modifications, including buffering element insertion and local mesh refinement, are performed in order to eliminate concave and distorted elements on the boundary. Finally, the optimization results of some examples are given to demonstrate the effectivity of the proposed approach.
16485753
An integrated approach to robust speaker identification and speech recognition
Conventional speaker identification and speech recognition algorithms cannot deal with noisy and multiple speaker environments. For example, IBM via Voice has low recognition rates if dictation is done in a noisy environment. In order to achieve high performance in speaker identification and speech recognition, we propose an integrated approach that takes every facet of the process into account. Here we summarize some preliminary results from the application of this integrated approach to robust speaker identification and speech recognition. A real-time stand-alone software prototype has been developed to evaluate the effectiveness of the approach.