Hadamard partitioned difference families and their descendants

If $D$ is a $(4u^2,2u^2-u,u^2-u)$ Hadamard difference set (HDS) in $G$, then $\{G,G\setminus D\}$ is clearly a $(4u^2,[2u^2-u,2u^2+u],2u^2)$ partitioned difference family (PDF). Any $(v,K,\lambda)$-PDF will be said of Hadamard-type if $v=2\lambda$ as the one above. We present a doubling construction which, starting from any such PDF, leads to an infinite class of PDFs. As a special consequence, we get a PDF in a group of order $4u^2(2n+1)$ and three block-sizes $4u^2-2u$, $4u^2$ and $4u^2+2u$, whenever we have a $(4u^2,2u^2-u,u^2-u)$-HDS and the maximal prime power divisors of $2n+1$ are all greater than $4u^2+2u$

New 22-designs from strong difference families

Strong difference families are an interesting class of discrete structures which can be used to derive relative difference families. Relative difference families are closely related to $2$-designs, and have applications in constructions for many significant codes, such as optical orthogonal codes and optical orthogonal signature pattern codes. In this paper, with a careful use of cyclotomic conditions attached to strong difference families, we improve the lower bound on the asymptotic existence results of $(\mathbb{F}_{p}\times \mathbb{F}_{q},\mathbb{F}_{p}\times \{0\},k,\lambda)$-DFs for $k\in\{p,p+1\}$. We improve Buratti's existence results for $2$-$(13q,13,\lambda)$ designs and $2$-$(17q,17,\lambda)$ designs, and establish the existence of seven new $2$-$(v,k,\lambda)$ designs for $(v,k,\lambda)\in\{(694,7,2),(1576,8,1),(2025,9,1),(765,9,2),(1845,9,2),(459,9,4)$, $(783,9,4)\}$.Comment: Version 1 is named "Improved cyclotomic conditions leading to new 2-designs: the use of strong difference families". Major revision according to the referees' comment

Frame difference families and resolvable balanced incomplete block designs

Frame difference families, which can be obtained via a careful use of cyclotomic conditions attached to strong difference families, play an important role in direct constructions for resolvable balanced incomplete block designs. We establish asymptotic existences for several classes of frame difference families. As corollaries new infinite families of 1-rotational $(pq+1,p+1,1)$-RBIBDs over $\mathbb{F}_{p}^+ \times \mathbb{F}_{q}^+$ are derived, and the existence of $(125q+1,6,1)$-RBIBDs is discussed. We construct $(v,8,1)$-RBIBDs for $v\in\{624,1576,2976,5720,5776,10200,14176,24480\}$, whose existence were previously in doubt. As applications, we establish asymptotic existences for an infinite family of optimal constant composition codes and an infinite family of strictly optimal frequency hopping sequences.Comment: arXiv admin note: text overlap with arXiv:1702.0750

The structure and the evolution of essential patents for standards: Lessons from three IT standards

This paper examines the structure and the evolution of the patents declared as essential for three major technical standards in information technology (MPEG2, DVD and W-CDMA). These standards have many essential patents, which are owned by many firms with different interests. Many patents have been applied even after the standard was set. We analyze three important reasons for why the essential patents are many and increase over time: they cover a number of different technology fields, there exist R&D competition even in a narrowly defined technology field and a firm can expand its patent portfolio by using continuations and other practices based on the priority dates of its earlier filed patent applications in the USA. Around 40% of the essential US patents for MPEG2 and DVD standards have been obtained by using these applications. However, our empirical analysis suggests that a firm with pioneering patents does not obtain more essential patents, using these practices.standard, essential patent, continuations

Have Differences in Credit Access Diminished in an Era of Financial Market Deregulation?

Over the past few decades, financial markets have become increasingly deregulated and household debt has expanded, sometimes rapidly. It is possible that greater deregulation led to improved credit access--measured by loan denials, discouraged applications, and costs of credit-- for typically underserved groups, such as minorities and low-income families, relative to their counterparts. Data from the Federal Reserve’s Survey of Consumer Finances however, shows no clear trend towards equalization of credit access from 1989 to 2004. While there were some gains by specific groups by certain measures (for example, the gaps in loan denials and discouraged applications improved for Hispanics, relative to Whites), the results indicate that differences in credit access did not decrease on a broad basis during a period of large scale financial deregulation.Household debt; credit access; costs of debt; interest rates; financial deregulation

The R&D process in the US and Japan: Major findings from the RIETI-Georgia Tech Inventor Survey

RIETI Discussion PaperThis paper analyzes and compares the objective, the nature and the performance of R&D projects in the US and Japan, based on the first large scale systematic survey of inventors, focusing on the R&D projects yielding triadic patents. Major findings are the following. First, the projects for enhancing the existing business line of a firm account for a large share of R&D projects in both countries, confirming the view that the R&D investment is significantly conditioned by the existing complementary asset of a firm. In both countries, the inventions from R&D for existing business have the highest in-house utilization rate but use least the scientific and technical literature for their conceptions, while the reverse is the case for the inventions from R&D for new technology base (or for cultivating seeds). R&D projects for enhancing the technology base are much more common in the US. This difference can be partly accounted for by US inventors being more likely to have a PhD, but not by the differences in the structure of finance. US government financial support is relatively more targeted to projects for existing business and US venture capital provides support mainly projects for creating new business (6% of them), but not for more upstream projects. Only about 20-30% of the projects are for process innovation in both countries, providing direct evidence for the earlier findings that were based on US patent information. Product innovation generates process patents more often in Japan than in the US (25% vs. 10%), while product innovation projects are relatively more numerous in Japan. In both countries a significant share of inventions (more than 20%) were not the result of an R&D project, and a substantial proportion of such inventions are valued among the top 10% of patents, suggesting that R&D expenditure significantly underestimates inventive activities. A US invention is more often an unexpected by-product of an R&D project (11%) than in Japan (3.4%). The two countries have surprisingly similar distributions of R&D projects in man month and the average team size. In both countries, smaller firms tend to have relatively more high-value patents. In the US, inventors from very small firms (with less than 100 employees) and universities jointly account for more than one quarter of the top 10% inventions, even though they account for only 14% of all inventions. Man-months expended for an invention has a significant correlation with the performance of the R&D projects for existing business, less so for new business and not at all for those enhancing the technology base,suggesting substantial heterogeneity by project types in the determinants of the performance and in the uncertainty. A PhD has a significant correlation with R&D project performance especially for new business