A Decomposition Theorem for Maximum Weight Bipartite Matchings

Let G be a bipartite graph with positive integer weights on the edges and without isolated nodes. Let n, N and W be the node count, the largest edge weight and the total weight of G. Let k(x,y) be log(x)/log(x^2/y). We present a new decomposition theorem for maximum weight bipartite matchings and use it to design an O(sqrt(n)W/k(n,W/N))-time algorithm for computing a maximum weight matching of G. This algorithm bridges a long-standing gap between the best known time complexity of computing a maximum weight matching and that of computing a maximum cardinality matching. Given G and a maximum weight matching of G, we can further compute the weight of a maximum weight matching of G-{u} for all nodes u in O(W) time.Comment: The journal version will appear in SIAM Journal on Computing. The conference version appeared in ESA 199

An Even Faster and More Unifying Algorithm for Comparing Trees via Unbalanced Bipartite Matchings

A widely used method for determining the similarity of two labeled trees is to compute a maximum agreement subtree of the two trees. Previous work on this similarity measure is only concerned with the comparison of labeled trees of two special kinds, namely, uniformly labeled trees (i.e., trees with all their nodes labeled by the same symbol) and evolutionary trees (i.e., leaf-labeled trees with distinct symbols for distinct leaves). This paper presents an algorithm for comparing trees that are labeled in an arbitrary manner. In addition to this generality, this algorithm is faster than the previous algorithms. Another contribution of this paper is on maximum weight bipartite matchings. We show how to speed up the best known matching algorithms when the input graphs are node-unbalanced or weight-unbalanced. Based on these enhancements, we obtain an efficient algorithm for a new matching problem called the hierarchical bipartite matching problem, which is at the core of our maximum agreement subtree algorithm.Comment: To appear in Journal of Algorithm

Cavity Matchings, Label Compressions, and Unrooted Evolutionary Trees

We present an algorithm for computing a maximum agreement subtree of two unrooted evolutionary trees. It takes O(n^{1.5} log n) time for trees with unbounded degrees, matching the best known time complexity for the rooted case. Our algorithm allows the input trees to be mixed trees, i.e., trees that may contain directed and undirected edges at the same time. Our algorithm adopts a recursive strategy exploiting a technique called label compression. The backbone of this technique is an algorithm that computes the maximum weight matchings over many subgraphs of a bipartite graph as fast as it takes to compute a single matching

On New Ventures’ Board of Directors: Formation, Adjustment, and Influences on Internationalization

To survive and grow, young firms must leverage different means, such as strategic alliances or founders' personal networks, to access and acquire necessary external resources to overcome, or at least mitigate, the liability of newness. In this study, we found that the board of directors can serve as a means of resource provision for new ventures. We conducted a historical analysis and case studies on high-tech new ventures, in order to delve deeply into the processes regarding how boards are formed, how board members provide these resources, and what factors influence the processes. Results showed that a board of directors is more likely to be formed when the funds are raised from institutional investors, rather of individual investors. Moreover, for founders, formation of the board connotes an exchange of partial ownership for critical external resources. When more resources are needed, founders adjust their boards. Adjustments of the board can be categorized into two: “planned board adjustments” are initiated by the founders to acquire external resources, while “required board adjustments” are set out by disgruntled board members, and reduced resource endowments of the firm. In addition, board members exploit their individual assets, experience, reputation, and personal networks to provide personally endowed resources to the new venture, and leverage their firms’ assets, reputation, and business networks to contribute organizationally endowed resources. Board members also facilitate new ventures’ internationalization

Inward FDI in Taiwan and its policy context

Taiwan has long maintained an explicit policy of attracting inward foreign direct investment (IFDI) as part of its growth strategy, although inflows have been subject to various restrictions. The primary objective of Taiwan's stance toward FDI was initially to attract export-oriented investment based upon the competitiveness of its highly educated and productive labor force. More recently, this objective has been modified to focus on attracting FDI into increasingly technology-intensive areas and to encourage or promote domestic technological spillovers. In recent years, although Taiwan's IFDI stock has more than tripled, from US$20 billion in 2000 to US$ 64 billion in 2010, it remains a relatively small recipient compared with its neighboring economies in the Asia-Pacific region. Annual IFDI flows to Taiwan have been in single-digit US$billion during 2000-2010, with a peak of US$ 7 billion in 2007 followed by a steady decline during 2008-2010. In 2010, Taiwan received inward FDI of US$ 2 billion only. It is, however, generally seen that the release of prohibition against mainland China investors on June 30, 2009, and the newly signed landmark cross-strait Economic Cooperation Framework Agreement (ECFA) on June 30, 2010 will reinforce Taiwan's robust investment climate and stimulate IFDI

A non-linear analytic stress model for the analysis on the stress interaction between TSVs

Thermo-elastic strain is induced by through silicon vias (TSV) due to the difference of thermal expansion coefficients between the copper (∼18 ppm/◦C) and silicon (∼2.8 ppm/◦C) when the structure is exposed to a thermal budget in the three dimensional integrated circuit (3DIC) process. These thermal expansion stresses are high enough to induce the delamination on the interfaces between the copper, silicon, and isolated dielectric. A compact analytic model for the strain field induced by different layouts of thermal copper filled TSVs with the linear superposition principle is found to result in large errors due to the strong stress interaction between TSVs. In this work, a nonlinear stress analytic model with different TSV layouts is demonstrated by the finite element method and Mohr’s circle analysis. The stress characteristics are also measured by the atomic force microscope-raman technique at a nanometer level resolution. This nonlinear stress model for the strong interactions between TSVs results in an electron mobility change ~2-6% smaller than that resulting from a model that only considers the linear stress superposition principle

Formation polarity dependent improved resistive switching memory characteristics using nanoscale (1.3 nm) core-shell IrOx nano-dots

Improved resistive switching memory characteristics by controlling the formation polarity in an IrOx/Al2O3/IrOx-ND/Al2O3/WOx/W structure have been investigated. High density of 1 × 1013/cm2 and small size of 1.3 nm in diameter of the IrOx nano-dots (NDs) have been observed by high-resolution transmission electron microscopy. The IrOx-NDs, Al2O3, and WOx layers are confirmed by X-ray photo-electron spectroscopy. Capacitance-voltage hysteresis characteristics show higher charge-trapping density in the IrOx-ND memory as compared to the pure Al2O3 devices. This suggests that the IrOx-ND device has more defect sites than that of the pure Al2O3 devices. Stable resistive switching characteristics under positive formation polarity on the IrOx electrode are observed, and the conducting filament is controlled by oxygen ion migration toward the Al2O3/IrOx top electrode interface. The switching mechanism is explained schematically based on our resistive switching parameters. The resistive switching random access memory (ReRAM) devices under positive formation polarity have an applicable resistance ratio of > 10 after extrapolation of 10 years data retention at 85°C and a long read endurance of 105 cycles. A large memory size of > 60 Tbit/sq in. can be realized in future for ReRAM device application. This study is not only important for improving the resistive switching memory performance but also help design other nanoscale high-density nonvolatile memory in future