Two-dimensional ferromagnetic semiconductor Cr2XP: First-principles calculations and Monte Carlo simulations

According to the Mermin Wagner theorem, two-dimensional material is difficult to have the Curie temperature above room temperature. By using the method of band engineering, we design a promising two-dimensional ferromagnetic semiconductor Cr2XP (X=P, As, Sb) with large magnetization, high Curie temperature and sizable band gap. The formation of gap is discussed in terms of the hybridizations, occupation and distribution of electronic states and charge transfer. Large magnetic moments about 6.16~6.37uB origin from the occupation of Cr-d electrons in crystal field.Competition and cooperation between d-d (Cr-d~Cr-d) and d-p-d (Cr-d~X-p~Cr-d) exchange interactions lead to the emergence of ferromagnetic ordering phase. Furthermore, Curie temperatures, approaching to 269 K, 332 K and 400 K for Cr2P2, Cr2AsP and Cr2SbP, are estimated by employing Monte Carlo simulation based on the Heisenberg model. Magnetic anisotropy energy of Cr2XP is determined by calculating the total energy dependence on the angle along different directions, and the origin is also discussed by the second-order perturbation theory. In addition, the Cr2XP possesses excellent thermodynamical, dynamical and mechanical stabilities, and can overcome their own gravity to keep their planar structure without the support of substrate. These above-mentioned advantages will offer some valuable hints for two-dimensional ferromagnetic semiconductor Cr2XP in spintronic devices

Generating CCG Categories

Previous CCG supertaggers usually predict categories using multi-class classification. Despite their simplicity, internal structures of categories are usually ignored. The rich semantics inside these structures may help us to better handle relations among categories and bring more robustness into existing supertaggers. In this work, we propose to generate categories rather than classify them: each category is decomposed into a sequence of smaller atomic tags, and the tagger aims to generate the correct sequence. We show that with this finer view on categories, annotations of different categories could be shared and interactions with sentence contexts could be enhanced. The proposed category generator is able to achieve state-of-the-art tagging (95.5% accuracy) and parsing (89.8% labeled F1) performances on the standard CCGBank. Furthermore, its performances on infrequent (even unseen) categories, out-of-domain texts and low resource language give promising results on introducing generation models to the general CCG analyses.Comment: Accepted by AAAI 202

Do cross-border mergers and acquisitions increase short-term market performance? The case of Chinese firms

Despite the new momentum in cross-border mergers and acquisitions (M&As) by emerging market firms, we have a limited understanding of the impact of these activities. Drawing on signalling theory and the institution-based view, this paper examines the extent of stock market reactions to the announcement of cross-border M&A deals, based on an event study of a sample of Chinese firms during the period 2000– 2012. The findings indicate that the announcement of cross-border M&As results in a positive stock market reaction; this effect is more significant in the mainland Chinese stock markets (Shanghai and Shenzhen) than that in the Hong Kong market. The shareholders of Chinese firms that acquire a target firm in a host country with a low level of political risk gain higher cumulative abnormal returns than those firms targeting companies in countries with a high level of political risk. The shareholders of Chinese state-owned enterprises experience lower abnormal returns compared with those of Chinese privately owned firms when engaging in cross-border M&A deals

Expatriates, subsidiary autonomy and the overseas subsidiary performance of MNEs from an emerging economy

Despite a growing body of research on the role of expatriates in subsidiary performance, the mechanisms through which expatriates affect subsidiary performance are still the subject of debate. Drawing on the resource dependence theory, we examine the indirect effect of expatriates on subsidiary performance via subsidiary autonomy based on a sample of Chinese multinational enterprises (MNEs). The findings show that an increase in expatriates reduces the level of subsidiary autonomy and thus negatively affects subsidiary performance. We also find that the institutional quality of host countries reinforces the negative impact of expatriates on subsidiary autonomy, but reduces the importance of the latter on subsidiary performance

On the minimum common integer partition problem.

We introduce a new combinatorial optimization problem in this paper, called the Minimum Common Integer Partition (MCIP) problem, which was inspired by computational biology applications including ortholog assignment and DNA fingerprint assembly. A partition of a positive integer n is a multiset of positive integers that add up to exactly n, and an integer partition of a multiset S of integers is defined as the multiset union of partitions of integers in S. Given a sequence of multisets S1, · · · , S k of integers, where k ≥ 2, we say that a multiset is a common integer partition if it is an integer partition of every multiset Si, 1 ≤ i ≤ k. The MCIP problem is thus defined as to find a common integer partition of S1, · · · , S k with the minimum cardinality. It is easy to see that the MCIP problem is NP-hard since it generalizes the wellknown Set Partition problem. We can in fact show that it is APX-hard. We will also present a -approximation algorithm for k ≥ 3