A New Reduction from Search SVP to Optimization SVP

It is well known that search SVP is equivalent to optimization SVP. However, the former reduction from search SVP to optimization SVP by Kannan needs polynomial times calls to the oracle that solves the optimization SVP. In this paper, a new rank-preserving reduction is presented with only one call to the optimization SVP oracle. It is obvious that the new reduction needs the least calls, and improves Kannan's classical result. What's more, the idea also leads a similar direct reduction from search CVP to optimization CVP with only one call to the oracle

Some Facts About Outward Foreign Direct Investment from China

According to the“2014 Statistical Bulletin of China’s Outward Foreign Direct Investment”, 2014 saw another episode of difficult and complicated recovery of global economy with a decline in global foreign direct investment. Facing the complex and volatile international situation, the Chinese government proactively promoted the establishment of “The Belt and Road Initiative”, and continuously sped up the facilitation to outward foreign investment, increasing the inner motivation of Chinese enterprises to “go global”. In 2014, with its outward foreign direct investment (FDI) reaching a historical record of $123.12 billion, China achieved the balance between outward and inward direct investment for the first time. 2014 saw another episode of difficult and complicated recovery of global economy with a decline in global foreign direct investment

Delay-dependent stability of high-order neutral systems

summary:In this note, we are concerned with delay-dependent stability of high-order delay systems of neutral type. A bound of unstable eigenvalues of the systems is derived by the spectral radius of a nonnegative matrix. The nonnegative matrix is related to the coefficient matrices. A stability criterion is presented which is a necessary and sufficient condition for the delay-dependent stability of the systems. Based on the criterion, a numerical algorithm is provided which avoids the computation of the coefficients of the characteristic function. Under some conditions, the presented results are less conservative than those reported. A numerical example is given to illustrate the main results

Past distribution of epiphyllous liverworts in China: The usability of historical data

Epiphyllous liverworts form a special group of bryophytes that primarily grow on the leaves of understory vascular plants in tropical and subtropical evergreen broadleaf forests. Being sensitive to moisture and temperature changes, epiphyllous liverworts are often considered to be good indicators of climate change and forest degradation. However, they are a poorly collected and taxonomically complicated group, with an only partly identified distribution pattern. In this study, we built four models based on 24 environmental variables at four different spatial resolutions (i.e., 1 km, 5 km, 10 km, and 15 km) to predict the past distribution of epiphyllous liverworts in China, using Maxent model and 63 historical location records (i.e., presence‐only data). Both area under the curve of the receiver operating characteristic (AUC) and true skill statistic (TSS) methods are used to assess the model performance. Results showed that the model with the predictors at a 15‐km resolution achieved the highest predictive accuracy (AUC=0.946; TSS=0.880), although there was no statistically significant difference between the four models (p > 0.05). The most significant environmental variables included aridity, annual precipitation, precipitation of wettest month, precipitation of wettest quarter, and precipitation of warmest quarter, annual mean NDVI, and minimum NDVI. The predicted suitable areas for epiphyllous liverworts were mainly located in the south of Yangtze River and seldom exceed 35°N, which were consistent with the museum and herbarium records, as well as the historical records in scientific literatures. Our study further demonstrated the value of historical data to ecological and evolutionary studies

Spatiotemporal Distribution of Eutrophication in Lake Tai as Affected by Wind

One common hypothesis is that wind can affect concentrations of nutrients (i.e., nitrogen and phosphorus) and chlorophyll-a (Chl-a) in shallow lakes. However, the tests of this hypothesis have yet to be conclusive in existing literature. The objective of this study was to use long-term data to examine how wind direction and wind speed affect the spatiotemporal variations of total nitrogen (TN), total phosphorus (TP) and Chl-a in Lake Tai, a typical shallow lake located in east China. The results indicated that the concentrations of nutrients and Chl-a tended to decrease from the northwest to the southeast of Lake Tai, with the highest concentrations in the two leeward bays (namely Meiliang Bay and Zhushan Bay) in the northwestern part of the lake. In addition to possible artificial reasons (e.g., wastewater discharge), the prevalent southeastward winds in warm seasons (i.e., spring and summer) and northwestward winds in cool seasons (i.e., fall and winter) might be the major natural factor for such a northwest-southeast decreasing spatial pattern. For the lake as a whole, the concentrations of TN, TP and Chl-a were highest for a wind speed between 2.1 and 3.2 m·s-1, which can be attributed to the idea that the wind-induced drifting and mixing effects might be dominant in the bays while the wind-induced drifting and resuspension effects could be more important in the other parts of the lake. Given that the water depth of the bays was relatively larger than that of the other parts, the drifting and mixing effects were likely dominant in the bays, as indicated by the negative relationships between the ratios of wind speed to lake depth, which can be a surrogate for the vertical distribution of wind-induced shear stress and the TN, TP and Chl-a concentration. Moreover, the decreasing temporal trend of wind speed in combination with the ongoing anthropogenic activities will likely increase the challenge for dealing with the eutrophication problem of Lake Tai. © 2017 by the authors

Self-Induced Fractional Fourier Transform and Revivable Higher Order Spatial Solitons in Strongly Nonlocal Nonlinear Media

The fractional Fourier transform (FRFT) naturally exists in the strongly nonlocal nonlinear (SNN) media and the propagation of optical beams in SNN media can be simply regarded as a self-induced FRFT. Through FRFT technic the evolution of fields in SNN media can be conveniently dealt with and an arbitrary square-integrable input field presents generally as a revivable higher order spatial soliton which reconstructs its profile periodically after every 4 times of Fourier transforms. The self-induced FRFT would illuminate the prospect of the SNN media in new applications such as continuously tunable nonlinearity-induced FRFT devices.Comment: Published in Phys. Rev.

P/polyP/poly Invalidity of the Agr17 Functional Encryption Scheme

Functional encryption (FE) is an advanced topic in the research of cryptography, and the Agr17 FE scheme is one of the major FE schemes. It took the BGG+14 attribute-based encryption (ABE) scheme as a bottom structure, which was upgraded into a `partially hiding predicate encryption\u27 (PHPE) scheme and combined with a fully homomorphic encryption (FHE) scheme. However, there is a remaining problem, the implementation of the modulus reduction, in the Agr17 FE scheme. First, a modulus reduction is necessary for the polynomial-time computability of the scheme. Second, the detailed steps of the modulus reduction were absent in the scheme (including its conference version and full version). Instead, the authors only pointed out several reference works. The author\u27s meaning seemed to be that the modulus reduction of the Agr17 FE scheme can be obtained by directly using or simply generalizing these reference works. Third, these reference works only described various modulus reductions of FHE schemes, without the hint of how to generalize them into the modulus reduction of FE schemes. Finally, any modulus reduction of FHE can not be simply generalized into the modulus reduction of the Agr17 FE scheme due to the following two facts: (1) The Agr17 FE scheme has two moduli, which are the modulus of the FHE ciphertext and of the ABE ciphertext, both are originally superpolynomial in size for processing $P/poly$ functions. (2) Both moduli need to be scaled down to polynomial size, and both of them need to be reduced to the same new modulus, otherwise, the correctness of the scheme will fail. In this paper, we demonstrate that the Agr17 FE scheme is $P/poly$ invalid. More specifically, we show that, when processing $P/poly$ functions, the Agr17 FE scheme cannot be implemented again after its modulus reduction. To show the soundness of our demonstration, we present the statements in two stages. At the first stage, we show that the modulus reduction of the Agr17 FE scheme should be a double modulus reduction, which includes two modulus reductions for the FHE ciphertext and ABE ciphertext, respectively. This double modulus reduction has the following three key points: (1) The modulus reduction for the FHE ciphertext should be seen as a series of Boolean operations, and converted into `attribute quasi-homomorphic operations\u27. (2) The modulus reduction for the ABE ciphertext is a learning-with-errors (LWE) -based modulus reduction, which is an ordinary modulus reduction. (3) The two modulus reductions should obtain the same new modulus, otherwise, the scheme would not be implemented again. At the second stage, we show that the modulus reduction for the ABE ciphertext will destroy the structure of ABE so that the subsequent decryption would not be executed. The reason lies in that the decryption of ABE is an LWE decryption with conditions rather than an ordinary LWE decryption, and the modulus reduction will destroy the conditions of decryption. Besides, to show such invalidity cannot be easily crossed by revising the scheme, we design two revised versions of the Agr17 scheme. The first revised version is a `natural\u27 revised version of the Agr17 scheme. The key point is to change the small modulus inner product into an arithmetic inner product, which can be obtained by the modulus inner product of the ABE ciphertext. The first revised scheme is valid, i.e., the decryption can be implemented correctly. However, the revised scheme is insecure because the decryptor knows much more secret information, and hence the scheme can be broken by collusion attacks with much less cost. The second revised version is an application of the GGH+13b verification circuit technology which transforms a $P/poly$ function into an $NC^1$ circuit. The second revised scheme is valid, but it is far from the design idea of the Agr17 scheme, and its function class is quite limited, that is, those functions which can be equally transformed from $P/poly$ into $NC^1$ by equal verification transformation, rather than any $P/poly$ functions

Ultra-fast self-assembly and stabilization of reactive nanoparticles in reduced graphene oxide films.

Nanoparticles hosted in conductive matrices are ubiquitous in electrochemical energy storage, catalysis and energetic devices. However, agglomeration and surface oxidation remain as two major challenges towards their ultimate utility, especially for highly reactive materials. Here we report uniformly distributed nanoparticles with diameters around 10 nm can be self-assembled within a reduced graphene oxide matrix in 10 ms. Microsized particles in reduced graphene oxide are Joule heated to high temperature (∼1,700 K) and rapidly quenched to preserve the resultant nano-architecture. A possible formation mechanism is that microsized particles melt under high temperature, are separated by defects in reduced graphene oxide and self-assemble into nanoparticles on cooling. The ultra-fast manufacturing approach can be applied to a wide range of materials, including aluminium, silicon, tin and so on. One unique application of this technique is the stabilization of aluminium nanoparticles in reduced graphene oxide film, which we demonstrate to have excellent performance as a switchable energetic material

A Systematic Approach and Analysis of Key Mismatch Attacks on Lattice-Based NIST Candidate KEMs

The research on the key mismatch attacks against the lattice-based KEMs is an important part of the cryptographic assessment of the ongoing NIST standardization. There have been a number of these attacks. However, a unified method to evaluate these KEMs\u27 resilience under key mismatch attacks is still missing. Since the key index of the efficiency of these attacks is the number of queries needed to successfully mount such an attack, in this paper, we propose and develop a systematic approach to find the lower bounds on the minimum average number of queries needed for such attacks. Our basic idea is to transform the problem of finding the lower bound of queries into finding an optimal binary recovery tree (BRT), where the computations of the lower bounds become essentially the computations of a certain Shannon entropy. The introduction of the optimal BRT approach also enables us to understand why, for some lattice-based NIST candidate KEMs, there is a big gap between the theoretical bounds and practical attacks, in terms of the number of queries needed. This further leads us to propose a generic improvement method for these existing attacks, which are confirmed by our experiments. Moreover, our proposed method could be directly used to improve the side-channel attacks against CCA-secure NIST candidate KEMs