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Flux observations are important for understanding the basic processes of carbon and water cycling in an ecosystem. In 2020 (1 January 2020 to 31 December 2020), we continuously monitored the surface energy fluxes of a shrub ecosystem using an eddy covariance system. Additionally, meteorological variables, such as temperature and rainfall, were measured. The study site was located in Chunhua of China, which is a gully region of the Chinese Loess Plateau. The diurnal and seasonal dynamic changes in the energy balance of this region were analysed, Bowen and energy balance ratios were calculated, and environmental factors affecting the variations in latent (LE) and sensible heat fluxes (H) were explored. The results showed that the annual net radiation (Rn), LE, H, and soil heat flux (G) were 2385.6, 1059.1, 787.6, and - 48.3 MJ/m2, respectively, with 490.58 MJ/m2 energy remaining undetected. The main part of the annual energy of the shrub ecosystem was latent heat, accounting for 44.4% of Rn. A seasonal variation in each energy component was evident, and the diurnal variation showed a single peak curve. LE in the growing season was dominant, and the proportion of LE and H in the net radiation in the non-growing season showed little difference. The Bowen ratio changed monthly and significantly fluctuated from 0.2 in July to 4.0 in December. It was high in winter and low in summer, with little fluctuation. The annual energy balance ratio was 0.8. The energy balance closure in the non-growing season was greater than that in the growing season. Both H and LE were significantly correlated with net radiation, and H was negatively correlated with rainfall, soil moisture, and soil temperature. Unlike H, LE was significantly positively correlated with soil temperature. In addition, LE was positively correlated with air humidity gradient and water vapour pressure difference.

Liquid biopsy provides non-invasive and real-time detection for cancer diagnosis, but the lack of specific markers targeted to liquid biopsy components, such as circulating tumor cells (CTCs) and exosomes, has impeded its effective utilization in clinical settings. W3 is an aptamer, and its target has been previously demonstrated to be a predictor of colorectal cancer (CRC) metastasis. Herein, we developed a W3-based molecular beacon (MAB-W3-3G) to specifically detect CTCs and exosomes derived from CRC patients by modifying the W3 sequence and adding a fluorescent group FAM at the 5' end and a quencher group BHQ1 at the 3' end, resulting in a detectable green fluorescence only in the presence of the target. MAB-W3-3G retained features similar to those of the original W3, including high specificity and affinity for metastatic CRC cells, as well as excellent plasma stability. Notably, W3 target-positive CTCs were visualized, positive exosomes were quantified in CRC patients' whole blood without any sample pretreatment, and both detections could be finished in one step without any routine washing procedures. For CRC, the W3 target-positive CTC enumeration in metastasis was higher than that in non-metastasis (

In the past, a great deal of research has been conducted to determine the fractal properties of river networks, and there are many kinds of methods calculating their fractal dimensions. In this paper, we compare two most common methods: one is geomorphic fractal dimension obtained from the bifurcation ratio and the stream length ratio, and the other is box-counting method. Firstly, synthetic fractal trees are used to explain the role of the junction angle on the relation between two kinds of fractal dimensions. The obtained relationship curves indicate that box-counting dimension is decreasing with the increase of the junction angle when geomorphic fractal dimension keeps constant. This relationship presents continuous and smooth convex curves with junction angle from 60° to 120° and concave curves from 30° to 45°. Then 70 river networks in China are investigated in terms of their two kinds of fractal dimensions. The results confirm the fractal structure of river networks. Geomorphic fractal dimensions of river networks are larger than box-counting dimensions and there is no obvious relationship between these two kinds of fractal dimensions. Relatively good non-linear relationships between geomorphic fractal dimensions and box-counting dimensions are obtained by considering the role of the junction angle. HIGHLIGHTS The role of the junction angle on the relation between two kinds of fractal dimensions is explained by synthetic fractal trees.; Two kinds of fractal dimensions of 70 actual river networks in China are compared.; Junction angle has a significant influence on fractal dimensions of river networks.

Many shallow aquifers in north China are seriously polluted and cannot be used any more. Therefore, the confined groundwater exploitation is steadily increasing. With the rapid decline of confined groundwater head, the risk of confined aquifer contamination by leaky recharge from shallow aquifer is significantly increased. In this paper, the cumulated time that the pollutant concentration at the top of confined aquifer exceeds the highest allowable limit is defined as the confined aquifer vulnerability indicator. This process-based indicator is used to assess the confined aquifer vulnerability of Jining, China. In order to obtain confined aquifer vulnerability indicator, three-dimensional numerical simulation models of groundwater flow and solute transport are established by MODFLOW and MT3D respectively. Calibration and verification results, with correlation coefficient of 0.98 and 0.8, confirmed the reliability of numerical models which is then used to calculate the vulnerability indicator. Assessment results show that the confined aquifer in Shizhong District is the most vulnerable to pollutants and should be given more attention. As an alternative, the central and east part of the study area has the potential for exploitation. Further analysis reveals that both water head pressure difference and aquitard thickness have an important impact on the aquifer vulnerability. The vulnerability assessment map obtained by GIS shows the most vulnerable area is where the pollutant concentration increases most. Our proposed method provides the basis for confined groundwater environmental protection.

Karst depressions play an important role in runoff generation and concentration processes of karst catchments. Storm water tends to be stored in karst depressions firstly before routing to the catchment outlet. However, simulating methods of runoff processes considering the impact of karst depressions are rarely reported. To fill this concept and technology gap, we propose a conceptual hydrological model considering the role of karst depressions in this study. A three serial tank model coupled with two soil tanks is established at each grid in each subcatchment, to simulate surface runoff, interflow, groundwater runoff, and soil moisture dynamics. During the process of flow concentration, surface runoff from each grid is reduced by karst depressions at its lower reach. The surface runoff loss is controlled by the area ratio of karst depression and corresponding subcatchment. River channel routing is carried out based on the Muskingum approach. The conceptual hydrological model is further calibrated and validated over the Hamajing catchment, a small karst catchment in Hubei Province, China. Results show that the proposed model can generally reproduce the runoff generation and concentration processes well. Nash-Sutcliffe efficiency (NSE) coefficient is 0.85 during the calibration period and 0.78 in the validation period. Root mean squared errors are 6.24 m3/s and 5.35 m3/s during calibration and validation periods respectively. Sensitivity analysis indicates that the parameters related to the first tank are most sensitive to the simulation results, whereas the change of parameters related to the second and third tanks cannot significantly influence the simulation results. Additionally, the area ratio of karst depression has great influence on the runoff processes in karst catchment. This proposed conceptual model provides a simple approach to simulate the hydrological processes in karst region.

The emergence of quantum computing threatens many classical cryptographic schemes, leading to the innovations in public-key cryptography for postquantum cryptography primitives and protocols that resist to quantum attacks. Lattice-based cryptography is considered to be one of the promising mathematical approaches to achieving security resistant to quantum attacks, which could be built on the learning with errors (LWE) problem and its variants. The fundamental building blocks of protocols for public-key encryption (PKE) and key encapsulation mechanism (KEM) submitted to the National Institute of Standards and Technology (NIST) based on LWE and its variants are called key consensus (KC) and asymmetric key consensus (AKC) by Jin et al. They are powerful tools for constructing PKE schemes. In this work, we further demonstrate the power of KC/AKC by proposing two special types of PKE schemes, namely, revocable attribute-based encryption (RABE). To be specific, on the basis of AKC and PKE/KEM protocols submitted to the NIST based on LWE and its variants, combined with full-rank difference, trapdoor on lattices, sampling algorithms, leftover hash lemma, and binary tree structure, we propose two directly revocable ciphertext-policy attribute-based encryption (DR-ABE) schemes from LWE, which support flexible threshold access policies on multivalued attributes, achieving user-level and attribute-level user revocation, respectively. Specifically, the construction of the ciphertext is derived from AKC, and the revocation list is defined and embedded into the ciphertext by the message sender to revoke a user in the user-level revocable scheme or revoke some attributes of a certain user in the attribute-level revocable scheme. We also discuss how to outsource decryption and reduce the workload for the end user. Our schemes proved to be secure in the standard model, assuming the hardness of the LWE problem. The two schemes imply the versatility of KC/AKC.

Aquitards can preserve paleo-saltwater and have a long and profound influence on the aquifer groundwater, yet they have received less attention. Here, five one-dimensional vertical profiles of the natural tracers, Cl−, Br−, δ2H, and δ18O of aquitard porewater were measured and combined with eight existing profiles collected from previous studies in three Eastern China coastal plains, Bohai bay, Laizhou bay, and Jiangsu coastal plain, to show the salinity origin and the timescale of the transport of porewater across aquitards since the mid-Holocene. Evidence of paleo-seawater impacted by Holocene transgression is noticed as peak Cl− concentration, enriched water isotopes, and lower Cl/Br ratios are observed in the porewater at about the bottom depth of Holocene of 25 m. The shape of Cl− profiles and associated 1-D transport models confirms Holocene seawater's presence in the sediment and the alternating transgression and regression control the salinity evolution of coastal aquitard porewater. Diffusion is the dominant transport across aquitard with an upward velocity between 0.03 and 0.6 mm/yr. Reverse advective flow has affected the solute transport in areas of extensive pumping. Anthropogenic activities enhance the leaching of salty porewater into aquifers in coastal areas, necessitating the need for research focused on marine aquitard salty water.

The Han River is the water source of the South-to-North Water Diversion Project and the “Han River to Wei River Water Diversion Project” in China. In order to ensure that the water quality and quantity are sufficient for the water diversion project, the natural forest protection project, river chief system and other measures have been implemented in the Han River by the government. At the same time, several large reservoirs have been built in the Han River basin and perform the functions of water supply and hydropower generation, which is an important type of clean power. Under the influence of human activities, the coupling interaction between humans and water in the upper reach of the Han River drives the socio-hydrological evolution process. In this study, from the perspective of socio-hydrology, a model of socio-hydrological evolution (SHE) in the Han River in southern Shaanxi was built to simulate the potential evolution path of the socio-hydrological system and determine possible measures for the sustainable governance of the river basin. By adjusting the model parameters, four future scenarios were established: natural continuation, economic development, environmental protection and industrial adjustment scenarios. Taking 2018 as the base year, the evolution of socio-hydrology in the upper reaches of the Han River was predicted under the four scenarios from 2019 to 2045. The simulation results show that: (1) In the entire study area, except for domestic water, the water consumption of other departments show an upward or stable trend. There are differences in water consumption changes in the upper and lower sections, which are related to the different socio-economic conditions. (2) Comparing different development scenarios, the industrial adjustment and environmental protection scenarios are superior to the other scenarios. Natural continuation and economic development scenarios appear to be unfavorable for the sustainability of water resources and the economy. (3) In addition, based on the development scenarios, some policy suggestions are put forward, such as reducing the irrigation water quota, appropriately adjusting the industrial structure and promoting the growth of the urban population and the development of urbanization.

Sichuan-Yunnan-Guizhou (SYG) carbonate-hosted Pb-Zn triangle is a world-class metallogenic belt and classified as Mississippi Valley-Type (MVT), which provides the greatest ore production in China. However, little is known about the effects of water-rock interactions involving the ore deposits and the modern hydrologic system. Measured chemical and isotopic compositions of the deep groundwater are used to evaluate water origins, potential circulation depth, reaction temperatures, and mixing process with shallow groundwater to assess possible linkages between regional hydrogeology and ore deposits. Within the Maoping sub-deposit, deep groundwater is warmer (21.2–32.0 °C), has lower pH, higher HCO3− and SO42− concentrations, higher average 87Sr/86Sr ratio (0.7148) and Sr concentration (4.1 mg/L), more positive δ13CDIC values (−4.5 to −4.2‰), and lighter average isotopic value (δD = −98 and δ18O = −13.7‰) relative to shallow groundwater, suggesting an origin distinct from modern surface recharge. The light isotopic composition of the deep warm water indicates recharge at a cooler temperature in the past, perhaps during the Last Glacial Maximum. The δ13CDIC values reflect isotopic equilibrium between deep groundwater and surrounding rocks along with a possible deep source of CO2. The oxidation process of sulfides, including H2S and pyrite linked to the ore-forming processes, could produce sulfuric acid that enhances carbonates dissolution and generates elevated HCO3− and SO42− concentrations. Reaction temperatures for the deep groundwater appear to have been around 50–65 °C based on quartz geothermometers and given a regional geothermal gradient of 24.1 °C/km suggest reactions occurred at depths ~1900 m below the land surface. Elevated Sr concentrations with radiogenic Sr isotope ratios reflect reaction with basement rocks and carbonates during the deep circulation. Sr concentration and isotope mixing models demonstrate different recharge sources and suggest the contribution of deep warm groundwater captured in mine drainage. These results reflect the importance of deep groundwater circulation and reactions in a large ore deposit that may improve understanding of potential effects of these important ore bodies on regional water compositions in the SYG triangle and other MVT ore deposits.

Let N = p q be an RSA modulus with balanced primes p and q. Suppose that the public exponent e and private exponent d satisfy ed - 1 = k ? ( N ) . We revisit the birthday attack against short exponent RSA proposed by Meng and Zheng at ACISP 2012. We show that if e k ( p + q ) , then N can be factored in both time and space complexity of O ? ( k ) . This improves the former result. We also give a detail explanation on how the baby-step giant-step method works. In short exponent RSA, decrypt and encrypt exponents are both short, then k is the smallest parameter. In this paper, we investigate a birthday attack to recover k, then factor RSA modulus N. This work improves the research of Meng and Zheng at ACISP 2012.Our result again shows that if there is a small parameter (other than d) in RSA equation, the RSA scheme may become vulnerable. Our algorithm is based on baby-step giant-step method. We also give a detail explanation on how the baby-step giant-step method works.

In this study, we use a finite difference method to solve low velocity non-Darcian flow to a well in the first kind of leaky aquifer system. Flow in the confined aquifer is assumed to be Darcian and horizontal, whereas flow in the aquitard is assumed to be non-Darcian and vertical. The threshold hydraulic gradient existence of non-Darcian flow in low permeability porous media is employed to describe the non-Darcian flow in the aquitard. A numerical solution has been obtained by using a finite difference method. This solution is compared with the previous solution for Darcian flow case in leaky aquifer system. The error has been analyzed. The comparison of this study and Darcian flow case (Hantush and Jacob, 1955) in leaky aquifer system indicates that the error is very small and can be neglected. However, the hydrogeological parameter calculation of leaky aquifer system is remarkably influenced by low velocity non-Darcian flow in aquitard. For the inflection point method (Hantush, 1956), the absolute values of estimated errors for coefficient of transmissibility of confined aquifer and vertical hydraulic conductivity of aquitard show negative relationship with the pumping rate. For the type curve-fitting method (Walton, 1962), the estimated errors for coefficient of transmissibility and elastic drainable porosity of confined aquifer are very small under small pumping rate. In general, the estimated errors for coefficient of transmissibility and elastic drainable porosity of confined aquifer can be controlled under certain level through adjusting pumping rate. The estimated error of vertical hydraulic conductivity of aquitard is quite large no matter which method is used, even up to nearly 300%.

Artificial neural network model (ANN) has been extensively used in hydrological prediction. Generally, most existing rainfall-runoff models including artificial neural network model are not very successful at simulating streamflow in karst watersheds. Due to the complex physical structure of karst aquifer systems, runoff generation processes are quite different during flood and non-flood periods. In this paper, an ANN model based on back-propagation algorithm was developed to simulate and predict daily streamflow in karst watersheds. The idea of threshold was introduced into artificial neural network model [hereafter called Threshold-ANN model (T-ANN)] to represent the nonlinear characteristics of the runoff generation processes in the flood and non-flood periods. The T-ANN model is applied to the Hamajing watershed, which is a small karst watershed in Hubei Province, China. The network input, the previous discharge, is determined by the correlative analysis, and the network structure is optimized with the maximum Nash coefficient as the objective function. And the precipitation and previous discharge are chosen as the threshold factors to reflect the effect of specificity of karst aquifer systems, respectively. By using the T-ANN, the simulation errors of streamflow have been reduced, and the simulation becomes more successful, which would be helpful for runoff prediction in karst watersheds.

Due to the pollution of shallow groundwater and the rapid development of society and economy which consume more freshwater, the exploitation of confined groundwater is steadily increasing in north China. Therefore, the rapid decline of the confined groundwater head increases the risk of confined aquifer pollution by leaky recharge from shallow aquifers. In this paper, a quantitative method for assessing confined aquifer vulnerability to contamination due to pumping has been developed. This method is based on the shallow and confined groundwater flow model and the advection and dispersion in the aquitard, including sorption. The cumulative time for the pollutant concentration at the top boundary of confined aquifer exceeding the maximum allowable level is defined as the confined aquifer vulnerability index, which can be obtained by numerically solving the solute transport equation. A hypothetical example is chosen as a case study to illustrate the whole process. The results indicate that the proposed method is a practical and reasonable assessment method of confined aquifer vulnerability.

A residual-based rainfall merging scheme using geographically weighted regression (GWR) has been proposed. This method is capable of simultaneously blending various satellite rainfall data with gauge measurements and could describe the non-stationary influences of geographical and terrain factors on rainfall spatial distribution. Using this new method, an experimental study on merging daily rainfall from the Climate Prediction Center Morphing dataset (CMOROH) and gauge measurements was conducted for the Ganjiang River basin, in Southeast China. We investigated the capability of the merging scheme for daily rainfall estimation under different gauge density. Results showed that under the condition of sparse gauge density the merging rainfall scheme is remarkably superior to the interpolation using just gauge data.

The baseflow is the drainage from the groundwater and soil water to the streamflow. As one important source of the streamflow, the baseflow could be the main source of the streamflow in the dry season. The Wei River, located in the semi-arid region of the Loess Plateau which is overlain by deep and loose soil, is the largest tributary of the Yellow River. According to former research, most of the streamflow in the dry season in the headwater of the Yellow River is baseflow. For the whole Yellow River basin, the baseflow is an important component of the streamflow, and accounts for about 44% of the annual runoff. Physically-based distributed hydrological models can simulate the runoff components separately, and are important tools to analyse the runoff components. Given the importance of the baseflow in the dry season for drought relief to support the ecological water requirement and irrigation, especially in the Wei River, the baseflow is analysed in this study. To investigate the baseflow in the Upper Wei River basin, a semi-distributed hydrological model based on a Representative Elementary Watershed approach (THREW) is employed to investigate the runoff generation process. To compare the results, an automatic baseflow separation method proposed by Arnold is used to separate the baseflow from the daily streamflow at Beidao hydrological station in Upper Wei River basin from 2001 to 2004. Based on the hydrological modelling and the Arnold separation method, the average annual baseflow index, i.e. the ratio of baseflow to the total runoff, is estimated as in the range of 0.30–0.36. The average intra-annual monthly baseflow index represents the seasonality of the baseflow due to the seasonality of the precipitation and evapotranspiration, and is also analysed.

Using distributed hydrological model to study runoff simulation in sub-watershed zones is important to understand the hydrological process in a river basin. In order to identify the sensitive parameters in different regions, in this paper, the SWAT model was constructed based in the upstream area of Shiquan hydrological station in the upper reach of the Han River. The SUFI-2 algorithm is used to analyze the parameter sensitivity of the five hydrological stations in Hanzhong, Yangxian, Shiquan, Youshuijie and Lianghekou, and the monthly runoff process of five stations and the daily runoff process at Shiquan hydrological station were calibrated in 2004-2009 and validated in 2010-2014, respectively. And the simulated results are evaluated at each station. The results show that, the parameter sensitivity of the hydrological stations is different. The value of NSE and R2 of the monthly runoff of each hydrological station were greater than 0.73 in calibration and validation period. The values of relative error are less than 18% except Yangxian station. The daily runoff simulation of Shiquan hydrological station also meets the accuracy requirement of the model. SWAT model has a good applicability in the upper area of Shiquan hydrological station, which provides a basis for the study of the impact of climate change and human activities on runoff in the upper reach of the Han River.

We give a probabilistic algorithm that constructs an RSA modulus M=pl with prescribed bit patterns, where primes p and l are both of n-bit size. Assume the Generalized Riemann Hypothesis. We show that the algorithm can generate an RSA modulus M with the ⌈n−3log2n⌉ least significant bits prescribed in advance, with time complexity of polynomial in n.

Hydrological processes simulation is an effective way for water resources evaluation and can provide scientific basis for sustainable utilization of water resources and ecological environment restoration. Compared with traditional watershed hydrological processes, hydrological processes in karst region have their unique in runoff generation and concentration stage because of the complexity and multiplicity of karst aquifer system. This paper reviews the two stages of hydrological processes simulation method in karst region: 1. systematic simulation model stage; 2. process based mechanism model stage. By analyzing the characteristics and limitation of two kinds of models, the tendency of future karst hydrological processes simulation method in two aspects are discussed: 1. quasi physically based model balancing physical senses and data richness; 2. scale adaptable model based on macro-scale applicable equations.

Let b1, b2 be any integers such that gcd(b1, b2) = 1 and c1|b1| < |b2| ≤ c2|b1|, where c1, c2 are any given positive constants. Let n be any integer satisfying gcd(n, bi) = 1, i = 1, 2. Let Pk denote any integer with no more than k prime factors, counted according to multiplicity. In this paper, for almost all b2, we prove (i) a sharp lower bound for n such that the equation b1p + b2m = n is solvable in prime p and almost prime m = Pk, k ≥ 3 whenever both bi are positive, and (ii) a sharp upper bound for the least solutions p, m of the above equation whenever bi are not of the same sign, where p is a prime and m = Pk, k ≥ 3.

We study the binary Goldbach problem with one prime number in a given residue class, and obtain a mean value theorem. As an application, we prove that for almost all sufficiently large even integers n satisfying n ≢ 2(mod 6), the equation p1 + p2 = n is solvable in prime variables p1, p2 such that p1 + 2 = P3, and for every sufficiently large odd integer \({\bar n}\) satisfying \({\bar n}\) ≢ 1(mod 6), the equation p1 + p2 + p3 = \({\bar n}\) is solvable in prime variables p1, p2, p3 such that p1 + 2 = P2, p2 + 2 = P3. Here Pk denotes any integer with no more than k prime factors, counted according to multiplicity.

It is proved that for almost all sufficiently large even integers n, the prime variable equation n = p 1 + p 2, p 1 ∈ P γ is solvable, with 13=15 < γ ≤ 1, where P γ = {p ∣ $$ p = {\left[ {m^{{\frac{1} {\gamma }}} } \right]} $$ ; for integer m and prime p} is the set of the Piatetski-Shapiro primes.

Let N be sufficiently large odd integer. It is proved that the equation N=n1+n2+n3 has solutions, where ni has a fixed number of prime factors, and an asymptotic formula holds for the number of representations.

Let N = pq be RSA modulus where primes p and q are of the same bit-length. If |ρq - p| = N1/4+γwhere ρ is a known constant satisfying 1 ≤ ρ ≤ 2 and the constant γ satisfies 0 < γ < 1/4, we show the factorization attack on N and weak key attack against RSA modulus N. We present algorithms to find the factorization of N in time O(Nγ+e) by some square root attacks, such as the baby-step giant-step method and a more sophisticated square root attack. Using similar techniques of Blomer and May (PKC 2004), we present a weak key attack and find new weak keys over the work of Maitra and Sarkar (ISC 2008).

In this paper, we cryptanalyze two knapsack-type cryptosystems. The first one is proposed by Hwang et al [4], which is based on a new permutation algorithm named Permutation Combination Algorithm. We show that this permutation algorithm is useless to the security of the cryptosystem. Because of the special super increasing structure, we can break this cryptosystem use a variant of the method provided by Shamir at Crypto'82. The second one is provided by Su et al [16], which is based on the elliptic curve discrete logarithm and knapsack problem. We show that one can recover the plaintext as long as he solve a knapsack problem. Unfounately, this knapsack problem can be solved by Shamir's method or the low density attack. Finally, we give a improved version of Su's cryptosystem to avoid these attacks.

Let N = pq be an LSBS-RSA modulus where primes p and q have the same bit-length and share the m least significant bits, and (p - 1, q - 1) = 2. Given (N, e) with e ∈ Z*Φ(N)/4 that satisfies ew + z ċ 22(m-1) = 0 (mod Φ(N)/4) with 0 < w ≤ 1/9√Φ(N)/e N1/4+θ and |z| ≤ c ew/Φ(N) N1/4-θ, we can find p and q in polynomial time. We show that the number of these weak keys e is at least N3/4+θ-e, where θ = m/log2 N, and there exists a probabilistic algorithm that can factor N in time O(N1/4-θ+e).