In this study, the characteristics of organic phosphorus (P
o) fractions in sediments of six lakes from the middle and lower reaches of Yangtze River region and Southwestern China Plateau, China were ...investigated using a soil P
o fractionation scheme, and the relationships between P
o, inorganic phosphorus (P
i) and pollution status were also discussed. The results show that the rank order of P
o fractions was: residual P
o
>
HCl-P
o
>
fulvic acid-P
>
humic acid-P
>
NaHCO
3-P
o, with their average relative proportion 8.7:4.6:3.2:2.1:1.0. P
o fractions, especially nonlabile P
o, were significantly correlated with organic matter, P
o and NaOH-P
i. Different distribution patterns of P fractions were observed in those two different regions. P
o fractions in the heavily polluted sediments were higher than those in moderately and no polluted sediments, it is suggested that P
o should be paid more attention in the lake eutrophication investigation.
Organic phosphorus fractions in sediments from 6 different trophic Chinese lakes were characterized using an improved fractionation scheme.
Index structures can significantly accelerate the data retrieval operations in data intensive systems, such as databases. Tree structures, such as B + -tree alike, are commonly employed as index ...structures; however, we found that the tree structure may not be appropriate for Non-Volatile Memory (NVM) in terms of the requirements for high-performance and high-endurance. This paper studies what is the best index structure for NVM-based systems and how to design such index structures. The design of an NVM-friendly index structure faces a lot of challenges. First, in order to prolong the lifetime of NVM, the write activities on NVM should be minimized. To this end, the index structure should be as simple as possible. The index proposed in this paper is based on the simplest data structure, i.e., linked list. Second, the simple structure brings challenges to achieve high-performance data retrieval operations. To overcome this challenge, we design a novel technique by explicitly building up a contiguous virtual address space on the linked list, such that efficient search algorithms can be performed. Third, we need to carefully consider data consistency issues in NVM-based systems, because the order of memory writes may be changed and the data content in NVM may be inconsistent due to write-back effects of CPU cache. This paper devises a novel indexing scheme, called "Virtual Linear Addressable Buckets" (VLAB). We implement VLAB in a storage engine and plug it into MySQL. Evaluations are conducted on an NVDIMM workstation using YCSB workloads and real-world traces. Results show that write activities of the state-of-the-art indexes are 6.98 times more than ours; meanwhile, VLAB achieves 2.53 times speedup.
We study a few transient effects of AT-cut quartz thickness-shear resonators, including resonator turning on and turning off as well as voltage amplitude and frequency fluctuations. Mindlin's ...two-dimensional plate equations are used and solved analytically. Both a sudden change and a gradual change of the driving voltage are studied. It is found that for a resonator with a frequency of 1.649430868 MHz and material quality factor of Q = 105, the characteristic time scale of the transient effects is of the order of 0.1 s.
Information on the chemical composition of sediment phosphorus (P) is fundamental to understanding P dynamics and eutrophication in lake ecosystems. In this study, the surface (10 cm) sediments were ...collected from seven lakes representing two contrasting ecological areas in China: the middle and lower reaches of Yangtze River region and the Southwestern China Plateau. Phosphorus in these sediments was extracted by NaOH-EDTA and characterized by solution 31P nuclear magnetic resonance spectroscopy. Results show that P in the extracts was dominated by inorganic orthophosphate (76.7-97.4% of the extracted P) and orthophosphate monoesters (1.8-14.3%), with smaller amounts of orthophosphate diesters (0.4-8.9%), pyrophosphate (0.1-0.7%), and phosphonates (0.1-0.2%). The relative abundance of orthophosphate was higher in hypertrophic and shallow lake sediments than in eutrophic and mesotrophic and deep lake sediments, whereas the relative abundance of orthophosphate monoesters was the opposite. These observations suggested that the relative abundance of the two types of P forms in sediments might be related to the degree of lake eutrophication.
In order to characterize the oxygen isotopic composition of internal phosphate and explore the possibility of using these data to identify phosphate sources, we measured oxygen isotopic compositions ...of phosphate（δ^18Op） in sediment pore water in Hongfeng Lake, a typical deep-water lake in a mountainous area. These data, in combination with δ^18Opin surface water samples and water column samples, were successfully used to identify phosphate sources. The δ^18Op value of sediment pore water ranged from 15.2% to 15.8%, with an average value of 15.5%—the δ^18Op value of internal phosphate. The δ^18Op values decreased gradually through the water column from 19.4% in surface water to 16.4% in deeper water, implying that internal phosphate had more negative δ^18Op values than external phosphate. This finding was substantiated by horizontal variations in δ^18Op values, which decreased with increasing distance from inflowing rivers. All collected evidence suggests that external and internal phosphate have distinctly different isotopic signatures and that these signatures have not been considerably altered by biological mediation in Hongfeng Lake. Therefore, δ^18Op can be used to distinguish phosphate sources. A two-endmember mixing model showed that internal phosphate had an average contribution of 40%, highlighting the influence of internal phosphorus loading on aqueous phosphate and eutrophication. This study illustrates the need to reduce the internal phosphorus load from sediment and provides guidance for nutrient management and in-lake restoration treatment in Hongfeng Lake. The data presented here are limited, but serve to highlight the great potential of δ^18Op as an effective tracer for identifying phosphate sources. Systematic investigations of the oxygen isotopic compositions of external phosphate, internal phosphate, and phosphate through the water column, in combination with in-lake P biogeochemical cycle study, would be desirable in further research.
We study the performance of the gradient play algorithm for stochastic games (SGs), where each agent tries to maximize its own total discounted reward by making decisions independently based on ...current state information which is shared between agents. Policies are directly parameterized by the probability of choosing a certain action at a given state. We show that Nash equilibria (NEs) and first-order stationary policies are equivalent in this setting, and give a local convergence rate around strict NEs. Further, for a subclass of SGs called Markov potential games (which includes the setting with identical rewards as an important special case), we design a sample-based reinforcement learning algorithm and give a non-asymptotic global convergence rate analysis for both exact gradient play and our sample-based learning algorithm. Our result shows that the number of iterations to reach an <inline-formula><tex-math notation="LaTeX">\epsilon</tex-math></inline-formula>-NE scales linearly, instead of exponentially, with the number of agents. Local geometry and local stability are also considered, where we prove that strict NEs are local maxima of the total potential function and fully-mixed NEs are saddle points.
The continuous release of nutrients from sediment is a major barrier to the remediation of black odorous rivers. This study used a long-term laboratory incubation experiment to investigate the ...effectiveness of sediment dredging, intermittent aeration, and in situ inactivation with modified clays to reduce the internal loading of sediment from a seriously polluted river. The results indicated that intermittent aeration and in situ inactivation were effective in reducing the TN and NH4+ concentrations in the water column. However, sediment dredging did not consistently reduce the TN and NH4+ concentrations in the water column. In contrast, the three methods were all effective in controlling the TP and PO43− concentrations in the water column. Except for dredging, >30% of NH4+ and 40% of PO43− fluxes from sediment were reduced when compared with a control sample after 120 days of remediation. Dredging induced a significant release of NH4+ from sediment. Dredging and aeration made nearly no change to the amount of extractable nitrogen in the sediment. However, inactivation may increase sediment-extractable ammonium in deep sediment layers with time due to vertical transportation of clay by intensive bioturbation. Dredging is the most effective way to reduce surface mobile phosphorus over time while the transported clays can reduce a large percentage of the mobile phosphorus in deeper sediment. The relative abundance of Nitrospira in the surface sediment increased significantly with each remediation measure, creating favorable conditions for the reduction of the ammonium released from sediment. Altogether, the results of this study indicated that clay inactivation is the best method for controlling the internal loading of both phosphorus and nitrogen in seriously polluted river sediment.
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•Dredging, aeration and inactivation were used to control river's internal loading.•Sediment dredging initially induces a significant NH4+ release from sediment.•Dredging and inactivation can reduce mobile P at various sediment depths with time.•Clay inactivation performs the best in the co-reduction of N and P in sediment.
This article considers a distributed reinforcement learning problem for decentralized linear quadratic (LQ) control with partial state observations and local costs. We propose a zero-order ...distributed policy optimization algorithm (ZODPO) that learns linear local controllers in a distributed fashion, leveraging the ideas of policy gradient, zero-order optimization, and consensus algorithms. In ZODPO, each agent estimates the global cost by consensus, and then conducts local policy gradient in parallel based on zero-order gradient estimation. ZODPO only requires limited communication and storage even in large-scale systems. Further, we investigate the nonasymptotic performance of ZODPO and show that the sample complexity to approach a stationary point is polynomial with the error tolerance's inverse and the problem dimensions, demonstrating the scalability of ZODPO. We also show that the controllers generated throughout ZODPO are stabilizing controllers with high probability. Last, we numerically test ZODPO on multizone HVAC systems.
The distribution characteristics of phosphorus （P） forms in the sediment profile of Lake Erhai, in southwestern China has been investigated by sequential extraction and 31p nuclear magnetic resonance ...spectroscopy （NMR） of NaOH extracts to understand P dynamics and its potential contribution to lake eutrophication. Contents of P fractions varied in the order of NH4C1 extracted P （NH4C1- P） 〈 bicarbonate-dithionite extracted P （BD-P） 〈 HC1-P, Residual-P 〈 NaOH extracted P （NaOH-P）. The highly available NH4C1-P represented less than 1% of total P （TP）. BD-P and NaOH extracted reactive P （NaOH-rP） averaged 39%, while the ratio of Fe/P was higher than 15, indicating low P release from the sediments under permanent oxic condition. The less bio-available HC1-P, NaOH extracted nonreactive P （NaOH-nrP） and residual-P contributed 61% of TP. Regression analysis revealed that BD-P, NaOH-rP and HC1-P were positively correlated with the contents of Fe and Mn, A1 and Fe, and Ca, respectively. The investigation of P compound groups in NaOH extracts by 31p NMR showed that ortho-P and monoester-P were the largest two constituents of the P pool, followed by diester-P, phosphonate and pyro-P. A comparison of vertical variations of P groups in the sediment profile suggested that these compounds were involved in the P recycling to different extents in Lake Erhai. In particular, the lake exhibits high potential for labile P release from the surface sediments, which should be taken into consideration even after the outsourced P runoff ceased.
We study the stationary points and local geometry of gradient play for stochastic games (SGs), where each agent tries to maximize its own total discounted reward by making decisions independently ...based on current state information which is shared between agents. Policies are directly parameterized by the probability of choosing a certain action at a given state. We show that Nash equilibria (NEs) and first-order stationary policies are equivalent in this setting by establishing a gradient domination condition for SGs. We characterize the structure of strict NEs and show that gradient play locally converges to strict NEs within finite steps. Further, for a subclass of SGs called Markov potential games, we prove that strict NEs are local maxima of the total potential function, thus locally stable under gradient play, and fully-mixed NEs are saddle points, thus unstable under gradient play.
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