Search

In order to solve the problem of delay oscillation and empty window caused by the bottleneck bandwidth and round-trip time(BBR) congestion control algorithm in the STARTUP phase due to not receiving the acknowledge character(ACK) in the campus network,the BBR unilateral adaptation algorithm is proposed.The algorithm only runs on the sender,and it is not restricted by network protocols and upper-layer applications.By improving the weighting coefficient of the delay estimator,we design the instantaneous average deviation estimator of the delay and use the estimation result as the oscillation smoothing factor of the delay estimator to improve the ability of the delay estimator to deal with severe delay jitter.To solve the inevitable empty window problem and sequence number wraparound as much as possible,a flow state machine and a STARTUP state machine are designed at the sending end to maintain a high link throughput.According to the specific transmission situation,the traffic is divided into 6 states:new,blocked,waiting,time_waiting,running,terminated,and according to the traffic feedback,the transmission performance of the STARTUP stage is divided into 3 states:GOOD,NORMAL,BAD.Experimental results show that the improved BBR has better transmission performance in the STARTUP phase than the original BBR algorithm and is better than the passive congestion control algorithm (Reno,CUBIC) currently.

Biological nitrogen (N) fixation is an important source of N in terrestrial ecosystems, but the response of soil microbial N fixation rate to N deposition in different forest ecosystems still remains uncertain. We conducted a field N addition experiment to simulate atmosphere N deposition in subtropical Pinus taiwanensis and Castanopsis faberi forests. We set up three levels of nitrogen addition using urea as the N source: 0 (control), 40 (low N), and 80 g N·hm -2 ·a -1 (high N) to examine the chemical properties, microbial biomass C, enzyme activities, and nifH gene copies of top soils (0-10 cm). We also measured the microbial N fixation rate using the 15 N labeling method. Results showed that N addition significantly reduced the soil microbial N fixation rate in the P. taiwanensis and C. faberi forests by 29%-33% and 10%-18%, respectively. Nitrogen addition significantly reduced N-acquiring enzyme (i.e., β-1, 4-N-acetylglucosaminidase) activity and nifH gene copies in both forest soils. There was a significant positive correlation between the microbial N fixation rate and soil dissolved organic C content in the P. taiwanensis forest, but a significant negative relationship between the rate of soil microbial nitrogen fixation and NH 4 + -N content in the C. faberi forest. Overall, soil microbial N fixation function in the P. taiwanensis forest was more sensitive to N addition than that in the C. faberi forest, and the factors affecting microbial N fixation varied between the two forest soils. The study could provide insights into the effects of N addition on biological N fixation in forest ecosystems, and a theoretical basis for forest management.

Soil phosphatases are important in the mineralization of organophosphates and in the phosphorus (P) cycle. The kinetic mechanisms of phosphatases in response to nitrogen (N) deposition remain unclear. We carried out a field experiment with four different concentrations of N: 0 g N·hm -2 ·a -1 (control), 20 g N·hm -2 ·a -1 (low N), 40 g N·hm -2 ·a -1 (medium N), and 80 g N·hm -2 ·a -1 (high N) in a subtropical Moso bamboo forest. Soil samples were then collected from 0 to 15 cm depth, after 3, 5 and 7 years of N addition. We analyzed soil chemical properties and microbial biomass. Acid phosphatase (ACP) was investigated on the basis of maximum reaction velocity ( V m ), Michaelis constant ( K m ), and catalytic efficiency ( K a ). Results showed that N addition significantly decreased soil dissolved organic carbon (DOC), available phosphorus, and organophosphate content, but significantly increased soil ammonium, nitrate-N content, and V m . There was a significant relationship between V m and the concentrations of available phosphorus, organophosphate, and soil DOC. In general, N addition substantially increased K a , but did not affect K m . The K m value in the high N treatment group was higher than that in the control group after five years of N addition. K m was significantly negatively associated with both available phosphorus and organophosphate. Medium and high N treatments had stronger effects on the kinetic parameters of ACP than low N treatment. Results of variation partition analysis showed that changes in soil chemical properties, rather than microbial biomass, dominated changes in V m (47%) and K m (33%). In summary, N addition significantly affected substrate availability in Moso bamboo forest soil and modulated soil P cycle by regulating ACP kinetic parameters (especially V m ). The study would improve the understanding of the mechanisms underlying soil microorganisms-regulated soil P cycle under N enrichment. These mechanisms would identify the important parameters for improving soil P cycling models under global change scenarios.

Objective: To systematically evaluate the efficacy and safety of anterior decompression and posterior decompression in the treatment of thoracolumbar fractures with spinal cord injury, so as to provide a good scientific basis for more effective treatment of thoracolumbar fractures with spinal cord injury., Methods: A clinical data about comparative study of anterior decompression and posterior decompression in the treatment of thoracolumbar fractures with spinal cord injury was searched and collected. The databases of Pubmed, Embase, Cochrane Library, CNKI, CBM, Wanfang Medical Network were searched by computer. Artificially collected journals included Spine, European Spine Journal, The Journal of Bone and Joint Surgery. Two spine surgeons independently screened the literature according to established inclusion and exclusion criteria and assessed the quality of the included studies. Meta-analysis was performed on the data using Review Manager 5.3 software, the indicators included operative time, intraoperative blood loss, postoperative tactile score, postoperative motor score, postoperative vertebral height, hospitalization time, neurological function recovery, efficiency of treatment, postoperative complications., Results: Fifteen randomized controlled trials (RCTs) were enrolled in a total of 1 360 patients, including 680 anterior decompression and 680 posterior decompression. The results of Meta-analysis showed that the anterior decompression group had longer operation time [MD=80.09, 95% CI(36.83, 123.34), P=0.000 3], more intraoperative blood loss [MD=225.21, 95%CI(171.07, 279.35), P <0.000 01], longer hospitalization time [MD=2.31, 95% CI(0.32, 4.31), P=0.02]. And the postoperative tactile score [MD=13.39, 95% CI(9.86, 16.92), P <0.000 01], postoperative motor score [MD=13.15, 95% CI(7.02, 19.29), P <0.000 1], vertebral height [MD=1.36, 95% CI(0.79, 1.92), P <0.000 01] in anterior decompression were higher than that in posterior decompression. There was no statistically significant differences in the efficacy of treatment [OR=1.14, 95% CI(0.56, 2.31), P=0.72], neurological recovery [OR=0.87, 95% CI(0.57, 1.33), P=0.52] between two groups., Conclusions: Compared with posterior decompression, the anterior decompression has the advantages of longer operating time, more intraoperative blood loss, longer hospitalization time, higher postoperative tactile score, higher postoperative motor score, and higher injury vertebral height, But there was no significant difference in the treatment efficiency and nerve function recovery between two groups., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© 2019 by the China Journal of Orthopaedics and Traumatology Press.)

Designing the nature reserves is an effective approach to protecting biodiversity. The traditional approaches to designing the nature reserves could only identify the core area for protecting the species without specifying an appropriate land area of the nature reserve. The site selection approaches, which are based on mathematical model, can select part of the land from the planning area to compose the nature reserve and to protect specific species or ecosystem. They are useful approaches to alleviating the contradiction between ecological protection and development. The existing site selection methods do not consider the ecological differences between each unit and has the bottleneck of computational efficiency in optimization algorithm. In this study, we first constructed the ecological value assessment system which was appropriated for forest ecosystem and that was used for calculating ecological value of Daiyun Mountain and for drawing its distribution map. Then, the Ecological Set Covering Problem (ESCP) was established by integrating the ecological values and then the Space-ecology Set Covering Problem (SSCP) was generated based on the spatial compactness of ESCP. Finally, the STS algorithm which possessed good optimizing performance was utilized to search the approximate optimal solution under diverse protection targets, and the optimization solution of the built-up area of Daiyun Mountain was proposed. According to the experimental results, the difference of ecological values in the spatial distribution was obvious. The ecological va-lue of selected sites of ESCP was higher than that of SCP. SSCP could aggregate the sites with high ecological value based on ESCP. From the results, the level of the aggregation increased with the weight of the perimeter. We suggested that the range of the existing reserve could be expanded for about 136 km 2 and the site of Tsuga longibracteata should be included, which was located in the northwest of the study area. Our research aimed at providing an optimization scheme for the sustai-nable development of Daiyun Mountain nature reserve and the optimal allocation of land resource, and a novel idea for designing the nature reserve of forest ecosystem in China.

G78 nitrogen deposition collector was used to investigate the background value of local nitrogen deposition flux in Daiyun Mountain National Nature Reserve of Fujian province. The results showed that dry and wet nitrogen deposition of Daiyun Mountain National Nature Reserve was 2.30 kg·hm -2 and 14.79 kg·hm -2 from March to October in 2015. 53% of dry deposition was in the form of dissolved organic nitrogen (DON, 1.21 kg·hm -2 ). The main form of inorganic nitrogen (DIN) in dry deposition was NO 3 - deposition (0.71 kg·hm -2 ), with NH 4 + deposition (0.37 kg·hm -2 ) being lower compared to NO 3 - deposition. DON and DIN flux in wet deposition was 5.38 kg·hm -2 and 9.41 kg·hm -2 , respectively. DIN flux in wet deposition was mainly in the form of NH 4 + deposition (6.07 kg·hm -2 ). Wet nitrogen deposition flux was found positively correlated with local precipitation. Wet nitrogen deposition in Daiyun Mountain National Nature Reserve might have significant negative effects on local water resource.