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Constructions and Applied Examinations of a Kind of Square-Conservative Schemes in High Precision in the Time Direction 被引量:1
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作者 季仲贞 王斌 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 1993年第3期315-324,共10页
In order to meet the needs of work in numerical weather forecast and in numerical simulations for climate change and ocean current, a kind of difference scheme in high precision in the time direction developed from th... In order to meet the needs of work in numerical weather forecast and in numerical simulations for climate change and ocean current, a kind of difference scheme in high precision in the time direction developed from the completely square-conservative difference scheme in explicit way is built by means of the Taylor expansion. A numerical test with 4-wave Rossby-Haurwitz waves on them and an application of them on the monthly mean current the of South China Sea are carried out, from which, it is found that not only do the new schemes have high harmony and approximate precision but also can the time step of the schemes be lengthened and can much computational time be saved. Therefore, they are worth generalizing and applying. 展开更多
关键词 completely square-conservative Explicit scheme High precision in the time direction Harmonious dissipative operator
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Time distribution characteristics of regional macroseismic activity in the Sichuan-Yunnan region and its significance to mid-long term prediction
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作者 黄玮琼 吴宣 《Acta Seismologica Sinica(English Edition)》 CSCD 2000年第4期368-374,共7页
The earthquakes with Ms≥6.0 are often gathered into belts or clusters and are roughly consistent with tectonic structure trends in the Sichuan-Yunnan (Chuan-Dian) region. The middle south part(98°-106°E, 21... The earthquakes with Ms≥6.0 are often gathered into belts or clusters and are roughly consistent with tectonic structure trends in the Sichuan-Yunnan (Chuan-Dian) region. The middle south part(98°-106°E, 21°-34°N) of South-North Seismic Zone can be zoned into seven small areas. There all were strong quakes with M_s≥7.0 historically in each small area. Ten earthquakes with M_s≥7.0 have occurred in this region since 1970 and they appeared in five small areas respectively. The relationships between occurrence-time and cumulative frequencies of strong quakes in these five areas are shown to be an exponential distribution or power function. By examining the inner coincidence it is indicated that these relationships are of definite significance to mid-long term macroseismic prediction of each area. 展开更多
关键词 macroseismic activity time distribution mid-long term prediction examination of inner coincidence
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Noiseless linear amplification for the single-photon entanglement of arbitrary polarization–time-bin qudit 被引量:1
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作者 Ling-Quan Chen Yu-Bo Sheng Lan Zhou 《Chinese Physics B》 SCIE EI CAS CSCD 2019年第1期210-217,共8页
Single-photon entanglement(SPE) is an important source in quantum communication. In this paper, we put forward a single-photon-assisted noiseless linear amplification protocol to protect the SPE of an arbitrary polari... Single-photon entanglement(SPE) is an important source in quantum communication. In this paper, we put forward a single-photon-assisted noiseless linear amplification protocol to protect the SPE of an arbitrary polarization–time-bin qudit from the photon transmission loss caused by the practical channel noise. After the amplification, the fidelity of the SPE can be effectively increased. Meanwhile, the encoded polarization–time-bin features of the qudit can be well preserved. The protocol can be realized under the current experimental conditions. Moreover, the amplification protocol can be extended to resist complete photon loss and partial photon loss during the photon transmission. After the amplification, we can not only increase the fidelity of the target state, but also solve the decoherence problem simultaneously. Based on the above features, our amplification protocol may be useful in future quantum communication. 展开更多
关键词 SINGLE-PHOtoN ENTANGLEMENT noiseless linear AMPLIFICATION polarization–time-bin QUDIT complete and partial photon loss
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Impact of Mobile Access to the Internet on Sales Completion Time in E-Commerce
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作者 Ushio Sumita Jun Yoshii 《Journal of Modern Accounting and Auditing》 2012年第4期503-528,共26页
Supported by a new generation of mobile devices, e-commerce is now in the process of being converted into m-commerce. While the traditional fixed PC access to the Internet continues to be important, the mobile access ... Supported by a new generation of mobile devices, e-commerce is now in the process of being converted into m-commerce. While the traditional fixed PC access to the Internet continues to be important, the mobile access appears to attract more people because of its flexibility. The purpose of this paper is to develop and analyze a mathematical model for capturing how e-commerce performance would be affected by the mobile access to the Internet, where the original paper by Sumita and Yoshii (2010) is extended for better reality. The traditional e-commerce via the fixed PC access is compared with m-commerce which accommodates both the fixed PC access and the mobile access. The distribution of the number of products purchased by time t and the distribution of the time required for selling K products are derived explicitly. Numerical examples are given for illustrating behavioral differences between m-commerce consumers and traditional e-commerce consumers. 展开更多
关键词 E-COMMERCE M-COMMERCE consumer behavior semi-Markov process sales completion time
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An Analysis of the Pre-writing Strategies Employed by Chinese College Students in the Timed Examination
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作者 Longfei Zhang 《Journal of International Education and Practice》 2021年第3期22-27,共6页
This thesis is trying to analyze the pre-writing strategies used by Chinese college students in a timed examination.The purposes of this study is to identify the possible strategies the Chinese college students claime... This thesis is trying to analyze the pre-writing strategies used by Chinese college students in a timed examination.The purposes of this study is to identify the possible strategies the Chinese college students claimed they used in the pre-writing stage of the timed examination,find if differences exist between the pre-writing strategies employed by skilled writers and unskilled writers,and find which strategy best facilitate writing in a timed condition. 展开更多
关键词 Pre-writing strategies Chinese college students In timed examination Skilled writers Unskilled writers
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Rescheduling to minimize total completion time under a limit on the makespan of the original jobs
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作者 MU Yun-dong GU Cun-chang 《通讯和计算机(中英文版)》 2009年第10期76-80,共5页
关键词 总完工时间 多项式时间 目标函数
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Is Minimizing Flow Completion Time the Optimal Way in Meeting Flow's Deadline in Datacenter Networks 被引量:3
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作者 XU Yakun LUO Hongbin REN Fei 《China Communications》 SCIE CSCD 2016年第S1期6-15,共10页
In modern datacenters, the most common method to solve the network latency problem is to minimize flow completion time during the transmission process. Following the soft real-time nature, the optimization of transpor... In modern datacenters, the most common method to solve the network latency problem is to minimize flow completion time during the transmission process. Following the soft real-time nature, the optimization of transport latency is relaxed to meet a flow's deadline in deadline-sensitive services. However, none of existing deadline-sensitive protocols consider deadline as a constraint condition of transmission.They can only simplify the objective of meeting a flow's deadline as a deadline-aware mechanism by assigning a higher priority for tight-deadline constrained flows to finish the transmission as soon as possible, which results in an unsatisfactory effect in the condition of high fan-in degree. It drives us to take a step back and rethink whether minimizing flow completion time is the optimal way in meeting flow's deadline. In this paper, we focus on the design of a soft real-time transport protocol with deadline constraint in datacenters and present a flow-based deadline scheduling scheme for datacenter networks(FBDS).FBDS makes the unilateral deadline-aware flow transmission with priority transform into a compound centralized single-machine deadlinebased flow scheduling decision. In addition, FBDS blocks the flow sets and postpones some flows with extra time until their deadlines to make room for the new arriving flows in order to improve the deadline meeting rate. Our simulation resultson flow completion time and deadline meeting rate reveal the potential of FBDS in terms of a considerable deadline-sensitive transport protocol for deadline-sensitive interactive services. 展开更多
关键词 DATACENTER NETWORKS DEADLINE PREEMPTIVE scheduling FLOW COMPLETION time
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Laparoscopic complete mesocolic excisions for colonic cancer in the last decade:Five-year survival in a single centre 被引量:1
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作者 Kristian Eeg Storli Kristin Bentung Lygre +2 位作者 Knut B?rge Iversen Maria Decap Geir Egil Eide 《World Journal of Gastrointestinal Surgery》 SCIE CAS 2017年第11期215-223,共9页
AIM To analyse clinical and long-term oncologic results after laparoscopic complete mesocolic excision(CME) for colonic cancer over a 10-year period.METHODS Consecutive patients who received laparoscopic CME at our ho... AIM To analyse clinical and long-term oncologic results after laparoscopic complete mesocolic excision(CME) for colonic cancer over a 10-year period.METHODS Consecutive patients who received laparoscopic CME at our hospital from 2007 to 2017 were prospectively registered and retrospectively analysed. In total, 341 patients were included with tumour-nodal-metastasis(TNM) stages 0-Ⅲ.RESULTS The mean age of the patients was 71.9 years. The median length of stay was 5 d. The mean lymph node harvest was 17.8. The mortality rate was 1.2%. Fifteen patients were reoperated on for anastomotic leaks. The local recurrence rate was 2.3%. Five-year TTR and cancer-specific survival CSS were 83.1% and 90.3%. The location of the tumour was not a significant variable for survival in unadjusted and adjusted survival analysis. TNM stage and anastomotic leaks were significant variables with respect to survival.CONCLUSION Laparoscopic CME results in acceptable complication rates and long-term oncologic results. It is important to avoid anastomotic leaks because of their negative effect on survival. 展开更多
关键词 complete mesocolic excision Central vascular ligature Colonic cancer Laparoscopic surgery time to recurrence Cancer specific survival
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Jade Bi and Gui: A Reconfirmation on Zhouli Completed in the Early Years of Han Dynasty Based on Sacrificial Ceremony
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作者 Tang Qicui Gong Weijun 《Journal of Literature and Art Studies》 2019年第6期582-596,共15页
As an classical book which disputes endlessly on the completed time but systematic and detailed record on official function, rituals and sacrificial vessels, Zhouli (Rites of Zhou) has become a paradoxical existence: ... As an classical book which disputes endlessly on the completed time but systematic and detailed record on official function, rituals and sacrificial vessels, Zhouli (Rites of Zhou) has become a paradoxical existence: on the one hand, it’s a crucial reference document frequently quoted for reconstructing the propriety in the past dynasties and explaining the ritual remains in modern archeology;on the other hand, its authenticity and edition age are always questioned. So the completed time of Zhouli is still a bottleneck problem and cannot be ignored. This article focuses on the tradition of sacrificial jade Bi and Gui based on the written documents and archeological findings, demonstrate once again that Zhouli was completed in early Han dynasty. 展开更多
关键词 Zhouli (Rites of Zhou) the completed time JADE BI and GUI of SACRIFICE Multiple EVIDENCE
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Complete genome of Cobetia marina JCM 21022T and phylogenomic analysis of the family Halomonadaceae 被引量:1
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作者 TANG Xianghai XU Kuipeng +2 位作者 HAN Xiaojuan MO Zhaolan MAO Yunxiang 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2018年第2期528-536,共9页
Cobetia marina is a model proteobacteria in researches on marine biofouling. Its taxonomic nomenclature has been revised many times over the past few decades. To better understand the role of the surface-associated li... Cobetia marina is a model proteobacteria in researches on marine biofouling. Its taxonomic nomenclature has been revised many times over the past few decades. To better understand the role of the surface-associated lifestyle of C. marina and the phylogeny of the family Halomonadaceae, we sequenced the entire genome of C. marina JCM 21022T using single molecule real-time sequencing technology (SMRT) and performed comparative genomics and phylogenomics analyses. The circular chromosome was 4 176 300 bp with an average GC content of 62.44% and contained 3 611 predicted coding sequences, 72 tRNA genes, and 21 rRNA genes. The C. marina JCM 2102U genome contained a set of crucial genes involved in surface colonization processes. The comparative genome analysis indicated the significant differences between C. marina JCM 21022T and Cobetia amphilecti KMM 296 (formerly named C. marina KMM 296) resulted from sequence insertions or deletions and chromosomal recombination. Despite these differences, pan and core genome analysis showed similar gene functions between the two strains. The phylogenomic study of the family Halomonadaceae is relationships were well resolved among every genera Cobetia, Kushneria, Zymobacter, and Halotalea. reported here for the first time. We found that the tested, including Chromohalobacter, Halomonas, 展开更多
关键词 Cobetia marina JCM 21022r Halomonadaceae complete genome sequence comparativegenomics PHYLOGENOMICS surface colonization single molecule real-time sequencingtechnology (SMRT)
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Model of Mediating Determinants of Time Differences in INDYCAR
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作者 Wilfrido Isidro Aldana Balderas Héctor Daniel Molina Ruiz +5 位作者 Enrique Martínez Muñoz Eleazar Villegas González Tirso Javier Hernández Gracia Arturo Sánchez Sánchez Cruz García Lirios Alfredo Barrera Escobar 《Journalism and Mass Communication》 2024年第4期232-240,共9页
The IndyCar series distinguishes itself by providing the same design and operation of the single-seater to its pilots.The difference in times is then attributable to the skills of the drivers,but considering the data ... The IndyCar series distinguishes itself by providing the same design and operation of the single-seater to its pilots.The difference in times is then attributable to the skills of the drivers,but considering the data from the races could test this assumption.The objective of this work was to establish a trajectory model to predict race times.A cross-sectional,correlational,and explanatory work was carried out with a sample of 18,474 records in the period from 2020 to 2023 of the IndyCar series.The results show that the time span predicts the time differences.In relation to the studies of acceptance of the technology,the adjustment of this to human capacities to explain the time differences in the series of racing cars is discussed. 展开更多
关键词 time differences ranking differences RANKING race time laps completed
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(3+1)-维时空分数阶Yu-Toda-Sasa-Fukuyama方程的精确解
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作者 陈进华 字德荣 《红河学院学报》 2024年第5期136-140,共5页
借助Jumarie’s modified Riemann-Liouville导数的性质,将(3+1)-维时空分数阶Yu-Toda-Sasa-Fukuyama方程简化为常微分方程.通过构造一元三次多项式,运用完全判别法得到了(3+1)-维时空分数阶Yu-Toda-Sasa-Fukuyama方程的7组精确解.
关键词 (3+1)-维时空分数阶Yu-toda-Sasa-Fukuyama方程 Jumarie’s modified Riemann-Liouville导数 精确解 多项式完全判别法 JACOBI椭圆函数
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Solving the Binary Linear Programming Model in Polynomial Time
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作者 Elias Munapo 《American Journal of Operations Research》 2016年第1期1-7,共7页
The paper presents a technique for solving the binary linear programming model in polynomial time. The general binary linear programming problem is transformed into a convex quadratic programming problem. The convex q... The paper presents a technique for solving the binary linear programming model in polynomial time. The general binary linear programming problem is transformed into a convex quadratic programming problem. The convex quadratic programming problem is then solved by interior point algorithms. This settles one of the open problems of whether P = NP or not. The worst case complexity of interior point algorithms for the convex quadratic problem is polynomial. It can also be shown that every liner integer problem can be converted into binary linear problem. 展开更多
关键词 NP-complete Binary Linear Programming Convex Function Convex Quadratic Programming Problem Interior Point Algorithm and Polynomial time
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Impact of interval between neoadjuvant chemoradiotherapy and surgery in rectal cancer patients 被引量:9
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作者 Shi-Wen Mei Zheng Liu +9 位作者 Fang-Ze Wei Jia-Nan Chen Zhi-Jie Wang Hai-Yu Shen Juan Li Fu-Qiang Zhao Wei Pei Zheng Wang Xi-Shan Wang Qian Liu 《World Journal of Gastroenterology》 SCIE CAS 2020年第31期4624-4638,共15页
BACKGROUND Epidemiologically,in China,locally advanced rectal cancer is a more common form of rectal cancer.Preoperative neoadjuvant concurrent chemoradiotherapy can effectively reduce the size of locally invasive tum... BACKGROUND Epidemiologically,in China,locally advanced rectal cancer is a more common form of rectal cancer.Preoperative neoadjuvant concurrent chemoradiotherapy can effectively reduce the size of locally invasive tumors and improve disease-free survival(DFS)and pathologic response after surgery.At present,this modality has become the standard protocol for the treatment of locally advanced rectal cancer in many centers,but the optimal time for surgery after neoadjuvant therapy is still controversial.AIM To investigate the impact of time interval between neoadjuvant therapy and surgery on DFS and pathologic response in patients with locally advanced rectal cancer.METHODS A total of 231 patients who were classified as having clinical stage II or III advanced rectal cancer and underwent neoadjuvant chemoradiation followed by surgery at the National Cancer Center/Cancer Hospital,Chinese Academy of Medical Sciences and Peking Union Medical College from November 2014 to August 2017 were involved in this retrospective cohort study.The patients were divided into two groups based on the different time intervals between neoadjuvant therapy and surgery:139(60.2%)patients were in group A(≤9 wk),and 92(39.2%)patients were in group B(>9 wk).DFS and pathologic response were analyzed as the primary endpoints.The secondary endpoints were postoperative complications and sphincter preservation.RESULTS For the 231 patients included,surgery was performed at≤9 wk in 139(60.2%)patients and at>9 wk in 92(39.8%).The patients’clinical characteristics,surgical results,and tumor outcomes were analyzed through univariate analysis combined with multivariate regression analysis.The overall pathologic complete response(pCR)rate was 27.2%(n=25)in the longer time interval group(>9 wk)and 10.8%(n=15)in the shorter time interval group(≤9 wk,P=0.001).The postoperative complications did not differ between the groups(group A,5%vs group B,5.4%;P=0.894).Surgical procedures for sphincter preservation were performed in 113(48.9%)patients,which were not significantly different between the groups(group A,52.5%vs group B,43.5%;P=0.179).The pCR rate was an independent factor affected by time interval(P=0.009;odds ratio[OR]=2.668;95%CI:1.276-5.578).Kaplan-Meier analysis and Cox regression analysis showed that the longer time interval(>9 wk)was a significant independent prognostic factor for DFS(P=0.032;OR=2.295;95%CI:1.074-4.905),but the time interval was not an independent prognostic factor for overall survival(P>0.05).CONCLUSION A longer time interval to surgery after neoadjuvant therapy may improve the pCR rate and DFS but has little impact on postoperative complications and sphincter preservation. 展开更多
关键词 Interval time Advanced rectal cancer Disease-free survival Pathologic complete response Neoadjuvant therapy SURGERY COMPLICATION Sphincter preservation
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Concise review of relaxations and approximation algorithms for nonidentical parallel-machine scheduling to minimize total weighted completion times 被引量:1
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作者 Li Kai Yang Shanlin 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2008年第4期827-834,共8页
A class of nonidentical parallel machine scheduling problems are considered in which the goal is to minimize the total weighted completion time. Models and relaxations are collected. Most of these problems are NP-hard... A class of nonidentical parallel machine scheduling problems are considered in which the goal is to minimize the total weighted completion time. Models and relaxations are collected. Most of these problems are NP-hard, in the strong sense, or open problems, therefore approximation algorithms are studied. The review reveals that there exist some potential areas worthy of further research. 展开更多
关键词 parallel machine SCHEDULING REVIEW total weighted completion time RELAXATION algorithm
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Optimizing the Resource Utilization of Datacenter Networks with OpenFlow 被引量:3
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作者 LIU Bo CHEN Ming +2 位作者 HU Chao HU Hui XU Bo 《China Communications》 SCIE CSCD 2016年第3期1-11,共11页
Decreasing the flow completion time(FCT) and increasing the throughput are two fundamental targets in datacenter networks(DCNs), but current mechanisms mostly focus on one of the problems. In this paper, we propose OF... Decreasing the flow completion time(FCT) and increasing the throughput are two fundamental targets in datacenter networks(DCNs), but current mechanisms mostly focus on one of the problems. In this paper, we propose OFMPC, an Open Flow based Multi Path Cooperation framework, to decrease FCT and increase the network throughput. OFMPC partitions the end-to-end transmission paths into two classes, which are low delay paths(LDPs) and high throughput paths(HTPs), respectively. Short flows are assigned to LDPs to avoid long queueing delay, while long flows are assigned to HTPs to guarantee their throughput. Meanwhile, a dynamic scheduling mechanism is presented to improve network efficiency. We evaluate OFMPC in Mininet emulator and a testbed, and the experimental results show that OFMPC can effectively decrease FCT. Besides, OFMPC also increases the throughput up to more than 84% of bisection bandwidth. 展开更多
关键词 datacenter flow completion times muitipath openflow
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EFFECTS OF DIGITAL ACUPRESSURE ON THE CAPILLARY ARTERIOLAR FLOW IN CEREBRAL PlA MATER OF THE DOG
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作者 韩凤岳 王肇普 董旭京 《Journal of Traditional Chinese Medicine》 SCIE CAS CSCD 1989年第2期135-139,共5页
Effects of digital acupressure on the blood flowin the capillary arterioles of the cerebral pia matercovering the posterior sigmoidal gyrus in domesticdog(Canis familiaris)were observed.The speed ofblood flow was foun... Effects of digital acupressure on the blood flowin the capillary arterioles of the cerebral pia matercovering the posterior sigmoidal gyrus in domesticdog(Canis familiaris)were observed.The speed ofblood flow was found increased to 185% after con-tinuous digital acupressure for 20 minutes.The in-crease was most prominent 15 minutes after the acu-pressure was completed;the effect subsided in 30minutes.It was also found that in cases of low basalspeed of flow before digital acupressure,the increasein the speed of blood flow after acupressure was morepronounced. 展开更多
关键词 minutes GYRUS completed CAPILLARY crease markedly FRONTAL stimulation examining SENSORY
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Research on the Trusted Energy-Saving Transmission of Data Center Network
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作者 Yubo Wang Bei Gong Mowei Gong 《China Communications》 SCIE CSCD 2016年第12期139-149,共11页
According to the high operating costs and a large number of energy waste in the current data center network architectures, we propose a kind of trusted flow preemption scheduling combining the energy-saving routing me... According to the high operating costs and a large number of energy waste in the current data center network architectures, we propose a kind of trusted flow preemption scheduling combining the energy-saving routing mechanism based on typical data center network architecture. The mechanism can make the network flow in its exclusive network link bandwidth and transmission path, which can improve the link utilization and the use of the network energy efficiency. Meanwhile, we apply trusted computing to guarantee the high security, high performance and high fault-tolerant routing forwarding service, which helps improving the average completion time of network flow. 展开更多
关键词 data center network architecture energy-saving routing mechanism trusted computing network energy consumption flow average completion time
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Factors Relevant to Knee Pain among Independent Community-Dwelling Older Adults: A Complete Cross-Sectional Study
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作者 Shinichiro Sato Yuta Nemoto +3 位作者 Noriko Takeda Yoshinori Kitabatake Kazushi Maruo Takashi Arao 《Open Journal of Preventive Medicine》 2020年第11期277-287,共11页
<strong>Objective:</strong> Knee pain is commonly observed among older adults. Therefore, the prevention of knee pain in older adults is a major public health issue. This study aimed to clarify factors rel... <strong>Objective:</strong> Knee pain is commonly observed among older adults. Therefore, the prevention of knee pain in older adults is a major public health issue. This study aimed to clarify factors relevant to knee pain among older adults. <strong>Methods:</strong> This study targeted all independent older adults (N = 6661) living in a local municipality in Japan. Participants’ health status and lifestyle habits were surveyed using a questionnaire. The survey was conducted from 15 January to 14 February 2016. Relationships between knee pain and physical activity, sitting time, nutrition, drinking, smoking, or body mass index (BMI) were examined using logistic regression analysis. Odds ratios (OR) and 95% confidence intervals (CI) adjusted for several confounding factors were calculated. <strong>Results:</strong> Older adults of 5311 responded to the questionnaire and 1843 reported knee pain. The prevalence of knee pain was 34.8%. Knee pain was significantly associated with BMI (OR: 0.60, 95% CI: 0.51 - 0.69, <em>P</em> < 0.001 in the group of normal range, OR: 0.38, 95% CI: 0.29 - 0.51, <em>P</em> < 0.001 in the group of <18.0), nutrition status (OR: 0.63, 95% CI: 0.54 - 0.75, <em>P</em> < 0.001), and physical activity (OR: 0.81, 95% CI: 0.71 - 0.92, <em>P</em> = 0.001). <strong>Conclusions:</strong> This study suggests that one in three independently-living older adults experiences chronic knee pain and that physical activity, BMI, and nutritional status are associated with knee pain. 展开更多
关键词 complete Survey Physical Activity Prevalence Rate Sitting time
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On the potential of documenting decadal-scale avifaunal change from before-and-after comparisons of museum and observational data across North America
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作者 Fernando Machado-Stredel Benedictus Freeman +12 位作者 Daniel Jiménez-Garcia Marlon E.Cobos Claudia Nunez-Penichet Laura Jiménez Ed Komp Utku Perktas Ali Khalighifar Kate Ingenloff Walter Tapondjou Thilina de Silva Sumudu Fernando Luis Osorio-Olvera A.Townsend Peterson 《Avian Research》 SCIE CSCD 2022年第1期1-10,共10页
Studies of biodiversity dynamics have been cast on either long(systematics)or short(ecology)time scales,leaving a gap in coverage for moderate time scales of decades to centuries.Large-scale biodiversity information r... Studies of biodiversity dynamics have been cast on either long(systematics)or short(ecology)time scales,leaving a gap in coverage for moderate time scales of decades to centuries.Large-scale biodiversity information resources now available offer opportunities to fill this gap for many parts of the world via detailed,quantitative comparisons of assemblage composition,particularly for regions without rich time series datasets.We explore the possibility that such changes in avifaunas across the United States and Canada before and after the first three decades of marked global change(i.e.,prior to 1980 versus after 2010)can be reconstructed and characterized from existing primary biodiversity data.As an illustration of the potential of this methodology for sites even in regions not as well sampled as the United States and Canada,we also explored changes at a single site in Mexico(Chichén-Itzá).We analyzed two large-scale datasets:one summarizing bird records in the United States and Canada before 1980,and one for the same region after 2010.We used probabilistic inventory completeness analyses to identify sites that have avifaunas that have likely been inventoried more or less completely.We prepared detailed comparisons between the two time periods to analyze species showing distributional changes over the time period analyzed.We identified 139 sites on a 0.05°grid that were demonstrably well-inventoried before 1980 in the United States and Canada,of which 108 were also well-inventoried after 2010.Comparing presence/absence patterns between the two time periods for 601 bird species,we found significant spatial autocorrelation in overall avifaunal turnover(species gained and lost),but not in numbers of species lost.We noted potential northward retractions of ranges of several species with high-latitude(boreal)distributions,while other species showed dominant patterns of population loss,either rangewide(e.g.,Tympanuchus cupido)or regionally(e.g.,Thryomanes bewickii).We developed linear models to explore a suite of potential drivers of species loss at relatively fine-grained resolutions(<6km),finding significant effects of precipitation increase,particularly on the eastern border of the United States and Canada.Our exploration of biotic change in Chichén-Itzáincluded 265 species and showed intriguing losses from the local avifauna(e.g.,Patagioenas speciosa),as well as vagrant and recent invasive species in the Yucatán Peninsula.The present work documents both the potential for and the problems involved in an approach integrating primary biodiversity data across time periods.This method potentially allows researchers to assess intermediate-time-scale biodiversity dynamics that can reveal patterns of change in biodiversity-rich regions that lack extensive time-series information. 展开更多
关键词 Biodiversity dynamics BIRDS Climate change Inventory completeness time scale TURNOVER
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