分类: 数学 >> 离散数学和组合数学 提交时间: 2024-02-18
摘要: Summary: In this paper we consider a variation of the classical Turn-type extremal problems. Let $S$be an $n$-term graphical sequence, and $\sigma(S)$be the sum of the terms in $S$. Let $H$be a graph. The problem is to determine the smallest even $l$such that any $n$-term graphical sequence $S$having $\sigma(S)\geq l$has a realization containing $H$as a subgraph. Denote this value $l$by $\sigma(H,n)$. We show $\sigma(C_{2m+1},n)=m(2n-m-1)+2$, for $m\geq 3$, $n\geq 3m$; $\sigma(C_{2m+2},n)=m(2n-m-1)+4$, for $m\geq 3$, $n\geq 5m-2$.''
分类: 数学 >> 离散数学和组合数学 提交时间: 2024-03-26
摘要: In 1975, P. Erd {o}s proposed the problem of determining the maximum number $f(n)$ of edges in a graph of $n$ vertices in which any two cycles are of different lengths. In this paper, it is proved that $$f(n) geq n+32t-1$$ for $t=27720r+169 , (r geq 1)$ and $n geq frac{6911}{16}t^{2}+ frac{514441}{8}t- frac{3309665}{16}$. Consequently, $ liminf sb {n to infty} {f(n)-n over sqrt n} geq sqrt {2 + {2562 over 6911}}.$
分类: 数学 >> 离散数学和组合数学 提交时间: 2024-03-26
摘要: In 1975,P.Erd {o}sproposedtheproblemofdeterminingthemaximumnumber$f(n)$ofedgesinagraphwith$n$verticesinwhichanytwocyclesareofdifferentlengths.Inthispaper,itisprovedthat$$f(n) geqn+ frac{107}{3}t+ frac{7}{3}$$for$t=1260r+169 , (r geq1)$and$n geq frac{2119}{4}t^{2}+87978t+ frac{15957}{4}$.Consequently,$ liminf sb{n to infty}{f(n)-n over sqrtn} geq sqrt{2+ frac{7654}{19071}},$whichisbetterthanthepreviousbounds$ sqrt2$ Y.Shi,DiscreteMath.71(1988),57-71 ,$ sqrt{2.4}$ C.Lai,Australas.J.Combin.27(2003),101-105 .Theconjecture$ lim_{n rightarrow infty}{f(n)-n over sqrtn}= sqrt{2.4}$isnottrue.
分类: 数学 >> 离散数学和组合数学 提交时间: 2024-03-26
摘要: 设f(n) 是没有等长圈的n个顶点的图的最大可能边数。确定f(n)的问题由Erdos在1975年提出。本文给出了f(n)的下界。
分类: 数学 >> 离散数学和组合数学 提交时间: 2024-02-18
摘要: In 1975, P. Erdős proposed the problem of determining the maximum number $f(n)$ of edges in a graph on $n$ vertices in which any two cycles are of different lengths. Let $f^{\ast}(n)$ be the maximum number of edges in a simple graph on $n$ vertices in which any two cycles are of different lengths. Let $M_n$ be the set of simple graphs on $n$ vertices in which any two cycles are of different lengths and with the edges of $f^{\ast}(n)$. Let $mc(n)$ be the maximum cycle length for all $G \in M_n$. In this paper, it is proved that for $n$ sufficiently large, $mc(n)\leq \frac{15}{16}n$. We make the following conjecture: $$\lim_{n \rightarrow \infty} {mc(n)\over n}= 0.$$
分类: 物理学 >> 核物理学 提交时间: 2024-01-03
摘要: Anonlinear dynamic simulation model based on coordinated control of speed and flow rate for the molten salt reactor and combined cycle systems is proposed hereto ensure the coordination and stability between the molten salt reactor and power system. This model considersthe impact of thermal properties of fluid variation on accuracy and has been validated with Simulink. This study reveals the capability of the control system to compensate for anomalous situations and maintain shaft stability in the event of perturbations occurring in high-temperature molten salt tank outlet parameters. Meanwhile, the control system's impact on the system's dynamic characteristicsunder molten salt disturbance is also analyzed. The results reveal that after the disturbance occurs, the controlled systembenefits from the action of the control, and the overshoot and disturbance amplitude are positively correlated while the systempower and frequency eventually return to the initial values. This simulation model provides a basis for utilizing molten salt reactors for power generation and maintaining grid stability.
分类: 计算机科学 >> 计算机科学的集成理论 提交时间: 2022-11-27 合作期刊: 《数据智能(英文)》
摘要: The introduction of a new technology or innovation is often accompanied by ups and downs in its fortunes. Gartner Inc. defined a so-called hype cycle to describe a general pattern that many innovations experience: technology trigger, peak of inflated expectations, trough of disillusionment, slope of enlightenment, and plateau of productivity. This article will compare the ongoing introduction of Open Science (OS) with the hype cycle model and speculate on the relevance of that model to OS. Lest the title of this article mislead the reader, be assured that the author believes that OS should happen and that it will happen. However, I also believe that the path to OS will be longer than many of us had hoped. I will give a brief history of the todays semi-open science, define what I mean by OS, define the hype cycle and where OS is now on that cycle, and finally speculate what it will take to traverse the cycle and rise to its plateau of productivity (as described by Gartner).
分类: 管理学 >> 管理学其他学科 提交时间: 2022-11-25 合作期刊: 《Economics & Management Review》
摘要: Agricultural green sustainable development has become an important strategy in every country, and whether this strategy can be realized depends on the development and popularization of the model of planting and breeding combined circular agriculture. Based on the related theories, a three-dimensional structure analysis model including the types of participants, project operation mode, planting and breeding structure and benefit is established in this paper. And by examining the typical case of green agriculture in China, in this study, three green farming models, namely, the animal-plant cycle model dominated by two agents, the three-dimensional cycle model with multi agents, and the three-stage cycle model dominated by individual investors, were summarized. Finally, through the comparison and induction of the models, the existing problems and optimization direction of the current basic models of planting and breeding cycle agriculture were put forward.
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间: 2016-05-08
摘要: Cell cycle; Replication initiation; Cell growth; DnaA; RNA polymerase
分类: 物理学 >> 核物理学 提交时间: 2024-05-17
摘要: A sustainability-oriented assessment of the nuclear energy system can provide informative and convincing decision-making support for nuclear development strategies in China. In our previous study, four authentic nuclear fuel cycle (NFC) transition scenarios were proposed, featuring different development stages and exhibiting distinct environmental, economic, and technical characteristics. However, because of the multiple and often conflicting criteria embedded therein, determining the top-priority NFC alternative for a sustainability orientation remains challenging. To address this issue, this study proposed a novel hybrid multi-criteria decision-making framework comprising fuzzy Analytic Hierarchy Process (AHP), Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE)-Geometrical Analysis for Interactive Aid (GAIA), and MOORA. Initially, an improved fuzzy AHP weighting model was developed to determine criteria weights under uncertainty and investigate the influence of various weight aggregation and defuzzification approaches. Subsequently, PROMETHEE-GAIA was used to address conflicts among the criteria and prioritize alternatives on a visualized k-dimensional GAIA plane. As a result, the alternative for direct recycling pressurized water reactor spent fuel in fast reactors is considered the most sustainable. Furthermore, a sensitivity analysis was conducted to examine the influence of criteria weight variation and validate the screening results. Finally, using MOORA, some significant optimization ideas and valuable insights were provided to support decision-makers in shaping nuclear development strategies.
分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2021-12-31
摘要: The advantages of once-through molten salt reactors include readily available fuel, low nuclear proliferation risk, and low technical difficulty. It is potentially the most easily commercialized fuel cycle mode for molten salt reactors. However, there are some problems in the parameter selection of once-through molten salt reactors, and the relevant burnup optimization work requires further analysis. This study examined a once-through graphite moderated molten salt reactor using enriched uranium and thorium. The fuel volume fraction (VF), initial heavy nuclei concentration (HN0), feeding uranium enrichment (EFU), volume of the reactor core, and fuel type were changed to obtain the optimal conditions for burnup. We found an optimal region for VF and HN0 in each scheme, and the location and size of the optimal region changed with the degree of EFU, core volume, and fuel type. The recommended core schemes provide a reference for the core design of a once-through molten salt reactor.
分类: 生物学 >> 生态学 提交时间: 2017-07-18
摘要: Apparent activation energy (Ea) is one of the most important and sensitive parameters that control soil organic C (SOC) decomposition in prevailing earth system models (ESMs). The variation of apparent Ea is affected by multiple soil environmental factors, among which soil moisture exerts a strong effect. Aiming to better inform temperature sensitivity parameterization in ESMs, here we examined the relationship between apparent Ea and soil moisture with both incubation experiment and field measurement in subtropical forests. We found that apparent Ea declined as soil moisture increased, consistently in both incubation and field experiments. We speculated that this phenomenon was due to altered microbial community composition from changing soil moisture. Our results suggest that future warming and changing precipitation would significantly affect the decomposition of recalcitrant carbon pools in subtropical forests. Lacking representation of the impact of soil moisture on SOC decomposition temperature sensitivity in current ESMs might have biased climate projection.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Copper sulfide (CuS) nanorods with the size of sub-10 nm are synthesized via a facile solegel method without postethermal treatment. The as-prepared CuS nanorods are characterized by X-ray diffraction, transmission electron microscope, and energy dispersive X-ray spectroscopy as hexagonal covellite CuS. The as-prepared CuS nanorods utilized as anode material exhibit a high reversible capacity and excellent cycling stability up to 250 cycles, as well as high Coulombic efficiency. The unique structure of the CuS nanorods should be responsible for their excellent electrochemical performance.
分类: 地球科学 >> 空间物理学 提交时间: 2017-10-31
摘要: The thermal structure and energy balance of upper atmosphere are dominated by solar activity. The response of Cold-Point-Mesopause(CPM) to solar activity is an important form. This article presents the response of Temperature-of-CPM(T-CPM) to solar activity using fourteen-year SABER data series over 80°S–80°N regions. These regions are divided into 16 latitude zones with 10° interval, and the spatial areas of 80°S—80°N,180°W—180°E are divided into 96 lattices with 10°(latitude)×60°(longitude) grid. The annual-mean values of T-CPM and F10.7 are calculated. The least squares regression method and correlation analysis are applied to these annual-mean series. First, the results show that the global T-CPM is significantly correlated to solar activity at the 0.05 level of significance with correlation coefficient of 0.90. The global solar response of T-CPM is 4.89±0.67K/100 Solar-Flux-Units(SFU). Then, for each latitude zone, the solar response of T-CPM and its fluctuation are obtained. The solar response of T-CPM becomes stronger with increasing latitude. The fluctuation ranges of solar response at middle latitude regions are smaller than those of equator and high latitude regions, and the global distribution takes on W-shape. The co-relationship analysis shows that the T-CPM is significantly correlated to solar activity at the 0.05 level of significance for each latitude zone. The correlation coefficients at middle latitude regions are higher than those of equator and high latitude regions, and the global distribution takes on M-shape. At last, for each grid cell, the response of T-CPM to solar activity and their correlation coefficient are presented.
分类: 生物学 >> 生物物理学 >> 细胞生物学 提交时间: 2016-05-15
摘要: GADD45A is a TP53-regulated and DNA damage-inducible tumor suppressor protein, which regulates cell cycle arrest, apoptosis, and DNA repair, and inhibits tumor growth and angiogenesis. However, the function of GADD45A in autophagy remains unknown. In this report, we demonstrate that GADD45A plays an important role in regulating the process of autophagy. GADD45A is able to decrease LC3-II expression and numbers of autophagosomes in mouse tissues and different cancer cell lines. Using bafilomycin A(1) treatment, we have observed that GADD45A regulates autophagosome initiation. Likely, GADD45A inhibition of autophagy is through its influence on the interaction between BECN1 and PIK3C3. Immunoprecipitation and GST affinity isolation assays exhibit that GADD45A directly interacts with BECN1, and in turn dissociates the BECN1-PIK3C3 complex. Furthermore, we have mapped the 71 to 81 amino acids of the GADD45A protein that are necessary for the GADD45A interaction with BECN1. Knockdown of BECN1 can abolish autophagy alterations induced by GADD45A. Taken together, these findings provide the novel evidence that GADD45A inhibits autophagy via impairing the BECN1-PIK3C3 complex formation.
分类: 数学 >> 离散数学和组合数学 提交时间: 2024-03-27
摘要: Let f(n) be the maximum number of edges in a graph on n vertices in which no two cycles have the same length. Erd¨os raised the problem of determining f(n). Erd¨os conjectured that there exists a positive constant c such that ex(n, C2k) ≥ cn1+1/k. Haj´os conjecture that every simple even graph on n vertices can be decomposed into at most n/2 cycles. We present the problems, conjectures related to these problems and we summarize the know results. We do not think Haj´os conjecture is true.
分类: 工程与技术科学 >> 工程与技术科学其他学科 提交时间: 2023-01-03 合作期刊: 《2022年第三届艺术设计、传播与工程科学研讨会》
摘要: Currently, the research field of industrial product service system design is immature and design models need to be improved. A territorialised design approach can effectively address these issues [1]. Geographical design refers to the use of design in system design to support the sustainable design of the system. While a new, more sustainable business model for production and consumption systems has begun to emerge internationally, this global generalisation does not necessarily lead to improvements in product service design. The construction of the ontology is based on the position and role in the design of industrial product service systems. The article suggests that advances in geobased information technology have made this situation more complex. Therefore, shifting the level of design from the global level to the regional or local level allows for a clearer, timely and pragmatic interpretation of sustainability. The article explores territorialisation as a new design approach to support the design of service systems for industrial products. In order to meet this need, designers need access to geographical information that enables them to be incorporated in an appropriate way into the design specifications for territorial product services. In this context, ontologies can play an important role in the analysis and discovery of GIS within the product lifecycle and associated service networks. Sustainability enhancements may be the result of this integration. The article focuses on the environmental pillar.
分类: 计算机科学 >> 计算机科学的集成理论 提交时间: 2022-11-27 合作期刊: 《数据智能(英文)》
摘要: Research Data Management (RDM) has become increasingly important for more and more academic institutions. Using the Peking University Open Research Data Repository (PKU-ORDR) project as an example, this paper will review a library-based university-wide open research data repository project and related RDM services implementation process including project kickoff, needs assessment, partnerships establishment, software investigation and selection, software customization, as well as data curation services and training. Through the review, some issues revealed during the stages of the implementation process are also discussed and addressed in the paper such as awareness of research data, demands from data providers and users, data policies and requirements from home institution, requirements from funding agencies and publishers, the collaboration between administrative units and libraries, and concerns from data providers and users. The significance of the study is that the paper shows an example of creating an Open Data repository and RDM services for other Chinese academic libraries planning to implement their RDM services for their home institutions. The authors of the paper have also observed since the PKU-ORDR and RDM services implemented in 2015, the Peking University Library (PKUL) has helped numerous researchers to support the entire research life cycle and enhanced Open Science (OS) practices on campus, as well as impacted the national OS movement in China through various national events and activities hosted by the PKUL.
分类: 环境科学技术及资源科学技术 >> 环境科学技术基础学科 提交时间: 2019-10-26 合作期刊: 《干旱区科学》
摘要: In recent year, desertification has become one of the most important environmental hazards all over the world, especially in developing countries such as Iran. Understanding the factors impacting on desertification and identifying the regions with high desertification potential are essential to control this phenomenon (i.e., desertification). The life cycle assessment (LCA) method is essential in assessing the desertification of ecosystems, especially for susceptible ecosystems with high degradation risks. The aim of the present study was to evaluate the desertification potential of Lorestan Province, Iran, based on the LCA method. We selected aridity, fire and dust as three indicators of desertification and collected data from 2000 to 2015. We divided the study area into 6 types of ecoregions according to the climate types (arid, semi-arid and dry sub-humid) and dominant species (Quercus brantii and Astragalus adscendens), and calculated the characteristic factor (CF) of each indicator (aridity, fire and dust) by combining the indicator layers and ecoregion layer of the study area. In a given ecoregion, the sum of CF values of aridity, dust and fire indicators represents the life cycle inventory (LCI) desertification value (the higher the LCI value, the greater the desertification potential). Then, we obtained the desertification potential map by combining and overlapping the ecoregions and the normalized indicators based on the LCA method. Aridity and fire exhibit significant impacts on desertification in the study area compared with dust. In the study area, semi-arid ecoregion with Quercus brantii as the dominant species is the largest ecoregion, while arid ecoregion with Quercus brantii as the dominant species is the smallest ecoregion. Arid ecoregion with Astragalus adscendens as the dominant species (LCI desertification value of 1.99) and dry sub-humid ecoregion with Quercus brantii as the dominant species (LCI desertification value of 0.79) show the highest and lowest desertification potentials, respectively. Furthermore, arid ecoregion with Quercus brantii as the dominant species also has a higher LCI desertification value (1.89), showing a high desertification potential. These results suggest the necessity of proper management and appropriate utilization in these ecoregions. In general, assessing desertification potential using the LCA method on a local and regional scale can possibly provide a new methodology for identifying and protecting areas with high degradation risks.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-15
摘要: Genotoxic stress activates checkpoint signaling pathways that activate the checkpoint kinases ATM and ATR, halt cell cycle progression, and promote DNA repair. A number of proteins act in concert with ATR to phosphorylate Chk1, including RAD17, the RAD9-RAD1-HUS1 complex, ATR/ATRIP and TopBp1. However, how these proteins involved act in concert with one another to propagate and maintain the checkpoint response is not well understood. Here, we reported that upregulation of RAD9 protein increased the quantity of ATRIP, suggesting that RAD9 activation will induce more efficient accumulation of ATRIP in vivo. Furthermore, the DNA damage-induced ATRIP foci formation was faster in the mRad9(-/-) ES cells. Also, ATRIP interacts specifically with RAD9, but not HUS1 and RAD1. Taken together, we suggested that RAD9 could affect both the ATRIP protein levels and DNA damage-induced ATRIP foci formation. Thus, we propose a role of RAD9 in the ATR-Chk1 pathway that is necessary for successful formation of the damage-sensing complex and DNA damage checkpoint signaling.