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: 数学 >> 离散数学和组合数学 提交时间: 2024-03-27
摘要: The set of all non-increasing nonnegative integers sequence π = (d(v1), d(v2), ..., d(vn)) is denoted by NSn. A sequence π ∈ NSn is said to be graphic if it is the degree sequence of a simple graph G on n vertices, and such a graph G is called a realization of π. The set of all graphic sequences in NSn is denoted by GSn. A graphical sequence π is potentially H-graphical if there is a realization of π containing H as a subgraph, while π is forcibly H-graphical if every realization of π contains H as a subgraph. Let Kk denote a complete graph on k vertices. Let Km −H be the graph obtained from Km by removing the edges set E(H) of the graph H (H is a subgraph of Km). This paper summarizes briefly some recent results on potentially Km −G-graphic sequences and give a useful classification for determining σ(H, n).
分类: 计算机科学 >> 计算机应用技术 提交时间: 2024-03-27
摘要: 大语言模型 (LLMs, Large Language Models) 能够从大量语料的上下文中学习到模式,其包括词语之间的关系、句子的结构甚至更复杂的语义和语用信息。然而,让预训练语言模型生成结构化、严格遵循约定的内容仍然是一项挑战。我们提出了一种引导大模型生成计算机高可用内容的方案,无需微调和额外的神经网络推理,通过提前约定的上下文无关文法 (CFG, Context-Free Grammar) 构建一个采用协程的约束装置,在自回归模型Transformer的解码阶段引导模型采样正确的词元,以构成符合程序约定的形式语言。这将保证计算机程序每次都能把语言模型生成内容解析为期望的数据结构、类型或指令,以便开发人员更容易地将大语言模型纳入具体应用程序。我们在多个任务数据集上进行了实验,包括JSON、Mermaid框图和函数调用表达式生成等任务,结果表明我们的方法能够有效地提高LLMs生成内容对计算机程序的可用性。
分类: 物理学 >> 凝聚态:电子结构、电、磁和光学性质 提交时间: 2024-03-26
摘要: Under typical circumstances, it is commonly believed that solutions carrying a single type of charge are either non-existent or unstable. We have investigated the principles of high-concentration charged solution preparation techniques, employing methods such as electrostatic attraction, gravity separation, positive feedback, and self-powered mechanisms to effectively separate anions and cations in solution. Through electrostatic repulsion and the use of electrostatic separation networks, the partition of homoelectric ions has been achieved. Through water and electric separation, the capability for sustained accumulation of single-charge species has been attained, thus overcoming application bottlenecks and establishing evidence for the existence of charged solutions. We have proposed voltage limits and predicted phenomena such as electrostatic boiling, topological ice crystals, and strange ice crystals, thereby opening new perspectives and possibilities for enriching the understanding and research of electrostatics and electrochemistry. The introduction of the high-concentration charged solution and its controllable preparation are expected to facilitate or pioneer research in various fields including seawater desalination, wastewater treatment, hydrovoltaic power generation, and topological ice crystals, etc. This advancement holds the potential to rectify relevant discussions in textbooks. Implementing the dual electrostatic method for self-powered desalination and purification, coupled with wind, solar, and pumped hydro storage technologies, can aid in mitigating the intermittency and waste of wind and solar power, thus advancing the cause of seawater for land.
分类: 图书馆学、情报学 >> 图书馆学 提交时间: 2024-03-26
摘要: 图书馆学具有深厚的文化基因,在与文化互动共生的发展进程中彰显了专业价值。文章采用纵向分析、对比研究和归纳演绎等方法,从动因、基础和指向3个维度考察了中国图书馆学与文化互动的逻辑关系,梳理中国图书馆学与文化共生过程中面临的定位模糊、能力弱化和体系不全等主要问题。面向文化自信自强的学科发展环境和现实要求,应通过重塑学科制度、深挖知识基因、提升核心能力和增强影响力等策略,驱动并实现图书馆学价值的再发现。
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: 动力与电气工程 >> 工程热物理学 提交时间: 2024-03-26
摘要: We conduct an experimental investigation on the integration of film cooling for thermal protection in a 72-mm cylindrical rotating detonation engine (RDE). The cooling scheme employs the injection of cooling air through a series of cat-ear-shaped film cooling holes densely distributed along the outer wall of the cylindrical combustor. Our findings reveal successful initiation of the RDE and sustained propagation of the rotating detonation wave (RDW) when film cooling is activated.
分类: 核科学技术 >> 粒子加速器 提交时间: 2024-03-25
摘要: 光核反应和紧凑型中子源是生产医用同位素的新兴工具,东华理工大学(ECUT)正在建设一种电子加速器驱动的光中子源(ECANS),用于医用同位素生产研究。本文在分析W- 100Mo光中子源的中子产额及99Mo产量的基础上,建立了中子能量调节层和中子反射层组成的放射性同位素产生模型,对不同天然氧化物材料(MoO3、Lu2O3、Y2O3)进行了放射性同位素的产生模拟及伴生产物分析,探讨了光核反应中子源生产医用同位素的可行性。研究结果显示,在高富集100Mo靶材中99Mo同位素的产量为54.1 Ci/day,在氧化物靶材中99Mo的产量为17.4 Ci/day、177Lu的产量为18.2 Ci/day以及90Y的产量为57.0 Ci/day。此外分析了天然氧化物在辐照条件下放射性杂质的含量,为后续分离纯化提供数据参考。
分类: 物理学 >> 核物理学 提交时间: 2024-03-22
摘要: 介子束流与原子核碰撞实验在中高能核物理和粒子物理研究领域发挥了重要推动作用,特别是在强子谱研究方面取得了一系列重要实验测量结果。本文对目前国际上几个比较典型的介子束流实验进行了梳理与总结,这包括了位于日本的 J-PARC 实验;欧洲核子中心的 COMPASS 实验、AMBER 实验以及计划中的 HIKE实验;美国 JLab 的 GlueX 实验和 EIC 项目。进一步,我们基于国内的 HIAF 装置对可能产生的次级介子束流的参数指标进行了分析估算,并讨论了可以开展的相关物理测量。通过对这些实验项目的调研分析,旨在为进一步规划和建造我国的介子束流实验装置并开展强子物理方面的研究有所启发和借鉴。
分类: 物理学 >> 核物理学 提交时间: 2024-03-19
摘要: The exploration of exotic shapes and properties of atomic nuclei, e.g., α cluster and toroidal shape, is afascinating field in nuclear physics. To study the decay of these nuclei, a novel detector aimed at detectingmultiple alpha-particle events was designed and constructed. The detector comprises two layers of double-sidedsilicon strip detectors (DSSD) and a cesium iodide scintillator array coupled with silicon photomultipliers arrayas light sensors, which has the advantages of their small size, fast response, and large dynamic range. DSSDscouple with cesium iodide crystal arrays are used to distinguish multiple alpha hits. The detector array has acompact and integrated design that can be adapted to different experimental conditions. The detector array wassimulated using Geant4, and the excitation energy spectra of some alpha-clustering nuclei were reconstructedto demonstrate the performance. The simulation results show that the detector array has excellent angularand energy resolutions, enabling effective reconstruction of the nuclear excited state by multiple alpha particleevents. This detector offers a new and powerful tool for nuclear physics experiments and has the potential todiscover interesting physical phenomena related to exotic nuclear structures and their decay mechanisms
分类: 物理学 >> 核物理学 提交时间: 2024-03-19
摘要: In recent years, the gap between the supply and demand of medical radioisotopes has increased, necessitating new methods for producing medical radioisotopes. Photonuclear reactions based on gamma sources have unique advantages in terms of producing high specific activity and innovative medical radioisotopes. However, the lack of experimental data on reaction cross sections for photonuclear reactions of medical radioisotopes of interest has severely limited the development and production of photonuclear transmutation medical radioisotopes. In this study, the entire process of the generation, decay, and measurement of medical radioisotopes was simulated using online gamma activation and offline gamma measurements combined with a shielding gammaray spectrometer. Based on a quasi-monochromatic gamma beam from the Shanghai Laser Electron Gamma Source (SLEGS), the feasibility of the measurement of production cross section for surveyed medical isotopes was simulated, and specific solutions for measuring medical radioisotopes with low production cross sections were provided. The feasibility of this method for high precision measurements of the reaction cross section of medical radioisotopes was demonstrated.
分类: 物理学 >> 核物理学 提交时间: 2024-03-19
摘要: 重离子碰撞过程中轻粒子的产生对于提取核物质状态方程的信息有着重要的作用。基于极端相对论量子分子动力学(UrQMD)模型,利用统计衰变模型GEMINI++处理预激发碎片的衰变,研究了预碎片的衰变对中能区Au+Au碰撞过程中轻粒子的集体流和核阻止本领的影响。研究发现,由于记忆效应,重离子碰撞过程中的预碎片的衰变产生的子核继承了母核的部分动力学性质,在考虑预碎片的衰变后可以更好地描述实验数据,并且这种效应对观测量的影响随碰撞能量的升高而减弱。结果表明,重离子碰撞过程中预碎片的衰变以及轻粒子的产生对敏感于核物质状态方程的观测量有着一定的影响。在利用这些观测量提取核物质状态方程的信息时应当仔细处理。
分类: 心理学 >> 社会心理学 提交时间: 2024-03-19
摘要: 一元论与多元论之争是道德心理学领域近些年最为活跃的理论交锋之一。道德一元论认为所有外在的道德现象与内在的道德结构都可以用一种因素来解释。道德多元论则认为道德不能只用单一因素来解释,而是存在多个不同质的道德维度,且具有文化敏感性。对应道德理论和道德基础理论是这场争议的典型代表。双方就伤害的解释力、道德失声现象、模块化道德与洁净维度独立性等方面展开论争。未来研究应从三个具体方面进一步探索道德之一元论与多元论难题,进而保持道德心理学领域的理论活力。
分类: 法学 >> 法律职业伦理 分类: 法学 >> 法律科技 提交时间: 2024-03-17
摘要: 法律职业共同体的研究在中国真正开展起来是2002年之后,到今也仅20余年的时间。而新时代与数字化的到来为法律职业共同体的建设提供了全新的政治环境与技术环境。近年来,域外研究对数字时代法律职业共同体的建设情况有着许多精深的评述,全球“四大”会计师事务所通过大规模投资技术重新进入了成熟的法律市场(美国、澳大利亚和英国)。本文首先分析中国法律职业共同体建设现状。同时考虑中国法律体制的复杂性,使用SLEPT模型对域内外的相关研究进行梳理,引入功能主义与韦伯解释主义,推测中国未来法律职业共同体的可能结构。以此结构为基准,本文分析了当前新兴的AI法律市场竞争情况。最后,本文在前述研究之上探索了当代中国法律职业共同体数字化建设的新思路。
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-03-15
摘要: 为提高空间堆中子学模拟的可靠性,基于国际临界安全手册中关于空间堆的临界基准实验(HMF005基准实验),采用蒙特卡罗程序对HMF005基准实验中堆芯排布进行建模,结合不同评价核数据库,计算6种堆芯排布下的keff计算值与实验值的偏差,并对计算值与实验值的比值的平均值、标准偏差、χ2和均方根误差等进行深入分析。研究发现,ENDF/B-VII.1、CENDL-3.2、ENDF/B-VIII.0和JEFF-3.3四种评价核数据库计算堆芯keff结果与实验值偏差处于三倍不确定度之内,其中ENDF/B-Ⅶ.1计算结果最接近实验值,CENDL-3.2与实验偏差稍大。CENDL-3.2库计算结果与实验值偏差稍大主要是由于评价库中的钼和铍核素导致,钼的同位素中92Mo的影响最大。同时还进行敏感性分析,92Mo和9Be的总反应敏感性系数主要跟弹性散射敏感性系数相关,CENDL-3.2和ENDF/B-Ⅶ.1中9Be的辐射俘获敏感性差异较大,两者偏差可达34.9%。
分类: 心理学 >> 实验心理学 提交时间: 2024-03-13
摘要: Abstract:Individuals have been observed to show higher propensity to make risk investments using non-labor income compared to labor income, although the underlying mechanisms behind this phenomenon remain unclear. In this study, we proposed that non-labor income leads to a higher prior expectation of risky investment and a reduced sensitivity towards losses. To quantitatively test this hypothesis, we employed computational modeling. A total 103 participants were recruited and completed the Balloon Analogue Risk Task (BART) with an equal monetary endowment, either as a token for completion of survey questionnaires (labor income) or as a prize from a lucky draw game (non-labor income). We found that individuals endowed with non-labor income made more risky investments in the BART compared to those with labor income. To formally compare the differences in the dynamic risk investment process between individuals with different source of income, we built four candidate computational models (Bayesian Sequential Risk-taking Model, Target Model, Scaled Target Learning Model and Scaled Target Learning with Decay Model (STL-D)). Through computational modeling, we found that within STL-D, the optimal model, the non-labor income group preset a higher targeted number of pumps at the beginning, showed a lower learning rate towards loss trials where the balloon exploded, and had lower behavioral consistency. Our study suggests that the increased tendency for risky investments with non-labor income can be attributed to an increase in prior expectations on risk-taking and a diminished sensitivity towards loss. These findings provide potential intervention targets to mitigate irrational investments associated with non-labor income.
分类: 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 提交时间: 2024-03-13
摘要: 工程中必须处理的以及人们在自然中碰到的流体,其流动在绝大多数情况下是湍动的,对这些流动的描述需要一种统计性的方法。容易描述的层流(Laminar flow)异常少见。我们相信,流体力学不能只局限于这些很少碰到的特殊情形,并且个别层流的经典描述虽然无疑重要而有价值,但是只能作为真正湍流理论的导引章节。在湍流理论中,研究的目标是宏观上相同外界条件下的流动系综的性质。
分类: 动力与电气工程 >> 电气工程 提交时间: 2024-03-07
摘要: 大规模新能源接入使得电网短路比降低,系统电压支撑强度下降,导致静态电压稳定和次/超同步振荡等稳定问题凸显。构网型变流器具有较强的电压支撑能力,在新能源场站配置一定比例的构网型变流器可以提升系统的稳定性,但构网型变流器容量与稳定裕度的解析关系不明,估算构网型变流器占比的理论值十分困难。为此,本文从小干扰稳定视角探讨构网型与跟网型变流器容量配比的估算方法及其典型值。首先,对构网型变流器进行电压源等值,并通过广义短路比指标分析了容量配比对系统强度以及稳定裕度的影响规律;其次,针对改造构网型风电机组和额外加装构网型变流器这两种技术方案,以行业相关标准为边界条件,结合典型升压变压器参数估算了实际工程中容量配比的典型值;最后,利用多风电场系统案例验证了结论的有效性。