Research on controlling long-term performance by tensioning post tendon of long-span continuous rigid-frame bridges

The problems like cracking of the girder in the mid-span and the ever-increasing vertical deflection appear during the long term usage of the long-span continuous rigid-flame bridge. Post-tension tendon with re- served duct can increase the pre-stress of the main beam effectively, and decrease the long term span deflection in order to improve the performance of the girder. At the same time, the proper tension position is very crucial to optimise the stress distribution of the bridge and control the deflection increase. Combining with practical en- gineering, the authors analyze the influence of different positions of post-tension tendon （ including top-, web- and bottom plate tendons） on the stress and deflection of the main beam, and find out the optimal position of post tendon.

Assessment of Durability and Long Term Performance of High Density Polyethylene Drainboards in the Gotthard Railway Tunnels

Drainage layers provide permanent relief of hydrostatic water pressure, while the waterproof liner prevents any ingress of water into the tunnel. The durability and aging resistance of drainage membranes are of primary concern. This paper describes advantages and concerns related to the usage of, and the design with, polymeric drainboards in tunnel construction. Common degradation mechanisms associated with HDPE （high density polyethylene） sheets are described. The stringent requirements for the Gotthard Alpine Railway Tunnel through the Swiss Alps, e.g., high ambient temperatures of up to 45 ℃ and an expected service life of up to 100 years require outstanding aging resistance of polymeric drainage materials. The paper describes the methods deployed to investigate the long-term performance of HDPE drainboards, focusing on aging mechanisms. Details associated with the test procedures developed to reflect the specific properties of drainboards, as well as the results obtained, are presented. A summary table shows recommended product specifications needed to confine the aging properties of drainboards and to design a system performing adequately during the entire lifetime of the structure.

Long-term Performance of Moderate Heat Portland Cement with Double-expansive Sources

The long-term performance of moderate heat Portland cement with double-expansive sources （DE cement） in the system of high MgO clinker and gypsum was studied by XRD, SEM/EDAX and test methods for strength and expansion of cement. Results indicate that the periclase particle, whose size was 5-7.5μm in DE cement clinker containing 4.8 % MgO, existed individually. The periclase hydration in hardened DE cement paste started at about 60 days and completed up to 2 000 days, and ettringite in the paste was stable from 3 days to 2 000 days. Under the conditions of 4.5%-5.0 % MgO in clinker and 2.8%-3.4 %SO3 in cement, ettringite expansion and brucite expansion in DE cement paste had a continuity, entirety and stability. At the ages of 90, 365,730 and 2 000 days the expansion of the paste reached 0.07%-0.11%, 0.16%-0.21%, 0.21%-0.27 %, and 0.29%-0.38%, respectively. The results suggest that by using this cement in mass concrete it may compensate its temperature shrinkage and autogenous shrinkage to some extent.

Estimation of unloading relaxation depth of Baihetan Arch Dam foundation using long-short term memory network

The unloading relaxation caused by excavation for construction of high arch dams is an important factor influencing the foundation’s integrity and strength.To evaluate the degree of unloading relaxation,the long-short term memory(LSTM)network was used to estimate the depth of unloading relaxation zones on the left bank foundation of the Baihetan Arch Dam.Principal component analysis indicates that rock charac-teristics,the structural plane,the protection layer,lithology,and time are the main factors.The LSTM network results demonstrate the unloading relaxation characteristics of the left bank,and the relationships with the factors were also analyzed.The structural plane has the most significant influence on the distribution of unloading relaxation zones.Compared with massive basalt,the columnar jointed basalt experiences a more significant unloading relaxation phenomenon with a clear time effect,with the average unloading relaxation period being 50 d.The protection layer can effectively reduce the unloading relaxation depth by approximately 20%.

TCP TRAFFIC PERFORMANCE IMPROVING IN LTE-A NETWORKS

This paper presents a novel way to improve Transmission Control Protocol (TCP) performance of the users at the edge areas of the macro cells in Long Term Evolution Advanced (LTE-A) systems. Previous works on improving wireless TCP performance are reviewed and current considerations on TCP in LTE-A are explained. However, those solutions are neither too complex nor limited to some presuppositions which are too restricting for the deployment of LTE-A networks. In this paper a substituted TCP acknowledgement transmission scheme based on Automatic Repeat reQuest (ARQ) information in layer 2 is proposed. The simulation result shows that the proposed method can reduce the delay and improve the throughput of the edging users of the cell, as well as reducing radio resources in LTE-A macro cells.

Performance Evaluation of IPv4/IPv6 Networks for Ubiquitous Home-Care Service

Abstract--- Because of rapid development in network technology, Internet usage has become widespread. It allows users with sensing devices to obtain medical data for healthcare, such as physiological signals, voice, and video streams from telemedicine systems, and to send the healthcare data to back-end database systems, creating a ubiquitous healthcare environment. However, this environment requires a widespread and suitable network. IPv6 （Internet protocol version 6） is the next-generation Internet protocol that will be the protocol of future networks; it improves many shortcomings of IPv4. In this paper, we propose an IPv6/IPv4 U-home-care test system and analyze the network＇s parameters though a series of tests by adjusting network parameters to find the optimal design for applications in the IPv6/IPv4 U-home-care service so as to assure good performance and high quality.

Mechanisms by which fibroblast growth factor 20 improves motor performance in a mouse model of Parkinson’s disease

Genome-wide studies have reported that Parkinson’s disease is associated with abnormal expression of various growth factors. In this study, male C57 BL/6 mice aged 10 weeks were used to establish Parkinson’s disease models using an intraperitoneal injection of 60 mg/kg 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. 28 days later, 10 or 100 ng fibroblast growth factor 20 was injected intracerebroventricularly. The electrophysiological changes in the mouse hippocampus were recorded using a full-cell patch clamp. Expression of Kv4.2 in the substantia nigra was analyzed using a western blot assay. Serum malondialdehyde levels were analyzed by enzyme-linked immunosorbent assay. The motor coordination of mice was evaluated using the rotarod test. The results showed that fibroblast growth factor 20 decreased A-type potassium current in neurons of the substantia nigra, increased long-term potentiation amplitude in the hippocampus, and downregulated Kv4.2 expression. A high dose of fibroblast growth factor 20 reduced serum malondialdehyde levels and enhanced the motor coordination of mice. These findings confirm that fibroblast growth factor 20 has a therapeutic effect on the toxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and its mechanism of action is associated with the inhibition of A-type K+ currents and Kv4.2 expression. All animal procedures were approved by the Animal Care and Use Committee of Qilu Hospital of Shandong University, China in 2017(approval No. KYLL-2017-0012).

基于企业绩效视角的知识产权文本信息披露有效性研究

本文基于《知识产权相关信息披露规定》颁布这一外生冲击构建连续型DID模型,基于企业绩效视角考察知识产权文本信息披露的有效性。结果表明:在信息披露的信息效应和内损效应的影响下,《规定》颁布后企业披露的知识产权文本信息对企业绩效存在异质性影响。知识产权信息披露短期内并未给企业带来盈利能力的提升,而从长期看知识产权信息披露反映了市场对公司的良好预期。债权融资水平的降低是知识产权信息披露降低企业短期绩效的潜在机制,权益资本成本的降低是知识产权信息披露提升企业长期绩效的潜在机制。按信息类型分类分析发现,优势信息和内容信息与短期绩效的负向关系更显著,内容信息、优势信息和风险信息对长期绩效的正向影响程度依次减弱。截面分组发现,成长期和衰退期企业知识产权信息披露与短期绩效的负向关系更显著,成长期和成熟期企业知识产权信息披露与长期绩效的正向关系更显著。研究不仅证明了知识产权信息披露对企业绩效存在的差异性影响,也对政府逐步完善知识产权信息披露政策,企业更好地开展知识产权信息披露的实践活动均具有借鉴意义。

考虑土-膨润土化学相容性的阻隔墙长期服役性能研究

考虑到填埋场渗滤液中较高Na^(+)和Ca^(2+)浓度会让土-膨润土的渗透系数显著增大,从而加速高危害性污染物击穿土-膨润土阻隔墙,建立了Na^(+)和Ca^(2+)作用下土-膨润土阻隔墙-含水层系统中有机物污染物运移数值模型。该模型可以考虑渗透系数和水动力弥散系数等参数随Na^(+)和Ca^(2+)浓度的变化。利用有限差分法,获得了该模型的数值解。通过将所建模型的计算结果分别与已有解析解计算结果和COMSOL软件计算结果进行对比分析,验证了模型的正确性。最后基于所建数值模型,以甲苯作为代表性有机污染物分析和讨论了考虑和未考虑土-膨润土化学相容性、水头差和膨润土掺量对阻隔墙长期服役性能的影响。结果表明:考虑土-膨润土化学相容性之后,阻隔墙从不会被击穿变成了服役75 a后被击穿,服役寿命大幅缩短;降低阻隔墙两侧水头差,能够有效延缓污染物的击穿时间;阻隔墙膨润土掺量的下限值应在原先防渗要求的基础上适当提高,以应对污染物作用下墙体防污阻隔性能的削弱。

融入课程知识图谱的KMAKT预测

现有多数深度知识追踪模型的知识追踪结果的可解释性弱,且忽视了习题与知识点的内在关联性对知识追踪效果与预测结果的影响。针对上述问题,提出一种用于学生表现预测的结合课程知识图谱与多头注意力机制的知识追踪(KMAKT)模型。首先,采用Word2Vec和双向长短期记忆(Bi LSTM)网络将习题作答序列数据转换为低维稠密向量,利用图嵌入模型Trans R进行课程知识图谱嵌入表示,并使用多头注意力机制计算过往习题作答序列对当前知识状态的贡献程度;然后,通过注意力网络挖掘前驱知识对预测结果的影响程度;最后,通过多层神经网络获取预测结果,提高模型的可解释性与预测精度。实验结果表明,KMAKT模型在ASSISTments2017数据集上的受试者工作特征曲线下的面积(AUC)、准确率和F1值相比于深度知识追踪(DKT)模型分别提升了约5.20、4.20和2.40个百分点,具有较好的预测性能。在湖南大学信号与系统(HNU_SYS)子数据集上的知识追踪可视化结果验证了KMAKT模型的知识追踪结果符合教育学认知规律且具备一定程度的可解释性。

可持续视角下预算绩效管理的现实要求与实践方向

面对财政收支矛盾突出的现实,提升预算可持续性成为现代财政制度建设的重要内容。从可持续视角出发,预算总量的可控性、绩效约束的有效性、中期框架下的绩效保证,体现了新时代预算绩效管理的新要求。具体而言,通过提升预算透明度与强化隐性债务绩效管理,加快推进阳光财政建设、有效化解预算风险;结合零基预算与绩效导向,合理确定预算优先序、加强预算绩效信息的有效应用;加强中期财政规划对年度预算的约束,并促进其与绩效管理的有效结合,进而实现预算绩效管理从年度向中期的可持续拓展。

中华优秀传统文化核心思想理念视角下预算绩效管理的优化研究

预算绩效管理是财政管理中的重要环节,也是当前我国财政管理改革的主要着力点。它对于完善财政管理体制和财政资金管理具有重要作用。但预算绩效管理制度舶来品的属性明显,本土化任务繁重。本文详尽分析中华优秀传统文化核心思想理念,发掘其蕴含的预算绩效管理价值,应用中华优秀传统文化核心思想理念重新诠释预算绩效管理,寻求优化路径。本文建议以“讲仁爱、重民本”为前提与出发点,推演人民至上观;以“守诚信、崇正义”为过程与手段,追求道德约束观;以“尚和合、求大同”为目标与方向,提炼长远全局观,从而实现预算绩效管理与中华优秀传统文化的融合发展,促进预算绩效管理有效实施。

麻雀搜索算法优化的外啮合齿轮泵泄漏量预测

预测齿轮泵泄漏量的变化趋势有助于定量分析其性能退化过程。变分模态分解(Variational Modal Decomposition, VMD)方法对齿轮泵原始泄漏量数据进行变分模态分解,得到本征模态函数IMF,提出一种结合麻雀优化算法(Sparrow Search Algorithm, SSA)和长短期记忆神经网络(Long-Short Term Memory, LSTM)的模型,建立VMD-SSA-LSTM模型预测齿轮泵泄漏量的变化情况,并对每一个分量进行单独预测,最后将预测结果进行叠加,获得完整的预测结果。通过对比不同时间段预测结果可知,VMD-SSA-LSTM模型较单一的LSTM模型预测结果的平均相对误差最高可减小25.2%,能够完成对泄漏量的有效预测。研究结论可为齿轮泵性能衰退的定量预测提供理论支持。

董监高履职风险缓释与企业“专精特新”转型——基于董监高责任险的经验证据

党的二十大明确将培育“专精特新”企业作为建设现代化产业体系的重要内容。然而,企业“专精特新”转型存在极大的不确定性,如何增加激励驱动转型成为培育“专精特新”企业的重要考量。本文从董监高履职风险缓释的视角探究了董监高责任险对企业“专精特新”转型的影响。研究发现,企业购买董监高责任险后的风险缓释能够促进企业“专精特新”转型。异质性分析表明,这一效应在小规模企业和高竞争性行业中更显著。本文有助于加深对我国董监高责任险制度运行成效的认识,并可从企业内部治理的角度为培育“专精特新”企业提供相关建议。

组织创造力与创新绩效:长期导向与战略柔性的联合调节作用

组织创造力被认为是能快速提升企业创新绩效、获取未来市场竞争优势的重要来源。然而,由于组织惯性阻碍了创造性想法的成功实施,因而如何降低组织惯性给创造性想法的实施带来的不利影响是提升企业创新效率的关键。以318家中国企业为研究对象,运用层次回归方法,分析并检验长期导向、战略柔性以及两者的交互对组织创造力与创新绩效关系的调节作用,并运用斜率逐对比较法对比在长期导向与战略柔性的不同交互状态下,组织创造力对创新绩效的差异化影响水平。实证结果表明:战略柔性以及长期导向与战略柔性的交互能增强组织创造力与创新绩效之间的关系;当长期导向与战略柔性均强时,组织创造力对创新绩效的影响最强。因此,企业在实施创造性想法的过程中应当采取一定的举措来提升战略柔性,帮助决策者尤其是高层管理者树立长期导向,促进组织创造力向创新绩效的成功转化。

基于LSTM-文本分析的量化选股模型

随着国民生活水平的提高,越来越多的人投身于股票市场.为了科学有效地量化选股,通过将量化投资、深度学习及文本分析进行有机结合,来建立量化选股模型.首先,通过文本分析筛选出基本面利好的股票;然后,通过长短期记忆(long-short term memory,LSTM)选出预测准确度良好的股票;最后,预测所选出的股票在未来几天的股价趋势.在实证分析方面,通过本模型对部分股票进行运算,选取预测效果较好的股票:赢合科技.

不同气候条件下预应力木梁柱节点长期转角计算方法

梁柱节点长期转角是评估预应力木框架结构长期适用性能的重要指标,过量的梁柱节点长期转角会引起木梁竖向变形的增大,降低结构适用性;因此准确预测预应力木梁柱节点转角的时变规律是保证预应力木结构长期安全服役的重要前提。该文提出了不同气候条件下预应力木梁柱节点长期转角的数值计算方法,该方法包括木材水分传输、时变预应力计算、弹性转角计算、蠕变和环境变形计算、节点长期转角更新五个模块。随后利用长期试验数据验证了计算方法的准确性。最后,基于验证的数值计算方法分析了不同气候条件、木材初始含水率和构件尺寸对预应力木梁柱节点长期转角的影响规律,依据50年服役期内的最大转角蠕变系数评估了节点长期变形的性能等级。结果表明:该文所提出的数值计算方法与试验结果吻合良好;气候年平均相对湿度越大,节点发生中等或严重变形的比例越高;木材初始含水率越高,节点发生中等或严重变形的比例越低;构件理论尺寸越大,节点长期变形越小。

基于知识追踪和知识网络的学生成绩预测

随着教育事业和数字技术的蓬勃发展,高校内大量学生学习数据开始以电子形式进行存储。预测学生在未来学习中的表现(如成绩)成为一个重要课题。在现有的学生成绩预测研究中,大多数忽略了学生历史习题之间隐含的关联性。因此,该文提出了基于知识追踪和知识网络的学生成绩预测方法,其主要思想是融合知识追踪和习题对应知识点的知识网络实现成绩预测。该方法将每个学生所做习题对应的知识点以及前驱知识点组成的知识网络作为输入之一,并在知识网络中标注出掌握程度大于给定阈值的知识点;结合LSTM神经网络,通过学生学习记录融合注意力机制来追踪学生知识水平,最终预测学生在未来做题中的表现。在公开数据集上的实验结果表明,该模型在Assistment2009数据集上较DKT、DKT+、DKVMN、SAKT、MFKT、MSKT分别提高了2.3%,2.2%,3.3%,3.4%,0.41%,2.0%,在Assistment2015数据集上分别提高了9.0%,9.4%,9.7%,9.3%,8.1%,8.5%,具有较好的模型精度。

多因素作用下混凝土梁长期性能时变劣化规律

为了探究混凝土梁在锈蚀、疲劳、徐变等多因素长期作用下的性能劣化规律,对21根试验梁开展了锈蚀、疲劳和徐变的正交分组试验,通过对钢筋锈蚀深度、梁的刚度和疲劳寿命的测量计算,研究了钢筋混凝土梁长期性能的时变劣化规律。研究结果表明:相较于无损梁,在2.5%、15.0%、60.0%疲劳寿命比和3、6个月持续荷载作用下,损伤混凝土梁的锈蚀深度扩大了1.337~1.934倍;随着钢筋锈蚀和疲劳损伤程度的加深,损伤梁的刚度下降了1.694 kN·m^(2),在持续荷载作用下,其刚度仅为无损梁的34.1%;在锈蚀和徐变相继作用后,损伤梁的疲劳寿命仅为无损梁的16.14%。根据试验研究结果,给出了损伤混凝土梁的临界锈蚀深度衰减系数、短期刚度降低系数、刚度退化系数和疲劳寿命衰减系数,以反映复杂荷载与环境作用对混凝土梁长期性能的影响,为混凝土结构的长期性能评估提供了科学依据。

短期老化对温拌橡胶沥青路用性能的影响

为了研究短期老化对温拌橡胶沥青路用性能的影响,首先利用质量损失实验对其老化前后组成成分的质量变化进行初步的评估与分析;采用针入度、软化点、动态剪切流变实验对旋转薄膜烘箱短期老化前后橡胶沥青材料路用性能的差异性进行比较,同时借助凝胶渗透色谱对作用机制进行分析与验证。研究表明:虽然老化前后橡胶沥青的路用性能稍微减弱,但改性作用仍然在可接受范围内,且均比普通基质沥青高出很多;虽然液态降黏减阻剂本身平均分子质量较小,在短期老化过程中容易蒸发,但这种作用保护了基质沥青当中的轻质组分,有效地减缓了老化进程,温拌橡胶沥青较普通橡胶沥青和基质沥青具有更好的抗老化性能。