SN2025钢与硬质合金的真空钎焊工艺研究

首先初选6种钎料,通过检测钎缝的机械性能(主要指剪切强度)并结合微观分析对钎料进行优选,确定了1～2种适用于钎焊SN2025钢与硬质合金的钎料;针对选定的钎料,进行真空钎焊工艺参数的正交优化试验,同样是通过检测钎缝的机械性能来判定最佳的工艺参数.     

基于ATmega128的无线数据采集系统

针对电力系统远程数据采集和控制,采用新型嵌入式单片机Atmega128、数传电台MDS设计的无线数据采集系统。介绍了高速异步FIFO芯片SN74ACT7808和高速A/D芯片的性能及该采集系统的接口电路.介绍了以ATmega128为核心的远控单元的设计及该单片机与数传电台的串行通信和硬件接口电路.简单介绍了串口通信C语言编程方法。     

基于信噪比的多目标决策方法及其工程应用

求解多目标优化问题得到非劣解集后,为了确定出最终的设计方案,研究简单而有效的多目标决策方法十分必要。为此,提出了一种基于信噪比的多目标决策方法。该决策方法在多目标优化设计中引入稳健设计的思想,运用信噪比的概念在非劣解集中选择最稳健的设计作为最终方案。基于信噪比的多目标决策方法,不仅可以方便地对非劣解进行评价和排序,而且考虑到工程实际中误差的客观存在,具有较大的工程应用价值。文中采用某轻型飞机齿轮箱多目标优化设计作为算例,验证了采用该决策方法的必要性和有效性。     

Selective attention to orientation and closure: An event-related potential study

Event-related potentials (ERPs) were recorded when the subjects attended selectively to stimuli in one visual field and responded to the targets including designated feature (orientation or closure) value. Attention to spatial location elicited enlarged PI and Nl at posterior electrodes contralater-al to the stimulus location, whereas selection to orientation or closure elicited selection negativity (SN) and a late negative component (LNC). The selection of spatial location was prior to the selection of orientation or closure. SN was elicited only by the stimuli in the attended visual field, suggesting that the selection of orientation and closure are contingent on the prior selection of location. Moreover, the onset latency of SN was earlier for closure selection than for orientation selection, indicating that the processing of closure occurred earlier than the processing of orientation. The results are consistent with the early-selection theories of attention and provide psycho-physiological evidence     

岩石分数阶蠕变损伤本构模型研究

红层边坡蠕滑现象显著,岩石具有较强的蠕变特性。为了反映岩石蠕变全过程,基于岩石蠕变的阶段特征,通过弹性体、基于分数阶微积分的软体元件和黏塑性体来分别描述岩石蠕变的弹性应变、黏弹性应变和黏塑性应变。将损伤变量加入弹性体,引入SN元件改进分数阶软体元件,综合改进后的考虑时效损伤的弹性体和基于分数阶微积分的非定常黏滞体和黏塑性体,构建新的三元件蠕变损伤本构模型。采用RLW-2000三轴流变试验系统开展红层泥岩三轴压缩蠕变试验,再引用相关文献中盐岩和红砂岩典型蠕变数据,通过三种岩石蠕变曲线对该模型进行验证,证明所建模型的合理性和适用性。     

南水北调中线渠段工程地基土的研究

简介南水北调中线工程的基本情况,通过多年的勘察和研究现已基本查明了南水北调中线工程地质条件,本文对渠段地基土的主要工程地质问题进行了专门的研究。特别是对特殊土地基、饱和砂土震动液化问题、采空区地面变形和不均匀沉降以及渠道地基渗漏等问题进行了分析,并提出了防治对策及建议。     

The Role of Nrf2 Transcription Factor and Sp1-Nrf2 Protein Complex in Glutamine Transporter SN1 Regulation in Mouse Cortical Astrocytes Exposed to Ammonia

Ammonia toxicity in the brain primarily affects astrocytes via a mechanism in which oxidative stress (OS), is coupled to the imbalance between glutamatergic and GABAergic transmission. Ammonia also downregulates the astrocytic N system transporter SN1 that controls glutamine supply from astrocytes to neurons for the replenishment of both neurotransmitters. Here, we tested the hypothesis that activation of Nrf2 is the process that links ammonia-induced OS formation in astrocytes to downregulation and inactivation of SN1 and that it may involve the formation of a complex between Nrf2 and Sp1. Treatment of cultured cortical mouse astrocytes with ammonia (5 mM NH₄Cl for 24 h) evoked Nrf2 nuclear translocation, increased its activity in a p38 MAPK pathway-dependent manner, and enhanced Nrf2 binding to Slc38a3 promoter. Nrf2 silencing increased SN1 mRNA and protein level without influencing astrocytic [³H]glutamine transport. Ammonia decreased SN1 expression in Nrf2 siRNA treated astrocytes and reduced [³H]glutamine uptake. In addition, while Nrf2 formed a complex with Sp1 in ammonia-treated astrocytes less efficiently than in control cells, treatment of astrocytes with hybrid-mode inactivated Sp1-Nrf2 complex (Nrf2 silencing + pharmacological inhibition of Sp1) did not affect SN1 protein level in ammonia-treated astrocytes. In summary, the results document that SN1 transporter dysregulation by ammonia in astrocytes involves activation of Nrf2 but does not require the formation of the Sp1-Nrf2 complex.     

Topology awareness algorithm for virtual network mapping

Network virtualization is recognized as an effective way to overcome the ossification of the Internet. However, the virtual network mapping problem (VNMP) is a critical challenge, focusing on how to map the virtual networks to the substrate network with efficient utilization of infrastructure resources. The problem can be divided into two phases: node mapping phase and link mapping phase. In the node mapping phase, the existing algorithms usually map those virtual nodes with a complete greedy strategy, without considering the topology among these virtual nodes, resulting in too long substrate paths (with multiple hops). Addressing this problem, we propose a topology awareness mapping algorithm, which considers the topology among these virtual nodes. In the link mapping phase, the new algorithm adopts the k-shortest path algorithm. Simulation results show that the new algorithm greatly increases the long-term average revenue, the acceptance ratio, and the long-term revenue-to-cost ratio (R/C).     

灵活运用SN388地震仪的应用软件

SN388仪器是目前世界上先进的地震仪之一，近几年来，该仪器应用于各种勘探项目中，随着勘探精度的提高和勘探市场的不断扩大，对地震仪器的性能也提出了更高的要求，本文介绍了如何灵活运用SN388系统软件，提高仪器性能，满足地震勘探的要求。