基于卷积神经网络的5G蜂窝网络无线定位方法

5G蜂窝网络发展迅猛，其覆盖面积将逐渐增大，因此使用5G蜂窝网络进行定位是有研究潜力的研究方向。本文提出一种新的深度学习技术来实现高效、高精度和低占用的定位，以代替传统指纹定位过程中繁重的指纹库生成以及距离计算。该方法建立了一个特殊的卷积神经网络，并根据5G天线信号的接收信号强度指示、相位和到达角等特征量，选择合适的输入数据格式构造样本组建训练集，对该卷积神经网络进行训练。训练得到的卷积神经网络可以替代指纹定位中的庞大指纹库，非常有利于直接在5G移动设备端实现定位。虽然卷积神经网络在训练过程中需要大量时间，但在训练完毕后直接进行分类定位的速度非常快，可以保障定位实现的实时性。本文所实现的卷积神经网络权重与偏置所占内存不到0.5 MB，且能够在实际应用环境中以95%的定位准确率以及0.1 m的平均定位精度实现高精度定位。     

Improved photoluminescence and multi-mode optical thermometry of Er3+/Yb3+ co-doped (Ba,Sr)3Lu4O9 phosphors

Contactless optical thermometers have attracted extensive attentions for applications in scientific research and technological fields due to their apparent advantages. Herein, a novel sequence of Ba_3-xSr_xLu₄O₉ (B_3-xS_xLO):Er³⁺/Yb³⁺ phosphors were successfully prepared to investigate the temperature sensing property. By establishing energy transfer from Yb³⁺ to Er³⁺ and regulating the local lattice environment, up-conversion luminescence of Er³⁺ is dramatically improved when excited by 980 nm laser. This can effectively promote signal-noise ratio and reduce the errors in temperature detection. Furthermore, a multi-mode optical thermometry, which includes the fluorescence intensity ratio (FIR) from two thermally coupled levels of ²H_11/2/⁴S_3/2, FIR based on non-thermally coupled system of ²H_11/2/⁴F_9/2 and fluorescence lifetime of ⁴S_3/2 state of Er³⁺, was explored systematically. The fabricated samples exhibit the superior temperature measurement performances containing wide temperature-sensing range, superior signal discriminability, high sensitivity and favorable repeatability, indicative of the enormous utilization prospects of B_3-xS_xLO:Er³⁺/Yb³⁺ for thermometry.     

The effect of turbulent jet induced by pre-chamber sparkplug on combustion characteristics of hydrogen-air pre-mixture

Effect of turbulent jet ignition induced by pre-chamber sparkplug (PCSP), a simper version of turbulent jet ignition pre-chamber system without fuel injection, on the air-hydrogen combustion characteristics was conducted based on an optical constant volume chamber under varied equivalence ratio conditions. The dynamic pressure sensor and schlieren system were used to evaluate the heat release and flame propagation characteristics. The results confirm the feasibility of PCSP type turbulent jet. The jet increase the flame propagation speed significantly compared to standard ignition, which shorten ignition delay and combustion duration, advance T50 largely, and increase the maximum combustion pressure slightly. As a result, the combustion intensity is increased largely, especially under lean regime, the combustion intensity index can be as high as 1.7 at certain equivalence ratio. In addition, the PCSP turbulent jet reduces the sensitivity of heat release to variation of equivalence ratio, which is helpful to simplify the combustion controlling strategy. Furthermore, with the enhancement of the flame propagation, the tendency of knocking combustion can be suppressed potentially.     

不同距离应变片测定Ⅰ型动态应力强度因子对比试验研究

基于线弹性断裂力学理论，采用应变片法开展了冲击动荷载作用下的三点弯曲试验，探讨距扩展裂纹不同距离的应变片测定Ⅰ型应力强度因子的差异。当应变片与扩展裂纹成特定锐角和钝角时，采用与裂纹扩展速度和应变片的位置相关的二项式表征裂纹尖端附近应变场，并结合理论解析和试验实测的应变与裂纹扩展时间曲线，推导得到了应力强度因子计算公式。同时，采用动焦散线试验对比分析应变片法测定的动态应力强度因子值。结果表明，应变片在裂纹尖端附近合理区域内，测定的裂纹尖端动态应力强度因子值与动焦散线试验结果吻合较好;明确了不同距离对测定Ⅰ型裂纹应力强度因子的影响，随着应变片粘贴距离变大，测定的动态应力强度因子值与动焦散线法相差增大。研究结果为进一步应用应变片法研究岩石类材料的断裂性能提供了试验基础。     

Productivity of lactating dairy cows fed diets with teff hay as the sole forage

Groundwater depletion is one of the most pressing issues facing the dairy industry in arid regions. One strategy to improve the industry's drought resilience involves feeding drought-tolerant forage crops in place of traditional forage crops such as alfalfa and corn silage. The objective of this study was to assess the productivity of lactating dairy cows fed diets with teff hay (Eragrostis tef) as the sole forage. Teff is a warm-season annual grass native to Ethiopia that is well adapted to drought conditions. Nine multiparous Holstein cows (185 ± 31 d in milk; mean ± standard deviation) were randomly assigned to 1 of 3 diets in a 3 × 3 Latin square design with 18-d periods (14 d acclimation and 4 d sampling). Diets were either control, where dietary forage consisted of a combination of corn silage, alfalfa hay, and native grass hay, or 1 of 2 teff diets (teff-A and teff-B), where teff hay [13.97 ± 0.32% crude protein, dry matter (DM) basis] was the sole forage. All 3 diets were formulated for similar DM, crude protein, and nonfiber carbohydrate concentrations. Control and teff-A were matched for concentrations of neutral detergent fiber (NDF) from forage (18.2 ± 0.15% of DM), and teff-B included slightly less, providing 16.6% NDF from forage. Dry matter intake, milk and component production, body weight, body condition score, as well as DM and NDF digestibility were monitored and assessed using mixed model analysis, with significance declared at P < 0.05. Treatment had no effect on dry matter intake (28.1 ± 0.75 kg/d). Similarly, treatment had no effect on milk production (40.7 ± 1.8 kg/d). Concentrations of milk fat (3.90 ± 0.16%) and lactose (4.68 ± 0.07%) were also unaffected by treatment. Teff-A and teff-B increased milk protein concentration compared with the control (3.07 vs. 3.16 ± 0.09%). Treatment had no effect on energy-corrected milk yield (43.4 ± 1.3 kg/d), body weight, or body condition score change. Additionally, treatment had no effect on total-tract DM or NDF digestibility. Results from this study indicate that teff hay has potential to replace alfalfa and corn silage in the diets of lactating dairy cattle without loss of productivity.     

双金属复合管缺陷弱磁检测影响因素仿真分析

应用ANSYS有限元软件对双金属复合管弱磁检测技术进行仿真,通过改变管道腐蚀面积、腐蚀深度、管道裂纹形状以及设置管道多缺陷组合,得到磁感应强度变化规律,分析不同缺陷对弱磁检测技术的影响。结果表明:磁感应强度变化规律不仅与裂纹形状的改变有一定的关系,且与管道腐蚀深度的改变有较大的关系,而腐蚀面积的改变以及多缺陷组合两种情况对磁感应强度变化规律影响较小。     

某贫磁赤铁矿石选矿工艺试验研究

为了使某矿山贫磁赤铁矿资源得到合理的开发利用，针对现开采部位矿石的性质和可选性问题，进行了工艺矿物学和可选性试验研究。试验结果表明：采用弱磁、强磁—阴离子反浮选工艺可得到精矿铁品位68.55%、精矿产率36.41%、金属回收率79.92%、尾矿品位9.86%的较好选别指标，说明矿石的可选性较好，为该矿石的合理开发利用提供了可靠的技术依据。     

一种波长调制干涉仪光强实时反馈控制系统

提出了一种实时反馈控制系统,保证波长调制干涉仪的激光光强在波长调谐过程中的稳定性,以减小波长调制干涉仪因激光光强的波动产生的相位误差。该控制系统由光电探测器、数据采集卡、光电调幅器和控制软件等组成。实验结果表明,该系统的响应速度超过了干涉仪获取干涉图的速度,不仅能够稳定输出理想的光强值,而且还提高了干涉仪的测量精度。     

钢铁生产的水能关系分析

从钢铁生产过程中水资源使用时的能耗角度研究了钢铁联合企业的水能关系，提出了水能强度的概念来评价企业生产过程中水资源利用的节能水平，建立了钢铁企业的水能关系模型。以中国某大型钢铁联合企业为例，计算并分析了该企业的水能关系。该企业总的水能量为55 709 kW·h/h，重复用水水能量占整个钢铁企业全部水能量的82%，补水水能量占16%，排水水能量占1%；各工序中热轧工序占比最大，其次是炼铁、炼钢工序，冷轧、烧结和炼焦工序较低。该企业的吨钢水能强度为0.208 kW·h/m3，炼铁工序的水能强度最高，热轧、炼钢工序次之，烧结、冷轧和炼焦工序较低。最后，从钢铁生产过程水资源利用的角度得到节能的方向及措施。     

时频非平稳地震动模型及结构随机振动应用

地震动具有显著的时域和频域非平稳性,传统的均匀调制地震动模型不能充分表征时频两域的非平稳性,并影响结构随机振动分析的精准度。为了克服上述不足,建立由多峰平滑包络和非平稳噪声信号点乘而成的非均匀调制地震动模型,该模型能够在时域上充分反映地震动的波动和衰减特性,同时其频谱特征也与真实信号相接近。在此基础上,建立同时以时间和频率为变量的非平稳地震动演变谱随机模型。分析结果表明,以上两种模型在时域和频域的合成精度上均优于均匀调制模型。针对以上地震动随机模型的形式和特点,对传统结构随机振动响应求解方法进行改进。通过算例证明,按照均匀调制模型计算结构随机响应不能充分获得结构时频域的非平稳特性且结果偏于不安全,而利用两种改进模型可以获得更精确的结构响应概率特征和更细致的非平稳性演变过程。