TIS320F2812构成的感应加热逆变控制器

针对现阶段感应加热领域逐渐数字化的趋势,将DSP芯片应用在感应加热电源的逆变器控制上,以达成频率跟踪与定角控制,从而实现智能控制,使得逆变器的控制与调整更加简单可行。分析了感应加热电源装置的发展趋势及其电源中逆变器的控制要求,设计了基于DSP的并联谐振式感应加热电源中的逆变器的控制主电路,成功实现了频率跟踪和定角控制。     

土壤中Pb、Cr元素激光诱导击穿光谱技术定量分析

采用激光诱导击穿光谱技术(Laser-induced b reakdown spectroscopy,LIBS)对土 壤样品中的Pb和Cr元素进行了分析,以PbI280.17 nm和CrI425.43 nm作为分析线,优化了透 镜到样品的距离(Lens to sample distance,LTSD)、延迟时间对光谱信号强度及信噪比 SNR 的影响。在最佳实验条件下,对两种元素的谱峰强度和元素浓度进行分析,针对外标法 和内标法分别建立了谱线峰值强度、谱线峰值积分面积与对应元素浓度的定标曲线。采用谱 线峰值积分面积法对土壤中重金属Pb和Cr元素的检测,相比于外标法,内标法将Pb和Cr元素 最大相对误差分别从13.56%和12.68%降低到了 6.7%;Pb和Cr元素定标曲线的拟合相关 系数R²分别从0.978和0.975提高到了0.996和0.991。实 验结果表明:采用LIBS技术对土 壤中Pb、Cr元素检测具有可行性,采用谱线峰值积分面积的内标法,可以降低最大相对误差 并提高测量精度。     

利用压缩感知实现随机变频雷达散射中心估计

随机变频信号体制不仅可以降低系统瞬时带宽和数据采样率,还具有很强的抗干扰能力,然而,信号频率的随机变化导致现有目标散射中心估计方法失效。推导了随机变频信号的回波模型,在分析回波稀疏特性的基础上,提出了一种基于压缩感知的散射中心模型参数估计方法,将参数估计问题转化为压缩感知理论中的稀疏信号重构问题,并分析了感知矩阵对稀疏信号的重构性能。实验结果表明,所提方法能够在降低数据采样率的情况下对目标散射中心参数进行有效估计。     

地源热泵的发展现状及新方法研究

简要的介绍了地源热泵的发展情况,对土壤源泵地埋管换热量及土壤热物性测试技术中存在的问题进行了分析,针对土壤热物性测试方法的不足,提出了改进方法,并指出高效节能的地源热泵系统具有良好的发展前景。     

Synergism in novel silver-copper/hydroxyapatite composites for increased antibacterial activity and biocompatibility

This study develops a novel silver-copper/hydroxyapatite composite (Ag–Cu/HA) with high biocompatibility and antibacterial activity. Two different materials were synthesized, namely silver-hydroxyapatite (Ag-HA) and copper-hydroxyapatite (Cu-HA) composites, with 0.1%, 0.5%, and 1.0% (mol) of each metal. These materials were mixed in a planetary mill to obtain the Ag–Cu/HA composites. The results of our characterization demonstrated the low cytotoxicity and hemolytic response. The composite showed higher percent-inhibition for bacterial growth compared to those in separated composites of silver or copper with hydroxyapatite. Hence, these new materials promise higher efficacy as antibacterial hydroxyapatites.     

Effects of geometry and position of the metal delivery tube on ultrasonic gas atomization

The effects of the geometry and the position of the metal delivery tube on the pressure condition in the gas-metal interaction zone were studied. The measurements were performed under conditions which simulated ultrasonic gas atomization experiments, but at low gas atomization pressures (50–200 psig, 345–1380 kPa). Low gas atomization pressures are used in spray atomization and deposition processes such as liquid dynamic compaction (LDC), and Osprey. Depending on the experimental conditions, either underpressure or overpressure in the metal delivery tube was detected. The magnitude of the underpressures and overpressures was found to increase with the gas atomization pressure; the maximum pressure differences with respect to the atomization tank pressure were about 3 psi (21 kPa) when argon was used as an atomization gas with a pressure of 200 psig (1380 kPa). Underpressure or overpressure effects of such magnitude have a large effect on the metal flow rate during gas atomization. The large pressure differences measured in the present work result from using an atomizer with gas jet diameters larger than those used in previous investigations. Using a large ultrasonic atomizer, argon gas flow rates of about 5 kg/min can be obtained for atomization pressures of 200 psig (1380 kPa).     

Structural,optical and temperature dependent photoluminescence properties of Cr3+-activated LaGaO3 persistent phosphor for optical thermometry

Cr³⁺ doped LaGaO₃ phosphor was prepared by hydrothermal reaction method with post-annealing treatment. XRD pattern showed the pure orthorhombic phase of LaGaO₃ at an annealing temperature of 1000 °C. TEM image showed the particles in the range 40-120 nm. The bandgap energy and Urbach tail increased in the doped sample as compared to the undoped sample as estimated from UV–visible diffuse reflectance spectra. PL excitation spectra showed peaks in UV, blue and orange regions. The emission spectra showed broadband with peaks in the NIR region due to emission from ⁴T₂ and ²E states. The intermediate strength of the crystal field has been calculated from the estimated spectroscopic parameter. The average lifetime was found to be in the ms range. Afterglow decay was also recorded. From the low-temperature PL, the zero phonon line, stokes shift energy, vibrational energy and Huang-Rhys parameter were calculated. With rising the temperature, PL emission peak intensity and lifetime values decreased and FWHM increased because of increased numbers of electrons in ⁴T₂ state and increasing non-radiative transition. Temperature-dependent peak intensity ratios and lifetime values were utilized for temperature sensing applications in below room temperature and above room temperature. The results indicate the possibility of present phosphor to be used as optical nanothermometer.     

融合残差上下文编码和路径增强的视杯视盘分割

目的 从眼底图像中分割视盘和视杯对于眼部疾病智能诊断来说是一项重要工作,U-Net及变体模型已经广泛应用在视杯盘分割任务中。由于连续的卷积与池化操作容易引起空间信息损失,导致视盘和视杯分割精度差且效率低。提出了融合残差上下文编码和路径增强的深度学习网络RCPA-Net,提升了分割结果的准确性与连续性。方法 采用限制对比度自适应直方图均衡方法处理输入图像,增强对比度并丰富图像信息。特征编码模块以ResNet34(residual neural network)为骨干网络,通过引入残差递归与注意力机制使模型更关注感兴趣区域,采用残差空洞卷积模块捕获更深层次的语义特征信息,使用路径增强模块在浅层特征中获得精确的定位信息来增强整个特征层次。本文还提出了一种新的多标签损失函数用于提高视盘视杯与背景区域的像素比例并生成最终的分割图。结果 在4个数据集上与多种分割方法进行比较,在ORIGA(online retinal fundus image database for glaucoma analysis)数据集中,本文方法对视盘分割的JC(Jaccard)指数为0.939 1,F-measure为...     

浅谈太阳能低温有机朗肯循环

叙述了太阳能低温有机肯循环技术,该技术解决了如何高效的收集太阳能的问题,同时相关设备易于制造成本较低,具有很高的应用价值和前景。     

微机相控整流式充电机的改进分析

对相控整流式充电机进行研究,从其充电方式、晶闸管移相控制原理及比例积分微分(PID)软件调节设计等方面作了详细分析。对WCD-Ⅳ型微机相控整流式充电机提出了进一步的改进措施:将单脉冲或双脉冲触发信号改进为一组宽度为120°、脉冲间隔为0.12°的脉冲列,并进行高频调制和功率放大,确保晶闸管的可靠导通;采用改进的不完全微分型PID控制算法,并引入积分分离法,通过分离法算式,实现理想调节特性,从而避免积分饱和、减小超调、加快过渡过程,得到了良好的空载稳压特性;增加了逆变放电、高精度全自动充电、温度补偿及相序自适应等功能。