有源子阵结构集成度高、电讯功能复杂,是影响有源相控阵天线维修性的重要因素。文中展示了一种高集成模块化X频段天线有源子阵。通过在子阵上设计安装导向装置,提高了有源子阵重复拆装的可靠性。利用分层盲插设计,避免了子阵装配维修过...有源子阵结构集成度高、电讯功能复杂,是影响有源相控阵天线维修性的重要因素。文中展示了一种高集成模块化X频段天线有源子阵。通过在子阵上设计安装导向装置,提高了有源子阵重复拆装的可靠性。利用分层盲插设计,避免了子阵装配维修过程中的连接器误接错插问题。基于模块化维修设计思路,在子阵内部合理定义现场可更换单元(Line Replaceable Unit, LRU),保障了子阵集成模块的互换性,提高了现场基层维修的效率。以平均修复时间(Mean Time To Repair, MTTR)为指标对有源子阵的维修性进行分析,结果表明该子阵满足X频段相控阵天线快速维修性的设计要求。展开更多
Objective To observe the imaging findings of congenital megaureter in order to enhance the understanding of this disease. Methods Image data of 5 patients with congenital megaureter and 2 misdiagnosed patients were a...Objective To observe the imaging findings of congenital megaureter in order to enhance the understanding of this disease. Methods Image data of 5 patients with congenital megaureter and 2 misdiagnosed patients were analyzed, and image findings of congenital megaureter were summarized. Elscint Prestig 2.0T superconductive magnetic resonance urography （MRLI） with conventional sequence （spin-echo, T 1W1560 ms/16 ms; fast spin-echo, T2WI 9600 ms/96 ms） was performed. Raw data were acquired with fast spin-echo sequence from heavy T2-weighted image （9600 ms/120 ms）. Post-processing method of MRH was the maximum in- tensity projection with three-dimensional reconstruction in the workstation. Intravenous pyelography （IVP） was conducted, in which X-ray films were taken 7 minutes, 15 minutes, and 30 minutes after injecting contrast agent, except that in 2 patients the films were taken delayed at 60 and 90 minutes. X-ray retrograde pyelography was performed on 2 patients, successful in one but failed in the other. Results The dilated ureter showed hypointensity on T1-weighted images and hyperintensity on T2-weighted images in conventional MRI. The mass wall was intact, uniform in thickness, and showing hy- pointensity on Tl-weighted and T2-weighted images. The MRH images showed a retroperitoneal mass appearing as an elongated tubular cystic structure spreading from kidney to bladder. MRLI also revealed dilated calices and renal pelvis, pelviureteric obstruction, and renal duplication. The main signs of congenital megaureter in X-urography was significant dilatation of ureter, or normal renal pelvis with ureter dilatation, hydronephrosis, deformity, and displacement. Conclusions MRH with X-urography could visualize the characteristics of congenital megaureter, including the dilation of renal pelvis and ureter, calculi, urinary tract duplication, and stenosis location. The two techniques can complement each other in disease diagnosis and provide more detailed information for preoperative treatment.展开更多
The system of a true-time delay line for X-band and 8-unit phased array antennas is introduced. Changing the length of a chirp grating with piezotranslator(PZT), the variable delay is obtained. The scheme is applied t...The system of a true-time delay line for X-band and 8-unit phased array antennas is introduced. Changing the length of a chirp grating with piezotranslator(PZT), the variable delay is obtained. The scheme is applied to X-band phased array radar whose searching data rate is 56/s. It is simulated that the beam squinting is influenced by the error of real time delay. The relation between the beamforming mode and its modifying volt is discussed.展开更多
We first obtained by impregnating the zeolite with salts U, W and V and examined the X-ray uranium catalyst SAPO-U, W, V based on natural zeolite Chankanayskogoe deposits for the oxidation of SO2 to SO3.
CCl4 （carbon tetrachloride） and n-C6H14 （n-hexane） sorption studies have been carried out on natural and dealuminated clinoptilolite-type zeolites. External surface area of the materials has been assessed using t...CCl4 （carbon tetrachloride） and n-C6H14 （n-hexane） sorption studies have been carried out on natural and dealuminated clinoptilolite-type zeolites. External surface area of the materials has been assessed using the αs-plots method. The high resolution αs-plots show that the isotherms are divided into four parts corresponding to adsorption in ultramicropores, intersections, supermicropores and external surface area, respectively. The mineralogies of natural zeolites are determined by X-ray analysis. N： low-pressure hysteresis loops, displayed by some substrata, are related to the micropore structure and to the ion-exchange treatment at which the natural precursors were subjected. The adsorption behavior of these substrata was examined in the range of relative pressures between 10^-5-1. Natural samples were used as reference materials to carry out the sorption analyses of the dealuminated samples. The effect of narrow micropore constrictions on the adsorption behavior of clinoptilolites was explored. The occurrence of a low-pressure hysteresis loop on the sorption isotherm of a modified sample is associated to the strong adsorption of the adsorbate molecules at the entrance of the necked-shape micropores, which interfere with the diffusion of the adsorbate molecules inside the porous structure.展开更多
提出了一种改进型自适应遗传算法,该算法用logistic函数拟合交叉概率和变异概率,以赌轮盘选择和精英保留相结合的方式,在全局寻找最优解.与经典遗传算法相比,改进型自适应遗传算法可以大大提高算法的求解质量.本文基于改进的自适应遗传...提出了一种改进型自适应遗传算法,该算法用logistic函数拟合交叉概率和变异概率,以赌轮盘选择和精英保留相结合的方式,在全局寻找最优解.与经典遗传算法相比,改进型自适应遗传算法可以大大提高算法的求解质量.本文基于改进的自适应遗传算法研究设计了-3 d B范围为0—12,-10 d B波束宽度为65,波束覆盖为65,天线频带范围为8.5—9.8 GHz,中心频率为9.05 GHz的X波段微带余割平方扩展波束天线阵.研究结果表明改进型自适应遗传算法对方向图的拟合程度具有较大提高,适应度值可以从0.07以下提升到0.09以上.展开更多
文摘有源子阵结构集成度高、电讯功能复杂,是影响有源相控阵天线维修性的重要因素。文中展示了一种高集成模块化X频段天线有源子阵。通过在子阵上设计安装导向装置,提高了有源子阵重复拆装的可靠性。利用分层盲插设计,避免了子阵装配维修过程中的连接器误接错插问题。基于模块化维修设计思路,在子阵内部合理定义现场可更换单元(Line Replaceable Unit, LRU),保障了子阵集成模块的互换性,提高了现场基层维修的效率。以平均修复时间(Mean Time To Repair, MTTR)为指标对有源子阵的维修性进行分析,结果表明该子阵满足X频段相控阵天线快速维修性的设计要求。
文摘Objective To observe the imaging findings of congenital megaureter in order to enhance the understanding of this disease. Methods Image data of 5 patients with congenital megaureter and 2 misdiagnosed patients were analyzed, and image findings of congenital megaureter were summarized. Elscint Prestig 2.0T superconductive magnetic resonance urography （MRLI） with conventional sequence （spin-echo, T 1W1560 ms/16 ms; fast spin-echo, T2WI 9600 ms/96 ms） was performed. Raw data were acquired with fast spin-echo sequence from heavy T2-weighted image （9600 ms/120 ms）. Post-processing method of MRH was the maximum in- tensity projection with three-dimensional reconstruction in the workstation. Intravenous pyelography （IVP） was conducted, in which X-ray films were taken 7 minutes, 15 minutes, and 30 minutes after injecting contrast agent, except that in 2 patients the films were taken delayed at 60 and 90 minutes. X-ray retrograde pyelography was performed on 2 patients, successful in one but failed in the other. Results The dilated ureter showed hypointensity on T1-weighted images and hyperintensity on T2-weighted images in conventional MRI. The mass wall was intact, uniform in thickness, and showing hy- pointensity on Tl-weighted and T2-weighted images. The MRH images showed a retroperitoneal mass appearing as an elongated tubular cystic structure spreading from kidney to bladder. MRLI also revealed dilated calices and renal pelvis, pelviureteric obstruction, and renal duplication. The main signs of congenital megaureter in X-urography was significant dilatation of ureter, or normal renal pelvis with ureter dilatation, hydronephrosis, deformity, and displacement. Conclusions MRH with X-urography could visualize the characteristics of congenital megaureter, including the dilation of renal pelvis and ureter, calculi, urinary tract duplication, and stenosis location. The two techniques can complement each other in disease diagnosis and provide more detailed information for preoperative treatment.
基金Natural Science Foundation from Universities in Jiangsu Province(06KJD510034)
文摘The system of a true-time delay line for X-band and 8-unit phased array antennas is introduced. Changing the length of a chirp grating with piezotranslator(PZT), the variable delay is obtained. The scheme is applied to X-band phased array radar whose searching data rate is 56/s. It is simulated that the beam squinting is influenced by the error of real time delay. The relation between the beamforming mode and its modifying volt is discussed.
文摘We first obtained by impregnating the zeolite with salts U, W and V and examined the X-ray uranium catalyst SAPO-U, W, V based on natural zeolite Chankanayskogoe deposits for the oxidation of SO2 to SO3.
文摘CCl4 （carbon tetrachloride） and n-C6H14 （n-hexane） sorption studies have been carried out on natural and dealuminated clinoptilolite-type zeolites. External surface area of the materials has been assessed using the αs-plots method. The high resolution αs-plots show that the isotherms are divided into four parts corresponding to adsorption in ultramicropores, intersections, supermicropores and external surface area, respectively. The mineralogies of natural zeolites are determined by X-ray analysis. N： low-pressure hysteresis loops, displayed by some substrata, are related to the micropore structure and to the ion-exchange treatment at which the natural precursors were subjected. The adsorption behavior of these substrata was examined in the range of relative pressures between 10^-5-1. Natural samples were used as reference materials to carry out the sorption analyses of the dealuminated samples. The effect of narrow micropore constrictions on the adsorption behavior of clinoptilolites was explored. The occurrence of a low-pressure hysteresis loop on the sorption isotherm of a modified sample is associated to the strong adsorption of the adsorbate molecules at the entrance of the necked-shape micropores, which interfere with the diffusion of the adsorbate molecules inside the porous structure.
文摘提出了一种改进型自适应遗传算法,该算法用logistic函数拟合交叉概率和变异概率,以赌轮盘选择和精英保留相结合的方式,在全局寻找最优解.与经典遗传算法相比,改进型自适应遗传算法可以大大提高算法的求解质量.本文基于改进的自适应遗传算法研究设计了-3 d B范围为0—12,-10 d B波束宽度为65,波束覆盖为65,天线频带范围为8.5—9.8 GHz,中心频率为9.05 GHz的X波段微带余割平方扩展波束天线阵.研究结果表明改进型自适应遗传算法对方向图的拟合程度具有较大提高,适应度值可以从0.07以下提升到0.09以上.
