混合励磁同步电动机分段弱磁控制

针对混合励磁同步电动机在高速区的弱磁运行特点,首先推导出其弱磁调速过程中保持平稳运行的电流变化关系,然后在此基础上提出了一种采用模糊控制与粒子群优化算法分阶段电流调节的效率最优控制方法。该控制方法的基本思想是,当电机处于弱磁调速过渡阶段时,通过模糊控制器对电流进行初步调节,使其迅速起动或进行状态调整,获得较高的动态性能;当电机进入稳态运行阶段后,以铜耗最小化为目标,采用粒子群优化算法对电流进行进一步调整,使其实现效率最优化控制。最后,通过仿真与实验结果分析验证了上述控制方法的有效性。     

基于模块化多电平变换器的电流滞环跟踪型并网控制策略

基于电流滞环型双闭环并网控制策略运用于模块化多电平变换器(MMC),实时监测电网电压、并网电流与给定电流误差,从而决定其网侧输出电压,使得并网电流快速、高效地跟踪给定电流;同时对并网电流脉动频率、开关频率做了详细分析,证明了该策略优越性。建立虚拟子模块,在此基础上根据子模块电容电压大小排序和桥臂电流方向,不断改变虚拟子模块与实际子模块驱动信号的循环映射关系,达到子模块电容电压动态平衡的目的。该控制方法适用于任意单元级联和任意电平数。设计了一台五电平MMC的实验样机对上述控制方法进行了实验验证。     

低管电流联合迭代重建算法对胸部体模T12骨密度值准确性和胸部图像质量的影响

目的 探讨低管电流联合迭代重建算法对仿真胸部体模T12骨密度（BMD）的准确性和胸部图像质量的影响。方法 选用成年男性胸部体模,管电压120 kV,管电流分别为20、30、40、50、60 mAs,联合滤波反投影算法（FBP）、混合迭代重建技术（iDose⁴,Level 4）及迭代模型重建（IMR,Level 2）行胸部扫描。比较采用不同管电流和重建技术时胸部体模T12的BMD及客观评价结果;比较管电流20 mAs、采用IMR算法与管电流60 mAs、采用FBP迭代算法的纵隔窗和肺窗图像质量的主观评分,并评价观察者间的一致性。结果 管电流、重建技术不同时,胸部体模T12的BMD和CT值差异均无统计学意义（P均>0.05）,而SD值差异有统计学意义（P均<0.001）。相同管电流下,采用IMR算法获得的SD值明显低于iDose⁴和FBP（P均<0.001）。管电流60 mAs、采用FBP算法时,2名观察者观察纵隔窗的一致性较好（Kappa=1,P<0.001）,观察肺窗的一致性中等（Kappa=0.64,P=0.002）;管电流20 mAs、采用IMR时,2名观察者观察纵隔窗的一致性中等（Kappa=0.64,P=0.002）,观察肺窗的一致性较好（Kappa=1,P<0.001）。结论 低管电流联合迭代重建算法可降低辐射剂量,同时满足骨密度测值的准确性及胸部图像诊断。     

彩色多普勒超敏血流显像技术显示孕11~13+6周胎儿心脏轴

目的 探讨彩色多普勒超敏血流（HD flow）显像技术在11~13⁺⁶周胎儿心脏轴显像中的价值。方法 采用灰阶超声及彩色多普勒HD flow显像技术对197胎孕11~13⁺⁶周胎儿进行心脏轴显像,比较两种方法对不同孕周胎儿心脏轴的显示率;采用两种方法测量55胎孕13~13⁺⁶周胎儿的心脏轴值,并进行比较。结果 孕11~13⁺⁶周,灰阶超声显像和HD flow显像对心脏轴的显示率分别为67.01%（132/197）、85.28%（168/197）,差异有统计学意义（P<0.01）;孕11~11⁺⁶周,显示率分别为32.39%（23/71）、69.01%（49/71）,差异有统计学意义（P<0.01）;孕12~12⁺⁶周,显示率分别为78.26%（54/69）、92.75%（64/69）,差异有统计学意义（P<0.01）;孕13~13⁺⁶周,两种方法显示率均为96.49%（55/57）。灰阶超声显像和HD flow显像测量心脏轴值分别为（45.34±3.99）°、（43.62±3.33）°,差异有统计学意义（t=7.11,P<0.01）。灰阶超声测得数值离散度较大,HD flow显像测得数值相对集中。结论 与灰阶超声显像相比,彩色多普勒HD flow显像可提高孕11~12⁺⁶周胎儿心脏轴显示率,且可降低13~13⁺⁶周胎儿心脏轴值的测量误差。     

混合励磁轴向磁场磁通切换型永磁电机静态特性

提出一种混合励磁轴向磁场磁通切换永磁电机，以一台12/11极电机为例分析电机的结构特点和工作原理。基于三维有限元方法研究该电机静态特性，对空载永磁磁场和气隙磁通密度进行分析，研究永磁磁链、反电动势、定位力矩及绕组电感等电磁特性，分析不同励磁电流下的气隙磁场分布和调磁特性。结果表明:该种电机的磁链和反电动势均为双极性的正弦分布，适于无刷交流运行场合；通过调节励磁电流，线圈匝链磁通变化明显，调磁效果较好。     

基于定有功电流限值控制的MMC型UPQC协调控制方法

对电压暂降期间MMC型UPQC串联侧补偿能力进行深入的理论分析。首先给出MMC型UPQC的工作原理，推导出暂降补偿幅值、补偿持续时间、主回路电气量及MMC参数之间关系的时域表达式；进而提出一种针对容量确定情况下UPQC串联侧过电流问题的协调控制设计方法，在传统定直流电压控制的基础上提出定有功电流限值控制；定义了划分MMC型UPQC处于上述两种控制状态的电压暂降临界值并给出数值计算表达式；最后PSCAD/EMTDC下的系统仿真结果验证了理论分析的正确性。仿真结果也表明，与传统协调控制方法相比，该文提出的协调控制方法可明显提高电压暂降的补偿幅值和持续时间。     

不同CT扫描参数与迭代去金属伪影算法效果的相关性

目的 探讨不同CT扫描参数对迭代去金属伪影（IMAR）效果的影响。方法 采用不同管电压、不同管电流量及不同辐射剂量的管电压和管电流组合条件对植入及未植入金属螺钉的仿真胸部体模行CT扫描。分别以迭代重建和IMAR算法重建图像，采用四分法主观评价IMAR图像质量，测量及计算金属螺钉邻近肺实质和椎旁软组织CT值、噪声（CT值的标准差，SD）及CT值偏差（ΔHU），比较各方法采集图像质量差异。结果 相同管电流量条件下，IMAR图像中金属伪影随管电压增加而减少，图像质量主观评分差异有统计学意义（P<0.05）；肺及椎旁软组织SD（r=-0.91、-0.99）和ΔHU（r=-0.85、-0.97）均与管电压呈高度负相关（P均<0.01）。相同管电压条件下，管电流量增加后，IMAR图像中金属伪影无明显变化，图像质量主观评分差异无统计学意义（P>0.05），肺实质SD及椎旁软组织ΔHU与管电流量低度相关（r=0.20、0.29，P均<0.01），肺实质ΔHU及椎旁软组织SD与管电流量呈中等负相关（r=-0.59、-0.56，P均<0.01）。不同辐射剂量管电压和管电流组合条件下，IMAR图像质量主观评分及客观指标差异均有统计学意义（P均<0.05），低辐射剂量下采用高管电压、低管电流量扫描图像中金属伪影少于中、高辐射剂量。结论 管电压是影响IMAR效果的主要因素。采用IMAR去除金属伪影时，增加管电压对于改善图像质量效果更佳；在增加管电压的同时减少管电流量可减轻金属伪影对图像质量的影响，并降低辐射剂量。     

基于耦合剂造影三维容积内插屏气检查(3D-VIBE)动态增强技术诊断直肠阴道瘘

目的 探讨基于超声耦合剂造影三维容积内插屏气检查（3D-VIBE）动态增强（DCE）MRI对直肠阴道瘘（RVF）的诊断价值。方法 回顾性分析23例经手术或肠镜证实的RVF患者，术前均接受MR检查，扫描前分别向肛管、阴道灌入适量超声耦合剂，而后采集矢状位、冠状位和轴位T1WI、轴位T2WI、轴位脂肪抑制T2WI、DWI和3D-VIBE DCE-MRI，记录瘘口数量、开口位置、瘘管支数及周围软组织病变情况，并与手术及肠镜结果进行对比。结果 23例患者中，12例经手术治疗，11例接受肠镜检查，共发现26个瘘口、27支瘘管，6例合并周围脓肿，3例存在放射状损伤。超声耦合剂造影+3D-VIBE DCE-MRI对于瘘口、瘘管的显示率及诊断周围脓肿、放射性损伤的准确率均高于各常规序列（P均<0.05）。结论 基于超声耦合剂造影3D-VIBE DCE-MRI对RVF诊断价值较高。     

256 iCT冠状动脉CTA降低辐射剂量扫描方案的优化

目的 采用256 iCT进行冠状动脉CTA(CCTA), 并联合多种技术优化扫描方案以降低辐射剂量。方法 纳入91例接受256 iCT CCTA(研究组)和30例接受64排CCTA(对照组)的可疑冠状动脉粥样硬化性心脏病患者。研究组根据患者心率设置6种扫描方案, 方案1采用前瞻性心电门控技术, 启动z轴方向自动管电流调节技术, 方案2、3采用回顾性心电门控技术+ECG电流调控(ECG-CTCM)技术, 方案4~6采用回顾性心电门控技术, 各扫描方案均根据BMI设置管电压。计算并比较各组及各扫描方案间有效剂量(ED)和图像质量评分差异。结果 研究组ED 明显低于对照组 。研究组扫描方案1 ED最低, 其次为扫描方案3, 两种扫描方案ED均明显低于其余扫描方案(P均 <0.05), 二者间差异亦有统计学意义(P <0.05), 扫描方案2、4~6两两比较差异均无统计学意义(P均 >0.05);各扫描方案中ED均随管电压下降而下降。各扫描方案间图像质量评分差异无统计学意义(F=0.610, P=0.858)。结论 CCTA中256 iCT辐射剂量低于64排螺旋CT;前瞻性心电门控技术、ECG电流调控技术和个体化扫描均可不同程度降低辐射剂量, 并不影响图像质量。     

低剂量扫描与低浓度对比剂联合迭代重建CTA在颈部血管模型中的应用

目的 探讨低剂量扫描与低浓度对比剂联合迭代重建技术对颈部血管模型CTA检查的应用价值。方法 建立9个颈部血管模型,CT扫描采用管电压120 kV、管电流250 mAs,分别进行滤波反投影（FBP）重建和iDose3、iDose4、iDose5重建。采用不同管电压（80、100 kV）和管电流（200、250、300、350 mAs）进行两两组合扫描,进行iDose5重建。对图像质量和辐射剂量进行评价,并进行统计学分析。结果 120 kV 250 mAs图像iDose5重建的CNR优于FBP重建 （P<0.05）。不同扫描条件的iDose5重建图像与120 kV 250 mAs FBP重建图像的CNR和SNR差异均有统计学意义（P均<0.05）,噪声差异均无统计学意义（P均>0.05）。与120 kV 250 mAs FBP重建图像比较,80 kV 200 mAs iDose5重建图像的CNR差异有统计学意义（P<0.05）;80 kV 200 mAs iDose5、80 kV 250 mAs iDose5、100 kV 350 mAs iDose5重建图像的SNR差异均有统计学意义（P均<0.05）。余扫描条件和重建方法图像的CNR、SNR两两比较,差异均无统计学意义（P均>0.05）。管电压不变时,iDose5重建的容积CT剂量指数（CTDIvol）、剂量长度乘积（DLP）、有效剂量（ED）随管电流的增加而增加;管电流不变时,iDose5重建的CTDIvol、DLP、ED随管电压的增加而增加。结论 低剂量扫描与低浓度对比剂联合迭代重建技术可获得高质量的CTA图像,且能够减低辐射剂量。     

Influence of Internal Current and Pacing Current on Pacemaker Longevity

The effects of lower pulse amplitude on battery current and pacemaker longevity were studied comparing the new, small-sized VVI pacemaker, Minix 8341, with the former model, Pasys 8329. Battery current was telemetrically measured at 0.8. 1.6, 2.5, and 5.0 V pulse amplitude and 0.05, 0.25, 0.5, and 1.0 msec pulse duration. Internal current was assumed to be equal to the battery current at 0.8 V and 0.05 msec. Pacing current was calculated subtracting internal current from battery current. The Minix pacemaker had a significantly lower battery current because of a lower internal current (Minix: 4.1 ±0.1 μA; Pasys: 16.1 ± 0.1 μA); pacing current of both units was similar. At 0.5 msec pulse duration, the programming from 5.0-2.5 V puise amplitude resulted in a greater relative reduction of battery current in the newer pacemaker (51% vs 25%). Projected longevity of each pacemaker was 7.9 years at 5.0 V and 0.5 msec. The programming from 5.0–2.5 V extended the projected longevity by 2.3 years (Pasys) and by 7.1 years (Minix). The longevity was negligibly longer after programming to 1.6 V. Conclusion: Extension of pacemaker longevity can be achieved with the programming to 2.5 V or less if the connected pacemakers need a low internal current for their circuitry.     

超音频单向脉冲电流离子导入法的初步探讨

通过对人体和体外实验模型进行“超音频”单向脉冲电（脉宽为２μｓ，重复频率６６ＫＨＺ）和直流电离子导入对比观察，结果证明当两者电流平均值相等时离子导入量相似，但“超音频”单向脉冲电对人体几乎没有刺痛感，优于直流电离导入法。     

干扰电流祛痰作用的实验及临床观察

应用我院研制的微电脑肺功能治疗机所输出的干扰电流,对23例排痰困难患者进行排痰治疗。治疗电极放置于胸背部。每天治疗1次,每次10～20min,7～10次为1疗程。总有效率为86.96％。应用小鼠酚红呼吸道排泌试验比较了3组不同差频的干扰电流的排痰作用,结果表明:干扰电流排痰治疗效果明显。这种疗法安全,使用方便,无明显副作用,值得在临床中推广。     

Cellular Electrophysiological Changes Induced In Vitro by Radiofrequency Current: Comparison with Electrical Ablation

The purpose of this study was to examine the cellular electrophysiological effects of radiofrequency energy delivery in an in vitro canine epicardial preparation and compare the effects to those of high energy electrical ablation in a similar preparation. Ten joules of direct current energy or 40 volts of radiofrequency energy were delivered by a 6 French 2-mm tip catheter to the epicardial surface of 2 × 3 cm epicardial strips superfused with Tyrode's solution. Direct current energy delivery produced a crater and central zone of necrosis surrounded by a border zone of viable but damaged tissue that extended up to 10–12 mm from the site of energy delivery. Cellular electrophysiological abnormalities that included a less negative resting membrane potential, decreased peak dV/dT, decreased action potential amplitude, and decreased action potential duration (APD) were approximately linearly related to the distance from the crater edge. In addition, viable and inexcitable cells were frequently interspersed. Between 2 and 5 mm from the crater edge, 36.4% of the cells were inexcitable whereas others displayed normal action potential characteristics. In contrast, radiofrequency current produced a central zone of necrosis surrounded by a smaller border zone. Cellular damage that was qualitatively similar to that produced by direct current energy extended only up to 6–8 mm from the edge of the crater. In addition, severe abnormalities were noted in intracellular potentials recorded within 2 mm of the ablation site, and only minor abnormalities further away. Lesions were relatively homogeneous. Between 2 and 5 mm from the ablation site only 2.6% of the cells were inexcitable (P < 0.05 vs direct current). In conclusion, radiofrequency current produces lesions that are smaller and more homogeneous than those produced by direct current ablation. Although the border zone is small, a region of partially depolarized but viable myocardium is present after radiofrequency current energy delivery. These findings provide a cellular basis for several clinical observations that have been made following radiofrequency current energy delivery.     

The Effects of Direct Current Countershock on Ventricular Late Potentials

Signal averaging is a noninvasive method of recording ventricular late potentials. These late potentials are present in many patients with sustained ventricular tachycardia. Analysis of ventricular late potential characteristics may develop as a useful marker of antiarrhythmic drug efficacy. Often antiarrhythmic drugs are tested acutely in the electrophysiology laboratory after direct current countershock (DC shock). The purpose of this study was to investigate the effects of DC shock delivered for cardioversion of sustained ventricular tachycardia or fibrillation on ventricular late potentials. Signal averaged electrocardiograms (SAEKGs) were recorded before and after 13 DC shocks. There was no significant change in QRS duration, duration of the high frequency filtered QRS, or duration of the high frequency signal under 40 microvolts. There was a small increase in the root mean square amplitudes of the terminal 40 milliseconds (41 microV to 49 microV). This degree of change is felt to be clinically insignificant. Except for one trial, no late potential appeared or disappeared after electrical cardioversion. We have shown that ventricular late potentials are only slightly altered by programmed ventricular stimulation, induced sustained ventricular tachycardia or ventricular fibrillation, and DC countershock. To analyze changes in ventricular late potentials after antiarrhythmic drug administration in the electrophysiology laboratory, in those patients requiring DC countershock, comparisons should be made to postshock SAEKGs rather than those obtained prestudy.     

变革型领导理论在护理管理领域的研究现状

变革型领导作为一种新型领导类型,已成为国外管理领域广泛关注的一个研究热点,并逐步为众多护理管理者所认识和接受。文章在回顾前人研究成果的基础上,总结了变革型领导的概念、结构模型以及其在护理管理领域的研究现状。     

浙江省被动吸烟暴露流行现况研究

目的 了解浙江省被动吸烟暴露流行程度,探索可能的影响因素,为烟草控制及卫生决策提供参考依据。 方法 采用多阶段、按地理位置进行整群随机抽样,针对浙江省15岁及以上居民,采用家庭入户调查方式,完成被动吸烟暴露问卷调查共2112份,这些数据被用来估算整个人口中被动吸烟暴露的程度。 结果 浙江省受到被动吸烟暴露的非吸烟者人数为1670.5万(56.69%),每天都受到被动吸烟暴露的非吸烟者人数1042.2万(35.37%);受到被动吸烟暴露的男性(62.34%)和女性(58.38%),城市居民(65.37%)和农村居民(53.67%);被动吸烟暴露的地点在家庭中(60.89%)和室内工作场所(65.34%),城乡、年龄、教育程度和收入等相关因素对被动吸烟暴露有影响。 结论 浙江省整体被动吸烟暴露情况严重,仅提高人群健康知识并不能减少人群被动吸烟暴露,需要制定更综合性策略保护人群免受被动吸烟的危害。     

Successful Radiofrequency Current Catheter Ablation of Sustained Ventricular Tachycardia

We performed radiofrequency current catheter ablation in two patients with nonischemic sustained ventricular tachycardia (VT). In one patient, two morphologically distinct VTs were induced by electrical stimulation. One showed right bundle branch block pattern and the other left bundle branch block pattern. The earliest site of activation during each VT was determined at the septum of the right ventricle. However, these two sites were close to the His-bundle elecfrogram recording area. In the other patient, a VT with a left bundle branch block pattern occurred spontaneously after the administration of isoproterenol. The earliest site of activation during VT was determined at the outflow tract of the right ventricle. During tachycardia, radiofrequency current ablation (40 W ± 30 sec) was delivered to the earliest site of activation, A few seconds after fulguration, each VT was terminated and additional radio-frequency currents were given near these sites. After the ablation, VT could not be induced by the electrical stimulations, nor did it recur. No side effects were observed and the atrioventricular conduction remained intact. We feel that nonischemic VTs could possibly be treated by using radiofrequency current catheter ablation.     

A Comparison of Ventricular Arrhythmias Induced with Programmed Stimulation Versus Alternating Current

In patients undergoing implantation and testing of the implantable cardio-verter defibrillator (ICD), alternating current (AC) may be used to induce ventricular tachyarrhythmias in a prompt, safe, and efficient manner. These arrhythmias have been previously reported to be similar to those induced during programmed electrical stimulation (PES). We compared the ventricular tachyarrhythmias induced by both methods in 14 patients: 8 male, 6 female; mean age 61 years; coronary disease in 10, cardiomyopathy in 4; mean ejection fraction 31%. The presenting arrhythmia was nonsustained ventricuiar tachycardia (VT) in four, sustained monomorphic ventricular tachycardia (SMVT) in five, ventricular fibrillation (VF) in four, and unknown in one patient with syncope. PES (single, double, triple extrastimuli; burst pacing) and AC (1–2 sec application) stimulation via right ventricular endocardial electrode catheter was performed off antiarrhythmic drugs in the nonsedated state. PES induced SMVT in nine, polymorphic VT in two, and VF in three. AC induced VF in all patients. Although AC can reliably induce ventricular tachyarrhythmias during de/ibrillation threshold and ICD testing, there is poor correlation to PES induced tachyarrhythmias.