ZnO对MnZn铁氧体磁导率和损耗温度特性的影响

采用氧化物陶瓷工艺制备MnZn功率铁氧体.通过对铁氧体断面微观形貌的表征及密度、电阻率和磁特性的测试,研究了ZnO含量对低损耗MnZn功率铁氧体起始磁导率(μ1)和损耗温度特性的影响.结果表明,随着ZnO摩尔分数的增加,室温下MnZn功率铁氧体的μi、饱和磁感应强度Bs、密度及电阻率均先增大后减小,损耗先减小后增大,居里温度一直降低.当x(ZnO)=14.5%时,室温下铁氧体的μ1、Bs、密度及电阻率均达到最大值,而磁滞损耗(Ph)、涡流损耗(Pe)及总损耗(Pcv)达到最小值.同时,铁氧体的μiT曲线Ⅱ峰及最低损耗所对应的温度点向低温移动.Ph-T曲线与μi-T曲线呈相反的变化趋势;Pe-T曲线与经典涡流损耗不一致,主要是由于与磁滞损耗有关的附加涡流损耗(Pe,exc)对总的涡流损耗有一定贡献.最终,当x(ZnO)=14.0%时,MnZn铁氧体材料的室温μi为3180,在25～120℃温度范围总损耗(Pcv)为280～350 kW/m3,具有优秀的宽温低损耗特性.     

ZrO2-Nb2O5复合添加对MnZn铁氧体结构和磁性能的影响

针对开关电源高频小型化需求,采用固相反应制备分子式为(Mn_0.766Zn_0.105Fe_0.129)Fe₂O₄的MnZn铁氧体材料,通过对铁氧体微结构的表征及磁性能的测试,研究了ZrO₂和Nb₂O₅复合添加对MnZn铁氧体显微结构、烧结密度d、初始磁导率μ_i、饱和磁通密度B_s、剩余磁通密度B_r、矫顽力H_c以及功耗P_cv特性的影响。结果表明,ZrO₂和Nb₂O₅复合添加有利于促进晶粒均匀化和致密化,从而提高了材料烧结密度,能显著降低材料的剩余磁通密度和矫顽力,实现材料的高起始磁导率以及高频低损耗。当ZrO₂和Nb₂O₅复合添加质量比为4∶6时,MnZn铁氧体的μ_i     

低失真MnZn铁氧体中ZnO含量对磁特性的影响

为了提高非对称数字用户线(ADSL)接入系统的网络传输质量,采用传统氧化物陶瓷工艺制备了低失真MnZn铁氧体,并研究了在Fe2O3含量不变的前提下,ZnO含量与其磁特性的关系。结果表明:适量的ZnO可以提高起始磁导率μi,降低磁滞常数ηB。随着ZnO含量的增加,μi值先增大后减少,截止频率fr先减少后增加。当x(ZnO)为23%时,其μi=8 100,ηB=0.42×10–6/mT。     

功率锰锌铁氧体材料的损耗分离

采用传统陶瓷工艺,制备了功率MnZn铁氧体材料。根据磁滞损耗、涡流损耗和剩余损耗与频率的关系,在Bm为50mT和200mT两种典型工作磁通密度下,对JPP—44、JPP—5两种典型低损耗MnZn铁氧体材料进行了损耗分离。结果表明:JPP—5材料的涡流损耗,最低可为JPP—44材料的1/10,而其磁滞损耗相当于甚至超过JPP—44材料,并深入分析了它们损耗组成不同的原因。     

Ti、Zn掺杂对Co2Z电磁性能的影响

用固相反应法制备了Ti4+、Zn2+取代的Co2Z(Ba3Co2Fe24-xMO41,M=Ti、Zn, x=0.2～0.6)平面六角结构软磁铁氧体并对其电磁特性进行了研究.X-射线衍射结果表明样品表现出典型的Z型平面六角铁氧体构型.Ti4+、Zn2+ 取代会增加铁氧体内载流子的浓度,从而影响Co2Z的电磁性能.实验中用4991A阻抗/材料分析仪测试室温条件下Ba3Co2Fe24-xTixO41(x=0、0.2、0.4)和Ba3Co2Fe24-xZnxO41(x=0、0.2、0.4、0.6)样品在5 MHz～1 GHz 范围内的磁导率频谱和介电常数频谱.实验结果表明,Ti4+取代Fe3+会增加Co2Z的起始磁导率,降低Co2Z的介电共振.而Zn2+取代Fe3+会引起起始磁导率的下降,增加Co2Z的介电共振,且在共振频率附近介电常数为负值.Co2Z的负介电常数特性使它可作为负介电常数介质用于左手材料的制备.     

宽频高阻抗贫铁MnZn铁氧体的掺杂改性研究

采用传统陶瓷工艺制备了MnZn和NiZn铁氧体材料。研究了贫铁MnZn铁氧体、富铁MnZn铁氧体及NiZn铁氧体的电阻率和阻抗的频率特性。结果表明:CaCO3-SiO2联合掺杂能大幅度提高贫铁MnZn铁氧体材料的电阻率,在最大添加量w(SiO2)为0.005%,w(CaCO3)为0.04%时,有最大电阻率10246Ω·m;贫铁MnZn铁氧体材料综合了富铁MnZn铁氧体材料的低频高阻抗和NiZn铁氧体材料的高频高阻抗特性;Fe2O3、TiO2含量的增加都会提高材料的低频阻抗,降低材料的高频阻抗。     

BBSZ玻璃掺杂对NiCuZn铁氧体性能的影响

采用传统的陶瓷工艺,低温烧结制备了Bi2O3-H3BO3-SiO2-ZnO(BBSZ)玻璃掺杂的NiCuZn铁氧体材料,研究了BBSZ掺杂量对铁氧体材料烧结密度、微观形貌和电磁性能的影响.研究表明,适量的BBSZ掺杂可以显著改善铁氧体的烧结性能和微观结构,进而对其电磁性能产生明显的影响.当BBSZ掺杂量为质量分数0.7...     

复合掺杂对高磁导率锰锌铁氧体磁性能的影响

用复合掺杂的方法制备了高性能的高磁导率MnZn铁氧体材料。研究了Nb2O5-P2O5复合掺杂对MnZn铁氧体微观结构及磁性能的影响。结果表明,适量的Nb2O5-P2O5复合掺杂有利于促进晶粒均匀致密,提高材料的起始磁导率,降低损耗。在配方中,当ζ(Nb2O5∶P2O5)为2∶8时,起始磁导率可达到11 823。     

预烧工艺对MnZn功率铁氧体的影响

采用传统的陶瓷工艺制备了MnZn功率铁氧体,研究了预烧工艺对预烧料的磁化率和振实密度的影响,并在此基础上,探讨了预烧温度对烧结样品微观结构和磁性能的影响。结果表明,升温速度和保温时间对预烧料的磁化率和振实密度的影响都很小,预烧温度对其起决定性作用。当预烧温度从700℃提高至1 000℃时,预烧料的磁化率提高了近10倍,振实密度提高约20%。当预烧温度为900℃时,所得MnZn功率铁氧体具有良好的烧结微观结构和最低的功率损耗。     

FeSiCr/SiO_2软磁复合材料的制备及磁性能研究

以正硅酸乙酯(TEOS)为硅源,聚乙烯吡咯烷酮(PVP)为偶联剂,采用溶胶-凝胶法,在Fe Si Cr软磁合金表面包覆上SiO_2壳层。对包覆粉末进行压制成型和退火热处理,制备了高频下低损耗的Fe Si Cr/SiO_2软磁复合材料。通过XRD、FTIR、XPS、SEM等手段对包覆粉末的相结构、成分及表面微结构进行表征,通过四探针电阻仪、B-H分析仪等对复合材料电阻率、磁导率、功率损耗、品质因数等性能参数进行研究。结果表明:通过SiO_2绝缘包覆处理可大幅度提高FeSiCr软磁合金电阻率,降低高频下功率损耗,提高材料品质因数;随着TEOS添加量提高,包覆效果及材料性能呈现先提升后恶化的趋势,添加量为12 m L时,软磁复合材料综合性能最佳。     

大鼠失血性休克所致肠道菌移位的超微形态观察

严重创伤、烧伤、休克、肝切除、胰腺炎、应用免疫抑制剂等多种因素均可引发肠源性感染 ,而肠道菌移位的机制至今尚未完全清楚 ,本实验利用大鼠失血性休克模型 ,观察肠道中细菌移位的过程 ,为探讨肠道菌的移位机制提供形态学基础。材料与方法清洁级雄性Ｓ .Ｄ .大鼠 ,体重 32 9.6± 36ｇ ,参照Ｂａｋｅｒ的方法复制失血性休克 ,通过放出和回输血液使大鼠血压保持在 30ｍｍＨｇ ,持续 70ｍｉｎ ,以回输所有放出血液的方法使动物复苏。在复苏后 0、2、6、1 2、2 4和 48ｈ各处死 1 0只动物 ,对照组不放出和回输血液 ,于插管 70ｍｉｎ后处死 ,分…     

纯氧与空气复苏对窒息新生大鼠心肌细胞超微结构的影响

目的：在建立新生大鼠窒息的动物模型基础上,研究纯氧与空气复苏对窒息新生大鼠心肌细胞超微结构的影响。方法：采用SD新生大鼠建立窒息模型,并分组进行纯氧与空气复苏。实验分组：1．正常对照组（n=5）;2．缺氧组（n=5）;3．纯氧复苏后24h组（n=5）;4．纯氧复苏后72h组（n=5）;5．空气复苏后24h组（n=5）;6．空气复苏后72h组（n=5）。按时间点取心肌组织,制作超薄切片,在透射电镜下观察各组心肌细胞超微结构变化。结果：与正常对照组相比,缺氧组心肌细胞的线粒体肿胀,嵴断裂,肌原纤维扭曲,肌丝断裂,细胞核内染色质边集。氧气复苏组肌原纤维间水肿,肌丝扭曲,线粒体肿胀,核膜不清,染色质浓集。空气复苏组,特别是24h组,心肌细胞严重水肿,肌丝断裂溶解,线粒体空泡化明显,细胞核肿胀,染色质淡染。结论：空气复苏较纯氧复苏后心肌细胞损伤严重,各组均以复苏后24h出现较明显变化,而复苏后72h心肌细胞有一定程度的再生修复。     

A shock model for software failures

In this paper we present a general shock model for software failures. We give the usually used Jelinski and Moranda model a new interpretation. Some other specific models which may be more realistic are also derived.     

A computer controller for vest cardiopulmonary resuscitation (CPR)

The authors recently developed a cardiopulmonary resuscitation (CPR) technique in which the airways are obstructed automatically during each chest wall compression. Energy loss accompanying air convection from the lungs during chest wall compression is limited so lung volume and intrathoracic pressures are increased. This technique required the development of a simple controller device to govern the pressure applied to ribcage and abdominal vests together with controller airflow at the airway opening. Experiments with the controller device on eight mongrel dogs showed that cardiac output increased obstructed expiratory cardiopulmonary resuscitation (OECPR) by 19% relative to the cardiac output during standard vest CPR (61% of the prearrest cardiac output relative to 24%, respectively). Furthermore, the OECPR technique without adjunct ventilation resolved the hypocapnic respiratory alkalosis that developed during the standard vest CPR with no ventilatory support. The authors give background information on the obstructed expiratory vest CPR and describe the controller device for delivering this CPR method     

激光冲击用柔性贴膜的研究

柔性贴膜作为一种集约束层与吸收层于一体的新手段,使激光冲击技术有了更好的工程实际应用性。为了解决原技术中约束效果较差的问题,采用丙烯酸合成树脂与聚氯乙烯胶来代替硅胶做约束层。试验结果表明,这二者的约束效果远优于硅胶,冲击后材料的硬度均达到33HV以上,最大残余压应力均在60MPa左右,接近光学玻璃约束的水平(硬度与残余应力分别约34HV,70MPa),很好地解决了硅胶约束效果较差的问题,使柔性贴膜技术更趋近于实用化。     

Rotary regenerative shock absorbers for automotive suspensions

The increasingly strict limits on pollutant emissions are pushing the car industry towards the electrification of the powertrain and chassis. This scenario has driven the automotive field to the use of energy harvesters. Among these, regenerative shock absorbers are mechatronic devices that enable the energy recovery from road irregularities, thus yielding benefits in terms of fuel saving and ride quality. The state of the art proposes different technologies for regenerative dampers. In this context, rotary dampers represent an unexplored field from the scientific point of view. These devices feature a linkage and a gearbox to convert the suspension linear motion into rotation of an electric machine. This work proposes a novel system-level design methodology for rotary regenerative shock absorbers and explores their performance from an experimental perspective. The design is focused in yielding a compact solution able to fulfill a given damping specification. Hence, the integrated definition of electric machine, gearbox and linkage is addressed by the proposed method. To support the methodology, a case study is presented. A fully functional prototype is produced and successfully validated in terms of damping capability, total conversion efficiency and acoustic behavior. The obtained results demonstrate the validity of the proposed methodology and the advantageous features of rotary dampers with respect to other regenerative suspension solutions.     

垂体腺瘤卒中的治疗及护理

目的：探讨了垂体腺瘤卒中的治疗及护理。方法：回顾分析36例垂体腺瘤卒中的临床表现以及手术治疗情况。结果：经蝶手术33例,经额手术3例。全切除26例,次全切除5例,部分切除5例。术后头痛缓解,呕吐停止,有意识障碍者逐渐清醒,术前视力在有光感以上者均有不同程度好转,眼肌麻痹均有改善。随访28例,治愈7例,缓解16例,无缓解2例,复发3例。结论：垂体腺瘤卒中尽早经蝶手术减压,术后严密监测病情变化及生命体征,有效护理对于改善预后意义重大。     

盐酸戊乙奎醚预处理对大鼠失血性休克致急性肺损伤时p38MAPK信号通路的影响

目的：观察盐酸戊乙奎醚预处理对大鼠失血性休克致急性肺损伤（ALl）时p38MAPK信号通路的影响,探讨盐酸戊乙奎醚对失血性休克致ALI的肺保护机制。方法：健康SD大鼠40只,体重200g至250g,随机分为5组（n=8）：假手术组（A组）、失血性休克组（B组）、盐酸戊乙奎醚低剂量组（C组）、中剂量组（D组）和高剂量组（E组）。A组仅行动静脉穿刺不放血,B组股动脉放血至40±5mmHg制作失血性休克模型,C、D、E组分别于放血前30min股静脉注射盐酸戊乙奎醚0.3mg/kg、1.0mg/kg、3.0mg/kg,随后制作失血性休克模型。各组复苏后4h处死大鼠取肺组织,RT-PCR检测肺组织TLR-4mRNA的表达水平,免疫组化法检测肺组织p38MAPK的蛋白表达：并测定肺湿/干重比（W/D）和观察肺组织病理学变化。结果：与A组比较,B组和C组TLR-4mRNA、p38MAPK蛋白表达水平及W/D比值升高（P〈0.05或P〈0.01）,与D组和E组差异无统计学意义（P〉0.05）;与B组比较,D组和E组TLR-4mRNA、p38MAPK蛋白表达水平及W/D比值降低（P〈0.05或P〈0.01）,C组上述指标差异无统计学意义（P〉0.05）;D组与E组上述指标差异无统计学意义（P〉0.05）。光镜观察：C组、D组、E组肺泡间隔增宽及多形核白细胞浸润程度均较B组减轻。结论：盐酸戊乙奎醚预处理可通过抑制p38MAPK信号转导通路的激活,减轻失血性休克所致的大鼠急性肺损伤,且有剂量依赖性。     

高超声速波系结构的彩色纹影显示技术

针对高超声速流场波系结构复杂、激波相互作用强、激波强度差别大等特点,发展了非侵入式、高灵敏度的彩色纹影流场显示技术,结合彩色滤光片设计技术和高速摄影技术,将彩色纹影系统的空间分辨率提高至0.1 mm 量级,时间分辨率达到1 s量级。在高超声速激波风洞中分别研究了斜激波相互作用产生的正规反射和马赫反射激波结构,以及斜激波与弓形激波相互作用产生的IV 型激波干扰,得到了清晰的彩色纹影照片,细致展现了待测流场的复杂结构,证明了该彩色纹影技术能够为高超声速流场诊断提供有力的技术支撑。     

Detection and quantification of intraperitoneal fluid using electrical impedance tomography

A prototype electrical impedance tomography system was evaluated prior to its use for the detection of intraperitoneal bleeding, with the assistance of patients undergoing continuous ambulatory peritoneal dialysis (CAPD). The system was sensitive enough to detect small amounts of dialysis fluid appearing in subtractive images over short time periods. Uniform sensitivity to blood appearing anywhere within the abdominal cavity was produced using a post-reconstructive filter that corrected for changes in apparent resistivity of anomalies with their radial position. The image parameter used as an indication of fluid quantity, the resistivity index, varied approximately linearly with the quantity of fluid added. A test of the system's response to the introduction of conductive fluid out of the electrode plane (when a blood-equivalent fluid was added to the stomach) found that the sensitivity of the system was about half that observed in the electrode plane. Breathing artifacts were found to upset quantitative monitoring of intraperitoneal bleeding, but only on time scales short compared with the fluid administration rate. Longer term breathing changes, such as those due to variations in the functional residual capacity of the lungs, should ultimately limit the sensitivity over long time periods