交流阻抗谱法研究燃料电池的极化阻力

电化学阻抗谱(Electrochemical Impedance Spectroscopy,EIS)是用于研究燃料电池电性能的一种重要手段,因其包含了大量的电池极化阻力等方面的信息。通过对电化学阻抗谱的分析可以得到电池的欧姆极化电阻、电化学极化电阻和浓差极化电阻等数据。分析了固体氧化物燃料电池常见的各种形状的交流阻抗谱,给出了各自的等效电路,并通过对等效电路的拟合求得了电池的极化电阻。与文献中普遍采用的直接读图法相比,拟合法得到的电池极化电阻数据更准确、更合理。     

Study of water clusters in insulating oils by Fourier transforminfrared spectroscopy

The electrical parameters of insulating oils applied in HV transformers strongly depend on the moisture content. The water/oil system was studied in the practical important concentration range of 0 to 130 μg/g to explain the unusual decrease of the breakdown strength. The relationship between water concentration and oil breakdown strength was determined in the range 0 to 50 μg/g, using almost 100 oil samples taken from functioning transformers from each part of Hungary. The plotted data can be approached by two straight lines having very different slope, from which we conclude that the water/oil system has two different structures in this concentration range. The water in oil structure was examined by both theoretical and experimental methods. By a Hartree-Fock calculation the distance between water and hydrocarbon molecules was estimated. The water molecules arrangement and distance were calculated by a geometrical model. Fourier transform infrared spectroscopy was applied for experimental structure determination. Three oil samples were selected in the range 0 to 50 μg/g. Assigning the OH vibration bands revealed that water is present in low concentration as monomer and at higher concentration in cluster forms (dimers, tetramers etc.). Similar graphs were found of the total dipole moment of water clusters vs. The resistance of insulating oil and the water concentration vs. the breakdown strength. The latter curve can be explained with the different state of water in oil. Water is present in molecular disperse state at ≳10 μg/g. Above this value water clusters appear. Due to the similar total dipole moments of different water clusters there is practically no change of the breakdown strength in the range 10 to 50 μg/g     

Applications of dielectric spectroscopy in time and frequency domain for HV power equipment

Dielectric spectroscopy in the time or frequency domain offers new opportunities for an off-line, on-site insulation condition assessment of HV electric power equipment and its predictive maintenance.     

Intraoperative application of optical spectroscopy in the presenceof blood

A simple but effective method of spectral processing was developed to minimize or remove the effects of the presence of superficial blood on tissue optical spectra and, hence, enhance the performance of optical-spectroscopic-based in vivo tissue diagnosis and surgical guidance. This spectral-processing algorithm was developed using the principles of absorption-induced light attenuation wherein the ratio of fluorescence intensity (F) and the hth power of diffuse reflectance intensity (Rd) at a given emission wavelength λ_m is immune to spectral distortions induced by the presence of blood on the tissue surface. Here, the exponent h is determined by the absorption coefficients of whole blood at the excitation and emission wavelengths. The theoretical basis of this spectral processing was verified using simulations and was experimentally validated. Furthermore, the optical spectra of brain tissues collected in vivo was processed using this algorithm to evaluate its impact on brain tissue differentiation using combined fluorescence and diffuse reflectance spectroscopy. Based on the simulation, as well as experimental results, it was observed that using F/Rd^h h can effectively reduce or remove spectral distortions induced by superficial blood contamination on tissue optical spectra. Thus, optical spectroscopy can also be used intraoperatively for applications such as surgical guidance of tumor resection     

Movement of blood cells in liquid by nonuniform traveling field

A study of the motion of biological cells in aqueous solution using a traveling-field-type electric curtain device is performed. Cells driven by such a device undergo circular motions induced by the rotating traveling field, and as a result of field nonuniformity and drift in the direction of the wave propagation. Electrolytic dissociations of the aqueous medium are avoided by limiting the applied voltage below the theoretical dissociation voltage, while the field strength necessary for the actuation of the cell motion is insured by making the electrode dimensions as small as 100 μm. The experiments are performed using sheep erythrocytes. The device shows a maximum performance with six-phase voltage of frequency 3 Hz and amplitude 1.5 V, where the transport of cells takes place without perceivable damage to the cells     

Application of LCModel for quality control and quantitative in vivo1H MR spectroscopy by short echo time STEAM sequence

The linear combination of model spectra (LCModel) calculation of a parameter for long-term quality control,k _T, was introduced, representing the ratio of the temporal and nominal intensities of CH₃ groups of lactate and acetate in a quality control phantom. This procedure is a part of the quality assurance of the scanner using fully automatic measurement and calculation ofk _T parameters, and utilizing Shewhart regulation control charts for continuous evaluation of the magnetic resonance (MR) scanner setting. The application of thek _T parameter for the correction of in vivo data increases the precision of molar concentration determination by about 4%. This was tested by the quantitative in vivo MR determination of the molar concentrations of 13 prominent metabolites (N-acetylaspartate (NAA),N-acetylaspartylgutamate, creatine and phosphocreatine (Cr), choline-containing compounds (Cho), myo-inositol, scyllo-inositol., γ-aminobutyric acid, glutamine, glutamate, glucose, lactate, alanine, taurine) in the white matter and hippocampus of the brain in groups of volunteers, using a short echo time stimulated echo acquisition mode sequence (echo time =10 ms) and the LCModel technique. The repeatability of the measurement of prominent metabolites such as NAA, Cr and Cho was found to be around 10% (relative standard deviation,n=6); precision in a group of volunteers (n=20 and 28, respectively) was in the range of approximately 13–20%. For other metabolites, which are measured with a lower signal-to-noise ratio, the precision can be much lower.     

弛豫时间分布函数应用于电化学阻抗谱分析

电化学阻抗谱作为一种现代测试手段,对测试和提高锂离子电池的性能提供了便利.由于电化学阻抗谱无法直观地反映电池内部的结构以及电化学过程,且常用的等效电路模型方法在分析电化学阻抗谱上存在一定的局限性,因此引入了弛豫时间分布函数方法用于分离和量化电池内部的电化学过程.构建了一套完整的用弛豫时间分布函数方法分析锂离子电池的电化学阻抗谱的流程,并成功应用于磷酸铁锂原型电池的电化学阻抗谱分析中.     

1H magnetic resonance spectroscopy of the brains of normal infants and after perinatal hypoxia-ischemia

The aims of this study were to define proton (¹H) metabolite peak-area ratios in the brains of normal infants and to investigate abnormalities after perinatal hypoxia-ischemia. Point-resolved spectroscopy (PRESS) data were collected at 2.4 T with an echo time (TE) of 270 ms from 8-ml voxels located in the thalamus or occipito-parietal region. Fourteen normal and 9 asphyxiated infants were studied. The gestational plus postnatal ages (GPA) of these two groups were 31–41 (median 36) and 27–41 (37) weeks, respectively, and the asphyxiated infants were studied aged 0–10 (2) days. Peak-area ratios were determined in the normal infants for choline-containing compounds (Cho), creatine plus phosphocreatine (Cr),N-acetylaspartate (NAA) and lactate (Lac). Lactate was detected in all the normal infants and Lac/NAA was higher in the occipito-parietal region than in the thalamus (p<0.005). Lac/NAA decreased with increasing GPA in both the thalamus (p=0.014) and the occipito-parietal region (p=0.033). In six of the nine asphyxiated infants, Lac/NAA was above 95% confidence intervals for either the thalamus and/or the occipito-parietal region. Of these six infants, two died and three were neurologically abnormal aged 2 months, indicating that elevated Lac/NAA after perinatal hypoxia-ischemia may convey a poor prognosis. Propan-l,2-diol (the phenobarbitone injection medium) was detected at 1.1 ppm in three infants.     

Influence of rise time on dielectric parameters extracted from time domain spectroscopy in the context of generator stator insulation

The low-frequency dielectric response of generator stator winding insulation materials was calculated from high voltage time domain spectroscopy measurements. These results were used to calculate the theoretical response after the application of a voltage function consisting of a ramped voltage followed by a constant level voltage. The rate of rise of the ramped portion of the voltage function was shown to influence the well known and much used polarization index (PI) and insulation resistance (IR) parameters.     

Investigation on the transformation of time domain spectroscopy data to frequency domain data for impregnated pressboard to reduce measurement time

The accuracy of different transformation methods for time domain dielectric response data to frequency domain and their limits are studied. First an approximated analytic function is considered, second an extended Debye model for the dielectric behavior of impregnated pressboard. The last method is a numerical integral form and Fast Fourier Transform. Hamon approximation relates time domain data at t to frequency domain data at f=0.1/t and gives the results by sole measurement of polarization current. Dielectric diagnosis of high voltage apparatus can be done by using Hamon approximation in minimum duration. All transformation methods show similar results and they are analyzed in order to demonstrate the limits of the methods.     

Detection of polyunsaturated omega-6 fatty acid in human malignant prostate tissue by 1D and 2D high-resolution magic angle spinning NMR spectroscopy

Object  

Polyunsaturated omega-6 fatty acids (PUFAs) have been shown to promote prostate cancer. Here, we describe the use of HRMAS NMR spectroscopy to detect omega-6 PUFA species in prostate tissues.     

用正规形方法研究负荷节点对电压稳定性的影响

不同的负荷节点对电压稳定性具有不同的影响程度。应用向量场正规形理论,分析电力系统潮流方程。提出以节点电压非线性参与因子作为依据,衡量负荷节点对电压稳定性的影响程度。所提出的方法可计及电力系统非线性特性对电压稳定性的影响,与线性化分析方法相比,该方法在系统具有强非线性特性的条件下,仍能准确识别负荷节点的重要程度。将所提出的方法用于New England 39节点系统,研究系统中负荷节点对电压稳定性的影响,通过对系统电压稳定性指标的比较,验证所提出方法的有效性。     

Study of polymers with various chemical structures and chain architectures by thermally stimulated currents and broadband dielectric spectroscopy

The origin of polarization phenomena occurring in amorphous polymers has been investigated, using dielectric dynamic spectroscopy and thermo stimulated current analysis. Linear polymers, e.g. poly(methyl methacrylates) and poly(ethyl methacrylates), show a molecular mobility which is increasingly delocalised along the backbone with increasing temperature. Dendrimers with a phosphorus core and increasingly complex radial branches showed a hierarchy of molecular mobility as a function of generation.     

Investigation of multidrug resistance in cultured human renal cell carcinoma cells by 31P-NMR spectroscopy and treatment survival assays

KTCTL-26 and KTCTL-2 are renal cell carcinoma (RCC) lines with high and lowexpression of P-170 glycoprotein, respectively. Inherent differences between the two cell lines in terms of phosphate metabolites and growth characteristics in culture were examined for possible association with multidrug resistance (MDR). Differences in response to drug treatment were investigated for 40 h incubations with various doses of vinblastine (VBL) alone or as cotreatments with various concentrations of the calcium antagonist diltiazem (DIL) and/or interferon–α (IFN-α). Treatment effects were quantitated using the MTT survival assay and ³¹P magnetic resonance spectroscopy (MRS) to determine phosphate metabolite profiles in intact cells. KTCTL-2 and KTCTL-26 cells exhibited significant inherent differences in phosphocholine, glycerophosphocholine, glycerophosphoethanolamine, and phosphocreatine levels. KTCTL-26 cells were more sensitive than KTCTL-2 to 0.011μM VBL alone (87% vs. 102% survival) or to 0.011μM BL + 10μM DIL (55% vs. 80% survival). The latter treatment resulted in a significant decrease in the ratio of phosphocholine to glycerophosphocholine in KTCTL-26 cells but no significant changes in phosphate metabolites in KTCTL-2 cells. Metabolomic ³¹P MRS detects different metabolite profiles for RCC cell lines with different MDR phenotypes and may be useful for noninvasive characterization of tumors in a clinical setting.This revised version was published online in August 2005 with a corrected sequence of authors.     

高精度GPS时间信息的研究与应用

本文介绍了GPS系统传递高精度时间信息的技术原理,提出了用GPS时间信息锁定高稳定度晶体振荡器的方法,建立了Kalman滤波模型,在GPS信号失效时通过滤波估计保持晶振正常输出.通过性能指标测量、分析,结果验证了GPS晶体频率标准具备较高的频率准确度和稳定性,能够用于时间频率的测量基准.     

Dielectric spectroscopy in time and frequency domain for HV power equipment. I. Theoretical considerations

Most dangerous breakdowns are caused by the aging effects of HV insulation systems used within HV components, and there is still a lack of appropriate tools to diagnose such systems non-destructively and reliably in the field. This review introduces the theoretical background of dielectric spectroscopy in the time and frequency domains and provides an overview about the specific measuring methods based on this background. The specific methods treated are used for diagnosing electric insulation materials used in power engineering. It indicates that some of these methods may not be sufficient to gain full information about the actual conditions of a test object and that either measurements of polarization and depolarization currents (PDC in the time domain or measurements of C-tan/spl delta/ values (or complex permittivity) in the frequency domain (FDS) should be preferred to obtain a "dielectric response function" which offers much more information to judge the actual state of an insulation material or system.     

玉米冻结时间试验研究

为了提高蔬果的品质,确保食品安全和营养成分完整,速冻技术成为重要的保鲜方式之一,因为水分流失少,在保证营养的同时还能保留其良好的口感。本次采用试验方法,对玉米速冻时间和速冻过程进行研究。研究结果表明:玉米冻结时间及冻结温度随摆放位置的不同而不同。     

Use of dielectrophoretic collection spectra for characterizingdifferences between normal and cancerous cells

An automated analysis system for the rapid measurement of dielectrophoretic collection spectra of mammalian cells is described. Cells are injected onto an electrode configuration having regions with different electric field gradients, and cell movement to or from these regions is determined by computerized image analysis as a function of the applied electric field frequency. Data are presented to show that cultured murine erythroleukemia cells undergo a significant alteration in their dielectrophoretic collection spectrum following treatment with hexamethylene bisacetamide or dimethylsulfoxide, agents that induce terminal differentiation in these otherwise malignant cells. These changes appear to arise from characteristic alterations in membrane capacitance and conductance as the cells differentiate     

以天然流量为判据提高葠窝水库汛限水位研究与应用

在总结水库汛限水位动态控制研究与应用现状的基础上,分析了目前两种提高水库汛限水位方法存在的共性问题,重点研究了提高水库汛限水位的新方法:以天然流量作为判断洪水量级指标提高水库汛限水位.以辽宁省葠窝水库为工程背景,详细阐述了该方法的基本思路和求解过程,并阐述了该方法在研究与应用中应注意的问题.