Effect of MR Field Strength on the Texture Features of Cerebral T2-FLAIR Images: A Pilot Study

Objective To investigate effect of MR field strength on texture features of cerebral T2 fluid attenuated inversion recovery(T2-FLAIR)images.Methods We acquired cerebral 3 D T2-FLAIR images of thirty patients who were diagnosed with ischemic white matter lesion(WML)with MR-1.5 T and MR-3.0 T scanners.Histogram texture features which included mean signal intensity(Mean),Skewness and Kurtosis,and gray level co-occurrence matrix(GLCM)texture features which included angular second moment(ASM),Contrast,Correlation,Inverse difference moment(IDM)and Entropy,of regions of interest located in the area of WML and normal white matter(NWM)were measured by ImageJ software.The texture parameters acquired with MR-1.5 T scanning were compared with MR-3.0 T scanning.Results The Mean of both WML and NWM obtained with MR-1.5 T scanning was significantly lower than that acquired with MR-3.0 T(P<0.001),while Skewness and Kurtosis between MR-1.5 T and MR-3.0 T scanning showed no significant difference(P>0.05).ASM,Correlation and IDM of both WML and NWM acquired with MR-1.5 T revealed significantly lower values than those with MR-3.0 T(P<0.001),while Contrast and Entropy acquired with MR-1.5 T showed significantly higher values than those with MR-3.0 T(P<0.001).Conclusion MR field strength showed no significant effect on histogram textures,while had significant effect on GLCM texture features of cerebral T2-FLAIR images,which indicated that it should be cautious to explain the texture results acquired based on the different MR field strength.

Investigation of the Value of Different Field Strength MRI Scans for the Diagnosis of Rotator Cuff in Juries

Objective: A comparison of the difference between the two types of field MR scan in diagnosis of shoulder joint injury. Method: Randomly selected 153 patients with arthroscopic or open arthroplasty who had shoulder pain or dysfunction treated in our hospital from 2014 to 2017 were divided into 1.5 T group and 3.0 according to the field strength of MRI examination. Postoperative pathology was a gold standard. The sensitivity, specificity, consistency, and predictive value of two field-strength MRI examinations in the diagnosis of rotator cuff tears were calculated and compared. Results: The sensitivity, specificity, crude consistency, positive predictive value, and negative predictive value of the 1.5 T group were 68.75%, 82.35%, 73.47%, 88.00%, and 58.33%, respectively. The 3.0 T group was 72.22%, 89.47%, 78.18%, 92.86% and 62.96%, the differences between the above indicators were not statistically significant (P > 0.05). Conclusion: There was no difference in the authenticity and benefit index of rotator cuff injury diagnosed by 1.5 T and 3.0 T MRI.

HF FIELD STRENGTH MEASUREMENTS OVER THE VERY LONG DISTANCE

It was ascertained that there is a great margin between the theoretical values and experimental medians of the field strength of RWM and RID signals during high solar activity period at Chinese Great Wall Station on Antarctica. The calculated values are, on average, less than the experimental, especially on the propagation path between RID and Antarctica. The field strength by the experiment may be used as the basic data for the research of HF propagation over the very long distance. Because of the large deviation it seems to be necessary to study HF propagation over the very long distance in details, especially the propagation model.

Incompleted Field Strength Calculation of the Potential Term Adopted from Landau-Ginzberg Theory Applied in Particle Physics

Completion of field strength calculation of the potential term originated in theories of condensed matter applied in particle physics is discussed.

Measurement of Breakdown Electric Field Strength for Vegetation and Hydrocarbon Flames

A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.

Evolution and spatial characteristics of tourism field strength of cities linked by high-speed rail （HSR） network in China

Traffic is an indispensable prerequisite for a tourism system. The ＂four vertical and four horizontal＂ HSR network represents an important milestone of the ＂traffic revolution＂ in China. It will affect the spatial pattern of tourism accessibility in Chinese cities, thus substan- tially increasing their power to attract tourists and their radiation force. This paper examines the evolution and spatial characteristics of the power to attract tourism of cities linked by China＇s HSR network by measuring the influence of accessibility of 338 HSR-linked cities using GIS analysis. The results show the following. （1） The accessibility of Chinese cities is optimized by the HSR network, whose spatial pattern of accessibility exhibits an obvious traf- fic direction and causes a high-speed rail-corridor effect. （2） The spatial pattern of tourism field strength in Chinese cities exhibits the dual characteristics of multi-center annular diver- gence and dendritic diffusion. Dendritic diffusion is particularly more obvious along the HSR line. The change rate of urban tourism field strength forms a high-value corridor along the HSR line and exhibits a spatial pattern of decreasing area from the center to the outer limit along the HSR line. （3） The influence of the higher and highest tourism field strength areas along the HSR line is most significant, and the number of cities that distribute into these two types of tourism field strengths significantly increases： their area expands by more than 100% HSR enhances the tourism field strength value of regional central cities, and the radiation range of tourism attraction extends along the HSR line.

Indoor field strength prediction based on FMM

In this article, the fast multipole method （FMM） is applied to analgze the field strength of an ultra-wideband （UWB） signal. Small coverage of UWB communication systems and high efficiency of the algorithm make it possible to calculate the amplitude of electric field accurately. A homogeneous dielectric body and a multilayered dielectric object are studied. The computational results obtained by applying the FMM agree well with those obtained by applying the method of moments （MoM）.

Field strength prediction of mobile communication network based on GIS

This article describes GIS-based models successfully developed for predicting the coverage of Cityphone cellular network,visualizing the predicted signal strength,and analyzing the field strength coverage.In order to predict the signal coverage strength of communication network more accurately,the spatial and nonspatial databases of a mobile cellular network are combined by GIS and produce the necessary parameters.A GIS model named COST-231-Walfisch–Ikegami model(WIM)is developed for signal coverage prediction in Ho Chi Minh City.Radio-line-of-sight and nonradio-lineof-sight conditions can be determined by this model.In addition,in case of nonradio-line-of-sight conditions,average building height,building separation,building width,incident radio path,and road orientation with respect to the direct radio path were obtained using GIS.Road orientation loss,multiscreen diffraction loss,and shadowing gain were predicted more accurate by this model.The scale of maps in the experiment was 1:2000 and the average of floor height was 3 m because there were no exact building height measurements.Statistical results show that the path loss predicted by the COST 231 WIM overcame the real path loss of each cell station.And this method can be used for signal coverage prediction of mobile cellular network in urban areas.Compared to the current situation with the Ho Chi Minh City Posts and Telecommunications system,this model can be effectively applied to improve the Cityphone mobile network quality as well as capability.Developed GIS models can help designers in predicting cell station coverage using real spatial maps that make the results more reliable.This research can help network operators improve the network quality and capability with the best investment efficiently.

LOW FREQUENCY EXTENDED RADIO SOURCES——MAGNETIC FIELD STRENGTH AND CLASSIFICATION ATTEMPT

Using very recently published X-ray and low frequency radio data we have calculated thelower limit of the magnetic field and several other related quantities for 25 clusters of galaxies（which are classified into 'normal', distant and steep spectrum clusters） and 12 radiogalaxies. Our main results are as follows: （1）The magnetic field in the extended lobes of radio galaxies is larger than 10-6 G.Thus radio galaxies, whether they belong to clusters or not, emit few X-rays through theinverse Compton effect. （2）The low frequency radio emission from clusters can be divided into two components:one or several radio galaxies, and an extended halo where the magnetic field is about 10-8G, and where inverse Compton X-rays are most probably emitted. （3）Our sample of distant clusters is biased towards high radio luminosity and givesresults comparable to those obtained for radio galaxies. This can naturally be explained bythe fact that the radio galaxy component daminates the radio emission. （4）In steep spectrum clusters, the equipartition magnetic field is the same as that in'normal' clusters, but the lower limit of the magnetic field has a rather high value andseems to increase with the spectral indcx. We explain this as follows: a high frequencyturnover can occur hi the weak intraculuster magnetic field; the extrapolation of the power lawelectron spectrum is then incorrect, and the magnetic field; the extrapolation of the power lawvalue.

Experimental studies on electrical breakdown field strength of electrode with water mist containing MC additives

Water mist is one of the effective candidates for halon replacement used in electrical environment fire protec-tion. Water mist additives may greatly enhance fire suppres-sion effectiveness. In electrical environment, electrical breakdown field strength (E) is one of the important factors that control the performance of electrical equipment. In this study the variation principles of electrical breakdown field strength and the electrical characteristics of MC additives were investigated by electrode discharging experiments. Ex-perimental results showed that electrical breakdown field strength was impacted obviously by the conductive metal ions and insulated fluorocarbon surfactants in MC additives. The attenuation percentages of E in different experimental cases were described, thus providing scientific guidance for the use of water mist and MC additives in electrical fire sup-pression.

High-Field-Strength Elements in Mafic Volcanics from North China Craton: Implications for Archean-Proterozoic Boundary and Source Composition

Archean to Cenozoic mafic volcanic rocks from the North China craton are studied. They show Archean Proterozoic (Ar Pt) boundary and geochemical anomalies in Cenozoic basalts. Proterozoic mafic volcanics are enriched in most of the high field strength elements (HFSE) compared with Archean ones. Nb, Ta and Th show a distinct sequence of incompatibility in Archean and Proterozoic. The Cenozoic basalts are enriched in HFSE and Ni and their REEs are strongly differentiated with positive Eu anomalies ( δ (Eu)=1.14). The Ar Pt boundary could be related to change in oxygen fugacity and requires an increasing importance of enriched mantle source. The geochemistry of Cenozoic basalts implies a mantle source similar to OIB. Residuum from subducting partial melting of old basaltic oceanic crust and continental crust is likely to contribute to the formation of the enriched mantle.

Vapor cell geometry effect on Rydberg atom-based microwave electric field measurement

The geometry effect of a vapor cell on the metrology of a microwave electric field is investigated. Based on the splitting of the electromagnetically induced transparency spectra of cesium Rydberg atoms in a vapor cell, high-resolution spatial distribution of the microwave electric field strength is achieved for both a cubic cell and a cylinder cell. The spatial distribution of the microwave field strength in two dimensions is measured with sub-wavelength resolution. The experimental results show that the shape of a vapor cell has a significant influence on the abnormal spatial distribution because of the Fabry-P6rot effect inside a vapor cell. A theoretical simulation is obtained for different vapor cell wall thicknesses and shows that a restricted wall thickness results in a measurement fluctuation smaller than 3% at the center of the vapor cell.

Breakdown Electric Field of Hot 30% CF_3I/CO_2 Mixtures at Temperature of 300–3500 K During Arc Extinction Process

We calculated the uniform dielectric breakdown field strength of residual 30% CF3I/CO2 gas mixtures during the arc extinction process over the temperature range 300-3500 K at 0.1 MPa. The limiting reduced field strengths are decided by a balance of electron generation and loss based on chemical reactions estimated by the electron energy distribution function （EEDF）, which employs the Boltzmann equation method with two-term expanding approximation in the steady-state Townsend （SST） condition. During the insulation recovery phase, the hot CF3I/CO2 gas mixtures have maximum dielectric strength at a temperature of about 1500 K. At room temperature 300 K, the electric strength after arc extinction （90.3 Td, 1 Td=10-21 V.m2） is only 38% of the original value before arc （234.9 Td）. The adverse insulation recovery ability of CF3I/CO2 gas mixtures in arc extinction hinders its application in electric circuit breakers and other switchgears as an arc quenching and insulating medium.

Investigation into Effects of Buildings near Broadcasting Antenna on Far Fields Using a Finite-Difference Method

A steady state finite difference method is used to calculate EM fields generated by an MW broadcasting antenna. The effects of buildings on the wave propagation is studied based on the numerical results and field measurements. Both the algorithm and results are useful in the design of broadcasting antennas, as well as in the selection of transmitting sites.

Design Optimization for Generating a High Static Magnetic Field

This paper details the creation of a device capable of generating a powerful and consistent static magnetic field. This apparatus serves the purpose of quantifying the magnetostrictive strain found in materials like annealed cobalt ferrite and Terfenol-D, specifically those shaped as cylindrical rods. In our investigation, the use of static magnetic fields proves most advantageous. This choice is made to mitigate the generation of eddy currents, which would inevitably occur if the magnetic field intensity were varied. The fundamental idea behind this design involves employing a C-shaped iron core constructed from low-carbon mild steel. On this core, three coils are mounted, each capable of producing one-third of the required 9000 Oersted (Oe) magnetic field strength. The test specimen is situated within the “jaws” of the C-shaped core, thus completing the magnetic circuit. To manage the heat generated by each coil, a cooling system consisting of copper tubes is employed. These tubes facilitate the flow of air to dissipate the heat. To model and predict the magnetic field strength produced by the coils, finite element analysis (FEMM) software is utilized, and the results align closely with the anticipated outcomes. This design effectively generates a robust and unchanging magnetic field measuring a stable 9000 Oe in total. Consequently, this equipment finds utility in characterizing the magnetic properties of specific materials.

Research Progress of Electromagnetic Field and Electromagnetic Compatibility of UHVDC Converter Valves

特高压直流换流阀的电磁场和电磁兼容性是其研制过程中的关键问题,国内外学者对此进行了系统研究。中国电力科学研究院成功研制出中国首个具有完全自主知识产权的800 kV/4 750 A特高压直流（ultra high voltage directcurrent,UHVDC）换流阀。针对电磁场和电磁兼容问题,利用三维电场边界元法实现换流阀寄生参数的提取,通过理论计算、数值仿真及试验测试等多种手段,对瞬态电磁干扰等问题提出了解决方案,为换流阀的研制和工程应用提供了必要的技术支撑。总结了上述领域的研究成果,对未来特高压直流换流阀电磁兼容领域的研究课题与解决方案提出了一些建议和设想。

A STUDY OF PLASMA PROPERTIES FOR VARIOUS MAGNETIC FIELDS IN A MICROWAVE MULTIPOLAR ECR PLASMA

A sputtering-type microwave multipolar ECR plasma processing for preparing thin films, is built with Nd-Fe-B magnets and 2.45 GHz, TE10 mode microwave. The plasma distributions in the axial direction, which is important for preparing thin films, are found to be very sensitive to the magnetic potential fields in plasma chamber. The plasma parameters are also influenced by the background gas pressure.

EFFECT OF SOLUTION TREATMENT IN AN ELECTRIC FIELD ON MECHANICAL PROPERTIES AND MICROSTRUCTURE OF 2091 Al—Li ALLOY

Solution treatment of 20% Al-Li alloy in an electric field has been studied. The results show that it increases the solubility of elements and accelerates the nucleation of T1-phase and promotes the formation of the precipitation free zones(PFZ), and increases the strength and decreases the plasticity of the alloy.

Effect of Plastic Deformation and H_2S on Dynamic Fracture Toughness of High Strength Casing Steel

The effects of plastic deformation and H2 S on fracture toughness of high strength casing steel（C110 steel） were investigated. The studied casing specimens are as follows： original casing, plastic deformation（PD） casing and PD casing after being immersed in NACE A solution saturated with H2S（PD＋H2S）. Instrumented impact method was employed to evaluate the impact behaviors of the specimens, meanwhile, dynamic fracture toughness（JId） was calculated by using Rice model and Schindler model. The experimental results show that dynamic fracture toughness of the casing decreases after plastic deformation. Compared with that of the original casing and PD casing, the dynamic fracture toughness decreases further when the PD casing immersed in H2 S, moreover, there are ridge-shaped feature and many secondary cracks present on the fracture surface of the specimens. Impact fracture mechanism of the casing is proposed as follows： the plastic deformation results in the increase of defect density of materials where the atomic hydrogen can accumulate in reversible or irreversible traps and even recombine to form molecular hydrogen, subsequently, the casing material toughness decreases greatly.

基于离散Hopfield神经网络的我国农口国家工程技术研究中心综合实力评价研究

农口国家工程技术研究中心是所有涉农国家工程技术研究中心的总称。在明确我国农口国家工程技术研究中心职能定位、梳理其发展现状的基础上,基于离散Hopfield神经网络方法,实现对农口国家工程技术研究中心综合实力的分级评价,并根据结果对评价指标提出修正建议。