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Sixteen secondary metabolites, including one new sesquiterpene (1, named isocyclonerodiol oxide), seven known sesquiterpenes (2–8), two sorbicillinoid polyketides (15, 16), and six known other compounds (9–14) were isolated from the fermentation broth of Trichoderma sp. T-4-1. The structure of 1 was determined by 1 D, 2 D NMR (HMBC, HSQC, 1H-1H COSY, NOESY), and HRESIMS spectra. In addition, sesquiterpenes and sorbicillinoid polyketides showed significant antiviral activities. [ABSTRACT FROM AUTHOR]

Simultaneously high permeability and permittivity results in a pronounced dimensional effect in Mn-Zn ferrite cores, which makes the measured complex permeability differ for cores with different dimensions. This paper provides a succinct method to solve an inverse problem of tracing dimension-independent or intrinsic complex permeability and permittivity for Mn-Zn ferrites using two toroidal and rectangular-cross-sectioned cores with different dimensions. The apparent complex permeability of ferrite cores with other dimensions can then be predicted from the traced intrinsic values, so will the effective impedance of common-mode chokes made of such cores. The traced intrinsic permeability is in good agreement with the measured apparent complex permeability of a very small toroidal ferrite core, in which dimensional effect can be ignored. The apparent complex permeabilities of ferrite cores with other dimensions are measured experimentally, and are also calculated from the determined intrinsic values. A very good agreement between the measured and calculated values is found. Index Terms--Complex permeability, complex permittivity, dimensional effect, Mn-Zn ferrite, Newton-Raphson method.

In the coaxial transmission line method, a factor that greatly influences the accuracy of the results is the air gaps between the material under test and the coaxial transmission line test fixture. In this paper, we discuss the influence of the air gaps and the measures that can be taken to minimize that influence when Mn-Zn ferrites are measured. We propose an improved simulation model of the coaxial transmission line test fixture holding the material under test in which the air gaps are filled with conductive materials. By combining the improved simulation model, the mode-matching method, and the Newton-Raphson method, the Mn-Zn ferrites' intrinsic complex permeability and permittivity can be determined accurately, even if the conductor-filled gaps are quite wide. We also examine the influence of the finite conductivity of the coaxial transmission line test fixture. We manufactured a coaxial transmission line test fixture to measure the intrinsic complex permeability and permittivity of Mn-Zn ferrites in the frequency range from 10 to 200 MHz. The intrinsic values thus determined have been experimentally verified. We describe the structure of the test fixture, its calibration issues, and the experimental results. Index Terms--Coaxial transmission line method, Mn-Zn ferrites, permeability, permittivity.

By combining the main features of the 2-D finite-difference time domain (FDTD) method and the traditional finite-difference frequency domain (FDFD) method, a 2-D FDFD method with nonuniform grids and perfectly matched layers (PML) is presented in this paper to analyze axially symmetrical coaxial discontinuity structures. Numerical results show that the 2-D FDFD method is much more efficient than the commonly used 2-D FDTD method in solving the frequency response of the structures. High accuracy of the 2-D FDFD method is shown in a simple numerical example which can be solved by using the mode matching method. Index Terms--Coaxial discontinuity structure, finite-difference frequency domain (FDFD) method, finite-difference time domain (FDTD) method, mode matching method, S parameters.

Limitations of the published lumped circuit methods for determination of the Mn--Zn ferrites' intrinsic complex permeability and permittivity are revealed by careful theoretical examination of their models used to calculate the impedances of the ferrite core inductor and the ferrite core capacitor. To eliminate those limitations, a method without dimensional assumptions on the measurement sample is presented. Theoretical and experimental comparison of the new method and the published methods shows that the new method has higher accuracy while maintaining high computational efficiency. Index Terms--Complex permeability, complex permittivity, lumped circuit method, Mn--Zn ferrite.

To identify the location of partial discharge occurring in a power cable, it is essential to obtain the intrinsic values of permittivity of cross-linked polyethylene (XLPE) material. This paper reveals that when the conventional two-parallel-electrode method is used, and due to the fringing effect, the measured permittivity of XLPE material pronouncedly differs from its intrinsic value, consequently significant measurement error could occur. An effective method based on the field-circuit coupled theory is presented in this paper to investigate the difference between the measured and intrinsic permittivity of XLPE insulation material. A capacitor constructed from a concentrically cylindrical XLPE sample is used. By assuming a certain value of the intrinsic permittivity for XLPE material, the electric field distribution in the XLPE material and the ambient is calculated. Then the total energy is determined, as well as the measurable permittivity. By assuming different values of intrinsic permittivity, corresponding measurable values of permittivity are determined, and a curve of measurable permittivity against its intrinsic value is then obtained, from which the intrinsic value can be found once its measurable value is obtained from experiment. The influence factors of the correction curve are analyzed, i.e. the sizes of sample and electrode. A measurement was carried out to verify this method. Index Terms--Permittivity, XLPE, complex power, field-circuit coupled method.

Analysis of the principle of the published lumped circuit methods for determination of the intrinsic complex permeability and permittivity of the Mn--Zn ferrites reveals that as long as the electric and the magnetic field distributions in the core(s) in two measurements are different, the two intrinsic values can be determined. Using this principle, we developed a set of general lumped circuit methods based on a toroidal Mn-Zn ferrite core as the measurement sample. We examined two possible different excitation modes: magnetic field excitation and electric field excitation. The two different excitation modes result in significantly different field distributions in the sample. Thus, high accuracy can be guaranteed in principle. For the magnetic field excitation, we present in this paper a general finite-difference method to solve the fields in the core and the impedance of the ferrite core inductor. To avoid the stray capacitance among the coils of the ferrite core winding inductor in the measurement, we made a set of short-ended coaxial test fixtures. We performed experiments to determine the intrinsic complex permeability and permittivity of a Mn--Zn ferrite core up to 10 MHz by using the two general methods and validated the measured intrinsic values experimentally. Index Terms--Finite-difference method, Mn--Zn ferrites, permeability, permittivity.

After setting up a mathematical model for rectangular-shaped Mn-Zn ferrite capacitors, this paper investigates dimensional effects on the intrinsic complex permittivity and the measured apparent complex permittivity of Mn-Zn ferrite blocks. The simple block structure of the samples guarantees their easy and precise preparation. Above a few hundred kilohertz, dimensional effects make the measured apparent complex permittivity deviate from its intrinsic value. This paper uses a Newton-Raphson based method to trace the intrinsic complex permittivity and permeability from the measured impedances of two rectangular-shaped Mn-Zn ferrite capacitors in the frequency range from a few hundred kilohertz to 40 MHz. From the traced intrinsic complex permittivity and permeability, the apparent complex permittivity of a third sample with different dimensions is then calculated theoretically. The papers also presents results of experiments carried out to measure the apparent complex permittivity of the third sample; agreement between the measured and the calculated values is very good. This justifies the validity of the method presented in this paper, when used to determine the dimension-independent intrinsic complex permittivity and permeability of Mn-Zn ferrites. Index Terms--Apparent complex permittivity, complex permeability, dimensional effects, Mn-Zn ferrite, Newton-Raphson method.

This paper presents a fast and efficient algorithm, based on the finite-difference method, to extract intrinsic complex permeability and permittivity from measured values for Mn-Zn ferrite cores. Our algorithm is considerably more efficient than the analytical solution-based Newton-Raphson method and reduces computing time from hours to tens of seconds. Index Terms--Finite-difference method, Mn-Zn ferrites, Newton-Raphson method, permeability, permittivity.