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1

A novel in-phase disposition SPWM pulse allocation strategy for cascaded H-bridge inverter

Zhang Y., Xiong J., Kong L., Wang X.

Archives of Electrical Engineering

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2018

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Vol. 67, nr 2

361–-375

EN

A novel in-phase disposition (IPD) SPWM pulse allocation strategy applied to a cascaded H-bridge (CHB) converter is presented in this paper. The reason causing the power of the CHB converter imbalance is analyzed according to the traditional structure, the conception of power imbalance degree is introduced and the principle of the novel in-phase disposition SPWM allocation strategy is deduced in detail. The new pulse allocation scheme can ensure the power balance in 3/4 cycles through interchanging the PWM pulse sequence of the different CHB cell, meanwhile it makes the full advantage of the IPD control strategy, lower the total harmonic distortion (THD) of line voltage compared to a carrier phase shifted (CPS) control strategy, which is verified by theoretical derivation. A seven-level cascaded inverter composed by three H-bridge cells is taken as the example. The simulation and experiment is performed. The results indicate the validity of the analysis and verify the effectiveness of the proposed SPWM allocation strategy.

2

Thermoelectric properties of Ni0.15Co3.85Sb12 and Fe0.2Ni0.15Co3.65Sb12 skutterudites prepared by HPHT method

Kong L., Ma H., Zhang Y., Guo X., Sun B., Liu B., Liu H., Liu B., Chen J., Jia X.

Materials Science Poland

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2017

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Vol. 35, No. 3

496--500

EN

N-type polycrystalline skutterudite compounds Ni0.15Co3.85Sb12 and Fe0.2Ni0.15Co3.65Sb12 with the bcc crystal structure were synthesized by high pressure and high temperature (HPHT) method. The synthesis time was sharply reduced to approximately half an hour. Typical microstructures connected with lattice deformations and dislocations were incorporated in the samples of Ni0.15Co3.85Sb12 and Fe0.2Ni0.15Co3.65Sb12 after HPHT. Electrical and thermal transport properties were meticulously researched in the temperature range of 300 K to 700 K. The Fe0.2Ni0.15Co3.65Sb12 sample shows a lower thermal conductivity than that of Ni0.15Co3.85Sb12. The dimensionless thermoelectric figure-of-merit (zT) reaches the maximal values of 0.52 and 0.35 at 600 K and 700 K respectively, for Ni0.15Co3.85Sb12 and Fe0.2Ni0.15Co3.65Sb12 samples synthesized at 1 GPa.

3

Anti-periodic solutions for a higher order difference equation with p-Laplacian

Kong L., Parsley J., Rizzo K., Russell N.

Journal of Applied Analysis

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2017

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Vol. 23, nr 2

111--125

EN

A higher order difference equation is studied. The equation is defined onℤand contains a p-Laplacian and both advance and retardation. Some criteria are established for the existence of infinitely many anti-periodic solutions of the equation. Several consequences of the main theorems are also included. Two examples are provided to illustrate the applicability of the results.

4

Multiple solutions for fourth order elliptic problems with p(x)-biharmonic operators

Kong L.

Opuscula Mathematica

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2016

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Vol. 36, no. 2

253--264

EN

We study the multiplicity of weak solutions to the following fourth order nonlinear elliptic problem with a p(x)-biharmonic operator [formula] where Ω is a smooth bounded domain in RN, [formula] is the p(x)-biharmonic operator, and λ > 0 is a parameter. We establish sufficient conditions under which there exists a positive number λ* such that the above problem has at least two nontrivial weak solutions for each λ > λ*. Our analysis mainly relies on variational arguments based on the mountain pass lemma and some recent theory on the generalized Lebesgue-Sobolev spaces [formula].

5

Theoretical study of the effect of probe shape on adhesion force between probe and substrate in atomic force microscope experiment

Yang L., Hu J., Kong L.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 1

235--241

EN

The quantitative description of adhesion force dependence on the probe shapes are of importance in many scientific and industrial fields. In order to elucidate how the adhesion force varied with the probe shape in atomic force microscope manipulation experiment, we performed a theoretical study of the influences of the probe shape (the sphere and parabolic probe) on the adhesion force at different humidity. We found that the combined action of the triple point and the Kelvin radius guiding the trend of the adhesion force, and these two fundamental parameters are closely related to the probe shape. Whilst, the theoretical results demonstrate that the adhesion force is in good agreement with the experiment data if the van der Waals force is taken into account.

6

Uniqueness and parameter dependence of positive doubly periodic solutions of nonlinear telegraph equations

Graef J. R., Kong L., Wang M.

Opuscula Mathematica

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2014

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Vol. 34, no. 2

363--373

EN

The authors study a type of second order nonlinear telegraph equation. The existence and uniqueness of positive doubly periodic solutions are discussed. The parametric dependence of the solutions is also investigated. Two examples are given as applications of the results.

7

Multiple solutions for systems of multi-point boundary value problems

Graef J. R., Heidarkhani S., Kong L.

Opuscula Mathematica

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2013

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Vol. 33, no. 2

293--306

EN

In this paper, we establish the existence of at least three solutions of the multi-point boundary value system [formula]. The approaches used are based on variational methods and critical point theory.

8

Experimental parameter investigation for development of a control system for assessment of cardiovascular response to stress in student airline pilots

Avolio A., Kong L., Middleton J., Quasem A., Frangakis G.

Image Processing & Communications

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2002

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Vol. 8, no 2

121-127

EN

This study describes an experimental investigation where cardiovascular response was measured for a range of stimuli. The aim was to obtain relationships between stimuli and physiological variables that could be implemented in a general control system where the appropriate stimulus is selected for a desired test. Reaction time (Tr), blood pressure (BP) and heart rate (HR) were measured in 14 first-year aviation students (10 males, 4 females, age 19-23 years) during different types of computer-based tests : visual, auditory, mathematical. For all test responses across all subjects mean BP increased in 95%, HR increased in 66%. Both BP and HR increased concomitantly in 61% of responses. Average Tr was 583msec (visual), 477msec (auditory) and 10.3 sec (math). There was also a positive relation between BP, HR and Tr. A difference in these parameters was also seen between males and females. Findings of this study show that response to stress results in increased BP but not HR for all subjects studied. This indicates that short-term regulatory mechanisms of BP and HR are manifest only in some subjects some of the time for similar stimuli. These results can be used to implement an assessment procedures and test response criteria in an automated system for testing young student pilots.