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1

An improved mathematical model for vehicle crashagainst highway guardrails

He L., Lin X.

Archives of Transport

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2018

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Vol. 48, iss. 4

41--49

EN

Highway guardrail is a kind of important road traffic safety facility. When a vehicle is travelling on a highway, it can lose control because of accident. The guardrail can prevent the vehicle from rushing directly out of the road, so as to reduce the injury to the driver in the vehicle. Therefore, the guiding performance, anti-collision performance and buffer performance of the guardrail are important indexes to reflect the highway guardrail safety in the traffic accidents between vehicle and guardrail. The process of collisions between vehicles and guardrails is a complex motion, affected by multiple factors such as the movement patterns and types of vehicles, the types of guardrail, the bending stiffness of the beams, the speed of collision, the angle of collision, etc. The accuracy of energy estimation when vehicle collides with guardrail is the foundation of highway guardrail design, installation and improvement. Many experts and scholars at home and abroad have done a lot of theoretical research and experimental verifications on the safety performance of highway guardrail, and analyzed the anti-collision ability and energy absorption effect of highway guardrail. Single degree of freedom model is the most widely used mathematical model of vehicle collision in highway guardrail. The traditional model is more suitable for calculating the maximum impact force of small vehicles, but it is not accurate for large vehicles. However, due to the unreasonableness of the model in the theoretical derivation process, there is a large error in the mathematical model, especially in estimating the accuracy of the energy value of the large vehicle collision guardrail. Practice shows that the current guardrail cannot withstand the impact of large vehicles. Once large vehicles collide with the corrugated beam guardrail, the guardrail will collapse in most cases, and the vehicle will rush out of the road directly, so it is very difficult to exert the protective function of the guardrail. The anti-collision performance of guardrail is poor, which is related to the existing calculation model, which results in insufficient strength in the design of guardrail.

2

An Improved Method for Voltage Sag Detection Based on Weighted Least-Squares Estimation with Harmonic Models

Lei H, Lin X., Kang Y., Duan Y., Qiu J.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 10a

238-241

EN

A rapid voltage sag detection method based on weighted least-squares estimation (WLSE) with harmonic models is proposed to satisfy the requirement of the dynamic voltage restorer. The covariance resetting technique is adopted to detect the voltage sag accurately and rapidly, even in condition the voltage contains considerable amount of harmonic components. The threshold of covariance resetting is larger than the steady state error between the sample and estimation of the voltage for the purpose of favorable covariance resetting only if the voltage sag occurs. The threshold of covariance resetting can be small because the steady state error will contain little harmonic components by the proposed WLSE method which have a positive impact on the detecting speed even if the depth of voltage sag is low. The algorithm has been tested under different conditions so as to verify its performance on voltage sag detection.

PL

Zaproponowano metodę szybkiej detekcji zapadu napięcia bazująca na określaniu średniej ważonej najmniejszych kwadratów. Do detekcji zapadu wykorzystuje się technikę kowariancji co umożliwia szybką detekcję nawet przy znacznej zawartości harmonicznych. (Ulepszona metoda detekcji zapadów napięcia bazująca na określaniu wartości ważonej najmniejszych kwadratów z uwzględnieniem harmonicznych)

3

A Dual Loop Control Strategy for Parallel Interleaved Three-Phase Four-Leg PWM Boost-Type Rectifier in UPS

Lei H., Xiao E., Lin X., Kang Y.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 10a

242-246

EN

This paper presents a dual-loop control strategy for parallel interleaved three-phase four-leg PWM boost-type rectifier in double conversion UPS. The interleaving method is adopted for its main benefit of harmonic cancellation. The current in the fourth leg is treated as a perturbation because the fourth leg is shared by rectifier and inverter, and the controller can be designed in a-b-c coordinate conveniently. The DCbus voltage feedback in outer control loop can be delayed by quarter-cycle to filter out the oscillating component when the load of UPS is unbalanced. The performance of proposed control scheme is verified by experimental results.

PL

W artykule zaprezentowano strategię dwóch pętli sterowania trójfazowym czterogałęziowym prostownikiem PWM typu boost w układzie UPS. Wykorzystano metodę z przeplotem w celu eliminacji wpływu harmonicznych. (Dwuobwodowa strategia sterowania trójfazowym prostownikiem PWM w układach UPS)

4

Efficient method for extraction and isolation of shionone from Aster tataricus L. f. by supercritical fluid extraction and high-speed counter-current chromatography

Wang D, Bai A, Lin X., Fang L., Shu X., Shi X., Sun Q., Wang X.

Acta Chromatographica

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2012

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Vol. 24, no. 4

615--625

EN

Supercritical fluid extraction (SFE) was used to extract shionone from Aster tataricus L. f. The effect of various parameters, i.e., temperature, pressure and sample particle size on yield was investigated with an analytical-scale SFE system to find the optimal conditions. The process was then scaled up by 50 times with a preparative SFE system under the optimized conditions of temperature 40 °C, pressure 30 MPa, and a sample particle size of 40–60 mesh. Then preparative high-speed counter-current chromatography was successfully used for isolation and purification of shionone from the SFE extract with a two-phase solvent system composed of n-hexane-methanol (2:1, volume ratio). The separation produced a total of 75 mg of shionone from 500 mg of the crude extract in one step separation with the purity of 98.7%, respectively, as determined by high-performance liquid chromatography (HPLC) and 92% recovery. The structure of shionone was identified by electrospray ionization-mass spectrometry (ESI-MS), hydrogen-1 nuclear magnetic resonance (1H-NMR), and carbon-13 nuclear magnetic resonance (13C-NMR).

5

A two-stage scheduling problem arising from locomotive dispatching in mine railway

Lin X., Wang X.

Foundations of Computing and Decision Sciences

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2007

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Vol. 32, No. 2

125-137

EN

A locomotive dispatching problem arose from a coal mining area in 1950's: 2n jobs are executed by a locomotive, where n preceding jobs J,: with deadlines di (1≤ i ≤ n] represent sending empty cars to n pits from the central station, while n successive jobs Jt- with release dates r( (1≤ i ≤ n] represent drawing back the loaded cars from n pits to the station; in order to reduce the detaining and increase the turnover rate of freight cars, we are asked to find a schedule of the locomotive so that the maximum flow-time is minimized. Here, the flow-time of a job is the difference between the deadline and the starting time (for a preceding job) or between the completion time and the release date (for a successive job). The present paper studies this two-stage single machine scheduling problem. The main result is a polynomial algorithm for solving it. Meanwhile, two variant models are discussed, one is easier and one is harder. The algorithms here can be regarded as generalizations of the EDD-ERD rule.

6

Bounded oscillation for a class of even order neutral difference equations

Lin X., Shen J.

Fasciculi Mathematici

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2002

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Nr 33

37-47

EN

We investigate bounded oscillation for the even order neutral delay difference equation delta'' (x(n) -cx(n-m) = pn(x-k), where u is even. The sufficient conditions obtained in this paper improve and generalize the results in related literature.