Wyniki wyszukiwania - BazTech

1

Ultimate strengths of FRC rectangular columns subjected to simulated seismic loading: Experimental database and new models

Cai G., Degée H.

Archives of Civil and Mechanical Engineering

|

2017

|

Vol. 17, no. 1

96--120

EN

While there are many experimental investigations focusing on seismic behaviour of fibre reinforced concrete (FRC) columns, the studies regarding the accuracies and conservativeness of existing seismic strength models of FRC columns are limited. This paper presents a seismic research database of 322 FRC columns obtained from a comprehensive literature investigation. The characteristic of the database and the effects of main variables on the seismic strengths of FRC columns are analyzed in detail, the accuracies of existing strength models of FRC column are also examined as well. In addition, using the database, considering the effects of fibre and other structural factors on FRC columns, Priestley et al. shear and CFB-FIP moment models are modified respectively. Results show that the two proposed strength models both present better evaluation than other models. On the other hand, a detailed method for assessing the potential failure mode of FRC column subjected to seismic loads is also suggested using the two strength models. The comparative results verify the feasibilities and accuracies of the assessment method in FRC columns.

2

Unidirectional Torsion Properties of Single Silk Fibre

Jiang S., Cao G., Cai G., Xu W., Li W., Wang X.

Fibres & Textiles in Eastern Europe

|

2016

|

Vol. 24, no. 3 (117)

26--30

EN

The unidirectional torsion properties of silk fibre were investigated on a purpose-built single fibre torsion tester. The torsional fracture angle and the number of cycles of torsion at breaking were recorded, and the effect of the gauge length and pretension together with the torsion speed on the torsion properties of single silk fibre was investigated in detail. Scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and a tensile tester were used to understand the morphology, structure and tensile properties of silk fibre after torsion deformation. SME photos show that silk fibre exhibits a ribbon-like profile after torsion, and fracture tends to occur at both ends of the silk fibre, where a larger number of twists can be observed. The crystallinity calculated from XRD spectra of silk fibre increases from 26.11% to 34.10% after torsion. The breaking stress and strain decreases slightly with an increase in the gauge length. The breaking cycle increases linearly with an increase in the gauge length, while the actual torsional fracture angle decreases gradually at the same time. The torsional fracture angle together with the breaking cycle decreases gradually as the pretension increases. The fracture angle together with the breaking cycle increases with an increase in the torsion speed. Understanding the unidirectional torsion properties of single silk fibre will benefit its further application in specific areas where the fibre will be subject to frequent torsion and deformation.

PL

Badania przeprowadzono za pomocą specjalnie zbudowanego urządzenia do badania skrętu włókien. Badano kąt przełomu oraz ilość cykli doprowadzających do zerwania. Sprawdzano również wpływ długości próbki oraz wstępnego naprężenia. Oceniono wpływ długości próbki wstępnego naprężenia, szybkości skrętu na właściwości wytrzymałościowe włókien jedwabnych. Stosowano SEM, XRD dla określenia morfologii i struktury włókien. Stwierdzono, że włókna jedwabne po badaniu wykazują formę podobną do taśmy. Na podstawie XRD stwierdzono, że krystaliczność wzrasta od ok. 26% do 34% po skręceniu. Naprężenie zrywające i odkształcenia zmniejszają się lekko przy wzroście długości próbki.

3

Study on Thermal Insulation Properties of Aluminised Aramid Fabrics

Cai G., Wang H., Luo Z., Wang Z.

Fibres & Textiles in Eastern Europe

|

2015

|

Vol. 23, no. 4 (112)

52--56

EN

In order to prevent or minimise skin burn damage resulting from high temperature, a kind of thermal insulation composite fabric, the surface of which is aluminised, was developed. In this study, the thermal insulation properties of aluminised aramid fabrics were investigated. The reflectance of aramid fabrics and aluminised aramid fabrics were measured using a UV–Vis–NIR spectrophotometer. The reflectance of aramid fabric increased from 63.6% to 92.3% as a result of aluminising. The thermal insulation of aluminised fabrics and nonaluminised fabrics was measured using a dry hot plate instrument, where the aluminised fabrics had a higher thermal resistance than those non-aluminised , and the thermal resistance of aramid fabric could be enhanced by almost 45% when aluminised. The aluminised and non-aluminised fabrics were exposed to a hot environment for a few minutes using self-designed apparatus. The results showed that the aluminised aramid fabrics had better thermal insulation performance than the non-aluminised aramid ones. Therefore aluminised aramid fabric exhibits great thermal insulation properties and can be used in the field of thermal protection.

PL

W celu zapobiegania i minimalizowania oparzeń skóry spowodowanych wysoką temperaturą zaproponowano kompozytowe pakiety włókiennicze o aluminiowanej powierzchni. W pracy badano właściwości termicznej izolacji tkanin aramidowych pokrytych aluminium. Mierzono odbicie promieniowania tkanin aramidowych i tkanin pokrytych aluminium za pomocą spektrofotometru UV-Vis-NIR. Odbicie promieniowania od tkanin aramidowych po pokryciu aluminium wzrosło z 63,6% do 92,3%. Izolację termiczną badanych tkanin mierzono stosując przyrząd z suchą gorącą płytą. Stwierdzono, że oporność termiczna tkanin aluminiowanych jest wyższa co najmniej o 45%. W czasie badań tkaniny były poddane działaniu gorącego środowiska przez kilka minut, przy zastosowaniu urządzenia skonstruowanego przez autorów.

4

Explicit Formulas for the Fourth Moment of Exponential Sums and Dirichlet Character Sums

Luo A., Chen H., Chen J., Cai G.

Przegląd Elektrotechniczny

|

2013

|

R. 89, nr 3b

122--124

EN

Exponential sums and Dirichlet character sums have important applications in electronic science and technology, such as ecommerce, e-government and so on. A new proof is proposed and some interesting computational formula and transformation formula are obtained.

PL

W artykule przedstawiono zagadnienie rozwiązywania wyrażenia zawierającego sumy wykładnicze oraz sumy operatorów Dirichleta. Zaproponowano nowy dowód, formułę obliczeń oraz formułę transformacji.

5

Apparatus for Measuring the Bending Fatigue Properties of High Performance Polyethylene Fibre

Cai G., Shi X., Yu W.

Fibres & Textiles in Eastern Europe

|

2012

|

Vol. 20, no. 4 (93)

37--40

EN

A test method for bending fatigue has been developed to determine the bending fatigue strength of fibres. This new equipment is capable of performing the bending fatigue testing of fibres under different pre-tensions, bending angles and temperatures. This article presents results from tests on single high performance polyethylene fibre (HPPE) to characterise its bending fatigue behaviour under cyclic loading and temperatures. The curve of the cyclic tension shows that the cyclic tension changes in periods during the cyclic bending process. The S-N and č-N curves indicated that the pre-tension and bending angle had great influences on the bending fatigue life of HPPE fibre. A CCD camera was utilised to allow observation of the bending fatigue fracture morphology of the fibre. It showed the fracture mechanism of the HPPE fibres. The bending fatigue life of HPPE fibre was tested at different temperatures to show that its bending fatigue strength is strongly influenced by the temperature.

PL

Opracowano metodę oceny wytrzymałości zmęczeniowej włókien polietylenowych przy zginaniu. Przewidziano możliwość badania włókien przy rożnym obciążeniu wstępnym, kącie zginania i temperaturze. Przeprowadzono próby badania włókien polietylenowych w różnych temperaturach i przy rożnym kącie zginania. Stwierdzono, że naprężenie zginające zmienia się okresowo podczas cyklicznego procesu zginania. Stwierdzono również, że wstępne naprężenie oraz kąt zginania mają istotny wpływ na wytrzymałość zmęczeniową badanych włókien. Kamerę CCD zastosowano dla obserwacji morfologii przełomu zmęczeniowego włókien, pozwalającego na identyfikację mechanizmu przełomu. Stwierdzono wyraźny wpływ temperatury, w której przeprowadzano próby.

6

Timed Petri-Net Based Formulation and an Algorithm for the Optimal Scheduling of Batch Plants

Gu T., Bahri P. A., Cai G.

International Journal of Applied Mathematics and Computer Science

|

2003

|

Vol. 13, no. 4

527-536

EN

The effective scheduling of operations in batch plants has a great potential for high economic returns, in which the formulation and an optimal solution algorithm are the main issues of study. Petri nets have proven to be a promising technique for solving many difficult problems associated with the modelling, formal analysis, design and coordination control of discrete-event systems. One of the major advantages of using a Petri-net model is that the same model can be used for the analysis of behavioural properties and performance evaluation, as well as for the systematic construction of discrete-event simulators and controllers. This paper aims at presenting a Petri-net based approach to the scheduling of operations in batch plants. Firstly, the short term of the `scheduling of batch plants' is formulated by means of a timed Petri net which can accommodate various intermediate storage policies, such as unlimited intermediate storage (UIS), no intermediate storage (NIS), finite intermediate storage (FIS), and mixed intermediate storage (MIS). Secondly, a heuristic search algorithm for the optimal scheduling of batch plants is given, which is based on generating and checking the markings in the reachability tree of the Petri-net model. Finally, the novel formulation and algorithm are tested with several simulation case studies.