Wyniki wyszukiwania - BazTech

1

Mobile robot visual homing by vector pre-assigned mechanism

Ji X., Zhu Q., Wang J., Cai C., Ma J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2019

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Vol. 67, nr 2

213--227

EN

In this paper, we present an optimization mechanism for two popular landmark-based mobile robot visual homing algorithms (ALV and HiSS), called vector pre-assigned mechanism (VPM). VPM contains two branches, both of which can promote the homing performance effectively. In addition, to make the landmark distribution satisfy the equal distance assumption, a landmark optimization strategy is proposed based on imaging principle of the panoramic vision. Experiments on both panoramic image database and a real mobile robot have confirmed the effectiveness of the proposed methods.

2

Mechanical behavior of parallel pipelines under foundation pit excavation

Han C., Ma J., Zhang J.

Engineering Transactions

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2018

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Vol. 66, iss. 1

93--106

EN

In order to study the effect of foundation pit excavation on mechanics of parallel pipeline, a pipeline-soil interaction model was established based on the finite element principle. The deformation of the pipeline by the foundation pit excavation were analyzed. Effect regulations of parallel distance, pipeline parameters and foundation pit parameters on the deformation of the pipeline were studied. The results show that there are two maximum stress areas in pipeline under the action of excavation. The upper and lower surfaces of the pipeline also appear the large stress area. The pipeline has horizontal and vertical displacements. With the increasing of the parallel distance, the deformation of the nearest pipeline increases, but the deformation of the farthest pipeline decreases. With the increasing of the radius-thickness ratio and distance between the foundation pit and the nearest pipeline, the deformation of the pipeline decreases. With the decreasing of the foundation pit width, the deformation of the pipeline decreases. Effect of the foundation pit’s length on the pipeline is not obvious.

3

ISEMIR-IR: A worldwide tool to optimize occupational radiation protection in industrial radiography

Fu J., Dojcanova L., Ma J.

Badania Nieniszczące i Diagnostyka

|

2018

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nr 4

80--82

EN

Industrial Radiography is widely used in non-destructive testing (NDT ) in the world. Workers in the sector exposure if incidents happen. The Information System on Occupational Exposure in Medicine, Industry and Research: Industrial Radiography so called ISE MIR-IR was developed by the IAEA as a web-based tool for a regular data collection and analysis of occupational exposure. The system was launched with full function in 2017. It was designed based on the data from an extensive research and results of the worldwide surveys. It assists NDT companies to benchmark their own companies and individual performance against others in the database. NDT companies all around the world are encouraged to participate in the database to enable it to become a worldwide tool for implementing optimization of occupational radiation protection.

PL

Radiografia przemysłowa jest szeroko stosowana w badaniach nieniszczących (NDT ) na świecie. Pracownicy tego sektora w przypadku wystąpienia incydentów mogą być narażeni na niebezpieczeństwo. System Informacji o narażeniu zawodowym w medycynie, przemyśle i badaniach: Radiografia przemysłowa (ang. The Information System on Occupational Exposure in Medicine, Industry and Research: Industrial Radiography) nazwany ISE MIR-IR został opracowany przez IAEA jako internetowe narzędzie do regularnego gromadzenia danych i analizy narażenia zawodowego. System został uruchomiony z pełną funkcjonalnością w 2017 roku. Zaprojektowano go w oparciu o dane pochodzące z obszernych badań i wyników światowych sondaży. Pomaga firmom z branży NDT w porównywaniu własnych i indywidualnych wyników z innymi wynikami w bazie danych. Firmy NDT na całym świecie są zachęcane do uczestnictwa w tworzeniu bazy danych, aby umożliwić jej stanie się światowym narzędziem do wdrażania optymalizacji ochrony przed promieniowaniem zawodowym.

4

Automation detection of driver fatigue using visual behavior variables

Wang Y., Ma J.

Archives of Civil Engineering

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2018

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Vol. 64, nr 2

175--185

EN

To examine the correlation of driver visual behaviors and subjective levels of fatigue, a total of 36 commercial drivers were invited to participate in 2-h, 3-h, and 4-h naturalistic driving tests during which their eye fixation, saccade, blinking variables, and self-awareness of their fatigue levels were recorded. Then, one-way ANOVA was applied to analyze the variations of each variable among different age groups over varying time periods. The statistical analysis revealed that driving duration had a significant effect on the variation of visual behaviors and feelings of fatigue. After 2h of driving, only the average closure duration value and subjective level of fatigue had an increase of one-fifth or more. After 4h of driving, however, all these variables had a significant change except for the number of saccades and pupil diameter measurements. Particularly, driver saccadic eye movement was more sensitive to driving fatigue, and the elderly were more likely to be affected by the duration of the drive. Finally, a predictor of driver fatigue was determined to detect the real-time level of fatigue and alert at the critical moment.

PL

Kierowcy zawodowi spędzają długie godziny za kierownicą i szybciej odczuwają zmęczenie podczas prowadzenia pojazdu. Z tego powodu, identyfikacja poziomu zmęczenia w czasie rzeczywistym ma kluczowe znaczenie dla zapewnienia bezpieczeństwa ruchu drogowego i zapobiegania wypadkom, w szczególności w odniesieniu do osób zajmujących się dalekobieżnym transportem komercyjnym. Łącznie 26 kierowców zawodowych w czterech grupach wiekowych zostało zaproszonych do udziału w naturalistycznym egzaminie na prawo jazdy, podczas którego każdy uczestnik został poproszony o ukończenie 2-godzinnych, 3-godzinnych i 4-godzinnych zadań związanych z prowadzeniem pojazdu, obejmujących przerwę na odpoczynek, na trzech drogach ekspresowych w Shandong, Chiny, celem zarejestrowania zmiennych skupienia wzroku, ruchu gałek ocznych i mrugania oczami, jak również subiektywnego poziomu zmęczenia. Następnie, zastosowano jednoczynnikową analizę wariancji w celu przeanalizowania zmienności każdego wizualnego wskaźnika według grup wiekowych w czasie, a analiza statystyczna wykazała, że nieprzerwana jazda ma istotny wpływ na zmiany wskaźników wizualnych i zgłaszany poziom zmęczenia. Po 2 godzinach prowadzenia pojazdu, zarówno średnia wartość czasu zamknięcia, jak i średni subiektywny poziom zmęczenia uległy znacznej zmianie. Po 4 godzinach prowadzenia pojazdu, wszystkie wizualne wskaźniki kierowcy, inne niź średnia liczba ruchów gałek ocznych i średnia średnica źrenicy, uległy znaczącej zmianie. Z drugiej strony, zmiana poziomu zmęczenia jest dodatnio związana ze zmianą średnicy źrenicy, czasem skupienia wzroku, częstotliwościmrugania, czasem mrugania i czasem zamknięcia. Z drugiej strony, zmiana poziomu zmęczenia była ujemnie związana z ilością skupień wzroku, kątem poszukiwań, liczbą ruchu gałek ocznych, szybkością ruchu gałek ocznych i amplitudą ruchu gałek ocznych. Mówiąc dokładniej, ruch gałek ocznych kierowcy był bardziej czuły na poziom zmęczenia podczas jazdy, a u osób starszych występowało większe prawdopodobieństwo, że wpłynie to na długość jazdy w zmienności zachowań wizualnych i uczucie zmęczenia. W przypadku kierowców zawodowych, przepisy ruchu drogowego powinny ściśle kontrolować długość nieprzerwanej jazdy, a osoby starsze powinny zyskać więcej czasu na odpoczynek. Wreszcie, czynnik prognostyczny zmęczenia kierowcy został określony poprzez zmianę współczynnika wizualnych zmiennych, w celu wykrycia poziomu zmęczenia i ostrzegania w krytycznym momencie, w czasie rzeczywistym.

5

Effect of curcumin and pirfenidone on toxicokinetics of paraquat in rat by UPLC–MS/MS

Wang S., Lin Z., Su K., Zhang J., Zhang L., Gao Z., Ma J., Wang X.

Acta Chromatographica

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2018

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Vol. 30, no. 1

26--30

EN

The rats were randomly divided into paraquat group, curcumin treatment group, and pirfenidone treatment group. The concentration of paraquat in rat plasma was determined by an ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method over the range of 10–2000 ng mL−1. Chromatographic separation was achieved on a BEH HILIC (2.1 mm × 100 mm, 1.7 μm) column. The mobile phase was consisted of acetonitrile and 10 mm ammonium formate buffer (containing 0.1% formic acid) with gradient elution pumped at a flow rate of 0.4 mL min−1. Protein precipitation with acetonitrile was used as sample preparation. Compared with the paraquat group, there is statistical toxicokinetic difference for curcumin treatment group and pirfenidone treatment group, AUC(0 − t) decreased (P < 0.05), clearance (CL) increased (P < 0.05) for curcumin or pirfenidone treatment group, and Cmax decreased (P < 0.05) for curcumin treatment group. The results showed that treatment by curcumin and pirfenidone could relieve acute paraquat poisoning in rats.

6

Multiscale simulation of major crack/minor cracks interplay with the corrected XFEM

Liu G., Zhou D., Bao Y., Ma J., Han Z.

Archives of Civil and Mechanical Engineering

|

2017

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Vol. 17, no. 2

410--418

EN

The present work aims at saving computational cost of multiscale simulation on major crack/minor crack interaction problems. The multiscale extended finite element method (MsXFEM) used for the numerical simulation is developed on multiscale projection technique which enables different scale decomposition, and transition of field variables between different scales. Both macroscale and microscale problems are solved independently and alternatively, in the framework of XFEM. The improvement made in this paper is to employ corrected XFEM on the macroscale level, so that a more accurate boundary condition can be obtained for the microscale problem. The modification leads to a reduced necessary microscale domain size, meanwhile a solution of higher accuracy and enhanced convergence rate can be achieved. The numerical examples of minor cracks near a major one are studied, which show that the effect of minor cracks on major crack can be efficiently captured.

7

Study of high-strength and high-conductivity Cu-Sn-Fe alloys

Zhang J., Cui X., Ma J., Wang Y.

Materials Science Poland

|

2016

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Vol. 34, No. 1

142--147

EN

Cu-Sn-Fe alloys with different compositions were developed by casting, normalizing treatment, cold roll and subsequent annealing treatment. The results showed that the tensile strength and resistivity of the Cu-xSn-xFe alloys (where x represents wt.%) improved with increasing the content of Sn and Fe. Compared with the as-cast alloys, the resistivity and tensile strength of the Cu-xSn-xFe alloys after normalizing and cold rolling treatment increased. In addition, the resistivity and mechanical properties of the alloys after the annealing treatment were improved significantly. Finally, a conclusion could be drawn that the annealed Cu-2Sn-5Fe alloy had good mechanical properties and resistivity, and the values of the tensile strength, mechanical elongation and resistivity reached 552 MPa, 32 % and 1.92 μΩ cm, respectively.

8

Gradient elution LC-MS determination of dasatinib in rat plasma and its pharmacokinetic study

Wen C, Zhang Q., He Y., Deng M, Wang X., Ma J.

Acta Chromatographica

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2015

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Vol. 27, no. 1

81--91

EN

A sensitive and simple liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for determination of dasatinib in rat plasma using one-step protein precipitation was developed. After addition of carbamazepine as internal standard (IS), protein precipitation by acetonitrile was used as sample preparation. Chromatographic separation was achieved on an SB-C18 (2.1 mm × 150 mm, 5 μm) column with methanol-0.1% formic acid as mobile phase with gradient elution. Electrospray ionization (ESI) source was applied and operated in positive ion mode; selective ion monitoring (SIM) mode was used to quantification using target fragment ions m/z 488.2 for dasatinib and m/z 338.7 for the IS. Calibration plots were linear over the range of 10–1000 ng mL−1 for dasatinib in rat plasma. Lower limit of quantification (LLOQ) for dasatinib was 10 ng mL−1. Mean recovery of dasatinib from plasma was in the range 82.2%–93.6%. Relative standard deviation (RSD) of intra-day and inter-day precision were both less than 8%. This developed method is successfully used in pharmacokinetic study of dasatinib in rats.

9

Irregular shaping of polystyrene nanosphere array by plasma etching

Luo H., Liu T., Ma J., Wang W., Li H., Wang P., Bai J., Jing G.

Materials Science Poland

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2013

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Vol. 31, No. 3

331--337

EN

The morphology of nanospheres is crucial for designing the nanofabrication in the nanosphere lithography. Here, by plasma etching, the controllable tailoring of the nanosphere is realized and its morphology dependence on the initial shape, microscopic roughness, and the etching conditions is investigated quantitatively. The results show that the shape evolution strongly depends on the etching gas, power, and process duration. Particularly, the aspect ratio (diameter/height) significantly increases with violent etching, turning the spherical shape into tiny ellipsoidal nanoparticles. The findings are practical to the protocol of non-uniform etching of nanoobjects and provide the useful design tool for the device fabrication at nanoscale.

10

A high acid mesoporous USY zeolite prepared by alumination

Ma J., Kang Y., Ma N., Hao W., Wang Y.

Materials Science Poland

|

2013

|

Vol. 31, No. 1

19-24

EN

A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of Brfinsted acid sites and strong Lewis acid sites increased whereas weak Lewis acid sites decreased twice. The mesoporous structure composed of inter-and intra-crystalline pores in the aluminated HUSY increased the external surface area of the zeolite, improving accessibility of molecules to the active sites and enhancing its catalytic ability. The realuminated HUSY zeolite supported with Ru catalyst exhibited a higher catalytic activity for benzene hydrogenation than the parent HUSY zeolite; the reaction rate in comparison to the mesozeolite increased by 5.5 times.

11

Optimization and validation of a method based on derivatization with methylating agent followed by HPLC-DAD for determining dithiocarbamates residues

Zhou L., Xu J., Luan L., Ma J., Gong Y., Qin D., Pan C.

Acta Chromatographica

|

2013

|

Vol. 25, no. 4

613--625

EN

Dithiocarbamates fungicides (DTCs) are worldwidely used fungicides. Residue analytical methods on DTCs are usually based on headspace gas chromatography, which are not much stable and precise. In this study, a specific, simple and reliable method for determining DTCs fungicides residues was optimized and validated. The DTCs in foods and soils were extracted with an alkaline solution of EDTA and L-cysteine, followed by pH adjusting and methyl derivatization in methyl iodine solution. The organic layer of the reactants was separated, concentrated under vacuum and reconstructed in acetonitrile. DTCs residues were eluted on a C18 column and detected by HPLC-DAD at 272 nm. The S-alkyl derivatives of thiram, mancozeb and propineb were separated at different retention times. At fortified levels of 0.05 mg/kg to 2 mg/kg (residue expressed as CS2, in mg/kg, the same below), it is found that recoveries for DTCs spiked in apple, cucumber, tomato, rice and soil samples ranged from 70.8% to 105.3%, with relative standard deviations (RSD) from 0.6% to 13.7%. Limits of detection (LODs) and quantification (LOQs) ranged from 0.003 to 0.026 mg/kg and from 0.011 to 0.105 mg/kg for various foods and soils. This method was also applied to real sample tests.

12

Prediction of Un-safety Driving Status in Automotive Vehicle Based on Hidden Markov

Yu D., Ma J., Yang J.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 1b

115-118

EN

Based on Hidden Markov Model, a new prediction method on driving status is advanced. In which, the velocity of following car, the velocity difference and distance headway is input as observation variables, the driving status is output as hidden variable. First the probability of observation status needed is calculated by forward algorithm, then the probability of observation status and driving status appeared together is calculated, at last, the prediction value of driving status could be got by conditional probability. The warning character of the prediction method could be evaluated not only by the accuracy but also by a new index [delta]ATp, which could show the degree of warning time at p probability. The results of simulation show that the method is right, which is in agreement with the result of eye movement checking method named PERCLOS, and it could complete the predictionprediction: when P%= 30%, �[delta]ATp = 2min7 sec, when P%= 40%,[delta]ATp = 1min51 sec; when; when P%= 50%, �[delta]ATp = 56 sec, when P%= 60%, [delta]ATp = 34 sec.

PL

Bazując na ukrytym modelu Markova przedstawiono nową metodę przewidywania status pojazdu. Jako obserwowalne zmiany podaje się szybkość pojazdu z tyłu, odległość a jako zmienne ukryte status pojazdu.

13

Optimal Roadside Gateway Deployment for VANETs

Xiong Y., Ma J., Wang W., Niu J.

Przegląd Elektrotechniczny

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2012

|

R. 88, nr 7b

273--275

EN

VANETs allowing the mobile vehicles exchange data with the roadside gateways are being used in various applications such as local electronic advertisement, intelligent transportation system and urban data collection. In this paper, we study the problem of deploying the gateways to provide the desired communication performance while minimizing the deployment cost. The key idea of our solution is to exploit the time-stable vehicular mobility pattern to find the optimal deployment places. We propose a graph model to characterize the observed mobility pattern. Then the gateway deployment problem is transformed into a vertex selection problem in a graph. By reducing it the minimum vertex coverage problem, we show the gateway deployment problem is NP-complete, so a heuristic algorithm MobGDeploy is proposed to search greedily the optimal deployment points. Extensive simulations are carried out to evaluate the performance, and the results show that the proposed algorithm outperforms others.

PL

W artykule analizowano problem rozlokowania wjazdów w celu osiągnięcia pożądanej jakości komunikacji. Przyjęto założenie stabilnej czasowo mobilności pojazdów. Zaproponowano model grafu do opisu mobilności pojazdów. Wykorzystano metodę VANET – vehicular ad hoc network.

14

On a New Approach to SNR Estimation of BPSK Signals

Moazzeni T., Amei A., Ma J., Jiang Y.

International Journal of Electronics and Telecommunications

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2012

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Vol. 58, No. 3

273-278

EN

Signal-to-noise ratio (SNR) information is required in many communication receivers and their proper operation is, to a large extent, related to the SNR estimation techniques they employ. Most of the available SNR estimators are based on approaches that either require large observation length or suffer from high computation complexity. In this paper, we propose a low complexity, yet accurate SNR estimation technique that is sufficient to yield meaningful estimation for short data records. It is shown that our estimator is fairly close to the (CRLB) for high SNR values. Numerical results also confirm that, in terms of convergence speed, the proposed technique outperforms the popular moment based method, M2M4.

15

HGRP: hybrid grid routing protocol for heterogeneous hierarchical wireless networks

Shen Y., Pei Q., Xu Q., Xi N., Ma J.

Control and Cybernetics

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2012

|

Vol. 41, no. 2

353-371

EN

The heterogeneous mobile terminals coexist in the next generation wireless networks. The most common routing schemes for mobile ad hoc networks are designed for homogeneous wireless networks. The heterogeneous wireless network routing protocols are needed urgently in many important applications. This paper improves the routing scheme utilizing different capability of terminals and the Hybrid Grid Routing Protocol (HGRP) is proposed. The network is organized in the grid form, that is, the network deployment area is divided into square cells according to the location. Each cell contains one backbone node and several ordinary nodes. This proposed protocol consists of four parts: grid construction, local routing, global routing, and routing correction. Analysis and simulation results indicate that the proposed protocol has the advantages of lower routing cost, lower energy consumption, smaller delay and higher throughput, compared to AODV and ZRP.

16

Radial distribution of fibres in compact-spun flax-cotton blended yarns

Xu B., Ma J.

Fibres & Textiles in Eastern Europe

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2010

|

Vol. 18, no. 1 (78)

24--27

EN

In recent years, compact spinning technology, recognized as a revolution in ring spinning, has been successfully used in the production of mono-fibre yarns and blended yarns. Understanding the radial distribution of fibres in compact-spun flax-cotton blended yarn is of importance for improvement in the performance of compact-spun flax-cotton blended yarns. This paper investigated the radial distribution of compact-spun flax-cotton blended yarn using the Hamilton migration index, and it was compared with traditional ring-spun flax cotton blended yarn. The results indicated that the fibre migration of traditional ring-spun flax-cotton blended yarn was more obvious than that of compact-spun flax-cotton blended yarn, and the radial distribution of fibres in compact-spun flax-cotton blended yarns was more random. Therefore the traditional migration rule does not fully apply to compact spinning technology and should be given more attention in practice.

PL

Wprowadzenie przędzenia kompaktowego stało się rewolucją w metodzie przędzenia obrączkowego, będąc techniką ogólnie stosowaną dla otrzymywania przędz wytwarzanych z określonego rodzaju włókien jak również przędz mieszankowych. Poznanie rozkładu promieniowego włókien w przędzach mieszankowych jest istotne dla poprawy jakości otrzymywanych przędz. W pracy przeprowadzono analizę struktury przędz mieszankowych stosując współczynnik migracji Hamiltona oraz przeprowadzono porównanie ze struktura tradycyjnych przędz obrączkowych. Wyniki wykazały, że migracja włókien w tradycyjnych przędzach mieszankowych obrączkowych len/bawełna jest bardziej oczywista niż w takich samych przędzach kompaktowych, podczas gdy promieniowy rozkład włókien w przędzach kompaktowych jest bardziej losowy. Dlatego tradycyjne zależności dotyczące migracji dla przędz mieszankowych nie są spełnione przy przędzach kompaktowych i więcej uwagi należy poświęcić eksperymentom.

17

Przyspieszone badania degradacji przy stałym naprężeniu w analizie diod superelektroluminescencyjnych i wrażliwości parametrycznej

Li X., Jiang T., Sun F., Ma J.

Eksploatacja i Niezawodność

|

2010

|

nr 2

21-26

PL

Ruchy Browna są jednym z najpotężniejszych procesów stochastycznych w ciągłym czasie i ciągłej przestrzeni, który ma też mocne podstawy fi zyczne. W analizie przyspieszonych badań degradacji (ADT), rozkład odwrotny gaussowski, będący rozkładem czasu pierwszego przejścia ruchu Browna z dryfem (drift Brownian motion), staje się bardzo popularnym modelem predykcji statystycznej życia i niezawodności produktów. Diody superelektroluminescencyjne (SLD) o długiej żywotności i wysokiej niezawodności mają wiele zalet fi zycznych, które sprawiają, że zastępują one diody laserowe (LD) oraz diody elektroluminescencyjne (świecące) (LED) i mają szerokie zastosowanie w czujnikach światłowodowych. W niniejszym artykule przeprowadzono badania ADT diody SLD przy stałym naprężeniu. Aby ocenić możliwość zastosowania rozkładu odwrotnego gaussowskiego do badań diod SLD, określono najpierw trwałość i niezawodność SLD na podstawie danych o spadku mocy optycznej uzyskanych z badania ADT prowadzonego przy stałym naprężeniu. Następnie przeprowadzono analizy wrażliwości parametrycznej w trzech wymiarach: niezawodności, czasu życia i parametru analitycznego. Wreszcie, kierując się wynikami analizy wrażliwościowej, przedstawiono niektóre zasady planowania i przeprowadzania testów ADT przy stałym naprężeniu.

EN

Brownian motion is one of the most powerful stochastic processes in continuous time and continuous space and has a good physics background. For the analysis of accelerated degradation testing (ADT), the inverse Gaussian (IG) distribution, which is the fi rst passage time distribution of the drift Brownian motion (DBM), becomes a very popular statistical prediction model of product life and reliability. Instead of laser diode (LD) and Light Emitting Diode (LED), long-life and high-reliability super-luminescent diode (SLD) has many physical advantages and has been widely used in optical fi ber sensors. In this paper, the constant stress ADT (CSADT) of SLD was conducted. In order to evaluate the applicability of IG distribution to SLD, we fi rst estimate the life and reliability of SLD based on the optical power degradation data collected in CSADT. Then parameter sensitivity analyses are conducted in the 3-dimensions of reliability, lifetime and the analytic parameter. Finally, according to the sensitive analysis results, some CASDT planning and testing principles are presented.

18

Preparation and characterization of La- and Ni-doped magnetite nanoparticles

Ma J., Ji Y., Tian M.

Materials Science Poland

|

2009

|

Vol. 27, No. 4/1

981--986

EN

La- and Ni-doped Fe3O4 nanocomposite particles with a high saturation magnetization were prepared by a homogeneous precipitation method in aqueous solutions. The obtained nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively-coupled plasma atomic emission spectroscopy (ICPAES) and vibrating sample magnetometry (VSM). The results showed the diameters of La- or Ni-doped Fe3O4 composite particles to be in the range of 10-25 nm. The specific saturation magnetization of La- or Ni-doped Fe3O4 was considerably higher than that of pure Fe3O4 nanoparticles. The nanocomposite particles exhibited superparamagnetic behaviour.

19

Investigation on resonant laser ablation spectrum of Fe in 281.5-285.5 nm wavelength region

Ma J., Ji X., Cui Z.

Optica Applicata

|

2008

|

Vol. 38, nr 2

405-411

EN

Laser ablation of solid Ti samples has been studied using a tunable pulsed dye laser. Six resonant laser ablation (RLA) spectral lines of Fe in the Ti sample are firstly measured in the 281.5-285.5 nm wavelength region. The initial state of the RLA spectral lines is a5F, the resonant states are z5H0, x5P0 and y5G0, respectively. The influence of laser power density on the intensities of RLA spectrum is discussed. The relationship between the laser wavelength and the photo-ionization cross sections of the resonant state 5G0 is analyzed.

20

Investigation on mechanical behaviour of AM60 magnesium alloys

Yan C., Bai R. X., Gu Y. T., Ma J.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

|

Vol. 31, nr 2

398-401

EN

Purpose: In this work, tension, impact, bend and fatigue tests were conducted in an AM60 magnesium alloy. The effects of environmental temperature and loading rates on impact and tension behavior of the alloy were also investigated. Design/methodology/approach: The tests were conducted using an Instron universal testing machine. The loading speed was changed from 1 mm/min to 300 mm/min to gain a better understanding of the effect of strain rate. To understand the failure behavior of this alloy at different environmental temperatures, Charpy impact test was conducted in a range of temperatures (-40;∼ 35*C). Plane strain fracture toughness (K IC) was evaluated using compact tension (CT) specimen. To gain a better understanding of the failure mechanisms, all fracture surfaces were observed using scanning electron microscopy (SEM). In addition, fatigue behavior of this alloy was estimated using tension test under tension-tension condition at 30 Hz. The stress amplitude was selected inó the range of 20;∼ 50 MPa to obtain the S-N curve. Findings: The tensile test indicated that the mechanical properties were not sensitive to the strain rates applied 3.3x10 -4 ∼ 0.1) and the plastic deformation was dominated by twining mediated slip. The impact energy is not sensitive to the environmental temperature. The plane strain fracture toughness and fatigue limit were evaluated and the average values were 7.6 MPa.m1/2 and 25 MPa, respectively. Practical implications: Tested materials AM60 Mg alloy can be applied among others in automotive industry aerospace, communication and computer industry. Originality/value: Many investigations have been conducted to develop new Mg alloys with improved stiffness and ductility. On the other hand, relatively less attention has been paid to the failure mechanisms of Mg alloys, such as brittle fracture and fatigue, subjected to different environmental or loading conditions. In this work, tension, impact, bend and fatigue tests were conducted in an AM60 magnesium alloy.