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1

Modeling and experimental investigation of a controllable rotary fluid damper

Cao X., Zhou J., Yu M., Wang Y.

Archives of Mechanics

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2023

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Vol. 75, nr 4

493--516

EN

Controllable rotary fluid damper (CRFD) is an efficient and cheap energy dissipation device, which is used to reduce the impact of vibration in mechanical systems. In this paper, the CRFD controlled by a servo motor is developed to reduce the effects of vibrations in the helicopter flight control system. The dynamic mechanical characteristic of the CRFD is experimentally investigated by the MTS machine. Due to the complex factors such as high shear thinning rate and compressibility of the damping medium, inertia of moving parts and internal friction, the CRFD studied has highly nonlinear hysteresis characteristics. The accuracy of the damper modeling is of great significance for designing effective vibration reduction methods. Therefore, a new generalized viscous–nonlinear elastic model is proposed to track the mechanical characteristics of CRFD. On the basis of parameter sensitivity analysis, the proposed generalized viscous–nonlinear elastic model is modified. According to the identification results of the modified model, the main parameters are fitted as polynomial functions of motor rotation angle. Through error analysis between analytical torques and experimental torques, it is concluded that the modified generalized viscous–nonlinear elastic model has the smallest error compared with Kwok and Maxwell models, which indicates that the proposed modified model can accurately describe the mechanical characteristics of the CRFD under different working conditions.

2

Research on key process technology for profile electrolytic finishing of large marine propeller impeller

Ding B., Chen Y., Zhou J., Chen P.

Polish Maritime Research

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2018

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S 2

158--163

EN

An electrolysis process method for free-form blade surface finishing is proposed for a free-form surface impeller, and a stepwise method is used to process the inter-blade channel of the overall impeller. The forming cathode is then used to finish the blade to meet the blade processing requirements. In the design, the forming cathode structure was improved by using motion simulation software, and the flow field simulation software was used to simulate and analyze the cathode flow channel. The cathode shape and the electrolyte flow rate between the electrodes meet the processing requirements. In the process of processing experiments, the motion path of the cathode was analyzed and optimized. The effect of the feed direction on the uneven distribution of the blade machining gap was reduced through optimization, and highfrequency pulse power processing was used to reduce the machining gap and improve the machining accuracy of the blade. The experimental results show that the process scheme is feasible and the precision of the processed impeller free-form surface is significantly improved. The material is a monolithic turbine disk of high-temperature alloys, and its large twisted blade processing has always been a problem in the manufacturing industry.

3

Application of affine NARMA model to design of adaptive power system stabilizer

Zhou J., Ke D., Chung C. Y., Sun Y.

Diagnostyka

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2018

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Vol. 19, No. 2

105--114

EN

An affine nonlinear autoregressive moving average (NARMA) model is derived from the neural network (NN) based general NARMA model in this paper, by using Taylor series expansion. The predictive error of this affine NARMA model will be quite acceptable, at least for the control purpose, if the amplitude of control input is properly limited. Therefore, an adaptive control scheme based on this model is proposed and applied to the design of adaptive power system stabilizer (APSS) since the amplitude of PSS output is usually well limited. The feature of this control scheme is that the control input can be online analytically obtained. Thus, comparing to the traditional NN based APSS (TAPSS), the affine NARMA model based APSS (AAPSS) does not need the training of a NN as neuro-controller, which may be a troublesome and time consuming step during the design. Moreover, the AAPSS can generally perform better than the TAPSS. Simulation studies on a single machine infinite bus system and a multi-machine system show that the AAPSSs can consistently well perform to damp electromechanical oscillations in the systems over a wide range of operating conditions.

4

Prediction of the height of overburden fractured zone in deep coal mining: case study

Han Y., Cheng J., Huang Q., Zou D. H. S., Zhou J., Huang S., Long Y.

Archives of Mining Sciences

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2018

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Vol. 63, no. 3

617--631

EN

In the process of coal extraction, a fractured zone is developed in the overburden above the goaf. If the fractured zone is connected with an aquifer, then water inrush may occur. Hence, research and analysis of the height of overburden fractured zone (HOFZ) are of considerable significance. This study focuses on the HOFZ determination in deep coal mining. First, general deformation failure characteristics of overburden were discussed. Second, a new method, numerical simulation by orthogonal design(NSOD), have been proposed to determinate the HOFZ in deep coal mining. Third, the validity of NSOD is verified in the practical application, compared with empiric al formula in Chinese Regulations and in-situ test. These three methods were applied to determine the HOFZ of working face No. 111303 in No. 5 coal mine. The pre dicted HOFZ of NSOD is found to be similar to the result of the in-situ test (8.9% relative error), whereas the HOFZ calculated by the empirical formula has extremely large error (25.7% relative error). Results show that the NSOD can reliably predict the HOFZ in deep coal mining and reduce time and expenses required for in-situ test.

PL

W trakcie prowadzenia wydobycia węgla w warstwie skalnej leżącej ponad zrobami powstaje strefa spękań. Jeśli nieciągłości te związane są z formacjami wodonośnymi, może nastąpić nagły wypływ wód do kopalni. Stąd też waga problemu i konieczność badania wysokości strefy spękań w warstwach nadkładu zalegających nad wyrobiskiem. W pracy tej główny nacisk położono na określenie wysokości strefy spękań warstwy nadkładu zalegającej ponad wyrobiskiem w kopalni podziemnej. W pierwszej części pracy przedstawiono główne charakterystyki powstawania deformacji i pęknięć w warstwach nadkładu. Następnie zaproponowano nową metodę symulacji numerycznych w układzie ortogonalnym i jej wykorzystanie do określania wysokości strefy spękań w warstwach nadkładu w kopalni podziemnej. Następnie powyższą metodę zweryfikowano w praktycznym zastosowaniu, jako poziomy odniesienia wykorzystano odpowiednie wzory empiryczne określone w przepisach obowiązujących w Chinach oraz wyniki pomiarów in-situ. Powyższe trzy metody zastosowane zostały do określenia wysokości strefy spękań w warstwach nadkładu przy prowadzeniu ściany 111303 w kopalni węgla nr 5. Wyniki obliczeń wysokości strefy spękań uzyskane w oparciu o zaproponowaną nową metodę w dużym stopniu pokrywały się z wynikami pomiarów in-situ (błąd względny 8.9%); podczas gdy obliczenia wysokości strefy spękań w oparciu o odpowiednie wzory empiryczne obarczone były dużym błędem (błąd względny 25.7%). Uzyskane wyniki wskazują wiarygodność obliczeń w oparciu o zaproponowaną metodę, co pozwoli na ograniczenie czasu i kosztów związanych z wykonywaniem pomiarów in-situ.

5

Experimental study of low cycle fatigue properties for epoxy resins with dibutyl phthalate (DBP)

Wang Z., Zhou J., Song L., Li L.

Archives of Civil Engineering

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2018

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Vol. 64, nr 2

147--159

EN

In order to improve the toughness of traditional epoxy resin, dibutyl phthalate (DBP) was introduced into the epoxy resin. The static mechanical performance of plasticized and unplasticized epoxy resin was evaluated. The test results showed that the DBP modified epoxy resin can obtain a higher toughness than conventional epoxy resin, but the elastic modulus and the tensile strength were slightly reduced. The low cycle fatigue test results indicated that the stress ratio and the stress level were two critical factors of fatigue life, which was increased with the growth of stress ratio. It was also found that the fatigue life of plasticized specimen was much less than that of the unplasticized specimen because of the plastic deformation. A logarithmic linear relationship was then established to predict the fatigue life for plasticized epoxy resin. The strain energy density was also applied to demonstrate the accumulation of energy loss. In addition, the fatigue toughness can be obtained by the hysteresis loop area method.

PL

W artykule przedstawiono właściwości zmęczeniowe żywicy plastyfikowanej z ftalanem dibutylu (DBP) oraz niemodyfikowanej żywicy epoksydowej. W celu zwiększenia wytrzymałości tradycyjnej żywicy epoksydowej, do źywicy epoksydowej wprowadzono ftalan dibutylu (DBP). Oceniono statyczną wytrzymałość mechaniczną plastyfikowanej oraz nieplastyfikowanej żywicy epoksydowej. Wyniki badania wykazały, że wydłużenie plastyfikowanej oraz nieplastyfikowanej żywicy wynosi odpowiednio 4,61% i 3,55%, co oznacza, że modyfikowana żywica epoksydowa z ftalanem dibutylu (DBP) może uzyskać wyższą wytrzymałość niż zwykła żywica epoksydowa. Jednakże moduł sprężystości i wytrzymałość na rozciąganie plastyfikowanej żywicy zostały nieznacznie zmniejszone. Niskocyklowe badanie zmęczeniowe w trzech różnych współczynnikach oraz poziomach naprężenia przeprowadzono w celu porównania wytrzymałości zmęczeniowej żywicy epoksydowej. Wyniki badania wykazały, że współczynnik oraz poziom naprężenia stanowiły dwa krytyczne czynniki trwałości zmęczeniowej, która została zwiększona wraz ze wzrostem współczynnika naprężenia. Stwierdzono również, że trwałość zmęczeniowa plastyfikowanej próbki była znacznie mniejsza niż w przypadku nieplastyfikowanej próbki z powodu odkształcenia plastycznego. Następnie ustalono logarytmiczną zależność liniową, aby przewidzieć trwałość zmęczeniową plastyfikowanej żywicy epoksydowej. Gęstość energii odkształcenia została również zastosowana w celu wykazania nagromadzenia strat energii. Ponadto wytrzymałość zmęczeniową można uzyskać za pomocą metody pola pętli histerezy. Obszar pętli histerezy oraz odpowiednia gęstość energii odkształcenia maleją wraz ze wzrostem współczynnika naprężenia zarówno dla plastyfikowanej i nieplastyfikowanej żywicy. Gęstość energii odkształcenia plastyfikowanej żywicy jest większa niż gęstość nieplastyfikowanej żywicy dla tego samego współczynnika naprężenia. Analiza szkód zmęczeniowych przy użyciu pętli histerezy może być uważana za jedną ze skutecznych metod dla żywicy.

6

A study of interfacial heat transfer and its effect on quenching when hot stamping AA7075

Xiao W., Wang B, Zheng K., Zhou J., Lin J.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 3

723--730

EN

The aim of this research was to investigate the effects of contact pressure and lubrication on the interfacial heat transfer coefficient (IHTC) between AA7075 sheet and H13 tool steel and the in-die quenching performance in hot stamping. Firstly, a series of designed in-die quenching experiments were performed using different contact pressures, 0.05–30 MPa and lubrication conditions to determine the IHTC values using an efficient methodology. Secondly, temperature evolution of the tools and blank during the in-die quenching was investigated. Mechanical properties of material in-die quenched under different process conditions, were measured to determine their relation to quench conditions. The results have shown that IHTC values increased with increasing contact pressure and use of lubricant. A strength level of T6 condition could be obtained using a contact pressure greater than 5 MPa in the lubricated condition.

7

Modeling and analysis of 12-pulse inverter in shipboard or aircraft

Che Y., Zhou J., Liu G., Xu J., Zhao Y.

Polish Maritime Research

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2017

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S 3

136--142

EN

With the development of DC distribution system within the isolated power system of a ship or an aircraft, more constant frequency loads will be supplied by inverters connected to DC main bus. In the operating mode conversion process of an isolated power system, inverters will inevitably suffer from serious disturbance and affect the stability of the system. Therefore, it is important to establish a model of the inverter that reflects its dynamic characteristics and based on which to conduct the stability analysis. This paper proposes a 12-pulse inverter model based on the generalized state space averaging (GSSA) method. This model can overcome the limitations of 12-pulse inverter state space averaging (SSA) model in transient analysis with good accuracy and fast analysis ability effectively. Three kinds of models for a 12-pulse aircraft inverter are built in MATLAB, namely GSSA model, SSA model and detail device model. The simulation results show the high accuracy of GSSA model in stability analysis. This study provides an effective analytical tool for stability analysis of 12-pulse inverter and also provides a reference for inverter modeling research of isolated power system such as in aircraft or ship.

8

Nitrogen Deposition Influences the Allelopathic Effect of an Invasive Plant on the Reproduction of a Native Plant : Solidago canadensis versus Pterocypsela laciniata

Wang C., Liu J., Xiao H., Zhou J., Du D.

Polish Journal of Ecology

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2017

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Vol. 65, nr 1

87--96

EN

This study aims to gain insights into the allelopathic effects (by using leaf extracts) of the notorious invasive Solidago canadensis L. on seed germination of the associated Pterocypsela laciniata (Houtt.) C. Shih under different nitrogen (N) forms added: inorganic (NO3- -N and NH4+ -N), organic (urea-N), and mixed N (a mixture of the three N forms at 1:1:1 ratio). Among the two used concentrations of S. canadensis leaf extracts the higher exhibited inhibitory allelopathic effects on seedling height and biomass, germination potential, germination index, and vigor index of P. laciniata. N demonstrated positive effects on seed germination of P. laciniata. The effects of mixed and organic N on the seedling biomass of P. laciniata were more pronounced than those of inorganic N and control treatment. The vigor index of P. laciniata under mixed N was significantly higher than those under single N form and control treatment. Thus, organic and mixed N showed higher ecological effects on seed germination of P. laciniata than inorganic and single N form. All N forms could alleviate the inhibitory allelopathic effects of S. canadensis on seed germination of P. laciniata. Overall, the inhibitory allelopathic impact of S. canadensis on seed germination of native species may be attenuated under increased and diverse N deposition, thus it could prevent its further invasion.

9

Fabric Defect Detection Using a Hybrid and Complementary Fractal Feature Vector and FCM-based Novelty Detector

Zhou J., Wang J., Bu H.

Fibres & Textiles in Eastern Europe

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2017

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Vol. 25, no. 6 (126)

46--52

EN

Automated detect detection in woven fabrics for quality control is still a challenging novelty detection problem. This work presents five novel fractal features based on the box-counting dimension to address the novelty detection of fabric defect. Making use of the formation of woven fabric, the fractal features are extracted in a one-dimension series obtained by projecting a fabric image along the warp and weft directions, where their complementarity in discriminating defects is taken into account. Furthermore a new novelty detector based on fuzzy c-means (FCM) is devised to deal with one-class classification of the features extracted. Finally, by jointly applying the features proposed and the FCM based novelty detector, we evaluate the method proposed for eight datasets with different defects and textures, where satisfying results are achieved with a low overall missing detection rate.

PL

Automatyczne wykrywanie defektów tkanin w celu kontroli ich jakości mimo wielu dotychczasowych badań nadal stanowi wyzwanie. Mając na celu opracowanie nowatorskiej metody wykrywaniem wad tkanin przedstawiono pięć cech fraktalnych. W celu klasyfikacji wyodrębnionych cech opracowano detektor wad tkanin oparty na zbiorze rozmytym wartości średnich (FCM). Poprzez wspólne zastosowanie proponowanych cech i opartego na FCM detektorze sprawdzono proponowaną metodę dla ośmiu zestawów danych z różnymi defektami i teksturami. Stwierdzono, że otrzymane wyniki są na satysfakcjonującym poziomie.

10

Phase Field Study of Microstructure Evolution in Eutectoid Phase Transformation – I Nucleation

Zhang D., Yin Y., Zhou J., Tu Z.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 3

155--162

EN

Eutectoid growth, as the important reaction mechanism of the carbon steel heat treatment, is the basis to control the microstructure and performance. At present, most studies have focused on lamellar growth, and did not consider the nucleation process. Mainly due to the nucleation theory is inconclusive, a lot of research can support their own theory in a certain range. Based on the existing nucleation theory, this paper proposes a cooperative nucleation model to simulate the nucleation process of eutectoid growth. In order to ensure that the nucleation process is more suitable to the theoretical results, different correction methods were used to amend the model respectively. The results of numerical simulation show that when the model is unmodified, the lateral growth of single phase is faster than that of longitudinal growth, so the morphology is oval. Then, the effects of diffusion correction, mobility correction and ledges nucleation mechanism correction on the morphology of nucleation and the nucleation rate were studied respectively. It was found that the introduction of boundary diffusion and the nucleation mechanism of the ledges could lead to a more realistic pearlite.

11

Effects of three pesticides on superoxide dismutase and glutathione-S-transferase activities and reproduction of Daphnia magna

Song Y., Chen M., Zhou J.

Archives of Environmental Protection

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2017

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Vol. 43, no. 1

80--86

EN

Applying pesticides to crops is one of the causes of water pollution by surface runoff, and chlorpyrifos, trifluralin and chlorothalonil are used respectively as insecticide, herbicide and fungicide for crop plants widely. To explore effects of three pesticides on aquatic organisms, superoxide dismutase (SOD) and glutathione S-transferase (GST) activities were determined after 24 h and 48 h exposure of D. magna with ages of 6–24 h to several low concentrations of chlorpyrifos (0.36, 0.72, 1.43, 2.86, 5.72 μg∙L−1), trifluralin (0.17, 0.33, 0.66, 1.33, 2.65 mg∙L−1) and chlorothalonil (0.09, 0.18, 0.36, 0.72, 1.43 mg∙L−1) respectively. Main reproductive parameters including first pregnancy time, first brood time, the number of first brood and total fecundity after 21 d exposures at the same concentrations of pesticides as described above were also measured. The results showed that the activities of GST increased in lower concentrations and decreased in higher concentrations after 24 h exposure to three pesticides, respectively. The activities of SOD showed the same changes after 48 h exposure. With the time prolonged, the activities of GST decreased while the activities of SOD increased. After 21 d exposure, the first pregnancy time and first brood time were delayed, while the number of the first brood and total fecundity per female decreased with increasing concentrations. These results corroborated that GST activity was more sensitive to those pesticides than SOD activity, and there was a significant relationship between total fecundity and pesticides-dose(r>0.94, n=6), GST activity after 48 h exposure and total fecundity after 21 d exposure (r>0.92, n=6).

12

Fracture mechanical properties of rock-like materials under half symmetric loading

Wang Z., Zhou J., Li L.

Archives of Civil Engineering

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2017

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Vol. 63, nr 4

71--82

EN

The authors studied the fracture mechanical properties under half-symmetric loading in this paper. The stress distribution around the crack tip and the stress intensity factor of three kinds of notched specimens under half symmetric loading were compared. The maximum tensile stress σmax of double notch specimens was much greater than that of single notch specimens and the maximum shear stress τmax was almost equal, which means that the single notch specimens were more prone to Mode II fractures. The intensity factors KII of central notch specimens were very small compared with other specimens and they induced Mode I fractures. For both double notch and single notch specimens, KII was kept at a constant level and did not change with the change of a/h, and KII was much larger than KI. KII has the potential to reach its fracture toughness KIIC before KI and Mode II fractures occurred. Rock-like materials were introduced to produce single notch specimens. Test results show that the crack had been initiated at the crack tip and propagated along the original notch face, and a Mode II fracture occurred. There was no relationship between the peak load and the original notch length. The average value of KIIC was about 0.602 MPa×m1/2, and KIIC was about 3.8 times KIC. The half symmetric loading test of single notch specimens was one of the most effective methods to obtain a true Mode II fracture and determine Mode fracture toughness.

PL

W niniejszej pracy przedstawiono właściwości mechaniczne pękania materiałów skalnych pod półsymetrycznym obciążeniem, w wyniku połączenia analizy teoretycznej, symulacji numerycznych oraz badań eksperymentalnych. W celu ujawnienia mechanizmu uszkodzenia, przygotowano trzy rodzaje próbek z karbem pod półsymetrycznym obciążeniem i zbadano rozkład naprężeń wokół pęknięcia podczas procesu obciążenia. Przyjęto metodę integralnej interakcji oprogramowania elementów skończonych ANSYS w celu obliczenia współczynnika intensywności naprężenia (SIF). Ponadto, wprowadzono pojedynczy element pęknięcia oraz element płaszczyzny 183 w strefie bez pęknięć. Zgodnie z analizą numeryczną i wynikami badań eksperymentalnych, maksymalne naprężenie rozciągające podwójnych próbek z karbem okazało się znacznie większe niż w przypadku pojedynczych próbek z karbem, a ich maksymalne naprężenie ścinające było prawie takie samo, co oznacza, że pojedyncze próbki z karbem były bardziej podatne na pęknięcie w trybie II. Współczynniki intensywności KII środkowych próbek z karbem były bardzo niskie w porównaniu z innymi próbkami oraz tymi, które wywoływały pęknięcia w trybie I. Zarówno w przypadku próbek z podwójnym i pojedynczym karbem, KII zostało utrzymane na stałym poziomie i nie uległo zmianie wraz ze zmianą a/h, a ponadto KII było znacznie większe niż KI. KII może potencjalnie osiągać odporność na kruche pękanie KIIC przed KI. W rezultacie mamy do czynienia z pęknięciami w trybie II. Wprowadzono materiały skalne w celu wytworzenia próbek z pojedynczym karbem. Pęknięcie rozpoczęło się na samej górze i rozprzestrzeniało się wzdłuż pierwotnej powierzchni karbu, w wyniku czego wystąpiło pęknięcie w trybie II. Nie zaobserwowano zależności pomiędzy szczytowym obciążeniem i oryginalną długością karbu. Średnia wartość KIIC była około 3,8 razy większa niż wartość KIC. Pęknięcia w górnej części były znacznie większe niż w innym miejscu, co oznacza, że koncentracja naprężeń pęknięcia w górnej części była oczywista, co z kolei może prowadzić do pęknięcia. Kąt maksymalnego głównego naprężenia wyniósł około 30°, co było zgodne z pęknięciem w trybie I w warunkach czystego obciążenia ścinającego. Badanie półsymetrycznego obciążenia próbek z pojedynczym karbem okazało się być jedną z najskuteczniejszych metod uzyskiwania prawdziwego pęknięcia w trybie II i określenia odporności na kruche pękanie.

13

Plastic Responses in Tree Architecture to Different Light Intensity Habitats : A Case of Chinese Cork Oak

Hu X., Zhang W., Zhou J.

Polish Journal of Ecology

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2016

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Vol. 64, nr 4

500--508

EN

The capacity of plants to occupy different habitats is made possible by the plastic responses of their presenting in heterogeneous habitats. Light directly influences the plastic responses of plant architectural traits. We measured five years-old saplings of Chinese cork oak growing in different light intensity habitats (forest edge, forest gap and understory). A suite of architectural and leaf morphological attributes indicated a pronounced ability of Chinese cork oak to adapt to shade. Under low light intensity habitats, Chinese cork oak had a significant tendency to invest more in crown growth, characterized by the highest crown area, the lowest crown length ratio and the largest angle of the inclination of the main stem to the vertical. It expressed marked plagiotropic growth in shade indicating a horizontal light-foraging strategy. In addition, Chinese cork oak significantly exhibited the highest specific leaf area and the lowest total leaf area under low light intensity habitats. In shade, they showed some plasticity in displaying most of their leaf area at the top of the crown to minimize self-shading and to enhance light interception. This differentiation can be defined as a plastic phenomenon, likely related to the higher efficiency of light interception and absorption by saplings.

14

Highly-efficient three-port output by metal-mirror-based grating

Li H., Wang B., Shu W., Chen L., Lei L., Zhou J.

Optica Applicata

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2016

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Vol. 46, nr 1

87--92

EN

A highly-efficient three-port output of metal-mirror-based grating is proposed in this paper. The metal-mirror-based grating can function as a beam splitter which can diffract the normal incident wave into the 0th and the +/- 1st orders for both TE and TM polarizations with the usual duty cycle of 0.5. The analysis of the grating parameters can be optimized by rigorous coupled-wave analysis. The high efficiency for TE and TM polarizations shall be realized. By means of the numerical simulation, the depth and connecting layer thickness of grating can be accurately calculated. The efficiency of per port is near 33.3%, so the novel three-port output grating with a connecting layer would be an excellent optical element.

15

Silhouette Identification for Apparelled Bodies

Tao C., Zhou J., Yin M.

Fibres & Textiles in Eastern Europe

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2016

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Vol. 24, no. 5 (119)

119--124

EN

This paper presents an approach to identify apparel silhouettes. A feature region of the human face was first proposed for conducting face detection in fashion pictures with the AdaBoost method, and the head was then located with its positional relation to the facial feature region. The linear relationship between the ratio of the body height to head length and the length of the lower body was ensured by restricting the RBH to a specific range. Under this condition, the apparelled body was divided into several parts, and the boundary of apparel on the lower body was determined considering the influence of the hemline. Based on the widths of the body parts and the apparel on the lower body, shape factors were established to express the extent to which the apparel silhouette approached a certain shape. A computer program was developed for implementation and demonstrated high accuracy in silhouette identification of an appareled body.

PL

Przedstawiono próbę identyfikacji sylwetki ubranego modelu. Opracowano system właściwości charakteryzujących twarz człowieka dla możliwości dalszego wyodrębnienia twarzy ze zdjęć modeli. Zastosowano metodę AdaBoost. Umożliwiło to usytuowanie głowy w stosunku do innych elementów ubioru. Zidentyfikowano liniowe zależności pomiędzy wysokościami całości sylwetki, jej dolnej części, i głowy. Na tej podstawie ubrana sylwetka człowieka była dzielona na szereg części i określano granice ubioru w stosunku do dolnej części sylwetki, uwzględniając wpływ dolnej krawędzi ubioru. Opierając się na szerokościach poszczególnych części ciała człowieka i ubioru dolnej części sylwetki, ustalono czynniki kształtu dla możliwości kwalifikacji sylwetki do odpowiedniego typu. Opracowano program komputerowy umożliwiający dużą dokładność identyfikacji sylwetki ubranego modelu.

16

Asymptotic solutions for generalized thermoelasticity with variable thermal material properties

Wang Y., Liu D., Wang Q., Zhou J.

Archives of Mechanics

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2016

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Vol. 68, nr 3

181--202

EN

In this paper, a unified generalized thermoelastic solution with variable thermal material properties is proposed in the context of different generalized models of thermoelasticity, including thermoelasticity with one thermal relaxation time (LS theory), thermoelasticity with two thermal relaxation times (GL theory) and thermoelasticity without energy dissipation (GN theory). The unified form of governing equations is presented by introducing unifier parameters. The unified formulations are derived and given for isotropic homogenous materials with variable thermal material properties. The Laplace transform techniques and the Kirchhoff’s transformation are used to obtain general solutions for any set of boundary conditions in the physical domain. Asymptotic solutions for a specific problem of an elastic half-space with variable thermal conductivity and a specific heat, whose boundary is subjected to a thermal shock, are derived by means of the limit theorem of Laplace transform. In the context of these asymptotic solutions, some generalized thermoelastic phenomena are observed. Especially, the jumps at the wavefronts induced by the propagation of finite signal speed for the heat are clearly noticed. In addition, the effect of variable characteristics of material properties on thermoelastic behaviors is revealed by a comparison with the results obtained in the case of constant material properties.

17

Numerical Simulation of Solidification Microstructure based on Adaptive Octree Grids

Yin Y., Li Y., Wu K., Zhou J.

Archives of Foundry Engineering

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2016

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Vol. 16, iss. 2

33--40

EN

The main work of this paper focuses on the simulation of binary alloy solidification using the phase field model and adaptive octree grids. Ni-Cu binary alloy is used as an example in this paper to do research on the numerical simulation of isothermal solidification of binary alloy. Firstly, the WBM model, numerical issues and adaptive octree grids have been explained. Secondary, the numerical simulation results of three dimensional morphology of the equiaxed grain and concentration variations are given, taking the efficiency advantage of the adaptive octree grids. The microsegregation of binary alloy has been analysed emphatically. Then, numerical simulation results of the influence of thermo-physical parameters on the growth of the equiaxed grain are also given. At last, a simulation experiment of large scale and long-time has been carried out. It is found that increases of initial temperature and initial concentration will make grain grow along certain directions and adaptive octree grids can effectively be used in simulations of microstructure.

18

Three-port beam splitter based on a sandwiched grating with an improved aspect ratio

Shu W, Wang B, Li H, Li W, Chen L., Lei L., Zhou J.

Optica Applicata

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2015

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Vol. 45, nr 3

279--284

EN

In this paper, a fused-silica transmission grating used as a three-port beam splitter is designed by using the rigorous coupled-wave analysis, which is based on the sandwiched grating structure at the wavelength of 800 nm under normal incidence. Firstly, it is feasible to realize such a grating with the prescribed grating duty cycle and grating period. Next, high efficiency can be also achieved for both TE and TM polarizations. Moreover, the aspect ratio of the grating depth to the ridge width can be improved, which is significant for practical applications. At last, the three-port beam splitter is designed with a covering layer on the surface, which can extend its life service.

19

Polarization-independent metal-dielectric grating with improved bandwidth

Wang B, Li H, Shu W, Li W, Li C, Lei L, Zhou J

Optica Applicata

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2015

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Vol. 45, nr 1

71--77

EN

A polarization-independent reflective grating with improved bandwidth is presented based on the mixed metal-dielectric grating. The novel grating is composed of the substrate, the metal slab, two dielectric layers, and the covering layer. The grating parameters are optimized for the special duty cycle of 0.6 at an incident wavelength of 1550 nm used in dense wavelength division multiplexing (DWDM). With the designed grating, high efficiency can be diffracted into the reflective –1st order for both TE and TM polarizations, where the polarization-independence is exhibited. Most importantly, the efficiency of more than 90% can be achieved within the incident wavelength bandwidth of 1262–1686 nm, where the bandwidth is improved greatly compared with the reported surface-relief single-layer grating. The reflective grating can have advantages of high efficiency, polarization-independence, and wide bandwidth, which should be useful for DWDM applications.

20

Impact of incorporation of chromium on electrochemical properties of LiFePO4/C for Li-ion batteries

Naik A., Zhou J., Gao C., Liu G., Wang L.

Materials Science Poland

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2015

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Vol. 33, No. 4

741--750

EN

LiFe0.95Cr0.05PO4/C was successfully synthesized by one-step solid-state reaction using a single mode microwave reactor. The effect of incorporation of chromium on LiFePO4 lattice parameters was systematically investigated by X-ray diffraction. Surface analysis was done by scanning electron microscopy and transmission electron microscopy. The ratio of amorphous to graphitic carbon was determined from Raman spectroscopic data. The influence of chromium incorporation on electrochemical properties was studied by recording charge/discharge cycles combined with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. It was found that Cr incorporation significantly enhanced the electrochemical performance of LiFePO4 at all current densities up to 10 C. LiFe0.95Cr0.05PO4/C prepared exhibited the best performance with an initial specific discharge capacity of 157.7, 144.8, 138.3, 131.0, 124.1 and 111.1 mAh.g(-1) at 0.1 C, 0.5 C, 1.0 C, 2.0 C, 5 C and 10 C, respectively. The doped sample displayed excellent capacity retention, which was substantially superior than that of pristine LiFePO4/C at a higher current rate.