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1

Influence of the number of turns on the performance of permanent magnet synchronous motor

Qiu H., Zhang Y., Yang C., Yi R.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2020

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Vol. 68, nr 3

429--436

EN

The current passed by the stator coil of the permanent magnet synchronous motor (PMSM) provides rotating magnetic field, and the number of turns will directly affect the performance of PMSM. In order to analyze its influence on the PMSM performance, a 3 kW, 1500 r/min PMSM is taken as an example, and the 2D transient electromagnetic field model is established. The correctness of the model is verified by comparing the experimental data and calculated data. Firstly, the finite element method (FEM) is used to calculate the electromagnetic field of the PMSM. The performance parameters of the PMSM are obtained. On this basis, the influence of the number of turns on PMSM performance is quantitatively analyzed, including current, no-load back electromotive force (EMF), overload capacity and torque. In addition, the influence of the number of turns on eddy current loss is further studied, and its variation rule is obtained, and the variation mechanism of eddy current loss is revealed. Finally, the temperature field of the PMSM is analyzed by the coupling method of electromagnetic field and temperature field, and the temperature rise law of PMSM is obtained. The analysis of this paper provides reference and practical value for the optimization design of PMSM.

2

Experimental and numerical study of the uniaxial compressive stress-strain relationship of a rock mass with two parallel joints

Xiong L. X., Yuan H. Y., Zhang Y., Zhang K. F., Li J. B.

Archives of Civil Engineering

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2019

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Vol. 65, nr 2

67--80

EN

A “rock bridge”, defined as the closest distance between two joints in a rock mass, is an important feature affecting the jointed rock mass strength. Artificial jointed rock specimens with two parallel joint fractures were tested under uniaxial compression and numerical simulations were carried out to study the effects of the inclination of the rock bridge, the dip angle of the joint, rock bridge length, and the length of joints on the strength of the jointed rock mass. Research results show: (1) When the length of the joint fracture, the length of the rock bridge, and the inclination of the rock bridge stay unchanged, the uniaxial compressive strength of the specimen gradually increases as the inclination of the joint fracture increases from 0° to 90°. (2) When the length of the joint fracture, the length of the rock bridge, and the inclination of the joint fracture stay unchanged, the uniaxial compressive strength of the specimen shows variations in trends with the inclination of the rock bridge increasing from 30° to 150° (3). In the case when the joint is angled from the vertical loading direction, when the dip angle of the joint fracture, the inclination of the rock bridge, and the length of the rock bridge stay unchanged, the uniaxial compressive strength of the specimen gradually decreases with an increasing length of joint fracture. When the dip angle of the joint fracture, the inclination of the rock bridge, and the length of the joint fracture stay unchanged, the uniaxial compressive strength of the specimen does not show a clear trend with an increase of the length of the rock bridge.

3

Postępy w kontroli emisji SO2 i NOx w chińskim przemyśle hutniczym

Liu Z., Zhang Y., Han B., Tan Z., Li Q.

Przemysł Chemiczny

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2018

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T. 97, nr 3

473--480

PL

Dokonano przeglądu najnowszych postępów w dziedzinie technologii kontroli emisji SO₂ i NOₓ w przemyśle hutniczym w Chinach. Technologie mokrego odsiarczania gazów (WFGD), w tym metodę wapienną FGD z produkcją gipsu, dwualkaliczną FGD, amoniakalną FGD oraz magnezytową FGD stosuje się w 85,2% działających instalacji odsiarczania. Metody te charakteryzuje dojrzałość, duża wydajność oraz zadowalające możliwości dostosowawcze. Mimo to największymi problemami pozostają korozja, wtórne zanieczyszczenie powietrza oraz niepożądane produkty uboczne. W porównaniu z technologiami WFGD technologie suchego i półsuchego odsiarczania mają mniejszy udział w rynku, pomimo małego zużycia rozpuszczalników i małego wtórnego zanieczyszczenia powietrza. Technologia de-NOx dla przemysłu hutniczego wciąż pozostaje na wczesnym etapie rozwoju, zaś w chińskim przemyśle hutniczym pracuje obecnie zaledwie kilka instalacji de-NOx. W technologii selektywnej redukcji katalitycznej (SCR) drzemie wielki potencjał dotyczący kontroli emisji NOₓ, pod warunkiem że katalizatory niskotemperaturowe będą dostępne w rozsądnych cenach. Trwa rozwój technologii jednoczesnego usuwania SO₂ i NOₓ, tak aby sprostać surowym normom emisji zanieczyszczeń powietrza dla przemysłu hutniczego w Chinach.

EN

A review, with 53 refs., of wet and semi-dry flue gas desulfurization technols. as well as of processes for catalytic redn. of N oxides. In particular, maturity, high efficiency, reasonable adaptability, corrosion, secondary air pollution, and unwanted byproducts were taken into consideration.

4

Study on optimization simulation of SCR denitration system for marine diesel engine

Du J., Li R. N., Wu X., Zhang Y.

Polish Maritime Research

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2018

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S 3

13--21

EN

With the rapid development of shipbuilding industry exhaust world is also very harmful one kind of environmental issues, and the ship marine diesel engine exhaust gas is mainly produced, so in recent years it has developed a diesel engine SCR system. SCR system can control emissions of nitrogen oxides in the exhaust of vessel, furthermore air pollution can be reduced. The main goal of article was using fluent software to correct SCR system selection and flue gas flow under different size best deflector arrangement is simulated. Next goal is further optimize the structure of the SCR system.

5

Simulation and experimental study of SCR injection system

Du J., Zhang Y., Cai Y.

Polish Maritime Research

|

2018

|

S 2

49--55

EN

According to actual engineering test, we design a linear controlled spray ammonia grille, and apply it to the SCR injection system of ship tail gas treatment. In this paper, the geometric model of ammonia injection grid was built in the flue of diesel engine, and the effects of spray atomization, ammonia uniformity and urea droplet distribution on spray atomization were simulated. Then the test bench was set up to observe the injection status of the ammonia injection grille. The NOx content of the outlet was measured by the original data of the flue gas, and the experimental data were processed. We calculate the denitrification rate by taking the average value to verify the correctness of the spray ammonia grid scheme.

6

Pre-concentration of graphite and LiCoO2 in spent lithium-ion batteries using enhanced gravity concentrator

Zhu X,-N., Tao Y.-J., He Y.-Q., Zhang Y., Sun Q.-X.

Physicochemical Problems of Mineral Processing

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2018

|

Vol. 54, iss. 2

293--299

EN

The pre-concentration of electrode material of spent lithium-ion battery has great significance on the resource utilization and environmental protection. The feasibility of separation of graphite and LiCoO2 based on density difference using the enhanced gravity concentrator was verified in this paper. Combustion characteristics of LiCoO2 and graphite were used to propose a simple evaluation index of separation efficiency. Separation tests were carried out to specify the influence of operating parameters on the separation efficiency. Moreover, the effect of particle size on the separation performance was studied. Combustion characteristics results showed that mass loss of graphite was much greater than that of LiCoO2. Thus, mass loss were used to evaluate the purity of product. Effective separation of graphite and LiCoO2 was achieved by the enhanced centrifugal separator. Separation results showed that increasing centrifugal force decreased the overflow yield and increased the graphite content of the overflow stream. In addition, yield of overflow grew an increase in fluidization water pressure, while the purity of graphite in overflow decreased. The effect of particle size on the separation efficiency was also significant, the separation efficiency decreased with the decreasing of particle size.

7

Flotation separation of scheelite from calcite using sodium polyacrylate as depressant

Zhang Y., Chen R., Li Y., Wang Y., Luo X.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 2

505--516

EN

The depressing properties of sodium polyacrylate (PA-Na) for calcite from scheelite were studied by microflotation experiments, zeta potentials, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculation. Flotation results revealed that the selective depression effect of PA-Na was better than that of sodium silicate (Na2SiO3), and PA-Na can depress calcite more effectively than scheelite. The flotation recovery of scheelite and calcite kept at about 75% and 15% respectively at the pulp pH 9.3~9.6 and PA-Na concentration from 37.5 mg/dm3 to 50 mg/dm3. The zeta potentials of the minerals were significantly altered and the zeta potential of calcite became more negative than scheelite. XPS analysis deduced the occurrence of chemisorption between PA-Na and mineral surfaces, and the chemisorption of PA-Na on calcite was stronger than on scheelite. The results from DFT calculation demonstrated that the absolute value of the adsorption energy in the presence of PA-Na on the surface of calcite {104} was larger than on the surface of scheelite {111}. With the combination of the analysis, it could be concluded that calcite was more easily depressed than scheelite, and this finding remarkably matched with the microflotation experimental results. Furthermore, by using PA-Na as depressant, the flotation separation of scheelite from calcite can be achieved by controlling the flotation pH and PA-Na dosage.

8

Solid-solid intercalation and optical properties of VO-8-hydroxyquinoline decoration of layered silicate magadiite

Zhang Y.

Materials Science Poland

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2018

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Vol. 36, No. 1

134--140

EN

Coordination of vanadyl (VO2+) ions with 8-hydroxyquinoline (8Hq) in the interlayer space of layered silicate magadiite (mag) was realized by solid-solid intercalation. Composition, structure and morphology of this compound were studied by X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The obtained results indicate that the basal spacing of decorated mag increased after intercalation and suggest that VO-8Hq decorated into the interlayer of mag (VO-mag-8Hq) was successfully synthesized for the first time. Optical properties of VO-mag-8Hq were studied by ultraviolet-visible (UV-Vis) and photoluminescence spectroscopy (PL). The findings reveal that VO-8Hq complexes in the interlayer space exhibit extraordinary fluorescence properties and the confined space of mag influences the optical properties of VO-8Hq complexes.

9

Analysis of future climate scenarios and their impact on agriculture in eastern Arkansas, United States

Magugu J. W., Feng S., Huang Q., Zhang Y., West G. H.

Journal of Water and Land Development

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2018

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no. 37

97--112

EN

Impact of climate change on crop growth is dynamic and difficult to quantify due to heterogeneity of the associated effects and their interactions within the Earth system. The main objective of this study is to establish how future climate change might affect agriculture, through an assessment of temperature and precipitation driven parameters. These include percentage number of rainy days with extreme precipitation, percentage of extreme precipitation relative to wet days, first fall frost days, last spring frost days, growing degree days, growing season length and the total precipitation. Results show modest increase in total precipitation with a slight increase in extreme precipitation, representing up to 2.2% increase by 2060 under representative concentration pathway (RCP 8.5) scenario. There would be late first fall frost days, early last spring frost days and increased growing season length by up to 2 weeks in 2060. The growing degree days are projected to increase under all scenarios for all crops, with cotton showing the largest increase of up to 37% relative to the baseline period.

PL

Wpływ zmian klimatu na wzrost upraw jest dynamiczny i trudny do ilościowej oceny z powodu różnorodności powiązanych efektów i ich interakcji w całym systemie Ziemi. Głównym celem badań prezentowanych w niniejszej pracy było ustalenie, jak zmiany klimatu w przyszłości mogą wpłynąć na rolnictwo, na podstawie oceny parametrów związanych z temperaturą i opadami. Analizowano następujące parametry: udział (w %) dni deszczowych z ekstremalnym opadem, udział ekstremalnych opadów w stosunku do opadów ogółem, pierwsze jesienne dni z mrozem, ostatnie wiosenne dni z mrozem, stopniodni w sezonie wegetacyjnym, długość sezonu wegetacyjnego, i sumę opadów. Wyniki wykazują umiarkowany wzrost całkowitych opadów i niewielki wzrost opadów ekstremalnych – do 2,2% do roku 2060 wg scenariusza Representative Concentration Pathway (RCP 8.5). W 2060 roku pierwsze jesienne dni z mrozem wystąpią później, ostatnie wiosenne dni z mrozem wystąpią wcześniej, a sezon wegetacyjny wydłuży się o ok. 2 tygodnie. Zgodnie ze wszystkimi scenariuszami przewiduje się, że liczba stopniodni w sezonie wegetacyjnym zwiększy się dla wszystkich upraw, a największy przyrost (maksymalnie o 37%) w stosunku do okresu bazowego prognozuje się dla upraw bawełny.

10

Dynamic and resonance response analysis for a turbine blade with varying rotating speed

Wang D., Hao Z., Chen Y., Zhang Y.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 1

31--42

EN

A coupling model between turbine blades with a varying rotating speed and oncoming vortices is constructed, where the coupling of the structure and the fluid is simulated by the van der Pol oscillation. Partial differential governing equations of motions for the coupled system are obtained and discretized by using the Galerkin method. The 1:2 subharmonic resonance and the 1:1 internal resonance are investigated with the multiple scale method and first-order averaged equations are then derived. Nonlinear responses and bifurcation characteristics are studied by a numerical integration method. Stability of bifurcation curves is determined by utilizing the Routh-Hurwitz criterion. The effect of system parameters including the detuning parameter, steady-state rotating speed, amplitude of periodic perturbation for the rotating speed and freestream velocity on vibration responses are investigated.

11

Simulation for instable floating of hydrodynamic guides during acceleration and at constant velocity

Zhang Y., Wittstock V., Putz M.

Journal of Machine Engineering

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2018

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Vol. 18, No. 3

5--15

EN

High speeds and the resulting hydrodynamic pressure lead to significant floating of the linear guides. During this movement, the floating behaviour shows phenomena that can be explained by the Reynolds equation. This paper presents a dynamic model of the floating behaviour, which adds tribological approaches to the common Reynolds equation since the floating behaviour does not only depend on the speed, but also on numerous other conditions. This developed simulation method is based on the use of finite difference elements and was implemented using Simulink and Matlab, allowing flexible implementation of further influences such as lubrication cycles and geometry of the sliding surface. After adapting the simulation model and determining the parameters, the calculated floating behaviour corresponds well with the experimental results.

12

Window of Visibility in the Display and Capture Process

Xiong F., Zhai G., Zhang Y.

International Journal of Electronics and Telecommunications

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2018

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Vol. 64, No. 3

315--320

EN

In normal conditions, the Critical Flicker Frequency is usually 60Hz. But in some special conditions, such as low spatial frequency and high contrast between frames, these special conditions have high probability to occur in some TPVM-based applications. So it’s extremely important to verify if a visual signal with a combination of temporal and spatial frequency can be recognize by human eyes. Based on the research in the last paper ’ ’Window of Visibility’ inspired security lighting system’, this paper introduces the measuring method of WoV of human eyes. In this paper we will measure critical flicker frequency in low spatial frequency and high contrast conditions, and we can witness a different conclusion from the normal conditions.

13

Ordovician seawater composition : evidence from fluid inclusions in halite

Meng F., Zhang Y., Galamay A. R., Bukowski K., Ni P., Xing E., Ji L.

Geological Quarterly

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2018

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Vol. 62, No. 2

344--352

EN

Fluid inclusions in halite can directly record the major composition of evaporated seawater; however, Ordovician halite is very rare. The Ordovician is a key time during the evolution history because profound changes occurred in the planet’s ecosystems. Marine life was characterized by a major diversification, the Great Ordovician Biodiversification Event and the Late Ordovician Mass Extinction, the first of the “big five” mass extinctions. However, so far there is no data on the Ordovician seawater. Data from the Ordovician-Silurian boundary were available only. In this study, we report the major compositions from Middle Ordovician halite in China to give the exact composition of Ordovician seawater. The basic ion composition (K+, Mg2+, Ca2+, and SO42-) of inclusion brines was established with the use of ultramicrochemical analysis. The data on the chemical composition of the brines in the primary inclusions indicated that the brines were of Na-K-Mg-Ca-Cl (Ca-rich) type, and cover a huge gap in the evolution of seawater chemistry. The chemical composition of the primary inclusion brine in halite confirmed the earlier results for the Cambrian and Silurian halite originating from other salt basins and the previous speculation of “calcite sea” during the Ordovician, indicating a higher potassium content in the Lower Paleozoic seawater than in the seawater of other periods of the Phanerozoic.

14

Cryptanalysis and Improvement for Certificateless Aggregate Signature

Li J., Yuan H., Zhang Y.

Fundamenta Informaticae

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2018

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Vol. 157, nr 1/2

111--123

EN

In order to satisfy application in resource constrained environment, aggregate signature schemes have been widely investigated. Recently, He et al. pointed out that certificateless aggregate signature (CLAS) scheme proposed by Xiong et al. was insecure against the Type II adversary and presented an possible improvement. In this article, we show that their improved scheme is not secure against a malicious-but-passive KGC attack. We analyze attack reason and propose an improved certificateless aggregate signature scheme. Based on the CDH difficult problem assumption, the proposed CLAS scheme is existentially unforgeable against adaptive chosen-message attacks in the random oracle model.

15

Time-dependent reliability of spur gear system based on gradually wear process

Zhu L., Zhang Y., Zhang R., Zhang P.

Eksploatacja i Niezawodność

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2018

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Vol. 20, no. 2

207--218

EN

To study dynamic evolution law of mechanical reliability caused by wear, gear transmission system is taken as a research object. Considering the effect of clearance caused by wear on gear teeth load in double meshing area, the formula of dynamic distribution load which is undertaken by two adjacent teeth is deduced. And the distributed pressure and meshing speed, which should be taken into account while calculating gear wear, are obtained based on the Winkler surface model and principle of tooth mesh. Based on the Archard’s wear model, numerical simulation model for wear in spur gear is deduced, and the wear depth of each meshing points on teeth outline with different wear cycles are obtained. The calculation wear model is replaced with a surrogate model with Neural Network and Kriging method to overcome time-consuming defect. Random process model is integrated with the surrogate model, and dynamic reliability for nonlinear stochastic structure with unknown distribution characteristic is obtained with Neural Network-based Edgeworth series technique and four moment methods, which is compared with Kriging-based Monte Carlo simulation method. The computational efficiency and accuracy are also demonstrated.

PL

W artykule badano prawo dynamicznej ewolucji niezawodności mechanicznej powodowanej zużyciem na przykładzie układu przekładni zębatej. Na podstawie rozważań nad wpływem luzu powstałego na skutek zużycia na obciążenie zębów przekładni w obszarze podwójnych zazębień, wyprowadzono wzór na dynamiczny rozkład obciążeń przyjmowanych przez pary sąsiadujących zębów. Rozłożone naciski i prędkość zazębiania, które należy uwzględnić przy obliczaniu zużycia przekładni, otrzymano na podstawie modelu powierzchniowego Winklera oraz zasady zazębienia. W oparciu o model zużycia Archarda, wyprowadzono numeryczny model symulacyjny zużycia w przekładni zębatej oraz obliczono głębokość zużycia każdego z punktów zazębienia na zarysie zębów przy różnych cyklach zużycia. Aby uniknąć problemu czasochłonności, obliczeniowy model zużycia zastąpiono modelami zastępczymi bazującymi na sieci neuronowej i metodzie krigingu. Model procesu losowego zintegrowano z modelem zastępczym, a dynamiczną niezawodność dla nieliniowej struktury stochastycznej o nieznanej charakterystyce rozkładu uzyskano za pomocą techniki serii Edgeworth opartej na sieci neuronowej oraz metody czterech momentów, którą porównano z metodą symulacji Monte Carlo opartą na krigingu. Wykazano także wydajność obliczeniową i dokładność omawianej metody.

16

A novel reliability model for multi-component systems subject to multiple dependent competing risks with degradation rate acceleration

Zhang Y., Ma Y., Liu L., Ouyang L.

Eksploatacja i Niezawodność

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2018

|

Vol. 20, no. 4

579--589

EN

The purpose of this paper is to establish a new reliability model of the system subject to multiple dependent competing risks. For a system subject to multiple dependent competing risks, the total degradation consists of natural degradation amount and sudden degradation increments (SDIs) caused by random shocks arriving at the system. Most researchers on this topic only focus on the SDIs. However, the impact of random shocks on degradation rate is ignored. In this paper, a novel reliability model considering degradation rate acceleration (DRA) caused by random shocks is proposed, in which the degradation model is based on the degradation path. The dependence relationship between multiple degradation processes is dealt with by copula method, and the arrival time of shocks is assumed to follow a non-homogeneous Poisson process (NHPP). Finally, the effectiveness of the proposed reliability model is demonstrated by an example of a series system. Moreover, the effect of model parameters is evaluated through sensitivity analysis.

PL

Celem niniejszej pracy było stworzenie nowego modelu niezawodności systemu narażonego na liczne zależne ryzyka konkurujące. W przypadku systemu eksponowanego na wiele zależnych ryzyk konkurujących, na wartość całkowitą degradacji składa się wartość degradacji naturalnej oraz wartość nagłych przyrostów degradacji (sudden degradation increments, SDI) powodowanych przez losowe zaburzenia systemu. Większość badaczy tej tematyki koncentruje się wyłącznie na SDI, ignorując tym samym wpływ zaburzeń losowych na tempo degradacji. W niniejszym artykule zaproponowano nowy model niezawodności uwzględniający przyspieszenie tempa degradacji powodowane zaburzeniami losowymi, w którym model degradacji opiera się na krzywej degradacji. Zależność między mnogimi procesami degradacji rozpatrywano za pomocą metody funkcji kopuły przy założeniu, że czas wystąpienia zaburzenia odpowiada niejednorodnemu procesowi Poissona. Skuteczność proponowanego modelu niezawodności zademonstrowano na przykładzie systemu szeregowego. Ponadto, wykorzystano analizę czułości do oceny wpływu parametrów modelu na niezawodność systemu.

17

A parallel algorithm of icsym forcomplexsymmetric linear systems in quantum chemistry

Zhang Y., Lv Q., Xiao M., Xie G., Breitkopf P.

Computer Science

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2018

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Vol. 19 (4)

385--401

EN

Computational effort is a common issue for solving large-scale complex symmetric linear systems, particularly in quantum chemistry applications. In order to alleviate this problem, we propose a parallel algorithm of improved conjugate gradient-type iterative (ICSYM). Using three-term recurrence relation and or- thogonal properties of residual vectors to replace the tridiagonalization process of classical CSYM, which allows to decrease the degree of the reduce-operator from two to one communication at each iteration and to reduce the amount of vector updates and vector multiplications. Several numerical examples are implemented to show that high performance of proposed improved version is obtained both in convergent rate and in parallel efficiency.

18

Performance optimization of organic Rankine cycles for waste heat recovery for a large diesel engine

Ma Z., Wu J., Zhang Y.

Archives of Thermodynamics

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2018

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Vol. 39, no 1

3--23

EN

In order to recover the low grade waste heat and increase system fuel economy for main engine 10S90ME-C9.2-TII(part load, exhaust gas bypass) installed on a 10000 TEU container ship, a non-cogeneration and single-pressure type of waste heat recovery system based on organic Rankine cycle is proposed. Organic compound candidates appropriate to the system are analyzed and selected. Thermodynamic model of the whole system and thermoeconomic optimization are performed. The saturated organic compound vapor mass flow rate, net electric power output, pinch point, thermal efficiency and exergy efficiency varied with different evaporating temperature are thermodynamically analyzed. The results of thermodynamic and thermoeconomic optimization indicate that the most appropriate organic compound candidate is R141b due to its highest exergy efficiency, biggest unit cost benefit and shortest payback time.

19

Study on distribution of CO and concentration prediction in blind gallery after blasting operation

Cao Y., Ji H., Zhang Y., Li S.

Archives of Mining Sciences

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2018

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Vol. 63, no. 2

283--300

EN

It is meaningful to study the issues of CO migration and its concentration distribution in a blind gallery to provide a basis for CO monitoring and calculation of fume-drainage time, which is of a great significance to prevent fume-poisoning accidents and improve efficiency of an excavation cycle. Based on a theoretical analysis of a differential change of CO mass concentration and the CO dispersion model in a fixed site, this paper presents several blasting fume monitoring test experiments, carried out with the test location to the head LP in arrange of 40-140 m. Studies have been done by arranging multiple sensors in the arch cross-section of the blind gallery, located at the Guilaizhuang Gold Mine, Shandong Province, China. The findings indicate that CO concentrations in the axial directions are quadratic functions with the Y and Z coordinate values of the cross-section of the blind gallery in an ascending stage of CO time-concentration curve, with the maximum CO concentrations in Y = 150 cm and Z = 150 cm. Also, the gradients of CO concentration in the gallery are symmetrical with the Y = 150 cm and Z = 150 cm. In the descending stage of CO time-concentration curve, gradients of CO concentration decrease in lateral sides and increase in the middle, then gradually decrease at last. The rules of CO concentration distribution in the cross-section are that airflow triggers the turbulent change of the CO distribution volume concentration and make the CO volume concentration even gradually in the fixed position of the gallery. Moreover, the CO volume concentrations decrease gradually, as well as volume concentration gradients in the cross-section. The uniformity coefficients of CO concentration with duct airflow velocities of 12.5 m/s, 17.7 m/s and 23.2 m/s reach near 0.9 at 100-140 m from the heading to the monitoring spot. The theoretical model of a one-dimensional migration law of CO basically coincides with the negative exponential decay, which is verified via fitting. The average effective turbulent diffusion coefficient of CO in the blind gallery is approximate to 0.108 m2/s. There are strong linear relationships between CO initial concentration, CO peak concentrations and mass of explosive agent, which indicates that the CO initial concentration and the CO peak concentration can be predicted, based on the given range of the charging mass. The above findings can provide reliable references to the selection, installation of CO sensors and prediction of the fume-drainage time after blasting.

PL

Badania migracji, rozpływu i rozkładu stężenia CO w ślepym wyrobisku są niezbędne, stanowią one bowiem podstawę do skutecznego monitorowania poziomu CO i obliczania czasu niezbędnego na usunięcie z wyrobiska szkodliwych gazów – jest to kwestia kluczowa dla zapobiegania wypadkom związanych z zatruciem spalinami oraz dla planowania przebiegu prac wydobywczych. W oparciu o teoretyczną analizę zmian stężenia masowego CO i wykorzystując model dyspersji gazu w stałym punkcie, w pracy przedstawiono wyniki eksperymentów przeprowadzonych w ramach monitorowania stężeń gazów powybuchowych w wyrobisku LP na odległości 40-140 m od czoła wyrobiska. Badania prowadzono przy wykorzystaniu zestawu czujników rozmieszczonych w wybranych punktach ślepego wyrobiska w kopalni złota Guilaizhuang, w prowincji Shandong, Chiny. Wyniki badań wskazują, że stężenia CO w kierunkach poosiowych są funkcjami kwadratowymi wartości współrzędnych Y i Z przekroju przekroju ślepego wyrobiska w zakresie krzywej opadającej na wykresie opisującym zależność stężenia CO od czasu, przy czym maksymalne stężenia CO stwierdzono dla Y =150 cm i Z = 150 cm. Ponadto, wykazano że gradienty stężenia CO w wyrobisku są symetryczne dla Y =150 cm i Z =150 cm. W zakresie krzywej rosnącej na wykresie zależności stężenia CO od czasu gradienty stężenia CO wykazują spadek w końcowych regionach wykresu, w środkowej części wykresu notuje się jego wzrost, po czym znów następuje spadek. Na rozkład stężenia CO w tym przekroju wpływ ma fakt że przepływ powietrza wywołuje turbulentne zmiany stężenia objętościowego CO, następnie stężenie objętościowe maleje systematycznie w dalszych częściach wyrobiska. Ponadto, stwierdzono że stężenie CO a także gradienty stężenia objętościowego w przekroju maleją stopniowo. Współczynniki wyrażające równomierność stężenia CO przy przepływach powietrza z prędkością 12.5 m/s 17.7 m/s i 23.2 m/s osiągają wartość 0.9 w punkcie kontrolnym odległym od wyrobiska o 100-140 m. Teoretyczny model jednowymiarowego rozpływu CO zasadniczo pokrywa się z wzorem zależności wykładniczej z wykładnikiem ujemnym, co zostało potwierdzone w procedurze pasowania. Średnia wartość współczynnika dyfuzji CO dla przepływu turbulentnego w ślepym wyrobisku wyniosła 0.108 m2/s. Stwierdzono istnienie silnej zależności liniowej pomiędzy początkowym stężeniem CO, szczytową wielkością stężenia oraz masą użytego materiału wybuchowego, która wskazuje na możliwość prognozowania początkowego i szczytowego stężenia CO w oparciu o zakres wielkości użytego ładunku wybuchowego. Przedstawione wyniki badań stanowić mogą wiarygodną podstawę dla wyboru rodzaju i miejsca zainstalowania czujników CO oraz do prognozowania czasu wymaganego na usuniecie szkodliwych gazów po zakończeniu prac strzałowych.

20

Y Addition Effects on Hot Deformation Behavior of Cu-Zr Alloys with High Zr Content

Tian K., Tian B., Volinsky A. A., Zhang Y., Liu Y., Du Y.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

875--882

EN

Isothermal hot compression experiments were carried out using the Gleeble-1500D thermal mechanical simulator. The flow stress of the Cu-1%Zr and Cu-1%Zr-0.15%Y alloys was studied at hot deformation temperature of 550°C, 650°C, 750°C, 850°C, 900°C and the strain rate of 0.001 s-1, 0.01 s-1, 0.1 s-1, 1 s-1, 10 s-1. Hot deformation activation energy and constitutive equations for two kinds of alloys with and without yttrium addition were obtained by correlating the flow stress, strain rate and deformation temperature. The reasons for the change of hot deformation activation energy of the two alloys were analyzed. Dynamic recrystallization microstructure evolution for the two kinds of alloys during hot compression deformation was analyzed by optical and transmission electron microscopy. Cu-1%Zr and Cu-1%Zr-0.15%Y alloys exhibit similar behavior of hot compression deformation. Typical dynamic recovery occurs during the 550-750°C deformation temperature, while dynamic recrystallization (DRX) occurs during the 850-900°C deformation temperature. High Zr content and the addition of Y significantly improved Cu-1%Zr alloy hot deformation activation energy. Compared with hot deformation activation energy of pure copper, hot deformation activation energy of the Cu-1%Zr and Cu-1%Zr-0.15%Y alloys is increased by 54% and 81%, respectively. Compared with hot deformation activation energy of the Cu-1%Zr alloy, it increased by 18% with the addition of Y. The addition of yttrium refines grain, advances the dynamic recrystallization critical strain point and improves dynamic recrystallization.