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1

Excavation‑induced structural deterioration of rock masses at different depths

Zhang R., Xie H. P., Ren Li, Deng H. I., Gao M. Z., Feng G., Zhang Z. T., LI X. P., Tan Q.

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e81, 1--15

EN

The excavation-induced deterioration of rock mass quality and integrity may significantly affect the stability of deep underground spaces. However, the influence of the burial depth on excavation-induced rock mass structural deterioration remains unclear. To address this issue, in the Jinping II auxiliary tunnels, borehole acoustic wave and digital panoramic borehole imaging tests were conducted at five depths, and the surrounding rock mass structure deterioration was comprehensively quantified at these depths. The results show that the wave curve significantly varies with increasing depth, and the deeper the tunnel section is, the more severe the rock damage is, the larger the excavation damage zone is, and the more complex the generated fracture network is. An excavation-damaged zone and excavation-disturbed zone (EdZ) were found in the rock masses at shallow depths, while a highly damaged zone (HDZ) and EdZ were observed at greater depths. Further investigation demonstrates that the formation pattern of excavation-damaged zones (EDZs) at deep depths follows a stress-concentration controlled mode, and at very shallow depths, horizontal unloading plays a dominant role in the EDZ formation process (yielding a pure unloading-controlled mode), while at intermediate depths, a mixed EDZ formation mode is observed.

2

Effects of CO2 Fumigation and Nitrogen Addition on Soil Respiration in a Wetland Ecosystem : Experimental Approach with Top Open Chambers

Wang J., Fu X., Wang J., Zhong H., Zhang R., Ni H.

Polish Journal of Ecology

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2018

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Vol. 66, nr 2

102--113

EN

Soil respiration plays a crucial role in global carbon cycling of terrestrial ecosystems. Changes in atmospheric CO2 and nitrogen (N) addition across the globe are likely to affect soil respiration. However, the effects of elevated CO2, and N addition on soil respiration are not fully understood especially in wetland ecosystems. To evaluate the effects of atmospheric CO2 and N availability on soil respiration, a paired, nested manipulative in situ experiment was performed, using CO2 fumigation within Open-Top Chambers as the primary factor, and N (as NH4NO3) as the secondary factor in a temperate wetland in northeastern China in 2010 and 2011. CO2 fumigation significantly enhanced soil respiration, according to repeated-measures ANOVA, and the stimulatory effect of CO2 fumigation on soil respiration was sustained during the whole experimental period regardless of N addition. However, the positive soil respiration effect of N addition alone weakened over time. Moreover, there was a significant interaction between CO2 fumigation and N addition. Soil temperature explained 50-66% of the variation in soil respiration. Moreover, soil respiration was positively correlated with the root N content and litter decomposition rate. The results suggested that elevated CO2 concentrations will accelerate soil respiration and ecosystem carbon cycling, thus, limiting soil carbon sequestration, especially when coupled with increasing N deposition.

3

Picea schrenkiana tree-ring chronologies development and vegetation index reconstruction for the Alatau Mountains, Central Asia

Zhang T., Zhang R., Lu B., Mambetov B. T., Kelgenbayev N., Dosmanbetov D., Maisupova B., Chen F., Yu S., Shang H., Huang L.

Geochronometria

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2018

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Vol. 45, no. 1

107--118

EN

In this study, a total of 176 tree cores from Schrenk spruce (Picea schrenkiana) were used to establish a tree-ring chronology and a 167-year July–October normalized differential vegetation index (NDVI) for the Alatau Mountains in Central Asia was reconstructed using this newly developed chronology. The tree-ring based NDVI reconstruction tracks the observed data well (r=0.577, p<0.01, n=25) and precisely captures the drought events recorded in historical documents that occurred over a large area in 1917 and 1938. After applying a 21-year moving average, three dense (1860–1870, 1891–1907, and 1950–1974) and three sparse (1871–1890, 1908–1949, and 1975–2006) vegetation coverage periods were found in this reconstruction. Spatial correlation proves that the reconstructed NDVI series contains climatic signals representative for a large area including southern Kazakhstan. Although a comparison between this reconstruction and four climatic reconstructions for southeastern Kazakhstan, Nilka (in the Ili region), the Issyk Lake, and the Aksu region reveals similar variations, the coherence between these reconstructions become weak with the increase in spatial distance from north to south. In addition to the local representation, it was also demonstrated that the newly developed NDVI index can indicate the large-scale circulations over Eurasia, with the higher NDVI associated with stronger westerly winds from the Atlantic to the Alatau Mountains, and the lower NDVI associated with the weaker winds.

4

A Provably Secure Anonymous Two-Factor Authenticated Key Exchange Protocol for Cloud Computing

Wei F., Zhang R., Ma C

Fundamenta Informaticae

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2018

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Vol. 157, nr 1/2

201--220

EN

Two-factor authenticated key exchange (TFAKE) protocols are critical tools for ensuring identity authentication and secure data transmission for cloud computing. Until now, numerous TFAKE protocols based on smart cards and passwords are proposed under this circumstance. Unfortunately, most of them are found insecure against various attacks. Researchers focus on cryptanalysis of these protocols and then fixing the loopholes. Little attention has been paid to design rationales and formal security models of these protocols. In this paper, we summarize the security requirements and put forward a formal security model for TFAKE protocols for cloud computing. We then present an efficient TFAKE protocol without using expensive asymmetric cryptology mechanisms to achieve high efficiency. Our protocol can be proven secure in the random oracle model and achieves user anonymity. Compared with other TFAKE protocols, our protocol is more efficient and enjoys provable security.

5

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.

6

Preparation of Twinned Dendrites of Al-Zn Alloy with High Zn Content

Gao K., Song W., Fan L., Ding Y., Guo X., Zhang R.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 4

1657--1662

EN

Twinned dendrites in Al-Zn alloy with high Zn content (40% wt.%) were successfully prepared by directional solidification. At different directional solidification rates (1000 and 1500 μm/s), microstructures and growth orientation variations of Al twinned dendrite and non-twinned dendrite were characterized. By using the inverted trapezoidal graphite sleeve at 1000 μm/s, Al twinned dendrite were formed to developed feather crystal structures in longitudinal section. Its primary and secondary twinned dendrite were grew along [110] direction. Moreover the deviation angle between [110] direction of Al twinned dendrite and the heat flow direction was about 27.15°. While not using the inverted trapezoidal graphite sleeve at 1000 and 1500 μm/s, Al dendrite was the non-twinned dendrite and the twinned dendrite was not appeared. The experimental results showed that the higher temperature gradient, a certain pulling rate and convection environment were the formation conditions of twinned dendrites.

7

Some q-rung orthopair linguistic Heronian mean operators with their application to multi-attribute group decision making

Li L., Zhang R., Shang X.

Archives of Control Sciences

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2018

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Vol. 28, No. 4

551--583

EN

The recently proposed q-rung orthopair fuzzy set (q-ROFS) characterized by a membership degree and a non-membership degree is powerful tool for handling uncertainty and vagueness. This paper proposes the concept of q-rung orthopair linguistic set (q-ROLS) by combining the linguistic term sets with q-ROFSs. There after, we investigate multi-attribute group decision making (MAGDM) with q-rung orthopair linguistic information. To aggregate q-rung orthopair linguistic numbers (q-ROLNs), we extend the Heronian mean (HM) to q-ROLSs and propose a family of q-rung orthopair linguistic Heronian mean operators, such as the q-rung orthopair linguistic Heronian mean (q-ROLHM) operator, the q-rung orthopair linguistic weighted Heronian mean (q-ROLWHM) operator, the q-rung orthopair linguistic geometric Heronian mean (q-ROLGHM) operator and the q-rung orthopair linguistic weighted geometric Heronian mean (q-ROLWGHM) operator. Some desirable properties and special cases of the proposed operators are discussed. Further, we develop a novel approach to MAGDM within q-rung orthopair linguistic context based on the proposed operators. A numerical instance is provided to demonstrate the effectiveness and superiorities of the proposed method.

8

Multiresidue determination of antibiotics in preserved eggs using a QuEChERS-based procedure by ultrahigh-performance liquid chromatography tandem mass spectrometry

Li Y., Chen Z., Wen S., Hou X., Zhang R., Ma M.

Acta Chromatographica

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2018

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Vol. 30, no. 1

9--16

EN

A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method and ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) were optimized and validated for 16 antibiotics belonging to three families (macrolides, quinolones, and sulfonamides) that were found in preserved eggs. Samples were extracted in 4 mL water and 10 mL acetonitrile with 1% acetic acid and subjected to a cleanup procedure using dispersive solid-phase extraction with C18 and primary secondary amine sorbents, prior to detection by UHPLC–MS/MS. Matrix-matched calibration was used for quantification to reduce the matrix effect with limits of quantification in the range of 0.3–3.0 μg/kg. Validation of the method was conducted by recovery and precision experiments. Recoveries of the spiked samples ranged from 73.8% to 127.4%, and the intra- and inter-day relative standard deviations were lower than 21.2% and 22.3%, respectively. This method was successfully applied to the analysis of antibiotics in preserved egg samples.

9

Analysis of chloramphenicol in drinking water using an evaporation preparative step and isotope dilution liquid chromatography–tandem mass spectrometry

Li Y., Liu X., Zhang R., ZomPa D., Luo P., Tang L., Liu X., Zhou Y., Wen S.

Acta Chromatographica

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2018

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Vol. 30, no. 1

17--20

EN

A reliable isotope dilution method for the determination of chloramphenicol (CAP) in drinking water was developed by using an evaporation preparative step. Each sample was monitored by ultrahigh-pressure liquid chromatography (UHPLC) coupled to tandem mass spectrometry (MS/MS) using an electrospray ionization interface (ESI) in negative ion modes. Recoveries of spiked samples were in the range from 93.2% to 95.7% with intra-day relative standard deviation lower than 6.7% and inter-day relative standard deviation lower than 8.2%. Limit of quantification (LOD) was 0.002 ng/mL. The developed method was successfully applied to the analysis of CAP in drinking water of Shannan region of Tibet.

10

Multi-AUV distributed task allocation based on the differential evolution quantum bee colony optimization algorithm

Li J., Zhang R.

Polish Maritime Research

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2017

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S 3

65--71

EN

The multi-autonomous underwater vehicle (AUV) distributed task allocation model of a contract net, which introduces an equilibrium coefficient, has been established to solve the multi-AUV distributed task allocation problem. A differential evolution quantum artificial bee colony (DEQABC) optimization algorithm is proposed to solve the multi-AUV optimal task allocation scheme. The algorithm is based on the quantum artificial bee colony algorithm, and it takes advantage of the characteristics of the differential evolution algorithm. This algorithm can remember the individual optimal solution in the population evolution and internal information sharing in groups and obtain the optimal solution through competition and cooperation among individuals in a population. Finally, a simulation experiment was performed to evaluate the distributed task allocation performance of the differential evolution quantum bee colony optimization algorithm. The simulation results demonstrate that the DEQABC algorithm converges faster than the QABC and ABC algorithms in terms of both iterations and running time. The DEQABC algorithm can effectively improve AUV distributed multi-tasking performance.

11

High Efficiency Covering Technology for Covered Yarns Production: Equipment and Experimente

Feng P., Zhang R., Gan J., Yang C.

Fibres & Textiles in Eastern Europe

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2017

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Vol. 25, no. 3 (123)

73--78

EN

A new covering technology for producing covered yarns is proposed in this article. On a traditional yarn covering machine, a hollow spindle rotates with a bobbin of the outer wrapping yarn. In the new equipment, the turntable rotates with only one single outer wrapping yarn. With a magnetic device, the bobbin of core yarns is suspended in a balloon formed by outer wrapping yarns. The rotation speed of the turntable can reach 40000 rpm. A series of experiments on the new equipment were conducted and some covered yarn samples were obtained. The performance of these samples were tested and compared with that produced by traditional machines.

PL

W artykule zaproponowano nową technologię przędzenia z owijaniem. W eksperymentach zastosowano 5 prędkości obrotowych: 12.000, 20.000, 27.000, 32.000 and 35.000 r.p.m. Przy użyciu mikroskopu porównano otrzymane przędze z przędzami otrzymanymi metodą tradycyjną. Stwierdzono, że tradycyjna przędza była bardziej puszysta, a przędza otrzymana nową metodą charakteryzowała się dobrą równomiernością. Po porównaniu dwóch rodzajów przędz stwierdzono, że równomierność skrętu przędzy uzyskanej nową metodą jest wyższa, ponieważ w nowym sposobie przędzenia zastosowano synchroniczny napęd taśmy, co skutkuje mniejszymi wahaniami prędkości obrotowej.

12

Effects on the Stability of the Balloon Shape in the Covered Yarn Process

Feng P., Zhang R., Yang C.

Fibres & Textiles in Eastern Europe

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2017

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Vol. 25, no. 3 (123)

68--72

EN

In the process of producing covered yarn, a single outer wrapping yarn forms a balloon when it rotates at high speed. In this work, we used a mathematical model of a balloon formed by polyamide, which is a common outer wrapping yarn, and verified its feasibility with a group of experimental data. The effects of yarn tension, rotation speed, balloon height and turntable radius on the balloon shape were analysed and the correctness simultaneously demonstrated.

PL

W procesie przędzenia z owijaniem, przędza owijająca obracając się z dużą prędkością tworzy balon. W pracy wykorzystano model matematyczny balonu utworzonego z poliamidowej przędzy owijającej i zweryfikowano jego wykonalność z grupą danych eksperymentalnych. Analizowano wpływ naprężeń przędzy, prędkości obrotowej, wysokości balonu i promienia stołu obrotowego na kształt balonu. Przedstawione wyniki mogą być podstawą do wyboru odpowiednich parametrów i uzyskania optymalnego kształtu balonu.

13

Reliability analysis for multi-state system based on triangular fuzzy variety subset bayesian networks

He Q., Zha Y., Zhang R., Sun Q., Liu T.

Eksploatacja i Niezawodność

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2017

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Vol. 19, no. 2

158--165

PL

W niniejszej pracy zaproponowano nową metodę analizy niezawodności systemów wielostanowych wykorzystującą sieci Bayesa (BN) oparte na rozmytych podzbiorach zmienności opisanych za pomocą trójkątnej funkcji przynależności. Metoda ta uwzględnia rozmyty charakter danych dotyczących uszkodzeń, wielostanowość systemu oraz zmienność prawdopodobieństwa wystąpienia uszkodzenia w czasie. BN, które znalazły zastosowanie w modelowaniu i metodach obliczeniowych, wykorzystuje się także do analizy niezawodności. W przedstawionych badaniach, analizę BN uzupełniono o elementy teorii zbiorów rozmytych wykorzystując do opisu prawdopodobieństwa wystąpienia uszkodzenia, podzbiory zmienności opisane przez trójkątną funkcję przynależności. Niepewność zależności logicznej pomiędzy awariami reprezentowanymi przez różne węzły sieci opisano za pomocą tabel rozmytego prawdopodobieństwa warunkowego. W pierwszej kolejności analizowano prawdopodobieństwo uszkodzenia każdego korzenia (węzła głównego) w funkcji czasu. Następnie, wyznaczono trójkątny rozmyty podzbiór zmienności, za pomocą którego opisano rozmyte prawdopodobieństwo uszkodzenia węzłów głównych. Podzbiór ten wykorzystano do analizy niezawodności systemu wielostanowego przy pomocy rozmytych BN. Artykuł kończy opis wypadku podczas ruchu wózka windy szybkobieżnej, który potwierdza skuteczność i możliwość praktycznego wykorzystania proponowanej metody. Wyniki pokazują, że proponowane podejście może skutecznie rozwiązywać na wczesnym etapie problemy związane z niepewnością informacji oraz wielostanowością systemu.

EN

In this paper, a novel reliability analysis method for multi-state system is proposed on the basis of triangular fuzzy variety subset Bayesian network (BN). The method considers fuzziness, multi-state, and variety of failure probability over time. With advantages in modeling and computation, the BN is utilized for reliability analysis. Fuzzy set theory is introduced into the BN analysis by using triangular fuzzy variety subset to describe failure probability. The uncertainty of fault logical relationship between different nodes is described through fuzzy conditional probability tables. As a function of time, the failure probability of each root node is analyzed first. Subsequently, the triangle fuzzy variety subset is established to describe the fuzzy failure probability of root nodes. This subset is applied to analyze the reliability of multi-state system fuzzy BN. Finally, a case study on the car free movement accident of flexible high-speed elevator lift system is used to demonstrate the effectiveness and practicality of the proposed method. Results show that the proposed approach could effectively address the problems on information uncertainty and multi-state in the early stage.

14

Tree-Ring Response to Snow Cover and Reconstruction of Century annual Maximum Snow Depth for Northern Tianshan Mountains, China

Qin L., Yuan Y., Zhang R., Wei W., Yu S., Fan Z., Chen F., Zhang T., Shang H.

Geochronometria

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2016

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Vol. 43, no. 1

9--17

EN

Heavy snowfall and extreme snow depth cause serious losses of human life and property in the northern Tianshan Mountains almost every winter. Snow cover is an important indicator of climate change. In this study, we developed five tree-ring-width chronologies of Schrenk spruce (Picea schrenkiana Fisch. et Mey) from the northern Tianshan Mountains using standard dendrochronological methods. Correlation analyses indicated that radial growth of trees in the northern Tianshan Mountains is positively affected by annual maximum snow depth. This relationship was validated and models of annual maximum snow depth back to the 18th century were developed. The reconstruction explains 48.3% of the variance in the instrumental temperature records during the 1958/59–2003/04 calibration periods. It indicates that quasi-periodic changes exist on 2.0–4.0-yr, 5.3-yr, 14.0-yr, and 36.0-yr scales. The reconstructed series shows that maximum snow depth exhibits obvious stages change, the periods characterized by lower maximum snow depth were 1809/10–1840/41, 1873/74– 1893/94, 1909/10–1929/30, 1964/65–1981/82, and the periods characterized by higher maximum snow depth were 1841/42–1872/73, 1894/95–1908/09, 1930/31–1963/64, and 1982/83–present. The lower period of annual maximum snow depth during the 1920s–1930s is consistent with the severe drought that occurred at this time in northern China. From the 1970s to the present, the maximum snow depth has increased clearly with the change to a warmer and wetter climate in Xinjiang. The reconstruction sheds new light on snow cover variability and change in a region where the climate history for the past several centuries is poorly understood.

15

Method of Structure Design and Heat Treatment of an Integrated Consolidation Sensor and Embedded Temperature Sensing Fabric

Zhang R., Deng N., Cheng B., Zhang R., Wu Y.

Fibres & Textiles in Eastern Europe

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2016

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Vol. 24, no. 5 (119)

68--72

EN

In order to solve the problem of temperature sensors easily slipping and improve the precision of temperature measurement in temperature sensing fabric, a specially designed fabric was developed. In this paper, the fabric comprised plain and multi-layered fabric. Sensors were embedded into the multi-layered fabric. The multi-layered fabric was treated by partial heat treatment to make the temperature sensors be fixed to the fabric. The temperature sensing fabrics were measured before and after the partial heat treatment. The results showed that during the heat treatment, the number of fabric layers and fabric organization had an effect on temperature measurement, and the values measured after partial heat treatment were closer to the true value than without treatment. In addition, with an increase in the number of fabric layesr, the values measured were closer to the real value. And the measurement results were closer to the true value when the multi-layered fabric’s organizational structure was plain.

PL

Dla uzyskania hybrydowego elementu pomiarowego opracowano taką strukturę tkaniny aby móc umieścić w niej czujniki temperatury. Wielowarstwową tkaninę poddano odpowiedniej obróbce termicznej umożliwiającej zamocowanie czujników w tkaninie. Stwierdzono, że ilość warstw tkaniny i ich rozmieszczenie ma wyraźny wpływ na uzyskiwaną dokładność pomiaru temperatury. Przy zwiększeniu ilości warstw wzrastała dokładność pomiaru.

16

Mathematical Model of Embedded Temperature Sensing Fabric Heat Transmission

Zhang R., Deng N., Cheng B., Zhang S., Wu Y.

Fibres & Textiles in Eastern Europe

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2016

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Vol. 24, no. 5 (119)

73--79

EN

In order to explore effect factors in the measurement of temperature sensing fabric, a heat transmission mathematical model of temperature sensing fabric was established. The concept of surface contact thermal resistance associated with the material thermal conductivity, fabric layer number and yarn linear density between the fabric and sensor was proposed in the model, whose surface contact thermal resistance was produced in the process of fabric heat transmission. Some test samples were woven to prove the rationality of the model. The results demonstrated that the value measured would be influenced by the performances of surface contact thermal resistance, which was consistent with the derivation of the theoretical model. The raw material, fabric layer number and yarn linear density of temperature sensing fabric had a great effect on the measurement value. The correlation coefficient reached more than 0.988 among the experimental and theoretical values, respectively, which proved that the heat transmission mathematical model of temperature sensing fabric could be applied in the research of this fabric.

PL

Opracowano matematyczny model przepływu ciepła przez tkaninę zawierającą wbudowane czujniki temperatury w celu określenia wpływu poszczególnych czynników na przebieg pomiarów. Brano pod uwagę oporność termiczną styku czujników z tkaniną związaną z przewodnością termiczną materiału, ilość warstw i masę liniową przędz w obrębie tkaniny i czujników. Uzyskane współczynniki korelacji pomiędzy wartościami eksperymentalnymi i teoretycznymi przekraczały 0,988 co potwierdza, że opracowany przez nas matematyczny model przepływu ciepła w tkaninie pomiarowej można zastosować w tego typu badaniach.

17

Direct synthesis of dimethyl carbonate and propylene glycol using potassium bicarbonate as catalyst in supercritical CO2

Wen Y., Zhang R., Cang Y., Zhang J., Liu L., Guo X., Fan B.

Polish Journal of Chemical Technology

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2015

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Vol. 17, nr 1

62--65

EN

The improved one-pot synthesis of dimethyl carbonate and propylene glycol from propylene oxide, supercritical carbon dioxide, and methanol with potassium bicarbonate as the catalyst has been reported in this paper. As far as we know, it is the first time to use potassium bicarbonate only as the catalyst in the production process which is simple and cheap. Satisfactory conversion rate of propylene oxide and yield of the products could be achieved at the optimized conditions with quite a small amount of by-products. Our new method offers an attractive choice for the production of dimethyl carbonate in large-scale industry efficiently and environmental friendly.

18

Graphene synthesis: a Review

Shams S. S., Zhang R., Zhu J.

Materials Science Poland

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2015

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Vol. 33, No. 3

566--578

EN

Graphene has achieved a great amount of popularity and interest from the science world because of its extraordinary physical, mechanical and thermal properties. Graphene is an allotrope of carbon, having one-atom-thick planar sheets of sp2 bonded carbon atoms densely packed in a honeycomb crystal lattice. Many methods to synthesize graphene have been developed over a short period and we believe it is necessary to create a list of the most notable approaches. This article focuses on the methods to synthesize graphene in an attempt to summarize and document advancements in the synthesis of graphene research and future prospects.

19

Experimental investigation of gas degradation by methanotrophs at different air flow-rates

Yu H., Feng T., Zhang R., Liu J.

Journal of Power Technologies

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2015

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Vol. 95, nr 2

112--118

EN

A technical approach based on microbial technology is proposed to help resolve the problems caused by explosive gases in coal mines. The proposed technique uses methanotrophic bacteria to oxidize methane. In laboratory experiments, the oxidation effect of hanging nets impregnated with liquid containing methanotrophic bacteria was investigated at different air flow-rates. The experimental results showed that the volume of gas degraded and the gradient of degradation both increased as the gas concentration increased at constant air flow-rates. At fixed gas concentrations, the volume of degraded gas increased with increasing flow-rates of air at low flow-rates. However, the volume of degraded gas slightly decreased with increasing flow-rates of air at high flow-rates. These experimental results provide a theoretical basis for the treatment of explosive gases during exploration for natural gas and to treat potentially dangerous concentrations of gas in gobs, caves and upper corners of mineshafts. They will also be of great practical significance in coal mining.

20

Predicted Crystal Structures, Analysis, Impact Sensitivities and Morphology of Solid High-Energy Complexes: Alkaline-Earth Carbohydrazide Perchlorates

Liu Y., Zhang R., Feng C.-G., Yang L., Zhang T.-L.

Central European Journal of Energetic Materials

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2015

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Vol. 12, no. 2

229--248

EN

The crystal structures, density of states, energy gap, thermodynamic properties, impact sensitivities and morphology of beryllium carbohydrazide perchlorate ([Be(CHZ)3](ClO4)2), magnesium carbohydrazide perchlorate ([Mg(CHZ)3](ClO4)2), calcium carbohydrazide perchlorate ([Ca(CHZ)3] (ClO4)2), strontium carbohydrazide perchlorate ([Sr(CHZ)3](ClO4)2) and barium carbohydrazide perchlorate ([Ba(CHZ)3](ClO4)2) were investigated using the density functional theory (DFT) and crystal morphology theory. The results show that all of the complexes have six-coordinated distorted octahedra, which is different from previous works. This was rationalised by consideration of the intermolecular interactions in the crystal structures. Hence the crystal structure is now more reliable. The chemical reactions of the whole molecule may be triggered by an electron transition of CHZ or ClO4 −. Furthermore the energy gaps were observed, and the values of the impact sensitivities were inferred to have the following sequence: [Be(CHZ)3](ClO4)2 > [Mg(CHZ)3](ClO4)2 > [Sr(CHZ)3](ClO4)2 > [Ca(CHZ)3](ClO4)2 > [Ba(CHZ)3](ClO4)2. In addition, the thermodynamic equations at 25-1000 K were obtained. The positive values of the standard molar free enthalpies shows that carbohydrazide perchlorates are stable at 298.15 K. The (1 0 -1) and (0 0 2) faces are the most important growth directions of the crystal morphologies, and have the minimum growth rates. From the cleaved main growth faces, it can be deduced that surface active agents with active hydrogen atoms in the functional groups could be used as crystal-control reagents to control the crystal morphology for alkaline-earth carbohydrazide perchlorates.