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1

The Microstructural Evolution in HMX Based Plastic-bonded Explosive During Heating and Cooling Process: an in situ Small-angle Scattering Study

Yan G., Tian Q., Liu J., Fan Z., Sun G., Zhang C., Wang Y., Chen B., Gong J., Zhou X., Yang Z., Nie F., Li J., Li X.

Central European Journal of Energetic Materials

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2016

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Vol. 13, no. 4

916--926

EN

The thermal damage in octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) based plastic-bonded explosive (PBX) was investigated using in situ small-angle neutron and X-ray scattering techniques. The microstructural evolution was quantitatively characterized by the model fitting parameters of total interfacial surface area (Sv) and void volume distribution. The Sv of HMX-PBX decreased markedly above 100 °C, indicating the movement of binder into the voids. After subsequent cooling to room temperature, the scattering intensity increased significantly with increasing storage time, and a new population of voids with average diameter of 20 nm was observed, accompanied by the gradual phase transition of HMX from δ- to β-phase. The experimental results implied that serious damage within the HMX-PBX was developed during storage after heating.

2

The American Lawn Revisited: Awareness Education and Culture as Public Policies Toward Sustainable Lawn

Zhang Y., Zheng B., Sun G., Fan P.

Problemy Ekorozwoju

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2015

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Vol. 10, nr 1

107--115

EN

Lawn has been used for landscaping, gardening, and beautification of homes and cities for a long time. The evolution of the lawn reflects important cultural and biophysical interactions between humans and nature. The American lawn, which was from Europe and has been a part of the American dream for home ownership and culture, has become an area going against nature for its extensively using chemicals and generated pollutions. Tracing how the lawn is becoming an important part of culture, this article focuses on more recent pollution and other environmental problems resulted from the lawn culture. It is argued, that awareness, education and changing culture of taste and preference can serve additional measures together with law and technological advancement toward sustainable lawn in the United States and the world.

PL

Trawnik już o dawna był używany w kształtowaniu krajobrazu, ogrodnictwie i upiększaniu domów. Ewolucja trawników odzwierciedla istotne kulturowe i biofizyczne interakcje pomiędzy ludźmi i przyrodą. Trawnik trafił do Ameryki z Europy i stał się częścią amerykańskiego snu o własności i kulturze domu. Później stał się on jednak obszarem przeciwstawiającym się naturze z uwagi na intensywnie stosowanie substancji chemicznych i generowanie zanieczyszczeń. Wykazując, w jaki sposób trawnik staje się ważną częścią kultury, ten artykuł skupia się na bardziej aktualnych kwestiach zanieczyszczeń i innych problemów środowiskowych. Wykształcenie świadomości, zmieniającą się kultura smaku i preferencje, łącznie z prawem i technologią, mogą stanowić dodatkowe środki prowadzące w kierunku zrównoważonego kształtowania trawników w Stanach Zjednoczonych i na świecie.

3

Higher Order Nonlinearity of Niho Functions

Sun G., Wu C.

Fundamenta Informaticae

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2015

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Vol. 137, nr 3

403--412

EN

The r-th order nonlinearity of Boolean functions is an important cryptographic criterion associated with some attacks on stream and block ciphers. It is also very useful in coding theory, since it is related to the covering radii of Reed-Muller codes. In this paper we investigate the lower bound of the higher-order nonlinearity of Niho Boolean functions f(x) = tr(λxd) over F2n, where... [formula]

4

Thermally induced damage in hexanitrohexaazaisowurtzitane

Tian Q., Yan G., Sun G., Huang C., Xie L., Chen B., Huang M., Li H., Liu X., Wang J.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 3

359--369

EN

The evolution of the microstructure of hexanitrohexaazaisowurtzitane (CL-20) after a thermal stimulus plays a key role in the performance of CL-20. In the current work, microstructural variations of CL-20 caused by thermal treatment were investigated by X-ray diffraction, in situ variable-temperature optical microscopy, atom force microscopy, and small-angle X-ray scattering. A wave-like process, an abrupt volume expansion, movement, and fragmentation of CL-20 particles during phase transition were observed. After the phase transition (160 °C) the CL-20 sample acquired a very rough surface with numerous dimple depressions, and during the thermal decomposition stage (200 °C) a large number of voids were produced in both the bulk and the surface of the CL-20.

5

Study on Adaptive Threshold Segmentation Method Based on Brightness

Zhao D., Dai X., Sun G., Lu T.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 9b

150-152

EN

Image segmentation is one of the most important steps before the image data analysis, which divided the image into several areas that have strong similarity. With the more and more widely application of the mesh fabric, the quality requirements are more stringent. As the impact of uneven illumination, the image brightness is inconsistent, which bring a great difficulty to the image segmentation of the mesh fabric. In order to eliminate the effect of uneven illumination in the image acquisition of linear CCD camera, the adaptive threshold segmentation method based on brightness is proposed. Compared with the Otsu method, it is better to eliminate the influence of the uneven illumination and provide a good foundation for subsequent data analysis.

PL

Analizowano system segmentacji obrazu polegający na podziale obrazu na obszary o dużym podobieństwie. Przy nierównym naświetleniu powstaje problem segmentacji. Zaproponowano adaptacyjny system progowej segmentacji bazujący na analizie jasności.

6

Multichannel comb filter based on linearly chirped fiber Bragg grating and DC phase shift

Sun G., Wang R., Pu Tao, Wang Hongbo, Wei Zhihu

Optica Applicata

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2011

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Vol. 41, nr 4

791--797

EN

A novel approach to implement high channel-count comb filters based on a DC phase shift is proposed. Various channel spacings can be achieved by a single chirped phase mask and a submicrometer-precision translation stage. Simulation and experiment show that arbitrary phase shifts introduced by DC refractive index modulation can be achieved. An multichannel comb filter with channel spacing of 100 GHz, 50 GHz and 40 GHz is implemented with the same phase mask. A comparison between the proposed DC phase shift and traditional discrete phase shift is made.

7

Contribution of the vegetation layers in the nitrous oxide emission from alpine Kobresia humilis Serg. meadow ecosystem on the Tibetan Plateau

Du Y., Cao G., Deng Y., Sun G., Cui X.

Polish Journal of Ecology

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2010

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Vol. 58, nr 1

115-124

EN

Nitrous oxide (N[2]O) was one of the major atmospheric greenhouse gases. Its budget was poorly understood in alpine meadow, a dominant vegetation type on the Tibetan Plateau. To characterize a Kobresia humilis meadow on the plateau, N[2]O emission rates were monitored from June 2003 to June 2006 in the study area located at 3280 m a.s.l. Nine plots with 1 m x 1 m each were divided into three treatments, i.e. intact herbaceous community (HCK), removal of aboveground plant biomass (CBK), and removal of both above and belowground plant biomass (BSK), to estimate contribution of plants, r hizosphere and bulk soil to the total N[2]O emission. N[2]O emission from plant aboveground biomass was calculated by flux difference between HCK and CBK, denoted as F[(HCK-CBK)], from rhizosphere by F[(CBK-BSK)], and from bulk soil was the flux in BSK treatment. Static chambers (height 50 cm, area 0.5 x 0.5 m2 )were used for gas collection. N[2]O emission rate was significantly correlated with soil temperature at 5 cm depth in both HCK and BSK (P <0.001). Both treatments demonstrated a seasonal peak rate in growing season and minimum rate in dormancy period. The mean emission rates in the three years were 39.7[plus or minus]2.9 and 30.6[plus or minus]2.5 [mu]g m[^-2] h[^-1] in HCK and BSK, respectively, with the former significantly higher than the latter (P <0.05). In CBK, however, the emission rate did not show consistent correlation with soil temperature, especially in growing season. Its three-year mean emission rate was 36.2[plus or minus]3.3 [mu]g m[^-2] h[^-1]. In the K. humilis meadow, bulk soil contributed much more than plants and rhizosphere. The mean emission rate was 3.5[plus or minus]2.9, 5.7[plus or minus]3.8, and 30.6[plus or minus]2.5 [mu]g m[^-2] h[^-1] (P <0.001) from plants, rhizosphere and bulk soil, and these accounted for 9, 14 and 77%, separately. Our results implied that N[2]O emission rate decreased little with grazing as indicated by the difference between HCK and CBK in K. humilis meadow (P <0.05). N2O emission from alpine meadow could not be ignored in addressing regional greenhouse gases budget on the Tibetan Plateau, considering the vast area and much higher radiative forcing of N[2]O.

8

The effect of habitat on methane emission from an alpine wetland

Chen H., Wu N., Gao Y., Yao S., Wang Y., Tian J., Sun G., Yuan X.

Polish Journal of Ecology

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2009

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Vol. 57, nr 2

377-381

EN

Alpine wetland is a source for methane (CH[4]), an important greenhouse gas, but little is known about how this habitat influences the emission. To understand this wetland habitats were selected at the altitude of 3430 m a.s.l. (in National Wetland Nature Reserve of Zoige, Quingle - Tibetan Plateau) and the methane flux was measured with static chambers in three different sites, including hollows with Carex muliensis Hand - Mazz. and Eleocharis valleculosa Ohwi f. setosa (Ohwi) Kitagawa., grass hummocks composed of Kobresia tibetica Maxim, Cremanthodium pleurocaule R. D. Good, Potentilla bifurca L. and Pedicularis sp. We have found that in alpine wetland these habitats significantly affect CH[4] emissions in the onset (April, 2006) and peak (August, 2005) stages of growing season. Hollows covered with Carex muliensis and Eleocharis valleculosa had higher values of emission than grass hummocks built by several grass species. Slight difference of CH[4] emission was found between two kinds of hollows with Carex muliensis and Eleocharis valleculosa. These results were consistent with the change of water table, which was found best correlated with CH4 emissions (r[^2] = 0.43, P <0.01) in the peak stage of growing season. Directly measured shoot biomass and plant heights were best related to CH[4] emissions (r[^2] = 0.59, P <0.01). However, in the onset stage of growing season, variation of CH[4] emission may not be simply ascribed to changes in water table and vegetation structure.

9

Non-stoichiometric boron carbide synthesized in moderate temperature conditions

Sun G., Li Y. W., Hu Q. K., Wu Q. H., Yu D. L.

Materials Science Poland

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2009

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Vol. 27, No. 4/1

1033--1039

EN

Non-stoichiometric boron carbide was successfully synthesized through a chemical synthetic route by using tribromide and carbon tetrachloride as reactants and metal sodium as co-reductant at 700 °C. The synthesized sample was characterized by X-ray powder diffraction, transmission selected area electron diffraction, electronic energy loss spectra (EELS) and scanning electron microscopy. The results of the analysis revealed that the synthesized boron carbide crystals have rhombohedral structure and equiaxial morphology. Results of the EELS analysis indicate that the compositions of the synthesized boron carbide are not uniform, the carbon content can range from 9 at. % to 11 at. %.