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1

Numerical Study of Extra-Large Parachute’s Pre-Inflation in Finite Mass Situation

Sun Z., Cheng H., Yang J.

Autex Research Journal

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2018

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Vol. 18, no. 2

130--136

EN

The extra-large parachutes were different from the common parachutes because of their size and opening process. Some undesirable inflation phenomena such as canopy winding and whipping usually appeared in their pre-inflation process. However, the mechanical mechanism of these phenomena was very difficult to be explained by experimental means. In this paper, the pre-inflation process in finite mass situation of an extra-large parachute was calculated by explicit finite elements. According to the results, the pre-inflation process can be subdivided into symmetric inflation stage, undesirable inflation stage, and stable inflation stage. The canopy winding and whipping mainly occurred in the second stage. With the continuous deceleration of parachute-payload system, the top of canopy without effective constraints would appear winding and whipping under the function of inertia force. The canopy winding and whipping increased the difficulty of canopy expanding and then caused asymmetric inflation. The above undesirable phenomena had a great influence on the deceleration effect and were easy to cause the recovery failure. The actual airdrop experiments also proved that the lack of effective constraints on the canopy top will cause undesirable inflation phenomena. The conclusions in this paper can also provide a reference for extra-large parachute design and research.

2

The effects of litter layer and soil properties on the soil-atmosphere fluxes of greenhouse gases in karst forest, Southwest China

Cheng J., Lee X., Zhou Z., Wang B., Xing Y., Cheng H., Tang Y.

Polish Journal of Ecology

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2013

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Vol. 61, nr 1

79--92

EN

Temporal variation is a major source of the uncertainty in estimating the fluxes of the greenhouse gases (GHGs) in terrestrial ecosystems, and the GHG fluxes and its affecting factors in the karst region of southwest China remains weakly understood. Using the static chamber technique and gas chromatography method, the CO2, CH4 and N2O fluxes were carried out between 9 and 11 a.m. at 15 day intervals from June 2008 to May 2009 in a Pinus massoniana forest. Two treatments were chosen for this study: undisturbed (soil with litter layer) and disturbed (surface litter removal). Both treatments were found to be the net source of atmospheric CO2 and N2O, but a sink of atmospheric CH4. The seasonality of soil CO2 emission coincided with the seasonal climate pattern, with high CO2 emission rates in the hot-wet season and low rates in the cool-dry season. In contrast, seasonal patterns of CH4 and N2O fluxes were not clear, although higher CH4 uptake rates were often observed in autumn and higher N2O emission rates were often observed in spring (dry-wet season transition). The litter was active in GHG fluxes, and removal of the litter layer reduced soil CO2 emission (17%) and increased CH4 uptake (24%) whereas N2O fluxes were not affected distinctly in the pine forest, indicating that litter layer had an important effect on C exchanges. In the pine forest, soil CO2 emissions and CH4 uptakes correlated significantly with soil temperature (r2 = 0.87, P <0.01; r2 = 0.34, P <0.05, respectively), but had no significant relationship with soil moisture. And there was a significant correlation between CH4 flux and NH4+-N (r2 = 0.39, P < 0.05) and soil inorganic N (r2 = 0.48, P <0.05), but no significant correlation was found between CH4 flux and NO3--N. Moreover, we found a significant negative logarithmic correlation between N2O flux and soil NO3--N concentration (r2 = 0.41, P <0.05), and the relationship between CO2 emission and soil inorganic N content (r2 = 0.35, P < 0.05). These results suggested that soil temperature and mineral N dynamics largely affected the temporal GHG exchanges between forest soil and atmosphere.

3

Monsoon-driven Dynamics of water quality by multivariate statistical methods in Daya Bay, South China Sea

Wu M-L., Wang Y-S., Sun C-C., Sun F-L., Cheng H., Wang Y-T., Dong J-D., Wu J.

Oceanological and Hydrobiological Studies

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2012

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Vol. 41, No. 4

66-76

EN

Eleven physicochemical parameters of data collected from 12 stations in Daya Bay in 2003 were analyzed by multivariate statistical analysis. Cluster analysis (CA) grouped data from 4 seasons into two groups, the northeast and southwest monsoon periods, representing different natural processes. During the northeast monsoon period, principal component analysis (PCA) and CA group the 12 monitoring sites into Cluster DA1 (S1, S2 and S6) and Cluster DA2 (S3-S5 and S7-S12). During the southwest monsoon period, PCA and CA group the 12 monitoring sites into Cluster WB1 (S1, S2, S7, S9 and S11) and Cluster WB2 (S3-S6, S8, S10, S11 and S12). The spatial heterogeneity within the bay was defined by different hydrodynamic conditions and human activities. These results may be valuable for achieving sustainable use of the coastal ecosystems in Daya Bay.

4

The experimental study on inner shift lining structure of freezing shaft in deep thick aquiferous soft rock

Yao Z. S., Song H. Q., Cheng H., Rong C. X.

AGH Journal of Mining and Geoengineering

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2012

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Vol. 36, no. 3

463-470

EN

Aimed at the supporting problems of inner shift lining of freezing shaft in the deep thick aquiferous soft rock of the west area in China, the mechanical characteristic of inner shaft is systematically studied by model test and theory analysis. First, the model of high strength reinforced concrete is designed and the test pieces are manufactured according to a similarity theory. Then, through loading test, the stress, strain and strength characteristics of this shaft lining structure are gained. The results indicate that the structure of high strength reinforced concrete shaft lining is under tri-axial compressive stresses states, the distortion is evidently restricted and the concrete compressive strength in the shaft lining structure increases 1.562-1.859 times than the monomial compressive strength, the actual carrying capacity is highly increased, and the concrete utmost compressive strain reached -3500 micro/eta. The shaft lining is fairly plastic when it was damaged. Then a formula for calculating the shaft lining's ultimate bearing capacity is given on the basis of the theoretical research and experimental results. Thus, the studied results can provide a reference for the theory study and engineering application of this shaft lining structure.

PL

Mając na uwadze problemy dotyczące przesunięcia wewnętrznego obudowy w szybach głębionych metodą zamrażania w wodonośnych skałach miękkich na dużej głębokości występujących w zachodnim rejonie Chin, wykonywane są systematyczne badania parametrów przesunięcia wewnętrznego obudowy przy użyciu testów modelowych i analizy teoretycznej. Badanie wymaga wykonania modelu z wytrzymałego żelbetu i elementów testowych zgodnie z teorią podobieństwa. Następnie przeprowadzany jest test obciążenia dla uzyskania charakterystyki naprężeń, odkształceń i wytrzymałości konstrukcji obudowy przesunięcia. Wyniki pokazują działanie naprężeń trójosiowych na ściskaną konstrukcję obudowy z wytrzymałego żelbetu, znaczne zmniejszenie zniekształceń, zwiększenie wytrzymałości betonu na ściskanie w strukturze obudowy 1,562-1,859-krotnie w stosunku do wartości jednomianowej, poprawę nośności rzeczywistej oraz wartość maksymalną wytrzymałości betonu na ściskanie - 3500 micro/eta. Po uszkodzeniu obudowa jest dość plastyczna. Następnie opracowywany jest wzór na obliczenie maksymalnej nośności obudowy na podstawie wyników badań teoretycznych i eksperymentalnych. Wyniki mogą zapewnić odniesienie dla badań teoretycznych i zastosowań technicznych konstrukcji obudowy przesunięcia wewnętrznego.

5

A study of the gas specificity of porous silicon sensors for organic vapours

Choi S. H., Cheng H., Park S. H., Kim H. J., Kim Y. Y., Lee K. W.

Materials Science Poland

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2009

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Vol. 27, No. 2

603--610

EN

A porous silicon sensor was investigated as a means to determine the response specificity for organic vapours. Porous silicon layers were fabricated by electrochemical anodization of p-type crystalline silicon in an HF ethanol solution under various conditions. The porous silicon sensors were placed in a gas chamber with various organic vapours, and the changes in electrical resistance under constant voltage of each sensor were used as detection signals. The sensors recorded various changes in resistivity for various organic vapours.

6

Planned Route Based Negotiation for Collision Avoidance Between Vessels

Hu Q., Yang C., Cheng H., Xiao B.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2008

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Vol. 2, no. 4

363--368

EN

Automatic vessel collision-avoidance systems have been studied in the fields of artificial intelligence and navigation for decades. And to facilitate automatic collision-avoidance decision-making in two-vessel-encounter situation, several expert and fuzzy expert systems have been developed. However, none of them can negotiate with each other as seafarers usually do when they intend to make a harmonious and more economic overall plan of collision avoidance in the COLREGS-COST-HIGH situations where collision avoidance following the International Regulations for Preventing Collisions at Sea(COLREGS) costs too much. A negotiation framework was put forward in our previous research to enable vessels to negotiate for optimizing collision avoidance in the COLREGS-COST-HIGH situations at open sea. In this paper, the negotiation framework is improved by considering the planned route of both vessels. The simulation results show that more economic overall plan of collision avoidance may be achieved by the improved framework when one or both parties deviate from their planed route or are approaching their next way points.