一枚拉火环(微型小说)

军荣的脖子上挂着一枚拉火环。这枚拉火环是卫国送给她的定情物。那还是卫国第一次探家时,她闭上眼睛,让卫国将一个凉丝丝的东西挂到了她的脖子上,卫国告诉她,那是一枚“真枪实弹”的拉火环,探家前一天刚刚爆炸过,立刻她的胸口就热了。卫国还告诉她,他们连队是抗美援朝英雄连,战士们个个都是神枪手,甩的都是真家伙,不信你闻闻,一闻果然还有火药香味。第一次探家后,她与卫国正式确立了恋爱关系。

Gate Annealing of an Enhancement-Mode InGaP/AlGaAs/InGaAs PHEMT

For enhancement-mode InGaP/A1GaAs/InGaAs PHEMTs,gate annealing is conducted between gate structures of Ti/Pt/Au and Pt/Ti/Pt/Au. Comparison is made after thermal annealing and an optimum annealing process is ob- tained. Using the structure of Ti/Pt/Au, about a 200mV positive shift of threshold voltage is achieved by thermal annea- ling at 320℃ for 40min in N2 ambient. Finally, a stable and consistent enhancement-mode PHEMT is produced successfully with higher threshold voltage.

神山即火山

自公元前4世纪起,海外神山已令许多君主神往.今人认为神山如同欧洲中世纪的福地,并归诸乌托邦.学术界特别是科技史界迄未对之正视.已有见解多关心它们究竟在哪里,欠考虑它们究竟是什么.笔者注意到先民的万物有灵观念,及其自然崇拜中表现出的神化倾向,遂根据文献、历史、地理及民族心理等方面的依据,综列旧说,提出新见,从火山学角度论证了神山即火山.

21世纪:网军如何作战

纵观２０世纪的历次战争，军事学家们总结出了一条“铁律”──打仗就是打装备。世纪之初的“英布”战争期间，枪支是士兵的“第二生命”；“一战”时期，坦克、飞机是战场上的新式武器，谁拥有性能优良的坦克、飞机，谁就是常胜将军；“二战”时期，美国在广岛、长崎扔下了两颗原子弹，才最终结束了这场“世纪浩动”；网络时代，没有信息技术、网络技术作支撑，传统的飞机、坦克就是一堆堆废铜烂铁。未来的网络战虽然还不可能产生机器人“终结者”那样无与伦比的武器，但是２１世纪的“军中骄子”──网军将有传统铁甲所不可比拟的全新的“软”装备。与武器装备的更新换代相适应，未来网军的作战样式、作战理念也必然发生“革命”。

Optical investigations on lean combustion improvement of natural gas engines via turbulence enhancement

In the global background of“Carbon Peak”and“Carbon Neutral”,natural gas engines show great advantages in energy-saving and pollution reduction.However,natural gas engines suffer from the issues of combustion instabilities when operating under lean burning conditions.In this paper,the role of turbulence enhancement in improving the lean combustion of natural gas was investigated in an optical SI engine with high compression ratios.Variable swirl control valves(SCV)were designed and intake tumble and swirl were combined to regulate turbulent motion and turbulent intensity.Particle image velocimetry was employed to measure in-cylinder turbulence,and transient pressure acquisition and high-speed photography were synchronously performed to quantify combustion evolutions.The results show that incylinder turbulent intensity is enhanced significantly through reducing SCV closing angles.Such that flame propagation speed and thermal efficiency are significantly improved with an increment of turbulent intensity,which indicated that mean effective pressures are not sensitive to spark timing.The analysis of flame images shows that the combined turbulence increases in the radial orientation from the spark plug to the cylinder wall,leading to an earlier flame kernel formation and a faster burning rate.Therefore,the combined turbulence has the potential in reducing the cyclic variations of lean combustion in natural gas engines.

Episodes of volcanic activity and their environmental effects in the Okinawa Trough during the last 150 ka

A piston core Z14-6 was used in this study. The core, 896 cm long, was collected from eastern slope of the Okinawa Trough （27°07＇N, 127°27＇E, water depth 739m）. The δ^18O and δ^13C values of the sediment bearing planktonic foraminifera G. sacculifer and N. dutertrei were determined; and the abundance of volcanic glass was analyzed. The volcanic glass content high occurred in early stage of polar ice-sheet growth period, or the beginning of cold climate periods corresponding to Milankovitch cycles （Peak Ⅰ, Ⅱ and V are corresponding to the beginnings of oxygen isotopic stages 2, 4 and 6, and Peak Ⅲ and Ⅳ are matching oxygen isotopic stage 5b-5d.）. It might be possible that volcanic episodes and climate changes were responding to orbital forcing in the Okinawa Trough in late Quaternary. The δ^18O difference between N. dutertrei and G. sacculifer shows no clear correlation to the volcanic glass content high, which suggests that the volcanic eruptions did not influence the structure of upper water column. However, the low δ^13C difference between G. sacculifer and N. dutertrei is coeval with the volcanic glass high or sub-high content. This fact suggests that volcanic eruptions might influence the reduction in vertical nutritional gradient and carbon cycle process in upper water column. A possible mechanism is that huge quantity of ash and dust had weakened the light intensity, resulting in photosynthesis reduction, productivity decrease, and biological pumping.

Understory vascular plant community assembly in relation to time-since-fire and environmental variables in a Chinese boreal forest

Understanding the response of understory vegetation to fire disturbance is vital to biodiversity conservation and management of boreal forests. We surveyed understory vascular plant richness and composition, and measured related environmental variables along a toposequence within three successional stages, initial （3 years post-fire）, early （13 years post-fire） and late （〉1oo years post-fire） successional stages. Using permutation multivariate ANOVA and nonmetric multidimensional scaling, we analyzed how understory species richness and composition change as time-since-fire proceeds, and their correlative relationships with environmental variables. Species richness and composition showed significant differences among the three successional stages. Understory species richness and abundance were significantly associated with time-since-fire, topographic position, elevation and organic layer depth. Among these variables, time-since-fire had the strongest effect and topographic position was the second major factor on affecting understorycommunity assembly. In overwhelmed the effects addition, time-since-fire of soil pH in the initial successional stage and gravimetric soil moisture in early and late successional stages on understory species composition

Effects of fire disturbance on forest hydrology

Fire is quite a common natural phenomenon closely related to forest hydrology in forest ecosystem. The influence of fire on water is indirectly manifested in that the post fire changes of vegetation, ground cover, soil and environment affect water cycle, water quality and aquatic lives. The effect varies depending upon fire severity and frequency. Light wildland fires or prescribed burnings do not affect hydrology regime significantly but frequent burnings or intense fires can cause changes in hydrology regime similar to that caused clear cutting.

Polycyclic aromatic hydrocarbon formation under simulated coal seam pyrolysis conditions

Coal seam pyrolysis occurs during coal seam fires and during underground coal gasification. This is an important source of polycyclic aromatic hydrocarbon （PAH） emission in China. Pyrolysis in a coal seam was simulated in a tubular furnace. The 16 US Environmental Protection Agency priority controlled PAHs were analyzed by HPLC. The effects of temperature, heating rate, pyrolysis atmosphere, and coal size were investigated. The results indicate that the 3-ring PAHs AcP and AcPy are the main species in the pyrolysis gas. The 2-ring NaP and the 4-ring Pyr are also of concern. Increasing temperature caused the total PAH yield to go through a minimum. The lowest value was obtained at the temperature of 600℃. Higher heating rates promote PAH formation, especially formation of the lower molecular weight PAHs. The typical heating rate in a coal seam, 5 ℃/min, results in intermediate yields of PAHs. The total PAHs yield in an atmosphere of N2 is about 1.81 times that seen without added N2, which indicates that an air flow through the coal seam accelerates the formation of PAHs. An increase in coal particle size reduces the total PAHs emission but promotes the formation of 5- and f-ring PAHs.

Coal fires in China

Coal fires have a very long history in China; the oldest coal fires have being burning for many million years. Up to now more than 56 coal fires spots were distin-guished. They mainly locate in West-North of China, North of China and East-North of China. About millions of tons of coal have been burned in fires every year. Xinjiang Autonomy is the most serious region in coal fires as it has 38 coal fires spots and about 6.85 million tons of coal was burned every year. Coal fires in China ignited by wildfires, spontaneous combustion and human being during mining activities. These fires have re-leased about 0.9 million tons of gasses (including CO, CO2, SO2, NO2 CH4, CO2, H2S etc.) into the atmosphere every year, most of which are brought to the east by wind and result-ing more heavier air pollution in northern China.

Post-fire cyclic behavior of reinforced concrete shear walls

The effects of fire exposure,reinforcement ratio and the presence of axial load under fire on the seismic behavior of reinforced concrete(RC) shear walls were investigated.Five RC shear walls were tested under low cyclic loading.Prior to the cyclic test,three specimens were exposed to fire and two of them were also subjected to a constant axial load.Test results indicate that the ultimate load of the specimen with lower reinforcement ratio is reduced by 15.8%after exposure to elevated temperatures.While the reductions in the energy dissipation and initial stiffness are 59.2%and 51.8%,respectively,which are much higher than those in the ultimate load.However,this deterioration can be slowed down by properly increasing reinforcement due to the strength and stiffness recovery of steel bars after cooling.In addition,the combined action of elevated temperatures and axial load results in more energy dissipation than the action of fire exposure alone.

Collision avoidance planning in multi-robot system based on improved artificial potential field and rules

For real-time and distributed features of multi-robot system,the strategy of combining the improved artificial potential field method and the rules based on priority is proposed to study the collision avoidance planning in multi-robot systems. The improved artificial potential field based on simulated annealing algorithm satisfactorily overcomes the drawbacks of traditional artificial potential field method,so that robots can find a local collision-free path in the complex environment. According to the movement vector trail of robots,collisions between robots can be detected,thereby the collision avoidance rules can be obtained. Coordination between robots by the priority based rules improves the real-time property of multi-robot system. The combination of these two methods can help a robot to find a collision-free path from a starting point to the goal quickly in an environment with many obstacles. The feasibility of the proposed method is validated in the VC-based simulated environment.

Characteristics and tectonic setting of volcanic rocks in Early Cretaceous Baiyingaolao Formation of Keyouzhongqi area,Inner Mongolia

The authors studied zircon LA-ICP-MS U-Pb dating,the zircon Hf isotope and geochemistry of acidic volcanic rocks in Baiyingaolao Formation of Keyouzhongqi area,Inner Mongolia,and discussed the chronology,source region and tectonic setting of the volcanic rocks in the studied area. The clear oscillatory zoning of zircons indicates a typical magmatic origin,and the results of dating show that the volcanic rocks of Baiyingaolao Formation were formed in Early Cretaceous( 121. 5 ± 1. 0 Ma). The features of major and trace elements show that the rocks are alkali-rich,poor in calcium and magnesium with enrichment in LILEs like Th,U,K and Gd and depletion in HFSEs,e. g. Nb,Ta,Sr and Ti. The fact implies that they were the products of partial melting of the crust. εHf( t) =( +6.30--+9.06) and TDM2= 600--835 Ma,suggest the magma originated from partial melting of the young crust. Combined with the evolution of regional tectonic structure,the authors conclude that the acidic volcanic rocks of Baiyingaolao Formation may be formed under the extensional environment related to the subduction of Paleo-Pacific Plate.

Study of Biodiversity Indices in Forest Formations of the Province of Saida （Algeria）

Biodiversity is a multidimensional concept involving several scientific disciplines. The study of biodiversity allows to initiate a multidisciplinary analysis and ecological reading of an environmental problem. The objective of this study is the knowledge of plant biodiversity and risk factors affecting the plant diversity in forest formations of Saida province （Algeria）. Plant biodiversity is estimated at 77 species with 37 best represented families （Asteraceae, Lamiaceae and Fabaceae）. The geophytes dominate with a rate of 44.15%. Among the degradation factors that threaten the biodiversity in the study area, the forest fires, overgrazing and trampling by domestic animals was mentioned.

Note on the Orchids of the Moutas Hunting Reserve--- Tlemcen （Western Algeria）

Through the Algerian orchid flora, several rare species remain endemic in the Maghreb. This note on the orchids will enrich the already existing data on the area of Tlemcen. Currently, the coexistence of orchids and species （such as Quercus faginea subsp. tlemcenensis （DC.） M., Lonicera implexa L. and Ruscus aculeatus L.） indicates an ecological environment of dominant forest. Nevertheless, the significant frequency of fires and human pressure is leading to erosion of this area orchids richness. This work enabled us to establish a complete inventory of the orchids species that exist, with an estimate of the populations and a taxon illustration for each of them. Fourteen species （14） were indexed, during the period of spring 2011 only, in this reserve and the scoured areas which do not exceed 2000 ha, representing 29% of the total Algerian orchids species. Among the rare taxa signed ourselves： Ophrys subfusca subsp. battandieri （Rchb.） Batt. and Dactylorhiza durandii （Boiss. and Reuter） M. Lainz in Oranie （O）＊

Laminar Diffusion Flames of Methane in a Co-annular Jet of Oxygen-Enriched Air

Oxygen rich combustion is a mean to increase the energy efficiency and to contribute to CO2 capture. Influence of oxygen enriched air on the stability of methane flames from non premixed laminar jets has been investigated experimentally. The burner consists of two coaxial jets： methane flowing out of the inner, oxidizer from the outer. The flame behavior is studied according to the proportion of oxygen in the oxidizer jet, the oxidizer and the methane jets velocities. The flame is either anchored to the burner, lifted, stationary or not or blown-out. The addition of oxygen produces a decrease of the lift height, a reduction of the length of the reaction zone and an increase in the soot emission. These results have been reported into diagrams of stability where the flame configurations are connected to the competition between the dynamic effect of the injection velocity and the chemical effect of oxygen addition.