检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

柴油机pn排放在极限环境下的变化趋势研究

重型汽车 2024年第3期 1-3页

作者：甄雷陈晓明黄继杰欧阳虎威邵宏鑫潍柴动力股份有限公司内燃机可靠性国家重点实验室

pn颗粒是国六法规中明确规定的排放污染物,柴油机的pn排放受多种耦合因素影响。文章系统分析了柴油机pn排放的影响因素,并将影响因素与极限环境变化因素相耦合,通过设计试验进行验证,探究了环境温度、环境湿度、排气温度以及海拔对柴油... 详细信息

pn颗粒是国六法规中明确规定的排放污染物,柴油机的pn排放受多种耦合因素影响。文章系统分析了柴油机pn排放的影响因素,并将影响因素与极限环境变化因素相耦合,通过设计试验进行验证,探究了环境温度、环境湿度、排气温度以及海拔对柴油机pn排放特性的影响。由试验结果可知,pn值随着试验环境温度、湿度的上升大幅度增加,平均温度每升高10℃,pn值增加约30%,湿度每升高10%,pn值增大约6%。温度的升高会极大促进再生反应速率,将碳烟氧化为小颗粒物排放到空气中,导致pn值升高,而湿度对pn排放的影响主要是由于湿度对于小颗粒聚集作用和水煤反应所致。其次,对在PEMS循环排温边界范围内,探究了进气压力减小与排气温度升高耦合条件下的pn排放规律。试验发现排气温度低于350℃时,随进气压力降低,pn值减小;排气温度高于350℃时,pn值随进气压力的减小而降低。此外,采用相同路谱,在不同海拔条件下探究了排气温度对pn排放特性的影响,结果表明在路谱50℃温升范围内,高原pn排放不会高于平原。最终得出结论为:以PEMS工况为边界,高寒、高原地区柴油机的pn排放风险均小于平原常温。最终得出结论为:以排放风险均小于平原常温。

关键词：柴油机 pn 极限环境排放特性

在线全文

学校读者我要写书评

暂无评论

国六车用柴油机整车PEMS排放试验研究

装备制造技术 2024年第6期 45-46+56页

作者：周承忠李明星叶宇黄豪中广西玉柴机器股份有限公司广西大学机械工程学院

随着排放法规日益严格，不仅要对发动机的排放进行台架排放认证，还需对整车排气污染物进行考核和抽检。为了优化整车排放性能，采用便携式排放测量系统（PEMS）进行市区-市郊-高速的实际道路测试，并进行了不同载荷下的排放试验。结果... 详细信息

随着排放法规日益严格，不仅要对发动机的排放进行台架排放认证，还需对整车排气污染物进行考核和抽检。为了优化整车排放性能，采用便携式排放测量系统（PEMS）进行市区-市郊-高速的实际道路测试，并进行了不同载荷下的排放试验。结果表明，随着转速和载荷的升高，pn排放显著增加，标载和高速工况是pn的风险项。应用SCR快速加热模式可以有效提高排温，使得后处理催化器的效率进一步提升，NOx尾排得到有效降低。油门开度急剧变化也是造成pn排放突增的原因之一。

关键词： PEMS 整车道路测试 NOx pn 后处理

Observable liveness of Petri nets with controllable and observable transitions

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2017年第11期60卷 256-264页

作者： Guanjun LIU Changjun JIANG Department of Computer Science Tongji University Key Laboratory of Embedded System and Service Computing of Ministry of Education Tongji University E-commerce Transactions and Information Services Collaborative Innovation Center of Shanghai University Knowledge Service Platform Tongji University

Observability and/or controllability are paid much attention to by researchers not only from the control science field[1–3]but also from the computer science field[4–9].Recently,Desel and Kilinc[4]proposed the notion of observable liveness for Petri nets with(un-)observable and(un-)controllable transitions.The purpose of defining observable liveness is to represent that"a user can always enforce the occurrence of any observable transition only by stimulating the net by choosing appropriate enabled controllable transition"[4].An important assumption of

关键词： net cot pn Observable liveness of Petri nets with controllable and observable transitions

The infrared spectral features of circumstellar envelope of evolved low- and intermediate-mass stars

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2008年第9期51卷 1187-1199页

作者： ZHANG Ke JIANG BiWei Department of Astronomy Beijing Normal UniversityBeijing 100875China

The circumstellar envelope of evolved stars of low- and intermediate-mass is an important site for dust formation. In comparison with the interstellar medium, they have more types of organics and different types of inorganics. Various infrared features in the circumstellar envelope can reveal the composition and abundance of dust, as well as the chemical and physical conditions of the circumstellar shell. Infrared features and their carriers are different in the C-rich or O-rich environment, and the mixed-environment where the C-rich and O-rich circumstellar materials co-exist. The C-rich sources exhibit a series of spectral features which are attrib- uted to organic molecules. They also show two prominent features at 21 μm and 30 μm which emit a large portion of infrared radiation. The O-rich sources exhibit the strong 9.7 μm and 18 μm features attributed to the Si-O bending and O-Si-O stretching modes of amorphous silicate dust. With the ISO/SWS spectrometer, about 50 narrow bands are identified with the crystalline silicate grains, mainly forsterite and enstatite. In addition, a series of features, at 13 μm, 16.8 μm, 19.5 μm and 31.8 μm, appearing to be correlated with each other, are attributed to oxides. Some objects simultaneously show the C-rich and O-rich features, e.g. some C-rich sources have silicate features. There is no well-accepted interpretation for such mixed appearance, though a binary model is suggested.

关键词： star: AGB post-AGB pn star: circumstellar matter infrared: star

Nitrogen isotopic fractionation of particulate organic matter production and remineralization in the Prydz Bay and its adjacent areas

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2020年第12期39卷 42-53页

作者： Chunyan Ren Min Chen Laodong Guo Jian Zeng Renming Jia Xiao Liu Minfang Zheng Yusheng Qiu College of Ocean and Earth Sciences Xiamen UniversityXiamen 361005China School of Freshwater Sciences University of Wisconsin-MilwaukeeMilwaukeeWI 53204USA

During the 29 th Chinese National Antarctic Research Expedition,spatial variations in nitrogen isotopic composition of particulate nitrogen(δ15Npn)and their controlling factors were examined in detail with regard to nitrate drawdown by phytoplankton and particulate nitrogen(pn)remineralization in the Prydz Bay and its adjacent areas.To better constrain the nitrogen transformations,the physical and chemical parameters,including temperature,salinity,nutrients,pn andδ15Npn in seawater column were measured from surface to bottom.In addition,the nitrogen isotopic fractionation factor of nitrate assimilation by phytoplankton in the mixed layer,and the nitrogen isotopic fractionation factor of pn remineralization below the mixed layer were estimated using Rayleigh model and Steady State model,respectively.Our results showed that suspended particles had its lowestδ15Npn in the surface layer,which was due to the preferential assimilation of 14 N in nitrate by phytoplankton.Theδ15Npn in the mixed layer of the Prydz Bay and its adjacent areas decreased from the inner shelf to the outer basin,ascribing to the effect of isotope fractionation during phytoplankton assimilation.In mixed layer,the spatial distribution ofδ15Npn associated with particulate organic matter(POM)production can be well interpreted according to Rayleigh model and Steady State model.The nitrogen isotope fractionation factor during phytoplankton assimilating nitrate was estimated as 10.0‰by Steady State model,which was more reasonable than that calculated by Rayleigh model.These results validate the previous reports of fractionation factor during nitrate assimilation by phytoplankton.Increasingδ15Npn with depth below the euphotic zone correlated with the decreasing pn contents,and it was attributed to preferential remineralization of 14 N in pn by bacteria.In subsurface and deep layer,theδ15Npn distributions also conformed to Rayleigh model and Steady State model during pn remineralization,with a fractionation factor of about 3.6‰and 3.2‰,respectively.It i

关键词： pn δ^(15)N^(pn) isotopic fractionation POM production remineralization Prydz Bay

Discussion on origin of pn velocity variation in China and adjacent region

在线全文

学校读者我要写书评

暂无评论

Acta Seismologica Sinica(English Edition) 2004年第1期17卷 1-11页

作者： PEI Shun-ping(裴顺平) XU Zhong-huai(许忠淮) WANG Su-yun(汪素云) Computational Geodynamics Laboratory Department of Geophysics Peking University Beijing 100871 China Institute of Geophysics China Seismological Bureau Beijing 100081 China Institute of Geophysics China Seismological Bureau Beijing 100081 China

pn velocity lateral variation and anisotropy images were reconstructed by adding about 50 000 travel times from the regional seismic networks to the datum set of near 40 000 travel times from National Seismic Network of China used by WANG, et al. We discussed the relation of pn velocity variation to Moho depth, Earths heat flow, distribution of Cenozoic volcanic rock and the result of rock experiment under high pressure and high temperature. The result of quantitative analysis indicates that pn velocity is positively correlated with the crust thickness and negatively correlated with the Earths heat flow. Two linear regression equations, one between pn velocity and crust thickness, and the other between pn velocity and heat flow, were obtained. The rate of variation of pn veloc-ity vP with pressure P, Pv/p, estimated from the velocity variation with crust thickness Hv/p, is close to the result obtained from the rock experiment under high pressure and high temperature. If the effect of crust thick-ness on pn velocity is deducted from the velocity variation, then the low pn velocity beneath Qinghai-Xizang pla-teau is more notable. The low pn velocity regions well agree with the Cenozoic volcanic rock. In the several re-gions with significant anisotropy, the direction of fast pn velocity is consistent with the orientation of maximum principal crustal compressive stress, and also with the direction of present-day crustal movement. It indicates that the fast pn velocity direction may be related to the deformation or flow of top mantle material along the direction of maximum pressure.

关键词： pn tomography anisotropy China and adjacent region

pn-wave velocity and anisotropy of the western Sichuan and Longmen Mountain region,China

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2010年第11期53卷 1665-1670页

作者： Xu Yi Li ZhiWei Huang RunQiu Liu JianHua Liu JinSong Chinese Acad Sci Inst Geol & Geophys Key Lab Petr Resources Res Beijing 100029 Peoples R China Chengdu Univ Technol State Key Lab Geohazard Prevent & Geoenvironm Chengdu 610059 Peoples R China

pn-wave velocity and anisotropy beneath the western Sichuan and adjacent region are inverted by a tomography method using arrival data from earthquakes recorded by the Sichuan Earthquake Network. It is followed by an analysis of the uppermost mantle structure of the Longmen Mountain region and the deep tectonics of the Ms8.0 earthquake in Wenchuan. Our results reveal a prominent velocity contrast across the Longmenshan fault: low velocities in the Songpan-Ganzi mountain range and high velocities in the Sichuan basin. They indicate that the Songpan-Ganzi mountain range is underlain by a weak uppermost mantle, which is easy to create ductile flow, whereas the Sichuan basin has a mechanically strong uppermost mantle. These features reflect a difference of the lithospheric mantle beneath tectonically active mountain range and stable basin. The boundary between the high and low velocities is coincident with the Longmenshan fault. Bordered by Wenchuan, the northern part of the boundary is parallel to the fault belt and aftershock distribution, but the southern part of the boundary deviates from the fault belt and is bent toward the Sichuan basin. The Ms8.0 earthquake in Wenchuan is located at the flexural part between them, where a strong heterogeneity is shown in the velocity variation across and parallel to the boundary. This area is reasonably believed as a potential location for regional stress accumulation and release in the Longmen Mountain region, reflecting a prominent character in the deep structure around Wenchuan. pn-wave anisotropy reveals the mantle flow that is consistent with the eastward movement of the Tibetan Plateau. This process provided deep dynamic sourse for tectonic deformation in the Longmen Mountain region and for the occurrence of the Wenchuan Ms8.0 earthquake, but it is clearly affected by the strong lithosphere of the Sichuan basin. There is no correlation between the pn-wave anisotropy and the Longmenshan fault, hence, this fault system is only restricted within the crust. However, the man

关键词： western Sichuan Longmen Mountain pn velocity anisotropy Wenchuan earthquake

Spatial and temporal variation of particulate organic carbon in the pn section of East China Sea

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2005年第5期24卷 89-99页

作者： ZHU Zhuoy WU Ying ZHANG Jing WEI Hao State Key Laboratory of Estuarine and Coastal Research East China Normal University Shanghai 200062 China College of Chemistry and Chemical Engineering Ocean University of China Qingdao 266003 China Physical Oceanography Laboratory Ocean University of China Qingdao 266003 China

Variations of the particulate organic carbon and nitrogen （POC/pn） along the pn section in the East China Sea （ECS） were examined based on POC/pn data obtained in September 2002. A comparison with others work indicates that POC is the highest in summer, followed by autumn and spring, and the lowest in winter. Generally, POC concentration decreases seawards, and the in situ productivity in September plays an important role in POC distribution. POC in the pn section is composed of terrestrial, resuspended, in situ produced carbon and carbon originated fi＇om the Kuroshio waters. The Changjiang River effects the ECS in the pn section, but the influence is mainly minimiged beyond 123.5° E because of barrier effect. The impact of Kuroshio subsurface water （KSSW） over shelf break can also effect POC distribution, with high POC concentration there.

关键词： POC pn East China Sea pn section

DEPOSITION OF TiBN HARD FILMS ON HOT-WORKING-STEEL DIES FOR ALUMINIUM EXTRUSION VIA A DUPLEX PROCESS

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2001年第6期14卷 408-414页

作者： K. Muller (Forschungszentrum Stranpressen, TU Berlin, 13355 Berlin, Germany) Forschungszentrum Stranpressen TU Berlin 13355 Berlin Germany

Hot working steels have been used as die materials for hot extrusion of aluminium. Due to tribological interaction at elevated temperature between the die bearing and the surface of extruded aluminium profiles, not only the surface quality of the extruded product, but also the lifetime of the dies decreases. Deposition of TiBN hard films on the die bearing could improve the die performance. Treatment should be done in a duplex process process combining a plasma nitriding pretreatment (pn) and a plasma assisted chemical vapour deposition (PACVD) of TiBN. In this study the influence of the process conditions on the properties of the duplex coatings was investigated. The relationship between structure and mechanical property was researched. For testing these TIBN hard films under elevated temperature conditions and for comparison with other possible coatings special extrusion dies with different coated bearings were used. The extrusion trials were performed on the 8MN-extrusion press at the research a nd development center for extrusion, Technical University of Berlin.

关键词： hard film plasma nitriding duplex process pn PA CVD and extrusion