1,278 research outputs found
Large scale magnetic fields of our Galaxy
No full textAbstractLarge-scale magnetic fields in the Galactic disk have been revealed by distributions of pulsar rotation measures (RMs) and Zeeman splitting data of masers in star formation regions, which have several reversals in arm and interarm regions. Magnetic fields in the Galactic halo are reflected by the antisymmetric sky distribution of RMs of extragalactic radio sources, which have azimuthal structure with reversed directions below and above the Galactic plane. Large-scale magnetic fields in the Galactic center probably have a poloidal and toroidal structure.</jats:p
Research on Algorithms based on Web Self-adaptive Study and Intelligent Test Paper Construction and their Applications
No full textAbstractA novel system based on Bernoulli Theorem of Large Number Law and the genetic algorithms was designed and realized in this paper, which had many advantages such as self-adaptive study for difficulty coefficient of item pool and intelligent test paper construction etc. At present, the system has applied in the examination of paperless computer tests of Jinlin university of finance and economics and some satisfactory results have been also obtained
An investigation on the effect of intake air humidification on the thermal balance of a turbocharged gasoline direct injection engine
No full textThis study analyzed the thermal balance of a turbocharged gasoline direct injection engine with intake air humidification and studied the reason why intake air humidification improved the thermal efficiency of the basic engine. The results showed that since the evaporation of the introduced water absorbed heat in the intake port that caused the decrease of the temperature of the intake air, and the specific heat capacity of working medium increased with intake air humidification. Therefore, an apparent decrease in the in-cylinder temperature. Each energy loss can be affected by intake air humidification in different degrees, among which the exhaust loss and heat transfer loss decreased evidently, while pumping loss and friction loss increased to some extent. Furthermore, the sum of the decrease of exhaust loss and heat transfer loss was higher than the sum of the increase of pumping loss and friction loss, hence, the thermal efficiency of the basic gasoline engine increased when the benefit gained from intake air humidification was greater than the negative impact
Comparative investigation of ignition behavior of butanol isomers using constant volume combustion chamber under diesel-engine like conditions
Full text linkButanol is a sustainable carbon–neutral fuel that can be derived from a variety of biomass resources. It can be potentially be used as an alternative fuel to blend with diesel to decrease greenhouse gas and pollutant emissions. In this paper, three butanol isomers (n-butanol, tert-butanol, and iso-butanol) are blended with diesel in various volume ratios. The combustion characteristics of butanol isomers are experimentally determined in a constant volume vessel under engine-like conditions. The effects of blend ratio, chamber temperature, and chamber pressure on ignition delay and combustion process are investigated. It is shown that the ignition delay decreases at high temperature and at low butanol blend ratio regardless of the isomer type. The combustion characteristics of butanol/diesel blends differ from neat butanol. Both low temperature heat release (LTHR) and high temperature heat release (HTHR) are observed for the three butanol isomers/diesel blends. Under current operating conditions, the ignition delay of three butanol isomer/diesel blends is ordered according to iso-butanol > n-butanol > tert-butanol. Notwithstanding its higher octane number, tert-butanol/diesel blends show the fastest LTHR and thereafter the shortest ignition delay. This is because of the absence of H atom on the alpha carbon of tert-butanol, which contributes to consumption of OH radicals. Consequently, oxidation of diesel is less suppressed. However, the HTHR of tert-butanol/diesel blends is much slower than that of n-butanol/diesel. At 80% blend ratio, a higher chamber pressure is required to improve the reactivity and ignition. Overall, the low reactivity of butanol is beneficial to be applied in diesel engines to increase the fuel/air mixing time so as to attenuate soot emissions
Effects of Butanol Isomers on the Combustion and Emission Characteristics of a Heavy-Duty Engine in RCCI Mode
No full textButanol is an attractive alternative fuel by virtue of its renewable source and low sooting tendency. In this paper, three butanol isomers (n-butanol, isobutanol, and tert-butanol) were induced via port injection respectively and n-heptane was directly injected into the cylinder to investigate reactivity controlled compression ignition in a heavy-duty diesel engine. This work evaluates the potential of applying butanol as low reactivity fuel and the effects of reactivity gradient on combustion and emission characteristics. The experiments were performed from low load to medium-high load. Due to the different reactivities among the butanol isomers, the exhaust gas recirculation rate and the direct injection strategy were varied for a specific butanol isomer and testing load. Particularly, isobutanol/n-heptane can be operated with single direct injection and no exhaust gas recirculation up to medium load due to the high octane rating. As the load increases, all three butanol isomers displayed increased peak cylinder pressure and pressure rise rate. Especially, n-butanol cases yielded a pressure rise rate of 23.4 bar/oCA at medium-high load because of sub-optimal combustion phasing. It constrains the high load limit of n-butanol/n-heptane operation. While tert-butanol cases presented the slowest heat release rate and consequently the lowest pressure rise rates. Extremely low NOx emissions were achieved for all three isomers. Interestingly, tert-butanol/n-heptane operation stands out for showing ignorable engine-out soot mass in the whole testing range. N-butanol cases require the most direct fueling to phasing the combustion properly and displayed the highest soot mass and the highest number of particles in the accumulation mode. Among the isomers, tert-butanol/n-heptane operation achieved the highest gross indicated efficiency (above 52%) in most operating loads
Effects of Butanol Isomers on the Combustion and Emission Characteristics of a Heavy-Duty Engine in RCCI Mode
No full textCampoplex monochroma Han & Achterberg & Chen 2021, sp. nov.
No full textCampoplex monochroma sp. nov. Figs. 51–52 Material examined. Holotype: female, Zhejiang, Lishui Fengyangshan, 9.VIII.2003, Wu Qiong, No 20042321 (ZJUH). Paratypes: 1 female, Guangdong, Shixing Chebaling, 25. V.2002, Xu Zaifu, No 201806185; 3 females, Henan, Neixiang Wangoulinchang, 11.VII. 1998, Chen Xuexin, No 985939; 1 female, Jilin, Fusong Donggangzhen, 30.VIII.1989, Li Lin, No 974169; 1 female, Neimeng, Gegentala, 16.VIII.2000, Ma Yun, No 200100852; 1 female, Shaanxi, Hanzhong Liubaxian, 20.VIII.2013, Tu Binbin, No 201309161; 3 females, Shenyang National Forest Park, 16. VII.2011, Yan Chenjin, No 201103694, 201103690, 201103695; 3 females, Zhejiang, Longquan Fengyangshan, 10.VIII.2003, Liu Jingxian, No 201804841, 201805167, 201804175; 2 females, Zhejiang, Longquan Fengyangshan, 22.VIII.1982, Song Qisheng, No 826561, 826560; 1 female, Zhejiang, Longquan Fengyangshan, 16.VIII.1982, Le Yanhua, No 826757; 1 female, Zhejiang, Qingyuan Baishanzu, 30.VII.1993, Wu Hong, No 945170; 1 female, Zhejiang, Suichang Jiulongshan, 18.VII.1994, Xu Zaifu, No 944491; 4 females, Zhejiang, Songyang, 17.VII.1994, Xu Zaifu, No 944382, 943976, 944195, 944197. Description. Female (Fig. 51) holotype. Body length 6.2 mm, fore wing length 4.3 mm. Head. Antenna with at least 34 flagellomeres; first flagellomere 1.15× longer than second flagellomere. Face (Fig. 52E) granulose-punctate. Clypeus (Fig. 52E) punctate, punctures larger than that on face, slightly convex, apical margin arched, thick medially. Malar space granulose, 0.5× basal width of mandible. Mandible with lamella basally, upper tooth equal to the length of lower tooth. Frons granulose, median carina absent. Vertex granulose. Interocellar distance (Fig. 52F) 1.5× ocello-ocular distance and 1.9× distance between median and lateral ocelli. Temple granulose, subpolished. Occipital carina evenly arched, reaching hypostomal carina above mandible base. Mesosoma. Pronotum punctate dorsally, subpolished, trans-striate below. Mesoscutum (Fig. 52G) granulose punctate, becoming rugose in notaulic region anteriorly. Scutellum with sparse and minute punctures, rugose posteriorly. Metanotum rugose-punctate. Mesopleuron (Fig. 52B) punctate, trans-striate below tegula, speculum smooth and shiny. Metapleuron (Fig. 52B) punctate. Propodeum (Fig. 52C) with area basalis triangular, long and narrow; area superomedia granulose medially and short rugose laterally, polished; area petiolaris trans-striate; area superomedia confluent with area petiolaris, slightly depressed; all carina distinctly developed; propodeal spiracle small and oval. Wing. Fore wing (Fig. 52A) areolet present and with a moderate stalk emitting 2m-cu vein from its apical part. Marginal cell short, distal part of surrounding vein 2.0× longer than proximal one. Vein 1cu-a opposite M&RS. External angles of second discal cell acute (65°). Hind wing with nervellus inclivous, intercepted at lower 0.3 of its length. Legs. Hind femur 4.0× longer than wide. Inner spur of hind tibia 0.5× as long as first tarsomere of hind tarsus. Tarsal claws pectinate. Metasoma. First metasomal segment (Fig. 52H) round in cross-section of basal 0.3, with weak dorso-lateral carina, and with a shallow groove. First tergite 2.5× longer than width of postpetiole. Postpetiole and second tergite granulose, mat. Second tergite 0.6× as long as first tergite, 0.85× its apical width; thyridium round, its distance from basal margin of tergite equal to its diameter. Third tergite 0.8× as long as its apical width. Metasoma not compressed apically. Sixth and seventh tergites without emarginations. Ovipositor sheath approx. 1.7× longer than hind femur, ovipositor (Fig. 52D) gradually upcurved. Colour. Black. Mandible except teeth, palpi, fore and middle legs entirely and tegula, yellow with telotarsus brownish; scape and pedicel yellowish brown anteriorly and brown dorsally; hind coxa black, trochanter except basally, femur and tibia yellowish brown, tibia unicolorous, slightly infuscated apically, tarsus brown; metasoma entirely black with second and third segments slightly blackish brown. Variation. First flagellomere 1.1–1.25× second flagellomere; face granulose to granulose-punctate; frons with median carina absent or present; pronotum granulose-punctate to punctate dorsally; specimens from Shenyang province with ovipositor thinner; scape and pedicel entirely brown or yellowish-brown anteriorly; specimens from Henan province with hind tibia banded. Distribution. China (Guangdong, Henan, Jinlin, Neimeng, Shaanxi, Shenyang, Zhejiang). Comparative diagnosis. This new species is similar to C. proportionis sp. nov., but differs from the latter by having second tergite 0.8–0.9× as long as its apical width, thyridium separated from the basal margin of tergite by its diameter, metasoma not compressed apically, malar space and frons granulose, and metanotum rugose-punctate. Etymology. Name derived from “mono-” (Greek for “single”), and “chroma” (Greek for “colour”), because its hind tibia is unicolorous.Published as part of Han, Yuan-Yuan, Achterberg, Kees Van & Chen, Xue-Xin, 2021, The genus Campoplex Gravenhorst, 1829 (Hymenoptera, Ichneumonidae, Campopleginae) from China, pp. 1-121 in Zootaxa 5066 (1) on pages 74-77, DOI: 10.11646/zootaxa.5066.1.1, http://zenodo.org/record/565393
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