A Triggering Mechanism for Enhanced Star-Formation in Colliding Galaxies

We propose a physical mechanism to explain the origin of the intense burst of massive-star formation seen in colliding/merging, gas-rich, field spiral galaxies. We explicitly take account of the different parameters for the two main mass components, H-2 and H I, of the interstellar medium within a galaxy and follow their consequent different evolution during a collision between two galaxies. We also note that, in a typical spiral galaxy-like our galaxy, the Giant Molecular Clouds (GMCs) are in a near-virial equilibrium and form the current sites of massive-star formation, but have a low star formation rate. We show that this star formation rate is increased following a collision between galaxies. During a typical collision between two field spiral galaxies, the H I clouds from the two galaxies undergo collisions at a relative velocity of approximately 300 km s-1. However, the GMCs, with their smaller volume filling factor, do not collide. The collisions among the H I clouds from the two galaxies lead to the formation of a hot, ionized, high-pressure remnant gas. The over-pressure due to this hot gas causes a radiative shock compression of the outer layers of a preexisting GMC in the overlapping wedge region. This makes these layers gravitationally unstable, thus triggering a burst of massive-star formation in the initially barely stable GMCs.The resulting value of the typical IR luminosity from the young, massive stars from a pair of colliding galaxies is estimated to be approximately 2 x 10(11) L., in agreement with the observed values. In our model, the massive-star formation occurs in situ in the overlapping regions of a pair of colliding galaxies. We can thus explain the origin of enhanced star formation over an extended, central area approximately several kiloparsecs in size, as seen in typical colliding galaxies, and also the origin of starbursts in extranuclear regions of disk overlap as seen in Arp 299 (NGC 3690/IC 694) and in Arp 244 (NGC 4038/39). Whether the IR emission from the central region or that from the surrounding extranuclear galactic disk dominates depends on the geometry and the epoch of the collision and on the initial radial gas distribution in the two galaxies. In general, the central starburst would be stronger than that in the disks, due to the higher preexisting gas densities in the central region. The burst of star formation is expected to last over a galactic gas disk crossing time approximately 4 x 10(7) yr. We can also explain the simultaneous existence of nearly normal CO galaxy luminosities and shocked H-2 gas, as seen in colliding field galaxies.This is a minimal model, in that the only necessary condition for it to work is that there should be a sufficient overlap between the spatial gas distributions of the colliding galaxy pair.

Lopsidedness in WHISP galaxies II. Morphological lopsidedness

The distribution of stars and gas in many galaxies is asymmetric. This so-called lopsidedness is expected to significantly affect the dynamics and evolution of the disc, including the star formation activity. Here, we measure the degree of lopsidedness for the gas distribution in a selected sample of 70 galaxies from the Westerbork Hi Survey of Spiral and Irregular Galaxies. This complements our earlier work (Paper I) where the kinematic lopsidedness was derived for the same galaxies. The morphological lopsidedness is measured by performing a harmonic decomposition of the surface density maps. The amplitude of lopsidedness A(1), the fractional value of the first Fourier component, is typically quite high (about 0.1) within the optical disc and has a constant phase. Thus, lopsidedness is a common feature in galaxies and indicates a global mode. We measure A(1) out to typically one to four optical radii, sometimes even further. This is, on average, four times larger than the distance to which lopsidedness was measured in the past using near-IR as a tracer of the old stellar component, and therefore provides a new, more stringent constraint on the mechanism for the origin of lopsidedness. Interestingly, the value of A(1) saturates beyond the optical radius. Furthermore, the plot of A(1) versus radius shows fluctuations that we argue are due to local spiral features. We also try to explain the physical origin of this observed disc lopsidedness. No clear trend is found when the degree of lopsidedness is compared to a measure of the isolation or interaction probability of the sample galaxies. However, this does not rule out a tidal origin if the lopsidedness is long-lived. In addition, we find that the early-type galaxies tend to be more morphologically lopsided than the late-type galaxies. Both results together indicate that lopsidedness has a tidal origin.

Origin of Disk Lopsidedness in Spiral Galaxies

In our work we have used the atomic hydrogen [HΙ] gas distribution in the HΙ 21-cm line emission to study the dark matter halo perturbations. For tHΙs analysis, the 2-D HΙ surface density and velocity maps (arcHΙval) of the galaxies in the Eridanus group (obtained using the GMRT) and in the Ursa Major group (obtained from WSRT) were used. In addition a few HΙckson Compact Groups of galaxies were also studied using the GMRT. The HΙ maps of these galaxies were Fourier analysed to estimate the asymmetry in the distribution and motion of gas. The average asymmetry parameter in the 1.5 to 2.5 K′-band scale lengths was found to be ~ 0.27 for the Eridanus group of galaxies wHΙle it was ~ 0.14 for the Ursa Major group of galaxies. The asymmetries in the distribution of HΙ as a function of Hubble type of galaxies were also studied and was found to be directly correlated with the compactness of the groups. In addition, the trend in the asymmetry as a function of the Hubble type of galaxies was opposite to that seen in the field galaxies, i.e., in the group galaxies, the early type galaxies showed more asymmetry than late type. These two aspects indicated that tidal interactions between the galaxies in a group environment to be the major cause of asymmetries. The observed asymmetry parameters were consistent with recent numerical simulations of asymmetries of gas disk caused by fly-by interactions. We have also estimated the perturbation of dark matter halo using the asymmetry parameter obtained from the Fourier series analysis of the surface density maps.

Battery-Powered RF Pre-Ionization System for the Caltech Magnetohydrodynamically-Driven Jet Experiment: RF Discharge Properties and MHD-Driven Jet Dynamics

This thesis describes investigations of two classes of laboratory plasmas with rather different properties: partially ionized low pressure radiofrequency (RF) discharges, and fully ionized high density magnetohydrodynamically (MHD)-driven jets. An RF pre-ionization system was developed to enable neutral gas breakdown at lower pressures and create hotter, faster jets in the Caltech MHD-Driven Jet Experiment. The RF plasma source used a custom pulsed 3 kW 13.56 MHz RF power amplifier that was powered by AA batteries, allowing it to safely float at 4-6 kV with the cathode of the jet experiment. The argon RF discharge equilibrium and transport properties were analyzed, and novel jet dynamics were observed.

Although the RF plasma source was conceived as a wave-heated helicon source, scaling measurements and numerical modeling showed that inductive coupling was the dominant energy input mechanism. A one-dimensional time-dependent fluid model was developed to quantitatively explain the expansion of the pre-ionized plasma into the jet experiment chamber. The plasma transitioned from an ionizing phase with depressed neutral emission to a recombining phase with enhanced emission during the course of the experiment, causing fast camera images to be a poor indicator of the density distribution. Under certain conditions, the total visible and infrared brightness and the downstream ion density both increased after the RF power was turned off. The time-dependent emission patterns were used for an indirect measurement of the neutral gas pressure.

The low-mass jets formed with the aid of the pre-ionization system were extremely narrow and collimated near the electrodes, with peak density exceeding that of jets created without pre-ionization. The initial neutral gas distribution prior to plasma breakdown was found to be critical in determining the ultimate jet structure. The visible radius of the dense central jet column was several times narrower than the axial current channel radius, suggesting that the outer portion of the jet must have been force free, with the current parallel to the magnetic field. The studies of non-equilibrium flows and plasma self-organization being carried out at Caltech are relevant to astrophysical jets and fusion energy research.

黄骅坳陷马东地区沙河街组重力流水道储层评价及剩余油研究

In this paper, taking Madong district of Huanghua depression as a case, based on the theory of sequence stratigraphy, sedimentology, reservoir geology and geophysics, according to core analysis, seismic attribute analysis, logging constrained inversion, multi-data correlation of strata, reservoir modeling, etc. the lower and middle first member of Shahejie formation of the study area was forecasted and evaluated. As a result, a number of reservoir prediction and remaining oil distribution methods suitable to oil exploitation of gravity flow channel reservoir are presented. Scientific foundation is provided to the next adjustment of development program and exploitation of the remaining oil. According to high resolution sequence stratigraphy theory, precise stratigraphic framework was founded, the facies types and facies distribution were studied under the control of stratigraphic framework, the technologies of seismic attribute abstraction and logging constrained inversion. Result shows that gravity flow channel, as the main facies, developed in the rising period of base-level cycle, and it was formed during the phase of contemporaneous fault growth. As the channel extends, channel width was gradually widened but thickness thined. The single channels were in possession of a great variety of integrated modes, such as isolated, branching off, merging and paralleling, forming a kind of sand-mud interblending complex sedimentary units. Reservoir quality differs greatly in vertical and horizontal direction, and sedimentary microfacies is main controlling factor of the reservoir quality. In major channel, deposition thickness is great, and petrophysical property is well. While in marginal channel, reservoir is thinner, and petrophysical property is unfavorable. Structure and reservoir quality are main factors which control the oil and gas distribution in the study area. On the basis of the research about the reservoir quality, internal, planar and 3-D reservoir heterogeneities are characterized, and the reservoir quality was sorted rationally. At last, based on the research of reservoir numerical simulation of key well group, combined with reservoir performance analysis and geological analysis above, remaining oil distribution patterns controlled by internal rhythm of gravity flow channel were set up. Through this research, a facies-restrained reservoir prediction method integrating multi-information was presented, and potential orientation of remaining oil distribution in gravity flow channel reservoir is clarified.

塔里木盆地轮南地区三叠系油气地质模型及油气预测研究

As an important measure to understand oil and gas accumulation during petroleum exploration and development, Petroleum geological model is an integrated system of theories and methods, which includes sedimentology, reservoir geology, structural geology, petroleum geology and other geological theories, and is used to describe or predict the distribution of oil and gas. Progressive exploration and development for oil and gas is commonly used in terrestrial sedimentary basin in China for the oil and gas generation, accumulation and exploitation are very intricate. It is necessary to establish petroleum geological model, adaptive to different periods of progressive exploration and development practice. Meanwhile there is lack of an integrated system of theories and methods of petroleum geological model suitable for different exploration and development stages for oil and gas, because the current different models are intercrossed, which emphasize their different aspects. According to the characteristics of exploration and development for the Triassic oil and gas pool in Lunnan area, Tarim Basin, the Lunnan horst belt was selected as the major study object of this paper. On the basis of the study of petroleum geological model system, the petroleum geological models for different exploration and development stages are established, which could be applied to predict the distribution of oil and gas distribution. The main results are as follows. (1) The generation-accumulation and exploration-development of hydrocarbon are taken as an integrated system during the course of time, so petroleum exploration and development are closely combined. Under the guidance of some philosophical views that the whole world could be understood, the present writer realizes that any one kind of petroleum geological models can be used to predict and guide petroleum exploration and development practice. The writer do not recognize that any one kind of petroleum geological models can be viewed as sole model for guiding the petroleum exploration and development in the world. Based on the differences of extents and details of research work during various stage of exploration and development for oil and gas, the system of classification for petroleum geological models is established, which can be regarded as theoretical basis for progressive petroleum exploration and development. (2) A petroleum geological model was established based on detailed researches on the Triassic stratigraphy, structure, sedimentology and reservoir rocks in the Lunnan area, northern Tarim Basin. Some sub-belt of hydrocarbon accumulation in the Lunnan area are divided and the predominate controlling factors for oil and gas distribution in the Lunnan area are given out. (3) Geological models for Lunnan and Jiefangqudong oil fields were rebuilt by the combinations of seismology and geology, exploration and development, dynamic and static behavior, thus finding out the distribution of potential zones for oil and gas accumulations. Meanwhile Oil and gas accumulations were considered as the important unit in progressive exploration and development, and the classification was made for Lunnan Triassic pools. Petroleum geological model was created through 3D seismic fine interpretation and detailed description of characteristics of reservoir rocks and the distribution of oil and gas, especially for LN3 and LN26 well zones. The possible distribution of Triassic oil traps and their efficiency in the Lunnan area has been forecasted, and quantitative analysis for original oil(water) saturation in oil pools was performed. (4) The concept of oil cell is proposed by the writer for the first time. It represents the relatively oil-rich zones in oil pool, which were formed by the differences of fluid flows during the middle stage of reservoir development. The classification of oil cells is also given out in this paper. After the studies of physical and numerical modeling, the dominant controlling factors for the formation of various oil cells are analyzed. Oil cells are considered as the most important hydrocarbon potential zones after first recovery, which are main object of progressive development adjustment and improvement oil recovery. An example as main target of analysis was made for various oil cells of Triassic reservoir in the LN2 well area. (5) It is important and necessary that the classification of flow unit and the establishment of geological model of flow unit based on analysis of forecast for inter-well reservoir parameters connected with the statistical analysis of reservoir character of horizontal wells. With the help of self-adaptive interpolation and stochastic simulation, the geological model of flow units was built on the basis of division and correlation of flow units, with which the residual oil distribution in TIII reservoir in the LN2 well area after water flooding can be established.

论大型拆离滑覆构造的特征、形成机制及其与油气成藏关系—以渤海湾盆地冀中坳陷饶阳凹陷为例

The studies of this paper is an important part of the "ninth five" science&technology-tackling project of CNPC -The oil and gas distribution regulation and the aims of explortion in jizhong depression. Basing on the former research results, with the materials of regional structural setting, major tectonic movements, bi-and tri-dimension seismic sections, oil well sections and reservoir sections, this paper involves studies of tectonic evolution, sedimentarv evolution, magma movement and reservoir prediction. The existence of huge stripping and gliding nappe is proved in the RaoYang Sag for the frist time. The properties, development, evolution and the relationship with reservoir of the stripping and gliding nappe are discussed in details in this paper. It is also talked about the affects of stripping and nappes to oil and gas exploration theoretically and practically in the paper. The marking attributes of the stripping and gliding nappe includes stripping and gliding plane, two deformation systems, stratigraphic repeat and hiatus close to the stripping and gliding plane, and the deformation attributes in the front and back of stripping and gliding nappe. The RaoYang stripping and gliding nappes can be divided into different belts in north-south direction and different zones in east-west direction. RaoYang Stripping and gliging nappes took place in the late Paleogene period and before the sedimentation of Neogene period. The sliding direction is NWW. The sliding distance is about 6km. The geothermal gradient in the separating slump area is low and stable. The formation of the stripping and gliding nappes is due to the regional structural setting, the sediments of Paleogene system, the soft roof and the uneven rising movement of structure units. The evolution of the stripping and gliding nappes can be divided into the following stages: regional differential elevation and subsidence, unstable gravity and gravitational sliding, the frist wholly stripping faults and sliding stage, and the following second and third stripping faults and sliding stages. The identification of RaoNan stripping and gliding nappes has an important role on the research of regional structure and oil and gas exploration. Basing on the properties of stripping and gliding nappes, we can identtify the gliding fractures, ductile compressional folds, the front and back structures of gliding nappes and gliding plane covered structures. Combination with different reservoir forming conditions, these structures can lead to different categories of reservoirs.

砂砾岩储层流动单元四维模型研究

This article is an important part of "95" technological subject of SINOPEC. It has a large number of difficulties and workloads, and has significant theoretical meanings and practical value. The study area is composed of sandstone & conglomerate reservoir of alluvial fan & fan delta, which belong to Sha3 lower member and Sha4 upper member of lower tertiary of Yong'an Town Oilfield in Dongying Depression. The target stataum develops in the hanging wall of the synsedimentary fault in the scarp zone of Dongying Depression. The frequently intense movements result in the variation of sandstone and conglomerate reservoir and the evolution of the time and space of Sha3 lower member and Sha4 upper member in Yong'an Town Oilfield. As a result, it is difficult for the individual reservoir correlation at the root of fan, which bring about a tackle problem for the exploitation of oilfield. In this background, the research of fluid units will be more difficult. In this article, the new concepts, the new methods, and the new techniques of sedimentology, petroleum geology, reservoir geology, physics of crystal surface, dynamic & static state reservoir description and well logging geology are synthetically applied, and the computer technology are made full uses of, and the identifying, dividing and appraising of the two-formation-type sandstone & conglomerate reservoir fluid units of Sha3 lower member and Sha4 upper member systemically analyzed in Yong'an Town Oilfield, Dongying Depression. For the first time, the single-well model, the section model, the plane model, the nuclear magnetism log model, the microcosmic network model, the 4-D geology model and the simulation model of the two-formation-type reservoir fluid units of the of sandstone & conglomerate reservoir of Sha3 lower member and Sha4 upper member are established, and the formative mechanism and distributing & enrichment laws of oil-gas of the two type of sandstone and conglomerate reservoir fluid units are revealed. This article established the optimizing, identifying, classifying and appraising standard of the two-formation-type reservoir fluid units of the of sandstone and conglomerate reservoir of Sha3 lower member and Sha4 upper member, which settles the substantial foundations for static state model of the fluid units, reveals the macroscopic & microcosmic various laws of geometrical static state of the fluid units, and instructs the oil exploitation. This article established static state model of the two-formation-type sandstone and conglomerate reservoir fluid units by using the multi-subject theories, information and techniques, and reveals the geometrical configuration, special distribution and the oil-gas enrichment laws of the sandstone and conglomerate reservoir fluid units. For the first time, we established the nuclear magnetism log model of the two-formation-type sandstone and conglomerate reservoir of Sha3 lower member and Sha4 upper member, which reveals not only the character and distributing laws of the porosity and permeability, bat also the formation and distribution of the movable fluid. It established six type of microcosmic net model of the two-formation-type sandstone and conglomerate reservoir of Sha3 lower member and Sha4 upper member in the working area by using the advanced theories, such as rock thin section, SEM, image analysis, intrusive mercury, mold, rock C.T. measure & test image etc., which reveals the microcosmic characteristic of porosity & throat, filterate mode and microcosmic oil-gas enrichment laws of the sandstone and conglomerate reservoir. For the first time, it sets up the 4-D model and mathematic model of the sandstone and conglomerate reservoir, which reveals the distributing and evolving laws of macroscopic & microcosmic parameters of the two-formation-type sandstone and conglomerate reservoir and oil-gas in 4-D space. At the same time, it also forecasts the oil-gas distribution and instructs the oilfield exploitation. It established reservoir simulation model, which reveals the filterate character and distributing laws of oil-gas in different porosity & throat net models. This article established the assistant theories and techniques for researching, describing, indicating and forecasting the sandstone and conglomerate reservoir fluid units, and develops the theories and techniques of the land faces faulted basin exploitation geology. In instructing oilfield exploitation, it had won the notable economic & social benefits.

A comprehensive life cycle water analysis framework for residential buildings

Most studies on the environmental performance of buildings focus on energy demand and associated greenhouse gas emissions. They often neglect to consider the range of other resource demands and environmental impacts associated with buildings, including water. Studies that assess water use in buildings typically consider only operational water, which excludes the embodied water in building materials or the water associated with the mobility of building occupants. A new framework is presented that quantifies water requirements at the building scale (i.e. the embodied and operational water of the building as well as its maintenance and refurbishment) and at the city scale (i.e. the embodied water of nearby infrastructures such as roads, gas distribution and others) and the transport-related indirect water use of building occupants. A case study house located in Melbourne, Australia, is analysed using the new framework. The results show that each of the embodied, operational and transport requirements is nearly equally important. By integrating these three water requirements, the developed framework provides architects, building designers, planners and decision-makers with a powerful means to understand and effectively reduce the overall water use and associated environmental impacts of residential buildings.

Seasonality and extent of extratropical TST derived from in-situ CO measurements during SPURT

We present airborne in-situ trace gas measurements which were performed on eight campaigns between November 2001 and July 2003 during the SPURT-project (SPURenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region). The measurements on a quasi regular basis allowed an overview of the seasonal variations of the trace gas distribution in the tropopause region over Europe from 35°-75°N to investigate the influence of transport and mixing across the extratropical tropopause on the lowermost stratosphere. From the correlation of CO and O3 irreversible mixing of tropospheric air into the lowermost stratosphere is identified. The CO distribution indicates that transport and subsequent mixing of tropospheric air across the extratropical tropopause predominantly affects a layer, which closely follows the shape of the local tropopause. In addition, the seasonal cycle of CO2 illustrates the strong coupling of that layer to the extratropical troposphere. Both, horizontal gradients of CO on isentropes as well as the CO-O3-distribution in the lowermost stratosphere reveal that the influence of quasi-horizontal transport and subsequent mixing weakens with distance from the local tropopause. The mixing layer extends to about 25 K in potential temperature above the local tropopause exhibiting only a weak seasonality. However, at large distances from the tropopause a significant influence of tropospheric air is still evident. The relation between N2O and CO2 indicates that a significant contribution of air originating from the tropical tropopause contributes to the background air in the extratropical lowermost stratosphere.

Um estudo algorítmico de problemas logísticos na indústria de petróleo e gás natural

This work consists on the study of two important problems arising from the operations of petroleum and natural gas industries. The first problem the pipe dimensioning problem on constrained gas distribution networks consists in finding the least cost combination of diameters from a discrete set of commercially available ones for the pipes of a given gas network, such that it respects minimum pressure requirements at each demand node and upstream pipe conditions. On its turn, the second problem the piston pump unit routing problem comes from the need of defining the piston pump unit routes for visiting a number of non-emergent wells in on-shore fields, i.e., wells which don t have enough pressure to make the oil emerge to surface. The periodic version of this problem takes into account the wells re-filling equation to provide a more accurate planning in the long term. Besides the mathematical formulation of both problems, an exact algorithm and a taboo search were developed for the solution of the first problem and a theoretical limit and a ProtoGene transgenetic algorithm were developed for the solution of the second problem. The main concepts of the metaheuristics are presented along with the details of their application to the cited problems. The obtained results for both applications are promising when compared to theoretical limits and alternate solutions, either relative to the quality of the solutions or to associated running time

Sistema de controle de escoamento de gás natural em dutos de distribuição com detecção de vazamentos utilizando redes neurais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The gaseous environment of radio galaxies: a new perspective from high-resolution x-ray spectroscopy

It is known that massive black holes have a profound effect on the evolution of galaxies, and possibly on their formation by regulating the amount of gas available for the star formation. However, how black hole and galaxies communicate is still an open problem, depending on how much of the energy released interacts with the circumnuclear matter. In the last years, most studies of feedback have primarily focused on AGN jet/cavity systems in the most massive galaxy clusters. This thesis intends to investigate the feedback phenomena in radio--loud AGNs from a different perspective studying isolated radio galaxies, through high-resolution spectroscopy. In particular one NLRG and three BLRG are studied, searching for warm gas, both in emission and absorption, in the soft X-ray band. I show that the soft spectrum of 3C33 originates from gas photoionized by the central engine. I found for the first time WA in 3C382 and 3C390.3. I show that the observed warm emitter/absorbers is not uniform and probably located in the NLR. The detected WA is slow implying a mass outflow rate and kinetic luminosity always well below 1% the L(acc) as well as the P(jet). Finally the radio--loud properties are compared with those of type 1 RQ AGNs. A positive correlation is found between the mass outflow rate/kinetic luminosity, and the radio loudness. This seems to suggest that the presence of a radio source (the jet?) affects the distribution of the absorbing gas. Alternatively, if the gas distribution is similar in Seyferts and radio galaxies, the M(out) vs rl relation could simply indicate a major ejection of matter in the form of wind in powerful radio AGNs.