Center Segregation Research Articles

Modification de la structure des enveloppes et du contenu en proteins d'Escherichia coli en survie dans l'eau de mer

A toxigenic strain of Escherichia coli displayed important structural modifications when placed in seawater which naturally lacked nutritive elements, as observed by electron microscopy. These include cell wall and cell body distortion, modification of the membranes, central segregation of the chromosome, and retraction of the cytoplasm. These modifications were accompanied by a decrease in cell protein content of approximately 40%. Certain cytoplasmic membrane proteins were lost, and new ones appeared. The development of these changes was considerably slower in cells that had previously been grown in a seawater medium. This suggests that osmotic regulation mechanisms, which enable E. coli to survive much longer in marine conditions, may have a protective influence.

連鋳製高炭素鋼線材の伸線加工性におよぼす中心偏析の影響

連鋳製高炭素鋼線材の伸線加工性におよぼす中心偏析の影響

電磁撹はんによる連鋳鋳片の中心偏析改善

電磁撹はんによる連鋳鋳片の中心偏析改善

Hydrogen Induced Cracking Susceptibility of High-Strength Line Pipe Steels

Abstract The effects of chemical compositions, rolling conditions, and homogenization treatment on hydrogen induced cracking (HIC) have been studied metallurgically using laboratory heats of chemical compositions corresponding to those of the center segregation zones in continuous cast slabs. The hardness of the center segregation zones in steel plates is one of the predominant factors affecting the HIC susceptibility of high-strength line pipe steels. An increase of the carbon equivalent (Ceq) or phosphorus content hardens the center segregation zones in conventional carbon steels produced by the controlled rolling (CR) process. Lowering the carbon content to the range of 0.01 to 0.05% markedly decreases the hardness of center segregation zone and reduces the HIC susceptibility, regardless of the increases in other alloy elements. Hot rolling at relatively lower temperature increases the hardness of the center segregation zone and results in a slightly high HIC susceptibility. The design of the chemical ...

Evolution of star clusters with a mass distribution of binaries

The dynamical evolution of star clusters with a initial population of binaries strongly depends on the parameters of the bounded pairs. We performed computational simulation with directN-body codes, on models withN=300 objects, with initial fraction of 20% of binaries with the same orbital semi-axis and with a Salpeter mass spectrum. The results are compared with previous analysis on similar equal-mass star models. The calculation points out that binaries with different mass companions determine an enhanced and sudden expansion of the system with neither core collapse nor central mass segregation.

Development of segregation etch print method and its application to investigation of CC slab segregation.

The segregation etch print (EP) method is a new method for detecting and recording segregation in low S and Ca added steels. This EP method can rapidly and conveniently detect segregation over a wide area with high resolving power. When EP was applied to CC slab, a coarse network structure was found in the equiaxed crystal zone, which could not be seen by the ordinary etching method for detecting the solidification structure. It was found that the fineness of the network structure was related to the segregation level and the fine structure remarkably suppressed not only central segregation but also V-shape segregation. Furthermore, the following casting conditions were considered to be important for making the network structure fine.1) Low casting velocity2) Low casting temperature3) Strong spray cooling4) Addition of REM5) Reduced thickness of slab

Effect of bulging and solidification structure on segregation in continuously cast slab.

By the use of a center segregation simulator evaluation method, a test of center segregation was made quantitatively in relation to the amount of bulging and solidification structure.It became clear from the test that segregation is insignificant when the amount of bulging is zero but intensifies when the amount of bulging exceeds 200μm.On the basis of the test result, short pitch divided roll segments were installed on a continuous slab caster and a segregation alleviating test was made. The test results revealed that center segregation can greatly be alleviated if the solidification structure of the slab is changed to an equiaxed structure, and the bulging of slab is reduced by the use of a short-pitch divided roll stand.Solidification phenomena in the part of segregation-spot are discussed theoretically. And the EPMA data of spot segregation are well explained by the results of theoretical analysis.

Metropolitan Housing Segregation in 1980

Metropolitan patterns of black/white housing segregation are analyzed through the 1980 census data for the St. Louis Metropolitan area. Using the index of dissimilarity as an indicator of segregation, it was found that there was no change in central city segregation, and only a modest decline in suburban segregation. Analysis of segregation within incorporated places revealed that most of the area's population lived in racially homogeneous or internally segregated communities, and that virtually all racially mixed suburbs away from the major sector of black population were highly segregated. It was found that most of the suburbs that did have low segregation indices were experiencing rapid black population growth, and thus may have been experiencing racial turnover. It is concluded that patterns of segregation which have historically existed in the central city are now being repeated in the suburbs.

Black Male Unemployment in U.S. Metropolitan Areas: The Role of Black Central City Segregation and Job Decentralization

Housing segregation has been suggested as an important cause of high unemployment among black Americans, because segregation restricts the black population to living in those central city areas which are losing jobs. Previous studies have not offered a conclusive test of this hypothesis, as they present conflicting findings and have a number of methodological difficulties. Using regression analyses on data from U.S. SMSAs, it is shown that the differential in unemployment rates between blacks and whites in U. S. SMSAs (and particularly SMSAs outside the South) is substantially influenced both by segregation patterns restricting blacks to the central city and by job decentralization. This black/while unemployment differential and the overall unemployment rate in an area determine the level of black unemployment in the area. Thus, central city segregation and job decentralization have important indirect effects on the black unemployment rates of U. S. metropolitan areas.

EFFECT OF ELECTROMAGNETICALLY DRIVEN REVERSE-TURN FLOWS ON STRUCTURE

In order to decrease center segregation together with center porosity, electromagnetic stirring has been applied to continuous casting of billets, blooms and slabs. As well known, however, the violent agitation in the pool is powerful to prevent center segregation, but promotes the formation of white band To tackle this problem, the turbulent electromagnetically driven flows in the pool are theoretically analyzed. Especially focusing on the effect of the electromagnetically driven reverse-turn flows on the structure, the solidification experiments were conducted by use of the Sn-10% Pb alloy Theoretical equation of the maximum velocity appearing at every half period for the reverse-turn flow is given as follows where, B = k3 yfr^/\(aw/ti)l/4B}.

Use of ultrasonics for the examination of hot billets and for cleanness assessment

AbstractThe two separate projects described both use ultrasonic beams for the interior inspection of steel, particularly in the billet stage. Progress in both areas has been made, and work continues. The inspection of hot steel for central pipe and segregation has led to the development of a machine for works trials based upon the use of rolling contact under pressure. The primary problems here are establishing coupling, and avoiding overheating the ultrasonic probes without drastically cooling the steel. Correlation is required to be established with cold ultrasonic inspection and sulphur printing and macro-etching. The second project is intended to provide for the ultrasonic assessment of background or general inclusion content over a substantial volume of steel. The detection of individual inclusions above a certain minimum size is also envisaged and is already an established technique. The immediate aim has been to establish correlation between optical measurements using the QTM, so that confidence ca...

湾曲型広幅スラブ連鋳鋳片の凝固組織について

It was observed that the macro structures of carbon steel slab produced by S type continuous wide slab casting machine were asymmetrical, that is, columnar crystal was generated in the upper site of the slab and branched columnar crystal or equiaxed crystal was generated preferentially in the under site.In order to clarify the cause for above-mentioned asymmetric feature, various investigations, model experiments with water and many operation tests were carried out.The results obtained are as follows:(1) The formation of macro structures of continuously cast steel slab was intensitively affected by “Inclination of strand (d.h. gravity)” and “unsolidified steel convection in the shell”. In view of this consideration. The formation process of macro structures was able to be separated into three zones.(2) Branched columnar crystal formed in the under site of C. C. slab is different from branched columnar crystal formed in steel ingot.(3) Conditions of equiaxed crystal formation in continuously cast steel slab are formation of lots of nucleus in liquid steel contacted by copper mould and transport of them to the zone of slow freezing rate inside the liquid crater of continuously cast strand.(4) The formation of center segregation is independent of contact of columnar zone in the center position of continuously cast slab.

連続鋳造ビレットの鋳造組織と偏析について

The macro structure and the segregation of continuously cast carbon steel billets with 80 to 250mm square and 260×370mm in section were investigated. The results were summarized as follows.1. The length of columnar crystal and the thickness of central segregated zone are increased, and the central porosity and segregation become worse, with increase of superheated casting temperature.2. The absolute thickness of central segregated zone is increased with increase of the section of square billet, but its relative value to billet thickness is decreased. The type of V segregation is changed from single V line to multi V line, in the case of high superheat temperature.3. The type of V segregation is changed from V line to V zone and the central segregation disappear, when the billet shape is changed to rectangular.4. The maximum positive segregation ratios of Mn and C are 1.3 and 1.8 respectively, which are obtained by the analysis of specimen with 3 mm in dia and 3 mm in depth taken from the central segregated zone high carbon billet with 160 mm square in section.5. The length of columnar crystal and the width of central segregated zone are increased in the order 0.3%C, 0.1%C and 0.6%C steel under the same condition of super heated casting temperature.6. The mechanism of formation of equiaxed dendrite and V segregation are discussed.