Heat sink effects on weld bead: VPPA process

An investigation into the heat sink effects due to weldment irregularities and fixtures used in the variable polarity plasma arc (VPPA) process was conducted. A basic two-dimensional model was created to represent the net heat sink effect of surplus material using Duhamel's theorem to superpose the effects of an infinite number of line heat sinks of variable strength. Parameters were identified that influence the importance of heat sink effects. A characteristic length, proportional to the thermal diffusivity of the weldment material divided by the weld torch travel rate, correlated with heat sinking observations. Four tests were performed on 2219-T87 aluminum plates to which blocks of excess material were mounted in order to demonstrate heat sink effects. Although the basic model overpredicted these effects, it correctly indicated the trends shown in the experimental study and is judged worth further refinement

Heat sink effects in VPPA welding

The development of a model for prediction of heat sink effects associated with the Variable Polarity Plasma Arc (VPPA) Welding Process is discussed. The long term goal of this modeling is to provide means for assessing potential heat sink effects and, eventually, to provide indications as to changes in the welding process that could be used to compensate for these effects and maintain the desired weld quality. In addition to the development of a theoretical model, a brief experimental investigation was conducted to demonstrate heat sink effects and to provide an indication of the accuracy of the model

The role of the equivalent blackbody temperature in the study of Atlantic Ocean tropical cyclones

Satellite measured equivalent blackbody temperatures of Atlantic Ocean tropical cyclones are used to investigate their role in describing the convection and cloud patterns of the storms and in predicting wind intensity. The high temporal resolution of the equivalent blackbody temperature measurements afforded with the geosynchronous satellite provided sequential quantitative measurements of the tropical cyclone which reveal a diurnal pattern of convection at the inner core during the early developmental stage; a diurnal pattern of cloudiness in the storm's outer circulation throughout the life cycle; a semidiurnal pattern of cloudiness in the environmental atmosphere surrounding the storms during the weak storm stage; an outward modulating atmospheric wave originating at the inner core; and long term convective bursts at the inner core prior to wind intensification

Predicting tropical cyclone intensity using satellite measured equivalent blackbody temperatures of cloud tops

A regression technique was developed to forecast 24 hour changes of the maximum winds for weak (maximum winds less than or equal to 65 Kt) and strong (maximum winds greater than 65 Kt) tropical cyclones by utilizing satellite measured equivalent blackbody temperatures around the storm alone and together with the changes in maximum winds during the preceding 24 hours and the current maximum winds. Independent testing of these regression equations shows that the mean errors made by the equations are lower than the errors in forecasts made by the peristence techniques

Stereographic cloud heights from the imagery of two scan-synchronized geostationary satellites

Scan synchronization of the sensors of two SMS-GOES satellites yields imagery from which cloud heights can be derived stereographically with a theoretical two-sigma random uncertainty of + or - 0.25 km for pairs of satellites separated by 60 degrees of longitude. Systematic height errors due to cloud motion can be kept below 100 m for all clouds with east-west components of speed below hurricane speed, provided the scan synchronization is within 40 seconds at the mid-point latitude, and the spin axis of each satellite is parallel to that of the earth

Curvature-Induced Instabilities of Shells

Induced by proteins within the cell membrane or by differential growth, heating, or swelling, spontaneous curvatures can drastically affect the morphology of thin bodies and induce mechanical instabilities. Yet, the interaction of spontaneous curvature and geometric frustration in curved shells remains still poorly understood. Via a combination of precision experiments on elastomeric spherical bilayer shells, simulations, and theory, we show a spontaneous curvature-induced rotational symmetry-breaking as well as a snapping instability reminiscent of the Venus fly trap closure mechanism. The instabilities and their dependence on geometry are rationalized by reducing the spontaneous curvature to an effective mechanical load. This formulation reveals a combined pressurelike bulk term and a torquelike boundary term, allowing scaling predictions for the instabilities in excellent agreement with experiments and simulations. Moreover, the effective pressure analogy suggests a curvature-induced buckling in closed shells. We determine the critical buckling curvature via a linear stability analysis that accounts for the combination of residual membrane and bending stresses. The prominent role of geometry in our findings suggests the applicability of the results over a wide range of scales.Comment: 12 pages, 9 figures (including Supporting Information

Air-sea interaction in the tropical Pacific Ocean

Charts of 3-month sea surface temperature (SST) anomalies in the eastern tropical Pacific Ocean were produced for the period 1949 to 1970. The anomalies along the United States and South American west coasts and in the eastern tropical Pacific appeared to be oscillating in phase during this period. Similarly, the satellite-derived cloudiness for each of four quadrants of the Pacific Ocean (130 deg E to 100 deg W, 30 deg N to 25 deg S) appeared to be oscillating in phase. In addition, a global tropical cloudiness oscillation from 30 deg N to 30 deg S was noted from 1965 to 1970, by using monthly satellite television nephanalyses. The SST anomalies were found to have a good degree of correlation both positive and negative with the following monthly geophysical parameters: (1) satellite-derived cloudiness, (2) strength of the North and South Pacific semipermanent anticyclones, (3) tropical Pacific island rainfall, and (4) Darwin surface pressure. Several strong direct local and crossequatorial relationships were noted. In particular, the high degree of correlation between the tropical island rainfall and the SST anomalies (r = +0.93) permitted the derivation of SST's for the tropical Pacific back to 1905. The close occurrence of cold tropical SST and North Pacific 700-mb positive height anomalies with central United States drought conditions was noted

Današnje stanje međulonca s pokrivnim troskama u ljevaonici slabova

Tundish metallurgy development, which has been focused on steel cleanliness improvement in last few years, affected also tundish slag systems. Molten slags are the most suitable for both absorbing and refining functions of tundish cover slags, while a system of extremely low density does satisfy their isolating functions in the best way. Hence it is obvious, that it is not possible to assure the main functions using one sort of tundish covering slags. In addition, traditional acid slags, are being replaced with basic covering slags, or combination of both types. In this work, we have tried to investigate the operation of tundish covering slag under the condition of slab continuous casting. A genesis of covering slag from applied cover powders its refining functions have been investigated, as well as the changes of covering slag chemical composition during one tundish casting sequence.Razvoj metalurgije međulonca koji se usmjerio na unapređivanje čistoće čelika tijekom zadnjih nekoliko godina odrazio se i na vrste troske u međuloncu. Rastaljena troska je najpogodnija kako za funkcije apsorbiranja tako i za funkcije rafiniranja pokrovne troske međulonca sve dok sistem krajnje male gustoće zadovoljava na najbolji način njene izolacione funkcije. Iz toga je jasno, da nije moguće osigurati glavne funkcije uporabom samo jedne vrste pokrovnih troski međulonca. Osim toga, tradicionalne kisele troske zamjenjuju se bazičnim pokrovnim troskama, ili se koristi kombinacija obadva tipa. U ovom članku se nastojalo istražiti rad pokrovne troske međulonca u uvjetima kontinuiranog lijevanja slabova. Istraživano je kako se uporaba pokrovne troske razvijala iz uporabe pokrovnih prahova te njene funkcije rafiniranja kao i promjene njenog kemijskog sastava tijekom jednog ciklusa lijevanja međulonca

Direct Metal Laser Sintering – Possibility of Application in Production Process

The article describes the Direct Metal Laser Sintering technology and its application in production process. In the introduction part, a brief description of DMLS technology is described, its principles with the subsequent advantages and disadvantages. The second part of the article focuses on characterization of the basic materials which are currently most commonly used in DMLS processes. This part aims at describing the basic properties of the individual materials and their demonstration. The final part of the article deals with the possibilities of applying the chosen method in the production process

Novel Bradykinin Analogues Modified in the N-Terminal Part of the Molecule with a Variety of Acyl Substituents

In the current work we present some pharmacological characteristics of ten new analogues of bradykinin (Arg–Pro–Pro–Gly–Phe–Ser–Pro–Phe–Arg) modified in the N-terminal part of the molecule with a variety of acyl substituents. Of the many acylating agents used previously with B2 receptor antagonists, the following residues were chosen: 1-adamantaneacetic acid (Aaa), 1-adamantanecarboxylic acid (Aca), 4-tert-butylbenzoic acid (t-Bba), 4-aminobenzoic acid (Aba), 12-aminododecanoic acid (Adc), succinic acid (Sua), 4-hydroxybenzoic acid, 4-hydroxy-3-methoxybenzoic acid, 3-(4-hydroxyphenyl)propionic acid and 6-hydroxy-2-naphthoic acid. Biological activity of the compounds was assessed in the in vivo rat blood pressure test and the in vitro rat uterus test. Surprisingly, N-terminal substitution of the bradykinin peptide chain itself with aforementioned groups resulted in antagonists of bradykinin in the pressor test and suppressed agonistic potency in the uterotonic test. These interesting findings need further studies as they can be helpful for designing more potent B2 receptor blockers