Coupled Simulation of a Vacuum Creation System and a Rectification Column Block

The purpose of this study was the coupling simulation of the vacuum block of the ethanolamine mixture separation unit to determine the optimal layout of the vacuum creation system. For this, a computational model of the vacuum unit, which was identified by comparing the computational data with the data of an industrial study of vacuum rectification columns, was synthesized in the Unisim Design R461 software package. To determine the required load on the vacuum system, a numerical experiment was carried out, during which it was discovered that the load on the system would be 9600 m3/h. It was proposed to replace individual column vacuum pumps with a single vacuum-generating system (VGS) based on a liquid ring vacuum pump (LRVP). When defining the layout, two possible schemes were considered, the models of which were created in Unisim Design R461. The system layout was determined by matching the characteristics of the system elements with the characteristics of the vacuum columns. A technical and economic comparison of the proposed solutions was carried out and the payback period for capital costs was calculated, which for Scheme 1 was 4.14 years, and for Scheme 2–3.59 years.

Shape Optimization of a Column under Generalized Load with a Force Directed towards Positive Pole

In this paper, the issue of shape optimization of a column subjected to the generalized load with a force directed towards the positive pole (L. Tomski’s load, specific load) was considered. Based on the Hamilton’s principle, the differential equations of movement and boundary conditions describing the system were formulated. Taking into account a kinetic criterion of stability loss and a condition of constant total volume, the scope of changes in natural frequency as a function of an external load was determined with selected geometrical and physical parameters of the loading structure. On the basis of obtained results, values of geometrical parameters of individual column segments were determined, at which the maximum critical load value was obtained. In order to find the maximum critical force, which is a function of many variables, the simulated annealing algorithm was used.

INNOVATIVE DESIGN AND ERECTION SOLUTION FOR PORTAL FRAME INDUSTRIAL STEEL BUILDING ROOFS

Traditional design and erection of long span steel portal frames for industrial buildings consists of individual column and rafter assemblies, with bolted connections at knee (Column-Beam) and apex joints (ridge). This method ensures expediency for an offsite member fabrication and application of the galvanized coating to individual members, before transportation to the work site followed by assembling and erection at the site. This traditional approach however also inherits safety risks associated with working at heights during member erection, alignment and jointing of individual member connections and during placement and fixing of cladding elements. In view of expediting the onsite construction and to mitigate the risk of working at height during erection, designers worked in tandem with contractors and fabricators to rearrange roof elements so as to allow the whole roof to be pre-fabricated on the ground and be lifted for installation matching with the column alignment. In particular, the portal connection at the column-beam knee joint was relocated and redesigned to suit installation ease. The impact of the proposed solution to the design is investigated herein. A rigorous risk analysis was employed to better understand the modes of failure and frame behavior, which in turn assisted in better identifying the design risks. Furthermore, the benefits achieved in the erection process through increased safety and efficiency are also highlighted.

Failure Analysis of Embedded Non-Volatile Memory with Nano- and Micro-Probing Techniques

Embedded non-volatile memory (NVM) technologies are used in almost all areas of semiconductor chip applications, as it becomes increasingly vital to retain information when the electronics power is off. Nano-probing techniques, such as atomic force probe (AFP), allow us to access individual devices at contact or via levels and characterize the details as much as possible before a decision can be made for physical analysis. This paper reports the application of AFP to characterize each individual bit at contact level or individual column at via1 level. It presents two cases to identify the failures encountered in fabricated embedded NVM: column-column leakage and single bit erase failure. The first case shows that silicide residual could cause column to column leakage by creating electrical path between active areas of adjacent columns, while the second case shows that single bit failures due to low erase current can be recovered with repeated program/erase cycle.

Examining the Effects of Scale, Mass Ratios and Column Shapes on the Vortex Induced Motion Response of a Semisubmersible Through CFD Analyses

The phenomenon of vortex induced motions (VIM) of a semisubmersible has been observed in the field and in model tests. The VIM response can be onerous to the fatigue live of SCR’s that are supported from the semisubmersible. Field observations indicate significantly smaller VIM amplitude than what present day model tests predict. The Scruton number is a parameter which affects the magnitude of the VIM response; the Scruton number includes the effect of mass ratio and damping. The effect of damping on VIM response has been examined in model test scale, and this analysis indicated that damping has a minimal effect on the VIM response amplitudes. The effect of the mass ratio and the effect of performing physical experiments at model scale are examined through CFD analyses. The objectives of the CFD analyses are to focus on the VIM phenomenon itself and to compare response magnitudes, while giving less importance to semisubmersible hull details and absolute response magnitudes. Hence, most of the CFD work is done in a 2D environment. Responses for various column cross-sectional shapes are examined; the column cross-sectional shapes include square, rectangular and five-sided. The VIM response is the result of pressures acting on the semisubmersible columns. The CFD analyses provide means to obtain the pressures at various locations at the various columns, and therefore can be used as a way to describe the phenomenon. These pressure data sets are evaluated to show where the majority of the excitation occurs and phase relationships between excitation forces acting on each individual column are presented.

Influence of Microbiological Activity on the Mobility of Redoxsensitive Radionuclides in Sediments

ABSTRACTThe influence of microbial activity on the transport and migration behaviour of redox-sensitive radionuclides (e.g. Technetium (Tc) and Selenium (Se)) in groundwater environment were investigated within an interdisciplinarary research program. Soil material and sediments were investigated with batch- and recircu-lation column experiments. The number of microorganisms in the water was determined by counting the colony forming units (CFU) on R2A agar at regular periods.The results of sterile and non sterile recirculation column experiments showed within 80 days a high fixation of the radionuclides in the unsterile samples (80% of Tc, 50% of Se compared with the initial concentration Ao), and no fixation in the sterile samples. There was no difference in the redox values.It could be shown that the immobilisation of the redox-sensitive elements Tc and Se are strongly determined by microbial activity, depending on the different sediments and their microbial live stock. There are indications that the microorganisms found in the non sterile columns are allochthonous bacteria which were dragged into the experimental systems and samples during laboratory work and sampling. The composition of the microbial flora was shown to be very heterogenous and different in each individual column and within the same column at different times. Thus these columns might have been contaminated with microorganisms during sampling and handling of the experimental systems under non sterile conditions, as done generally in most laboratories.