The role of BT-dependent flows on W accumulation at the edge of the confined plasma

Near-separatrix impurity accumulation between the crown and the outer midplane of tokamaks is a common feature in results from codes such as SOLPS-ITER and DIVIMP; however, experimental evidence of accumulation has only recently been obtained and is reported here. The codes find that the poloidal distribution of impurity ions in the scrape-off layer (SOL) depends primarily on toroidal field (BT)-dependent parallel flow patterns of the background plasma and the parallel ion temperature gradient (∇||Tion) force. Experimentally, Mach probes used in L-mode plasmas with favorable (for H-mode access) BT measure fast (M~0.3-0.5) inner-target-directed (ITD) background plasma flows at the crown of single-null discharges. This study reports a set of DIVIMP simulations for two similar H-mode discharges from the DIII-D W Metal Rings Campaign differing primarily in BT-direction to assess the effect that fast ITD flows have on the distribution of W ions in the SOL. It is found that for imposed ITD flows of M = 0.3, W ions that otherwise accumulate due to the ∇||Tion-force are largely flushed out. It is also found that doubling the radial diffusion coefficient from 0.3 to 0.6 m2/s prevents accumulation due to rapid cross-field transport into the far-SOL, where background plasma flows drain W ions to the divertors. Far-SOL W distributions from DIVIMP are then used to specify input to the impurity transport code 3DLIM, which is used to interpretively model collector probe deposition patterns measured in the “wall-SOL.” It is demonstrated that the deposition patterns are consistent with the DIVIMP predictions of near-SOL accumulation for the unfavorable-BT direction, and little/no accumulation for the favorable-BT direction. The wall-SOL collector probes have thus provided the first experimental evidence, albeit indirect, of near-SOL W accumulation – finding it occurs for the unfavorable-BT direction only. For the favorable-BT direction, fast flows can largely prevent accumulation from occurring.

Research on the Physical Characteristics of Hot-Pressed Sintering Preparing Self-Fluxing Filler by X-Ray Diffraction

In this paper, Al-12Si self-fluxing filler metal ring was prepared with Al-12Si alloying powders and KAlF4 flux by hot pressed sintering (HPS) method. The microstructure and mechanical properties of the brazing alloy and the brazed 3003 aluminum alloy joint were investigated. The results showed that Al-12Si self-fluxing filler metal ring could be successfully obtained by HPS at 470°C using a pressure of 300MPa. The prepared filler metal ring was dense and defect-free and the microstructure was mainly composed of Si phase with KAlF4 flux grain uniformly distributed in the Al matrix. The 3003 aluminum alloy joint interface brazed by the prepared filler metal was also well bonded and no pore and defect was found. A quite high joint strength of 75MPa was obtained which is equal to the strength of joint brazed using commercial Al-Si self-fluxing wires prepared by hot extrude method. The results revealed that the filler metal rings fabricated by HPS process had great potentiality in brazing of aluminum alloy especially for the Al-Al pipes joining due to its high joint strength, low cost and the convenience for industrial application.

Numerical Investigations on the Shape Optimization of Stainless-Steel Ring Joint with Machine Learning

Since pipes used for water pipes are thin and difficult to fasten using welding or screws, they are fastened by a crimping joint method using a metal ring and a rubber ring. In the conventional crimping joint method, the metal ring and the rubber ring are arranged side by side. However, if water leaks from the rubber ring, there is a problem that the adjacent metal ring is rapidly corroded. In this study, to delay and minimize the corrosion of connected water pipes, we propose a spaced crimping joint method in which metal rings and rubber rings are separated at appropriate intervals. This not only improves the contact performance between the connected water pipes but also minimizes the load applied to the crimping jig during crimping to prevent damage to the jig. For this, finite element analyses were performed for the crimp tool and process analysis, and the design parameters were set as the curling length at the top of the joint, the distance between the metal rings and rubber rings, and the crimp jig radius. Through FEA of 100 cases, data to be trained in machine learning were acquired. After that, training data were trained on a machine learning model and compared with a regression model to verify the model’s performance. If the number of training data is small, the two methods are similar. However, the greater the number of training data, the higher the accuracy predicted by the machine learning model. Finally, the spaced crimping joint to which the derived optimal shape was applied was manufactured, and the maximum pressure and pressure distribution applied during compression were obtained using a pressure film. This is almost similar to the value obtained by finite element analysis under the same conditions, and through this, the validity of the approach proposed in this study was verified.

On-column cryofocusing and analyte enrichment device for gas chromatography systems

The objective of this work was to design, construct and test the sample focusing and concentration enrichment device for gas chromatography. The device was based on four metal rings, between which a capillary column and two wire heaters were placed. The metal rings were connected to each other and cooled down using liquid nitrogen. The column was connected to the gas chromatography system using a heated transfer line. The research was conducted on how the length of the cooled column influences focusing and enrichment capabilities of the system. It was found that the analytes were focused better by using a longer cooled part of the column. The longer cooled column was also able to retain a greater volume of the analytes, injected consecutively. By using the 95 cm cooled column length, it was possible to retain 20 injections and detect a 20 times bigger peak area. By changing the temperature of the cooling zone, it was also observed that peak symmetry is heavily dependent on it. Lower cooled zone temperatures produced narrower and more symmetrical peaks.

Sazonalidade da mesofauna edáfica em fragmentos de vegetação de caatinga no semiárido nordestino do Brasil

<p>The edaphic mesofauna comprises litter-decomposing organisms deposited on the surface that directly participate in the process of nutrient cycling and the formation of organic matter, essential to maintain soil quality. The aim of this research was to quantify the abundance, richness and diversity of the edaphic mesofauna in caatinga environments in the semiarid region of Alagoas. For this research, two areas of native caatinga were selected, located in Olho D’Água do Casado (area I) and Delmiro Gouveia (area II), in the state of Alagoas, whose areas of vegetation are characterized as hypoxophilous caatinga. The collections were conducted bimonthly between February 2012 and October 2013. For the collection of mesofauna, twenty pre-selected points were used, from which samples of soil + litter were taken, with the aid of metal rings, 5 cm soil depth. The samples were taken to the battery of extractors Berlese-Tullgren, which was modified for the extraction of the organisms, and later the captured organisms were quantified and identified in the order of the large taxonomic groups. To measure the wealth of the groups, Shannon’s Diversity Index and Pielou’s Equability Index were used. The dominant groups of soil mesofauna in area I were Acarina, Collembola, Isoptera and Psocoptera, while in area II were Acarina, Collembola, Psocoptera and Hymenoptera.</p>

Controlled Deposition of Polyamide Nanofibers Through an Innovative Electrospinning Device

Electrospinning is a straightforward, cheap and unique method to produce novel fibers with diameter in the range of 100 nm and even less. Those nanofibers have a wide variety of applications such as: filters, membranes, composite reinforcement, drug delivery, protective barriers, sensors, wound dressings and tissue-engineered scaffolds where their unique properties contribute to product functionality. However, this process is characterized by a chaotic oscillation of the electrospinning jet which leads to the formation of beads an uneven nanofiber. This research work envisages the development of an apparatus to control the deposition of electrospun nanofibers through the use of a series of charged metal rings and the addition of a secondary power source, which enables a greater control over the polymer jet stream. Keywords: Nanotechnology, Electrospinning, Nanofibres, Controled deposition, Polyamides