Upgrade of an integrated Langmuir probe system on the closed divertor target plates in the HL-2A tokamak

A newly designed divertor Langmuir probe diagnostic system has been installed in a rare closed divertor of the HL-2A tokamak and steadily operated for the study of divertor physics involved edge-localized mode (ELM) mitigation, detachment and redistribution of heat flux, etc. Two sets of probe arrays including 274 probe tips were placed at two ports (approximately 180° separated toroidally), and the spatial and temporal resolutions of this measurement system could reach 6 mm and 1 s, respectively. A novel design of the ceramic isolation ring can ensure reliable electrical insulation property between the graphite tip and the copper substrate plate where plasma impurities and the dust are deposited into the gaps for a long experimental time. Meanwhile, the condition monitoring and mode conversion between single and triple probe of the probe system could be conveniently implemented via a remote control station. The preliminary experimental result shows that the divertor Langmuir probe system is capable of measuring the high spatiotemporal parameters involved the plasma density, electron temperature, particle flux as well as heat flux during the ELMy H-mode discharges.

Wear Performance Evaluation of Minimum Quantity Lubrication With Exfoliated Graphite Nanoplatelets in Turning Titanium Alloy

This paper evaluates the performances of dry, minimum quantity lubrication (MQL), and MQL with nanofluid conditions in turning of the most common titanium (Ti) alloy, Ti-6Al-4 V, in a solution treated and aged (STA) microstructure. In particular, the nanofluid evaluated here is vegetable (rapeseed) oil mixed with small concentrations of exfoliated graphite nanoplatelets (xGnPs). This paper focuses on turning process that imposes a challenging condition to apply the oil or nanofluid droplets directly onto the tribological surfaces of a cutting tool due to the uninterrupted engagement between tool and work material during cutting. A series of turning experiments was conducted with uncoated carbide inserts, while measuring the cutting forces with a dynamometer under the dry, MQL and MQL with nanofluid conditions supplying oil droplets externally from our MQL device. The inserts are retrieved intermittently to measure the progress of flank and crater wear using a confocal microscopy. This preliminary experimental result shows that MQL and in particular MQL with the nanofluid significantly improve the machinability of Ti alloys even in turning process. However, to attain the best performance, the MQL conditions such as nozzle orientation and the concentration of xGnP must be optimized.

Performance Evaluation of Minimum Quantity Lubrication With Exfoliated Graphite Nanoplatelets in Turning Titanium Alloy

This paper evaluates the performances of dry, minimum quantity lubrication (MQL) and MQL with nanofluid in turning the most common titanium (Ti) alloy, Ti-6Al-4V, in a solution treated and aged (STA) microstructure. In particular, the nanofluid evaluated here is vegetable oil (rapeseed) mixed with small concentrations of exfoliated graphite nanoplatelets (xGnP). The focus of this paper is on turning process because it poses a challenging condition to apply oil droplets directly onto the tribological surfaces of a cutting tool due to the continuous engagement of tool and work material. A series of turning experiments was conducted with uncoated carbide inserts while measuring the cutting forces with the dynamometer under various conditions to determine its effectiveness and optimal MQL condition in turning. The worn inserts are retrieved to measure flank and crater wear using confocal microscopy. This preliminary experimental result shows that the use of MQL and nanofluid is effective in improving the machinability of Ti alloys in turning processes.

Numerical Simulation of Gas-Liquid Two-Phase Flow in a Horizontally Placed Hydrophobic Rectangular Channel (Part 2, Influence of Abrupt Contraction)

This paper computationally visualizes two-phase flow patterns through a horizontally placed hydrophilic or hydrophobic rectangular channel with an abrupt contraction. The rectangular duct used in this study has a thickness narrower than the Laplace constant so that the surface tension governs the fluid system rather than the inertia force. In particular, the computed bubble behavior at the abrupt contraction seemed to be a similar nature against the preliminary experimental result.

BDD-Based Combinatorial Keyword Query Processing under a Taxonomy Model

Digital libraries are one of the key systems for an IT society, and supporting easy access to them is an important technical issue between a human and an intelligent system. Here the authors consider a publish/subscribe system for digital libraries which continuously evaluates queries over a large repository containing document descriptions. The subscriptions, the query expressions and the document descriptions, all rely on a taxonomy that is a hierarchically organized set of keywords, or terms. The digital library supports insertion, update and removal of a document. Each of these operations is seen as an event that must be notified only to those users whose subscriptions match the document's description. In this chapter, the authors present a novel method of processing such keyword queries. Their method is based on Binary Decision Diagram (BDD), an efficient data structure for manipulating large-scale Boolean functions. The authors compile the given keyword queries into a BDD under a taxonomy model. The number of possible keyword sets can be exponentially large, but the compiled BDD gives a compact representation, and enabling a highly efficient matching process. In addition, the authors' method can deal with any Boolean combination of keywords from the taxonomy, while the previous result considered only a conjunctive keyword set. In this chapter, they describe the basic idea of their new method, and then the authors show their preliminary experimental result applying to a document set with large-scale keyword domain under a real-life taxonomy structure.

Using Logic Synthesis and Circuit Reasoning for Equivalence Checking

The existing SAT based algorithms combines two circuits into a miter, and then convert the miter into a CNF formula. After that, a SAT solver is invoked to check the satisfiability of the CNF formula. However, when a miter is converted into CNF formula, the structure information of the circuit is lost. Therefore,we are motivated to solve the problem of miter satisfiability using circuit reasoning. We use logic synthesis first to simplify the circuit, and then use a backtracking method to check the satisfiability of the miter. The preliminary experimental result sindicate that our approach is efficient.

Development of a New Vibrator for Elliptical Vibration Texturing

Inspired by the idea of vibro-mechanical texturing, which adds a tertiary motion to the tool tip in the conventional turning process, and the elliptical vibration cutting process, which adds vibrations both in the cutting direction and feed direction, this paper proposes a new design for an ultrasonic vibrator for the elliptical vibration texturing process. The elliptical locus lies in the plane that is defined by the cutting and the radial directions. The device could be easily adapted for elliptical cutting applications by changing the orientation of the tool tip. The vibrator works in the resonant mode, with in-phase and anti-phase vibration modes at a nearly identical natural frequency. Simulations and experiments have been carried out to study and verify different vibration modes of the system. Different design parameters have been analyzed to control the elliptical trajectory of the tool tip. A set of preliminary experimental result of elliptical vibration texturing is also provided.

BDD-Based Combinatorial Keyword Query Processing under a Taxonomy Model

Digital libraries are one of the key systems for an IT society, and supporting easy access to them is an important technical issue between a human and an intelligent system. Here we consider a publish/subscribe system for digital libraries which continuously evaluates queries over a large repository containing document descriptions. The subscriptions, the query expressions and the document descriptions, all rely on a taxonomy that is a hierarchically organized set of keywords, or terms. The digital library supports insertion, update and removal of a document. Each of these operations is seen as an event that must be notified only to those users whose subscriptions match the document‘s description. In this chapter, the authors present a novel method of processing such keyword queries. Our method is based on Binary Decision Diagram (BDD), an efficient data structure for manipulating large-scale Boolean functions. The authors compile the given keyword queries into a BDD under a taxonomy model. The number of possible keyword sets can be exponentially large, but the compiled BDD gives a compact representation, and enabling a highly efficient matching process. In addition, our method can deal with any Boolean combination of keywords from the taxonomy, while the previous result considered only a conjunctive keyword set. In this chapter, they describe the basic idea of their new method, and then the authors show their preliminary experimental result applying to a document set with large-scale keyword domain under a real-life taxonomy structure.