Ultra-short lifetime isomer studies from photonuclear reactions using laser-driven ultra-intense {\gamma}-ray

Isomers, ubiquitous populations of relatively long-lived nuclear excited states, play a crucial role in nuclear physics. However, isomers with half-life times of several seconds or less barely had experimental cross section data due to the lack of a suitable measuring method. We report a method of online {\gamma} spectroscopy for ultra-short-lived isomers from photonuclear reactions using laser-driven ultra-intense {\gamma}-rays. The fastest time resolution can reach sub-ps level with {\gamma}-ray intensities >10^{19}/s ({\geqslant} 8 MeV). The ^{115}In({\gamma}, n)^{114m2}In reaction (T_{1/2} = 43.1 ms) was first measured in the high-energy region which shed light on the nuclear structure studies of In element. Simulations showed it would be an efficient way to study ^{229m}Th (T_{1/2} = 7 {\mu}s), which is believed to be the next generation of nuclear clock. This work offered a unique way of gaining insight into ultra-short lifetimes and promised an effective way to fill the gap in relevant experimental data

Semi-Supervised Deep Kernel Active Learning for Material Removal Rate Prediction in Chemical Mechanical Planarization

The material removal rate (MRR) is an important variable but difficult to measure in the chemical–mechanical planarization (CMP) process. Most data-based virtual metrology (VM) methods ignore the large number of unlabeled samples, resulting in a waste of information. In this paper, the semi-supervised deep kernel active learning (SSDKAL) model is proposed. Clustering-based phase partition and phase-matching algorithms are used for the initial feature extraction, and a deep network is used to replace the kernel of Gaussian process regression so as to extract hidden deep features. Semi-supervised regression and active learning sample selection strategies are applied to make full use of information on the unlabeled samples. The experimental results of the CMP process dataset validate the effectiveness of the proposed method. Compared with supervised regression and co-training-based semi-supervised regression algorithms, the proposed model has a lower mean square error with different labeled sample proportions. Compared with other frameworks proposed in the literature, such as physics-based VM models, Gaussian-process-based regression models, and stacking models, the proposed method achieves better prediction results without using all the labeled samples

A new high-precision timely monitoring and metering system for early kick and loss

Kick and loss are two complicated incidents that affect the construction safety in oil and gas well drilling. The commonly-used kick/loss monitoring methods are disadvantageous with monitoring lag and low metering precision, which may cause well collapse, pipe sticking and well blowouts due to untimely detection and improper treatment. In this paper, a new type of kick/loss monitoring and metering system was designed based upon a comparative analysis of several kick/loss monitoring methods commonly used on rig sites. This new system has the functions of early monitoring and alarm, kick/loss velocity metering, total loss metering and automatic filling, and its feasibility was verified through laboratory experiments. And the following research results were obtained. First, the monitoring tank of this new system is divided into two chambers, i.e., a main chamber and a secondary chamber. The return of drilling fluid partially flows back to the shale shaker through the main chamber, and the rest overflows into the secondary chamber. Second, the internal cross section area of the secondary chamber is small, which increases the response sensitivity to liquid level change, so kick/loss can be detected in time. Third, the water head of the outlet pipeline of the main chamber remains constant and the outlet flow is stable, so kick/loss velocity and total kick/loss can be calculated quantitatively based on the change of liquid level in the secondary chamber. And the monitoring error of kick/loss velocity is less than 8%. Fourth, in the process of tripping out, the drilling fluid in the monitoring tank flows into the wellbore under the action of self weight to keep the full liquid level of the wellbore all the time. As a result, lagged filling and partial filling are eliminated. In conclusion, this new kick/loss monitoring system is economical and practical, and giving a full play to the advantages of ground survey and alarm timely and accurately. Keywords: Early kick, Early loss, Monitoring and metering system, Main and secondary chambers, Monitoring tank, Leakage velocity, Total loss, Automatic fillin

Fabrication of an anode-supported yttria-stabilized zirconia thin film for solid-oxide fuel cells via wet powder spraying

The wet powder spraying (WPS) technique was used for the deposition of dense and thin (Y2O3)(0.08)(ZrO2)(0.92) (YSZ-8) films on an anode substrate being used for fuel cell applications. Both agglomeration of the powder and the presence of organics in the substrate have a significant effect on the quality and densification of the thin electrolyte layer. High-energy ball milling effectively broke up the agglomerates and enhanced the packing density of the green layer. Pre-calcination of the substrate at similar to 1000 degrees C enhanced the match of sintering shrinkage between the electrolyte layer and the substrate and improved the quality of the YSZ-8 thin film significantly. Crack-free dual-layer assembly with a highly densified YSZ-8 film as thin as 10 mu m was successfully fabricated by optimizing the fabrication parameters. The cells with a La0.8Sr0.2MnO3 cathode showed a high open circuit voltage of 1.071 V and a peak power density of 894 mW cm(-2) at 850 degrees C operated with hydrogen fuel. (C) 2008 Elsevier B.V. All rights reserved

Toward reducing the operation temperature of solid oxide fuel cells: our past 15 years of efforts in cathode development

The development of clean and efficient energy conversion and storage systems is becoming increasingly vital as a result of accelerated global energy consumption. Solid oxide fuel cells (SOFCs) as one key class of fuel cells have attracted much attention, owing to their high energy conversion efficiency and low emissions. However, some serious problems appeared because of the scorching operating temperatures of SOFCs (800–1000 °C), such as poor thermomechanical stability and difficult sealing, resulting in a short lifespan and high cost of SOFCs. Therefore, lowering the operating temperature of SOFCs to mid-range and even low range has become one of the main goals for SOFC development in the recent years. Looking for new cathode materials with high electrocatalytic activity and robust stability at relatively low temperatures is one of the essential requirements for intermediate-to-low-temperature SOFCs (ILT-SOFCs). During the past 15 years, we put considerable efforts into the development of alternative cathode materials for ILT-SOFCs. In this review, we give a summary of our progress from such efforts. We first summarize several strategies that have been adopted for developing cathode materials with high activity and durability toward reducing operating temperatures of SOFCs. Then, our new ideas and progress on cathode development with respect to activity and stability are provided. Both the cathodes of oxygen-ion-conducting SOFCs and protonic-conducting SOFCs are discussed. In the end, we outline the opportunities, challenges, and future approaches for the development of cathodes for ILT-SOFCs

High performance tubular solid oxide fuel cells with BSCF cathode

Compared with planar SOFCs, tubular SOFCs have the advantages of facile sealing and easy scale up. In this study, a tubular anode-supported thin-film YSZ electrolyte SOFC was successfully fabricated by extrusion of the anode substrate in combination with wet powder spraying of the electrolyte layer. The fuel cell performance was tested by applying either hydrogen or methane as the fuel and ambient air as the cathode atmosphere. Peak power densities of 432 and 145 mW cm were achieved respectively at 800 and 600°C for a cell with conventional LSM and silver wire as the cathode and the current collector. The performance was further improved by adopting BSCF cathode with an SDC buffer layer. EIS demonstrated the large electrode polarization resistance is the main source of cell resistance, while the contact resistance is also not negligible. The performance of the cell directly operating on methane fuel was also investigated. A special operation mode by alternatively operating on methane and hydrogen fuels was adopted, which can effectively increase the cell operational stability