Volumetric Efficiency Improvement by Overflow in Rolling Piston Compressor

The rotary compressor with rolling piston is a widely used compressor with less clearance volume, while it is minimized from normal scale to meso or micro scale, the input and exit ports dimension is limited by port requirement and lead to a certain clearance volume, therefore, keeping or improving its volume efficiency is an important issue. Although rolling piston compressor is a kind of compact structure compressor, the existence of the clearance volume is inevitable in a compressor, the more the clearance volume, the lower the volumetric efficiency of compressor. The overflow is a method to improve the volumetric efficiency of a compressor which had been discussed in wankel compressor, in the overflowing process the clearance space with high pressure is connected directly with the space with lower pressure, mostly that is in the moment, one of the chambers in the rotary compressor is at the end of the exhaust process, and another chamber is at the sucking stage or the initial compression process. The gas pressure in the clearance volume is visibly higher than that in the compression chamber. The high-pressure gas in the clearance volume flows into the compression cylinder via a certain way; this flow considerably increases the pressure in the compression cylinder and decreases the pressure in the clearance volume. Thus, the intake and exhaust times means to be extended, and the volumetric efficiency and the cooling capacity of the compressor can be substantially enhanced. In this paper, we introduce the effect of input and exit dimensions on the volume efficiency of rolling piston compressor, and the overflow design on a rolling piston compressor that fully uses the high-pressure gas in the clearance volume, and discuss its effect on the performance of a compressor by theoretical analyses. Usually, the coefficient of performance of a vapor refrigeration cycle with the compressor overflow has a certain decrease compared with the conventional compressor, but the volumetric efficiency of the compressor with overflow and the cooling capacity of the thermodynamic cycle recesses are visibly higher than those of the conventional compressor in terms of the same operation and dimension parameters. The overflow has beneficial effect on miniaturizing the compresso

Co-attention Propagation Network for Zero-Shot Video Object Segmentation

Zero-shot video object segmentation (ZS-VOS) aims to segment foreground objects in a video sequence without prior knowledge of these objects. However, existing ZS-VOS methods often struggle to distinguish between foreground and background or to keep track of the foreground in complex scenarios. The common practice of introducing motion information, such as optical flow, can lead to overreliance on optical flow estimation. To address these challenges, we propose an encoder-decoder-based hierarchical co-attention propagation network (HCPN) capable of tracking and segmenting objects. Specifically, our model is built upon multiple collaborative evolutions of the parallel co-attention module (PCM) and the cross co-attention module (CCM). PCM captures common foreground regions among adjacent appearance and motion features, while CCM further exploits and fuses cross-modal motion features returned by PCM. Our method is progressively trained to achieve hierarchical spatio-temporal feature propagation across the entire video. Experimental results demonstrate that our HCPN outperforms all previous methods on public benchmarks, showcasing its effectiveness for ZS-VOS.Comment: accepted by IEEE Transactions on Image Processin

Simulation of the effect of stand-off parameter on collapse behaviours of a single cavitation bubble in jet drilling

Cavitation jet drilling has been extensively employed for the exploitation of geo-energy resources. The dynamics of cavitation bubbles in close proximity to the solid boundary have been a subject of great interest during jet drilling, as they play a crucial role in determining the cavitation performance. In present work, the dynamics of a single cavitation bubble near a solid surface is numerically investigated by using the axisymmetric Navier-Stokes equations and the volume of fluid method with considering the surface tension of gas-liquid interface, liquid viscosity and compressibility of gas in bubble. The simulated profiles are qualitatively and quantitatively consistent with the experimental images, which proves the reliability of employed numerical model. The effects of stand-off distance on the bubble profiles, bubble volume and collapse time have been analysed. Moreover, the cavitation erosion patterns towards the solid wall are also revealed for different dimensionless standoff distances. The simulation results reveal two distinct collapse patterns for the bubble profiles. The solid wall significantly impedes the shrinkage rate of the bubble, resulting in the longest collapse time when the dimensionless stand-off distance is 1.0. Three erosion patterns of cavitation bubbles towards the solid wall are observed, with the shock wave and micro-jet both contributing significantly to the damage caused by cavitation erosion. The shock wave sweeps the wall resulting in circular corrosion pits with a severely eroded centre, while the micro jet penetrates the wall leading to small spot corrosion pits.Document Type: Original articleCited as: Wu, X., Zhang, Y., Huang, H., Hui, C., Hu, Z., Li, G. Simulation of the effect of stand-off parameter on collapse behaviours of a single cavitation bubble in jet drilling. Advances in Geo-Energy Research, 2023, 8(3): 181-192. https://doi.org/10.46690/ager.2023.06.0

Characteristic Compounds Identification and Authenticity Evaluation of Heptapleurum Honey

In order to clarify the characteristic compounds and establish the authenticity evaluation method of heptapleurum honey, high-performance liquid chromatography coupled with quadrupole-time-of-flight tandem mass spectrometry (HPLC-Q/TOF-MS/MS) was used to qualitative and quantitative analysis of characteristic compounds in heptapleurum honey. Five compounds were identified including 4-(1'-cyclodiethyl ether-3'-butanediol)-3,5,5-trimethyl-2-cyclohexenone (Unedone B), 3,4,5-trimethoxy cinnamyl alcohol, 4-(1'2'-dihydroxy-3'epoxypropane) -3,5,5-2-cyclohexenone (Unedone C), trans, trans abscisic acid, and cis, trans abscisic acid. Notably, 3,4,5-trimethoxy cinnamyl alcohol was first found in honey, and it could be a marker of heptapleurum honey. Moreover, 10 raw heptapleurum honey samples with different geographic origins were collected to establish HPLC fingerprint. The authenticity of six commercial heptapleurum honey samples were evaluated by combining characteristic compound with HPLC fingerprint. The results demonstrated that three brands of sample were genuine pure heptapleurum honey, two brands of sample might be mixed with other honeys. A brand sample did not contain characteristic compound and were significantly different with the standard fingerprints of heptapleurum honey. It was inferred that the sample was not heptapleurum honey. This study provides theoretical reference for the authenticity evaluation of heptapleurum honey

Enhancement of Radiative Efficiency with Staggered InGaN Quantum Well Light Emitting Diodes

The technology on the large overlap InGaN QWs developed in this program is currently implemented in commercial technology in enhancing the internal quantum efficiency in major LED industry in US and Asia. The scientific finding from this work supported by the DOE enabled the implementation of this step-like staggered quantum well in the commercial LEDs

A Comprehensive Model for Real Gas Transport in Shale Formations with Complex Non-planar Fracture Networks

A complex fracture network is generally generated during the hydraulic fracturing treatment in shale gas reservoirs. Numerous efforts have been made to model the flow behavior of such fracture networks. However, it is still challenging to predict the impacts of various gas transport mechanisms on well performance with arbitrary fracture geometry in a computationally efficient manner. We develop a robust and comprehensive model for real gas transport in shales with complex non-planar fracture network. Contributions of gas transport mechanisms and fracture complexity to well productivity and rate transient behavior are systematically analyzed. The major findings are: simple planar fracture can overestimate gas production than non-planar fracture due to less fracture interference. A “hump” that occurs in the transition period and formation linear flow with a slope less than 1/2 can infer the appearance of natural fractures. The sharpness of the “hump” can indicate the complexity and irregularity of the fracture networks. Gas flow mechanisms can extend the transition flow period. The gas desorption could make the “hump” more profound. The Knudsen diffusion and slippage effect play a dominant role in the later production time. Maximizing the fracture complexity through generating large connected networks is an effective way to increase shale gas production

Impact of electrical contacts design and materials on the stability of Ti superconducting transition shape

The South Pole Telescope SPT-3G camera utilizes Ti/Au transition edge sensors (TESs). A key requirement for these sensors is reproducibility and long-term stability of the superconducting (SC) transitions. Here, we discuss the impact of electrical contacts design and materials on the shape of the SC transitions. Using scanning electron microscope, atomic force microscope, and optical differential interference contrast microscopy, we observed the presence of unexpected defects of morphological nature on the titanium surface and their evolution in time in proximity to Nb contacts. We found direct correlation between the variations of the morphology and the SC transition shape. Experiments with different diffusion barriers between TES and Nb leads were performed to clarify the origin of this problem. We have demonstrated that the reproducibility of superconducting transitions can be significantly improved by preventing diffusion processes in the TES–leads contact areas

Performance and characterization of the SPT-3G digital frequency-domain multiplexed readout system using an improved noise and crosstalk model

The third-generation South Pole Telescope camera (SPT-3G) improves upon its predecessor (SPTpol) by an order of magnitude increase in detectors on the focal plane. The technology used to read out and control these detectors, digital frequency-domain multiplexing (DfMUX), is conceptually the same as used for SPTpol, but extended to accommodate more detectors. A nearly 5× expansion in the readout operating bandwidth has enabled the use of this large focal plane, and SPT-3G performance meets the forecasting targets relevant to its science objectives. However, the electrical dynamics of the higher-bandwidth readout differ from predictions based on models of the SPTpol system due to the higher frequencies used and parasitic impedances associated with new cryogenic electronic architecture. To address this, we present an updated derivation for electrical crosstalk in higher-bandwidth DfMUX systems and identify two previously uncharacterized contributions to readout noise, which become dominant at high bias frequency. The updated crosstalk and noise models successfully describe the measured crosstalk and readout noise performance of SPT-3G. These results also suggest specific changes to warm electronics component values, wire-harness properties, and SQUID parameters, to improve the readout system for future experiments using DfMUX, such as the LiteBIRD space telescope

MECHANISM OF HYDRAULIC PULSED AND CAVITATING JET IMPROVING ROP AND APPLICATION IN CHINA OFFSHORE DRILLING Organized and Sponsored by WJTA ® -IMCA ®

ABSTRACT Offshore drilling has attracted much more attention than ever before due to the increasing worldwide energy demand especially in China. The issues challenge offshore drilling are cost control, shorter drilling cycle, and speed up the drilling process. First of all, the mechanism of pulsed and cavitating jet improving ROP had been studied in this paper, which include: 1) negative pressure pulse changes the flow field at the bottom hole and lowers the rock breaking strength; 2) negative pressure pulse can accelerate rock debris to break away from the bottom hole; and 3) self-resonating cavitating jet can improve the rock breaking efficiency. Secondly, the hydraulic pulsed and cavitating jet generator was designed based on the China offshore drilling technologies and parameters and then the generator's characteristics was collected through the laboratory and field tests. At the same time the paper designed hydraulic pulsed and cavitating jet drilling technique parameters and bottom hole assemblies matching with drilling collar, positive displacement motor, and rotary steerable system, etc. The last, application of the hydraulic pulsed and cavitating jet technique has been successfully conducted in more than 10 offshore wells in China offshore drilling. The depth of the applied wells ranges from 2000-4100 meters with wellbore diameters of 311 mm and 215 mm. The field application results show that hydraulic pulsed and cavitating jet techniques have good applicability to bit types and formations, and significantly improve the ROP by more than 25%