Review of exploration and production technology of natural gas hydrate

Natural gas hydrate is an ice-like substance which is sometimes called “combustible ice” since it can literally be lighted on fire and burned as fuel. Natural gas hydrate is characterized by widespread distribution, large reserves and little pollution. This paper introduced the distributions of hydrate, hydrate reserves and properties of hydrate. The main exploration methods, such as geophysical exploration and geochemical exploration have been presented. In addition, the main production techniques of natural gas hydrate including depressurization, thermal stimulation and chemical injection have been summed up. Finally, the challenges and outlooks of natural gas hydrate production have been proposed.Cited as: Cui, Y., Lu, C., Wu, M., Peng, Y., Yao, Y., Luo, W. Review of exploration and production technology of natural gas hydrate. Advances in Geo-Energy Research, 2018, 2(1): 53-62, doi: 10.26804/ager.2018.01.0

Radially Symmetrical Heat Hydrate Dissociation Model with a Density Difference

The hydrate dissociation is viewed as a phase change process in which hydrates transform from a solid phase into gas and liquid phase at a moving dissociation boundary. The boundary separates the dissociation zone containing gas and water from the undissociated zone containing the hydrates, leading to a density difference. Based on the assumption of a density difference between the dissociation zone and the hydrate zone, the authors propose a mathematical model to study hydrate dissociation under thermal stimulation in an infinite radially symmetrical reservoir. Analytical solutions to the temperature distribution are derived by using the self-similarity transformation. Considering the effect factors of the initial heated-water temperature and hydrate density, the authors conducted a thorough investigation of the temperature distribution and the location of the dissociation front for a sample hydrate reservoir. The results from our model show that the heated-water temperature and hydrate density exert significant influence on the hydrate dissociation. With the injection time unchanged, the dissociation distance tends to be increased as the heated-water temperature is increased, leading to a larger dissociation zone. Additionally, a smaller hydrate density can result in a larger dissociation distance. For hydrate thermal stimulation, a higher heated-water temperature and a lower hydrate density can lead to a larger dissociation distance with the injection time unchanged. As the hydrate dissociation proceeds, the dissociation rate is decreased

A Survey of Author Name Disambiguation Techniques of Academic Papers

[Purpose/Significance] This paper investigates the research on author name disambiguation published in recent years, and reviews the development context of relevant research from the perspective of the impact of data on author name disambiguation methods, so as to provide reference for further research. [Method/Process] The papers related to author name disambiguation were collected from English research databases such as Web of Science, Scopus, Google Academic, ACM Digital Library, IEEE Xplore, ScienceDirect, Scopus and Springer Link, and Chinese research databases such as CNKI, CQVIP and WANFANG. The search results cover the relevant papers published from 1998 to 2021. On the premise of giving consideration to authority, influence and novelty, 46 publicationswere selected for review. There are many types and structures of author name disambiguation data. For example, literature feature information is generally presented in unstructured text, and the extracted features can be stored and represented in two-dimensional tables; Citation information and interpersonal relationship are network relational data, which can be stored and represented by graphs, key value pairs or two-dimensional tables. The fundamental reason for different data structures lies in their semantic differences, but the data structure itself determines its applicable algorithm. According to the structure of characteristic data used in the author name disambiguation task and the different corresponding data processing algorithms, the relevant research is divided into three categories: 1) disambiguation method based on literature characteristics, 2) disambiguation method based on social network and 3) disambiguation method by integrating external knowledge. The impact of data on the author name disambiguation method is examined from the data level. [Results/Conclusions] The analysis found that with the progress of technology, deep learning methods have been widely used. Compared with the improvement of the model, the feature learning and representation based on deep learning can significantly improve the effect of the author name disambiguation algorithm. In addition, in order to overcome the problem of insufficient data utilization by a single method and improve the utilization efficiency of data, the three methods show the trend of mutual combination and complementary gain. From the literature research results, there are few related studies on incremental author name disambiguation and multi-language author name disambiguation, which could be one of the directions for further research

Endogenous Ceramide Contributes to the Transcytosis of oxLDL across Endothelial Cells and Promotes Its Subendothelial Retention in Vascular Wall

Oxidized low density of lipoprotein (oxLDL) is the major lipid found in atherosclerotic lesion and elevated plasma oxLDL is recognized to be a risk factor of atherosclerosis. Whether plasma oxLDL could be transported across endothelial cells and initiate atherosclerotic changes remains unknown. In an established in vitro cellular transcytosis model, the present study found that oxLDL could traffic across vascular endothelial cells and further that the regulation of endogenous ceramide production by ceramide metabolizing enzyme inhibitors significantly altered the transcytosis of oxLDL across endothelial cells. It was found that acid sphingomyelinase inhibitor, desipramine (DES), and de novo ceramide synthesis inhibitor, myriocin (MYR), both decreasing the endogenous ceramide production, significantly inhibited the transcytosis of oxLDL. Ceramidase inhibitor, N-oleoylethanolamine (NOE), and sphingomyelin synthase inhibitor, O-Tricyclo[5.2.1.02,6]dec-9-yl dithiocarbonate potassium salt (D609), both increasing the endogenous ceramide production, significantly upregulated the transcytosis of oxLDL. In vivo, injection of fluorescence labeled oxLDL into mice body also predisposed to the subendothelial retention of these oxidized lipids. The observations provided in the present study demonstrate that endogenous ceramide contributes to the transcytosis of oxLDL across endothelial cells and promotes the initiating step of atherosclerosis—the subendothelial retention of lipids in vascular wall

Efficacy of angiotensin receptor neprilysin inhibitor in Asian patients with refractory hypertension

Abstract Sacubitril/valsartan, simultaneously inhibits neprilysin and angiotensin II receptor, showed an effect in reducing blood pressure (BP). The authors aimed to study whether it can be used as an antihypertensive agent in patients with refractory hypertension who have already been treated. A total of 66 Chinese patients with refractory hypertension were enrolled. Patients received sacubitril/valsartan  200 instead of angiotensin II receptor blocker or angiotensin converting enzyme inhibitor while other agents continued. If BP was uncontrolled after 4 weeks, sacubitril/valsartan was increased to 400 mg. The BP reduction was evaluated by office BP and ambulatory BP monitoring after 8‐week treatment. The baseline office BP and mean arterial pressure (MAP) were 150.0/95.0 mmHg and 113.3 mmHg. BP and MAP reduced to 130.6/83.2 mmHg and 99.0 mmHg at week 8. Office BP and MAP reductions were 19.4/11.8 mmHg and 14.3 mmHg at endpoint (all p < .001). The 24‐h, daytime and nighttime ambulatory BP were 146.2/89.1, 148.1/90.3, and 137.5/83.7 mmHg, respectively at baseline, and BP reduced to 129.6/79.8, 130.6/81.1, and 121.7/75.8 mmHg, respectively at week 8. The 24‐h, daytime and nighttime ambulatory BP reductions were 16.6/9.3, 17.5/9.2, and 15.8/7.9 mmHg, respectively at endpoint (all p < .001). Sacubitril/valsartan significantly reduced office and ambulatory BP in refractory hypertension patients. Our study provided new evidence for sacubitril/valsartan in refractory hypertension

Research on the scale of pedestrian space in underground shopping streets based on VR experiment

The staying activity in shopping street has an inseparable relation with the spatial scale of the street. Neither too narrow nor too wide scale of street could bring a good walking experience to pedestrian, so it is especially important to find a suitable scale. Most of the researches are qualitative investigations related to human psychology, and few of them are about underground shopping street. This research made a quantitative investigation on the relationship between the spatial scale of underground shopping street and the staying activity there, defined the concept of staying activity coefficient to quantify the staying activity in shopping street, and used virtual reality experimental method to study the influence of spatial scale changes on the staying activity in shopping street. The research results show that the height and width of underground shopping street as well as the aspect ratio could significantly affect human activity in the pedestrian spaces of underground shopping street. Meanwhile, the most suitable scale of pedestrian spaces in underground street for people to have staying activity is also derived