Study on Axial Clearance Size and Leakage of Canned Motor Pump under Axial Force Self-Balance State

Canned motor pump is widely used in chemical industry. Due to the particularity of its application, it is necessary to ensure that the medium does not leak completely. If the axial force of impeller is too large, it will directly affect the performance of canned motor pump. Therefore, the floating impeller could be used in the pump to balance the axial force. In this paper, the relationship between axial clearance and leakage rate at the key part of canned motor pump is studied by means of numerical calculation and experimental verification. It is found that the fitting curve is highly consistent with the calculated value, which provided a good theoretical basis for further study of axial clearance control axial force and experimental axial force self-balance. In addition, the leakage rate increases with the increase of axial clearance. The static pressure in the axial clearance first increases and then decreases with the decrease of radius, and the maximum static pressure value is about 10.5% ∼ 15.8% near the clearance inlet. This study is of great significance to the theoretical research on the self-balance state of axial force of impeller.

Astragaloside IV Alleviates Cerebral Ischemia-Reperfusion Injury through NLRP3 Inflammasome-Mediated Pyroptosis Inhibition via Activating Nrf2

As one of the fundamental components of Astragalus membranaceus, astragaloside IV (AST IV) exerts protective effects against cerebral ischemia-reperfusion injury (CIRI). Nevertheless, the underlying mechanisms have not yet been conclusively elucidated. To do so, here, we report on the regulatory effects of Nrf2 on NLRP3 inflammasome-mediated pyroptosis. CIRI was induced by middle cerebral artery occlusion-reperfusion (MCAO/R) in Sprague Dawley rats and modeled by oxygen and glucose deprivation/reoxygenation (OGD/R) in SH-SY5Y cells. Cerebral infarct volume and neurological deficit score served as indices to evaluate MCAO/R injury. In addition, the CCK-8 assay was used to assess cell viability, the LDH leakage rate was used as a quantitative index, and propidium iodide (PI) staining was used to visualize cells after OGD/R injury. The NLRP3/Caspase-1/GSDMD pathway, which produces the pores in the cell membrane that are central to the pyroptosis process, was assessed to investigate pyroptosis. Nrf2 activation was assessed by detecting Nrf2 protein levels and immunofluorescence analysis. We show that after MCAO/R of rats, the infarct volume and neurological deficit score of rats were strongly increased, and after OGD/R of cell cultures, cell viability was strongly decreased, and the LDH leakage rate and the proportion of PI-positive cells were strongly increased. In turn, MCAO/R and OGD/R enhanced the protein levels of NLRP3, Caspase-1, IL-1β, GSDMD, and GSDMD-N. Moreover, Nrf2 protein levels increased, and Nrf2 translocation was promoted after CIRI. Interestingly, AST IV (i) reduced the cerebral infarct volume and the neurological deficit score in vivo and (ii) increased the cell viability and reduced the LDH leakage rate and the proportion of PI-positive cells in vitro. AST IV reduced the protein levels of NLRP3, Caspase-1, IL-1β, GSDMD, and GSDMD-N, inhibiting NLRP3 inflammasome-mediated pyroptosis. AST IV also increased the protein levels of Nrf2 and promoted the transfer of Nrf2 to the nucleus, accelerating Nrf2 activation. Particularly revealing was that the Nrf2 inhibitor ML385 partly blocked the above effects of AST IV. Taken together, these results demonstrate that AST IV alleviates CIRI through inhibiting NLRP3 inflammasome-mediated pyroptosis via activating Nrf2.

Security Guarantee for Vehicular Message Transmission Based on Dynamic Social Attributes

Effective message forwarding between vehicles can reduce the occurrence of traffic accidents and improve the driving experience. Vehicle clustering can improve message utilization, but attackers in the network pose a serious threat to message forwarding. Based on vehicle clustering, we propose a message forwarding strategy for Vehicular Ad hoc Network. Specifically, the vehicles are clustered based on their directions and speeds. Besides, the friendship of vehicles is evaluated in terms of the interaction friendship and reference friendship. Based on the friendship of vehicles, the optimal vehicle can be selected as the cluster head. Thereafter, the double key technology is designed to encrypt vehicular messages such that the messages can be forwarded more safely and efficiently. The analysis results show that the proposed strategy can effectively improve the message delivery rate, reduce the message leakage rate, and improve the network performance.

Study of Relationships between Ceiling Smoke Leakage Rate and Evacuation Time in the Ward

With reference to the requirements of CNS 15038 and testing principles, this study proposes a set of equipment for measuring the leakage volume of ceilings and provides detailed assembly specifications for future users. In this study, a total of 405 tests were conducted as part of a set of experiments for measuring the leakage volume of ceilings, using various ceiling materials, ceiling sizes, and construction methods, in conjunction with the principles of fluid mechanics, to propose a method for evaluating the leakage volume of ceilings of various sizes and materials. Two cases—bottom-up airflow and top-down airflow—were considered. According to our research findings, in the case of bottom-up airflow, the pressure difference, panel weight, and panel size were correlated with the leakage volume; the more significant the pressure difference, the larger the leakage volume; the heavier the panel weight, the more minor the leakage volume; and the larger the panel size, the more significant the leakage volume. On the other hand, in the case of top-down airflow, different leakage volumes were observed for different ceiling materials, even if the ceiling size was identical. On the other hand, when the ceiling material was the same, and the ceiling size was different, there was not a positive relationship between the leakage volume and a larger panel size; instead, the leakage volume observed for the largest panel was the smallest. Finally, in this study we propose a volumetric leakage assessment table for assessing a ceiling as a whole, which can be utilized by engineers in the future to calculate the smoke leakage value and to estimate the smoke fall time for ward escape designs.

Comparison of Two Circular-Stapled Techniques for Esophageal Cancer: A Propensity-Matched Analysis

ObjectiveThe optimal technique for the thoracoscopic construction of an intrathoracic esophagogastric anastomosis continues to be a subject of controversy. The aim of this study was to compare the perioperative outcomes of circular-stapled anastomosis using a transorally inserted anvil (Orvil™) with those of circular-stapled anastomosis using a transthoracically placed anvil (non-Orvil™) in totally minimally invasive Ivor Lewis esophagectomy (Ivor Lewis TMIE).MethodsThe data of 272 patients who underwent Ivor Lewis TMIE for esophageal cancer at multiple centers were collected from January 1, 2014 to December 31, 2017. After propensity score matching (1:1) for patient baseline characteristics, 65 paired cases were selected for statistical analysis. Logistic regression analysis was performed to investigate the significant factors of anastomotic leakage.ResultsIn the propensity score-matched analysis, compared with the non-Orvil™ group, the Orvil™ group was associated with a significantly shorter operation time (p=0.031), less intraoperative hemorrhage (p<0.001), lower need for intraoperative transfusions (p=0.009), earlier postoperative oral feeding time (p=0.010), longer chest tube duration (p<0.001), shorter postoperative hospital stays (p=0.001), lower total hospitalization costs (p<0.001) and a lower postoperative anastomotic leakage rate (p=0.033). Multivariate logistic regression analysis showed that anastomotic technique and pulmonary infection were independent factors for the development of postoperative anastomotic leakage (p< 0.05).ConclusionsOrvil™ anastomosis exhibited better perioperative effects than non-Orvil™ anastomosis after the propensity score-matched analysis. Remarkably, the Orvil™ technique contributed to a lower postoperative anastomotic leakage rate than the non-Orvil™ technique.

ENERGY EFFICIENCY BASED OPERATION OF COMPRESSED AIR SYSTEM ON SHIPS TO REDUCE FUEL CONSUMPTION AND CO2 EMISSION

Energy efficiency subject has been gaining importance in maritime sector. The compressed air is a valuable energy source in operational manner, by the reason of intrinsic lack of efficiency in pressurization process. Operational pressure and leakage rate are the major variables which affect operational efficiency of the system. This study aims to reveal potential energy saving for the compressed air system. To this end, several pressure ranges, 29-30 bars to 14-18 bars, and different leakage rates 2.4% to 45% are evaluated. After the data was obtained from ships, thermodynamic calculations had been carried out. Optimization of pressure saves 47.3% in daily power requirement, 58,2% in compressed air unit cost, 18.4 and 57.4 tons of reduction in fuel consumption and CO2 emissions in a year respectively. High leakage rates can cause 2.7 times more power and fuel consumption. Finally, operating load, as an important indicator of compressor, makes imperfections identifiable.

Subsea Re-Abandonment Strategies for High-Risk Wells to Minimize Leakage Risk in a Depleted Field for CO2 Storage

CO2 storage in a depleted field comes with the risk that is associated with wells integrity which is often defined as the ability to contain fluids with minimum to nil leakage throughout the project lifecycle. The targeted CO2 storage reservoir in offshore Malaysia has existing abandoned exploration/appraisal, and development wells. With a view of developing such CO2 storage sites, it is vital to maintain the integrity of the abandoned wells. High-risk characterized wells need to be analyzed and remedial action plan to be defined by understanding the complexity involved in restoring the integrity. This will safeguard CO2 containment for decades. Abandoned exploration/appraisal wells in the identified field are >40 years old and were not designed to withstand CO2 corrosion environment. Downhole temperature and pressure conditions may have further degraded the wellbore material strength elevating corrosion susceptibility. The reservoir simulation predicts that the CO2 plume will reach to these abandoned wells during the initial phase of total injection period. Single well was selected to assess the loss of containment through the composite structure along the wellbore and to determine the complexity in resorting the well integrity. CO2 leakage rates through all possible pathways were estimated based on numerical models and the well is characterized for its risk. For unacceptable leakage risk, the abandoned well needs to be re-entered to restore the performance of barriers. Minimum plug setting depth (MPSD) and caprock restoration considers original reservoir pressure(3450psia) anticipating the pressure buildup upon CO2 injection and is derived based on fracture gradient and maximum horizontal stress. This paper elaborates unique challenges associated with locating abandoned wells that are submerged below seabed. Top and side re-entry strategies are discussed to overcome challenges. Based on past abandonment scheme, leakage rate modeling calculates estimated leakage rate of ~460SCFD at higher differential pressure of around 3036psia at shallowest barrier and ~15SCFD for differential pressure of 1518psia at deepest barrier. Sensitivity analysis has been carried out for critical barrier parameters (cement permeability, cracks, fractures) to the containment ability and improving understanding of quality of barriers, uncertainties, and complexities for CO2 leakage risk. The paper proposes two(2) minimum plug setting depths (3550ft & 3750ft) derived based on fracture gradient and maximum horizontal stress. Perforate-wash-cement (PWC) and section milling were compared for operational efficiencies to achieve caprock restoration. for MPSD out strategic options to restore well integrity by remediating casing/cement barriers at by performing best fit abandonment technique to contain CO2 in the reservoir. Well integrity risk is assessed for existing plugged and abandoned (P&A) wells in a carbon storage site. Optimized remedial actions are proposed. Quantification of all the uncertainties are resolved that may affect long-term security of CO2 storage site.

Vesselplasty versus vertebroplasty in the treatment of osteoporotic vertebral compression fractures with posterior wall rupture

Objective This study was performed to compare the effectiveness and safety of vesselplasty versus vertebroplasty in the treatment of osteoporotic compression fractures with posterior wall rupture. Methods Patients who underwent treatment of a single osteoporotic vertebral compression fracture with posterior wall rupture from January 2016 to February 2020 were retrospectively reviewed. They were divided into a vesselplasty group (n = 17) and a vertebroplasty group (n = 43). Pain relief, radiographic outcomes, and bone cement leakage were compared between the two groups. Results There were no significant differences in the operation time, postoperative pain relief, vertebral compression recovery, or local Cobb angle improvement between the two groups. However, the overall bone cement leakage rate (29.4% vs. 67.4%) and spinal canal leakage rate (0.0% vs. 30.2%) were significantly lower in the vesselplasty group than vertebroplasty group. Conclusions Vesselplasty offers similar pain relief and vertebral compression recovery but lower spinal canal leakage compared with vertebroplasty. Vesselplasty is thus a better option than vertebroplasty for patients with osteoporotic compression fractures with posterior wall rupture.

Novel Method of the Seal Aerodynamic Design to Reduce Leakage by Matching the Seal Geometry to Flow Conditions

This paper presents a novel method of labyrinth seals design. This method is based on CFD calculations and consists in the analysis of the phenomenon of gas kinetic energy carry-over in the seal chambers between clearances. The design method is presented in two variants. The first variant is designed for seals for which it is impossible to change their external dimensions (length and height). The second variant enables designing the seal geometry without changing the seal length and with a slight change of the seal height. Apart from the optimal distribution of teeth, this variant provides for adjusting chambers geometry to flow conditions. As the result of using both variants such design of the seal geometry with respect to leakage is obtained which enables achieving kinetic energy dissipation as uniform as possible in each chamber of the seal. The method was developed based on numerical calculations and the analysis of the flow phenomena. Calculation examples included in this paper show that the obtained reduction of leakage for the first variant ranges from 3.4% to 15.5%, when compared with the initial geometry. The relation between the number of seal teeth and the leakage rate is also analyzed here. The second variant allows for reduction of leakage rate by 15.4%, when compared with the geometry with the same number of teeth. It is shown that the newly designed geometry reveals almost stable relative reduction of leakage rate irrespective of the pressure ratio upstream and downstream the seal. The efficiency of the used method is proved for various heights of the seal clearance.