Application of Dynamic Centrifugal Compressor Model for Mechanical Vapor Recompression System Simulation

In order to reducing energy costs and CO2 foot-print, mechanical vapor recompression system (MVR) is used for thermal separation processes such as evaporation and distillation are energy intensive instead of multiple-effect evaporation system. For medium and high capacities, centrifugal compressor (fan) is the most commonly used type for gas compression with a limited operational range and control of the compressors is crucial for safe and efficient operation. The model based on first principles is developed for dynamic performance, which is determined from the compressor geometry and not from the experimentally determined characteristic performance curves. Impeller losses are studied: incidence, skin friction, choking, jet-wake mixing, blade loading, hub to shroud, tip clearance, shock and distortion losses. The vaneless diffuser outlet is calculated using a one-dimensional numerical solution to the underlying differential equations. Dynamic model of a centrifugal compressor capable of system simulation computational environment is presented. A model has been created for simulation of a separation and gas compression system. Based on the theory for centrifugal compressors and control theory a control strategy has been applied to the model based on the available equipment. The model has been used to investigate how the gas compression system responds to changes in the compressor inlet flows and conditions. The model has been used to investigate the performance of the gas compression system at off-design conditions. The surge line for the compressor can also be determined from the simulation results. Furthermore, the model presented here provides a valuable tool for evaluating the system performance as a function of various operating parameters

A feature extraction method based on LMD and its application for fault diagnosis of reciprocating compressor annular valve

Taking the reciprocating compressor annular valve as the research object, the vibration signal of the reciprocating compressor ring valve was tested by the accelerometer vibration sensor. Through local mean decomposition (LMD), several PF components corresponding to the signal were obtained, The three characteristic parameter factors of these PF components are extracted, including the skewness coefficient (gi), kurtosis coefficient (qi) and total energy ratio (Ei/E). Then the valve is damaged to varying degrees, including sawing the valve plate, removing some springs from the valve and drilling the valve plate, the same analysis on the operating vibration signal of the damaged valve plate was done to obtain the corresponding parameters factors, and compared with corresponding parameter factors of the normal valve. The results show that in the valve sawing and part springs removing two states, the valve vibration signal obtained by the corresponding characteristic parameter factor will reflect the abnormal value of the fault, but the valve disc perforated state is not obvious. The above shows that although the LMD method has some limitations, it can accurately and effectively evaluate the reciprocating compressor valve vibration signal, and classify the working status and the type of fault of the valve, so it is a practical method to study the diagnosis of valve failure

FHPM: Fine-grained Huge Page Management For Virtualization

As more data-intensive tasks with large footprints are deployed in virtual machines (VMs), huge pages are widely used to eliminate the increasing address translation overhead. However, once the huge page mapping is established, all the base page regions in the huge page share a single extended page table (EPT) entry, so that the hypervisor loses awareness of accesses to base page regions. None of the state-of-the-art solutions can obtain access information at base page granularity for huge pages. We observe that this can lead to incorrect decisions by the hypervisor, such as incorrect data placement in a tiered memory system and unshared base page regions when sharing pages. This paper proposes FHPM, a fine-grained huge page management for virtualization without hardware and guest OS modification. FHPM can identify access information at base page granularity, and dynamically promote and demote pages. A key insight of FHPM is to redirect the EPT huge page directory entries (PDEs) to new companion pages so that the MMU can track access information within huge pages. Then, FHPM can promote and demote pages according to the current hot page pressure to balance address translation overhead and memory usage. At the same time, FHPM proposes a VM-friendly page splitting and collapsing mechanism to avoid extra VM-exits. In combination, FHPM minimizes the monitoring and management overhead and ensures that the hypervisor gets fine-grained VM memory accesses to make the proper decision. We apply FHPM to improve tiered memory management (FHPM-TMM) and to promote page sharing (FHPM-Share). FHPM-TMM achieves a performance improvement of up to 33% and 61% over the pure huge page and base page management. FHPM-Share can save 41% more memory than Ingens, a state-of-the-art page sharing solution, with comparable performance

Synchronization and Lag Synchronization of Hyperchaotic Memristor-Based Chua’s Circuits

A memristor-based five-dimensional (5D) hyperchaotic Chua’s circuit is proposed. Based on the Lyapunov stability theorem, the controllers are designed to realize the synchronization and lag synchronization between the hyperchaotic memristor-based Chua’s circuits under different initial values, respectively. Numerical simulations are also presented to show the effectiveness and feasibility of the theoretical results

Excessively tilted fiber grating based Fe3O4 saturable absorber for passively mode-locked fiber laser

A novel approach to saturable absorber (SA) formation is presented by taking advantage of the mode coupling property of excessively tilted fiber grating (Ex-TFG). Stable mode-locked operation can be conveniently achieved based on the interaction between Ex- TFG coupled light and deposited ferroferric-oxide (Fe3O4) nanoparticles. The central wavelength, bandwidth and single pulse duration of the output are 1595 nm, 4.05 nm, and 912 fs, respectively. The fiber laser exhibits good long-term stability with signal-to-noise ratio (SNR) of 67 dB. For the first time, to the best of our knowledge, Ex-TFG based Fe3O4 SA for mode-locked fiber laser is demonstrated

New insights into a microvascular invasion prediction model in hepatocellular carcinoma: A retrospective study from the SEER database and China

Background and AimsThe prognosis of liver cancer is strongly influenced by microvascular infiltration (MVI). Accurate preoperative MVI prediction can aid clinicians in the selection of suitable treatment options. In this study, we constructed a novel, reliable, and adaptable nomogram for predicting MVI.MethodsUsing the Surveillance, Epidemiology, and End Results (SEER) database, we extracted the clinical data of 1,063 patients diagnosed with hepatocellular carcinoma (HCC) and divided it into either a training (n = 739) or an internal validation cohort (n = 326). Based on multivariate analysis, the training cohort data were analyzed and a nomogram was generated for MVI prediction. This was further verified using an internal validation cohort and an external validation cohort involving 293 Chinese patients. Furthermore, to evaluate the efficacy, accuracy, and clinical use of the nomogram, we used concordance index (C-index), calibration curve, and decision curve analysis (DCA) techniques.ResultsIn accordance with the multivariate analysis, tumor size, tumor number, alpha-fetoprotein (AFP), and histological grade were independently associated with MVI. The established model exhibited satisfactory performance in predicting MVI. The C-indices were 0.719, 0.704, and 0.718 in the training, internal validation, and external validation cohorts, respectively. The calibration curves showed an excellent consistency between the predictions and actual observations. Finally, DCA demonstrated that the newly developed nomogram had favorable clinical utility.ConclusionsWe established and verified a novel preoperative MVI prediction model in HCC patients. This model can be a beneficial tool for clinicians in selecting an optimal treatment plan for HCC patients

Safety and efficacy of laparoscopic digestive tract nutrition reconstruction combined with conversion therapy for patients with unresectable and obstructive gastric cancer

BackgroundTo explore the safety, efficacy, and survival benefits of laparoscopic digestive tract nutrition reconstruction (LDTNR) combined with conversion therapy in patients with unresectable gastric cancer with obstruction.MethodsThe clinical data of patients with unresectable gastric cancer with obstruction who was treated in Fujian Provincial Hospital from January 2016 to December 2019, were analyzed. LDTNR was performed according to the type and degree of obstruction. All patients received the epirubicin + oxaliplatin + capecitabine regimen as conversion therapy.ResultsThirty-seven patients with unresectable obstructive gastric cancer underwent LDTNR, while thirty-three patients received chemotherapy only. In LDTNR group patients, the proportion of nutritional risks gradually decreased, the rate of severe malnutrition decreased, the proportion of neutrophil-lymphocyte ratio (NLR) <2.5 increased, the proportion of prognosis nutrition index (PNI) ≥45 increased, and the Spitzer QOL Index significantly increased at day 7 and 1 month postoperatively (P<0.05). One patient (6.3%) developed grade III anastomotic leakage and was discharged after the endoscopic intervention. The median chemotherapy cycle of patients in LDTNR group was 6 cycles (2-10 cycles), higher than that in Non-LDTNR group (P<0.001). Among those who received LDTNR therapy, 2 patients had a complete response, 17 had a partial response, 8 had stable disease, and 10 had progressive disease, which was significantly better than the response rate in Non-LDTNR group(P<0.001). The 1-year cumulative survival rates of the patients with or without LDTNR were 59.5% and 9.1%. The 3-year cumulative survival rate with or without LDTNR was 29.7% and 0%, respectively (P<0.001).ConclusionsLDTNR can improve the inflammatory and immune status, increase compliance with chemotherapy, and have potential benefits in improving the safety and effectiveness of and survival after conversion treatment

Evaluation of the antibacterial activity of Elsholtzia ciliate essential oil against halitosis-related Fusobacterium nucleatum and Porphyromonas gingivalis

The broad-spectrum antimicrobial activity of Elsholtzia ciliate essential oil (ECO) has been previously reported, but its effectiveness against halitosis-causing bacteria such as Fusobacterium nucleatum and Porphyromonas gingivalis is not well understood. In this study, we investigated the bacteriostatic activity of ECO against planktonic cells and biofilms of F. nucleatum and P. gingivalis, as well as its ability to inhibit bacterial metabolism and production of volatile sulfur compounds (VSCs) at sub-lethal concentrations. Our findings revealed that ECO exhibited comparable activities to chlorhexidine against these oral bacteria. Treatment with ECO significantly reduced the production of VSCs, including hydrogen sulfide, dimethyl disulfide, and methanethiol, which are major contributors to bad breath. As the major chemical components of ECO, carvacrol, p-cymene, and phellandrene, were demonstrated in vitro inhibitory effects on F. nucleatum and P. gingivalis, and their combined use showed synergistic and additive effects, suggesting that the overall activity of ECO is derived from the cumulative or synergistic effect of multiple active components. ECO was found to have a destructive effect on the bacterial cell membrane by examining the cell morphology and permeability. Furthermore, the application of ECO induced significant changes in the bacterial composition of saliva-derived biofilm, resulting in the elimination of bacterial species that contribute to halitosis, including Fusobacterium, Porphyromonas, and Prevotella. These results provide experimental evidence for the potential clinical applications of ECOs in the prevention and treatment of halitosis