► Cavitating flow around a twisted hydrofoil is studied by PANS method. ► Evolution of cavitation patterns are well predicted compared to experiments. ► The reasons for the primary and secondary ...shedding are discussed. ► The mechanism of cavitating horse-shoe vortex production is illustrated.
Cavitating turbulent flow around hydrofoils was simulated using the Partially-Averaged Navier–Stokes (PANS) method and a mass transfer cavitation model with the maximum density ratio (ρl/ρv,clip) effect between the liquid and the vapor. The predicted cavity length and thickness of stable cavities as well as the pressure distribution along the suction surface of a NACA66(MOD) hydrofoil compare well with experimental data when using the actual maximum density ratio (ρl/ρv,clip=43391) at room temperature. The unsteady cavitation patterns and their evolution around a Delft twisted hydrofoil were then simulated. The numerical results indicate that the cavity volume fluctuates dramatically as the cavitating flow develops with cavity growth, destabilization, and collapse. The predicted three dimensional cavity structures due to the variation of attack angle in the span-wise direction and the shedding cycle as well as its frequency agree fairly well with experimental observations. The distinct side-lobes of the attached cavity and the shedding U-shaped horse-shoe vortex are well captured. Furthermore, it is shown that the shedding horse-shoe vortex includes a primary U-shaped vapor cloud and two secondary U-shaped vapor clouds originating from the primary shedding at the cavity center and the secondary shedding at both cavity sides. The primary shedding is related to the collision of a radially-diverging re-entrant jet and the attached cavity surface, while the secondary shedding is due to the collision of side-entrant jets and the radially-diverging re-entrant jet. The local flow fields show that the interaction between the circulating flow and the shedding vapor cloud may be the main mechanism producing the cavitating horse-shoe vortex. Two side views described by iso-surfaces of the vapor volume fraction for a 10% vapor volume, and a non-dimensional Q-criterion equal to 200 are used to illustrate the formation, roll-up and transport of the shedding horse-shoe vortex. The predicted height of the shedding horse-shoe vortex increases as the vortex moves downstream. It is shown that the shape of the horse-shoe vortex for the non-dimensional Q-criterion is more complicated than that of the 10% vapor fraction iso-surface and is more consistent with the experiments. Further, though the time-averaged lift coefficient predicted by the PANS calculation is about 12% lower than the experimental value, it is better than other predictions based on RANS solvers.
This study aims to evaluate the effects of a receptive music therapy intervention on cognitive functions and depressive symptoms in older adults with MCI. A randomized controlled trial was conducted ...in Wuhan, China. Eighty older adults, over 65, who had MCI and depression symptoms were randomly divided into the intervention and control groups. The intervention group received usual nursing care plus receptive music therapy intervention four times a week, for eight weeks; the control group received usual nursing care during the same period. The linear regression analysis was used to compare the difference between groups. There was a significant difference in the intervention group for the pre-intervention and post-intervention scores of cognitive function and depression. There was no significant difference in the control group before and after the study period and a significant between-group difference in both cognitive function and depression. In conclusion, receptive music therapy intervention significantly improved cognitive function and reduced depressive symptoms in older adults with MCI. It could be widely used in communities and nursing homes to improve the quality of life of older adults.
Recent experiments showed that there is an interaction between the fluid vortex formation and cavitation, but the mechanism is still an open problem. In the present paper, the structure of the ...cavitating flow around a twisted hydrofoil was investigated numerically using the mass transfer cavitation model and the modified RNG k-ε model with a local density correction for turbulent eddy viscosity. The predicted three dimensional cavity structures and the shedding frequency agree fairly well with experimental observations. Three types of flow behavior along the suction side of the twisted hydrofoil are discussed. Further analysis of the flow field reveals that cavitation promotes vortex production and increases the boundary layer thickness with local separation and the flow unsteadiness. Finally, the influence of cavitation on the vorticity distribution is illustrated using the vorticity transport equation in a variable density flow and is demonstrated by the contribution of vortex stretching, vortex dilatation and baroclinic torque terms.
•3D cavitating turbulent structure around a twisted hydrofoil is simulated.•Three types of flow behavior along the hydrofoil suction side are illustrated.•The mechanism of cavitation–vortex interaction is discussed.
This study proposes a centrifugal pump that features a single-suction pipe with a double-suction impeller to enhance dynamic characteristics. Performance tests were conducted at 10000 r/min to ...investigate the effects of single- or double-suction impellers on pressure oscillation and radial force. Results indicate good agreement between numerical and experimental data. Transient-state numerical simulations were performed for centrifugal pumps equipped with both single- and double-suction impellers. The results demonstrate that pumps with double-suction impellers reduces pressure oscillation and significantly alleviates radial force, with a 24 % reduction in peak-to-peak value compared with pumps with single-suction impellers. Internal flow analysis reveals that a double-suction impeller promotes a relatively uniform flow at the impeller exit and mitigates the interaction effects between the impeller and the volute casing. Therefore, a centrifugal pump with a double-suction impeller is promising for special applications that demand stable and safe fluid transportation.
To evaluate the effect of repetitive transcranial magnetic stimulation (rTMS) paired with cognitive training on cognitive function in Alzheimer's Disease (AD) patients.
PubMed, The Cochrane Library, ...Embase, CINAHL Complete (EBSCO), China National Knowledge Infrastructure (CNKI) and WanFang Database were searched. The risk of bias was appraised through the Cochrane collaboration tool. A meta-analysis was conducted, including an assessment of heterogeneity.
Ten studies comprising 408 participants were included. The addition of rTMS significantly improved overall cognition in patients compared with cognitive intervention alone (
< 0.05 for all tests). The treatment also had some continuity, with significant improvements in cognitive function within weeks after the treatment ended (
< 0.05 for all tests).
Repetitive transcranial magnetic stimulation combined with cognitive training (rTMS-CT) is a valuable technique for the cognitive rehabilitation of AD patients. It is beneficial to improve the cognitive ability of patients and restore their overall functional state. The results of the study may provide a basis for clinical providers to implement interventions that facilitate the design of more rigorous and high-quality interventions.
The number of studies and sample size in our study were small. We did not explore possible interactions between rTMS and medications and mood improvement after rTMS due to inadequate data.
This study was registered on PROSPERO with registration number CRD42023405615.
In this study, a modified partially averaged Navier-Stokes model (MSST PANS) is proposed by treating a modified shear stress transport (SST)
k
-
ω
model as the parent turbulence model. The unstable ...turbulent flow in a centrifugal pump that considers the curvature and rotation effect is investigated as the test case to evaluate the performance of the MSST PANS model and analyze the flow instability in a centrifugal pump. The SST
k
-
ω
and the standard
k
-
ε
PANS models are also evaluated for comparison. Results show that the MSST PANS model exhibits excellent performance and delivers the most satisfactory prediction results of the positive slope of the characteristic curve, time-averaged internal flows, and velocity profiles. The energy loss based on the energy balance equations is adopted to provide an explanation of the internal flow evolutions in pumps. The findings also indicate energy loss distribution is associated with the positive slope phenomenon. The high-velocity gradient flows at the entrance of the blade-to-blade passage and the reverse flows at the impeller exit are the main reasons for the high turbulent kinetic energy in the impeller. The MSST PANS model demonstrates promising applications in the field of hydraulic machinery, where unstable turbulent flows are prevalent.
► Cavitating flow around propellers in non-uniform wake is studied. ► Evolution of cavitation and pressure fluctuation are predicted well compared to experiments. ► The relationship of cavity volume ...and pressure fluctuation is discussed. ► The physical mechanism of excited pressure by cavitation is illustrated.
Unsteady cavitating turbulent flows around a conventional marine propeller in a non-uniform wake were analyzed to predict the excited pressure fluctuations. The numerical simulations of the propeller cavitation were based on the Navier–Stokes equations solved with a mass transfer cavitation model, the k–ω SST turbulence model and a sliding mesh. The evolution of the unsteady cavitation and the pressure fluctuations around the propeller in the non-uniform flow are predicted fairly well compared to experimental results. The CFD results verify the connection between the pressure fluctuations and the changing cavitation patterns as the blades sweep through the high velocity wake region. Furthermore, to better demonstrate the physical mechanism of the cavity-generated pressure field, the cavity volume was calculated and analyzed to illustrate the relationship between the cavity evolution and the pressure fluctuations. The analysis shows that the acceleration due to the cavity volume changes is the main source of the pressure fluctuations excited by the propeller cavitation. These results demonstrate that this numerical methodology is suitable for simulating unsteady cavitating flows around a propeller.
Background
Surgical resection is currently indicated for all potentially resectable intrahepatic cholangiocarcinoma (ICC), but the survival outcomes and the prognostic factors have not been ...well-documented due to its rarity. This study aims to assess these in a large, consecutive series of patients with ICC treated surgically.
Methods
A retrospective study was conducted on 1,333 ICC patients undergoing surgery between January 2007 and December 2011. Surgical results and survival were evaluated and compared among different subgroups of patients. Univariate and multivariate analyses were performed to identify prognostic factors.
Results
R0, R1, R2 resection and exploratory laparotomy were obtained in 34.8, 44.9, 16.4, and 3.9 % of the patients, respectively. The overall 1-, 3-, and 5-year survival rates for the entire cohort were 58.2, 25.2, and 17.0 %, respectively, with corresponding rates of 79.1, 42.6, and 28.7 % for patients with R0 resection; 60.5, 20.1, and 13.9 % for patients with R1 resection; 20.5, 7.4, and 0 % for patients with R2 resection; and 3.8, 0, and 0 % for patients with an exploratory laparotomy. Independent factors for poor survival included positive resection margin, lymph node metastasis, multiple tumors, vascular invasion, and elevated CA19-9 and/or CEA, whereas hepatitis B virus infection and cirrhosis were independently favorable prognosis indicators.
Conclusions
R0 resection offers the best possibility of long-term survival, but the chance of a R0 resection is low when surgery is performed for potential resectable ICC. Further randomized trials are warranted to refine indications for surgery in the management of ICC.
A centrifugal rotary blood pump was treated to investigate the effects of blade thickness by numerical simulation, where Reynolds averaged Navier-Stokes method coupling with k-ω SST turbulence model ...is applied. For comparison, five pumps were designed with different blade thickness distribution from the leading edge to trailing edge. The numerical methods were validated by the comparison of hydraulic performance between the simulation and the experiment for a test pump. Results showed that the thicker blade near leading edge suppresses the separation flow in blade-to-blade passage of pump impeller, and can improve hydraulic efficiency at low flow rate. On the other hand, the blade shape modification by trimming suction side near trailing edge is helpful to reduce the hydraulic loss by suppressing the flow mixing downstream impeller exit. Power loss analysis based on the simulated internal flow indicated that viscous dissipation of mean kinetic energy (VDKE) and turbulence kinetic energy production (TKEP) are main source terms contributing to power loss for the blood pump. The blade thickness near trailing edge changes the interaction between volute tongue and impeller blade, and the trimmed blade is helpful for decreasing the large values of VDKE and TKEP in pump volute compared with the conventional blade. The analysis further indicates that the blade modifications with thickness increment seem to slightly increase the degree of RBCs damage, and the effect of blade thickness on the hemolysis index of the blood pump should be carefully considered. The results are expected to be beneficial to the wide application of centrifugal rotary blood pumps.
Dementia is characterized by significant cognitive decline that results in disturbance of daily activities. Increasing number of meta-analyses has examined the efficacy of cognitive stimulation ...therapy (CST) for dementia. However, there is a lack of comprehensive reports that specifically discuss the strength of evidence to support CST for dementia.
This study aimed to summarize evidence regarding the efficacy of CST on people with dementia.
Umbrella review of systematic reviews and meta-analyses.
We searched Cochrane Library, PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang Data, China Biology Medicine disc (CBMdisc), and VIP databases from inception to December 31, 2022. The methodological quality of the identified studies was assessed using A Measurement Tool to Assess Systematic Reviews 2 (AMSTAR 2). Studies scoring 9–12 (moderate quality) points or higher were further analyzed using Grades of Recommendations Assessment, Development and Evaluation (GRADE) principles.
A total of 14 systematic reviews and meta-analyses were included in the umbrella review. The methodological quality of most included reviews was rated as moderate according to AMSTAR 2 rating system. In these studies, we summarized the characteristics of the content, providers, frequency, period and setting of CST, and examined eight health outcomes related to CST, including cognition, depression, behavioral symptoms, quality of life (QoL), activities of daily living (ADL), language and communication, anxiety, and memory. Eleven studies with low to high rating of overall confidence (OC) consistently reported that CST could significantly improve cognition of people with dementia, including high-quality supporting evidence. However, the effect of CST on other health outcomes for people with dementia (e.g., depression, behavioral symptoms, QoL, ADL) is inconsistent, with low- to moderate-quality evidence ratings. Compared with the above results, few studies have reported the effects of CST on communication, anxiety, and memory for people with dementia.
In the future, the design and reporting of systematic reviews and meta-analyses should incorporate high-quality research metrics in accordance with AMSTAR 2 criteria. The current review supports CST as an effective treatment for improving cognitive function in patients with dementia. Multi-component interventions are more effective than single-component interventions and need to be delivered regularly. Registration: The protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42022364259).
•There is no high-quality evidence to support the long-term benefits of CST on cognitive function.•The efficacy of CST on neuropsychiatric and behavioral symptoms, QoL, and ADL on patients with dementia cannot be concluded, and the quality of evidence is low to moderate.•CST has great heterogeneity in terms of intervention content, delivery approach, frequency and period.•Multi-component interventions are more effective than single-component interventions and need to be delivered regularly.
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