h. zhang

In pursuit of enhanced accuracy in the performance prediction and optimization of high-load compressors, this study emphasizes the significance of empirically measured clearance values associated with variable guide vanes and stators in engineering applications. Utilizing these empirical data, we conduct a refined modeling approach for the variable guide vanes and stators. A comprehensive three-dimensional numerical simulation methodology is employed to examine the impact and underlying flow mechanisms of the adjustable blades with clearances in a nine-stage compressor, concurrently optimizing the positional parameters of the clearances to augment the aerodynamic performance of the compressor. The findings of this investigation reveal that the omission of clearances and platform geometry of adjustable blades in numerical simulations can lead to an overestimation of both maximum flow rates and the overall stability margins. Driven by the pressure differential between the suction and pressure sides, clearance leakage flow is generated at the leading edge of the end wall of adjustable blades, exacerbating flow separation in the end wall corner region and potentially resulting in corner stall phenomena. By adjusting the platform of the adjustable stators, which experience corner stall predominantly, the leading edge separation resulting from the interaction of the flow near the end wall and the leakage flow from the leading edge clearance is mitigated. Consequently, the maximum flow rate of the compressor is increased by approximately 0.48 kg/s, the overall stability margin is enhanced by approximately 7.52%, and the peak efficiency experiences an improvement of about 0.4%.

The Axisymmetric Vectoring Exhaust Nozzle (AVEN) has been extensively studied in thrust vectoring technology due to its ability to achieve 360° vector deflection. A key observation is that thermal loads are closely linked to joint clearance, which introduces significant complexity and unpredictability to the system’s dynamic response. This paper investigates the impact of thermal loads on joint forces using a finite element model. A fluid field analysis method was developed based on the operational conditions of the AVEN. The inner wall temperature obtained from this fluid analysis was then used as a boundary condition in the structural thermal analysis model. The results indicate that, for the relative angle of the joint, the combined aerodynamic and thermal loads contribute to the total aerodynamic-thermal interaction effects. Furthermore, structural stress in the steering control ring segment is primarily influenced by aerodynamic loads, while the convergence regulator ring segment is mainly affected by thermal loads.

Centrifugal fans are widely used in the ventilation and domestic appliance industries. Their aerodynamic and aeroacoustic characteristics vary significantly in different application scenarios and operating conditions. This study applied a double-suction multiblade centrifugal fan to a range hood. The full three-dimensional flow and acoustic field were calculated synchronously using direct computational aeroacoustics (CAA) based on the lattice Boltzmann method (LBM) to investigate the internal flow, aerodynamic noise, and acoustic source characteristics of the fan under different operating conditions. We focused on two typical operating conditions: the maximum volume flow rate and working volume flow rate. The accuracy of the numerical simulation was verified using experimental data measured from the performance test bench and the semianechoic chamber. The flow field results show that more than 70% of the airflow enters the volute from the main wind inlet; this asymmetric wind intake condition creates an asymmetric flow pattern inside the volute. Acoustic waves radiate to the far-field mainly through the inlet and outlet of the range hood. The propagation characteristics of a dipole source are not very obvious and the tonal noise associated with the blade passage frequency (BPF) is not significant. In addition to the acoustic sources identified in the impeller region, the volute tongue, and the gap between the impeller and the inlet nozzle, two other significant acoustic sources are identified in the outlet collector and inlet nozzle regions.

Investigating the aerodynamic characteristics of an ultrahigh-speed elevator between the car and counterweight during the staggering process is crucial for the development of drag reduction and noise abatement technologies. In this study, an actual operating ultrahigh-speed elevator is selected as the research object, and an unsteady flow numerical simulation model for three-dimensional, has been constructed using the method of dynamic mesh. The aerodynamic behaviours of the elevator at various interleaving operating speeds are analysed. The impacts of the counterweight on the flow velocity, pressure, lateral force, aerodynamic drag, and sound pressure level (SPL) of the car are investigated. The results show that a streamlined counterweight can stabilize airflow between the windward areas of the car and counterweight, reducing turbulence, the lateral lift, surface pressure gradients, and SPL, while also lessening the effects of reduced car-counterweight spacing. At a speed of 6 m/s, a bi-arc counterweight with a radius of 250 mm demonstrates superior performance in reducing lateral lift force and aerodynamic drag compared to a traditional rectangular counterweight, with reductions of 12.2% in lateral lift force and 9.3% in aerodynamic drag. Additionally, the simulation and test errors are within 10%, confirming the accuracy of the numerical calculation method.

Surge phenomenon is investigated for an axial compressor through a set of experiments. In addition, the full-annulus numerical simulation method is used to numerically simulate the surge phenomenon and analyze the flow field details during the surge process. The results identified four distinct stages in the surge: forward deceleration, reverse flow, forward recovery, and chamber recovery. The forward recovery stage, the flow field experiences stall with the occurrence of unevenly distributed stall regions. In contrast, the chamber recovery stage at the same flow rate exhibits a more uniform flow field without stall regions. These findings highlight the capability of the capability of the full-annulus calculation method to provide insights into the flow field details during the surge process. The information can serve as a reference for the development of accurate surge models and the study of the influence of surge on the internal flow of the compressor passage.

The present work aims to investigate the influence of vane clocking effect on fluctuating characters and radial force on impeller for centrifugal pump. Numerical simulations were conducted with validation by experiments, at four different relative angular position between vane and tongue. The power consumption and work done by blades are evaluated in time-history. The radial velocity, circumferential velocity at impeller-diffuser clearance is depicted by expanding the turning surface, for comparison under different diffuser position to reveal the flow distortion affected by clocking effect. The results indicate that when vane trailing edge is at tongue (θd1), the corresponding diffuser channel is placed against small flow section in volute leading to a blocking effect that results in significant circumferential inhomogeneity at diffuser outlet. The interaction between impeller blade and different diffuser vane presents distinct intensity, causing the unsteady fluctuation intensity of power consumption of impeller at different vane positions is significantly different, and so is the radial force. As the diffuser vane moves away from tongue (at θd4), the blocking effect reduces and the flow field becomes more evenly distributed among each channel. Resulting in weaker fluctuations in the power consumption, blade load and radial force.

To explore the radiomics features of osteoporotic and malignant neoplastic vertebral compression fractures (VCFs), and to analyze the application value of radiomics in differential diagnosis of osteoporotic and malignant neoplastic VCFs.

Fifty-one patients with VCFs caused by malignant tumors and forty-nine patients with osteoporosis-induced VCFs treated in the Xiaoshan Hospital Affiliated to Hangzhou Normal University from January 2020 to June 2023 were retrospectively collected into a training set (70 cases) and a verification set (30 cases) according to a stratified random sampling design and a 7:3 ratio. The radiomics parameters of T2WI images of the diseased vertebral bodies were extracted, and the parameters with statistical differences were screened out by dimensionality reduction, so as to build a prediction model. Receiver operating characteristic (ROC) curves were drawn to evaluate the differential diagnosis performance of radiomics for the etiology of vertebral fractures.

Eight radiomics features were obtained after dimensionality reduction using the LASSO algorithm. The constructed model was effective in differentiating osteoporotic and malignant neoplastic VCFs, with an area under the ROC curve (AUC) of 0.95; while the AUC for the validation set was 0.84.

The radiomics features of T2WI images of vertebral fractures have high efficiency in the differential diagnosis of fracture etiology.

Brucella outer membrane proteins (OMPs) are highly immunogenic, and lipopolysaccharides (LPS) are also considered significant antigens, making them potential candidates for subunit vaccines.

To investigate the effects of Brucella OMPs and LPSs on mouse bone marrow-derived dendritic cells (BMDC) activation and T-lymphocyte proliferation.

BMDC were isolated and cultured in vitro, and subsequently co-cultured with Brucella recombinant proteins (rOMP10, rOMP19, rBP26, rOMP25, and rOMP31), as well as smooth LPS (S-LPS) or rough LPS (R-LPS). The expression of maturation markers on the surface of BMDCs was determined using flow cytometry, while the expression of TLR receptors was determined using RT-PCR. The levels of inflammatory cytokines were measured using iELISA, and the impact on the proliferation of mouse T-lymphocytes was assessed using the MTT method.

The impact of LPS on BMDC maturation, TLRs-mediated cytokine secretion, and antigen presentation was found to be limited. In contrast, rOMP10, rOMP19, and rBP26 were observed to promote BMDC maturation, increase the expression of TLR-2 and TLR-4 mRNA, and activate T-lymphocyte proliferation by significantly increasing the expression of pro-inflammatory cytokines (TNF-α, IFN-γ, IL-6, IL-12) and antigen-presenting molecules. However, rOMP25 and rOMP31 did not promote BMDC maturation, inhibited the expression of MHCI and MHCII antigen-presenting molecules, and increased the expression of inflammation-suppressing cytokines (IL-10 and IL-4), resulting in the inhibition of T-lymphocyte proliferation.

Brucella OMP10, OMP19, and BP26 play an important role in activating the host immune response, while OMP25 together with OMP31 may play a role in Brucella immune escape.

The hydrodynamic coefficient of an underwater manipulator varies with changes in posture and flow field, presenting significant challenges for precise control and localization. This study, conducted numerical simulations to investigate the patterns of variation in flow field and hydrodynamic coefficients. Results showed that hydrodynamic performance remained consistent when the posture of the manipulator was either axisymmetric or origin-symmetric. Upon rotation, axial flow extended across the entire downstream surface, and the Karman vortex street entirely eliminated. Pressure coefficients on the back pressure surface of the manipulator increased with the Reynolds number within the range of 6×103 ≤ Re ≤ 3×104, while the pressure coefficient on the upstream surface remained unchanged. Within this range, drag coefficients for the upper and lower arms decreased by 27.4% and 23.9%, respectively. The hydrodynamic performance of the lower arm was independent of the upper arm's posture, with a maximum drag coefficient of 1.48 achieved at α = −90°. As the posture angle of the manipulator varied from 30° to 60°, the pressure coefficient on the upstream surface decreased from 0.75 to 0.25.

Building a risk prediction model, validating it, and researching the risk variables for radiation dermatitis in patients receiving post-operative radiotherapy for early breast cancer. A total of 326 patients with early-stage breast cancer who underwent postoperative radiotherapy in hospital between August 2020 and August 2023 were selected and divided into 198 in the modeling group and 128 in the validation group; and the modeling group was divided into an occurrence group and a non-occurrence group according to whether they had radiation dermatitis. Logistic regression was used to investigate the risk factors for the development of dermatitis, and the predictive effect of the model was tested by the receiver operating characteristic curve (ROC). Combined diabetes, conventional split radiotherapy, compensatory membrane application, and albumin <40g/L were independent risk factors for radiation dermatitis (P < 0.05); the area under the curve (AUC) was 0.821 and 0.908 in the modeling and validation groups, respectively, P < 0.001, with goodness-of-fit test (Hosmer-Leme-show, H-L) validity. Clinically, it is important to consider the risk factors of radiation dermatitis among patients who receive postoperative radiotherapy for early-stage breast cancer. Utilizing a risk prediction model, doctors can identify and evaluate patients' risk levels, aiding in the timely implementation of preventive measures.

Cytotoxic lesions of the corpus callosum (CLOCC) represent secondary injuries associated with various clinical etiologies. These lesions, characterized by restricted diffusion on cranial magnetic resonance imaging (MRI), manifest as small and reversible abnormalities in the splenium of the corpus callosum. Despite their distinct radiological features, they often pose a diagnostic challenge, mimicking acute cerebral infarction in clinical presentation. Herein, we present the case of a 47-year-old male with a history of two episodes of transient syncope, transient bilateral blindness, multiple episodes of diarrhea, and high fever. Initially suspected to have acute splenial infarction secondary to sepsis and gastrointestinal infection, further evaluation including cranio-cervical computed tomography angiography (CTA) and electroencephalography, in conjunction with neurology consultation, led to the diagnosis of CLOCC. Prompt initiation of antimicrobial and antipyretic therapy resulted in rapid neurological improvement within 48 hours. Splenial lesions in the context of sepsis often masquerade as infarction due to their association with coagulopathy and microvascular thrombosis. However, emerging evidence suggests that isolated infarction in this region is exceedingly rare, with reversible lesions characteristic of CLOCC being more commonly encountered. Management primarily entails addressing the underlying systemic condition, with a generally favorable prognosis observed in most cases.

This study explores the predictive value of Computerized Tomography (CT) perfusion imaging, serum D-dimer (D-D), and serum matrix metalloproteinase-9 (MMP-9) levels for hemorrhagic transformation (HT) in patients with acute cerebral infarction post-thrombolysis. Patients with acute cerebral infarction who underwent thrombolytic therapy from February 2021 to February 2022 were included. CT perfusion imaging was conducted within a week post-operation. The study compared CT perfusion parameters and serum markers, analyzing differences and conducting univariate and multivariate analyses to explore their predictive value for HT. No significant differences were found in hypertension, hyperlipidemia, stroke history, mean arterial pressure, fasting blood glucose, and platelet count pre-thrombolysis (P > 0.05). However, infarct diameter ≥ 5 cm and atrial fibrillation were more common in the study group, with higher pre-thrombolysis National Institutes of Health Stroke Scale (NIHSS) score, D-D, and MMP-9 levels (P < 0.05). CT perfusion showed lower relative cerebral blood volume (rCBV, relative cerebral blood flow (rCBF, and higher relative mean transit time (rMTT), relative time to peak (rTTP) in the study group (P < 0.05). D-D and MMP-9 levels were negatively correlated with rCBV, rCBF, and positively with rTTP, CTP integration index (P < 0.05). CT perfusion imaging, serum D-D, and MMP-9 levels are effective predictors of hemorrhagic transformation in acute cerebral infarction patients post-thrombolysis. These findings are valuable for guiding clinical treatment and monitoring.

The hydrodynamic coefficients of underwater manipulators constantly change during their operation. In this study, the hydrodynamic coefficients of an underwater manipulator were calculated using the finite volume method to better explain its hydrodynamic performance. The drag, lift, and moment coefficients and the Strouhal number of an underwater manipulator for different postures were investigated. The results indicated that in each motion range, the coefficients first increase and then decrease.  Meanwhile, when the attitude of the underwater manipulator is axis-symmetric or origin-symmetric, the hydrodynamic coefficients and the Strouhal number obtained are approximately the identical. The drag coefficient, lift coefficient and moment coefficient reach their maximum values of 3.59, 3.29, and 1.78 at angles of 30°, 150°, and 150°, respectively， with minimum values at 90°, 50° and -30°. Furthermore, the leading-edge shape of the underwater manipulator had a significant effect on the hydrodynamic coefficient. Maximum reductions of 44%, 25%, and 50.5% were obtained in the drag, lift, and moment coefficients, respectively, by comparing the semicircular leading edge with the right-angle leading edge. A maximum Strouhal number of 0.219 was obtained when the semicircular leading edge of the underwater manipulator was the upstream surface. This study will provide theoretical guidance to reveal the hydrodynamic performance of the underwater manipulators. It also serves as a reference for the structural design of the underwater manipulators.

The plunger valve has an important role in a large compressor system as its operating characteristics directly affect the aerodynamic boundary condition of the compressor equipment. In this study, dynamic modeling and analysis method of the plunger valve are proposed for an accurate control of the system. By considering the interaction between the dynamic flow in the valve and actuator action, a lumped parameter model for the fluid–structure interaction force and multibody dynamic model of the actuator are developed based on intrinsic correlation parameters. A combination analysis to simultaneously predict valve flow and actuator dynamic characteristics is proposed. The predicted results are in a good agreement with experimental data, which validates the proposed model and analysis method. The analysis results show that the coupling effect between the valve flow and actuator is significant and has an important role in valve control, particularly when the valve opening is smaller. Compared to the experimental data and computational fluid dynamics results, the presented methods are accurate for valve control and effective for prediction of flow rate.

To probe the impact of portable vaginal irrigator in patients with cervical cancer undergoing radiotherapy.

A total of 100 patients with advanced cervical cancer who received radiotherapy in our hospital from January 2021 to December 2022 were chosen and separated into control group (CG, n=50) and research group (RG, n=50). After radiotherapy, patients in the CG control group adopted extrusion balloon irrigator for vaginal irrigation, while patients in the RG adopted portable vaginal irrigator for vaginal irrigation. The cleanliness, vaginal length, vaginal width, comfort ratio, patient satisfaction, and occurrence of complications in both groups were compared.

The number of patients with a white blood cell count of 15-30 in the RG was less than that of the CG (P<0.05). The number of patients in cleanliness degree I in the RG was higher relative to the CG (P<0.05), while the number of patients in cleanliness degree III in the RG was lower compared to the CG (P<0.05). Three months after radiotherapy, the vaginal length and vaginal width of the RG were higher relative to the CG (P<0.05). The comfort ratio and satisfaction of patients in the RG was higher compared to the CG (P<0.05). The occurrence of complications in the RG was declined compared to the CG (P<0.05).

The use of portable vaginal irrigation device realizes the comfortable feeling of patients in the process of use, improves the effect of vaginal irrigation, reduces the occurrence of complications after radiotherapy, which is worthy of clinical promotion.

The effects of inflow variations due to the working environment and flight attitude changes on turbomachines are considerable in the real world. Nevertheless, uncertainty quantification can be adopted to assess mean performance changes and perform the aerodynamic shape design as well as optimization. Thus, an uncertainty quantification method of adaptive sparse grid collocation (ASGC) was first introduced to address the inflow uncertainties’ effect issue effectively and accurately. Then, ASGC was utilized to evaluate the impacts of inlet incidence perturbations at different perturbation scales and reference inflow Mach numbers on the aerodynamic performance of a controlled diffusion cascade. The results showed that compared with the Monte Carlo simulation and static sparse gird collocation, the statistical accuracy and response accuracy of ASGC were maintained, and meanwhile its model construction efficiency was significantly improved because of the nested adaptive sampling feature. Under the perturbations of inlet incidences with high reference incidences, the mean aerodynamic loss always aggravates. The changes in aerodynamic loss nonlinearly depend on the inlet incidence perturbations, and the nonlinear dependence becomes greater when the perturbation scale. expands. At the same perturbation scale, the nonlinear dependence on the inlet incidence perturbations is further enhanced when the reference inflow Mach number rises. Finally, uncertainty quantification of the flow field revealed that the fluctuation of flow accelerations at the leading edge plays a fundamental role in determining the uncertainty of the aerodynamic loss.

The load capacity and static stiffness of the existing air hydrostatic guideways are relatively low, and the static performance of the air film is degraded when external forces are increased during the process. Therefore, this study considered an aerostatic guideway of an ultra-precision micromachine tool as the research object. Single- and double-row orifice structures were designed on the guideway, and linear, extended, and X-shaped pressure-equalizing groove (PEG) structures with rectangular cross-sections were designed on the working surface of the guideway. By establishing a computational fluid dynamics model of the guideway air film, the pressure contour was obtained through simulation, and finally, the advantages of the double-row orifice structure were determined. Then, the influences of the structure, width, and depth of PEG and the diameter and number of orifices on the load capacity, stiffness, and air consumption were studied, which provided a theoretical basis for improving the load performance of the aerostatic guideway. The results showed that the design of the PEG effectively improved the load performance but increased the air consumption. The extended PEG exhibited the best load performance. When the eccentricity was large, the width of the PEG moderately increased, improving the load capacity and stiffness. While increasing the depth only improved the stiffness, it had little effect on the load capacity and air consumption. When the eccentricity was small, the diameter and number of orifices moderately increased. The experimental data were consistent with the simulation results, demonstrating the accuracy of the simulation method.

Improving the output flow quality of the high-precision micro bidirectional gear pump can effectively improve the position control accuracy and dynamic characteristics of the electro-hydraulic actuator. In order to meet the appeal requirements and reduce the vibration and noise of the gear pump and prolong its working life, this paper starts with the research of the key part of the gear pump–the unloading groove structure. The three characteristics of trapped oil phenomenon, cavitation phenomenon, and flow were used as key indices to evaluate gear pump performance. Using numerical simulation analysis, the dynamic grid simulation method was used to explore the influence of unloading groove spacing on the transient multi-flow field characteristics of the gear pump under conventional design range. Our results show that reducing the distance between unloading grooves can greatly reduce the trapped oil pressure and the amount of gas precipitation in the flow field, while reducing flow pulsation and improving volumetric efficiency. However, when the unloading groove spacing is too small, the instantaneous flow curve loses the pulsation characteristics and the flow stability decreases. Considering the influence of the gear pump on the accuracy of the electro-hydraulic actuator and the performance of the gear pump itself, the analytic hierarchy process was used to obtain the 1 mm unloading slot spacing, which best meets the engineering requirements of high flow accuracy and low vibration noise. The results provide a basis for work on the structural optimization of high-precision micro gear pumps.

Unsteady numerical simulation of single passage was carried out on NASA Rotor 35 to study the influence of the radial inclined angle of self-circulation casing treatment (SCT) on the performance and stability of a transonic compressor at 100% design speed. The radial inclined angles were set to 0°(D0), °(D30) and 60°(D60), respectively. The calculated result indicates an increase in the stall margin improvement (SMI) and the design efficiency improvement (DEI) as the radial inclined angle increases gradually. The SMI of the SCT with a 60° radial inclined angle is 12.5%, the biggest among the three SCTs, and the peak efficiency improvements (PEI) of the SCTs are almost the same. The radial inclined angle is provided with the effect of strengthening the self-circulation casing treatment effect, which further improves the stable working range of the compressor, and the efficiency loss is also lower than that of the 0° angle structure. The flow conditions inside the bleeding part can be improved by radially skewing the self-circulating structure toward the rotor rotating direction.

The aim of this study was to make a comparison of plan quality between MLC-based EDGE and the cone-based CyberKnife systems in SBRT of localized prostate cancer.

Ten patients with target volumes from 34.65 to 82.16 cc were included. Treatment plans were created for both systems using the same constraints. Dosimetric indices including target coverage, conformity index (CI), homogeneity index (HI), gradient index (GI) were applied for target, while the sparing of critical organs was evaluated with special dose-volume metrics and integral dose. Meanwhile, the delivery time and monitor units (MUs) were also estimated. The radiobiological indices such as equivalent uniform dose (EUD), tumor control probability (TCP) and normal tissue complication probability (NTCP) were also analyzed.

Both plans produced similar target coverage, HI and GI. For EDGE, more conformal dose distribution as well as reduced exposure of critical organs were obtained together with reduction of 91% delivery time and 72% MUs. EDGE plans also got lower EUD for bladder, rectum, urethra and penile bulk, which associated with reduction of NTCPs. However, higher values of EUD and TCP for tumor were obtained with CK plans.  

It indicated that both systems were capable of producing almost equivalent plan quality and can meet clinical requirements. CyberKnife has higher target dose while EDGE system has more advantages in normal tissue sparing and delivery efficiency.

Breast cancer (BC) is a global threat to women’s health. Volumetric intensity modulated arc therapy (VMAT) is effective for the local control of BC. This study evaluated the pulmonary and cardiac radiotherapeutic dosage to provide information for estimating normal tissue complication probability (NTCP) once malignant tumors appear in patients’ left and right breasts.

We conducted a retrospective analysis of VMAT regimen of 40 patients with BC, among whom 20 patients (group 1) were diagnosed with right BC and 20 patients (group 2) with left BC. The pulmonary and cardiac dose volume histogram (DVH) parameters were acquired and compared between patients with left and right BC treated with VMAT.

Generally, the pulmonary and cardiac dosages in patients with right BC were larger than in those with left BC. For the lung, the V20 and V5 of right BC patients were significantly higher, relative to the left BC patients (P<0.05). For the heart, the V5 and V10 of right BC patients were significantly lower, compared to left BC patients, with differences of up to 20% and 10%, respectively (both P<0.05). V20, V30, and V40 as low as zero were observed for right BC patients.

When treating left BC, image guidance and respiratory management techniques should be applied to limit radiotherapy complications that occur in the heart because of patient positioning and respiratory movement.

Bladder pheochromocytoma, as a rare bladder tumor, which originated from the chromaffin tissue of the sympathetic nervous system. It is difficult to distinguish from other non-epithelial tumors on imaging. This study reported a 31-year-old female, whose physical examination revealed a bladder mass for 50 days. The patient’s main clinical symptoms included sudden headache, dizziness, increased blood pressure, and chest palpitations after intermittent micturition. However, laboratory tests showed that the 24-hour urine catecholamine levels (norepinephrine, vanillylmandelic acid [VMA] and metanephrine) were normal. Magnetic resonance imaging (MRI) showed a mass in the posterior bladder wall, the typical performance is“light-bulb” bright lesion on T2-weighted imaging. The mass was surgically excised, and histopathological examination revealed that it was a pheochromocytoma. During the first 3-month of postoperative follow-up, the patient’s symptoms gradually subsided. To our knowledge, this is the first case reporting on the use of MRI imaging and specific image features of this rare bladder pheochromocytoma. Due to the better soft tissue resolution and multi-parameter on MRI, changes in the size and internal signal of the lesion can be clearly displayed. Thus, MRI is an indispensable tool in tumor diagnosis and prognosis assessment.

Combined bearing, which consists of spherical roller bearing and thrust spherical roller bearing, is an important support in various low-speed and heavy load institutions and the stability of its running state is a strong guarantee for the normal operation of the supporting mechanism. Basing on the wellbore trajectory control tool, the loading distribution of combined bearing under pure radial and axial forces is studied theoretically. Two kinds of limit state of rolling elements movement named "Odd press" state and "Even press" state is considered and the Hertzian line elastic contact model is used to deal with the contact between roller and raceway. The calculation results of contact stress and radial displacement are very close to the analysis results, and the accuracy of the analysis results is verified by the radial displacement experiment. The results show that the radial load will lead to the radial displacement of the combined bearing axis, which is about 5.81×10-3 mm. The radial displacement can affect the guiding accuracy of the tool to a certain extent. The radial displacement can be reduced by adjusting the bearing structure design parameters .This research can be used to design SRB and TSRB combined Bearing in actual engineering problem.

Casing treatment is a powerful method for improving the stability of aircraft compressors. An optimized slot-type casing treatment was tested on the first rotor of a highly-loaded two-stage compressor, and the results showed that the casing treatment could not increase the compressor stability at the design and off-design speeds. A coupled casing treatment (CCT), which is built with an injector, a bridge, a plenum chamber, and several slots for a recirculating loop, is proposed and optimized to enhance the stability of the compressor in the present study. The optimized CCT improves the compressor stability and efficiency under the design condition by 75.8% and 0.71%, respectively. The coupling effect, which is established with an inner circulation in the slots and an outer circulation from the slots to the injectors, accounts for the excellent stability enhancement. The coupling effect reduces the amount of tip leakage flow, depresses the development of the tip leakage vortex (TLV), and greatly decreases the blockage in the rotor tip which is primarily induced by the interaction of the shock-wave and boundary-layer at the blade suction surface. The parametric study shows that improving the coupling effect has a positive effect on reducing the rotor tip blockage, but a negative effect on the stability of the compressor stage. This is because the inflow condition of the stator is tremendously distorted while the coupling effect is excessively strong, which can cause a stall in the stator rather than in the rotor. The compressor stability can be maximally enhanced by adjusting the strength of the coupling effect to make a compromise of the improved rotor tip flow and the deteriorated stator flow.

As Rotating-sleeve Flow Distribution System (RFDS) running, the cavitation of the hydraulic pump may lead to the decreased volume efficiency, increment of vibration and noise, then affecting the operation of system. To deeply analyze the cavitation characteristics of RFDS, the Singhal cavitation model of RFDS was established, meanwhile corresponding experiments were carried out. Cavitation characteristics of RFDS were investigated under various revolving speed, inlet pressure and CAM groove profile. The results demonstrate that the variation trend of experimental volumetric efficiency is the same as that of simulation results. The maximum error is 2% and 3.2% at different rotating speeds and different inlet pressures respectively. Maximum gas volume fraction and cavitation time ratio increase monotonically as the rotating speed increases, and volumetric efficiency increases first and then decreases with the increase of rotating speed. Volumetric efficiency reaches up to 92.13% under the rotating speed of 500r/min. The increased inlet pressure can slow down the cavitation of RFDS and improve volumetric efficiency. Linear profile exhibits the best cavitation characteristic under both different rotating speed and inlet pressure.