Evaluation and prediction of earth pressure balance shield performance in complex rock strata:A case study in Dalian,China

This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.

Ultrasound based estimate of central venous pressure:Are we any closer?

Central venous pressure(CVP)serves as a direct approximation of right atrial pressure and is influenced by factors like total blood volume,venous compliance,cardiac output,and orthostasis.Normal CVP falls within 8-12 mmHg but varies with volume status and venous compliance.Monitoring and managing disturbances in CVP are vital in patients with circulatory shock or fluid disturbances.Elevated CVP can lead to fluid accumulation in the interstitial space,impairing venous return and reducing cardiac preload.While pulmonary artery catheterization and central venous catheter obtained measurements are considered to be more accurate,they carry risk of complications and their usage has not shown clinical improvement.Ultrasound-based assessment of the internal jugular vein(IJV)offers real-time,non-invasive measurement of static and dynamic parameters for estimating CVP.IJV parameters,including diameter and ratio,has demonstrated good correlation with CVP.Despite significant advancements in non-invasive CVP measurement,a reliable tool is yet to be found.Present methods can offer reasonable guidance in assessing CVP,provided their limitations are acknowledged.

Effect of impeller reflux balance holes on pressure and axial force of centrifugal pump

The size of impeller reflux holes for centrifugal pump has influence on the pressure distribution of front and rear shrouds and rear pump chamber, as well as energy characteristics of whole pump and axial force. Low specific-speed centrifugal pump with Q=12.5 m3/h, H=60 m, n=2950 r/min was selected to be designed with eight axial reflux balance holes with 4.5 mm in diameter. The simulated Q-H curve and net positive suction head(NPSH) were in good agreement with experimental results, which illustrated that centrifugal pump with axial reflux balance holes was superior in the cavitation characteristic; however, it showed to little superiority in head and efficiency. The pressure in rear pump chamber at 0.6 times rate flow is 29.36% of pressure difference between outlet and inlet, which reduces to 29.10% at rate flow and 28.33% at 1.4 times rate flow. As the whole, the pressure distribution on front and rear shrouds from simulation results is not a standard parabola, and axial force decreases as flow rate increases. Radical reflux balance holes chosen to be 5.2 mm and 5.9 mm in diameter were further designed with other hydraulic parts unchanged. With structural grids adopted for total flow field, contrast numerical simulation on internal flow characteristics was conducted based on momentum equations and standard turbulence model(κ-ε). It is found that axial force of pump with radical reflux balance holes of5.2 mm and 5.9 mm in diameter is significantly less than that with radical reflux balance holes of 4.5 mm in diameter. Better axial force balance is obtained as the ratio of area of reflux balance holes and area of sealing ring exceeds 6.

INVESTIGATION INTO EFFECT OF SPRING PRESSURE ON PERFORMANCE OF BALANCED MECHANICAL SEALS

The loads acting on the sealing elements of balanced mechanical seals are analyzed. When the balance factor approaches the back pressure factor, the spring pressure will become main part of the face pressure. The leakage model of balanced mechanical seals is established on the base of M-B model for rough surface. Several GY-70 type balanced mechanical seals are tested. The influences of the spring pressure both on the leakage rate and on the friction characteristic of balanced mechanical seals are investigated. The research results indicate that as spring pressure increases, both the clear-ance between two end faces and the leakage rate will decrease, and the friction will be more serious because lubrication medium between the rotating ring and the stationary ring reduces, though the increase of the spring pressure may not be enough to change the face friction state of mechanical seals. There exists an optimum spring pressure for mechanical seal operation. Under this spring pres-sure, not only leakage rate is small, but also the seal end surfaces have a fine friction characteristic. Under different operating conditions, identical type mechanical seals may possess different spring pressure. Appropriate selection of spring pressure is valuable to realize long-period and small leakage rate operating of balanced mechanical seals.

Feasibility study of tar sands conditioning for earth pressure balance tunnelling

This paper presents the results of laboratory test on the feasibility of soil conditioning for earth pressurebalance （EPB） excavation in a tar sand, which is a natural material never studied in this respect. Thelaboratory test performed is based on a procedure and methods used in previous studies with differenttypes of soils, but for this special complex material, additional tests are also conducted to verify particularproperties of the tar sands, such as the tilt test and vane shear test usually used in cohesive materials, anda direct shear test. The laboratory test proves that the test procedure is applicable also to this type of soiland the conditioned material can be considered suitable for EPB excavations, although it is necessary touse a certain percentage of fine elements （filler） to create a material suitable to be mixed with foam. Thetest results show that the conditioned material fulfils the required standard for an EPB application.

Discrete element simulation of mechanical characteristic of conditioned sands in earth pressure balance shield tunneling

The discrete element method (DEM) was used to simulate the flow characteristic and strength characteristic of the conditioned sands in the earth pressure balance (EPB) tunneling. In the laboratory the conditioned sands were reproduced and the slump test and the direct shear test of the conditioned sands were implemented. A DEM equivalent model that can simulate the macro mechanical characteristic of the conditioned sands was proposed,and the corresponding numerical models of the slump test and the shear test were established. By selecting proper DEM model parameters,the errors of the slump values between the simulation results and the test results are in the range of 10.3%-14.3%,and the error of the curves between the shear displacement and the shear stress calculated with the DEM simulation is 4.68%-16.5% compared with that of the laboratory direct shear test. This illustrates that the proposed DEM equivalent model can approximately simulate the mechanical characteristics of the conditioned sands,which provides the basis for further simulation of the interaction between the conditioned soil and the chamber pressure system of the EPB machine.

Optimal arrangement for pressure measurement points in working chamber of earth pressure balance shield

In order to exactly provide scientific basis for pressure dynamic balance control of working chamber of earth pressure balance shield (EPBS),study on optimal arrangement of pressure measurement points in working chamber was conducted. Based on mathematical description of optimal arrangement for pressure measurement points,fuzzy clustering analysis and discriminant analysis were used to divide pressure regions of nodes on bulkhead. Finally,the selection method of optimal measurement points was proposed,and by selecting d6.28 m EPBS as study object,the case study was conducted. By contrast,based on optimal arrangement scheme of pressure measurement points,through adopting weighted algorithm,the absolute error mean of equivalent pressure of working chamber is the smallest. In addition,pressure curve of optimal arrangement points presents parabola,and it can show the state of pressure distribution on bulkhead truly. It is concluded that the optimal arrangement method of pressure measurement points in working chamber is effective and feasible,and the method can provide basis for realizing high precision pressure control of EPBS.

Modeling approaches to pressure balance dynamic system in shield tunneling

In order to deal with modeling problem of a pressure balance system with time-delay, nonlinear, time-varying and uncertain characteristics, an intelligent modeling procedure is proposed, which is based on artificial neural network(ANN) and input-output data of the system during shield tunneling and can overcome the precision problem in mechanistic modeling(MM) approach. The computational results show that the training algorithm with Gauss-Newton optimization has fast convergent speed. The experimental investigation indicates that, compared with mechanistic modeling approach, intelligent modeling procedure can obviously increase the precision in both soil pressure fitting and forecasting period. The effectiveness and accuracy of proposed intelligent modeling procedure are verified in laboratory tests.

Blood Pressure Balance as a Marker for Early Detection of Cerebral Infarction and a Criterion for Inclusion/Exclusion from Acupuncture Treatment

Background: Early detection of cerebral infarction (CI) by home acupuncturists might be helpful in reducing stroke mortality. We compared vital signs of patients who developed CI and those who did not to ascertain if blood pressure balance is a useful marker for the early detection of CI and for distinguishing cases with potentially effective/ineffective acupuncture treatment. Methods: In this retrospective study, vital signs such as body temperature, pulse, and blood pressure, were simultaneously obtained from the right and left arms of patients who received weekly acupuncture treatment. We focused on the differences between values obtained from the right and left arms (the balance) and compared the values of patients who developed CI [CI (+)] (n = 18) and those of age-/gender-matched patients who did not [CI (−)] (n = 18). Results: Left/right blood pressure was significantly more unbalanced in the CI (+) group than in the CI (−) group, especially immediately before the onset of CI. Moreover, all CIs occurred on the side with a lower blood pressure. Discussion and Conclusions: Blood pressure balance might aid in the early detection of CI and to determine whether treatment with traditional or modern medicine is more appropriate. Acupuncture may thus help maintain patients’ quality of life.

Assessment of the Plantar Pressure, Muscle Strength and Balance in Patients with Type 2 Diabetes Mellitus in Cyprus

Aims: Diabetes Mellitus (DM) is a metabolic disorder which affects whole systems of human body. This study aimed to compare the strength of foot muscles, dynamic balance, and peak plantar pressure between diabetic patients before developing polyneuropathy and healthy peers. Methods: 21 people, 11 diabetic patients and 10 age-matched healthy peers, were included in the study. A manual muscle tester (model 01163 Lafayette) was used to assess muscle strength. Pedobarography was the device to determine the distribution of plantar pressure into nine regions of foot. Dynamic balance was also measured by using a mobile platform (Techno-body, PK 200 WL, Italy). Results: Diabetic and control groups had similar muscle strength and dynamic balance (p > 0.05). Most of the plantar pressure findings were also similar (p > 0.05). There were significant differences in only two regions of foot between two groups (p < 0.05). Conclusion: Diabetes Mellitus is not a factor influencing balance and muscle strength before polyneuropathy. However, it is possible to state that it may negatively affect the distribution of plantar pressure so clinians should assess and treat this distribution in the patients with DM.

COMPUTER SIMULATION OF VENTILATION PRESSURE BALANCING FOR THE PREVENTION OF SPONTANEOUS COMBUSTION IN MINES

Qualitative analysis plus trial and error method are still the routine to achieve ventilation pressure balancing. These methods may cause large errors in pressure balancing so that sometimes the spontaneous combustion can not be extinguished effectively. This paper introduces a quantitative analysis of pressure balancing for different causes of ventilation networks and develops a computer program (SPFPB) specifically written for pressure balancing between faces and connected gobs. It allows a user to choose different metheds to meet his various needs and the underground conditions. The different balancing results are compared, and the proper locations and sizes of the control devices are recommended.

Differences in standing balance between patients with diplegic and hemiplegic cerebral palsy

Maintaining standing postural balance is important for walking and handling abilities in patients with cerebral palsy. This study included 23 patients with cerebral palsy （seven with spastic diplegia and 16 with spastic hemiplegia）, aged from 7 to 16 years of age. Standing posture balance measurements were performed using an AMTI model OR6-7 force platform with the eyes open and closed. Patients with diplegic cerebral palsy exhibited greater center of pressure displacement areas with the eyes open and greater center of pressure sway in the medial-lateral direction with the eyes open and closed compared with hemiplegic patients, Thus, diplegic patients exhibited weaker postural balance control ability and less standing stability compared with hemiplegic cerebral palsy patients.

基于Nintendo Wii Balance Board的平衡测量及神经反馈训练提高健康人平衡能力的初步研究（英文）

神经反馈训练在提高认知能力及治疗精神疾病方面具有积极效果,但其在健康人平衡能力方面的作用还没有研究.本文对神经反馈训练用于提高健康人平衡能力进行了初步研究.为了经济有效地检测平衡能力及神经反馈后的平衡能力变化,首先研究了作为平衡测量系统的Nintendo Wii Balance Board(WBB),实验结果表明WBB具有良好的可靠性及灵敏度.对一位年轻健康的受试者做了连续5天的神经反馈训练,并在神经反馈训练前后用WBB测量了其平衡能力.神经反馈训练以后,该受试者左脚睁眼站立的平衡能力得到了改善.

Cyclic moving average control approach to cylinder pressure and its experimental validation

Cyclic variability is a factor adversely affecting engine performance. In this paper a cyclic moving average regulation approach to cylinder pressure at top dead center （TDC） is proposed, where the ignition time is adopted as the control input. The dynamics from ignition time to the moving average index is described by ARMA model. With this model, a one-step ahead prediction-based minimum variance controller （MVC） is developed for regulation. The performance of the proposed controller is illustrated by experiments with a commercial car engine and experimental results show that the controller has a reliable effect on index regulation when the engine works under different fuel injection strategies, load changing and throttle opening disturbance.

Hydrodynamics of air-kerosene bubble column under elevated pressure in homogeneous flow regime

A multiphase computational fluid dynamics(CFD)model coupled with the population balance equation(PBE)was developed in a homogeneous air-kerosene bubble column under elevated pressure(P).The specific pressure drop(ΔP/L),gas holdup(α_(G)),and Sauter mean diameter(d_(32))were experimentally measured in the bubble column with 1.8 m height and 0.1 m inner diameter,which was operated at a superficial gas velocity of 12.3 mm·s^(-1),and P=1-35 bar(1 bar=10^(5) Pa).A modified drag coefficient model was proposed to consider the effect of bubble swarm and pressure on hydrodynamics of the bubble column.The Luo breakage model was modified to account for liquid density,viscosity,surface tension and gas density.TheΔP/L,α_(G),and d_(32) obtained from the CFD model were compared with experimental data,and the gas density-dependent parameters of the CFD model were identified.With increasing P from 1 to 35 bar,theα_(G) varied from 5.4%to 7.2% and the d32 decreased from 2.3 to 1.5 mm.The CFD-PBE model is applicable to predict hydrodynamics of pressurized bubble columns for gas-organic liquid in the homogeneous regime.

The Effect of Nitrous Oxide on the Intraocular Pressure in Patients Undergoing Abdominal Surgery under Sevoflurane and Remifentanil Anesthesia

Introduction: Although inhalational anesthesia and nitrousoxide (N2O) are known to affect the intraocular pressure (IOP), little is known about the effect of nitrousoxide on the IOP during sevoflurane and remifentanil anesthesia. In the present study, we examined the effect of balanced anesthesia on the IOP. Materials and Methods: After obtaining informed consent, the patients undergoing abdominal surgery under general anesthesia were divided into two groups: N2O group (n = 10) and control group (n = 12). General anesthesia was maintained with remifentanil (0.05 - 0.3 μg/kg/min), 33% O2 and 1.2% sevoflurane to keep ETCO2 of 35 - 40 mmHg following tracheal intubation. After baseline measurement of IOP (T0, 20 minutes after injection of anesthesia), the patients in the N2O group received 67% nitrousoxide, and the patients in the control group received air, with O2 and 1.2% sevoflurane. Then, IOP was measured at 1 hour (T1), 2 hours (T2), and 3 hours (T3) after anesthesia induction in the supineposition. Blood pressure and heart rate were recorded at the same time interval. Results: There was no significant difference in the IOP at any period between the two groups. In both groups, the IOP at the T3 was significantly higher than that at T0. Conclusion: These results suggest that N2O does not affect the IOP in patients undergoing abdominal surgery under sevoflurane and remifentanil anesthesia.

Balance Performance in Female Collegiate Athletes

Proper balance is essential for athletes during competition and training as sport places different balance requirements on the human body. The purpose of the study was to analyze balance performance among female athletes using COP （center of pressure） sway parameters. Twenty one NCAA （National Collegiate Athletic Association） division I female athletes （soccer, volleyball and dance） completed the study. Static balance was assessed using UST （unilateral stance test） and dynamic balance was assessed using MCT （motor control test） on the NeuroCom Equitest. Sway velocities, root mean square sway and reaction time latencies were used to quantify balance. A one-way between subjects ANOVA （analysis of variance） was performed to analyze these balance parameters. Significant （p 〈 0.05） differences between groups were found and post hoc comparisons revealed that the volleyball and dance groups had better static balance compared to soccer players, while both soccer and volleyball groups had better dynamic balance compared to the dance group. The results from the study indicate two points： first, differences in balance performance among female athletes in different sporting discipline; second, there is no relationship between static and dynamic balance. This indicates that it may be more beneficial to assess and train for static and dynamic balance individually.

Local dynamic balance theory and technology of flow field in multilayer gob area

Flow field in multilayer gob area, which formed in small hiden-depth, multi-coal layer groups, close distance, hard coal layer, and hard roof, possesses characteristics such as complex, changeable and unstable. Dynamic balance theory of local flow field in multilayer gob area was built based on the realistic requirement that the serious threat on current mining coal layer by large-scale spontaneous combustion fire on close spontaneous combustion coal layer group of Datong Coal mining area at the ＇di-hard＇ conditions was caused by small coal pit mining. The kernel was in dynamic balance between flow field pressures of working face and local flow field in multilayer gob area was kept by transformation. Corresponding technology and set of devices were developed.

Research on New Testing Method and Instrument of Clothing Pressure

This paper discusses the formation of the fabric clothingpressure,the efforts of the human body and the impor-tance of the clothing pressure measurement.Several as-pects such as setting up the scientific and simple measur-ing method of the clothing pressure,the designing andmaking the measuring instruments are emphasized.Bymeans of experimental testing and analysis,some usefulresults can be derived from these works.

Experimental investigation of thermal transfer coefficient by a simplified energy balance of fault arc in a closed air vessel

The themial transfer coefficient that represents the portion of energy heating the surrounding gas of fault arc is a key parameter in evaluating the pressure effects due to fault arcing in a closed electrical installation.This paper presents experimental research on the thermal transfer coefficient in a closed air vessel for Cu,Fe and A1 electrode materials over a currcni range from 1-20 kA with an electrode gap from 10-50 mm and gas pressure from 0.05-0.4 MPa.With a simplified energy balance including Joule heating,arc radiation,ihc energies related to electrode melting,vaporization and oxidation constructed,and the influences of different factors on thermal transfer coefficient are studied and evaluated.This quantitative estimation of the energy components confirmed that the pressure rise is closely related to the change in heat transport process of fault arc.particularly in consideration of the evaluation of Joule healing and radiation.Factors such as the electrode material,arc current,filling pressure and gap length between electrodes have a considerable effect on the thermal transfer coefficient and thus,the pressure rise due to the differences in the energy balance of fault arc.