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.

OPTIMUM OF PRESSURE RATIOS OF MULTI-STAGE RECIPROCATING COMPRESSOR WITH PRACTICAL INTER-COOLING

The optimum pressure ratio distribution of a multistage reciprocating compressor is presented based on the assumption, i.e. the inter stage cooling is perfect and there are no pressure losses. The optimization of the two or three stage pressure ratio is analyzed in two cases of constant heat transfer rate for the inter cooler or constant inter stage inlet temperature, based on the minimum of the sum of theoretical compression power at each stage about a multi stage reciprocating compressor. Furthermore, with an example of two stage compressor the influence on the sum of the power of each stage is analyzed when practical pressure ratio deviates from the optimum value. It is obtained that under different cooling conditions the optimum pressure ratio distribution of the multi stage compression is various, and the change of the optimum pressure ratio within a small range has little influence on the sum of the power each stage. For the two stage compression, this range can be represented as ε 1=(0 96～1 06)ε 1j .

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.

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.

Computation of compressible flows with high density ratio and pressure ratio

The WENO method, RKDG method, RKDG method with original ghost fluid method, and RKDG method with modified ghost fluid method are applied to singlemedium and two-medium air-air, air-liquid compressible flows with high density and pressure ratios： We also provide a numerical comparison and analysis for the above methods. Numerical results show that, compared with the other methods, the RKDG method with modified ghost fluid method can obtain high resolution results and the correct position of the shock, and the computed solutions are converged to the physical solutions as themesh is refined.

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.

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.

Relationship between the Current Account Balance Ratio and Salary Ratio in Japanese Municipal Hospitals

Background: While public municipal hospitals in Japan are supported by public financing and are less likely to fail than private hospitals, more than half are in financial deficit. Hospitals running at a deficit may have poorer outcomes and less investment in maintenance of human or physical capital, as well as increased rates of patient adverse events. We sought to clarify the relationship between municipal hospital surpluses or deficits and salary expenditures. Methods: We extracted financial data for 253 general hospitals of 300 beds or more from financial statements for the 2013 fiscal year available in the Yearbook of Public Firms, Edition for Hospital. From these data, we calculated account balance ratios and compared the average value of the ratio of labor to the output (salary ratio) for each group using analysis of variance (ANOVA). Results: The salary ratios of hospitals in the surplus group were significantly lower than the salary ratios of hospitals in the deficit group (55.5% vs. 49.4%;p p = 0.342). In the surplus group, the average value of salary ratios was different among the three-bed count groups (mean salary ratio: 53.0% vs. 48.5% vs. 47.4%;ANOVA p = 0.012). In addition, there was a significant difference in mean value between the 300-bed group and ≥500 beds group (mean salary ratio: 53.0% vs. 47.4%;p = 0.002). Conclusion: This study suggests that maintaining a favorable salary ratio to the current account balance is a useful proxy of fiscal health, and interventions to improve the salary ratio may be effective in improving municipal hospital management. Furthermore, among well-managed municipal hospitals, larger hospital size may confer some advantage in purchasing power.

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.

Study on the Micrometeorological Characteristics and Energy Balance of Winter Wheat Canopy

[Objective] The micrometeorology features and energy balance of winter wheat canopy were studied.[Method] By means of micrometeorological data of winter wheat canopy at booting stage,heading and flowering stage,filling stage and mature stage and the data from local meteorological station,the temporal and spatial variation law of micrometeorology features of winter wheat canopy were researched,and the daily and seasonal variation of energy balance were further analyzed.[Result] The daily variation of winter wheat canopy temperature and air temperature showed sinusoidal trend,and air temperature changed with height,while temperature was highest at heading and flowering stage.The daily variation of humidity also showed sinusoidal trend,and humidity was highest and saturation deficit was lowest in the middle of canopy,while the maximum humidity appeared at heading and flowering stage.In addition,the daily variation of wind speed in the upper canopy showed single peak trend.There was obvious daily variation and seasonal variation of energy balance in winter wheat field,and the daily variation of net radiation also showed single peak trend,while sensible heat flux was highest at filling stage and lowest at heading and flowering stage,and latent heat flux was highest at heading and flowering stage and lowest at booting stage.[Conclusion] Our study could provide scientific evidence for the study of disaster prevention and mitigation and the improvement of yield and quality of winter wheat.

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.

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.

China＇s Sovereign Balance Sheet and Its Risk Assessment

Using available data and necessary estimations, this paper provides a tentative picture of the balance sheet of China＇s sovereign account between 2000 and 2010. The main findings indicate that the net worth of China＇s sovereign assets had been positive and increasing during the period under review. This implies that the Chinese government has sufficient sovereign assets to cover its sovereign liabilities, therefore the likelihood of a sovereign debt crisis in China is extremely low in the near term. Moreover, although China＇s leverage ratio （total liabilities/GDP） is far lower compared to advanced economies, it seems higher than that of other major emerging economies such as Brazil, Russia, and India （BRIC）. In fact, the leverage ratio has been increasing rapidly over recent years and requires special attention. In particular, according to sector-specific analysis, high corporate liability ratios （percentage to GDP） constitute a major concern of China＇s national balance sheet. In 2010, this liability ratio exceeded l OO percent, which exceeds the 90 percent level observed in OECD countries. Lastly, this paper concludes that a sustainable economic growth and structural transformation of growth model are the fundamental means to taming China＇s balance sheet risks.

An investigation on changes in glacier mass balance and hypsometry for a small mountainous glacier in the northeastern Tibetan Plateau

Mass balance is a key indicator of the sensitivity of glaciers to climate change. Field measurement is one of the most important ways to study the mass balance of glaciers. Based on observations of mass balance in the ablation zone of Shuiguan Glacier No.4, Qilian Mountains, China, combined with the balance ratio between accumulation and ablation, we established a linear relation between mass balance and altitude. The results show that the mean annual mass balance of this glacier was ~510 mm w.e. from 2010 to 2013. The uncertainty in the balance ratio value does not lead to a significant difference in the mass balance. The equilibrium-line altitude rose by 180 m from 1972 to 2013, while the accumulation–area ratio decreased from 0.68 to 0.25. These variations may be caused by changes in air temperature. Meanwhile, the glacier is at present not in a steady state, and it may continue to shrink by a further ~900 m, even without further climate warming. In the western Lenglongling Mountains, assuming that the glaciers are in a steady state and the Equilibrium-line altitudes(ELAs)remain similar, there will be only 46 glaciers left, covering a total area of 19.2 km^2, in other words, only 22.3% of the glaciers area in 1972.

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.

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.

Mineral Balance Plasticity of Cloudberry (<i>Rubus chamaemorus</i>) in Quebec-Labrador Bogs

The “ionome”, or plant elemental signature, is the elemental composition of an organisms, that may vary with genotypic traits and phenotypic plasticity. Cloudberry (Rubus chamaemorus L.) is a circumboreal wild berry naturally growing in oligotrophic oceanic bogs ofQuebecandLabrador. Our objective was to relate cloudberry stand productivity to the ionomes of female ramets and explore the cause of nutrient imbalance in low-performing stands. We analyzed 13 elements in female ramets collected in 86 natural sites where crop productivity varied widely. We computed orthogonally arranged balances reflecting plant stoichiometric rules and soil biogeochemistry. Balances were expressed as isometric log ratios (ilr) between ad hoc sub-compositions. Balances were synthesized into a Mahalanobis distance optimized based on receiving operating characteristics (ROC). The critical Mahalanobis distance was found to be 5.29 for cutoff berry yield of3.8 g.m-2 with test performance of 0.88, as measured by the area under the ROC curve. Although past research on cloudberry focused mainly on the N/P ratio, this exploratory mineral balance analysis indicated that imbalance in the [P,N | S,C] and [Al | Nutrients] partitions appeared to be the factors limiting the most cloudberry productivity in the bogs. Some highly productive stands showed relatively high C fixation and K use efficiency. Due to the complexity of interactions, diagnosis should be conducted computing first a global imbalance index (Mahalanobis distance), then examining in the balance domain binary partitions departing most from reference, and finally appreciating relative shortage, sufficiency or excess of elements in the concentration domain.