THE APPLICATION OF STRAIN-BASED DESIGN TO PIPELINES AND THE REQUIREMENTS ON PIPE MATERIALS

ABSTRACT With the sharply rising demand of oil and gas, the pipeline industry has been experiencing a rapid development in recent years. Pipelines in the areas of ground movement from slope instability, seismic sideslip, loess collapse, mining subsidence, frost heave and thaw settlement in discontinuous permafrost can experience displacement-controlled plastic strain. The current paper describes the application of strain-based design of pipelines and introduces relevant codes, standards, and criteria of other countries. Some major issues in strain-based design such as geologic conditions, strain limits, mechanical performance, etc., are mentioned. The prospect of strain-based design of pipelines is discussed with reference to the geologic conditions and the state of the pipeline industry. Finally the requirements on parameters of line pipe materials, including yield stress, yield and tensile strength ratio, stress ratio, weld mismatch, anisotropy etc., and their influence on strain-based design are discussed

Calculation of Admittance Capacity of Wind Farms under Harmonic Constraints

The harmonic voltage at the wind farm interconnection point does not exceed the harmonic distortion limits of all voltage levels stipulated by the national standard. The allowable value of the harmonic current injected into the power system shall be allocated in proportion to the total capacity and installed capacity of the harmonic source equipment. However, judging from the status quo of the implementation of harmonic national standard, there is still much controversy over this standard. One of the focal points of controversy is determining the limits of whether different types of harmonic sources should be treated differently. Based on the theoretical research, this paper selects the typical wind farm interconnection points and calculates the admittance capacity limits under different harmonic constraints of the wind farm based on the historical data and the level of harmonic planning, and analyzes the rationality of the calculation results

Calculation of Admittance Capacity of Wind Farms under Harmonic Constraints

The harmonic voltage at the wind farm interconnection point does not exceed the harmonic distortion limits of all voltage levels stipulated by the national standard. The allowable value of the harmonic current injected into the power system shall be allocated in proportion to the total capacity and installed capacity of the harmonic source equipment. However, judging from the status quo of the implementation of harmonic national standard, there is still much controversy over this standard. One of the focal points of controversy is determining the limits of whether different types of harmonic sources should be treated differently. Based on the theoretical research, this paper selects the typical wind farm interconnection points and calculates the admittance capacity limits under different harmonic constraints of the wind farm based on the historical data and the level of harmonic planning, and analyzes the rationality of the calculation results

Experimental Study on Dynamic Structure of Propeller Tip Vortex

Propeller cavitation is a main source of fluctuating pressure and noise induced by propellers, and the tip vortex cavitation is the principal source. The present study measures the flow fields near the blade tip using the 2D-PIV technique. The experimental setup and scheme are introduced. We monitor the process of generation and shedding of the propeller tip vortex in real time and analyse the dynamic structure of the tip vortex by testing the propeller wake field under different phases of the axial plane. The distribution characteristics of radial and axial velocity are also analysed. The influence range and the vorticity of the tip vortex and trailing vortex are obtained. All of the measured quantitative data are useful for future propeller design

Study of Hydrodynamic Interference of Vertical-Axis Tidal Turbine Array

The hydrodynamic interference between tidal turbines must be considered when predicting their overall hydrodynamic performance and optimizing the layout of the turbine array. These factors are of great significance to the development and application of tidal energy. In this paper, the phenomenon of hydrodynamic interference of the tidal turbine array is studied by the hydrodynamic performance forecast program based on an unsteady boundary element model for the vertical-axis turbine array. By changing the relative positions of two turbines in the double turbine array to simulate the arrangement of different turbines, the hydrodynamic interference law between the turbines in the array and the influence of relative positions on the hydrodynamic characteristics in the turbine array are explored. The manner in which the turbines impact each other, the degree of influence, and rules for turbine array arrangement for maximum efficiency of the array will be discussed. The results of this study will provide technical insights to relevant researchers

Experimental Study on Dynamic Structure of Propeller Tip Vortex

Propeller cavitation is a main source of fluctuating pressure and noise induced by propellers, and the tip vortex cavitation is the principal source. The present study measures the flow fields near the blade tip using the 2D-PIV technique. The experimental setup and scheme are introduced. We monitor the process of generation and shedding of the propeller tip vortex in real time and analyse the dynamic structure of the tip vortex by testing the propeller wake field under different phases of the axial plane. The distribution characteristics of radial and axial velocity are also analysed. The influence range and the vorticity of the tip vortex and trailing vortex are obtained. All of the measured quantitative data are useful for future propeller design

Study on Hydrodynamic Configuration Parameters of Vertical-Axis Tidal Turbine

In this paper, a numerical code for predicting the hydrodynamic performance of vertical-axis tidal turbine array is developed. The effect of the tip speed ratio, solidity, and preset angle on the hydrodynamic performance are discussed using a series of calculations. The load principle of the rotor and the variation principle of the turbine power coefficient are studied. All these results can be considered as a reference for the design of vertical-axis tidal turbines

Study on Hydrodynamic Configuration Parameters of Vertical-Axis Tidal Turbine

In this paper, a numerical code for predicting the hydrodynamic performance of vertical-axis tidal turbine array is developed. The effect of the tip speed ratio, solidity, and preset angle on the hydrodynamic performance are discussed using a series of calculations. The load principle of the rotor and the variation principle of the turbine power coefficient are studied. All these results can be considered as a reference for the design of vertical-axis tidal turbines

Differences in inpatient performance of public general hospitals following implementation of a points-counting payment based on diagnosis-related group: a robust multiple interrupted time series study in Wenzhou, China

Objectives This study measures the differences in inpatient performance after a points-counting payment policy based on diagnosis-related group (DRG) was implemented. The point value is dynamic; its change depends on the annual DRGs’ cost settlements and points of the current year, which are calculated at the beginning of the following year.Design A longitudinal study using a robust multiple interrupted time series model to evaluate service performance following policy implementation.Setting Twenty-two public general hospitals (8 tertiary institutions and 14 secondary institutions) in Wenzhou, China.Intervention The intervention was implemented in January 2020.Outcome measures The indicators were case mix index (CMI), cost per hospitalisation (CPH), average length of stay (ALOS), cost efficiency index (CEI) and time efficiency index (TEI). The study employed the means of these indicators.Results The impact of COVID-19, which reached Zhejiang Province at the end of January 2020, was temporary given rapid containment following strict control measures. After the intervention, except for the ALOS mean, the change-points for the other outcomes (p<0.05) in tertiary and secondary institutions were inconsistent. The CMI mean turned to uptrend in tertiary (p<0.01) and secondary (p<0.0001) institutions compared with before. Although the slope of the CPH mean did not change (p>0.05), the uptrend of the CEI mean in tertiary institutions alleviated (p<0.05) and further increased (p<0.05) in secondary institutions. The slopes of the ALOS and TEI mean in secondary institutions changed (p<0.05), but not in tertiary institutions (p>0.05).Conclusions This study showed a positive effect of the DRG policy in Wenzhou, even during COVID-19. The policy can motivate public general hospitals to improve their comprehensive capacity and mitigate discrepancies in treatment expenses efficiency for similar diseases. Policymakers are interested in whether the reform successfully motivates hospitals to strengthen their internal impetus and improve their performance, and this is supported by this study