Application of High Density Resistivity Method in Karst Exploration: A Case Study

During engineering and construction activities, water and mud burst, house and ground collapse, as well as other hazards often occur in places where karst develops, which can seriously threaten the safety of people\u27s life and property and limit the development of local society and economy. Therefore, it is a meaningful work to figure out the locations of karst development so that corresponding prevention measures could be taken in advance. In this study, a case was introduced by using high density resistivity method to study the karst ground collapse. The geological characteristics, distribution law and control factors of karst ground collapse were clarified through high density resistivity method. Based on the results, the development trend was predicted, and the corresponding treatment measures and suggestions were proposed. The results show that 2 karst developing belts and 3 karst seriously-developed centers were delineated in the study region, which indicates that the high density resistivity method can effectively identify abnormal underground areas in the study region. The results shown in this research would provide the whole site for future drilling and the useful experience for underground karst exploration in similar areas

Effect of doubly fed induction generatortidal current turbines on stability of a distribution grid under unbalanced voltage conditions

This paper analyses the effects of doubly fed induction generator (DFIG) tidal current turbines on a distribution grid under unbalanced voltage conditions of the grid. A dynamic model of an electrical power system under the unbalanced network is described in the paper, aiming to compare the system performance when connected with and without DFIG at the same location in a distribution grid. Extensive simulations of investigating the effect of DFIG tidal current turbine on stability of the distribution grid are performed, taking into account factors such as the power rating, the connection distance of the turbine and the grid voltage dip. The dynamic responses of the distribution system are examined, especially its ability to ride through fault events under unbalanced grid voltage conditions. The research has shown that DFIG tidal current turbines can provide a good damping performance and that modern DFIG tidal current power plants, equipped with power electronics and low-voltage ride-through capability, can stay connected to weak electrical grids even under the unbalanced voltage conditions, whilst not reducing system stability

Sensorless Control of Dual Three-Phase IPMSM Based on Frequency Adaptive Linear Extended State Observer

The sensorless control of interior permanent magnet synchronous motor (IPMSM) based on the conventional linear extended state observer (LESO) does not have sufficient capability to eliminate the steady-state position estimation error. To solve this issue, a frequency adaptive LESO (FA-LESO) is proposed to estimate the back electromotive force (BEMF) accurately. The gains of the proposed observer are designed according to the pre-designed transfer function of a second-order complex-coefficient filter, whose stability is guaranteed by the generalized Routh criterion. The linearized model of the proposed FA-LESO is established and the design guideline of the observer gains is presented. Compared with the conventional LESO, the proposed FA-LESO can eliminate the steady-state position estimation error without any phase compensation. Meanwhile, it exhibits better high-frequency noise immunity without additional filters being required. The feasibility and effectiveness of the proposed FA-LESO are verified by the comparative experiments on a dual three-phase IPMSM platform

Compound Option Pricing under Fuzzy Environment

Considering the uncertainty of a financial market includes two aspects: risk and vagueness; in this paper, fuzzy sets theory is applied to model the imprecise input parameters (interest rate and volatility). We present the fuzzy price of compound option by fuzzing the interest and volatility in Geske’s compound option pricing formula. For each α, the α-level set of fuzzy prices is obtained according to the fuzzy arithmetics and the definition of fuzzy-valued function. We apply a defuzzification method based on crisp possibilistic mean values of the fuzzy interest rate and fuzzy volatility to obtain the crisp possibilistic mean value of compound option price. Finally, we present a numerical analysis to illustrate the compound option pricing under fuzzy environment

Torque Enhancement of Dual Three-Phase PMSM by Harmonic Injection

The torque enhancement of dual three-phase permanent magnet synchronous machine (DT-PMSM) drive system by full exploitation of flux-linkage and current harmonics are comparatively studied in this paper. The torque capability of DT-PMSM is previously evaluated with strategies of harmonics utilization, i.e. Strategy-1 of 3rd harmonic utilization and Strategy-2 of 5th and 7th harmonic utilization, which can extend the torque capability by 18.2% and 9.0% respectively. However, the full exploitation of harmonics including 3rd, 5th and 7th harmonics in the dual three-phase system are not addressed. In this paper, the Strategy-3 of 3rd, 5th and 7th harmonic utilization is also included. Its corresponding harmonic current control is proposed and the average torque and harmonic torque are analyzed in detail. Based on a test rig with existing prototype DT-PMSM, the torque with Strategy-3 is increased up to 26.5%, which is superior to the previous strategies

Flux-Weakening Control of Dual Three-Phase PMSM Based on Vector Space Decomposition Control

This paper proposes a flux-weakening (FW) control for dual three-phase ermanent magnet synchronous machine (DT-PMSM) based on vector space decomposition (VSD) control, where the output voltage in αβ sub-plane is employed for voltage feedback in the flux-weakening control loop. As the fundamental components are mapped to αβ sub-plane while the 5th and 7th harmonics are projected to harmonic z1z2 sub-plane, the flux-weakening current from this new control in αβ sub-plane is sixth harmonic-free regardless of the 5th and 7th harmonics being resulted from the non-sinusoidal back EMF or inverter non-linearity. The proposed control is compared with the conventional FW feedback control extended for DT-PMSM, where the FW control is applied to the two sets of three-phase windings separately. The experimental results show that the proposed FW control based on VSD is superior to the conventional FW control in terms of reduction in current unbalance and harmonic currents

3,6-Didehydro-5-hy­droxy-1,2-O-iso­propyl­idene-5-C-nitro­meth­yl-α-d-gluco­furan­ose

The title compound, C10H15NO7, consists of one methyl­enedi­oxy ring and two fused tetra­hydro­furan rings. The three fused rings exhibit cis arrangements at the ring junctions. One O atom of a tetra­hydro­furan ring and the H atoms bound to the neighboring C atoms are disordered over two orientations with site-occupancy factors of 0.69 (1) and 0.31 (1). intra­molecular O—H⋯O and C—H⋯O inter­actions stabilize the mol­ecular conformation. In the crystal structure, inter­molecular O—H⋯O and C—H⋯O inter­actions link the mol­ecules into a three-dimensional network

Molecular Epidemiology and Risk Factors of Ventilator-Associated Pneumonia Infection Caused by Carbapenem-Resistant Enterobacteriaceae

Ventilator-associated pneumonia (VAP) infection caused by carbapenem-resistant Enterobacteriaceae (CRE) is becoming more prevalent, thus seriously affecting patient outcomes. In this paper, we studied the drug resistance mechanism and epidemiological characteristics of CRE, and analyzed the infection and prognosis factors of VAP caused by CRE, to provide evidence for effective control of nosocomial infection in patients with VAP. A total of 58 non-repetitive CRE strains of VAP were collected from January 2016 to June 2018. To explore the risk factors of CRE infection, 1:2 group case control method was used to select non CRE infection patients at the same period as the control group. Among the 58 CRE strains, the most common isolates included Klebsiella pneumoniae and Escherichia coli. All strains were sensitive to polymyxin B, which features better sensitivity to other antibiotics such as minocycline, trimethoprim/sulfamethoxazole, and amikacin. Multiple drug resistance genes were detected at the same time in most strains. KPC-2 was the most common carbapenemase-resistant gene in Klebsiella pneumoniae, whereas NDM-1 was more common in Escherichia coli. The risk factors correlated with CRE infection included intensive care unit (ICU) occupancy time >7 days (OR = 2.793; 95% CI 1.439~5.421), antibiotic exposure during hospital stay including those to enzyme inhibitors (OR = 1.977; 95% CI 1.025~3.812), carbapenems (OR = 3.268; 95% CI 1.671~6.392), antibiotic combination therapy(OR = 1.951; 95% CI 1.020~3.732), and nerve damage (OR = 3.013; 95% CI 1.278~7.101). Multivariable analysis showed that ICU stay >7 days (OR = 1.867; 95% CI 1.609~20.026), beta-lactamase inhibitor antibiotics (OR = 7.750; 95% CI 2.219~27.071), and carbapenem (OR = 9.143; 95% CI 2.259~37.01) are independent risk factors for VAP carbapenem caused by Carbapenem-resistant Enterobacteriaceae. A high resistance rate of CRE isolated from VAP indicated that the infected patients featured higher mortality and longer hospital stay time than the control group. Multiple risk factors for CRE infection and their control can effectively prevent the spread of VAP

Design, Optimization and Numerical Modelling of A Novel Floating Pendulum Wave Energy Converter with Tide Adaptation

A novel floating pendulum wave energy converter (WEC) with the ability of tide adaptation is designed and presented in this paper. Aiming to a high efficiency, the buoy’s hydrodynamic shape is optimized by enumeration and comparison. Furthermore, in order to keep the buoy’s well-designed leading edge always facing the incoming wave straightly, a novel transmission mechanism is then adopted, which is called the tidal adaptation mechanism in this paper. Time domain numerical models of a floating pendulum WEC with or without tide adaptation mechanism are built to compare their performance on various water levels. When comparing these two WECs in terms of their average output based on the linear passive control strategy, the output power of WEC with the tide adaptation mechanism is much steadier with the change of the water level and always larger than that without the tide adaptation mechanism