Direct-push multilevel sampling system for unconsolidated aquifers

A Direct Power Feeding System for AC Railway Networks Using Modular Multilevel Converter

Abstract Traditional railway power supply systems impose substantial power quality problems (PQ) on the utility network, such as unbalance, harmonics and a large amount of reactive power. This paper proposes a topology based on three-phase to single-phase modular multilevel converters (MMC) to obviate these problems. The MMC based traction substations (TSS) are connected directly to the utili...

NMR Logging to Estimate Hydraulic Conductivity in Unconsolidated Aquifers.

Nuclear magnetic resonance (NMR) logging provides a new means of estimating the hydraulic conductivity (K) of unconsolidated aquifers. The estimation of K from the measured NMR parameters can be performed using the Schlumberger-Doll Research (SDR) equation, which is based on the Kozeny-Carman equation and initially developed for obtaining permeability from NMR logging in petroleum reservoirs. T...

Direct Push

24-sector direct torque control for multilevel drives

this paper gives a detailed analysis of direct torque control (dtc) strategy in a five-level drive and proposes a 24-sector switching table. the overvoltage problem due to high dv/dt is reduced compared to the 12-sector dtc. using all vectors leads to better flexibility and reduces speed oscillations. simulation and experimental results for a 3kva prototype confirm the proposed solutions. a tms...

Hydraulic conductivity profiling with direct push methods

Spatial variations in hydraulic conductivity (K) are a primary control on contaminant movement in groundwater, but characterization of these variations has proven difficult. Over the last two decades, significant progress has been made in utilizing Direct Push (DP) technology to characterize K variations in unconsolidated settings. Profiling methods have been developed based on empirical correl...