Showing papers by "Simon S. Park published in 2019"

High-Performance, Room Temperature Hydrogen Sensing With a Cu-BTC/Polyaniline Nanocomposite Film on a Quartz Crystal Microbalance

Abstract: In this paper, we demonstrate a high-performance hydrogen sensor under ambient conditions by growing a Cu-BTC/polyaniline (PANI) nanocomposite film on a quartz crystal microbalance (QCM) using intense pulsed light. The QCM was first sputter coated with a 200-nm-thin layer of copper. The copper layer was then oxidized by sodium hydroxide and ammonium persulfate. A solution containing the organic ligand (BTC) and PANI was then dropped and dried on the copper hydroxide surface of a QCM with intense pulsed light which resulted in Cu-BTC/PANI nanocomposite film on a QCM. The gas sensing performance of the Cu-BTC film and Cu-BTC/PANI composite film was compared under ambient conditions. It was found selectivity and sensitivity of the Cu-BTC/PANI nanocomposite film to hydrogen were significantly improved. In addition, a fast response time (from 2 to 5 s), operation at room temperature even in the presence of high relative humidity (up to 60%), good repeatability were achieved with the Cu-BTC/PANI nanocomposite film-grown QCM sensor.

Low power direct laser-assisted machining of carbon fibre-reinforced polymer

Abstract: The direct laser-assisted machining (DLAM) technique is introduced to improve the CFRP machining process. The DLAM technique applies focused laser at the tool edge through a sapphire tool. A fibre laser with 4.3 W power was used to have the desired temperature, estimated from the finite element model. Experimental orthogonal cutting tests were performed to compare the DLAM technique to the conventional dry cutting of the woven CFRP. We have observed reduced cutting forces in both in-plane and side cutting orientations. Observations with 3D surface profilometer also showed a decrease in defects and improved surface roughness when DLAM was applied.

Intense Pulsed Light Conversion of Anatase to Rutile TiO 2 for Hybrid TiO 2 -SnO 2 /MWCNTs/PVB Room Temperature VOCs Sensor

Abstract: Volatile organic compounds (VOCs) are toxic air pollutants that require cost effective and accurate sensors for environmental monitoring. A VOCs sensing device was fabricated by spin coating low quantities of TiO2-SnO2 loaded multi-walled carbon nanotubes (MWCNTs) with a polyvinyl butyral (PVB) support matrix onto a quartz crystal microbalance (QCM). TiO2 was partially converted from anatase to rutile phase using rapid microwave and the intense pulsed light (IPL) techniques. Microwave facilitated the drying of the solution and crystal growth while IPL enabled the conversion of TiO2 from anatase to rutile. The sensing properties were investigated with different VOCs, including ethanol, methanol, isopropanol, and toluene, at different concentrations. The anatase and rutile hybrid TiO2-SnO2/MWCNTs/PVB sensing composite film showed an average of 8.8 times higher responses to VOCs compared with pure anatase TiO2-SnO2/MWCNTs/PVB composite film prepared without IPL. The hybrid sensors exhibited negative motional resistance responses to VOCs and positive motional resistance responses to non-VOCs. The hybrid nanocomposite film also showed good stability at room temperature and the highest response towards ethanol with a limit of detection of 1 ppm.

Intelligent Wellbore Path Estimation Using Multiple Integrated MEMS Sensors

Abstract: To improve magnetic disturbance rejection and robustness of wellbore survey measurements, an adaptive neuro network-based fuzzy inference system (ANFIS) filter for wellbore position calculation is presented. This technique significantly improves magnetic disturbance rejection and reduces sensor error influence for borehole survey measurements. The new approach for the ANFIS filter is based on two redundant sets of IMUs which are located in different positions in the BHA at a known, constant distance. The distance between these two sets of IMUs will physically fade the effect of the magnetic disturbances. Each IMU set outputs position estimation based on the splines method which is then input into an ANFIS filter. The inputs of the splines calculation are azimuth, inclination angles and measurement depth, and the outputs are moving distance in three directions (Northing, Easting and True Vertical Depth). However, the accuracy of the splines method highly depends on the accuracy of the inputs, which are difficult to obtain during the measurement while drilling process even under pure clean environments (without any magnetic disturbances). Furthermore, the distorted azimuth caused by magnetic interference affects the borehole position accuracy. In order to deal with those problems, the designed ANFIS filter has a two-level structure. First a local level position estimation (splines method or well trained local ANFIS based on the sensor accuracy) for two sensor sets is used. If the sensor measurement accuracy is low, this local ANFIS will correct the position estimation. Then the outputs of the local modules were input into ANFIS for second level filtering (global filter) to remove the error which caused by unknown magnetic disturbances. According to the judgement of the ANFIS, the IMU set with the smaller magnetic disturbance is given greater weight to reduce the interference effect on the borehole position estimation. This two-level filter is compared to the traditional splines method under different tests situations. First, we evaluate this method by comparing with GPS positioning, from this test we know that the ANFIS filter shows a good performance when the magnitude of magnetic disturbance is within the training magnitude range. Even when the magnitude of magnetic disturbance is above the training range, the ANFIS filter shows a higher robustness than the traditional splines method. Also, this method was applied to borehole data with two IMU containing accelerometers and one magnetometer measurements. In order to apply our method, we duplicated one more magnetometer measurement data under magnetic interference for assessment. The results proved its magnetic disturbance robustness in borehole position estimation. Finally, we demonstrate the full potential using a laboratory experimental setup.

Operational Modal Response Characterization of Pipeline Systems Through Reynolds Number Variation

Abstract: An operational modal response method for application to the structure health and integrity of pipelines is investigated. The modal response characteristics of externally supported pipe structures are quantified through flow Reynolds number (Red) variation. Pipe flow turbulence and the resulting hydrodynamic pressure fluctuations on the interior pipe wall provide the structural forcing mechanism, and signals from wall-mounted accelerometers provide the system response. During experiments, the Reynolds number is varied from 51,000 to 154,000. Over this Reynolds number range, the pipe flow turbulence was found sufficient enough to excite the structure at frequencies up to 400 Hz. Modal response characteristics obtained through Reynolds number variation were found to be in agreement with results from impact hammer modal testing. The in-situ modal response method developed was applied to two different structural health monitoring investigations, one involving loss-of-material and the other involving loss-of-fluid. The loss-of-material scenario simulated the process of external pipe wall corrosion, and the developed method was able to detect material loss as small as 1.4%. The loss-of-fluid scenario simulated a small leak. Despite the low operating pressure of 0.024 MPa, the methodology was able to detect fluid loss as low as 0.1% of the bulk flow rate. The developed method has the potential to offer in-situ continuous pipeline health monitoring that relies on the continuous changes (flow rate, product viscosity, product density) that are inherent to an operational pipeline system.

A Novel Tribometer Designed to Evaluate Geological Sliding Contacts Lubricated by Drilling Muds

Abstract: Great interest in improving lubricity, or reducing friction, of drilling muds used for horizontal oil well drilling is motivated by increasing the horizontal reach that can be attained by a single drilling site. However, there are a limited number of commercially available devices that can be used to evaluate novel drilling mud solutions under sliding conditions that accurately replicate those encountered in the field, and those that are available are often prohibitively expensive. Here, the design of a low-cost lubricity meter, or tribometer, is documented. The purpose-built tribometer is capable of varying rotating speeds, applied normal loads, temperature, and counter surface materials. In particular, the counter surface of the tribometer can be either a steel surface, as is often used in the industrial lubricity meters available in corporate laboratories, or a geological core specimen taken from the drill site. The novel instrument was then used to evaluate four commercially available water-based drilling fluid lubricant additives, dissolved in distilled water, for both a steel-on-steel contact and a steel-on-rock contact. The steel-on-steel contact shows that the tribometer replicates the results of tests typically conducted in drilling fluid labs, thus verifying the performance of the newly developed tribometer. Additional results show that the friction and performance of the lubricant depend significantly on the materials used: steel-on-steel contacts show much lower friction than steel-on-sandstone contact. Finally, a weak dependence on the applied load is shown for a number of lubricant additives examined.

Near field electrospinning of nanowires for multi-modal hydrogen sensing

Abstract: Hydrogen gas is a common byproduct in industrial and chemical processes. It is also frequently used in transportation applications such as fuel cell vehicles. It has no smell and no taste, but it may pose immediate safety risks because it is combustible in air. Multi-modal hydrogen sensors are developed by depositing nanofibers on quartz tuning forks (QTF). Near field electrospinning (NFES) was used to produce flexible, semi-conductive nanofibers that can be integrated into electronic systems as environmental gas sensors. The electrospinning parameters, especially tip-to-collector distance, were optimized to increase sensor performance. Treated multi-walled carbon nanotubes, camphorsulfonic acid doped polyaniline and platinum nanoparticles were used as the sensing materials with polyethylene oxide being used as an electrospinning guide. Intense pulsed light and sputter coating were used to maximize adhesion of the fibers onto the devices. The QTF sensor combines mechanical and electrochemical sensing methodologies. Changes in the resonance frequency were used to determine gas adsorption. Changes in the electrical resistance were used to determine the gas properties. As a result, the sensors were selective to hydrogen versus other gases and vapors including methane, hexane, toluene, ammonia, ethanol and carbon dioxide. Furthermore, the sensors can detect ppm levels of hydrogen even in the presence of high humidity.