| 1. |
- Singh, Vijay Kumar, et al.
(författare)
-
Novel Genetic Algorithm (GA) based hybrid machine learning-pedotransfer Function (ML-PTF) for prediction of spatial pattern of saturated hydraulic conductivity
- 2022
-
Ingår i: Engineering Applications of Computational Fluid Mechanics. - : Taylor & Francis. - 1994-2060 .- 1997-003X. ; 16:1, s. 1082-1099
-
Tidskriftsartikel (refereegranskat)abstract
- Saturated hydraulic conductivity (Ks) is an important soil characteristic that controls water moves through the soil. On the other hand, its measurement is difficult, time-consuming, and expensive; hence Pedotransfer Functions (PTFs) are commonly used for its estimation. Despite significant development over the years, the PTFs showed poor performance in predicting Ks. Using Genetic Algorithm (GA), two hybrid Machine Learning based PTFs (ML-PTF), i.e. a combination of GA with Multilayer Perceptron (MLP-GA) and Support Vector Machine (SVM-GA), were proposed in this study. We compared the performances of four machine learning algorithms for different sets of predictors. The predictor combination containing sand, clay, Field Capacity, and Wilting Point showed the highest accuracy for all the ML-PTFs. Among the ML-PTFs, the SVM-GA algorithm outperformed the rest of the PTFs. It was noticed that the SVM-GA PTF demonstrated higher efficiency than the MLP-GA algorithm. The reference model for hydraulic conductivity prediction was selected as the SVM-GA PTF paired with the K-5 predictor variables. The proposed PTFs were compared with 160 models from past literature. It was found that the algorithms advocated were an improvement over these PTFs. The current model would help in efficient spatio-temporal measurement of hydraulic conductivity using pre-available databases.
|
|
| 2. |
- Kalkal, Ashish, et al.
(författare)
-
Recent advances in 3D printing technologies for wearable (bio)sensors
- 2021
-
Ingår i: Additive Manufacturing. - : ELSEVIER. - 2214-8604 .- 2214-7810. ; 46
-
Forskningsöversikt (refereegranskat)abstract
- Wearable (bio)sensors driven through emerging three-dimensional (3D) printing technologies are currently considered the next-generation tools for various healthcare applications due to their exciting characteristics such as high stretchability, super flexibility, low cost, ultra-thinness, and lightweight. In this context, 3D printing, an emerging advanced additive manufacturing technology has revolutionized the concept of free form construction and end-user customization owing to its multifarious peculiarities that involve ease of operation, on-demand and rapid fabrication, precise and controlled deposition, as well as versatility with various soft functional materials. The customized functional structures with controllable geometry and design can be autonomously printed on the desired surfaces using the 3D printing technologies excluding the prerequisite amenities of microfabrication technologies. To accomplish this, both academics and industry experts have worked persistently to fabricate smaller, faster, and more efficient wearable devices using readily available 3D printing technologies. The contribution of 3D printing technologies in developing novel 3D structures for wearable applications using printable soft and functional materials is highlighted in this article. Moreover, the process of 3D printing along with major techniques, namely vat photopolymerization, material jetting, and material extrusion are summarized. Besides this, a number of 3D printed (bio)sensing platforms such as glucose sensors, lactate sensors, sweat sensors, strain sensors, tactile sensors, wearable oximeters, smart bandages, artificial skin, tattoo sensors, electroencephalography (EEG), electrocardiography (ECG) sensors, etc., are discussed in terms of design specifications and fabrication strategies of devices obtained via 3D printing techniques.
|
|
| 3. |
- Ganvir, Ashish, 1991-, et al.
(författare)
-
Effect of suspension characteristics on the performance of thermal barrier coatings deposited by suspension plasma spray
- 2020
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:1, s. 272-283
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the influence of suspension characteristics on microstructure and performance of suspensions plasma sprayed (SPS) thermal barrier coatings (TBCs). Five suspensions were produced using various suspension characteristics, namely, type of solvent and solid load content, and the resultant suspensions were utilized to deposit five different TBCs under identical processing conditions. The produced TBCs were evaluated for their performance i.e. thermal conductivity, thermal cyclic fatigue (TCF) and thermal shock (TS) lifetime. This experimental study revealed that the differences in the microstructure of SPS TBCs produced using varied suspensions resulted in a wide-ranging overall TBC performance. All TBCs exhibited thermal conductivity lower than 1 W/(m. K) except water-ethanol mixed suspension produced TBC. The TS lifetime was also affected to a large extent where 10 wt % solid loaded ethanol and 25 wt % solid loaded water suspensions produced TBCs exhibited the highest and the lowest lifetime, respectively. On the contrary, TCF lifetime was not as significantly affected as thermal conductivity and TS lifetime, and all ethanol suspensions showed marginally better TCF lifetime than water and ethanol-water mixed suspensions deposited TBCs. © 2020
|
|
| 4. |
- Kumar, Ravinder, et al.
(författare)
-
A Surface Modification Approach to Overcome Wetting Behavior of Gallium-Based Liquid Metal Droplets
- 2022
-
Ingår i: IEEE Transactions on Nanotechnology. - 1941-0085 .- 1536-125X. ; 21, s. 158-162
-
Tidskriftsartikel (refereegranskat)abstract
- Gallium based eutectic alloys are one of the promising substitutes for mercury. These alloys are nontoxic and environment friendly and have similar or equivalent properties as that of mercury. These alloys exhibit good electrical and thermal properties. However, these alloys form oxides when in contact with oxygen atoms. Due to this, the material surface tension changes, which renders them unsuitable for those applications where the mobility of the fluid is a valuable factor, such as in thermometers and blood pressure monitoring devices. There are few methods reported to remove the oxide layer from the surface of the gallium-based alloys, like acid and base treatment prior to use, but all these methods are not durable and long-lasting. Here in this work, we report gallium oxide coating as a simple approach to convert mercury manometer glass tube, which has glass as a substrate to a nonwetting surface against surface-oxidized gallium-based liquid metal alloys. These alloys form an oxidized layer in ambient air (O-2 >1 ppm) and show stickiness to almost all surfaces that impact the residue-free movement of the liquid metal droplets. Herein, the physical vapor deposition technique was used for gallium oxide coating on substrates such as silicon wafer and glass slide. Moreover, various characterizations were carried out to support our outcomes. This method does not require any micro/nano machining or specific nanoscale surface topology. The contact angle was measured with or without coated gallium oxide film on the glass substrate, and the static contact angle (c.a.) 137.69 degrees and with bared glass 94.30 degrees.
|
|
| 5. |
- Jain, Prakhar, et al.
(författare)
-
Comparative study of knee joint torque estimations for linear and rotary actuators using bond graph approach for stand–sit–stand motions
- 2020
-
Ingår i: International Journal of Advanced Robotic Systems. - London : Sage Publications. - 1729-8806 .- 1729-8814. ; 17:5, s. 1-13
-
Tidskriftsartikel (refereegranskat)abstract
- Stand–sit–stand (STS) motions are the most frequently performed activities of everyday life and require extensive movement of knee joint. People suffering from knee joint disorders face difficulties in performing this motion. The compact knee exoskeleton (KE) has proven to be a viable, less complex, and cheaper alternative to the available entire lower-, upper-, and full-body exoskeletons. With growing number of technical glitches and finite battery life problems, there exist risks of sudden failure of the actuator of KE that could be detrimental for the vulnerable users. To overcome this problem, there is a need to accommodate a backup actuator in KE which can continue providing assistance during movement if the primary actuator ceases to function. This article provides a performance comparison of a four-bar mechanism-driven KE that can accommodate both the linear and the rotary actuators. The modelling and simulation of the system are performed using the bond graph (BG) technique. The results successfully showed that both actuators offered desired ranges of motions needed for STS motion. Furthermore, the knee joint torques developed by the linear and rotary actuators were found to be 40 Nm and 57 Nm, respectively, which corresponds to 60% and 85% of the total torque required by the knee joint to perform STS motions, thereby reducing the user effort to 40% and 15%, respectively. Thus, both actuators are self-capable to provide necessary assistance at the knee joint even if the primary actuator ceases to work due to a sudden fault, the secondary actuator will provide the required rotation of the thigh link and will continue to deliver the assistive torque. The article also effectively shows the application of BG approach to model the multidisciplinary systems like KE as it conveniently models the system containing various elements in different energy domains.
|
|
| 6. |
- Jain, Prakhar, et al.
(författare)
-
Linear actuator–based knee exoskeleton for stand–sit–stand motions: a bond graph approach
- 2022
-
Ingår i: Simulation (San Diego, Calif.). - : Sage. - 0037-5497 .- 1741-3133. ; 98:8, s. 627-644
-
Tidskriftsartikel (refereegranskat)abstract
- People with knee disorders often find it difficult to perform common mobility tasks, such as stand–sit–stand motions. High knee torque is required to complete such transitions, as the chances of toppling increase during these motions. Most of the existing conventional approaches, such as wheelchairs and crutches, have failed to provide complete independence to the users. Conversely, contemporary systems like lower body exoskeletons which are bulky, complex, and expensive do not specifically target the knee joint instead of assisting other joints. Hence, there is a need to aid the knee joint using a robotic knee exoskeleton capable of accurately providing the desired knee torque. In the present work, to assist the user in performing the stand–sit–stand motions, an electromyography sensor-based four-bar knee exoskeleton actuated by a linear actuator is proposed. The modeling of the complete exoskeleton is developed using bond graph technique, as the components exist in different energy domains and it is possible to frame a dynamic bond graph model using only kinematic equations. The prototype is fabricated, and experiments are carried out on an artificial limb to prove the efficacy of the design of the current knee exoskeleton. The assistive torque developed by the actuator at the knee joint of the exoskeleton is found to be suitable to assist the wearer. As a result, little effort is required by the wearer for performing the stand–sit–stand motions. The rotation of the thigh link of the developed exoskeleton was found to be suitable for performing the stand–sit–stand activity.
|
|
| 7. |
- Raudvere, Tarvo, et al.
(författare)
-
The ForSyDe semantics
- 2002
-
Ingår i: Proceedings of Swedish System-on-Chip Conference.
-
Konferensbidrag (refereegranskat)
|
|
| 8. |
|
|
| 9. |
- Ganvir, Ashish, 1991-
(författare)
-
Design of Suspension Plasma Sprayed Thermal Barrier Coatings
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermal barrier coatings (TBCs) are widely used on gas turbine components to provide thermal insulation, which in combination with advanced cooling, can enable the gas turbine to operate at significantly higher temperatures even above the melting temperature of the metallic components. There is a permanent need,mainly due to environmental reasons, to increase the combustion temperature inturbines, hence new TBC solutions are needed. By using a liquid feedstock in thermal spraying, new types of TBCs can be produced. Suspension plasma/flame or solution precursor plasma spraying are examples of techniques that can be utilized for liquid feedstock thermal spraying. This approach of using suspension and solution feedstock, which is an alternative to the conventional solid powder feedstock spraying, is gaining increasing research interest since it has been shown to be capable of producing coatings withsuperior performance. The objective of this research work was to identify relationships between process parameters, coating microstructure, thermal conductivity and lifetime in suspension plasma sprayed TBCs. A further objective was to utilize these relationships to enable tailoring of the TBC microstructure for superior performance compared to state-of-the-art TBC used in industry today, i.e. solid feedstock plasma sprayed TBCs. Different spraying techniques, namely suspension high velocity oxy fuel, solution precursor plasma and suspension plasma spraying (with axial and radial feeding) were explored and compared to solid feedstock plasma spraying. A variety of microstructures, such as highly porous, vertically cracked and columnar, were produced and investigated. It was shown that there are strong relationships between microstructure, thermo-mechanical properties and performance of the coatings. Specifically, axial suspension plasma spraying wasshown as a very promising technique to produce various microstructures as wellas highly durable coatings. Based on the experimental results, a tailored columnar microstructure design for a superior TBC performance is also proposed.
|
|
| 10. |
- Ganvir, Ashish, 1991-, et al.
(författare)
-
Failure analysis of thermally cycled columnar thermal barrier coatings produced by high-velocity-air fuel and axial-suspension-plasma spraying : A design perspective
- 2018
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 44:3, s. 3161-3172
-
Tidskriftsartikel (refereegranskat)abstract
- Axial-suspension-plasma spraying (ASPS) is a fairly recent thermal spray technology which enables production of ceramic top coats in TBCs, incorporating simultaneously the properties of both the conventional-plasma sprayed (highly insulating porous structures) and electron-beam-physical-vapor-deposited (strain-tolerant columnar structures) top coats. TBCs are required to insulate the hot components in a gas turbine engine against high temperature and harsh operating conditions. Periodic heating and cooling of turbine engines during operation can create severe thermal cyclic fatigue conditions which can degrade the performance of these coatings eventually leading to the failure. An in-depth experimental investigation was performed to understand the failure behavior of columnar TBCs subjected to thermal cyclic fatigue (TCF) test at 1100 C. The study revealed that the TCF performance was influenced to an extent, by the top coat microstructure, but was primarily affected by the severity of thermally grown oxide (TGO) growth at the bond coat-top coat interface. Mixed failure modes comprising crack propagation through the bond coat-TGO interface, through TGO and within the top coat were identified. Based on the analysis of the experimental results and thorough discussion a novel design of microstructure for the high TCF performance columnar TBC is proposed. © 2017 Elsevier Ltd and Techna Group S.r.l.
|
|
