Akhilesh Soni

Publications

1. 1. An Integer Programming Approach to Subspace Clustering with Missing Data

   Soni, Akhilesh, Linderoth, Jeff, Luedtke, Jim, and Pimentel-Alarcón, Daniel

   Informs Journal on Optimization, Accepted, Yet to appear, 2024
2. 2. PhD Dissertation: Discrete Optimization Methods for Scheduling and Matrix Completion

   Soni, Akhilesh

   The University of Wisconsin-Madison, 2023

   Abstract Paper

   The thesis consists of research in mixed integer linear programming with applications to scheduling and matrix completion.

3. 3. Mixed-integer linear programming for scheduling unconventional oil field development

   Soni, Akhilesh, Linderoth, Jeff, Luedtke, James, and Rigterink, Fabian

   Optimization and Engineering, 2021

   Abstract Paper

   The scheduling of drilling and hydraulic fracturing of wells in an unconventional oil field plays an important role in the profitability of the field. A key challenge arising in this problem is the requirement that neither drilling nor oil production can be done at wells within a specified neighborhood of a well being fractured. We propose a novel mixed-integer linear programming (MILP) formulation for determining a schedule for drilling and fracturing wells in an unconventional oil field. We also derive an alternative formulation which provides stronger relaxations. In order to apply the MILP model for scheduling large fields, we derive a rolling horizon approach that solves a sequence of coarse time-scale MILP instances to obtain a solution at the daily time scale.

4. 4. Integer Programming Approaches To Subspace Clustering With Missing Data

   Soni, Akhilesh, Linderoth, Jeff, Luedtke, Jim, and Pimentel-Alarcón, Daniel

   OPT2021: 13th Annual Workshop on Optimization for Machine Learning, NeurIPS, 2021

   Abstract Paper

   In the Subspace Clustering with Missing Data problem, we are given a collection of n data points, and each of the data points is observed only on a subset of its coordinates. The data points are assumed to be concentrated near a union of low-dimensional subspaces. The goal is to cluster the vectors as per their subspace membership. State-of-the-art algorithms can perform poorly on instances with a large amount of missing data o if the data matrix is nearly full-rank. We propose a novel integer programming-based method for SCMD. The approach is based on dynamically determining a set of candidate subspaces and optimally assigning points to selected subspaces. The problem structure is identical to the classical facility-location problem, with subspaces playing the role of facilities and data points that of customers. We propose a column-generation approach for identifying candidate subspaces combined with a Benders decomposition approach for solving the linear programming relaxation of the formulation. An empirical study demonstrates that the proposed approach can achieve better clustering accuracy than state-of-the-art methods when the data is high-rank or the percentage of missing data is high.

5. 5. Binary matrix completion over finite field

   Soni, Akhilesh, Linderoth, Jeff, Luedtke, Jim, and Pimentel-Alarcón, Daniel

   In Preparation
6. 6. Experimental analysis of geometrical parameters on the performance of an inline jet plate solar air heater

   Soni, Akhilesh, and Singh, S.N.

   Solar Energy, 2017

   Abstract Paper

   An experimental investigation has been carried out to study flow and heat transfer in solar air heater for inline holes inserted between absorber and back plate. The analysis has been carried out for cross flow conditions. The effect of flow and geometrical parameters, especially jet diameter and hydraulic diameter has been studied. Mass flow rate for the study is varied corresponding to the Reynolds number range of 4600–12,000. The jet diameter, streamwise pitch, and spanwise pitch, each normalized by hydraulic diameter, i.e. Dj/Dh, X/Dh, and Y/Dh, are in the range: 0.053–0.084, 0.53–0.63, and 0.53–0.63 respectively. Performance is studied in terms of Temperature Rise Parameter (TRP), collector efficiency, and Nusselt number. Hourly variations of solar intensity have also been shown. Collector efficiency increases and Temperature Rise Parameter decreases with increase in mass flow rate for all geometrical configurations. All the above-listed performance parameters are found to be maximum at jet diameter to hydraulic diameter ratio of 0.07. A correlation for Nusselt number in terms of Reynolds number, jet diameter, and hydraulic diameter has also been developed.

7. 7. Effect of geometrical parameters on the performance of chevron type plate heat exchanger

   Kumar, Bhupal,  Soni, Akhilesh, and Singh, S.N.

   Experimental Thermal and Fluid Science, 2018

   Abstract Paper

   This work reports the effects of geometrical parameters on the hydraulic and thermal performance of a single pass U-type plate heat exchanger for the range of Reynolds number 800-2300. Influence of chevron angle on mean channel friction factor, mean channel pressure drop, and effectiveness is experimentally investigated. The current investigation also presents the in-depth analysis of flow non-uniformity or maldistribution on the performance of plate heat exchangers Two symmetrical plates set with chevron angle, β=60°/60° and 30°/30°, and one unsymmetrical plate set with chevron angle β=60°/30° are used. The experiments are conducted for 21 channels (11 cold fluid and 10 hot fluid) plates set using water as the fluid. Chevron angle significantly affects the fluid flow distribution in the channels which eventually has a severe impact on the thermal performance and power consumption of a PHE. The increase in mean channel pressure drop on increasing chevron angle from (30°/30°) to (60°/30°) and (60°/30°) to (60°/60°) is found to be 22.05% and 37.9% respectively. For the same increments of chevron angle, enhancement in effectiveness is found to be 17.73% and 22.05% respectively. Effectiveness is also found to be monotonically decreasing with increase in mass flow rate for all the chevron angles. Based on the experimental data, empirical correlations for the friction factor and effectiveness, taking into consideration chevron angle and enlargement factor, are developed.

8. 8. Adaptable wind/solar powered hybrid system for household wastewater treatment

   Soni, Akhilesh, Stagner, Jacqueline A., and Ting, David S.-K.

   Sustainable Energy Technologies and Assessments, 2017

   Abstract Paper

   Sustainable and cost-effective water treatment systems are critical elements to developing nations. In India, the human population is escalating while the water availability is lagging behind. An adaptable, affordable, and sustainable wastewater treatment system powered by wind/solar energy is proposed based on proven theory and technology. A household in India is singled out to illustrate the workings of the proposed system, where the wastewater is recirculated through a hybrid of water purifiers powered by solar/wind energy. The system demonstrated here is specifically designed for small-scale applications, i.e., for a single household. The solar still has been divided into four stages. Partial vacuum is created inside the still so as to obtain boiling point temperatures of 70°C, 67°C, 62°C and 50°C in the four stages. Dhanbad, India 23.79°N, 86.43°E, with an average solar intensity of 850W/m2 for 6h a day, has been used for this study. A lumped parameter mathematical model was developed for this study. With an aperture area of 2.5m2, the total amount of water distilled is found to be 43.3kg/day. The system proposed is more efficient than existing systems as it is able to achieve efficiencies as high as 53%. The effect of wind speed on distillate output yield has also been discussed.