Welcome to Ranak Homepage!

I’m a PhD Student (final year) at UCSD CSE with a specialization in Data Mining, advised by Professor Jingbo Shang and Professor Rajesh K. Gupta. I am grateful to Qualcomm and Halıcıoğlu Data Science Institute for their fellowship to support my research.

I spent several summers working as an Applied Scientist II Intern at AWS AI, a Data Science Intern at Bell Labs, and a Software Development Engineer Intern at AWS Redshift.

Research Interests

I’m broadly interested in Data Mining Applications in Human-Centric AI:

  • Human Motion Understanding
  • Health Analytics
  • Audio & Speech Processing

My projects focus on self-supervised learning to build data-efficient and robust algorithms from sensor-based time series (wearable sensors, physiological signals, PPG, ECG, EEG). During my internships, I worked on Music LLMs and Accent Robust Speech Recognition. To learn more about my work, please look into my projects and relevant publications.

Latest News

[April 2024] First survey on Large Language Models for Time Series accepted at IJCAI ‘24.

[February 2024] Pre-print Downstream Task Guided Masking Learning in Masked Autoencoders Using Multi-Level Optimization is now available.

[September 2023] Physics-Informed Data Denoising for Real-Life Sensing Systems has been accepted to SenSys ‘23.

[August 2023] Gave an invited talk on PrimeNet: Pre-Training for Irregular Multivariate Time Series at SIGKDD ‘23 Workshop on Machine Learning in Finance, Long Beach, CA, USA.

[August 2023] Unleashing the Power of Shared Label Structures for Human Activity Recognition has been accepted to CIKM ‘23.

[June 2023] Returned to Amazon Web Services (AWS) AI as an Applied Scientist II Intern at the Speech Science Group. Worked on MusicLLM.

[March 2023] Presented my Thesis Proposal on Data-Efficient Learning for Sensory Time Series. Advanced to Ph.D. candidacy.

[February 2023] Towards Diverse and Coherent Augmentation for Time-Series Forecasting has been accepted to ICASSP ‘23.

[November 2022] PrimeNet: Pre-Training for Irregular Multivariate Time Series has been accepted to AAAI ‘23.

[October 2022] Started working with the Qualcomm Sensing Machine Learning Team.

[August 2022] Won the Qualcomm Innovation Fellowship 2022 for our proposal on Robust Machine Learning for Mobile Sensing.

[June 2022] Joined Amazon Web Services (AWS) AI as an Applied Scientist II Intern at the Speech Science Group. Worked on Accent Robust Speech Recognition.

Work Experience

Applied Scientist II Intern                                                                  Jun 2023 - Sep 2023

MusicLLM: Music Understanding with LLMs
Built an LLM-enabled music understanding framework to solve music tasks, like captioning, retrieval, tagging, and classification in a text-to-text fashion. The model takes music file and task prompts as inputs and generate text responses. Used audio features from Encodec and an instruction-tuned FLAN-T5 LLM. [Slide]

Research Fellow                                                                                  Oct 2022 - Sep 2023

Context Aware Learning for IoT
Worked on two projects: 1) PILOT: Integrated physics-based constraints to improve data denoising for Inertail Navigation, CO2 Monitoring, and Air Handling in HVAC Control System [Paper | Slide], 2) ZeroHAR: Used sensor environment knowledge and fine-grained biomechanical information from LLMs to improve Zero-Shot Wearable Human Action Recognition.

Applied Scientist II Intern                                                                  Jun 2022 - Sep 2022

MARS: Multitask Pre-training for Accent Robust Speech Recognition
Built a pre-trained model for accent-robust speech representation that improves performance on several downstream tasks, like Speech Recognition by 20.4% and Speaker Verification by 6.3%, across 12 minority accents with few minutes of data. [Slide]

Data Science Intern                                                                              Jun 2021 - Aug 2021

Automated Ticket Resolution from Semi-Structured Log Data
Developed an ML pipeline to automate ticket resolution by conducting data cleaning, preprocessing, and visualization on time-series semi-structured system-level log corpus, followed by statistical feature extraction and classification. [Slide]

Software Development Engineer Intern                                        Jun 2020 - Sep 2020

Model Explainability from SQL Surface for Redshift ML
Built a SHAP-based Explainability tool for AWS Redshift ML, enabling users to write SQL queries to introspect model predictions. Improved execution speed by 2x and reduced memory footprint by 90% over existing workflow in AWS Sagemaker.
Preview | Press Release | Blog | Documentation | Slide

Research Assistant                                                                              Jan 2019 - Aug 2019

Real-Time Principal Component Analysis
Innovated a data dimensionality reduction algorithm for streaming data, that uses a data-driven heuristic to learn a robust, noise-resilient eigenspace. Algorithm proven experimentally by spectral analysis and Bhattacharyya Distance.
Conference | Journal | Poster | Slide

Projects

Large Language Models for Time Series: A Survey
Pioneered the first survey on how LLMs can solve time-series tasks through prompting, time-series quantization, alignment of time-series with text, using vision as bridge, and using LLMs as output tools.

ZeroHAR: Contextual Knowledge Augments Zero-Shot Wearable Human Activity Recognition
Innovated a Zero-Shot Wearable Human Activity Recognition framework that integrates contextual knowledge about activities from LLMs and sensory environment information to improve Zero-Shot F1 Score by 20%.

MLO-MAE: Downstream Task Guided Masking Learning in Masked Autoencoders Using Multi-Level Optimization
Developed a Multi-level Optimized Mask Autoencoder that improves image classification by integrating model pretraining with fine-tuning to allow fine-tuning performance guide an optimal masking strategy for pretraining.

PILOT: Physics-Informed Data Denoising for Real-Life Sensing Systems
Established a physics-informed data denoising scheme that integrates physics equations as constraints into training loss, ensuring the cleaned data complies with fundamental physical constraints, thereby improving data quality.

SHARE: Unleashing the Power of Shared Label Structures for Human Activity Recognition
Built an encoder-decoder architecture to model label name semantics that harnesses the shared sub-structure of label names to distill knowledge across classes, improving accuracy of human activity recognition tasks by 1.7%.

MusicLLM: Music Understanding with LLMs
Developed an LLM with music integration that generates text responses, including music genre, instruments used, mood, and theme, based on music files. Used Encodec audio features in conjunction with FLAN-T5 LLM.

STAug: Towards Diverse and Coherent Augmentation for Time-Series Forecasting
Crafted a time-series data augmentation strategy that incorporates both time- and frequency-domain knowledge through mix-up and Empirical Mode Decomposition, respectively, improving time-series forecasting by 10.7%.

PrimeNet: Pre-Training for Irregular Multivariate Time Series
Crafted a self-supervised pretraining method for irregular, asynchronous time-series through sampling density-aware contrastive learning and time-sensitive data reconstruction techniques, improving few-shot downstream performance.

TARNet: Task-Aware Reconstruction for Time-Series Transformer
Developed a self-supervised task-aware data reconstruction technique that uses end-task knowledge to customize the learned representation to boost end task performance, improving time-series classification by 2.7%.

MARS: Multitask Pre-training for Accent Robust Speech Recognition
Built a pre-trained model for accent-robust speech representation that improves performance on several downstream tasks, like Speech Recognition by 20.4% and Speaker Verification by 6.3%, across 12 minority accents with few minutes of data.

ESC-GAN: Extending Spatial Coverage of Physical Sensors
Devised a globally-attentive multiscale Super-Resolution GAN that uses irregularly spaced sparse data to generate high-resolution spatiotemporal data for regions with no physical sensors, reducing reconstruction loss by 3.7%.

UniTS: Short-Time Fourier Inspired Neural Networks for Sensory Time Series Classification
Innovated a Fourier-transform (FT) inspired weight initialization and learnable Short-Time FT layer redesign to integrate time and frequency domain information, improving F1 score for sensory time-series classification by 2.3%.

Automated Ticket Resolution from Semi-Structured Log Data
Developed an ML pipeline to automate ticket resolution by conducting data cleaning, preprocessing, and visualization on time-series semi-structured system-level log corpus, followed by statistical feature extraction and classification.

RIoT: Towards Robust Learning for Internet-of-Things
Built a comprehensive evaluation strategy and a model-agnostic training framework to facilitate robustness of machine learning models to missing feature sets in time-series data, achieving a 22% improvement in robustness.

Model Explainability for Redshift ML
Built a SHAP-based Explainability tool for AWS Redshift ML, enabling users to write SQL queries to introspect model predictions. Improved execution speed by 2x and reduced memory footprint by 90% over existing workflow in AWS Sagemaker.

Generating Rationale in Visual Question Answering
Developed a model that generates a rationale behind selecting a multiple choice answer in visual question answering. Trained a joint visual-linguistic model to build multimodal image- and text-representation and a GPT-2 model to generate text.

Real-Time Principal Component Analysis
Innovated a novel algorithm for dimensionality reduction on streaming data that learns a robust, noise-resilient eigenspace representation using a simple, fast heuristic, achieving Bhattacharyya Distance of over 0.90.

Extracting Real-Time Insights from Stock Market and Twitter
Built and deployed a web application, based on Real Time PCA, to generate real-time analytics on streaming data fetched from Twitter, Google Search Trends, Bangladeshi Online News Portals and Dhaka Stock Exchange.

Stock Price Forecasting from Historical Prices and News Trends
Devised a multi-modal model to forecast stock prices based on historical prices and latest news trends. Used an LSTM to model the stock prices, Word2Vec to represent news headlines and an MLP to concatenate the features.

Publications

For latest publications, please visit my Google Scholar profile.

Large Language Models for Time Series: A Survey
Xiyuan Zhang, Ranak Roy Chowdhury, Rajesh Gupta, Jingbo Shang
International Joint Conference on Artificial Intelligence (IJCAI), 2024.
Paper | Code

ZeroHAR: Contextual Knowledge Augments Zero-Shot Wearable Human Activity Recognition
Ranak Roy Chowdhury, Ritvik Kapila, Ameya Panse, Xiyuan Zhang, Diyan Teng, Rashmi Kulkarni, Dezhi Hong, Rajesh Gupta, Jingbo Shang
[Under Submission]

MLO-MAE: Downstream Task Guided Masking Learning in Masked Autoencoders Using Multi-Level Optimization
Han Guo, Ramtin Hosseini, Ruiyi Zhang, Sai Ashish Somayajula, Ranak Roy Chowdhury, Rajesh Gupta, Pengtao Xie
[Under Submission]
Paper | Code

MusicLLM: Music Understanding with LLMs
Ranak Roy Chowdhury, Rohit Paturi, Sundararajan Srinivasan
[Under Preparation]

PILOT: Physics-Informed Data Denoising for Real-Life Sensing Systems
Xiyuan Zhang, Xiaohan Fu, Diyan Teng, Chengyu Dong, Keerthivasan Vijayakumar, Jiayun Zhang, Ranak Roy Chowdhury, Junsheng Han, Dezhi Hong, Rashmi Kulkarni, Jingbo Shang, Rajesh Gupta
Conference on Embedded Networked Sensor Systems (SenSys), 2023.
Paper | Slide

PrimeNet: Pre-training for Irregular Multivariate Time-Series
Ranak Roy Chowdhury, Jiacheng Li, Xiyuan Zhang, Dezhi Hong, Rajesh Gupta, Jingbo Shang
AAAI Conference on Artificial Intelligence (AAAI), 2023. [Travel Grant]
Paper | Code | Poster | Slide

SHARE: Unleashing the Power of Shared Label Structures for Human Activity Recognition
Xiyuan Zhang, Ranak Roy Chowdhury, Dezhi Hong, Rajesh K. Gupta, Jingbo Shang
Conference on Information and Knowledge Management (CIKM), 2023.
Paper | Code | Slide | Package

MARS: Self-supervised Multi Task Pre-training for Accent Robust Speech Representation.
Ranak Roy Chowdhury, Anshu Bhatia, Haoqi Li, Srikanth Ronanki, Sundararajan Srinivasan
[Under Submission]

STAug: Towards Diverse and Coherent Augmentation for Time-Series Forecasting
Xiyuan Zhang, Ranak Roy Chowdhury, Jingbo Shang, Rajesh Gupta, Dezhi Hong
International Conference on Acoustics, Speech, and Signal Processing (ICASSP), 2023.
Paper | Code | Poster | Slide

TARNet: Task-Aware Reconstruction for Time-Series Transformer
Ranak Roy Chowdhury, Xiyuan Zhang, Jingbo Shang, Rajesh K. Gupta, Dezhi Hong
SIGKDD Conference On Knowledge Discovery and Data Mining (SIGKDD), 2022. [Travel Grant]
Paper | Code | Poster | Slide

ESC-GAN: Extending Spatial Coverage of Physical Sensors
Xiyuan Zhang, Ranak Roy Chowdhury, Jingbo Shang, Rajesh K. Gupta, Dezhi Hong
International Conference on Web Search and Data Mining (WSDM), 2022.
Paper | Code | Poster | Slide

UniTS: Short-Time Fourier Inspired Neural Networks for Sensory Time Series Classification
Shuheng Li, Ranak Roy Chowdhury, Jingbo Shang, Rajesh K. Gupta, Dezhi Hong
Conference on Embedded Networked Sensor Systems (SenSys), 2021.
Paper | Code | Slide

RIoT: Towards Robust Learning for Internet-of-Things
Ranak Roy Chowdhury, Dezhi Hong, Rajesh K. Gupta, Jingbo Shang
[Under Submission]
Paper

Real-Time Principal Component Analysis
Ranak Roy Chowdhury, Muhammad Abdullah Adnan, Rajesh K. Gupta
Transactions on Data Science (TDS), Volume 1, Issue 2.
Paper | Poster | Slide

Real-Time Principal Component Analysis
Ranak Roy Chowdhury, Muhammad Abdullah Adnan, Rajesh K. Gupta
International Conference on Data Engineering (ICDE), 2019.
Paper | Poster | Slide

Education

University of California San Diego

Ph.D. in Computer Science                                                                               Sep 2019 - Present

University of California San Diego

M.S. in Computer Science                                                                             Sep 2019 - Mar 2022

Bangladesh University of Engineering and Technology

B.Sc. in Computer Science and Engineering                                                   Jul 2014 - Oct 2018

Honors & Awards

  • Invited Keynote Speaker at SIGKDD 2023 Workshop on Machine Learning in Finance, Long Beach, CA, USA. [Workshop | Slide]
  • Qualcomm Innovation Fellowship 2022 for our proposal on "Robust Machine Learning for Mobile Sensing". One of the 19 winners among 132 participants across North America. [News | Proposal]
  • Recipient of Travel Award: AAAI 2023, SIGKDD 2022
  • Halıcıoglu Data Science Institute Graduate Fellowship 2019 to fund investigations in data science, in recognition of my research accomplishments. One of the 10 winners among 3906 applicants. [News]
  • Selected to participate at The Heidelberg Laureate Forum 2020. [Certificate]
  • Selected to participate at The Cornell, Maryland, Max Planck Pre-doctoral Research School 2019, Saarbrucken, Germany. [Certificate]
  • Research Fellowship awarded by Department of CSE, UCSD to support graduate studies.
  • Dean's List and University Merit Scholarship awarded by Department of CSE, BUET, in recognition of excellent undergraduate academic performance.

Services

  • Program Committee Member: SIGKDD 2024
  • Teaching: TA for CSE 158 - Web Mining and Recommender Systems
  • Mentored 2 UCSD CSE MS students on a research project.

Skills

Python, C, C++, Java, Matlab, SQL, PostgreSQL, Linux, Git, PyTorch, Keras, Tensorflow, fairseq, Hugging Face, NumPy, pandas, SciPy, Matplotlib, Seaborn, scikit-learn, statsmodels, sktime, tslearn, torchdyn, Pillow, OpenCV, NLTK, CoreNLP, spaCy.