Civil Engineering

TechTalk – Wireless AI Perception: A New Sense for Machine Intelligence Beyond Vision

September 21 2023 (Thursday) 4:30-5:30pm
Can machines sense without cameras or sensors? Computer vision allows machines to “see,” but their perception capabilities based on cameras are fundamentally limited to a specific field of view and good lighting conditions – they cannot see through any occlusions or in the dark. In this talk, I will introduce Wireless AI Perception that opens a new sense for machine perception to decipher the physical world, even in absolute darkness and through walls and obstacles. To achieve this, Wireless AI leverages ambient wireless signals for sensing and turns any Wi-Fi devices from a pure communication medium into a ubiquitous all-in-one sensing platform. We will first introduce the concepts, principles, and grand challenges of Wi-Fi sensing, and then share our unique solution of Wireless AI, which has been commercialized and deployed as real-world products, such as motion sensing, sleep monitoring, fall detection, indoor tracking, just to name a few. We foresee that Wi-Fi Sensing will enter billions of devices and millions of homes, and today is just the beginning of this revolution.

TechTalk – Simulation, Optimization and Artificial Intelligence for On-demand Ride Service Operations

September 14, 2023 (Thursday) 4:30-5:30pm
On-demand ride services or ride-sourcing services, offered by transportation network companies like Uber, Lyft and Didi, have been experiencing fast development and steadily reshaping the way people travel in the past decade. Various mathematical models and optimization algorithms, including reinforcement learning approaches, have been developed in the literature to help ride-sourcing platforms design better operational strategies to achieve higher operational efficiency. However, due to cost and reliability issues (implementing an immature algorithm for real operations may result in system turbulence), it is commonly infeasible to validate these models and train/test these optimization algorithms within real-world ride sourcing platforms. Acting as a useful test bed, a simulation platform for ride-sourcing systems will thus be very important for both researchers and industrial practitioners to conduct algorithm training/testing or model validation through trails and errors. While previous studies have established a variety of simulators for their own tasks, it lacks a fair and public platform for comparing the models/algorithms proposed by different researchers. In addition, the existing simulators still face many challenges, ranging from their closeness to real environments of ride-sourcing systems, to the completeness of different tasks they can implement. To address the challenges, we propose a novel multi-functional and open-sourced simulation platform for ride-sourcing systems, which can simulate the behaviors and movements of various agents (including drivers and passengers) on a real transportation network. It provides a few accessible portals for users to train and test various optimization algorithms, especially reinforcement learning algorithms, for a variety of tasks, including on-demand matching, idle vehicle repositioning, and dynamic pricing. Evaluated by experiments based on real-world datasets, the simulator is demonstrated to be an efficient and effective test bed for various tasks related to on-demand ride service operations.

Young Scholar TechTalk – Blowing Bubbles in Membranes for More Efficient Freshwater Production

Global scarcity and contamination of freshwater pose a significant threat to sustainable development. To address this crisis, reverse osmosis (RO) technology has been playing a pivotal role in desalination and water reuse for freshwater production. The effectiveness of the RO membrane filtration is highly dependent on its surface functional rejection layer. My research focuses on shaping this rejection layer to be a voids-bearing structure, resembling blowing bubbles within the layer. This technique will result in a thinner rejection layer with a larger surface area, favoring water transport. On this basis, shaping branch bubbles to resemble a tree or coral can potentially achieve an exponential increase in water filtration efficiency, resulting in faster production of freshwater with significantly lower energy consumption.

Young Scholar TechTalk – Understanding Rainfall-induced Slope Failures from an Integrated Perspective

Climate change increases the frequency and intensity of extreme rainfall events and magnifies the threat of rainfall-induced slope failure. The consequences of these failures can be dramatic and devastating if flow slides are triggered. While considerable efforts have been made in the past decades to understand the failure mechanisms and develop techniques to mitigate the hazards, the complexity of interplays of various factors causes it to remain an area of uncertainty and difficulty in geotechnical engineering. This talk will briefly review and discuss the main factors affecting rainfall-induced slope failures from a perspective integrating the geotechnical, hydrological, and climatological aspects. The two deadly landslides in Sau Mau Ping, Hong Kong, in June 1972 and August 1976, which caused 165 casualties, are revisited. We raise an intriguing question that has long been overlooked: why were the slopes able to withstand the 1972 rainfall but failed in the 1976 rainfall event, given that the rainfall intensity of the latter event was only half of the former. We explore the roles of geological and hydrological settings and the rainfall characteristics to look into the causes and mechanisms of these failures. Implications of the new findings for practice will also be discussed.

TechTalk – Soils by Design: A Reality, Not A Pipe Dream

Soils are vital for several sectors of the economy: transportation, energy, water, food security, historical heritage. Soils deteriorate over time, in response to cyclic processes (seasonal effects) and extreme events (from heatwaves to heavy rainfall). Mitigation is frequently based on intrusive and heavy engineering solutions. In this Tech Talk, Dr. Sérgio Lourenço will focus on how soil properties can be controlled or tuned as needed. Recent advances which borrow on ideas from allied fields, will be presented, from bioengineering to surfaces and interfaces. The potential of adaptable, sensing and self-healing soils as the way forward, will be discussed.

TechTalk – Understanding the Turkey-Syria Earthquakes with Methane Gas Refined Fault Theory of Tectonic Earthquakes

At 4:17 am (Turkey time), Feb. 6, 2023, a damaging Mw 7.8 (or 8.0) earthquake struck southern and central Turkey and western Syria and was followed by many aftershocks including an unusually powerful Mw 7.8 (or 7.5) that occurred at 13:24. The earthquakes caused widespread damage including collapsing of many buildings. So far over 11,000 deaths were reported. Figures were projected to rise dramatically by World Health Organization.
In this Teck Talk, Professor Yue will present his understanding of the causes of the earthquakes and the associated building collapses using his methane gas refined fault theory of tectonic earthquakes. Each earthquake involved a rapid release of highly compressed methane gas expansion energy that was previously stored in deep aperture of rock fault zone. The highly compressed gas mass can rapidly expand, rupture, penetrate, and flow from the deep fault zone to shallow ground at a speed of 3 to 1 km/s. The rapid gas flow and expansion in fault rock zone generate massive seismic waves and induce huge concentrated damage to localized grounds and buildings. The earthquake is a cooling process since the gas expansion absorbs heat and cools the surrounding materials in the ground and sky, which can cause local weather changes including the occurrence of air temperature drop-down, rainfall and/or snow.

TechTalk – An Innovative Way of Water Resources Management for Sustainable Development: Utilization of Atmospheric Water Resources

Due to rapid population growth and climate change, there are severe spatiotemporal variations of water resources in the globe, and our society is facing serious challenges in securing sufficient water. To tackle the water shortage, we need to find other water sources. An effective and possible way is to utilize atmospheric water resources, which are the precipitable water in the atmosphere. With relatively stable temporal and spatial distribution, this part of water resources can be exploited and utilized through artificial precipitation enhancement operations which is also known as cloud seeding. In this talk, Professor Chen will introduce the situation of atmospheric water resources and the method that implements low frequency acoustic waves to stimulate and enhance precipitation. Through indoor experimental analysis and a large number of field tests, the effect has been tested. The development and utilization of atmospheric water resources would provide an innovative measure to obtain more freshwater for a certain region. He will also discuss the atmospheric water resources in the Greater Bay Area.

TechTalk – Environmental Materials for Urban Resource Recovery

Substantial material resource recovery opportunities exist in the urban environment to support more sustainable urban development. However, the ability to produce safe and quality recoverable requires in-depth environmental materials studies and state-of-the-art fabrication and characterization technologies. For example, the quantitative X-ray diffraction (QXRD) technique has accurately monitored the transfer and behavior of targeted hazardous metals when being beneficially used for ceramic products in the construction industry. The work of recovering metallic lead from waste cathode ray tube (CRT) glass serves as an excellent example to reflect how environmental materials techniques assisted the development of transforming urban electronic waste into new metal resources. Lastly, the demonstration of recovering phosphorus from wastewater streams as quality slow-releasing fertilizer for agriculture applications leads to new solutions to tackle critical resource challenges with the fast-developing urban mining concept around the world.

TechTalk – To See a World in a Grain of Sand: A Geotechnical Researcher’s Perspective

Many large earth structures (e.g. slopes, dams, and artificial islands) are made up of sand or sandy soil. The stability of these structures is a major concern of the public as well as the professional. The bitter memories of the deadly slope failures in Hong Kong in 1972 remind us of the importance of proper stability evaluation. The difficulty in predicting the mechanical behavior of sand and sandy soil mainly comes from the granular nature of these materials. A sand or sandy soil is an assembly of numerous small grains of varying size, shape and even mineral composition. It can exist over a spectrum of states that corresponds to a variety of responses, ranging from fluid-like flow to solid-like strain hardening. The groundwater brings additional difficulty and uncertainty. This talk will present some results and findings yielded from our long-term research endeavor at HKU, which is aimed to advance scientific understanding of the complex behaviors of granular earth materials and thereby provide better engineering solutions. Focus will be placed on the fascinating roles played by the small constituent particles. The significance of these findings to engineering practice will be open to discussion.