It is commonly believed that, in a real-world environment, samples can only be drawn from observational and interventional distributions, corresponding to Layers 1 and 2 of the *Pearl Causal Hierarchy*. Layer 3, representing counterfactual distributions, is believed to be inaccessible by definition. However, Bareinboim, Forney, and Pearl (2015) introduced a procedure that allows an agent to sample directly from a counterfactual distribution, leaving open the question of what other counterfactual quantities can be estimated directly via physical experimentation. We resolve this by introducing a formal definition of realizability, the ability to draw samples from a distribution, and then developing a complete algorithm to determine whether an arbitrary counterfactual distribution is realizable given fundamental physical constraints, such as the inability to go back in time and subject the same unit to a different experimental condition. We illustrate the implications of this new framework for counterfactual data collection using motivating examples from causal fairness and causal reinforcement learning. While the baseline approach in these motivating settings typically follows an interventional or observational strategy, we show that a counterfactual strategy provably dominates both.

This paper presents a fully integrated continuous-scalable conversion-ratio (CSCR) switched-capacitor voltage regulator (SCVR), capable of supporting a wide range of voltage conversion ratios and high load current for SOCs used in computing and other applications. This design can achieve both step-down and step-up voltage conversion and has phase-merged turbo modes to deliver higher output current. It can autonomously and dynamically transition between step-down and step-up modes based on conversion ratio and between regular and turbo modes depending on load current. This SCVR is designed using Intel’s 3nm FinFET technology and is capable of an output voltage range of 0.5V-1.2V from an input of 1.1V. Furthermore, the input voltage can be in the range 1.1-1.3V for the same output voltage range. It can deliver up to 8A of load current at a 1GHz flying capacitor switching frequency and exhibits a peak efficiency of 88%. This design minimizes the added die area for the converter by implementing the flying capacitors over the load domain and achieves a maximum active area power density of 14W/mm$^{2}$. The converter uses a fast asynchronous voltage droop detector, in combination with auto-transition to turbo modes, to achieve excellent transient response-an output voltage droop of 37.5mV was measured for a fast (100ps) load current step from 0.1A to 6A. It also features configurable maximum switching frequency reduction and clock interleaving to achieve an output voltage ripple of 20mV.

We present a new dataset for learning to solve, explain, and generate university-level STEM questions from 27 courses across a dozen departments in seven universities. We scale up previous approaches to questions from courses in the departments of Mechanical Engineering, Materials Science and Engineering, Chemistry, Electrical Engineering, Computer Science, Physics, Earth Atmospheric and Planetary Sciences, Economics, Mathematics, Biological Engineering, Data Systems, and Society, and Statistics. We visualize similarities and differences between questions across courses. We demonstrate that a large foundation model is able to generate questions that are as appropriate and at the same difficulty level as human-written questions.

The long-term evolution (LTE) is the newly adopted technology to offer enhanced capacity and coverage for current mobility networks, which experience a constant traffic increase and skyrocketing bandwidth demands. This new cellular communication system, built upon a redesigned physical layer and based on an orthogonal frequency division multiple access (OFDMA) modulation, features robust performance in challenging multipath environments and substantially improves the performance of the wireless channel in terms of bits per second per Hertz (bps/Hz). Nevertheless, as all wireless systems, LTE is vulnerable to radio jamming attacks. Such threats have security implications especially in the case of next-generation emergency response communication systems based on LTE technologies. This proof of concept paper overviews a series of new effective attacks (smart jamming) that extend the range and effectiveness of basic radio jamming. Based on these new threats, a series of new potential security research directions are introduced, aiming to enhance the resiliency of LTE networks against such attacks. A spread-spectrum modulation of the main downlink broadcast channels is combined with a scrambling of the radio resource allocation of the uplink control channels and an advanced system information message encryption scheme. Despite the challenging implementation on commercial networks, which would require inclusion of these solutions in future releases of the LTE standard, the security solutions could strongly enhance the security of LTE-based national emergency response communication systems.