Rate-distortion function for finite block codes: Analysis of symmetric binary hamming problem

Shannon's rate-distortion theory provides an asymptotic analysis, where delays are allowed to grow unbounded. In practice, real-time applications, such as video streaming and network storage, are subject to certain maximum delay. Accordingly, it is imperative to develop a finite-delay framework for analyzing the rate-distortion limit. In this backdrop, we propose an intuitive generalization of Shannon's asymptotic operational framework to finite block codes. In view of the extreme complexity of such framework, we obtain insight by specializing to the symmetric binary hamming problem. Even upon such specialization, the proposed framework is computationally so intensive that accurate evaluation of the finite-delay rate-distortion function is practical only upto a block length of three. In order to obtain further insight, we then propose a lower-complexity lower bound, based on the partition function of natural numbers, whose computation is practical upto a block length of six. Finally, using a simple combinatorial argument, we propose an upper bound to localize the desired rate-distortion function between our lower and upper bounds

Precision Attitude Stabilization with Intermittent External Torque

The attitude stabilization of a micro-satellite employing a variable-amplitude cold gas thruster which reflects as a time varying gain on the control input is considered. Existing literature uses a persistence filter based approach that typically leads to large control gains and torque inputs during specific time intervals corresponding to the 'on' phase of the external actuation. This work aims at reducing the transient spikes placed upon the torque commands by the judicious introduction of an additional time varying scaling signal as part of the control law. The time update mechanism for the new scaling factor and overall closed-loop stability are established through a Lyapunov-like analysis. Numerical simulations highlight the various features of this new control algorithm for spacecraft attitude stabilization subject to torque intermittence.Comment: Presented as paper AAS 21-402 at the 31st AAS/AIAA Space Flight Mechanics Meeting, Virtual, February 1-4 202

HTA: A Scalable High-Throughput Accelerator for Irregular HPC Workloads

We propose a new architecture called HTA for high throughput irregular HPC applications with little data reuse. HTA reduces the contention within the memory system with the help of a partitioned memory controller that is amenable for 2.5D implementation using Silicon Photonics. In terms of scalability, HTA supports 4 × higher number of compute units compared to the state-of-the-art GPU systems. Our simulation-based evaluation on a representative set of HPC benchmarks shows that the proposed design reduces the queuing latency by 10% to 30%, and improves the variability in memory access latency by 10% to 60%. Our results show that the HTA improves the L1 miss penalty by 2.3 × to 5 × over GPUs. When compared to a multi-GPU system with the same number of compute units, our simulation results show that the HTA can provide up to 2 × speedup

Designing a Magnetic Measurement Data Acquisition and Control System with Reuse in Mind: A Rotating Coil System Example

Accelerator magnet test facilities frequently need to measure different magnets on differently equipped test stands and with different instrumentation. Designing a modular and highly reusable system that combines flexibility built-in at the architectural level as well as on the component level addresses this need. Specification of the backbone of the system, with the interfaces and dataflow for software components and core hardware modules, serves as a basis for building such a system. The design process and implementation of an extensible magnetic measurement data acquisition and control system are described, including techniques for maximizing the reuse of software. The discussion is supported by showing the application of this methodology to constructing two dissimilar systems for rotating coil measurements, both based on the same architecture and sharing core hardware modules and many software components. The first system is for production testing 10 m long cryo-assemblies containing two MQXFA quadrupole magnets for the high-luminosity upgrade of the Large Hadron Collider and the second for testing IQC conventional quadrupole magnets in support of the accelerator system at Fermilab

Amino­guanidinium hydrogen succinate

The title compound, CH7N4 +·C4H5O4 −, is a molecular salt containing discrete amino­guanidinium and succinate ions. The amino­guanidinium cation is nearly planar, with a maximum deviation of 0.035 (1) Å. The dihedral angle between the amino­guanidinium cation and the succinate anion is 3.35 (6)°. The crystal packing exhibits inter­molecular N—H⋯O and O—H⋯·O hydrogen bonds

Вимоги видавничого відділу ІМФЕ ім. М. Т. Рильського до оформлення авторами рукописів

Industrial parts are manufactured to tolerances as no production process is capable of delivering perfectly identical parts. It is unacceptable that a plan for a manipulation task that was determined on the basis of a CAD model of a part fails on some manufactured instance of that part, and therefore it is crucial that the admitted shape variations are systematically taken into account during the planning of the task. We study the problem of orienting a part with given admitted shape variations by means of pushing with a single frictionless jaw. We use a very general model for admitted shape variations that only requires that any valid instance must contain a given convex polygon PI while it must be contained in another convex polygon PE. The problem that we solve is to determine, for a given h, the sequence of h push actions that puts all valid instances of a part with given shape variation into the smallest possible interval of final orientations. The resulting algorithm runs in O(hn) time, where n=|PI|+|PE|

Co-targeting strategy for precise, scarless gene editing with CRISPR/Cas9 and donor ssODNs in Chlamydomonas

Programmable site-specific nucleases, such as the clustered regularly interspaced short palindromic repeat (CRISPR)/ CRISPR-associated protein 9 (Cas9) ribonucleoproteins (RNPs), have allowed creation of valuable knockout mutations and targeted gene modifications in Chlamydomonas (Chlamydomonas reinhardtii). However, in walled strains, present methods for editing genes lacking a selectable phenotype involve co-transfection of RNPs and exogenous doublestranded DNA (dsDNA) encoding a selectable marker gene. Repair of the dsDNA breaks induced by the RNPs is usually accompanied by genomic insertion of exogenous dsDNA fragments, hindering the recovery of precise, scarless mutations in target genes of interest. Here, we tested whether co-targeting two genes by electroporation of pairs of CRISPR/Cas9 RNPs and single-stranded oligodeoxynucleotides (ssODNs) would facilitate the recovery of precise edits in a gene of interest (lacking a selectable phenotype) by selection for precise editing of another gene (creating a selectable marker)— in a process completely lacking exogenous dsDNA. We used PPX1 (encoding protoporphyrinogen IX oxidase) as the generated selectable marker, conferring resistance to oxyfluorfen, and identified precise edits in the homolog of bacterial ftsY or the WD and TetratriCopeptide repeats protein 1 genes in ~1% of the oxyfluorfen resistant colonies. Analysis of the target site sequences in edited mutants suggested that ssODNs were used as templates for DNA synthesis during homology directed repair, a process prone to replicative errors. The Chlamydomonasacetolactate synthase gene could also be efficiently edited to serve as an alternative selectable marker. This transgene-free strategy may allow creation of individual strains containing precise mutations in multiple target genes, to study complex cellular processes, pathways, or structures

Seeing through Network-Protocol Obfuscation

ABSTRACT Censorship-circumvention systems are designed to help users bypass Internet censorship. As more sophisticated deep-packetinspection (DPI) mechanisms have been deployed by censors to detect circumvention tools, activists and researchers have responded by developing network protocol obfuscation tools. These have proved to be effective in practice against existing DPI and are now distributed with systems such as Tor. In this work, we provide the first in-depth investigation of the detectability of in-use protocol obfuscators by DPI. We build a framework for evaluation that uses real network traffic captures to evaluate detectability, based on metrics such as the false-positive rate against background (i.e., non obfuscated) traffic. We first exercise our framework to show that some previously proposed attacks from the literature are not as effective as a censor might like. We go on to develop new attacks against five obfuscation tools as they are configured in Tor, including: two variants of obfsproxy, FTE, and two variants of meek. We conclude by using our framework to show that all of these obfuscation mechanisms could be reliably detected by a determined censor with sufficiently low false-positive rates for use in many censorship settings

LLM: Realizing Low-Latency Memory by Exploiting Embedded Silicon Photonics for Irregular Workloads

As emerging workloads exhibit irregular memory access patterns with poor data reuse and locality, they would benefit from a DRAM that achieves low latency without sacrificing bandwidth and energy efficiency. We propose LLM (Low Latency Memory), a codesign of the DRAM microarchitecture, the memory controller and the LLC/DRAM interconnect by leveraging embedded silicon photonics in 2.5D/3D integrated system on chip. LLM relies on Wavelength Division Multiplexing (WDM)-based photonic interconnects to reduce the contention throughout the memory subsystem. LLM also increases the bank-level parallelism, eliminates bus conflicts by using dedicated optical data paths, and reduces the access energy per bit with shorter global bitlines and smaller row buffers. We evaluate the design space of LLM for a variety of synthetic benchmarks and representative graph workloads on a full-system simulator (gem5). LLM exhibits low memory access latency for traffics with both regular and irregular access patterns. For irregular traffic, LLM achieves high bandwidth utilization (over 80% peak throughput compared to 20% of HBM2.0). For real workloads, LLM achieves 3 × and 1.8 × lower execution time compared to HBM2.0 and a state-of-the-art memory system with high memory level parallelism, respectively. This study also demonstrates that by reducing queuing on the data path, LLM can achieve on average 3.4 × lower memory latency variation compared to HBM2.0

Nanosecond Ultrasonics to Study Phase Transitions in Solid and Liquid Systems at High Pressure and Temperature

This report describes the development of a high-frequency ultrasonic measurement capability for application to the study of phase transitions at elevated pressure and temperature. We combined expertise in various aspects of static high-pressure technique with recent advances in wave propagation modeling, ultrasonic transducer development, electronic methods and broadband instrumentation to accomplish the goals of this project. The transduction and electronic systems have a demonstrated bandwidth of 400 MHz, allowing investigations of phenomena with characteristic times as short as 2.5 nS. A compact, pneumatically driven moissanite anvil cell was developed and constructed for this project. This device generates a high-pressure environment for mm dimension samples to pressures of 3 GPa. Ultrasonic measurements were conducted in the moissanite cell, an LLNL multi-anvil device and in a modified piston cylinder device. Measurements for water, and elemental tantalum, tin and cerium demonstrate the success of the methods. The {gamma}-{alpha} phase transition in cerium was clearly detected at {approx}0.7 GPa with 75 MHz longitudinal waves. These results have direct application to important problems in LLNL programs, as well as seismology and planetary science