Revisiting Recency Abstraction for JavaScript Towards an Intuitive, Compositional, and Efficient Heap Abstraction

International audienceJavaScript is one of the most widely used programming languages. To understand the behaviors of JavaScript programs and to detect possible errors in them, researchers have developed several static analyzers based on the abstract interpretation framework. However, JavaScript provides various language features that are difficult to analyze statically and precisely such as dynamic addition and removal of object properties, first-class property names, and higher-order functions. To alleviate the problem, JavaScript static analyzers often use recency abstraction, which refines address abstraction by distinguishing recent objects from summaries of old objects. We observed that while recency abstraction enables more precise analysis results by allowing strong updates on recent objects, it is not monotone in the sense that it does not preserve the precision relationship between the underlying address abstraction techniques: for an address abstraction A and a more precise abstraction B, recency abstraction on B may not be more precise than recency abstraction on A. Such an unintuitive semantics of recency abstraction makes its composition with various analysis sensitivity techniques also unintuitive. In this paper, we propose a new sin-gleton abstraction technique, which distinguishes singleton objects to allow strong updates on them without changing a given address abstraction. We formally define recency and singleton abstractions, and explain the unintuitive behaviors of recency abstraction. Our preliminary experiments show promising results for singleton abstraction

Daily Life Changes and Life Satisfaction among Korean School-Aged Children in the COVID-19 Pandemic

The recent COVID-19 pandemic has been disrupting the daily lives of people across the world, causing a major concern for psychological well-being in children. This study aimed to examine (1) how life satisfaction and its potential predictors have been affected by the pandemic among school-aged children in Korea, and (2) which factors would predict their life satisfaction during the pandemic. We surveyed 166 fourth-graders in the Seoul metropolitan area to assess their psychological well-being and potentially related variables during the pandemic. The data were compared with those available from two pre-COVID-19 surveys, the 2018 Korean Children and Youth Panel Survey (n = 1236) and the 2019 Korean Children and Youth Well-being Index Survey (n = 334). Higher levels of stress were observed in children during the COVID-19 pandemic; however, the level of their life satisfaction remained unchanged when compared with data from the pre-COVID-19 surveys. The pandemic also affected peer relationship quality and susceptibility to smartphone addiction, but not perceived parenting style nor academic engagement. Interestingly, peer relationship quality no longer predicted life satisfaction during the pandemic; perceived parenting styles and parent-child conversation time predicted life satisfaction. The results suggest a central role of parent-child relationship in supporting the psychological well-being of school-aged children during the pandemic

Daily Life Changes and Life Satisfaction among Korean School-Aged Children in the COVID-19 Pandemic

The recent COVID-19 pandemic has been disrupting the daily lives of people across the world, causing a major concern for psychological well-being in children. This study aimed to examine (1) how life satisfaction and its potential predictors have been affected by the pandemic among school-aged children in Korea, and (2) which factors would predict their life satisfaction during the pandemic. We surveyed 166 fourth-graders in the Seoul metropolitan area to assess their psychological well-being and potentially related variables during the pandemic. The data were compared with those available from two pre-COVID-19 surveys, the 2018 Korean Children and Youth Panel Survey (n = 1236) and the 2019 Korean Children and Youth Well-being Index Survey (n = 334). Higher levels of stress were observed in children during the COVID-19 pandemic; however, the level of their life satisfaction remained unchanged when compared with data from the pre-COVID-19 surveys. The pandemic also affected peer relationship quality and susceptibility to smartphone addiction, but not perceived parenting style nor academic engagement. Interestingly, peer relationship quality no longer predicted life satisfaction during the pandemic; perceived parenting styles and parent-child conversation time predicted life satisfaction. The results suggest a central role of parent-child relationship in supporting the psychological well-being of school-aged children during the pandemic.Y

A 65-nm CMOS 2 x 2 MIMO Multi-Band LTE RF Transceiver for Small Cell Base Stations

This paper presents a 680 MHz-6 GHz 2 x 2 multiple-input and multiple-output (MIMO) long-term evolution (LTE) RF transceiver in 65-nm CMOS for low-cost and multi-band capable femtocell base stations. The transceiver integrates two receivers (RXs), two transmitters (TXs), and two frequency synthesizers, for the 2x 2 MIMO operation to support both the frequency division duplex (FDD) and the time division duplex (TDD) modes. Each pair of an RX and a TX features eight single-ended low noise amplifiers (LNAs), and eight TX outputs that extensively share active and passive circuits with minimal performance degradation. In the measurement, each RX illustrates the noise figure (NF) from 2.9 to 5.2 dB, the input-referred third-order intercept point (IIP3) of more than -2 dBm, and the IIP2 of more than 48 dBm, over the entire frequency range at the maximum gain. Each TX achieved the adjacent channel leakage ratio (ACLR) that was less than -54 dBc at -5-dBm output power with -157-dBc/Hz phase noise at the RX band, while achieving an error-vector-magnitude (EVM) of less than 2.8%, over the entire frequency range. The transceiver, packaged in a flip-chip chip-scale package (fcCSP), is mounted on the board of the commercial femtocell of the LTE Band5, along with a commercial duplexer, power amplifier, and modem. The femtocell achieved -100-dBm reference sensitivity without the use of an external LNA. It also achieved -51-dBc TX ACLR and 1.68% TX EVM at 20-dBm output power in the LTE 10-MHz mode with the 2 x 2 MIMO configuration, without applying a digital pre-distortion (DPD) technique