Worcester Polytechnic Institute

About: Worcester Polytechnic Institute is a education organization based out in Worcester, Massachusetts, United States. It is known for research contribution in the topics: Population & Data envelopment analysis. The organization has 6270 authors who have published 12704 publications receiving 332081 citations. The organization is also known as: WPI.

Wideband radio propagation modeling for indoor geolocation applications

Abstract: A framework for statistical modeling of the wideband characteristics of the frequency-selective fading multipath indoor radio channel for geolocation applications is presented. Multipath characteristics of the channel are divided into three classes according to availability and the strength of the direct line of sight (DLOS) path with respect to the other paths. Statistics of the error in estimating the time of arrival of the DLOS path in a building is related to the receiver's sensitivity and dynamic range. The effects of external walls on estimating the location of the DLOS path are analyzed.

ZombieLoad: Cross-Privilege-Boundary Data Sampling

Abstract: In early 2018, Meltdown first showed how to read arbitrary kernel memory from user space by exploiting side-effects from transient instructions. While this attack has been mitigated through stronger isolation boundaries between user and kernel space, Meltdown inspired an entirely new class of fault-driven transient-execution attacks. Particularly, over the past year, Meltdown-type attacks have been extended to not only leak data from the L1 cache but also from various other microarchitectural structures, including the FPU register file and store buffer. In this paper, we present the ZombieLoad attack which uncovers a novel Meltdown-type effect in the processor's fill-buffer logic. Our analysis shows that faulting load instructions (i.e., loads that have to be re-issued) may transiently dereference unauthorized destinations previously brought into the fill buffer by the current or a sibling logical CPU. In contrast to concurrent attacks on the fill buffer, we are the first to report data leakage of recently loaded and stored stale values across logical cores even on Meltdown- and MDS-resistant processors. Hence, despite Intel's claims, we show that the hardware fixes in new CPUs are not sufficient. We demonstrate ZombieLoad's effectiveness in a multitude of practical attack scenarios across CPU privilege rings, OS processes, virtual machines, and SGX enclaves. We discuss both short and long-term mitigation approaches and arrive at the conclusion that disabling hyperthreading is the only possible workaround to prevent at least the most-powerful cross-hyperthread attack scenarios on current processors, as Intel's software fixes are incomplete.

100% Recycled Hot Mix Asphalt: A Review and Analysis

Abstract: a b s t r a c t A holistic evaluation of the feasibility of producing 100% recycled mixtures is presented Eleven tech- nologies readily available for producing 100% Reclaimed Asphalt Pavement (RAP) hot asphalt mixtures are described in the article and the complementary video (http://youtube/coj-e5mhHEQ) The recorded performance of 100% RAP mixtures is analyzed along with identification of typical high RAP distresses Recommended mix design procedures and the best RAP management strategies are described A cradle- to-gate analysis of environmental effects indicated 18 kg or 35% CO2eq savings per t of produced 100% RAP asphalt mixture compared to virgin mix, while cost analysis showed at least 50% savings in material related expenses

Distribution of Ti3+ Surface Sites in Reduced TiO2

Abstract: We describe a DFT + U study of the (110) rutile surface with oxygen vacancies (Ov's). Oxygen vacancies leave behind two excess unpaired electrons per Ov, leading formally to the formation of two Ti3+ ions. We investigate the location of the Ti3+ ions within the first three surface layers. In total, we obtained 49 unique solutions of possible Ti3+ pairs, to examine the stability of all Ti types (e.g., five-coordinated surface Ti, six-coordinated surface Ti, subsurface sites, etc.). Our results show that subsurface sites are preferred but that many configurations are close in energy, within up to 0.3−0.4 eV of each other. In contrast to findings in previous work, we show that sites directly adjacent to the Ov's are unstable. Analysis of our results shows that the two Ti3+ ions within a pair behave independently of each other, as there are little electronic interactions between the excess electrons associated with these sites. We also examined the migration of Ti3+ sites from the surface into the bulk and fi...

Missing responses in generalised linear mixed models when the missing data mechanism is nonignorable

Abstract: SUMMARY We propose a method for estimating parameters in the generalised linear mixed model with nonignorable missing response data and with nonmonotone patterns of missing data in the response variable. We develop a Monte Carlo EM algorithm for estimating the parameters in the model via the Gibbs sampler. For the normal random effects model, we derive a novel analytical form for the E- and M-steps, which is facilitated by integrating out the random effects. This form leads to a computationally feasible and extremely efficient Monte Carlo EM algorithm for computing maximum likelihood estimates and standard errors. In addition, we propose a very general joint multinomial model for the missing data indicators, which can be specified via a sequence of one-dimensional conditional distributions. This multinomial model allows for an arbitrary correlation structure between the missing data indicators, and has the potential of reducing the number of nuisance parameters. Real datasets from the International Breast Cancer Study Group and an environmental study involving dyspnoea in cotton workers are presented to illustrate the proposed methods.