The Bayesian sampler : generic Bayesian inference causes incoherence in human probability

Human probability judgments are systematically biased, in apparent tension with Bayesian models of cognition. But perhaps the brain does not represent probabilities explicitly, but approximates probabilistic calculations through a process of sampling, as used in computational probabilistic models in statistics. Naïve probability estimates can be obtained by calculating the relative frequency of an event within a sample, but these estimates tend to be extreme when the sample size is small. We propose instead that people use a generic prior to improve the accuracy of their probability estimates based on samples, and we call this model the Bayesian sampler. The Bayesian sampler trades off the coherence of probabilistic judgments for improved accuracy, and provides a single framework for explaining phenomena associated with diverse biases and heuristics such as conservatism and the conjunction fallacy. The approach turns out to provide a rational reinterpretation of “noise” in an important recent model of probability judgment, the probability theory plus noise model (Costello & Watts, 2014, 2016a, 2017; Costello & Watts, 2019; Costello, Watts, & Fisher, 2018), making equivalent average predictions for simple events, conjunctions, and disjunctions. The Bayesian sampler does, however, make distinct predictions for conditional probabilities and distributions of probability estimates. We show in 2 new experiments that this model better captures these mean judgments both qualitatively and quantitatively; which model best fits individual distributions of responses depends on the assumed size of the cognitive sample

Thick-film Piezoelectric Vibration Harvesting –A HUMS Application

A vibration energy scavenger, manufactured entirely by thick-film construction, has been developed to power autonomous subsystems in an embedded health and useage system. The device is constrained to a 2mm thickness and has been designed for a specific helicopter application. The resulting power output is capable of powering an ‘off-the-shelf’ microcontroller based system

Vibration energy harvesting using the Halbach array

This paper studies the feasibility of vibration energy harvesting using a Halbach array. A Halbach array is a specific arrangement of permanent magnets that concentrates the magnetic field on one side of the array while cancelling the field to almost zero on the other side. This arrangement can improve electromagnetic coupling in a limited space. The Halbach array offers an advantage over conventional layouts of magnets in terms of its concentrated magnetic field and low-profile structure, which helps improve the output power of electromagnetic energy harvesters while minimizing their size. Another benefit of the Halbach array is that due to the existence of an almost-zero magnetic field zone, electronic components can be placed close to the energy harvester without any chance of interference, which can potentially reduce the overall size of a self-powered device. The first reported example of a low-profile, planar electromagnetic vibration energy harvester utilizing a Halbach array was built and tested. Results were compared to ones for energy harvesters with conventional magnet layouts. By comparison, it is concluded that although energy harvesters with a Halbach array can have higher magnetic field density, a higher output power requires careful design in order to achieve the maximum magnetic flux gradient

Analysis of Smartphone Traffic

Smartphones have become the central communication and computing devices in our daily life because of their nearly ubiquitous Internet access through various communication capabilities such as WiFi, 3G, or even 4G networks, their user-friendly interfaces supporting touch and gesture based input, and their numerous applications and games. Operating system (OS) detection, the first step to launch security attacks on a target smartphone, enables an adversary to tailor attacks by exploiting the known vulnerabilities of the target system. We investigate OS identification against smartphones that use encrypted traffic. We evaluate the identification algorithms against collected smartphone traffic. The experiments results show that the algorithms can identify a smartphones OS accurately.https://engagedscholarship.csuohio.edu/u_poster_2014/1033/thumbnail.jp

Probabilistic biases meet the Bayesian brain

Bayesian cognitive science sees the mind as a spectacular probabilistic inference machine. But Judgment and Decision Making research has spent half a century uncovering how dramatically and systematically people depart from rational norms. This paper outlines recent research that opens up the possibility of an unexpected reconciliation. The key hypothesis is that the brain neither represents nor calculates with probabilities; but approximates probabilistic calculations through drawing samples from memory or mental simulation. Sampling models diverge from perfect probabilistic calculations in ways that capture many classic JDM findings, and offers the hope of an integrated explanation of classic heuristics and biases, including availability, representativeness, and anchoring and adjustment

Sampling as a resource-rational constraint

Resource rationality is useful for choosing between models with the same cognitive constraints but cannot settle fundamental disagreements about what those constraints are. We argue that sampling is an especially compelling constraint, as optimizing accumulation of evidence or hypotheses minimizes the cost of time, and there are well-established models for doing so which have had tremendous success explaining human behavior

Improving Output Power of Piezoelectric Energy Harvesters using Multilayer Structures

This paper studies the feasibility of increasing the output power of vibration piezoelectric energy harvesters using multilayer structures. In this study, single-layer, double-layer and triple-layer devices with the same resonant frequency were compared. Two design cases were studied-: In the first case, the overall thickness of all PZT layers is fixed and each PZT layer has the same thickness. In the second case, the thickness of one PZT layer is fixed. The output power of these generators was studied and compared for the conditions where all the PZT layers were connected in parallel and in series. In all cases, the multilayer structure increased the output power over the single layer structure in piezoelectric energy harvesting