Learning Elastic Constitutive Material and Damping Models

Commonly used linear and nonlinear constitutive material models in deformation simulation contain many simplifications and only cover a tiny part of possible material behavior. In this work we propose a framework for learning customized models of deformable materials from example surface trajectories. The key idea is to iteratively improve a correction to a nominal model of the elastic and damping properties of the object, which allows new forward simulations with the learned correction to more accurately predict the behavior of a given soft object. Space-time optimization is employed to identify gentle control forces with which we extract necessary data for model inference and to finally encapsulate the material correction into a compact parametric form. Furthermore, a patch based position constraint is proposed to tackle the challenge of handling incomplete and noisy observations arising in real-world examples. We demonstrate the effectiveness of our method with a set of synthetic examples, as well with data captured from real world homogeneous elastic objects.     

Book reviews

The Annals of Regional Science -     

THE IMPLICATIONS OF ENERGY AND OTHER INPUT USE FOR CONSERVATION TILLAGE

An important issue with regard to the overall effectiveness of conservation tillage practices in reducing the impact of agricultural production on the environment concerns what happens to energy, pesticide and fertilizer use as these practices are more extensively adopted. To gain some insight into this, the conservation tillage adoption decision is modelled. Starting with the assumption that the conservation tillage adoption decision is a two step procedure — the first is the decision whether or not to adopt a conservation tillage production system and the second is the decision on the extent to which conservation tillage should be used — appropriate models of the Cragg and Heckman (dominance) type are estimated. Based on farm-level data on corn production in the United States for 1987, the profile of a farm on which conservation tillage was adopted is that the cropland had above average slope and experienced above average rainfall, the farm was a cash grain enterprise, and had an above average expenditure on pesticides, a below average expenditure on energy and a below average expenditure on custom pesticide applications. Additionally, for a farm adopting a no-tillage production practice, an above average expenditure was made on fertilizer. © 1997 by John Wiley and Sons, Ltd., Int. J. Energy Res., vol. 21, 429–446 (1997)     

The impact of the proposed reduction in the motor fuels excise tax in the United States

The analysis in this paper examines the impact of reducing the excise tax on gasoline and diesel fuel on the United States economy. The analytical approach used in the analysis consists of a computable general equilibrium model composed of fourteen producing sectors, fourteen consuming sectors, six household categories classified by income and a government. The effects of a 4·3 cents per gallon reduction in the excise tax on gasoline and diesel fuel on prices and quantities are examined. The results suggest, for example, a decrease in the tax would result in higher output by the producing sectors (by about $2·86 billion), a expansion in the consumption of goods and services (by about $3·48 billion), and an increase in welfare (by about $3·59 billion). The government would realize a decrease in revenue of about $2·37 billion. When subjected to a sensitivity analysis, the results are reasonably robust with regard to the assumption of the values of the substitution elasticities. © 1997 John Wiley & Sons, Ltd.     

Experimental validation of an optimization formulation of the human grasping quality sense

An experimental procedure that evaluates the quality of a grasp is developed. In this procedure human subjects grasp a rigid object that is subjected to an external load. Three formulations that capture the sense of grasping quality through the energy level stored in the gripper, maximum value of the applied finger forces, and through the distribution of the grasping forces are considered. The applied finger forces are measured and the quality values of the grasp based on these three different formulations are computed. These grasping quality values are compared with numerical human assessments, that are obtained via a psychophysical magnitude estimation method. We derive an augmented weighted functional that combines these three formulations, and show that it exhibits a high correlation with human quality assessment. Our results demonstrate that the most dominant mechanism that characterizes the quality of a rigid body grasp is the uniformity level of the contact forces. © 1997 John Wiley & Sons, Inc.     

Quantum information processing in self-assembled crystals of cold polar molecules

We discuss the implementation of quantum gate operations in a self-assembled dipolar crystal of polar molecules. Here qubits are encoded in long-lived spin states of the molecular ground state and stabilized against collisions by repulsive dipole–dipole interactions. To overcome the single site addressability problem in this high density crystalline phase, we describe a new approach for implementing controlled single and two-qubit operations based on resonantly enhanced spin–spin interactions mediated by a localized phonon mode. This local mode is created at a specified lattice position with the help of an additional marker molecule such that individual qubits can be manipulated by using otherwise global static and microwave fields only. We present a general strategy for generating state and time dependent dipole moments to implement a universal set of gate operations for molecular qubits and we analyze the resulting gate fidelities under realistic conditions. Our analysis demonstrates the experimental feasibility of this approach for scalable quantum computing or digital quantum simulation schemes with polar molecules.     

Shallow circuits and concise formulae for multiple addition and multiplication

A theory is developed for the construction of carry-save networks with minimal delay, using a given collection of carry-save adders each of which may receive inputs and produce outputs using several different representation standards.The construction of some new carry-save adders is described. Using these carry-save adders optimally, as prescribed by the above theory, we get {, , }-circuits of depth 3.48 log₂ n and {, , }-circuits of depth 4.95 log₂ n for the carry-save addition ofn numbers of arbitrary length. As a consequence we get multiplication circuits of the same depth. These circuits put out two numbers whose sum is the result of the multiplication. If a single output number is required then the depth of the multiplication circuits increases respectively to 4.48 log₂ n and 5.95 log₂ n.We also get {, , }-formulae of sizeO (n ^3.13) and {, }-formulae of sizeO (n ^4.57) for all the output bits of a carry-save addition ofn numbers. As a consequence we get formulae of the same size for the majority function and many other symmetric Boolean functions.     

Intrusion detection for mobile devices using the knowledge-based, temporal abstraction method

In this paper, a new approach for detecting previously unencountered malware targeting mobile device is proposed. In the proposed approach, time-stamped security data is continuously monitored within the target mobile device (i.e., smartphones, PDAs) and then processed by the knowledge-based temporal abstraction (KBTA) methodology. Using KBTA, continuously measured data (e.g., the number of sent SMSs) and events (e.g., software installation) are integrated with a mobile device security domain knowledge-base (i.e., an ontology for abstracting meaningful patterns from raw, time-oriented security data), to create higher level, time-oriented concepts and patterns, also known as temporal abstractions. Automatically-generated temporal abstractions are then monitored to detect suspicious temporal patterns and to issue an alert. These patterns are compatible with a set of predefined classes of malware as defined by a security expert (or the owner) employing a set of time and value constraints. The goal is to identify malicious behavior that other defensive technologies (e.g., antivirus or firewall) failed to detect. Since the abstraction derivation process is complex, the KBTA method was adapted for mobile devices that are limited in resources (i.e., CPU, memory, battery). To evaluate the proposed modified KBTA method a lightweight host-based intrusion detection system (HIDS), combined with central management capabilities for Android-based mobile phones, was developed. Evaluation results demonstrated the effectiveness of the new approach in detecting malicious applications on mobile devices (detection rate above 94% in most scenarios) and the feasibility of running such a system on mobile devices (CPU consumption was 3% on average).