Condensed-phase biogenic–anthropogenic interactions with implications for cold cloud formation

Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil fuel combustion can acquire a coating of SOA. We investigate SOA-soot biogenic-anthropogenic interactions and their impact on ice nucleation in relation to the particles' organic phase state. SOA particles were generated from the OH oxidation of naphthalene, α-pinene, longifolene, or isoprene, with or without the presence of sulfate or soot particles. Corresponding particle glass transition (Tg) and full deliquescence relative humidity (FDRH) were estimated using a numerical diffusion model. Longifolene SOA particles are solid-like and all biogenic SOA sulfate mixtures exhibit a core-shell configuration (i.e. a sulfate-rich core coated with SOA). Biogenic SOA with or without sulfate formed ice at conditions expected for homogeneous ice nucleation, in agreement with respective Tg and FDRH. α-pinene SOA coated soot particles nucleated ice above the homogeneous freezing temperature with soot acting as ice nuclei (IN). At lower temperatures the α-pinene SOA coating can be semisolid, inducing ice nucleation. Naphthalene SOA coated soot particles acted as ice nuclei above and below the homogeneous freezing limit, which can be explained by the presence of a highly viscous SOA phase. Our results suggest that biogenic SOA does not play a significant role in mixed-phase cloud formation and the presence of sulfate renders this even less likely. However, anthropogenic SOA may have an enhancing effect on cloud glaciation under mixed-phase and cirrus cloud conditions compared to biogenic SOA that dominate during pre-industrial times or in pristine areas

Optical nano and micro actuator technology

In Optical Nano and Micro Actuator Technology, leading engineers, material scientists, chemists, physicists, laser scientists, and manufacturing specialists offer an in-depth, wide-ranging look at the fundamental and unique characteristics of light-driven optical actuators. They discuss how light can initiate physical movement and control a variety of mechanisms that perform mechanical work at the micro- and nanoscale. The book begins with the scientific background necessary for understanding light-driven systems, discussing the nature of light and the interaction between light and NEMS/MEMS

Printed Graphene Derivative Circuits as Passive Electrical Filters

The objective of this study is to inkjet print resistor-capacitor (RC) low pass electrical filters, using a novel water-based cellulose graphene ink, and compare the voltage-frequency and transient behavior to equivalent circuits constructed from discrete passive components. The synthesized non-toxic graphene-carboxymethyl cellulose (G-CMC) ink is deposited on mechanically flexible polyimide substrates using a customized printer that dispenses functionalized aqueous solutions. The design of the printed first-order and second-order low-pass RC filters incorporate resistive traces and interdigitated capacitors. Low pass filter characteristics, such as time constant, cut-off frequency and roll-off rate, are determined for comparative analysis. Experiments demonstrate that for low frequency applications (<100 kHz) the printed graphene derivative circuits performed as well as the circuits constructed from discrete resistors and capacitors for both low pass filter and RC integrator applications. The impact of mechanical stress due to bending on the electrical performance of the flexible printed circuits is also investigated

ARCHAEO-SCAN: Portable 3D Shape Measurement System for Archaeological Field Work

Accurate measurement and thorough documentation of excavated artifacts are the essential tasks of archaeological fieldwork. The on-site recording and long-term preservation of fragile evidence can be improved using 3D spatial data acquisition and computer-aided modeling technologies. Once the artifact is digitized and geometry created in a virtual environment, the scientist can manipulate the pieces in a virtual reality environment to develop a realistic reconstruction of the object without physically handling or gluing the fragments. The ARCHAEO-SCAN system is a flexible, affordable 3D coordinate data acquisition and geometric modeling system for acquiring surface and shape information of small to medium sized artifacts and bone fragments. The shape measurement system is being developed to enable the field archaeologist to manually sweep the non-contact sensor head across the relic or artifact surface. A series of unique data acquisition, processing, registration and surface reconstruction algorithms are then used to integrate 3D coordinate information from multiple views into a single reference frame. A novel technique for automatically creating a hexahedral mesh of the recovered fragments is presented. The 3D model acquisition system is designed to operate from a standard laptop with minimal additional hardware and proprietary software support. The captured shape data can be pre-processed and displayed on site, stored digitally on a CD, or transmitted via the Internet to the researcher\u27s home institution

Pneumatic Hyperelastic Actuators for Grasping Curved Organic Objects

Soft robotic grippers often incorporate pneumatically-driven actuators that can elastically deform to grasp delicate, curved organic objects with minimal surface damage. The complexity of the actuator geometry and the nonlinear stress–strain behavior of the stretchable material during inflation make it difficult to predict actuator performance prior to prototype fabrication. In this work, a scalable modular elastic air-driven actuator made from polydimethylsiloxane (PDMS) is developed for a mechanically compliant robotic gripper that grasps individual horticultural plants and fungi during automated harvesting. The key geometric design parameters include the expandable surface area and wall thickness of the deformable structure used to make contact with the target object. The impact of these parameters on actuator displacement is initially explored through simulation using the Mooney–Rivlin model of hyperelastic materials. In addition, several actuator prototypes with varying expandable wall thicknesses are fabricated using a multistep soft-lithography molding process and are inserted in a closed ring assembly for experimental testing. The gripper performance is evaluated in terms of contact force, contact area with the target, and maximum payload before slippage. The viability of the gripper with PDMS actuators for horticultural harvesting applications is illustrated by gently grasping a variety of mushroom caps

An alternative methodology to represent B-spline surface for applications in virtual reality environment

B-spline representation is one of the main methods for free-form surface modeling and has become the standard for CAD systems. However, in Virtual Reality (VR) environment, when a B-spline surface deforms, the blending functions need to be continuously computed. The high computational cost of continuously calculating the blending functions for merging, collision detection and physics-based deformation system, while the model is deforming, restricts the use of B-spline representation in a VR environment. This paper presents an alternative methodology to represent B-spline surface patches for an interactive VR environment. A uniformly discretized B-spline surface patch can be represented by a set of control points and two precalculated B-spline blending matrices. The proposed technique exploits the fact that these B-spline blending matrices are independent of the position of control points and therefore can be pre-calculated. The blending matrices enable the algorithm to merge B-spline surface patches, accurately check the collision, and generate nodes for the mass spring system to determine deformation using the physics-based model. This technique does away with the need to calculate computationally intensive blending functions for the Bspline surfaces, and inverse of large matrices during the run-time.Peer reviewed: YesNRC publication: Ye

B-spline surface based concept design module for applications in virtual reality environment

Over the past decade, B-spline modeling has become the standard mathematical model for representing freeform or organic objects in CAD/CAM systems. Using a Bspline surface to represent the virtual model in a haptic concept design module helps to streamline the exchange of the information with existing CAD/CAM systems. Bspline surfaces also help increase visual realism because these represent continuous surface. At the same time, physically based virtual deformable models provide a sense of realism to the user. However, the algorithms used for interaction with the virtual model should be efficient to maintain acceptable level of virtual realism and perceive the simulation as continuous with no time lag. This paper presents a B-spline surface based concept design framework, which can be used to generate various concepts, evaluate these concepts, and provide user training. The proposed framework assumes that all deformable models are represented as B-spline surfaces. The tools used to interact with the deformable models can be implicit surface, tessellated surface, Bspline surface, or point-based. The technique exploits blending matrices for the Bspline surface that are independent of the control point positions and, hence, can be pre-calculated prior to haptic interaction. Once determined, the pre-calculated blending matrices are used to generate discrete points on the B-spline surface. Mass spring system is used to incorporate material properties to the virtual objects. Practical illustrations of the concept design framework are presented for modeling and evaluation of concepts and provide training to the intended user segment.Peer reviewed: YesNRC publication: Ye