MODELING CHAIN PACKING IN COMPLEX PHASES OF SELF-ASSEMBLED BLOCK COPOLYMERS

Block copolymer (BCP) melts undergo microphase seperation and form ordered soft matter crystals with varying domain shapes and symmetries. We study the con- nection between diblock copolymer molecular designs and thermodynamic selection of ordered crystals by modeling features of variable sub-domain geometry filled with individual blocks within non-canonical sphere-like and network phases that together with layered, cylindrical and canonical spherical phases forms “natural forms” of self- assembled amphiphilic soft matter at large. First, we present a model to revise our understanding of optimal Frank-Kasper sphere-like morphologies by advancing the- ory to account for varying domain volumes. We then develop generic approaches to quantify local changes to domain thickness or packing frustration using medial sets and show its application to morphologies with arbitrary domain topologies and sym- metries in both theoretical models and experimental data. We further use medial sets as a proxy for terminal boundaries of blocks within different domains and revise thermodynamic models of BCP assembly in the strong segregation limit. Finally, we use this revised model to study effect of elastic stiffness asymmetry on relaxing packing frustration experienced by BCPs in tubular and matrix domains leading to equilibrium double gyroid network morphology in diblock copolymers

Characterization of Common Videos with Signatures Extracted from Frame Transition Profiles

People have access to a tremendous amount of video nowadays, both on television and Internet. The amount of video that a viewer has to choose from is so large that it is infeasible for a human to go through it all to find a video of interest. Organizing video into categories will make the process of large number of videos much faster and improves the ease of access. A profile created by observing the rate at which the contents of video frame changes helps in categorization of videos in different types. The experiments we conducted on three types of videos (News, Sports, and Music) show that a profile built on a set of frame transition parameter measurements could be applied to automatically distinguish the types of these videos. We have researched a way to automatically characterize videos into their respected video type, such as a news, music, or sports video clips, by comparing the content value transitions among the video frames. The objective of this research is to see if some measurements extracted from frame transitions are used to show the differences between different categories of videos. In other words, we want to see if such kind of values and measurements can be used to tell different kind of videos or the genre of videos, e.g., with respect to the authors. Our program extracts the statistical data from the video frames based on the histograms of the grayscale pixel intensity changes in the frame transitions. A variety of videos were tested to categorize them using the extracted signatures from these frame transition profiles. The signatures extracted presents a problem of classification that can be addressed using the machine learning algorithms. Time complexity of the evaluation is decreased when compared to other methods in video classification as the video is processed in a single step where all the features are extracted and analysis is performed on the obtained signatures. This provides a simple approach in classifying the videos, additional signatures will be extracted to create a more efficient profiling system to better reveal the nature and characteristics of the video categorization

Process Improvement by Lean Thinking in Trucking Industry

Manufacturing industries with complex production systems are struggling with designing optimal process to increase throughput. Companies will require high amount of labor and process improvement resources to sustain growth and delivery quality products to its customers. A chain of value added activities when designed and deployed with help of lean based methodologies can create high efficiency process. In this paper we have studies and implemented value added process based on the lean manufacturing methodologies which was adapted on the shop floor. In many traditional truck body production industries have facing many problems like low production rate, big lead times, material flow issues, nonlinear layout, late customer delivery and low quality. To address this problems, a mythology has been designed with implementing process techniques for low efficiency work stations. This study and implementation is conducted in crucial bottle neck areas. Tools used to conduct this study are time analysis, motion analysis, Standard working procedure (SWP), value stream analysis, 5S, Value layout, and bottleneck analysis. The value process implementation has converted production of two truck per day to three truck per day. Increase in production rate, quality and customer delivery have been witness when process is implemented and sustained

Medial packing and elastic asymmetry stabilize the double-gyroid in block copolymers

Triply-periodic networks are among the most complex and functionally valuable self-assembled morphologies, yet they form in nearly every class of biological and synthetic soft matter building blocks. In contrast to simpler assembly motifs – spheres, cylinders, layers – networks require molecules to occupy variable local environments, confounding attempts to understand their formation. Here, we examine the double-gyroid network phase by using a geometric formulation of the strong stretching theory of block copolymer melts, a prototypical soft self-assembly system. The theory establishes the direct link between molecular packing, assembly thermodynamics and the medial map, a generic measure of the geometric center of complex shapes. We show that “medial packing” is essential for stability of double-gyroid in strongly-segregated melts, reconciling a long-standing contradiction between infinite- and finite-segregation theories. Additionally, we find a previously unrecognized non-monotonic dependence of network stability on the relative entropic elastic stiffness of matrix-forming to tubular-network forming blocks. The composition window of stable double-gyroid widens for both large and small elastic asymmetry, contradicting intuitive notions that packing frustration is localized to the tubular domains. This study demonstrates the utility of optimized medial tessellations for understanding soft-molecular assembly and packing frustration via an approach that is readily generalizable far beyond gyroids in neat block copolymers

Stable Frank-Kasper phases of self-assembled, soft matter spheres

Single molecular species can self-assemble into Frank Kasper (FK) phases, finite approximants of dodecagonal quasicrystals, defying intuitive notions that thermodynamic ground states are maximally symmetric. FK phases are speculated to emerge as the minimal-distortional packings of space-filling spherical domains, but a precise quantitation of this distortion and how it affects assembly thermodynamics remains ambiguous. We use two complementary approaches to demonstrate that the principles driving FK lattice formation in diblock copolymers emerge directly from the strong-stretching theory of spherical domains, in which minimal inter-block area competes with minimal stretching of space-filling chains. The relative stability of FK lattices is studied first using a diblock foam model with unconstrained particle volumes and shapes, which correctly predicts not only the equilibrium {\sigma} lattice, but also the unequal volumes of the equilibrium domains. We then provide a molecular interpretation for these results via self-consistent field theory, illuminating how molecular stiffness regulates the coupling between intra-domain chain configurations and the asymmetry of local packing. These findings shed new light on the role of volume exchange on the formation of distinct FK phases in copolymers, and suggest a paradigm for formation of FK phases in soft matter systems in which unequal domain volumes are selected by the thermodynamic competition between distinct measures of shape asymmetry.Comment: 40 pages, 22 figure

Efficient multi channel, 0.2 nJ/bit transmitter with tuning for process variation for biomedical telemetry in the MedRadio band of 401-457MHz, An

2016 Spring.Includes bibliographical references.With the increasing applications of bio-integrated telemetric systems, there is a growing demand for wireless transceivers in these systems to interface with the outside world. The use of wireless transceivers is desirable because they allow complete untethering of medical devices from patients. Applications of the medical devices that have transceivers may include, but not limited to, neuro-prosthetics for stimulation, sensing vital signs, wireless monitoring of neuro chemicals in the brain, wireless endoscopy, and remote medical diagnosis and therapy. The implantable medical devices to introduce impulses to the central nervous system to treat the diseases efficiently and/or to provide relief to pain are usually in the medical implantable communication services band of 401-406 MHz. The spectrum of 401-457 MHz band is called medical device radio communications service (MedRadio) band, was allocated by FCC on secondary basis. There exists various transmitter designs for the MedRadio band aimed at high energy efficiency (i.e. low energy per bit transmitted), as low as 0.16 nJ/bit. A few designs are targeted to work at high dc power transmission efficiency, as high as 22%. But, the existing designs fail to be truly MedRadio-standard complaint with short-comings either in terms of not using all the channels in the MedRadio band, low transmitter efficiency, or low output power emitted. The search for better designs of transmitters that can utilize all the channels with high transmission efficiency and high emitted output power continues. This thesis proposes an efficient multichannel transmitter circuit design in the MedRadio band at 401-457 MHz. The transmitter circuit consists of a multichannel phase locked loop (PLL) with rail to rail quadrature output voltage controlled oscillator (VCO), a low power digital synchronous programmable integer N-divider, bang bang Phase frequency detector (PFD), charge pump and a 3rd order loop filter, a passive mixer and a power amplifier (PA). The VCO of the transmitter is designed to account for process variation. The proposed transmitter uses quadrature phase shift keying (QPSK) modulation scheme to transmit data. The power consumption of the transmitter is 460 µW at the power supply voltage of 1.2 V, and consumes only 0.2 nJ of energy for every bit transmitted in the MedRadio band. The output power emitted by the power amplifier of the transmitter is -10.8 dBm. The transmitter is able to hop through all the 10 channels of 300 kHz bandwidth of each from 402 to 405 MHz, all the 4 channels of 6MHz bandwidth of each from 413 to 457 MHz. The overall global efficiency of the transmitter is 13.9 %. The proposed transmitter meets all the FCC requirements for the MedRadio band. This proposed work is implemented in a 180nm CMOS process. The proposed transmitter working in the MedRadio band consumes only 0.2 nJ/bit compared to 0.65 nJ/bit of the only other MedRadio-band compliant design. The transmitter energy consumption is low at 460 µW and efficiency is high at 13.9% when compared to mW energy consumption and single-digit efficiency achieved by existing designs

Source Data for Block copolymers beneath the surface: measuring and molding complex morphology at the sub-domain scale

https://scholarworks.umass.edu/data/1140/thumbnail.jp

Tracing chirality from molecular organization to triply-periodic network assemblies: Threading biaxial twist through block copolymer gyroids

Chirality transfer from the level of molecular structure up to mesoscopic lengthscales of supramolecular morphologies is a broad and persistent theme in self-assembled soft materials, from biological to synthetic matter. Here, we analyze the mechanism of chirality transfer in a prototypical self-assembly system, block copolymers (BCPs), in particular, its impact on one of the most complex and functionally vital phases: the cubic, triply-periodic, gyroid network. Motivated by recent experimental studies, we consider a self-consistent field model of ABC* triblock copolymers possessing an end-block of chiral chain chemistry and examine the interplay between chirality at the scale of networks in alternating double network phases and the patterns of segmental order within tubular network domains. We show that while segments in gyroids exhibit twist in both polar and nematic segmental order parameters, the magnitude of net nematic twist is generically much larger than polar twist, and more surprising, reverses handedness relative to the sense of polar order as well as the sense of dihedral twist of the network. Careful analysis of the intra-domain nematic order reveals that this unique chirality transfer mechanism relies on the strongly biaxial nature of segmental order in BCP networks and relates the biaxial twist to complex patterns of frame rotation of the principal directors in the intra-domain texture. Finally, we show that this mechanism of twist reversal leads to chirality selection of alternating gyroid networks in ABC* triblocks, in the limit of very weak chirality

Source Data for Medial packing and elastic asymmetry stabilize the double-gyroid in block copolymers

Source code and data for Medial packing and elastic asymmetry stabilize the double-gyroid in block copolymers. Readme included in zip file.https://scholarworks.umass.edu/data/1155/thumbnail.jp

CFD modelling of airborne virus diffusion characteristics in a negative pressure room with mixed mode ventilation

COVID-19 caused by severe acute respiratory syndrome (SARS) has accounted for huge collateral damage and as the virus is spreading faster and faster this study deals with isolation rooms or negative pressure rooms with 12 or more air changes per hour and maintaining a pressure difference of 2.5 pa which can help in reducing the transmission of the virus from affected to not affected persons. ANSI/ASHRAE/ASHE Standard 170–2008 recommendations are followed for hospital applications, to facilitate effective ventilation. These negative pressure rooms prevent the spread of the contaminated particles to the surroundings and by creating a negative pressure in the room whenever the door is opened the atmospheric air is sucked in and not the one which is present inside the room. The Computational fluid dynamics simulations are performed to investigate the diffusion of airbone virus inside a negative pressure room with mixed mode ventilation system. It was identified that the mixed mode ventilation system is more effective in controlling the spread of virus droplets inside the roo