Simulation-aided Design of Thread Milling Cutter

AbstractThread milling has become quite popular in recent years as an alternative to tapping or other forms of threading because of diversity and complexity of parts and flexibility of the process in industries such as biomedical applications, aerospace and die-mold manufacturing. Today the design of the tooth profile is, however, predominantly feasible by the expertise and “trial and error” principle. Presented in this paper are a novel methodology to design the tooth profile of the thread mill by comparing the “to-be” thread profile and the “as-is” thread profile which is analyzed by means of NC cutting simulation. The simulation kernel enables to continually subtract the swept volume of thread milling cutter undergoing helical movement from the workpiece and to calculate the virtual workpiece (VWP). Combined with the standardized “to-be” thread profile, the tooth profile of to-be-designed thread mill is adaptively modified until the thread profile on VWP and the “to-be” thread profile become congruent with each other. The proposed methodology could be integrated into CAD/CAM systems

GaIA: Graphical Information Gain based Attention Network for Weakly Supervised Point Cloud Semantic Segmentation

While point cloud semantic segmentation is a significant task in 3D scene understanding, this task demands a time-consuming process of fully annotating labels. To address this problem, recent studies adopt a weakly supervised learning approach under the sparse annotation. Different from the existing studies, this study aims to reduce the epistemic uncertainty measured by the entropy for a precise semantic segmentation. We propose the graphical information gain based attention network called GaIA, which alleviates the entropy of each point based on the reliable information. The graphical information gain discriminates the reliable point by employing relative entropy between target point and its neighborhoods. We further introduce anchor-based additive angular margin loss, ArcPoint. The ArcPoint optimizes the unlabeled points containing high entropy towards semantically similar classes of the labeled points on hypersphere space. Experimental results on S3DIS and ScanNet-v2 datasets demonstrate our framework outperforms the existing weakly supervised methods. We have released GaIA at https://github.com/Karel911/GaIA.Comment: WACV 2023 accepted pape

Topological band-order transition and quantum spin Hall edge engineering in functionalized X-Bi(111) (X = Ga, In, and Tl) bilayer

Functionalized X-Bi bilayers (X = Ga, In, and Tl) with halogens bonded on their both sides have been recently claimed to be the giant topological insulators due to the strong band inversion strengths. Employing the first-principles electronic structure calculation, we find the topological band order transition from the order p-p-s of the X-Bi bilayers with halogens on their both sides to the new order p-s-p of the bilayers (especially for X = Ga and In) with halogen on one side and hydrogen on the other side, where the asymmetric hydrogen bonding simulates the substrate. We further find that the p-s bulk band gap of the bilayer bearing the new order p-s-p sensitively depends on the electric field, which enables a meaningful engineering of the quantum spin Hall edge state by controlling the external electric field. © 2016 The Author(s).1

Molecular adsorption at solid/liquid interfaces using self-assembled monolayer films

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999.Includes bibliographical references.Many areas of technology rely on interfacial events that are controlled by nanometer-level interactions present at solid/liquid interfaces. Properties of wetting, corrosion inhibition, and molecular recognition provide convenient examples. To investigate such interactions at the molecular level, self-assembled monolayers (SAMs) have been employed as a model system as they offer the ability to produce well-defined organic surfaces of controlled composition. This thesis addresses the development and characterization of such films for controlling the adsorptive properties of surfaces toward various surfactant-like molecules and for proteins. Adsorption is controlled to facilitate the organized assembly of molecular precursors, retard the non-specific adsorption of proteins, provide a specificity for the adsorption of select proteins, and the use of molecular adsorption to generate local surface energy gradients useful for directing self propelled drop movement. A common theme in these studies is the importance of controlling the energetics and compositions of surfaces at the molecular level to influence microscopic events that translate into macroscopically observable changes in behavior. The first part of this thesis details the formation of monolayer films by the solution-phase adsorption of n-alkyl-chained adsorbates [CH 3(CH2)~ Y] onto the polar surfaces of terminally substituted SAMs [Au/S(CH)mX]. The polar tail groups (X and Y) of the adsorbate and SAM included amine, carboxylic acid, and amide groups, and the formation of the adsorbed monomolecular films on the SAMs relied on non-covalent interactions between X and Y. Highly organized monomolecular adlayers could be produced that were as densely packed as the alkanethiolate SAMs on gold comprising the first layer. This thesis also used this molecular adsorption process to cause liquid drops to move spontaneously on surfaces by creating local changes in surface energy. The drops could be directed to move along specified paths using patterned substrates that contained inner tracks of polar functionality and exterior domains of oleophobic methyl groups. The adsorption process allowed sequential transport of two drops on a common track and also regeneration of the initial high energy surface for reuse. The developed system provides an experimental platform for examining reactive flow and offers a novel "pumpless" method for sequentially delivering multiple drops along surfaces and within microfluidic devices. The second part of this thesis discusses various oligo(ethylene glycol)-terminated alkyltrichlorosilanes [C13Si(CH2)11(OCH2CHnX; X = -OCH 3 or -O 2CCH 3, n= 2- 4] that can form robust films on glass and metal oxide surfaces and control the adsorption of proteins. The adsorption of the methyl-capped trichlorosilanes produces densely packed, oriented monolayer films that are 2-3 nm in thickness. The trichlorosilyl group anchors the molecules to the surface, and the resulting film exposes the ethylene glycol units at its surface, as noted by its moderate hydrophilicity. The films are robust with stabilities similar to those of other alkylsiloxane coatings. These oligo(ethylene glycol)-terminated silane reagents produce films that exhibit resistances against the non-specific adsorption of proteins and that are better than for films prepared from octadecyltrichlorosilane. These oligo(ethylene glycol)-siloxane coatings offer performance advantages and could easily provide a direct and superior replacement for protocols that presently use silane reagents to generate hydrophobic, "inert" surfaces. This thesis also discusses the development of an acetate-capped oligo(ethylene glycol)-terminated silane to produce a HO-terminated oligo(ethylene glycol)-based coating on glass and metal oxide surfaces. The HO-termini of these films provide sites for covalently grafting biomolecules to the parent surface. As a demonstration, biotin and mannose moieties were covalently attached to the HO-surfaces to provide a means to induce the specific adsorption of proteins. For these surfaces, the presence of oligo(ethylene glycol) groups reduces the nonspecific adsorption of other competing proteins. The results indicate that the developed systems could offer a strategy to arrange biomolecules selectively on glass and metal oxide surfaces.by Seok-Won Lee.Ph.D

Optical spectroscopic investigation on the coupling of electronic and magnetic structure in multiferroic hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films

We investigated the effects of temperature and magnetic field on the electronic structure of hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films using optical spectroscopy. As the magnetic ordering of the system was disturbed, a systematic change in the electronic structure was commonly identified in this series. The optical absorption peak near 1.7 eV showed an unexpectedly large shift of more than 150 meV from 300 K to 15 K, accompanied by an anomaly of the shift at the Neel temperature. The magnetic field dependent measurement clearly revealed a sizable shift of the corresponding peak when a high magnetic field was applied. Our findings indicated strong coupling between the magnetic ordering and the electronic structure in the multiferroic hexagonal RMnO3 compounds.Comment: 16 pages including 4 figure

High-efficiency Bidirectional Buck-Boost Converter for Residential Energy Storage System

This paper proposes a bidirectional dc-dc converter for residential micro-grid applications. The proposed converter can operate over an input voltage range that overlaps the output voltage range. This converter uses two snubber capacitors to reduce the switch turn-off losses, a dc-blocking capacitor to reduce the input/output filter size, and a 1:1 transformer to reduce core loss. The windings of the transformer are connected in parallel and in reverse-coupled configuration to suppress magnetic flux swing in the core. Zero-voltage turn-on of the switch is achieved by operating the converter in discontinuous conduction mode. The experimental converter was designed to operate at a switching frequency of 40-210 kHz, an input voltage of 48 V, an output voltage of 36-60 V, and an output power of 50-500 W. The power conversion efficiency for boost conversion to 60 V was >= 98.3% in the entire power range. The efficiency for buck conversion to 36 V was >= 98.4% in the entire power range. The output voltage ripple at full load was <3.59 V-p.p for boost conversion (60 V) and 1.35 V-p.p for buck conversion (36 V) with the reduced input/output filter. The experimental results indicate that the proposed converter is well-suited to smart-grid energy storage systems that require high efficiency, small size, and overlapping input and output voltage ranges.11Ysciescopu

Salmonella typhimurium harboring plasmid expressing interleukin-12 induced attenuation of infection and protective immune responses

IL-12 is known to be an essential cytokine which appears to provide protective immunity against intracellular bacteria, such as Salmonella. In this study, we investigated the possibility of developing a vaccine using IL-12 against virulent Salmonella. We used the host defense system activated by cytokine IL-12. The highly virulent Salmonella strain (Salmonella typhimurium UK-1) was transformed with cytokine-expressing plasmids. These live, wild-type pathogens were used as vaccine strains without undergoing any other biological or genetic attenuating processes. The newly developed strains induced partial protection from infections (30-40%). Of note, the interleukin-12 transformed pathogen was safe upon immunization with low doses (103 CFU), induced IgG responses, and stimulated protective immune responses against Salmonella Typhimurium in mice (80-100%). These results suggest that IL-12 induced attenuation of wild-type Salmonella in the host infection stage and vaccine development using the wild-type strain harboring IL-12 secreting plasmids may be considered as an alternative process for intracellular bacterial vaccine development without the inconvenience of time-consuming attenuation processes