Conventional Assembly Research Articles

Adjusting the Ion Permeability of Polyelectrolyte Multilayers through Layer-by-Layer Assembly under a High Gravity Field.

The layer-by-layer (LbL) assembled multilayer has been widely used as good barrier film or capsule due to the advantages of its flexible tailoring of film permeability and compactness. Although many specific systems have been proposed for film design, developing a versatile strategy to control film compactness remains a challenge. We introduced the simple mechanical energy of a high gravity field to the LbL assembly process to tailor the multilayer permeability through adjusting film compactness. By taking poly(diallyldimethylammonium chloride) (PDDA) and poly{1-4[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl sodium salt} (PAzo) as a model system, we investigated the LbL assembly process under a high gravity field. The results showed that the high gravity field introduced effectively accelerated the multilayer deposition process by 20-fold compared with conventional dipping assembly; the adsorption rate was positively dependent on the rotating speed of the high gravity equipment and the concentration of the building block solutions. More interestingly, the film compactness of the PDDA/PAzo multilayer prepared under the high gravity field increased remarkably with the growing rotational speed of the high gravity equipment, as demonstrated through comparisons of surface morphology, cyclic voltammetry curves, and photoisomerization kinetics of PDDA/PAzo multilayers fabricated through the conventional dipping method and through LbL assembly under a high gravity field, respectively. In this way, we have introduced a simple and versatile external form of mechanical energy into the LbL assembling process to improve film compactness, which should be useful for further applications in controlled ion permeability, anticorrosion, and drug loading.

Uncertainty Analysis of Static Plane Problems by Intervals

We present a new interval-based formulation for the static analysis of plane stress/strain problems with uncertain parameters in load, material and geometry. We exploit the Interval Finite Element Method (IFEM) to model uncertainties in the system. Overestimation due to dependency among interval variables is reduced using a new decomposition strategy for the structural stiffness matrix and the nodal equivalent load vector. Primary and derived quantities follow from minimization of the total energy and they are solved simultaneously and with the same accuracy by means of Lagrangian multipliers. Two different element assembly strategies are introduced in the formulation: one is Element-by-Element, and the other resembles conventional assembly. In addition, we implement a new variant of the interval iterative enclosure method to obtain outer and inner solutions. Numerical examples show that the proposed interval approach guarantees to enclose the exact system response.

Evaluation of Shear Resistance of Bolted Connections in Wood/Wood and Wood/Steel Plate/Wood

This study was based on the combination of simple and quick techniques to substitute the conventional manufacturing system assembly of metal truss connected by wood structures for free environments and less movement. Although simple in its use, the bolted connections are extremely complex in their analysis and behavior. The study was based on evaluating bolted wood/wood and wood/wood with a metal divider interface connections, just to observe the strength of the set's performance under real loads of support coming from the roof elements of the work. Load tests to evaluate the shear behavior nonlinear of the connecting bolts were carried out with loads until 10 ton. On prototypes previously dimensioned according to NBR 6120 to determination of the values of the loads, with two, three and four bolts of the type SAE J 429 grade 5. It was observed that the insertion of a metal plate between the pieces of wood increased by about 50% in the shear strength of the connection. The models A1 and B1, with two bolts with or without plate, were the ones with least resistance, while with three bolts were most loads resisted. Simulations with FEMAP-Finite Element Modeling and Post-processing/NASTRAN were performed for comparison.

High power pulsed magnetron sputtering: A method to increase deposition rate

High power pulsed magnetron sputtering (HPPMS) is a state-of-the-art physical vapor deposition technique with several industrial applications. One of the main disadvantages of this process is its low deposition rate. In this work, the authors report a new magnetic field configuration, which produces deposition rates twice that of conventional magnetron's dipole magnetic field configuration. Three different magnet pack configurations are discussed in this paper, and an optimized magnet pack configuration for HPPMS that leads to a higher deposition rate and nearly full-face target erosion is presented. The discussed magnetic field produced by a specially designed magnet assembly is of the same size as the conventional magnet assembly and requires no external fields. Comparison of deposition rates with different power supplies and the electron trapping efficiency in complex magnetic field arrangements are discussed.

Materials and characterization techniques for high-temperature polymer electrolyte membrane fuel cells.

The performance of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC) is critically dependent on the selection of materials and optimization of individual components. A conventional high-temperature membrane electrode assembly (HT-MEA) primarily consists of a polybenzimidazole (PBI)-type membrane containing phosphoric acid and two gas diffusion electrodes (GDE), the anode and the cathode, attached to the two surfaces of the membrane. This review article provides a survey on the materials implemented in state-of-the-art HT-MEAs. These materials must meet extremely demanding requirements because of the severe operating conditions of HT-PEMFCs. They need to be electrochemically and thermally stable in highly acidic environment. The polymer membranes should exhibit high proton conductivity in low-hydration and even anhydrous states. Of special concern for phosphoric-acid-doped PBI-type membranes is the acid loss and management during operation. The slow oxygen reduction reaction in HT-PEMFCs remains a challenge. Phosphoric acid tends to adsorb onto the surface of the platinum catalyst and therefore hampers the reaction kinetics. Additionally, the binder material plays a key role in regulating the hydrophobicity and hydrophilicity of the catalyst layer. Subsequently, the binder controls the electrode–membrane interface that establishes the triple phase boundary between proton conductive electrolyte, electron conductive catalyst, and reactant gases. Moreover, the elevated operating temperatures promote carbon corrosion and therefore degrade the integrity of the catalyst support. These are only some examples how materials properties affect the stability and performance of HT-PEMFCs. For this reason, materials characterization techniques for HT-PEMFCs, either in situ or ex situ, are highly beneficial. Significant progress has recently been made in this field, which enables us to gain a better understanding of underlying processes occurring during fuel cell operation. Various novel tools for characterizing and diagnosing HT-PEMFCs and key components are presented in this review, including FTIR and Raman spectroscopy, confocal Raman microscopy, synchrotron X-ray imaging, X-ray microtomography, and atomic force microscopy.

NeatFreq: reference-free data reduction and coverage normalization for De Novo sequence assembly.

BackgroundDeep shotgun sequencing on next generation sequencing (NGS) platforms has contributed significant amounts of data to enrich our understanding of genomes, transcriptomes, amplified single-cell genomes, and metagenomes. However, deep coverage variations in short-read data sets and high sequencing error rates of modern sequencers present new computational challenges in data interpretation, including mapping and de novo assembly. New lab techniques such as multiple displacement amplification (MDA) of single cells and sequence independent single primer amplification (SISPA) allow for sequencing of organisms that cannot be cultured, but generate highly variable coverage due to amplification biases.ResultsHere we introduce NeatFreq, a software tool that reduces a data set to more uniform coverage by clustering and selecting from reads binned by their median kmer frequency (RMKF) and uniqueness. Previous algorithms normalize read coverage based on RMKF, but do not include methods for the preferred selection of (1) extremely low coverage regions produced by extremely variable sequencing of random-primed products and (2) 2-sided paired-end sequences. The algorithm increases the incorporation of the most unique, lowest coverage, segments of a genome using an error-corrected data set. NeatFreq was applied to bacterial, viral plaque, and single-cell sequencing data. The algorithm showed an increase in the rate at which the most unique reads in a genome were included in the assembled consensus while also reducing the count of duplicative and erroneous contigs (strings of high confidence overlaps) in the deliverable consensus. The results obtained from conventional Overlap-Layout-Consensus (OLC) were compared to simulated multi-de Bruijn graph assembly alternatives trained for variable coverage input using sequence before and after normalization of coverage. Coverage reduction was shown to increase processing speed and reduce memory requirements when using conventional bacterial assembly algorithms.ConclusionsThe normalization of deep coverage spikes, which would otherwise inhibit consensus resolution, enables High Throughput Sequencing (HTS) assembly projects to consistently run to completion with existing assembly software. The NeatFreq software package is free, open source and available at https://github.com/bioh4x/NeatFreq.Electronic supplementary materialThe online version of this article (doi:10.1186/s12859-014-0357-3) contains supplementary material, which is available to authorized users.

Microvibration analysis of a cantilever configured reaction wheel assembly

This article discusses the microvibration analysis of a cantilever configured reaction wheel assembly. Disturbances induced by the reaction wheel assembly were measured using a previously designed platform. Modelling strategies for the effect of damping are presented. Sine-sweep tests are performed and a method is developed to model harmonic excitations based on the corresponding test results. The often ignored broadband noise is modelled by removing spikes identified in the raw signal including a method of identifying spikes from energy variation and band-stop filter design. The validation of the reaction wheel disturbance model with full excitations (harmonics and broadband noise) is presented and flaws due to missing broadband noise in conventional reaction wheel assembly microvibration analysis are discussed.

Sintering of Frustum Shaped Polycrystalline Diamond Compact at Non-Hydrostatic Pressure

This work present the study of the sintering of polycrystalline diamond compact with hyperbolic truncated cone profile using hexagonal boron nitride assembly, rather than salt mold, which is different from conventional assembly and this kind of polycrystalline diamond compact is widely used in percussion rock bits and roller cone rock bits. The well-sintered polycrystalline diamond compact without transition layer is prepared on a WC-10wt% Co substrate at temperature 1450°C for 3 min at non-hydrostatic high pressure of 5.5Gpa.Different analyzing techniques, such as X- ray diffraction, micro-Raman spectroscopy, scanning electron microscopy were applied to characterize the micro-structure, residual stress and sintering behavior. The SEM analysis indicates that diamond-diamond (D-D) direct bonding had formed in the polycrystalline diamond layer. The Raman spectroscopy shows compressive stress in the polycrystalline diamond layer is much higher than that sintered using traditional assembly.

Manufacturing Readiness of BVA™ Technology for Fine-Pitch Package-on-Package

Ever increasing performance demands in a rapidly evolving smart phone market have led to a need for higher density interconnections linking memory components with logic devices in a standard package on package (PoP) configuration. While existing solutions present a technological roadblock at 350–400μm PoP pitch, new Bond Via Array (BVA™) technology provides a cost effective and scalable alternative that can achieve 240μm and below pitch values while utilizing conventional wirebond package assembly processes and tools. BVA is a high density, ultra-fine pitch package-on-package (PoP) interconnect solution that enables more than 1000 high aspect ratio connections between memory and processor components in a standard outline PoP. This increase significantly improves PoP capability and correspondingly provides increased bandwidth for the next generation of mobile devices. Here we discuss the 1020 IO BVA demonstration test vehicle, associated manufacturing process details, reliability performance and bi-level socket hardware developed to test these wire bond based novel interconnects. Furthermore the overall high volume manufacturing (HVM) readiness state of this technology for PoP applications will be described. The 1020 IO BVA prototype features 5 rows of vertical interconnects at 0.24mm pitch within an industry standard 14 x14mm package footprint. Although BVA interconnects were primarily developed for PoP packages, they offer many benefits over traditional vertical interconnects and can be implemented in a variety of other applications.

Ecological water quality assessment in the Guapiaçu-Macacu hydrographic complex (Rio de Janeiro, Brazil) using multiple indicators

A quick diagnosis of the ecological quality of five sections of the Macacu-Guapiacu hydrographic complex was performed using visual assessment protocol (VAP), conventional analysis, composition and structure of ciliates and the occurrence of benthic macro invertebrates. Water samples were collected from five sampling stations (A-E) in July of 2010. Protists were sampled with aid of artificial substrates, and macro invertebrates were sampled using the multi-habitat method. A total of 22 taxa of protozoa and 51 taxa of macro invertebrates was registered at the five stations. Reference station (A) showed greater protist diversity and higher values of BMWP-CETEC and IBE-IOC indices relating to macro invertebrates. The impacted stations (B and E) presented lower diversity and higher abundance of protozoa, as well as the lowest values for the rates. The four methods used were convergent to diagnose reference station (A), the impacted stations (B and E) and those in intermediate conditions (C and D). Thus, the methods were complementary, as the conventional parameters and ciliate assembly were more sensitive to detecting the increase in organic pollution and VAP and macro invertebrate assembly detected changes in geomorphology and habitat degradation.

Interfacial Modification of Magnetic Montmorillonite (MMT) Using Covalently Assembled LbL Multilayers

Constructing stable and reliable interfaces around pseudo two-dimensional clay materials is a key process in achieving advanced and reliable performance of related composite materials. However, the effective surface modification of pseudo two-dimensional clay has been a challenging research topic. In this study, we have developed an effective and facile method for the interfacial modification of magnetic montmorillonite (MMT) nanocomposite by using covalent layer-by-layer (LbL) assembly. The method involves conventional LbL assembly around the magnetic MMT followed by infiltration of a bifunctional photoactive small molecule and then covalent cross-linking of the LbL multilayers upon UV irradiation. After covalent LbL modification, the nanocomposite presented ample organic species around its interfaces and displayed stable organic interfaces even in extreme solution conditions such as in basic (pH =14) solutions. The covalent cross-linking of the multilayers proved to be indispensable in keeping the LbL multilayers stable around the MMT composites. After modification, the composite particles kept their magnetic properties. In addition, the release profile of the composite particles for methyl blue indicated that the composite particles preserved the capacity to carry loads and release them in retarded speed. This method will potentially integrate the merits of LbL multilayers with MMT to achieve advanced functional materials.

Ligation-based assembly for constructing mouse synthetic scFv libraries by chain shuffling with in vivo-amplified VH and VL fragments

In vitro assembly of two or three PCR fragments using primers is a common method of constructing scFv fragments for display on the surface of phage. However, mismatch annealing often occurs during in this step, leading to cloning and display of incomplete Fab or scFv fragments. To overcome this limitation, we developed a ligation-based two-fragment assembly (LTFA) protocol that involved separately cloning VH and Vκ fragments into the high-copy-number plasmid pUC18. The VH and Vκ fragments had randomized complementarity-determining region 3 (CDR3) and were joined with a peptidyl linker composed of (G4S)3. Using this approach, complete sequences of scFv fragments were successfully constructed, and the sequencing of 83 scFv clones revealed that none of the sequences, including the linker region, contained deletions or mutations. In contrast, linker sequences generated using a conventional two-fragment PCR assembly (TFPA) protocol often contained sequence anomalies, including large truncations. Using the LTFA protocol, a final library size of 1.0×108cfu was achieved. Examination of the amino acid profiles of the generated scFv fragments within the randomized regions introduced using degenerate codons did not detect any bias from that expected based on stochastic distribution. After several cycles of panning with this library, antigen-specific scFvs against two reference antigens, hen egg lysozyme and streptavidin were detected. In addition, scFvs with specificity against peptidyl antigens in the loop region of the Medaka ortholog of human C6orf89, which encodes a histone deacetylase enhancer that interacts with the bombesin receptor, were also obtained. The LTFA protocol developed here is robust and allows for the easy construction of integral scFv fragments compared with conventional TFPA. Utilizing LTFA, other CDRs can be readily combined. This approach also allows for the in vitro maturation of scFv fragments by separately introducing randomization in CDRs or using error-prone PCR for the amplification of pre-selected sequences as a template scaffold.

Experiments with a pressure-driven Stirling refrigerator with flexible chambers

We report on the design and experimental testing of a Stirling refrigerator that uses air as the working fluid, and where the conventional piston-cylinder assemblies are replaced by pressure-driven flexible chambers. The two chambers are periodically compressed by pneumatic actuators resulting in airflow through the regenerator and in a net temperature difference between the chambers. An experimental setup is used to investigate the performance of the refrigerator under different operating conditions with particular attention to actuation frequencies, driving pressure differences, and phase angles between the two inputs. The time constant of the temperature difference between the two chambers is determined, and the temperature difference is measured as a function of the system parameters. The results of several tests conducted under different operating conditions show that the refrigerating effect is very robust and allows good performance even for modulated inputs. The frequency response is radically different from that of a traditional motion-driven device. This work suggests that mechanical to thermal energy conversion devices based on this principle can be successfully powered by human motion.

In vitro method to observe E-selectin-mediated interactions between prostate circulating tumor cells derived from patients and human endothelial cells.

Metastasis is a process in which tumor cells shed from the primary tumor intravasate blood vascular and lymphatic system, thereby, gaining access to extravasate and form a secondary niche. The extravasation of tumor cells from the blood vascular system can be studied using endothelial cells (ECs) and tumor cells obtained from different cell lines. Initial studies were conducted using static conditions but it has been well documented that ECs behave differently under physiological flow conditions. Therefore, different flow chamber assemblies are currently being used to studying cancer cell interactions with ECs. Current flow chamber assemblies offer reproducible results using either different cell lines or fluid at different shear stress conditions. However, to observe and study interactions with rare cells such as circulating tumor cells (CTCs), certain changes are required to be made to the conventional flow chamber assembly. CTCs are a rare cell population among millions of blood cells. Consequently, it is difficult to obtain a pure population of CTCs. Contamination of CTCs with different types of cells normally found in the circulation is inevitable using present enrichment or depletion techniques. In the present report, we describe a unique method to fluorescently label circulating prostate cancer cells and study their interactions with ECs in a self-assembled flow chamber system. This technique can be further applied to observe interactions between prostate CTCs and any protein of interest.

IoT and Cloud Computing in Automation of Assembly Modeling Systems

After the technologies of integrated circuits, personal computers, and the Internet, Internet of Things (IoT) is the latest information technology (IT) that is radically changing business paradigms. However, IoT's influence in the manufacturing sector has yet been fully explored. On the other hand, existing computer-aided software tools are experiencing a bottleneck in dealing with complexity, dynamics, and uncertainties in their applications of modern enterprises. It is argued that the adoption of IoT and cloud computing in enterprise systems (ESs) would overcome the bottleneck. In this paper, the challenges in generating assembly plans of complex products are discussed. IoT and cloud computing are proposed to help a conventional assembly modeling system evolve into an advanced system, which is capable to deal with complexity and changes automatically. To achieve this goal, an assembly modeling system is automated, and the proposed system includes the following innovations: 1) the modularized architecture to make the system robust, reliable, flexible, and expandable; 2) the integrated object-oriented templates to facilitate interfaces and reuses of system components; and 3) the automated algorithms to retrieve relational assembly matrices for assembly planning. Assembly modeling for aircraft engines is used as examples to illustrate the system effectiveness.

DNA Nanoflowers for Multiplexed Cellular Imaging and Traceable Targeted Drug Delivery

AbstractWe present a facile approach to make aptamer‐conjugated FRET (fluorescent resonance energy transfer) nanoflowers (NFs) through rolling circle replication for multiplexed cellular imaging and traceable targeted drug delivery. The NFs can exhibit multi‐fluorescence emissions by a single‐wavelength excitation as a result of the DNA matrix covalently incorporated with three dye molecules able to perform FRET. Compared with the conventional DNA nanostructure assembly, NF assembly is independent of template sequences, avoiding the otherwise complicated design of DNA building blocks assembled into nanostructures by base‐pairing. The NFs were uniform and exhibited high fluorescence intensity and excellent photostability. Combined with the ability of traceable targeted drug delivery, these colorful DNA NFs provide a novel system for applications in multiplex fluorescent cellular imaging, effective screening of drugs, and therapeutic protocol development.

DNA nanoflowers for multiplexed cellular imaging and traceable targeted drug delivery.

We present a facile approach to make aptamer-conjugated FRET (fluorescent resonance energy transfer) nanoflowers (NFs) through rolling circle replication for multiplexed cellular imaging and traceable targeted drug delivery. The NFs can exhibit multi-fluorescence emissions by a single-wavelength excitation as a result of the DNA matrix covalently incorporated with three dye molecules able to perform FRET. Compared with the conventional DNA nanostructure assembly, NF assembly is independent of template sequences, avoiding the otherwise complicated design of DNA building blocks assembled into nanostructures by base-pairing. The NFs were uniform and exhibited high fluorescence intensity and excellent photostability. Combined with the ability of traceable targeted drug delivery, these colorful DNA NFs provide a novel system for applications in multiplex fluorescent cellular imaging, effective screening of drugs, and therapeutic protocol development.

타이어 종류 (Wide Base Tire and Dual Tire Assembly)에 따른 아스팔트 포장 반응 평가

PURPOSES : The first generation of wide base tires introduced in the early 1980s was found to cause a significant increase in pavement damage compared to dual-tire assemblies. However, wide base tires have evolved considerably, and a new generation of wide base tire is thought to be comparable to conventional dual tires for pavement damage. A challenge associated with using wide base tires is the accurate quantification of pavement damage induced by these tires. The objective of this study was to investigate the responses of flexible pavement to continuously moving vehicular loading under various tire configurations. METHODS : The comparison of the strain/stress responses of full-depth pavement caused by conventional dual tire assembly and new generation of wide-base tires was performed. The FE model incorporates linear viscoelasticity of asphalt material and continuous moving load using implicit dynamic analysis. RESULTS AND CONCLUSIONS : The result demonstrates that the new wide-base tires caused slightly more fatigue damage and less primary rutting damage in HMA layer than a dual-tire assembly, but caused more secondary rutting damage in subgrade than a dual tire assembly.

A general strategy for one-step fabrication of one-dimensional magnetic nanoparticle chains based on laser ablation in liquid

Assembly of one-dimensional (1D) magnetic nanoparticle (NP) chains is attractive due to considerable technical demand in new materials and devices. Conventional assemblies are usually divided into two steps: one is the synthesis of NPs and the other is the fabrication of 1D NP chains. Here, we demonstrate a general strategy for fabricating 1D magnetic NP chains within one step, i.e. the magnetic field assisted laser ablation in liquid (MF-LAL), which combines NPs’ synthesis and 1D chains’ fabrication within one step. This is a green and facile LAL-based approach. Using this technique, we assemble 1D chains of submicron cobalt carbide spheres, which are ferromagnetic with anomalous giant magnetizations of 232 emu g−1 at room temperature, the highest reported so far for cobalt-based magnetic nanomaterials. The blocking temperature of the chains is more than 300 K, which is ascribed to the anisotropy of the configuration. We establish a theoretical model to pursue the fabrication of 1D magnetic NP chains, in which the basic physics and chemistry involved in the MF-LAL fabrication are discussed. These findings can guide researchers choosing interesting target and liquid for the assembly of 1D magnetic NP chains for the purpose of fundamental research and potential applications.

Ultrahigh PEMFC Performance of a Thin‐Film, Dual‐electrode Assembly with Tailored Electrode Morphology

A dual-electrode membrane electrode assembly (MEA) for proton exchange membrane fuel cells with enhanced polarization under zero relative humidity (RH) is fabricated by introducing a phase-separated morphology in an agglomerated catalyst layer of Pt/C (platinum on carbon black) and Nafion. In the catalyst layer, a sufficient level of phase separation is achieved by dispersing the Pt catalyst and the Nafion dispersion in a mixed-solvent system (propane-1,2,3-triol/1-methyl-2-pyrrolidinone).The high polymer chain mobility results in improved water uptake and regular pore-size distribution with small pore diameters. The electrochemical performance of the dual-film electrode assembly with different levels of phase separation is compared to conventional electrode assemblies. As a result, good performance at 0 % RH is obtained because self-humidification is dramatically improved by attaching this dense and phase-separated catalytic overlayer onto the conventional catalyst layer. A MEA prepared using the thin-film, dual-layered electrode exhibits 39-fold increased RH stability and 28-fold improved start-up recovery time during the on-off operation relative to the conventional device. We demonstrate the successful operation of the dual-layered electrode comprised of discriminatively phase-separated agglomerates with an ultrahigh zero RH fuel-cell performance reaching over 95 % performance of a fully humidified MEA.