Conventional Assembly Research Articles

Performance Based Simulations for Membrane-based Enclosures

Conventional energy-efficient wall assemblies suffer from thermal bridging and moisture entrapment due to thick insulation cavities and multiple layers of sheathing. The experimental house demonstrates that by combining advanced membrane technology with a tensile enclosure, an assembly with high thermal performance can be produced, while reducing thermal bridging and moisture entrapment The design was informed by modeling thermal and hygrothermal performance using a number of different software tools including the thermodynamic and hygrothermal analysis tools WUFI Passive and WUFI Plus, and the day lighting simulation tool DIVA. Our prototype demonstrated an innovative low U-value wall assembly structure with an insulation system that was quick to install, lightweight, and adjustable to many forms while minimizing thermal bridging and moisture buildup.

Enhanced DC-Operated Electroluminescence of Forwardly Aligned p/MQW/n InGaN Nanorod LEDs via DC Offset-AC Dielectrophoresis.

We introduce an orientation-controlled alignment process of p-GaN/InGaN multiquantum-well/n-GaN (p/MQW/n InGaN) nanorod light-emitting diodes (LEDs) by applying the direct current (DC) offset-alternating current (AC) or pulsed DC electric fields across interdigitated metal electrodes. The as-forwardly aligned p/MQW/n InGaN nanorod LEDs by a pulsed DC dielectrophoresis (DEP) assembly process improve the electroluminescence (EL) intensities by 1.8 times compared to the conventional AC DEP assembly process under DC electric field operation and exhibit an enhanced applied current and EL brightness in the current-voltage and EL intensity-voltage curves, which can be directly used as the fundamental data to construct DC-operated nanorod LED devices, such as LED areal surface lightings, scalable lightings (micrometers to inches) and formable surface lightings. The enhancement in the applied current, the improved EL intensity, and the increased number of forwardly aligned p/MQW/n InGaN nanorods in panchromatic cathodoluminescence images confirm the considerable enhancement of forwardly aligned one-dimensional nanorod LEDs between two opposite electrodes using DC offset-AC or a pulsed DC electric field DEP assembly process. These DC offset-AC or pulsed DC electric field DEP assembly processes suggest that designing for these types of interactions could yield new ways to control the orientation of asymmetric p/MQW/n InGaN diode-type LED nanorods with a relatively low aspect ratio.

Stimuli-Responsive Dipeptide-Protein Hydrogels through Schiff Base Coassembly.

Different from the conventional irreversible covalent conjugations, a simple and efficient dynamic Schiff base covalent assembly is developed to construct the stable and smart dipeptide-protein hydrogels under mild conditions. Diphenylalanine-hemoglobin hydrogel is chosen to investigate the gelation formation process and mechanism. It is found that such assembled dipeptide-protein hydrogels are sensitive to pH variation, and simultaneously the proteins can be released without changing the native secondary structures from the gels. Furthermore, these adaptive hydrogels can encapsulate a series of small molecules, multicomponent proteins, and functional nanoparticles. These versatile hydrogels may find a great potential in bioapplications.

Polymer-entanglement-driven coassembly of hybrid superparamagnetic nanoparticles: Tunable structures and flexible functionalization

In this study, we report a facile and versatile strategy for preparing a type of pH-responsive superparamagnetic hybrid coassemblies featuring a series of controls over the morphology and multi-functionalization simultaneously and efficiently. Via the entanglement interactions, the combine of fixed PEG-b-P4VP modified Fe3O4 NPs (D-Fe3O4@mPEG-b-P4VP) and different well-designed free PEG-b-P4VP, which are analogous to two amphiphiles, contributes these hybrid superstructures with multiple, well-defined morphologies and targeted fluorescent properties. In contrast to other studies, our work overcame several defects (e.g., interior NPs’ randomness, cumbersome assembly parameter adjustment and functionalization) of the conventional assembly of modified inorganic NPs and demonstrated that this coassembly strategy can be used as a versatile tool for the controllable assembly of other NPs or polymers. Finally, taking the coassembly C1 as a desirable drug delivery carrier, good biocompatibility and pH-triggered drug release were successfully verified. The current study indicated that these magnetic coassemblies are promising as multifunctional and multipurpose carriers in biological, medical, catalytic, and coating applications.

THE EFFECT OF TWO MANDIBULAR CLASS I REMOVABLE PARTIAL DENTURE DESIGNS ON THE PERIODONTAL HEALTH OF THE ABUTMENT TEETH: A RANDOMIZED SPLIT-MOUTH CLINICAL TRIAL

The aim of this study was to assess the effect of RPI direct retainer designs in mandibular Kennedy’s class I removable partial denture cases, on the periodontal conditions of their abutment teeth.Materials and methods: A total of 10 systemically healthy Patients were selected with mandibular Kennedy class I with symmetrical healthy periodontium at first premolar abutments split mouth mandibular class I removable partial denture designs RPI, I-bar (Rest, proximal plate and I bar) in one side (side A) and a modified RPI clasp assembly (Rest, proximal plate connected by lingual bracing arm to the rest and I Bar) in other side (side B) were constructed. Clinical evaluation(gingival index, pocket depth and clinical attachment loss) and recording of GCF levels of Interlukin1s IL1 –β using ELISA were carried out for all patients at base line (time of denture insertion), 3 months and 6 months after denture insertion at mandibular free end saddle abutments.Results: A statistically significant increase in the mean IL-1s levels after 3 months with further significant increase after 6 months was recorded in both sides (P ≤ 0.05) further, side B showed a statistically increased IL-β levels compared to side A. Regarding clinical parameters, side B showed a statistical significant increase at 6 months compared to side A regarding PD with no significant difference between the 2 sides at 3 months ,as for CAL and GI, although side B showed an increased readings in 6 months and 3 months compared to side A, a non significant difference was recorded between the 2 sides, as well, a non significant change in GI and CAL was recorded in both sides over the study period .Conclusion: within the limitation of our study, the modified RPI clasp induced increasing of proinflammatory cytokines IL- 1s levels in GCF compared conventional RPI clasp assembly. Both Clasp designs have an effect on periodontal health of free end saddle’s partial denture abutments.

The dynamics of a complex machine assembly: Vibration-induced drag on the rotation

An engineering system of complex real machine assembly is considered that, in contrast to a conventional assembly, has additional degrees of freedom. These degrees of freedom are considered to be latent, i.e., those that modify the dynamics of the basic degree of freedom on average. According to this approach, the authors obtained an averaged equation that has the form of a classical equation of a simple real assembly, but contains an additional moment of load that considers resonance phenomena. The derivation of the equation is exemplified by a vehicle that moves along an uneven road.

A Productivity Improvement of an Assembly Line through Line Balancing and Automated Work-Part Feeder

The purpose of this paper is to improve line productivity using line balancing technique and a reduction of work variation using an automated part feeder. This is due to the fact that the conventional assembly line manually feeds a part on to the production line by a worker. The feeding cycle is not constant and varies from time to time. Thus, the production rate is not constant and varied by the worker feeding speed. In addition, the assembly line itself does not fully balance. The operation time of each station is not well designed; as a result, all of the stations but the bottle-neck one experience an idle time. The balance efficiency is only at 40.33 percent which means that 59.67 percent of the total production time is balanced delay. Once the automated feeding machine which a buffer is designed and implemented. The cycle time can be set at 6 sec. and with the line balance technique the operator can be reduced from 11 to 9 persons. As a result, the productivity is substantially increasing around 138 percent and the new balance efficiency is 85.12 percent.

Mechanical connections of the precast concrete columns with detachable metal plates

SummaryThe aim of this study is to develop laminated metal plates for a moment connection of the precast concrete columns. Metal plates were proposed as a time‐ and cost‐saving alternative to conventional monolithic cast‐in‐place joints for connecting precast concrete frames. This study investigated the possibility of using mechanical joints for the connections of both steel‐concrete composite precast frames and reinforced concrete precast frames. A full erection test of precast columns connected with laminated metal plates was performed to demonstrate the efficiency and simplicity of the proposed method. It was shown that the use of the novel mechanical joints with steel plates significantly reduces construction time compared with the conventional monolithic assembly. The total precast column assembly time was approximately 10–20 min, eliminating pour forms and curing times required for the conventional concrete frames. This study also presents an analytical modeling of the proposed connection for multibay precast frames to explore the strains and stress exerted on the joints.

Self-Assembly of Polymer Nanostructures through Halogen Bonding Interactions of an Iodoperfluoroarene-Functionalized Polystyrene Derivative

A structurally novel iodoperfluoroarene-substituted polystyrene has been synthesized, and its noncovalent halogen bonding interactions with polymeric Lewis bases have been studied. RAFT polymerization was used to generate halogen bond donating polystyrene derivatives with low dispersities. Coassembly of the halogen bond donor polymer with an amine-functionalized methacrylate block copolymer was achieved using a solvent switching protocol and studied by electron microscopy and dynamic light scattering analysis. The structures obtained include spheres, wormlike structures, and vesicles as well as “inverted” morphologies such as hexagonally packed hoops and bicontinuous structures, which have been challenging to access by conventional assembly methods. The ability to access such inverted structures suggests that complexes generated by noncovalent interactions between complementary macromolecules can display high effective packing parameters, giving rise to behavior that has generally required unconventional ...

A circumferentially non-uniform fuel model and its application to thermal-hydraulic code

In the fuel assemblies in reactor core, the distribution of temperature is not uniform in the fuel rod along the circumferential direction. The circumferential temperature difference could be neglected for conventional assembly design but increases significantly in a tight lattice. To investigate the circumferential non-uniformity of heat transfer in rod bundles, this paper firstly establishes mathematical model and makes theoretical analyses, based on which influential non-dimensional numbers are summarized. Then, a semi-empirical correlation describing this phenomenon is proposed based on theoretical results and CFD sensitivity analyses. Finally, a three-dimensional model for cylindrical fuel is introduced in the thermal-hydraulic code to predict circumferential heat transfer non-uniformity in different geometry and flow conditions. To validate this model, some results are compared with experimental data of bundle test for subcritical and supercritical water. The three-dimensional fuel model for sub-channel code is a new numerical tool to predict the peak cladding and fuel temperature and can be applied in thermal-hydraulic analysis of fuel assemblies of tight lattice design. Copyright © 2017 John Wiley & Sons, Ltd.

Numerical and experimental study of free convection on wire-bonded QFN64b electronic package

PurposeThe wire-bonded version of the quad flat non-lead with 64 leads (QFN64b) is increasingly integrated in modern arrangements, given its thermal and electrical characteristics suited for specific applications. Temperature control is thus essential for its proper operation, particularly when the heat exchange with the environment is done by natural convection. This work aims to consider a conventional assembly consisting of a large printed circuit board (PCB) on which is welded a QFN64b generating a power in the range 0.01-0.1 W. The PCB could be inclined at an angle varying between 0° and 90° (horizontal and vertical positions, respectively) according to the intended application.Design/methodology/approachThe 3D numerical approach done by means of the finite volume method is complemented by thermal and electrical measurements for all the configurations numerically processed. The low deviations obtained between the calculations and the measurements validate the adopted model. These results complement recent work that considers the same assembly equipped with a tilted and low-powered QFN64 basic model subjected to free convection.FindingsThe surface temperature in any part of the assembly has been determined. The influence of the power generated by the device and the PCB’s inclination angle relative to the gravity field have been quantified. The work shows that the radiative heat transfer is negligible given the temperatures reached and that the thermal state of the considered assembly is different from the one equipped with the QFN64 basic model. The QFN’s temperature is lowered, while that of the PCB is increased. The temperature distribution is also different from that of assemblies equipped with other QFN models with and without wire-bonding.Originality/valueThe correlations proposed in this survey help optimize the thermal design of the QFN64b electronic package used in many engineering fields.

Tuneable superradiant thermal emitter assembly

Superradiance is a signature effect in quantum photonics that explains the collective enhancement of emission power by a factor of ${N}^{2}$ when $N$ emitters are placed in subwavelength proximity. Although the effect is inherently transient, successful attempts have been made to sustain it in the steady-state regime. Until recently, the effects of superradiance were not considered to be applicable to thermal emitters due to their intrinsic incoherent nature. Novel nanophotonic thermal emitters display favorable coherent characteristics that enable them to obey principles of superradiance. However, published analytical work on conventional superradiant thermal emitter assemblies shows an anomalous power scaling of $1/N$, and therefore increasing the number of thermal emitters leads to a degeneration of power at resonance. This phenomenon immediately renders the effect of thermal superradiance futile since it cannot outperform noncoupled emitters in the steady-state regime. We propose an alternative assembly of thermal emitters with specific features that improves the power scaling while maintaining the effects of superradiance. In essence, we show that our emitter assembly achieves superior power delivery over conventional noncoupled emitter systems at resonance. Additionally, this assembly has the ability to be tuned to operate at specific resonant frequencies, which is a vital requirement for applications such as photothermal cancer therapy.

(Invited) Opportunities for Additive Manufacturing of Membraneless Electrolysis Devices

3D printing technology has a tremendous potential to transform how electrochemical devices and products are manufactured. This opportunity is particularly rich for water electrolysis devices, or electrolyzers, which are used to produce hydrogen (H2) fuel from water and electricity. In this work, we explore how 3D printing can simplify the fabrication of low-cost electrolysis devices by significantly reducing the number of parts and associated device assembly. These efforts are focused on membraneless electrolyzers based on angled mesh flow-through electrodes, which are a substantial departure from conventional membrane-electrode assembly (MEA) and alkaline electrolyzer architectures. Membranes and dividers can be costly, prone to fouling and mechanical failure, and constrain the pH range of operation. Recently, our group has demonstrated 3D printed membraneless electrolyzers that separate the O2 and H2 product species using flowing electrolyte and contain as few as three parts. [1] In this presentation, we present new 3D printed electrolyzer and photovoltaic (PV)-electrolyzer designs that achieve high product purity using buoyancy-induced product separation that obviates the need for actively pumped electrolyte. As a part of this talk, we highlight challenges and opportunities for commercially viable 3D printed membraneless electrolyzers. [1] O’Neil G. D., Christian C. D., Brown D. E. and Esposito D. V. 2016 Hydrogen Production with a Simple and Scalable Membraneless Electrolyzer J. Electrochem. Soc. 163 3012–9

Thermal state of electronic assemblies applied to smart building equipped with QFN64 device subjected to natural convection

The performance and reliability of electronic components and assemblies strongly depend on their thermal state. The knowledge of the temperature distribution throughout the assembly is therefore an essential element to ensure their correct operation. This is the main objective of this work that examines the case of a conventional assembly equipped with a quad flat non-lead QFN64 subjected to free convection. This active electronic package is welded on a PCB which may be inclined by an angle varying between 0° and 90° (horizontal and vertical positions respectively) and generates during its operation a high power ranging from 0.1 to 1W. Thermoregulation of the assembly is ensured by natural convection, given its many well known advantages in this engineering field. Accurate relationships are proposed to determine the temperature on different areas of the device and the PCB. They are determined by means of a 3D numerical approach based on the finite volume method confirmed by measurements on an actual installation. These relationships allow reliability improvement of these electronic assemblies that are widely used in many engineering fields such as computing industry, mobile telephony, home automation, automotive, embarked electronics and the smart building applications considered in this work. The present survey complements a recent study which quantifies the natural convective heat transfer on the considered electronic assembly equipped with the QFN64 device, for the same power range and angle of inclination.

Highly-Efficient Self-Compact Monopulse Antenna System With Integrated Comparator Network for RF Industrial Applications

A highly-efficient monopulse antenna system is proposed for radar tracking system application. In this study, a novel integrated front-end and back-end complicated three-dimensional (3-D) system is realized practically to achieve high-level of self-compactness. A wideband and compact monopulse comparator network is developed and integrated as the back-end circuit in the system. Performance of the complete monopulse system is verified together with the front-end antenna array. To ensure the system's electrical efficiency and mechanical strength, a 3-D metal-direct-printing technique is utilized to fabricate the complicated structure, avoiding drawbacks from conventional machining methods and assembly processes. Experimental results show the monopulse system can achieve a bandwidth of 12.9% with VSWR less than 1.5 in the Ku-band, and isolation is better than 30 dB. More than 31.5 dBi gain can be maintained in the sum-patterns of wide bandwidth. The amplitude imbalance is less than 0.2 dB and null-depths are lower than −30 dB in the difference-patterns. In particular, with the help of the metal-printing technique, more than 90% efficiency can be retained in the monopulse system. It is a great improvement compared with that obtained from traditional machining approaches, indicating that this technique is promising for realizing high-performance RF intricate systems electrically and mechanically.

Chemiresistive properties regulated by nanoscale curvature in molecularly-linked nanoparticle composite assembly.

Interparticle spatial properties influence the electrical and functional properties of nanoparticle-structured assemblies. This report describes the nanoscale curvature-induced change in chemiresistive properties of molecularly-linked assemblies of gold nanoparticles on multiwalled carbon nanotubes, which are exploited for sensitive detection of volatile organic compounds. In addition to using linking/capping molecules to define interparticle spatial distances, the nanoscale curvature radius of the carbon nanotubes provides intriguing tunability of the interparticle spatial properties to influence electrical properties, which contrast with those observed for nanoparticle thin films assembled directly on chemiresistor devices. The electrical characteristics of the nanoparticle-nanotube composite give positive response profiles for the vapor molecules that are distinctively different to those observed for conventional nanoparticle thin-film assemblies. The dominant effect of electron coupling on overall chemiresistive properties is shown in relation to that of nanoscale curvature radius on the nanoparticle thin-film sensing properties. Sensing data are also further assessed in correlation with the solubility parameters of the vapor molecule. These findings have significant implications for the design of sensitive interfaces with nanocomposite-structured sensing materials and microfabricated chemiresistor devices.

Catalyst morphology matters for lithium–oxygen battery cathodes

The effectiveness of using catalyst nanoparticles to reduce the overpotential and energy efficiency of lithium–oxygen (or lithium–air) batteries (LOBs) is usually attributed to the inherent catalytic properties of individual nanoparticles. Here, we demonstrate that the morphology of the catalyst layer is equally important in maintaining integrity of the catalyst coating during product formation in LOBs. We demonstrate this by comparing the performance of smooth, conformal coated Mn2O3 catalyst nanoparticles prepared by electric field-assisted deposition, and more irregular coatings using conventional film assembly techniques both on three-dimensional mesh substrates. Smooth coatings lead to an improved overpotential of 50 mV during oxygen reduction and 130 mV during oxygen evolution in addition to a nearly 2X improvement in durability compared to the more irregular films. In situ electrochemical impedance spectroscopy combined with imaging studies elucidates a mechanism of morphology-directed deactivation of catalyst layers during charging and discharging that must be overcome at practical electrode scales to achieve cell-level performance targets in LOBs.

Potentials for Energy Saving and Quality Improvement of Assembly Presses Using Data Mining

Modern assembly lines are usually optimized towards output and tact time as well as process capability and quality. Yet, approaches for energy saving are hardly used in assembly presses. Therefore, assembly lines are using more electric power and compressed air than necessary. Especially at high load, during handling phases and in different idle modes there is a huge potential for energy savings. Current research is focusing on high-power consuming turning and milling machines as well as laser welding. Energy saving projects usually focus on whole factory halls instead of manufacturing lines and single assembly machines. Therefore, this paper presents a new methodology using a top-down-approach and data mining analysis regarding a conventional assembly press as well as a whole assembly line. Here, relevant information types like process data, quality factors, expenditure of energy per produced part and power consumption are used to generate more insight into chained assembly processes. Various tools like energy analysis, process flow and correlation analysis are used to identify focus stations of a whole assembly line for energy saving projects and quality improvements. This novel holistic approach regards the electrical power and compressed air consumption of each relevant station and its machine components during different operating states as well as its correlations between process data, quality factors and energy consumption. Besides tact-time-analysis of the process, the scheduled and unplanned downtimes of the machine are also regarded. Furthermore, it enables predictions of tool wear and breakdown, quality impacts of supplied parts, as well as energy savings on process and machine level. Due to an increased quality, the material efficiency may rise as well.

Experimental and numerical investigation of coupled microvibration dynamics for satellite reaction wheels

Microvibrations of a satellite reaction wheel assembly are commonly analysed in either hard-mounted or coupled boundary conditions, though coupled wheel-to-structure disturbance models are more representative of the real environment in which the wheel operates. This article investigates the coupled microvibration dynamics of a cantilever configured reaction wheel assembly mounted on either a stiff or flexible platform. Here a method is presented to cope with modern project necessities: (i) need of a model which gives accurate estimates covering a wide frequency range; (ii) reduce the personnel and time costs derived from the test campaign, (iii) reduce the computational effort without affecting the quality of the results. The method involves measurements of the disturbances induced by the reaction wheel assembly in a hard-mounted configuration and of the frequency and speed dependent dynamic mass of the reaction wheel. In addition, it corrects the approximation due to missing speed dependent dynamic mass in conventional reaction wheel assembly microvibration analysis. The former was evaluated experimentally using a previously designed and validated platform. The latter, on the other hand, was estimated analytically using a finite element model of the wheel assembly. Finally, the validation of the coupled wheel-structure disturbance model is presented, giving indication of the level of accuracy that can be achieved with this type of analyses.

An Experimental Framework for Investigating the Hygrothermal Properties of Multi-Functional Wood Fibre and XPS Panels for Residential Buildings

In this paper, an experimental setup developed for an ongoing project to investigate the hygrothermal performance of wall systems under different climate conditions is presented. As a step toward establishing the hygrothermal performance of various wood-frame wall assemblies, this research focuses on field experimentation of two types of multi-functional panels (MFPs), along with a conventional wall assembly, in two different locations in Canada: Vancouver, British Columbia, and Edmonton, Alberta. The three wall assembly types are adjacent to one another along the north- and south-facing walls of the test huts in the two cities. This experiment focuses on the effect of the various ambient weather conditions on the two innovative MFPs and on the conventional wall assembly, and on determining the long-term hygrothermal performance of the tested assemblies; it also establishes the passive solar effect on the south-facing assemblies compared to the corresponding north-oriented assemblies. Both MFPs are fixed on the exterior side of a conventional wood-frame wall assembly. The components of the first MFP are 6.4 mm Oriented Strand Board (OSB), 40 mm wood-fiber insulationäóîan environmentally-friendly and fully recyclable materialäóîand 6.4 mm OSB, while those of the second MFP are 6.4 mm OSB, 25 mm Extruded Polystyrene (XPS) core, and 6.4 mm OSB. Along with the details of the experimental setups, some sample data is presented.