Metal Base Plate Research Articles

Clinical and radiological results of reverse total shoulder arthroplasty with or without lateralization as revision procedure for failed arthroplasty

BackgroundAs reverse total shoulder arthroplasty (rTSA) becomes a common treatment option in the revision setting, common problems associated with Grammont’s design such as scapular notching, instability, and rotator cuff weakening occur. Design changes associated with superior outcomes in primary rTSA, such as glenoid or humeral lateralization have not yet been examined in the revision settings. The purpose of this consecutive series of revision rTSA is to evaluate the clinical and radiological short-term results after aseptic and septic revision rTSA and explore potential benefits of metallic glenoid and humerus lateralization. MethodsIn this study, patients treated with a rTSA between 2014 and 2020 after failed shoulder arthroplasty were included. Fifty-nine consecutive patients were divided into comparative groups using lateralized rTSA with metallic baseplate augmentation (latrTSA) and additional humeral lateralization using a 145° onlay curved stem (bi-latrTSA); or no baseplate offset with a Grammont-type 155° stem (non-latrTSA). Further, outcome of post-infection revision rTSAs was compared to aseptic loosening. Constant-Murley-Score (CS), Subjective-Shoulder-Value (SSV), shoulder range of motion (ROM) including Apley’s scratch test, abduction strength and pain levels were assessed. Radiographs were reviewed for implant loosening, scapular notching, fractures and osteolysis. Lateralization (LSA) and Distalization Shoulder Angle (DSA) were measured at final follow-up. ResultsThirty-eight patients showed significant improvement in all functional measurements at final two-year follow-up compared to baseline (p<0.01). There were no significant differences in favor of glenoid or bipolar lateralization. However, no scapular notching was seen in patients with both humeral and glenoid lateraliazion (non-latrTSA: 33%; latrTSA: 8%; bi-latrTSA: 0%; p=0.103), with no signs of implant loosening. Patients with bi-latrTSA showed significantly greater LSA (p=0.017); DSA was lower, but not significantly (p=0.230). Post-infectious rTSA (n=17; 45%) presented better internal rotation (p=0.036). The overall complication rate was 16% and 8% leading to revision. ConclusionRTSA is a viable option for revision cases and presents good results after failed shoulder arthroplasty, including the infected shoulder. The effect of metallic augmentation on clinical results is not comparable to those in literature in primary rTSA setting due to advanced preoperative medialization. However, scapular notching was prevented in all cases with bipolar lateralization.

Complications and revisions in metal-backed anatomic total shoulder arthroplasty: a comparative study of revision rates between stemless and stemmed humeral components

BackgroundThe primary objective of this study was to evaluate and compare the incidence of complications and revision surgeries between in two of convertible metal-back glenoid systems in total shoulder arthroplasty (aTSA) groups over a follow-up period of up to five years. MethodsA retrospective analysis included 69 shoulders from 65 patients with primary aTSA. Patients were divided into Group 1 (n=31), receiving convertible cementless stemmed aTSA (Lima SMR) and Group 2 (n=38), receiving humeral head replacement aTSA (Arthrex, Eclipse) both with metal-back glenoid components. Clinical and radiological assessments were conducted at 2, 5, and 10 years postoperatively. Assessments included the following: Constant Score, DASH, SPADI, SSV, Glenohumeral Distance, Critical Shoulder Angle and Lateral Acromion Index. In addition, we compared complications, revision rates and survival rates between groups using Kaplan-Maier curves and Log-Rank-test. ResultsBaseline demographics and preoperative outcome scores showed no significant differences between groups (p≥0.05). The overall revision rate did not significantly differ between groups (Group 1:32% vs. Group 2:24%, p=0.60), nor did the mean time to revision (p=0.27). The mean follow-up was 71±41 months (Group 1: 94±48 months, Group 2: 53±23 months, p<0.001). Kaplan-Meier analysis showed similar mid-term survival probabilities (p=0.94). Revision reasons included rotator cuff insufficiency (n=4 in Group 1, n=2 in Group 2) and glenoid wear/loosening (n=5 in Group 1, n=7 in Group 2). Interestingly, Group 1 demonstrated no occurrence of glenoid metal baseplate or humeral loosening, while complex revisions were more common in the Group 2. At 2 and 5 years, non-revised patients in both groups had similar outcome scores. ConclusionMetal-backed glenoid implants in combination with both stemless and stemmed humeral components in aTSA exhibit comparable revision rates and survival probabilities. Rotator cuff insufficiency and polyethylene wear are the two most common complications leading to revision. To facilitate ongoing monitoring and optimize patient safety, we implemented a modification in the follow-up protocol, transitioning to annual appointments or earlier when necessary. This study underscores the unsolved disadvantages in metal-back components and the importance of a mid- to long-term longitudinal assessment of those patients.

The calibration device research for assessing the impact exposure level of rubber balls in architectural acoustics

In order to accurately measure the impact exposure level of rubber balls used in architectural acoustics, a calibration device is designed based on a force sensor, signal analyzer, programmable stepper motor and Infinite Impulse Response (IIR) filter. A weighing sensor with a range of 200 kg is selected to match the range of impact forces of rubber balls. The sensor is installed on a specially designed metal base plate of a rubber ball measuring fixture and connected to the signal analyzer. The rubber ball is dropped from a predetermined height in a free-fall manner to impact the sensor, generating an impact waveform. The force exposure level is then calculated by using software algorithms built into the device. The accuracy and reliability of the calibration device are evaluated by conducting repeated measurements on rubber balls and comparing the results with a known standard force exposure level curve. The experimental results demonstrate that the calibration device can consistently and stably measure the force exposure level of rubber balls, showing consistency with the known standard values. However, due to limitations such as a limited variety of measured objects and insufficient measurement repetitions, further research will be conducted to increase the number of tested rubber balls and enhance the device’s capabilities. This will provide technical support for the further development and application of the device.

Early to short-term radiographic follow-up of metal-augmented baseplates in reverse shoulder arthroplasty for treatment of glenoid deformity in glenohumeral arthritis and rotator cuff arthropathy

Hypothesis and backgroundAs reverse total shoulder arthroplasty (rTSA) has evolved, the use of augmented glenoid baseplates has increased. While there are benefits of metal augmentation, literature concerning the mid- to long-term follow-up of these implants is emerging. The purpose of this study is to report early to short-term radiographic follow-up of patients with glenoid deformity treated with a metal-augmented glenoid baseplate. Our hypothesis is that we will see a low incidence of osteolysis, loosening, complications, and revision of these implants regardless of diagnosis, augment type, or patient demographics. MethodsWe performed a single-center retrospective review of all patients undergoing primary reverse shoulder arthroplasty with an augmented metallic baseplate for rotator cuff arthropathy and glenohumeral arthritis. Patients undergoing revision procedures or reverse arthroplasty for fractures were excluded. All patients had a minimum of 1-year radiographic follow-up. Preoperative imaging was reviewed to confirm the diagnosis and glenoid deformity classification. Postoperative radiographs were reviewed for evidence of complications, revisions, osteolysis, baseplate loosening, and failure. Clinical data were reviewed for complications. ResultsPrimary rTSA with a metal-augmented baseplate (38 full wedge and 22 half wedge augments) was performed on 60 patients who met inclusion criteria (mean age 74 ± 7). The average radiographic follow-up of all patients was 17 months. In our cohort, there was one patient with aseptic loosening of a full wedge implant that was not revised. There were no other complications, revision surgeries, baseplate failures, or acromial stress fractures. Six patients developed scapular notching, and five patients were found to have asymptomatic glenoid osteolysis. Two patients with full wedge implants developed aseptic humeral loosening. Pearson chi-square post hoc analysis found no correlation between augment type, gender, or glenoid deformity classification and radiographic changes such as glenoid or humeral osteolysis, loosening, or scapular notching. We did find a statistically significant correlation (P = .018) between patients with body mass index > 35 and glenoid osteolysis. Discussion and conclusionPrimary rTSA for patients with rotator cuff arthropathy or glenohumeral arthritis with glenoid deformity corrected with metal-augmented glenoid baseplates results in a low complication rate and an acceptable outcome at a minimum 1-year follow-up. Compared to other similar cohorts, our patients did not experience any acromial stress fractures, and only one patient had loosening of the glenoid component that was not ultimately revised. Further studies with longer follow-up will be needed, but early outcomes are promising and support the increase in the use of these implants.

Direct selective laser sintering of silicon carbide: Realizing the full potential through process parameter optimization

Direct-Selective Laser Sintering (D-SLS) is a promising Additive Manufacturing (AM) technology for Silicon Carbide (SiC). The appropriate values for the process parameters should be employed to achieve considerable success in the D-SLS of SiC. These process parameters include laser power, scanning speed, layer thickness, hatching space, and compaction ratio. A numerical model has been developed to determine the optimal process parameters for the D-SLS of SiC to be used as a guide during the experimental research. SiC samples were successfully printed using the estimated parameters from the numerical model, proving the reliability of the developed numerical model. With varying layer thicknesses of 22, 30, and 40 μm, the scanning speed at various values, including 100, 250, and 500 mm/s, was investigated. It was possible to print SiC samples with a relative density of 82% directly on a metallic base plate using low scanning speeds and layer thicknesses as low as 22 and 30 μm. This result was the first study to print SiC directly on a metallic baseplate. This remarkable finding will enable many applications that previously required metallic and ceramic materials to adhere together during SLS/M-based 3D printing. The process parameters were optimized to achieve a relative density of 87%, resulting in a laser power of 45 W, a scanning speed of 100 mm/s, and a hatching space of 40 μm. The evaluation of mechanical performance should be considered a future study.

Thermal resistance of Open-Cell metal foam with thermal interface materials (TIM)

• This study proposes an alternative joining metal foam with other metals and TIM. • The thermal resistance decreases with increasing compression load and varies with TIM hardness. • The thermal resistance of the hard TIM sample is reduced to a maximum of 62% when a 30N compression load is applied. • The soft TIM sample has a thermal resistance difference of 19% higher than that of hard TIM. This study investigated the thermal resistances of sandwich structures consisting of open-type metal foams, base plates/surfaces, and thermal interface materials (TIMs) in two types of sandwiching configurations, namely Type 1 and Type 2. Samples were prepared using metal foam structures of 20, 40, and 60 pores per inch (PPIs), representing five commercial TIMs, i.e., pyrolytic graphite sheet (PGS), T621, SFT90, PC93, and PC94. They were categorised into two types: (i) thin and hard films (PGS, T621, SFT90) and (ii) thick and soft pads (PC93 and PC94). The thermal resistance and the thickness were measured under compression loadings of 0 – 60 N using an in-house thermal resistance tester developed according to the ASTM D5470 standard. Based on the nanoindentation test, PGS showed the highest hardness (0.2660 GPa), followed by T621 (0.0322 GPa), SFT90 (0.0235 GPa), PC93 (0.0007 GPa), and PC94 (0.0004 GPa). In general, thermal resistances were dependent on compression forces; they decreased with increasing compression loads. At a 30 N load for 60 PPI, the thermal resistance of the hard TIM sample was reduced to 62% with a 1.5% reduction in compression thickness at the Type 1 configuration. The resistance decreased as much as 8% when PPIs increased from 20 to 60. By contrast, at a 30 N load for 60 PPI, the thermal resistance of the soft TIM sample was reduced to 58% with a 16% reduction in compression thickness at the Type 1 configuration. When PPIs increased from 20 to 60, the resistance decreased by just 5%. Despite a lower thermal resistance reduction than the hard TIM, the soft TIM was 19% higher in thermal resistance difference. This study showed that joining metal foam, TIM, and base plate reduced thermal resistances while increasing their performance.

Broadband Frequency Selective Rasorber Based on Spoof Surface Plasmon Polaritons.

A broadband frequency selective rasorber (FSR) based on spoofsurface plasmon polaritons (SSPP) is proposed. The FSR is composed of a multi-layer structure comprising frequency selective surface (FSS)-polyresin (PR)-indium tin oxide (ITO)-PR-FSS and placed vertically on a metal base plate. A periodic square cavity structure is formed. The transmission characteristics of the FSR are studied by full-wave simulation and equivalent circuit method. The simulation results demonstrate that under normal incidence, the absorption rate of the structure remains 95% in the 5-30 GHz band, and the absorption rate is also 80% in the 3.5-5 GHz band. As the incident angle of the electromagnetic wave increases to 40°, the absorption rate in the 15-20 GHz band decreases to 70% in the transverse electric (TE) mode, and the absorption rate in the transverse magnetic (TM) mode is almost the same as that of vertical incidence. The transmission response of the structure is measured in an anechoic chamber. The measurement results agree well with the simulation results, proving the reliability of the design and fabrication. The structure is less sensitive to the incident angle of magnetic waves and has a better broadband absorbing ability.

Liquid-cooled heat sink design for a multilevel inverter switch with considerations for heat spreading and manufacturability

Multilevel inverter switches (MIS) present a thermal management challenge by virtue of their small size yet high power operation. In this contribution, a water-cooled heat sink for an MIS was designed and optimized through a series of computational fluid dynamics simulations and surrogate modeling. The parameters under consideration were technical metrics (thermal resistance, pressure loss, and temperature uniformity) and manufacturing costs. The stark difference between air-cooled and liquid-cooled heat sinks was demonstrated in parallel modeling efforts. The heat sink consisted of a metallic baseplate with pin-fins and a separate resin manifold containing an array of nozzles for flow impingement and fluid extraction. The pin–fin baseplate was parametrically designed using three different fin densities: restricted array (RA), variable array semifull (VAS), and variable array (VA), where fin diameter and pitch were correlated. The manufacturability of each design iteration was determined by obtaining quotes from a vendor. Since all heat sinks had the same inlet manifold, the pressure drop was similar across heat sink designs, indicating that the fin distribution had a minimum effect on the overall pumping power required for circulating the flow through the heat sinks. Effective thermal resistance calculations illustrated a complex interplay between fin diameter and pitch spacing. The complexity was better visualized using a feedforward neural network (FNN) and an overall performance metric (PPTR). A sensibility analysis using the FNN indicated that the fin pitch was the dominant variable in the determination of the overall heat sink performance. The PPTR allowed the creation of a ranking system that matched the FFN outcome and indicated that the VA2D1 design was the most technically promising; nonetheless, once manufacturing cost was considered in the analysis, as PPTR-$, the RA1D1 was the most commercially viable as it satisfied technical cooling goals per the lowest unit cost.

Si-IGBT and SiC-MOSFET hybrid switch-based 1.7 kV half-bridge power module

• Design guidelines, fabrication process, and evaluation of a 1.7-kV and 300-A multi-chip half bridge power module using the novel Si-IGBT and SiC-MOSFET hybrid switch in each switch position. • The module achieves its maximum DC current rating with a 6:1 current ratio of Si to SiC. • A novel custom-designed TPG-encapsulated metal base plate is proposed. • Silver clips for top-side interconnect in the module, facilitating a wire bond-less interconnection, high reliability, and low power loop inductance. • High thermal dissipation capability while maintaining a near-isolated thermal path for the SiC MOSFET to operate at a higher temperature than the Si-IGBT. This paper informs the design guidelines, fabrication process, and evaluation of a 1.7-kV and 300-A multi-chip half bridge power module using the novel Si-IGBT and SiC-MOSFET hybrid switch in each switch position. The module achieves its maximum DC current rating with a 6:1 current ratio of Si to SiC. This high current ratio yields significant cost savings compared to an all-SiC power module. The module employs high-reliability silver clips, which replaces conventional wire bonds for top-side interconnection, to partly enable a low power loop inductance of 12.38 nH. A novel thermal pyrolytic graphite-encapsulated metal baseplate is key to reducing the thermal coupling among the adjacent Si and SiC die, enabling higher junction temperature for SiC die relative to the Si die.

Treating posteriorly eroded glenoids with augmented baseplate or bony increased-offset reverse shoulder arthroplasty: a finite element comparison

BackgroundAugmented reverse shoulder arthroplasty (RSA) implants restore glenohumeral joint alignment in cases of asymmetric glenoid wear. However, no consensus has been reached on whether the use of metallic augmented RSA baseplates and bone graft reconstruction are equivalent in terms of implant fixation and risk of implant loosening. Therefore, the purpose of this study was to compare 2 augmented RSA designs by assessing the amount of interfacial micromotion generated under realistic physiological loading. MethodsFinite element analysis models of 9 scapulae with Walch-type B2 or B3 glenoid morphology were virtually implanted with both a metallic augmented baseplate (AUG-RSA) and using the angled bony increased-offset RSA procedure (BIO-RSA). Simulation of physiological loading was performed on each of the 18 finite element analysis models. The relative tangential and normal micromotion at the implant-to-glenoid interface was compared in each anatomical quadrant. ResultsThe AUG-RSA and angled BIO-RSA showed similar magnitudes of micromotion in most anatomical quadrants of the glenoid. Within the superior quadrant, AUG-RSA displayed a higher magnitude of mean and maximum tangential micromotion (mean: 16.6 ± 2.4 μm, P < .000; maximum: 35.1 ± 5.3 μm, P < .000). The proportion of the posterior quadrant experiencing >50 microns of micromotion was also statistically greater with AUG-RSA (5.8 ± 2.5 %, P = .047). ConclusionBecause of its statistically greater micromotion and portions of contact exceeding the accepted 50-micron threshold, the AUG-RSA may be more likely to have inhibited bone on-growth. However, the clinical importance of these differences remains unclear.

Response of a CMS HGCAL silicon-pad electromagnetic calorimeter prototype to 20–300 GeV positrons

The Compact Muon Solenoid collaboration is designing a new high-granularity endcap calorimeter, HGCAL, to be installed later this decade. As part of this development work, a prototype system was built, with an electromagnetic section consisting of 14 double-sided structures, providing 28 sampling layers. Each sampling layer has an hexagonal module, where a multipad large-area silicon sensor is glued between an electronics circuit board and a metal baseplate. The sensor pads of approximately 1.1 cm2 are wire-bonded to the circuit board and are readout by custom integrated circuits. The prototype was extensively tested with beams at CERN's Super Proton Synchrotron in 2018. Based on the data collected with beams of positrons, with energies ranging from 20 to 300 GeV, measurements of the energy resolution and linearity, the position and angular resolutions, and the shower shapes are presented and compared to a detailed Geant4 simulation.

Computational characterization of millimetre-wave heat exchangers with an AlN:Mo susceptor of multiple cylindrical elements

A concept for a millimetre-wave (MMW) heat exchanger (HX) featuring AlN:Mo ceramic composite structures as electromagnetic absorbing elements (susceptors) has been recently introduced as a receiving device in power beaming applications. Earlier computational studies of electromagnetic and thermal processes have shown reasonable energy efficiency and exceptional uniformity of MMW-induced temperature fields in a single cubic susceptor with concentration of Mo doping on the level of 3–4% by volume. As part of ongoing research, a MMW HX comprised of an array of cylindrical susceptors is proposed to potentially enable increased robustness against thermal stress and reduced manufacturing cost. In this paper, we computationally study the effects driven by such a change and demonstrate feasibility of the designs based on multiple cylinders. We present the output of electromagnetic and coupled electromagnetic-thermal simulations of a prospective physical prototype of a HX with five cylinders on a square metal base plate. Three alternative layouts with four, nine, and sixteen cylindrical elements that are suggested by the highest density packing of equal circles in a square are also analyzed. It is shown that, in comparison with the previously studied case of a single cubic susceptor, energy efficiency of all systems with Mo = 3–4% is down from 50–55% to 35–45%. While temperature distribution within each individual cylinder remains highly uniform, maximum temperatures of different cylinders may be different by up to 30–40 °C; when the angle of incidence deviates from normal, this difference further increases: e.g. when the angle is 10°, in the sixteen-cylinder system, it may reach 120–130 °C.

Influence of Alloying Elements on the Mechanical Properties of Anodized Aluminum and on the Adhesion of Copper Metallization.

The active development of the power electronics market and a constant increase in the prices of components require new materials and approaches, including a power module packaging technology. The use of aluminum instead of copper in the power module baseplate is an interesting and promising solution. The insulated metal baseplate is one of the most extensively developed technologies nowadays. The object of this study is an insulated metal substrate based on anodized aluminum. The main goal of the article is the comparison of copper topology adhesion to an anodized aluminum oxide layer formed on different aluminum alloys with aluminum content of at least 99.3 wt %. Peel test and pull-off adhesions showed a twofold difference for both aluminum alloys. The high ordered defect-free anodized alumina formed on alloys with copper content of 0.06 wt % had a mean pull-off adhesion of 27 N/mm2 and hardness of 489 HV. In the case of the alloy with copper content of around 0.15 wt %, it had hardness of 295 HV and a mean pull-off adhesion of 12 N/mm2. The results of our microstructure investigation showed that anodized alumina based on alloys with copper content of around 0.15 wt % is fragile due to spherical holes. Summing up the results, it can be concluded that not all initial impurities are critical for anodized alumina, but some, specifically copper, dramatically decreased the mechanical properties of anodized alumina.

Accuracy of a titanium maxillary complete denture baseplate fabricated by using the electron beam melting technique: An in vitro study

Statement of problemElectron beam melting (EBM) is a promising additive manufacturing technique for fabricating denture baseplates; however, studies evaluating its accuracy are sparse. PurposeThe purpose of this in vitro study was to compare the fit accuracy of titanium maxillary complete denture baseplates fabricated by using the EBM technique with those fabricated by using the conventional casting technique and to evaluate the dimensional accuracy of the EBM baseplate by using a 3-dimensional inspection software program. Material and methodsDefinitive casts of an edentulous maxilla were prepared. After the casts were optically scanned, computer-aided designs for the EBM baseplate were created by using a software program for standard tessellation language file editing. The EBM baseplates were fabricated with an EBM machine by using a Grade II titanium powder as the raw material. The cast baseplates were fabricated with a lost-wax casting technique by using refractory casts duplicated from the definitive casts. After fitting the EBM and cast baseplates to their corresponding definitive cast, they were embedded in a Type IV stone. The embedded baseplates on the casts were sectioned at 3 regions: posterior palatal seal, molar, and premolar. The maximum gaps between the baseplate and definitive cast were measured in these 3 regions. The virtual casts obtained by scanning the EBM baseplate were superimposed on the computer-aided design to evaluate the dimensional accuracy. Distribution color maps were then generated, and the mean absolute deviations and root mean square deviations were calculated. One-way analysis of variance and t tests were used for statistical analysis (α=.05). ResultsNo significant differences in the maximum gaps among the 3 regions were found in the cast or EBM baseplate groups (P>.05). The EBM baseplate group showed significantly lower values than the cast baseplate group in all regions (premolar: P=.008; molar: P=.003; posterior palatal seal: P=.004). The mean maximum gap for the 3 regions in the cast baseplates was 168.0 μm and that in the EBM baseplates was 60.7 μm. The distribution color map of the EBM baseplate showed a favorable dimensional accuracy. The mean absolute deviation value was 19.7 μm, and the root mean square deviation value was 25.1 μm. ConclusionsThe EBM baseplates had a significantly higher fit accuracy than the cast baseplates. Thus, the fit accuracy of the EBM technique is suitable for fabricating metal baseplates.

Prospective multicentre mid-term clinical and radiological outcomes of 159 reverse total shoulder replacements and assessment of the influence of post-operative complications.

The aim of our prospective multicentre study is to evaluate the five-year follow-up outcomes of primary reverse shoulder replacement utilizing two different designs of glenoid baseplates. There were 159 reverse shoulder replacements (91 cemented and 68 uncemented stems, 67 Trabecular Metal baseplates and 92 Anatomical Shoulder baseplates in 152 patients (99 women) with a mean age of 74.5 (58-90) years. The principal diagnosis was rotator cuff arthropathy in 108 shoulders. Clinical and functional results improved significantly overall; the adjusted Constant Murley score improved from 28.2 ± 13.3 pre-operatively to 75.5 ± 22.8 (p < 0.0001) and the mean Subjective Shoulder Value improved from 27.5 ± 20 to 73.8 ± 21.3 points (p < 0.0001). Radiologically, there was good bony stability in 88% and 86% of cemented and uncemented stems without significant impact on the Constant Murley score and Subjective Shoulder Value at one, two and five years post-surgery. There were no significant clinical differences between Trabecular Metal and Anatomical Shoulder baseplates at five years. There were four cases of intraoperative shaft fractures that were managed with cables. Although the Trabecular Metal baseplates showed better integration radiologically, there was no significant difference in the mean of Constant Murley, Subjective Shoulder Value and the range of motion depending on the grade of inferior scapular notching at one-, two- and five-year intervals. Reverse total shoulder arthroplasty restores the function in shoulder with significant improvements in function and moderate complications with minor differences between both designs of baseplates that were not reflected clinically.

Investigation of the thermal parameters of an aluminum heater with nanoporous alumina

An important task faced in the industry of permanently installed heating systems addressed by a large number of manufacturers is power saving. Heating systems may have variegated designs, yet there are basic design requirements, i.e., high operational reliability, resource saving, environmental resistivity and stability of electric parameters. The key component of any heating unit is the heater. Flat resistive heaters have found wide application in heating units aimed at sustaining healthy indoor microclimate, maintaining preset process parameters on industrial premises, as well as in anti-icing systems, agriculture and general industry. We studied the thermal parameters of flat aluminum heating units containing carbon fiber ribbon heaters. To ensure the required insulation of the heater from the metallic base plate, the aluminum surface had a 20 mm thick porous aluminum oxide layer. The ends of the carbon fiber were metalized with a layer of copper for further soldering upon integration into the electric heating unit assembly. The electrical resistance of the heater with a carbon fiber was 60 Ohm. The propagation of heat flows inside a plate of aluminum with nanoporous aluminum oxide was studied using thermal imaging measurements. Temperatures on the surface of the aluminum heater cover and on the opposite heat emitting side were shown as a function of heating time. The experimental results suggest that the heat generated by the linear carbon fiber heater distributes rapidly in the entire bulk of the aluminum heater plate. This indicates a high heat conductivity of the heater aluminum base plate whose parameters provide for the required thermal parameters of the heating unit.

Inexpensive, Underwater Filming of Rare Fishes in High Definition

Generating public interest in fish and their biology is often challenging. Many aquatic species are cryptic and largely invisible to the public. Therefore, increasing public awareness of cryptic fishes and elevating their visibility to broad audiences requires innovation. Inexpensive technological advancements now provide fisheries biologists, managers, and researchers with means never before possible for documenting fish in their natural habitat via underwater videography. We investigated cost efficient and simple methods for capturing and creating high quality, high definition, and informative underwater videos that could be used by people with little or no previous experience in videography. We tested 1) a variety of filming equipment including cameras and camera recording settings, lenses, batteries, and memory cards; 2) active and passive camera deployment techniques; and 3) a variety of free and paid postproduction software and compared them for ease of use, expense, and quality of output. Highest quality footage, i.e., highest resolution, clearest, and most stable, was obtained using a GoPro action camera deployed underwater in a stationary position mounted to a metal base plate using a combination of stock and macro lenses, and filming in 4K resolution at 30 frames per second. Final production videos were created using Adobe Premiere Pro.

Precipitation Strengthening in Ni–Cu Alloys Fabricated Using Wire Arc Additive Manufacturing Technology

Two Ni–Cu alloys, Monel K500 and FM60, with various contents of Ti, Mn, Al, Fe and C were deposited in the form of plates on a metal base plate using wire arc additive manufacturing technology. Three deposition speeds have been applied: 300, 400 and 500 mm/min. To modify the as-welded microstructure and properties, the deposited walls/plates have been subjected to two heat treatment procedures: annealing at 1100 °C for 15 min, slow cooling to 610 °C, ageing at this temperature for 8 h and either (i) air cooling to room temperature or (ii) slow cooling to 480 °C, ageing at this temperature for 8 h and air cooling to room temperature. The microstructure characterisation and mechanical properties testing have been conducted for each of the 18 chemistry/processing conditions. The dependences of the precipitate’s parameters (size, number density and chemistry), mechanical properties and wear resistance on the alloy composition, deposition speed and heat treatment have been obtained. In Monel K500, the precipitates were mainly of the TiC/TiCN type, and in FM60, they were of the MnS and TiAlMgO types. Monel K500 has shown higher hardness, strength, toughness and wear resistance in all studied conditions. Ageing at 610 °C improved properties in both alloys following the precipitation of new particles. Ageing at 480 °C could result in a properties loss if the particle coarsening (decrease in number density) took place.

A comparative study of dimensional stability of two popular commercially used denture base resins

Background: A good dimensional stability is a necessary prerequisite for successful complete denture retention and its functional efficacy. This study was conducted keeping in mind the cost factor and the need of a common man. Out of many available products, conventional heat cure resin (Dental Products of India [DPI] and Lucitone 199 [LUC]) are the standard of choice. For suitable understanding of these two products in accordance to the above-stated statement, the current study was conducted. Aim: This in vitro study was carried out to compare the dimensional stability of commercially available polymethylmethacrylate (PMMA) DPI and high-impact LUC denture base materials processed using a long curing cycle, with and without terminal boiling. Methodology: By using a chrome cobalt metal base plate, a total of forty specimens of acrylic base plates were fabricated. They consisted of two major groups of twenty specimens each, fabricated from conventional heat cure DPI and LUC heat cure resins. Each group so fabricated was further subdivided into two equal subgroups of ten specimens each, which were subjected to long curing cycle, with and without terminal boiling. The results for each group were compared by paired sample t-test for the studied objective, and data were analyzed by SPSS software version 20 (IBM Corporation, Armonk, NY USA). The level of statistical significance was fixed at the customary level ≤0.05. Results: The dimensional stability values of LUC were found superior (P Conclusion: PMMA reinforced with butadiene styrene fabricated using long curing cycle with terminal boiling showed the highest value of dimensional stability and the least was seen with conventional PMMA processed with long curing cycle without terminal boiling.

Modelling of constrained layer damping for bending waves in frequency domain using finite shell elements

AbstractConstrained layer damping (CLD) is a damping principle which utilizes a viscoelastic layer between two elastic covering layers. Bending of the resulting plate structure mainly causes shear deformation in the viscoelastic layer which in theory leads to more efficient dissipation than damping due to pure strain deformation. This principle is brought into application by applying damping tape to the surface of a metallic base plate. Since extensive use of damping tape is economically expensive, a common aim is to achieve maximum dissipation with a limited amount of modified area. Therefore, there is an interest in predicting the optimal distribution of a given amount of damping tape by numerical simulations. In most applications where the Finite Element Method (FEM) is applied, shell elements are preferred over volume elements, because the shell elements are computationally more efficient. To be able to model CLD with shell elements, a mechanical model has to be derived first that represents the three layer structure with homogenized parameters. In this contribution, CLD is modelled in two different ways and solved with FEM: First, an experimentally validated volume model of a CLD‐structure and second, an effective material model using shell elements. The frequency responses of both models are compared.