The 3.2m all SiC Telescope for SPICA

Theoretical investigation of the post-combustion recovery process in cobalt-based zero-carbon fuels

In surveillance applications there is a need for infrared zoom systems which give two fields of view. For such systems long operation range is the most critical parameter which is bound up with focal length and transmittance of systems. In this paper the design of an infrared zoom system with rotating lens group is described. Different from the conventional axially moving zoom systems, this system is based on a rotating mechanism consisting of two separated lenses. The system achieves dual FOVs due to different magnifications. In narrow field of view mode, the system has long focal length and higher transmittance because the rotating lens group is outside the optical path. The final design is an infrared zoom system operating in 3μm~5μm, with a F number of 4.0, EFL of 250mm/62.5mm. This paper contains the calculation of first-order parameter, the optimum design of rotating motion, the analysis of aberrations, MTF, and Narcissus, This designed system has diffraction limited image quality of in both FOVs.

While wireless sensor nodes based on conventional semiconductor technology have revolutionized our understanding of the world in which we live, they are limited to operating in benign environments. This limitation precludes their use in a wide range of industrial, automotive and geological applications, where the required operating temperatures can exceed 200°C. Silicon-on-insulator technology has enabled the development of high temperature electronics, however applications requiring higher temperature operation are becoming apparent. Battery technologies capable of sustaining the required power level in these extreme environments are also a significant challenge. In this work, we present the integration of analog functional primitive circuits capable of interrogating resistive and capacitive sensors to form a wireless sensor node based on silicon carbide technology. The electrical power is provided from the output of a novel self-starting boost converter connected to a thermoelectric generator. Data can be transmitted from the node via frequency modulation of a Colpitts oscillator, for remote post processing. The signal conditioning is realised using JFET based amplifier circuits, designed using a novel JFET compact model, which enables a greater level of confidence than existing models in the literature.

Use of slotted liner as a sand control device is widespread in SAGD operations in Western Canada. Operating temperatures in such thermal EOR wells can be extreme, sometimes exceeding 270 °C (518 °F), and the associated compressive axial mechanical strain imposed by constrained thermal expansion can load the pipe material beyond its proportional limit. Selection of an appropriate slotted liner configuration is critical to ensure structural stability (and hence sand control) is reliably maintained during operation. Mechanical properties of the tubular material at elevated temperature strongly influence the compressive stability of the liner structure, but lower-temperature properties also affect the ease of pipe slotting on a production scale, which is typically achieved by plunging thin saw-blades through the pipe wall. Common slotting issues include breakage or unacceptably high blade wear rates. This paper describes the development basis for a new tubular material formulation that is specifically optimized for thermal structural stability in SAGD applications without compromising slotting performance. Elevated-temperature mechanical properties are designed to prevent compressive buckling failures and to minimize strain localization potential. Results of analytical and experimental work (including stability analysis of the liner structure, thermo-mechanical material testing, and bench-scale slotting trials) are described. Introduction Ongoing rapid development of bitumen reserves in Western Canada has led to an increased focus on developing robust tubular design bases for extreme service conditions in in-situ recovery schemes such as SAGD. Specifically, cemented or frictionally constrained tubulars are subjected to thermallyinduced, deformation-controlled loading that leads to a unique set of design challenges and more stringent requirements for post-yield material response than those employed in traditional elastic design. Slotted liner is used as a sand control device in a majority of SAGD wells. Slotted liners used in thermal applications must provide a stable structure under extreme thermally-induced compressive loading in order to maintain wellbore access and to prevent excessive sand from entering the wellbore. While the deformation resistance of slotted liners depends on geometric attributes such as pipe wall thickness, slotting configuration, and slot geometry, material properties have a considerable impact on structural stability and localization resistance. Materials typically employed in slotted liner installations include API grades such as K-55 and L-80. However, the API mechanical property requirements for such materials are defined at room temperature, and the variability permitted by the API specification is large. Efforts to develop engineering design bases for liners in specific fields must consider the operating conditions of the application, and generally result in a more specific requirement for post-yield material properties than is offered by API. Hence, an API grade designation is not considered to be a sufficient description of material requirements for such tubulars. The manufacturing process for slotted liner involves plunging a series of thin sawblades through the wall of the tubular. Typical slot quantities are in the hundreds per metre of pipe length, and with individual well lengths of 600 m to 1000 m, an efficient slotting process is desirable.

In the laser metal direct manufacturing, gas-solid two-phase flow theory is adopted to simulate the flow field of powders in coaxial nozzle to fabricate complex parts of compact structure. The separate model in FLUENT is used to evaluate the concentration distribution rule and the focusing characteristics of the powder flow field. The results indicate that the focal concentrations of the coaxial powder nozzle in radial direction and axial direction are approximately obeyed by the Gaussian distribution. When the cone angle of coaxial nozzle is invariable, the cone ring gap is smaller, the focal point concentration in the powder flow field is bigger; the focus radius is smaller, the focal distance is also smaller, and the gathering characteristic is better. When the cone ring gap of the coaxial powder nozzle is invariable, the cone angle getting too big or too small is harmful for powder gathering. When other conditions are invariable, extreme protective gas velocity (too large or too small) is harmful for powder gathering. When the protective gas velocity approaches to 6 m/s, the gathering characteristic of the coaxial nozzle achieves its best performance.

In this paper the results of the thermo-elastic analysis performed on the Stereo Imaging Channel of the imaging system SIMBIO-SYS for the BepiColombo ESA mission to Mercury is presented. The aim of the work is to determine the expected stereo reconstruction accuracy of the surface of the planet Mercury, i.e. the target of BepiColombo mission, due to the effects of the optics misalignments and deformations induced by temperature changes during the mission lifetime. The camera optics and their mountings are modeled and processed by a thermo-mechanical Finite Element Model (FEM) program, which reproduces the expected optics and structure thermo-elastic variations in the instrument foreseen operative temperature range, i.e. between -20 °C and 30 °C. The FEM outputs are elaborated using a MATLAB optimization routine: a non-linear least square algorithm is adopted to determine the surface equation (plane, spherical, n^th polynomial) which best fits the deformed optical surfaces. The obtained surfaces are then directly imported into ZEMAX raytracing code for sequential raytrace analysis. Variations of the optical center position, boresight direction, focal length and distortion are then computed together with the corresponding image shift on the detector. The overall analysis shows the preferable use of kinematic constraints, instead of glue classical solution, for optical element mountings, this minimize the uncertainty on the Mercury Digital Terrain Model (DTM) reconstructed via a stereo-vision algorithm based on the triangulation from two optical channels.

The drive inverter represents a central component of an electric vehicle (EV) drive train, being responsible for the DC/AC power conversion between the battery and the electrical machine. In this context, novel converter topologies adopting modern 600/650V wide bandgap (WBG) semiconductor devices will play a crucial role in improving the performance of next-generation drive inverters. In fact, WBG devices theoretically allow to achieve both higher inverter power density and higher conversion efficiency with respect to conventional silicon (Si) IGBT based solutions. Even though silicon carbide (SiC) devices are already well established in the automotive industry, high-voltage gallium nitride (GaN) devices are rapidly entering the market, promising higher theoretical performance but featuring a lower degree of maturity. As a consequence, it is currently not clear which semiconductor technology is most suited for future EV drive inverters. Therefore, this paper aims to address this gap providing a comparative performance evaluation of state-of-the-art SiC and GaN 600/650V active switches. In particular, a novel figure-of-merit (FOM) representing the minimum theoretical semiconductor losses under hard-switching operation is introduced. Remarkably, this FOM enables a fair and accurate performance comparison among semiconductor devices, allowing to clearly determine the best performing technology for a given set of application-specific conditions. The results of the comparative assessment show that currently available SiC and GaN active switch technologies can outperform each other depending on the semiconductor operating temperature and the converter switching frequency.

Recently, while eco-friendly energy storage/conversion technologies have been attracting attention, researches have been reported to improve performance and provide multiple functions by applying three-dimensional nano-/micro-structures to energy devices. In general energy devices, the electrolyte and electrodes located on both sides have been designed to have a flat interface, but in the end, developed structures in consideration of three-dimensional efficiency should be required. Among them, in solid oxide fuel cells (SOFCs), which have advantages such as high efficiency and fuel flexibility, studies on the use of advanced cell structures were conducted to lower the operating temperature. Although micro-SOFC using etching or laser processing has been reported, there are limitations in practical operation due to poor material/structural stability and low pattern resolution. In this paper, we developed a novel ceramic micropatterning process by imprinting a pyramid-shaped polymer mold made by soft lithography on the anode support. Furthermore, we have implemented a three-dimensional SOFC with record-high cell performance through the combination of thin film process and large-area cell manufacturing technology. For microscale patterning of the anode, polymer-ceramic anode films with low elastic modulus was prepared by the tape casting process, and the anode support with pyramidal patterns was fabricated through the subsequent imprinting process. The imprinted pattern was maintained after the sintering process. Then, through RF sputtering and pulsed laser deposition (PLD) process, the nanoscale anode functional layer (nAFL), Y2O3-stabilized ZrO2 (YSZ), Gd0.1Ce0.9O1.95 (CGO) and La0.6Sr0.4CoO3- δ (LSC) layer were deposited to fabricate a full cell. To analyze the electrochemical effect of three-dimensional electrode/electrolyte interface, 3DA-cell with ceramic micropatterning process and Planar-cell with flat interface were compared. Interestingly, 3DA-cell showed higher performance than Planar-cell at all operating temperatures, and resulted in 55 % enhanced maximum power density (PDmax) and 19 %, 52 % decreased polarization, ohmic resistance at 500 °C, respectively. Notably, the CGO-based 3DA-cell using CGO as the main electrolyte material recorded a high PDmax of 0.931 W/cm2 at 500 °C. Therefore, to find the factors that improve the electrochemical performance, the microstructures of two different cells were analyzed by scanning electron microscope (SEM), transmission electron microscopy (TEM) and 3D reconstruction method. From the 3D reconstruction result, the nAFL/YSZ interface area, CGO/LSC interface area, and active TPB length of AFL of 3DA-cell increased by about 33 %. 23 %, and 64 % compared to Planar-cell, whereas pore volume ratio of AFL did not change. Therefore, it was confirmed that the increase of the electrode/electrolyte interface area by ceramic micropatterning had a direct effect on the improvement of cell performance, and the internal structure of AFL was not affected by the imprinting process. Furthermore, to demonstrate the versatility of ceramic micropatterning process, a 5 cm x 5 cm large-area three-dimensional thin film SOFC was fabricated and its performance was evaluated. As a result, we set a new milestone in SOFC technology by reporting a power of ~ 13 W at 500 °C, and confirmed the consistency of our process through a cell reproducibility test. Additionally, the stability of the three-dimensional structure was verified through the operation without notable degradation for 500 hours under the condition of 5 A and 8 A current load. This work exhibits an outstanding breakthrough to accomplish high-performance, high-stable large-area SOFCs, and can accelerate commercialization to the portable and transportation devices.

Proton-exchange membrane fuel cells (PEMFC) are regarded as a possible alternative power source for stationary and mobile applications. Due to the catalyst costs, many researchers have been studying the membrane and the electrode assembly (MEA) manufacturing processes that can reduce the content of Pt in the electrocatalyst layer while maintaining the performance. The MEA is the heart of the PEMFC and the catalyst plays an important role in the fuel cell operation.There are different methods to prepare MEA. In this work, the catalyst ink was straightly applied on the gas diffusion layer (GDL) by an aerograph. Then, this electrode was assembled to the membrane by hot press.From the point of view of operation, the main variables are: temperature, pressure and time of press. Operational range was established from previous experiments to find roughly the optimal conditions. Finally, these MEAs were tested in a 5 cm2 PEMFC. The operational temperature was 30°C. Due to higher temperatures it was difficult to keep the humidity of the membrane constant. The operational pressure and flow were constant throughout the experiments. Different techniques to characterize the MEAs, linear sweep voltammetry and cyclic voltammetry were applied. With these techniques the permeation of hydrogen and the electrochemically active surface area of electrode catalyst were determined.With the results obtained in the experiments, the optimal values of the fabrication parameters were established.

Simplicity, low cost, and easy replacement make labyrinth seals the primary seal type in gas turbines. However, excessive leakage and potential for rotordynamic instability are well known issues. Brush seals effectively control leakage in air breathing engines, albeit only applied for relatively low pressure differentials. Hybrid brush seals (HBSs) are an alternative to resolve poor reliability resulting from bristle tip wear while also allowing for reverse rotation operation. The novel configuration incorporates pads contacting the shaft, which under rotor spinning lifts off due to the generation of a hydrodynamic pressure. The ensuing gas film prevents intermittent contact, thus lowering the operating temperature and thermal distortions and even eliminating bristle wear. The hybrid brush seal improves sealing, is more durable and reliable than conventional brush seals, and allows reverse shaft rotation without seal damage. This paper presents measurements of power loss and leakage in a HBS for increasing pressure differentials over a range of rotor speeds. The test HBS, Haynes-25 bristle pack (∼850 bristles∕cm) and 45 deg lay angle, is 166.4 mm in diameter and integrates 20-arcuate pads connected with thin electrical-discharge machined webs (EDM-webs) to the seal casing. The webs are designed with low radial stiffness to allow for rotor excursions and high axial stiffness to avoid pad pitching motions resulting from high pressure differentials across the seal. Measured drag power at low rotor speeds (<11 m∕s at 1300 rpm) decreases as the pressure differential across the seal increases. At a fixed rotor speed, a significant drop in drag torque (and drag power) ensues as the supply pressure increases, thus demonstrating that a gas film separates the rotor from the seal pads. Additionally, the operating temperature measured at the rotor/seal interface remains approximately constant (∼24°C) during tests with shaft rotation (power loss and drag torque measurements) under pressurized conditions, indicating that the rotor and seal pads are not in contact. Flow rate measurements at room temperature (25°C) show an improved sealing ability with a leakage reduction of about 36% when compared with a first generation shoed-brush seal. The HBS calculated effective clearance (∼50 μm) is approximately 70% smaller than the radial clearance (∼180 μm) of an ideal noncontacting seal with similar rotor diameter. Improved brush seal technology will increase the efficiency of gas turbines while also aiding to improve the engine stability and to reduce vibrations.

This review attempts to examine two key elements in the evolution of cognitive impairment in the elderly who develop heart failure. First, major left side heart parts can structurally and functionally deteriorate from aging wear and tear to provoke hemodynamic instability where heart failure worsens or is initiated; second, heart failure is a major inducer of cognitive impairment and Alzheimer's disease in the elderly. In heart failure, when the left ventricular myocardium of an elderly person does not properly contract, it cannot pump out adequate blood to the brain, raising the risk of cognitive impairment due to the intensification of chronic brain hypoperfusion. Chronic brain hypoperfusion originates from chronically reduced cardiac output which progresses as heart failure worsens. Other left ventricular heart parts, including atrium, valves, myocardium, and aorta can contribute to the physiological shortfall of cardiac output. It follows that hemodynamic instability and perfusion changes occurring from the aging heart's blood pumping deficiency will, in time, damage vulnerable brain cells linked to specific cognitive regulatory sites, diminishing neuronal energy metabolism to a level where progressive cognitive impairment is the outcome. Could cognitive impairment progress be reversed with a heart transplant? Evidence is presented detailing the errant hemodynamic pathways leading to cognitive impairment during aging as an offshoot of inefficient structural and functional heart parts and their contribution to heart failure.

Natural citric acid assisted synthesis of CuO nanoparticles: Evaluation of structural, optical, morphological properties and colloidal stability for gas sensor applications

Study of electronic structure, elastic properties and thermodynamic properties of three PbTe phases: First-principles calculations

Solving the thermal induced degradation problem of magnetorheological (MR) actuators is crucial for expanding the operational temperature range. Current strategies for mitigating temperature effects primarily focus on developing precise temperature-viscosity models and implementing thermal design optimizations. However, refined numerical models cannot compensate for temperature-induced performance losses, while thermal design solutions face practical limitations due to size constraints, spatial restrictions, and external energy requirements. Notably, the viscous friction heat from MR fluids and Joule heat from coils constitute redundant energy within MR systems. This study aims at establishing a self-regulating torque compensation mechanism utilizing this systemic redundant energy to resolve thermally induced degradation. We present a shape memory alloy-based MR brake (SMA-MRB) that integrates multiple deployable structures on its shaft surface. Thermal activation of the SMA structures transforms the actuator's operational mode from pure shear to combined shear-flow, enabling performance compensation under elevated temperatures. A dedicated rotational speed-torque testing system was developed to evaluate the braking performance of the SMA-MRB. Experimental results demonstrate that SMA deployment increases the maximum braking differential from 191 rpm to 313 rpm. The SMA-MRB achieves up to 64.7% performance enhancement at operating temperatures exceeding 42°C, completely eliminating thermal degradation effects. This demonstrates that the SMA-MRB completely eliminates the effects of thermal degradation, which expands the application boundaries of MR brakes.

The impact of microporouslayer (MPL) on the heat- and mass-transfercharacteristics and power generation performance of a polymer electrolytefuel cell using a thin polymer electrolyte membrane (PEM) and a thingas diffusion layer (GDL) is investigated in this paper. The powergeneration is investigated at the operational temperatures of 90 and100 °C which are the target temperatures from year 2020 to 2025according to the New Energy and Industrial Technology DevelopmentOrganization’s road map in Japan. The in-plane temperaturedistributions on the separator back at the anode and the cathode arealso measured by a thermograph. As a result, it is found that thevoltage drop with the MPL at a high current density is larger comparedto that without the MPL irrespective of the initial temperature ofthe cell and relative humidity conditions. The study also revealedfrom the anode side observation that the in-plane temperature distributionwith the MPL is wider compared to that without the MPL, especiallyat the initial temperature of 90 °C of the cell . Similarly,from the cathode side observation, the in-plane temperature distributionswith the MPL were found to be wider compared to that without the MPL.This study has concluded that the MPL is not effective in obtaininga high performance and even an in-plane temperature distribution fora polymer electrolyte fuel cell with the thin PEM and the thin GDLat a high operational temperature range.