Improved Temperature Stability Research Articles

Optimization of Erbium-Doped Fiber to Improve Temperature Stability and Efficiency of ASE Sources

The ASE (Amplified Spontaneous Emission) light source, based on erbium-doped fiber (EDF), is a broadband light source with advantages such as high power, excellent temperature stability, and low coherent light generation. It is widely used in the field of fiber optic sensing. However, traditional ASE sources suffer from temperature sensitivity and low efficiency, which can compromise the accuracy and stability of the output light’s average wavelength. This study focuses on optimizing the erbium-doped fiber (EDF) to improve the temperature stability and efficiency of the ASE light source. Through simulations, we found that the appropriate doping concentration and length of the EDF are key factors in enhancing the stability and efficiency of the ASE source. Inorganic metal chloride vapor-phase doping combined with an improved chemical vapor deposition process was used to fabricate the erbium-doped fiber, ensuring low background loss, minimal OH− absorption, and uniform distribution of the erbium ions in the core of the fiber. The optimized EDFs were integrated into the ASE source, achieving a power conversion efficiency of 53.6% and a temperature stability of 0.118 ppm/°C within the temperature range of −50 °C to 70 °C. This study offers a practical approach for improving the performance of ASE light sources and advancing the development of high-precision fiber optic sensing technologies.

Cooperative control strategy of variable evaporation temperature and variable superheat degree for a VRF system to improve temperature stability in multiple rooms

The energy consumption of variable refrigerant flow (VRF) systems can be reduced by adopting the variable evaporation temperature and constant superheat degree (VECS) control strategy instead of constant evaporation temperature and constant superheat degree (CECS) control strategy. However, the constant superheat degree control strategy may weaken the adjustment ability of cooling capacity of indoor units, and result in obvious room temperature fluctuations. In order to decrease room temperature fluctuations and reduce energy consumption simultaneously, a cooperative control strategy of variable evaporation temperature and variable superheat degree (VEVS) is proposed, i.e. one indoor unit is chosen to be controlled by variable evaporation temperature and the rest of the indoor units are controlled by variable superheat degrees. In this control strategy, the target value of evaporation temperature is the lowest value among the upper limits of the evaporation temperatures of all indoor units, and the target values of the superheat degrees of indoor units are predicted according to the cooling demands of rooms. Comparative experiments on room temperature fluctuation and energy consumption among the control strategies of CECS, VECS and VEVS are done. It is shown that both the control strategies of VECS and VEVS achieve smaller room temperature fluctuation and lower energy consumption than those of CECS; compared with the VECS control strategy, the average room temperature fluctuation of the VEVS control strategy is decreased from 1.1 °C to 0.5 °C due to variable superheat degree, and the energy consumption of the VEVS control strategy is reduced by 4.4 %.

Functional recycling of grain boundary diffusion processed Nd-Fe-B sintered magnets

Sintered Nd-Fe-B magnets industrially produced employing the grain boundary diffusion process (GBD) were recycled by the so-called functional or short-loop recycling approach, based on hydrogen decrepitation (HD). Microstructural and magnetic differences between the original and the recycled materials were analyzed. The functional recycling of GBD magnets leads to the dissolution of the core (heavy rare earth lean) - shell (heavy rare earth rich) structure through the different heat treatment steps which include hydrogen decrepitation, sintering, and annealing. The recycled magnets show similar rectangular demagnetization curves with squareness of 96 %, and only a slightly decreased remanence of 5 % to 1.31 T, but a larger decrease in coercivity of 21 % to 1703 kA/m. A new GBD step using 1.5 wt.% Tb with a pure Tb-foil as diffusion source leads again to the formation of a core-shell structure with 0.5 µm thick Tb-shells which is similar to the microstructure of the original magnets prior to recycling. The coercivity of the recycled magnets is increased by 35 % from 1315 kA/m to 1780 kA/m at 50 °C and shows similar magnetic values as the original industrial magnets at 150 °C and 200 °C, respectively. The temperature coefficients for the remanence, α, and for the coercivity, β, can also be fully restored and even exceed the original values which leads to an improved temperature stability of the recycled magnets compared to the original magnets.

Optimizing giant dielectric performance in CCTO ceramics through Cr and Zn co-doping

The CaCu3Ti4O12 and CaCu2.95Zn0.05Ti4-xCrxO12 (x = 0, 0.05, and 0.10) ceramics were synthesized via solid-state reaction and sintered at 1110 °C for 3 h. XRD analysis confirmed that all samples maintained a single phase, free from impurities. SEM images revealed minor differences in grain size when comparing the undoped ceramic to those with co-doping. Notably, the co-doped CaCu2.95Zn0.05Ti3.95Cr0.05O12 ceramic exhibited significantly enhanced dielectric properties, including a high dielectric permittivity of 4.17 × 104 and a low loss tangent of 0.027. This ceramic also demonstrated stable dielectric permittivity with less than a 22 % variation from −60 to 90 °C, meeting the X5S and Y5S ceramic capacitor standards. In our first-principles calculations, we selected the CaCu2.95Zn0.05Ti3.95Cr0.05O12 structure because of its superior dielectric characteristics compared to the others. Our total energy calculations revealed that the Cr and Zn dopants are likely to be far apart from each other, indicating the absence of defects caused by the Zn and Cr dopants in the grains of our samples. The electrical property results indicate that the substitution of Zn2+ and Cr3+ ions into the CCTO lattice may help reduce oxygen loss during the sintering process at high temperatures. As a result, the need for charge compensation of Cu and Ti ions is diminished, leading to an increase in the grain and grain boundary resistances in the CaCu2.95Zn0.05Ti3.95Cr0.05O12 ceramic. Based on these results, the electrical conductivity of the material decreases, which contributes to a lower loss tangent value and improved temperature stability of the dielectric permittivity. The experimental and computational results indicated that the high dielectric permittivity is primarily due to the formation of an internal barrier layer capacitor, while improvements in dielectric properties may be associated with changes in intrinsic defects, which enhance the grain boundary response.

Active phase and amplitude temperature control method for cryostat: A case in the thermodynamic temperature international comparison system

Achieving highly stable temperature control is essential for cryostats. However, the cryocooler used in cryostats, such as the pulse tube cryocooler, produces regular sinusoidal temperature fluctuations due to its inherent working principles. To establish a highly stable temperature environment, an active phase and amplitude control method for suppressing temperature fluctuation is proposed in this paper, by which the optimal phase and amplitude can be predicted in theory. To validate this approach, a thermal response model was developed based on experiments conducted in the thermodynamic temperature international comparison cryostat at approximately 3.7 K. Based on this model, we conducted both single-stage and multi-stage active temperature control experiments. The results demonstrate that the temperature control effect is the best when the active temperature control current is added at the second cold head, the fluctuation of the comparison copper block from 3.3mK to 0.166mK with 94.9 % suppression rate. The multi-stage joint temperature control reduced the temperature fluctuation with an attenuation rate of 95.4 %. These findings offer significant potential for improving temperature stability in future thermodynamic temperature comparison experiments.

Semi-rational engineering of ω-transaminase for enhanced enzymatic activity to 2-ketobutyrate

Transaminases (EC 2.6.1.X, TAs) are important biocatalysts in the synthesis of chiral amines, and have significant value in the field of medicine. However, TAs suffer from low enzyme activity and poor catalytic efficiency in the synthesis of chiral amines or non-natural amino acids, which hinders their industrial applications. In this study, a novel TA derived from Paracoccus pantotrophus (ppTA) that was investigated in our previous study was employed with a semi-rational design strategy to improve its enzyme activity to 2-ketobutyrate. By using homology modeling and molecular docking, four surrounding sites in the substrate-binding S pocket were selected as potential mutational sites. Through alanine scanning and saturation mutagenesis, the optimal mutant V153A with significantly improved enzyme activity was finally obtained, which was 578 % higher than that of the wild-type ppTA (WT). Furthermore, the mutant enzyme ppTA-V153A also exhibited slightly improved temperature and pH stability compared to WT. Subsequently, the mutant was used to convert 2-ketobutyrate for the preparation of L-2-aminobutyric acid (L-ABA). The mutant can tolerate 300 mM 2-ketobutyrate with a conversion rate of 74 %, which lays a solid foundation for the preparation of chiral amines.

Preparation and in vitro evaluation of tissue plasminogen activator-loaded nanoliposomes with anticoagulant coating

The clinical efficacy of tissue plasminogen activator (tPA) is limited by its lack of specific delivery, requiring large therapeutic doses that increase the risk of intracerebral hemorrhage, bleeding at the surgical site, and patient mortality after angioplasty. To address these limitations, this study aimed to develop a chitosan polysulfate (CsPs)-coated liposomal formulation for the sustained release of tPA. The CsPs-coated liposomes containing tPA (Liposome-tPA/CsPs) were fabricated using the thin-film hydration technique and their properties were compared to tPA-encapsulated nanoliposomes without a coating layer (Liposome-tPA). Liposome-tPA/CsPs showed a quasi-spherical morphology with a hydrodynamic diameter of 110 nm, while Liposome-tPA had a diameter of 80 nm. The thermal analysis showed that the degradation temperature and glass transition temperature (Tg) of Liposome-tPA/CsPs were higher than that of tPA alone, indicating improved temperature stability. The in vitro release study demonstrated a slow and sustained release of tPA from the Liposome-tPA/CsPs, with a concentration of 0.02 mg/ml at 1 h and 0.23 mg/ml at 180 h. The CsPs coating layer enhanced the antibacterial and antioxidant activity of the nanoliposomes. Liposome-tPA/CsPs exhibited higher cell viability compared to Liposome-tPA. It also achieved a higher percentage of thrombolysis, with complete clot dissolution observed after 3 h of treatment. These findings suggest that the Liposome-tPA/CsPs can be a promising approach to overcome the limitations associated with the systemic administration of tPA, potentially enhancing its clinical efficacy while reducing the risk of adverse events.

Low temperature sintering and improvement of temperature Stability of Ba3P4O13 microwave dielectric ceramics by BCB additions

In our previous study, Ba3P4O13 ceramic was found to exhibit good microwave dielectric performance with a low permittivity (εr), a high Q × f (Q = 1/dielectric loss, f = resonant frequency) value but a large positive τf value (TCF, temperature coefficient of resonant frequency), which limits its application in low-temperature co-fired ceramic (LTCC) technology. BaCu(B2O5) (BCB) additions were selected in this study to adjust τf value of Ba3P4O13 ceramic samples. It was found that as BCB contents increased, sintering temperatures decreased from 840 °C (without BCB addition) to 820 °C (with 2 wt. % BCB), meanwhile τf values of ceramic samples were reduced from + 48 ppm/ °C to − 2 ppm/ °C. Moreover, BCB added Ba3P4O13 ceramic showed a good chemical compatibility with Cu electrode. These results indicate that BCB added Ba3P4O13 ceramics are promising candidate for LTCC applications.

Investigation of coherent interface on relaxation behavior and reliability of Mg-doped BaTiO3 dielectric ceramics: Experiments and first-principle calculations

The addition of Mg generally enhances the high-temperature stability and reliability of BaTiO3-based multilayer ceramic capacitors (MLCCs). Herein, a series of Mg-doped BaTiO3-based ceramics and ultra-thin MLCCs were successfully fabricated, and the coherent and semi-coherent interface has been observed in samples. Based on the density functional theory (DFT) calculations, the improvement in temperature stability is due to changes in the coherent interface and electronic structure that promote the formation of polar nano-regions (PNRs) and induce relaxation behavior. Based on the atomic displacement, it is found that the excess substitution released the coherent stresses in the form of defects and formed semi-coherent interfaces. The reliability degradation of MLCCs is mainly due to the evolution of the semi-coherent interfaces. This work points out an avenue to obtain high-temperature stability and high reliability in BaTiO3-based MLCCs.

Sandwiched structure for temperature compensated laterally excited bulk wave resonators based on lithium niobate film

Recently, lithium niobate thin film laterally excited bulk wave resonators (XBARs) have attracted much attention because of their advantage of high frequency and outstanding electromechanical coupling factor (K2) enabling wide filter bandwidths. These can satisfy the increasing 5G communication demand. However, their large temperature coefficient limits their development to some extent. To improve their temperature stability with little K2 reduction, this paper has proposed a sandwiched structure for temperature compensated XBARs (TC XBARs). This structure includes the top silicon dioxide (SiO2) layer and the bottom SiO2 layer. One layer can improve temperature stability, and the other layer can increase K2. The optimized XBARs have a temperature coefficient of frequency (TCF) of −90.77 ppm⁄°C. The common two-layer TC XBARs can achieve a TCF of −22 ppm⁄°C sacrificing K2 to 8%. However, the proposed sandwiched TC XBARs can achieve a K2 of 12.15 and a TCF of −28.94 ppm⁄°C simultaneously, with a large FoM. Meanwhile, spurious modes can be suppressed in the sandwiched structure. Thus, this sandwiched structure can provide a good solution for the high performance of XBARs.

Thermoelectric active cooling for transient hot spots in microprocessors

Modern microprocessor performance is limited by local hot spots induced at high frequency by busy integrated circuit elements such as the clock generator. Locally embedded thermoelectric devices (TEDs) are proposed to perform active cooling whereby thermoelectric effects enhance passive cooling by the Fourier law in removing heat from the hot spot to colder regions. To mitigate transient heating events and improve temperature stability, we propose a novel analytical solution that describes the temperature response of a periodically heated hot spot that is actively cooled by a TED driven electrically at the same frequency. The analytical solution that we present is validated by experimental data from frequency domain thermal reflectance (FDTR) measurements made directly on an actively cooled Si thermoelectric device where the pump laser replicates the transient hot spot. We herein demonstrate a practical method to actively cancel the transient temperature variations on circuit elements with TEDs. This result opens a new path to optimize the design of cooling systems for transient localized hot spots in integrated circuits.

Contact engineering for temperature stability improvement of Bi-contacted MoS2 field effect transistors

Contact engineering for temperature stability improvement of Bi-contacted MoS2 field effect transistors

Control-oriented thermal model and load identification for circulating cooling water system in precision process applications

With the increasing precision in machining and measurement, there is a growing demand for improved temperature stability in cooling water systems used in industrial processes. Accurate thermal models and load states are essential for developing efficient controllers to enhance temperature performance. This paper focuses on the development of thermal models for various components of circulating water systems in precision water-cooling processes. It presents a control-oriented thermal model framework that segregates the water circulation cycles and defines system inputs and processes. A novel identification algorithm is proposed to address thermal inertia and cyclic nonlinearity by extracting the cyclic period and cycle change rate. The algorithm can simultaneously estimate the state–space model and unmeasurable load disturbances. A validation experimental setup was constructed, and the results demonstrate that, for different flow scenarios, the estimated load and thermal model parameters align well, with correlations exceeding 0.85 and error ratios close to 10%. Additionally, the circulating water output temperature can be accurately predicted. The fitting degrees surpass 84% within five cycles, with correlations exceeding 0.97 and error standard deviations below 0.22 °C.

Effects of the geometric characteristics of graphene nanoplatelets on the physico-rheological properties of asphalt binder

While graphene nanoplatelets (GnPs) have emerged as promising nano-modifiers of asphalt binder in recent years, much is still unknown in terms of the existing correlations between the physical, chemical, and geometric characteristics of this nanofiller and observed asphalt binder properties. In this work, we investigate the important correlation between the geometric characteristics of GnPs and the rheological properties of the GnP-modified asphalt binder at high temperatures. Our results indicate that, in general, incorporating GnPs with large mean particle diameters (> 14 μm) and thicknesses (> 8 nm) enhances the high-temperature performance of the asphalt binder. The results of the multiple stress creep and recovery tests confirm that including GnPs in asphalt binder can decrease its permanent deformation by 33.2% and enhance its elastic recovery by 53.9%. Phase contrast images obtained by atomic force microscopy further indicate that the presence of GnPs with large mean particle diameters alters the morphology of the asphalt binder, leading to improved temperature stability and less susceptibility to permanent deformation.

Stable macro-performance at extreme cold region for KNN-based ceramics with modified phase boundary

High performance with good stability is important for practical application of electronic devices. As abundant researches related to the stability at room temperature and above have been adopted, the characteristic at extreme cold region is little concentrated on, impeding the development of plateau section. Herein, the stability of electrical properties is emphasized on at extreme cold region for the KNN ceramics with polycrystal phase boundary. Rhombohedral-orthorhombic (R-O) phase boundary is successfully formed from extreme cold region to room temperature. Notably, stable polarization is revealed with maintained R-O phase boundary. Little changed piezoelectric response is gained with modified R-O phase boundary, indicating that abundant O and lesser R phases coexistence is beneficial of improving temperature stability at extreme cold region. Thus, this work demonstrates a tool for optimizing performance at extreme cold region of lead-free ceramics, accelerating the application of electronic devices at plateau-climate regions.

Exploring the Implementation of GaAsBi Alloys as Strain-Reducing Layers in InAs/GaAs Quantum Dots.

This paper investigates the effect of GaAsBi strain reduction layers (SRLs) on InAs QDs with different Bi fluxes to achieve nanostructures with improved temperature stability. The SRLs are grown at a lower temperature (370 °C) than the usual capping temperature for InAs QDs (510 °C). The study finds that GaAs capping at low temperatures reduces QD decomposition and leads to larger pyramidal dots but also increases the threading dislocation (TD) density. When adding Bi to the capping layer, a significant reduction in TD density is observed, but unexpected structural changes also occur. Increasing the Bi flux does not increase the Bi content but rather the layer thickness. The maximum Bi content for all layers is 2.4%. A higher Bi flux causes earlier Bi incorporation, along with the formation of an additional InGaAs layer above the GaAsBi layer due to In segregation from QD erosion. Additionally, the implementation of GaAsBi SRLs results in smaller dots due to enhanced QD decomposition, which is contrary to the expected function of an SRL. No droplets were detected on the surface of any sample, but we did observe regions of horizontal nanowires within the epilayers for the Bi-rich samples, indicating nanoparticle formation.

Temperature fluctuations during embryo transfer can be mitigated by optimizing transfer protocol

Research QuestionWhat impact do variations in embryo transfer catheter loading and movement procedures have on temperature and pH fluctuations during embryo transfer? DesignMock embryo transfers were conducted to test the impact of airflow/movement, use of catheter coverings and the type of workstation used for catheter loading on catheter temperature. A thermocouple probe inserted into the tip of the outer catheter or taped to the exterior of the inner catheter recorded temperature within the catheter every 5 sec from time of mock embryo loading (TL) up to 60 sec (TL +60s). Fluctuations in culture medium pH in embryo transfer dishes were monitored. ResultsCatheter temperature was lower at TL+15s (26.8 ±0.61°C) than TL (30.5 ±0.81°C, P <0.05). The rate of cooling during transit was slower when catheters were covered to reduce the cooling effect of air movement (P<0.05). Temperature was better maintained when catheters were loaded in a crib compared to a heated stage, until initiation of transit, when the rate of temperature decrease was similar. Culture medium pH increased faster when embryo transfer dishes remained on a heated stage during the procedure compared to within an open crib. ConclusionsTemperature loss during the ET procedure can be mitigated by reducing transit time and using catheter coverings. Use of a crib for catheter loading only improved temperature stability while the catheter remained in the crib, not during transit, and it reduced pH fluctuations during the procedure.

Large Tolerance of Lasing Properties to Impurity Defects in GaAs(Sb)‐AlGaAs Core‐Shell Nanowire Lasers

AbstractGaAs‐AlGaAs based nanowire (NW) lasers hold great potential for on‐chip photonic applications, where lasing metrics have steadily improved over the years by optimizing resonator design and surface passivation methods. The factor that will ultimately limit the performance will depend on material properties, such as native‐ or impurity‐induced point defects and their impact on non‐radiative recombination. Here, the role of impurity‐induced point defects on the lasing performance of low‐threshold GaAs(Sb)‐AlGaAs NW‐lasers is evaluated, particularly by exploring Si‐dopants and their associated vacancy complexes. Si‐induced point defects and their self‐compensating nature are identified using correlated atom probe tomography, resonant Raman scattering, and photoluminescence experiments. Under pulsed optical excitation the lasing threshold is remarkably low (&lt;10 µJ cm−2) and insensitive to impurity defects over a wide range of Si doping densities, while excess doping ([Si]&gt;1019 cm−3) imposes increased threshold at low temperature. These characteristics coincide with increased Shockley‐Read‐Hall recombination, reflected by shorter carrier lifetimes, and reduced internal quantum efficiencies (IQE) . Remarkably, despite the lower IQE the presence of self‐compensating Si‐vacancy defects provides an improved temperature stability in lasing threshold with higher characteristic temperature and room‐temperature lasing. These findings highlight an overall large tolerance of lasing metrics to impurity defects in GaAs‐AlGaAs based NW‐lasers.

Boosting the performance of PBDB-T/ITIC based organic solar cell: A theoretical analysis utilizing SCAPS-1D

Solar cells have become the centre of academic research in recent times, primarily owing to their ability to generate cost-effective and environmentally friendly sustainable energy on a commercial and industrial level. In this study, we propose the initiation of a research attempt focused on polymer solar cells that employ PBDB-T/ITIC as the active material. To facilitate this investigation, we have employed SCAPS-1D, a robust simulation program widely recognized for its effectiveness in the field. The objective of this study is to enhance the efficiency of a polymer solar cell composed of PBDB-T/ITIC as the absorber, P3HT as the Hole Transport Layer (HTL), and WS2 as the Electron Transport Layer (ETL) through the utilization of SCAPS simulation techniques. By systematically manipulating various parameters within the SCAPS device simulator, we have successfully incorporated the impact of temperature, thickness, defect density, and metal contacts on key performance parameters such as Open Circuit Voltage (Voc), Short Circuit Current density (Jsc), Fill Factor (FF), and Power Conversion Efficiency (PCE). We have developed a novel polymer-based solar cell utilizing the PBDB-T/ITIC material, which exhibits enhanced efficiency, improved temperature stability, and reduced environmental impact. The findings of our study may have the potential to assist the thin-film photovoltaic industry in the development of economically feasible and highly efficient polymer based solar cells.

Improved temperature stability of low-fired Li2Mg3SnO6 microwave dielectric ceramics by using (La0.5Na0.5)TiO3 additives

The (1-x)Li2Mg3SnO6-x(La0.5Na0.5)TiO3-4wt%LiF (x = 0.05, 0.10, 0.15, 0.20) ceramics were prepared in order to produce an alternative material for communication components. Its phase structure composition, sintering properties, microstructure and dielectric performances with the addition of (La0.5Na0.5)TiO3 were studied. All sintered samples exhibit a phase structure composed of main phases Li2Mg3SnO6 and La2Sn2O7 with a small amount of Li2SnO3. The sample showed a densification sintering in 875 °C–950 °C sintering range. Influenced by the amount of (La0.5Na0.5)TiO3 added, the value of temperature coefficient of resonant frequency (τf) is gradually adjusted from negative to positive. When x is equal to 0.15, the good comprehensive property of dielectric constant (εr) ∼ 11.9, quality factor (Q×f) ∼ 10400 GHz, and τf ∼ −6.4 ppm/°C can be obtained for 0.85Li2Mg3SnO6-0.15(La0.5Na0.5)TiO3-4wt%LiF ceramics at 900 °C. This material is suitable for development as an alternative to LTCC applications.