Search Results (435)

The hybridization of additive manufacturing (AM) with conventional manufacturing processes in tooling applications allows the customization of the tool. Examples include weight reduction, improving the vibration-dampening properties, or directing the coolant to the critical zones through intricate conformal cooling channels aimed at extending the tool life. In this regard, metallurgical challenges like the need for a post-processing heat treatment in the AM segment to meet the thermal and mechanical properties requirements persist. Heat treatment can destroy the dimensional accuracy of the pre-manufactured heat-treated wrought segment, on which the AM part is built. In the case of dissimilar joints, heat treatment may further impact the interface properties through the ease of diffusional reactions at elevated temperatures or buildup of residual stresses at the interface due to coefficient of thermal expansion (CTE) mismatch. In this communication, we report on the laser powder bed fusion (L-PBF) processing of MAR 60, a weldable carbon-free maraging powder, to manufacture a hybrid tool holder for general turning applications, comprising a wrought segment in 25CrMo4 low-alloy carbon-bearing tool steel. After L-PBF process optimization and manipulation, as-built (AB) MAR 60 steel was characterized with a hardness and tensile strength of ~450 HV (44–45 HRC) and >1400 MPa, respectively, matching those of pre-manufactured wrought 25CrMo4 (i.e., 42–45 HRC and 1400 MPa). The interface was defect-free with strong metallurgical bonding, showing slight microstructural and hardness variations, with a thickness of less than 400 µm. The matching strength and high Charpy V-notch impact energy (i.e., >40 J) of AB MAR 60 eliminate the necessity of any post-manufacturing heat treatment in the hybrid tool. Full article

As the trend towards the densification of integrated circuit (IC) devices continues, the complexity of interfaces involving dissimilar materials and thermo-mechanical interactions has increased. Highly integrated systems in packages now comprise numerous thin layers made from various materials. The interfaces between these different materials represent a vulnerable point in ICs due to imperfect adhesion and stress concentrations caused by mismatches in thermo-mechanical properties such as Young’s modulus, coefficients of thermal expansion (CTE), and hygro-swelling-induced expansion. This study investigates the impact of thermal variations on the fracture behavior of three bi-material interfaces used in semiconductor packaging: epoxy molding compound–silicon (EMC–Si), silicon oxide–polyimide (SiO₂–PI), and PI–EMC. Using double cantilever beam (DCB) tests, we analyzed these interfaces under mode I loading at three temperatures: −20 °C, 23 °C, and 100 °C, under both quasi-static and cyclic loading conditions. This provided a comprehensive analysis of the thermal effects across all temperature ranges in microelectronics. The results show that temperature significantly alters the failure mechanism. For SiO₂–PI, the weakest point shifts from silicon at low temperatures to the interface at higher temperatures due to thermal stress redistribution. Additionally, the fracture energy of the EMC–Si interface was found to be highly temperature-dependent, with values ranging from 0.136 N/mm at low temperatures to 0.38 N/mm at high temperatures. SiO₂–PI’s fracture energy at high temperature was 42% less than that of EMC–Si. The PI–EMC interface exhibited nearly double the crack growth rate compared to EMC–Si. The findings of this study provide valuable insights into the fracture behavior of bi-material interfaces, offering practical applications for improving the reliability and design of semiconductor devices, especially in chip packaging. Full article

Alumina is one of the most studied and used ceramic materials, but increasing its fracture toughness is still a challenge for many specific impact applications. Adding a second phase with a low coefficient of thermal expansion (CTE) to an alumina matrix can enhance the matrix’s mechanical properties, reduce its sintering temperature, and increase its toughness by generating compressive stresses on the alumina particle surface. In this study, nanostructured alumina/eucryptite composites were prepared to achieve enhanced toughness. First, eucryptite (Li₂O·Al₂O₃·2SiO₂) nanoparticles were successfully synthesised via colloidal heterocoagulation. These nanoparticles were then used to reinforce alumina matrices through slip casting followed by conventional sintering. Complete crystallisation of eucryptite was achieved at 850 °C with a CTE of 0.46 × 10 ⁻⁶ °C ⁻¹. Transmission electron microscopy analysis revealed that the average particle size was 28.5 ± 14.5 nm. To achieve a relative density of 95.3%, the composite containing 5 vol.% eucryptite required sintering for 1 h at 1400 °C whereas pure alumina required 2 h at 1600 °C. This reduction in sintering temperature (by up to 200 °C) helped to improve the fracture toughness, with the alumina grain size decreasing from 2.3 to 0.9 µm. The advantages of the new composite are the more economically viable and environmentally friendly way of producing the lithium aluminosilicate nanoparticles, compared to the production of ceramic frits at high temperatures (~1500 °C). Full article

Atopic dermatitis (AD) is a common inflammatory skin disease characterized by recurrent eczema and chronic itching, affecting a significant portion of the global population. This study investigated the effects of Corydalis Tuber 70% ethanol extract (CTE) on tumor necrosis factor-α- and interferon-γ (TI)-stimulated human keratinocytes (HaCaT) and a house dust mite-induced AD mouse model, elucidating its mechanism via transcriptome analysis. A total of 13 compounds, including columbamine, corydaline, dehydrocorydaline, and glaucine, were identified in CTE using ultra performance liquid chromatography-tandem mass spectrometry. CTE downregulated pathways related to cytokine signaling and chemokine receptors in TI-stimulated HaCaT cells. It significantly inhibited C-C motif chemokine ligand (CCL)5, CCL17, and CCL22 levels by blocking the Janus kinase-signal transducers and activators of transcription and nuclear factor kappa-light-chain-enhancer of activated B cells pathways. In the AD mouse model, topical CTE significantly decreased dermatitis scores, epidermal thickening, and inflammatory cell infiltration. Plasma levels of histamine, immunoglobulin E, CCL17, CCL22, corticosterone, and cortisol were reduced. Lesions showed decreased thymic stromal lymphopoietin, CD4⁺ T cells, interleukin-4, and intercellular adhesion molecule-1 expression. The findings demonstrate that CTE alleviates AD by modulating inflammatory mediators, cytokines, and chemokines, reducing inflammatory cell infiltration, and alleviating stress-related factors. Full article

Making transparent aromatic polymers with high T_g and low thermal expansion behavior, like glass, is challenging. We report transparent and soluble poly(amide-imide)s (PAIs) with high dimensional stability synthesized from the new monomer, trifluoromethylated trimellitic anhydride. Insertion of trifluoromethyl (CF₃) groups into polymer chains enhanced solubility and the optical properties of polymers without sacrificing high thermal stability. Model reactions were utilized to study how the CF₃ group in trimellitic anhydride affects the polymerization reaction with aromatic diamine monomers, and a series of new PAIs were synthesized. All the polymers were soluble in polar organic solvents and can be solution-cast into nearly colorless and flexible freestanding films. The obtained PAI films possessed high thermal stability (T_d5: 437–452 °C in N₂) and high transparency (84~87% transmittance at 550 nm). Interestingly, PAIs prepared in this study exhibited high thermodimensional stability with low CTE values from 9 to 26 ppm/°C. The transparent poly(amide-imide) film with low CTE value finds its application in display and optical devices that require flexible and transparent form factors. Full article

Polymer films with combined properties of good thermoplasticity, good electrical properties, and good thermal endurance are highly required for two-layer flexible copper clad laminate (FCCL) applications. Meanwhile, the black appearance is also required for specific FCCL applications. Therefore, in the present work, a series of ester-linked polyimide (PEsI) films were designed and developed via the copolymerization chemistry of an ester-containing dianhydride of biphenyl dibenzoate-3,3′,4,4′-tetracarboxylic acid dianhydride (BPTME), a rigid-rod dianhydride of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA), an ester-bridged diamine of 2-(4-aminobenzoate)-5-aminobiphenyl (ABABP), and a functional diamine of 4,4′-iminodianiline (NDA). The molar proportion of the BPTME/BPDA was fixed to be 20:80 and that of ABABP/NDA increased from 50:50 for PEsI-1 to 0:100 for PEsI-VI. The afforded PEsI films showed obviously enhanced blackness with the increasing molar ratio of NDA in the polymers. The PEsI-VI film exhibited the optical transmittance values of 0 and 27.4% at the wavelength of 500 nm (T₅₀₀) and 760 nm (T₇₆₀), respectively. The values were apparently lower than those of the standard PI-ref produced from common pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) (T₅₀₀ = 63.2%; T₇₆₀ = 86.3%). Meanwhile, the PEsI-V film showed good blackness with the CIE Lab optical parameters of 1.83 for L*, 11.46 for a*, 3.13 for b*, and 0 for haze. The PEsI samples exhibited good thermoplasticity and the storage and loss modulus of the films rapidly decreased around the glass transition temperatures (T_g) in the dynamic mechanical analysis (DMA) tests. The PEsI samples revealed the T_g values from 247.2 °C to 286.1 °C in the differential scanning calorimetry (DSC) measurements. The PEsI samples exhibited the linear coefficients of thermal expansion (CTE) of (27.1~33.4) × 10⁻⁶/K from 50 to 250 °C, which was comparable to that of the PI-ref sample (CTE = 29.5 × 10⁻⁶/K), however, a bit higher than that of the copper foil (CTE = 17.0 × 10⁻⁶/K). Full article

This study explores the magnitude of shareholders’ say-on-pay (SOP) votes and its impact on CEO compensation. This study draws its sample from US Russell 3000 companies, the largest US companies, from 2011 to 2019. By creating a dummy variable, we further divided our sample into Russell 3000 and S&P 500 for peer comparison. This study employs descriptive statistics, correlation analysis, and pooled OLS regression and finds that CEO compensation has a significant negative association with pay gap opposition. The coefficient and t-statistic were greater for the S&P 500 than for the Russell group. The study also finds that the CEO-to-employee pay ratio (CTE) is positively correlated with the number of shareholders’ dissenting votes. The coefficient and t-statistic were greater for the Russell group than for the S&P 500 group. Each additional point of CTE increases shareholder dissent votes by 1.4% for the Russell 3000 companies. This study has important implications for corporate directors, investors, and policymakers. The study contributes to the corporate governance literature, particularly on executive compensation. Our findings support the perspective of social comparison theory and contend that shareholders view CEO compensation as a biased evaluation of their contribution to the firm. We have developed a unique measure of the CEO-to-employee pay ratio, which is based on SEC methodology. Our findings provide empirical evidence for investors and policymakers in the U.S. and other jurisdictions. Full article

Nanotheranostics integrates diagnostic and therapeutic functionalities using nanoscale materials, advancing personalized medicine by enhancing treatment precision and reducing adverse effects. Key materials for nanotheranostics include metallic nanoparticles, quantum dots, carbon dots, lipid nanoparticles and polymer-based nanocarriers, each offering unique benefits alongside specific challenges. Polymer-based nanocarriers, including hybrid and superparamagnetic nanoparticles, improve stability and functionality but are complex to manufacture. Polymeric nanoparticles with aggregation-induced emission (AIE) present promising theranostic potential for cancer detection and treatment. However, challenges such as translating the AIE concept to living systems, addressing toxicity concerns, overcoming deep-tissue imaging limitations, or ensuring biocompatibility remain to be resolved. Recently, cluster-triggered emission (CTE) polymers have emerged as innovative materials in nanotheranostics, offering enhanced fluorescence and biocompatibility. These polymers exhibit increased fluorescence intensity upon aggregation, making them highly sensitive for imaging and therapeutic applications. CTE nanoparticles, crafted from biodegradable polymers, represent a safer alternative to traditional nanotheranostics that rely on embedding conventional fluorophores or metal-based agents. This advancement significantly reduces potential toxicity while enhancing biocompatibility. The intrinsic fluorescence allows real-time monitoring of drug distribution and activity, optimizing therapeutic efficacy. Despite their potential, these systems face challenges such as maintaining stability under physiological conditions and addressing the need for comprehensive safety and efficacy studies to meet clinical and regulatory standards. Nevertheless, their unique properties position CTE nanoparticles as promising candidates for advancing theranostic strategies in personalized medicine, bridging diagnostic and therapeutic functionalities in innovative ways. Full article

With the development of high-density integrated chips, low-k dielectric materials are used in the back end of line (BEOL) to reduce signal delay. However, due to the application of fine-pitch packages with high-hardness copper pillars, BEOL is susceptible to chip package interaction (CPI), which leads to reliability issues such as the delamination of interlayer dielectric (ILD) layers. In order to improve package reliability, the effect of CPI at multi-scale needs to be explored in terms of package integration. In this paper, the stress of BEOL in the flip-chip chip-scale packaging (FCCSP) model during thermal cycling is investigated by using the finite-element-based sub-model approach. A three-dimensional (3D) multi-level finite element model is established based on the FCCSP. The wiring layers were treated by the equivalent homogenization method to ensure high prediction accuracy. The stress distribution of the BEOL around the critical bump was analyzed. The cracking risk of the interface layer of the BEOL was assessed by pre-cracking at a dangerous location. In addition, the effects of the epoxy molding compound (EMC) thickness, polyimide (PI) opening, and coefficient of thermal expansion (CTE) of the underfill on cracking were investigated. The simulation results show that the first principal stress of BEOL is higher at high-temperature moments than at low-temperature moments, and mainly concentrated near the PI opening. Compared with the oxide layer, the low-k layer has a higher risk of cracking. A smaller EMC thickness, lower CTE of the underfill, and larger PI opening help to reduce the risk of cracking in the BEOL. Full article

A good quantitative knowledge of regional sources and sinks of atmospheric carbon dioxide (CO₂) is essential for understanding the global carbon cycle. It is also a key prerequisite for elaborating cost-effective national strategies to achieve the goals of the Paris Agreement. However, available estimates of CO₂ fluxes for many regions of the world remain uncertain, despite significant recent progress in the remote sensing of terrestrial vegetation and atmospheric CO₂. In this study, we investigate the feasibility of inferring reliable regional estimates of the net ecosystem exchange (NEE) using column-averaged dry-air mole fractions of CO₂ (XCO₂) retrieved from Orbiting Carbon Observatory-2 (OCO-2) observations as constraints on parameters of the widely used Vegetation Photosynthesis and Respiration model (VPRM), which predicts ecosystem fluxes based on vegetation indices derived from multispectral satellite imagery. We developed a regional-scale inverse modeling system that applies a Bayesian variational optimization algorithm to optimize parameters of VPRM coupled to the CHIMERE chemistry transport model and which involves a preliminary transformation of the input XCO₂ data that reduces the impact of the CHIMERE boundary conditions on inversion results. We investigated the potential of our inversion system by applying it to a European region (that includes, in particular, the EU countries and the UK) for the warm season (May–September) of 2021. The inversion of the OCO-2 observations resulted in a major (more than threefold) reduction of the prior uncertainty in the regional NEE estimate. The posterior NEE estimate agrees with independent estimates provided by the CarbonTracker Europe High-Resolution (CTE-HR) system and the ensemble of the v10 OCO-2 model intercomparison (MIP) global inversions. We also found that the inversion improves the agreement of our simulations of XCO₂ with retrievals from the Total Carbon Column Observing Network (TCCON). Our sensitivity test experiments using synthetic XCO₂ data indicate that the posterior NEE estimate would remain reliable even if the actual regional CO₂ fluxes drastically differed from their prior values. Furthermore, the posterior NEE estimate is found to be robust to strong biases and random uncertainties in the CHIMERE boundary conditions. Overall, this study suggests that our approach offers a reliable and relatively simple way to derive robust estimates of CO₂ ecosystem fluxes from satellite XCO₂ observations while enhancing the applicability of VPRM in regions where eddy covariance measurements of CO₂ fluxes are scarce. Full article

Arterial hypertension has a high prevalence in the population and is considered both a cardiovascular disease and an important risk factor for the development of other cardiovascular diseases. Tea consumption shows antihypertensive effects due to its composition in terms of bioactive substances such as flavan-3-ols and xanthines. The aim of this study was to assess the possible beneficial effects of two tea extracts, one of white tea (ADM^® White Tea; WTE) and another one composed of a mixture of black tea and green tea (ADM^® Tea Complex; CTE), on the cardiovascular alterations induced by angiotensin II (AngII) infusion in mice. For this purpose, four groups of C57BL/6J male mice were used: (1) mice fed on a standard diet for 8 weeks and infused with saline for the last 4 weeks (controls); (2) mice fed on a standard diet for 8 weeks and infused with AngII for the last 4 weeks (AngII); (3) mice fed on a standard diet supplemented with 1.6% WTE and infused with AngII for the last 4 weeks (AngII + WTE); (4) mice fed on a standard diet supplemented with 1.6% TC and infused with AngII for the last 4 weeks (AngII + CTE). Both tea extracts exerted anti-inflammatory and antioxidant effects in arterial tissue and reduced AngII-induced endothelial dysfunction in aorta segments. Moreover, supplementation with WTE or CTE reduced the Ang-II-induced overexpression of AT1R and increased AngII-induced downregulation of AT2R in arterial tissue. However, only supplementation with CTE significantly increased the circulating levels of angiotensin 1-7 and reduced systolic blood pressure. In the heart, supplementation with both tea extracts attenuated AngII-induced cardiac hypertrophy and reduced ischemia-reperfusion-induced oxidative stress and apoptosis in myocardial tissue. In conclusion, supplementation with WTE or CTE attenuates AngII-induced cardiovascular damage through their anti-inflammatory, antioxidant, and antiapoptotic effects. In addition, supplementation with CTE also exerts antihypertensive effects, and so it may constitute an avenue through which to support cardiovascular health. Full article

Super invar, with its near-zero coefficient of thermal expansion (CTE), has a great potential to be used in the design and fabrication of high-precision optical structures, such as optical mirror substrates. In order to reduce the weight and maintain the strength of the mirror substrate, several biomimetic lattice designs were investigated in this paper. The static modeling provides a systematic study on different types of biomimetic mirror substrates. The impact of structure parameters, such as the wall thickness, lattice unit length, height of the lattice structure, and the thickness of the side plate, are also studied. It turns out that the three-layer lattice-structured composite mirror substrate has the best performance. With AM techniques, three-layer gyroid optical structures, which are not possible to fabricate with conventional manufacturing technology, were designed and printed with our in-house-built AM machine. The stiffness test of the gyroid specimens was in good agreement with the modeling results. The gyroid structure shows about a 20% improvement over the honeycomb structure. The gyroid design reduces the equivalent density to 1.8 g/cm³ and has an order-of-magnitude improvement on the thermal deformation, while maintaining a comparable strength with that of beryllium. Full article

The low coefficient of thermal expansion of Invar 36 represents a significant consideration in light of its potential effects, particularly in industrial applications where thermal stability is of paramount importance. In light of this, a three-step heat treatment was employed, to reduce the thermal expansion coefficient, and enhance the thermal dimensional stability. The ingots produced by vacuum induction melting were subjected to a warm-rolling process at 900 °C, followed by a three-step heat treatment consisting of water quenching at 850 °C, tempering at 350 °C with a holding time of 1 h, and aging at 100 °C for 24 h. This process enabled the coefficient of thermal expansion to remain almost unchanged, exhibiting values between 0.5 and 0.6 × 10⁻⁶/°C up to 150 °C. Following the heat treatment, the total elongation increased up to 40% as a natural consequence of the reduction of residual stresses, while a slight decrease in tensile strength was observed. The implementation of a three-step heat treatment process has facilitated an enhancement of the soft magnetic property, which has exhibited a decline in coercivity and an increase in saturation magnetization. As a consequence, three-step heat-treated Invar 36 alloys are emerging as a potential candidate for utilization in the aerospace and precision electronics industries, given their satisfactory physical and mechanical characteristics. Full article

Interferometric radiometers operating at L-band, such as ESA’s SMOS mission, enable crucial Earth observations providing high-resolution measurements of soil moisture, ocean salinity, and other geophysical parameters. However, the increasing electromagnetic spectrum utilization has led to significant Radio Frequency Interference (RFI) challenges, particularly critical given the sensors’ fine temperature resolution requirements of less than 1 K. This work presents the hardware implementation of an advanced RFI detection and mitigation algorithm specifically designed for interferometric radiometers, targeting future L-band missions. The implementation processes 1-bit quantized signals at 57.69375 MHz from multiple receivers, employing time-frequency analysis and polarimetric detection techniques while optimizing Field Programmable Gate Array (FPGA) resource utilization. Novel optimization strategies include overclocked processing cores operating at 230.775 MHz, efficient resource sharing through operation serialization, and strategic memory management. The system achieves real-time processing capabilities while maintaining detection probabilities above 63% with false alarm rates below 1% for typical interference scenarios. Performance validation using synthetic datasets demonstrates robust operation across various RFI conditions, making this implementation suitable as part of the RFI detection and mitigation efforts for future interferometric radiometer missions beyond SMOS. Full article

With the rapid advancement of technology, precision agriculture, as a modern agricultural production model, has seen significant progress in recent years. Its widespread adoption is gradually transforming traditional farming methods, providing strong support for the modernization of global agriculture. In particular, the application of positioning technology plays a crucial role in precision agriculture. This paper focuses on an automated agricultural machinery positioning system based on Bluetooth technology. The system uses Bluetooth at the 2.4 GHz frequency for transmission, processing Constant Tone Extension (CTE) and Received Signal Strength Indicator (RSSI) signals collected from blind nodes. The Propagator Direct Data Acquisition (PDDA) algorithm is employed to calculate angle information from CTE signals, while the Two-Ray Ground Reflection Model is applied to manage the correlation between RSSI and distance, making it suitable for outdoor environments. These two types of data are fused for positioning, with an optimized objective function converting the positioning task into an optimization problem. An Adaptive Secretary Bird Optimization Algorithm (ASBOA) is introduced to enhance the accuracy and efficiency of the positioning process. In the simulation, anchor and blind nodes are deployed to simulate a real farm environment. Anchor nodes receive CTE and RSSI signals from blind nodes. Considering that the tags mounted on agricultural machinery are set at a fixed height in real scenarios, the simulation also fixes the tags at this height. We then compare the accuracy of five algorithms in both static and dynamic tracking. The final simulation results indicate that ASBOA achieves satisfactory high-precision positioning, both for static points and dynamic tracking, theoretically meeting the needs for continuous positioning and laying a solid foundation for future field trials. Full article