bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Analysis of Immersed Confined Coaxial Liquid Jet Impingement Heat Transfer for Electronics Thermal Management
Authors: Kahbandeh Faramarz , Harris Daniel , Arik Mehmet
Published: November 2024

A large amount of data has been loaded into data centers as well as faster computational time due to the current emergence of artificial intelligence (AI), augmented reality (AR), 5G mobile networks, and digital currencies. These data require a significant amount of processing power, and as a result, this enormous processing performance generates heat in electronic chips and data center racks specifically. Conventional cooling methods are not capable of answering thermal management requirements in electronic systems. Therefore, novel techniques are needed to meet aggressive demands. One of those candidate cooling approaches is dielectric liquid impingement heat transfer. A computational study has been performed to understand the impact on chip cooling. The current study uses a constant heat flux thermal boundary condition to computationally analyze a confined coaxial impingement water jet on a heated flat plate. Four velocity ratios, three jet to target distances, and three different Re numbers have been studied through numerical simulations. The finite volume method (FVM) was used to solve the governing equations on discretized elements with RANS SST k-ω turbulence model. It has been noted that the local heat transfer coefficients increase with increasing Re numbers. On the heated flat plate, increasing the jet to target distance and decreasing the velocity ratio cause turbulence effects and increase in Nu number over the radial distance especially in the stagnation region. Additionally, it was revealed that the coaxial jet’s attained higher heat transfer characteristics than the single circular jet’s.
Effect of Passivation Layer and Line Thickness on Damage Mechanism of Flexible Ag Nanowire Interconnects Under High Density Current
Authors: Hisasue Kazuki , Sasagawa Kazuhiko , Fujisaki Kazuhiro , Miura Kotaro , Souma Yusuke
Published: November 2024

In recent years, the demand of flexible electronic circuits has been increasing with the development of wearable devices. Ag nanowire network structures are attracting attention as a material for flexible transparent conductive films because of their low cost, flexibility and light transmittance. In general, the density of electric current flowing through the interconnect line increases as devices become smaller. The increase in density of electric current leads to problems of line failure due to electromigration (EM), and it is known that resistance EM damage can be improved by passivation layer coating. In previous studies, it has been found that Ag nanowires were damaged by EM. However, the EM damage mechanism of network-structured Ag nanowire line under high-density current and the effect of passivation layer have not been clarified. Then, in this study, Ag nanowire network line coated with a passivation layer was fabricated. Furthermore, Ag nanowire networked line intentionally expanded in thickness direction was fabricated to measure the line thickness change with damage. We conducted accelerated electric current loading tests on these test lines and observed the damage morphology after the tests to investigate the damage mechanism under high-density current.
Maturation of Pumped Two-Phase Liquid Cooling to Commercial Scale-Up Deployment
Authors: Tipton Russell , Wise Ashley , Mutabdzija Srdan , Shores Craig , Kulkarni Devdatta
Published: November 2024

Applying cold plates to primary heat sources of high-performance compute (HPC) or Artificial Intelligence (AI) servers and pumping refrigerant through them is known as pumped two-phase (P2P) liquid cooling. Refrigerant to air (RA) and refrigerant to liquid (RL) versions of P2P direct to chip liquid cooling of artificial intelligence / machine learning (AI/ML) IT equipment have been developed and their performance was evaluated at commercial scale. P2P captures heat from the silicon and transports it to outdoor air. Matching silicon power map to the cold plate is critical and its design is in the IT manufacturer’s domain. Therefore, collaboration with transport system designer is necessary for optimized P2P performance. The transport system includes working fluid conveyance from coolant distribution unit (CDU) pump to an array of two-phase cold plates, return to CDU condenser, and back to CDU pump. The condenser transfers heat from the secondary fluid, refrigerant, to primary fluid which is either the whitespace air of an air-cooled data center or facility cooling system of an economized chiller.

Important performance parameters demonstrated in this paper include distribution and flow regulation of necessary refrigerant flow to each set of cold plate array; stability of CDU operation over the full range of zero to 100% IT load and during transient and asymmetric IT loading; CDU stable operation at startup as server population varies from zero to full population and while hot-swapping servers from racks. Demonstration of safe operation during abnormal conditions including pump switch over and loss of heat rejection is discussed. Lessons learned are included from commissioning P2P CDU and flow conveyance including charging, flushing, and start-up. Advantages of P2P in achieving sustainability goals and insights into a TCO analysis of RA and RW comparing 1P to 2P LC are discussed.
Investigation of Server Level Direct-To-Chip Two Phase Cooling Solution for High Power GPUs
Authors: Narayanan Akshith , Wang Qingyang , Ozguc Serdar , Bonner Richard W.
Published: November 2024

As artificial intelligence and technology advance, top end server CPU and GPUs are getting more and more powerful. Conventional air-cooling struggles to keep up with the surging processor power densities, leaving room for an efficient and scalable solution. This investigation focuses on the Nvidia H100 GPU architecture in a mimic 1U server with four-way GPUs. While direct to chip two phase cooling offers high heat transfer coefficients and heat capacity, there are technical challenges associated with pressure drop and flow maldistribution to understand the requirements and cost of its use. A single sled test bench is built to conduct systematic experiments with in-house designed Thermal Test Vehicles (TTVs) that replicate the form factor of Nvidia H100 GPUs. The facility is used to characterize pressure drops, die temperature, pumping power and thermal resistance at varying heat loads and flow rates, using R1233zd(E) as the working fluid. Flow restrictors were carefully chosen to balance the flow between the chips, making sure each of them receives sufficient liquid in all usage cases. The results show that the thermal resistance of the cold plate assembly varies between 0.02–0.03W/K. Higher power tests, up to 1.35kW, were conducted to understand how future-proofed the cold plate design is, in terms of rapidly scaling heat loads in the market. Results show that with sufficient flow, the system operates extremely well. The flow restrictors chosen scale quadratically with pressure drop and mass flow rate, and they efficiently suppress the maldistribution between chips on the server level and can be expanded to balancing flow on the rack level. The investigation concludes that pumped direct-to-chip two-phase cooling offers an elegant and scalable solution to the rapidly increasing power densities of CPUs and GPUs, while maintaining efficiency and minimizing the leak risks compared with using a water-based solution.
Minimizing Die Cracking Risk by Copper Pillar Design Optimization for Advanced 5nm Silicon Node
Authors: Ramdas Shrinath Shrinivas , Chauhan Tushar , Patterson Mark , Shirley Dwayne R. , Zhang Lijuan , Coccioli Roberto
Published: November 2024

To enable higher computing power in a single chip, there is demand for increasing die and substrate size for high performance applications in advanced nodes. Chip package interaction (CPI) performance is very critical for package reliability, specifically for advanced low-k 5nm, 3nm technology node chips including extreme low-k (ELK) and low-k (LK) dielectric materials. The material property coefficient of thermal expansion (CTE) mismatch between dielectric materials, copper, silicon can induce significant stresses, causing ELK-LK cracking or delamination and chip failure in electronic packages. For advanced semiconductor nodes like 5nm and 3nm, the Back End of Line (BEOL) structure mechanical strength is reduced due to the presence of porous material with low-dielectric constant which makes it more prone to thermal mechanical failures. On the other hand, use of stiff first level interconnect (copper pillars) together with large die, and package size causes an increased level of stress transfer from package to chip. For these reasons, die BEOL cracking or delamination due to Chip Package Interaction (CPI) is becoming more and more critical in advanced nodes and therefore necessary design optimizations should be done during initial package design phase to avoid any CPI related cracking or delamination failures in package. This study investigates in detail the impact of copper pillar design parameters such as copper pillar height, under bump metallization (UBM) diameter, copper pillar plating chemistry on die cracking or delamination within die BEOL structure. Novel fracture mechanics and stress-based with detail BEOL structure multi-level finite element analysis (FEA) simulation methodology based on the energy release rate (ERR) driving delamination using J-integral approach is developed to assess impact of various package parameters on cracking or delamination in die BEOL layer and used to assess die ELK cracking risk for advanced 5nm packages. Energy release rate (ERR) is the change in the elastic strain energy with respect to change in crack area. Critical ERR (ERRc) is material property also known as fracture toughness and it is used to estimate if the crack will propagate or not (crack will propagate if, ERR ≥ ERRc). This work is expected to provide design guidelines for package designers and help to optimize copper pillar structure for advanced 5nm packages.
Advancing in Data Centers Thermal Management: Experimental Assessment of Two-Phase Liquid Cooling Technology
Authors: Heydari Ali , Al-Zu'bi Omar , Manaserh Yaman , Gharaibeh Ahmad R. , Tipton Russ , Mehrabikermani Mehdi , Rodriguez Jeremy , Sammakia Bahgat
Published: November 2024

In response to the exponential growth of online platforms and the rise of web-based Artificial Intelligence (AI), the demand for computational power and the expansion of data centers have surged significantly. This trend necessitates advanced cooling strategies and heightened energy efficiency to address the increasing power densities of Information Technology (IT) equipment and the consequent rise in energy consumption. Consequently, there is a significant pivot towards efficient cooling mechanisms that emphasize thermal management and energy efficiency. Against this backdrop, our study thoroughly evaluates a two-phase direct-to-chip liquid cooling system’s ability to effectively manage and dissipate heat in high-density rack environments. Central to our research is the deployment of a highly efficient Refrigerant-to-Liquid (R2L) Coolant Distribution Unit (CDU) across multi-racks, which face high thermal demands. This innovative system, featuring an in-row pumped two-phase CDU with a cooling capacity of 160 kW, is intricately integrated with row and rack manifolds and server cooling loops to ensure optimal cooling performance. To accurately simulate the thermal loads encountered in real-world data center operations, the study employs Thermal Testing Vehicles (TTVs). These 3U TTVs are equipped with 2.5 kW heaters, covering an extensive area of 2500 mm2, thereby effectively replicating server thermal loads up to 10 kW. The investigation starts with a detailed description of the system’s design and continues with the commissioning process. This process includes extensive hydraulic and thermal testing, along with a comprehensive assessment of the impact of pressure drops across the system, focusing on supply manifolds, cooling loops, dry breaks, and return manifolds, utilizing Cooling Loops (CLs) each containing four Cold Plates (CPs). The study culminates in the analysis of experimental data from heating the TTVs, focusing on the efficiency of two-phase cooling in transferring heat from the TTVs to chilled water using R134a refrigerant as the performance benchmark. Future directions include exploring eco-friendly cooling practices by investigating alternative green refrigerants with low Global Warming Potential (GWP) to replace R134a, aligning with global sustainability goals and the imperative to reduce greenhouse gas emissions. The observed maximum values were calculated at a specific volumetric flow rate of 0.48 LPM/kW and a Tcase as low as 56.4 °C was achieved. These results demonstrate the system’s capability to significantly enhance thermal management in data centers, tackle the challenges presented by high-power density chips, and encourage broader adoption of two-phase cooling technologies as a sustainable strategy for thermal regulation in the face of increasing computational demands.
Enhanced Pool Boiling Heat Transfer Using Re-Entrant Surfaces
Authors: Zhou Yimin , Adera Solomon
Published: November 2024

Boiling is an essential heat and mass transfer process that is employed in numerous applications ranging from power generation and seawater desalination to thermal management of electronic components. Nucleate boiling, where vapor bubbles nucleate, grow, and depart from active nucleation sites, provides high heat transfer coefficient due to the large latent heat of phase change and the enhanced mixing of liquid near the heated surface caused by continuous bubble departure. Strategies for enhancing the nucleate boiling heat transfer include increasing active nucleation site density with micro/nano-sized roughness, improving vapor/gas entrainment in cavities, and increasing the apparent contact angle of the working fluid. Millimeter- or submillimeter-scale re-entrant grooves fabricated on metallic surfaces have been shown to enhance the heat transfer coefficient during nucleate boiling. Here, we experimentally measure the heat transfer coefficient of surfaces with microscale re-entrant cavities during pool boiling of de-ionized water. Boiling experiments were conducted on silicon surfaces with different surface structures, including vertical/cylindrical and re-entrant microcavities. The results reveal that, compared to the vertical microcavity surfaces, the reentrant microcavity surface reaches a maximum of 50% higher heat transfer coefficient under the same heat flux. Importantly, we observed a sudden temperature drop and heat flux rise at the onset of nucleate boiling for re-entrant microcavity surfaces. The heat transfer enhancement is attributed to the stronger vapor entrapment ability (that is, resistance to wetting by the working fluid) of the re-entrant microcavities. The results of this study provide design guidelines for re-entrant cavities for enhancing boiling heat transfer rate.
Thermal Management System of an Outer-Rotor-Motor-Based Traction Drive With Integrated Power Electronics in its Central Cavity
Authors: Kekelia Bidzina , Cousineau J. Emily , Chaudhary Rajneesh , Tomerlin Jeff , Narumanchi Sreekant , Rallabandi Vandana , Wilkins Jon , Chowdhury Shajjad , Barua Himel , Mohammad Mostak , Ozpineci Burak
Published: November 2024

Increasing power densities of electric vehicle traction drive systems necessitates combining the electric motor and the power electronics into one unit. A compact, integrated traction drive unit with fewer components also drives production costs down, enabling wider adoption of electric vehicles. However, the integration of power electronics in the electric machine is associated with challenges of designing an effective thermal management solution for the combined traction drive system. This paper focuses on the thermal management approach selected for Oak Ridge National Laboratory’s outer-rotor-motor-based integrated traction drive and evaluates its potential performance. The outer-rotor-motor configuration provided an opportunity for integration of the six-phase inverter in the available space in the central cavity of the internal stator. A cylindrical inverter enclosure with integrated coolant (water-ethylene glycol) channels in its walls was designed to enable heat removal from the power electronics. Numerical thermal-fluid modeling and initial channel/fin optimization results for the cylindrical heat sink are presented here. As permanent magnets are integrated in a high-speed (20 000 RPM) outer rotor, forced air convection provides cooling for the magnets. The magnets were segmented axially to mitigate the eddy current losses. Heat generated in the stator windings and laminations is removed by water-ethylene glycol coolant circulating in interpolar T-shape ceramic heat exchangers inserted between windings. General design concepts and numerical thermal-fluid simulations illustrating the electric motor thermal management solution are also presented.
Numerical Study of Two-Phase Immersion Cooling Limits for Bare Die Packages With Novec 649
Authors: Liu Tanya , Khalili Sadegh , Padilla Jorge , Iyengar Madhusudan
Published: November 2024

As chip power densities continue to increase, there is renewed interest in using two-phase immersion cooling (2PIC) as a passive thermal management mechanism to improve data center power density and operating efficiency. Traditional air cooling approaches are challenging to scale for high power chips due to costly requirements on cooling footprint, fan power, and increasingly untenable levels of acoustic noise. Single-phase liquid cooling can address some of these challenges but requires the introduction of complex fluid delivery manifolds, cold-plate loops and active pumps.

In this study, we use a semi-empirical, numerical approach to investigate two-phase immersion cooling limits for bare die packages with Novec 649, a low global warming potential (GWP) coolant. This simplified modeling method enables rapid parametric studies to extract relevant 2PIC thermal system design information without requiring experimental tanks or computationally expensive two-phase simulations.

From the results, we identify 2PIC thermal design power limits for bare die packages of various sizes with different distributions of heat sources and different boiler plate designs. We also identify key contributors to the 2PIC thermal resistance stack up and provide recommendations on potential improvements to overall junction to fluid resistance. Finally, we compare the 2PIC results against a single-phase, water-cooled coldplate case study and discuss pros and cons of both.
Numerical Study of Single-Phase Immersion Cooling Limits for Bare Die Packages
Authors: Khalili Sadegh , Liu Tanya , Padilla Jorge , Iyengar Madhusudan
Published: November 2024

Advances in packaging and semiconductor manufacturing have driven relentless increases in chip performance and power. As a result, air cooling powerful processors is becoming less effective and expensive. Single-phase immersion cooling has emerged as one of prominent technologies to enhance both cooling performance and efficiency. This paper aims to explore the boundaries of cooling performance of single-phase immersion cooling with a focus on the impacts of chip heat density and system-level constraints. Computational fluid dynamics (CFD) simulations were employed to conduct a parametric study on the influence of chip heat density and heat concentration on the cooling capabilities of immersion cooling. To push limitations of immersion cooling, forced convection immersion cooling is investigated. Furthermore, cooling capability limitations of immersion cooling are analyzed using a pseudo-ideal heatsink. Finally, results of single-phase immersion cooling are compared with direct liquid cooling (DLC) with cold plates.
Process-Performance Interactions Under Exposure to Sustained High Temperature for Additively Manufactured Electronics and SMT Assembly With Low-Temperature Curable Adhesives
Authors: Lall Pradeep , Bimali Sabina , Miller Scott
Published: November 2024

Rapid progress in technology necessitates an in-depth understanding of the enduring reliability of flexible printed circuitry constructed using different connecting materials. The adaptability of flexible printed circuits and their potential applications in a wide range of electronic devices, from automotive systems to wearable electronics, has garnered substantial interest in recent years. Thermal aging is an important factor that might potentially compromise the structural integrity and performance of electronic assemblies used in real-world applications. The reliability of flexible printed circuit assembly, particularly the bonding materials employed, is critical to the effective integration of flexible printed circuits into various applications. To gain a better understanding of the adhesive’s reliability under thermal aging, this study intends to carefully examine the effects of thermal aging on flexible printed circuitry. The objective of this study is to fill a gap in the literature by thoroughly investigating how thermal aging affects flexible printed circuit assemblies that are fabricated with room-temperature curable adhesives and high-temperature curable adhesives. This paper investigates processes aimed at achieving interconnects suitable for room-temperature processes, along with the use of water-based inks in printed electronics. The research delves into the examination of electrical performance and reliability tests within functional electronic circuitry. A comparison is made between the performance of low-temperature processable interconnects, coupled with water-based inks, and high-temperature processable interconnects for both test designs: individual components test and functional circuit test. The study includes the realization of a differentiator circuit through aerosol jet printing, employing low-temperature interconnects for component attachment. The circuit’s response is then compared with the simulated output. Finally, both the fabricated circuits are subjected to a thermal aging test for 1000 hours at a temperature of +85°C.
Performance and Reliability of In-Mold Direct-Write Signal Processing Circuits in Sustained High-Temperature Operation
Authors: Lall Pradeep , Sarwar Md Golam , Miller Scott
Published: November 2024

As additive in-mold technologies gain traction in the automotive sector, there is a growing need for long-term reliability data under harsh conditions and acceleration factors to predict the technology’s lifespan. This paper aims to investigate how the performance and reliability of a system or device evolve over time under continuous, elevated temperature conditions. The research methodology involves thorough investigations into materials, manufacturing processes, and testing procedures to assess the reliability of in-mold flexible electronics. To simulate the harsh conditions typically encountered by automotive components, printed thermoformed samples are subjected to prolonged exposure to high temperatures in this study. The nScrypt direct write platform is utilized for printing connection materials and conductive traces. Stretchable electrically conductive adhesive (ECA) is the connecting medium, while in-mold capable silver ink is utilized for the conductive traces. Thermoformable polycarbonate sheets are employed as substrate materials, with Formech-508FS utilized for thermoforming purposes. To evaluate the performance of the additively printed thermoformed circuit, an impedance analyzer is employed. A functional circuit schematic is constructed and tested using OrCAD PSpice to simulate the application. The actual output of the printed thermoformed circuit before exposure to high thermal conditions and during High-Temperature Operating Life (HTOL) testing is compared with the simulated performance of the circuit.
Oscillator Performance on Thermoformed Additive In-Mold Electronics for Automotive Applications
Authors: Lall Pradeep , Harsha Aditya , Kulkarni Shriram , Miller Scott
Published: November 2024

The concept of In-Mold Electronics (IME) has emerged as a highly transformative technology. IME offers huge potential for innovation by enabling automobile manufacturers to smoothly integrate electronic circuits with varied structures and surfaces across different products. Nevertheless, there is a lack of comprehensive study of the electrical attributes related to the IME circuits, specifically the screen-printed circuits on polycarbonate substrate followed by the thermoforming process to use in automobile applications. This study aims to investigate the influence of manufacturing parameters related to screen-printing and thermoforming on IME circuit performance, which is dedicated to its application in the automobile industry.
Additively Printed Circuits Using Biodegradable Substrates on Aerosol-Jet With Aqueous-Based Silver Conductive Paste Using ECA and Low-Temperature Interconnects
Authors: Lall Pradeep , Karakitie Daniel , Miller Scott
Published: November 2024

Traditionally, the manufacture of printed circuits relied on volatile organic solvent-based inks, a practice now scrutinized due to growing environmental concerns. There’s a notable shift towards water-based inks, offering a reduced environmental footprint by replacing volatile solvents with water as the carrier medium. However, despite their promising attributes, the functionalities and performances of circuits created with these sustainable inks remain relatively unexplored compared to their non-sustainable counterparts. This study addresses this knowledge gap, focusing on the innovative use of biodegradable PET substrates in the aerosol jet printing process. The research includes a comprehensive analysis of circuits created with sustainable water-based inks, with a specific focus on their application on biodegradable PET substrates. Key components were attached to these circuits using electrically conductive adhesives and low-temperature adhesives to compare the various effects of interconnects on the component attachment and the performance of the circuit using these interconnect adhesive materials. The evaluation involved a detailed analysis of component performance, particularly RLC components, in relation to operating frequency, and electron dispersive x-ray spectroscopy analysis. Extensive testing was performed to delineate the electrical and mechanical properties of the resulting circuits, with a specific focus on resistance values across varying sintering temperatures and durations. Preliminary findings indicate that modifying these parameters can enhance electrical properties, and optical methods were employed to characterize the printed trace outcomes.
Sequential High-Temperature Aging and High Humidity Exposure of Chip/Underfill Interfaces to Investigate the Evolution of Interfacial Stress Intensity Factor in FCBGA Stress Intensity
Authors: Lall Pradeep , Pandurangan Aathi , Choudhury Padmanava
Published: November 2024

In the realm of automotive applications, the reliability of Flip-Chip Ball Grid Array (FCBGA) packages is critical, and this study delves into the sequential effects of high-temperature aging and high humidity exposure on chip/underfill interfaces within FCBGA packages. The primary objective is to comprehensively investigate the evolution of interfacial stress intensity factors, crucial for predicting and mitigating potential failures in FCBGA packages used in automotive applications. Through systematic experimentation, the chip/underfill specimens undergo rigorous aging processes at elevated temperatures and subsequent exposure to high humidity conditions. High temperature and moisture-induced failures are some of the major contributing factors to failure in underhood automotive electronics. Exposure to high temperature and moisture weakens the critical interfaces in the FCBGA packages. Conventional studies on package-level interfaces often concentrate on the effects of individual environmental factors. Yet, real-world automotive electronics encounter a multitude of harsh conditions. The critical need to assess the impact of mechanical loads creates a substantial knowledge gap in our comprehension of these interfacial behaviors. Delamination at the chip/underfill (UF) interfaces is a common failure mode, evaluating interfacial fracture toughness crucial for assessing reliability. Any crack in this interface could propagate to the solder joints, leading to system failure. This study aims to investigate the failure modes of chip/UF Interfaces. Calculate the fracture toughness parameter and strain energy release rate for the interface fracture. Understand the effect of high-temperature aging at the chip/underfill and EMC/substrate Interface.
Investigation of Interfacial Reliability and Comparison Non-PFAS Underfills in FCBGAs Under Humidity and High-Temperature Exposure
Authors: Lall Pradeep , Pandurangan Aathi , Choudhury Padmanava
Published: November 2024

Poly-fluoroalkyl substances (PFAS) are fundamental to the intricate world of semiconductors, the engines powering our modern lives. Electronics on the automotive platform play a vital role in ensuring the safe and efficient operation of automobiles. In these applications, underfill materials are employed to reinforce the interfaces between substrates and semiconductor dies to enhance the durability and reliability of Flip-Chip Ball Grid Array (FCBGA) packages. They play a crucial role in various aspects of chip manufacturing, from specialized chemical formulations to intricate manufacturing tools and vital infrastructure. Due to potential health impacts, non-PFAS materials are considered as an alternative. While traditional underfill often contains PFAS, concerns about their environmental persistence and potential health effects have cast a shadow over their continued use. Recognizing this, the semiconductor industry is determined to find robust, non-PFAS alternatives. While existing studies on packages explore the effects of temperature on full FCBGA packages, a critical knowledge gap remains regarding the interfacial reliability of chip/underfill (UF) interfaces, especially with the growing demand for non-PFAs underfills and the additional complexities introduced by mechanical loads. Delamination is one of the most prevalent failure modes encountered at the chip/underfill (UF) interfaces. When assessing the reliability of these interfaces, important parameters to consider are bulk underfill characterization and interfacial fracture toughness. The samples are subjected to humidity exposure and isothermal aging. To investigate the failure modes of non-PFAs underfills in chip/UF Interfaces, tensile tests are conducted on bulk underfill samples, and fracture toughness parameters and strain energy release rate are determined for the chip/UF interfaces.
Hygrothermal Aging Evolution of Non-PFAS FCBGA Interfaces
Authors: Lall Pradeep , Choudhury Padmanava , Pandurangan Aathi , Kasturi Madhu
Published: November 2024

Per-polyfluoroalkyl substances, also known as forever chemicals, have uniquely useful characteristics that have made them ubiquitous in their use for industrial, commercial, and electronics applications, but there are several epidemiological studies linked to severe health effects such as liver diseases, thyroid malfunctions to these PFAS chemicals. A unified approach must be taken to remove these chemicals from electronics applications so that there is a minimum amount of waste generation of PFAS chemicals. Our solution is to show that non-PFAS materials have the same reliability in the end-use environment as in the case of PFAS so that the industry moves away from PFAS materials. The study aims to assess the interface between non-PFAS TIM/Copper and compare degradation properties with PFAS counterparts when subjected to high temperature and humidity end-use conditions.
Frequency line detection in spectrograms using a deep neural network with attention
Authors: Jiang DingLin , Luo Xinwei , Shen Qifan
Published: November 2024

In this paper, a frequency line detection network (FLDNet) is proposed to effectively detect multiple weak frequency lines and time-varying frequency lines in underwater acoustic signals under low signal-to-noise ratios (SNRs). FLDNet adopts an encoder-decoder architecture as the basic framework, where the encoder is designed to obtain multilevel features of the frequency lines, and the decoder is responsible for reconstructing the frequency lines. FLDNet includes attention-based feature fusion modules that combine deep semantic features with shallow features learned by the encoder to reduce noise in the decoder's deep feature representation and improve reconstruction accuracy. In addition, a composite loss function was constructed by using the continuity of frequency lines, which improved the detection performance of frequency lines. After training through simulated signal sets, FLDNet can effectively detect frequency lines in spectrograms of simulated and measured signals. The experimental results indicate that FLDNet is superior to other state-of-the-art methods, even at SNRs as low as −28 dB.
The vacuolar K
+
/H
+
exchangers and calmodulin-like CML18 constitute a pH-sensing module that regulates K
+
status in Arabidopsis
Authors: Daniel-Mozo Miguel , Rombolá-Caldentey Belén , Mendoza Imelda , Ragel Paula , De Luca Anna , Carranco Raul , Alcaide Ana M. , Ausili Alessio , Cubero Beatriz , Schumacher Karin , Quintero Francisco J. , Albert Armando , Pardo José M.
Published: November 2024

Shifts in cytosolic pH have been recognized as key signaling events and mounting evidence supports the interdependence between H
+
and Ca
2+
signaling in eukaryotic cells. Among the cellular pH-stats, K
+
/H
+
exchange at various membranes is paramount in plant cells. Vacuolar K
+
/H
+
exchangers of the NHX (Na
+
,K
+
/H
+
exchanger) family control luminal pH and, together with K
+
and H
+
transporters at the plasma membrane, have been suggested to also regulate cytoplasmic pH. We show the regulation of vacuolar K
+
/H
+
exchange by cytoplasmic pH and the calmodulin-like protein CML18 in Arabidopsis. The crystal structure and physicochemical properties of CML18 indicate that this protein senses pH shifts. Interaction of CML18 with tonoplast exchangers NHX1 and NHX2 was favored at acidic pH, a physiological condition elicited by K
+
starvation in Arabidopsis roots, whereas excess K
+
produced cytoplasmic alkalinization and CML18 dissociation. These results imply that the pH-responsive NHX-CML18 module is an essential component of the cellular K
+
- and pH-stats.
Experience-dependent, sexually dimorphic synaptic connectivity defined by sex-specific cadherin expression
Authors: Liao Chien-Po , Majeed Maryam , Hobert Oliver
Published: November 2024

Early-life experience influences subsequent maturation and function of the adult brain, sometimes even in a sex-specific manner, but underlying molecular mechanisms are poorly understood. We describe here how juvenile experience defines sexually dimorphic synaptic connectivity in the adult
Caenorhabditis elegans
nervous system. Starvation of juvenile males disrupts serotonin-dependent activation of the CREB transcription factor in a nociceptive sensory neuron, PHB. CREB acts through a cascade of transcription factors to control expression of an atypical cadherin protein, FMI-1/Flamingo/CELSR. During postembryonic development, FMI-1 promotes and maintains synaptic connectivity of PHB to a command interneuron, AVA, in both sexes, but a serotonin-dependent transcriptional regulatory cassette antagonizes FMI-1 expression in males, thereby establishing sexually dimorphic connectivity between PHB and AVA. A critical regulatory node is the CREB-target LIN-29, a Zn finger transcription factor that integrates four layers of information: sexual specificity, past experience, time and cell-type specificity. Our findings provide the mechanistic details of how an early juvenile experience defines sexually dimorphic synaptic connectivity.
Self-organizing nervous systems for robot swarms
Authors: Zhu Weixu , Oğuz Sinan , Heinrich Mary Katherine , Allwright Michael , Wahby Mostafa , Christensen Anders Lyhne , Garone Emanuele , Dorigo Marco
Published: November 2024

We present the self-organizing nervous system (SoNS), a robot swarm architecture based on self-organized hierarchy. The SoNS approach enables robots to autonomously establish, maintain, and reconfigure dynamic multilevel system architectures. For example, a robot swarm consisting of
n
independent robots could transform into a single
n
–robot SoNS and then into several independent smaller SoNSs, where each SoNS uses a temporary and dynamic hierarchy. Leveraging the SoNS approach, we showed that sensing, actuation, and decision-making can be coordinated in a locally centralized way without sacrificing the benefits of scalability, flexibility, and fault tolerance, for which swarm robotics is usually studied. In several proof-of-concept robot missions—including binary decision-making and search and rescue—we demonstrated that the capabilities of the SoNS approach greatly advance the state of the art in swarm robotics. The missions were conducted with a real heterogeneous aerial-ground robot swarm, using a custom-developed quadrotor platform. We also demonstrated the scalability of the SoNS approach in swarms of up to 250 robots in a physics-based simulator and demonstrated several types of system fault tolerance in simulation and reality.
How much initiative should a service robot have?
Authors: Murphy Robin R.
Published: November 2024

Adrian Tchaikovsky’s new novel
Service Model
humorously imagines a robot Jeeves coping with the end of civilization.
Study of a brief online and group focusing intervention: a protocol for a randomised clinical trial
Authors: Aguiar Clara , Oliveira Cláudia , Monteiro Marina , Paiva Alexandra , Salgado João
Published: November 2024

Introduction

Emotion dysregulation is a transdiagnostic characteristic that affects many people with many psychopathological problems. Two mechanisms that have been frequently associated with emotional regulation are immersion and distancing. Focusing is a task that combines these two mechanisms of emotion regulation through the phase of creating a working distance and subsequently the phase of reassigning meaning. However, the benefit of its use in Portuguese population without a moderate to severe symptomatology for promoting mental health remains unclear.

Methods and analysis

Participants aged between 18 and 65 years who wish to improve their awareness and understanding of their emotions will be recruited and then, randomised into two groups: the intervention group (IG) and the control group (CG; delayed intervention). The IG will have access to two focusing sessions and the CG will only have access to the intervention 4 weeks later. Both groups will be evaluated at five different times. Primary outcomes include positive and negative affect, attitudes towards focusing (emotions and bodily sensations), the ability to perform focusing and emotion regulation. Secondary outcomes include mental health and psychological well-being, depression and anxiety symptoms and self-esteem.

Ethics and dissemination

Our study has been approved by the Council of Ethics and Deontology of the University of Maia. Findings will be disseminated via manuscripts, presentations and the lead author’s thesis.

Trial registration number

NCT16974329
.
Pain control post total knee replacement in patients given local infiltrative analgesia combined with adductor canal block compared to either modality alone: a systematic review and meta-analysis
Authors: Mott Andrew , Brady Samantha , Briggs Isabelle , Barrett Maggie , Fulbright Helen , Hamilton Thomas William , Hewitt Catherine , Palan Jeya , Pandit Hemant
Published: November 2024

Objectives

Optimising postoperative pain following knee replacement is important for patients, healthcare professionals and healthcare funders. Adductor canal blocks (ACB) are widely used but there is uncertainty about their efficacy when combined with local infiltration analgesia (LIA) compared with either LIA or ACB alone.

Design

A systematic review and meta-analyses of randomised controlled. The primary outcome was pain over the first 72 hours. Secondary outcomes included morphine use, range of movement, distance walked, length of hospital stay, health economic outcomes and reported adverse events.

Data sources

MEDLINE, Embase, EB Health - KSR Evidence, Cochrane Central Register of Controlled Trials, CINAHL, International HTA database, ClinicalTrials.gov and the International Clinical Trials Registry Platform (WHO) were searched up to June 2023.

Eligibility criteria

Randomised controlled trials involving patients undergoing primary total knee replacement comparing LIA combined with ACB to either LIA or ACB alone.

Data extraction and synthesis

All eligible studies were data extracted independently by two reviewers. Studies were pooled for each outcome at each timepoint in a random effects meta-analysis.

Results

We identified 13 completed studies including 1154 participants. 12 studies compared LIA vs combination and 5 compared ACB vs combination. We identified that participants receiving the combination had lower pain scores at rest at 24 hours compared with LIA alone (SMD 0.42, 95% CI 0.20 to 0.64) or ACB alone (SMD 0.63, 95% CI 0.42 to 0.83). Pain on movement at 24 hours was also lower for patients with combination vs LIA alone (SMD 0.37, 95% CI 0.01 to 0.73) or ACB alone (SMD 0.81, 95% CI 0.35 to 1.26). We also identified that patients on combination used less morphine than on LIA alone (MD 1.06, 95% CI −0.09 to 2.20) or ACB alone (MD 5.94, 95% CI −2.41 to 14.29). The same was seen with range of motion at 24 hours with combination having a larger improvement than LIA alone (MD −5.19, 95% CI −5.55 to −4.83) or ACB alone (MD −3.80, 95% CI −4.37 to −3.23). These findings were consistent across all time points; however, there were no studies deemed to be at a low risk of bias.

Conclusions

Further well-designed and conducted randomised controlled trials are needed to confirm if a combination of LIA and ACB is superior to either option alone for patients undergoing primary total knee arthroplasty.

PROSPERO registration number

CRD42023436895.
Conducting observational analyses with the target trial emulation approach: a methodological systematic review
Authors: Simon-Tillaux Noémie , Martin Guillaume L , Hajage David , Scheifer Carole , Beydon Maxime , Dechartres Agnes , Tubach Florence
Published: November 2024

Objectives

Target trial emulation is an approach that is increasingly used to improve transparency in observational studies and help mitigate biases. For studies declaring that they emulated a target trial, we aimed to evaluate the specification of the target trial, examine its consistency with the observational emulation and assess the risk of bias in the observational analysis.

Design

Methodological systematic review reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.

Data sources

The database MEDLINE (Medical Literature Analysis and Retrieval System Online) was interrogated for all studies published from 1 January 2021 to 3 July 2022. We performed an additional manual search of 20 general medical and specialised journals that spanned the same period.

Eligibility criteria

All studies that declared emulating a hypothetical or real randomised trial were eligible.

Data extraction and synthesis

Two independent reviewers performed the whole systematic review process (screening and selection of studies, data extraction and risk of bias assessment). The main outcomes were the definition of the key protocol components of the target trial and its emulation, consistency between the target trial and its emulation and risk of bias according to the ROBINS-I (Risk Of Bias In Non-randomised Studies - of Interventions) tool.

Results

Among the selected sample of 100 studies, 24 (24%) did not specify the target trial. Only 40 studies (40%) provided detailed information on all components of the target trial protocol. Eligibility criteria, intervention strategies and outcomes were consistent between the target trial and its emulation in 35 studies (46% of those specifying the target trial). Overall, 28 studies (28%) exhibited serious risk of bias and 41 (41%) had misalignments in the timing of eligibility assessment, treatment assignment and the start of follow-up (time-zero). As compared with studies that did not specify the target trial, those that did specify the trial less frequently seemed to have both time-zero issues (39% vs 52%) and serious risk of bias (26% vs 33%).

Conclusions

One-quarter of studies declaring that they emulated a target trial did not specify the trial. Target trials and their emulations were particularly inconsistent for studies emulating a real randomised trial. Risk of methodological issues seemed lower in observational analyses that specified versus did not specify the target trial.
Adaptive Prediction Structure for Learned Video Compression
Authors: Yang Jiayu , Zhai Yongqi , Jiang Wei , Yang Chunhui , Gao Feng , Wang Ronggang
Published: November 2024

Learned video compression has developed rapidly and shown competitive rate-distortion performance compared with the latest traditional video coding standard H.266 (VVC). However, existing works were restricted to fixed prediction direction and GoP size. The inflexibility on prediction structure hinders learned video compression towards optimal compression efficiency in diverse motion scenarios. In this article, we propose to advance learned video compression with adaptive prediction structure decision. Specifically, we propose a unified compression framework that supports both forward prediction and bi-directional prediction. The framework can flexibly switch to different prediction direction to achieve better prediction performance. Meanwhile, we propose a low-complexity prediction structure decision algorithm, where prediction direction and GoP size are adaptively determined based on motion complexity to achieve optimal compression efficiency. Experimental results demonstrate that the proposed unified framework with adaptive decision algorithm improves compression efficiency of pure forward prediction-based or bi-directional prediction-based framework with neglectable (

\(0.9\%\)

) encoding time increment. Meanwhile, it achieves comparable compression performance with VVC and recent learned video coding methods.
Acetone Gas Sensor with SnO2-Modified MoS2 Nanospheres
Authors: Juang Feng-Renn , Lan Hung-Chieh
Published: November 2024

This study employed a hydrothermal method to prepare molybdenum disulfide (MoS2) and a two-step hydrothermal process to synthesize tin oxide (SnO2)-modified MoS2 nanostructured materials. The manufacturing process is simple and cost-effective, and the produced materials were analyzed using various techniques to confirm their high purity and crystallinity. The SnO2-modified MoS2 nanostructured materials were then utilized to fabricate acetone gas sensors. The high surface area of MoS2, coupled with the heterojunction interfaces formed by SnO2 modification, enhances the performance of the gas sensor. At 150 °C, the sensor exhibits a remarkable response of 37.1% to 100 ppm acetone gas. The dynamic response, including response and recovery times, is also impressive. Gas sensors developed with this material can effectively detect acetone concentrations in various environmental conditions.