bluuebunny/crossref_metadata_2025 huggingface dataset:
Continuous‐time stochastic gradient descent for optimizing over the stationary distribution of stochastic differential equations
Authors: Wang Ziheng , Sirignano Justin
Published: November 2023

We develop a new continuous‐time stochastic gradient descent method for optimizing over the stationary distribution of stochastic differential equation (SDE) models. The algorithm continuously updates the SDE model's parameters using an estimate for the gradient of the stationary distribution. The gradient estimate is simultaneously updated using forward propagation of the SDE state derivatives, asymptotically converging to the direction of steepest descent. We rigorously prove convergence of the online forward propagation algorithm for linear SDE models (i.e., the multidimensional Ornstein–Uhlenbeck process) and present its numerical results for nonlinear examples. The proof requires analysis of the fluctuations of the parameter evolution around the direction of steepest descent. Bounds on the fluctuations are challenging to obtain due to the online nature of the algorithm (e.g., the stationary distribution will continuously change as the parameters change). We prove bounds for the solutions of a new class of Poisson partial differential equations (PDEs), which are then used to analyze the parameter fluctuations in the algorithm. Our algorithm is applicable to a range of mathematical finance applications involving statistical calibration of SDE models and stochastic optimal control for long time horizons where ergodicity of the data and stochastic process is a suitable modeling framework. Numerical examples explore these potential applications, including learning a neural network control for high‐dimensional optimal control of SDEs and training stochastic point process models of limit order book events.
Tropical cyclone winds and precipitation stimulate cone production in the masting species longleaf pine (Pinus palustris)
Authors: Cannon Jeffery B. , Rutledge Brandon T. , Puhlick Joshua J. , Willis John L. , Brockway Dale G.
Published: November 2023

Many trees exhibit masting – where reproduction is temporally variable and synchronous over large areas. Several dominant masting species occur in tropical cyclone (TC)‐prone regions, but it is unknown whether TCs correlate with mast seeding.

We analyzed long‐term data (1958–2022) to test the hypothesis that TCs influence cone production in longleaf pine (Pinus palustris). We integrate field observations, weather data, satellite imagery, and hurricane models to test whether TCs influence cone production via: increased precipitation; canopy density reduction; and/or mechanical stress from wind.

Cone production was 31% higher 1 yr after hurricanes and 71% higher after 2 yr, before returning to baseline levels. Cyclone‐associated precipitation was correlated with increased cone production in wet years and cone production increased after low‐intensity winds (≤ 25 m s−1) but not with high‐intensity winds (> 25 m s−1).

Tropical cyclones may stimulate cone production via precipitation addition, but high‐intensity winds may offset any gains. Our study is the first to support the direct influence of TCs on reproduction, suggesting a previously unknown environmental correlate of masting, which may occur in hurricane‐prone forests world‐wide.
Development of nonliteral interpretations in typically developing Spanish speaking children: light verb constructions and figurative expressions
Authors: Castroviejo Elena , Ponciano Marta , Hernández‐Conde José V. , Vicente Agustín
Published: November 2023

In this paper we present a study about the typical development of the comprehension of expressions that exhibit an ambiguity between a literal and a nonliteral interpretation in Spanish, and whose most frequent use is nonliteral. Such expressions include light verb constructions (LVC) such as to make the bed and expressions in a metaphor‐hyperbole‐idiom continuum (MHI) such as to sleep with angels. We ran a forced‐choice experiment where children aged 3 to 9 (N = 143) heard an ambiguous expression and had to choose the correct picture on the face of three options: one target item and two distractors. There were two counterbalanced lists, so that each critical item would be present in either the literal or the nonliteral condition. We collected accuracy data as well as reaction times. We encountered different developmental trends for LVC than for MHI, observing a literalist stage in MHI which we did not observe in LVC.
Multi‐omics‐driven advances in the understanding of triacylglycerol biosynthesis in oil seeds
Authors: Li Hui , Che Ronghui , Zhu Jiantang , Yang Xiaohong , Li Jiansheng , Fernie Alisdair R. , Yan Jianbing
Published: November 2023

Vegetable oils are rich sources of polyunsaturated fatty acids and energy as well as valuable sources of human food, animal feed, and bioenergy. Triacylglycerols, which are comprised of three fatty acids attached to a glycerol backbone, are the main component of vegetable oils. Here, we review the development and application of multiple‐level omics in major oilseeds and emphasize the progress in the analysis of the biological roles of key genes underlying seed oil content and quality in major oilseeds. Finally, we discuss future research directions in functional genomics research based on current omics and oil metabolic engineering strategies that aim to enhance seed oil content and quality, and specific fatty acids components according to either human health needs or industrial requirements.
LD-SAFE Project: Laser Dismantling Environmental and Safety Assessment - Laser Cutting Demonstration for Nuclear Power Reactors Dismantling
Authors: Daguin Pierre , Roulet Damien , Doyen Ioana , Brizzi Lucas , Favrichon Julien , Porcheron Emmanuel , Francois Patrice , Masseau Xavier , Sigfrids Timmy , Nulens Anton , Wolfs Cédric , Recio Miranda Tomas Adrian
Published: November 2023

Dismantling the internals of Nuclear Power Reactors is known to be the most challenging part technically, mechanically and in terms of safety. This task currently requires years of planning and at least a year longer to execute. The purpose of LD-SAFE project (H2020 project composed of an European Consortium of 6 companies: ONET Technologies, CEA, IRSN, Tecnatom, EQUANS and Vysus Group) is to demonstrate that both in-air and underwater laser cutting technologies are operational for the dismantling of the most challenging components of Nuclear Power Reactors. To do so, the project intends to demonstrate that, laser cutting technique is as safe as the best cutting techniques currently used, even safer for the workers and environment, does not add any new constraints, is cost effective to dismantle the challenging power reactor components, is simpler to implement on site and suited to the complex dismantling of reactor internals.
Progress in Structural Design and Testing of the Used Fuel Container for Long-Term Management of Nuclear Waste in a Deep Geological Repository
Authors: Zhang Xuan , Doyle Dave
Published: November 2023

The Nuclear Waste Management Organization (NWMO) is implementing the Adaptive Phased Management program since 2007 for the long-term management of Canada’s used nuclear fuel. The end point of this program is to contain and isolate the used fuel in a centralized Deep Geological Repository (DGR). The DGR is composed of a multiple barrier system that includes a suitable rock formation and several engineered barriers. A key component of the engineered barrier system is the Used Fuel Container (UFC). This is the containment vessel in which used fuel will be packaged. The current reference UFC design (i.e., the Mark II design) is a small sized cylindrical container with hemispherical heads. The container is made of carbon steel with a copper coating applied to the external surface for corrosion protection. This unique design is driven by the optimal long-term performance under the repository conditions and the characteristics of the natural uranium CANDU fuel, which represents the majority of the used fuel inventory in Canada. The development of the design involves many years of work in all fronts of the subject, including corrosion and material degradation, structural integrity, manufacturing processes, inspection and testing.

This paper focuses on the structural design of the UFC at the NWMO. The main challenges in the design of disposal containers are reviewed, followed by the examination of the applicability of existing codes and standards, such as the ASME BPVC. Then the developments of the container design methodology, criteria and constraints are discussed. The impact and dependency of the container design activities on other aspects of the project, e.g., container manufacturing and inspection, safety assessment, geoscience investigations and facility operations, are also briefly discussed. Finally, the design verification and validation testing programs, including the full scale external pressure tests, are presented.
Numerical Investigation of Cemented-Based Material to Be Used for Packaging System
Authors: Lo Frano Rosa , Cancemi Salvatore Angelo
Published: November 2023

The selection of immobilization waste technologies based on cementation should demonstrate that the obtained matrices are reliable, durable, and stable. This study deals with the numerical simulation of cemented package. Both the normal and accidental storage condition are considered.

The FE numerical model is adopted to benchmark several RLOW simulants composition and correlate/compare the structural properties. A 3D cylindrical shaped model was implemented. Homogeneous mechanical material properties of defined stiffness were assumed.

The thermal properties have been obtained experimentally by performing hot wire test on several samples of the cement inert matrix. These data were used as input for the numerical simulation. Moreover, pseudo-dynamic analysis was carried out in order to determine the damage level in the case of an accidental drop. Ageing effects have been also investigated. Results indicate that the thermal conductivity monotonically decreases of 20% as the temperature increases up to 800 °C.

The compressive strength, even reduced mainly as consequence of increased material porosity, confirmed to be dependent on w/c ratio. The results obtained were consistent with literature values, indicating a strong correlation between the simulation results and the established knowledge in the field.
Safety Study on Korean Deep Geological Repository for High-Level Radioactive Waste: (1) Procedures for Conducting Risk Assessment
Authors: Son Kibeom , Choi Karyoung , Heo Gyunyoung , Kim Hyungdae , Chang Kunok
Published: November 2023

In Korea, a safety case development study of deep geological repository for high-level radioactive waste is being conducted, and the safety case includes safety assessment of repository as a component. In the field of disposal, the safety assessment is performed through a kind of evaluation method called a scenario in consideration of waste’s characteristics.

Meanwhile, the general guidelines provided by the International Atomic Energy Agency or top-tier regulatory requirements addressed by each country do not mention detailed methods of ‘how to develop framework of safety assessment and scenarios by combining features, events, and processes’. In Korea, unlike the regulatory requirements of existing low and intermediate-level waste repository, the standards of main safety indicator based on risk for events, so it is necessary to differentiate the methodology.

Based on these backgrounds, this paper suggests the detailed requirements for the safety assessment methodology of deep geological repository for high-level radioactive waste, and presents an example systematic framework reflecting these ideas. It is expected that this study will help to understand the safety assessment of deep geological repository for high-level radioactive waste from the perspective of features, events, and processes and scenario.
CONTAS: Design and Qualification of a High Integrity Container for Intermediate Level Solid Waste
Authors: Coltella Thomas , Di Prinzio Matteo , Lazzaretti Maurizio , Giorgi Luciano , Firpo Gabriele , Orzelli Francesco , Frignani Michele , Frogheri Monica Linda , Ricci Cristina
Published: November 2023

Ansaldo Nucleare S.p.A. has designed, fabricated and qualified a high integrity container, CONTAS, for the conditioning, transportation and long term storage of solid ILW with low content of α-emitter radionuclides.

CONTAS is a carbon steel forged cylindrical container 1500mm high by 1100mm in external diameter, offering a general shielding wall thickness of 160mm and an internal usable volume of approximately 0,5m3.

Based on national and international norms and standards, CONTAS complies with stringent requirements to ensure protection of persons and environment:

• UNI 11784 [1] (the reference norm in Italy for solid heterogenous ILW conditioning and storage)

• IAEA SSR-6 [3] as Type IP-3 package

• Raccolta V.S.R. [7] as pressure equipment for nuclear purpose

CONTAS design, within the scope of a proper defined Qualification Plan, has been successfully qualified through a mix of experimental and analytical tests, performed on material samples, full-scale prototypes, FEM models, arranging the test sites in compliance with the criteria defined by standards and involving qualified Suppliers and Laboratories. The experimental tests include free drop tests, thermal test, degradation tests, leak tightness tests, pressure test, functional tests.

Several innovative elements of CONTAS, especially concerning the sealing systems, are currently patent pending.
Nuclear Waste Treatment: Vitrification of Iron-Phosphate Sludge
Authors: Coltella Thomas , Valente Francesca , Pierantoni Veronica , Ricci Cristina , Frignani Michele , Frogheri Monica Linda , Di Prinzio Matteo , Mariani Mario , Macerata Elena , Tiozzo Simone
Published: November 2023

Within the framework of developing advanced processes for nuclear waste treatment, Ansaldo Nucleare is developing and testing an innovative technology to perform the conditioning of radioactive ferrous waste materials, classified as Low and Intermediate Level Waste (LILW), resulting from decommissioning activities of Nuclear Facilities.

This technology is based on a patented process dedicated to the treatment of decontamination solutions coming from the pickling process of the metallic components, with the aim to minimize the waste to be disposed, in an inert final product, and maximize the freely released material, that once it is decontaminated can be recycled. The process results in the production of a radioactive sludge, made mostly of iron-phosphate salts, which can be thermally treated to produce a ready-to-storage, homogenous and chemically resistant glass product. The process was first tested at laboratory scale and then in a pilot plant, installed at Politecnico di Milano.

The main strengths of this innovative technology are:

• Lower amount of fresh materials/chemicals requested for the waste treatment, resulting in lower costs associated with the process, also thanks to the continuous recycling of the pickling solution;

• Lower volume and higher long-term stability of the nuclear waste for the final storage;

• Facility with reduced footprint and transportable, designed to be installed in commercial containers.
Towards a Harmonised Application of the International Regulatory Framework in Waste Management and Decommissioning
Authors: Szőke Réka , Jacops Elke , Fowler Linda , Szőke István , Schatz Timothy , Maes Norbert , Karlsson Mikael , Pancotti Federica , Banford Anthony , Holt Erika , Marzo Giuseppe A.
Published: November 2023

The 3-year Euratom project, “HARPERS: HARmonised PracticEs, Regulations and Standards in waste management and decommissioning,” aims to establish and clarify the benefits and added value of more aligned practices, methodologies, and approaches in decommissioning and radioactive waste management, including possibilities for shared processing, storage and disposal facilities between Member States (MS). HARPERS aims to reinforce the activities of the European Joint Programme on Radioactive Waste Management (EURAD), Pre-disposal Treatment of European Radioactive Waste Streams (PREDIS) and Stakeholder-based Analysis of Research for Decommissioning (SHARE) projects. HARPERS will also connect with the wider European Community through, e.g., SNETP, DigiDECOM, NEA, IGDTP, IAEA, ENSREG, ERDO and will encourage interaction between different national programmes. The project will evaluate the Strengths, Weaknesses, Opportunities and Threats, identify the obstacles & issues preventing implementation of a more common regulatory approach, covering e.g., nuclear, industrial safety, occupational health, environmental, ... aspects. A TECOP analysis will identify a multitude of potential changes, which will be reviewed further in terms of strategic impacts for stakeholders. The high-level benefits of more aligned practices, methodologies and approaches are related to 1) greater business opportunities 2) better understanding between diverse groups serving wider markets 3) improved cost efficiency 4) waste minimisation and 5) improved final disposability of waste.

This paper gives a general overview on HARPERS and presents results of the two on-line workshops on WP5 Advanced Technologies.
A Holistic Approach to Digitalisation and Robotics in the Nuclear Back-End
Authors: Szőke István , Hartmann Christian , Szőke Réka , Stephane Lucas , Zahra Omar , Benkrid Abdenour
Published: November 2023

Decommissioning and waste management are essential parts of the lifecycle of nuclear and other industrial sites/facilities to consider in terms of sustainability, as it often involves risks to workers or the environment. Robots can offer a solution by performing tasks in hazardous environments, handling contaminated materials, and performing repetitive and monotonous tasks. Making robots more autonomous through integration with AI-enabled digital twins is essential for a safe and efficient digitalization of the back-end. Through simulation and analysis of the performance of robots and facilities under various conditions, safe and sustainable robot deployments can be ensured. HADRON is a holistic approach that aims to optimize working processes while keeping humans away from dangerous, dull, and dirty tasks. This approach has been the core of the RoboDECOM project where heterogeneous mobile robots, integrated with digital and physics modeling technologies, were utilized in a pilot study to carry out a set of subtasks representative of the decommissioning process. This study presents findings related to HADRON from the RoboDECOM project, several EURATOM projects like SHARE (providing an innovation roadmap based on a large scale survey of innovation needs and opportunities in the nuclear back-end), PREDIS (specifically about a digital decision making platform for waste predisposal activities) and HARPERS (specifically about harmonizing safety standards and regulations with outlook into impacts of application of digital and robotic systems in the nuclear) or PLEIADES (providing one interface for digital tools and allow an exchange of the data between them).
WASTREAM for Supporting the Dismantling of Nuclear Installations
Authors: Thomas Robin , Delannay Nicolas , Helman Thibaut
Published: November 2023

This paper presents the WASTREAM software suite developed by Tractebel to support an integrated decommissioning project.

In the framework of dismantling a nuclear installation, being able to correctly estimate the waste and material fluxes is crucial. Indeed, the preparation of dismantling activities and the drafting of regulatory files such as dismantling plans and safety analysis reports require estimations of waste and effluent productions, discharges, etc.

Therefore, it is necessary to gather a description of the dismantling activities and an estimation of the waste they produce, which in turn enables to evaluate the storage capacities to be installed. Moreover, logistics calculations performed in order to design the dismantling facilities (generally incorporating treatment units and buffer storage spaces) require also a precise evaluation of the waste masses as well as their radiological content during the dismantling activities.

Those waste estimations are then based on several sources of information: the installation physical inventory, the radiological characterization of the assets, the dismantling schedule and the description of material and waste streams (succession of the treatments and conditioning that the materials undergo from their dismantling to their interim storage/final disposal or clearance). Regular updates are necessary for these evaluations.

The WASTREAM software suite has been developed for this purpose. The software allows, on the one hand to define waste stream models and, on the other hand to establish the link between the installation physical inventory, the waste streams and the dismantling phase. It then provides means for calculating, analyzing and visualizing the quantities of waste produced. It is designed to be fast running and compatible with a wide variety of physical inventory databases and dismantling schedule.

In particular, WASTREAM has been connected to the platform developed in the framework of the PLEIADES project (European Commission funded project for connecting digital tools for smarter nuclear decommissioning). 3D models and databases of the PLEIADES case studies are used to showcase WASTREAM capabilities for supporting nuclear installations’ dismantling.
Erasmus Mundus Joint Master Degree in Decommissioning And Environmental Remediation (MINDER)
Authors: Dinis Maria de Lurdes , Abelshausen Bieke , Oughton Deborah , Amaral Eliana , Monken Fernandes Horst , Nanba Kenji , Alencar de Aguiar Laís , Lagos Leonel , Ramalho Franklin Mariza
Published: November 2023

Training and building capacity in Decommissioning and Environmental Remediation (D&ER) is challenging and complex as these activities demand the integration of a series of cross-cutting disciplines, effective project planning and managerial skills. Extensive D&ER programmes have been implemented in many countries. While some of these countries have achieved substantial progress with their programmes, many others face significant difficulties. One of the main constraints is the lack of skilled professionals. The demand for expertise in these areas, i.e., professionals with solid technical and scientific backgrounds who grasp the complexities and multidisciplinary character of D&ER programmes, is already a problem for many organizations, and the existing gap will soon increase. A Joint Master in Nuclear Decommissioning and Environmental Remediation (MINDER) is being developed under the European Commission Erasmus Mundus. The Consortium comprises the University of Porto (Coordinator), Vrije Universiteit Brussel, Norwegian University of Life Sciences, Fukushima University, Florida International University, and the Institute of Radiation Protection. The programme will have the support of Associated Partners from Industry (e.g. Wismut GmbH), Academia (e.g. Oregon State University, US), International Organizations (e.g. IAEA) and Research Laboratories (e.g. PNNL, US). These partners will provide access to world-class infrastructure for research and development and opportunities for students to continue their studies.
Nochar Technologies for the Solidification of Complex L/ILW Liquid Radioactive Waste: Global Case Studies of Applications and Disposal Options
Authors: Kelley Dennis , Campbell Dennis
Published: November 2023

Legacy liquid radioactive waste streams from the Cold War still exist and newly generated waste streams from nuclear power plants and research institutes go untreated and expose environmental hazards at many nuclear sites. The nature of the waste is diverse, depending upon the source or the process from which it originated. The most problematic waste streams include complex liquids such as organic (tri-butyl-phosphate TBP) solutions contaminated with Pu and U isotopes, mixed organic and aqueous sludge types, nitric and mixed acid waste streams, H-3 contaminated organic and aqueous streams, etc. Technological, environmental and economic challenges continue to exist for the treatment and disposal of such waste streams.

A proven technology since 2001 that has been applied to liquid radioactive waste (LRW) on a global basis provides one option as a low-cost solution to legacy streams, large and small volume complex LRW frequently found during decommissioning and standard operations at nuclear power plants, research institutes, medical waste centers and weapons sites. The engineered polymer technology from Nochar, USA, is capable of solidifying standard and highly complex LLW and ILW waste streams for interim or final storage, or for incineration.
Convection Cooling of Power Electronics Operating in Deep-Space
Authors: Harsono Jessica , Kozak Joseph P. , Tomey Hala , Yerkes William , Neville Jonathan
Published: November 2023

Due to the need for an atmosphere or working fluid, forced convection cooling has seen limited use in space applications. This paper considers an ideal candidate — the Dragonfly Lander, a rotocraft being sent into Deep-space to conduct experiments on Saturn’s largest moon, Titan. A forced convection based thermal management solution is presented for the Rotor Drive Electronics (RDE) unit, a high power electronics box responsible for controlling the rotors that allow the Lander to fly on Titan. A thermal flow model is built in Solidworks Flow Simulation to evaluate the effectiveness of a fan system used as the primary method for cooling the RDE. The model is validated with temperature data collected from a representative test setup. By utilizing forced convection, temperatures within the tightly packaged RDE are able to remain within operational limits when conductive and radiative heat transfer alone are insufficient. Through modeling, RDE thermal behavior is captured for an environment never before operated in, and it is shown that Titan’s dense atmosphere makes forced convection a particularly efficient method of heat transfer. This research may guide the use of forced convection in other space or non-traditional environments.
Wetting Behavior of Droplet on Inclined Surface: From Inkjet Printing on Non-Paper Media
Authors: Kawano Riki , Yamazaki Kimiharu , Kuramoto Shinichi , Kato Koichi , Fushinobu Kazuyoshi
Published: November 2023

Inkjet printers are being developed to enable printing on surfaces other than paper, such as building walls, the ground, and clothes. The challenge for printers that print on surfaces other than paper is the formation of a liquid film after the ink has landed on the surface. On uneven surfaces other than paper, the droplets are affected by gravity and their shape is distorted, resulting in a reduction in image quality. To improve these problems, it is necessary to understand how high viscosity ink used in printing spread on the substrate. In this paper, it is examined whether the droplet motion model based on Newton’s second law of motion can explain the motion of highly viscous droplets. The results show that it is necessary to consider models that take into account changes in droplet shape and velocity over time and dynamic changes when the Reynolds number is large, and to establish a method for estimating Boc when the receding contact angle does not move.
Electrochemical Additive Manufacturing Based Design of a Heat Sink for Single Phase Natural Convection Immersion Cooling Application
Authors: Lamotte-Dawaghreh Jacob , Herring Joseph , Pundla Sai , Suthar Rohit , Nair Vivek , Bansode Pratik , Gupta Gautam , Agonafer Dereje , Madril Joseph , Ouradnik Tim , Matthews Michael , Winfield Ian
Published: November 2023

To fulfill the increasing demands of data storage and data processing within modern data centers, a corresponding increase in server performance is necessary. This leads to a subsequent increase in power consumption and heat generation in the servers due to high performance processing units. Currently, air cooling is the most widely used thermal management technique in data centers, but it has started to reach its limitations in cooling of high-power density packaging. Therefore, industries utilizing data centers are looking to singlephase immersion cooling using various dielectric fluids to reduce the operational and cooling costs by enhancing the thermal management of servers. In this study, heat sinks with TPMS lattice structures were designed for application in singlephase immersion cooling of data center servers. These designs are made possible by Electrochemical Additive Manufacturing (ECAM) technology due to their complex topologies. The ECAM process allows for generation of complex heat sink geometries never before possible using traditional manufacturing processes. Geometric complexities including amorphous and porous structures with high surface area to volume ratio enable ECAM heat sinks to have superior heat transfer properties. Our objective is to compare various heat sink geometries by minimizing chip junction temperature in a single-phase immersion cooling setup for natural convection flow regimes. Computational fluid dynamics in ANSYS Fluent is utilized to compare the ECAM heat sink designs. The additively manufactured heat sink designs are evaluated by comparing their thermal performance under natural convection conditions. This study presents a novel approach to heat sink design and bolsters the capability of ECAM-produced heat sinks.
Virtual Testbed for Economical and Reliability Analysis of Battery Thermal Management Control Strategies
Authors: Singh Sagar , Olyaei Mostafa , Jiang Katherine , Gurumukhi Yashraj , Goodson Kenneth , Asheghi Mehdi , Miljkovic Nenad
Published: November 2023

A virtual testbed simulation framework is created for the economical and reliability analysis of battery thermal management control strategies in electric vehicles (EVs). The economic benefit of extending battery lifetime by optimal thermal conditioning is weighed against the corresponding energy cost of the operation, allowing for the adoption of economy-conscious strategies under different conditions. The system-level model is created in the MATLAB environment using the Simscape library and custom components as required. A lumped-parameter coupled electro-thermal model with temperature and state of charge dependent cell parameters is adapted from the literature to characterize battery performance. Suitable cell capacity degradation models are implemented to capture the cycle aging and calendar aging of the battery. Active cooling of the battery using a refrigerant system along with a preconditioning strategy is benchmarked against passive cooling by a radiator for operating cost, battery lifetime, and net savings. Active cooling can maintain optimal battery temperature but requires an additional 90–200 $/year in electrical costs compared to passive cooling. However, this cost is more than compensated for by the increase in battery lifetime by 1.5–3.2 years leading to a net savings of 325–1100 $/year.
Performance of SAC305 Solder Joints Under Simultaneous Tensile and Electromigration Stressing
Authors: Vinson Whit , Huitink David
Published: November 2023

The results contained within this paper examine the combined influence of electromigration stressors (elevated current density and elevated ambient temperature) and tensile stress on the lifetime of SAC305 solder joints (300[μm] diameter) compared to either individual stress condition acting singularly. Tensile stresses of 0 to 5 [MPa] were applied to samples already experiencing electromigration conditions of 9,100 [A/cm2] (4.611 [A]) at ambient temperatures of 100 and 150 [°C]. The testing duration was limited to 48 hours per sample. All samples tested without an applied tensile stress (i.e. 0 [MPa]) survived the 48 hour period. The same was true for only five of 24 samples tested under combined electromigration and tensile stressing conditions. Post failure analysis of the samples tested under combined electromigration and tensile stress showed necking or breakage at the Cu/SAC305 interface on the upstream side of electron flux. Cross-sectional analysis of tested samples is consistent with findings from other studies regarding electromigration failure in Cu/SAC305/Cu solder joint assemblies, where the intermetallic regions at Cu/SAC305 interfaces grow asymmetrically. Inherent process-voids in the experimental samples are discussed as a source of error and a brief computational examination of the impact of process-related voiding on current density and self-heating within solder samples is provided.
Predictive Modeling of High-G Potted Assemblies With Fine Pitch Electronics After Sustained High-Temperature Exposure
Authors: Lall Pradeep , Pandurangan Aathi Raja Ram , Blecker Ken
Published: November 2023

Electronic components designed for commercial purposes are subjected to high G shock loads and thermo-mechanical loads in defense and aerospace applications, making reliability a crucial factor in these harsh environments. To improve the reliability of printed circuit boards in such applications, they are potted, but interfacial delamination at the potting/PCB interface remains a major failure mode. The interfacial properties of the potting/PCB interface evolve over time with sustained exposure to high temperatures, which makes it necessary to investigate the effects of such exposure on the interface properties. The present study focuses on investigating the evolution of interfacial properties at the potting/PCB interface with respect to high-temperature exposure and the use of restraint mechanisms. A circular printed circuit board with fine-pitch electronic packages and multilayer ceramic chip capacitors is assembled, and bimaterial specimens of potting/PCB are made to investigate the evolution of interfacial properties. The specimens are tested under four-point bend loading, and the interfacial fracture toughness properties and cohesive zone parameters are determined for each of the interfaces. Additionally, potted circular printed circuit boards with four different potting materials are tested for pristine and 90-day aging at 150°C. The boards are subjected to shock levels of 10,000g and 25,000g to evaluate the efficacy of the potting compounds on the solder joint reliability of fine-pitch electronics and large discrete components. The study investigates an aspect of potting electronics that has not been reported earlier and could have practical implications for manufacturers. The cohesive zone parameters obtained from the bi-material samples are validated and used to develop a predictive finite element high G shock model for the circular board assemblies. The experimental test conditions are validated with the predictive model output to provide a better understanding of the interfacial properties of the potting/PCB interface. The study also discusses the potential use of the predictive model in the design of electronic components for harsh environmental applications. In summary, the study investigates the evolution of interfacial properties at the potting/PCB interface with respect to high-temperature exposure and the use of restraint mechanisms. The study also evaluates the efficacy of different potting compounds on the solder joint reliability of fine-pitch electronics and large discrete components for various aging durations. The cohesive zone parameters obtained from the bi-material samples are validated and used in the development of a predictive finite element high G shock model. The study could have practical implications for manufacturers designing electronic components for harsh environmental applications, and it provides valuable insights into the interfacial properties of the potting/PCB interface.
Study of Flow-Dependent Characteristics of HFE 7500 Coolant Dielectric Strength
Authors: Tunon Bryan , Huitink David
Published: November 2023

The use of dielectric fluids in direct cooling techniques offers an opportunity to address the thermal demands of highpower electronics that current external-to-case methods are struggling to meet. However, limited understanding about the voltage isolation performance of these fluids under different flow conditions limits their application. This effort seeks to understand the flow-dependent behavior of dielectric fluids, specifically of HFE 7500, when applied in force convective cooling method. To help understand this behavior, the flow characteristics of the dielectric fluid flowing over a needle-to-needle electrode configuration are compared to the partial discharge behavior when high voltages are applied. First, partial discharge data is collected for different flow rates in a closed flow loop containing the test section with the electrodes separated by a gap of 1 mm. Next, the test section is slightly pressurized to measure breakdown voltage and partial discharge on the dielectric fluid. The initiation of vortices due to flow over the needle configuration past a certain flow range creates low pressure zones that periodically detach from the electrodes. These low-pressure zones could impact the dielectric strength of the fluid as seen in the increased partial discharge rate for certain flow regimes. A lower breakdown voltage of HFE 7500 is observed when negative static gauge pressures are maintained in the test chamber, further supporting this hypothesis.
Development of Thermal Metrology Standards for Experimental Characterization of Thermal Resistance for Single-Phase Liquid Cold Plates
Authors: Ortega Alfonso , Martinez Victor A. , Caceres Carol , Heydari Ali , Chowdhury Uschas
Published: November 2023

Over the last decade, a significant number of investigations have been performed to develop and optimize cold plates for direct-to-chip cooling with cold plates attached to processor packages. Many investigations have reported computational simulations using commercially available CFD tools that are compared to experimental data. Generally, the simulations and experimental data are in qualitative agreement but often not in quantitative agreement. The computational simulations are used for thermal and hydraulic characterization of these cold plates and are used to perform parametric analysis to address the cold plate’s optimal design. Unfortunately, the experimental characterizations have high uncertainty due to lack of proper attention to the basic measurements, particularly of temperature. Extensive experimental evaluations reported in this paper will be used to demonstrate the frequent errors in experimental thermal measurements used in forming the defined thermal resistance and the experimental artifacts during testing that lead to unacceptable inconsistency and uncertainty in the reported results. By comparing experimental thermal data such as the temperature at multiple points on the processor lid, and using that data to extract a meaningful measure of thermal resistance, it will be shown that the data uncertainty and inconsistency is primarily due to three factors: (1.) inconsistency in the thermal boundary condition supplied by the TTV to the cold plate; (2.) errors in the measurement and interpretation of the surface temperature of a solid surface, such as the heated lid surface or the base of the cold plate, and (3.) errors introduced by improper contact between cold plate and TTV. A standard thermal test vehicle (STTV) was designed and used to provide reproducible thermal boundary conditions to the cold plate. An uncertainty analysis was performed in order to discriminate between the sources of inconsistencies in the reporting of thermal resistance, including parameters such as mechanical load distribution, methods for measuring the cold plate base, and TTV surface temperatures.
Quick Turn Methodology for High Temperature Solder Fatigue Reliability
Authors: Norris Matthew , Huitink David
Published: November 2023

Coefficient of thermal expansion (CTE) mismatch is responsible for most of the failures experienced in electronics packaging. Traditional means of life testing include thermal shock, thermal cycling, and power cycling; however there are several drawbacks to these methods. Thermal shock produces high thermal gradients which can present inaccuracies in time to failure (TTF) calculations through inconsistent fatigue behavior. Power cycling is the fastest of the three methods at cycling rates of up to 6 cycles per hour, which minimizes the time that a test can be observed during a standard workday/week. All of the processes require a large amount of power either through the repetitive heating and cooling of an oven, or the power dissipated by the electronics themselves, leading to unnecessary energy expenditures. Since these tests need to be performed for any given geometry and material, a more efficient test method was required. By equating CTE mismatch to mechanically cycled fatigue testing the lifetime of the sample can be approximated with at least a 10x reduction in TTF, as proposed by [1]. This allows for materials to be decoupled from a system and tested individually at cycle rates up to 1 cycle per second. We present a comparison of different lead-free solders using this accelerated test method. The test involves utilizing a modified tribometer to apply a sinusoidal force with peaks of ±20 N to a soldered sample using spring displacement according to Hooke’s law. Elevated temperature testing was utilized, at a homologous temperature of 0.8, to further accelerate TTF, in increasing the contribution of plasticity where the solders accumulate a significant amount of work per cycle without risk of reflow. As lead-free solder and solder pastes become more popular, a solid characterization of different attachment materials is required to make an informed selection for cost effectiveness versus robustness in a design. In this paper, we examined three different compositions. The control sample of gold-tin (AuSn) solder was used to compare against tin-antimony at compositions of 90:10 (Sn90Sb10) and 95:05 (Sn95Sb5). The footprint geometry was kept constant across all samples. Post failure, the mode of failure was examined via visual inspection under optical microscope and SEM imaging. The microhardness of samples was then captured in different regions confirming variation between hardness experienced by locations of different failure modes. Additionally, due to process, voiding was present in many samples. This voiding was examined and found to be inversely proportional to life, leading to a better understanding of the importance of process control.
Investigation of Performance and Repairability of Additively Printed Functional Circuits With Water-Based Silver Ink on an Inkjet Platform
Authors: Lall Pradeep , Kulkarni Shriram , Miller Scott
Published: November 2023

Additive printing techniques, particularly inkjet printing, have gained significant traction in the manufacturing of electronic circuits due to their cost-effective and time-efficient nature. Inkjet printing offers several advantages over traditional methods like screen printing, including printing fine lines and utilizing a broader range of conductive inks. Water-based silver ink is an environmentally friendly and highly conductive option. The water-based formulation eliminates the need for toxic solvents, ensuring a safer manufacturing and disposal process. This paper focuses on evaluating the performance of functional circuits additively printed with water-based silver ink using an inkjet platform. The circuits were printed onto a flexible Polyimide substrate using an inkjet printer with a piezoelectric printhead. Functional circuits comprising High-Pass and Low-Pass Signal Filters were printed using water-based silver ink, with discrete commercial-off-the-shelf (COTS) components attached. The frequency response of these circuits was measured and compared to simulated responses to determine any deviations in electrical performance. The viability of repairing printed circuits was studied by intentionally detaching and reattaching the components. The repaired circuits were then compared to the pristine circuits in terms of their electrical performance.
The Dual Role of “Coffee-Ring“ Effect in Colloidal Microchannel Formation
Authors: Dumont Ryan , Thammisetty Spandana , Li Bo
Published: November 2023

In order to address the challenges presented by future electronics with complex functionality and architecture, new materials and fabrication methods must be developed. In contrast to traditional top-down approaches, bottom-up self-assembly has emerged as a robust means of organizing nanoscopic building blocks into highly ordered structures and materials. In particular, topographical micropatterns are typically fabricated using complicated lithographic methods that are expensive and time-consuming and not suitable for high throughput manufacturing. Colloidal cracks, also known as colloidal microchannels, have been identified as a simple and robust strategy for the fabrication of scalable microchannels. Despite extensive theoretical modeling to understand the mechanism of crack formation, the influence of the “coffee-ring” effect on crack formation remains largely unexplored. Herein, we explore how the “coffee-ring” effect determines the colloidal microchannel formation by leveraging the kinetic control of the non-equilibrium deposition process of PS latex nanoparticles. Surprisingly, by tuning the particle size, we found the “coffeering” effect plays a dual role in determining the colloidal microchannel formation. In addition, temperature-concentration phase diagrams of colloidal microchannel formation are also provided in this work. Overall, the study presented offers crucial insights into controlling the self-assembly of colloidal particles to form microchannels, which is essential for the low-cost and large-scale fabrication of topographical templates. This study has important applications in microfluidics, geometry confinement for functional materials deposition, and alignment.
Evaluation of Antibacterial Activities for Poly-DL-Lactic Acid Nanosheet on the Biomimetic Sharkskin
Authors: Nakano Shunsuke , Ananthan Alyssa Asong , Ibrahim Mohd Danial , Abang Mahmod Dayang Salyani , Awang Husain Awang Ahmad Sallehin , Ngieng Ngui Sing , Sunami Yuta
Published: November 2023

The purpose of this study is to quantitatively examine whether antimicrobial activity varies with the thickness of the PDLLA nanosheets when placed on a PDMS surface with or without biomimetic shark skin surfaces. Sharks are known to have an antifouling property due to the rivulet structure of grooves spaced tens of μm apart covering their skin. The riblet structure reduces the area to which organisms adhere and prevents contact with small dirt and bacteria. In this study, a PDMS elastomer-embedded stamping method consisting of polydimethylsiloxane PDMS was used to achieve the biomimicry of sharkskin. The surface morphology before and after the nanosheet was applied was then observed with a scanning electron microscope to create a bacterial mass reference line to evaluate its antimicrobial activity. As a result, a decrease in antimicrobial activity was observed in the biological model compared to the flat surface. In addition, a small decreasing trend in antimicrobial effect was seen when the film thickness exceeded 100 nm in nanosheets with different film thicknesses, indicating that the antimicrobial activity on the surface increased as the film thickness became thicker and less able to follow the surface irregularities.